Improvement of lubrication and cooling in grinding

The presence of air boundary layer around a grinding wheel impedes the proper entry of cutting fluid into grinding zone and thereby lubrication and cooling are hampered. It leads to the thermal damage to the workpiece and rapid wheel wear. This experimental work is aimed at increasing the lubrication and cooling effects in grinding by a novel method of using scraper board. The experiments are conducted, using the scraper board, to find the critical region where the air pressure is zero. The coolant jet has then impinged into the grinding zone which is maintained within the critical region. The requirement of specific energy, surface texture, and mechanical properties of the ground surface are analyzed and compared with the traditional grinding and the grinding at various positions of scraper board. Results show that the grinding ratio improved by 35.6and 119%, surface roughness decreased by 36 and 54.2%, while the requirement of specific energy is reduced by 50.8 and 57.3% when scraper board is positioned at the critical distance in comparison to the 57.5° position and no scraper board, respectively. The results indicate that the introduction of fluid in the present method can improve the process efficiency and the product quality effectively.     

Analysis of externally pressurized porous gas journal bearings —II

A theoretical analysis of load-carrying capacity generated by vibration of the journal (the squeeze-film effect) of an externally pressurized porous gas journal is made. The flow of gas in the porous media is in three dimensions and obeys Darcy's law. The solution has been obtained by the perturbation method. The journal is assumed to vibrate either by translatory motion or by rotational motion around the transverse axis. The dimensionless squeeze load, moment, load- and moment-phase angles are given for various squeeze numbers, feeding parameters and a porosity number.     

On the origin of decay of spin current with temperature in organic spintronic devices

This article addresses the most challenging question facing the organic spintronics community today – what causes the universal loss of Giant Magnetoresistance (GMR) signal in organic spin valve devices made with different spin-polarized electrodes and organic semiconductor spacers? Careful analysis of our own and other experimental results available in literature indicate that transition of transport from polaron tunneling limit (suggested by the variable range hopping model) to thermally activated hopping limit (in the temperature range of 40–58 K) marks the most significant decrease of spin relaxation in organic semiconductors. With increasing occupancy of the available hopping sites by the thermally activated carriers, chances of spin flip inside the organic semiconductors increases significantly causing fast spin relaxation in the spin-valves.     

超低温强热型"数码涡旋"的应用与发展

如何提高空调机组的能效目前已经成为空调行业的发展方向。在小型中央空调领域,日本厂家从90年代初开始着手将变频技术成功应用于"商用多联机系统",并从90年代的"交流变频"技术发展到2003年开始采用"直流变频"技术。同时,艾默生旗下的环境优化技术部门从1993年开始着手研发"数码涡旋"变容量技术,并从1997年开始在机房空调应用中测试,相继开发船舶用冷冻机组,并供应亚洲与中国市场。     

Analysis of Clinic Layouts and Patient-Centered Procedural Innovations Using Discrete-Event Simulation

Abstract

Given that healthcare costs in the U.S. continue to climb, engineering managers can help address this situation by identifying designs for cost savings. Using discrete-event simulation, the layout of four different healthcare clinic scenarios considered in a redesign program named Patient Aligned Care Teams were studied. Model 1 is an existing layout in many clinics and Model 2 is staff-centered, while Models 3 and 4 provide additional space including common hallway(s). Our main conclusion is that Model 4 reduces patient travel distances and average queueing waits, while also providing the best privacy in accordance with HIPAA and the most security for the staff.     

Common entanglement witnesses and their characteristics

We investigate the issue of finding common entanglement witness for certain class of states and extend this study to the case of Schmidt number witnesses. We also introduce the notion of common decomposable and non-decomposable witness operators which is specially useful for constructing a common witness where one of the entangled states is with a positive partial transpose. Our approach is illustrated with the help of suitable examples of qutrit systems.     

The impacts of speed cameras on road accidents: An application of propensity score matching methods

This paper aims to evaluate the impacts of speed limit enforcement cameras on reducing road accidents in the UK by accounting for both confounding factors and the selection of proper reference groups. The propensity score matching (PSM) method is employed to do this. A naïve before and after approach and the empirical Bayes (EB) method are compared with the PSM method. A total of 771 sites and 4787 sites for the treatment and the potential reference groups respectively are observed for a period of 9 years in England. Both the PSM and the EB methods show similar results that there are significant reductions in the number of accidents of all severities at speed camera sites. It is suggested that the propensity score can be used as the criteria for selecting the reference group in before-after control studies. Speed cameras were found to be most effective in reducing accidents up to 200 meters from camera sites and no evidence of accident migration was found.     

Polystyrene composites of single‐walled carbon nanotubes‐graft‐polystyrene

Single‐walled carbon nanotubes (SWCNTs) dispersed in N‐methylpyrrolidone (NMP) were functionalized by addition of polystyryl radicals from 2,2,6,6‐tetramethyl‐1‐piperidinyloxy‐ended polystyrene (SWCNT‐g‐PS). The amount of polystyrene grafted to the nanotubes was in the range 20‐25 wt% irrespective of polystyrene number‐average molecular weight ranging from 2270 to 49 500 g mol^?1. In Raman spectra the ratios of D‐band to G‐band intensity were similar for all of the polystyrene‐grafted samples and for the starting SWCNTs. Numerous near‐infrared electronic transitions of the SWCNTs were retained after polymer grafting. Transmission electron microscopy images showed bundles of SWCNT‐g‐PS of various diameters with some of the polystyrene clumped on the bundle surfaces. Composites of SWCNT‐g‐PS in a commercial‐grade polystyrene were prepared by precipitation of mixtures of the components from NMP into water, i.e. the coagulation method of preparation. Electrical conductivities of the composites were about 10^?15 S cm^?1 and showed no percolation threshold with increasing SWCNT content. The glass transition temperature (T_g) of the composites increased at low filler loadings and remained constant with further nanotube addition irrespective of the length and number of grafted polystyrene chains. The change of heat capacity (ΔC_p) at T_g decreased with increasing amount of SWCNT‐g‐PS of 2850 g mol^?1, but ΔC_p changed very little with the amount of SWCNT‐g‐PS of higher molecular weight. The expected monotonic decrease in ΔC_p coupled with the plateau behavior of T_g suggests there is a limit to the amount that T_g of the matrix polymer can increase with increasing amount of nanotube filler. Copyright © 2012 Society of Chemical Industry     

Wavelength conversion using rare earth doped oxides in polyolefin based nanocomposite films

Nanocomposites are a new class of polymeric materials which include organic or inorganic nano‐phase materials. These nanocomposite films can show interesting properties which have many applications for wavelength conversion and energy saving. In this paper, we present polyolefin based nanocomposite films prepared using wavelength‐converting red ‘phosphors’ such as Y₂O₃: Eu³⁺ and LiAl₅O₈:Fe³⁺ and blue ‘phosphor’ CaMgSi₂O₆: Eu²⁺. The durability of the polymer chain is unaffected by incorporation of inorganic nanoparticles as there is no direct interaction between them. The addition of surfactant in the nanocomposite film helps to improve the dispersion ability of the nanoparticles and increase the flexibility of the polymer film. Wavelength‐converting ‘nanophosphors’ incorporated in a polymer matrix help to increase the tensile strength of the film. The films show excellent wavelength conversion ability of UV light into the visible and near IR range. These nanocomposite films have great application in energy saving devices. Copyright © 2012 Society of Chemical Industry     

Some studies on uncertainty management in dynamical systems using cybernetic approaches and fuzzy techniques with applications

Uncertain information processing by fuzzy if–then rules has received much attention. Here we have taken a different path to model a system, about which we do not have precise information, namely modelling the system by fuzzy-valued functions without resorting to fuzzy if–then rules. As a result, the phase (state) space of the system becomes a fuzzy set and the underlying fuzzy mapping becomes a fuzzy attainability set mapping. Uncertain or fuzzy dynamical systems have been defined in terms of fuzzy attainability set mappings. Fuzzy differentiable dynamical systems have been discussed with a particular emphasis on fuzzy differential inclusion (FDI) relations. An evolutionary algorithm for solving one-dimensional FDIs has been developed. A model of the creation of a tropical cyclone in the form of a vortex, created by winds coming from different directions and colliding under certain conditions, has been proposed in terms of FDIs. A model has been considered for the highly uncertain system of evolution of a tumour in a human body and an FDI relation model of the whole system has been proposed and simulated. The model of an evolution of turbulence, as a random occurrence of vortices in a three-dimensional dynamic fluid, has been proposed and simulated, where each vortex is modelled by a fuzzy-valued function, where uncertain parameter and variable values are fuzzy numbers. All the systems represented by FDI relations have been simulated with the help of the evolutionary algorithm mentioned above.