• The Journal of Asian Finance, Economics and Business
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• 제7권4호
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• pp.309-316
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• 2020

This research aims to revisit the hypothesis that bribery hurts firm performance in the context of a perceptibly corrupt country. Specifically, we use micro-data from Vietnamese small and medium firm surveys in 2013 and 2015 to examine whether bribery impedes firm revenue growth and labor productivity growth. An issue arising in this type of research is the potential endogeneity between firm bribing behaviors and firm performance. To go around the issue, we follow the literature to instrument bribery variable with the average probability of bribery in other provinces. We further employ the Analysis of Variance technique (ANOVA) to unveil if the effect of bribery is dependent on bribing purposes. The regression results show that firm performance is significantly influenced by firm size, firm age and firm bribing behavior. Larger firms are more likely to grow faster while firm performance tends to be negatively related to firm age. Particularly, we find that bribery significantly impedes firm revenue growth and labor productivity growth. The analysis of variance shows that the effect of bribery on firm performance may vary across bribing purposes. Our findings, therefore, support the sand-the-wheels hypothesis that bribery hurts firm performance even in a highly corrupt business environment.

• 한국소음진동공학회논문집
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• 제19권11호
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• pp.1144-1150
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• 2009

Appropriate vibration model is required to predict in advance the vibration level of a large vehicle which carries sensitive electronic/mechanical equipments and drives often on the unpaved and/or off-road conditions. Central tire inflation system(CTIS) is recently adopted to improve the mobile operation of military and bulletproof vehicles. In this paper, full vehicle model(FVM) having 11 degrees of freedom and equipped with CTIS has been developed for a large vehicle which has $8\times8$ wheels$\times$driving wheels. Usability of the developed model is validated via road tests for three different modes (i.e. highway, country, and mud/sand/snow modes) and for various velocity conditions. The developed FVM can be used to predict the vibration level of the large vehicle as well as to determine the driving velocity criterion for different road conditions.

• 한국산업융합학회 논문집
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• 제12권3호
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• pp.129-135
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• 2009

This paper describes traveling systems consisting of one major-wheel and three minor-wheels attached to each tip of three spokes. A link of inter-axle plays an important role of the system. It connects secondary axle to the major wheel axle. Its length is determined to ascend stably various stairs. The systems was designed to mount a cart for carrying agricultural products. The systems was applied to ascend stairs, travel on sand and cross a obstacle, despite of simple design.

• Elastomers and Composites
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• 제55권2호
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• pp.88-94
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• 2020

Automobile industry, along with the automobile steering system, is rapidly changing and developing. The constant velocity joint transmits power to the wheels of vehicles without changing their angular velocity based on the movement of the steering wheel. Moreover, it controls their movement to act as a buffer. In order to prevent the excessive increase in temperature caused by the movement of vehicles, boots are attached to the constant velocity joint and lubricant is injected into the boots. The boots maintain the lubrication and protect the constant velocity joint from sand, water, and so on. As the wheels of the vehicle rotate, the boots are acted upon by forces such as bending, compression, and tension. Additionally, self-contact occurs to boots. Therefore, their durability deteriorates over time. To prevent this problem, polychloroprene rubber was initially used however, it was replaced by thermoplastic polyester elastomers due to their excellent fatigue durability. In this study, the structural analysis of boots was conducted. The results showed the deformation patterns of the boots based on the translation and rotation of the constant velocity joint. Moreover, it confirmed the location that was vulnerable to deformation. This study can be used to potentially design high-quality constant velocity joint boots.

• 한국재료학회지
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• 제9권7호
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• pp.715-723
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• 1999

마그네슘은 20여년간 자동차 산업에서 휠소재로 사용되어 왔다. 마그네슘 휠은 무게가 알루미늄 휠보다 25% 가벼워서 주행성이 우수하다. 이 연구의 목적은 사형주조 및 영구금형주조 공정에 의한 AZ91D 합금제 췰을 개발하는 것이다 보호개스$(SF_6+CO_2)$를 사용하는 비플럭스 용해기술을 적용하여 용탕의 산화와 불순물의 유입을 배제하였다 마그네슘 용탕은 가압식 펌프시스템을 사용하여 가열된 파이프를 통하여 모울드에 자동으로 공급된다. 열처리 및 인고트의 조성에 따른 AZ91B 합금제 휠의 기계적 특성을 조사하였다.

• The Journal of Asian Finance, Economics and Business
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• 제7권5호
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• pp.259-268
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• 2020

This study aims to provide empirical evidence on the causal relationship between bribery and firm innovation. To this end, we use a micro-dataset of small and medium firms in Vietnam surveyed in 2015. Given the binary nature of the dependent variable, a simple probit regression model is employed. However, as bribery variable is potentially endogenous, a simple probit regression may give biased estimates. We deal with the potential endogeneity by making use of the bivariate probit model. A property of the bivariate probit model is that it can produce efficient estimates of a typical probit model with endogenous binary explanatory variable. A Hausman-like likelihood ratio test is implemented following the estimation to test the existence of endogeneity. We find that bribery significantly undermines firm innovation. Also, firms run by household appear less innovative. The probability of innovation diminishes significantly if firm owners or managers have previous experience in firm products. As expected, larger firms seem to be more innovative. Exporters tend to be more innovative compared to non-exporters. Our findings provide support to the hypothesis that bribery is detrimental to firm innovation and, thus, innovation may be a mediating channel, through which, bribery impedes firm long-term performance.

• Journal of Biosystems Engineering
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• 제27권1호
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• pp.25-32
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• 2002

This study was conducted to develop a dry paddy seeder of strip tillage. The prototype is 8 rows drill seeder, which is composed of a strip tillage, sowing and fertilizing device, and pressing wheels to do the strip tillage, sowing, fertilizing, and draining ditch, simultaneously. The performances of prototype was evaluated through the investigation of fuel consumption, tillage torque, ratio of soil breaking, and economical efficiency and the results were compared with these of a dry paddy seeder that needs whole tillage. According to the USDA textural classification, the experiment field was composed of sandy loam which consisted of 56.8 of sand, 30.2 of silt and 13.0 % of clay, respectively. Its hardness ranged from 952 to 1,673 kPa depending on the soil depth, and its soil moisture content was 24.9%(d. b.) Fuel consumption of the prototype was 5,015g/hr at 2,000 rpm of engine, which was consequently 64% smaller than that of the conventional dry paddy seeder. For the tillage torque, it ranged from 132 to 206N$.$m depending on the tillage pitch, which was 10∼30% smaller than that of the conventional dry paddy seeder. The ratio of soil braking of the prototype was 87∼98%, whereas that of the conventional dry paddy seeder was 80∼97%. The working performance of the prototype was surveyed to be 3.8hours/ha, which was about 5 times higher than that of the conventional dry paddy seeder. The cost reduction of 26.3% was obtained by using the prototype.