• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.1
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• pp.89-97
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• 2009

In this paper, a computer software for dynamic analysis of a high mobility tracked vehicle with pre/post processor is developed. Model of a tracked vehicle is composed of chassis, turret, mount, gun, and road-wheel assembly. Track is modeled as an extensible cable and the track tensions are applied on the wheels as external forces. The system equations of motion and constraint acceleration equations are derived in the joint coordinate space using the velocity transformation method. The pre and post processors are developed using the Visual C++.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.18 no.2
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• pp.137-143
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• 2009

This paper presents the fabrication of inchworm motor for high precision actuator system of large displacement and high force. The inchworm motor consists of a extend actuator that provides displacement of tool guide and two clamping actuators which provide the holding force. In order to avoid the PZT fracture, design of pre-load housing was conducted by flexure hinge structure, because PZT actuator has low tensile and shear. To design the pre-load housing and optimize the clamping mechanism, the static and dynamic analysis were conducted by finite element method. From these results, a prototype of the inchworm motor was fabricated and dynamic characteristic with respect to the various frequency was tested. The maximum velocity of the inchworm motor was $41.1{\mu}m/s$ at 16Hz.

• Journal of environmental and Sanitary engineering
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• v.23 no.4
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• pp.13-21
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• 2008

With the rise in membrane applications, residuals management has become a growing challenge for membrane system. The primary residuals of MF/UF (microfiltration/ultrafiltration) system results from the wastes generated during backwashing. Many regulatory agencies, utilities, and water process engineers are unfamiliar with the characteristics and methods for treatment and disposal of membrane residuals. Therefore, this study was performed to investigate the backwash residuals water quality from the pressurized system with and without pre-coagulation, and to suggest approaches for the backwash residuals treatment. Pressurized MF system was installed at Guui water intake pumping station and operated with raw water taken from the Han River. We compared performances with and without the recycling backwash residuals at flux conditions, 50 LMH and 90 LMH with and without pre-treatment (coagulation). Based on the results, recycling of backwash residuals in pressurized system with pre-coagulation showed applicability of backwash residuals managements. Moreover, the recovery rate also increased up to over 99%.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.6
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• pp.112-122
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• 1995

As an alternative fuel producing less exhaust emissions, natural gas is of interest for use both in SI and CI engines. The potential of natural gas fuelled dual-fuel engine is considered high enough. However, much effort has to be made so that gaseous fuel is used efficiently with simultaneous minimum use of pilot oil. Hence, a simplified three-dimensional model, using a finite volume method in cylindrical coordinates, has been developed to facilitate an understanding of the dual-fuel combustion phenomena and to predict the complex interactions between the pilot distillate and natural gas. The computer model was calibrated by comparing it with the experimental results obtained from diesel engine like combustion bomb tests. In the pre-mixed natural gas combustion, the fuel burning was highly reliant on the injection condition and subsequent burning nature of the pilot distillate.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.5
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• pp.1144-1149
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• 1994

Damage caused in CFRP laminates by low energy impact of steel ball are investigated ultrasonically. Two types of laminated specimens having different stacking sequence are used as a target material. The effects of pre-bending on the behaviors of impact damage are specifically discussed. The initiation and progagation behaviors of delamination were largely dependent upon the bending rigidity of each specimen. Specimen C having higher bending rigidity produced larger delamination damage than the Specimen D having relatively low bending rigidity, however it was little for the Specimen C. Application of pre-bending increased the apparent bending rigidity of target during impacting, it produced delamination at lower impact energy level compared to the case of no preload.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.2
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• pp.476-483
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• 2010

If the data are pre-whitened, then gradient adaptive algorithms which are simpler than higher order statistics algorithms can be used in adaptive blind signal estimation. In this paper, we propose a blind subband affine projection algorithm for multiple-input multiple-output adaptive equalization in the blind environments. All of the adaptive filters in subband affine projection equalization are decomposed to polyphase components, and the coefficients of the decomposed adaptive sub-filters are updated by defining the multiple cost functions. An infinite impulse response filter bank is designed for the data pre-whitening. Pre-whitening procedure through subband filtering can speed up the convergence rate of the algorithm without additional computation. Simulation results are presented showing the proposed algorithm's convergence rate, blind equalization and blind signal separation performances.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.4
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• pp.176-181
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• 2001

As the data rate between chip-to-chip gets high, the skin effect and load of pins deteriorate noise margin. With these, noise disturbances on the bus channel make it difficult for receiver circuits to read the data signal. This paper has proposed a new pre-emphasis driver circuit which achieves wide noise margin by enlarging the signal voltage range during data transition. When data is transferred from a memory chip to a controller, the output boltage of the driver circuit reaches the final values through the intermediate voltage level. The proposed driver supplies more currents applicable to a packet-based memory system, because it needs no additional control signal and realizes very small area. The circuit has been designed in a 0.18 ${\mu}m$ CMOS process, and HSPICE simulation results have shown that the data rate of 1.32 Gbps be achieved. Due to its result, the proposed driver can achieved higher speed than conventional driver by 10%.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.458-461
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• 2005

In this paper, a new type of inchworm motion actuator is developed in fabrication of actuators for micro-press machine. This is consisted of three piezoelectric actuators, one is for moving the tool guide and the other are for clamping the guide. The inchworm motor provides both high load and large displacement in small size actuator. PZT has compressive strength and often fails under tensile stress and pulling. Thus, in order to prevent failure, we have designed pre-load housing and accomplished FEM analysis. The pre-load housing was used for determining the optimal design condition by comparing the von-mises stresses with the change of hinge stiffness. Also, in order to predict the performance of the motor under certain conditions, the system model was simulated using MATLAB. This is open loop control actuator and driven by the period of input voltage.

• Journal of Korean Institute of Industrial Engineers
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• v.24 no.4
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• pp.601-611
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• 1998

The machining accuracy of CNC machine tools will decrease the production lead time because the coordinate compensation of the tool path will be unnecessary to meet design specifications. Improving the accuracy of machined parts enhances the reliability and functionality of the assembly as well as the life of the product. Among various factors affecting the accuracy of machined parts, the ambient temperature is the major factor that refers to the temperature surrounding the machine and workpiece. In this study, an experiment was conducted to confirm the dimensional variations caused by changes in the ambient temperature. The ambient temperature resulted in overcutting when it increased. A developed pre-processor converts the CNC program to compensate the dimensional variations caused by temperature changes. This methodology can be used to determine the machining accuracy and improve the positioning accuracy of a machine tool.

• Environmental engineer
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• s.172
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• pp.48-54
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• 2000