• Title, Summary, Keyword: Decay Function

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Friction of a Brownian Particle in a Lennard-Jones Solvent: A Molecular Dynamics Simulation Study

  • Lee, Song-Hi
    • Bulletin of the Korean Chemical Society
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    • v.31 no.4
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    • pp.959-964
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    • 2010
  • In this work, equilibrium molecular dynamics (MD) simulations in a microcanonical ensemble are performed to evaluate the friction coefficient of a Brownian particle (BP) in a Lennard-Jones (LJ) solvent. The friction coefficients are determined from the time dependent friction coefficients and the momentum autocorrelation functions of the BP with its infinite mass at various ratios of LJ size parameters of the BP and solvent, ${\sigma}_B/{\sigma}_s$. The determination of the friction coefficients from the decay rates of the momentum autocorrelation functions and from the slopes of the time dependent friction coefficients is difficult due to the fast decay rates of the correlation functions in the momentum-conserved MD simulation and due to the scaling of the slope as 1/N (N: the number of the solvent particle), respectively. On the other hand, the friction coefficient can be determined correctly from the time dependent friction coefficient by measuring the extrapolation of its long time decay to t=0 and also from the decay rate of the momentum autocorrelation function, which is obtained by time integration of the time dependent friction coefficient. It is found that while the friction coefficient increases quadratically with the ratio of ${\sigma}_B/{\sigma}_s$ for all ${\sigma}_B$, for a given ${\sigma}_s$ the friction coefficient increases linearly with ${\sigma}_B$.

Photoluminescence Studies of InP/InGaP Quantum Structures Grown by a Migration Enhanced Molecular Beam Epitaxy

  • Cho, Il-Wook;Ryu, Mee-Yi;Song, Jin Dong
    • Applied Science and Convergence Technology
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    • v.25 no.4
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    • pp.81-84
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    • 2016
  • InP/InGaP quantum structures (QSs) grown on GaAs substrates by a migration-enhanced molecular beam epitaxy method were studied as a function of growth temperature (T) using photoluminescence (PL) and emission-wavelength-dependent time-resolved PL (TRPL). The growth T were varied from $440^{\circ}C$ to $520^{\circ}C$ for the formation of InP/InGaP QSs. As growth T increases from $440^{\circ}C$ to $520^{\circ}C$, the PL peak position is blue-shifted, the PL intensity increases except for the sample grown at $520^{\circ}C$, and the PL decay becomes fast at 10 K. Emission-wavelength-dependent TRPL results of all QS samples show that the decay times at 10 K are slightly changed, exhibiting the longest time around at the PL peak, while at high T, the decay times increase rapidly with increasing wavelength, indicating carrier relaxation from smaller QSs to larger QSs via wetting layer/barrier. InP/InGaP QS sample grown at $460^{\circ}C$ shows the strongest PL intensity at 300 K and the longest decay time at 10 K, signifying the optimum growth T of $460^{\circ}C$.

A Study on the Shear Behaviors of Geosynthetic-soil Interface in the Waste Landfill Site (폐기물 매립장 차수시설 접촉면 전단특성에 관한 연구)

  • Park, Inn-Joon;Kwak, Chang-Won;Park, Jum-Bum;Cho, Jun-Sik
    • Journal of the Korean Geotechnical Society
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    • v.28 no.3
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    • pp.45-54
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    • 2012
  • Various geosynthetics are widely applied to civil structures and waste landfill site for reinforcement and water resistance. The use of geosynthetics inevitably involves the coupled behaviors of different materials which include large displacement and strain-softening behaviors, etc. In this study, the effect of chemical element in the leachate on the interface shear strength under the cyclic loading condition was analyzed. The Multi-purpose Interface Apparatus (M-PIA) has been modified and cyclic direct shear tests have been performed. The submerging period of each specimen is 200 days. Additionally, the Field-Emission Scanning Electronic Microscopy (FIB) analysis has been also performed to induce the reason of the variation of disturbance function and verify the hypothesis on the decay-proof ability of geosynthetics. Consequently, the charateristics of chemical degradation of geosynthetic-soil interface are verified and the variation of the disturbance function is mainly caused by the different type of soil mineral decay, based on the FIB results.

Prediction of Axial Solid Holdups in a CFB Riser

  • Park, Sang-Soon;Chae, Ho-Jeong;Kim, Tae-Wan;Jeong, Kwang-Eun;Kim, Chul-Ung;Jeong, Soon-Yong;Lim, JongHun;Park, Young-Kwon;Lee, Dong Hyun
    • Korean Chemical Engineering Research
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    • v.56 no.6
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    • pp.878-883
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    • 2018
  • A circulating fluidized bed (CFB) has been used in various chemical industries because of good heat and mass transfer. In addition, the methanol to olefins (MTO) process requiring the CFB reactor has attracted a great deal of interest due to steep increase of oil price. To design a CFB reactor for MTO pilot process, therefore, we has examined the hydrodynamic properties of spherical catalysts with different particle size and developed a correlation equation to predict catalyst holdup in a riser of CFB reactor. The hydrodynamics of micro-spherical catalysts with average particle size of 53, 90 and 140 mm was evaluated in a $0.025m-ID{\times}4m-high$ CFB riser. We also developed a model described by a decay coefficient to predict solid hold-up distribution in the riser. The decay coefficient developed in this study could be expressed as a function of Froude number and dimensionless velocity ratio. This model could predict well the experimental data obtained from this work.

Inhibitory Effects of Natural Antimicrobial Agenton Postharvest Decay in Fruits and Vegetables under Natural Low Temperature (천연 항균제처리를 병용한 과채류의 자연 저온저장기술 개발에 관한 연구)

  • 조성환;정진환;류충호
    • Journal of the Korean Society of Food Science and Nutrition
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    • v.23 no.2
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    • pp.315-321
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    • 1994
  • In order to prevent the postharvest decay and to promote the freshness retention of fruits and vegetables grapefruit seed extract(GFSE), natural microorganism control agent, was applied to the preservation of fresh fruits and vegetables. Freshfruits and vegetables treated with GFSE and stored in polyethylene film (0.1mm) at 1$0^{\circ}C$-15$^{\circ}C$ of natural low temperature low kept better qualities in color and texture than the GFSE -not- treated control. The treatment using GFSE ina 250ppm to 500ppm concentration seemed to be an effective one for the control of Botrytis cinerea isolated in red wine grapes. After 4 weeks of storage the firmness rate of cucumbers treated with the dilute GFSE was four times higher than that of non-treated ones. GFSE showed effective inhibitory action towards plant pathological bacteria and fungi which were involved in the decay of fruits and vegetables. Minimum inhibitory concentrations of GFSE towards them were in the range of 250ppm to 500ppm .Direct visualization of microbial cells and spores using electron microscopy showed microbial cells and fungal spores the function of which was destroyed by treating with the dilute solutions of GFSE. It was observed that GFSE would reduced disease damages and have bactericide & fungicide properties during the storage of such fruits and vegetables as egg plant, wild edible greens , kumquat, and kiwi fruit.

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Development of 3-Dimensional Static Infinite Elements with Various Decay Characteristics for Tunnel Analysis (터널해석을 위한 다양한 감쇠특성의 3차원 정적무한요소 개발)

  • Koo, Hee-Dae;Koh, Hyun-Moo
    • Journal of The Korean Society of Civil Engineers
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    • v.26 no.3A
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    • pp.439-445
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    • 2006
  • Analysis problems of tunnels whose geometrical dimensions are very small compared with surrounding media can be treated as infinite region problems. In such cases, even if finite element models can be applied, excessive number of elements is required to obtain satisfactory accuracy. However, inaccurate results may be produced due to assumed artificial boundary conditions. To solve these problems, a hybrid model, which models the region of interest with finite elements and the surrounding infinite media with infinite elements, is introduced for the analysis of infinite region. Three-dimensional isoparametric infinite elements with various decay characteristics are formulated in this paper and the corresponding parameters are presented by means of parametric studies. Three-dimensional tunnel analysis performed on a representative example verifies the applicability of hybrid model using infinite elements.

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Photoisomerization of Symmetric Carbocyanines

  • 민형식;강유남;박정희
    • Bulletin of the Korean Chemical Society
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    • v.19 no.7
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    • pp.747-753
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    • 1998
  • The phoisomerization process of symmetric carbocyanine dyes such as 3,3'-diethyloxadicarbocyanine iodide (DODCI), 3,3'-diethylthiadicarbocyanine iodide (DfDCI), 1,1'-diethyl-2,2'-dicarbocyanine iodide (DDI), 1,1'-diethyl-2,2'-carbocyanine iodide (DCI), and cryptocyanine (1,1'-diethyl-4,4'-carbocyanine) iodide (CCI) have been studied by measuring the steady state and time resolved fluorescence spectra and the ground-state recovery profiles. The steady-state fluorescence spectrum of photoisomer as a function of concentration and excitation wavelength provides the evidence that the fluorescence of photoisomer is formed by the radiative energy transfer from the normal form and the quantum yield for the formation of photoisomer is increased by decreasing the excitation wavelength. The fluorescence decay profiles have been measured by using the time correlated single photon counting (TCSPC) technique, showing a strong dependence on the concentration and the detection wavelength, which is due to the formation of excited photoisomers produced either by the radiative energy transfer from the non-nal form or by absorbing the 590 nm laser pulse. We first report the fluorescence decay time of photoisomers for these cyanine dyes. The experimental results are explained by introducing the semiempirical calculations. The ground state recovery profiles of DTDCI, DDI, and CCI normal forms have been measured, showing that the recovery time from the singlet excited state is similar with the fluorescence decay time.

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Design of Inverse Optimal TS Fuzzy Controllers (역최적 TS 퍼지 제어기의 설계)

  • 임채환;곽기호;박주영
    • Proceedings of the Korean Institute of Intelligent Systems Conference
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    • pp.137-140
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    • 2001
  • In this paper, we design 75(Takagi-Sugeno) fuzzy controllers for the systems that can be represented by the 75 fuzzy model. We use inverse optimal approach in which the cost function is determined later than the Lyapunov function and its corresponding control input satisfying the design requirements such as stability and decay rate. The obtained design procedure is in the form of solving LMI(Linear Matrix Inequalities), thus very efficient in practice.

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Buyer's Price and Inventory Policy with Price Dependent Demand for Decaying Items Day terms Supplier Credit in a Two-stage Supply Chain

  • Shinn, Seong-Whan
    • International Journal of Advanced Culture Technology
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    • v.6 no.3
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    • pp.151-162
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    • 2018
  • In deriving the economic order quantity (EOQ) formula, it is tacitly assumed that the buyer has to pay product price while receiving the product from the supplier. However, as a marketing policy, some suppliers permit a delay in payments to the buyers to increase demand for the product they made. Credit transactions would have a positive effect on both suppliers and buyers. For a supplier who offers trade credit, it is an effective means of price differentiation to increase the demand for the product. Availability of opportunity to delay the payment in buyer effectively reduces the cost of holding stocks and therefore, the buyer has a lot of price options to choose his sales price for a customer. Since the buyer's order is affected by the customer's demand, the problems of determining the sales price and EOQ are interdependent and must be solved simultaneously. From this perspective, this paper evaluates the problem of determining the optimal sales price and EOQ for the buyer at the same time when the supplier allows a delay in payments for the product whose demand is represented as a function that decreases linearly with the sales price. For the analysis, it is also assumed that inventory is exhausted not only by customer's but also by decay.

Effects of 3D Compression Pants and Kinesio Taping on Isokinetic Muscular Function of Leg During Knee Joint Flexion Motion (3D 밀착형 팬츠와 키네시오 테이핑이 무릎관절의 등속성 굴곡 운동 시 하지의 근기능에 미치는 영향)

  • Choi, Jiyoung;Park, Heegeun;Lee, Wanglok;Hong, Kyunghi
    • Journal of the Korean Society of Clothing and Textiles
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    • v.40 no.2
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    • pp.240-257
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    • 2016
  • This study determines the effect of 3D compression pants and Kinesio taping on muscular function of the leg during knee joint flexion and extension. Eight males participated in the experiment, wearing basic pants (BP), Kinesio taping on bare skin (KT), 3D compression pants with (KTP) and without Kinesio taping (CP). The test protocol for isokinetic muscular function was composed of four sets at three angular velocities (60, 180, $240^{\circ}/sec$) using Cybex 660. Peak torque and work per repetition of the lower limbs of eight males were analyzed from the result of Cybex. Agility and power of the subjects were examined from side step and sergeant jump. Peak torque, average power, work per repetition, force decay time of subjects wearing CP and KTP were significantly better than BP or KT, especially at low angular velocity of $60^{\circ}/sec$. The time to generate peak torque of subjects wearing BP was the longest, while the force-decay time of BP was the shortest. The application of Kinesio tape on skin did not increase muscle peak torque, work and power, but did shorten the time to generate peak torque.