• Progress in Medical Physics
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• v.8 no.1
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• pp.53-67
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• 1997

General hospitals have being under the influence of various and specific environment of electromagnetic field. The factors are development of medical electric equipment and device with enlarged functional demands, in high power and multi-frequency. It has all of both faces, EMI(electromagnetic interference) and EMS(electromagnetic susceptibility). In additional, expansion of personal communication system(cellular phone) has many unreliable factor of using time and area, making noise of electromagnetic fields. We studied actual conditions of EMI in the medical site, where is numerous medical equipment, especially central operation room and ICU(intensive care unit), AKR(artificial kidney room : hemo-dialysis unit), etc. The influence, most of medical equipments made electromagnetic nosie has various factors in its band of frequency, harmonics and strength. In the experimental use of electro-surgical unit and cellular phone, noticeable and considerable noise of eletromagnetic fields were measured. All of that can make trouble and errors on the steadiness of bioelectrical devices. In conclusion, It is necessary to reconsiderations of reallocating EMI source vs. EMS factor, and set to definite forbiding area of using cellular phone. For maintenance of steady normal conditions, in spite of existing any other legal standards of safty level, it need considering all of alternative electromagnetic situations on a case-by-case basis.

• Geophysics and Geophysical Exploration
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• v.2 no.1
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• pp.17-25
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• 1999

A traveltime tomography has been carried out by transforming electromagnetic data in frequency domain to wave-like domain. The transform uniquely relates a field satisfying a diffusion equation to an integral of the corresponding wavefield. But direct transform of frequency domain magnetic fields to wave-field domain is ill-posed problem because the kernel of the integral transform is highly damped. In this study, instead of solving such an unstable problem, it is assumed that wave-fields in transformed domain can be approximated by sum of ray series. And for further simplicity, reflection and refraction energy compared to that of direct wave is weak enough to be neglected. Then first arrival can be approximated by calculating the traveltime of direct wave only. But these assumptions are valid when the conductivity contrast between background medium and the target anomalous body is low enough. So this approach can only be applied to the models with low conductivity contrast. To verify the algorithm, traveltime calculated by this approach was compared to that of direct transform method and exact traveltime, calculated analytically, for homogeneous whole space. The error in first arrival picked by this study was less than that of direct transformation method, especially when the number of frequency samples is less than 10, or when the data are noisy. Layered earth model with varying conductivity contrasts and inclined dyke model have been successfully imaged by applying nonlinear traveltime tomography in 30 iterations within three CPU minutes on a IBM Pentium Pro 200 MHz.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.4
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• pp.34-40
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• 2004

In this paper, we have studied the OCT(Optical Coherence Tomography) system which has been advantages of high resolution, 2-D cross-sectional images, low cost and small size configuration. The characteristics of light source determine the resolution and coherence length. The light source has a commercial SLD with a central wavelength of 1,285 ill11, 35.3 nm(FWHM). The optical delay line is necessary to make equal with the optical path length to scattered light or reflected light from a sample. In order to make equal the optical path length, the stage that is attached to a reference mirror is controled by a step motor. And the interferometer is configured with the Michelson interferometer by using a single mode fiber, and the scanner can be focused on the sample by using a reference ann Also, the 2-dimension cross-sectional images were measured with scanning the transverse direction of the sample by using a step motor. After detecting the internal signal of lateral direction, a scanner is moved to obtain the cross-sectional image of 2-dimension by using step motor. A photodiode, which has high detection sensitivity and excellent noise characteristics has been used. The detected small signal has a noise and interference. After filtering and amplifying the signal, the output signal is demodulated the waveform And then, a cross-sectional image is seen through converting this signal into a digitalized signal by using an AID converter. The resolution of the sample is about 30${\mu}{\textrm}{m}$, which corresponds to the theoretical resolution. Also, the cross-sectional images of onion cells were measured in real time scheme.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.2
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• pp.85-90
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• 2012

In this paper, we compared and analyzed 3D silicon-oxide-nitride-oxide-silicon (SONOS) multi layer flash memory devices fabricated on nitride or oxide layer, respectively. The device fabricated on nitride layer has inferior electrical properties than that fabricated on oxide layer. However, the device on nitride layer has faster program / erase speed (P/E speed) than that on the oxide layer, although having inferior electrical performance. Afterwards, to find out the reason why the device on nitride has faster P/E speed, 1/f noise analysis of both devices is investigated. From gate bias dependance, both devices follow the mobility fluctuation model which results from the lattice scattering and defects in the channel layer. In addition, the device on nitride with better memory characteristics has higher normalized drain current noise power spectral density ($S_{ID}/I^2_D$>), which means that it has more traps and defects in the channel layer. The apparent hooge's noise parameter (${\alpha}_{app}$) to represent the grain boundary trap density and the height of grain boundary potential barrier is considered. The device on nitride has higher ${\alpha}_{app}$ values, which can be explained due to more grain boundary traps. Therefore, the reason why the devices on nitride and oxide have a different P/E speed can be explained due to the trapping/de-trapping of free carriers into more grain boundary trap sites in channel layer.

• Geophysics and Geophysical Exploration
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• v.20 no.1
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• pp.33-42
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• 2017

Recently, the grounded electrical-source airborne transient electromagnetic (GREATEM) system with high power source was introduced to achieve deeper investigation depth and to overcome high noise level. Although the GREATEM is a transient electromagnetic system using a long grounded wire as the transmitter, GREATEM data have been interpreted with 1D earth models because 2D or 3D modeling and inversion of vast airborne data are complicated and expensive to calculate. Generally, 1D inversion is subsequently applied to every survey point and combining 1D images together forms the stitched conductivity-depth image. However, the stitched models often result in abrupt variations in neighboring models. To overcome this problem, laterally constrained inversion (LCI) has been developed in inversion of ATEM data, which can yield layered sections with lateral smooth transitions. In this study, we analysed the GREATEM data through 1D numerical modeling for a curved grounded wire source. Furthermore, we developed a laterally constrained inversion scheme for continuous GREATEM data based on a layered earth model. All 1D data sets and models are inverted as one system, producing layered sections with lateral smooth transitions. Applying the developed LCI technique to the GREATEM data, it was confirmed that the laterally constrained inversion can provide laterally smooth model sections that reflect the layering of the survey area effectively.

• 전기의세계
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• v.43 no.1
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• pp.13-19
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• 1994

전자식 안정기는 최근 에너지 절약 정책과 관련하여 조명기기분야의 관심의 대상이 되었고, 절전 효율이 높은 고품질의 전자식 안정기에 대한 연구 개발 및 보급이 점점 더 확대되고 있는 추세이다. 일반적으로 전자식 안정기는 수십 KHz의 고주파에서 형광등을 구동시킴으로써 빛의 깜박거림과 가청잡음이 없으며, 저주파(60Hz)에서 사용하는 재래식 안정기(choke coil 방식)에 비해 높은 절전 효과를 얻을 수 있다[1-4]. 특히, 빌딩 사무실의 경우 낮에도 창가의 형광등이 켜져 있어서 막대한 전력을 낭비하고 있는 실정이므로, 일조량에 따른 자동 전력 조절이 가능한 전자식 형광등의 출현이 기대되고 있다. 전자식 안정기의 보급 확대를 위해서는 절전 효과 뿐만 아니라, 품질 문제, 수명 문제등을 고려하여야 하는 바, 예를 들면 순간 점등으로 방전초기의 sputtering 현상에 의한 lamp의 수명 단축, 미소 입력전압 변동에 따른 급격한 광출력의 변화로 절전 효과의 상실과 이상동작에 의한 스위칭 소자의 파괴 현상, 고주파 스위칭시 발생되는 전력손실과 noise등에 대한 대책이 요구되고 있다. 이러한 점을 개선하기 위해 추가되는 회로는 전자식 안정기 시스템을 더욱 복잡하게 만들고, 경제적으로 원가 부담을 주기 때문ㅇ 고품질의 전자식 안정기를 보급하는데 어려운 점으로 부각되고 있다. 본 고에서는 이러한 문제를 해결하기 위하여 조광기능을 포함한 다양한 제어회로와 보호회로를 조광기능을 포함한 다양한 제어회로와 보호회로를 1 chip에 수용하는 고품질의 전자식 안정기 제어용 집적회로에 대해서 기술하고자 한다.되어 나아갈 기술의 조류에도 부합하는 형태라 하겠다. 그러나 이 방식은 기 언급한 바와 같이 분산처리를 관장하는 운영체계의 개발에 상당한 고전이 따르리라 보여지며, 또한 보다 상세한 연구가 선행되어야 하겠지만 개발된 상용의 통신 프로토콜로서는 병렬처리의 성능을 극대화 하기에는 여러가지 제약이 있을 것으로 예측된다.기기들이 어떻게 응용되고 있는지 살펴보기로 하자. real informations would be available. Results are compared with those of optimal power flows.기능시험을 완료했으며 실제 line-of-sight(LOS) 시스템 구현에 적용중이다. 시대를 살아 갈 회원들이다. '컨텐츠의 시대'가 개막되는 것이며, 신세기통신과 SK텔레콤은 선의의 경쟁 과 협력을 통해 이동인터넷 서비스의 컨텐츠를 개발해 나가게 될 것이다. 3배가 높았다. 효소 활성에 필수적인 물의 양에 따른 DIAION WA30의 라세미화 효율에 관하여 실험한 결과, 물의 양이 증가할수록 그 효율은 감소하였다. DIAION WA30을 라세미화 촉매로 사용하여 아이소옥탄 내에서 라세믹 나프록센 2,2,2-트리플로로에틸 씨오에스터의 효소적 DKR 반응을 수행해 보았다. 그 결과 DIAION WA30을 사용하지 않은 경우에 비해 반응 전환율과 생성물의 광학 순도는 급격히 향상되었다. 전통적 광학분할 반응의 최대 50%라는 전환율의 제한이 본 연구에서 찾은 DIAION WA30을 첨가함으로써 성공적으로 극복되었다. 또한 고체 염기촉매인 DIAION WA30의 사용은 라세미화 촉매의

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.278-284
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• 1998

This paper describes a l0b CMOS A/D converter (ADC) for HDTV applications. The proposed ADC adopts a typical multi-step pipelined architecture. The proposed circuit design techniques are as fo1lows: A selective channel-length adjustment technique for a bias circuit minimizes the mismatch of the bias current due to the short channel effect by supply voltage variations. A power reduction technique for a high-speed two-stage operational amplifier decreases the power consumption of amplifiers with wide bandwidths by turning on and off bias currents in the suggested sequence. A typical capacitor scaling technique optimizes the chip area and power dissipation of the ADC. The proposed ADC is designed and fabricated in s 0.8 um double-poly double-metal n-well CMOS technology. The measured differential and integral nonlinearities of the prototype ADC show less than ${\pm}0.6LSB\;and\;{\pm}2.0LSB$, respectively. The typical ADC power consumption is 119 mW at 3 V with a 40 MHz sampling rate, and 320 mW at 5 V with a 50 MHz sampling rate.

• Journal of IKEEE
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• v.14 no.1
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• pp.65-74
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• 2010

The Digital TV(DTV) standard has ushered in a new era in TV broadcasting and raised a great demand for DTV tuners. There are many challenges in designing a DTV tuner, of which the most difficult part is the frequency synthesizer. This paper presents the design of a frequency synthesizer for DTV Tuners in a $0.18{\mu}m$ CMOS process. It satisfies the DTV(ATSC) frequency band(54~806MHz). A scheme is proposed to cover the full band using only one VCO. The VCO has been designed to operate at 1.6~3.6GHz band such that the LO pulling effect is minimized, and reliable broadband characteristics have been achieved by reducing the variations of VCO gain and frequency step. The simulation results show that the designed VCO has gains of 59~94MHz(${\pm}$17.7MHz/V,${\pm}$23%) and frequency steps of 26~42.5MHz(${\pm}$8.25MHz/V,${\pm}$24%), and a very wide tuning range of 76.9%. The designed frequency synthesizer has a phase noise of -106dBc/Hz at 100kHz offset, and the lock time is less than $10{\mu}$sec. It consumes 20~23mA from a 1.8V supply, and the chip size including PADs is 2.0mm${\times}$1.8mm.

• Journal of IKEEE
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• v.14 no.1
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• pp.25-32
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• 2010

In this paper, we analyze the location accuracy of real-time locating systems (RTLS) in multipath environments, where the RTLS complies with an ISO/IEC 24730-2 international standard. RTLS readers should have an ability not only to recover the transmitted signal but also provide arrival timing information from the received signal. In the multipath environments, in general, the transmitted signal goes through both direct and indirect paths, and then it becomes some distorted form of the transmitted signal. Such multipath components have a critical effect on deciding the first arrival timing of the received signal. To analyze the location error of the RTLS in the multipath environments, we assume two multipath components without considering an additive white Gaussian noise. Through the simulation and real test results, we confirm that the location error does not occur when the time difference between two paths is more than 1.125Tc, but the location error of about 2.4m happens in case of less than 0.5Tc. In particular, we see that the resolvability of two different paths depends largely on the phase difference for the time difference of less than 1Tc.

• Journal of Astronomy and Space Sciences
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• v.14 no.2
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• pp.312-319
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• 1997

The magnetometer is one of the most important payloads for scientific satellite to monitor the near-earth space environment. The electromagnetic variations of the space environment can be observed with the electric and magnetic field measurements. In practice, it is well known that the measurement of magnetic fields needs less technical complexities than that of electric fields in space. Therefore the magnetometer has long been recognized as one of the basic payloads for the scientific satellites. In this paper, we discuss the scientific fluxgate magnetometer which will be on board the KITSAT-3. The main circuit design of the present magnetometer is based on that of KITSAT-1 and -2 but its facilities have been re-designed to improve the resolution to about 5nT for scientific purpose. The calibration and noise level test of this circuit have been performed at the laboratory of the Tierra Tecnica company in Japan.