• Journal of Power Electronics
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• 제16권5호
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• pp.1964-1980
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• 2016

This paper presents a new simplified harmonics extraction algorithm based on the synchronous reference frame (SRF) for an indirect current controlled (ICC) three-level neutral point diode clamped (NPC) inverter-based shunt active power filter (SAPF). The shunt APF is widely accepted as one of the most effective current harmonics mitigation tools due to its superior adaptability in dynamic state conditions. In its controller, the SRF algorithm which is derived based on the direct-quadrature (DQ) theory has played a significant role as a harmonics extraction algorithm due to its simple implementation features. However, it suffers from significant delays due to its dependency on a numerical filter and unnecessary computation workloads. Moreover, the algorithm is mostly implemented for the direct current controlled (DCC) based SAPF which operates based on a non-sinusoidal reference current. This degrades the mitigation performances since the DCC based operation does not possess exact information on the actual source current which suffers from switching ripples problems. Therefore, three major improvements are introduced which include the development of a mathematical based fundamental component identifier to replace the numerical filter, the removal of redundant features, and the generation of a sinusoidal reference current. The proposed algorithm is developed and evaluated in MATLAB / Simulink. A laboratory prototype utilizing a TMS320F28335 digital signal processor (DSP) is also implemented to validate effectiveness of the proposed algorithm. Both simulation and experimental results are presented. They show significant improvements in terms of total harmonic distortion (THD) and dynamic response when compared to a conventional SRF algorithm.

• 한국문헌정보학회지
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• 제45권2호
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• pp.61-74
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• 2011

The author analyses the challenging activities of Japanese libraries in this decade by launching two keywords; "product-sharing" and "outcome generation." "Product-sharing" means that libraries share knowledge, skills, and records which are produced as the result of the services or in the process of activities. And "outcome generation" means that libraries generate any efficiency or effectiveness through their services to users. Using these concepts, reported are the current situation and aspects of Japanese libraries which try to make various contributions to the society; research and learning of the people, and education and training for professional librarians, and so on. In the analysis, the author shows some examples of "product-sharing" at first, including the records of reference transaction and the multi-functioned online public access catalogue. Especially, focused is on the various possibility and adoptability of the Collaborative Reference Database System of the National Diet Library of Japan. This system is one of digital reference service in Japan, and the database of reference transaction records is expected to be useful for research and academic studyies as knowledge-base of professional librarians. And the system is also expected to be a platform for LIS education and professional development in the e-learning environment. Secondly, as the examples of "outcome generation", explained are the problem-solving-type activities, and provision of the collection about books on struggling against disease and illness. A few examples of outcome in the problem-solving-type activities are these; increase of sales in the services for shop managers, business persons, and entrepreneurs, contribution to affluent daily life by providing the local information services to residents and neighbourhoods, and etc. And for both the patients with serious cases and their family or those who nurse them, books about other persons' notes or memorandum are the greatest support, and sometime healing. The author discuss the 'raison d'etre' of these activities focusing on public libraries in Japan.

• 한국전자파학회논문지
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• 제15권4호
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• pp.414-420
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• 2004

Orthogonal frequency-division multiplexing(OFDM)은 무선 환경에서 고속 데이터 전송에 적합한 방식이다. 그러나 높은 peak-to-average power ratio(PAPR)로 인하여 비선형 왜곡의 문제점이 있다. 여러 PAPR 저감 방법 중에서 partial transmit sequences(PTS)는 매우 유연하고 스펙트럼 왜곡이 발생하지 않는 좋은 방법으로 평가된다. 이 방법의 문제점은 최적화된 rotation factor에 대한 부가 정보를 수신기에 전송해야만 데이터를 정확히 복원할 수 있다는 점이다. 본 논문에서는 기존 PTS 방식에서 기준 심볼을 이용하여 부가 정보를 전송하는 기법을 새롭게 제안한다. 이 기법은 rotation factors의 정보를 기준 심볼의 위상으로 표현하는 방법이다. 시뮬레이션 결과를 통해 제안 방식이 종전의 PTS와 동일한 PAPR 저감 성능을 가지면서 정확하게 데이터를 복원하여 요구 BER이 만족됨을 확인하였다. 또한, 제안 방식은 변조 방식에 무관하며, 간단하게 시스템을 구현할 수 있다.

• Spatial Information Research
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• 제15권3호
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• pp.301-310
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• 2007

현재 우리나라에는 전국에 약 21,000점의 측량용 국가기준점이 표석 형태로 매설되어 있으며, 대부분이 시통을 위해 산 정상에 매설되어 있어 일반인들의 사용과 접근이 어렵다. 최근 유비쿼터스 환경이 구축되어 감에 따라 위치정보 및 위치정보 기반의 정보를 일반인들에게 손쉽게 제공할 수 있는 서비스가 요구되고 있다. 본 연구에서는 RFID 태그와 2차원 바코드를 이용하여 위치정보를 손쉽게 제공할 수 있는 새로운 개념의 기준점 프로토타입을 제작하였다. 본 논문에서는 개발된 인텔리전트 기준점을 실용화하여 실제로 서비스하기 위해 필요한 사항에 대해 고려하여 보았으며, 실제 테스트를 통해 사용 가능성을 검증해보았다.

• 대한치과교정학회지
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• 제49권2호
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• pp.97-105
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• 2019

Objective: This study was performed to evaluate the accuracy and reliability of a newly designed method to achieve mandibular dental model superimposition, using voxel-based cone-beam computed tomography (CBCT) registration. Methods: Fourteen dry cadaveric mandibles and six teeth extracted from patients with severe periodontitis were used to establish 14 orthodontic tooth-movement models. The protocol consisted of two steps: in the first step, voxel-based CBCT mandible superimposition was performed; the reference comprised the external portion of the symphysis, extending to the first molar. The laser-scanned dental model image was then integrated with the CBCT image to achieve mandibular dental model superimposition. The entire process required approximately 10 minutes. Six landmarks were assigned to the teeth to measure tooth displacement, using tooth displacement on the superimposed laser-scanned mandibles as the reference standard. Accuracy was evaluated by comparing differences in tooth displacement based on the method and the reference standard. Two observers performed superimposition to evaluate reliability. Results: For three-dimensional tooth displacements, the differences between the method and the reference standard were not significant in the molar, premolar, or incisor groups (p > 0.05). The intraclass correlation coefficients for the inter- and intra-observer reliabilities of all measurements were > 0.92. Conclusions: Our method of mandibular dental model superimposition based on voxel registration is accurate, reliable, and can be performed within a reasonable period of time in vitro, demonstrating a potential for use in orthodontic patients.

• 정보관리학회지
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• 제37권4호
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• pp.151-179
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• 2020

본 연구는 대학도서관 이용자를 대상으로 도서관 챗봇을 설계하고 구현하여 언택트 시대의 새로운 비대면 디지털 참고정보서비스를 모색하고자 했다. 데이터 분석을 통해 이용자 요구 및 도서관 서비스를 분석하고, 적합한 챗봇 개발 방법을 선정하여 시나리오를 설계했다. 이용자 친화적인 상호작용을 위해 챗봇의 퍼스널리티를 설계하고 이용자 인터페이스를 디자인하여 사용성을 평가했다. 또한 챗봇의 응답정확도 평가 및 성능평가를 통해 정확도를 검증하고, 이용자 만족도 조사를 통해 챗봇의 효용성을 평가했다. 챗봇 운영관리 및 서비스 품질 유지를 위해 이용자-챗봇 간의 대화를 주기적으로 모니터링하고, 이용자 피드백을 반영하여 서비스를 개선했다. 챗봇 개발 과정 및 결과를 다각도로 분석하여 도서관 챗봇 설계 및 구현을 위한 구체적인 방안을 제시하고자 했다.

• Restorative Dentistry and Endodontics
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• 제46권2호
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• pp.23.1-23.11
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• 2021

Objectives: This study assessed the reliability of digital color measurements using images of resin composite specimens captured with a cellphone. Materials and Methods: The reference color of cylindrical specimens built-up with the use of resin composite (shades A1, A2, A3, and A4) was measured with a portable spectrophotometer (CIELab). Images of the specimens were obtained individually or pairwise (compared shades in the same photograph) under standardized parameters. The color of the specimens was measured in the images using RGB system and converted to CIELab system using image processing software. Whiteness index (WI_D) and color differences (ΔE₀₀) were calculated for each color measurement method. For the cellphone, the ΔE₀₀ was calculated between the pairs of shades in separate images and in the same image. Data were analyzed using 2-way repeated-measures analysis of variance (α = 0.05). Linear regression models were used to predict the reference ΔE₀₀ values of those calculated using color measured in the images. Results: Images captured with the cellphone resulted in different WI_D values from the spectrophotometer only for shades A3 and A4. No difference to the reference ΔE₀₀ was observed when individual images were used. In general, a similar ranking of ΔE₀₀ among resin composite shades was observed for all methods. Stronger correlation coefficients with the reference ΔE₀₀ were observed using individual than pairwise images. Conclusions: This study showed that the use of cellphone images to measure the color difference seems to be a feasible alternative providing outcomes similar to those obtained with the spectrophotometer.

• The Journal of Advanced Prosthodontics
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• 제15권6호
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• pp.290-301
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• 2023

PURPOSE. The study aimed to determine the influence of implant angulation on the trueness of multi-unit implant impressions taken through different techniques and strategies. MATERIALS AND METHODS. As reference models, three partially edentulous mandibular models (Model 1: No angulation; Model 2: No angulation for #33, 15-degree distal angulation for #35 and #37; Model 3: No angulation for #33, 25-degree distal angulation for #35 and #37) were created by modifying the angulations of implant analogues. Using a lab scanner, these reference models were scanned. The obtained data were preserved and utilized as virtual references. Three intraoral scanning (IOS) strategies: IOS-Omnicam, ISO-Quadrant, and IOS-Consecutive, as well as two traaditional techniques: splinted open tray (OT) and closed tray (CT), were used to create impressions from each reference model. The best-fit alignment approach was used to sequentially superimpose the reference and test scan data. Computations and statistical analysis of angular (AD), linear (LD), and 3D deviations (RMS) were performed. RESULTS. Model type, impression technique, as well as interaction factor, all demonstrated a significant influence on AD and LD values for all implant locations (P < .05). The Model 1 and SOT techniques displayed the lowest mean AD and LD values across all implant locations. When considering interaction factors, CT-Model 3 and SOT-Model 1 exhibited the highest and lowest mean AD and LD values, respectively. Model type, impression technique, and interaction factor all revealed significant effects on RMS values (P ≤ .001). CT-Model 3 and SOT-Model 1 presented the highest and lowest mean RMS values, respectively. CONCLUSION. Splinted-OT and IOS-Omnicam are recommended for multi-unit implant impressions to enhance trueness, potentially benefiting subsequent manufacturing stages.

• 정보저장시스템학회논문집
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• 제8권2호
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• pp.44-49
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• 2012

We measured the surface flatness of both sides for refractive media using the transmitted digital holography method. To enhance the accuracy of the result, phase-shifting system was used. With two different phase modulation of reference beam, the phase profile of object can be easily obtained. Thus, we proposed the surface measurement method which can measure large area fast, compared with conventional methods. To guarantee the reliability of obtained result, we compared with Zygo measurement system. With the proposed method, the surface flatness of $3.45{\mu}m$ resolution could be obtained.

• Imaging Science in Dentistry
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• 제30권1호
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• pp.16-22
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• 2000

Purpose : To evaluate the bone densities measured on copper-equivalent image of cross sectional view of mandibular edentulous premolar area obtained by multifuctional panoramic x-ray machine, PM 2002 CC with transversal slicing system. Materials and Methods: Panoramic cross sectional views with 8 mm focal layer of aluminum step and blocks, of hydroxyapatite (RA) step, 6 HA blocks and copper step wedge having 0.03 mm thickness of each step, and of 3 bone blocks cutted by 8 mm thickness mesiodistally and a dry mandible with copper step wedge were taken by using transversal slicing system in PM 2002 Cc. All reference-equivalent images were made and analyzed by NIH image program. Results: The average copper-equivalent value of cancellous bone of bone blocks on the panoramic cross sectional view was 0.026 ± 0.020 mm Cu. The calculated average bone density was 0.38g/cm². There was no significant difference (P>0.1) between the bone densities on intraoral digital view and on the panoramic digital cross sectional view. Conclusion: The copper-equivalent image of panoramic digital cross sectional view obtained by PM 2002 CC with very thin copper step wedge was supposed to be useful to measure the bone density of cancellous bone of mandible at the premolar edentulous area.