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We report oxygen sensing behavior of (Eu1-xCax)Ba2Cu3O7-δ (x = 0.0,0.1) ceramics rods with formation of oxygen sensitive hot-spot upon application of external voltage. Oxygen response behavior of the x = 0.1 rod showed constant current plateau with increasing voltage and displayed better stability and reproducibility compared to x = 0 rod probably due to increased intrinsic hole concentration and reduction in activation energy as a result of Ca2+ substitution.. [ABSTRACT FROM AUTHOR]

We present direct optical initiation (DOI) of energetic materials using coherent control of localized energy deposition. DOI requires depositing energy into the material to produce a critical size hot spot, which allows propagation of the reaction and thereby initiation. The hot spot characteristics needed for growth to initiation can be studied using quantum controlled initiation (QCI). Achieving QCI in condensed phase energetic materials requires optimally shaped ultrafast laser pulses to coherently guide the energy flow along desired paths. As a test of our quantum control capabilities we have successfully demonstrated our ability to control the reaction pathway of the chemical system stilbene. An acousto-optical modulator based pulse shaper was used at 266 nm, in a shaped pump/supercontinuum probe technique, to enhance and suppress the relative yields of the cis- to trans-stilbene isomerization. The quantum control techniques tested in the stilbene experiments are currently being used to investigate QCI of the explosive hexanitroazobenzene (HNAB). [ABSTRACT FROM AUTHOR]

Oxygen sensing properties of HoBa2Cu3O7-δ ceramic rods utilizing hot-spot phenomenon have been characterized. The rods were prepared from high purity oxides using the conventional solid-state reaction method. I-V characterization showed increase in output current with voltage before the appearance of the hot spot. After the appearance of the hot-spot, the output current strongly depended on oxygen partial pressure. The rod showed stable sensing characteristics with good electrical stability and reproducibility with higher sensitivity at low oxygen partial pressure. The sensing property is associated with the absorption of oxygen and dissociation into holes and oxide ions. Ho123 is more sensitive at pO2 below 20% compared to Er123 possibly due to differences in oxygen activation energy related to RE ionic radius. [ABSTRACT FROM AUTHOR]

Firstly, the shadowing model was studied here as a volume scattering kernel, because of its high correlation with the measured BRDF values. In addition, it gave a sharp hot spot surge in the backward scattering direction, whereas previously proposed BRDF kernelels, such as the Li-Sparse, the Ross-thick and Roujean models, failed to give a hot spot surge. It was possible to explain most of the measured BRDF characteristics of various land objects, assuming either the shadowing model alone or the shadowing model with combined use of the Li-Sparse (or Roujean) model. [ABSTRACT FROM AUTHOR]

We present recent results from hot spot investigations in imploding Al wire array z-pinches on the COBRA generator at Cornell University using x-ray diagnostics. Measurements of the temporal and spatial distribution of hot spots in stagnating plasmas by an x-ray streak-camera are included. Experiments show that hot spots have nanosecond lifetime and appear randomly along the array axis after plasma stagnation in secondary pinches in 8 mm diameter and during plasma stagnation in the arrays with 4 mm diameter. [ABSTRACT FROM AUTHOR]

Oxygen sensing properties of Er123 ceramic material utilizing hot-spot phenomenon have been investigated. Bulk Er123 ceramic with relative density of 72 % was synthesized using solid-state method and single-phase structure of the material was confirmed by X-ray diffraction. The Er123 sensor was fabricated by cutting the bulk sample into a rectangular rod shape. I-V characterizations of the sensor before and after appearance of the hot spot were conducted in a chamber with controlled flow rate and partial pressure of oxygen and nitrogen gases. After appearance of the hot spot, the output current strongly depended on oxygen partial pressure (pO2) at a particular selected voltage. The sensor showed good sensing properties with minimum required electric field of about 1.7 V/cm for 0.025% to 100% pO2. The sensor showed very good reproducibility and stability of output current. The oxygen sensing properties are explained in terms of absorption of oxygen gas by the hot spot before dissociating into oxide ions and holes. The conductivity for 5% to 100% pO2 showed good agreement with theoretically predicted proportional relation of conductivity to pO21/6 derived from the mass action law. [ABSTRACT FROM AUTHOR]