• 한국콘텐츠학회:학술대회논문집
• /
• 한국콘텐츠학회 2009년도 춘계 종합학술대회 논문집
• /
• pp.889-894
• /
• 2009

Accompanied by the rapid development of Computer Vision, Visual surveillance has achieved great evolution with more and more complicated processing. However there are still many problems to be resolved for robust and reliable visual surveillance, and the cast shadow occurring in motion detection process is one of them. Shadow pixels are often misclassified as object pixels so that they cause errors in localization, segmentation, tracking and classification of objects. This paper proposes a novel cast shadow removal method. As opposed to previous conventional methods, which considers pixel properties like intensity properties, color distortion, HSV color system, and etc., the proposed method utilizes observations about edge patterns in the shadow region in the current frame and the corresponding region in the background scene, and applies Laplacian edge detector to the blob regions in the current frame and the background scene. Then, the product of the outcomes of application determines whether the blob pixels in the foreground mask comes from object blob regions or shadow regions. The proposed method is simple but turns out practically very effective for Gaussian Mixture Model, which is verified through experiments.

• 한국재료학회지
• /
• 제12권6호
• /
• pp.436-441
• /
• 2002

Effect of Sn addition on the stress corrosion cracking(SCC) resistance of the Al-Cu-Mn cast alley was investigated by C-ring teat and electrical conductivity measurement, The electrical conductivity and SCC resistance increased by Sn addition. The alley containing 0,10%Sn showed maximum electrical conductivity and the best SCC resistance. At the same composition, the electrical conductivity and SCC resistance increased from peak aged condition to ever aged condition. The PFZ and coarse precipitates along the grain boundary were observed from TEM micrographs. The fracture mode of the alloy was confirmed as intergranular type and showed brittle fracture surface. The SCC mechanism of the alloy was concluded as the anodic dissolution model, The maximum hardness was increased from 130Hv in the Sn-free alloy to 156Hv in the 0.10%Sn added alloy.

• 소성∙가공
• /
• 제19권6호
• /
• pp.329-336
• /
• 2010

Ring forging process is more appropriate for high-length and thin walled ring, because it utilizes the forging press and hence does not require heavy-duty ring rolling mill. Although ring forging process is very simple and economic for facilities, the process is not efficient because of multi-forging-step and low material utilization. An effective ring forging process is developed using a hollow ingot. When a hollow ingot is used with a workpiece, the ingot can be forged into a final ring without multi-stage pre-forging process, such as, cogging, upsetting, and piercing, etc.. Finally it has advantages of the material utilization and process improvement because a few reheating and forging process are not necessary to make workpiece for ring forging. The important design variables are the applied plastic deformation energy to eliminate cast structure and make uniform properties. In this study, the mechanical properties after forging of hollow cast ingot were investigated from the experiment using circumferential sectional model. Also, the effects of process variables were studied by FEM simulation on the basis of thermo-visco-plastic constitutive equation. Applied strain is different at each position in length direction because diameter of hollow ingot is different in length direction. The different strain distribution become into a narrow gap by additional plastic deformation during diameter extension process.

• Earthquakes and Structures
• /
• 제23권1호
• /
• pp.101-113
• /
• 2022

A new type of fabricated subway station construction technology can effectively solve these problems. For a new type of metro structure form, it is necessary to clarify its mechanical properties, especially the seismic performance. A soil-structure elastoplastic finite element model is established to perform three-dimensional nonlinear dynamic time-history analysis based on the first fabricated station structure-Yuanjiadian station of Changchun Metro Line 2, China. Firstly, the nonlinear seismic response characteristics of the fabricated and cast-in-place subway stations under different seismic wave excitations are compared and analyzed. Then, a comprehensive analysis of several important parameters that may affect the seismic response of fabricated subway stations is given. The results show that the maximum plastic strain, the interlayer deformation, and the internal force of fabricated station structures are smaller than that of cast-in-place structure, which indicates that the fabricated station structure has good deformation coordination capability and mechanical properties. The seismic responses of fabricated stations were mainly affected by the soil-structure stiffness ratio, the soil inertia effect, and earthquake load conditions rarely mentioned in cast-in-place stations. The critical parameters have little effect on the interlayer deformation but significantly affect the joints' opening distance and contact stress, which can be used as the evaluation index of the seismic performance of fabricated station structures. The presented results can better understand the seismic responses and guide the seismic design of the fabricated station.

• 대한토목학회논문집
• /
• 제30권5A호
• /
• pp.463-473
• /
• 2010

이 연구의 목적은 프리캐스트 세그먼트 PSC 교각의 조립식 코핑부의 성능을 파악하는데 있다. 제안된 프리캐스트 시스템은 현장에서의 작업을 줄이고 공사기간의 단축을 가져올 수 있다. 조립식 코핑부는 프리캐스트 세그먼트 PSC 교각의 현장타설 코핑부를 대체할 목적을 갖고 있다. 조립식 코핑부 실험체는 단조증가 하중 하에서 파괴 실험을 수행하였다. 그 결과 제안된 조립식 코핑 시스템은 기존의 현장타설 시스템과 동등한 소요성능을 보임을 확인하였다. 연계논문에서는 프리캐스트 세그먼트 PSC 교각의 조립식 코핑부의 성능평가를 위해 실험 및 해석적 연구를 수행하였다.

• 대한치과보철학회지
• /
• 제19권1호
• /
• pp.17-27
• /
• 1981

This study was conducted to determine the chemical composition and the mechanical properties of four commercially available low gold-based crown and bridge alloy produced in Korea. Four dental casting gold-silver-palladium alloys, i.e., A, B, C and D (code of alloys) were selected for the evaluation of chemical composition, ultimate tensile strength, elongation. values and Vickers hardness. The chemical composition of test specimens was analyzed by both emission spectrography and wet gravitation method with a 1.5gm of low gold ingot. The tensile properties and Vickers hardness was determined with cast specimens treated in following three conditions; as-cast, softening heat treatment and hardening heat treatment. The tensile testing bars were cast in accordance with the model designed by Gettleman and Harrison (1969) which was modified from the A. D. A. Specification No. 14 for dental chromium-cobalt casting alloy. Nine tensile test specimens were made from a split silicone mold for each of the test alloys to the size of 2.5mm in diameter and a gauge length of 10mm. All four alloys were handled in accordance with conventional methods used in Type III gold alloys. Ultimate tensile strength and elongation were measured on an Instron Universal Tensile Testing Machine (Model 1125, Japan) operated at a crosshead rate of 0.1cm/min. Elongation values were measured using Digital Measuring Microscope (MS-152, FUSOH, Japan). Vickers hardness was determined with a Vickers Hardness Tester (Model VKH-l, Japan) at a 1.0kg load on a mounted tensile test specimen. The following results were obtained from this study; 1. All tested alloys were composed of Au, Ag, Pd, Cu, Zn and Fe in common. The composition rate of gold for all four alloys was found in the range of $42{\sim}47$ weight % as shown below. Alloy A; Au 45%, Ag 40.2%, Pd 5.76%, others 9.04%. Alloy B; Au 47.1%, Ag 29.03%, Pd 6.98%, others 16.92%. Alloy C; Au 45%, .Ag 26.9%, Pd 6.83%, others 21.07%. Alloy D; Au 41.8%, Ag 34.4%, Pd 6.95%, others 16.85%. 3. The ultimate tensile strength of the four alloys was in the range of $31{\sim}82kg/mm^2$. The test results were shown in the below order from the highest value; As-cast condition; D, B, C, A. Softening heat treament; B, C, D, A. Hardening heat treatment; D, B, C, A. 4. The test :results of the elongation rate for each alloy were in the range of $0.5{\sim}18%$. The test results were shown in the below order from the highest value; As-cast condition; A, D, B, C. Softening heat treatment; A, C, D, B. Hardening heat treatment; C, D, B, A. 5. Vickers hardness for each of the four alloys was in the range of $120{\sim}230$. The test results were shown in the below order from the highest value; As-cast condition; C, B, D, A Softening heat treatment; D, B, C, A. Hardening heat treatment; D, A, C, B. 6. There were no differences in the physical properties between as-cast condition and softening heat treatment.

• 대한치과보철학회지
• /
• 제42권2호
• /
• pp.238-247
• /
• 2004

Statement of problem: Major objective in making on implant-supported prosthesis is the production of superstructure that exhibits a passive fit when connected to multiple abutments. One requirement to ensure passive fit is to make an accurate impression. Purpose : The purpose of this study was to compare the accuracy of master cast fabricated by using different impression methods at the different impression levels. Material and method: The master model used in this study was resin block having low implant analogs. Impression method studied were 1) direct method on fxiture level (Group FIX-D), 2) indirect method on fixture level(Group FIX-I), 3) modified indirect method on fixture level(Group FIX-M), 4) direct method on abutment level(Group AB-D) and 5) indirect method on abutment level(Group AB-I). Each of the five groups took 10 impressions. Fifty impressions were made for master cast by using Impregum $F^{(R)}$ impression material loaded on individual tray. Three dimensional measuring microscope was used to measure the inter-implant distance. Error rate of each inter-implant distance were calculated and evaluated. Results : The results were as follows. 1. Group FIX exhibited higher accuracy than group AB. 2. In group FIX, modified indirect method showed the highest accuracy, while indirect method showed the lowest accuracy. In group Ab, indirect method showed the higher accuracy than direct method. 3. Group FIX showed larger horizontal error than group AB. But, group AB showed the larger vertical error than group FIX. 4. Group Fix-M showed smallest vertical and horizontal error. Conclusion: An impression method have more effect on accuracy of master model than an impression level. A modified indirect method showed smallest vertical and horizontal error.

• The Journal of Advanced Prosthodontics
• /
• 제10권4호
• /
• pp.279-285
• /
• 2018

PURPOSE. The aim of this clinical study was to assess the accuracy of the implants placed using a universal digital surgical guide. MATERIALS AND METHODS. Among 17 patients, 28 posterior implants were included in this study. The digital image of the soft tissue acquired from cast scan and hard tissue from CBCT have been superimposed and planned the location, length, diameter of the implant fixture. Then digital surgical guides were created using 3D printer. Each of angle deviations, coronal, apical, depth deviations of planned and actually placed implants were calculated using CBCT scans and casts. To compare implant positioning errors by CBCT scans and plaster casts, data were analyzed with independent samples t-test. RESULTS. The results of the implant positioning errors calculated by CBCT and casts were as follows. The means for CBCT analyses were: angle deviation: $4.74{\pm}2.06^{\circ}$, coronal deviation: $1.37{\pm}0.80mm$, and apical deviation: $1.77{\pm}0.86mm$. The means for cast analyses were: angle deviation: $2.43{\pm}1.13^{\circ}$, coronal deviation: $0.82{\pm}0.44mm$, apical deviation: $1.19{\pm}0.46mm$, and depth deviation: $0.03{\pm}0.65mm$. There were statistically significant differences between the deviations of CBCT scans and cast. CONCLUSION. The model analysis showed lower deviation value comparing the CBCT analysis. The angle and length deviation value of the universal digital guide stent were accepted clinically.

• 융합정보논문지
• /
• 제7권3호
• /
• pp.73-81
• /
• 2017

일반화된 허프변환(GHough)은 임의의 2차원 모델 추출을 위해 사용되는 유용한 기법이다. 그러나 GHough는 모델의 회전과 축척 관련 사전 정보가 없을 경우 모든 경우의 수를 나열하는 변환 방식을 택하기 때문에 4차원 패러미터 배열이라는 방대한 메모리 사용이 불가피하며 실행시간 또한 오래 걸릴 수밖에 없다. 이를 개선하기 위해 제안된 몇몇 n-to-1 변환 방식 들은 4차원 대신 2차원 패러미터 배열 사용만으로도 임의의 모델 추출을 가능케 한 반면 2차원 패러미터 공간에 던져지는 무작위 투표 때문에 모델 추출 오류 가능성 또한 높다 하겠다. 본 논문은 이와 같은 2차원 패러미터 공간에 던져지는 무작위 투표를 감소시키기 위한 방안으로 모델 내부의 추가적인 그레디언트 정보 활용을 제안하며 모델 윤곽선 정보에 추가로 모델 내부 그레디언트 정보를 활용할 경우 2차원 패러미터 공간에 던져지는 무작위 투표수를 효과적으로 줄일 수 있으며 따라서 실행시간 또한 단축될 수 있음을 실험을 통해 입증한다.

• 대한치과보철학회지
• /
• 제35권4호
• /
• pp.662-673
• /
• 1997

The purpose of this study was to compare the accuracy between future impression and abutment impression using strain gauges. The master model used in this study was a partially edentulous mandibular metal cast with two fixture analogs on both sides. On the left, two future analogs were parallel, whereas right side, posterior future analog exhibiting a 15-degree lingual inclination. From master cast, 10 impressions were made for each of the three impression methods. The master frameworks was fabricated on the master model, and two-element strain gauge was attached to a master framework. The master framework was seated on each cast, and gold screws were tightened to 10 Ncm using a torque controller AI-1600 strain measurement system was used for strain measuring. Impression methods studied were : Group 1:abutment impression Group 2:fixture impression Group 3:combined impression (anterior:fixture impression, posterior:abutment impression) The results were as followed. 1. The strain values on X-axis and Y-axis according to the three impression methods showed no significant difference. 2. The strain values on parallel and angulated groups according to the three impression methods showed no significant difference. 3. The parallel group exhibited significantly higher accuracy in adaptation than angulated group for all experimental groups (p<0.05). In conclusion, it is considered that accuracy of implant prostheses is more affected by implant angulation than impression methods.