• Title/Summary/Keyword: energy space

Search Result 3,298, Processing Time 0.031 seconds

Characteristics Modeling of Junction Barrier Schottky Diodes for ultra high breakdown voltage with 4H-SiC substrate (탄화규소(4H) 기판의 초고내압용 접합 장벽 쇼트키 다이오드의 특성 모델링)

  • Song, Jae-Yeol;Bang, Uk;Kang, In-Ho;Lee, Yong-Jae
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
    • /
    • 2007.10a
    • /
    • pp.200-203
    • /
    • 2007
  • Devices of junction barrier schottky(JBS) structure using 4H-SiC substrates with wide energy band gaps was designed and fabricated. As a measurement results, the device of reverse I-V characteristics was shown as more than 1000 V, its design optimum length of p-grid was $3{\mu}m$ space. In this paper, I-V characteristics was modeled by using of device fabricated process conditions parameters and it was extracted that the I-V property parameters, and it was compared and analyzed with between device parameters and model parameters.

  • PDF

A Study on Relationship Between Basic Frictional Angle and Mineral Composition for Granite Sample (화강암 시험편의 광물조성과 기본마찰각의 상관성에 관한 연구)

  • Lee, Bong-Hyun;Lee, Seung-Joong;Choi, Sung-Oong
    • Tunnel and Underground Space
    • /
    • v.24 no.1
    • /
    • pp.32-45
    • /
    • 2014
  • Basic frictional angle is a parameter that can estimate shear strength of rock, and is a design parameter employed in slope stability analysis. Basic frictional angle generates various results in accordance with mineral composition, apart from rock surface roughness itself. This paper describes the correlation of basic frictional angle and mineral composition. The basic frictional angle is measured with the aid of the modified tilt testing apparatus, and its reliability is improved by the statistical method. Also, mineral composition is identified through the photographic analysis on rock specimen, and verified through the thin section analysis.

Evaluation Method of Rock Characteristics using X-ray CT images (X-ray CT 이미지를 이용한 암석의 특성 평가 방안)

  • Kim, Kwang Yeom;Yun, Tae Sup
    • Tunnel and Underground Space
    • /
    • v.29 no.6
    • /
    • pp.542-557
    • /
    • 2019
  • The behavior of rock mass is influenced by its microscopic feature of internal structure generating from forming and metamorphic process. This study investigated a new methodology for characterization of rock based on the X-ray CT (computed tomography) images reflecting the spatial distribution characteristics of internal constituent materials. The X-ray image based analysis is capable of quantification of heterogeneity and anisotropy of rock fabric, size distribution and shape parameter analysis of rock mineral grains, fluid flow simulation based on pore geometry image and roughness evaluation of unexposed joint surface which are hardly acquired by conventional rock testing methods.

Identification of Noise Source of the HVAC Using Complex Acoustic Intensity Method (복소음향인텐시티법을 이용한 HVAC의 소음원 검출)

  • Yang, Jeong-Jik;Lee, Dong-Ju
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.20 no.11
    • /
    • pp.1089-1096
    • /
    • 2010
  • The relation between the vibration induced from machinery and the radiated sound is complicated. Acoustic intensity method is widely used to obtain the accuracy of noise measurement and noise identification. In this study, as groundwork, the complex acoustic intensity method is performed to identify noise source and transmission path on different free space point source fields. As an industrial application, the complex acoustic intensity method is applied to HVAC to identify sound radiation characteristics in the near field. Experimental complex acoustic intensity method was applied to HVAC, it is possible to identify noise sources in complicated sound field characteristics which noise sources are related with each other, and certificate the validity of complex acoustic intensity. Especially, it can be seen that complex acoustic intensity method using both of active and reactive intensity is vital in devising a strategy for identification of noise. Also, the vector flow of acoustic intensity was investigated to identify sound intensity distributions and energy flow in the near field of HVAC.

A Study on Dynamic Characteristics of 3-axis Actuator for the Slim Type Pick-Up (3축 구동이 가능한 Slim형 Pick-Up Actuator 개발 및 동특성 분석)

  • 박관우;서민석;홍삼열;김영중;최인호;김진용
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2002.05a
    • /
    • pp.373-377
    • /
    • 2002
  • In this study, we suggested a slim-type actuator that can be controlled in radial direction for compensating coma aberration in high-capacity optical storage devices. To deal successfully with narrow space in slim-type optical pick-up for notebook pc device, additional yokes for tilting motion are integrated into main yoke of the actuator. And the location of tilting coils is determined for mass-b3lancing effect to achieve optimal configuration for high driving sensitivity. We also suggested new concept of lens holder to guarantee excellent stability of control system by enhancing the gain margin at secondary resonant frequency. The concept was realized by forming damping sections in the lens holder, which prevent vibrational energy from transferring to lens. An exclusive measurement system was newly developed for fast and precise measurement of dynamic characteristics of actuators and utilized for the practical use. We hope to make good use of this system also in time to come.

  • PDF

Improving Data Accuracy Using Proactive Correlated Fuzzy System in Wireless Sensor Networks

  • Barakkath Nisha, U;Uma Maheswari, N;Venkatesh, R;Yasir Abdullah, R
    • KSII Transactions on Internet and Information Systems (TIIS)
    • /
    • v.9 no.9
    • /
    • pp.3515-3538
    • /
    • 2015
  • Data accuracy can be increased by detecting and removing the incorrect data generated in wireless sensor networks. By increasing the data accuracy, network lifetime can be increased parallel. Network lifetime or operational time is the time during which WSN is able to fulfill its tasks by using microcontroller with on-chip memory radio transceivers, albeit distributed sensor nodes send summary of their data to their cluster heads, which reduce energy consumption gradually. In this paper a powerful algorithm using proactive fuzzy system is proposed and it is a mixture of fuzzy logic with comparative correlation techniques that ensure high data accuracy by detecting incorrect data in distributed wireless sensor networks. This proposed system is implemented in two phases there, the first phase creates input space partitioning by using robust fuzzy c means clustering and the second phase detects incorrect data and removes it completely. Experimental result makes transparent of combined correlated fuzzy system (CCFS) which detects faulty readings with greater accuracy (99.21%) than the existing one (98.33%) along with low false alarm rate.

Experiments of dimethyl ether autothermal reforming optimization (디메틸에테르(DME) 자열개질 운전조건 최적화에 관한 연구)

  • Choi, Seunghyeon;Bae, Joongmyeon;Kim, Taehun;Jang, Duckjin;Kim, Doyoun
    • 한국신재생에너지학회:학술대회논문집
    • /
    • 2011.11a
    • /
    • pp.97.1-97.1
    • /
    • 2011
  • Dimethyl ether (DME) is an attractive fuel as a hydrogen carrier for mobile PEMFC applications. However, its reforming technologies are rarely studied especially by using autothermal reforming (ATR) method. This work explored the impact of operating conditions to the performance of DME ATR. Temperature, Steam to carbon ratio(SCR), Oxygen to carbon ratio(OCR) and Gas hourly space velocity(GHSV) were considered as the operating conditions. As results, conversion efficiency was increased as the temperature increased, but saturated around $700^{\circ}C$. There was no significant effect of SCR on conversion efficiency, but high SCR led reactions in endothermic manner. High OCR substantially suppressed conversion efficiency, but it helped to sustain the temperature by stimulating exothermic reactions. Conversion efficiency was decreased as GHSV increased. The optimized operating conditions was suggested: $700^{\circ}C$, SCR of 1.5, OCR of 0.45 and GHSV below 15000/h and conversion efficiency was ~85% at the conditions.

  • PDF

Seismic stability analysis of tunnel face in purely cohesive soil by a pseudo-dynamic approach

  • Huang, Qi;Zou, Jin-feng;Qian, Ze-hang
    • Geomechanics and Engineering
    • /
    • v.23 no.1
    • /
    • pp.1-13
    • /
    • 2020
  • To give a solution for seismic stability of tunnel faces subjected to earthquake ground shakings, the pseudo-dynamic approach is originally introduced to analyze tunnel face stability in this study. In the light of the upper-bound theorem of limit analysis, an advanced three-dimensional mechanism combined with pseudo-dynamic approach is proposed. Based on this mechanism, the required support pressure on tunnel face can be obtained by equaling external work rates to the internal energy dissipation and implementing an optimization searching procedure related to time. Both time and space feature of seismic waves are properly accounted for in the proposed mechanism. For this reason, the proposed mechanism can better represent the actual influence of seismic motion and has a remarkable advantage in evaluating the effects of vertical seismic acceleration, soil amplification factor, seismic wave period and initial phase difference on tunnel face stability. Furthermore, the pseudo-dynamic approach is compared with the pseudo-static approach. The difference between them is illustrated from a new but understandable perspective. The comparison demonstrates that the pseudo-static approach is a conservative method but still could provide precise enough results as the pseudo-dynamic approach if the value of seismic wavelengths is large or the height of soil structures is small.

A Study on the Volume Change in Unsaturated Clayey Soil (불포화 정성토의 체적변화에 대한 연구)

  • Chang, Pyoung-Wuck;Gil, Sang-Choon
    • Magazine of the Korean Society of Agricultural Engineers
    • /
    • v.40 no.5
    • /
    • pp.37-42
    • /
    • 1998
  • This study was performed to evaluate the characteristics of volume change is unsaturated clayed soil. The medium-plastic clay was selected and compacted by 50% of Proctor standard compaction energy at 6% higher moisture content than its OMC. A series of isotropic compression tests and triaxial shear tests were performed. The results of the study are summarized as follows. At each matric suction, when the matric suction was increased, the yield stress was increased and slope of volume change was decreased. The more net mean stress was, the less the quantity of volume change was. In shear test, the volumetric strain was much rapidly changed in large matric than in low matric suctions. But the effect of matric suction to volume change disappeared under high net mean stress. At lower deviator stress the more matric suction was, the higher volume change was. But As the matric suction was increasing, the behavior of the unsaturated clayey soil was similar to that of saturated clayey soil. Volume change in the unsaturated clayey soil can be represented as a unique plane in three-dimensional space, which is the axes of net mean stress, matric suction and void ratio.

  • PDF

Studies on the Performance Evaluation of Downsized High-efficiency Cooling Module (높이 축소형 고효율 냉각모듈의 성능 평가에 관한 연구)

  • Jung, Jung-Hun;Shin, Yoon-Hyuk;Park, Sung-Wook;Jeong, Sun-An;Kim, Sung-Chul
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.19 no.6
    • /
    • pp.61-67
    • /
    • 2011
  • The cooling module needs enough space (or distance) from hood to absorb the energy from any pedestrian collision. Downsized cooling module for pedestrian protection is important to reduce the severity of pedestrian injury. When a vehicle collision happens, the downsized cooling module is required to reduce the risk of injury to the upper legs of adults and the heads of children. In this study, the performance of cooling module to cool the engine was investigated under 25% height reduction. The heat dissipation and pressure drop characteristics have been experimentally studied with the variation of coolant flow rate, air inlet velocity and A/C operation ON/OFF for the downsized cooling module. The results indicated that the cooling performance was about 94% level compared to that of the conventional cooling module. Therefore, we checked that the cooling module had good performance, and expected that the cooling module could meet the same cooling performance as conventional cooling module through optimization of components efficiency.