• Journal of Welding and Joining
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• 제33권6호
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• pp.13-20
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• 2015

Many automotive companies are endeavoring to improve the quality of resistance spot welding by updating body-in-white (BIW) production line with adaptive control spot welding system to compensate the process disturbances such as gap, electrode wear, oxidized surfaces, poor fit up and adhesive etc. Most of the commercial adaptive weld controllers require proper "Initial Welding Schedule" or "Reference weld" to achieve compensation in welding parameters during real time welding. In this study, the compensation of a commercial adaptive weld controller had been observed and analyzed thoroughly for various process disturbances to find optimal initial welding schedule. It was observed that 90 percent of the expulsion current in constant current control as reference welding schedule conferred the maximum button diameter in adaptive control welding. Finally, effects of each disturbance in combined field disturbances system with adaptive control had also been confirmed with the design of experiment (DOE) by minitab(R)16 for combined disturbances situation and suitability of optimum initial weld current had also established with real body part validation test.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권5호
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• pp.223-230
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• 2006

The reliability of imprint patterns molded by stamps for industrial application of nanoimprint lithography (NIL), is an important issue. Usually, defects can be produced by incomplete filling of negative patterns and the shrinkage phenomenon of polymers in conventional NIL. In this paper, the patterns that undergo a varied temperature or varied pressure period during the thermal NIL process have been investigated, with the goal of resolving the shrinkage and defective filling problems of polymers. The effects on the formation of polymer patterns in several profiles of imprint processes are also studied. Consequently, it is observed that more precise patterns are formed by the varied temperature (VT-NIL) or varied pressure (VP-NIL). The NIL (VT-NIL or VP-NIL) process has a free space compensation effect on the polymers in stamp cavities. From the results of the experiments, the polymer's filling capability can be improved. The VT-NIL is merged with the VP-NIL for the better filling property. The patterns that have been imprinted in the merged NIL are compared with the results of conventional NIL. In this study, the improvement in the reliability for results of thermal NIL has been achieved.

• 대한전자공학회논문지SD
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• 제40권4호
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• pp.42-50
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• 2003

본 논문에서는 시스템의 클럭을 안정적으로 공급하는 집적화 한 내장형 RC oscillator의 구현에 관한 논문이다. 기존의 RC oscillator는 온도에 따라 주파수변화가 약 15%정도 변화가 있는데 이는 온도에 따른 저항값의 변화와 schmit trigger의 기준전압이 온도에 따라 변화하기 때문이다. 본 연구에서는 온도에 따른 주파수 변화를 최소화하는 방법으로 CMOS bandgap과 온도에 따른 전류의 변화를 이용하였다. CMOS bandgap으로 기준 전압을 얻고 온도에 따라 증가하는 전류원과 온도에 따라 감소 하는 전류원을 서로 합하면 온도에 따라 일정한 전류를 얻어 주파수의 변화를 약 3%이내로 유지하는 회로를 제안한다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.285-288
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• 2002

This paper presents external load disturbance compensation that used to deadbeat load torque observer and regulation of the compensation gain by parameter estimator As a result, the response of PMSM follows that of the nominal plant. The load torque compensation method is compose of a deadbeat observer To reduce of the noise effect, the post-filter, which is implemented by MA process, is adopted. The parameter compensator with RLSM(recursive least square method) parameter estimator is suggested to increase the performance of the load torque observer and main controller The proposed estimator is combined with a high performance load torque observer to resolve the problems. As a result, the proposed control system becomes a robust and precise system against the load torque and the parameter variation. A stability and usefulness, through the verified computer simulation, are shown in this paper.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.389-392
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• 2001

This paper presents neural load disturbance observer that used to deadbeat load torque observer and regulation of the compensation gain by parameter estimator. As a result, the response of PMSM follows that of the nominal plant. The load torque compensation method is compose of a neural deadbeat observer. To reduce of the noise effect, the post-filter, which is implemented by MA process, is proposed. The parameter compensator with RLSM (recursive least square method) parameter estimator is suggested to increase the performance of the load torque observer and main controller. The proposed estimator is combined with a high performance neural torque observer to resolve the problems. As a result, the proposed control system becomes a robust and precise system against the load torque and the parameter variation. A stability and usefulness, through the verified computer simulation, are shown in this paper.

• 통상정보연구
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• 제15권1호
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• pp.3-34
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• 2013

본 연구에서는 실험을 통해 유형의 제품과 무형의 제품으로 구분하여 각각 다른 보상프로그램에 따른 소비자의 불평행동에 대한 회복과 행동의도에 미치는 영향을 규명하였다. 실험 1에서는 기업의 과실로 인한 불평행동을 경험한 소비자는 기업이 제공하는 보상프로그램을 통해 선호회복이 이루어졌으나, 불평행동을 유발한 제품 간의 소비자 선호회복에는 차이가 있었다. 연구의 결과에 따르면 노트북이 패밀리레스토랑에서의 외식 보다 선호회복이 명확하였음을 확인하였다. 또한 소비자들의 감정회복은 보상을 통해 가능하며, 노트북과 패밀리레스토랑에서의 외식 간 제품유형에 따른 감정회복에는 차이가 있었으나 보상물의 형태에 따른 감정회복 차이는 없었다. 결국 불평을 경험한 소비자는 보상을 통해 선호, 감정, 행동의도를 회복시킬 수 있는데 서비스보다는 유형 제품의 경우 회복이 더욱 컸으며, 동일한 유형제품이라도 보상물의 유형에 따른 회복에는 차이가 없으나 노트북 컴퓨터처럼 유형제품이면서 구매노력이 큰 제품은 감정반응자극이 더욱 효과적임을 알 수 있었다. 실험2에서는 구매습관이 서로 다른 한국과 일본의 대학생 소비자 사이의 구매 후 불평행동과 이의 회복과정이 차이가 있는지를 확인하고자 하였다. 불평행동을 경험한 양국 소비자는 보상을 통한 선호회복에는 차이가 있었으며, 감정과 행동의도의 회복은 차이가 없었다. 이 실험에서는 한국의 대학생은 과시구매형인 반면 일본의 대학생은 유명구매형으로 노트북컴퓨터의 구매과정 및 구매 후 평가에 차이를 보이고 있음을 알 수 있었다. 특히 한국학생은 타인의 의식하는 경향이 강해 보상을 통한 선호회복이 일본의 학생에 비해 빠름을 알 수 있었다. 그러나 감정의 회복과 재구매 회복은 차이가 없기에 불평에 따른 보상프로그램은 감정과 행동의도에 영향을 주는 요인으로 확인되었다.

• 소성∙가공
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• 제21권7호
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• pp.397-402
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• 2012

The flange hub is a main component in an automotive steering system. In general, the flange hub are fabricated by mechanical machining, which is a process where material waste is inevitable. It is well-known that a net-shape cold forging cannot only reduce material waste but can also improve the mechanical strength of the final product. Thus, a forging process design was conducted for production of a flange hub. Significant spring-back occurs around the flange due to its small thickness in conjunction with the residual stresses after forging. In order to achieve the required dimensional accuracy, a process design with appropriate spring-back control is needed. In this study, a modification of the forging die was designed based on FE analysis with the purpose of spring-back compensation. Four kinds of different die designs were evaluated and the optimum design has two times less spring-back than the initial design. The compensation angle of the optimum design is 0.5 degrees. The results have been experimentally confirmed by cold forging of a flange hub and comparing the amount of spring-back between the actual component and the FE analysis.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.151-156
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• 1995

This paper presents a methodology for real-time detecting and identifying the runout geometry of an end mill. Cutter runout is a common but undesirable phenomenon in multi-tooth machining such as end-milling process because it introduces variable chip loading to insert which results in a accelerated tool wear,amplification of force variation and hence enlargement vibration amplitude. Form understanding of chip load change kinematics, the analytical sutting force model was formulated as the angular domain convolution of three dynamic cutting force component functions. By virtue of the convolution integration property, the frequency domain expression of the total cutting forces can be given as the algebraic multiplication of the Fourier transforms of the local cutting forces and the chip width density of the cutter. Experimental study are presented to validata the analytical model. This study provides the in-process monitoring and compensation of dynamic cutter runout to improve machining tolerance tolerance and surface quality for industriql application.

• Safety and Health at Work
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• 제5권2호
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• pp.91-96
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• 2014

Background: Chronic obstructive pulmonary disease (COPD) is an important cause of occupational mortality in miners exposed to coal mine dust. Although the inflammatory mediators involved in COPD have not been defined, many studies have shown that inflammatory mediators such as reactive oxygen and nitrogen species are involved in orchestrating the complex inflammatory process in COPD. Methods: To investigate the relevance of exhaled biomarkers of oxidative and nitrosative stress in participants with COPD, we determined the levels of hydrogen peroxide, malondialdehyde (MDA), and 3-nitrotyrosine (3-NT) in exhaled breath condensate (EBC) in 90 retired elderly coal miners (53 non-COPD and 37 COPD participants). Results: Mean levels of MDA (4.64 nMvs. 6.46 nM, p = 0.005) and 3-NT (3.51 nMvs. 5.50 nM, p = 0.039) in EBC were significantly higher in participants with COPD. The median level of MDA did show statistical difference among the COPD severities (p = 0.017), and the area under the receiver operating characteristic curve forMDA (0.67) for the diagnostic discrimination of COPD indicated the biomarker. The optimal cutoff values were 5.34 nM (64.9% sensitivity and 64.2% specificity) and 5.58 nM (62.2% sensitivity and 62.3% specificity) forMDA and 3-NT, respectively. The results suggest that high levels ofMDA and 3-NT in EBC are associated with COPD in retired elderly miners. Conclusion: These results showed that the elevated levels of EBC MDA and EBC 3-NT in individuals with COPD are biomarkers of oxidative or nitrosative stress.

• 대한기계학회논문집A
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• 제32권11호
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• pp.990-996
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• 2008

Nowadays, the trend to a lightweight design accelerates the use of advanced high strength steel (AHSS) in automotive industry. Springback phenomena is a hot issue in the sheet metal forming, especially bending process using AHSS. Several analytical methods for that have been proposed in recent years. Each of method has their advantages and disadvantages. There are only a few optimal solutions which can minimize the two objectives simultaneously. In this study, an effective method optimized the multi objective value. The method by the design of experiments(DOE) and artificial neural network(ANN) was presented to compensate springback of bending parts. This method was applied to L and V bending process. The effective method could be optimized to multiple object. It was confirmed that the proposed method was more efficient than traditional manual FEA procedure and the trial and error approach for springback compensation.