• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.7
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• pp.633-639
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• 2007

This paper presents a new homing guidance law based on well-known BPN to achieve an impact time constraint as well as an impact angle constraint. The guidance commands are synthesized by introducing an additional command to control impact-time. The structure of the additional command has a BPN-based loop multiplied by time-varying gains being proportional to the time difference between the required time-to-go and the estimated time-to-go by BPN. Moreover, the proposed homing loop converges to BPN as the time-to-go error is reduced. The performance of the proposed guidance law is evaluated by the computer simulations.

• Atmosphere
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• v.31 no.3
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• pp.251-265
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• 2021

This study examined the impact of assimilating the bending angle (BA) obtained via the global navigation satellite system radio occultation (GNSS RO) of the three new satellites (KOMPSAT-5, FY-3C, and FY-3D) on analyses and forecasts of a numerical weather prediction model. Numerical data assimilation experiments were performed using a three-dimensional variational data assimilation system in the Korean Integrated Model (KIM) at a 25-km horizontal resolution for August 2019. Three experiments were designed to select the height and quality control thresholds using the data. A comparison of the data with an analysis of the European Centre for Medium-Range Weather Forecasts (ECMWF) integrated forecast system showed a clear positive impact of BA assimilation in the Southern Hemisphere tropospheric temperature and stratospheric wind compared with that without the assimilation of the three new satellites. The impact of new data in the upper atmosphere was compared with observations using the infrared atmospheric sounding interferometer (IASI). Overall, high volume GNSS RO data helps reduce the RMSE quantitatively in analytical and predictive fields. The analysis and forecasting performance of the upper temperature and wind were improved in the Southern and Northern Hemispheres.

• The KSFM Journal of Fluid Machinery
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• v.18 no.6
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• pp.5-11
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• 2015

In a pressurized water reactor (PWR), control rod assembly (CRA) falls into the guide tubes of a fuel assembly due to gravity for scram. Various theoretical approaches and numerical analyses have been performed because its shape is simple and its design was completely developed several decades ago. A control rod assembly for a sodium-cooled faster reactor (SFR) which is geometrically more complicated is being actively developed in Korea nowadays. Drop time and impact velocity of a CRA are important parameters with respect to reactivity insertion time and the mechanical robustness of a CRA and a guide duct. In this paper, computational method considering simultaneously the equation of motion for rigid body and the Navier-Stokes equations for fluid is suggested and verified by comparison with theoretical analysis results. Through this valuable CFD analysis method, drop time and impact velocity of initially designed SFR CRA are evaluated before performing scram tests with it.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.6
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• pp.787-796
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• 2008

When the manipulator collides with surroundings, there occurs an impulse. To reduce the impulse, the self motion should maintain the manipulator's position by the minimally effective mass. At this time, we can use the local joint torque minimization algorithm to resolve the redundancy. In this study, to reduce the impulse and damages by the impact between the manipulator and surroundings, new control algorithm for the minimization of the joint torque using the kinetic redundancy and the impact minimization is proposed. It adapts fuzzy logic and genetic algorithm to the conventional local joint torque minimization algorithm. The proposed algorithm is applied to a 3-DOF redundant planar manipulator. Simulation results show that the proposed algorithm works well.

• Journal of Drive and Control
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• v.17 no.4
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• pp.46-53
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• 2020

In this paper, the development of a manually and continuously variable impact force control mechanism for hydraulic breakers was studied. Generally, a hydraulic breaker has one or two piston strokes. Hydraulic breakers, which have two strokes, have two valve-switching ports and make short and long piston strokes. The piston stroke valve controls the piston stroke by opening and closing a short stroke-switching port. The short piston stroke mode is used to break soft rock, concrete, or asphalt. This stroke control valve system is not popular for small hydraulic breakers mounted on 1 to 14-ton excavators. To preserve the carrier-like excavator, proper breaking force is needed, and it can be easily controlled by multiple piston stroke control valves. The easiest way to control these breakers is to use several switching ports and valves but they are not easy to install in small hydraulic breakers and are expensive. To use only one switching port and valve, a method can be used to change the open area of the switching port to delay valve switching. This method provides multiple piston strokes.

• Geomechanics and Engineering
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• v.14 no.4
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• pp.367-376
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• 2018

Samples composed of coal and rock show different mechanical properties of the pure coal or rock mass. For the same coal seam with different surrounding rocks, the frequency and intensity of rock burst can be significantly different in. First, a method of measuring the strain variation of coal in the coal-rock combined sample was proposed. Second, laboratory tests have been conducted to investigate the influences of rock lithologies, combined forms and coal-rock height ratios on the deformation and failure characteristics of the coal section using this method. Third, a new bursting liability index named combined coal-rock impact energy speed index (CRIES) was proposed. This index considers not only the time effect of energy, but also the influence of surrounding rocks. At last, a new approach considering the influences of roof and/or floor was proposed to evaluate the impact capability of coal seam. Results show that the strength and elastic modulus of coal section increase significantly with the coal-rock height ratio decreasing. In addition, the values of bursting liability indexes of the same coal seam vary greatly when using the new approach. This study not only provides a new approach to measuring the strain of the coal section in coal-rock combined sample, but also improves the evaluation system for evaluating the impact capability of coal.

• Asia pacific journal of information systems
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• v.5 no.1
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• pp.112-128
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• 1995

The information system control includes organizational structure, control mechanism, and management tools which contribute to accomplish the goals of information system: asset safeguarding, data integrity, effectiveness, and efficiency. Information system audit is the process to evaluate whether the information system accomplishs the goals. Information system auditor examine the reliability of information system control and suggest recommendations to improve the information system control. Both information system control and information system audit activities contribute to prevent and detect the computer crime for the organization. This paper proposes a causal model of information system control/audit and the perceived risk of computer crime, and tests the model using a survey on 38 financial institutions in Korea. Statistical results show that information system control and audit significantly reduce the computer crime risk perceived by the user group. The general control has a stronger impact than the application control. In addition, it turns out that the greater the deviation between the importance and the actual level of information system control is, the higher the perceived risk of computer crime is.

• Proceedings of the KOR-KST Conference
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• 1996.12a
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• pp.7-16
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• 1996

In this paper a modeling paradigm is described for answering the following questions: What would be the economic impact A, the social impact B, the demographic impact C, the land-use impact D, the environmental impact E and the user benefit F, over geographic scale G for a transport investment H at time T. The paradigm is illustrated for two ITS technologies: Advanced Transportation Management System (ATMS)and Advanced Vehicle Control Systems (AVCS).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.949-953
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• 1996

Force shape control for impact test is required in order to simulate dynamic reponse of structures which is subjected to impact force. In this paper, the mechanisms of contact and impact force generation are analyzed and tested with a simple test equipment. It was carried out for the pre-design of impact force reconstruction apparatus.

• Journal of Information Management
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• v.36 no.3
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• pp.183-193
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• 2005

Korean Academy of Medical Sciences began developing Korean Medical Citaton Index(KoMCI) database in 2002, and has announced the impact factors of Korean medical journals published since 2000. In July 2005, Korea Research Foundation also announced the KCI impact factor of journals covering all subject areas for the 2003 and 2004. We compared the impact factor(IF), impact factor excluding self-citation(ZIF), and self-citation impact factor(SIF) of KoMCI 2004 and KCI 2004 in order to disclose why there is such a great difference in the values of impact factors between two databases. Out of 72 medical journals in both database, 59 journals were compared after excluding the missing data in KCI. Mean IF of KoMCI 2004 was 0.2 and that of KCI 2004 was 0.03(p=0.0000). Mean ZIF of KoMCI was 0.06 and that of KCI was 0.01(p=0.000). Mean SIF of KoMCI was 0.139 and that of KCI was 0.02(p=0.0000). We presumed that the major difference in the impact factor values was originated from the fact that KCI does not control the authority of journal names cited in the references. We strongly recommend that it is necessary to control the authority especially if Korea Research Foundation wants to ensure the validity and reliability of KCI data in the evaluation of korean journals.