• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3D
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• pp.189-196
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• 2012

South Korea has achieved economic development rapidly during last 50 years. However, such fast economic development with industrialization caused skyrocketing increase of automobiles. The increase of automobile has created various problems in the cities. Problems like traffic congestion and accident, environmental pollution, noise, and vibration have done human beings, who are the principal agents harm. They have made citizens understand how important Green transportation, especially pedestrian movement, is. Recently, installation of pedestrian facilities has been expanded. If walking facilities are incorrectly designed, they can create inconvenience, danger and the state of emergency due to the lack of safety and pleasant feelings. However, since the importance of the facility designs has been neglected due to the lack of understanding, it is hard to improve the facilities. Therefore, we need various studies of walking simulation in order to research the designs for pedestrians' safety and convenience. The objective of this study is to analyze the pedestrians' behavior and movement in a transfer subway station. The improvement of walking environment was made after chasing and analyzing the pedestrians' movement which is investigated in the actual field using SimWalk simulation program.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.8
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• pp.638-651
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• 2000

When the bandwidth resources in a packet-switched network are shared among sessions by MAX-MIN flow control each session is required to transmit its data into the network subject to the MAX-MIN fair rate which is solely determined by network loadings. This passive behavior of sessions if fact can cause seri-ous QoS(Quality of Service) degradation particularly for real-time multimedia sessions such as video since the rate allocated by the network can mismatch with what is demanded by each session for its QoS. In order to alleviate this problem we extend the concept of MAX-MIN fair bandwidth allocations as follows: Individual bandwidth demands are guaranteed if the network can accommodate them and only the residual network band-width is shared in the MAX-MIN fair sense. On the other hand if sum of the individual bandwidth demands exceeds the network capacity the shortage of the bandwidth is shared by all the sessions by reducing each bandwidth guarantee by the MAX-MIN fair division of the shortage. we present a novel flow control algorithm to achieve this extended MAX-MIN fairness and show that this algorithm can be implemented by the existing ATM ABR service protocol with minor changes. We not only analyze the steady state asymptotic stability and convergence rate of the algorithm by appealing to control theories but also verify its practical performance through simulations in a variety of network scenarios.

• The KIPS Transactions:PartC
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• v.12C no.5 s.101
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• pp.695-700
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• 2005

To provide the fair rate and achieve the fair bandwidth allocation, many per-flow scheduling algorithms have been proposed such as fair queueing algorithm for congestion control. But these algorithms need to maintain the state, manage buffer and schedule packets on a per-flow basis; the complexity of these functions may prevent them from being cost-effectively implemented. In this paper, therefore, to acquire cost-effectively for implementation, we propose a CS-FNE(Core Stateless FNE) algorithm that is based on FM(Flow Number Estimation), and evaluated CS-FNE scheme together with CSFQ(Core Stateless Fair Queueing), FRED(Fair Random Early Detection), RED(Random Early Detection), and DRR(Dynamic Round Robin) in several different configurations and traffic sources. Through the simulation results, we showed that CS-FNE algorithm can allocate fair bandwidth approximately than other algorithms, and CS-FNE is simpler than many per-flow basis queueing mechanisms and it can be easily implemented.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.10B
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• pp.1979-1985
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• 1999

In this paper, we offer an analysis method for SL/D/1/K queueing system, where the shifting-level (SL) process proposed in the part I of this study[1]. Since an exact analysis of SL/D/1/K queueing system is very difficult, we propose an approximation method, where the queze sizes at input state transition epochs is quantized and thus the name 'quantization reduction method'. We provide the upper and lower bounds of the approximation for the system size distribution also, In addition, since the continuos version of well-known DAR(1) model is a kind of SL process with exponential correlation term only, the proposed method can be directly applied to the analysis of DAR(1)/D/1/K queueing system as well.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.1
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• pp.70-75
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• 2018

Smart Factory is an intelligent factory that can enhance productivity, quality, customer satisfaction, etc. by applying information and communications technology to the entire production process including design & development, manufacture, and distribution & logistics. The precise amount of data generated in a smart factory varies depending on the factory's size and state of facilities. Regardless, it would be difficult to apply traditional production management systems to a smart factory environment, as it generates vast amounts of data. For this reason, the need for a distributed big-data processing system has risen, which can process a large amount of data. Therefore, this article has designed a Gluster File System (GlusterFS)-based distributed big-data processing system that can be used in a smart factory environment. Compared to existing distributed processing systems, the proposed distributed big-data processing system reduces the system load and the risk of data loss through the distribution and management of network traffic.

• Journal of Advanced Navigation Technology
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• v.18 no.5
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• pp.461-467
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• 2014

Active queue management (AQM) algorithms run on routers and detect incipient congestion by typically monitoring the instantaneous or average queue size. When the average queue size exceeds a certain threshold, AQM algorithms infer congestion on the link and notify the end systems to back off by proactively dropping some of the packets arriving at a router or marking the packets to reduce transmission rate at the sender. Among the existing AQM algorithms, random early detection (RED) is well known as the representative queue-based management scheme by randomizing packet dropping. To reduce the number of timeouts in TCP and queuing delay, maintain high link utilization, and remove bursty traffic biases, the RED considers an average queue size as a degree of congestions. However, RED do not well in the specified networks conditions due to the fixed parameters($P_{max}$ and $TH_{min}$) of RED. This paper addresses a extended RED to be adapted in various networks conditions. By sensing network state, $P_{max}$ and $TH_{min}$ can be automatically changed to proper value and then RED do well in various networks conditions.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.07a
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• pp.100-102
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• 2015

In recent years, using a smart phone that can access the Internet becomes routine in society through development of information and communication technology. On land, as especially actual accidents and research results show risk that using the smart phone while driving at the same time, and there are traffic laws and regulations that restriction of using of smart phone. But the regulations on the use of smart phones at sea is incomplete state. On this paper. We invested present status of use and reality of smart phone at sea and analyzed the subjective risk for judging to apply to regulation. And we analyzed risk quantitatively by using the simulation experiment; it Suggested a direction of guideline for use of smart phone at sea.

• IE interfaces
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• v.17 no.spc
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• pp.111-121
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• 2004

In this paper, we propose an urgency and efficiency based wireless packet scheduling (UEPS) algorithm that is able to schedule real time (RT) and non-real time (NRT) traffics at the same time. The proposed UEPS algorithm is designed to support wireless downlink packet scheduling in the OFDMA system which is a strong candidate wireless system for the next generation mobile communications. The UEPS algorithm uses the time-utility function as a scheduling urgency factor and the relative status of the current channel to the average one as an efficiency indicator of radio resource usage. The design goal of the UEPS algorithm is to maximize throughput of NRT traffics with satisfying QoS requirements of RT traffics. The simulation study shows that the proposed UEPS algorithm is able to give better throughput performance than existing wireless packet scheduling algorithms such as proportional fair (PF) and modified-largest weighted delay first (M-LWDF) while satisfying QoS requirements of RT traffics such as the average delay and the packet loss rate under various traffic loads.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.312-312
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• 2013

GaN based light emitting diodes (LEDs) are important devices that are being used extensively in our daily life. For example, these devices are used in traffic light lamps, outdoor full-color displays and backlight of liquid crystal display panels. To realize high-brightness GaN based LEDs for solid-state lighting applications, the development of p-type ohmic electrodes that have low contact resistivity, high optical transmittance and high refractive index is essential. To this effect, indiumtin oxide (ITO) have been investigated for LEDs. Among the transparent electrodes for LEDs, ITO has been one of the promising electrodes on p-GaN layers owing to its excellent properties in optical, electrical conductivity, substrate adhesion, hardness, and chemical inertness. Sputtering and e-beam evaporation techniques are the most commonly used deposition methods. Commonly, ITO films on p-GaN by sputtering have better transmittance and resistivity than ITO films on p-GaN by e-bam evaporation. However, ITO films on p-GaN by sputtering have higher specific contact resistance, it has been demonstrated that this is due to possible plasma damage on the p-GaN in the sputtering process. In this paper, we have investigated the advanced sputtering using plasma damage-free p-electrode. Prepared the ITO films on the GaN based LEDs by e-beam evaporation, normal sputtering and advanced sputtering. The ITO films on GaN based LEDs by sputtering showed better transmittance and sheets resistance than ITO films on the GaN based LEDs by e-beam evaporation. Finally, fabricated of GaN based LEDs by using advanced sputtering. And compared the electrical properties (measurement by using C-TLM) and structural properties (HR-TEM and FE-SEM) of ITO films on GaN based LEDs produced by e-beam evaporation, normal sputtering and advanced sputtering. As a result, It is expected to form plasma damage free-electrode, and better light output power and break down voltage than LEDs by e-beam evaporation and normal sputter.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.1
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• pp.341-363
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• 2016

Haze or fog is a common natural phenomenon. In foggy weather, the captured pictures are difficult to be applied to computer vision system, such as road traffic detection, target tracking, etc. Therefore, the image dehazing technique has become a hotspot in the field of image processing. This paper presents an overview of the existing achievements on the image dehazing technique. The intent of this paper is not to review all the relevant works that have appeared in the literature, but rather to focus on two main works, that is, image dehazing scheme based on atmospheric veil and image dehazing scheme based on dark channel prior. After the overview and a comparative study, we propose an improved image dehazing method, which is based on two image dehazing schemes mentioned above. Our image dehazing method can obtain the fog-free images by proposing a more desirable atmospheric veil and estimating atmospheric light more accurately. In addition, we adjust the transmission of the sky regions and conduct tone mapping for the obtained images. Compared with other state of the art algorithms, experiment results show that images recovered by our algorithm are clearer and more natural, especially at distant scene and places where scene depth jumps abruptly.