• Title/Summary/Keyword: Z-method

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Hybrid Anti-aliasing Method for 3D Object represented by Point Sampling (포인트 샘플링으로 표현된 3차원 객체를 위한 하이브리드 앤티앨리어싱 방법)

  • Kim, Hak-Ran;Park, Hwa-Jin
    • Journal of Digital Contents Society
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    • v.8 no.1
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    • pp.85-91
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    • 2007
  • This paper proposes a new hybrid anti-aliasing method for reducing aliasing appearing on an implicit surface using the point sampling. The hybrid anti-aliasing method is a method that finds differences in the values of pixel shown in Z-buffers for an implicit surface and thereby uses each of three types of Z-buffer. After determining the level of differences, it expresses a 3 dimensional object by using a multi Z-buffer if the level is severe, a double Z-buffer for a middle level, and only the original Z-buffer for a negligible difference. In comparison with the existing method in which multi Z-buffers have been entirely used for enhancing the anti-aliasing effect, the hybrid anti-aliasing method is an efficient method demonstrating an effect similar to the one using a multi Z-buffer while reducing the number of Z-buffers to be used.

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Modification of the ASME Code Z-Factor for Circumferential Surface Crack in Nuclear Ferritic Pipings (원전 페라이트 배관내의 원주방향 표면균열에 대한 ASME Code Z-Factor의 수정)

  • Park, Y. H.;Y. K. Chung;W. Y. Koh;Lee, J. B.
    • Nuclear Engineering and Technology
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    • v.28 no.2
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    • pp.185-196
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    • 1996
  • The purpose of this paper is to modify the ASME Code Z-Factor, which is used in the evaluation of circumferential surface crack in nuclear ferritic pipings. The ASME Code Z-Factor is a load multiplier to compensate plastic load with elasto-plastic load. The current ASME Code Z-Factor underestimates pipe maximum load. In this study, the original SC. TNP method is modified first because the original SC. TNP method has a problem that the maximum allowable load predicted from the original SC. TNP method is slightly higher than that measured from the experiment. Then the new Z-Factor is developed using the modified SC. TNP method. The desirability of both the modified SC. TNP method and the new Z-Factor is examined using the experimental results for the circumferential surface crack in pipings. The results show that (1) the modified SC. TNP method is good for predicting the circumferential surface crack behavior in pipings, and (2) the Z-Factor obtained from the modified SC. TNP method well predicts the behavior of circumferential surface crack in ferritic pipings.

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Extraction of Initial Conditions For a Recursive Numerical Inverse z-Transform Method (차분방정식에 의한 역 z변환 계산을 위한 초기 조건의 추출)

  • Lee, Jae-Seok;Jeong, Tae-Sang
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.51 no.8
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    • pp.368-373
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    • 2002
  • The inverse z-transform of a z-domain expression of a sequence can be Performed in many different methods among which the recursive computational method is based on the difference equation. In applying this method, a few initial values of the sequence should be obtained separately. Although the existing method generates the right initial values of the sequence, its derivation and justification are not theoretically in view of the definition of z-transform and its shift theorems. In this paper a general approach for formulating a difference equation and for obtaining required initial values of a sequence is proposed, which completely complies to the definition of the z-transform and an interpretation of the validity of the existing method which is theoretically incorrect.

Development of New Z-Factor for the Evaluation of Circumferential Surface Crack In Ferristic Steel Pipings (페라이틱 강 배관내의 원주방향 표면균열 평가를 위한 새로운 Z-Factor의 개발)

  • Choi, Yeong-Hwan;Chung, Yeon-Ki;Lee, Jeong-Bae;WilkowsKi, Gery
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.6
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    • pp.1798-1809
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    • 1996
  • The purpose of this paper is to develop new Z-Factors to evaluate the behavior of circumferential surface crack in ferritic steel piping including base metal and Submerged Arc Weld(SAW) metal in nuclear power plant. The Z-factor is a load multiplier to convert plastic load to elasto-plastic load. However the current Z-Factor is a load multiplier to convert plastic load to elasto-plastic load. However the current Z-Factor gives too conservative results. In this study, a J-estimation method, SC.TNP method, which is based on GE/EPRI expression, is used to develop new Z-Factors. The desirabilities of both the SC.TNP mehtod and the new Z-Factors are examined using the previous experimental results for the circumferential surface crack in ferritic steel pippings. The results are as follows ; (1) The SC.TNP mehtod is good for describing the circumferential surface crack behavior in farritic steel pipings, while the well-known R6 mehtod and DPFAD method give too conservative results. (2) The ASME-Z-Factor method using nwe Z-Factors well predicts the behavior of circumferential surface crack in ferritic steel pipings including base emtal and SAW metal.

An Analytic Study On the Mutual Relation between Method(1) and (2) of ZIEGLER-NICHOLS Control Parameter Tuning (지글러-니콜스 제어파라미터 조정법(1),(2)의 상호 연관성에 대한 해석적 연구)

  • 강인철;최순만;최재성
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2001.11a
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    • pp.112-119
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    • 2001
  • Parameter tuning methods by Ziegler-Nickels for control systems are generally classified into Z-N(1) and Z-N(2). The purpose of this paper is to describe what relations exist between methods of Z-N(1) and Z-N(2), or how Z-N(1) method can be originated from Z-N(2) method by analyzing one loop control system of P or PI controller and time delay process. The formulas of Z-N(1) consist of process parameters, L(time delay), $K_m$(gain) and $T_m$(time constant), but Z-N(2) method is based only on the ultimate gain $K_u$ and the ultimate period $T_u$ acquired normally by practical trial without any parameters of Z-N(1). In this paper, for the first step to seek mutual relations, the simple formulas of Z-N(2) are transformed into the formulas composed of the same parameters as Z-N(1) which is derived from the analysis of frequency characteristics. Then, the approximation of the actual ultimate frequency is proposed as important premise in the translation between Z-N(1) and (2). Such equalization and approximation brings a simple approximated formula which can explain how Z-N(1) is originated from the Z-N(2) in the form of formula. And a model system is adopted to compare the approximated formula to Z-N(1) and Z-N(2) methods, the results of which show the effectiveness of the proposals.

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PWM Control of Reduced Switch Z-Source Inverter (스위치 저감형 Z-Source Inverter PWM 제어)

  • Kim, Seong-Hwan;Park, Tae-Sik
    • Journal of IKEEE
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    • v.23 no.1
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    • pp.53-57
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    • 2019
  • In this paper, we propose a new Z-source inverter structure to reduce switching elements and PWM pulse control method. Z-network is connected between the inverter backplane and ground, rather than between the DC voltage and the inverter in an improved Z-source inverter. And the improved Z-source inverter has the advantages of limiting the capacitor inrush current and reducing the capacitor voltage stress. We have proposed a topology of a new type of switch-reduced improved Z-source inverter that reduces the number of switches from six to four in an improved Z-source inverter and developed a PWM control method suitable for the proposed topology. The characteristics and the performance of the proposed method were verified by using PSIM simulation.

Z. Cao's Fuzzy Reasoning Method using Learning Ability (학습기능을 이용한 Z. Cao의 퍼지추론방식)

  • Park, Jin-Hyun;Lee, Tae-Hwan;Choi, Young-Kiu
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.12 no.9
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    • pp.1591-1598
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    • 2008
  • Z. Cao had proposed NFRM(new fuzzy reasoning method) which infers in detail using relation matrix. In spite of the small inference rules, it shows good performance than mamdani's fuzzy inference method. In this paper, we propose Z. Cao's fuzzy inference method with learning ability which is used a gradient descent method in order to improve the performances. It is hard to determine the relation matrix elements by trial and error method. Because this method is needed many hours and effort. Simulation results are applied nonlinear systems show that the proposed inference method using a gradient descent method has good performances.

Analytic Problems in Applying the Properties of teh Modified z-Transform (변형 Z변환의 특헝의 적용상의 해석적 문제)

  • Chung, Tae-Sang;Lee , Jae-Seok
    • The Transactions of the Korean Institute of Electrical Engineers D
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    • v.51 no.12
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    • pp.549-555
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    • 2002
  • While the z-transform method is a basic mathematical tool to relate the imput/output signals only at the sampling instants in analyzing and designing sampled-data control systems, the modified z-transform which is a variation of the z-transform is widely used to represent the details of continuous signals between the sampling instants. To relate the modified z-transform to the corresponding regular z-transform, some properties were established regarding the modified z-transform method. This paper will show that these properties, in their current forms, cause come analytic problems, when they are applied to the signals with discontinuities at the sampling instants, which accordingly limit their applications significantly. In this paper, those analytic problems will be investigated, and the theorems of the modified z-transform will be revised by adopting new notations on the z-transform so that those can be correctly interpreted and used without any analytic problems. Also some additional useful schemes of applying the modified z-transform will be developed.

The Advanced z-Transform and Analysis of Sampled-Data Systems

  • Chung, Tae-Sang
    • Proceedings of the KIEE Conference
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    • 1996.11a
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    • pp.49-51
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    • 1996
  • The z-transform method is a basic mathematical tool in analyzing and designing sampled-data control systems. However, since the z-transform method relates only the sampling-instants signals, another mathematical tool is necessary to describe the continous signals between the sampling instants. For this purpose the delayed and the modi fled z-transform methods were developed. The definition of the modi fled z-transform includes a sample in the interval [-T,0] of the original signal in its series expression, where the signal value is always zero for any physical system. From this reason one step skew of the time index always appears in its application formulas. This introduces an unnecessary operation and a gap in linking the mathematical formula and its physical interpretation. Considering the conceptual difficulty and application inconvenience, a method of using the advanced z-transform in analysis of sampled-data control systems is developed as a replacement of the modi fled z-transform. With one formulation of the advanced z-transform, now it is possible to relate both the signals of the sampling instants and those in between without any complication and conceptual difficulty.

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