• Journal of Positioning, Navigation, and Timing
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• v.12 no.2
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• pp.149-155
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• 2023

In urban areas it can be difficult to utilize global navigation satellite systems (GNSS) due to signal reflections and blockages. It is thus crucial to detect reflected or blocked signals because they lead to significant degradation of GNSS positioning accuracy. In a previous study, a classifier for global positioning system (GPS) signal reception conditions was developed using three features and the support vector machine (SVM) algorithm. However, this classifier had limitations in its classification performance. Therefore, in this study, we developed an improved machine learning based method of classifying GPS signal reception conditions by including an additional feature with the existing features. Furthermore, we applied various machine learning classification algorithms. As a result, when tested with datasets collected in different environments than the training environment, the classification accuracy improved by nine percentage points compared to the existing method, reaching up to 58%.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.5
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• pp.57-68
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• 1995

A general procedure for the numerical solution of coupled, nonlinear, differential two-point boundary-value problems, solutions of which are crucial to the controller design, has been developed and demonstrated. A fixed-end-points, free-terminal-time, optimal-control problem, which is derived from Pontryagin's Maximum Principle, is solved by an extension of Davidenko's method, a differential form of Newton's method, for algebraic root finding. By a discretization process like finite differences, the differential equations are converted to a nonlinear algebraic system. Davidenko's method reconverts this into a pseudo-time-dependent set of implicitly coupled ODEs suitable for solution by modern, high-performance solvers. Another important advantage of Davidenko's method related to the time-optimal problem is that the terminal time can be computed by treating this unkown as an additional variable and sup- plying the Hamiltonian at the terminal time as an additional equation. Davidenko's method uas used to produce optimal trajectories of a single-degree-of-freedom problem. This numerical method provides switching times for open-loop control, minimized terminal time and optimal input torque sequences. This numerical technique could easily be adapted to the multi-point boundary-value problems.

• Korean Journal of Acupuncture
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• v.30 no.1
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• pp.37-46
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• 2013

Objectives : The Meridians and acupuncture points are the fundamental theories for acupuncture therapy. They have been associated with nervous system, but It is not well defined. We investigated that the effects of acupuncture at the river points(LU8, HT4, PC5, SP5, KI7, LR4) on the changes in the expression of nNOS, iNOS, eNOS, and NE in rats. Methods : The Male Sprague-Dawley rats were divided into 6 groups each non-acupuncture and acupuncture group. We inserted needle and retained for 5 minutes on both left and right sides of LU8, HT4, PC5, SP5, KI7, LR4 which were the river points of five transport points for 6 yin meridian vessels. After that, blood was drawn via cardiac puncture, and tissues for each point near meridian vessels were extracted to examine the changes in the changes of nNOS, eNOS, iNOS and NE. Results : The LU8 and HT4 group showed a significant decrease on nNOS. In terms of eNOS and iNOS, the LU8 group decreased significantly while the KI7 group increased significantly. However, the experimental groups didn't show any significant changes on the plasma and tissue norepinephrine without plama NE in SP5 group. Conclusions : The effect on the nNOS, iNOS, eNOS of acupuncture at LU8 and KI7 could be observed, and it is considered that the effect of acupuncture related with on nervous system could be studied by additional researches based on this one.

• Journal of Korea Society of Digital Industry and Information Management
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• v.8 no.3
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• pp.65-74
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• 2012

A barcode is a representative means of cognition. It is either printed on the package of a product or attached to it as a sticker. It is used for the fast cognition of a product at a store. It is considerably cheap to make a barcode. Also, it is possible to read it fast by using a barcode reader. Because of such convenience provided by the barcode, a new system using the barcode as a means of settling payments like a currency or a credit card has been developed. However, due to its characteristics, it is easy to reduplicate, forge or falsify a barcode easily. Therefore, this study focuses on the case of applying the system using barcodes as a means of settling payments without providing solutions for the potential weaknesses. Also, this study suggests various points to consider regarding the creation of safe barcodes as one of the related measures, while providing various methods using additional means of certification other than the one of using barcodes in addition to the way of applying complexity with barcode numbers. Throughout this study, it will be possible to safely establish and operate the payment-settlement system using barcodes.

• Progress in Superconductivity and Cryogenics
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• v.22 no.4
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• pp.45-50
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• 2020

In this research, the variation of round-trip efficiency in a liquid air energy storage system (LAES) is calculated and an optimal configuration is found. The multiple stages of cold energy storage are simulated with several materials that process latent heat at different temperature ranges. The effectiveness in the charging and discharging processes of LAES is newly defined, and its relationship with the round-trip efficiency is examined. According to defined correlation, the effectiveness of the discharging process significantly affects the overall system performance. The round-trip efficiency is calculated for the combined cold energy storage materials of aqueous dimethyl sulfoxide (DMSO) solution, ethanol, and pentane theoretically. The performance of LAES varies depending on the freezing point of the cold storage materials. In particular, when the LAES uses several cold storage materials, those materials whose freezing points are close to room temperature and liquid air temperature should be included in the cold storage materials. In this paper, it is assumed that only latent heat is used for cold energy storage, but for more realistic analyzes, the additional consideration of the transient thermal situation to utilize sensible heat is required. In the case of such a dynamic system, since there is certainly more increased heat capacity of the entire storage system, the volume of the cold energy storage system will be greatly reduced.

• Journal of Biomedical Engineering Research
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• v.27 no.6
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• pp.392-401
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• 2006

Image Guided Surgery (IGS) system which has variously tried in medical engineering fields is able to give a surgeon objective information of operation process like decision making and surgical planning. This information is displayed through 3D images which are acquired from image modalities like CT and MRI for pre-operation. The technique of image registration is necessary to construct IGS system. Image registration means that 3D model and the object operated by a surgeon are matched on the common frame. Major techniques of registration in IGS system have been used by recognizing fiducial markers placed on the object. However, this method has been criticized due to additional trauma, its invasive protocol inserting fiducial markers in patient's bone and generating noise data when 2D slice images are acquired by image modality because many markers are made of metal. Therefore, this paper developed shape-based registration technique to improve the limitation of fiducial marker based IGS system. Iterative Closest Points (ICP) algorithm was used to match corresponding points and quaternion based rotation and translation transformation using closed form solution applied to find the optimized cost function of transformation. we assumed that this algorithm were used in Total Knee replacement (TKR) operation. Accordingly, we have developed region-based 3D registration technique based on anatomical landmarks and this registration algorithm was evaluated in a femur model. It was found that region-based algorithm can improve the accuracy in 3D registration.

• Korean Journal of Acupuncture
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• v.29 no.2
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• pp.300-314
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• 2012

Objectives : This study is to observe the changes in the expression of neurotransmitters, such as NO, nNOS, and NE, upon the needle insertion to the sea points, which is one of the five transport points. Methods : Needles were inserted into rats, on both left and right sides of all sea points, including the LU5, PC3, HT3, LI11, TE10, SI8, SP9, LR8, KI10, ST36, GB34, and BL40, which are the sea points of five transport points for 12 meridian vessels. After insertion, needles were retained for five minutes. After the retention, blood was drawn via cardiac puncture, and tissues of each point near meridian vessels were extracted to examine the changes in the expression of NO, nNOS and NE. Results : In terms of the effect in NO production, there was a significant decrease only in the LU5 point, whereas there was a significant increase in the TE10 point alone. In terms of the expression of nNOS within tissues, none of the experimental groups showed significant changes based on the results of immunohistochemistry and western blotting. Regarding the formation of norepinephrine within tissues, the HT3, SP9, and KI10 point showed a significant decrease, while the PC3 and LR8 point showed a significant increase. Production of plasma norepinephrine was significantly increased at the TE10, SP9, LR8, GB34, and BL40 point. Conclusions : The effect of needles applied at the sea points of five transport points of 12 meridian vessels on the functions of NO, nNOS, and NE could be observed, and it is considered that the effect of needle stimulation on nervous system disorders could be studied through additional researches based on this one.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.667-672
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• 2009

In case of high-levelled platform in the urban railway system, a certain width of gap is inevitably formed between the train and the platform, and the gap gets wider when it is concerned with curved portion of the tracks at platform. This gap greatly contributes to decrease of passengers' safety while boarding and alighting a train. In particular, it endangers children's safety. Gap filler system is often fitted out to minimize gap and to overcome this safety problem at platform. However, as existing gap fillers are in most case structurally complex and organized to be powered from separate supply unit, there are a range of non-favorable points from the viewpoint of cost, installation and maintenance. In addition, existing gap fillers are due to cause disruptions in operation of train, with failures such as malfunctioning of control system. In this study, the authors will review on the gap filler applicable to the platforms of various height types, which neither requires any modifications of the train nor causes any operational disruptions. The proposed gap filler system here is a by-stage retractile type and based on the idea of interlocking it with train doors open-close mechanism, without any additional power supply unit or control system.

• Journal of Technologic Dentistry
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• v.39 no.4
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• pp.235-242
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• 2017

Purpose: The aim of this study was to evaluate the marginal and internal gap of zirconia copings fabricated by CAD/CAM system and to research the effect of cement space on the fit of zirconia prosthesis. Methods: Zirconia copings were designed using 3shape software and then milled from presintered zirconia blocks by Kavo dental milling machine. The cement space was set at $0{\mu}m$ around the margins for all groups, and additional cement space appling 1 mm above the finish lines of tooth. The samples were classified into 4 groups according to the cement space setting(Cs-0, Cs-40, Cs-80, Cs-120). Replica technique used to investigate marginal and internal gap. The silicone film thickness was recorded using a optical microscope with image software analysis system at 75${\times}$magnification. The assessment performed on the six points in bucco-lingual and mesio-distal sections(4 groups, 10 copings per group, 12 measuring points per coping). The data were statistically analyzed with one-way ANOVA followed by pair-wise Tukey's post hoc tests(${\alpha}$<0.05). Results: Better marginal and internal fit values were exhibited by $80{\mu}m$ cement space. The results showed that different cement space values had statistically significant effect on the marginal and internal gap of zirconia copings(p<0.001). The gap of margin and axial wall area was smaller than that the gap of occlusal area in all groups(p<0.001). Conclusion : Effect of different cement spaces on the marginal and internal gap of zirconia copings.

• Convergence Security Journal
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• v.6 no.1
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• pp.13-23
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• 2006

It is more desirable to execute AV software on server systems rather than on clients for the minimization of damages due to malicious codes. AV software on server system, however, may aggravate the load of server system. In this paper, we propose a new AV software executed on server system without additional loads with a monitor and multi-agent model. The new AV software supports dynamic load balancing that reflects the features of AV engine, and thus it can be executed efficiently on server systems. The results of performance evaluation on the AV software attest to the strong points of the new AV software.