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  • 1
    Electronic Resource
    Electronic Resource
    Determination of the critical slip surface in slope stability computations (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 4 (1980), S. 333-359 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The analysis of the stability of slopes using limiting equilibrium considerations necessitates the determination of the critical slip surface which yields the minimal factor of safety. The numerous methods currently available for slope stability analysis provide a procedure for assigning a factor of safety to a given slip surface, but do not consider the problem of identifying the critical conditions.This paper presents an effective minimization procedure based on dynamic programming by which the minimal factor of safety, and the corresponding surface, are determined simultaneously. This procedure SSDP (Slope Stability by Dynamic Programming), couples the minimization scheme with Spencer's method of slope stability analysis. It may be applied to slopes of any geometry, layering, pore pressure and external load distributions. No arbitrary restrictions are placed on the shape of the slip surfaces, and the analysis satisfies all equilibrium equations.Application of the procedure to slope stability problems reported in the literature shows that for a given slip surface the procedure yields factors of safety which are almost identical to those reported, but in every case a more critical slip surface, with a lower factor of safety, may be found.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610040405
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Letters to the editor (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 7 (1983), S. 385-393 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610070309
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  • 3
    Electronic Resource
    Electronic Resource
    Three dimensional analysis of slope stability (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 9 (1985), S. 199-223 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: A 3-D mathematical approach to slope stability, which is based on limiting equilibrium and variational analysis, is presented. In the initial formulation there are three unknown functions: the slip surface, the normal stress and the shear stress direction over this surface. The minimum factor of safety is sought through variational extremization. The analysis indicates that the factor of safety is independent of the normal stress distribution over the critical slip surface. It also indicates that the direction of the elementary shear force over the slip surface depends on the slip surface function, but not on the normal stress function. The analysis yields a non-linear first order partial differential equation, relating the slip surface and its first partial derivatives. By limiting the analysis to symmetrical problems an ordinary differential equation, governing the slip surface path on the plane of symmetry, is derived. This equation enables the development of a numerical procedure to determine the minimal factor of safety of symmetrical 3-D slopes. Two possible failure modes are determined for homogeneous slopes. One mode consists of finite 3-D sliding body and the second represents cylindrical failure. Numerical analyses for some simple cases, of homogencous slopes are presented.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610090302
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  • 4
    Electronic Resource
    Electronic Resource
    Induced anisotropy during plastic straining (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 8 (1984), S. 167-185 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The restrictions imposed by the form-invariance principle on the structure of the elasto-plastic constitutive law for small strains are examined. It is shown that the yield and plastic potential functions may depend on the joint invariants of the stress and plastic strain tensors in addition to their dependence on the direct invariants of these tensors and additional scalar hardening parameters such as the plastic work; inclusion of the joint invariants as parameters in the constitutive functions allows for induced anisotropy during plastic deformation. It is demonstrated that the physical meaning of the joint invariants is related to the deviation of the principal directions of the stress tensor from those of the plastic strain tensor. It is also shown that only three cases of anisotropy (orthorhombic, transverse and isotropy) are possible in the types of material models discussed herein. The model proposed in this paper does not imply coaxiality between the principal directions of the stress and, plastic strain increment tensors; however, implications of the assumption of coaxiality on the structure of the constitutive equations is investigated. It is shown that coaxiality does not necessarily imply isotropy, but no deviations from coaxiality can be expected in isotropic materials.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610080206
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  • 5
    Electronic Resource
    Electronic Resource
    Slope stability analysis for undrained loading conditions (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 17 (1993), S. 15-43 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: The current state of art for limit equilibrium analysis of slope stability problems lacks a satisfactory procedure for stability evaluation under general, rapid (undrained) loading conditions. Some procedures are available for the analysis of rapid drawdown, but these suffer from several shortcomings and, furthermore, are not applicable to other types of rapid loading. An approach is presented which overcomes these limitations. The approach integrates four components-establishment of soil behaviour on the basis of laboratory testing, estimation of steady-state conditions in the slope using a boundary value analysis, estimation of distribution of undrained strength in the slope using undrained stress paths, and identification of the critical slip surface followed by calculation of its factor of safety. The approach is illustrated through its application to the stability analysis of an earth dam under rapid drawdown and earthquake conditions.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610170103
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  • 6
    Electronic Resource
    Electronic Resource
    Letters to the Editor (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 5 (1981), S. 323-324 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610050308
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  • 7
    Electronic Resource
    Electronic Resource
    Consequences of deviatoric normality in plasticity with isotropic strain hardening (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 6 (1982), S. 383-390 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: For many soils experimental evidence suggests that deviation from normality between the plastic strain increments and the yield function is exhibited mainly in the volumetric behaviour, whereas the deviatoric behaviour exhibits normality. An analysis of the consequence of this observation is presented, and it leads to an expression for the plastic potential function as composed of two functions, a yield function and another dependent only on the hydrostatic pressure; the latter is considered to constitute the concept of correction functions presented recently by Desai and Siriwardane13.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610060308
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  • 8
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    The High Energy Telescope for STEREO (2008)
    In:  CASI
    Details
    Publication Date: 2018-08-10
    Description: The IMPACT investigation for the STEREO Mission includes a complement of Solar Energetic Particle instruments on each of the two STEREO spacecraft. Of these instruments, the High Energy Telescopes (HETs) provide the highest energy measurements. This paper describes the HETs in detail, including the scientific objectives, the sensors, the overall mechanical and electrical design, and the on-board software. The HETs are designed to measure the abundances and energy spectra of electrons, protons, He, and heavier nuclei up to Fe in interplanetary space. For protons and He that stop in the HET, the kinetic energy range corresponds to approx. 13 to 40 MeV/n. Protons that do not stop in the telescope (referred to as penetrating protons) are measured up to approx. 100 MeV/n, as are penetrating He. For stopping He, the individual isotopes He-3 and He-4 can be distinguished. Stopping electrons are measured in the energy range approx. 0.7 - 6 MeV.
    Keywords: Astronomy
    Type: To appear in Space Science Reviews
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Development of Tiled Imaging CZT Detectors for Sensitive Wide-Field Hard X-Ray Surveys to EXIST (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Motivated by the proposed EXIST mission, a "medium-class" space observatory to survey black holes and the Early Universe proposed to the 2010 NAS/NRC Astronomy and Astrophysics Decadal Survey, we have developed the first "large" area 256 sq cm close-tiled (0.6 mm gaps) hard X-ray (20-600 keV) imaging detector employing pixelated (2.5 mm) CdZnTe (CZT) detectors, each 2 x 2 x 0.5 cubic cm. We summarize the design, development and operation of this detector array (8 x 8 CZTs) and its performance as the imager for a coded aperture telescope on a high altitude (40 km) balloon flight in October. 2009, as the ProtoEX1STl payload. We then outline our current development of a second-generation imager, ProtcEXIST2. with 0.6 mm pixels on a 32 x 32 array on each CZT, and how it will lead to the ultimate imaging system needed for EXIST. Other applications of this technology will also be mentioned.
    Keywords: Astronomy
    Type: GSFC.JA.6610.2012
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    The Design and Performance of the Astro-E/XRS Signal Processing System (1999)
    In:  Other Sources
    Details
    Publication Date: 2019-07-17
    Description: We describe the signal processing system of the Astro-E XRS instrument. The Calorimeter Analog Processor (CAP) provides bias and power for the detectors and amplifies the detector signals by a factor of 20,000. The Calorimeter Digital Processor (CDP) performs the digital processing of the calorimeter signals, detecting X-ray pulses and analyzing them by optimal filtering. We describe the operation of pulse detection, pulse height analysis, and risetime determination. We also discuss performance, including the three event grades (hi-res, mid-res, and low-res), anticoincidence detection, counting rate dependence, and noise rejection.
    Keywords: Astronomy
    Type: Jul 18, 1999 - Jul 23, 1999; Denver, CO; United States
    Format: text
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    NASA TECHNICAL REPORTS
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