• Structural Engineering and Mechanics
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• 제86권2호
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• pp.221-235
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• 2023

To calculate the vibrations of a tout cable subjected to axial support excitations, a nonlinear relationship of cable force and the support displacement under static situations are employed to depict the quasi-static vibration of the cable. The dynamic components of quasi-static vibration are inputted as "direct loads" to cause the parametric vibrations on the cable. Both the governing equations of motion and deformation compatibility for parametric vibrations are then derived, which indicates the high coupling of cable parametric force and deformation. Numerical solutions, based on the finite difference method, are put forward for the parametric vibrations, which is validated by the finite element method under periodic axial support excitations. For the quasi-static response, the shorter cables are more sensitive to support excitations than longer ones at small cable force. The quasi-static cable force makes the greatest contribution to the total cable force, but the parametric cable force is responsible for the occurrence of cable loosening at large excitation amplitudes. Moreover, this study also revealed that the traditional approach, assuming a linear relationship between quasi-static cable force and axial support displacement, would result in some great error of the cable parametric responses.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 추계학술대회 논문집
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• pp.204-209
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• 1998

The acceleration of the performance of machine tools influences the development of the semi-conductor and optical technology as the development of NC and measurement technology. We can mention that a traction role of the acceleration for the development like that depends on the development of the measurement technics Stylus instrument method, STM, SEM, Laser interferometer method which are used for measuring the quasi-static error of machine tools. Because the measurement has been done to unload condition without considering of mechanical stiffness in the case of machining center as we measure the quasi-static error of machine tools on general studies, people who works on the spot has many problems on the data value. Therefor we will help working more accurately on the spot by measuring, analyzing, displaying the deflection of the table and support shaft when we load on the table and the support shaft of machining center using laser interferometer. Also we try to settle new conception of the measurement method and more accurate grasp of the deflection tendency by verifing the tendency of the error measured through the comparison of the simulated error using ANSYS, a common finite element analysis program, which is able to measure heat deformation, material deformation, and error resulted form this study.

• International Journal of Contents
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• 제14권1호
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• pp.18-27
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• 2018

The objective of this study was to derive approximate closed-form error rates for M-ary burst symbol transmission (MBST) of dual-hop adaptive decode-and-forward (ADF) cooperative relay systems over quasi-static Rayleigh fading channels. Within a burst, there are pilot symbols and data symbols. Pilot symbols are used for channel estimation schemes and each relay node's transmission mode selection schemes. At first, our focus was on ADF relay systems' error-events at relay nodes. Each event's occurrence probability and probability density function (PDF) were then derived. With error-event based approach, we derived a tractable form of PDF for combined signal-to-noise ratio (SNR). Averaged error rates were then derived as approximate expressions for arbitrary link SNR with different modulation orders and numbers of relays. Its accuracy was verified by comparison with simulation results.

• 한국생산제조학회지
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• 제8권6호
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• pp.55-63
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• 1999

The acceleration of the performance of machine tools influences the development of the semi-conductor and optical technology as the development of NC and measurement technology. Because the measurement has been done to unload condition without considering of mechanical stiffness in the case of machining center as we measure the quasi-static error of machine tools on general study people who works on the spot has many problems on the data value. Also there are no satisfiable results until now in spite of many studys about this because the deflections of the table and the shaft supporting a workpiece influence, influence the accuracy of the table and shaft supporting a workpiece influence the accuracy of the workpiece. And there is doubt about the inspection method of measured error. In this paper Therefor we will help working more accurately on the spot by measuring analyzing displaying the defoec-tion of the table and support shaft when we load on the table and the support shaft of machining center using laser interfer-ometer. Also we try to settle new conception of the measurement method and more accurate grasp of the deflection tenden-cy by verifing the tendency of the error measured through the comparison of the simulated error measured through the comparison of the simulated error using ANSYS a common finite element analysis program which is able to measure heat deformation material deformation and error resulted from this study.

• 한국자동차공학회논문집
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• 제24권3호
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• pp.273-278
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• 2016

This study makes a relative comparison of the results of tensile test and quasi-static analysis using AGL(Adjuster Guide Loop) model that plays a role in adjusting the height of shoulder belt, of the components of the vehicle seatbelt system and attempts to propose a method of reducing the error rate of the quasi-static analysis technique effectively. This study selects two major factors affecting the result of an analysis, draws the result of analysis through the method of experimental design, one of the statistical techniques and understands the contribution rate of the major factors affecting the result of the analysis through ANOVA(Analysis of Variance).

• Journal of Communications and Networks
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• 제11권5호
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• pp.473-479
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• 2009

Conventional frequency domain equalization (FDE) schemes were originally devised for quasi-static channels. Thus, such equalization schemes could suffer from significant performance degradation in fast-fading channels. This paper proposes a frequency domain equalization algorithm to mitigate the effect of fast time-varying fading. First, a mathematical expression is derived to quantify the total interference resulting from the time variation of the channel. Then, the proposed approach attempts to eliminate the effect of time-variations of the channel. This cancellation allows efficient use of the classical FDE structures in fast time-varying fading environments, although they are built upon the quasi-static channel model. Simulation results of bit-error-rate performance are provided to demonstrate the effectiveness of the proposed algorithm.

• 한국정밀공학회지
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• 제16권8호
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• pp.122-129
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• 1999

A 5-axis CNC machine tool is more useful compared with a 3-axis machine tool, because the position and the orientation of a tool tip can be controlled simultaneously. Unlike the 3-axis machine tool, the 5-axis machine tool has the volumetric position error and volumetric orientation error due to the quasi-static error of each machine tool joint which is a major source of machined part error. So, the generalized error synthesis model of the 5-axis CNC machine tool was developed to predict and to compensate for the volumetric position error and the volumetric orientation error. It was proposed that a compensation algorithm to correct simultaneously the volumetric position error and the volumetric orientation error of the 5-axis CNC machine by error inverse kinematic.

• 전자공학회논문지
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• 제51권6호
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• pp.43-49
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• 2014

본 논문에서는 4개의 전송 안테나 시스템에서 좌표축 인터리빙된 직교 신호로 디자인(Coordinate interleaved orthogonal design: CIOD)된 시 공간 블록 부호(Space time block code: STBC)가 시간 선택적 페이딩 채널인 1차 Markov 채널을 통과하였을 때에 성능 분석을 다룬다. 채널이 준 정지 페이딩 채널(Quasi-static fading channel)일 경우 STBC-CIOD는 최대 전송률과 최대 다이버시티(Full rate full diversity: FRFD)를 만족하고, 단일 심볼 복호가 가능한(single symbol decodable: SSD) 코드이나, 시간 선택적 페이딩 환경에서는 신호간의 간섭이 생기므로 FRFD을 만족시키더라도 단일 심볼 복호를 수행하였을 때 간섭에 의한 성능 열화가 생길 것이다. 심볼 오류율(Symbol error rate: SER)의 Union bound를 신호 쌍 오류 확률(pairwise error probability)을 유도하여 구한다. 그리고 4-ary PSK 신호에 대한 모의실험을 통하여 유도된 심볼 오류율을 구하고 이를 수식으로 구한 심볼 오류율의 union bound 와 비교한다.

• Journal of Communications and Networks
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• 제10권3호
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• pp.253-257
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• 2008

In this paper, the performance of generic orthogonal space-time block codes (OSTBCs) introduced by Alamouti [2], Tarokh [3], and Su and Xia [11] is analyzed. We first define one-dimensional component symbol error function (ODSEF) from the exact expression of the pairwise error probability of an OSTBC. Utilizing the ODSEF and the bit error probability (BEP) expression for quadrature amplitude modulation (QAM) introduced by Cho and Yoon [9], the exact closed-form expressions for the BEP of linear OSTBCs with QAM in quasi-static Rayleigh fading channel are derived. We also derive the exact closed-form of the BEP for some OSTBCs which have at least one message symbol transmitted with unequal power via all transmit antennas.

• 한국정밀공학회지
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• 제19권9호
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• pp.34-40
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• 2002

Machining accuracy is affected by quasi-static errors of machining center. Since machine errors have a direct influence upon both the surface finish and geometric shape of the finished workpiece, it is very important to measure the machine errors and to compensate these errors. The laser measurement method for identifying geometric errors of machine tool has the disadvantages such as high cost, long calibration time and usage of volumetric error synthesis model. Accordingly, this paper deals with analysis of the geometric errors of a machine tool using ball bar test without using complicated error synthesis model. Statistical analysis method was adopted in this paper for deriving geometric errors using hemispherical helix ball bar test. As a result of experiment, geometric errors of the vertical machining center are compensated by 88%.