Standard Multi Research Articles

Novel plenoptic Imager for 3D Particle Tracking Velocimetry for Fluid Structure Interactions

We show a novel plenoptic camera architecture and demonstrate its ability to perform three-dimensional three-component velocimetry using standard multi camera processing techniques. The novel architecture needs only a custom lens assembly with no modification to the camera body. This allows the use of any camera with an appropriate sensor size. The architecture directly creates multiple views of a scene side by side on the camera sensor which can be separated and treated as if they originated from independent cameras. Standard calibration techniques for creating 3D to 2D correspondence on the images can then be implemented to reconstruct 3D scene information. For this case we focus on performing 3D PTV using the commercial software DaVis and the "shake-the-box" algorithm. We look at the flow induced by an oscillating rod and compare the results with the analytical solution to validate the results.

Design of an Axial Transonic Rotor by Modified Spanwise Loading Distribution

Improving the aerodynamic performance of the transonic fan in a turbofan engine can be beneficial for both the fuel consumption and maneuverability of an airplane. Deep insight into the supersonic aerodynamics is needed for the simultaneous improvement of all operating parameters of a transonic rotor, including the pressure ratio, efficiency, and surge margin. A design method was developed for an axial transonic rotor by using a combination of radial equilibrium theory, the free vortex method, and a distributed span-wise diffusion factor. The loading distribution obtained by this method was the highest in the hub section and gradually decreased in the tip section. To evaluate the method, a transonic rotor was designed using the geometric parameters and operating conditions of NASA rotor 67. A code was developed to determine a geometry for the new rotor and to modify it. The code was coupled with a RANS flow solver for 3D modification of the new designed rotor. Only standard multi- and double-circular arc airfoils were applied in different radial sections of the new rotor with no blade profile optimization. The results of the RANS equations solution for the new designed rotor showed 1.5% higher efficiency, 3% higher pressure ratio, and more than 1.5 times larger operating range in comparison to NASA rotor 67. The new designed method seems to be an efficient approach that not only improved the efficiency and pressure ratio but also increased the operating range of an axial transonic rotor.

An exploratory study about the Challenges with Pilot Training and Recruitment in Europe

Pilot training and recruitment is of fundamental importance for the aviation industry. Yet, a number of Commercial Pilot’s License (CPL) applicants trained by Approved Training Organizations (ATOs) fail their airline assessments. To provide some clarity on why this is happening, we conducted in-depth interviews with twelve industry professionals and a detailed documentary analysis was undertaken. We found that the main reasons are: (1) Lack of preparation or technical knowledge; (2) Poor communication skills; and (3) Poor display of teamwork and leadership. The paper suggests that regulation should be implemented for ATO’s to use screening processes on potential students to increase quality or Airline Pilot Standard Multi Crew-Cooperation (APS MCC) system, as an additional training system on top of what is being taught in ATOs. Regulations should further be linked with regular audits in place for smaller airlines to increase the effectiveness of their pilot assessments and recruitment processes in order to increase safety. Areas of further research as also identified.

Regressor-free adaptive vibration control of constrained smart beams with axial stretching

This paper proposes an adaptive approximation control AAC technique (or so-called regressor-free adaptive control) for vibration regulation of constrained flexible smart beams with axial stretching. The key idea of the AAC is to control/regulate the target dynamic system while estimating the uncertainty using weighting and basis function terms with guaranteed stability based on Lyapunov theory. Accordingly, the dynamic equation of transverse vibration of the pinned–pinned smart beam is derived considering the effect of axial stretching. Due to the presence of a coupled tension-bending effect, a nonlinearly coupled cubic stiffness term appears in beam modelling making the dynamic system highly nonlinear. The resulted partial differential equation of the vibrating smart beam is discretized into definite N-mode shapes (definite degrees-of-freedom) using the Galerkin approach and a standard multi–input–multi–output ordinary differential equations system is established. Then two decoupled nonlinear control algorithms are designed based on the AAC for vibration attenuation of the nonlinear vibrating beam system. A pinned–pinned piezoelectrically-actuated/sensed flexible beam is simulated and the results show the validity of the proposed control architecture.

Low-cost surface micromachined microhotplates for chemiresistive gas sensors

Microhotplate (MHP) based gas sensors have gained significant attention recently due to their small size, low power and feasibility for integration of electronics on the same chip. This study presents the detailed work on design, fabrication and complete characterization of microhotplates based on a standard multi user MEMS process (MUMPs). Suspended-membrane type MHPs were designed using the available layer combinations of MUMPs. FEM simulations were carried out to optimize the heater design by spatially varying the heater current density to achieve uniform temperature distribution over the sensing area. Topography measurements confirmed that the X–Y–Z dimensions of the fabricated MHPs were in accordance with the design. From electro-thermal characterization, the thermal efficiency of the MHPs was evaluated as ~ 10 °C/mW. The suspended membrane showed a homogeneous temperature of ~ 450 °C at 35–40 mW heater power, which was well above the typical operating temperature of chemiresistive gas sensors. The results presented in this paper provide a pathway for realizing cost effective MHPs for gas sensors based on MUMPs.

Design, simulation and fabrication of piezoresistive microcantilevers using standard multi user MEMS process

Microcantilevers are extensively used in Micro Electro Mechanical Systems for a variety of sensing applications. This study presents the modeling, design and simulation of piezoresistive microcantilevers with an embedded heater based on Multi User MEMS Process. Simulations were carried out for the heater, microcantilever and the piezoresistor using a commercially available Finite Element Solver. Electro-thermal analysis of the embedded heater showed >75% temperature uniformity on the microcantilever surface. It was observed that the deflection of the microcantilever tend to become nonlinear with load at elevated temperatures. Piezoresistive simulation showed an increase in sensitivity (ΔI/I), with displacement magnitude of the microcantilever. Fabricated microcantilevers showed that the piezoresistor stayed nearly at ambient temperature up to 5 V heater bias.

Investigation on electrical transport properties of CdZnTe pixel detector

Semi-insulating cadmium zinc telluride (CdZnTe or CZT) is an excellent material candidate for fabricating room-temperature nuclear radiation semiconductor detectors due to its high resistivity and good carrier transport behaviors. It is widely used in nuclear security, nuclear medicine, space science, etc. Nevertheless, the traditional CdZnTe planar detector is subjected to the effect of hole trailing on its hole transport characteristic, where its energy resolution and the photoelectric peak efficiency both decrease, and thus deteriorating the detection performance. In order to eliminate the effect of hole capture, the electrode with pixel structure for CdZnTe detector is designed for detecting single carriers that are only electrons. In this paper, a 10 mm10 mm2 mm wafer cut from an In doped Cd0.9Zn0.1Te single crystal, grown by the modified vertical Bridgman method, is employed to fabricate a 44 CdZnTe pixel detector, which is composed of 16 small pixel units with an area of 2 mm2 mm. Each of the pixel units is linked up with ASIC multichannel preamplifier and shaping amplifier by flip chip technology. Finally, the signal is treated by an integrated sensing chip. In the first case, the electrical properties and carrier transport properties of CdZnTe pixel detector are characterized by current-voltage (I-V) measurement via an Agilent 4155C semiconductor parameter analyzer and ray energy spectrum response via a standard Multi Channel Analyzer 6560 spectra measurement system, respectively. In the second case, the differences between CdZnTe planar detector and 44 pixel detector in the detection performance are discussed in detail. The results indicate that the bulk resistivity of CdZnTe pixel detector is determined to be about 1.7310 cm by a linear fit of I-V curve. The maximum leakage current of a single pixel is less than 2.2 nA for a bias voltage of 100 V. Furthermore, the carrier transport behaviors are evaluated with the mobility-lifetime product for electron in CdZnTe detector, which is 5.4110-4 cm2V-1 estimated by ray energy spectroscopy response under various bias voltages from 50 to 300 V at room temperature. The energy resolutions of the two CdZnTe detectors can reflect the ability of them to distinguish different energy gays during operation. The best energy resolution of a single pixel in CdZnTe pixel detector for 241Am@59.5 keV ray increases up to 5.78% under a 300 V bias voltage, whereas that of CdZnTe planar detector is only 6.85% in the same conditions. As a consequence, the detection performance of 44 CdZnTe pixel detector is better than that of the planar detector.

LTR-MDTS structure - a structure for multiple dependent time series prediction

The subject of research presented in this paper is to model a neural network structure and appropriate training algorithm that is most suited for multiple dependent time series prediction / deduction. The basic idea is to take advantage of neural networks in solving the problem of prediction of synchronized basketball referees? movement during a basketball action. Presentation of time series stemming from the aforementioned problem, by using traditional Multilayered Perceptron neural networks (MLP), leads to a sort of paradox of backward time lapse effect that certain input and hidden layers nodes have on output nodes that correspond to previous moments in time. This paper describes conducted research and analysis of different methods of overcoming the presented problem. Presented paper is essentially split into two parts. First part gives insight on efforts that are put into training set configuration on standard Multi Layered Perceptron back propagation neural networks, in order to decrease backwards time lapse effects that certain input and hidden layers nodes have on output nodes. Second part of paper focuses on the results that a new neural network structure called LTR - MDTS provides. Foundation of LTR - MDTS design relies on a foundation on standard MLP neural networks with certain, left-to-right synapse removal to eliminate aforementioned backwards time lapse effect on the output nodes.

Investigation of the Factors Affecting the Academic Resilience of Economically Disadvantaged High School Students

The main aim of this study was to investigate whether certain variables namely school attachment, perceived social support, cognitive flexibility and gender can predict the resilience of senior high school students that are economically disadvantaged. Another aim of the research is to reveal the relation between the level of academic resilience and gender variable. This study also seeks to examine the differences between academically resilient students with different levels of resilience in terms of the stated variables. For these purposes, a quantitative research method, a correlational research model, was used. The participants consisted of 304 senior students enrolled in 18 Anatolian High Schools during the 2014-2015 academic year in the three districts of the Ankara province, Turkey. Data was collected using ‘the Resilience Scale for Adults’, ‘School Attachment Scale for Children and Adolescents’, ‘the Multidimensional Scale of Perceived Social Support’, ‘Cognitive Flexibility Inventory’ and the student information form which was designed by the authors. To analyze the collected data, a Standard Multi Regression Analysis, a Multivariate Analysis of Variance (MANOVA) and a Chi-square Test were employed. The results of the Multi Regression Analysis revealed that cognitive flexibility and perceived social support significantly predicted the level of academic resilience of economically disadvantaged high school students. However, school attachment was not found to be a significant predictor. The three variables given above accounted for approximately 41% of variance in the resilience scores of the participants. Furthermore, the results obtained from MANOVA showed no difference between students with high and low academic resilience in terms of cognitive flexibility, school attachment and perceived social support. Moreover, there was a significant relationship between the two groups in terms of gender according to the results of the Chi-square Test.

Structural Health Monitoring Procedure for Composite Structures through the use of Artificial Neural Networks

In this paper different architectures of Artificial Neural Networks (ANNs) for structural damage detection are studied. The main objective is to investigate an ANN able to detect and localize damage without any prior knowledge on its characteristics so as to serve as a real-time data processor for Structural Health Monitoring (SHM) systems. Two different architectures are studied: the standard feed-forward Multi Layer Perceptron (MLP) and the Radial Basis Function (RBF) ANNs. The training data are given, in terms of a Damage Index ℑD, properly defined using a piezoelectric sensor signal output to obtain suitable information on the damage position and dimensions. The electromechanical response of the assembled structure has been computed by means of a Multidomain Boundary Element code developed in the framework of piezoelectricity. On this basis, the neural networks are then used to recognize the location of the damage and its characteristics and the numerical results highlight the main differences on the performances of the two different ANNs analyzed.

Application of the Boosted MED process for low-grade heat sources — A pilot plant

The Boosted MED technology is a thermal desalination process dedicated to low-grade waste heat sources. By augmenting the standard Multi Effect Distillation (MED) process with an additional Booster Module, the system is capable of further exploiting the heating medium output stream of the basic MED system and boosting the freshwater production of the system in an effective manner.This paper experimentally evaluates the principal design basis of the Boosted MED technology. A state-of-the-art pilot plant consisting of two evaporator modules in a serial connection is used to assess the additional vapour production from the downstream evaporator, which adequately mimics the booster unit, at heat source temperatures of 68°C to 93°C, cooling water temperatures of 20°C to 35°C, and two feedwater salinities.Additional vapour production rates ranging from 33% to 57% at sufficiently high temperatures demonstrate the general viability of the design hypothesis. The stable operation and the very high distillate quality achieved by the pilot plant augur well a favourable system characteristic.The process simulation model developed for designing and optimising Multi Effect Distillation based technologies has been experimentally demonstrated to be consistent with the pilot plant performance.

Compressed Sensing Single–Breath-Hold CMR for Fast Quantification of LV Function, Volumes, and Mass

ObjectivesThe purpose of this study was to compare a novel compressed sensing (CS)–based single–breath-hold multislice magnetic resonance cine technique with the standard multi–breath-hold technique for the assessment of left ventricular (LV) volumes and function. BackgroundCardiac magnetic resonance is generally accepted as the gold standard for LV volume and function assessment. LV function is 1 of the most important cardiac parameters for diagnosis and the monitoring of treatment effects. Recently, CS techniques have emerged as a means to accelerate data acquisition. MethodsThe prototype CS cine sequence acquires 3 long-axis and 4 short-axis cine loops in 1 single breath-hold (temporal/spatial resolution: 30 ms/1.5 × 1.5 mm2; acceleration factor 11.0) to measure left ventricular ejection fraction (LVEFCS) as well as LV volumes and LV mass using LV model–based 4D software. For comparison, a conventional stack of multi–breath-hold cine images was acquired (temporal/spatial resolution 40 ms/1.2 × 1.6 mm2). As a reference for the left ventricular stroke volume (LVSV), aortic flow was measured by phase-contrast acquisition. ResultsIn 94% of the 33 participants (12 volunteers: mean age 33 ± 7 years; 21 patients: mean age 63 ± 13 years with different LV pathologies), the image quality of the CS acquisitions was excellent. LVEFCS and LVEFstandard were similar (48.5 ± 15.9% vs. 49.8 ± 15.8%; p = 0.11; r = 0.96; slope 0.97; p < 0.00001). Agreement of LVSVCS with aortic flow was superior to that of LVSVstandard (overestimation vs. aortic flow: 5.6 ± 6.5 ml vs. 16.2 ± 11.7 ml, respectively; p = 0.012) with less variability (r = 0.91; p < 0.00001 for the CS technique vs. r = 0.71; p < 0.01 for the standard technique). The intraobserver and interobserver agreement for all CS parameters was good (slopes 0.93 to 1.06; r = 0.90 to 0.99). ConclusionsThe results demonstrated the feasibility of applying the CS strategy to evaluate LV function and volumes with high accuracy in patients. The single–breath-hold CS strategy has the potential to replace the multi–breath-hold standard cardiac magnetic resonance technique.

A straightforward experimental method to evaluate the Lamb–Mössbauer factor of a 57Co/Rh source

In analyzing Mössbauer spectra by means of the integral transmission function, a correct evaluation of the recoilless fs factor of the source at the position of the sample is needed. A novel method to evaluate fs for a 57Co source is proposed. The method uses the standard transmission experimental set up and it does not need further measurements but the ones that are mandatory in order to center the Mössbauer line and to calibrate the Mössbauer transducer. Firstly, the background counts are evaluated by collecting a standard Multi Channel Scaling (MCS) spectrum of a tick metal iron foil absorber and two Pulse Height Analysis (PHA) spectra with the same life-time and setting the maximum velocity of the transducer at the same value of the MCS spectrum. Secondly, fs is evaluated by fitting the collected MCS spectrum throughout the integral transmission approach. A test of the suitability of the technique is presented, too.

Analysis of Transparent and non-Transparent relay modes in IEEE 802.16j Mobile Multi-Hop relay networks

Two different relay modes are defined in IEEE 802.16j WIMAX standard: transparent mode and non-transparent mode. The non transparent mode is used to extend the coverage area of base stations, where low cost relay station of equal capacity as that of base station is placed at suitable position. Time taken to accept mobile stations and Bandwidth allocation are main problems in non transparent mode. In this we have studied the IEEE 802.16j standard multi hop relay WIMAX networks. We have used relay stations to extend the coverage of base stations. We have also analyzed the throughput between mobile stations with in the coverage area and outside coverage area of base stations. We have simulated the IEEE 802.16j transparent and non transparent mode multi hop WIMAX relay networks using NCTUns Tool.

Right-of-Way Acquisition Duration Prediction Model for Highway Construction Projects

AbstractA key element in moving a highway construction project forward is the ability to acquire the right-of-way (ROW) in a timely manner. Delay in the acquisition process can lead to major delays to the construction phase. Identifying the delay factors will allow for a better acquisition management process. Thirty-five projects, with 1,478 parcels, acquired by the Mississippi Department of Transportation (MDOT) were randomly selected for analysis to determine the factors affecting acquisition duration. The data were analyzed using Statistica7 software with t-test, correlation, scatter plot, and analysis of variance to gain understanding of the dataset; to test the null hypothesis (Ho) that no correlation exists between the control and experimental variables; and to statistically quantify the factors that contribute to acquisition duration delay through significance and standard multi- regression analysis. Condemnation ratio, number of revisions (design changes), and number of parcels per project were id...

Node splitting: A constructive algorithm for feed-forward neural networks

A constructive algorithm is proposed for feed-forward neural networks, which uses node-splitting in the hidden layers to build large networks from smaller ones. The small network forms an approximate model of a set of training data, and the split creates a larger more powerful network which is initialised with the approximate solution already found. The insufficiency of the smaller network in modelling the system which generated the data leads to oscillation in those hidden nodes whose weight vectors cover regions in the input space where more detail is required in the model. These nodes are identified and split in two using principal component analysis, allowing the new nodes to cover the two main modes of each oscillating vector. Nodes are selected for splitting using principal component analysis on the oscillating weight vectors, or by examining the Hessian matrix of second derivatives of the network error with respect to the weights. The second derivative method can also be applied to the input layer, where it provides a useful indication of the relative importances of parameters for the classification task. Node splitting in a standard Multi Layer Perceptron is equivalent to introducing a hinge in the decision boundary to allow more detail to be learned. Initial results were promising, but further evaluation indicates that the long range effects of decision boundaries cause the new nodes to slip back to the old node position, and nothing is gained. This problem does not occur in networks of localised receptive fields such as radial basis functions or gaussian mixtures, where the technique appears to work well.

Support for Data Acquisition and FASTBUS Testing with TRIUMF's IORFI FASTBUS Interface

This paper describes the extensions added to the standard TRIUMF MULTI data acquisition software to support a Fastbus interface. It also describes a menu-driven program for setting-up specific Fastbus modules and a program performing general Fastbus operations.