• Journal of Powder Materials
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• v.14 no.4
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• pp.238-244
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• 2007

The electrophoretic deposition process of Ni nano-particles in organic suspension was employed for self-repairing of heat exchanger tubes. For this purpose, Ni nano-particles prepared by levitational gas condensation method were dispersed into the solution of ethanol with the addition of dispersant Hypermer KD2. For electrophoretic deposition of Ni nano-particles on the Ni alloy specimen, constant electric fields of 20 and 100 V $cm^{-1}$ were applied to the specimen in Ni-dispersed solution. It was found that as electrophoretic deposition proceeds, the size of the pit or crack remarkably decreased due to the agglomeration of Ni nano-particles at the pit or crack. This strongly suggests that the electrophoretic mobility of the charged particles is larger for the damaged part with a higher current value rather than outer surfaces with a lower current value.

• Journal of Korean Society on Water Environment
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• v.23 no.2
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• pp.244-250
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• 2007

This study was carried out to obtain the optimum design factors for an eletrolytric flotation reactor. When the effluent of the leachate treatment facility was treated under the condition of 10 volts, 30 minutes, at the Al-Al electrode system; COD removal efficiency was 45%, and total phosphorus removal efficiency was 98%. The high removal efficiency was caused by the fact that phosphate was removed by leaching $Al^{3+}$ from two electrodes. The leachate containing high ammonium nitrogen concentration was treated by a batch test under the condition of 60 minutes reaction time and added chloride ion; ammonium nitrogen removal efficiency was 89%. This high efficiency was affected by added chloride ion to wastewater. To find the optimum current density and voltage of the leachate containing chloride ion (ratio of $Cl^-/NH_4-N$ is 11) a electrochemical polarization curve was used. These values were found to be $4.5mA/cm^2$ and about 2.1 V, respectively. When C-Al electrode system was used at a batch test, the total nitrogen removal efficiency was increased by 1.8 to 3.3 times, compared to Al-Al electrode system due to high $Cl_2$ gas production.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2803-2815
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• 2021

This paper addresses the uncertainty quantification and sensitivity analysis of a depleted light-water fuel assembly of the Turkey Point-3 benchmark. The uncertainty of the fuel assembly decay heat and isotopic densities is quantified with respect to three different groups of diverse parameters: nuclear data, assembly design, and reactor core operation. The uncertainty propagation is conducted using a two-step analysis code system comprising the lattice code STREAM, nodal code RAST-K, and spent nuclear fuel module SNF through the random sampling of microscopic cross-sections, fuel rod sizes, number densities, reactor core total power, and temperature distributions. Overall, the statistical analysis of the calculated samples demonstrates that the decay heat uncertainty decreases with the cooling time. The nuclear data and assembly design parameters are proven to be the largest contributors to the decay heat uncertainty, whereas the reactor core power and inlet coolant temperature have a minor effect. The majority of the decay heat uncertainties are delivered by a small number of isotopes such as ²⁴¹Am, ¹³⁷Ba, ²⁴⁴Cm, ²³⁸Pu, and ⁹⁰Y.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.2830-2838
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• 2021

This work deals with the assessment of the burnup capabilities of the Serpent Monte Carlo code to predict spent nuclear fuel (SNF) isotopic concentrations for low-enriched uranium (LEU) fuel at different burnup levels up to 47 MWd/kgU. The irradiation of six UO₂ experimental samples in three different VVER-1000 reactor units has been simulated and the predicted concentrations of actinides up to ²⁴⁴Cm have been compared with the corresponding measured values. The results show a global good agreement between calculated and experimental concentrations, in several cases within the margins of the nuclear data uncertainties and in a few cases even within the reported experimental uncertainties. The differences in the performances of the JEFF3.1.1, ENDF/B-VII.1 and ENDF/B-VIII.0 nuclear data libraries (NDLs) have also been assessed and the use of the newly released ENDF/B-VIII.0 library has shown an increased accuracy in the prediction of the C/E's for some of the actinides considered, particularly for the plutonium isotopes. This work represents a step forward towards the validation of advanced simulation tools against post irradiation experimental data and the obtained results provide an evidence of the capabilities of the Serpent Monte-Carlo code with the associated modern NDLs to accurately compute SNF nuclide inventory concentrations for VVER-1000 type reactors.

• Tuberculosis and Respiratory Diseases
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• v.56 no.3
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• pp.280-288
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• 2004

Background : Lung protective strategies, using low tidal volume in ARDS, improve survival rate in ARDS. However, low tidal volume ventilation may promote alveolar de-recruitment. Therefore, alveolar recruitment is necessary to maintain arterial oxygenation and to prevent repetitive opening and closure of collapsed alveoli in lung protective strategies. There has been a recent report describing improvement in arterial oxygenation with use of recruitment maneuver. However, impact of recruitment on outcome of ARDS is unknown. We evaluated whether short-term survival difference existed in patients with ARDS, who were performed alveolar recruitment maneuver(ARM) and prone position, according to response of alveolar recruitment or not. Methods : All patients who were diagnosed with ADRS and received mechanical ventilation were included. ARM were sustained inflation($35-45cmH_2O$ CPAP for 30-40 sec.) or increasing level of PEEP. If these methods were ineffective, alveolar recruitment with prone position was done for at least 10 hours. $P_aO_2/FiO_2$(P/F) ratio was determined before and at 0.5 and 2 hours after ARM. We defined a responder if the P/F ratio was increased over 50% of baseline value. We compared 10-days and 30-days survival rate between responders and non-responders. Results : 20 patients(M:F=12:8, $63{\pm}14age$) were included. Among them, 12 patients were responders and 8 patients were non-responders. In responders, P/F ratio was increased from $92{\pm}25mmHg$ to $244{\pm}85mmHg$. In non-responders, P/F ratio increased from $138{\pm}37mmHg$ to $163{\pm}60mmHg$. Among non-responders, P/F ratio was improved over 50% in 2 patients after prone position. Overall, 14 patients were responders after ARM and prone position. The 10-days and 30-days survival rate in responders was significantly higher than in non-responders(86%, 57% in responders and 33%, 0% in non-responders)(p<0.05). There was no significant difference between responders and non-responders in age($71{\pm}11$, $60{\pm}14$), lung injury score($2.8{\pm}0.2$, $2.9{\pm}0.45$), simplified acute physiology score(SAPS) II ($35{\pm}4.6$, $34{\pm}5.7$), positive end-positive pressure level($15.6{\pm}1.9cmH_2O$, $14.5{\pm}2.1cmH_2O$). Conclusion : ARM may improve arterial oxygenation in some patients with ARDS. These responders in patients with ARDS showed significant higher 10-days and 30-days survival rate than non-responders patients with alveolar recruitment.

• Journal of Gastric Cancer
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• v.6 no.4
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• pp.244-249
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• 2006

Purpose: Tumor size has been reported to be one of the prognostic factors in the preoperative setting and 8 cm has been confirmed as a cut-off value for large gastric tumors with respect to postoperative complications. The aim of this study was to investigate the clinicopathologic features and the prognosis in patients with tumors larger than 8 cm in diameter. Materials and Methods: We retrospectively studied 2,260 patients with gastric cancer who underwent a gastrectomy from 1983 to 2001 at the Department of Surgery, Korea University College of Medicine. For a comparative analysis we divided the cases into the large and the small groups according to tumor size. The clinicopathological factors associated with large gastric tumors were analyzed by using univariate and multivariate analyses. To determine which variables were independent prognostic factors for overall survival, we applied the Cox proportional hazards model and we used P<0.05 as the cutoff value for statistical significance. Results: Univariate and multivariate analyses disclosed that tumor location (P<0.001), resection type (P<0.001), curability (P<0.001), depth of invasion (P<0.001), number of metastatic lymph nodes (P<0.001), differentiation (P<0.001) and combined resection (P<0.001) were significantly different between the two groups. The independent factors for survival identified by using the Cox proportional hazards model for large gastric tumors were nodal status (P<0.001), curative resection (P<0.001), depth of invasion (P=0.010), type of resection (P=0.018) and age (P=0.033). Conclusion: Large gastric tumors showed more aggressive local findings than their smaller counterparts. In patients with large gastric tumors, a curative resection was the most important factor for the prognosis. Therefore, we suggest that every effort should be made to do a curative gastrectomy and an accurate preoperative examination. (J Korean Gastric Cancer Assoc 2006;6:244-249)

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.416-417
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• 2013

최근 질화물계 발광다이오드(light emitting diode, LED) 소자는 핸드폰, 스마트 TV 등의 디스플레이 분야와 실내외조명, 감성조명, 특수조명 등의 조명분야에 그 응용분야가 급속히 확대되고 있다. 이러한 LED 소자는 에너지 절감과 친환경에 장점을 가지고, 가까운 미래에 조명시장을 대체할 것으로 예상된다. 이를 만족하기 위해서는 현재보다 더 높은 효율을 갖는 LED 개발이 요구되어지고 있는 상황이다. 일반적으로 질화물계 LED 소자의 효율은 내부양자 효율, 광추출 효율 등으로 나타낼 수 있다. 내부 양자효율은 성장된 결정의 질의 개선 및 다층의 이종접합 또는 다중양자우물 구조와 같이 활성층의 캐리어 농도를 높이는 접합구조로 설계되어 80% 이상의 효율을 나타낸다. 그러나 광추출 효율은 이에 미치지 못하고 있다. 이는 반도체 재료의 높은 굴절률로 인하여 빛이 외부로 탈출하지 못하고 내부로 반사되거나 물질 안에서 흡수가 일어나기 때문이다. 따라서 이러한 문제를 해결하기 위해 많은 연구 그룹들은, 표면에 패턴 형성하여 빛의 전반사를 줄여 그 효율을 올리는 연구결과를 보고하고 있다. 대표적인 방법으로는 wet etching, 전자빔 리소그라피, 나노임프린트 리소그라피, 레이저 홀로 리그라피, 나노스피어 리소그라피 등이 사용되고 있다. 이 중, 나노스피어 리소그라피는 폴리스틸렌 혹은 실리카 등과 같은 나노 크기의 bead를 사용하여 반도체 기판 표면에 단일층으로 고르게 코팅한 마스크로 사용하여 패턴을 주는 방법이다. 이 방법의 장점으로는 대면적에 균일한 패턴을 형성할 수 있고, 공정비용이 저렴하여 양산하기에 적합하다는 특징이 있다. 나노스피어 리소그라피를 통해서 표면에 생성된 패턴 모양의 각도에 따라서, 식각되는 깊이에 변화에 따라 실험한 결과들은 있지만, 아직까지 크기가 다른 나노입자들의 마스크 이용하여 형성된 패턴 밀도에 따른 광 추출 효과에 대한 연구가 많이 미흡하다. 따라서 본 연구에서는 다양한 크기의 실리카로 패턴을 형성시켜 패턴 밀도에 대한 광추출 효율의 효과에 대해서 조사하였다. 실험 방법으론, DI, 에탄올, TEOS, 암모니아의 순서대로 그 혼합 비율을 조정하여 100, 250, 500 nm 크기의 나노입자를 합성하였고 이것을 질화물계 LED의 표면 위에 단일층으로 스핀코팅 방법을 통해 코팅을 하였다. 그 후 ICP-RIE 방법으로 필라 패턴을 형성하였는데, 그 결과 100 nm SiO2 입자를 이용한 경우 $4.5{\times}10^9$/$cm^2$, 250 nm의 경우 $1.4{\times}10^9$/$cm^2$, 500 nm의 경우 $0.4{\times}10^9$/$cm^2$의 패턴의 밀도를 보여주었다(Fig. 1). 패턴의 밀도에 따라 전계광학적 특성을 확인하여 보았는데, 그 결과는 평평한 표면과 비교하였을 때 100 nm에서 383%, 250 nm에서는 320%, 500 nm에서는 244% 상승하는 결과를 보여주었다(Fig. 2). 이번 실험을 통해서 LED의 광추출 효율은 표면 모양과 깊이 뿐 아니라 밀도가 커질수록 그 효율이 올라간다는 사실을 알 수 있었다.

• Korean Journal of Medicinal Crop Science
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• v.6 no.4
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• pp.239-244
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• 1998

This experiment was to determine the effects of soil pH on crude components and aromatic constituents of Codonopsis lanceolata. Vine length of Codonopsis lanceolata grown at soil pH of 6.5 was longer(299cm) compared to that grown under other soil pHs. Fresh root weight increased at soil pH of 5.5 and 6.5, showing 17.9 and 15.6g per plant, respectively. Contents of crude components such as protein, fat, fiber, and ash decreased as soil became alkalized and crude ash content ranged from 2.99% to 3.85 %, showing a similar response to soil pH. Forty-eight volatile aromatic compounds in the root of Codonopsis lanceolata were identified by GC/MS. Major aromatic compounds were 1-hexanol, cis-3-hexanol, and trans-2-hexanol. In particular, trans-2-hexanol was highest in soil pH of 6.5, attaining the 156.87% area. Essential oil content was also highest at soil pH of 6.5 with 0.007%. As a result, it was considered that the soil pH of 6.5 was most effective for the improvement of essential oil and aromatic constituents in the roots of Condonopsis lanceolata Trautv.

• Journal of The Korean Society of Grassland and Forage Science
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• v.24 no.3
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• pp.237-244
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• 2004

This experiment was carried out to determine the growth characteristics, dry matter and TDN yield of corn for silage (Zea mays L.), soil nitrate in infiltration water by chemical fertilizer and different manure application(C; chemical fertilizer + chemical fertilizer, T1; Lime +chemical fertilizer + chemical fertilizer, T2; swine manure + swine manure, T3; Lime + swine manure + swine manure, T4; swine manure +chemical fertilizer). The results obtained are summarizes as follows; The mean growth characteristics of T3 treatment(soil treatment: lime + base fertilizer: liquid manure + additional fertilizer: chemical fertilizer) was higher than those of other treatments. The highest yield of dry matter and TDN was obtained in T3 treatment with 18,611 and 13,746 kg/ha, respectively(P<0.05), and the lowest in T1 treatment with 13,529 and 9,541 kg/ha, respectively(P<0.05). The contents of NDF and ADF were not significant different among treatments. However, NDF and ADF content among treatments were the highest with T1 treatment and the lowest with T3 treatment. $NO_3$ level of soil was hardly influenced by the different manure application treatment, and not affected during the experiment time.

• Journal of the Korean Electrochemical Society
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• v.8 no.2
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• pp.88-93
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• 2005

Anode-supported solid oxide fuel cell (SOFC) was investigated to increase the cell power density at intermediate temperature through control of the cathode structure. The anode-supported SOFC cell were fabricated by wet process, in which the electrolyte of $8mol\%\;Y_2O_3-stabilized\;ZrO_2 (YSZ)$ was coated on the surface of anode support of Ni/YSA and then the cathode was coated. The cathode has two- or three- layered structure composed of $(La_{0.85}Sr_{0.15})_{0.9}MnO_{3-x}(LSM),\;LSM/YS$ composite (LY), and $La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_3{LSCF)$ with different thickness. Their single cells with different cathode structures were characterized by measuring the cell performance and ac impedance in the temperature range of 600 to $800^{\circ}C$ in humidified hydrogen with $3\%$ water and air. The cell with $LY\;9{\mu}m/LSM\;9{\mu}m/LSCF\;17{\mu}m$ showed best performance of $590mW/cm^2$, which was attributed to low polarization resistance due to LY and to low interfacial resistance due to LSCF.