• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.241.1-241.1
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• 2014

The large-area high-power radio-frequency (RF) driven ion sources based on the negative hydrogen (deuterium) ion beam extraction are the major components of neutral beam injection (NBI) systems in future large-scale fusion devices such as an ITER and DEMO. Positive hydrogen (deuterium) RF ion sources were the major components of the second NBI system on ASDEX-U tokamak. A test large-area high-power RF ion source (LAHP-RaFIS) has been developed for steady-state operation at the Korea Atomic Energy Research Institute (KAERI) to extract the positive ions, which can be used for the NBI heating and current drive systems in the present fusion devices, and to extract the negative ions for negative ion-based plasma heating and for future fusion devices such as a Fusion Neutron Source and Korea-DEMO. The test RF ion source consists of a driver region, including a helical antenna and a discharge chamber, and an expansion region. RF power can be transferred at up to 10 kW with a fixed frequency of 2 MHz through an optimized RF matching system. An actively water-cooled Faraday shield is located inside the driver region of the ion source for the stable and steady-state operations of RF discharge. The characteristics and uniformities of the plasma parameter in the RF ion source were measured at the lowest area of the expansion bucket using two RF-compensated electrostatic probes along the direction of the short- and long-dimensions of the expansion region. The plasma parameters in the expansion region were characterized by the variation of loaded RF power (voltage) and filling gas pressure.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.7 no.2
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• pp.127-131
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• 2007

The control of electrical appliances residing in the home network can be accomplished via Internet with the UPnP expansion without modifying an existing UPnP. In this paper, we propose the Internet Gateway that consists of an UPnP IGD(Internet Gateway Device) DCP(Device Control Protocol) and an UPnP Bridge as a system to control electrical appliances of home network. UPnP IGD DCP is to enable the configurable initiation and sharing of Internet connections as well as assuring advanced connection-management features and management of host configuration service. It also supports transparent Internet access by non-UPnP-certified devices. UPnP Bridge searches for local home network devices by sending control messages, while control point of UPnP Bridge looks up devices of interest on the Internet, subsequently furnishing the inter-networking controlling among devices which belong to different home network systems. With our approach, devices on one home network can control home electrical appliances on the other home network via Internet through IGD DCP with control commands of UPnP.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1844-1852
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• 2001

Recent developments in microfluidic devices based on microelectromechanical systems (MEMS) technique find many practical applications, which include electronic chip cooling devices, power MEMS devices, micro sensors, and bio-medical devices among others. For the design of such micro devices, flows characteristics inside a microchannel have to be clarified which exhibit somewhat different characteristics compared to conventional flows in a macrochannel. In the present study microchannels of various hydraulic diameters are fabricated on a silicon wafer to study the pressure drop characteristics. The effect of abrupt contraction and expansion is also studied. It is found from the results that the friction factor in a straight microchannel is about 15% higher than that in a conventional macrochannel, and the loss coefficients in abrupt expansion and contraction are about 10% higher than that obtained through conventional flow analysis.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.322-322
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• 2008

Low-temperature co-fired ceramics (LTCC) have turned out to be very promising technology in accordance with the rapid developments in semiconductor technology. The demands for compact electrical assemblies, smaller power loss as well as high signal density can be fulfilled by LTCC. And for the multi-layered ceramic devices with embedded passive components such as high dielectric constant decoupling capacitor, LTCC materials require the several conditions to avoid delamination and internal cracks. For the present study, diopside-based glass is chosen as the LTCC substrate material in view of its high coefficient of thermal expansion (CTE). From the experimental resultsn the influence of each element on the CTE change can be revealed.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.208-211
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• 2007

Separation Devices have two functions. These two functions are to bond and to separate two bodies. This paper is about separation devices which use explosives to separate their bodies. Explosive bolt is separated with two bodies when the explosives in the body detonated. The good things of explosive bolt are that it has simple operational system and it is made of few parts. But it has side effects; fragment and pyre-shock. To avoid these side effects gas expansion separation(GES) bolt and pressure cartridge actuation separation(PAS) devices are invented. These use pressure to separate their bodies. The pressure is generated when explosives are burned. But the sizes of PAS devices are bigger than explosive bolts. And GES bolt has a mechanically lower bonding ability than that of explosive bolt. When you design separation devices, it is recommended to know operational system and characteristics of separation devices, to design best one.

• Korean Journal of Materials Research
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• v.19 no.5
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• pp.288-292
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• 2009

This article shows various factors that influence the thermal-cycling reliability of semiconductor devices utilizing the lead-on-chip (LOC) die attach technique. This work details how the modification of LOC package design as well as the back-grinding and dicing process of semiconductor wafers affect passivation reliability. This work shows that the design of an adhesion tape rather than a plastic package body can play a more important role in determining the passivation reliability. This is due to the fact that the thermal-expansion coefficient of the tape is larger than that of the plastic package body. Present tests also indicate that the ceramic fillers embedded in the plastic package body for mechanical strengthening are not helpful for the improvement of the passivation reliability. Even though the fillers can reduce the thermal-expansion of the plastic package body, microscopic examinations show that they can cause direct damage to the passivation layer. Furthermore, experimental results also illustrate that sawing-induced chipping resulting from the separation of a semiconductor wafer into individual devices might develop into passivation cracks during thermal-cycling. Thus, the proper design of the adhesion tape and the prevention of the sawing-induced chipping should be considered to enhance the passivation reliability in the semiconductor devices using the LOC die attach technique.

• Archives of Plastic Surgery
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• v.44 no.6
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• pp.523-529
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• 2017

Background Serial tissue expansion is performed to remove giant congenital melanocytic nevi. However, there have been no studies comparing the expansion rate between the subsequent and preceding expansions. In this study, we analyzed the rate of expansion in accordance with the number of surgeries, expander location, expander size, and sex. Methods A retrospective analysis was performed in pediatric patients who underwent tissue expansion for giant congenital melanocytic nevi. We tested four factors that may influence the expansion rate: The number of surgeries, expander location, expander size, and sex. The rate of expansion was calculated by dividing the 'inflation amount' by the 'expander size'. Results The expansion rate, compared with the first-time group, was 1.25 times higher in the second-or-more group (P=0.04) and 1.84 times higher in the third-or-more group (P<0.01). The expansion rate was higher at the trunk than at other sites (P<0.01). There was a tendency of lower expansion rate for larger expanders (P=0.03). Sex did not affect the expansion rate. Conclusions There was a positive correlation between the number of surgeries and the expansion rate, a positive correlation between the expander location and the expansion rate, and a negative correlation between the expander size and the expansion rate.

• Archives of Plastic Surgery
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• v.47 no.6
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• pp.551-558
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• 2020

Background Giant congenital melanocytic nevus (GCMN) is a rare disease, for which complete surgical resection is recommended. However, the size of the lesions presents problems for the management of the condition. The most popular approach is to use a tissue expander; however, single-stage expansion in reconstructive surgery for GCMN cannot always address the entire defect. Few reports have compared tissue expansion techniques. The present study compared single and serial expansion to analyze the risk factors for complications and the surgical outcomes of the two techniques. Methods We retrospectively reviewed the medical charts of patients who underwent tissue expander reconstruction between March 2011 and July 2019. Serial expansion was indicated in cases of anatomically obvious defects after the first expansion, limited skin expansion with two more expander insertions, or capsular contracture after removal of the first expander. Results Fifty-five patients (88 cases) were analyzed, of whom 31 underwent serial expansion. The number of expanders inserted was higher in the serial-expansion group (P<0.001). The back and lower extremities were the most common locations for single and serial expansion, respectively (P =0.043). Multivariate analysis showed that sex (odds ratio [OR], 0.257; P=0.015), expander size (OR, 1.016; P=0.015), and inflation volume (OR, 0.987; P=0.015) were risk factors for complications. Conclusions Serial expansion is a good option for GCMN management. We demonstrated that large-sized expanders and large inflation volumes can lead to complications, and therefore require risk-reducing strategies. Nonetheless, serial expansion with proper management is appropriate for certain patients and can provide aesthetically satisfactory outcomes.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.11a
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• pp.49-54
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• 1993

This paper discusses the reliability of solder joints of electronic devices on printed circuit board. Solder application is usually done by screen printing method for the bonding between outer leads of devices and thick film(Ag/Pd) pattern on Hybrid IC as wel1 as Cu lands on PCB. As result of thermal stresses generated at the solder joints due to the differences of thermal expansion coefficients between packge body and PCB, Micro cracking often occurs due to thermal fatigue failure at solder joints. The initiation and the propagate of solder joint crack depends on the environmental conditions, such as storage temperature and thermal cycling. The principal mechanisms of the cracking pheno- mana are the formation of kirkendal void caused by the differences in diffusion rate of materials, ant the thermal fatigue effect due to the differences of thermal expansion coefficient between package body and PCB. Finally, This paper experimentally shows a way to supress solder joints cracks by using low-${\alpha}$ PCB and the packages with thin lead frame, and investigates the phenomena of diffusion near the bonding interfaces.

• ETRI Journal
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• v.25 no.4
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• pp.266-269
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• 2003

Polymeric multi-channel optical interconnection devices that are usually fabricated by transfer molding are indispensable for parallel interconnection in high speed, high capacity optical communication systems. This paper proposes a design technique considering the thermal behavior of materials, such as shrinkage and expansion during the molding process, to satisfy geometrical requirements that have less than 1 ${\mu}m$ tolerance. We also designed molds considering the thermal effects of the materials and fabricated multi-channel optical fiber connectors that have less than 1 ${\mu}m$ tolerance.