• Journal of Welding and Joining
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• 제17권6호
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• pp.90-99
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• 1999

Significant portion of the total manufacturing time for a pipe fabrication process is spent on the welding following primary machining and fit-up processes. To achieve a reliable weld bead appearance, automatic seam tracking and adaptive control to fill the groove are urgently needed. For the seam tracking in welding processes, the vision sensors have been successfully applied. However, the adaptive filling control of the multi-torches system for the appropriate welded area has not been implemented in the area of SAW(submerged arc welding) by now. The term adaptive control is often used to describe recent advances in welding process control by strictly this only applies to a system which is able to cope with dynamic changes in system performance. In welding applications, the term adaptive control may not imply the conventional control theory definition but may be used in the more descriptive sense to explain the need for the process to adapt to the changing welding conditions. This paper proposed various types of methodologies for obtaining a good bead appearance based on multi-torches welding system with the vision system in SAW. The methodologies for adaptive filling control used welding current/voltage, arc voltage/welding current/wire feed speed combination and welding speed by using vision sensor. It was shown that the algorithm for welding current/voltage combination and welding speed revealed sound weld bead appearance compared with that of voltage/current combination.

• 대한기계학회논문집B
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• 제28권11호
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• pp.1348-1358
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• 2004

The filling pattern and an adaptive grid refinement based on the finite element method and Eulerian mesh advancement approach have been developed to analyze incompressible transient viscous flow with free surfaces. The governing equation fur flow analysis is Navier-Stokes equation including inertia and gravity effects. The mixed FE formulation and predictor-corrector method are used effectively for unsteady numerical simulation. The flow front surface and the volume inflow rate are calculated using the filling pattern technique to select an adequate pattern among seven filling patterns at each tetrahedral control volume. By adaptive grid refinement, the new flow field that renders better prediction in flow surface shape is generated and the velocity field at the flow front part is calculated more exactly. In this domain the elements in the surface region are made finer than those in the remaining regions for more efficient computation. The collapse of a water dam and the filling of a fluidity spiral have been analyzed. The numerical results have been in good agreement with the experimental results and the efficiency of the adaptive grid refinement and filling pattern techniques have been verified.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.1476-1479
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• 1996

발전설비나 자동차 그리고 항공우주분야에 사용되는 각종 bearing, 원형부품들에 사용되는 ring을 생산하는 방법중, 가장 효과적이고 경제적인 방법은 ring rolling (ring 압연)이다. 이 방법은 직경 50cm에서 2m이상의 원형 ring을 연속적으로 짧은 시간내에 (한 ring당 약 1분) 생산 가능하다. 이제까지의 수학적 모델을 사용한 제어시스템은 ring의 단면적이 사각형인 제품에는 최소한의 오차로 생산 가능하였으나, plant의 생산성과 제품의 다양성을 위하여 ring의 단면적이 복잡한 것을 생산시에는 문제점이 노출되었다. 왜냐하면 기존의 수학적모델이 roll gap 또는 metal forming zone에 근거하여 modelling하였기 때문이다. 본 논문에서는, 이러한 문제점을 고전적인 수학적 모델을 기초로한 adaptive control system의 방법대신에, 축적된 control system설계와 운용 경험을 이용하여 설계한 퍼지제어기 및 그것의 실적용 그리고 그 결과를 소개한다. 실적용 결과는, 제조된 단면적이 상대적으로 복잡한 bearing의 형상이 (filling grad)이 제어기의 제어정도 판단기준이었는데, 99.5%의 형상도를 보임으로서 industry에서 요구하는 제품기준을 만족시켰다. 또한 짧은 제어기 설계 및 on-line optimization 기간 또한 이 제어기의 장점이었다.

• 대한기계학회논문집B
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• 제28권4호
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• pp.395-405
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• 2004

The filling pattern and an adaptive grid refinement based on the finite element method and Eulerian mesh advancement approach have been developed to analyze incompressible transient viscous flow with free surfaces. The governing equation for flow analysis is Navier-Stokes equation including inertia and gravity effects. The mixed FE formulation and predictor-corrector method are used effectively for unsteady numerical simulation. The flow front surface and the volume inflow rate are calculated using the filling pattern technique to select an adequate pattern among four filling patterns at each triangular control volume. By adaptive grid refinement, the new flow field that renders better prediction in flow surface shape is generated and the velocity field at the flow front part is calculated more exactly. In this domain the elements in the surface region are made finer than those in the remaining regions for more efficient computation. Using the proposed numerical technique, the collapse of a water dam has been analyzed to predict flow phenomenon of fluid and the predicted front positions with respect to time have been compared with the reported experimental results.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1999년도 특별강연 및 추계학술발표대회 개요집
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• pp.47-50
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• 1999

The term adaptive control is often used to describe recent advances in welding process control but strictly this only applies to system which are able to cope with dynamic changes in system performance. In welding applications, the term adaptive control may not imply the conventional control theory definition but may be used in the more descriptive sense to explain the need for the process to adapt to the changing welding conditions. This paper proposed a methodology for obtaining a good bead appearance based on multi-torches welding system with the vision system in SAW. The methodologies for adaptive filling control used the welding current/voltage, arc voltage/welding current/wire feed speed combination and welding speed by using the vision sensor. It was shown that the algorithm for the welding current/voltage combination and welding speed revealed the sound weld bead appearance compared with that of the voltage/current combination.

• Restorative Dentistry and Endodontics
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• 제42권4호
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• pp.332-341
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• 2017

Objectives: To determine the incidence of crack formation and propagation in apical root dentin after retreatment procedures performed using ProTaper Universal Retreatment (PTR), Mtwo-R, ProTaper Next (PTN), and Twisted File Adaptive (TFA) systems. Materials and Methods: The study consisted of 120 extracted mandibular premolars. One millimeter from the apex of each tooth was ground perpendicular to the long axis of the tooth, and the apical surface was polished. Twenty teeth served as the negative control group. One hundred teeth were prepared, obturated, and then divided into 5 retreatment groups. The retreatment procedures were performed using the following files: PTR, Mtwo-R, PTN, TFA, and hand files. After filling material removal, apical enlargement was done using apical size 0.50 mm ProTaper Universal (PTU), Mtwo, PTN, TFA, and hand files. Digital images of the apical root surfaces were recorded before preparation, after preparation, after obturation, after filling removal, and after apical enlargement using a stereomicroscope. The images were then inspected for the presence of new apical cracks and crack propagation. Data were analyzed with ${\chi}^2$ tests using SPSS 21.0 software. Results: New cracks and crack propagation occurred in all the experimental groups during the retreatment process. Nickel-titanium rotary file systems caused significantly more apical crack formation and propagation than the hand files. The PTU system caused significantly more apical cracks than the other groups after the apical enlargement stage. Conclusions: This study showed that retreatment procedures and apical enlargement after the use of retreatment files can cause crack formation and propagation in apical dentin.

• 대한치과보철학회지
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• 제9권1호
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• pp.29-34
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• 1969

Occlusal force is a critical factor affecting the condition and structure of the periodontium. When the occlusal forces exceed the physiologic adaptive capacity of the tissues, tissue damage ensues. Such damage is referred to as trauma from occlusion. Excessive pressure causes compression, degeneration and realignment of the periodontal ligament fibers so that they are paralleled perpendicular to the tooth and bone. By inducing excessive occlusal forces with a high amalgam filling on rat's molar, the author observed histologic alterations of the periodontal ligament fibers by means of Hematoxylin-eosin, Van Gieson and Aldenyde fuchsin stainings. The results of the study were observed as follows: 1) The excessive occlusal forces altered arrangement of the collagenous fibers. 2) The arrangement of the oblique fibers showed appreciable differences between the control group and the group subjected to 10 days experimental trauma from occlusion. 3) The realignment of the transseptal fibers was not found. 4) The arrangement of the oblique fibers after 15 days of trauma from occusion was similar to that of 10 days experimental group. 5) The oxytalan fibers were more abundant at the cementum rather than at the alveolar bone. 6) The excessive occlusal forces produced funnel-shaped widening of the oxytalan fibers, which followed wavy course. 7) The oxytalan fibers appeared to be distributed mainly around the middle third of the root rather than that of the apical third of the root during the experimental trauma from occlusion.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권10호
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• pp.5149-5167
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• 2017

Reducing energy consumption in a wireless video sensor network (WVSN) is a crucial problem because of the high video data volume and severe energy constraints of battery-powered WVSN nodes. In this paper, we present an adaptive dynamic resizing approach for a SRAM communication buffer in a WVSN node in order to reduce the energy consumption and thereby, to maximize the lifetime of the WVSN nodes. To reduce the power consumption of the communication part, which is typically the most energy-consuming component in the WVSN nodes, the radio needs to remain turned off during the data buffer-filling period as well as idle period. As the radio ON/OFF transition incurs extra energy consumption, we need to reduce the ON/OFF transition frequency, which requires a large-sized buffer. However, a large-sized SRAM buffer results in more energy consumption because SRAM power consumption is proportional to the memory size. We can dynamically adjust any active buffer memory size by utilizing a power-gating technique to reflect the optimal control on the buffer size. This paper aims at finding the optimal buffer size, based on the trade-off between the respective energy consumption ratios of the communication buffer and the radio part, respectively. We derive a formula showing the relationship between control variables, including active buffer size and total energy consumption, to mathematically determine the optimal buffer size for any given conditions to minimize total energy consumption. Simulation results show that the overall energy reduction, using our approach, is up to 40.48% (26.96% on average) compared to the conventional wireless communication scheme. In addition, the lifetime of the WVSN node has been extended by 22.17% on average, compared to the existing approaches.