• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.7
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• pp.669-677
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• 2009

In general, the pitch momentum biased system that induces inherently nutational motion in roll/yaw plane, has been adapted for geosynchronous communications satellites. This paper discusses the method of roll attitude control using yaw axis momentum management method for a low earth orbit(LEO) satellite which is a pitch momentum biased system equipped with only two reaction wheels. The robustness of wheel momentum management method with PI-controller is investigated comparing with wheel torque control method. The transfer function of roll/yaw axis momentum management system that is useful for attitude controller design is derived. The disturbance effect of roll/yaw axis momentum management system for attitude control is investigated to identify design parameters such as magnitude of momentum bias and to get the insight for controller design. As an example, the PID controller design result of momentum management system for roll/yaw axis control is provided and the simulation results are presented to provide further physical insight into the momentum management system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.3
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• pp.85-94
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• 2003

A geosynchronous Satellite in general, has two momentum management logics to maintain its wheel momentum tin the stable region. The one is applied in order to control accumulative wheel momentum in the momentum dumping mode and the other is utilized in order to control attitude errors during the stationkeeping. In this paper, the momentum management logics are explained for dumping/sationkeeping mode and the logics are verified by simulation on the 3 attitude subsystem.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.7
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• pp.365-373
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• 2021

This paper investigates the presence of momentum profits in the Saudi stock market. The study applied a quantitative method by utilizing monthly closing prices of 194 listed firms on Tadawal (Saudi Stock Market). The data from January 2010 to February 2019 is taken from the Tadawal market database for analysis. The sample is further divided into two equal sub-samples based on the structural changes that occurred in the Saudi stock market. Moreover, the high- and low-value traded portfolios are also constructed to examine the presence of momentum profits. Sixteen investment strategies are formed for each sample. The results show a very strong presence of momentum profits in the Saudi stock market for the full sample as well as for the sub-samples. The momentum profits are observed for a longer investment horizon. The results confirm that the short or medium-term formation of portfolios produces negative momentum returns for high-value traded stocks. The low-value traded stocks portfolios give similar results to the full sample results in terms of momentum profits. The results suggest that an investor should keep an eye on the past performance of desired stocks for at least three-nine months in which they are willing to invest.

• The Journal of Asian Finance, Economics and Business
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• v.8 no.3
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• pp.361-372
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• 2021

This research aimed to analyze the momentum strategy of foreign investors with the smallest trading transactions in the Indonesian stock market. This study applied a quantitative method approach using intraday transaction data of companies listed on the LQ-45 Index for March, April, and May 2017, obtained from the Indonesia Capital Market Institute (TICMI) which is a subsidiary of the Indonesia Stock Exchange (IDX). The number of companies with available data is 35 companies, consisting of 23 non-government stocks and 12 government stocks. The number of observations from the 35 companies was 8,686,030 observations where the government companies recorded 2,751, 545 and the non-government companies 1,387,016 observations. All data was then squeezed and grouped into small, medium, and large trade transaction orders. The data analysis method used was paired t-test with SPSS to analyze cumulative abnormal returns in the formulation and test periods. This study found that small foreign investors carried out momentum strategies on stocks listed on the LQ-45 Index. However, re-testing was done by separating government and non-government shares. It turned out that small foreign investors performed a momentum strategy on non-government and a contrarian strategy on government.

• The Korean Journal of Financial Management
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• v.26 no.1
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• pp.189-220
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• 2009

This study tests the significance of momentum and contrarian strategy which challenge the weak efficient market hypothesis (EMH). If momentum and contrarian strategy can make extra return above the market, this can be a significant critics to the weak EMH. By using Monte Carlo simulation we have found that many existing returature, which test the significance of momentum and contrarian strategy, have a significance distortion problem. We test the significance of momentum and contrarian strategy by using reality check test of White(2000) which solve the problem of data snooping bias. The results are following. When we use the KOSPI index as the benchmark portfolio, we can get the best strategy of momentum strategy in the case of mean return. But in the case of Sharp ratio which is the performance measure adjusting risk, we find that the best strategy in the momentum and contrarian strategy can not dominate the performance of benchmark portfolio. Therefore we argue that weak EMH can not be rejected because of superior performance of momentum and contrarian strategy when we consider risk.

• The Korean Journal of Financial Management
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• v.23 no.2
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• pp.1-25
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• 2006

This paper studied the performance of momentum strategy and contrarian strategy based or past stock return ratio of Korean stock market. The comparative study shows that the volatility of stock markets that can be found the performance of momentum strategy is smaller than that of emerging stock market. Accordingly, This paper examines that the performances of momentum strategy and contrarian strategy are affected by the larger volatility in Korean stock market. Further analysis using the 6 years sub-portfolios reveals that the momentum strategy is significant only during 1980 to 1986 time period when it had the least market volatility. Additionally, we investigate whether firm-level volatility as well as market volatility influence on the performance of contrarian strategy, and figure out that the momentum strategy is significant for the portfolio composed of firms with smaller volatility for previous period, while not significant for the portfolio composed of firms with larger volatility.

• Korean Management Science Review
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• v.29 no.1
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• pp.57-71
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• 2012

In this paper, we deal with a sector investment strategy by implementing the black-litterman model that incorporates expert evaluation and sector rotation momentum. Expert evaluation analyzes the relative performance of the industry sector compared with the market, while sector rotation momentum reflects the price impact of significant sector anomaly. In addition, we consider the portfolio impact of sector cardinality and weight constraints within the context of mean-variance portfolio optimization. Finally, we demonstrate the empirical viability of the proposed sector investment strategy with KOSPI 200 data.

• Journal of Korean Society for Quality Management
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• v.48 no.1
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• pp.13-27
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• 2020

Purpose: The purpose of this study is to present a recoil measurement and analysis of K2 rifle for the development of a virtual reality marksmanship training in the Republic of Korea Army. Methods: For the recoil measurement, a test-bed is built by a barrel that has exact dimensions of K2 rifle and three piezoelectric pressure sensors mounted on the barrel. Data of over 200 rounds of 5.56mm M193 and K100 bullets are collected and analyzed from live fire experiments. For the recoil analysis, both the free recoil method and the gas exhaust aftereffect method are used to calculate a recoil velocity, momentum and kinetic energy of K2 rifle by applying the law of conservation of momentum. In addition, a new method is proposed that uses the third law of motion and the chamber pressure model for the recoil measurement Results: The results show how different between the previous and proposed methods with respect to M193 and K100 bullets of K2 rifle. In M193, the free recoil method demonstrates 1.113, 4.197, and 2.335, the gas exhaust aftereffect method computes 1.698, 6.407, and 5.441, and the proposed method calculates 0.990, 3.734, and 1.848 in recoil velocity, momentum and kinetic energy, respectively. In K100, the free recoil method demonstrates 1.190, 4.487, and 2.669, the gas exhaust aftereffect method computes 1.776, 6.699, and 5.949, and the proposed method calculates 1.060, 3.998, and 2.119 in recoil velocity, momentum and kinetic energy, respectively. Conclusion: This study implements live fire experiments to provide recoil velocity, momentum, and kinetic energy of K2 rifle using both M193 and K100 bullets. For the development of the army virtual reality marksmanship, the results in this paper would be useful to design and produce a gun and/or a rifle of virtual reality.

• Health Policy and Management
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• v.30 no.2
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• pp.139-141
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• 2020

Coronavirus disease 2019 (COVID-19) is currently in progress. Although it is difficult to predict the end of currently increasing COVID-19, it is expected to last for a long time. The COVID-19 is making a lot of changes. Due to physical distancing and living distancing, non-contacts such as wearing facial masks, online lectures, online medical services, telecommuting, and telemarketing are becoming common. In the era of post-COVID-19, online and offline will coexist. Many countries following China's lockdown strategy, which is agreed with the World Health Organization, should be changed to Taiwan's facial mask strategy for reducing the economic problems. The prolonging COVID-19 will add to the economic difficulties, and the US-China confrontation will be difficult to rebound the global economy. COVID-19, such as plaque, smallpox, and Spanish influenza, will be a historical momentum. How to respond to the crisis of COVID-19 and post-COVID-19 will determine the future of the world and Korea.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.10a
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• pp.371-374
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• 2004

The ultimate purpose of Supply Chain Management (SCM) is maximizing the profits of the overall Supply Chain (SC) through increasing customer satisfaction and decreasing operating cost. It can be successfully accomplished only when SC system balances demands with supply activities coordinated by aggregate planning, mid-term level of Supply Chain Planning(SCP). However, the existing measures to mainly estimate the specific function of SCM are not enough to evaluate the state of SC with respect to the balance between supply and demand in operating. To solve this problem, we develop a new SC performance measure, Balancing Point, using momentum concept. a fundamental knowledge of physics. Momentum concept can explain the relation among objects so that it can consider the balance between supply and demand in SC operating. The developed measure can not only consider the current state of the SC system but also take planned but not executed supply activities and upcoming demands into account. Therefore, using Balancing point, we can be aware of the unbalanced state of SC in advance.