• 한국지하수토양환경학회지:지하수토양환경
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• 제19권6호
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• pp.13-17
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• 2014

Subcritical water acts like an organic solvent at elevated temperature in terms of its physicochemical properties. Taking into account this advantage, the remediation experiments of benzo[a]pyrene contaminated soil (8.45 mg/kg of initial concentration) were conducted using subcritical water extraction apparatus. The effect of operating factors on the removal efficiency was studied at the varying the conditions of the water temperature ranging $200{\sim}300^{\circ}C$, extraction time 30~90 min, and flow rate 0.3~2.0 mL/min. 12 g of benzo[a]pyrene contaminated soil was inserted into the extraction cell and placed into the reactor and then the subcritical water was driven through the cell. In this study, the removal efficiency of benzo[a]pyrene was increased from 55.1 to 98.1% when the temperature increased from 200 to $300^{\circ}C$. The removal efficiency was decreased from 97.0 to 77.0% when the flow rate increased from 0.3 to 2.0 mL/min, suggesting that the extraction is limited by intra-particle diffusion. The 30 min reaction time was determined as an effective treatment time at $250^{\circ}C$. Based on the results, the optimum condition for the remediation of benzo[a]pyrene contaminated soil was suggested to be $250^{\circ}C$, 30 min, and 0.3 mL/min.

• Nuclear Engineering and Technology
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• 제53권12호
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• pp.3879-3891
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• 2021

A heat pipe residual heat removal system is proposed to be incorporated into the reactor driven subcritical (RDS) facility, which has been proposed by MIT Nuclear Reactor Laboratory for testing and demonstrating the Fluoride-salt-cooled High-temperature Reactor (FHR). It aims to reduce the risk of the system operation after the shutdown of the facility. One of the main components of the system is an air-cooled heat pipe heat exchanger. The alkali-metal high-temperature heat pipe was designed to meet the operation temperature and residual heat removal requirement of the facility. The heat pipe model developed in the previous work was adopted to simulate the designed heat pipe and assess the heat transport capability. 3D numerical simulation of the subcritical facility active zone was performed by the commercial CFD software STAR CCM + to investigate the operation characteristics of this proposed system. The thermal resistance network of the heat pipe was built and incorporated into the CFD model. The nominal condition, partial loss of air flow accident and partial heat pipe failure accident were simulated and analyzed. The results show that the residual heat removal system can provide sufficient cooling of the subcritical facility with a remarkable safety margin. The heat pipe can work under the recommended operation temperature range and the heat flux is below all thermal limits. The facility peak temperature is also lower than the safety limits.

• 대한수학회지
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• 제53권2호
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• pp.247-262
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• 2016

In this paper, we consider the following $Schr{\ddot{o}}dinger$-Poisson system: $$\{\begin{array}{lll}-{\Delta}u+u+{\lambda}{\phi}u={\mu}f(u)+{\mid}u{\mid}^{p-2}u,\;\text{ in }{\Omega},\\-{\Delta}{\phi}=u^2,\;\text{ in }{\Omega},\\{\phi}=u=0,\;\text{ on }{\partial}{\Omega},\end{array}$$ where ${\Omega}$ is a smooth and bounded domain in $\mathbb{R}^3$, $p{\in}(1,6]$, ${\lambda}$, ${\mu}$ are two parameters and $f:\mathbb{R}{\rightarrow}\mathbb{R}$ is a continuous function. Using some critical point theorems and truncation technique, we obtain three multiplicity results for such a problem with subcritical or critical growth.

• 대한기계학회논문집
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• 제10권3호
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• pp.277-284
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• 1986

본 연구에서는 상호작용하는 난류경계층의 여러가지 상류상태를 이론적인 방 법으로 묘사하여, 상류상태를 정의하는 매개변수의 각각의 독립적인 영향을 살펴보았 다.

• 물과 미래
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• 제26권3호
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• pp.103-111
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• 1993

자연하천의 수면곡선을 계산하기 위하여 표준축차계산법에 근거하 HEC-2모형을 이용하는 것이 일반적이다. 상류흐름에서 수면곡선의 계산은 일반적으로 하류에서 상류로 수행해 나간다. 그러나 이와 반대로 기준수면고가 상류지점에만 있는 경우, 하류쪽의 수면고들을 계산하고자 할 때는 많은 노력과 시간이 필요하게 된다. 이러한 경우에도 HEC-2를 이용하여 간편하게 상류에서 하류로 수면곡선을 계산하는 방법을 제안하였으며, 이 방법을 균일수로와 자연하천에 적용하여 타당성과 정밀도를 검토하였다.

• 한국세라믹학회지
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• 제22권4호
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• pp.26-32
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• 1985

The subcritical crack growth of sintered SiC is investigated under various corrosive atmospheres such as distilled water Murakami solution and saturated KOH solution. The KI-V diagrams are obtained by the load relaxation method and incremental displacement rate method using the double torsion technique. The obtained fracture mechanics parameters (n) of sintered SiC are 79 in Murakami solution and 39 in saturated KOH solution. These data indicate that the subcritical crack growth of sintered SiC is taking place in these two conditions and the stress-corrosion cracking is suggested to be the mechanism. With these KI-V diagrams the life of sintered SiC in these conditions is predicted.

• 대한수학회보
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• 제54권3호
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• pp.1023-1036
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• 2017

In this paper, we study the existence of positive solutions to the p-Kirchhoff elliptic equation involving general subcritical growth $(a+{\lambda}{\int_{\mathbb{R}^N}{\mid}{\nabla}u{\mid}^pdx+{\lambda}b{\int_{\mathbb{R}^N}{\mid}u{\mid}^pdx)(-{\Delta}_pu+b{\mid}u{\mid}^{p-2}u)=h(u)$, in ${\mathbb{R}}^N$, where a, b > 0, ${\lambda}$ is a parameter and the nonlinearity h(s) satisfies the weaker conditions than the ones in our known literature. We also consider the asymptotics of solutions with respect to the parameter ${\lambda}$.

• Journal of Industrial and Engineering Chemistry
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• 제68권
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• pp.301-310
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• 2018

Various catalysts such as formic acid, acetic acid, sodium hydroxide, sodium bicarbonate, carbon dioxide and nitrogen gas were used for hydrolyzates production from deoiled mackerel muscle by subcritical water hydrolysis. Above 99% hydrolysis yield was obtained using sodium bicarbonate catalyst at $260^{\circ}C/70bar$. Histamine and heavy metals concentration were reduced in hydrolyzates. Highest amount of amino acid (400.36 mg/g) and reducing sugar (24.75 mg/g) were found in hydrolyzate obtained at $260^{\circ}C/70bar$ and $220^{\circ}C/30bar$, respectively with sodium bicarbonate catalyst. Antioxidant and ACE-inhibitory activities were significantly higher in hydrolyzates obtained using sodium bicarbonate than that of others.

• Nuclear Engineering and Technology
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• 제53권7호
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• pp.2133-2150
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• 2021

In this work, Esfahan light water subcritical reactor (ELWSCR) is analysed using experimental and theoretical diagnostic methods. Important neutronic parameters of the system such as prompt neutron lifetime, delayed neutron fraction, prompt neutron decay constant, negative reactivity of the core, fuel and moderator temperature coefficient of reactivity, and overall and local void coefficient of reactivity are estimated. Also, neutron flux distribution, reflector saving, water level effect, and lattice pitch of the core including operating point of the facility are studied in details. Theoretical results are calculated by MCNPX and measurements are performed utilizing zero power reactor noise method. Detailed descriptions of the results are explained in the text.

• 대한환경공학회지
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• 제37권2호
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• pp.113-119
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• 2015

본 연구에서는 대표적 난분해성 유기화합물인 PCBs (Polychlorinated Biphenyls) 및 기타 난분해성 물질 오염토양을 정화하기 위하여 고온고압의 물을 이용하였다. 먼저, PCBs 오염토 적용시 반응온도에 따른 영향에서는 아임계수 조건에서 온도가 증가함에 따라 처리효율이 선형적으로 증가하였고 반응시간의 증가에 따라서도 처리효율은 증가함을 보였다. 처리입경별 실험에서는 미세토의 경우가 처리효율이 약간 낮았다. 아임계수와 영가철에 의한 PCBs 분해 기작을 예측하기 위해 Ion chromatography 및 GC-MS 분석을 한 결과 탈염화 반응산물이 생성되었으며 헤드스페이스 실험결과 PCBs분해기작은 대부분 산화이며, 일부만이 탈염화에 의한 것임을 확인하였다. TPH, BTEX, TCE/PCE, 클로르피리포스 등의 난분해성 물질 오염토처리를 위해 $300^{\circ}C$ 아임계수 조건을 적용한 결과 모두 90% 이상의 처리효율을 나타냈으며, 처리효율과 반응부산물 등의 검토를 통해 PCBs 오염토 외에 다른 난분해성 물질 오염토 처리분야에도 적용가능함을 확인하였다.