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旋转壳-流体耦合系统频率响应的动态设计 被引量:2
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作者 魏发远 李世其 钟毅芳 《振动与冲击》 EI CSCD 北大核心 2001年第3期35-39,共5页
基于流固耦合理论 ,对浸水旋转壳频率响应的动态设计进行了比较全面的研究。针对动态设计中动力学重分析计算量大的问题 ,在对旋转壳 -流体耦合系统进行动力学建模时 ,对于旋转壳 ,根据其结构特点引入了既能保证计算精度又能大大提高计... 基于流固耦合理论 ,对浸水旋转壳频率响应的动态设计进行了比较全面的研究。针对动态设计中动力学重分析计算量大的问题 ,在对旋转壳 -流体耦合系统进行动力学建模时 ,对于旋转壳 ,根据其结构特点引入了既能保证计算精度又能大大提高计算效率的有限条法 ;对于流场 ,则采用边界元法来解决无限域问题和提高计算效率 ;然后利用凝聚降阶减小计算量 ,通过一种改进的模态迭加技术获得系统响应。计算结构动力响应及其灵敏度时 ,将灵敏度分析方法与动力响应计算方法相结合 ,得到动态灵敏度分析的快速算法。采用多目标优化方法 ,以重量、响应作为设计目标 ,对旋转壳结构进行了动力优化设计。计算实例表明 ,本文方法有效 ,并满足工程需要。 展开更多
关键词 浸水旋转壳 频率频应 动态设计 流固耦合 结构设计 动力学理论 结构振动 旋转壳-流体耦合系统
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Testing an improved cymbal hydrophone
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作者 陈晟 林关成 《Journal of Marine Science and Application》 2009年第4期328-332,共5页
Cymbal hydrophones have small volume and high sensitivity, but their reception is not stable enough, and their reception is in too narrow a frequency band. In order to overcome these inadequacies, the structure of the... Cymbal hydrophones have small volume and high sensitivity, but their reception is not stable enough, and their reception is in too narrow a frequency band. In order to overcome these inadequacies, the structure of the cymbal hydrophone was improved. The single ceramic piezoelectric element was replaced with a double one, the radius of the ceramic piezoelectric element was reduced, and a parallel circuit was added. A static analysis of this new structure was developed, and then simulations were made of both the traditional and new hydrophone structure using finite element software. Tests were then conducted in a tank. The results showed that the improved hydrophone has reception in a wider frequency band, reception performance is stable within this frequency band, and sensitivity is still high. 展开更多
关键词 cymbal hydrophone sensitivity resonance frequency parallel connection frequency band
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A Novel 4/5 Prescaler with Automatic Power Down
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作者 曾隆月 朱思奇 阎跃鹏 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2008年第8期1449-1452,共4页
An "automatic power down" method is introduced to design a 4/5 prescaler,with the characteristic of making one of its D-flip-flops power down when it operates in divide-by-4 mode. Implemented with the TSMC 0.25vm mi... An "automatic power down" method is introduced to design a 4/5 prescaler,with the characteristic of making one of its D-flip-flops power down when it operates in divide-by-4 mode. Implemented with the TSMC 0.25vm mixed-sig- nal CMOS process,the 4/5 MOS current mode logic prescaler is designed with this automatic power down technique. The simulation results show that the new 4/5 prescaler is immune to the "wake-up" issue and thereby retains the same maxi- mum operating frequency as the conventional prescaler. An integer-N divider with this proposed prescaler and with the di- vision ratio 66/67 is manufactured,and it is estimated to save more than 20% of the power compared with the conventional 4/5 prescaler. 展开更多
关键词 MCML prescaler automatic power down frequency synthesizer
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A Σ-Δ Fractional-N PLL Frequency Synthesizer with AFC for SRD Applications 被引量:1
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作者 章华江 胡康敏 洪志良 《Journal of Semiconductors》 EI CAS CSCD 北大核心 2008年第7期1298-1304,共7页
A fractional-N frequency synthesizer for 433/868MHz SRD applications is implemented in a 0.3μm CMOS process. A wide-band VCO and an AFC are used to cover the desired bands. A 3bit third order sigma-delta modulator is... A fractional-N frequency synthesizer for 433/868MHz SRD applications is implemented in a 0.3μm CMOS process. A wide-band VCO and an AFC are used to cover the desired bands. A 3bit third order sigma-delta modulator is adopted to reduce the out-band phase noise. The measurements show a VCO tuning range from 1.31 to 1.88GHz with AFC working correctly,an out-band phase noise of -139dBc/Hz at 3MHz offset frequency, and a fractional spur of less than - 60dBc. The chip area is 1.5mm × 1.2mm and the total current dissipation including LO buffers is 19mA from a single 3.0V supply voltage. 展开更多
关键词 short range device phase locked loop adaptive frequency calibration frequency synthesizer SIGMA-DELTA
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Frequency in Middle of Magnon Band Gap in a Layered Ferromagnetic Superlattice 被引量:1
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作者 邱荣科 赵健 应彩虹 《Communications in Theoretical Physics》 SCIE CAS CSCD 2010年第12期1144-1150,共7页
The frequency in middle of magnon energy band in a five-layer ferromagnetic superlattice is studied by using the linear spin-wave approach and Green's function technique. It is found that four energy gaps and corresp... The frequency in middle of magnon energy band in a five-layer ferromagnetic superlattice is studied by using the linear spin-wave approach and Green's function technique. It is found that four energy gaps and corresponding four frequencie in middle of energy gaps exist in the magnon band along Kx direction perpendicular to the superlattice plane. The spin quantum numbers and the interlayer exchange couplings all affect the four frequencies in middle of the energy gaps. When all interlayer exchange couplings are same, the effect of spin quantum numbers on the frequency wg1 in middle of the energy gap Δw12 is complicated, and the frequency wg1 depends on the match of spin quantum numbers in each layer. Meanwhile, the frequencies wg2, wg3, and wg4 in middle of other energy gaps increase monotonously with increasing spin quantum numbers. When the spin quantum numbers in each layer are same, the frequencies wg1, wg2, wg3, and wg4 all increase monotonously with increasing interlayer exchange couplings. 展开更多
关键词 layered ferromagnetic superlattice magnon energy band frequency in middle of the magnon energy gap spin quantum number interlayer exchange couplings
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RESEARCH OF BJMOSFET FREQUENCY CHARACTERISTICS
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作者 Zeng Yun Yang Hongguan +3 位作者 Shang Yuquan Li Xiaolei Zhang Yan Wu Yonghui 《Journal of Electronics(China)》 2006年第4期590-593,共4页
The parasitic capacitance effect and its influence to the performance have been investigated in Bi-polar Junction Metal-Oxide-Semiconductor Field-Effect Transistor (BJMOSFET). The frequency characteristic equivalent c... The parasitic capacitance effect and its influence to the performance have been investigated in Bi-polar Junction Metal-Oxide-Semiconductor Field-Effect Transistor (BJMOSFET). The frequency characteristic equivalent circuit and high frequency response model of BJMOSFET have been presented. The frequency characteristic of BJMOSFET is simulated using the multi-transient analytical method and PSPICE9 simulator. The conclusions that BJMOSFET owns less total capacitance, wider frequency band, better transient charac-teristic and better frequency responses are reached by comparing with the traditional MOSFET at the same structure parameters and bias conditions. BJMOSFET, as a novel promising high frequency device, would be desired to find application in future integrated circuit. 展开更多
关键词 Bipolar Junction Metal-Oxide-Semiconductor Field-Effect Transistor (BJMOSFET) Frequency characteristic High frequency device PSPICE
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Structural safety criteria for blasting vibration based on wavelet packet energy spectra 被引量:14
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作者 Zhong Guosheng Li Jiang Zhao Kui 《Mining Science and Technology》 EI CAS 2011年第1期35-40,共6页
Given multi-resolution decomposition of wavelet packet transforms,wavelet packet frequency band energy has been deduced from different bands of blasting vibration signals.Our deduction reflects the total effect of all... Given multi-resolution decomposition of wavelet packet transforms,wavelet packet frequency band energy has been deduced from different bands of blasting vibration signals.Our deduction reflects the total effect of all three key elements(intensity,frequency and duration of vibration)of blasting vibration. We considered and discuss the dynamic response of structures and the effect of inherent characteristics of controlled structures to blasting vibration.Frequency band response coefficients for controlled structures by blasting vibration have been obtained.We established multi-factor blasting vibration safety criteria,referred to as response energy criteria.These criteria reflect the total effect of intensity, frequency and duration of vibration and the inherent characteristics(natural frequency and damping ratio)of dynamic responses from controlled structures themselves.Feasibility and reliability of the criteria are validated by an example. 展开更多
关键词 Blasting vibrationWavelet packet transformResponse energySafety criteria
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Correction of Dynamic Error Result from Measurement System Limitations 被引量:1
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作者 张志杰 王代华 +1 位作者 王文廉 王巍 《Journal of Measurement Science and Instrumentation》 CAS 2010年第4期307-311,共5页
The main cause of dynamic errors is due to frequency response limitation of measurement system. One way of solving this problem is designing an effective inverse filter. Since the problem is ill-conditioned, a small u... The main cause of dynamic errors is due to frequency response limitation of measurement system. One way of solving this problem is designing an effective inverse filter. Since the problem is ill-conditioned, a small uncertainty in the measurement will came large deviation in reconstncted signals. The amplified noise has to be suppressed at the sacrifice of biasing in estimation. The paper presents a kind of designing method of inverse filter in frequency domain based on stabilized solutions of Fredholm integral equations of the fast kind in order to reduce dynamic errors. Compared with previous several work, the method has advantage of generalization. Simulations with different Signal-to-Noise ratio (SNR) are investigated. Flexibility of the method is verified. Application of correcting dynamic error is given. 展开更多
关键词 dynamic error inverse filters oorrection of dynamic dlaracteristic measurement system
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Ku80 gene G-1401T promoter polymorphism and risk of gastric cancer 被引量:1
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作者 Jia-Qi Li Jie Chen +4 位作者 Nan-Nan Liu Li Yang Ying Zeng Bin Wang Xue-Rong Wang 《World Journal of Gastroenterology》 SCIE CAS CSCD 2011年第16期2131-2136,共6页
AIM:To evaluate the possible relationship between the Ku80 gene polymorphism and the risk of gastric cancer in China.METHODS:In this hospital-based case-control study of gastric cancer in Jiangsu Province,China,we inv... AIM:To evaluate the possible relationship between the Ku80 gene polymorphism and the risk of gastric cancer in China.METHODS:In this hospital-based case-control study of gastric cancer in Jiangsu Province,China,we investigated the association of the Ku80 G-1401T (rs828907) polymorphism with gastric cancer risk.A total of 241 patients with gastric cancer and 273 age-and sexmatched control subjects were genotyped and analyzed by polymerase chain reaction-restriction fragment length polymorphism.RESULTS:The frequencies of genotypes GG,GT and TT were 65.6%,22.8% and 11.6% in gastric cancer cases,respectively,and 75.8%,17.6% and 6.6% in controls,respectively.There were significant differences between gastric cancer and control groups in the distribution of their genotypes (P=0.03) and allelic frequencies (P=0.002) in the Ku80 promoter G-1401T polymorphism.CONCLUSION:The T allele of Ku80 G-1401T may be associated with the development of gastric cancer. 展开更多
关键词 KU80 Gastric cancer POLYMORPHISM PROMOTER CARCINOGENESIS
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Influence of surface treatments on fatigue life of a two-stroke free piston linear engine component using random loading
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作者 RAHMAN M.M. ARIFFIN A.K. +1 位作者 JAMALUDIN N. HARON C.H.C. 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2006年第11期1819-1830,共12页
This paper describes the finite element (FE) analysis technique to predict fatigue life using the narrow band frequency response approach. The life prediction results are useful for improving the component design meth... This paper describes the finite element (FE) analysis technique to predict fatigue life using the narrow band frequency response approach. The life prediction results are useful for improving the component design methodology at the very early development stage. The approach is found to be suitable for a periodic loading but requires very large time records to accurately describe random loading processes. This paper is aimed at investigating the effects of surface treatments on the fatigue life of the free piston linear engine’s components. Finite element modelling and frequency response analysis were conducted using computer aided design and finite element analysis commercial codes, respectively. In addition, the fatigue life prediction was carried out using finite element based fatigue analysis commercial code. Narrow band approach was specially applied to predict the fatigue life of the free piston linear engine cylinder block. Significant variation was observed between the surface treatments and untreated cylinder block of free piston engine. The obtained results indicated that nitrided treatment yielded the longest life. This approach can determine premature products failure phenomena, and therefore can reduce time to market, improve product reliability and customer confidence. 展开更多
关键词 Vibration fatigue Finite element (FE) Power spectral density function Frequency response Surface treatment
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Improving the high frequency response of a loudspeaker using hydrogen-free diamond-like carbon film coating at low temperature 被引量:2
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作者 LIN ChiiRuey LIU ShinHwa +1 位作者 LIOU WangJeng CHANG ChienKuo 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2012年第3期385-391,共7页
Hydrogen-free diamond-like carbon (DLC) thin films were deposited at low temperature (less than 100~C) by an RF magne- tron sputtering facility. DLC films have the ability to change the sound velocity (E/p) in l... Hydrogen-free diamond-like carbon (DLC) thin films were deposited at low temperature (less than 100~C) by an RF magne- tron sputtering facility. DLC films have the ability to change the sound velocity (E/p) in loudspeakers for applications of hard coating. The hydrogen-free DLC films were coated onto PEI diaphragm substrates. The ID/IG ratio and the surface roughness are 2.09 and less than 0.86 nm (Ra) with a scanning area of 50 um x 50 um, respectively. Frequency response analysis of the DLC films on the diaphragm shows that the high frequency response increases by 0.2 dB-5.1 dB (6 kHz-ll.2 kHz), -0.4 dB-1.8 dB (11.8 kHz-20 kHz) on average. On the basis of the results of this study, we validated that it was feasible to sputter hydrogen-free DLC films on polymer substrates for mass production. These results also provided useful parameters for future applications of electro-acoustic devices. 展开更多
关键词 DLC thin films coating DIAPHRAGM frequency response physical vapor deposition
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