Sorption Properties of Vacuum-Dried Strawberries

This work demonstrates the influence of changes in parameters of vacuum drying (temperature and pressure) on the sorption properties of dried strawberries. Fruits were dried at 50 and 70°C under pressures of 4 and 16 kPa. Vacuum drying was also conducted during the first 4 h at 70°C and then the temperature was decreased to 50°C at a pressure of 4 kPa. The other combination included increasing the pressure after the first 4 h from 4 to 16 kPa at a drying temperature of 70°C. Sorption isotherms were determined in the dried strawberries. It was shown that with increasing drying temperatures, there was a notable deterioration in the capacity for absorbing water vapor by the vacuum-dried fruit. On the other hand, the pressure at which vacuum drying proceeded did not significantly affect water vapor absorption. Changing the parameters of vacuum drying—that is, temperature in the range of 50–70°C and pressure in the range of 4–16 kPa—affected the shape and structure of the resultant dried strawberries. The combination of vacuum drying with convective drying also influenced the shape and structure of the dried fruit.     

Formation Mechanism of AlN–SiC Solid Solution by Combustion Nitridation in Si3N4–Si-Al-C System

The synthesis of solid solutions of AlN–SiC was investigated through the combustion reaction between Si₃N₄, aluminum, and carbon powders and nitrogen gas at pressures ranging from 0.1 to 6.0 MPa. The combustion reaction was initiated locally and then the wave front propagated spontaneously, passing through the cylindrical bed containing the loose powder. In the presence of Si₃N₄ as a reactant, it was feasible to synthesize solid solutions at an ambient pressure (0.1 MPa). The relationship between nitrogen pressure and full-width at half-maximum of the (110) peak of the product showed that lower pressures produced more-homogeneous solid solutions. Some aspects of formation of the AlN–SiC solid solutions were discussed with special emphasis on the influence of nitrogen pressure and reactant stoichiometry.     

Fabrication and properties of multistage gradient doping Yb:YAG laser ceramics

In order to fully pump and smoothen the temperature gradient of the gain medium, multistage gradient doping Yb:YAG laser ceramics were designed. The composite green bodies were fabricated by tape casting, and multistage gradient doping Yb:YAG ceramics with high optical quality were prepared by vacuum sintering and hot isostatic pressing. For samples pre-sintered at 1740°C for 30 h and then HIP-ed at 1700°C for 3 h in argon at 200 MPa, the in-line transmission values at 1100 nm of YAG, 0.6 at.%Yb:YAG, and 1.5 at.%Yb:YAG ceramics were found to be 83.9%, 84.1%, and 83.3%, respectively. Finally, the 940 nm laser diode was used as the pump source to realize the 1030 nm laser output of multistage gradient doping Yb:YAG ceramic slab with a total energy of 3.43 J. The corresponding optical-to-optical conversion and slope efficiencies were 30% and 45%.     

Metal complexation of thiacrown ether macrocycles by electrospray ionization mass spectrometry

In the present study, electrospray ionization mass spectrometry is used to evaluate the metal-binding selectivities of an array of novel caged macrocycles for mercury(II), lead(II), cadmium(II), and zinc(II) ions. In homogeneous methanol/chloroform solutions as well as extractions of metals from aqueous solution by macrocycles in chloroform, it is found that the type of heteroatom (S, O, N), cavity size, and presence of other substituents influence the metal selectivities. Several of the macrocycles in this study bind mercury ion very selectively and efficiently in the presence of many other metal ions and have an avidity toward mercury that was tunable by the size and combination of heteroatoms in the macrocycle ring and the number of cage groups attached. The extraction mechanism was further investigated by determining the variation in extraction selectivity as a function of the counterions of the mercury salts.     

Optimal sensor placement for joint parameter and state estimation problems in large-scale dynamical systems with applications to thermo-mechanics

We consider large-scale dynamical systems in which both the initial state and some parameters are unknown. These unknown quantities must be estimated from partial state observations over a time window. A data assimilation framework is applied for this purpose. Specifically, we focus on large-scale linear systems with multiplicative parameter-state coupling as they arise in the discretization of parametric linear time-dependent partial differential equations. Another feature of our work is the presence of a quantity of interest different from the unknown parameters, which is to be estimated based on the available data. In this setting, we employ a simplicial decomposition algorithm for an optimal sensor placement and set forth formulae for the efficient evaluation of all required quantities. As a guiding example, we consider a thermo-mechanical PDE system with the temperature constituting the system state and the induced displacement at a certain reference point as the quantity of interest.     

Effects of a nonuniform vertical profile of chlorophyll concentration on remote-sensing reflectance of the ocean

Numerical simulations of radiative transfer were used to examine the effects of a nonuniform vertical profile of the inherent optical properties of the water column associated with the vertical profile of chlorophyll concentration, Chl(z), on the spectral remote-sensing reflectance, Rrs(gamma), of the ocean. Using the Gaussian function that describes the Chl(z) profile, we simulated a relatively broad range of open-ocean conditions characterized by the presence of a subsurface Chl maximum at depths greater than or equal to 20 m. The simulations for a vertically nonuniform Chl(z) were compared with reference simulations for a homogeneous ocean whose Chl was identical to the surface Chl of inhomogeneous cases. The range of values for the Gaussian parameters that produce significant differences in Rrs(gamma) (> 5%) was determined. For some vertical structures of Chl(z) considered, the magnitude of Rrs(gamma) and the blue-to-green band ratios of Rrs(gamma) differ significantly from the reference values of homogeneous ocean (> 70% in extreme cases of low surface chlorophyll of 0.02 mg m(-3) and shallow pigment maximum at 20 m). The differences are small or negligible when the nonuniform profiles are characterized by a surface Chl greater than 0.4 mg m(-3) or a depth of Chl maximum greater than 45 m (65 m in extremely clear waters with a surface Chl of 0.02 mg m(-3) or less). The comparison of modeling results with the current algorithm for retrieving the global distribution of chlorophyll from satellite imagery of ocean color suggests that strong effects of the subsurface chlorophyll maximum on reflectance at low surface chlorophyll concentrations can lead to a severalfold overestimation in the algorithm-derived surface chlorophyll. Examples of field data from the Sea of Japan and the north polar Atlantic Ocean are used to illustrate various nonuniform pigment profiles and their effect on the blue-to-green ratio of Rrs(gamma).     

A Modular Superconducting Generator for Offshore Wind Turbines

In this study, a new claw-pole type transverse flux superconducting generator topology is presented. The machine has a stationary superconducting field winding, which eliminates electrical brushes and cryocouplers. The machine is specifically designed for low-speed high torque applications such as large offshore wind turbines. The proposed machine is robust and has a modular structure. A 30 kW, 100 rpm prototype is planned to be manufactured to prove the concept. MgB2, YBCO, and BSSCO wires are compared in terms of wire length, operating temperature, and critical temperature. The magnetic flux penetrating into superconducting wire has been simulated using 3D FEA software. Moreover, mechanical loads are estimated and the deflections in the structure are analysed.     

New diketopyrrolopyrrole based D–A–D π-conjugated molecules: Synthesis,optical, electrochemical,morphological and photovoltaic properties

Two solution processable donor–acceptor, π-conjugated molecules that consist of diketopyrrolopyrrole (DPP) central acceptor unit with dibenzofuran (DPP-DBF) or acenaphtene (DPP-ACN) donor substituents, were prepared by Suzuki coupling reaction. The optical, electrochemical and film forming properties of these D–A–D molecules were investigated and used as active materials in bulk heterojunction solar cells.     

Estimation of scattering error in spectrophotometric measurements of light absorption by aquatic particles from three-dimensional radiative transfer simulations

We present an approach based on three-dimensional Monte Carlo radiative transfer simulations for estimating scattering error in measurements of light absorption by aquatic particles with a typical laboratory double-beam spectrophotometer. The scattering error is calculated by combining the weighting function describing the angular distribution of photon losses that are due to scattering on suspended particles with the volume scattering function of particles. We applied this method to absorption measurements made on marine phytoplankton, a diatom Thalassiosira pseudonana and a cyanobacterium Synechococcus. Assuming that the scattering phase function is described by the Henyey-Greenstein formula, we determined the backscatter probability of phytoplankton, which yields the best correction for scattering error at a light wavelength of 750 nm, where true absorption is null. The backscattering ratio estimated for both phytoplankton species is significantly higher than previously reported data based on Mie-scattering calculations for homogeneous spheres. Depending on the type of particles, the corrected absorption spectra obtained with our method may be similar or significantly different from spectra obtained with the null-point correction based on wavelength-independent scattering error.