• Journal of Adhesion and Interface
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• v.21 no.3
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• pp.86-92
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• 2020

We confirmed the effects on the device performances and the charge injection characteristics of organic field-effect transistor (OFET) by selectively differently controlling the surface energies on the contact region of the substrate where the source/drain electrodes are located and the channel region between the two electrodes. When the surface energies of the channel and contact regions were kept low and increased, respectively, the field-effect mobility of the OFET devices was 0.063 ㎠/V·s, the contact resistance was 132.2 kΩ·cm, and the subthreshold swing was 0.6 V/dec. They are the results of twice and 30 times improvements compared to the pristine FET device, respectively. As the results of analyzing the interfacial trap density according to the channel length, a major reason of the improved device performances could be anticipated that the pi-pi overlapping direction of polymer semiconductor molecules and the charge injection pathway from electrode is coincided by selective surface treatment in the contact region, which finally induces the decreases of the charge trap density in the polymer semiconducting film. The selective surface treatment method for the contact region between the electrode and the polymer semiconductor used in this study has the potential to maximize the electrical performances of organic electronics by being utilized with various existing processes to lower the interface resistance.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.4
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• pp.425-442
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• 2004

Statement of problem: A difficulty in achieving a passive-fitting prosthesis can be overcome by individual crown restoation of multiple implants. But individualized crown has another difficulty in control of contact tightness and stress distribution. Purpose: This in vitro study is to evaluate the stress distribution and the magnitude in the supporting tissues around Endopore implants with different crown lengths, interproximal contact tightness, and the splinting effects. Material & methods: Three Endopore implants($4.1{\times}9mm$) were placed in the mandibular posterior edentulous area distal to the canine and photoelastic model was made with PL-2 resin(Measurements Group, Raleigh, USA). Restorations were fabricated in two crown lengths: 9, 13 mm. For non-splinted restorations, individual crowns were fabricated on three custom-milled titanium abutments. After the units were cemented, 4 levels of interproximal contact tightness were evaluated: open, ideal($8{\mu}m$ shim stock drags without tearing), medium($40{\mu}m$), and heavy($80{\mu}m$). For splinted restorations, 3-unit fixed partial dentures were fabricated. This study was examined under simulated non-loaded and loaded conditions(6.8 kg). Photoelastic stress analysis was carried out to measure the fringe order around the implant supporting structure. Results: 1. When restorations were not splinted, the more interproximal contact tightness was increased among the three implants, the more stress was shown in the cervical region of each implant. When crown length was increased, stresses tended to increase in the apex of implants but there were little differences in stress fringes. 2. When nonsplinted restorations were loaded on the first or third implant, stresses were increased in the apex and cervical region of loaded implant. Regardless of interproximal contact tightness level, stresses were not distributed among the three implants. But with tighter interproximal contact, stresses were increased in the cervical region of loaded first or third implant. 3. When the nonsplinted restorations were not loaded, there were little stresses on the supporting structure of implants, but low level stresses were shown in the splinted restorations even after sectioning and soldering. 4. With splinted restorations, there were little differences in stresses between different crown lengths. When splinted restorations were loaded, stresses were increased slightly on the loaded implant, but relatively even stress distribution occurred among the three implants. Conclusions: Splinting the crowns of adjacent implants is recommended for Endopore implants under the overloading situation.

• Structural Engineering and Mechanics
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• v.44 no.1
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• pp.61-72
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• 2012

The paper is on contact analysis of a spherical ball with a deformable flat, considering the effect of tangent modulus on the contact parameters of a non-adhesive frictionless elastic-plastic contact. The contact analysis of this model has been carried out using analysis software Ansys and Abaqus. The contact parameters such as area of contact between two consecutive steps, volume of bulged material are evaluated from the formulated equations. The effect of the tangent modulus is considered for determining these parameters. The tangent modulus are accounted between 0.1E and 0.5E of materials E/Y value greater than 500 and less than 1750. Result shows that upto an optimal tangent modulus values the elastic core push up to the free surface in the flat. The simulation is also carried out in Abaqus and result provide evidence for the volume of bulged material in the contact region move up and flow into the free surface of the flat from the contact edge between the ball and flat. The strain energy of the whole model is varied between 20 to 40 percentage of the stipulated time for analysis.

• The Journal of Korean Academy of Prosthodontics
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• v.29 no.3
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• pp.141-170
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• 1991

This study was to analyze the displacement and the magnitude and mode of distribution of the stresses in the lower overdenture, the mucous membrane, the abutment teeth and the mandibular supporting bone when various abutment designs were subjected to different loading schemes. For this study, the two-dimensional finite element method was used. The models of overdenture and mandibe with the canine and the second premolar remaining, were fabricated. In the first design, a 1 mm space was prepared between the denture and the dome abutment with the height of 2 mm(OS). In the second design, a contact between the denture and the occlusal third of the dome abutment with the hight of 2 mm was prepared(OC). In the third design, a 0.5 mm space was prepared between the denture and 8 degree tapered cylindrical abutments with the height of 7 mm(TS). In the fourth design, a contact between the denture and the occlusal two thirds of the conical abutments with the height of 7 mm was prepared(TC). In order to represent the same physiological condition as the fixed areas of the mandible under loading schemes, the eight nodes which lie at the mandibular angle, the coronoid process and the mandibular condyle were assumed to be fixed. Each model was loaded with a magnitude of 10 Kgs on the first molar region (P1) and 7 Kgs on the central incisor region (P2) in a vertical direction. The force of 10 Kgs was then applied distributively from the first premolar to the second molar of each motel in a vertical direction (P3). The results were as follows: 1. The vertical load on the central incisor region(P2) produced the higher displacement and stress concentration than that on the posterior region(P1, P3). 2. The case of space between abutment and denture base produced higher displacement than that of contact, and the case of long abutment produced higher displacement than that of short abutment because of low rigidity of denture base. 3. The magnitude of the torque and vertical force to the abutment teeth and the stress distribution to the denture base was higher in the telescope coping than in the overdenture coping. 4. The vertical load on the central incisor region(P2) produced higher equivalent stress in the mandible than that on the posterior region(P1, P3). 5. The case of space between abutment and denture base produced better stress distribution to the farther abutment from the loading point than that of contact. 6. In case of sound abutment teeth, the type of telescope coping can be used, hilt in case of weak abutment, the type of overdenture coping is considered to be favorable generally.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.3
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• pp.50-54
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• 2008

This study is analyzed by the simulation of heat exchanger. As heat conduction happens as contact begins, the temperature increases until $70^{\circ}C$ at the contact part. The displacement increases until 33mm at its maximum and maximum equivalent stress at final stage increases 20 times as much as that of first contact. The expenses about maintenance, repair and management of parts can be reduced largely by applying the simulation about various parts of heat exchanger.

• Tribology and Lubricants
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• v.18 no.6
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• pp.389-395
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• 2002

The surface temperature at the interface of bodies in a sliding contact is one of the most important factors influencing the behavior of machine components. The calculation of the surface temperature at a sliding contact interface has been an interesting and important subject for tribologist. Temperature analyses were usually performed under the consideration contacted two bodies as semi-infinite. But the analysis was difficulty in being applied to finite body and considering the boundary condition. In this study, contact temperature rise of two finite bodies and surfaces due to frictional heating under the rectangular and the circular sliding contact is calculated. Heat partition factor is calculated using semi-infinite solid analysis and the temperature of the finite bodies is calculated using FVM. It will be shown that Most frictional heat in the fore part of contact region for sliding direction is conducted into body that has a moving heat source and the site of the maximum temperature rise moves to the opposite direction of sliding during sliding.

• Journal of Multimedia Information System
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• v.5 no.3
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• pp.179-188
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• 2018

In order to overcome the problems of contact palmprint recognition, a non-contact palmprint recognition system is developed on personal computer (PC) platform. Three methods, namely "double-line-single-point" (DLSP), "double-assistant-crosshair" (DAC) and "none-assistant-graphic" (NAG), are implemented for the palmprint localization to solve the severe technical challenges, including the complex background, variant illuminations, uncontrollable locations and gestures of hands. In NAG, hand segmentation and the cropping of region of interest are performed without any assistant graphics. The convex hull contour of hand helps detect the outside contour of little finger as well as the valley bottom between thumb and index finger. The three methods of palmprint localization have good operating efficiency and can meet the performance requirements of real-time system. Furthermore, an attendance system on PC platform is designed and developed based on non-contact palmprint recognition.

• International Journal of Precision Engineering and Manufacturing
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• v.5 no.3
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• pp.5-10
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• 2004

Electric contacts serve the purpose of transmitting electric signals across two conducting components. In this paper, the effects of contact conditions such as surface roughness, oxidation, and contamination were investigated with respect to electrical resistance variation of a connector in a direct current circuit. Such change in the electrical resistance is particularly important for low power circuits. The experimental results showed that compared with the effects of contact surface scratch or oxidation, the effect of contamination on the resistance variation was the most significant. In order to minimize failure due to electrical resistance change at the contact region, proper sealing to prevent contamination from entering the interface is needed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.292-300
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• 1995

According to the number of cold-rolled coils, the amount of roll wear and thermal expansion, and roll gap profile were calculated, by using the actual data from the finishing mill. Also, based on those data, the calculations of the deflection, the flattening, and the contact pressure of vwork rolls and backup rolls were made respectively. Specially, in the calculation of contact pressure, the numerical results were obtained not only during the normal rolling, but also during the abnormal rolling, by modeling mathematically the dynamic impact force which occurs when the head section of the strip is threading through rolls. With those results the growth of the fatigue region and the fatigue damage of rolls were predicted. Also the optimum roll-grinding depth was determined to maximize the roll life.

• Transactions of the Society of Information Storage Systems
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• v.7 no.2
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• pp.65-69
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• 2011

Head Disk Interface (HDI) in a Hard Disk Drive (HDD) has decreased to achieve high areal density. Thus, the contact between a slider and a disk becomes more important. The contact between the slider and the disk can cause severe wear and damage of both the slider and the disk. Especially, Touch Down (TD) that the contact occurs continuously and repeatedly is extremely dangerous. Therefore, it is necessary to analyze the unstable bouncing vibration of the slider in head-disk interface. In this paper, we investigate the characteristic and causes of the Touch Down.