A new comparison between solid-state thermionics and thermoelectrics

It is shown that equations for electrical current in solid-state thermionic and thermoelectric devices converge for devices with a width equal to the mean free path of electrons, yielding a common expression for intensive electronic efficiency in the two types of devices. This result is used to demonstrate that the materials parameters for thermionic and thermoelectric devices are equal, rather than differing by a multiplicative factor as previously thought

Micromagnetic characteristics of transverse diffuse domain boundaries in permalloy thin films

Transverse domain boundaries propagating in the longitudinal direction at speeds one to three orders of magnitude faster than normal domain walls are responsible for most of the lower speed reversals in magnetic thin films. Using a 10-ns exposure time Kerr magnetooptic camera, these boundaries have been photographed for a variety of applied fields in several films with thicknesses ranging from 500 to 3500 Å. High-magnification photographs of the boundary transition region reveal that the boundaries consist of small isolated areas of reversed and partially reversed magnetization in a nonreversed background. Propagation occurs by the nucleation of additional small areas of reverse magnetization within and ahead of the transition region. In a given film the width of the transition region increases as the applied field is increased. By approximating the divergence of the magnetization at the boundary as a line charge, a model has been derived which predicts the boundary widthWto beW = \frac{8M_{s}t}{H_{n}}\frac{1}{(1-H/H_{n})}where Msis the saturation magnetization andHis the applied field. The nucleation threshold Hnis the threshold at which nucleation is observed over all the film. The experimental data fit this predicted dependence quite well. The rapid increase in width of the transition region with applied field is correlated with a rapid nonlinear increase in the velocity of propagation

Characteristics of the Bed of the Lower Columbia Glacier, Alaska

An unplanned, but unique, experiment has given an in situ measurement of the strength of deforming subglacial till under the central region of a major valley glacier. We report on both planned and unplanned borehole investigations of the subglacial shear zone of Columbia Glacier, southeast Alaska. Basal samples, coring and down-hole water samples show that the fiord-filling lower reach of the glacier is underlain by a thin, ∼ 7-cm, veneer of rock debris. Fluidized debris intruded at least a meter up the borehole. At a higher site, 13 km from the terminus and above the fiord, probing, samples, and the bending of a drill stem, which was stuck in the basal zone for 5 days, showed that the basal till layer was ∼ 65 cm thick. Horizontal velocity of the till decreased monotonically downward from the ice/till interface. Till at the interface moved with the ice velocity. Plastic deformation of the drill stem gave an estimate of the strength of the basal till, which is normally described as a viscoplastic material. If the till is assumed to be either perfectly plastic or Newtonian viscous, then the strengths are as follows; the plastic yield strength of the till was 5.5×10^3 Pa (0.055 bar) with an upper bound of 1.3 ×10^4 Pa (0.13 bar), while the nominal viscosity was of the order of 2×10^8 Pa s (2×10^9 poise), with an upper bound of 5×10^8 Pa s. In neither case is the till “strength” enough to supply the bulk basal shear stress to resist the glacier flow

Group 8 metal alkynyl complexes for nonlinear optics

International audienceStudies of the nonlinear optical (NLO) properties of Group 8 metal alkynyl complexes are summarized, with particular focus on results since 2003; structure-NLO property relationships are developed, optical nonlinearities of multipolar alkynyl complexes are described, and switching of the NLO response of molecules and molecular materials derived from Group 8 metal alkynyl complexes is discussed

Mechanical and hydrologic basis for the rapid motion of a large tidewater glacier 2. Interpretation

The data presented in part 1 of this paper (Meier et al., this issue) are here used to assess the role of water input/output, water storage, and basal water pressure in the rapid movement of Columbia Glacier, Alaska. Consistently high basal water pressures, mostly in the range from 300 kPa below to 100 kPa above the ice overburden pressure, are responsible in an overall way for the high glacier flow velocities (3.5–9 m d^−1), which are due mainly to rapid basal sliding caused by the high water pressure. Diurnal fluctuation in basal water pressure is accompanied by fluctuation in sliding velocity in what appears to be a direct causal relation at the upglacier observation site. The water pressure fluctuation tracks the time-integrated water input (less a steady withdrawal), as expected for the diurnally fluctuating storage of water in the glacier far from the terminus. At the downglacier site, the situation is more complex. Diurnal peaks in water level, which are directly related to intraglacial water storage as well as to basal water pressure, are shifted forward in time by 4 hours, probably as a result of the effect of diurnal fluctuation in water output from the glacier, which affects the local water storage fluctuations near the terminus. Because of the forward shift in the basal water pressure peaks, which at the downglacier site lead the velocity peaks by 6 hours, a mechanical connection between water pressure and sliding there would have to involve a 6-hour (quarter period) delay. However, the nearly identical nature of the diurnal fluctuations in velocity at the two sites argues for a single, consistent control mechanism at both sites. The velocity variations in nondiurnal “speed-up events” caused by extra input of water on the longer timescale of several days are only obscurely if at all correlated with variations in basal water pressure but correlate well with water storage in the glacier. It appears that small variations in water pressure (≤100 kPa) sufficient to produce the observed velocity variations (15–30%) are mostly masked by pressure fluctuations caused by spontaneous local reorganizations of the basal water conduit system on a spatial scale much smaller than the longitudinal coupling length over which basal water pressure is effectively averaged in determining the sliding velocity. At the achieved level of observation the clearest (though not complication free) control variable for the sliding velocity variations is basal water storage by cavitation at the glacier bed

Basal conditions and glacier motion during the winter/spring transition, Worthington Glacier, Alaska, U.S.A.

Observations of the motion and basal conditions of Worthington Glacier, Alaska, U.S.A., during late-winter and spring melt seasons revealed no evidence of a relationship between water pressure and sliding velocity. Measurements included borehole water levels (used as a proxy for basal water pressure), surface velocity, englacial deformation, sliding velocity, and time-lapse videography of subglacial water flow and bed characteristics. The boreholes were spaced 10-15 m apart; six were instrumented in 1997, and five in 1998. In late winter, the water-pressure field showed spatially synchronous fluctuations with a diurnal cycle. The glacier\u27s motion was relatively slow and non-cyclic. In spring, the motion was characterized by rapid, diurnally varying sliding. The basal water pressure displayed no diurnal signal, but showed high-magnitude fluctuations and often strong gradients between holes. This transition in character of the basal water-pressure field may represent a seasonal evolution of the drainage system from linked cavities to a network of isolated patches and conduits. These changes occurred as the glacier was undergoing a season-velocity peak. The apparent lack of correlation between sliding velocity and water pressure suggests that local-scale water pressure does not directly control sliding during late winter or early in the melt season

Data Transfer to Non-volatile Memory (or Persistent Memory) During Input Power Loss

In a critical server losing its input voltage/power, the server goes down after 10/20ms of hold-up time. In these hold-up time the data need to be transferred from volatile memory to non-volatile memory (NVDIMM). For years this process is being done successfully, by transferring the data during this 10/20ms hold-up time. However, this process is having the disadvantage of the server going down for each and every event of input power loss using NVDIMMs platforms. To overcome this disadvantage, a new method or technique is proposed in this publication/disclosure (Fig 1). The proposed technique utilizes the signal (called bulk voltage). Whenever, the energy levels (called bulk voltage) in a power supply becomes low, the server starts transferring the data (compared to each loss of input power earlier) to non-volatile memory reducing the number of shut downs of the server. If the input power loss duration is from 10ms to 80ms depending upon the load on the server, the shutdown of the server can be avoided completely. The cost of this feature is miniscule compared to the cost of adding UPS/mega cell/Super cap in each and every server/platform

Word co-occurrence graphs for design and manufacture knowledge mapping

Design & Manufacture Knowledge Mapping is a critical activity in medium-to-large organisations supporting many organisational activities. However, techniques for effective mapping of knowledge often employ interviews, consultations and appraisals. Although invaluable in providing expert insight, the application of such methods is inherently intrusive and resource intensive. This paper presents word co-occurrence graphs as a means to automatically generate knowledge maps from technical documents and validates against expert generated knowledge maps

Ariel - Volume 12 Number 2

Executive Editors David G. Polin Larry H. Pastor Business Manager Alex Macones Jean Lien Editorial Page Editor Deepak Kapoor Sports Editor Todd Hoover Photography Editors Lois Leach Ken Yonemur