• Journal of Korean Society of Transportation
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• v.25 no.6
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• pp.161-170
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• 2007

The purpose of this study is to find the solution that overcomes the existing assumption of symmetric cost functions in multi-class assignment. In the assignment problem, the assumption of a symmetric cost function means that the link cost is determined by each unique mode and is not affected by any other modes. In this study, the authors have applied a diagonalized algorithm and a heuristic model based on column generation to a multi-class assignment model and analyzed the result. Through the study, the authors found that the diagonalized algorithm produces equilibrium solutions by the initial convergence condition. In contrast to the diagonalized algorithm, the column generation algorithm has improved the solution model to overcome the problem of equilibrium solutions in the diagonalized algorithm.

• Journal of the Korean GEO-environmental Society
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• v.4 no.2
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• pp.57-64
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• 2003

Marston (1913) and Spangler's (1982) theory was widely used in the analysis of the earth pressure of the narrow and long excavated ditch type backfield ground. Their theory was more clearly explained by expressing the minor principle stress arch connecting the minor principle stress link induced by interaction between the excavated wall surface and the backfilled earth. which was done by R.L. Handy(1985). Later C.G. Kellogg(1993) extended the study from vertical symmetric to incline symmetric in the backfill space type research. In the C.G. Kellogg's study, it is assumed that the resistance of wall friction on the sloping wall could be replaced by the internal friction angle in the sloping section bottom. In the study, the resistance of wall friction in the sloping section bottom, which was applied by C.G. Kellogg, would be different in magnitude with the resistance of wall friction in sloping section. The magnitude is expected to affect in the earth pressure calculation and verified by the soil test box, the C.G. Kellogg's theory, the numerical analysis and the modified C.G. Kellogg's theory considering the friction resistance to influence the incline wall.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.3
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• pp.101-113
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• 2008

The new wireless multimedia environment is coming because of the variety of an user requirement and a traffic increase which we can not accept in the IMT-2000 present systems. To offer the wireless multimedia service the world wireless communication company which included the ITU-R is developing the standard and technique of 4G systems. We analyzed the technique criteria of the 4G wireless communication system in this paper which is based on that of WiBro System. The mobile communication traffic is predicted Up/Down-link of non-symmetric in the future. And we proposed the PHY layer parameters of occupied frequency bandwidth of Up/Down-link with both 1:3 and 1:6. And we verified this through the simulation. So we proposed the technique criteria for 4G wireless communication in this paper.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.5
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• pp.343-354
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• 2020

Bi-stable mechanism is a system that has two different stable equilibrium positions within its range of motion. It has an ability to stay in two different positions without external power input and despite small disturbances. One of the most bi-stable applied mechanism is a morphing system, such as deployable structures, switch systems, and robot grippers. However, due to the complexity of mechanism and limitation of structure configuration, it is difficult to apply on a morphing system with rotating link mechanism. In this paper, an implementation method of rotational bi-stable mechanism using cylindrical permanent magnets is proposed. The magnetic field and the magnetic force were calculated from electromagnet model of the cylindrical permanent magnet. Based on the model, the force relation between two links containing the cylindrical permanent magnets was estimated. An array of cylindrical permanent magnets was selected for symmetric bi-stability, and an experiment on the link structure with the proposed bi-stable mechanism was performed to investigate the stability against a external torque.

• Journal of the Korea Society of Computer and Information
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• v.13 no.6
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• pp.173-180
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• 2008

Certified e-Document Authority keep it with protection legal as a system a guarantee and identifies originality of an e-Record, It presume to be authenticity e-Records and contents of an e-Record prove what was not changed. But, e-Records has high medium degree of dependence and loss danger of information has very high problems. In addition, Because correction(attachment and deletion) and a revision of information are easy, a problem for integrity and the originality of an e-Record is caused. Existing system show the following inefficient. For the originality guarantee, an existing e-Documents encryption method accomplishes a encrypted process of a whole document with a symmetric key, if the information revised midway, the whole documents content must accomplish re-scanning and re-encryption process again. To get over such inefficient, this paper maximize efficiency which occurred at the time of partial information revision request by encryption and managing using the link information based on the linkage characteristics of the each page on the registered requested e-Documents, It was able to increase security configuration by minimizing problems on an information exposure through increasing complicated of the key management.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.9
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• pp.1811-1818
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• 2009

This paper is about the research to maintain and enhance the flow of data of the wireless traffic control. Various types of burst traffic that were found at TCP window flow control have been removed or mitigated using the two-way traffic control. Currently, TCP ACK Compression problem appears during the transmission of the wireless communication control channel because the queues are mostly located at the end system. Therefore, in this paper, the periodic bursty characterist of the source IP queue wilt be analyzed to predict the maximum value of queues. And then the prediction tool will be applied to wireless communication traffic control to handle symmetric traffic as to increase the throughput and improve the performance.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.9
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• pp.971-977
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• 2012

Redundant actuated parallel kinematic machines (PKMs) have been widely researched to increase stiffness of PKMs. This paper presents theoretical analyses on the stiffness of non-redundant and redundant actuated PKM. Stiffness of each mechanism is defined by summation of actuator and structural stiffness; the actuator stiffness is determined from displacements of actuators, and the structural stiffness is determined from deformations of links by external forces. Calculated actuator and structural stiffness of non-redundant PKM show same distribution in entire workspace. On the contrary, the actuator and the structural stiffness of a redundant PKM has very different distribution in the workspace; so, we conclude the structural stiffness of redundant PKM should be considered to design the redundant PKM. The results can be used to design and analyze non-redundant and redundant PKMs.

• Journal of Medicine and Life Science
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• v.19 no.3
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• pp.130-133
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• 2022

Several studies have reported a possible link between anti-aquaporin-4 antibody and vitamin B12 deficiency in neuromyelitis optica spectrum disorder (NMOSD). Bilaterally symmetric hyperintense signals on magnetic resonance imaging (MRI) of the posterior columns, called the inverted V sign, are a characteristic feature of subacute combined degeneration associated with vitamin B12 deficiency. We report a patient with anti-aquaporin-4 antibody-positive NMOSD and an inverted V sign on MRI of the spinal cord and address the association between anti-aquaporin-4 antibody and functional vitamin B12 deficiency.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.3
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• pp.890-910
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• 2014

This paper investigates the spectrum hole utilization of cooperative schemes for the two-way relaying model in order to improve the utilization efficiency of limited spectrum holes in cognitive radio networks with imperfect spectrum sensing. We propose two specific bidirectional secondary data transmission (BSDT) schemes with two-step and three-step two-way relaying models, i.e., two-BSDT and three-BSDT schemes, where the spectrum sensing and the secondary data transmission are jointly designed. In the proposed cooperative schemes, the best two-way relay channel between two secondary users is selected from a group of secondary users serving as cognitive relays and assists the bi-directional communication between the two secondary users without a direct link. The closed-form asymptotic expressions for outage probabilities of the two schemes are derived with a primary user protection constraint over Rayleigh fading channels. Based on the derived outage probabilities, the spectrum hole utilization is calculated to evaluate the percentage of spectrum holes used by the two secondary users for their successful information exchange without channel outage. Numerical results show that the spectrum hole utilization depends on the spectrum sensing overhead and the channel gain from a primary user to secondary users. Additionally, we compare the spectrum hole utilization of the two schemes as the varying of secondary signal to noise ratio, the number of cognitive relays, and symmetric and asymmetric channels.

• Journal of Communications and Networks
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• v.10 no.4
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• pp.412-421
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• 2008

We observe simultaneous transmission of relay stations (RSs) allowed in current IEEE 802.16j draft standard for multi-hop relay networks may involve severe interference among the RSs, hence leading to throughput degradation. Allowing only 1/3 of the RSs to simultaneously transmit instead of 1/2 RSs as in the current draft standard reduces the interference but results in reduced throughput. To remedy this problem, we devise schemes to incorporate network coding at link-layer level (decode-and-forward) into the simultaneous transmission of RSs. Data movement is rearranged to maximize coding gain. Formula is derived to dictate exact movement of packets traveling between base station (BS) and mobile stations (MSs) via intermediate RSs. The frame structure in the current IEEE 802.16j draft standard does not allow broadcast needed for network coding. We devise a new frame structure which supports the broadcast. A new R-MAP (pointers to the burst data) is introduced to implement the broadcast. Since our new frame structure is used only for BS to RS or RS to RS communication, our schemes retain backward compatibility with legacy MSs based on IEEE 802.16e standard. Simulation based on simple configuration of RSs shows considerable improvement in terms of system throughput and round trip delay. For a 4-hop relay network with 1 BS and 4 RSs with symmetric traffic in uplink (UL) and downlink (DL), throughput is improved by 49% in DL and by 84% in UL traffic compared with IEEE 802.16j draft standard under the assumption that omni-directional antennae are used in BS and RSs.