• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.3
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• pp.177-182
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• 2003

In the case of the flash memory, various kinds of transistors and the wide range of operation voltage are necessary to achieve the read/write operations. Therefore, the characteristics of transistors are measured in the silicon for the circuit design, and the test vehicle run must be processed. In this study, an efficient design flow is suggested using TCAD tools. The test vehicle is replaced with well-calibrated TCAD simulation. First, the calibration methodology is introduced and tested for flash memory device. The calibration errors are less than 5% of a full chip operation, which is accepted by the designers. The results of the calibration were used to predict I-V curves and model parameter of the various transistors for the design of flash device.

• Publications of The Korean Astronomical Society
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• v.16 no.1
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• pp.31-36
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• 2001

We present the characteristics of the 2K CCD camera at the Bohyunsan Optical Astronomy Observatory of the Korea Astronomy Observatory at the time of its development. The purpose of this paper is to support the observers who may need detailed information on the characteristics of the camera and to provide helpful information on the optimization' of a CCD camera for those who try to develop their own camera. The 2K CCD camera was optimized to have a gain of $1.8e^-/ADU$ and a read out noise of $7e^-$ from an experiment using radioactive $^{55}Fe$ X-ray source. The charge transfer efficiency was measured as 0.9999976 for serial and 0.9999942 for parallel direction, which means $0.5\%$ charge loss along the serial direction and $1.2\%$ along the parallel direction across the chip. The quantum efficiency of the camera was measured from an experiment using a homogeneous light source consisting of a halogen lamp and an integrating sphere with a monochromator. The resulting quantum efficiency of the camera peaked at the wavelength range 600-700 nm with the value of $\~0.89$.

• Phonetics and Speech Sciences
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• v.6 no.4
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• pp.17-26
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• 2014

The present study examined epenthetic vowels produced by Korean learners of English in read sentences, in terms of acoustic measures and extra-phonological factors. The results demonstrated three main findings. First, epenthetic vowels had relatively high F1 values and a wide range of F2 values. Most of the epenthetic vowels were inserted near Korean high central vowels, but some vowels were inserted near front vowels due to co-articulation with surrounding vowels. Second, vowel epenthesis was affected by the context. The results showed that the epenthesis was frequently seen with word junctions between obstruents (e.g., stops-fricatives). Third, Korean learners were not affected by English background and were very weakly affected by orthography. English experience, which is one of the extra-phonological factors, was not related to epenthesis production. However, orthography, the other extra-phonological factor, very weakly affected the amount of epenthesis production. Nine percent of all epenthesis production was affected by the English past-tense suffix '-ed'; approximately 70% of the participants were affected by this suffix. The findings of the present study contributed to understanding vowel epenthesis. First, the study revealed that the epenthetic vowels produced by Korean learners of English were close to the high central vowel, supporting previous studies that the epenthetic vowel is quite close to the shortest vowel. Second, the study examined the various phonetic environments of epenthetic vowels, revealing that vowel epenthesis occurred more frequently in a certain phonetic circumstance.

• Phonetics and Speech Sciences
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• v.8 no.3
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• pp.11-20
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• 2016

It is well known that vowels are shorter before voiceless consonants than voiced ones in English, as in many other languages. Research has shown that the ratio of vowel durations in voiced and voiceless contexts in English is in the range of 0.6~0.8. However, little work has been done as to whether the ratio of vowel durations varies depending on English variety. In the production experiment in this paper, seven speakers from three varieties of English, New Zealand, British, and American English, read 30 pairs of (C)VC monosyllabic words which differ in coda voicing (e.g. beat-bead). Vowel height, phonemic vowel length, and consonant manner were varied as well. As expected, vowel-shortening effects were found in all varieties: vowels were shorter before voiceless than before voiced codas. Overall vowel duration was the longest in American English and the shortest in New Zealand (NZ) English. In particular, vowel duration before voiceless codas is the shortest in New Zealand English, indicating the most radical degree of shortening in this variety. As a result, the ratio of vowel durations in varying voicing contexts is the lowest in NZ English, while American and British English do not show a significant difference each other. In addition, consonant closure duration was examined. Whereas NZ speakers show the shortest vowel duration before a voiceless coda, their voiceless consonants have the longest closure duration, which suggest an inverse relationship between vowel duration and closure duration.

• IEMEK Journal of Embedded Systems and Applications
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• v.11 no.2
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• pp.67-78
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• 2016

The emerging Spin-Transfer Torque RAM (STT-RAM) is a promising component that can be used to improve the efficiency as a result of its high storage density and low leakage power. However, the state-of-the-art STT-RAM is not ready to replace SRAM technology due to the negative effect of its write operations. The write operations require longer latency and more power than the same operations in SRAM. Therefore, a hybrid cache with SRAM and STT-RAM technologies is proposed to obtain the benefits of STT-RAM while minimizing its negative effects by using SRAM. To efficiently use of the hybrid cache, it is important to place write intensive data onto the cache. Such data should be placed on SRAM to minimize the negative effect. Thus, we propose a technique that optimizes placement of data in main memory. It drives the proper combination of advantages and disadvantages for SRAM and STT-RAM in the hybrid cache. As a result of the proposed technique, write intensive data are loaded to SRAM and read intensive data are loaded to STT-RAM. In addition, our technique also optimizes temporal locality to minimize conflict misses. Therefore, it improves performance and energy consumption of the hybrid cache architecture in a certain range.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.6
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• pp.445-450
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• 2012

We have developed an implantable wireless sensor for real time pressure monitoring of blood circulation system. MEMS (micro-electro-mechanical system) technology was adopted as a sensor development method. The sensor is composed of photolithographically patterned inductors and a distributed capacitor in gap between the inductors. A resulting LC resonant system produces its resonant frequency in range of 269 to 284 MHz at 740 mmHg. To read the resonant frequency changed by blood pressure variation, we developed a custom readout system based on a network analyzer functionality. The bench-top testing of the pressure sensors showed good mechanical and electrical functionality. A sensor was implanted into tibial artery of farm pig, and interrogated wirelessly with accurate readings of blood pressure. After 45 days, the sensor's electrical response and histopathology were studied with good frequency reading and biocompatibility.

• Journal of Preventive Medicine and Public Health
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• v.6 no.1
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• pp.65-70
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• 1973

The study in the fild of medical instrument has been out of the interest by any of the life scientist in Korea. Especially, the recent developments in the medical electromics are remarkable one. Authors planned this study to ascertain the possibility of setting up the thermister thermometer with available accessories of demestic prouducts including some specific foreign assembly parts. By proper use of the thermister as one of the wheatstone bridge, we could detect tile resistance variations due to the environmental temperature variace. The intensive care for the bridge circuit and compensation scheme was required. The calibration procedure adopted here makes it possible to read the current as the temperature. The temperature range was determined by the examination and construction of the graph of the resistance-temperature variation. The determination of electric current, available ambient-temperature, the reduction of excessive current and self-heating of the thermister were made. Renovation in response-velocity was under taken too. This electronic thermometer was designed and assembled by the circuitry developed in accordance with the maximum availability of domestic products with some foreign-made parts. The result of our experiment showed very stable function and proved to be the most promissing item in the actual application as long as the thermistor thermister is concerned.

• Journal of Biosystems Engineering
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• v.27 no.5
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• pp.425-432
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• 2002

This study was carried out to develop an automatic mixing system of nutrient solution for closed-loop hydroponics using ion electrodes. The results of the study are summarized as follows: 1. It appeared that ion-electrodes had not to be soaked into nutrient solution for a long time since it was much less durable than EC or PH sensors. Once ion-electrodes were soaked into real nutrient solution for a long time, they became unstable. 2. ion measurement modules, which were able to sample recirculated nutrient solution and easily wash and dry ion-electrodes, were developed in order to use ion-electrodes continuously. 3. The results of calibration tests on three kinds of ion electrodes presented that the time required to read measurement data was over 30 seconds. Using the calibration data the regression equations for the ion electrodes were developed. 4. An automatic nutrient-solution mixing system using the three kinds of ion electrodes was developed and then its accuracy was examined. The control errors of the mixing system using ion electrodes were in the range of 9.8 to 12%.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.3
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• pp.248-253
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• 2008

This paper presents a sensing system for smart home which can detect an location transition events such as entrance/exit of a member and identify the user in a group at the same time. The proposed system is compose of two sub-systems; a wireless sensor network system and a database server system. The wireless sensing system is designed as a star network where each of sensing modules with ultrasonic sensors and a Bluetooth RF module connect to a central receiver called Bluetooth access point. We propose a method to discriminate a user by measuring the height of the user. The differences in the height of users is a key feature for discrimination. At the same time, the each sensing module can recognize whether the user goes into or out a room by using two ultrasonic sensors. The server subsystem is a sort of data logging system which read the detected event from the access point and then write it into a database system. The database system could provide the location transition information to wide range of context-aware applications for smart home easily and conveniently. We evaluate the developed method with experiments for three subjects in a family with the installation of the developed system into a real house.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.3
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• pp.195-203
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• 2005

Recently, a novel multi-bit nonvolatile memory based on double gate (DG) MOSFET is proposed to overcome the short channel effects and to increase the memory density. We need more complex voltage schemes for DG MOSFET devices. In view of peripheral circuits driving memory cells, one should consider various voltage sources used for several operations. It is one of the key issues to minimize the number of voltage sources. This criterion needs more caution in considering a DG nonvolatile memory cell that inevitably requires more number of events for voltage sources. Therefore figuring out the permissible range of operating bias should be preceded for reliable operation. We found that reliable operation largely depends on the depletion conditions of the silicon channel according to charge amount stored in the floating gates and the negative control gate voltages applied for read operation. We used Silvaco Atlas, a 2D numerical simulation tool as the device simulator.