Computer program for the attenuation of high bypass turbofan engine noise

Two computer programs determine effect of boundary layer on attenuation of sound in a circular duct lined with material used in noise suppresion in fan inlet and exhaust ducts of turbofan engines

Even graphs

A nontrivial connected graph G is called even if for each vertex v of G there is a unique vertex [bar v] such that d(v,[bar v]) = diam G. Special classes of even graphs are defined and compared to each other. In particular, an even graph G is called symmetric if d(u,v) + d(u,[bar v]) = diam G for all u, v V(G). Several properties of even and symmetric even graphs are stated. For an even graph of order n and diameter d other than an even cycle it is shown that n ≥ 3d - 1 and conjectured that n ≥ 4d - 4. This conjecture is proved for symmetric even graphs and it is shown that for each pair of integers n, d with n even, d ≥ 2 and n ≥ 4d - 4 there exists an even graph of order n and diameter d. Several ways of constructing new even graphs from known ones are presented

Label-connected graphs and the gossip problem

A graph with m edges is called label-connected if the edges can be labeled with real numbers in such a way that, for every pair (u, v) of vertices, there is a (u, v)-path with ascending labels. The minimum number of edges of a label-connected graph on n vertices equals the minimum number of calls in the gossip problem for n persons, which is known to be 2n − 4 for n ≥ 4. A polynomial characterization of label-connected graphs with n vertices and 2n − 4 edges is obtained. For a graph G, let θ(G) denote the minimum number of edges that have to be added to E(G) in order to create a graph with two edge-disjoint spanning trees. It is shown that for a graph G to be label-connected, θ(G) ≤ 2 is necessary and θ(G) ≤ 1 is sufficient. For i = 1, 2, the condition θ(G) ≤ i can be checked in polynomial time. Yet recognizing label-connected graphs is an NP-complete problem. This is established by first showing that the following problem is NP-complete: Given a graph G and two vertices u and v of G, does there exist a (u, v)-path P in G such that G−E(P) is connected

Acoustic attenuation design requirements established through EPNL parametric trades

An optimization procedure for the provision of an acoustic lining configuration that is balanced with respect to engine performance losses and lining attenuation characteristics was established using a method which determined acoustic attenuation design requirements through parametric trade studies using the subjective noise unit of effective perceived noise level (EPNL)

Thrombosis in the critically ill neonate: incidence, diagnosis, and management

Among children, newborn infants are most vulnerable to development of thrombosis and serious thromboembolic complications. Amongst newborns, those neonates who are critically ill, both term and preterm, are at greatest risk for developing symptomatic thromboembolic disease. The most important risk factors are inflammation, DIC, impaired liver function, fluctuations in cardiac output, and congenital heart disease, as well as exogenous risk factors such as central venous or arterial catheters. In most clinically symptomatic infants, diagnosis is made by ultrasound, venography, or CT or MRI angiograms. However, clinically asymptomatic vessel thrombosis is sometimes picked up by screening investigations or during routine imaging for other indications. Acute management of thrombosis and thromboembolism comprises a variety of approaches, including simple observation, treatment with unfractionated or low molecular weight heparin, as well as more aggressive interventions such as thrombolytic therapy or catheter-directed revascularization. Long-term follow-up is dependent on the underlying diagnosis. In the majority of infants, stabilization of the patients’ general condition and hemodynamics, which allows removal of indwelling catheters, renders long-term anticoagulation superfluous. Nevertheless, in certain types of congenital heart disease or inherited thrombophilia, long-term prophylaxis may be warranted. This review article focuses on pathophysiology, diagnosis, and acute and long-term management of thrombosis in critically ill term and preterm neonates

Incompressible viscous flow near the leading edge of a flat plate admitting slip

The shear stress at the leading edge, calculated on basis of the Navier-Stokes equations and the no-slip boundary condition, approaches infinity. However, taking into account the mean free path of the molecules, which implies admitting a certain slip, the shear stress becomes inversely proportional to the square root of the Knudsen number κ if κ→0. κ is defined as the ratio between the mean free path and the viscous length. The new boundary condition modifies the shear stress only within the Knudsen region of which the size is of the order of 3 to 4 times the mean free path.

The proof of the pudding is in the eating? Implementation of cooperative learning:Differences in teachers’ attitudes and beliefs

In the current study differences between primary school teachers classified as high-performing in their implementation of cooperative learning (CL) in their classrooms and teachers who were less successful in implementing cooperative learning were investigated. The levels of implementation of cooperative learning differed significantly between teachers, especially in teaching students the needed cooperative behaviours. Based on semi-structured interviews, it was found that low-performing CL teachers struggle more with student behaviour during cooperative learning, while high-performing CL teachers feel more able to regulate student behaviour. We concluded that teachers who differed in their teacher performance of implementation of cooperative learning also differed in their attitudes and beliefs about this approach. An integrated model on professional development and teacher change is proposed to interpret the results of differences between teachers. This model shows that positive attitudes and beliefs before implementation, but also experiencing positive student outcomes (incl. positive student behaviour) during implementation are important factors in making cooperative learning successful in practice. We suggest that teachers should be prevented from entering a negative spiral in which they experience student behaviour during cooperative learning only as difficult and, therefore, do not succeed in improving students’ cognitive and behavioural outcomes