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MHz cut-off frequency and permeability mechanism of iron-based soft magnetic composites

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Chinese Physics B 2024年第9期33卷 560-564页

作者： Xiao-Wei Jin Tong Li Hui-Gang Shi De-Sheng Xue Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education LanzhouUniversityLanzhou 730000China

The lack of soft magnetic composites with high power density in MHz frequency range has become an obstacle in the efficient operation of the electrical and electronic ***,a promising method to increase the cut-off frequency of iron-based soft magnetic composites to hundreds of MHz is *** cut-off frequency is increased from 10 MHz to 1 GHz by modulating the height of the ring,the distribution of particles,and the particle *** mechanism of cut-off frequency and permeability is the coherent rotation of domain modulated by inhomogeneous field due to the eddy current *** empirical formula for the cut-off frequency in a magnetic ring composed of iron-based particles is established from experimental *** work provides an effective approach to fabricate soft magnetic composites with a cut-off frequency in hundreds of MHz.

关键词： cut-off frequency permeability eddy current effect soft magnetic composites

Effect of cut-off frequency of Butterworth Filter on Detectability and Contrast of Hot and Cold Regions in Tc-99m SPECT

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International Journal of Medical Physics, Clinical Engineering and Radiation Oncology 2016年第1期5卷 100-109页

作者： Inayatullah Shah Sayed Nor Syahirah Mohamed Nasrudin Department of Diagnostic Imaging and Radiotherapy Kulliyyah (Faculty) of Allied Health Sciences International Islamic University of Malaysia Kuantan Malaysia

In SPECT, noise is one of the major limitations that degrade image quality. To suppress the noisy signals in an image, digital filters are most commonly applied. However, in SPECT image reconstruction, selection of an appropriate filter and its functions has always remained a difficult task. In this work an attempt was made to investigate the effects of varying cut-off frequencies and in keeping the order of Butterworth filter constant on detectability and contrast of hot and cold re-gions images. A new insert simulating hot and cold regions which provides similar views in a reconstructed image was placed in the phantom’s cylindrical source tank and imaged. Tc-99m radionuclide was distributed uniformly in the phantom. SPECT data were collected in a 20% energy window centered at 140 keV by a Philips ADAC Forte dual head gamma camera mounted with a LEHR collimator. Images were generated by using the filtered backprojection technique. A Butterworth filter of order 5 with cut-off frequencies 0.35 and 0.45 cycles·cm-1 was applied. Images were examined in terms of hot and cold regions, detectability and contrast. Results show that the hot and cold regions’ detectability and contrast vary with the change of cut-off frequency. With a 0.45 cycles·cm-1 cut-off frequency, a significant enhancement in contrast of cold regions was achieved as compared to a 0.35 cycles·cm-1 cut-off frequency. Furthermore, the detectability of hot and cold regions improved with the use of a 0.45 cycles·cm-1 cut-off frequency. In conclusion, image quality of hot and cold regions affected in a different way with a change of cut-off frequency. Thus, care should be taken in selecting the filter cut-off frequency prior to reconstruction of images;particularly, when both types of regions are expected in the reconstructed image.

关键词： Detectability SPECT Noise Image Quality cut-off frequency Mathematical Filters

Radio-frequency transistors from millimeter-scale graphene domains

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Chinese Physics B 2014年第11期23卷 470-475页

作者：魏子钧傅云义刘竞博王紫东贾越辉郭剑任黎明陈远富张酣黄如张兴 Institute of Microelectronics Peking University State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of China School of Physics Peking University

Graphene is a new promising candidate for application in radio-frequency （RF） electronics due to its excellent elec- tronic properties such as ultrahigh carrier mobility, large threshold current density, and high saturation velocity. Recently, much progress has been made in the graphene-based RF field-effect transistors （RF-FETs）. Here we present for the first time the high-performance top-gated RF transistors using millimeter-scale single graphene domain on a SiO2/Si substrate through a conventional microfabrication process. A maximum cut-off frequency of 178 GHz and a peak maximum os- cillation frequency of 35 GHz are achieved in the graphene-domain-based FET with a gate length of 50 nm and 150 nm, respectively. This work shows that the millimeter-scale single graphene domain has great potential applications in RF devices and circuits.

关键词： millimeter-scale graphene domain radio-frequency transistor cut-off frequency maximum oscil-lation frequency

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Organic optocouplers

Science China Chemistry 2011年第7期54卷 1017-1026页

作者： SUN QiuJian DONG GuiFang WANG LiDuo QIU Yong Key Laboratory of Organic Optoelectronics & Molecular Engineering of Ministry of Education Department of ChemistryTsinghua UniversityBeijing 100084China

Organic optocoupler(OOC) or organic photocoupler,optical coupler is a novel and one of the most promising organic optoelectronic devices for its well electrical isolation and anti-jamming ability in long-distance and real-time digital *** performance parameters of OOC were greatly raised during the past decade,and its development was strongly associated with basic organic devices such as organic light emitting diodes(OLED),organic photodiodes(OPD) and organic phototransistors(OPT) *** we describe the principles of OOC,review recent breakthroughs in this field,and summarize the photosensor and light emitting parts which could be used in the *** technical points,such as current transfer ratio,frequency,matching and stability were also discussed in this paper.

关键词： organic optocoupler organic photocoupler photodiodes phototransistors light emitting diode current transfer ratio cut-off frequency

Indium antimonide based HEMT for RF applications

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Journal of Semiconductors 2014年第11期35卷 20-22页

作者： T.D.Subash T.Gnanasekaran K.N.S.K College of Engineering Nagercoil-629901India RMK College of Engineering and Technology Tamil Nadu601206India

We report on an indium antimonide high electron mobility transistor with record cut-off frequency characteristics. For high frequency response it is important to minimize parasitic resistance and capacitance to improve short-channel effects. For analog applications adequate pinch-off behavior is demonstrated. For proper device scaling we need high electron mobility and high electron density. Toward this end, the device design features and simulation are carried out by the Synopsys TCAD tool. A 30 nm InSb HEMT exhibits an excellent cut-off frequency of 586 GHz. To the knowledge of the authors, the obtained cut-off frequency is the highest ever reported in any FET on any material system.

关键词： HEMT InSb gate length cut-off frequency short-channel effects

Performance Evaluation and Effectiveness of the Reverberation Room

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Sound & Vibration 2021年第1期55卷 43-55页

作者： Mohamed Abd-Elbasseer Hatem Kh Mohamed Acoustics Laboratory National Institute of Standards(NIS)GizaEgypt

This research presents a thorough evaluation of the reverberation room at Acoustics Laboratory in National Institute of Standards(NIS)according to the related international *** evaluation aims at examining the room performance and exploring its effectiveness in the frequency range from 125 Hz to 10000 Hz according to the international standard *** room,which was designed and built several years ago,is an irregular rectangular shape free from *** volume is about 158.84 m^(3),which meets the requirement of the ISO 354 standard Lmaxcut-off frequencies of one and one-third octave are 63 Hz and 100 Hz respectively;however Schroder frequency is 400 *** of cut-off frequency and modal density showed adequate modes that give acceptable uniformity starting comfortably from frequency of 125 *** room has a reverberation time that is suitable for its size over the frequency range of *** room sound absorption surface area and its sound absorption coefficient satisfy the criteria given in ISO 3741 and ISO *** is an accepted diffuse sound field inside the room due to the standard deviation of measured sound level,which is less than 1.5 dB over all the frequency *** only exception was 125 Hz which may be due to a lack of diffusivity of the sound field at this *** evaluation proves that the NIS reverberation room is in full agreement with the international standards,which in turns qualifies the room to host measurements inside without concerns.

关键词： Reverberation room cut-off frequency sound absorption spatial uniformity modal counts

FORCED WAVE PROPAGATION IN VISCOELASTIC CABLE WITH SMALL SAG

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Acta Mechanica Solida Sinica 2001年第2期14卷 147-154页

作者： Li Yinghui Jian Kailin~1 Gao Qing Yin Xuegang~1 (Department of Applied Mechanics and Engineering, Southwest Jiaotong University, Chengdu 610031, China) (1 State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400044, China) Dept. of Appl. Mechanics and Eng. Southwest Jiaotong University Chengdu 610031 China Stt. Key Lab. of Mech. Transmission Chongqing University Chongqing 400044 China

Based on the linear viscoelastic differential constitutive law andcable structural model, the coupled longitudinal-transverse wavesthat propagate along a viscoelastic cable with small curvature isinvesti- gated. A mathematical model is presented that describes thethree-dimensional nonlinear response of a vis- coelastic cable. Anasymptotic form of this model is obtained for the linear response ofcables having small equilibrium curvature.

关键词： viscoelastic cable small equilibrium curvature cut-off frequency

On the Spectral Moments of Wind Waves

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China Ocean Engineering 2002年第1期17卷 135-140页

作者： LI Luping(李陆平) HUANG Peiji(黄培基) First Institute of Oceanography State Oceanic Adminustration Qingdao 266061 China First Institute of Oceanography State Oceanic Adminustration Qingdao 266061 China

In order to obtain high order spectral moments, the residual moment M(w(n))(i) = integral(0)(wn) w(i)S(w)dw, as proposed by Denis s, is presented for approximate estimation of spectral moment m(i) = integral(0)(infinity) w(i)S(w)dw. Glazman's partial averaging idea is discussed. It is pointed out that Glazman's method and definition of non-dimensional spectral moment can not be used to estimate spectral moments for engineering purposes and that method is not supported by theory and computation. The non-dimensional spectral moment of PM spectrum, which should be expressed as [GRAPHICS] is related to wind speed. The 0 - 8th moments of PM spectrum are estimated for wind speeds of 10, 20 and 30 m/s and some discussions are given.

关键词： spectral moment high order moment residual moment cut-off frequency

Design and Realization of Schottky Barrier Didoes in 130nm CMOS Process

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Journal of Beijing Institute of Technology 2017年第2期26卷 223-227页

作者： Junyu Shi Dasheng Cui Haidong Hao Haixia Wu Xin Lyu School of Information and Electronics Beijing Institute of Technology Beijing 100081 China

A polysilicon separated CMOS Schottky barrier diode is designed and tested in this *** replacing the shallow trench isolation（STI）of a ploy ring,the series resistances of Schottky diodes are reduced,leading to an improvement in cut-off *** device structure is detailed and a device model is *** analysis on the device shows that the cut-off frequency increases with the decreasing of the Schottky contact *** on this observation,the Schottky contact area is set to0.38×0.38μm^2,which is the minimum contact diffusion area allowed by the process *** distance between the anode and the cathode is also *** with different dimensions are fabricated and *** extensive measurements,the optimum dimensions are *** with a reduced area are used to improve the measurement *** measurement results show that these diodes can achieve a cut-off frequency of 1.5 ***,it is possible to use these diodes in THz detection.

关键词： Schottky barrier diodes cut-off frequency silicon THz detection