• 대한설비공학회지:설비저널
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• 제8권4호
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• pp.254-259
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• 1979

Radiation data on south-facing surfaces required for the simplified design pro cedures for solar energy systems, have been computed using the method by Liu and Jordan. For the five localities of South Korea selected from reference 6, the factor R for the conversion of the monthly average daily total radiation on a horizontal surface to that on an inclined surface is presented in Table 5. For the other localities, the convession factor R can by computed using Table 2 through Table 4.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 Techno-Fair 및 추계학술대회 논문집 전기물성,응용부문
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• pp.138-139
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• 2007

The use of conventional Twyman and Fizeau interferometers inevitably fails in testing high precision optics because of errors always existing in reference elements producing the reference wavefront. Therefore it is necessary to apply to this task the interferometers of a radically new type, which are able to produce perfect reference wavefront with the help of light diffraction by a small obstacle or pinhole. In this paper new theoretical approaches and schematics of point diffraction interferometers are considered in detail with paying attention to constructive reliability. Such interferometers do not use reference optical surfaces and readily provide adequate estimation of errors and aberrations value of 0.01 wavelengths.

• 한국CDE학회논문집
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• 제12권6호
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• pp.441-451
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• 2007

In this paper, the method to modify a surface through three dimensional vector field technique is presented, In this method two guide surfaces are required as a shape reference. One is the shape of original surface, the other is the target shape for the result surface. Proposed method is consists of two steps. The first step is to calculate the mapping points on original and target guide surfaces so that the shape error may be minimized. The second step is to construct the smooth vector field from mapping points of the first step. The developed method is applied to shoe design system which makes the surface modeling very easy and effective.

• Journal of Ship and Ocean Technology
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• 제10권2호
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• pp.24-36
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• 2006

Ship hullform is usually designed with a curve network, and smooth hullform surfaces are supposed to be generated by filling in (or interpolating) the curve network with appropriate surface patches. Tensor-product surfaces such as B-spline and $B\'{e}zier$ patches are typical representations to this interpolating problem. However, they have difficulties in representing the surfaces of irregular topological type which are frequently appeared in the fore- and after-body of ship hullform curve network. In this paper, we proposed a method that can automatically generate discrete $G^1$ continuous B-spline surfaces interpolating given curve network of ship hullform. This method consists of three steps. In the first step, given curve network is reorganized to be of two types: boundary curves and reference curves of surface patches. Especially, the boundary curves are specified for their surface patches to be rectangular or triangular topological type that can be represented with tensor-product (or degenerate) B-spline surface patches. In the second step, surface fitting points and cross boundary derivatives are estimated by constructing virtual iso-parametric curves at discrete parameters. In the last step, discrete $G^1$ continuous B-spline surfaces are generated by surface fitting algorithm. Finally, several examples of resulting smooth hullform surfaces generated from the curve network data of actual ship hullform are included to demonstrate the quality of the proposed method.

• KIEAE Journal
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• 제15권1호
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• pp.117-127
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• 2015

The cool surface ratio could be used as a proxy of the overall thermal environment contributing to heat islands in urban area. This research proposes a comparative evaluation framework in an objective and quantitative way for measuring cool surface ratios. Two university campuses (Kyungpook National University: KNU, South Korea and UC Davis: University of California, Davis, USA) were selected as case study sites in order to monitor cool surface condition. Google Earth combined with digital maps realistically identified the major type of cool surfaces such as cool roofs and water bodies in the study area. Cool surfaces were sparsely identified over the KNU campus while the UC Davis campus was heavily covered by cool surfaces such as cool roofs and water bodies, resulting in almost four times more first-grade cool surfaces, as compared to KNU. It is confirmed that standard remote sensing technology can offer the viable method of measuring and comparing the campus-wide cool surface condition. It is anticipated that this research output could be used as a valuable reference to initiate a nation-wide cool surface strategy since objective evidence has been provided based on area-wide measurement for the cool surface in the two university context.

• Computers and Concrete
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• 제21권2호
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• pp.127-137
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• 2018

In this study, the behavior of the number of anchorage bolts on the glass-fiber reinforced polymer (GFRP) plates adhered to the surfaces of reinforcing concrete (RC) T-beams was investigated analytically. The analytical results were compared to the test results in term of shear strength, and midpoint displacement of the beam. The modelling of the beams was conducted in ABAQUS/CAE finite element software. The Concrete Damaged Plasticity (CDP) model was used for concrete material modeling, and Classical Metal Plasticity (CMP) model was used for reinforcement material modelling. Model-1 was the reference specimen with enough sufficient shear reinforcement, and Model-2 was the reference specimen having low shear reinforcement. Model-3, Model-4 and Model-5 were the specimens with lower shear reinforcement. These models consist of a single variable which was the number of anchorage bolts implemented to the GFRP plates. The anchorage bolts of 2, 3, and 4 were mutually mounted on each GFRP plates through the beam surfaces for Model-3, Model-4, and Model-5, respectively. It was found that Model-1, Model-3, Model-4 and Model-5 provided results approximately equal to the test results. The results show that the shear strength of the beams increased with increasing of anchorage numbers. While close results were obtained for Model-1, Model-3, Model-4 and Model-5, in Model-2, the rate of increase of displacement was higher than the increase of load rate. It was seen, finite element based ABAQUS program is inadequate in the modeling of the reinforced concrete specimens under shear force.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.1032-1035
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• 2000

Increasing demands on precision machining with computerized numerical control (CNC) machines have necessitated that the tool to move not only position error as small as possible, but also with smoothly varying feedrates in space. This paper presents a new high precision interpolation algorithm for 3-dimensional (3D) Non-Uniform Rational B-Spline (NURBS) curve in the reference-pulse CNC technique. Based on the minimum path error strategy, real-time NURBS interpolator was developed in software and this was implemented with a PC-NC milling machine. The several experimental results have shown that the proposed NURBS interpolator is useful for the high precision machining of complex shapes. It is expected that this algorithm can be applied to the CNC machines for the machining of 3D free-form surfaces.

• Journal of Periodontal and Implant Science
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• 제51권5호
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• pp.298-315
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• 2021

Purpose: Peri-implantitis therapy and implant maintenance are fundamental practices to enhance the longevity of zirconia implants. However, the use of physical decontamination methods, including hand instruments, polishing devices, ultrasonic scalers, and laser systems, might damage the implant surfaces. The aim of this systematic review was to evaluate the effects of physical decontamination methods on zirconia implant surfaces. Methods: A systematic search was conducted using 5 electronic databases: Ovid MEDLINE, PubMed, Scopus, Web of Science, and Cochrane. Hand searching of the OpenGrey database, reference lists, and 6 selected dental journals was also performed to identify relevant studies satisfying the eligibility criteria. Results: Overall, 1049 unique studies were identified, of which 11 studies were deemed suitable for final review. Air-abrasive devices with glycine powder, prophylaxis cups, and ultrasonic scalers with non-metal tips were found to cause minimal to no damage to implantgrade zirconia surfaces. However, hand instruments and ultrasonic scalers with metal tips have the potential to cause major damage to zirconia surfaces. In terms of laser systems, diode lasers appear to be the most promising, as no surface alterations were reported following their use. Conclusion: Air-abrasive devices and prophylaxis cups are safe for zirconia implant decontamination due to preservation of the implant surface integrity. In contrast, hand instruments and ultrasonic scalers with metal tips should be used with caution. Recommendations for the use of laser systems could not be fully established due to significant heterogeneity among included studies, but diode lasers may be the best-suited system. Further research-specifically, randomised controlled trials-would further confirm the effects of physical decontamination methods in a clinical setting.

• 한국정밀공학회지
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• 제31권7호
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• pp.605-613
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• 2014

Scanning white-light interferometry is an important measurement option for many surfaces. However, serious profile measurement errors can be present when measuring free-form surfaces being highly curved or tilted. When the object surface slope is not zero, the object and reference rays are no longer common path and optical aberrations impact the measurement. Aberrations mainly occur at the beam splitter in the interference objective and from misalignment in the optical system. Both effects distort the white-light interference signal when the surface slope is not zero. In this paper, we describe a modified version of white-light interferometry for eliminating these measurement errors and improving the accuracy of white-light interferometry. Moreover, we report systematic errors that are caused by optical aberrations when the object is not flat, and compare our proposed method with the conventional processing algorithm using the random ball test.

• 치과방사선
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• 제28권1호
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• pp.37-46
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• 1998

The purpose of this study was to evaluate the diagnostic performance of the senior dental students for the proximal dental caries on intraoral radiographs and to compare it with the dental hospital residents, the reference group. It was also investigated the diagnostic performance according to the carious lesion depth. Thirty-five intraoral periapical and bitewing radiographs with 213 proximal surfaces included in this study were selected from the dental patients at Chonnam National University Hospital. The observers were 181 senior dental students from 5 dental schools and 40 dentists who were second year resident from 5 dental hospitals. They were asked to evaluate the presence or the absence of the proximal dental caries. The results were as follows: 1. The mean of the hitting rate for the overall observers was 184.51 surfaces and the diagnostic accuracy was 86.62％. 2. The diagnostic performance of the sound proximal tooth surfaces was very high, i.e., 91.5％ true negative rate and 8.5％ false positive rate. 3. The diagnostic performance of the dentist group was higher than the student group(P<0.05). 4. The proximal dental caries perceptibility increased as the lesion depth increased significantly(P<0.001) except no difference between the carious lesion depth III and IV (P>0.001).