Neville H Fletcher

Size Effect in Heterogeneous Nucleation

Assuming a spherical nucleating particle, the effect of particle size and surface properties upon nucleation efficiency is investigated. A general result is derived which is then applied to the condensation, sublimation, and freezing of water on foreign nuclei. The size effect is found to become important in the range 100–1000 A of particle radius. For particles larger than this, nucleation efficiency is substantially independent of size, while for smaller particles the efficiency is very greatly reduced.

The Chemical Physics of Ice

Preface 1. The water molecule 2. Structure and energy of ordinary ice 3. Other forms of ice 4. Liquid water and freezing 5. Crystal growth 6. Thermal properties and lattice dynamics 7. Point defects 8. Mechanical properties 9. Electrical properties References Subject Index.

The physics of rainclouds

Preface 1. The dynamics of clouds 2. The microphysics of clouds 3. The condensation of water-vapour 4. Condensation nuclei in the atmosphere 5. The microstructure of non-freezing clouds 6. Theory of the development of non-freezing clouds 7. Rain from non-freezing clouds 8. Nucleation of the ice-phase 9. Ice-forming nuclei in the atmosphere 10. The growth of ice-crystals 11. Rain from sub-freezing clouds 12. Artificial modifications of clouds 13. Production and properties of silver iodide nuclei 14. Large-scale rain-making experiments Appendix References and author index Supplementary references Subject index.

Springer Handbook of Acoustics

Acoustics, the science of sound, has developed into a broad interdisciplinary field encompassing the academic disciplines of physics, engineering, psychology, speech, audiology, music, architecture, physiology, neuroscience, and others. The Springer Handbook of Acoustics is an unparalleled modern handbook reflecting this richly interdisciplinary nature edited by one of the acknowledged masters in the field, Thomas Rossing. Researchers and students benefit from the comprehensive contents spanning: animal acoustics including infrasound and ultrasound, environmental noise control, music and human speech and singing, physiological and psychological acoustics, architectural acoustics, physical and engineering acoustics, signal processing, medical acoustics, and ocean acoustics. This handbook reviews the most important areas of acoustics, with emphasis on current research. The authors of the various chapters are all experts in their fields. Each chapter is richly illustrated with figures and tables. The latest research and applications are incorporated throughout, e.g. computer recognition and synthesis of speech, physiological acoustics, psychological acoustics, thermoacoustics, diagnostic imaging and therapeutic applications and acoustical oceanography. With a Foreword by Manfred R. Schroeder

Surface structure of water and ice

Abstract The state of molecular orientation in a pure water surface is examined and it is concluded that the surface molecules are almost completely oriented with their negative vertices outward. Because of inter-molecular bonding this orientation decays approximately exponentially beneath the surface, the depth of orientation being about ten molecular layers. The driving energy for this orientation is supplied by the electrical asymmetry of the water molecule. When the surface of ice is examined it is found that the free energy of the system can be lowered if the ice surface is covered by a thin liquid layer. Molecules in the liquid surface are oriented, and the orientation decays in the depth of the layer. Thermodynamic calculations based on a molecular model suggest that the equilibrium film thickness is finite above a temperature of about −30°C and that the film thickness increases greatly as the melting point is approached. Typical film thicknesses are of the order of tens of Angstroms.

Optimization of energy storage density in ceramic capacitors

A theoretical treatment, based on the Devonshire theory of ferroelectrics, is presented to describe the storage of electrostatic energy in ferroelectric and paraelectric materials at very high field strengths. In all cases, optimal energy density is achieved by using compositions with Curie temperatures well below the operating temperature. The theory is applied to barium - strontium titanate ceramics and optimal compositions are deduced for energy storage at given working fields. The theory is supported by experimental data showing energy densities up to 8 J at 100 kV .

Active Sites and Ice Crystal Nucleation

Abstract The concept of active nucleation sites is examined in the light of standard nucleation theory and it is suggested that these sites are probably small re-entrant corners or jogs in growth steps on the surface of the nucleating particle. The nucleation behavior of a spherical particle with a conical pit on its surface is examined in detail and the activity of a population of particles having a log-normal distribution of such pits is worked out. The parameters involved in the theory can be evaluated within acceptable limits and the resulting curves exhibit the phenomena observed experimentally. Generalized activity curves are given in parametric form for more detailed comparison with experiment.

Autonomous vibration of simple pressure‐controlled valves in gas flows

Pressure‐controlled gas‐flow valves are responsible for sound generation in woodwind and brass instruments, and in the vocalization of many animals. When only a single degree of freedom is allowed for the valve motion, four simple configurations are possible, depending upon the effect upon the valve opening of static overpressures applied at either inlet or outlet ports in the presence of the flow. It is shown that, depending upon the valve configuration, there exist particular ranges of acoustic impedance for the inlet and outlet ducts to the valve within which self‐sustained valve oscillation is possible. The results are particularly simple when the lengths of these ducts are less than one‐quarter of a wavelength at the resonant frequency of the valve, in which circumstance oscillation takes place close to that resonance frequency. The analysis treats only the initiation of oscillations of small amplitude, as a precursor to the maintenance of large‐amplitude nonlinear oscillations.

Some Aspects of the Design of Power Transistors

This paper discusses some factors which have to be taken into account in the design of high power transistors. An effect of great importance is the reduction of emitter bias caused by transverse current flow in the base region. This effect is examined in some detail and the results of the discussion are applied to the design of improved transistor types. Finally, a short discussion of thermal stability and mechanical design is given.

A simple frequency-scaling rule for animal communication

Different animals use widely different frequencies for sound communication, and it is reasonable to assume that evolution has adapted these frequencies to give greatest conspecific communication distance for a given vocal effort. Acoustic analysis shows that the optimal communication frequency is inversely proportional to about the 0.4 power of the animals body mass. Comparison with observational data indicates that this prediction is well supported in practice. For animals of a given class, for example mammals, the maximum communication distance varies about as the 0.6 power of the animals mass. There is, however, a wide spread of observed results because of the different emphasis placed upon vocal effort in the evolution of different animal species.