Plastic Spheres Research Articles

電子写真システム設計のための粉体シミュレーション

Powder simulation which supports the design of electro photographic system is described. The simulation of the charging behavior of toner particles is performed by using the charge transfer equation obtained by impact experiments between plastic spheres and plastic or metal plate. This simulation method, which gives the relation between the charging properties and the chemical components of toner particles, can be applied to the design of toner particles with the optimum charging behavior.The development and flow behavior of a two-component developer are simulated by large scale discrete element method taking into account the magnetic and electrostatic interactions between developing particles. The proposed simulation gives very useful information for the design of a two-component development system. New simulation methods of melting behavior of toner particles in fixing process and blade cleaning behavior are proposed.

Microscopic Approaches to Decomposition and Burning Processes of a Micro Plastic Resin Particle under Abrupt Heating

To elucidate the possibility and availability of thermal recycling of waste plastic resin from a basic and microscopic viewpoint, a series of abrupt heating processes of a spherical micro plastic particle having a diameter of about 200 μm is observed, when it is abruptly exposed to hot oxidizing combustion gas. Three ingenious devices are introduced and two typical plastic resins of polyethylene terephthalate and polyethylene are used. In this paper the dependency of internal and external appearances of residual plastic embers on the heating time and the ingredients of plastic resins is optically analyzed, along with appearances of internal micro bubbling, multiple micro explosions and jets, and micro diffusion flames during abrupt heating. Based on temporal variations of the surface area of a micro plastic particle, the apparent burning rate constant is also evaluated and compared with those of well-known volatile liquid fuels.

Hydrodynamics studies of direct-drive cone-in-shell, fast-ignitor targets on OMEGA

Experiments have been performed on the OMEGA Laser Facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] to study the hydrodynamics of directly driven cone-in-shell, fast-ignitor targets. A 35° or 70° opening-angle gold cone was inserted into spherical plastic shells of ∼24-μm thickness and ∼870-μm diameter, which were imploded with up to 21kJ of 351-nm laser light. A backlighter was used on some experiments to compare the fuel assembly of targets with or without a high-pressure fill gas. The shock breakthrough to the inside of the cone, where the ultrafast laser propagates in integrated fast-ignitor experiments, was studied using a streaked optical pyrometer. No plasma was seen inside the cone before the assembled core reached peak compression.

Effect of liquid distribution on the organic removal in a trickle bed filter

Abstract The effect of liquid distribution on the biological removal of propylene glycol methyl ether (PGME) in a trickle bed filter was investigated using a 0.3 m diameter column filled with 2-cm plastic spheres. Various liquid flowrates, bed heights (the ratio of bed height to bed diameter H / D = 2.3 and 4.6) and initial concentrations of PGME were used in experiments. The effect of initial liquid distribution was also examined using the multipoint (MPD) and single-point liquid distributors (SPD). The effect of liquid flow rate on liquid distribution, and hence, the BOD 5 removal was found more significant for the short bed ( H / D = 2.3). The BOD 5 removal using MPD increased about 29% when the liquid flow rate was increased from 0.184 to 0.918 kg m −2 s −1 . On the other hand, for H / D = 4.6 with both MPD and SPD, the effect of liquid flowrate on the BOD 5 removal was insignificant although the dynamic liquid hold-up increased about two fold. It was also found that local distribution of the BOD 5 removal corresponded well with local liquid distribution in the bed. In addition, a 37% decrease in the percentage BOD 5 removal was observed while the BOD 5 removal amount increased from 62 to 211 mg L −1 with increases in the initial concentration from 100 to 500 ppm. Based on the Monod kinetic model, the maximum BOD 5 removal rate in the trickle bed filter was found to be 11.7 mg L −1 h −1 and the Monod constant was 759 mg L −1 .

Radioactive spheres without inactive wall for lesion simulation in PET

With the growing importance of PET and PET/CT in diagnosis, staging, therapy monitoring and radiotherapy planning, appropriate tools to simulate lesions in phantoms are important. Normally hollow spheres, made of plastic or glass, which can be filled with radioactive solutions, are used. As these spheres have an inactive wall they do not reflect the real situation in the patient and lead to quantification errors in the presence of background activity. We propose spheres made of radioactive wax, which are easy to produce, give a high flexibility to the user and a more accurate quantification. These wax spheres were evaluated for their applicability in PET phantoms and it was found that the activity is not diffusing into the surrounding water in relevant quantities, that they show a sufficient homogeneity, and that their attenuation properties are equivalent to water for photons of PET energies. Recovery coefficients for the wax spheres were measured and compared with those obtained for fillable plastic spheres for diameters of 28, 16, 10, and 6 mm in the presence of background activity. Recovery coefficients of the wax spheres were found to be up to 21% higher than for the fillable spheres.

SU‐DD‐A4‐03: A Validation Study of Concurrent Multimodality Segmentation

Purpose: The acquisition of multiple images of varied yet complementary information is rapidly becoming the norm in radiotherapy treatment planning. Beside CT data sets, PET and/or MRI or MRS images are also being used to aid in the definition of the target volume (or normal structures) for treatment optimization. We have been developing new methods to integrate available imaging information (anatomical and/or physiological) for concurrent target registration and segmentation. Towards this goal, we have investigated several clustering and active contour methods for simultaneous 2D/3D segmentation/registration of multi‐modality images consisting of combinations of PET, CT, or MRI datasets. In this work, we present a phantom validation study of this approach. Method and Materials: A commercial anthropomorphic head phantom of average human size was used. Targets consisting of plastic spheres and rods were placed throughout the cranium section of the phantom. Tap water was used for CT imaging. For MRI and PET imaging, the water inside the phantom was doped with CuNO3 and 18F‐FDG, respectively. The cold spots spheres were considered as the segmentation targets (four spheres each is 25.4 mm in diameter). The rods were used as landmarks to assist in alignment. A geometric deformable model known as the multi‐valued level set (MVLS) method was applied as our computational vehicle. Results: The MVLS algorithm achieved 90% segmentation accuracy and less than 2% volume error when integrating all of the three modalities. This is contrasted with 74% segmentation accuracy and 4.4% volume error when using CT‐based systems only. Conclusion: We have validated a semi‐automatic method for integrating information from different imaging modalities. Our phantom study demonstrates the feasibility of the proposed image integration approach. This approach could potentially provide radiologists/oncologists with reliable and efficient tools to analyze simultaneously different modality data in different cancer sites.This work was supported by ACS‐IRG‐58‐010‐50 grant.

A spinning-tube device for dynamic friction coefficient measurement of granular fertiliser particles

This paper describes the development of a device capable of measuring the dynamic friction coefficient of particles accelerated in a tube spinning in a horizontal plane. The dynamic friction coefficient is not the classical Coulomb friction coefficient, but a lumped parameter influenced by the Coulomb friction coefficient between particle and tube, aerodynamic effects, bouncing effects, as well as particle size, shape and texture. The principle consists of measuring the time interval associated with particles travelling through a known distance along a tube section. This time interval served as an input for a model that infers the dynamic friction coefficient. The results for plastic spheres showed that (1) the mean dynamic friction coefficient was higher than expected (0.25), and (2) there was significant variability in the data (standard deviation (SD) 0.03) even though the particles were inserted using a precise and reproducible method. The variability in dynamic friction coefficient was inversely proportional to the rotational velocity of the tube. This led to the conjecture that owing to the higher Coriolis forces, the particles more closely follow a straight trajectory along the inner sidewall of the tube. Owing to the lower variability, the dynamic friction coefficient measured at the highest rotational velocity (800 min −1 ) was assumed most reliable. The mean dynamic friction coefficient of irregularly shaped potassium chloride fertiliser was measured as 0.44, SD 0.05, and for the quasi-spherical ammonium nitrate fertiliser a mean value of 0.31, with an SD of 0.03 was obtained.

Determining the collision properties of semi-crystalline and amorphous thermoplastics for DEM simulations of solids transport in an extruder

To improve application of the distinct element method (DEM) to polymer processing applications it was necessary to evaluate the contact mechanics of a selection of commonly used polymers. The contact behaviors of high-density polyethylene (HDPE), polystyrene (PS) and polycarbonate (PC) were revealed in this paper from a series of impact studies where spherical polymeric particles struck a steel anvil at various angles of incidence and impact velocity. The coefficients of restitution and friction were calculated from high-speed video analysis of individual impacts. The collected data was used to evaluate the relevance of several popular normal contact force–displacement models to determine their suitability for the tested semi-crystalline and glassy polymers. The models considered were those proposed by Walton and Braun [1986. Viscosity, granular-temperature, and stress calculations for shearing assemblies of inelastic, frictional disks. Journal of Rheology 30, 949–980], with constant (WBCE) and variable (WBVE) normal restitution coefficient, and Thornton [1997. Coefficient of restitution for collinear collisions of elastic-perfectly plastic spheres. Journal of Applied Mechanics 64, 383–386], based on elastic–plastic collisions. Comparison of the impact data with DEM simulations using the various contact force–displacement models revealed that the WBVE model provides the best overall agreement with the viscoelastic-fully plastic behavior of HDPE, while the almost purely elastic nature of PC and PS agreed well with all three models studied in this paper. The influence of the normal force–displacement models on the solids transport zone of an extruder was subsequently discussed based on the findings from the impact study.

A microsphere-surface impact model for implementation in computational fluid dynamics

Two microsphere-surface impact models have been developed for implementation with computational fluid dynamic software. The models consider either normal or oblique incidence of a microsphere with the surface. The first model includes the effects of microsphere-surface roughness, and Hertzian and adhesion damping during surface contact. The second model considers the impact of elastic–plastic sphere and a surface, with and without interface adhesion. Analytical solutions for the coefficients of restitution are presented in terms of the impact velocity and material properties. These algebraic models were validated by comparison with the experimental results of several investigators. A user-defined function representing the model was developed to interface with the commercial software package FLUENT ® . The combined modelling package's predictions were compared with high-speed digital images of microparticle contact with the surface located on the floor of a wind tunnel.

Cleaning of Dust between Interactive Contact Surfaces by Application of Normal Loads of Artificial Stainless-Cantilever in AFM

In this study, we investigated that interactive contact surfaces were affected by dust and applied normal loads of cantilever such as bristles. In order to study the effect of interactive contact surfaces, spherical particles (dry borosilicate glass sphere, plastic sphere) with curvature radius (R=5 μm, R=10 μm) were glued to artificial stainless cantilevers (spring constant k=576.7 N/m). The experiments were performed on various normal applied loads using an AFM (Atomic force microscope). The results indicate that spheres with a small curvature radius removed dust more effectively than did either of those with a large curvature radius, abraded by using the stainless cantilever, over the wide contact area (50 μmx50 μm). The plastic spheres tend to deform more than do the borosilicate glass spheres under the same applied load and the spheres with a smaller curvature radius tend to deform than do those with a larger curvature radius and the same material properties. Therefore, it had an influence on interactive surface forces. Restructuring dust aggregates by sliding a cantilever, as well as applying loads and contact pressure, forms a new micro contact area, which influences micro surface forces.

A unified framework for scene illuminant estimation

Most existing illuminant estimation algorithms work with assumptions of specific source types (e.g. directional light source or point light source). The assumptions bring up two main limitations which significantly restrict their applicabilities: first, the prior knowledge about source types is needed; second, it can not handle complex scenes where multiple source types co-exist. In this paper, we develop a general light source model which is designed to model arbitrary light sources. With the general source model, we are able to estimate multiple illuminants of different types within a single unified framework. We use a plastic sphere to probe both diffuse and specular reflections of a scene. With specular reflections, we estimate geometric parameters of the illuminants by a novel ray tracing and matching algorithm. The diffuse reflections are used to estimate photometric parameters of the illuminants. We also notice that common source types are degenerate cases of the general source model under certain conditions. Therefore, we can approximate light sources with common source types by checking the conditions. The approximations serve as type determinations of light sources, which makes our framework extremely useful for lighting related algorithms which need prior knowledge about light sources. Experiment results on a variety of real images demonstrate the efficiency and accuracy of our algorithm.

An evaluation of expansion equations for fluidized solid–liquid systems

Numerous equations can be found in the literature for the prediction of bed expansion during liquid–solid fluidization. There is no general agreement regarding which equation is the most accurate. In this work, fluidization experiments have been carried out with plastic and glass spheres of 11 different sizes, varying from 1.11 mm to 6.01 mm. Water was used as the fluidizing medium in all the experiments. Widely used correlations are compared and evaluated using the data collected in this work and certain long-standing data from the literature. A new equation with a simple and meaningful form is developed for the prediction of bed expansion in liquid fluidized beds of spheres. The proposed correlation is based on an extension of the fixed-bed friction factor concept to fluidized beds. The new equation has a number of advantages such as a wider operating range, improved accuracy, simple and continuous form, and a fundamental basis.

Light-emitting diode illumination design with a condensing sphere

An illumination system is described that comprises a glass or plastic sphere, an embedded light-emitting diode (LED) source, and a reflecting or scattering mirror. The rays from the LED are either refracted in the forward direction or totally internally reflected by the sphere. The mirror breaks the total internal reflection and thus sends the rays in the forward direction. The illumination pattern and efficiency of the system are analyzed. This system is extremely compact and efficient and is a good starting point for a complex illumination system design.

A general elastic–plastic approach to impact analisys for stress state limit evaluation in ball screw bearings return system

A methodology for stress state limit recovering in ball screws return system is presented in this paper. A lot of different researches and standards have been already performed for rolling bearings load static and dynamic rating (ISO 76, ISO 281), but nothing has been said for ball screws except in some drafting standards (Draft standard DIN 69051-4). Also the overall stress limits introduced for rolling bearings in ISO standards are not valid for ball screws bearing because of their different contact geometry. Moreover, the plastic contact due to impact between the spheres and the ball return system, very important for ball screw bearing life determination, has been investigated in very recent works only for nominal impacts by Hung et al. [Impact failure analysis of re-circulating mechanism in ball screw. Eng Failure Anal 2004;11:561–73]. A general model for the elastic–plastic contact between two curved bodies, derived from the models introduced by Thornton [Coefficient of restitution for collinear collisions of elastic perfectly plastic spheres. ASME J Appl Mech 1997;64:383], and Thornton and Zemin Ning [A theoretical model for the stick/bounce behaviour of adhesive, elastic–plastic spheres. Powder Technol 1998;99:154–62], is introduced in this paper to describe the elastic–plastic impact behaviour of two general curved bodies. By using this approach the influence on the stress state due to geometric properties, materials and impact velocities is established using an experimental plastic deformation limit. So one can finally estimate an equivalent elastic Hertz stress limit (EHSL) useful for ball screw bearing design through the typical elastic Hertz formulas. Finally the optimal correlation between the EHSL and the experimental results for “conventional” ball bearings is recovered, moreover the EHSL for a lot of different ball screw return systems are evaluated.

EUV and particle generations from laser-irradiated solid- and low-density targets

Properties of extreme ultraviolet (EUV) and particle emissions from laser-produced tin (Sn) plasma were experimentally investigated for use in industrial applications. Dependence of EUV emission on the initial thickness of Sn overcoat on a plastic sphere was studied to clarify the minimum mass needed to keep sufficient conversion to EUV and minimize plasma debris. EUV emission from low-density targets showed narrower spectra peaked at 13.5nm, attributed to reduction of satellite line emissions in the spectrum foot and opacity broadening at the peak. It is shown that not only the EUV generation but also ion spectra are significantly affected by the Sn coat thicknesses.

Braid theory and Zipf-Mandelbrot relation used in microparticle dynamics

A study is presented of the dynamics of a few body system of microparticles by using rank-ordering statistics in order to gain insight in the magneto-rheological properties of ferrofluids. This dynamical system is made up of micrometer sized plastic spheres dispersed in a ferrofluid driven by external magnetic fields. The world lines of the microspheres are captured and the dynamical modes are described by mathematical braid theory. Rank-ordering statistics on these modes shows a wide power law region consistent with the Zipf-Mandelbrot relation. We have also performed numerical simulations of the experimental system which show results in agreement with the observations.

Jules Rimet's bananas

For a whole month from June 9 of this year civilised activity and conversation will be silenced by the quadrennial competition for association football's World Cup, the Jules Rimet trophy, in which 32 national teams will try to slot an air-filled plastic sphere through a rectangle measuring 2·4 by 7·2 m. This is not as easy as it sounds. For example, on Saturday, March 18, one-third of the sides competing in the top nine English and Scottish football leagues did not succeed once during 90 min of endeavour. Even with no goals and despite many unattractive features, on and off the field, this is still called “the beautiful game”. The wall set up against a direct free kick is anything but elegant, with its serried row of defenders blocking the straight path to goal and nervously protecting other sensitive sites with hands (when male) crossed below the waistband. There is a counter to this ploy, the banana kick, and recent research with real players and a virtual arena suggests that bent trajectories are very difficult to read. 1 Craig CM Berton E Rao G Fernandez L Bootsma RJ Judging where a ball will go: the case of the curved free kicks in football. Naturwissenschaften. 2006; 93: 97-101 Crossref PubMed Scopus (69) Google Scholar No doubt the better performers have always been able to make footballs, both moving and static, play tricks but the all-deceiving swerve became headline news in 1997 when a Brazilian called Roberto Carlos appeared to kick a ball so wide that a distant ballboy ducked—yet it landed in the net behind several stunned Frenchmen. The England captain, David Beckham, is another exponent. 2 Chadha G Bend it like Beckham [film]. Fox Searchlight Pictures, Los Angeles2002 Google Scholar

Multiple loading–unloading of an elastic–plastic spherical contact

A model for multiple repeated loading and unloading of an elastic–plastic sphere and a rigid flat is presented to cover a wide range of loading conditions far beyond the elastic limit. The sphere material is modeled as elastic linear isotropic hardening and follows the von Mises yield criterion. It is shown that although most of the plastic deformation occurs during the first loading, secondary plastic flow may evolve during the first unloading. The occurrence of this secondary plastic flow depends on the level of first loading and is strongly affected by the Poisson’s ratio and material hardening. The region of secondary plastic flow may propagate during the very first loading–unloading cycles, reaching a steady state after which the following loading–unloading cycles become fully elastic.

Deviation of skin marker from bone target during movement of the scapula

BackgroundRecording movement of the scapula by noninvasive techniques is fraught with technical difficulty. One convenient method involves placing a single marker on the skin overlying the acromion. The purpose of this study was to compare translatory discrepancies between marker and underlying bone for seven markers affixed to the skin overlying different parts of the scapula. MethodsThe markers were small plastic spheres filled with machine oil, clearly visible on magnetic resonance imaging (MRI), placed over seven loci of the scapula, including the acromion, spine, medial border, lateral border, and inferior angle. Nine healthy men participated, assuming three positions in the MRI apparatus: (1) arm at the side of the trunk (starting position); (2) arm in full elevation over the head; and (3) hand placed behind the back at the thoracolumbar area. Visible markers and three loci of the scapula itself were digitized on each MRI scan, enabling calculation of changes in location of each marker relative to the scapula between the starting position and either of the other two positions. ResultsAmong the seven loci examined, the marker placed atop the acromion deviated least from its target, 39±15mm (mean±standard deviation) for full elevation and 15±11mm for moving the hand behind the back. Markers along the medial border and at the inferior angle exhibited relatively large deviations, on the order of 87mm for full elevation and 33mm for moving the hand behind the back. ConclusionsFor the two movements studied, involving full range of motion in the shoulder complex, translation of the scapula is most accurately recorded if the marker is placed over the acromion, but the systematic error is too large for such tracking to be deemed precise.

体幹部における３検出器型高速回転ＳＰＥＣＴ撮像法の開発―肺血流シンチ・ファントムスタディ―

A chest phantom study was conducted to evaluate the image quality of newly developed high-speed rotation multiplied projection-single photon emission computed tomography (HSRMP-SPECT) images. HSRMP-SPECT images of a chest phantom consisting of a simulated lung structure filled with 5000 ml of water containing 185 MBq Tc-99m-pertechnetate, and several small 11 mm simulated lung nodules of glass balls and one large 35 mm simulated lung nodule of a plastic sphere filled with water were obtained using a triple-headed SPECT system. During image acquisition, this phantom was regularly moving in the head-to-caudal direction with a range of 12 mm at a frequency of 15 cycles/min to simulate respiratory motion, and 360 degrees projection data of this moving phantom was acquired with an image acquisition time of 20 sec, which was repeated 10 times. To eliminate the setting time between projection and acquisition of multiple temporal samples of data, each detector was continuously rotated in the clockwise direction for 20 sec around a 120-degree arc. On the perspective SPECT images reconstructed from various numbers of the 20-sec projection data, the perfusion heterogeneity of the simulated lungs and perfusion defect clarity of the simulated nodules were assessed by the coefficient of variation (CV) of pixel counts and the defect-to-lung radioactivity ratios, respectively. The results were compared with those on conventional SPECT images of the moving phantom obtained with a data acquisition time of 8 min, and SPECT images of the standing phantom obtained with the same data acquisition time. The average CV value of 0.28+/-0.01 on the SPECT image reconstructed from 5 projection data sets was not significantly different from that of 0.27+/-0.01 on the SPECT image reconstructed from 10 projection data sets (p<0.05). The perfusion defect contrast of the simulated nodules obtained from 5 projection data was significantly higher than that on conventional SPECT images (0.50 vs. 0.73) . The present phantom study indicated that HSRMP-SPECT could be a useful technique for quickly obtaining high-quality SPECT images of a moving subject, thereby improving perfusion defect clarity in comparison with the conventional technique. This technique may have potential utility for obtaining high-quality breath-hold SPECT images of the chest in clinical practice.