• Title/Summary/Keyword: Composite numbers

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Effect of Levy Flight on the discrete optimum design of steel skeletal structures using metaheuristics

  • Aydogdu, Ibrahim;Carbas, Serdar;Akin, Alper
    • Steel and Composite Structures
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    • v.24 no.1
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    • pp.93-112
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    • 2017
  • Metaheuristic algorithms in general make use of uniform random numbers in their search for optimum designs. Levy Flight (LF) is a random walk consisting of a series of consecutive random steps. The use of LF instead of uniform random numbers improves the performance of metaheuristic algorithms. In this study, three discrete optimum design algorithms are developed for steel skeletal structures each of which is based on one of the recent metaheuristic algorithms. These are biogeography-based optimization (BBO), brain storm optimization (BSO), and artificial bee colony optimization (ABC) algorithms. The optimum design problem of steel skeletal structures is formulated considering LRFD-AISC code provisions and W-sections for frames members and pipe sections for truss members are selected from available section lists. The minimum weight of steel structures is taken as the objective function. The number of steel skeletal structures is designed by using the algorithms developed and effect of LF is investigated. It is noticed that use of LF results in up to 14% lighter optimum structures.

The Properties of BST Thin Films by Thickness (두께 변화에 따른 BST 박막의 특성)

  • Hong, Kyung-Jin;Min, Yong-Ki;Cho, Jae-Cheol
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11b
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    • pp.455-458
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    • 2001
  • The thin films of high pemitivity in ferroelectric materials using a capacitor are applied to DRAMs and FRAMs. (Ba, Sr)$TiO_3$ thin films as ferroelectric materials were prepared by the sol-gel method and made by spin-coating on the Pt/Ti/$SiO_2/Si$ substrate at 4,000 [rpm] for 10 seconds. The devices of BST thin films to composite $(Ba_{0.7},Sr_{0.3})TiO_3$ were fabricated by changing of the depositing layer number on $Pt/Ti/SiO_2/Si$ substrate. The thin film capacitor to be ferroelectric devices was investigated by structural and electrical properties. The thickness of BST thin films at each coating numbers 3, 4 and 5 times was $2500[\AA]$, $3500[\AA]$, $3800[\AA]$. The dielectric factor of thin film when the coating numbers were 3, 4 and 5 times was 190, 400 and 460 on frequency l[MHz]. The dielectric loss of BST thin film was linearly increased by increasing of the specimen area.

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The Properties of BST Thin Films by Thickness (두께 변화에 따른 BST 박막의 특성)

  • 홍경진;민용기;조재철
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2001.11a
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    • pp.455-458
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    • 2001
  • The thin films of high permitivity in ferroelectric materials using a capacitor are applied to DRAMs and FRAMs. (Ba, Sr)TiO$_3$ thin films as ferroelectric materials were prepared by the sol-gel method and made by spin-coating on the Pt/Ti/SiO$_2$/Si substrate at 4,700 [rpm] for 10 seconds. The devices of BST thin films to composite (Ba$\_$0.7/Sr$\_$0.3/)TiO$_3$ were fabricated by changing of the depositing layer number on Pt/Ti/SiO$_2$/Si substrate. The thin film capacitor to be ferroelectric devices was investigated by structural and electrical properties. The thickness of BST thin films at each coating numbers 3, 4 and 5 times was 2500[${\AA}$], 3500[${\AA}$], 3800[${\AA}$]. The dielectric factor of thin film when the coating numbers were 3, 4 and 5 times was 190, 400 and 460 on frequency 1[MHz]. The dielectric loss of BST thin film was linearly increased by increasing of the specimen area.

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A COMPARATIVE STUDY ON THE STRENGTH AND THE BONE FORMATION AT THE RATS CALVARIAL DEFECTS OF DFDB GRAFT AND THOSE OF THE COMPOSITE GRAFT WITH DFDB AND RESORBABLE HYDROXYAPATITE (백서 두개골 결손부에 동결 건조 동종 탈회골을 단일매식한 경우와 동결 건조 동종 탈회골과 흡수성 수산화인회석을 복합매식한 경우의 강도 및 골형성에 관한 비교 연구)

  • Seo, Young-Ho;Yim, Chang-Joon;Lee, Jae-Il
    • Journal of the Korean Association of Oral and Maxillofacial Surgeons
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    • v.26 no.6
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    • pp.557-564
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    • 2000
  • The bone graft materials can be grossly divided into autogenous bone, allogenic bone, xenogenic bone, and alloplastic material. Much care was given to other bone graft materials away from autogenous bone due to its additional operation for harvesting, delayed resorption and limitation of quantity. Demineralized freeze-dried bone(DFDB) and hydroxyapatite are the representatives of bone graft materials. As resorbable hydroxyapatite is developed in these days, the disadvantage of nonresorbability can be overcome. So we planned to study on the strength and the bone formation at the rats calvarial defects of DFDB graft and those of the composite graft with DFDB and resorbable hydroxyapatite. We used the 16 male rats weighting range from 250 to 300 gram bred under the same environment during same period. After we made the 6mm diameter calvarial defect, we filled the DFDB in 8 rats and DFDB and resorbable hydroxyapatite in another 8 rats. We sacrificed them at the postoperative 1 month and 2 months with the periostium observed. As soon as the specimens were delivered, we measured the compressive forces to break the normal calvarial area and the newly formed bone in calvarial defect area using Instron(Model Autograph $S-2000^{(R)}$, Shimadzu, Japan). The rest of the specimens were stained with H&E(Hematoxylin & Eosin) and evaluated with the light microscope. So we got the following results. 1. In every rats, there was no significant difference between the measured forces of normal bone area and those of the bone graft area. 2. In 1 month, the measured forces at DFDB graft group were higher than those of the DFDB and resorbable hydroxyapatite composite graft group(P<0.05). 3. In 2 months, there was no significant differences between the measured forces of DFDB graft group and those of the DFDB and resorbable hydroxyapatite composite graft group. 4. In lightmicroscopic examination, most of the grafted DFDB were transformed into bone in 1 month and a large numbers of hydroxyapatite crystal were observed in DFDB and resorbable hydroxyapatite composite graft group in 1 month. 5. Both group showed no inflammatory reaction in 1 month. And hydroxyapatite crystals had a tight junction without soft tissue invagination when consolidated with newly formed bone. 6. In both groups, newly formed bone showed the partial bone remodeling and the lamellar bone structures and some of reversal lines were observed in 2 months. From the above results, it is suggested that DFDB and resorbable hydroxyapatite composite graft group had a better resistance to compressive force in early stage than DFDB graft group, but there would be no significant difference between two groups after some period. And it is suggested that the early stage of bone formation procedure of DFDB and resorbable hydroxyapatite composite graft group was slight slower than that of DFDB graft group, but there would be no significant difference between two groups after some period.

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STUDY OF THE TENSILE BOND STRENGTH OF COMPOSITES RESINS APPLIED TO ACID-ECHED ENAMEL (산처리(酸處理)된 Enamel표면(表面)에 대(對)한 Composite resin의 인장접착강도(引張接着强度)에 관(關)한 연구(硏究))

  • Lee, Young-Kun;Min, Byung-Soon;Choi, Ho-Young;Park, Sung-Jin
    • Restorative Dentistry and Endodontics
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    • v.12 no.2
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    • pp.45-53
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    • 1987
  • The purpose of this study was to evaluate the tensile bond strength between composite resin and the human enamel. Three composite resin systems, two chemical (Clearfil Posterior, and Clearfil Posterior-3) and one light cure (Photo Clearfil-A), used with and without an intermediate resin (clearfil bonding agent), were evaluated under different amounts of load (10g, 200g and 200g for a moment) for in vitro tensile bond strength to acid-eched human enamel. Clinically intact buccal or lingual surfaces of 144 freshly extracted human permanent molars, embedded in acrylic were flattened with No #600 carborundum discs. Samples were randomly assigned to the different materials and treatments using a table of random numbers. Eight samples were thus prepared for each group(Table 2) these surfaces were etched with an acid etchant (Kurarey Co. Japan) in a mode of etching for 30 seconds, washing for 15 seconds, and drying for 30-seconds. During the polymerization of composite resin on the acid-etched enamel surfaces with and without bonding agent 10-gram, 200 gram and temporary 200 gram of load were applied. The specimens were stored in 50% relation humidity at $37^{\circ}C$ for 24 hours before testing. An universal Testing machine (Intesco model No. 2010, Tokyo, Japan) was used to apply tensile loads in the vertical directed (fig 5), and the force required for separation was recorded with a cross head speed of 0.25 mm/min and 20 kg in full scale. The results were as follow: 1. The tensile bond strength was much greater in applying a bonding agent than in not doing that. 2. The tensile bond strength of chemical cure composite resin was higher than that of light cure composite resin with applying on bonding agent on the acid-etched enamel. 3. In case of not applying a bonding agents on the acid-etching enamel, the highest tensile bond strength under 200 gram of load was measured in light cure composite resin. 4. The tensile bond strength under 200-gram of load has no relation with applying the bonding agent. 5. Under the load of 10-gram, There was significant difference in tensile bond strength as applying the bonding agent.

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Energy Absorption Characteristics of Composite Laminated Structural Member According to the Interface Number (복합적층 구조부재의 계면수 변화에 따른 에너지흡수특성)

  • Hwang, Woo-Chae;Lee, Kil-Sung;Cha, Cheon-Seok;Jung, Jong-An;Han, Gil-Young;Yang, In-Young
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.20 no.1
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    • pp.17-22
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    • 2011
  • Ultimate goals in vehicle design can be summarized as environment-friendliness and safety. Along with these requirements, the importance of natural environment conservation has been focused lately. Therefore, reduced emission from vehicle and improved efficiency has become the top priority projects throughout the world. CFRP(Carbon Fiber Reinforced Plastics) of the advanced composite materials as structure materials for vehicles, has a widely application in lightweight structural materials of air planes, ships and automobiles because of high strength and stiffness. This study is to investigate the energy absorption characteristics of CFRP hat-shaped section members under the axial impact collapse test. The CFRP hat-shaped section members which manufactured from unidirectional prepreg sheets were made of 8plies. The axial impact collapse tests were carried out for each section members. The collapse mode and energy absorption characteristics were analyzed for CFRP hat-shaped section member according to the interface numbers(2, 3, 4, 6 and 7).

AN EXPERIMENTAL STUDY ON HARDNESS IN VISIBLE LIGHT-CURED COMPOSITE RESIN AT VARYING DEPTH (가시광선(可視光線) 복합(復合)레진의 심부경도(深部硬度) 측정(測定)에 관(關)한 실험적(實驗的) 연구(硏究))

  • Myoung, Jae-Keun;Lee, Myoung-Jong
    • Restorative Dentistry and Endodontics
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    • v.11 no.1
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    • pp.43-52
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    • 1985
  • The purpose of this study was to measure the Micro-Knoop Hardness of three commercial visible light-cured composite resins (Plurafil-super, He1iosit and Durafi) according to the difference of depth and shade. Specimens of the resin were prepapared in plastic tubes 5mm in diameter with height of 5mm, and the tubes were put into the columned holes in stone molds. The molds were exposed to the visible light through the hole 5mm in diameter in metal plate. Specimens were sectioned (longitudinally) with disk. Knoop Hardness measurements were made at the depth of surface, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0mm from the surface to the deep portion. Knoop Hardness numbers were taken on each depth under 20gm load for 10 seconds with Shimadzu Tester. The following results were: 1. The highest hardness value was measured at 0.5mm depth. Then the deeper the depth, the lesser the hardness was observed. 2. The value of hardness was directly propotional to the time of exposure to the light. 3. The hardness of light shade resin was higher than the that of the dark shade. 4. The pattern of hardness change at varying depth is similar to all the experimental materials with no relation to the shade nor exposure time.

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Binomial Filters for Spectrum Sensing in Cognitive Radio System (인지 무선 시스템에서 스펙트럼 센싱을 위한 이항 필터)

  • Seong, JinSuk;Kim, Myungsup;Lee, Seong Ro
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.39C no.11
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    • pp.1132-1138
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    • 2014
  • In this paper, we proposed three types of binomial filter for spectrum sensing in cognitive radio system. Three filters are binomial, negative binomial and composite binomial filters and the frequency responses of their transfer functions are analyzed and the numbers of stages to meet the required attenuation are driven. As a result of performance analysis in terms of the number of stages, negative and composite binomial filters are superior to the binomial filter. Since the proposed three filters have a unified cascaded structure and are easy to be implemented without any multiplier, it is expected that they will have wide applications.

An Experimental Study on TR-CFT Columns subjected to Axial Force and Cyclic Lateral Loads (축력과 반복수평력을 받는 TR-CFT기둥에 관한 실험적 연구)

  • Park, Jai Woo;Kim, Jin Ho;Hong, Young Kyun;Hong, Gi Soup
    • Journal of Korean Society of Steel Construction
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    • v.19 no.4
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    • pp.403-411
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    • 2007
  • CFT (Concrete filled steel tube) column has become popular for building construction due to not only its composite effect but also economic effect. However, the conventional CFT column also has its own disadvantages having plastic buckling at the end of column followed by the reduction of strength by yielding of steel tube. An experiment on TR-CFT (Transversely reinforced CFT) column are conducted for making up for conventional CFT column's disadvantages. The experiment parameters are strength of concrete, the layer numbers of carbon fiber sheet. In this study, hysteretic curve, initial stiffness, strength, plastic deformation capacity, and dissipated energy are compared and analyzed between CFT and TR-CFT columns.

Investigating dynamic response of porous advanced composite plates resting on Winkler/Pasternak/Kerr foundations using a new quasi-3D HSDT

  • Rabhi, Mohamed;Benrahou, Kouider Halim;Yeghnem, Redha;Guerroudj, Hicham Zakaria;Kaci, Abdelhakim;Tounsi, Abdelouahed;Hussain, Muzamal
    • Structural Engineering and Mechanics
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    • v.83 no.6
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    • pp.771-788
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    • 2022
  • This research investigates the free vibration of porous advanced composite plates resting on Winkler/Pasternak/ Kerr foundations by using a new hyperbolic quasi three dimensional (quasi-3D) shear deformation theory. The present theory, which does not require shear correction factor, accounts for shear deformation and thickness stretching effects by parabolic variation of all displacements across the thickness, and satisfies the stress-free boundary conditions on the upper and lower surfaces of the plate. In this work, we consider imperfect FG plates with porosities embedded within elastic Winkler, Pasternak or Kerr foundations. Implementing an analytical approach, the obtained governing equations from Hamilton's principle according to FG plates are derived. The closed form solutions are obtained by using Navier technique, and natural frequencies of FG plates are found, for simply supported plates, by solving the results of eigenvalue problems. A comprehensive parametric study is presented to evaluate effects of the geometry of material, mode numbers, porosity volume fraction, Power-law index and stiffness of foundations parameters on free vibration characteristics of FG plates.