• Korean Journal of Applied Biomechanics
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• v.17 no.2
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• pp.145-156
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• 2007

The purposes of this study were to investigate kinematic parameters of racket head and upper extremities during squash back hand stroke and to provide quantitative data to the players. Five Korean elite male players were used as subjects in this study. To find out the swing motion of the players, the land-markers were attached to the segments of upper limb and 3-D motion analysis was performed. Orientation angles were also computed for angular movement of each segment. The results were as follows. 1) the average time of the back hand swing (downswing + follow-through) was 0.39s (0.24 s + 0.15 s). 2) for each event, the average racket velocity at impact was 11.17m/s and the velocity at the end of swing was 8.03m/s, which was the fastest swing speed after impact. Also, for each phase, 5.10m/s was found in down swing but 7.68m/s was found in follow-through. Racket swing speed was fastest after the impact but the swing speed was reduced in the follow-through phase. 3) in records of average of joints angle, shoulder angle was defined as the relative angle to the body. 1.04rad was found at end of back swing, 1.75rad at impact and it changes to 2.35 rad at the end of swing. Elbow angle was defined as the relative angle of forearm to upper arm. 1.73rad was found at top of backswing, 2.79rad at impact, and the angle was changed to 2.55rad at end of swing. Wrist angle was defined as the relative angle of hand to forearm. 2.48rad was found at top of backswing, 2.86rad at impact, and the angle changes to 1.96rad at end of swing. As a result, if the ball is to fly in the fastest speed, the body has to move in the order of trunk, shoulder, elbow and wrist (from proximal segment to distal segment). Thus, the flexibility of the wrist can be very important factor to increase ball speed as the last action of strong impact. In conclusion, the movement in order of the shoulder, elbow and the wrist decided the racket head speed and the standard deviations were increased as the motion was transferred from proximal to the distal segment due to the personal difference of swing arc. In particular, the use of wrist (snap) may change the output dramatically. Therefore, it was concluded that the flexible wrist movement in squash was very important factor to determine the direction and spin of the ball.

• Applied Microscopy
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• v.41 no.2
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• pp.99-107
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• 2011

Light microscope, and scanning and transmission electron microscopy were used to investigate the fine structure of sperm of the Korea squirrel, Tamias sibiricus. The sperm head of T. sibiricus was paddle in shape. The total length of T. sibiricus sperm was 67.8 ${\mu}m$. The length of sperm head was 7.8 ${\mu}m$, and the tail (60.0 ${\mu}m$) was consisted of four major segments: the neck (1.0 ${\mu}m$), middle (8.0 ${\mu}m$), principal (48.5 ${\mu}m$) and end piece (2.5 ${\mu}m$), respectively. Especially, the length of the middle piece is short, and end piece was very shorter than those of other rodents. The post-nuclear cap was occupied about a fifth of nucleus. The equatorial segment is located between the post-nuclear cap segment and acrosomal cap on the nuclear surface. Nine segmented columns were surrounded by the mitochondria, and numbers of gyres of mitochondria were 26. One segmented column was consisted ten to twelve knobs, and each of segmented column in the neck region connected with the nine outer dense fiber in the middle piece. Numerous satellite-like fibers were scattered around the segmented columns. Nos. 1, 5 and 6 of the outer dense fibers in the middle piece were larger than the others. A fibrous sheath and longitudinal column of the principal piece were in evidence, but the fibrous sheath and longitudinal column was not seen at the end piece. In conclusion, the structural features of sperm head and tail may be useful information to patterns of sperm evolution and classification of species.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.9
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• pp.82-88
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• 1999

The object of this study is to find new evaluation index for in-cylinder flow chracteristics istead of current swirl, tumble coefficient using steady flow test rig on intake port system. To this end, port flow system. To this end, port flow rig test was conducted on DOHC head varying intake valve lift respectively. Finally combination angular coefficient and inclination angle were introduced as new evaluation index for in-cylinder angularflow characteristics instead of swirl and tumble coefficient.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4272-4286
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• 2016

In resource constrained sensor networks, usage of efficient routing protocols can have significant impact on energy dissipation. To save energy, we propose an energy efficient routing protocol. In our approach, which integrates clustering and routing in sensor networks, we perform network coding during data routing in order to achieve additional power savings in the cluster head nodes. Efficacy of the proposed method in terms of the throughput and end-to-end delay is demonstrated through simulation results. Significant network lifetime is also achieved as compared with other techniques.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.6
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• pp.1503-1513
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• 1998

This paper is related to a performance analysis of B-NT system, which is essential compositional equipment of B-ISDN access network. A simulator enabling performance analysis according to the change of network configuration topology and the change of user traffic is developed in this study. The developed B-NT, system simulator consists of graphic user interface module, simulation program automatic generator module, and B-NT system model library module. As examples of the results of performance analysis using the simulator, end-to-end user cell transmission delay time, queueing delay time in each system, and cell loss rate in the head node switch are presented. The simulator developed in this paper can be utilized in determining the network topology of B-NT system.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.616-621
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• 2004

In this paper, the crush characteristics of a tilting train express (TTX) M-car design are evaluated with a head-on collision scenario. Its body shell is divided into three parts - front end, middle section, and rear end. For each part, crush-force relation is evaluated numerically through 3-dimensional shell element analysis with LS-DYNA. TTX's embody structure is a hybrid type structure made of steel and composite materials. Composite sandwich panels are modeled as layered shells whose layers have different material properties. And a damage material model is used to consider the effect of stiffness degradation during deformation. The crush characteristics obtained from these calculations will be used as material modeling data of full-rake collision analyses.

• Journal of Drive and Control
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• v.9 no.3
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• pp.29-36
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• 2012

The hydraulic cylinder is used for actuating the roller-link type rotating floodgate which controls the volume of water in the reservoir. The locating points of hydraulic cylinder are restricted to the limited space and determined to minimize the cylinder force necessary for actuating the floodgate. Generally, the head end point of cylinder is fixed at underground and the rod end point of cylinder is connected to the support link. Therefore there exist three design variables to be determined to minimize the cylinder force within the rotating range of floodgate. First, the mathematical model of the roller-link type rotating floodgate is derived to find the cylinder force corresponding to the floodgate angle. Then, the optimal locating point of hydraulic cylinder is searched using the complex method that is one kind of constrained direct search method.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.5
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• pp.96-103
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• 2001

The quality requirements for thickness accuracy in cold rolling continue to become more stringent, particularly in response to exacting design specification from automotive customers. One of the major impacts from the tighter tolerance level is more unusable product on the head end and tail end of tandem mill coils when the mill is in transition to or from steady state rolling condition. A strip thickness control system for a tandem cold steel rolling mills is composed with blocked non-interacting controller and controllers for strip thickness and tension control of each rolling stands. An intelligent mathematical model included an elastic deformation of strip has been developed and applied to the field in order to predict the rolling force. The simulated results showed that the effect of elastic recovery should be included the model, even if the effect of elastic compression was not important.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2160-2164
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• 2008

Miniature Joule-Thomson cryocoolers have been widely used for rapid cooling of infrared detectors, probes of cryosurgery, thermal cameras, missile homing head and guidance system, due to their special features of simple configuration, compact structure and rapid cool-down characteristics. The cool-down time, the temperature at the cold end, the running time and the gas consumption are the important indicators of the performance of the J-T cryocooler. In this study, the initial cool-down stages of the J-T cryocooler were investigated by numerical simulations. The results show the effects of the initial charging pressures of gas on the cool-down time and the temperature at the cold end and the gas consumptions.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.2 no.1
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• pp.39-49
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• 1996

The techniques of joint mobilization and traction are used to improve joint mobility or to decrease pain by restoring accessory movements to the shoulder joints and thus allowing full, nonrestriced, pain-free range of motion. In the glenohumeral joint, the humeral head would be the convex surface, while the glenoid fossa would be the concave surface. The medial end of the clavicle is concave anterioposteriorly and convex superioinferiorly, the articular surface of the sternum is reciprocally curved. The acromioclavicular joint is a plane synovial joint between a small convex facet on lateral end of the clavicle and a small concave facet on the acromion of the scapula. The relationship between the shape of articulating joint surface and the direction of gliding is defined by the convex-concave rule. If the concave joint surface is moving on a stationary convex surface, gliding occur in the same direction as the rolling motion. If the convex surface is moving on a stationary concave surface, gliding will occur in an opposite direction to rolling. Hypomobile shoulder joint are treated be using a gliding technique.