• Title, Summary, Keyword: Saturation Factor

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An Analytical DC Model for HEMT's (헴트 소자의 해석적 직류 모델)

  • Kim, Young-Min
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.26 no.6
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    • pp.38-47
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    • 1989
  • A purely analytical model for HEMT's based on a two dimensional charge control simul-ation[4] is proposed. In this model proper treatment of diffusion effect of electron transport along a 2-DEG (two dimensional electron gas) channel is perfoemed. This diffusion effect is shown to effectively increase the bulk mibility and threshold voltage of the I-V curves compared to the existing models. The channel thickness and gate capacitance are expressed as functions of gate voltages covering subthreshold characteristics of HEMT's analytically. By introducing the finite channel opening and an effiective channel-length modulation, the solpe of the saturation region of the I-V curves ws modeled. The smooth transition of the I-V curves at linear-to-saturation regions of the I-V curves was possible using the continuous Troffimenkoff-type of field dependent mobility. Furthermore, a correction factor f was introduced to account for the finite transition section forming between a GCA and a saturated section. This factor removes large discrepancies in the saturation region of the I-V curve predicted by existing l-dimensional models.

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Modified Ammonia Removal Model Based on Equilibrium and Mass Transfer Principles

  • Shanableh, A.;Imteaz, M.
    • Bulletin of the Korean Chemical Society
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    • v.31 no.7
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    • pp.1920-1926
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    • 2010
  • Yoon et $al.^1$ presented an approximate mathmatical model to describe ammonia removal from an experimental batch reactor system with gaseous headspace. The development of the model was initially based on assuming instantaneous equilibrium between ammonia in the aqueous and gas phases. In the model, a "saturation factor, $\beta$" was defined as a constant and used to check whether the equilibrium assumption was appropriate. The authors used the trends established by the estimated $\beta$ values to conclude that the equilibrium assumption was not valid. The authors presented valuable experimental results obtained using a carefully designed system and the model used to analyze the results accounted for the following effects: speciation of ammonia between $NH_3$ and $NH^+_4$ as a function of pH; temperature dependence of the reactions constants; and air flow rate. In this article, an alternative model based on the exact solution of the governing mass-balance differential equations was developed and used to describe ammonia removal without relying on the use of the saturation factor. The modified model was also extended to mathematically describe the pH dependence of the ammonia removal rate, in addition to accounting for the speciation of ammonia, temperature dependence of reactions constants, and air flow rate. The modified model was used to extend the analysis of the original experimental data presented by Yoon et $al.^1$ and the results matched the theory in an excellent manner.

The Modeling of ISL(Intergrated Schottky Logic) Characteristics by Computer Simulations (컴퓨터 시뮬레이션에 의한 ISL 특성의 모델링)

  • 김태석
    • Journal of Korea Multimedia Society
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    • v.3 no.5
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    • pp.535-541
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    • 2000
  • In this paper, we analyzed the characteristics of schottky junction to develop the voltage swing of ISL, and simulated the characteristics with the programs at this junctions. Simulation programs for analytic characteristics are the SUPREM V, SPICE, Medichi, Matlab. The schottky junction is rectifier contact between platinum silicide and silicon, the characteristics with programs has simulated the same conditions. The analytic parameters were the turn-on voltage, saturation current, ideality factor in forward bias, and has shown the results of breakdown voltage between actual characteristics and simulation characteristics in reverse bias. As a result, th forward turn-on voltage, reverse breakdown voltage, barrier height were decreased but saturation current and ideality factor were increased by substrates increased concentration variations.

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The Results Comparison of Measurement and Simulations in ISL(Integrated Schottky Logic) Gate (ISL 게이트에서 측정과 시뮬레이션의 결과 비교)

  • 이용재
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.5 no.1
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    • pp.157-165
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    • 2001
  • We analyzed the electrical characteristics of platinum silicide schottky junction to develope the voltage swing in Integrated Schottky Logic gates, and simulated the characteristics with the programs in this junctions. Simulation programs for analytic characteristics are the Medichi tool for device structure, Matlab for modeling and SUPREM V for fabrication process. The silicide junctions consist of PtSi and variable silicon substrate concentrations in ISL gates. Input parameters for simulation characteristics were the same conditions as process steps of the device farications process. The analitic electrical characteristics were the turn-on voltage, saturation current, ideality factor in forward bias, and has shown the results of breakdown voltage between actual characteristics and simulation characteristics in reverse bias. As a result, the forward turn-on voltage, reverse breakdown voltage, barrier height were decreased but saturation current and ideality factor were increased by substrates increased concentration variations.

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Parameter Analysis of Platinum Silicide Rectifier Junctions acceding to measurement Temperature Variations (측정 온도 변화에 따른 백금실리사이드 정류성 접합의 파라미터 분석)

  • 장창덕;이용재
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • pp.405-408
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    • 1998
  • In this paper, We analyzed the current-voltage characteristics with n-type silicon substrates concentration and temperature variations (Room temperature, 5$0^{\circ}C$, 75$^{\circ}C$) in platinum silicide and silicon junction. Measurement electrical parameters are forward turn-on voltage, reverse breakdown voltage, barrier height, saturation current, ideality factor, dynamic resistance acceding to junction concentration of substrates and temperature variations. As a result, the forward turn-on voltage, reverse breakdown voltage, barrier height and dynamic resistance were decreased but saturation current and ideality factor were increased by substrates concentration variations. Reverse breakdown voltage and dynamic resistance were increased by temperature variations.

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Characterization of gas-water flow in tight sandstone based on authentic sandstone micro-model

  • Liu, Yuqiao;Lyu, Qiqi;Luo, Shunshe
    • Geosystem Engineering
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    • v.21 no.6
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    • pp.318-325
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    • 2018
  • Eight tight sandstone reservoir samples from $He_8$ and $Shan_1$ Formations of the Sulige Gas field were selected to perform gas-water micro-displacement experiment based on authentic sandstone micro-model. The gas pressure-relief experiment was proposed for the first time to simulate the pressure change and gas-water percolation characteristics in the process of gas exploitation. The experiment results show that: (1) In the process of gas accumulation, the gas preferentially flows into the well-connected pores and throats with large radius, but rarely flows into the area without pores and throats. (2) Under sufficient gas drive, the water in pores and throats usually exists in the forms of 'thin water film', 'thick water film', and 'water column', but under insufficient gas drive, gas fails to flow into new pathways in time, so that the reservoirs with large pores and throats are high in water cut. (3) Under the same water saturation, the reservoirs with better petrophysical properties has higher gas recovery factor within unit time. Under the same petrophysical conditions, the reservoirs with lower water saturation show higher gas recovery factor within unit time. The higher the permeability, the stronger the liquid carrying capacity of reservoirs.

THE TEMPERATURE DEPENDENCE OF THE MAGNETIZATION OF THE AMORPHOUS $Co_{80+x}TM_{12}B_{8-x}$ (TM = Ti, Zr, Hf, Nb) ALLOYS

  • Han, Seung-Man;Yu, Seong-Cho;Kim, Kwang-Youn;Noh, Tae-Hwan;Kim, Hi-Jung
    • Journal of the Korean Magnetics Society
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    • v.5 no.5
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    • pp.496-499
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    • 1995
  • Amorphous $Co_{80+x}TM_{12}B_{8-x}$ (TM = Ti, Zr, Hf, Nb and x = 0, 2, 4 at%) alloys were prepared by single roll melt spinning technique. Saturation magnetization of the amorphous ribbons was measured by SQUID and vibrating sample magnetometer from 5 to 800 K under applied fields up to 10 kOe. Typical thermo-magnetization curves were observed and the average values of the spectroscopic splitting g factor were estimated from the ferromagnetic resonance curve. For all the amorphous alloys studied here the saturation magnetization in the temperature range 5 K up to about $0.3T_{c}$ can be described by the Bloch relation: $M_{s}(T)\;=\;M_{s}(0)(1-BT^{3/2}-CT^{5/2})$. From the values of $M_{s}(0)$, B and spectroscopic splitting g factor the spin wave stiffness constants were calculated.

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Cell morphology of microcellular foaming injection molding products with pressure drop rate (초미세 발포 사출 시 핵 생성장치를 이용한 셀 크기의 변화)

  • 김학빈;차성운
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.491-495
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    • 2004
  • The industries use polymer materials for many purposes for they have many merits. The costs of these materials take up too great a proportion of the overall cost of products that use these materials as their major material. It is advantage for polymer industries to reduce these costs. The microcellular foaming process was developed in the early 1980s to solve this problem and proved to be quite successful. Microcellular foaming process uses inert gases such as $CO_2$, $N_2$. As these gases solve into polymer matrices, many properties are changed. The microcellular foaming process makes the glass transition temperature of polymers to low, and diminish the residual stress of polymer matrices. Besides, the microcellular foaming process has several merits, impact strength elevation, thermal insulation, noise insulation, and raw material saving etc. This characteristic of microcellular foaming process has influenced by cell morphology. The cell morphology means cell size and cell density. The cell morphology has influenced by many factors. The examples of factor are pressure drop rate, foaming temperature, foaming time, saturation pressure, saturation time etc. Among their factors, pressure drop rate is the most important factor for cell morphology in microcellular foaming injection molding process. This paper describes about the cell morphology change in accordance with the pressure drop rate of microcellular foaming injection molding process.

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Effects of Open or Closed Suctioning on Lung Dynamics and Hypoxemia in Mechanically Ventilated Patients (기관 내 흡인 유형이 인공호흡기 대상자의 폐기능과 저산소혈증에 미치는 효과)

  • Lee, Eun Young;Kim, Su Hyun
    • Journal of Korean Academy of Nursing
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    • v.44 no.2
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    • pp.149-158
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    • 2014
  • Purpose: This study was conducted to compare effects of open and closed suctioning methods on lung dynamics (dynamic compliance, tidal volume, and airway resistance) and hypoxemia (oxygen saturation and heart rate) in mechanically ventilated patients. Methods: This study was a cross-over repeated design. Participants were 21 adult patients being treated with endotracheal intubation using a pressure-controlled ventilator below Fraction of Inspired Oxygen ($FiO_2$) 60% and PEEP $8cmH_2O$. Data were collected at baseline and 1, 2, 3, 4, 5, and 10 minutes after suctioning. Data were analyzed using two-factor ANOVA with repeated measures on time and suctioning type. Results: Effects of the interaction between suction type and time were significant for oxygen saturation and heart rate but not significant for dynamic compliance, tidal volume, or airway resistance. Prior to performance of suctioning, tidal volume and oxygen saturation were significantly lower, but airway pressure and heart rate were significantly higher using the closed suctioning method as compared with the open suctioning method. Conclusion: For patients on ventilator therapy below $FiO_2$ 60% and PEEP $8cmH_2O$, open suctioning performed after delivery of 100% $FiO_2$ using a mechanical ventilator may not have as much negative impact on lung dynamics and hypoxemia as closed suctioning.

Suggestion of the Modified Archie's Formula for Calculating Water Saturation of Clean Sandstone and Carbonate Rocks (청결 사암 및 탄산염암의 물 포화도 산출을 위한 수정 Archie 경험식의 제안)

  • Lee, Sang-Hee;Ko, Eun-Ji;Kim, Jin-Hoo
    • Geophysics and Geophysical Exploration
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    • v.18 no.3
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    • pp.125-132
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    • 2015
  • The water saturation ($S_w$), which is very important to estimate hydrocarbon reserves in the reservoir, has been determined from resistivity index (RI) by using the Archie's formula. However, in many cases, it has been reported that n is not constant for a given formation and it could be varied with water saturation. In addition, it frequently happens that the line obtained by linear regression analysis on log-log scale does not pass through the origin. In order to overcome these drawbacks, we suggested a modified Archie's formula, which can handle almost all the RI vs. $S_w$ cross-plots whether the trend is straight or curved and whether it passes through the origin or not. We also demonstrated that how to determine conductivity exponent ${\mu}$, critical water saturation $S_c$, and saturation distribution factor b in the laboratory to use the modified Archie's formula. Since the modified Archie's formula takes into account pore structure, pore water distribution, and wettability of reservoir such as clean sandstone and carbonate rocks, it might improve field applicability.