Asymptotic behaviour of monotone multi-valued dynamical systems

We introduce the concept of a monotone multi-valued semi-flow as an order-preserving map. This definition is motivated by the applications in the theory of differential equations without uniqueness of solutions. For an order-preserving multi-valued semi-flow we prove several results on the structure of the global attractor. Some applications to models governed by ordinary differential equations and delay equations with continuous right-hand side are presented. In particular, the abstract results are applied to a biochemical control circuit.     

Practical sensorless control for inverter-fed BDCM compressors

Brushless DC motors (BDCMs) possess higher efficiencies than the conventional induction motors and BDCMs have therefore been used widely in inverter-fed compressors. Since the Hall position sensors cannot work well in the high-temperature environment of refrigerants, sensorless control schemes play an important role in the application of inverter-fed BDCM compressors. Sensorless control for actual BDCM compressor is proposed and implemented. First, the sensorless circuits used have been analysed in detail to find the design rules of the circuit parameters for various compressor motors. Then, the limitations of sensorless control are discussed to develop a practical speed controller for BDCM compressors. The developed starting strategy and sensorless algorithms are presented and digitally implemented. Finally, some experimental results are displayed to demonstrate the proposed sensorless speed control for BDCM compressors.     

Fault section estimation for distribution substations using on-chip design

A new fault detection circuit for on-chip design is presented in this article. The circuit function to detect substation faults has been investigated and verified on an Altera DE1 platform with Cyclone II 2C20 field-programmable gate array. The experimental results showed that the hardware prototyping is feasible for practical applications. Compared to existing fault diagnosis methods, the proposed hardware implementation is more suitable for real-time applications as it is able to achieve high-speed inference. Additionally, the computational burden on host computers in a supervisory control and data acquisition system can thus be reduced through the presented framework.     

Logarithmic Analog-to-Digital Converters: A Survey

Analog-to-digital converters (ADC) with logarithmic law are receiving particular attention from system and circuit designers. They can be applied to solve many problems of data acquisition and encoding found in almost all the fields of experimental physics and instrumentation dealing with analog variables with several decades of dynamic range, where a constarnt relative accuracy, rather than a constant absolute accuracy, is required. Spme proposals and realizations of logarithmic ADC (LADC) already presented in the literature are discussed as well as some new ideas organized according to three classes of schemes. The first can be viewed as the cascade connection of an analog logarithmic information converter and a conventional ADC; while in the second, the LADC is entirely digital and follows the ADC; and in the third, the logarithmic conversion and the A/D conversion are performed by the same structure and cannot be easily distinguished. An analysis is made of the performances of the various possible realizations as well as of their complexity.     

When Bio Meets Technology: Biohybrid Neural Interfaces

The development of electronics capable of interfacing with the nervous system is a rapidly advancing field with applications in basic science and clinical translation. Devices containing arrays of electrodes can be used in the study of cells grown in culture or can be implanted into damaged or dysfunctional tissue to restore normal function. While devices are typically designed and used exclusively for one of these two purposes, there have been increasing efforts in developing implantable electrode arrays capable of housing cultured cells, referred to as biohybrid implants. Once implanted, the cells within these implants integrate into the tissue, serving as a mediator of the electrode–tissue interface. This biological component offers unique advantages to these implant designs, providing better tissue integration and potentially long-term stability. Herein, an overview of current research into biohybrid devices, as well as the historical background that led to their development are provided, based on the host anatomical location for which they are designed (CNS, PNS, or special senses). Finally, a summary of the key challenges of this technology and potential future research directions are presented.     

Micromachined water vapor sensors: a review of sensing technologies

The measurement of water vapor is important in many applications ranging from predicting changes in the weather to ensuring heating and cooling comfort in homes. In manufacturing, water vapor measurements help to control performance properties of engineered materials and optimize fuel efficiency in power generation. This paper presents a technology review of water vapor sensors and manufacturing techniques. Micromachining, more commonly known as MEMS or microelectromechanical systems, is an enabling technology based upon standard semiconductor manufacturing. MEMS technology makes possible solid-state sensors with greatly reduced power consumption and low operating voltage that are fully compatible with digital electronics and can be manufactured in high volumes at low cost. A water vapor microsensor just becomes another part on the circuit board. A "technology roadmap" for water vapor microsensors is defined where the sensing technologies have been organized into four major transduction schemes: capacitive, mass-sensitive, optical and resistive. Sensing element type, key geometric features and excitation scheme provides further classification. Operating principles and general performance characteristics are also presented     

Stability analyses of self-saturating magnetic amplifiers with capactive load

Analyses of the self-saturating magnetic amplifiers are generally restricted to the pure resistive load cases. There are a few reports related to capacitive loads and some others on inductive loads. The possibility of occurrence of abnormal phenomena in the self-saturating magnetic amplifier with capacitive load has been reported, but their mechanism of circuit behavior is not yet clear. In this paper, the circuit operation is analyzed in detail from the stability point of view and the mechanism of peculiar modes is investigated. The circuit operation is represented by the nonlinear difference equations which are derived from the continuity of both charge and flux linkage. Linear difference equations for small disturbances occurring at the equilibrium state directly suggest the stability of the equilibrium state and possibility of occurrences of the peculiar modes. Further, the control characteristics and the transient responses are calculated and the criteria for prevention of the peculiar modes are found in simple forms. The theoretical analyses show good agreement with experimental results.     

Young’s modulus and volume porosity relationships for additive manufacturing applications

Recent advancements in additive manufacturing (or rapid prototyping) technologies allow the fabrication of end-use components with defined porous structures. For example, one area of particular interest is the potential to modify the flexibility (bending stiffness) of orthopedic implants through the use of engineered porosity (i.e., design and placement of pores) and subsequent fabrication of the implant using additive manufacturing processes. However, applications of engineered porosity require the ability to accurately predict mechanical properties from knowledge or characterization of the pore structure and the existence of robust equations characterizing the property–porosity relationships. As Young’s modulus can be altered by variations in pore shape as well as pore distribution, numerous semi-analytical and theoretical relationships have been proposed to describe the dependence of mechanical properties on porosity. However, the utility and physical meaning of many of these relationships is often unclear as most theoretical models are based on some idealized physical microstructure, and the resulting correlations often cannot be applied to real materials and practical applications. This review summarizes the evolution and development of relationships for the effective Young’s modulus of a porous material and concludes that verifiable equations yielding consistently reproducible results tied to specific pore structures do not yet exist. Further research is needed to develop and validate predictive equations for the effective Young’s modulus over a volume porosity range of 20–50 %, the range of interest over which existing equations, whether based on effective medium theories or empirical results, demonstrate the largest disparity and offers the greatest opportunity for beneficial modification of bending stiffness in orthopedic applications using currently available additive manufacturing techniques.     

Mathematical Analysis of Piezoelectric Sandwich Torsion Transducers Based on the d36-Effect

In the present article, we analyze a d₃₆-effect piezoelectric torsion transducer following the Saint-Venant torsion theory taking the electrical field into account. A representation of the stress function, the electric potential, and the warping function are derived and solved with finite differences. Then, the one-dimensional governing equations at the structural beam level, including the constitutive relations as well as the balance equations for the dynamics of the transducer, are presented. The axial moment and the total charge are computed as functions of the rate of twist and the applied potential difference. As an example, a cantilevered transducer is studied.     

Using the parametric time-varying analog filter to average-evoked potential signals

Processing of the brainstem auditory-evoked potential (BAEP) signal is achieved with a simple averaging over a number of realizations. The proposed filtering method of the BAEP signal is an extremely attractive alternative for long-duration examination with a repeated stimulus. Repetitive stimulation (20-30 times) allows additional averaging to be performed on the signal under extremely high noise conditions. Using averaging in time with a parametric filter (in real time) and then averaging over realizations is a completely new approach to the averaging of the BAEP signal. When we visually compare shapes of responses after a number of realization, we notice that the result of 20 realizations with simultaneous averaging in time with parametric filters is much better than simple, standard averaging with 20 realizations, and also as good as averaging with 1000 realizations. Simple calculations show that the time of examination could be reduced many times.     

Design and Uncertainty Evaluation of a Strain Measurement System

Strain measurement is very important in various industrial applications as well as different disciplines of science and technology for direct and indirect observations of certain parameters. Designing signal conditioning circuit is always a challenging and important task for satisfactory and reliable performance of a sensor as well as the system. The design and implementation details of a signal conditioning circuit of resistive sensor (strain gauge) for strain measurement are presented in this paper. Also the important aspects in designing a signal conditioning circuit for resistive sensor are presented and a novel method for the measurement of strain is discussed. Quarter bridge configuration with AC voltage excitation is used for the measurement along with the necessary circuitry to get a suitable and measurable output DC voltage. The measurement system is calibrated using a cantilever of stainless steel and the details of calibration are presented in the paper. The uncertainty associated with the measurement system is evaluated.     

Convergence of schemes for stochastic differential equations

In many applications of stochastic calculus, like stochastic dynamical systems, stochastic differential equations are involved, the coefficients of which are not globally, but only locally Lipschitz. For instance, in order to study technics using one trajectory of a process defined by differential equations of oscillators associated to structures submitted to a white noise excitation, such as the random decrement, one need to simulate a trajectory for such a process. Different schemes are proposed to numerically solve such stochastic differential equations: Euler, Milshtein or Newmark schemes for example. In this paper, the almost sure convergence of some of the most important schemes is studied under locally Lipschitz assumptions and a speed of convergence is established.     

Dynamic generalized fast initial response for EWMA control schemes for monitoring processes with startup and post-startup problems

The exponentially weighted moving average (EWMA) control schemes have been proven to be very effective at monitoring random shifts or disturbances in a given process. However, EWMA is somewhat insensitive to the shifts at the process startup. Consequently, fast initial response feature (FIR) or headstart has often been used to increase the sensitivity of EWMA at the process startup. Although FIR feature significantly increases the sensitivity of the EWMA at the startup, its effects diminished after few observations thereby making FIR-based schemes less sensitive compared to the classical EWMA at the process post-startup. In this paper, we proposed the dynamic generalized fast initial response for the EWMA control schemes for monitoring processes with startup and post-startup problems. The proposed scheme is highly sensitive at the startup and has a sensitivity equal to that of the classical EWMA at the process post-startup. The average run length based performance comparisons of the proposed chart and its counterparts are presented. Real-life examples are offered to demonstrate the applications of the proposed scheme.     

Q235碳钢在滨海盐土中腐蚀的电极过程特点

为了研究含水量对Q235碳钢在滨海盐土中腐蚀电极过程的影响,分别在10%、20%和34%含水土壤中,在±50mV极化及开路条件下对Q235碳钢的电化学阻抗谱进行了测量.实验结果表明:在低含水量(10%)时,Q235腐蚀的阴极过程主要受电荷转移电阻和结合层电阻控制,结合层对阳极过程的阻碍明显大于阴极过程;在中、高含水量(20%,34%)时,其阴极过程表现为明显的扩散控制特征,结合层主要影响阳极溶解过程,其对阴极反应的影响可以忽略不计.随含水量的增加,Q235的阳极反应电荷转移电阻逐渐降低;阴极扩散控制作用越来越明显.     

压电加速度传感器输出信号可变增益控制

针对压电加速度传感器信号调理电路中标定过程繁琐、标定效率低下、系统在运行过程中输出信号增益不能改变的问题,提出了在电荷放大器之后由微控制器控制数字电位器组成可调增益的电压放大电路,实现加速度计输出信号的自动标定和增益的可变控制.分析压电式加速度计的信号调理电路,在电压放大电路中选择使用数字电位器的方法实现可变增益控制,...     

The biocompatibility of titanium in a buffer solution: compared effects of a thin film of TiO<Subscript>2</Subscript> deposited by MOCVD and of collagen deposited from a gel

This study aims at evaluating the biocompatibility of titanium surfaces modified according two different ways: (i) deposition of a bio-inert, thin film of rutile TiO₂ by chemical vapour deposition (MOCVD), and (ii) biochemical treatment with collagen gel, in order to obtain a bio-interactive coating. Behind the comparison is the idea that either the bio-inert or the bio-active coating has specific advantages when applied to implant treatment, such as the low price of the collagen treatment for instance. The stability in buffer solution was evaluated by open circuit potential (OCP) for medium time and cyclic voltametry. The OCP stabilized after 5·10⁴ min for all the specimens except the collagen treated sample which presented a stable OCP from the first minutes. MOCVD treated samples stabilized to more electropositive values. Numeric results were statistically analysed to obtain the regression equations for long time predictable evolution. The corrosion parameters determined from cyclic curves revealed that the MOCVD treatment is an efficient way to improve corrosion resistance. Human dermal fibroblasts were selected for cell culture tests, taking into account that these cells are present in all bio-interfaces, being the main cellular type of connective tissue. The cells grew on either type of surface without phenotype modification. From the reduction of yellow, water-soluble 3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT cytotoxicity test), MOCVD treated samples offer better viability than mechanically polished Ti and collagen treated samples as well. Cell spreading, as evaluated from microscope images processed by the program Sigma Scan, showed also enhancement upon surface modification. Depending on the experimental conditions, MOCVD deposited TiO₂ exhibits different nanostructures that may influence biological behaviour. The results demonstrate the capacity of integration in simulated physiologic liquids for an implant pretreated by either method.     

Convolution connection paradigm neural network enables linear system theory-based image enhancement

A new type of robust numeric solution of one form of the Fredholm integral equations of the first king has been discovered. This discovery has its most immediate and important applications in the deconvolution or deblurring of data acquired using scientific instruments. A solution of this integral equation has very general applications. For example, investigator-controlled mapping of the instrumental point-spread function to a more useful form is made feasible. The solution of the linear systems imaging model integral equation results from operations performed on the instrumental kernel, response, or point-spread function with the direct result being the production of a robust, effective inverse kernel. The effective inverse is robust even in the presence of noise. The generation of the inverse kernel in no way depends on the observational data. Therefore, the image enhancement produced by this method contrasts with other numeric schemes that operate only on the observed data. This is an important distinction. This technique, which uses simple numeric operations, offers the possibility of attaining real-time data enhancements for observational instruments. The concept of taking control of the instrument kernel or point-spread function forms the basis of the work presented. Investigations of the application of artificial neural networks to resolution enhancement of Hubble Space Telescope imagery have led to a novel extended instrument paradigm that permits reliable and robust resolution enhancement. In addition to resolution enhancement, the fruits of this investigation have provided a powerful data mapping tool that permits nontrivial, numeric apodization of observed data. The applications of the novel convolution connection paradigm neural network has a great potential for multidisciplinary applications such as resolution enhancement of image and spectral data.     

Modelling nonlocal processes in semiconductor devices with exponential difference schemes

In this paper nonlocal quasi-hydrodynamic mathematical models describing non-equilibrium physical processes in semiconductor devices are considered. These processes cannot be adequately described with conventional drift-diffusion models. The primary numerical difficulty arises in the energy balance equation. Details of the discretisation for the continuity equations will be described along with a transformation of the energy balance equations to give computationally convenient forms. Effective exponential difference schemes are constructed and applied to modelling transport phenomena in semiconductors. Stability conditions, computational convergence and algorithmic realisations of the proposed schemes are discussed and numerical examples are given.     

Physiologic Inhibitors of Coagulation in Patients on Chronic Hemodialysis

Patients on hemodialysis are at increased risk for bleeding and thromboses. The intriguing balance between these risks is more complex than once thought, as endogenous clotting factors and their regulators come into contact with bioincompatible dialyzer membranes, in the setting of an extracorporeal circuit of blood flow, in the face of the uremic state. In this review, we summarize the current data on the interaction between the physiologic inhibitors of coagulation and hemodialysis. Data sources and study selection were obtained from research and review articles related to the endogenous anticoagulation pathway published in English on MEDLINE from 1972 to 2002. While protein C activity and protein S antigen concentrations are increased, there is no change in antithrombin III levels during hemodialysis in relation to predialysis levels. Plasma protein Z, which has only recently been studied in uremic subjects, is increased as well. In addition, hemodialysis leads to elevated tissue factor plasminogen inhibitor, thrombomodulin, tissue plasminogen activator, and plasminogen activator inhibitor-1 activities. The potential functional significance of these observations is discussed. Finally, as erythropoietin is commonly prescribed to uremic patients and is recognized to be prothrombotic, an appraisal of its interaction with the naturally occurring anticoagulants is presented. It is apparent that we are only beginning to realize the complexity of the interplay between this myriad of serum factors and hemodialysis. Further research is needed to shed light on this underexplored area of hemodialysis.