• Bulletin of the Korean Mathematical Society
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• v.42 no.4
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• pp.875-887
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• 2005

In M/G/1 retrial queueing system with two types of customers and feedback, we derived the joint generating function of the number of customers in two groups by using the supplementary variable method. It is shown that our results are consistent with those already known in the literature when ${\delta}_k\;=\;0(k\;=\;1,\;2),\;{\lambda}_1\;=\;0\;or\;{\lambda}_2\;=\;0$.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.246-250
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• 2005

Recommand Systems are being used by an ever-increasing number of E-Commerce to help customers find products to purchase. Recommend Systems offer a technology that allows personalized recommendations of items of potential interest to users based on information about similarities and dissimilarities among different customers tastes. In this paper, we design and build a Recommend System using the historical customer movie purchase transactions and extracts the knowledge needed to make association recommendations to new customers.

• Journal of Korea Society of Industrial Information Systems
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• v.12 no.4
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• pp.107-118
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• 2007

A single-server queueing model with infinite buffer and batch arrival of customers is considered. In contrast to the standard batch arrival when a whole batch arrives into the system at one epoch, we assume that the customers of an accepted batch arrive one-by one in exponentially distributed times. Service time is exponentially distributed. Flow of batches is the stationary Poisson arrival process. Batch size distribution is geometric. The number of batches, which can be admitted into the system simultaneously, is subject of control. Analysis of the joint distribution of the number batches and customers in the system and sojourn time distribution is implemented by means of the matrix technique and method of catastrophes. Effect of control on the main performance measures of the system is demonstrated numerically.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.19 no.4
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• pp.443-457
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• 2015

We consider the M/M/c/c queues in which the customers blocked to enter the service facility retry after a random amount of time and some of idle servers can leave the vacation. The vacation time and retrial time are assumed to be of phase type distribution. Approximation formulae for the distribution of the number of customers in service facility and the mean number of customers in orbit are presented. We provide an approximation for M/M/c/c queue with general retrial time and general vacation time by approximating the general distribution with phase type distribution. Some numerical results are presented.

• Journal of Korea Society of Digital Industry and Information Management
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• v.15 no.3
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• pp.197-206
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• 2019

Telemarketing has been used in finance due to the reduction of offline channels. In order to select telemarketing target customers, various machine learning techniques have emerged to maximize the effect of minimum cost. However, there are problems that the class imbalance, which the number of marketing success customers is smaller than the number of failed customers, and the recall rate is lower than accuracy. In this paper, we propose a method that solve the imbalanced class problem and increase the recall rate to improve the efficiency. The hybrid sampling method is applied to balance the data in the class, and the stacked deep network is applied to improve the recall and precision as well as the accuracy. The proposed method is applied to actual bank telemarketing data. As a result of the comparison experiment, the accuracy, the recall, and the precision is improved higher than that of the conventional methods.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.9
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• pp.1646-1650
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• 2011

SAIDI(System Average Interruption Duration Index) is the index that signifies the power quality of customers. SAIDI is also used to know how well utilities operate their systems. The annual interruption time in the areas that consists of widely distributed customers, is generally longer than that in the areas that consists of heavily concentrated customers. The Reliability index of huge system is not necessarily better or worse than that of small system, because SAIDI is irrelevant to the total amount of power sold or the total number of customers. This paper proposes a customer density very relevant to SAIDI. The proposed customer density is used to modify the existing SAIDI to more clearly express the service level of power supply. A modified WSAIDI(weighted SAIDI) can be a useful indicator helping utilities improve the reliability of their systems and customers evaluate the service level of receiving power.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.10
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• pp.1733-1750
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• 2011

In the early stages of a software project, it is critical to understand the needs of the customers and elicit their customer requirements. Various requirements elicitation methods have been proposed. However, existing methods still have the limitations such as a limited number of target customers, limited expression of customers' opinions, and difficulty in collecting the customers' opinions continuously. A novel method for eliciting customer requirements is proposed by utilizing a social network service (SNS), which is a shared source of raw information of the customers' needs and opinions. The proposed method is validated to show its effectiveness in overcoming the limitations of existing methods.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.2
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• pp.7-14
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• 1998

This paper presents an approach to quantitatively evaluate customers' effect due to automatic reclosing of power distribution systems. This proposed approach assess the customers' effect on equip ment halt by predicting a momentary interruption and voltage sag and analyzing the impact of customers' equipment sensitive to electric disturbances. Simulation results show that the increment of the number of reclosing improves the service reliability, but deteriorates the power quality for customers. The proposed approach utilizes the determination of automatic reclosing scheme and distribution system planning.anning.

• Proceedings of the KIEE Conference
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• 2003.11a
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• pp.196-198
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• 2003

The impacts of electric service interruption to customers depend on customer and interruption characteristics. Customer characteristics include demographic aspects(residential type, and number of household members) and power supply types whereas interruption characteristics include frequency, duration, time, and day of interruption. Accordingly evaluation of these customer interruption costs is very complicated and subjective. For residential customers, customer survey method seems most appropriate because interruption impact to residential customers is intangible. In other words, the value of housework or lost leisure due to interruption is individual. Accordingly, this paper selected the customer survey method to assess the interruption costs for residential customers.

• The Journal of Information Systems
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• v.15 no.4
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• pp.99-124
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• 2006

The development of IT has made it possible to use various terminal systems for financial transaction and demands for financial survices are getting more and more diversified at the same time. Among others, mobile banking service market based on IC chips has been expanded its service areas and the number of mobile banking users has been increased. The study analyzes and tests the dynamic effects of the inflow of potential customers on mobile banking market condition by using system dynamics methodology to identify the dynamic structure of mobile banking market. The simulation model is designed to track the variation in the number of subscribers of mobile banking servides according to two scenarios, and the results are as follows; First the effect of word of mouth by customers who have used the service already is significant. The satisfactory level of early adopters is reflected in WOM, and as a test result shows, increase in word-of-mouth causes the growth of potential customers' demands for mobile banking service. Second, perceived attractiveness of mobile banking service market is another important construct. Factors such as convenience, mobility, time saving, security, and various services explain the construct perceived attractiveness of the service, and it makes the potential customers adopt the service, causing the increase of demands.