• Journal of Mechanical Science and Technology
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• v.18 no.4
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• pp.681-688
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• 2004

For use of the thermal cycle of the biochemical fluid sample, the isothermal temperature source with a large surface area was designed, fabricated and its thermal characterization was experimentally evaluated. The comprehensive overview of the technology trend on the temperature control devices was detailed. The large surface area isothermal temperature source was realized by using the vapor chamber heat spreader. The cost-effectiveness and simple manufacturing process were achieved by using the metal-etched wick structure. The temperature distribution was quantitatively investigated by using IR temperature imaging system at equivalent temperatures to the PCR thermal cycle. The standard deviation was measured to be within 0.7$^{\circ}C$ for each temperature cycle. This concludes that the presented isothermal temperature source enables no temperature gradient inside bio-sample fluid. Furthermore it can be applied to the cooling of the electronic devices due to its slimness and low thermal spreading resistance.

• Journal of Urban Science
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• v.7 no.1
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• pp.5-9
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• 2018

The nickel-titanium shape memory alloy (SMA), referred to as Nitinol, exhibits a superelastic effect that can be restored to its original shape even if a significant amount of deformation is applied at room temperature, without any additional heat treatment after removal of the load. Owing to these unique material characteristics, it has widely used as displacement control devices for seismic retrofitting in civil engineering fields as well as medical, electrical, electronic and mechanical fields. Contrary to ordinarty carbon steel, superelastic SMAs are very resistant to fatigue, and have force-displacement properties depending on loading speed. The change for the mechanical properties of superelastic SMAs are experimentally inviestigated in this study when loading cycle numbers and loading speeds are different. In addition, the standardized force-displacement properties of such superelastic SMAs are proposed with an aim to efficiently design the seismic retrofitting devices made of these materials.

• Journal of information and communication convergence engineering
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• v.10 no.4
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• pp.337-342
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• 2012

The medical industries are integrated with information technology with mobile devices and wireless communication. The advent of mobile healthcare systems can benefit patients and hospitals, by not only providing better quality of patient care, but also by reducing administrative and medical costs for both patients and hospitals. Security issues present an interesting research topic in wireless and pervasive healthcare networks. As information technology is developed, many organizations such as government agencies, public institutions, and corporations have employed an information system to enhance the efficiency of their work processes. For the past few years, healthcare organizations throughout the world have been adopting health information systems (HIS) based on the wireless network infrastructure. As a part of the wireless network, a mobile agent has been employed at a large scale in hospitals due to its outstanding mobility. Several vulnerabilities and security requirements related to mobile devices should be considered in implementing mobile services in the hospital environment. Secure authentication and protocols with a mobile agent for applying ubiquitous sensor networks in a healthcare system environment is proposed and analyzed in this paper.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.64.2-64.2
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• 2011

Recently, Silicon Germanium (SiGe) alloys have been received considerable attention for their great potentials in advanced electronic and optoelectronic devices. Especially, microcrystalline SiGe is a good channel material for thin film transistor due to its advantages such as narrow and variable band gap and process compatibility with Si based integrated circuits. In this work, microcrystalline silicon-germanium films (${\mu}c$-SiGe) were deposited by DC/RF magnetron co-sputtering method using Si and Ge target on Corning glass substrates. The film composition was controlled by changing DC and RF powers applied to each target. The substrate temperatures were changed from $100^{\circ}C$ to $450^{\circ}C$. The microstructure of the thin films was analyzed by x-ray diffraction (XRD) and Raman spectroscopy. The analysis results showed that the crystallinity of the films enhances with increasing Ge mole fraction. Also, crystallization temperature was reduced to $300^{\circ}C$ with $H_2$ dilution. Hall measurements indicated that the electrical properties were improved by Ge alloying.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.17.1-17.1
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• 2011

Inorganic III-V light emitting diodes (LEDs) have superior characteristics, such as long-term stability, high efficiency, and strong brightness compared to conventional incandescent lamps and OLED. However, due to the brittle property of bulk inorganic semiconductor materials, III-V LED limits its applications in the field of high performance flexible electronics. This seminar introduces the first flexible and implantable GaN LED on plastic substrates that is transferred from bulk GaN on Si substrates. The superb properties of the flexible GaN thin film in terms of its wide band gap and high efficiency enable the dramatic extension of not only consumer electronic applications but also the biosensing scale. The flexible white LEDs are demonstrated for the feasibility of using a white light source for future flexible BLU devices. Finally a water-resist and a biocompatible PTFE-coated flexible LED biosensor can detect PSA at a detection limit of 1 ng/mL. These results show that the nitride-based flexible LED can be used as a type of implantable LED biosensor and as a therapy tool.

• Vacuum Magazine
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• v.1 no.1
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• pp.21-26
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• 2014

The new materials such as graphene and other nano scale structured materials are attracting great attention due to its expandability for the future electronic devices. In this presentation, a variety of analysis techniques will be introduced for the latest new material applications such as graphene and organic materials with number of metals. The basic properties of next generation device should be carefully analyzed without being exposed to ambient surrounding since the physical and chemical properties of new material or interface states are easily and drastically changed by ambient condition. With the combination of the fabrication process and precise analysis instruments, it is expected to set the facilities supporting the nanotechnology industry and other research groups. This system will give strong support nanotechnology and other complex science with qualified data and information on basic knowledge on the new-forthcoming materials for the future.

• KIEAE Journal
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• v.2 no.2
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• pp.33-38
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• 2002

There are a number of practical uses for devices which are capable of piping large amounts of light: illumination of areas where there would be maintenance, safety, or security problems with electronic light sources; piping sunlight into indoor areas for illumination; and the conversion of high luminous efficacy, good color quality, high intensity discharge lamps into more acceptable linear of area sources of light. Prism light guides are hollow structures which pipe light by means of total internal reflectin(TIR). These devices are unique in their ability to combine the efficiency of TIR with the relatively low cost of hollow structure. An important application stems from their ability to transform a point source of light such as an incandescent or discharge lamp into a linear or area source of light or illumination. We report the development of an economical, flexible prismatic film for fabricating the light guide wall. This guide geometries and films are currently under development.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.2
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• pp.77-82
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• 2020

IoT devices frequently require input resources to communicate with various sensors or IoT platforms. IoT device wastes a lot of time as idle time or waiting time to check the data of the input resource and use the input resource. In addition, IoT devices use various input resources. We compares and analyzes input idle time and input waiting time generated from hardware serial input resource, software serial input resource, digital port input resource, and analog port input resource using Arduino widely used as IoT device. In order to design the IoT device framework, it is necessary to understand the characteristics of input resources and to design them to minimize unnecessary input idle time and input waiting time. The analog input wait time has a much larger input wait time than the digital input wait time, so it must be designed to receive analog information periodically at the appropriate timing. The characteristics of the input resources analyzed in this way help to design an efficient IoT device.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.129-157
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• 1999

Low-dislocation-density large-diameter GaAs single crystals with low-residual-strain have been strongly required. We have developed dislocation-free 3-inch Si-doped GaAs crystals for photonic devices [1], and low-dislocation-density low-residual-strain 4-inch to 6-inch [2, 3] semi-insulating GaAs crystals for electronic devices by Vertical Boat (VB) technique. We confirmed that VB substrates with low-residual-strain have higher resistance against slip-line generation during MBE process. VB-GaAs single crystals show uniform radial profile of resistivity reflecting to the flat solid-liquid interface during the crystal growth. Uniformity of micro-resistivity of VB-GaAs substrate is much better than that of the LEC-GaAs substrate, which is due to the low-dislocation-density of VB-GaAs single crystals.

• Journal of information and communication convergence engineering
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• v.16 no.1
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• pp.60-65
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• 2018

The Internet of Things (IoT) is happening now. By implementing IoT, we can build smart home system. Smart home is an application that is a combination of technology and services that specialize in the home environment with specific functions aimed at improving the efficiency, comfort and security of the occupants. Smart homes filled with connected products are loaded with possibilities to make our lives easier, more convenient, and more comfortable. This intelligent home system uses a microcontroller to process functions that provided by smart home system, such functions as RFID for door access and PIR sensors for motion detection. By using Android users could control the sensors anytime and anywhere. Microcontroller used is Arduino IDE with WeMos D1R2 board. Based on the testing process, there was a successful communication between the components of the device, sensors, and Android devices. Users could open or close the solenoid, users can also turn off or turn on electronic devices using Android.