Noise emission assessment of a hybrid electric mid-size truck

In the attempt to improve urban environmental conditions, city or national incentives encourage the use of cleaner vehicles, including hybrid electric vehicles. This paper explores the actual noise impact of this alternative drivetrain technology on the noise emission of a mid-size delivery truck powered by a parallel hybrid powertrain, compared with an equivalent internal combustion engine truck on the basis of pass-by noise measurements. It investigates jointly the overall emission, the main noise sources and the vertical directivity of the vehicle. The essential benefit results from the existence of a full-electric mode below 50 km/h, with a significant noise reduction which may exceed 8 dB(A) at low constant speed. Even if smaller, this noise advantage is still valuable when the vehicle is accelerating or braking. Due to weaker noise emitted upwards, the benefit should be even greater for residents living on upper building floors. The rolling noise associated with the drive wheel/road contact is the main noise source in all driving situations in electric mode, and beyond 50 km/h in the configurations with engine.     

Dynamic model of worm propagation in computer network

In this paper, an attempt has been made to mathematically formulate a compartmental susceptible – exposed – infectious – susceptible with vaccination (that is, anti-virus treatment) (SEIS-V) epidemic transmission model of worms in a computer network with natural death rate (which depends on the total number of nodes). The stability of the result is stated in terms of modified reproductive number R_v. We have derived an explicit formula for the modified reproductive number R_v, and have shown that the worm-free equilibrium, whose component of infective is zero, is globally asymptotically stable if R_v < 1, and unstable if R_v > 1. The contribution of vertical transmission to the modified reproductive number is also analyzed. Numerical methods are employed to solve and simulate the system of equations developed and interpretation of the model yields interesting revelations. Analysis of efficient antivirus software is also performed.     

Strategic upfront marketing channel integration as an entry barrier

This paper investigates an organizational design problem concerning whether duopolistic firms competing in a product market should vertically integrate or separate their marketing channels in a dynamic noncooperative game setting. Previous operational research models have shown that the separation of the marketing channel with the adoption of a two-part tariff contract is the dominant strategy compared with integration for each firm if the two firms face retail price competition, and thereby constitutes the subgame perfect Nash equilibrium (SPNE). Contrary to this previous insight, this paper demonstrates that if exogenous parameters that characterize fixed costs, product substitutability, and a demand function fall into a specific region, marketing channel integration dominates the separation strategy when one of the two firms is the incumbent firm while the other is a potential entrant. In other words, the well-known result in the price-setting game can be reversed when we take entry threats into consideration. Specifically, we show that upfront vertical integration of the marketing channel enables the incumbent to deter the entry of the potential competitor and to monopolize the market in the SPNE. This result has operational implications for a firm confronting the threat of potential rivals entering the market, in that the firm can use this apparently inferior strategy as a commitment device, which creates a virtual entry barrier.     

Asymptotic behaviour of solutions to cable stayed bridge equations

Asymptotic behaviour of solutions to the nonlinear variational equations of the two basic types of cable stayed bridges is studied. The equations describe vertical and torsional oscillations of the center span, which is the part of road bed between pylons. Due to damping, amplitude and velocity of oscillations remain bounded if wind force is bounded as well. Moreover, the solution to the nonlinear equations converges to the solution of the steady state problem if wind drops. If the center span has certain aerodynamical properties and the initial state is near to the solution of the steady state problem, then the solution converges to the steady state solution even if the forces representing wind do not vanish.     

A microfluidic chip capable of switching W/O droplets to vertical laminar flow for electrochemical detection of droplet contents

Analysis of droplet contents is a key function involved in droplet-based microfluidic systems. Direct electrochemical detection of droplet contents suffers problems such as relatively poor repeatability, interference of capacitive current and relatively poor detectability. This paper presents a novel hybrid polydimethylsiloxane-glass chip for highly sensitive and reproducible amperometric detection of droplet contents. By wettability-patterning of the channel surface of the hybrid chip, water in oil droplets generated in the upstream part of the central channel can be switched to a two-phase vertical laminar flow (i.e., a continuous oil stream flowing atop a continuous aqueous stream) in the downstream part of the channel. The vertical laminar flow keeps the analyte in the underneath-flowing aqueous stream in direct contact with the sensing electrodes located on the bottom surface of the channel. Therefore, steady-state current signals with high sensitivity (1.2 A M⁻¹ cm⁻² for H₂O₂), low limit of detection (0.12 μM, S/N = 2), and good reproducibility (RSD 1.1% at 0.3 mM H₂O₂) were obtained. The methods for patterning of the inner channel surface are presented, and the behaviors of the microchip in flow profile switching and amperometric detection are discussed. The application of the developed microchip to enzyme kinetics study is also demonstrated.     

南海夏季海洋环境噪声与海面风速相关特性分析

海洋环境噪声是影响潜艇作战及远程目标探测和定位的重要参数,由于海洋环境噪声具有很强的时空变异性,因此只能通过试验数据测量和处理了解环境噪声的统计特性。本文以2013年4月30日至8月1日,南海典型海域布放海洋环境噪声测量潜标系统所收录的环境噪声为研究对象,数据处理结果表明,在整个频率范围内,海洋环境噪声与对数风速具有很好的线性关系,但环境噪声随风速变化的斜率与频率相关,在1kHz附近达到最大值。本文通过波束形成分析了海洋环境噪声的垂直指向性,并给出了“垂直方向噪声”、“水平方向噪声”和“全向噪声”与风速相关性分析结果,可以看出,在风浪噪声与远处航船噪声都有贡献的中频段,“垂直方向噪声”与海面风速的相关性好于“全向噪声”和“水平方向噪声”与海面风速的相关性,且“垂直方向噪声”随风速变化的斜率略大于“全向噪声”随风速变化的斜率。     

Analysis of Potential Energy Surface for Butanone Isomerization

The potential energy surfaces for butanone isomerization have been investigated by density function theory calculation. Six main reaction pathways are confirmed using the intrinsic reaction coordinate method, and the corresponding isomerization products are 1-buten-2-ol, 2-buten-2-ol, butanal or 1-buten-l-ol, methyl 1-propenyl ether, methyl allyl ether, and ethyl vinyl ether, respectively. Among them, there are three pathways through butylene oxide, indicating butylene oxide is an important intermediate product during butanone isomer ization. The calculated vertical ionization energies of the reactant and its products are in a good agreement with the experimental values available. From the consideration for the relative energies Of transition states and the number of high-energy barriers we infer that the reaction pathway butanone-＊l-buten-2-ol---2-buten-2-oi is the most competitive. The obtained results are informative for future studies on isomerization of ketone molecules.     

Structural relaxation and avalanche dynamics of particle piles under vertical vibration

Granular matter can exhibit solid or liquid behavior, which contains complex physical mechanisms. In this work, we experimentally investigated the structural relaxation and avalanche dynamics of particle piles under vertical vibration. The influence of vibration parameters on the avalanche process was studied. The morphological features of avalanches were recorded and classified using high-speed camera. The effects of vibration parameters and particle properties on the relaxation mode are obtained. It is found that the evolution of particle pile height with time can be described by an exponential decay function. The relaxation rate and avalanche characteristics of four types of particles with different sizes are discussed. At the same acceleration level, for two larger particles, a smaller amplitude (A = 0.025 mm) leads to a faster relaxation rate, while for two smaller particles, a large amplitude (A = 0.500 mm) leads to a faster relaxation rate. The analogy powder surface tension is introduced to address the cohesion and flowability evolution of particles under vibration.     

Fabrication and characterization of 1.55 μm single transverse mode large diameter electrically pumped VECSEL

We report on the design, fabrication, and characterization of InP-based 1.55 μm wavelength large diameter (50 μm) electrically pumped vertical external cavity surface emitting lasers (EP-VECSELs). The hybrid device consists of a half vertical cavity surface emitting laser (1/2-VCSEL) structure assembled with a concave dielectric external mirror. The 1/2-VCSEL is monolithically grown on InP substrate and includes a semiconductor Bragg mirror and a tunnel junction for electrical injection. Buried (BTJ) and ion implanted (ITJ) tunnel junction electrical confinement schemes are compared in terms of their thermal and electrical characteristics. Lower thermal resistance values are measured for BJT, but reduced current crowding effects and uniform current injection are evidenced for ITJ. Using the ITJ technique, we demonstrate Room-Temperature (RT) continuous-wave (CW) single transverse mode laser operation from 50-μm diameter EP-VECSEL devices. We show that the experimental laser optical output versus injected current (L–I) curves are well-reproduced by a simple analytical thermal model, consistent with the thermal resistance measurements performed on the 1/2-VCSEL structure. Our results indicate that thermal heating is the main mechanism limiting the maximum CW output power of 50-μm diameter VECSELs, rather than current injection inhomogeneity.     

Position-selective growth of vertically aligned carbon nanotubes for application of electronic-measuring nanoprobes

Position-selective growth of carbon nanotubes (CNTs) and vertically aligned CNTs (VACNTs) on patterned metal electrodes have been prepared by thermal chemical vapor deposition (TCVD) and DC plasma enhanced chemical vapor deposition (PECVD). We propose newly a position-controlling method of CNTs by controlling not only a position of Ni as catalysts but also the morphology of Mo as underlayers for the catalysts. The position-selective growth of CNTs was achieved at the edges of the patterned metal by TCVD. The morphologies of the Mo underlayer at the selected area were rough and porous. No CNTs grew on smooth Mo surfaces. The minimum width of selectively grown CNTs, ca. 2.6 μm, was approximately one-eightieth of the patterned metal, 200 μm. VACNTs were synthesized by a PECVD method, however, the VACNTs grew up all over the patterned metal. The Ni catalysts formed into fine particles on rough surfaces of the Mo underlayer. Then the selective growth was achieved by Ni fine particles formed only at the edges of the metal pattern. The results of PECVD suggest that the plasma promoted the Ni catalysts to become fine particles on smooth surfaces of Mo. Conclusively a position-controlling method of CNTs was demonstrated in the optimum conditions of the TCVD.