The first large format Si:Sb BIB arrays

The first 128×128 Si:Sb blocked impurity band (BIB) detectors, manufactured by Rockwell International, are sensitive detectors from 10 to at least 40 m. While further work is required to make these arrays suitable for the low backgrounds of space infrared telescopes, they can be used now for observations from the ground and aircraft.     

黄土塬区二维地震施工技术初步研究

某勘探区位于宁夏回族自治区南部固原市,具黄土高原地貌特征：黄土冲沟发育,地形切割剧烈,部分沟壁近乎直立,地形总体北低南高,最大高差大568m。该区基岩少有裸露,大多数被第四系所覆盖,盖层厚度一般大于100m,地震激发条件属Ⅲ类区,原始资料存在严重的静校正问题。该区目的层主频率为30Hz,通过试验,采用井深20m、药量3kg及多井组合激发,同时增加排列长度,提高覆盖次数等野外技术措施,改善资料品质。     

Pressure resistance of the corrugated stainless steel membranes of LNG carriers

Corrugated stainless steel membranes have been used as the primary barriers for LNG carriers to reduce thermal stresses at cryogenic temperatures. As the capacity of the LNG cargo is increased, however, the corrugated stainless steel membranes suffer from buckling and collapse due to increased sloshing loads in large-capacity LNG cargo carriers. In this study, the pressure resistance of the corrugated part of the stainless steel membrane was evaluated using a finite element method for better design of the LNG containment system, and an experimental equipment was developed and the pressure resistance of the stainless steel corrugations was measured and compared with the calculated results. In addition, a new membrane with high-pressure resistance and its reinforcing method were developed and evaluated experimentally.     

大气冰核研究进展

大气冰核在冷云降水物理过程、人工影响天气、云和气溶胶的气候效应乃至全球变化等对大气和气候方面的研究中具有重要的意义。本文主要从大气冰核的观测方法、来源、化学组成、成冰活性、浓度时空分布及其与气象条件如天气系统、天气现象、气象因子等各方面综述了国内外近几十年大气冰核的研究进展,并在探讨国内外大气冰核研究现状的基础上,提出...     

Additions to the echinoid fauna of New Zealand

Seven species of echinoids are added to the New Zealand fauna, two being described as new species of the genera Caenopedina and Spatangus Described species, new to the fauna, are Gracilechinus multidentatus (H. L. Clark), Pourtalesia laguncula A. Agassiz, Hemiaster expergitus gibbosus A. Agassiz, and Gymnopatagus magnus A. Agassiz and H. L. Clark. Fragments of Spatangus, possibly hybrid S. thor Fell, and fragments of Echinocardium, almost certainly not E. cordatum (Pennant), are also described.     

大柏舍深井地电阻率观测布极方式分析

为了评估观测质量,本文结合大柏舍地震台电测深资料,采用水平层状介质模型分析了该台站对称四极装置深井地电阻率观测时影响系数随电极深度和观测极距的变化。分析结果表明：大柏舍台现有的深井地电阻率观测水平测道虽然能有效地抑制来自地表的干扰,但是由于观测极距较小,不能很好地反映深部介质电阻率的变化信息;垂直测道因电极埋深位于地下水位变动层位,观测数据受地下水位波动影响较大,较难识别来自深部介质的信息。为有效地记录可能的孕震信息,水平测道极距AB/2取250~350 m、埋深H>150 m能满足需求,并建议增加NS向水平测道观测。     

Estimation of Nonlinear Time-dependent Soil Behavior in Strong Ground Motion Based on Vertical Array Data

To improve our understanding of nonlinear elastic properties of soils, a method is proposed of estimation of stress-strain relations of soils in situ in strong ground motion based on vertical array data. Strong motion records provided by seismic vertical arrays allow estimation of nonlinear stress-strain relations in soil layers at different depths, from the surface down to the location of the deepest device. As an example, records obtained during the main shock of the 1995 Kobe earthquake at Port-Island, SGK, and TKS sites were used to estimate the stress-strain relations in the soil profiles. For different layers, different types of nonlinear stress-strain relations were selected, according to the profiling data. To account for temporal changes in the soil behavior, consecutive parts of records were examined, and for successive time intervals, the relations were found showing the best-fit approximation to the observed data. At Port Island and SGK sites, where the strongest accelerations were recorded, the obtained stress-strain relations showed systematic changes in the upper layers (0–14 m), such as, a progressive reduction of the slopes of the stress-strain curves due to liquefaction at Port Island and reduction and recovery of the slopes at SGK and TKS sites. At the three sites, the stress-strain relations remained stable in layers below 11–14 m. Thus, the proposed approach gives us a representation of the soil behavior in layers at different depths in strong ground motion; it allows calculation of the propagation of arbitrary seismic signals in the studied profiles and estimation of nonlinear components in the ground response by the nonlinear system identification technique. The method can also be applied to evaluate the ground response at sites where profiling data are available and an imposed motion can be estimated.     

Theoretical and experimental study of time domain-induced polarization in water-saturated sands

A theoretical model of spectral-induced polarization (IP) of sand is presented. In the proposed model, contacts of sand grains and intergrain solution-filled space are considered as electrical current passages of varying thickness, which differ in values of ion transport number. Ion-selective narrow passages are considered as active zones, large passages as passive. The proposed model describes spectral IP characteristics for the medium where the length of passive zones is much greater than the length of active ones. The model is called short narrow pores (SNP) model. The SNP model predicts a growth of IP time constant with increase of length of ion-selective zone. Both the time domain and frequency domain parameters are described. The parameters of Cole–Cole model corresponding to the SNP model were also found.The behaviour of model parameters is compared with experimental data obtained on natural and sieved sands using time domain technique. The natural sand spectra correspond neither to the simple SNP model nor simple Cole–Cole model with single time constant because the lengths of ion-selective zones vary, reflecting the grain-size distribution.The spectra of sieved sand compared with the theoretical SNP spectra reveal close correspondence between experimental data and theoretical parameters. For four sieved sands, both the theoretical and experimental data show that the time constant of the IP is proportional to the square of the average grain size.     

A parametric study of borehole influence in resolving seismic velocity in well-to-well tomograms

The data collected in a well-to-well tomography experiment is inherently incomplete even when augmented by VSP data. The nature of the experiment suggests a geometric limitation to the resolution of any central structure.A parametric model has now been developed which examines the effect on reconstructed velocity due to the borehole size, transducer standoff, altered annulus, and the degree of velocity attenuation of the altered annulus, using a range of host velocities and hole separations.It was found that there are significant velocity variations caused by perturbations in borehole size. These errors are particularly significant for boreholes with large diameters and small transducer offsets. For an altered annulus, errors in both the dimensions and the degree of velocity alteration gave significant velocity variation in reconstructed velocity, particularly with large boreholes. In all cases it is observed that the variation and alteration in reconstructed velocities increased as hole separation is decreased.