Analysis of ultrasound-assisted convective heating/cooling process: Development and application of a Nusselt equation

In this study, the convective heating/cooling process assisted by US irradiation is analyzed with the aims of developing a new convective heat transfer correlation. Heat transfer experiments were conducted with different copper machined geometries (cube, sphere and cylinder), fluid velocities (0.93–5.00 × 10⁻³ m/s), temperatures (5–60 °C), and US intensities (0–6913 W/m²) using water as heat transfer fluid. The Nusselt (Nu) equation was obtained by assuming an apparent Nu number in the US-assisted process, expressed as the sum of contributions of the forced convection and cavitation-acoustic streaming effects. The Nu equation was validated with two sets of experiments conducted with a mixture of ethylene glycol and water (1:1 V/V) or a CaCl₂ aqueous solution (30 g/L) as immersion media, achieving a satisfactory reproduction of experimental data, with mean relative deviations of 17.6 and 17.8%, respectively. In addition, a conduction model with source term and the proposed correlation were applied to the analysis of US-accelerated heating kinetics of dry-cured ham reported in literature. Results demonstrated that US improves heating of ham slices because of the increased heat transfer coefficients and the direct absorption of US power by the foodstuff.     

Optimization of Transducer Location for Novel Non-Intrusive Methodologies of Diagnosis in Diesel Engines

The health monitoring has been studied to ensure integrity of design of engine structure by detection, quantification, and prediction of damages. Early detection of faults may allow the downtime of maintenance to be rescheduled, thus preventing sudden shutdown of machines. In cylinder pressure developed, vibrations and noise emissions data provide a rich source of information about condition of engines. Monitoring of vibrations and noise emissions are novel non-intrusive methodologies for which positioning of various transducers are important issue. The presented work shows applicability of these diagnosis methodologies adopted in case of diesel engines. The effects of changing various fuel injection parameters was analyzed. Scope of using non-intrusive technique has been analyzed by changing locations of microphone. Novelty of this worklies in exploring signal processing methods for various locations around the engine test set up. Various frequency ranges of contributing noise and vibration sources were identified. Time-Frequency analysis showed the onset of various cyclic. Based on the identification of various frequency bands, it is possible to device suitable filters in order to extract more information.     

Impact of Multi-Component Surrogates on the Performances,Pollutants, and Exergy of IC Engines

Even though there is a pressing interest in clean energy sources, compression ignition (CI) engines, also called diesel engines, will remain of great importance for transportation sectors as well as for power generation in stationary applications in the foreseeable future. In order to promote applications dealing with complex diesel alternative fuels by facilitating their integration in numerical simulation, this paper targets three objectives. First, generate novel diesel fuel surrogates with more than one component. Here, five surrogates are generated using an advanced chemistry solver and are compared against three mechanisms from the literature. Second, validate the suggested reaction mechanisms (RMs) with experimental data. For this purpose, an engine configuration, which features a reacting spray flow evolving in a direct-injection (DI), single-cylinder, and four-stroke motor, is used. The RNG k-Epsilon coupled to power-law combustion models is applied to describe the complex in-cylinder turbulent reacting flow, while the hybrid Eulerian-Lagrangian Kelvin Helmholtz-Rayleigh Taylor (KH-RT) spray model is employed to capture the spray breakup. Third, highlight the impact of these surrogate fuels on the combustion properties along with the exergy of the engine. The results include distribution of temperature, pressure, heat release rate (HRR), vapor penetration length, and exergy efficiency. The effect of the surrogates on pollutant formation (NOX, CO, CO2) is also highlighted. The fifth surrogate showed 47% exergy efficiency. The fourth surrogate agreed well with the maximum experimental pressure, which equaled 85 Mpa. The first, second, and third surrogates registered 400, 316, and 276 g/kg fuel, respectively, of the total CO mass fraction at the outlet. These quantities were relatively higher compared to the fourth and fifth RMs.     

IMD-MgB2超导线材的研究进展

中心镁扩散技术(IMD)自2003年被Giunchi等人首创以来,国内外学者系统地揭示了Mg与B反应机制,MgB_(2)烧结成相过程及掺杂物的影响;IMD-MgB_(2)线材具有致密的MgB_(2)层,J_(e)远高于同等条件下传统PIT法制备的线材.目前IMD-MgB_(2)百米级线材已被成功制备,为IMD-MgB_(2)超导线材的生产应用奠定了基础.本文首先简要介绍了IMD-MgB_(2)超导线材的发展历程,其次讨论了对线材超导性能影响的相关因素,包括B粉和C掺杂、有效的MgB_(2)层密度、晶粒尺寸、粉末填充系数、线材直径、热处理条件及线材的交流损耗,最后简述了IMD-MgB_(2)超导线材目前存在的技术难题及未来的工作重心.     

定量型多指标决策的层次分析法探讨

本文采用等级标度与层次分析综合的方法对定量型多指标决策问题进行了讨论，它既是层次分析法在定量型多指标决策中的合理推广，同时也为定量型多指标决策问题提供了一种行之有效的方法．     

An economic¯X-chart approach to the joint control of the means of independent quality characteristics

Summary In controlling the mean of a multivariate normally distributed quality characteristic the main disadvantage of the globalT ²-control charts is that they don't indicate the component of the quality characteristic which gives rise to an alarm. To avoid this disadvantage the joint use of¯x-charts is proposed in this paper, where — for the sake of simplicity — the investigations are restricted to the case of independent components and to one-sided¯x-charts. On the basis of an economic objective function an approximation to the optimal design of the¯x-charts procedure is derived and discussed. It turns out that at least in the bivariate case the nearly optimal economic design is very close to the exact solution.Supported by the Deutsche Forschungsgemeinschaft (DFG).     

可编程通用阵列逻辑器件应用技术讲座

本讲座通过介绍专用集成电路(ASIC)入手,简叙可编程逻辑器件(PLD)的原理和结构,从应用角度介绍通用阵列逻辑器件(GAL)的结构和特点,着重阐述PLD的编程技术,最后给出几个PLD器件应用编程实例.     

小型化直流电源发展动态

随着电子整机向小型化、轻量化方向的发展，对整机所用的直流稳压电源也提出了小型化的要求。本文叙述了国外ＤＣ／ＤＣ变换器的研究与开发情况，介绍了国内发展集成化直流稳压电源的现状，分析了国内市场对ＤＣ／ＤＣ变换器的需求。对国内外在该领域的技术水平进行了比较，提出了发展我国小型化直流电源的对策。     

场发射示器矩阵寻址高压驱动电路的设计研究

提出了矩阵寻址方式的场发射驱动电路。设计出16级灰度显示的阴极驱动电路以及栅极驱动电路,并对其进行了性能仿真,仿真结果显示驱动电路性能优越。开发出与0.8μm标准CMOS工艺兼容的高压CMOS工艺,有效提高了驱动电路的集成度,并降低了生产成本。成功研制出用于场发射驱动电路输出端的100 V高低压电平转换电路,实验测得空载情况下电路的上升时间和下降时间分别为35,60 ns,能够满足高压驱动电路的频率要求。     

基于CMOS多功能数字芯片的ESD保护电路设计

基于CSMC 2P2M 0.6 μm CMOS工艺设计了一种ESD保护电路。整体电路采用Hspice和CSMC 2P2M 的0.6 μm CMOS工艺的工艺库(06mixddct02v24)仿真,基于CSMC 2P2M 0.6 μm CMOS工艺完成版图设计,并在一款多功能数字芯片上使用,版图面积为1 mm×1 mm,参与MPW(多项目晶圆)计划流片,流片测试结果表明,芯片满足设计目标。