In the current research, the use of a micromachined cantilever resonator as a platform for chemical gas sensing was examined. The microcantilever resonator integrates an electrothermal driving unit and a piezoresistive detecting unit, and it is fabricated by direct bonding a silicon-on-insulator (SOI) wafer. With a particular polymer layer coated on the surface of the microcantilever, a gas sensor for volatile organic components (VOCs) detection can be realized. The operation mechanism provides the microcantilever resonator with integrated circuit (IC) compatibility in terms of both the fabrication process and operating voltage. The configuration of the microcantilever resonator can optimize the performance of the gas sensor. The SOI wafer provides a solution for the integrated fabrication of the microstructure, transducers, electronics, and the precise control of the resonator parameters. In this paper, the principles, design, analysis, process, and demonstration of the gas sensor based on the microcantilever resonator are presented. The experimental results provide confirmation that the polymer-coated microcantilever resonator has excellent performance with regard to VOC detection.

Error model is the basis for accuracy-related computations and analyses for parallel kinematic machines (PKMs). Traditional error modeling methods are usually based on differentiation of kinematic solutions, but the solving process is often complex and has limitations for certain specialized PKMs. A concise numerical error modeling method with the inverse kinematic solution as its only requirement is presented in this paper. To avoid complex Jacobian matrix computations, the difference matrix that can be quickly calculated by kinematic solutions was used to replace the differential matrix. The quasi-Newton method, which has high speed and high precision, was introduced to solve the numerical forward kinematic problem. To verify the efficiency of this numerical error modeling method, three applications in error transformation matrix (ETM) modeling, error analysis, and kinematic calibration were simulated on a 4RRR PKM. A comparison with the results obtained by the traditional method shows that the numerical method is accurate, convenient, and has lower requirements and wider applicability, especially for certain specialized and manufactured PKMs.

This paper deals with a periodic review inventory system serving multiple demand classes that are differentiated by the treatment for shortages. Shortages of some classes were treated according to lost- sales, while those of the others were backlogged. In each period, both replenishment decisions of inventory and allocation for all classes were made by a setup cost for each replenishment. By using the approach of stochastic dynamic programming formulation, the optimal replenishment policy is a state-dependent (s, S) policy, and the optimal allocation decision follows a state-dependent prioritization policy.

In order to overcome the drawbacks of 3RRR non-redundant parallel manipulators, a redundantly actuated planar parallel manipulator, the 4RRR manipulator, was examined. In the current study, three types of workspace were analyzed. In the analysis of the reachable workspace, the shape of the workspace of 4RRR PMs was illustrated, and the relationship between the parameters of parallel mechanisms (PMs) and this kind of workspace was discussed. In the analysis of the m-orientation workspace, a procedure for calculating this type of workspace was presented, and the relationship between this type of workspace and the requirement of rotational displacement was revealed. In the analysis of the nonsingular workspace, the singularity of 4RRR PMs was discussed, the boundary of the singularity was illustrated, and a scheme to maximize the nonsingular workspace was presented. Depicting the properties of 4RRR PMs from different perspectives, the analyses of these three kinds of workspace can serve as helpful references for the structure design and mechanism control of 4RRR PMs.

A non-invasive software upgrade method for permanent implantable medical devices was developed to alleviate patients' suffering due to malfunctions because of software faults, which may cause serious adverse health consequences or require enhancements with new software. The programs distributed to the internal implantable pulse generator (IPG) from the external programmer have been developed so that the upgrade service program in the IPG is simplified with most complex functions executed by the external programmer. A bidirectional protocol including frame definition and transmission mode was designed to insure secure upgrades. A neuro-stimulator was used to verify the upgrade solution with no additional elements, to maintain the hardware reliability. This study emphasizes how to insure a secure and stable upgrade process and reduce power consumption for special wireless and life safety-critical applications. Tests on rhesus monkeys to evaluate the feasibility of the approach for an IPG used for brain stimulation evaluation show that the software upgrade can be implemented stably with good tolerance to the wireless data transmissions.

The current research analyzes the reliability of a dissected frame of heavy equipment in terms of stress distribution, integrality, and fatigue. Through the use of the finite element analysis method, the results demonstrated that the stress field and deformation of the dissected frame were identical to those of the integral frame. Under the working condition, slight slides existed along the dissecting planes between arch beams and columns. On the other dissecting positions, there were no slides during either the working state or the pre-stressed state. The wires and frames both appeared to have limitless fatigue lives. Fatigue of the dissected frame was the same as that of the integral frame. This experiment illustrates that dissected frames can meet the requirements of integrality much better than integral frames. At the same time, local slides or detachments along dissecting planes would not expand during long-term service.

Uncapped double stacked In_0.5Ga_0.5As quantum dots (QDs) with different spacer layer thicknesses were grown using metal-organic chemical vapour deposition (MOCVD). The precursors used for the growth of the GaAs layer and In_0.5Ga_0.5As QDs were trimethylgallium (TMGa), trimethylindium (TMIn), and arsine (AsH₃). The morphology and optical properties of the self-assembled In_0.5Ga_0.5As QDs were investigated and characterized using atomic force microscopy (AFM) and photoluminescence (PL). The AFM images revealed that the sizes of the dots on the topmost were not uniformly distributed. The average size of the dots fluctuated as the GaAs spacer layer thickness increased. A room temperature PL measurement was used to establish the quality and quantity of the stacked QDs. The PL peak position remained at 1148 nm for all samples of QDs; however, the PL intensity increased as spacer layer thickness increased. The structure of the spacer layer in the stacked QD affected the morphology of the topmost surface of the QDs. The PL measurement coherently reflected the AFM characterization, in which the strong PL spectra were caused by the uniformity and high density of the QDs. The surface morphology, structure, and optical properties of the stacked QDs are attributed to seed-layer (first layer) formation of dots and spacer layer structures.

The objective of this paper is to investigate the different effects of disuse and estrogen deficiency on bone loss and the underlying mechanisms. A mechanical-biological factors coupled computational model was built to simulate different patterns of bone loss induced in female rats by hind limb unloading, ovariectomy, or both in an animal study. A remodeling analysis was performed on a representative cross section of 6 mm² of cancellous bone in the distal femoral metaphysis of the rats. The BMU activation frequency, the refilling rate, and the principal compressive strain in the state of mechanical unloading and estrogen deficiency were simulated to interpret the underlying mechanisms. Simulated bone loss patterns due to mechanical unloading, estrogen deficiency, or both all corresponded with the experimental observations. The results show that mechanical unloading and estrogen deficiency cause different bone loss patterns; moreover, mechanical unloading induces a greater degree of bone loss than estrogen deficiency, which can lead to improved treatment and prevention strategies for osteoporosis.

The purpose of this paper is to analyze an accuracy design method for reconfigurable parallel manipulators including a 6-SPS and a 6-PSS parallel manipulator. An error analysis method, based on the module error model, was used to express the relationship between the module error and the terminal error in the error transmission equation of the reconfigurable parallel manipulator. In addition, an error distribution method using a manufacturing and assembly difficulty coefficient was used to analyze each error module to determine a maximum terminal error. The error distribution result was then used to set up a reconfigurable parallel manipulator. Error experiments with a reconfigurable parallel manipulator show that the error analysis and distribution method for reconfigurable parallel manipulators are effective and the maximum terminal errors of the reconfigurable parallel manipulators are less than 50 μm.

In this study, a zonal grid refinement method based on the solution of weakly compressible flow equations with large eddy simulation in the finite volume method (FVM) and dynamic subgrid-scale model framework was used to simulate the turbulence structures of a plane-wall flow with Reynolds number Re = U₀δ/ν = 10 000. Comparison and analysis were conducted on the distributions of time-averaged velocity and velocity fluctuations, as well as on the actual near-wall structures, to verify the accuracy of the turbulence features that were simulated using the zonal grid refinement method. The results show that the zonal embedded grid is a very efficient way to illustrate the turbulence structures of the near-wall region. The present method is easy to implement and extend to small Mach number flow modeling on a collocated irregular FVM mesh system.

The surface vortex in a spillway tunnel intake was investigated in a physical model of the Xiluodu hydropower station. The velocity fields were measured using the particle tracking velocimetry technique. The tangential velocity formula of the surface flow field was derived based on the Navier-Stokes equations, and this formula greatly improved the consistency between the numerical and experimental data. Also, the formula has the advantage of describing the tangential velocity more accurately than previous formulas. The current research is based on established engineering practices, and the results provide a valuable reference for actual projects designed to prevent and eliminate surface vortexes.

High-performing wearability and corrosion resistance are required for an exposed aluminum alloy bridge deck, but existing experimental research remains limited. In this paper, feasible test methods are proposed based on an experimental study on the wearability and corrosion resistance of the aluminum alloy bridge deck of the Bengbu Bridge in Tianjin, China. The line friction test of standard specimens was adopted, and the aluminum alloy bridge deck's wearability was calculated. The electrochemical test was conducted to measure the corrosion rate and morphology characteristics of specimens that were corroded in various solutions that simulated the atmospheric environment. The test results show that the wearability and corrosion resistance of the aluminum alloy bridge deck are sufficient and met the project's requirements. The test methods proposed have practical significance for future engineering research, and the test results are useful for other engineering applications of aluminum alloys.

The dissolved oxygen concentration in a flow changes with distance downstream of the spillway crest and depends on the geometric configuration of the spillway and the hydraulic and operating conditions. A mathematical model was developed to simulate the turbulent structure of the flow over the spillway of the Three Gorges Dam at the 145 m reservoir water level to study the aeration characteristics and the gas transport. The model was calibrated and verified with measured data. The analysis of distribution of the aeration and the dissolved oxygen showed that the downstream water level, upstream dissolved oxygen content, and the flow discharge all affect the dissolved oxygen saturation downstream of the sluicing dam. The simulation provides guidance for controlling the dissolved oxygen supersaturation and environmentally friendly operation of the Three Gorges Dam.

Enhancement of the cometabolic biotransformation of 4-chlorophenol (4-cp) and phenol were studied using chemically and thermally granular activated carbons (GACs). It was found that both chemically activated and thermally activated GAC effectively adsorb phenol and 4-cp. More than 80% adsorped substrates were later desorpted, showing a reversible sorption behaviour in the GAC. For each activated carbon type, 4-cp was preferentially adsorbed over phenol and the desorption efficiencies of both phenol and 4-cp were found to increase linearly with the initial mass of adsorbate in the adsorbent. The biodegradation of 500 mg/L phenol by Pseudomonas putida took 24 h while the biodegradation of 4-cp took 32 h. Inhibitions during the cometabolic biodegradation of 4-cp and phenol were alleviated by the addition of the GACs. The system with chemically-activated coconut type GAC had better system stability over thermally-activated peat type GAC. The results show that GAC can be regenerated by the cells enhancement of the cometabolic biotransformation of 4-cp and phenol can be accomplished using chemically-activated coconut type GAC.

The operating efficiency of container shipping lines depends on proper resource allocation of container shipping. A deterministic model was developed for shipping lines based on the equilibrium principle. The objective was to optimize the resource allocation for container lines considering ship size, container deployment, and slot allocation. The deterministic model was then expanded to a robust optimization model accounting for the uncertain factors, while ship size was treated as the design variable and slot allocation as the control variable. The effectiveness of the proposed model is demonstrated using a pendulum shipping line as an example. The results indicate that infeasible solutions will increase and the model robustness will be enhanced by an increased penalty coefficient and the solution robustness will be enhanced by increasing the preference coefficient. The optimization model simultaneously considers demand uncertainty, model robustness, and risk preference of the decision maker to agree better with actual practices.

With the rapid urbanization of Chinese cities, access to jobs and amenities is becoming increasingly valued in household's choice of residential locations. In this paper, we estimate the implicit value of access to jobs and amenities in Beijing using the hedonic pricing model. The spatial distributions of jobs and amenities in the Beijing Metropolitan Area are quite centralized, supporting the traditional monocentric model in the urban economics literature. Accessibility indices are developed to measure the accessibilities to jobs and amenities of 129 Jiedaos (residential zones). We then employ the hedonic pricing equations to estimate the capitalization effects of these accessibility indices in the prices of new residential properties. The empirical results show that the accessibility indices are important determinants of residential property prices in Beijing, which means that urban residents have a willingness to pay for access to high quality amenities.

This paper explores the mitigation of terrorism risks based on dynamic interactions between terrorist organizations and governments with asymmetric information. Uncertainties in the objectives and capabilities of terrorists complicate defensive resource allocations for the public safety. Simultaneous and sequential game models are developed to investigate the asymmetric information effects on defensive strategies and terrorism risk analysis. The government can detect explicit or implicit signals to support decisions and update its beliefs according to a Bayesian law after it receives a terrorist threat. Analyses of the equilibrium for the signaling game indicate that the optimal government defensive strategy will significantly impact the actions of the terrorists. Asymmetric information is shown to play a crucial role in security decision making and terrorism risk mitigation, with the optimal defensive strategy changing according to terrorists and government capabilities.