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Compressed natural gas (CNG) is regarded as one of the most promising alternative fuels. In the spark-ignition (SI) engine, direct injection (DI) technology can significantly increase the engine volumetric efficiency and reduce 'pumping losses' in engines without a throttle valve. DI allows engine operation with the stratified charge which enables relatively higher combustion efficiency. In this study, a combustion chamber with a visualization system is designed. The spray development and combustion propagation process of spark-ignition direct injection (SIDI) CNG were digital recorded and analyzed. The ignition probability was also examined. The results of this study can contribute important data for the design and optimization of the SIDI CNG engine. [ABSTRACT FROM AUTHOR]

PurposeTo evaluate the degree of three-dimensional (3D) perception and ocular and systemic discomfort in patients with abnormal binocular vision (ABV), and their relationship to stereoacuity while watching a 3D television (TV).MethodsPatients with strabismus, amblyopia, or anisometropia older than 9 years were recruited for the ABV group (98 subjects). Normal volunteers were enrolled in the control group (32 subjects). Best-corrected visual acuity, refractive errors, angle of strabismus, and stereoacuity were measured. After watching 3D TV for 20 min, a survey was conducted to evaluate the degree of 3D perception, and ocular and systemic discomfort while watching 3D TV.ResultsOne hundred and thirty subjects were enrolled in this study. The ABV group included 49 patients with strabismus, 22 with amblyopia, and 27 with anisometropia. The ABV group showed worse stereoacuity at near and distant fixation (P<0.001). Ocular and systemic discomfort was, however, not different between the two groups. Fifty-three subjects in the ABV group and all subjects in the control group showed good stereopsis (60 s of arc or better at near), and they reported more dizziness, headache, eye fatigue, and pain (P<0.05) than the other 45 subjects with decreased stereopsis. The subjects with good stereopsis in the ABV group felt more eye fatigue than those in the control group (P=0.031). The subjects with decreased stereopsis showed more difficulty with 3D perception (P<0.001).ConclusionsThe subjects with abnormal stereopsis showed decreased 3D perception while watching 3D TV. However, ocular and systemic discomfort was more closely related to better stereopsis. [ABSTRACT FROM AUTHOR]

In this paper, the radical induced (RI) ignition method was applied into a compressed natural gas (CNG) engine to achieve rapid bulk combustion. The experimental RI-CNG engine was modified from a diesel engine. The combustion chamber of the modified diesel engine was divided into a sub-chamber and a main-chamber. The sub-chamber is physically separated from the main-chamber above the piston and is connected to the main-chamber via several passage holes. CNG is injected into the sub-chamber during the intake stroke and then ignited before the top dead center (TDC) by a spark plug. As the ignition occurs in the sub-chamber, the pressure rises, forcing the gases which contain a number of active radicals out into the main-chamber to ignite the unburned mixture. The purpose of this paper is to study the engine operating limit and the combustion characteristics of the RI-CNG engine. The engine operating limit was accessed with different engine speeds and injection timings. The obtained data including the coefficient of variation (COV), brake specific fuel consumption (BSFC), mass fraction burned and emissions were analyzed. [ABSTRACT FROM AUTHOR]

Compressed natural gas (CNG) is regarded as one of the most promising alternative fuels, and maybe the cleanest fuel for the sparkignition (SI) engine. In the SI engine, direct injection (DI) technology can significantly increase the engine volumetric efficiency and decrease the need of throttle valve. During low load and speed conditions, DI allows engine operation with the stratified charge, and the use of extremely lean fuel-air mixture enables relatively higher combustion efficiency. In this study, a combustion chamber with a visualization system is designed. The spray development and combustion propagation processes SIDI CNG were digital recorded. It was found that high injection pressure reduced the ignition probability significantly because of quenching of flame kernel. To improve the ignition probability, three kinds of impingement-walls were designed to help the mixture preparation. It was found that the CNG-air mixture can be easily formed after spray-wall impingement and the ignition probability was also improved. The results of this study can contribute important data for the design and optimization of spark-ignition direct injection (SIDI) CNG engine. [ABSTRACT FROM AUTHOR]

This article introduces an on-demand microfluidic hydrogen generator that can be integrated with a micro-proton exchange membrane (PEM) fuel cell. The catalytic reaction, reactant circulation, gas/liquid separation, and autonomous control functionalities are all integrated into a single microfluidic device. It generates hydrated hydrogen gas from an aqueous ammonia borane solution which is circulated and exchanged between the microfluidic reactor and a rechargeable fuel reservoir without any parasitic power consumption. Ammonia borane is chosen instead of sodium borohydride because of its faster hydrogen generation rate, higher hydrogen storage capability, stability, and better catalyst durability. The self-circulation of the ammonia borane solution was achieved using directional growth and selective venting of hydrogen bubbles in micro-channels, which leads to agitation and addition of fresh solution without consumption of electrical power. The self-regulation mechanism ensures that hydrogen can be supplied to a fuel cell according to the exact demand of the current output of the fuel cell. The circulation flow rate of ammonia borane solution is also automatically regulated by the venting rate of hydrogen at the gas outlet. Design, fabrication, and testing results of a prototype system are described. The hydrogen generator is capable of generating hydrogen gas at a maximum rate of 0.6 ml/min (2.1 ml/min cm) and circulating aqueous ammonia borane at a maximum flow rate of ~15.7 μl/min. The device has also been connected with a micro-PEM fuel cell to demonstrate the feasibility of its practical applications in a high-impedance system. [ABSTRACT FROM AUTHOR]

Healthcare personnel (HCP) can acquire influenza and transmit it to patients and other hospital staff. The aim of this study was to evaluate the attack rate of HCP by the 2009 H1N1 influenza virus during the 2009 pandemic influenza season in Korea. HCP infected with H1N1 virus were asked to fill out a questionnaire, which included job type, method of diagnosis, facility type, history of contact with patients infected by H1N1 virus, vaccination status, and use of personal protective equipment. A total of 328 HCP (female 68.6%, 225/328) were infected with H1N1 virus at the nine study centers. The highest attack rate was in physicians, followed by nurses and nurses' aides. Transmission occurred primarily after contact with outpatients (27.8%), followed by contact with inpatients (21.6%). Most (77.3%) of the infected HCP never used an N95 mask during contact with patients. Surgical masks were always used by 29.4% of the subjects and usually or intermittent used by 46.9%. The peak incidence of the H1N1 infection among HCP preceded that among the general population. Among HCPs, physicians, nurses, and nurses' aides were at the greatest risk of H1N1 infection. HCP should be more vigilant and protect themselves with appropriate personal protective equipment during the influenza season. [ABSTRACT FROM AUTHOR]

The sub-chamber type gasoline engine was suggested to be a type of clean engine, but the presence of residual gas in the sub-chamber was a serious fault. In this experimental study, the CNG direct injection method was applied to scavenge residual gas from the sub-chamber. The CVC (constant volume chamber) is divided into the sub-chamber and main-chamber and used as the main experimental apparatus. Because each combustion chamber of the CVC has an injector, the injector can be used freely, at the same time or individually. Therefore, the scavenging efficiency can be improved by changing injection times for the sub-chamber. The experimental results demonstrated that when all the fuel was injected into the sub-chamber, the combustion duration was shortened by 30% compared to that of injection into the main-chamber. Although residual gas was observed in the CVC, when the frequency of injections into the sub-chamber increased, good combustion characteristics were obtained. [ABSTRACT FROM AUTHOR]

An artificial neural network (ANN) model was applied to simulate the phase volume fraction of titanium alloy under isothermal and non-isothermal hot forging condition. For isothermal hot forging process, equilibrium phase volume fraction at specific temperature was predicted. For this purpose, chemical composition of six alloy elements (i.e. Al, V, Fe, O, N, and C) and specimen temperature were chosen as input parameter. After that, phase volume fraction under non-isothermal condition was simulated again. Input parameters consist of initial phase volume fraction, equilibrium phase volume fraction at specific temperature, cooling rate, and temperature. The ANN model was coupled with the FE simulation in order to predict the variation of phase volume fraction during non-isothermal forging. Ti−6A1−4V alloy was forged under isothermal and non-isothermal condition and then, the resulting microstructures were compared with simulated data. [ABSTRACT FROM AUTHOR]