Influence of mechanical properties in carbon black (CB) filled isotactic polypropylene (iPP) and propylene-ethylene block copolymer

The mechanical properties of isotactic polypropylene (iPP) and propylene-ethylene block copolymer (Co-PP) with carbon black (CB) were added as a filler. By mixing appropriate amounts of the two components through melt-blending in a twin-screw extruder, the blended pellets were prepared to a series of test specimens by injection molding. A scanning electron microscopic study was performed of the morphologies of the impact fractured surfaces. The blending of CB in Co-PP not only improves the impact strength, but also improves the flexural modulus and tensile strength; however, the heat distortion temperature (HDT) of the Co-PP/CB blends decreased with greater filler content. Furthermore, the filler of CB improves the tensile yield strength only at low filler content in iPP/CB blends, and the heat distortion temperature (HDT) and flexural modulus of the iPP/CB blends increased with greater filler content. The impact behavior is not good for the iPP/CB blends. Overall, Co-PP/CB has better interaction of molecules than iPP/CB. © 1996 John Wiley & Sons, Inc.     

Soapless emulsion polymerization of methyl methacrylate. II. Simulation of polymer particle formation

In this work, a generalized mathematical model was developed to estimate the variation of particle concentration during the entire course of soapless emulsion polymerization of methylmethacrylate (MMA). All of the factors, such as oligomeric radical absorption or desorption by polymer particles, coagulation between polymer particles, and the termination effect on the formation mechanism of polymer particles, were considered and included in this model. When appropriate parameters were selected, this model could be successfully used to interpret the experimental behavior of particle concentration during the entire reaction. Under different conditions, the rate of polymerization, the number of radicals in each particle, the instantaneous average molecular weight of polymers, and the rate constant of termination were also calculated. All of them coincided with the experimental results quite well. © 1996 John Wiley & Sons, Inc.     

Self-assisted wound healing using piezoelectric and triboelectric nanogenerators

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Fabrication and Thermal Dissipation Properties of Carbon Nanofibers Derived from Electrospun Poly(Amic Acid) Carboxylate Salt Nanofibers

Polyimides (PIs) possess excellent mechanical properties, thermal stability, and chemical resistance and can be converted to carbon materials by thermal carbonization. The preparation of carbon nanomaterials by carbonizing PI‐based nanomaterials, however, has been less studied. In this work, the fabrication of PI nanofibers is investigated using electrospinning and their transformation to carbon nanofibers. Poly(amic acid) carboxylate salts (PAASs) solutions are first electrospun to form PAAS nanofibers. After the imidization and carbonization processes, PI and carbon nanofibers can then be obtained, respectively. The Raman spectra reveal that the carbon nanofibers are partially graphitized by the carbonization process. The diameters of the PI nanofibers are observed to be smaller than those of the PAAS nanofibers because of the formation of the more densely packed structures after the imidization processes; the diameters of the carbon nanofibers remain similar to those of the PI nanofibers after the carbonization process. The thermal dissipation behaviors of the PI and carbon nanofibers are also examined. The infrared images indicate that the transfer rates of thermal energy for the carbon nanofibers are higher than those for the PI nanofibers, due to the better thermal conductivity of carbon caused by the covalent sp² bonding between carbon atoms.     

Hour-ahead wind power and speed forecasting using simultaneous perturbation stochastic approximation (SPSA) algorithm and neural network with fuzzy inputs

Wind energy is currently one of the types of renewable energy with a large generation capacity. However, since the operation of wind power generation is challenging due to its intermittent characteristics, forecasting wind power generation efficiently is essential for economic operation. This paper proposes a new method of wind power and speed forecasting using a multi-layer feed-forward neural network (MFNN) to develop forecasting in time-scales that can vary from a few minutes to an hour. Inputs for the MFNN are modeled by fuzzy numbers because the measurement facilities provide maximum, average and minimum values. Then simultaneous perturbation stochastic approximation (SPSA) algorithm is employed to train the MFNN. Real wind power generation and wind speed data measured at a wind farm are used for simulation. Comparative studies between the proposed method and traditional methods are shown.     

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.     

What proportion of renewable energy supplies is needed to initially mitigate CO2 emissions in OECD member countries?

In spite of increasing numbers of countries having established renewable energy development mechanisms for carbon dioxide (CO₂) emissions reduction, the CO₂ emissions problem continues to worsen along with the growth of the world economy. This leads us to examine the threshold effect of the proportion of renewable energy supply for CO₂ emissions reduction by means of the panel threshold regression model (PTR). Economic growth and the price of energy are also both taken into account in the model in measuring the specific influence that each of them has on CO₂ emissions. The empirical panel data encompass all 30 member countries of the OECD and cover a period of about a decade in length from 1996 to 2005. Our empirical results provide clear evidence of the existence of a single threshold effect that may be divided into lower and higher regimes. Based on the specific estimates of the slope coefficients in each regime distinguished, we find that a renewable energy supply accounting for at least 8.3889% of total energy supply would mean that CO₂ emissions would start to be mitigated. Furthermore, real GDP and the CPI of energy are significantly and positively and insignificantly and negatively correlated with CO₂ emissions, respectively. These findings lead us to conclude that the authorities ought to enhance the proportion of renewable energy supply to more than 8.3889% of all energy supplied, which might help resolve the dilemma between economic growth and CO₂ emissions. Realizing the effects of CO₂ emissions reduction via energy price reforms or the levying of a carbon tax levy may, however, still remain a puzzle.     

Experimental investigation of heat-transfer characteristics of aluminum-foam heat sinks

The demand of high speed and miniaturization of electronic components results in increased power dissipation requirement for thermal management. In this work, the effects of porosity (ε), pore density (PPI) and air velocity on the heat-transfer characteristics of aluminum-foam heat sinks are investigated experimentally. The phenomenon of non-local thermal equilibrium (NLTE) is also observed and reported. Results show that the Nu increases as the pore density increases, due to the fact that aluminum foam with a larger pore density has a larger heat-transfer area. The Nusselt number also increases with the increase of porosity due to the same reason. It is noted that temperatures of the solid and gas phases of the aluminum foam decrease as Reynolds number increases, caused by the increased convective heat-transfer rate at higher Reynolds number. The deduced temperature difference between the solid and gas phases clearly indicates the existence of non-local thermal equilibrium condition within the aluminum-foam heat sink. The increase of the porosity and the pore density enhances the phenomenon of non-local thermal equilibrium. The temperature difference increases with the decrease of Reynolds number and the distance away from the heat source.     

A comparison study of Taiwanese He-Yuan Architecture between the ethically spatial order and the condition of physical environment

Since the 21st century, problems such as global warming and energy depletion have become important issues to scientists and architects. The architectural design nowadays often relies on large amount of mechanical equipment to create a comfortable environment for the users. However, it burdens and deteriorates the nature. On the other hand, some of the traditional architecture in the past can cope with the local humid and hot climate, achieving good passive heat control for the environment. Therefore, this study explores the relation between traditional residents in Taiwan’s use of space and the external environment and climate through modern environment measurement technique, restores and conducts quantitative analysis on the interior thermal environment and light environment of Lin-An-Tai Historical House in the past through Ecotect Analysis, and analyzes the results of the calculation in terms of its spatial allocation, openings, and outer walls, etc. This study also evaluates the effects of lighting and user’s sense of comfortable temperature under its environmental conditions according to the standards of residential quality nowadays. It further studies the ancestor of traditional architecture by reviewing its spatial order and compares to the current situation in order to feedback the modern architecture design. Part of the results of the simulation show that the variation of temperature indoors in each space is less dynamic than that of outdoors. The temperature in the space at the right of the main hall (northwestern side) is generally higher than that in the left (southeastern side). The highest temperature in the space farther away from the interior patio is usually higher than that in the space closer to the interior patio. The temperature near the outer side of the space above Hulong is higher than that in the middle. Accordingly, the location is closely related to the interior temperature. As to human’s sense of comfortable temperature, the results show that in summer, the Predicted Mean Vote (PMV) in the space at the left of the main hall (southeastern side) is generally higher than that in the right (northwestern side). In winter, the sense of comfortable temperature in the rooms in the corner is lower than that in other rooms at the inner side, the comparison between the space ethical order and the evaluation result did not show any obvious relationship. For the evaluation of lighting, the main hall and the restaurant at the outer left Hulong have better lighting while other space does not have sufficient and even lighting. Artificial lighting is needed to make the space more functional, the results shows that lighting conditions of space did not metaphor to the space ethical order.     

Synthesis and properties of castor oil-based polyurethane containing short fluorinated segment

This study successfully incorporated a short-segment fluorine-containing chain extender (2,2,3,3-tetrafluoro-1,4-butanediol [TF]) into castor oil-based polyurethane (COPU) to synthesize TF/COPUs. The interactions between TF and COPU components were identified by Fourier transform infrared and X-ray photoelectron spectroscopies, the results revealed that the increase in the TF content increased the van der Waals forces in C F…CO and the hydrogen bonding force in C F…H N. Atomic force microscopy indicated that the addition of more TF contributed to a higher level of microphase separation in the TF/COPUs. Thermogravimetric analysis showed that the TF component can enhance the thermal resistance of TF/COPUs. Differential scanning calorimetry and dynamic mechanical analysis indicated that the glass transition temperature (T_g) of TF/COPUs increased with the TF content. The stress–strain testing showed that the tensile strength and elongation at break values decreased with the TF content. This tensile behavior may be due to the molecular weight of a TF/COPU decreased with the TF content as evidenced by the gel permeation chromatography results. The hydrolytic degradation tests of dipping TF/COPUs in 3 wt% NaOH solution indicated that TF could lower the surface free energy and enhance the degradation stability of TF/COPUs.