• 대한기계학회논문집A
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• 제24권12호
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• pp.2899-2908
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• 2000

Methodology of volumetric error identification is presented to improve the accuracy of NC machine tools by using a reference artifact and a touch trigger probe. Homogeneous transformation matrix and kinematic chain are used for modeling the geometric and thermal errors of a three-axis vertical machining center. The reference artifact is designed and fabricated to identify the model parameters by machine tool metrology. Parameters in the error model are able to be identified and updated by direct measurement of the reference artifact on the machine tool under the actual conditions which include the thermal interactions of error sources. The proposed method can speed up and simplify volumetric error identification processes.

• 한국CDE학회논문집
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• 제10권5호
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• pp.303-313
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• 2005

This paper proposes a generalized NURBS model, called Volumetric NURBS or VNURBS for representing volumetric objects with multiple attributes embedded in multidimensional space. This model provides a mathematical framework for modeling complex structure of heterogeneous objects and analyzing inside of objects to discover features that are directly inaccessible, for deeper understanding of complex field configurations. The defining procedure of VNURBS, which explains two directional extensions of NURBS, shows VNURBS is a generalized volume function not depending on the domain and its range dimensionality. And the recursive a1gorithm for VNURBS derivatives is described as a computational basis for efficient and robust volume modeling. In addition, the specialized versions of VNURBS demonstrate that VNURBS is applicable to various applications such as geometric modeling, volume rendering, and physical field modeling.

• 한국생산제조학회지
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• 제22권3호
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• pp.394-401
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• 2013

A new Rockwell hardness (HRC) model using a volumetric parameter by a least square and fractal interpolation method is suggested. The results are also investigated in comparison to real measured hardness data. For this purpose, the measurement of an indented volume is performed using a confocal laser scanning microscope (CLSM), and the captured height encoded image (HEI) is used as an original surface for the calculation of the indented volume. After configuring the surface, the constructed volume is calculated and used as an independent variable for HRC hardness modeling. The hardness model is established using an experimental modeling technique involving a least square algorithm and fractal interpolating model, and this suggested model can be used to reliably predict the Rockwell hardness. These techniques can also be applied to the modeling of the Brinnell and Vickers hardnesses using a volumetric variable.

• 한국기계가공학회지
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• 제10권5호
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• pp.1-6
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• 2011

Machine tool errors have to be characterized and predicted to improve machine tool accuracy. Therefore, it is very important to assess errors in machine tools. Volumetric error analysis has been developed by many researchers. This paper presents a useful technique for analyzing the volumetric errors in machine tools using the ball bar. The volumetric error model is proposed in specific vertical machining center and the program is developed for generating NC code, acquiring the ball bar data, and analyzing the volumetric errors. The developed system assesses the volumetric errors such as positional, straightness, squareness, and back lash. Also this system analyzes the dynamic performance such as servo gain mismatch. The radial data acquired by ball bar on 3D space is used for analyzing these errors. It is convenient to test the volumetric errors on 3D space because all errors are calculated at once. The developed system has been tested using an actual vertical machining center.

• Restorative Dentistry and Endodontics
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• 제46권1호
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• pp.2.1-2.8
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• 2021

Objectives: New premixed bioceramic root repair materials require moisture for setting. Using micro-computed tomography (micro-CT), this study evaluated the filling ability and volumetric changes of calcium silicate-based repair materials (mineral trioxide aggregate repair high-plasticity [MTA HP] and Bio-C Repair, Angelus), in comparison with a zinc oxide and eugenol-based material (intermediate restorative material [IRM]; Dentsply DeTrey). Materials and Methods: Gypsum models with cavities 3 mm deep and 1 mm in diameter were manufactured and scanned using micro-CT (SkyScan 1272. Bruker). The cavities were filled with the cements and scanned again to evaluate their filling capacity. Another scan was performed after immersing the samples in distilled water for 7 days to assess the volumetric changes of the cements. The statistical significance of differences in the data was evaluated using analysis of variance and the Tukey test with a 5% significance level. Results: Bio-C Repair had a greater filling ability than MTA HP (p < 0.05). IRM was similar to Bio-C and MTA HP (p > 0.05). MTA HP presented the largest volumetric change (p < 0.05), showing more volume loss than Bio-C and IRM, which were similar (p > 0.05). Conclusions: Bio-C Repair is a new endodontic material with excellent filling capacity and low volumetric change. The gypsum model proposed for evaluating filling ability and volumetric changes by micro-CT had appropriate and reproducible results. This model may enhance the physicochemical evaluation of premixed bioceramic materials, which need moisture for setting.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 춘계학술대회
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• pp.76-77
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• 2022

본 논문에서는 다시점에서의 자세 추정 결과를 정합하여 3D 볼류메트릭 데이터 시퀀스의 3D 자세 추정 결과의 떨림을 줄이는 방법을 제안한다. 볼류메트릭 모델을 중심으로 원을 그리며 일정 각도 간격의 시점에서 본 모델을 평면에 투사한다. 투영하여 얻은 2D 영상에 대해 Openpose를 이용하여 2D 자세 추정을 진행한 뒤, 2D 관절 정보를 정합하여 3D 관절 위치를 국한한다. 각도 간격에 따라 다른 3D 관절의 떨림의 정도를 수치화하여 표로 나타내고, 안정적인 결과를 위한 최소 조건을 확인하였다.

• 방송공학회논문지
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• 제27권5호
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• pp.751-761
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• 2022

디지털 기술의 발전에 따라 메타버스가 콘텐츠 시장의 주요 트렌드로 자리하면서 고품질의 3D(dimension) 모델을 생성하는 기술에 대한 수요가 급증하고 있다. 이에 따라 디지털 휴먼으로 대표되는 고품질 3D 가상 인간의 제작과 관련된 다양한 기술적 시도가 이루어지고 있다. 3D 볼류메트릭 캡처는 기존의 3D 모델 생성 방식보다 빠르고 정밀한 3D 인체모형을 생성할 수 있는 기술로 각광 받고 있다. 본 연구에서는 볼류메트릭 3D 및 4D 모델 생성 분야에서 적용되는 기술들과 콘텐츠 제작의 애로사항에 대해 실제 사례를 바탕으로 3D 고정밀 페이셜 제작 기술의 분석을 시도한다. 그리고 실제 볼류메트릭 캡처를 통한 모델의 구현 사례를 바탕으로 3D 가상인간의 얼굴 제작에 대한 기술들을 고찰하고 효율적인 휴먼 페이셜 생성을 위한 그래픽스 파이프라인을 활용하여 새로운 메타휴먼을 제작하였다.

• 한국정밀공학회지
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• 제19권9호
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• pp.34-40
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• 2002

Machining accuracy is affected by quasi-static errors of machining center. Since machine errors have a direct influence upon both the surface finish and geometric shape of the finished workpiece, it is very important to measure the machine errors and to compensate these errors. The laser measurement method for identifying geometric errors of machine tool has the disadvantages such as high cost, long calibration time and usage of volumetric error synthesis model. Accordingly, this paper deals with analysis of the geometric errors of a machine tool using ball bar test without using complicated error synthesis model. Statistical analysis method was adopted in this paper for deriving geometric errors using hemispherical helix ball bar test. As a result of experiment, geometric errors of the vertical machining center are compensated by 88%.

• Korean Chemical Engineering Research
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• 제53권6호
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• pp.746-754
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• 2015

본 연구는 이온교환법을 통해 Ni촉매를 담지한 저등급 석탄(인도네시아 Eco탄)과 바이오매스(대한민국 상록수)의 혼합물로부터 제조된 촤(char)를 $700{\sim}900^{\circ}C$ 등온조건에서 온도가 반응속도에 미치는 영향에 대해 알아보았다. $Char-CO_2$ 가스화 반응은 700, 750, 800, 850, $900^{\circ}C$의 온도에서 진행하였으며, 기-고체 반응의 가스화 거동특성을 알아보기 위하여 각각 다른 가정을 갖고 있는 shrinking core model(SCM), volumetric reaction model(VRM), random pore model(RPM), modified volumetric reaction model(MVRM)을 실험결과에 적용하여 비교하였다. Arrhenius equation를 이용하여 Ni-coal/biomass와 Non-catalyst coal/biomass의 활성화에너지를 구하였고 이를 비교하였다.

• Korean Chemical Engineering Research
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• 제55권1호
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• pp.99-106
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• 2017

본 연구에서는 인도네시아 저등급 석탄인 Kideco탄을 이용하여 질소 분위기 하에 등온상태에서 촤(char)를 생성한 후 반응가스(스팀,이산화탄소)를 주입하여 합성가스를 생성하는 가스화를 진행하였다. 온도가 반응속도에 미치는 영향을 알아보기 위해 $850^{\circ}C$ 이하의 운전온도(700, 750, 800, $850^{\circ}C$)에서 반응을 진행하였다. 촉매가 미치는 영향을 알아보기 위해 알카리계 촉매인 탄산칼륨과 금속촉매인 니켈을 이용하였으며 두가지 촉매의 혼합비율(1:9, 3:7, 5:5, 7:3, 9:1)을 다르게 하여 연구를 수행하였다. 탄산칼륨은 물리적 혼합을 통해 니켈은 이온교환법을 통해 준비하였다. 기-고체 반응 특성을 알아보기 위해 열중량분석기와 가스크로마토그래피를 통해 얻은 실험결과를 shrinking core model (SCM), volumetric reaction model (VRM), random pore model (RPM) and modified volumetric reaction model (MVRM)에 적용하여 비교하였다.