Numerical investigation of V/STOL jet induced interactions

Direct numerical simulation using the full three dimensional, time dependent Navier-Stokes equations is used to investigate V/STOL jet induced interactions. The objective of this numerical simulation is to compute accurately the details of the flow field and to achieve a better understanding of the physics of the flow, including the role of initial turbulence in the jet, the influence of forward motion on hover aerodynamics, the collision zone and fountain characteristics. Preliminary results are presented

User's manual for an aerodynamic optimization scheeme that updates flow variables and design parameters simultaneously

This user's manual is presented for an aerodynamic optimization program that updates flow variables and design parameters simultaneously. The program was developed for solving constrained optimization problems in which the objective function and the constraint function are dependent on the solution of the nonlinear flow equations. The program was tested by applying it to the problem of optimizing propeller designs. Some reference to this particular application is therefore made in the manual. However, the optimization scheme is suitable for application to general aerodynamic design problems. A description of the approach used in the optimization scheme is first presented, followed by a description of the use of the program

Foreign body inhalation in the pediatric population: Lessons learned from 106 cases

SummaryObjectivesTo review the cases encountered in a tertiary care center so as to assess the incidence of foreign body aspiration in the pediatric population and to draw on our experience to improve prevention and early diagnosis.Patients and methodsRetrospective study of 106 children under the age of 15years, admitted to the Hôtel-Dieu de France hospital for flexible and/or rigid bronchoscopy between November 1998 and January 2010, for suspected foreign body aspiration (FBA).ResultsAmong the children, 56.6% were aged between one and three years. Peanuts or pistachios were found in 48% of cases. In 73% of cases, the FB was bronchial, and slightly more frequently on the right side (60%); 17.8% of cases presented in emergency immediately after inhalation; 12% presented with life-threatening symptoms; 29% presented within 24hours and 49% were seen later than 72hours. In 81% of subjects, a typical penetration syndrome was found on interviewing the parents. Physical pulmonary examination was normal in 21% of patients and chest X-ray in 21.8%. Rigid bronchoscopy was preceded by flexible bronchoscopy in 12% of cases. Parental underestimation of the gravity of the situation was a significant factor in delayed diagnosis. Among the patients, 64% examined 24hours after inhalation were initially treated for another pathology. Delay in diagnosis and organic vs inorganic FB did not significantly correlate with duration of bronchoscopy. The rate of complications did not significantly increase after a 24-hour diagnostic delay threshold.ConclusionFB aspiration is a serious problem. A high index of suspicion is required in health care providers (ENT, pediatricians and family physicians). Physician and especially parental education are the main guarantors of significantly reduced morbidity and mortality in this pathology

Improving the energy efficiency for the WBSN bottleneck zone based on random linear network coding

The reduction of energy consumption and the successful delivery of data are important for the Wireless Body Sensor Network (WBSN). Many studies have been proposed to improve energy efficiency, but most of them have not focussed on the biosensor nodes in the WBSN bottleneck zone. Energy consumption is a critical issue in WBSNs, as the nodes that are placed next to the sink node consume more energy. All biomedical packets are aggregated through these nodes forming a bottleneck zone. This paper proposes a novel mathematical model for body area network (BAN) topology to explain the deployment and connection between biosensor nodes, simple relay nodes, network coding relay nodes and the sink node. Therefore, this paper is dedicated to researching both the energy saving and delivery of data if there is a failure in one of the links of the transmission, which relates to the proposed Random Linear Network Coding (RLNC) model in the WBSN. Using a novel mathematical model for a WBSN, it is apparent that energy consumption is reduced and data delivery achieved with the proposed mechanism. This paper details the stages of the research work

Aerodynamic effects of nearly uniform slipstreams on thin wings in the transonic regime

A simplified model is used to describe the interaction between a propeller slipstream and a wing in the transonic regime. The undisturbed slipstream boundary is assumed to coincide with an infinite circular cylinder. The undisturbed slipstream velocity is rotational and is a function of the radius only. In general, the velocity perturbation caused by introducing a wing into the slipstream is also rotational. By making small disturbance assumptions, however, the perturbation velocity becomes nearly potential, and an approximation for the flow is obtained by solving a potential equation

Energy saving and reliability for Wireless Body Sensor Networks (WBSN)

In healthcare and medical applications, the energy consumption of biosensor nodes affects the collection of biomedical data packets, which are sensed and measured from the human body and then transmitted toward the sink node. Nodes that are near to the sink node consume more energy as all biomedical packets are aggregated through these nodes when communicated to sink node. Each biosensor node in a wireless body sensor networks (WBSNs) such as ECG (Electrocardiogram), should provide accurate biomedical data due to the paramount importance of patient information. We propose a technique to minimise energy consumed by biosensor nodes in the bottleneck zone for WBSNs, which applies the Coordinated Duty Cycle Algorithm (CDCA) to all nodes in the bottleneck zone. Superframe order (SO) selection in CDCA is based on real traffic and the priority of the nodes in the WBSN. Furthermore, we use a special case of network coding, called Random Linear Network coding (RLNC), to encode the biomedical packets to improve reliability through calculating the probability of successful reception (PSR) at the sink node. It can be concluded that CDCA outperforms other algorithms in terms of energy saving as it achieves energy savings for most biosensor nodes in WBSNs. RLNC employs relay nodes to achieve the required level of reliability in WBSNs and to guarantee that the biomedical data is delivered correctly to the sink nod

Tracking Performance of Online Stochastic Learners

The utilization of online stochastic algorithms is popular in large-scale learning settings due to their ability to compute updates on the fly, without the need to store and process data in large batches. When a constant step-size is used, these algorithms also have the ability to adapt to drifts in problem parameters, such as data or model properties, and track the optimal solution with reasonable accuracy. Building on analogies with the study of adaptive filters, we establish a link between steady-state performance derived under stationarity assumptions and the tracking performance of online learners under random walk models. The link allows us to infer the tracking performance from steady-state expressions directly and almost by inspection