进口螺旋国产部件的研制

介绍了进口螺旋的结构特点 ,阐述了对进口螺旋部件进行测绘和计算的方法 ,并对测绘数据的正确性作出了论证 ,最后总结了国产部件的优点     

Distribution of trace metals in a ling (Genypterus blacodes) fish fillet

The distribution of trace metals in a ling (Genypterus blacodes) fish fillet was determined from ICP-MS measurements of digests prepared using nitric acid and hydrogen peroxide, followed by microwave digestion. Most trace elements were inhomogeneously distributed in the muscle tissue of the ling with a non-linear increase in concentration towards the tail end of the fillet. This distribution pattern may be connected to the size variation of the individual muscle cells or the change in the ratio of connective tissue to muscle tissue, suggesting that the observed inhomogeneity of muscle elemental distribution may be inherent to all fish species. The concentration of an element in a sample of fish muscle tissue thus depends on the physical location within the fish from which the sample was dissected. Significant differences in trace element concentrations were also detected between the red and white muscle fibres of ling, as well as between the belly flap and the rest of the musculature.     

An independent but not identically distributed bit error model for heavy-tailed wireless channels

The error patterns of a wireless channel can be represented by a binary sequence of ones(burst) and zeros(run),which is referred to as a trace.Recent surveys have shown that the run length distribution of a wireless channel is an intrinsically heavy-tailed distribution.Analytical models to characterize such features have to deal with the trade-off between complexity and accuracy.In this paper,we use an independent but not identically distributed(inid) stochastic process to characterize such channel behavior and show how to parameterize the inid bit error model on the basis of a trace.The proposed model has merely two parameters both having intuitive meanings and can be easily figured out from a trace.Compared with chaotic maps,the inid bit error model is simple for practical use but can still be deprived from heavy-tailed distribution in theory.Simulation results demonstrate that the inid model can match the trace,but with fewer parameters.We then propose an improvement on the inid model to capture the ’bursty’ nature of channel errors,described by burst length distribution.Our theoretical analysis is supported by an experimental evaluation.     

Computer Control of the Gilford Model 252-1 Spectrophotometer Modernization System

ABSTRACT

The construction of an interfacing device between a Gilford Model 252-1 Spectrophotometer Modernization System and a Commodore PET microcomputer is described. Modifications to the Gilford automatic cuvette positioner to allow computer control are also described. The program for operation of the modified system is listed. A comparison between computer and manually obtained rates is included.     

定量求解重力谷糙分离机工作面上物料的运动

定量求解重力谷糙分离机工作面上物料的运动较为困难，迄今尚未见有文献报道，但这一问题可采用解析和数值解结合的方法求解。文中详细介绍了具体步骤和实例计算结果。     

Functional magnetic nanoshells integrated nanosensor for trace analysis of environmental uranium contamination

Transuranic radionuclides such as uranium tend to be a pervasive environmental contaminant. It is absorbed through the intestine or a lung, deposited in the tissues, predominantly kidney and bone, and is carcinogenic. A novel nanosensor system has been developed for voltammetric tracing of environmental uranium contamination.The sensor consists of an organophosphorous ligand, (t-butylphenyl)-N,N-di-(isobutyl) carbamoylmethylphosphineoxide (CMPO) functionalized superparamagnetic core-shell magnetic nanoparticles and magnet based electrodes. It exploits the natural affinity of uranium for phosphate molecules to fabricate a highly specific and reproducible sensor. The small dimension along with a dramatically increased contact surface has lead to a faster response and higher sensitivity. The system uses an external magnetic field gradient for preconcentration and removal of the analyte from the surrounding aqueous media. The redox properties of the analyte are exploited for enumeration of variables by electrochemical techniques such as square wave voltammetry. The detection limit of the system is observed to be in parts-per-billion (ppb) of the uranyl concentration.     

Trace metals in cut trough shell (Spisula subtruncata) from Belgian coastal waters

In the period 1985-1996 concentrations of mercury, cadmium, lead, copper, zinc and chromium in cut trough shell (Spisula subtruncata) sampled on 11 stations on the Belgian Continental Shelf were determined. On the whole, contents of trace metals showed a tendency to decrease. No significant differences in concentrations were found between the stations, except on one site for lead and chromium. Average concentrations (all stations) were (in mg/kg wet weight): 0.02 for mercury, 0.08 for cadmium, 0.38 for lead, 2.5 for copper, 12.7 for zinc and 0.47 for chromium. These values were well below legally authorized limits.     

Weight Distribution of the Hermitian Forms Codes

 We recall the construction of the hermitian-forms codes and some results about hermitians forms and exponential sums. With the help of these results, we give the weight distribution of the hermitian-forms codes and give some examples for which experimental computations have been made. Received: September 8, 1993; revised version: October 4, 1995     

SZ36—1—1井碳酸盐质砾岩段的层位归属及成因分析

ＳＺ３６－１－１井碳酸协质砾岩段长期以来被划归东营组。在详细观察并分析岩心，岩屑的基础上，综合运用微体古生物，微量元素，粘土矿物和测井的资料，认为该砾岩段应划归上寒武统，其成因与黔东，湘西地区中，上寒武统碳酸盐重力流砾屑灰岩成因相似，应为深水斜坡上固结程度较差的薄层灰岩在重力作用下，形成具层流特征的粘性碎屑流缓慢进入泥质环境中，成为准同生碳酸盐质砾泥岩或碳酸盐质砾岩。     

用大气压离子质谱法测量高纯氮中的氧

大气压离子质谱（ＡＰＩ－ＭＳ）法以其高灵敏度及特效性，特别适合于分析高纯气体中的痕量物质。我们用ＡＰＩ－ＭＳ法对高纯氮中的痕量氧进行了定量分析，结果表明，测量灵敏度达１×１０－９ｍｏｌ／ｍｏｌ，而测量精度优于±１０％。文中介绍了有关的取样技术及定量方法，并讨论了高纯氮中的Ｈ２Ｏ、ＣＯ２和ＮＯ等含氧化合物对氧含量测量的影响