Spectral domain analysis of frequency-selective surfaces on biaxially anisotropic substrate

A full-wave analysis is presented of frequency-selective surfaces (FSSs) on a biaxially anisotropic substrate. The integral equations are first transformed into the spectral domain ones through the use of the Floquet theorem and then solved by the method of moments. Since the wave immittance of the biaxially anisotropic substrate is derived in a closed form, the resulting impedance matrix can be obtained conveniently by using the spectral domain immittance approach (SDI). The validity of theoretical formulations is verified by illustrative numerical results and their comparisons. The obtained results are compared with the existing data and other analyses and good agreements are observed. The effects of biaxially anisotropy on the FSS have been studied and discussed     

An Efficient Volume Integral Equation Solution to EM Scattering by Complex Bodies With Inhomogeneous Bi-Isotropy

A generalized volume integral equation method is formulated for electromagnetic scattering by arbitrarily shaped complex bodies with inhomogeneous bi-isotropy. Based on the volume equivalence principle, the integral equations are represented in terms of a pair of coupled bi-isotropic polarized volume electric and magnetic flux densities. Reduction of the integral equations into the corresponding matrix equations is obtained using the method of moments (MoM) combined with the tetrahedral mesh. In the MoM solution, the three-dimensional solenoidal function is incorporated as the basis function defined over each tetrahedral element and the details of implementation, particularly the treatment of integral singularities, will be elucidated. The efficiency and accuracy of the proposed method are validated by illustratively supported examples.     

A Spectral Multigrid Method Combined With MLFMM for Solving Electromagnetic Wave Scattering Problems

A new spectral multigrid method (SMG) combined with the multilevel fast multipole method (MLFMM) is proposed for solving electromagnetic wave scattering problems. The MLFMM is used to speed up the matrix-vector product operations and the SMG is employed to accelerate the convergence rate of the Krylov iteration. Unlike traditional algebraic multigrid methods (AMG), the spectral multigrid method is an algebraic two-grid cycle built on a preconditioned Krylov iterative method that is used as the smoother, and the grid transfer operators are defined using the spectral information of the preconditioned matrix. Numerical experiments indicate that this class of multigrid method is very effective with the MLFMM and can reduce both the iteration number and the overall simulation time significantly.     

Mechanism for the Cellular Uptake of Targeted Gold Nanorods of Defined Aspect Ratios

Biomedical applications of non‐spherical nanoparticles such as photothermal therapy and molecular imaging require their efficient intracellular delivery, yet reported details on their interactions with the cell remain inconsistent. Here, the effects of nanoparticle geometry and receptor targeting on the cellular uptake and intracellular trafficking are systematically explored by using C166 (mouse endothelial) cells and gold nanoparticles of four different aspect ratios (ARs) from 1 to 7. When coated with poly(ethylene glycol) strands, the cellular uptake of untargeted nanoparticles monotonically decreases with AR. Next, gold nanoparticles are functionalized with DNA oligonucleotides to target Class A scavenger receptors expressed by C166 cells. Intriguingly, cellular uptake is maximized at a particular AR: shorter nanorods (AR = 2) enter C166 cells more than nanospheres (AR = 1) and longer nanorods (AR = 4 or 7). Strikingly, long targeted nanorods align to the cell membrane in a near‐parallel manner followed by rotating by ≈90° to enter the cell via a caveolae‐mediated pathway. Upon cellular entry, targeted nanorods of all ARs predominantly traffic to the late endosome without progressing to the lysosome. The studies yield important materials design rules for drug delivery carriers based on targeted, anisotropic nanoparticles.     

A framework for testing first-order logic axioms in program verification

Program verification systems based on automated theorem provers rely on user-provided axioms in order to verify domain-specific properties of code. However, formulating axioms correctly (that is, formalizing properties of an intended mathematical interpretation) is non-trivial in practice, and avoiding or even detecting unsoundness can sometimes be difficult to achieve. Moreover, speculating soundness of axioms based on the output of the provers themselves is not easy since they do not typically give counterexamples. We adopt the idea of model-based testing to aid axiom authors in discovering errors in axiomatizations. To test the validity of axioms, users define a computational model of the axiomatized logic by giving interpretations to the function symbols and constants in a simple declarative programming language. We have developed an axiom testing framework that helps automate model definition and test generation using off-the-shelf tools for meta-programming, property-based random testing, and constraint solving. We have experimented with our tool to test the axioms used in Auto-Cert, a program verification system that has been applied to verify aerospace flight code using a first-order axiomatization of navigational concepts, and were able to find counterexamples for a number of axioms.     

White-light fluorescent nanoparticles from self-assembly of rhodamine B-anchored amphiphilic poly(poly(ethylene glycol)methacrylate)-b-poly(glycidyl methacrylate) block copolymer

Rhodamine B (RhB)-anchored amphiphilic poly(poly(ethylene glycol)methacrylate)-b-poly(glycidyl methacrylate) block copolymer (PPEGMA-b-PGMA/RhB) has been prepared by a sequential atom transfer radical polymerization and post-functionalization of RhB. The chemical structure of PPEGMA-b-PGMA/RhB is characterized with gel-permeation chromatography, Fourier-transform infrared spectroscopy, and ¹H nuclear magnetic resonance spectroscopy. PPEGMA-b-PGMA/RhB has shown self-assembly behaviors in tetrahydrofuran and aqueous solutions. The RhB aggregation induced with the inter-molecular interaction of RhB results in the various core–shell structures of the assembled nanoparticles. The photoluminescent properties of the PPEGMA-b-PGMA/RhB nanoparticles are structure-dependent and exhibit yellow-light, blue-light, and white-light emissions. The fluorescent organic nanoparticles of PPEGMA-b-PGMA/RhB in aqueous solution show low cytotoxicity and have been used as a bio-dye for cell labelling. Internalization of PPEGMA-b-PGMA/RhB nanoparticles into HELA cells to exhibit fluorescent images has been demonstrated.     

Construction quality in China during transition: A review of literature and empirical examination

Proper management processes were often regarded as the most important factors affecting construction quality, while the availability of capital, plant, and labour were taken for granted and the demands of property users were always ignored. The phenomenon that the construction quality of projects undertaken by State-Owned Enterprises (SOEs) was better than that of non-SOEs revealed that in developing countries such as China during transition, the availability of resources could be very important to construction quality. By utilizing regression models to evaluate 550 robust province level data from 1993 to 2001, this paper will offer an insight into the hard factors affecting construction quality. It is found that higher power of machinery per labourer, the use of more plants or machinery per m² of floor space, properties with larger unit areas, the growth of GDP, the higher labour productivity tender to be associated with higher quality.     

Machinability improvement of titanium alloy (Ti–6Al–4V) via LAM and hybrid machining

Titanium alloy (Ti–6Al–4V) is one of the materials extensively used in the aerospace industry due to its excellent properties of high specific strength and corrosion resistance, but it also presents problems wherein it is an extremely difficult material to machine. The cost associated with titanium machining is also high due to lower cutting speeds (<60 m/min) and shorter tool life. Laser-assisted machining (LAM) and consequently hybrid machining is utilized to improve the tool life and the material removal rate. The effectiveness of the two processes is studied by varying the tool material and material removal temperature while measuring the cutting forces, specific cutting energy, surface roughness, microstructure and tool wear. Laser-assisted machining improved the machinability of titanium from low (60 m/min) to medium-high (107 m/min) cutting speeds; while hybrid machining improved the machinability from low to high (150–200 m/min) cutting speeds. The optimum material removal temperature was established as 250 °C. Two to three fold tool life improvement over conventional machining is achieved for hybrid machining up to cutting speeds of 200 m/min with a TiAlN coated carbide cutting tool. Tool wear predictions based on 3-D FEM simulation show good agreement with experimental tool wear measurements. Post-machining microstructure and microhardness profiles showed no change from pre-machining conditions. An economic analysis, based on estimated tooling and labor costs, shows that LAM and the hybrid machining process with a TiAlN coated tool can yield an overall cost savings of ～30% and ～40%, respectively.     

A continuous ultrasound‐assisted packed‐bed bioreactor for the lipase‐catalyzed synthesis of caffeic acid phenethyl ester

BACKGROUND: The focus of this paper is the ultrasound‐assisted synthesis of caffeic acid phenethyl ester (CAPE) from caffeic acid and phenyl ethanol in a continuous packed‐bed bioreactor. Immobilized Novozym^® 435 (from Candida antarctica) is used as the catalyst. A three‐level–three‐factor Box–Behnken design and a response surface methodology (RSM) are employed to evaluate the effects of temperature, flow rate, and ultrasonic power on the percentage molar conversion of CAPE. RESULTS: Based on ridge max analysis, it is concluded that the optimum condition for synthesis is reaction temperature 72.66 °C, flow rate 0.046 mL min^?1, and ultrasonic power 1.64 W cm^?2. The expected molar conversion value is 97.84%. An experiment performed under these optimal conditions resulted in a molar conversion of 92.11 ± 0.75%. The enzyme in the bioreactor was found to be stable for at least 6 days. CONCLUSIONS: The lipase‐catalyzed synthesis of CAPE by an ultrasound‐assisted packed‐bed bioreactor uses mild reaction conditions. Enzymatic synthesis of CAPE is suitable for use in the nutraceutical and food production industries. Copyright © 2011 Society of Chemical Industry     

Synthesis and properties of poly(ether imide)s derived from 2,5‐bis(3,4‐dicarboxyphenoxy)biphenyl dianhydride and aromatic ether–diamines

A series of poly(ether imide)s (PEIs) with light colors and good mechanical properties were synthesized from 2,5‐bis(3,4‐dicarboxyphenoxy)biphenyl dianhydride and various aromatic ether–diamines via a conventional two‐step polymerization technique that included ring‐opening polyaddition at room temperature to poly(amic acid)s (PAAs) followed by thermal imidization. The precursor PAAs had inherent viscosities ranging from 0.71 to 1.19 dL/g and were solution‐cast and thermally cyclodehydrated to flexible and tough PEI films. All of the PEI films were essentially colorless, with ultraviolet–visible absorption cutoff wavelengths between 377 and 385 nm and yellowness index values ranging from 10.5 to 19.9. These PEIs showed high thermal stabilities with glass‐transition temperatures of 206–262°C and decomposition temperatures (at 10% weight loss) higher than 478°C. They also showed low dielectric constants of 3.39–3.72 (at 1 MHz) and low water absorptions below 0.85 wt %. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009