Thermo-indicating paint for damage warning

Thermal analysis coupled with the measurement of temperatures at which colour changes are observed in situ was used to test various inorganic pigments with the aim of introducing them into the compositions of thermo-indicating paints. Through a reversible or irreversible modification of the colour these can indicate an undesired increase in temperature of a fluid in a metallic enclosure. Three such pigments are described, which indicate temperatures of 110, 300 and 400°C. The paint contains the thermo-indicator pigment, soluble glass as binder and either ultrafine silica or silica gel, or a mixture of Na₂SiF₆ and finely-ground sand as hardener. Such paints are used for damage warning.     

HOMOPOLYMERIZATION AND COPOLYMERIZATION OF VINYL ACETATE IN NON-IONIC ICROEMULSIONS. I. A STUDY OF HOMOGENEITY DOMAINS

Abstract

The homogeneity ranges of the systems consisting of the monomer (vinyl acetate or vinyl acetate + di-2-ethyl hexil maleate), cosurfactant (ethanol, n-propanol, n-butanol), surfactant (nonylphenol ethoxylate with 25 moles of ethylene oxide) and water were studied. Addition of the more hydrophobic comonomer requires utilization of a more hydrophobic cosurfactant. The increase of surfactant concentration entails the widening of the homogeneity range. The effect of the cosurfactants mentioned is accounted for by the modification of the cluster structure of water. Therefore the refractive indexes and the signals of protons in NMR spectra vary non-linearly with the composition of homogeneous systems. DSC analysis of the systems obtained has come out with two crystallization temperatures of water undercooled to ?60°C in systems of concentrations close to those of organic and aqueous phases. The results plead for the existence of a structure which differs from that of the ideal solutions of the systems studied.     

From the Hamiltonian to the Lagrangean formalism for 1-reducible theories. The Freedman-Townsend model

The paper presents a possible path to the sp(3) BRST Lagrangean formalism for a 1-reducible gauge field theory starting from the Hamiltonian one. This appears to be not at all a trivial attempt and will allow explanation of the structure of generators and the form of the master equations in the Lagrangean sp(3) theories. The Freedman-Townsend model, for which a Lagrangean (covariant) sp(3) theory is important, is presented.     

Asymptotic results for renewal risk models with risky investments

We consider a renewal jump–diffusion process, more specifically a renewal insurance risk model with investments in a stock whose price is modeled by a geometric Brownian motion. Using Laplace transforms and regular variation theory, we introduce a transparent and unifying analytic method for investigating the asymptotic behavior of ruin probabilities and related quantities, in models with light- or heavy-tailed jumps, whenever the distribution of the time between jumps has rational Laplace transform.     

Thermal analysis of Romanian ancient ceramics

The present work is focused on thermoanalytical investigations as thermogravimetric analysis (TG) and derivative thermal analysis (DTG), applied for the characterization of some samples collected from archaeological sites (Brasov and Trofeum Traiani) located in different regions of Romania. New informations derived about ceramic technologies concerning raw materials and binding materials (mineralogical components) have been obtained. All these experimental results have been correlated with related techniques as X-ray diffraction (XRD), energy-dispersive X-ray fluorescence (EDXRF) and inductively coupled plasma—atomic emission spectrometry (ICP-AES). By progressive heating in static air atmosphere and in the temperature range of 20–800 °C, all investigated materials exhibit three main successive processes, associated with the dehydration and thermo-oxidative degradations. The rate of the first thermooxidative process, temperatures corresponding to the maximum rate of the second thermooxidative process and shrinkage temperature were associated with the damage of the investigated materials due to environmental impact. Heating also affects the contact between the fine-sized clay matrix and mineral clast fragments, appearing in reaction rims, sometimes showing newly formed phases. The temperature at which ancient ceramics and pottery were fired varies over a wide range (600–800 °C) depending on the type of clay used, although firing temperatures not above 30–400 °C have also been suggested. Clay minerals, as the main material for production of ceramics and pottery, show some characteristic reactions (dehydroxylation, decomposition, transformation) in the course of firing (heating effects) and several thermoanalytical criteria can be used for reconstruction of former production conditions.     

An efficient step method for a system of differential equations with delay

Using the step method, we study a system of delay differential equations and we prove the existence and uniqueness of the solution and the convergence of the successive approximation sequence using the Perov''s contraction principle and the step method. Also, we propose a new algorithm of successive approximation sequence generated by the step method and, as an example, we consider some second order delay differential equations with initial conditions.     

Synthesis, Characterization of Complexes of N-benzoyl-n'-2-nitro-4-methoxyphenyl-thiourea with Cu, Ni, Pt, Pd, Cd and Hg

A series of coordination complexes with the compositions CuL, NiL×2H₂ O, ML₂ Cl₂ (M =Pt(II), Hg(II)) and M(L-H)₂ (M =Pd(II)), Cd(II)), where L =N-benzoyl-N'-2-nitro-4-methoxyphenylthiourea, were synthesized and characterized by conductance, EPR, IR and electronic spectral studies and thermogravimetric analysis. The IR and electronic spectra suggest coordination through the thiocarbonyl S and carbonyl O in the Pd(II) and Cd(II) complexes, and S bonding for the Pt(II) and Hg(II) complexes. The Cu(II) and Ni(II) complexes have polymeric structures in which the ligand is coordinated via the N, O and S atoms. This revised version was published online in July 2006 with corrections to the Cover Date.     

Smeared and Unsmeared Chiral Vertex Operators

We prove unboundedness and boundedness of the unsmeared and smeared chiral vertex operators, respectively. We use elementary methods in bosonic Fock space, only. Possible applications to conformal two-dimensional quantum field theory, perturbation thereof, and to the perturbative construction of the sine-Gordon model by the Epstein-Glaser method are discussed. From another point of view the results of this paper can be looked at as a first step towards a Hilbert space interpretation of vertex operator algebras. Received: 16 October 1997 / Accepted: 7 July 1998     

Exergetic Analysis of a Cryogenic Air Separation Unit

This case study analyzes a cryogenic air separation unit (ASU) with a production of V˙O2=58,300 [m3Nh] of gaseous oxygen with a concentration greater than 98.5%, operating in Romania on a steel plant platform. The goal of the paper is to provide an extensive model of exergetic analysis that could be used in an optimization procedure when decisional parameters are changed or structural design modifications are implemented. For each key part of the Air Separation Unit, an exergetic product and fuel were defined and, based on their definition, the coefficient of performance of each functional zone was calculated. The information about the magnitude of the exergetic losses offers solutions for their future recovery. The analysis of the exergy destructions suggests when it is worth making a larger investment. The exergetic analysis of the compression area of the ASU points out an exergy destruction and loss of 37% from the total plant’s electrical energy input. The exergy loss with the heat transferred to the cooling system of compressors can be recovered; for the exergy destruction portion, the challenge between investment and operating costs should be considered. The exergy destruction of the air separation columns found the High Pressure Column (HPC) to be more destructive than the Low Pressure Column. The share of the exergy destruction in the total plant’s electrical energy input is 8.3% for the HPC. The local COP of the HPC, calculated depending on the total exergy of the local product and fuel, is 62.66%. The calculus of the air separation column is performed with the ChemSep simulator.     

Elemental analysis through X-ray techniques applied in archeological gold authentication — the case of Transylvanian gold and of the Dacian bracelets

To identify the provenance of gold archeological metallic artifacts, trace elements are more significant than the main components. The most promising elements are Platinum Group Elements (PGE), Sn, Sb, Hg, Pb, Te, and Cu. Several minute fragments of natural Transylvanian gold – placers and primary – were studied by micro Particle Induced X-ray Emission (micro-PIXE) at Forschungszentrum Dresden-Rossendorf, Germany and micro Synchrotron Radiation X-Ray Fluorescence (micro SR-XRF) at ANKA Synchrotron Radiation Facility of the Forschungszentrum Karlsruhe, Germany. The goal of the study was to identify the trace elements characterizing Transylvanian gold, especially Sn, Sb, Pb and Te. A spectacular application of these measurements to the authentication of nine Dacian gold bracelets is presented.