Empirical expression for base transit time in bipolar transistors

A new and compact formula for the base transit time, τ _b , of a modern high speed npn bipolar transistor with exponential base doping profile is derived considering doping dependence of mobility, bandgap narrowing effect, high injection effect and carrier velocity saturation at the base edge of the collector–base junction. The collector current density, J _c , and minority carrier stored charge, Q _b , in the base are separately expressed as a function of the injected electron density n _o in the base in order to find an empirical expression for τ _b . The modelling of J _c , Q _b and τ _b is essential for the design of high-speed bipolar transistor. The expressions are applicable for arbitrary injection before the onset of the Kirk effect and they are simple and straight forward to give insight into device operation. The base transit time calculated analytically is compared with simulation results in order to demonstrate the validity of the assumptions made in deriving the expression. The closed form expressions for collector current density and base transit time offer a physical insight into device operation and are a useful tool in device design and optimization.     

Thermoelectric Generators Using p-Pb0.925Yb0.075Te:Teand n-Pb0.925Yb0.075Se0.2Te0.8 Thin Films Preparedby the Thermal Evaporation Method

In this study, p-Pb_0.925Yb_0.075Te:Te and n-Pb_0.925Yb_0.075Se_0.2Te_0.8 ingots were used in a standard solid-state microwave synthesis route for fabricating thermally evaporated thin films. The nanostructure and composition of the films were studied through x-ray diffraction, field-emission scanning electron microscopy, and energy-dispersive x-ray spectroscopy. Measurements of the Seebeck coefficient and electrical conductivity were performed at 298 K to 523 K. The microthermoelectric devices were composed of 20 pairs and 10 pairs of p-Pb_0.925Yb_0.075Te:Te and n-Pb_0.925Yb_0.075Se_0.2Te_0.8 thin films on glass substrates, respectively. The 20-pair p–n thermocouples in series generated a maximum output open-circuit voltage of 275.3 mV and a maximum output power of 54.37 nW at a temperature difference ΔT = 162 K, and 109.4 mV and 16.68 nW at ΔT = 162 K for 10 pairs, respectively.     

A novel approach for measuring hyperspectral similarity

Hyperspectral measures are used to capture the degree of similarity between two spectra. Spectral angle mapper (SAM) is an example of such measures. SAM similarity values range from 0 to 1. These values do not indicate whether the two spectra are similar or not. A static similarity threshold is imposed to recognize similar and dissimilar spectra. Adjusting such threshold is a troublesome process. To overcome this problem, the proposed approach aims to develop learnable hyperspectral measures. This is done through using hyperspectral measures values as similarity patterns and employing a classifier. The classifier acts as an adaptive similarity threshold. The derived similarity patterns are flexible, as they are able to capture the specific notion of similarity that is appropriate for each spectral region. Two similarity patterns are proposed. The first pattern is the cosine similarity vector for the second spectral derivative pair. The second pattern is a composite vector of different similarity measures values. The proposed approach is applied on full hyperspectral space and subspaces. Experiments were conducted on a challenging benchmark dataset. Experimental results showed that, classifications based on second patterns were far better than first patterns. This is because first patterns were concerned only with the geometrical features of the spectral signatures, while second patterns combined various discriminatory features such as: orthogonal projections information, correlation coefficients, and probability distributions produced by the spectral signatures. The proposed approach results are statistically significant. This implies that using simple learnable measures outperforms complex and manually tuned techniques used in classification.     

Real-time occlusion tolerant detection of illegally parked vehicles

Illegally parked vehicle detection systems are considered crucial elements in the development of any video-surveillance based traffic-management system. The major challenges in this task lie in making the end solution real time, illumination invariant and occlusion tolerant. A two-stage application framework is presented which efficiently identifies vehicles parked illegally in restricted parking-zones. A real-time approach has been followed and an improved foreground segmentation method based on Segmentation History Images (SHI) is developed to identify stationary objects. A three step pixel based classification method is applied on the background segmentation output to segment adjacent moving pixels that become stationary for certain periods of time. The process then locks on to all identified stationary pixel patches, parts of which overlap with the regions of interest marked interactively a priori. The second stage of the process is applied subsequently to track all the stationary pixel patches detected during the first stage using an adaptive edge orientation based tracking method. Experimental results show that the tracking technique gives more than a 90% detection success rate, even if objects are partially occluded. The technique has been tested on the UK Home Office i-LIDS Parked Vehicle video sequences along with the University of Sussex Traffic Dataset and results are compared with other available state of the art methods.     

The Good,the Bad,and the Ugly Face Challenge Problem

The Good, the Bad, and the Ugly Face Challenge Problem was created to encourage the development of algorithms that are robust to recognition across changes that occur in still frontal faces. The Good, the Bad, and the Ugly consists of three partitions. The Good partition contains pairs of images that are considered easy to recognize. The base verification rate (VR) is 0.98 at a false accept rate (FAR) of 0.001. The Bad partition contains pairs of images of average difficulty to recognize. For the Bad partition, the VR is 0.80 at a FAR of 0.001. The Ugly partition contains pairs of images considered difficult to recognize, with a VR of 0.15 at a FAR of 0.001. The base performance is from fusing the output of three of the top performers in the FRVT 2006. The design of the Good, the Bad, and the Ugly controls for posevariation, subject aging, and subject “recognizability.” Subject recognizability is controlled by having the same number of images of each subject in every partition. This implies that the differences in performance among the partitions are a result of how a face is presented in each image.     

Efficient accurate syntactic direct translation models: one tree at a time

A challenging aspect of Statistical Machine Translation from Arabic to English lies in bringing the Arabic source morpho-syntax to bear on the lexical as well as word-order choices of the English target string. In this article, we extend the feature-rich discriminative Direct Translation Model 2 (DTM2) with a novel linear-time parsing algorithm based on an eager, incremental interpretation of Combinatory Categorial Grammar. This way we can reap the benefits of a target syntactic enhancement that leads to more grammatical output while also enabling dynamic decoding without the risk of blowing up decoding space and time requirements. Our model defines a mix of model parameters, some of which involve DTM2 source morpho-syntactic features, and others are novel target side syntactic features. Alongside translation features extracted from the derived parse tree, we explore syntactic features extracted from the incremental derivation process. Our empirical experiments show that our model significantly outperforms the state-of-the-art DTM2 system.     

Acute hemodialysis complications in end‐stage renal disease patients: The burden and implications for the under‐resourced Sub‐Saharan African health systems

Little is known about the challenges of routine renal replacement therapy in Sub‐Saharan Africa. We investigated the fatal and nonfatal acute hemodialysis (HD) complications in patients with end‐stage renal disease (ESRD) in two main dialysis centers in Cameroon. 1000 consecutive HD sessions incurred over a 4‐month period by 129 patients (96 men, 74%) with ESRD, receiving two weekly HD sessions of 4 hours each, were considered. Personal and clinical profiles before, during, and within 24 hours after HD sessions were used to diagnose complications. Participants were aged 7 to 80 years (mean 46 years). In all, 452 acute complications were recorded in 411 (41%) of the 1000 HD sessions. Of the 11 types of complications, hypotension (25%), muscular cramps (22%), hypertensive crisis (14%), pruritus (10%), and fever (7%) were the most frequent. Three hundred and six complications (67.7%) occurred during understaffed nighttime. The vascular access was the main bleeding site with 64%. Being diabetic and ultrafiltration rate >1000 mL/h were associated with hypotension and muscle cramps. The shorter duration in dialysis was associated with the risk of bleeding and the disequilibrium syndrome while longer duration was associated with muscle cramps. Four deaths (three from bleeding and one from disequilibrium syndrome) occurred, all during nighttime. Nearly half of dialysis sessions in these settings are associated with acute complications, some of which are fatal. Those complications occurred mostly during understaffed periods. Urgent strategies are needed to quickly solve the human capital crisis in the health care sector.     

The effect of short duration NaCl exposure on the surface pore structure of concrete containing GGBFS

The purpose of this study is to evaluate the effect of chloride-binder interactions on the physical pore structure of concrete containing 0?C60% ground granulated blast furnace slag (GGBFS) as cement replacement. Physical and chemical chloride binder interaction was measured based on chloride binder isotherms. Physical chloride binder interaction was estimated to be the difference between the total binding capacity and chemically bound chloride. In this study it was assumed that the chemical binding is the binding capacity of the alumina phases which was estimated, using differential scanning calorimetry, as the area under the Friedel??s salt peaks. The assumption that chemical binding capacity is controlled by alumina phases is supported by multiple linear regression analysis that was conducted to assess the relationship between Fruendlich isotherm constants and the concrete??s chemical composition. To determine the effect physical and/or chemical chloride-binder interaction on the physical microstructure, paste samples were exposed to distilled water and 0.5?M NaCl solution for 6?h, and the total porosity and pore size distribution was evaluated using mercury intrusion porosimetry. Three key findings from this study are: (i) At a chloride concentration up to 0.5?M, and for mixtures containing 0 and 40% GGBFS the contribution of physically and chemically bound chloride are similar. (ii) At chloride concentrations greater than 0.5?M and less than 1?M, the total bound chloride is predominantly chemically bound for the 40% GGBFS mixture. (iii) Concrete specimens exposed to NaCl solution for 6?h exhibited different pore characteristics in comparison to concrete exposed to distilled water. The differences in the concrete microstructure are not linearly dependant on GGBFS content, but are found to be mutually influenced by the total bound chloride content, the percentage of chemically bound chlorides, and the pore size distribution of the mixture.     

A-Eye: Automating the role of the third umpire in the game of cricket

Cricket is a sport that involves two teams, say Team A and Team B, and two field umpires. Initially, Team A bats to score some runs, while Team B balls. Then, Team A balls and Team B bats to overcome the score of Team A. If this happens, then Team B wins. Otherwise, Team A wins. The balling team can dismiss a batsman from scoring through a Run-Out, i.e., the batsman fails to enter an area before three stumps are dislodged in that area. In this case, a third umpire makes the ‘Run-Out/Not-Out’ decision through video technology. This process can consume around one minute which disrupts the pace of the game. In this paper, we propose and validate a novel technology called A-Eye, which automates the role of the third umpire. By applying A-Eye to a set of autonomously-filmed Run-Out videos, we show that it is efficient as compared to the third umpire, and almost as accurate. Also, it can be used to estimate a rating for the field umpires. These results have been recognized internationally, and have convinced our local cricket council to employ A-Eye within a professional cricket tournament.     

A Chaotic Interleaving Scheme for the Continuous Phase Modulation Based Single-Carrier Frequency-Domain Equalization System

In this paper, we propose a chaotic interleaving scheme for the continuous phase modulation based single-carrier frequency-domain equalization (CPM-SC-FDE) system. Chaotic interleaving is used in this scheme to generate permuted versions from the sample sequences to be transmitted, with low correlation among their samples, and hence a better bit error rate (BER) performance can be obtained. The proposed CPM-SC-FDE system with chaotic interleaving combines the advantages of the frequency diversity, the low complexity, and the high power efficiency of the CPM-SC-FDE system and the performance improvements due to chaotic interleaving. The BER performance of the CPM-SC-FDE system with and without chaotic interleaving is evaluated by computer simulations. Also, a comparison between the proposed chaotic interleaving and the conventional block interleaving is performed. Simulation results show that, the proposed chaotic interleaving scheme can greatly improve the performance of the CPM-SC-FDE system. Furthermore, the results show that this scheme outperforms the conventional block interleaving scheme in the CPM-SC-FDE system. The results also show that, the proposed CPM-SC-FDE system with chaotic interleaving provides a good trade-off between system performance and bandwidth efficiency.