• 한국자동차공학회논문집
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• 제2권6호
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• pp.76-86
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• 1994

Combustion of diesel engine depends on the mixing of air and evaporating fuel during ignition delay greatly. Variation of air-fuel mixing rate and ignition delay for engine operating condition causes difference of combustion, performance and exhaust emissions. This study is investigated in a turbocharged diesel engine of IDI swirl chamber type. In the results, As injection timing is advanced until $12.6^{\circ}$ BTC, ignition delay decreases. NOx concentration and smoke level in exhaust gas increases for advanced injection timing Ignition delay, combustion period, pressure rise rate and exhaust gas temperature are increased with increasing engine speed. And ignition delay at high load is more decreased than that at low load. Ignition delay and combustion period are decreased with increasing intake pressure. Power increases, temperature and CO, NOx concentration in exhaust gas decreases as intake pressure increases. With increasing load, ignition delay is decreased and combustion period, motoring pressure are increased.

• 통상정보연구
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• 제19권2호
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• pp.3-24
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• 2017

국가의 정보화 수준은 해당 국가의 경쟁력에 중요한 영향을 미치는 기본 인프라로써 경제성과에 영향을 미친다. 세계화의 확산과 함께 전자 무역 등 정보화 관련 경제활동이 점차 활발해 지며 국가 ICT의 중요성은 더욱 커지고 있는 실정이다. 본 연구는 정보화 수준을 접근, 이용 그리고 활용 능력 세 가지 차원으로 세분화하여 국가의 경제적인 성과에 미치는 영향을 분석하고자 하였다. 특히, 국가의 경제발전 단계에 따라 정보화 수준의 경제적 영향력의 차이를 분석하여 선진국과 개발도상국의 국제 정보격차(digital divide)를 효과적으로 해소할 수 있는 방안을 도출하고자 하였다. 나아가 정부의 규제와 각국의 기업이 갖는 국제시장에서 경쟁 우위의 원천이 국가의 ICT가 가져오는 경제적 영향력에 대하여 조절적 역할을 수행하는지 검증하고자 하였다. International Telecommunication Union(ITU)의 ICT development Index(IDI)와 World Economic Forum(WEF), World bank에서 데이터를 수집하여 패널분석을 실시한 결과, 국가의 정보화 수준은 접근과 활용 측면에서 경제성장에 일관되게 유의미한 정의 영향을 미치는 것으로 나타났으며, 특히 개발도상국의 경우 영향력이 큰 것으로 분석되었다. 또한, 정보화 수준과 경제성장의 관계에 대하여 선진국의 경우 기업의 경쟁우위가, 개발도상국의 경우 정부의 규제가 유의하게 조절효과를 갖는 것을 확인하였다. 본 연구 결과에 따른 시사점에 대하여 논의하였다.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• 제4권3호
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• pp.173-183
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• 2000

This study measured the zeta potential of both latex colloidal particles with carboxylate surface groups and glass beads (collectors) with silanol surface group employing various solution with different chemical characteristics. The results have been compared with the surface chemistry theory. The zeta potential of the particle and collector increased with increasing pH up to 5.0 regardless of the solution chemistry. For a monovalent electrolyte solution(sodium chloride solution) the zeta potential steadily increased until the pH reached 9.5. In contrast, little change in zeta potential was made between 5.0 and 9.5 for a divalent electrolyte solution (sodium chloride solution) the zeta potential steadily increased until the pH reached 9.5. In contrast, little change in zeta potential was made between 5.0 and 9.5 for a divalent electrolyte solution (calcium chloride solution). In other words, the more the pH decreases, the larger the effect of neutral salts, such as NaCl and CaCl$_2$, have on the ζ-potential values. In this study, the PZPC(point of zero proton condition) of the particle and collector occurred below a pH of 3.1, H(sup)+ and OH(sup)- acted as a PDI (potential determining ion), and Na(sup)+ acted as an IDI(indifferent ion). The magnitude of the negative ζ-potential values of the particle and collector monotonically increased as the concentrations of Na(sup)+ or Ca(sup)2+([Na(sup)+] or [Ca(sup)2+]) decreased (the values of pNa or pCa increased). In the case of latex particles, the ζ-potential should aproach zero (isoelectric point; IEP) asymptotically as the pNa approaches zero, while in the case of calcium chloride electrolyte, ζ-potential reversal may be expected to occur around 3.16$\times$10(sup)-2MCaCl$_2$(pCa=1.5). pH, valance and ionic strength can be used in various ways to improve the water treatment efficiency by modifying the charge characteristics of the particle and collector. Predictive capability is far less certain when EDL(electrical double layer) repulsive forces exist between the particle and collector.

• 에너지공학
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• 제18권3호
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• pp.169-174
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• 2009

본 연구에서는 수송용 경유를 연료로 사용하고 있는 간접분사식 디젤기관에 있어서 연료에 초음파 에너지를 조사하였을 때의 기관성능 및 배출물질 특성 변화에 대해 조사하였다. 실험은 경유에 초음파 에너지를 조사한 연료와 상용 경유를 간접분사식 디젤기관에 적용하여 다음과 같은 결론을 얻었다. 본 운전조건하에서, 초음파 에너지를 조사한 경유로 디젤기관을 운전하였을 경우,상용 경유 운전 시에 비해 지압선도, 열발생율 및 출력이 상승하고 질량연소율이 단축되었으며 제동연료소비율과 매연은 감소하였다. 또한, 보다 안정화되면서 완전한 연소가 이루어졌으며 질소산화물은 증가하였다.

• 응용통계연구
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• 제22권1호
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• pp.1-16
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• 2009

최근 대부분 기업에서는 통합 데이터베이스 정보를 모델화하고 이를 전략적으로 활용하는 움직임이 가속화되고 있다. 이는 고객과의 커뮤니케이션 및 관계유지로 대변되는 CRM(Customer Relationship Management)이 기업들의 가장 중요한 이슈 중 하나로 부각되고 있기 때문이다. 본 연구에서는 이런 관점에서 CRM의 핵심 요소인 데이터 마이닝 기법을 이용하여 개발한 고객 스코어링 모델을 마케팅 층(Marketing Layer)에 연결해주는 스코어링 캠페인 시스템을 개발 하고자 한다. 개발한 시스템은 고객 스코어링 결과 및 캠페인 대상자 선정 작업을 쉽게 할 수 있도록 GUI환경에서 제공해 줌으로서 일반 사용자들이 쉽게 활용할 수 있도록 하였다.

• Structural Engineering and Mechanics
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• 제68권2호
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• pp.247-259
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• 2018

In this study (Part I), an advanced empirical formulation was proposed to predict the ultimate strength of initially deflected steel plate subjected to longitudinal compression. An advanced empirical formulation was proposed by adopting Initial Deflection Index (IDI) concept for plate element which is a function of plate slenderness ratio (${\beta}$) and coefficient of initial deflection. In case of initial deflection, buckling mode shape, which is mostly assumed type in the ships and offshore industry, was adopted. For the numerical simulation by ANSYS nonlinear finite element method (NLFEM), with a total of seven hundred 700 plate scenarios, including the combination of one hundred (100) cases of plate slenderness ratios with seven (7) representative initial deflection coefficients, were selected based on obtained probability density distributions of plate element from collected commercial ships. The obtained empirical formulation showed good agreement ($R^2=0.99$) with numerical simulation results. The obtained outcome with proposed procedure will be very useful in predicting the ultimate strength performance of plate element subjected to longitudinal compression.

• The Korean Journal of Pain
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• 제31권3호
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• pp.199-205
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• 2018

Background: Sleep disturbance and depression are becoming more recognized as important symptoms among individuals with chronic low back pain. This study evaluated the effect of stabilization exercise on pain-related disability, sleep disturbance and the psychological status of patients with non-specific chronic low back pain (NSCLBP). Methods: A total of 26 patients (M/F = 17/9) with NSCLBP with a mean age of $50.0{\pm}15.5$ took part in this study. Participants were recruited from selected hospitals in Lagos state. Ethical approval was sought and obtained from the health research and ethics committee of Lagos University Teaching Hospital Idi-araba, Lagos, Nigeria. Participants performed stabilization exercise for eight weeks consecutively and were assessed for pain-related disability, anxiety, depression, and sleep disturbance using the pain-disability index, hospital anxiety and depression scale, and the insomnia severity index at baseline, the 4th week, and the 8th week, postintervention. Results: The participants studied recorded significant reduction in pain-related disability (P = 0.001). There was also improvement in the sleep quality (P = 0.001), depression level (P = 0.001), and anxiety level (P = 0.001), post intervention. Conclusions: This study revealed that stabilization exercise is very useful in the management of sleep disturbance, pain-related disability, depression, and anxiety in NSCLBP patients.

• 한국미생물·생명공학회지
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• 제46권2호
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• pp.114-119
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• 2018

Astaxanthin is one of the major carotenoids used in pigment has a great economical value in pharmaceutical markets, feeding, nutraceutical and food industries. This study was to increase the production of astaxanthin by co-expression with transformed Escherichia coli using six genes involved in the non-mevalonate pathway. Involved in the non-mevalonate biosynthetic pathway of the strain Kocuria gwangalliensis were cloned dxs, ispC, ispD, ispE, ispF, ispG, ispH and idi genes in order to increase astaxanthin production from the transformed E. coli. And co-expression with the genes to compared the amount of astaxanthin production. This engineered E. coli, containing both the non-mevalonate pathway gene and the astaxanthin biosynthesis gene cluster, produced astaxanthin at $1,100{\mu}g/g$ DCW (dry cell weight), resulting in approximately three times the production of astaxanthin.

• 대한기계학회논문집B
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• 제26권12호
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• pp.1756-1762
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• 2002

To effectively meet current regulations on the exhaust emissions of diesel engine required to control the deterioration of air pollution in the whole world, this study is to investigate the effects of water induction through the air intake system on the characteristics of combustion and exhaust emissions in IDI diesel engine. A method fur supplying water through the air intake system to reduce the exhaust emissions has been considered with other methods such as water introduction in the form of water-in-fuel emulsion or water injection directly into the combustion chamber, but it has not been studied about the effects of water on the combustion concepts and the characteristics of exhaust emissions in detail until now. In this study, the formation of NOx was significantly suppressed by decreasing the gas peak temperature during the initial combustion process because the water play a role as a heat sink during evaporating in the combustion chamber, but the smoke was slightly increased by increasing water amount.

• 정보저장시스템학회:학술대회논문집
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• 정보저장시스템학회 2005년도 추계학술대회 논문집
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• pp.96-102
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• 2005

The tribocharge build-up in the slider disk interface can cause ESD (electrostatic discharge) damage. In turn, ESD can cause severe melting damage to MR or GMR heads. We investigated the tribovoltage/current build-up with smooth and textured disks in HDD, operating at increasing disk accelerations. We found that tribe-voltage/current were generated during pico-slider/disk interaction and those levels were about 0.1 ${\~}$ 0.3 V and 10 ${\~}$ 40 pA, respectively. Tribovoltage/current were abruptly increased and dissipated within the acceleration time in the case of textured disk but in the case of smooth disk tribovoltage was continuously increased until the end of uniform velocity region and the tribocurrent did not dissipate within the acceleration time. In the case of textured dist tribovoltage/current was reduced with increasing disk acceleration, but in the case of smooth disk it was increased.