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  • Articles  (56,199)
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  • 1995-1999  (56,199)
  • Physics  (47,789)
  • Geosciences  (13,656)
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  • Articles  (56,199)
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  • 1
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    GPS solutions 2 (1999), S. 1-2 
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
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  • 2
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    GPS solutions 2 (1999), S. 24-36 
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    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.
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  • 3
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    GPS solutions 2 (1999), S. 18-23 
    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.
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  • 4
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    GPS solutions 2 (1999), S. 37-40 
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  • 5
    ISSN: 1521-1886
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    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.
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  • 6
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    GPS solutions 2 (1999), S. 41-49 
    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.
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  • 7
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    GPS solutions 2 (1999), S. 63-69 
    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.
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  • 8
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    GPS solutions 2 (1999), S. 50-62 
    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.
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  • 9
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
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    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.
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  • 10
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    GPS solutions 2 (1999), S. 79-80 
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  • 11
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    GPS solutions 2 (1999), S. 81-83 
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  • 12
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    GPS solutions 2 (1999), S. 76-78 
    ISSN: 1521-1886
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    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.
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  • 13
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    GPS solutions 2 (1999), S. 1-6 
    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.
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  • 14
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    GPS solutions 2 (1999), S. 35-43 
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
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    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.
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  • 15
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    GPS solutions 2 (1999), S. 44-51 
    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.
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  • 16
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    GPS solutions 2 (1999), S. 7-21 
    ISSN: 1521-1886
    Source: Springer Online Journal Archives 1860-2000
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    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.
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  • 17
    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.
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  • 18
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    GPS solutions 2 (1999), S. 57-59 
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  • 19
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    GPS solutions 2 (1999), S. 64-66 
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  • 20
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    GPS solutions 2 (1999), S. 60-63 
    ISSN: 1521-1886
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    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.
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    GPS solutions 2 (1999), S. 52-56 
    ISSN: 1521-1886
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    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.
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  • 22
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    GPS solutions 3 (1999), S. 1-1 
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  • 23
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    GPS solutions 3 (1999), S. 2-4 
    ISSN: 1521-1886
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    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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  • 24
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    GPS solutions 3 (1999), S. 17-25 
    ISSN: 1521-1886
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    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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  • 25
    ISSN: 1521-1886
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    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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  • 26
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    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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    GPS solutions 3 (1999), S. 26-31 
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    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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    GPS solutions 3 (1999), S. 32-41 
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    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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    GPS solutions 3 (1999), S. 42-49 
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    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 solutions 3 (1999), S. 50-58 
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    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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    GPS solutions 3 (1999), S. 77-78 
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    GPS solutions 3 (1999), S. 59-72 
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    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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    GPS solutions 3 (1999), S. 79-81 
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    GPS solutions 3 (1999), S. 73-76 
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    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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    GPS solutions 3 (1999), S. 82-84 
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    GPS solutions 3 (1999), S. 11-18 
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    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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    GPS solutions 3 (1999), S. 19-27 
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    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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    GPS solutions 3 (1999), S. 28-39 
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    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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  • 39
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    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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    GPS solutions 3 (1999), S. 66-68 
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    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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    GPS solutions 3 (1999), S. 48-52 
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    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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    GPS solutions 3 (1999), S. 40-47 
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    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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  • 43
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    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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    GPS solutions 3 (1999), S. 72-74 
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    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 solutions 3 (1999), S. 75-77 
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  • 47
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    Notes: Summary Synchrotron radiation has been used to record the diffraction patterns from Poly(ethylene terephthalate) for a range of draw rates (0.1 to 10sec−1) and temperatures (90 to 120°C). The patterns were analysed to derive the development of the 〈P 2(cosθ)〉 order parameter and the rates of crystallisation. The effects of temperature and draw rate can be unified with a WLF time-temperature shift factor. Comparison with estimates of chain relaxation processes show that, when the draw rate is faster than the chain retraction process, the onset of crystallisation is delayed until the end of drawing. Crystallisation is very sensitive to both temperature and orientation and has an approximate 4th power dependence on 〈P2(cosθ)〉.
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  • 48
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    Notes: Summary The glass transition temperatures of several blends of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene have been measured by DSC, and the T g -composition data have been described on the basis of a thermodynamic treatment. A negative enthalpy of mixing and a positive entropy of mixing have been found, in agreement with the well known miscibility of the blend. The presence of a singolarity point in the T g -composition plot has been evidenced and considered at the light of a theoretical treatment recently proposed.
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    Polymer bulletin 43 (1999), S. 157-163 
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    Notes: Summary Two AB-type poly(ether imide)s were prepared by one-pot polyimidization in N-methyl-2-pyrrolidone(NMP)/pyridine or N,N-dimethylacetamide(DMAc)/Et3N solution in the presence of triphenylphosphite(TPP) activator. The polymers were obtained with inherent viscosities of 1.16(5a) and 0.54(5b) dL/g and were highly thermostable up to at least 552°C with 5% weight loss. The polymers showed chemical resistance against chloroform even at higher temperature but could readily be dissolved in m-cresol and concentrated sulfuric acid. Wide-angle X-ray diffractograms revealed that the polymers were semi-crystalline.
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    Notes: Summary Organocobalt poly(arylene-vinylene)s composed of 1,2- or 1,3- linkage at their cyclobutadiene moieties (3 and 4, respectively) were prepared by the Heck reaction of p-divinylbenzene with (cyclobutadiene)cobalt-containing monomers having two aryl bromide moieties (1 and 2, respectively). The number average molecular weights (M n) of the obtained organocobalt poly(arylene-vinylene)s (3 and 4) were 4,100 and 4,000, respectively (GPC, on the basis of polystyrene). UV-vis spectra of 3 and 4 exhibited main π-π* absorption peaks at 362 and 397 nm, respectively, which were ca. 60 nm bathochromically shifted from those of the corresponding monomeric units. Both polymers were found to show thermotropic liquid crystallinity in the range of room temperature to ca. 80 °C by employing differential scanning calorimetry (DSC) and the optical measurement using crossed polarizers.
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    Polymer bulletin 43 (1999), S. 171-175 
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    Notes: Summary Copolymers containing vinyltrimethoxysilane (VTMOS) and 2-vinylpyridine (2VPy) at different compositions were synthesized and characterized. The monomer reactivity ratios r1 and r2 were estimated by using the classical Fineman-Ross and Kelen Tüdos linear fitting procedures. Moreover, these parameters were also estimated using a nonlinear computational fitting known as Reactivity Ratios Error in Variable Method (RREVM). Attempts to obtain the corresponding copolymer with vinyltrimethylsilane (VTMS) were performed but only hompolymerization 2VPy is observed due to the non-reactivity of VTMS under this conditions. The results were analysed in terms of the relative comonomeric structures and compared with similar related systems. The reactivities are interpreted in terms of the resonance and stabilization effects together with the chemical structure.
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  • 52
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    Notes: Summary Polymers having Fischer-type alkoxycarbenes in the side chain were synthesized by the reaction of pendant hydroxy groups with pentacarbonyltungsten acetoxyphenylcarbene [(CO)5W=C(Ph)O2CCH3, 2]. Namely, copolymers of methyl methacrylate with 4-hydroxybutyl methacrylate [poly(MMA-co-HBMA), 3b] were prepared and subjected to the reaction with 2 derived from tetramethylammonium salt of pentacarbonyltungsten hydroxyphenylcarbene [(CO)5W=C(Ph)ON(CH3)4, 1] with acetyl chloride. Soluble copolymers (4b) with pendant metal-carbene segments were obtained, and 1H NMR and UV spectroscopic analyses indicated that the metal-carbene moiety was introduced onto 20–70% of hydroxy groups of the copolymers. In contrast, the introduction of carbene moiety into a copolymer of MMA with 2-hydroxyethyl methacrylate [poly(MMA-co-HEMA), 3a] was unsuccessful because no reaction with 2 took place. The formed polymer (4b) served as a polymeric catalyst for the polymerization of phenylacetylene under the photo-irradiation.
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  • 53
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    Notes: Summary A novel polymer homolog of N,N-dimethylacetamide (DMAc) having amide groups on all main chain carbons, poly(N,N-dimethylcarbamoylmethylene) 1, was prepared by heating poly(di-t-butyl fumarate) 2 at 180 °C for 2 hours followed by treatment with hexamethylphosphoramide at 180 °C for 5 hours. The structure of the obtained polymer 1 was confirmed by 1H-, 13C-NMR and IR spectroscopy. The polymer 1 actually showed the properties based on its repeating structures. 1 had the amphiphilicity and was soluble both in protic and aprotic solvents. Furthermore, 1 showed the miscibility with commodity polymers such as poly(N-vinylpyrrolidone), poly(vinyl alcohol) and poly(vinyl chloride). In comparison with another polymer homolog of DMAc, poly(2-methyl-2-oxazoline), the polymer 1 exhibited better miscibility with poly(N-vinylpyrrolidone).
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    Polymer bulletin 43 (1999), S. 191-198 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Biocompatible and potentially biodegradable polyamides (PAs) containing in the chain both peptide bonds and hydrophilic triethyleneoxide segments have been prepared by interfacial polycondensation of sebacoyl dichloride with amide-diamines derived from the 4,7,10-trioxa-1,13-tridecanediamine and α-aminoacids such as glycine, L-valine and L-phenylalanine. These PAs exhibit moderate inherent viscosity values and show limited solubilities in CHCl3, DMF and DMSO. 1H-NMR and FTIR spectroscopy analysis confirmed the expected structures. DSC and X-rays diffraction spectra indicated crystallinity degrees from 19 to 31%. The melting temperatures range between 135–238 °C. Liquid water absorption measurements indicate a high equilibrium weight-uptake when a glycine residue is present in the amide-diamine moiety. In vitro tests carried out using cultures of human fibroblasts showed the biocompatibility of the prepared PAs.
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    Polymer bulletin 43 (1999), S. 199-206 
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    Notes: Summary W(NO)2(O2CR)2 - Lewis acid (LA) catalysts (LA=TiCl4, SnCl4; R=-CH(C2H5)(CH2)3CH3) induce substituted acetylenes (phenylacetylene, propargyl ether, 1,6-heptadiyne, diphenylacetylene) to polymerize or oligomerize. Their catalytic ability strongly depends on the Lewis acid and solvent. The polymerization reactions of phenylacetylene always accompany the cycolotrimerization reactions. In the system with TiCl4 in CH2Cl2 the yield of polymer equals to 56% at 80% conversion of a monomer. However, in the system with SnCl4 in benzene, 42% cyclotrimers arise at 57% conversion of phenylacetylene. The mechanism of these reactions as well as the structure of the obtained polymers were determined.
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    Notes: Summary Transesterification reactions between bisphenol-A polycarbonate and polydimethylsiloxane-polycaprolactone block copolymers were studied in melt at 270°C. Influence of the composition of reaction mixture and the catalyst type on the formation and properties of the products obtained were investigated by spectroscopic, chromatographic and thermal methods. Both of the catalysts used, zinc acetate and lanthanum acetylacetonate are very efficient transesterification catalysts for the system studied. GPC and DSC results clearly show the formation of novel polymers displaying combined properties of the polycarbonate and the silicone-ester copolymer.
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    Notes: Summary A new method for determining the dominant termination mechanism in radical polymerization based on ultrasonic scission of long chains is used to study the termination of polystyrene and polymethyl methacrylate. The method is extended to obtain the disproportionation/combination ratio. Long dead polymer chains in solution were broken by ultrasound. The chain radicals thus formed were then allowed to terminate in the presence and absence of a chain terminating agent (radical trap). The resulting molecular weights are compared to find the dominant termination mechanism. It is found that the dominant mechanism in polystyrene is combination and that in polymethyl methacrylate is disproportionation. These results are in accordance with those quoted in the literature and obtained by other methods.The effectiveness of the radical trap used (2-chloroethyl benzene) was tested by NMR and it was found that when the trapping agent is present it terminates 100% of the polymethyl methacrylate chains. The time evolution of the degree of polymerization was compared to simulations based on Schmid's model. The disproportionation/combination ratios were found for polymethyl methacrylate as 2 and for polystyrene as 1/7 respectively through simulation studies.
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    Notes: Summary Poly((3-hydroxypropyl β malate) has been synthesized starting from aspartic acid and benzyloxy-1-propanol as precursors. This new polymer was characterized by 1H and 13C NMR, size exclusion chromatography and differential scanning calorimetry. Homopolymer is soluble in water. Two kinds of amphiphilic copolymers were also prepared and characterized. Such polymers have been synthesized with a view to preparing non-charged degradable associating networks or drug carriers.
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    Polymer bulletin 43 (1999), S. 305-310 
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    Notes: Summary Polymerization of phenylacetylenes containing imino groups with a variety of transition metal catalysts was investigated. The monomers employed were N-(4-ethynylbenzylidene)aniline (1), N-(3-ethynylbenzylidene)aniline (2), N-(4-ethynylbenzylidene)-2,6-diisopropylaniline (3), N-(4-ethynylbenzylidene)-4-hexylaniline (4), N-(4-ethynylbenzylidene)butylamine (5), and N-(4-ethynylbenzylidene)octylamine (6). All of the monomers smoothly polymerized with [(nbd)RhCl]2-Et3N to give polymers in excellent yields, whereas no polymerization took place with W, Mo, and Fe catalysts. The produced polymers were orange to red solids and soluble in common organic solvents except for poly(1). UV-vis spectra of the polymers indicated that the main chains possess a similar degree of conjugation to that of poly(phenylacetylene). However, the stability of polymer backbone toward oxidative cleavage in solution remarkably improved, which is contributed by the electron-withdrawing character of imino groups.
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    Notes: Summary The radical polymerization of methylmethacrylate and ethylacrylate was carried out in the presence of tris(4,4'-dimethyl-2,2'-bipyridine) copper(II) hexafluorophosphate complexes and aluminium isopropoxide. The molecular weight of the synthesized polyethylacrylates increased proportionally with conversion, whereas the polymerization of methylmethacrylate revealed a nonlinear behavior. The polydispersities of the molecular weight distributions observed were between 1.09 and 1.34. Poly(styrene-block-polymethylmethacrylate) was synthesized by sequential monomer addition.
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    Notes: ABSTRACT : We have investigated a novel monomer having two pendent phenyl imido groups for preparing new cycloaliphatic-aromatic polyamides. Novel polyamides were synthesized by direct polycondensation reaction of N,N'-diphenyl-2,3,5,6-diimido cyclohexane-1,4-dicarboxylic acid(PICA) and various aromatic diamines such as p-phenylene diamine, 4,4'-oxydianiline and 4,4'-methylene dianiline. A direct polycondensation was carried out by a Yamazaki method which is typical of using triphenyl phosphite, lithium chloride, and pyridine. Inherent viscosity of these resulting polyamides are ranged 0.20 ∼ 0.45 dl/g. A transparent flexible and tough film was casted. The glass transition temperature of the polyamide from the PICA and 4,4'-oxydianiline is 147 °C. The decomposition temperature of these polyamides are ranged from 350 ∼ 360 °C and the ash contents of them orders MDA 〉 p-PDA 〉 ODA according to kinds of the using diamines. And the solubilities of these polyamides are good in aprotic solvents such as DMAc, NMP, DMF.
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  • 62
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    Notes: Summary In order to investigate the polymerization behavior of allytrimethylsilane as a comonomer, ethylene was copolymerized with allyltrimethylsilane at 80°C in toluene using methylaluminoxane (MAO) activated metallocene catalysts. The catalytic activity of the polymerization strongly depended on both the type of the catalysts and the concentration of allyltrimethylsilane. End group analysis of the copolymers by means of 1H and 13C NMR spectroscopy revealed that allyltrimethylsilane rather act as a chain transfer agent in the copolymerization, even though considerable amount of allyltrimethylsilane was incorporated in the polymer chain with rac-Et(Ind)2ZrCl2 catalysts. The chain transfer reaction influence strongly the molecular weight and comonomer content of the copolymers.
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    Polymer bulletin 43 (1999), S. 341-347 
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    Notes: Summary Five copolymers from N-(hydroxyethyl)ethyleneimine as nucleophilic monomer and phenylsuccinic anhydride (PhSAn) as electrophilic monomer, were synthesized according to the spontaneous copolymerization concept. These copolymers were characterized by elemental analysis, FT-IR, 1H-NMR, and 13C-NMR spectroscopy. The copolymer composition determined from the 1H-NMR spectra showed that the copolymers are not alternating. According to all the data, it was suggested a copolymer structure which includes ester and anhydride bonds. The molecular weights determined by vapor pressure osmometry ranged between 5.100 and 6.100 g/mol.
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    Notes: Summary This work describes the kinetics of triethyleneglycol dimethacrylate (TEGDM) polymerization, photoinitiated by camphorquinone (CQ) / N-phenylglycine (NPG) and CQ /D,L α-phenylglycine (α-PG), in air and/or in N2. The rates of polymerization (Rp), double bond conversion (p), monomer conversion (pmax), at different concentration of NPG and α-PG were measured and analysed. It was found that CQ/NPG is much more effective photoinitiator system than CQ/α-PG, regarding to the different their chemical structure and H-atom donor ability.
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    Polymer bulletin 43 (1999), S. 395-402 
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    Notes: Summary Thermal and mechanical properties of poly(methylmethacrylate-co-dodecylmethacrylate) nanocomposites based upon exfoliated organophilic layered silicates, were investigated as a function of the silicate and comonomer content. Layered silicates such as sodium bentonite were rendered organophilic by means of ion-exchanging sodium cations for N,N,N,N-dioctadecyl-dimethyl-ammonium cations. Silicate exfoliation was enhanced by means of 5 and 10 wt.-% dodecyl-methacrylate (LMA) addition to afford translucent reinforced acrylic nanocomposites. In contrast to conventional filled acrylic polymers, only 10 wt.-% organophilic silicate was sufficient to increase Young's modulus from 2200 to 4030 MPa, glass temperature from 72 to 80 °C and degradation temperature from 220 to 256 °C with respect to the neat MMA/LMA (90 wt.-%/10 wt.-%) copolymer. Flammability studies, performed on a cone calorimeter, revealed that the maximum heat release rate of MMA/LMA copolymer nanocomposite decreased from 837 kW/m2 to 566 kW/m2. The nanocomposite morphology was examined by means of transmission electron microscopy (TEM).
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    Polymer bulletin 42 (1999), S. 25-32 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The aim of this study was to investigate the bile salts adsorption behavior of the diethylaminoethyl (DEAE)-chitosan, in vitro. In order to prepare the DEAE-chitosan, where the DEAE groups are specifically introduced onto 6-OH groups of chitosan with minimal by-product, DEAE-chitin was prepared by reacting chitin with N,N-diethylaminoethyl chloride, and direct N-deacetylation of DEAE-chitin was carried out in 10% of an aqueous sodium hydroxide solution containing sodium borohydride. DEAE chitosan samples were incubated with cholic acid sodium salt and deoxycholic acid sodium salt in a tromethane buffer solution (pH 7.5) for 1 hour, and the bile salts adsorption performances of the samples were examined by HPLC. The modified chitosan samples showed improved bile salts adsorption performances compared to chitosan, and the absorption amount of bile salt to the samples increased with increase in the DEAE groups introduced. In most cases, the adsorption amount of deoxycholate to the samples was greater than that of cholate.
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    Polymer bulletin 42 (1999), S. 41-46 
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    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Room temperature polymerization of three naturally occurring bile acids, cholic, lithocholic and deoxycholic, was carried out using a mixture of diisopropyl carbodiimide (DIPC), and a 1:1 salt of dimethyl amino pyridine and p-toluenesulfonic acid (DMAP/PTSA). The corresponding polymers were characterized by IR, NMR, Thermal Analysis and X-ray diffraction. Molecular weights were calculated by gel permeation chromatography in the range 50,000–60,000, using polystyrene standards. The polymers were also characterized by mass spectrometry, using matrix assisted laser desorption ionization-time of flight, MALDI-TOF.
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  • 68
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    Notes: Summary Poly(phenylacetylene)s bearing dialkylamino groups were prepared by the polymerization of p-(N,N-dialkylamino)phenylacetylenes with [Rh(nbd)Cl]2, and their electrochemical behavior was examined. Rh-catalyzed polymerization of p-(N,N-diethylamino)phenylacetylene (DEAPA) and p-(N,N-di-n-butylamino)phenylacetylene (DBAPA) in toluene in the presence of triethylamine gave good yields of the polymers (86 and 90%, respectively). Poly(DEAPA) was soluble in chloroform and dichloromethane, and poly(DBAPA) dissolved in various solvents such as toluene, THF, dichloromethane and chloroform. Poly(DEAPA) and poly(DBAPA) showed onset temperatures at 248 and 190°C, respectively, and absorptions around 300–400 nm. Electrochemical doping of the polymer films resulted in the shift of the absorptions to a region around 680 nm, which accompanied a color change of the polymer films from green ocher to deep blue.
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    Polymer bulletin 42 (1999), S. 149-152 
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    Notes: Summary Hydrogenation of poly(vinyl cinnamate) was performed with RhH(CO)(PPh3)3 catalyst with intent to clarify the photoalignment mechanism of liquid crystals on poly(vinyl cinnamate) alignment layer. The hydrogenated cinnamate side group shows the characteristic peaks at 2.9 ppm and 2.5 ppm in 1H-NMR spectrum, and a decreasing peak at 280 nm in UV spectrum. This reaction can reveal the role of dimerized or residual cinnamate groups in the applications of the polymeric layer for electronic devices.
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  • 70
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    Notes: Summary The reactions of α,ω-diyne, HC≡C(CH2)mC≡CH (m = 6 and 8), with 3,3'-diaminobenzidine and with 3,3'-diamino-4,4'-dihydroxybiphenyl in the presence of RU3(CO)12-PPh3 catalyst give the corresponding poly(alkylenebenzoxazole)s and poly(alkylenebenzimidazole)s, respectively. The former polymers obtained from the equimolar reaction of the monomers are partly soluble in polar organic solvents such as DMF, DMSO, and NMP, while the poly(benzimidazole)s are soluble in these solvents. GPC measurement shows the molecular weights of the polymers, M n of 4.8−14.1×103 and M w of 6.4−19.7×103.
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    Polymer bulletin 42 (1999), S. 159-166 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The procedures for the purification of commercial chitosan samples as hydrochlorides and in the neutralized form are described. Thermal analysis reveals that, independently of the purification method, all samples are highly pure. The agreement between values of degrees of acetylation determined by conductimetric titrations and by 1H nmr spectroscopy is very good. The aqueous solutions of both forms of purified chitosan were free of aggregation as evaluated by their Huggins constants. The potential use of solutions of chitosan hydrochloride in acid-free aqueous NaCl for the studies aiming to characterize the solution behavior of chitosan is demonstrated.
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  • 72
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    Notes: Summary Two nonlinear optical (NLO) methacrylate monomers, 2-methyl-acrylic acid 2-(ethyl-{4-[2-(6-nitro-quinolin-2-yl)-vinyl]-phenyl}-amino)-ethyl ester (5) and 2-methyl-acrylic acid 6-{3-[2-(6-nitro-quinolin-2-yl)-vinyl]-carbazol-9-yl}-hexyl ester (7) were newly synthesized and copolymerized with methylmethacrylate to give NLO polymers, P1 and P2. These polymers were well soluble in organic solvents and showed glass transition temperatures at 145 °C and 114 °C, respectively. The number average molecular weights (Mn) were 26,600 for P1 and 9,300 for P2. The SHG coefficients (d33) of corona-poled films of P1 and P2 measured with 1.064 μm Nd-YAG laser were 32.2 pm/V and 17.6 pm/V, respectively.
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  • 73
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    Notes: ABSTRACT: We have investigated a new 1,2-type aromatic dibromide monomer for preparing a modified π -conjugated poly(p-phenylenevinylene). A novel π -conjugated poly(p-phenylenevinylene) was prepared by dehalogenation polycondensation of a dibromoaromatic compound with a squaric unit as a monomer with zerovalent nickel [Ni(0)] complex. The monomer and the polymer were characterized by FT-IR, 1H-NMR, Elemental Anaylsis, TGA, DSC, GPC and UV-Visible. The resultant polymer had good solubility to polar aprotic, solvents, e.g. DMF, DMAc, DMSO and NMP and solvatochromism in DMAc.
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  • 74
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    Notes: Mechanical degradation and mechanochemical reaction in heterogeneous systems of the solid poly(vinyl chloride)-poly(vinyl alcohol) aqueous solutions have been studied by ultrasonic irradiation at 30 °C. The rate of decrease in the viscosity-average degree of polymerization of the degraded poly(vinyl chloride) was much faster than that of the degraded poly(vinyl alcohol). Mechanochemical reaction occurred by free radicals produced from the chain scissions of both polymers by ultrasonic waves. The copolymer was obtained and the molar ratio of the vinyl chloride and the vinyl alcohol units in its copolymer can be determined. In addition, the changes in the composition of the total block copolymer, the unreacted poly(vinyl chloride), and the unreacted poly(vinyl alcohol) were obtained.
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    Polymer bulletin 42 (1999), S. 221-227 
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    Source: Springer Online Journal Archives 1860-2000
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    Notes: The fracture toughness of the semi-IPN's of crosslinked epoxy and linear polysulfone(PSf) having morphology spectrum was investigated. The epoxy resin was based on diglycidyl ether of bisphenol A(DGEBA) and diaminodiphenylsulfone(DDS). The morphology spectrum, which has the gradual change of the morphological feature resulting from the concentration gradient of PSf in the epoxy resin can be obtained by inserting a PSf film in DGEBA/DDS mixture before cure. The relative rate of the dissolution of the PSf in the epoxy oligomer and the rate of curing reaction determine the concentration gradient of the PSf. In the region where the PSf concentration is less then 5%, sea(epoxy)-island(PSf) morphology is observed. As the concentration of PSf increases, the morphology changes to nodular structure, inverted sea-island, and PSf/epoxy homogeneous phase. Up to overall 10wt% of PSf, the fracture toughness of the PSf modified epoxy with morphology spectrum was higher than that of the counterpart with uniform concentration of PSf. These results were ascribed to the plastic deformation of the continuous PSf rich phase which was present in the morphology spectrum.
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    Polymer bulletin 42 (1999), S. 265-272 
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    Notes: Summary Homopolymerization of allylbenzene was carried out with various metallocene/methylaluminoxane (MAO) catalysts. Different polymerization behavior was observed depending upon the catalysts empolyed. rac-Et(Ind)2ZrCl2 and rac-Me2Si(Ind)2ZrCl2 gave semicrystalline polyallylbenzenes while i-Pr(CpFlu)ZrCl2 and CpTiCl3 did not give any polymeric product. The Cp2ZrCl2 gave amorphous polyallylbenzene with low molecular weight. The effect of temperature on the polymerization was investigated with a constant Al/Zr ratio. The temperature showing maximum catalyst activity is higher for the ansa metallocene catalysts than Cp2ZrCl2 catalyst. The IR and NMR spectra indicated that the polyallylbenzene consisted of allylbenzene repeating unit and no isomerization occurred.
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    Polymer bulletin 42 (1999), S. 237-244 
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    Notes: Summary 5-Nitro-2-(2′-vinyloxyethoxy)benzylidenemalononitrile (2a), methyl 5-nitro-2-(2′-vinyloxyethoxy)benzylidenecyanoacetate (2b), 3-nitro-4-(2′-vinyloxyethoxy)benzylidenemalononitrile (4a), and methyl 3-nitro-4-(2′-vinyloxyethoxy)benzylidenecyanoacetate (4b) were prepared by the condensation of 5-nitro-2-(2′-vinyloxyethoxy)benzaldehyde (1) and 3-nitro-4-(2′-vinyloxyethoxy)benzaldehyde (3) with malononitrile or methyl cyanoacetate, respectively. Vinyl ether monomers 2a-b and 4a-b were polymerized with boron trifluoride etherate as a cationic initiator to yield poly(vinyl ethers) 5-6 having nitrooxybenzylidenemalononitrile and nitrooxycyanocinnamate, which is effective chromophore for second-order nonlinear optical applications. Polymers 5-6 were soluble in common organic solvents such as acetone and DMSO. T g values of the resulting polymer were in the range of 70–81°C. Electrooptic coefficient (r33) of the poled polymer films were in the range of 19–27 pm/V, which was improved by introducing of nitro group. Polymers 5–6 showed a thermal stability up to 300°C in TGA thermograms, which is acceptable for NLO device applications.
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    Polymer bulletin 42 (1999), S. 257-264 
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    Notes: Summary Oligo(ɛ-caprolactone)s functionalised with acid groups were prepared by reacting hydroxyl terminated oligo(ɛ-caprolactone)s with succinic anhydride, maleic anhydride or glutaric anhydride. Quantitative conversion of the hydroxyl functionality was achieved in the melt at 130 °C. The resulting acid terminated oligo(ɛ-caprolactone)s were characterised by 1H and 13C NMR spectroscopy. The reactivity of these oligomers was enhanced by conversion of the acid functionality in an acid chloride functionality using thionyl chloride or an anhydride functionality using acetic anhydride. It was shown that these activated oligo(ɛ-caprolactone)s can be used for coupling reactions with compounds containing alcohol- or amino functionalities.
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  • 79
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    Keywords: Keywords: Nucleophilic and electrophilic monomers; spontaneous copolymerization; non-alternating copolymers.
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    Notes: Summary The copolymerization of p-chlorophenylmaleimide (1) as electrophilic monomer with 2-methyl-2-oxazoline (2) as nucleophilic monomer without initiator in solution under different experimental conditions was investigated. Copolymers were characterized by FT-IR and 1H-NMR spectroscopy. The copolymer composition was determined from 1H-NMR spectra. Molecular weights ranged between 1700 and 5400 g/mol by vapor pressure osmometry.
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  • 80
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    Notes: Summary The heat of base-catalyzed alcoholysis of poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalenedicarboxylate) (PEN) as well as several related aromatic and aliphatic esters has been measured using a high-pressure calorimeter. The process is essentially thermoneutral, and heats of CH3ONa-catalyzed methanolysis of PET and PEN are +1.8±0.6 and +9.3±0.2 kJ/mol-carboxyl group, respectively. Furthermore, the heats of Zn(OCOCH3)2-catalyzed alcoholysis of PET with ethylene glycol and benzyl alcohol are also calculated as +5.8±0.2 and +6.6±0.8 kJ/mol-carboxyl group, respectively. These values are comparable to those for ethyl esters of p-substituted benzoic acids and propionic acid.
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    Polymer bulletin 42 (1999), S. 301-307 
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    Notes: Summary Allylbenzene was polymerized in the presence of two types of homogeneous zirconocene catalysts (co-catalyst methylaluiminoxane). Selective chain termination through β-hydride elimination or chain transfer to aluminum was observed depending upon the catalysts employed. The rac-Et(Ind)2ZrCl2, and rac-Me2Si(Ind)2ZrCl2, catalysts gave the polyallylbenzenes with saturated end groups due to chain transfer to aluminum, while the Cp2ZrCl2 catalyst gave the polyallylbenzenes with vinylidene end groups due to β-hydride elimination.
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    Polymer bulletin 42 (1999), S. 373-378 
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    Notes: Summary Radical polymerization of the methacryloyl isocyanate containing 1-adamantanol (Ad-MAI) with AIBN in different solvents at 60°C was investigated. It is observed that polymerization is slower in polar solvents than in nonpolar ones. The rate of polymerization for Ad-MAI was found to be slower than those of Adph-MAI and MMA both in photopolymerization and in thermal polymerization. Copolymerization of Ad-MAI (M1) with styrene (M2) in benzene was studied at 60°C. The monomer reactivity ratio was calculated to be r1=1.53 and r2=0.76 according to the method of Fineman-Ross. The prominent glass transition temperature for poly(Ad-MAI) was observed at 142°C from global TSC spectrum.
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  • 83
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    Notes: Summary Monoaldehydes have been synthesized from tri- and tetra(ethylene glycol) monosubstituted derivatives and introduced into chitosan by the reductive alkylation technique to give comb-shaped polysaccharide hybrids. The reaction of chitosan with the aldehydes in the presence of sodium cyanoborohydride proceeded efficiently to give chitosan derivatives having oligo(ethylene glycol) side chains at the amino groups. The products were characterized by high affinity for organic solvents as well as water in sharp contrast to the original chitin and chitosan. They showed significant adsorption capacity toward metal cations.
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  • 84
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    Notes: Summary : Nonlinear optical poly(ether imides) with an adequate thermal stability has been synthesized by direct coupling of hydroxy poly(ether imides) and NLO chromophores with a quantitative yield. The resultant amorphous NLO poly(ether imides) exhibited good solubility in common organic solvents, providing optical-quality thin films by spin coating. The glass transition temperatures of the polymers are at around 180 °C. The electrooptic coefficients (r33, @1.3μm) of PEI-DR1 was 12.3 pm/V with an electrical poling field of 100 V/μm and it decayed about 10 % over 10 months at 90 °C under atmospheric conditions.
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  • 85
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    Notes: Summary Crystalline polymers, such as poly(ɛ-caprolactone) (PCL), poly(ethylene adipate) (PEA), and polyethylene (PE), were successfully grafted onto carbon black surface by direct condensation of terminal groups of these polymers with carboxyl groups on the surface using N,N'-dicyclohexylcarbodiimide as a condensing agent. The electric resistance of a composite prepared from these crystalline polymer-grafted carbon black drastically increased to 104–105 times of initial resistance in good solvent vapor of grafted polymer and returned to initial resistance when it was transferred into dry air. However, the change of electric resistance of the composite hardly observed in poor solvent vapor. These results suggest that these composite can be applied as a novel gas sensor.
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    Polymer bulletin 42 (1999), S. 575-578 
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    Notes: Summary The orientational behavior of liquid crystalline polymers with para-nitro azobenzene as side chains under electric field was studied by UV-visible spectroscopy. The results showed that λmax of the poled polymer films was around 394nm, compared to that of the unpoled films, the absorption decreased due to poling. The orientational parameters increased linearly with the increase of the electric field. The temporal stability of the poled polymer film is good at room temperature. This kind of materials showed promise application as nonlinear optical component in photorefractive polymers
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    Polymer bulletin 42 (1999), S. 579-586 
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    Notes: Summary The molecular orientation behaviour of epoxy networks on the basis of the diglycidyl ether of bisphenol-A (DGEBA) and various linear aliphatic diols was studied by rheo-optical FTIR spectroscopy. Uniaxial deformation was performed above and below the glass transition temperature. The influence of diol chain length and molar ratio on the mechanical properties and the orientation parameter will be discussed.
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    Notes: Summary The electro-optical response of two novel side chain liquid crystalline polysiloxane copolymers containing chiral pendant groups was investigated. It was found that both copolymers possessed N* phase with a long pitch and therefore the origin of the electro-optical response detected in this phase was considered to be the electroclinic effect.
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    Polymer bulletin 42 (1999), S. 611-618 
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    Notes: Summary Alternating propene-carbon monoxide copolymers (P-CO) were melt-blended with polystyrene, poly(styrene-co-acrylonitrile) (SAN), and with poly(styrene-co-maleic anhydride) (SMA). P-CO forms homogeneously miscible blends with SAN containing 25 wt% AN at the investigated blend compositions. The transparent blends have single, intermediate glass transition temperatures that fit the Fox equation. The elastic properties of P-CO at room temperature disappear upon blending with SAN because the T g is driven above RT. Polystyrene and SMA are not miscible with P-CO and form heterogeneous blends with two glass transitions. This demonstrates that both the polarity of the styrenic copolymer and the nature of the comonomer govern its phase behavior.
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    Polymer bulletin 42 (1999), S. 635-639 
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    Notes: Summary We have studied the polymerization of methyl methacrylate (MMA) using biscyclopentadienylcalcium (Cp2Ca) and bis(pentamethylcyclopentadienyl)calcium (Cp2 *Ca) as initiators. Polymerizations initiated with CP2Ca produced poly(methyl methacrylate), PMMA, with %rr = 80. This polymerization was conducted in 1,2-dimethoxyethane at 0°C; monomer conversion was 57% after 19 h. Lindsell and co-workers reported a much higher syndiotacticity for the same initiator. While 80%rr is higher than a free radical polymerization of MMA at the same temperature, the broad polydispersity and low conversions make this polymerization method unattractive. Use of the more soluble initiator Cp2 *Ca significantly increases monomer conversion but produces PMMA with lower syndiotacticity.
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  • 91
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    Notes: Summary Diethyleneglycoldivinylether (DVE2) and triethyleneglycoldivinylether (DVE3) were photopolymerised together with monovinylethers and hydroxyalkylvinylethers, in order to study the curing reaction and to evaluate the properties of the films obtained. In the presence of the monovinylethers, the flexibility of the cured films increased and the Tg values decreased. In the presence of a hydroxyalkylvinyl ether, a stronger plasticisation effect was obtained and attributed to a chain transfer reaction involving -OH groups.
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    Polymer bulletin 42 (1999), S. 655-660 
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    Notes: Summary The synthesis and metal ion responsive properties of Congo Red-based polyamide are reported. The polymer was prepared by simple interfacial polymerization between Congo Red and sebacoyl chloride. The polymer showed decrease in electronic absorption when exposed to metal ions. The absorbance tends to decrease linearly in a measurable range according to metal ion concentration. It is found that the polymer showed high sensitivity toward Ca2+ and Fe3+.
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  • 93
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    Notes: Summary Poly(amide-imide)s(PAIs) with different microstructures were prepared based on trimellitimide and 4,4'-diphenylether with varying the reaction conditions. The microstructures of PAIs were examined by 500MHz 1H-NMR spectroscopy. The head-to tail (HT-) PAI showed a sharp peak in WAXD curve, a large shift at around 1670 cm−1 for −C=O stretching in FT-IR spectra, and poor solubility in organic solvents, high density, Tg, tensile strength and modulus compared to head-to-head (HH-) PAI and copolymers of HT and HH. These results might be due to the higher packing tendency of the HT PAI than HH PAI or copolymers.
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    Polymer bulletin 42 (1999), S. 683-688 
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    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Metathesis polymerization has been employed for the synthesis of polyphenylacetylene (PPA) containing redox-active ferrocene groups at both ends. Two reversible one electron oxidation waves were detected in CV. The ΔE values decreased with increase in chain length of the polymer, indicating that the metal-metal interaction decreases by increasing the chain length.
    Type of Medium: Electronic Resource
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  • 95
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 42 (1999), S. 693-699 
    ISSN: 1436-2449
    Keywords: Key Words: poly(o-toluidine); enzyme electrode; amperometric biosensor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary An amperometric biosensor for glucose was constructed in a one-step procedure by the electropolymerization of o-toluidine in the presence of glucose oxidase on Pt substrates in KCl aqueous electrolyte at a potential of 0.5 V vs Ag / AgCl. The amperometric responses of the prepared polymeric biosensor to the glucose were measured at a potential of 0.7 V in PBS solution. Results showed that this polymeric sensor exhibited a fast amperometric response time (4–5 s) and a linear range up to 6 mM glucose with poor stability. Also, it was seen that biosensor responded successfully to glucose injections in the presence of some interfering species such as lactose, sucrose and urea.
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  • 96
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The miscibility of a series of poly(ethyl methacrylate-co-4-vinylpyridine) with poly(styrene-co-cinnamic acid), is investigated by differential scanning calorimetry. The results show that each blend is miscible as ascertained by a single composition dependent glass transition temperature. The Tg's of the blends exhibit positive deviations from the weight average Tg's of the blend components. The thermograms data exploited according to the Kwei and Schneider approaches suggest the occurrence of strong specific intermolecular attractive interactions within the binary systems. The strength of these interactions, as estimated from the Kwei q-values, increases with the proton donor and proton acceptor contents in the copolymers.
    Type of Medium: Electronic Resource
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  • 97
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 42 (1999), S. 709-716 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary γ- and UV-irradiation was successfully used for the preparation of mixed networks on the basis of high molecular weight polyoxyethylene (POE) and/or N-isopropylacrylamide and poly(N-isopropylacrylamide) (PNIPAAm). These gels preserve the swelling transition temperature of the pure PNIPAAm and shrink faster above this temperature due to the hydrophilic POE chains. It was found that in a collapsed state these gels retain alkaline organic salts from aqueous solutions.
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  • 98
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 42 (1999), S. 717-724 
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Jet erosion tests of outdoor insulating silicone and EPDM rubbers were carried out by means of a modified sandblasting equipment. The presence of relatively large, non-reinforcing filler particles increased the erosion rate of the silicone rubber compounds. The erosive wear of highly filled compounds strongly depended on the incident angle of the eroding particles. Rubbers with low amount or very finely dispersed reinforcing filler showed a good resistance to solid particle erosion. The mechanisms of material removal were studied by scanning electron microscopy and discussed.
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  • 99
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary 6,6-Diethyl- (1a) and 6-methyl-6-propyl-5,7-dioxa-4,8-dioxo-1-vinylspiro[2.5]octane (1b) were synthesized by the acetalization of 2-vinylcyclopropane-1,1-dicarboxylic acid with 2- or 3-pentanone. The new monomers were characterized by IR, 1H NMR and 13C NMR spectroscopy. The radical polymerization of the monomers 1a and 1b, in addition of 6,6-methyl-5,7-dioxa-4,8-dioxo-1-vinylspiro[2.5]octane (1c) and (exo/endo)-7-ethoxycarbonyl-2-oxo-7-vinyl-bicyclo[4.1.0]heptane (1d), was carried out in bulk with 2,2`-azoisobutyronitrile (AIBN) as the initiator. The polymer yield with 1d was only low. The polymerization of the monomers 1a and 1c resulted in cross-linked polymers, whereas in case of the polymerization of monomer 1b soluble polymers in a high yield were obtained.
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  • 100
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The Ru(II)-centered star-shaped polymer was prepared by coordination of 2,2'-bipyridyl-terminated poly(propylene glycol) with ruthenium ion. The structure was confirmed by GPC analysis and UV/Vis spectrum. The resulting polymer complex was well-soluble in various organic solvents and water.
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