• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.4
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• pp.1-8
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• 2000

A defect of decrease in TCP throughput can be investigated in asymmetric environment of different uplink and downlink bandwidths. Under two-way TCP traffic, the total link utilization is decreased by the successive injection of data packets in buffer. To solve these problems, terminal ACK filtering and packet scheduling mechanisms are introduced in this paper. ACK filtering eliminates the buffered ACK packets and transmits recent ACK packets in the uplink with limited bandwidth. Packet scheduling is the method of preventing 'clustering' and 'ack compression' states which are generated in the two-way TCP traffic. The guarantee of the data traffic in reverse TCP connection and the high throughput in forward TCP connection are investigated by simulation.

• Journal of IKEEE
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• v.24 no.1
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• pp.1-8
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• 2020

In this paper, a semi-infinite array analysis method is proposed to analyze the defects that may occur during the fabrication of the frequency selective radome. In the analysis of N×N finite array structure using 3D analysis software, much analysis time and memory are required, whereas the semi-infinite array structure analysis proposed in this paper can predict relatively accurate electromagnetic performance while reducing the analysis time. In comparison with the results of the periodic simulation, the simulation of the semi-infinite array structure confirmed the error within ±3%. To verify the results of the simulation, the results were compared with the measured results, and the same tendency at the point of performance change and similar performance degradation at the band of interest were investigated. Using the proposed semi infinite array structure analysis, it is confirmed that the analysis of defects in the electromagnetic periodic structure is possible.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1096-1101
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• 2004

By a tremendous expansion of Internet users, there's a number effects that cause the phenomenon of bottlenecked switching packets from routers. In order to tear down this problem, distributed system is applicable to almost every highly performed router systems. The main processor of distributed system, which manages routing table, commands IPC to delivering the forwarding table line processor that eases functionalities of the router. This makes the system having wired-speed forwarding function based on the hardware so that the performance of the network can be enhanced. Therefore, IPC, which assign a part of router, is necessary to exchange data smoothly and the constitution of IPC using Ethernet is widely adapted as a method for saving investment. In this paper, R-IPC mechanism improve the packet-processing rate over 10% through changed from defect of conventional Ethernet IPC, that is, 2 layer processing to TCP/IP or UDP/ IP into 1 layer processing for efficient packet forwarding.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1188-1193
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• 2004

So far, there have been grossly 3 types of studies on GF(2m) multiplier architecture, such as serial multiplication, array multiplication, and hybrid multiplication. Serial multiplication method was first suggested by Mastrovito (1), to be known as the basic CF(2m) multiplication architecture, and this method was adopted in the array multiplier (2), consuming m times as much resource in parallel to extract m times of speed. In 1999, Paar studied further to get the benefit of both architecture, presenting the hybrid multiplication architecture (3). However, the hybrid architecture has defect that only complex ordo. of finite field should be used. In this paper, we propose a novel approach on developing serial multiplier architecture based on Mastrovito's, by modifying the numerical formula of the polynomial-basis serial multiplication. The proposed multiplier architecture was described and implemented in HDL so that the novel architecture was simulated and verified in the level of hardware as well as software. The implemented GF(2m) multiplier shows t times as fast as the traditional one, if we modularized the numerical expression by t number of parts.

• Korean Journal of Construction Engineering and Management
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• v.8 no.3
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• pp.66-75
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• 2007

Recently, After Service(AS) management in apartment housing projects has been appeared as one of the major factors for improving customer satisfaction, and increasing competitiveness and raising image of a company in construction industry. The primary objective of this paper is to propose a web-based AS management system which enables field engineers to effectively collect AS information required from customers and effectively manage the statuses and results of AS performed. It is anticipated that the effective use of the system proposed in this paper would be able to improve communication efficiency among the AS participants, and help field engineers systematically manage and accumulate data that might be utilized as a reference in future construction projects.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.2
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• pp.135-143
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• 2013

Friction Stir Welding (FSW) was developed, it is successfully commercialized in the field of transportation vehicles. In this study, we analyzed the defects of A2024-T4 alloy using non-destructive test of radiograph, ultrasonic, electrical conductivity and destructive test of microstructure observation, tensile strength. As the results of experiment, mapping of defects was obtained. Fine defects which were not detected in radiograph test were detected in ultrasonic test, and it enabled efficient detection of defects by difference of sound pressure and color. The values of electrical conductivity was decreased as amount of defects was increasing. Joint efficient of defect-free weldment that found by non-destructive and destructive test was 91%. Therefore it was considered that non-destructive test of friction stir welded A2024-T4 Alloy was an efficient method.

• Journal of the Korean Magnetics Society
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• v.23 no.1
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• pp.18-25
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• 2013

MFL PIG (Magnetic Flux Leakage Pipeline Inspection Gauge) is called the system which detects the defect for underground pipelines by using magnetic flux leakage method in nondestructive testing. This method is very suitable for testing pipelines because pipeline has high magnetic permeability. MFL PIG generates the magnetic fields to the pipe axially oriented, and detect the signal of leakage flux by using hall sensor. However, MFL PIG is hard to detect the axially oriented crack with small size because the magnetic flux leakage is not enough to be occurred. To detect the small size and axially oriented crack, the circumferential MFL (CMFL) PIG is being proposed and it can maximize the leakage flux for the axial crack by performing magnetic fields circumferentially on the pipe. In this paper, CMFL PIG is applied to detect the axially oriented crack with small size and the analysis for the distribution and the amplitude of the leakage flux signal is performed by using three dimensional finite element method. From sensing signals, the method how to determine the shape of axially oriented cracks is proposed and verified with experiment.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.4 no.1
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• pp.29-34
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• 2010

The fully implantable hearing devices (FIHDs) have been studied to compensate the defect of conventional hearing aids. Typically, a microphone for FIHDs was implanted under the skin of the temporal bone. So, implantable microphone characteristics can be affected by the eating food, chattering teeth and moving artifact. In this paper, we fabricated the physical model that was similar to characteristics of human temporal bone and skin, and we measured implanted microphone sensitivity for effect of bone conducted noise signal. For the measurement of microphone sensitivity, we applied 1 kHz pure sounds that were transmitted to implanted microphone and sine wave vibrations of varied frequency were simultaneously transmitted through the artificial bone. As a result, sensitivity of implanted microphone can be modified by bone conducted signal and this phenomenon was confirmed at varied frequency band.

• Polymer(Korea)
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• v.36 no.4
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• pp.536-541
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• 2012

The effects of silica content were studied on UV curing characteristics and defect formations in imprinted patterns of hundreads nanometer size for the photo-curable imprinting composites with silica particles. An increase in elasticity and a decrease in shrinkage were observed with an increase in silica content in the imprinting resin which was UV cured at room temperature. However, the patterned nano-pillars were stuck together with neighboring nano-pillars if the amount of silica is more than 7 wt%. This can be ascribed to the increased viscosity of imperfectly cured resin due to the obstruction of the photo-reaction by silica particles. Addition of silica to the imprinting resin is useful in enhancing the strength of the cured resin although it is difficult to get good imprinted patterns for the resin with more than 7 wt% of silica due to the reduction of photo-reaction conversion.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.18 no.36
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• pp.49-59
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• 1995

The vehicle navigation system is developed for helping driver to retrieve driving information more easily and fastly. Navigation System informs driver many pieces of driving information - roadway structure and system, on-line traffic condition, the position of vehicle, route guidance, destination and other information service. As the style of information is diverse and the amount of information is large, driver may have mental and visual overload. The display of information can disturb the driver's attention and this can cause accidents. This state is caused by the defect of human-machine interactions. When the navigation system is designed, human factors - cognitive, judgment, operating - must be considered. The display style must be designed simply and easily, not to be obstacle of human -machine interface. In this study, outside-in view display style and inside-out view display style are compared each other. Two factors are measured. One is cognitive factor-time of cognition on information that is displayed by screen display, cognition error rate. The other is image of screen display - subject's feeling about several styles of display, degree of subject's preference. The prototype of roadway is four kinds - Cross, T-cross, Y-cross and O-cross. Roadway display for test is taken from paper maps. Traffic condition display style, vehicle position display style and route guidance display style are taken from current display style. Traffic condition display style is symbol. Vehicle position display style and route guidance display style are described as color and symbol. The test on screen display is implemented doing given tasks. Then the test is analyzed statistically, The result of test analysis gives the guideline to the designer for the map display of the vehicle navigation system.