• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.365-371
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• 2019

In this study, the flame temperature distribution of the diffusion flame burner for SiO₂ deposition was analyzed by the computational fluid analysis. This corresponds to the previous step for simulating the SiO₂ preform deposition process for manufacturing optical fibers using environmentally friendly raw materials. In order to model premixed combustion, heat flow, convection, and chemical reactions were considered, and Reynolds-averaged Navier-Stokes equations and k-ω models were used. As a result, the temperature distribution of the flame showed a tendency to increase the distance from the nozzle surface to the maximum temperature when the flow rate of the auxiliary oxygen increased. In addition, it was confirmed that the temperature distribution due to incomplete combustion was large in the combustion reaction with a large equivalence ratio of the mixed gas.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.4
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• pp.276-282
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• 2008

The effects of hydrogen enrichment to methane have been investigated with swirl-stabilized premixed hydrogen-enriched methane flame in a laboratory-scale pre-mixed combustor. The hydrogen-enriched methane fuel and air were mixed in a pre-mixer and introduced to the combustor through different degrees of swirl vanes. The flame characteristics were examined for different amount of hydrogen addition to the methane fuel and different swirl strengths. The hydrogen addition effects and swirl intensity on the combustion characteristics of pre-mixed methane flames were examined using micro-thermocouple, particle image velocity meter (PIV) and chemiluminescence techniques to provide information about flow field. The results show that the flame area increases at upstream of reaction zone because of increase in ignition energy from recirculation flow for increase in swirl intensity. The flame area is also increased at the downstream zone by recirculation flow because of increase in swirl intensity which results in higher centrifugal force. The higher combustibility of hydrogen makes reaction faster, raises the temperature of reaction zone and expands the reaction zone, consequently recirculation flow to reaction zone is reduced. The temperature of reaction zone increases with hydrogen addition even though the adiabatic flame temperature of the mixture gas decreases with increase in the amount of hydrogen addition in this experiment condition because the higher combustibility of hydrogen reduces the cooler recirculation flow to the reaction zone.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1465-1472
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• 2009

The effect of heat loss rate on NOx formation of $CH_4/air$premixed flame were examined numerically in a perfectly stirred reactor. The following conclusions were drawn. Under the adiabatic wall condition, an increase in the residence time causes a remarkable increases in NOx emission. Under the heat loss conditions, however, NOx decreases significantly as the heat transfer coefficient and residence time increase. As the heat loss rate increases, Thermal NO mechanism and Re-burning NO mechanism play an important role in the NOx reduction, but Prompt NO mechanism and $N_2O$-intermediate NO mechanism lead to the increase in NOx production. Although the NOx formation is actually related to complex NOx mechanism with the changes in the heat transfer coefficient and residence time, it was found that NOx concentration can be represented by independent Thermal NO mechanism. From these results, new NOx correlation combined with the heat loss rate and residence time was suggested for predicting the NOx concentration in a practical $CH_4/air$premixed combustor.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1992.05a
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• pp.57-57
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• 1992

Teicoplanin은 actinoplanes teicomyceticus의 발효산물로서 vancomycin과 같은 glycopeptide 계열의 항균제이며, 그 작용기전은 세포벽 합성과정중 peptidoglycan의 중합을 억제하는 것으로 vancomycin과 유사하나 vancomycin과 달리 근육에 주사할 수 있으며 "red man's syndrome"이 생기지 않고 vancomycin보다 반감기가 길다. 그람양성균 감염증에 대한 teicoplanin의 효능 및 안전성을 조사하기 위하여, 그람양성균에 의한 감염증 또는 그람양성균과 그람음성균에 의한 혼합감염증이 확인되거나 의심되었던 환자 46명을 대상으로 teicoplanin과 vancomycin을 투여하였다. 투약 환자중 임상적인 반응을 평가할 수 있는 환자의 수는 vancomycin의 경우 투약환자 22명중 21명, teicoplanin의 경우 24명중 19명이였다. Vancomycin군중 임상적 반응의 평가에서 제외된 1명은 수술 후 흉막강에 MRSA 에 의한 농양으로 투약 29일째에 뇌출혈로 사망하였던 예로, 추적-배양검사에서는 MRSA가 제거 되었다. Teicoplanin군에서는 항균제 투여 중 간경변증에 의한 식도출혈 1예, 수술후 위장관 출혈 1예, 뇌 색전중 1예가 사망하였고, 1예는 Teicoplanin에 의한 심한 피부발진으로, 다른 1예는 봉와직염의 임상진단이 조직검사결과 악성종양의 근육침범으로 밝혀져 투약을 중단하였다.

• Proceedings of the Korea Multimedia Society Conference
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• 2012.05a
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• pp.262-263
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• 2012

다중 센서의 영상, 예를 들어 가시광 영상과 적외선 영상은 서로 다른 특징을 가지고 있기 때문에 본 논문에서는 IR 영상의 특징을 보존한 새로운 혼합기법을 제안하다. 이러한 혼합기법은 의료 영상, 보안 영상 등에서 매우 중요하고 다양하게 다루어진다. 일반적인 혼합기법을 사용하게 되면 영상간의 특색 때문에 혼합 시 조화롭지 못하는 문제점을 가진다. 이러한 문제점을 해결하기 위해서 본 논문에서는 중요도 맵을 추출하고 그 영역에 대하여 포아송 블랜딩을 통해 두 개의 다른 특징을 가시광 영상을 혼합한다. 제안한 알고리즘은 기존의 연구와 다르게 혼합할 영역을 수동으로 지정하는 것이 아니라 자동적으로 추출하고, 가시광 영상에 IR 영상에서만 검출되는 영역을 결합한 새로운 결과를 얻을 수 있었다.

• Journal of Korean Orthopaedic Sports Medicine
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• v.10 no.1
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• pp.18-26
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• 2011

Purpose: This study is to compare the clinical results of ACL reconstruction between three groups using hamstring tendon autograft, mixed and tibialis tendon allograft. Materials and Methods: Between August 2003 and August 2008, we analyzed 169 cases of ACL reconstruction, 66 cases used hamstring tendon autograft, 42 cases used mixed graft and 61 cases used tibialis tendon allograft, with a minimum follow-up of 12 months. For the clinical evaluation, we evaluated the Lysholm score, Telos stress test device and IKDC score. Results: The average side to side difference in Telos stress test decreased from $7.5{\pm}1.0$ mm to $1.6{\pm}1.0$ mm in autograft group, from $7.6{\pm}1.1$ mm to $1.4{\pm}1.1$ mm in mixed graft group and from $7.4{\pm}1.3$ mm to $2.5{\pm}1.3$ mm in allograft group. The average Lysholm knee score improved from 58.6 to 92.3 in autograft group, from 60.6 to 92.6 in mixed graft group and from 55.3 to 91.5 in allograft group. There was no significant difference between three groups in clinical results. At second look arthroscopy, tension of ligament and synovial coverage were good result in autograft and mixed graft than allograft group. Conclusion: All hamstring tendon autograft, mixed graft and tibialis tendon allograft groups showed satisfactory clinical results, with no significant difference in outcomes between the groups. Both hamstring tendon autograft and mixed graft showed good synovial coverage in second look arthroscopy. So mixed graft will be considered as good alternative in case of shorter or thin harvested hamstring tendon.

• The Journal of Korean Orthopaedic Ultrasound Society
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• v.2 no.1
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• pp.13-17
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• 2009

Purpose: The purpose of this study was to know the cause of the tenderness at pes anserinus. Materials and Methods: Out of 24 patients with tenderness at pes anserinus, 23 patients were female and 1 patient was male, and their average age was 65.9 years old. We checked the tenderness at pes anserinus by history taking & physical examniation and then, checked the pes anserinus for the presence of bursitis by US in outpatient clinic. With no evidence of bursitis by US, we injected steroid-lidocaine mixture intraarticularly and checked whether the tenderness disappeared after 2~3 minutes. Results: There was no case with bursitis at pes anserinus by US. The tenderness at pes anserinus diminished in 2-3 minutes after the intraarticular injection of the steroid-lidocaine mixture. After 6 weeks follow up, 16 patients(66.7%) had little or no tenderness at pes anserinus. 8 cases had the recurrence of tenderness recurred, 4 cases underwent arthroscopic operation on the meniscal tear, and 1 case underwent total knee arthroplasty. All cases underwent any operations had the tenderness at pes anserinus disappeared. The others 3 cases did not undergo total knee arthroplasty despite of radiologic obliteration of knee joint adequate for Kellgren-Lawrence grade IV. Conclusion: Without the bursitis at Pes Anserinus, patients the osteoarthritis may have the tenderness due to the referred pain.

• Transactions of the Korean Society of Automotive Engineers
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• v.19 no.1
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• pp.1-8
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• 2011

In recent years, there has been an interest in early-injection diesel engines as it has the potential of achieving a more homogeneous and leaner mixture close to TDC compared to standard diesel engine. The more homogeneous mixture may result in reduced NOx and soot emissions and higher efficiency in homogeneous charge compression ignition engines. While earlier studies have shown that a reduction in NOx emissions from HCCI engine is possible, there are some significant problems including the control of ignition timing and combustion rate. In order to investigate the effect of EGR and hydrogen enriched gas on combustion characteristics and emissions, an experiments with single cylinder CRDi engine were carried out concerning the formation of various premixed charge, which can achieved by early injection, EGR and hydrogen enriched gas. EGR was not effective to further reduce NOx and PM emissions. It was found that NOx emissions were decreased with an introduction of hydrogen enriched gas and an adequate diesel fuel amount.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.4
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• pp.425-432
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• 2004

The objective of this study is a qualitative comparison between line-integrated OH chemiluminescence(OH$\^$*/) image and its Abel inverted image to investigate the flame structure at different phase of the oscillating pressure field. PIV(Particle Image Velocimetry) measurements were conducted under non-reacting conditions to see the global flow structure and NOx emission was measured to investigate the effect of fuel-air premixing on combustion instability and emission characteristics. Experiments were carried out in an atmospheric pressure, laboratory-scale dump combustor operating on natural gas. Combustion instabilities in present study exhibited a longitudinal mode with a dominant frequency of ∼341.8㎐, which corresponded to a quarter wave mode of combustor. Heat release and pressure waves were in-phase when instability occurred. Results gave an insight about the location where the strong coherence of pressure and heat release existed. Also an additional information on active control to suppress the combustion instabilities was obtained. For lean premixed combustion, strong correlation between OH$\^$*/ and NOx emissions was expected largely due to the exponential dependence of thermal NOx mechanism on flame temperature.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.3
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• pp.43-49
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• 2013

This work investigated the effects of engine speed and injection timing on combustion and emissions characteristics in a partially premixed charge compression ignition (pPCCI) engine fueled with DME. pPCCI engine especially has potential to achieve more homogeneous mixture in the cylinder, which results in lower NOx and smoke emission. In this study single cylinder engine was equipped with common rail and injection pressure is 700 bar. Total injected fuel mass is 64.5 $mm^3$ per cycle. The amount of pilot injection of the entire injection 12.5% is tested. Results show that NOx emission is decreased while IMEP is increased as the retard of injection timing. Besides, NOx emissions are slightly rised as well as IMEP is increased with the increase of engine speed.