• Journal of Advanced Marine Engineering and Technology
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• 제33권7호
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• pp.1003-1011
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• 2009

This study aims at precise control of oil outlet temperature in the oil cooler system of machine tools for enhancement of working speed and processing accuracy. PID control logic is adopted to obtain desired oil outlet temperature of the oil cooler system with hot-gas bypass method. We showed that the gains of PID controller could be easily determined by using gain tuning methods to get the gain of PID controller without any mathematical model. We also investigated various gain tuning methods to design the gains of PID and compared each control performance for selecting the optimal tuning method on the hot gas bypass method through experiments. Moreover, we confirmed excellent control performance with proposed PI controller gain even though disturbances were abruptly added to the experimental system.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.821-826
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• 2009

Due to environmental concerns $CO_2$ has been reintroduced as a potential candidate to replace HFCs in refrigeration systems. Oils are always required in a vapor-compression cycle, and thus actual working fluid in the system is $CO_2$-oil mixtures even though the oil concentrations are low at the heat exchangers and the expansion device. The cooling heat transfer coefficients for $CO_2$-oil mixtures under supercritical condition are required to designing of the gas cooler in the $CO_2$ refrigeration system properly. In the present study, the gas cooling heat transfer coefficients for $CO_2$-PEC9 was estimated by using the Gnileinski correlation, and the Kim and Ghajar model through the previous prediction models for the thermo-physical properties of $CO_2$-oil mixture. The Gnileinski correlation was used when the oil wt.% in the mixture is less than 1.0, and for the higher oil concentration the Kim and Ghajar model was applied. The estimated results agree with the experimental results conducted by the Dang et al.

• 동아시아경상학회지
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• 제4권4호
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• pp.21-23
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• 2016

There are so much oil and gas reserves in Iran. Therefore extraction from these reserves and sell extracted oil and gas in international markets causes to high oil income for Iran. Especially in some years which oil price increases, our oil income was too high. In this paper, we want to reveal that, high oil income is not cause to rise of nonoil export. For this aim, we use from data of 1971-2013 and with Johansen co-integration test and Error Correction Model (ECM) extract short run and long run relations. Results of estimation reveal that in Iran high oil income is not cause to many non oil exports in long run and short run. Therefore, we should allocate oil income to import industrial machines and reallocate them to agriculture and industrial sectors which causes to raise national production which will cause to high non oil export. Then, in this condition, our needy exchanges are provided from non oil export and our dependence to oil income will be declined.

• 한국자동차공학회논문집
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• 제16권5호
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• pp.22-28
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• 2008

A closed type crankcase ventilation system has been adopted to engines to prevent emission of blow-by gas to atmosphere. In the early closed type crankcase ventilation system, blow-by gas which contains engine lubricating oil is re-circulated into the intake system. The blow-by gas containing oil mist leads to increased harmful emissions and engine problems. To reduce loss of the engine oil, a highly-efficient oil separation device is required. Principle of a cyclone oil separator is to utilize centrifugal force in the separator and, therefore, oil separator designs depend on rotational flow which causes the centrifugal force. In this paper, flow characteristics and oil separation performances for cyclone type designs are calculated with CFD methodology. In the CFD model, oil particle was injected on a inlet surface with Rosin-Rammler distribution and uniform distribution. The major design parameters considered in the analysis model are inlet area, cone length and outlet depth of the oil separator. As results, reducing inlet area and increasing cone length increase oil separation performance. Changes in outlet depth could avoid interference between rotational flow and outlet flow in the cyclone oil separator.

• Journal of Advanced Marine Engineering and Technology
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• 제30권1호
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• pp.88-92
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• 2006

This study is intended to check the flame temperature to raise in burning grade C heavy fuel oil and emulsion fuel oil in a boiler and to measure the concentration of Dry Shoot(DS) and Soluble Organic Fraction(SOF) after collecting the Particulate Matters (PM). The flames temperature in boiler was measured by burning grade C heavy oil and oil-water emulsion (C heavy oil $70\%\;and\;30\%$ of water) Combustion characteristics of two fuels was also compared by trapping particulate matters (PM) in exhaust gas and measuring the generated quantities of DS and SOF in fuel gas.

• The Journal of Asian Finance, Economics and Business
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• 제8권3호
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• pp.987-996
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• 2021

The development of Internet technology can affect firm value through the use of social media by business people. Nowadays, social media affect businesses of all sizes in several different ways. Despite the various benefits obtained by using social media, research at the organizational level and its impact on business performance have not grown as fast as desired. This research aims to examine the effect of social media on oil and gas firms' value. The research sample consists of 9 oil and gas firms listed on the Indonesian Stock Exchange 2013-2018. Social media proxies are firms' social media, other social media mentions, and social media sentiment. Firm value is measured by the market value to assets ratio. Data analysis uses a random-effect regression test. Based on the analysis, the social media account of a firm has a positive effect on firm value. It indicates that social media give advantages for oil and gas firms to give a signal of business prospect, make use of opportunities related to industry alliances, recruit employees globally, and c. On the other hand, the positive sentiment on social media has no effect on oil and gas firms' value.

• Geomechanics and Engineering
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• 제7권4호
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• pp.403-430
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• 2014

Shale gas formations exhibit strong mechanical and strength anisotropies. Thus, it is necessary to study the effect of anisotropy on the hydraulic fracture initiation pressure. The calculation model for the in-situ stress of the bedding formation is improved according to the effective stress theory. An analytical model of the stresses around wellbore in shale gas reservoirs, in consideration of stratum dip direction, dip angle, and in-situ stress azimuth, has been built. Besides, this work established a calculation model for the stress around the perforation holes. In combination with the tensile failure criterion, a prediction model for the hydraulic fracture initiation pressure in the shale gas reservoirs is put forward. The error between the prediction result and the measured value for the shale gas reservoir in the southern Sichuan Province is only 3.5%. Specifically, effects of factors including elasticity modulus, Poisson's ratio, in-situ stress ratio, tensile strength, perforation angle (the angle between perforation direction and the maximum principal stress) of anisotropic formations on hydraulic fracture initiation pressure have been investigated. The perforation angle has the largest effect on the fracture initiation pressure, followed by the in-situ stress ratio, ratio of tensile strength to pore pressure, and the anisotropy ratio of elasticity moduli as the last. The effect of the anisotropy ratio of the Poisson's ratio on the fracture initiation pressure can be ignored. This study provides a reference for the hydraulic fracturing design in shale gas wells.

• Korean Chemical Engineering Research
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• 제48권1호
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• pp.68-74
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• 2010

본 실험은 오일샌드에 함유된 역청을 회수함에 있어 유동층 열분해 실험을 통한 역청 회수의 적합성을 확인하기 위하여 수행하였다. 본 실험에 사용된 캐나다 Alberta 오일샌드는 역청을 11.9%를 함유하고 있으며 열분해 공정을 통하여 회수한 열분해 오일은 오일샌드에 함유되어 있는 역청에 비하여 경질화되는 특성을 갖는다. 본 실험을 위하여 높이 170 cm의 반응기를 설치하였으며 1 atm, $500^{\circ}C$의 반응 조건 하에서 연속 운전 실험을 실시하였고 유동화 가스는 $N_2$를 사용하여 $1.62U_{mf}$ 조건에서 오일샌드의 열분해 반응특성을 연구하였다. 오일샌드 유동층 열분해 실험 결과 역청의 전환율은 87.76%이며 액체 생성물은 74.45%, 가스 생성물은 13.31%의 결과를 얻었다. 오일샌드 유동층 열분해 실험 중 발생하는 열분해 가스는 실시간 가스분석기를 사용하여 $H_2$, $O_2$, CO, $CO_2$, $CH_4$, NO를 분석하였으며 탄화수소 $C_1-C_4$의 분석은 가스크로마토그래피를 사용하여 분석하였다. 열분해 오일은 회수하여 원소분석, 발열량 분석, 중금속 분석과 아스팔텐(asphaltenes) 분석을 실시하였으며 SIMDIS 분석을 통하여 열분해 오일의 특성을 분석하였다. 분석 결과 나프타(naphtha)는 11.50%, 중간유분(middle distillation)은 44.83%, 중질유(heavy oil)는 43.66%의 결과를 얻었다. 이는 역청과 비교하여 나프타와 중간유분 함량이 높은 경질화된 열분해 오일이 회수되었음을 알 수 있다.

• 한국건설관리학회논문집
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• 제8권1호
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• pp.116-123
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• 2007

최근 오일 가스 플랜트 분야는 국제 유가의 상승, 에너지 수요의 증가로 인하여 프로젝트 발주가 증가하고 있으며, 중동지역과 전 세계 지역으로 시장규모가 증대되고 있다. 오일 가스 플랜트는 제조 및 처리공정과 기술개발에 따른 라이센스 관리 및 기술관리가 프로젝트의 성패에 중요한 사항이다. 오일 가스 플랜트의 경우 다수의 해외공사 수행 형태를 가지며 해외 선진 업체와의 경쟁이 더욱 중요하다. 이러한 시장에서 기술 경쟁력과 기술 우위를 확보하기 위해서는 기술개발에 따른 체계적인 경영 방식을 도입하여야 한다. 하지만 국내 오일 가스 플랜트 업체의 경우 해외 선진 업체보다 라이센스, 설계단계의 기술 경쟁력이 부족하며 '기술 투자 비용 대 효과를 최대화' 하는 요소기술의 기술경영 도입이 어려운 현실이다. 이는 기술개발 및 관리의 인식 부족과 연구개발 인프라 구축에 따른 부담이 커서 장기적인 기술전략이 부족하기 때문이다. 따라서 본 연구에서는 오일 가스 플랜트 산업의 대외 경쟁력 확보를 위한 기술경영 도입방안을 분석함으로서 중장기적 기술개발 지원과 기술경영 도입방안을 제시하였다.

• 자원환경지질
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• 제41권5호
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• pp.617-624
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• 2008

카스피해에 인접한 아제르바이잔은 200여 년 전부터 석유개발을 시작하여 20세기 초에는 세계 석유의 50%를 생산하는 석유자원의 부국이 되었으며 소련 연방에서 분리 독립한 1991년 이후 카스피해 해상광구에 대하여 우리나라를 포함한 외국기업투자가 많이 이루어지고 있는 나라이다. 아제르바이잔 하류부문 석유산업은 상류부문에 비하여 낙후되어 있으나, 아제르바이잔에서 시작되는 BTC, SCP, NERP 및 WREP와 같은 파이프라인은 카스피해 석유 및 가스를 서방세계에 전달하는 중요한 역할을 하고 있다. 아제르바이잔 육상광구는 생산활동이 상당부문 이루어진 성숙유전들이다. 최근 유가의 급등으로 인하여 경제성이 높아진 해상 심해 광구는 탐사의 성공 잠재성은 있으나 위험부담율이 커서 신중한 투자가 필요하다.