• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.558-563
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• 2012

In this paper, a novel planar type magnetic levitation system without other assistant devices is proposed and it can move with 6 degree of freedom (X, Y, Z, ${\theta}_X$, ${\theta}_Y$, ${\theta}_Z$) in wafer size as well as in nano scale positioning.The mover is composed with 2-D Halbach permanent magnet array and the stator is composed with $10{\times}10$ coil arrays.It was composed in laboratory and tested with short stroke (4 [mm]) and long stroke (160 [mm])movements. The errors of short movement test is [X, Y, Z, ${\theta}_X$, ${\theta}_Y$, ${\theta}_Z$]${\leq}$ [${\pm}200nm$, ${\pm}200nm$, ${\pm}250nm$, ${\pm}3urad$, ${\pm}2urad$, ${\pm}1urad$]The errors of long stroke movement test is [X, Y, Z, ${\theta}_X$, ${\theta}_Y$, ${\theta}_Z$]${\leq}$ [${\pm}200nm$, ${\pm}200nm$, ${\pm}250nm$, ${\pm}1.5urad$, ${\pm}2urad$, ${\pm}0.5urad$].

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.1084-1087
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• 1997

In this paper, we developed the micro NCT system for punching the thin plates, which is driven is driven by the standalone type microprocessor. In order to adjust the alignment between the punch and die in-situ punching procedures, the non-contact type laser sensor for measuring the burr and micro-driving system for punching die with using the differential screw are developed. The height of burr in four directions in the punched hole of test specimen are measured, and the measured data are transferred to the personal computer by RS232C serial communication technology. In the personal computer, by using the graphic user interface type monitoring program and data handling procedures which includes the filtering algorithms, the direction and length of movement of the die position is decided and these data are transferred back to the microprocessor. The microprocessor drives the micro positioning stage based on these data. Even if this method is not a perfect solution for the in-situ alignment in micro punching, but this alignment methodology is accomplished in the same stage just after the punching that we hope to solve the alignment problem in the punching system based on this technology.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.6
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• pp.99-107
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• 1996

When GPS (global positioning system) is used as synchronous signal in CDMA digital cellular base station system and high speed digital synchronous communication network, antenna cable length is increased, comparing with other GPS application such as positioning or car navigation. In this paper, it is proposed that a type of new GPS antenna system including RF stage for reduction of cable loss in case of long cable.The antenna system with TMPA(truncated-corners microstrip patch antenna) is designed and fabricated because GPS signal has RHCP (right-hand circular polarization), consequently antenna size can be made small size. LNA (low noise amplifier) is designed by using HEMT(high electron mobility transistor)which has lower noise figurae and better AGC characteristics at low voltage than GaAs FET, and we equiped mixer, in GPS antenna unit, which converts from 1575.42MHz to 75.42MHz. As result of comparing between typical system and proposed system when cable length is 60m, 63dB, 55dB and 25dB gain are obtained for RG-316/U, RG-58C/U and RG-213/U, and better characteristics are achieved than typical system as far as cable length is longer.

• Imaging Science in Dentistry
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• v.50 no.4
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• pp.281-290
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• 2020

Purpose: The objective of the present study was to evaluate the prevalence of dental implants positioning errors and their associations with adjacent structures and anatomical variations by means of cone-beam computed tomography (CBCT). Materials and Methods: CBCT images of 207 patients (584 dental implants) were evaluated by 2 oral radiologists. The distance between the implant and the adjacent teeth/implants was measured and classified as adequate (≥1.5 mm and ≥3 mm, respectively) or inadequate. The presence of thread exposure, cortical perforation, implant dehiscence, implant penetration into adjacent structures, and anatomical variations was also recorded. The incisor canal diameter and the depth of the concavity of the submandibular fossa were measured in order to evaluate their correlations with the frequency of implant penetration in these structures. Descriptive analyses, the Fisher exact test, and Spearman correlation analysis were performed (α=0.05). Results: The overall prevalence of positioning errors was 82.9%. The most common error was the inadequate distance between the implant and the adjacent teeth/implants. The presence of anatomical variations did not significantly influence the overall prevalence of errors (P>0.05). There was a positive correlation between the diameter of the incisor canal and the frequency of implant penetration in this structure (r=0.232, P<0.05). Conclusion: There was a high prevalence of dental implant positioning errors, and positioning errors were not associated with the presence of anatomical variations. Professionals should be aware of the space available for implant placement during the preoperative planning stage.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1453-1459
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• 2012

The dual stage manipulator is composed of the voice coil motor (VCM) and piezoelectric ceramics transducer (PZT), which can produce the high precise displacement and express a well dynamic performance. However, inaccurate modeling of the dual stage will exacerbate the positioning accuracy. This paper presents an approach to model the dual stage system by using bond graph theory. And the state space equations can be derived through the bond graph straightforwardly, which can be used in computing simulations. Through designing the compensators for the dual stage system and simulating, the dual stage performs better dynamics characteristic than the single actuator system.

• Journal of the korean academy of Pediatric Dentistry
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• v.21 no.2
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• pp.510-517
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• 1994

It is a relatively common clinical experience to see a impacted maxillary central incisor. This is apparent at the dental age of about eight years and over, when the patient is in the early mixed dentition stage. The adjacent teeth may tilt toward the site of the missing tooth with resulting space closure and midline deviation. Most often, the central incisor is impacted labially. The labial impaction has been indicated as the most difficult to manage. Each of the current articles describing labial impactions shows at least one case with mucogingival recession or a minimal zone of attached gingiva. This report described the surgical uncovering and orthodontic-physiologic positioning methods with labially impacted maxillary central incisors. Through surgical exposure and direct bonding of lingual botton, the central incisors were brought into proper eruption path with elastic traction. The case 1 and 2 were treated with the physiologic erupting forces. The case 3 was applied with continuous orthodontic force. The case 1 and 2 resulted in good positioning, good esthetics and adequate width of keratinised gingiva. The case 3 resulted in local inflammation and inadequate width of keratinised gingiva.

• Journal of Korea Multimedia Society
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• v.20 no.1
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• pp.74-81
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• 2017

In learning stage of the preliminary Cut-off indoor positioning scheme, RSSI and UUID data received from beacons at each reference point(RP) are stored in fingerprint map. The fingerprint map and real-time beacon information are compared to identify the nearest K reference points through which the user position is estimated. If the number of K is zero, this scheme cannot estimate user position. We have improved the preliminary Cut-off scheme to get the estimated user position even in the case. The improved scheme excludes the beacon of the weakest signal received by user mobile device and identifies neighborhood reference points using the other beacon information. This procedure are performed repetitively until K > 0. The simulation results confirm that the proposed scheme outperforms K-Nearest-Neighbor (KNN), Cluster KNN and the conventional Cut-off scheme in terms of accuracy while the constraints are guaranteed to be satisfied.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.1
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• pp.1-9
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• 2023

The problem of classifying a non-line-of-sight (NLOS) signal in a multipath channel is important to improve global navigation satellite system (GNSS) positioning accuracy in urban areas. Conventional deep learning-based NLOS signal classifiers use GNSS satellite measurements such as the carrier-to-noise-density ratio (CN_0), pseudorange, and elevation angle as inputs. However, there is a computational inefficiency with use of these measurements and the NLOS signal features expressed by the measurements are limited. In this paper, we propose a Convolutional Neural Network (CNN)-based NLOS signal classifier that receives successive Auto-correlation function (ACF) outputs according to a time-series, which is the most primitive output of GNSS signal processing. We compared the proposed classifier to other DL-based NLOS signal classifiers such as a multi-layer perceptron (MLP) and Gated Recurrent Unit (GRU) to show the superiority of the proposed classifier. The results show the proposed classifier does not require the navigation data extraction stage to classify the NLOS signals, and it has been verified that it has the best detection performance among all compared classifiers, with an accuracy of up to 97%.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.129-135
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• 2006

In this study, a two-axis ultra-precision stage driven by piezoelectric elements is presented. The stage has a flexure-type parallel linear guide mechanism consisting of quad-symmetric simple parallel linear springs and quad-symmetric double compound linear springs. While the simple parallel linear springs guide the linear motion of a moving plate in the stage, the double compound linear springs follow the motion of the simple parallel linear spring as well as compensate the parasitic motions caused by the simple parallel linear springs. The linear springs are designed by rectangular beam type flexures that are deformed by bending deflection rather than axial extension, because the axial extension is smaller than the bending deflection at the same force. The designed guide mechanism is analyzed by finite element method(FEM). Then two-axis parallel linear stage is implemented by the linear guide mechanism combined with piezoelectric elements and capacitance type displacement sensors. It is shown that the manufactured ultra-precision stage achieves 3 nm of resolution in x- and y-axis within 30 ${\mu}m$ of operating range.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.4
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• pp.26-31
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• 2008

본 논문은 정밀 위치결정 시스템의 잔류진동을 효과적으로 제거할 수 있는 입력성형기법을 소개하고, 실시간 입력성형기법을 적용하는 방법을 설명하였다. 또한 두 가지 응용 분야에 대한 실험결과를 바탕으로 입력성형기법의 성능을 고찰하였다. 일반적으로 입력성형기법은 정밀 위치결정 시스템에 대해 동작 완료시간을 단축시키는 효과가 있을 뿐만 아니라 위치결정 정밀도를 향상시키는 효과가 있다. 그리고 되먹임제어 방법에 비해 적용방법도 간단하며 저렴하게 구성할 수 있다는 장점이 있으므로 많은 정밀 위치결정 시스템에 유용할 것으로 생각된다.