• ETRI Journal
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• v.39 no.6
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• pp.866-873
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• 2017

We propose a multilayered-substrate-based power semiconductor discrete device package for a low switching loss and high heat dissipation. To verify the proposed package, cost-effective, low-temperature co-fired ceramic, multilayered substrates are used. A bare die is attached to an embedded cavity of the multilayered substrate. Because the height of the pad on the top plane of the die and the signal line on the substrate are the same, the length of the bond wires can be shortened. A large number of thermal vias with a high thermal conductivity are embedded in the multilayered substrate to increase the heat dissipation rate of the package. The packaged silicon carbide Schottky barrier diode satisfies the reliability testing of a high-temperature storage life and temperature humidity bias. At $175^{\circ}C$, the forward current is 7 A at a forward voltage of 1.13 V, and the reverse leakage current is below 100 lA up to a reverse voltage of 980 V. The measured maximum reverse current ($I_{RM}$), reverse recovery time ($T_{rr}$), and reverse recovery charge ($Q_{rr}$) are 2.4 A, 16.6 ns, and 19.92 nC, respectively, at a reverse voltage of 300 V and di/dt equal to $300A/{\mu}s$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.4
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• pp.251-265
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• 2001

As the device scaling proceeds, the operating voltage(VDD) of giga-bit DRAMs is expected to be reduced to 1.5V or down, fir improving the device reliability and reducing the power dissipation. Therefore the low-voltage circuit design techniques are required to implement giga-bit DRAMs. In this work, state-of-art low-voltage DRAM circuit techniques are reviewed, and four kinds of low-voltage circuit design techniques are newly proposed for giga-bit DRAMs. Measurement results of test chips and SPICE simulation results are presented for the newly proposed circuit design techniques, which include a hierarchical negative-voltage word-line driver with reduced subthreshold leakage current, a two-phase VBB(Back-Bias Voltage) generator, a two-phase VPP(Boosted Voltage) generator and a bandgap reference voltage generator.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.307-308
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• 2007

This work shows the experimental results obtained from ageing at a temperature of 100 C for 48, 70 and 312 h, although the application of AC electrical tension in samples and the measuring of current leakage are presented. The measurements in samples were carried out with samples prepared from the deformulated commercial materials and respectively reformulated into thin films. The obtained results showed the mechanisms of conduction of samples in low and high electric fields. It was also identified an electric tension transition showing that in low fields it prevails the Ohm's law conduction, and in high electric fields it prevails the conduction of space charge limited current (SCLC). These results can support the natural rubber formulation process having as their main objective the reducing of the mechanisms that occur under high conduction current in high electric fields, which leads the material to a dielectric breakdown. Raw Natural rubber in Brazil is extracted from rubber trees (Hevea brasiliensis) in farms in So Paulo State by using some new plantation technology in smaller spaces, with trees placed a few meters from each other. In the Amazon rain forest the rubber trees are found naturally and their spacing may be of hundreds of meters or even kilometers between them. It is necessary to research this raw material from different internationally standard clones to characterize dielectric and electric properties for industrial applications. Moreover, this natural material has a low commercial price when compared to the synthetic ones.

• Smart Structures and Systems
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• v.6 no.5_6
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• pp.675-687
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• 2010

Structural Health Monitoring (SHM) is the science and technology of monitoring and assessing the condition of aerospace, civil and mechanical infrastructures using a sensing system integrated into the structure. Impedance-based SHM measures impedance of a structure using a PZT (Lead Zirconate Titanate) patch. This paper presents a low-power wireless autonomous and active SHM node called Autonomous SHM Sensor 2 (ASN-2), which is based on the impedance method. In this study, we incorporated three methods to save power. First, entire data processing is performed on-board, which minimizes radio transmission time. Considering that the radio of a wireless sensor node consumes the highest power among all modules, reduction of the transmission time saves substantial power. Second, a rectangular pulse train is used to excite a PZT patch instead of a sinusoidal wave. This eliminates a digital-to-analog converter and reduces the memory space. Third, ASN-2 senses the phase of the response signal instead of the magnitude. Sensing the phase of the signal eliminates an analog-to-digital converter and Fast Fourier Transform operation, which not only saves power, but also enables us to use a low-end low-power processor. Our SHM sensor node ASN-2 is implemented using a TI MSP430 microcontroller evaluation board. A cluster of ASN-2 nodes forms a wireless network. Each node wakes up at a predetermined interval, such as once in four hours, performs an SHM operation, reports the result to the central node wirelessly, and returns to sleep. The power consumption of our ASN-2 is 0.15 mW during the inactive mode and 18 mW during the active mode. Each SHM operation takes about 13 seconds to consume 236 mJ. When our ASN-2 operates once in every four hours, it is estimated to run for about 2.5 years with two AAA-size batteries ignoring the internal battery leakage.

• Korean Journal of Bronchoesophagology
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• v.15 no.1
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• pp.35-40
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• 2009

Background: Surgical treatment of corrosive esophageal stricture with colon interposition was very widely used. The colon interposition advantage is low reflux esophagitis risk and preservation of gastric capacity and peristalsis. This procedure was introduced by Orsoni and much improved. But, if stomach injury was minimal, gastric interposition is useful due to simple technique and low complication. Material and Method: Esophageal reconstruction by the transhiatal esophagectomy and intracervical esophagogastrostomy was done in 7 patients of corrosive esophageal stricture at Dong-San medical center from January 1998 to December 2007. Result: There were six female and one male patients raBackground Surgical treatment of corrosive esophageal stricture with colon interposition was very widely used. The colon interposition advantage is low reflux esophagitis risk and preservation of gastric capacity and peristalsis. This procedure was introduced by Orsoni and much improved. But, if stomach injury was minimal, gastric interposition is useful due to simple technique and low complication. Material and Method: Esophageal reconstruction by the transhiatal esophagectomy and intracervical esophagogastrostomy was done in 7 patients of corrosive esophageal stricture at Dong-San medical center from January 1998 to December 2007. Result: There were six female and one male patients ranging from 29 to 69 years of age. The complication was two anastomosis site leakage, one gastric necrosis and one mortality due to bowel strangulation and sepsis. Conclusion: Transhiatal esophagectomy and intracervical esophagogastrostomy is safety and useful method at selection case even though corrosive esophageal resection is debated.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.16 no.6
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• pp.25-35
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• 2006

Radio Frequency identification (RFID) will become an important technology in remotely object identification systems. However, the use of RFID tags may create new threats to the sniな and Privacy of individuals holding RFID tags. These threats bring several problems which are information leakage of a tag, location trace of individuals and impersonation of a tag. Low-cost RFID systems have much restrictions such as the limited computing power, passive power mechanism and low storage space. Therefore, the cost of tag's computation should be considered as an important factor in low-cost RFID systems. We propose an authentication protocol, OHLCAP which requires only one one-way hash function operation and hence is very efficient. Furthermore, our protocol is suitable to distribution database environment. Hence our scheme can be applied to ubiquitous computing environment.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.11B no.4
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• pp.180-184
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• 2001

The high operation frequency mainly reduces transformer volume in the power supply. A high frequency and high voltage pulse transformer is designed, fabricated, and tested. Switching frequency of the transformer is 100 kHz. Input and output voltages of the transformer are 250 V and 4 kV, respectively. Normal operation power of the transformer is 3 kW. Maximum volume of the transformer is 400 $cm^3$. The power density is thus 7.5 W/$cm^3$. The transformer will be installed in a metal box that has nominal operation temperature of 85 degree centigrade. The transformer and other high voltage components in the box will be molded with Silicon RTV(Room Temperature Vulcaniza) that has a very low thermal conductivity. Procedure of design and test results are discussed. Analytical as well as experimental results of varous paramters such as transformer loss, leakage inductance, distributed capacitance are also discussed. In addition, thermal analysis results from ANSYS code for three different operation conditions are discussed.

• Tribology and Lubricants
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• v.27 no.5
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• pp.275-280
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• 2011

Automotive wheel bearing grease helps to reduce stresses and prevent wear of wheel bearings. But it is easily contaminated by water and other contaminants. In this study, we investigated the property change of automotive wheel bearing grease under water contamination. The result showed that some properties such as dropping point, work penetration and oxidation stability were not influenced by water content. However, most of properties such as work stability, water washout characteristics, leakage tendency, oil separation, evaporation loss and rust protection became worse after water was added. This is thought that added water makes the interaction weak between thickener and base oil of grease.

• International Journal of Fluid Machinery and Systems
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• v.6 no.2
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• pp.49-55
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• 2013

Water lubricated guide bearing was newly released and has been applied to actual hydro turbines with vertical shaft. As a result, they can have not only high bearing performance but environmental advantages in meeting the demand for reducing river pollution by oil leakage from oil lubricated guide bearing. The PTFE composite guide bearing was tested by experimental equipment operated under conditions similar to those of actual hydro turbines. Circumferential and axial tilting bearing segments help to improve the bearing performance and efficiency due to low friction loss in the bearing system. Furthermore, bearing cooling systems could be eliminated and maintenance periods could be extended, thus the initial investment and operating costs of the hydroelectric power plant are reduced.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.39-39
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• 2009

We fabricated p-channel TFTs based on poly Silicon. The 35nm thickness silicon dioxide layer structure got higher $I_{on}/I_{off}$ ratio, field-effect Mobility and output current than 10nm thickness. And 35nm layer showed low leakage current and threshold voltage. So, 35nm thickness silicon dioxide layer TFTs are faster reaction speed and lower power consumption than 10nm thickness.