Application of boundary element method to 3-D problems of coupled thermoelasticity

This paper deals with a new boundary element method for analysis of the quasistatic problems in coupled thermoelasticity. Through some mathematical manipulation of the Navier equation in elasticity, the heat conduction equation is transformed into a simpler form, similar to the uncoupled-type equation with the modified thermal conductivity which shows the coupling effects. This procedure enables us to treat the coupled thermoelastic problems as an uncoupled one, A few examples are computed by the proposed BEM, and the results obtained are compared with the analytical ones available in the literature, whereby the accuracy and versatility of the proposed method are demonstrated.     

Thermal Analysis of CNT-Based Nano-Composites by Element Free Galerkin Method

This paper deals with the thermal analysis of carbon nanotube (CNT) based composites by meshless element free Galerkin method. Cylindrical representative volume element (cylindrical RVE) has been chosen to evaluate the thermal properties of nano-composites using multi-domain and simplified approaches. The values of temperature have been calculated at different points and plotted against RVE length and RVE radius. A sensitivity analysis of RVE as well as CNT dimensions has been carried out in detail. The present computations show that the equivalent thermal conductivity is a function of CNT length, CNT radius, RVE length and RVE radius. Based on present numerical simulations, an approximate formula is proposed to calculate the equivalent thermal conductivity of nano-composites. The results obtained by simplified approach have been found in good agreement with those obtained by multi-domain approach.     

Synthesis and optimization of high surface area mesoporous date palm fiber-based nanostructured powder activated carbon for aluminum removal

Date palm fiber (DPF) derived from agrowaste was utilized as a new precursor for the optimized synthesis of a cost-effective, nanostructured, powder-activated carbon (nPAC) for aluminum (Al3+) removal from aqueous solutions using carbonization, KOH activation, response surface methodology (RSM) and central composite design (CCD). The optimum synthesis condition, activation temperature, time and impregna-tion ratio were found to be 650 ℃, 1.09 hour and 1:1, respectively. Furthermore, the optimum conditions for removal were 99.5％and 9.958 mg·g-1 in regard to uptake capacity. The optimum conditions of nPAC was analyzed and characterized using XRD, FTIR, FESEM, BET, TGA and Zeta potential. Moreover, the adsorption of the Al3+ conditions was optimized with an integrated RSM-CCD experimental design. Regression results revealed that the adsorption kinetics data was well fitted by the pseudo-second order model, whereas the adsorption isotherm data was best represented by the Freundlich isotherm model. Optimum activated carbon indicated that DPF can serve as a cost-effective precursor adsorbent for Al3+removal.     

Preparation and structural characterization of Co/Al2O3 catalysts for the ozonation of pyruvic acid

A series of Co/Al₂O₃ catalysts were prepared by the incipient wetness impregnation method using γ-Al₂O₃ support and (CH₃COO)₂Co·4H₂O solutions, followed by calcination at 500–800 °C. Characterization of catalysts was accomplished by several techniques such as thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), physisorption of nitrogen, mercury and helium-based pycnometries, Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and pH of zero charge (PZC). Impregnation of support produced a moderate decrease of its surface area and pore volume and also led to minor changes of its PZC. Depending on preparation conditions (i.e., calcination atmosphere and temperature and metal loading), one or more of the following Co-containing compounds were identified: CoO, Co₃O₄ and CoAl₂O₄. The support and prepared Co/Al₂O₃ catalysts were tested to catalyze the ozonation of aqueous pyruvic acid at pH 2.5. Pyruvic acid was shown refractory towards single ozonation but the use of γ-Al₂O₃ and Co/Al₂O₃ catalysts resulted in 56–96% pyruvic acid conversion and 41–78% decrease in DOC after 2 h of ozonation of phosphate-buffered solutions. In the absence of the buffer, conversion rate was enhanced likely as a result of pH increase during the course of the process thus giving rise to the indirect way of ozonation through hydroxyl radicals. Acetic acid was found as the main by-product of pyruvic acid ozonation. Depending on the catalyst used, yield of acetic acid varied from 32 to 49%, values noticeably lower that that obtained from the control non-catalytic ozonation experiment (73%). Differences in catalytic activity amongst the various Co/Al₂O₃ catalysts investigated were attributed to the different Co active phases deposited on the γ-Al₂O₃ surface. The following sequence of increasing activity can be inferred from experimental results: CoO, CoAl₂O₄ and Co₃O₄. All the Co/Al₂O₃ catalysts prepared showed good stability as the percentage of cobalt leached out was rather low.     

Phenolic resin‐crosslinked natural rubber/clay nanocomposites: Influence of clay loading and interfacial adhesion on strain‐induced crystallization behavior

Nanocomposites of natural rubber (NR) and pristine clay (clay) were prepared by latex mixing, then crosslinked with phenolic resin (PhOH). For comparative study, the PhOH‐crosslinked neat NR was also prepared. Influence of clay loading (i.e., 1, 3, 5, and 10 phr) on mechanical properties and structural change of PhOH‐crosslinked NR/clay nanocomposites was studied through X‐ray diffraction (XRD), transmission electron microscopic (TEM), wide‐angle X‐ray diffraction (WAXD), tensile property measurement, and Fourier transform infrared spectroscopy (FTIR). XRD and TEM showed that the clay was partly intercalated and aggregated, and that the dispersion state of clay was non‐uniform at higher clay loading (>5 phr). From tensile test measurement, it was found that the pronounced upturn of tensile stress was observed when the clay loading was increased and a maximum tensile strength of the PhOH‐crosslinked NR/clay nanocomposites was obtained at 5 phr clay. WAXD observations showed that an increased addition of clay induced more orientation and alignment of NR chains, thereby lowering onset strain of strain‐induced crystallization and promoting crystallinity of the NR matrix during tensile deformation. FTIR investigation indicated a strong interfacial adhesion between NR matrix and clay filler through a phenolic resin bridge. This suggested that the PhOH did not only act as curative agent for crosslinking of NR, but it also worked as coupling agent for promoting interfacial reaction between NR and clay. The presence of strong interfacial adhesion was found to play an important role in the crystallization process, leading to promotion of mechanical properties of the PhOH‐crosslinked NR/clay nanocomposites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43214.     

Homogeneous iron-catalyzed photochemical degradation of muconic acid in water

Iron photochemical oxidation has been used to remove muconic acid from water. Two different light systems were used: black lamps and solar irradiation. The effect of iron concentration, intensity of incident radiation, pH and presence of oxalic acid was investigated. The first two variables yield positive effects on the removal rate of muconic acid while higher efficiency was achieved at pH 3. Oxalic acid enhances the oxidation rate because of the formation of photoactive ferrioxalate ion. Stoichiometric results indicated formation of two hydroxyl radicals to degrade 1 mol of muconic acid. At similar experimental conditions, initial oxidation rates of muconic acid were higher when solar light was used to irradiate the aqueous solutions, although in this case, the oxidation process is stopped because of the consumption of photoactive species.     

Evaluation of counting efficiencies of a whole-body counter using Monte Carlo simulation with voxel phantoms

In the 2007 recommendations of the International Commission on Radiological Protection, it is mentioned that the reference voxel phantoms are used for calculation of effective dose. From the standpoint of internal dosimetry services, calibration methods of whole-body counters using the voxel phantoms are of considerable practical interest. In the present study, counting efficiencies of a whole-body counter at the Japan Atomic Energy Agency (JAEA) were evaluated using Monte Carlo simulations with two voxel phantoms, 'MAX06', which has organ masses corresponding to those of the reference male, and 'Otoko', which is a representation for average Japanese male. To validate the calculation methods of the present study, calculations for the bottle manikin absorption phantom were also performed and compared with experiments. Consequently, it was found that the Monte Carlo simulation with voxel phantoms is a significant tool for the calibration of the JAEA whole-body counter.     

Scan-Along Polygonal Approximation for Data Compression of Electrocardiograms

Three fast and efficient "scan-along" algorithms for compressing digitized electrocardiographic data are described. These algorithms are "scan-along" in the sense that they produce the compressed data in real time as the electrocardiogram is generated. The algorithms are based on the minimum perimeter polygonal approximation for digitized curves. The approximation restricts the maximum error to be no greater than a specified value. Our algorithms achieve a compression ratio of ten on a database of 8000 5-beat abnormal electrocardiograms sampled at 250 Hz and a compression ratio of eleven on a database of 600 3-beat normal electrocardiograms (different from the preceding database) sampled at 500 Hz.     

The absence of corpus luteum formation alters the endocrine profile and affects follicular development during the first follicular wave in cattle

We previously established a bovine experimental model showing that the corpus luteum (CL) does not appear following aspiration of the preovulatory follicle before the onset of LH surge. Using this model, the present study aimed to determine the profile of follicular development and the endocrinological environment in the absence of CL with variable nadir circulating progesterone (P(4)) concentrations during the oestrous cycle in cattle. Luteolysis was induced in heifers and cows and they were assigned either to have the dominant follicle aspirated (CL-absent) or ovulation induced (CL-present). Ultrasound scanning to observe the diameter of each follicle and blood collection was performed from the day of follicular aspiration or ovulation and continued for 6 days. The CL-absent cattle maintained nadir circulating P(4) throughout the experimental period and showed a similar diameter between the largest and second largest follicle, resulting in co-dominant follicles. Oestradiol (E(2)) concentrations were greater in the CL-absent cows than in the CL-present cows at day -1, day 1 and day 2 from follicular deviation. The CL-absent cows had a higher basal concentration, area under the curve (AUC), pulse amplitude and pulse frequency of LH than the CL-present cows. After follicular deviation, the CL-absent cows showed a greater basal concentration, AUC and pulse amplitude of growth hormone (GH) than the CL-present cows. These results suggest that the absence of CL accompanying nadir circulating P(4) induces an enhancement of LH pulses, which involves the growth of the co-dominant follicles. Our results also suggest that circulating levels of P(4) and E(2) affect pulsatile GH secretion in cattle.