• Proceedings of the KSME Conference
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• 2002.08a
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• pp.259-262
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• 2002

Application of combustion stabilization devices such as baffle and acoustic cavity to liquid propellant rocket engine is investigated to suppress high-frequency combustion instability, i.e., acoustic instability. First, these damping devices are designed based on linear damping theory. As a principal design parameter, damping factor is considered and calculated numerically in the chambers with various specifications of these devices. Next, the unbaffled chambers with/without acoustic cavities are tested experimentally for several operating conditions. The unbaffled chamber shows the specific stability characteristics depending on the operating condition and has small dynamic stability margin. The most hazardous frequency is clearly identified through Fast Fourier Transform. As a result, the acoustic cavity with the present design has little stabilization effect in this specific chamber. Finally, stability rating tests are conducted with the baffled chamber, where evident combustion stabilization is observed, which indicates sufficient damping effect. Thrust loss caused by baffle installation is about $2{\%}$.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.8 s.239
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• pp.887-894
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• 2005

This paper describes effects of incidence angle on the wake turbulent flow of a high-turning turbine rotor blade. For three incidence angles of -5, 0 and 5 degrees, energy spectra as well as profiles of mean velocity magnitude and turbulence intensity at mid-span are reported in the wake. Vortex shedding fiequencies are obtained from the energy spectra. The result shows that as the incidence angle changes from -5 to 5 degrees, the suction-side wake tends to be widened and the deviation angle is increased. Strouhal numbers based on the shedding fiyequencies have a nearly constant value, regardless of the tested incidence angles.

• Asia pacific journal of information systems
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• v.14 no.1
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• pp.43-58
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• 2004

Recently, a market size for IT outsourcing has grown. As internet technology has been developed for accessing information resources, information systems have become internet-based, which is called an ASP(Application Service Provider); evaluating the performance for ASP becomes important. Therefore, this paper attempts to investigate the salient characteristics of ASP. An ASP success model is proposed based on information systems success models found in the literature. Our model is tested through a survey from 291 small companies. LISREL is used to demonstrate the suitability of our model, and the success factors for ASP are also investigated. Our result is likely to help provide useful guidelines for the successful ASP implementations.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.267-272
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• 2002

The electric heat pump requiring HCFCs as a refrigerant has been for most residential air-conditioners in Korea. They cause a surge up electric power demand during summer. Moreover, the use of HCFCs and HFCs causes a serious problem to the global environment such as global warming and ozone layer destruction. An absorption chiller and heater could solve such problems. It was built and tested for analyzing the performance of the absorption chiller/heater. Experiment was done with a 1.5RT household absorption chiller and heater. It was experimented that the cooling capacity, gas capacity, COP were researched by the temperature of cooling water. The change of the cooling water temperature have effect the temperature(or pressure) of the parts on absorption chiller The result of the change of the cooling water temperature have the effects of the absorption chillers. This data will help to operate the household absorption chiller and heater.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.8 s.197
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• pp.67-73
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• 2007

A sandwich plate with a truss core is composed of two face sheets and a pyramidal truss core between face sheets. This paper shows how to estimate the shear modulus of a truss core, experimentally. To determine the shear modulus of truss cores, 3-point bending tests are performed. For tests, metallic sandwich beams with truss cores are fabricated. Two kinds of truss cores are tested to investigate the shear modulus. Each test is repeated under different widths in order to increase accuracy. As a result, the shear modulus of sandwich beam is properly calculated. The deflection of a sandwich beam with a truss core by shear deformation takes the major contribution of the total deflection and the shear modulus of sandwich beam should be considered whenever it is designed.

• Korean Journal of Pharmacognosy
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• v.33 no.4 s.131
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• pp.372-375
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• 2002

Mutagenic acivity of essential oils was tested using Salmonella typhimurium TA100 in the presence or absence of 59 fraction prepared from the mouse liver. Growth inhibitory effect of the oils on the bacteria was measured to warrant the mutagenic effect. Most oils were (round to be very strongly toxic against the bacteria at a high dose $(2,000{\mu}g/plate)$. At lower doses than this concentration, the Curcuma longa oil was found to be the most mutagenic with S9 fraction whereas it was not mutagenic without the fraction suggesting that this oil could undergo activation for the mutagenicity by cytochrome P45O. However, the mutagenicity of the Eugenia caryohpylata oil was disappeared under S9 fraction. Other oils obtained from Cinnamomum cassia, Chrysanthemum sibiricum, Paeonia moutan the flower of Artemisia princeps var. Orientalis, Allium sativum, were not mutagenic. This result suggested that antimutagenicity assay on the essential oil is necessary for the biological available substances.

• Journal of Power System Engineering
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• v.15 no.6
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• pp.41-46
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• 2011

Refrigerant oil reduces friction between piston and cylinder of compressor and is normally hard to mix or dissolve in refrigerant. Oil separator deprives refrigerating oil from mixed solution of refrigerant and refrigerant oil. Sometimes much machine oil is carried into an evaporator and is applied to surface of the evaporator, and then disturbs heat transfer through it. Well-made oil separator helps refrigerating system stable and evaporator sustain full capacity. In this paper, new oil separate with different way to structure is suggested and tested. As result the new separates is 13% higher at 0C with 10% mixture and 6% higher at 0C with 20% mixture.

• Journal of Korean Society for Quality Management
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• v.30 no.1
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• pp.22-46
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• 2002

Recently, increasing attention has been paid to building the software quality and software productivity due to ongoing software crisis. To overcome such problem, one of the many alternatives is to use the capability maturity model (CMM) suggested by the Software Engineering Institute(SEI), focusing on the improvement of software progress. This research is proposed the theoretical framework for CMM based on the previous studies, and review the status of software process on the software development organization. We then examine the impact of the software process capability on the organizational performance including financial measures and non-financial measures. Hypotheses on software process capability were tested 144 organizational units. The 62.5% of foreign companies are distribute to the second and third level, the Korean firms in this study are indicated the first level. Result indicate that maturity of software process may be served the key predictor of organizational performance, in particular the positive relationship between the software process and non-financial performance index such as customer service, IT Infrastructure, marketing, supplier and purchaser, production and operation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.830-834
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• 2008

Resilient materials are generally used for the floating floors to reduce the floor impact sound. Dynamic stiffness of resilient material, which has the most to do with the floor impact sound reduction. The resilient materials available in Korea include EPS (Styrofoam), recycled urethane types, EVA (Ethylene Vinylacetate) foam rubber, foam PE (Polyethylene), glass fiber & rock wool, recycled tire, foam polypropylene, compressed polyester, and other synthetic materials. In this study, we tested floor impact sound reduction characteristic to a lot of kinds of resilient material. The result of test showed that the amount of the Light-weight impact sound reduction appeared by being influenced from this dynamic stiffness of resilient material. As the decreasing dynamic stiffness of resilient material, the impact sound reduction amount is increased, especially in the low frequency domain.

• The Journal of the Acoustical Society of Korea
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• v.19 no.8
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• pp.26-34
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• 2000

This paper presents a new adaptive impulse noise cancelling technique based on the adaptive nonlinear suppressing function. The proposed "adaptive threshold algorithm (ATA)" is controlled by the normalized power prior input data term, and this adaptive threshold makes the cancelling system highly robust against additive impulse noise. For the performance evaluation, we have tested the proposed algorithm with the observed signals simulated in various impulsive noise environments and real EMG signals. As a result the proposed algorithm shows superior performance of 51.7% to the available techniques in the points of SNR and MSE.