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In order to investigate the long-term behavior of contact resistance in low-voltage contactors under the influence of electric arcs in polymer housings, a new model switch was developed. The model switch permits the modification of different factors such as contact gap, contact force, closing and/or separation speed of the contacts, and arc-chamber materials among others. Several experimental series using Ag/Ni10 contacts were carried out as a reference. The contact resistance was determined using two different measurement current sources. Contact resistance data were analyzed using Weibull functions as well as nonparametric statistics. Information regarding surface structures, their chemical composition, and formed crystalline phases of contact and ambient materials on the contact surfaces was obtained through several material analysis methods. This paper presents the main characteristics of the model switch and some experimental results about contact resistance behavior under the influence of ac-arcs in outgassing polymer surroundings. [ABSTRACT FROM AUTHOR]

Higher-order logic theorem proving method is applied to analyze fractional order PD control systems in this paper. Theorem proving is based on rigorous logic and correct mathematics theory. Firstly, existent conditions and formal model of fractional calculus Caputo definition is established in higher order logic theorem prover. Then some properties are verified, including homogeneity, linearity property, fractional differential of constant and relationship between integer order differential and fractional differential. And formalization of Laplace transform based on fractional calculus Caputo definition is given and we apply it to illustrate advantages of fractional calculus Caputo definition. Initial values based on fractional calculus Caputo definition have exact physical meanings. And then formal modeling of fractional order PD controller is verified based on the above properties. We also verify the stability and other properties of fractional order PD controller by theorem proving method. Lastly, steady-state error is analyzed based on formalization of fractional calculus Caputo definition. It shows that fractional order PD controller can achieve a better control performance than integer order PD controller. [ABSTRACT FROM AUTHOR]

The operating regimes for a pilot-scale rotating-disc contactor (RDC) were investigated by a computational fluid dynamics/population balance model (CFD-PBM) simulation. The model successfully predicted the critical rotor speed, which divided the entire operating range into two regions. In the low rotor speed region, the input energy was insufficient to break droplets, resulting in an almost constant droplet diameter. Therefore, the increasing revolution slightly affected the interfacial area, while the axial mixing became severe. In contrast, the interfacial area increased significantly in the high rotor speed region because of the increased breakage rate. Moreover, the axial mixing extent increased slightly because the dispersed-phase accumulation enhanced the advection effect. The results indicate that the CFD-PBM approach can be applied to engineering practice for extractors. [ABSTRACT FROM AUTHOR]

With the development of the scanning tunneling microscope, and other high resolution “microscopies”, researchers could examine and adapt synthetic processes to control particles on the nanometer scale. Since then there have been an explosion of techniques for fabricating nanoparticles. So called “top-down” synthetic techniques start with large particles and make them smaller via grinding, spraying or pyrolysis while “bottom-up” techniques start with precursors and build up to nanoparticles (NPs) using deposition techniques or self-assembly of molecules. An ideal process for fabricating NPs would be tunable to a specific size or shape, using few industrially-available, nontoxic reagents, and the produced-NPs should be shelf-stable and in a concentrated suspension, with a narrow size distribution. In this work, we provide a summary meta-review of how membranes have been used to produce ~100 nm entities and provide observations that membranes could be used to enable rational processes for industrially-friendly, continuous production of NPs. Our meta-review focuses on nano-sized entities created in a suspension versus using the membrane as a potentially “sacrificial” template, thus, we consider three nominal, membrane device operating modes: dispersion, emulsion, and contactor. [ABSTRACT FROM AUTHOR]

through the process of refining the control system simulation of construction waste. This system includes two major subsystems. The first subsystem - the collection, sorting and transportation of construction waste. The second subsystem - recycling of construction waste. Specifies the required input data, a clear view of the model and algorithm of the system development process through the relationship of subsystems with the definition of the volume of construction waste and related production facilities. [ABSTRACT FROM AUTHOR]

In this work, a rotating packed bed (RPB) contactor was applied to adsorb Direct Red 23 dye onto commercially available activated carbon. A RPB is a doughnut shaped contactor, which rotates on a vertical axis and centrifugal force acts as the driving force for fluid-particle contact in the contactor. This centrifugal force, which is several times higher than the gravitational force, aids the adsorption process with enhanced mass transfer coefficient. The commercially available activated carbon used in this work had moderate BET surface area of 583 m2 g−1and was mainly meso-porous with an average pore size of 22 Å. The adsorption characteristics of the activated carbon were studied in a shake flask and a RPB. The dye removal in RPB was 93% compared to 55% in a shake flask in 5 h for the same amount of activated carbon and dye solution. Rotor speed and feed rate were important parameters for the removal of the dye in a RPB. It was found that rotor speed of 628 rpm and feed rate of 40 L h−1yielded the best adsorption efficiency. [ABSTRACT FROM AUTHOR]

Accurate and efficient contact models for wheel–rail interaction are essential for the study of the dynamic behaviour of a railway vehicle. Assessment of the contact forces and moments, as well as contact geometry provide a fundamental foundation for such tasks as design of braking and traction control systems, prediction of wheel and rail wear, and evaluation of ride safety and comfort. This paper discusses the evolution and the current state of the theories for solving the wheel–rail contact problem for rolling stock. The well-known theories for modelling both normal contact (Hertzian and non-Hertzian) and tangential contact (Kalker's linear theory, FASTSIM, CONTACT, Polach's theory, etc.) are reviewed. The paper discusses the simplifying assumptions for developing these models and compares their functionality. The experimental studies for evaluation of contact models are also reviewed. This paper concludes with discussing open areas in contact mechanics that require further research for developing better models to represent the wheel–rail interaction. [ABSTRACT FROM AUTHOR]

In this study, the computational fluid dynamics–population balance model (CFD–PBM) was developed for a five-compartment pilot-scale rotating disc contactor (RDC) using the solving methods of finite volume method (FVM) and quadrature method of moments (QMOM) as implemented in Fluent 14.0 . The differences between a simplified two-dimensional (2D) axisymmetric swirl model and a full three-dimensional (3D) model were investigated, and a pseudo-three-dimensional (pseudo-3D) model was developed to combine the benefits of both the 2D and 3D frameworks. The comparison results of the velocity distributions, droplet mean diameter and turbulent dissipation rate indicated that the 3D approach was suitable for quantitative investigations, whereas the 2D axisymmetric swirl model had only qualitative predictive capabilities. The differences are probably attributed to the 2D framework ignoring the cylindrical geometry characteristics of the problem. Based on this knowledge, a pseudo-3D model was proposed by constructing a fan-shaped geometry to overcome this disadvantage, and a parametric study was conducted to determine the angle of the sector. The results showed that the pseudo-3D model had nearly the same computational accuracy as the full 3D simulation, which verified the approach. Moreover, the sector angle had almost no effect on the simulated results, and only two layers of grids in the tangential direction were sufficient. Thus, the pseudo-3D model was found to be a powerful tool with computational costs approximate to those of the 2D framework, but with a calculation accuracy near that of the 3D model. [ABSTRACT FROM AUTHOR]

Considering the importance of liquid static holdup in liquid-liquid extraction columns, a novel experimental approach for predicting the mentioned parameter in a rotary sieved disc contactor has is presented in this research. One chemical system without mass transfer was used, in which distilled water and butyl acetate were employed as the continuous and the dispersed phase, respectively. The static holdup has been measured using the draining method. Based on the experimental results, one correlation was proposed to predict the static holdup as a function of stage position in the column and rotating speed in the form of Reynolds numbers and also the dimensionless mother drop size. Changes in static holdup caused by each factor have been discussed and graphically illustrated. It was revealed that an increase in mother drop size will cause the growth of static holdup, while the rise of rotating speed will decrease the amount of static holdup. Furthermore, it was proven that static holdups in upper positions in the column are less than those in the lower positions. [ABSTRACT FROM AUTHOR]

In this work, a bifurcation analysis of steady states in a multistage agitated contactor (MAC) was conducted for typical gas-liquid processes. A cascade of stirred tank reactors with a backflow was used to model the reactive flow in the MAC, and second-order reaction kinetics was employed to represent typical gas-liquid processes. In the developed model, the effect of temperature on gas solubility was taken into account. The multiplicity behaviour of steady states in such a reactor was investigated using a continuation method. Nonlinearity behaviours such as limit points and Hopf points were detected under various process parameters investigated in this work. A stability analysis was also conducted to determine whether the multiple steady state solutions observed were stable. The results suggested that a medium adiabatic temperature rise and small temperature difference are preferred to avoid system instability in operating such reactors. [ABSTRACT FROM AUTHOR]

A control system described by fractional evolution integro-differ-ential equations and fractional integral nonlocal control conditions is investigated. This posed system is subjected to mixed multivalued control constraints whose values are nonconvex closed sets. Along with the original system, we consider the system in which the constraints on the controls are the closed convex hulls of the original constraints. More precisely, existence results for the mentioned nonlocal control systems are proved. Furthermore, we study relations between the solution sets of both two systems. [ABSTRACT FROM AUTHOR]

The problem of regeneration of a carbon dioxide physical absorbent in gas-liquid membrane contactor has been addressed using water as the absorbent. An analytical solution for the mass transfer equation has been obtained with taking into account not only axial, but also radial diffusion of the solute in the liquid flow and thereby significantly extending the area of applicability of the solution. The kinetics of carbon dioxide desorption from aqueous solutions has been described for the membrane contactor based on asymmetric gas separation membrane made of polyvinyltrimethylsilane (PVTMS). It has been shown that the model agrees well with experimental data for different pressures of water saturation with carbon dioxide and desorption temperatures. [ABSTRACT FROM AUTHOR]

Optimal Control is a big opportunity for energy efficiency since it involves much smaller investments than those usually applied to technological building elements integration, by providing new ways for sustainable energy saving solutions. Nevertheless optimal management requires the development of a new class of predictive control logics, behaving consistently in changing environments. This class of control systems embed advanced predictive models, directly coupled with an environment monitoring sensor network, that are capable of interpreting sensed data (both indoor and environmental) and of forecasting future states. The design of the monitoring system is a critical passage as it is subjected to a number of operational and cost constraints, but also has to guarantee a reliable interpretation of the environmental behaviour of the building. This paper discusses this issue and presents the engineering framework and a methodology developed for supporting the design of monitoring networks integrated in optimal control system of large and complex environments. The application of the methodology to the case of a subway station is briefly presented too. This research is part of the European Research Project SEAM4US (Sustainable Energy Management for Underground Stations). The proposed solution is based on the definition and development of the set of models needed for both supporting the definition of the monitoring sensor network and being embedded in the final control system implementation. The development of this class of environmental models for large underground environments such as subway stations involves the elaboration and the integration of different simulation models. The simulation results constitute the knowledge that can support an efficient design of sensor networks even in large buildings. [ABSTRACT FROM AUTHOR]

Highlights: [•] Nitratation in an OLAND RBC could be controlled through the immersion level. [•] 85–89% of the O2 input was directly absorbed during the air exposure of the discs. [•] Process control strategies solely based on DO level did not seem to be effective. [ABSTRACT FROM AUTHOR]

Hydrophobic surface can be produced by either lowering the surface free energy or enhancing the surface roughness or a combination of both. This study explored a novel method to form a highly hydrophobic organic–inorganic composite hollow fiber membrane by incorporating the fluorinated silica (fSiO2) inorganic layer on the polyetherimide (PEI) organic substrate. The formation of the composite membrane was examined and confirmed by ATR-FTIR, TGA and SEM. Ultrasonication test was conducted to examine the structural stability of the composite membrane. The experimental results revealed that the fSiO2 layer was tightly bonded to the PEI substrate through silane chemical reactions. The incorporation of the fSiO2 layer on the membrane surface could enhance the surface roughness and greatly reduce the surface free energy due to the hydrophobic compound perfluorodecyltriethoxysilane (PFTS). The hydrophobicity of the composite membrane surface was dramatically elevated, as evidenced by the dynamic contact angles increment, e.g. from original 66.7° to 124.8° for advancing values, and from 49.5° to 100.6° for receding values. In addition, it was observed the mechanical property of the composite membrane was better than some of the conventional polymeric membranes such as polyethersulfone (PES), and polyvinylidene fluoride (PVDF). The composite membrane was also not as brittle as the pure inorganic membrane. Highly hydrophobic membrane is the core element in gas–liquid membrane contactor and the newly developed PEI-fSiO2 composite hollow fiber membranes were intended for the use in such application. The CO2 absorption flux of the composite membranes was investigated in both physical and chemical absorptions in a gas–liquid membrane contactor system. Moreover, the membrane contactor showed a reasonably stable performance throughout the 31 days long-term operation using a 2M sodium taurinate aqueous solution as the liquid absorbent and pure CO2 as the feed gas. The chemical compatibility test indicated that after the long-term constant contact with the sodium taurinate, the hydrophobicity of the PEI-fSiO2 composite membrane still maintained and was much higher than that of original PEI substrate and conventional hydrophobic polymeric membranes such as PVDF. The incorporation of the fSiO2 inorganic layer not only offered high hydrophobicity, but also would protect the polymeric substrate from the attacks of chemical absorbents, making the membrane a longer lifespan. [ABSTRACT FROM AUTHOR]

Among the availablemembranes, dense polymer composite hollow-fibermembranes are promising for gas permeation applications coupled withthe use of gas/liquid contactors, but they are also used in othermembrane processes such as pervaporation. This study focuses on acoating process, starting from a polymer solution, to control thethickness and regularity of the coated polymer. The thickness of theliquid film coated onto a fiber is related to the coating velocity,the physical and chemical properties of the liquid, and the coatinggeometry. Depending on the dominating forces, several regimes aredefined: two unstable regimes, in which a thin and regular polymerlayer cannot be produced, and two stable regimes, which are of interestfor reaching our objectives at the laboratory or industrial scale.The theoretical laws were compared to experimental coatings with solutionsof poly(trimethylsilyl)propyne (PTMSP) dissolved in cyclohexane coatedonto poly(ether sulfone) (PES) hollow fibers. The viscosities, surfacetensions, and densities of the solutions used were measured. The experimentalthicknesses of coated polymer layers were compared to values calculatedfrom Landau’s law, which describes the thickness behavior inthe viscocapillary regime. The results showed good behavior agreement,but the experimental thickness was underestimated by the calculations.Four different kinds of composite membranes were prepared using twodifferent porous supports (MicroPES and Oxyphan) and two differentpermeable polymers (PTMSP and Teflon AF2400) for coating. The obtainedcomposites hollow fibers were characterized. All four presented low-energysurfaces with no wetting phenomena. They also exhibited high CO2and N2permeabilities with CO2/N2selectivities between 3.4 and 2.5. The mechanical propertiesof the composites remained stable except for composites based on PESaffected by the drying step during the coating process. [ABSTRACT FROM AUTHOR]

Annular centrifugal contactors were developed as single, compact units utilized to transfer desired species between immiscible fluid phases. Critical to understanding the mass-transfer characteristics in the annular mixing region is a clear picture of the distribution of droplet sizes of the fluids involved. To date, very little experimental data appears in the literature. We fill that void by using laser fluorescence and optical methods to directly observe and measure drop-size distributions for a silicone oil/water system in a centrifugal contactor. The shape and characteristics of the log-normal distributions, including the Sauter mean diameter and distribution means, are elucidated in terms of rotor speed and organic phase fraction. The size distribution of entrained air bubbles is also examined. The results presented here will be invaluable in validating and expanding the predictive capacity of the many models that have been developed to describe the flow within these devices. Published 2013 American Institute of Chemical Engineers AIChE J, 59: 2219-2226, 2013 [ABSTRACT FROM AUTHOR]

This paper reports on results from steady-state Reynolds-averaged Navier-Stokes simulation (RANSS) of the flow and passive nonreactive tracer transport inside a multichambered, laboratory-scale ozone contactor using a structured, collocated, finite-volume discretization. Simulations are posed following a physical laboratory experiment. Simulations performed on different grids lead to varying degrees of short-circuiting and dispersion, which ultimately leads to differences in the residence time distribution (RTD) of the tracer (released at the inflow as a pulse) and in particular index. The predicted index depends on grid density and RANS turbulence model. For fine grids that resolve the viscous sublayer, a model with proper behavior within this sublayer has to be applied for accurate prediction of . Simulations on all considered grids with proper turbulence model yield cumulative RTD and associated index in good agreement with the experimental data despite the underresolution of the flow by the RANSS methodology relative to a large-eddy simulation (LES) of the same flow. [ABSTRACT FROM AUTHOR]

Using an earnings management model in which managers manipulate information when the firm's control system fails, I introduce a measure of earnings quality, based on the notion of integral precision, that has solid theoretical foundations. A trade-off between the frequency and the magnitude of overstatements is shown: overstatements are larger when misreporting is less likely. Overall, the model generates a distribution of earnings announcements similar to its empirical analogue and provides a structural method to identify the likelihood and magnitude of misreporting by exploiting information from the moments of the distribution of reported earnings. [ABSTRACT FROM AUTHOR]

In this study, we examine the effect of incentive contract framing on agent effort in an incomplete contract setting. Prior research suggests that when governed by complete incentive contracts, agents exert greater effort under penalty contracts relative to bonus contracts. However, in an incomplete contract setting, in which the incentive contract does not govern all tasks for which the agent is responsible, the agent's trust in the principal is relevant. In this setting, we predict that bonus contracts create a more trusting environment, and this effect spills over to tasks not governed by the incentive contract, such that bonus contracts elicit greater effort on these tasks as compared to penalty contracts. We develop and experimentally validate a theoretical model of the effects of contract frame on trust and effort in this incomplete contract setting. The main intuition behind the model is that the framing of an incentive contract affects the degree to which the contract terms are interpreted by the agent as a signal of mistrust. More specifically, penalty contracts engender greater distrust than do bonus contracts and, therefore, when contracts are incomplete, penalty contracts lead to lower effort on tasks not governed by the contract than do bonus contracts. [ABSTRACT FROM AUTHOR]

Gas-liquid hollow fiber membrane contactor can be a promising alternative for the CO2 absorption/stripping due to the advantages over traditional contacting devices. In this study, the structurally developed hydrophobic polyvinylidene fluoride (PVDF) hollow fiber membranes were prepared via a wet spinning method. The membranes were characterized in terms of morphology, permeability, wetting resistance, overall porosity and mass transfer resistance. From the morphology analysis, the membranes demonstrated a thin outer finger-like layer with ultra thin skin and a thick inner sponge-like layer without skin. The characterization results indicated that the membranes possess a mean pore size of 9.6 nm with high permeability and wetting resistance and low mass transfer resistance (1.2 x 104 s/m). Physical CO2 absorption/stripping were conducted through the fabricated gas-liquid membrane contactor modules, where distilled water was used as the liquid absorbent. The liquid phase resistance was dominant due to significant change in the absorption/stripping flux with the liquid velocity. The CO2 absorption flux was approximately 10 times higher than the CO2 stripping flux at the same operating condition due to high solubility of CO2 in water as confirmed with the effect of liquid phase pressure and temperature on the absorption/stripping flux. [ABSTRACT FROM AUTHOR]

A new approach to the design of the central output H-controller was proposed. It is based on defining the controller's structure in compliance with the principle of division which is applicable equally to the standard nondegenerate problem and the degenerate problems such as the singular filtration problem (no measurement noise) and singular control problem (no component containing control in the controlled output). Within the framework of the given approach, the general problem of designing the output controller was shown to fall down into two special design problems-under full information and full control. For the degenerate problem, the dimension of the central controller at that drops, and the solution itself is coordinated with the problem of H-optimization. An example illustrating solution of the singular filtration problem was presented, and the results obtained were analyzed. [ABSTRACT FROM AUTHOR]

We study the stability of the periodic motions for systems with pulse modulated control of the first kind, that are described by differential equations with discontinuous right-hand sides. As an example we consider a control system with pulse-width modulation of the first kind. [ABSTRACT FROM AUTHOR]

The main of this paper is to draw attention to the new potential hidden in the combined discrete dynamic systems, which could represent new type of distributed systems for the industrial automation and could contribute to the faster design and development of the control system. [ABSTRACT FROM AUTHOR]

Abstract: The present study examines the performances of a hybrid air-conditioning system in which a vapour-compression inverse cycle is integrated with an air dehumidification system working with hygroscopic solution and hydrophobic membrane. This model may be a valid alternative to traditional summertime air-conditioning system, in which the air is cooled to below its dew-point temperature and subsequently reheated. The proposed hybrid system involves simultaneously cooling and dehumidifying the air conveyed to the conditioned ambient in an air-solution membrane contactor. An LiCl solution is cooled by means of a vapour-compression inverse cycle using the refrigerant KLEA 407C. The solution is regenerated in another membrane contactor by exploiting the heat rejected by the condenser. A SIMULINK calculation programme was designed in order to simulate the system under examination in steady-state conditions. The performances of the system were analysed on varying a few significant operating parameters, and were compared with those of a traditional direct-expansion air-conditioning plant in typical summertime conditions. The results of the simulations revealed significant energy savings, which, in particular operating conditions, may exceed 50%. [ABSTRACT FROM AUTHOR]

This paper proposes a hybrid H∞-based waveletneural- network (WNN) position tracking controller as a new robust motion-control system for permanent-magnet synchronous motor (PMSM) servo drives. The combinations of both WNN and H∞ controllers would insure the robustness and overcome the uncertainties of the servo drive. The new controller combines the merits of the H∞ control with robust performance and the WNN control (WNNC) which combines the capability of NNs for online learning ability and the capability of wavelet decomposition for identification ability. The online trained WNNC is utilized to predict the uncertain system dynamics to relax the requirement of uncertainty bound in the design of the H∞ controller. The WNNC generates an adaptive control signal to attain robust performance regardless of parameter uncertainties (PU) and load disturbances. Systematic methodology for both controllers' design is provided. A computer simulation is developed to demonstrate the effectiveness of the proposed WNN-based H∞ controller. An experimental system is established to validate the effectiveness of the drive system. All control algorithms are implemented in a TMS320C31 DSP-based control computer. The simulated and experimental results confirm that the newmotion controller grants robust performance and precise dynamic response regardless of load disturbances and PMSM PU. [ABSTRACT FROM AUTHOR]

The article provides information on determining the quantity and composition of clinical staff in an inpatient nursing unit. It states that identifying the nursing staff's composition is the responsibility of nursing leadership as well as the staffing office. It presents the necessary steps to calculate the optimal number of nurses and support staff that includes determining the patients' needs, quantity, and acuity in each unit, determining caregivers' quantity and skill, and determining the number of people to hire. It mentions that getting the patient population is the primary step to compute the quantity and composition of staff needed. It discusses the development of a control system that complements one's budgeted expenses. It also highlights the importance of variability in census.

Abstract: Nanosized calcium carbonate was prepared as a model product in a continuous gas–liquid membrane contactor for the first time. The effects of Ca(OH)2 concentration, CO2 partial pressure and liquid flow velocity on the absorption rate were estimated according to the gas–liquid reaction theory. The results showed that, with the increase in Ca(OH)2 concentration, CO2 partial pressure and liquid flow velocity, the absorption rate increased. The theoretical predictions were in agreement with the experimental data. [Copyright &y& Elsevier]

Abstract: In this contribution, a practical controller design for non-contact mechanism and contact mechanism is discussed. The design procedure is applicable and totally independent of friction characteristic. Thus, designer does not need to consider the friction characteristic of a mechanism and it is a valuable controller approach in industry. The practical controller design procedure which based on current Nominal Characteristic Trajectory Following (NCTF) controller is proposed and improved. The NCTF controller is comprehensive, comprising of a Nominal Characteristic Trajectory (NCT) and a PI compensator, which is free from exact modeling and parameter identification. In NCTF controller design, the NCT is constructed from the open-loop responses of the mechanism. The designed input signal for open-loop experiment is needed to satisfy the following two conditions: (1) the displacement by the input signal must be smaller than the working range of the mechanism to avoid any damage to the mechanism; (2) the suitable input signal needs to produce sufficient rapid and smooth response during deceleration to satisfy the desired specifications because the response significantly influences the reference following characteristic of the control system. So far, the NCTF controllers had been implemented to the mechanisms which have sufficient large damping characteristics and it was natural to satisfy the condition (1). However, non-contact and low damping mechanisms do not have sufficient damping characteristics. Since the high damping characteristics of the mechanism have been used before, the condition (2) is still not yet been considered. Therefore, the design procedure of the input signal satisfying the two conditions is proposed and verified by experiments in this paper. The common conditions of the input signal which is independent of friction characteristic of the mechanisms are discussed. Then, the experimental verifications are performed using non-contact mechanism and contact mechanism. In this paper, the performance evaluation is discussed separately in two parts. In part 1, by using the non-contact mechanism, the positioning results of two different NCTs are compared in order to show the usefulness of the modified suitable input. In part 2, the contact mechanism is used to show the effectiveness of the NCTF controller with its simple and practical design procedure, which is independent of friction characteristic. The effectiveness of the Continuous Motion NCTF controller is verified with the PID controller experimentally in positioning control and tracking control. The experimental results prove that the displacements of the open-loop responses for NCTs are always smaller than the working range and the design procedure of the input signal is successfully independent of the friction characteristic of the mechanism. Overall, the Continuous Motion NCTF controller which has simple and practical design procedure exhibits the high performance in positioning and tracking control with contact mechanism and non-contact mechanism, as compared to the PID controller. The PID controller shows the low adaptability in motion control performances for both conditions of mechanism. [Copyright &y& Elsevier]

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The Henrico County VA Water Treatment Facility has been in operation since April 2004, making use of intermediate ozone for primary disinfection to take advantage of both the disinfection and DBP benefits. Since the summer of 2007 the staff at the Henrico WTF has embarked on an optimizing journey with their ozone system. This paper overviews the significant milestones accomplished on this journey as well as ongoing improvements. Optimizing efforts to reduce operating costs while achieving disinfection goals included: Staff training workshops; Automating ozone data collection and access; Operating system at optimum ozone concentration; Selecting optimum contactor sampling locations and number of contactors; Overcoming minimum gas flow limitations; Solenoid contactor sampling system issues and improvements; Disinfection calculation constraints; Excessive buildup of liquid oxygen (LOX) tank pressure. Each of these items is discussed following an overview of this 55 MGD surface water treatment facility. [ABSTRACT FROM AUTHOR]

Abstract: Present work deals with oxygen mass transfer in an oil-in-water biphasic medium, employed in the production of γ-decalactone by the biotransformation of methyl ricinoleate. A bubble column contactor was used to carry out the absorption experiments. The influence of operating conditions (gas flow-rate and organic phase composition) upon the gas–liquid interfacial area and mass transfer coefficient has been analysed and experimental results allow describing the mechanism of oxygen transfer from gas phase into the biphasic medium. [Copyright &y& Elsevier]

In recent years, control system reliability has received much attention with an increase of situations where computer-controlled systems such as robot control systems are used. In order to improve reliability, control systems need to have abilities to detect a fault (fault detection) and maintain the stability and the control performance (fault tolerance). This paper deals with the strain gauge sensor fault of a flexible arm robot. In order to achieve a fault-tolerant control system, the effect of the fault is identified as dual Youla parameter by regarding the estimation error of the faulty sensor signal as the faulty plant output. Moreover, Youla parameter is designed so as to suppress the effect of dual Youla parameter. Youla parameter is implemented in GIMC (Generalized Internal Model Control) structure proposed by Zhou. Since GIMC structure includes a conditional feedback, it is suitable for achieving a fault-tolerant control system. The effectiveness of the proposed fault-tolerant control system is confirmed by experiments. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(3): 48–58, 2009; Published online in Wiley InterScience (www. interscience.wiley.com). DOI 10.1002/eej.20830 [ABSTRACT FROM AUTHOR]

We investigated the influence of feedback conditions on the effectiveness of a balance prosthesis. The balance prosthesis used an array of 12 tactile vibrators (tactors) placed on the anterior and posterior surfaces of the torso to provide body orientation feedback related to several different combinations of angular position and velocity of body sway in the sagittal plane. Control tests were performed with no tactor activation. Body sway was evoked in subjects with normal sensory function by rotating the support surface upon which subjects stood with eyes closed. Body sway was analyzed by computing root mean square sway measures and by a frequency-response function analysis that characterized the amplitude (gain) and timing (phase) of body sway over a frequency range of 0.017-2.2 Hz. Root mean square sway measures showed a reduction of surface stimulus evoked body sway for most vibrotactile feedback settings compared to control conditions. However, frequency-response function analysis showed that the sway reduction was due primarily to a reduction in sway below about 0.5 Hz, whereas there was actually an enhancement of sway above 0.6 Hz. Finally, we created a postural model that accounted for the experimental results and gave insight into how vibrotactile information was incorporated into the postural control system. [ABSTRACT FROM AUTHOR]

A discrete time stochastic feedback control system consisting of a nonlinear plant, a sensor, a controller, and a noisy communication channel between the sensor and the controller is considered. The sensor has limited memory and, at each time, it transmits an encoded symbol over the channel and updates its memory. The controller receives a noise-corrupted copy of the transmitted symbol. It generates a control action based on all its past observations and all its past actions. This control action is fed back to the plant. At each time instant the system incurs an instantaneous cost depending on the state of the plant and the control action. The objective is to choose encoding, memory update, and control strategies to minimize an expected total cost over a finite horizon, or an expected discounted cost over an infinite horizon, or an average cost per unit time over an infinite horizon. A solution methodology for obtaining a sequential decomposition of the global optimization problem is developed. This solution methodology is extended to the case when the sensor makes an imperfect observation of the state of the plant. [ABSTRACT FROM AUTHOR]

This article deals with the problem of L2-gain for a class of networked control systems with time-varying network delay in both forward and feedback channels. An improved network predictive control scheme is proposed to compensate the effects of network delay and data dropout using a switching control strategy. Based on the average dwell time method, the restrictions that the original delay-compensation strategy imposes on the subsystems are relaxed and a sufficient condition for weighted L2-gain is developed for a class of switching signal. An example illustrates the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In robot contact tasks on planar surfaces with frictional contacts, kinematic uncertainties of the contacted surface affect the control system performance and distort control targets. An adaptive controller that uses force and joint position/velocity measurements to simultaneously learn the surface orientation and achieve the desired goal is proposed. Simulation examples are used to illustrate the theoretical results and the performance of the proposed controller in practical cases. [ABSTRACT FROM AUTHOR]

This paper describes an adaptive control to realize the desired steering characteristics on a vehicle. As is well known, the steering characteristics indicate handling performance on a vehicle and are important for safe driving. In this paper, a strategy to adjust it to a driver's preference easily using a Steer-by-Wire system is proposed. The control system including the proposed method intervenes only when the front tire cornering stiffness undergoes many changes. Then, the estimated self-aligning torque is fed back to the steering wheel so that a driver can feel reaction torque from the road. This is one of the remarkable features in the proposed Steer-by-Wire system. Numerical simulation and experiment are carried out to show the validity of the proposed method. [ABSTRACT FROM AUTHOR]

R&D activities have been carried out for decades by many researchers in order to improve electromechanical contactor performance employing electronic control. This includes electronic controlled contactor opening to minimize contact erosion, and closing to reduce contact bounce, but the improvement is limited with significant increase of cost and size due to the inherent design structure of contactors: simultaneously switching of all three poles. Meanwhile, solid-state motor starters have shown great benefit with point-on-wave (POW) switch-on to minimize transient current and torque .stress of induction machines during motor starting process. However, cost and size is a premium. A novel technology that employs asynchronous modular concept and POW switching has been developed. .This improves motor starting and contactor switching performances in respect to switching transients and contact erosion while utilizing small size and low cost electromechanical contactors. These contactors are assembled into a flexible modular contactor assembly that allows each pole to be switched independently with precise POW switching control. This paper will focus on motor starting applications to achieve significant reduction of motor starting transients and contactor switching capability improvement. Asynchronous modular contactor prototypes with newly developed 24-VDC controlled contactors have been developed. The evaluation tests of the prototype proved significant transient current and torque stress reduction during motor starting. [ABSTRACT FROM AUTHOR]

The air flow control in a segment of an underground ventilation network is proposed. It consists of the control channels for stationary fan and air flow in a tunnel adjacent to a subway station platform. Mathematical models of the system components and the optimal airing control criteria are developed. The numerical test data on adequacy of the proposed mathematical description are presented. [ABSTRACT FROM AUTHOR]

Abstract: The state-delay is always existent in the practical systems. Analysis of the delay phenomenon in a continuous-time domain is sophisticated. It is appropriate to obtain its corresponding discrete-time model for implementation via digital computer. In this paper, we propose a new scheme for the discretization of nonlinear systems using Taylor series expansion and the zero-order hold assumption. This scheme is applied to the sample-data representation of a nonlinear system with constant state time-delay. The mathematical expressions of the discretization scheme are presented and the effect of the time-discretization method on equilibrium properties of nonlinear control system with state time-delay is examined. The proposed scheme provides a finite-dimensional representation for nonlinear systems with state time-delay enabling existing controller design techniques to be applied to them. The performance of the proposed discretization procedure is evaluated using a nonlinear system. For this nonlinear system, various sampling rates and time-delay values are considered. [Copyright &y& Elsevier]

The development of a compact 1 cm rotor diameter annular centrifugal contactor suited for experimental testing of nuclear fuel reprocessing processes in a hot cell environment is described. Twelve-stage and 50-stage batteries of the 1 cm contactor are used to implement the extraction hot test processes for the cleanup of nuclear waste liquids in hot cells in Germany and China, respectively. The advances are: (1) a simple way of assembly and disassembly between the rotor and housing of the contactor, making manipulator operation easy; (2) compact multistage housing system; (3) easy inter-stage link; (4) compact miniature size of the contactor, taking up less space in the hot cell; (5) automatic sampling from housing of contactor in the hot cell; and (6) rotor speed control. [ABSTRACT FROM AUTHOR]

Abstract: This work presents a mathematical model for a microporous hollow fiber membrane contactor operated under non-wet or partially wetted conditions, in order to analyze the simultaneous absorption of carbon dioxide and hydrogen sulfide into an aqueous solution of diethanolamine (DEA). The diffusion-reaction processes for both acid gases were modeled based on the assumption that all reactions are reversible in the liquid bulk as well as the wetted parts of the membrane pores. A numerical scheme was developed to solve the simultaneous nonlinear mathematical expressions, and the results from the model were validated with the available experimental data in the literature. The model allows one to predict the gas phase concentration and velocity profile in the axial direction inside the shell, the liquid concentration profile in the axial and radial directions inside the fibers, and also those within the wetted parts of the pores. The results indicate that the membrane contactor can sequestrate both sour gases very effectively. Membrane wetting decreases the removal efficiency of both gases significantly in high wetting fractions. However, it mainly affects the carbon dioxide recovery in low wettings. The effects of various parameters on hydrogen sulfide selectivity were investigated, and it was found that the wetting of the membrane in low fractions increases the selectivity considerably. However, it has the opposite influence in high wetting fractions. [Copyright &y& Elsevier]