• 한국정밀공학회지
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• 제20권2호
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• pp.184-191
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• 2003

A parallel manipulator has high stiffness and all the joint errors on the device are not accumulated at the end -effector unlike a serial manipulator. These are the reasons why the parallel manipulator has been widely used in many fields of industry. In the parallel manipulator, it is very important to predict the exact pose of the end-effector when we want to control the end-effector motion. Installation errors have to be determined in order to predict and control the actual position and pose of the end-effector. This paper presents an algorithm to find the whole 36 joint error components with joint clearance errors and measurement errors considered, when a link length measurement sensor is used and data more than 36 times are acquired for 36 different configurations. A simulation test using this algorithm is performed with a Matlab program which uses the Levenberg-Marquardt method that is known to be efficient for non-linear optimization.

• 한국지반공학회논문집
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• 제29권12호
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• pp.105-111
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• 2013

국내외에서 널리 사용 중인 표준관입시험(Standard Penetration Test, SPT)은 작업의 용이성, 다양한 지반정수와 강도정수를 결정방법 등의 장점을 지니고 있다. 이러한 SPT 수행시에 발생하는 해머 에너지는 N치의 산정 및 보정에 매우 중요한 영향인자가 된다. SPT시험시 해머 타격에 의하여 롯드로 응력파가 전달되는 현상이 말뚝 항타 시에 발생하는 현상과 동일하다하여 SPT에 PDA장비를 적용하여 관입에너지를 측정하는 방법이 개발되어 사용 중에 있다. 본 연구에서는 SPT 롯드를 말뚝으로 가정하여 SPT 에너지 효율 측정롯드를 SPT시험과 동적콘관입시험에 적용하여 얻어진 힘과 속도의 파형을 매칭기법(CAPWAP, CAse Pile Wave Analysis Program) 분석을 수행하여 매입말뚝에 대한 극한선단지지력을 예측하는 기법을 제안하였다. 또한, SPT 에너지 효율 측정롯드에서 예측된 선단지지력과 실물 말뚝정재하시험을 통하여 산정된 선단지지력을 비교분석하였다. 연구결과를 토대로 SPT나 동적콘관입시험을 통하여 매입말뚝의 지지력을 간편하게 예측할 수 있는 경험식을 제시하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 춘계학술대회 논문집
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• pp.890-893
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• 2000

In this paper, the test of machinability according to the cutting positions when the ball end milling of hemispheric workpiece is carried out to find the optimum cutting position of free form surface die. Tool runout, cutting force. and chip form are measured. The results show that the optimum cutting condition to get the constant feed per tooth is the inclined angle of 40 degree of workpiece.

• 한국가구학회지
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• 제11권1호
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• pp.61-68
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• 2000

This study was carried out to investigate the effect of grain and veneer thickness on drying rate, required energy consumption, and drying defects such as checking, end waving, and burning during a far-infrared radiation drying process of decorative veneers of hard maple and beech. Most of the veneer could be dried from green to in-use moisture content within 30 to 360 seconds. The drying rates were significantly affected by veneer thickness, but there was little difference between edge-and flat-sliced veneers. The formation of checking during drying test was none or very slight. The percentages of the veneers defected by checks were higher in the flat-sliced veneers than in the edge-sliced veneers. The maximum end wavinesses in the flat-sliced veneers were almost 1.6 to 3 times larger than that in the edge-sliced veneers. All veneers were fee from burned marks during drying test.

• Structural Engineering and Mechanics
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• 제88권2호
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• pp.189-200
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• 2023

Silicate glass is usually a brittle and plate-like material, and it is difficult to measure the elastic modulus by the traditional method. This paper develops a test method for the glass elastic modulus based on the fundamental frequency of the cantilever beam with an elastic support and a free end. The method installs the beam-type specimen on a semi-rigid support to form an elastic support-free end beam. The analytic solution of the stiffness coefficients of the elastic support is developed by the fundamental frequency of the two specimens with known elastic modulus. Then, the glass elastic modulus is measured by the fundamental frequency of the specimens. The method significantly improves the measurement accuracy and is suitable for the elastic modulus with the beam-type specimen whether the glass is homogeneous or not. Several tests on the elastic modulus measurement are conducted to demonstrate the reliability and validity of the test method.

• 한국생산제조학회지
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• 제18권3호
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• pp.294-299
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• 2009

Micro end-milling has been becoming an important machining process to manufacture a number of small products such as micro-devices, bio-chips, micro-patterns and so on. Many related researches have given grand effects to micro end-milling phenomenon, for example, micro end-milling mechanism, cutting force modeling and machinability. This paper strongly concerned actual problem, micro tool deflection, which causes excessive machining errors on the workpiece. Machining error were predicted and measured through a series of test micro cutting and analysis of their SEM images and FEM analysis. Experiments are carried out to validate the approaches.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.422-427
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• 2004

The tool geometry parameters and cutting process have complex relationships. Until now, various cutting test were needed to acquire optimal design of end mill for the purpose of high speed machining, due to the insufficient knowledge about cutting process in high speed machining. Using various tools with different geometry, relationships between tool geometry parameter (rake angle, clearance angle, length of cutter) and cutting process (cutting force, surface accuracy, surface roughness) have been studied. Acquired data can be used to design optimal tool for high speed machining and to develop a software for design of end mill geometry.

• 한국정보과학회 언어공학연구회:학술대회논문집(한글 및 한국어 정보처리)
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• 한국정보과학회언어공학연구회 2016년도 제28회 한글 및 한국어 정보처리 학술대회
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• pp.56-61
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• 2016

본 논문에서는 Sequence-to-sequence 모델을 생성요약의 방법으로 한국어 문서요약에 적용하였으며, copy mechanism과 input feeding을 적용한 RNN search 모델을 사용하여 시스템의 성능을 높였다. 인터넷 신문기사를 수집하여 구축한 한국어 문서요약 데이터 셋(train set 30291 문서, development set 3786 문서, test set 3705문서)으로 실험한 결과, input feeding과 copy mechanism을 포함한 모델이 형태소 기준으로 ROUGE-1 35.92, ROUGE-2 15.37, ROUGE-L 29.45로 가장 높은 성능을 보였다.

• International Journal of Concrete Structures and Materials
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• 제8권2호
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• pp.129-139
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• 2014

In this study, the concrete fracture energy was obtained using the three point notched beam test method developed by Hillerborg et al. (Cem Concr Res 6(6):773-782, 1976). A total of 12 notched concrete beams were tested under two different loading conditions: constant stroke control and constant crack mouth opening displacement (CMOD) control. Despite individual fracture energies obtained from the two different loading conditions showing some variation, the average fracture energy from both loading conditions was very similar. Furthermore, the results obtained support the idea that a far tail constant "A" could change the true fracture energy by up to 11 %, if it is calculated using CMOD instead of LVDT. The far tail constant "A" is determined using a least squares fit onto a straight line according to Elices et al. (Mater Struct 25(148):212-218, 1992) and RILEM report (2007). It was also observed that the selection of the end point can produce variations of the true fracture energy. The end point indicates the point in the experiment at which to stop. An end point of 2 mm has been recommended, however, in this study other end points were also considered. The final form of the bilinear softening curve was determined based on Elices and Guinea's methods (1992, 1994) and RILEM report (2007). This paper proposes a bilinear stress-crack opening displacement curve according to test results as well as the CEB-FIP model code.

• Structural Engineering and Mechanics
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• 제77권1호
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• pp.75-87
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• 2021

The present study pertains to the introduction of two new types of grip adaptor for universal testing machines, namely Polyvinyl Chloride (PVC) and Polyoxymethylene (POM) grip adaptors, and their application to tension testing of FRP bars with different fiber and surface finish types. The tabs are connected to the FRP bar sample with the help of mechanical anchors, i.e. bolts. These new adaptors offer vital superiorities over the existing end tab designs (anchors with filling material or mechanical anchorage), including the reduction in the time and labor for production, reusability and the mild nature, i.e. low hardness of the tab material, which retards and even prevents peeling and crushing in the gripping regions of an FRP sample. The methods were successfully applied to FRP bars with different types of fiber (CFRP, GFRP and BFRP) and different types of surface texture (ribbed, wrapped, sand-coated and wound). The test results indicated that the both types of end caps prevented slip of the bar, crushing and peeling in the gripping zone. The mechanical properties from the material tests with the new caps were in perfect agreement with the ones from the material tests with steel tubular caps.