This work presents a new technique based on Walsh Hadamard Transform (WHT) to improve the robustness of the space-frequency block coded orthogonal frequency division multiplexing (SFBCOFDM) systems. Simulation results proved that the proposed system enhance the OFDM system performance in static and time varying channel models compared to conventional SFBC, space time block coded (STBC) in time varying channels. In addition, the performance of the proposed system was compared with other precoded SFBC-OFDM systems.
In this paper, we study cooperative spectrum sensing over composite fading channels. First, we consider the Mixture of Gaussian distribution to model the composite channel statistics and derive a simple generic approximation for the average probability of detection which can be efficiently applied to any composite fading channel. Second, we derive the optimal voting rule for hard combining in cooperative spectrum sensing over composite fading channels. In particular, we derive an exact closed form expression for the optimal decision fusion rule (k-out- of-N) that minimizes the total sensing error in cognitive radio networks.
Differential distributed space-time coding has been proposed for wireless relay network. It provides spatial diversity without channel state information (CSI) at the transmitter or receiver side. Differential detection for vehicle-to-vehicle (V2V) has been studied in the literature for single Rayleigh channel. However, experimental and theoretical studies have reports that double Rayleigh channel considered as an appropriate fading model for V2V network. This paper investigates the BER performance of a distributed differential space-time coding for V2V network. Simulation results show that the bit error rate (BER) performance degrades severely in fast-fading channel.
Atherosclerosis is one of the cardiovascular diseases that has become dramatically prevalent and contributed to an increase in morbidity rates globally. It is defined as an inflammatory health condition characterized by accumulation of plaque inside the blood vessels, decreasing blood flow and leading to stroke or myocardial infarction in severe cases. Atherosclerosis involves a highly regulated and sophisticated network of interactions between the endothelium, inflammatory cells through cytokines which are the signaling factors that initiate the events. In this short review, light is shed on few recent studies that investigated the disease through in vitro models, and their results are summarized here.
Interstitial fluid flow, represented by the movement of fluid through the extra cellular matrix or more precisely between blood and lymphatic vessels, is considered to be one of the main factors that influences morphology and migration of tumor cells in addition to leukocytes, endothelial cells, fibroblasts mesenchymal cells and other types. Understanding the cellular migration phenomena and how it relates to tumor development, invasion and metastasis will lead to major development in cancer treatments (1). Thus, many researches have been conducted in order to come up with mathematical models, microfluidic-based in-vitro assays and devices that can better quantify and control the tumor micro-environmental factors (2; 3). These studies also helped in understanding the biochemical, physical and mechanical environment of the tumor which provided them with major advancement in drug delivery techniques. This short review will cover different methods used by various labs across the world to understand the relationship.
The generation of a functional bioengineered blood vessel requires the application of appropriate biomechanical/biochemical signals, a suitable cell source, and a biomaterial scaffold template for tissue maturation. We have shown that elastin addition to 3D collagen scaffold sheets can play a major role in the scaffold biological and mechanical response. In particular, elastin addition resulted in a more native viscoelastic response and also earlier gene expression of mid/late stage smooth muscle cell contractile proteins, which are necessary to achieve vasoactivity. This biomimetic biomaterial was subsequently fabricated into a physiologically relevant bilayered tubular structure consisting of an inner dense film layer for endothelium development, and a porous outer layer for medial layer development. Following 21 days culture the construct was remodelled into a dense, organised tissue resulting in mechanically robust bioengineered vessels capable of sustained mechanical conditioning in a custom designed bioreactor.
Radiation safety for pediatric of different age groups is extremely important because of the higher radiation risks associated with radiation exposure in children compared to adults. This chest examination study was performed on phantoms to measure the incident air kerma (Ki). Entrance skin dose (ESD), Ke, was determined indirectly via tube output measurements and from knowledge of X-ray exposure factors. The effective dose (ED) was estimated using Monte Carlo dose calculation software. Five pediatric patient age groups were chosen as: newborn, 0-<1, 1-<5y, 5-<10y, 10-<15y The ESD results for these age groups were 37.53, 37.56, 43.01, 57.3 and 61.81 ?Gy, respectively, and the ED were 18.71, 12.89, 14.96, 19.44 and 25.55 ?Sv, respectively. Our Results were lower than other published data and the higher ED was for the patient of age group 10-<15y.
This study attempts to estimating the U-turn and Left-turn adjustment factors at selected signalized intersections in Doha, as well as measuring the base saturation flow rate. It also compares the results with the Highway Capacity Manual and previous studies. To estimate the base saturation flow rate for Doha, 86 queues for the through lane were used. The results found the base saturation flow rate to be 2,323 pc/h/ln. To develop the left-turn adjustment factor, 88 queues were used. The left-turn adjustment factor was found to be 0.947, which is similar to the 0.95 value suggested by the HCM. To measure the U-turn adjustment factor, 198 queues were used to develop a regression model with the headway as the dependent variable and the U-turn percentage as the independent variable. The results show the U-turn adjustment factor ranges from 0.76 for 100% of U-turn traffic to 0.95 for 10% of U-turn traffic.
Strengthening of reinforced concrete (RC) structures is frequently required due to poor structural design, changes in structural loading and/or corrosion of steel reinforcement. Since the late 1980s, externally-bonded fiber-reinforced polymer (EB-FRP) composites have been used successfully in strengthening of RC structures. The EB-FRP system exhibits some undesirable properties such as incompatibility of the epoxy adhesive with concrete and poor performance at high temperatures. An alternative composite strengthening system known as textile-reinforced mortar (TRM) has emerged recently and is being proven to provide a comparable increase in structural capacity as that of the FRPs, while circumventing the problems associated with FRPs. This study investigates the effectiveness of using TRM composites in shear strengthening of RC beams. The influence of amount of internal stirrups and external TRM layers on shear response has been investigated. The performance of the TRM-strengthened specimens is also compared with that of specimens strengthened with textilereinforced polymer (TRP).
Flexural deficiency could happen in reinforced concrete (RC) floor slabs due to an error in design, omission of steel during construction, or other construction defects. Such deficiencies would compromise the serviceability and flexural capacity of RC slabs. This paper examines the effectiveness of using near surface mounted (NSM) carbon fiber-reinforced polymer (CFRP) composites to improve the flexural response of deficient continuous RC slab strips. The deficiency location and amount of NSM-CFRP reinforcement were the test parameters in six two-span continuous RC specimens. The enhancement in load capacity caused by strengthening was in the range of 29% to 45% for the specimens having a deficiency in the sagging region, and 14% to 29% for the specimens with a deficiency in the hogging region. The ductility of the strengthened specimens decreased with an increase in the amount of NSM-CFRP strips.
