• Korean Journal of Materials Research
• /
• v.16 no.1
• /
• pp.37-43
• /
• 2006

Carbon nanotube cathodes (CNT cathodes) were fabricated by a screen printing method using multi-walled carbon nanotubes. The effects of surface treatment on CNT cathodes were investigated for use in high efficiency field emission displays. The optimum surface treatment for a CNT cathode is dependent on a relative bonding force of CNT films on the cathode after a heat treatment. Because of the high bonding force used in the Liquid method, this method is recommended for CNT cathodes which are heat-treated at $390^{\circ}C$ in a $N_2$ atmosphere. The Rolling method is applicable for CNT cathodes fabricated at $350^{\circ}C$ in an atmosphere of air. The results of this study provide basic criteria for the selection of an appropriate surface treatment for large area CNT cathodes.

• The Journal of the Korean dental association
• /
• v.55 no.12
• /
• pp.850-860
• /
• 2017

Orthodontic treatment with premolar extraction is usually performed to correct bialveolar protrusion. These methods require the use of stiff rectangular working archwire which requires lengthy alignment and leveling before insertion. In this case report, interproximal reproximation was performed instead of extraction. To establish clearance between the archwire and resin domes fixing the archwire, an archwire was inserted into a water-soluble tube before fabricating resin domes. This tube is solved away by the saliva. During fabrication of resin domes, the archwire was deflected intentionally reflecting the displacement of teeth from their ideal position. This can be called as deflection-based bonding (DBB) technique. DBB is different from conventional method of positioning the brackets on its ideal position and then inserting an archwire to align the brackets. Because the orthodontic force of the archwire comes from its deflection from passive configuration, deflecting an archwire as needed can move the teeth more predictably than just bonding brackets on its ideal position. Also, areas with good alignment before orthodontic treatment can be maintained simply by not deflecting the archwire during bonding in these areas. After initial alignment, interproximal reproximation was performed to create 4.8 mm space in the maxillary arch and 4.2 mm space in the mandibular arch. These spaces were closed using orthodontic mini-implant anchorage thus retracting the maxillary incisors 4 mm posteriorly accompanied with 0.7 mm and 0.3 mm distal movement of right and left molars. By using interproximal reproximation and water-soluble tube with DBB, mild bialveolar protrusion was successfully treated without extraction.

• Restorative Dentistry and Endodontics
• /
• v.28 no.3
• /
• pp.203-208
• /
• 2003

The purpose of this study was to evaluate the effect of salivary contamination of teeth on bonding efficacy of self-priming and self-etching DBSs. The materials used were Single Bond(SB, self-priming system, 3M), Unifil Bond(UB, self-etching system, GC), and Scotchbond Multi-Purpose Plus(SM, 3M) as control. Forty five human molars randomly allocated to three groups as dentin bonding systems tested and embedded in epoxy resin. Then the specimens were wet-ground to expose flat buccal enamel surface or flat occlusal dentin surface and cut bucco-lingually to form two halves with slow speed diamond saw. One of them was used under non-contamination, other under contamination with saliva. The bonding procedure was according to the manufacturer's directions and resin composite(Z-100, 3M Dental Products, St. Paul, MN) was built-up on the bonded surface 5mm high. The specimens were ground carefully at the enamel-composite interface with fine finishing round diamond bur to create an hour-glass shape yielding bonded surface areas of $1.5{\pm}0.1\textrm{mm}^2$. The specimens were bonded to the modified microtensile testing apparatus with cyanoacrylate, attached to the universal testing machine and stressed in tension at a CHS of 1mm/min. The tensile force at failure was recorded and converted to a tensile stress(MPa). Mean values and standard deviations of the bond strength are listed in table. One-way ANOVA was used to determine significant difference at the 95% level. The bond strength of SBMP and SB were not affected by salivary contamination, but that of UB was significantly affected by salivary contamination. These results indicate that DBSs with total etch technique seems less likely affected by salivary contamination in bonding procedure.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2018.06a
• /
• pp.102-102
• /
• 2018

Electronic industry had required the finer size and the higher performance of the device. Therefore, 3-D die stacking technology such as TSV (through silicon via) and micro-bump had been used. Moreover, by the development of the 3-D die stacking technology, 3-D structure such as chip to chip (c2c) and chip to wafer (c2w) had become practicable. These technologies led to the appearance of HBM (high bandwidth memory). HBM was type of the memory, which is composed of several stacked layers of the memory chips. Each memory chips were connected by TSV and micro-bump. Thus, HBM had lower RC delay and higher performance of data processing than the conventional memory. Moreover, due to the development of the IT industry such as, AI (artificial intelligence), IOT (internet of things), and VR (virtual reality), the lower pitch size and the higher density were required to micro-electronics. Particularly, to obtain the fine pitch, some of the method such as copper pillar, nickel diffusion barrier, and tin-silver or tin-silver-copper based bump had been utillized. TCB (thermal compression bonding) and reflow process (thermal aging) were conventional method to bond between tin-silver or tin-silver-copper caps in the temperature range of 200 to 300 degrees. However, because of tin overflow which caused by higher operating temperature than melting point of Tin ($232^{\circ}C$), there would be the danger of bump bridge failure in fine-pitch bonding. Furthermore, regulating the phase of IMC (intermetallic compound) which was located between nickel diffusion barrier and bump, had a lot of problems. For example, an excess of kirkendall void which provides site of brittle fracture occurs at IMC layer after reflow process. The essential solution to reduce the difficulty of bump bonding process is copper to copper direct bonding below $300^{\circ}C$. In this study, in order to improve the problem of bump bonding process, copper to copper direct bonding was performed below $300^{\circ}C$. The driving force of bonding was the self-annealing properties of electrodeposited Cu with high defect density. The self-annealing property originated in high defect density and non-equilibrium grain boundaries at the triple junction. The electrodeposited Cu at high current density and low bath temperature was fabricated by electroplating on copper deposited silicon wafer. The copper-copper bonding experiments was conducted using thermal pressing machine. The condition of investigation such as thermal parameter and pressure parameter were varied to acquire proper bonded specimens. The bonded interface was characterized by SEM (scanning electron microscope) and OM (optical microscope). The density of grain boundary and defects were examined by TEM (transmission electron microscopy).

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.421-425
• /
• 2007

In the fabrication of dry adhesive structure, increasing contact-points or contact-area is the primary goal because the adhesive force grows in proportion to the contact-area. The simplest way to extend the contact surface is the fabrication by using soft materials. However, the column-array structure could confront the matting phenomenon which columns are stuck together. Therefore, we need a novel design to reduce the effective stiffness with adequate stiff materials like a gecko's setae. In this study, we propose a novel design for the dry adhesive structure. Moreover, we analyzed whether the adhesive structure conforms the rough surface sufficiently through finite element method adopted the non-bonding interaction as the body force. Also, we fabricated the novel structures via UV lithography and some techniques. In addition, we examined the adhesive force of the novel structures.

• Proceedings of the KSME Conference
• /
• 2003.11a
• /
• pp.1448-1452
• /
• 2003

A scratch tester was developed to evaluate the adhesive strength at interface between thin-film and substrate(silicon wafer). Under force control, the scratch tester can measure the normal and the tangential forces simultaneously as the probe tip of the equipment approaches to the interface between thin-film and substrate of wafer. The capacity of each component of force sensor is 0.1 N ${\sim}$ 100 N. In addition, the tester can detect the signal of elastic wave from AE sensor(frequency range of 900 kHz) attached to the probe tip and evaluate the bonding strength of interface. Using the developed scratch tester, the feasibility test was performed to evaluate the adhesive strength of thin-film.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.04a
• /
• pp.830-834
• /
• 2013

This study presents a method to monitor cable force of a long-span cable-stayed bridge using a smart piezoelectric sensor system. The following approaches are implemented in order to achieve the objective. Firstly, the method to utilize piezoelectric materials for the health monitoring of stay cables is presented. For strain measurement of a stay cable, a PZT-embedded smart skin is designed to overcome the difficulties of bonding PZT sensors directly on stay cables. Secondly, a piezoelectric strain monitoring system for stay cables is designed. For the operation of the sensor board, the Imote2 sensor platform is used to provide the computation, wireless communication and power supply units. The feasibility of the proposed monitoring system is then evaluated on a full-scale cable of a cable-stayed bridge.

• Journal of Sensor Science and Technology
• /
• v.21 no.2
• /
• pp.121-126
• /
• 2012

Piezoresistive type contact force sensor array is fabricated by (111) Silicon bulk micromachining for continuous blood pressure monitoring. Length and width of the unit sensor structure is $200{\mu}m$ and $190{\mu}m$, respectively. The gap between sensing elements is only $10{\mu}m$. To achieve wafer level packaging, the sensor structure is capped by PDMS soft cap using wafer molding and bonding process with $10{\mu}m$ alignment precision. The resistance change over contact force was measured to verify the feasibility of the proposed sensor scheme. The maximum measurement range and resolution is 900 mm Hg and 0.57 mm Hg, respectively.

• Asian Journal for Public Opinion Research
• /
• v.3 no.1
• /
• pp.1-21
• /
• 2015

A recent public opinion survey found that the anti-corporate sentiment of South Korean citizens is primarily due to the misbehavior of Korean corporations. South Korean citizens' skepticism of corporations may hinder the democratic and economic development of the country. As a driving force for community development, social capital is considered to enable citizens to collaborate with one another to resolve a shared problem. Specifically, this study pays attention to the relationship among social capital, corporate capacity, and trust, which may perhaps contribute to developing a democratic environment in Korean society. The study aims to explore whether Korean citizens' perceived corporate bonding and bridging social capital affect corporate capacity for collaborative action and trust in corporations. A Web survey of 385 South Koreans was conducted. The findings show that perceived bonding social capital among employees is positively related to corporate capacity for collaboration action. Moreover, perceived bonding among employees and bridging social capital between employees and local residents are positively related to corporate capacity for collaboration action and trust in corporations. These findings suggest that researchers and practitioners for organizational development and community-building need to enhance corporate social capital.

• Journal of the Korean Wood Science and Technology
• /
• v.38 no.2
• /
• pp.117-123
• /
• 2010

The objective of this research was executed to investigate the effect of molar ratio of formaldehyde to urea and melamine (F/(U+M)) of urea-melamine-formaldehyde (UMF) resin on bonding high and low moisture content veneers. For that purpose, UMF resin types with 5 different F/(U+M) molar ratios (1.45, 1.65, 1.85, 2.05, and 2.25) synthesized were used in present study. First, their curing behavior was evaluated by differential scanning calorimetry. Second, their adhesion performance in bonding high and low moisture content veneers was evaluated by probe tack and dry and wet shear strength tests. Curing temperature and reaction enthalpy decreased with the increase of F/(U+M) molar ratio. And the dry and wet shear strengthsof plywood manufactured from low moisture content veneers were higher than thoseof plywood manufactured from high moisture content veneers. Also, the maximum initial tack force on the low moisture content veneer was higher than that on the high moisture content veneer.