• Title/Summary/Keyword: approximate model

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Nonlinear bending and post-buckling behaviors of FG small-scaled plates based on modified strain gradient theory using Ritz technique

  • Ghannadpour, S. Amir M.;Khajeh, Selma
    • Advances in nano research
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    • v.13 no.4
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    • pp.393-406
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    • 2022
  • In the present article, functionally graded small-scaled plates based on modified strain gradient theory (MSGT) are studied for analyzing the nonlinear bending and post-buckling responses. Von-Karman's assumptions are applied to incorporate geometric nonlinearity and the first-order shear deformation theory is used to model the plates. Modified strain gradient theory includes three length scale parameters and is reduced to the modified couple stress theory (MCST) and the classical theory (CT) if two or all three length scale parameters become zero, respectively. The Ritz method with Legendre polynomials are used to approximate the unknown displacement fields. The solution is found by the minimization of the total potential energy and the well-known Newton-Raphson technique is used to solve the nonlinear system of equations. In addition, numerical results for the functionally graded small-scaled plates are obtained and the effects of different boundary conditions, material gradient index, thickness to length scale parameter and length to thickness ratio of the plates on nonlinear bending and post-buckling responses are investigated and discussed.

A Methodology of Optimal Design for Solar Heating and Cooling System Using Simulation Tool

  • Lee, Dongkyu;Nam, Hyunmin;Lee, Byoungdoo
    • International conference on construction engineering and project management
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    • 2015.10a
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    • pp.540-543
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    • 2015
  • Solar energy is one of the most important alternative energy sources which have been shown to meet high levels of heating and cooling demands in buildings. However, the efficiencies to satisfy these demands using solar energy significantly vary based on the characteristics of individual building. Therefore, this paper is focused on developing the methodology which can help to design optimal solar system for heating and cooling to be in cooperated within the existing buildings according to their load profiles. This research has established the Solar Heating and Cooling (SHC) system which is composed of collectors, absorption chiller, boiler and heat storage tank. Each component of SHC system is analyzed and made by means of Modelica Language and Pistache tool is verified the results. Sequential approximate optimization (SAO) and meta-models determined to 15 design parameters to optimize SHC system. Finally, total coefficient of performance (COP) of the entire SHC system is improved approximately 7.3% points compared to total COP of the base model of the SHC system.

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A Study on the IoT Network Traffic Shaping Scheme (IoT 네트워크의 트래픽 쉐이핑 기법 연구)

  • Changwon Choi
    • Journal of Internet of Things and Convergence
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    • v.9 no.6
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    • pp.75-81
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    • 2023
  • This study propose the traffic shaping scheme on IoT Network. The proposed scheme can be operated on the gateway which called sink node and control the IoT traffic with considering the traffic type(real-time based or non real-time based). It is proved that the proposed scheme shows a efficient and compatible result by the numerical analysis and the simulation on the proposed model. And the efficient of the proposed scheme by the numerical analysis has a approximate result of the simulation.

Numerical and analytical investigation of cyclic behavior of D-Shape yielding damper

  • Kambiz Cheraghi;Mehrzad TahamouliRoudsari;Sasan Kiasat;Kaveh Cheraghi
    • Structural Engineering and Mechanics
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    • v.89 no.4
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    • pp.411-420
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    • 2024
  • The purpose of this research was to investigate the cyclic behavior of the D-shaped dampers (DSD). Similarly, at first, the numerical model was calibrated using the experimental sample. Then, parametric studies were conducted in order to investigate the effect of the radius and thickness of the damper on energy dissipation, effective and elastic stiffness, ultimate strength, and equivalent viscous damping ratio (EVDR). An analytical equation for the elastic stiffness of the DSD was also proposed, which showed good agreement with experimental results. Additionally, approximate equations were introduced to calculate the elastic and effective stiffness, ultimate strength, and energy dissipation. These equations were presented according to the curve fitting technique and based on numerical results. The results indicated that reducing the radius and increasing the thickness led to increased energy dissipation, effective stiffness, and ultimate strength of the damper. On the other hand, increasing the radius and thickness resulted in an increase in EVDR. Moreover, the ratio of effective stiffness to elastic stiffness also played a crucial role in increasing the EVDR. The thickness and radius of the damper were evaluated as the most effective dimensions for reducing energy dissipation and EVDR.

An approximate method for aerodynamic optimization of horizontal axis wind turbine blades

  • Ying Zhang;Liang Li;Long Wang;Weidong Zhu;Yinghui Li;Jianqiang Wu
    • Wind and Structures
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    • v.38 no.5
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    • pp.341-354
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    • 2024
  • This paper presents a theoretical method to deal with the aerodynamic performance and pitch optimization of the horizontal axis wind turbine blades at low wind speeds. By considering a blade element, the functional relationship among the angle of attack, pitch angle, rotational speed of the blade, and wind speed is derived in consideration of a quasi-steady aerodynamic model, and aerodynamic loads on the blade element are then obtained. The torque and torque coefficient of the blade are derived by using integration. A polynomial approximation is applied to functions of the lift and drag coefficients for the symmetric and asymmetric airfoils respectively, where specific expressions of aerodynamic loads as functions of the angle of attack (which is a function of pitch angle) are obtained. The pitch optimization problem is investigated by considering the maximum value problem of the instantaneous torque of a blade as a function of pitch angle. Dynamic pitch laws for HAWT blades with either symmetric or asymmetric airfoils are derived. Influences of parameters including inflow ratio, rotational speed, azimuth, and wind speed on torque coefficient and optimal pith angle are discussed.

Effect of zero imputation methods for log-transformation of independent variables in logistic regression

  • Seo Young Park
    • Communications for Statistical Applications and Methods
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    • v.31 no.4
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    • pp.409-425
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    • 2024
  • Logistic regression models are commonly used to explain binary health outcome variable using independent variables such as patient characteristics in medical science and public health research. Although there is no distributional assumption required for independent variables in logistic regression, variables with severely right-skewed distribution such as lab values are often log-transformed to achieve symmetry or approximate normality. However, lab values often have zeros due to limit of detection which makes it impossible to apply log-transformation. Therefore, preprocessing to handle zeros in the observation before log-transformation is necessary. In this study, five methods that remove zeros (shift by 1, shift by half of the smallest nonzero, shift by square root of the smallest nonzero, replace zeros with half of the smallest nonzero, replace zeros with the square root of the smallest nonzero) are investigated in logistic regression setting. To evaluate performances of these methods, we performed a simulation study based on randomly generated data from log-normal distribution and logistic regression model. Shift by 1 method has the worst performance, and overall shift by half of the smallest nonzero method, replace zeros with half of the smallest nonzero method, and replace zeros with the square root of the smallest nonzero method showed comparable and stable performances.

Improving Dynamic Missile Defense Effectiveness Using Multi-Agent Deep Q-Network Model (멀티에이전트 기반 Deep Q-Network 모델을 이용한 동적 미사일 방어효과 개선)

  • Min Gook Kim;Dong Wook Hong;Bong Wan Choi;Ji Hoon Kyung
    • Journal of Korean Society of Industrial and Systems Engineering
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    • v.47 no.2
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    • pp.74-83
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    • 2024
  • The threat of North Korea's long-range firepower is recognized as a typical asymmetric threat, and South Korea is prioritizing the development of a Korean-style missile defense system to defend against it. To address this, previous research modeled North Korean long-range artillery attacks as a Markov Decision Process (MDP) and used Approximate Dynamic Programming as an algorithm for missile defense, but due to its limitations, there is an intention to apply deep reinforcement learning techniques that incorporate deep learning. In this paper, we aim to develop a missile defense system algorithm by applying a modified DQN with multi-agent-based deep reinforcement learning techniques. Through this, we have researched to ensure an efficient missile defense system can be implemented considering the style of attacks in recent wars, such as how effectively it can respond to enemy missile attacks, and have proven that the results learned through deep reinforcement learning show superior outcomes.

Study on bond strength between recycled aggregate concrete and I-shaped steel

  • Biao Liu;Feng Xue;Yu-Ting Wu;Guo-Liang Bai;Zheng-Zhong Wang
    • Computers and Concrete
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    • v.34 no.4
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    • pp.427-446
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    • 2024
  • The I-shaped steel reinforced recycled aggregate concrete (SRRC) composite structure has the advantages of high bearing capacity and environmental protection, and the interfacial bond strength is an important theory. To this end, the I-shaped SRRC bond strength and its calculation based on artificial neural network (ANN) will be studied. Firstly, 39 push out tests of I-shaped SRRC were conducted, the load-slip curve has obvious regularity, which is divided into 4 segments by 3 regular points. Three bond strengths were defined based on these three rule points, and the approximate ranges of their values and the laws of influence of each factor on them were found. Secondly, the Elman ANN model used for the prediction of bond strength was established, and the parameters of Elman ANN predicting I-shaped SRRC bond strength were studied, and the effects of detailed parameters on the prediction results were revealed. Finally, the bond strength of SRRC was predicted using Elman and BP (back propagation) neural network models, both of which showed good prediction results. This study is a theoretical basis for the design and fine simulation of I-shaped SRRC composite structures.

Development of the Approximate Cost Estimating Model Using Statistical Inference for PSC Box Girder Bridge Constructed by the Incremental Launching Method (통계적 기법을 활용한 ILM압출공법 교량 상부공사 개략공사비 산정모델 개발 연구)

  • Kim, Sang-Bum;Cho, Ji-Hoon
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.2
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    • pp.781-790
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    • 2013
  • This research focuses on development of the conceptual cost estimation models for I.L.M box girder bridge. The current conceptual cost estimation for public construction projects is dependent on governmental average unit price references which has been regarded as inaccurate and unreliable by many experts. Therefore, there have been strong demands for developing a better way of conceptual cost estimating methods. This research has proposed three different conceptual cost estimating method for a P.S.C. girder bridge built with the I.L.M method. Model (I) attempts to seek the proper breakdown of standard works that are accountable for more than 95 percentage in total cost and calculates the amount of standard work's materials from the standard section and volume of I.L.M box girder bridge. Model (II) utilizes a correlation analysis (coefficient over 0.6 or more) between breakdown of standard works and input data that would be considered available information in preliminary design phase. Model(III) obtains conceptual estimating through multiple-regression analysis between the breakdown of standard works and all of input data related to them. In order to validate the clustering of coverage in the preliminary design phase, the variation of I.L.M cost coverage from multiple-regression analysis[model(III)] has been investigated which result in between -3.76% and 11.79%, comparing with AACE(Association for the Advancement of Cost Engineering) which informs its variation between -5% and +15% in the design phase. The model proposed from this research are envisioned to be improved to a great distinct if reliable cost date for P.S.C. girder bridges can be continually collected with reasonable accuracies.

Development of an Approximate Cost Estimating Model for Bridge Construction Project using CBR Method (사례기반추론 기법을 이용한 교량 공사비 추론 모형 구축)

  • Kim, Min-Ji;Moon, Hyoun-Seok;Kang, Leen-Seok
    • Korean Journal of Construction Engineering and Management
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    • v.14 no.3
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    • pp.42-52
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    • 2013
  • The aim of this study is to present a prediction model of construction cost for a bridge that has a high reliability using historical data from the planning phase based on a CBR (Case-Based Reasoning) method in order to overcome limitations of existing construction cost prediction methods, which is linearly estimated. To do this, a reasoning model of bridge construction cost by a spreadsheet template was suggested using complexly both CBR and GA (Genetic Algorithm). Besides, this study performed a case study to verify the suggested cost reasoning model for bridge construction projects. Measuring efficiency for a result of the case study was 8.69% on average. Since accuracy of the suggested prediction cost is relatively high compared to the other analysis methods for a prediction of construction cost, reliability of the suggested model was secured. In the case that information for detailed specifications of each bridge type in an initial design phase is difficult to be collected, the suggested model is able to predict the bridge construction cost within the minimized measuring efficiency with only the representative specifications for bridges as an improved correction method. Therefore, it is expected that the model will be used to estimate a reasonable construction cost for a bridge project.