bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlations between relaxation time spectrum and melt spinning behavior of polypropylene. II: Melt spinning simulation from relaxation time spectrum
Authors: Fulchiron R. , Michel A. , Verney V. , Roustant J. C.
Published: December 2004

Using an integral nonlinear constitutive equation including the Log‐Normal relaxation spectrum, the fiber‐spinning behavior of commercial polypropylenes is studied. The relaxation spectrum is strongly related to the molecular weight distribution. Moreover, by means of a finite element analysis, simulated stress and velocity profiles are obtained either in isothermal or nonisothermal cases. In the isothermal case, broadening the relaxation spectrum leads to more pronounced curvature of the velocity profile. In the nonisothermal case, the critical draw ratio is sensitive to the mean relaxation time which depends on both average molecular weight and distribution breadth. It is shown that increasing the average relaxation time leads to a less rapid growth of the velocity. Furthermore, this effect is less pronounced when the relaxation spectrum is wider.
Diffusion of butanediol in poly(butylene terephthalate) (PBT) melt and analysis of pbt polymerization reactor with surface renewal
Authors: Yoon Kwan Han , Park O. Ok
Published: December 2004

A reactor with surface renewal, originally designed for poly(ethylene terephthalate) (PET) polymerization, was applied for poly(butylene terephthalate) (PBT) polymerization. A comprehensive model including side reactions was developed and compared with the experimental results. The diffusivity of butanediol (BD) in PBT melt was measured separately by desorption experiments (Db − 1.08 × 106 exp(−32600 / RT) (m2/min)). Optimum operating temperature for PBT polymerization was found to be around 250°C in order to avoid degradation.
A constitutive theory for polyolefins in large amplitude oscillatory shear
Authors: Giacomin A. J. , Jeyaseelan R. S.
Published: December 2004

A versatile transient network theory has been used as a framework for the interpretation of large amplitude oscillatory behavior of polyolefin melts in terms of their entanglement kinetics. The model reasonably describes all previously published measurements of the large amplitude oscillatory shear behavior on melts. Seven polyolefins are examined, three new materials and four previously studied. A qualitative difference in the nonlinear behavior in large amplitude oscillatory shear has been identified between the polyethylenes examined and the two other polyolefins, polystyrene and polyisobutylene.
Effect of short chain branching on the viscoelastic behavior during fatigue fracture of medium density ethylene copolymers
Authors: Showaib E. A. , Moet A. , Sehanobish K.
Published: December 2004

A method to determine viscoelastic changes in medium density polyethylene (MDPE) pipe specimens associated with the crack tip during fatigue crack initiation (FCI) and propagation (FCP) experiments is described. The load‐displacement curves are analyzed to obtain the phase angle, δ. Changes in δ are related to the number of cycles of crack initiation of three different MDPE copolymers: hexene (H), butene (B), and methyl pentene (MP) copolymers. These changes are related to craze formation and growth at the notch tip, leading to crack initiation and to the irreversible work, Wi, expended on them. Within a given material, step wise increments in δ distinguish the onset of crack initiation and the brittle‐to‐ductile transition in crack growth. The magnitudes of tan δ and Wi are noted to be in quantitative agreement with the resistance of the three copolymers to FCI and brittle propagation that rank in the order: isobutyl (MP) > ethyl (B) > butyl (H). Similar crystallinity of the three copolymers insinuates a hypothesis that variance in the nature of chain entanglements associated with the respective branch type might be accountable for the observed differences in viscoelastic character. The final stage of failure by ductile tearing is dominated by large scale plastic flow that seemingly overshadows the material differences governing time dependent brittle fracture.
Effect of mean strain on the cyclic deformation and stress relaxation in polypropylene
Authors: Ariyama Takashi
Published: December 2004

The influence of mean strain Changes in the range from 0 to 4% on the cyclic deformation and stress‐relaxation properties is investigated using rod specimens of polypropylene. An extensometer measures and controls the axial strain in a closed‐loop, electrohydraulic, servocontrolled mechanical testing machine. The hysteresis loop at different numbers of cycles N of N = 35, 45, and 50 are irregular in shape, and the tensile portion decreases in size as the number of cycles was increased. The stress value of the tensile portion for three mean strains of ϵm = 1.0%, 2.0%, and 4.0% remains constant, but the value of the compressive portion decreases as the mean strain was increased. The stress level at a strain width of 3% changes little with mean strain. For the strain widths of 5% and 7%, however, the minimum stress levels at N = 35, 45, and 50 increase with increasing mean strain, in contrast to the behavior of maximum stress level. The stressrelaxation tests show that the drop of stress decreases with an increase in number of cycles. The discrepancy in the results of relaxation tests is due to the effect of the difference in strain rates.
A method for measuring PVT relationships of thermoplastics using an injection molding machine
Authors: Chiu Cheng‐Ping , Liu Kuo‐Ann , Wei Jong‐Hwei
Published: December 2004

The objective of this study is to establish a feasible method for generating pressure‐specific volume‐temperature (PVT) data for thermoplastics on a microcomputer‐controlled injectionmolding machine (IMM). This method utilizes the injection barreel of the IMM as a pressure chamber for determining the specific volume of thermopla;stics at various pressure and temperature conditoins. An empirical equation of state based on the Tait equation s used to fit the PVT data of three resins — low‐density polythelene (LDPE), polystyrene (PS), and acrylonitrile‐butadiene‐styrene copolymer (ABS). The comparsion between LPDE's PVT data generating from the IMM and from the classical bellows method indicated that the present method can be reasonably applied for determining the specific volume of thermoplastics as a function of presure and temperature.
The effect of drawing temperature on multi‐stage drawn ultra‐high molecular weight polyethylene
Authors: Lee Dah‐Ming , Chen Wei‐Liang , Yeh Ming‐Tao , Chen Tin‐Soy
Published: December 2004

The effect of drawing temperature on multi‐stage drawn ultra‐high molecular weight polyethylene (UHMWE) fiber, produced by gel spinning, has been studied. Drawing at higher temperature generally gives higher crystal orientation, as expected. The activation energy of drawing increased with the draw ratio and raw 4sequence. It varied at a given draw ratio and draw stage between two temperature ranges, 85 to 115°C and 115 to 135°C. Thus, for the first draw stage, the activation energy is ∼ 19—35 KJ/Moe in the range of 85 to 115°C, and ∼ 60—99 KJ/mole in the range of 115 to 135°C. In the second stage, the activation energy is 40 KJ/mole in the range of 105 to 115°C and 70—99 KJ/mole in the range of 115 to 135°C. In the third stage, the activation energy is ∼ 92—100 KJ/mole in the range of 115 to 135°C.
Blends of thermotropic liquid crystalline polyesters and poly(butylene terephthalate): Thermal, mechanical, and morphological properties
Authors: Chang Jin‐Hae , Jo Byung‐Wook , Jin Jung‐Il
Published: December 2004

Blends of poly(butylene terephthalate) (PBT) with three different thermotropic liquid crystalline polyesters (TLCPs) were prepared. The first TLCP (HBH‐6) consists of diad aromaticester type mesogenic units and the hexamethylene spacers along the main chain, and the second (TB‐S6) is a wholly aromatic polyester TLCP having alkoxy side groups on the terephthaloyl moiety. The last (TR‐4,6) is an LC copolymer comsisting of triad aromatic ester type mesogenic units and two differents spacers; tetramethylene and hexamethylene units. Blends of TLCP with PBT were melt spum at different LCP contents and differnt draw ratios to produce monofilaments. For the HBH‐6/PBT and TB‐S6/PBT blends, the ultimate tensile strength showed a maximum value at the 5 wt% level of LCP in the blends, and then it decreased when the LCP content was increased up to 20%. On the other hand, the initial modulus monotonically increased with increasing LCP content in all cases. The blends with TB‐S6 showed the highest tensile properties of the three blends systems. This can be ascribed to the highest rigidity of the polymer chain, which still carries relatively long alkoxy substituents that promote sufficient adhesion between the LCP and PBT matrix. When compared with the PBT fiber itself, the fibers obtained from the 5% TB‐S6/PBT blends exhibited an improvement in tensile strength by > 25% and in tensile modulus by ∼ 200%.
Factors influencing microstructure formation in polyblends containing liquid crystalline polymers
Authors: He Jiasong , Bu Wensheng , Zhang Hongzhi
Published: December 2004

Four isotropic polymers, poly(butylene terephthalate) (PBT), polycarbonate (PC), polyethersulfone (PES) and polysulfone (PSU), were blended by extrusion with a thermotropic liquid crystalline polymer (LCP) at different temperatures. The morphology of extrudates was observed by means of scanning electron microscopy and the intrinsic aspect ratio of LCP fibrils and particles separated from matrix resin was measured with an image analysis. Special attention was paid to the LCP fibrillation in these four matrices in a wide temperature range from 270 to 360°C and the internal relations among the effects of processing parameters, such as viscosity ratio, extrusion temperature, and LCP concentration. The results show that the viscosity ratio of the dispersed LCP phase to the continuous phase is a decisive factor determining the formation of LCP fibrils, but its effect closely relates with the LCP content. In the range of viscosity ratios investigated, 0.004 to 6.9, and lower LCP content of 10%, significant fibrillation took place only at viscosity ratios below 0.01. It is predicted that the upper limit of the viscosity ratio for LCP fibrillation will increase with increasing LCP content. A comparison of the morphologies of LCP/PES blends with different LCP concentrations reveals that the LCP phase becomes continuous at a concentration of less than 50%, and high LCP content does not always favor the formation of long and uniform LCP fibrils. The extrusion temperature has a marked effect on the size of the minor LCP domains. For fibril forming systems, the percentage of LCP fibrils with larger aspect ratios increases with increasing extrusion temperatures. All these results are explained by the combined role of deformation and coalescence of the LCP disperesed phase in the blend.
The leveling of thermosetting waterborne coatings. Part IV: Effects of film thickness
Authors: Kojima Shunji , Moriga Toshinori , Takenouchi Ken
Published: December 2004

The influence of film thickness on the leveling of a thermosetting waterborne coating (WBC) was examined. The theory of Patton has been revised to give the proper force balance and modified to include the changes in surface tension and viscosity during leveling by the evaporation of volatile components. However, the predicted leveling process by a numerical method did not coincide with the observed results. Thus, the driving force in the theory, the hydrostatic pressure gradient in the film, was considered to be insufficient to describe the leveling process of the WBC. The hydrostatic pressure gradient can be a component of the driving force to promote leveling, but the existence of an additional component is suggested.
The germination of fundraising in Central Asia
Authors: Sinavbarov Muallimsho
Published: December 2004

This chapter delineates the appearance and nature of nonprofits in Central Asia and reviews similarities and differences within the region.
Rheological Study of Loosened Bulk Granular Materials
Authors: Gottschalk Jürgen
Published: December 2004

Loosened bulk materials occur, for example, during grinding in a tube mill. Thus, a rheological study of bulk granular materials which are loosened by fluidisation should lead to a better characterization of the flow and conveying properties of the material when ground in the mill.

For this measurement of fluidised bulk materials an agitating device and a rotary viscosimeter have been developed, designed and tested.

First results are presented and discussed showing the fluidisation behaviour and density of the bulk material as a function of grain size as well as the flow properties as a function of the grain size and degree of fluidisation.

Finally, a projection of further research work is given.
An Investigation into Capillary Hydrodynamic Chromatography
Authors: de Jaeger Nikolaas C. , Trappers Jan L. , Lardon Paul
Published: December 2004

Now fifteen years ago, Small and co‐workers [1, 2], introduced Hydrodynamic Chromatography (HDC) as a simple method for the sizing of submicron particles. The particles are fractionated when flowing through a packed column of uniform impermeable beads and emerge in order of decreasing diameter. Noel et al. [4] and Mullins and Orr [3] reported a variant of the technique using a long open capillary tube which has been called Capillary Hydrodynamic Chromatography (CHDC).

Recently Brough et al. [5] were able to expand the size range of CHDC down to particle diameters of 0.07 μm and showed that the technique is also able to achieve fractionation in organic solvents.

In an attempt to obtain the same particle size analysis range with CHDC as with the recently commercialised HDC (Micromeritics), we investigated the CHDC performance in very small capillaries (0.1 and 0.15 mm). The emphasis of the study has been led on the nature and the concentration of the eluent composition. Indeed an effective reduction in capillary diameter can be obtained if one uses a commercial block copolymer as eluent material. Adsorption of the block copolymer both on the capillary wall and the particles gives rise to a sterical barrier which reduces further the effective capillary diameter and enhances the resolution of the column towards smaller particle sizes.

In our view CHDC represents more possibilities in analysing real particle systems, i. e. dispersions with relatively high polymer or polyelectrolyte concentrations. For such systems classical HDC results mostly in the clogging of the column. A series of dispersions and emulsions in concentrated gelatine have been analysed and the P. S. are compared with the results obtained by LCS.
Small Angle Light Scattering Patterns from Micrometer‐Sized Spheroids
Authors: Ravey Jean‐Claude
Published: December 2004

By using a physical optics approximation, the scattering functions, i1 (θ), may be calculated for spheroidal particles of parameter sizes larger than 10. Emphasis is put on the angular location of their first extrema, as function of the refractive index, shape, size and orientation of the spheroid, which may greatly influence the outlook of their small angle 2 D patterns.
The Use of Calibration Techniques for the Development and Application of Optical Particle Sizing Instruments
Authors: Hemsley D. J. , Yeoman M. L. , Bates C. J. , Hadded O.
Published: December 2004

This paper describes seven different methods of calibrating optical particle sizing instruments based on single particle scattering theory. The results presented were obtained from a Laser Doppler Anemometer (LDA) using two concentric probe volumes of different diameters and colours. Measurements of the Doppler signal frequency, amplitude and visibility can yield the absolute particle size and velocity of individual particles providing that the optics and processor are correctly designed and implemented.

The requirements for signal processing without validation bias are discussed together with the use of a Doppler signal generator for testing the processor. Calibration of the system is then described using a scanning pinhole unit, calibration plate and aerosols of bronze spheres. The other techniques described are the use of glass spheres mounted on thin stalks, Berglund‐Lui monodisperse particle generator and latex spheres entrained in a recirculating cell. The discussion indicates the sizing range over which the above techniques are applicable. This covers a total size range from 1 micron to 1 millimetre.
Increased Resolution of Size Distributions with the Coulter Counter
Authors: Harfield John G. , Wharton Robert A.
Published: December 2004

The limiting resolution of Coulter size measurements, the size within which two separate populations can be distinguished, is discussed in relation to the standard aperture.

Electronic pulse editing, by comparing pulse height to width, enables small particles to be resolved from baseline instrument noise, but can give incomplete resolution of ultra‐narrow distributions from artefactually produced peaks using the standard aperture. Improvements in the minimum measurable size and in sizing resolution of narrow size ranges are also shown to be possible by improving the signal quality from the Coulter aperture.

A novel mathematical approach is described for the derivation of true size spectra for narrow particle size distributions by deconvolution of the composite spectra resulting from the effect of the inhomogeneous electric field in the Coulter aperture. Simple empirical equations are used derived from the location and amplitude of the spurious peaks observed in such composites relative to the genuine peaks.

The method is applied to three “industrial” materials (wide size range samples) to determine the likelihood that such size ranges are affected by the spurious or artefactual peaks. A fresh blood sample deconvoluted by this method is shown to be apparently composed of more than one population of cells.
Characterization of Powder and Pressings Based on Geometric Fundamentals
Authors: Frisch Bertram
Published: December 2004

In addition to chemical composition, geometric properties such as particle size, particle shape, specific surface area and microporosity are important for the production of sintered materials. They influence, e.g., the packing density of green bodies, the sinter activity and the microstructure of the final products. Different measuring methods are surveyed, with a critical view of sensitivity and evaluation of measurement data, and new devices are discussed, including laser and centrifuge methods for particle size measurement and sorption methods with krypton as adsorbate for the measurement of specific surface area and microporosity. Finally, a correlation between the particle size and the specific surface area using fractals is discussed.
Single Particle Light Scattering Size Analysis: Quantification and elimination of the effect of particle shape and structure
Authors: Bottlinger Michael , Umhauer Heinz
Published: December 2004

When measuring scattered light from single particles (as realized in various methods of scattered light‐particle size counting analysis) nonspherical particles and particles with inner structure produce different signal heights (scattered light intensities) when differently oriented in the measuring volume. To study the influence of the particle shape and structure, the representative spectrum of all signal heights reflecting all of the possible orientations of the particle in the measuring volume was recorded from individual particles of a definite material in each case. Additionally from every particle an equivalent diameter was determined.

The measurements lead to a very precise calibration curve and to a transformation matrix, that describes the influence of shape and structure on scattered light‐counting analyses in case of the specific material. It is then possible to simulate measurements to determine the loss in resolution caused by the influence of shape and structure and to eliminate this effect from conventional scattered light analyses.

The paper presents the concept together with results of simulation and elimination calculations for the material limestone and quartz. The corrected size distributions are compared with results by other methods. On the basis of this comparison it is discussed how successful the method is to recover a higher resolution.
The Fundamentals of Particle Size Analysis by Means of Ultrasonic Spectrometry
Authors: Riebel Ulrich , Löffler Friedrich
Published: December 2004

The interaction of suspended particles with ultrasonic waves can lead to changes in the sonic velocity and also to extinction of the waves. An evaluation of the frequency dependence of ultrasonic extinction offers the most appropriate means of determining the concentration and size distribution of particles suspended in a fluid. With an experimental apparatus covering the frequency range from 1.7 to 81 MHz, particles ranging from about 20 to 1000 μm in diameter can be analysed. The measurements can be conducted with particle concentrations as high as 10% by volume.
Spectral Properties of the Regularized Inversion of the Laplace Transform
Authors: Ross Douglas A. , Nguyen Thoai H.
Published: December 2004

Inversion of the Laplace integral equation, used in the laser scattering measurement of colloidal particle size distributions, presents sever numerical and experimental difficulties. In the presence of noise the variance of the inversion integral is infinite, indicating maximum uncertainty in the accuracy of the inversion. The regularized inversion of the Laplace intergral equation provides a convenient computational algorithm which requires no a priori knowledge of the unknown linewidth distribution. Using the eigenfunction decomposition of the Laplace kernel, the spectral properties of the regularized inversion may be seen.

Regularized inversion represents a type of low pass filter which preserves the properties of the inversion spectrum at low frequencies, but provides a cutoff at a point controlled by the regularization parameter. This filtering reduces the variance of the inversion to a finite value. Regularized inversion is somewhere between optimal filtering and the abrupt truncation used in singular value decomposition and other similar methods. Two examples, a monodisperse and a bimodal linewidth distribution, are used to compare the performance of regularized inversion to that obtained through an optimal filter.
Alignment Errors in Phase Doppler Receiving Optics
Authors: Sellens Richard W.
Published: December 2004

It is shown that if the pinhole in a phase Doppler system' s collection optics is misaligned, even by a matter of micrometers, the effective collection aperture will be different from the aperture of the collection lens. This directly alters the phase characteristics of the resulting signal and can produce systematic and random errors in drop size measurements. The results of misalignment in a simple system are calculated, experimental evidence of the errors presented, and it is shown that replacing pinholes with vertiacl slits will reduce the sensitivity to such errors.
Application of Laser/Phase Doppler Anemometer to Dispersed Two‐Phase Jet Flow
Authors: Hishida Koichi , Maeda Masanobu
Published: December 2004

A confined jet flow involving glass particles was examined to clarify fundamental aspects of the turbulence structure of two‐phase flow. Spherical glass particles of mean diameter 62.4 m̈m were loaded in a primary jet at a mass loading ratio of 0.3. The primary jet diameter was 13 mm and exit velocities at the centre line were set at 20 and 30 m/s. The confined pipe diameter was 60 mm and velocities were set at 10 and 15 m/s. The particle and gas flow characteristics, such as local mean velocities, their fluctuations and size distribution, are discussed for three flow conditions which were obtained by changing the velocities of primary and secondary flows.

Laser Doppler anemometry was applied to measure the flows of both particles and tracer, discriminated by scattering light intensity, and the precise particle size, for examining the dependence of particle size on the flow, by phase Doppler anemometry. The signal processing of the phase Doppler anemometer was based on a fast Fourier transform method to detect not only Doppler frequency for velocity but also the phase shift of Doppler signals for particle sizing. The processing system consisted of conventional fast analogue to digital converters, multi‐digital signal processor units and a host microcomputer.
Laser Sheet Scattering by Spherical Particles
Authors: Ren Kuan Fang , Gréhan Gérard , Gouesbet Gérard
Published: December 2004

This paper is devoted to the description of the interaction between a spherical particle and a laser sheet beam (Gaussian beam focused by a cylindrical lens) by using the generalized Lorenz‐Mie theory (GLMT). Comparisons between the scattering properties of laser sheet, Gaussian beam and plane wave are carried out.
On‐line Surface Area Measurement of Concentrated Slurries using low field spin‐lattice relaxation NMR
Authors: Thoma Steven B. , Smith Douglas M. , Boughton John , Davies Reg
Published: December 2004

A method for the rapid on‐line determination of surface area and solids content in flowing concentrated slurries using low field NMR spin‐lattice relaxation measurements has been developed and demonstrated. The relationship between flow and spin‐lattice relaxation time (T1) of protons in water at 20 MHz was examined using aqueous copper sulfate solutions. The ability to measure surface area and solids concentration in both stagnant (stopped flow) and flowing systems via NMR was demonstrated using several different concentrated aqueous titania and glass slurries (20 to 80 weight percent) for which the dried powder surface area was previously determined via nitrogen adsorption/BET analysis and the solids content determined gravimetrically. Surface areas were also calculated from particle size analysis and found to vary by up to an order of magnitude from the adsorption and NMR results.
Sizing Large Hollow Micro‐Balloons with the phase doppler interferometer
Authors: Sankar Subramanian V. , Kamemoto Derek Y. , Bachalo William D.
Published: December 2004

A combined theoretical and experimental study has been conducted to evaluate the effectiveness of using large, hollow micro‐balloons as LDV seed particles. The study has focused on the ability of phase Doppler systems to size hollow microballoons, the ability of large micro‐balloons to respond to high frequency spatial and temporal flow field variations, and the overall advantages and disadvantages of using large microballoons instead of conventional LDV seed particles, such as very small water droplets or polystyrene latex (PSL) particles. This paper discusses the development of a theoretical phase Doppler response model for stratified spheres, the experimental facility, and the theoretical and experimental results.
A Study of the Fracture of Pellets Fired Against a Target
Authors: Austin Leonard G. , Trubelja Paula M. , Scarlett Brian
Published: December 2004

Pellets of sintered Al2O3 of approximately 3 mm diameter and length were broken in the Brazilian mode and the distribution of strength obtained. It was found that there was also a distribution of Young's modulus E. Hertzian theory implies that the maximum impact force of a pellet fired against a rigid target would depend on E. However, since the pellets can strike in different geometries there is a distribution of impact force for a fixed E. Comparison of theory with data obtained with a force‐time transducer as the target showed that the major variation of maximum recorded force could be assigned to the variation of E. The median of the maximum recorded force varied with velocity as v6/5, implying that the pellets behaved approximately as impacting spheres. An attempt was made to predict the probability of breakage in one impact from convoluting the distribution of impact force with the strength distribution from the Brazilian test converted to the equivalent strength distribution expected for impacting spheres. This gave the correct order of magnitude but did not accurately predict the experimental values.
Precision of the Grain Size Coefficient (K‐Coefficient) of concrete aggregates — a problem of sampling, sample division and sieve analysis
Authors: Rasemann Winfried , Schmatz Petra
Published: December 2004

Concrete quality is influenced to a high degree by the granulometry of the aggregates used. In the construction industry, the grain size coefficient of K‐coefficient is used as a quantity for the characterization of granulometry. In practice, this quantity is determined experimentally, and it is therefore a random variable influenced by material heterogeneity and errors in sampling, sample preparation and size analysis. Depending on the final use, in concrete production often an aggregate is required, the grain size coefficient of which can be adjusted to a given value Krequ with a prescribed precision. For this reason, continuous supervision of the aggregate quality is necessary using, e. g., automatic sampling and opto‐electronic measuring equipment. In order to determine the optimum conditions for the installation of such equipment, the variances of the possible errors must be established. Further, methods for their restriction are necessary. In this paper, investigations involving hand sampling and hand sieving and on the example of a reference gravel plant are reported. The investigations reveal that, for the materials involved, primary samples of at least 1600 g were necessary, which then could be reduced to 200 g by sample splitting, in order to obtain the accuracy desired.
Innovative Phase Doppler Systems and their Applications
Authors: Naqwi Amir A.
Published: December 2004

Theoretical and practical limits on the applicability of PDA are established, using generalized theoretical formulations of various physical processes governing the operation of a phase Doppler system. Furthermore, several innovative solutions are introduced to prevent the commonly occuring problems of PDA, such as Gaussian profile effect, non‐monotonic response and 2π‐ambiguity. Generalized formulations have also enabled new applications, such as sizing of submicron particles, particle material recognition, measurements with non‐standard geometries. Selected results of measurements in particulate flows, using innovative PDA systems, are also presented.
Reconstruction of Real Size Distributions Hidden in Phase‐Doppler Anemometry results obtained form droplets of inhomogeneous liquids
Authors: Manasse Uwe , Wriedt Thomas , Bauckhage Klaus
Published: December 2004

Real process fluids such as emulsions and suspensions are optically absordent as well as inhomogeneous. Using phase‐Doppler anemometry (PDA)for investigating the spray cone, the inhomogeneites have led to incomprehensible size distributions. In this paper, solutions of instant coffee and condensed milk, representing typical process fluids, were chosen for PDA measurements in comparison with PDA applied to water droplets with the same atomization process in order to clarify the reasons for the measured broad size distributions. By applying PDA to monodisperse droplets and to “monodisperse” and real polydisperse sprays consisting of such fluids, it is shown how the measured size distributions arise, Based on this knowledge, the real size distributions are reconstructed and compared with that of water atomization. Therefore, PDA can in future also be applied to real process fluids, and process control, based on the information provided by PDA, is coming nearer.
The Use of Azimuthal Intensity Variations in Diffraction Patterns for Particle Shape Characterization
Authors: Heffels Cameil M. G. , Heitzmann Daniel , Dan Hirleman E. , Scarlett Brian
Published: December 2004

Forward light scattering is a well established technique for measuring particle size distributions. The light intensity fluctuations which can be observed in the diffraction plane of the instrument can be used to stabilize the inversion process [1]. Particle shape information is also present in these fluctuations. It is shown that an azimuthal‐type of detector can be used to extract this information from the statistical correlations of the detector signals.
Development of a Mathematical Model for Light Scattering by statistically irregular particles
Authors: Al‐Chalabi Souad A. M. , Jones Alan R.
Published: December 2004

A mathematical model is described to predict Fraunhofer diffraction by statistically irregular particles. It is demonstrated that the particles are characterised by a probability distribution of radius and a correlation function in the surface. The results of calculation show that at angles not too far from the forward scattering direction and for irregularity heights within a limited range, the irregular particles may be represented approximately by spheres with a size distribution equal to the probability distribution of radius. However, the calculations are highly sensitive to the exact nature of the probability functions. Comparisons of the results with those of a simpler model are not satisfactory beyond the first forward scattering lobe.
Imaging of Drop and Vapour Clouds in an Evaporating Fuel Spray by ultraviolet and visible lasers
Authors: Suzuki Mamoru , Nishida Keiya , Hiroyasu Hiroyuki
Published: December 2004

A laser‐based method was developed for the simultaneous and quantitative imaging of drop and vapour clouds in an evaporating fuel spray. The method was based on extinction of two wavelengths, that is, ultraviolet and visible laser light through the fuel spray due to absorption by the vapour and scattering by the drops. α‐Methylnaphthalene was selected as an injection fuel, since it absorbs the ultraviolet laser light but does not absorb the visible laser light. Subtraction of the transmissivity of the visible laser light from that of the ultraviolet laser light made it possible to image the distribution of the vapour cloud in the evaporating fuel spray. The distribution of the drop cloud is imaged by the transmissivity of the visible laser light. The method was applied to the fuel spray injected from a nozzle of a direct injection diesel engine into high‐pressure and high‐temperature nitrogen gas in a bomb.
Size of the Detection Area of a Phase‐Doppler Anemometer for reflecting and refracting particles
Authors: Schöne Frank , Bauckhage Klaus , Wriedt Thomas
Published: December 2004

Measurements of particle size distributions in multi‐phase flows with a phase‐Doppler anemometer yield incorrect results if polydisperse particles are investigated. For weighting biased size distributions, different in situ methods, requiring the size of the detection area, are known, but all of these weighting procedures are restricted to very small measuring volumes if off‐axis instrument configurations are considered. Moreover, the weighting functions have some disadvantages in the case of poor statistics in single size classes or the results are not suitable for determining the size of the detection area for particles which are larger than the beam waist.

Therefore, the intention in this work was to measure the size of the detection area for different kinds of monodisperse particles, different instrument configurations and varied instrument sensitivities experimentally and to develop an improved weighting procedure that copes with the above difficulties. The application of the results obtained from the investigations with monodisperse particles to measured particle size distributions and volume flux densities of polydisperse water droplets in a spray cone of an atomizer confirms the applicability of this weighting procedure. It is still restricted to directed flows, perpendicular to the fringes.
A More General Treatment of Abrasion‐Chipping Processes applicable to FAG/SAG Milling
Authors: Austin Leonard G. , Tangsripongkul Sukanya
Published: December 2004

Equations are derived for the rate of loss of mass from a screen interval when the size reduction process is an abrasion‐chipping process which follows a wear law of the Bond form or the Davis form, giving cores and fragments. The treatment is extended to steady‐state continuous grinding in a fully‐mixed reactor, and to the case where first‐order disintegrative fracture processes also occur.
Multiple Wavelength Extinction Technique for Particle Characterization in Dense Particle Clouds
Authors: Dittmann Rolf , Feld Heinz‐Jürgen , Samenfink Wolfgang , Wittig Sigmar
Published: December 2004

In utilizing the advantages of extinction measurements in micron and especially submicron particle characterization, the properties of a multiple wavelength extinction technique have been the subject of extended theoretical studies. Furthermore, an experimental set‐up was designed which provides high flexibility owing to its modular design. The performance of the technique described is demonstrated by a large variety of applications in aerosol and combustion research and in large‐scale industrial systems. It was found to be a reliable tool in characterizing dense particulate systems.
A method for investigating the orientational behaviour of fibrous particles in gaseous flow
Authors: Hirst Edwin , Kaye Paul H. , Buckley Keith M. , Saunders Spencer J.
Published: December 2004

A method is described by which the angular orientation distribution of fibrous particles carried in a gaseous stream may be investigated. The method is based upon the interpretation of the spatial intensity distribution or scattering profile of laser light scattered by individual fibres. The scattering instrument used to capture the profiles is described, and the mathematical computation required to ascertain the orientation of each particle at the measurement point is detailed. Illustrative results are given for a study of airborne micromachined silicon particles of 12 μm length and 1.0 μm by 1.5 μm cross‐section. The method is currently being employed by the authors to investigate ways of improving the orientation control over nonspherical particles in systems such as aerodynamic particle sizers and particle shape classifiers, since lack of particle orientation control is known to adversely affect the measurement accuracy of both these types of instrument.
Particle Shape Investigations with a light‐scattering optical instrument
Authors: Neeße Thomas , Dück Johann , Thaufelder Thomas
Published: December 2004

A light‐scattering instrument that is normally used for particle size analysis was applied to obtain information about particle shape. Micro‐cuboids of dimensions a × b × c in the range between 10 and 1000 μm, which can be accurately manufactured employing special technology, were used as labelled samples for the determination of 3‐D features. Particle projections at different orientations due to turbulent motion were measured sequentially. The laser diffraction of cuboids rotating in a turbulent flow is described theoretically using a simplified model, i.e. rotation of a rectangle. The change in the projection areas of rotating cuboids is connected with their rotational velocity. The power spectrum density of rotational velocity of cuboids and spheres was determined and the influence of particle shape on the power spectrum density established. The frequency distribution of projection sizes was found to be suitable for particle shape estimation.
On‐line Determination of Particle Size Distribution during the manufacture of compound feed
Authors: Heidenreich Eberhard , Sundermeier Thomas
Published: December 2004

Experimental investigations were carried out with mainly a Mogensen‐Sizer, compared with test screening and additionally laser diffraction and light extinction, in order to check the qualification for on‐line determination of particle size distribution under the specific conditions of feed milling. The different components of compound feed, the degree of milling, the difference in measured particle characteristics and the possibility of sample dispersion affect the comparability of the results. The results show that laser diffraction is a manysided method with accurate recording of the distribution. The modified Mogensen‐Sizer can be a robust low‐price alternative if the control of selected distribution parameters is sufficient.
Barium Sulfate Precipitation: Crystallization kinetics and the role of the additive PMA‐PVS
Authors: van Drunen Michiel A. , Merkus Henk G. , Scarlett Brian , van Rosmalen Gerda M.
Published: December 2004

The precipitation of barium sulfate was investigated by photon correlation spectroscopic (PCS) measurements of the growing crystals combined with electrical conductivity measurements of the mother solution. Small silica seeds (36nm) were added to the solution. Therefore, heterogeneous nucleation did not take place on the walls and on the stirrer, which is usually the case, but on the seeds. Hence the growth of the crystals which had nucleated on the seeds could be studied by PCS. In order to avoid the ill‐conditioned inversion of the measured raw data, the autocorrelation functions, a population balance model was used to calculate these functions with the help of a kinetic model taken from the literature. The measured an the calculated autocorrelation functions could coincide and adjustable parameters were found from a least‐squares fit. The measurements revealed that nucleation is strongly enhanced by PMA‐PVS (polymaleic acid–polyvinylsulfonic acid). However, a simple model which assumes langmuir adsorption of PMA‐PVS on the crystal surface did not describe the kinetics very well. The nucleation rate in the absence of the additive was found to be J=1.3·1010 exp(−27/In2S) [m−3s−1], while the growth rate was G=2.6·10−8(S−1)2/3 S1/3 exp(−29/3 In S) [ms−1]. These results match results taken from the literature fairly well.
Sizing of Irregular Particles Using a Phase Doppler System
Authors: Naqwi Amir A.
Published: December 2004

Response of a phase Doppler system to irregularly shaped particles is examined and shown to deviate qualitatively as well as quantitatively from the spherical particles. Nevertheless, the measured phase distributions based on an ensemble of particles exhibit a high degree of order and simplicity. The experimental data and the stochastic modeling of the process have shown that the phase Doppler technique can be used successfully for in‐situ sizing and velocimetry of irregular particles. In the case of irregular crystalline particles, mean size and standard deviation can be deduced without requiring any assumptions regarding the functional form of the size distribution. As opposed to other optical techniques, phase Doppler can be used, in principle, near the backscattering location, so that a single optical window would be employed for transmission of laser light and collection of the scattered signals. Furthermore, size measurements can be velocity‐resolved, i.e. a size distribution can be associated with each bin of the velocity histogram.
Modeling of a Rotary Drum Granulator for Control
Authors: Reddy Bathala C. , Murthy Dodlaty V. S. , Rao Chamarti D. P.
Published: December 2004

A phenomenological model with 12 parameters for rotary drum granulation with the help of material balance equations taking into account the growth and death functions was developed. Experiments were conducted and the data were used to obtain model parameters with reference to the operating conditions and for validation of the model. It was concluded that the proposed model is adequate for the representation of dynamics and hence this model can be recommended for dynamic simulation leading to improved control of granulation circuits.
Detonation Velocity of PETN in Small confined cylindrical charges
Authors: Dinegar R. H.
Published: December 2004

Steady state detonation velocities have been measured in small brass‐confined pressings of PETN. These velocities were found to vary linearly with the reciprocal of the charge diameter and directly with the compact density. For a pressing density of 950 kg/m3 the velocity at infinite diameter was calculated to be 5.27 km/s (50.02 kmk) and the Eyring‐type „reaction‐zone length”︁ 0.54 mm (±0.02 mm).
Detonability of Slurry Blasting Agents
Authors: Michot C. , Bigourd J.
Published: December 2004

The detonability of slurry blasting agents is characterized by their critical detonation diameter and their cap sensitivity. A quick method using conical charges permits the critical detonation diameter to be measured.

The influence of density on the detonability was examined. Density of the slurry was varied by gassing before shotfiring or by compressing the slurry on firing. The results are different according as the slurry contains an explosive or non‐explosive sensitizer.
Growth of 1,3,5‐Triamino‐2,4,6‐trinitrobenzene (TATB) I. Anisotropic thermal expansion
Authors: Kolb John R. , Rizzo H. F.
Published: December 2004

Expansion of TATB is studied on a molecular level by means of x‐ray crystallography. Continuous monitoring of the cell constants of TATB between 214 K and 377 K allows calculation of a volume change of +5.1% for this molecular system. Expansion of the pure material is almost exclusively a function of a 4% linear increase in the c axis (the perpendicular distance between sheets of hydrogen‐bonded TATB). Calculated from these data, the volume coefficient of thermal expansion for crystalline TATB is 30.4 × 10−5 K−1. The structural features of crystalline TATB and its anisotropic thermal‐expansion behaviour are compared with those of graphite and boron nitride. Two other crystalline products in the bulk TATB are either actual polymorphs of TATB or impurities.
Réflexions sur la sensibilité des explosifs polynitrés aromatiques
Authors: Brassy C. , Roux M. , Auzanneau M.
Published: December 2004

Des publications récentes sur la sensibilité à l'impact et la sensibilité thermique des explosifs polynitrés aromatiques sont commentées.

En sensibilité à I'impact, Kamlet et Adolph ont remarqué l'existence de deux familles d'explosifs pour lesquelles h 50% est une fonction linéaire du bilan en oxygène OB100. Ces deux corrélations peuvent se ramener à une seule si dans le calcul du bilan en oxygéne on ne tient pas compte des CH en a des groups NO2. Pour les groupements attachés au cycle benzénique , on peut calculer des incréments de sensibilité.

En sensibilité thermique, les résultats de Zeman et ceux d'Hutchinson, Krishna Mohan et Millar peuvent être interprétés. L'knergie EA d'activation de décomposition thermique est une fonction linéare de log A, logarithme du facteur préexponentiel. En conséquence, ΔH* I'enthalpie d'activation est proportionelle à log A, ΔH* est proportionelle à ΔS* l'entropie d'activation, ΔH* est proportionelle, pour les tétryls, à ΔG l'enthalpie libre d'activation calculke pour la moyenne harmonique des températures.

Il serait intéressant de donner une signification physique au bilan en oxygène défini par Kamlet et Adolph, à relation enthalphie‐entro‐ pie et à la relation enthalpie‐enthalpie libre.
On the use of Redundant Pyrotechnic Delays
Authors: Yaniv A.
Published: December 2004

The performance of redundant pyrotechnic delays is analyzed. It is found that the average delay time of a redundant cluster of delays is shorter than the corresponding average of the individual delays. Also, the standard deviation of the cluster delay time is smaller than the corresponding individual delay standard deviation. These two effects are found to be monotonic functions of the number of delays in the cluster. The effect of the delay reliability on the cluster statistics is shown to be qualitatively similar to a reduction in the effective cluster size.