• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.2
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• pp.111-117
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• 2013

In this paper, we have proposed novel technique to improve maintainability for training vehicle of underwater weapon system. In case of under water weapon, the fire procedure is related with operation of expulsion system in submarines. So the submarine crews should practice the complex fire procedure of weapon system by using training vehicle, which is safer and cheaper than operational weapon. After emitted from submarine, the training vehicle rise to the surface and should be withdrawn from the sea. The recovered training vehicle is transported to maintenance depot and pass through the recycling procedure including disassembling the vehicle, data acquisition & analysis, battery charge, replacing expandable components, testing the captive equipment, and assembling the vehicle. The disassembling & assembling of training vehicle which is composed of watertight section or airframe, is time-consuming work. So in this paper, we have studied the elements of recycling procedure and propose the method to exclude the assembling & disassembling work for maintainability improvement.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.1
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• pp.482-494
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• 2019

In this paper, the oblique water-entry impact of a vehicle with a disk cavitator is studied experimentally and numerically. The effectiveness and accuracy of the numerical simulation are verified quantitatively by the experiments in this paper and the data available in the literature. Then, the numerical model is used to simulate the hydrodynamic characteristics and flow patterns of the vehicle under different entry conditions, and the axial force is found to be an important parameter. The influences of entry angle, entry speed and cavitator area on the axial force are studied. The variation law of the force coefficient and the dimensionless penetration distance at the peak of the axial force are revealed. The research conclusions are beneficial to engineering calculations on the impact force of a vehicle with a disk cavitator over a wide range of water-entry parameters.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.131-136
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• 2017

High speed under water vehicle by using solid rocket motor, which is a natural cavitation type, was tested. The vehicle's speed and running distance was measured, and pressure sensors installed on the surface of the vehicle show pressure-time history of pressures according to the development of the supercavitation. Underwater cameras installed on the wall of the test pool recorded whole processes from the onset of the supercavitation to fully developed one. CNU-SuperCT based on 2-dimensional inviscid theoretical analysis was used to simulate the test result. In consideration of CNU-SuperCT does not include the control fins of the vehicle, simulation results agree with test results very well. Also, pictures from underwater cameras support the test results.

• Journal of Biosystems Engineering
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• v.38 no.4
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• pp.240-247
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• 2013

Purpose: This study was conducted to develop a rubber-crawler type vehicle as a traveling device for harvesting water-dropwort cultivated in water contained paddy rice field in winter season. Methods: A commercial rubber-crawler type vehicle was used to investigate application of rubber crawler to the paddy rice field as preliminary test. As the result of the preliminary test, a both prototype traveling device with rubber crawlers for a water-dropwort harvest was designed with inclination of $45^{\circ}$ at the front-end and rear-end of crawler under the basic water depth of 0.6 m in the paddy rice field. The device was fabricated and attached to the experimental harvesting test devices on the front of the prototype vehicle. The size of the prototype crawler vehicle with a harvesting part is $2,800{\times}1,460{\times}1,040 $ (mm) ($L{\times}W{\times}H$) with weight of 9.21 kN (maximum). Sizes of the crawler of prototype vehicle are ground contact length of 900 mm, width of 180 mm, height of 1,070 mm and distance between center to center of crawlers of 720 mm. The side-overturn angle of the prototype was $26.4^{\circ}$. Results: Driving performance of the prototype vehicle in water contained paddy field were good at both forward and reverse (backward) directions as weights were applied. The drawbar pull and the maximum sinking depth of the prototype vehicle were 3.5 kN and 0.13 m respectively at water depth of 0.5 m, when the weight and bearing capacity of the prototype rubber crawler in the paddy field were 8.51 kN and 26.3 $kN/m^2$, respectively. Conclusions: Results of the driving test performance of the prototype crawler in paddy rice field at the water depth of 0.5 m were satisfactory. The prototype had enough drawbar pull and driving ability in the deep water contained paddy field.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.6
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• pp.547-552
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• 2010

In this study, we suggested an integrated humidification system for a fuel cell electric vehicle (FCEV) as an efficient method of humidification under the various driving condition of the fuel cell vehicle and system. It is improving air humidification system combined the existing membrane humidifier and water injection. As a result, we verified it through experiments and the vehicle test and could get a result of improvement of humidification performance. The results show that an integrated humidification system is a useful method for FCEV applications.

• Journal of the Society of Naval Architects of Korea
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• v.58 no.4
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• pp.253-261
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• 2021

This paper describes the process of evaluating maneuverability in still water of an unmanned surface vehicle based on data measured by performing sea trials. First, we set up a test scenario that is easy to analyze the maneuverability of the unmanned surface vehicle and to identify and verify the dynamics model. Since the attitude of hull varies according to the speed of the unmanned surface vehicle which has a planing hull shape, the relationship between waterjet RPM, speed and attitude is analyzed by performing straight forward tests at various speeds. The turning tests of the unmanned surface vehicle in which the waterjet angle rotates while turning are performed by changing the waterjet rotation angle under the condition of two representative speeds to analyze turning ability. The turning ability of the unmanned surface vehicle includes speed reduction, yaw rate, heel, and turing diameter at steady turning phase according to the speed and RPM.

• Journal of the Korean Electrochemical Society
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• v.15 no.2
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• pp.74-82
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• 2012

Proton exchange membrane fuel cell performance is changed by the complicated physical phenomenon. In this study, water discharge performance of proton exchange membrane fuel cell were performed numerically to compare serpentine channel flow fields of 5-pass 4-turn serpentine and 25 $cm^2$ reaction surface between with and without sub-channel at the rib. Through the supplement of sub channel flow field, it is shown from the results that water removal characteristic inside channel improves because the flow direction of under-rib convection is changed into the sub channel. Reacting gases supplied from entrance disperse into sub channel flow field and electrochemical reaction occurs uniformly over the reaction surface. The results obtained that total current density distributions become uniform because residence time of reacting gases traveling to sub-channel flow field is longer than to main channel.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.2
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• pp.123-134
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• 2012

A typical cooling system of an engine relies on a water pump that circulates the coolant through the system. The pump is typically driven by the crankshaft through a mechanical link with engine starting. In order to reduce the friction and warm-up time of an engine, the clutch-type water pump (CWP) was applied in 2.0 liter diesel vehicle. The clutch-type water pump can force cooling water to supply into an engine by the operation of an electromagnetic clutch equipped as the inner part of pump system. The onset of CWP is decided by temperature of cooling water and engine oil. And, the control logic for an optimal operation of the clutch-type water pump was developed and applied in engine and vehicle tests. In this study, the warm-up time was measured with the conventional water pump and clutch-type water pump in engine tests. And the emission and the fuel consumption were evaluated under NEDC mode in vehicle tests. Also, tests were carried out for the various temperature conditions starting the operation of CWP. From the results of the study, the application of CWP can improve the fuel consumption and $CO_2$ reduction by about 3%.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.12
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• pp.961-967
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• 2009

A 3-dimensional numerical investigation of a WIG effect vehicle with DUP (direct underside pressurization) is performed to predict aerodynamic characteristics and the static height stability. DUP can considerably reduce take-off speed and minimize the hump drag while the vehicle accelerates on the water to take off. The DUP of the model vehicle, Aircat, consists of a propeller in the middle of the fuselage and an air chamber under the fuselage. The air accelerated by the propeller comes into the camber through the channel in the middle of fuselage and augments lift by changing its dynamic pressure to static pressure dramatically. However, the air accelerated by a propeller produces excessive drag and reduces static height stability.

• Journal of Environmental Health Sciences
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• v.35 no.5
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• pp.417-425
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• 2009

The purpose of this study was to investigate the whitening effect of Angelicae dahuricae Radix water extract (ADWE) by its application on artificial tanning spots which were induced by 1,500 $mJ/cm^2$ of UVB radiation on the backs of brown guinea pigs weighing approximately 450~500 g. Thirty ${\mu}l$ of ADWE, at each application, were applied twice a day, 5 days a week, for 8 weeks to the guinea pigs. The artificial tanning spots were divided into 3 groups which were vehicle control group [propylene glycol: ethanol: water (5:3:2)], positive control group (2% hydroquinone) and experimental group (2% ADWE). The visible whitening effect and changes in melanin index were evaluated once a week. On completion of the experiment, the animals were sacrificed under anesthetization, and the artificial tanning spots were excised by biopsy punch and stained with Hematoxylin and Eosin (H&E) to observe histological change and also stained with Fontana-Masson's silver (F-M) and S-100 to observe melanin pigmentation and melanocytes. In the gross observation, the experimental group showed higher pigmentation than the positive control group but lower pigmentation than the vehicle control group. Histological observation confirmed that ADWE had a positive whitening effect by showing a lower distribution of melanin and melanocytes in the epidermis of experimental group than in the vehicle control group.