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The primary goal of the paper is to monitor the health of the spindle in machine tools to ensure optimal performance and reduce costly downtimes. Spindle health monitoring is essential to detect wear and cracks in spindle bearings, which can be challenging due to their gradual development and hidden locations. The proposed approach combines physics-based modeling and data-driven techniques to monitor spindle health effectively. In Part I and Part II of the paper, mathematical models of bearing faults and spindle imbalance are integrated into the digital model of the spindle. This allows for simulating the operation of the spindle both with and without faults. The integration of fault models enables the generation of vibrations at sensor locations along the spindle shaft. The generated vibration data from the physics-based model are used to train a recurrent neural network-based (RNN) fault detection algorithm. The RNN learns from the labeled vibration spectra to identify different fault conditions. Bayesian optimization is used to automatically tune the hyperparameters governing the accuracy and efficiency of the learning models during the training process. The RNN classifiers are further fine-tuned using a small set of experimentally collected data for the generalization of the model on real-world data. Once the RNN classifier is trained, it can distinguish between different types of damage and identify their specific locations on the spindle assembly. The proposed algorithms achieved an accuracy of 98.43% on experimental data sets that were not used in training the network. [ABSTRACT FROM AUTHOR]

The post-buckling behavior of a beam that is subjected to lateral constraints is of relevance to a range of medical and engineering applications, such as endoscopic examination of internal organs, the insertion of a guidewire into an artery in-stent procedures, root growth, deep-drilling, and more. In this paper, we address a disconnect between the existing literature and the reality of these systems, in which the lateral constraints are flexible and experience nonlinear deformations. As a step towards bridging this gap, we consider a beam undergoing planar deformations that is laterally constrained by a nonlinear springy wall, i.e., a wall that is laterally pushed by the beam against a nonlinear spring. Based on a simplified mathematical model, we obtain closed-form analytical solutions, which provide valuable insights and intuition. For example, we show that important features of the behavior, such as the transition from point contact to line contact and switching to the next mode, are dictated solely by a non-dimensional force, regardless of all other parameters of the system, and that the full description of the behavior is possible by means of two non-dimensional quantities that describe the relative stiffness of the nonlinear spring compared to that of the beam. The results also highlight the fundamental differences between the behavior with a stiffening spring or with a softening spring, such as the number of attainable modes and the monotonicity of the overall force-displacement relation. These results are then validated by experiments. [ABSTRACT FROM AUTHOR]

Face gear drive has been widely investigated in the aviation field as a power split device on the helicopter main reducer. However, high-speed and heavy-load condition makes the face gear prone to tooth surface pitting, leading to deterioration of transmission performance. To improve the load-bearing capacity of face gear, this paper proposes a design and modification method based on gear skiving process for face gear drives. First, gear skiving mathematical models for a face gear pair are established, and a continuously profile-shifted modification method is presented based on these mathematical models. Then, the load-bearing capacity of the modified face gear pair is minutely analyzed and discussed through contact analysis. The contact stress of the modified face gear is reduced by 47.78% on the right side and 41.1% on the left side compared with an unmodified face gear. Finally, gear skiving experiments and meshing performance tests of face gear pairs are conducted. The measurement results show consistency with the calculation results. Thus, the proposed design and continuously profile-shifted modification method based on the gear skiving process is feasible and contributes to load-bearing capacity improvement. [ABSTRACT FROM AUTHOR]

In this paper, we show how autonomous vehicles performing a certain task can be controlled from one command center in order to achieve certain goals. The command center provides individual feedback gains to each vehicle in the form of one compounded feedback gain that in fact carries feedback gain information for each individual vehicle. Vehicles may be of different nature: satellites, cars, tanks, drowns, robots, unmanned aircraft, underwater vehicles, and ships. It is assumed that their dynamic is weakly coupled, namely, dynamics of each individual vehicle is weakly coupled to dynamics of all other vehicles and that they have the same control input. The weak coupling among the vehicles is represented either by physical interactions among vehicles or coordinating or communication signals. The results obtained are applicable to vehicles having different mathematical linear/linearized state space models. In the case when no interaction/coordination/communication among vehicles is present, and all feedback signals come from the command center (central controller) controller, the vehicle mathematical models can be identical. An important feature of the presented results is that different local feedback controllers can be facilitated for different vehicles using a unique global feedback controller signal designed by the command center. In this paper, we will consider cases of two and three vehicles, but the presented multistage feedback design methodology can be potentially extended to N vehicles. The presentation is done in continuous time. Similar derivations hold in the discrete-time domain. [ABSTRACT FROM AUTHOR]

This paper presents a physics-constrained data-driven method that variationally embeds measured data in the modeling and analysis framework. The physics-based model is augmented with sparse but high-fidelity data through a variationally derived loss function. The structure of the loss function is analyzed in the context of variational correction to the modeled response wherein loss function penalizes the difference in the modeled response from the measured data that represents the local response of the system. The variationally embedded measured data (VEMD) method results in forward simulations that are not only driven by boundary and initial conditions but are also augmented by real measurements taken at only a small number of observation points. In the context of forward simulations, the proposed approach can be seen as inducing inductive biases that exploit the difference between the computed and measured quantities in the parametric space. With the help of a model problem, we show that the proposed method learns from the sparse high-fidelity datasets while preserving conservation properties of the balance laws. Method is applied to a non-smooth model problem and the mathematical attributes of the formulation are investigated in the context of high-fidelity sparse datasets. [ABSTRACT FROM AUTHOR]

Researchers have been studying the pain sensation extensively in the past few decades. Quantitative simulation and theoretical modeling of pain sensation based on experimental results are necessary for pain research. Many theories have been proposed to explain the mechanism of pain from molecular, cellular, and neuron network perspectives. But some phenomena in pain sensation are not fully understood, including wind-up and ramp-off. This paper focused on the theoretical model of wind-up and ramp-off phenomena in the pain sensation. With the addition of the transduction model, the generation mechanism of wind-up and ramp-off is better explained. The simulations were carried out to analyze the skin pain sensation under the mechanical stimulus, consisting of four different parts: the mechanical model of skin, transduction, transmission, modulation, and perception. The stress distribution on the skin was obtained based on the elastic theory. And the modified Hodgkin and Huxley model and the mathematical model of gate control theory were utilized to analyze the process of transduction, modulation, and perception, respectively. The numerical experiments demonstrated the wind-up occurs with a frequent stimulus of 1 Hz and 2 Hz, and ramp-off appears with the withdrawal of constant mechanical stimulus, which could contribute to the understanding of the pain sensation mechanism. [ABSTRACT FROM AUTHOR]

Ultrasonic-assisted magnetic abrasive flow machining (UAMAFM) process shows enhanced finishing performance compared to conventional abrasive flow machining (AFM). In this present research paper, mathematical models for MR and Ra have been developed for the UAMAFM process by considering both steady-state and transient phenomena. The external ultrasonic and magnetic field assistance enhanced the velocity and length of contact of active abrasives, calculated from the kinematic analysis. The resultant finishing forces have also been evaluated by considering these external aids. The steady-state material removal per finishing cycle remains constant and depends on the velocity of motion, length of contact, resulting forces, number of active abrasives, and work material hardness. The transient material removal per finishing cycle was calculated in terms of the volume of irregularities present over the work surface, i.e., initial surface roughness. The mathematical model for surface roughness was developed in terms amount of material removed (MR), and initial (Ra0) and critical surface roughness (Racr)?. The predicted values of material removed and surface roughness from developed mathematical models agreed with experimental results with a deviation of 7.80% and 2.44%, respectively. [ABSTRACT FROM AUTHOR]

The implantation of stents and instruments with capillary action demands super-finished internal surfaces of the manufactured product. Elasto-abrasives magneto-spiral finishing (EAMSF) is the attempt made in this paper to enhance finishing productivity by incorporating the abrasive flow in spiral motion due to the presence of the magnetic field. Here, novel impregnated elasto-magnetic abrasive particles (IMPs) are used in a magnetic field-assisted environment to polish the inner walls of the workpiece. In EAMSF, magnetic force provides excess finishing pressure to the abrasives. In contrast, the high-impact polystyrene (HIPS) elasticity absorbs the extra force of the IMPs on the finishing surface. An Indigenous mathematical relation considering the physics of this superfinishing process indicating material removal shows a close resemblance to the experimental results with an error percentage of 1.03 has been developed. The results of the experimentation reveal that 50% concentration of abrasives and a magnetic field density of 18mT yield a superior surface finish with a Ra value equal to 0.053 µm and maximum material removal of 6.9 mg, while in the absence of a magnetic field, excellent surface finish with a Ra = 0.266 µm and maximum material removal of 5.4 mg is achieved. In the presence of magnetic field density, significant enhancement of material removal, surface finish, and burr removal is observed. Finishing the surface at 50% abrasive concentration with a magnetic field represents regular finishing, and the trench marks on the original surface are removed after finishing. [ABSTRACT FROM AUTHOR]

Heliostat tracking is a critical component of the solar field of concentrating solar power tower (SPT) systems and can be the source of significant losses in power and profit when it lacks the necessary accuracy. This paper presents an advanced heliostat drive system for the SPT generation plant. An integrated model for the heliostat drive system based on dual axes tracking is proposed using an inexpensive angle sensor. The mathematical model of the integrated drive system is developed, including the solar, tower, and heliostat models. The matlab simulation model for the proposed integrated drive system is developed and evaluated. An experimental prototype for a dual-axis heliostat is built using Class-E direct current choppers and an inexpensive Gyro angle sensor. The prototype is tested and considered in the Dhahran region in Saudi Arabia under different operating conditions. A comparative study between simulation and experimental results is conducted to assess the efficacy and accuracy of the proposed controller drive system and validate the developed integrated model. Both simulation and experimental results demonstrate the effectiveness of the proposed dual-axis trackers to follow the sunbeams throughout the year. [ABSTRACT FROM AUTHOR]

An open path synthesis method for a spatial revolute-revolute-spherical-spherical (RRSS) mechanism is presented in this paper. The mathematical model for the trajectory curve is established. The characteristics of an RRSS mechanism in a standard installation position are revealed: the projection points of the coupler curve on the Oxy plane rotate by the corresponding input angles around the z-axis, and the generated points lie on an ellipse. Based on this finding, a 17-dimensional path generation problem can be translated into two lower-dimensional matching recognition problems and one actual size and installation position calculation problem. The path generation can be achieved by three steps. First, a database of four dimensional rotation angle parameters is established. By comparing the similarities between the mechanism feature curve of the prescribed open curve and its corresponding mechanism feature ellipse (MFE), the angles of installation, the initial angle of the input link, and the elliptic feature parameters of the desired RRSS mechanism can be approximately determined. Then, a 13-dimensional dynamic self-adapting numerical atlas database is established, which contains six basic dimensional types (BDTs) and seven wavelet feature parameters, and the BDTs of the desired RRSS mechanism are obtained. Finally, based on the relationship between the MFE of the prescribed curve and the BDTs of the desired RRSS mechanism, the calculation models for the actual link lengths and installation positions of the desired RRSS mechanism were established. Three examples are presented in this paper. [ABSTRACT FROM AUTHOR]

High-definition metrology (HDM) has gained significant attention for surface quality inspection since it can reveal spatial surface variations in detail. Due to its cost and durability, such HDM measurements are occasionally implemented. The limitation creates a new research opportunity to improve surface variation characterization by fusing the insights gained from limited HDM data with widely available low-resolution surface data during quality inspections. A useful insight from state-of-the-art research using HDM is the revealed relationship and positive correlation between surface height and certain measurable covariates, such as material removal rate (MRR). Such a relationship was assumed spatially constant and integrated with surface measurements to improve surface quality modeling. However, this method encounters challenges when the covariates have nonstationary relationships with the surface height over different surface areas, i.e., the covariate-surface height relationship is spatially varying. Additionally, the nonstationary relationship can only be captured by HDM, adding to the challenge of surface modeling when most training data are measured at low resolution. This paper proposes a transfer learning (TL) framework to deal with these challenges by which the common information from a spatial model of an HDM-measured surface is transferred to a new surface where only low-resolution data are available. Under this framework, the paper develops and compares three surface models to characterize the nonstationary relationship including two varying coefficient-based spatial models and an inference rule-based spatial model. Real-world case studies were conducted to demonstrate the proposed methods for improving surface modeling. [ABSTRACT FROM AUTHOR]

Bore holes with a large length to diameter ratio of up to l/d = 100 are typically produced using the single-tube deep hole drilling method also named BTA (Boring and Trepanning Association) deep hole drilling method. However, there are various technical applications requiring deep, complex, epitrochoid-similar and helical inner contours, such as stators used in Moineau motors and pumps. According to the current state of the art, epitrochoid-similar contours for small diameters with large drilling depths can only be produced using a special machining process which is referred to a chamber-boring process. In this paper, a developed mathematical model will be presented that describes the epitrochoid-similar contour exactly. This allows the determination of the position-dependent speed and acceleration of the tool, which are necessary for designing the joints and components of the tool system. In addition, this mathematical model can be used for a subsequent Laplace-transformation, so that could be used for a further optimization of the process dynamic in the future. [ABSTRACT FROM AUTHOR]

In this paper, a mathematical model of a single-channel photovoltaic thermal (PVT) air collector incorporated with a thermoelectric (TE) module has been presented. The overall electrical energy obtained from the photovoltaic thermal-thermoelectric (PVT-TE) collector is 5.78% higher than the PVT collector. Further, the grasshopper optimization algorithm (GOA) and hybrid grasshopper optimization algorithm with simulated annealing (GOA-SA) have been proposed and implemented to optimize the parameters of opaque PVT-TE collector. Although there are different parameters that influence the performance of PVT-TE system, yet in this study only four parameters, viz., length of the channel (L), width of the channel (b), mass flowrate of air in the channel (mair), and temperature of air at the inlet of channel (Tair,i) are considered for optimization. The simulation result demonstrates that the hybrid GOA-SA algorithm turned out to be an exceptionally effective method for optimal tuning of the parameters of the PVT-TE system. The result explicitly shows that the average value of overall electrical efficiency and exergy gain are 15.27% and 27.0565 W, respectively, when the parameters are optimized by the suggested GOA-SA algorithm which is way ahead with respect to the outcomes obtained with that of the calculated values or using GOA algorithm alone. [ABSTRACT FROM AUTHOR]

Mechanical insufflation-exsufflation (MI-E) secretion clearance system is usually utilized to help patients to clear secretion. In this paper, to obtain the essential dynamic characteristics of volume-controlled (VC) MI-E secretion clearance system with double lungs, a dimensionless model of the MI-E secretion clearance system is derived. Furthermore, for the validation of the mathematical model, a prototype VC MI-E secretion clearance system is proposed. Finally, to reveal the impact of key parameters on VC MI-E secretion clearance system, a dimensionless orthogonal experiment with four factors and five levels was processed. And then, coupling effects of two lungs on VC MI-E secretion clearance system were illustrated. This paper can be referred to in treatment of secretion clearance with VC secretion clearance system. [ABSTRACT FROM AUTHOR]

Estimation of thermal properties or diffusion properties from transient data requires that a model is available that is physically meaningful and suitably precise. The model must also produce numerical values rapidly enough to accommodate iterative regression, inverse methods, or other estimation procedures during which the model is evaluated again and again. Bodies of infinite extent are a particular challenge from this perspective. Even for exact analytical solutions, because the solution often has the form of an improper integral that must be evaluated numerically, lengthy computer-evaluation time is a challenge. The subject of this paper is improving the computer evaluation time for exact solutions for infinite and semi-infinite bodies in the cylindrical coordinate system. The motivating applications for the present work include the line-source method for obtaining thermal properties, the estimation of thermal properties by the laser-flash method, and the estimation of aquifer properties or petroleum-field properties from well-test measurements. In this paper, the computer evaluation time is improved by replacing the integral-containing solution by a suitable finite-body series solution. The precision of the series solution may be controlled to a high level and the required computer time may be minimized, by a suitable choice of the extent of the finite body. The key finding of this paper is that the resulting series may be accurately evaluated with a fixed number of terms at any value of time, which removes a long-standing difficulty with series solution in general. The method is demonstrated for the one-dimensional case of a large body with a cylindrical hole and is extended to two-dimensional geometries of practical interest. The computer-evaluation time for the finite-body solutions are shown to be hundreds or thousands of time faster than the infinite-body solutions, depending on the geometry. [ABSTRACT FROM AUTHOR]

The objective of this study is to find an optimized thin-layer mathematical model suitable for drying kinetics of turmeric. Turmeric has a high moisture content which necessitates effective drying. A 10 kg, sample batch, of turmeric was dried in a solar dryer. Drying air temperatures and air velocity were observed in the range of 55 °C-68 °C and 0.7 m/s-1.4 m/s, respectively, in the drying experiments. It is seen that the moisture content of the turmeric is reduced from 77% to 11.93% in 22 h when compared with open sun drying, which required 60 h for the same reduction in the moisture content. Scheffler dish was used to generate steam for the dryer. Seven thin-layer mathematical models, cited in the literature, had been used for the study. These models were applied for different trays placed in the dryer. The result of the research and experimentation showed that the Page model fits best for drying in the steam-based dryer and open sun drying. Experimental results showed 63.33% saving in drying time, and the drying efficiency was found as 29.85%. Uncertainty in the drying efficiency was observed as 0.67%. Experimental investigation and the findings from the mathematical modeling are presented in this paper. [ABSTRACT FROM AUTHOR]

Prior to the development of sophisticated computer numerical control (CNC), both face milling (FM) and face hobbing (FH), the two most popular technologies for bevel gear production, required cradle-type machines with diverse and complicated mechanisms. In the last two decades, however, the gear industry has replaced these traditional machines with six-axis CNC bevel gear cutting machines that have superior efficiency and accuracy. One such machine is a vertical six-axis machine with a vertical spindle arrangement, which offers two industrially proven advantages: compact design and maximum machine stiffness. The technical details of this machine, however, remain undisclosed; so, this paper proposes a mathematical model that uses inverse kinematics to derive the vertical machine's nonlinear six-axis coordinates from those of a traditional machine. The model also reduces manufacturing errors by applying an effective flank correction method based on a sensitivity analysis of how slight variations in the individual machine setting coefficients affect tooth geometry. We prove the model's efficacy by first using the proposed equations to derive the nonlinear coordinates for pinion and gear production and then conducting several cutting experiments on the gear and its correction. Although the numerical illustration used for this verification is based only on FM bevel gears produced by an SGDH cutting system, the model is, in fact, applicable in the production of both FM and FH bevel gears. [ABSTRACT FROM AUTHOR]

Tool errors are inevitable in an actual gear-manufacturing environment and may directly affect the accuracy of machined tooth surfaces. In this paper, tool errors including spheric radius, pressure angle, rake angle, regrind angle, and cutting side relief angle errors for three-face blade are defined and considered to establish the accurate tooth surface mathematical model for face-hobbed hypoid gears based on the manufacturing process and the meshing theory. The simulation flowchart for tooth surface modeling and tooth surface topography deviation analysis are proposed and performed. Results show that the tooth surface deviation is positive with positive spheric radius and rake angle errors and contrary results can be found for other three tool errors. In addition, the impact of the pressure angle error is the strongest. In addition, the rake angle error has the weakest effect and the influence of spheric radius error on the tooth surface deviation is unsubstantial. For location of tooth surface deviation, the maximum deviation is at the top on the heel and the minimum deviation is at the middle on the toe for spheric radius error. The maximum and minimum deviations are at the top and the middle tooth on the heel for other factors, respectively. [ABSTRACT FROM AUTHOR]

Gear shaping, a widely used machining method for circular gears, was generalized to noncircular gears in recent works using a 3-linkage machine tool. As the pitch curve normals of noncircular gears change constantly in processing, angles may exist between the pitch curve normals and the cutter relieving direction, bringing in turn cutter retracting interference. Regarding this, the paper proposes a 4-linkage shaping method. Through linkage motion of 4 machine tool axes, noncircular gear pitch normals are along the cutter relieving direction, avoiding completely cutter retracting interference. On such basis, a mathematical model is first established, the cutting process is then discussed and a cutting experiment is finally carried out, proving the validity of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a mathematical model to simulate the pressure and flow rate characteristics of a spool valve is derived. To improve the simulation accuracy, the discharge coefficient through the spool valve ports is assumed to be a function of both the Reynolds number and the orifice geometry rather than treating it as a constant. Parameters of the model are determined using the data obtained by computational fluid dynamics (CFD) analyses conducted on two-dimensional axisymmetric domains using ANSYS Fluent 15® commercial software. For turbulence modeling, shear stress transport (SST) k-ω model is preferred after a comparison of performance with the other available turbulence model options. The resulting model provides consistent pressure and flow rate estimations with CFD analyses and a smooth transition between different geometrical conditions. The ultimate aim of this study is to fulfill the need for a model to precisely determine the geometrical tolerances of spool valve components for optimum performance. Estimations of the developed model is compared with the experimental data of a spool valve, and the model is proved to be able to accurately estimate the maximum leakage flow rate, the pressure sensitivity, and the shapes of leakage flow/load pressure curves. [ABSTRACT FROM AUTHOR]

This paper deals with the design of fixed-structure controllers for two-input two-output (TITO) systems using frequency-domain data. In standard control approaches, a plant model is first derived, then a suitable controller is designed to meet some user-specified performance specifications. Basically, there are two common ways for obtaining mathematical models: white-box modeling and black-box modeling. In both approaches, it is difficult to obtain a simple and accurate model that completely describes the system dynamics. As a result, errors associated with the plant modeling may result in degradation of the desired closed-loop performance. Moreover, the intermediate step of plant modeling introduced for the controller design is a time-consuming task. Hence, the concept of data-based control design is introduced as a possible alternative to model-based approaches. This promising methodology allows us to avoid the under-modeling problem and to significantly reduce the time and workload for the user. Most existing data-based control approaches are developed for single-input single-output (SISO) systems. Nevertheless, a large class of real systems involve several manipulated and output variables. To this end, we attempt here to develop an approach to design controllers for TITO systems using frequency-domain data. In such a method, a set of frequency-domain data is utilized to find an adequate decoupler and to tune a diagonal controller that meets some desired closed-loop performance measures. Two simulation examples are presented to illustrate and demonstrate the efficacy of the proposed method. [ABSTRACT FROM AUTHOR]

Geomaterials such as vuggy carbonates are known to exhibit multiple spatial scales. A common manifestation of spatial scales is the presence of (at least) two different scales of pores with different hydromechanical properties. Moreover, these pore-networks are connected through fissures and conduits. Although some models are available in the literature to describe flows in such media, they lack a strong theoretical basis. This paper aims to fill this gap in knowledge by providing the theoretical foundation for the flow of incompressible single-phase fluids in rigid porous media that exhibit double porosity/permeability. We first obtain a mathematical model by combining the theory of interacting continua and the maximization of rate of dissipation (MRD) hypothesis, and thereby provide a firm thermodynamic underpinning. The governing equations of the model are a system of elliptic partial differential equations (PDEs) under a steady-state response and a system of parabolic PDEs under a transient response. We then present, along with mathematical proofs, several important mathematical properties that the solutions to the model satisfy. We also present several canonical problems with analytical solutions which are used to gain insights into the velocity and pressure profiles, and the mass transfer across the two pore-networks. In particular, we highlight how the solutions under the double porosity/permeability differ from the corresponding ones under Darcy equations. [ABSTRACT FROM AUTHOR]

Check valve dynamics plays an important role in many fluid systems, such as in compressors, hydraulic pumps, and hydraulic switching converters. Plate type check valves are a frequently employed valve type in dynamically challenging cases. Despite the relevancy of plate valve dynamics, only few exhaustive works can he found in the literature, focusing on the behavior of hydraulic check valves for high-frequency applications. This paper presents an in-depth characterization of a plate valve designed as rectifier of a high-frequency oscillation pump working at 300 Hz. The aim is to identify a sufficiently simple mathematical model, which permits to optimize the design of the valve for the considered application. The paper analyses the different phenomena contributing to the dynamics of such a valve and presents the results of simulation and experimental activity. The results show how small details in the design and manufacturing of those valves (namely, the contact surfaces) have important consequences on the dynamics of the pump system. In general, a good agreement between model and reality is achieved. [ABSTRACT FROM AUTHOR]

Most components used in gas and steam turbines are metallic parts produced by either casting or forging processes. Although process control works to eliminate defects, there can be variation in microporosity from component to component. Previously, this microporosity was only able to be detected destructively using metallography. Using computer tomography (CT), one can find voids in the range of a few tenths of a millimeter and know the location of the voids with high precision. This allows one to map the defects present in each component onto the stress and temperature fields for that component. However, there is not yet universal agreement upon a consistent method to evaluate the effect of these small porosities on a components lifetime. Having a robust analysis tool to understand the impact of microporosity would decrease development costs, decrease the time to bring a product to market, and increase the likelihood of failure-free operation. This paper presents an approach using equivalent low-cycle fatigue (LCF) material properties which avoids the need to explicitly model the morphology of the microstructure in the region of the microporosity. The homogenization methodology calculates new LCF curves depending on porosity ratios in material. This approach uses Morrows correlation factor of LCF cycles to crack initiation regarding energy amount dissipated in stable cycling (shakedown) and ultimate strain energy under monotonic loading. The paper generalizes Morrows postulate and formulates the hypothesis that energy stored and dissipated in the material under shakedown conditions corresponds directly to the number of LCF cycles to crack initiation. The paper demonstrates that the reduction of LCF life based on the porosity ratio agrees well with the experimental results. These results also show that the methodology is very sensitive to the void orientation and loading direction. [ABSTRACT FROM AUTHOR]

This paper presents an accurate and computationally efficient time-domain design method for the proportional-integral-derivative (PID) control of first-order and second-order plants in the presence of discrete time delays. As time delays would generally deteriorate the achievable performance of the PID controllers, their effects should be thoroughly considered in the controller design and parameter tuning process. This paper is thereby motivated to propose a time-domain semi-analytical method for the parameter tuning and stability analysis of PID controllers of the time-delay systems. To facilitate this development, the transfer functions of the investigated plants associated with the PID controllers are first rewritten as linear periodic delayed differential equations (DDEs) in state-space form. Then, the differential quadrature method (DQM) is adopted to estimate the time derivative of the state-space function at each sampling grid point within a duration of the time delay by the weighted linear sum of the function values over the whole sampling grid points. In this way, the DDEs in the time-delay duration are discretized as a series of algebraic equations, and the transition matrix can be obtained by combining these discretized algebraic equations. Thereafter, the stability boundary can be determined and the optimal control gains are obtained by minimizing the largest absolute eigenvalue of the transition matrix. As the minimum problems are commonly solved by the gradient descent approaches, the analytical form of the gradient of the largest absolute eigenvalue of transition matrix with respect to the control gains is explicitly presented. Finally, extensive numeric examples are provided, and the proposed DQM is proven to be an accurate and computationally efficient way to tune the optimal control gains and estimate the stability region in the control gain space. [ABSTRACT FROM AUTHOR]

The increasing complexities of wellbore geometry imply an increasing well cost. It has become more important than ever to achieve an increased rate of penetration (ROP) and, thus, reduced cost per foot. To achieve maximum ROP, an optimization of drilling parameters is required as the well is drilled. While there are different optimization techniques, there is no acceptable universal mathematical model that achieves maximum ROP accurately. Usually, conventional mathematical optimization techniques fail to accurately predict optimal parameters owing to the complex nature of downhole conditions. To account for these uncertainties, evolutionary-based algorithms can be used instead of mathematical optimizations. To arrive at the optimum drilling parameters efficiently and quickly, the metaheuristic evolutionary algorithm, called the "shuffled frog leaping algorithm, (SFLA) is used in this paper. It is a type of rising swarm-intelligence optimizer that can optimize additional objectives, such as minimizing hydromechanical specific energy. In this paper, realtime gamma ray data are used to compute values of rock strength and bit-tooth wear. Variables used are weight on bit (WOB), bit rotation (N), and flow rate (Q). Each variable represents a frog. The value of each frog is derived based on the ROP models used individually or simultaneously through iteration. This optimizer lets each frog (WOB, N, and Q) jump to the best value (ROP) automatically, thus arriving at the near optimal solution. The method is also efficient in computing optimum drilling parameters for different formations in real time. The paper presents field examples to predict and estimate the parameters and compares them to the actual real-time data. [ABSTRACT FROM AUTHOR]

This paper presents a system modeling technique for a high-speed gantry-type machine tool driven by linear motors. One feed axis of the investigated machine tool is driven by the joint thrust from two parallel linear motors. These two parallel motors are coupled mechanically to form the Y-axis while another standalone motor fixed to a support forms the X-axis. The components in the X-axis, which is treated as the mechanical coupling, are carried by the slides of the Y-axis motors. This configuration is applied to improve the dynamic stiffness of the system and operation speed/acceleration. However, the precise synchronous control of the two parallel and coupled motors would be the major challenge. To overcome this challenge, a multivariable system identification method is developed in this paper. This method is used to construct an accurate system mathematical model for the target coupled system. A synchronous control scheme is then applied to the model obtained using the proposed technique. The performance of the system is experimentally verified with a high-speed S-curve motion profile. The results substantiate the constructed system model and demonstrate the effectiveness of the control scheme. [ABSTRACT FROM AUTHOR]

A conference paper about the use of thermodynamics in explaining useful work or entropy and its application to fuel needs and fuel utilization. Topics discussed include the laws of thermodynamics based on the work produced from hydraulic engines, the relationship between useful work and fuel usage and the difference of available useful work from Gibbs free energy and enthalpy. A mathematical computation of the available useful work from oxidation of methylene (CH2) is described.

Despite the tremendous effort of researchers and manufacturing engineers in improving the predictability of the air bending process, there is still a strong need for comprehensive and dependable prediction models. Currently, available modeling approaches all present some relevant limitations in practical applications. In this paper, we propose a new method, which represents an improvement over all existing modeling and prediction techniques. The proposed method can be used for accurate prediction of the main response variables of the air bending process: the angle a after springback and the bend deduction BD. The metamodeling method is based on the hierarchical fusion of different kinds of data: the deterministic low-fidelity response of numerical finite element method (FEM) simulations and the stochastic high fidelity response of experimental tests. The metamodel has been built over a very large database, unprecedented in the scientific literature on air bending, made of more than 500 numerical simulations and nearly 300 experimental tests. The fusion is achieved first by interpolating the FEM simulations with a kriging predictor; then, the hierarchical metamodel is built as a linear regression model of the experimental data, using the kriging predictor among the regressors. The accuracy of the method has been proved using a variant of the leave-one-out cross validation technique. The quality of the prediction yielded by the proposed method significantly over-performs the current prediction of the press brake on-line numerical control. [ABSTRACT FROM AUTHOR]

All of the cutting edges on an hourglass worm gear hob have different shapes and spiral angles. If the spiral angles are small, straight flutes are typically adopted. However, for hobs with multiple threads, the absolute values of the negative rake angles on one side of the cutting teeth will greatly affect the cutting performance of the hob if straight flutes are still used. Therefore, spiral flutes are typically adopted to solve this problem. However, no method to determine the spiral flute of an hourglass worm gear hob has been proposed until now. Based on the curved surface generating theory and the hourglass worm forming principle, a method for generating the spiral flute of the planar double enveloping hourglass worm gear hob is proposed in this paper. A mathematical model was built to generate the spiral flute. The rake angles of all cutting teeth of the hob are calculated. The laws of the rake angles of the cutting teeth for four hobs with different threads from one to four threads were analyzed when straight flutes and spiral flutes are adopted. The laws between the value of the negative rake angles of the hob with four threads and the transmission ratio were studied. The most appropriate transmission ratio for generating the spiral flute was obtained. The machining of the spiral flutes was simulated using a virtual manufacturing system, and the results verify the correctness of the method. [ABSTRACT FROM AUTHOR]

This paper develops a passivity-based robust motion controller for a robot used in prosthetic leg performance studies. The mathematical model of the robot and passive prosthesis corresponds to a three degree of freedom, underactuated rigid manipulator. A form of robotic testing of prostheses involves tracking reference trajectories obtained from human gait studies. The robot presented in this paper emulates hip vertical displacement and thigh swing, and we consider a prosthesis with a passive knee for control development. The control objectives are to track commanded hip displacements and thigh angles accurately, even in the presence of parametric uncertainties and large disturbance forces arising from ground contact during the stance phase. We develop a passivity based controller suitable for an underactuated system and compare it with a simple independent-joint sliding mode controller (IJ-SMC). This paper describes the mathematical model and nominal parameters, derives the passivity-based controller using Lyapunov techniques and reports success in real-time implementation of both controllers, whose advantages and drawbacks are compared. [ABSTRACT FROM AUTHOR]

This paper deals with the analysis of the main features of forced microconvection of liq-uid and gas flows through microchannels. A critical overview of the main effects that tends to play an important role in the determination of Nusselt number in microchannels is presented. Some experimental data obtained at the Microfluidics Lab of the University of Bologna together with the main results which appeared recently in the open literature both for liquids and gases are used in order to highlight the peculiar characteristics of the convective heat transfer through microchannels and to suggest the guidelines for a physically based interpretation to the experimental results. By means of specific exam-ples, it is shown that the thermal behavior at microscale of gas and liquid flows through microchannels in terms of convective heat transfer coefficients can be strongly affected by scaling and micro-effects but also by practical issues linked to the geometry of the test rig, the real thermal boundary conditions, the presence of fittings, position and type of the sensors, and so on. All these aspects have to be taken into account during the data post processing in order to obtain a correct evaluation of the Nusselt numbers. It is also highlighted how it is always useful to couple to the experimental approach a complete computational thermal fluid-dynamics analysis of the whole tested microsystem in order to be able to recognize "a priori" the main effects which can play an important role on the convective heat transfer analysis. It is demonstrated in this paper that this "a priori" analysis is crucial in order to: (i) individuate the main parameters which influence the convective heat transfer coefficients (this is important for the development of new corre-lations); (ii) compare in a right way the conventional correlations with the experimental results. [ABSTRACT FROM AUTHOR]

This paper presents performance metrics that can be used to evaluate the response sensi-tivity of a tension leg platform (TLP) to its tendons. An uncoupled TLP model ignores the intrinsic dynamics and environmental loads on the cables by treating each tendon as an ideal massless spring. A coupled TLP system, in contrast, considers the effects of distrib-uted mass and drag along the tendon. Under certain operating conditions, an uncoupled dynamics model can produce results comparable to its coupled counterpart. This paper defines the conditions under which it is acceptable to model a TLP tendon as a linear spring, as opposed to one that considers the cable dynamics. The analysis is performed in the frequency domain and, for generality, the results are nondimensionalized. The findings indicate that a more elaborate set of conditions than the platform-to-cable mass ratio must be satisfied for the two models to provide similar results. To conclude this study, two simulations are performed and compared against the performance metrics derived in this paper. [ABSTRACT FROM AUTHOR]

This paper describes, qualitatively and through visual observations, the ice-sheet interac-tion with a shoulder ice barrier (SIB) during model tests. The model tests were performed in the Hamburg Ship Model Basin (HSVA) during July 2007. Since the SIB represents a new concept in ice barrier structures, model tests were intended to evaluate the general performance of the SIB. The paper describes seven different experiments where the ice thickness, the ice flexural strength, and the shoulder angle of the SIB are the parameters which are varied among them. The results are presented in two sections. The first part refers to observations common to all the experiments, where the ice failure mode and shoulder performance are given special attention. The second part describes the phenom-ena observed in each particular experiment in more detail. The former analysis allows for the visual identification of three phases (as mentioned in previous publications) and gives a deeper insight into the characteristics of each phase. The latter analysis on the contrary, allows us to achieve interesting conclusions about the SIB performance under different ice conditions and with different shoulder inclinations. A comparison between the failure mode observed during the model tests and observations presented in the litera-ture of full scale vertical and sloped structures, ice interaction with rubble accumulation, is performed. The similarities found in the study between the model and full scale obser-vations lead us to assume that the observed model test behavior may be expected during ice-SIB interaction in full scale conditions. However, some events that could be associ-ated with the problems of the model, such as ice scaling, are highlighted. As a conclusion regarding the SIB performance, it is shown that the shoulder section, which is the princi-pal innovation of the concept, satisfactorily accomplishes its task and represents a key modification to traditional ice barriers in generating smaller ice pieces and avoiding ice overriding. [ABSTRACT FROM AUTHOR]

Optimization techniques have been applied to neuron models for a variety of purposes, including control of neuron firing rates and minimizing input stimulus current magnitudes. Optimal control is used to minimize a quantity of interest; often, the time or energy needed to complete an objective. Rather than attempting to control or modify neuron dynamics, this paper demonstrates that optimal control can be used to obtain an optimal input stimulus current i"(t) which causes a six dimensional Hodgkin-Huxley type neuron model to approximate a specified reference membrane voltage. The reference voltages considered in this paper consist of one or more action potentials as evoked by an input current i(t). In the described method, the user prescribes a balance of low squared integral of input stimulus current (input stimulus "energy") and accurate tracking of the original reference voltage. In a previous work, the authors applied this approach to a reduced order neuron model. This paper demonstrates the applicability of this technique to biologically plausible higher dimensional conductance based neuron models. For each investigated neuron response, the method discovered optimal input stimuli current i"(t) having a lower energy than the original i(t), while still providing accurate tracking of the reference voltage. [ABSTRACT FROM AUTHOR]

This study examined the use of bond graphs for the modeling and simulation of a fluid power system component. A new method is presented for creating the bond graph model, based upon a previously developed mathematical model. A nonlinear dynamic bond graph model for a two-stage pressure relief valve has been developed in this paper. Bond graph submodels were constructed considering each element of the studied valve assembly. The overall bond graph model of the valve was developed by combining these submodels using junction structures. Causality was then assigned in order to obtain a computational model, which could be simulated. The simulation results of the causal bond graph model were compared with those of a mathematical model, which had been also developed in this paper based on the same assumptions. The results were found to correlate very well both in the shape of the curves, magnitude, and response times. The causal bond graph model was verified experimentally in the dynamic mode of operation. As a result of comparison, bond graphs can quickly and accurately model the dynamics in a fluid power control system component. During the simulation study, it was found that nonlinearity occur due to three factors: changes in pressure, which cause nonlinear velocity changes of the flow rate; changes in the throttling area of the valve restriction, which usually changes nonlinearly; and changes in the discharge coefficient of the throttling area of the valve restriction, which does not remain constant. [ABSTRACT FROM AUTHOR]

Roll-to-roll (R2R) printing is a continuous process in which thin flexible materials such as paper are passed through a printing press to print the required pattern onto the mate-rial. Each printing press may have several printing units depending on the number of col-ors to be printed and the complexity of the pattern. The flexible material, often referred to as a "web," is passed successively through each print unit to create a multicolor pattern. Print registration is the process of overlapping successive printed patterns to form a com-plex multicolor pattern and the registration error is the position misalignment in the overlapped patterns. This paper develops a machine direction print registration model in a printing press with multiple print units whose print cylinders are driven using mechani-cal line shafts. The registration model considers the effects of interaction between adja-cent print units due to variations in material strain and machine dynamics, including various dynamic elements, such as the print cylinder, doctor blade assembly, print unit compensator roller, print unit motor, friction at various locations, etc. Measured data from typical production runs on an industrial printing press are used to corroborate the developed print registration model. Mechanical design and control design recommenda-tions to reduce registration error in print units are also provided. The developed registra-tion model is applicable to many R2R printing technologies, such as offset, flexo, and rotogravure printing. [ABSTRACT FROM AUTHOR]

In this paper, we study the continuum physics model equations for condensation (two phase flow problems) in vertical tubes with small diameter and obtain reduced model equations. We found that generalization of dimensional analysis to multiple spatial dimensions is an excellent tool for that purpose, so that a review of this method is also part of the paper. We obtain the nondimensional numbers of the problem and derive reduced bulk and inteiface equations. The problem is characterized by three length scales, tube radius R, tube length L, and initial film thickness H. For small ratio e = H/L, we derive a single ordinary differential equation for the condensate film thick-ness as function of axial position with tube radius as parameter, which agrees well with commonly used (parametric) models from literature. Our model is based on the physical dimensions of the problem which gives a greater geometrical flexibility and a wider range of applicability. We also discuss the effect of surface tension and the limit of the model. [ABSTRACT FROM AUTHOR]

In this paper, performance of the initial fine alignment for the stationary nonleveling strapdown inertial navigation system (SDINS) containing low-grade gyros is analyzed. First, the observability is analyzed by conducting a rank test of an observability matrix and by investigating the normalized error covariance of the extended Kaiman filter based on the ten-state model. The results show that the accelerometer biases on horizontal axes are unobservable. Second, the steady-state estimation errors of the state variables are derived using the observability equation. It is verified that the estimates of the state varia-bles have errors due to the unobservable state variables and nonleveling attitude angles of a vehicle containing the SDINS. Especially, this paper shows that the larger the atti-tude angles of the vehicle are, the greater the estimation errors are. Finally, it is shown that the performance of the eight-state model excluding the two unobservable state varia-bles is better than that of the ten-state model in the fine alignment by a Monte Carlo simu-lation. [ABSTRACT FROM AUTHOR]

In this paper, analytical solutions are derived for the case when an elastic water-backed plate (WBP) is subject to an exponential shock loading near a fixed solid boundary. Two cases, a rigid plate and an elastic plate represented by two mass elements connected by a spring and a dashpot, are studied. The analytical solution is extended from Taylor's (1963, "The Pressure and Impulse of Submarine Explosion Waves on Plates," Scientific Papers of Sir Geoffrey Ingram Taylor, Vol. 3, G. K. Batchelor, ed., Cambridge University Press, Cambridge, UK, pp. 287-303) floating air-backed plate (ABP) model and the water-backed plate model of Liu and Young (2008, "Transient Response of Submerged Plates Subject to Underwater Shock Loading: An Analytical Perspective," J. Appl. Mech., 75(4), 044504; 2010, "Shock-Structure Interaction Considering Pressure Pre-cursor," Proceedings of the 28th Symposium on Naval Hydrodynamics, Pasadena, CA). The influences of five parameters are studied: (a) the distance of the fixed boundary from the back plate d, (b) the fluid structure interaction (FSI) parameter ɸ of the plate, (c) the stiffness of the plate as represented by the natural frequency of the system T, (d) the mate-rial damping coefficient CD of the plate, and (e) the pressure precursor (rise) time θr. The results show that the pressure responses at the front and back surfaces of the plate are greatly affected by the proximity to the fixed boundary, the fluid-structure interaction parameter, the ratio of the shock decay time to the natural period of the structure, and the rise time of incident pressure. The effect of structural damping (assuming a typical material damping coefficient of 5%) is found to be practically negligible compared to the other four parameters. [ABSTRACT FROM AUTHOR]

Control design for multivariable nonlinear systems has cultivated into a mature research area. A variety of control design methodologies have been well established. In most of the approaches, however, it is implicitly assumed that an analytically mathematical model can be available. This is not always feasible since in many practical control problems, system dynamics may be represented by nonanalytical modules, such as look-up tables, c or Fortran codes, etc. As a consequence, conventional methods can only be performed after analytical models are obtained. In this paper, an approach is proposed where the nonanalytical modules can be handled directly. Important results are obtained on optimal control laws and their implementation; robust control is achieved using a new online tuning method; input saturation and stability issues are also discussed. A numerical study is provided to validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Different researches have been developed during the past years aiming addressing challenges still faced in petroleum exploration. Rate of penetration and specific energy studies have been the main focuses in trying to boost operational efficiency. The combination of both techniques accomplished with a preoperational test (drill-rate test) may allow as a new trending tool the best side of the drillability optimization to take place. Further, by having these implemented in real-time, an interesting methodology result in seeing the penetrating processes as a step-by-step where drilling mechanics parameters can be more dynamically adjusted. Thus, the main focus of this paper is to address a combination of rate of penetration together with a specific energy formulation in parallel with a possible dynamic and real-time drill-rate test plotted graphs for sake of the drilling optimization enhancement. [ABSTRACT FROM AUTHOR]

Nonthermal irreversible electroporation (NTIRE) is an new minimally invasive tissue ablation modality that uses high electric field pulses to produce irreversible permeation of the cell membrane (irreversible electroporation) while avoiding thermal damage and is applied to treat malignant tumors. This paper describes efforts to develop NTIRE as a new minimally invasive treatment modality for uveal melanoma, the most common pri-mary intraocular malignancy in adults, and other ocular malignancies. The paper deals with a 3D mathematical simulation model of the eye that employs the simultaneous solution to the electric field equation and to the Pennes bioheat equation to predict the electric field in the eye as well as the rise in eye temperature in response to the application of a high power electric pulse. Treatment efficacy was defined as the fraction of tumor vol-ume in which the electric field exceeded a predefined target field and treatment safety was calculated by the ratio of the electric field in the tumor to the electric field in the vitreous humor or in the macula. Results show that treatment efficacy and safety are criteria that can be used to optimize the NTIRE treatment protocol. [ABSTRACT FROM AUTHOR]

This paper deals with the modeling and the prediction of the dynamic behavior of uncertain nonlinear systems. An efficient method is proposed to treat these problems. It is based on the Wiener-Haar chaos concept resulting from the polynomial chaos theory and it general-izes the use of the multiresolution analysis well known in the signal processing theory. The method provides a powerful tool to describe stochastic processes as series of orthonormal piecewise functions whose weighting coefficients are identified using the Mallat pyramidal algorithm. This paper shows that the Wiener-Haar model allows an efficient description and prediction of the dynamic behavior of nonlinear systems with probabilistic uncertainty in parameters. Its contribution, compared to the representation using the generalized poly-nomial chaos model, is illustrated by evaluating the two models via their application to the problems of the modeling and the prediction of the dynamic behavior of a self-excited uncertain nonlinear system. [ABSTRACT FROM AUTHOR]

This paper develops the models for the structural performance of the loading and probabilistic characterization for the fatigue and the serviceability limit states for the support structure of offshore wind energy converters. These models and a sensitivity study are part of a risk based assessment and monitoring framework and will be applied for estab-lishing the "as designed and constructed" reliability as prior information for the assessment and the design of monitoring systems. The constitutive physical equations are introduced in combination with the fatigue and serviceability limit state requirements as the starting point for the development of the structural performance and loading models. With these models introduced in detail, several modeling aspects for both limit states are analyzed. This includes analyses of the influence on the hot spot stresses by applying a contact formulation for the pile guide brace connection and the application of a finite element formulation using solid elements. Further, the comparison of the natural frequencies of a discrete rotor model with a continuous rotor model is documented. To account for uncertainties associated with the structural and loading models, a probabilistic model is derived on the basis of literature review and measurement data from a prototype Multibrid M5000 support structure. The sensitivity study is based on the calculation of a nonlinear coefficient of correlation in conjunction with predetermined designs of experiments. This is conducted by a systematic analysis of the influence of the random variables on limit state responses and hence on the structural reliability. Integrating the analyses and sensitivity studies of the fatigue and serviceability limit state models developed in this paper as well as the ultimate limit state models in Thons et al. ("Ultimate Limit State Model Basis for Assessment of Offshore Wind Energy Con-verters," ASME J. Offshore Mech. Arct. Eng.), the model basis for the assessment is completed. The process of establishing and analyzing such a model basis contributes to a detailed understanding of the deterministic and probabilistic characteristics of the structure and provides valuable insights in regard to the significance of available data. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical model to find the wheel location in grinding a given helical flute of an end mill. Two new setting parameters are introduced to define the relative wheel location in workpiece coordinates. This model allows the wheel-axis orientation be expressed explicitly as a function of the design factors and machine setting parameters. By utilizing this explicit form of the wheel orientation and analyzing the influence of setting parameters on design parameters, a new efficient search algorithm is proposed, and the performance shows that the required wheel location is found within 1.5 s to machine a given flute profile. Moreover, the rake angle can be produced more precisely compared with the conventional methods, which have been used with approximations. A comprehensive development of the software for designing and grinding the helical flute of the end mill is presented, which provides a technology and good foundation for the development of a computer-aided design and computer-aided manufacturing (CADICAM) system for manufacturing end mills. The results of the experiment, simulation, and design are compared in order to verify of the proposed method. [ABSTRACT FROM AUTHOR]

Safe and reliable automatic pressure regulation of the oxygen mask is a primary consideration for the oxygen supply system. One kind of electronic oxygen regulator (EOR) structure is proposed, and its operation principle is explained in this paper. To avoid long controller design cycle, herein, some simulations are carried out on matlab for analysis by establishing a mathematical model according to the EOR flow dynamic characteristics. In the simulations, the all-coefficient adaptive control method based on a characteristic model (CM) and the proportional-integral-derivative (RID) algorithm are applied, and the results are thoroughly investigated by considering some disturbance, such as the user's changing pulmonary ventilation parameters, the air leakage of the mask, and the sensor noise. Results suggest that the all-coefficient control method is more effective to guarantee superior lower inspiratory resistance than the PID method with the environmental disturbance, which may be a plausible reference for the EOR controller design. [ABSTRACT FROM AUTHOR]

Dynamic vibration and quasi-static deformation will occur simultaneously for flexible space structures subjected to sudden thermal loads. In this paper, the integrated controller based on modified positive position feedback (PPF) compensator is proposed as an innovative controller for active deformation reduction in flexible space trusses. The controller uses the concept of positive acceleration feedback combined with integral position feedback to provide effective vibration suppression of multiple modes and compensator of quasi-static deformation. To solve the problem of placement optimization for both sensors and actuators, the discrete glowworm swarm optimization (GSO) algorithm based on genic binary coding is suggested. A cantilevered truss is taken as an example for numerically evaluating the performance of the controller for thermally induced deformation control. Numerical results demonstrate that the discrete GSO algorithm is feasible in solving the combinatorial optimization problem. And the proposed controller is significantly effective in controlling both steady-state deformation and transient vibration. [ABSTRACT FROM AUTHOR]

This paper presents numerical simulations of annular laminar film condensation heat transfer in microchannels of different internal shapes. The model, which is based on a fi-nite volume formulation of the Navier-Stokes and energy equations for the liquid phase only, importantly accounts for the effects of axial and peripheral wall conduction and nonuniform heat flux not included in other models so far in the literature. The contribu-tions of the surface tension, axial shear stresses, and gravitational forces are included. This model has so far been validated versus various benchmark cases and versus experi-mental data available in literature, predicting microchannel heat transfer data with an average error of 20% or better. It is well known that the thinning of the condensate film induced by surface tension due to gravity forces and shape of the surface, also known as the "Gregorig" effect, has a strong consequence on the local heat transfer coefficient in condensation. Thus, the present model accounts for these effects on the heat transfer and pressure drop for a wide variety of geometrical shapes, sizes, wall materials, and working fluid properties. In this paper, the conjugate heat transfer problem arising from the cou-pling between the thin film fluid dynamics, the heat transfer in the condensing fluid, and the heat conduction in the channel wall has been studied. In particular, the work has focused on three external channel wall boundary conditions: a uniform wall temperature, a nonuniform wall heat flux, and single-phase convective cooling are presented. Ai the scale of the problem is reduced, i.e., when moving from mini- to microchannels, the results show that the axial conduction effects can become very important in the prediction of the wall temperature profile and the magnitude of the heat transfer coefficient and its distribution along the channel. [ABSTRACT FROM AUTHOR]

This paper presents the first results of a wide experimental investigation on the aerodynamics of a vertical axis wind turbine. Vertical axis wind turbines have recently received particular attention, as interesting alternative for small and micro generation applications. However, the complex fluid dynamic mechanisms occurring in these machines make the aerodynamic optimization of the rotors still an open issue and detailed experimental analyses are now highly recommended to convert improved flow field comprehensions into novel design techniques. The experiments were performed in the large-scale wind tunnel of the Politecnico di Milano (Italy), where real-scale wind turbines for micro generation can be tested in full similarity conditions. Open and closed wind tunnel configurations are considered in such a way to quantify the influence of model blockage for several operational conditions. Integral torque and thrust measurements, as well as detailed aerodynamic measurements were carried out to characterize the 3D flow field downstream of the turbine. The local unsteady flow .field and the streamwise turbulent component, both resolved in phase with the rotor position, were derived by hot wire measurements. The paper critically analyses the models and the correlations usually applied to correct the wind tunnel blockage effects. Results highlight that the presently available theoretical correction models do not provide accurate estimates of the blockage effect in the case of vertical axis wind turbines. The tip aerodynamic phenomena, in particular, seem to play a key role for the prediction of the turbine performance; large-scale unsteadiness is observed in that region and a simple flow model is used here to explain the different flow features with respect to horizontal axis wind turbines. [ABSTRACT FROM AUTHOR]