Characteristics and uniformity of group V implanted and annealed HgCdTe heterostructure

This work presents characterization of implanted and annealed double layer planar heterostructure HgCdTe for p-on-n photovoltaic devices. Our observation is that compositional redistribution in the structure during implantation/ annealing process differs from that expected from classical composition gradient driven interdiffusion and impacts the placement of the electrical junction with respect to the metallurgical heterointerface, which in turn affects quantum efficiency and R_oA. The observed anomalous interdiffusion results in much wider cap layers with reduced composition difference between base and cap layer composition. The compositional redistribution can, however, be controlled by varying the material structure parameters and the implant/anneal conditions. Examples are presented for dose and implanted species variation. A model is proposed based on the fast diffusion in the irradiation induced damage region of the ion implantation. In addition, we demonstrate spatial uniformity obtained on molecular beam epitaxy (MBE) material of the compositional and implanted species profile. This reflects spatial uniformity of the ion implantation/annealing Processes and of the MBE material characteristics.     

Progress in CdZnTe substrate producibility and critical drivers of IRFPA yield originating with CdZnTe substrates

With the goal of maximizing the yield of infrared focal plane arrays (IRFPAs), Santa Barbara Research Center’s (SBRC) Infrared Materials Producibility Program (IRMP) has focused on assessing and improving the quality, yield, and throughput of CdZnTe substrates. A baseline detector lot was fabricated to identify the critical drivers of IRFPA yield coming from the substrates and to evaluate the quality and yield of the current vendor base for CdZnTe substrates. Substrate induced defects and impurities that can potentially affect device performance and operability were carefully mapped out in detail on 44 × 67 mm² size substrates, received from IRMP substrate vendors as well as SBRC. This paper will report on the correlations found between this substrate characterization data base and the IRFPA level defect distributions. Key results from these correlation studies are: (1) extended defects found on the substrates with the Nakagawa etch correlated well with responsivity reduction in the final IRFPA; (2) cross-hatch patterns that were evident in the responsivity map correlated well with similar features seen by x-ray topography on LPE double layers; and (3) a possible correlation of device performance (leakage current at 78K) with copper and lithium impurities in the substrate. Recent initiatives toward improving the quality and yield of the substrate growth process have focused on improving purity in the pre-growth charge preparation, modification of growth parameters to reduce defects and scaling up of the vertical Bridgman growth process from its current 67 mm diameter boule size to 92 mm diameter boules. Promising initial results from the large diameter boule growth process will be shown. The 92 mm diameter CdZnTe boule (6 kg charge) shows two predominant single crystal grains encompassing 75% of boule volume. Defect characterization of boules grown under baseline and modified conditions is discussed.     

Photoresponsive Fiber Array: Toward Mimicking the Collective Motion of Cilia for Transport Applications

Remote transport of material is an utmost useful, but challenging, property expanding the design possibilities of many applications such as microfluidics or robotics where species can be carried without interfering with its environment. Nature has solved the problem of transport in e.g., the respiratory system by a concerted motion of cilia. This study addresses a new method to fabricate an array of small parallel fibers acting as cilia placed side by side on a substrate. The fibers consist of a crosslinked liquid crystal main chain polymer functionalized with coreactant azobenzene molecules. The fibers bend toward a light source in a concerted manner. When placed in a liquid, the cooperative bending motion of the fibers creates a flow able to efficiently carry objects. The proposed fabrication process of the fibers is scalable to large area and requires an optimized rheology which is achieved by converting low molecular weight reactive liquid crystal acrylate monomers to oligomers using a multiplication of the monomeric units by the Michael addition reaction with dithiol. The oligomer properties and the elasticity of the fibers are adjusted by changing the thiol spacer leading to optimized manufacturing and maximized optical response.     

A non-antibacterial oxazolidinone derivative that inhibits epithelial cell sheet migration

We have developed a high-throughput assay for screening chemical libraries for compounds that affect cell sheet migration during wound closure in epithelial cell monolayers. By using this assay, we have discovered a new inhibitor of cell sheet migration. This compound (UIC-1005) is a 3,4-disubstituted oxazolidinone that bears an electrophilic alpha,beta-unsaturated N-acyl group required for activity. UIC-1005 also inhibits growth in an epithelial cell proliferation assay. The molecule does not display general toxicity at concentrations at which it potently inhibits cell sheet migration and growth. Unlike certain 3,5-disubstituted oxazolidinones, it exhibits no antibacterial activity. UIC-1005 therefore represents a new class of bioactive oxazolidinone derivative that may prove useful as a probe for signaling pathways leading to cell motility.     

Assessment of strain gradients affecting the performance of 3-D strain rosettes – relevant to the analysis of cement mantle strains in total hip replacements

A large scale model analysis, using embedded strain gauges, of the strain distribution in the cement mantle surrounding a femoral prosthesis is underway. In order to predict, and so avoid, positions of locally high strain gradients in this model, a finite element and experimental analysis of a similar problem was undertaken. For this purpose, a loose fitting rectangular steel insert inside a surrounding rectangular epoxy sheath was used to model an extreme case of the torsional and bending components of hip joint load. The axial component of joint load was modelled using an axisymmetric finite element model of a tapered shaft. The finite element results were used to determine suitable positions for embedding gauges in the experimental model. Results showed that the finite element analysis failed to adequately model the close sliding fit between the steel insert and epoxy. Altering the experimental model to artificially replicate the finite element contact conditions produced good correlation in bending, with experimental strains agreeing with simple bending theory to within 6%. Satisfactory correlation under torsional loading was not obtained, but strain magnitudes were low. Predicted positions for embedding gauges give conservative results, lessening the possibility of strain gradient induced error in the large scale model test of the cement mantle and prosthesis.     

A Far Infrared Super Radiant FEL

The basic physics, results of 3–D simulations, and relevant parameters for the design of a far infrared FEL, which operates in the SASE superradiant short bunch regime, are presented. It is shown that a quite interesting device can be easily developed, with rather new features, producing coherent laser pulses with ～10 psec duration and around 7 MW peak power.     

The survey on ARM processors for HPC

The Journal of Supercomputing - The ongoing effort to reach the exascale computing barrier has led to a myriad of research and publications in the topic of alternative energy-efficient...     

Virtual human animation in natural language visualisation

Simulation motion of Virtual Reality (VR) objects and humans has experienced important developments in the last decade. However, realistic virtual human animation generation remains a major challenge, even if applications are numerous, from VR games to medical training. This paper proposes different methods for animating virtual humans, including blending simultaneous animations of various temporal relations with multiple animation channels, minimal visemes for lip synchronisation, and space sites of virtual human and 3D object models for object grasping and manipulation. We present our work in our natural language visualisation (animation) system, CONFUCIUS, and describe how the proposed approaches are employed in CONFUCIUS’ animation engine.     

Intelligent planning and the design of a new risk-based,intelligent flight plan

A safe flight starts with effective performance of the pre-flight flight planning and briefing task. However, several problems related to the execution of this task can be identified. Potentially, the introduction of an improved flight plan provides an opportunity to improve the quality and availability of information provided to Flight Crew, thereby enhancing the quality of crew briefings. The proposed risk-based, intelligent flight plan is designed from the perspective of the current operational concept (e.g. fixed routes and ATC managerial role for separation), and associated airline Flight Planning and Dispatch functions. In this case, the focus is sharing information across specific airline stakeholders (e.g. Flight Operations Management and Safety functions) and Maintenance, to support a safe and efficient flight operation. Overall, the introduction of this new flight plan will result in the definition of new operational and organisational processes, along with a new way of performing the pre-flight, planning and briefing task. It is anticipated that this will impact positively on the operational and safety outcome of the flight.