Metamaterial-based electronically controlled transmission-line structure as a novel leaky-wave antenna with tunable radiation angle and beamwidth

A metamaterial-based electronically controlled transmission-line structure is presented and demonstrated as a novel leaky-wave (LW) antenna with tunable radiation angle and beamwidth functionalities. This structure is, in essence, a composite right/left-handed (CRLH) microstrip structure incorporating varactor diodes for fixed-frequency voltage-controlled operation. Angle scanning at a fixed frequency is achieved by modulating the capacitances of the structure by adjusting the (uniform) bias voltage applied to the varactors. Beamwidth tuning is obtained by making the structure nonuniform by application of a nonuniform bias voltage distribution of the varactors. A rigorous analysis based on an extension of the CRLH concept is proposed and the corresponding dispersion curves, obtained by equivalent-circuit formulas with LC parameters extracted from full-wave simulation, are shown. A 30-cell LW antenna structure, incorporating both series and shunt varactors for optimal impedance matching and maximal tuning range, is designed. This prototype exhibits continuous scanning capability from 50/spl deg/ to -49/spl deg/ by tuning the bias voltages from 0 to 21 V at 3.33 GHz. A maximum gain of 18 dBi at broadside is also achieved. In addition, it provides half-power beamwidth variation of up to 200% with comparison to the case of uniform biasing. The effect of intermodulation due to the nonlinearity of the varactors is shown to be negligible for antenna applications. The antenna is tested in a 10-Mb/s binary phase-shift keying transmission link and successful recovery of the baseband data is demonstrated.     

A novel phase noise reduction technique in oscillators usingdefected ground structure

A new technique to reduce the phase noise in microwave oscillators is developed using the resonant characteristic of the defected ground structure (DGS). Two kinds of oscillators have been designed and measured for the examination of the reduction of phase noise by the DGS. The first adopts the DGS section under the microstrip line at the gate circuit, while the second has only the conventional microstrip line. Measurement shows reduced phase noise by 10-15 dB in the oscillator with the DGS compared to the conventional one     

A compact-size microstrip spiral resonator and its application to microwave oscillator

This letter presents a compact size microstrip spiral resonator and its application to a low phase noise oscillator. This resonator has stopband characteristics to be used in the series feedback oscillator topology. The whole circuit area of the proposed resonator is within 1/10 wavelength, which results in the reduction of the circuit area and cost. A 10-GHz oscillator incorporated with this resonator was designed, fabricated and measured. It shows low phase noise performance of -95.4-dBc/Hz at 100 kHz offset.     

输尿管开口囊肿、狭窄及膀胱颈部挛缩的HO:YAG激光治疗

目的利用HOYAG激光的软组织切割及止血作用,对输尿管开口囊肿、狭窄及膀胱颈部挛缩的患者行激光治疗,并观察疗效.方法采用HOYAG激光对6例输尿管开口囊肿,15例输尿管开口狭窄(其中3例合并输尿管结石),32例膀胱颈部挛缩进行治疗,观察术中出血、术后并发症、膀胱挛缩患者手术前后Qmax.结果总计53例患者通过HOYAG激光治疗,均获得满意临床疗效,术中几乎无出血,输尿管开口囊肿及狭窄患者,术毕能顺利留置F7双猪尾巴导管.膀胱颈部挛缩患者术后最大尿流率提高了7.6ml/s(7.2～14.8ml/s).结论HO;YAG激光对输尿管开口囊肿、狭窄及膀胱颈部挛缩是一种行之有效的治疗方法,且无出血,易于操作、安全、恢复快.尤其是输尿管结石合并输尿管开口狭窄患者,可通过HOYAG激光一次手术解决.     

Advanced Concentration Gradient Cathode Material with Two‐Slope for High‐Energy and Safe Lithium Batteries

Li[Ni_0.65Co_0.13Mn_0.22]O₂ cathode with two‐sloped full concentration gradient (TSFCG), maximizing the Ni content in the inner part of the particle and the Mn content near the particle surface, is synthesized via a specially designed batch‐type reactor. The cathode delivers a discharge capacity of 200 mAh g^?1 (4.3 V cutoff) with excellent capacity retention of 88% after 1500 cycles in a full‐cell configuration. Overall electrochemical performance of the TSFCG cathode is benchmarked against conventional cathode (CC) with same composition and commercially available Li[Ni_0.8Co_0.15Al_0.05]O₂ (NCA). The TSFCG cathode exhibits the best cycling stability, rate capability, and thermal stability of the three electrodes. Transmission electron microscopy analysis of the cycled TSFCG, CC, and NCA cathodes shows that the TSFCG electrode maintains both its mechanical and structural integrity whereas the NCA electrode nearly pulverizes due to the strain during cycling.     

Real‐Time License Plate Detection in High‐Resolution Videos Using Fastest Available Cascade Classifier and Core Patterns

We present a novel method for real‐time automatic license plate detection in high‐resolution videos. Although there have been extensive studies of license plate detection since the 1970s, the suggested approaches resulting from such studies have difficulties in processing high‐resolution imagery in real‐time. Herein, we propose a novel cascade structure, the fastest classifier available, by rejecting false positives most efficiently. Furthermore, we train the classifier using the core patterns of various types of license plates, improving both the computation load and the accuracy of license plate detection. To show its superiority, our approach is compared with other state‐of‐the‐art approaches. In addition, we collected 20,000 images including license plates from real traffic scenes for comprehensive experiments. The results show that our proposed approach significantly reduces the computational load in comparison to the other state‐of‐the‐art approaches, with comparable performance accuracy.     

电站锅炉引风机提高出力的改造

通过对朝阳电厂锅炉引风机出力不足原因的分析,提出了增加叶轮直径提高引风机出力的方法,改造后实际运行表明引风机性能完全满足锅炉额定负荷的要求,从根本上解决引风机出力不足的问题。     

A 12-b, 10-MHz, 250-mW CMOS A/D converter

A 12-b, 10-MHz, 250-mW, four-stage analog-to-digital converter (ADC) was implemented using a 0.8-μm p-well CMOS technology. The ADC based on a digitally calibrated multiplying digital-to-analog converter (MDAC) selectively employs a binary-weighted capacitor array in the front-end stage and a unit-capacitor array in the remaining back-end stages to obtain 12 b level linearity while maintaining high yield. All the analog and digital circuit functional blocks are fully integrated on a single chip, which occupies a die area of 15 mm² (4.2 mm×3.6 mm). Measured differential nonlinearity (DNL) and integral nonlinearity (INL) of the prototype are less than ±0.8 LSB and ±1.8 LSB, respectively     

A dynamic frequency grid allocation scheme for the efficient designof equiripple FIR filters

In the design of a digital filter, the frequency response is often optimized to meet a given set of specifications on a dense grid of frequency points. The density of the frequency grid points must be sufficiently high so that the frequency response of the filter does not violate the specifications at frequencies in between the grid points. However, the computational complexity of the design process and the storage requirements of the computer increase with the number of frequency grid points. We propose a novel dynamic: grid point allocation technique for the design of minimax optimum FIR filter. It uses a sparse frequency grid but will produce a design that is the same as one designed on very dense frequency grid points. It requires significantly less computer time and memory resources compared with fixed grid point algorithms     

天然气增压卸车工艺的模拟与分析

为了克服LNG槽车空温气化器自增压卸车工艺流程复杂、效率低、卸车时间长、受环境因素干扰大、占地面积大的缺点,提出了一种天然气增压卸车工艺流程。采用流程数值模拟软件,建立天然气增压卸车工艺的计算模型,研究计算天然气增压卸车过程中LNG槽车储罐内压力、温度、液位等参数随时间的变化过程,计算卸车过程所需时间及天然气流量。分析表明,天然气增压卸车流程简单、卸车时间短、效率高,且不受环境条件影响,能够大幅提高卸车撬的利用率。