Effect of growth orientation and diameter on the elasticity of GaN nanowires. A combined in situ TEM and atomistic modeling investigation

We characterized the elastic properties of GaN nanowires grown along different crystallographic orientations. In situ transmission electron microscopy tensile tests were conducted using a MEMS-based nanoscale testing system. Complementary atomistic simulations were performed using density functional theory and molecular dynamics. Our work establishes that elasticity size dependence is limited to nanowires with diameters smaller than 20 nm. For larger diameters, the elastic modulus converges to the bulk values of 300 GPa for c-axis and 267 GPa for a- and m-axis.     

The effect of recent and remote frames of reference on temporal judgments of schizophrenic patients.

"46 schizophrenic patients were compared with 80 control Ss with respect to their estimation of one clock second's duration under long and short anchor conditions, where anchor represented the extreme duration in a series. In addition, the interaction of recent and more remote anchors was studied." The findings suggested that the schizophrenic is likely to overestimate the duration of a clock second and that they responded only to the pulling effect of immediate anchors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prediction of incidence effects on oscillating airfoil aerodynamics by a locally analytical method

A complete mathematical model is formulated to analyse the effects of mean flow incidence angle on the unsteady aerodynamics of an oscillating airfoil in an incompressible flow field. A velocity potential formulation is utilized. The steady flow is independent of the unsteady flow field. However, the unsteady flow is coupled to the steady flow field through the boundary conditions on the oscillating airfoil. The numerical solution technique for both the steady and unsteady flow fields is based on a locally analytical method. In this method, analytical solutions are incorporated into the numerical technique, with the discrete algebraic equations which represent the differential flow field equations obtained from analytic solutions in individual local computational grid elements. This flow model and locally analytic numerical solution method are then verified through the excellent correlation obtained with the Theodorsen oscillating flat plate and Sears transverse gust classical solutions. The effects of mean flow incidence on the steady and oscillating airfoil aerodynamics are then investigated.     

Bioassays of segregating plants

Solanum chacoense is a wild potato species resistant to the Colorado potato beetle,Leptinotarsa decemlineata. Most genotypes ofS. chacoense synthesize the glycoalkaloids solanine (sol) and chaconine (chac) and are hosts of the beetle. A few rare genotypes have a gene(s) for acetylation of carbon-23 of the steroid aglycone of sol and chac. Laboratory bioassays and replicated field tests of clones differing in the presence or absence of the acetyl moiety showed that acetylation of sol and chac markedly affects the response of both adults and larvae to the foliage. Adult feeding deterrency conferred by acetylated forms of sol and chac (leptines) in leaf-disk preference tests was consistent with the degree of antixenosis measured in the field. Development of larvae on foliage of clones with leptines was also inhibited. The studies support the validity of using laboratory bioassays of plants segregating for levels of a suspected defense compound to determine the role the compound has in defending the plant from attack by an insect predator in the field.     

Radiation environment of HERMES III

A model that has been tested experimentally on HELIA is used to predict the radiation environment of the HERMES III gamma-ray simulator. This model demonstrates the potential capability of HERMES III for generating intense, uniform radiation exposures over areas from 500 to 2500 cm². Initial experiments at a reduced voltage using a graphite anode-converter beam dump at a rate of five shots per day are encouraging and confirm the validity of the model for the design and analysis of future experiments on HERMES III. Scaling to design voltage and a tantalum converter indicates that design specifications can be met     

Development of an expert system for diagnosing component-levelfailures in a shuttle car

The development of a rule-based expert system (referred to as SCAR) for assisting electricians in diagnosing electrical faults in a shuttle car is discussed. Insight 2+, a microcomputer-based expert-system development tool by Level Five Research, Inc. was used in creating the system. The program requires the user to specify the initial symptoms of the failed machine; then the most probable cause of failure is traced through the knowledge base, with the software requesting additional information, such as voltage or resistance measurements, as needed. A causal-reasoning approach, which was used to develop the production rules, is described. The organization, implementation, and limitations of the knowledge base are also presented, along with a brief discussion of the ongoing development of a new system, SCAR.2     

Aerodynamic detuning for control of supersonic rotor forced response

A mathematical model is developed to analyze the aerodynamically forced response characteristics of a detuned rotor operating in a supersonic inlet flow field with a supersonic axial component. Alternate blade aerodynamic detuning is considered, with the aerodynamic detuning accomplished by alternating the circumferential spacing of adjacent blades. The unsteady aerodynamics are determined by developing an influence coefficient technique which is appropriate for both aerodynamically tuned and detuned rotor configurations. Rotor forced response is then analyzed by combining this unsteady aerodynamic model with a single-degree-of-freedom structural model. The effects of this detuning on the forced response characteristics of supersonic axial flow rotors is then demonstrated by applying this model to baseline twelve bladed rotors.List of symbols c airfoil chord - [CM] ⁿ gust influence coefficient of airfoil, n - [CM] ⁿ motion-induced influence coefficient of airfoil, n - I mass moment of inertia - K linear spring constant - k reduced frequency _c/U - M dimensionless unsteady aerodynamic moment - M inlet Mach number - r dimensionless radius of gyration - S airfoil spacing - u dimensionless perturbation chordwise velocity - v dimensionless perturbation normal velocity - w complex amplitude of gust - x ₀ elastic axis location measured from leading edge - amplitude of airfoil oscillations - complex oscillatory displacement - interblade phase angle - _d detuned interblade phase angle - level of aerodynamic detuning - mass ratio - oscillatory frequency - ₀ reference frequency     

Analysis of high-Q,gallium nitride nanowire resonators in response to deposited thin films

Gallium nitride nanowires (GaN-NWs) are systems of interest for mechanical resonance-based sensors due to their small mass and, in the case of c-axis NWs, high mechanical quality (Q) factors of 10,000–100,000. We report on singly-clamped NW mechanical cantilevers of roughly 100 nm diameter and 15 μm length that resonate near 1 MHz and describe the behavior of GaN-NW resonant frequencies and Q factors following coating with various materials deposited by atomic layer deposition (ALD), including alumina (Al₂O₃), ruthenium (Ru), and platinum (Pt). Changes in the GaN-NW resonant frequencies with ALD deposition clearly distinguish conformal film growth versus island film growth. Conformal films lead to a stiffening of the NW and typically increase resonant frequency, whereas island films simply increase the NW mass and cause decreased resonant frequencies. We find that conformal growth of ALD alumina leads to stiffening of ～4 kHz per nm of alumina, in agreement with previously measured material properties. Conformal growth of Ru and Pt, respectively, qualitatively confirm our analytical predictions of positive and negative resonant frequency shifts. Island growth of ALD Ru has demonstrated a decrease in resonant frequency consistent with mass loading of ～0.2 fg for a 150 ALD-cycle film, also consistent with analytical predictions. Resonant Q factors are found to decrease with ALD film growth, offering the additional possibility of studying mechanical dissipation processes associated with the ALD-NW composite structures.