• Journal of Hydrogen and New Energy
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• v.25 no.1
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• pp.59-71
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• 2014

An experimental study has been conducted to investigate the heat transfer characteristics of laminar syngas/air mixture with 10% hydrogen content impinging normally to a flat plate of cylinder. Effects of impinging distance, Reynolds number and equivalence ratio as major parameters on heat fluxes of stagnation point and radial direction were examined experimentally by the direct photos and data acquisitions from heat flux sensor. In this work, we could find the incurved flame behavior of line shaped inner top-flame in very closed distance between flat plate and burner exit, which has been not reported from general gas-fuels. There were 3 times of maximum and 2 times minimum heat flux of stagnation point with respect to the impinging distance for the investigation of Reynolds number and equivalence ratio effect. It was confirmed that the maximum heat flux of stagnation point in 1'st and 2'nd peaks increased with the increase of the Reynolds number due to the Nusselt number increment. There was a third maximum rise in the heat flux of stagnation point for larger separation distances and this phenomenon was different each for laminar and turbulent condition. The heat transfer characteristics between the stagnation and wall jet region in radial heat flux profiles was investigated by the averaged heat flux value. It has been observed that the values of averaged heat flux traced well with the characteristics of major parameters and the decreasing of averaged heat flux was coincided with the decreasing trend of adiabatic temperature in spite of the same flow condition, especially for impinging distance and equivalence ratio effects.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.8
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• pp.839-845
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• 2011

We performed numerical simulations of freely propagating premixed flames at atmospheric pressure to investigate the influence of trifluoromethane on $CH_4/O_2/N_2$ flames under oxygen enrichment. Trifluoromethane significantly contributed toward a reduction in flame speed, the magnitude of which was larger in terms of the physical effect than the chemical effect. More trifluoromethane could be added and consumed on oxygen-enriched $CH_4/O_2/N_2$ flames. $CHF_3$ was decomposed primarily via $CF_3{\rightarrow}CF_2{\rightarrow}CF{\rightarrow}CF:O{\rightarrow}CO$ and $CHF_3+M{\rightarrow}CF_2+HF+M$ played an important role in oxygen-enhanced flames. When an inhibitor was added to oxygen-enriched flames, the position of the maximum concentration of active radicals was shifted to a relatively low temperature range, and the net rate of OH became higher than that of H.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2181-2185
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• 2008

Fuel processing systems which convert HC fuel into $H_2$ rich gas (such as stream reforming, partial oxidation, auto-thermal reforming) need high temperature environment($600-1000^{\circ}C$). Generally, anode-off gas or mixture of anode-off gas and LNG is used as input gas of fuel reformer. In order to make efficient and low emission burner system for fuel reformer, it is necessary to elucidate the combustion and emission characteristic of fuel reformer burner. The purpose of this study is to develop a porous premixed flat ceramic burner that can be used for 1-5kW fuel cell reformer. Ceramic burner experiments using natural gas, hydrogen gas, anode off gas were carried out respectively to investigate the flame characteristics by heating capacity and equivalence ratio. Results show that the stable flat flames can be established for natural gas, hydrogen gas, anode off gas and mixture of natural & anode off gas as reformer fuel. For all of fuels, their burning velocities become smaller as the equivalence ratio goes to the lean mixture ratio, and a lift-off occurs at lean limit. Flame length in hydrogen and anode off gas became longer with increasing the heat capacity.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2198-2203
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• 2008

Hydrogen which can be produced through reforming process of hydrocarbon fuel is supplied into anode side of fuel cell system. In the fuel cell, only 70% of hydrogen is consumed through electrochemical reaction and 30% hydrogen passed by as anode off gas. When electrical output of fuel cell is within range of 1.0 to 3.0kW, burner for the reformer uses only anode off gas. And it uses mixture gas of anode off gas and LNG within range of 3.5 to 5.0kW in electrical output. CHEMKIN 4.1 program's Premixed code was used for calculating the properties of each gas. Results show that burning velocity and adiabatic flame temperature are 34.4cm/s, 1681.7K at equivalence ratio 0.8 within range of 1.0kW to 3.0kW and for cases of 3.5kW, 5.0kW, of electrical output, burning velocity and adiabatic flame temperature represent 30.5, 29.8cm/s and 1722.8, 1750K respectively. CO shows the lowest emission index at equivalence ratio 0.8 and NOx reveals the highest emission index at equivalence ratio 1.

• Computational Structural Engineering
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• v.10 no.2
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• pp.255-263
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• 1997

The optimum design of most structural systems used in practice requires considering design variables as discrete quantities. The present paper shows that the linear approximation method is very effective as a tool for the discrete optimum designs of unsymmetric composite laminates. The formulated design problem is subjected to a multiple in-plane loading condition due to shear and axial forces, bending and twisting moments, which is controlled by maximum strain criterion for each of the plys of a composite laminate. As an initial approach, the process of continuous variable optimization by FDM is required only once in operating discrete optimization. The nonlinear discrete optimization problem that has the discrete and continuous variables is transformed into the mixed integer programming problem by SLDP. In numerical examples, the discrete optimum solutions for the unsymmetric composite laminates consisted of six plys according to rotated stacking sequence were found, and then compared the results with the nonlinear branch and bound method to verify the efficiency of present method.

• Tuberculosis and Respiratory Diseases
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• v.44 no.6
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• pp.1440-1446
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• 1997

The radiologically detectable pulmonary involvement of NHL at diagnosis is about 4%. The commonest intrathoracic manifestations of secondary pulmonary lymphoma are mediastinal or hilar lymph node enlargement And the most frequent manifestations of pulmonary parenchymal lymphoma are lymphomatous nodules. But, when patients with newly diagnosed lymphoma exhibit rapidly progressive parenchymal lesions, an infection, such as pneumonia, is usually suspected. We present a report of a patient who developed rapidly progressive pulmonary involvement with T cell lymphoma, which was considered to be pneumonia because of high fever and rapidly progressive radiologic findings.

• Journal of the Korean Chemical Society
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• v.21 no.3
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• pp.180-186
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• 1977

The preparation of 1-chloro-2-iodoperfluorocycloalkenes was achieved with a short reaction time and a high yield when the starting compound was iodinated via the metalation process using an alkyllithium reagent. Especially, the high yield of 1-chloro-2-iodo-perfluorocyclohexene was obtained when 1,2-dichloroperfluorocyclohexene was iodinated via the same reaction conditions. The coupling reaction of 1,2-dihaloperfluorocycloalkenes was also achieved with a lower reaction temperature and a shorter reaction time when the equal slurry mixture of fluorocycloolefines and DMF was reacted at a high pressure in a sublimer. The yield of the coupling product was greatly improved by this process. For a typical example, the coupling reaction of the 1-chloro-2-iodotetrafluorocyclobutene was proceeded with a higher yield of the product than that of the reported reaction, when the present method was adopted. A plausible reaction mechanism of the present coupling reactiont was proposed and the physical characteristics of the coupling product were confirmed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.17-17
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• 1998

연소반응을 가지는 후류(wake)는 가스터빈 연소실의 flame holder 등에서 발생한다. 후류유동의 안정성 혹은 불안정성은 이러한 유동에 있어서 많은 영향을 끼치므로 상당히 중요하다. 본 연구는 위와 같이 연소 반응에 의한 밀도구배를 가지는 후류유동에 대하여 불안정성 해석을 수행하였다. 교란에 대한 지배방정식은 Navier-Stokes 방정식에서 점성항을 제외한 Euler 방정식을 고려하였다. 충류유동의 압력은 일정하다고 가정하였다. 교란 방정식을 유도하기 위하여 충류 유동이 평행하여 유동 방향에 수직한 방향의 구배만이 존재한다고 가정하였다. 모든 변수들은 충류 유동의 값과 움직이는 파장의 형태를 가지는 작은 교란의 합으로 생각하여 압력에 대한 교란방정식을 구하며, shooting법과 Newton-Raphson법에 근거를 두는 반복법을 사용하여 풀었다. 불안정성 해석을 수행하는 기본 유동의 속도장 및 온도장은 불안정성 해석을 수행하는 기본 유동의 속도장 및 온도장은 비압축성의 경우 우선 Gaussian Profile 가정함과 동시에 연소반응을 포함하는 유동장을 보다 정확히 구하기 위하여 Navier-Stokes 방정식으로부터 구한 결과를 사용하였다. 연소반응을 포함하는 유동장을 구할 때에는 해석상 편의를 위해 예혼합물질은 이상기체로, 화학반응은 1단계의 비가역반응으로 가정하였으며, 반응열로 인한 부력의 효과는 무시하였다. 위와 같은 유동장을 가지고 불안정성 해석을 수행한 결과 후류유동은 두 개의 변곡점을 가지며 sinuous 모드와 varicose모드의 두 개의 불안정성 모드가 있음을 보였다. 밀도 변화가 있는 경우나 밀도 변화가 없는 경우 모두 sinuous 모드의 가장 불안정한 모드가 varicose 모드의 가장 불안정한 모드보다 더 불안정함을 보여주어 후류 유동은 자유 유동에 가까운 위상 속도를 가지는 sinuous 모드에 의해 지배될 것임을 예측할 수 있다. 연소반응이 완전연소에 가까울수록 그리고 압축성 효과가 클수록 유동내부의 온도가 증가하고 점성 또한 증가하여 후류유동은 안정됨을 알 수 있었다 유동변수들의 contour로부터 유동의 특성을 예측한 결과 baroclinic 항이 dilatational 항보다 상대적으로 크며, 중심선 상하에 생기는 vortex를 더욱 성장시킬 것으로 생각된다.

• Korean Journal of Food Science and Technology
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• v.37 no.4
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• pp.642-647
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• 2005

Lonicerae Flos was extracted with methanol and successively fractionated with petroleum ether, chloroform, ethyl acetate, and methanol to investigate their antimicrobial effects against food-borne pathogens and food spoilage bacteria using paper disc method. Ethyl acetate extracts of L. Flos showed highest antimicrobial activity against Shigella dysenteriae. Synergistic effect in inhibition was observed when L. Flos extract was mixed with Artemisa capillaris extract as compared to using each extract alone. Growth inhibition curves were determined using ethyl acetate extracts of L. Flos against Staphylococcus epidermidis and S. dysenteriae. Ethyl acetate extract of L. Flos had antimicrobial activity against S. dysenteriae at 3,000 ppm, retarding growth of S. dysenteriae up to 12 hr.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7718-7728
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• 2015

Semantic similarity between words can be applied in many fields including computational linguistics, artificial intelligence, and information retrieval. In this paper, we present weighted method for measuring a semantic similarity between words in a document. This method uses edge distance and depth of WordNet. The method calculates a semantic similarity between words on the basis of document information. Document information uses word term frequencies(TF) and word concept frequencies(CF). Each word weight value is calculated by TF and CF in the document. The method includes the edge distance between words, the depth of subsumer, and the word weight in the document. We compared out scheme with the other method by experiments. As the result, the proposed method outperforms other similarity measures. In the document, the word weight value is calculated by the proposed method. Other methods which based simple shortest distance or depth had difficult to represent the information or merge informations. This paper considered shortest distance, depth and information of words in the document, and also improved the performance.