Velocity field measurement of a round jet using quantitative schlieren

This paper utilizes the background oriented schlieren (BOS) technique to measure the velocity field of a variable density round jet. The density field of the jet is computed based on the light deflection created during the passage of light through the understudy jet. The deflection vector estimation was carried out using phase-based optical flow algorithms. The density field is further exploited to extract the axial and radial velocity vectors with the aid of continuity and energy equations. The experiment is conducted at six different jet-exit temperature values. Additional turbulence parameters, such as velocity variance and power spectral density of the vector field, are also computed. Finally, the measured velocity parameters are compared with the hot wire anemometer measurements and their correlation is displayed.     

Simplified gateway selection scheme for multihop relay in vehicular ad hoc network

Integrating vehicular ad hoc network (VANET) and universal mobile telecommunication system (UMTS) could be a promising architecture for future machine‐to‐machine applications. This integration can help vehicles have steady Internet connection through the UMTS network and in communicating with other vehicles. However, dead spot areas and unsuccessful handoff processes caused by the high speed of vehicles can disrupt the implementation of this kind of architecture. In this paper, a new simplified gateway selection (SGS) scheme for multihop relay in a VANET‐UMTS integration network is proposed. The proposed scheme extends the coverage or/and calming of the frequent handoff process and allows vehicles to continue to be connected to the UMTS infrastructure network. An integrated simulation environment that combines VanetMobiSim and NS2 is used to simulate and evaluate the proposed scheme. The simulation results show that the SGS scheme performed better when it was implemented with ad hoc on a demand distance vector routing and destination‐sequenced distance vector routing protocols. Furthermore, the SGS scheme is compared with other cluster‐based gateway selections used in the previous works. The results show that our SGS scheme outperforms other cluster‐based gateway selections scheme in terms of selection delay, control packet overhead, packet delivery ratio, and overall throughput. Copyright © 2013 John Wiley & Sons, Ltd.     

Polynomial approximation of shape function gradients from element geometries

A method is presented for the polynomial approximation of shape function gradients based solely on the geometry of finite element boundaries. The method is founded on a least squares approach which leads to an integration scheme satisfying a necessary condition for convergence. In its simplest form the method reduces to the well‐known uniform strain approach for finite elements. The method is applicable to a broad class of problems such as connecting dissimilar meshes, mesh adaptivity and transitioning, and the construction of finite elements with variable topologies. Finite elements based on the polynomial approximations are shown to pass patch tests of various orders. In contrast to standard elements, higher‐order patch tests are passed without the need for nodes internal to element boundaries. Less sensitivity to volumetric locking under plane strain conditions is demonstrated through comparisons with a standard element formulation. Copyright © 2001 John Wiley & Sons, Ltd.     

Flame development characteristics at variable swirl level inductions in a stratified CNG direct injection combustion engine

The study of flame development characteristics is crucial in the study of flame propagation, extinction, and for the investigation of combustion cyclic variability in SI engine. The aim of this study is to investigate the characteristics of flame development in a lean-stratified combustion of Natural Gas Engine （CNG） in a single cylinder direct injection （DI） engine at a specific motor speed, and fixed injection timing and air-fuel ratio by varying only the swirl level at the intake. The engine was set to run at 1800 rpm with half-load throttled. The ignition advance was set at 21.5 BTDC, and to create an overall lean and stratified mixture, injection timing was set at 61 BTDC with an air-fuel-ratio of 40.5 （λ=2.35）. Variable turbulent flow conditions near spark-plug were created by positioning the swirl control valves （SCV） at the intake port just before the two intake valves. This was done by setting one of the valves at full open position and the other one at 0% closed, 50% closed and 100% closed positions in order to achieve medium tumble （no swirl）, medium swirl and high swirl flows in the cylinder, respectively. An endoscope and CCD camera assembly was utilized to capture the flame images from the tumble plane at the intake side of the engine ever）, 2 CA degrees after ignition timing （AIT） for 40 CAs. It was observed that flame growth rate and flame convection velocity are increasing with increasing the swirl level. The total combustion duration is, thus, shorter in swirl induced combustion than without. However, COV in IMEP is greater in swirl induced flow cases than the medium tumble.     

Role of fever in infection: has induced fever any therapeutic potential in HIV infection?

Ancient societies had no rational understanding of fever. The Greeks were the first to recognise that it may be part of nature's method of effecting cure in some diseases. How best to assist nature went through many trials and errors. Appreciation of the prognostic value of fever and how it may be controlled was slow to appear. That there was a place in the therapeutic arsenal for induced fever came only with the 20th century. Finding a suitable, safe, and satisfactory means came slowly. The curative power of well controlled and reproducible levels of fever was proved by the arrest of one deadly and incurable complication of a sexually transmitted disease in the first half of this century. The purpose of this review is to promote discussion and, hopefully, well ordered laboratory and clinical trials aimed at learning whether or not induced fevers have a place in the care of patients with HIV/AIDS.     

Upon sector elements for two-dimensional problems

Different sector elements for two-dimensional problems for linear elastic analysis are developed and their utility for different types of problems is discussed. One of these elements (Type 1) fulfils the rigid body criterion for the two translatory motions as well as interelement compatibility conditions. This element is used together with a triangular element for the solution of Kirsch's problem. A considerable accuracy of the results is obtained with a relatively small number of elements.     

The relation between ketone bodies, glucose and minerals contents in bovine blood under various physiological conditions

The interrelationship between the concentration of ketone bodies, glucose, minerals (Na, K, Ca, Mg, P, Cl) in serum and in TCA soluble whole blood under different physiological conditions in 110 cows was investigated. There was a certain relationship (partly high significant) between the mineral content, ketone bodies and glucose levels in blood. However, there is no clear explanation for the qualification of blood minerals as an indicator of the content of ketone bodies and glucose in serum and whole blood. The age of animals and the seasons had no influence on the concentration of ketone bodies in serum and whole blood. Significant positive relationship was found between the time of lactation, pregnancy and serum glucose and negative relation with ketone bodies. There was no correlation between milk production and ketone bodies. The hours after feeding were positively correlated with ketone bodies.     

Analysis of three-phase AC-DC converters under unbalanced supplyconditions

A three-phase AC-DC converter is analyzed, and the performance of the converter under balanced conditions is evaluated. It has been observed that the level of unbalance plays a significant part in the converter characteristics, especially at the lower output voltage range     

Amorphous binary alloys obtained by electrolytical and chemical methods

Amorphous alloys, generally obtained by splat cooling condensation on a cold support or sputtering, were prepared in our laboratory at ambient temperature by two other methods. The first one, the oxidoreduction in liquid phase, gives films, the thickness of which is 500 to 2000 A, deposited on an isolating support — glas, plastic or ceramic. The second one, electrolysis of adapted solutions, allows us to obtain some thick layers the thickness of which is in this case, 1 to 100 microns. The support is a conductor, for example, a copper leaf.Experiments reveal a local order characterized by the absence of diffraction peaks in the experimental interference function which is chiefly formed by diffuse rings. We can obtain amorphous materials at ambient temperature if the bath composition leads to an alloy which contains at least 15% of atoms of the metalloid in the case of phosphorous, and 20% of atoms with boron. The upper limits are, respectively, 25 and 35%. It does not seem possible to obtain a bigger quantity of metalloid with these two methods.The local order can be represented by an assembly of clusters in which chemical bonds exist between the metal and metalloid atoms. Every cluster is surrounded by a domain where atomic position is distributed following a Gaussian function. Beyond that the material is completely amorphous.