• 해양환경안전학회지
• /
• 제18권4호
• /
• pp.371-377
• /
• 2012

본 연구에서는 자유낙하하는 직사각형 해양구조물($800{\times}250{\times}50mm^3$)의 슬래밍 충격압력 및 유동특성을 알아보고자 실험을 수행하였다. 유동장의 계측은 2-프레임 그레이레벨 상호상관 PIV기법을 이용하였으며, 자유낙하하는 모델의 충격압력은 압력계측장비(Dewatron)를 이용하였다. 모델과 자유수면간 이루는 각은 $10^{\circ}$와 $20^{\circ}$를 적용하였다. 속도장은 접수보다 이수에서 빠른 유동특성을 나타냈다. 모델 하부에서 충격압력이 가장 높은 지점인 P2 지점에서 $10^{\circ}$보다 경사각이 큰 $20^{\circ}$에서 약 6 % 상승하였다.

• 한국전자거래학회지
• /
• 제7권1호
• /
• pp.107-127
• /
• 2002

Database system parameter tuning is one of database system tuning that achieve to improve performance of database system with application program tuning and data model tuning. By parameter tuning adjusts value of entry that is staled in data dictionary's parameter file that is included to database system, it is thing which make relevant database system can display performance of most suitable. And, it is that achievement is one o( possible tuning method immediately without occurrence of additional expense or involved hardware for database system performance elevation and ashes composition of software. But, it is actuality that administration about parameter practical use is not achieved, and is using Default Value of parameter that database management system offers just as it is systematically. So, this paper presents parameter tuning process that can ：achieve Parameter tuning of database system that is operating present systematically, and parameter tuning process each activity important input urea and tuning achievement product. And explain about effect and result that happen by sort database system performance and parameters that it is affinity systematically, and grasp relationships between parameter, and change parameter of string database system. And not that parameter uses contents that specify by fixing when establish database administration system, is going to emphasize and explain that must utilize changing continuously during database system operation. It changes parameter entry value how in various kinds different operation environment and present if must apply, and will arrange effect that this parameter enoy value alteration gets in performance liking into account point that is actuality that is using parameter that define database administrators when install the database system just as it is continually without alteration.

• 한국유통학회지:유통연구
• /
• 제2권2호
• /
• pp.153-172
• /
• 1997

The distribution sector is affected by a wide range of regulations. Many of these are related to health and safety, others are related to urban planning and environmental issues, whereas some mainly have an economic basis. But, regulations many be unduly restrictive, in which case they can drive up costs and ultimately prices, or they may, in some cases, reduce consumer choice. Unduly restrictive regulations could also increase costs indirectly, by reducing competition and thus lead to lower productivity growth. In the past few years, distribution sector has gone through drastic changes due to deregulation and market opening. Implementation of regulatory reforms served as an opportunity to change laws and systems which had been an obstacle to development of distribution sector. Market opening of distribution sector became a turning point to promote competition among domestic and foreign firms. However, for small and medium scale of the typical retail enterprises which were in no position to compete in terms of prices, additional facilities, and services, faced a threat of diminished trading area, and even of their existence. Because, large firms may have greater market power than small firms, as they can more easily extract favorable terms when procuring goods, and may also be able to deter entry by advertising outlays or access to the best sites. In addition, larger chain stores armied with sufficient capital dominated trading area and reduced customer's welfare by abusing their monopoly power when competing with other shops, and are often cited as an example of adverse effects of local monopoly. In order to minimize such adverse effects and to foster competition, regulatory reforms in distribution sector should set its goal to promote sound and stable distribution activities through market principle and restoring competition principle, and ultimately to boost customers welfare. Therefore, deregulation in distribution sector should be implemented in a way to promote customers welfare, eliminate entry barriers, and expand competition principle such as productivity and efficiency competition. However, it should be also recognized that deregulation of system alone is not enough to develop the distribution sector. To compete in a increasingly concentrated industry, small enterprises increasingly engage in co-operative arrangements, such as buying groups, strategic alliances or franchise agreements.

• 한국환경농학회지
• /
• 제35권1호
• /
• pp.15-23
• /
• 2016

BACKGROUND: Water quality is of concern to water utility operators, public health officials, and populations using the water. If any contaminant is released from a point of entry, it could be spread rapidly throughout the water stream. So the identification of the location of the points of entry and its release history are critical informations to establish the management strategy.METHODS AND RESULTS: Aniline, nonylphenol, pentachlorophenol and formaldehyde in 39 surface water samples were analysed using Gas chromatography-mass spectrometry (GC-MS) methods. Formaldehyde, aniline and nonylphenol were mainly detected in the near sites where industrial waste water and domestic sewage were discharged into stream. But pentachlorophenol was detected in the downstream samples where pulp manufacturing plants were operated.CONCLUSION: Results indicate that pentachlorophenol found in main stream of Guem river was mainly introduced from pulp manufacture industries. Otherwise, formaldehyde, aniline and nonylphenol were mainly contaminated from the industrial waste water and domestic sewage.

• International Journal of Aeronautical and Space Sciences
• /
• 제14권3호
• /
• pp.247-255
• /
• 2013

The flight control of re-entry vehicles poses a challenge to conventional gain-scheduled flight controllers due to the widely spread aerodynamic coefficients. In addition, a wide range of uncertainties in disturbances must be accommodated by the control system. This paper presents the design of a roll channel controller for a non-axisymmetric reentry vehicle model using the trajectory linearization control (TLC) method. The dynamic equations of a moving mass system and roll control model are established using the Lagrange method. Nonlinear tracking and decoupling control by trajectory linearization can be viewed as the ideal gain-scheduling controller designed at every point along the flight trajectory. It provides robust stability and performance at all stages of the flight without adjusting controller gains. It is this "plug-and-play" feature that is highly preferred for developing, testing and routine operating of the re-entry vehicles. Although the controller is designed only for nominal aerodynamic coefficients, excellent performance is verified by simulation for wind disturbances and variations from -30% to +30% of the aerodynamic coefficients.

• 한국건설관리학회:학술대회논문집
• /
• 한국건설관리학회 2007년도 정기학술발표대회 논문집
• /
• pp.652-655
• /
• 2007

최근 해외건설시장은 정체된 국내시장에 대한 대안으로서 국내 건설업체의 관심과 신규 진출이 지속적으로 증가하고 있다. 하지만 해외건설시장은 국내 시장에 비해 상대적으로 건설업체가 직면하게 되는 리스크 부담이 크기 때문에 시장 진출에 대해서 신중하고 합리적인 의사결정이 요구되고 있다. 이에 따라 기존의 많은 연구들이 관심이 증가하고 있는 개별 시장의 리스크에 대해 분석하고 있으며, 이를 고려한 시장 진출 의사결정 모델에 관한 연구도 이루어져 왔다. 본 연구에서는 건설기업의 입장에서 신규시장 진출을 재무적인 측면에서 고려하기 위한 모델을 제시하였다. 이를 위해 시장진출 시의 경쟁 상황을 고려한 실물옵션 게임 (real options game)을 통해 시장 모형을 도출하고, 이를 통해 해당 시장진출에 대한 투자 여부를 판단하기 위한 모델을 제시하였다. 본 연구를 통해서 도출된 시장진출모형은 가정을 통해 제약된 조건 상황 속에서의 특수 모델로서, 추후 연구를 통해 정보의 불균형성, 경쟁 기업 수의 일반화 등을 고려하여 보다 현실성 있는 모델을 제시하고자 한다.

• 한국도로학회논문집
• /
• 제15권1호
• /
• pp.111-119
• /
• 2013

PURPOSES: Though the situation that the roundabouts are actively constructed, researches on the effect of the roundabouts focus mainly on the analysis of the expected effects of using only traffic simulation on the operation. Considering such problems, this study is conducted to analyze the effects of the various aspects based on field observation studies. METHODS: This study evaluated and analyzed the effects from the aspects of traffic operation, traffic safety, and traffic behavior by performing field observation studies with six roundabouts with/without signal controls on the pilot project areas for the roundabouts installed in 2010. RESULTS: Through the study results, it was found that the average travel time decreases by 14.7% and 2.4% on the signalized intersections and unsignalized intersections, respectively. The average travel speed increases by 9.7 and 5.8km/h on the roundabouts with/without signal lights. Regarding traffic safety, the speed deviation among individual vehicles decreases by approximately 18.4 to 32.7km/h, thus confirming the safety effects. As the decrease of the number of conflicts, it might be explained that car crashes and collision with pedestrians decreased by 62.2% and 66.7%. Also the result shows that the lowest point of speed in roundabouts appears near the yield line on the entry area on the roundabouts. When passing through the roundabouts, vehicles enter at a speed of 20-30km/h, which is the design speed of the circulatory lane and drive out the roundabout with a higher speed than the entry speed. CONCLUSIONS: When a roundabout is introduced at the intersections below certain traffic volume there are effects of traffic operation, traffic safety, and traffic behavior.

• 한국정보통신학회논문지
• /
• 제22권11호
• /
• pp.1531-1537
• /
• 2018

해운 물류에서 대량의 컨테이너는 선박, 트럭, 철도 등 복합 운송의 형태로 항만을 거쳐 목적지로 이동된다. 선사, 화주와 같은 물류 주체는 화물의 주요 물류 거점에 대한 실시간 반 출입 정보를 필요로 한다. 특히 항만은 해운과 내륙을 연결하는 중요한 공간으로써 물류 주체의 관심이 높다. 본 논문에서는 GPS를 이용한 위치 추적을 점 단위가 아닌 면 단위를 기반으로 동적으로 나타낸다. 즉 어느 항만의 영역 안으로 들어가는지, 나가는지, 또는 통과하는지와 같은 동적인 위치 추적을 나타내고 있다. 이전 연구의 위치 추적 알고리즘을 기반으로 능동형(Active) IP-RFID 기술을 활용한 항만 진출입, 항만 내부에서의 실시간 위치 추적 알고리즘을 제안한다.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2003년도 춘계학술대회논문집
• /
• pp.343-346
• /
• 2003

In order to construct the extrusion die surface of arbitrarily shaped sections, an automatic surface construction method based on NURBS surface and area mapping method is proposed in the present work. In the present study, a center point for area mapping is determined by introducing the marring concept based on constant area proportionality between original billet and final product. The characteristic points of inlet profile is determined using the traditional area mapping method and the root finding numerical method. The inlet and outlet profiles are precisely described with NURBS curves using the characteristic points of entry and exit sections. For the construction of NURBS surface, an interpolation method for the pre-determined two section curves has been developed to be used in the generation of interior control points and weights. To show the validity of the proposed method, automatic die surface generation is carried out for the several kinds of shaped sections.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2003년도 춘계학술대회논문집
• /
• pp.168-171
• /
• 2003

Generally RF AGC (Roll Force Automatic Gauge Control) controls the roll gap using the variation of rolling force caused by the roll eccentricity and the entry thickness of material, but RE AGC takes the bad effect of the roll eccentricity. The Feed-forward (FF) AGC method, which controls the next stand roll gap by the estimation of the thickness variation due to skid mark is needed to supplement the shortage of RF AGC. In this paper, an adaptive filtering method which takes account of the kind of material, the final objective thickness and the rolling speed is proposed to predict skid mark thickness variation. In addition, an improved estimation method of control point using a speedometer and looper angle is suggested. Via on line test, the performance improvement of the suggested FF AGC method is verified.