Carpet Plot Research Articles

Quantifying cerebral blood arrival times using hypoxia-mediated arterial BOLD contrast

Cerebral blood arrival and tissue transit times are sensitive measures of the efficiency of tissue perfusion and can provide clinically meaningful information on collateral blood flow status. We exploit the arterial blood oxygen level dependent (BOLD) signal contrast established by precisely decreasing, and then increasing, arterial hemoglobin saturation using respiratory re-oxygenation challenges to quantify arterial blood arrival times throughout the brain. We term this approach the Step Hemoglobin re-Oxygenation Contrast Stimulus (SHOCS). Carpet plot analysis yielded measures of signal onset (blood arrival), global transit time (gTT) and calculations of relative total blood volume. Onset times averaged across 12 healthy subjects were 1.1 ± 0.4 and 1.9 ± 0.6 for cortical gray and deep white matter, respectively. The average whole brain gTT was 4.5 ± 0.9 s. The SHOCS response was 1.7 fold higher in grey versus white matter; in line with known differences in tissue-specific blood volume fraction. SHOCS was also applied in a patient with unilateral carotid artery occlusion revealing ipsilateral prolonged signal onset with normal perfusion in the unaffected hemisphere. We anticipate that SHOCS will further inform on the extent of collateral blood flow in patients with upstream steno-occlusive vascular disease, including those already known to manifest reductions in vasodilatory reserve capacity or vascular steal.

Translaminar mode-I fracture toughness experiment of pultruded GFRP laminates using extended compact tension specimen

This paper conducted experiments and theoretic analysis of the fracture performance of pultruded GFRP (Glass Fiber Reinforced Polymers) laminates. The mode-I fracture toughness of pultruded GFRP laminates was evaluated by the eccentrically loaded, Extended Compact Tension (ECT) specimen. The geometry of specimen and experimental procedure refer to ASTM E1922. A total of 16 specimens were tested, which included 0° and 90° roving orientation. Finite element analysis with the Virtual Crack Closure Technique (VCCT) was implemented to calibrate the experimental results. A correction function for normalized notch length was proposed for pultruded GFRP translaminar fracture toughness. Carpet plot was designed to discuss the relationship between fiber volume ratio and fracture toughness, which demonstrated that the fracture toughness strongly correlated with the fiber volume ratio. Also, the effect of fraction of 0° layers on fracture toughness and material orthotropy was studied. The relationship of material orthotropy parameter and fracture toughness was discussed.

Optimization and Mapping of the Deep Drawing Force Considering Friction Combination

Deep drawing is characterized by extremely complex deformation that is influenced by process characteristics such as die and punch shapes, blank shape, blank holding force, material properties, and lubrication. The optimization of the deep drawing process is a challenging issue due to the complicated functions that define and relate the process parameters. However, the optimization is essential to enhance the productivity and the product cost in the deep drawing process. In this paper, a MATLAB toolbox (Pattern Search) was employed to minimize the maximum deep drawing force (Fd-min) at different values of the operating and the geometrical parameters. As a result, a minimum deep drawing force chart (carpet plot) was generated to show the best combination of friction coefficients at the blank contact interfaces. The extracted friction coefficients guided the selection of proper lubricants while minimizing the deep drawing force. A finite element analysis (FEA) was applied through 3D model to simulate the deep drawing process. The material modeling was implemented utilizing the ABAQUS/EXPLICIT program with plastic anisotropy. The optimization results showed that the deep drawing force and the wrinkling decrease when compared with experimental and numerical results from the literature.

Using carpet plots to analyze transit times of low frequency oscillations in resting state fMRI

A “carpet plot” is a 2-dimensional plot (time vs. voxel) of scaled fMRI voxel intensity values. Low frequency oscillations (LFOs) can be successfully identified from BOLD fMRI and used to study characteristics of neuronal and physiological activity. Here, we evaluate the use of carpet plots paired with a developed slope-detection algorithm as a means to study LFOs in resting state fMRI (rs-fMRI) data with the help of dynamic susceptibility contrast (DSC) MRI data. Carpet plots were constructed by ordering voxels according to signal delay time for each voxel. The slope-detection algorithm was used to identify and calculate propagation times, or “transit times”, of tilted vertical edges across which a sudden signal change was observed. We aim to show that this metric has applications in understanding LFOs in fMRI data, possibly reflecting changes in blood flow speed during the scan, and for evaluating alternative blood-tracking contrast agents such as inhaled CO2. We demonstrate that the propagations of LFOs can be visualized and automatically identified in a carpet plot as tilted lines of sudden intensity change. Resting state carpet plots produce edges with transit times similar to those of DSC carpet plots. Additionally, resting state carpet plots indicate that edge transit times vary at different time points during the scan.

Identifying and removing widespread signal deflections from fMRI data: Rethinking the global signal regression problem

One of the most controversial procedures in the analysis of resting-state functional magnetic resonance imaging (rsfMRI) data is global signal regression (GSR): the removal, via linear regression, of the mean signal averaged over the entire brain. On one hand, the global mean signal contains variance associated with respiratory, scanner-, and motion-related artifacts, and its removal via GSR improves various quality-control metrics, enhances the anatomical specificity of functional-connectivity patterns, and can increase the behavioral variance explained by such patterns. On the other hand, GSR alters the distribution of regional signal correlations in the brain, can induce artifactual anticorrelations, may remove real neural signal, and can distort case-control comparisons of functional-connectivity measures. Global signal fluctuations can be identified visually from a matrix of colour-coded signal intensities, called a carpet plot, in which rows represent voxels and columns represent time. Prior to GSR, large, periodic bands of coherent signal changes that affect most of the brain are often apparent; after GSR, these apparently global changes are greatly diminished. Here, using three independent datasets, we show that reordering carpet plots to emphasize cluster structure in the data reveals a greater diversity of spatially widespread signal deflections (WSDs) than previously thought. Their precise form varies across time and participants, and GSR is only effective in removing specific kinds of WSDs. We present an alternative, iterative correction method called Diffuse Cluster Estimation and Regression (DiCER), that identifies representative signals associated with large clusters of coherent voxels. DiCER is more effective than GSR at removing diverse WSDs as visualized in carpet plots, reduces correlations between functional connectivity and head-motion estimates, reduces inter-individual variability in global correlation structure, and results in comparable or improved identification of canonical functional-connectivity networks. Using task fMRI data across 47 contrasts from 7 tasks in the Human Connectome Project, we also present evidence that DiCER is more successful than GSR in preserving the spatial structure of expected task-related activation patterns. Our findings indicate that care must be exercised when examining WSDs (and their possible removal) in rsfMRI data, and that DiCER is a viable alternative to GSR for removing anatomically widespread and temporally coherent signals. All code for implementing DiCER and replicating our results is available at https://github.com/BMHLab/DiCER.

A comprehensive development methodology for testing and evaluating algorithms for a vehicle suspension control system

Introduction. Full-scale tests remain the most important quality indicator of the developed design solutions. At the same time, high-performance simulation computational systems are becoming more and more relevant, which can significantly reduce field tests of newly developed prototypes of vehicles. The task of building a transparent connection between full-scale and virtual tests is always relevant for a high-quality and effective study of the tested object behavior. This article touches on topical engineering issues in the development of complex assessment techniques for controlled vehicle systems. The purpose of the study was to solve the problem of the cumulative assessment of various control algorithms for the suspension system for solving the integration problem of comparing control algorithms, regardless of their implementation. The results of solving this problem are recommendations for improving the vehicle movement algorithms in various conditions and modes. Methodology and research methods . The article provides a rationale and general description of a comprehensive methodology for a controlled suspension system for a vehicle chassis, a sequence of planning experiments and the analysis of the results achieved. The sequence of construction of the estimated “conflict diagram” (Carpet plot) from the test data is given. The analysis of the results is presented and considered in the diagram as an example. Scientific novelty and results . The approaches outlined in the article were used by the authors at the initial stages of the controlled chassis suspension system development, which made it possible to improve the quality and efficiency of the achieved result in the shortest possible time. The developed and approved comprehensive test method and methods for assessing the controlled chassis suspension system is a scientific novelty, since such methods and approaches have not been used before. Practical signifi cance . The developed complex test methodology and assessment methods are used at FSUE “NAMI” at the initial stages of designing controlled chassis suspension systems.

The impact of inlet flow conditions on the aerodynamic performance of an NACA submerged intake for ground vehicle applications

Results are presented following a series of experimental measurements on a submerged NACA-type intake oriented between −30° and +30° yaw to the free stream in an atmospheric boundary layer wind tunnel at a unit Reynolds number of nominally 1 × 106. The intake was subjected to a range of upstream wall boundary layer conditions, and the mass flow into the intake (as measured by an orifice plate) was monitored to assess the aerodynamic performance. The mass flow data are supported by qualitative flow visualisation within the duct, using a smoke filament illuminated in a laser light sheet in order to gain insight into the flow physics. The intake performance, expressed in terms of a non-dimensional flow momentum coefficient, is seen to degrade both with increasing intake orientation to the free stream (changes of nominally 40% are seen for the angle range tested) and with increasing upstream boundary layer displacement thickness (changes of nominally 30% are seen for the range tested). These data are presented as a graphical carpet plot; it is intended that this is used as a guide to performance prediction in non-aeronautical applications where there are often significant changes in both the local flow direction and the boundary layer thickness. Flow visualisation studies show that the degradation in the intake performance with increasing yaw angle can be attributed to a progressive change in the vortex-pair structure within the intake as the local flow angle is increased. Both an increase in the lateral separation and an increase in the size of the respective vortex cores are considered to act so as to reduce the magnitude of the induced inflow into the intake.

Maximum Local Thermal Effects Carpet Plot for Symmetric Laminated Composite Plates

Maximum local thermal effects carpet plots for symmetric laminated composite plates used in the design and optimization for material under heat loads are produced and demonstrated. The independent variables considered in this paper are the proportions of 0, 45, and 90 degrees ply orientations in the laminates. The carpet plots are presented in such a way that when the failure stress or strain of a composite lamina is known, all possible safe ply orientation proportion can be determined. In addition, the dependency of the carpet plots in correspondence to the temperature change is investigated. It is found that the shapes of both thermal stress and strain plots are practically identical.

Lay-Up Design of Low Wind Speed Composite Turbine Blade

Glass fiber reinforced polymer (GFRP) is a common composite material used for wind turbine blades because of its good strength to weight ratio. This paper describes the design process of GFRP material for a low wind speed (LWS) turbine blade. The wind turbine analyzed in this study is a 3-blades horizontal axis wind turbine (HAWT) with NACA 4415 airfoil and rotor diameter of 5 m. Parameters for the blade are thickness of skin and spar, lamination angle, and stacking sequence of the laminae. The design approach uses Carpet Plot Method based on Tsai-Hill failure criteria. Materials analyzed in this study are unidirectional E-glass fiber/epoxy composite and plain weave woven roving WR200 E-glass fiber/epoxy composite. There are 15 material configurations analyzed using a finite element software. The result shows top five of the composites configuration consisting of minimum 3 plies of 0°/90 direction fiber for the skin and ±45° direction fiber for the spar. The optimum configuration is [(0/90)]3 for the skin and (±45) for the spar both using plain weave woven roving WR200 E-glass fiber/epoxy composite. This configuration has margin of safety of 1.42 based on maximum principal stress and maximum deflection of 346 mm which is 0.14 of the total blade length. The predicted overall weight of the blade is 1.52 kg.

Multidisciplinary aircraft design and evaluation software integrating CAD, analysis, database, and optimization

The development of an overall strategy to design the aircraft using analysis codes is presented. The procedure is automated through the integrated software MADE (multidisciplinary aircraft design and evaluation) developed in this research that enables the determination of an optimum set of aircraft configurations. The core ingredients of MADE are (i) analysis codes, which utilizes initial sizing, aerodynamics, mass, stability and control, propulsion, performance, and RCS (radar cross section) analyses, (ii) optimization utilizing gradient-based optimization technique, response surface modeling, and Carpet plot, (iii) database utilizing commercial Oracle 8i database management system (DBMS) and OCI (Oracle call interface) to save design parameters and aircraft configurations. The complexity of input and output containing massive amounts of data has previously placed severe limitations on the use of aircraft analysis codes by the general aerospace engineering community. By using C++ and the Microsoft Foundation Classes to develop a graphical user interface (GUI) and using DBMS, it is believed that use of MADE can avoid the additional cumbersome, and sometimes tedious, task of preparing the required input files manually and can make the transition to general usability in an aerospace engineering environment. For detail explanation, examples of E–R diagram, class diagram, and data flows between codes for the MADE are also presented.

Development and comparative study on tire models in the AutoDyn7 program

In this paper, several tire models (Magic formula, Carpet plot, UA tire, DADS tire and STI tire) are implemented and compared. Since the STI (System Technology Inc.) tire model in the AutoDyn7 program is in a good agreement to NADSdyna STI tire model and experiment, it is selected as a reference tire model for the comparison. To compare tire models, input parameters of each tire model are extracted from the STI tire model to preserve the same tire properties. Several simulations are carried out to compare performances of tire models, i. e., bump simulation, lane change simulation, and pulse steering simulation. The performances in vehicle maneuverability are also compared with the four parameter evaluation method.

Nano metrology of cylinder bore wear

Cylinder bores are multi-process surfaces whose roughness is difficult to characterise for tribological purposes by conventional methods. Statistical approaches may be used to compute asperity densities, summit curvatures and so on, but suffer from the usual disadvantage of tending to infinite values in the absence of a short-wavelength cutoff. A useful advance in tribological roughness assessment would be to find a means of establishing an appropriate scale of measurement. Using a form of the plasticity index corrected for anisotropy, a short-wavelength limit λ p is derived below which asperities will not take part in long-term tribological interactions. A general relationship is obtained between three dimensionless numbers, the short-wavelength limit λ p normalised by the topothesy Λ, the fractal dimension D and the material ratio (the ratio of the Hertzian elastic modulus E′ to the hardness H). From this relationship, presented as a carpet plot, the appropriate scale of roughness measurement for any tribological investigation of a fractal surface may be determined. With a stylus instrument and an atomic force microscope, a number of cylinder bores were measured at locations of both high and medium wear before and after running in. By inspection of an ensemble of structure functions, it is shown that cylinder bore surfaces are multifractal, with a transition point (the so-called “corner frequency”) at about 20 μn, corresponding to the average size of a honing grit. Below this length the surfaces are self-similar fractals down to the limits of AFM resolution. The short wavelength limit using the above formulation appears to be about 40 nm, weI1 below the range of instruments usually employed to measure tribological surface roughness.

The Selection of Fan Blade Geometry for Optimum Efficiency

A method for selecting C5 circular arc camber aerofoils for optimum efficiency is described. The results for a typical design are presented and compared with the carpet plot method of Hay, Metcalfe and Reizes.