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Cobalt-doped MoSe2/nitrogenated graphene composite has been successfully synthesized via a facile hydrothermal route and is investigated as an electrocatalyst for hydrogen evolution reaction (HER). The as-prepared samples are well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and Raman spectrum. The results reveal that Co-doped MoSe2 nanosheets which are characteristic of few layers (2–4 layers) and abundant exposed active edge sites are well anchored on the nitrogen-doped graphene sheets to constitute robust composites. When evaluated as catalysts for HER, the obtained composites demonstrate superior electrocatalytic activities toward HER.

A group of materials including water and silicon exhibit many anomalous behaviors, e.g., density anomaly and diffusivity anomaly (increase upon compression). These materials are hypothesized to have a liquid-liquid phase transition (LLPT) and the critical fluctuation in the vicinity of the liquid-liquid critical point is considered as the origin of different anomalies. Liquid gallium was also reported to have a LLPT, yet whether it shows similar water-like anomalies is not yet studied. Using molecular dynamics simulations on a modified embedded-atom model, we study the thermodynamic, dynamic, and structural properties of liquid gallium as well as its LLPT. We find that, similar to water-like materials predicted to have the LLPT, gallium also shows different anomalous behaviors (e.g., density anomaly, diffusivity anomaly, and structural anomaly). We also find that its thermodynamic and structural response functions are continuous and show maxima in the supercritical region, the loci of which asymptotically approach to the other and merge to the Widom line. These phenomena are consistent with the supercritical phenomenon in a category of materials with a liquid-liquid critical point, which could be common features in most materials with a LLPT.

Sulfur-doped SnO2 nanoparticles with ultrafine sizes have been successfully prepared by a one-pot hydrothermal method. The obtained samples are characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HRTEM), thermogravimetric (TG), analyzer UV-Vis spectroscopy, photoluminescence (PL) and electrochemical impedance spectroscopy (EIS). The experimental results indicate that the doping level of sulfur element as well as the bandgaps of SnO2 can be controlled to a certain extent by varying the amount of L-cysteine (L-cys). When evaluated as photocatalysts in the degradation of rhodamine B (RhB) and reduction of Cr(VI) under visible light region, the resultant sulfur-doped SnO2 nanoparticles demonstrate obviously enhanced photocatalytic activities due to the markedly improved visible light response and effective separation of the photo-generated electron–hole pairs.

We introduce a two-step hydrothermal and microwave method to prepare novel SnO2/MoS2 composites. The as-prepared samples are well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The experimental results indicate that the SnO2/MoS2 composites are composed of MoS2 nanosheets and ultrafine SnO2 nanoparticles with mean size of 3–4[Formula: see text]nm which are well-distributed and anchored on the surface of MoS2 nanosheets. The resultant composites demonstrate prominently improved electrochemical performances, which could be attributed to the unique and robust microstructures and synergetic effect between MoS2 and SnO2.

The self-consistent scheme (Budiansky, 1965) is one of the analytical methods to predict the effective properties of heterogeneous material. However, it has been noticed that this scheme cannot take the micro-structural information into the estimation. The full scale numerical simulation considering elaborately the micro-morphological characteristics, under certain conditions, needs too much computational resources (memory and time). A numerical version of self-consistent scheme based on finite element analysis is proposed to overcome the above drawbacks by combining the characteristics of numerical simulation and self-consistent scheme. As a demonstration, such scheme is applied to estimate the effective mechanical properties of bi-continuous composite in which all the constituent phases are on the equal status. The prediction is in good agreement with the full scale numerical simulation while the requirement on computational resource is reduced dramatically.

Hierarchical ZnO nanostructures were fabricated via a rapid and facile microwave-assisted route with different zinc salts as reactants. The obtained hierarchical ZnO nanostructures have good crystallinity and high purity. Moreover, it was found that various zinc salts have an obvious effect on the morphologies and microstructures of the final products. Additionally, the photocatalytic activity of the obtained ZnO samples under visible-light irradiation was also evaluated by degradation of Rhodamine B (RhB).

In modern numeric control (NC) servo systems, manual tuning approaches are still dominant in servo parameters regulation due to systems' complexity. In manual tuning, it is not easy to evaluate the regulated systems from frequency responses. With regard to such problems, in this paper, we put forward a fuzzy comprehensive evaluation method, where three different features are proposed based on expert experiences to specify the effectiveness of tuned parameters from system responses in low, medium and high frequency spectrums. This fuzzy comprehensive evaluation method has been validated against experiment results, which clearly demonstrates that these features can provide an objective judgment on the tuned parameters.

This paper has discussed the simulation and analysis to beam-forming of broadband parametric array in both rectangle and loop transducer array conditions. The simulation result shows that with a condition of same elements N=9 and similar array size r m =49mm, the main-lobe −3db beam width for difference frequency beam in rectangle array is about 6.3° (7.4° for the loop array) and the side-lobe amplitude is one percent less than the value of main-lobe peak (10% for the loop array). The rectangle transducer array is more effective in improving main-lobe directivity and inhibiting side-lobe amplitude. The method of element signal time-delay adopted to achieve parametric array beam-steering in rectangle transducer array in this paper, and the simulation and analysis about it are completed too. As a result of Beam-steering, the beam main-lobe turned to width more, its peak value of amplitude reduce obviously, and it doesn't point to the direction which is planned to. The causations about these problems are discussed in this paper, and it is verified that these problems can be modified by adding more elements and increasing array sizes.

Gait training is very important in the rehabilitation of neurological patients like stroke patients and spinal cord injury patients. To help those patients, a lower limb rehabilitation robot is developed. For obtaining a feasible gait, more accurate models based on ergonomics are necessary. We did gait experiment of human walking in order to reproduce the human gait. As a result of this experiment, we confirmed the effectiveness of the models to be established. Mathematical models in different phase are built based on the experiment. Kinematics modeling was presented. Finally, dynamic models based on Newton-Euler equations of the lower limbs rehabilitation robot during different phase were established. These models will provide more accurate data for the control system.

Several scenarios exist for the protein crystallization and aggregation in solutions near a metastable fluid-fluid phase separation below the solubility line. Based on computations, it was proposed that the fluid-fluid critical point enhances the crystallization rate by many orders of magnitude, while, based on experiments, it was proposed that the fluid-fluid spinodal controls the crystallization rate. Using molecular dynamic simulations for an isotropic model with sticky interaction, we show that neither of these scenarios adequately describes the crystallization mechanism near a metastable fluid-fluid phase separation. We find that the emergence of the high-density fluid inside the spinodal drastically enhances the crystal nucleation in the subcritical region following Ostwald's rule of stages.

We use molecular dynamics simulations to study the effects of confinement on the phase behavior of a water-like monatomic liquid that exhibits a liquid-liquid phase transition (LLPT) and a liquid-liquid critical point (LLCP). The liquid is confined between parallel walls and we focus on the effects of wall separation and surface chemistry (solvophobicity/solvophilicity) on the location of the LLCP, temperature of maximum density (TMD) line, and loci of compressibility maxima (CM). It is found that, independently of the surface solvophobicity/solvophilicity, the LLCP, TMD, and CM lines shift rapidly towards higher pressures and lower temperatures as the wall separation is reduced. It follows that the effects of confinement on the TMD and CM lines are indicative of the confinement effects on the LLCP/LLPT. Confinement effects are observable already when the liquid particles form ≈15 layers between the walls. For the case of water, this corresponds to a separation of ≈4-5 nm between the surfaces, larger than the confining dimension of the nanopores commonly used to study the hypothesized LLPT in confined water. Hence, our results suggest that such experiments should not be interpreted in terms of the phase diagrams proposed for bulk water.

This paper focuses on the design optimization of the applications of electrothermal polysilicon microactuators with the considerations of uncertainties from mathematical models and random variables. The deflections and actuation forces in the micro-cantilevers are modeled based on experiment results; furthermore, the non-negligible errors due to extrapolations are estimated numerically. The response models are utilized to formulate Reliability-Based Design Optimization problems. The Hybrid Reliability Approach is utilized to accurately and efficiently solve the probabilistic problems by adaptively selecting the reliability analyses from the accurate Modified Reliability Index Approach and the efficient Performance Measure Approach. Lastly, three different micro-actuators are designed and optimized with various levels of bound conditions.

This paper presents system-level modeling and simulation of force-balance MEMS comb accelerometers. The work focuses on the theoretical principles of the sense element and the interface electronics at first. Based on that, the parametric model of the sense element is established in this paper, and the simulation results of this model match well with the theoretical results, which can prove we can use the parametric model of the sense element to establish the system-level model of force-balance MEMS comb accelerometers. The system-level model of force-balance MEMS comb accelerometers including the parametric model of the sense element and the interface electronics is established in MATLAB. The simulation results show that the designed force-balance comb accelerometer has high sensitivity, wide range, low nonlinear distortion and wide bandwidth.

Water confined in narrow nanopores that prevent ice crystallization is usually studied as a means to understand the anomalous behavior of bulk liquid water. Nevertheless, there is no agreement on the similarity of the thermodynamics of bulk and nanoconfined liquid water. In this work, we use molecular dynamics simulations with the mW water model to investigate the phase behavior of liquid water in bulk and confined in a 1.5 nm cylindrical pore with water-surface interactions identical to water-water interactions. Through analysis of the isochors of bulk liquid water V(T,p) we extrapolate the locus of a putative liquid-liquid critical point (LLCP) in bulk mW water at 190 K and 1215 atm. This is a "virtual LLCP", as it would lie in a region of the phase diagram where fast crystallization of water impedes equilibration of the liquid. We find that confinement has a weak effect on the loci of the thermodynamic anomalies: the maxima in density and heat capacity of confined water occur at T,p similar to that in bulk. The heat capacity peak of confined water is due to a transformation within the confined liquid; we verify that ice does not form in the pores. Confined mW water presents a heat capacity maximum C(p)(max)(p) up to the highest pressure we investigated, 4000 atm. The magnitude of the heat capacity peak C(p)(max)(p) has a nonmonotonous dependence with pressure, attaining a maximum at conditions close to those of the locus of the bulk water's virtual LLCP. We do not find, however, direct evidence of a first-order liquid-liquid transition in confined water for pressures above or below the locus of the maximum response function. The extreme value of the response functions of confined water could be a rounded manifestation of an equivalent feature in the free energy surface of bulk water.

We report recent efforts to understand a broad range of experiments on confined water and protein hydration water, many initiated by a collaboration between workers at the University of Messina and MIT-the editors of this special issue. Preliminary calculations are not inconsistent with one tentative interpretation of these experiments as resulting from the system passing from the high-temperature high-pressure 'HDL' side of the Widom line (where the liquid might display non-Arrhenius behavior) to the low-temperature low-pressure 'LDL' side of the Widom line (where the liquid might display Arrhenius behavior). The Widom line-defined to be the line in the pressure-temperature plane where the correlation length has its maximum-arises if there is a critical point. Hence, interpreting the Messina-MIT experiments in terms of a Widom line is of potential relevance to testing, experimentally, the hypothesis that water displays a liquid-liquid critical point.

Based on T-M model and H-M model, the author analyzes empirically stock selection and market timing of 100 open-end securities investment funds in China under bull market. The research result shows that the most of open-end securities investment funds have some stock selection ability, but it isn't notable in statistics; the most of open -end securities investment funds have some market timing ability; but it isn't notable in statistics.

Utilization modes for micro audio near-distance directional loudspeaker in portable multimedia devices are investigated to examine a novel auditory experience. This novel loudspeaker can provide private listening service by emitting the audible sound with high directivity. Two kinds of micro transducer array as the emitter of the directional loudspeaker are presented. One of them is fabricated by MEMS technology and another is assembled by PZT ceramic transducers. The testing results of impedance, frequency response and sound pressure level characteristics are described and compared. It indicates that the performance of PZT ceramic transducer array is better than the MEMS-based transducer array. But the MEMS-based array is the best solution because of the advantage of micro size even though its performance should be further improved and optimized. In the end, A prototype based on PZT ceramic transducer array is constructed for mobile phone usage and its acoustic characteristics are measured. The experiment result indicates the feasibility of utilizing the audio near-distance directional loudspeaker with low power consumption and micro size in portable multimedia devices.

Most genetic changes that promote tumorigenesis involve dysregulation of G1 cell cycle progression. A key regulatory site in G1 is a growth factor–dependent restriction point (R) where cells commit to mitosis. In addition to the growth factor–dependent “R,” which maps to a site about 3.5 hours after mitosis, there is another checkpoint later in G1 that is dependent on nutritional sufficiency that has also been referred to as R. However, this second site in late G1 can be distinguished both temporally and genetically from R. We are proposing that the late G1 regulatory site be more appropriately referred to as a “cell growth” checkpoint to distinguish it from R. This checkpoint, which likely has an evolutionary relationship to the yeast cell cycle checkpoint START, is regulated by signals governed by mTOR, the mammalian target of rapamycin. This review summarizes evidence that distinguishes R from the proposed cell growth checkpoint. Since both checkpoints are dysregulated in most, if not all, human cancers, distinguishing between these 2 distinct G1 regulatory checkpoints has significance for rational therapeutic strategies targeting oncogenic signals.

Two WSSV envelope proteins, VP31 and VP33, contain a conserved Arg-Gly-Asp (RGD) sequence. In order to investigate the role of the RGD motif, wild-type and RGD-mutated VP31 and VP33 were recombinantly expressed in E. coli. The cell adhesion ability of the proteins was investigated in crayfish haemocytes using a fluorescence assay. The results showed that recombinant wild-type VP31 and VP33 had cell adhesion activity, and the RGD motif in VP31 was required for cell adhesion, which could be inhibited by an RGDT peptide. In contrast, the interaction of VP33 with cells did not require the RGD motif. These data indicate that the RGD motif plays an important role in the interaction between VP31 and host cells.

Lack of efficient gene delivery and expression methods is the major obstacle for crustacean research in the cellular level. Here, we reported the construction of an expression vector with a strong promoter from shrimp white spot syndrome virus. This vector could efficiently express foreign genes in the primary culture of crayfish hemocytes with the transfection efficiency between 5 and 10% by electroporation. Our findings provide a method for in vitro gene functional study in primary crayfish cells.

The synthesis of gold nanoparticles (AuNPs) by UV irradiation of the solution of polystyrene-block-poly(2-vinyl pyridine)/HAuCl4 (PS-b-PVP/HAuCl4) complexes was investigated. AuNPs with block copolymer shell structures can be easily generated by simply control of the block copolymer concentration and the loading ratio of the HAuCl4 precursor. The cross-linked block copolymer shell structures were determined by transmission electron microscopy (TEM), contact angle measurement and thermogravimetic analysis (TGA). The obtained AuNPs with copolymer shells are stable in organic solvents and biochemical buffers.

White spot syndrome virus (WSSV) is a large enveloped virus, but the organization of its envelope proteins remains largely unknown. In the present study, we used blue native polyacrylamide gel electrophoresis (BN-PAGE) and SDS-PAGE in combination with mass spectrometry to analyze the envelope protein complexome of WSSV. Our results show that the viral envelope consists of multi-protein complexes (MPCs). Within them, the envelope protein VP19 exists as a homotrimer, while another major envelope protein, VP28, mainly exists as a homotetramer. The most notable feature is that the majority of MPCs include VP26 and VP24, suggesting that these two proteins might serve as hub proteins to recruit low-abundance proteins to MPCs and play crucial roles in the process of protein complex formation. Furthermore, we found significant evidence for interactions between several low-abundance proteins, such as VP52B/VP38/VP33 and VP12/VP150. The result of this study may promote the further research on WSSV envelope assembly.

based on the classical laminated plate theory and the piezoelectric plate and shell theory, this paper presents an analytical analysis of a circular piezoelectric actuator used in micro-systems. The actuator consists of four layers: piezoelectric ceramic, metal, electrodes and epoxy resin. Each layer has different dimensions, material properties and initial stress. For the simply supported boundary conditions, equations for the calculation of first-order resonance frequency and dynamic displacement of structure are derived by Rayleigh-Ritz method. A circular piezoelectric composite plate with elastic support is considered, and the results obtained from equations are consistent with the results from Finite Element simulation. The consistency of theoretical and simulation results validated the correctness and the validity of theoretical model. For various dimensions and material parameters, this analytical model can be used to predict the change of resonance frequency and dynamic displacement of the actuator. The analytical solution presented in this paper is significant for the optimization of piezoelectric actuator used in piezoelectric transducers

This paper discusses about microwave sulfur lamp. It is a kind of electrodeless lamp which can produce a pleasant spectrum similar to the sun in the plasma state excited by microwave energy in a resonant cavity, which can be used in large scale lighting, such as stadium, train station, air port, and disaster's relief and so on. Some typical applications of sulfur lamp, which have been made by us and Midea Group, used in golf course and moveable lighting.

Influenced by the economic cycle, power demand in china shows some cyclical fluctuations, which is unhealthy for the development of national economy and production efficiency of electric power industry. Correctly forecasting the fluctuation rule of power demand and the turning points in China is helpful to make the corresponding strategy complied with the cycle. With the full consideration of power demand fluctuations, the paper establishes a forecasting model based on maximum entropy method and ARMA model: firstly, the paper makes a spectrum analysis on the growth rate of power demand and the major cycle of the cyclical fluctuations can be correspondingly obtained, then a periodic function which can reflect the fluctuation features is employed through the least square method; secondly, the paper establishes an ARMA model on the residual series which can be obtained by eliminating the periodic sequence from the original series; at last, the hybrid forecasting model is obtained by combining the periodic function and ARMA model. Experimental results show that the proposed model is effective and reasonable.

Fluorescence PCR was applied to investigate the genetic diversities of 9 indigenous Chinese goat breeds and 1 exotic breed with 10 microsatellite DNA markers recommended by the Food and Agriculture Organization of the United Nations and the International Livestock Research Institute of Animal Genetics, which provide data for the preservation and utilization of indigenous goat breeds genetic resource. We found that the 7 breeds were high polymorphic while 3 breeds were moderate polymorphic. We also detected 119 alleles, and the effective allele number ranged from 1.4641 to 9.2911. The average heterozygosity of loci and breeds respectively varied from 0.2618 to 0.7672 and from 0.5196 to 0.7024. As well as SRCRSP23 site and Hexi cashmere goat had the highest average heterozygosity. Then we analyzed the phylogenetic trees (NJ and UPGMA), and found both of them were generally in accordance with their original breeding history and localities.

This paper presents a capacitive micromachined accelerometer with a comb-finger and cantilever beam structure. The principle of operation of the accelerometer, open-loop performance and closed-loop performance are introduced. A comparison between FEA and theoretical analysis is given, and the result is in good agreement with the prediction. Based the simulation result, the sensor behavior strongly depend on various design parameters. The desired performance parameters, displacement sensitivity and resolution can be obtained by adjusting the structure. The beam design optimization is performed, and the optimized design parameters are achieved, including beam length 500um, beam width 600um, and beam thickness 6um.

Coupled extensional and flexural vibrations of an ultrasonic piezoelectric transducer are studied in the paper. The ultrasonic piezoelectric transducer is made of piezoelectric polymer PVDF films and modeled as a corrugated cylindrical shell with a finite width in the ridge direction, which consists of multiple pieces of circular cylindrical surfaces smoothly connected along their ridges. The classical shell theory is used to obtain the theoretical solution. Effects of the edge constraints on vibrational characteristics of the resonant frequencies, mode shapes, and internal forces are investigated for a corrugated ultrasonic piezoelectric transducer consisting of a few circular pieces each with a thickness of about 40 microm, radius of 5 mm, and span angle of 120 degrees.

We use extensive molecular dynamics simulations with the monatomic model of water (mW) to characterize the thermodynamics and kinetics of the liquid-vapor (wetting-drying) equilibrium of water confined between nanoscopic hydrophobic plates. The transition in confined water is first-order-like, with two well-defined states (wet and dry) separated by a free energy barrier. Different from its bulk counterpart, the confined system oscillates between liquid and vapor: the two phases coexist in time but not in space. Also different from the phase behavior in bulk, there is a finite range of the thermodynamic variables (e.g., temperature or separation between the plates) for which the liquid and vapor state coexist in dynamical equilibrium. We determine the range of temperatures and plate separations for which reversible oscillations can be observed between a stable and metastable phase, compute the time scales of the phase transition along the equilibrium coexistence line, and investigate the pathway for drying along simple collective coordinates that describe the opening of a vapor bubble. The results of the simulations are compared with a simple capillary model for the thermodynamics and transition state theory for the kinetics of phase oscillations.

An equivalent electrical model of the MEMS comb accelerometer is presented in this paper, including the readout interface circuit. The accelerometer has only one proof mass, symmetrically suspended by four cantilevers. The displacement change of the proof mass is converted to the change of differential capacitance between the proof mass and adjacent fixed electrodes. In order to establish the mechanical characteristics of the accelerometer in this equivalent electrical model, we use the so-called analog behavioral modeling library to describe the mechanical part of the system. Through combining the electrical model of the acceleration sensor and the readout interface circuit, we get the system-level model of the MEMS comb accelerometer. The simulation results are in good accordance with theoretical analysis.

Optimization for a piezoelectric micromachined ultrasonic transducer on electromechanical coupling coefficient is investigated theoretically. The transducer is composed of (Au/Cr)/PZT/(Au/Cr)/Ti(Adhesive)/Si/SiO 2 /Si multimorph, while titanium is used as adhesive layer, (Au/Cr) as the electrodes,PZT as exciting element, Si as substrate material. A theoretical model of a circular thin-film piezoelectric actuator on a clamped elastic plate is cited to predict the performance of piezoelectric micromachined ultrasonic transducer. The model is used to explore the effect of design and process parameters, such as Si thickness, PZT thickness and adhesive thickness, on the electromechanical coupling coefficient. The results show that an optimum ratio of PZT to Si thickness can be found to achieve the maximum coupling coefficient. The results can be used to form a set of design guidelines for the performance optimization of piezoelectric micromachined ultrasonic transducer.

We study coupled extensional and flexural vibrations of a 1-D array of partially electroded, multilayered piezoelectric transducers. The classical theory for laminated plates is used. A theoretical solution is obtained. Based on the solution, basic vibration characteristics of resonant frequencies, mode shapes, and admittance are calculated. Their dependence on geometric parameters is examined. The present analysis represents a significant progress of existing analyses on a single cell of a transducer array.

We determine by a theoretical analysis the optimal dimension of a piezoelectric actuator attached to a multilayered elastic plate clamped at both ends. The dimension is optimal in the sense of producing maximal plate center flexural displacement. The first-order theory for laminated piezoelectric plates is used. A theoretical solution is obtained. Numerical results calculated from the solution show that when the actuator length takes a particular value, the center flexural displacement of the elastic plate reaches a maximum. For PZT4 and PZT5A actuators this happens when the actuator length is about 55% of the plate length. Basic vibration characteristics of the structure at the first resonance near the optimal actuator length are also calculated. It is found that the admittance is also maximal when the electrode length is optimal.

The acoustic boundary element method is applied to solve the Helmholtz boundary integral equation for the sound field problem in the exterior region. Basing on the acoustic boundary element method, the SYSNOISE software is used to numerically calculate the far field sound pressure in the exterior region of piezoelectric micromachined ultrasound transducer array. On the other hand, according to given test conditions, the test platform is putted up, and the frequency response curve chart of the sound pressure level is plotted in the frequency domain. It's shown that the results obtained by the two methods make a good agreement with each other, and that the acoustic boundary element method with SYSNOISE software in this paper can be used to predict the performance of piezoelectric micromachined ultrasound transducer array at the stage of preliminary design.

This paper presents a piezoelectric micro-bridge structure as a resonant gas sensor. The proposed micro-sensor is designed to expand the narrow range of frequency changing and make correction convenient for detection. The mechanical performance was simulated to obtain optimum design parameters by finite element method. The relationship between dimensions, layer thickness and resonance frequency is discussed. The results show that resonance frequency increased by about 0.6 MHz with a 8.25e-16 kg mass rise in gas-sensing layer in the frequency range of 8 GHz to 8.5 GHz. Thus, the sensor is very sensitive to the change of membrane mass and this makes it very suitable for concentration sensitive detector. Finally the fabrication process for the sensor suitable for batch fabrication is proposed.

The parametric loudspeaker takes advantage of the non-linearity property of the air to create new frequency sound components, which can be used to reproduce audible sound from the ultrasonic waves generated by the transducer. Compared with the traditional loudspeaker, the audible sound from the transducer of the parametric loudspeaker has very sharp directivity pattern, which makes its possible to create a sound beam. The problem is also from the non-linearity interaction, which brings great harmonic distortion to the audible sound. As a result of that, many signal processing methods have been proposed to reduce THD (total harmonic distortion), including square-rooter method, DSB (double sideband) modulation, and SSB (single sideband) modulation etc. In this paper, the SSB modulation used in parametric loudspeaker has been analyzed in detail and its testing results are also included, which show that SSB modulation has great advantage over the other processing methods.

We present evidence from experiments and computer simulations supporting the hypothesis that ∈dex{polyamorphism}water displays polyamorphism, i.e., water separates into two distinct liquid phases. This concept of a new ∈dex{liquid-liquid phase transition}liquid–liquid phase transition is finding potential application to other liquids as well as water, such as silicon and silica. Here we review the relation between changes in dynamic and thermodynamic anomalies arising from the presence of the liquid–liquid critical point in (i) Two models of water, TIP5P and ST2, which display a first order liquid–liquid phase transition at low temperatures; (ii) Two spherically symmetric two-scale potentials known to possess a liquid–liquid critical point, in which the competition between two liquid structures is generated by repulsive and attractive ramp interactions; and (iii) A Hamiltonian model of water where the idea of two length/energy scales is built in. This model also displays a first order liquid–liquid phase transition at low temperatures besides the first order liquid-gas phase transition at high temperatures. We find a correlation between the dynamic fragility crossover and the locus of specific heat maxima CP max (“Widom line”) emanating from the critical point. Our findings are consistent with a possible relation between the previously hypothesized liquid-liquid phase transition and the transition in the dynamics recently observed in neutron scattering experiments on confined water. More generally, we argue that this connection between C P max and the dynamic crossover is not limited to the case of water, a hydrogen bonded network liquid, but is a more general feature of crossing the Widom line, an extension of the first-order coexistence line in the supercritical region.

We study the phase behavior of systems of particles interacting through pair potentials with a hard core plus a soft repulsive component. We consider several different forms of soft repulsion, including a square shoulder, a linear ramp and a quasi-exponential tail. The common feature of these potentials is the presence of two repulsive length scales, which may be the origin of unusual phase behaviors such as polyamorphism both in the equilibrium liquid phase and in the glassy state, water-like anomalies in the liquid state and anomalous melting at very high pressures.

We study coupled extensional and flexural cylindrical vibrations of a corrugated cylindrical shell piezoelectric transducer consisting of multiple pieces of circular cylindrical surfaces smoothly connected along their generatrices. Using the classical shell theory, a theoretical solution is obtained. Based on the solution, basic vibration characteristics of resonant frequencies, mode shapes, and internal forces are calculated and examined for the corrugated transducers, consisting of a few circular pieces each about 50 mum thick, with radius of 5 mm and span angle of 120 degrees. For these transducers the first resonance is of the order of 10-100 Hz.

According to the Hilbert transform properties, the self-demodulated signalpsilas distortion of the single side band (SSB) method for parametric loudspeaker is analyzed theoretically by employing the orthogonal envelope detection method. It is proved that there is no distortion in the self-demodulated signal of the single side band method when a single-frequency signal is inputted, but the distortion is quite high when a wide-band signal is inputted, by which the incorrect concept existing for a long time that there is no distortion existing in the self-demodulated signal of the single side band method is rectified. Furthermore, a squared envelope distortionless condition for the signal processing methods of parametric loudspeaker is presented to provide an effective criterion for their development. A method to reduce the inter-modulation distortion of the single side band method for parametric loudspeaker by introducing a modulation factor is proposed, and it is also claimed that the method will result in a lower output power of the self-demodulated signal.

In the paper, a dynamic model that has two inputs (voltage and load) is presented. Nonlinearities in piezoceramics when they are subject to two inputs are classified into memory storage mechanisms and the memoryless mechanisms. A multi-layer neural network is presented in order to describe the memoryless mechanism, which represents the cross coupling effects between two inputs. A numerical form of the model is derived for the computer implementation. The effectiveness of the model is assessed experimentally.

The paper describes a method to estimate the power consumption of miniature audio directional transducer using KZK equation according to a larger transducer with the same structure and the same material. A theoretical analysis of sound propagation and sound power for concave-convex cylindrical transducers is presented, which are made by PVDF film of 28 mum with two-sided silver ink of 10 mum at each side. Experimental investigations using 270 times 240 mm2 and 50 times 50 mm2 transducers are performed. Experiments and theoretical estimation of power consumption of smaller transducer of 50 times 50 mm2 used in mobile media devices are presented according to the experimental results of 270 times 240 mm2 transducer. And the theoretical results agree with the experimental result and meet the power requirement (< 5W) of mobile media devices.

The application of coating process is a conventional part of the photolithography which is widely used in the IC fabrication and the manufacturing of micro-electro-mechanical systems (MEMS). The uniform experimental design method combined with regression analysis is applied to investigate the protective coating process aimed to protect the die from silicon contaminations in the die preparation phase of the IC assembly. Ten experimental runs based on the randomization principle and the uniform design tables are executed. The weight of the flux coated on the substitute coupon is measured and adopted as the quality target of the coating process and four control parameters, the scale of micrometer valve, the flux pressure, the dispenser velocity and the atomizing pressure are selected as experimental factors in this study. A significant regression model is obtained based on the experimental data and the scale of micrometer valve, the flux pressure and the dispenser velocity are found to be significant factors in the protective coating process. Such model could be used as the mathematical prediction of the flux weight and help to improve the coating velocity without violating the weight constraint required for its protection purpose.

Audio beam system is a revolutionary way of projecting audio signal in a highly directional manner to listener. This paper focuses on the power management of audio beam system. A specific loudspeaker, which is fabricated by polyvinylidene fluoride (PVDF), is proposed according to the theory of corrugated structure for PVDF film. Based on the test and analysis results, a unique digital amplifier, Class D power amplifier is designed specially for the corrugated piezoelectric loudspeaker. It is composed of power MOSFETs, type IRFU2407, in a full H-Bridge configuration driven by HIPxxxxA circuits in bootstrap mode. A proper design of the peripheral circuits and the configuration of the parameters solve the problem induced by the capacitance of transducer around the resonant frequency, leading to a stable high-power driving ability to the load. Finally, the experiment with the corrugated loudspeaker driven by the Class D amplifier verifies that the amplifier designed maintains high efficiency output onto the load, which leads to the novel power management of the audio beam system with specific corrugated loudspeaker.

Aimed at solving the harmonic distortion problem of the DSB (Double Side Band) method which is employed in audio directional loudspeaker, an improved amplitude modulation (AM) method is investigated. According to the parametric acoustic array principle and self-demodulation theory, the theoretical self-demodulation model of the improved AM method is established, and a conclusion that the variational phase in the improved AM method hardly affects the second pressure is drawn. Furthermore, the harmonic distortion of the improved AM method is analyzed theoretically and tested by experiments, and the results show that the improved AM method has a far smaller total harmonic distortion than the DSB method when their modulation factors are equal. However, the improved AM method can only be applied reasonably when the modulation factor is small, because its total harmonic distortion is notable when the modulation factor is high.

A directional audible sound could be generated from the nonlinear interaction of ultrasound in the propagation medium. The demodulated audible signal is proportional to the second time derivative of the square of the ultrasound envelope, described in Berktaypsilas Far-field solution, which is nonlinear to the process of sound reproduction. Double side-band modulation (DSB) is proposed to amplitude-modulate the ultrasound carrier with audio signal. Total harmonic distortion (THD) is calculated for signal with single frequency firstly, and it increases with the increase of the modulation index. However, itpsilas more complex for input with two frequencies or multi-frequency. Except for the interaction between the modulated ultrasound and the carrier, the intermodulation distortion (IMD) is generated from the interaction of modulated signal with multi-frequencies. Hence, Single side band modulation (SSB) is proposed for reducing the THD and IMD. There is no 2nd harmonic frequency or higher frequencies for input with single frequency. And the amplitudes of harmonics are only related to the modulation index for input with two frequencies or wideband. SSB is recommended to reduce THD or IMD.