Risk management is vital to a product’s lifecycle. The current practice of reducing risks relies on domain experts or management tools to identify unexpected engineering changes, where such approaches are prone to human errors and laborious operations. However, this study presents a framework to contribute to requirements management by implementing a generative probabilistic model, the supervised latent Dirichlet allocation (LDA) with collapsed Gibbs sampling (CGS), to study the topic composition within three unlabeled and unstructured industrial requirements documents. As finding the preferred number of topics remains an open-ended question, a case study estimates an appropriate number of topics to represent each requirements document based on both perplexity and coherence values. Using human evaluations and interpretable visualizations, the result demonstrates the different level of design details by varying the number of topics. Further, a relevance measurement provides the flexibility to improve the quality of topics. Designers can increase design efficiency by understanding, organizing, and analyzing high-volume requirements documents in confirmation management based on topics across different domains. With domain knowledge and purposeful interpretation of topics, designers can make informed decisions on product evolution and mitigate the risks of unexpected engineering changes.

In this paper, an innovative piezoelectric energy harvesting unit (PEHU) for the piezoelectric energy harvesting system (PEHS) from highway traffic is introduced. The proposed PEHU contains a non-linear force amplification mechanism, which substantially increases the electricity output of the PEHU in contrast to the conventional designs with direct loading to the piezoelectric stacks. Quasi-static laboratory tests have been performed to validate the design and the mathematical model. In a quasi-static load cycle of 1333N, a preloaded PEHU prototype is able to generate a voltage of 128V and a potential electric energy of 120mJ with a displacement as small as 2.54mm. The energy density that the PEHS can potentially deliver is estimated to be 8.64J/(m.pass.lane) and is the highest reported in the literature. This level of power generation suggests that the PEHU has a great potential for roadway energy harvesting.

The mathematical model of a strain wave gear (SWG) composed of a flexspline (FS), an elliptical wave generator (WG), and a circular spline (CS) was developed and the performance was simulated by two-dimensional (2-D) finite element analysis. A rack cutter exhibiting a double-circular-arc normal section was utilized to generate the FS, and the conjugate CS was also developed based on the theory of gearing and enveloping equation. Computer program developed in Visual C++ was completed for the geometry and 2-D mesh generation. The performances as well as the rotational motion of the SWG with double-circular-arc profile were simulated and investigated by 2-D finite element analysis.

Additional lateral load tests, with improved techniques, were conducted on M22 stainless bolts to supplement the series of metric system stainless bolt tests which were conducted previously. Using the strain gage-deflection data collected from the entire set, i.e., of different sizes and different lengths, of the bolt tests, the “rigidity coefficient”, which is used in calculating the deflection of the bolts under lateral loads, using the conventionally assumed effective shank length, is derived. Alternatively, a new analytical effective shank length, which is more accurate than the conventional assumed effective shank length, derived from the test data, is proposed.

The temperature drop of waxy crude oil after a shutdown is the basic premise for restarting relative mechanical calculation. However, computational accuracy has been paid much more attention excessively in the relevant techniques proposed in the previous researches for this calculation but ignoring the practicability of the calculation results. In this paper a new mathematical model is established for a buried hot crude oil pipeline during shutdown with the simplified complex physical process of oil cooling process reasonably, in which the heat transfer mode of crude oil is divided into pure convection heat transfer and pure heat conduction with stagnation point temperature neglecting the difference of radial temperature. The quasi periodic property theory of soil temperature field is referenced to be as the boundary condition for the thermal influence region. A numerical solution with a structured grid and an analytical solution under polar coordinate are respectively applied for the soil region and other regions including pipe wall, wax layer and insulation layer. The finite volume method is adopted to discretize the heat transfer control equation at the same time the boundary conditions are treated by the additional source term method. The simulation results of the new model are verified by a temperature field tested experiment, especially analyzing the temperature deviation between the simulation and the equivalent mean value of actual oil temperature. At last the effect of buried depth of pipeline on the temperature profiles during normal operation and the temperature drop process of crude oil were investigated based on the simplified model.

Safe and efficient operation of a power plant is the system designers’ target. Regenerative system improves the Rankine Cycle efficiency of a power station. However, it is quite difficult to monitor the regenerative system’s performance in an accurate, economical and real-time way at any operation load. There are two main problems about this. One is that most model based on numerical and statistics approaches cannot be explained by the actual operation mechanism of the actual process. The other is that most mechanism models in the past could not be used to monitor the system performance accurately at real-time. This paper focuses on solving these two problems and finds a better way to monitor the regenerative system’s performance accurately in a real-time by the analysis of the mechanism models and numerical methods. It is called the dominant factor method. Two important parameters (characteristic parameter and dominant factor) and characteristic functions are introduced in this paper. Also, this paper described the analysis process and the model building process. In the paper, the mathematics model building process is based on a 1000MW unit’s regenerative system. Characteristic functions are built based on the specific operating data of the power unit. Combing the general mechanism model and the characteristic function together, this paper builds up a regenerative system off-design mathematical model. First, this paper proved the model accuracy by computer simulation. Then, the models were used to predict the pressure of the piping outlet, the temperature of the outlet feedwater and drain water of heaters in a real-time by computers. The results show that the deviation rate between the theoretical predictions and the actual operation data is less than 0.25% during the whole operation load range. At last, in order to test the fault identification ability of this model, some real tests were done in this 1000MW power plant during the actual operation period. The performance changes are identified via the difference between the predict value and the real time value. The result of the tests shows that the performance’s gradient change and sudden change could be found by the model result easily. In order to verify the adaptability of the model, it was used for another 300MW unit, and done some operation test. The results show that this method can also be used for the 300MW unit’s regenerative system. And it can help the operator to recognize the fault heater. The results of this paper proved that the dominant factor method is feasible for performance monitoring of the regenerative system. It can be used to monitor and find the fault of the regenerative system at any operation load by an accurate and fast way in real-time.

Used widely in military and civil applications, autonomous robots have shown promising in planet exploration, seabed survey, and disaster rescue. A lot of robotic research concentrates on localization and mapping dealing with the basic problems in robotic research: “Where I am?” and “How is the environment like?”. The two problems consist a coupled problem named Simultaneous Localization and Mapping (SLAM) in unknown environment exploration. This problem is summarized by Hugh D. Whyte in his paper published in 1991 [1]. Forced by requirement of motion in unknown environment, many researchers in robotics make efforts to solve SLAM problem in recent decades.

Laboratory experiments play a critical role in earthquake engineering research for seismic safety evaluation of civil engineering structures. Servo-hydraulic actuators play a vital role to maintain the compatibility on boundaries between the analytical and experimental substructures in a real-time hybrid simulation. Previous study has indicated that actuator delay could significantly affect the accuracy of real-time hybrid simulation involving viscous dampers. Identifying the amount of actuator delay therefore is critical for reliability assessment of experimental results to properly interpret the performance of viscous dampers for seismic hazard mitigation. In this study a frequency domain based approach is applied for real-time hybrid simulation of viscous dampers with the presence of actuator delay. Computational simulations are conducted to assess the accuracy of the approach for estimating the delay when the substructures develop nonlinear behavior for reliability interpretation of real-time hybrid simulation.

In this study, a PCR free technique for effective detection of hepatitis B virus (HBV) DNA obtained directly from clinical samples was presented. The honeycomb-like barrier layer of an anodic aluminum oxide (AAO) film having a uniform nanohemisphere array was used as the substrate of the sensing electrode. A gold thin film about 30 nm thick was radio-frequency (RF) magnetron sputtered onto the AAO barrier-layer surface as the electrode for the successive deposition of gold nanoparticles (GNPs) on the hemisphere surface. A specially designed single-strand 96-mer gene fragment of the target genomic DNA of HBV based on the genome sequences of HBV from the National Center for Biotechnology Information (NCBI) was immobilized on the nanostructured electrode as the capture probe. Complementary target HBV DNA (3020–3320 mer) obtained from clinical samples were further hybridized to the sensing probes. Detection results through electrochemical impedance spectroscopy (EIS) illustrate that two dynamic linear ranges, 0–10 3 and 10 3 –10 5 copies/mL, having R 2 values of 0.973 and 0.998, respectively, could be obtained. A detection limit of 186 copies/mL could be achieved. The proposed simple and high performance HBV DNA detection technique in this study is highly feasible for future clinical applications.

Laboratory experiments play a critical role in earthquake engineering research for seismic safety evaluation of civil engineering structures. Real-time hybrid simulation provides a viable alternative for shake table testing to evaluate seismic performances of structures with rate-dependent seismic devices. Servo-hydraulic actuators play a vital role in a real-time hybrid simulation to maintain the boundary condition between the analytical and experimental substructures. Compensation of actuator delay is critical to minimize synchronization error from actuator delay and to achieve a successful real-time hybrid simulation. Research on how actuator delay can affect the real-time hybrid simulation involving viscous fluid damper is presented in this study. It is demonstrated that although the viscous fluid damper can help stabilize the real-time hybrid simulation with actuator delay, the experimental results need to be interpreted appropriately to evaluate the performance of viscous fluid damper for seismic hazard mitigation.

The Delta robot system is widely used in high speed (4 cycles/s at 25-200-25 mm) pick-and-place process in production line. Some industrial applications include photo-voltaic (PV), food process, and electronic assembly, and so on. The energy saving and system cost are two critical parameters for designing the next generation of pick-and-place system. To achieve these goals, a light-weight moving structure with sufficient strength to overcome the excited vibration will be one of the solutions. In this paper, an asymmetric arm design is proposed and fabricated to gain the benefit of strength-to-weight. The asymmetric arm is designed by reinforcing a specific direction and is validated the vibration suppression capability both by simulation and experiment. A position controller that is derived from the kinematic model of Delta robot is utilized to manipulate the robot under a forward-backward motion with a polynomial trajectory with 200 mm displacement. The residual vibration, then, was measured after the forward-backward motion to compare the settling performance between symmetric- and asymmetric-arms on the Delta robot system, respectively. The results conclude as following: (1) The asymmetric arms perform slightly worse (0.03 sec more in settling time) than symmetric arm but there is 15% weight reducing comparing to symmetric arm. (2) Both energy saving and system cost reducing would be achieved by utilizing actuators with lower power consumption and fabrication on carbon fiber arms with mass customization.

This paper investigates the contact ellipse and contact stress of a modified curvilinear gear set with localized bearing contact. The proposed modified curvilinear gear set with profile modifications was generated by male fly cutters with a circular-arc normal section. This gear drive exhibits point contact and parabolic transmission error under an ideal meshing condition according to the results of tooth contact analysis. The principal directions and curvatures of the mating pinion and gear surfaces were derived from those of the generating surfaces on the basis of differential geometry and theory of gearing. The Hertzian contact stress and contact ellipses of the mating tooth surfaces were determined with our developed computer program based on formulae of curvature analysis and Hertzian contact theory. Numerical examples were also provided to demonstrate the computational results.

Control rod drive mechanism is very important to the operation and safety of reactors, therefore, requiring good mechanical properties and a high degree of reliability. The control rod drive mechanism of high-temperature-reactor pebble-bedmodule (HTR-PM) is powered by permanent magnet stepping motor and damped by the permanent magnetic damper. Therefore, the performance of both motor and damper have important impact on the control rod drive mechanism. However, the performance of permanent magnets is very sensitive to high-temperature. This paper describes the impact of the high temperature on the performance of critical components in the HTR-PM control rod drive mechanism. A Full-size thermal test bench is used to determine the performance of the key components within the scope from room temperature (20 ° C) to 250 ° C, with these data we can calculate the emergency insertion time. And further work plan is introduced too.

Branching microchannel networks have been considered as an effective liquid cooling system for electronic components. In this paper, an asymmetric angled branching design of microchannel network is introduced and compared with the parallel branching cooling system. Full CFD models based on finite-element analysis are established to analyze their thermal performances under uniform heat distribution. Performances of angled branching network and a series of parallel networks are compared for a pressure range from 0.5psi to 4psi. Results indicate that the angled branching network dissipates heat better at lower provided pressure drop due to its small flow resistance and flexibility in fluid transportation. On the other hand, a lower peak temperature is noted for the parallel branching network at higher pressure head.

Constrained by low thermodynamic efficiencies, thermoelectric generators (TEGs) require a comparatively large amount of heat to produce a given quantity of electricity. Therefore, further improvements in thermoelectric designs are needed. In this paper, a coupled-field thermoelectric model, which presents a rigorous interfacial energy balance by capturing Joule heating, Seebeck, Peltier and Thomson effects, is developed to gauge the feasibility of the two promising solutions to enhance power generated by the TEGs, utilizing the commercial FEA package COMSOL™ through the Physics Interface Builder. First, the patterned topography on wall surfaces is implemented and the improved performance has been observed by introducing stirred flows into the heat exchangers and equalizing the temperature across the channels. Referring to the analysis, approximately 10% enhancement in power generation can be addressed for the base-relief TEG. Second, the prospect of increasing the thermal transport capability of water by loading CuO nanoparticles in the TEGs with multi-scale heat exchangers is explored. It is found that the conversion performance of the water/CuO nanofluid-based TEG is superior when compared to the water-based TEG at the micro-scale, where the flow rate is relatively low. The significant insight is gained to fabricate the ideal TEGs with optimum power performance.

Mechanical stimulation affects the functioning and outgrowth of neurons and has the potential capacity for regeneration. Mechanoreceptors in sensory neurons act as a conduit to respond to pain and touch while neurites experience mechanical stimulation during the process of animal growth. To understand mechanotransduction in neural outgrowth, we used a custom fabricated device to investigate the effects of static mechanical stretching while examining molecular connections such as advillin and actin. Our results have the potential of providing greater understanding of mechanotransduction in neuroblasts, as well as providing insight into mechanical approaches that might be used in increasing neural outgrowth.

Demands for higher computational speed and miniaturization have already resulted in extremely high heat fluxes in microprocessors. Fractal tree-shaped microchannel liquid cooling systems are novel heat transfer enhancement systems to keep the temperature of the microprocessors in a safe range. Due to the complexity of these systems, their full field numerical modeling for simulation of the flow and temperature fields is too time consuming and costly, particularly to be used within iterative optimization algorithms. In this paper, a quick but still accurate compact modeling approach based on Flow Network Modeling (FNM) is introduced for analysis of the flow filed in fractal microchannel liquid cooling systems. The compact method is applied to a representative fractal microchannel cooling system and the obtained velocity and flow rate distribution are validated against a full Computational Fluid Dynamics (CFD)-based model for three different designs. The compact model shows good agreement with the CFD results and robustness on different designs, while requiring much less computational capability and time. Afterwards, the compact model is used for optimization of the geometry of the fractal cooling system to achieve maximum flow rate and uniform flow distribution among the channels for a fixed pressure drop.

A pressure correction method is developed to simulate fluid-particle interaction flows. In this Paper, the three-dimensional solid-fluid mixture flows are investigated. The pressure corrected method coupled with the direct-forcing immersed boundary (IB) and the volume of fluid (VOF) methods is used to simulate the mixture flows. A discrete element method (DEM) together with a multi-time-step algorithm is introduced into the pressure correction method to calculate the forces and torques between solid bodies and between solid bodies and walls. As a demonstration of the efficient and capabilities of the present method, four test cases are simulated. They include sedimentation of one spherical particle in an enclosure, collapse of six solid-cylinder layers, two-dimensional solid-fluid mixture flow, and three-dimensional solid-fluid mixture flow.