• 한국공작기계학회논문집
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• 제14권5호
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• pp.21-26
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• 2005

It is important to measure the rotational accuracy of NC lathe spindle as it affects to the qualities of all machines machined by the NC lathe using in industries. The bad rotational accuracy of NC lathe spindle are caused mainly by wearness of the spindle in using and quality of spindle when machining and using low level bearings. It occurs especially in case of NC lathes because the cutting force acting to work-piece act on one side to the spindle not to both sides symmetrically. Therefore in this study, constructing experimental appratus for measuring of rotational accuracy by using eddy current type gap sensors, converters, screw terminal, data acquisition board inserted in computer and software f3r data acquisition, DT VEE ver. 5.0 and then error data acquired in the rotational accuracy test of NC lathe spindle are analysed in plots and statistical treatments.

• 한국산업정보학회논문지
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• 제8권1호
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• pp.9-17
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• 2003

본 논문에서는 시간영역 유한차분법(FDTD)을 이용하여 서로 다른 두 원형 도파관의 정합을 위한 원형도파관 정합기를 해석하였다. 축대칭 구조이므로 3차원 문제를 2차원 문제로 변환한 2차원 FDTD 알고리즘을 사용하였고, 상대적으로 반경의 차이가 큰 불연속 도파관에 적용되는 두종류의 정합기를 제안하였다. 하나는 유전체가 부분적으로 채워진 정합기이고, 다른 하나는 테이퍼된 유전체봉이 삽입된 정합기이다. 제안된 정합기에서 정합기의 길이와 직경 및 유전체의 직경 등의 파라미터 변화에 따른 특성을 수치해석하여 비교하였다.

• Journal of electromagnetic engineering and science
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• 제1권1호
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• pp.37-42
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• 2001

This paper presents the basic characteristics of a cutoff cavity-hacked slot antenna, for the application of spacetenna, with a feed post and a parasitic post inserted parallel to the slot. This type of antenna might effectively excite the slot and forcibly resonate the cavity by adding external reactance to the parasitic post. The Galerkin\`s method of moments is used to analyze integral equations for the unknown electric current on each post and electric field in the slot. The value of external reactance for forced resonance is discussed by deriving a determining equation, the current distribution on each post and the radiation patterns are considered. The analysis is in excellent agreement with the experiment for the radiation patterns.

• Journal of Magnetics
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• 제3권3호
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• pp.69-73
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• 1998

A drum type magnetic separator was designed and optimized by computer simulation. The separator consisted of rotating outer shell of drum, magnetic flux generator drum which was assembled with numbers of disk type magnet holders, and drum axis around which the magnet holders were fixed. NdFeB magnet blocks were inserted into the disks, and the disks were assembled layer by layer along the drum axis. Magnetic circuits of the separator were simulated on the basis of highest magnetic strength, least cost, and high yield of separation by using a Vector Field S/W employing the Opera-2D program. The separator proved a separation yield of 95% in removing fine iron-base particles, and installed at Hot Rolling Mill of Pohang Iron & Steel Co. In Korea.

• 동력기계공학회지
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• 제18권6호
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• pp.45-50
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• 2014

In the previous paper, we have reported on the development of foaming sponge seat with the auxiliary spring member and suggested new possibility of the special seat with the auxiliary plastic member for movie theater chair. In this study, we have examined the major design parameters needed in the development of a foaming sponge seat in which the mesh type plastic member are inserted to improve the vibration transfer effect of a chair seat. Through analyzing several prototypes by applying experimentation as well as the experimental modal analysis method, it was confirmed that the effect of vibration transfer can be improved through the use of a mesh type plastic member and applied to the design of practical chair seat.

• Journal of Chest Surgery
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• 제46권1호
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• pp.68-71
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• 2013

A 67-year-old female patient was treated with conventional total arch replacement and insertion of a stented elephant trunk (SET) graft into the descending thoracic aorta for acute DeBakey type I aortic dissection at one time. She had been treated with right coronary artery stent insertion for acute myocardial infarct 4 days earlier, and at that time, she was diagnosed with acute DeBakey type I aortic dissection from the ascending aorta to the suprarenal artery based on trans-esophageal echocardiography and aorta computed tomography. Through a median sternotomy, we inserted the SET graft through the opened aorta to the descending aorta. We also performed anastomosis between the proximal stented graft and the distal aortic arch, and then performed total arch replacement. For acute DeBakey type I aortic dissection, we report total arch replacement with insertion of a SET graft as a combination of conventional surgery and the interventional technique.

• Archives of Plastic Surgery
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• 제34권4호
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• pp.413-419
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• 2007

Purpose: In this study, porous type I collagen scaffolds were cross-linked using dehydrothermal(DHT) treatment and/or 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide(EDC), in the presence and absence of chondroitin-6-sulfate(CS) and cultured autologous chondrocytes(Chondro) for cartilage regeneration. Methods: Cartilage defects were created in the proximal part of the ear of New Zealand rabbits. Four prepared types of scaffolds(n=4) were inserted. The groups included Chondro-Collagen-DHT(Group 1), Chondro- Collagen-DHT-EDC(Group 2), Chondro-CS-Collagen- DHT(Group 3), and Chondro-CS-Collagen-DHT-EDC (Group 4). Histomorphometric analysis and cartilage-specific gene expression of the reconstructed tissues were evaluated 4, 8, and 12 weeks after implantation. Results: EDC cross-linked groups 2 and 4 regenerated more cartilage than other groups. However, calcification was observed in the 4th week after implantation. CS did not increase chondrogenesis in all groups. Cartilage-specific type II collagen mRNA expression increased in the course of time in all groups.Conclusion: EDC cross-linking methods maintain the scaffold and promote extracellular matrix production of chondrocytes.

• 한국컴퓨터정보학회논문지
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• 제23권11호
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• pp.85-93
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• 2018

In recent years, there has been an increasing number of ways to distribute document-based malicious code using vulnerabilities in document files. Because document type malware is not an executable file itself, it is easy to bypass existing security programs, so research on a model to detect it is necessary. In this study, we extract main features from the document structure and the JavaScript contained in the stream object In addition, when JavaScript is inserted, keywords with high occurrence frequency in malicious code such as function name, reserved word and the readable string in the script are extracted. Then, we generate a machine learning model that can distinguish between normal and malicious. In order to make it difficult to bypass, we try to achieve good performance in a black box type algorithm. For an experiment, a large amount of documents compared to previous studies is analyzed. Experimental results show 98.9% detection rate from three different type algorithms. SVM, which is a black box type algorithm and makes obfuscation difficult, shows much higher performance than in previous studies.

• 한국전자파학회논문지
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• 제21권9호
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• pp.965-970
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• 2010

NC-OFDM(Non-Contiguous Orthogonal Frequency Division Multiplexing) 기반의 무선 통신 시스템은 많은 부반송파의 수로 인해 높은 PAPR(Peak-to-Average Power Ratio)을 갖는다. Comb type pilot은 시변 채널 추정에 있어서 block type pilot보다 낮은 계산 복잡도를 가지며 더 효율적이다. 그러나 CAZAC(Constant Amplitude Zero Auto-Correlation) 행렬 변환이 뛰어난 PAPR 저감 효과를 보임에도 불구하고, comb type pilot이 데이터 심볼에 삽입되게 되면 PAPR이 다시 증가하는 문제가 있다. 따라서, 본 논문에서는 이러한 comb type pilot 배치로 인해 증가된 PAPR을 개선하기 위해 추가적으로 새로운 방식의 SLM(Selective Mapping)을 적용하였다. 또한, 본 논문에서 사용된 새로운 방식의 SLM 기법은 일반적인 SLM 기법과 달리, SLM의 선택 정보를 전송하기 위한 추가적인 대역폭을 사용하지 않음으로써 대역 효율을 높인다. 따라서, 본 논문에서 제안된 시스템은 제한된 주파수 대역을 이용하여 고효율의 데이터 전송을 얻을 수 있다.

• 대한치과기공학회지
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• 제42권2호
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• pp.91-98
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• 2020

Purpose: This study is to compare the flexural strength and modulus by inserting a mesh and stick type fiberglass reinforcement into resin specimens. Methods: Wax specimens (length 64 mm, width 39 mm, thickness 5 mm) are prepared according to ISO 20795-1:2013. Mesh type and stick type glass fiber reinforcements were prepared. The prepared wax specimens were used plaster and flask for investment. The flask was separated and the wax was removed. The heat curing resin was injected into the flask, and then a mesh type and stick type fiberglass reinforcement were inserted. The prepared resin specimen was cut into three equal parts (length 64 mm, width 10 mm, thickness 3.3 mm). The mesh type glass fiber reinforcement (MT group) and the stick type glass fiber reinforcement (ST group) were classified into two groups. The prepared specimen was measured using a universal testing machine (UTM). The data were analyzed by Mann-Whitney U test, and the significance level was set to 0.05. Results: In the flexural strength, the ST group was higher than the MT group, and there was a significant difference between the two groups (p<0.05). In the flexural modulus, the ST group was higher than the MT group, and there was a significant difference between the two groups (p<0.05). Conclusion: The stick-type glass fiber inreased the flexural strength than the mesh-type glass fiber reinforcement.