• Title/Summary/Keyword: Density design variable

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An Efficient Overlapped LDPC Decoder with a Upper Dual-diagonal Structure

  • Byun, Yong Ki;Park, Jong Kang;Kwon, Soongyu;Kim, Jong Tae
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.13 no.1
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    • pp.8-14
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    • 2013
  • A low density parity check (LDPC) decoder provides a most powerful error control capability for mobile communication devices and storage systems, due to its performance being close to Shannon's limit. In this paper, we introduce an efficient overlapped LDPC decoding algorithm using a upper dual-diagonal parity check matrix structure. By means of this algorithm, the LDPC decoder can concurrently execute parts of the check node update and variable node update in the sum-product algorithm. In this way, we can reduce the number of clock cycles per iteration as well as reduce the total latency. The proposed decoding structure offers a very simple control and is very flexible in terms of the variable bit length and variable code rate. The experiment results show that the proposed decoder can complete the decoding of codewords within 70% of the number of clock cycles required for a conventional non-overlapped decoder. The proposed design also reduces the power consumption by 33% when compared to the non-overlapped design.

Frequency-constrained polygonal topology optimization of functionally graded systems subject to dependent-pressure loads

  • Thanh T. Banh;Joowon Kang;Soomi Shin;Lee Dongkyu
    • Steel and Composite Structures
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    • v.51 no.4
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    • pp.363-375
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    • 2024
  • Within the optimization field, addressing the intricate posed by fluidic pressure loads on functionally graded structures with frequency-related designs is a kind of complex design challenges. This paper thus introduces an innovative density-based topology optimization strategy for frequency-constraint functionally graded structures incorporating Darcy's law and a drainage term. It ensures consistent treatment of design-dependent fluidic pressure loads to frequency-related structures that dynamically adjust their direction and location throughout the design evolution. The porosity of each finite element, coupled with its drainage term, is intricately linked to its density variable through a Heaviside function, ensuring a seamless transition between solid and void phases. A design-specific pressure field is established by employing Darcy's law, and the associated partial differential equation is solved using finite element analysis. Subsequently, this pressure field is utilized to ascertain consistent nodal loads, enabling an efficient evaluation of load sensitivities through the adjoint-variable method. Moreover, this novel approach incorporates load-dependent structures, frequency constraints, functionally graded material models, and polygonal meshes, expanding its applicability and flexibility to a broader range of engineering scenarios. The proposed methodology's effectiveness and robustness are demonstrated through numerical examples, including fluidic pressure-loaded frequency-constraint structures undergoing small deformations, where compliance is minimized for structures optimized within specified resource constraints.

3-D Topology Optimization by a Nodal Density Method Based on a SIMP Algorithm (SIMP 기반 절점밀도법에 의한 3 차원 위상최적화)

  • Kim, Cheol;Fang, Nan
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.412-417
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    • 2008
  • In a traditional topology optimization method, material properties are usually distributed by finite element density and visualized by a gray level image. The distribution method based on element density is adequate for a great mass of 2-D topology optimization problems. However, when it is used for 3-D topology optimization, it is always difficult to obtain a smooth model representation, and easily appears a virtualconnect phenomenon especially in a low-density domain. The 3-D structural topology optimization method has been developed using the node density instead of the element density that is based on SIMP (solid isotropic microstructure with penalization) algorithm. A computer code based on Matlab was written to validate the proposed method. When it was compared to the element density as design variable, this method could get a more uniform density distribution. To show the usefulness of this method, several typical examples of structure topology optimization are presented.

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Topology Optimization of a HDD Actuator Arm

  • Chang, Su-Young;Cho, Ji-Hyon;Youn, Sung-Kie;Kim, Cheol-Soon;Oh, Dong-Ho
    • Computational Structural Engineering : An International Journal
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    • v.1 no.2
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    • pp.89-96
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    • 2001
  • A study on the topology optimization of a Hard-Disk-Driver(HDD) actuator arm is presented. The purpose of the present wert is to increase the natural frequency of tole first lateral mode of the HDD actuator arm under the constraint of total moment of inertia, so as to facilitate the position control of the high speed actuator arm. The first lateral mode is an important factor in the position control process. Thus the topology optimization for 2-D model of the HDD actuator arm is considered. A new objective function corresponding to multieigenvalue optimization is suggested to improve the solution of the eigenvalue optimization problem. The material density of the structure is treated as the design variable and the intermediate density is penalized. The effects of different element types and material property functions on the final topology are studied. When the problem is discretized using 8-node element of a uniform density, tole smoothly-varying density field is obtained without checker-board patterns incurred. AS a result of 7he study, an improved design of the HDD actuator arm is suggested. Dynamic characteristics of the suggested design are compared computationally with those of the old design. With the same amount of the moment of inertia, the natural frequency of the first lateral mode of the suggested design is subsequently increased over the existing one.

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Topology Optimization of a HDD Actuator Arm (HDD 구동기 팔의 위상 최적화)

  • Chang, Su-Young;Youn, Sung-Kie;Kim, Cheol-Soon;Oh, Dong-Ho
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.7 s.178
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    • pp.1801-1809
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    • 2000
  • A study on the topology optimization of Hard-Disk-Driver(HDD) actuator arm in free vibration is presented. The purpose of this research is to increasse the natural frequency of the first lateral mode of the HDD actuator arm under the constraint of total moment of inertia, so as to facilitate the position control of high speed actuator am. The first lateral mode is an important factor in the position control process. Thus the topology optimization for 2-D model of the HDD actuator arm is considered. A new objective function corresponding to multieigenvalue optimization is suggested to improve the solution of the eigenvalue optimization problem. The material density of the structure is treated as the design variable and the intermediate density is penalized. The effects of different element types and material property functions on the final topology are studied. When the problem is discretized using 8-node element of a uniform density, the smoothly-varying density field is obtained without checker-board patterns incurred. As a result of the study an improved design of the HDD actuator arm is suggested. Dynamic characteristics of the suggested design are compared computationally with those of the old design. With the same amount of the moment of inertia, the natural frequency of the first lateral mode or the suggested design is subsequently increased over the existing one.

A Fundamental Study on the Development of Variable Preload Device Using Rubber Force (고무압을 이용한 가변예압장치 개발을 위한 기초 연구)

  • Choi, Chi-Hyuk;Kim, Dong-Hyeon;Lee, Choon-Man
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.4
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    • pp.416-421
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    • 2011
  • Recently there has been increase in need for high precision and high speed machining due to economic and environmental reasons. It is a very important issue that determines the optimal preload that is to be applied to bearings in order to satisfy the performance required in bearings according to its operation conditions. This study introduces a variable preload device that can automatically adjust the preload applied in a machine tool spindle using centrifugal force as opposed in existing rubber instrument. In this study, the deformation of the rubber device by the centrifugal force is analyzed and it is discussed that the proposed device can be worked properly through changes of the collar density.

Design of a Variable Inductor Using MR Fluid Gap for Wide Load Range Efficiency Improvement of a Soft-Switching High-Power Density Bidirectional Dc-Dc Converter

  • Ahmed, Furqan;Kim, Su-Han;Cha, Honnyong
    • Proceedings of the KIPE Conference
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    • 2013.07a
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    • pp.184-185
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    • 2013
  • In this paper, design of a variable inductor using MR Fluid Gap is proposed for wide load range efficiency improvement of a bidirectional DC-DC converter. As compared to conventional constant value inductor designed to have negative current for ZVS at heavy load but suffers high losses at light load due to its small inductance, the proposed variable inductor not only have small inductance at high current for ZVS but also it has large inductance at low current to decrease light load losses.

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Analysis of HTS Current Lead with Variable Area (단면적 변화를 가지는 고온초전도체 전류도입선 해석)

  • 문성수;설승윤
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2000.02a
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    • pp.22-25
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    • 2000
  • To improve the performance of high temperature superconducting current leads, variable cross-sectional area is considered. The cross-sectional area is varied as a function of current density to fix the safety factor along lead length. New integration method is devised to find optimum cross-sectional area distribution. New design of current lead has low heat leak into cryostat and less material than constant cross-sectional area leads. Conduction cooled lead is considered. The developed method is applied to Bi2223 current leads sheathed Ag-Au alloy.

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Topology Design Optimization of Nonlinear Thermoelasticity Problems (비선형 열탄성 연성 구조물에 대한 위상 최적설계)

  • 문세준;하윤도;조선호
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2004.10a
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    • pp.347-354
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    • 2004
  • Using an efficient adjoint variable method, we develop a unified design sensitivity analysis (DSA) method considering both steady state nonlinear heat conduction and geometrical nonlinear elasticity problems. Design sensitivity expressions with respect to thermal conductivity and Young's modulus are derived. Beside the temperature and displacement adjoint equations, another coupled one is defined regarding the obtained adjoint displacement field as the adjoint load in temperature field. The developed DSA method is shown to be very efficient and further extended to a topology design optimization method for the nonlinear weakly coupled thermo-elasticity problems using a density approach.

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Analysis of activation, ohmic, and concentration losses in hydrogen fuelled PEM fuel cell

  • Rohan Kumar;K.A Subramanian
    • Advances in Energy Research
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    • v.8 no.4
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    • pp.253-264
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    • 2022
  • This paper deals with the effects of design (active area, current density, membrane conductivity) and operating parameters (temperature, relative humidity) on the performance of hydrogen-fuelled proton exchange membrane (PEM) fuel cell. The design parameter of a PEM fuel cell with the active area of the single cell considered in this study is 25 cm2 (5 × 5). The operating voltage and current density of the fuel cell were 0.7 V and 0.5 A/cm2 respectively. The variations of activation voltage, ohmic voltage, and concentration voltage with respect to current density are analyzed in detail. The membrane conductivity with variable relative humidity is also analyzed. The results show that the maximum activation overpotential of the fuel cell was 0.4358 V at 0.21 A/cm2 due to slow reaction kinetics. The calculated ohmic and concentrated overpotential in the fuel cell was 0.01395 V at 0.76 A/cm2 and 0.027 V at 1.46 A/cm2 respectively.