• Progress in Superconductivity and Cryogenics
• /
• v.24 no.2
• /
• pp.1-6
• /
• 2022

This paper reviews the literature that has been published since 1980s related to cryogenic refrigeration systems for quantum computing. The reason why such a temperature level of 10-20 mK is necessary for quantum computing is that the superconducting qubit is sensitive to even very small thermal disturbances. The entanglement of the qubits may not be sustained due to thermal fluctuations and mechanical vibrations beyond their thresholds. This phenomenon is referred to as decoherence, and it causes an computation error in operation. For the stable operation of the quantum computer, a low-vibration cryogenic refrigeration system is imperative as an enabling technology. Conventional dilution refrigerators (DR), so called 'wet' DR, are precooled by liquid helium, but a more convenient and economical precooling method can be achieved by using a mechanical refrigerator instead of liquid cryogen. These 'dry' DRs typically equip pulse-tube refrigerators (PTR) for precooling the DRs around 4 K because of its particular advantage of low vibration characteristic. In this review paper, we have focused on the development status of 4 K PTRs and further potential development issues will be also discussed. A quiet 4 K refrigerator not only serves as an indispensable precooler of DR but also immediately enhances the characteristics of low noise amplifiers (LNA) or other cryo-electronics of various type quantum computers.

• Korean Journal of Digital Imaging in Medicine
• /
• v.5 no.1
• /
• pp.64-77
• /
• 2002

DR has had an important fact not only in the department of radiology but also in productivity or work efficiency of a whole hospital. The environment of DR has more various parameter than CR, so it is able to supply high quality of medical services. The current environment of radiology department in each hospital has been changed from Film-Screen system to DR through Full-PACS. This hospital which uses Full-PACS became to study the proper condition of CR and DDR and how the image quality of them is expressed among general photographing systems in the DR environment. From this experiment, the image quality of DDR is better than CR under the same exposure condition. And in the DDR system, the score of image which uses AEC is a little higher than the score which doesn't use it. Especially it can be known that the function of AEC of DDR is useful to improve the image quality in the part of skull and chest. (The function of AEC : It is the tool that detects the ionized current of x-ray which goes through objects with using the ion chamber which is in the detector. Also it controls the examination of X-ray when the proper density is reached.) Because the proper degree of density can be represented by this system, the photographing can be taken much easily without consideration of the exposure condition with the thickness of various objects. From the result of this experiment, it can be known that the selection of proper exposure condition plays an important rule to gain good Image Quality. More researches will be necessary about DDR system which has potential ability in the future.

• Journal of Institute of Control, Robotics and Systems
• /
• v.15 no.12
• /
• pp.1192-1196
• /
• 2009

Recently, the environment contamination problem and energy saving are the social issues. So, the Green IT based Smart Grid was suggested. The smart grid will let rates fluctuate even more dynamically, depending on conditions using energy. Thus, green IT includes the dimensions of environmental sustainability and the economics of energy efficiency. The smart controller in which it is controlled by DR in order to manage the energy consumption by using AMI is needed in order to apply its technology to the real life. In this paper, DR_WTIM of the IEEE1451.5 base which has the DR function for connecting to AMI of the wireless base is developed. By using this apparatus for the power control system, the energy saving effect is shown. Moreover, by using the IEEE1451.5 technology, the problem of energy consumption is solved in order to apply to power controller designed for efficient use energy.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.14 no.4
• /
• pp.147-155
• /
• 2006

The drag reduction (DR) and heat transfer efficiency reduction (ER) of non-ionic surfactant were investigated as a function of fluid velocity, temperature, and surfactant concentration. An experimental apparatus consisting of two temperature controlled water storage tanks, pumps, test specimen pipe and the piping network, two flow meters, two pressure gauges, a heat exchanger, and data logging system was built. From the experimental results, it was concluded that existing alkyl ammonium surfactant (CTAC Cethyl Trimethyl Ammonium Chloride) had DR of $0.6{\sim}0.8$ at $1,000{\sim}2,000ppm$ concentration with fluid temperature ranging between $50{\sim}60^{\circ}C$. However, the DR was very low when the fluid temperature was $70{\sim}80^{\circ}C$. The new amine oxide and betaine surfactant(SAOB Stearyl Amine Oxide + Betaine) had lower DR at fluid temperatures ranging between $50{\sim}60^{\circ}C$ compared with CTAC. However, with fluid temperature ranging between $70{\sim}80^{\circ}C$ the DR was $0.6{\sim}0.8$ when the concentration level was $1,000{\sim}2,000ppm$.

• Speech Sciences
• /
• v.1
• /
• pp.213-223
• /
• 1997

This paper deals with a general review of Mieko S. Han, who made a significant contribution to the studies of Korean phonetics during the 1960' s and early 1970' s. As both a single and joint author, Dr. Han published important papers in both quantity and quality, which have been cited among Korean phoneticians until today. Before Dr. M. Han' s work, professor of USC in the department of East Asian Languages & Cultures, there were only a few phonetics-related publications in Korea, most of which are papers or books based on non-experimental traditional approach. It is known that there was coexistence between traditionalism and structuralism in the field of Korean linguistics. It was, however, fortunate that we had two important phoneticians (M. Han and Chin-W Kim) abroad at that time. Mieko Han' s concern was to investigate experimental characteristics of the system of Korean vowels and consonants using a Spectrograph, which was the single most important tool for analysing phonetic data at that time. Dr. Han conducted her experimental studies on Korean phonetics, mostly funded by the Office of Naval Research, in terms of duration, fundamental frequency, Voice Onset Time (VOT), intensity, and so on. This paper aims to re-appreciate Dr. Han's specific contribution to the study of Korean phonetics since she played an important role as a pioneer of early Korean phonetics. Further, it is highly recommended that Dr. Han's works can be extremely useful for a graduate student, who seriously would like to specialize in Korean phonetics in the first step.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.19 no.2
• /
• pp.133-141
• /
• 2007

The drag reduction (DR) and heat transfer efficiency reduction (HTER) of nonionic surfactant according to the fluid velocity, temperature and surfactant concentration were investigated experimentally. For this study, several kinds of new surfactant which contains amine-oxide and betaine were developed. And experimental apparatus equipped with two water storage tanks temperature controlled, pumps, testing pipe network, two flowmeters, two pressure gauges, heat exchanger, and data logging system was built. Results showed that existing alkyl ammonium surfactant (CTAC) had DR of $0.6{\sim}0.8$ for $1,000{\sim}2,000\;ppm$ in fluid temperature of $50{\sim}60^{\circ}C$ and had very low DR in fluid temperature over $70^{\circ}C$. And new amino oxide and betaine surfactant (SAOB) had lower DR in fluid temperature of $50{\sim}60^{\circ}C$ compared with CTAC but in fluid temperature of $70{\sim}80^{\circ}C$ DR was $0.6{\sim}0.8$ for 1$1,000{\sim}2,000\;ppm$.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2006.11a
• /
• pp.613-616
• /
• 2006

본 연구에서는 신 수요관리 기법인 DR(Demand Response)시스템의 개발 및 운영현황을 알아 보았다. 특히 DR 시스템의 구성 방안과 각 모듈들의 설계시 검토 및 요구 사항을 분석하였다. 그리고 공급자와 수요자를 잇는 네트워크는 국가전력 IT과제에서 Portal의 개념을 도입하여 CP(Consumer Portal) 및 DP(Device Portal)에 의한 채널의 표준화를 시도하고 있다. DR의 개념은 수요관리와 가격 응답으로 공급자의 관리 기능과 가격 또는 인센티브 등이 제공되는 수요자가 참여하는 서비스의 양면을 가지고 있다. 이와 같은 시스템이 개발될 경우에는 전력사와 소비자 사이의 양방향 통신 채널이 형성되고 따라서 실시간 수요의 측정이 가능해진다. 또한 이를 토대로 DR 시스템을 사전 검토 및 계획상의 문제점을 분석하여 한국형 DR 시스템의 개발에 대한 기반을 조성하고자 하였다.

• Journal of Advanced Navigation Technology
• /
• v.14 no.6
• /
• pp.791-799
• /
• 2010

In this paper, integrated navigation algorithm is designed for land transport sector which is needed high accuracy and monitoring program is developed for lane departure warning. High accuracy position information which is possible lane separation is needed for lane departure warning, so position detection algorithm based GPS/DR which combine GPS with dead reckoning is proposed. For the verification of the designed integrated navigation algorithm, we drived to acquire data and showed post-processing experiment results with monitoring program. Vehicle driving movie and aerial photograph in monitoring program is designed to show lane keeping and lane separation.

• Journal of Radiation Protection and Research
• /
• v.38 no.1
• /
• pp.29-36
• /
• 2013

The aim of this study was to determine the correlation between exposure index (EI) and dose factors related to radiation dose optimization in digital radiography (DR) system. Two phantoms with built-in regional test object for quantitative assessment of images were used to produce image signals that acquired in chest radiography background. EI and entrane surface dose (ESD) increased proportionally with rise of radiation dose (kVp, mAs) in both DR and CR systems. Especially, DR detector was effective to form good contrast and hence, reached easily to improvement of image quality with minimal dose changes. It made operators possible to expect the accuracy of EI values deeply related to absorbed dose of the detector. The evaluation of images was obtained specially employed calculation of noise to signal ratio (NSR) and contrast to noise ratio (CNR). These measurements were performed for how exposure factors affect image quality. NSR was inversely proportional to kVp and mAs and low NSR represented high signal detection efficiency. Consequently, EI values was the measure of the amount of exposure received by the image receptor and it was proportional to exposure factors. Therefore the EI in a recommended range from manufacturer can offer optimal image quality. Also, continuous monitoring of EI values in the digital radiography can reduce the unnecessary patient dose and help the quality control of the system.

• Journal of Institute of Control, Robotics and Systems
• /
• v.7 no.5
• /
• pp.454-464
• /
• 2001

In this paper, a personal navigation system is developed using GPS and dead reckoning sensors. This personal navigation system can be used to track a person inside a building, on an urban street, and in the mountain area. GPS can provide accurate absolute position information, but it cant be used without receiving enough satellite signals. Although the inertial sensors such as gyro an accelerometer and be used without this diggiculty, the inertial sensors severely suffer from their drift errors and the magne-tometer can be easily distorted by surrounding electromagnetic field. GPS and DR sensors can be inte-grated together to overcome these problems. A new personal navigation system that can be carried wit person is developed. A pedometer. actually vertically mounted accelerometer, detects ones footstep and gyro detects heading angle. These DR sensors are integrated with GPS and the humans walking pattern provides additional navigation information for compensating the DR sensors. The field testes are performed to evaluated the proposed navigation algorithm.