Numerical Estimate of Tangshan Earthquake Damage

The initial stress is first calculated quasi-statically under various loading conditions by using 3-dimenaional finite element model with double nodes to simulate the locked Tangsban fault. Once the shear stress at the front of fault tip reaches rupture criterion, the accumulated stress is suddenly released accompanying with frictional slip along the fault plane, the new state of stress imposed during faulting is re-calculated by reducing the shearing resistance of the hypocenter with the same boundary condition. Then the stress difference before and during shock is regarded as the driving force to generate ground motion. Numerical results show that both the fault mode and the loading system play an important role on the behavior of ground motion. To cause a greater damage and a tremendous depression on the seaward side of the fault, there must be a pre-existing oblique fault and the body force should be considered in addition to the horizontal stressing

Analysis of cyclic delay diversity on DVB-H systems over spatially correlated channel

The objective of this work is to research and analyze the performance of Cyclic Delay Diversity (CDD) with two transmit antenna on DVB-H systems operating in spatially correlated channel. It is shown in this paper that CDD can achieve desirable transmit diversity gain over uncorrelated channel with or without receiver diversity. However, in reality, the respective signal paths between spatially separated antennas and the mobile receiver is likely to be correlated because of insufficient antenna separation at the transmitter and the lack of scattering effect of the channel. Under this spatially correlated channel, it is apparent that CDD cannot achieve the same diversity gain as obtained under the uncorrelated channel. In this paper, a new upper bound on the pairwise error probability (PEP) of the CDD with spatial correlation of two transmit antennas is derived. The upper bound is used to study the CDD theoretical error performance and diversity gain losses over a generalized spatially correlated Rayleigh channel. This theoretical analysis is validated by the simulation of DVB-H systems with two transmit antennas and the CDD scheme. Both the theoretical and simulated results give the valuable insight that the CDD ability to perform well with a certain amount of channel correlation

Medium energy proton radiation damage to (AlGa)As-GaAs solar cells

The performance of (AlGa)As-GaAs solar cells irradiated by medium energy 2, 5, and 10 MeV protons was evaluated. The Si cells without coverglass and a number of GaAs solar cells with 12 mil coverglass were irradiated simultaneously with bare GaAs cells. The cell degradation is directly related to the penetration of depth of protons with GaAs. The influence of periodic and continuous thermal annealing on the GaAs solar cells was investigated

GaAs solar cells for concentrator systems in space

Cells for operation in space up to more than 100 suns were made, and an AMO efficiency of 21% at 100 suns with these cells was obtained. The increased efficiency resulted not only from the higher open circuit voltage associated with the higher light intensity (higher short circuit current); it also benefitted from the increase in fill factor caused by the lower relative contribution of the generation recombination current to the forward bias current when the cell's operating current density is increased. The experimental cells exhibited an AMO efficiency close to 16% at 200 C. The prospect of exploiting this capability for the continuous annealing of radiation damage or for high temperature missions (e.g., near Sun missions) remains therefore open. Space systems with concentration ratios on the order of 100 suns are presently under development. The tradeoff between increased concentration ratio and increased loss due to the cell's series resistance remains attractive even for space applications at a solar concentrator ratio of 100 suns. In the design of contact configuration with low enough series resistance for such solar concentration ratios, the shallow junction depth needed for good radiation hardness and the thin AlGaAs layer thickness needed to avoid excessive optical absorption losses have to be retained

Analysis of DVB-H network coverage with the application of transmit diversity

This paper investigates the effects of the Cyclic Delay Diversity (CDD) transmit diversity scheme on DVB-H networks. Transmit diversity improves reception and Quality of Service (QoS) in areas of poor coverage such as sparsely populated or obscured locations. The technique not only povides robust reception in mobile environments thus improving QoS, but it also reduces network costs in terms of the transmit power, number of infrastructure elements, antenna height and the frequency reuse factor over indoor and outdoor environments. In this paper, the benefit and effectiveness of CDD transmit diversity is tackled through simulation results for comparison in several scenarios of coverage in DVB-H networks. The channel model used in the simulations is based on COST207 and a basic radio planning technique is used to illustrate the main principles developed in this paper. The work reported in this paper was supported by the European Commission IST project—PLUTO (Physical Layer DVB Transmission Optimization)

Germanium-on-silicon mid-infrared waveguides and Mach-Zehnder interferometers

In this paper we describe Ge-on-Si waveguides and Mach-Zehnder interferometers operating in the 5.2 - 5.4 mu m wavelength range. 3dB/cm waveguide losses and Mach-Zehnder interferometers with 20dB extinction ratio are presented

A binary signature in the non-thermal radio-emitter Cyg OB2 #9

Aims: Non-thermal radio emission associated with massive stars is believed to arise from a wind-wind collision in a binary system. However, the evidence of binarity is still lacking in some cases, notably Cyg OB2 #9 Methods: For several years, we have been monitoring this heavily-reddened star from various observatories. This campaign allowed us to probe variations both on short and long timescales and constitutes the first in-depth study of the visible spectrum of this object. Results: Our observations provide the very first direct evidence of a companion in Cyg OB2 #9, confirming the theoretical wind-wind collision scenario. These data suggest a highly eccentric orbit with a period of a few years, compatible with the 2yr-timescale measured in the radio range. In addition, the signature of the wind-wind collision is very likely reflected in the behaviour of some emission lines.Comment: accepted by A&A, 4 p, 3figure

A novel low complexity local hybrid pseudo-SSIM-SATD distortion metric towards perceptual rate control

The front-end block-based video encoder applies an Image Quality Assessment (IQA) as part of the distortion metric. Typically, the distortion metric applies uniform weighting for the absolute differences within a Sub-Macroblock (Sub-MB) at any given time. As video is predominately designed for Humans, the distortion metric should reflect the Human Visual System (HVS). Thus, a perceptual distortion metric (PDM), will lower the convex hull of the Rate-Distortion (R-D) curve towards the origin, by removing perceptual redundancy and retaining perceptual clues. Structured Similarity (SSIM), a perceptual IQA, has been adapted via logarithmic functions to measure distortion, however, it is restricted to the Group of Picture level and hence unable to adapt to the local Sub-MB changes. This paper proposes a Local Hybrid Pseudo-SSIM-SATD (LHPSS) Distortion Metric, operating at the Sub-MB level and satisfying the Triangle Equality Rule (≤). A detailed discussion of LHPSS's Psuedo-SSIM model will illustrate how SSIM can be perceptually scaled within the distortion metric space of SATD using non-logarithmic functions. Results of HD video encoded across different QPs will be presented showing the competitive bit usage under IbBbBbBbP prediction structure for similar image quality. Finally, the mode decision choices superimposed on the Intra frame will illustrate that LHPSS lowers the R-D curve as homogeneous regions are represented with larger block size

Test-bed development & measurement plan for evaluating transmit diversity in DVB networks

This paper presents a test-bed development and measurement plan for evaluating transmit diversity in the DVB network. Transmit diversity reduces the complexity and improves the power consumption of the personal receiving devices by improving the transmission of signals in NLOS cluttered environments. Also, it is more practical than receive diversity due to the difficulty of locating two receive antennas far enough apart in a small mobile device. Test service scenarios were developed to illustrate the benefits of such technologies so that effectiveness can be researched in a variety of service and terrain scenarios using purpose built test systems. The laboratory tests were designed to validate the theoretical measurements from the theoretical analysis and these results will be verified by a field measurement campaign in short and long time spans