• Korean Journal of Computational Design and Engineering
• /
• v.11 no.4
• /
• pp.265-272
• /
• 2006

For the design and analysis of 3D object featuring complexity and irregularity in shape, sectional digital images measured by an industrial CT scanner are employed to generate a finite element model with uniform voxels. The voxel model plays a key role in developing an integrated reverse engineering system including geometric modeling, simulation and optimization. Design examples applied to topology optimization show that the proposed approach can provide a remarkable reduction in time cost at the conceptual and detail design stages.

• Journal of applied mathematics & informatics
• /
• v.33 no.3_4
• /
• pp.317-325
• /
• 2015

Proved that the two topoloies(spectral topology and D−topology) coincide on SpecR, MaxR and MinspecR iff R is complemented, normal and stone ADL respectively.

• Bulletin of the Korean Chemical Society
• /
• v.35 no.2
• /
• pp.651-654
• /
• 2014

• Proceedings of the KIPE Conference
• /
• 2001.10a
• /
• pp.301-303
• /
• 2001

In this paper we present a Capacitor Charging Power Supply (CCPS) using a series-resonant three-level inverter topology to improve voltage regulation and use semiconductor switches having low blocking voltage capability such as MOSFETs. This inverter can be operated with two modes, Full Power Mode (FPM) and Half Power Mode (HPM). In FPM inverter supplies the high frequency step up transformer with full DC-link voltage and in HPM with half DC-link voltage. HPM switching method will be adopted when CCPS output voltage reaches the preset target value and operates in refresh mode-charge is maintained on the capacitor. In this topology each semiconductor devices blocks a half of the DC-link voltage[2]. A 15kW, 30kV CCPS has been built and will be tested for an electric precipitator application. The CCPS operates from an input voltage of 500VDC and has a variable output voltage between 10 to 30kV and 1kHz repetition rate at 44nF capacitive load [3]. A resonant frequency of 67.9kHz was selected and a voltage regulation of $0.83\%$ has been achieved through the use of half power mode without using the forced cut off the switch current [1]. The theory of operation, circuit topology and test results are given.

• Structural Engineering and Mechanics
• /
• v.76 no.4
• /
• pp.529-540
• /
• 2020

Concurrent topology optimization of macrostructure and microstructure has attracted significant interest due to its high structural performance. However, most of the existing works are carried out under deterministic conditions, the obtained design may be vulnerable or even cause catastrophic failure when the load position exists uncertainty. Therefore, it is necessary to take load position uncertainty into consideration in structural design. This paper presents a computational method for robust concurrent topology optimization with consideration of load position uncertainty. The weighted sum of the mean and standard deviation of the structural compliance is defined as the objective function with constraints are imposed to both macro- and micro-scale structure volume fractions. The Bivariate Dimension Reduction method and Gauss-type quadrature (BDRGQ) are used to quantify and propagate load uncertainty to calculate the objective function. The effective properties of microstructure are evaluated by the numerical homogenization method. To release the computation burden, the decoupled sensitivity analysis method is proposed for microscale design variables. The bi-directional evolutionary structural optimization (BESO) method is used to obtain the black-and-white designs. Several 2D and 3D examples are presented to validate the effectiveness of the proposed robust concurrent topology optimization method.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.38 no.3
• /
• pp.309-314
• /
• 2014

The structural layout of mechanical and civil structures is commonly obtained using conventional methods. For example, the shape of structures such as electric transmission towers and offshore substructures can be generated systematically. However, with rapid advancements in computer graphic technology, advanced structural analyses and optimum design technologies have been implemented. In this study, the structural shape of a jacket substructure for an offshore wind turbine is investigated using a topology optimization technique. The structure is subjected to multiple loads that are intended to simulate the loading conditions during actual operation. The optimization objective function is defined as one that ensures compliance of the structure under the given boundary conditions. Optimization is carried out with constraints on the natural frequency in addition to the volume constraint. The result of a first step model provides quick insights into the optimum layout for the second step structure. Subsequently, a 3D model in the form of the frustum of a quadrilateral pyramid is developed through topology optimization.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.15 no.4
• /
• pp.897-904
• /
• 2011

In this paper, a novel circuit topology of a low-noise amplifier tunable at 1.8GHz band for PCS and 2.4GHz band for WLAN using a CMOS active inductor is proposed. This circuit topology to reduce higher noise figure of the low noise amplifier with the CMOS active load is analyzed. Furthermore, the noise canceling technique is adopted to reduce more the noise figure. The noise figure of the proposed circuit topology is analyzed and simulated in $0.18{\mu}m$ CMOS process technology. Thus, the simulation results exhibit that the noise performance enhancement of the tunable low noise amplifier is about 3.4dB, which is mainly due to the proposed new circuit topology.

• Architectural research
• /
• v.11 no.1
• /
• pp.15-23
• /
• 2009

An application of the constrained adaptive topology optimization (CATO) algorithm is described for three-dimensional topology optimization of engineering structures. The enhanced assumed strain lower order solid finite element (FE) is used to evaluate the values of objective and constraint functions required in optimization process. The strain energy (SE) terms such as elastic and modal SEs are employed as the objective function to be minimized and the initial volume of structures is introduced as the constraint function. The SIMP model is adopted to facilitate the material redistribution and also to produce clearer and more distinct structural topologies. The linearly weighted objective function is introduced to consider both static and dynamic characteristics of structures. Several numerical tests are tackled and it is used to investigate the performance of the proposed three-dimensional topology optimization process. From numerical results, it is found to be that the CATO algorithm is easy to implement and extremely applicable to produce the reasonable optimum topologies for three dimensional optimization problems.

• Convergence Security Journal
• /
• v.22 no.4
• /
• pp.169-178
• /
• 2022

In general, organizations operating multi-domain networks find it difficult to represent and manage multiple domain net works on a single screen space. Instead, most of them are managed with multiple screens visualizing network topology by domain or partitioning one screen area into multiple domains. We propose an efficient method to visualize the topology using only minimal connection information between domain-agnostic nodes in this work. This method visualizes the topology by utilizing centrality indices representing the influence of nodes in the network. Furthermore, the method dynamically segments the entire node's display area using virtual Root nodes to auto-separate domains and weights of child nodes and placing nodes in 3D space. Thus, although it is a straightforward method, the multi-domain network topology can be visualized with only minimal connection information between nodes.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.3B
• /
• pp.225-234
• /
• 2009

Recently IPTV service is penetrating to the ordinary home users very swiftly. One of the first phase of IPTV service is considered to be VoD, and a nationwide availability of the VoD service imposes tremendous pressure to the network resource due to its requirements for the broad bandwidth, the inherent nature of unicast technology, and the large scalability, etc. This work suggests a novel and practical method to the design of network resource for the VoD service. Especially, we explore the distributed content storage problem that takes into account the popularity of the video contents and its corresponding link dimensioning problem that takes into account the grade of service for the flow level quality of service about the VoD service. By assuming a realistic topology for the nationwide IP backbone network of Korea, which is a typical tree topology, we suggest an analytic method for the design of VoD service.