AN INTERFEROMETRIC INVESTIGATION OF NATURAL CONVECTION IN A PARTIALLY OPENED ENCLOSURE WITH A DISCRETE HEAT SOURCE

Natural convection in an enclosure with an opening in the right vertical wall and a heat source on the bottom surface was investigated using a holographic interferometric technique. In particular, emphasis was placed on the effects caused by changing the opening length, divider height, and heat source temperature. When the enclosure was partially opened, warm air from inside escaped from the upper part of the opening and was replaced by surrounding air, which flowed into the enclosure from the lower part of the opening. The flow rates of inflow and outflow through this opening increased with larger opening length, smaller divider height, and higher heater temperature. When the opening length was small, the opening did not significantly affect the upward flow of warm air from the heater, and resulted in a symmetrical temperature distribution. The divider prevented the development of upward flow from the heat source such that the temperature in the absence of a divider was generally higher than that for the longest divider. For cases with a large opening length, the upward flow was forced to move into the enclosure's left-hand side by the increased inflow. The effect of the divider height was not significant due to the increased flow rates through the increased opening length. The temperatures achieved with the longest divider were a little higher than those for the other cases due to the lower cold flow rate and the blocking of the cold air inflow by the longest divider.     

How to obtain higher-order multivariate Hermite expansion of Maxwell–Boltzmann distribution by using Taylor expansion?

We obtain the higher-order multivariate Hermite expansion of the Maxwell–Boltzmann distribution by using a new, compact tensorial notation and present a method to obtain the nth order multivariate Taylor expansion, which is identical to the nth order multivariate Hermite expansion of the Maxwell–Boltzmann distribution. This study enables us to find higher-order models of discrete kinetic theories such as the lattice Boltzmann theory.     

Polyvinylpyrrolidone (PVP) assisted single‐step synthesis of kesterite Cu2ZnSnS4 nanoparticles by solvothermal process

Quaternary kesterite‐type Cu₂ZnSnS₄ (CZTS) nanoparticles (NPs) were successfully synthesized by a single‐step solvothermal process. Semiconductor CZTS nanoparticles were obtained from ethylene glycol (EG) and CZTS precursor after solvothermal process at 180 °C for 30 h in polyvinylpyrrolidone (PVP) medium. The synthesized CZTS NPs were further annealed at 450 °C in nitrogen atmosphere and used for further characterizations. The CZTS NPs were characterized using X‐ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), micro Raman spectroscopy, high resolution transmission electron microscopy (HRTEM) and X‐ray photoelectron spectroscopy (XPS). The optical properties of the CZTS NPs were recorded by UV–vis absorption spectroscopy. The results showed that the synthesized CZTS nanoparticles are kesterite‐type CZTS, with good crystallinity and a stoichiometric composition. Moreover, the prepared nanoparticles have a size ranging from 5–7 nm and a band gap of ～1.5 eV.

     

A branch-and-bound method for discretely-constrained mathematical programs with equilibrium constraints

We present a branch-and-bound algorithm for discretely-constrained mathematical programs with equilibrium constraints (DC-MPEC). This is a class of bilevel programs with an integer program in the upper-level and a complementarity problem in the lower-level. The algorithm builds on the work by Gabriel et al. (Journal of the Operational Research Society 61(9):1404–1419, 2010) and uses Benders decomposition to form a master problem and a subproblem. The new dynamic partition scheme that we present ensures that the algorithm converges to the global optimum. Partitioning is done to overcome the non-convexity of the Benders subproblem. In addition Lagrangean relaxation provides bounds that enable fathoming in the branching tree and warm-starting the Benders algorithm. Numerical tests show significantly reduced solution times compared to the original algorithm. When the lower level problem is stochastic our algorithm can easily be further decomposed using scenario decomposition. This is demonstrated on a realistic case.     

Correlated electronic structure of LaO1-xFxFeAs

We compute the electronic structure, momentum resolved spectral function and optical conductivity of the new superconductor LaO1-xFxFeAs within the combination of the density functional theory and dynamical mean field theory. We find that the compound in the normal state is a strongly correlated metal and the parent compound is a bad metal at the verge of the metal insulator transition. We argue that the superconductivity is not phonon mediated.     

Monte Carlo simulation of film growth in a phase separating binary alloy model

Using a kinetic Monte Carlo method, we simulate binary film (A_0.5B_0.5/A) growth on an L×L square lattice with the focus on the domain growth behaviour. We compute the average domain area, A(t), as a measure of domain size. For a sufficiently large system, we find that A(t) grows with a power law in time with A(t)∼t^2/3 after the initial transient time. This implies that the dynamic exponent for domain growth with non-conserved order parameter is z=3, a value which was theoretically predicted for the conserved order parameter case. Further analysis reveals that such a power-law behaviour emerges because the order parameter is approximately conserved after the early stage of growth.     

Composite support vector quantile regression estimation

In this paper we propose a new nonparametric regression method called composite support vector quantile regression (CSVQR) that combines the formulations of support vector regression and composite quantile regression. First the CSVQR using the quadratic programming (QP) is proposed and then the CSVQR utilizing the iteratively reweighted least squares (IRWLS) procedure is proposed to overcome weakness of the QP based method in terms of computation time. The IRWLS procedure based method enables us to derive a generalized cross validation (GCV) function that is easier and faster than the conventional cross validation function. The GCV function facilitates choosing the hyperparameters that affect the performance of the CSVQR and saving computation time. Numerical experiment results are presented to illustrate the performance of the proposed method     

Thickness dependence of thermally induced changes in surface and bulk properties of Nafion® nanofilms

Thermally induced changes in surface wettability, dewetting behavior, and proton transport of “self‐assembled” nanothin Nafion^® films (4–300 nm) on SiO₂ substrate is reported. Thermal annealing induces switching of the surface wettability of 55 nm and thinner films from hydrophilic to super‐hydrophobic. Thickness dependence of this behavior is observed with higher annealing temperature required for lower thickness films, indicating highly restrictive mobility of Nafion^® ionomer as film thickness decreases. Dewetting is only observed for 4‐nm thin film. Significant suppression in proton conductivity upon thermal annealing was noted. Similarly, two other bulk properties, water uptake and swelling, were found to decrease upon annealing. This work reports a systematic examination of the thickness dependence of thermally induced changes in both surface and bulk properties of ultra‐thin Nafion^®. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 1267–1277     

Effect of dual fullerenes on lifetimes of charge-separated States of subphthalocyanine-triphenylamine-fullerene molecular systems

Photoinduced intramolecular electron-transfer events of the newly synthesized subphthalocyanine-triphenylamine-fullerene triad (SubPc-TPA-C60) and subphthalocyanine-triphenylamine-bisfullerene tetrad (SubPc-TPA-(C(60))(2)) were studied. The geometric and electronic structures of the triad were probed by ab initio B3LYP/3-21G method, which predicts SubPc-TPA(*+)-C(60)(*-) as a stable charge-separated state. The photoinduced events via the excited singlet state of SubPc were monitored by time-resolved emission measurements as well as transient absorption techniques. Efficient charge-separations via the excited states of SubPc were observed with the rates of approximately 10(10) s(-)1. Compared with the SubPc-TPA dyad, a long-lived charge-separated state was observed for the SubPc-TPA-C(60) triad with the lifetime of the radical ion pairs (tau(RIP)) of 670 ns in benzonitrile. Interestingly, further charge stabilization was achieved in the charge-separated state of SubPc-TPA-(C(60))(2), in which the tau(RIP) was found to be 1050 ns in benzonitrile.     

Analytical procedure to simultaneously measure trace amounts of trenbolone acetate and beta-trenbolone residues in porcine muscle using HPLC-UVD and MS

The current study was undertaken to validate the performance for the determination of both TBA and beta-trenbolone (beta-TB) residues in porcine muscle at concentrations required to monitor compliance with the maximum residue limit (MRL). The method involves a one phase liquid-liquid extraction, cleanup with low-temperature fat precipitation, separation of the respective compounds by HPLC on a Capcell pak C(18) column, use of a methanol-water isocratic system as an eluent, and measurement by UV absorbance detection at 340 nm. Both compounds were confirmed using LC-MS/MS with electrospray interface (ESI) and a triple quadrupole (QqQ) analyzer. The method was found to be precise and accurate, with a linearity range of 1-10 microg/kg (r(2) >0.973). The intra- and interday precision showed good reproducibility with RSDs < or =13.25%. The LODs were 0.12 and 0.22 microg/kg, and the LOQs were 0.37 and 0.66 microg/kg, for TBA and beta-TB, respectively. The applicability of the method was demonstrated by analyzing real samples collected from major cities in the Republic of Korea. No residues of the selected compounds were detected in any of the samples. The advantages of our method are that it is: selective, sensitive, requires a short time for analysis (13 min), and performs simple sample extraction and clean-up procedure with low-temperature fat precipitation as compared to the previously published methods.