• Journal of Institute of Control, Robotics and Systems
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• v.9 no.3
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• pp.218-226
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• 2003

Due to the friction characteristics of pump, cylinder packing and passenger car, in the elevation system actuated with hydraulic inverter, there exist dead zones. which cannot be controlled by a PID controller. To overcome the drawbacks, in this paper, we propose a new hybrid fuzzy-sliding mode control scheme, which controls the controller output between a sliding mode control output and a PID control output by fuzzy control method. The proposed hybrid control scheme achieves an improved control performance by using both controllers. We first propose a design method of the hybrid controller far a hydraulic system controlled by inverters, then propose a design method of a hybrid fuzzy-sliding mode centre] scheme. The effectiveness of the proposed control scheme is shown by simulation results, in which the proposed hybrid control method yields better control performance then the PID controlled scheme, not only in the zero-crossing speed region but also in the overall control region including steady-state region.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.8B
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• pp.739-746
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• 2004

An ATM/AAL2 is standardized to transmit delay sensitive application services, which has small size packet, efficiently. An AAL2 transmission scheme is used to deliver voice and data traffic on the lob interface between base station (Node-B) and Radio Network Controller (RNC) in UMTS network. To predict AAL2 performance, a detailed end-to-end UMTS network performance simulator was developed. We performed detailed simulation(cell packing density and bandwidth gain) for voice and data services in UTRAN. The results indicate that the maximum bandwidth gain in Node-B is about 17% and the bandwidth gain of AAL2 multiplexing in $I_{ub}$ for data services is less than that for voice service. Futhermore, the more offered load increase the more the bandwidth gain decreases in a concentrator.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.123-124
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• 2006

Usually, hydraulic cylinder is widely used as the actuator in the equipment of construction machines, airplane and military machines. In case of these devices, due to use under severe environment such as water, $SiO^2$ and dust, etc. seal which has high packing ability and long service life has been required. These characteristics are largely influenced by material and geometries of seal such as approach angle, withdrawal angle and interference. Recently, many a study about seal material has been performed so that many materials have been developed. But the concrete studies including the relationships between geometry of seal and sealing performance have hardly been performed yet. Therefore, in this study, we predicted the deformation behavior and contact normal distribution of dust seal with the variation of geometries of seal lip using finite element analysis. And based on the results of analyses, we discussed the effects of the design variables fur sealing performance of the dust seal.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.5
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• pp.942-946
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• 2009

A scan order converter has to be placed before the JPEG encoder to provide $8{\times}8$ blocks from the pixels in raster scan order. Recently a hardware architecture has been proposed to implement a scan converter based on the single line memory. Since both read and write accesses happen at each cycle, however, the largest part of the entire power budget is occupied by the SRAM itself. In this paper, the data packing and unpacking procedure is inserted in the processing chain, such that the access frequency to the SRAM is reduced to 1/8 by adopting a packed larger data unit. The simulation results show that the resultant power consumption is reduced down to 16% for the SXGA resolution.

• Nuclear Engineering and Technology
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• v.47 no.5
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• pp.546-558
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• 2015

Chord length sampling method in Monte Carlo simulations is a method used to model spherical particles with random sampling technique in a stochastic media. It has received attention due to the high calculation efficiency as well as user convenience; however, a technical issue regarding boundary effect has been noted. In this study, after analyzing the distribution characteristics of spherical particles using an explicit method, an alternative chord length sampling method is proposed. In addition, for modeling in finite media, a correction method of the boundary effect is proposed. Using the proposed method, sample probability distributions and relative errors were estimated and compared with those calculated by the explicit method. The results show that the reconstruction ability and modeling accuracy of the particle probability distribution with the proposed method were considerably high. Also, from the local packing fraction results, the proposed method can successfully solve the boundary effect problem. It is expected that the proposed method can contribute to the increasing of the modeling accuracy in stochastic media.

• Journal of the Korean Institute of Navigation
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• v.14 no.1
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• pp.21-38
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• 1990

This paper discusses the various modes of operations of cargo ships which are liner operations, tramp shipping and industrial operations, and mathematical programming, simulation , and heuristic method that can be used to solve ships routing and scheduling problems for each of these operations. In particular, this paper put emphasis on a crude oil tanker scheduling problem. The problem is to achieve an optimal sequence of cargoes or an optimal schedule for each ship in a given fleet during a given period. Each cargo is characterized by its type, size, loading and discharging ports, loading and discharging dates, cost, and revenue. Our approach is to enumerate all feasible candidate schedate schedules for each ship, where a candidate schedule specifies a set of cargoes that can be feasibly carried by a ship within the planning horizon , together with loading and discharging dates for each cargo in the set. Provided that candidate schedules have been generated for each ship, the problem of choosing from these an optimal schedule for each ship is formulated as a set partitioning problem, a set packing problem, and a integer generalized network problem respectively. We write the PASCAL programs for schedule generator and apply our approach to the crude oil tanker scheduling problem similar to a realistic system.

• Structural Engineering and Mechanics
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• v.76 no.5
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• pp.653-661
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• 2020

The paper presents a study regarding rubber compressibility behavior. The objective is to analyze the effect of compression degree of rubber on its mechanical properties and propose a new methodology based on reverse engineering to predict compressibility degree based on uniaxial stretching test and Finite Element Analysis (FEA). In general, rubbers are considered to be almost incompressible and Poisson's ratio is close to 0.5. Since this property is intimately related to the rubber packing density, little changes in Poisson's ratio can lead to significant changes regarding mechanical behavior. The deviatory hyperelastic constants were obtained through experimental data fitting by least squares method for the most relevant constitutive models implemented in commercial software Abaqus, such as: Neo-Hooke, Mooney-Rivlin, Ogden, Yeoh and Arruda-Boyce, whereas the hydrostatic part was determined through an optimization algorithm implemented in the Abaqus environment by Python scripting. The simulation results presented great influence of the Poisson's ratio in the rubber specimen mechanical behavior mainly for high strain levels. A conventional pure volumetric compression test was also carried out in order to compare the results obtained by the proposed methodology.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.1
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• pp.56-62
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• 2024

By introducing curing kinetics and chemo-rheology for the epoxy resin formulation for ultra-high voltage gas insulated switchgear (GIS) Insulating Spacers, a study was conducted to simulate the curing behavior, flow and warpage analysis for optimization of the molding process in automatic pressure gelation. The curing rate equation and chemo-rheology equation were set as fixed values for various factors and other physical property values, and the APG molding process conditions were entered into the Moldflow software to perform optimization numerical simulations of the three-phase insulating spacer. Changes in curing shrinkage according to pack pressure were observed under the optimized process conditions. As a result, it was confirmed that the residence time in the solid state was shortened due to the lowest curing reaction when the curing holding pressure was 3 bar, and the occurrence of deformation due to internal residual stress was minimized.

• Applied Chemistry for Engineering
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• v.18 no.5
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• pp.424-432
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• 2007

With the aiming to improve the comprehension of an expansion process of perlite, a numerical study has been carried out, concerning a water vapor bubble growth in a softened perlite melt. Isothermal case of the model is investigated and compared with the experimental results. Water content is an intrinsic parameter in a perlite expansion. With increasing water content, the expansion time is faster. But it can not be changed easily in an industrial process. Initial temperature is a changeable parameter in an industrial process. Higher initial temperature hastens the expansion time and this can be a key parameter in an industrial process. Experimental results are observed by SEM. Increasing initial temperature, perlite shape becomes close to sphere. Calculated bubble growth results are compared with experimental results. Packing density is measured and compared with simulated results. These results indicate that some other factors are applied on the model during heat transformation to work.

• Journal of KIISE
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• v.44 no.2
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• pp.115-123
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• 2017

A message processor is server software that receives non-realtime messages as well as realtime messages from clients that need to be processed within a deadline. With the recent advances of micro-processor technologies and Linux, the message processor is often implemented in Linux-based multi-core servers and it is important to use cores efficiently to maximize the performance of system in multi-core environments. Numerous research efforts on a real-time scheduler for the efficient utilization of the multi-core environments have been conducted. Typically, though, they have been conducted theoretically or via simulation, making a subsequent real-system application difficult. Moreover, many Linux-based real-time schedulers can only be used in a specific Linux version, or the Linux source code needs to be modified. This paper presents the design of a Linux-based message processor for multi-core environments that maps the threads to the cores at user level. The message processor is implemented through a modification of the traditional RM algorithm that consolidates the real-time messages into certain cores using a first-fit-based bin-packing algorithm; this minimizes the response-time delay of the non-real-time messages, while guaranteeing the violation rate of the real-time messages. To compare the performances, the message processor was implemented using the two multi-core-scheduling algorithms GSN-EDF and P-FP, which are provided by the LITMUS framework. The benchmarking results show that the response-time delay of non-real-time messages in the proposed system was improved up to a maximum of 17% to 18%.