• Journal of Biosystems Engineering
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• 제19권1호
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• pp.62-69
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• 1994

This study was designed to seek information on the heat charging and discharging characteristics of a multi-capsule type LTES(Latent Heat of Fusion Thermal Energy Storage) system, and especially prediction equation of outlet water temperature from the system. During heat charging process, the water temperature in the LTES tank increased very slowly in comparison with a predicted one and was kept near the melting point of the PCM for about 25 minutes. During heat discharging process, the latent heat discharging period of the outlet water temperature became longer as the inlet water temperature became higher and/or mass flow rate became lower. The dimensionless temperature of the outlet water was predicted by linking three equations of ${\theta}=1.1Exp(-{\tau}/0.82)$, ${\theta}=-0.06{\tau}+0.3$, ${\theta}=0.8Exp(-{\tau}/1.4)$ ($r^2{\leq}0.88$) depending on discharging period regardless of mass flow rates on the case of the inlet water temperature at $21.5^{\circ}C$.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권3호
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• pp.361-366
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• 2013

This paper presents the effect on application of the flywheel energy storage system (FESS) for load frequency control (LFC) of an interconnected 2 area power system. To do this, the control characteristics with the FESS were compared with that of the conventional governor controller. The controller for the FESS control and the governor control used a PID type controller. Both the FESS PID controller and the governor PID controller using genetic algorithm (GA) were designed to optimize the PID parameters. The frequency and generation output characteristics with the only FESS controller and with the only conventional governor controller were compared. To verify robust performance of the FESS controller, the computer simulations were performed under various disturbances. The simulation results showed that the FESS controller provided better dynamic responses in comparison with the conventional governor controller.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.280-286
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• 2018

A sensorless active damping scheme for LCL filters in grid-connected parallel inverters for battery energy storage systems is proposed. This damping method is superior to the conventional notch filter and virtual damping methods with respect to robustness against the variation of the resonance of the filter and unnecessary additional current sensors. The theoretical analysis of the proposed damping method is explained in detail, along with the characteristic comparison to the conventional active damping methods. The performance verification of the proposed sensorless active damping method shows that its performance is comparable to that of the conventional virtual damping method, even without additional current sensors. Finally, simulation and experimental results are provided to examine the overall characteristics of the proposed method.

• 한국초지조사료학회지
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• 제16권4호
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• pp.307-314
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• 1996

An experiment was carried out to determine effect of cultivar and preservative on the characteristics and quality of baled oat(Avena sativa L.) hay after 60 days of storage. Ihe main plots consisted of the cultivars such as 'Foothill' and 'Swan', and the subplots consisted of preservatives such as commercial propionic acid(CA), lactic bacteria inoculant(LB) and control(C0). Bale temperature of 'Foothill' oat hay maintained higher than that of 'Swan' oat hay during storage. Bale temperature of oat hay treated with CA remained lowest during the earlier storage period and no significant difference was found among preservatives during the latter storage period. Visual assessment of bale of 'Swan' oat hay was better in the evaluation of mold, odor and color than that of 'Foothill' oat hay after storage. DM content of Foothill oat hay increased markedly than that of 'Swan' oat hay through the storage period. CFU(Colony fodng unit) of total viable micmrganism of oat hay bales was not quite different between preservatives, but that of lactic bacteria of 'Swan' oat hay and 'Foothill' was different by over 16 and lo4, respectively. Total nitrogen content of 'Swan' and 'Foothill' oat hay was 1.45 and 2.22%, respectively(P<0.05) and effect of preservatives on total N content was higher in the order of LB, CA, and CO. ADIN content of 'Swan' was lower than that of 'Foothill'(P

• 한국식품저장유통학회지
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• 제30권2호
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• pp.205-223
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• 2023

Fresh mushrooms are vulnerable to browning and tissue changes after harvest. This study monitored the external appearance, physicochemical quality indicators, and nutritional and functional components of a white beech mushroom (Hypsizygus marmoreus) variety (EG2020) newly developed in Korea during cold storage for up to 42 days. Two existing varieties of white H. marmoreus, namely H6 from Korea and HKT from Japan, were used for comparison. The mechanical texture of EG2020 was superior to H6 and HKT due to the increasing hardness of the pileus with time. Browning, in terms of the total color difference during storage, was found to be the most severe in HKT. In terms of composition, EG2020 had the highest total free sugar content, a large amount of organic acids, and higher sugar content than H6 and HKT. EG2020 also contained the largest amount of 𝛽-glucan, and its amount increased during storage. In sensory evaluation, EG2020 received higher scores than HKT in flavor, taste, appearance, and texture. Therefore, the EG2020 variety is more stable than HKT during storage and distribution.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.484-487
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• 2005

In order to get the surface characteristics of the HDI of HDD, the surface damage mechanisms must be totally understood. Particle contamination in hard disk drives is a big concern in today's magnetic recording industry since they are major sources of reliability problems. Namely upon contact with the slider or a contaminant particle, the disk may be scratched or the particles may be embedded into the disk surface. In this work, comparison of scratches was made between those found on actual hard disks and those created using a scratch tester. It was found that ramp loading method is an effective way to make similar scratches as the actual ones. From the ramp loading condition, the relationship between the pressure and the scratch track width could be identified.

• 한국축산식품학회지
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• 제39권2호
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• pp.345-353
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• 2019

Various commercial collagen mixtures aimed at improving the quality of meat products are available, but the optimal composition is unclear. This study aimed to compare the functional properties, including physicochemical characteristics and lipid oxidative stability, of loin ham marinated with three commercial collagen mixtures sold as food additives. The addition of collagen mixtures led to significant increases in the moisture content, water holding capacity (WHC), cooking yield, and instrumental tenderness, regardless of the type of collagen mixture. In particular, meat samples containing collagen mixture C showed the highest (p<0.05) WHC and tenderness among all groups. Furthermore, collagen mixture B induced increases (p<0.05) in pH values in both raw and cooked samples. The $a^*$ values of samples with collagen mixtures were lower (p<0.05) than those of samples without collagen mixtures. All collagen mixtures effectively improved oxidative stability during 7 days of storage at $4^{\circ}C$. The samples containing collagen mixture B had the lowest lipid oxidation (p<0.05) among groups. These results indicated that collagen mixture C could be used in injection brine to enhance the quality characteristics of meat products, particularly the WHC and tenderness. Collagen mixture A could be used for meat products with high fat contents based on its ability to improve lipid oxidative stability during long-term storage.

• 전력전자학회논문지
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• 제12권3호
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• pp.267-275
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• 2007

본 논문은 현재 청정에너지의 개념으로 대두되고 있는 에너지원 가운데 기계적인 에너지로 저장하여 필요 시 꺼내어 사용할 수 있는 플라이휠 에너지 저장장치에 대한 에너지 입, 출력 모델링 및 PWM 인버터 시스템의 해석 및 제어에 관한 논문으로서, 플라이휠 저장장치 특성 및 시스템 모델링에 관해 논의한다. 재질에 따른 플라이휠의 특성과 플라이휠 에너지 저장장치의 속도 특성에 따른 전압과 전류의 변화량을 수식으로 간략화 하여 분석하고, 시뮬레이션을 통하여 플라이휠의 에너지 저장상태를 분석하였다. 또한, 부하측 전원의 이상유무에 관계없이 에너지를 공급할 수 있는 Online UPS로 사용하기 위해 PDFF 제어기법을 이용하여 전압제어 및 전류제어의 이중루프 제어로 구성된 단상 PW방식의 인버터 시스템 제작하였으며, 실험을 통하여 실제로 0.1[p.u], 1[p.u]에서의 제어되는 전압, 전류제어파형 및 THD 특성에 관하여 평가한다.

• 한국식품저장유통학회지
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• 제5권3호
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• pp.239-246
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• 1998

폴리이미드 고분자막을 사용한 질소부하 장치를 설계하고, 이를 CA 저장에 활용하기 위한 기술적 기본 데이터를 제시하였다. 순수 산소 및 질소의 투과특성은 dual-mode sorption 모델로서 설명될 수 있었으며, 공기 중의 산소의 투과율은 공기 중에 존재하는 질소의 영향으로 순수 산소의 투과율에 비해 크게 감소하나, 공기 중의 질소의 투과율은 산소의 영향으로 순수 질소의 투과율에 비해 증가하였다. 수행한 압력 및 온도 범위 내에서 이상분리인자는 5에서 6 사이의 값을 나타내었으며, 공기의 분리인자는 이상분리인자보다 작은 값을 나타내었다. 산소의 투과활성화에너지가 질소의 투과 활성화에너지보다 커서 이상분리인자는 온도가 증가함에 따라 증가하였다. 제품회수율이 증가함에 따라 농축부의 질소농도는 급격히 감소하였으며, 이로부터 제품회수율은 CA 저장고에서 요구되는 질소농도를 얻기 위한 주요 조업인자임을 알 수 있었다. Polyimide 막 시스템을 이용한 CA 저장 공정의 가상적인 모형을 설정하고, 시스템의 조업시간에 따른 저장고의 질소농도를 예측할 수 있는 관계식을 제시하였다.

• Journal of Forest and Environmental Science
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• 제15권1호
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• pp.71-76
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• 1999

본 연구는 춘천시의 도심지와 자연지 토양을 표본추출하여 그것의 물리화학적 특성과 탄소저장량을 비교 분석하였다. 토양산도는 도심지에서 평균 6.6, 자연지에서는 그보다 낮은 5.0이었고, 따라서 치환성양이온도 자연지에서 약간 더 낮았다. 유기물함량과 양이온치환능은 자연지에서 도심지보다 각각 1.4배, 1.7배 높은 반면, 유효태인산은 도심지에서 약 3.2배 높았다. 유기탄소저장량은 도심지 평균 $24.8{\pm}1.6$(표준오차) t/ha, 자연지 $31.6{\pm}1.6t/ha$로서, 자연지가 도심지보다 약 1.3배 더 많았다. 수목의 낙엽, 낙지 및 낙근에 의한 연간 탄소유입량에서 분해에 의한 연간 탄소유출량을 제감한 자연지 토양내 단위면적당 연간 탄소축적량은 1.3 t/ha/yr이었다. 춘천시 토양에 저장된 총탄소량은 연간탄소배출량 (245,590 t/yr)의 약 31%에 해당하였다.