Static electricity of polymers reduced by treatment with iodine

Treating organic polymers with iodine improves the electrical conductivity. Diffusion enables products of desired properties to be custom formulated. This eliminates a buildup of static electricity and the need for fillers or bound metal salts

Possible mechanism for achieving glass-like thermal conductivities in crystals with off-center atoms

In the filled Ga/Ge clathrate, Eu and Sr are off-center in site 2 but Ba is on-center. All three filler atoms (Ba,Eu,Sr) have low temperature Einstein modes; yet only for the Eu and Sr systems is there a large dip in the thermal conductivity, attributed to the Einstein modes. No dip is observed for Ba. Here we argue that it is the off-center displacement that is crucial for understanding this unexplained difference in behavior. It enhances the coupling between the "rattler" motion and the lattice phonons for the Eu and Sr systems, and turns on/off another scattering mechanism (for 1K < T < 20K) produced by the presence/absence of off-center sites. The random occupation of different off-center sites produces a high density of symmetry-breaking defects which scatters phonons. It may also be important for improving our understanding of other glassy systems.Comment: 4 pages, 1 figure (2 parts) -- v2: intro broadened; strengthened arguments regarding need for additional phonon scattering mechanis

A thermodynamical fiber bundle model for the fracture of disordered materials

We investigate a disordered version of a thermodynamic fiber bundle model proposed by Selinger, Wang, Gelbart, and Ben-Shaul a few years ago. For simple forms of disorder, the model is analytically tractable and displays some new features. At either constant stress or constant strain, there is a non monotonic increase of the fraction of broken fibers as a function of temperature. Moreover, the same values of some macroscopic quantities as stress and strain may correspond to different microscopic cofigurations, which can be essential for determining the thermal activation time of the fracture. We argue that different microscopic states may be characterized by an experimentally accessible analog of the Edwards-Anderson parameter. At zero temperature, we recover the behavior of the irreversible fiber bundle model.Comment: 18 pages, 10 figure

Classical field theory. Advanced mathematical formulation

In contrast with QFT, classical field theory can be formulated in strict mathematical terms of fibre bundles, graded manifolds and jet manifolds. Second Noether theorems provide BRST extension of this classical field theory by means of ghosts and antifields for the purpose of its quantization.Comment: 30 p

IT-technology in the budgeting

Budgeting plays an important role in modern organization, it is the tool that is necessary for the survival of the company in a competitive environment. Budgeting has become necessary business management process, and like any management activities, it requires automation

Stability and mixing of submerged turbulent jets at low Reynolds numbers

Originally presented as the first author's thesis (M.S.), Temperature reduction in a submerged vertical jet in the laminar-turbulent transition, M.I.T. Dept. of Civil EngineeringAn experimental study is made of the variation of volume and centerline dilution as a function of Reynolds number in non- buoyant and buoyant round jets discharged vertically from a submerged nozzle. The jet Reynolds numbers covered the laminar- turbulent transition with values ranging from Re = u D/v = 100 to 20,000 where u = jet exit velocity, D = jet diameter, and V = kinematic viscosity. Measurements of jet temperature profiles are obtained by using both fast and slow thermistor probes. Turbulent dilution is found to be independent of Reynolds number for non-buoyant jets above a critical Reynolds number of about 1,500. For buoyant jets (densimetric Froude numbers in the range 25 to 50), the critical Reynolds number is about 1,200. Reasonable agreement is obtained with the results of previous investigators for dilution values at high Reynolds numbers. Dye studies of transition Reynolds numbers are compared with a study by A.F. Pearce (1966) and good agreement is found. The results are useful in determining the minimum length scale ratio for hydro-thermal model studies, especially those of submerged multiport diffusers. It is concluded that modeling of turbulent jets is acceptable provided the model Reynolds number is larger than the critical Reynolds number and provided no other constraint becomes binding. In addition, the model jet's laminar length, if any, must be insignificant when compared to the total length of the path of the jet.New England Electric System and Northeast Utilities Service Company under the M.I.T. Energy Laboratory Electric Power Progra

Stability and mixing of a vertical round buoyant jet in shallow water

Also issued as a M.S. thesis in the Department of Civil Engineering at Massachusetts Institute of TechnologyDischarging heated water through submerged vertical round ports located at the bottom of a receiving water body is a currently used method of waste heat disposal. The prediction of the temperature reduction in the near field of the buoyant jet is a problem of environmental concern. The mechanics of a vertical axisymmetric buoyant jet in shallow water is theoretically and experimentally investigated. Four flow regimes with distinct hydrodynamic properties are discerned in the vicinity of the jet: the buoyant jet region, the surface impingement region, the internal hydraulic jump, and the stratified counterflow region. An analytical framework is formulated for each region. The coupling of the solutions of the four regions yields a prediction of the near field stability as well as the temperature reduction of the buoyant discharge. It is found that the near field of the buoyant jet is stable only for a range of jet densimetric Froude numbers and submergences. A theoretical solution is given for the stability criterion and the dilution of an unstable buoyant jet. A series of experiments were conducted to verify the theory. The experimental results are compared to the theoretical predictions. Good agreement is obtained

Centrifugal terms in the WKB approximation and semiclassical quantization of hydrogen

A systematic semiclassical expansion of the hydrogen problem about the classical Kepler problem is shown to yield remarkably accurate results. Ad hoc changes of the centrifugal term, such as the standard Langer modification where the factor l(l+1) is replaced by (l+1/2)^2, are avoided. The semiclassical energy levels are shown to be exact to first order in $\hbar$ with all higher order contributions vanishing. The wave functions and dipole matrix elements are also discussed.Comment: 5 pages, to appear in Phys. Rev.

Superconductivity and magnetism on flux grown single crystals of NiBi3

We present resistivity, magnetization and specific heat measurements on flux grown single crystals of NiBi3. We find typical behavior of a type-II superconductor, with, however, a sizable magnetic signal in the superconducting phase. There is a hysteretic magnetization characteristic of a ferromagnetic compound. By following the magnetization as a function of temperature, we find a drop at temperatures corresponding to the Curie temperature of ferromagnetic amorphous Ni. Thus, we assign the magnetism in NiBi$_3$ crystals to amorphous Ni impurities