• 제목/요약/키워드: Screw motion

검색결과 168건 처리시간 0.021초

Swept Volumes Generated by Polyhedral Objects Through Screw Motions (스크류 운동을 하는 다면체의 스웹 볼륨 생성)

  • 김재정;정채봉;서경천;강민우
    • Korean Journal of Computational Design and Engineering
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    • 제7권4호
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    • pp.211-218
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    • 2002
  • Swept volumes have been used in a wide variety of applications, and the literature contains much discussion of methods for computing the swept volumes in many situations. However, the commercially available CAD systems do not support the operations of generating the swept volumes enough to satisfy a variety of users' needs. In this paper, we present a new, simple and efficient algorithm for computing the swept volume of moving a polyhedron in 3-D region. The screw motion is used to describe the sweep motion of a polyhedron, because of its simplicity and computational advantages. The boundary of a swept volume is the result of combining the envelope surfaces and the partial boundaries at the initial and final position of a polyhedron. Some portions of these boundaries are inside the swept volume. We develop the algorithm to remove these interior portions. Then, to implement our algorithm, it is performed to integrate our program with the commercial CAD software, CATIA.

A Study on the Prediction of Maneuvering Motion for a Twin-Screw Twin-Rudder Ship at Initial Design Stage (초기설계 단계에서 2축2타선의 조종운동 추정에 관한 연구)

  • 이승건;이경우;이승재
    • Journal of the Korean Institute of Navigation
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    • 제21권1호
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    • pp.103-108
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    • 1997
  • Mathematical model of maneuvering motion for a single-screw single-rudder ship is established and several applications to the special situations of maneuvering are attempted. While, the mathematical model for twin-screw twin-rudder ship is not presented so much, because that type of ship is not popular. Lee et al. have examined the characteristics of such ship by captive model tests in 1988, in Japan. This paper proposes new mathematical models for propeller effective wake (1 -${\omega}_p$) and effective neutral rudder angle ${delta}_R$ in the case of twin-screw twin-rudder ship. And some maneuvering motionse are calculated with proposed models and compared with exact simulations.

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Investigation of Surface Roughness Characteristics according to Tool Runout Variations in Side Milling Cutter for Worm Screw (사이드 밀링 커터를 이용한 워엄 스크루 가공에서 공구 런아웃이 표면조도에 미치는 영향분석)

  • Kim, Sun Ho
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • 제8권4호
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    • pp.76-82
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    • 2009
  • A worm screw is widely used in a geared motor unit for motion conversion from rotation to linear motion. For mass production of a high quality worm, the current roll forming process is substituted with the milling cutter process. Since the milling cutter process enables the integration of all machining operations of worm manufacturing on a CNC(Computer Numerical Control) lathe, productivity can be remarkably improved. The tooling system for side milling cutter on the CNC lathe to improve machinability is developed. However, the runout of spindle and cutting tips are important factors to be considered for producing high quality worms because the tooling system has multiple tips. In this study, surface roughness variations accuracy according to runout was investigated in side milling cutter for worm screw. The result shows by simulation and experiment.

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A Study on the Prediction of Maneuvering Motion for a Twin-Screw Twin-Rudder Ship at Initial Design Stage (초기설계 단계에서 2축2타선의 조종운동 계산에 관한 연구)

  • 이승건;이경우;이승재
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 한국항해항만학회 1996년도 The Korean Institute of Navigation 1996년도 한·중 국제학술 심포지움 및 추계학술발표회 논문집
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    • pp.81-88
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    • 1996
  • Mathematical model of maneuvering motion for a single-screw single-rudder ship is established and several applications to the special situations of maneuvering are attempted. While the mathematical model for twin-screw twin-rudder ship is not studied presented so much because that type of ship is not popular. Lee et al. have examined the characteristics of such ship by captive model tests in 1988 in Japan. This paper proposes new mathematical models for propeller effective wake (1-wp) and effective neutral rudder angle $\delta$R in the case of twin-screw twin-rudder ship. And some maneuvering motions are calculated with proposed models and compared with exact simulations.

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A Dynamic Modeling & State Sensitivity Analysis of the Surface Mounting Device (Surface Mounting Device의 동역학적 모델링 및 상태 민감도 해석)

  • Jang, Jinhee;Han, Changsoo;Kim, Jungduck
    • Journal of the Korean Society for Precision Engineering
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    • 제13권7호
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    • pp.90-99
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    • 1996
  • In the area of assembly process of micro-chips and electronic parts on the printed circuit board, surface mounting device(SMD) is used as a fundamental tool. Generally speaking, the motion of the SMD is based on the ball screw system operated by any type of actuators. The ball screw system is a mechanical transformed which converts the mechanical rotational motion to the translational one. Also, this system could be considered as an efficient motion device against mechanical backlash and friction. Therefore a dynamic modeling and state sensitivity analysis of the ball screw system in SMD have to be done in the initial design stage. In this paper, a simple mathematical dynamic model for this system and the sensit- ivity analysis are mentioned. Especially, the bond graph approach is used for graphical modeling of the dynamic system before analysis stage. And the direct differentiation method is used for the state sensit- ivity analysis of the system. Finally, some trends for the state variables with respect to the design variables could be suggested for the better design and faster operating based on the results of dynamic and state sensitivity.

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Numerical Study of Internal Flow in Twin Screw Extruder and Its Mixing Performance Analysis (이축 스크루 압출기내 유동의 수치 해석과 혼합 성능 분석)

  • Kim, Nak-Soo;Kim, Hong-Bum;Lee, Jae-Wook
    • Transactions of the Korean Society of Mechanical Engineers A
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    • 제30권1호
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    • pp.32-41
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    • 2006
  • We analyzed the non-Newtonian and non-isothermal flow in the melt conveying zone in co-rotating and counter-rotating screw extruder system with the commercial code, STAR-CD, and compared the mixing performance with respect to screw speed and rotating direction. The viscosity of fluid was described by power-law model. The dynamics of mixing was studied numerically by tracking the motion of particles in a twin screw extruder system. The extent of mixing was characterized in terms of the residence time distribution and average strain. The results showed that high screw speed decreases the residence time but increases the shear rate. Therefore higher screw speed increases the strain and has better mixing performance. Counter-rotating screw extruder system and co-rotating screw extruder has the similar shear rate with the same screw speed in spite of different rotating direction. However, the counter-rotating screw has good mixing performance, which is resulted from longer residence time than that of co-rotating screw extruder.

Biomechanical Comparison of Spinal Fusion Methods Using Interspinous Process Compressor and Pedicle Screw Fixation System Based on Finite Element Method

  • Choi, Jisoo;Kim, Sohee;Shin, Dong-Ah
    • Journal of Korean Neurosurgical Society
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    • 제59권2호
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    • pp.91-97
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    • 2016
  • Objective : To investigate the biomechanical effects of a newly proposed Interspinous Process Compressor (IPC) and compare with pedicle screw fixation at surgical and adjacent levels of lumbar spine. Methods : A three dimensional finite element model of intact lumbar spine was constructed and two spinal fusion models using pedicle screw fixation system and a new type of interspinous devices, IPC, were developed. The biomechanical effects such as range of motion (ROM) and facet contact force were analyzed at surgical level (L3/4) and adjacent levels (L2/3, L4/5). In addition, the stress in adjacent intervertebral discs (D2, D4) was investigated. Results : The entire results show biomechanical parameters such as ROM, facet contact force, and stress in adjacent intervertebral discs were similar between PLIF and IPC models in all motions based on the assumption that the implants were perfectly fused with the spine. Conclusion : The newly proposed fusion device, IPC, had similar fusion effect at surgical level, and biomechanical effects at adjacent levels were also similar with those of pedicle screw fixation system. However, for clinical applications, real fusion effect between spinous process and hooks, duration of fusion, and influence on spinous process need to be investigated through clinical study.

Modeling and controller design of crabbing motion for auto-berthing (선박 자동접안을 위한 순수 횡 이동 모델링 및 제어기 설계)

  • Park, Jong-Yong;Kim, Nakwan
    • Journal of Ocean Engineering and Technology
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    • 제27권6호
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    • pp.56-64
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    • 2013
  • Crabbing motion is the pure sway motion of a ship without surge velocity. Thus, it can be applied to a berthing operation. Crabbing motion is induced by a peculiar operation method called the push-pull mode. The push-pull mode is induced by using a combination of the main propeller and side thruster. Two propellers generating the same amounts of thrust and rotating in opposite directions produce some yawing moment on a vessel but do not induce longitudinal motion. With the additional operation of side thrusters, the push-pull mode is used to induce a large amount of lateral force. In this paper, three-degree-of-freedom equations of motion such as for the surge, sway, and yaw are constructed for the crabbing motion. Based on these equations of motion, a feedback linearization control method is applied to auto-berthing control for a twin-screw ship with side thrusters. The controller can deal with the nonlinearity of a system, which is present in the berthing maneuver of a twin screw ship. A simulation of the auto-berthing of a ship is performed to validate the performance of the designed controller.

Implant Removal after Percutaneous Short Segment Fixation for Thoracolumbar Burst Fracture : Does It Preserve Motion?

  • Kim, Hyeun Sung;Kim, Seok Won;Ju, Chang Il;Wang, Hui Sun;Lee, Sung Myung;Kim, Dong Min
    • Journal of Korean Neurosurgical Society
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    • 제55권2호
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    • pp.73-77
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    • 2014
  • Objective : The purpose of this study was to evaluate the efficacy of implant removal of percutaneous short segment fixation after vertebral fracture consolidation in terms of motion preservation. Methods : Between May 2007 and January 2011, 44 patients underwent percutaneous short segment screw fixation due to a thoracolumbar burst fracture. Sixteen of these patients, who underwent implant removal 12 months after screw fixation, were enrolled in this study. Motor power was intact in all patients, despite significant vertebral height loss and canal compromise. The patients were divided into two groups by degree of osteoporosis : Group A (n=8), the non-osteoporotic group, and Group B (n=8), the osteoporotic group. Imaging and clinical findings including vertebral height loss, kyphotic angle, range of motion (ROM), and complications were analyzed. Results : Significant pain relief was achieved in both groups at final follow-up versus preoperative values. In terms of vertebral height loss, both groups showed significant improvement at 12 months after screw fixation and restored vertebral height was maintained to final follow-up in spite of some correction loss. ROM (measured using Cobb's method) in flexion and extension in Group A was $10.5^{\circ}$ ($19.5/9.0^{\circ}$) at last follow-up, and in Group B was $10.2^{\circ}$ ($18.8/8.6^{\circ}$) at last follow-up. Both groups showed marked improvement in ROM as compared with the screw fixation state, which was considered motionless. Conclusion : Removal of percutaneous implants after vertebral fracture consolidation can be an effective treatment to preserve motion regardless of osteoporosis for thoracolumbar burst fractures.

Maisonneuve Fractures Treated with Percutaneous Screw Fixation (경피적 나사못 고정술로 치료한 Maisonneuve 골절)

  • Jung, Chol-Yong;Son, Young-Chan;Bae, Jun-Bum;Choi, Moon-Do
    • Journal of Korean Foot and Ankle Society
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    • 제4권2호
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    • pp.61-66
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    • 2000
  • Purpose: To evaluate the clinical validity of percutaneous screw fixation in Maisonneuve fracture. Material and Methods: Out of 5 Maisonneuve fracture patients hospitalized in the department of orthopedic surgery of Seigang hospital from February 1995 to May 1998, 4 patients were treated with percutaneous screw fixation and 1 patient was treated with percutaneous screw fixation and repair of deltoid ligament altogether. The results were evaluated on the clinical and radiological finding. Results: In all cases, the range of motion of ankle joint was normal, the complication such as postoperative pain and post-traumatic arthritis were not found. Widening of medial clear space or talar shift were not found in the follow up X-ray and tibiofibular distance, compared with normal ankle joint was same on follow up CT. Conclusion: Percutaneous screw fixation is simple, less invasive and more effective method in the treatment of Maisonneuve fracture.

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