Experimental Characterization of Thermoelectric Modules and Comparison with Theoretical Models for Power Generation

The interest in thermoelectrics for power generation applications has dramatically increased over the past decade as a result of recent advancements in thermoelectric materials. Although measuring thermoelectric properties of materials has received significant attention, measuring thermoelectric module (TEM) power generation performance has received less attention. Characterizing TEMs is vital for validating module-level models used in optimizing TEM designs. Measurements of module performance can also be used for the optimal incorporation of TEMs into power generation systems. A TEM test apparatus has been developed and characterized to test current and future modules under a wide range of temperature and loading conditions. In addition to temperatures and electrical performance metrics, heat rates, and mechanical loading conditions are monitored. The developed technique extracts module parameters, which can be used for system-level design, to measure performance of advanced TEMs, and to validate theoretical models for module design optimization. Experimental results are compared with standard analytical TEM models and a newly developed model.     

Studies on Y2O3:Eu phosphor with different particle size prepared by wet chemical method

Europium activated yttrium oxide phosphors were prepared by reagent simultaneous addition technique, using oxalic acid as precipitating reagent. The aim of the paper is to establish the flux influence and thermal regime on photoluminescence and morpho-structural characteristics of phosphor powders. In this respect different mineralising agents such as sodium/lithium carbonate, sodium tetraborate ans sodium pyrophosphate were used during the thermal synthesis stage. Thermal analysis, X-ray diffraction, scanning electron microscopy, infrared spectroscopy and photoluminescence measurements were used to investigate precursor and phosphor powders. The correlation between the phosphor properties and precursor quality enabled us to select the optimal synthesis conditions.     

Characterization of oil exhibiting high γ-linolenic acid from a genetically transformed canola strain

The seed oil from a genetically transformed canola (Brassica napus) containing 43% (w/w) of γ-linolenic acid (G, 18∶3n−6), 22% linoleic acid (L, 18∶2n−6), and 16% oleic acid (O, 18∶1n−9) was evaluated. In this high γ-linolenic acid canola oil (HGCO), the predominant 18∶3n−6-containing triacylglycerol (TG) molecular species were GGL (23%), GLO (20%), and GGG (11%). In the total TG, approximately 75% of the 18∶3n−6 was located at the sn-1,3 positions, while only 34% of linoleic acid was at the sn-1,3 positions. The GGL molecular species of HGCO contained approximately equal amounts of GLG and GGL positional isomers, while the GLO molecular species had 95% GOL and 5% GLO isomers. The general characteristics and the tocopherol and phytosterol contents were mostly similar between HGCO and nontransformed canola oil. No detectable amounts of amino acids and nucleotides were observed in the HGCO.     

Magnetic properties and electronic structures of GdCo3−xSix compounds

Magnetic measurements and band structure calculations were performed on GdCo_3−xSi_x system with x ≤ 0.3. The experimentally determined magnetizations are in rather good agreement with those obtained from band structure calculations. The composition dependence of cobalt moments, at various lattice sites, are analyzed in correlation with the effects of Co 3d–Si 3p bands hybridization.     

Urethane dimethacrylate oligomers for dental composite matrix: Synthesis and properties

Two urethane poly(ethylene oxide) dimethacrylates based on polyether diol of variable length (M_n: 300 and 1000 g/mol), isophorone diisocyanate and 2‐hydroxyethyl methacrylate, were synthesized and characterized to be used as comonomers for dental composites. The polymerization process initiated with benzoyl peroxide/amine or camphorquinone/tertiary amine couple was followed by a combination of FTIR spectroscopy and fluorescence technique using a pyrene probe for the in situ monitoring of microscopic changes in the polymeric systems. Difference in the polymerization kinetics of the oligomers and low‐molecular‐weight monomer is presented in connection with the chemical structure of the urethane dimethacrylate, taken together with another partners (bisGMA, TEGDMA, filler) with effect on the mobility and reactivity of the formed polymeric network. The results suggest a higher reactivity of the oligomeric forms and are in agreement with the fluorescence measurements induced of the pyrene molecule, whosemonomer fluorescence emission significantly increased with irradiation time as the network formation occurred. Measurements of the contact angle showed the maintenance of the hydrophilic nature of these resins, while the values of polymerization shrinkage and diametral tensile and compressive strengths of the three specimens indicated that the incorporation of dimethacrylate urethane oligomers in the organic matrix (18 wt%) led to materials with good properties. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Inhibition of acrylamide formation in asparagine/d-glucose model system by NaCl addition

Addition of 1, 5 and 10% of NaCl to equimolar mixture of asparagine/D-glucose was applied to study any affects of this food additive on acrylamide formation in the mixture. The samples were heated at 171.17°C for 10 min and the content of acrylamide was followingly determined by GC-MS technique using negative chemical ionization procedure. For comparison purposes, acrylamide formation was studied also in the mixture without NaCl addition at the same conditions. The results proved considerable inhibiting effects of NaCl on the acrylamide formation in all mixtures with addition NaCl, when the acrylamide content was lowered roughly by 32, 36 and 40% in comparison to mixture without NaCl addition. Very important is a fact, that effective lowering of acrylamide content was observed already at 1% of NaCl addition what could make possible to apply this knowledge also in real technological procedures of food processing.     

Thermal Expansion Discontinuities of Mullite

Thermal expansion data of mullite were collected between 25° and 800°C with high accuracy by means of an X-ray high-temperature Guinier powder camera, and high-resolution single-crystal Bond techniques. 3/2-type mullites, synthesized from chemically coprecipitated precursors and 2/1-type fused-mullite single crystals, were used for the measurements. Mullite displays low and nonlinear thermal expansions along the crystallographic a, b , and c axes below about 200°C, and linear expansions between 200° and 400°C. Between about 400° and 500°C, expansion curves are discontinuous. Above 500°C, a, b , and c expansions are linear again. The temperature-induced expansion discontinuities are relatively strong parallel to a , but are much weaker parallel to b and c . The slopes of the a and volume expansion curves are higher above the expansion discontinuity than below, while there is no significant tendency for those of b and c . Thermal expansion coefficients and discontinuity effects are reversible without any hysteresis. The increase of the a and volume expansion curves above the expansion discontinuities may be due to possible deformations, rotations, and tiltings of the [AlO₆] octahedra. Another factor responsible for the higher a and volume expansion coefficients at high temperatures may be a geometrical deformation of the [Al^⋆O₄] tetrahedra. At present, no conclusive model exists to explain the discontinuous change of thermal expansion coefficients between 400° and 500°C.     

Peak Non-Gaussian Wind Effects for Database-Assisted Low-Rise Building Design

Current procedures for estimating the peaks of the stochastic response of tall buildings to wind are based on the assumption that the response is Gaussian. Those procedures are therefore inapplicable to low-rise buildings, in which time histories of wind-induced internal forces are generally non-Gaussian. In this paper, an automated procedure is developed for obtaining from such time histories sample statistics of internal force peaks for low-rise building design and codification. The procedure is designed for use in software for calculating internal force time series by the database-assisted design approach. A preliminary step in the development of the procedure is the identification of the appropriate marginal probability distribution of the time series using the probability plot correlation coefficient method. The result obtained is that the gamma distribution and a normal distribution are appropriate for estimating the peaks corresponding, respectively, to the longer and shorter tail of the time series’ histograms. The distribution of the peaks is then estimated by using the standard translation processes approach. It is found that the peak distribution can be represented by the Extreme Value Type I (Gumbel) distribution. Because estimates obtained from this approach are based on the entire information contained in the time series, they are more stable than estimates based on observed peaks. The procedure can be used to establish minimum acceptable requirements with respect to the duration and sampling rate of the time series of interest, so that the software used for database-assisted design will be both efficient and accurate.     

Beitr?ge zur Kenntnis der geh?rteten ?le und zum Nachweise der Arachins?ure

Ohne ZusammenfassungMitteilung aus dem Laboratorium des Kantons-Chemikers Basel-Stadt.     

Progress in performance and stability of a contactor-type Catalytic Membrane Reactor for wet air oxidation

Catalytic Membrane Reactors combine a membrane that controls transfers and a catalyst that provides conversion. This paper focuses on the catalytic performance stability of interfacial contactor membranes in the wet air oxidation of formic acid. Stable catalytic membranes with high activity have been developed.