Multi-element System Research Articles

Planar detectors for multielement systems of millimeter-wave imaging

We discuss the concept of developing a millimeter-wave multielement matrix receiver on the basis of planar antennas with directly coupled low-barrier Schottky diodes. Three main problems are considered which involve choosing and developing a design of the planar antenna coupled with the low-barrier Schottky diode, optimizing the parameters of the low-barrier Schottky diodes for obtaining maximum sensitivity, and ensuring compact arrangement with weak mutual influence of the planar detectors in a two-dimensional array. We propose a design of the slot antenna with an active resistance of about 800 Ω at a resonant frequency of 94 GHz. The detection characteristics of diodes with the differential Schottky-barrier resistance in the range Rj = 0.4–1000 kΩ for a zero bias are studied experimentally. The mutual influence of the neighboring antennas is examined for developing the multielement radio-imaging system. The conditions of weak cross influence of the closely located planar detectors are determined.

공기부양선의 추진 및 부양축계 종진동 해석에 관한 연구

In this study, axial vibration analysis has been conducted on a propulsion and lift shafting system for an air cushion vehicle using ANSYS code. The shafting system is totally flexible multi-elements system including wood composite material of air propeller, aluminum alloy of lift fan and thin walled shaft with flexible coupling. The analysis calculated the axial natural frequencies and mode shapes of the shafting system taking into account an equivalent mass-elastic model for shafting system as well as the three-dimensional models for propeller blade and fan impeller. Such a flexible shafting system has very intricate vibrating characteristics and especially, axial natural frequencies of flexible components such as propeller blade and impeller of lift fan can be lower to the extent that causes a resonance in the range of operating revolution. The results for axial vibration analysis are presented and compared with the results of axial vibration test for lift fan conducted during Sea Trial.

Spatial Correlation of Radio Waves for Multi-Antenna Applications in Indoor Multipath Environments

This paper presents the results of a concerted effort in characterizing the spatial correlation of radio waves detected by a multi-element antenna system in indoor environments. The number of arriving paths and their directions are first studied through a series of measurements. The results are then used in a simulation to obtain spatial correlation indoors. It is found that generally an antenna array positioned near the center of the room will experience more rapidly decreasing correlation with spacing, which is a desired trait. In addition, a linear array oriented perpendicular to the length of the room in general shows better characteristics in terms of faster slope of correlation compared to the one in parallel with the length of the room. The average correlation indoors is also found to be similar to the correlation function arising from the two-dimensional circularly distributed random scatterers proposed by Clarke. For practical implementation of antenna arrays in small terminals for indoor wireless applications, it is suggested that the inter-element spacing be made 0.3? in the least.

Soft Magnetic Devices Applied for Low Zero Excursion (0.01$^{\circ}$/h) Four-Mode Ring Laser Gyro

Soft magnet devices have a wide variety of applications in aerospace, military, and industrial sectors. Generally, devices used in industrial applications are required to operate satisfactorily under ambient temperatures of +10 degC to +50 degC under normal pressure, whereas those used in aerospace and military applications will face a wider range of temperatures from -60 degC to +80 degC and generally high pressure. In most of the soft magnetic materials, the use of a temperature compensating and stress-sensitive alloy will introduce changes in their normal performance. Therefore, an attempt is made to devise a method that ensures inherent temperature compensation and stress proof. Recent work in characterizing the performance of multielement high-entropy magnetic nanocomposite systems will be described. Specifically, we have developed soft magnetic alloys that exhibit tolerance of high stress and large temperatures changing above current operating ranges for four-mode ring laser gyro (RLG) devices

공기부양선의 추진 및 부양축계 비틀림진동 해석 연구

A propulsion and lift shafting system in an air cushion vehicle is flexible multi-elements system which consists of two aeroderivative gas turbines with own bevel gears, four stage lift fan reduction gear, two stage propulsion reduction gear, air propellers and high capacity of lifting fans. In addition, the system includes the multi-branched shafting with multi-gas turbine engines and thin walled shaft with flexible coupling. Such a branched shafting system has very intricate vibrating characteristics and especially, the thin walled shaft with flexible couplings can lower the torsional natural frequencies of shafting system to the extent that causes a resonance in the range of operating revolution.<BR> In this study, to evaluate vibrational characteristics some analytical methods for the propulsion and lift shafting system are studied. The analysis, including natural frequencies and mode shapes, for five operation cases of the system is conducted using ANSYS code with a equivalent mass-elastic model.

Towards the Design of Synthetic-jet Actuators for Full-scale Flight Conditions

Due to the large parameter space that is involved in the design of synthetic-jet actuators used for flow separation control, it is essential to develop low-dimensional models for actuator-performance prediction and establish the conditions for design optimisation so that candidate actuators can be identified at the initial design stage. In Part 2 of this paper, three low-dimensional models that are capable of predicting actuator performance for synthetic jet actuators of different scales are described. Using these models the parametric relationships required for optimising the actuator performance are established. Finally, based on a better understanding of the fluid mechanics of synthetic jets (described in Part 1) and the improved modelling capacity, a methodology for designing synthetic-jet actuators used for flow separation control at full-scale flight conditions is developed. This methodology is illustrated in the design of actuators for delaying flow separation on the leading and trailing edge devices of a multi-element high-lift system of a typical commercial-aircraft wing at take-off conditions.

Performance of the compact HVE 1 MV multi-element AMS system

HVE has tested the performance of its first compact 1MV AMS system. The system is primarily designed for the measurement of 14C, 10Be and 26Al, but additionally supports the measurement of heavy ions like iodine and plutonium. The tests confirmed the flexibility of a system that results from its 1MV nominal terminal voltage, as it allows the use of various charge states for the analysis of e.g. 14C, supports 10Be analysis with good detection efficiency and permits the analysis of heavy ions like 129I and Pu. For the analysis of 10Be, the isobaric 10B is removed by means of the nuclear charge dependent energy loss in an absorber foil in front of the electrostatic analyser. The results of the performance tests for 14C-, 10Be- and 26Al-analyses are presented in this paper.

Aberration coefficients of multi-element cylindrical electrostatic lens systems for charged particle beam applications

In order to analyze the imaging properties of an electrostatic lens system, it is necessary to know how various sources of aberration combine to increase the size of final image or spot. In this paper, we investigated the spherical and chromatic aberration coefficients of multi-element electrostatic lens systems as a function of the lens voltages and magnification, using the electron ray tracing simulation programs S imion and L ensys. These programs can be used to obtain electron optical aberration integrals which involve the axial potential distribution and its derivative, and two independent trajectories and their derivatives for the determination of the third- or fifth-order aberration coefficients of multi-element lenses. Optical simulation of the intensity distribution has quantitatively shown that the aberration in the crossover image causes an electron beam blur and a positioning error on the focus spot. If a high positive voltage with respect to the first element's potential is applied to the lens elements, the aberrations as well as the minimum beam divergence can be reduced. The reason, obtained from numerical simulation, is that a positive voltage increases the electron velocity, shortening the electron drift time across the region with aberrant field.

Computer-guided alignment I : Phase and amplitude modulation of alignment-influenced optical wavefront

As the first part of a development programme on computer-guided alignment (CGA), we model the alignment influence on the optical wavefront in terms of the phase and amplitude modulation. This modulation is derived from the interaction between alignment parameters and influence functions, both expressed in complex form. The alignment influence model is used to approximate the ray-traced target wavefront of a randomly mis-aligned multi-element system. The approximated wavefront shows a factor of ~ 100 improvement in predicting the target, when coupled non-linear influences among elements are included. This demonstrates the significance of the inter-element effect. We discuss the possibility of adopting the model for rectifying mis-alignment of multi-element systems.

Fast full-view photoacoustic imaging by combined scanning with a linear transducer array

We present a fast full-view photoacoustic imaging system for visualizing tissue structures using a linear transducer array with combined scan. In this system, a 128-element linear transducer array was used to detect photoacoustic signals by combined scanning of electronic scan and mechanical scan. An improved limited-field filtered back projection algorithm with directivity factors was applied to reconstruct the optical absorption distribution. The experiments of phantoms and in vivo blood vessels in a rat brain were performed with this system. And a clear view of the curve boundaries of objects and the network of blood vessels of rat's brain were acquired. The experimental results demonstrate the multi-element photoacoustic imaging system has the ability of imaging complicated structures of objects.

Characterization and modeling of multi-element electrostatic lens systems

Electrostatic cylinder lenses are widely used to control beams of charged particles with different energies and directions in several fields, especially in electron spectroscopy. In this study, we investigated the zoom-lens properties of the three-, four- and five-element electrostatic lens systems as a function of the lens voltages and their dimensions. Lens systems, which consist of cylindrical electrodes, each spaced 0.1 diameter apart, were designed by using the SIMION and LENSYS programs. Three different lens configurations were studied to form an image at a specific position for use in experimental studies. We also discussed the line-shape profile of a three-element lens system as a function of the focusing voltage for einzel lens configuration.

Feed-forward control of a redundant motor system

We describe a model of feed-forward control of a redundant motor system and validate it using, as examples, tasks of multi-finger force production. The model assumes the existence of two input signals at an upper level of the control hierarchy, related and unrelated to a task variable. Knowledge of the Jacobian of the system is assumed at the level of generation of elemental variables (variables at the level of effectors). Variance at the level of elemental variables is considered as the sum of two components, related and unrelated to variability in the task variable. An index of stabilization of the task variable is similarly introduced as to how it was done in several studies using the framework of the uncontrolled manifold hypothesis. Several phenomena have been simulated including data point distributions corresponding to presence and absence of force-stabilizing synergies in two-finger tasks, changes in synergies with practice, and changes in synergy indices in preparation to a fast action. The model is discussed in comparison to other models of control of multi-element systems based on feedback processes. It shows that patterns of structured variability in the space of elemental variables can result from feed-forward processes. Relations of the model to the equilibrium-point hypothesis are also discussed.

Anticipatory adjustments of multi-finger synergies in preparation for self-triggered perturbations

We studied changes in multi-finger synergies associated with predictable and unpredictable force perturbations applied to a finger during a multi-finger constant total force production task. The main hypothesis was that indices of multi-finger synergies can show anticipatory changes in preparation for a predictable perturbation. Subjects sat in a chair and pressed on force sensors with the four fingers of the right hand. The task was to produce a constant level of total force. The fingers acted against loads that produced upward directed forces. The loads (applied either to the index or to the ring finger) could be disengaged either by the subject or by the experimenter. An index of finger co-variation, DeltaV was computed across sets of 12 trials at each time sample and for all tasks separately. During steady-state force production, all subjects showed positive DeltaV values corresponding to strong negative covariation among finger forces interpreted as a force-stabilizing synergy. Prior to self-triggered unloading, subjects showed an anticipatory drop in DeltaV that started 100-125 ms prior to the unloading time. Such early changes were absent in trials with experimenter-triggered unloading. After an unloading, subjects changed forces of both perturbed and unperturbed fingers and reached a new sharing pattern of the total force. In experimenter-triggered conditions, changes in the forces of unperturbed fingers could be seen as early as 120 ms following an unloading. The index DeltaV dropped following a perturbation and then recovered; the recovery occurred faster in self-triggered conditions. We conclude that humans can use feed-forward changes in multi-finger synergies (anticipatory synergy adjustments) in anticipation of a predictable perturbation. These changes may help avoid prolonged weakening of a multi-digit force-stabilizing synergy. We discuss a possibility that anticipatory postural adjustments may represent a particular case of the phenomenon of anticipatory synergy adjustments and suggest a hierarchical control scheme that incorporates a possibility of independent control over the output of a multi-element system and covariation patterns among outputs of its elements.

A compact 1 MV multi-element AMS system

HVE has designed and built a compact 1MV multi-element AMS system with a footprint of 3.8m×6.3m. The system is primarily designed for the analysis of light elements like beryllium, carbon and aluminium, but it also supports the measurement of heavy ions like iodine and plutonium. The analysis of 14C is done using the charge state 1. For this, the accelerator terminal is designed for high stripper gas thickness to efficiently destroy the interfering molecules like 13CH and 12CH2. For the analysis of 10Be, suppression of the isobaric 10B is achieved using an absorber foil that can be inserted in front of the electrostatic analyser. The analysis of 26Al can be done using charge-state 1 or 3. The rare isotopes are identified in a dual-anode high-resolution detector and a two-dimensional data acquisition system.

Seeking Churchman's system for guaranteeing knowledge claims

This paper will present a system for guaranteeing knowledge claims (research findings, conclusions) relevant to human design activities including research. It draws from the ideas developed by the systems thinker C. West Churchman (1914–2004), who wished to integrate individual experience, experimentation, alternative explanations and ethical considerations into a multi-element system to help designers and researchers reflect on knowledge claims. This paper will explore the conjecture that Churchman's five-element system provides a pragmatic for ‘guaranteeing’ design knowledge claims. The evidence to support this argument draws on some of the ideas Churchman presented in his book The Design of Inquiring Systems, as well as the more generic argumentative inquiry, systems perspectives literature. A list of ‘guarantor’ questions for designer and researchers is provided as a summary. Copyright © 2006 John Wiley & Sons, Ltd.

Fast multielement phase-controlled photoacoustic imaging based on limited-field-filtered back-projection algorithm

In this paper, the multielement phase-controlled technique and the limited-field -filtered back-projection algorithm are used to investigate the two-dimensional fast noninvasive photoacoustic imaging. By the use of the former to collect photoacoustic signals, which are of high signal-to-noise ratio, one needs not to average the data and can acquire them in less than 5s. The later can greatly improve the lateral resolution of the multielement linear transducer array imaging system from 1.5mmto0.24mm. This method and system can provide a fast and reliable approach to photoacoustic imaging that could be applied to noninvasive imaging and clinic diagnosis.

Twin shaping filter techniques to compensate the signals from CZT/CdTe detectors

A Gamma Ray Burst Monitor (GRBM) has been proposed to form part of the LOBSTER experiment, approved by ESA for a Phase A study for a future flight (2009) aboard the International Space Station (ISS). The GRBM detector would be based on CdZnTe array modules, maintained, together with the front-end electronics, at a temperature of about 250 K by using Peltier effect or passive cooling systems. To improve the detector performance several hardware (HW) and software (SW) techniques are being tested. In addition to the strip readout technique for rejecting charged particles interacting with the detector, we have investigated a method which employs a pair of active filters (one slow and one fast) to analyze differently shaped signals from the same charge sensitive preamplifier. This technique could be particularly useful for application with multi-element detection systems requiring dedicated front end and readout integrated circuits (ASICs) especially designed for the implementation of the HW correction procedure. Some experimental results are presented from the application of the biparametric technique on CdZnTe/CdTe detectors with planar and segmented electrodes in order to study the influence of the correction parameters and to verify the efficiency of the correction algorithm on groups of neighboring pixels.

Multi-element cylindrical electrostatic lens systems for focusing and controlling charged particles

This paper describes theoretical modeling of electrostatic lenses based on three, four and five closely spaced cylindrical electrodes. In each case, modeling is carried out numerically using commercial packages SIMION and LENSYS, and a variety of performance parameters are obtained. Special cases such as a zoom lens (i.e., lenses whose magnification may be changed without losing focus) are considered. Results are obtained as a function of the ratios of the electrode lengths and gaps, and as a function of ratios of the controlling voltages. As a result, how a multi-element lens system can be operated with the whole focal properties in a useful mode for experimental studies is shown.

Automatic Transition Prediction and Applicationto High-Lift Multi-Element Configurations

A Reynolds-averaged Navier-Stokes (RANS) solver, a laminar boundary layer code and an e(N)-database method for transition prediction were coupled in order to perform RANS computations of two-dimensional high-lift multi-element systems with automatic laminar-turbulent transition prediction and transitional flow regions. It will be shown, that the coupled system represents a RANS-based CFD tool that provides accurated values of the transition locations during the ongoing RANS computation automatically and fast without the need for the intervention by the code user. Thus, RANS computations of two-dimensional high-lift multi-element configurations with transition can be carried out without a priori knowledge of the transition characteristics of the specific flow problem. The coupling structure and the underlying algorithm of the transition prediction procedure as well as the physical modelling of transitional flow regions and their generation in the RANS computational grid are described. The testing of the transition prediction procedure is described and documented. The computational results are compared to experimental data.

Selective and in-situ determination of carbonate and oxide particles in aqueous solution using laser-induced breakdown spectroscopy (LIBS) for wearable information equipment

Laser-induced breakdown spectroscopy (LIBS) has been applied for quantitative analysis of Al2O3, CaCO3 and MgO particles suspended in water. In the single elemental system, the plasma emission intensities of Al, Ca and Mg were linearly increased with concentration of elements in the range of 1.0×10−5–1.0×10−3 M, 1.0×10−4–2.0×10−3 M and 8.0×10−5 –4.0×10−3 M, respectively. We also investigated the concentration dependence of breakdown spectra for suspended mixtures of Al2O3, CaCO3 and MgO particles. The emission lines, such as Al I, Ca I, Ca II and Mg I, were appeared in the LIBS spectrum simultaneously, and each emission peak could be deconvoluted. The plasma emission intensities of Al, Ca and Mg in the multielemental system were also linearly increased with their concentrations in the range of 1.0×10−5–1.0×10−3 M, 1.0×10−4–2.0×10−3 M and 4.0×10−4–2.0×10−3 M, respectively. LIBS was found to be available for quantitative and qualitative measurement of the concentrations of Al2O3, CaCO3 and MgO particles suspended in water. The present results suggest that LIBS is a potentially useful tool for in-situ analysis on particles composition and concentrations for environmental monitoring by the wearable information equipments.