• International Journal of Control, Automation, and Systems
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• 제6권6호
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• pp.873-883
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• 2008

This paper presents a parametric study on the controller design scheme for a gyro-accelerometer to have robust performance under some parameter variations. In particular, an integral and derivative based controller design method is suggested to achieve the desired performances of stability margin, bandwidth, and uniformity of scale for both gyroscopes and accelerometers with uncertainties of quality factor and resonant frequency. The simulation result shows that the control loop based on the suggested method gives satisfactory performance robustness under parameter variations, demonstrating the usefulness of the proposed design scheme.

• Wind and Structures
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• 제7권6호
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• pp.405-420
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• 2004

In common approaches, bridge dynamics under wind action is analyzed by modeling the interaction between fluid and structure by means of transient wind loads acting over the structure itself. Amid various possible manners to describe such types of loads, a representation based on families of 'indicial functions' is adopted here. The aim is to investigate its flexibility to capture the main features of wind-bridge interaction. A set of coefficients is involved in indicial functions. The values that one may attribute to them suffer uncertainties coming from experimental errors affecting data. Here, the sensitivity of a 2-DOF schematic model to the variations of these coefficients is investigated at fixed values of dynamic derivatives and for various types of indicial functions. It is shown how parameter variations influence phase portraits.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 추계학술대회 논문집
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• pp.40-44
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• 2002

In this paper, robust control method using fuzzy PI parameter tuning is proposed to control constant thrust force on load variation. First, a structure and thrust force equations of the LPM are described. Second, an controller with PI parameter-tuning using a fuzzy theory is proposed to achieve high-precision position with constant thrust force of the LPM. Finally, the effectiveness of an fuzzy PI controller is demonstrated by some simulated and experimental results. Accurate tracking response and superior dynamic performance can be obtained due to the powerful on-line Fuzzy PI gain tuning method with regard parametric variations and load thrust force variations.

• 설비공학논문집
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• 제11권5호
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• pp.561-569
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• 1999

The effects of longitudinal heat conduction on the performance of heat transfer surfaces are investigated by using a single-blow method. In the transient testing method for determining the heat transfer characteristics, exponential inlet temperature variations are made by using screen-mesh heater with small time constant and low frontal velocities of the test section, and the experimentally determined inlet temperature profile is used as the inlet fluid temperature condition. The effects of longitudinal heat conduction are negligible only if $\gamma^\act<0.05\;and \;N_{tu}\le3$ and should be considered if $N_{tu}\le3$ The test results ate compared with the existing theoretical and experimental data and the validity of this technique is confirmed by the good agreement.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.971-976
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• 2001

Numerical studies were performed to investigate the seismic performance of Flat Plate System. For the numerical studies, a computer program for Finite Element analysis was developed. Parametric studies were performed to investigate variations of strength and ductility of flat plate with major parameters: gravity load, reinforcement ratio, thickness, column sizes. The numerical results provide a valuable insights on the behavior of flat plates. The comparison with the current design method shows that the current design methods for strength and ductility need to be improved in some aspects.

• Structural Engineering and Mechanics
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• 제6권5호
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• pp.543-554
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• 1998

Space truss structures may be fabricated in any of several common grid configurations. With different configurations, the truss performance varies considerably affecting both its competitiveness and suitability for specific applications. The work presented in this paper is an assessment of the most commonly adopted truss configurations and their effect on truss characteristics such as the stiffness/weight value, member stress distribution, number of joints and members, degree of redundancy and cost. The study is parametric and covers wide variations of truss aspect ratios, boundary conditions and span/depth ratios. The results of this study could be of significant value to the design of space truss structures.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.611-616
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• 2000

Numerical studies were carried out to investigate the long-term behavior of late plates in basement, subjected to combined in-plane compressive and transverse loads. For the numerical studies, a computer program of nonlinear finite element analysis was modified by adding function of creep and shrinkage analysis. This numerical method was verified by comparison with the existing experiments. Parametric studies were performed to investigate the strength variations of flat plates with three parameters; 1) loading sequence of floor load, compression and time 2) uniaxial an biaxial compression and 3) the ratio of dead to live load.

• 한국안전학회지
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• 제27권6호
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• pp.115-121
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• 2012

This paper, being the second in a two-part series, presents the robust performance of the proposed design method which can enhance a reliability-based design optimization(RBDO) under the uncertainties of probabilistic models. The robust performances of the solutions obtained by the proposed method, described in the Part 1, are investigated through the parametric studies. A 10-bar truss example is considered, and the uncertain parameters include the number of data observed, and the variations of applied loadings and allowable stresses. The numerical results show that the proposed method can produce a consistent result despite of the large variations in the parameters. Especially, even with the relatively small data set, the analysis results show that the exact probabilistic model can be successfully predicted with optimized design sections. This consistency of estimating appropriate probability model is also observed in the case of the variations of other parameters, which verifies the robustness of the proposed method.

• Steel and Composite Structures
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• 제21권1호
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• pp.217-247
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• 2016

Five extended cylindrical reticulated shells are proposed by changing distribution rule of diagonal rods based on three fundamental types. Modeling programs for fundamental types and extended types of cylindrical reticulated shell are compiled by using the ANSYS Parametric Design Language (APDL). On this basis, conditional formulas are derived when the grid shape of cylindrical reticulated shells is equilateral triangle. Internal force analysis of cylindrical reticulated shells is carried out. The variation and distribution regularities of maximum displacement and stress are studied. A shape optimization program is proposed by adopting the sequence two-stage algorithm (RDQA) in FORTRAN environment based on the characteristics of cylindrical reticulated shells and the ideas of discrete variable optimization design. Shape optimization is achieved by considering the objective function of the minimum total steel consumption, global and locality constraints. The shape optimization for three fundamental types and five extended types is calculated with the span of 30 m~80 m and rise-span ratio of 1/7~1/3. The variations of the total steel consumption along with the span and rise-span ratio are analyzed with contrast to the results of shape optimization. The optimal combination of main design parameters for five extended cylindrical reticulated shells is investigated. The total steel consumption affected by distribution rule of diagonal rods is discussed. The results show that: (1) Parametric modeling method is simple, efficient and practical, which can quickly generate different types of cylindrical reticulated shells. (2) The mechanical properties of five extended cylindrical reticulated shells are better than their fundamental types. (3) The total steel consumption of cylindrical reticulated shells is optimized to be the least when rise-span ratio is 1/6. (4) The extended type of three-way grid cylindrical reticulated shell should be preferentially adopted in practical engineering. (5) The grid shape of reticulated shells should be designed to equilateral triangle as much as possible because of its reasonable stress and the lowest total steel consumption.

• 전자공학회논문지
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• 제51권7호
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• pp.122-129
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• 2014

스마트 기기 시장의 눈부신 성장으로 핵심 SoC (System on Chip)에 대한 고성능 다기능 요구와 더불어 전력 소모 또한 급속도로 증가하고 있다. 그러나 이러한 요구 사항을 만족시키기 위해 점점 더 미세화된 공정을 사용하게 되면서 심화된 공정변이(process variation)문제로 인해 설계 마진(design margin)이 증가하여 성능과 전력소모를 악화시켜 궁극적으로 수율에 심각한 악영향을 주고 있다. Voltage binning 기법은 효과적인 post silicon tuning 기법중의 하나로, 개별 칩이 아닌 일정한 범위의 속도와 누설 전류에 따라 칩들을 선별 그룹핑한 bin 단위의 공급 전압 조절을 통해 경제적으로 공정 변이로 인한 parametric 수율 손실을 줄일 수 있다. 본 논문에서는 수율 손실 없이 추가적으로 평균 전력 소모를 개선하기 위한 voltage binning 기반의 최적화된 공급 전압 조절 방법을 제안한다. 제안한 기법은 칩 속도와 누설전류의 특성에 따른 공정 코너들의 서로 다른 LVCC (Low VCC) 마진을 고려하여 전압 마진의 편차를 최적화함으로써 전력 소모를 개선할 수 있다. 제안한 방식을 30나노급 모바일 SoC 제품에 적용한 결과 전통적인 voltage binning 방법 대비 동일조건에서 약 6.8%까지 평균 전력 소모를 줄일 수 있었다.