3,619 research outputs found
Total Reflection and Negative Refraction of Dipole-Exchange Spin Waves at Magnetic Interfaces: Micromagnetic Modeling Study
We demonstrated that dipole-exchange spin waves traveling in geometrically
restricted magnetic thin films satisfy the same laws of reflection and
refraction as light waves. Moreover, we found for the first time novel wave
behaviors of dipole-exchange spin waves such as total reflection and negative
refraction. The total reflection in laterally inhomogeneous thin films composed
of two different magnetic materials is associated with the forbidden modes of
refracted dipole-exchange spin waves. The negative refraction occurs at a 90
degree domain-wall magnetic interface that is introduced by a cubic magnetic
anisotropy in the media, through the anisotropic dispersion of dipole-exchange
spin waves.Comment: 13 pages, 5 figure
Health and Safety Issues of Older Workers Surveyed in the Construction Industry
The study aimed to gain a better understanding of age-related construction worker’s health and safety issues and discuss practical solutions to improve safety and health of the older workers in the construction industry. A two-page survey questionnaire was developed and sent out to the safety managers, directors, or coordinators in the construction firms. The participants were employed in 27 companies that employed 12,452 employees and have been in business for an average of 75 years. All of the companies had a written safety program, but only 50% of the companies represented in the survey had the Health and Wellness programs. The findings suggested that the construction industry was in fact well aware of the worker health concerns that the aging construction workforce has been facing. The survey also revealed that there was an overwhelming agreement that older workers were still very valuable to the industry. The occupational ergonomic, health and safety professionals should pay more attend to develop creative and effective health/wellness programs that any size organization can use, with the ultimate goal being to have a sustainable and healthier aging workforce in the industry. The results of other findings are also discussed in detail
Safety Climate as an Indicator and Predictor of Safety Performance: A Case Study
This study compared and objectively gauged the safety climate in the manufacturing facilities (high safety performing vs. low safety performing) to identify the most impactful areas to focus to reduce or prevent workplace injuries. In order to accomplish the study objective, we employed the Nordic Safety Climate Questionnaire (NOSACQ-50) consisted of 50 items across seven dimensions. A total of 116 operations employees in the paper laminate manufacturing completed the survey. The two sites were both within the United States and had structured the same operations. The results of the comparisons showed that there was a significant difference in the total scores for the sites. The high performance site had significantly higher NOSACQ-50 scores than the underperforming site in all dimensions. The high performing site had the greater safety climate scores in the area of “management safety priority & ability”. The underperforming site recorded comparatively lower scores in the areas of “management safety empowerment”, “group safety priority”, and “worker safety commitment”. We provided the recommendations of three focus areas: commitment, involvement, and accountability. The outcomes from this study could be useful to apply resources and focus to the appropriate areas in order to make safety improvements. In turn, improving safety climate can have positive impacts on increasing employee safety while improving the viability of the organization
Decoherence Driven Quantum Transport
We propose a new mechanism to generate a dc current of particles at zero bias
based on a noble interplay between coherence and decoherence. We show that a dc
current arises if the transport process in one direction is maintained coherent
while the process in the opposite direction is incoherent. We provide possible
implementations of the idea using an atomic Michelson and an atomic
Aharonov-Bohm interferometer.Comment: 4 pages, 3 figure
Characteristics of switching plasma in an inverse-pinch switch
Characteristics of the plasma that switches on tens of giga volt-ampere in an inverse-pinch plasma switch (INPIStron) have been made. Through optical and spectroscopic diagnostics of the current carrying plasma, the current density, the motion of current paths, dominant ionic species have been determined in order to access their effects on circuit parameters and material erosion. Also the optimum operational condition of the plasma-puff triggering method required for azimuthally uniform conduction in the INPIStron has been determined
Degradation mechanism of Schottky diodes on inductively coupled plasma-etched n-type 4H-SiC
The degradation mechanism of Ta Schottky contact on 4H-SiC exposed to an inductively coupled plasma (ICP) was studied using deep-level transient spectroscopy and angle-resolved x-ray photoelectron spectroscopy (XPS). Four kinds of traps T1, T2, T3, and T4 were observed in the ICP-etched sample. The T4 trap was deep in the bulk, but the shallower levels, T1, T2 and T3, were localized near the contact. From angle-resolved XPS measurements, the ICP-etched surface was found to be carbon deficient, meaning the production of carbon vacancies by ICP etching. The activation energies 0.48 (T3 trap) and 0.60 eV (T4 trap) agreed well with the previously proposed energy level of V-C (0.5 eV). The ICP-induced traps provided a path for the transport of electrons at the interface of metal with Sic, leading to a reduction of the Schottky barrier height and an increase of the gate leakage current.open6
Large and homogeneous mass enhancement in the rattling-induced superconductor KOsO
We have determined the Fermi surface in KOsO ( = 9.6 K and
32 T) via de Haas-van Alphen (dHvA) oscillation measurements and
a band structure calculation. We find effective masses up to 26(1) (
is the free electron mass), which are unusually heavy for compounds where the
mass enhancement is mostly due to electron-phonon interactions. Orbit-resolved
mass enhancement parameters are large but fairly homogeneous,
concentrated in the range 5 -- 8. We discuss origins of the large homogeneous
mass enhancement in terms of rattling motion of the K ions.Comment: Minor revisions, Fig.2a modifie
Electrochemically Controlled Reconstitution of Immobilized Ferritins for Bioelectronic Applications
Site-specific reconstituted nanoparticles were fabricated via electrochemically-controlled biomineralization through the immobilization of biomolecules. The work reported herein includes the immobilization of ferritin with various surface modifications, the electrochemical biomineralization of ferritins with different inorganic cores, and the electrocatalytic reduction of oxygen on the reconstituted Pt-cored ferritins. Protein immobilization on the substrate is achieved by anchoring ferritins with dithiobis-N-succinimidyl propionate (DTSP). A reconstitution process of site-specific electrochemical biomineralization with a protein cage loads ferritins with different core materials. The ferritin acts as a nano-scale template, a biocompatible cage, and a separator between the nanoparticles. This first demonstration of electrochemically controlled site-specific reconstitution of biomolecules provides a new tool for biomineralization and opens the way to produce the bio-templated nanoparticles by electrochemical control. The nanosized platinum-cored ferritins on gold displayed good catalytic activity for the electrochemical reduction of oxygen, which is applicable to biofuel cell applications. This results in a smaller catalyst loading on the electrodes for fuel cells or other bioelectronic devices
Criterion for transformation of transverse domain wall to vortex or antivortex wall in soft magnetic thin-film nanostripes
We report on the criterion for the dynamic transformation of the internal
structure of moving domain walls (DWs) in soft magnetic thin-film nanostripes
above the Walker threshold field, Hw. In order for the process of
transformation from transverse wall (TW) to vortex wall (VW) or antivortex wall
(AVW) occurs, the edge-soliton core of the TW-type DW should grow sufficiently
to the full width at half maximum of the out-of-plane magnetizations of the
core area of the stabilized vortex (or antivortex) by moving inward along the
transverse (width) direction. Upon completion of the nucleation of the vortex
(antivortex) core, the VW (AVW) is stabilized, and then its core accompanies
the gyrotropic motion in a potential well (hill) of a given nanostripe. Field
strengths exceeding the Hw, which is the onset field of DW velocity breakdown,
are not sufficient but necessary conditions for dynamic DW transformation
Bio-Nanobattery Development and Characterization
A bio-nanobattery is an electrical energy storage device that utilizes organic materials and processes on an atomic, or nanometer-scale. The bio-nanobattery under development at NASA s Langley Research Center provides new capabilities for electrical power generation, storage, and distribution as compared to conventional power storage systems. Most currently available electronic systems and devices rely on a single, centralized power source to supply electrical power to a specified location in the circuit. As electronic devices and associated components continue to shrink in size towards the nanometer-scale, a single centralized power source becomes impractical. Small systems, such as these, will require distributed power elements to reduce Joule heating, to minimize wiring quantities, and to allow autonomous operation of the various functions performed by the circuit. Our research involves the development and characterization of a bio-nanobattery using ferritins reconstituted with both an iron core (Fe-ferritin) and a cobalt core (Co-ferritin). Synthesis and characterization of the Co-ferritin and Fe-ferritin electrodes were performed, including reducing capability and the half-cell electrical potentials. Electrical output of nearly 0.5 V for the battery cell was measured. Ferritin utilizing other metallic cores were also considered to increase the overall electrical output. Two dimensional ferritin arrays were produced on various substrates to demonstrate the feasibility of a thin-film nano-scaled power storage system for distributed power storage applications. The bio-nanobattery will be ideal for nanometerscaled electronic applications, due to the small size, high energy density, and flexible thin-film structure. A five-cell demonstration article was produced for concept verification and bio-nanobattery characterization. Challenges to be addressed include the development of a multi-layered thin-film, increasing the energy density, dry-cell bionanobattery development, and selection of ferritin core materials to allow the broadest range of applications. The potential applications for the distributed power system include autonomously-operating intelligent chips, flexible thin-film electronic circuits, nanoelectromechanical systems (NEMS), ultra-high density data storage devices, nanoelectromagnetics, quantum electronic devices, biochips, nanorobots for medical applications and mechanical nano-fabrication, etc
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