Monte Carlo,hypothesis-tests for rare events superimposed on a background

We describe two techniques to search for small numbers of counts under a peak of known shape and superimposed on a background with statistical fluctuations. Many comparisons of a single experimental spectrum with computer simulations of the peak and background are made. From these we calculate the probability that y hypothesized counts in the peaks of the simulations, will result in a number larger than that observed in a given energy interval (bin) in the experimental spectrum. This is done for many values of the hypothesized number y. One procedure is very similar to testing a statistical hypothesis and can be analytically applied. Another is presented which is related to pattern recognition techniques and is less sensitive to the uncertainty in the mean. Sample applications to double beta decay data are presented.     

A photoelastic determination of Ki stress intensity factors

The quantitative relation between the exact solution of the stress field at the vicinity of a crack tip derived fron Westergaard's formulation and the well-known Irwin singular solution was established and results obtained were correlated with photoelastic data for the study of the reigon near the crack tip. The maximum shear stress distribution expressed by the isochromatic pattern for the exact and the singular solution were calculated respectively for uniaxial and biaxial tension. The region where accurate measurements in the isochromatic pattern are possible to evaluate the stress intensity factor to any desired decree of accuracy was established and the extrapolation law for the analysis of the region near the crack tip from data obtained fron the far-field of isochromatics was demonstrated. Experimental evidence corroborated this technique. The method was compared with other already existing experimental methods for the determination of K_I.     

Ultrathin polymer Langmuir-Blodgett films for microlithography

We describe photolithographic properties of poly(N-dodecylmethacrylamide-co-t-butyl 4-vinylphenyl carbonate) [p(DDMA-tBVPC)], which has a structure being subject to main chain scission and deprotection of t-butoxycarbonyloxy group by deep UV irradiation. Positive-tone patterns of the p(DDMA-tBVPC) Langmuir-Blodgett (LB) film with 60 layers were obtained by deep UV light irradiation followed by development with alkaline aqueous solution. The resolution of the pattern was 0.75 μm, which is the resolution limit of the photomask employed. The etching resistance of p(DDMA-tBVPC) LB film deposited for the pattern of the gold film is also investigated.     

Spontaneously resolved chiral arylsulfonamides

Our recent studies have shown that cocrystallization of 1:1 solutions of (R)-X and (S)-X′ (where X and X′ represent two sterically similar molecules) often form quasiracemic crystals, in which approximately centrosymmetric molecular pairs cocrystallize in an arrangement that resembles a “true” racemic structure. As part of an ongoing study of the influence of molecular shape on crystal packing, the present work centers on the design, synthesis and X-ray structure determination of four homologous N-(α-methylbenzyl)-4-substituted benzenesulfonamides. Crystallization of a solution of these (±)-arylsulfonamides unexpectedly yields enantiomerically pure crystals via a Pasteurian-type resolution process. This mode of crystallization presumably also deters the cocrystallization of different, but structurally similar, arylsulfonamides to form quasiracemates. The X-ray crystal structures of the four sulfonamides reveal the dominance of N–H⋅⋅⋅O–S hydrogen bonds that form infinite helical C(4) molecular chains. For three of the structures this pattern is extended by short inter- and intramolecular π⋅⋅⋅π interactions to form two-dimensional molecular architectures.     

Electrochemical lithium insertion in Nb8−xW9+xO47 (1≤x≤6)

Electrochemical lithium insertion have been carried out in different compositions within the solid solution Nb_8−xW_9+xO₄₇ (1≤x≤6). Through galvanostatic and potentiostatic techniques, we have detected that lithium insertion proceeds by at least two reduction steps. These processes seem to be related to the molar ratio Nb/W. The maximum lithium content reached during the discharge process leads to a specific capacity of 170 Ah/kg. Nevertheless, due to irreversible structural transformations in the matrix-host, such capacity is lost after the first cycle. A detailed analysis about the insertion kinetic process will be discussed in this work.     

Modeling frost heave in freezing soils

A generalized model for secondary frost heave in freezing fine-grained soils is presented. The cryostatic suction effect, which causes an increase in upward water permeation, ice-lens growth during freezing, and, as a consequence, the increase of soil heave, is considered to be the main mechanism of moisture transfer. Although the model in this paper has a number of approaches in common with the model of Fowler and Krantz (1994) it differs in at least several important respects. We recognize the need to determine the distribution of the moisture within the frozen fringe by approximation of the experimental data for the equilibrium unfrozen water content. This distribution is the result of the complicated interaction between water, ice and the mineral skeleton during the freezing process. The generalization of the Clapeyron relation, which is used in the work cited above, only estimates the drop in initial freezing temperature and does not define the connection with the external temperature gradient ∇T, which is responsible for the frost heave process. This very important aspect is discussed in detail in the Introduction to our paper. Another difference is the fact that our solution is based on a dimensionless system of equations. We take into account the ratio Pe/Ste ≠ 1 (where Pe << 1). This approach allows us to obtain both a more general solution as well as analyze frost heave and propagation of the freezing front as they depend upon the convective (Pe) and phase transition (Ste) characteristics (criteria) of the process. The theoretical results derived from our solution of the analysis for fine-grained soils are compared, in good agreement, with experimental investigations and numerical models. A singularity of the solution at the initial point in time is discussed. In this respect the asymptotic solution for short and long times is obtained. The results are compared with both solutions (modeling and asymptotic). The model presented predicts the frost heave and freezing processes in porous media with reasonable accuracy and satisfactorily reflects observed phenomena, and thus can be suitable for engineering practice.     

Impact of reaction temperature,stirring and cosolvent on the solvothermal synthesis of anatase TiO2 and TiO2/titanate hybrid nanostructures: Elucidating the growth mechanism

One-dimensional anatase TiO₂ and hybrid TiO₂/titanate nanostructures are synthesized by a simple low temperature solvothermal route followed by the Na⁺/H⁺ ion-exchange and final calcination process. We investigated the impact of reaction temperature, stirring conditions and cosolvent on the morphologies of the as-prepared nanostructures. Nanotubes and nanorods are formed in alkaline solution, while nanorods/nanowires and nanoporous nanoribbons are formed in alkaline water–ethanol and alkaline water–ethylene glycol mixed solvents, respectively. X-ray diffraction, Raman scattering and high-resolution transmission electron microscopy studies are employed to identify the structure and phase composition. The formation of different morphologies of the as-synthesized nanostructures is investigated by field emission scanning electron microscopy and transmission electron microscopy. The growth mechanism and reaction process of the as-prepared nanostructures are explained based on the experimental observations. The photoluminescence, optical absorption and the tuning of band gap of the prepared samples are also studied. This work will be valuable for understanding the growth mechanism of various nanostructured TiO₂ and to explore the commercial applications of nanoporous nanoribbons of TiO₂.     

Variations du pourcentage de ZnS dans des solutions solides de ZnxCd1−xS obtenues par pulvérisation cathodique reactive

Films of the solid solution system Zn_xCd_1?xS have been produced by co-sputtering a two semidisk target of Zn and Cd in a H₂S-argon mixture. The optical absorption edge was measured for each film. Expressions have been derived for the deposition profile on the basis of Knudsen's cosine law, and from the experimental results. Electron diffraction patterns show a wurtzite structure whatever the ZnS concentration in the solid solution.     

Simultaneous removal of copper and lead ions from a binary solution by sono-sorption process

The aim of this work is to compare the simultaneous sorption of copper and lead ions from a binary aqueous solution in the presence and in the absence of ultrasound. The experiments under sonication were carried out by 20-kHz apparatus. Results indicated that the removal of copper and lead ions from a binary aqueous solution was greater in the presence of ultrasound than in control method. The removal of these ions was examined by varying experimental conditions such as the amount of sorbent, contact time, and temperature. In addition, the competitive sorption of ions was considered with different concentrations of each ion under the constant total concentration. The Langmuir isotherm model fits adequately the experimental data. In point of kinetics, the second-order kinetic model describes the sorption process for both ions. It was found that more than 90% of the lead and 60% of the copper ions was removed in less than 2 min from the solution under sonication. The thermodynamic parameters such as ΔG°, ΔH°, and ΔS° were determined for the sorption of Cu²⁺ and Pb²⁺ from the temperature dependence of the sorption process.     

Scaling of turbulent separating flows

The present work investigates the scaling of the turbulent boundary layer in regions of adverse pressure gradient flow. For the first time, direct numerical simulation and experimental data are applied to the theory presented in Cruz and Silva Freire [Cruz, D. O. A., & Silva Freire, A. P. (1998). On single limits and the asymptotic behaviour of separating turbulent boundary layers. International Journal of Heat and Mass Transfer, 41, 2097-2111] to explain how the classical two-layered asymptotic structure reduces to a new structure consistent with the local solutions of Goldstein and of Stratford at a point of zero wall shear stress. The work discusses in detail the behaviour of an adaptable characteristic velocity (u_R) that can be used in regions of attached as well as separated flows. In particular, u_R is compared to velocity scales based on the local wall shear stress and on the pressure gradient at the wall. This is also made here for the first time. A generalized law of the wall is compared with the numerical and experimental data, showing good agreement. This law is shown to reduce to the classical logarithmic solution and to the solution of Stratford under the relevant limiting conditions.     

Studies on synthesis,growth and characterization of a novel third order nonlinear optical 4-Dimethylaminopyridinium p-Toluenesulfonate single crystal

Good quality single crystals of 4-Dimethylaminopyridinium p-Toluenesulfonate (4DMAPPTS) possessing third order nonlinearity were grown by slow evaporation solution technique (SEST). Single crystal X-ray diffraction analysis reveals that 4DMAPPTS belongs to monoclinic crystal system with centrosymmetric space group P2₁/n. FT-IR spectral studies were carried out to identify the functional groups present in 4DMAPPTS. NMR spectral study confirms the molecular structure of the grown crystal. Dielectric measurements were made over a wide range of frequencies for different temperatures. The grown crystal was subjected to Vickers microhardness test to study the mechanical property. The etching studies reveal the growth pattern and dislocations present in the grown title crystal. The important optical parameters such as absorption coefficient, extinction coefficient, refractive index and optical band gap were estimated from UV–Visible spectral analysis. The negative third order nonlinear optical parameters like refractive index (n₂), absorption coefficient (β) and susceptibility (χ⁽³⁾) were estimated by Z-scan studies.     

Synthesis and properties of solid solutions of hexagonal YCu0.5Ti0.5O3 with YMO3 (M = Mn, Cr, Fe, Al, Ga, and In)

Solid solutions of the type Y(Cu_0.5Ti_0.5)_1−xM_xO₃ with a hexagonal structure were prepared for M = Mn, Fe, Cr, Al, Ga, and In. A complete solid solution could be obtained only in the case of M = Mn. The green color of YCu_0.5Ti_0.5O₃ was found to be enhanced by small substitutions of Al, Ga, and In. All compositions containing Mn were black in color. Suppression of magnetic transitions is observed upon co-doping of Cu/Ti into YMnO₃. Measurements of dielectric constant suggest some magneto-electric coupling may be present in the Y(Cu_0.5Ti_0.5)_1−xMn_xO₃ solid solution.     

The modelling of the freezing process in fine-grained porous media: Application to the frost heave estimation

The solution of the moving-boundary problem, related to heat- and mass-transfer processes in freezing, fine-grained, porous media under phase-transition conditions is presented. It is assumed that a freezing zone, characterized by a wide temperature range of phase transitions, is formed. Therefore a three-zone model is developed. The preservation of the term ∂L/∂t(L is the ice content) in the system of equations has made it possible to determine the ice distribution within the frozen and the freezing zones. For loamy soils the dependence of the freezing process on the characteristic parameters, the Stefan and Lewis numbers, was analyzed. It was found that increasing the enthalpy of phase transition, i.e., decreasing the Stefan number Ste, resulted in diminution of the frozen zone but, at the same time, the ice content within this zone increased. Intensification of the migration process, i.e., increasing the Lewis number Le, also led to diminution of the frozen zone, in which the ice content and, consequently, the total moisture (including ice) were increased. For large Lewis numbers the freezing zone was observed to decrease. When the water migration process is absent (Le = 0), the calculations, which were based on the described model show that in the course of freezing the redistribution takes place only between moisture and ice contents. The total moisture remains constant and equal to the initial water content. The theoretical conceptions and results derived from the analytical solution are in agreement with experimental findings. The presented model predicts the freezing process in porous media and satisfactorily reflects observed phenomena. The utilization of the considered problem solution to the prediction of the frost heave phenomenon in soils freezing processes shown that the calculated frost heave curve matches the experimental results very closely indicating that the model can well reproduce the frost heaving process associated with the freezing. Propagation of the freezing front in the test is predicted the experimental results with reasonable accuracy.     

Adsorption of copper(II) onto sewage sludge-derived materials via microwave irradiation

The materials with adsorbent properties were produced from urban sewage sludge by two different procedures via microwave irradiation: (1) by one single pyrolysis stage (SC); (2) by chemical activation with ZnCl₂ (SZ). The BET, SEM and FT-IR have been used to evaluate the pore structural parameters and surface chemistry of the adsorbents, respectively. Subsequently they were used for adsorption of Cu(II) from aqueous solutions. The effects of various experimental parameters, such as pH, temperature were investigated in a batch-adsorption technique. The results showed that the adsorption of Cu(II) was maximal at pH 5.0. The kinetic study demonstrated that the adsorption process was followed the second-order kinetic equation. The experimental adsorption isotherm data were well fitted with Langmuir model and the maximum adsorption capacity of Cu(II) were found to be 3.88 and 10.56 mg/g for SC and SZ, respectively, in the solution of pH 5.0. Thermodynamic parameters such as changes in the enthalpy (ΔH⁰), entropy (ΔS⁰) and free energy (ΔG⁰) indicate that Cu(II) adsorption onto SC and SZ is an endothermic and spontaneous process in nature at 15-45 °C. These results indicate that the sewage sludge-derived material via microwave induced ZnCl₂ activation is an effective and alternative adsorbent for the removal of Cu(II) from aqueous solution.     

Coupled P and SV waves propagating in spherical elastic layers: Exact solution and interpretation

We study the propagation of coupled P and SV waves emitted by a source point placed outside a given finite set of concentric elastic spherical layers. We show that the system of boundary conditions of this pattern is a linear combination of the boundary conditions of the simpler problem of reflectionrefraction phenomenon of a wave at a spherical surface. From this result the exact solution follows for all regions of the multilayered structure without using Cramer's technique. This solution is written as a series of which each element is interpreted directly in terms of multiple reflection-refraction. It gives a simple explanation for triggering of resonance phenomena. The solution contains many particular bases of which several are investigated.     

Fabrication and structural characterization of (Ba,Sr)TiO3 thin films produced by Electrostatic Spray Assisted Vapour Deposition

Thin films of perovskite (Ba,Sr)TiO₃ (BST) system are promising candidates for microelectronic devices that can be integrated into semiconductor technology. The lead-free solid solution Ba_xSr_1−xTiO₃ is a high permittivity dielectric material with low loss and suitable for use in dynamic random access memory cells, tunable microwave devices, by-pass capacitors and infrared detectors. A versatile and cost-effective Electrostatic Spray Assisted Vapour Deposition (ESAVD) process has been used to fabricate nanostructured BST film. The crystal structure, surface morphology and homogeneity of composition of BST thin films have been investigated using a combination of XRD, SEM, AFM, Raman spectroscopy and XPS techniques.     

Closed-form buckling analysis of stiffened composite plates and identification of minimum stiffener requirements

Longitudinal stiffeners attached to composite plates may significantly increase the overall buckling loads of the resultant stiffened structure. As long as the bending stiffness EI of the stiffener remains beneath some a priori unknown threshold value EI_min (with E being Young’s modulus and I being the bending moment of inertia), the buckling pattern will usually be of a more or less global nature, meaning that both the plate and the stiffener will exhibit some certain buckling modes. Once a threshold value EI_min for the bending stiffness, also called minimum stiffness, is exceeded, the stiffener more or less remains in its original position in the state of the onset of buckling while the buckling pattern of the stiffened plate is dominated by local buckling modes of the plate itself. The knowledge of this minimum bending stiffness EI_min of longitudinal stiffeners of composite plates is of high practical importance and a predominant design criterion and will be considered in this paper. For the basic load cases uniform compression and pure shear and their combination, simple closed-form analytical approaches will be presented which enable a straightforward and quick yet accurate estimation of the buckling loads (compression) and (shear) of stiffened composite plates on the one hand, and the minimum bending stiffness EI_min of the attached stiffeners on the other hand.     

Analytical evaluation of pull-out tests—The inverse problem

A numerical solution routine is proposed, which provides a simple and straightforward analytical method to evaluate the prevailing bond characteristics of a composite by means of a bond stress versus slip relation τ(s) using experimental data from pull-out tests. Time consuming and sometimes nonconvergent optimization procedures which have been used so far to determine τ(s) can be avoided. The proposed solution routine is applied and validated using experimental data from pull-out tests which were carried out at steel fiber/concrete systems. It is also shown that the underlying bond stress versus slip relation τ(s) is a material parameter, since it is not dependent on geometric factors of fiber and matrix, for example fiber diameter and embedded length.     

pH-Sensitive biodegradable PMAA2-b-PLA-b-PMAA2 H-type multiblock copolymer micelles: synthesis,characterization, and drug release applications

pH-Sensitive biodegradable polymethacrylic acid-block-polylactic acid-block-polymethacrylic acid (PMAA₂-b-PLA-b-PMAA₂) H-type multiblock copolymers were synthesized by atom transfer radical polymerization. The copolymer structure and molecular weight were characterized by FT-IR, ¹H NMR, and gel permeation chromatography. The physicochemical characterization revealed that the copolymers could spontaneously form spherical core–shell micelles in aqueous solution, with critical aggregation concentration of about 19.7–32.5 mg L^?1 and the hydrodynamic diameters below 200 nm. Zeta potentials measurements disclosed that the copolymer micelles were negatively charged due to ionized carboxyl groups in various PBS solutions. The H-type block copolymer micelles exhibited pH- sensitivity, as expected; and the hydrophobic anticancer drugs, 10-hydroxycamptothecin, and paclitaxel, had faster release rate in PBS solution of pH 5.6–7.4 than in PBS of pH 1.4, which was important for applications in the therapy of small intestine cancers. The copolymer micelle aggregates were proved to be biodegradable, and the degradation rates changed with copolymer compositions and environmental media. The micelle drug formulation indicated pH-dependent cytotoxicity and was thus capable of effectively killing the intestinal cells while avoiding doing harm to stomach. The biodegradable pH-sensitive PMAA₂-b-PLA-b-PMAA₂ H-type copolymer micelles can be used as water-insoluble drug targeting release carriers for targeted treatment of intestine cancers.     

Effect of delamination failure in crashworthiness analysis of hybrid composite box structures

In the present paper the effects of delamination failure of hybrid composite box structures on their crashworthy behaviour will be studied and also their performance will be compared with non-hybrid ones. The combination of twill-weave and unidirectional CFRP composite materials are used to laminate the composite boxes. Delamination study in Mode-I and Mode-II with the same lay-ups was carried out to investigate the effect of delamination crack growth on energy absorption of hybrid composite box structures. The end-loaded split (ELS) and double-cantilever beam (DCB) standard test methods were chosen for delamination studies. In all hybrid composite boxes the lamina bending crushing mode was observed. Regarding the delamination study of hybrid DCB and ELS the variation of the specific energy absorption (SEA) versus summation of G_IC and G_IIC were plotted to combine the effect of Mode-I and Mode-II interlaminar fracture toughness on the SEA. From this relationship it was found the hybrid laminate designs which showed higher fracture toughness in Mode-I and Mode-II delamination tests, will absorb more energy as a hybrid composite box in crushing process. The crushing process of hybrid composite boxes was also simulated by finite element software LS-DYNA and the results were verified with the relevant experimental result.