• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.301-303
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• 2004

In this work, we develop on-line traffic prediction algorithm for real-time VBR traffic. There are a number of important issues: (i) The traffic prediction algorithm should exploit the stochastic characteristics of the underlying traffic and (ii) it should quickly adapt to structural changes in underlying traffic. GOP ARIMA model effectively addresses this issues and it is used as basis in our bandwidth prediction. Our prediction model deploy Kalman filter to incorporate the prediction error for the next prediction round. We examine the performance of GOP ARIMA based prediction with linear prediction with LMS and double exponential smoothing. The proposed prediction algorithm exhibits superior performam againt the rest.

• Journal of Communications and Networks
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• v.8 no.3
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• pp.351-359
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• 2006

In this article, we present a new slow-start variant, which improves the throughput of transmission control protocol (TCP) Vegas. We call this new mechanism Gallop-Vegas because it quickly ramps up to the available bandwidth and reduces the burstiness during the slow-start phase. TCP is known to send bursts of packets during its slow-start phase due to the fast window increase and the ACK-clock based transmission. This phenomenon causes TCP Vegas to change from slow-start phase to congestion-avoidance phase too early in the large bandwidth-delay product (BDP) links. Therefore, in Gallop-Vegas, we increase the congestion window size with a rate between exponential growth and linear growth during slow-start phase. Our analysis, simulation results, and measurements on the Internet show that Gallop-Vegas significantly improves the performance of a connection, especially during the slow-start phase. Furthermore, it is implementation feasible because only sending part needs to be modified.

• Bulletin of the Korean Chemical Society
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• v.19 no.4
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• pp.471-475
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• 1998

Phase shift spectroscopy is applied to Eu(Ⅲ) luminescence from $Eu^{3+}$-exchanged Y zeolite. The phase shift and intensity modulation of luminescence following intensity-modulated excitation are measured as a function of modulation frequency and they are fitted into a double exponential decay. The fast decay component, compared with the slow one, has narrower spectral bandwidth and is emitted from the $Eu^{3+}$ that has more polar and definite environment with higher symmetry and that interacts more easily with hydrated water molecules. The fast decay component is attributed to $Eu^{3+}$ at site Ⅱ' while the slow one to $Eu^{3+}$ at sites Ⅰ' and Ⅰ.

• The Transactions of the Korea Information Processing Society
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• v.6 no.1
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• pp.175-181
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• 1999

There are issues regarding how some of traffic parameters should be set so that ATM and non-ATM service parameters can be compatible. For example, policing method used by frame relay based on CIR(committed information rate) will not exactly match the ATM UPC(Usage Parameter Control) method. ATM and the frame relay have different transfer modes and traffic parameters. The cells and frames are police by their own traffic control schemes. For the same information, the real traffic of the ATM side takes greater bandwidth than that of the frame relay side caused by ATM cell format and AAL5 format. IN both networks this bandwidth than that of the frame relay side caused by ATM cell format and AAL5 format. In both networks this bandwidth ratio should be considered on traffic parameter mapping to maintain their QoS and to perform efficient network resource management. In this paper we describe traffic parameter mapping schemes between frame relay and ATM in ATM network and how to expect the bandwidth ratio to maintain FR QoS in ATM network. We assumed frame length distribution to Erlang or Exponential probability density function.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.11
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• pp.3916-3936
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• 2014

Smartphone applications like games, image processing, e-commerce and social networking are gaining exponential growth, with the ubiquity of cellular services. This demands increased computational power and storage from mobile devices with a sufficiently high bandwidth for mobile internet service. But mobile nodes are highly constrained in the processing and storage, along with the battery power, which further restrains their dependability. Adopting the unlimited storage and computing power offered by cloud servers, it is possible to overcome and turn these issues into a favorable opportunity for the growth of mobile cloud computing. As the mobile internet data traffic is predicted to grow at the rate of around 65 percent yearly, even advanced services like 3G and 4G for mobile communication will fail to accommodate such exponential growth of data. On the other hand, developers extend popular applications with high end graphics leading to smart phones, manufactured with multicore processors and graphics processing units making them unaffordable. Therefore, to address the need of resource constrained mobile nodes and bandwidth constrained cellular networks, the computations can be migrated to resourceful servers connected to cloud. The server now acts as a bridge that should enable the participating mobile nodes to offload their computations through Wi-Fi directly to the virtualized server. Our proposed model enables an on-demand service offloading with a decision support system that identifies the capabilities of the client's hardware and software resources in judging the requirements for offloading. Further, the node's location, context and security capabilities are estimated to facilitate adaptive migration.

• Journal of KIISE:Information Networking
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• v.27 no.3
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• pp.301-314
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• 2000

As the number of World Wide Web (Web) users grows, Web traffic continues to increase at an exponential rate. Currently, Web traffic is one of the major components of Internet traffic. Also, high bandwodth usage due to Web traffic is observed during peak periods while leaving bandwidth usage idle during off-peak periods. One of the solutions to reduce Web traffic and speed up Web access is through the use of Web caching. Unfortunately, Web caching has limitations for reducing network bandwidth usage during peak periods. In this paper, we focus our attention on the use of a prefetching algorithm for reducing bandwidth during peak periods by using off-peak period bandwidth. We propose a statistical, batch, proxy-side prefetching scheme that improves cache hit rate while only requiring a small amount of storage. Web objects that were accessed many times in previous 24 hours but would be expired in the next 24 hours, are selected and prefetched in our scheme. We present simulation results based on Web proxy and show that this prefetching algorithm can reduce peak time bandwidth using off-peak bandwidth.

• Journal of Ocean Engineering and Technology
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• v.35 no.4
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• pp.257-265
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• 2021

Many studies have been performed to predict a reliable and accurate stress-range distribution and fatigue damage regarding the Gaussian wide-band stress response due to multi-peak waves and multiple dynamic loads. So far, most of the approximation models provide slightly inaccurate results in comparison with the rain-flow counting method as an exact solution. A step-by-step study was carried out to develop new approximate spectral moments that are close to the rain-flow counting moment, which can be used for the development of a fatigue damage model. Using the special parameters and bandwidth parameters, four kinds of parameter-based combinations were constructed and estimated using the R-squared values from regression analysis. Based on the results, four candidate empirical formulas were determined and compared with the rain-flow counting moment, probability density function, and root mean square (RMS) value for relative distance. The new approximate spectral moments were finally decided through comparison studies of eight response spectra. The new spectral moments presented in this study could play an important role in improving the accuracy of fatigue damage model development. The present study shows that the new approximate moment is a very important variable for the enhancement of Gaussian wide-band fatigue damage assessment.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.11
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• pp.830-835
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• 2006

Because of its exponential growth of data and voice transmissions through wireless communications, efficient resource management became more important factor when we design wireless networks. One of those limited resources in the wireless communications is frequency bandwidth. As a solution of increasing reusability of resources, the efficient frequency assignment problems on wireless networks have been widely studied. One suitable approach to solve these frequency assignment problems is transforming the problem into traditional graph coloring problems in graph theory. However, most of frequency assignments on arbitrary network topology are NP-Complete problems. In this paper, we consider the Chromatic Bandwidth Problem on the cellular topology wireless networks. It is known that the lower bound of the necessary number of frequencies for this problem is $O(k^2)$. We prove that the lower bound of the necessary number of frequencies for the Chromatic Bandwidth Problem is $O(k^3)$ which is tighter lower bound than the previous known result.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.7
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• pp.63-73
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• 2015

In the end to end data transfer protocols, it is very important to correctly estimate available bandwidth. In UDT (UDP based Data Transfer), receiver estimates the MTR (Maximum Transfer Rate) of the current link using pair packets transmitted periodically from sender and, then sender finally decides the MTR through EWMA (Exponential Weighted Moving Average) algorithm. Here, MTR has to be exactly estimated because available bandwidth is calculated with difference of MTR and current transfer rate. However, when network is congested due to traffic load and where competing flows are coexisted, it bring about a severe fairness problem. This paper proposes a congestion degree based MTR estimation algorithm. Here, the congestion degree stands a relative index for current congestion status on bottleneck link, which is calculated with arriving intervals of a pair packets. The algorithm try to more classify depending on the congestion degree to estimate more actual available bandwidth. With the network simulation results, our proposed method showed that the fairness problem among the competing flows is significantly resolved in comparison with that of UDT.

• Computers and Concrete
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• v.16 no.1
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• pp.179-190
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• 2015

An experimental program has been carried out to investigate the effect of edge-slope on compressive strength of concrete specimens. In this study, effect of such slope was investigated by testing 100 standard cylinder specimens and 40 standard cubes. When molds are put on a slanted place, wet concrete starts to flow through the open end of mold. It keeps flowing until it reaches to a parallel surface with the place over which it was placed. That creates a sloped surface over the loading area. Experimental results revealed significant relationships between failure loads and slope of loading surface for cylinders. Angled cracks occurred in sloped cylinder specimens. Tension cracks occurred in cube specimens. Fracture mechanisms were also evaluated by using finite element analyses approach. Experiments yielded an exponential curve with bandwidth for cylinders. Average value of curve is $y={\frac{\pi}{2}}e^{-cf}$ between slope and compressive strength. Inclination is much effective parameter for cylinders than cubes.