• Journal of IKEEE
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• v.24 no.1
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• pp.132-139
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• 2020

The ionizer module used in this air cleaner supplies high voltages of 3.5KV / -4KV to the discharge electrode HV+ / HV- using a winding transformer to generate positive and negative ions by electric field radiation of carbon fiber brush. The ionizer module circuit using the existing MCU has the disadvantage of large PCB size and expensive price, and the gate driver chip using the existing ring oscillator has oscillation period sensitive to PVT (Process-Voltage-Temperature) fluctuation and there is risk of fire or electric shock because there is no fault detection function by short circuit of HV+ and GND as well as HV- and GND. Therefore, in this paper, even though PVT fluctuates, by using 7-bit binary up counter, HV+ voltage reaches the target voltage by adjusting oscillation period. And an HV+ short fault detection circuit for detecting a short circuit between HV+ and GND, an HV- short fault detection circuit for detecting a short circuit between HV- and GND, and an OVP (Over-Voltage Protection) for detecting that HV+ rises above an overvoltage are newly proposed.

• Korean Journal of Construction Engineering and Management
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• v.19 no.1
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• pp.90-102
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• 2018

In preparation of the increase in the domestic debts and the rise in the US interest rate, the Korean government has started to strengthen the regulation on the property market since 2017. So, it is likely that the sales in the domestic construction market would be decreased. Even in the overseas plant projects market, as there has been the continuous increase in the cost and the resulting increase in the losses, it looks hard for the large construction companies to keep their credit ratings as they are now. This study is designed to check Korean government's property policy and any possible problems caused by the overseas and domestic economic environment, which include the property market policy, interest rate, rise in the property price and lackluster sales in housing market. It showed the change in the credit ratings by finding out the sales, work capability, sales in non-governmental projects, operating profits and PF contingency liabilities. For this study, the questionnaires were sent to 30 practical experts to analyze the effect of the risk factor on the outside credit rating of large construction companies.

• Journal of the Korea Institute of Building Construction
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• v.14 no.5
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• pp.415-422
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• 2014

There is growing difference between a planned value and an actual cost for increasing as an risk of construction cost. A construction cost index is an alternative to redeem a problem, but it is still very difficult to reduce an actual differential as a price fluctuation. Furthermore an existing theory of a construction cost index is overly complex, and is unsuitable for using in working-level. This study suggests an optimum correction rate in respect of a total construction cost. It is analyzing the actual cost of 53 public buildings that the Public Procurement Service ordered. The objects are main processes that include architectural works, mechanical works, electrical works, telecommunication works, and service facilities. It is compared a total construction cost based on absolute error rate using the median from frequentist principle. For this, it is selected the suitable regression model and set a correction rate.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.2
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• pp.191-196
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• 2015

There have been many studies on statistical forecasting on firm's performance and stock price by applying various financial indicators such as debt ratio and sales growth rate. Selecting predictors for constructing a prediction model among the various financial indicators is very important for precise prediction. Most of the previous studies applied variable selection algorithms for selecting predictors. However, the variable selection algorithm is considered to be at risk of eliminating certain amount of information from the indicators that were excluded from model construction. Therefore, we propose a firm's performance prediction model which principal component analysis is applied instead of the variable selection algorithm, in order to reduce dimensionality of input variables of the prediction model. In this study, we constructed the proposed prediction model by using financial data of American IT companies to empirically analyze prediction performance of the model.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.643-646
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• 2007

As increase of the land price at downtown area, it makes people more and more interested of improving the space utilization such as makes buildings bigger, deeper and higher. Therefore, the importance of the underground construction which is the basic principle has been increased. As constructors have to complete underground construction as soon as possible with the minimum costs, they concentrate on the whole process of underground structure. Although they makes every these efforts, construction failure still happen because of the uncertainty of the condition of soil and the unexpected danger of underground construction. To make matter worse, there are only some examples without detailed information like 'how much this breakdown damage to the construction?' so it is the anther problem that most of people doesn't recognize the economical negative impact of underground structure breakdown. This report would make people understood the importance and risk of the underground construction by showing some analysis which was assumed from the real accidents.

• Environmental and Resource Economics Review
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• v.20 no.4
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• pp.761-796
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• 2011

The purpose of this paper is to derive fuel mix of electricity generating system with the lowest cost considering energy security and climate change mitigations as the target of energy policy. Energy Security Price Index(ESPI), based on the measure of market concentration in fossil fuel market and political risk of exporting countries, is chosen to assess the level of energy security. The methodology of Energy Conservation Supply Curve(CSC) is applied to fuel mix to meet the carbon emission mitigation through increasing the alternatives participation and introduction of new technologies. These also represent an improvement on the level of energy security, having the complementarity between two objectives. The alternative measure for improving energy security is exploration and production(E&P) of fossil fuel for energy sufficiency. Fuel mix of electricity generating system to achieve certain objectives in 2020 can be derived with the lowest cost considering energy security and carbon emission mitigations.

• Asia pacific journal of information systems
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• v.19 no.4
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• pp.29-45
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• 2009

In the information age, cheap price of information processing and advances in personalization technology have allowed companies to enhance the relationships with their existing customers and to expand their customer base by effectively attracting new customers. However, most customers are reluctant to provide their personal information to companies. This study explores the tension between companies' desire to collect personal information to offer personalized services and their customers' privacy concerns. The psychological reactance theory suggests that when individuals feel that their behavioral choice is threatened or restricted, they are motivated to restore their freedom. Therefore, despite the expected benefits from personalized services, customers may perceive the services to be restrictive of their freedom to choose. This adverse effect may undermine the relationships between companies and their customers. We conducted experiments to explore the dynamic roles of transactional and environmental factors in motivating customers to provide personal information. We revisited online privacy issues from the perspective of psychological reactance. For the experiments, we created an online shop and randomly assigned the participants to one of the two experimental conditions-high and low levels of information requirements. The results of the experiment indicate that threatening the free choice serves as a transactional cost in online profiling. On the other hand, the expected benefits of personalization services have positive correlations with customers' willingness to provide personal information. This study explains privacy based on transactional and environmental factors. Our findings also indicate that the environmental factors such as the Internet privacy risk and trust propensity do not significantly affect the willingness to provide personal information when firms required much personal information. Implications and contributions are discussed.

• Journal of Convergence for Information Technology
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• v.11 no.5
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• pp.94-103
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• 2021

This study aims to propose technical trading rules for Bitcoin futures and empirically analyze investment performance. Investment strategies include standard trading rules such as VMA, TRB, FR, MACD, RSI, BB, using Bitcoin futures daily data from December 18, 2017 to March 31, 2021. The trend-following rules showed higher investment performance than the comparative strategy B&H. Compared to KOSPI200 index futures, Bitcoin futures investment performance was higher. In particular, the investment performance has increased significantly in Sortino Ratio, which reflects downside risk. This study can find academic significance in that it is the first attempt to systematically analyze the investment performance of standard technical trading rules of Bitcoin futures. In future research, it is necessary to improve investment performance through the use of deep learning models or machine learning models to predict the price of Bitcoin futures.

• Journal of the Korean Society of Mineral and Energy Resources Engineers
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• v.55 no.6
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• pp.624-634
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• 2018

Indonesia has become a net crude oil importer because of the reduction of a new oil field discovery, and Indonesia is attempting to raise investment funds through the Kerja Sama Operasi (KSO) contract to develop a small-scale field. However, the KSO has a high-risk and low-return contract system for investors, necessitating an economic evaluation to examine the feasibility of the project. This study performed economic evaluation on the development of an Indonesian small-scale field by applying the KSO contract conditions, and identified the major economic parameters through a sensitivity analysis. As a result, the oil price, CAPEX and OPEX were identified as influential factors for economic evaluation. The results also indicate that commercial production in small-scale fields is difficult. In the future, this study can be used as a reference resource for investment in oil and gas development projects in Indonesia.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.1
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• pp.50-60
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• 2021

For conventional AESA radars, DC-DC power modules using 300 Vdc have low efficiency, high volume, heavy weight, and high price, which have problems in modularity with T/R module groups. In this paper, to improve these problems, we propose a distributed DC-DC power module with high-voltage 800 Vdc and high-efficiency Step-down Converter. In particular, power requirements for modern and future marine weapons systems and sensors are rapidly evolving into high-energy and high-voltage power systems. The power distribution of the next generation Navy AESA radar antenna is under development with 1000 Vdc. In this paper, the proposed highvoltage, high-efficiency DC-DC power modules increase space(size), weight, power and cooling(SWaP-C) margins, reduce integration costs/risk, and reduce maintenance costs. Reduced system weight and higher reliability are achieved in navy and ground AESA systems. In addition, the proposed architecture will be easier to scale with larger shipboard radars and applicable to other platforms.