On Criticality for Competing Influences of Boundary and External Field in the Ising Model

We continue a study of Schonmann (1994), Schonmann and Shlosman (1996), and Greenwood and Sun (1997) regarding the competing influences of boundary conditions and external field for the Ising model. We find a critical point B ₀ in the competing influences for low temperature in dimension d 2A7E; 2.     

Pre-averaged kernel estimators for the drift function of a diffusion process in the presence of microstructure noise

We consider estimation of the drift function of a stationary diffusion process when we observe high-frequency data with microstructure noise over a long time interval. We propose to estimate the drift function at a point by a Nadaraya–Watson estimator that uses observations that have been pre-averaged to reduce the noise. We give conditions under which our estimator is consistent and asympotically normal. Its rate and asymptotic bias and variance are the same as those without microstructure noise. To use our method in data analysis, we propose a data-based cross-validation method to determine the bandwidth in the Nadaraya–Watson estimator. Via simulation, we study several methods of bandwidth choices, and compare our estimator to several existing estimators. In terms of mean squared error, our new estimator outperforms existing estimators.     

Twenty-five years of progress in vacuum arc research andutilization

Progress in understanding and applying vacuum arcs is reviewed. Laser diagnostics have demonstrated the existence of micron-sized regions in the cathode spot plasma having electron densities exceeding 10²⁶ m^-3. The expanding plasma produces a highly ionized jet whose ions typically have charge states of 1-3 and energies of 50-150 eV. Gas dynamic and explosive emission models have been formulated to explain cathode spot operation. In cases where the arc is constricted at the anode, forming an anode spot, or the anode is thermally isolated, forming a hot anode vacuum arc, material emitted from the anode may dominate the interelectrode plasma. Evaporation from liquid droplets may also provide a substantial component of the plasma, and the presence of these droplets can have deleterious consequences in applications. The vacuum arc has been extensively utilized as a plasma source, particularly for the deposition of protective coatings and thin films, and as a switching medium in electrical distribution circuit breakers     

An Inter-Temporal Multi-Goal Linear Programming Model for Optimizing University Tuition and Fee Structures

This paper reports on the use of a multi-goal linear programming model to establish the tuition and fee policy at a major state university over a three-year period. The process of establishing tuition and fee charges is characterized by multiple and conflicting goals. Further complicating the process is the fact that multiple parties are involved in or impact on the decision process, including the various academic and administrative units of the university, the state legislature, parents and students. The charges are established based on the institution's anticipated operating costs and fiscal needs, state-level policies and requirements, projected enrolment patterns, charges at peer institutions, and the university's philosophy concerning differential charges between various student categories. The modelling process employed provides university administration with the maximum possible flexibility in stating and prioritizing university goals and objectives regarding the tuition and fee structure.     

Homogeneous and inhomogeneous manifolds

All metaLindelöf, and most countably paracompact, homogeneous manifolds are Hausdorff. Metacompact manifolds are never rigid. Every countable group can be realized as the group of autohomeomorphisms of a Lindelöf manifold. There is a rigid foliation of the plane.

     

Electric power switches

A review is given of the physics and engineering behavior of arcs in vacuum and axial gas blast under the conditions found in high-voltage circuit breakers. The topics included are: the zero energy switch; current limiting switches; arc control; the gas-blast circuit breakers; the low-current gas-blast arc; arcing with ablation; interruption dynamics; arc modeling; vacuum as a switching element; the vacuum arc; the constricted arc; and the properties of SF₆     

Gamma-ray emission from 134Ce and levels in 134La

The decay of ¹³⁴Ce to doubly odd ¹³⁴La has been studied using Ge(Li) and Si(Li) photon detectors. Samples of the ¹³⁴Ce(75.9 h)- ¹³⁴La(6.67 min) have been produced by ≈ 800 MeV proton bombardment of Pr foils in LAMPF, followed by chemical and mass separation. To increase the sensitivity (by up to a factor ≈ 50) for detection of ¹³⁴Ce γ-rays in the presence of the interfering ¹³⁴La activity, the ¹³⁴Ce-¹³⁴La samples were loaded onto a HDEHP column and the ¹³⁴La eluted off continuously. Gamma-ray singles and γ-γ coincidence measurements were made using the ¹³⁴Ce activity remaining on the column as the source. Some 32 γ-rays, ranging in energy up to 355 keV, are observed to be associated with this decay. Approximately 30 of these have been fitted into a level scheme for ¹³⁴La with excited states at energies of 31, 54, 93, 136 or 148, 162, 187, 150 or 205, 252, 294 and 355 keV. Only limits can be set for the spin and parity values of each of these states. The observation of γ-rays with energies up to 355 keV indicates that the previously reported values of ≈ 0.1 MeV for the ¹³⁴Ce electron-capture decay energy, inferred from the K-electron capture probability, are incorrect.