• Structural Engineering and Mechanics
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• v.61 no.3
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• pp.359-370
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• 2017

This study presents a particle swarm optimization algorithm integrated with weighted particle concept and improved fly-back technique. The rationale behind this integration is to utilize the affirmative properties of these new terms to improve the search capability of the standard particle swarm optimizer. Improved fly-back technique introduced in this study can be a proper alternative for widely used penalty functions to handle existing constraints. This technique emphasizes the role of the weighted particle on escaping from trapping into local optimum(s) by utilizing a recursive procedure. On the other hand, it guaranties the feasibility of the final solution by rejecting infeasible solutions throughout the optimization process. Additionally, in contrast with penalty method, the improved fly-back technique does not contain any adjustable terms, thus it does not inflict any extra ad hoc parameters to the main optimizer algorithm. The improved fly-back approach, as independent unit, can easily be integrated with other optimizers to handle the constraints. Consequently, to evaluate the performance of the proposed method on solving the truss weight minimization problems with discrete variables, several benchmark examples taken from the technical literature are examined using the presented method. The results obtained are comparatively reported through proper graphs and tables. Based on the results acquired in this study, it can be stated that the proposed method (integrated particle swarm optimizer, iPSO) is competitive with other metaheuristic algorithms in solving this class of truss optimization problems.

• Structural Engineering and Mechanics
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• v.65 no.1
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• pp.111-120
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• 2018

This paper presents a new and simple solution for determining the natural frequencies of framed tube combined with shear-walls and tube-in-tube systems. The novelty of the presented approach is based on the bending moment function approximation instead of the mode shape function approximation. This novelty makes the presented solution very simpler and very shorter in the mathematical calculations process. The shear stiffness, flexural stiffness and mass per unit length of the structure are variable along the height. The effect of the structure weight on its natural frequencies is considered using a variable axial force. The effects of shear lag phenomena has been investigated on the natural frequencies of the structure. The whole structure is modeled by an equivalent non-prismatic shear-flexural cantilever beam under variable axial forces. The governing differential equation of motion is converted into a system of linear algebraic equations and the natural frequencies are calculated by determining a non-trivial solution for the system of equations. The accuracy of the proposed method is verified through several numerical examples and the results are compared with the literature.

• Steel and Composite Structures
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• v.35 no.1
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• pp.129-145
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• 2020

In typical, structural topology optimization plays a significant role to both increase stiffness and save mass of structures in the resulting design. This study contributes to a new numerical approach of topologically optimal design of Mindlin-Reissner plates considering Winkler foundation and mathematical formulations of multi-directional variable thickness of the plate by using multi-materials. While achieving optimal multi-material topologies of the plate with multi-directional variable thickness, the weight information of structures in terms of effective utilization of the material at the appropriate thickness location may be provided for engineers and designers of structures. Besides, numerical techniques of the well-established mixed interpolation of tensorial components 4 element (MITC4) is utilized to overcome a well-known shear locking problem occurring to thin plate models. The well-founded mathematical formulation of topology optimization problem with variable thickness Mindlin-Reissner plate structures by using multiple materials is derived in detail as one of main achievements of this article. Numerical examples verify that variable thickness Mindlin-Reissner plates on Winkler foundation have a significant effect on topologically optimal multi-material design results.

• Earthquakes and Structures
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• v.18 no.3
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• pp.321-335
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• 2020

The aim of the present contribution is to consider and underline the essential interactions among the historical knowledge, the seismic vulnerability assessment, the investigation experimental tools, the preservation of the architectural quality and the strengthening design in regard to architectural heritage conservation. These topics are argued in relation to Palazzo Murena in Perugia, designed in the eighteenth century by the famous Architect Luigi Vanvitelli, and currently headquarters of the city's University. Based on the surveys and the visual inspections, a preliminary a priori global analysis has been performed by means of the FME method. The obtained results permitted to plan an experimental tests campaign inclusive of structural health monitoring. The new achieved "knowledge" of the building allowed to refine the seismic safety assessment. In particular it was highlighted that the "mezzanine floor" can be a vulnerable element of the building with the collapse of its masonry walls. Preserving the architectural characteristics, a local reinforcement intervention is proposed for the above-mentioned level; this consists of the application of plaster with FRCM, assuring an adequate strength, without burden the masonry structure with additional weight, and therefore a decreasing of the seismic vulnerability. The necessity to consider, in this ongoing research, other local mechanisms is highlighted in the unfolding of the last part of work.

• IEMEK Journal of Embedded Systems and Applications
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• v.13 no.5
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• pp.253-259
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• 2018

Recently, small satellite industries are rapidly changing. Demand for high performance small satellites is increasing with the expansion of Earth Observation Satellite market. A next-generation small satellites require a higher resolution image storage capacity than before. However, there is a problem that the HW configuration of the existing small satellite image storage device could not meet these requirements. The conventional data storing system uses SDRAM to store image data taken from satellites. When SDRAM is used in small satellite platform of a next generation, there is a problem that the cost of physical space is eight times higher and satellite price is two times higher than NAND Flash. Using the same satellite hardware configuration for next-generation satellites will increase the satellite volume to meet hardware requirements. Additional cost is required for structural design, environmental testing, and satellite launch due to increasing volume. Therefore, in order to construct a low-cost, high-efficiency system. This paper shows a next-generation solid state recorder unit (SSRU) using MRAM and NAND Flash instead of SDRAM. As a result of this research, next generation small satellite retain a storage size and weight and improves the data storage space by 15 times and the storage speed by 4.5 times compare to conventional design. Also reduced energy consumption by 96% compared to SDRAM based storage devices.

• International Journal of Aerospace System Engineering
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• v.7 no.1
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• pp.16-20
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• 2020

The recent trend is increasing towards the usage of polymer matrix composites since they have a wide variety of applications. They have applications in the field of aircraft and space industry, sporting goods, medical devices, marine and automotive applications and also in commercial usage. The most commonly used fibre-reinforced polymer matrix composite is Glass fibre reinforced epoxy (GFRE) composite which is used in aviation, sports and automotive industries. However, the strength of GFRE composites is not adequate for structural applications. Therefore, the current research focuses on increasing the strength of GFRE composites by reinforcing with micro Graphite (Gr) particulates. The Gr used is an ultra-fine powder with particle size 250 ㎛. Gr is known to have good wear resistance, thermal conductivity and can operate at high temperatures. Gr particulates are mixed with the epoxy matrix in various weight ratios. Hand-lay technique is used for fabricating the composites. Mechanical properties such as tensile strength, elongation, compressive strength and flexural strength are obtained experimentally to study the effect of change in Gr content (0-5 wt. %). The tests were done as per ASTM standards.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.8
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• pp.76-83
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• 2010

Metallic sandwich panels with pyramidal truss structures are high-stiffness and high-strength materials with low weight. In particular, bulk structures have enough space for additional multi-functionalities. In this work, in order to fabricate 3-D structures efficiently, Layered Manufacturing Method (LMM) which was composed of three steps, including crimping process, stacking process and bonding process using rapid infrared brazing, was proposed. The joining time was drastically reduced by employing infrared brazing of which heating rate and cooling rate were faster than those of conventional furnace brazing. By controlling the initial cooling rate slowly, the bonding strength was improved up to the level of strength by conventional vacuum brazing. The observation of infrared brazed specimens by optical microscope and SEM showed no defect on the joining sections. The experiments of 1-layered pyramidal structures and 2-layered pyramidal structures subject to 3-point bending were conducted to determine structural advantages of multilayered structures. From the results, the multi-layered structure has superior mechanical properties to the single-layered structure.

• Journal of Power System Engineering
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• v.20 no.6
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• pp.80-86
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• 2016

In this study, The watertight damper was designed to improve conventional DN 350A butterfly valve. The FSI(Fluid-Structure Interaction) analysis has performed to investigate the safety factor for the watertight damper. When watertight damper of disk was closed, the disk of pressure value is constant. However depending on the opening angle of disk, the flow velocity and pressure are changed. The maximum velocity was appeared at the end of disk on the small outlet area of duct. When the opening angel of disk is $90^{\circ}$, the maximum velocity was appeared at the center of ending disk. So we were found the opening angle of disk is bigger, the flow rate is increased and velocity is also increased from the result of FSI analysis. We can find the least deformation and stress when the opening angel of damper is $90^{\circ}$. When the $45^{\circ}$ opening angle of disk, the largest deformation and stress was found and the minimum safety factor 1.3 was calculated. As a result, we found that the structure of watertight damper is safe enough irrespective of opening angel.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.143-146
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• 2007

Birnessite-type manganese dioxide($MnO_2$) was coated uniformly onto carbon nanotubes (CNTs) through a spontaneous direct redox reaction between CNTs and permanganate ions($MnO_4\;^-$). The initial specific capacitance of the $MnO_2/CNT$ nanocomposite in an organic electrolyte at a large current density of 1 A/g was 250 F/g, which is equivalent to 139 mAh/g based on the total weight of the electrode material including the electroactive material, conducting agent and binder. The specific capacitance of the $MnO_2$ in the $MnO_2/CNT$ nanocomposite was as high as 580 F/g (320 mAh/g), indicating excellent electrochemical utilization of the $MnO_2$. The addition of CNTs as a conducting agent can improve the high rate capability of $MnO_2/CNT$ nanocomposite considerably. An analysis of the in-situ X-ray absorption near-edge structure (XANES) showed an improvement in the structural and electrochemical reversibility of the $MnO_2/CNT$ nanocomposite by heat-treatment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.913-920
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• 2000

The hall and the projection room of the multiplex cinema being constructed on the sixth and seventh floors at Jeonpo-dong market, Pusan, is composed of structural beams and decks considering the structures self weight problem, and the following problems are expected: - Vibration and noise generated on the floors by moving audiences may annoy the audiences in the other hall - Vibration and noise generate on the floor of the nearby hall as the audiences walk through the alley near the projection room - Vibration and noise generate on the floor of the hall nearby the projection room as the film drops This study measured and reviewed the vibration amount of the seven representative transferring routes that were selected for the halls and the alley near the projection room. Based on the analysis, the model hall was constructed and the vibration in the hall was estimated after cutting the deck. Also, this study constructed the steel stairs and investigated the vibration transferring characteristics to decide whether to construct the steel stairs in the building. Finally, the results were evaluated by actually using the stairs and reviewed the appropriateness of the measurement.