• 소성∙가공
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• 제12권2호
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• pp.116-122
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• 2003

In the Prestressed die design for cold working, many constraining conditions should be considered to insure the die safety and to improve the dimension accountancy products. Among the constraining conditions, yielding conditions, diameter ratios and interferences between rings are very important. . In this paper, therefore, flexible tolerance method was used in order to search the optimum values of design variables. The maximum inner pressure is used as objective function in this numerical analysis. In the design Process, it was also involved the safety factor to the yield strength of each ring by considering the allowable tensile or compressive hoop stress in each ring. The proposed technique has been applied to the die design of backward extrusion process, and it's analytical results have been compared with that of the conventional design method.

• Journal of Welding and Joining
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• 제16권6호
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• pp.97-103
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• 1998

The bracket tilt among automobile parts is weld parts which construct the column assembly bracket tilt of equipments and accurate dimension after welding is more essential than weldment strength. By the way, it is insufficient that systematic study about this parts which have an importance on welding deformation. The reason is that welding deformation is complex problem with shape, size, material of parts and welding sequence, conditions etc. For reduction and removal of welding deformation, therefore, it is necessary that the security of welding deformation data and systematic examination about equipment, costs, work environment, manufacturing process etc. It is all the better that the prediction of welding deformation using simulation of welding process by FEA is supplemented. In this study, the countermeasure for this welding deformation of bracket tilt is brought up through experimental inspection before the choice of the optimum welding conditions with minimum welding deformation by simulation of welding process.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.655-658
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• 1997

In this paper, we intend to develop optimized design algorithm by deciding design parameters which are considered in the first design stage of inkjet printer head. thus, the parameters are such as electric pulse, input voltage of actuator to operate actuator, shape dimension of actuator an so on. in the first design stage, according to such parameters, a lot of time and money to develop inkject printer head are needed. to reduce trial and error and to save development time in the first design stage, optimized design algorithm is required all the more. design algorithm was developed via commercial FE analysis code(ANSYS & COENTOR) for the readability and convenience of algorithm. the reasonability of algorithm was verified by implementing analysis of system stage based on the data of piezoelectric actuator which was designed through algorithm.

• 공업화학
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• 제10권5호
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• pp.711-717
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• 1999

다층구조 고분자 재료의 비결정성 영역에서의 파괴 역학 변형과정을 통하여 ductile 및 brittle층을 동시에 함유하는 다층 구조 가공물을 이용하여 단층 구조물과의 물성을 비교, 조사하였다. 그 결과 거의 유사한 유리 전이온도($T_g$) 및 동일한 dimension에서 다층 구조물의 충격강도가 단일층 구조물보다 현격히 높게 나타났으며, toughness는 약 2배 이상 향상됨을 알 수 있었다. 이것은 ductile층과 brittle층의 두께 비에는 임계값이 있으며, 그 이하에서는 brittle한 재료이더라도 ductile하게 나타날 수 있다는 toughening 원리가 본 실험의 측정 속도 영역 및 온도 범위에서 적용되고 있음을 의미한다. 또한 고속 균열이 진행하는 경우의 운동 응력(kinetic stress wave) 효과를 해석하기 위하여 충격파동 중첩의 원리(superposition principle of impact pulse)를 도입하였다. 그 결과 다층 구조물의 최종 toughness 향상은 ductile/brittle 비율의 최적설계에 있음을 알 수 있었다.

• 대한조선학회논문집
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• 제54권6호
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• pp.485-491
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• 2017

An experimental study on the reduction of vertical motion of floating body using floating-submerged body interaction was performed in a two-dimensional wave channel. The system consisting of a floating and submerged body that only move vertically was modeled. This experiment was designed based on the results of theoretical analysis of two-body interaction. The results showed a tendency to significant reduction of heave RAO of floating body due to submerged body. Various connection line stiffness and dimension of the submerged body were applied to investigate the effect of two-body interaction on the vertical motion of the bodies, Heave RAOs of the floating-submerged body were compared with those of single body. From the comparison study, we obtained an optimum condition of connection line and dimension of submerged body for maximum heave reduction at the resonant period of single body.

• Bioinformatics and Biosystems
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• 제1권1호
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• pp.67-72
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• 2006

The aim of this paper is to discuss the effect of missing values in detecting differentially expressed genes in a cDNA microarray experiment in the context of a one sample problem. We conducted a cDNA micro array experiment to detect differentially expressed genes for the metastasis of colorectal cancer based on twenty patients who underwent liver resection due to liver metastasis from colorectal cancer. Total RNAs from metastatic liver tumor and adjacent normal liver tissue from a single patient were labeled with cy5 and cy3, respectively, and competitively hybridized to a cDNA microarray with 7775 human genes. We used $M=log_2(R/G)$ for the signal evaluation, where Rand G denoted the fluorescent intensities of Cy5 and Cy3 dyes, respectively. The statistical problem comprises a one sample test of testing E(M)=0 for each gene and involves multiple tests. The twenty cDNA microarray data would comprise a matrix of dimension 7775 by 20, if there were no missing values. However, missing values occur for various reasons. For each gene, the no missing proportion (NMP) was defined to be the proportion of non-missing values out of twenty. In detecting differentially expressed (DE) genes, we used the genes whose NMP is greater than or equal to 0.4 and then sequentially increased NMP by 0.1 for investigating its effect on the detection of DE genes. For each fixed NMP, we imputed the missing values with K-nearest neighbor method (K=10) and applied the nonparametric t-test of Dudoit et al. (2002), SAM by Tusher et al. (2001) and empirical Bayes procedure by $L\ddot{o}nnstedt$ and Speed (2002) to find out the effect of missing values in the final outcome. These three procedures yielded substantially agreeable result in detecting DE genes. Of these three procedures we used SAM for exploring the acceptable NMP level. The result showed that the optimum no missing proportion (NMP) found in this data set turned out to be 80%. It is more desirable to find the optimum level of NMP for each data set by applying the method described in this note, when the plot of (NMP, Number of overlapping genes) shows a turning point.

• 구강회복응용과학지
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• 제16권3호
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• pp.171-185
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• 2000

The treatment objectives of the complete oral rehabilitation are : (1) comfortably functioning temporomandibular joints and stomatognathic musculature, (2) adherence to the basic principle of occlusion advocated by Schuyler, (3) anterior guidance that is in harmony with the envelope of function, (4) restorations that will not violate the patient's neutral zone. There may be many roads to achieving these objectives, but they all convey varing degrees of stress and strain on the dentist and patient. There are no "easy" cases of oral rehabilitation. Time must be taken to think, time must be taken to plan, and time must be taken to perform, since time is the critical element in both success and failure. Moreover, a systematized and integrated approach will lead to a prognosis that is favorable and predictable. This approach facilitates development of optimum oral function, comfort, and esthetics, resulting in a satisfied patient. Such a systematized approach consists of four logical phase : (1) patient evaluation, (2) comprehensive analysis and treatment planning, (3) integrated and systematic reconstruction, and (4) postoperative maintenance. Firstly, we must evaluate the mandibular position. The results of a repetitive, unstrained, nondeflective, nonmanipulated mandibular closure into complete maxillomandibular intercuspation is not so much a "centric" occlusion as it is a stable occlusion. Accordingly, we ought to concern ourselves less with mandibular centricity and more with mandibular stability, which actually is the relationship we are trying to establish. The key to this stability is intercuspal precision. Once neuromuscular passivity has been achieved during an appropriate period of occlusal adjustment and provisionalization, subsequent intercuspal precision becomes the controlling factors in maintaining a stable mandibular position. Secondly, we must evaluate the planned vertical dimension of occlusion in relationship to what may now be an altered(generally diminished), and avoid the hazard of using such an abnormal position to indicate ultimate occlusal contacting points. There are no hard and fast rules to follow, no formulas, and no precise ratios between the vertical dimension of occlusion. Like centric relation, it is an area, not a point.

• 한국기계가공학회지
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• 제20권5호
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• pp.27-34
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• 2021

This study analyzes machining characteristics and presents optimal cutting conditions by measuring the surface roughness, dimensional accuracy, and dimension straightness based on the feed rate after processing the inner diameter hall of SCM415 steel using an automatic CNC(Computerized Numerical Control) lathe. The testing material was cut using an 11.8 mm-diameter Chamdrill after mounting the 32 mm-diameter round bar on an automatic CNC lathe. The cut depth was set at 3 mm, and the cutting speed was fixed at 1500 rpm. The surface roughness, dimensional accuracy, and dimension straightness of 15 testings were measured by changing the feed rate to 0.05, 0.1, and 0.15 mm/rev, respectively. It was difficult to process more than 15 tests during the maching due to noise or break. Additionally, the optimum cutting of SCM415 steel showed excellent surface roughness in the 10^th and 11^th of testing at cutting speed and feed speed of 1500 rpm and 0.05 mm/rev, respectively. The dimensional accuracy was measured in three dimensions after drilling, which showed good results with an average range of 0.0138-0.0208 mm. Moreover, the lower the feed speed, the higher the accuracy. Additionally, the measurement results of the dimensional straightness showed that the straightness is the straightness was the best at the 1^th and 2^th cutting regardless of the feed speed.

• Advances in concrete construction
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• 제8권3호
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• pp.207-215
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• 2019

Application of nanotechnology can be used to tailor made cementitious composites owing to small dimension and physical behaviour of resulting hydration products. Because of high aspect ratio and extremely high strength, carbon nanotubes (CNTs) are perfect reinforcing materials. Hence, there is a great prospect to use CNTs in developing new generation cementitious materials. In the present paper, a parametric study has been conducted on cementitious composites reinforced by two types of multi walled carbon nanotubes (MWCNTs) designated as Type I CNT (10-20 nm outer dia.) and Type II CNT (30-50 nm outer dia.) with various concentrations ranging from 0.1% to 0.5% by weight of cement. To evaluate important properties such as flexural strength, strain to failure, elastic modulus and modulus of toughness of the CNT admixed specimens at different curing periods, flexural bending tests were performed. Results show that composites with Type II CNTs gave more strength as compared to Type I CNTs. The highest increase in strength (flexural and compressive) is of the order of 22% and 33%, respectively, compared to control samples. Modulus of toughness at 28 days showed highest improvement of 265% for Type II 0.3% CNT composites. It is obvious that an optimum percentage of CNT could exists for composites to achieve suitable reinforcement behaviour and desired strength properties. Based on the parametric study, a tentative optimum CNT concentration (0.3% by weight of cement) has been proposed. Scanning electron microscope image shows perfect crack bridging mechanism; several of the CNTs were shown to act as crack arrestors across fine cracks along with some CNTs breakage.

• 한국생산제조학회지
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• 제24권4호
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• pp.400-406
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• 2015

This study researched the structure of the source of an ion milling machine used to fabricate a scanning electron microscope (SEM) sample. An ion source is used to mill out samples of over 1 mm dimension using a broad ion beam to generate plasma between the anode and cathode using a permanent magnet. To mill the sample in the vacuum chamber, the ion source should be greater than 6 kV for a positive ion current over $200{\mu}A$. To discover the optimum operating conditions for the ion miller, the diameter of the extractor, anode shape, and strength of the permanent magnet were varied in the experiments. A silicon wafer was used as the sample. The sputter yield was measured on the milled surface, which was analyzed using the SEM. The wafer was milled by injecting 1 sccm of argon gas into the 0.5 mTorr vacuum chamber.