A review of metal foam and metal matrix composites for heat exchangers and heat Sinks

Recent advances in manufacturing methods open the possibility for broader use of metal foams and metal matrix composites (MMCs) for heat exchangers, and these materials can have tailored material properties. Metal foams in particular combine a number of interesting properties from a heat exchanger's point of view. In this paper, the material properties of metal foams and MMCs are surveyed, and the current state of the art is reviewed for heat exchanger applications. Four different applications are considered: liquid-liquid, liquid-gas, and gas-gas heat exchangers and heat sinks. Manufacturing and implementation issues are identified and discussed, and it is concluded that these materials hold promise both for heat exchangers and heat sinks, but that some key issues still need to be solved before broad-scale application is possible

Experimental program for real gas flow code validation at NASA Ames Research Center

The experimental program for validating real gas hypersonic flow codes at NASA Ames Rsearch Center is described. Ground-based test facilities used include ballistic ranges, shock tubes and shock tunnels, arc jet facilities and heated-air hypersonic wind tunnels. Also included are large-scale computer systems for kinetic theory simulations and benchmark code solutions. Flight tests consist of the Aeroassist Flight Experiment, the Space Shuttle, Project Fire 2, and planetary probes such as Galileo, Pioneer Venus, and PAET

H\u3csup\u3e-\u3c/sup\u3e and He in a uniform magnetic field: Ground-state wave functions, energies, and binding energies for fields below 10\u3csup\u3e9\u3c/sup\u3e G

Wave functions, energies, and binding energies for the lowest singlet states of H- and He in uniform magnetic fields B\u3c109 G are calculated using an adiabatic approximation in hyperspherical coordinates. In computing the angular part of the wave functions, a coupled expansion in one-electron oblate spheroidal angle functions is used. In addition to contracting the two-electron wave function radially, the magnetic field is found to distort the angular part of the wave function mainly by reducing the ss1S character of the state and replacing it with an sd 1D character. Results for energies and binding energies are comparable with those obtained in variational calculations. In order to compute the binding energies of H- and He we have also calculated the binding energies of the ground states of H and He+ in uniform magnetic fields B\u3c109 G using the adiabatic oblate-spheroidal-coordinate method of Starace and Webster

H\u3csup\u3e-\u3c/sup\u3e and He in a uniform magnetic field: Ground-state wave functions, energies, and binding energies for fields below 10\u3csup\u3e9\u3c/sup\u3e G

Wave functions, energies, and binding energies for the lowest singlet states of H- and He in uniform magnetic fields B\u3c109 G are calculated using an adiabatic approximation in hyperspherical coordinates. In computing the angular part of the wave functions, a coupled expansion in one-electron oblate spheroidal angle functions is used. In addition to contracting the two-electron wave function radially, the magnetic field is found to distort the angular part of the wave function mainly by reducing the ss1S character of the state and replacing it with an sd 1D character. Results for energies and binding energies are comparable with those obtained in variational calculations. In order to compute the binding energies of H- and He we have also calculated the binding energies of the ground states of H and He+ in uniform magnetic fields B\u3c109 G using the adiabatic oblate-spheroidal-coordinate method of Starace and Webster

Fronthaul evolution: From CPRI to Ethernet

It is proposed that using Ethernet in the fronthaul, between base station baseband unit (BBU) pools and remote radio heads (RRHs), can bring a number of advantages, from use of lower-cost equipment, shared use of infrastructure with fixed access networks, to obtaining statistical multiplexing and optimised performance through probe-based monitoring and software-defined networking. However, a number of challenges exist: ultra-high-bit-rate requirements from the transport of increased bandwidth radio streams for multiple antennas in future mobile networks, and low latency and jitter to meet delay requirements and the demands of joint processing. A new fronthaul functional division is proposed which can alleviate the most demanding bit-rate requirements by transport of baseband signals instead of sampled radio waveforms, and enable statistical multiplexing gains. Delay and synchronisation issues remain to be solved

Perceptions of health risk among parents of overweight children: a cross-sectional study within a cohort.

OBJECTIVE: To identify the socio-demographic and behavioural characteristics associated with perceptions of weight-related health risk among the parents of overweight children. METHODS: Baseline data from a cohort of parents of children aged 4-11 years in five areas in England in 2010-2011 were analysed; the sample was restricted to parents of overweight children (body mass index ≥ 91(st) centile of UK 1990 reference; n=579). Associations between respondent characteristics and parental perception of health risk associated with their child's weight were examined using logistic regression analyses. RESULTS: Most parents (79%) did not perceive their child's weight to be a health risk. Perception of a health risk was associated with recognition of the child's overweight status (OR 10.59, 95% CI 5.51 to 20.34), having an obese child (OR 4.21, 95% CI 2.28 to 7.77), and having an older child (OR 2.67, 95% CI 1.32 to 5.41). However, 41% of parents who considered their child to be overweight did not perceive a health risk. CONCLUSIONS: Parents that recognise their child's overweight status, and the parents of obese and older children, are more likely to perceive a risk. However, many parents that acknowledge their child is overweight do not perceive a related health risk