• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.10 s.340
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• pp.39-50
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• 2005

In this paper, we propose a performance improving MAC algerian for the IEEE 802.11 DCF. WLAN based IEEE 802.11 uses two control methods called 'Distributed Coordination Function(UF)' and 'Point Coordination Function(PCF)'. The nF controls the Urnsmission based on carrier sense multiple access with collision detection(CSMA/CA), that decides a random backoff time with the range of contention window for each terminal. Normally, each terminal the CW double after collision, and reduces the CW to the minimum after successful transmission. This paper proposes an enhanced DCF algorithm that decreases the CW smoothly after successful transmission in order to reduce the collision Probability by utilizing the current status information of WLAN. We also analyze the throughput and delay performance for the unsaturated case mathematically. Simulation results show that our algorithm enhances the saturation throughput of WLAN. They also coincide well with the analytical results.

• Analytical Science and Technology
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• v.15 no.3
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• pp.317-320
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• 2002

The layer structure of the title compound, $[Ni(en)_2(H_2O)_2](CH_3C_6H_4SO_3)_2(H_2O)$ (en = ethylenediamine), consists of discrete cations, anions, and solvate water molecules linked by a hydrogen bonding network. The central Ni atom of the cation layer has a slightly distorted octahedral coordination geometry with the ethylenediamine ligands functioning as a N,N'-bidentate and the water ligands bonding through oxygen in a trans arrangement. The p-toluenesulfonate of the anion layer has an alternate sulfonate group directed toward opposite side of the cation layer. This layer structure is stabilized by a hydrogen bond involving the O atoms of the sulfonate, the water ligand, solvate water molecule, and the N atoms of the ethylenediamine.

• Analytical Science and Technology
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• v.8 no.4
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• pp.529-534
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• 1995

The metal ion selective resins were prepared by surface template polymerization using monooleyl phosphoric acid (1), oleyl methyl phosphoric acid (2) or oleyl ethyl phosphoric acid (3) as an amphiphilic host surfactant. The $Cu^{2+}$-imprinted resins prepared in the presence of $Cu^{2+}$ adsorbed $Cu^{2+}$ much more effectively than did their reference resins. On the other hand, the $Cu^{2+}$-imprinted resins showed much less binding ability to $Zn^{2+}$. The template-dependent selectivity should be ascribed to a favorable placement of the surface-anchored metallophilic groups for multidentate coordination to specific metal ion.

• Analytical Science and Technology
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• v.14 no.6
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• pp.535-539
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• 2001

One-dimensional coordination polymer of cadmium(II) complex, $[Cd(SCN)_2(C_4H_6N_2]_n$, has been prepared and characterized by X-ray single crystallography. Structure analysis reveals that each cadmium(II) atom is six-coordinated in distorted octahedral fashion with $CdS_2N_4$ composition. $CdS_2N_4$ composition contains two S and two N atoms from four thiocyanates and tow N atoms from two 4-methylimidazole ligands. Central cadmium(II) atoms are run in parallel to the a-axis and are doubly bridged with neighboring cadmium(II) atoms by the thiocyanate and isothiocyanate ligands. Thus, this complex has a one-dimensional polymer structure in which the 4-methylimidazole is in the trans conformation.

• Structural Engineering and Mechanics
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• v.77 no.5
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• pp.601-612
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• 2021

To study the vibration characteristics of a high-speed railway continuous girder bridge-track coupling system (HSRCBT), a coupling vibration analysis model of an m-span continuous girder bridge-subgrade-track system with n-span approach bridge was established. The model was based on the energy and its variational method, where both the interlaminar slip and shear deformation effects were considered. In addition, the free vibration equations and natural boundary conditions of the HSRCBT were derived. Further, according to the coordination principle of deformation and mechanics, an analytical method for calculating the natural vibration frequencies of the HSRCBT was obtained. Three typical bridge-subgrade-track coupling systems of high-speed railway were taken and the results of finite element analysis were compared to those of the analytical method. The errors between the simulation results and calculated values of the analytical method were less than 3%, thus verifying the analytical method proposed in this paper. Finally, the analytical method was used to investigate the influence of the number of the approach bridge spans and the interlaminar stiffness on the natural vibration characteristics of the HSRCBT based on the degree of sensitivity. The results suggest the approach bridges have a critical number of spans and in general, the precision requirements of the analysis could be met by using 6-span approach bridges. The interlaminar vertical compressive stiffness has very little influence on the low-order natural vibration frequency of HSRCBT, but does have a significant influence on higher-order natural vibration frequency. As the interlaminar vertical compressive stiffness increases, the degree of sensitivity to interlaminar stiffness of each of the HSRCBT natural vibration characteristics decrease and gradually approach zero.

• Analytical Science and Technology
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• v.28 no.3
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• pp.204-211
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• 2015

Lanthanide complexes have attracted much attention because of their unique light emitting property. The light-emitting efficiencies of europium β-diketonate complexes were compared with those of complexes coordinated by the ligands of amines or phosphine oxides. The results demonstrated that the complexes that were coordinated by phosphine oxides had higher light-conversion performance than those coordinated by amines. The highest light-emitting efficiency was observed when the ligand of trioctylphosphine oxide was coordinated. In order to determine the coordination equivalency of trioctylphosphine oxide in the above complexes, 31P-NMR and their photoluminescence spectra were measured. The findings showed that the europium β-diketonate complex had one or two coordination equivalencies of trioctylphosphine oxide according to the steric hindrance of its original ligand.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.2
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• pp.111-118
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• 2008

In this paper a novel medium access control mechanism is investigated as a means to support real-time services. The primary goal is to provide constant-bit-rate voice call services to pairs of autonomous mobile nodes operating in ad hoc networks. Here, a time-slot reservation based MAC is considered to provide real-time voice calls and a new MAC called the time-slot reservation coordination function(TRCF) is presented. In addition to this isochronous type MAC protocol development, the proposed protocol is modeled using a Markov chain in order to predict its behavior. The performance of TRCF is analytically derived and the performance measures such as average wait time taken for a call connection and throughput are obtained.

• Structural Engineering and Mechanics
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• v.88 no.1
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• pp.53-65
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• 2023

With the gradual implementation of long-span suspension bridges into high-speed railway operations, the main beam's bending stiffness contribution to the live load response permanently grows. Since another critical control parameter of railway suspension bridges is the beam-end rotation angle, it should not be ignored by treating the main beam deflection as the only deformation response. To this end, the current study refines the existing method of the main cable shape and simply supported beam bending moment analogy. The bending stiffness of the main beam is considered, and the main beam's analytical expressions of deflection and rotation angle in the whole span are obtained using the cable-beam deformation coordination relationship. Taking a railway suspension bridge as an example, the effectiveness and accuracy of the proposed analytical method are verified by the finite element method (FEM). Comparison of the results by FEM and the analytical method ignoring the main beam stiffness revealed that the bending stiffness of the main beam strongly contributed to the live load response. Under the same live load, as the main beam stiffness increases, the overall deformation of the structure decreases, and the reduction is particularly noticeable at locations with original larger deformations. When the main beam stiffness is increased to a certain extent, the stiffening effect is no longer pronounced.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.10a
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• pp.535-538
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• 2004

Coordination between supply chain partners is viewed critical to effective supply chain management. Depending on the bargaining power balance between them, it is determined who will be able to exert more influence in making decisions related with such coordination. We consider two cases of the decision-making structure in the context of a simple supply chain consisting of two players, i.e., (1) the first case in which a supply chain partner dominates the decision-making process and the other passively follows the dominant player's decision, and (2) the other case in which the two players share the decision-making process equally. In this paper, we examine which of the cases is better for the companies and where comes the value of the better case. To answer the research questions, we set up an optimal control theory model and derive an analytical solution. The analysis outcome indicates that the shared decision-making in general produces better results for both companies in the supply chain, and the value of the shared decision-making comes from more effective resource utilization than the dominated case.

• Proceedings of the Ginseng society Conference
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• 1978.09a
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• pp.85-92
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• 1978

The aim of the double blind test was to assess the prophylactic and therapeutic efficacy of the preparation GINSANA, containing the standardized ginseng extract PHARMATON G115,. The determination was carried out with special emphasis on the following features : general physical condition, physical performance, mental performance, enjoyment of life/mood, concentration and memory, as well as sleeping habits. Sixty test persons took part in the study, men and women between the ages of 22 and 80. The 90-day test was carried out in the form of a double blind experiment. Experimental measurements were made and the persons were also questioned. The reaction time, the optical merging threshold, the coordination of both hands and the recovery quotients, as well as the recovery rates were analyzed. The results for the serum group were clearly better than those for the placebo group, particularly for the characteristics: general physical condition, physical performance and sleeping habits. The results of the test methods used, especially with regard to the reaction time, the coordination of both hands, the recovery quotient and the recovery period, permit the following conclusion to be drawn: when administered for several weeks, GINSANA has a positive action, in the sense of an activation of the entire personality by the ginseng glycosides contained in the standardized Extracts G115.