• 한국환경과학회지
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• 제32권10호
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• pp.731-739
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• 2023

In this study, lab-scale phosphorus coagulation/precipitation experiments were performed using three types of polyaluminum chloride (PAC) with different Al contents (10%, 12%, and 17%). The PO₄-P removal efficiencies at various operating conditions, such as initial PO₄-P concentration, initial pH, and Al/P molar ratio, were evaluated, and correlations among the operating factors affecting phosphorus coagulation/precipitation with PAC were derived to optimize the process efficiency. When the initial PO₄-P concentration was 0.065 and 0.161 mmol P/L under an initial pH of 8-10, the optimal PAC dose was 0.126-0.378 and 0.189-0.667 mmol Al/L, respectively. Under these conditions, the Al/P molar ratio was 2.16-6.18 and 1.28-4.30, respectively, and the PO₄-P removal efficiency was in the range of 40.2-92.5%. When the Al/P molar ratio was 2 or less under an initial pH condition of 6-8, the PO₄-P removal efficiency was approximately ≤40% owing to insufficient Al³⁺ ions. However, when the Al/P molar ratio is 3-5, the PO₄-P removal efficiency improved to approximately 80-90%. Thus, the optimal Al/P molar ratio to achieve a PO₄-P removal efficiency of over 90% was determined to be approximately 4 in the PO₄-P coagulation/precipitation process using PAC.

• 전기화학회지
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• 제2권3호
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• pp.163-170
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• 1999

AFC 단전지에서 운전조건의 영향은 이제까지 자세히 연구된 바 없다. 본 연구에서는 초기 전해질 농도와 가스 운전압력의 영향을 살펴보기 위하여 1차원 등온 모델을 이용해 전산모사를 수행하였다. 결과에 의하면, base-case에서 최적 전해질 농도는 $3.0\~3.5M$사이에 있는 것으로 발견되었다. 전해질 농도에 따른 전지 성능의 변화는 주로 양쪽 전극의 전하전달 저항과 용해된 기체의 헨리상수 및 액상확산이 원인인 것으로 밝혀졌다. 또한, 운전 압력의 증가는 반응속도와 가스의 용해도를 증가시켰으며, 이것으로 인해 전지 성능이 상당히 향상되는 것으로 조사되었다

• 한국결정학회지
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• 제4권1호
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• pp.42-48
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• 1993

K6P4Ol3 응제를 사용하여 TSSG법에 의해 KTP(K Tiop04) 단결정을 성장시켰다. 가열로의 내부에 heatpipe와 복사방열판을 설치하여 도가니 내의 온도 안정성 및 균일도를 향상시켰다. 크고 양질의 단결정을 얻기 위한 목적으로 조업온도 구간,초기 냉각속도, 강제교반, 융제의 재사용과 같은 몇 가지 조업변수들에 따른 영향을 비교 고찰하였다. 본 융제의 조건하에서(0.6g KTP/lg flux), 초기 냉각속도가 0.1℃/hr 이하까지 느릴수록, 적절한 결정 회전이 수반될수록 양질의 단결정성장에 유리하였다. 최대 44 × 39 ×17체 크기의 KTP단결정을 얻을 수 있었으며, 단순가공 상태하에서도 21.3% SHG 변환효율을 나타내었다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1997년도 춘계학술발표회논문집(1)
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• pp.508-513
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• 1997

One of the moot important constants to be Installed In COLSS, a monitoring system in CE typed reactors, is ROPM which would limit the operating space. This static ROPM was calculated from digital transient analysis assuming that every design basis transient was initiated from the most severe initial condition combination (LCO). Once It could be assured that core condition would not be located at none other than LCO, this static ROPM could be replaced with dynamic ROPM calculated at that condition and the dynamic ROPM would be definitely less than the static ROPM. In order to do, It must be required to calculate the transient discrete sensitivity parameters and parameters change distribution. The purpose of this report is just to propose the enlargement method for thermal margin.

• 대한조선학회논문집
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• 제51권6호
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• pp.489-494
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• 2014

Estimation of correct ice load under various operating conditions is important during the design and the operation stages of an icebreaker. Normal operating conditions are expected from the official field ice trials and also from general ice transit action. In this paper ice load for the Korean icebreaking research vessel, ARAON, under normal operating condition, is discussed. Published ice load data from full-scale sea trials of six icebreakers were analysed to derive an empirical ice load prediction formula. The IBRV ARAON had sea ice trials during 2010 and 2012 summer season. Strain gauge signal were recorded during her icebreaking voyage and the measured strain data were converted to the equivalent hull stress values. The effect of ARAON's speed in ice and the hull stresses are investigated. By comparing the empirical formula and ice load calculation based von measured data, it is recommended to use the empirical ice load estimation formula for the initial design stage.

• 에너지공학
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• 제12권1호
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• pp.11-16
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• 2003

지상 정적 상태에 있는 항공기내 연료온도의 변화가 유한차분식에 의하여 해석되었다. 수정 Dufort-Frankel 기법의 explicit 방법에 의해 수치계산이 수행되었다. 항공기는 지상 정적상태에서 1% hot day 대기조건에 따른 태양의 복사 및 바람의 속도와 함께 반복되는 일일주기의 공기온도에 노출되어 있다고 가정되었다. 항공기는 난류유동장내에 있는 것으로 가정되었다. 항공기 표면과 외부대기사이의 열전달을 계산하기 위하여 Eckert에 의해 제안된 평판위의 난류 열전달계수가 사용되었다. 본 해석에 사용된 지배방정식은 연료에 대한 에너지방정식이다. 본 해석으로부터, 주익탱크의 연료온도가 다른 탱크들 가운데 가장 높게 나타났으며 온도변화율 또한 가장 크게 나타났다. 본 온도해석에 대한 결과는 여러 비행임무에 있어서 항공기내의 연료온도 변화 해석을 위한 초기치로서 사용될 수 있다. 또한, 본 해석방법은 항공기 열에너지 관리시스템의 해석 및 설계에 사용될 수 있다.

• 수산해양기술연구
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• 제50권3호
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• pp.378-384
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• 2014

Trawlers are divided into stern and side types by the method of shooting and hauling net, but the latter is difficult to find beside Korea. In East Sea of Korea, the side type used to be in early 2000's, but it improved to stern type because of its inefficient operating method. The aims of this paper is to make clear the stability of the side trawler in the East Sea, and then confirm whether it satisfy the IMO rule or not, the degree of the transverse inclining angle of the ship when hauling net at hull side. In results, the stability of the ship in initial inclining range satisfied the IMO rule and the domestic rule, but not satisfied those rule in over the range. The limit load of the ship that was coincide with the angle of beam end in hauling net at side was about 26 tons, 18 tons in normal sea condition and storm warning condition respectively. The transverse inclining angles of the ship in hauling net were much higher from 3.3 to 5.5 times than the longitudinal inclining angle of the stern trawler, although those angles were slightly changed with depending on the loading and sea condition.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.132-137
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• 2008

A failure analysis of ammonia converter which suffered hydrogen attack in two years since its initial operating time was presented. It is constructed from 2.25 Cr.1 Mo steel. Analysis showed that the failure on closing seam weld joint was due to local improper post weld heat treatment (PWHT). Improper PWHT can introduce high residual stresses in thick-walled pressure vessel. High residual stress level in weld joint is very prone to hydrogen attack for any components which are operating in hydrogen gas environment. The repair procedures based on the principle to decrease the residual stress then proposed. The repair was controlled very carefully by applying several nondestructive tests in the each stage of repair. To assure the successful of the proposed repair, after one year since repair time, high temperature ultrasonic and TOFD methods were applied on-stream to this equipment in order to evaluate its post repair condition. The two methods showed good results on the repaired area.

• 대한금속재료학회지
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• 제56권12호
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• pp.893-899
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• 2018

In the present study, we investigated the sulfur poisoning of the Ni anode in solid oxide fuel cells (SOFCs) as a function of operating conditions. Anode supported cells were fabricated, and sulfur poising tests were conducted as a function of current density, $H_2S$ concentration and humidity in the anode gas. The voltage drop was significant under the higher current density (${\sim}714mA/cm^2$) condition, while it was much reduced under the lower current density (${\sim}389mA/cm^2$) condition, at 100 ppm of $H_2S$. A secondary voltage drop, which occurred only at the high current density, was attributed to Ni oxidation in the anode. Thus, operation at high current density with high $H_2S$ concentration may lead to permanent deterioration in the anode. The effect of water content (10%) on the sulfur poisoning was also investigated through a constant current test (${\sim}500mA/cm^2$) at 10 ppm of $H_2S$. The cell operating with 10% wet anode gas showed a much smaller initial voltage drop, in comparison with a dry anode gas. The present study indicates that operating conditions, such as gas humidity and current density, should be carefully taken into account, especially when fuel cells are operated with $H_2S$ containing fuel.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.244-249
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• 1997

Internal and external heat sources will cause to deform to machine elements in the contact joint of structure,which results in the change of contact pressure distribution different from initial assembly. Heat induced variations of contact pressure will change the static and dynamic properties such as contact stiffness,damping as well as contact heat conduction in the structure. In order to design and control the intelligent machine tool operating in variant conditions more sophisticatedly, the good prediction for the changes of prescribed propeties are strongly required especially in the contact elements adjacent to the rotational or linear bearing This paper presents some computational and experimental results in regard to static and dynamic characteristics of the press-fitted bush and shaft assembly which is a model of the bearing innerrace and shaft assembly. In the condition of heat generation on the outer surface of the bush,the effects of changes in the negative clearance and the heat flux on pressure distribution and dynamic properties are investigated. Results of this study show that the edge effect of the bush and the initial clearance have effects on the transient dynamic characteristics significantiy.