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The work concerns the parameter estimation in the context of the mechanistic modelling of a pulp digester. The problem is cast as a box bounded nonlinear global optimization problem in order to minimize the mismatch between the model outputs with the experimental data observed at a real pulp and paper plant. MCSFilter and Simulated Annealing global optimization methods were used to solve the optimization problem. While the former took longer to converge to the global minimum, the latter terminated faster at a significantly higher value of the objective function and, thus, failed to find the global solution.The work concerns the parameter estimation in the context of the mechanistic modelling of a pulp digester. The problem is cast as a box bounded nonlinear global optimization problem in order to minimize the mismatch between the model outputs with the experimental data observed at a real pulp and paper plant. MCSFilter and Simulated Annealing global optimization methods were used to solve the optimization problem. While the former took longer to converge to the global minimum, the latter terminated faster at a significantly higher value of the objective function and, thus, failed to find the global solution.

International audience; The present paper is devoted to characterizing the three-dimensional effects in a cavitating flow generated in a Venturi-type profile. Experimental measurements based on 2D3C(Two-dimensionalthree-component) stereoscopic PIV(Particle Image Velocimetry) are conducted to obtain the three components of the velocity field in multiple vertical planes aligned with the main flow direction, from the center of the channel to the side walls. Time-resolved acquisitions are conducted, so not onlytime-averaged quantities but also velocity fluctuations can be discussed. The attention was focused on configurations of cloud cavitation, where the attached cavity experiences large-scale periodical oscillations and shedding of clouds of vapor. Although the water channel is purely two-dimensional, some significant flow velocities in the third direction (depth of the test section) were measured. Some of those velocities were found to be related to small differences between the boundary conditions on the two sides, such as minor gaps between the sides and the bottom wall, while others reflect intrinsic three-dimensional mechanisms inside the cavitation area, such as side jets that contribute to the periodical instability process. These mechanisms are discussed, and a possible 3D(Threedimensional) structure of the cavitating flow is proposed.

In Portugal, the first public housing policies were developed in a high state-control context: the Salazar dictatorship (1933-1968). Until the 1950s, the Estado Novo (the dictatorial regime) actions had an evident paternalistic character by constructing small-scale housing focused on the most urgent cases or aimed at controlling specific sectors of the population. The public effort focused on promoting housing in the country's central districts and cities, given that the population was abandoning rural areas to seek better living conditions in the large cities with a higher level of industrialisation. In this context, the official architectural discourse defended the ideal of the Casa Portuguesa [Portuguese House] as an affirmation of the ideological discourse of the regime. This model advocated a ruralising architecture style by integrating architectural and decorative elements of the region's traditional architecture, including an outdoor garden to grow vegetables, store agricultural, farming or fishing tackle. The single-family dwelling was presented as the only residential type capable of assuming the Nation's principles as seen by the regime, with low-rise and low-density urban designs typical of the garden city. It would become an excellent instrument to enforce the traditional family model and preserving the existing social order. In this regard, the paper proposes to study the first social housing neighbourhoods built in the medium-sized city of Setúbal: Afonso Costa, Nossa Senhora da Conceição, Pescadores and Famílias Pobres. Setúbal has historically played a significant role in the region due to its strategic location within its territorial structure around the Sado Estuary. Linked to the fishing tradition, the city overgrew in the first decades of the 20th century thanks to the canning industry, making it a recipient of the migratory processes that gave rise to social housing construction. The research has identified that these four neighbourhoods respond to a simple-line architecture close to the Modern Movement, especially in their spatial organisation. However, their external image and their urban planning link them to the “Portuguese House” ideals. Most of them consist of one- or two-storey houses, detached or semi-detached with gardens, and their façades incorporate elements typical of the popular architecture.

The analysis of big data, namely in inhomogeneous large-scale data under the regression analysis context, is a research topic with growing interest in recent years, where bagging and magging are two well-known aggregation procedures. As this kind of data may be recorded in different time regimes or may be taken from multiple sources, inhomogeneities are expected to be present, compromising regression modelling. The classical framework of independent and identically distributed errors related to a single underlying model does not apply and the usual alternatives (such as time-varying coefficients models or mixture models, for instance) may represent prohibitive computational burden. This paper revises the methodology developed in a recent work where an aggregation procedure based on normalized entropy was proposed, with very promising results, and illustrates its performance with real data applications considering distinct scenarios. published

Multiphase machine models can be accurately designed and represented by means of MATLAB Simulink. This is because the dq-axis flux linkages and the torque response of the multiphase machines can be accurately expressed and described by means of lookup tables-based finite element method (FEM) simulations. However, the power electronic converters are easily implemented using MATLAB Simscape. Hence, the two MATLAB blocks should be connected together to provide the whole drive system. However, there will be a problem to easily connect the two MATLAB blocks directly. Consequently, this paper introduces a detailed description of the proposed interconnector that can be used to interface the two MATLAB blocks. A five-phase induction motor Simulink model connected to a five-phase voltage source inverter Simscape model will be presented to analyze and describe the implementation of the proposed interconnector. Finally, the simulation result of the five-phase squirrel cage induction motor, the five-phase voltage source inverter and the proposed interconnector are displayed.

A statistical mechanical model of allosteric transition of proteins is developed by extending the structure-based model of protein folding to cases that a protein has two different native conformations. Partition function is calculated exactly within the model and free-energy surfaces associated with allostery are derived. In this paper, the model of allosteric transition proposed in a previous paper [Proc. Natl. Acad. Sci. U.S.A 134, 7775 (2010)] is reformulated to describe both fluctuation in side-chain configurations and that in backbone structures in a balanced way. The model is applied to example proteins, Ras, calmodulin, and CheY: Ras undergoes the allosteric transition between guanosine diphosphate (GDP)-bound and guanosine triphosphate (GTP)-bound forms, and the model results show that the GDP-bound form is stabilized enough to prevent unnecessary signal transmission, but the conformation in the GTP-bound state bears large fluctuation in side-chain configurations, which may help to bind multiple target proteins for multiple pathways of signaling. The calculated results of calmodulin show the scenario of sequential ordering in Ca(2+) binding and the associated allosteric conformational change, which are realized though the sequential appearing of pre-existing structural fluctuations, i.e., fluctuations to show structures suitable to bind Ca(2+) before its binding. Here, the pre-existing fluctuations to accept the second and third Ca(2+) ions are dominated by the side-chain fluctuation. In CheY, the calculated side-chain fluctuation of Tyr106 is coordinated with the backbone structural change in the β4-α4 loop, which explains the pre-existing Y-T coupling process in this protein. Ability of the model to explain allosteric transitions of example proteins supports the view that the large entropic effects lower the free-energy barrier of allosteric transition.

The conversion of solar energy to heat can be performed in direct absorption solar collectors, where the radiation from the sun is absorbed by a fluid. There are various types of fluids that can be used, and recently, nanofluids (i.e., liquids with immersed nanoparticles) have been investigated by researchers. Nevertheless, nanofluids have inherent drawbacks such as cost, toxicity, and clogging. This paper considers the use of fluids that are inexpensive and neutral to the environment, namely, coffee colloids. These types of fluids have already been tested for solar energy applications, but they have not yet been compared with nanofluids. In this research, we conducted a series of simple experiments where both coffee colloids and carbon black nanofluids were analyzed under the same conditions. According to our results, the thermal efficiency of coffee colloid and the nanofluid systems is, respectively, 12% and 16% greater than that of pure water. In addition to the experiments, we developed a mathematical model that is based on the Beer–Lambert law and a heat balance equation. Despite its simplicity, the model predicts the results relatively well. publishedVersion

The energy from solar can easily harnessed to be used for various applications and grid injection. For cooking, different techniques can be utilized. Some people use the sun to cook. Other people use batteries and inverters even at noon. Hence, the cooking system becomes expensive. In fact, Photovoltaic panels did not decrease considerably in price. This paper proposes a simple electronic circuit that a Photovoltaic system can directly be used for cooking. The circuit aims at facilitating a cooking plate user to set a duty ratio. The duty ratio is limited to maintain the array voltage above a minimal level to avoid that it operates too far away from the maximal power point when less power is available. Moreover, it shows to be cost-effective compared to Photovoltaic grid connected and to charcoal. REFERENCES

To mitigate the adverse consequences of chronic hyperglycemia, patients with type 1 diabetes mellitus must provide their bodies with insulin to control their blood glucose. In most cases, insulin therapy consists of a combination of basal insulin and bolus insulin, the so-called basal-bolus insulin therapy. To determine the bolus insulin, patients must know not only the carbohydrate content of each meal but also the values of the insulin-to-carbohydrate ratio and the insulin sensitivity factor. Although important, the blood glucose complex dynamics make determining these parameters a difficult and error-prone task, usually performed by experienced diabetologists using high-quality data. Moreover, the insulin-to-carbohydrate ratio and the insulin sensitivity factor vary over the day due to several factors. Thus, daily, patients use approximate values to determine their prandial bolus. In this paper, we propose an analytic method to find the safe maximum interval for the error in the estimates of the insulin-to-carbohydrate ratio and, therefore, avoid dysglycemia. Our study suggests that slimmer patients with smaller insulin-to-carbohydrate ratios need to be more careful when estimating it. Another significant finding of our work is that in such cases, having small meals reduces the adverse effect of inaccurate insulin-to-carbohydrate ratio estimates in the postprandial blood glucose. 911A-2C18-106F | Carlos Jorge Enes Capit?o de Abreu N/A

In this paper the tecno-economic assessment of two novel hydrogen production plants for small refueling stations is analyzed and compared. In the first one renewable ammonia, that is the hydrogen carrier, is cracked in a Solid Oxide Fuel Cell (SOFC) power unit that cogenerates the required hydrogen and the electric power needed for the hydrogen separation and storage. In the second one the hydrogen production is based on the autothermal reforming of the biogas obtained from an anaerobic digester and the electric power consumption for the hydrogen separation and storage is supplied by an SOFC power unit fed with part of the syngas exiting the biogas processing unit. In both the plant configurations the product hydrogen is separated by means of a Pd-Ag membrane separation unit and is compressed up to 820 bars by using an ionic compression system. The economic performance comparison is based on the evaluation of the levelized cost of the hydrogen (LCOH) for a decentralized hydrogen refueling station (HRS).

Highly crosslinked polyethylene polymers (XLPE) are used in many human-contact applications that require assurance on aspects of durability, longevity and safety. The work described in this paper focuses on applications in the medical field and in the construction industry. These are related to the use of XL-UHMWPE for articulating surfaces in orthopaedic implants particularly in total hip and knee replacements, and the use of XL-HDPE for potable water pipes. Safety, performance and durability of the end-use products are mandatory for their approval and use in such applications. However, it has long been recognised that the stabilisation of such highly crosslinked polymers by commercial antioxidants (AO) faces many challenges including the possible interference of the AOs with the crosslinking step, as well as the issues of safety associated with AO leaching and migration of into the human-environment. Here, the effect of AOs on the long-term oxidative stability of the end-use polymer artefacts in these applications is examined and compared with that obtained with some new alternative stabilisation systems. Results show that, in both applications, it was possible to achieve superior levels of retention of the AO in the polymer and long-term thermal stabilising (LTTS) performance (ageing) with minimum interference with the crosslinking process, thereby addressing issues of stabilisation, health and safety of polymers used in direct contact with the human environment.

Paper published as part of the Proceedings of the 22nd Topical Conference on High-Temperature Plasma Diagnostics, San Diego, California, April 2018; International audience; A theory for data interpretation is presented for a cylindrical Langmuir probe in plasma parallel to the magnetic field direction. The theory is tested in a linear low-temperature plasma device Aline, in a capacitive radio-frequency (RF) discharge. The probe is placed on a 3D manipulator and a position scan is performed. To exclude strong RF perturbations the probe is RF compensated. Using the theory electron densities are obtained from the current at the plasma potential, where no sheath is present. Results are calibrated by line-integrated density measurements of a 26.5 GHz microwave interferometer. Reasonable agreement is observed for probe and interferometer measurements. Furthermore, preceding, more general probe theory is compared to the one developed in the current work and the application limits are discussed.

Articular cartilage is a specialised, aneural and avascular connective tissue that lines the end of synovial joints. Its main functions are minimising friction and wear during the movements between the joint surfaces, and spreading and transmitting loads and shocks over a larger area within articulations. Many studies have been performed to shed light on the outstanding tribological features of this soft poroelastic material. However, despite the effort expended, many aspects remain unclear. This paper presents an experimental investigation on the effect of the load and static loading time over the frictional properties of adult bovine articular cartilage.

In the present paper, we investigate the dynamics of a model in which the real part of the economy, described within a multiplier-accelerator framework, interacts with a financial market with heterogeneous speculators, in order to study the channels through which the two sectors influence each other. Employing analytical and numerical tools, we investigate stability conditions as well as bifurcations and possible periodic, quasi-periodic, and chaotic dynamics, enlightening how the degree of market interaction, together with the accelerator parameter and the intervention of the fiscal authority, may affect the business cycle and the course of the financial market. In particular, we show that even if the steady state is locally stable, multistability phenomena can occur, with several and complex dynamic structures coexisting with the steady state. Finally, simulations reveal that the proposed model is able to explain several statistical properties and stylized facts observed in real financial markets, including persistent high volatility, fat-tailed return distributions, volatility clustering, and positive autocorrelation of absolute returns.

Low-dimensional lead-free luminescent halides have emerged as highly promising phosphors for white-light emission. Recently, we reported a broadband blue-emitting copper(I) iodide-based material, Cs3Cu2I5, with a high photoluminescence quantum yield (PLQY) (∼90%) and a zero-dimensional nature, providing significant dimensionality for the photoactive site. However, this material is insufficient as a white-light emitter owing to the deficient yellow emission. In this paper, we report a novel yellow luminescent phosphor, CsCu2I3, with a 1D structure for the photoactive site. This material exhibits a broadband emission centered at ∼560 nm with a PLQY of ∼8%. We demonstrate a thin film with white-light emission that can be fabricated using one-step spin-coating of a mixed precursor solution of 1D CsCu2I3 (yellow) and 0D Cs3Cu2I5 (blue).

© 2016 Author(s). Doped LaMnO3 and SmCoO3 are important solid oxide fuel cell cathode materials. The main difference between these two perovskites is that SmCoO3 has proven to be a more efficient cathode material than LaMnO3 at lower temperatures. In order to explain the difference in efficiency, we need to gain insight into the materials' properties at the atomic level. However, while LaMnO3 has been widely studied, ab initio studies on SmCoO3 are rare. Hence, in this paper, we perform a comparative DFT + U study of the structural, electronic, and magnetic properties of these two perovskites. To that end, we first determined a suitable Hubbard parameter for the Co d-electrons to obtain a proper description of SmCoO3 that fully agrees with the available experimental data. We next evaluated the impact of oxygen and cation vacancies on the geometry, electronic, and magnetic properties. Oxygen vacancies strongly alter the electronic and magnetic structures of SmCoO3, but barely affect LaMnO3. However, due to their high formation energy, their concentrations in the material are very low and need to be induced by doping. Studying the cation vacancy concentration showed that the formation of cation vacancies is less energetically favorable than oxygen vacancies and would thus not markedly influence the performance of the cathode.

This paper describes a modelling approach suitable for assessments of future scenarios for renewable energy integration in large and interconnected power systems, based on sequential optimal power flow computations that take into account variability in power consumption, in renewable power production, energy storage, and flexible demand. The approach and the implementation as an open source Python package called Power Grid And Market Analysis is described in some detail. Particular emphasis is put on the modelling of energy storage systems, and the use of storage values as a means to define storage utilisation strategies. A case study representing a 2030 scenario for the Western Mediterranean region is then analysed using this approach. The main aim of this study is to assess the benefit for the system of adding flexibility in terms of storage associated with concentrated solar power or flexible demand. But other results are also presented, such as the resulting energy mix, generation costs, price variations, and grid congestion.

XRM 2014: Proceedings of the 12th International Conference on X-Ray Microscopy Proceedings of the 12th International Conference on X-Ray Microscopy, XRM 2014, Melburn, Australia, 26 Oct 2014 - 31 Oct 2014; AIP conference proceedings 1696, 020008 (2016). doi:10.1063/1.4937502, The Helmholtz-Zentrum Geesthacht operates the P05 Imaging Beamline at the DESY storage ring PETRA III. This beamline is dedicated to micro- and nanotomography with two endstations. This paper will present the nanotomography endstation layout and first results obtained from commissioning and test experiments.First tests have been performed with CRLs as X-ray objectives and newly developed rolled X-ray prism lenses as condenser optics. This setup allows a resolution of 100 nm half period with an effective detector pixel size of 15nm. A first tomograph of a photonic glass sample was measured in early 2014., Published by AIP, Melville, NY

This paper addresses the problem of finding a Bayesian net representation of the probability function that agrees with the distributions of multiple consistent datasets and otherwise has maximum entropy. We give a general algorithm which is significantly more efficient than the standard brute-force approach. Furthermore, we show that in a wide range of cases such a Bayesian net can be obtained without solving any optimisation problem.

The isotropic properties of Soft Magnetic Composites (SMC) favor the design of new machine topologies and their granular structure can induce a potential decrease of the dynamic loss component. This paper is devoted to the characterization of the broadband magnetic losses of different SMC types under alternating and circular induction. The investigated materials differ by their grain size, heat treatment, compaction rate, and binder type. It is shown that, up to peak polarization J p = 1.25 T, the ratios between the rotational and the alternating loss components (classical, hysteresis, and excess) are quite independent of the material structural details, quite analogous to the known behavior of nonoriented steel laminations. On the contrary, at higher inductions, it is observed that the J p value at which the rotational hysteresis loss attains its maximum, related to the progressive disappearance of the domain walls under increasing rotational fields, decreases with the material susceptibility.

In this paper we present an application of a new technique, based on recent work done by Liu & Ricca (2012), to quantify structural complexity by means of topological methods. These rely on the derivation of the Jones polynomial from the helicity of ideal fluid flows. The techniques discussed here can be extended and applied to real fluid flows subject to continuous topological restructuring.

A detailed electronic and microstructural characterization is reported for the LiBH4-MgH2 reactive hydride composite system with and without titanium isopropoxide as additive. Surface characterization by x-ray photoelectron spectroscopy combined to a morphological study by scanning electron microscopy as well as elemental map composition analysis by energy dispersive x-ray emission are presented in this paper for the first time for all sorption steps. Although sorption reactions are not complete at the surface due to the unavoidable superficial oxidation, it has been shown that the presence of the additive is favoring the heterogeneous nucleation of the MgB2 phase. Ti-based phases appear in all the samples for the three sorption steps well dispersed and uniformly distributed in the material. Li-based phases are highly dispersed at the surface while the Mg-based ones appear, either partially covered by the Li-based phases, or forming bigger grains. Ball milling is promoting mixing of phases and a good dispersion of the additive what favors grain refinement and heterogeneous reactions at the interfaces. © 2011 American Institute of Physics.

In this paper we find a new asymptotic expansion valid in enzymatic reactions where the total amount of enzyme exceeds greatly the total amount of substrate. In such case it is well known that the Michelis‐Menten approximation is no longer valid; therefore our asymptotic expansion is a new tool to approximate in a closed form the concentrations of the reactants in presence of an enzyme excess.

The excess noise observed during the resistive transition of a superconducting material can be used to shed light on the microscopic processes underlying the transition itself. In a previous paper [1] it has been proposed a model to explain the large noise observed during the resistive transition of MgB2 superconducting films, obtained by slowly increasing the specimen temperature across its critical value when a d.c. bias current is applied. The amplitude and frequency behaviour of the noise power spectrum, simulated with this model, are in good agreement with the experimental data. The model is based on the onset of correlated transition of large sets of grains forming resistive layers through the specimen cross section, giving rise to resistance steps. It is assumed that these events produce the large noise, of 1/f3 type in the low frequency range, observed in the experiments. To compare this model with alternative ones, based on dissipative effects produced by fluxoid dynamics, new results, obtained b...

Recent developments on micro‐structuring of ferroelectric crystals, such as LiNbO3, have opened up new possibilities for several devices in nonlinear and electro optics. In this paper, after describing the basics of LiNbO3 based integrated electro‐optic modulators, we will show how techniques such as etching, domain inversion and thin film processing can be used to realize new geometries which can take the performance to unprecedented levels. In particular we will report recent results on the use of domain inversion on a micron scale to tailor and improve the electro‐optic response of LiNbO3 waveguide modulators, showing that these applications for domain inversion techniques might be even more important and commercially valuable than those in nonlinear optics (e.g. quasi‐phase‐matched optical parametric devices). With respect to standard single‐domain structures, larger bandwidths and lower driving voltages can be obtained, thus achieving figure of merits for the electro‐optic response that are up to 50%...

In this paper, the elementary energy transfer between the two-point average of a velocity field and the two-point difference has been examined. The equations related to the two-point quantities are derived from the Navier-Stokes equations applied to incompressible flows. Some interesting aspects of this simple transfer of energy are discussed both from the point of view of the filtered equations associated with the two-point velocity average and from the point of view of the properties of the structure functions associated with the two-point velocity difference. A new inertial relation valid for homogeneous flows is finally presented.

Although solutions for detection and sizing of longitudinal and circumferential cracks in pipeline walls exist, reliable detection and sizing of SCC in pipelines has been a challenge for Non Destructive Evaluation (NDE) for many years. Detection and sizing are impeded by the fact that SCC can have very irregular morphology and can occur in random orientations. NDE as an industry on the other hand has suffered from the emerging of many new UT techniques and a difficult jargon, making easy understanding of the actual problems and solutions impossible for an outsider (i.e. the pipeline operator). This paper presents a novel approach to provide insight into the capabilities of common NDE methods using finite difference simulation software developed by RTD. Simulations are performed on the most common morphologies of SCC using the most commonly used in-the-ditch NDE methods. Using the parameters of the actual inspection procedure a picture is painted of what works and doesn't work about the most common ways of accessing SCC. © 2006 American Institute of Physics.

The response of polymers to shock loading is becoming of increasing importance, both as binder systems in plastic-bonded explosives (PBXs) and as structural materials in their own right. In this paper, we report on the shock Hugoniot of hydroxy-terminated polybutadiene (HTPB), which is commonly used as a binder system in PBXs, but whose shock response has yet to be presented in the open literature. Results indicate that the shock velocity --- particle velocity relationship is linear, similar to some but not all polymer-based materials.

The well-known gyrokinetic problem regards the perturbative expansion related to the dynamics of a charged particle subject to fast gyration motion due to the presence of a strong magnetic field. Although a variety of approaches have been formulated in the past to this well known problem, surprisingly a purely canonical approach based on Lie transform methods is still missing. This paper aims to fill in this gap and provide at the same time new insight in Lie-transform approaches., Comment: 6 pages, 1 figure. Contributed to the Proceedings of the 24th International Symposium on Rarefied Gas Dynamics, July 10-16, 2004 Porto Giardino Monopoli (Bari), Italy

PVLAS is an experiment which aims at the direct detection of photon-field scattering: it employs optical methods and a large rotating superconducting magnet, and its large, compact structure is affected by both mechanical and electrical noises. This paper introduces briefly the data analysis methods used in the experiment and summarizes the mechanical and electrical noise situation., 8 pages, 14 figures, PDF only, talk given by E. Milotti at the QNDE 2002 conference, Bellingham (WA), July 14-19 2002

The 8th European Particle Accelerator Conference, EPAC2002, Paris, France, 3 Jun 2002 - 7 Jun 2002; AIP 2706-2708 (2002). doi:10.1063/1.1638357, To perform a proof of principle experiment of a SASE based Free Electron Laser operating at wavelength between 70-160 nanometer a 15 m long permanent magnet undulator has been installed in the TESLA Test Facility (TTF) linac phase 1. The type of magnets used (NdFeB) is known to be sensitive to radiation damages if exposed to high energy electrons. Already beam losses in the order of 10−6 of the nominal TTF beam current (64μA) are critical for the undulator and can cause an irreversible damage of its magnets after a few months of operation. To protect the undulator against radiation a two stage spoiler-absorber collimation system has been implemented to the beamline in front of the undulator. In this paper the design and the performance limits of the collimator system are presented., Published by AIP

MAXIMA is a balloon-based bolometric experiment to measure the temperature anisotropy of the CMB over spatial frequency range 36 ≤ l ≤ 1235. The MAXIMA-1 flight produced a 124 square degree temperature anisot0ropy map with a beam diameter of 10 arcmin. These data have been used to produce a power spectrum which is in excellent agreement with data from BOOMERANG and DASI, but covers a wider range of angular scales. The MAXIMA power spectrum is consistent with the prediction of Lambda CDM models and has been used to constrain cosmological models. The MAXIMA experiment is described and an outline is given of the contents and significance of papers written by the MAXIMA team. MAXIMA is being modified to measure the polarization anisotropy of the CMB. A brief description of this MAXIPOL experiment is also given.

It is well established that in magnetized partially ionized plasmas, the dispersion of the shear Alfve´n waves is strongly influenced by the ion–neutral collisions. In the case of inhomogeneous plasmas, the study of these collisions on Alfve´n surface waves can become important, especially in understanding resonant absorption of Alfv\grave{e}n waves. In this paper, the dispersion equation for the surface waves in partially ionized plasma along a plasma–plasma interface is derived and it is shown that ioneutral collisions can cause a drastic change in the Alfv\grave{e}n surface waves’ propagation characteristics. For the case when ion–neutral coupling is weak, the wave propagates along the interface with the natural frequency of Alfve´n surface waves in the charged medium without friction. When coupling is strong, this frequency is determined by the mass densities of both ions and neutrals in both media. When the ionization fraction is low, these two frequencies can differ by several orders of magnitude. There also exists a range of frequencies, depending on the collisions, in which the surface waves do not propagate. The damping of surface waves due to ion–neutral collisions can be very small in the case of strong coupling. For weak coupling, this damping can become large due to large collision frequencies. The effect of this on the resonant absorption of surface waves is discussed briefly. The possibility of propagation of surface waves along thin plasma–plasma interfaces is also considered in the context of some astrophysical systems.

Barkhausen effect (BE) phenomenology in iron‐based ferromagnetic alloys is investigated by a proper experimental method, in which BE experiments are restricted to the central part of the hysteresis loop, and the amplitude probability distribution, P0(Φ), and power spectrum, F(ω), of the B flux rate Φ are measured under controlled values of the magnetization rate I and differential permeability μ. It is found that all of the experimental data are approximately consistent with the law P0(Φ)∝Φc−1 exp(−cΦ/〈Φ〉), where all dependencies on I and μ are described by the single dimensionless parameter c>0. Also the parameters describing the shape of F(ω) are found to obey remarkably simple and general laws of dependence on I and μ. The experimental results are interpreted by means of the Langevin theory of domain‐wall dynamics proposed in a companion paper. The theory is in good agreement with experiments, and permits one to reduce the basic aspects of BE phenomenology to the behavior of two parameters ...

Lonberg and Meyer [Phys. Rev. Lett. 55, 718 (1985)] have recently discovered in polymer nematics the existence of a critical value rc=0.303 for the ratio r=K2/K1 between the twist and splay Frank elastic constants, below which a periodic splay-twist distortion is energetically favored with respect to the well-known aperiodic splay distortion which appears in a Freedericksz transition. In this paper the effect of weak-anchoring conditions on the critical r value and on the other parameters of interest is theoretically investigated. Analytical expressions between these parameters are given. It is shown that the periodic transition is not allowed in the range 0.5