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Mathematical modelling of river processes is, nowadays, a key element in river engineering and planning. River modelling tools should rest on conceptual models drawn from mechanics of sediment transport, river mechanics, and river hydrodynamics. The objectives of the present work are (i) to describe conceptual models of sediment transport, deduced from grain-scale mechanics of sediment transport and turbulent flow hydrodynamics, and (ii) to present solutions to specific river morphology problems. The conceptual models described are applicable to the morphologic evolution of rivers subjected to the transport of poorly sorted sediment mixtures at low shear stresses and to geomorphic flows featuring intense sediment transport at high shear stresses. In common, these applications share the fact that sediment transport and flow resistance depend, essentially, on grain-scale phenomena. The idealized flow structures are presented and discussed. Numerical solutions for equilibrium and nonequilibrium sediment transport are presented and compared with laboratory and field data.

The size of the largest horizontal coherent structures (HCSs) of turbulence in open-channel flows is investigated experimentally on the basis of three series of flow velocity measurements. These are further used to explore the dynamics and morphological consequences of HCSs. The flow velocity measurements were carried out in a 21 m long and 1 m wide channel, with a bed formed by sand with average grain size of 2 mm. The bed surface was flat. The turbulent and subcritical flow under investigation was uniform, with a flow depth of 4 cm. The bed slope of 0.0015 was such that, for the present flow depth, the bed shear stress acting on the bed was substantially below the threshold for initiation of motion, thus ensuring that the bed remained flat throughout the measurements. To the knowledge of the writers, this work is a first attempt to systematically investigate HCSs in open-channel flows. It should be viewed as an extension to the case of horizontal structures of work previously carried out by a number of authors on large-scale organized turbulence motion in open-channel flows, so far focusing exclusively on vertical coherent structures (VCSs). The horizontal burst length was found to be between five and seven times the flow width. A slight internal meandering of the flow caused by the superimposition of burst sequences on the mean flow was detectable. Both of these findings lend support to the longstanding belief expressed by many prominent researchers that the formation of large-scale river forms is directly related to the large-scale turbulence. In particular, the present measurements for the first time provide some direct evidence in support of hypotheses previously raised by Yalin and da Silva regarding the formation of alternate bars and meanders through the action of HCSs on the mean flow and the mobile bed and banks.

Effects of suction pressure and permeability on the steam heating characteristics of the wet paper are studied. Experimental results show that suction pressure enhances the energy absorption in the wet paper and effects of suction pressure strongly appear in the high-permeability paper, and also absorbed energy rate is decreased with increasing in heating time. From the numerical simulation results it is found that increase in moisture content and decrease of pressure gradient reduce the absorbed energy rate. Dimensionless numbers are derived from the basic equations to summarize the experimental and numerical simulation results.

Relating to real contact area against plane smooth surface, effects of the measuring conditions on paper friction, surrounding atmosphere and applied pressure, were examined. An optical interference method using a scanning laser microscope was adopted to measure the real contact area against a plane smooth surface. The estimated contact area of paper is around 1% of nominal area for common papers. The increase in the contact area with increasing relative humidity is considered as a cause of the increase in the friction coefficient with an increase in relative humidity. The contact area of paper generally increased in a ratio of two-thirds power of the apparent pressure over a wide range of pressure. It suggested that contact of paper was generally elastic and this fact was one reason describing the decrease in the coefficient with increasing apparent pressure. However the decrease in the coefficient is little and the frictional behavior of paper can not be fully described by the contact area against a smooth surface.

Dielectric testing techniques, in both time and frequency domains, are currently widely used by power utilities for assessment of the condition of transformer oil-paper insulation systems. However, it has been reported that results of these tests are highly influenced by the operating temperature during measurements. The distribution, migration and equilibrium of moisture between oil and paper in a complicated insulation system is highly temperature dependent. It requires adequate experience and proper understanding to interpret the dielectric response results in the presence of temperature variations and thermal instability. Proper analysis of the dielectric test result is only possible with an understanding of the physical behavior of the insulation system in response to temperature. A circuit model, which describes the dielectric behavior of the transformers main insulation system, has been investigated in this paper. The values of the parameters of the model have been identified from the dielectric tests. A correlation has been observed between the operating temperature and the equivalent model parameters that can be used as additional information for better interpretation of the dielectric test results. This paper thus reports a detailed study on the effects of temperature on dielectric measurements of a transformer under controlled laboratory conditions. Some results of practical on-site testing are also presented to demonstrate the possibility of errors that may be introduced in dielectric test results analysis unless temperature effects are taken into consideration.

Our intention in this write-up is to give a reply for the specious comment of Asterios Pantokratoras on the paper “On Cattaneo-Christov heat flux model for Carreau fluid flow over a slendering sheet, Hashim and Masood Khan, Results in Physics, 7 (2017) 310–319 (Hashim and Masood Khan, 2017)”. The authors talked about each of those comments in detail. In brief, the authors do not comply with those specious comments made by Asterios Pantokratoras (2017).

The present comment concerns some doubtful results included in the above paper.

Out-of-plane deformations of paper, such as fluting, significantly deteriorate the quality of a printed product. There are several explanations of fluting presented in the literature but there is no unanimously accepted theory regarding fluting formation and retention which is consistent with all field observations. This paper first reviews the existing theories and proposes a mechanism that might give an answer to most of the questions regarding fluting. The fluting formation has been considered as a post-buckling phenomenon which has been analysed with the help of the finite element method. Fluting retention has been modelled by introducing an ink layer over the paper surface with the ink stiffness estimated from experimental results. The impact of fast drying on fluting has been assessed numerically and experimentally. The result of the study suggests that fluting occurs due to small-scale hygro-strain variations, which in turn are caused by the moisture variations created during fast convection (through-air) drying. The result also showed that ink stiffening alone cannot explain the fluting amplitudes observed in practice, but that high drying temperatures promote inelastic (irreversible) deformations in paper and this may itself preserve fluting.

This paper presents and verifies a new mathematical model to explain the dynamic behavior of characteristic gases in the oil-cellulose insulation of high voltage devices like power transformers. The model is based on the diffusion process. Parameters of the model are already quantified from experiments and presented in previous publications. The mathematical model and assumptions are presented here. The model solution is obtained analytically and gas concentration change inside the paper insulation as a function of time is simulated. The results are converted to the concentration change in the oil using the principle of conservation of mass and validated with experimental measurements. The presented model can be used to reduce the error of dissolved gas analysis due to the migration of characteristic gases inside a healthy power transformer.

Paper drying is an exergy costly operation, so also a few percent saving may be of importance. The entropy production for the paper drying process was therefore optimised for a conventional multi-cylinder drying machine, the PM2 newsprint machine at Norske Skog ASA in Skogn, Norway. The machine has 51 cylinders grouped in three drying groups; the cylinders are either heated from the inside by steam, unheated or operated under vacuum conditions. The same inlet drying air is supplied in all upper air-pockets of the machine. Our drying model for the paper temperature profile was first compared with measured data from the machine. The total entropy production of the drying process was next calculated, and then minimised subject to a fixed outlet paper moisture content. Inlet humidity and cylinder group conditions were varied. Optimum conditions were obtained for a range of inlet air humidities, and for different cylinder groupings. We found that it was very favourable to increase the inlet air humidity. Other changes had a negligible effect on the total entropy production. The results further pointed to the need for a revision of the current paper drying model, as the second-law of thermodynamics was violated at high air humidities with this model.

Paper angle, environment friendly packaging material, has been mainly used as an edge protector, But, in the future, paper angle will be applied to package design of heavy product such as strength reinforcement or unit load system (ULS). Therefore. understanding of buckling behavior fur angle itself, compression strength and quality standard are required. The objectives of this study were to characterize the buckling behavior by theoretical and finite element analysis, and to develop compression strength model by compression test for symetric and asymetric paper angle. Based on the result of theoretical and finite element analysis, as applied load level was bigger and/or the length of angle was longer, incresing rate of buckling of asymmetric paper angle was higher than that of symmetric paper angle. Decreasing rate of minimum principal moment of inertia significantly increased as the extent of asymmetric angle increased, and buckling orientation of angle was open- direction near the small web. Incresing rate of maximum compression strength (MCS) for thickness of angle decreased as the web size increased in symmetric angle. MCS of asymmetric angle of 4357 and 3367 decreased and , and change of buckling increased and , respectively.

Large-eddy simulations of high-Reynolds-number flow around a non-cambered, ellipticleading- edge circulation control airfoil (using a Coanda wall jet blowing over a rounded trailing edge) are performed to investigate detailed turbulence characteristics of the flow. The freestream Reynolds number based on the airfoil chord is 0.49 million, the radius of the rounded trailing edge is 9.46% chord, and the jet-slot height is 2.43% trailing-edge radius. The main focus of the study is on the turbulent Coanda flow separating from the rounded trailing edge. A sufficiently large computational domain in the spanwise (periodic) direction is employed to capture natural development of turbulent coherent structures in the flow. Two different jet-blowing rates are simulated, which correspond to jet Reynolds numbers of about 4500 and 7200 based on the jet-slot height; the lower jet-blowing case agrees well with experiments. A number of backward-tilted hairpin vortices are found to be generated downstream of the jet exit and to develop until they finally disappear prior to the flow separation. These hairpins are located in the outer shear layer of the wall jet, create a strong upwash between their legs, and thus lift the high-momentum flow below the hairpins upward. Detailed turbulence statistics are also calculated.

Extensive computer simulations have been carried out to model imbibition of a coating fluid into a paper. The microstructure of the paper's pore space is represented by a network of interconnected channels or pore throats that are formed between the paper's fibers. The geometrical characteristics of the channels, such as their effective radius and length, as well as their connectivity, are selected from the experimental data presented in Part II of this series. The imbibition process that we simulate is the result of forcing the coating fluid into the pore space by applying a time-dependent flow-driven pressure distribution to the external surface of the paper, or is driven only by capillary forces. The dynamic pressure distribution is representative of a high-speed coating process. The simulations indicate that the connectivity of the pore throats, the anisotropic structure of the paper's pore space, and the dynamic pressure distribution all have a strong influence on imbibition of a coating fluid into a paper's pore space and, hence, on the quality of the coating.

This paper describes theoretical and experimental studies of the velocity characteristics of a paper transport mechanism that consists of a short rubber-layered roller and a steel roller. The deformation and strain of surface of the driving rubber roller are numerically calculated based on Boundary Element Method by using Green's function that has been derived in the polar coordinates under the in-plane stress assumption. The effects of the normal load F and the paper tension T on the strain of the rubber roller are calculated. The velocity ratio of the paper transport velocity to the tangential velocity of the rubber roller is derived from the strain of the rubber roller. In order to verify the numerical results, an experimental setup of a friction drive mechanism for an endless paper was prepared. The paper transport velocity and the tangential velocity of the rubber roller were measured by changing the operating conditions. It was shown that the theoretical result can predict precisely the effect of the normal load F, the paper tension T and the rubber thickness on the velocity ratio in the range of-0.1?T/F?0.2 when 69°Hs rubber roller is used.

Unlike a rubber balloon, a kamifusen has a hole left open to the surrounding air. So why doesn’t it collapse when you bat it around?

An experimental study was performed for the flow in a modeled hydraulic headbox of paper making machines. The turbulent boundary layer generated on the partition plate in the dispartion part and the wakes formed downstream of the plates were investigated by using the flow visualization technique of a smoke wire method and by hot-wire measurements. Those controls were explored for several kinds of test channels and the plates that differ in convergence and trailing edge shape, respectively. As a result, the rectification by contracting the channel is effective in making the distribution of the average velocity uniform and in attenuating and unifying the turbulence intensity. Furthermore, the uniformalization of the average velocity is high for the trailing edges of a tapered and a wavy shape, while the homogeneity of the turbulence intensity is excellent for the tapered edge.

We develop a constitutive model of paper’s in-plane biaxial tensile response accounting for the elastic–plastic hardening behavior, and its orthotropic character. The latter aspect is motivated by machine-made papers, which, in contrast to isotropic laboratory handsheets, are strongly oriented. We focus on modeling paper’s response under monotonic loading, this restriction allowing us to treat the elastic-plastic response as a physically nonlinear elastic one. A strain energy function of a hyperbolic tangent form is developed so as to fit the entire range of biaxial and uniaxial experiments on a commercial grade paper. This function may then be introduced as the free energy function into a model based on thermomechanics with internal variables. # 2003 Published by Elsevier Ltd.

The quality of a wound roll is highly dependent upon the in-roll stress distribution, which is controlled by the operating parameters of the center-wind torque, nip and tension. With increasing demands for higher performance of paper winding systems in terms of higher winding speeds, wider web widths and larger wound roll diameters, it becomes of vital importance to determine and understand the optimum operating conditions of these machines. In this paper, a numerical formulation for estimating the in-roll stress of a wound roll is proposed with taking account of the effect of nonlinearity in web compressibility, air-entrainment and permeance. The in-roll stress is calculated as the superposition of the stress increments caused by each winding. The theory of elasto-hydrodynamic lubrication with the compressibility of air is introduced to evaluate the effect of air-entrainment at the roll-inlet. Permeance of air is newly incorporated into the winding model, which is expressed under the assumption that permeance is proportional to the pressure difference of both sides of a web. In order to assure the applicability of the proposed theory, winding tests were conducted using the dry-end section of the paper-making pilot machine. The numerical analysis and experimental observation show the significant effect of the air-entrainment and permeance upon the in-roll stress.

A substantial portion of the CO and other gaseous smoke constituents generated in the combustion and pyrolysis zones could diffuse out of a cigarette rod through the paper wrapper. In this work, a 2-D model is developed from the basic principles that can predict the fraction of the gas diffusion out of a cigarette rod. The model incorporates the radial diffusion and axial convection of the gaseous species in a porous media. A closed form solution is obtained that eliminates the need for the numerical solution of the partial differential equations. The model was validated by comparing the predictions with the available experimental data. A parametric study was performed to investigate the effects of the above parameters. The results show that the CO diffusion increases as the length of the cigarette, paper permeability, or the external velocity of air increases. The reverse is true when the cigarette diameter, the paper thickness, and or the gas delivery is increased. The model confirms that gases with larger diffusion coefficient diffuse out at a higher rate.

In this investigation, the slip-phenomenon that occurs in the paper feeding system and deteriorates the accuracy of printing is studied. The system presented in this paper is such that the printing paper is pinched with two rollers. The driving roller has protrusions on their surface and the driven roller is coated with rubber. The slip value that is calculated by the velocities of the driving roller and the paper is used to represent the amount of slip-phenomenon in this paper. In the experimental study, characteristics and contribution ratios of various factors with respect to the slip value are found. In theoretical study, mathematical model of the paper feeding system based on elastic theory is developed to calculate the slip value. Consequentially, the slip value is calculated with these results. The analytical results show good agreement with the experimental ones.

Both feed and separation process of a separation roller type feed system in printers are simulated by FEM software MARC. The feed system is composed of a feed roller rotating at a constant velocity and a separation roller with reverse torque. In the simulation, a modified Coulomb friction modeos used, where the friction force is a function of slipping velocity as well as vertical load and coefficient of friction. The results show that the feed and separation processes are successfully simulated. The paper feed velocity decreases and separation of two papers increase as the reverse torque becomes larger. The friction forces acting between two papers and rollers are almost the same in magnitude and equal the value obtained by dividing the reverse torque by the separation roller radius. The simple equations predicting the paper velocities are presented.

Change in flow regime from subcritical to supercritical flow or opposite can be met during a dam break flow propagation but also during floods in urban areas, particularly near crossroads. Detailed laboratory measurements of flow discharge distribution and flow depths are carried out for transcritical dividing flows in a 90° sharp-edged, rectangular junction formed by horizontal open-channels of equal width. These measurements are used to assess the uncertainty of numerical predictions obtained using a two-dimensional (2-D) depth-averaged model. A sensitivity analysis to four parameters, i.e., space step, friction coefficient, diffusion coefficient, and downstream boundary condition, is carried out. For the water depths in the vicinity of the intersection, uncertainty linked to the calibration of the four aforementioned parameters can be higher than 50% because of the difficulty in representing the location and amplitude of the hydraulic jumps while, for the flow ratio between the downstream branches, uncertainty is limited to 10%.

Separation and feed process of stuck papers under a friction pad type feed system are simulated by FEM software MARC. The system composed of a feed roller, friction pad and tray is widely used in printers and copiers. In the simulation, a modified Coulomb friction model is used, where the friction force is a function of slipping velocity as well as vertical load and coefficient of friction. The results show that the normal feed, double feed and non-feed processes in the paper feed system are successfully simulated. The friction forces acting between papers and system elements are almost the same in magnitude in the initial feed stage, even though the friction coefficients are different. The simple equations, which predict the paper velocities and friction force, are presented.

In order to study the influence of temperature on the frequency domain spectroscopy (FDS) of the oil-paper insulation system, the 72.5kV bushing test model was fabricated according to the actual size, and the FDS of the bushing was tested at different temperatures. According to the test curves of the dielectric constant at different temperatures, the influence of temperature on FDS is analysed, and then the extended Debye equivalent circuit model is used to fit the FDS test curves at different temperatures. The characteristic parameters that could be used to characterize the temperature characteristics are extracted, and the relationship between the characteristic parameters and the temperature is established. The results show that dielectric constant tend to move in the high frequency with the increase of temperature. The parameters of the equivalent circuit model are sensitive to the temperature, the insulation resistance Rg and the maximum time constant branch parameter R1 show the exponential function with the temperature, the minimum time constant branch parameter R3 and the temperature show a power function relationship, so the variation of characteristic parameters can be applied to evaluate the influence of temperature on the FDS of the oil-paper insulation bushing.

A paper feeding system using friction force of rubber rolls is commonly used in the printer and copy machine family, but the accuracy of paper positioning by rubber rolls is poor so rubber rolls have difficulty feeding long lengths of paper without lateral deviation. Here we propose a dynamic skew-roll paper feeding system (SRPFS), in which a steel roll has a small skew angle against a rubber roll thereby controlling the lateral motion of the feed paper. We theoretically analyzed the motion of paper fed by this new system and discussed its characteristics. Analytical results were verified experimentally. As a result, we could clarify the following properties. (1) SRPFS only causes the lateral motion to be proportional to the skew angle between steel roll and rubber roll, and has a negligible effect on longitudinal motion. Moreover SRPFS does not induce rotary motion of the paper. (2) When the distribution of load along the contact nip is asymmetrical and the skew angle is zero, rotary motion of constant velocity is generated without any significant effect on lateral or longitudinal motion.

In a watt balance, stray capacitances exist between the coil and the magnet. Since the electric current flowing in the coil originates a difference between the coil and magnet electric-potentials, their electrostatic interactions must be taken into account. This paper reports the results of a finite element analysis of the forces acting on the coil., 13 pages, 10 figures, submitted to Metrologia

Paper feeding systems with rubber-covered roller drive are widely used in information processing devices such as copy machines, printers and ATM. It is important in their designs to control the paper velocity with precision. Accordingly, the experimental verification is carried out to estimate the effects of the normal load between two rollers, the back tension of a paper sheet and also the change of the frictional coefficient on the velocity ratios of the paper translation to the roller rotation. Next, the behaviors of a rubber-covered roller driving a loaded paper sheet together with a rigid roller are simulated in transition from the micro-slip contact to the rolling contact with non-linear finite element analyses. And furthermore, the variations of the shearing stress distributions and the deformations of the rubber as well as the local slippage in the various kinds of conditions are investigated by enforcing the rotating condition on the rubber-covered roller. As a result, the effects of the normall load, the tension force and the driving configuration on the velocity ratios are studied by using the presented mechanical model, which is based on the deformation mode and the micro-slip zone in the contact nip.

In this paper, a numerical technique is used to study the temperature distribution within the heated bonded paper web placed in a waveguide. The parameters of the problem were selected so as to best locate the test sample that would generate the desired absorbed power. The method of false transient was utilized to accelerate the numerical convergence and the equations were discretized with central difference in both time and space. The resulting system of equations was solved using an Alternating Direction Implicit scheme. Good agreement was achieved between the numerical solutions and the experimental validations.

The assumption that pressures of water and gas in concrete at high temperature are equal one to another and its theoretical consequences are discussed. The results of hygro-thermal simulations performed by Tenchev and Purnell are analysed and compared to the Authors’ results based on the assumption about local thermodynamic equilibrium. � 2006 Elsevier Ltd. All rights reserved.

In this paper, a numerical method is developed to calculate deformations and stresses of the body of dry gas holders under gas pressure. The deformations of the wall plates are decomposed into out-of-plane bending and in-plane deformation. The out-of-plane bending of the wall plates is described by the theory of orthotropic plates and the in-plane deformation by the biharmonic equation of flat plates under plane stress. The theories of beam columns and beams are employed to analyze the columns and corridors, respectively. By considering compatibility conditions between the members and boundary conditions, equations for the determination of deformations and stresses of dry gas holders under gas pressure are obtained. Both the proposed approach and the finite element method are used to investigate the deformations and stresses of the body of a dry gas holder under gas pressure. The results from the proposed method agree with those from the finite element method. Because far fewer unknowns are involved, the proposed method is computationally more efficient than both the finite element method and the series method developed from the theory of stiffened plates.Key words: numerical approach, body of dry gas holders, gas pressure.

A flexible sheet clamped at both ends and submitted to a permanent wind is unstable and propagates waves. Here, we experimentally study the selection of frequency and wavenumber as a function of the wind velocity. These quantities obey simple scaling laws, which are analytically derived from a linear stability analysis of the problem, and which also involve a gravity-induced velocity scale. This approach allows us to collapse data obtained with sheets whose flexible rigidity is varied by two orders of magnitude. This principle may be applied in the future for energy harvesting., Comment: 20 pages, 7 figures

Crack mechanics in single–notched sheets of paper is analysed by an approach that combines the concept of virtual crack trajectory ensemble with self–affine crack mechanics formalism. The crack initiation criterion is determined for three kinds of paper. The probability distributions of crack roughness and strength parameters are established. A probabilistic model of self–affine crack propagation in paper is proposed.

For the pressurized propellant supply system of liquid rocket, feed pressure is determined with respect to the chamber pressure of normal combustion state. However, during ignition period the initial chamber pressure is atmosopheric. This may cause overflow, hard-start and even critical damage for the engine. This paper proposes an improved propellant feed system for the stable combustion of liquid rocket. The proposed system utilizes the cavitating venturi to provide stable mass flow rate. Cavitating venturi offers unique flow control capabilities at normal and abnormal combustion state, because flow rate is soley dependent on the upstream absolute pressure and fluid properties, but independent on th downstream condition. Experimental variables are propellant feed pressure and chamber pressure. The effectiveness of cavitating venturi increased when the ratio of actual feed pressure to the cavitating venturi design pressure is increased. It is also found that Kerosene if more effective to supply stable mass flow rate than LOx.

This study investigates drop impingement on highly wetting porous films and papers. Experiments reveal previously unexplored impingement modes on porous surfaces designated as necking, spreading, and jetting. Dimensional analysis yields a nondimensional parameter, denoted the Washburn-Reynolds number, relating droplet kinetic energy and surface energy. The impingement modes correlate with Washburn-Reynolds number variations spanning four orders of magnitude and a corresponding energy conservation analysis for droplet spreading shows good agreement with the experimental results. The simple scaling laws presented will inform the investigation of dynamic interactions between porous surfaces and liquid drops.

In this paper the equipment to measure the flow fiber suspension. A method of testing submersible vortex flowmeters takes into account both the hydrodynamics in a pipeline running meter and properties of the fiber suspension (concentration, degree of grinding, temperature). The mathematical relationships explaining test equipment. Presents the results of research submersible vortex flowmeter for fiber suspension with different concentrations, the degree of grinding and temperature., В работе исследуется оборудование для измерения расхода волокнистой суспензии. Предложен метод испытания погружных вихревых расходомеров, учитывающий как гидродинамику работающего в трубопроводе расходомера, так и свойства волокнистой суспензии (концентрация, степень помола, температура). Приведены математические соотношения, поясняющие работу испытательного оборудования. Даны результаты исследования работы погружного вихревого расходомера на волокнистой суспензии с различной концентрацией, степенью помола и температурой.

Flow of water in Whatman #17 chromatography paper and the interpretation of the capillary suction time method for determining filterability of suspensions is examined. Filter paper water flow is described by well-established theory of water flow in porous media. This theory is based on material balance for the water and Darcy’s law. Assuming that the matric potential or suction (arising from the interaction of water with the solid surfaces and their geometry) and the hydraulic conductivity of both the filter paper and the suspension are well-defined functions of the water content, one-dimensional capillary suction time is analysed from considerations of material balance and continuity of water potential on the paper/suspension interface. Experiments agree with theory and illustrate that flow in the paper is unsaturated, with the advance of a wetting front in paper a function of the interaction of the sorptivity-matric potential functions of both the paper and the suspension. Extension of the approach to radial flow in the filter paper is too complicated to permit simple interpretation of wetting front advance. The capillary suction time method must remain a useful empirical tool for practicing engineers. Its weaknesses should be recognised, however, and constant pressure filtration tests, for example, which provide both sorptivity-, and equilibrium water content– pressure relations simply and accurately must ultimately be preferable.

Controlled centrifugal instabilities (called Dean vortices) resulting from flow in helical tubes have been used to reduce concentration polarization and membrane fouling during nanofiltration. These vortices enhance back-migration of solute through convective flow away from the membrane–solution interface and allow for increased membrane permeation rates. Based on the theory of Dean vortex flow, a new prototype vortex generating tubular nanofiltration element was designed. Two sets of nanofiltration modules were constructed; a linear module and a new module containing hollow fibers wrapped around rods of small diameter in helical geometry. Optimization of the design is discussed with respect to the diameter and thickness of the hollow fibers. Axial pressure drop and energy consumption measurements for the helical module agreed very well with available correlations for various experimental conditions. Water permeabilities for the helical modules were similar to those of the conventional linear modules. No significant effect of pH was observed on the water permeability.

Dimensional stability, especially paper curl is one of the most important properties of paper. Paper curl caused by heatroller heating in copymachines and laserprinters, influences the runnability and the end quality of paper. Recently, curl specifications have become more stringent as the development of hardware has progressed. In this study, we made a heatroller heating apparatus with variable heating conditions to investigate the relationship between different heating conditions and the resulting curl behavior. The apparatus utilizes a high pressure nip with one high temperature roll and one low temperature roll to induce non-uniform heating of the paper.Results of this paper show that the curl behavior induced by heatroller heating is influenced by different heating conditions, such as heating temperature, heating speed, and nip width. There is a direct relationship between heating time and paper curl, however, this relationship is affected greatly by changes in the pre-heated moisture content of the sheet. All of these factors have a large influence on how much moisture is lost during the heating process. When the reduction of moisture content is small, curl toward heated side occurs. On the other hand, when the reduction of moisture content is large, curl toward unheated side occurs. The roll nip restrains paper shrinkage in direction of roll pivot, thus the direction in which the paper is feed influences the curl axis. This is useful knowledge when designing a grade of paper where curl is an important property.

In this paper, the influence of streaming electrification on the creeping discharge of an oil-paper insulation system has been investigated, using experimental models. Experimental results indicate that the initial creeping discharge voltage of the oil-paper insulation system decreases with oil flow rate. The creeping discharge path develops toward the oil entrance, and there are polarity and position effects on the creeping discharge under oil flowing conditions. Reasons for failure due to dendritic discharge on the surface of barrier boards in power transformers have been revealed in these experiments.

To realize engineered materials and structures via origami methods and other folding construction techniques, fundamental understanding of paper folding mechanics and their dependency on paper micro/nanostructure is needed. Using selected papers commonly used in origami designs, we establish the relationship between the mechanical properties of fibrous paper and their corresponding ability to form and retain simple creases and mountain/valley folds. Using natural fiber paper (abaca), synthetic fiber paper (Tyvek), and a metal-fiber laminate paper, we studied how the fold radius depends on the load applied using a controlled rolling apparatus. After folding, we examined the resultant micro- and nanoscale deformation using electron microscopy. In general we found that the fold radius follows a power law, decreasing with the applied rolling force. At a critical strain, each paper exhibits a transition between elastic and plastic behavior, after which the trend asymptotically approaches the minimum fold radius with increased applied force. Finally, we present examples of centimeter-scale two-dimensionally “mountain fold” patterns and relate the folding characteristics observed in these designs to the mechanical properties of the papers in folding.Copyright © 2013 by ASME

The pressure distributions on a semi-span wing 1/12 scale mode and sic component aerodynamic forces and moments on a complete 1/16 scale advanced trainer model were measured. To reduce wing-tip vortex strength, 3 wing-tip jet slot shaped(forward direction, straigt direction, backward direction) and 3 blowing coefficents (0.004, 0.009, 0.017) were considered. From experiment results, the case of straight direction and blowing coefficent of 0.017 was the best effective in the reduction of drag and in increase of lift-drag ratio and A rate of drag decrease and a rate of lift-drag ratio increase were of most effective on angle of attack 8 degree.

The effects of sideslip on the vortex over a delta wing was investigated experimentallu at a free strean velocity of 40 m/sec, corresponding to a Reynolds number of 1.76, based on the root chord. The angles of attack ranged from to , and the sideslip angles treated were , , and . It was observed that the sideslip decreased the strengths of the vortices of both windward and leeward sides of the wing, and promoted the vortex breakdown on the windward side. At sideslip angle of , the vortex strength of leeward side was increased as the angle of attack increased. This asymmetric development and breakdown of vortices in sideslip condition would cause an abrubt change of the rolling moment at a high angle of of attack, which could be considered as a rolling moment instability