Simulation of Radiation Field in Multilamp Photoreactor Using the LSDE Model

Determination of a radiation field in a multilamp photoreactor is rather difficult due to the blockage of light by the neighbouring lamps in the reactor. Shadow zones in the photoreactor caused by the lamp blockage vary according to the different lamp arrangements. In addition, the reactor shape also has an effect on the average light intensity, since light is absorbed by the reactor wall if it reaches the wall. In this study, selected aspects of reactor configuration and lamp arrangement were investigated in order to achieve the maximum average light intensity. A line source with a diffused emission (LSDE) model, which shows sufficient accuracy and simplicity, was selected to simulate the light field in the test reactor. Simulation indicates that the square and cylindrical reactors with two and four lamps installed symmetrically exhibited superior performance to elliptical and rectangular reactors. For a multilamp reactor, a triangular pitch of lamp arrangement with 33° is recommended for maximum average light intensity.     

A novel smart hybrid-Trefftz finite element for smart laminated composite plates

A novel smart hybrid-Trefftz finite element ( HTFE ) has been developed for the analysis of smart laminated composite plates. The substrates of the smart plates are symmetric and antisymmetric cross-ply plates. The derivation of this HTFE is devoid of the complicated task of finding the particular solutions of simultaneous governing partial differential equations. The Trefftz functions are constructed from the finite number of free-field exact solutions of the homogeneous simultaneous governing partial differential equations of the element domain in a straightforward manner without transforming them into a single governing equation. The HTFE is validated with the exact solutions of the smart composite plates. It is observed that this HTFE is an efficient finite element and can be utilized for the analysis of active control of smart composite structures.     

Enhancement of electrical conductivity and emission stability of oxide cathodes using Ni addition

An investigation has been carried out into the use of conductive phase additions to enhance the conductivity and emission behavior of the oxide cathode coating as used in CRTs. Electrical and emission characteristics have been studied for various additions of filamentary nickel (Ni) added to the sprayed strontium-barium carbonate precursors prior to spray deposition, followed by conventional thermal conversion and activation processes in vacuum. The conductivity and the electronic activation energy have been studied as a function of temperature in the range 300 to 1250 K, during conversion and activation processes allowing the conduction behavior to be compared to conventional materials. The conduction behavior has been found to change as a function of heat-treatment temperature as the conduction paths develop and subsequently evolve in the microstructure of the resultant composite coating during conversion, activation and subsequent aging/service life conditions, with metallic-dominated conduction at temperatures below 850 K and pore conduction mechanisms dominating at higher temperatures. The emission characteristics immediately after conversion are impaired by the Ni addition, however, the long-term emission characteristics show improvement with the conductive phase.     

Interline Transfer CCD Camera for Gated Broadband Coherent Anti-Stokes Raman-Scattering Measurements

Use of an interline transfer CCD camera for the acquisition of broadband coherent anti-Stokes Raman-scattering (CARS) spectra is demonstrated. The interline transfer CCD has alternating columns of imaging and storage pixels that allow one to acquire two successive images by shifting the first image in the storage pixels and immediately acquiring the second image. We have used this dual-image mode for gated CARS measurements by acquiring a CARS spectral image and shifting it rapidly from the imaging pixel columns to the storage pixel columns. We have demonstrated the use of this dual-image mode for gated single-laser-shot measurement of hydrogen and nitrogen CARS spectra at room temperature and in atmospheric pressure flames. The performance of the interline transfer CCD for these CARS measurements is compared directly with the performance of a back-illuminated unintensified CCD camera.     

Hyperporous Sponge Interconnected by Hierarchical Carbon Nanotubes as a High‐Performance Potassium‐Ion Battery Anode

Recently, commercial graphite and other carbon‐based materials have shown promising properties as the anode for potassium‐ion batteries. A fundamental problem related to those carbon electrodes, significant volume expansion, and structural instability/collapsing caused by cyclic K‐ion intercalation, remains unsolved and severely limits further development and applications of K‐ion batteries. Here, a multiwalled hierarchical carbon nanotube (HCNT) is reported to address the issue, and a reversible specific capacity of 232 mAh g^?1, excellent rate capability, and cycling stability for 500 cycles are achieved. The key structure of the HCNTs consists of an inner CNT with dense‐stacked graphitic walls and a loose‐stacked outer CNT with more disordered walls, and individual HCNTs are further interconnected into a hyperporous bulk sponge with huge macropore volume, high conductivity, and tunable modulus. It is discovered that the inner dense‐CNT serves as a robust skeleton, and collectively, the outer loose‐CNT is beneficial for K‐ion accommodation; meanwhile the hyperporous sponge facilitates reaction kinetics and offers stable surface capacitive behavior. The hierarchical carbon nanotube structure has great potential in developing high‐performance and stable‐structure electrodes for next generation K and other metal‐ion batteries.     

Strong,Conductive, Foldable Graphene Sheets by Sequential Ionic and π Bridging

The goal of this work is to develop an inexpensive low‐temperature process that provides polymer‐free, high‐strength, high‐toughness, electrically conducting sheets of reduced graphene oxide (rGO). To develop this process, we have evaluated the mechanical and electrical properties resulting from the application of an ionic bonding agent (Cr³⁺), a π–π bonding agent comprising pyrene end groups, and their combinations for enhancing the performance of rGO sheets. When only one bonding agent was used, the π–π bonding agent is much more effective than the ionic bonding agent for improving both the mechanical and electrical properties of rGO sheets. However, the successive application of ionic bonding and π–π bonding agents maximizes tensile strength, toughness, long‐term electrical stability in various corrosive solutions, and resistance to mechanical abuse and ultrasonic dissolution. Using a combination of ionic bonding and π–π bonding agents, high tensile strength (821 MPa), high toughness (20 MJ m^?3), and electrical conductivity (416 S cm^?1) were obtained, as well as remarkable retention of mechanical and electrical properties during ultrasonication and mechanical cycling by both sheet stretch and sheet folding, suggesting high potential for applications in aerospace and flexible electronics.     

Evaluation of low cost water purification systems for humanitarian assistance and disaster relief (HA/DR)

Following a natural disaster, access to safe drinking water by the affected population is a high priority. Low cost water purification systems, which can be used for both short-term (immediate) and long-term (sustainable) response to serve the needs of the affected communities, are ideal for these scenarios. The University of Hawaii has developed three low cost water purification technologies for use during humanitarian assistance and disaster relief (HA/DR) missions. A UH team participated in joint USA and partner nation training exercises, such as Crimson Viper 2010 and 2011, organized by the Marine Corps Forces Pacific Experimentation Center (MEC) in Sattahip, Thailand, to demonstrate the effectiveness of these technologies to purify water from local sources. Three technologies were selected for Crimson Viper 2010: (1) a backpack filter unit, (2) a bicycle pump powered reverse osmosis (RO) unit, and (3) a model slow sand filtration unit. For Crimson Viper 2011, improved versions of the backpack and RO units were deployed. This article discusses and evaluates the results obtained during the demonstration of the three technologies at these exercises.     

On anisotropic elasticity and questions concerning its Finite Element implementation

We give conditions on the strain–energy function of nonlinear anisotropic hyperelastic materials that ensure compatibility with the classical linear theories of anisotropic elasticity. We uncover the limitations associated with the volumetric–deviatoric separation of the strain–energy used, for example, in many Finite Element (FE) codes in that it does not fully represent the behavior of anisotropic materials in the linear regime. This limitation has important consequences. We show that, in the small deformation regime, a FE code based on the volumetric–deviatoric separation assumption predicts that a sphere made of a compressible anisotropic material deforms into another sphere under hydrostatic pressure loading, instead of the expected ellipsoid. For finite deformations, the commonly adopted assumption that fibres cannot support compression is incorrectly implemented in current FE codes and leads to the unphysical result that under hydrostatic tension a sphere of compressible anisotropic material deforms into a larger sphere.     

Estimation of oxide related electron trap energy of porous silicon nanostructures

Estimation of electron trap energy (E_t), with respect to bulk Si valence band, of oxidized porous silicon (PS) nanostructures is reported. Photoluminescence (PL) spectra of oxidized PS prepared with different formation parameters have been investigated and the room temperature PL characteristics have been successfully explained on the basis of oxide related trap assisted transitions. PL peak energy for the oxidized samples with low porosity exhibited a blue shift with increasing formation current density (J). For the high porosity samples double peaks appeared in the PL spectra. One of these peaks remained constant at ∼730 nm while the other was blue shifted with increase in J. Evolution of PS nanostructure was correlated to the formation parameters using a simple growth mechanism. PS nanostructure was modelled as an array of regular hexagonal pores and the average value of E_t was estimated to be 1.67 eV.     

Athermalized low-loss echelle-grating-based multimode dense wavelength division demultiplexer

A high-density wavelength division demultiplexer (DEMUX) capable of demultiplexing eight-channel 200-GHz optically spaced signals into a 62.5-microm multimode-fiber array is reported. The wavelength range of operation is from 1549.32 to 1560.61 nm within the International Telecommunication Union grid. The measured wavelength accuracy is within 0.04 nm. The mean insertion loss of this DEMUX is 1.95 dB. Thermal analysis and temperature testing results are reported. The temperature test cycling from 20 degrees C to 60 degrees C indicates that the wavelength thermal drift is less than 0.8 pm/degrees C. Adjacent cross talk is measured to be better than -45 dB. The measured data transmission bit rate of this device is higher than 3.5 Gb/s.