Method of determination of emission properties of very weakly emitting species ensuring elimination of emission of impurities

This paper describes a new type of spectrofluorimeter, composed of a high-performance liquid chromatography (HPLC) system directly connected to a fluorescence detector and an absorption photodiode array detector, designed for studying the emission of weakly emitting species. Procedures for measurements of emission spectra (ES), emission excitation spectra (EES), and quantum yields of emission (PhiE) for very weakly emitting systems (PhiE>or=10(-7)) have been proposed. The original methodical solution allows verification of whether the emission observed comes solely from the compound studied (and not from its impurities) or from some photochemical or thermal process taking place during measurements. Thanks to the use of this new type of spectrofluorimeter, it is possible to establish with a high probability that the dependence of the shape and position of the ES on the excitation wavelength and the differences between EES and absorptance spectra are due to photophysical and/or photochemical properties of the compound studied and not due to the presence of emitting impurities. An especially interesting application of this method is to study the emission of species whose very weak emission is related to a very short lifetime as well as a low radiative rate constant. It is particularly suitable to the study of the emission properties of flexible molecules that can occur in a few conformers of different absorption and emission properties. The performance of the method is illustrated by the results of the emission studies carried out for Nalpha-acetyl-2-(uracil-5-yl)-L-tryptophan N-ethylamide.     

An investigation of the stability of numerical solutions of the equations of viscoelasticity

In this paper the correspondence principle is used to reduce the equations of viscoelasticity to the equations of elasticity by means of a Laplace transform. The finite element technique is used to approximate these equations in Laplace transform space. The approximating equations are then inverted to obtain a set of simultaneous Volterra integral equations. It is then shown how the introduction of certain auxiliary variables can be used to develop an integration scheme which considerably reduces computer storage requirements. The conditions under which this integration scheme is conditionally stable and unconditionally stable are both investigated and illustrated by means of examples.     

用多齿分度台检定经纬仪竖盘测角的不确定度评定

本文着重介绍了用多齿分度台作为基准经纬仪检定装置的结构，它由多齿分度台和平行光管作为角度标准器，模拟经纬仪使用环境进行检定；还介绍了该装置检定经纬仪竖盘的使用方法，分析了该装置经纬仪竖直方向测角不确定度组成和经纬仪一测回竖直角标准偏差不确定度组成，并对检定经纬仪竖盘的测角和一测回标准差两项检定的不确定度分量进行合成和扩展，得出符合检定规程的要求的结论。     

Assessment of the cause of cracking of hydraulic hose clamps

The aim of this study was to determine the cause of failure of the shells of hydraulic hose crimped fittings. For the purpose of examination the damaged crimped shells, undamaged crimped shells and shells prior to crimping were used. Fractographic and metallographic analysis, including chemical microanalysis of inclusions, were performed to determine the cause of failure. For this investigation, optical and scanning electron microscopes and hardness measurement were used. Damaged crimped shells contained higher amount of inclusions compared to undamaged crimped shells and substantially differed in microstructure and hardness. Furthermore, different geometry of the cross section at outer edge containing more effective stress concentrators was observed on failed crimped shells. Based on microstructural observation in cross section, hardness measurements and analysis of inclusions, the conclusion is that cracking of the shells occurred mainly due to deviations in the manufacturing process, combined with lower quality of shell material. Modifications to the technology were suggested to prevent this kind of failure.     

中国传统工艺振兴语境下的工匠精神

目的针对目前国家大力保护非物质文化遗产、倡导传统工艺振兴的语境下,如何传承和发扬好工匠精神,以促进当前我国非遗的保护和传统手工艺的传承与发展。方法以文献考据的方式,详细论述我国历史上不同时期关于工匠和工匠精神的解读,从古代"工"或"匠"到现代"大师"的演变,以及数千年来我国工艺文化传统所凝结成的大匠气度和大师境界,即将技艺臻于极致,将作品琢至完美的"工于技艺,匠心独运"的当代工匠精神。结论传承和发扬工匠精神须从政府加强指导、社会全力推崇、艺人珍视声誉等几方面形成合力,从而推动我国传统工艺行业的健康发展。     

一起空分设备主换热器过冷故障的分析

在KDON-6000/3500型空分设备调试过程中,由于经验不足、操作不当,造成主换热器发生过冷故障。停运一台膨胀机,采用液氧返充操作使空分设备恢复正常工况。介绍故障发生经过和原因分析过程,以及防止同类故障再次发生的预防措施。     

Inverse Problem of Evaluation of the Coefficient of Friction of Layers According to the Data of Measurements of the Surface Displacements

We consider a one-dimensional model of friction contact of two layers of different nature. The lower surface of the first layer is elastically fixed and the second layer is pressed to the upper surface of the first layer and moves along this surface with variable velocity. As a result of friction, heat is produced on the contact surface according to the Amonton's law. For known boundary and initial conditions, we pose the problem of evaluation of the friction coefficient and the intensity of friction heat flux according to given values of the vertical displacements of the upper surface of the second layer. The posed problem is reduced to the inverse contact problem of thermoelasticity described by the Volterra integral equation of the first kind. The solution of the problem obtained by the method of averaging of functional corrections enables us to study the time behavior of the indicated quantities for the entire period of interaction of the bodies and establish the dependence of the friction coefficient on the basic parameters of the process (sliding velocity, contact pressure, and temperature of the contact surface). The solution of the direct contact problem of thermoelasticity is used to perform the numerical verification of the proposed method for the solution of the inverse problem.     

Analysis of the effect of pressure on compression moulding of UHMWPE

Ultra-high molecular weight polyethylene (UHMWPE) powder is effectively processed by compression moulding due to its very high melt viscosity. Compression moulding involves application of temperature and pressure as a function of time. The pressure applied during processing has a significant influence on the part properties. The effect of pressure applied during compression moulding was studied by moulding parts at different pressures. Increase in the applied pressure causes increase in the melting and recrystallization temperatures. An increase in the pressure applied at the melt temperature (140°C) from 7.8 MPa to 15.6 MPa caused the crystallinity to increase from 54% to 61%, the stiffness of the moulded part to increase from 257 MPa to 435 MPa and oxidative index to increase from 0.055 to 0.059. Further increase in the pressure applied at the melt to 23 MPa caused the crystallinity to fall to 49%, the modulus to reduce significantly to 302 MPa and the oxidative index to change to 0.063. Increase in the pressure applied at the recrystallization temperature (91°C) from 38 MPa to 78 MPa increased the crystallinity from 54% to 65%, increased the modulus from 257 MPa to 279 MPa and increased the oxidative index from 0.055 to 0.065. Further increase in the applied pressure to 97 MPa, caused the crystallinity to drop slightly to 61% the modulus to reduce to 269 MPa, and the oxidative index to reduce to 0.057. The experiments showed that for obtaining maximum crystallinity and stiffness, the applied pressure should be within a narrow range. The highest recrystallization pressure (97 MPa) indicated the formation of extended-chain crystals in addition to the chain-folded crystals. The change in pressure applied at the melt temperature had a significantly greater effect on Young's modulus, as compared to change in pressure applied at the recrystallization temperature. Fourier transform–infrared spectroscopy analysis of the samples moulded at different pressures revealed that the increase in crystallinity and stiffness was accompanied by increase in oxidation within the part. By filling the die in a nitrogen atmosphere instead of air, the oxidation level in the moulded parts was reduced by almost 60%, without adversely affecting the crystallinity and the modulus. © 1998 Chapman & Hall     

聚丁内酰胺的生物降解性研究进展

目的 介绍聚丁内酰胺(Polybutyrolactam,PA4)的生物降解性研究现状,综述聚丁内酰胺及其衍生物在海洋、土壤、堆肥等自然环境中的生物降解速率及降解机制,为聚丁内酰胺的改性和应用研究提供指导.方法 采用分类总结的方法,对比聚丁内酰胺及其衍生物在不同环境下的降解行为,阐述目前关于其降解机制的研究进展.结论 聚丁内酰胺可在自然环境中短期内降解,其优异的生物降解性与亲水性有关,同时自然环境中长期存在的某些菌群能够分泌胞外酶水解酰胺键,使得聚丁内酰胺可在自然环境中快速降解.结构改性对聚丁内酰胺的降解速率具有一定影响,探究聚丁内酰胺改性后生物降解性的变化,有助于开拓控制其降解速率的新思路.聚丁内酰胺具有极高的气体阻隔性和出色的力学性能,未来作为可降解材料在食品包装方面应用具有极高的应用前景,通过合适的改性手段实现PA4热塑加工,并保留PA4良好的生物降解性,明确环境微生物对PA4及其改性产物的代谢和降解途径,也是未来研究的难点和热点.     

Effect of addition of carbon on magnetic properties of sputter-deposited CoCr film

The addition of carbon changes Ms, Hkeff and Hc(perp) of sputter-deposited CoCr films: Ms is always increased, while Hkeff and Hc(perp) are either increased or decreased by the addition of up to 0.32 at% carbon. How the substrate temperature and the Cr content in the film influence the effect of added carbon is investigated. Higher substrate temperature tends to stimulate the increase in Ms caused by the addition of carbon. A higher substrate temperature and higher Cr content tend to stimulate the increase in Hkeff and Hc(perp) and to prevent the decrease in Hkeff and Hc(perp) caused by the addition of carbon. The increase in Ms with the addition of carbon seems to be caused by an increase in the degree of compositional segregation. The increase and decrease in Hkeff may be attributed to an increase and decrease in Ku, respectively. The increase in Hc(perp) caused by the addition of carbon is probably due to the increase in Ku and/or to the refinement of the magnetic domain. The decrease in Hc(perp) may be attributed to the decrease in Ku even though the magnetic domain is refined.     

Possibilities of Decreasing the Errors of Determination of the Height of the Pole of a Sessile Drop of Melt

We analyze the possibilities of decreasing the errors of measuring the height of the pole of a sessile drop of melt above its equator by determining the position of the equator according to the midpoints of vertical chords of the image of the drop. The optimal distance between these chords and the edge of the image of the drop is chosen within 10–20% of the radius of the equator. The proposed method guarantees the same level of errors of evaluation of the height of the pole and the radius of the equator, which enables one to substantially increase the accuracy of evaluation of the capillary constant and the surface energy of the melt according to the geometric parameters of the sessile drop.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

The accuracy of calculation of orbits of best approach

A new formulation and solution of the problem of calculation of orbits of best approach is discussed. A qualitatively analytical approach to the organization of observations of the motion of artificial Earth satellites is used that makes it possible to calculate and to allow for optimal celestial-mechanics conditions, and to eliminate the effect of systematic observation errors, the effect of the Earth's gravitational field, and other regular perturbations on the solution accuracy.Translated from Izmeritel'naya Tekhnika, No. 6, pp. 28–29, June, 1993.     

Method of Solution of a System of Equations Describing the Continuous Process of Polymerization under Conditions of a Polyaddition Reaction

A method of solution of a system of equations which describe the continuous process of polymerization of butadiene on a cobalt catalyst accompanied by the polyaddition reaction is proposed. The moments of second and third orders as functions of the distribution of macromolecules by the degree of polymerization and the number of active centers in each reactor are compared. The values of the conversion of a monomer for which the moments go to infinity (which means gelation in the reactor) are determined. The solution is based on the replacement of variables which made it possible to reduce the equation of the fourth degree for the moments to a quadratic equation and to single out the branch corresponding to the actual process. The algebraic transformations and calculation were carried out with the use of the Matematika 3.0 package.     

Comparison of relative signal-to-noise ratios of different classes of imaging spectrometer

The continued development of new and fundamentally different classes of imaging spectrometer has increased both the scope and the complexity of comparisons of their relative signal-to-noise ratios. Although the throughput and multiplex advantages of Fourier-transform spectrometers were established in the early 1950s, the application of this terminology to imaging spectrometers is often ambiguous and has led to some confusion and debate. For comparisons of signal-collection abilities to be useful to a system designer, they must be based on identical requirements and constraints. We present unambiguous definitions of terminology for application to imaging spectrometers and comparisons of signal-collection abilities and signal-to-noise-ratios on a basis that is useful to a systems designer and inclusive of six fundamentally different classes (both traditional and novel) of imaging spectrometers.     

东盟国家技术标准特点与我国的出口贸易对策

本文从顺应中国-东盟自贸区建成需要的角度,对东盟国家技术标准的特点进行了分析,对中国产品出口东盟在技术性贸易措施上应采取的对策进行了探讨,为促进中国-东盟贸易的发展提供标准技术支撑。     

Analaysis of failures encountered during rolling of rings of maraging steel

Large‐sized rings of maraging steel X 2 NiCoMo 18 8 5 (Werkstoff Nr. 1.6359) find application in aerospace. The rings are required to demonstrate high strength and fracture toughness in both radial and axial directions. The processing is accordingly carried out under controlled conditions to realize a microstructure capable of attaining the specified strength and toughness after heat treatment. The rings rolled during initial trials failed to attain the required fracture toughness. Precipitation of carbonitrides at prior austenitic grain (PAG) boundaries in the temperature range 820–980 ^oC contributed to the failure. Efforts were made to do final rolling through this temperature range, to prevent a microstructure comprising of PAG boundaries decorated by carbonitrides from evolving. To this end relatively low preheating temperatures (1100–1150 ^oC) were adopted. Failures were encountered in realizing the desired final size and shape of the rings. The mill tripped before the ring rolling could be completed. Failure was analyzed and it was concluded that the problem was due to the high flow stress levels encountered during ring rolling and the relatively low radial loads the mill was capable of delivering.     

奇正思想对赫哲族旅游产品包装图案设计的启示

目的赫哲族图案是一种既历史悠久又具有深厚文化的艺术形式,将孙子兵法中的奇正思想应用到赫哲族旅游纪念品包装图案设计当中,使得赫哲族图案被更多的人认识和关注,并为创建和完备我国少数民族传统图案设计发展提供有效途径。方法深入挖掘奇正思想的内涵,力图从奇正思想内涵中找出适合赫哲族旅游产品包装图案设计的观点,获得赫哲族旅游产品包装图案设计的可持续发展途径。结论发现了奇正思想与赫哲族旅游产品包装图案设计的结合点,为赫哲族传统图案设计的发展寻求有效途径,增强少数民族传统图案文化的影响力和传播力,使其获得一种由低到高的传承发展能力。