• 한국수학사학회지
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• 제32권1호
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• pp.17-25
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• 2019

This essay elucidates the way the geometries of space-time theories explain material bodies' motions. A conventional attempt to interpret the way that space-time geometry explains is to consider the geometrical structure of space-time as involving a causally efficient entity that directs material bodies to follow their trajectories corresponding to the laws of motion. Newtonian substantival space is interpreted as an entity that acts but is not acted on by the motions of material bodies. And Einstein's curved space-time is interpreted as an entity that causes the motions of bodies. This essay argues against this line of thought and provides an alternative understanding of the way space-time geometry explain the laws of motion. The workings of the way that Newton's flat and Einstein's curved space-time explains the law of motion is such that space-time geometry encodes the principle of inertia which specifies straight lines of moving bodies.

• 한국수자원학회논문집
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• 제50권12호
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• pp.877-887
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• 2017

도시유역의 중 하류부에 주로 설치되는 4방향 합류맨홀에서 과부하 흐름에 의한 에너지 손실은 도심지 침수피해를 가중시키는 주요 원인이다. 과부하 4방향 합류맨홀에는 유입관의 유입조건에 따라 흐름 양상이 크게 변화되며, 중간맨홀 뿐만 아니라 3방향(T형) 합류맨홀의 흐름조건을 구성한다. 그러므로 유입관의 유입유량 변화에 따른 과부하 4방향 합류맨홀의 에너지 손실 변화 분석 및 손실계수 산정이 필요하다. 본 연구에서는 하수도시설기준을 준용하여 맨홀직경 및 관경을 1/5로 축소 한 수리실험 장치를 제작하였다. 과부하 사각형 4방향 합류맨홀에서 유입관의 유입유량비 변화에 따른 손실계수를 산정하기 위하여 유입관(주 유입관 및 양측면 유입관)의 유입유량비를 10% 간격으로 변화시켜 다양한 유량조건(40 case)을 선정하였다. 실험 결과 중간맨홀에서 0.40의 가장 낮은 손실계수가, $90^{\circ}$ 접합맨홀에서 1.58의 가장 높은 손실계수가 산정되었다. 또한 합류맨홀(T형, 4방향)의 경우 측면 유입유량이 한쪽으로 편향될수록 보다 큰 손실계수를 나타냈다. 유입관의 유입유량 조건 변화에 따른 손실계수를 산정하여 손실계수 범위도를 작도하였으며, 과부하 사각형 4방향 합류맨홀에서 모든 흐름조건을 고려할 수 있는 손실계수 산정식을 제시하였다. 제시된 산정식은 유입관의 유입유량이 변화하는 배수시스템의 설계 및 검증에 적용이 가능할 것으로 판단된다.

• Journal of Computational Design and Engineering
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• 제1권1호
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• pp.13-26
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• 2014

Recently, renovations of plant equipment have been more frequent because of the shortened lifespans of the products, and as-built models from large-scale laser-scanned data is expected to streamline rebuilding processes. However, the laser-scanned data of an existing plant has an enormous amount of points, captures intricate objects, and includes a high noise level, so the manual reconstruction of a 3D model is very time-consuming and costly. Among plant equipment, piping systems account for the greatest proportion. Therefore, the purpose of this research was to propose an algorithm which could automatically recognize a piping system from the terrestrial laser-scanned data of plant equipment. The straight portion of pipes, connecting parts, and connection relationship of the piping system can be recognized in this algorithm. Normal-based region growing and cylinder surface fitting can extract all possible locations of pipes, including straight pipes, elbows, and junctions. Tracing the axes of a piping system enables the recognition of the positions of these elements and their connection relationship. Using only point clouds, the recognition algorithm can be performed in a fully automatic way. The algorithm was applied to large-scale scanned data of an oil rig and a chemical plant. Recognition rates of about 86%, 88%, and 71% were achieved straight pipes, elbows, and junctions, respectively.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제15권3호
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• pp.201-222
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• 2011

In the present work, the mathematical model of wire coating in a straight annular die is developed for unsteady second grade fluid in the form of partial differential equation. The Optimal Homotopy Asymptotic Method (OHAM) is applied for obtaining the solution of the model problem. This method provides us a suitable way to control the convergence of the series solution using the auxiliary constants which are optimally determined.

• 한국운동역학회지
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• 제26권4호
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• pp.407-412
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• 2016

Objective: The aim of this study was to analyze the net joint moment and joint power of the lower extremity during squat in female patients with genu varum. Method: Eight female patients with genu varum were asked to do regular squats, and their net joint moment and joint power were compared to those of another eight female participants with straight legs. Their video recordings and ground reaction force data were analyzed to be used as a theoretical evidence of squatting effectively for female patients with genu varum. Results: Squats had a higher impact on internal knee joint rotation and ankle joint flexion moments in the genu varum group than in the straight leg group due to their weak and short hip joint muscles. Conclusion: There is a need to develop a squat movement that is appropriate for women with genu varum in order to distribute overload efficiently among the hip, knee, and ankle joints and to strengthen the muscles in a balanced way.

• 한국전문물리치료학회지
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• 제13권3호
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• pp.102-110
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• 2006

To improve trunk stability, various exercise protocols were introduced into the clinical field. Trunk and lumbar stability exercises on unstable surfaces are especially recommended to improve lumbar stability. The purpose of this study was to compare abdominal oblique muscle activity during leg raising in hook-lying position among 3 different type of surface conditions (on floor (F), vestibular board (VB), and foam roll (FR)). Sixteen able-bodied volunteers, who had no medical history of lower extremity or lumbar spine disease, were recruited for this study. Surface electromyography (EMG) activity was recorded from the internal and external oblique muscles of both sides. The normalized EMG activity was compared using a one-way repeated ANOVA. The results showed that the EMG activities of the internal oblique and external oblique of the lifted leg side during straight leg raising significantly increased under the FR condition when compared to the F condition. There was no significant difference of the EMG activity in abdominal oblique muscles between the VB and the FR conditions. The EMG activity of the internal oblique of supported leg side during the straight leg raising was significantly greater under the FR condition than the VB and F conditions (p<.05). The composition ratio of EMG activity of internal oblique muscles during straight leg raising was significantly increased under the FR condition. Therefore, straight leg raising exercise on foam roll in hook lying position could be beneficial to improve trunk and lumbar stability.

• Restorative Dentistry and Endodontics
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• 제21권2호
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• pp.517-529
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• 1996

The purpose of this study was to evaluate the apical sealing ability of the Thermafil endodontic obturation technique and to compare it with lateral condensation technique. 42 straight canals from extracted human anterior teeth and 42 curved canals(> $25^{\circ}$) from maxillary and mandibular molar teeth were selected. And 80 of them were divided into four groups, 20 canals respectively. The teeth in prior two groups had straight canals and the other two groups had curved canals. The rest of four canals served as positive and negative controls. After resecting anatomical crowns, all canals were prepared using a standard step-back technique. Lateral condensation was used to obturate two groups, one group of straight ones the other curved. And Thermafil obturators were also used in the same two groups. Obturated teeth were infiltrated by India ink for a week, decalcified and cleared with 5% nitric acid and methyl salicylate. The apical leakage and the frequency of filled lateral and accessory canals were measured with stereomicroscope and also apical extrusion of sealer and gutta-percha and obturation time were checked and the data were analyzed statistically(one-way ANOVA, t-test, Chi-square test). The results were as follows : 1. There was no significant difference in the degree of dye penetration between Thermafil and lateral condensation groups(p>0.05). 2. Apical extrusion of sealer and gutta-percha occurred significantly more often with Thermafil obturators in straight canals(p<0.05), but not significantly different in curved canals(p>0.05). 3. Canal obturation time with Thermafil obturators was significantly faster than lateral condensation (p<0.05). 4. The Thermafil groups showed a higher frequency of filled lateral and accessory canals than in the lateral condensation groups. But the difference was not statistically significant (p>0.05).

• 한국산학기술학회논문지
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• 제17권12호
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• pp.327-332
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• 2016

스팅은 1985년 첫 솔로앨범인 를 필두로 세련된 감각과 폭넓은 음악적 스펙트럼을 선보이며 1억 장 이상의 앨범 판매고를 올린 영국을 대표하는 아티스트다. 본 논문에서는 스팅이 솔로 아티스트로서 폴리스 해체 이 후 30년이 넘도록 다양하고 폭넓은 자신만의 음악적 색채를 인정받는데 큰 발판이 되었던 음반에 수록되어 있는 곡들 중 'Straight To My Heart'와 'Be Still My Beating Heart'의 리듬 편곡에 대해 중점적으로 분석 할 것이다. 음반에 있는 곡들은 전체적으로 드럼파트는 기본적인 연주를 벗어나지 않고 전체적인 리듬분할의 역할을 여러 가지 퍼커션을 통해 하거나 신디사이저를 코드악기로서의 역할보다는 리듬악기로서의 역할에 더 비중을 둔 곡들이 많은 것을 볼 수 있다. 솔로 초기 스팅 만의 독특한 악기별 리듬구성과 역할배분은 다른 뮤지션들의 음반과는 사뭇 다른 그 만의 독특한 사운드를 창출해낸다. 이에 본 논문에서는 이 시기의 음반에 두드러지게 나타난 편곡적인 특징과 리듬적 특성, 즉 드럼비트를 쪼개서 리듬을 분할하는 통상적인 방식에서 벗어나 퍼커션을 포함한 다른 악기들의 리듬분할을 통해 곡의 기본적인 흐름을 이끌어가는 방법에 대해 설명 하고자 한다.

• 한국항해항만학회지
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• 제32권10호
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• pp.743-750
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• 2008

최근 세계 각지에서는 선박 통항 수역에 해상교량의 건설 운영, 건설 계획 중에 있어 이 해역을 통항하는 선박에게는 위험요소로 작용하여 해양사고를 유발하고 있다. 이 연구는 미국 및 유럽, 일본을 대상으로 해상교량과 관련한 해양사고 인자 분석을 통하여 해상교량 건설 및 기 설치된 해상교량의 안전한 선박통항을 위하여 필요한 환경 요소가 무엇이며 이 환경 요소가 어떻게 설정되어야 하는지에 대하여 분석하였다. 해상교량과 관련한 해양사고 관련 인자는 선박운항자의 실수 이외에 주경간폭, 통항하는 선박크기, 직선거리, 선박교통량 등이 관련하고 있는 것으로 조사되었다. 해양사고 분석을 통한 최소 해상교량 주경간폭은 300m 이상이며, 선박크기가 150m 이상의 선박이 통항하는 해역에서는 주경간폭이 500m 이상이 필요한 것으로 분석되었다. 또한 해상교량 진입 직전 직선거리는 최소한 5L이상이 필요하며 8L(L:선박의 길이) 이상의 확보를 통하여 해양사고를 최소화하여야 할 것이다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.954-957
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• 2010

Line 2 is being operated in 10 cities and it composed the amount of rolling stock combination. Line 2 rails have more curved than straight rails. So, wheels and rails were damaged. Accidents or delays caused many social problems. so it is important that wheel and rail are efficiently managed. Here, find out the cause of wheel-slip characteristics and workarounds were studying. Chapter 1 Background and Purpose. Chapter 2 about wheel slip problem and seek way improving adhesiveness. Chapter 3 Conclusion.