• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.64-70
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• 2018

Rollover is a major concern for vehicles with a higher center of gravity and for improving driving performance. This study investigates a tilting system to prevent rollover, which was successfully implemented for high-speed trains. It may be useful to apply the concept of the tilting system to a large truck such as a trailer. Even a small adjustment in the tilting angle can improve the driving stability during a steep turn. The equation of motion was derived from a dynamic model of the trailer with the tilting system. The balance of the centrifugal force and normal force determines the rollover critical speed for a given radius of the turn and load. To obtain a more conservative criterion, the rollover critical state was defined as the instant when any side wheel loses contact with the road. To actuate the tilting system, the optimal tilting angle must be calculated from the steering angle and the vehicle speed. Using a simplified model of a large truck, the effects of the tilting angle and load on the rollover critical speed were investigated.

• Journal of Korea Water Resources Association
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• v.51 no.10
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• pp.895-903
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• 2018

There are a large number of weirs installed in rivers of Korea, and these characteristics are not common in other countries. When the flow passes through a structure such as a weir, discontinuous flow occurs. In terms of numerical simulation, it affects the numerical instability due to the balance between the flow term and the source term. In order to solve these problems, many researchers used empirical formulas or numerical scheme simplification. Recently, researches have been conducted to use more accurate numerical scheme. K-River was developed to reflect the characteristics of domestic rivers and calculate the discontinuous flow more accurately. For the verification of K-River, 1) numerical experiment simulations with a bump in the bed, 2) laboratory experiment of hydraulic jump simulation, 3) real river were performed. K-River verified its applicability by simulating results similar to the exact solution and observed value in all simulations.

• Journal of the Korean Applied Science and Technology
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• v.40 no.6
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• pp.1249-1258
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• 2023

The purpose of this study was to reveal the effect of COP variable of support feet on relative reach distance and composite score of active feet during YBT. 29 adults in their 20s(age: 24.4±3.0 yrs, height: 171.0±10.5 cm, weight: 72.1±12.1 kg, leg length: 88.2±5.8 cm) participated in the study. Using YBT, relative reach distance and composite score of active feet were calculated, and COP variables of support feet were measured on left and right support feet. Multiple regression analysis was used to determine the effect of COP variables of support feet during YBT on relative reach distance and composite score. As a result of the study, during YBT, when supporting right feet, the influence of AP COP velocity, ML COP velocity and COP velocity in posterolateral direction was significant, and when supporting left feet, the influence of AP COP velocity, ML COP velocity in posteromedial direction improved relative reach distance and composite score.

• Journal of Korean Society of Transportation
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• v.25 no.6
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• pp.19-31
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• 2007

When estimating the benefits from an investment project in the transportation sector, errors caused by many factors may exist. This study focuses on user equilibrium traffic assignment methods and stopping criteria. According to previous studies, when using a user equilibrium assignment model, the benefits of travel time savings can be effected by the relative gap value. As the stopping criteria decreases, the time needed for traffic assignment increases, so that lowering the criteria cannot be the best solution. Therefore, an effort is necessary to reduce this change rate and thus improve reliability. This paper considers three methods: reducing the links subject to benefit calculation, extracting sub-area O/D tables and networks, and applying the mean value of successive traffic assignment results. The results of the analysis show that the method using the mean value of five results is more proper than the other methods. Using the sub-area analysis method, if the study area is small the benefits of a project might be over- or under-estimated. This paper used a nationwide O/D table and network at peak time as a case study. The resulting patterns can differ according to basic data to be used in analysis. So further analysis using the data from metropolitan areas are needed.

• Journal of Technology Innovation
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• v.20 no.1
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• pp.17-43
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• 2012

Alliance formation has been recognized as an important strategy for firms who seek to survive through acquisition of sustainable competitive advantages. Specifically in high-tech industries, firms may consider formation of strategic alliances in order to access valuable external knowledge. These firms tend to be situated in a dilemma that they should choose between exploration and exploitation, which are two types of strategic choices suggested by March (1991). Working out the dilemma has been extensively discussed in the area of strategy or organization learning. Recently, however, an increasing number of studies have stressed on a balance between exploration and exploitation. Regarded as 'ambidextrous organizations' (Lavie and Rosenkopf, 2006), these firms that simultaneously pursue exploration and exploitation have emerged in high-tech industries, and many studies have provided evidence of positive association between organizational ambidexterity and firm performance. In the strategic alliance research, accordingly, scholars began to pay attention to the balanced choice between exploration-and exploitation-oriented alliances. Given these backgrounds, this study examines the relationship between alliance ambidexterity and firm performance. While previous research approached alliance ambidexterity mainly from the number of alliances, our study suggests ambidexterity in terms of alliance portfolio and alliance partner. Our dataset consists of biotechnology or pharmaceutical firms in the United States, which spans time period between 1990 and 2005. We conduct panel data analysis. The results show the strong link between alliance ambidexterity and firm performance, highlighting the balance between exploration and exploitation when firms make strategic decisions.

• Korean journal of applied entomology
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• v.17 no.1 s.34
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• pp.23-28
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• 1978

The study has been carried to confirm the pathotypes of Kresek inducing isolates of X. oryzae, and its reaction to the test plants when they were inoculated by the use of various methods. Induction of Kresek symptom by 23 isolates which randomly samplified from 123 Kresek areas through the country also were examined. The specificity of Pathotypes I, II, V in causing Kresek and the potenciality of infected rice straw is a first inoculum for Kresek epidemics in nature were tested. Fifteen out of 23 isolates from kresek area belonged to pathotype group I, while the rest of 8 isolates 5 howed group II reaction, and the most of isolates were originated from infected rice plant of Milyang #23. All of five pathotype groups were abled to produce 'Kresek' symptom although they showed some differences in each group of pathotype. The varieties Milyang #21, 22 and 23 were attacked by all isolates of group I, II and V while the Gogyoku group varieties including Yushin produced kresek symptom only by pathotype group II. Infected and dried straw maintained the pathogens during the winter period, and these straw acted as a first inoculum of Kresek disease when the straw were cutted and used as a manure just before transplanting of rice seedling.

• Journal of the Institute of Convergence Signal Processing
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• v.21 no.1
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• pp.21-28
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• 2020

In this paper, a new type of electric wheelbarrow is proposed and developed. The developed electric wheelbarrow is equipped with an attitude reference system(ARS) sensor, which consists of 3-axis acceleration sensor and 2-axis Gyro sensor so that it can estimate pitch angle and roll angle. When an operator tilts the wheelbarrow up and down, the pitch angle is detected. The sign of the pitch angle is interpreted as the operator's intention for moving the wheelbarrow forward or backward and the controller drives the wheel of the wheelbarrow with the velocity according to the magnitude of the detected pitch angle. A cargo box of the wheelbarrow is designed to rotate and is controlled to maintain level always, so an operator can handle the electric wheelbarrow easily and safely. The wheelbarrow consists of an in-wheel motor, a DC motor, motor drives, an ARS sensor considering economical use in industrial field. Three experiments are performed to verify the feasibility and stability of the electric wheelbarrow.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.1
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• pp.79-86
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• 2007

The Magnus effect measurement apparatus was designed and built for spinning wind tunnel model which would simulate the rotation of projectiles. Prior to the high speed test, the ground functional test and the low speed test were carried out in the Agency for Defense Development's Low Speed Wind Tunnel(ADD-LSWT) at spin rates from about 6,000 to 10,000 rpm. Magnus force and moment were measured on the spinning projectile model at velocity of 100 m/s. It was shown that the Magnus force and moment were linear function of spin parameter. The test results were compared with Magnus test run on the same configuration in the Arnold Engineering Development Center's Propulsion Tunnel 4T(AEDC-4T).

• Proceeding of EDISON Challenge
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• 2014.03a
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• pp.347-358
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• 2014

본 논문에서는 양자 역학적 분자 동역학(Quantum Mechanical/Molecular Mechanical-Molecular Dynamics, QM/MM-MD)을 통해 수용액에 녹아 있는 Potassium Thiocyanate의 dynamics를 연구했다. Umbrella sampling technique을 활용하여 association/dissociation에 해당하는 Free energy surface를 구했다. 두 개의 Free energy minimum이 녹아 있는 두 이온의 center of mass 사이의 거리가 $4{\AA}$일 때와 $5{\sim}6{\AA}$ 부근일 때 나타났으며 $4{\AA}$일 때 더 안정 했다. 본 논문에서는 $4{\AA}$일 때를 Contact Ion Pair(CIP) $6{\AA}$일 때를 Dissociation Ion Pair(DlP)라고 칭했다. 이 minimum들이 무엇인 지를 밝혀 내기 위해 추가 연구를 수행하였다. Free energy 상에서 가장 안정 할 때(CIP) solute인 Potassium thiocyanate의 구조를 살펴 봤더니 Potassium ion은 Thiocyanate ion의 Sulfur보다 Nitrogen side를 선호하였다. 그 원인을 알아보기 위해 salvation shell의 구조를 Radial distribution function을 통해 살펴 봤더니 물 분자가 Nitrogen보다 Sulfur와 더 강한 상호작용을 하고 있었다. 그로 인해 Potassium ion이 Nitrogen을 선호한단 결과가 나온 것이다. 한편, 두 번째 minimum은 물 분자가 Potassium 이온과 Thiocyanate 이온 사이에 flexible하게 bridging을 하는 구조였다. 또한 단순 양자 계산을 통해서도 비슷한 구조를 얻을 수 있었다. 그러나 QM 계산은 0K에서 수행하는 것이기 때문에 엔트로피 효과가 없는 계산이지만 본 연구는 온도 300K로 실제 용매와 가깝게 수행함으로써 고정되어 있는 구조가 아니라 엔트로피와 엔탈피가 균형적으로 존재하는 실제 용액 속에서의 구조를 처음으로 보여주는 것이다.

• Journal of Nutrition and Health
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• v.46 no.4
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• pp.346-356
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• 2013

This study investigated the daily physical activity level, energy expenditure, energy balance, and body composition and their relationship with university students. The participants were 130 male students ($19.5{\pm}0.5$ yrs) and 139 female students ($19.5{\pm}0.3$ yrs) at a university in Chungnam province. Physical activity level was evaluated by an equation based on 24 hr-activity record and dietary nutrient intake was evaluated using the food record method during a three-day period consisting of two week days and one weekend. Body composition was measured using Inbody 430 (Biospace Co., Cheonan, Korea). As a result, mean body mass index (BMI) of subjects indicated that they had normal weight, however mean body fat ratio was $19.1{\pm}5.4%$ for males and $28.4{\pm}5.0%$ for females, indicating that they had higher than normal weight. Daily mean physical activity level was 1.55 for males and 1.47 for females, which was regarded as 'low active', respectively. Females had more light activity than males (p<0.01). Daily mean energy expenditure was $2,803.5{\pm}788.9$ kcal/d for males and $1,915.4{\pm}510.2$ kcal/d for females (p<0.001). Daily mean dietary energy intake was $2,327.0{\pm}562.5$ kcal/d for males and $1,802.1{\pm}523.6/d$ for females (p<0.001), and daily mean energy balance was $-476.5{\pm}955.9$ kcal/d for males and $-113.3{\pm}728.1$ kcal/d for females (p<0.01). Daily mean dietary intake of protein, vitamins, and minerals, except Ca, satisfied recommended nutrient intake. Daily energy expenditure was positively related to body weight (p<0.01), BMI (p<0.01), and fat free mass ratio (p<0.05), but was negatively related to body fat ratio (p<0.01). In conclusion, subjects had a negative energy balance and low physical activity. They had a normal weight by BMI but had a more fat than normal weight by body fat ratio. This appears to be related to their low physical activity. Thus, nutrition education should be provided for university students in order to increase their physical activity for maintenance of normal weight by body composition and health promotion.