• Journal of Advanced Research in Ocean Engineering
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• 제3권2호
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• pp.83-101
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• 2017

In this study, the added resistances of the large container ship in head and oblique seas are evaluated using a time-domain Rankine panel method. The mean forces and moments are computed by the near-field method, namely, the integration of the second-order pressure directly on the ship surface. Furthermore, a weakly nonlinear approach in which the nonlinear restoring and Froude-Krylov forces on the exact wetted surface of a ship are included in order to examine the effects of amplitudes of waves on ship motions and added resistances. The computation results for various advance speeds and heading angles are validated by comparing with the experimental data, and the validation shows reasonable consistency. Nevertheless, there exist discrepancies between the numerical and experimental results, especially for a shorter wave length, a higher advance speed, and stern quartering seas. Therefore, the accuracies of the linear and weakly nonlinear methods in the evaluation of the mean drift forces and moments are also discussed considering the characteristics of the hull such as the small incline angle of the non-wall-sided stern and the fine geometry around the high-nose bulbous bow.

• 한국정밀공학회지
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• 제20권12호
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• pp.25-33
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• 2003

A burr has been defined as undesirable projection of material formed as a result of plastic flow from a cutting or shearing operation. It is unavoidable in all kinds of machining operation. As a result, burr makes troubles on manufacturing process due to deburring cost, quality of products and productivity. In this study, the primary interest is about exit burr. The burr formation mechanism in each type of burr is classified. Data bases are developed to predict burr formation result. In the milling operation, we develop an algorithm to analyze the burr formation mechanism by the geometrical analysis on the multi featured workpiece with multi cutting path. The algorithm includes three steps, i. e., the feature identification, the cutting condition identification, and the analysis on exit burr formation. We can predict which portion of workpiece would have the exit burr in advance so that we can manage to find a way to minimize the exit burr formation in an actual cutting. Also, this algorithm can be implemented in a commercial CAM package so that we can simulate the NC code to review the burr formation in advance.

• 한국안전학회지
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• 제33권5호
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• pp.120-126
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• 2018

The traffic accident types are largely classified into vehicle to vehicle accident, vehicle-to-person accident and single-vehicle. Especially, the single-vehicle accident types are severe when the vehicle crashed into road facilities such as bridge, piers, utility poles. The severity of single-vehicle accidents are ten times higher than that of all other accidents types. It is needed to consider to reduce accident severity. This study was conducted to develop crash worthy safety design facility to ensure the vehicle occupant safety. The simulation and the crash tests were conducted for assessment of the safety performance to check the criteria of CC2(Crash Cushion 2) level. THIV(Theoretical Head Impact Velocity) and PHD(Post-impact Head Deceleration) were used to assess occupant impact severity for crashes. The non-redirection collision test conditions for 900 kg and 1,300 kg-head on crash tests, 900 kg-1/4 offset crash tests, 1,300 kg-head on crash test with $15^{\circ}$angle were conducted. The simulation and experiment test result showed that THIV values were below 44 km/h criterion, PHD values were below the 20G. The development non-redirective crash cushion is expected to be used for the fixed object such as bridge piers for assuring occupant safety.

• 한국운동역학회지
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• 제14권1호
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• pp.145-160
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• 2004

The purposes of this study to provide quantitative data in necessary to advance techniques kinematic analysis of Cucarachas which is an action of Rumba. Then, this study is performed on 5 female players who have won within the third prize at a national athletic meeting. When whole foot reached to floor, Displacement of right-left hip joint (until $E1{\sim}E3$ average moved 15.15cm)is found at right-left direction since the hip joint is turned to right back. On the other side, large displacement is shown because Rumba Cucaracha Movement is expressed by maximum shift of hip joint to right and left direction. Displacement of right hip joint(E3$57.40{\pm}7.46$) is found in front and in rear direction since hip joint is moved in rear and in front to turn the hip joint. It may be stated that this is ideal displacement expressed by movement of whole body with artistic poise and presentation because role of hip joint is very important in technical and artistic side. Angle of right shoulder joint E2($105.44{\pm}9.64$) is got wider. It may be stated that player shifts up and abduct elbow joint to right since center of gravity of player is exceedingly shifted to right in this motion of Cucarachas. On the other hand, since this motion is abducted right elbow and shrunk external abdominal oblique to him center of body to left front of hip joint, the angle becomes narrow. It is shown that angle of knee in right knee joint E4($75.44{\pm}2.61$) is large since right leg and hip joint is turned by foot using reaction of ground and so center of body is shifted to left. Large angle of ankle E4($134.40{\pm}10.50$) in Cucaracha Movement is shown by the action of twist force using narrow part of foot and compression force against ground with adduction speed of arm. The various kinematic analyses associated with motions of dance sport have not been sufficiently peformed so far, and thus a number of research projects for dance sport should be proposed and performed to be continuous.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.1816-1819
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• 2003

As a result of milling operation, we expect to have burr at the outward edge of workpiece. Also, it causes undesirable problems such as deburring cost, low quality of machined surface, and bottleneck in manufacturing process. Though it is impossible to totally remove burr in machining, it is necessary to plan a machining process that minimizes the occurrence of burr. In this paper, a scheme is proposed which identifies the tool path of the milling operation with minimum burr. In the previous research, a Burr Expert System was developed where the feature identification, the cutting condition identification, and the analysis on exit burr formation are the key steps in the program. The Burr Expert System predicts which portion of workpiece would have the exit burr in advance so that we can calculate the burr length of each milling operation. Here, the critical angle determines whether the burr analyzed is an exit burr or not. So the burr minimization scheme becomes to minimize the burr with critical angle. By iterating all the possible tool paths in certain milling operation, we can identify the tool path with minimum burr.

• Nuclear Engineering and Technology
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• 제31권4호
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• pp.423-431
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• 1999

A radiotracer technique has been developed to monitor the rotational movement of two piston rings in one cylinder during engine operation. The rings were labeled with two different kinds of radioisotopes, i.e. $^{60}$ Co and $^{192}$ Ir, for identification of the top ring from the second ring. The radiotracers were implanted in a small hole bored on the inner side of each piston ring. The rings were installed in a single cylinder hydrogen engine and three Nal scintillation detectors were mounted around the engine block to measure the gamma radiation. The angle of ring-gap orientation was determined from the radiation counts measured with the three detectors during engine operation. Two windows (upper window for $^{60}$ Co and lower window for $^{192}$ Ir) were set on each ratemeter to count radiation from the two isotopes separately. Procedure to convert the radiation counts to the position of the ring gap was established. With the software programmed with MS-Visualbasic, radiation counts were compared with the reference responses that were measured at angular intervals of 10$^{\circ}$for each piston ring in advance of the experiment. The result was used for the evaluation of the relationship between the orientation of ring-gaps and oil consumption. It was found that an increase in the oil consumption rate of a specific operation condition was closely related to the relative phase angle of the two piston rings.

• 대한조선학회논문집
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• 제57권4호
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• pp.230-240
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• 2020

The aim of this study was to investigate the manoeuvrability of a ship in different Center of Gravity (CG) conditions. Free Running Model Tests (FRMT), such as 35°turning circle tests, 20/20 zigzag manoeuvring tests, and 10/10 zigzag manoeuvring tests, were conducted in three GM and three trim conditions with 1/65.83 scaled KRISO Container Ship (KCS). The test results indicated that KCS in the lower GM condition and the trim by bow condition showed reduced advance and tactical diameter in turning circle tests and increased overshoot angles in zigzag tests, and those manoeuvring indices were strongly related with roll angle. In addition, sensitivity indices for three-axis CG position were suggested with prior research, and it showed that y-axis CG position significantly affected manoeuvrability of KCS due to the low GM. Therefore, in the case of KCS, it is evident that the roll angle during manoeuvre is closely related with manoeuvring indices.

• International journal of advanced smart convergence
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• 제11권4호
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• pp.129-140
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• 2022

The purpose of this study to improve the shoulder wheel that is used frequently during shoulder circumduction exercise in a park, to link the shoulder wheel to a game application comprising various shoulder circumduction exercise and shoulder ROM exercise, and to enjoy the game during the exercises. A step motor was added to the shoulder wheel, and the rotating speed and rotating angle, and rotating direction can be controlled. The shoulder height, different for different people, can be controlled as well, so that any user can use this device. The developed application content includes the game elements, to enjoy the repetitive and boring exercise with fun and interest, and the control to adjust the degree of difficulty. This was to help users heighten their desire to rehabilitate by inducing active participation during repetitive shoulder rehabilitation exercise because the game vests users with intrinsic motivation and immersion. If the shoulder wheel and application contents proposed in this study are used, shoulder diseases can be prevented in advance by performing muscle strengthening exercises required in an aging society. This study is expected to contribute to the field of research related to serious games and rehabilitation.

• 수산해양교육연구
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• 제21권1호
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• pp.52-58
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• 2009

항행중에 두 선박이 접근하여 충돌의 위험이 있을 경우 안전한계접근거리 즉 피항을 시작해야할 시점에 대해서 실선시험을 통한 자료에 근거를 하여 조종성지수를 산출하고 안전한계접근거리를 계산하여 제공함으로써 항행중에 선박의 조선자들이 상대선박과 피항동작을 취해야 할 경우에 경험이나 감각에만 의존함으로써 생기는 착오를 방지하고자 하였다. 앞의 논의 과정을 요약하면 다음과 같다. 1. 조우각도가 같을 경우에도 타각을 10도사용하면 타각을 30도 사용할 때보다도 안전한계접근거리는 최소 1.3배에서 최대 1.8배정도 더 증가하므로 해상상태, 자선의 적하상태를 고려해서 대타각의 전타가 어려울 경우 특히 피항개시 시점을 충분히 주의해야한다. 2. 선박의 크기에 상관없이 조우각도가 90도 부근에서 충돌의 위험이 가장 커서 안전한계접근거리는 소형선(300톤급)에서는 자선 길이의 5.0배에서, 대형선(100,000톤급)에서는 10.7배로서 대형선일수록 피항개시 시기를 놓치지 않도록 해야 한다. 3. 조우각도가 적을 경우가 클 경우보다도 안전한계접근거리가 훨씬 크게 나타났고 대형선에서 더욱 두드러지게 나타났다.

• 한국가정과교육학회지
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• 제12권2호
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• pp.81-93
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• 2000

This study is designed to identify the current condition of male students ostracized as the black ship (Wangtta in Korean) in middle schools and the effects of the Guardian Angle program on the decrease in Wangtta. 428 frist graders of two junior high schools were devided into two groups, a test group (n=195) and a control group (n=233). SPSS/PC+ program was used for analysis of the data, including frequency analysis, ANOVA and x(sup)2-test. The outcome of research can be summed up as the following 74.7% of the subjects thinks that there is Wangtta going on in there classes. Wangtta often comes to pass during the recesses (74.2%) and lunch times (51.6%). Those who are easily exposed to Wangtta are most likely to be both snobbish and pedantic. Those who lead Wangtta turn out to be good at fighting (56.4%) and dominant in the hegemony of the class depending on the way of ignoring or not playing with the victims(69.3%) In the case of bearing witness to Wangtta. 36.9% of the subjects try to overlook the case. Now let me take a look at the effect of the guardian angle program on the decrease in Wangtta. The program has a significant effect on the decrease (p<0.05) in the number and the phenomena of Wangtta perceived by students in both advance and post tests. The program makes a significant difference in the aspects of students’ behavior in relation to Wangtta in a desirable way (p<.01) Though the sociality index of the victims doesn’t show any significant difference statistically, it exerts a generally positive effect.