• Journal of Biosystems Engineering
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• 제33권1호
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• pp.38-44
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• 2008

The freight vehicle is mostly used to transport the fruit. Shock and impact generated by the freight vehicle may give serious damage to fruits hence to reduce the fruits damage, the optimum packaging design during transportation by vehicle is required. In order to design the packaging system for fruit transportation optimally, the comprehension of characteristic for vibration and shock acting on vehicles under various road conditions and loading methods is required. This research was performed to analyze the shock characteristics, acceleration level and power spectral density (PSD) of the fruit transportation vehicles under several travel roads and positions. The vibration signal was measured and analyzed at the transportation vehicle operating on the road of three different surface conditions. The maximum acceleration was measured at the rear-end of the vehicle, and the acceleration in the direction of up-and-down (z-axis) was much greater than those in the directions of back-and-forth (x-axis) or right-and-left (y-axis). The peak acceleration in the direction of up-and-down (z-axis) at the vehicle driving on the expressway, the local road paved with concrete, and unpaved local road were 5.3621 G, 8.232 G, and 14.162 G respectively. PSD at 2.44 Hz showed maximum value at all road conditions. The maximum values of PSD on the expressway, a local road paved with concrete, and unpaved local road were 0.0075222 $G^2/Hz$, 0.058655 $G^2/Hz$, and 0.24598 $G^2/Hz$ respectively. The value of PSD decreased with an increase of the vibration frequency of the transportation vehicle. In most cases, the vibration frequency was below 20 Hz during transportation.

• 한국자동차공학회논문집
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• 제3권6호
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• pp.154-161
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• 1995

There are several kinds of driving conditions according to the characteristic of each vehicle diver. Automaker produces vehicle strong enough to satisfy this several driving conditions at the point of vehicle durability. In order to develop the car in a short period, Automaker engineer tests vehicle at serveral accelerated durability test roads. Before testing the vehicle durability, test engineer must know how much this test road severe than general field road which is composed of high way, city road, paved road and unpaved road. This paper suggests two types of road severity test method that is using relative fatigue life prediction method and using absolute fatigue life prediction method, and also present the merits and demerits of two test methods.

• 한국군사과학기술학회지
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• 제12권3호
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• pp.266-271
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• 2009

Electronic equipments and a missile carried by heavy trucks are often subjected to vibration and shock excitation during their transportation. Electronic equipments are so vulnerable to vibration and shock input that it is necessary to know in advance the vibration level of the truck which cause the damage of equipments. Road tests of a heavy truck carrying a canister on different road conditions such as paved road, unpaved road, and washboard are performed and the effect of road conditions on the vibration characteristics are analyzed. Vibration levels were measured at various locations of the truck along the path through which vibration was transmitted. This study reveals that the velocity of the truck as well as the road surface conditions are main factors which affect the vibration levels of the truck. The power spectrum density of the measured vibration signal and the factors affecting the PSD are also analyzed in this paper.

• 한국환경복원기술학회지
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• 제18권3호
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• pp.13-22
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• 2015

Unpaved forest roads are common accessways in mountain areas being used for forestry purposes. The presence of forest roads produces large volumes of surface runoff and sediment yield due to changes in soil properties and hillslope profile. Rainfall simulation experiments were conducted to estimate the impacts of above-ground vegetation and antecedent soil water condition on hydrology and sediment processes. A total of 9 small plots($1m{\times}0.5m$) were installed to represent different road surface conditions: no-vegetation(3 plots), vegetated surface(3 plots), and cleared vegetation surface(3 plots). Experiments were carried out on dry, wet, and very wet soil moisture conditions for each plot. Above ground parts of vegetation on road surface influenced significantly on surface runoff. Runoff from no-vegetation roads(39.24L) was greater than that from vegetated(25.05L), while cleared-vegetation condition is similar to no-vegetation roads(39.72L). Runoff rate responded in a similar way to runoff volume. Soil erosion was also controlled by land cover, but the magnitude is little than that of surface runoff. Even though slight differences among antecedent soil moisture conditions were found on both runoff and soil erosion, runoff rate and soil losses were increased in very wet condition, followed by wet condition. The experiments suggest that vegetation cover on forest road surface seems most effective way to reduce surface runoff and soil erosion during storm periods.

• 한국자동차공학회논문집
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• 제6권1호
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• pp.73-79
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• 1998

For the design and development of the wheel type excavator, the dynamic effects of travelling on the performance of the equipment should be first analyzed and conside- red in the initial design stage. In order to test the durability of the equipment in a short period, th travelling test should be performed over accelerated durability test tracks. which is more severe than general field roads such as city road, paved road, unpaved road and rough road. In this paper, a parametric study is performed in order to determine important design parameters of durability test track of a wheel type excavator. A rigid body model is developed using DADS and dynamic analysis is performed for the equipment travelling over several test roads with different severity. A comparison of test and analysis results is also presented.

• 한국환경생태학회지
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• 제23권1호
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• pp.41-49
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• 2009

두루미류의 취식무리 크기 및 구성과 도로 유형별, 취식무리 규모에 따른 분포거리 연구를 월동기인 2005년 12월에서 2006년 2월까지 총 8회 실시하였다. 두루미와 재두루미의 취식무리는 주로 $2{\sim}4$개체로 구성된 무리였다. 두루미와 재두루미 모두 혼종무리 보다는 단일종의 취식무리가 많았다. 두루미와 재두루미간 취식무리 크기별 비율은 유의한 차이가 있었다. 두루미의 포장도로(PR)와의 평균거 리는 비포장농로(UPR), 포장농로(PFR), 비포장농로(UPFR) 도로와의 거리에 비하여 멀었다. 재두루미의 경우 도로로부터의 이격거리는 농로로부터의 거리와 차이가 있었다. 두루미와 재두루미 종간 도로유형별 이격거리는 포장도로에서만 유의미한 차이가 있었다. 이 결과는, 두루미류가 차량 출입이 잦은 도로를 차량 출입이 낮은 농로에 비하여 선호하지 않는 것을 보여준다. 포장도로에서 5개체 이상의 두루미 취식무리는 전체 취식무리와 5개체 미만의 취식무리에 비하여 도로로부터 이격거리가 멀었다. 재두루미는 5개체 이상의 취식무리가 5개체 미만의 취식무리에 비하여 포장도로 및 포장농로와 비포장농로에서 이격거리가 멀었으며, 비포장도로에서는 무리크기에 따른 이격거리의 차이가 없었다. 결과적으로, 무리의 크기가 큰 경우 방해요인에 대한 영향이 일부 더 크게 나타났다. 이러한 결과는 두루미류의 큰 취식무리가 주변을 감시하는 효율이 무리크기가 작은 경우보다 높은 것과 관련이 있을 것으로 보인다.

• 농촌계획
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• 제8권2호
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• pp.42-49
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• 2002

Since legislation of Rural Minor Road Improvement Act 1990, a quarter of its total length had been paved now. However, over 80% of arterial road length(national+provincial roads) had been paved, so, road improvement policy should be focussed on the local road(county+rural minor roads) from now. Generally, in the greater part of coastal plain and island areas, arterial road intensity(total road length/total catchment area) is relatively low, but local road intensity is relatively high. So, in terms of balanced development, much more efforts for rural minor road improvement should be concentrated in coastal plain and islands areas. In Chonnam Province, the maximum differentials of minor rural road improvement ratio was over 20%(the lowest; 14.1% in Goheung, the highest; 35.6% in Goksung) in 1999, but the improvement budget have been allocated in proportion to unpaved road length of each county by the provincial government. However, the differentials should not be fairly narrowed in the near future if the present budget allocation policy be maintained. To solve this problem, target differentials of rural minor road improvement between regions should be set up for each planning year and road improvement budget be allocated according to this policy change.

• 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.

• 한국자동차공학회논문집
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• 제10권2호
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• pp.166-173
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• 2002

The wheel bearing hub unit is developed type of wheel bearing unified with the hub parts. It has advantage of reducing the weight and the number of components. And, it also improves uniformity of manufacturing quality, In order to design the wheel bearing hub units, many techniques are used such as load analysis, structure analysis and bearing characteristics analysis and so forth. These techniques need highly accurate load conditions founded on service conditions. In this study, to design the wheel bearing hub units used widespread in passenger cars, the service load was measured through driving tests on the public roads and in the special events. The public roads are classified into highway, intercity road, rural road, urban road, and unpaved road so as to know what the characteristics of the road loads are. The results of the tests showed that the wheel force was relative to the lateral acceleration, and also could be calculated from the lateral acceleration. The lateral acceleration was measured from 0.0G to 0.6G in general driving on the public roads, with different distributions in each road type. In special events, the maximum lateral acceleration was measured from 0.8G to 1.3G.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
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• pp.517-518
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• 2007

A method to recognize unpaved road region using a 3D depth measurement system is proposed for mobile robots. For autonomous maneuvering of mobile robots, recognition of obstacles or recognition of road region is the essential task. In this paper, the 3D depth measurement system which is composed of a rotating mirror, a line laser and mono-camera is employed to detect depth, where the laser light is reflected by the mirror and projected to the scene objects whose locations are to be determined. The obtained depth information is converted into an image. Such depth images of the road region represent even and plane while that of off-road region is irregular or textured. Therefore, the problem falls into a texture identification problem. Road region is detected employing a simple spatial differentiation technique to detect the plain textured area. Identification results of the diverse situation of Nonlinear trail are included in this paper.