• 한국해양공학회지
• /
• 제34권6호
• /
• pp.394-405
• /
• 2020

To assess the station-keeping performance of floating structures in the Arctic region, the ice load should be considered along with other environmental loads induced by waves, wind, and currents. However, present methods for performance evaluation in the time domain are not effective in terms of time and cost. An ice load generation module is proposed based on the experimental data measured at the KRISO ice model basin. The developed module was applied to a time domain simulation. Using the results of a captive model test conducted in multiple directions, the statistical characteristics of ice loads were analyzed and processed so that an ice load corresponding to an arbitrary angle of the structure could be generated. The developed module is connected to commercial dynamic analysis software (OrcaFlex) as an external force input. Station-keeping simulation in the time domain was conducted for the same floating structure used in the model test. The mooring system was modeled and included to reflect the designed operation scenario. Simulation results show the effectiveness of the proposed ice generation module and its application to station-keeping performance evaluation. Considering the generated ice load, the designed structure can maintain a heading angle relative to ice up to 4°. Station-keeping performance is enhanced as the heading angle conforms to the drift direction. It is expected that the developed module will be used as a platform to verify station-keeping algorithms for Arctic floating structures with a dynamic positioning system.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
• /
• pp.82-85
• /
• 2004

This paper proposes the development of delay compensator to minimize performance degradation caused by time delays in network-based real-time control systems. The delay compensator uses the time-stamp method as a direct delay measuring method to measure time delays generated between network nodes. The delay compensator predicts the network time delays of next period in the views point of time delays and minimizes performance degradation from network through considering predicted time delays. Control output considering network time delays is generated by the defuzzification of probable time delays of next period. The time delays considered in the delay compensator are modeled by using a timed Petri net model. The proposed delay prediction mechanism for the delay compensator is evaluated through some simulation tests by measuring deviation of the predicted delays from simulated delays.

• Asia pacific journal of information systems
• /
• 제16권2호
• /
• pp.111-122
• /
• 2006

This paper investigated the causal relationship between IT investment and economic performance with the office, computing and accounting machinery (OCAM) and gross domestic product (GDP) statistics from the United States for the period 1961 to 2001. Due to non-stationary aspects of the series, found by unit root tests, it was deemed applicable to apply growth models using the first difference of the series. The results indicate that IT investment growth at the country level do not only cause economic performance growth, but are also caused by economic performance growth. While IT investment growth affect economic performance growth over shorter time periods, economic performance growth affect IT investment growth over longer time periods. As a result, this study reveals IT investment growth have the preceding effect on economic performance growth, and then economic performance growth impact subsequently on IT investment growth.

• 산업경영시스템학회지
• /
• 제17권32호
• /
• pp.227-232
• /
• 1994

In the performance domain, physical performance is a measure that represents some degree of system, subsystem, component or device success in a continuous sense, as opposed to a classical binomial sense (success or failure). If applicable sensing and monitoring means exist, physical performance can be observed over time, along with explanatory variables or covariables. Performance-based reliability represents the probability that performance will remain satisfactory over a finite period of time or usage cycles in the future when a performance critical limit (which represents an appropriate definition of failure in terms of performance) is set at a fixed level, based on application requirements. In the case of inadequate knowledge of the failure mechanics, this physical based empirical modeling concept along with performance degradation knowledge can serve as an important analysis tool in reliability work in product and process improvement.

• 한국수학교육학회지시리즈C:초등수학교육
• /
• 제9권2호
• /
• pp.107-118
• /
• 2005

The purposes of this study were to investigate the practice of performance assessment in elementary mathematics classes especially focused on 4th grade. To achieve this, three research questions were posed as follow: First, What do they prepare for performance assessment? Second, What kinds of tests do they use in mathematics performance assessment? Third, What kinds of difficulties do they have for performance assessment and what should be changed for a successful performance assessment in mathematics? To Answer the research questions, three 4th grade classes were selected from three different elementary schools in seoul and three teachers were interviewed. From the data analysis, several conclusion were drawn. First, a plan for mathematics performance assessment was not set by the class teacher who are in charge of the class. The main reason was lack of time. Second, in most of the assessment, written tests were used and the items in the tests were skill-oriented. Third, teachers thought that performance assessment was needed in mathematics. But lack of their time, knowledge and competency, it is difficult to do performance assessment in mathematics.

• 산업경영시스템학회지
• /
• 제35권1호
• /
• pp.87-92
• /
• 2012

This study examines the relationship between R&D investment and subsequent outputs of the research activity. Usually, there is some time difference between the production of research outputs, such as academic papers and application or registration of patents, and the investment of R&D expenditure. The time lag for producing this kind of research outputs should be considered to evaluate the performance of research activity exactly. The purpose of this study is to identify time lag effect between the times of input and output of a R&D activity and to derive the degree of time lag using the data set of a long term R&D program supported by Korean government. A modified Almon model is suggested to identify the time lag effect between input and output of research activities performed by this program. Time-series cross-section data from 16 research centers between 2001 and 2009 are used to find time lag effect.

• 한국환경보건학회지
• /
• 제34권3호
• /
• pp.233-239
• /
• 2008

In order to improve reactor performance of existing sewage treatment plants, the feasibility of enhancing reactor performance by bioaugmentation using EM as bioaugmentation agent and the effects of anoxic: oxic time ratio on reactor performance were investigated. Continuous and intermittent aeration modes were compared under the 6 hr of HRT. Three different types of intermittent aeration modes, that is, 15 min, of anoxic:45 min of oxic, 30 min of anoxic: 30 min of oxic, and 45 min of anoxic: 15 min oxic respectively were chosen as test modes to study the effects of anoxic : oxic time ratios on reactor performance. The optimum anoxic: oxic time ratio was 30 min:30 min when considering simultaneous removal of organic, nitrogen and phosphorus. When applying EM into a continuously aerated reactor under the varying dosing rates of 50-200 ppm, reactor performance in terms of organic and nitrogen removal efficiencies was not improved at all. Nitrogen removal efficiency was increase when the EM dosing rate was increased. However the degree of improvement was slight when the EM was injected above 100 ppm. However optimum phosphorus removal was found at the EM dosing of 200 ppm. Thus it was found that optimum injection concentration of EM is 200 ppm. It is apparent that putting EM into a sewage treatment plant significantly affects the T-N removal efficiency of the reactor by enhancing denitrification efficiency especially in operational conditions of relatively long anoxic periods. To achieve reciprocal condition in a reactor with intermittent aeration it is necessary to enhance the reactor performance by EM injection. In the case of modifying existing continuously aerated reactors into intermittent aerated reactors, it is obvious that operating costs of aeration would be reduced by reducing aeration time when compared with existing conventional sewage treatment plants.

• Steel and Composite Structures
• /
• 제2권2호
• /
• pp.113-128
• /
• 2002

The performance of steel MRF with rigid connections, proportioned by adopting different capacity design criteria, is evaluated in order to highlight the effectiveness of static non-linear procedure in predicting the structural seismic behavior. In the framework of the performance-based design, some considerations are made on the basis of the results obtained by both dynamic time histories and push-over analyses, particularly with reference to the damage level and the structure ability to withstand a strong earthquake.

• 수산경영론집
• /
• 제47권2호
• /
• pp.43-59
• /
• 2016

This study investigated the difference of the effects of public loan programs in fishery industry on management performance from a balanced score card (BSC) perspective depending on the type of loan, scale of fund, period of support and business category, using the financial data of fisheries firms having the balance of loan at the end of 2014. The key factors influencing credit rating change were also analyzed after public loan support. From a integrative perspective, results show that the firms supported by working fund have higher management performance than the firms supported by facility fund. The firms received large scale fund showed higher management performance than the firms received small scale fund. While management performance was decreasing or slowing down over time after financial support, management performance of the firms supported by facility fund improved over time. From a non-financial perspective, the firms received facility fund invested more in education and growing perspective than the firms received working fund. As the size of fund increased, the investment in education, growing, internal process and customer increased. Personnel expenses and employee benefits for education and growing has increased over time. However, the firms with facility fund restricted the expenses of education, personnel expenses and employee benefits as time goes by. Because the effects of public loan on credit rating of fisheries corporations have no statistical significance, it has become known that the financial support of public loan program has no influence on the change of credit rating of fisheries corporations. This study attempted performance analysis from a BSC perspective which combine factors of non-financial perspective with factors of financial perspective. Findings from this study suggest the direction of microscopic performance analysis of public loan in fishery industry.

• 대한전자공학회논문지TC
• /
• 제46권1호
• /
• pp.89-93
• /
• 2009

본 논문은 에너지 검출기에 시간 지연 장치를 채택하여 복수번의 확인 과정을 갖는 향상된 스펙트럼 검출기에서 센싱 시간에 따른 성능의 영향을 알아본다. SNR은 1dB, 그리고 오보 확률은 0.1로 고정하고 3, 60, 100km/h의 다양한 이동 속도를 고려한 스즈키 채널 하에서 시뮬레이션을 통해 센싱 성능을 고찰하고 이를 기존의 에너지 검출기의 경우와 비교한다.