On the working time budget of the university teacher

Results of a self-observation of the working time distribution of an university teacher for a period of 28 years are reported. Averaged over the whole period, the teaching activities take 18%, scientific work −20%, and the various kinds of administrative, organizational and technical activities −51% of the working time. The changes of the working time distribution and of the working day duration during the years and the respective data related to the months in the year are presented. The working time data are compared with the growth of the scientific production of the observed person.     

An interactive multi-objective algorithm for decentralized decision making in product design

To remain competitive and gain new shares of the market, industries must develop their products quickly while meeting the multiple customer requirements. To reduce product development time, the design step is often accomplished by several working groups working in parallel. These working groups are often decentralized and are supervised by a director. This paper focuses on solving a multi-objective problem in a setting that is called a “decentralized environment.” Collaborative optimization is a strategy used for solving problems in a decentralized environment. This strategy divides a problem into subproblems in order to give more autonomy to working groups, thus facilitating work in parallel. In this paper, collaborative optimization is paired with an interactive algorithm to solve multi-objective problems in a decentralized environment. It can be easily adjusted within the structure of a development process in a given industry and allows collaboration between the director and his/her working groups. The algorithm captures the director’s and the working groups’ preferences and generates several Pareto-optimal solutions. The algorithm was tested on a two-bar structure problem. The results obtained match those published in the literature.     

Effect of different working gases on the performance of a small thermoacoustic Stirling engine

The performance of a small thermoacoustic Stirling heat engine (TASHE) was investigated with three kinds of working gases experimentally and numerically. The examined performances focused on the operating frequency, onset temperature, pressure amplitude and some temperature characteristics after onset. The working frequency with nitrogen, argon and helium as the working gas was 45 Hz, 42 Hz and 130 Hz, respectively. The engine worked with helium in a much wider range of mean pressure than with nitrogen and argon. There was an optimal mean pressure for the minimum onset temperature for each working media. Using nitrogen and argon as working gas rather than helium, another optimal mean pressure for the highest pressure ratio was obtained in the experiment. The loop dimension was indispensable in determining the frequency and the highest pressure ratio was observed in the resonator cavity.     

Test and simulation of a solar powered solid sorption cooling machine

At the Institut für Thermodynamik und Wärmetechnik (ITW) a solar powered cooling machine with no moving parts has been built for demonstration purposes. The main part of the device is an absorber/desorber unit which is mounted inside a concentrating solar collector. The heat of absorption is transported out of the solar collector by means of two horizontally working heatpipes. The working pair consists of NH₃ used as the refrigerant and SrCl₂ as the absorbing medium. The performance of the solar refrigeration unit was measured in a field test.The working principle of a discontinuously working, solid sorption cooling machine will be explained using the demonstration machine as an example. Results obtained from a field test performed in 1995 are presented and discussed. Furthermore, a simulation program for the numerical simulation of a solar powered solid sorption cooling machine has been developed and tested.Finally, to confirm a problem-free continuous operation of a solid sorption system, a long term study over 14 months was carried out using NH₃/SrCl₂ as the working pair.     

Electrical and optical properties of ZnO:Al thin films grown by magnetron sputtering

The properties of transparent conductive ZnO:Al thin films grown by R.F. magnetron sputtering method are investigated. The working pressure (argon gas) is changed from 2.5 to 40.0 mTorr to study its influence on the characteristics of ZnO:Al thin films. The ZnO:Al thin films have better texture due to the increase in the surface mobility, which resulted from the increase in the mean free path of sputtering gas under lower working pressure. The microstructure of ZnO:Al films is found to be affected obviously by changing the working pressure. It is shown that the grain size of ZnO:Al thin films decreases with the increase of working pressure. The X-ray diffraction patterns indicate that the poor crystallized structure of ZnO:Al films is obtained at higher working pressure. Except 40 mTorr, the highly (002)-oriented ZnO:Al thin films can be found at the measured range of working pressure. Moreover, the growth rate of the films decreases from 1.5 to 0.5 nm/min as the working pressure increases from 2.5 to 40.0 mTorr. The results of optical transmittance measurement of ZnO:Al thin films reveal a high transmittance (>80%) in visible region and exhibit a sharp absorption edge at wavelength about 350 nm.     

Fabrication strain rate-stress corrosion property correlations of thermomechanically treated 15Cr-15Ni-2-2Mo titanium modified austenitic stainless steel

Abstract

A 15Cr-15Ni-2.2Mo titanium modified austenitic stainless steel was thermomechanically worked to a strain of 30% in a single stage at temperatures between 873 and 1473 K and at strain rates of 0.15, 1.0, and 100S^-l. These strain rates were obtained by working the alloy in a hydraulic press, a rolling mill, and aforge hammer, respectively. At all strain rates, the yield strength (YS) increased while ductility and stress corrosion cracking (SCC) resistance significantly decreased on thermomechanically working the solution annealed alloy at temperatures below 1173 K. Thereafter, the YS decreased and ductility along with SCC resistance increased substantially towards valuesfor the solution annealed alloy on thermomechanical treatment at and above 1273 K. The highest ductility was obtained on working the alloy at a strain rate of less than 1.0 S^-l. However, the best SCC resistance was obtained on working the material at the highest strain rate of l00 S^-l. The improvement in SCC resistance has been attributed to the finer grain size obtained on working the alloy at higher strain rates. Fractographic examination indicated failure by transgranular SCC. The size ofthefan shaped patterns increased with increasing temperature of working, and decreased with increasing strain rate offabrication.     

Investigation of optical and electrical properties of ZnO thin films

Zinc oxide (ZnO) thin films were deposited on Si substrates using various working pressures by magnetron sputter. The resistivity of the deposited ZnO films decreases with working pressure, and the resistivity of 4.3 × 10⁻³ Ω cm can be obtained without post annealing. According to the optical transmittance measurements, the optical transmittance above 90% in the wavelength longer than 430 nm and about 80% in the wavelength of 380 nm can be found. Using time-resolved photoluminescence measurement, the carrier lifetime increases with working pressure due to the reduction of nonradiative recombination rate. The reduction of nonradiative recombination rate is originated from the decrease of oxygen vacancies in the ZnO films deposited at a higher working pressure. This result is verified by the photoluminescence measurements. Besides, by increasing the working pressure, the absorption coefficient was decreased and the associated optical energy gap of ZnO thin films was increased.     

综采对拉工作面回采期间治水管理探讨

综采工作面回采期间老塘水[1]流至工作面,影响煤质,加速刮板输送机等机电设备老化,严重影响工作面文明施工,同时给安全生产带来很大的隐患,2703综采对拉工作面实施“五项并举治水方法”大大降低工作面水害对煤流系统不利影响,节省了财力,在很大程度上改善了作业环境,保证了工作面安全生产。     

Simulation of ternary ammonia–water–salt absorption refrigeration cyclesSimulation des cycles frigorifiques à absorption à ammoniac / eau / sel

This paper proposes a new working fluid for refrigeration cycles utilizing low temperature heat sources. The proposed working fluid consists of the ammonia–water working fluid mixture and a salt. The salt is used to aid the removal of ammonia from the liquid solution. This effect is a manifestation of the well known “salting-out” effect. While the addition of salt improves the generator performance, it also has a detrimental effect on the absorber. The overall effects on the performance of three absorption cycles using the NH₃–H₂O–NaOH working fluid have been investigated using computer simulations. The results indicated that salting out can lower the generator operating temperature while simultaneously improving the cycle performance. Furthermore, limiting the salt to the generator suggests potential for further improvement in cycle performance.     

A study of the differences and characteristics between the nations,in the measured values of the human body and the working area

This paper deals with: (1) measuring 61 body features of Koreans; (2) comparing the dimensions of body features among the nations; (3) constructing the working area of a Korean from the measured data; (4) comparing working areas among the nations. Some physical characteristics and variations in body features and in working areas are discussed.     

Selection of parameters for testing magnetic properties of permanent magnets

Conclusions The testing of the parameters B_r, H_c, B_d, and H_d does not always provide an unambiguous estimation of whether the PM whose working point lies on the regression line is suitable for utilization in a magnetic system.The evaluation of the PM efficiency by means of the induction at the working regressionline departure point and the induction at the intersection point of the working regression line with the conductance line corresponding to the condition of the magnet in an assembled product is more efficient and universal, since it is virtually independent of the working regression-line departure-point position and it serves to halve the number of tested parameters.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 49–50, February, 1979.     

Study on corrosion resistance of aluminium coating deposited on magnesium-zinc-yttrium-calcium alloy by cold spray

Pure aluminium coatings were prepared on magnesium-zinc-yttrium-calcium alloy substrate via cold spraying technology with different scanning speeds and working gas temperature. The correlation between the corrosion resistance of the coatings and the different spraying process was studied. While the working gas temperature is 600 °C and the scanning speed is 1 mm/s, aluminium coating has less porosity and the coating was well combined with the substrate. Higher temperature of working gas increases the plastic deformation of particles, which lead to a dense aluminium coating. The relationship of corrosion resistance on working gas temperature and scanning speed of aluminium coatings has also been investigated by immersion corrosion test and electrochemical impedance spectroscopic techniques. The results show that the cold sprayed aluminium coatings revealed a lower porosity and higher corrosion resistance with the decreasing scanning speed and the increasing temperature of working gas. The porosity and corrosion current densities were 0.938 vol.% and 2.427 ⋅ 10⁻⁶ A/cm². The experimental results show that the aluminium coating prepared by cold spraying has a good protective effect on magnesium alloy.     

Influence of the thickness of a working layer on properties of hot-forged powder layered composites

Results of investigations of main physicomechanical and tribological properties of hot-forged layered powder composites based on Kh18N15 corrosion-resistant steel are presented. We use a powder composite of Kh18N15 steel with 25 mass % of Cr₃C₂ and 5 mass % of MoS₂ as a working layer and the same steel with 0.6 mass % of carbon as a base material. It is established that the bending strength of the obtained materials depends substantially on the thickness of the working layer, whereas the hardness of the working layer barely depends on it.     

Thermodynamic and numerical analysis of intake air humidification of a turbocharged GDI engine

Reducing the temperature and increasing the specific heat capacity of working medium of gasoline engines are the most efficient methods of mitigating knock tendency. The charge cooling effect of intake air humidification is helpful for decreasing the initial temperature of intake air, and the increase of the specific heat capacity of working medium can reduce the temperature rise in the in-cylinder process. This study established a mathematical model of intake air humidification of gasoline engines, and analyzed the effects of the technique on the thermodynamic process of a turbocharged gasoline engine with Ricardo WAVE Code. The results indicated that the intake air humidification is an isenthalpic process; the vapor influences the working process of the engine by altering the thermodynamic parameters of the working medium. A decrease in the initial temperature and adiabatic index and an increase in the specific heat capacity of working medium lowered the in-cylinder temperature and pressure, hence suppressing the knock occurrence. After the humidification of intake air, the engine performance slightly increased, and the thermal efficiency showed different levels of improvements at all the working conditions.     

Estimation of differential heat of dilution for aqueous lithium (bromide,iodide, nitrate,chloride) solution and aqueous (lithium,potassium, sodium) nitrate solution used in absorption cooling systems

The differential heat of dilution data are estimated theoretically using Duhring's diagrams for water/LiBr, water/(LiBr + LiI + LiNO₃ + LiCl) with mass compositions in salts of 60.16%, 9.55%, 18.54% and 11.75%, respectively, and water/(LiNO₃ + KNO₃ + NaNO₃) with mass compositions in salts of 53%, 28% and 19%, respectively, as these can be potentially utilized as working fluids in absorption cooling systems. The differential heat of dilution data obtained were correlated with simple polynomial equations for the three working fluids as a function of the solution concentration and temperature. The results showed that the differential heat of dilution of the non-conventional working fluid mixtures is lower than that of water/LiBr at typical operating temperature and concentration of interest in absorption cooling cycles employing these working fluid mixtures. The correlations developed could be useful in predicting the differential heat of dilution value while performing heat and mass transfer analyses of these potential non-conventional working fluid mixtures in absorption cooling systems.     

Human-autonomy teaming in military settings

ABSTRACT

In this Thematic Issue ‘Human-Autonomy Teaming’ of Theoretical Issues in Ergonomics Science, five U.S. military-funded research efforts are presented to discuss human factors issues in a variety of military human-autonomy teaming mission environments: dismounted infantry working with a small ground robot; intelligence analysis; human working with an intelligent agent to manage a team of heterogeneous unmanned vehicles; vehicle-mounted ground penetrating radar. The research issues addressed in this Issue are diverse – from display designs to operator performance and trust in the systems. The results and insights documented in these five articles should provide useful resources to researchers and practitioners working on intelligent and autonomous systems.     

Stability of residual stresses in surface layers of pump rods during use

Summary A combined method of surface strengthening has been devised for pump shafts, which involves producing compressive residual stresses in the surface by means of shot-blast working with the subsequent deposition of metallization and polymer coatings.When a pump rod has operated for three years in a borehole, the compressive residual stresses provided by the combined treatment are substantially redistributed and change sign. In such cases, there is a reduction in the resistance to corrosive fatigue failure. To improve the working life of pump shafts working in boreholes, repeat hardening is required periodically.Translated from Fiziko-Khimicheskaya Mekhanika Marerialov, Vol. 26, No. 3, pp. 120–122, May–June, 1990.     

Replanning working time under annualised working hours

Using annualised hours (i.e., distributing working hours irregularly over a year) grants a company the flexibility needed to meet the seasonal nature of demand. Since annualised hours can lead to a worsening of the staff's working conditions, many laws and collective bargaining agreements contain constraints that affect the distribution of working time. In the past few years, efforts have been made to develop methods for optimally solving planning problems involving annualised working hours. However, to our knowledge, the problem of replanning work time with annualised working hours has not been addressed in the literature. Herein, we explore different ways of achieving said replanning, using mixed-integer linear programming models. Two main objectives are considered: the cost of the new plan and the stability of the scheduling of workers’ working time. Solving the models for various scenarios yields the quantitative information that is needed to replan an annualised hours system.     

带窄凸缘圆筒形零件的整形

通过对药盒整形工艺进行了分析,介绍了工艺计算方法、模具结构及工作过程,同时,对模具主要工作部分零件的设计做了介绍,给出了生产中注意的问题。     

基于人机工程学的堆高车造型设计

目的针对当前国内堆高车存在的操作安全隐患,为仓管作业人员设计出更为合理、安全、舒适的机械化装载设备,使作业人员在保障自身安全的前提下更好地提高工作效率。方法根据搜集整理国内外对堆高车的研究与分析,分析了堆高车的发展现状,在人机工程学设计理念的基础指导下,以堆高车的外观造型设计为研究对象进行创新设计,为仓管作业人员提供更具有保障性、功能性、舒适性和可操作性的车辆装载机械设备。结论对堆高车进行外观及驾驶室结构的设计改良,使其符合人机工程学的尺寸设计,在有效提高工作效率的同时提升作业的安全性,从而提升并改善操作者工作环境的舒适度,大大降低了机械设备对人体的损害。