• 제목/요약/키워드: electrical resistivity method

검색결과 839건 처리시간 0.025초

High Resolution HC$_3$N Observations toward the Central Region of Sagittarius B2

  • H.S-Ching;Oh, M.ishi;M.Morimoto
    • 한국우주과학회:학술대회논문집(한국우주과학회보)
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    • 한국우주과학회 1993년도 한국우주과학회보 제2권2호
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    • pp.17-17
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    • 1993
  • The wall shear stress in the vicinity of end-to end anastomoses under steady flow conditions was measured using a flush-mounted hot-film anemometer(FMHFA) probe. The experimental measurements were in good agreement with numerical results except in flow with low Reynolds numbers. The wall shear stress increased proximal to the anastomosis in flow from the Penrose tubing (simulating an artery) to the PTFE: graft. In flow from the PTFE graft to the Penrose tubing, low wall shear stress was observed distal to the anastomosis. Abnormal distributions of wall shear stress in the vicinity of the anastomosis, resulting from the compliance mismatch between the graft and the host artery, might be an important factor of ANFH formation and the graft failure. The present study suggests a correlation between regions of the low wall shear stress and the development of anastomotic neointimal fibrous hyperplasia(ANPH) in end-to-end anastomoses. 30523 T00401030523 ^x Air pressure decay(APD) rate and ultrafiltration rate(UFR) tests were performed on new and saline rinsed dialyzers as well as those roused in patients several times. C-DAK 4000 (Cordis Dow) and CF IS-11 (Baxter Travenol) reused dialyzers obtained from the dialysis clinic were used in the present study. The new dialyzers exhibited a relatively flat APD, whereas saline rinsed and reused dialyzers showed considerable amount of decay. C-DAH dialyzers had a larger APD(11.70${\pm}$1.32mmHg/min)compared to CF dialyzers(4.32${\pm}$0.55mmHg/min)(p<0.05). However, there was no observable difference in the UFR between the two dialyzers. Neither APD nor UFR showed any significant increase with an increasing number of reuses for up to more than 20reuses. A substantial number of failures observed in APD(larger than 20mmHe/min)on the reused dialyzers(2 out of 40 CP and S out 26 C-DAK) were attributed to the Possible damage on the fibers. The CF 15-11 HFDs which failed APD test did not show changes in the UFR compared to normal dialyzers indicating that APD is a more sensitive test than UFR test to evaluate the integrity of the fibers. 30527 T00401030527 ^x For quantitative measurement of reflected light from a clinical diagnostic strip, a prototype old reflectance photometer was designed. The strip loader and cassette were made to obtain more accurate reflectance parameters. The strip was illuminated at 45˚c through optical fiber and the intensity of reflected light was determined at rectanguLat angle using a photodiode. The kubelka-munk coefficient and reflection optical density were determined ar four different wavelengths(500,550,570 and 610nm) for blood glucose strip. For higher concentration than 300mg/41 about glucose, a saturation state of abforbance was observed at 500,550 and 570nm. The correlation between glucose concentration and parameters was the best at 610nm. 30535 T00401030535 ^x Radiation-induced fibrosarcoma tumors were grown on the flanks of C3H mice. The mice were divided into two groups. One group was injected with Photofrin II, intravenously (2.5mg/kg body weight). The other group received no Photofrin II. Mice from both groups were irradialed for approximately 15 minutes at 100,300, or 500 mW/cm2 with the argon (488nm/514.5 nm), dye(628nm) and gold vapor (pulsed 628 nm) laser light. A photosensitizer behaved as an added absorber. Under our experimental conditions, the presence of Photolfrin II increased surface temperature by at least 40% and the temperature rise due to 300 mW/cm2 irradiation exceeded values for hyperthermia. Light and temperature distributions with depth were estimated by a computer model. The model demonstrated the influence of wavelength on the thermal process and proved to be a valuable tool to investigate internal temperature rise. 30536 T00401030536 ^x We investigated the structural geometry of thirty-eight Korean femurs. The purpose of this study is to identify major geometrical differences between Korean femurs 3nd others that we believe belong to Caucasians so that we would be able to get insights into the femoral component design that fits Asians including Koreans. We utilized computerized tomography (CT) images of femurs extracted from cadavers. The CT images were transformed into bitmap data by using a film scanner, and then analyzed by using a commercially available software called Image v.1.0 and a Macintosh IIci computer.The resulting data were compared with already published data. The major results show that the geometry of the Korean femurs is significantly different from that of Caucasians: (1) the anteversion angle and the canal flare index are greater by the amount of approximately 8˚ and 0.5, respectively, (2) the shape of the isthmus cross section is more round, and (3) the distance between the teaser trochanter and the proximal border of the isthmus is shelter by about 15 mm. The results suggested that the femoral component suitable for Asians should be different from the currently-used components designed and manufactured mostly by European or American companies. 30537 T00401030537 ^x It is well known that nonlinear propagation characteristics of the wave in the tissue may give very useful information for the medical diagnoisis. In this paper, a new method to detect nonlinear propagation characteristics of the internal vibration in the tissue for the low frequency mechanical vibration by using bispectral analysis is proposed. In the method, low frequency vibration of f0( = 100Hz) is applied on the surface of the object, and the waveform of the internal vibration x (t) is measured from Doppler frequency modulation of silmultaneously transmitted probing ultrasonic waves. Then, the bispectra of the signal x (t) at the frequencies (f0, f0) and (f0, 2f0) are calculated to estimate the nonlinear propagation characteristics as their magnitude ratio, w here since bispectrum is free from the gaussian additive noise we can get the value with high S/N. Basic experimental system is constructed by using 3.0 MHz probing ultrasonic waves and the several experiments are carried out for some phantoms. Results show the superiority of the proposed method to the conventional method using power spectrum and also its usefulness for the tissue characterization. 30541 T00401030541 ^x This paper describes the implementation of a computerized radial pulse diagnosis by aids of a clinical expert. On this base, we composed of the radial pulse diagnosis system in korean traditional medicine. The system composed of a radial pulse wave detection system and a radial pulse diagnosis system. With a detection system, we detected Inyoung and Cheongu radial pulse wave and processed it. Then, we have got the characteristic parameters of radial pulse wave and also quantified that according to the method of Inyoung-Cheongu Comparison Radial Pulse Diagnosis. We defined the jugement standard of radial pulse diagnosis system and then we confirmed the possibility for realization of automatic radial pulse diagnosis in korean traditional medicine. 30545 T00401030545 ^x Microspheres are expected to be applied to biomedical areas such as solid-phase immunoassays, drug delivery systems, immunomagnetic cell separation. To synthesize microspheres for biomedical application, "two stage shot growth method" was developed. The uniformity ratio of synthesized microspheres was always smaller than 1.05. And the surface charge density (or the number of ionizable functional groups) of the microspheres synthesized by "two stage shot growth method" was 6~13 times higher than that of the microspheres synthesized by conventional seeded batch copolymerization. As a previous step for biomedical application, adsorption experiments of bovine albumin on microspheres were carried out under various conditions. The maximum adsorbed amount was obtained in the neighborhood of pH 4.5. Isoelectric point of bovine albumin is pH 5.0, so experimental result shows that it shifted to acid area. The adsorption isotherm was obtained, the plateau region was always reached at 2.Og/L (bulk concentration of bovine albumin).The effect of the kind and the amount of surface functional group was also examined. 30575 T00401030575 ^x A medical image workstation was developed using multimedia technique. The system based on PC-486DX was designed to acquire medical images produced by medical imaging instruments and related audio information, that is, doctors' reporting results. Input information was processed and analyzed, then the results were presented in the form of graph and animation. All the informations of the system were hierarchically related with the image as the apex. Processing and analysis algorithms were implemented so that the diagnostic accuracy could be improved. The diagnosed information can be transferred for patient diagnosis through LAN(local area network). 30592 T00401030592 ^x In the conventional infrared imaging system, complex infrared lens systems are usually used for directing collimated narrow infrared beams into the high speed 2-dimensional optic scanner. In this paper, a simple reflective infrared optic system with a 2-dimensional optic scanner is proposed for the realization of medical infrared thermography system. It has been experimentally proven that the intfrared thermography system composed of the proposed optic system has the temperature resolution of 0.1˚c under the spatial resolution of lmrad, the image matrix size of 256 X 240, and tile imaging time of 4 seconds. 30593 T00401030593 ^x In this paper, MIIS (Medical Image Information System) has been designed and implemented using INGRES RDBMS, which is based on a client/server architecture. The implemented system allows users to register and retrieve patient information, medical images and diagnostic reports. It also provides the function to display these information on workstation windows simultaneously by using the designed menu-driven graphic user interface. The medical image compression/decompression techniques are implemented and integrated into the medical image database system for the efficient data storage and the fast access through the network. 30594 T00401030594 ^x In this paper, computerized BEAM was implemented for the space domain analysis of EEG. Trans-formation from temporal summation to two-dimensional mappings is formed by 4 nearest point inter-polaton method. Methods of representation of BEAM are two. One is dot density method which classify brain electrical potential 9 levels by dot density of gray levels and the other is colour method which classify brain electrical 12 levels by red-green colours. In this BEAM, instantaneous change and average energy distribution over any arbitrary time interval of brain electrical activity could be observed and analyzed easily. In the frequency domain, the distribution of energy spectrum of a special band can easily be distinguished normality and abnormality. 30608 T00401030608 ^x Laboratory information system (LIS) is a key tool to manage laboratory data in clinical pathology. Our department has developed an information system for routine hematology using down-sized computer system. We have used an IBM 486 compatible PC with 16MB main memory, 210 MB hard disk drive, 9 RS-232C port and 24 pin dot printer. The operating system and database management system were SCO UNIX and SCO foxbase, respectively. For program development, we used Xbase language provided by SCO foxbase. The C language was used for interface purpose. To make the system use friendly, pull-down menu was used. The system connected to our hospital information system via application program interface (API), so the information related to patient and request details is automatically transmitted to our computer. Our system interfaced with fwd complete blood count analyzers(Sysmex NE-8000 and Coulter STKS) for unidirectional data tansmission from analyzer to computer. The authors suggests that this system based on down-sized computer could provide a progressive approach to total LIS based on local area network, and the implemented system could serve as a model for other hospital's LIS for routine hematology. 30609 T00401030609 ^x To develop an artificial bone substitute that is gradually degraded and replaced by the regenerated natural bone, the authors designed a composite that is consisted of calcium phosphate and collagen. To use as the structural matrix of the composite, collagen was purified from human umbilical cord. The obtained collagen was treated by pepsin to remove telopeptides, and finally, the immune-free atelocollagen was produced: The cross linked atelocollagen was highly resistant to the collagenase induced collagenolysis. The cross linked collagen demonstrated an improved tensile strength. 30618 T00401030618 ^x This paper is a study on the design of adptive filter for QRS complex detection. We propose a simple adaptive algorithm to increase capability of noise cancelation in QRS complex detection with two stage adaptive filter. At the first stage, background noise is removed and at the next stage, only spectrum of QRS complex components is passed. Two adaptive filters can afford to keep track of the changes of both noise and QRS complex. Each adaptive filter consists of prediction error filter and FIR filter The impulse response of FIR filter uses coefficients of prediction error filter. The detection rates for 105 and 108 of MIT/BIH data base were 99.3% and 97.4% respectively. 30619 T00401030619 ^x To develop an artificial bone substitute that is gradually degraded and replaced by the regenerated natural bone, the authors designed and produced a composite that is consisted of calcium phosphate and collagen. Human umbilical cord origin pepsin treated type I atelocollagen was used as the structural matrix, by which sintered or non-sintered carbonate apatite was encapsulated to form an inorganic-organic composite. With cross linking atelocollagen by UV ray irradiation, the resistance to both compressive and tensile strength was increased. Collagen degradation by the collagenase induced collagenolysis was also decreased. 30620 T00401030620 ^x We have developed a monoleaflet polymer valve as an inexpensive and viable alternative, especially for short-term use in the ventricular assist device or total artificial heart. The frame and leaflet of the polymer valve were made from polyurethane, To evaluate the hemodynamic performance of the polymer valve a comparative study of flow dynamics past a polymer valve and a St. Jude Medical prosthetic valve under physiological pulsatile flow conditions in vitro was made. Comparisons between the valves were made on the transvalvular pressure drop, regurgitation volume and maximum valve opening area. The polymer valve showed smaller regurgitation volume and transvalvular pressure drop compared to the mechanical valve at higher heart rate. The results showed that the functional characteristics of the polymer valve compared favorably with those of the mechanical valve at higher heart rate. 30621 T00401030621 ^x Explosive evaporative removal process of biological tissue by absorption of a CW laser has been simulated by using gelatin and a multimode Nd:YAG laser. Because the point of maximun temperature of laser-irradiated gelatin exists below the surface due to surface cooling, evaporation at the boiling temperature is made explosively from below the surface. The important parameters of this process are the conduction loss to laser power absorption (defined as the conduction-to-laser power parameter, Nk), the convection heat transfer at the surface to conduction loss (defined as Bi), dimensionless extinction coefficient (defined as Br.), and dimensionless irradiation time (defined as Fo). Dependence of Fo on Nk and Bi has been observed by experiment, and the results have been compared with the numerical results obtained by solving a 2-dimensional conduction equation. Fo and explosion depth (from the surface to the point of maximun temperature) are increased when Nk and Bi are increased.To find out the minimum laser power for explosive evaporative removal process, steady state analysis has been also made. The limit of Nk to induce evaporative removal, which is proportional to the inverse of the laser power, has been obtained. 30622 T00401030622 ^x N1 and N2 gross neural action potentials were measured from the round window of the guinea pig cochlea at the onset of the acoustic stimuli. N1-N2 audiograms were made by means of regulating stimulant intensities in order to produce constant N1-N2 potentials as criteria for different input tone pip frequencies. The lowest threshold was measured with an input tone pip I5 dB SPL in intensity and 12 KHz in frequency when the animal was in normal physiological condition. The procedure of experimental measurements is explained in detail. This experimental approach is very useful for the investigation of the Cochlear function. Both noN1inear and active functions of the Cochlea can be monitored by N1-N2 audiograms. 30623 T00401030623 ^x In electrical impedance tomography(EIT), we use boundary current and voltage measurements toprovide the information about the cross-sectional distribution of electrical impedance or resistivity. One of the major problems in EIT has been the inaccessibility of internal voltage or current data in finding the internal impedance values. We propose a new image reconstruction method using internal current density data measured by NMR. We obtained a two-dimensional current density distribution within a phantom by processing the real and imaginary MR images from a 4.77 NMR machine. We implemented a resistivity mage reconstruction algorithm using the finite element method and sensitivity matrix. We presented computer simulation results of the mage reconstruction algorithm and furture direction of the research. 30624 T00401030624 ^x A new method of digital image analysis technique for discrimination of cancer cell was presented in this paper. The object image was the Thyroid eland cells image that was diagnosed as normal and abnormal (two types of abnormal: follicular neoplastic cell, and papillary neoplastic cell), respectively. By using the proposed region segmentation algorithm, the cells were segmented into nucleus. The 16 feature parameters were used to calculate the features of each nucleus. A9 a consequence of using dominant feature parameters method proposed in this paper, discrimination rate of 91.11% was obtained for Thyroid Gland cells. 30625 T00401030625 ^x An electrical stimulator was designed to induce locomotion for paraplegic patients caused by central nervous system injury. Optimal stimulus parameters, which can minimize muscle fatigue and can achieve effective muscle contraction were determined in slow and fast muscles in Sprague-Dawley rats. Stimulus patterns of our stimulator were designed to simulate electromyographic activity monitored during locomotion of normal subjects. Muscle types of the lower extremity were classified according to their mechanical property of contraction, which are slow muscle (msoleus m.) and fast muscle (medial gastrocneminus m., rectus femoris m., vastus lateralis m.). Optimal parameters of electrical stimulation for slow muscles were 20 Hz, 0.2 ms square pulse. For fast muscle, 40 Hz, 0.3 ms square pulse was optimal to produce repeated contraction. Higher stimulus intensity was required when synergistic muscles were stimulated simultaneously than when they were stimulated individually. Electrical stimulation for each muscle was designed to generate bipedal locomotion, so that individual muscles alternate contraction and relaxation to simulate stance and swing phases. Portable electrical stimulator with 16 channels built in microprocessor was constructed and applied to paraplegic patients due to lumbar cord injury. The electrical stimulator restored partially gait function in paraplegic patients. 30626 T00401030626 ^x Two-Dimensional modelling of the Cochlear biomechanics is presented in this paper. The Laplace partial differential equation which represents the fluid mechanics of the Cochlea has been transformed into two-dimensional electrical transmission line. The procedure of this transformation is explained in detail. The comparison between one and two dimensional models is also presented. This electrical modelling of the basilar membrane (BM) is clearly useful for the next approach to the further. Development of active elements which are essential in the producing of the sharp tuning of the BM. This paper shows that two-dimension model is qualitatively better than one-dimensional model both in amplitude and phase responses of the BM displacement. The present model is only for frequency response. However because the model is electrical, the two-dimensional transmission line model can be extended to time response without any difficult. 30627 T00401030627 ^x A method has been proposed for the fully automatic detection of left ventricular endocardial boundary in 2D short axis echocardiogram using geometric model. The procedure has the following three distinct stages. First, the initial center is estimated by the initial center estimation algorithm which is applied to decimated image. Second, the center estimation algorithm is applied to original image and then best-fit elliptic model estimation is processed. Third, best-fit boundary is detected by the cost function which is based on the best-fit elliptic model. The proposed method shows effective result without manual intervention by a human operator. 30628 T00401030628 ^x The intelligent trajectory control method that controls moving direction and average velocity for a prosthetic arm is proposed by pattern recognition and force estimations using EMG signals. Also, we propose the real time trajectory planning method which generates continuous accelleration paths using 3 stage linear filters to minimize the impact to human body induced by arm motions and to reduce the muscle fatigue. We use combination of MLP and fuzzy filter for pattern recognition to estimate the direction of a muscle and Hogan's method for the force estimation. EMG signals are acquired by using a amputation simulator and 2 dimensional joystick motion. The simulation results of proposed prosthetic arm control system using the EMf signals show that the arm is effectively followed the desired trajectory depended on estimated force and direction of muscle movements. 30638 T00401030638 ^x A new neural network architecture for the recognition of patterns from images is proposed, which is partially based on the results of physiological studies. The proposed network is composed of multi-layers and the nerve cells in each layer are connected by spatial filters which approximate receptive fields in optic nerve fields. In the proposed method, patterns recognition for complicated images is carried out using global features as well as local features such as lines and end-points. A new generating method of matched filers representing global features is proposed in this network. 30659 T00401030659 ^x An implementation scheme of the magnetic nerve stimulator using a switching mode power supply is proposed. By using a switching mode power supply rather than a conventional linear power supply for charging high voltage capacitors, the weight and size of the magnetic nerve stimulator can be considerably reduced. Maximum output voltage of the developed magnetic nerve stimulator using the switching mode power supply is 3,000 volts and switching time is about 100 msec. Experimental results or human nerve stimulations using the developed stimulator are presented. 30768 T00401030768 ^x In this paper, we describe the design methodology and specifications of the developed module-based bedside monitors for patient monitoring. The bedside monitor consists of a main unit and module cases with various parameter modules. The main unit includes a 12.1" TFT color LCD, a main CPU board, and peripherals such as a module controller, Ethernet LAN card, video card, rotate/push button controller, etc. The main unit can connect at maximum three module cases each of which can accommodate up to 7 parameter modules. They include the modules for electrocardiograph, respiration, invasive blood pressure, noninvasive blood pressure, temperature, and SpO2 with Plethysmograph.

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Random Forest 기법을 이용한 도심지 MT 시계열 자료의 차량 잡음 분류 (Classification of Transport Vehicle Noise Events in Magnetotelluric Time Series Data in an Urban area Using Random Forest Techniques)

  • 권형석;류경호;심익현;이춘기;오석훈
    • 지구물리와물리탐사
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    • 제23권4호
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    • pp.230-242
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    • 2020
  • 201 6년 9월에 발생한 경주지진원 구역에 대한 정밀 지질구조 규명을 위해 MT 탐사를 적용하였다. 경주지역의 MT 측정자료는 조사지역 인근의 지하철, 전력선, 공장, 주택, 농경지에서 발생된 전기적 잡음과 철도, 도로에서의 차량잡음 등으로 인해 측정자료 왜곡이 심하게 발생되었다. 이 연구에서는 고속철도 및 고속도로와 인접한 4개소의 MT 탐사자료에 기계학습 기법을 적용하여 차량잡음이 포함된 시계열을 분류하였다. 고속열차 잡음이 포함된 시계열에 대해서는 확률적 경사 하강법, 서포트 벡터 머신과 랜덤 포레스트 3가지의 분류모델을 적용하여 그 결과를 비교하였다. 대형트럭 잡음이 포함된 시계열 자료에 대해서는 Hx 성분, Hy 성분과 Hx & Hy 합성성분 크기에 대한 3가지의 샘플 자료를 준비하였으며 랜덤 포레스트 분류모델을 구성하여 그 성능을 평가하였다. 마지막으로 차량잡음 제거 효과 분석을 위하여 차량잡음 제거 전후의 시계열, 진폭 스펙트럼과 겉보기비저항 곡선을 비교하였으며, 이를 통해 차량잡음이 영향을 미치는 주파수 대역과 차량잡음 제거 시 발생될 수 있는 문제점에 대해 고찰하였다.

바이오 상변화 Template 위한 전극기판 개발 (Developing the Electrode Board for Bio Phase Change Template)

  • 리학철;윤중림;이동복;김수경;김기범;박영준
    • Korean Chemical Engineering Research
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    • 제47권6호
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    • pp.715-719
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    • 2009
  • 본 연구에서는 DNA 정보를 상변화 물질의 전기저항 변화특성으로 검출할 수 있는 상변화 전극 기판을 개발하였다. 이를 위해 반도체 공정에서 사용하는 Al을 사용하여 전극 기판을 제작하였다. 하지만 주사전자현미경을 이용하여 Al 전극의 단면 상태를 확인해 본 결과 PETEOS(plasma enhanced tetraethyoxysilane) 내에서 보이드(void)가 발생하여 후속공정인 에치백과 세정공정 분위기에 과도하게 노출되어 심하게 손상되어 전극과 PETEOS 사이에 홀(hole)로 변형된다. 이 문제점을 해결하기 위하여 에치백 및 세정 공정을 진행하지 않으면서 $Ge_2Sb_2Te_5$(GST) 박막의 단차피복성(stepcoverage)을 좋게 할 수 있고, 열역학적으로 GST 박막과의 반응성을 고려했을 때 안정적이면서 비저항이 낮은 TiN 재료를 사용하여 상변화 전극 기판을 제작하였다. 주사전자현미경을 통하여 전극의 단면의 상태를 관찰하였으며 TiN 전극과 GST 박막이 정상적으로 연결되어 있는 것을 확인하였다. 또한 저항측정 장비를 사용하여 TiN 상변화 전극 기판 위에 증착된 GST의 비정질과 결정질의 저항을 측정하였고, GST의 비정질과 결정질저항의 차이는 약 1,000배 정도로 신호를 검출하는데 충분함을 확인하였다.

삼상 슬러리 기포탑의 세 기능영역 체류량 특성 (Holdup Characteristics of Three Functional Regions in a Slurry Bubble Column)

  • 장지화;임대호;강용;전기원
    • Korean Chemical Engineering Research
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    • 제48권3호
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    • pp.359-364
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    • 2010
  • 직경이 0.152 m인 삼상슬러리 기포탑에서 연속 슬러리상 영역(${\varepsilon}_f$), 기포영역(${\varepsilon}_b$) 그리고 기포의 후면에서 기포와 같이 상승하는 소용돌이 영역인 wake 영역(${\varepsilon}_w$)의 세 종류의 기능영역을 분류하여 이들 각 영역의 체류량을 구하였다. 기포탑에서 기포영역과 wake 영역의 체류량은 전기저항 탐침법에 의해 결정하였다. 기체유속($U_G$)과 슬러리상에서 고체입자의 농도($S_c$)가 삼상슬러리 기포탑에서 각 기능영역의 체류량에 미치는 영향을 검토하였다. 슬러리 기포탑에서 기체유속이 증가하면 연속 슬러리상의 체류량은 감소하였으나, 기포와 wake의 체류량은 증가하였다. 슬러리상에서 고체입자의 농도가 증가함에 따라 연속 슬러리상 영역의 체류량은 증가하였으나, 기포와 wake 영역의 체류량은 감소하는 경향을 나타내었다. wake 영역의 체류량은 기포영역 체류량의 15~40% 정도를 나타났으며, 기체유속이 증가함에 따라 wake 영역의 기포영역에 대한 분율은 감소하였다. 본 연구의 범위에서 세 기능영역의 체류량은 각각 실험 변수의 상관식으로 나타낼 수 있었다.

90% $Bi_2Te_3-10% Bi_2Se_3$ 단결정의 밴드갭 에너지와 열전특성 (Band-Gap Energy and Thermoelectric Properties of 90% $Bi_2Te_3-10% Bi_2Se_3$ Single Crystals)

  • 하헌필;현도빈;황종승;오태성
    • 한국재료학회지
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    • 제9권4호
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    • pp.349-354
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    • 1999
  • Dopant를 첨가하지 않은 시료와 donor dopant로 $CdI_2$를 첨가한 $Bi_2Te_3-10%$ 단결정을 Bridgman법으로 성장시키고 Hall 계수, 전하이동도, 전기비저향, Seebeck 계수, 열전도도 빛 성능지수를 77~600K의 온도범위에서 측정하였다. Dopant를 첨가하지 않은 90% $Bi_2Te_3-10% Bi_2Se_3$ 단결정에서 포화정공농도는 $5.85\times10_{18}cm^{-3}$ 이고 degenerate 온도는 127K 이었£며, 전하 이동에 대한 산란인자는 -0.23 이고 전자이동도와 정꽁이동도의 비 ($\mu_e/\mu_h)$는 1.45 이었다. 90% $Bi_2Te_3-10% Bi_2Te_3$ 단결정의 OK 에서의 밴드갭 에너지는 0.200 eV 로서 $Bi_2Te_3-Bi_2Se_3$계 단결정에서눈 $Bi_2Se_3$의 놓도가 증가할수록 밴 드갭 에너지가 증가하였다. Donor dopant로 $CdI_2$를 첨가한 90% $Bi_2Te_3-Bi_2Se_3$ 조성의 n형 단결정에서 성능지수의 최대값은 $CdI_2$를 0.05 wt% 첨가한 경우에 약 230K에서 $3.2\times10^{-3}/K$를 나타내었다.

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풍력 발전단지내 아두이노를 활용한 스마트 다기능 대지 고유 저항 측정 장치 개발 (Development of Smart Multi-function Ground Resistivity Measuring Device using Arduino in Wind Farm)

  • 김홍용;윤동기;신승중
    • 한국인터넷방송통신학회논문지
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    • 제19권6호
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    • pp.65-71
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    • 2019
  • 기존의 대지저항률과 접지저항 현장 측정 방식은 일정한 간격의 측정전극을 설치하여 전류를 인가하여 대지의 저항값에 따른 전압강하를 측정하게 되는데 현장 대지의 층상 구조가 특이성을 갖게 되면 역산 시 경계 조건의 오차를 발생하게 되고 접지 설계 시 중요한 대지저항률 분석이 시뮬레이션 상과 많은 차이를 보이게 된다. 본 연구는 정보통신 융합환경에서 아두이노 모듈과 스마트 접지 측정 기술를 활용하여 대지의 층상이 특이성을 갖는 구조라도 신뢰할 수 있는 스마트 대지 저항 측정장치를 개발하여 대지저항을 분석하고 데이터를 축적하여 대지의 경년변화를 예측한다. 현장의 지형적인 특성을 고려하여 접지저항과 대지저항 측정 시 각도와 거리를 정확하게 위치시켜 보조전극을 설치할 수 있는 접지저항 측정장치 및 측정방법을 제안한다. 정확한 접지저항 값을 선정할 수 있게 하기 위해 설치된 전극을 통해 접지저항 값뿐만 아니라, 대지저항률을 취득할 수 있어 유사지역에 전기시설물 설치 시에 유용한 자료로 활용할 수 있다. 또한 신뢰성 높은 데이터를 활용하고 현장의 대지구조를 분석하여 공사비용 뿐 아니라 접지설계에서 중요한 비중을 차지하는 대지에 대한 정밀한 분석으로 전위상승 등의 접지설비설계에서 많은 활용이 기대된다.

V2O5 도핑한 페라이트 페이스트로 제조된 칩인덕터의 자기적 특성 (Magnetic Properties of Chip Inductors Prepared with V2O5-doped Ferrite Pastes)

  • 제해준
    • 한국자기학회지
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    • 제13권3호
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    • pp.109-114
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    • 2003
  • NiCuZn 페라이트에 $V_2O_{5}$를 0~0.5 wt% 첨가하여 페라이트 페이스트를 준비한 후,스크린 인쇄법으로 내부전극이 4.5회 회전된 임의의 크기(7.7$\times$4.5$\times$l.4 mm)의 칩인덕터를 제조하여, $V_2O_{5}$ 첨가량에 따른 미세구조 및 자기적 특성 변화를 분석하였다. $V_2O_{5}$첨가량이 증가할수록 액상소결이 발달하여 페라이트 입계에 내부전극 Ag의 확산과 Cu 석출 현상이 촉진되고, 이로 인하여 과대입자성장이 발달되었다. 이러한 현상은 칩인덕터의 자기적 특성에 큰 영향을 미쳐,900 $^{\circ}C$에서 소결된 $V_2O_{5}$ wt% 첨가시편의 주파수 10 MHz에서의 인덕턴스 값이 3.7$\mu$H로 0.3 wt% 첨가 시편의 4.2 $\mu$H보다 작게 나타났는데, 이는 Ag와 Cu의 석출량이 많아짐에 따라 잔류응력 발생이 심화되기 때문으로 생각된다 또한 $V_2O_{5}$ 0.5 wt% 첨가한 시편의 경우 소결온도가 증가함에 따라 품질계수 값이 감소하였는데, 이 결과도 페라이트 입계에서의 Ag나 Cu의 금속성분의 석출량 증가 및 과대입자성장에 의한 입자크기 증대로 인하여 전체 전기비저항이 감소되기 때문인 것으로 생각된다. 결론적으로 자기적 특성을 고려할 때 0.3 wt%가 적정 첨가량으로 나타났다.

충북 증평 지질학습장 시험부지에 대한 물리탐사 및 지질공학 자료의 해석 (Interpretation of Geophysical and Engineering Geology Data from a Test Site for Geological Field Trip in Jeungpyung, Chungbuk)

  • 김관수;윤현석;사진현;서용석;김지수
    • 지질공학
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    • 제26권3호
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    • pp.339-352
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    • 2016
  • 지하 매질의 물리적인 성질을 정확히 평가하기 위한 가장 일반적인 방법은 해당 지점에서 시추하여 채취한 암편을 대상으로 해석한 지질공학적인 실내시험 결과와 시추공 안에 삽입한 탐사 기구를 통해 얻은 지구물리학적인 자료를 함께 복합적으로 해석하는 것이다. 이 연구에서는 충북 증평의 지질학습장으로 예정된 시험부지 중의 한 곳에서 시추공 탐사 대신 수집한 지표 탄성파탐사(굴절법 및 표면파법) 자료로부터 얻은 P파 및 S파 속도구조와 이를 토대로 작성된 포아송 비 단면을 통해 노두에 좁은 폭으로 드러난 암석 환경(적색퇴적암, 회색화산암, 풍화 화산암) 및 접촉선에서 관찰된 단열, 파쇄대가 확인되는지 알아보았다. 또한 탐사 지역에 주로 분포하는 회색 화산암과 적색 퇴적암을 대상으로 지표지질 조사와 실내 지질공학 실험을 수행하였다. 탐사자료에서 평가된 동적 탄성계수 영률은 지질공학 자료의 정적 탄성계수보다 높았다. 실내 시험에서 회색화산암에 비해 공극률이 작고 함수비가 작은 것으로 평가된 적색퇴적암은 추가적으로 건기와 우기에 실시한 전기탐사(비저항 및 자연전위) 결과에서 건우기와 관계없이 상대적으로 전기비저항이 높고 그 변화 폭이 매우 작은 영역으로 확인되었다. 특히 높은 함수비와 공극률을 갖는 풍화된 회색 화산암과 함께 접촉선에서 좁게 발달한 단열 파쇄대가 우기 때의 충전율을 높이는 열린 통로의 역할을 한 것으로 해석된다.

$ZrO_2$를 나노개재물로 첨가한 p형 $(Bi,Sb)_2Te_3$ 나노벌크 가압소결체의 열전특성 (Thermoelectric Characteristics of the p-type $(Bi,Sb)_2Te_3$ Nano-Bulk Hot-Pressed with Addition of $ZrO_2$ as Nano Inclusions)

  • 여용희;김민영;오태성
    • 마이크로전자및패키징학회지
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    • 제17권3호
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    • pp.51-57
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    • 2010
  • p형 $(Bi,Sb)_2Te_3$ 분말을 용해/분쇄법으로 제조하여 가압소결 후 가압소결조건에 따른 열전특성을 분석하였으며, 나노개재물로서 $ZrO_2$의 첨가에 따른 열전특성의 변화거동을 분석하였다. 가압소결온도를 $350^{\circ}C$에서 $550^{\circ}C$로 증가시킴에 따라 가압소결체의 Seebeck 계수가 275 ${\mu}V$/K에서 230 ${\mu}V$/K로 감소하였으며, 전기비저항이 6.68 $m{\Omega}m$-cm에서 1.86 $m{\Omega}$-cm로 감소하였다. 1 vol% 이상의 $ZrO_2$ 함량 증가에 따라 power factor가 계속 감소하는 거동으로부터 $(Bi,Sb)_2Te_3$ 가압소결체의 최대 power factor를 얻을 수 있는 $ZrO_2$ 나노개재물의 최적 함량은 1 vol% 미만으로 판단되었다.

투명 전도성 산화물 전극으로의 응용을 위한 산화아연(ZnO) 코팅막의 습식 식각 특성연구 (Study on Wet chemical Etching Characterization of Zinc Oxide Film for Transparency Conductive Oxide Application)

  • 유동근;김명화;정성훈;부진효
    • 한국진공학회지
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    • 제17권1호
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    • pp.73-79
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    • 2008
  • 투명 전도성 산화물 전극(transparent conductive oxide electrodes)에 적용하기 위하여 RF 마그네트론 스퍼터링 방법에 의해 유리 기판 위에 산화아연 박막을 증착하였다. 투명 전극으로써 응용되기 위한 최적의 조건으로 기판온도를 상온으로 유지하고 RF power 200 W, 타겟과 기판사이의 거리(Dts)가 30 mm일 때 증착된 산화아연 박막으로부터 가장 낮은 비 저항값($7.4{\times}10^{-3}{\Omega}cm$)을 얻어 낼 수 있었으며, 85% 이상의 높은 투과율을 만족하는 박막을 얻을 수 있었다. 실질적인 소자로써의 응용을 위해 photo lithography를 통한 pattern을 형성, 습식 식각을 통하여 그 특성을 알아보고자 하였다. 습식 식각에서 사용된 식각용액(etchant)으로는 다양한 산 용액(황산, 옥살산, 인산)을 사용하였으며, 산의 농도 변화에 따른 식각특성과 식각시간 및 식각 이미지(표면형상)의 변화를 알아보았다. 결과적으로 산화아연의 습식식각은 산의 종류와 무관하게 산 용액의 농도(즉, pH)에 크게 의존하며, pH가 증가함에 따라 식각율이 지수함수적으로 감소하고 아울러 다양한 식각 이미지가 나타남을 최초로 고찰할 수 있었다.