• Steel and Composite Structures
• /
• 제44권5호
• /
• pp.685-690
• /
• 2022

In this paper, the equivalent material properties of cellular metamaterials with different types of perforations have been presented using finite element (FE) simulation of tensile test in Abaqus commercial software. To this end, a Representative Volume Element (RVE) has been considered for each type of cellular metamaterial with regular array of circular, square, oval and rectangular perforations. Furthermore, both straight and perpendicular patterns of oval and rectangular perforations have been studied. By applying Periodic Boundary conditions (PBC) on the RVE, the actual behavior of cellular material under uniaxial tension has been simulated. Finally, the effective Young's modulus, Poisson's ratio and mass density of various metamaterials have been presented as functions of relative density of the RVE

• 건축역사연구
• /
• 제18권6호
• /
• pp.47-64
• /
• 2009

This research was to analyze the inland signal-fire which is the main facility of military protective duty for safety of land in chosun dynasty. The results of this research were described separately as follows. 1. Five types of site plan of signal-fire were observed, which is circle, oval, rectangular, indeterminate form. The majorities were oval type. 2. Plan configuration of brazier which is separated with circle, rectangular type roughly was constructed with circle type generally. The height of brazier was about 3~4.5m. The diameter of brazier was 1.5~2.5m. Building base that protect ground moisture and infilteration of rainfall was found in 5 inland singal-fire, the height of it was about 0.3m~2.5m. 3. The heigh to protective wall remained until present was about 1m, the depth was about average 1.2m. 4. Entrance was mainly stairs or open type and average width was 1.0~1.2m. However the depth was almost observed as 1m, originally, it was estimated it has more depth. 5. The storage of inland signal-fire has rectangular dimension, several types of $1.8{\times}1.2m{\sim}5.7{\times}4.4m$, square(間) of $1{\times}1{\sim}2{\times}1$. The building material was stone and located below or near the brazier.

• 대한기계학회논문집B
• /
• 제26권8호
• /
• pp.1115-1122
• /
• 2002

The present experiment investigates the effects of pore density f of aluminum foam heat sinks, the jet-to-jet spacing X and the nozzle plate-to-target surface spacing H of 3$\times$3 square impinging arrays on the averaged Nusselt number. The performance of the aluminum foam heat sinks and the rectangular plate heat sink is evaluated in terms of the enhancement factor. /equation omitted/. The multiple impinging jet with X/d=4.0 displays higher Nusselt numbers than single impinging jet for 12.0$\leq$H/d$\leq$20.0. With the variation of the jet-to-jet spacing, the aluminum foam heat sink of 10 PPI show higher Nusselt numbers than the 20 and 40 PPI aluminum foam heat sinks. Further, the 10 PPI aluminum foam heat sink demonstrates 26% higher enhancement factor than the rectangular plate heat sink in the range of 7000$\leq$Re$\leq$11000.

• 한국전산유체공학회지
• /
• 제4권1호
• /
• pp.27-33
• /
• 1999

Spiral tube heat exchangers can find numerous applications in many engineering fields. Flow in spiral tubes is interest to engineers due to occurrence of secondary flow which enhances the cross-sectional mixing and the heat transfer rate. In the present study, an incompressible viscous 3-D flow in spiral tubes with rectangular cross-section of various torsion rate and Reynolds number is studied by using a finite volume method. It is shown that the axial velocity profile is affected by the secondary flow motion. Because there is some difference from correlation proposed by Hur et al., a lot of analysis and arrangement of experimental results are needed. This study showed the results of variation of hydrodynamic entry length for torsion and Re numbers.

• 한국전기전자재료학회논문지
• /
• 제24권9호
• /
• pp.733-738
• /
• 2011

A novel design of a simple square-frame USM (ultrasonic motor) was proposed. The stator of the motor consists of a square-frame shape elastic body and four rectangular plate ceramics. The four ceramics were attached to inner surfaces of the square frame elastic body. The same phase voltages were applied to the ceramics on horizontal surfaces, and 90 degree phase difference voltage were applied to the ceramics on vertical surfaces. To find a model that generates elliptical motion at outside of the stator, the finite element analysis program ATILA was used. The analyzed results were compared to the experimental results. As result, the model EL10EH3ET0.5CL4 which generates the maximum elliptical displacement was chosen by analyzing the resonance mode according to changes in frequency.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2001년도 추계 학술대회논문집
• /
• pp.112-117
• /
• 2001

A numerical investigation is made of unsteady double-diffusive convection of a Boussinesq fluid in a rectangular cavity subject to time-periodic thermal excitations. The fluid is initially stratified between the top endwall of low solute concentration and the bottom endwall of high solute concentration. A time-dependent heat flux varying in a square wave fashion, is applied on one sidewall to induce buoyant convection. The influences of the imposed periodicity on double-diffusive convection are scrutinized. A special concern is on the occurrence of resonance that the fluctuations of flow and attendant heat and mass transfers are mostly amplified at certain eigenmodes of the fluid system. Numerical solutions are analyzed to illustrate the characteristic features of resonant convection.

• 한국정보통신학회논문지
• /
• 제19권2호
• /
• pp.450-454
• /
• 2015

본 논문에서는 평면상에 가중치를 가진 점들이 주어질 때, 임의의 상수 r에 대해서 변의 길이 r인 정사각형 영역을 고려해서 이 안에 속하는 점들의 가중치 합이 최대가 되는 영역을 찾고자 한다. 변의 길이가 정해져 있지 않은 경우에 임의의 사각형 영역을 찾는 문제에 대한 연구가 있었다. 본 논문에서는 상수 r이 주어질 때, 변의 길이 r인 정사각형 영역을 찾는 문제를 다룬다. 우리는 동적 환경 하에서의 일차원 문제를 풀고, 이를 이용해서 O(nlogn+rn) 시간 복잡도를 갖는 알고리즘을 제안한다.

• 전산구조공학
• /
• 제3권2호
• /
• pp.77-88
• /
• 1990

환경조건 및 내부의 유공부 크기와 위치가 변화함에 따라 평판의 두개의 고유치(고유 진동수와 탄성 임계하중)는 어떻게 변화하며, 이들 고유치 상호간의 관계는 어떻게 되는지 검토 하기로 한다. 이상과 같은 검토 목적에는 수치 해석법이 적당한데 본 논문에서는 그 중의 하나인 유한 요소법을 채택하기로 한다. 유한 요소법에서 이용할 요소는 각 절점에서 자유도가 3, 따라서 요소 전체의 자유도가 12인 사각형 요소이다.

• 지구물리
• /
• 제9권2호
• /
• pp.99-103
• /
• 2006

3D object recognition independent of translation and rotation using an ultrasonic sensor array, invariant moment vectors and SOFM(Self Organizing Feature Map) neural networks is presented. Using invariant moment vectors of the acquired 16×8 pixel data of square, rectangular, cylindric and regular triangular blocks, 3D objects could be classified by SOFM neural networks. Invariant moment vectors are constant independent of translation and rotation. The recognition rates for the training and testing data were 95.91% and 92.13%, respectively.

• Steel and Composite Structures
• /
• 제52권2호
• /
• pp.145-163
• /
• 2024

This paper presents six novel hybrid machine learning (ML) models that combine support vector machines (SVM), Decision Tree (DT), Random Forest (RF), Gradient Boosting (GB), extreme gradient boosting (XGB), and categorical gradient boosting (CGB) with the Harris Hawks Optimization (HHO) algorithm. These models, namely HHO-SVM, HHO-DT, HHO-RF, HHO-GB, HHO-XGB, and HHO-CGB, are designed to predict the ultimate strength of both rectangular and circular reinforced concrete (RC) columns. The prediction models are established using a comprehensive database consisting of 325 experimental data for rectangular columns and 172 experimental data for circular columns. The ML model hyperparameters are optimized through a combination of cross-validation technique and the HHO. The performance of the hybrid ML models is evaluated and compared using various metrics, ultimately identifying the HHO-CGB model as the top-performing model for predicting the ultimate shear strength of both rectangular and circular RC columns. The mean R-value and mean a20-index are relatively high, reaching 0.991 and 0.959, respectively, while the mean absolute error and root mean square error are low (10.302 kN and 27.954 kN, respectively). Another comparison is conducted with four existing formulas to further validate the efficiency of the proposed HHO-CGB model. The Shapely Additive Explanations method is applied to analyze the contribution of each variable to the output within the HHO-CGB model, providing insights into the local and global influence of variables. The analysis reveals that the depth of the column, length of the column, and axial loading exert the most significant influence on the ultimate shear strength of RC columns. A user-friendly graphical interface tool is then developed based on the HHO-CGB to facilitate practical and cost-effective usage.