• International Journal of Air-Conditioning and Refrigeration
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• 제17권3호
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• pp.100-106
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• 2009

As an effort to prevent environmental problems caused by ozone depletion and global warming, alternative refrigerants are being developed, and one of the candidates is carbon dioxide. To overcome slightly low efficiency of $CO_2$ refrigeration system, air-conditioning cycle using an ejector was suggested. Ejector compensates throttling loss in an expansion device by reducing compression work. In this study, the ejector refrigeration cycle using $CO_2$ as a refrigerant is investigated to understand the effect of the mixing section diameter and refrigerant charge amount on the performance. If mixing section diameter is too large or too small, either cases show low performance. The optimum refrigerant charge amount which gives the best performance is found for standard operating conditions. The air-conditioning cycle was analyzed for several operating conditions.

• 전기화학회지
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• 제18권4호
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• pp.137-142
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• 2015

$Mn_{1+X}Co_{2-X}O_4$ solid solutions with various Mn/Co ratios were synthesized by a combustion method, and used as cathode catalysts for lithium/air secondary battery. Their electrochemical and physicochemical properties were investigated. The morphology was examined by transmission electron microscopy (TEM), and the crystallinity was confirmed by X-ray diffraction (XRD) analyses. For the measurement of electrochemical properties, charge and discharge measurements were carried out at a constant current density of $0.2mA/cm^2$, monitoring the voltage change. Electrochemical impedance spectroscopy (EIS) analyses were also employed to examine the change in charge transfer resistance during charge-discharge process. $Mn_{1+X}Co_{2-X}O_4$ solid solutions showed enhanced cycleability as a cathode of Li/air secondary battery, and the performance was found to be strongly dependent on Mn/Co ratio. Among synthesized catalysts, $Mn_{1.5}Co_{1.5}O_4$ exhibited the best performance and cycleability, due to high charge transfer rate.

• 대한토목학회논문집
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• 제26권1D호
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• pp.49-58
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• 2006

본 연구는 도시개발밀도와 교통시설용량 간의 영향관계를 실증적으로 분석하여, 교통성과(transportation performance)를 극대화하기 위한 토지이용방안을 모색하는 것이다. 이를 위해 서울시 도심을 사례분석지역으로 선정하여 다양한 개발밀도 시나리오에 따라 교통용량의 한계를 감안한 개발용량을 산정하였다. 개발밀도 변화에 따른 교통영향분석을 위한 분석모형으로 SECOMM모형이 제시되었고, 이를 활용하여 20개의 다양한 개발밀도 대안의 영향을 분석하였다. 분석 결과, 도심고밀개발시교통 관점에서 볼 때 분석상 교통적으로 가장 지속가능성이 높은 수준은 도심혼잡통행료를 징수하고 용적률을 460% 까지 개발했을 때인 것으로 나타났다. 한편 도심용적률이 460%를 상회해도 서울시 전체적인 교통상황이 지속적으로 개선되는 것으로 분석되어, 통행료 수준을 높임으로써 지속가능한 교통여건을 달성하는 것이 보다 바람직할 것으로 판단된다. 한편, 도심에서 혼잡통행료를 부과하지 않는다면 도심에서 최대 용적률 430%까지 밖에 고밀화를 진행할 수 없고 이때 서울시 전체적으로 개선폭도 그리 크지 않은 것으로 분석되었다. 따라서 도심고밀화를 위해서는 교통수요관리시책(TDM)과 병행하는 것이 필수적일 것으로 사료된다.

• 대한환경공학회지
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• 제28권9호
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• pp.905-910
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• 2006

본 연구는 강원도의 환경기초시설 설치에 따른 주민지원금의 현황을 파악하고 처리형태에 따른 합리적인 주민지원금을 산정하기 위하여 수행되었다. 강원도에 지원된 주민지원금은 환경기초시설 설치비용에 $1.6{\sim}75.0%$로 과도하게 지원된 것으로 조사되었다. 합리적 주민지원금 산정방안은 평균 인구분포, 주민지원금 지원현황, 법적기준 및 전문가 설문조사 결과를 적용하여 수행하였다. 본 연구에서 산정한 처리형태별 주민지원금 범위는 폐기물 처리시설은 설치비용의 20% 범위, 음식물류 폐기물처리시설은 10% 범위, 하수 분뇨합병처리시설은 $3{\sim}5%$ 범위로 산정되었다.

• 한국환경교육학회지:환경교육
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• 제16권2호
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• pp.1-14
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• 2003

This study aims to review the present condition of human resources development in environment technology area and to explore the direction of human resources development plans, based on the results of a survey targeting experts in this area. Related papers & literatures are referred and a survey for experts' opinions are carried out. The survey was oriented to the importance and effectiveness of policies designed by Korea Ministry of environment. The main findings of this study are as follows; firstly, an emphasis should be put on generating professionals in charge of creating domestic demand for environmental purposes for promotion to make excellent environmental techniques being of practical use and help them go into businesses was turned out crucial; secondly, it is advised to upgrade the level of qualifications of environmental technicians by reforming into a graduate schoolcentered educational system on a human resource-rearing phase; thirdly, retraining should be provided by law to ensure the enhancement of re-educating the existing environmental technicians; fourth, efforts should be made to promptly develope new techniques and unify declining traditional items, deterring national technical qualification system oriented toward cultivating superintendents in the environment field.

• 한국분말재료학회지
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• 제28권6호
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• pp.470-477
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• 2021

Energy storage systems should address issues such as power fluctuations and rapid charge-discharge; to meet this requirement, CoFe₂O₄ (CFO) spinel nanoparticles with a suitable electrical conductivity and various redox states are synthesized and used as electrode materials for supercapacitors. In particular, CFO electrodes combined with carbon nanofibers (CNFs) can provide long-term cycling stability by fabricating binder-free three-dimensional electrodes. In this study, CFO-decorated CNFs are prepared by electrospinning and a low-cost hydrothermal method. The effects of heat treatment, such as the activation of CNFs (ACNFs) and calcination of CFO-decorated CNFs (C-CFO/ACNFs), are investigated. The C-CFO/ACNF electrode exhibits a high specific capacitance of 142.9 F/g at a scan rate of 5 mV/s and superior rate capability of 77.6% capacitance retention at a high scan rate of 500 mV/s. This electrode also achieves the lowest charge transfer resistance of 0.0063 Ω and excellent cycling stability (93.5% retention after 5,000 cycles) because of the improved ion conductivity by pathway formation and structural stability. The results of our work are expected to open a new route for manufacturing hybrid capacitor electrodes containing the C-CFO/ACNF electrode that can be easily prepared with a low-cost and simple process with enhanced electrochemical performance.

• 화약ㆍ발파
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• 제41권1호
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• pp.32-45
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• 2023

국내의 환경규제는 산업현장에서 발파를 수행하는데 있어 상당히 보수적인 기준을 가지고 있다. 이에 따라, 환경 규제 및 민원의 발생을 고려한 발파 설계가 진행되어 불가피하게 발파의 효율 및 경제성이 저하되는 경우가 빈번하게 발생하고 있다. 따라서, 발파공해를 저감하는 동시에 시공성 및 경제성을 향상시키는 발파공법이 요구되는 실정이다. 본 연구에서는 파라핀 지관을 에어갭으로 활용한 원리상 일종의 Air Decoupled Charge 공법을 적용한 PA-Deck(Paraffin Air- Deck) 발파공법의 발파 공해 저감 및 발파 효과에 대한 분석을 수행하였다. 또한, 발파 진동 자료를 수집하는데 있어 새롭게 적용한 장비의 효용성을 검토하고 폭약의 폭굉속도와 진동속도간의 관계를 도출하였다. 발파 진동속도 분석 결과, PA-Deck 발파공법이 일반 발파공법에 비하여 현저히 낮은 진동속도를 보이는 것으로 확인되었으며, 균일한 작은 형태의 파쇄석들이 더욱 많이 발생하는 것으로 판단되었다.

• 한국환경농학회지
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• 제35권4호
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• pp.235-240
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• 2016

BACKGROUND: To determine effect of phosphate (P) application on Cadmium (Cd) extractability and its uptake by rice plant in Cd contaminated paddy soil, dipotassium ($K_2HPO_4$) which was the most effective of P materials to decrease Cd extractability in previous study was selected as P fertilizer. METHODS AND RESULTS: Dipotassium phosphate was applied at the rates of 0, 78, 234, and 390 kg $P_2O_5/ha$, and then rice was cultivated in submerged paddy soil from Jun. to Oct. in 2015. Cadmium concentrations in grain, straw, and root of rice plant decreased significantly with increasing application rate of $K_2HPO_4$. The trend of 1 M $NH_4OAc$ extractable Cd concentration in soil was similar to that of Cd uptake by rice plant. One M $NH_4OAc$ extractable Cd concentration was negatively related to soil pH and negative charge. Alleviation of Cd phytoavailability of rice in paddy soil might be attributed to increase in pH and negative charge of soil. Using a quadratic response model, amount of grain yield were related to $K_2HPO_4$ application rates as Grain yield = $5.38+2.39{\times}10^{-3}K_2HPO_4-6.65{\times}10^{-6}K_2HPO{_4}^2$ (model $R^2=0.968$). Using this equations, the greatest grain yield (5.6 Mg/ha) was at the rate of 180 kg $P_2O_5/ha$. At this application rate of P, the Cd concentration in grain was 0.53 mg/kg, implying ca. 23% lower than the control. CONCLUSION: From the view point of heavy metal safety and crop productivity, it might be good P management to apply P fertilizer with 4 times higher rate than recommendation (45 kg/ha).

• 대한토목학회논문집
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• 제31권1D호
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• pp.51-63
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• 2011

현재 유료도로인 창원터널은 출 퇴근 시간대에 지 정체 현상이 상습적으로 일어나 교통혼잡비용을 가중시키고, 이용차량들의 불만이 날로 증대되고 있는 실정이며, 무료화에 위한 많은 민원들이 요구되어 왔으나, 유료도로인 창원터널의 조기 무료화 도입이 민원의 해소는 가능하나 제2창원터널의 개통없이는 용량 초과에 따른 지체가 더욱더 가중될 것으로 보여 근본적인 해결방안이 될 수 없음이 기정사실화 되고 있다. 따라서 본 논문에서는 용량 초과된 터널구간의 지정체가 더욱 더 심화되지 않도록 교통시설 개선과 교통수요 관리 등으로 개선 방안을 제시하는 것이 바람직하며, 유료도로의 조기 무료화는 대안별 시뮬레이션 분석 및 교통혼잡비용 추정 결과에 따른 객관적인 분석을 통해 이루어져야 하며, 건설소요 상환금을 조기 해결하고 유지 관리를 위한 최소한의 경비 확보가 우선시되어야 하므로 통행료에 따른 수익자 부담의 원칙을 준수하는 것이 불특정다수의 피해를 최소화할 수 있어 유료도로의 조기 무료화에 따른 실익을 신중하게 추진하는 것에 그 목적이 있다.

• 한국환경과학회지
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• 제15권11호
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• pp.1027-1034
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• 2006

Antimicrobial powder was made by exchanging silver ion on calcined oyster shell. On the purpose of application to water clarifier, bail-type media mixed with antimicrobial powder and $0{\sim}30%$ white kaoline were made. The sterilization effect, pore size distribution and zeta potential was tested to indicate the condition for the media of water clarifier. From these tests, it was confirmed that this media have an excellent sterilization power on $G^-\;and\;G^+$ germs. As the concentration of the exchanged silver ion increased, the surface charge density of the anions on the surface of the media also increased. The surface pore size decreased with the concentration of silver ion and 20% more white kaoline ratio. Consequently, mixing ratio of white kaoline would appear to indicate the optimun condition as media have sterilization power.