Design of a superconducting low beta niobium resonator

The proposed high current injector for the superconducting Linac at the Inter-University Accelerator Centre will have several accelerating structures, including a superconducting module which will contain low beta niobium resonators. A prototype resonator for the low beta module has been designed. The resonator has been carefully modelled to optimize the electromagnetic parameters. In order to validate them, a room-temperature copper model has been built and tested. In this paper we present details of the electromagnetic design of the low beta resonator, briefly discuss the mechanical and engineering design, and present results from the measurements on the room-temperature copper model.     

Study and design of RF coupler for Chinese ADS HWR superconducting cavity

An RF power coupler is a key component of the superconducting accelerating system in Chinese ADS proton linac injector I, which is used to transmit 15 kW RF power from the power source to the superconducting HWR cavity. According to the requirement of working frequency, power level, transmission capability and cooling condition, the physics design of coupler has been finished, which includes RF structure optimization, thermal simulation, thermal stress analysis and so on. Based on this design, the prototype of HWR coupler has been fabricated, and it has successfully passed the high power test.     

Engineering two-mode squeezed states of cold atomic clouds with a superconducting stripline resonator

A scheme is proposed for engineering two-mode squeezed states of two separated cold atomic clouds positioned near the surface of a superconducting stripline resonator. Based on the coherent magnetic coupling between the atomic spins and a stripline resonator mode, the desired two-mode squeezed state can be produced via precisely control on the dynamics of the system. This scheme may be used to realize scalable on-chip quantum networks with cold atoms coupling to stripline resonators.     

Mechanical and thermodynamic properties of infrared transparent low melting chalcogenide glass

The properties of infrared (IR) transparent chalcogenide glass Se₅₇I₂₀As₁₈Te₃Sb₂ have been studied for the first time by dynamic mechanical analysis (DMA). This glass demonstrates both high transparency in a broad IR band (1–12 μm) and a particularly low softening point (near 50 °C). It is known as one of the best adhesives intended for the binding of IR optics elements. The DMA method gives valuable information about the complex Young’s modulus of the glass in its softening region. In parallel with the study of mechanical properties of the glass the character of its glass transition process has been investigated. Our results of DMA were then compared with our thermodynamic data obtained by scanning calorimetry. The peak of mechanical losses in DMA appears to be situated considerably higher than the calorimetrically determined glass transition temperature.     

Mechanical and Thermal Properties of Polyurethane Elastomers Synthesized with Toluene Diisocyanate Trimer

A series of polyurethane elastomers (PUE) incorporating TDI (toluene diisocyanate) trimer were synthesized via an in-situ polymerization and prepolymer process. It was found that for the sample with 10 wt% or less TDI trimer, the stress–strain curves of PUE exhibited the characteristics of a ductile failure with relatively high tensile strength and elongation at break. However, with incorporation 20～30 wt% of TDI trimer, the samples changed to brittle fracture. All PUE samples exhibited a loss peak corresponding to the glass transition temperature (T_g ) of the soft-segments, which shifted to higher temperature and decreased in peak height by incorporation of the three-functional isocyanurate rings. Although the TDI trimer modified PUE showed only slightly higher onset and peak degradation values than that of PUE in the absence of TDI trimer, there were still big differences in the end temperatures of the second stage. The value of activation energy and frequency factor fluctuated for varying samples, indicating that the thermal stability of PUE can be improved to a certain degree by incorporation of TDI trimer, but not so remarkably.     

Mechanical and Thermal Performance of High-Density Polyethylene/Alumina Nanocomposites

High-density polyethylene (HDPE) nanocomposites reinforced with pristine and vinyltrimethoxysilane (VTMS)-treated alumina nanoparticles of 2, 4, and 6 wt% were melt-compounded in a twin-screw extruder followed by injection molding. Their structure, thermal and mechanical behaviors were studied. Fourier transform infrared (FTIR) spectra showed that VTMS was successfully covalently grafted to the alumina nanoparticles. The X-ray diffraction (XRD) patterns indicated that the alumina nanoparticle additions broadened the characteristic peak width of HDPE, indicating that they reduced the crystallite size of HDPE. The heat deflection temperature and thermogravimetric analyses demonstrated that the dimensional and thermal stability of HDPE were enhanced markedly by adding pristine and silane-treated alumina nanoparticles. The alumina nanoparticle additions were also beneficial in enhancing Young's modulus and yield strength of HDPE. The reinforcing effect was particularly apparent in the silane-treated nanocomposites due to improved filler–matrix interactions.     

连续变焦距镜头结构设计及焦距实时输出分析

机械补偿式变焦距镜头以其自身的优点受到了广泛的关注和应用。介绍机械补偿式三组元连续变焦系统的基本工作原理及组成,根据实际使用要求,设计出保证变倍过程中变倍组和补偿组按一定函数规律运动的圆柱凸轮结构、导向机构及相应的加工工艺,从变倍运动方程和设计的变焦结构形式出发,分析变焦过程中焦距实时输出的实现方法和存在的问题,并提出相应的解决措施,对焦距值实时输出精度的提高以及变焦距镜头的设计和装调具有借鉴作用。     

Parametric resonance and Hopf bifurcation analysis for a MEMS resonator

We study the response of a MEMS resonator, driven in an in-plane length-extensional mode of excitation. It is observed that the amplitude of the resulting vibration has an upper bound, i.e., the response shows saturation. We present a model for this phenomenon, incorporating interaction with a bending mode. We show that this model accurately describes the observed phenomena. The in-plane (“trivial”) mode is shown to be stable up to a critical value of the amplitude of the excitation. At this value, a new “bending” branch of solutions bifurcates. For appropriate values of the parameters, a subsequent Hopf bifurcation causes a beating phenomenon, in accordance with experimental observations.     

Structure and Mechanical Stability of Epoxy Modified Polyurethane Foam Under Heat and Stress

A series of phenolic epoxy resin (PEP) modified polyurethane foams (PUF) were prepared via an in-situ polymerization, one step process. It was found that the epoxy modified PUF foam exhibited a perforated network structure with larger cell size, higher open cell porosity and enhanced ovality compared with pure PUF. With increasing content of PEP, the tensile strength, elongation at break and low temperature modulus of PUF decreased. A single T_g was observed for PEP modified PUF, indicating that the two component phases of the polyurethane-epoxy were miscible. With increasing PEP content, the T_g of PUF shifted slightly to higher temperature, tan δ_max dropped to lower values, and the retention value of the storage modulus at ?20 and ?10?°C increased. For pure PUF, the cell walls degraded and the structure became disordered after aging under heat and stress, while for PUF/20wt%PEP, the degradation degree was obviously reduced, and an orientation of the cells along the stress direction and a density increase was observed. During aging at 200?°C, the retention of the mechanical properties of PUF/20wt% PEP was much higher than that of pure PUF, and it showed superior stability under heat and stress, attributed to incorporation of the thermally resistant oxazolidone rings and benzene rings in the PU backbones, the highly cross-linked networks of the polyurethane-epoxy systems and the obvious orientation of the cells under stress.     

Numerical analysis of non-confocal configurations of a hybrid stable-unstable resonator

The results of numerical simulations are reported modeling the behavior of a unidimensional Hybrid Stable-Unstable Resonator (HSUR) in strongly non-confocal configurations. Our analysis shows that such a resonator setup can produce cavity losses consistent with our design requirements and extract a Beam with Propagation Parameter better than 3 mm mrad.     

Mechanical properties an undercut evaluated resonance test and of silicon nanobeams with by combining the dynamic finite element analysis

Mechanical properties of silicon nanobeams are of prime importance in nanoelectromechanical system applications. A numerical experimental method of determining resonant frequencies and Young＇s modulus of nanobeams by combining finite element analysis and frequency response tests based on an electrostatic excitation and visual detection by using a laser Doppler vibrometer is presented in this paper. Silicon nanobeam test structures are fabricated from silicon-oninsulator wafers by using a standard lithography and anisotropic wet etching release process, which inevitably generates the undercut of the nanobeam clamping. In conjunction with three-dimensional finite element numerical simulations incorporating the geometric undercut, dynamic resonance tests reveal that the undercut significantly reduces resonant frequencies of nanobeams due to the fact that it effectively increases the nanobeam length by a correct value △L, which is a key parameter that is correlated with deviations in the resonant frequencies predicted from the ideal Euler-Bernoulli beam theory and experimentally measured data. By using a least-square fit expression including △L, we finally extract Young＇s modulus from the measured resonance frequency versus effective length dependency and find that Young＇s modulus of a silicon nanobeam with 200-nm thickness is close to that of bulk silicon. This result supports that the finite size effect due to the surface effect does not play a role in the mechanical elastic behaviour of silicon nanobeams with thickness larger than 200 nm.     

Mechanical properties of silicon nanobeams with an undercut evaluated by combining the dynamic resonance test and finite element analysis

Mechanical properties of silicon nanobeams are of prime importance in nanoelectromechanical system applications.A numerical experimental method of determining resonant frequencies and Young’s modulus of nanobeams by combining finite element analysis and frequency response tests based on an electrostatic excitation and visual detection by using a laser Doppler vibrometer is presented in this paper.Silicon nanobeam test structures are fabricated from silicon-oninsulator wafers by using a standard lithography and anisotropic wet etching release process,which inevitably generates the undercut of the nanobeam clamping.In conjunction with three-dimensional finite element numerical simulations incorporating the geometric undercut,dynamic resonance tests reveal that the undercut significantly reduces resonant frequencies of nanobeams due to the fact that it effectively increases the nanobeam length by a correct value △L,which is a key parameter that is correlated with deviations in the resonant frequencies predicted from the ideal Euler-Bernoulli beam theory and experimentally measured data.By using a least-square fit expression including △L,we finally extract Young’s modulus from the measured resonance frequency versus effective length dependency and find that Young’s modulus of a silicon nanobeam with 200-nm thickness is close to that of bulk silicon.This result supports that the finite size effect due to the surface effect does not play a role in the mechanical elastic behaviour of silicon nanobeams with thickness larger than 200 nm.     

Optimization and analysis of series-coupled microring resonator arrays

In terms of the coupled mode theory and transfer matrix technique, novel formulas of the amplitude coupling ratios and transfer functions are presented for a series-coupled microring resonator (MRR) array. By using these formulas, parameters are optimized, and transmission characteristics including the transmission spectrum and the insertion loss are analyzed for a SiN/SiO₂ series-coupled MRR array on Si substrate. The box-like spectral response is successfully obtained owing to the proper selection of the amplitude coupling ratio between the channel and the ring, and that between adjacent rings, as well as the number of series-coupled rings.     

Mechanical passive and active models of the human basilar membrane

Simple three-dimensional passive and active models of the human basilar membrane were built, solved using the Finite Element Method and tested. In the active model an active mechanism connected with electromotility of outer hair cells was included. In the active model the active mechanism was incorporated in the form of additional, local pressure load. In the passive model the active mechanism was neglected. Hydrodynamic coupling between the cochlear partition and cochlear fluid was excluded in both models. Geometrical and physical parameters of the model were chosen to be adequate to those of humans in the best possible way. However, some of these parameters had to be estimated. The models were tested by calculation of typical curves known from cochlear measurements performed mostly on animals. For the passive model a linear input-output function and very small values of the basilar membrane velocities were obtained. This behaviour is to be expected for the passive model and for the basilar membrane in the poor physiological condition. For the active model the compressed input-output functions, tuning curves, isointensity curves and reasonable BM velocities were obtained. Possible inadequacies, which could explain the differences between numerical results and measurements were described.     

Organic Nano-Montmorillonite for Simultaneously Improving the Flame Retardancy,Thermal Stability,and Mechanical Properties of Intumescent Flame-Retardant Silicone Rubber Composites

The flammability of room temperature vulcanized silicone rubber (RTVSR) composites filled with melamine phosphate (MP) as intumescent flame-retardant additives was characterized by limiting oxygen index (LOI), UL-94 test, and cone calorimeter. In addition, the thermal degradation of the composites was studied using thermogravimetric analysis (TGA). Furthermore, in order to relate to actual application requirements, the comprehensive performance of the RTVSR/MP composites was optimized by adding organic nano-montmorillonite (OMMT) as a partial substitute for the MP. The as-prepared intumescent flame-retardant RTVSR/MP/OMMT nanocomposites were characterized by LOI, UL-94 test, TGA, cone calorimetry, scanning electron microscopy (SEM), and mechanical tests. The residue morphology formed after the burning of the nanocomposites was analyzed by its SEM and digital photographs. The results showed that the flame-retardant nanocomposites filled with 10 phr OMMT and 35 phr MP displayed the best comprehensive performance in terms of the flame retardancy, mechanical properties, and heat stability at low cost. It is expected that the intumescent flame-retardant silicone rubber composites with simultaneously improved flame retardancy, thermal stability, and mechanical properties will meet more requirements of the increasingly complex applications.     

Thermal stability of microstructures and mechanical properties in a Fe-based Fe-Cr-Mn-Cu-Mo multi-component alloy

A Fe-based multi-component alloy, 60Fe-12Cr-10Mn-15Cu-3Mo, was designed and fabricated for nuclear applications in the present study. The crystal structure of the alloy is a ～85% body – and 15% face–centered cubic. A detailed microstructure analysis indicated that Cu segregated in the alloy to form Cu-rich precipitates, and the Cu precipitates grew during high temperature annealing at up to 773?K. The high temperature tensile test of the alloys showed that both the yield stress and tensile strength of the 60Fe-12Cr-10Mn-15Cu-3Mo were greater than those of typical austenitic and ferritic stainless steels at 773?K. The Vickers microhardness of the designed alloy did not change after high temperature annealing for 1?h at up to 1073?K. The results indicated that the designed alloy has the potential to be used for high temperature applications.     

Comment on “a stable yag resonator yielding a beam of very low divergence and high output energy”

The explanation is given for experimental results on a stable YAG resonator proposed by Sarkies.     

圆形高斯镜平凹腔腔镜变形时激光模场分析

把圆形高斯镜平凹腔自再现模的衍射积分方程转化为有限阶的矩阵方程,在平面输出镜呈高斯分布的镜面变形时,数值计算了激光场模式的场强、相位分布和模式本征值。结果表明,当变形量较小时,随着变形量的增加,镜面上光场的分布范围增大,也就说明模体积增大,但镜面光场仍保持拉盖尔-高斯光束基模特征,相位由平面慢慢变得凸起,远场分布变化不明显。当变形量较大时,光场分布开始发生畸变。从模式本征值的变化看,在一定的变形范围内,本征值下降不多,说明较小的变形量对激光损耗影响不大,仍能使激光较稳定输出。在圆形高斯镜平凹腔输出镜发生不大的高斯状变形的情况下,仍有维持输出高质量激光束的能力。     

The Effect of Talc on the Mechanical,Crystallization and Foaming Properties of Poly(Lactic Acid)

Poly(lactic acid) (PLA)/talc composites containing different contents of talc were prepared by melt blending. Multiple properties of the prepared composites were investigated including mechanical, rheological and crystallization as well as foaming properties. Tensile test results indicated that the mechanical properties of the composite with 3% wt. talc showed significant reinforcement and toughening effect. When the talc content reached 10%, Young's modulus of the composite was increased by 35% compared with pure PLA. The morphological results showed that the talc layers were partially delaminated and uniformly dispersed in the PLA matrix at low loading. Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) results indicated that 3% wt. talc significantly increased the crystallinity of the PLA matrix. The thermogravimetric analysis (TGA) results demonstrated that the thermal stability of PLA/talc composites was enhanced as well. Moreover, talc at low loading could act as a plasticizer in the polymer flow, which was investigated by rheological tests. The batch foaming experiments revealed that 3% wt. talc loading had the most notable heterogeneous nucleation effect, with the cell size decreasing from 15.4 μm for neat PLA to 8.5 μm and the cell density increasing by 298%.