• Journal of Information Processing Systems
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• v.17 no.3
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• pp.489-504
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• 2021

By distributing computing tasks among devices at the edge of networks, edge computing uses virtualization, distributed computing and parallel computing technologies to enable users dynamically obtain computing power, storage space and other services as needed. Applying edge computing architectures to Internet of Vehicles can effectively alleviate the contradiction among the large amount of computing, low delayed vehicle applications, and the limited and uneven resource distribution of vehicles. In this paper, a predictive offloading strategy based on the MEC load state is proposed, which not only considers reducing the delay of calculation results by the RSU multi-hop backhaul, but also reduces the queuing time of tasks at MEC servers. Firstly, the delay factor and the energy consumption factor are introduced according to the characteristics of tasks, and the cost of local execution and offloading to MEC servers for execution are defined. Then, from the perspective of vehicles, the delay preference factor and the energy consumption preference factor are introduced to define the cost of executing a computing task for another computing task. Furthermore, a mathematical optimization model for minimizing the power overhead is constructed with the constraints of time delay and power consumption. Additionally, the simulated annealing algorithm is utilized to solve the optimization model. The simulation results show that this strategy can effectively reduce the system power consumption by shortening the task execution delay. Finally, we can choose whether to offload computing tasks to MEC server for execution according to the size of two costs. This strategy not only meets the requirements of time delay and energy consumption, but also ensures the lowest cost.

• Journal of Korean Society of Transportation
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• v.25 no.6
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• pp.185-196
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• 2007

The aim of this research is to develop a signal control algorithm using internal metering to minimize total delay that vehicles go through, in case a network is oversaturated. To calculate total delay on the network, the authors first detect vehicles' arrivals and departures in the network through the detecting system, and chase the vehicles' flow in the links with a platoon dispersion model. Following these, the authors calculate the queue length in all the inks of the network through the chase of vehicles, deduce the stopped time delay, and finally convert the stopped time delay to the approach delay with a time-space diagram. Based on this calculated delay, an algorithm that calculates the level of the internal metering necessary to minimize the deduced approach delay is suggested. To verify effectiveness of this suggested algorithm, the authors also conduct simulation with the micro-simulator VISSIM. The result of the simulation shows that the average delay per vehicle is 82.3 sec/veh and this delay is lower than COSMOS (89.9sec/veh) and TOD (99.1sec/veh). It is concluded that this new signal control algorithm suggested in this paper is more effective in controlling an oversaturated network.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.8
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• pp.327-336
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• 2007

Lots of effort toward design optimizations have been paid for a cost-effective system design in various ways from a transistor level to RTL designs. In this paper, we propose a bit level optimization of an adder design for expanding its design space. For the bit-level optimization, a heterogeneous adder organization utilizing a mixture of carry propagation schemes is proposed to design a delay-area efficient adder which were not available in an ordinary design space. Then, we develop an optimization method based on Integer Linear Programming to search the expanded design space of the heterogeneous adder. The novelty of the Proposed architecture and optimization method is introducing a bit level reconstruction/recombination of IPs which have same functionality but different speed and area characteristics for producing more find-grained delay-area optimization.

• Journal of the Economic Geographical Society of Korea
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• v.15 no.4
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• pp.628-641
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• 2012

This research investigates a dynamic mechanism underlying the co-evolution between network and space by applying hype-curve model, typical phenomenon which shows how new technologies and ideas initially adapted in the society. This study analysis the knowledge intensive industry of digital contents using social network analysis (SNA) in terms of structural, spatial, and temporal aspects, year of 2000, 2005, and 2010 focused on Seoul area. First of all, network and space establish 'inter-feedback' as a result of evolution and differentiation process. Second, it happen temporal 'delay' through the learning process stage of 'peak of inflated expectation' and 'trough of disillusionment.' As a result, Seoul develops with the technology commercialized-orient strategy affect government policy. This trend changes to technology-oriented development in Seoul area in the late of 2000 established 'self-organization' with geographical proximity organizations through learning process.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3C
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• pp.248-256
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• 2003

Space-time coding was designed for an efficient transmit diversity technique to improve performance of wireless communication. For the transmit diversity using space-time coding, the receiver requires to estimate channel parameters corresponding to each transmit antennas. In this paper, we propose an efficient channel estimation scheme based on trigonometric polynomial approximation in OFDM systems with transmit diversity using space-time coding. The proposed scheme is more efficient than the conventional scheme in terms of the computational complexity. For QAM modulation, when the size of FFH is 128, the conventional scheme with significant tap caching of 7 requires 9852 complex multiplications for TU, HT and BU channels. But the proposed scheme requires 2560, 7680 and 3584 complex multiplications for TU, HT and BU channels, respectively. Especially, for channels with smaller Doppler frequency and delay spreads, the proposed scheme has the improved BER performance and complexity. In addition, we evaluate the performance of maximum delay spread estimation in unknown channel. The performance of the proposed scheme is investigated by computer simulation in various multi-path fading environments.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.20 no.5
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• pp.59-74
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• 2021

The domestic road space is reaching the limit of planar space distribution, and Increasingly, the importance of three-dimensional space distribution through the development of underground space. therefore, In this study, a study was conducted on a traffic control method that can safely induce two different traffic flows in the connection between the ground road and the underground road. Through VISSIM, we calculated the appropriate amount of outflow and inflow traffic compared to the capacity of the main line when there is a Merge/Diverge section in the underground road. and Through the analysis of the number of conflicts, the appropriate traffic control level for safety in the underground, A basic study was conducted on the level of risk in the underpass according to the level of delay in the ground part through the analysis of the delay scenario of the ground road.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.47-51
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• 2006

Among Solar activities' events, the geomagnetic storms are believed to cause the largest atmospheric effects. The geomagnetic storm is a complex process of solar wind/magnetospheric origin. It is well known to affect severely on the ionosphere. However, this effect of this complex process will maybe act at various altitudes in the atmosphere, even including the lower layer and the neutral middle atmosphere, particularly the stratosphere. Nowadays, the GPS-derived ZTD (zenith tropospheric delay) can be transformed into the precipitable water vapor (PWV) through a function relation, and further has been widely used in meteorology, especially in improving the precision of Numerical Weather Prediction (NWP) models. However, such geomagnetic effects on the atmosphere are ignored in GPS meteorology applications. In this paper, we will investigate the geomagnetic storms' effects on the middle atmosphere and troposphere (0-100km) by GPS observations and other data. It has found that geomagnetic storms' effect on the atmosphere also appears in the troposphere, but the mechanism to interpret correlations in the troposphere need be further studied.

• ETRI Journal
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• v.26 no.6
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• pp.622-634
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• 2004

In this paper, we discuss the design problem and the robustness of space-frequency trellis codes (SFTCs) for multiple input multiple output, orthogonal frequency division multiplexing (MIMO-OFDM) systems. We find that the channel constructed by the consecutive subcarriers of an OFDM block is a correlated fading channel with the regular correlation function of the number and time delay of the multipaths. By introducing the first-order auto-regressive model, we decompose the correlated fading channel into two independent components: a slow fading channel and a fast fading channel. Therefore, the design problem of SFTCs is converted into the joint design in both slow fading and fast fading channels. We present an improved design criterion for SFTCs. We also show that the SFTCs designed according to our criterion are robust against the multipath time delays. Simulation results are provided to confirm our theoretic analysis.

• Journal of Advanced Marine Engineering and Technology
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• v.25 no.2
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• pp.351-356
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• 2001

In this paper, a general one-loop control system was assumed as a model system which has a time-delay element connected with a first order-lag element in series. After the corresponding parameter set causing stability limit condition for the model system was obtained by mathematical procedures, their loci on the parameter space was taken according of frequency change,. The parameter set loci of stability limit showed a specific pattern, and particularly the curves on the Kp-Ti parameter space were able to generalized in the form of an exponential formula. These properties were also compared with the results taken from experimental procedures by Nyquist response method and Ziegler & Nichols method on the time domain, and both results were confirmed to be nearly same.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.59.2-59.2
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• 2015

국립고흥청소년우주체험센터는 2014년부터 덕흥천문대에 설치된 SBIG사의 "Seeing Monitor"로 시상을 측정하고 있다. "Seeing Monitor"는 북극성을 대상으로 TDI(Time Delay and Integration) 방식을 적용하여 얻어진 시상을 분 단위로 저장해준다. 따라서 구름이 없는 맑은 날의 분 단위 시상 자료와 주변 환경 정보를 조합하여 시상에 영향을 미치는지 환경 요인을 정량적으로 분석하는 것이 가능하다. 그 첫 단계로 측정된 시상 자료와 기상청의 온도 습도 풍속 자료, 그리고 GFS(Global Forecast System)의 고도별 상층 풍속 자료를 비교하여 기상정보와 시상과의 관계를 분석해보았다. 습도와 바람이 시상에 가장 큰 영향을 주었으며, 지상 풍속 1~2m/s, 습도 75% 이하, 제트기류 풍속은 250km/h 이하 일 때 좋은 시상 값을 얻을 수 있었다. 이를 통해 덕흥천문대에서 기상정보를 통해 시상이 안정적인 날을 예측할 수 있다면, 앞으로 도입될 1m 망원경으로 훌륭한 관측 자료를 얻을 수 있을 것이라 기대된다.