Distortion of the electric field distribution induced in the brain during transcranial magnetic stimulation

In this study, the effects of various parameters, such as the geometrical head model, conductivity condition and stimulus position, on the electric field induced in the brain during transcranial magnetic stimulation are thoroughly examined. It is revealed that the distortion of the induced field causes the movement of the maximum field point and also leads to the deviation of the field focusing region from the stimulus centre. Numerical results show that the induced field distortion is primarily caused by the spatial asymmetry of the head geometry with respect to the stimulus centre and the induced field distribution is further deformed by imposing the heterogeneous conductivity condition. For verification purposes, an elaborate phantom head model has been constructed and the experimental results have been compared to the predicted fields yielding good agreement.     

Designing systems for new users

This paper discusses the relationship between a system and ‘noncaptive’ users and the qualities which make a good system. Various methods for designing systems are considered and the author's development of meeting design (shared experience events) is presented.     

Designing of Halbach cylinder based magnetic assembly for a rotating magnetic refrigerator. Part 1: Designing procedure

Generation of the alternating strong and almost zero homogeneous magnetic field that the magnetocaloric material has to be exposed to is a major challenge in magnetic refrigeration. With this paper we start a series of publications considering designing of Halbach cylinder based magnet assemblies for non simultaneous cycles. In present, for the first part we define a designing procedure which, applied to the Halbach cylinder, allows creation of two or higher pole number magnet assemblies. We consider here two and four pole cases in great details. Each designing procedure step is accompanied by 3D finite element simulation. The achieved final magnet designs fulfill the predefined requirements of particular field distribution in the air gap, maximized ratio of high field volume to the permanent magnet volume, best utilization of magnets and magnetocaloric materials and constructional simplicity. A short comparison of two and four pole arrangements is given.     

Designing particular magnetic field profiles by computer

A design of specific magnetic-field profiles was performed by a power series of the general field formulas up to the 11th term. The application of this method, instead of the usual integration, was required to increase the speed of the calculation by a factor of a few hundreds and to decrease the memory capacity needed permanently for the stored data. For given magnetic parameters, the program has a self-consistent procedure to gain the prescribed homogeneity taking into account the layer distribution. The operation can be extended to the planning of strongly inhomogeneous magnetic systems as well. The elaborated method is also applicable to conventional, superconducting, multifilamentary, and high-T_c magnets     

Designing mechanical systems for optimum diagnosability

An analysis and modeling method of the diagnostic characteristics for electro-mechanical systems is presented. Diagnosability analysis is especially relevant given the complexities and functional interdependencies of modern-day systems, since improvements in diagnosability can lead to a reduction of a system’s life-cycle costs. Failure and diagnostic analysis leads to system diagnosability modeling with the failure modes and effects analysis (FMEA) and component-indication relationship analysis. Methods are then developed for translating the diagnosability model into mathematical methods for computing metrics such as distinguishability and No Fault Found. These methods involve the use of matrices to represent the failure and replacement characteristics of the system. Diagnosability metrics are extracted by matrix multiplication. These metrics are useful when comparing the diagnosability of proposed designs or predicting the life-cycle costs of fault isolation.     

Designing piezoelectric films for micro electromechanical systems

Piezoelectric thin films are of increasing interest in low-voltage micro electromechanical systems for sensing, actuation, and energy harvesting. They also serve as model systems to study fundamental behavior in piezoelectrics. Next-generation technologies such as ultrasound pill cameras, flexible ultrasound arrays, and energy harvesting systems for unattended wireless sensors will all benefit from improvements in the piezoelectric properties of the films. This paper describes tailoring the composition, microstructure, orientation of thin films, and substrate choice to optimize the response. It is shown that increases in the grain size of lead-based perovskite films from 75 to 300 nm results in 40 and 20% increases in the permittivity and piezoelectric coefficients, respectively. This is accompanied by an increase in the nonlinearity in the response. Band excitation piezoresponse force microscopy was used to interrogate the nonlinearity locally. It was found that chemical solution-derived PbZr(0.52)Ti(0.48)O(3) thin films show clusters of larger nonlinear response embedded in a more weakly nonlinear matrix. The scale of the clusters significantly exceeds that of the grain size, suggesting that collective motion of many domain walls contributes to the observed Rayleigh behavior in these films. Finally, it is shown that it is possible to increase the energy-harvesting figure of merit through appropriate materials choice, strong imprint, and composite connectivity patterns.     

Designing performance measurement systems for just-in-time operations

Results of a study conducted to understand how performance is evaluated in just-in-time (JIT) operations are reported in this paper. The purpose of the study was to develop a series of propositions concerning the performance criteria, standards, measurement techniques, and reporting methods that are appropriate in JIT environments. Ten propositions are provided.     

Designing and upgrading model of pre-denitrification systems

This paper reports a three-substrate steady-state integrated model, whose unknowns are expressed in explicit terms once concentrations of nitrogen compounds in the effluent flow are fixed. The model can be applied both to design and to upgrade wastewater treatment plants. The model is also able to evaluate the flexibility of existing wastewater treatment plants, which represents the capacity of the system to operate under different working conditions caused by increases in influent load or reductions in effluent quality standards. In this case the admissible variation of influent load or effluent concentration can be measured using suitable dimensionless flexibility indexes.List of symbols Q influent flow [L³ T^–1] - R₁ sludge recycle flow ratio - R₂ aerated mixed liquor recycle flow ratio - V_D denitrification reactor volume [L³] - V_N nitrification reactor volume [L³] - S biodegradable organic substrate concentration [M L^–3] - N-NH₄ ammonia nitrogen concentration [M L^–3] - N-NO₃ nitrate nitrogen concentration [M L^–3] - N_tot total nitrogen concentration [M L^–3] - O₂ oxygen concentration in the nitrification reactor [M L^–3] - X_H heterotrophic biomass concentration [M L^–3] - X_AUT autotrophic biomass concentration [M L^–3] - maximum removal rate of biodegradable organic substrate for an assigned value of temperature [T^–1] - maximum removal rate of nitrate for an assigned value of temperature [T^–1] - maximum removal rate of ammonia nitrogen for assigned values of pH and temperature [T^–1] - _S removal rate of biodegradable organic substrate [T^–1] - _D removal rate of nitrate [T^–1] - _N removal rate of ammonia nitrogen [T^–1] - K_S saturation coefficient for biodegradable organic substrate [M L^–3] - K_D saturation coefficient for nitrate [M L^–3] - K_SD saturation coefficient for organic substrate in the denitrification kinetic [M L^–3] - K_N saturation coefficient for ammonia nitrogen [M L^–3] - saturation coefficient for oxygen [M L^–3] - Y_H yield coefficient for heterotrophic microorganisms in the biodegradable organic substrate removal process - Y_D yield coefficient for heterotrophic microorganisms in the nitrate nitrogen removal process - Y_AUT yield coefficient for autotrophic microorganisms in the ammonia nitrogen removal process - (X_H)_r heterotrophic biomass concentration in the recycle sludge [M L^–3] - (X_AUT)_r autotrophic biomass concentration in the recycle sludge [M L^–3] - biodegradable organic mass consumption for unitary nitrate nitrogen mass reduction in the denitrification reactor - nitrogen consumption in the biodegradable organic oxidation process by mean of heterotrophic biomass     

Designing an efficient resistive magnet for magnetic resonance imaging

We present an alternative procedure to design a 0.1 T resistive magnet for magnetic resonance imaging. The procedure considers the conductor to be uniformly located over the cylindrical surface and treats it as coil elements. It applies the linear programming method with upper and lower bounds to constrain the current density to a fixed value in order to produce a desired magnetic field over a region of interest. The approach minimizes the power and preserves the predefined homogeneity, resulting in spatial clusters that define the coil's magnet. We demonstrate the method in a practical design situation.     

Designing integrated cellular manufacturing systems with tactical decisions

In this paper, we aim to design cellular manufacturing systems that optimize the performance of a manufacturing system subject to the optimization aspects of production planning. Consequently, the demand for each part – one of the production planning features – plays a vital role in determining the part families and the formation of machine cells in each period. In our study, holding and backorder costs follow a probabilistic structure, and they are described by a set of stochastic scenarios. In this model, five objective functions are employed: one of them minimizes the expected total holding and backorder costs in order to evaluate the risk in the model. The aim of this model is to select and optimize the assignment of parts and machines to different cells as well as the number of each produced part in each period. A new heuristic algorithm based on the optimization method is established to yield the best solution for this complicated mathematical formulation. Further, the performance of the proposed algorithm is verified using certain test problems in which the obtained results are compared with those obtained using the branch-and-bound algorithm and heuristic procedures.     

Designing cellular manufacturing systems with dynamic part populations

The effectiveness of a cellular manufacturing system is sensitive to fluctuations in the demand for products and the product mix. This paper presents a new formulation of the part family/machine cell formation problem that addresses the dynamic nature of the production environment by considering a multi-period forecast of product mix and demand during the formation of part families and machine cells. The goal of the multi-period formulation is to obtain a cellular design that continues to perform well with respect to the design objectives as the part population changes with time.     

Designing of epoxy resin systems for cryogenic use

The mechanical and thermal properties of several types of epoxy systems were designed based on the chemical structure, network structure and morphology aiming at cryogenic application. In this research di-epoxies or multifunctional epoxies were cured by several kinds of hardeners such as anhydride, amine or phenol and were blended with polycarbonate, carboxyl-terminated butadiene acrylonitrile copolymer or phenoxy. The mechanical properties and thermal properties of these cured epoxies were measured at room and liquid nitrogen temperature. It was found that the two-dimensional network structured linear polymer shows high performance even at cryogenic temperature. It was concluded that the controls of the structures are very important to optimize epoxy systems for cryogenic application.     

Critical properties of random magnetic systems

A review of the recent applications of renormalisation group techniques to the calculations of the critical properties of random magnetic systems is presented.     

Noise autocorrelation in magnetic recording systems

This paper describes a new technique for measuring the noise autocorrelation in magnetic recording systems. Unlike the spectrum, the autocorrelation function characterizes non-stationary noise as well as stationary noise so it is particularly suitable for signal dependent noise often found in disks. In addition, noise sources can be separated by properly choosing the sample space. Many interesting properties of particulate and metal film disks were found by this technique.