Cerebrovascular transit characteristics of DyDTPA-BMA and GdDTPA-BMA on normal and ischemic cat brain

PURPOSE: To compare the efficacy of two nonionic T2*-shortening contrast agents, DyDTPA-BMA dysprodiamide injection and GdDTPA-BMA gadodiamide injection, as perfusion-sensitive MR imaging agents in normal and acutely ischemic brain. METHODS: The magnetic susceptibility effects of intravenous injections of 0.10-0.50 mmol/kg of each contrast agent were quantified on T2-weighted spin-echo images of cat brain before and after unilateral occlusion of the middle cerebral artery by measuring signal intensity changes in the same regions-of-interest in parietal cortex. RESULTS: In normal brain, DyDTPA-BMA produced a significantly greater loss of signal intensity than equimolar doses of GdDTPA-BMA. The magnitude of the signal intensity attenuation was dosage-dependent and proportional to the square of the magnetic moments of the two contrast agents. Restoration of baseline image signal intensity was observed within 30 min after each injection. However, injection of GdDTPA-BMA also produced a delayed, persistent hyperintensity on T2-weighted images, presumably due to its underlying T1-shortening effect. Following unilateral occlusion of the middle cerebral artery, unenhanced T2-weighted images failed to show evidence of cerebral injury for 1.5-3 hours. Administration of 0.10-1.0 mmol/kg DyDTPA-BMA shortened the time for detection of perfusion deficits (residual hyperintensity) in 22 of 36 (61%) treated cats, often to within 30 min after arterial occlusion. DyDTPA-BMA enhancement also improved lesion conspicuity in 26 of 36 (72%) cases, and disclosed very small infarcts that were not visible on T2-weighted precontrast images. Perfusion deficits in areas of partial ischemia were seen more clearly on DyDTPA-BMA-enhanced images than after equimolar injections of GdDTPA-BMA. CONCLUSIONS: Magnetic susceptibility contrast-enhanced MR imaging enables detection of perfusion deficits associated with acute cerebral ischemia well in advance of conventional T2-weighted spin-echo MR imaging without contrast. DyDTPA-BMA appears to delineate regions of ischemic damage better than GdDTPA-BMA.     

Blind audio watermarking algorithm based on DCT,linear regression and standard deviation

This paper proposes a blind audio watermarking algorithm to embed data and extract them by changing the Discrete Cosine Transform (DCT) coefficients. The key idea is to divide the selected frequency band of DCT into short frames and change the samples of each frame based on the watermark bits that are embedded in. The proposed idea uses linear regression and standard deviation to extract watermark bits. The experimental results show that the method has a high capacity about 3000 bps data payload, without significant perceptual distortion. Moreover, this idea provides robustness against common signal processing attacks such as Additive White Gaussian Noise, Resampling, Re-quantizing and Echo.     

Case Study of Application of FRP Composites in Strengthening the Reinforced Concrete Headstock of a Bridge Structure

Worldwide interest is being generated in the use of fiber-reinforced polymer composites (FRP) in the rehabilitation of aged or damaged reinforced concrete structures. As a replacement for the traditional steel plates or external posttensioning in strengthening applications, various types of FRP plates, with their high strength-to-weight ratio and good resistance to corrosion, represent a class of ideal material in externally retrofitting. This paper describes a solution proposed to strengthen the damaged reinforced concrete headstock of the Tenthill Creeks Bridge, Queensland, Australia, using FRP composites. A decision was made to consider strengthening the headstock using bonded carbon FRP laminates to increase the load carrying capacity of the headstock in shear and bending. The relevant guidelines and design recommendations were compared and adopted in accordance with AS 3600 and Austroads bridge design code to estimate the shear and flexural capacity of a rectangular cracked FRP reinforced concrete section.     

Efficient numerical algorithms for the solution of “good” Boussinesq equation in water wave propagation

This paper proposes three fast and high accuracy numerical methods for solving a nonlinear partial differential equation (PDE) describing water waves and called the Boussinesq (Bq) equation. We numerically solve the Bq equation with fourth-order time-stepping schemes in combination with discrete Fourier transform. We discretize the original PDE with discrete Fourier transform in space and obtain a system of ordinary differential equations (ODEs) which will be solved with fourth-order time-stepping methods. After transforming the equation to a system of ODEs, the linear operator is not diagonal, but we can implement the methods such as diagonal case which reduces the CPU time. Comparing numerical solutions with analytical solutions demonstrates that those methods are accurate and readily implemented. Also we investigate the conservation of mass for Bq equation.     

Robust attitude and vibration control of a nonlinear flexible spacecraft

In this paper, the problem of attitude control of a three dimension nonlinear flexible spacecraft is investigated. Two nonlinear controllers are presented. The first controller is based on dynamic inversion, while the second approach is composed of dynamic inversion and µ‐synthesis schemes. It is assumed that only three torques in three directions on the hub are used. Actuator saturation is also considered in the design of controllers. To evaluate the performance of the proposed controllers, an extensive number of simulations on a nonlinear model of the spacecraft are performed. The performances of the proposed controllers are compared in terms of nominal performance, robustness to uncertainties, vibration suppression of panel, sensitivity to measurement noise, environmental disturbance and nonlinearity in large maneuvers. Simulation results confirm the ability of the proposed controller in tracking the attitude trajectory while suppressing the panel vibration. It is also verified that the perturbations, environment disturbances and measurement errors have only slight effects on the tracking and suppression performances. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

An operational matrix based on Chelyshkov polynomials for solving multi-order fractional differential equations

Recent advancement in learning and teaching methodology experimented with virtual reality (VR)-based presentation form to create immersive learning and training environment. The quality of such educational VR applications not only relies on the virtual model, but the 2D presentation materials such as text, diagrams and figures. However, manual designing or seeking these educational resources is both labor intensive and time-consuming. In this paper, we introduce a new automatic algorithm to detect and extract presentation slides in educational videos, which will provide abundant resources for creating slide-based immersive presentation environment. The proposed approach mainly involves five core components: shot boundary detection, training instances collection, shot classification, slide region detection and slide transition detection. We conducted comparison experiment to evaluate the performance of the proposed method. The results indicate that, in comparison with peer method, the proposed method improves the precision of slide detection from 81.6 to 92.6% and recall from 74.7 to 86.3% on average. With the detected slides, content analyzer can be employed to further extract reusable elements, which can be used for developing VR-based educational applications.

     

Multi‐step solution for QoS management in wireless mesh networks

Wireless mesh networks (WMNs) as community‐ and city‐wide type networks are required to extend their capability to offer real‐time multimedia services. While technologies exist to support quality of service (QoS) at node level, we propose here a network‐wide multi‐step solution to manage and offer QoS across a WMN. From a provider perspective, the provisioning and fulfillment of QoS‐based services fall under the realms of service management, network and traffic engineering functions. We describe the relevant functions required to design, implement and operate a WMN for providing a qualitative QoS to end‐users. Our proposed solution considers network planning aspects, including node placement, node clustering and frequency assignments, route discovery between ingress–egress points and appropriate QoS provisioning across the network. Route‐level QoS provisioning is defined as the process of allocating resources to the nodes along the identified routes to meet a priori known aggregated traffic demands in order to satisfy the QoS requirements for different types of application. Simulation and experimental tests are conducted to validate the correct behavior of processes/algorithms and to access the solution in achieving QoS for aggregate user traffic. Copyright © 2012 John Wiley & Sons, Ltd.     

N-Containing Carbons Derived from Microporous Coordination Polymers for Use in Post-Combustion Flue Gas Capture

Herein, novel carbons that, owing to a high density of micropores (up to 79%) and N-content (up to 14.9%), offering exciting potential for post-combustion CO₂ capture are reported. Given that little is known about how starting materials impact the structure and performance of carbons, three different microporous materials are pyrolyzed. These include a Co-(metal-organic framework) (MOF), a Co-MOF-polymer composite, and a coordination polymer derived from the same monomer and cobalt ions. Notably, the cobalt, which is required to drive the polymerization, is subsequently leached from the carbons via acid for its reuse in MOF synthesis. Next, various metrics including CO₂ capacity, selectivity, isosteric heat of adsorption, breakthrough time and cyclability are assessed. The acid treated carbons adsorb 0.21, 0.99, and 1.11 mmol CO₂ g⁻¹, respectively, (313 K, 0.15 bar) with CO₂/N₂ selectivity ranging from 37 to 52. Due to superior capacity, the polymer-derived carbons also reveal impressive breakthrough times in simulated flue gas mixtures (15% CO₂/85% N₂, 80% RH, 313 K) ranging from 33 to 40 min g⁻¹. Similar performance is also observed under dry conditions and after pre-saturation with water for 1.5 h. Remarkably, no loss in working capacity is observed after 100 CO₂ TSA cycles (313 K/393 K).     

Beamforming and power allocation in the downlink of MIMO cognitive radio systems based on multiobjective optimization

In this paper, power allocation and beamforming are considered in a multiple input multiple output (MIMO) downlink cognitive radio (CR) communication system, which a base station (BS) serves one primary user (PU) and one secondary user (SU). In order to design the CR system, a constrained multiobjective optimization problem is presented. Two objectives are the signal to noise plus interference ratios (SINRs) of PU and SU. Since PU has a spectrum license for data communication, a constraint in the optimization problem is that the SINR of PU must be greater than a predefined threshold based on the PU demand requirement. Another constraint is a limitation on power in BS. By considering the mentioned model, three iterative algorithms are proposed. At each iteration of all algorithms, the receiver beamforming vectors are derived based on the maximization of PU and SU SINRs, by assuming that the allocated powers and BS beamforming vectors are known. Also, power is assigned to users such that the constraint of power limitation is satisfied. The difference between the algorithms is in the obtaining of transmitter beamforming parameters. We evaluate the performance of the proposed algorithms in terms of bit error rate (BER) in simulations. Also, the computational complexity of the proposed algorithms is obtained.     

On the time‐frequency symbol density of FBMC/QAM systems

Filter bank multicarrier (FBMC) systems suffer from an inherent interference, which needs to be eliminated at the detection process. Orthogonal frequency division multiplexing/offset quadrature amplitude modulation (OFDM/OQAM) is a well‐known FBMC system, which transmits real‐valued symbols. In OFDM/OQAM, the time and frequency spacing between adjacent transmitted symbols are organized such that the inherent interference becomes pure imaginary and can be removed by a real‐taking operation. Although OFDM/OQAM provides the maximal bandwidth efficiency, it falls short in handling the spatial multiplexing techniques in multi‐input multi‐output channels. In this regard, those modified FBMC systems, which transmit complex QAM symbols (FBMC/QAM) are used to support the spatial multiplexing techniques. In this article, we present a novel matrix formulation for the FBMC/QAM transmission procedure. On the basis of this presentation, we show that the maximal achievable time‐frequency symbol density of FBMC/QAM, with the ability of perfectly removing the interference, is equal to that of the primer OFDM/OQAM.