• 한국지리정보학회지
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• 제1권1호
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• pp.8-17
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• 1998

본 논문에서는 지상기준점의 데이터베이스 구축과 영상 GCP의 활용을 소개한다. 고해상도 위성영상 또는 항공사진의 정밀 기하학적 보정을 위해서는 정확한 지상기준점을 추출하는 작업이 필수적이다. 이러한 지상기준점 추출의 편의성과 정확성을 향상시키기 위하여 지상기준점 정보의 데이터베이스를 구축하고 더불어 영상 GCP를 저장하였다. 원시영상의 보정을위해 GCP 추출을 반복할 필요 없이 데이터베이스의 GCP를 이용함으로써 재사용의 이점을 얻는다. 또한 영상 GCP에 대응하는 원시영상의 좌표계를 결정할 수 있는 알고리즘의 구현을 통해서 데이터베이스에 저장된 정확한 GCP들의 값을 다른 원시영상의 보정에 전이시킬 수 있는 효과를 얻을 수 있다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.749-752
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• 2005

In the industry, three-dimensional coloring has been needed for realistic prototype from rapid prototyping. Z-corporation developed a 3D printer which provides three-dimensional colored prototype. However, the existing process cannot be adopted to models from other rapid prototyping process. In addition, time and cost for manufacturing colored prototype still remain to be improved. In this study, a new coloring process using ink-jet head is proposed for color printing on three-dimensional prototype surface. Process parameters such as the angle and the distance between ink-jet nozzle and the three-dimensional surface should be investigated from experiments. The correction matrix according to sloped angle to minimize the distortion of 2D image was proposed by analysis of printing error. Therefore, approximated method for angle and discrete length according to the radius of curvature for printing on the curved surface was proposed. By printing image on the doubly curved surface, the method was verified. As a practical example, helmet was chosen for printing images on the curved surface. The character images were applied with approximated method for angle and discrete length and was printed on the helmet surface.

• 정보과학회 컴퓨팅의 실제 논문지
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• 제21권12호
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• pp.798-803
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• 2015

DGPS는 기존 GPS의 위치측위 정밀도를 지상 기준국의 보정정보를 이용하여 향상시킬 수 있는 기술이다. 현재 전국을 대상으로 DGPS 보정정보 송출이 가능하도록 인프라가 구축되어 있으나, 고가의 DGPS 전용장비가 필요하다는 제약으로 제한된 분야에서만 활용되고 있다. 스마트폰을 이용한 DGPS 단말의 개발은 이러한 한계를 극복하고 다양한 위치기반 서비스에 DGPS를 적용할 수 있도록 함으로써, 위치기반 서비스의 새로운 서비스 모델의 구현이 가능하게 할 수 있다. 본 논문에서는 스마트폰 환경에서 DMB 방송망, 이동통신망을 통해서 수신된 DGPS 보정정보를 활용하여 고정밀 위치측위가 가능한 DGPS 단말 개발에 대해서 소개하고자 한다.

• 한국정밀공학회지
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• 제20권6호
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• pp.88-95
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• 2003

This paper presents the measurement and correction method of PCB alignment errors for PCB screen printer. Electronic equipment is getting smaller and yet must satisfy high performance standard. Therefore, there is a great demand for PCB with high density. However conventional PCB screen printer doesn't have enough accuracy to accommodate the demand fur high-resolution circuit pattern and high-density mounting capacity of electronic chips. It is because the alignment errors of PCB occur when it is loaded to the screen printer. Therefore, this study focuses on the development of the system which is able to measure and correct alignment errors with high-accuracy. An automatic optical inspection part measures the PCB alignment errors using machine vision, and the high-accuracy 3-axis stage makes correction for these errors. This system used two CCD cameras to get images of two fiducial marks of PCB. The geometrical relationship between PCB, cameras, and xy$\theta$ stage is derived, and analytical equations for alignment errors are also obtained. The unknown parameters including camera declining angles and etc. can be obtained by initialization process. Finally, the proposed algorithm is verified by experiments by using test bench.

• 한국정밀공학회지
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• 제20권6호
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• pp.96-104
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• 2003

This paper presents the measurement and correction method of PCB alignment errors for PCB screen printer. Electronic equipment is getting smaller and yet must satisfy high performance standard. Therefore, there is a great demand for PCB with high density. However conventional PCB screen printer doesn't have enough accuracy to accommodate the demand for high-resolution circuit pattern and high-density mounting capacity of electronic chips. It is because the alignment errors of PCB occur when it is loaded to the screen printer. Therefore, this study focuses on the development of the system which is able to measure and correct alignment errors with high-accuracy. An automatic optical inspection part measures the PCB alignment errors using machine vision, and the high-accuracy 3-axis stage makes correction for these errors. This system used two CCD cameras to get images of two fiducial marks of PCB. The centers of fiducial marks are obtained by using moment, gradient method. The first method is calculating the centroid by using first moment of blob, and the latter method is calculating the center of the circle whose equation is obtained by curve-fitting the boundaries of fiducial mark. The operating system used to implement the whole set-up is carried in Window 98 (or NT) environment. Finally we implemented this system to PCB screen printer.

• 한국정밀공학회지
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• 제19권7호
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• pp.80-87
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• 2002

Liquefied petroleum gas (LPG) is used in spark ignition (SI) engines. Fuel injection rate of an injector is affected by fuel temperature and pressure in LPG liquid injection systems for either a multi-point-injection (MPI) or a direct injection (DI) engine. Even fuel injection conditions are varied, the air-fuel ratio should be accurately controlled to reduce exhaust emissions. In this study, a correction factor fur the fuel injection rate of an injector is derived from density ratio and pressure difference ratio. A compensation method of injected fuel amount is proposed for a fuel injection control system. The experimental results for the LPG liquid injection system in a SI engine show that this system works well fur a full range of engine speed and load condition, and the air-fuel ratio is accurately controlled by the proposed correction factor.

• Quantitative Bio-Science
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• 제37권2호
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• pp.133-141
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• 2018

Graphical lasso is one of the most popular methods to estimate a sparse precision matrix, which is an inverse of a covariance matrix. The objective function of graphical lasso imposes an ${\ell}_1$-penalty on the (vectorized) precision matrix, where a tuning parameter controls the strength of the penalization. The selection of the tuning parameter is practically and theoretically important since the performance of the estimation depends on an appropriate choice of tuning parameter. While information criteria (e.g. AIC, BIC, or extended BIC) have been widely used, they require an asymptotically unbiased estimator to select optimal tuning parameter. Thus, the biasedness of the ${\ell}_1$-regularized estimate in the graphical lasso may lead to a suboptimal tuning. In this paper, we propose a two-staged bias-correction procedure for the graphical lasso, where the first stage runs the usual graphical lasso and the second stage reruns the procedure with an additional constraint that zero estimates at the first stage remain zero. Our simulation and real data example show that the proposed bias correction improved on both edge recovery and estimation error compared to the single-staged graphical lasso.

• Journal of Positioning, Navigation, and Timing
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• 제12권4호
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• pp.349-358
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• 2023

The Satellite-Based Augmentation System (SBAS) plays a significant role in the fields of aviation and navigation: it corrects signal errors of the Global Navigation Satellite System (GNSS) and provides integrity information to facilitate precise positioning. These SBAS systems have been adopted as international standards by the International Civil Aviation Organization (ICAO). In recent SBAS system design, the Minimum Operational Performance Standards (MOPS) defined by the Radio Technical Commission for Aeronautics (RTCA) must be followed. In October 2014, South Korea embarked on the development of a Korean GPS precision position correction system, referred to as Korea Augmentation Satellite System (KASS). The goal is to achieve APV-1 Standard of Service Level (SoL) service level and acquisition of CAT-1 test operating technology. The first satellite of KASS, KASS Prototype 1, was successfully launched from the Guiana Space Centre in South America on June 23, 2020. In December 2022 and June 2023, the first and second service signals of KASS were broadcasted, and full-scale KASS correction signal broadcasting is scheduled to start at the end of 2023. The aim of this study is to analyze the precision of both the GNSS system and KASS system by comparing them. KASS is also compared with Japan's Multi-functional Satellite Augmentation System (MSAS), which is available in Korea. The final objective of this work is to validate the usefulness of KASS correction navigation in the South Korean operational environment.

• 한국공작기계학회논문집
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• 제17권4호
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• pp.112-118
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• 2008

In order to meet the optical performance in the process of the micro lens manufacturing with plastics, it is important to embody accuracy in shape and surface roughness to the intended design. Since it is difficult to machine exactly the mold core of lens fit to the designed shape, in this paper, a simple program using MATLAB is developed for shape correction of the mold core after first machining it. This program evaluates correction parameters(aspheric coefficients and curvature) and generates aspheric NC data for compensating the core surface in prior machining process. The program provides the way to manufacture plastic injection molding lens with aspheric shape of high precision, and is expected to be effective for correction and to shorten the processing time.

• 대한임베디드공학회논문지
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• 제9권5호
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• pp.285-292
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• 2014

The commonly used Newton-Raphson's floating-point number divider algorithm performs two multiplications in one iteration. In this paper, a tentative K'th Newton-Raphson's floating-point number divider algorithm which performs K times multiplications in one iteration is proposed. Since the number of multiplications performed by the proposed algorithm is dependent on the input values, the average number of multiplications per an operation in single precision and double precision divider is derived from many reciprocal tables with varying sizes. In addition, an error correction algorithm, which consists of one multiplication and a decision, to get exact result in divider is proposed. Since the proposed algorithm only performs the multiplications until the error gets smaller than a given value, it can be used to improve the performance of a floating point number divider unit. Also, it can be used to construct optimized approximate reciprocal tables.