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Number of results: 54
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Abstract

The issue of maximizing penetration depth with concurrent retaining or enhancement of image resolution constitutes one of the time invariant challenges in ultrasound imaging. Concerns about potential and undesirable side effects set limits on the possibility of overcoming the frequency dependent attenuation effects by increasing peak acoustic amplitudes of the waves probing the tissue. To overcome this limitation a pulse compression technique employing 16 bits Complementary Golay Sequences (CGS) Code was implemented at 4 MHz. In comparison with other, earlier proposed, coded excitation schemes, such as chirp, pseudo-random chirp and Barker codes, the CGS allowed virtually side lobe free operation. Experimental data indicate that the quality — resolution, signal penetration and contrast dynamics — of CGS images is better than the one obtain for standard ultrasonography using short burst excitation.
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Abstract

An overview of the important techniques for detection of optical radiation from the ultraviolet, through visible to infrared spectral regions is presented. At the beginning single-point devices are considered. Next, di.erent application circuits used in direct detection systems together with elucidation of the design of front-end circuits and discussion of their performance are presented. Third part of the paper is devoted to advanced techniques including coherent detection. Finally, the updated information devoted to readout of signals from detector arrays and focal plane arrays is included. It is shown that detector focal plane technology has revolutionized many kinds of imaging in the past 25 years.
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Abstract

There is a growing need for a more accurate assessment of the load carrying capacity of highway bridges. The traditional approach is based on consideration of individual components rather than structures. Consequently, the acceptance criteria are formulated in terms of the allowable stress, or ultimate moment, in a component. However, it has been observed that the load carrying capacity of the whole structure (system) is often much larger than what is determined by the design of components. The difference can be attributed to the system behaviour. Quantification of this difference is the subject of the system reliability. There is a need to take advantage of the available system reliability methods and advanced structural analysis methods and apply them in the design of bridges and evaluation of existing structures. The current advanced analytical procedures allow for a numerically accurate but deterministic analysis of strain/stress in a bridge. Mathematical procedures exist for the calculation of reliability for various idealized systems: parallel, series, and combinations. There are also new developments in materials, technology, and field testing which can be used to improve bridge design and evaluation. This paper deals with calculation of the reliability of the whole bridge structure, taking into account realistic boundary conditions, and site-specific load and resistance parameters.
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Abstract

Abstract. In this paper we present a new class of neuro-fuzzy systems designed for system modelling and pattern classi.cation. Our approach is characterized by automatic determination of fuzzy inference in the process of learning. Moreover, we introduce several .exibility concepts in the design of neuro-fuzzy systems. The method presented in the paper is characterized by high accuracy which outperforms previous techniques applied for system modelling and pattern classi.cation.
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Abstract

Shape memory alloys are characterised by interesting properties, i.e. shape memory effect and pseudoelasticity, which enable their increasing application. Thermomechanical aspects of martensitic and reverse transformations in TiNi shape memory alloy subjected to tension tests were investigated. The stress-strain characteristics obtained during the tests were completed by the temperature characteristics. The temperature changes were calculated on the basis of thermograms determined by an infrared camera. Taking advantages from the infrared technique, the temperature distributions on the specimen’s surface were found. Heterogeneous temperature distributions, related to the nucleation and development of the new martensite phase, were registered and analysed. A significant temperature increase, up to 30 K, was registered during the martensitic transformation. The similar effects of the heterogeneous temperature distribution were observed during unloading, while the reverse transformation, martensite into austenite took place, accompanied by significant temperature decrease.
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Abstract

The problem of the design of a perfect reduced-order unknown-input observer for standard systems is formulated and solved. The procedure of designing the observer using well-known canonical form is proposed and illustrated with a numerical example. Necessary and sufficient conditions for the solvability of the procedure are given.
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Abstract

This paper describes a design process of HALE PW-114 sensor-craft, developed for high altitude (20 km) long endurance (40 h) surveillance missions. Designed as a blended wing (BW) configuration, to be made of metal and composite materials. Wing control surfaces provide longitudinal balance. Fin in the rear fuselage section together with wingtips provide directional stability. Airplane is equipped with retractable landing gear with controlled front leg that allows operations from conventional airfields. According to the initial requirements it is twin engine configuration, typical payload consists of electro-optical/infra-red FLIR, big SAR (synthetic aperture radar) and SATCOM antenna required for the longest range. Tailless architecture was based on both Horten and Northrop design experience. Global Hawk was considered as a reference point – it was assumed that BW design has to possess efficiency, relative payload and other characteristics at least the same or even better than that of Global Hawk. FLIR, SAR and SATCOM containers were optimised for best visibility. All payload systems are put into separate modular containers of easy access and quickly to exchange, so this architecture can be consider as a „modular”. An optimisation process started immediately when the so-called “zero configuration”, called PW-111 was ready. It was designed in the canard configuration. A canard was abandoned in HALE PW-113. Instead, new, larger outer wing was designed with smaller taper ratio. New configuration analysis revealed satisfactory longitudinal stability. Calculations suggested better lateral qualities for negative dihedral. These modifications, leading to aerodynamic improvement, gave HALE PW-114 as a result. The design process was an interdisciplinary approach, and included a selection of thick laminar wing section, aerodynamic optimisation of swept wing, stability analysis, weight balance, structural and flutter analysis, many on-board redundant systems, reliability and maintability analysis, safety improvement, cost and performance optimisation. Presented paper focuses mainly on aerodynamics, wing design, longitudinal control and safety issues. This activity is supported by European Union within V FR, in the area Aeronautics and Space.
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Abstract

In this work studies ofM OVPE growth of InAlGaAs/AlGaAs/GaAs heterostructures are presented. The HRXRD and SIMS measurements indicate the high structural and optical properties as well as high uniformity oft hickness and composition ofI nAlGaAs quantum wells. This work is the .rst step towards elaboration oft he technology oft he strained InAlGaAs/GaAs heterostructures for advanced optoelectronic devices working in the visible part oft he spectrum. The investigations ofSi (n-type), Zn (p-type) .-doped GaAs epilayers and centre Si-.-doped InxGa1-xAs single quantum well (SQW) are presented. The .-doping layer was formed by SiH4 or DEZn introduction during the growth interruption. The electrical and optical properties oft he obtained structures were examined using C-V measurement, EC-V electrochemical pro.ler, Raman spectroscopy (RS), photore.ectance (PR) and photocurrent (PC) spectroscopies. Technology oft hick GaN layers grown on sapphire by HVPE is very promising as a part off reestanding GaN substrates manufacturing. Further works will be focused on the optimisation of growth, separating layers from substrates and surface polishing. The in.uence oft he growth parameters on the properties of( Ga, Al)N/Al2O3 and Mg dopant incorporation was studied.
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Abstract

In the paper, the problem of isothermic DNA sequencing by hybridization, without any errors in its input data, is presented and an exact polynomial-time algorithm solving the problem is described. The correctness of the algorithm is con.rmed by an enumerative proof.
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Abstract

The In this paper stabilisation problem of LC ladder network is established. We studied the following cases: stabilisation by inner resistance, by velocity feedback and stabilisation by dynamic linear feedback, in particularly stabilisation by first range dynamic feedback. The global asymptotic stability of the respectively system is proved by LaSalle’s theorem. In the proof the observability of the dynamic system plays an essential role. Numerical calculations were made using the Matlab/Simulink program.
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Abstract

The aim of this paper is to study the applicability of the theory of micropolar fluids to modelling and calculating flows in microchannels depending on the geometrical dimension of the flow field. First, it will be shown that if the characteristic linear dimension of the flow becomes appropriately large, the equations describing the micropolar fluid flow can be transformed into Navier-Stokes equations. Next, Poiseuille flows in a microchannel is studied in detail. In particular, the maximal cross-sectional size of the channel for which the micropolar effects of the fluid flow become important will be established. The experimentally determined values of rheological constants of the fluid have been used in calculations.
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Abstract

The In the paper, we investigate two single processor problems, which deal with the process of negotiation between a producer and a customer about delivery time of final products. This process is modelled by a due interval, which is a generalization of well known classical due date and describes a time interval, in which a job should be finished. In this paper we consider two diffierent mathematical models of due intervals. In both considered problems we should find such a schedule of jobs and such a determination of due intervals to each job, that the generalized cost function is minimized. The cost function is the maximum of the following three weighted parts: the maximum tardiness, the maximum earliness and the maximum due interval size. For the first problem we proved several properties of its optimal solution and next we show the mirror image property for both of considered problems, which helps us to provide an optimal solution for the second problem.
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Abstract

Pulse electrochemical machining (PECM) provides an economical and e.ective method for machining high strength, heat-resistantmaterials into complex shapes such as turbine blades, die, molds and micro cavities. Pulse Electrochemical Machining involves the application of a voltage pulse at high current density in the anodic dissolution process. Small interelectrode gap, low electrolyte .ow rate, gap state recovery during the pulse o.-times lead to improved machining accuracy and surface .nish when compared with ECM using continuous current. This paper presents a mathematical model for PECM and employs this model in a computer simulation of the PECM process for determination of the thermal limitation and energy consumption in PECM. The experimental results and discussion of the characteristics PECM are presented.
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Abstract

Semiconductive - resistive sensors of toxic and explosive gases were fabricated from nanograins of SnO2 using thick-.lm technology. Sensitivity, selectivityand stabilityof sensors working in di.erent temperature depend on the way the tin dioxide and additives were prepared. A construction also plays an important role. The paper presents an attitude towards the evaluation of transport of electrical charges in semiconductive grain layer of SnO2, when dangerous gases appear in the surrounding atmosphere.
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Abstract

The notion of the normal transfer matrix and the notion of the structure decomposition of normal transfer matrix for 2D general model are introduced. Necessary and sufficient conditions for the existence of the structure decomposition of normal transfer matrix are established. A procedure for computation of the structure decomposition is proposed and illustrated by the numerical example. It is shown that the impulse response matrix of the normal model is independent of the polynomial part of its structure decomposition.
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Abstract

The paper deals with the problem of force and torque calculation for linear, cylindrical and spherical electromechanical converter. The electromagnetic field is determined analytically with the help of separation method for each problem. The results obtained can be used as test tasks for electromagnetic field, force and torque numerical calculations. The analytical relations for torque and forces are also convenient for analysis of material parameters influence on electromechanical converter work.
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Abstract

Conceptions of analogue electronics circuit based on a multiple-input floating gate field-effect transistor MOS (MIFGMOS) have been presented. The simple add and differential voltage amplifiers with one and two MIFGMOS transistors and multiple-input operational amplifiers with their application have been proposed. One of them was used for the realisation of a controlled floating resistor. Results of circuit simulations in SPICE programme using the simple substitute macromodel of MIFGMOS transistor have been shown.
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Abstract

This paper presents revised and extended version of theory proposed in the late 1970-ties by A. ˇCyras and his co-workers. This theory, based upon the notion of duality in mathematical programming, allows us to generate variational principles and to investigate existence and uniqueness of solutions for the broad class of problems of elasticity and plasticity. The paper covers analysis of solids made of linear elastic, elastic-strain hardening, elastic-perfectly plastic and rigid-perfectly plastic material. The novelty with respect to ˇCyras’s theory lies in taking into account loads dispersed over the volume and displacements enforced on the part of surface. A new interpretation of optimum load for a rigid-perfectly plastic body is also given.
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Abstract

The second part of the paper presents finite-dimensional models of linear elastic, elastic-strain hardening, elastic-perfectly plastic and rigid-perfectly plastic structures. These models can be seen as a result of discretisation procedure applied to the models of solids derived in the Part I. The implications of sub-dividing degrees of freedom into those with prescribed external forces and those with given displacements are discussed. It is pointed out that the dual energy principles given in this part of the paper can serve as a direct basis for numerical computations.
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Abstract

DNA sequencing remains one of the most important problems in molecular and computational biology. One of the methods used for this purpose is sequencing by hybridization. In this approach usually DNA chips composed of a full library of oligonucleotides of a given length are used, but in principle it is possible to use another types of chips. Isothermic DNA chips, being one of them, when used for sequencing may reduce hybridization error rate. However, it was not clear if a number of errors following from subsequence repetitions is also reduced in this case. In this paper a method for estimating resolving power of isothermic DNA chips is described which allows for a comparison of such chips and the classical ones. The analysis of the resolving power shows that the probability of sequencing errors caused by subsequence repetitions is greater in the case of isothermic chips in comparison to their classical counterparts of a similar cardinality. This result suggests that isothermic chips should be chosen carefully since in some cases they may not give better results than the classical ones.
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Abstract

In the paper, a feedforward linearization method for differential-pair operational transconductance amplifier (OTA) is discussed. The proposed technique is developed using simple differential pair transconductors and linear reference resistor. The concept leads not only to very efficient linearization ofa transfer characteristic oft he OTA but also others the possibility of effffective phase compensation. Due to this, the circuit can be used in applications requiring precise phase response (e.g. filters). SPICE simulations show that for the circuit working with a ±1.25V power supply, total harmonic distortion (THD) at 0.8Vpp is less then 0.1% in comparison to 10.2% without linearization. Moreover, the input voltage range ofline ar operation is increased. Power consumption oft he overall circuit is 0.94mW. The 3rd order elliptic filter example has been designed and simulated. It turns out that the proposed compensation scheme significantly improves the performance of the filter at higher frequencies.
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Abstract

Necessary and sufficient conditions for robust stability of the positive discrete-time interval system with time-delays are established. It is shown that this system is robustly stable if and only if one well de?ned positive discrete-time system with time-delays is asymptotically stable. The considerations are illustrated by numerical example.
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Abstract

A short overview of the developments of functional materials featuring miniaturisation and integration is illustrated by examples taken from the ?eld of ceramic functional materials. To obtain new materials new methods are required. Most of them are microfabrication processes developed by the "top-down" approach.
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Abstract

Swing-up control of a single pendulum from the pendant to the upright position is firstly surveyed. The control laws are comparatively studied based on swing-up time from a given initial state to the upright position. The State Dependent Riccati Equation is found effective for designing the swing-up control law under saturating control input. The control law is extended to a linear combination of sine function of the angle and the angular velocity, and a variable structure control with a sliding mode given by the linear combination. Making the swing-up time correspond to a colour, which is similar to the Fractal analysis, colour maps of the swing-up time for given control parameters and initial conditions yield interesting Fractal-like figures.
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