The onset of Darcy‐Brinkman convection in a porous medium layer with vertical throughflow and variable gravity field effects

In this study, the influence of constant throughflow and varying downward gravity field on the onset of Darcy‐Brinkman convection in a porous medium layer is examined numerically. We considered two cases of gravity field variations: (a) linear and (b) parabolic. A higher‐order Galerkin‐weighted residual technique and QZ procedure are used to get the numerical solution for the entire Darcy numbers amid $\text{Da}=0$ (Horton‐Rogers‐Lapwood convection) and $\text{Da}\to \infty$ (Rayleigh Bénard Convection). It is obtained that the throughflow, the downward gravity field and the Darcy number are to holdup the beginning of convection. It is also obtained that the system is more stable for linear variation of gravity field in comparison to the parabolic variation.     

Effects of addition of different vegetable oils to lactating dairy ewes' diet on meat quality characteristics of suckling lambs reared on the ewes' milk

The effect of different vegetable oils used in the diet of lactating ewes on the meat quality of their suckling lambs has been evaluated. Lambs (males and females) were slaughtered at 11 kg. Fortyeight lactating Churra ewes (prolificacy 1.5) and their suckling lambs were assigned to four treatments according to the oil added (3% on weight basis) to the ewes' daily ration: palm oil as control (CON); olive oil (OLI); soybean oil (SOY); and linseed oil (LIN). Analyses of pH, colour, thiobarbituric acid reactive substances (TBARS), tocopherol levels, volatile compounds and a sensory evaluation were carried out on suckling lambs' meat. Results showed no substantial effect on pH, colour, TBARS and tocopherol levels. Volatiles typically derived from lipid oxidation were higher in SOY group. However, panellists were only able to correctly identify samples from LIN group. Furthermore, the meat from LIN group showed lower scores towards odour and flavour quality and overall liking than that from the rest of treatments.     

采用光反馈控制白光LED的降压稳压器

由于大功率、高效率白光（以及其它颜色）LED的实现,采用LED的照明更受关注（参考文献1）。由于LED是一种电流控制器件,典型控制电路是调节通过LED的电流来保持一致的亮度。为了最好地利用电能,用户经常将开关转换电路用于LED,根据输入直流电压的不同,可以是降压（Buck）或升压转换器。图1是典型的降压和升压转换器白光LED驱动电路的结构。白光LED增加了串接电阻R,     

Geometrical model and experimental evidence for the growth of Ag-doped YBa2Cu3O7?x thin films

The improvement in the properties of laser-ablated Ag-doped YBa₂Cu₃O_7–x (YBCO) thin films in both normal and superconducting states has been interpreted using a growth model. The model is simple and is based on the widely accepted characteristics of Ag such as its flux action at high temperature and nonreactivity with YBCO phase.     

Experimental investigation of top burr formation in high-speed micro-end milling of titanium alloy

ABSTRACT

Superalloys with burr-free parts are most preferably used in biomedical, aerospace, marine and automotive applications. In order to reduce the global pollution content, industries strive to execute stringent green manufacturing technologies. There is a need to investigate the different available tools in high-speed micro-milling process to achieve desired burr free with good surface finish on super alloys without using traditional coolants. In machining of titanium and its alloys, because of low thermal conductivity and reactivity with tool materials instigate the burr formation on work material and lowers the tool performance. The main objective of this article is to investigate the top burr formation in high-speed micro-end milling of alpha + beta-titanium alloy-grade 23 ELI (Ti-6Al-4V) under dry cutting conditions using Uncoated and physical vapor deposition coated AlTiN, TiAlN tungsten carbide end mills. Machining performance of the three cutting tools was compared. From the comparison of cutting tools for machining titanium alloy-grade 23, it is found that coated TiAlN tools produce less burr formation than coated AlTiN and uncoated tungsten carbide tools.     

Fiber-optic liquid level sensor based on coupling optical path length variation

The concept for a new and simple fiber-optic liquid level sensor is presented and experimental results are shown to demonstrate the principle. The sensing principle is based on light intensity modulation when rising and falling mode of liquid level causes coupling optical path distance variation between two optical fibers. Near continuous mode of liquid level variation could be monitored with resolution as low as 1 mm can be measured in the length scale of 25 cm.     

Time resolved numerical modeling of oil jet cooling of a medium duty diesel engine piston

In medium to heavy duty diesel engines, ever increasing power densities are threatening piston's structural integrity at high engine loads and speeds. This investigation presents the computational results of the heat transfer between piston and an impinging oil jet, typically used to keep the pistons cool. Appropriate boundary conditions are applied and using numerical modeling, heat transfer coefficient (h) at the underside of the piston is predicted. This predicted value of heat transfer coefficient significantly helps in selecting right oil (essentially right oil grade), oil jet velocity, nozzle diameter (essentially nozzle design) and distance of the nozzle from the underside of the piston. It also predicts whether the selected grade of oil will contribute to oil fumes/mist generation. Using numerical simulation (finite element method), transient temperature profiles are evaluated for varying heat flux (simulating varying engine loads) to demonstrate the effect of oil jet cooling. The model, after experimental validation, has been used to understand the transient temperature behavior of the piston and the time taken in achieving steady state. High speed CCD camera is used to investigate the oil jet breakup, localized pool boiling and mist generation due to impinging jet on the piston's underside.     

Deposition of silicon films in presence of nitrogen plasma—A feasibility study

A design, development and validation work of plasma based ‘activated reactive evaporation (ARE) system’ is implemented for the deposition of the silicon films in presence of nitrogen plasma on substrate maintained at room temperature. This plasma based deposition system involves evaporation of pure silicon by e-beam gun in presence of nitrogen plasma, excited by inductively coupled RF source (13.56 MHz). The activated silicon reacts with the ionized nitrogen and the films get deposited on silicon substrate. Different physical and process related parameters are changed. The grown films are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and ellipsometry. The results indicate that the film contains silicon nitride and a phase of silicon oxy nitride deposited even at room temperature. This shows the feasibility of using the ARE technique for the deposition of silicon films in nitrogen plasma.