• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.2
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• pp.97-104
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• 2013

This paper introduces waiting time based periodic packet discard policy for frame based scheduler. This policy can be used with conventional packet discard policy or buffer management schemes, such as drop-tail or random early detection. Proposed discard policy discards packets, which are stayed in the buffer longer than threshold, at every period of scheduling. This decision of discard is based on waiting time of packet. In this paper, mathematical analysis is performed with situation of network congestion. Also, the simulation is performed to evaluate the performance of proposed discard policy. In the result, proposed discard policy can limit queuing delay by threshold. Also, if the packet discard is performed before scheduling and threshold is set with smaller value than frame length, it can limit the throughput of traffic.

• Journal of Korean Society of Transportation
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• v.27 no.3
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• pp.141-148
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• 2009

An inappropriate evaluation of capacity leads to the incorrect and impractical result due to the transfer of error to the analysis and the evaluation on highway system. The traffic accident which reduces the capacity of road temporarily generates unpredictable congestion, causing difficulties in congestion management. Therefore, this research aims on the measurement of the capacity of the road in accordance to the speed at the accident which is a basic factor when performing analysis. Based on the given approach, the behavior of a vehicle in highway is understood to develop model of critical gap and model of maximum flow rate with respect to the speed of traffic flow. With the established model, the reduction rate of the capacity in highway system at the accident is measured. The result shows that the capacity is reduced by 37% when the speed of the traffic flow is 40km/h. Although the developed model can't be verified clearly, this research has shown that the reduction rate of the capacity in road system has a close relation to the speed.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.2072-2072
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• 2009

최근 연구들에서, 증강 현실(Augmented Reality; AR) 환경에서의 촉각 상호작용에 대한 가능성이 논의되었다. 비젼 기반의 트래킹을 기초로 한 증강 현실 기술은 미리 정의된 2차원 마커(marker)를 이용하여, 카메라로부터 획득된 실시간 영상 위에 가상 물체를 증강한다. 그러나, 카메라로부터 획득된 데이터는 몇몇 오차 요인들, 예를 들어 마커의 위치를 인식하는데 나타나는 오차, 카메라 안에 존재하는 센서 잡음 등으로 인해서 마커 잡음(마커를 인식하면서 나타나는 잡음)이 불가결하게 발생하게 된다. 이러한 이유로 인해서, 사용자가 한 손에는 마커를, 다른 한 손으로는 촉감 장치를 이용하여, 마커에 증강된 물체를 만질 때, 마커 잡음은 힘의 떨림(force trembling)을 발생시킨다. 심지어, 이러한 현상은 정지된 마커에 증강된, 마커가 움직이지 않는 상황에서도 발생한다. 게다가, 마커 위에 증강된 물체가 약간 빠른 속도로 이동하게 될 경우, 측정된 이동 거리는 연속적인 프레임(frame)들 간의 불연속적일 수 있다. 만약 사용자가, 대략 30Hz로 위치와 방향이 갱신되는 가상물체를 촉각적으로 상호작용하려 한다면, 계산되는 반력은 급작스런 힘의 변화를 생성하게 될 수도 있다. 이러한 현상을 극복하기 위해서, 마커 잡음을 최소화하기 위해서 정적 임계값(constant threshold)을 이용할 뿐만 아니라, 보간법을 같이 사용한 방법이 있었다. 하지만, 이러한 방법은 정적 임계값을 이용하고, 영상 프레임 갱신 속도와(video frame rate)와 촉각 프레임 갱신 속도가 일정하다는 가정을 사용하였기 때문에, 여전히 힘의 불연속적인 발생이 나타난다. 따라서, 이 논문에서는 두 가지 방법을 이용하여 증강 현실 내에서, 발생할 수 있는 힘의 불연속적인 변화를 보정하는 두 가지 방법, 잡음 제거를 위한 확장된 칼만 필터(Extend Kalman Filter)와 영상과 촉각 갱신 속도 차이에 따른 갑작스런 힘의 변화를 제거하기 위한 적응적 외삽법(Adaptive Extrapolation method)을 제안한다.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.173-177
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• 2009

With the advent of light-weight daily physiological signal monitoring sensors, intelligent inference and analysis method for physiological signal monitoring application, commercialized products and services are released. However, practical constraints still remain for daily physiological signal monitoring. Most devices provide rough health check function and analyze with randomly sampled measurements. In this work, we propose the probabilistic modeling of physiological signal analysis. This model represent the relationship between previous user measurement (history), other group`s type, model and current observation. From the experiment, we found that the personalized analysis with long term regular data shows reliable result and reduces the analyzing errors. In addition, participants agree that the personalized analysis shows reliable and adaptive information than other standard analysis method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9B
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• pp.823-833
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• 2003

To satisfy the requirements of the real-time Internet services, queue management and scheduling schemes should be enhanced to accommodate the delay and jitter characteristic of them. Although the existing queue management schemes can address the congestion problems of TCP flows, they have some problems in supporting real-time services. That is, they show performance degradation when burst traffics are continuously going into the system after the queue is occupied at a predefined threshold level. In addition, under the congestion state, they show large jitter, which is not a desirable phenomenon for real-time transmissions. To resolve these problems, we propose a SDRED (State Dependent Random Early Detection) and dynamic scheduling scheme that can improve delay and jitter performances by adjusting RED parameters such as ma $x_{th}$ and $w_{q}$ according to the queue status. The SDRED is designed to adapt to the current traffic situation by adjusting the max,$_{th}$ and $w_{q}$ to four different levels. From the simulation results, we show that the SDRED decreases packet delays in a queue and has more stable jitter characteristics than the existing RED, BLUE, ARED and DSRED schemes.mes.mes.

• The Journal of the Korea Contents Association
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• v.8 no.8
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• pp.253-260
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• 2008

The research for a 3-axial accelerometer sensor has increased dramatically in the fields of cellular phone, PDA, etc. In this paper, we develop a human walking detection algorithm using 3-axial accelerometer sensor and a user interface system to show the activity expenditure in real-time. To measure a walking number more correctly in a variety of walking activities including walking, walking in place, running, slow walking, we propose a new walking number detection algorithm using adaptive threshold value. In addition, we calculate the activity expenditure base on counted walking number and display calculated activity expenditure on UI in real-time. From the experimental results, we could obtain that the detection rate of proposal algorithm is higher than that of existing algorithm using a fixed threshold value about $5{\sim}10%$. Especially, it could be found out high detection rate in walking in place.

• Archives of Reconstructive Microsurgery
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• v.9 no.2
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• pp.120-126
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• 2000

Microsurgical reconstruction of the hand demands recovery of the sensation of the reconstructed free flap as well as microsurgeon's intelligence, technique and experience. Even with adequate soft tissue coverage and skeletal mobility, an insensate hand is prone to further injury and is unlikely to be useful to the patients. Authors have performed 8 cases of neurosensory free flaps in the hand, 4 cases of wrap around, 3 dorsalis pedis and 1 lateral arm flap, from July 1992 through June 1999 and followed up average 4 years and 4 months. Wrap around flap was performed for reconstruction of 4 cases of thumb, repairing deep peroneal nerve and superficial radial nerve by epineurial neurorrhaphy, and followed up for average 3 years and 10 months and calculated 9mm in the static 2 point discrimination test. Dorsalis pedis flap were 3 cases for reconstruction of the ray amputation, extensor tendon exposure and wrist exposure. Deep peroneal nerve and branch of the ulnar nerve was repaired by epineurial neurorrhaphy calculating 6mm and superficial peroneal nerve and superficial radial nerve averaging 18mm in the static 2 point discrimination test for follow up average 2 years and 9 months. Lateral arm flap was 1 case for reconstruction of the ray amputation in the hand repairing posterior cutaneous nerve to the arm to the superficial radial nerve calculating 20mm for follow up 6 years and 8 months.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.1
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• pp.105-115
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• 2014

A numerical analysis on the smoke behavior and evacuee safety has been performed with computational fluid dynamics. The purpose of this study is to build computational processes for an evacuation and prevention of a fire disaster of a 3 km-length tunnel in Korea. To save computational cost, 1.5 km of the tunnel that can include a few cross-passing tunnels is considered. We are going to assess the fire safety in a road tunnel according to the smoke level, which consists of the smoke density and the height from the floor. The smoke density is obtained in detail from three-dimensional unsteady CFD analysis. To obtain proper temperature distributions on the tunnel wall, one-dimensional conduction equation is considered instead of an adiabatic wall boundary or a constant heat flux. The tunnel considered in this study equips the cross passing tunnels for evacuees every 250 m. The distance is critical in both safety and economy. The more cross passing tunnels, the more safe but the more expensive. Three different jet fan operations can be considered in this study; under- and over-critical velocities for normal traffic condition and 0-velocoty operation for the traffic congestion. The SE (smoke environment) level maps show a smoke environment and an evacuating behavior every moment.

• Journal of Korean Society of Transportation
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• v.21 no.5
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• pp.97-110
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• 2003

The sight distance at unsignalized intersections is the one of the fundamental geometric design elements, and can ensure safety and efficient operations. Despite its importance, little research attention has been directed in Korea compared to developed countries such as European countries, the United States, and Japan. AASHTO ISD policies have been applied to the intersection design in Korea without any revise, which can produce unrealistic and unadoptable design values. Those values are emerged from several reasons because the AASHTO ISD has been calibrated based on the local data. Therefore the ISD hardly takes into account the local characteristics of Korea such as driving behavior. vehicular movement and roadway conditions. The objective of this study is to calculate the appropriate ISD values for unsignalized intersections in the urban area in Korea. In this study, we employed the ISD model of AASHTO(2001), which is based on gap acceptance theory and can account for and take the driving and roadway conditions in Korea into consideration. The approach can also consider the complex driving maneuvers at the intersections in a proper and simple manner. The results in this study show that the ISD design criteria currently used in Korea are more conservative(safer) than those of the USA. In other words, the ISD using field data collected in this study has generally smaller values than those in USA.

• Journal of Internet Computing and Services
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• v.18 no.4
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• pp.51-59
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• 2017

With the growth of Cloud computing, it is important to consider resource management techniques to minimize the overall costs of management. In cloud environments, each host's utilization and virtual machine's request based on user preferences are dynamic in nature. To solve this problem, efficient allocation method of virtual machines to hosts where the classification of virtual machines and hosts is undetermined should be studied. In reducing the number of active hosts to reduce energy consumption, thresholds can be implemented to migrate VMs to other hosts. By using Fuzzy logic in classifying resource requests of virtual machines and resource utilization of hosts, we proposed an adaptive VM allocation and migration approach. The allocation strategy classifies the VMs according to their resource request, then assigns it to the host with the lowest resource utilization. In migrating VMs from overutilized hosts, the resource utilization of each host was used to create an upper threshold. In selecting candidate VMs for migration, virtual machines that contributed to the high resource utilization in the host were chosen to be migrated. We evaluated our work through simulations and results show that our approach was significantly better compared to other VM allocation and Migration strategies.