• Title/Summary/Keyword: Initial pressure

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The use of neural networks for the prediction of swell pressure

  • Erzin, Yusuf
    • Geomechanics and Engineering
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    • v.1 no.1
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    • pp.75-84
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    • 2009
  • Artificial neural networks (ANNs) are a new type of information processing system based on modeling the neural system of human brain. The prediction of swell pressures from easily determined soil properties, namely, initial dry density, initial water content, and plasticity index, have been investigated by using artificial neural networks. The results of the constant volume swell tests in oedometers, performed on statically compacted specimens of Bentonite-Kaolinite clay mixtures with varying soil properties, were trained in an ANNs program and the results were compared with the experimental values. It is observed that the experimental results coincided with ANNs results.

Demonstration of Robust Micromachined Jet Technology and Its Application to Realistic Flow Control Problems

  • Chang Sung-Pil
    • Journal of Mechanical Science and Technology
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    • v.20 no.4
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    • pp.554-560
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    • 2006
  • This paper describes the demonstration of successful fabrication and initial characterization of micromachined pressure sensors and micromachined jets (microjets) fabricated for use in macro flow control and other applications. In this work, the microfabrication technology was investigated to create a micromachined fluidic control system with a goal of application in practical fluids problems, such as UAV (Unmanned Aerial Vehicle)-scale aerodynamic control. Approaches of this work include: (1) the development of suitable micromachined synthetic jets (microjets) as actuators, which obviate the need to physically extend micromachined structures into an external flow; and (2) a non-silicon alternative micromachining fabrication technology based on metallic substrates and lamination (in addition to traditional MEMS technologies) which will allow the realization of larger scale, more robust structures and larger array active areas for fluidic systems. As an initial study, an array of MEMS pressure sensors and an array of MEMS modulators for orifice-based control of microjets have been fabricated, and characterized. Both pressure sensors and modulators have been built using stainless steel as a substrate and a combination of lamination and traditional micromachining processes as fabrication technologies.

A Numerical Analysis of the NO Emission Characteristics in $CH_4/Air$ Counterflow Premix Flame (메탄/공기 대향류 예혼합화염의 NO 발생특성에 관한 수치해석)

  • Cho, Eun-Seong;Chung, Suk-Ho
    • Journal of the Korean Society of Combustion
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    • v.9 no.4
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    • pp.22-27
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    • 2004
  • Lean premix combustion is a best method in low $NO_x$ gas turbine combustor and we must know the characteristics of NO emission in high temperature and pressure condition in premix flame. Numerical analysis was performed to investigate the NO emission characteristics by adopting a counterflow as a model problem using detailed chemical kinetics. Methane $(CH_4)$ was used as a test fuel which is the main fuel of natural gas. The tested parameters were stretch rate, equivalence ratio, initial temperature, and pressure in premix flame. Results showed that NO emission was high in low stretch rate, near stoichiometric equivalence ratio, high initial temperature, and high pressure. Also, the pressure effect was sensitive in high temperature condition.

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Combustion characteristics in small combustion chamber that has high surface to volume ratio (고 표면적-체적 비를 가지는 소형 연소실 환경에서의 연소특성)

  • Lee, Dae-Hoon;Choi, Kwon-Hyoung;Kwon, Se-Jin
    • 한국연소학회:학술대회논문집
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    • 2000.12a
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    • pp.212-216
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    • 2000
  • Combustion phenomenon in scale-downed combustor is investigated. As the combustor volume decreases surface to volume ratio increases. for increased surface to volume ratio means increased heat loss and this increased heat loss affects reaction in combustion chamber. Plastic mini combustor is made. Stoichiometricaly premixed Hydrogen I air gas is used as fuel. Initial chamber pressure and chamber size are varied and the effects are evaluated. Peak pressure decreases with the decrease in chamber height. As initial chamber pressure decreases peak pressure decreases. And this change is more important than scale down effect till the chamber height of 1mm. With this result and further information following the experiments design parameter for micro engine can be established.

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A Numerical Study on Normal and Abnormal Combustion in Hydrogen Premixture (수소 예혼합기의 정상 및 이상연소에 관한 수치해석)

  • 손채훈;정석호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.8
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    • pp.1989-1998
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    • 1995
  • Characteristics of the flame propagation for normal and abnormal combustion in hydrogen premixture in a cylindrical constant-volume combustion chamber are studied numerically. A detailed hydrogen oxidation kinetic mechanism, mixture transport properties and a model describing spark ignition process are used. The calculated pressure-time history of the stable deflagration wave propagation agrees well with the experiment. The ignition of the premixture in the unburned gas, initiated by the hot spot, causes a transition from deflagration to detonation under some initial temperature and pressure. Under the initial conditions with high temperature and pressure, excessive ignition energy initiates a strong blast wave and a detonation wave that follows. The chemical reaction in the detonation wave is much more vigorous than that in the deflagration wave and the peak pressure in the detonation wave is much higher than the equilibrium value.

A Study on the Formation of Smoke Layer and the Zone modelling in Compartment Fire (건물화재시 연기층 형성과 영역모델에 관한 연구)

  • 허만성
    • Journal of the Korean Society of Safety
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    • v.12 no.4
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    • pp.70-78
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    • 1997
  • The objective of this research is to study on the upper and lower layer temperature, interface height and pressure in case of carpet, chair, trashcan and wardrobe fires in a residential room by performing the theoretical and experimental studies. The theoretical results of the upper and lower layer temperature, the interface height and the pressure were qualitatively well coincided with the experimental results. The uniformly distributed fire in case of carpet showed that the ignition and the initial growth period were relatively short while the fully developed period was considerably long. The concentrated fires such as the wardrobe showed that the ignitions and the initial growth periods were relatively long. The interface heights were around 1m as the steady state. However, at the time of the maximum temperature, the interface height was lowered to 0.5m from the floor. The pressure variation in the fire room ranged between 0.1mmAq and 0.4mmAq, and the temperature reached the highest while the pressure was maximum.

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INFLUENCE OF INITIAL COMBUSTION IN SI ENGINE ON FOLLOWING COMBUSTION STAGE AND CYCLE-BY-CYCLE VARIATIONS IN COMBUSTION PROCESS

  • Lee, Kyung-Hwan;Kim, Kisung
    • International Journal of Automotive Technology
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    • v.2 no.1
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    • pp.25-31
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    • 2001
  • It is necessary to understand the combustion process and cycle-by-cycle variation in combustion to improve the engine stability and consequently to improve the fuel economy and exhaust emissions. The pressure related parameters instead of mass fraction burned were compared for the effect of initial combustion pressures on the following combustion and the analysis of cycle-by-cycle variation in combustion for two pen injected SI engines. The correlation between IMEP and pressures at referenced crank angles showed almost the same trends for equivalence ratios, but the different mixture preparations indicated different tendency. The dependency of IMEP on pressure at the referenced crank angles increases as the mixture becomes leaner for both engines. The mixture distribution in the combustion chamber was varied with the coolant temperature and intake valve deactivation due to the evaporation of fuel and air motion. The correlation between pressure related parameters were also compared for the coolant temperatures and air motion.

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Combustion Characteristics in Small Combustion Chamber Size about Quenching Distance (소염 거리에 근접하는 소형 연소실 환경에서의 연소특성)

  • Lee, Dae-Hoon;Choi, Kwon-Hyoung;Kwon, Se-Jin
    • Journal of the Korean Society of Combustion
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    • v.5 no.2
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    • pp.63-68
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    • 2000
  • Combustion phenomenon in scale-downed combustor is investigated. As the combustor scale decreases surface to volume ratio increases and chamber size approaches quenching distance. As the combustor scales down surface to volume ratio increases resulting increased heat loss. And this heat loss can affect quenching and instability of the flame. To investigate this effect plastic mini combustor is made. Stoichiometricaly premixed Hydrogen / air gas is used as fuel. Initial chamber pressure and chamber size are varied and the effects are evaluated. Peak pressure decreased with the decrease in chamber height. As initial chamber pressure decreases peak pressure decreases and this change is more important than scale down effect till the chamber height of 1mm. With this result and further information following the experiments design parameter for micro engine can be established.

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Experimental Investigation on the Pressure-Drop Instabilities in Boiling Channel (비등유로의 압력강하 불안정성에 대한 실험적 고찰)

  • Kim, B.J.;Shin, K.S.
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.5 no.3
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    • pp.179-186
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    • 1993
  • The characteristics of pressure-drop oscillations(PDO) in boiling channel are studied experimentally. The effects of initial and boundary conditions on PDO are investigated in terms of oscillation period and amplitude. The period and amplitude of PDO are increased with the increase in the compressible volume in surge tank and heat input. However the amplitude of PDO is decreased with fluid temperature under low subcooling condition. Higher initial insurge flowrate resulted in almost invariant oscillation period but lower amplitude. At higher heat input the oscillation of heater wall temperature is significant, whose period is the same as that of pressure-drop instability.

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Electrical and Physical Properties of Sheath-core Type Conductive Textile Sensor with Home-Textile (Sheath-core 구조 전도사 섬유센서의 Home-Textile 적용을 위한 전기·물리학적 특성연구)

  • Cho, Kwang-Nyun;Jung, Hyun-Mi
    • Fashion & Textile Research Journal
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    • v.16 no.1
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    • pp.145-152
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    • 2014
  • The usage of textile-based sensors has increased due to their many advantages (compared to IT sensors) when applied to body assessment and comfort. Textile-based sensors have different detecting factors such as pressure, voltage, current and capacitance to investigate the characteristics. In this study, textile-based sensor fabrics with sheath-core type conductive yarns were produced and the relationship between capacitance changes and applied load was investigated. The physical and electric properties of textile-based sensor fabrics were also investigated under various laminating conditions. A textile based pressure sensor that uses a sheath-core conductive yarn to ensure the stability of the pressure sensor in the textile-based sensor (the physical structure of the reaction characteristic of the capacitance) is important for the stability of the initial value of the initial capacitance value outside the characteristic of the textile structural environment. In addition, a textile based sensor is displaced relative to the initial value of the capacitance change according to pressure changes in the capacitance value of the sensor due to the fineness of the high risk of noise generation. Changing the physical structure of the fabric through the sensor characteristic of the pressure sensor via the noise generating element of laminating (temperature, humidity, and static electricity) to cut off the voltage output element to improve the data reliability could be secured.