• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.196-202
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• 1997

A reinforced hydraulic hoses,caiied a resonator hoses,with fixible metal tube are commonly used in automotive power steering hydraulic systems to attenuate and eliminate the objectionable fluid borne noise(pressure ripple) or vibration produced by a pump or steering gear. To achieve better nose attenuation in automotile vehicles, the investigations on propagation and attenuation characteristics of fluid borne pressure ripple in power steering hydraulic ciruit are required. So, this paper descibes a mathematical model of hydraulic hoses to support design the power steering hydraulic circuit and analyze the attenuation characteristics of flow and pressure ripples. The model is based on the transfer matrix approach. The experimental results show that the pulsation attenuation characteristics of hydraulic house is remarkably affected by the flexible metal tube inserted coaxially inside a hydraulic hose with a finite length as well as viscoelastic properties of house wall. It is also shown that the predicted results bymodel proposed here agree well with the measured results over a wide frequency range. These results will assist in the modeling and design of hydraulic hoses, and hear, should provide a means for designing a quieter automotive power steering hydraulic systems.

• The Journal of Asian Finance, Economics and Business
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• 제8권2호
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• pp.873-882
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• 2021

The study investigates the key factors that affect the adoption of the International Financial Reporting Standards (IFRS) by companies listed on Ho Chi Minh Stock Exchange (HOSE) in Vietnam. The factors that are studied in this research include total debt-to-equity ratio, firm size, return-on-equity ratio, audit quality, foreign investment, and financial institution category. The authors have utilized quantitative and qualitative analyses in combination with a logistics regression model and other available analytical tools for conducting the research. All statistics processed in the paper were based on 379 audited financial statements issued in 2018. The results reveal that factors like firm size, return on equity (ROE), audit quality, foreign investment, and financial institution category positively affect the IFRS adoption of HOSE-listed companies, while total debt-to-equity ratio negatively impacts the adoption. The findings suggest Vietnamese law and policy-makers, when promoting the adoption of IFRS by listed companies, should focus more on five variables with positive influence and they can disregard the total debt-to-equity ratio that is insignificant as a factor affecting the adoption of IFRS. This implication could be applied for other firms in Vietnam and for enterprises in other countries, which are in the same stage of IFRS application.

• 한국가스학회지
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• 제27권1호
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• pp.38-47
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• 2023

수소연료전지 차량 충전 과정에서, 충전소에서의 공급압력과 차량 내 저장 탱크의 압력 차이에 의해 수소가 흐르게 되고 유량은 압력 차에 의존한다. 따라서 충전 과정에서 발생하는 수소의 압력강하에 대한 고려는 필수적이며 이의 분석을 통해 수소 충전 과정의 효율성을 높일 수 있다. 본 연구에서는 충전라인 중 호스, 노즐/리셉터클, 파이프, 밸브에 대하여 압력강하를 분석하였다. 호스와 파이프는 도관에서의 압력강하로, 노즐/리셉터클은 흐름 노즐 식으로, 밸브는 기체 유량 식으로 계산하였다. 또한 각 구성요소에서 발생하는 압력강하 효과를 종합 분석한 결과 전체 충전라인에서 압력강하에 가장 큰 영향을 주는 요소는 밸브에서의 압력강하임이 밝혀졌다. 이번 연구는 추후 수소 충전을 포함한 수소 유동 해석으로 수소 충전 과정의 모델 개발에 활용될 수 있을 것이다.

• The Journal of Asian Finance, Economics and Business
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• 제7권9호
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• pp.135-145
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• 2020

This paper provides the practical application of a linear shrinkage framework on Vietnam stock market. The cumulative data points observed in this analysis are 468 weeks from January 2011 to December 2019. All the companies listed on Ho Chi Minh City Stock Exchange (HOSE), except the companies under two years period from Initial Public Offering (IPO), are considered. The cumulative number of stocks picked is therefore 350 companies. The VNINDEX, which is the Vietnam Stock Index, is used as a reference index for shrinking to a single-index model. The empirical results show that the shrinkage of covariance matrix for portfolio optimization gives the promising results for the investors on Vietnam stock market. The shrinkage method helps the investors to produce the optimal portfolio in the sense of having higher profit with lower levels of risk compared to the portfolio of the traditional SCM method. Moreover, the portfolio turnover of shrinkage method is always kept at low magnitudes, and this makes the shrinkage portfolios save much transaction costs and reduce the liquidity risks in the trading process. In addition, the ability of shrinkage method in making profit is once again confirmed by the Alpha coefficient that achieves a high positive value.

• The Journal of Asian Finance, Economics and Business
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• 제7권11호
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• pp.107-115
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• 2020

This study is concerned with the relationship between firm's ownership structure and the co-movement of the stock return with the market return. Four different types of firm ownership, including managerial ownership, state ownership, foreign ownership, and concentrated ownership, are among the main features of the company's governance mechanism and have been separately documemented in the previous research to understand their impact on stock price synchronicity. We constructed the regression model, using stock price synchronicity as the dependent variable and the above four components of ownership structure as explanantory variables. The pooled OLS, the fixed effects model, and the random effects are employed to investigate the outcome of the study. Data used in the reserch are of public firms listed on the Ho Chi Minh City Stock Exchange (HOSE) during the five-year period term from 2015 to 2019. The data sample contains 235 companies from 10 industries with 1135 observations. The results revealed by the fixed effects model, the large ownership and the managerial ownership are found to have adverse effect on the stock price synchronicity, whereas the foreign ownership model is revealed to have positive influence on the stock return co-movement. The effect of the state ownership on the stock price synchronicity is not confirmed.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2011년도 춘계학술발표대회 논문집
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• pp.281-288
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• 2011

Hydraulic hose assemblies deliver a fluid power in various oil pressure equipments such as construction machinery, automobile, aircraft, industrial machinery, machine tools, and machinery for ships, or they are used as pipes in oil pressure circuit. However, as the traditional measure for estimating life under the influence of various external factors incurs hardship in terms of time and expenses, it is essential to take accelerated life test by choosing the factor that suits the usage condition of the test object. The objective of the this study is to propose a acceleration model that takes both temperature and pressure without flexing condition into consideration. The life that is calculated by the equation for evaluating life and the test data show similar slopes as a result of comparing and analyzing the equation for evaluating life that is obtained in this research and the test data, which illustrates that they estimate life similarly, and the proposed equation is proved to be an accelerated life equation that presents the test results.

• 한국통신학회논문지
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• 제11권1호
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• pp.16-24
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• 1986

본 연구는 버퍼 삽입 프로토콜을 사용한 LAN시스템을 모델링하여 그 모델에 대한 큐잉지연 시간과 응답시간을 도출하여, 파라메터 값을 변화시키면서 throughput rate에 대한 응답 시간 특성을 구하여 performance를 분석하였다. 응답시간은 Data rate를 높일 때 개선되었고, ACK신호를 호스트에서 전송할 경우에 비해 Network Interface Unit(NIU)에서 보낼 경우 챈널 Udilization이 0.8 부근에 이를 때까지 0.7mesc정도 개선되었다. 또한, 버퍼 삽입 프로토콜을 구현하기 위한 H/W구성에 대하여 연구하였다.

• The Journal of Asian Finance, Economics and Business
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• 제6권4호
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• pp.53-63
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• 2019

The paper examines the influence of profitability on distance to default (DD) in Vietnam securities market. The investigated sample consists of 211 companies listed on HOSE during 18 years from 2010 to 2017. We apply KMV model to calculate distance to default and use both macroeconomics factors and firm specific factors as independent variables. Using General Least Squared (GLS) method, we find evidence to confirm the positive relationship between profitability and distance to default. This result showed that, although profitability did not directly reflect the cash flow generated, a good profitable enterprise would be an important factor to help facilitate and generate cash flow and at the same time debt was guaranteed when it was due. Besides, the test results revealed that the financial structure and sales on assets have the inverse effect on the distance to default at the significance level of 5%. The results also revealed that a group of macro factors had an influence on the distance to default of businesses, including spread, GDP and trade balance (via exchange rates). Gross domestic income had certain impacts on the distance to default of businesses. This was also a basic indicator measuring the national economic cycle.

• Fibers and Polymers
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• 제7권4호
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• pp.389-397
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• 2006

The beneficial effects of graduated compression stockings (GCS) in prophylaxis and treatment of venous disorders of human lower extremity have been recognized. However, their pressure functional performances are variable and unstable in practical applications, and the exact mechanisms of action remain controversial. Direct surface pressure measurements and indirect material properties testing are not enough for fully understanding the interaction between stocking and leg. A three dimensional (3D) biomechanical mathematical model for numerically simulating the interaction between leg and GCS in dynamic wear was developed based on the actual geometry of the female leg obtained from 3D reconstruction of MR images and the real size and mechanical properties of the compression stocking prototype. The biomechanical solid leg model consists of bones and soft tissues, and an orthotropic shell model is built for the stocking hose. The dynamic putting-on process is simulated by defining the contact of finite relative sliding between the two objects. The surface pressure magnitude and distribution along the different height levels of the leg and stress profiles of stockings were simulated. As well, their dynamic alterations with time processing were quantitatively analyzed. Through validation, the simulated results showed a reasonable agreement with the experimental measurements, and the simulated pressure gradient distribution from the ankle to the thigh (100:67:30) accorded with the advised criterion by the European committee for standardization. The developed model can be used to predict and visualize the dynamic pressure and stress performances exerted by compression stocking in wear, and to optimize the material mechanical properties in stocking design, thus, helping us understand mechanisms of compression action and improving medical functions of GCS.

• 연구논문집
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• 통권32호
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• pp.35-43
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• 2002

This study was performed to develop accelerated life test method of machanical parts using cumulative damage theory that used to model the fatigue of parts that receive variable load. The cumulative damage theory was introduced, and the estimation of life and calculation of accelerated life test time was illustrated. As the actual application example, accelerated life test method of agricultural tractor transmission was described. Life distribution of agricultural tractor transmission was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (MTBF) 3,000 hours and 90% reliability for one test sample. According to the cumulative damage theory, because test time can shorten in case increase test load, test time could be reduced by 482 hours when we put the load 1.1 times of rated load than 0.73 times of rated load that is equivalent load calculated by load spectrum of the agricultural tractor. This time, acceleration coefficient was 11.7. This accelerated test method was used to develop accelerated test method of gear reducer, hydraulic hose and bearing as well as agricultural tractor transmission and it is considered to be applied comprehensively to machanical parts the fatigue of which is happened by load or pressure etc.