• Proceedings of the KSR Conference
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• 2002.10a
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• pp.54-59
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• 2002

In general, the aluminum extrusions are used to the light construction of the high speed rail vehicle structures. However, the research works ok the crashworthy design of the high speed rail vehicle structures are not published sufficiently because the crash test of high speed rail vehicle structures costs high and is complicated. So, a method that can predict crash characteristics of a large size structure like a high speed tail vehicle should be suggested. In this study, the scale model studies are performed to predict the impact energy absorption characteristics of full scale model. In the first place, we verified the theory of scale law using FE-simulation from the crashworthiness point of view. Secondly, we performed the crush test using scale model, made of aluminum sub structure. As a result, we could predict the crash characteristics using scale model by 10∼20% error.

• International Journal of Automotive Technology
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• v.4 no.3
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• pp.141-147
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• 2003

For improving high-safety, convenience, and ride comfort, the automotive design suffers from radical increase of the weight, the recycling-related rules, regulations on the waste gas, and environmental protection of the resources. Among them, it is well known that the weight increase is the most critical. Thus, in order to minimize the weight of the body-in-white that takes up 20-30% of the whole weight of the automobile, most automotive manufacturers have attempted to develop the aluminum intensive body-in-white using aluminum space frames. In this research, the crush test and simulation for aluminum extrusions are performed to evaluate the collapse characteristics of that light weighted material. Also. the same test and simulation was done for aluminum extrusions filled with structural foam. Then, these results are analyzed and compared. From these studies, the effectiveness of structural foam is evaluated in improving automotive crashworthiness. Finally, the design strategy and guideline of the structural form are suggested in order to improve the crashworthiness for aluminum space frame in the vehicle.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.2
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• pp.49-56
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• 2009

In this study, a side collision accident reconstruction using database based on the deformed shape information from the collision test using model cars is suggested. A deformation index and angle index related to the deformed shape is developed to set the database for the collision accident reconstruction algorithm. Two small size RC cars are developed to carry out the side collision test. Several side collision tests according to the velocity and collision angles are performed for establishing the side collision database. A high speed camera with 1000fps is used to capture the motion of the car. A side collision accident reconstruction algorithm is developed and applied to find the collision conditions before the accident occurs. Two collision cases are tested to validate the database and the algorithm. The results obtained by the reconstruction algorithm show good match with original conditions with regard to the velocity and angle.

• Journal of the Korean Geosynthetics Society
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• v.10 no.4
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• pp.123-130
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• 2011

In the precedent study it was presented that the comparison of thermal resistivity using various backfill materials including river sand regarding water content, dry unit weight and particle size distribution. Based on the precedent study, this study focused on developing the optimized backfill material that would improve the power transfer capability and minimize the thermal runaway due to an increase of power transmission capacity of underground power cables. When raw materials, such as river sand, recycled sand, crush rock and stone powder, are used for a backfill material, they has not efficient thermal resistivity around underground power cables. Thus, laboratory tests are performed by mixing Fly-ash, slag and floc with them, and then it is found that the optimized backfill material are required proper water content and maximum density. Through various experimental test, when coarse material, crush rock, is mixed with recycled sand, stone powder, slag or floc for a dense material, the thermal resistivity of it has $50^{\circ}C$-cm/Watt at optimum moisture content, and the increase of thermal resistivity does not happen in dry condition. The result of experiments approach the optimization of the backfill materials for underground power cables.

• Journal of the Korean Society of Physical Medicine
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• v.15 no.1
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• pp.43-54
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• 2020

PURPOSE: This study examined the effects of mild-intensity exercise (MIE) and high-intensity interval exercise (HIIE) on the recovery of the motor function over time in sciatic nerve crush injury rats. METHODS: The MIE group ran on a treadmill at a speed of 8.3 m/min to perform low-intensity training with maximum oxygen uptakes ranging from 40 to 50%. The HIIE group ran on the treadmill at a speed of 25 m/min to perform high-intensity training with a maximum oxygen uptake of 80%. The interval training was performed based on a 1:1 work-to-rest ratio. The effects of each form of exercise on the rats' walking abilities following their recovery from the peripheral nerve injuries were evaluated based on the results of behavior tests performed at one and 14 days. RESULTS: According to the test results, the MIE group showed significant improvements in the rats' ankle angle in the initial stance phase, and in the ankle and knee angles in the toe-off phase (p<.05). The HIIE group exhibited significant improvements in the ankle and knee angles in the initial stance phase, SFI(p<.05). CONCLUSION: The state of such patients can be improved by applying the results of this study in that MIE and HIIE on a treadmill can contribute to the recovery of the peripheral nerve and motor skill. In particular, MIE is used as a walking functional training in the toe-off stance phase, while HIIE is suitable in the initial stance stage.

• International Journal of Highway Engineering
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• v.6 no.4 s.22
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• pp.101-108
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• 2004

Asphalt overlay method is a general method to extend the of life old concrete pavements. However, reflection cracks are the typical problem of the AC overlay on distressed concrete pavement. Joint sealing, stress absorbtion layer have been used to prevent reflection cracks however partial success of to delay the timing of reflection cracking was recognized. Reflection crack problem can be eliminated by using rubblization method, which crush concrete pavement slab into piece of aggregate size that can be used base material. Previous research on rubblization method indicated that the size of rubblized PCC ranged 40-70mm at upper layer, and more than 100mm at lower layer. In this study, the adequate depth of rubblized PCC that ran prevent reflection cracking of AC overlay is estimated base on the simulation test of reflection cracking with 0, 10, 20cm rubblized PCC base.

• Journal of Korean Society of Transportation
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• v.18 no.4
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• pp.107-115
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• 2000

We suggest a method which solves the planar, two vehicle collision reconstruction problem. The method based on the Principle of impulse and momentum determines the pre-impact velocity components from Post-impact velocity components, vehicle Physical data and collision geometry. A novel feature is that although the impact coefficients such as the restitution coefficient and the impulse ratio are unknown, the method can estimate automatically the coefficients and calculate the pre-impact velocity components. This reverse calculation is important for vehicle accident reconstruction, since the pre-impact velocities are unknown and Post-impact Phase is the starting Point in a usual collision analysis. However. an inverse solution is not always Possible with the analytical rigid-body impact model. Mathematically, one does not exist under the common velocity condition. On the other hand, our method has a capability of reverse calculation under the condition if the absorbed energy during the collision process can be estimated using the crush profile. To validate the developed collision reconstruction a1gorithm, we use car-to-car collision test results. The analysis and experimental results agree well in the impact coefficients and the Pre-impact velocity components.

• Journal of the Korean Society of Propulsion Engineers
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• v.1 no.2
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• pp.91-102
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• 1997

In order to evaluate the effects of aging on the ignition performance, pyrotechnic igniters were separated from twelve-year-old, fifteen-year-old, and sixteen-year-old live rocket motors. The characteristic values of the ignition material were measured, and the firing tests of the igniters were performed. The moisture content, the outer dimension, the crush strength, the thermal decomposition characteristics, and the heat of formation the B/$KNO_3$ ignition pellet were measured. The crush strength was increased and the heat of formation was reduced as aged, but no change was detected for other characteristic values. The burning test results of the igniter pellet in the closed bomb and the inert motor showed that the burning rate of the ignition pellet was increased by 10%, and the integration of pressure $P_t$ of the p-t curve was reduced by 15% for aged samples. It was inferred that the burning rate was increased as the crack was appeared in the pellet and $P_t$ could be proportionally decreased with the heat of explosion.

• Asian-Australasian Journal of Animal Sciences
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• v.32 no.5
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• pp.734-741
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• 2019

Objective: The objective of the study was to determine the relationship between plasma and salivary cortisol concentrations in beef cattle that were subjected to handling prior to sampling. Methods: Twenty-one Nguni cows of three age categories; 5 to 7 yr (n = 7), 8 to 10 yr (n = 6), and 11 to 13 yr (n = 8) were handled for five consecutive weeks. In the pen, a human avoidance test was performed and cattle responses to restraint in the chute and crush were observed. In addition, rectal temperature readings were taken and, faecal samples were collected and analysed for glucocorticoid metabolites. Through the handling and restraint process, excretory and vocalisation behaviour, as a sign of stress were observed and recorded. Thereafter, six cows were randomly selected and subjected to an adrenocorticotropic hormone (ACTH) challenge. Blood and saliva samples were extracted to determine cortisol concentrations. Results: Repeated handling affected (p<0.05) faecal glucocorticoid metabolites, rectal temperatures, avoidance distance, crush scores as well as urination and defaecation behaviour. Acclimation to handling was variable based on each respective parameter. Saliva cortisol concentrations increased and decreased significantly (p<0.001). A peak value of $136.78{\pm}15.869nmol/L$ was observed 30min after administration of ACTH, from a baseline value of $8.75{\pm}15.869nmol/L$. Plasma cortisol concentrations did not differ (p>0.05) across the time of sampling. A low and insignificant correlation (r = 0.0131, p>0.05) between plasma and saliva cortisol was therefore observed. Conclusion: We conclude that if beef cows are subjected to handling prior to sampling, a weak relationship exists between plasma and salivary cortisol levels.

• Steel and Composite Structures
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• v.49 no.4
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• pp.393-405
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• 2023

In this paper, the energy absorption capability of a novel cruciform composite lattice structure was evaluated through the simulation of compression tests. For this purpose, several test samples of Polylactic acid cellular reinforced with continuous glass fibers were prepared for compression testing using the additive manufacturing method of material extrusion. Using a conventional path design for material extrusion, multiple debonding is probable to be occurred at the joint regions of adjacent cells. Therefore, an innovative printing path design was proposed for the cruciform lattice structure. Afterwards, quasistatic compression tests were performed to evaluate the energy absorption behaviour of this structure. A finite element model based on local material property degradation was then developed to verify the experimental test and extend the virtual test method. Accordingly, different combinations of unit cells' dimensions using the design of the experiment were numerically proposed to obtain the optimal configuration in terms of the total absorbed energy. Having brilliant energy absorption properties, the studied cruciform lattice with its optimized unit cell dimensions can be used as an energy absorber in crashworthiness applications. Finally, a cellular structure will be suitable with optimal behavior in crush load efficiency and high energy absorption.