• 한국운동역학회지
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• 제23권4호
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• pp.295-306
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• 2013

The purpose of this study was to provide high school male shot putters training methods of gliding and delivery motion through comparative analysis of kinematic characteristics. To accomplish this purpose, three dimensional motion analysis was performed for the subjects(PKC, KKH, YDL) who participated in high school male shot putter competition on 92nd (2011), 93rd (2013) National Sports Festival. The subjects were filmed by four Sony HXR-MC2000 video cameras with 60 fields/s. The three-dimensional kinematic data of the glide, conversion and delivery phase were obtained by Kwon3d 3.1 version. The data of the shoulder rotational angles and projection angles were calculated with Matlab R2009a. The following conclusions had been made. With the analysis of the gliding and stance length ratio, the gliding length was shorter at the TG than the SG with short-long technique but the gliding and stance length ratio was 46.8:53.2% respectively. The deviation of the shots trajectory from APSS(Athlete-plus-shot-system) revealed that the PKC showed similar to "n-a-b-c-I" of skilled S-shape type, KKH and YDL showed "n-a-d-f-I'" of unskilled type. Furthermore, they showed smaller radial distance from the central axis of the APSS and the shots were away from the linear trajectory. From this characteristics, The PKC who performed more TG than SG had shorter glide with S-shape of APSS(skilled type) showed the better record than others with technical skill. But KKH and YDL had bigger glide ratio with "n-a-d-f-I'" of unskilled type and improved their records with technical factor. The projection factor had an effect on the record directly. Because PKC maintained more lower glide and transition posture with momentum transfer through COG's rapid horizontal velocity respectively the subject possessed the characteristics of high horizontal and vertical velocity with large turning radius from shot putter to APSS.

• 한국해양학회지
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• 제8권2호
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• pp.68-74
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• 1973

The present paper concerns the age determination and growth of butter fish, Pampus argenteus from the southwestern waters of Korea by otolith reading. 743 specimens taken by stow-net in the southern part of the Yellow Sea and northeastern part of the East China Sea during the period from October 1972 to September 1973 were examined. Results of the study are summarized as follows: 1. Sex ratio of females to males was found to be 2:1. 2. Ring marks on the otolith were found to be formed twice a year, once during the period of January-May and the other time in September. 3. The Lee's phenomenon was observed on the otolith sample. 4. The relationship between the radius of otolith(R) and fork length(L) was found to be as follows: R=0.3069+0.0133L 5. Calculated fork length at the time of otolith ring formation are found to be as follows:I-ring,71.67mm; II-ring, 125.05mm; III-ring, 168.65mm; IV-ring, 201.74mm; V-ring, 225.80mm; VI-ring, 240.84mm. 6. Maximum fork length calculated according to the diagram of Walford's growth transformation was found to be 281.5mm. 7. Growth curve, when related to the von Bertalanffy's equation, was laid out as $L_{t}=281.5[1-e$^{-0.674(t-0.128)}]$

• Advances in nano research
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• 제8권4호
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• pp.307-322
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• 2020

In this article, free vibration of double-walled carbon nanotubes (DWNT) based on nonlocal Kelvin's model have been investigated. For this purpose, a nonlocal Kelvin's model is established to observe the small scale effect. The wave propagation is employed to frame the governing equations as eigenvalue system. The influence of nonlocal parameter subjected to different end supports has been overtly examined. The new set of inner and outer tubes radii investigated in detail against aspect ratio. The influence of boundary conditions via nonlocal parameter is shown graphically. Due to small scale effect fundamental frequency ratio decreases as length to diameter ratio increases. Small scale effect becomes negligible on all end supports for the higher values of aspect ratio. With the smaller inner tube radius double-walled CNT behaves more sensitive towards nonlocal parameter. The results generated furnish the evidence regarding applicability of nonlocal model and also verified by earlier published literature.

• 동력기계공학회지
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• 제13권1호
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• pp.19-25
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• 2009

This paper is a study on the link composition design of a double link type level luffing jib crane using path generation synthesis passing through three precision points according to parameters, the length of backstay, the ratio of fly jib length between two moving hinges to the total length of fly jib, the location of a intermediate passing point etc. when the maximum and minimum working radius of the crane are given. The performance of the crane depends on the deviation of the luffing trajectory at fly jib tip. The luffing trajectories according to the above parameters are analyzed and shown in graphs by the developed computer program. In a real-life design, some trials are needed to arrive at a proper link composition design. Therefore, it is expected that the present computer program can rapidly and exactly deal with a link composition design proper to the design criteria of the crane.

• 대한기계학회논문집A
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• 제20권3호
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• pp.968-977
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• 1996

The linear/nonlinear vibration response of the rotating hybrid cylindrical shell with simply supported boundary condition is studied. The Ritz-Galerkin method is applied to obtain the nonlinear frequency equation, which excludes in-plane and rotatory inertia but includes bending stretching coupling terms. The bifurcation phenomena for the linear frequency and the frequency ratio(nonlinear/linear frequency ratio) are presented. The hybrid cylindrical shells are composed of composite(GFRP, CFRP) metal(aluminium, steel) with symmetric and antisymmetric stacking sequence. The effects of the Coriolis and centrifugal force are considered The results also present the effects of length-to- radies ratio, radius-to-thickness ratio, the circumferential wave number, the stacking sequence, the material property, the initial excitation amplitude and the rotating speed. The present linear frequency results are compared with those of the available literature.

• 한국구조물진단유지관리공학회 논문집
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• 제10권1호
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• pp.205-215
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• 2006

본 연구는 3차원 쉘요소를 이용한 유한요소해석을 통해 다이아프램으로 보강된 곡선 강박스거더교의 거동을 분석하였다. 매개변수연구를 통해 기존의 제안식과 비교함으로써 모델링의 타당성을 검증하였고, 뒤틀림 응력에 크게 영향을 미치는 인자는 중심내각, 지간길이, 다이아프램간격임을 확인하였다. 또한, 다이아프램의 간격, 개구율, 형상을 변수로 하여 해석한 결과에서는 지간이 30m, 곡률 반경이 40m인 해석모델에 대한 적정 다이아프램간격은 5m인 것으로 나타났다. 다이아프램의 형상 효과에 대해서는 라멘식 다이아프램의 경우가 개구율 0.4~0.6의 범위에서 개구부가 없는 충복판식 다이아프램보다 휨과 뒤틀림의 응력비가 낮아 거동에 유리한 것으로 나타났으며, 충복판식 다이아프램과 X형 트러스 방식의 다이아프램 비교에서는 동일한 강성을 가지더라도 충복판식 다이아프램이 뒤틀림응력을 보다 효과적으로 제어하였다.

• 대한토목학회논문집
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• 제11권1호
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• pp.17-27
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• 1991

본 논문에서는 구조물의 응력확대 계수를 균열선단주위에서 정의되는 표면적분법에 의하여 구하는 방법을 연구하였다. 통상의 J적분법을 변형시켜 표면 적분법을 유도하였으며 물체력을 고려하는 경우도 포함시켰다. 유한요소 해석결과를 입력변수로 받아들여 표면적분법으로 응력확대계수 $K_I$과 $K_{II}$를 구하는 프로그램을 작성하였다. 형상비(요소길이/균열길이)가 25% 정도인 요소망에서 본 논문에서 제안한 포물선형태의 평활곡선함수를 사용한 결과, 외측적분반경이 균열길이의 1/3~1 되는 구간에서 비교적 정확한 응력확대 계수가 얻어지는 것을 알수 있었다.

• 한국태양에너지학회 논문집
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• 제22권3호
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• pp.31-37
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• 2002

This experimental study represents the results of an analysis on the characteristics of flux density distributions in the focal region of solar concentrator. The characteristics of flux density distributions are investigated to optimally design and position a cavity receiver. This deemed very useful to find and correct various errors associated with a dish concentrator. We estimated the flux density distribution on the target placed along with focal lengths from the dish vertex to experimentally determine the focal length. It is observed that the actual focal point exists when the focal length is 2.17 m. We also evaluated the position of flux centroid, and it was found that there were errors within 2 cm from the target center. The total integrated power of 2467 W was measured under focal flux distributions, which corresponds to the intercept rate of 85.8%. As a result of the percent power within radius, approximately 90% of the incident radiation is intercepted by about 0.06 m radius.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1672-1679
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• 2002

This paper provides an engineering J estimation equation for cylinders with finite internal axial surfacecracks under internal pressure. The proposed equation is the J estimation equation based on deformation plasticity using Ramberg-Osgood (R-O) materials. Based on detailed 3-D FE results using deformation plasticity, plastic influence functions for fully plastic J components are tabulated for practically interesting ranges of the mean radius-to-thickness ratio, the crack depth-to-length ratio, the crack depth-to-thickness ratio. the strain hardening index for the R-O material, and the location along the semi-elliptical crack front. Based on tabilated plastic influence functions, the J estimation equation along the crack front is proposed and validated for R-O materials. Good agreements between the FE results and the proposed J estimation provide confidence in the use of the proposed method to elastic-plastic fracture mechanics of pressurized piping.

• Archives of Plastic Surgery
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• 제42권6호
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• pp.753-760
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• 2015

Background A number of conditions can alter a person's fingernail configuration. The ratio between fingernail width and length (W/L) is an important aesthetic criterion, and some underlying diseases can alter the size of the fingernail. Fingernail curvature can be altered by systemic disorders or disorders of the fingernail itself. Although the shape and curvature of the fingernail can provide diagnostic clues for various diseases, few studies have precisely characterized normal fingernail configuration. Methods We measured the W/L ratio of the fingernail, transverse fingernail curvature, hand length, hand breadth, and distal interphalangeal joint width in 300 volunteers with healthy fingernails. We also investigated whether age, sex, height, and handedness influenced the fingernail W/L ratio and transverse fingernail curvature. Results In women, fingernail W/L ratios were similar across all five fingers, and were lower than those in men. The highest value of transverse fingernail curvature was found in the thumb, followed by the index, middle, ring, and little fingers. Handedness and aging influenced transverse fingernail curvature, but not the fingernail W/L ratio. Fingernails were flatter on the dominant hand than on the non-dominant hand. The radius of transverse fingernail curvature increased with age, indicating that fingernails tended to flatten with age. Conclusions Our quantitative data on fingernail configuration can be used as a reference range for diagnosing various diseases and deformities of the fingernail, and for performing reconstructive or aesthetic fingernail surgery.