Neighborhood Assistance Corporation of America

About: Neighborhood Assistance Corporation of America is a based out in . It is known for research contribution in the topics: Boundary layer & Supersonic speed. The organization has 153 authors who have published 144 publications receiving 3468 citations.

Current status of farming practices of striped catfish, Pangasianodon hypophthalmus in the Mekong Delta, Vietnam

Abstract: article i nfo Aquaculture of catfish, Pangasianodon hypophthalmus (Sauvage), locally known as "ca tra", and commonly referred to as striped catfish, river catfish and sutchi catfish, in Vietnam, having recorded a production of 683,000 tonnes in 2007, valued at about 645 million US$ is one of the largest single species based farming system, restricted to a small geographical area, in the world. The product is almost totally exported to over 100 countries as frozen fillets, as an acceptable alternative to white fish. Catfish is farmed mostly in earthen ponds, up to 4 m deep, in nine provinces in the Mekong Delta in South Vietnam. The results of the grow-out system of catfish farming in the Mekong Delta from a survey of 89 farms are presented. The farm size ranged from 0.2 to 30 ha with a mean of 4.09 ha. The frequency distribution of the yield in tonne/ha/crop and tonne/ ML/crop corresponded to a normal distribution curve, where 75% of the farms yielded 300 tonnes/ha/crop or more. It was found that the yield per crop was significantly correlated (p<0.05) to stocking density, pond depth and volume but not to pond surface area. Yields per crop was significantly different (p<0.05) between upper and lower provinces of the Mekong Delta and water source (river versus channels), amongst others. It was evident that diseases and/or symptoms were observed to occur mostly in accordance with the onset of rains. In this paper the history of the catfish farming in the Mekong Delta is briefly traced, and current harvesting and marketing procedures as well as pertinent social elements of the farming community are dealt with.

Effect of Leading-Edge Separation on the Lift of a Delta Wing

Abstract: There are a large class of important fluid flows which involve the effects of fluid viscosity and yet do not constitute flows having restrictive amounts of viscous dissipation. Examples of such flows are the flow over slender bodies in which vortex shedding occurs, swept wings having separated leading edges and-so forth. The important feature of these flows is the production of free vortex sheets in which large dissipation ultimately occurs but only at great distances downstream of the generating body; hence, these flow fields may be approximated by potential flow solutions. The present paper presents an application of this technique to slender triangular wings having leading edge separation. Curves are presented showing the lift versus angle of attack, pressure distributions, and integrated span loadings. I t is shown that leading edge separation leads to nonlinear lift curves with lift greater than that obtained from potential flow theory. Comparison of lift curve with experiment is made.

An Investigation of Effects of Certain Types of Structural NonHnearities on Wing and Control Surface Flutter

Abstract: This paper presents some effects of nonlinear structural terms on the flutter of a wing capable of bending and twisting and, also, of a system including a control surface. Several type , of nonlinearities in the stiffness are investigated, including free play, a hysteresis loop, and cubic variations. These are introduced in the torsional degree of freedom of the wing and in the aileron stiffness in the three degree of freedom system. Calculations have been made on an analog computer. A wind-tunnel investigation of one case having free play in the torsional degree of freedom has been made, and good correlation between theory and experiment is shown. The results indicate that the stability of a nonlinear system is highly dependent on the magnitude of initial displacements of the system from equilibrium. I t is shown that in many cases the flutter speed is decreased by increasing the initial disturbance. The results also indicate that when a nonlinear system becomes unstable its flutter may become self-limited.

Steady laminar heat transfer in a circular tube with prescribed wall heat flux

Abstract: An analysis is performed to determine the heat transfer characteristics for a laminar forced convection flow in a circular tube with prescribed wall heat flux. Results are first obtained for the case of uniform heat flux, and these are then generalized to apply to the situation of arbitrary longitudinal variation of wall heat flux. The solution contains a series expansion whose form is similar to that obtained by Graetz for the uniform wall temperature problem.

On Reducing Aerodynamic Heat-Transfer Rates by Magnetohydrodynamic Techniques

Abstract: The possibility of reducing stagnation point heat-transfer rates on blunt bodies at hypersonic speeds by means of a magnetic field is considered. The modification of the flow within and external to the viscous boundary layer is analyzed. It is concluded that the primary mechanism which serves to reduce the heat transfer is an alteration of the inviscid flow external to the boundary layer. The existence of a magnetic-fluid boundary layer is indicated for fluids of high electrical conductivit}^ This magnetic boundary layer is seen to parallel viscous boundary-layer theory closely. On the basis of a cursory examination it does not seem practicable to reduce significantly the aerodynamic heating load on flat plates by magnetic techniques unless the electrical conductivity of air is artificially enhanced.