An experimental study on the effects of impingement-walls on the spray and combustion characteristics of SIDI CNG

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.     

0–30?V common mode range, 120?dB CMRR, and 10?nV/ \sqrt {\text{Hz}} noise floor current shunt monitor IC with an embedded ΣΔ modulated digital interface

Sensing and controlling current flow is a fundamental requirement for many electronic systems, including power management (DC?CDC converters and LDOs), battery chargers, electric vehicles, solenoid positioning, motor control, and power monitoring. Current shunt monitor (CSM) system enables current measurement across an external sense resistor (R _S ) in series to current flow. Proposed CSM system can sense a system (power supply) current from 1 to 500?mA across a typical board Cu-trace resistance of 1??? with less than 10???V input-referred offset, 150?nV/°C offset drift and 0.1% accuracy. Instead of using a costly zero-TC sense resistor (R _S ) that is used in typical CSM systems; proposed method uses existing Cu board trace for sensing. The sense amplifier uses chopper stabilization in the signal chain of the amplifier to suppress input-referred offset down to less than 10???V. Switching current-mode (SI) FIR filtering is used at the instrumentation amplifier output to filter out the chopping ripple at the harmonics of the chopping frequency. A frequency domain Sigma Delta (????FD) ADC enables a digital interface to processor applications. The CSM is fabricated on a 0.7???m CMOS process with three levels of metal with maximum Vds tolerance of 8?V, and operates across a common mode range of 0?C30?V achieving less than 10?nV/ $ \sqrt {\text{Hz}} $ of flicker noise at 100?Hz. By using a semi-digital SI FIR filter, residual chopper ripple is suppressed by more than 7.5?mV_pp from the base line of 8?mV_pp, which is equivalent to 25?dB suppression.     

Chemical and electronic properties of Ba/bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) interfaces for organic light-emitting diodes

The chemistry, electronic structure, and electron-injecting characteristics at the interfaces that were formed between bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (BAlq) and barium (Ba) were investigated using ultraviolet photoemission spectroscopy, near-edge X-ray absorption fine structure spectroscopy, X-ray photoemission spectroscopy, and current-voltage-luminance measurements. The device performance of organic light-emitting diodes (OLEDs), which have a glass/ITO/MoO3/2-TNATA/NPB/BAlq/Ba/Au structure, was significantly improved by inserting a Ba coverage (thetaBa) of 0.2 nm between BAlq and the cathode. For thetaBa'S that were thicker than 0.2 nm, however, even though the electron-injecting barrier heights at the Ba-on-BAlq interfaces were all 0.1 eV, the device performance of the OLEDs with Ba at the interface was degraded with increasing thetaBa. This result indicates that the device performance is largely dependent on the interfacial chemical degradation of the BAlq molecule itself, rather than the electron-injecting barrier height that is determined by the width and chemical structure of the interface, and the formation of barium-induced new gap states at the Ba-on-BAlq interface.     

Simulation study of biobutanol production in a polymer-loaded two-phase partitioning bioreactor (PL-TPPB): Simulation and strategy for biobutanol production

A simulation study was performed for a two-phase partitioning bioreactor (TPPB) with polymer beads, Dowex Optipore L-493, as a second phase. When the initial glucose concentration is less than 30 g/L, a single-phase bioreactor is preferred, because it consumed all the glucose with 40% of biobutanol yield. Any glucose over the concentration remained in the single-phase bioreactor because cells were completely inhibited by products, mainly biobutanol, and thus glucose availability became less than 100%. The TPPB with 10% polymer beads completely consumed up to 120 g/L glucose and more polymer beads were required for the higher glucose concentration. Instead of increasing the proportion of polymer beads, 2 vvm of nitrogen gas was introduced continuously into the TPPB for the stripping of products, reducing product inhibitions. By applying gas stripping to the TPPB containing 10% polymer beads, 150 g/L of glucose was completely consumed and 99.7% acetone, 46.8% butanol and 82.5% ethanol was stripped out of the TPPB. Finally, on the basis of these estimations, a novel strategy based on the initial glucose concentration was suggested for high biobutanol production.     

Electrically assisted blanking using the electroplasticity of ultra-high strength metal alloys

The electroplastic tensile behavior of ultra-high strength steels (UHSS) subject to a single pulse of electric current is briefly introduced, and electrically-assisted (EA) blanking, which utilizes this electroplastic characteristic, is suggested. The experimental result shows that the blanking load of EA blanking is clearly lower than that of blanking with local resistance heating, which is lower than that of cold blanking. No significant change in material properties was observed in the EA blanked parts at the electric energy densities selected in the present study. EA blanking or trimming is expected to minimize or even eliminate the need for expensive and time-consuming laser trimming in the manufacture of automotive parts using UHSS.     

Basis weight uniformity analysis in nonwovens

It is widely recognized that nonwoven basis weight uniformity affects various properties of nonwovens, including appearance, physical properties, or mechanical properties. However, it is one of the nonwoven characteristics that is most difficult to characterize. This paper reports on the methodology based on the well-known quadrant method that objectively quantifies uniformity of nonwoven fabrics.     

An efficient optimistic message logging scheme for recoverable mobile computing systems

A number of checkpointing and message logging algorithms have been proposed to support fault tolerance of mobile computing systems. However, little attention has been paid to the optimistic message logging scheme. Optimistic logging has a lower failure-free operation cost compared to other logging schemes. It also has a lower failure recovery cost compared to the checkpointing schemes. This paper presents an efficient scheme to implement optimistic logging for the mobile computing environment. In the proposed scheme, the task of logging is assigned to the mobile support station so that volatile logging can be utilized. In addition, to reduce the message overhead, the mobile support station takes care of dependency tracking and the potential dependency between mobile hosts is inferred from the dependency between mobile support stations. The performance of the proposed scheme is evaluated by an extensive simulation study. The results show that the proposed scheme requires a small failure-free overhead and the cost of unnecessary rollback caused by the imprecise dependency is adjustable by properly selecting the logging frequency.     

The optimum operational condition of membrane bioreactor (MBR): cost estimation of aeration and sludge treatment

A methodology to obtain the most economical operational condition of membrane bioreactor (MBR) is developed. In order to achieve the optimum design parameters of MBR with which operational costs are minimized, aeration and sludge treatment costs were estimated for various operational conditions. Generally sludge treatment cost and aeration cost were inversely proportional to each other, which means sludge treatment cost is minimized when aeration cost is maximized and vice versa. Therefore, there might exist an optimum point between the two extreme cases. However, sludge treatment cost turned out to overwhelm the aeration cost over the reasonable operational conditions. Therefore, sludge minimization was considered to be a key for the economical operation of MBR. In the case of typical municipal wastewater of which COD was 400mgL(-1), steady-state MLSS was expected to increase from 11,000 to 15,000mg/L without sludge removal when HRT was decreasing from 16 to 12h. For the range of operational conditions considered in this study, economically optimum HRT and target MLSS were turned out to be 16h and 11,000mg/L, respectively. Under this condition, aeration for the biodegradation of organic matters would be 13.3m(3) air/min when influent was 1000m(3)/day.