• Journal of Energy Engineering
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• v.11 no.2
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• pp.160-165
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• 2002

The heavy-duty LPG-fueled single cylinder engine was designed and developed as a fundamental equipment for analyzing combustion processes and emission performances. The cylinder head and the piston crown were modified to fire the LPG in the engine. The flywheel was also fabricated to minimize the vibration of the single cylinder engine. The size of bore and stroke of the tested engine are 130 mm and 140 mm, respectively. Compression ratios were varied 8 to 9 with different piston crown shapes. The developed single cylinder engine operates at 1,000 rpm for this work. The major conclusions of this work are; (1) the power of the developed engine was peaked at the condition of equivalence ratio 1.0 at three different compression ratios; (2) the power is slightly increased with the increase of compression ratio; (3) the optimum ignition timing is retarded with the increase of compression ratio ranged 2 to 10 crank angle.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.10a
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• pp.218.3-219
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• 2003

백편을 만들 때 멥쌀가루 100에 찹쌀가루를 총중량의 0%, 5%, 10%, 15%, 20%, 25%, 30% 첨가하고 저장시간 0시간, 24시간, 48시간, 72시간 저장한 후 (4$^{\circ}C$에서) reheating 한 백편의 기호성과 조직감(Texture)에 어떠한 영향을 끼치는 가를 관능검사와 기계적 검사에 의해 측정한 결과를 다음과 같이 요약할 수 있다 1. 관능검사 결과 백편의 Color 는 찹쌀의 첨가량이 증가할수록 누런색이 짙어졌으며, 24, 48, 72 시간 저장한 후 reheating 한 백편도 누런색이 짙어지는 경향을 나타냈다. Coarseness 는 찹쌀의 첨가량이 증가할수록 증가하는 경향이었으나 저장전의 백편은 유의적인 경향을 나타내지 않았다. 찹쌀의 첨가량이 증가할수록 Softness, Dryness, crumblyness는 감소경향을 나타냈으며 24, 48, 72 시간을 저장한 후 reheating 한 백편도 유의적인 감소경향을 나타냈다. 외관의 기호도는 찹쌀의 첨가율이 5% 인 백편을 가장 좋아했고, 조직감 및 종합적인 기호도는 찹쌀의 첨가율이 10~20%인 백편을 좋아했다. 2. Rhemeter에 의한 백편의 Texture는 찹쌀의 첨가량이 증가할수록 Compression force, gumminess, Chewiness가 증가하는 경향을 나타냈다. 24, 48, 72 시간 저장한 후 reheating 한 백편은 저장전보다 점점 감소경향을 나타냈다가 72시간 저장한 후 reheating 하면 다시 증가경향을 나타냈다. Work ratio 및 Recovered height는 찹쌀의 첨가량과 저장시간의 변화에 크게 영향을 미치지 않았다. Recovered 하지 않고 0, 24, 48, 72 시간 저장한 백편의 Compressing force는 찹쌀의 첨가량이 증가할수록 증가경향이 컸고 저장시간이 경과함에 따라 Compression force가 증가하였는데 특히 24시간 저장하는 동안 급격히 증가하였다. 3. 찹쌀 첨가량이 증가할수록 수분함량은 증가하였고, 저장시간이 경과함에 따라 수분함량은 감소경향을 나타냈으나 24시간 저장한 후 reheating 한 백편만이 수분함량의 증가경향을 나타내었다. 4. qoruvs의 Softness 는 Compression force 및 Work ratio 와 유의적인 상관관계를 나타내었으며, Dryness 와 Crumblyness 는 Work ratio와 유의적인 상관관계를 나타내고 있어 백편의 조직감은 Compression force 와 Work ratio로 대치할 수 있을 것이라고 사료된다. 수분함량은 기계적 검사보다 관능검사와 더욱 높은 상관관계를 나타냈다.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.209-213
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• 2008

In this work, we have proposed a method for calculating the residual stress developed during the PCB thermo-compression bonding precess. Residual stress is the most important factor that causes PCB warpage in accordance with the pattern design. In this work, a single-layed double-sided PCB, which is comprised of the dielectric (FR-4) substrate in the middle and copper cladding on the both top and bottom sides, is considered. A reference temperature, where all stress is free, is calculated by comparing the calculated and measured warapge of a PCB of which copper cladding of the top side is removed. Then, the reesidual stress values is calculated for the double-sided PCB.

• International Journal of Computer Science & Network Security
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• v.23 no.6
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• pp.140-146
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• 2023

A detailed survey, applications and challenges of video encoding-decoding systems is discussed in this paper. A novel architecture has also been set aside for future work in the same direction. The literature reviews span the years 1960 to the present, highlighting the benchmark methods proposed by notable academics in the field of video compression. The timeline used to illustrate the review is divided into three sections. Classical methods, conventional heuristic methods, and current deep learning algorithms are all used for video compression in these categories. The milestone contributions are discussed for each category. The methods are summarized in various tables, along with their benefits and drawbacks. The summary also includes some comments regarding specific approaches. Existing studies' shortcomings are thoroughly described, allowing potential researchers to plot a course for future research. Finally, a closing note is made, as well as future work in the same direction.

• Proceedings of the KSR Conference
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• 1998.05a
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• pp.596-603
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• 1998

The entry compression wave, which is generated at the entrance of the tunnel, is almost always associated with the pressure transients in the tunnel as well as the impulse noise at the exit of the tunnel. It is highly required to design the train nose shape that can minimize such undesirable phenomena. The objective of the current work is to investigate the effects of the train nose shape on the entry compression wave. Numerical computations were applied to one-dimensional unsteady compressible flow in high-speed railway train/tunnel systems. A various shape of train noses were tested for a wide range of train speeds. The results showed that the strength of the entry compression wave is not influenced by the train nose shape, but the time variation of pressure in the entry compression wavefront is strongly related to the train nose shape. The current method of the characteristics was able to represent a desirable nose shape for various train speeds. Optimum nose shape was found to considerably reduce the maximum pressure gradient of the entry compression wave.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.521-529
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• 2012

Since the energy demand for refrigeration and air-conditioning has greatly increased all over the world, thermally activated refrigeration cycle has attracted much attention. This study carries out a performance analysis of a vapor compression cycle (VCC) driven by organic Rankine cycle (ORC) utilizing low-temperature heat source in the form of sensible heat. The ORC is assumed to produce minimum net work which is required to drive the VCC without generating an excess electricity. Effects of important system parameters such as turbine inlet pressure, condensing temperature, and evaporating temperature on the system variables such as mass flow ratio, net work production, and coefficient of performance (COP) are thoroughly investigated. The effect of choice of working fluid on COP is also considered. Results show that net work production and COP increase with increasing turbine inlet pressure or decreasing condensing temperature. Out of the five kinds of organic fluids considered $C_4H_{10}$ gives a relatively high COP in the range of low turbine inlet pressure.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.355-360
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• 2001

This study addresses a computational work of the impulsive wave which is discharged from the open end of a pipe. An initial compression wave inside the pipe is assumed to propagate toward atmosphere. The over pressure and wave-length of the initial compression wave are changed to investigate the characteristic values of the impulsive wave. The second order total variation diminishing (TVD) scheme is employed to solve the axisymmetric, compressible, unsteady Euler equations. The relationship between the initial compression wave form and impulsive wave is characterized in terms of the peak pressure of the impulsive wave and its directivity. The results obtained show that for the initial compression wave of a large wave-length the peak pressure of the impulsive wave does not depend on the over pressure of the initial compression wave, but for the initial compression wave of a very short wave-length, like a shock wave, the peak pressure of the impulsive wave is increased with an increase in the over pressure of the initial compression wave. The directivity of the impulsive wave to the pipe axis becomes significant with a decrease in the wave-length of the initial compression wave.

• Journal of Advanced Marine Engineering and Technology
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• v.11 no.1
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• pp.53-62
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• 1987

The Performance of Pre-combustion Chamber Diesel Engine mainly depends upon the compression, combustion and Expansion Processes. The analysis of varying tendency of the work factors for crank angles during these processes, which are consisted of 5 items such as exothermic energy, flow work, work in nozzle part, kinetic energy and cooling energy, are considered important as basic elements for effective combustion and performance improvement. In this paper, varying tendencies of the theoretical factors are investigated with pressure data through experiments. By the results, the trends of work factors are presented as basic data for comparing the influencing effects on work.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.9
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• pp.1416-1422
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• 2001

The objective of this work was to characterize mechanical properties of thermoplastic composites with various forming conditions in compression molding. Randomly oriented long glass fiber reinforced polypropylene(PP) was used in this work. The composite materials contained 20%, 30%, and 40% glass fiber by weight. Compression molding was conducted at various mold temperatures and charge sizes. The temperatures on the mold surface and at the material in the mid-plain were monitored during the molding. Differential Scanning Calorimeter was used to measure crystallinity at both in-side and out-side of the sheet material. Crystallinity at each temperature was also measured by X-ray diffractometer. Dimensional stability was studied at various conditions with the spring forward angle. Among the processing parameters, the crystallization time at the temperature above 130$^{\circ}C$, was found to be the most effective. Spring-forward angle was reduced and the tensile modulus was increased as the mold temperature increased.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.3 s.234
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• pp.417-423
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• 2005

This paper describes the engine performance of a Homogeneous Charge Compression Ignition(HCCI) engine according to Exhaust Gas Recirculation(EGR), cylinder-to-cylinder, fuel of propane and butane. HCCI engines are being considered as a future alternative for diesel and gasoline engines. HCCI engines have the potential for high efficiency, very low NOx emissions and very low particulate matter(PM). On experimental work, we have done an evaluation of operating conditions in a 4-cylinder compression engine. The engine has been run with propane and butane fuels at a constant speed of 1800rpm. This work is intended to investigate the HCCI operation of the engine in this configuration that has been modified from the base diesel engine. The performance and emissions of the engine are presented. In this paper, the start of combustion(SOC) is defined as the $50{\%}$ point of the peak rate of heat release. SOC is delayed slightly with increasing EGR. As expected, NOx emissions were very low for all EGR range and nbuned HC and CO emission levels were high. CO and HC emissions are lower with using propane than butane as fuels of HCCI engines.