Structural, electronic and optical properties of orthorhombic distorted perovskite TbMnO3

This paper calculates the structural parameters, electronic and optical properties of orthorhombic distorted perovskite-type TbMnO₃ by first principles using density functional theory within the generalised gradient approximation. The calculated equilibrium lattice constants are in a reasonable agreement with theoretical and experimental data. The energy band structure, density of states and partial density of states of elements are obtained. Band structures show that TbMnO₃ is an indirect band gap between the O 2p states and Mn 3d states, and the band gap is of 0.48 eV agreeing with experimental result. Furthermore, the optical properties, including the dielectric function, absorption coefficient, optical reflectivity, refractive index and energy loss spectrum are calculated and analysed, showing that the TbMnO₃ is a promising dielectric material.     

基于DSP的数字测深仪

随着电子技术特别是数字信号处理器的迅速发展，回声测深仪进入了数字化时代；计算机技术与数字信号处理器的结合，使测深仪一改其单一的旧“面孔”，人机操控显示界面、结构组成呈多样性。详细介绍了最近研制的基于数字信号处理器的数字测深仪的结构和组成、采用的信号处理技术以及试验测试情况。     

掺Ga对ZnO电子态密度和光学性质的影响

采用密度泛函理论下的第一性原理平面波赝势方法,研究了掺Ga对纤锌矿ZnO电子态密度和光学性质的影响.从晶体配位场理论分析了掺Ga前后ZnO的成键情况及态密度的变化.计算得到掺Ga后电子浓度为2.42×10²¹ cm^-3,ZnO的载流子浓度提高了10⁴倍.比较分析掺Ga前后ZnO的介电函数、复折射率、吸收光谱和反射光谱可得,ZnO光吸收边向高能端移动,光学带隙增大.在可见光区,ZnO光吸收系数与反射率减小,光透过率显著提高,使ZnO:Ga成为     

A pressure tolerant TV camera

The pressure tolerant TV (PTTV) camera is a significant advance in underwater TV cameras. Pressure tolerant means the camera is not protected from the ambient pressure, no matter at what depth it is operating. All the electronics, including the imager, and the lens are exposed to ambient pressure, though protected from the water in a fluid filled case. Though the PTTV camera is small (less than 7.5 cm diameter by 15 cm long), it is but the first step in the evolution of smaller (less than 64 cm³), lighter (less than 100 g), inexpensive underwater TV cameras. The PTTV camera began as a commercial charge-coupled device (CCD) imager TV camera. The electronic components were either modified for operation as pressure tolerant components or replaced with components that were known to be pressure tolerant. A liquid filled housing was fabricated for the camera as was a liquid filled lens. The completed PTTV camera was then tested to a depth of 6500 m and found to operate as well at this depth as at the surface.     

N掺杂SnO2材料光电性质的第一性原理研究

采用全电势线性缀加平面波(full potential linearized augmented plane wave method,简记为FP-LAPW)方法,基于密度泛函理论第一性原理计算分析N掺杂SnO₂材料,研究了在N替代O原子和N替代Sn原子情况下的电子态密度、电荷密度分布以及光学性质.研究表明N掺杂替代Sn较之N掺杂替代O原子的带隙要宽,都宽于SnO₂的本征带隙,且两种情况下N分别处于负氧化态和正氧化态,其介电函数谱也与带隙对应发生蓝移,从理论上指出     

遥感溢油识别的电子海图设计与功能实现

针对遥感溢油识别的电子海图显示应用系统的开发,进行功能需求分析并提出系统设计方案。在分析了几种常见的电子海图显示平台开发模式的基础上,基于MapObjects组件开发实现了电子海图显示应用平台,具备海图显示、数据叠加、海图分析、添加标注、地图输出等功能。     

Visible and infrared radiometer on Seasat-1

The visible and infrared radiometer (VIRR) is a scanner for the collection of digital data in the visible and thermal-infrared portions of the spectrum over broad swaths of the earth's surface [1]. Some of the essential electronic and mechanical details of the system are described; and the results of an engineering assessment of its operation in orbit are given. The set of algorithms used to transform the raw VIRR data to calibrated geophysical measurements is discussed. Some of the results of a preliminary geophysical evaluation are presented.     

Mitobs: A seismometer system for ocean-bottom earthquake studies

The MIT ocean-bottom seismometer is a free-fall, pop-up instrument capable of recording three components of seismic data on the sea floor for periods of at least one month. Data are recorded in digital format on a specially designed magnetic tape recorder. An event recording scheme and semiconductor memories assure both efficient data storage and preservation of first motion information. Sensors and recording electronics are housed in a cylindrical pressure vessel, which sits vertically atop an expendable base plate on the ocean bottom. Attached to the pressure case are three glass spheres for buoyancy. After a pre-set time interval, a motor-driven mechanical latch release frees the instrument to float to the ocean surface for recovery.     

钒酸盐可见光催化防污材料研究进展

生物污损是海洋工程材料在服役过程中面临的重要问题之一,因此,开发高效、环保的新型防污材料具有重要意义。基于半导体材料的可见光催化防污技术绿色、广谱、高效,在海洋防污领域有巨大的应用前景。本文从可见光催化防污材料和作用机理的角度,阐述了近年来在钒酸盐半导体材料体系方面的研究进展。作为一种新型的防污材料,基于钒酸盐的可见光催化防污技术有望在海洋防污领域中提供一种新的策略。     

低维半导体异质结中的量子相干红外发射机理理论研究

给出了一种在非粒子反转条件下量子阱和量子点激光器的红外发射机理. 此种红外发射是基于在同一作用区产生并作为红外场相干源的两种带间跃迁激光场的共振非线性混合. 这种频率下转换机理并不依赖于在半导体激活媒质中的长时相干假定条件,在室温和泵注入电流条件下仍然有效. 频率下转换的固有效率可以达到相当于每个可见光子产生一个红外光子的量子极限值. 根据红外发射的可参变特性,这种非粒子反转的方法尤其适用于长波红外工作范围.     

海洋油气田工程设施可视化查询系统

随着信息技术的发展,对基于数据库式的信息系统提出了更高的要求,如互联网图形用户界面、电子海图、数据可视化等更具交互性的操作方式。针对这种需求提出了一种新的解决方案：以ION为基础结合ASP技术,采用目前流行的三层Browser／Server体系结构。其中,ION可实现电子海图的可视化,而ASP可实现动态查询功能．     

基于LabVIEW的深水网箱鱼群监测系统的信号处理

深水网箱鱼群活动状态的实时监测是开展深水网箱渔业资源可持续发展中急需解决的关键技术。文中介绍了深水网箱鱼群监测系统中基于LabVIEW的数据信号处理方法。该方法采用软件编程技术取代传统的硬件电路设计,实现了深水网箱鱼群监测系统的时间增益补偿、信号相关处理、图像处理和鱼群量估计等功能,海上现场实验证明系统具有较高的抗噪声和混响干扰能力,鱼群回波图像显示简洁、海上操作方便,采用鱼群回波能量积分方法能较好地估计鱼群量大小。     

翡翠贻贝足丝器的组织结构观察

用光镜和电镜技术初步探讨了翡翠贻贝Ｐｅｒｎａｖｉｒｉｄｉｓ足丝器（Ｂｙｓｓａｌａｐｐｒａｔｕｓ）的三大组成部分之间的空间结构关系，着重观察足丝柄部发生器（ＢＳＧ）的片层结构，揭示小片具有典型的胶原原纤维电镜特征。此外，通过足丝丝部的表面结构观察，发现可用众多的突起来解释足丝表面对放射性碘的强机械吸附作用；利用足丝丝部横切片，计算出其长径约１０５μｍ，短径约４０μｍ。     

The complex dielectric constant of snow at microwave frequencies

The complex dielectric constant of snow has been measured at microwave frequencies. New and old snow at different stages of metamorphosis have been studied. The results indicate that the complex dielectric constant is practically independent of the structure of snow. For dry snow, the dielectric constant is determined by the density. For wet snow, the imaginary part and the increase of the real part due to liquid water have the same volumetric wetness dependence. The frequency dependence of the complex dielectric constant of wet snow is the same as that of water. A nomograph for determining the density and wetness of wet snow from its dielectric constant is given. A snow sensor for field measurement of the dielectric constant has been developed. It can be used for determining the density and the wetness of snow by a single measurement.     

基于电子鼻和HS-SPME-GC-MS方法研究 海水中七氯的快速检测技术

为了建立海水中有机氯农药的快速检测技术, 本文基于电子鼻和顶空固相微萃取气质联用法(HS-SPME-GC-MS)对海水中的七氯进行检测。结果表明, 电子鼻可以识别海水中的挥发性七氯成分及浓度, 最低检测限0.01mg/L。利用线性判别分析方法(LDA)的累计判别贡献率和欧氏距离、判别函数法、相关性对未知样品的识别率均达到了80%以上, 具有良好的区分效果; PLS模型预测七氯浓度跟实际值之间的相对误差在0.49%—16%之间。HS-SPME-GC-MS检测浓度小于0.10mg/L时, 相对误差在10%左右; 而大于此浓度时, 相对误差随之增大。检测到的主要挥发性物质基本呈现规律性的变化, 与电子鼻确认结果一致。对比两种检测技术, 发现电子鼻检测方法比HS-SPME-GC-MS更迅速、灵敏, 检测限更低, 相对误差也更小, 仪器便携、投资相对较小。     

基于电子经纬仪的子午线基准测量方法

针对导航实验室内部子午线基准的测量,提出利用电子经纬仪和授时GPS组合使用,构成一套自主式测量系统。在北极星任意时角法的基础上,重点对测量系统的组成和工作原理进行介绍,并对测量精度进行了分析。实验结果证明,测量精度为1.9″,满足使用要求。     

High-resolution well-log derived dielectric properties of gas-hydrate-bearing sediments, Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

A dielectric logging tool, electromagnetic propagation tool (EPT), was deployed in 2007 in the BPXA-DOE-USGS Mount Elbert Gas Hydrate Stratigraphic Test Well (Mount Elbert Well), North Slope, Alaska. The measured dielectric properties in the Mount Elbert well, combined with density log measurements, result in a vertical high-resolution (cm-scale) estimate of gas hydrate saturation. Two hydrate-bearing sand reservoirs about 20 m thick were identified using the EPT log and exhibited gas-hydrate saturation estimates ranging from 45% to 85%. In hydrate-bearing zones where variation of hole size and oil-based mud invasion are minimal, EPT-based gas hydrate saturation estimates on average agree well with lower vertical resolution estimates from the nuclear magnetic resonance logs; however, saturation and porosity estimates based on EPT logs are not reliable in intervals with substantial variations in borehole diameter and oil-based invasion.EPT log interpretation reveals many thin-bedded layers at various depths, both above and below the thick continuous hydrate occurrences, which range from 30-cm to about 1-m thick. Such thin layers are not indicated in other well logs, or from the visual observation of core, with the exception of the image log recorded by the oil-base microimager. We also observe that EPT dielectric measurements can be used to accurately detect fine-scale changes in lithology and pore fluid properties of hydrate-bearing sediments where variation of hole size is minimal. EPT measurements may thus provide high-resolution in-situ hydrate saturation estimates for comparison and calibration with laboratory analysis.     

海水COD测量仪中光电测量单元技术研究

论文对海水COD测量仪中的光电测量技术作了全面介绍,内容包括：光谱特性的测量和测量波长的确定方法;光电器件的灵敏度、信噪比以及光源和光电探测器的选取。     

Effect of electrode contact impedance on A.C. electrical properties of a wet hematite sample

Electrode polarization is a major problem in the determination of dielectric properties of samples, particularly at low frequencies. Understanding of these interfacial phenomena is essential in order to measure correctly the electrical properties of a sample of interest. This paper presents a comparative study of the effect of electrode contact impedance on A.C. electrical properties of a partially and fully saturated hematitic sandstone sample. The electrical properties of the sample were first measured using stainless steel electrodes with high contact impedance, and measured again with a four terminal Cu–CuSO₄ electrode of low contact impedance. Complex impedance measurements at room temperature (~16°C) were performed in the frequency range from 1 Hz to 100 kHz. Measured electrical spectra vary strongly with the electrode type. The difference in the electrical properties between the two electrode types (stainless steel and Cu–CuSO₄) may be attributed to the surface contact impedance between the sample and the electrode. Experimental data indicate that the electrical properties vary strongly with water saturation. The dielectric constant decreases with frequency and increases with saturation up to a certain saturation limit then decreases. Charge transport can occur either through the bulk of the solid matrix (hematite or sand) or along the grain boundaries of aggregates (water). When soil minerals are exposed to water, exchangeable ions go into solution. Most of the ionic or covalent bonded rock forming minerals such as quartz, mica, and feldspars are nonconductors. When the surfaces of these minerals come into contact with liquid water, electrolytes are formed and ionic drift associated with the electrical field causes electrical conduction. The anomalous dielectric properties of partially saturated rocks can be interpreted using percolation theory. This theory predicts that when the conductive fraction (water) increases, clustering of conductive inclusions develops, and the thickness of insulating gaps between conductive clusters decreases, causing a large increment in the capacitance of the sample. Further increases in the conductive component causes the shunting of insulating capacitive gaps.