Comparison of the morphology and structure of WO3 nanomaterials synthesized by a sol-gel method followed by calcination or hydrothermal treatment

Tungsten (VI) oxide (WO₃) nanomaterials were synthesized by a sol-gel method using WCl₆ and C₂H₅OH as precursors followed by calcination or hydrothermal treatment. X-Ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) equipped with energy dispersive X-ray spectroscopy (EDX) were used to characterize the structure and morphology of the materials. There were significant differences between the WO₃ materials that were calcinated and those that were subjected to a hydrothermal process. The XRD results revealed that calcination temperatures of 300°C and 400°C gave hexagonal structures and temperatures of 500°C and 600°C gave monoclinic structures. The SEM images showed that an increase in calcination temperature led to a decrease in the WO₃ powder particle size. The TEM analysis showed that several nanoparticles agglomerated to form bigger clusters. The hydrothermal process produced hexagonal structures for holding times of 12, 16, and 20 h and monoclinic structures for a holding time of 24 h. The SEM results showed transparent rectangular particles which according to the TEM results originated from the aggregation of several nanotubes.     

Transmission and control of an emerging influenza pandemic in a small-world airline network

The avian influenza virus H5N1 and the 2009 swine flu H1N1 are potentially serious pandemic threats to human health, and air travel readily facilitates the spread of infectious diseases. However, past studies have not yet incorporated the effects of air travel on the transmission of influenza in the construction of mathematical epidemic models. Therefore, this paper focused on the human-to-human transmission of influenza, and investigated the effects of air travel activities on an influenza pandemic in a small-world network. These activities of air travel include passengers’ consolidation, conveyance and distribution in airports and flights. Dynamic transmission models were developed to assess the expected burdens of the pandemic, with and without control measures. This study also investigated how the small-world properties of an air transportation network facilitate the spread of influenza around the globe. The results show that, as soon as the influenza is spread to the top 50 global airports, the transmission is greatly accelerated. Under the constraint of limited resources, a strategy that first applies control measures to the top 50 airports after day 13 and then soon afterwards to all other airports may result in remarkable containment effectiveness. As the infectiousness of the disease increases, it will expand the scale of the pandemic, and move the start time of the pandemic ahead.     

Statistical analysis and modeling of the temperature-dependent sleep behavior of drosophila

The sleep behavior of drosophila is analyzed under different temperatures. The activity per minute of the flies is recorded automatically. Sleep for a fruit fly is defined as the periods without any activity and longer than 5 minutes. Several parameters such as total sleep time, circadian sleep profile, quality of sleep are analyzed. The sleep behaviors are significantly different for flies at different temperature. Interestingly, the durations of daytime sleep periods show a common scale-free power law distribution. We propose a stochastic model to simulate the activities of the population of neurons which regulate the dynamics of sleep–wake process to explain the distribution of daytime sleep.     

The reversible plasticization of the aromatic copolyester of poly(ethylene terephthalate) and 60 mol % p-acetoxybenzoic acid with 1,1,1,3,3,3-hexafluoro-2-propanol

In recent mechanooptical studies with solution cast films of the aromatic copolyester of poly(ethylene terephthalate) and 60 mol % p-acetoxybenzoic acid from 1,1,1,3,3,3-hexafluoro-2-propanol, a volatile solvent with bp 59°C, we observed that the solvent plasticizes and affects considerably the stress–strain behavior of the copolyester at ambient temperature. Whereas a dry copolyester film is typically brittle failing at ≤ 10% strain, a film containing 12% w/w 1,1,1,3,3,3-hexafluoro-2-propanol can be stretched readily to ≥ 300% strain. When the solvent is removed by evaporation or by heating at an elevated temperature (≥ 120°C), the films lose their ductility, indicating that the plasticization is reversible.     

A study of electrical discharge grinding using a rotary disk electrode

This study aims to investigate the electrical discharge grinding (EDG) using a rotary disk electrode. From a practical perspective, the electrode is designed to mimic the machining process of a surface grinder with horizontal spindles. First, the machining ability of cold working tool steel AISI D2 by EDG is investigated. Then, the optimal machining parameters are found through ANOVA analysis. The experimental results show that both the lower electrode wear rate and the higher materials removal rate are obtained when a rotary disk electrode with positive polarity is conducted on EDG. In addition, the roughness of machined surfaces using an electrode with negative polarity can reach about 2 μm Rt, and no incidence of concentrated discharge or short circuit are found in any machining conditions.     

Water bamboo husk reinforced poly(lactic acid) green composites

The water bamboo husk is one of major agricultural wastes in Taiwan. In this study, the powder obtained from the water bamboo husk was added to poly(lactic acid) (PLA) to form novel reinforced biodegradable composites. Morphologies, mechanical properties, and heat resistance of these water bamboo powder reinforced composites were investigated. The results indicate that the char yields were increased as plant powder was incorporated to PLA. In addition, the mechanical properties were also enhanced due to the addition of powders. The increments of storage moduli of PLA were about 50–200%. Moreover, the increments of loss moduli of PLA were about 70–200%. On the other hand, the T_g of PLA was slightly decreased by the addition of powder, and this may improve the brittle characteristics of PLA. Furthermore, this type of reinforced PLA would be more environmental friendly than the artificial additive‐reinforced one. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Effects of Impact Inertia and Surface Characteristics on Deposited Polymer Droplets in Microcavities

Microflow visualization and computational fluid dynamics (CFD) are complementarity performed to study the evolution of a single poly(ethylenedioxythiophene) (PEDOT) droplet ejected from a piezoelectric ink-jet printhead and the equilibrium film characteristic of the droplet deposition in a microfabricated cavity. The verified CFD code is further applied to investigate the influences of contact angles thetas_s of the PEDOT droplet/air interface and the PEDOT droplet/cavity sidewall interface as well as droplet impact velocity Vd on the transient deposition process in the micro cavity. Impact inertia was studied by varying the droplet Weber number from 30.3 to 42.6. The surface characteristics are explored by choosing thetas_s of 10deg, 30deg, 50deg, 70deg, 90deg, and 110deg. The influences of impact inertia are also examined by increasing Vd from 2.0 to 12.0 m/s at 2.0 m/s interval. The computed results are found in good agreement with the experimental ones. For the first time, critical Weber numbers have been found relating to the ability of the droplet to wet the side walls and fill a microcavity with a uniform film. The results are also new in terms of the identifications of the critical contact angle (thetas_s)_C and critical impact velocity (Vd)_c. At (thetas_s)_C and at and beyond (Vd)_c, the formation of an intact flat film in the cavity is fulfilled.     

Dispersion of gas pollutant in a fan-filter-unit (FFU) cleanroom

Numerical simulation and experimental measurement of flow and concentration fields in a working fan-filter-unit (FFU) cleanroom have been conducted in this study. The purpose of the study is to find out the unsteady concentration distribution of a leaking gas pollutant. The standard K–ε model was used for the simulation of the flow field. To obtain the gas concentration field, SF₆ gas with a certain concentration was released as a simulated leaking source from a valve manifold box (VMB) for 5 or 10 min, respectively. Three Fourier transform infrared spectrometers (FTIRs) were simultaneously used to measure the spatial and temporal distributions of SF₆ concentrations. The measured data were then compared with the numerical results and the agreement is seen to be quite good. From the numerical results, the pollutant hot spots, peak pollutant concentration at the end of leaking, and time taken for the concentration to reduce to near background level are obtained.     

Dynamic airflow simulation within an isolation room

In many hospitals, isolation rooms are used to contain patients who are highly infectious, and the spread of air and bacteria within the isolation room is closely relates to room air distribution. This article uses the computational fluid dynamics (CFD) method to investigate the effects of a moving person and the opening and closing of a sliding door on room air distribution, including velocity, pressure and contaminant fields. Dynamic meshes are employed to simulate the movement of the walking person and sliding door. According to numerical results, the impact of those moving objects on room air distribution is addressed in this study.     

Thermally Formed Oxide Films on Al–XSi Alloys Heated in Different Gases

Thermogravimetric analysis (TGA) testing was used to measure the change in weight of polished samples of Al–XSi (X = 0 and 1.2 mass%) alloys. The samples were heated at 843 K for 6 h in dry air or nitrogen gas. X-ray diffraction was used to monitor the formation of the oxide films on the surface of the samples. The surface oxide films were more compact after the Al alloy samples were heated in air, and the oxide films showed some cracks after being heated in nitrogen gas. The thermally formed surface oxide films on the Al–1.2 mass% Si alloy samples heated in air and in nitrogen gas possessed loose structures, which comprised mainly γ-alumina, diaspore, and gibbsite, along with metallic silicon and/or aluminum. The weight variation curve of the films appeared serrated; this can be attributed to chain reactions (3Si + 3O₂ → 3SiO₂ + 4Al → 3Si + 2Al₂O₃) that occurred within the film.