• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.5B
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• pp.318-325
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• 2008

HomePlug AV(HPAV) is the standard for distribution of Audio/video content as well as data within the home by using the power line. It uses a hybrid access mechanism that combines TDMA with CSMA/CA for MAC technology. The CSMA/CA protocol in HPAV has two main control blobs that can be used for access control: contention window(CW) size and deferral counter(DC). In this paper, we extensively investigate the impacts of CW and DC on performance through simulations, and propose an adaptive mechanism that adjusts the CW size to enhance the throughput in HPAV MAC. We find that the CW size is more influential on performance than the DC. Therefore, to make controlling the network easier, our proposal uses a default value of DC and adjusts the CW size. Our scheme simply increases or decreases the CW size if the network is too busy or too idle, respectively, We compare the performance of our proposal with those of the standard and other competitive schemes in terms of throughput and fairness. Our simulation and analysis results show that our adaptive CW mechanism performs very well under various scenarios.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.1
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• pp.12-21
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• 2012

IEEE 802.11 MAC protocol standard, DCF(CSMA/CA), is originally designed to ensure the fair channel access between mobile nodes sharing the local wireless channel. It has been, however, revealed that some misbehavior nodes transmit more data than other nodes through artificial means in hot spot area spreaded rapidly. The misbehavior nodes may modify the internal process of their MAC protocol or interrupt the MAC procedure of normal nodes to achieve more data transmission. This problem has been referred to as a selfish node problem and almost literatures has proposed methods of analyzing the MAC procedures of all mobile nodes to detect the selfish nodes. However, these kinds of protocol analysis methods is not effective at detecting all kinds of selfish nodes enough. This paper address this problem of detecting selfish node using Tsallis-Entropy which is a kind of statistical method. Tsallis-Entropy is a criteria which can show how much is the density or deviation of a probability distribution. The proposed algorithm which operates at a AP node of wireless LAN extracts the probability distribution of data interval time for each node, then compares the one with a threshold value to detect the selfish nodes. To evaluate the performance of proposed algorithm, simulation experiments are performed in various wireless LAN environments (congestion level, how selfish node behaviors, threshold level) using ns2. The simulation results show that the proposed algorithm achieves higher successful detection rate.

• Journal of Veterinary Clinics
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• v.27 no.6
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• pp.668-673
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• 2010

This study was to evaluate the effects of tramadol and medetomidine administration on minimum alveolar concentration (MAC) of isoflurane in dogs. MAC of isoflurane was determined in four occasions; 1 ml saline (Control), $2{\mu}g$/kg medetomidine (M2), 4 mg/kg tramadol (T4), $2{\mu}g$/kg medetomidine-4 mg/kg tramadol combination (M2T4). Heart rate, blood pressure, respiratory rate, end-tidal carbon dioxide concentration, saturation of hemoglobin with oxygen and body temperature were recorded. After administration of M2 ($0.81{\times}0.18%$), T4 ($0.81{\times}0.14%$) and M2T4 ($0.62{\times}0.12%$), less isoflurane was required than the control value ($1.13{\times}0.19%$). Significantly lower heart rate than the control value was detected after treatment of M2, T4, and M2T4. When only M2T4 was administered, blood pressure was significantly higher than the control value. In conclusion, administrations of tramadol, medetomidine and medetomidine-tramadol combination decreased the MAC of isoflurane in dogs. Especially, medetomidine-tramadol combinations could be useful as a premedication because of the anesthetic sparing effect and moderate changes in cardiovascular system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.2
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• pp.93-100
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• 2014

IEEE 802.11 Wireless LAN Medium Access Control(MAC) supports two transmission methods, a DCF basic and a RTS/CTS in contention-based access. Even though the RTS/CTS method has been optionally introduced to solve the hidden terminal problem, it is able to produce better performance in some network environments than the basic transmission method. In this paper, the collision probability of wireless channel is mathematically analyzed and applied to measure network throughput using real transmission parameters so that a reference value between throughputs of two methods is obtained. We also confirmed that control signal rates affect overall network throughput and evaluated network throughputs considering collision probability, number of stations, and contention window size of Backoff between two methods respectively.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2001.11a
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• pp.340-347
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• 2001

Security operating system applied to MAC(Mandatory Access Control) or to MLS(Multi Level Security) gives both subject and object both Security Level and value of Category, and it restrict access to object from subject. But it violates Security policy of system and could be a circulated course of illegal information. This is correctly IPC(Interprocess Communication)mechanism and Covert Channel. In this thesis, I tried to design and implementation as OS kernel in order not only to give confidence of information circulation in the Security system, but also to defend from Covert Channel by Storage and IPC mechanism used as a circulated course of illegal information. For removing a illegal information flow by IPC mechanism. I applied IPC mechanism to MLS Security policy, and I made Storage Covert Channel analyze system call Spec. and than distinguish Storage Covert Channel. By appling auditing and delaying, I dealt with making low bandwidth.

• Proceedings of the Korea Society of Mathematical Education Conference
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• 2007.06a
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• pp.7-19
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• 2007

During the past 20 years, a small but potentially powerful initiative has established itself in the mathematics education landscape: Mathematics Across the Curriculum (MAC). This curricular reform movement was designed to address a serious problem: Not only are students unable to demonstrate understanding of mathematical ideas and their applications, but also they harbor misconceptions about the meaning and purpose of mathematics. This paper chronicles the brief history of the MaC movement. The sections of the paper correspond loosely tn the typical steps one might take to solve a mathematics problem. The Problem Takes Shape presents a discussion of the social and economic forces that led to the need for increased articulation between mathematics and other fields in the American educational system. Understanding the Problem presents the potential value of exploiting these connections throughout the curriculum and the obstacles such action might encounter. Devising a Plan provides an overview of the support systems provided to early MAC initiatives by government and professional organizations. Implementing the Plan contains a brief description of early collegiate programs, their approaches and their differences. Extending the Solution details the adoption of MAC principles to the K-12 sector and throughout the world. The paper concludes with Retrospective, a brief discussion of lessons learned and possible next steps.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3441-3449
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• 2023

We determined the radiation shielding properties for 10CaO-xPbO-(90-x) deteriorated silica gel (DSG) glass system (x = 20, 25, 30, 35, 40, and 45 mol.%). The mass attenuation coefficient (MAC) has been estimated at photon energies of 74.23, 97.12, 122, 662, 1173, and 1332 keV using a narrow beam X-ray attenuation and transmission experiment, the XCOM program, and a PHITS simulation. The obtained MAC values were applied to estimate the half value layer (HVL), mean free path (MFP), effective atomic number, and effective electron density. Results show that the MAC value of the studied glasses ranges between 0.0549 and 1.4415 cm²/g, increases with the amount of PbO, and decreases with increasing photon energy. The HVL and MFP values decrease with increasing PbO content and increase with increasing photon energy. The recycled glass, with the addition of PbO content (20-45 mol.%), exhibited excellent radiation shielding capabilities compared to standard barite and ferrite concretes and some glass systems. Moreover, the experimental radiation shielding parameters agree with the XCOM and PHITS values. This study suggests that this new waste-recycled glass is an effective and cost-saving candidate for X-ray and gamma-ray shielding applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1A
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• pp.81-89
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• 2000

In this paper, we analyzed the performance for CATV/LAN added priority problem. Upstrea nm channel which analyzed very deeply for CATV/LAN network have the preferential access property depending upon that positionand unidirectional property. To solve that fairness problem and priority, we propose the CSMA-CD/U/P-P protocolthat transmit as P1 probability if data packets happen. We assumed 2-Class priority(high, low). As the analyticresult and simulation, we obtained P1, value and its average delay time under priority problem assumed twoscenarios. Also, we get its variance value and queue length. Especially, the mean delay time increases nearer thanposition from H/E

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.6
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• pp.159-164
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• 2016

This paper proposes an improved superframe structure with one : N situation of the network as a target for efficiency battery and communication performance used in the existing standard IEEE 702.15.4 MAC layer. The proposed superframe transforms and adds a two structures. First, we add the proposed scheduling interval after the arrival of the beacon. Second, we change to a structure in which one of the contention access period is divided into two. The contention access period and the contention-free access period of active portion are divided according to the LQI value of the device. Through this system-level simulation written by $c{^+^+}$, as a results show that the battery consumption and transmission performance has been increased.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.11
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• pp.37-43
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• 1998

This paper proposes a new echo canceller that can be used in a full-duplex digital subscriber loop modem. The proposed echo canceller uses a NLMS-based parallel adaptation NLMS (PA-NLMS) algorithm. The PA-NLMS algorithm that an estimate of the nonstationarity to additive noise ratio (NNR) gained from two distinct NLMS processes is used to select the value of NLMS convergence-controlling parameter has been developed. Numerical results based on computer simulation show that the proposed algorithm has a convergence rate approaching that of the fastest possible NLMS process while improving on its MAC performance considerably.