• 신재생에너지
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• 제4권2호
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• pp.74-80
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• 2008

To improve the blue responses of screen-printed single crystalline silicon solar cells, we investigated an emitter etch-back technique to obtain high emitter sheet resistances, where the defective dead layer on the emitter surface was etched and became thinner as the etch-back time increased, resulting in the monotonous increase of short circuit current and open circuit voltage. We found that an optimal etch-back time should be determined to achieve the maximal performance enhancement because of fill factor decrease due to a series resistance increment mainly affected by contact and lateral resistance in this case. To elucidate the reason for the fill factor decrease, we studied the resistance analysis by potential mapping to determine the contact and the lateral series resistance. As a result, we found that the fill factor decrease was attributed to the relatively fast increase of contact resistance due to the dead layer thinning down with the lowest contact resistivity when the emitter was contacted with screen-printed silver electrode.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2008년도 춘계학술대회 논문집
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• pp.390-393
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• 2008

To improve the blue responses of screen-printed single crystalline silicon solar cells, we investigated an emitter etch-back technique to obtain high emitter sheet resistances, where the defective dead layer on the emitter surface was etched and became thinner as the etch-back time increased, resulting in the monotonous increase of short circuit current and open circuit voltage. We found that an optimal etch-back time should be determined to achieve the maximal performance enhancement because of fill factor decrease due to a series resistance increment mainly affected by contact and lateral resistance in this case. To elucidate the reason for the fill factor decrease, we studied the resistance analysis by potential mapping to determine the contact and the lateral series resistance. As a result, we found that the fill factor decrease was attributed to the relatively fast increase of contact resistance due to the dead layer thinning down with the lowest contact resistivity when the emitter was contacted with screen-printed silver electrode.

• 디지털산업정보학회논문지
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• 제9권2호
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• pp.41-54
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• 2013

In this paper, We collected location based services of the user's past moving paths through the GPS. Using the collected by location-based services through the analysis of the similarity between the user's of service level agreement recommended of mobile contact area(SLA) proposed that can be. S-RCA method based on Service Level Agreement of the users in order to provide the service user's path distance, time, and to predict the direction of the movement paths and collect. The data collected by the interests and requirements of users through classification with the same interests and the needs of users to move between the analysis of the similarity between the path is used to analyze the results of analysis of the path-specific tolerance range (distance, time, and space) is determined according to the difference in the contact area. From a small area of the error range for users first to recommended and through their smartphones recommended contact area (S-RCA) to meet with the other party to make a choice of recommended methods. We verify through experiments that proposed method(S-RCA) a valid and reliable mobile contact area were recommended.

• Journal of Welding and Joining
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• 제22권4호
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• pp.35-42
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• 2004

Contact tips are required to have a higher resistance to wear and thus to have an extended life time under the advanced GMAW welding process. Several requirements have been specified and employed by domestic industries for selecting their tips for such a purpose. However no attempt has been made to justify their requirements based on the experimental data of wear resistance or life time of contact tips. In this study, five different contact tips with three different compositions were employed for actual GMA welding up to 4 hours and were evaluated their wear resistance by measuring in every one hour the area of enlarged hole at the exit side. Experimental results clearly showed that the Cr-containing tips strengthened by precipitation hardening have much better resistance to wear than those made by work hardening. It was further noticed that Cr is an excellent alloying element for improving the wear resistance of contact tips only when it is in an properly aged condition. Initial hardness may play some role in the early stage of wear but not in the later stage of welding because the microstructure of tip changes significantly by the prolonged exposure to welding arc heat. Based on these results, critical review has been made on the current requirements employed by domestic industries. Of importance is that a new guideline has been confirmed to be more reasonable.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 A
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• pp.455-459
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• 1995

Catenary/pantograph system consists of overhead lines which have non-uniform elasticity and pantographs which move at high speed and give force to the lines, therefore happen to be failed in contacts between both from time to time. In this study, as the first step to develop a dynamic simulation program, the general theory is discussed for catenary/pantograph system and appropriate modelling. And comparison is conducted with the references after making a program which referred to the contact force equation algorithm. On this algorithm, the unknown contact force is computed by the equations which was induced as combining catenary and pantograph motion equations expressed in finite difference form. Another simulation program based on the assumed contact forces algorithm was developed. In this algorithm, numerical integraion of both the overhead line and pantograph equations, which without combining, are effected for two assumed values of contact force. The correct contact force is then obtained from these two sets of results by linear interpolation to satisfy the contact condition. Through the comparative review on the outputs from this program, it is verified that this algorithm is reliable.

• 한국소음진동공학회논문집
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• 제24권1호
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• pp.45-53
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• 2014

For the time integration solution of the impulsive dynamic contact problem of high-speed rotating disks formulated by the finite element technique, the velocity and acceleration contact constraints as well as the displacement contact constraint are imposed for the numerical stability without spurious oscillations. The solution of the present technique is checked by the numerical simulation using the concentric high-speed rotating disks with the clearance and impulsive loading. It is shown that the almost steady state solution agrees with the corresponding analytical solution of the elasticity and that the differentiated constraints are crucial for the numerical stability of such high-speed contact problems of the disks under impulsive loading.

• Structural Engineering and Mechanics
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• 제72권5호
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• pp.557-568
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• 2019

Accurate modeling of contact interface in bolted joints is crucial in predicting the dynamic behavior for bolted assemblies under external load. This paper presents a contact pressure distribution based non-uniform virtual material method to describe the joint interface of assembly structure, which is connected by sparsely distributed multi-bolts. Firstly, the contact pressure distribution of bolted joints is obtained by the nonlinear static analysis in the finite element software ANSYS. The contact surface around bolt hole is divided into several sub-layers, and contact pressure in each sub-layer is thought to be evenly. Then, considering multi-asperity contact at the micro perspective, the relationship between contact pressure and interfacial virtual material parameters for each sub-layer is established by using the fractal contact theory. Finally, an experimental platform for the dynamic characteristics testing of a beam lap structure with double-bolted joint is constructed to validate the efficiency of proposed method. It is found that the theoretical results are in good agreement with experimental results by impact response in both time- and frequency-domain, and the relative errors of the first four natural frequencies are less than 1%. Furthermore, the presented model is used to examine the effect of rough contact surface on dynamic characteristics of bolted joint.

• 제어로봇시스템학회논문지
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• 제12권5호
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• pp.457-463
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• 2006

Recently proposed control scheme for a stable teleoperation, which was based on two-port time-domain passivity approach[21], has been successful for a contact with high stiffness environments. However, we found several conservatisms during the contact with deformable environments and unconstrained motion. The two-port time-domain passivity controller was excessively dissipating energy even though it was not necessary for some cases of an unconstrained motion and soft contact. The main reason of those conservatisms was on the fact that the two-port time-domain passivity controller was activated without considering the amount of energy dissipation at the master and slave manipulators. Especially, the exclusion of the slave manipulator from the two-port was the dominant reason of the conservatisms. In this paper, we consider the amount of energy dissipation at slave manipulator for designing the time-domain passivity observer and controller. The measured interaction force between slave manipulator and environment allow the time-domain passivity observer to include the amount of energy dissipation at the slave manipulator. Based on the modified passivity observer, reference energy following method[24] is applied to satisfy the passivity condition in real-time. The feasibility of the developed methods is proved with experiments. Improved performance is obtained for an interaction with deformable environments and an unconstrained motion.

• Archives of Reconstructive Microsurgery
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• 제2권1호
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• pp.82-92
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• 1993

A comparative study was undertaken to evaluate the contact Neo-dymium : yttrium aluminum garnet(Nd:YAG) laser system for vascular anastomosis of small caliber blood vessels(diameter 0.5-1.2 mm) in the animal model. In this study 40 femoral arteries and 40 femoral veins of Sprague-Dawley rats were anastomosed by contact laser assisted microvascular anastomosis(LAMA) utilizing 3 stay sutures which were placed 120 degrees apart and the intervals welded with contact Nd:YAG laser unit, conventionally sutured anastomosis(CSA) served as controls. The time needed for vascular anastomosis, patency rate(immediate postoperative, postoperative 2nd day, postoperative 1 week, postoperative 4 weeks), gross and microscopic evaluations were compared to conventional microsurgical suture technique. The results are as follows: 1. Postoperative patency rate was 82.5% for femoral artery and 75% for femoral vein by contact LAMA technique compared to 90% and 75% by CSA technique at postoperative 4 weeks. 2. Less time-consumed for arterial anastomosis by 6 minutes 23 seconds and venous anastomosis by 8 minutes 55 seconds with contact LAMA technique compared to CSA technique. 3. Grossly almost complete healing had taken place by postoperative 1 week by contact LAMA technique. 4. Aneurysm formation was 5% for femoral artery and 15% for femoral vein by contact LAMA technique compared to 5% and 10% respectively by CSA technique. 5. Microscopically, re-endothelization was complete by postoperative 7th day by contact LAMA technique. There was less medial hypertrophy and hyperplasia and also less inflammatory response compared to CSA.

• Journal of Oral Medicine and Pain
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• 제19권2호
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• pp.153-168
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• 1994

The aim of the present study was to investigate a relation between occlusal wear area and occlusal contact patterns. For the purpose, occlusal wear area were measured in 58 dental students and in 129 patients with temporomandibular disorders(TMDs) from dental casts. Teeth used in this study were from canine to second molar on both sides in upper arch, totally ten. Occlusal wear area on casts was marked by pencil and photocopies, and then, the area was measured with planimeter. Occlusal relation was clinically examined with regard to Angle's classification, chewing side preference, lateral guidance pattern and bruxing and/or clenching habit. T-Scan, electronic occlusal contact analyzer, was used to record occlusal contact number, contact force, contact time and occlusal balance that is TLR(total left-right statistics) during tooth contact. All measurement were repeated 3 times and the average value was used for data processing. The obtained results were as follows : 1. Mean value of occlusal wear area did not differ significantly between dental students and patients. 2. There ws not significant difference in wear area between chewing side and non-chewing side in both groups. 3. Occlusal wear area was significantly increased with age in both groups. 4. Three subgroups divided by Angle's classification did not show any difference in occlusal wear area among them, but three subgroups divided by lateral guidance pattern showed slightly significant difference between canine guide subgroup and group function subgroup in patients. Occlusal wear ares\a in group function subgroup wear larger than canine guide subgroup. 5. Mean value of wear area in patients with bruxing and/or clenching habit did not differ from those in patients without such habit. 6. Correlationship among items related to occlusal contact pattern were highly consistent and significant in dental students and only one item significantly correlated with occlusal wear area was tooth contact time.