• The Journal of Society for e-Business Studies
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• v.12 no.2
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• pp.155-194
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• 2007

Currently, Ubiquitous Computing Technology(UCT)-based service scenarios play an important role in estimating the potential of UCT-based service. The purpose of the study is to propose a multidimensional evaluation(ME) methodology for UCT-based service scenarios regarding their possibilities of realization for the future. Our approach contributes to extend service level management in Information Technology Service Management(ITSM) by evaluating the level of a new service in advance. ME consists of three dimensions: technological evaluations, business-oriented evaluations, and user-oriented evaluations. The three types of evaluations are mutually harmonized to check the overall possibility of realization and validity for certain UCT-based service scenarios. Theoretically, ME is developed to overcome the extant evaluation methods for UCT-based service scenarios, which are limited in the number of evaluation criterions. It is also conceived to cope with the limitation of economical evaluation methods (e.g., technological valuation, estimation of financial outcomes such as ROI, ROA, etc. that are difficult to give meaningful results because most of UCT-based services are not fully realized so far. From the practical perspectives, in addition, our approach can be applied to a variety of scenarios due to its domain-independent approach.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.1
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• pp.124-135
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• 2000

In this study, a numerically efficient method for the analysis of microstrip structures is considered in conjunction with the use of closed-form spatial Green's functions. As is well-known, the use of the closed-form Green's functions can reduce the evaluation time of impedance matrix elements. However the problematic aspect that in general the evaluation results of diagonal elements of the matrix converge slowly, has been observed. The main cause of the slow convergence has been due to the terms of closed-form Green's functions with small exponent. In other to resolve the problematic aspect, a method of numerical integration based on the change of variable is considered in evaluating matrix elements. The present method is applied for the analysis of a coaxial-fed microstrip antenna. When the present results are compared with the previous results in order to check the validity of the present method, fairly good agreements between them are observed.

• Journal of Ocean Engineering and Technology
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• v.29 no.6
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• pp.454-462
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• 2015

An extended study was conducted on the fracture criterion by Choung et al. (2011; 2012) and Choung and Nam (2013), and the results are presented in two parts. The theoretical background of the fracture and the results of new experimental studies were reported in Part I, and three-dimensional fracture surface formulations and verifications are reported in Part II. How the corrected true stress can be processed from the extrapolated true stress is first introduced. Numerical simulations using the corrected true stress were conducted for pure shear, shear-tension, and pure compression tests. The numerical results perfectly coincided with test results, except for the pure shear simulations, where volume locking appeared to prevent a load reduction. The average stress triaxialities, average normalized lode parameters, and equivalent plastic strain at fracture initiation were extracted from numerical simulations to formulate a new three-dimensional fracture strain surface. A series of extra tests with asymmetric notch specimens was performed to check the validity of the newly developed fracture strain surface. Then, a new user-subroutine was developed to calculate and transfer the two fracture parameters to commercial finite element code. Simulation results based on the user-subroutine were in good agreement with the test results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.10
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• pp.1912-1918
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• 2016

MPTCP(Multipath Transmission Control Protocol) is able to compose many TCP paths when two hosts connect and the data is able to be transported through these paths simultaneously. When a new path is added, the authentication between both hosts is necessary to check the validity of host. So, MPTCP exchanges a key when initiating an connection and makes a token by using this key for authentication. However the original MPTCP is vulnerable to MITM(Man In The Middle) attacks because the key is transported in clear text. Therefore, we applied a ECDH(Elliptic Curve Diffie-Hellman) key exchange algorithm to original MPTCP and replaced the original key to the ECDH public key. And, by generating the secret key after the public key exchanges, only two hosts is able to make the token using the secret key to add new subflow. Also, we designed and implemented a method supporting encryption and decryption of data using a shared secret key to apply confidentiality to original MPTCP.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.633-636
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• 2017

This thesis is about the evaluation method of field uniformity for radiated immunity test of vehicle component. Radiated immunity test is to find out whether a EUT has enough immunity or hold normal operation during applied electromagnetic interference. Field Uniformity(FU) measurement is essential for generate uniform field on DUT and Harness. But Standard of Radiated Immunity(RI) test for vehicle component based on ISO 11452-2 has not been specified a Field Uniformity(FU). So compared and analyzed with other standard which is defined by a specified a Field Uniformity. As a result, deviation occurs in the difference test condition and test method. In this thesis, proposal new measurement method of field uniformity that is considered test conditions of ISO 11452-2 and check the validity through actual test.

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.30-36
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• 2018

In this study, a small-scaled test system for a tip jet rotor was developed to contribute to the research on unmanned compound rotorcraft. The performance and dynamic characteristics of the tip jet rotor were investigated using the test system. The diameter of the tip jet rotor was set to 2m in consideration of the size of the test site and the pneumatic supply capacity of the. The rotating speed of the rotor was controlled by the pressure of the compressed air. The thrust and forces during the rotor rotation were measured using a load measuring device. A hydraulic actuator was installed for the dynamic test and full-bridge strain gages were attached to the root of each blade to measure the flap, lag, and torsion-wise responses generated when the rotor is excited by the actuator. The performance and dynamic characteristic tests were conducted at various rotor speeds and blade pitches. In order to check the validity of the test results, the results were also compared with the CAMRAD II analysis.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.11
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• pp.1038-1043
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• 2015

When the study on the relationship between the Head-of-Bed (HOB) angle and ventilator-associated pneumonia is performed, the fact that the HOB angle can only be measured intermittently imposes a significant limitation on the study. Therefore, there has been demand for the development of a device that can measure the HOB angle continuously. In this paper, we propose the rapid prototyping of an HOB measurement system using open-source hardware and software. The proposed system helps to maintain the HOB angle at a particular angle by displaying the angle and helps the medical study of pneumonia patients by enabling continuous data acquisition. Firstly, we eliminate the process of making an MCU board by utilizing an open-source hardware mbed LPC1768. Secondly, we reduce the software development time by using libraries and hence enabling the easy use of peripherals. Thirdly, for rapid prototyping, we build the enclosure of the proposed system using a 3D printer. The proposed system can be attached and detached to and from a bed. Therefore, we can attach it to the bed of a patient for whom measurement of the HOB angle is necessary. Finally, we check the measurement performance and the validity of the proposed system through an experiment utilizing an incremental encoder.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.115-123
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• 2011

Distribution system loss minimization re-configuration is 0-1 planning problem, and the number of combinations requiring searches is extremely large when dealing with typical system scales. For this reason, the application of a genetic algorithm (GA) seems a tractive to solve this problem. Although Genetic algorithms are a type of random number search method, they incorporate a multi-point search feature and are therefore superior to one-point search techniques. The incorporate of GAs for solving large combinational problem has received wide attention. Further, parallel searching can be performed and the optimal solution is more easily reach ed. In this paper, for improving GA convergence characteristics in the distribution system loss minimization re-configuration problem, a chromosome "Limited Life" concept is introduced. Briefly, considering the population homogenization and genetic drift problems, natural selection is achieved by providing this new concept, in addition to natural selection by fitness. This is possible because individuals in a population have an age value. Simulation were carried out using a model system to check this method's validity.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.4
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• pp.27-37
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• 1998

The sloshing is very important in a safe transport of the liquid cargo by a ship. With the increasing number of supertanker and LNG carriers, this problem has become increasingly more important. In order to study the magnitude and characteristics of impact pressures due to sloshing, experiments ware performed with a rectangular tank and compared with numerical results. Structural responses of tank wall under impulsive pressures were measured. Structural vibrations induced by the sloshing load were analysed by including hydroelastic erects in terms of added mass and damping. To check the validity of the numerical model, the natural frequencies of plate in air and water were compared with measurements, and a good agreement was found. In the case that a plate vibrates under impulsive loads, the pressure on the flexible plate is larger than that on the rigid plate without hydroelastic effects, which was confirmed experimentally. The frequency of oscillatory pressure as well as accel%pion coincides with the natural frequency of plate in water.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.3
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• pp.287-298
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• 2001

Analysis of nonlinear behavior of prestressed concrete frame structures on PC is a time-consuming computing job if the problem size increase to a certain degree. Cluster system has emerged as one of promising computing environments due to its good extendibility, portability, and cost-effectiveness, comparing it with high-end work-stations or servers. In this paper, a parallel nonlinear analysis procedure of prestressed concrete frame structure is presented using cluster computing. Cluster system is configured with readily available pentium III class PCs under Win98 or Linux and fast ethernet. Parallel computing algorithms on element-wise processing parts including the calculation of stiffness matrix, element stresses and determination of material states, check of material failure and calculation of unbalanced loads are developed using MPL. Validity of the method is discussed through typical numerical examples. For the case of 4 node system, maximum speedup is 3.15 and 3.74 for Win98 and Linux, respectively. Important issues for the efficient use of cluster computing system based un PCs and ethernet are addressed.