Surface Micromachining of Bulk Acoustic Wave Filters

The most common typical bulk acoustic wave (BAW) filters are fabricated using bulk micromachining technology, but they have several disadvantages. This paper describes a new structure for front end passband BAW filters manufactured using surface micromachining. Porous silicon is used as a thick sacrificial layer. The structure reduces the influence of the support film on the filter to improve the VLSI compatibility as well as the filter quality. The cross-talk between resonators with different frequencies can be dramatically reduced by using resonators with a self-supporting structure.     

Effect of ash on coal structure and combustibility

Four bituminous coals and one anthracite were used in this study. On the basis of the similar volatile matter contents of the four bituminous coals, the effects of ash in coal on the microstructure, carbonaceous structure, and chemical composition of pulverized coal were studied. Thermogravimetric analysis was used to study the effect of the addition of anthracite on the combustibility of four different bituminous coals. The results showed that with the increase of ash content in pulverized coal, the microstructure of carbon particles in coal was not much different. However, the analysis results of Raman spectroscopy and X-ray diffraction pattern showed that as the ash content increased, the degree of graphitization of coal carbonaceous structure gradually decreased. The combustibility of the four bituminous coals were better than that of the anthracite. When bituminous coal and anthracite were mixed and burned, the combustibility of the mixed sample decreased as the ash content increased.     

Formation and distribution of disinfection by-products during chlorine disinfection in the presence of bromide ion

The influences of contact time and pH value on the formation and distribution of four species of trihalomethanes and five species of haloacetic acids during chlorination in the presence of bromine were investigated. Results showed that the distribution of molar fraction of trihalomethanes varied with contact time due to the change of bromide ion concentration during chlorination. Most of the trihalomethanes comprising bromine-containing species and the favored products of the haloacetic acids were chlorine-containing species after 24 h of chlorination. The extent of bromine incorporation in trihalomethanes and haloacetic acids both decreased with time. The contact time also had influence on the formation rate of different species of haloacetic acids, The formation and distribution of trihalomethanes and haloacetic acids strongly depended on the chlorination pH value. All of the trihalomethanes species formation increased with the increase of pH value except the bromoform that had not been detected, The molar fraction of bromodichloromethane and dibromochloromethane containing bromine increased with pH value while chloroform without bromine decreased. Under the pH range studied in this experiment, the predominant haloacetic acids species were trichloroacetic acid and dichloroacetic acid which all decreased with the increase of pH value and the level of TCAA was higher than that of DCAA.     

Biomimetic preparation of elastomeric fibers with micro/nano structures on the surfaces

Bioinspired by the spinning of spider silks, the biomimetic preparation of elastomeric fibers with micro/nano structures on the surfaces was attempted, and as a result, three types of ultrafine fullvulcanized powdered nitrile-butadiene rubber (UFPNBR)/thermoplastic polyurethane (TPU) fibers were made. The first fiber was only decorated by the micron-sized grooves on the surface, and the second fiber was dotted by both the micron-sized grooves and nanometer-sized spheres on the surface, while the third fiber was helical and with a concave–convex surface. The biomimetic preparation mainly consisted of four steps, and the formation mechanism was described as an integrated mechanism of diffusion, coagulation, self assembly, and microphase separation. The micro/nano structures on the fibers were controlled by changing the mass ratio of UFPNBR to TPU and environment of vertical stretching. The UFPNBR/TPU elastomeric fibers were hoped to have an integrated function of superhydrophobicity, self cleaning, and mechanical improvement of toughness or strength.     

Influences of interphase on dynamic effective properties of composites reinforced by dispersed spherical particles

The influences of interphase on dynamic effective properties of composites reinforced by randomly dispersed spherical par ticles were studied. A thin homogeneous elastic interphase with different shear and bulk moduli, located between the reinforced particle and the host matrix, was introduced to model the interfacial bonding state. The effects of such an interphase on the coherent plane waves were studied numerically. Numerical simulations were carried out for SiC-Al composites with four typical cases of interphase. It was found that the property of interphase has significant influences on the effective propagation constants of coherent waves and the dynamic effective elastic moduli of the composites. The influences on the coherent longitudinal wave and the coherent shear waves were different and dependent upon the frequency range. Moreover, several imperfect interface models, i.e., the spring model, mass model, and spring-mass model, were studied numerically and compared with the interphase model. It was found that the spring model is a more suitable model than the mass model for the light and weak interphase whereas the mass model is a more suitable model than the spring model for the heavy and strong interphase.     

采用超声组装与滚压工艺制备铝–碳纳米管复合材料

This study introduced a novel fabrication of aluminum–carbon nanotube (CNT) composites by employing bulk acoustic waves and accumulative roll bonding (ARB). In this method, CNT particles were aligned using ultrasonic standing wave in an aqueous media, and the arrayed particles were precipitated on the aluminum plate substrate. Then, the plates rolled on each other through the ARB process with four passes. Optical and scanning electron micrographs demonstrated the effective aligning of CNTs on the aluminum substrate with a negligible deviation of arrayed CNTs through the ARB process. The X-ray diffraction pattern of the developed composites showed no peaks for carbon and aluminum carbide. In addition, tensile tests showed that the longitudinal strength of the specimens processed with aligned CNTs was significantly greater than that of the specimens with common randomly dispersed particles. The proposed technique is beneficial for the fabrication of Al–CNT composites with directional mechanical strength.     

Effect of Media on the in vitro Degradation of Biodegradable Ureteral Stent

The biodegradable ureteral stent should retain their supporting properties for defined period and then gradually degrade to small particles with the flow of urine. The mechanism and process of the stent’s degradation should be investigated and understood well due to its direct impact on the stents’ usage. An enhanced braidbased degradable ureteral stent composed of poly-glycolic acid(PGA) and the copolymer of lactic and glycolic acid(PGLA) was evaluated in vitro in this study with four kinds of degradable media:human urine(HU,pH = 7. 4),artificial urine(AU,pH = 5. 8),and phosphate buffer solutions( PBS,pH = 5. 8 and 7. 4) so as to compare the effects of media on the degradation of stents. The mechanical properties and morphology were observed at different degradaing time intervals of 0,7,14,21,28,and 35 d. The in vitro degradation behaviors of stents in four kinds of media were extremely different. The degradation rate of stents in HU was the highest. The impact of media’s pH to the degradation is not obvious while the components in the media contribute much to the difference.     

Separation and Anti-Hantaan Virus Activity of Extracts from Alternanthera philoxcroides in vitro and in vivo

A water-soluble substance was extracted from the Chinese herb, Alternantheraphiloxcroides with hot water and alcohol. Aliquots of this initial extract were further fractionated by treatment with ether, ethyl acetate and alcohol respectively. The four extracts were assayed for anti-viral activity against three serum, Hantaan virus 114 （HV114）, HV435 and A9 strains. Results show that the four extracts are capable of inhibiting Hantaan virus propagation, of which extract No. 1 has the best efficiency. The three dosage of extract No. 1, which are used upon three Hantaan virus serum IC50, are 153, 157, 154 μg/mL. New-born mice were made to be infected with HV114 and then fed in vivo with extract No.l on the 3rd, 10th and 14th days after being infected by the virus. The treatment continued for 8 days with a dosage of 2.5 g/kg. Result shows that survival rates of mice were 75%, 50% and 0, respectively. The median time to death （MTDs） of the three groups were 37, 30, 23 days.     

Effect of different atmospheres on dry friction behavior of steel sliding against brass at high speed

The atmosphere components have an influence on tribological behaviors of tribo-pairs. Through changing the atmosphere component, the effect of atmosphere component on the tribological behaviors of CrNiMo steel against brass at high sliding velocity was investigated. The wear test was carried out on a high-speed friction and wear test rig whose test atmosphere could be controlled. The tests were performed at four sliding velocities （30, 40, 50, 60 m/s）, one contact pressure （1.33 MPa） and two atmosphere components （N2 or O2）. The morphologies of the worn surfaces of various pins were observed with a scanning electron microscope. The chemical compositions of the surfaces and subsurfaces for steels were determined with an energy dispersion spectroscopy. The results showed that the wear rate of the steel pins were low all the time with the sliding velocity increasing in oxygen atmosphere, and that the wear rate of the steel pin in nitrogen atmosphere was higher than that of the steel pin in oxygen atmosphere. It was found that the thin and compact oxidation layer formed on the worn surface of the steel in oxygen atmosphere played a key role in wear resistance. However, the wear rate of the steel pin increased rapidly with the sliding velocity increasing in nitrogen atmosphere, which was attributed to the thick and loose surface layer formed on the worn surface of the steel.     

RELIABILITY OF AEROCRAFT GEAR FATIGUE STRENGTH

With the method of group test, fourty pairs of carburization-quenching gears made from 16NCD13 steel for aerocraft were tested to research the contacting fatigue strength on tooth flank. As a result, the samples of fatigue life at the moments when the pitting appears and reaches failure criterion were obtained at four stressing levels respectively. The distribution rule of fatigue life were distinguished, and the distribution parameters were estimated by statistical analysis. Based on that, the R-S-N curves with confidence 95% of contacting fatigue on gear tooth flank were evaluated. Therefore, the basic data were provided for the reliability design of the gears and prediction of their life.     

Study of GaAlAs/GaAs Planar Lightwave Filters

1Introduction　wavelength divisionmultiplex(WDM)opticalnetworkhasbecomethemaintrendofthesuper speedcommunicationsnetworkdevelopment,andthewavelength divisionmultiplexerbasedonwavefilteringisthekeyoftheWDMapplication .Thedesignandfabricationofopticalfiltershasdrawntheresearchattentionofvariouscountries.Thecommonopticalfiltersincludegratingfilter[1] ,interferentialfilter[2 ] ,andresonatorfilter[3 ] etc .Basedontheplanarlight wavecircuit (PLC) ,theresonatoropticalfilterhastheadvantagesofcompa…     

新型开环谐振器带通滤波器的设计

提出一组新型的方形开环谐振器,使用这种新型的谐振器设计微带线带通滤波器,可以有效地减小滤波器的尺寸.利用其中一种新型的谐振器,设计加工了一个小型化带通滤波器,仿真与测试结果显示,该滤波器有很好的频率选择性、阻带特性和较小尺寸.与传统的开环谐振滤波器比较,尺寸减小了30%.     

基于脊型波导的跑道型环形谐振器的偏振模式分离特性分析

设计和分析了基于绝缘体上硅的脊型波导的偏振模式分离谐振腔。通过分析超小脊型波导的模式双折射,将该微环谐振腔应用到定向耦合器,实现从准TE和准TM偏振模式在特定波长范围内同一输出端口的分离。试验证明,准TM偏振模式分离后的Q值达23 000±1 000,是未分离时的两倍。该新型跑道型环形谐振腔的特点在光学元件中的应用非常有前景,为新型环形耦合器的深入研究提供了理论参考。     

基于改进渐进空间映射算法的滤波器设计方法

提出了改进渐进空间映射算法的新的滤波器设计方法．首先，将初始映射矩阵改进为单变量偏导矩阵．其次，在参数抽取过程中巧妙地引入柯西法，从而在保证精度的前提下，加快了参数抽取的速度．最后，通过一个4腔的同轴腔体滤波器的设计实例验证了该文的方法．滤波器的电磁仿真结果与理论综合结果吻合良好，证实了该方法的有效性．     

基于组合多通带谐振器的三频滤波器设计

提出了一种基于组合多通带谐振器的三频滤波器设计方法，该方法可以独立调节三个通带的中心频率及带宽.组合多通带谐振器是由一个阶跃阻抗谐振器(SIR)和一个普通半波长谐振器组成，其中SIR可以产生第一和第三通带，另外一个谐振器产生第二通带，引入新的馈电结构对两个谐振器同时进行激励。文中分别利用级联型和伪交指型组合谐振器设计三频滤波器，每种结构都有足够的自由度来获得所需的带宽和中心频率，最后设计并加工了两个工作在WLAN(2.45GHz,5.25GHz) 和WiMAX(3.5GHz)频段的三频滤波器，测量结果与仿真结果吻合良好.     

声表面波谐振滤波器中纵横向耦合模式的研究及其复合应用

在通常的声表面波谐振滤波器中,由于采用的模式不同,纵向耦合谐振器具带宽大和插损低,带外抑制较差的特点;而横向耦合谐振器则具有带外抑制高,低插损及通带较窄的特点．为了综合两种滤波器的优点,采用了一种改进的滤波器结构,可同时利用纵向与横向耦合模式,得到既有较大带宽又有高带外抑制的声表面波谐振滤波器．运用耦合膜理论对纵横向模式的复合进行了分析,并在计算机上对这种结构的滤波器特性作了模拟,实验结果与模拟结果得到了较好的吻合．     

双臂折叠谐振器及其带通滤波器应用

为了实现微波滤波器的小型化,提出了一种新型的微型化双臂折叠谐振器,给出了该微型谐振器的耦合、馈电结构,并通过电磁仿真计算了其特性曲线;应用该微型谐振器,分别设计制作了一个带一对传输零点的四阶交叉耦合滤波器和一个六阶交叉耦合滤波器,测试结果与设计结果能较好的吻合.该微型谐振器的面积仅为方形开环谐振器的1/3,特别适合构成小型化、高选择性的微波带通滤波器.     

Optimization of PZT-Based Radio-Frequency Filters

Analytical solutions are presented for the wave equation for the electrode-piezoelectric-electrode sandwich structure in film bulk acoustic resonators (FBAR). The impedance for lead-zirconate-titanate (PZT)-based FBAR was derived using the proper boundary conditions and material parameters. A method is presented to adjust the resonant frequency based on the process and material properties. Ferroelectric-based radio-frequency filters were designed using FBARs. An accurate result is given for the filter impedance which can be used for other piezoelectric devices.     

高温超导滤波器研制

设计并制作了中心频率为2 007.5MH z,带宽为15MH z的6阶T l2B a2C aCu2O8高温超导微带滤波器.采用在谐振器之间插入微带条来微调耦合间距的办法,提高了设计的精确度.实测结果表明滤波器的最小插入损耗为0.25 dB,带外抑制约60 dB,带内波纹为0.16 dB,中心频率、带宽以及边带陡峭度等都与仿真结果吻合较好,验证了设计与制作的一致性.