• Title/Summary/Keyword: Nonlinear Characteristics

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Suggestion of Modified Compression Index for secondary consolidation using by Nonlinear Elasto Viscoplastic Models (비선형 점탄소성 모델을 이용한 2차압밀이 포함된 수정압축지수개발)

  • Choi, Bu-Sung;Im, Jong-Chul;Kwon, Jung-Keun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.10a
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    • pp.1115-1123
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    • 2008
  • When constructing projects such as road embankments, bridge approaches, dikes or buildings on soft, compressible soils, significant settlements may occur due to the consolidation of these soils under the superimposed loads. The compressibility of the soil skeleton of a soft clay is influenced by such factors as structure and fabric, stress path, temperature and loading rate. Although it is possible to determine appropriate relations and the corresponding material parameters in the laboratory, it is well known that sample disturbance due to stress release, temperature change and moisture content change can have a profound effect on the compressibility of a clay. The early research of Tezaghi and Casagrande has had a lasting influence on our interpretation of consolidation data. The 24 hour, incremental load, oedometer test has become, more or less, the standard procedure for determining the one-dimensional, stress-strain behavior of clays. An important notion relates to the interpretation of the data is the ore-consolidation pressure ${\sigma}_p$, which is located approximately at the break in the slope on the curve. From a practical point of view, this pressure is usually viewed as corresponding to the maximum past effective stress supported by the soil. Researchers have shown, however, that the value of ${\sigma}_p$ depends on the test procedure. furthermore, owing to sampling disturbance, the results of the laboratory consolidation test must be corrected to better capture the in-situ compressibility characteristics. The corrections apply, strictly speaking, to soils where the relation between strain and effective stress is time independent. An important assumption in Terzaghi's one-dimensional theory of consolidation is that the soil skeleton behaves elastically. On the other hand, Buisman recognized that creep deformations in settlement analysis can be important. this has led to extensions to Terzaghi's theory by various investigators, including the applicant and coworkers. The main object of this study is to suggestion the modified compression index value to predict settlements by back calculating the $C_c$ from different numerical models, which are giving best prediction settlements for multi layers including very thick soft clay.

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Separation Characteristics of Mandelic Acid in Kromasil HPLC Column (Kromasil HPLC 칼럼에서 Mandelic Acid의 분리특성)

  • Kim, Byung Lip;Kim, Jong Min;Kim, Woo Sik;Kim, In Ho
    • Korean Chemical Engineering Research
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    • v.46 no.4
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    • pp.681-685
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    • 2008
  • Chiral separation of racemic mandelic acid was achieved on a Kromasil KR100-5CHI-TBB column. Some chromatographic parameters (resolution, number of theoretical plates, capacity factor) are calculated under different separation conditions such as changes of mobile phase compositions (hexane/t-BME = 85/15 - 10/90) as well as formic acid concentrations for adjusting pH (0.1, 0.5, 1.0 v/v%). Flow rate versus number of theoretical plates was compared to evaluate column efficiency. To determine the adsorption isotherms, PIM (Pulse Input Method) was carried out. At the concentrations of racemic mandelic acid between 0.1 and 0.3 mg/ml, L- and D-mandelic acids have the same retention times of 8.8 and 9.4 min respectively. Mandelic acid isotherms show a linear form under the concentrations of 0.3 mg/ml with eluent (hexane/t-BME = 75/25). As the concentrations of mandelic acids increase, nonlinear Langmuir isotherms were observed as $C_{S,L}=3.358C_{M,L}/(1+0.0897C_{M,L})$ for L-mandelic acid and, $C_{S,D}=3.692C_{M,D}/(1+0.1457C_{M,D})$ for D-mandelic acid.

The Design of Predistortion Linearizer with Polar Function Generator for Cellular Band Using Even Order Harmonic Signals (2차 고조파 신호를 이용한 극 함수 발생기를 갖는 셀룰라 밴드용 전치 왜곡 선형화기 설계)

  • Kim, Ell-Kou;Jeon, Ki-Kyoung;Kim, Young;Kwon, Sang-Keun;Yoon, Young-Chul
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.17 no.11 s.114
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    • pp.1050-1057
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    • 2006
  • This paper proposes a new predistortion linearizer with amplitude modulator and PFG(Polar Function Generator) using second order harmonic signals. This linearizer consists of PFG that combine with in-phase and quadrature-phase of second harmonic signals and amplitude modulator in main path. The predistorted third order intermodulation distortion(IMD3) signals that are generated by amplitude modulator with fundamental and PFG signals, improve a amplifier nonlinear characteristics. The proposed linearizer and amplifier have been manufactured and tested to operate in cellular base-station transmitting band$(869\sim894MHz)$. The test results show that IMD3 can be removed by more than 22.5 dB in case of CW 2-tone signals ${\Delta}f=1$ MHz, and the adjacent channel power ratio(ACPR) also can be improved by more than 8.4 dB for CDMA IS-95 1FA signals.

Wideband Class-J Power Amplifier Design Using Internal Matched GaN HEMT (내부정합된 GaN HMET를 이용한 광대역 J-급 전력증폭기 설계)

  • Lim, Eun-Jae;Yoo, Chan-Se;Kim, Do-Gueong;Sun, Jung-Gyu;Yoon, Dong-Hwan;Yoon, Seok-Hui;Rhee, Young-Chul
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.28 no.2
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    • pp.105-112
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    • 2017
  • In order to satisfy the diffusion of multimedia service in mobile communication and the demand for high-speed communication, it is essential to modify and improve high efficiency, wideband and nonlinear characteristic of multiband power amplifier. This research is designed to implement a single-stub matching circuit as a 2nd harmonic one that meets conditions of the Class-J power amplifier. Low characteristic impedance of the single-stub line is necessary to suit conditions of wideband Class-J. This research uses ceramic substrates having high permittivity to implement the single-stub line with low characteristic impedance, which eventually results in an amplifier satisfying the output impedance terms of Class-J in wideband frequency range. This result attributes to use of GaN HEMT packaged with a 2nd harmonic matching circuit and external fundamental circuit. The measurement results of the Class-J amplifier confirms the following characteristics: more than output power of 50 W(47 dBm) in bandwidth of 1.8~2.7 GHz(0.9GHz), maximum drain efficiency of 72.6 %, and maximum PAE characteristic of 66.5 %.

Evaluation of Accuracy of Modified Equivalent Linear Method (수정된 등가선형해석기법의 정확성 평가)

  • Jeong, Chang-Gyun;Kwak, Dong-Yeop;Park, Duhee;Kim, Kwangkyun
    • Journal of the Korean GEO-environmental Society
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    • v.11 no.6
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    • pp.5-20
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    • 2010
  • One-dimensional equivalent linear site response analysis is widely used in practice due to its simplicity, requiring only few input parameters, and low computational cost. The main limitation of the procedure is that it is essentially a linear method, in which the time dependent change in the soil properties cannot be modeled and constant values of shear modulus and damping is used throughout the duration of the analysis. Various forms of modified equivalent linear analyses have been developed to enhance the accuracy of the equivalent linear method by incorporating the dependence of the shear strain with the loading frequency. The methods are identical in that it uses the shear strain Fourier spectrum as the backbone of the analysis, but differ in the method in which the strain Fourier spectrum is smoothed. This study used two domestically measured soil profiles to perform a series of nonlinear, equivalent linear, and modified equivalent linear site response analyses to verify the accuracy of two modified procedures. The results of the analyses indicate that the modified equivalent linear analysis can highly overestimate the amplification of the high frequency components of the ground motion. The degree of overestimation is dependent on the characteristics of the input ground motion. Use of a motion rich in high frequency contents can result in unrealistic response.

Flow sensor using stress-balanced membrane and thin film thermocouple (스트레스균형이 이루어진 멤버레인 및 박막 열전대를 응용한 유체센서)

  • Ahn, Yeong-Bae;Kim, Jin-Sup;Kim, Myung-Gyoo;Lee, Jong-Hyun;Lee, Jung-Hee
    • Journal of Sensor Science and Technology
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    • v.5 no.6
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    • pp.51-59
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    • 1996
  • A flow sensor has been fabricated by preparing thin film Pt-heater and Bi-Sb thermocouples array on 150 nm-$Si_{3}N_{4}$/300 nm-$SiO_{2}$/150 nm-$Si_{3}N_{4}$ dielectric diaphragm which has low thermal conductivity and balanced stress with silicon substrate for the purpose of improving the thermal isolation between heater and silicon substrate. Pt-heater showed nonlinear I-V characteristics due to the thermal isolation effect of the diaphragm. Its temperature coefficient of resistance was about $0.00378\;/^{\circ}C$ and Seebeck coefficient of Bi-Sb thermocouple was about $97\;{\mu}V/K$. The sensor showed that thermoelectric voltage decreased as thermal conductivity of gas increased, and flow sensitivity increased as heater voltage increased or as the distance between heater and thermocouple decreased. When heater voltage was about 2.5 V, $N_{2}$-flow sensitivity and thermal response time of the sensor were about $1.27\;mV{\cdot}(sccm)^{-1/2}$ and 0.13 sec., respectively.

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A Study on 3[kW] PMA-RSG Optimal Design for Mobile Power Supply (이동형 전원장치용 3[kW] PMA-RSG의 최적 설계에 대한 연구)

  • Baik, Jei-Hoon;Toliyat, Hamid A.;Kim, Nam-Hun
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.23 no.6
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    • pp.109-117
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    • 2009
  • In this paper, an analytical model using equivalent magnetic circuits for the PMA-SynRG is presented. The lumped parameter model (LPM) is developed from machine geometry, stator winding and machine operating specifications. By the LPM, magnetic saturation of rotor bridges is incorporated into model and it provides effective means of predicting machine performance for a given machine geometry. The LPM is not as accurate as finite element analysis but the equivalent magnetic circuits provide fast means of analyzing electromagnetic characteristics of PMa-SynRG. It is the main advantage to find the initial design and optimum design. The initial design of PMa_RSG is performed by LPM model and FEM analysis, and the final PMA-RSG design is optimized and identified by FEM analysis considering actual machine design. The linear LPM and the nonlinear LPM are programmed using MATLAB and all of machine parameters are calculated very quickly. To verify justification of the proposed design of PMa-RSM, back-EMF is measured.

Robust Trajectory Tracking Control of a Mobile Robot Combining PDC and Integral Sliding Mode Control (PDC와 적분 슬라이딩 모드 제어를 결합한 이동 로봇의 강인 궤도 추적 제어)

  • Park, Min-soo;Park, Seung-kyu;Ahn, Ho-kyun;Kwak, Gun-pyong;Yoon, Tae-sung
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.19 no.7
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    • pp.1694-1704
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    • 2015
  • In this paper, a robust trajectory tracking control method of a wheeled mobile robot is newly proposed combining the PDC and the ISMC. The PDC is a relatively simple and easy control method for nonlinear system compared to the other non-linear control methods. And the ISMC can have robust and stable control characteristics against model uncertainties and disturbances from the initial time by placing the states on the sliding plane with desired nominal dynamics. Therefore, the proposed PDC+ISMC trajectory tracking control method shows robust trajectory tracking performance in spite of external disturbance. The tracking performance of the proposed method is verified through simulations. Even though the disturbance increases, the proposed method keeps the performance of the PDC method when there is no disturbance. However, the PDC trajectory tracking control method has increasing tracking error unlike the proposed method when the disturbance increases.

Modelling and Analysis of Roll-Type Steel Mats for Rapid Stabilization of Permafrost (I) - Modeling - (영구동토 급속안정화를 위한 롤타입강재매트의 모델링과 해석(I) - 해석모델의 수립 -)

  • Moon, Do Young;Kang, Jae Mo;Lee, Janggeun;Lee, Sang Yoon;Zi, Goangseuo
    • Journal of the Korean Geosynthetics Society
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    • v.13 no.4
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    • pp.97-107
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    • 2014
  • Finite element modelling and analysis were conducted for the roll-type steel mats which were placed on loose sand and subjected to a standard truck wheel load in this study. The roll-type steel mats mean that the steel mats can be folded as a circle shape for the carrying to fields in cold regions where workability is limited and are developed for a rapid rehabilitation method for roadway across soft ground which is caused by thawing during the summer season in cold regions. The model is composed of link elements to simulate nonlinear behavior of connections between steel mats, thick shell elements to have flexural stiffness of the steel mats, and springs to simulate characteristics of foundation soils. The structural behaviors of the shell, link elements, and springs were verified at each modelling step through experiment and analysis. Beam and shell analysis without the link elements were conducted and compared to results obtained from the model presented in this study. Significant vertical displacement is shown in the shell model with hinge connections. Therefore, the results demonstrate that the analysis model for the roll-type steel mats on loose sand needs further detail parametric studies.

Determination of the Optimized Structure of Self-Organizing Map for the Rainfall-Runoff Analysis in Naju (나주지점의 강우-유출 해석을 위한 최적의 SOM 구조 결정)

  • Kim, Yong-Gu;Jin, Young-Hoon;Park, Sung-Chun;Jeong, Choen-Lee
    • Journal of Korea Water Resources Association
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    • v.41 no.10
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    • pp.995-1007
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    • 2008
  • Studies on modeling the rainfall-runoff relationship which shows nonlinear trend strongly use artificial neural networks theory not only for the prediction but also for the characteristics analysis of the data used by pattern classification. For the pattern classification, the results from Self-Organizing Map (SOM) mention that the map size and array for the SOM training have significantly influenced on the SOM performance. Since there is no deterministic method or theoretical equation to determine the number of rows and columns for the map size, hexagonal array is generally used for the map array. Therefore, this study present a determination of the optimized map structure for the rainfall-runoff analysis in Naju station considering the map size and array simultaneously which can represent the classified characterization of rainfall-runoff relationship. The result showed that the map size of 20$\times$16 hexagonal array with 8-clustered patterns was selected as an appropriate map structure for rainfall-runoff analysis in Naju station.