Recognition of Complex Settings by Aggregating Atomic Scenes

This approach imitates human reasoning to enable flexible context recognition. Its usefulness is demonstrated by employing audio-signal processing to recognize several everyday situations.     

Performance analysis of a threshold-based discrete-time queue using maximum entropy

The provision of guaranteed QoS for various Internet traffic types has become a challenging problem for researchers. New Internet applications, mostly multimedia-based, require differentiated treatments under certain QoS constraints. Due to a rapid increase in these new services, Internet routers are facing serious traffic congestion problems. This paper presents an approximate analytical performance model in a discrete-time queue, based on closed form expressions using queue threshold, to control the congestion caused by the bursty Internet traffic. The methodology of maximum entropy (ME) has been used to characterize closed form expressions for the state and blocking probabilities. A discrete-time GGeo/GGeo/1/{N₁, N₂} censored queue with finite capacity, N₂, external compound Bernoulli traffic process and generalised geometric transmission times under a first come first serve (FCFS) rule and arrival first (AF) buffer management policy has been used for the solution process. To satisfy the low delay along with high throughput, a threshold, N₁, has been incorporated to slow the arrival process from mean arrival rate λ₁ to λ₂ once the instantaneous queue length has been reached, otherwise the source operates normally. This creates an implicit feedback from the queue to the arrival process. The system can be potentially used as a model for congestion control based on the Random Early Detection (RED) mechanism. Typical numerical experiments have been included to show the credibility of ME solution against simulation for various performance measures and to demonstrate the performance evaluation of the proposed analytical model.     

Stability and performance analysis of randomly deployed wireless networks

A growing demand for mobile services is taking the deployment of wireless local area networks away from the notion of carefully planned and carefully managed settings into randomly deployed and independently managed (if at all) network settings. This results in contentious networks that serve highly mobile nodes. In fact, research reveals that in most metropolitan cities in Europe and the US the size of closely located and contentious access points is overwhelmingly high (in the order of thousands). Subsequently, the performance of these networks is often unstable and unpredictable. This paper aims to investigate the extent of performance fluctuations in randomly deployed networks. It also aims to investigate the contribution of various adaptation strategies at different abstraction layers to deal with these fluctuations. We present the outcome of an exhaustive simulation for different applications, including VoIP, HTTP, and FTP. We will demonstrate that collision due to hidden-terminals is a minor influence on the performance and stability of these networks, whereas dynamic channel allocation greatly affects them. Moreover, HTTP applications are less affected by both inter- and intra-channel interferences compared with FTP and VoIP applications.     

Symptomatic and asymptomatic left-ventricular systolic dysfunction in an urban population

BACKGROUND: In most previous epidemiological studies on the prevalence of chronic heart failure (CHF) the disorder has been defined on clinical criteria. In a cross-sectional survey of 2000 men and women aged 25-74, randomly sampled from one geographical area, we assessed left-ventricular systolic function by echocardiography. METHODS: 1640 (83%) of those invited took part. They completed a questionnaire on current medication, history, and symptoms of breathlessness. Blood pressure was measured and electrocardiography (ECG) and echocardiography were done. Left-ventricular ejection fraction was measurable in 1467 (89.5%) participants by the biplane Simpson's rate method. FINDINGS: The mean left-ventricular ejection fraction was 47.3%. The prevalence of definite left-ventricular systolic dysfunction (defined as a left-ventricular ejection fraction < or = 30%) was 2.9% overall (43 participants); it increased with age and was higher in men than in women (4.0 vs 2.0%). The left-ventricular systolic dysfunction was symptomatic in 1.5% of participants and asymptomatic in 1.4%, 83% of participants with left-ventricular systolic dysfunction had evidence of ischaemic heart disease (IHD) from history or ECG criteria compared with 21% of those without this abnormality (p < 0.001). Hypertension was also more common in those with left-ventricular systolic dysfunction (72 vs 38%, p < 0.001), but there was no difference between those with and without left-ventricular systolic dysfunction in the rate of hypertension without IHD. INTERPRETATION: Left-ventricular systolic dysfunction was at least twice as common as symptomatic heart failure defined by clinical criteria. The main risk factors are IHD and hypertension in the presence of IHD; screening of such high-risk groups for left-ventricular systolic dysfunction should be considered.     

Modelling the energy cost of a fully operational wireless sensor network

Several applications have been proposed for wireless sensor networks, including habitat monitoring, structural health monitoring, pipeline monitoring, precision agriculture, active volcano monitoring, and many more. The energy consumption of these applications is a critical feasibility metric that defines the scope and usefulness of wireless sensor networks. This paper provides a comprehensive energy model for a fully functional wireless sensor network. While the model uses toxic gas detection in oil refineries as an example application, it can easily be generalized. The model provides a sufficient insight about the energy demand of the existing or proposed communication protocols.     

Candoxatril improves exercise capacity in patients with chronic heart failure receiving angiotensin converting enzyme inhibition

AIMS: To assess the effect of candoxatril, a novel neutral endopeptidase inhibitor, on exercise capacity, clinical status and quality of life in patients with mild to moderate chronic heart failure receiving angiotensin converting enzyme inhibition. METHODS AND RESULTS: Patients were recruited from 16 centres throughout the United Kingdom. Following a 4-week single-blind placebo 'run-in' phase of weekly exercise tests, patients underwent double-blind randomization to receive either candoxatril (100 mg twice daily) or placebo for the next 84 days. Patients were then reassessed every 28 days. Of 110 patients randomized, 56 received candoxatril and 54 placebo. Over the study period, the overall improvement in mean total exercise time in the candoxatril group in comparison to the placebo group was 34.1 s (P=0.02: 95% confidence interval: 5.1 to 63.0). There were no significant changes in functional class, clinical status or quality of life scores between the two groups. There was a trend for a small reduction in blood pressure in the candoxatril group. CONCLUSION: Candoxatril confers an improvement in exercise capacity in patients with chronic heart failure who are receiving maintenance angiotensin converting enzyme inhibitor therapy.     

Pre-operative echocardiographic abnormalities and adverse outcome following renal transplantation

BACKGROUND: Premature cardiovascular disease is now the leading cause of death in renal transplant recipients. Although patients with progressive renal disease have many of the conventional risk factors for cardiovascular disease these do not have the same predictive power as they do in the general population. Echocardiographic abnormalities, notably left ventricular hypertrophy, have been shown to be associated with adverse outcome in patients on dialysis. METHODS: The echocardiograms were studied from 141 patients who were examined on the eve of renal transplantation between 1988 and 1990 to try to identify factors predicting outcome. Thirty-four patients have since died, 22 of cardiovascular disease. Ninety-three of the survivors and 27 of the dead patients had echocardiographic traces suitable for analysis. RESULTS: Left ventricular mass index was increased in those patients who died (median 167 vs 134 g/m2; P=0.03), as were end-systolic (4.3 vs 3.4 cm; P<0.01) and end-diastolic (5.8 vs 5.2 cm; P<0.01) diameters. Systolic function was also more severely impaired (fractional shortening, 27 vs 33%; P<0.01). Apart from age, only systolic function and end systolic diameter were independent predictors of outcome in multivariate analysis. CONCLUSIONS: This pattern of echocardiographic abnormality is similar to that reported in long-term dialysis populations, despite the adverse effects on survival. Moreover, despite potential benefits of transplantation on cardiac function, left ventricular hypertrophy, ventricular dilatation and systolic dysfunction were all associated with adverse outcome following transplantation. We conclude that echocardiography identifies markers for premature death following transplantation and provides targets for therapeutic intervention.     

Adaptive Audio-Based Context Recognition

Context recognition is an essential aspect of intelligent systems and environments. In most cases, the recognition of a context of interest cannot be achieved in a single step. Between measuring a physical phenomenon and the estimation or recognition of what this phenomenon represents, there are several intermediate stages which require a significant computation. Understanding the resource requirements of these steps is vital to determine the feasibility of context recognition on a given device. In this paper, we propose an adaptive context-recognition architecture that accommodates uncertain knowledge to deal with sensed data. The architecture consists of an adaptation component that monitors the capability and workload of a device and dynamically adapts recognition accuracy and processing time. The architecture is implemented for an audio-based context recognition. A detail account of the tradeoff between recognition time and recognition accuracy is provided.     

Phase separation-driven stratification in conventional and inverted P3HT:PCBM organic solar cells

We have used neutron reflectivity to investigate the stratification of poly(3-hexylthiophene) (P3HT) and phenyl-C₆₁-butyric acid methyl ester (PCBM) blend films. Films were spun-cast on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and titanium oxide (TiOx) layers to mimic the procedures followed for the fabrication of conventional and inverted organic photovoltaics respectively. The resultant scattering length density profiles reveal a PCBM-rich layer is formed in the vicinity of PEDOT:PSS or TiOx, while PCBM is depleted at the free surface of the film. PCBM segregation close to the substrate is further enhanced by annealing. This stratification is considered to be favorable only for inverted devices.