Boundary integral methods in low frequency acoustics

Abstract

This expository paper is concerned with the direct integral formulations for boundary value problems of the Helmholtz equation. We discuss unique solvability for the corresponding boundary integral equations and its relations to the interior eigenvalue problems of the Laplacian. Based on the integral representations, we study the asymptotic behaviors of the solutions to the boundary value problems when the wave number tends to zero. We arrive at the asymptotic expansions for the solutions, and show that in all the cases, the leading terms in the expansions are always the corresponding potentials for the Laplacian. Our integral equation procedures developed here are general enough and can be adapted for treating similar low frequency scattering problems.     

Lan interconnection via ATM networks using the reverse multiplexing technique

Abstract

We propose an ATM‐LAN interconnection solution using multiple virtual channel connections, so that each MAC frame can be divided into cells and be transmitted via several parallel links simultaneously. The performance of the ATM‐LAN gateway in such setups, including multiplexing gain and the end‐to‐end delay, is studied via approximate analysis and simulations. Our approach is shown to provide better multiplexing effects under various traffic environments.     

On‐line atc estimator using hybrid principal component analysis network

Abstract

Deregulation has had a great impact on the electric power industry in many countries. The independent system operator (ISO), responsible for ensuring the secure, economic, and efficient dispatches, has to calculate the Available Transfer Capability (ATC) for bilateral contract customers. However, a large number of calculations using the power flow approach is required to calculate the ATC. In this paper, a method involving the hybrid Principal Component Analysis and multi‐layer feedforward neural networks is used to estimate the ATC. The simulation results obtained from a six‐bus and the IEEE 30‐bus system show the applicability of the proposed method for on‐line use.     

The Properties and Preparation of Chitosan/Silica Hybrids Using Sol-Gel Process

Chitosan/silica hybrids (Chitosan/SiO₂) using a sol-gel process were prepared at a wide range of in situ silica content from 0% to 100%. This work was undertaken to investigate the thermal properties, optical, adsorption, and biodegradability properties of this type of hybrid. Fourier transform infrared (FTIR) spectra were recorded to depict the interfacial interaction. Thermogravimetric analysis was used to determine the actual silica content forming in the hybrids and to evaluate the enhanced heat resistance of hybrids resulting from silica. Crystallography was illustrated using an X-ray diffractometer. Fracture surface was revealed through a scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) to probe the dispersion degree of SiO₂, which in turn confirmed the results of optical property on the formation of nanocomposites. To prevent the dissolution of chitosan and silica in the acid and alkaline solution, respectively, all prepared hybrids are capable of chelating Cu (II) as well as Fe (III) in a large degree. In addition, the hybrids are biodegradable based on the lysozyme treatment. Thus, chitosan/silica hybrids are of benefit as suitable environmental biomaterials and adsorbents under a wide range of conditions.     

Annealing effect and photovoltaic properties of nano-ZnS/textured p-Si heterojunction

The preparation and characterization of heterojunction solar cell with ZnS nanocrystals synthesized by chemical bath deposition method were studied in this work. The ZnS nanocrystals were characterized by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Lower reflectance spectra were found as the annealing temperature of ZnS film increased on the textured p-Si substrate. It was found that the power conversion efficiency (PCE) of the AZO/ZnS/textured p-Si heterojunction solar cell with an annealing temperature of 250°C was η = 3.66%.     

Evaluation of a 7‐Methoxycoumarin‐3‐carboxylic Acid Ester Derivative as a Fluorescent,Cell‐Cleavable,Phosphonate Protecting Group

Cell‐cleavable protecting groups often enhance cellular delivery of species that are charged at physiological pH. Although several phosphonate protecting groups have achieved clinical success, it remains difficult to use these prodrugs in live cells to clarify biological mechanisms. Here, we present a strategy that uses a 7‐methoxycoumarin‐3‐carboxylic acid ester as a fluorescent protecting group. This strategy was applied to synthesis of an (E)‐4‐hydroxy‐3‐methyl‐but‐2‐enyl diphosphate (HMBPP) analogue to assess cellular uptake and human Vγ9Vδ2 T cell activation. The fluorescent ester displayed low cellular toxicity (IC₅₀>100 μm ) and strong T cell activation (EC₅₀=0.018 μm ) relative to the unprotected anion (EC₅₀=23 μm ). The coumarin‐derived analogue allowed no‐wash analysis of biological deprotection, which revealed rapid internalization of the prodrug. These results demonstrate that fluorescent groups can be applied both as functional drug delivery tools and useful biological probes of drug uptake.     

Biological properties of acidic cosmetic water from seawater

This current work was to investigate the biological effects of acidic cosmetic water (ACW) on various biological assays. ACW was isolated from seawater and demonstrated several bio-functions at various concentration ranges. ACW showed a satisfactory effect against Staphylococcus aureus, which reduced 90% of bacterial growth after a 5-second exposure. We used cultured human peripheral blood mononuclear cells (PBMCs) to test the properties of ACW in inflammatory cytokine release, and it did not induce inflammatory cytokine release from un-stimulated, normal PBMCs. However, ACW was able to inhibit bacterial lipopolysaccharide (LPS)-induced inflammatory cytokine TNF-α released from PBMCs, showing an anti-inflammation potential. Furthermore, ACW did not stimulate the rat basophilic leukemia cell (RBL-2H3) related allergy response on de-granulation. Our data presented ACW with a strong anti-oxidative ability in a superoxide anion radical scavenging assay. In mass spectrometry information, magnesium and zinc ions demonstrated bio-functional detections for anti-inflammation as well as other metal ions such as potassium and calcium were observed. ACW also had minor tyrosinase and melanin decreasing activities in human epidermal melanocytes (HEMn-MP) without apparent cytotoxicity. In addition, the cell proliferation assay illustrated anti-growth and anti-migration effects of ACW on human skin melanoma cells (A375.S2) indicating that it exerted the anti-cancer potential against skin cancer. The results obtained from biological assays showed that ACW possessed multiple bioactivities, including anti-microorganism, anti-inflammation, allergy-free, antioxidant, anti-melanin and anticancer properties. To our knowledge, this was the first report presenting these bioactivities on ACW.     

Modelling of the material flow of Nd-Fe-B magnets under high temperature deformation via finite element simulation method

Abstract

Hot deformation of Nd-Fe-B magnets has been studied for more than three decades. With a good combination of forming processing parameters, the remanence and (BH)_max values of Nd-Fe-B magnets could be greatly increased due to the formation of anisotropic microstructures during hot deformation. In this work, a methodology is proposed for visualizing the material flow in hot-deformed Nd-Fe-B magnets via finite element simulation. Material flow in hot-deformed Nd-Fe-B magnets could be predicted by simulation, which fitted with experimental results. By utilizing this methodology, the correlation between strain distribution and magnetic properties enhancement could be better understood.     

Diels-Alder Reaction of [60]Fullerene with Dienes Having an Ester Substituent at 1-Position

Abstract

Treatment of [60]fullerene with ethyl trans, trans-hexa-2,4-dienoate (1) and methyl trans, trans-octa-2,4-dienoate (2) at 70 ～ 100 °C afforded products 3 and 4, respectively, which are resulted from Diels-Alder addition of the dienoates to a 6/6 ring junction of [60]fullerene.