• Title, Summary, Keyword: dissipation

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Numerical simulation of electrokinetic dissipation caused by elastic waves in reservoir rocks

  • Zhang, Xiaoqian;Wang, Qifei;Li, Chengwu;Sun, Xiaoqi;Yan, Zheng;Nie, Yao
    • Geomechanics and Engineering
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    • v.19 no.1
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    • pp.11-20
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    • 2019
  • The use of electrokinetic dissipation method to study the fluid flow law in micro-pores is of great significance to reservoir rock microfluidics. In this paper, the micro-capillary theory was combined with the coupling model of the seepage field and the current field under the excitation of the harmonic signal, and the coupling theory of the electrokinetic effect under the first-order approximation condition was derived. The dissipation equation of electrokinetic dissipation and viscous resistance dissipation and its solution were established by using Green's function method. The physical and mathematical models for the electrokinetic dissipation of reservoir rocks were constructed. The microscopic mechanism of the electrokinetic dissipation of reservoir rock were theoretically clarified. The influencing factors of the electrokinetic dissipation frequency of the reservoir rock were analyzed quantitatively. The results show that the electrokinetic effect transforms the fluid flow profile in the pores of the reservoir from parabolic to wavy; under low-frequency conditions, the apparent viscosity coefficient is greater that one and is basically unchanged. The apparent viscosity coefficient gradually approaches 1 as the frequency increases further. The viscous resistance dissipation is two orders of magnitude higher than the electrokinetic effect dissipation. When the concentration of the electrolyte exceeds 0.1mol/L, the electrokinetic dissipation can be neglected, while for the electrolyte solution (<$10^{-2}M$) in low concentration, the electrokinetic dissipation is very significant and cannot be ignored.

A Modeling of CMOS Inverter for Maximum Power Dissipation Prediction (CMOS 인버터의 최대 전력소모 예측을 위한 모델링)

  • 정영권;김동욱
    • Proceedings of the IEEK Conference
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    • pp.1057-1060
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    • 1998
  • Power Dissipation and circuit speed become the most importance parameters in VLSI system maximum power dissipation for VLSI system design. We remodeled CMOS inverter according to the operating region, saturation region or linear regin, and calculate maximum power dissipation point of CMOS inverter. The result of proposed maximum power dissipation model compared with those from SPICE simulation which results that the proposed maximum power dissipation model has the error rate within 10% to SPICE simulation.

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Dissipation Pattern of Excess Pore Pressure after Liquefaction in Saturated Sand Deposits (포화된 모래지반의 액상화후 과잉간극수압 소산양상)

  • 하익수;박영호;김명모
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.90-97
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    • 2003
  • The purpose of this study is to understand the dissipation pattern of excess pore pressure after liquefaction which governs the post-liquefaction behavior of liquefied sand deposits. 1-g shaking table tests were carried out on 5 different kinds of sands, all of which had high liquefaction potentials. During the tests excess pore pressure at various depths, and surface settlements were measured. The measured curve of the excess pore pressure dissipation was simulated using the solidification theory, and from the analysis of the velocity of dissipation, the dissipation pattern of excess pore pressure after liquefaction was examined. The dissipation velocity of excess pore pressure after liquefaction had a linear correlation with the effective grain size ( $D_{10}$) divided by the coefficient of uniformity ( $C_{u}$), and the increase in the initial relative density of the ground played a role in shifting this correlation curve toward an increased dissipation velocity. From the correlation, an approximate method was recommended for prediction of the dissipation curve of excess pore pressure after liquefaction in saturated sand deposits.s.s.

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Investigation on energy dissipation and its mechanism of coal under dynamic loads

  • Feng, Junjun;Wang, Enyuan;Shen, Rongxi;Chen, Liang;Li, Xuelong;Xu, Zhaoyong
    • Geomechanics and Engineering
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    • v.11 no.5
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    • pp.657-670
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    • 2016
  • The energy dissipation of coal under dynamic loads is a major issue in geomechanics and arising extensive concerns recently. In this study, dynamic loading tests of coal were conducted using a split Hopkinson pressure bar (SHPB) system, the characteristics of dynamic behavior and energy dissipation of coal were analyzed, and the mechanism of energy dissipation was discussed based on the fracture processes of coal under dynamic loads. Experimental results indicate that the energy dissipation of coal under dynamic loads has a positive linear correlation with both incident energy and dynamic compressive strength, and the correlation coefficients between incident energy, dynamic compressive strength and the energy dissipation rate are 0.74 and 0.98, respectively. Theoretical analysis demonstrates that higher level of stress leads to greater energy released during unstable crack propagation, thus resulting in larger energy dissipation rate of coal under dynamic loads. At last, a semi-empirical energy dissipation model is proposed for describing the positive relationship between dissipated energy and stress.

A New Resource Allocation Algorithm of Functional Units to Minimize Power Dissipation (전력소비 최소화를 위한 새로운 펑션유닛의 자원 할당 알고리듬)

  • Lin, Chi-Ho
    • Journal of IKEEE
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    • v.8 no.2
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    • pp.181-185
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    • 2004
  • This paper reduces power dissipation with the minimum switching activity of functional units that have many operators. Therefore, it has more effects of power dissipation that operator dissipation to reduce power dissipation of whole circuit preferentially. This paper proposes an algorithm that minimize power dissipation in functional units operations that affect much as power dissipation in VLSI circuit. The algorithm has scheduled operands using power library that has information of all operands. The power library upgrades information of input data in each control step about all inputs of functional units and the information is used at scheduling process. Therefore, the power dissipation is minimized by functional units inputs in optimized data. This paper has applied algorithm that proposed for minimizing power dissipation to functional unit in high level synthesis. The result of experiment has effect of maximum 9.4 % for minimizing power dissipation.

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Experimental Investigation of Scalar Dissipation Rates in Lean Hydrocarbon/Air Premixed Flames

  • Chen, Yung-Cheng;Bilger, Robert W.
    • Journal of the Korean Society of Combustion
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    • v.6 no.2
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    • pp.43-49
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    • 2001
  • Instantaneous, three-dimensional scalar dissipation rates of the reaction progress variable are measured in turbulent premixed Bunsen flames of lean hydrocarbon/air mixtures with the two-sheet, two-dimensional Rayleigh scattering technique. The flames investigated are located in the turbulent flame-front regime on a newly proposed combustion diagram for premixed flames. The conditionally-averaged mean scalar dissipation rates, $N_{\zeta}$ are found to be lower than the calculated laminar values, indicating a locally broadened flame front. In agreement with previous measurements, the maximum of $N_{\zeta}$, decreases strongly with increasing Karlovitz numbers. The conditional probability density functions are close to a log-normal distribution for scalar dissipation rates conditioned at the progress variable value where the scalar dissipation is maximum in unstretched laminar flame calculations. The time scale for the Favre-averaged mean scalar dissipation rate decreases in general across the turbulent flame brush from the unburnt to burnt side.

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Flexural Pinching and Energy Dissipation Capacity (휨핀칭과 에너지 소산능력)

  • 박흥근;엄태성
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.275-285
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    • 2003
  • Pinching is an important property of reinforced concrete member which characterizes its cyclic behavior. In the present study, numerical studies were performed to investigate the characteristics and mechanisms of pinching behavior and the energy dissipation capacity of flexure-dominated reinforced concrete members. By analyzing existing experimental studies and numerical results, it was found that energy dissipation capacity of a member is directly related to energy dissipated by re-bars rather than concrete that is a brittle material, and that it is not related to magnitude of axial compressive force applied to the member. Therefore, for a member with specific arrangement and amount of re-bars, the energy dissipation capacity remains uniform regardless of the flexural strength that is changed by the magnitude of axial force applied. Due to the uniformness of energy dissipation capacity pinching appears in axial compression member. The flexural pinching that is not related to shear force becomes conspicuous as the flexural strength increases relatively to the uniform energy dissipation capacity. Based on the findings, a practical method for estimating energy dissipation capacity and damping modification factor was developed and verified with existing experiments.

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Numerical Analysis of Hydrodynamic Performance of a Movable Submerged Breakwater Using Energy Dissipation Model (에너지 소산 모델을 이용한 잠수된 가동식 방파제의 유체동역학적 성능 수치해석)

  • Kim, Do-Hyun;Koo, Weon-Cheol
    • Journal of the Society of Naval Architects of Korea
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    • v.49 no.4
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    • pp.287-295
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    • 2012
  • Hydrodynamic performance of a movable submerged breakwater was analyzed using energy dissipation model. Based on two-dimensional boundary element method the equation of motion including a viscous dissipation term proportional to velocity squared was solved by Newton-Raphson method. Energy dissipation coefficients as well as reflection and transmission coefficients of a submerged flat plate were calculated with various plate lengths and thickness. Both real and imaginary components of body displacement and forces were used to solve the motion of breakwater accurately. The effect of the magnitude of dissipation coefficient on the body displacement was evaluated. The results from the potential theory with no dissipation term were found to be an overestimate in resonance frequency.

Evaluation of Similitude Laws for Dissipation Velocity of Excess Pore Pressure after Liquefaction using Impulse Load Tests (충격하중시험을 이용한 액상화 후 과잉간극수압 소산속도의 상사비 연구)

  • Kim, Dong-Hwi;Ha, Ik-Soo;Hwang, Jae-Ik;Kim, Myoung-Mo
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.714-721
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    • 2004
  • The purpose of this study is to find out the similitude laws for dissipation velocity of excess pore pressure after liquefaction according to magnitude of input accelerations and height of model soils from the results of impulse load tests. In impulse load tests, model soils were constructed to the height of 25cm, 50cm, and 100cm in acrylic tubes whose inside diameters were 19cm and 38cm respectively, and impulse loads were applied at the bottom of each model soil to liquefy the entire model soil. Excess pore pressure distribution by depth and settlement of soil surface were measured in each test. Dissipation curves of excess pore pressure measured in each tests were simulated by solidification theory, and dissipation velocities of excess pore pressure were determined from the slope of simulated dissipation curves. From the results of impulse load tests, dissipation velocity of excess pore pressure was not affected by magnitude of input acceleration, and from this fact, dissipation process was proved to be different from dynamic phenomenon. However, dissipation velocity of excess pore pressure increased as height of model soil increased and showed little difference as diameter of model soil increased. Therefore, the similitude law for dissipation velocity could be expressed by the similitude law for model height to 0.2 without regard to the diameter of model soil.

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Development and Its Characteristics of a Dissipation Factor Standard (손실계수 표준기 제작 및 그 특성)

  • Kim, Han-Jun;Kang, Jeon-Hong;Han, Sang-Ok
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.527-528
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    • 2006
  • A dissipation factor standard of decade type having the range of 1 to 0.0001 at the frequency of 1 kHz and 10 kHz was fabricated using "T" networks combined R and C components. The values of the fabricated dissipation factor standard were adjusted within 1% of the nominal values at 0.0001 dial range and 0.05% at the others. This dissipation factor standard is used as a working standard for calibration of a impedance measurement meter at KRISS and as a primary standard of dissipation factor field at NML-SIRIM in Malaysia.

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