Non-invasive investigations of a wall painting using optical coherence tomography and hyperspectral imaging

Multispectral and hyperspectral imaging are efficient methods of measuring spectral reflectance at high spatial resolution. This non-invasive technique has been applied to the imaging of paintings over the last 20 years. PRISMS (Portable Remote Imaging System for Multispectral Scanning) was designed specifically for imaging wall paintings. Optical Coherence Tomography (OCT) is a low coherence interferometric technique capable of fast non-invasive imaging of subsurface microstructure. This paper shows the first application of in situ OCT imaging of a wall painting. The combination of PRISMS and OCT gives information on the varnish and paint layer structure, pigment identification, the state of degradation of the paint and varnish layers and informing curators on the painting schemes and techniques

Continuous detonation reaction engine

Reaction engine operates on the principles of a controlled condensed detonation rather than on the principles of gas expansion. The detonation results in reaction products that are expelled at a much higher velocity

Development of detonation reaction engine

Reaction engine operates on the principle of a controlled condensed detonation. In this engine the gas products that are expelled from the engine to produce thrust are generated by the condensed detonation reaction. The engine is constructed of two basic sections consisting of a detonation wave generator section and a condensed detonation reaction section

Active suspension design for a Large Space Structure ground test facility

The expected future high performance requirements for Large Space Structures (LSS) enforce technology innovations such as active vibration damping techniques e.g., by means of structure sensors and actuators. The implementation of new technologies like that requires an interactive and integrated structural and control design with an increased effort in hardware validation by ground testing. During the technology development phase generic system tests will be most important covering verification and validation aspects up to the preparation and definition of relevant space experiments. For many applications using advanced designs it is deemed necessary to improve existing testing technology by further reducing disturbances and gravity coupling effects while maintaining high performance reliability. A key issue in this context is the improvement of suspension techniques. The ideal ground test facility satisfying these requirements completely will never be found. The highest degree of reliability will always be obtained by passive suspension methods taking into account severe performance limitations such as non-zero rigid body modes, restriction of degrees of freedom of motion and frequency response limitations. Passive compensation mechanisms, e.g., zero-spring-rate mechanisms, either require large moving masses or they are limited with respect to low-frequency performance by friction, stiction or other non-linear effects. With active suspensions these limitations can be removed to a large extent thereby increasing the range of applications. Despite an additional complexity which is associated with a potential risk in reliability their development is considered promising due to the amazing improvement of real-time control technology which is still continuing

First-principles calculations of the vibrational properties of bulk CdSe and CdSe nanowires

We present first-principles calculations on bulk CdSe and CdSe nanowires with diameters of up to 22 \AA. Density functional linear combination of atomic orbitals and plane wave calculations of the electronic and structural properties are presented and discussed. We use an iterative, symmetry-based method to relax the structures into the ground state. We find that the band gap depends on surface termination. Vibrational properties in the whole Brillouin zone of bulk CdSe and the zone-center vibrations of nanowires are calculated and analyzed. We find strongly size-dependent and nearly constant modes, depending on the displacement directions. A comparison with available experimental Raman data is be given

Using particle shape to induce tilted and bistable liquid crystal anchoring

We use Monte Carlo simulations of hard Gaussian overlap (HGO) particles symmetrically confined in slab geometry to investigate the role of particle-substrate interactions on liquid crystalline anchoring. Despite the restriction here to purely steric interactions and smooth substrates, a range of behaviours are captured, including tilted anchoring and homeotropic-planar bistability. These macroscopic behaviours are all achieved through appropriate tuning of the microscopics of the HGO-substrate interaction, based upon non-additive descriptions for the HGO-substrate shape parameter.</p

RSFQ devices with selective dissipation for quantum information processing

We study the possibility to use frequency dependent damping in RSFQ circuits as means to reduce dissipation and consequent decoherence in RSFQ/qubit circuits. We show that stable RSFQ operation can be achieved by shunting the Josephson junctions with an $RC$ circuit instead of a plain resistor. We derive criteria for the stability of such an arrangement, and discuss the effect on decoherence and the optimisation issues. We also design a simple flux generator aimed at manipulating flux qubits

Composite infrared bolometers with Si_3N_4 micromesh absorbers

We report the design and performance of 300-mK composite bolometers that use micromesh absorbers and support structures patterned from thin films of low-stress silicon nitride. The small geometrical filling factor of the micromesh absorber provides 20× reduction in heat capacity and cosmic ray cross section relative to a solid absorber with no loss in IR-absorption efficiency. The support structure is mechanically robust and has a thermal conductance, G < 2 × 10^(−11) W/K, which is four times smaller than previously achieved at 300 mK. The temperature rise of the bolometer is measured with a neutron transmutation doped germanium thermistor attached to the absorbing mesh. The dispersion in electrical and thermal parameters of a sample of 12 bolometers optimized for the Sunyaev–Zel’dovich Infrared Experiment is ±7% in R (T), ±5% in optical efficiency, and ±4% in G