• Title/Summary/Keyword: Curve

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Pencil Curve Tracing via Virtual Digitizing (가상 측정을 통한 펜슬곡선 추출)

  • 박정환;김보현;최병규
    • Korean Journal of Computational Design and Engineering
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    • v.2 no.4
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    • pp.253-266
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    • 1997
  • Pencil-curve machining, which is a single-pass ball-end milling along a concave edge on adie surface, is widely employed in die-surface machining. The cutter-path used for pencil-curve machining, which is the trajectory of the “ball-center point” of a ball-endmill sliding along a concave-edge region on the die surface, is called pencil-curve. Presented in the paper is a pencil-curve tracing algorithm in which “concave-type” sharp edges are computed from a “virtually digitized” model of the tool-envelope surface. The resulting “initial” pencil-cures are then refuted by applying a series of fairing operations. illustrative examples and methods for enhancing accuracy are also presented. The proposed pencil-curve tracing algorithm has been successfully implemented in a commercial CAM system specialized in die-machining and in the CAD/CAM system CATIA.

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Off-Design Performance Prediction of Multi-Stage Axial-Compressor by Stage-Stacking Method (단 축적법을 이용한 다단 축류 압축기 탈설계 성능예측)

  • Park, Tae-Jin;Baek, Je-Hyun;Yoon, Sung-Ho
    • Proceedings of the KSME Conference
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    • pp.789-794
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    • 2001
  • In this study, a program for the off-design performance prediction of multi-stage axial-compressors is developed based on stage-stacking method. To account for the increased losses at off-design conditions, generalized performance curve is applied. The purpose of this study is to investigate the influence of the choice of generalized performance curve and stator exit angle. For this purpose, we tested various generalized performance curves and stator exit angles. In conclusion, Muir's pressure coefficient curve gives a good prediction results regardless of the efficiency curve for a low-stage compressors. On the other hand, for high-stage compressors, The combination of Muir's pressure coefficient curve and Stone's efficiency curve gives a optimistic results. Stator exit angle has a small effect on overall performance curve.

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Determination of the Tension-Softening Curve of Concrete at Different Strength Level using Fictitious Crack Model (가상균열모델에 의한 강도 수준이 다른 콘크리트의 인장연화곡선 결정)

  • 오성진;박현재;김희성;진치섭
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.125-130
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    • 2002
  • The most important material parameters are fracture energy and the stress-crack opening displacement($\sigma$-w) curve to determine the behavior of concrete. Especially, the relationship between the $\sigma$-w curve is strongly important to determine the load-displacement curve of concrete that has a major influence on the fracture behavior of a concrete. In this paper, notched plain concrete beams with different strength level were tested under three-point bending and fracture energy, the load-deflection curve, and the load-crack mouth opening displacement(CMOD) curve were obtained from the experimental data. Also, the fictitious crack model(FCM) was applied to determine the load-deflection curve of notched plain concrete beams using various types of $\sigma$-w curve model proposed by Petersson and we compared experimental results with numerical ones carried out by Finite Element Method(FEM).

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Performance Study of genus 3 Hyperelliptic Curve Cryptosystem

  • Gupta, Daya;De, Asok;Chatterjee, Kakali
    • Journal of Information Processing Systems
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    • v.8 no.1
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    • pp.145-158
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    • 2012
  • Hyperelliptic Curve Cryptosystem (HECC) is well suited for all kinds of embedded processor architectures, where resources such as storage, time, or power are constrained due to short operand sizes. We can construct genus 3 HECC on 54-bit finite fields in order to achieve the same security level as 160-bit ECC or 1024-bit RSA due to the algebraic structure of Hyperelliptic Curve. This paper explores various possible attacks to the discrete logarithm in the Jacobian of a Hyperelliptic Curve (HEC) and addition and doubling of the divisor using explicit formula to speed up the scalar multiplication. Our aim is to develop a cryptosystem that can sign and authenticate documents and encrypt / decrypt messages efficiently for constrained devices in wireless networks. The performance of our proposed cryptosystem is comparable with that of ECC and the security analysis shows that it can resist the major attacks in wireless networks.

Intersection between a Surface of Extrusion and a Free-Form Surface (평행이동곡면과 자유곡면 사이의 교차곡선 계산)

  • Kim, Ku-Jin;Kim, Myung-Soo
    • Journal of the Korea Computer Graphics Society
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    • v.6 no.4
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    • pp.29-34
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    • 2000
  • This paper classifies the structure of the intersection curve between a surface of extrusion and a free-form surface. Our algorithm computes the silhouette curve of the free-form surface with respect to the unique ruling direction of the surface of extrusion. By intersecting the silhouette curve and the base curve of the surface of extrusion, we can classify the topological structure of the intersection curve, and compute all singularities in the intersection curve. Moreover, we can determine which ruling lines of the surface of extrusion intersect the other free-form surface and how many times. This classification provides a robust and efficient method for computing the intersection curve.

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The Construction of Productivity Improvement Model with Group Technology Style through the Utilization of Learning curve (Learning Curve를 이용한 G.T형 생산성향상 모델 구축)

  • 윤상원;신용백
    • Journal of the Society of Korea Industrial and Systems Engineering
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    • v.15 no.26
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    • pp.77-84
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    • 1992
  • This paper constructs Croup Technology process-based learning curve model adjusted to a Group Technology environment which accounts for shared learning that occurs when multiple products utilize some of the same process steps. Through this constructed model, the estimated times and productivity of labor calculated by the Group Technology process-based learning curve model are compared with those generated by employing product-based 1 earning curve model. For sensitivity analysis of the model, the impact of learning rate and the ordered production quantity on the ratio differences between Group Technology process-based learning curve model and product-based learning curve model are examined. These results indicate the critical importance of employing Group Technology process-based learning curve model when a process spans multiple products.

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A study on Three Dimensional Configuration Scan by Photographing Parameters (스퍼기어의 3차원 모델링과 검증에 관한 연구)

  • 김세민;김민주;이승수;김순경;전언찬
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • pp.369-374
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    • 2001
  • Gear is general mechanical elements that used for power transmission between two shafts that interval is comparatively short. and it delivers big power as accurate ratio of speed. The profile of Spur gear which is the most basic factor is divided into Trochoidal fillet curve and Involute curve. Involute curve is used a lot of a shaped curve of machine parts such as a gear, a scroll compressor and a collar of centrifugal pump. However, it is poor to study the modeling of Trochoidal fillet curve and the three dimensions model shaped mathematical curve. This paper describes a mathematical model of profile shifted involute gear. and this model is based on Camus's theory. We draw three dimensions gear have accurate mathematical function using ADS, VisualLISP. and To check accuracy and perfection, we make a program of checking Interference. and use for this study.

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A Study on the Three-dimensional Gear Modeling for CAD/CAM (CAD/CAM을 위한 3차원 기어 모델링에 관한 연구)

  • 주만식;김민주;이승수;전언찬
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.1008-1012
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    • 1997
  • This study is on a mathematical model of profile shifted involute gear, and this model is based on Camus's theory. Gear is general mechanical elements that used for power transmission between two shafts that interval is comparatively short. and it delivers bit power as accurate ratio of speed. The profile of Spur gear which is the most basic factor is divided into Trochoidal fillet curve and Involute curve. Involute curve is used a lot of a shape curve of machine parts such as a gear, a scroll compressor and a collar of centrifugal pump. However, It is poor to study the modeling of Trochoidal fillet curve and the three dimensions model shaped mathematical curve. So we draw three dimensions gear have accurate mathematical function using ADS(Automatic Drawing system), VisualLISP. To check accuracy and perfection, we make a program of checking Interference. and use for this study.

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Antisymmetric S-curve Profile for Fast and Vibrationless Motion (고속 저진동 운동을 위한 비대칭 S-커브 프로파일)

  • Rew Keun-Ho;Kwon Jeong-Tae;Park Kyoung-Woo
    • Journal of Institute of Control, Robotics and Systems
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    • v.12 no.10
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    • pp.1012-1017
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    • 2006
  • By breaking the symmetry of the velocity profile in the S-curve, we developed a fast starting and smooth ending motion profile, named asymmetric S-curve(AS-curve). The problem for generating motion profile is formulated, and the algorithm for the AS-curve is derived and the flow chart of the AS-curve is illustrated. By various simulations, the derived algorithm is tested and shows the validity. This AS-curve can be applied to the high precision machines where fast and vibrationless motion is required in the near future.

Final Settlement Prediction Methods of Embankments on Soft Clay by Back Analysis (역해석에 의한 연약지반 최종침하량 추정)

  • Lim, Seong Hun;Kang, Yea Mook;Lee, Dal Won
    • Korean Journal of Agricultural Science
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    • v.25 no.2
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    • pp.247-259
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    • 1998
  • Analyses which loads were regarded as instant load and gradual step load were performed with data measured on gradually loaded field, and the results were inspected to find effect of load condition, and final settlements predicted by Hyperbolic, Tan's, Asaoka's, and Monden's method were compared with each other. According to above analyses, the following conclusions were obtained. Settlement curves which loads were regarded as instant load and gradual step load were beginning to coincide at time of twice duration of embankment. On the ground installed vertical drain, the result of Hyperbolic, Tan's, Asaoka's, Monden's, curve fitting I, and curve fitting II (simple, Carrillo) methods make conclude that Asaoka, curve fitting I, and curve fitting II methods agree with measured settlement.

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