• Journal of Microbiology and Biotechnology
• /
• v.25 no.2
• /
• pp.185-195
• /
• 2015

Glucoamylase is an important industrial enzyme. Glucoamylase production by industrial Aspergillus niger strain featured with two major problems: (i) empirical substrate feeding methods deteriorating the fermentation performance; and (ii) the high raw materials cost limiting the economics of the glucoamylase product with delegated specification. In this study, we first proposed a novel three-stage varied-rate substrate feeding strategy for efficient glucoamylase production in a 5 L bioreactor using the standard feeding medium, by comparing the changing patterns of the important physiological parameters such as DO, OUR, RQ, etc., when using different substrate feeding strategies. With this strategy, the glucoamylase activity and productivity reached higher levels of 11,000 U/ml and 84.6 U/ml/h, respectively. The performance enhancement in this case was beneficial from the following results: DO and OUR could be controlled at the higher levels (30%, 43.83 mmol/l/h), while RQ was maintained at a stable/lower level of 0.60 simultaneously throughout the fed-batch phase. Based on this three-stage varied-rate substrate feeding strategy, we further evaluated the economics of using alternative carbon sources, attempting to reduce the raw materials cost. The results revealed that cornstarch hydrolysate could be considered as the best carbon source to replace the standard and expensive feeding medium. In this case, the production cost of the glucoamylase with delegated specification (5,000 U/ml) could be saved by more than 61% while the product quality be ensured simultaneously. The proposed strategy showed application potential in improving the economics of industrial glucoamylase production.

• The Journal of the Korea Contents Association
• /
• v.19 no.7
• /
• pp.36-46
• /
• 2019

If stock market is efficient, any well-devised trading rule can't consistently outperform the average stock market returns. This study aims to verify whether the strategy based on bid-ask volume information can beat the stock market. I suggested a day trading strategy using order imbalance indicator and empirically analyzed its profitability with the KOSPI 200 index futures data from 2001 to 2018. Entry rules are as follows: If BSI is over 50%, enter buy order, otherwise enter sell order, assuming that stock price rises after BSI is over 50% and stock price falls after BSI is less than 50%. The empirical results showed that the suggested trading strategy generated very high trading profit, that is, its annual return runs to minimum 71% per annum even after the transaction costs. The profit was generated consistently during 18 years. This study also improved the suggested trading strategy applying the genetic algorithm, which may help the market practitioners who trade the KOSPI 200 index futures.

• Journal of Electrical Engineering and Technology
• /
• v.4 no.3
• /
• pp.315-322
• /
• 2009

Penetration and installation of a new dynamic technology known as Flexible AC Transmission Systems (FACTS) in a practical and dynamic network requires and force expert engineer to develop robust and flexible strategy for planning and control. Unified Power Flow Controller (UPFC) is one of the recent and effective FACTS devices designed for multi control operation to enhance the power system security. This paper presents a dynamic strategy based on Particle Swarm Optimization (PSO) for optimal parameters setting of UPFC to enhance the system loadability. Firstly, we perform a multi power flow analysis with load incrementation to construct a global database to determine the initial efficient bounds associated to active power and reactive power target vector. Secondly a PSO technique applied to search the new parameters setting of the UPFC within the initial new active power and reactive power target bounds. The proposed approach is implemented with Matlab program and verified with IEEE 30-Bus test network. The results show that the proposed approach can converge to the near optimum solution with accuracy, and confirm that flexible multi-control of this device coordinated with efficient location enhance the system security of power system by eliminating the overloaded lines and the bus voltage violation.

• Journal of Advanced Navigation Technology
• /
• v.15 no.2
• /
• pp.307-312
• /
• 2011

In the macro/femto cellular networks, the portion of channels assigned to each cell is a critical factor which sets the stability and the performance of the whole system. To grasp the concrete influence that the channel split portion have on the system, we present the queueing model for IP based macro/femto cellular networks, and find the stability conditions. Additionally we provide the strategy to decide the portion of channels allocated to each cell. Through the experiments, we prove that the proposed strategies operate feasibly in various network environments, and on the basis of these results we discuss the efficient system structure plan.

• Korea Journal of Hospital Management
• /
• v.22 no.3
• /
• pp.105-117
• /
• 2017

This study was performed to provide medical service providers with useful information for their market competitiveness and decision making. It is regarding positioning map and repositioning map strategy to enforce market competitiveness through bench marking of a specific hospital which has been relatively underestimated in the market. With AHP and biplot analyses for this study, we could identify priority of properties that medical service consumers consider when they choose a university hospital and market competitiveness of alternative university hospitals. It is expected that the study of repositioning strategy to Strengthening Market Competitiveness will provide efficient problem solving method to allocation restricted resources by repositioning the specific university hospital through benchmarking with evaluation factors of the most market competitiveness university hospital. When Inje University Paik Hospital was benchmarked and repositioned, the share of Paik hospital increased and there was only 3.1% difference from Dongah Dong-A University Hospital, which occupied the first place in market competitiveness. Such the results of this study may suggestion management strategies to provide efficient problem solving methods when companies responding to rapidly changing management environments allocation restricted resources.

• Journal of the Korean School Mathematics Society
• /
• v.6 no.1
• /
• pp.19-26
• /
• 2003

The purpose of this study is twofold: (i) to argue the importance of problem solving strategy in education and (m to propose an efficient way to use the problem-solving strategy, which is based on the survey to find out how well elementary school teachers recognize the importance of the strategy. Forty elementary school teachers participated in the survey. The result of the survey shows that they do not use various strategies when they solve problems. It also shows that the rate of wrong answers the teachers get when solving problems is pretty high because they adopt a wrong strategy. It is prerequisite that teachers recognize the importance of the strategy when solving problems and put into practice various strategies in order to help their students improve their problem-solving abilities.

• The Journal of Information Systems
• /
• v.17 no.4
• /
• pp.207-232
• /
• 2008

As electronic commerce is growing to be a part of everyday business life for companies, enterprises are required to establish the appropriate strategy to effectively realize their business visions. The correct choice of strategy enables organizations to make efficient use of internal resources and adjust to the external environment, affecting their performance. The nature of the firms' strategy has been currently focused on the new business model such as e-commerce. In the beginning of e-commerce, the decreasing cost of business transactions was a major benefit affecting its success. However, e-commerce firms are currently facing new advanced information technology, various business models and serious competition. To deal with these new challenges, there is an increasing demand for right strategy direction to effectively and efficiently manage a corporation's internal resources and external environments that are related to electronic commerce. Moreover, it is necessary both to set up the feasible strategy direction and to evaluate its outcome. The purpose of this study attempts to provide appropriate e-commerce strategy, which is well matched with e-commerce performance, as the different strategies affect different results of e-commerce. On the basis of the results of this research, we can see that the strategies selected by e-commerce companies differ according to the e-commerce type and firm's size.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.47 no.3
• /
• pp.163-173
• /
• 2024

This study aims to establish an online shopping mall marketing strategy based on big data analysis methods. The customer cluster analysis method was utilized to analyze customer purchase patterns and segment them into customer groups with similar characteristics. Data was collected from orders placed over one year in 2023 at 'Jeonbuk Saengsaeng Market', the official online shopping mall for agricultural, fish, and livestock products of Jeonbuk Special Self-Governing Province. K-means clustering was conducted by creating variables such as 'TotalPrice' and 'ElapsedDays' for analysis. The study identified four customer groups, and their main characteristics. Furthermore, regions corresponding to customer groups were analyzed using pivot tables. This facilitated the proposal of a marketing strategy tailored to each group's characteristics and the establishment of an efficient online shopping mall marketing strategy. This study is significant as it departs from the traditional reliance on the intuition of the person in charge to operate a shopping mall, instead establishing a shopping mall marketing strategy through objective and scientific big data analysis. The implementation of the marketing strategy outlined in this study is expected to enhance customer satisfaction and boost sales.

• Journal of Internet Computing and Services
• /
• v.10 no.3
• /
• pp.85-94
• /
• 2009

In this work we propose an energy-efficient transmission strategy for wireless sensor networks that operate in a strict energy-constrained environment. Our transmission algorithm consists of two components: a binary-decision based transmission and a channel-aware backoff adjustment. In the binary-decision based transmission, we obtain the optimum threshold for successful transmission via Markov decision process (MDP) formulation. A channel-aware backoff adjustment, the second component of our proposal, is introduced to favor sensor nodes seeing better channel in terms of transmission priority. Extensive simulations are performed to verify the performance of our proposal over fading wireless channels.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.33 no.4
• /
• pp.10-22
• /
• 2010

The first full-scale u-City operation has started in Dongtan u-City. As local cities take over and operate the u-City, unexpected issues arise such as securing the budget of operating costs and self-providing the costs with business models utilizing the u-City assets. The paper presents a strategy for solving these issues. The strategy provides a foundation(infrastructure) for long-term operation models which may reduce the long-term operating costs. In order to establish the economic operating framework of u-City, suggested are some cost-reduction models based on the operating costs structure. For each model, a base framework with comparative analysis of operating costs is provided. With these models, each u-City may select a relevant model according to the characteristics of it. We hope that the framework provides the foundation for efficient and sustainable u-City operations.