Characteristics and Sensing Properties of the La1-xNdxCo0.3Fe0.7O3 System for CO Gas Sensors

A series of nanostructured La1-xNdxCo0.3Fe0.7O3 perovskite-type (x ranging from 0 to 1) were prepared using the co-precipitation method. CO gas sensing properties of La1-xNdxCo0.3Fe0.7O3 sensors were performed. La0.7Nd0.3Co0.3Fe0.7O3 sensor showed the highest response at 250 °C (S=52.8)

Q2Q^2--Dependence of the Gerasimov-Drell-Hearn Sum Rule

We test the Gerasimov-Drell-Hearn (GDH) sum rule numerically by calculating the total photon absorption cross sections $\sigma_{1/2}$ and $\sigma_{3/2}$ on the nucleon via photon excitation of baryon resonances in the constituent quark model. A total of seventeen, low-lying, non-strange baryon resonances are included in this calculation. The transverse and longitudinal interference cross section, $\sigma_{1/2}^{TL}$, is found to play an important role in the study of the $Q^2$ variation of the sum rule. The results show that the GDH sum rule is saturated by these resonances at a confidence level of 94%. In particular, the $P_{33}(1232)$ excitation largely saturates the sum rule at $Q^2 = 0$, and dominates at small $Q^2$. The GDH integral has a strong $Q^2$-dependence below $Q^2= 1.0 {GeV}^2$ and changes its sign around $Q^2= 0.3 {GeV}^2$. It becomes weakly $Q^2$-dependent for $Q^2 > 1.0 {GeV}^2$ because of the quick decline of the resonance contributions. We point out that the $Q^2$ variation of the GDH sum rule is very important for understanding the nucleon spin structure in the non-perturbative QCD region.Comment: revtex, 17 pages, 3 ps figs include

Three-phase four-leg flying-capacitor multi-level inverter-based active power filter for unbalanced current operation.

This study describes a new application of flying capacitor multi-level inverters whereby a three-phase, four-leg three-level inverter is used for harmonic current cancellation and unbalanced current compensation in a four-wire system. A direct three-dimensional-pulse-width modulation (3D-PWM) scheme is developed to deal with the increased state redundancy in the four-leg flying capacitor multi-level inverter. Test results show much superior performance in the four-leg case, which may allow the use of smaller DC supply capacitors. A new modified dead-beat current control algorithm is proposed and combined successfully with the 3D-PWM modulation technique in a hardware demonstrator of a complete active filter

Investigation of the Dimensional Variation of Microstructures Through the μMIM Process

The mass production of components with dimensions in the micron and sub-micron range is anticipated to be one of the leading technology areas for the present century and to be of high market potential. Micro metal injection molding (μMIM) has the potential to be an important contributor to this industry as it can produce precise metallic microstructures in large quantities at a relatively low production cost. The μMIM process is a miniaturization of metal injection molding (MIM) methods. The process comprises of four main steps: mixing, injection molding, debinding and sintering. A metallic powder is mixed with a binder system to form the feedstock. The feedstock is then injection molded into the required shape and the binder removed via thermal or other means. The final microstructures are obtained by sintering the remaining powder in a controlled environment. In this work, the dimensional variation of the microstructures, in particular the warpage, roughness and volume variation, at each stage of the μMIM process was quantified and compared. The results of a preliminary study of the sensitivity of warpage of the microstructures to the packing pressure are also reported.Singapore-MIT Alliance (SMA

Contact Deformation Behavior of an Elastic Silicone/SiC Abrasive in Grinding and Polishing

An elastic abrasive of the new type having the advantage of effectively controlled contact pressure and uniform deformation was developed. It provides complete lamination of the surface, effective treatment of the curved mold cavity, as well as improves the processing efficiency. It permits of fine cavity surface finishing.Розроблено пружний абразив нового типу, що дозволяє ефективно регулювати контактний тиск у поєднанні з рівномірним деформуванням. Пружний абразив забезпечує повне ламінування поверхні, збільшує ефективність обробки вигнутої порожнини ливарної форми та дозволяє виконувати тонку обробку поверхні порожнини.Разработан упругий абразив нового типа, позволяющий эффективно регулировать контактное давление в сочетании с равномерным деформированием. Упругий абразив обеспечивает полное ламинирование поверхности и эффективную обработку изогнутой полости литейной формы, а также позволяет выполнять тонкую отделочную обработку поверхности полости

Photo-production of Nucleon Resonances and Nucleon Spin Structure Function in the Resonance Region

The photo-production of nucleon resonances is calculated based on a chiral constituent quark model including both relativistic corrections H{rel} and two-body exchange currents, and it is shown that these effects play an important role. We also calculate the first moment of the nucleon spin structure function g1 (x,Q^2) in the resonance region, and obtain a sign-changing point around Q^2 ~ 0.27 {GeV}^2 for the proton.Comment: 23 pages, 5 figure

Sodium atoms and clusters on graphite: a density functional study

Sodium atoms and clusters (N<5) on graphite (0001) are studied using density functional theory, pseudopotentials and periodic boundary conditions. A single Na atom is observed to bind at a hollow site 2.45 A above the surface with an adsorption energy of 0.51 eV. The small diffusion barrier of 0.06 eV indicates a flat potential energy surface. Increased Na coverage results in a weak adsorbate-substrate interaction, which is evident in the larger separation from the surface in the cases of Na_3, Na_4, Na_5, and the (2x2) Na overlayer. The binding is weak for Na_2, which has a full valence electron shell. The presence of substrate modifies the structures of Na_3, Na_4, and Na_5 significantly, and both Na_4 and Na_5 are distorted from planarity. The calculated formation energies suggest that clustering of atoms is energetically favorable, and that the open shell clusters (e.g. Na_3 and Na_5) can be more abundant on graphite than in the gas phase. Analysis of the lateral charge density distributions of Na and Na_3 shows a charge transfer of about 0.5 electrons in both cases.Comment: 20 pages, 6 figure

Prospects of Scintillating Crystal Detector in Low-Energy Low-Background Experiments

Scintillating crystal detector offers potential advantages in low-energy (keV-MeV range) low-background experiments for particle physics and astrophysics. The merits are discussed using CsI(Tl) crystal as illustrations. The various physics topics which can be pursued with this detector technology are summarized. A conceptual design for a generic detector is presented.Comment: 20 pages, 1 tables, 7 figures, submitted to Astroparticle Physic