Dynamic data compression algorithms in speech coding

Abstract

The single transverse mode AlGaAs/GaAs laser array with pulsed peak power up to 100 mW has been fabricated successfully. The ridge waveguide laser structure was chosen since it needs only one step liquid phase epitaxy which greatly improves the yield. The ridge waveguide was formed by etching the top p‐type cladding layer through a 4 μm to 5 μm mask down to the neighborhood of the active layer to form a lateral refraction index difference. It is found that when the spacing between ridge is 5 μm, individual lasers are not coupled, and the far field pattern displays a diverged single lobe with a half width of 18° similar to that of a single laser. When an end broad area region is inserted, however, the laser array starts to couple and forms a narrow two‐lobe beam with a half width of 5°. The near‐field pattern can be used to analyze the coupling condition.     

Implementation of design of experiments approach for the micronization of a drug with a high brittle–ductile transition particle diameter

Objective: To optimize air-jet milling conditions of ibuprofen (IBU) using design of experiment (DoE) method, and to test the generalizability of the optimized conditions for the processing of another non-steroidal anti-inflammatory drug (NSAID).

Methods: Bulk IBU was micronized using an Aljet mill according to a circumscribed central composite (CCC) design with grinding and pushing nozzle pressures (GrindP, PushP) varying from 20 to 110?psi. Output variables included yield and particle diameters at the 50th and 90th percentile (D₅₀, D₉₀). Following data analysis, the optimized conditions were identified and tested to produce IBU particles with a minimum size and an acceptable yield. Finally, indomethacin (IND) was milled using the optimized conditions as well as the control.

Results: CCC design included eight successful runs for milling IBU from the ten total runs due to powder “blowback” from the feed hopper. DoE analysis allowed the optimization of the GrindP and PushP at 75 and 65?psi. In subsequent validation experiments using the optimized conditions, the experimental D₅₀ and D₉₀ values (1.9 and 3.6?μm) corresponded closely with the DoE modeling predicted values. Additionally, the optimized conditions were superior over the control conditions for the micronization of IND where smaller D₅₀ and D₉₀ values (1.2 and 2.7?μm vs. 1.8 and 4.4?μm) were produced.

Conclusion: The optimization of a single-step air-jet milling of IBU using the DoE approach elucidated the optimal milling conditions, which were used to micronize IND using the optimized milling conditions.     

An AlGaAs/GaAs oxide‐stripe double‐heterostructure laser

Abstract

An AlGaAs/GaAs oxide‐stripe double‐heterostructure (DH) laser is fabricated by liquid‐phase epitaxy (LPE) successfully. This laser consists of four epilayers, i.e., (N) Al_0.35Ga_0.65As cladding layer, (p) Al_0.05Ga_0.95As active layer, (P) Al_0.35Ga_0.65As cladding layer and (p) Al_0.05Ga_0.95As contact layer, and a top SiO₂ insulating layer. The stripe window opened through the SiO₂ layer is either 5 or 10 μm wide. The emission properties of the laser diodes were all measured under pulse mode. The lowest threshold current measured is 95 mA for a 10, μm‐wide stripe laser which corresponds to a threshold current density of 3,200 A/cm². The best power output is more than 30 mW per facet with a differential quantum efficiency of 10% per facet. In addition, the single filament operation is also observed in a 5 μm‐wide stripe laser. The lasing wavelength is centered around 8,500 Å.     

A frequency‐locked position servo control system by microprocessor‐based slope‐varied technique

Abstract

A microprocessor‐based slope‐varied frequency‐pumped controller (μP‐SVFPC) for improving the locking performance of the frequency‐locked position servo control system (FLPS) is presented. The presented slope‐varied pump technique is to perform the position control process fast for a long distance servo, while nearly similar acquisition times for different distance servos are obtained during the servo range. The motion profiles for system locking are adaptively generated according to the coming frequency error. No motion profiles are required to be pre‐installed in the controller. A prototype of μP‐FLPS is realized, simulated, and tested. Computer simulation and experimental result confirm that the system acquisition times of μP‐FLPS for short, middle, and long distance servos are nearly similar to each other. In comparison with the basic FLPS system, the acquisition times of the presented μP‐FLPS for the middle and long distance servos are improved by about 58% and 85%, respectively.     

Establishing an invar leveling calibration system

Abstract

Precise height systems are widely utilized in civil engineering projects such as high‐speed railroads, and highways and bridge construction. However, highly precise height data is obtained using precise leveling. An extremely precise invar leveling rod is necessary for obtaining precise results.

In this study, an automatic calibration system for invar leveling has been established by the National Measurement Laboratory (NML). The content belongs to the long scales calibration system of D17 of the NML. This system utilizes a steady frequency laser interferometer, a CCD microscopic monitor, and a precise moving mechanism. With this system, an invar rod and a mark invar leveling rod are applied to estimate uncertainty with a 95% confidence level. Uncertainty results are 22 μm and 21 μm for the invar leveling rods and mark invar leveling rods, respectively.     

Synthesis of 4‐link function generating mechanisms for optimum transmission angle

Abstract

A combined equation of the expression of optimum transmission angle μ and the loop displacement equation is presented for the synthesis of plane 4‐link function generating mechanisms with the highest minimum (or optimum) μ. The expression of optimum μ is derived via the sensitivity of a function generator, and covers various types of equal deviations of μ between |90 deg‐μ_min | and |90 deg‐|μ_max |. A numerical example is given.     

Correlation between properties and microstructure of laser sintered porous β-tricalcium phosphate bone scaffolds

Abstract

A porous β-tricalcium phosphate (β-TCP) bioceramic scaffold was successfully prepared with our homemade selective laser sintering system. Microstructure observation by a scanning electron microscope showed that the grains grew from 0.21 to 1.32 μm with the decrease of laser scanning speed from 250 to 50 mm min^?1. The mechanical properties increased mainly due to the improved apparent density when the laser scanning speed decreased to 150 mm min^?1. When the scanning speed was further decreased, the grain size became larger and the mechanical properties severely decreased. The highest Vickers hardness and fracture toughness of the scaffold were 3.59 GPa and 1.16 MPa m^1/2, respectively, when laser power was 11 W, spot size was 1 mm in diameter, layer thickness was 0.1–0.2 mm and laser scanning speed was 150 mm min^?1. The biocompatibility of these scaffolds was assessed in vitro with MG63 osteoblast-like cells and human bone marrow mesenchymal stem cells. The results showed that all the prepared scaffolds are suitable for cell attachment and differentiation. Moreover, the smaller the grain size, the better the cell biocompatibility. The porous scaffold with a grain size of 0.71 μm was immersed in a simulated body fluid for different days to assess the bioactivity. The surface of the scaffold was covered by a bone-like apatite layer, which indicated that the β-TCP scaffold possesses good bioactivity. These discoveries demonstrated the evolution rule between grain microstructure and the properties that give a useful reference for the fabrication of β-TCP bone scaffolds.     

Synthesis of Au microwires by selective oxidation of Au–W thin-film composition spreads

Abstract

We report on the stress-induced growth of Au microwires out of a surrounding Au–W matrix by selective oxidation, in view of a possible application as ‘micro-Velcro’. The Au wires are extruded due to the high compressive stress in the tungsten oxide formed by oxidation of elemental W. The samples were fabricated as a thin-film materials library using combinatorial sputter deposition followed by thermal oxidation. Sizes and shapes of the Au microwires were investigated as a function of the W to Au ratio. The coherence length and stress state of the Au microwires were related to their shape and plastic deformation. Depending on the composition of the Au–W precursor, the oxidized samples showed regions with differently shaped Au microwires. The Au₄₈W₅₂ composition yielded wires with the maximum length to diameter ratio due to the high compressive stress in the tungsten oxide matrix. The values of wire length (35 μm) and diameter (2 μm) achieved at the Au₄₈W₅₂ composition are suitable for micro-Velcro applications.     

Generation of microgrooved silica nanotube membranes with sustained drug delivery and cell contact guidance ability by using a Teflon microfluidic chip

Abstract

Silica nanotubes have been extensively applied in the biomedical field. However, very little attention has been paid to the fabrication and application of micropatterned silica nanotubes. In the present study, microgrooved silica nanotube membranes were fabricated in situ by microgrooving silica-coated collagen hybrid fibril hydrogels in a Teflon microfluidic chip followed by calcination for removal of collagen fibrils. Scanning electron microscopy images showed that the resulting silica nanotube membranes displayed a typical microgroove/ridge surface topography with ～50 μm microgroove width and ～120 μm ridge width. They supported adsorption of bone morphogenetic protein 2 (BMP-2) and exhibited a sustained release behavior for BMP-2. After culturing with osteoblast MC3T3-E1 cells, they induced an enhanced osteoblast differentiation due to the release of biologically active BMP-2 and a strong contact guidance ability to directly align and elongate osteoblasts due to the presence of microgrooved surface topography, indicating their potential application as a multi-functional cell-supporting matrix for tissue generation.     

A study of uv preionization pulsed tea CO2 laser

Abstract

A uniform volumetric discharge was obtained by means of an auxiliary UV preionization in a home‐made TEA CO₂ laser. The maximum output pulse energy of this laser system was about 12J per pulse with a pulse duration of 80 ns. The ratio of electric field to neutral particle density (E/N) in this laser was 7.6×10^‐16 V cm². The peak power and pulse shape of the laser were studied. The time delay between the predischarge and the maindischarge during the stable operation of this laser system has also been studied. It was observed that the laser was operating with uniform glow discharges when the time delayed between the predischarge and the maindischarge was in the range of 1.0 μs to 6.0 μs. The spark array used as a preionizer for producing the UV radiation in this system is new, simple, durable, and can be easily fabricated.     

Hollow waveguide integrated optics: A novel approach to 10 μm laser radar

Abstract

A novel integrated optic approach to the manufacture of 10.6μm coherent laser radar systems is described and demonstrated. The approach uses hollow waveguides to guide light between system components which are integrated into a common substrate. The design, manufacture and operation of a seven-element subsystem which is compact and rugged and provides a mixing efficiency in excess of 80% of the theoretical maximum are discussed. The demonstration of the subsystem as a simple homodyne vibrometer is also outlined.     

Ultraviolet-nanoimprinted packaged metasurface thermal emitters for infrared CO2 sensing

Abstract

Packaged dual-band metasurface thermal emitters integrated with a resistive membrane heater were manufactured by ultraviolet (UV) nanoimprint lithography followed by monolayer lift-off based on a soluble UV resist, which is mass-producible and cost-effective. The emitters were applied to infrared CO₂ sensing. In this planar Au/Al₂O₃/Au metasurface emitter, orthogonal rectangular Au patches are arrayed alternately and exhibit nearly perfect blackbody emission at 4.26 and 3.95 μm necessary for CO₂ monitoring at the electric power reduced by 31%. The results demonstrate that metasurface infrared thermal emitters are almost ready for commercialization.     

Ultra-flattened negative dispersion for residual dispersion compensation using soft glass equiangular spiral photonic crystal fiber

Abstract

We present a numerical investigation of an equiangular spiral photonic crystal fibre (ES-PCF) in soft glass for negative flattened dispersion and ultra-high birefringence. An accurate numerical approach based on finite element method is used for the simulation of the proposed structure. It is demonstrated that it is possible to obtain average negative dispersion of –526.99 ps/nm/km over 1.05–1.70 μm wavelength range with dispersion variation of 3.7 ps/nm/km. The proposed ES-PCF also offers high birefringence of 0.0226 at the excitation wavelength of 1.55 μm. The results here show that the idea of using the proposed fibre can be potential means of effectively directing for residual dispersion compensation, fibre sensor design, long distance data transmission system and so forth.     

A minimum zone method for evaluating flatness error of gage blocks measured by phase‐shifting interferometry

Abstract

A new method called “Control Plane Rotation Scheme (CPRS)” has been developed here for the analysis of flatness error in terms of the minimum zone definition, which conforms to the ISO/R1101 specification. An application of the phase‐shifting interferometry was performed for on‐line measurement of gage blocks. Experimental results were quite consistent with the specified grade of the inspected gage block with only an uncertainty of up to 0.005 μm.     

Stability test of novel combined formulated dry powder inhalation system containing antibiotic: physical characterization and in vitro–in silico lung deposition results

Objective: The aim was to study the stability of dry powder inhaler (DPI) formulations containing antibiotic with different preparation ways – carrier-based, carrier-free, and novel combined formulation – and thereby to compare their physicochemical and in vitro–in silico aerodynamical properties before and after storage. Presenting a novel combined technology in the field of DPI formulation including the carrier-based and carrier-free methods, it is the most important reason to introduce this stable formulation for the further development of DPIs.

Methods: The structure, the residual solvent content, the interparticle interactions, the particle size distribution and the morphology of the samples were studied. The aerodynamic values were determined based on the cascade impactor in vitro lung model. We tested the in silico behavior of the novel combined formulated samples before and during storage.

Results: The physical measurements showed that the novel combined formulated sample was the most favorable. It was found that thanks to the formulation technique and the use of magnesium stearate (MgSt) has a beneficial effect on the stability compared with the carrier-based formulation without MgSt and carrier-free formulations. The results of in vitro and in silico lung models were consistent with the physical results, so the highest deposition was found for the novel combined formulated sample during the storage.

Conclusions: It can be established that after the storage a novel combined formulated DPI contained amorphous drug to have around 2.5?μm mass median aerodynamic diameter and nearly 50% fine particle fraction predicted high lung deposition in silico also.     

Fabrication of optimized oil–water separation devices through the targeted treatment of silica meshes

Abstract

Efficient oil–water separation is achieved using an optimized superhydrophobic material, generated by the zeolitic roughening and subsequent hydrophobic surface treatment of silica filter membranes. The material is both highly rough and intrinsically hydrophobic, resulting in superhydrophobic membranes which show a substantial affinity for hydrophobic solvents and oils. The membranes are syringe-mounted, suction pressure is applied and the selective collection of oil is achieved. The membranes are extremely robust, which is a result of the zeolitic roughening process, they possess small pores (0.7 μm), as a result these devices can perform complete separation and operate at a range of suction pressures. The devices could be readily used in a range of real-world applications, including oil spill clean-up and industrial filters.     

Preparation and evaluation of a timolol maleate drug–resin ophthalmic suspension as a sustained-release formulation in vitro and in vivo

Abstract

The aim of this work was to assess the performance of resin as an ocular delivery system. Timolol maleate (TM) was chosen as the model drug and an ion exchange resin (IER) as the carrier. The drug–resin complex was prepared using an oscillation method and then characterized regarding particle size, zeta potential, morphology, and drug content. After in vitro drug release study and corneal permeation study were performed, in vivo studies were performed in New Zealand albino rabbits using a suspension with particles sized 4.8?±?1.2?μm and drug loading at 43.00?±?0.09 %. The results indicate that drug released from the drug–resin ophthalmic suspension permeated the cornea and displayed a sustained-release behavior. Drug levels in the ocular tissues after administration of the drug–resin ophthalmic suspension were significantly higher than after treatment with an eye drop formulation but were lower in body tissues and in the plasma. In conclusion, resins have great potential as effective ocular drug delivery carriers to increase ocular bioavailability of timolol while simultaneously reducing systemic drug absorption.     

Enhanced coherent terahertz emission from indium arsenide

Abstract

We present results showing enhancement of terahertz (THz) emission from indium arsenide (InAs) which demonstrate that at 170 K and magnetic fields (B) up to B = 8 T, increased visible to terahertz conversion efficiencies are possible. With an average total power of 1μW at B = 0 T and 12μW at B = 8 T, we have observed an order of magnitude increase in total conversion efficiency with no visible saturation. The InAs sample was placed within an optical cryostat and illuminated by Ti:Sapphire laser pulses with duration 100 fs. The terahertz powers were recorded using a calibrated He-cooled bolometer. Free space electro-optic sampling (EOS) measurements confirmed the coherent nature of this radiation over the field and temperature range investigated. The optical cryostat could produce magnetic fields of B = 8 T at temperatures from 3 to 300 K. We therefore present a comprehensive study of the terahertz generation as a function of both these variables and a brief comparison with an alternative material system, InSb.     

Anisotropic multi-step etching for large-area fabrication of surface microstructures on stainless steel to control thermal radiation

Abstract

Controlling the thermal radiation spectra of materials is one of the promising ways to advance energy system efficiency. It is well known that the thermal radiation spectrum can be controlled through the introduction of periodic surface microstructures. Herein, a method for the large-area fabrication of periodic microstructures based on multi-step wet etching is described. The method consists of three main steps, i.e., resist mask fabrication via photolithography, electrochemical wet etching, and side wall protection. Using this method, high-aspect micro-holes (0.82 aspect ratio) arrayed with hexagonal symmetry were fabricated on a stainless steel substrate. The conventional wet etching process method typically provides an aspect ratio of 0.3. The optical absorption peak attributed to the fabricated micro-hole array appeared at 0.8 μm, and the peak absorbance exceeded 0.8 for the micro-holes with a 0.82 aspect ratio. While argon plasma etching in a vacuum chamber was used in the present study for the formation of the protective layer, atmospheric plasma etching should be possible and will expand the applicability of this new method for the large-area fabrication of high-aspect materials.     

Wavelet transform in the context of quantum mechanics and new orthogonal property of mother wavelets in parameter space

Based on the quantum mechanical version of wavelet transform (WT) W _ψ f(μ,s)?=??ψ|U(μ,s)|?f?? [Fan, H.Y.; Lu, H.L. Opt. Lett. 2006, 31, 407] we further prove Parseval theorem and inversion formula for WT in the context of quantum mechanics. The concise proof not only manifestly shows the merit of Dirac's representation theory, but also leads to a new orthogonal property of mother wavelets in parameter space.