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  • Articles  (6,409)
  • Springer  (5,286)
  • American Meteorological Society  (1,123)
  • American Association for the Advancement of Science
  • 1995-1999  (6,409)
  • 1990-1994
  • 1999  (6,409)
  • Geosciences  (6,409)
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  • Articles  (6,409)
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  • 1995-1999  (6,409)
  • 1990-1994
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  • 1
    Electronic Resource
    Electronic Resource
    Letter from the Editor (1999)
    Springer
    GPS solutions 2 (1999), S. 1-2 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012751
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  • 2
    Electronic Resource
    Electronic Resource
    The Discription and Performance of a Multisensor Precision Pointing System (1999)
    Springer
    GPS solutions 2 (1999), S. 24-36 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The purpose of this article is to report on an integrated system that uses GPS and other low cost sensors for azimuth and pitch determination. The ability of the integrated system to maintain a solution over periods of induced GPS outage is also demonstrated. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012753
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  • 3
    Electronic Resource
    Electronic Resource
    Discussion of GPS Anti-Jam Technology (1999)
    Springer
    GPS solutions 2 (1999), S. 18-23 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The Global Positioning System (GPS) satellita navigation aiding system, sometimes called NAVSTAR, has become a utility to the military and many civilian areas. GPS, currently consisting of 24 satellites, is used by the military for navigation, precision weapons delivery, and the future digital battlefield. In the civilian sector, GPS is widely used as the primary or secondary aid for land, water, and air navigation; as a surveying aid; as a vehicle location system; and as a precision time standard for cellular and ATM sites. In the aviation community, GPS is becoming an integral part of the WAAS (Wide Area Augmentation System) and the LAAS (Local Area Augmentation System) for en route navigation in North America and Category II and III precision approach, and for surface navigation. The vulnerability of GPS have become the vulnerabilities of WAAS and LAAS, and require consideration of interference mittigation techniques. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012752
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  • 4
    Electronic Resource
    Electronic Resource
    IGS/BIPM Time Transfer Pilot Project (1999)
    Springer
    GPS solutions 2 (1999), S. 37-40 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012755
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  • 5
    Electronic Resource
    Electronic Resource
    A GPS-Supported Gravity Survey in the Amazon of Ecuador (1999)
    Springer
    GPS solutions 2 (1999), S. 3-17 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The growing importance and effectiveness of the Global Positioning System (GPS) in positioning geophysical surveys is now well established. In Ecuador's Amazon basin the use of GPS was the determining factor in the successful completion of a gravity survey carried out in 1994. Over 500 gravity stations, spaced from 1 to 5 km apart and positioned by GPS, were collected in the jungle environment in the country's southeast, where the preexisting data, of variable and unknown quality, were mostly confined to areas along the major rivers. This station densification, which includes the reoccupation of selected points, contributed to increase the gravity coverage; it also allowed us to evaluate and correct 1100 preexisting data points in the area, so that the different surveys can be merged. The composite data set is used for a geologic analysis of the study area, where previously unknown structures are discovered. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012754
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  • 6
    Electronic Resource
    Electronic Resource
    Seasonal Motion in the Annapolis, Maryland GPS Monument (1999)
    Springer
    GPS solutions 2 (1999), S. 41-49 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The permanent GPS tracking site at Annapolis, MD shows a 7-mm seasonal signal primarily in its horizontal position. It is suggested that thermal expansion of the pier on which the antenna rests is the source of this motion. A simple numerical model of the pier reproduces the observed motion of the GPS antenna, lending credence to this hypothesis. Although adding an additional level of complexity, this motion is predictable and the site retains it s value for high precision monitoring. Although the arrangement of this GPS site it somewhat uncommon, these results emphasize the importance of the underlying antenna monumentation when measuring crustal motions. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012756
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  • 7
    Electronic Resource
    Electronic Resource
    The Reliability of GPS Ambiguity Resolution (1999)
    Springer
    GPS solutions 2 (1999), S. 63-69 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: GPS ambiguity resolution is the process of resolving the unknown cycle ambiguities of double-difference (DD) carrier-phase data as integers. It is the key to fast and high-precision relative GPS positioning. Critical in the application of ambiguity resolution is its reliability. Unsuccessful ambiguity resolution, when passed unnoticed, will too often lead to unacceptable errors in the positioning results. High success rates are required for ambiguity resolution to be reliable. In this contribution we will introduce and evaluate such diagnostic measures. They complement existing methods of ambiguity resolution and allow the user and/or analyst to infer their reliability. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012758
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  • 8
    Electronic Resource
    Electronic Resource
    A New Solar Radiation Pressure Model for GPS Satellites (1999)
    Springer
    GPS solutions 2 (1999), S. 50-62 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The largest error in currently used GPS orbit models is due to the effect of solar radiation pressure. Over the last few years many improvements were made in modeling the orbits of GPS satellites within the International GPS Service (IGS). Howeer, most improvements were achieved by increasing the number of estimated orbit and/or solar radiation pressure parameters. This increase in the number of estimated satellite parameters weakens the solutions of all estimated parameters (not only orbit parameters). Because of correlations the additional orbit parameters may introduce biases in other estimated quantities, for example the length of day. We present a recently developed solar radiation pressure model for the GPS satellites. This model is based on experiences and results gained at the Center for Orbit Determination in Europe (CODE) in the context of its IGS activities since June 1992. The performance of the new model is almost an order of magnitude better than that of the existing ROCK models. It also allows a reduction of the number of orbit parameters that have to be estimated. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012757
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  • 9
    Electronic Resource
    Electronic Resource
    Monitoring Isostatic Rebound in Antarctica with the Use of Continuous Remote GPS Observations (1999)
    Springer
    GPS solutions 2 (1999), S. 70-75 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: A solar-powered GPS receiver has been installed near Beaver Lake, Antarctica, to monitor postglacial isostatic rebound that may be occurring as a result of ice thinning near the Lambert Glacier since the last glacial maximum. The equipment is 400 km from the nearest Australian Antarctic base and is completely automated. It is expected that there will be sufficient solar power to operate the equipment from January 1998 to May 1998, but the data will not be recovered until the following summer season. The scatter in height computed from the first 25 days of data is ± 7.5 mm. If such precision is representative of the accuracy of the height estimates, isostatic rebound of 〈 1 mm/yr will be able to be detected after a few years of observations at the site. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012759
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  • 10
    Electronic Resource
    Electronic Resource
    Eye on the Iosophere (1999)
    Springer
    GPS solutions 2 (1999), S. 79-80 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012761
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  • 11
    Electronic Resource
    Electronic Resource
    GPS & GLONASS Current Bibiography (1999)
    Springer
    GPS solutions 2 (1999), S. 81-83 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012762
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  • 12
    Electronic Resource
    Electronic Resource
    Automated GPS Data Analysis Service (1999)
    Springer
    GPS solutions 2 (1999), S. 76-78 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Automatic analysis of geodetic-quality GPS data is available with the use of e-mail and ftp (file transfer program) as an interface to a computer at the Jet Propulsion Laboratory (JPL), where precise transmitter parameters – GPS ephemerides and clock errors – are computed regularly. The interface is such that e-mail from an external user causes the JPL computer to fetch the user's data. The computer than analyzes the data, and places the results in an area accessible to the user. An e-mail to the user gives information on the location of the analysis results, which the user can subsequently fetch. Operations on the JPL computer are entirely automatic, and require essentially no labor. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012760
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  • 13
    Electronic Resource
    Electronic Resource
    United States' Nationwide Differential Global Positioning System (1999)
    Springer
    GPS solutions 2 (1999), S. 1-6 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: This article describes the Nationwide Differential Global Positioning System (NDGPS) service being developed in the United States and the enormous benefits to federal agencies, state governments, and the general public. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012763
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  • 14
    Electronic Resource
    Electronic Resource
    Variances of GPS Phase Observations: The SIGMA-ɛ Model (1999)
    Springer
    GPS solutions 2 (1999), S. 35-43 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The noise term of GPS phase data can be calculated from the measured carrier-to-noise power density ratios (C/N0). The C/N0 values are used in the proposed SIGMA-ɛ model to calculate the variance matrix of double-differenced GPS phase data. Examples show the capability of this model to yield higher accuracies for GPS surveys than the use of the standard weighting scheme. Most importantly, the SIGMA-ɛ model allows the use of noisier phase data from very low elevation satellites to overcome poor satellite geometry problems. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012765
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  • 15
    Electronic Resource
    Electronic Resource
    A Regional GPS Network Solution for Monitoring Deformations of the Southeastern Eurasian Plata (1999)
    Springer
    GPS solutions 2 (1999), S. 44-51 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Investigations of deformation styles in Asia have already led to new kinematic models that predict the spatial and temporal evolution of deformations in the region. Testing these models is now within realm of current GPS technology. In this study, GPS data during 4 months from six stations in Asia, including a new station from Hong Kong whose data were not in public domain, were analyzed for generating kinematic geophysical constraints for the deformations at the regional scale. Processing of 4 months' continuous GPS data from all stations shows small relative station velocities (Wuhan, Shanghai, Xian, and Hong Kong stations in China), except the Lhasa station, which has a northeasterly velocity of about 3 cm/year with respect to the fixed GPS station operating in Taiwan. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012766
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  • 16
    Electronic Resource
    Electronic Resource
    Differentiation for High-Precision GPS Velocity and Acceleration Determination (1999)
    Springer
    GPS solutions 2 (1999), S. 7-21 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Accurate estimates of the velocity and acceleration of a platform are often needed in high dynamic positioning, airborne gravimetry, and geophysics. In turn, differentiation of GPS signals is a crucial process for obtaining these estimates. It is important in the measurement domain where, for example, the phase measurements are used along with their instantaneous derivative (Doppler) to estimate position and velocity. It is also important in postprocessing, where acceleration is usually estimated by differentiating estimates of position and velocity. Various methods of differentiating a signal can have very different effects on the resulting derivative, and their suitability varies from situation to situation. These comments set the stage for the investigations in this article. The objective is twofold: (1) to carry out a comprehensive study of possible differentiation methods, characterizing each in the frequency domain; and (2) to use real data to demonstrate each of these methods in both of the measurement and position domains, in conditions of variable, high, or unknown dynamics. Examples are given using real GPS data in both the measurement domain and in the position and velocity domain. The appropriate differentiator is used in several cases of varying dynamics to derive a Doppler signal from carrier phase measurements (rather than using the raw Doppler generated by the receiver). In the statistic case, it is seen that the accuracy of velocity estimates can be improved from 4.0 mm/s to 0.7 mm/s by using the correct filter. In conditions of medium dynamics experienced in an airborne gravity survey, it is demonstrated that accelerations as the 2–4 mGal level (1 mGal = 0.00001 m/s2) can be obtained at the required filtering periods. Finally, a precision motion table is used to show that when using the correct filter, velocity estimates under high dynamics can be improved by an order of magnitude to 27.0 mm/s. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012771
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  • 17
    Electronic Resource
    Electronic Resource
    Assessment of the LandStar Real-Time DGPS Service under Several Operational Conditions (1999)
    Springer
    GPS solutions 2 (1999), S. 22-34 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: LandStar is a differential global positioning service (DGPS) that provides 24-h real-time positioning for various applications on land, water, and air in North America, Australia, New Zealand, Europe, and Africa. Its focus is on real-time applications requiring a submeter positioning capability such as agriculture, forestry, Geospatial Information Systems (GIS), survey/mapping, and land/vehicular navigation. LandStar uses a Wide Area Network of reference stations to derive DGPS corrections to model the variation of GPS error sources over a large area. These model parameters are used by the Virtual Reference Station processors to calculate standard corrections that are available for all predefined locations in the network. The corrections are transmitted to the user by L-band satellite communication in the standard RTCM SC104 DGPS correction format. This article investigates the performance of the LandStar Mk III system under various operational conditions and assesses its performance in both static and kinematic modes. Four field tests were conducted during 12 months that tested the sysem in clear static and kinematic conditions as well as suboptimal environments associated with low and heavy foliage conditions. Both the accuracy and availability of the system under these conditions is investigated, with an emphasis on whether the above variables are caused by the LandStar system differential corrections, the GPS measurements, or a combination of both. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012764
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  • 18
    Electronic Resource
    Electronic Resource
    GNSS Activities – Report (1999)
    Springer
    GPS solutions 2 (1999), S. 57-59 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012768
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  • 19
    Electronic Resource
    Electronic Resource
    GPS & GLONASS Current Bibliography (1999)
    Springer
    GPS solutions 2 (1999), S. 64-66 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012770
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  • 20
    Electronic Resource
    Electronic Resource
    Eye on the Ionosphere: Measuring Ionospheric Scintillation Effects from GPS Signals (1999)
    Springer
    GPS solutions 2 (1999), S. 60-63 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: From time to time, this column will include short contributions from invited guest contributors on specialized subjects pertaining to inonospheric effects on GPS signals. In this issue, Dr. A. J. Van Dierendonck discusses the required specifications of a civilian GPS receiver specially designed to make quantitative measurements of both ionospheric amplitude and carrier phase scintillation effects from GPS signals. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012769
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  • 21
    Electronic Resource
    Electronic Resource
    A Modular Approach to Precise GPS Positioning (1999)
    Springer
    GPS solutions 2 (1999), S. 52-56 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: A modular approach consisting of three steps is presented for precise positioning with GPS: integrity, monitoring (data validation), ambiguity resolution, and positioning. Results of one step are used as input for the next. After a brief description of reliability and testing and techniques for GPS ambiguity resolution, the observation equations for the geometry-free GPS model are given, used for integrity monitoring, followed by those for single-difference relative positioning with the double-difference ambiguities removed. © 1999 John Wiley & Sons, Inc.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012767
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  • 22
    Electronic Resource
    Electronic Resource
    Letter from the Editor: EOW and Y2K Issues (1999)
    Springer
    GPS solutions 3 (1999), S. 1-1 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00012772
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  • 23
    Electronic Resource
    Electronic Resource
    Y2K and Other Stories (1999)
    Springer
    GPS solutions 3 (1999), S. 2-4 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: GPS technology will face not one but two critical rollover dates over the next eight months. One is the millennium (Y2K) rollover. The other is the GPS week 1024 rollover also known as the GPS End of the Week (EOW). Each rollover dat has the potential to cause severe problems in GPS receivers and related software. This article expolres the reasons why these dates are a problem and describes choices that must be made as to their solution. The paper also describes some verification methods that may be used to test GPS receivers and software. © 1999 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1007/PL00012775
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  • 24
    Electronic Resource
    Electronic Resource
    GPS Application to Time Transfer and Dissemination (1999)
    Springer
    GPS solutions 3 (1999), S. 17-25 
    Details
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The Global Positioning System (GPS), in addition to providing precise navigation and positioning information, produces precise time and frequency measurements. These measurements result from the atomic clocks in the GPS satellites, which are closely coupled to Universal Coordinated Time as maintained by the U. S. Naval Observatory [UTC(USNO)]. The application of these measurements to timekeeping and other systems requiring precise time and frequency is distinct from the navigation/positioning mission. This article will describe the differences in application of GPS to time and frequency uses. These uses will be described in the major areas of timekeeping; stationary uses, such as communications networking; and mobile use for aircraft and shipboard applications. The major considerations in application and operation with precise and less-capable oscilators will be described. Examples and data will be presented to illustrate the applications. © 1999 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1007/PL00012774
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  • 25
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    Single-Epoch Ambiguity Resolution for Real-Time GPS Attitude Determination with the Aid of One-Dimensional Optical Fiber Gyro (1999)
    Springer
    GPS solutions 3 (1999), S. 5-12 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: High-accuracy real-time GPS-based attitude determination requires that integer ambiguities be resolved very quickly so that the attitude angles can be output with minimum delay. This article describes an attitude determination algorithm that can resolve integer ambiguities instantaneously, relative to one antenna of a multi-antenna array configuration. The carrier phase and pseudorange observations are used with fixed baseline length constraints and fiberoptic gyro data. Real-time stochastic model improvement using empirical elevation-dependent standard deviation function and an estimated scale factor are a feature of this algorithm. Integer ambiguity search using the LAMBDA method, sophisticated validation criteria, and an adaptive procedure has also been implemented within the software. An experiment was carried out using four Leica dual-frequency GPS receivers (but only the L1 carrier phase and pseudorange data were used) and a low-cost fiberoptic on a car. The results indicate that integer ambiguities can be resolved on a single-epoch basis with a 98.9% success rate. © 1999 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1007/PL00012779
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  • 26
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    Electronic Resource
    Propagating PZ 90 to WGS 84 Transformation Parameters (1999)
    Springer
    GPS solutions 3 (1999), S. 13-16 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The 29th Research Institute recently published its latest transformation parameters for WGS and PZ 90. Because these tranformation parameter estimates were derived from stations located within Russia, variance-covariance propagation was carried out to study the benefits of a better global distribution of stations. An example that includes two stations in North America is presented. The transformation improves significantly. © 1999 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1007/PL00012773
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  • 27
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    Timing and Positioning with GLONASS and GPS (1999)
    Springer
    GPS solutions 3 (1999), S. 26-31 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Considering GLONASS as one of the pillars of the international Global Navigation Satellite System (GNSS), the Russian Federation works toward the integration of GLONASS with other navigation systems, cooperates with the internal user community, and contributes to the development and coordination of standards concerning GLONASS and the combined use of GLONASS and the global positioning system (GPS). This work is pursued in conformity with recommendations of respective international organizations. Most users recognize that the GLONASS/GPS combination has better characteristics in terms of availability, accuracy, integrity, and so on. However, the combined use of these satellite systems raises problems that must be addressed. This article reviews problems encountered when using two different navigation systems. Solutions developed thus far are outlined. The potential of GLONASS and approaches for high accuracy UTC time transfer are discussed. The transformation between the WGS 84 and PZ 90 reference frames and their conformity with the international terrestrial reference frame (ITRF) is considered. Various solutions are viewed in connections with recommendations made by the International Civil Aviation Organization (ICAO), the Global Navigation Satellite System Panel (GNSP), and the Consultative Committee for Definition of the Second (CCDS) concerning the desirability of using either or both systems interchangeably. © 1999 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1007/PL00012776
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  • 28
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    Hybrid GPS + GLONASS (1999)
    Springer
    GPS solutions 3 (1999), S. 32-41 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The hybridization of GPS with GLONASS has formed a first stage in GNSS development. We examine the performance of the hybrid system in the position domain for both code and carrier phase cases. Several major differences exist between GPS and GLONASS; most significant is GLONASS's signal frequency diversity, which can lead to measurement bias, particularly so when a pair of receivers are operating at different temperatures. Unless signal frequency diversity is addressed either on-receiver or at the data processing stage, positioning errors can occur at the centimeter level. We outline the difficulties of combining observations from the two systems and discuss how these may be overcome. © 1999 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1007/PL00012777
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    TEQC: The Multi-Purpose Toolkit for GPS/GLONASS Data (1999)
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    GPS solutions 3 (1999), S. 42-49 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: For many common GPS/GLONASS native receiver formats, a single freeware program called TEQC now allows the user to translate from the binary receiver format to the standard Receiver Independent Exchange (RINEX) format, to edit existing RINEX files, and to quality-check the data before postprocessing. TEQC is 100% noninteractive and has a command line interface modeled after common UNIX commands. This combined with TEQC's extensive documentation makes it simple to use for new and experienced users and in automated processing scripts. © 1999 John Wiley & Sons, Inc.
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    GPS Antenna Calibration at the National Geodetic Survey (1999)
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    GPS solutions 3 (1999), S. 50-58 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The precise point whose position is being measured when a GPS baseline is determined is generally assumed to be the phase center of the GPS antenna. However, the phase center of a GPS antenna is neither a physical point nor a stable point. For any given GPS antenna, the phase center will change with the changing direction of the signal from a satellite. Ideally, most of this phase center variation depends on satellite elevation. Azimuthal effects are only introduced by the local environment around each individual antenna site. These phase center variations affect the antenna offsets that are needed to connect GPS measurements to physical monuments. Ignoring these phase center variations can lead to serious (up to 10 cm) vertical errors. This article will describe the procedure by which the National Geodetic Survey is calibrating GPS antennas and how this information may be obtained and used to avoid problems from these antenna variations. © 1999 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1007/PL00012780
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    Notes on GPS Modernization (1999)
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    GPS solutions 3 (1999), S. 77-78 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
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    URL: http://dx.doi.org/10.1007/PL00012783
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    IGS Earth Rotation Parameters (1999)
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    GPS solutions 3 (1999), S. 59-72 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Since its official start in January 1994, the International GPS Service (IGS) has been distributing, as part of its product combination, two distinct Earth rotation parameter (ERP) series: the IGS Rapid series and the IGS Final series. Initially, the IGS Rapid ERP values were interpolations of the International Earth Rotation Service (IERS) Bulletin A, whereas the IGS Final ERP series was based on the IERS Bulletin B. Since June 1996, the IGS has been generating its own Final ERP series consistent with the IGS combined orbit products and based on weighted means of individual IGS analysis center (AC) solutions. At first, only the polar motion (PM) coordinates and their rates were combined. Length of Day (LOD) and Universal Time (UT) solutions, also based on separate weighted mean combinations, followed in March 1997. Currently, the IGS Rapid and Final combinations are produced and made available within 17 hours and 11 days, respectively, after the last observation. Both IGS and the best AC series are consistent and precise at the 0.1-milliarcsecond (mas) level for PM and at about 30 μs for LOD. Biases in some AC solutions may exceed these consistency levels. Comparisons of both IGS ERP series with external standards, such as the IERS multitechnique Bulletins and atmospheric angular momentum series, confirm the estimated precisions. © 1999 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1007/PL00012781
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    Eye on the Ionosphere (1999)
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    GPS solutions 3 (1999), S. 79-81 
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    ISSN: 1521-1886
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    URL: http://dx.doi.org/10.1007/PL00012784
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    Testing JPL's PPP Service (1999)
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    GPS solutions 3 (1999), S. 73-76 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The Jet Propulsion Laboratory's (JPL's) automated GPS data analysis service, which is available via the Internet, has been tested. This service is attractive not only because data submission and retrieval are entirely automated on the Internet, but also because it makes centimeter positioning possible for individual dual-frequency receivers. To learn more about this service, the repeatability of position solutions were investigated by means of two simple experiments. The positions of a continuously operating reference station have been computed repeatedly for observation times ranging from 1 hour to 24 hours. In addition, short baseline repeatability and accuracy were tested. Centimeter-level results were obtained. The difference in the vertical definition of the electronic center for antennas of different types could readily be identified. The JPL service is easy to use, even in its present form (which one might label version 1.0). © 1999 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1007/PL00012782
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    GPS & GLONASS Current Bibliography (1999)
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    GPS solutions 3 (1999), S. 82-84 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
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    URL: http://dx.doi.org/10.1007/PL00012785
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    The Influence of Code Multipath on the Estimated Parameters of the Geometry-Free GPS Model (1999)
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    GPS solutions 3 (1999), S. 11-18 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: In this article, the influence of biases in GPS code observations on the estimated parameters of the geometry-free model is investigated. This is done for undifferenced as well as double-differenced data from short baselines, that is, baselines for which ionospheric effects may be assumed absent. It is shown how introducing a linear model for code multipath affects the original model parameters. The performance of the original and extended model is illustrated by analyzing data from a single receiver and a short baseline. © 1999 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1007/PL00012787
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    Vulnerability of the GPS Signal to Jamming (1999)
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    GPS solutions 3 (1999), S. 19-27 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The Global Positioning System (GPS) and Wide Area Augmentation System (WAAS) provide lower power signals that are susceptible to interference. The potential exists for a person or organization to jam GPS or WAAS signals, causing a loss of service over a large area. Accidental interence by extraneous radio transmissions on the GPS frequency also can cause loss of service. Jamming has become a serious issue for GPS, and the U. S. military is making a significant effort to mitigate jamming effects. While jamming is a major concern of the military, interference is of a no lesser concern to the civilian sector. In fact, with varying emphasis both jamming and interference are concerns of the entire GPS user community. This article explores jamming and interference threats to the GPS. We provide a general overview of the GPS signal structure, discuss jamming effects on the GPS, and consider mitigating options. © 1999 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1007/PL00012788
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    European GNSS – Competitive, Yet Cooperative (1999)
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    GPS solutions 3 (1999), S. 28-39 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The management of the Global Positioning System (GPS) by the U. S. Department of Defense (DoD) has been the subject of persistent criticism by the global community of users in general and particularly in Europe. The European Union (EU) is considering various global navigation satellite systems (GNSS) that would provide it with varying degrees of control, autonomy, and specificity of use. The gamut of options includes various augmentations of GPS, a combination of GLONASS and GPS, and its own GNSS, dubbed Galileo. We discuss the concerns of the global community with respect to GPS and the motives that drive the GPS globalization debate. We also describe the various European GNSS concepts and initiatives, and the likelihood for their realization as substitutes to the GPS. © 1999 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1007/PL00012789
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    Time and Frequency Transfer Using GPS Codes and Carrier Phases: Onsite Experiments (1999)
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    GPS solutions 3 (1999), S. 1-10 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Recent studies have shown the capabilities of Global Positioning System (GPS) carrier phases for frequency transfer based on the observations from geodetic GPS receivers driven by stable atomic clocks. This kind of receiver configuration is the kind primarily used within the framework of the International GPS Service (IGS). The International GPS Service/Bureau International des Poids et Mesures (IGS/BIPM) pilot project aims at taking advantage of these GPS receivers to enlarge the network of Time Laboratories contributing to the realization of the International Atomic Time (TAI). In this article, we outline the theory necessary to describe the abilities and limitations of time and frequency transfer using the GPS code and carrier phase observations. We report on several onsite tests and evaluate the present setup of our 12-channel IGS receiver (BRUS), which uses a hydrogen maser as an external frequency reference, to contribute to the IGS/BIPM pilot project. In the initial experimental setup, the receivers had a common external frequency reference; in the second setup, separate external frequency references were used. Independent external clock monitoring provided the necessary information to validate the results. Using two receivers with a common frequency reference and connected to the same antenna, a zero baseline, we were able to use the carrier phase data to derive a frequency stability of 6 × 10−16 for averaging times of one day. The main limitation in the technique originates from small ambient temperature variations of a few degrees Celsius. While these temperature variations have no effect on the functioning of the GPS receiver within the IGS network, they reduce the capacities of the frequency transfer results based on the carrier phase data. We demonstrate that the synchronization offset at the initial measurement epoch can be estimated from a combined use of the code and carrier phase observations. In our test, the discontinuity between two consecutive days was about 140 ps. © 1999 John Wiley & Sons, Inc.
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    IGEX-98: International GLONASS Experiment (1999)
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    GPS solutions 3 (1999), S. 66-68 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: GLONASS is a Russian military navigation satellite system. Even if the constellation is far from being operational, a large community is potentially interested in using its signal in combination with GPS to improve availability, integrity, or precision. The goal of this article is to present the international GLONASS campaign, named IGEX-98, which is really the first attempt to obtain precise GLONASS orbits for geodetic applications. A world-wide network of GLONASS receivers has been deployed and is still operational. Several analysis centers process the GLONASS data on a regular basis in the same way it is done for GPS within the International GPS Service. © 1999 John Wiley & Sons, Inc.
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    Space Rockets, Polar Bears, and Tundra Buggies – And a GPS Link to the Seventeenth Century (1999)
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    GPS solutions 3 (1999), S. 48-52 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The use of the Global Positioning System (GPS) for position and attitude determination has been exploited for many years. In these systems, it was required that multiple antennas maintained phase lock to common view satellites for long periods of time in order to determine integer ambiguities. The challenge to overcome with the ballistic space probe is the high rotational spin of this particular rocket. The antennas, mounted on the outside skin of the rocket, are in full view of each satellite only for a fraction of a second before the rocket core eclipses them as it rotates. The antennas rarely see common satellites. This article describes as system that overcomes these obstacles and provides position, acceleration, attitude, and rotation rate. The approach uses a two-antenna system. One antenna is mounted either side of the rocket facing out. A hybrid tracking channel combines signals from both antennas to overcome the signal blockage due to the rocket core as well as to defeat the effect on the tracking channel due to the spin. The amplitude and phase of the spin rotation signature from each satellite is extracted from the dual antenna data and used to compute the attitude and spin rate of the vehicle. © 1999 John Wiley & Sons, Inc.
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    URL: http://dx.doi.org/10.1007/PL00012791
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    Receiver Architectures for Improved Carrier Phase Tracking in Atenuation, Blockage, and Interference (1999)
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    GPS solutions 3 (1999), S. 40-47 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: A significant impediment to real-time centimeter survey and vehicle guidance in difficult reception environments is the underlying signal tracking performance of the receiver. A number of researchers have investigated receiver signal tracking enhancements that take advantage of intersatellite path correlations, of particular benefit in environments with multiple satellite attenuations and blockages. This article surveys work in the area, with a focus upon an optimal estimation scheme known as integrated demodulation/navigation (IDN). By contrast with other techniques, IDN employs a high update rate extended Kalman filter to combine and process raw correlator data across satellites. Nonlinear loop simulations of real time kinematic (RTK) tracking during high-g aircraft maneuvers with vehicle-induced blockages are used to illustrate the filtering method and it s robustness. © 1999 John Wiley & Sons, Inc.
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    Centimeter-Level Positioning of a U. S. Coast Guard Buoy Tender (1999)
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    GPS solutions 3 (1999), S. 53-65 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: With the availability of high-accuracy, differential global positioning system (GPS) results in real-time, there is a new opportunity to use GPS to accurately measure a marine vessel's dynamic draft (settlement and squat) and 3D attitude (roll, pitch, and heading). The National Geodetic Survey (NGS) and the Coast Survey (CS), offices of the National Ocean Service (NOS), National Oceanic and Atmospheric Administration (NOAA), propose to transfer this technology to the shipping industry. The overall goal of this project is to provide the position of a vessel's keel in real time to within 10 cm (about 4 inches) relative to the bottom of the shipping channel. In support of this phase of the project, there were three meetings hosted by the Port of Oakland, California and NOS to discuss the real-time positioning of vessels project. On December 3 and 4, 1996, CS, NGS, Trimble Navigation Ltd., and the U. S. Coast Guard (USCG) performed GPS tests on a USCG buoy-tender ship. GPS data were used to compute the vessel's dynamic draft and 3D attitude. During the test, five receivers continually collected data; one receiver was located at a base station on the USCG pier on Yerba Buena Island, and four were on the ship: two on the stern and two on the bow. CS installed a TSS-335B vertical reference unit (to measure heave, pitch, and roll) in the engine room of the ship. NOS processed the GPS data and computed the vessel's dynamic draft and 3D attitude. The results indicate that the linear equivalent to the vessel's dynamic draft and 3D attitude were accurate to the 10-cm level using GPS. It was also demonstrated how a ship can be used to measure local water-level changes and actual water-level values everywhere it travels. © 1999 John Wiley & Sons, Inc.
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    GNSS Activities – Report (1999)
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    GPS solutions 3 (1999), S. 72-74 
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    Topics: Architecture, Civil Engineering, Surveying , Geosciences
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    URL: http://dx.doi.org/10.1007/PL00012795
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    Eye on the Ionosphere: Potential Solar Radio Burst Effects on GPS Signal to Noise (1999)
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    GPS solutions 3 (1999), S. 69-71 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: A. J. VanDierendonck joins the regular contributors to this column to discuss potential solar radio burst effects on GPS. While this topic does not spedivically involve ionospheric effects on GPS, it falls under the general area of environmental concerns that are of importance to the GPS community. © 1999 John Wiley & Sons, Inc.
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    GPS & GLONASS Current Bibliography (1999)
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    GPS solutions 3 (1999), S. 75-77 
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    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
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    Propriétés géotechniques de quelques formations géologiques propices aux glissements de terrains dans l'agglomération de Constantine (Algérie) (1999)
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    Bulletin of engineering geology and the environment 57 (1999), S. 301-310 
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    ISSN: 1435-9537
    Keywords: Mots clés Glissement de terrain ; Caractéristiques mécaniques ; Essais in-situ ; Néotectonique ; Constantine ; Key words Landslides ; Geotechnical characteristics ; In situ tests ; Neotectonic ; Constantine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract  The article can be conveniently divided into two parts. The first part of the paper describes certain forms of landslides observed in the urban area of Constantine which indicate neotectonic activity. The detailed surveys of present and fossil ground movements showed the geological formations to be of Mio-Pliocene age and to consist of two lithological groups: clayey marls and conglomerates. The slope terrain and potential for instability varies considerably with the two lithologies. The clayey-marl group contain local sand and gravel horizons of varying thickness. These water-bearing levels are confined and hence if the natural egress points become blocked, the increased water pressure within the material causes instability. Landslides rarely occur within the conglomerates, even when they are at quite steep angles. However, where conglomerates are found interbedded with the marly sediments, significant landslides can take place, The location and geology of the El Menia (1), Bardo (2), Aouinet El Foul (3) and Oued zied (4) slides are presented. The second part of the paper presents some geotechnical characteristics of the unstable geological formations, obtained by in situ and laboratory testing and the correlations drawn between them.
    Notes: Résumé L'étude présentée se compose de deux parties. La première explique certaines formes de glissement de terrain observées dans l'agglomération de Constantine comme témoins d'une activité néotectonique. La seconde partie présente quelques caractéristiques géotechniques, des formations géologiques instables, obtenues par différents moyens: les essais de laboratoire, les essais in-situ, les corrélations.
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    Importance du facteur lithologique sur le développement des ravins du bassin versant d'Oued Maiez en Tunisie Centrale (1999)
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    Bulletin of engineering geology and the environment 57 (1999), S. 285-293 
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    ISSN: 1435-9537
    Keywords: Mots clés Ravins ; Lithologie ; SIG ; Densité des ravins ; Susceptibilité ; Terrassement ; Key words Gullies ; Lithology ; GIS ; Gull density ; Susceptibility ; Terracing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract  Gully development in Central Tunisia is contributing to the fast decrease of agricultural land. Fieldwork has shown the most salient feature influencing the gully morphology and density is the surficial geology. A network of dense V-shaped gullies has developed on the gypsum clay of Lutetian-Priabonian age while deep and narrow U-shaped gullies form in the semi-consolidated fine sandstone of early Oligocene age. The research reported studied the relationship between the geological materials and the growth rate of gullies in the 1500-ha basin of the Oued Maiez, Central Tunisia. An accurate superficial geology map with interpreted geological cross sections has been constructed at a scale of 1 : 12,500. Eight rock units were identified within the drainage basin. The 1963 and 1989 aerial photographs were enlarged to the 1 : 12,500 scale and the gully network indicated in the photographs superimposed on the geological maps. The gully lengths and areas for each geological unit were numerically determined using the Geographic Information System (GIS) Arc/info software. The gully density was found to vary depending on the geological formation. From the 1989 aerial photograph it was 101 m/ha for the Cherichera formation (early and middle Oligocene) while for the unit 2 formation (Lutetian-Priabonian age) it was 285 m/ha. Substantial differences in gully density between 1963 and 1989 were noted. During this 27-year period the growth rate of gullies was found to vary depending on the geological units. The highest growth rate of 100% was found in the semi-consolidated fine sandstone of the Cherichera formation whereas in the unit 8 formation (coarse sands and conglomerates of Quaternary age) it was only 45%. Gully geometry was described for each rock type and it was found that the width/depth ratio also varies according to rock type. In a 64 ha terraced area in the Oued Maiez basin, terracing in 1985 reduced gully density by as much as 27%.
    Notes: Résumé L'érosion ravinante réduit de plus en plus les terres cultivables en Tunisie Centrale en les transformant en badland. Le développement des ravins est variable dans l'espace et dans le temps suite à la variabilité des paramètres physiques et naturels qui régissent l'accroissement des ravins. Nous nous sommes proposés dans cette recherche d'étudier l'effet des formations lithologiques sur le développement des ravins dans le bassin versant de 1500 ha d'Oued Maiez situé en Tunisie Centrale. Les cartes du réseau hydrographique de 1963 et 1989 ont étéétablies à partir des photographies aériennes au 1/12,500 non redressées. La prospection du terrain nous a permis de constater que la nature lithologique des différentes unités géologiques et superficielles identifiées comme relativement homogènes dans le bassin versant est un facteur déterminant dans le développement des ravins. Ainsi, les argiles gypseuses de la formation Chérichéra (Lutétien-Priabonien) présentent un chevelu de ravins dense alors que les sables fins de l'Oligocène inférieur sont incisés par des ravins en forme de gorges étroites dont la profondeur dépasse souvent les 5 m (Fig. 7). Nous avons alors établi un levé cartographique détaillé au 1/12,500 de ces différentes unités qui sont au nombre de 8. La détermination de la densité du ravinement, définie comme étant le rapport de la longueur des ravins dans une unité lithologique sur sa superficie, a été faite par la numérisation des cartes du réseau hydrographique et géologique et l'extraction à l'aide du système d'information géographique (SIG) Arc/info des ravins inclus dans chacune de ces unités (Figs. 9, 10). Il ressort de cette quantification que, dans les unités dont la superficie varie entre 33.96 ha et 416.86 ha, la densité du ravinement varie entre 101 m/ha et 285 m/ha en 1989 (Tableau 2). La plus faible densité se trouve dans la formation Chérichéra datée de l'Oligocène inférieur à moyen et constituée par la superposition de plusieurs séquences élémentaires d'argile feuilletée verte, de silt et de grès roux coquillier à ciment calcaire. La plus forte densité se trouve dans l'unité 2 datée du Lutétien supérieur- Priabonien et composée d'argiles verdâtres à violacées riches en gypses lamellaires. L'étude diachronique de la densité du ravinement par unité lithologique entre 1963 et 1989 a montré des taux d'évolution variant entre 45% et 100% en 27 ans (Tableau 2). Cela a permis d'effectuer un classement de la susceptibilitéà l'érosion de ces différentes unités. Les travaux de terrassement par des banquettes en 1985 dans une zone couvrant 64 ha de terres agricoles ravinées (Fig. 11) ont permis de réduire la densité des ravins de 27%.
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    Discussion on "Aspects of rock strength", by A. B. Hawkins, Bull Eng Geol Env (1998) 57 : 13–30 (1999)
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    Bulletin of engineering geology and the environment 57 (1999), S. 319-320 
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    ISSN: 1435-9537
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
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    Reply to "Discussion" by E. Arioğlu, Bull Eng Geol Env (1999) 57 : 319–320 (1999)
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    Bulletin of engineering geology and the environment 57 (1999), S. 321-321 
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    ISSN: 1435-9537
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
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    Modélisation du processus de sédimentation-consolidation des vases estuariennes: approche continue unidimensionnelle (1999)
    Springer
    Bulletin of engineering geology and the environment 57 (1999), S. 311-318 
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    ISSN: 1435-9537
    Keywords: Mots clés Sédimentation ; Consolidation ; Vase ; Modélisation ; Key words Sedimentation ; Consolidation ; Mud ; Modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract  Nowadays numerical models tend to replace physical models for the study of sediment transport processes in fluvial or marine environments. The variability of both the materials and the environments make the processes complex in areas of major economic importance such as estuaries. The representativeness of current models depends much on the evaluation of the material which is deposited and/or re-suspended, hence the modelling of the deposit and consolidation phenomena. The paper proposes a unidimensional analysis of the sedimentation-consolidation process based on a continuous action and taking account of the complexity of the sedimentary materials. The distinction between sedimentation (the fall of isolated grains in a fluid medium) and consolidation (compression of a solid deposit by evacuation of pore water) is difficult to determine in the case of muds. In muds, particles frequently interact (for example in flocculation and deflocculation) although the grains remain separated by a film of water at a microscopic scale. In the 1980s and 1990s, several authors attempted to unify the two phenomena. This paper reviews the most significant works on sedimentation and consolidation and discusses their limitations, noting that there is always a boundary between the two processes. The model proposed in this paper assumes a continuity of the sedimentation-consolidation process which remains compatible with previous theories. It is based on wide assumptions, postulating the effective stress can be time dependent and the infiltration velocity is not necessarily governed by Darcy's law. A system of equations is derived which are valid for a polyphasic medium (solid, liquid, gas) and where the solid phase can be composed of isolated grains and aggregates. State equations, equations of mass conservation and equations of mechanical equilibrium are completed by laws derived from the experimental approaches described in this paper or from those of other authors. The model allows the introduction of various shapes of constitutive laws, incorporating time in the effective stress function (taking account of creep phenomena) and a filtration velocity which does not follow Darcy's law (notably for the very low hydraulic gradients). This new model is applicable to a great number of sedimentation and/or consolidation cases, e.g. – Under water sedimentation-consolidation cyclic   load (swell, tide, etc.). – Consolidation of mud in ground deposits. – Consolidation of soft clay layers. The model has been validated by means of the sedimentation-consolidation simulation tests as undertaken by Been (1981). Despite the use of simple constitutive laws, the model gives a theoretical evolution of density profiles which is very similar to the experimental one for the same initial conditions. This model of the transition between sedimentation and consolidation has a wide field of application, including civil engineering, medicine, the food industry, chemical engineering and ecology.
    Notes: Résumé L'étude de la sédimentation et de la consolidation des sédiments cohésifs présente un grand intérêt scientifique par son aspect interdisciplinaire, à la frontière hydraulique-géotechnique et en raison de l'importance de ses applications à la gestion des zones cotières. Nous proposons d'associer les points de vue hydraulique et géotechnique en vue d'établir un modèle continu du processus de sédimentation-consolidation basé sur les équations de conservation de deux phases compressibles. Ce modèle, général et évolutif, permet d'envisager la prise en compte de phénomènes négligés jusqu'alors: fluage, floculation, écoulements non-darciens, ... Il constitue donc un élément fondamental pour une modélisation globale et précise de la dynamique sédimentaire en estuaire.
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    Obituary –Jean ducellier (1999)
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    Bulletin of engineering geology and the environment 57 (1999), S. 325-326 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
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    URL: http://dx.doi.org/10.1007/s100640050054
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    Analyse de la stabilite des talus sous sollicitation dynamique: application a la mine de lignite d'Afsin-Elbistan (Turquie) (1999)
    Springer
    Bulletin of engineering geology and the environment 57 (1999), S. 327-336 
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    ISSN: 1435-9537
    Keywords: Mots clefs Stabilité de talus ; Mine ; Lignite ; Seisme ; Turquie ; Key words Slope stability ; Mine ; Lignite ; Seism ; Turkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract  A slope stability analysis of the Afsin-Elbistan lignite mine in Turkey was prepared taking into account the seismic environment of the mine. In a first paper, Kiliç, du Mouza and Arnould (1997) presented the general conditions of the pit – its geology, hydrogeology and soil mechanical properties – together with computations of safety coefficients using a static approach such as those developed by Bishop, Carter and Sarma. This paper presents a pseudostatic approach and compares it with that used by Kiliç and al (1997). This method of analysis was considered realistic as the mine is located in a seismic area. Having considered the seismic context, a regional seismic coefficient k was derived from the Bath method. This was then introduced into the safety coefficient computations, according to each model used. This coefficient, applied to the weight of the soil likely to move, provides a value of the elastic strength equivalent to the stresses in the dynamic state. As in the static approach, the results highlight the main influence of the hydrogeological and geometrical slope conditions, for each of which several assumptions were tested. Solution I corresponds to the slope geometry proposed during the mine planning stage which was adopted at the commencement of the exploitation. Three important landslides occurred resulting in a change in the slope geometry and leading to the choice of Solution II. Computations made during this work have shown that for this configuration the slopes could be unstable in a saturated state. For this reason Solution III was designed, reducing the slope angles. The variation in the safety coefficients between the static and pseudostatic approach is clearly evident. The difference between the slope geometry assumed in Solution II and that proposed to prevent any slope instability (Solution III) is some 20%. The latter proved to be the only geometry which could be considered stable whatever the hydrogeological conditions.
    Notes: Résumé Le but de ce travail a été d'effectuer une analyse de la stabilité des talus de la mine d'Afsin-Elbistan (Turquie) en prenant en compte le contexte sismique de la mine par une approche pseudo-statique qui a été développée en complément de l'étude statique présentée dans un article précédent. Cette analyse s'impose dans ce cas car la mine est située dans une région sismique. Les calculs des coefficients de sécurité ont été effectués en mode pseudo-statique en utilisant les méthodes de Bishop, de Carter et de Sarma. Comme dans l'approche statique, ces résultats montrent l'influence primordiale des conditions hydrogéologiques et de la géométrie choisie pour les talus de la fosse. Ils mettent aussi clairement en évidence la variation des coefficients de sécurité entre l'approche statique et pseudo-statique.
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    Effect of incremental loading on the creep behaviour of chemically grouted sand (1999)
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    Bulletin of engineering geology and the environment 57 (1999), S. 353-358 
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    ISSN: 1435-9537
    Keywords: Key words Sand ; Chemical grout ; Stress ratio ; Single-stage creep ; Multi-stage creep
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé Cet article présente les résultats d'une étude sur le comportement mécanique en fonction du temps (fluage) d'échantillons de sables de Leighton Buzzard injectés par un produit silicaté (silicate-Hardener 600B), soumis à un chargement progressif discontinu. Des essais de fluage, avec ou sans contrainte latérale, en plusieurs étapes de chargement ont été réalisés sur des échantillons de sables injectés par différents produits silicatés couvrant la gamme généralement utilisée dans la pratique professionelle. Les résultats de laboratoire ont montré que les déformations de fluage s'accroissent avec l'accroissement du rapport des contraintes entrainant une augmentation du taux de déformation qui conduit en définitive à une rupture par fluage (rupture totale). Cependant, un accroissement du rapport des contraintes ne modifie pas la relation linéaire entre le logarithme du taux de déformation et le logarithme du temps, suggérant que la relation phénoménologique à trois paramètres de Singh et Mitchell (1968) peut convenir pour décrire le comportement en fluage, avec plusieurs étapes de chargement, de sables injectés par un produit silicaté (silicate-Hardener 600B).
    Notes: Abstract  This paper describes the results of a study on the stress-strain time dependent (creep) behaviour of silicate-Hardener 600B grouted Leighton Buzzard sand specimens when subjected to incremental loading at certain time intervals. Unconfined and confined multi-stage creep tests were conducted on sand specimens injected with different silicate content grouts which cover the range generally used in engineering practice. The laboratory results showed that creep movements increase with the increase in stress ratio causing a rise in strain rate which ultimately leads to creep rupture (complete failure). However, an increase in the stress ratio does not affect the linear relationship between logarithm of strain rate and the logarithm of time suggesting that the three parameter phenomenological relationship of Singh and Mitchell (1968) may be suitable to describe the multi-stage creep behaviour of silicate-Hardener 600B grouted sand.
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    Natural Aggregates at Makkah Governate, Western Saudi Arabia (1999)
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    Bulletin of engineering geology and the environment 57 (1999), S. 343-352 
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    ISSN: 1435-9537
    Keywords: Key words Natural aggregates ; Wadi aggregate ; Concrete ; Engineering properties ; Makkah ; Saudi Arabia ; Mots clés Granulats ; Oued ; Propriétés ; Béton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé Des agrégats naturels grossiers et fins accumulés le long de six oueds sélectionnés dans la région de Makkah ont été analysés d'un point de vue qualitatif et quantitatif. Les six oueds ont pour noms Numan, Al-Yamanyah, Al-Shamyah, Hwarah, Alaf et Faydah. Plus de 440 échantillons ont été prélevés et leurs propriétés physiques, mécaniques et chimiques déterminées. Des études pétrographiques sur des échantillons de graviers ont été réalisées pour caractériser les types de granulats. Les résultats ont été comparés aux spécifications ASTM et au British Standard. Les granulats étaient généralement dans les limites acceptables pour des granulats pour béton, bien que des valeurs relativement élevées en chlorures, sulfates et sels totaux dissous dans les granulats fins des oueds Alaf, Hwarah et Faydah, aient été trouvées. Neuf échantillons de granulats fins issus de dépôts des cours supérieur, moyen et inférieur de ces oueds salins ont été percolés par des eaux distillées ; après quoi, les granulats présentaient des caractéristiques acceptables pour des bétons de structures. Des indications sur les substances susceptibles d'être la cause d'alcali-réaction à partir des granulats grossiers de l'oued Wadi Faydah ont été données. L'étude a démontré l'existence de réserves de 12,5 millions de m3 de granulats grossiers et de 23 millions de m3 de granulats fins.
    Notes: Abstract  Natural coarse and fine aggregates which accumulated along six selected wadis in the region of Makkah were assessed both qualitatively and quantitatively. The six wadis were Numan, Al-Yamanyah, Al-Shamyah, Hwarah, Alaf and Faydah. More than 440 aggregate samples were collected and their physical, mechanical and chemical properties determined. Petrographic studies on the gravel samples were undertaken to characterise the aggregate types. The results were compared with ASTM and British Standard specifications. The aggregates were generally within the acceptable limits for use in concrete although there were the relatively high values of chloride, sulphate and total dissolved salts in the fine aggregates in Wadis Alaf, Hwarah and Faydah. Nine fine aggregate samples representing upstream, midstream and downstream deposits from these saline wadis were washed in distilled waters after which the aggregates were within the acceptable limits for structural concrete. There were indications of material which could cause alkali-silica in the coarse aggregate at Wadi Faydah. The study proved reserves of 12.5 million m3 of coarse aggregate and 23 million m3 of fine aggregate.
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    Geodiary (1999)
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    Bulletin of engineering geology and the environment 57 (1999), S. 397-398 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
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    Modification de la marée par le creusement du chenal d'un estuaire (1999)
    Springer
    Bulletin of engineering geology and the environment 57 (1999), S. 369-376 
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    ISSN: 1435-9537
    Keywords: Mots clés Niveau de la mer ; Dragage ; Marée ; Surcote de tempête ; Estuaire de la Loire ; France ; Key words Sea level ; Dredging ; Tide ; Storm surge ; Loire estuary ; France
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract  The present study compares the tide measurements on the left and right banks of the mouth of the river Loire (France) which flows into the Atlantic Ocean and two others points on the French Brittany coast (Fig. 1, 2), for the last twentyfive years. In order to simplify the location of the sites, the points have been numbered from the north to the south as follows: • Point 1 : Le Conquet • Point 2: Port Tudy, île de Groix • Point 3: St.-Nazaire • Point 4: Pointe de St.-Gildas The observed tide levels in the estuary of the river Loire show important changes since 1903 (Fig. 3). These modifications can be linked to the dredging works in the navigation channel between Paimboeuf and Nantes (55 km upstream) where the bottom level has been excavated from –2.50 m to –3.00 m in 1929 and to –5.50 m in 1969. Whereas the chart datum (hydrographic zero reading), which in France corresponds to the lowest possible seas for safe navigation, had been set at the end of the last century at 3.03 m under the terrestrial chart datum, on January 1st 1996, the SHOM, Naval Hydrographic and Oceanographic Service, indicated that on all the nautical documents it publishes this chart datum was now being set at 3.43 m under the terrestrial chart datum for the right bank of the mouth of the estuary (corresponding to the northern side of the estuary) while the one for the left bank, although only 15 km away, remained unchanged. The statistical study of surges for a period of twenty five years (1965–90) on both sides of the external estuary shows that the surges are significantly greater on the north-eastern side. It also highlights the incoherence of certain results. The study of level readings on 3 500 high and low tides effected by 4 tide gauges spread out along 300 km of coastline highlighted that a single badly zeroed tide gauge could lead to false results with regards to the average tide level at point 3. The work shows that this discrepancy is neither due to the blocking of fresh river water nor to a set of compartment faults but to the displacement and dredging of the channel along the right bank of the mouth of the estuary. The storm surges have also been studied between 1985 and 1990 using a dynamic model where surge levels depend on the duration of the meteorological disturbances. In this model the surge associated with a stationary meteorology S∞ depends on the wind (velocity and direction) and the atmospheric pressure. The theoretical law for the surge due to atmospheric pressure is valid in the 4 points studied; for each hectoPascal of lowering of barometric pressure, the sea level increase is 1 cm. For a wind of constant velocity and direction, the model shows that the surges are greater at points 3 and 4 than at points 1 and 2. This fact can be explained by the local morphology of the external part of the estuary; it also gives an explanation for the coastal erosion of this area. This model confirms that the reduction of the extreme low water level observed at point 3 is a local disturbance. In fact, the increase of the mean sea level is approximately 0.10 m per century at points 1 and 2 as in Brest harbour where level measurements have been undertaken since 1808. In contrast, this level appears to be stable at the two points situated on the estuary while the amplitude of the tide increases. This phenomenon is better marked at point 3 in the north of the estuary. Finally, this study shows that the installation of a mobile dam in the Loire estuary (similar to the one existing in the Thames estuary) would permit regulation of the upper water levels above the dam although the amplitude of the tide could be enhanced downstream of the dam.
    Notes: Résumé Des mesures des niveaux de basses mers réalisées par les autorités portuaires dans l'estuaire de la Loire montrent qu'entre 1969 et 1993 ce niveau est descendu d'une façon significative. Ceci s'explique par les dragages récents dans le chenal externe de l'estuaire qui ont modifié la propagation de la marée dans ce site, ce qui a conduit à une correction officielle de –0,40 m pour le zéro des cotes marines. Afin d'expliquer ce phénomène, les niveaux extrêmes de la marée ont été analysés en quatre sites de la côte bretonne occidentale entre 1965 et 1990. L'analyse statistique des données montre une nette amplification des surcotes dans la partie nord-est de l'embouchure de l'estuaire qui contribue à une érosion de ce site. L'étude phénoménologique des surcotes et des vents de 1985 à 1990 sur les deux rives de la Loire montre que le niveau moyen de la mer y reste stable.
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    The effect of seasonal rainfall on landslides in the highlands of Ethiopia (1999)
    Springer
    Bulletin of engineering geology and the environment 58 (1999), S. 9-19 
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    ISSN: 1435-9537
    Keywords: Key words Rainfall ; Landslides ; Ethiopia ; Blue Nile ; Mots clés Pluie ; Glissements de terrain ; Éthiopie ; Nil Bleu
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé Dans les hautes terres densément peuplées de l'Éthiopie, où l'altitude dépasse 1750 m, l'augmentation du nombre et de la taille des glissements de terrain pendant les 30 dernières années préoccupe gravement la société. De 1993 à 1998, 300 personnes ont trouvé la mort, plus de 200 maisons ont été détruites, 100 km de route ont été endommagés, et plus de 500 ha de terres ont été dévastés. L'article décrit les relations existant entre les pluies et les mécanismes de glissements de terrain. Une formule est proposée pour aider à estimer les problèmes d'instabilité. Un facteur Lf, principalement déterminéà partir du rapport entre la hauteur d'eau cumulée lors de l'événement pluvieux et le module pluviométrique annuel, conduit à une probabilité d'occurrence de rupture. Il est montré que des fissures et des signes indicateurs de mouvements sont observés quand Lf se situe entre 15 et 30%, tandis que des valeurs supérieures à 30% indiquent une probabilité d'occurrence beaucoup plus grande de glissements de terrain.
    Notes: Abstract  In the densely populated highland area of Ethiopia, where altitudes exceed 1750 m, the increase in the number and size of landslides during the last 30 years is causing considerable concern among the society. From 1993 to 1998 alone, about 300 lives have been lost, more than 200 houses demolished, greater than 100 km of road damaged and in excess of 500 ha of land devastated. The paper discusses the relation between the mechanism of landslides and rainfall. A formula is suggested which could help in assessing the problems of instability. An Lf factor, determined mainly from the ratio between the cumulative precipitation and the mean annual rainfall, is proposed to indicate the likelihood of occurrence of failure. It is shown that cracks and signs of slope movement are observed when Lf is in the range of 15–30%, while values exceeding 30% indicate a much greater probability of landslide occurrence.
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    Landslide hazard assessment: summary review and new perspectives (1999)
    Springer
    Bulletin of engineering geology and the environment 58 (1999), S. 21-44 
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    ISSN: 1435-9537
    Keywords: Keywords Landslides ; Hazard ; Risk Assessment ; Neural Networks ; G.I.S ; Mots clés glissement de terrain ; aléa ; évaluation du risque ; réseaux neuronaux ; S.I.G.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé Cet article traite de plusieurs aspects de l'évaluation de l'aléa et du risque de glissement de terrain. Ces dernières années, l'intérêt pour ce sujet a grandement augmenté et de nombreux articles techniques s'y référant ont été publiés. Cet article présente un bilan résumé et une classification des principales approches qui ont été développées de par le monde. La première étape consiste à distinguer les méthodes qualitatives et quantitatives. Le premier groupe est basé principalement sur l'expérience régionale d'experts, avec une notion de prédisposition aux glissements déterminée directement sur le terrain ou par combinaison de différentes cartes d'indices. Les approches du second groupe sont théoriquement plus rigoureuses. Il est possible de différencier des analyses statistiques (bivariées ou multivariées) et des méthodes déterministes qui font intervenir l'étude de pentes ou de sites particuliers, basée sur des modèles géomécaniques. De telles analyses peuvent être déterministes ou probabilistes. Parmi les méthodes quantitatives présentées, on trouve l'approche par les réseaux neuronaux qui n'a été que récemment appliquée à des problèmes de géologie de l'ingénieur. Enfin, plusieurs considérations relatives au concept de risque acceptable et de gestion du risque sont présentées.
    Notes: Abstract This paper deals with several aspects of the assessment of hazard and risk of landsliding. In recent years the interest in this topic has increased greatly and there are many technical papers dealing with this subject in the literature. This article presents a summary review and a classification of the main approaches that have been developed world-wide. The first step is the subdivision between qualitative and quantitative methods. The first group is mainly based on the site-specific experience of experts with the susceptibility/hazard determined directly in the field or by combining different index maps. The approaches of the second group are formally more rigorous. It is possible to distinguish between statistical analyses (bivariate or multivariate) and deterministic methods that involve the analysis of specific sites or slopes based on geo-engineering models. Such analyses can be deterministic or probabilistic. Among the quantitative methods discussed is the Neural Networks approach which has only recently been applied to engineering geology problems. Finally several considerations concerning the concept of acceptable risk and risk management are presented.
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    Mesure et modélisation des contraintes naturelles. Application au projet de tunnel ferroviaire Maurienne–Ambin (1999)
    Springer
    Bulletin of engineering geology and the environment 58 (1999), S. 45-59 
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    ISSN: 1435-9537
    Keywords: Mots clés Tunnel ; Alpes ; Contraintes in situ ; Mesures de contraintes ; Méthode HTPF ; Modélisation ; Key words Tunnel ; Alps ; In-situ stresses ; Stress measurements ; HTPF method ; Modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Abstract  The 52 km running tunnel of the proposed Lyon–Turin railway link will be excavated through different geological formations across the Franco-Italian Alps. The overburden of most of the route is greater than 1000 m, and it reaches 2500 m in the Ambin Massif, a regular micaschistic dome. As part of the reconnaissance program for this project, stress measurements using the HTPF (Hydraulic Testing on Pre-existing Fractures) method have been carried out in 13 deep boreholes, which provides a unique opportunity to better understand the regional stress field. After a presentation of the HTPF method and of its possible interpretation methods, the paper presents and discusses the results obtained. The influences of topography and tectonics are highlighted with the support of numerical modelling with the Finite Difference Method (FLAC code). Despite a great scatter of information on stress values and directions, three main stress regimes can be distinguished in three different geological-topographical contexts. The first one is found near the Arc valley, which is the main topographic feature in the area: the vertical stresses are greater than the weight of overburden and the horizontal stresses are highly anisotropic, σh being approximately perpendicular to the valley. This suggests a strong topographic influence of the Arc valley, especially for those measurements closest to its axis. Two other regimes have been encountered in the Ambin Massif. On the one hand, in the heart of the massif, under two small valleys, horizontal stresses are anisotropic with σh parallel and σh perpendicular to the valleys; but curiously vertical stresses are nearly 20% lower than the weight of overburden and are in both cases the minor principal stresses. On the other hand, under its Italian border and in a slope situation, the measured states of stress are those classically obtained in soils: vertical stresses are equal to the weight of overburden and horizontal stresses are nearly isotropic, equal to the half of the vertical ones. In order to better understand these measurements and their relation to the regional state of stress, a series of numerical calculations of increasing complexity were undertaken. They all take into consideration the effects of both the simplified topography and, in a parametrical manner, the tectonic stresses. The results are consistent with most of the global trends presented above, and particularly for the first and third stress regimes. For the second one, however, in the heart of the Ambin Massif, modelling gives only a first qualitative explanation for the low measured vertical stresses.
    Notes: Résumé Dans le cadre de la conception d'un futur grand tunnel à travers les Alpes, des mesures de contraintes naturelles ont été faites dans 13 forages profonds, dans des contextes géologiques et topographiques variés. L'article en propose une analyse critique en insistant sur l'influence des méthodes d'interprétation employées, et s'appuie pour les interpréter sur des modélisations simplifiées prenant en compte la topographie et la tectonique. Malgré la dispersion des résultats, trois grands types d'états de contraintes se dégagent. A proximité de la vallée de l'Arc, les contraintes horizontales sont fortement anisotropes, orientées suivant la vallée et les contraintes verticales sont fortes, ce qui traduit un effet topographique classique. Sous deux vallons du massif d'Ambin, les contraintes horizontales sont anisotropes et supérieures aux verticales. Enfin, sous la retombée orientale de ce massif, on trouve plutôt un état de contraintes de "type K0". Tous ces résultats sont en bonne concordance avec les modélisations présentées, à l'exception des faibles contraintes verticales du massif d'Ambin.
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    Geodiary (1999)
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    Bulletin of engineering geology and the environment 58 (1999), S. 87-88 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
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    Modern geostatistics: computational BME analysis in the light of uncertain physical knowledge – the Equus Beds study (1999)
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 1-26 
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    ISSN: 1436-3259
    Keywords: Key words: Spatiotemporal ; stochastic ; mapping ; Bayes ; entropy ; computational approach ; physical knowledge bases ; epistemology.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract This paper is concerned with a computational formulation of the Bayesian maximum entropy (BME) mapping method, which can handle rigorously and efficiently spatiotemporal applications of considerable practical importance. BME is a method of modern geostatistics that can integrate and process physical knowledge that belongs to two major bases: general knowledge (i.e., obtained from general principles and laws, summary statistics and background information), and specificatory knowledge (i.e., obtained through experience with the specific situation). BME allows considerable flexibility regarding the choice of an appropriate spatiotemporal map, offers a complete assessment of the mapping uncertainty and contributes to the scientific understanding of the underlying natural phenomenon. Valuable insight is gained by studying a spatiotemporal data set representing water-level elevations at the Equus Beds aquifer (Kansas). Numerical results show that, as was expected in theory, classical geostatistics analysis is obtained as a special case of the considerably more general BME approach. Moreover, modern geostatistical analysis in terms of BME offers more accurate and informative results in practice, by incorporating various sources of physical knowledge that cannot be processed by the classical methods.
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    URL: http://dx.doi.org/10.1007/s004770050029
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    Stochastic environmental risk analysis: an integrated methodology for predicting cancer risk from contaminated groundwater (1999)
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 27-47 
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    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Stochastic environmental risk assessment considers the effects of numerous biological, chemical, physical, behavioral and physiological processes that involve elements of uncertainty and variability. A methodology for predicting health risks to individuals from contaminated groundwater is presented that incorporates the elements of uncertainty and variability in geological heterogeneity, physiological exposure parameters, and in cancer potency. An idealized groundwater basin is used to perform a parametric sensitivity study to assess the relative impact of (a) geologic uncertainty, (b) behavioral and physiological variability in human exposure and (c) uncertainty in cancer potency on the prediction of increased cancer risk to individuals in a population exposed to contaminants in household water supplied from groundwater. A two-dimensional distribution (or surface) of human health risk was generated as a result of the simulations. Cuts in this surface (fractiles of variability and percentiles of uncertainty) are then used as a measure of relative importance of various model components on total uncertainty and variability. A case study for perchloroethylene or PCE, shows that uncertainty and variability in hydraulic conductivity play an important role in predicting human health risk that is on the same order of influence as uncertainty of cancer potency.
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    URL: http://dx.doi.org/10.1007/s004770050030
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    Analysis of macrodispersion through volume averaging: comparison with stochastic theory (1999)
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 66-84 
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    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Velocity variability at scales smaller than the size of a solute plume enhances the rate of spreading of the plume around its center of mass. Macroscopically, the rate of spreading can be quantified through macrodispersion coefficients, the determination of which has been the subject of stochastic theories. This work compares the results of a volume-averaging approach with those of the advection dominated large-time small-perturbation theory of Dagan [1982] and Gelhar and Axness [1983]. Consider transport of an ideal tracer in a porous medium with deterministic periodic velocity. Using the Taylor-Aris-Brenner method of moments, it has been previously demonstrated [Kitanidis, 1992] that when the plume spreads over an area much larger than the period, the volume-averaged concentration satisfies the advection-dispersion equation with constant coefficients that can be computed. Here, the volume-averaging analysis is extended to the case of stationary random velocities. Additionally, a perturbation method is applied to obtain explicit solutions for small-fluctuation cases, and the results are compared with those of the stochastic macrodispersion theory. It is shown that the method of moments, which uses spatial averaging, for sufficiently large volumes of averaging yields the same result as the stochastic theory, which is based on ensemble averaging. The result is of theoretical but also practical significance because the volume-averaging approach provides a potentially efficient way to compute macrodispersion coefficients. The method is applied to a simplified representation of the Borden aquifer.
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    URL: http://dx.doi.org/10.1007/s004770050032
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    Determination of hydraulic diffusivity of aquifers by spectral analysis (1999)
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 85-99 
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    ISSN: 1436-3259
    Keywords: Key words: Hydraulic diffusivity ; groundwater ; spectral analysis ; stochastic boundaries.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract: This study uses the cyclical frequency to develop the mathematical relationship between hydraulic diffusivity and spectral density functions calculated from groundwater level variation. Such relationship can be applied to (1) unsteady state, one-dimensional confined aquifer with time-dependent water level on both end boundaries, and (2) linearized unconfined aquifer with or without vertical recharge. The spectral density functions of groundwater fluctuations are largely affected by the spectral density functions obtained from time-dependent end boundaries and their cross-spectral density functions. Hydraulic diffusivity of an aquifer can be solved by type-curve matching technique at a specified frequency band under the conditions of (1) confined aquifer having equal time-dependent boundaries on both ends, (2) unconfined aquifer having equal time-dependent boundaries on both ends with surface recharge, and (3) unconfined aquifer subjected to surface recharge but neglecting the water table fluctuations on both end boundaries.
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    URL: http://dx.doi.org/10.1007/s004770050033
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    Approximation of Sahelian rainfall fields with meta-Gaussian random functions (1999)
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 113-130 
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    ISSN: 1436-3259
    Keywords: Key words: Climatology ; meso-scale convective systems ; classification ; anisotropy ; intermittency ; ergodicity ; upscaling ; level sets.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract: The meta-Gaussian model is fitted to a set of 258 sahelian rainfields. The hypotheses underlying this model are discussed with a special emphasis on its ergodic properties, the scale of the phenomenon and the scale of observation. Then the ability of this model to reproduce some observed features, in particular upscaling properties, is checked from a distributional point of view. Finally, some simple properties of the thresholds which are linked to the area threshold method are described.
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    URL: http://dx.doi.org/10.1007/s004770050035
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    Approximation of Sahelian rainfall fields with meta-Gaussian random functions (1999)
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 100-112 
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    ISSN: 1436-3259
    Keywords: Key words: Geostatistic ; Gaussian random functions ; anamorphosis ; intermittency ; discontinuous c.d.f ; valid covariance ; internal consistency.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract: For the purpose of numerically studying sahelian storm rainfields, a family of random functions is described with a characterization of its finite dimensional law. Some problems appearing when fitting its functional parameters are put forward and two solutions to bypass those problems are provided, according to the regularity properties of the marginal cumulative distribution function. An illustration of this method is implemented on a set of sahelian rainfields of event accumulation displaying a strong spatial intermittency.
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    URL: http://dx.doi.org/10.1007/s004770050034
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    Solute transport in heterogeneous media: The impact of anisotropy and non-ergodicity in risk assessment (1999)
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 365-379 
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    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract. Conceptual model selection is a key issue in risk assessment studies. We analyze the effect of a number of conceptual aspects related to solute transport in two-dimensional heterogeneous media. The main issues addressed are non-ergodicity, anisotropy in the correlation structure of the transmissivity field, and dispersion at the local scale. In particular, we study the development of a solute plume when mean flow is oriented at an angle with respect to the principal directions of anisotropy. The study is carried out in a Lagrangian framework using Monte Carlo analysis. Of special interest is the evolution of individual plumes. A number of aspects are analyzed, namely the location of the center of mass for each plume and the different ways to compute the angles that the main axes of the plume develop with respect to the direction of the mean flow. Stochastic theories based upon ergodicity conclude that the plume gets oriented in the mean flow direction. In our non-ergodic simulations, the mean of the offset angles, for each individual plume in each particular realization, is offset from the mean flow direction towards the direction of maximum anisotropy. If, instead, the analysis is performed on the ensemble plume (superposition of all different simulations), it is then found oriented closer to the direction of the mean flow than the average offset angle for the different plumes considered separately. This last result adds an extra word of caution to the use of ensemble averaged values in solute transport studies. Serious implications for risk assessment follow from the conceptual model adopted. First, in any single realization there will a large uncertainty in locating the plume at any given time; second, real dilution would be less than what would be expected if the macrodispersion values obtained for ergodic conditions were applied; third, the volume that is affected by a non-zero concentration is smaller than that predicted from macrodispersion concepts; fourth, the orientation of the plume does not correspond to that of the mean flow; and fifth, accounting for local dispersion helps reducing uncertainty.
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    URL: http://dx.doi.org/10.1007/s004770050056
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    Asymptotic transport parameters in a heterogeneous porous medium: Comparison of two ensemble-averaging procedures (1999)
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 396-415 
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    ISSN: 1436-3259
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract. We analyze the movement of a solute cloud in a saturated aquifer, resulting from a point-like instantaneous solute injection. Physical heterogeneities of the medium due to spatial variations of the hydraulic conductivity, as well as the chemical heterogeneities due to variations in the linear adsorption coefficient and the degradation rate, are modeled as spatial stochastic processes with exponential autocorrelation functions. Furthermore, cross-correlations between the chemical properties and the conductivity are taken into account. For large transport times, the movement of the solute cloud is characterized by its center-of-mass velocity, by the macroscopic dispersion constant, and the macroscopic degradation rate. These quantities are evaluated using perturbation theory and two different averaging procedures. The first procedure derives the large-scale properties from the central moments of the concentration distribution in a given aquifer realization, and averages over the ensemble afterwards. The second method which is mathematically less demanding obtains large scale transport coefficients from the central moments of the ensemble-averaged concentration distribution. Under the assumption that both prescriptions lead to the same macro-scale quantities, the second approach is usually preferred in literature. The present paper is an extension of the work of Metzger et al. (1996). We show that the two averaging procedures lead to different results in one-dimensional systems, whereas the difference vanishes for higher dimensions. Taking into account the influence of small scale dispersion, we give explicit results for the macroscopic parameters characterizing the solute plume. We analyze the various contributions to these parameters and show how the physical origin of these contributions can be traced back uniquely to fluctuations in the retardation factor, in the flow field, and in the degradation rate, and to the cross-correlations between these inhomogeneities, respectively.
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    URL: http://dx.doi.org/10.1007/s004770050046
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    Sequential kriging and cokriging: Two powerful geostatistical approaches (1999)
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 416-435 
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    ISSN: 1436-3259
    Keywords: Key words: Sequential linear estimator, successive linear estimator, conditional covariance, interpolation with large data sets.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract. A sequential linear estimator is developed in this study to progressively incorporate new or different spatial data sets into the estimation. It begins with a classical linear estimator (i.e., kriging or cokriging) to estimate means conditioned to a given observed data set. When an additional data set becomes available, the sequential estimator improves the previous estimate by using linearly weighted sums of differences between the new data set and previous estimates at sample locations. Like the classical linear estimator, the weights used in the sequential linear estimator are derived from a system of equations that contains covariances and cross-covariances between sample locations and the location where the estimate is to be made. However, the covariances and cross-covariances are conditioned upon the previous data sets. The sequential estimator is shown to produce the best, unbiased linear estimate, and to provide the same estimates and variances as classic simple kriging or cokriging with the simultaneous use of the entire data set. However, by using data sets sequentially, this new algorithm alleviates numerical difficulties associated with the classical kriging or cokriging techniques when a large amount of data are used. It also provides a new way to incorporate additional information into a previous estimation.
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    URL: http://dx.doi.org/10.1007/s004770050047
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    Modeling cancer incidence in A-bomb survivors: a perspective (1999)
    Springer
    Stochastic environmental research and risk assessment 13 (1999), S. 48-65 
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    ISSN: 1436-3259
    Keywords: Key words: Excess relative risk model ; two-stage model ; Poisson random variable
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Several manuscripts have been published which implement regression methods or stochastic processes methodology to model the incidence of a variety of cancers obtained via epidemiologic studies of radiation exposure. Cancer incidence data obtained from the Life Span Study (LSS) cohort have been of particular interest due to the extensive amount of information available from numerous years of follow-up of the Japanese A-bomb survivors. Conventional methods of exploring goodness-of-fit within each model class have indicated that both types adequately fit the data, but the model predicted curves for excess relative risk (ERR) and excess absolute risk (EAR) can vary dramatically. A simulation study is carried out to compare and contrast an excess relative risk regression model to a stochastic two-stage cancer model to determine the extent of the model predicted risk differences and why they occur.
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    URL: http://dx.doi.org/10.1007/s004770050031
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    Crystal structure of the molecular inclusion complex of 5, 17-di-t-butyl-26, 28-disubstituted calix[4]arene with acetone (1:3) (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 1121-1125 
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    ISSN: 1572-8854
    Keywords: calix[4]arene ; acetone ; inclusion complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Crystal structure of inclusion complex of 5, 17-di-t-butyl-26, 28-disubstituted calix[4]arene 3 with acetone, [(C54H58N2O6·CH3COCH3)·2CH3COCH3], was determined by X-ray crystallographic analysis. It possesses space group C2/c, with a = 26.277(8), b = 12.967(5), c = 20.355(4) Å, β = 124.845(14)°, and D calc = 1.173 mg/m3 for Z = 4. Crystal data indicate that action of one molecule of compound 3 upon three molecules of acetone forms a clathrate intermolecular inclusion complex.
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    URL: http://dx.doi.org/10.1023/A:1009514026129
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    The molecular structures of two melampolides (1999)
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    Journal of chemical crystallography 29 (1999), S. 111-114 
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    ISSN: 1572-8854
    Keywords: Melampolides ; sesquiterpene lactones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The melampolide-class sesquiterpene lactone 11βH,13-dihydro-14-hydroxy-(1,10)-cis-parthenolide, C15H22O4, 1, crystallizes in orthorhombic space group P212121 with a = 7.435(2), b = 12.678(2), c = 14.991(2) Å, V = 1413.1(8) Å3 and Z = 4. The aldehyde analog, C15H20O4·H2O, 2, crystallizes as the monohydrate in orthorhombic space group P212121 with a = 9.061(2), b = 9.295(2), c = 17.761(4) Å, V = 1495.8(9) Å3, and Z = 4. The 10-membered rings of the two molecules adopt approximate chair-boat conformations. In both compounds, the double bond at C1=C10 position of the cyclodecene ring is Z, while the C4=C5 is epoxidized with an E-configuration. The C15 methyl is β and H5 is α. The lactone ring is trans fused at the C6 and C7 positions to the 10-membered ring. The C13 methyl group has an α orientation in both molecules.
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    X-ray diffraction and self condensation reaction of thionicotinamide S-oxide (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 115-119 
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    ISSN: 1572-8854
    Keywords: Aminosulphines ; thionicotinamide S-oxide ; thiobenzamid ; X-ray structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Thiobenzamide and thionicotnamide S-oxide were prepared as intermediates in the dimerization of corresponding thioamides to 1,2,4-thiadiazoles and the X-ray crystal structure of thionicotinamide S-oxide water solvate was determined. Crystals belong to orthorhombic Pbca space group with a = 14.129(3), b = 7.299(2), c = 15.277(3)Å, and Z = 8. The geometry of the molecule accords well with that found in similar compounds; an intramolecular N–H···O hydrogen bond is present, while the packing is mainly determined by the hydrogen bond system involving the water molecule and the side-chain of the organic molecule. The contacts between pyridine moieties, stacked along the [010] axis, complete the packing.
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    URL: http://dx.doi.org/10.1023/A:1009591819303
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    Molecular structure of P-(2,4,6-tri-tert-buthylphenyl)-phenylmethylene(phenylsulfonylimino)-σ3λ5-phosphorane (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 1277-1280 
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    ISSN: 1572-8854
    Keywords: molecular structure ; ab initio calculations ; σ3λ5-phosphoranes ; electron withdrawing substituents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of P-(2,4,6-tri-tert-buthylphenyl)-phenylmethylene (phenylsulfonylimino)-σ3λ5-phosphorane, 2,4,6-But 3-C6H2-P(=CHPh)(=N--SO2Ph), has been determined. Crystal data: triclinic, $$P\bar 1$$ , a = 9.472(5), b = 11.427(5), c = 13.684(5) Å, α = 90.61(3), β = 101.21(4), γ = 97.02(4)°, V = 1441.1 Å3, Z = 2, D c = 1.20 g cm−3. The observed in 1 noticeable elongation of the P=N bond 1.563(3) Å and shortening of the P=C bond 1.617(3)Å have been discussed in terms of the electron withdrawing ability of substituents on the basis of ab initio (HF/6−31+G**) calculations of the model systems.
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    Synthesis and crystal structures of 5-amino-1-(2-hydroxyethyl)imidazole-4-carboxamide and 5-amino-1-(2-chloroethyl)-4-cyanoimidazole (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 1281-1286 
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    ISSN: 1572-8854
    Keywords: amino-imidazoles ; intramolecular hydrogen bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Both 5-amino-1-(2-hydroxyethyl)imidazole-4-carboxamide (AHIC) and 5-amino-1-(2-chloroethyl)-4-cyanoimidazole (ACCI) have been synthesized and crystallized in the monoclinic space group P21/c, Z = 4, with a = 8.420(2), b = 9.759(2), c = 10.583(2) Å, β = 111.80(2)° for AHIC and a = 6.139(1), b = 8.522(2), c = 15.156(3) Å, β = 96.71(2)° for ACCI. Differences in the molecular geometries of the two compounds are attributed to the differences in the substituents at the 1- and 4-positions of the imidazole ring. The molecular conformation of AHIC is stabilized by intramolecular hydrogen bonding between the 5-amino and the vicinal carboxamide moiety, resulting in an extended planar structural pattern. The presence of the cyano group in the 4-position of ACCI prevents the formation of such an intramolecular hydrogen bond. Both the crystal structures are stabilized by networks of intermolecular hydrogen bonds.
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    Structure of an unusual cage dimer diol (1999)
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    Journal of chemical crystallography 29 (1999), S. 1261-1263 
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    ISSN: 1572-8854
    Keywords: cage molecule ; decacycloicosane ; molecular rearrangement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound arises from an unexpected rearrangement and oxidation. The molecules contain a center of symmetry and are held together by hydrogen bonds. The relatively strain-free molecules are closely packed with a density of 1.441 g cm−3. The compound crystallizes in space group P-1 with cell dimensions a = 8.999(3), b = 9.142(2), c = 8.625(3) Å, α = 95.47(3), β = 105.06(3), and γ = 83.08(2)° There are two independent molecules per cell with each sitting on a center of symmetry.
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    Crystal structure of an analog of the anticonvulsant lamotrigine, 3,5-diamino-6-(2,3,5-trichlorophenyl)-1,2,4-triazine·dimethanolate, and structure comparisons with related analogs (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 163-167 
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    ISSN: 1572-8854
    Keywords: lamotrigine ; triazine ; heteroaromaticity ; epilepsy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The compound 3,5-diamino-6-(2,3,5-trichlorophenyl)-1,2,4-triazine crystallizes with two methanol solvent molecules in the triclinic space group P1¯, with a = 7.372(4), b = 10.476(4), c = 11.863(11) Å, α = 72.18(5), β = 79.73(6), γ = 79.47(4)°. There is substantial distortion between the phenyl and triazine rings as illustrated by the value of the nonbonded angle C3t—C6t—C4 of 173.60° and the C4 atom being −0.4487 Å from the plane calculated for the triazine ring atoms. The lengths of the bonds of the triazine moiety suggest that there is a potential decrease in the degree of aromaticity of the ring. Comparisons are made between this structure, and other lamotrigine analog structures that have been reported.
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    Conversion of 2,4-dihydroxybenzaldehyde to 2-benzoyloxy-4-hydroxybenzaldehyde and structural characterization of both precursor and product (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 185-191 
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    ISSN: 1572-8854
    Keywords: 2-Benzoyloxy-4-hydroxybenzaldehyde ; 2,4-dihydroxybenzaldehyde ; hydrogen bonding ; x-ray structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 2,4-Dihydroxybenzaldehyde can be acylated at the 2 position if the more reactive 4 position is first protected as the methylmethoxy ether. Deprotection permits isolation of 2-benzoyloxy-4-hydroxybenzaldehyde. 2,4-Dihydroxybenzaldehyde, C7H6O3, crystallizes in P21/c, with a = 7.3762(6), b = 11.7455(9), c = 7.3149(6) Å, β = 90.533(2)°, Z = 4, and D X = 1.448 g cm−3. The individual molecules are characterized by an intramolecular hydrogen bond. The molecules form sheets with additional intermolecular hydrogen bonds. 2-Benzoyloxy-4-hydroxybenzaldehyde, C14H10O2, crystallizes in Pca21, with a = 24.2629(14), b = 3.8445(2), c = 12.3727(8) Å, Z = 4, and D X = 1.394 g cm−3. The molecules consist of two planar halves twisted by 51.63(5)° about the ester linkage. Intermolecular hydrogen bonding joins the molecules into ribbons approximately parallel to c.
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    Crystal structure of [Mn2(III)(salpa)2Cl2(H2O)2] (H2salpa = 1-(salicylaldeneamino)-3-hydroxypropane) (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 203-206 
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    ISSN: 1572-8854
    Keywords: Manganese(III) ; Schiff base ; hydrogen bonding ; crystal structure ; Jahn-Teller distortion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The manganese complex, (Mn2(III)(salpa)2Cl2(H2O)2], has been prepared and its structure determined using x-ray crystallography. The dimer is a di-μ2-alkoxo complex which is a six-coordinate manganese dimer with unsupported alkoxide bridges and a rare example of a chloride- and water-containing manganese dimer. The complex crystallizes in the monoclinic space group P21/c with a = 9.315(5), b = 11.130(4), c = 11.637(5) Å, β = 104.33(3)°, V = 1169.0(9) Å3, and Z = 2. The structure comprises discrete binuclear clusters in which the metal atoms are bridged by two alkoxo oxygens of the salpa2− ligands. The Mn—O and Mn—N distances are in good agreement with those found for other manganese(III) Schiff base complexes. The Mn—Cl and Mn—O3 distances are 2.585(2) and 2.371(2) Å, respectively, and the Mn ··· Mn distance is 3.001(1) Å. In the crystal, there are two types of hydrogen bonding between the H2O molecule and the Cl atom with Cl ··· H(H2O) distance of 2.33(6) (intramolecule: −1 + x, y, −1 + z) and 2.68(6) Å (intermolecule: −1 + x, 0.5−y, −0.5 + z).
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    Synthesis and structure determination of a new layered zincophosphate: [H2N2C6H16]0.5[Zn2(PO4)(HPO4)(H2O)]·H2O (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 217-221 
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    ISSN: 1572-8854
    Keywords: Structure determination ; zinc phosphate ; organic template ; powder diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The synthesis and crystal structure of a new microporous zincophosphate are described. [H2N2C6H16]0.5[Zn2(PO4)(HPO4)(H2O)]·H2O crystallizes in the triclinic space group P1¯ with a = 8.822(4), b = 9.236(4), c = 8.451(3) Å, α = 67.19(3), β = 91.32(3), γ = 111.10(3)°, V = 586.7(4) Å3 and Z = 2. This new material consists of infinite two-dimensional anionic layers alternated with planes containing organic diprotonated templates, N, N, N′, N′-tetramethylethylenediamine [H2N2C6H16]2+ molecules. The framework structure is built up of ZnO4, ZnO3OH2, PO4, and PO3OH tetrahedra, linked through oxygen vertices. The presence of terminal OH2 and OH groups, leads to an open structure containing four- and eight-rings. The organic molecules are interconnected to the framework through hydrogen bonds.
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    Structure of (2,2′-bipyridine)lead(II) saccharinate monohydrate (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 233-237 
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    ISSN: 1572-8854
    Keywords: Structure ; (2,2′-bipyridine)lead(II) saccharinate monohydrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of (2,2′-bipyridine)lead(II) saccharinate monohydrate has been investigated by X-ray diffraction. The compound crystallizes in the monoclinic space group P2 1/n with a = 22.903(7), b = 12.608(3), c = 8.682(2) Å, β = 96.76(3)°, and Z = 4. The structure consists of Pb2+ cations, 2,2′-bipyridine ligands, saccharinato anions and water molecules. The Pb2+ cation is surrounded by two O atoms and four N atoms. The two saccharinato ions are nonequivalent. The water molecule forms hydrogen bonds of OW···OCO [2.810(16) Å] and OW···OSO2 [2.893(16) Å] type.
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    Molecular structure of ThBr4(DME)2 (DME = 1,2-dimethoxyethane) (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 243-246 
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    ISSN: 1572-8854
    Keywords: Thorium ; dimethoxyethane ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The molecular structure of ThBr4(DME)2 (DME = 1,2-dimethoxyethane), the first structurally characterized thorium complex containing a simple bidentate ether ligand, is described. The eight-coordinate complex presents a distorted dodecahedral geometry, with Th—Br and Th—O bond lengths in the ranges 2.8516(13)–2.8712(13) Å and 2.564(8)–2.620(8) Å, respectively. ThBr4(DME)2 is monoclinic, space group P21/n, a = 7.672(1), b = 14.581(1), c = 15.847(2) Å, β = 102.24(1)°, V = 1732.4(3) Å3, and Z = 4.
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    Index Abstracts (1999)
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    Journal of chemical crystallography 29 (1999), S. 255-259 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
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  • 85
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    Synthesis and crystal structure of the copper(II) complex with novel Schiff base ligand: Cu(C8H7O2N)2(OH2) (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 295-298 
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    ISSN: 1572-8854
    Keywords: Copper ; crystal structure ; synthesis ; Schiff base ligand
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title complex Cu(C8H7O2N)2(OH2) crystallized in the orthorhombic space group, Pbca with unit cell parameters: a = 15.242(2), b = 11.782(4), c = 17.946(4) Å, and Z = 8. Two nitrogen atoms, two phenolic oxygen atoms of the ligand, and one water molecule are coordinated with copper to form a distorted tetragonal pyramidal polyhedron.
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    Synthesis and crystal structures of quadruply carboxylate-bridged dimeric lanthanide(III) complexes of betaine (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 309-316 
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    ISSN: 1572-8854
    Keywords: Europium ; terbium ; betaine ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Three dimeric lanthanide(III) complexes, [Eu2(bet)8(H2O)4](CIO4)6 (1), [Tb2(bet)8(H2O)4](ClO4)6 (2), and [Eu2(bet)4(H2O)8] Cl6·6H2O (3) (bet = Me3N+CH2COO−, trimethyl-aminoacetate), have been prepared and structurally characterized by X-ray crystallography. Complex 1 crystallizes in the monoclinic space group P21/c, with a = 11.7807(8), b = 27.757(5), c = 11.7980(8) Å, β = 99.500(4)°, V = 3805.1(8) Å3, and Z = 2. Complex 2 is isomorphous to complex 1, crystallizing in the monoclinic space group P21/c, with a = 11.7769(14), b = 27.725(3), c = 11.795(5) Å, β = 99.668(14)°, V = 3797(2) Å3, and Z = 2. Complex 3 crystallizes in the orthorhombic space group Pbca, with a = 12.5664(8), b = 17.8645(9), c = 22.2573(8) Å, V = 4996.6(4) Å3 and Z = 4. Both complexes 1 and 2 comprise quadruply carboxylate-O,O′-bridged [M2(bet)4]6+ dimeric cores (M = Eu, Tb), and each metal ion is further coordinated by two terminal aqua ligands and two monodentate bet carboxylates to form a distorted square-antiprismatic coordination geometry. Complex 3 also has a [Eu2(bet)4]6+ core, in which two bet ligands act in the η1:η1:μ2 bridging fashion, and the other two bet ligands in the less common η2:η1:μ2 bridging fashion, namely bridging-chelate mode. Each europium(III) ion in complex 3 is further coordinated by four water molecules to complete a monocapped square antiprism.
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    Structural study of the molecular complex in crystals of brucine with pantolactone (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 121-125 
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    ISSN: 1572-8854
    Keywords: Crystal structure ; brucine ; pantolactone ; molecular complex ; chiral resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We have determined an X-ray crystal structure, a = 12.482(1), b = 14.349(1), c = 14.342(1) Å, orthorhombic, P212121 for a molecular complex of brucine with pantolactone. The crystal structure is composed of corrugated sheets of brucine molecules containing the guest pantolactone molecules. The conformational twist of the pyrrolidine ring in brucine may probably be important in projecting the amine N2 to provide a strong and specific binding site for a chiral complexation. The pseudo-equatorial orientation of the hydroxyl group of the pantolactone anchors itself for binding via hydrogen bonding. In the crystal packing, the pantolactone molecules form helices and the brucine molecules are attached to these helices by O=H···N hydrogen bonds.
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    Copper, a chemical Janus: two copper(II) complexes with different ligand in one single crystal (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 1085-1088 
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    ISSN: 1572-8854
    Keywords: crystal structure ; copper(II) complexes ; dinuclear complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A chemical Janus, binuclear copper(II) complexes, {[Cu(TPA)Cl][Cu(BPA)Cl]}(ClO4)2 (TPA = Tris(2-pyridylmethyl) amine, BPA = bis-(2-pyridylmethyl)amine) containing two different ligands has been synthesized and characterized by X-ray single crystal analysis. Crystal data: triclinic, space group P1$sm, a = 12.529(3), b = 12.655(3), c = 13.458(3) Å, α = 70.48(3), β = 67.40(3), γ = 75.81(3)°, D x = 1.648 mg m−3, and Z = 2. The molecular structure shows that the binuclear copper complex consists of two positive cation and two perchlorate anions. The positive cations moieties have different ligands. Cu(1) is coordinated by four nitrogen atoms from TPA and one chloride atom, forming a square-pyramidal geometry, whereas the coordinate number of Cu(2) is four, three of which are from BPA, one from chloride. There are two weak bonds between the Cl(2a) ion and the Cu(2) ion (2.844 Å) and the distance of Cu(2)=O(13) is 2.750(9) Å.
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    The crystal and molecular structures of two bromo bis(N,N-dipropylthiocarbamoyl) sulfidocopper(I) complexes (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 211-216 
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    ISSN: 1572-8854
    Keywords: Copper(I) ; alkylthiocarbamoyl sulfide ; complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The reaction of copper(I) bromide, CuBr, with the tetraalkylthiurammonosulfides R4tms (R = iPr, nPr) affords the copper(I) complexes iPr4tmsCuBr (I) (C14H28BrCuN2S2, orthorhombic, Pna21, Z = 4, a = 12.487(2), b = 12.699(2), c = 12.742(2) Å) and nPr4tmsCuBr (II) (C14H28BrCuN2S3, monoclinic, P21/n, Z = 4, a = 9.092(5), b = 23.408(11), c = 10.082(7) Å, β = 104.90(5)°), which exist in the solid as monomeric units featuring three-coordinate copper(I). The ligands are bidentate and coordination is completed by the bromine atoms. The configurations of the six-membered metal-ligand ring in (I) and (II) are more severely distorted than the previously reported structurally related complexes of ethyl series. The crystal structural studies are complemented and confirmed by IR and 1H-NMR spectroscopies, as well as room temperature, magnetic, solution conductivity, and molecular weight studies.
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    Structural dimorphism of N-(3-hydroxysalicylidene)-2,4,6-trimethylaniline (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 1111-1115 
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    ISSN: 1572-8854
    Keywords: structural dimorphism ; tautomeric equilibrium ; photochrome ; thermochrome ; intermolecular hydrogen bonds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound N-(3-hydroxysalicylidene)-2,4,6-trimethylaniline exhibits dimorphism. The structure of (I) is orthorhombic Pbca with a = 22.222(3), b = 16.200(2), c = 7.596(2) Å, V = 2735(1) Å3, and Z = 8. The structure of (II) is monoclinic P21/c with a = 11.734(1), b = 15.734(1), c = 7.432(2) Å, β = 100.97(1)°, V = 1347.0(5)Å3, and Z = 4. The two structures are analyzed in relation with the possibility of an equilibrium between two tautomeric phenol and quinone forms by rapid hydrogen transfer. The molecules associated by intermolecular hydrogen bonds form centrosymmetric dimers. The compounds are thermochromic. The results are compared with the photochromic analog N-(hydroxysalicylidene)-2,4,6-trimethylaniline (compound III) and with the thermochromic one N-(5-hydroxysalicylidene)-2,4,6-trimethylaniline (compound IV). It is concluded that the 3-hydroxyl substituent of the salicylidene moiety enables the intermolecular hydrogen transfer from oxygen to nitrogen.
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    Piscidinol-C, a triterpenoid from Walsura piscidia leaves (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 1141-1143 
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    ISSN: 1572-8854
    Keywords: triterpenoid ; natural compound ; Walsura piscidia roxb ; X-ray crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray crystal structure of the triterpenoid piscidinol-C from the leaves of Walsura piscidia is determined. The compound, which is an apotirucallane derivative, crystallizes in the orthorhombic space group C2221 with a = 18.985(4), b = 13.092(5), c = 24.690(7) Å, and D calc = 1.209 g cm−1 for Z = 8.
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    4,5-Bis(benzylthio)-1,3-dithiole-2-thione compounds: crystal structures of [(p-XC6H4CH2)(p-XC6H4CH2)dmit: X=Y=OMe; X=Y=NO2; and X=OMe, Y=NO2] (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 1165-1172 
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    ISSN: 1572-8854
    Keywords: 4,5-Bis(benzylthio)-1,3-dithiole-2-thiones ; 1,3-dithiole-2-thione-4,5-dithiolates, dmit compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 4,5-Bis(benzylthio)-1,3-dithiole-2-thiones, [(p-XC6H4CH2)(p-XC6H4CH2)dmit: X=Y=OMe (2); X=OMe, Y=NO2 (3); and X=NO2] (4)] have been prepared from benzyl chlorides and [NEt4]2[Zn(dmit)2]. Isostructural compounds, 2 and 3, crystallize in the triclinic space group $$P\bar 1$$ (Z = 2) with a = 5.2920(10), b = 10.537(2), c = 18.961(4) Å, α = 102.79(3), β = 96.33(3), γ = 98.67(3)° for 2; a = 5.292(8), b = 10.528(12), c = 19.01(2) Å, α = 102.74(9), β = 96.26(11), γ = 98.56(11)° for 3. Compound 4 also crystallizes in the space group $$P\bar 1$$ (Z = 4), with a = 9.296(8), b = 13.993(18), c = 16.186(4) Å, α = 106.68(3), β = 89.63(3), γ = 99.38(6)°. Molecular differences between 2 and 3, on one hand, and 4, on the other, arise in the disposition of the aryl rings relative to the dmit group. Short S---S contacts in 2 of 3.320(2) Å [S3---S3 i (symmetry operation: i: −x + 1, −y + 1, −z)] and in 3 of 3.314(5) Å [S3---S3 i (symmetry operation: i: −x + 1, −y, −z + 1)] link molecules into pairs. In 4, an S5A---S2B contact of 3.516(5) Å links two independent molecules, A and B, into bimolecular units, which are further connected into chains by S2A---S5B i contacts (symmetry operation: i: x, y, z − 1) at 3.569(5) Å. C–H---O hydrogen bonds are also present in 3 and 4.
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    X-ray crystallographic and theoretical studies of substituted phenyl 3,5-di[N-methyl] carbamoyl-1,4-dihydropyridines: Targets for Ca2+ antagonist (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 481-491 
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    ISSN: 1572-8854
    Keywords: dihydropyridines ; single crystal X-ray diffraction ; semiempirical AM1 MO calculations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A series of 4(x-substituted phenyl)-1,4-dihydropyridines (x=2—CF3 (1), 2-CH3 (2), 2-OCH3 (3) and 2,4-Cl (4)) with a new substituent, the N-methylcarbamoyl (CONHCH3) group at C3 and C5 are crystallographically characterized and a comparison has been made with important conformational parameters obtained theoretically. The dihydropyridine rings are in shallow boat conformation. The phenyl substituent orientation is synperiplanar. Both the carbonyl groups are oriented anticlinal in 1, 2 and 3; but in 4, one is synclinal and the other synperiplanar with the adjacent double bond. The presence of solvent molecules in 1 (CH3OH), 2 (CH3OH), and 3 (H2O) has significantly changed the hydrogen bonding pattern. Theoretical studies at the semiempirical AM1 MO level reproduces the general features of the structures. The near planarity of the DHP ring and the orientation of the phenyl substituent make 1 and 2 encouraging targets for pharmacological, study. Crystallographic Data:1: a = 8.793(2), b = 29.962(5), c = 8.215(2) Å, β = 115.28(2)°, Monoclinic, P21/c; 2: a = 8.799(2), b = 15.789(3), c = 14.074(2) Å, β = 100.25(2)°, Monoclinic, P21/n; 3: a = 8.347(1), b = 8.986(1), c = 13.749(2) Å, α = 97.50(1), β = 94.78(1), γ = 101.38(1)° Triclinic, P1¯4: a = 12.928(3), b = 14.506(3), c = 9.740(2) Å, Orthorhombic, Pca21.
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    Index Abstracts (1999)
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    Journal of chemical crystallography 29 (1999), S. 505-511 
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    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
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    Molecular gears: Structures of (9,10-triptyceno) crown ethers (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 513-521 
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    ISSN: 1572-8854
    Keywords: nanotechnology ; molecular devices ; triptycene ; crown ether ; crystal structure ; thallium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The incorporation of 9,10-triptycene unit in a crown ether is examined from a structural perspective. Insertion of a triptycene group into 18-crown-6 stretches the crown into an ellipse, as seen in structures presented here of 9,10-triptyceno-22-crown-6 and its thallium complex. Symmetric addition of two triptycene groups into 18-crown-6 results in the sterically congested bis(9,10-triptyceno)-26-crown-6, whose crown cavity is filled with the π-clouds of two arene groups. The larger bis(9,10-triptyceno)-32-crown-8 is more sterically relaxed. The structures of these bis(triptyceno)crown ether molecules are the first with two triptycene groups simultaneously linked through their 9 and 10 positions, thereby forming a simple molecular gearing mechanism. The compound 9,10-triptyceno-22-crown-6 (1) crystallizes in the orthorhombic space group Pbca with a = 10.7962(7), b = 15.826(3), c = 31.147(5) Å, V = 5321.8(12) Å3, and Z = 8; its complex with TlNO3 (Tl-1) crystallizes in the monoclinic space group P21/c with a = 8.1884(14), b = 19.552(2), c = 20.575(4) Å, β = 97.062(8)°, V = 3269.2(9) Å3, and Z = 4; bis(9,10-triptyceno)-26-crown-6 (2) crystallizes in the triclinic space group P $$\bar 1$$ with a = 8.6488(11), b = 10.7718(12), c = 12.3324(12) Å, α = 111.58(1), β = 100.55(1), γ = 106.43(1)°, V = 970.3(5) Å3, and Z = 1; and bis(9,10-triptyceno)-32-crown-8 (3) crystallizes in the orthorhombic space group Pna21 with a = 20.186(3), b = 8.558(2), c = 25.623(2) Å, V = 4426.2(14) Å3, and Z = 4.
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    The structure of bis(trimethylammonium) undecachlorotriantimonate(III) [(CH3)3NH]2Sb3Cl11 containing a novel antimony(III) anion (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 555-560 
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    ISSN: 1572-8854
    Keywords: alkylammonium chloroantimonates(III) ; hydrogen bonds ; disorder ; lone electron pair ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of [(CH3)3NH]2Sb3Cl11 (space group P21/n; a = 10.374(2), b = 23.723(5), c = 11.884(2) Å, β = 113.46(3)°; V = 2682.9(9) Å3) consists of a structurally novel [Sb3Cl2− 11] anion and two crystallographically nonequivalent trimethylammonium cations. The anion is composed of three deformed octahedra in the asymmetric part of the unit cell. The octahedra are connected with each other by edges and corners forming a characteristic polyanionic layer. Trimethylammonium cations, one ordered and one disordered, are connected to the inorganic sublattice by N—H· · ·Cl hydrogen bonds.
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    Crystal structure of the Λ-[4M] enantiomer of cis-diaqua-bis(1,3-dimethylpteridine-2,4(1H,3H)-dione-N5,O4) copper(II) perchlorate monohydrate (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 571-574 
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    ISSN: 1572-8854
    Keywords: crystal structure ; complexes ; pteridine ; lumazine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Single-crystal X-ray diffraction studies have been performed on the complex cis-diaqua-bis(1,3-dimethylpteridine-2,4(1H,3H)-dione-O4,N5) copper(II) perchlorate monohydrate, [Cu(DLM)2(H2O)2](ClO4)2 · H2O. This compound crystallizes in the orthorhombic system, P212121 space group, Z = 4 with a = 8.749(1) Å, b = 14.213(1) Å, c = 21.200(2) Å, and V = 2636.2(4) Å3. The metal ion is surrounded in octahedral geometry by two mutually quasi-perpendicular N5,O4-coordinated lumazine chelators with the O4 atoms trans and the N5 atoms cis. The polyhedron is completed by two cis-coordinated water molecules. The absolute configuration of the complex can be described, following Bailar's nomenclature, as the enantiomer Λ of the stereoisomer 4M. A three-dimensional hydrogen-bond network is defined by water molecules, perchlorate anions, and the O2 of the pteridine A.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009548803103
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  • 98
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    Synthesis and characterization of the dodecanuclear heterobimetallic Mo—Cu—S cage cluster: (Ph4P)2[{Mo2Cu2O2S2(S2)2}3(μ6-S)] (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 581-586 
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    ISSN: 1572-8854
    Keywords: dodecanuclear heterobimetallic ; molybdenum-copper cluster ; cage ; μ6-S ; crystal structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The complex (Ph4P)2[Mo2S2O2(S2)(S4)] reacts with CuBr to give the dodecanuclear heterobimetallic Mo—Cu—S cage cluster: (Ph4P)2[{Mo2Cu2O2S2(S2)2}3(μ6-S)] (1), which crystallizes in the triclinic space group P1¯, a = 14.445(5), b = 15.396(5), c = 18.858(5) Å, α = 103.12(3), β = 101.93(2), γ = 113.92(3)°, and V = 3517(2) Å3 for Z = 2. The anion 1 can be described as a cage with S2− at the center binding to six Cu atoms; the cage has two big windows each composed of a puckered Cu3S6 9-membered ring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009552904012
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  • 99
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    Electronic Resource
    Crystal and molecular structure of five coordinate copper(II) complex with 2,6-bis[1-(methoxycarbonylmethyl–hydrazono)ethyl] pyridine (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 575-580 
    Details
    ISSN: 1572-8854
    Keywords: copper(II) complexes ; 2,6-diacetylpyridine derivative ; open-chain ligand ; crystal structure ; trigonal-bipyramidal geometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The title compound was obtained by a template synthesis from 2,6-diacetylpyridine, ethylhydrazinoacetate and CuCl2·2H2O (molar ratio 1:2:1, in methanol), and its structure has been determined by single-crystal X-ray diffraction: monoclinic space group P21/c, a = 13.906(5), b = 18.199(6), c = 16.641(6) Å, β = 107.18(3)°, and z = 4. The ligand was found to be tridentate in a trigonal-bipyramidal coordination geometry with two chloride ligands. There are two independent complex molecules, one of which is hydrogen bonded to the water of crystallization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009500919942
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  • 100
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    Electronic Resource
    Instructions to contributors (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 635-638 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1017232407646
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