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Optical-Fiber Corrosion Sensor Based on Deposit of Au/Ni–P

The realization of an optical-fiber corrosion sensor (OFCS) has been achieved using two different methods. In the first method, a plastic clad silica (PCS) fiber whose uncladded part (2 cm in length) has been metallized through deposition using nickel–phosphorus. In the second method, metallization used gold and nickel–phosphorus. The light power [P(α)] at the exit end of the fiber is recorded as a function of the angle (α, angle of incidence) made by the axis of the fiber and a beam from a laser diode at a 670 nm wavelength applied at the entrance of the fiber. It is observed that the corrosion of the coating material (nickel–phosphorus) modifies the P(α) curves, be it by immersion in phosphoric acid solutions. The full width at half-maximum of these curves increases with increasing corrosion pit density. Kinetic curves of corrosion have been obtained for different concentrations of phosphoric acid. This type of sensor is important because it can be inserted in metallic infrastructures to monitor the corrosion state of the structure in situ.

Powder evolution at low powers in silane-argon discharge

Powder formation in a 13.56-MHz radio frequency (rf) capacitive glow discharge plasma of silane-argon mixture has been studied by in situ laser light-scattering measurements. The rf power density (Prf) was varied from 18to53mW∕cm2. At high Prf the light scattering occurs all along the discharge and extends even beyond the exit end of the electrodes toward the pumping system. With decreasing Prf the maximum intensity of the light scattering decreases and the scattering zone shrinks and moves toward the exit end. With Prf≈20mW∕cm2 a very bright scattering zone only a few centimeters wide appears located at the electrodes outlet. The powders studied by transmission electron microscopy did not show a drastic decrease of their sizes with Prf though clear coagulation of small particles is observed at high Prf. In this paper we have tried to link the laser light-scattering evolution with Prf to various parameters such as the microstructure factor, the deposition rate, the electron mobility×lifetime product, the density of states, and the minority-carriers diffusion length of the films in an attempt to link the effect the evolution of powder formation to the films properties.

Adiabatic compression of parallel-plate metal waveguides for sensitivity enhancement of waveguide THz time-domain spectroscopy

We demonstrate the efficient coupling of THz pulses into and out of an adiabatically compressed parallel-plate metal waveguide. The plate separation of the 63.5-mm long, compressed waveguide was fixed at 103μm at the entrance and exit ends for efficient coupling, but could be reduced in the middle. The experimental results show strong transmission of the THz signal through the compressed waveguide for a minimum midpoint separation of only 8μm. This technique can be used to achieve efficient coupling together with higher sensitivity for waveguide THz-TDS.

Improved quality of life (QoL) among seasonal allergic rhinitis (SAR) patients treated with olopatadine HCl nasal spray, 0.4% and olopatadine HCl nasal spray, 0.6% compared to vehicle

Rationale Since SAR causes a considerable impact on QoL, the Rhinoconjunctivitis Quality of Life (RQLQ) Questionnaire was used to assess the QoL impact of olopatadine HCl nasal spray compared to the vehicle. Methods The 28-item RQLQ, consisting of 7 domains (activities, sleep, non-hayfever symptoms, practical problems, nasal symptoms, eye symptoms, and emotional), was used to collect QoL data during a multicenter, randomized, double-masked SAR (mountain cedar) trial comparing olopatadine HCl nasal spray, 0.6% and 0.4% against the olopatadine vehicle. Patients, recruited with at least a 2-yr history of non-recalcitrant SAR, filled out the questionnaire at baseline (randomization visit), and again after 2 weeks at the exit (end of treatment) visit. Results Olopatadine 0.6% (−1.1 + −1.4) and 0.4% (−1.1 + −1.3) nasal sprays were superior ( p<0.05) to vehicle (−0.8 + −1.2) for the mean change from baseline in overall RQLQ score in the intent-to-treat population (lower RQLQ score=better QoL). Additionally, olopatadine HCl spray, 0.6% was superior to vehicle in all RQLQ domains except non-hayfever symptoms ( p<0.10), and olopatadine HCl spray, 0.4% was superior to vehicle in 5 RQLQ domains: non-hayfever symptoms, practical problems, nasal symptoms, eye symptoms, and emotional symptoms( p<0.05). Conclusions Both olopatadine HCl nasal sprays are superior to vehicle in improving overall QoL. While patients receiving olopatadine HCl nasal spray, 0.6% had significantly demonstrable improvement in all areas of their life except non-hayfever symptoms, patients receiving olopatadine 0.4% nasal spray had significant improvement in 5 out of the 7 total QoL areas.

Design of high-power ISOL targets for radioactive ion beam generation

In this report, we provide lists of refractory oxides, carbides and refractory metals suitable for use as targets for producing short-lived, proton-rich isotopes of elements (He through Pu) and neutron-rich isotopes of elements (As through Dy) for potential use at high-energy, ISOL-based radioactive ion beam facilities. Complex structure, highly permeable C matrices are described for coating with optimum thicknesses of any type of refractory target material (metal, carbide or oxide). Prescriptions are given for the design and fabrication of custom-engineered targets with diffusion lengths compatible with the release of isotopes of interest within their lifetimes. Computationally derived thermal analysis information is presented for selected low-density, fibrous, highly permeable targets, subjected to direct irradiation with 1 GeV, 100–400 kW proton beams. From these studies, internal thermal radiation is reconfirmed as an important heat transfer (cooling) mechanism within low-density, fibrous and composite targets. By utilization of the radiation cooling effect and beam manipulation techniques, in combination with placement of additional heat shielding on the exit end of targets, beam power depositional densities can be controlled and temperatures homogenized to acceptable levels within fast diffusion release, fast effusive-flow ISOL targets subjected to irradiation with 400 kW proton beams, as required at next-generation radioactive ion beam facilities.

MAXIMAL HEAT TRANSFER DENSITY IN VERTICAL MORPHING CHANNELS WITH NATURAL CONVECTION

In this article we show numerically that the entire flow geometry of a vertical diverging or converging channel with laminar natural convection can be optimized for maximal heat transfer rate density (total heat transfer rate per unit of flow system volume). The geometry is free to change in three ways: (1) the spacing between the walls, (2) the distribution of heating along the walls, and (3) the angle between the two walls. Numerical simulations cover the Rayleigh number range 105 ≤ RaH ≤ 107, where H is the channel height. Nonuniform wall heating is modeled as an isothermal patch of varying height H 0 (≤H) on each wall, which is placed either at the bottom (entrance) end of the channel, or at the top (exit) end. The results confirm that the use of upper unheated sections enhances the chimney effect and the heat transfer. The new aspect is that the heat transfer rate density decreases because the unheated sections increase the total volume. It is shown that for maximal heat transfer rate density it is better to place the H 0 sections at the channel entrance. It is also shown that the optimal angle between the two walls is approximately zero when Ra H is large, i.e., for maximal heat transfer rate density the walls should be parallel or nearly parallel. Finally, the optimized spacing (1) developed in the presence of (2) and (3) as additional degrees of freedom is of the same order of magnitude as the optimal spacing reported earlier for parallel isothermal walls, i.e., in the absence of features (2) and (3). The robustness of the optimized flow architecture is discussed. Additional degrees of freedom and global objectives that may be incorporated in this constructal approach are the curvature of the facing walls and the mechanical strength and stiffness of the confining walls.

A combined source of electron bunches and microwave power

In this article, the possibility of using a high power klystron amplifier simultaneously as a microwave power source as usual and an electron bunches source by extracting the spent beam with a magnet and also as an oscillator by feedback is investigated. The purpose of this study is to demonstrate the feasibility of constructing a very compact electron linear accelerator or for other applications of electron bunches. The feasibility of the idea was first examined by computer simulation of the electron motion in a 5 MW klystron and the characteristics of the klystron spent beam. Experimental study was then carried out by installing a radio frequency cavity and a Faraday cage in sequence at the exit end of a bending magnet located at the top of the klystron collector. The energy and current of the chopped spent electron beam can then be measured. By properly choosing the feedback circuit elements, the frequency stability of the klystron in oscillator mode was proved to be good enough for linac operation. According to the results presented in this article, it is evident that an extremely compact linac for research and education with better affordability can be constructed to promote the applications of linacs.

Visualization of return flow structure in mixed convection of gas over a heated circular plate in a horizontal flat duct

Experimental flow visualization is conducted here to investigate the buoyancy-induced return flow structure in mixed convection of gas over a heated circular plate mounted on the bottom of a horizontal flat duct, simulating that in a horizontal longitudinal flow reactor. In particular, how the return flow induced in the upstream portion of the duct is related to the vortex flow in the downstream is delineated. The results show that at a low buoyancy-to-inertia ratio only steady longitudinal vortex rolls (L-rolls) are induced in the exit half of the duct and no return flow appears in the duct. At an intermediate buoyancy-to-inertia ratio a small flow recirculation exists around the duct inlet near the top wall and the L-rolls become unsteady. When the buoyancy-to-inertia ratio is high and the Reynolds number is small with Re<10, the upstream return flow is strong and occupies a large region. There is another return flow zone around the exit end of the duct. Over the heated circular plate the flow is dominated by the moving transverse rolls (T-rolls). Moreover, the return flow around the duct inlet at steady or statistically stable state is in the form of a semicircular roll around the upstream edge of the circular plate. Flow visualization also reveals that the splitting of the downstream tip of the return flow zone and the rising of the buoyancy-driven spanwisely extended thermal under the tip generate a pair of counter-rotating transverse rolls in the entry portion of the duct. In addition, the criterion for the onset of the return flow near the duct inlet, the size and the center position of the return flow, based on the present experimental data, are correlated empirically.

Refractive wave muffler

Within an exhaust duct are positioned a plurality of concentrically arranged, open ended, right cylinders supported axially within the exhaust duct, wherein each of the cylinders includes an inlet end and an exit end. The inlet ends are positioned in sequential downstream order from the outermost of the cylinders to the innermost of the cylinders. The cylinders are graduated in length sequentially with the outermost cylinder being shortest in length and the innermost cylinder being longest in length. The inlet ends of each of the cylinders provide a circular leading edge with a sawtooth conformation. An elongated smooth rod is positioned on the longitudinal axis of the exhaust duct with a downstream end of the rod providing a flared portion positioned at the mouth of the innermost of the cylinders. A plurality of radially directed flow directing vanes are engaged along thier outer edge with an inside surface of the exhaust duct and also along an inside edge with each of the cylinders and the rod for securing them in place within the exhaust duct. These flow directing vanes extend upstream of the outermost of the cylinders and downstream of the innermost of the cylinders.

Measurement of external ion injection and trapping efficiency in the ion trap mass spectrometer and comparison with a predictive model

The efficiency of injecting and trapping ions from an external ion source in a quadrupole ion trap mass spectrometer was measured and compared against a simulation employing a simple hard-sphere collision model. A commercial ion trap mass spectrometer was modified with the addition of a variable energy ion gun, split Faraday cup/electron multiplier detector, and the capability to measure the ion current incident on the ion trap inlet and exit end caps. The entire instrument was modeled using the ion optics simulation program SIMION and user programs were applied in SIMION which modeled the collisions between the injected ions and the helium buffer gas. The model was based on simple hard-sphere collision physics with randomized collision angles and collision probability converging to the mean free path (mfp); the helium buffer gas was assumed to be at rest relative to the injected ions. The measured trapping efficiency of Cs + with helium buffer gas at optimum conditions was 3–5%. The trapping efficiency predicted by the model and the dependence on buffer gas pressure (mfp) agreed with the measured efficiencies within the uncertainties of the model predictions and experimental variance. The fidelity of the simulation was shown to be sensitive to the spatial resolution of the model when predicting the dependence of trapping efficiency on q z. It was concluded that a hard-sphere collision model was adequate for predicting the effects of helium buffer gas pressure on ion injection and trapping within the range of injection energies and buffer gas pressures tested.

Superluminal pulse propagation through one-dimensional photonic crystals with a dispersive defect.

The propagation of a pulse through one-dimensional photonic crystals that contain a dispersive and absorptive defect layer doped with two-level atoms is discussed. The dynamical evolution of the pulse inside the photonic crystal is presented. Superluminal negative group velocity (the peak appears at the exit end before it reaches the input end) is discovered. Although the group velocity is larger than c and even negative, the velocity of energy propagation never exceeds the vacuum light speed. The appearance of the superluminal advance or subluminal delay of the pulse peak inside the photonic crystal or at the exit end is due to the wave interference from Bragg reflections.

Irradiation facility for boron neutron capture therapy application based on a rf-driven D–T neutron source and a new beam shaping assembly (abstract)

Selecting the best neutron source for boron neutron capture therapy (BNCT) requires optimizing neutron beam parameters. This involves solving many complex problems. Safety issues related to the use of nuclear reactor in hospital environments, as well as lower costs have led to interest in the development of accelerator-driven neutron sources. The BNCT research programs at the Nuclear Departments of Pisa and Genova Universities (DIMNP and DITEC) focus on studies of new concepts for accelerator-based DT neutron sources. Simple and compact accelerator designs using relatively low deuteron beam energy, ∼100 keV, have been developed which, in turn, can generate high neutron yields. New studies have been started for optimization of moderator materials for the 14.1 MeV DT neutrons. Our aim is to obtain an epithermal neutron beam for therapeutic application at the exit end, with minimal beam intensity losses, the specific goal is to achieve an epithermal neutron flux of at least of 1×109 n/cm2 s at the beam port, with low gamma and fast neutron dose contamination. According to the most recent neutron BNCT beam parameters some moderating and spectrum shifter materials and geometrical configurations have thus far been tested, and neutron and gamma beam data at beam port have been computed. A possible beam shaping assembly model has been designed. This research demonstrates that a DT neutron source could be successfully implemented for BNCT application, with performance surpassing the minimum requirements stated above, using DT neutron sources with yields in the range 1013–1014 n/s. The latest Monte Carlo simulation results of an accelerator based facility which relies on a rf-driven DT fusion neutron generator will be presented.

Controlled Blasting for Removal of Concrete Plugs in Draft Tube Tunnels at Sardar Sarovar Project

During construction of the Sardar Sarovar (Narmada) Hydro Electric Project in India, an unprecedented flood entered the power house cavern through draft tube tunnels and caused damage to underground structures. After this incident, these draft tubes were plugged with concrete/reinforced concrete to prevent future flooding. After heavy gates were erected at the exit end of the draft tube tunnels, these plugs had to be removed by drilling and blasting without causing any damage to the concrete lining and the ribs erected in the tunnels. Controlled blasting was designed and executed successfully for removal of the plugs in the same manner as for tunnel blasting. This paper describes the details of concrete plugs, details of drilling and blasting adopted, and some interesting observations in respect of drilling and blasting in the concrete plugs. A seismic method based on the measurement of P-wave velocity in the concrete lining before and after blasting was used to quantify the changes (damage) to concrete lining.

Recent trends in the biosorption of heavy metals: A review

Considerable attention has been focused in recent years upon the field of biosorption for the removal of metal ions from aqueous effluents. Compared to other technologies, the advantages of biosorption are the high purity of the treated waste water and the cheap raw material. Really, the first major challenge for the biosorption field is to select the most promising types of biomass. Abundant biomass types either generated as a waste by-product of large-scale industrial fermentations particularly fungi or certain metal-binding seaweeds have gained importance in recent years due to their natural occurrence, low cost, and, of course, good performance in metal biosorption. Industrial solutions commonly contain multimetal systems or several organic and inorganic substances that form complexes with metals at relatively high stability forming a very complex environment. When several components are present, interference and competition phenomena for sorption sites occur and lead to a more complex mathematical formulation of the process. The most optimal configuration for continuous flow-biosorption seems to the packed-bed column which gets gradually saturated from the feed to the solution exit end. Owing to the competitive ion exchange taking place in the column, one or more of the metals present even at trace levels may overshoot the acceptable limit in the column effluent before the breakthrough point of the targeted metal. Occurrence of ‘overshoot's and impact on heavy metal removal has not been analyzed enough. New trends in biosorption are discussed in this review.

An investigation into melt flow dynamics during repetitive pulsed laser drilling of transparent media

This paper presents an investigation into the dynamics of repetitive pulsed laser drilling of a visually transparent media using a CO 2 laser source. This enabled the use of a high-speed imaging system for observing, in real time, the behaviour of the drilling process in the laser drilled cavity of 1.5 mm diameter holes of up to 18.5 mm in depth. The work revealed that the instantaneous drilling velocity within each laser pulse can vary considerably from the average drilling velocity as a result of the non-uniform temporal pulse shape and the oscillation of the melt ejection rate. During beam breakthrough, both upward and downward melt ejections were observed to occur inside the drilled hole for a short period of time, after which the material was ejected through the exit end of the holes. It has been shown in this work that the downward melt flow velocity increases with hole depth for a positively tapered hole (from 0.09 to 1.43 m/ s) and decreases with hole depth for a negatively tapered hole geometry (from 0.4 to 0.1 m/ s ), as a result of the change in the assist gas velocity inside the drilled hole with respect to the hole taper geometry. The mechanisms of forming the positively and negatively tapered holes in the transparent media have been correlated with the hole geometry and melt flow velocity. The work has demonstrated a new method of studying the melt dynamics in laser drilling.

Shape measurement based on fiber-optic technique for complex internal surface

Reverse engineering based on fiber-optic technique is a very new topic in CAD/CAM fields. A novel single-mode fiber-optic sensor is presented based on the principle of beam reflection to implement the digitizing of complex surface shape. The fibers in the sensor probe are arranged like a spoke with eight symmetrically cross-arranged receiving fibers and one centered emitting fiber. Thus, the sensor can compensate for the offsets caused by fluctuations of surface reflectivity and light power and is fit for application under rough and formidable conditions with noncontact, fast shape measurement. A prototype was developed based on the simulation results to verify the feasibility. With the GRIN lens on the exit end of the single-mode emitting fiber, the lateral resolution was greatly improved compared with former multimode fiber-optic displacement sensors. Preliminary experiments indicated that the estimated uncertainty of displacement measurement was better than ±2 μm, and the uncertainty of ±5.6 μm can be obtained when measuring a MJ20×1.5 thread.

Calculation and optimization of plasma-optic focusing devices

(i) The focusing of an ion beam by a Morozov lens formed by a current ring in a plasma is calculated using an exact expression for the magnetic field and taking into account the nonparaxial character of the focused beam. The possible ways of optimizing such a lens are considered. (ii) Different versions of extended plasmaoptic devices in which spherical aberrations are minimized are analyzed. It is proposed to optimize extended plasma-optic devices by changing the magnetic field from the entrance end to the exit end of the solenoid in such a way that the boundary magnetic surface always coincides with the boundary surface of the focused beam. It is shown that, under the same conditions, the focusing power of the optimized devices is one to two orders of magnitude higher than that of traditional thin plasma lenses. (iii) The problem of creating a magnetic field whose strength is optimized as a function of the longitudinal coordinate is solved by the Tikhonov regularization method. (iv) An extended plasma-optic device with an optimized solenoid for focusing 1-MeV ion beams is calculated, and the ion trajectories in the device are traced. (v) It is proved expedient to develop special-purpose computer codes aimed at modeling and optimizing the existing and planned experimental plasma-optic focusing devices.

THE INFLUENCE OF GRASS AND POROUS BARRIER STRIPS ON RUNOFF HYDROLOGY AND SEDIMENT TRANSPORT

A series of experiments was conducted in a large tilting flume to investigate the effects of buffer strips on flowhydrology and sediment transport/deposition in and around the strips. Changes in flow depth caused by buffer strips of eithernails or grass were recorded, photographed, and measured with a high degree of accuracy. Flow retardation took place atsome distance ahead of the strips, causing the water level to rise. This distance is dependent upon flume slope and strip densityfor any given flow rate. With any increase in flume slope, the point at which water depth increased moved closer to the strip,entering it at around 6% slope. An exponential relationship exists between flume slope and backwater length. Backwaterlength is also dependent on strip density, and the relationship between these two factors is linear. Under our experimentalconditions, sediment deposition did not take place within the strips, but before and after it. The lack of deposition inside thestrips appears to be contrary to the common expectation from this technique. The bulk of sediment load in the sedimentladenflow approaching the strips was deposited ahead of the strips, commencing at the point where flow depth started to rise. Thefiner fraction of sediment load that entered the strip with the flow emerged from the other end unchanged. Some depositiontook place as fans downstream of the strips, an indication of resistive flow velocity being slower before and after the stripsthan within them. When the soil or sand were not consolidated, significant erosion took place inside the strips, creating a headfall at the exit end of the strips, which moved upslope within the strips as experiments continued. For the range of slopes andstrip widths studied, the efficiency of the grass or nail strips in slowing down the flow and unloading its sediment in thebackwater region was independent of the width of strips in the flow direction. Grass strips thus appear to behave more likegrass barriers or grass buffers than filter strips, as they are referred to in some literature. The process interpretationof these results is discussed in this article.

Simple interface for capillary electrophoresis–inductively coupled plasma atomic emission spectrometry

A simple interface has been developed to couple capillary electrophoresis (CE) to inductively coupled plasma atomic emission spectrometry (ICP-AES) for metal speciation. A concentric glass nebulizer with elongated tip is used as the CE–ICP interface. The CE capillary is the central tube of the nebulizer. A platinum wire is wrapped across the exit end of the CE capillary to provide electrical connection to the CE power supply. No sheath flow of buffer solution is needed. A simple cooling system has also been developed. A peristaltic pump circulates water through a plastic tube that encloses the section of the CE capillary between the CE instrument and the ICP spectrometer. Characteristics of the CE–ICP interface, e.g., elution time, nebulization and transport efficiency and peak broadening, versus carrier gas flow-rate have been studied. Comparisons to a previous design with the Pt electrode inserted into the end of the CE capillary are made where appropriate. The reproducibility (RSD) in ICP emission intensity of the system is <4%. Detection limits of Cr and Cu are ∼5 ng/ml.

Thermal imaging through ordered bundles of infrared-transmitting silver-halide fibers

Ordered bundles of infrared-transmitting silver-halide (AgClxBr1−x) fibers were fabricated by extrusion. Bundles of total area 5–20 mm2 and lengths 5–50 cm included 100–2500 individual fibers and the packing fraction was 0.2–0.3. Each of the individual fibers was transparent in the spectral range 3–30 μm, and therefore, the whole bundle was suitable for thermal imaging. The modulation transfer function was studied using the “bar chart” and the “knife-edge” methods. The resolution was found to be 4–5 lines/mm for a 900 fiber bundle. Thermal images of objects at room temperature were transmitted from the entrance ends to the exit ends of the bundles.