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Lethal untrackable debris objects pose the highest risk to the sustainability of the space environment, and thus, shall be included in the assessment of the long-term effect of mitigation and remediation measures to the space debris problem. The introduction of centimetre-sized particles in the debris evolutionary models represents a challenge from a computational cost point of view. To answer this need, this work proposes a novel probabilistic debris environment propagator. The method classifies the objects population into intact objects and fragmentation debris. The evolution of the former population is retrieved through an individual definition of each object's mission profile. A continuum approach is adopted for the characterisation of the fragments, whose density distribution in orbital elements is propagated in time through the continuity equation. The intrinsic computational efficiency of the density-based fragments cloud models is leveraged to make the method agnostic to the lowest fragments size considered. A second classification of the population of intact objects into species, such as payloads, rocket bodies, mission related objects and constellations, ensures a faithful replication of their orbit evolution. Fragmentation debris caused by intact objects explosion and accidental fragments-intact object collision are included in a probabilistic fashion at the detected fragmentation epoch, to account for their feedback effect onto the environment. The model is applied to estimate the evolution of the space debris population in low-Earth orbit up to 200 years from the reference epoch, with and without the inclusion of a future launch traffic pattern, and considering a different fulfilment of the post-mission disposal phase. • Density-based methods are introduced into a complex space debris evolutionary model. • Intact objects are divided in species to observe debris environment dependency on mission design. • Effect of different adherence to post-mission disposal guidelines is analysed. • Predictions on the evolution of the space environment 200 years from now are presented. [ABSTRACT FROM AUTHOR]

The permanent power loss and the deviation of the trajectory of satellites impacted by centimetre and sub-centimetre sized debris have highlighted the need of taking into account such small fragments in the evolutionary models of the debris population and in the assessment of the in-orbit collision risk. When scaling down to the centimetre-millimetre range, deterministic models for propagating the fragments' orbit suffer from the massive computational cost required. The continuum approach for modelling the debris clouds is a well-established alternative to the piece-by-piece propagation. A density function is formulated to describe the distribution of fragments over a suitable phase space. Accurate and efficient continuum formulations have been developed to propagate clouds of fragments under atmospheric drag and J 2 perturbations, but a general model able to work under any dynamical regime has still to be found. This paper proposes a continuum approach that combines the method of characteristics with the discretisation of the domain in Keplerian elements and area-to-mass ratio into bins. The problem of using a binning approach with such a multi-dimensional phase space is addressed bounding and partitioning the domain, through probabilistic models on the way the fragments distribute over the phase space, as consequence of a fragmentation event. The proposed approach is applied to the modelling and propagation of a space debris cloud under the full set of orbital perturbations, and compared against a Monte Carlo simulation in terms of objects' number and distribution. The method proves to be accurate on the medium scale, in both space and time, and guarantees statistical validity with a reduced computational effort, leveraging its probabilistic nature. [ABSTRACT FROM AUTHOR]

MXenes, as two-dimensional (2D) transition metal carbides, carbonitrides, and nitrides, have very excellent electrical properties and surface activity and are increasingly used in supercapacitors, batteries, electromagnetic interference shielding, and composite materials. Still, the poor stability of MXene when exposed to aqueous oxygen and the poor ability to interact with the polymer matrix have become important factors limiting its' practical applications. To enhance stability, highly conductive and stretchable Ti 3 C 2 MXene/TPU sensing elements were prepared by a simple spraying process using thermoplastic polyurethane (TPU) as a substrate, and the sensing elements were encapsulated by polydimethylsiloxane (PDMS) to obtain MXene-TPU/PDMS constructed flexible strain sensors with excellent performance. This strain sensor features low detection limits (less than 0.005%, 0.5 μm), a wide sensing range (0–90%), a short response time (120.1 ms), and excellent durability (>3000 cycles). This strain sensor can be applied to a range of applications such as health detection, motion signals, detection of robot movements, and wearable electronic devices. [ABSTRACT FROM AUTHOR]

This study investigates the absorption mechanisms of carbon dioxide (CO 2), hydrogen sulfide (H 2 S), and methane (CH 4) molecules in two imidazolium-based ionic liquids, namely 1-ethyl-3-methylimidazolium thiocyanate ([EMIM][SCN]) and 1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]). We employed molecular dynamics (MD) simulations applying umbrella sampling technique to calculate free energy profiles (FEPs) for gas molecules in the ILs. The results reveal CO 2 's pronounced affinity for the interface over the bulk in both ionic liquids (IL), whereas H 2 S exhibits facile penetration into both regions. CH 4 shows limited penetration into the IL bulk, remaining predominantly near the interface. We further explore the influence of ILs' anionic structures on gas accumulation sites by performing normal MD simulations. For instance, density profiles also confirm CO 2 's higher density in [EMIM][DCA] compared to [EMIM][SCN], reflecting the influence of anionic composition on CO 2 solubility. These insights offer valuable knowledge for designing efficient ILs for gas capture and separation applications. [ABSTRACT FROM AUTHOR]

Online multi-information detection of mineral properties and composition plays a vital role in the realization of digital mining and digital concentrating mill, and the way of machine vision technology is put forward as a cost-effective and safe approach at present. This paper presents an exploratory study employing a bench-scale approach to detect the multi-information of coal quality online by machine vision simultaneously, including particle size distribution, density distribution, the ash content of each density fraction, and the total ash content. Firstly, we adopt a Finite-Erosion-and-Exact-Dilation (FEED) algorithm and a particle-on-edge region segmentation algorithm to segment overlapped particles and ensure the full analysis of target regions. Moreover, twenty-nine features are extracted and optimized to enable the particle mass estimation model, particle size characterization, classification model of density fraction, and prediction model of ash content to be implemented. Finally, an experimental study shows the merits of the proposed approach, and the average prediction errors of size distribution, density distribution, and ash content of each density fraction are 1.85%, 2.57%, 3.36%, respectively. The total ash content error is 2.54%. Results derived using the proposed approach reveal that it has the potential to be applied to the coal processing industry. Technical route of multi-information online detection of coal quality based on machine vision. Unlabelled Image • We proposed innovative FEED and PERS segmentation algorithms for online coal images. • An online multi-information detection approach of coal quality was proposed systematically. • The average errors of multi-information online detection were less than 3.5%. [ABSTRACT FROM AUTHOR]

• Exploring network partitioning impacts on the reliability relation in large networks. • Proposing a modified dynamic methodology to partition a large-scale network. • Comparing two proposed approaches in literature to define the reliability relation. • Results show that sub-trajectory method is more consistent with network partitioning. • Positive impacts of partitioning on the reliability parameter estimation for clusters. Network travel time reliability can be represented by a relationship between network space-mean travel time and the standard deviation of network travel time. The primary objective of this paper is to improve estimation of the network travel time reliability with network partitioning. We partition a heterogeneous large-scale network into homogeneous regions (clusters) with well-defined Network Fundamental Diagrams (NFD) using directional and non-directional partitioning approaches. To estimate the network travel time reliability, a linear relationship is estimated that relates the mean travel time with the standard deviation of travel time per unit of distance at the network level. The impact of different partitioning approaches, as well as the number of clusters, on the network travel time reliability relationship are also explored. To estimate individual vehicle travel times, we use two distinct approaches to allocate vehicle trajectories to different time intervals, namely trajectory and sub-trajectory methods. We apply the proposed framework to a large-scale network of Chicago using a 24-h dynamic traffic simulation. Partitioning and travel time reliability estimation are conducted for both morning and afternoon peak periods to demonstrate the impacts of travel demand pattern variations. The numerical results show that the sub-trajectory method for the network travel time reliability estimation and the directional partitioning with three clusters have the highest performance among other tested methods. The analyses also demonstrate that partitioning a heterogeneous network into homogeneous clusters may improve network travel reliability estimation by estimating an independent relationship for each cluster. Also, comparing morning and afternoon peak periods suggests that the estimated parameter for the linear network travel time reliability relationship is directly related to the coefficient of variation of density as a measure of spatial distribution of congestion across the network. [ABSTRACT FROM AUTHOR]

A plasma density distribution that arises due to a finite observation volume or is inherent due to turbulence, needs to be accounted for when using spectral lines for plasma diagnostics. Such a distribution distorts line shapes in a non-trivial way and alters their intensities. In the present study, these effects are analyzed. The results are presented analytically and also tabulated for two types of the density distribution, Gaussian and log-normal, over a wide range of the distribution variance. The results are applicable to practically any type of spectral lines used for plasma density diagnostics. Provided also are considerations for choosing spectral lines to minimize uncertainties if a density distribution is expected but its extent is unknown. In addition, an approach for inferring the density distribution based on the line-shape asymmetry is suggested. • Effects of a plasma density distribution on the shape of spectral lines are studied. • Gaussian and log-normal (e.g., due to a turbulence) distribution types are analyzed. • The results are tabulated over a wide range of the density distribution variance. • An approach to infer the distribution based on the line-shape asymmetry is suggested. [ABSTRACT FROM AUTHOR]

The shape and internal structure of an asteroid is a result of its violent collisional history, and Asteroid 25143 Itokawa is an important target for investigating the internal structure and formation processes associated with rubble pile asteroids. The surface of Itokawa contains numerous boulders and is very rough, but 20% of the surface is covered with centimeter-sized gravels that are called "smooth terrain". These flat areas are associated with low areas of the gravitational potential and are considered to be formed by down-slope migration and accumulation of pebbles. We propose a method to constrain the interior density distribution of an asteroid by modeling the gravity field and fitting the smooth terrains to equi-potential surfaces. Density models that are composed of two distinct lobes best explain the data if the "head" and "body" have different densities of 2,450 kg/m3 and 1,930 kg/m3, respectively. Alternatively, the two lobes could have comparable densities if there was a compressed "neck" of higher density between the two. Three layer models that treat the densities of the head, neck and body separately are largely unconstrained. However, when using an independent estimate of the center-of-mass/center-of-figure offset as determined from modeling the YORP spin-up of Itokawa, our models require the density of the head to be larger than the global average. • Interior density distribution within asteroid Itokawa was estimated. • Fitting a simulated equi-potential surface for an observed smooth terrain. • Itokawa is likely to have mass concentration in the head or neck region. • Our technique could be effective for constraining small bodies' interiors. [ABSTRACT FROM AUTHOR]

Spray-dried refractory carbide and metal powder mixtures, containing tungsten carbide, is compacted and sintered during the production of conventional cutting tool inserts. Since friction between the pressing tool and the powder gives rise to density gradients in the powder compact, shrinkage during sintering is uneven. The shape of the sintered blank is important and can be predicted with finite element (FE) simulations. To validate the simulation of the pressing procedure, the density gradients in the powder compacts must be measured with a high spatial resolution. Since tungsten has a high atomic number, it is hard to penetrate with X-rays and even cold neutrons. We show here that by using a polychromatic beam of thermal neutrons, along with beam-hardening correction, such measurements can be successfully realized. The obtained results show good agreement with corresponding FE-simulations. Also, deliberate differences in the compaction process could be verified with the neutron measurements. Unlabelled Image • For the first time, density distributions in cemented carbide compacts are measured. • Good agreement is found between measurements and FEM-simulations. • Process characteristics related to rate-dependence and creep are determined. [ABSTRACT FROM AUTHOR]

The constant growth of livestock husbandry in China in recent years has raised grave concerns about severe environmental pollution. A countrywide, comprehensive assessment of the quantity and distribution of livestock excrement (LE) production could significantly promote contamination control methods and biogas development in China. Previous researchers have reported an excessively wide range of LE quantities and have failed to reach a consensus conclusion. By using the latest updated LE definitions and calculation coefficients, LE and its biogas potential were assessed for 14 types of livestock in this study according to China's husbandry statistics data. LE increased by 10.9% from 1563.2 Mt in 2007 to 1755.0 Mt in 2015 at a rate of 12.3% in fresh weight and increased by 12.8% from 367.1 Mt to 414.5 Mt in dry weight. The mean annual LE from 2013 to 2015 was estimated on a dry weight basis as 414.9 Mt. Most of the LE produced from 2013 to 2015 was by cattle (including draft cattle, beef cattle, and dairy cows), followed by sheep (including goats), poultry (including broiler chickens, egg chickens, ducks, and geese), pigs, and other livestock (including horses, donkeys, mules, camels, and rabbits). Among the six regions, from 2013 to 2015, the LE was distributed in ascending order in the Northwest, Northeast, Southwest, North, Central-south, and East regions on a dry weight basis. The average LE produced among the 31 provinces in China ranged widely from just 0.8 Mt (Shanghai) up to 42.4 Mt (Shandong), with the latter having the highest LE density distribution (275.7 t km-2) on a dry weight basis. The east-middle provinces, Liaoning, Shandong, Henan, Hebei, Tianjin, Jiangsu, and Anhui, exhibited relatively higher levels of LE density distribution (111.2–275.7 t km-2) than those of other regions. The yearly total LE generated from commercial scale husbandry feedlots (CSHF) for 2015 was estimated at 141.5 Mt, which amounts to a biogas potential of 60.6 billion m3 (Billion refers 1 × 109). Scenario analysis predicts that by 2030, the annual LE from CSHF could range from 201.1 to 258.9 Mt, corresponding to biogas potential of 86–111 billion m3. The results of this countrywide study suggest that there are significant opportunities to improve LE management and to achieve ecological livestock husbandry in China. • Livestock excrement rose by 12.8% from 367 to 414 Mt (dry) in 2007–2015 in China. • In 2013–2015, 36% of it was from cattle and 18–19% from sheep, pigs, and poultry. • The 7 provinces in east-middle area showed highest excrement density distribution. • The biogas potential of excrement from commercial feedlots was 6.1 × 1010 m3 in 2015. • Biogas from it could range from 8.6 × 1010 to 1.1 × 1011 m3 under 4 scenarios by 2030. [ABSTRACT FROM AUTHOR]

The design of contraflow left-turn (CL) lane has effectively improved the capacity of left-turn vehicles at signalized intersections and has been widely used. Existing studies have focused more on the coordination and optimization of the main signal and pre-signal as well as capacity, delay time and queue dissipation. However, the vehicles lane-changing behaviors for CL lane design have not been adequately studied. Therefore, it is necessary to study of left-turn vehicles lane-changing behaviors at signalized intersections with contraflow lane and the traffic evolution law of the road. In this study, a cellular automaton (CA) model that simulates left-turn traffic flow at signalized intersections with CL lane was developed and verified by field data. Various factors are considered, including the length of CL lane and lane-changing area, as well as the location of the vehicles. The simulation results show that the density distribution of traditional left-turn (TL) lane is more influenced by the length of the lane-changing area when the probability of vehicle injection is small (α ≤ 0.1). Furthermore, when the probability of vehicle injection is larger (α > 0.1), the density distribution of CL lanes is more influenced by length of the lane-changing area. In addition, the departure ratios of CL and TL lanes is close to 50% when the probability of vehicles injection and length of the lane-changing area are larger (α > 0.1 and LB ≥ 20 cells), which is almost consistent with the peak hour vehicle departure ratios in the real scenario. Finally, this study can provide a reference for the actual application of CL lane design. • The lane-changing behavior of contraflow left-turn vehicle at the pre-signal is divided. • New lane-changing rules and lane-changing probability are proposed. • The modified comfortable driving model is introduced. • The density distribution depends on the vehicle injection probability and length of the lane-changing area. • The departure ratios of vehicles in CL and TL lanes are close to 50%, respectively. [ABSTRACT FROM AUTHOR]

Roll compaction is a continuous manufacturing process aiming to produce particulate granules from powders. A roll press typically consists of a screw feeding system, two rolls and a side sealing. Despite its conceptual simplicity, numerical modelling of the process is challenging due to the complexity involving two different mechanisms: feeding by the screw and powder compaction between the rolls. To represent the materials' behaviour both in the feeding zone and in the compaction area, a combined three-dimensional Discrete Elements Method (DEM) and Finite Elements Method (FEM) is developed in this work. The DEM, which is a more suitable method to describe the flow of granular material, is used to model the motion of particles in the feeding zone. As the granular material deforms under high pressure between rolls, FEM offers a more versatile approach to represent the powder behaviour and frictional conditions. In the proposed approach the DEM and FEM are treated as complementary methods, enabling us to take advantages of the strengths of both. In this proposed approach, the time dependent velocity field of the particles at the end of the screw feeder is evaluated as a continuous field using the coarse graining (CG) framework, which was used as input data for the FEM model. FEM is then used to simulate the powder compaction in between the rolls, and the resultant roll pressure and ribbon relative density are obtained. Our results show a direct correlation between the particle velocity driven by the screw conveyor and the roll pressure, both oscillating with the same period. This translates into an anisotropic ribbon with a density profile varying sinusoidally along its width, with a period equal to the duration of a screw turn. [ABSTRACT FROM AUTHOR]

The ribbon relative density is one of the key quality attributes during roll compaction/dry granulation, as it primarily determines the granule porosity and granule size distribution. In this study, a new approach to measure the ribbon relative density in-line was investigated. A thermographic camera was used to record freshly produced ribbons as they left the gap. In a first step a principal correlation of the measured ribbon temperature and the ribbon density was proven. Furthermore, the cooling rate after compaction was identified as an additional characteristic that can be used to determine the ribbon density. Interestingly the thermographic images also revealed temperature distributions within the ribbon that could be matched with density distributions measured by X-ray micro-computed tomography. In the following, additional characteristics that are equally important for the practical application as an in-line measuring tool were further investigated. The technique showed short reaction times to changes in the process and in a long term experiment no temperature drift over time could be detected. This study demonstrated the applicability of a thermographic camera as an in-line analytical tool for the determination of ribbon relative density. [ABSTRACT FROM AUTHOR]

• Smoke propagation under subcritical ventilation is experimentally studied. • Models are proposed to predict propagation velocities at both sides of the source. • Two flow mechanisms are observed in terms of the propagation velocities. • Correlation of reduced gravities at both sides of the source is quantified. • Thickness of backlayering flow at different locations is determined. In the early stage of tunnel fires, longitudinal ventilation velocity is often smaller than the critical velocity to preserve the smoke stratification and therefore facilitate the evacuation. A series of brine-water experiments are conducted to investigate the unsymmetrical propagation of the stratified smoke flow under subcritical ventilation. A light attenuation technique is used to measure the distribution of the reduced gravity in the tunnel. The ventilation velocity V and the source buoyancy flux per unit width B 0 are two dominant parameters for the flow. The reduced gravities at both sides of the source are quantitatively compared, and then a model is proposed to estimate the reduced gravities under different B 0 and V. In terms of the propagation velocity, two flow regimes are observed. When V / B 0 1 / 3 is smaller than 0.56, both the propagation velocity of the downstream smoke front, u d , and that of the backlayering smoke front, u b , are independent of time; moreover, u d is smaller than the propagation velocity of the smoke following the downstream smoke front. However, when V / B 0 1 / 3 is larger than 0.56, u d is still independent of time, but u b decreases with time; furthermore, u d is approximately equal to the propagation velocity of the smoke following the front. Prediction models regarding the propagation velocities at both sides of the fire are established. As the backlayering flow advances forward, its thickness approximately linearly decreases. The maximum thickness of the backlayering flow is correlated with V / B 0 1 / 3 . The study might be useful for determining the ventilation and evacuation strategies in tunnel fires. [ABSTRACT FROM AUTHOR]

To evaluate the compaction uniformity effectively, firstly, the feasibility of using density and void distribution as compaction uniformity evaluation index was demonstrated by laboratory test. Secondly, relying on the project of Tong-Xun Highway, reasonable detection interval of non-nuclear density gauge PQI was determined, and quantitative evaluation index of density distribution uniformity was also proposed. Next, core samples at representative density point were drilled and of which the voids distribution characteristic on sectional image of core sample was analyzed by image processing technology, and further on, the evaluation index of void distribution uniformity was put forward. Finally, the accurate detection method of compaction uniformity based on density and void distribution was exampled relying on entitative engineering. The results show that it is feasible to evaluate the compaction uniformity of asphalt pavement with its density and void distribution. The reasonable lateral detection interval of PQI is 1.5 m, and the reasonable longitudinal detection space is 50 m. Density statistical index such as S r , S R , k and h can reflect the density distribution uniformity on detection section. Voids number uniform coefficient UC N and voids ratio uniform coefficient UC R of core samples can reflect the compaction uniformity of asphalt pavement from the aspect of micro structure. [ABSTRACT FROM AUTHOR]

Purpose: The impact of isolated malleolar fractures on the intra-articular load distribution within the ankle joint has been studied in several biomechanical cadaver studies during the last decades. Recently, computed tomography osteoabsorptiometry (CT-OAM) has been proposed as a valuable tool to assess intra-articular joint load distribution in vivo. The purpose of this retrospective matched pair analysis was to apply CT-OAM to evaluate in vivo changes of talar load distribution after lateral malleolar fractures in patients treated with open anatomic reduction and internal fixation (ORIF) compared to patients treated non-operatively.Methods: Ten matched pairs of patients with isolated lateral malleolar fractures with a maximum fracture dislocation of 3mm and a median follow-up of 42 month were included into the study. Patients were matched for age, gender, and fracture dislocation. Range of ankle motion (ROM), the AOFAS hindfoot score and the Short Form 36 (SF-36) were evaluated. CT-OAM analysis of the injured and the uninjured contralateral ankles were performed.Results: Patients treated with ORIF showed a significant lower ROM compared to the uninjured contralateral ankle. No differences were found regarding clinical scores between patients treated by ORIF and those treated non-operatively. CT-OAM analysis showed symmetrical distribution of subchondral bone mineralization in comparison to the uninjured contralateral ankles for both groups of patients.Conclusions: The data of this study suggest that isolated lateral malleolar fractures with fracture gaps up to 3mm are not associated with a change of the tibio-talar joint load distribution in vivo. Therefore, patients with isolated minimally displaced lateral malleolar fractures may achieve good clinical long-term outcome following non-operative treatment.Level Of Evidence: Level III, retrospective cohort study. [ABSTRACT FROM AUTHOR]

Due to the collision and lateral compression of the Indian-Asian plate, the Lancangjiang fault has become one of the most active strike-slip faults in the Qiangtang plate. The Qamdo 2013 Ms 6.1 earthquake was induced from the northern section of the fault (the northern Lancangjiang fault). The destruction of the earthquake seriously endangers human activities and the construction of the Sichuan-Tibet Railway. However, there are few high-resolution geophysical data in this area, which limits the understanding of the deep structure, motion mode and seismic activity of the northern Lancangjiang active fault. In this paper, new gravity data were observed at a scale of 1: 200,000, covering an area of 1500km2. Based on wavelet multiscale decomposition, scratch analysis and 3-D inversion of gravity data methods, we obtained gravity anomalies of different scales, faults distribution and density structure. The results show that the overall crustal density change in Qamdo area is obvious and closely related to the distribution of faults. The Qamdo earthquake occurred at the layered interface with steep density change and the result from scratch analysis shows that the stress is concentrated at this position. We believe that the existence of stratigraphic density difference leads to different ability of strata to withstand regional tectonic stress, which is an important cause of the Qamdo earthquake. We analyzed the differences magnitude of earthquake activity between the northern Lancangjiang fault and Kamaduo-Gangtuo fault and believe that the northern Lancangjiang fault is more conducive to the preparation of large earthquakes. Otherwise, this paper provides geophysical evidence for the hypothesis that the northern Lancangjiang fault thrusts to the Qamdo Basin at a high angle. • Crustal density change in the Qamdo is more complex. • Crustal density characteristics are linked to distribution of faults. • The northern Lancangjiang fault thrusts into the Qamdo Basin at a high angle. • The northern Lancangjiang fault is conducive to the preparation of large earthquakes. • The Qamdo earthquake occurred at the layered interface with steep density change. [ABSTRACT FROM AUTHOR]

Muography is a method for estimating the density distribution inside an object by using muons produced by cosmic rays. Multidimensional muon tomography has recently become popular for counting muons from multiple directions using an inversion technique to reconstruct multidimensional density distributions. This study investigated anomaly detectability in multidimensional muon tomography under a trade-off relationship between anomaly size, density contrast, and exposure time. The L1- and L2-norm regularised least squares methods (LSMs), which are two different inversion methods based on the least squares method, were used and compared to reconstruct density distributions. Additionally, to investigate the applicability of an objective and automated evaluation method for anomaly detection, machine learning and outlier tests (OT) were used as two criteria for anomaly detection. The merit of anomaly detection visualization based on machine-learning techniques was demonstrated. Finally, a quantitative relationship was derived between anomaly size, density contrast, and exposure time. Notably, there are no universal inversion techniques or anomaly detection methods for all cases. Thus, it is necessary to evaluate the performance of multidimensional muon tomography based on the observation situation and exploration target by applying the approach proposed in this study. • Extension of previous 1D anomaly detection evaluation in muography to 3D. • Visualization of anomaly detection based on a machine learning technique. • Quantitative trade-off relationship between anomaly size, density contrast, and exposure time. [ABSTRACT FROM AUTHOR]

Non-destructive and quantitative investigation of density distribution of round tablets was the objectives of this study. The density distribution of round tablets was observed using X-ray computed tomography (X-ray CT). The distribution images were visualized by fractionating the CT images into 25 unit cells and averaging the CT number for each cell. The profiles of the distribution were analyzed with respect to the compression pressure by partial least squares (PLS) method. Analysis using the PLS method resulted in regression and loading vectors depicting the contribution of the change in density due to the variation of compression pressure. The vectors were also composed of 25 positions and used to reconstruct density mapping. The reconstructed maps quantitatively indicated the regions reflecting changes in density. At the upper and lower surface of tablets, increasing the compression pressure increased density in the edge region and decreased density in the center region. The center region under the upper surface was weakly affected by the pressure change. These results well agreed with the simulation results of finite elemental method. We suggest that the effects of compression pressure visually revealed in each region of the tablet by the X-ray CT and PLS methods are generated by density imbalance resulting from high pressure compression. [ABSTRACT FROM AUTHOR]

Roll compaction is a commonly used dry granulation process in pharmaceutical, fine chemical and agrochemical industries for materials sensitive to heat or moisture. The ribbon density distribution plays an important role in controlling properties of granules (e.g. granule size distribution, porosity and strength). Accurate characterisation of ribbon density distribution is critical in process control and quality assurance. The terahertz imaging system has a great application potential in achieving this as the terahertz radiation has the ability to penetrate most of the pharmaceutical excipients and the refractive index reflects variations in density and chemical compositions. The aim of this study is to explore whether terahertz pulse imaging is a feasible technique for quantifying ribbon density distribution. Ribbons were made of two grades of microcrystalline cellulose (MCC), Avicel PH102 and DG, using a roll compactor at various process conditions and the ribbon density variation was investigated using terahertz imaging and section methods. The density variations obtained from both methods were compared to explore the reliability and accuracy of the terahertz imaging system. An average refractive index is calculated from the refractive index values in the frequency range between 0.5 and 1.5 THz. It is shown that the refractive index gradually decreases from the middle of the ribbon towards to the edges. Variations of density distribution across the width of the ribbons are also obtained using both the section method and the terahertz imaging system. It is found that the terahertz imaging results are in excellent agreement with that obtained using the section method, demonstrating that terahertz imaging is a feasible and rapid tool to characterise ribbon density distributions. [ABSTRACT FROM AUTHOR]

The formation of plasma channel with the use of eight spark discharge sources was experimentally investigated in a high current pulsed electron beam (HCPEB) equipment. A triple Langmuir probe system was developed to diagnose the real-time plasma parameters. The spark discharges were initiated by using a high-voltage pulse of −7.0 kV and decoupling resistors of 40 Ω. Displacing the measurement positions, the plasma density distributions in a column of diameter 60 mm and length 175 mm were obtained. The duration of spark discharge is 11.0 μs and the maximum discharge current of 1.4 kA appears at 4.3 μs. Initially, the plasma concentrates in the peripheral region. With the accumulation in radial direction, the plasma density in the central region increases. After 6.6 μs, the maximum plasma density of 8.4 × 1018 m−3 appears at the center of the plane where the spark sources located. Thereafter, the plasma dissipation plays a dominant role. The plasma maintains about 20 μs. Depending on the formation features of plasma channel, the selection of timing control available was illustrated, while the transportation of HCPEB can be realized effectively within a limited distance, i.e. less than 60 mm beyond the source outlet in this case. • Eight spark sources were utilized to form plasma channel in HCPEB equipment. • Triple Langmuir probe system was developed to diagnose the plasma parameters. • Plasma density distributions in the cylindrical space were obtained. • Selection of timing control available was illustrated with experimental results. • HCPEB transportation can be realized effectively within a limited distance. [ABSTRACT FROM AUTHOR]

The fusion cross-section of 9 Li + 70 Zn system is analyzed for different cluster models and various density distributions of the 9 Li nucleus by using the optical model at energies near and below Coulomb barrier. To make a comprehensive analysis and show the effect of neutron rich 9 Li nucleus, our study consists of two parts. First, we obtain five different density distribution of the 9 Li nucleus. As a second part, we evaluate some cluster models of 9 Li which consist of 4 He + 3 H + n + n , 6 He + 3 H, 7 Li + n + n and 8 Li + n. The microscopic nucleon-nucleon double folding potential for real and imaginary parts is applied. It is seen that the results obtained with this study are in better agreement with the experimental data than previous works, especially at low energies. Finally, we acquire the R B and V B parameters for all the densities and cluster cases of the 9 Li + 70 Zn fusion reaction. [ABSTRACT FROM AUTHOR]

Finite elements method was used to study the influence of tablet thickness and punch curvature on the density distribution inside convex faced (CF) tablets. The modeling of the process was conducted on 2 pharmaceutical excipients (anhydrous calcium phosphate and microcrystalline cellulose) by using Drucker–Prager Cap model in Abaqus ® software. The parameters of the model were obtained from experimental tests. Several punch shapes based on industrial standards were used. A flat-faced (FF) punch and 3 convex faced (CF) punches (8R11, 8R8 and 8R6) with a diameter of 8 mm were chosen. Different tablet thicknesses were studied at a constant compression force. The simulation of the compaction of CF tablets with increasing thicknesses showed an important change on the density distribution inside the tablet. For smaller thicknesses, low density zones are located toward the center. The density is not uniform inside CF tablets and the center of the 2 faces appears with low density whereas the distribution inside FF tablets is almost independent of the tablet thickness. These results showed that FF and CF tablets, even obtained at the same compression force, do not have the same density at the center of the compact. As a consequence differences in tensile strength, as measured by diametral compression, are expected. This was confirmed by experimental tests. [ABSTRACT FROM AUTHOR]

Feature selection has aroused extensive attention and aims at selecting features that are highly relevant to classification from raw datasets to improve the performance of a learning model. Fuzzy rough set theory is a powerful mathematical method for feature selection. The classical fuzzy rough set model is very sensitive to the noise while the noise samples in classification data often appear. In addition, fuzzy rough set theory does not fit well when the density distribution of the samples in the dataset varies greatly. Thus, it is of great significance to improve the robustness of fuzzy rough set models and its adaptability to data for feature selection. Inspired by these issues, we focus on the robust fuzzy rough set approach for feature selection. We first propose a robust fuzzy rough set model based on data distribution to achieve the purpose of anti-noise i.e. , Noise-aware Fuzzy Rough Sets (NFRS) model. This model proposes a novel search mechanism, which weakens the sensitivity of the approximation operator to noise by considering the distribution of samples in the decision classes to weight the samples, further obtains three kinds of samples, i.e. , intra-class samples, boundary samples, and outlier samples. Then, the degrees of relevance of the feature for class is defined by the dependency function based on the NFRS model to evaluate the significance of the feature subset. On this basis, an evaluation function about feature significance is constructed, which simultaneously considers the relevance and redundancy of a candidate feature provided for the selected subset and the remaining feature subset. A novel forward greedy search algorithm is presented to select a feature sequence. The selected features are subsequently evaluated with downstream classification tasks. Experimental using real-world datasets demonstrate the effectiveness of the proposed model and its superiority against comparison baseline methods. [ABSTRACT FROM AUTHOR]

Abstract: Langevin dynamics simulations are performed to study polyelectrolyte brushes by varying the chain grafting density σ g, the added salt valence Z, and concentration C s. The brush thickness H follows a scaling relation in monovalent salt solutions as , decreasing more slowly than the scaling prediction. In divalent and trivalent salt solutions, H acquires a minimum value at the stoichiometric point, and then levels off and slightly increases, respectively. The shape and orientation of the chains change with C s accordingly. An electric double layer is formed around the brush rim, revealed by the calculation of vertical charge distribution. Increasing σ g, Z, C s reduces the width of the layer. Side-view density study further shows how the three parameters transform the brush profile from an individual-chain distribution to a homogeneous one. Finally, about 90% of chain charges are neutralized by the ions trapped in the brushes. It is found that ion condensation on the chains can be described by Manning's theory in sparse grafting and dilute salt conditions. [Copyright &y& Elsevier]

There are large amounts of nanoscale rough pores in shale, which provides the sites for methane adsorption. Proper understanding of the mechanisms of methane adsorption in nanoscale rough slits is important for estimating the shale gas reserves. In this study, graphene was used instead of shale to construct nanoscale slits with different widths and roughness, and the effects of roughness, slit width and pressure on the methane adsorption characteristics are investigated by using the GCMC and molecular dynamics methods. The results showed that the methane adsorption configurations are influenced by the slit width and surface roughness. The adsorption layers in rough slits are discontinuous and weak second adsorption layers are formed in large slits at high pressures. The inaccessible volume increases with the roughness resulting in the reduction of accessible volume. Therefore, both the excess adsorption and absolute adsorption decrease with the roughness, and they increase with the slit width in the microscopic scale due to the increased adsorption. While decrease slightly with the slit width in the mesoscopic scale due to the reduction of adsorbed phase density. The excess adsorption isotherms are well fitted by the Langmuir-Freundlich model. The adsorption is found more stable in smaller and rougher slits due to the superposition of adsorption potentials through the analysis of adsorbate potential energy and adsorption heat. • Adsorption configurations are affected by the slit width and surface roughness. • Both the absolute and excess adsorption decrease with the roughness. • Adsorption is more stable in small and rough slits. • Slit surface area and inaccessible volume increase with the roughness. • Absolute adsorption first increases then decreases with the slit width. [ABSTRACT FROM AUTHOR]

Highlights: [•] Use mineral physics modeling and observed MOI to constrain Mars composition. [•] In the mantle, Fe content is between 9.9–11.9mol%; Al content <1.5mol%. [•] S content in the Martian core is between 10.6–14.9wt%. [•] The Fe/Si ratio in Mars is between 1.55–1.95. [•] We cannot distinguish if Mars has the same composition as that of C1 chondrite. [Copyright &y& Elsevier]

We present terahertz pulsed imaging (TPI) as a novel tool to quantify the hardness and surface density distribution of pharmaceutical tablets. Good agreement between the surface refractive index (SRI) measured by TPI and the crushing force measured from diametral compression tests was found using a set of tablets that were compacted at various compression forces. We also found a strong correlation between TPI results and tablet bulk density, and how these relate to tablet hardness. Numerical simulations of tablet surface density distribution by finite element analysis exhibit excellent agreement with the TPI measured SRI maps. These results show that TPI has an advantage over traditional diametral compression and is more suitable for nondestructive hardness and density distribution monitoring and control of pharmaceutical manufacturing processes. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:2179-2186, 2013 [ABSTRACT FROM AUTHOR]

Abstract: The possible existence of a “bubble” structure in the proton density of 34Si has recently attracted a lot of research interest. To examine the existence of the “bubble” structure in low-lying states, we establish a relativistic version of configuration mixing of both particle-number and angular-momentum projected quadrupole deformed mean-field states and apply this state-of-the-art beyond relativistic mean-field method to study the density distribution of the low-lying states in 34Si. An excellent agreement with the data of low-spin spectrum and electric multipole transition strengths is achieved without introducing any parameters. We find that the central depression in the proton density is quenched by dynamic quadrupole shape fluctuation, but not as significantly as what has been found in a beyond non-relativistic mean-field study. Our results suggest that the existence of proton “bubble” structure in the low-lying excited and states is very unlikely. [Copyright &y& Elsevier]

Abstract: This paper investigates the compaction of pharmaceutical powders using different shapes of punches. We introduce a model of mechanical behaviour Drucker–Prager Cap (DPC), using the approach of compressible continuous media. The model parameters that are depending on the material density, were identified from experimental data and a calibration process was applied on Microcrystalline Cellulose (MCC) powder. In addition, the mathematical formulation of the boundary problem of compaction in rigid tools brings back to an optimization problem with constraint, which is solved by finite element method. The Drucker–Prager Cap model, which is implemented in Abaqus/Standard software, was employed using a user subroutine, USDFLD. Three kinds of typical pharmaceutical tablets are considered: flat-face tablet and concave face tablet with two different depths. Results of simulations of die compaction cycle as compression, decompression and ejection, reproduce the powder compaction process for the studied shaped punches. The effects of the punch's shape on the compaction process were observed on the distribution and the maximum of stress and density in the compact. Examination of the density gradient according to the shape, suggests a capping tendency, which increases with the punch depth. This study illustrates the potentiality of the FEM method, which could be used as an efficient tool to predict the density and the stress distributions into shaped compacts and to provide a diagnostic of the capping problems. [Copyright &y& Elsevier]

Abstract: The ecological project of shelterbelts in oasis–desert ecotone is a main measure to wind–sand damage, which is one of the most serious eco-environment problems in arid regions. The effectiveness of shelterbelts with a non-uniform density distribution, planted perpendicular to the prevailing wind direction, was studied through field observations. The results showed that the main factor influencing wind speed is the density distribution of a particular shelterbelt of a specifically given tree specie. In this study, the shelter effects of a sparse shelterbelt was compared with a dense shelterbelt and it corresponded with most previous reports, namely that dense shelterbelts resulted in a higher wind reduction whilst the sparse shelterbelts have a longer shelter distance at the leeward side of the belt. For shelterbelts with a non-uniform density distribution and wind blowing from high density to low density, wind speed changes will be similar to that of a high-density shelterbelt at both the windward and leeward sides of the shelterbelt. However, when the wind blows from the opposite direction, the flow fields change greatly as compared to an evenly distributed shelterbelt. A combined effect of density manifested, thus providing better shelter effects by balancing the reduction in wind speed with the shelter distance. [Copyright &y& Elsevier]

Abstract: This paper continues the effort to validate the finite element based analysis of tableting. A three-dimensional capsule shaped tablet is studied using a Drucker–Prager cap constitutive model and a coupled thermomechanical analysis. Predictions of the model for the internal distribution of porosity and temperature are found to be in agreement with X-ray microtomography measurements of relative density and infrared camera measurements of surface temperatures of the ejected tablet. The fact that the model is calibrated using data from a cylindrical flat-faced tablet which can predict the compaction of a completely different shape proves the capability offered by finite element analysis. In addition, this method demonstrates the role it can play in the optimization of tableting operations in the spirit of quality by design principles. [Copyright &y& Elsevier]

Abstract: The variation in the distribution of density in colloidal spherical particles was evaluated by transmission electron microscopy (TEM), without utilizing a high-resolution mode, and quantified by image processing. The method eliminates the dependency of the image contrast on sample crystallinity. The advantage of such approach is manifested by the short time sample preparation, fast instrument tune-up, rapid image acquisition and analysis, all of which shorten the processing time. Colloid silver spheres and gold nanoparticles were examined and compared to amorphous silica and acrylate–methacrylate polymer spheres. The latter can be considered as ideal homogeneous model samples. Image files having *.dm3 extension, obtained from TEM, were processed with ImageJ software, and later analyzed with script written in Microsoft Visual C++. It is shown that the radial distribution of density of highly crystalline gold nanoparticles resembles the used models, while in larger polycrystalline silver spheres it differs significantly from the “ideal” case. Deviations from linearity for gold and silver were interpreted in terms of finite polydispersity and internal inhomogeneities. The described method made it possible to estimate rapidly and accurately the number of subunits needed to achieve properties of an equivalent sphere, without considering the crystalline nature of such particles. [Copyright &y& Elsevier]

Abstract: Inhomogeneous density distributions after die filling are a ubiquitous problem in powder technological part production. In this paper, numerical simulations of the die filling process in realistic, three-dimensional (3D) cavities are presented using the discrete element method with both multi-sphere and single sphere grain models. Good agreement was found between calculated and experimentally measured density distributions. The formation of an inhomogeneous distribution is discussed by a time-resolved analysis of the filling process. Grain rearrangement and densification during subsequent feeding shoe passages are characterized. The shoe velocity was tested for its influence on the density homogeneity. Suggestions for density homogenization with the application of cavity oscillations or volumetric filling are given. A density homogeneity index is introduced. The application of a coarse graining scheme circumvents the intrinsic difficulty of non-manageable grain numbers in 3D filling simulations. The validity and limitations of this scheme are discussed. [Copyright &y& Elsevier]

Abstract: Chain-length and tacticity effects on the conformational behavior, including density distributions and conformations, of MMA-oligomer thin films deposited on an Au (111) substrate at room temperature were investigated using molecular dynamics (MD) simulations. Three kinds of MMA-oligomer thin film with the oligomers containing m repeat units with m =5, 10, and 20, respectively, were selected to examine the chain-length effects. Three types of MMA-oligomer thin film (made of isotactic, syndiotactic, and atactic PMMA isomers, respectively) were utilized to inspect the tacticity effects. For ease of investigation, the thin film was divided into three regions (the contact, the bulk, and the surface regions) according to the through-thickness distribution of density of the thin film. For short-chain thin films (with m =5 and 10), the density distribution had a remarkable peak in the contact region of the thin film. The density peak, however, was not evident for the long-chain thin film (with m =20). Regarding tacticity, the isotactic thin films had a prominent peak density in the contact region as compared with the syndiotactic and atactic thin films. Moreover, the MMA oligomers were found to exhibit a flattened conformation parallel to the Au substrate in the contact region and a slightly flattened conformation in the surface region for both the short-chain and the long-chain thin films. The flattened conformation remained in the bulk region of the long-chain thin film. However, it was not present in the bulk region of the short-chain thin film, which had a randomly orientated conformation–a characteristic similar to bulk MMA. It was also observed that the tacticity of the MMA-oligomer thin films did not have obvious effects on the conformations of the thin films for both the short-chain and the long-chain cases. [Copyright &y& Elsevier]

Abstract: Roller compaction is one stage in a dry granulation process to produce free flowing granules. Its proper understanding is essential in optimising manufacturing efficiency and product quality. Roller compaction produces a compacted strip or “ribbon”, which is then milled to produce granules. For a given milling condition, the density distribution in the ribbons determines the properties of the granules (particularly their size distribution and strength). Therefore, knowing the density distributions in the ribbons is very important in improving the effectiveness of the roller compaction process and the quality of the granules produced. In this paper, the density distribution in roller-compacted ribbons of microcrystalline cellulose (Avicel PH102) has been examined using three different techniques: (1) sectioning; (2) micro-indentation and (3) X-ray micro-computed tomography. It has been shown that with proper calibration all three techniques can essentially produce the same results, but with a different degree of resolution (scale of scrutiny). In addition, the influence of process conditions, such as roll gap, roll speed and the presence or absence of lubrication, on the ribbon density distributions has also been investigated. Flow into the press is often constrained by the presence of “cheek plates”, which prevent lateral powder movement. In this type of arrangement, it is found that non-uniform powder feeding occurs in the compaction region, induced by the friction between the powder and the cheek plates; as a result, the densities in the middle of the ribbon width are generally higher than those close to the edges. It has also been shown that higher average ribbon densities are obtained when the roll gap, roll speed, or the friction between the powder and the side cheek plates is reduced. [Copyright &y& Elsevier]

Abstract: We observed four experimental results which suggest the existence of unidentified species other than metal atoms and metal ions in magnetron sputtering discharges employing metal targets. The most probable species which are compatible with the experimental observations are clusters (mainly dimers and trimers) of metal atoms. According to the experimental results, it is speculated that the amount of clusters is comparable to that of metal atoms. In other words, the present experimental results suggest a possibility that dimers and trimers are major sputtering products from metal targets. [Copyright &y& Elsevier]

Abstract: This work describes the procedure for investigation into dynamics of shock-wave compression of aerogel with the help of synchrotron radiation (SR). The aim of the experiments was to measure intensity both of transmitted radiation, giving information on substance density variation, and of radiation scattered through small angles (small-angle X-ray scattering (SAXS)), that can be used for reconstruction of pore evolution. The studies have shown that the SAXS signal vanishes while the shock wave is passing, i.e. the pores practically get shut. The porous structure of the substance recovers after the shock wave has passed, however, with a different pore size-grade distribution. [Copyright &y& Elsevier]

Abstract: This article describes the procedure and results of high-speed X-ray tomography application to reconstruct density distribution of detonation products of condensed explosives from the results of measurements with synchrotron radiation. Data obtained for a cylindrical charge (12.5mm in diameter) of pressed TNT of density of 1.6g/cm3 are compared with the results of solution of the corresponding gas-dynamic problem of stationary detonation. Qualitative and satisfactory quantitative compliance of the experimental and calculated results is established. Particularities of the procedure and the distribution obtained are analyzed. It is noted that the procedure on the whole and the results can be used to define the known equations of state of detonation products more accurately and to construct new ones. [Copyright &y& Elsevier]

Abstract: The adsorption behavior (capacity, density distribution and packing density) and the isosteric heat versus loading in a slit pore whose walls contain defective graphene layers are investigated in this paper. The defective wall is characterized by the extent and size of the defect. Simulation results obtained with the Grand Canonical Monte Carlo method reveal complex patterns of isosteric heat, and this complex behavior is a result of the interplay between three factors: (i) the surface heterogeneity (solid–fluid interaction, sites with varying degree of affinity), (ii) fluid–fluid interaction and (iii) the overlapping of potentials exerted by the two defective walls. We illustrate this with argon adsorption in pores of various sizes, and results obtained from the simulation agree qualitatively with the experimental data at 77K on Saran microporous S600H and micro-mesoporous S84 charcoals of Beebe et al. [R.A. Beebe, B. Millard, J. Cynarski, J. Am. Chem. Soc. 75 (1953) 839]. The S600H was found to contain pores predominantly in the neighborhood of 7Å with 30% of defect and a defective size of 2.84Å. This is consistent with the argument made by Beebe et al. that this sample is a microporous solid and most pores can accommodate only one layer. The other sample, S84, has larger pores than S600H, and it is found that it has a wider pore size distribution and the pore width is centered at about 12Å. [Copyright &y& Elsevier]

Abstract: In this paper, we try to predict the distribution of bone density and elastic constants in a human mandible, based on the stress level produced by mastication loads using a mathematical model of bone remodelling. These magnitudes are needed to build finite element models for the simulation of the mandible mechanical behavior. Such a model is intended for use in future studies of the stability of implant-supported dental prostheses. Various models of internal bone remodelling, both phenomenological and more recently mechanobiological, have been developed to determine the relation between bone density and the stress level that bone supports. Among the phenomenological models, there are only a few that are also able to reproduce the level of anisotropy. These latter have been successfully applied to long bones, primarily the femur. One of these models is here applied to the human mandible, whose corpus behaves as a long bone. The results of bone density distribution and level of anisotropy in different parts of the mandible have been compared with various clinical studies, with a reasonable level of agreement. [Copyright &y& Elsevier]

Abstract: This paper describes the use of 1H nuclear magnetic resonance (NMR) for 3D mapping of the relative density distribution in pharmaceutical tablets manufactured under controlled conditions. The tablets are impregnated with a compatible liquid. The technique involves imaging of the presence of liquid which occupies the open pore space. The method does not require special calibration as the signal is directly proportional to the porosity for the imaging conditions used. The NMR imaging method is validated using uniform density flat faced tablets and also by direct comparison with X-ray computed tomography. The results illustrate (1) the effect of die wall friction on density distribution by compressing round, curved faced tablets using clean and pre-lubricated tooling, (2) the evolution of density distribution during compaction for both clean and pre-lubricated die wall conditions, by imaging tablets compressed to different compaction forces, and (3) the effect of tablet image on density distribution by compressing two complex shape tablets in identical dies to the same average density using punches with different geometries. [Copyright &y& Elsevier]

Abstract: Direct compaction is a complex process that results in a density distribution inside the tablets which is often heterogeneous. Therefore, the density variations may affect the compact properties. A quantitative analysis of this phenomenon is still lacking. Recently, X-ray microtomography has been successfully used in pharmaceutical development to study qualitatively the impact of tablet shape and break-line in the density of pharmaceutical tablets. In this study, we evaluate the density profile in microcrystalline cellulose (Vivapur 12®) compacts obtained at different mean porosity (ranging from 7.7% to 33.5%) using X-ray tomography technique. First, the validity of the Beer–Lambert law is studied. Then, density calibration is performed and density maps of cylindrical tablets are obtained and visualized using a process with colour-scale calibration plot which is explained. As expected, important heterogeneity in density is observed and quantified. The higher densities in peripheral region were particularly investigated and appraised in regard to the lower densities observed in the middle of the tablet. The results also underlined that in the case of pharmaceutical tablets, it is important to differentiate the mechanical properties representative of the total volume tablet and the mechanical properties that only characterize the tablet surface like the Brinell hardness measurements. [Copyright &y& Elsevier]

Abstract: Compaction localization was observed in Diemelstadt sandstone during triaxial experiments over a broad range of effective pressures (60–165MPa). High resolution X-ray CT imaging was used to resolve the 3D the geometry of the localization features developed as tabular bands subperpendicular to the maximum compressive stress. While the raw X-ray attenuation data provide very low contrast between relatively intact and deformed areas as opposed to similar studies involving dilatancy, skewness (asymmetry of the distribution of attenuation values) and local standard deviation were demonstrated to be useful in locating and delineating the complex geometry of the compacted zones. Complementary microstructural study including damage mapping confirmed the observed features as compaction bands. Geometric attributes such as average thickness, tortuosity and orientation were evaluated from the CT data. Our study underscores the advantage of working with an image resolution of about 0.1mm in granular media, which is intermediary to synchrotron (∼1μm) and conventional medical CT (1mm) resolutions. Our methodology can be used for imaging other compactant localization features, such as compactive shear bands and diffuse compaction bands in naturally deformed samples, provided that the undeformed rock does not possess preexisting heterogeneities comparable with those expected from compaction localization. [Copyright &y& Elsevier]

Abstract: This paper investigates the axial density distribution during the single action compaction of pharmaceutical powders in rigid dies. Experimental results of the compaction of microcrystalline cellulose are compared to those predicted with an analytical model and with numerical analysis. The axial density distribution within tablets compacted at different loads are measured using a mercury porosimeter of slices from tablets. The analytical model based on the Janssen–Walker analysis coupled with the Heckel equation is applied to determine the axial density distribution. Representing the mechanical behaviour of the powder compaction with the Drucker-Prager/Cap model and by measuring the die wall friction, computation of the axial density within the tablet is also obtained by solving the boundary problem with finite element method for the loading–unloading cycle. Results of the axial density obtained with the analytical model and numerical method at end of the loading step show a qualitative agreement with the measured data. However, the measurements are better predicted with the numerical results obtained with the simulation of the loading–unloading phases. [Copyright &y& Elsevier]

The radial density distributions of fractal clusters generated in both DLCA and RLCA conditions by Monte-Carlo off-lattice cluster–cluster aggregation have been investigated. It has been computed by averaging a large number of clusters of same mass to form an average cluster, which is then considered as spherically symmetric. It is found that the radial density distribution, calculated using the mass center of the cluster as the center point, does not follow the fractal scaling, as sometimes assumed in the literature. An empirical model has been proposed to describe the dependence of the radial density distribution on the number of particles in the cluster. The obtained radial density distribution is used to compute permeability profile of the fractal cluster using several literature models, which is then applied to estimate the cluster hydrodynamic radius, , by considering the cluster as a porous permeable object and using the solution of Brinkman equations for the fluid flow inside the cluster. The so obtained values are compared to those in the literature, computed using the Kirkwood–Riseman (KR) theory. It has been found that, among the five permeability models examined, only the model proposed by Davis (Proceedings of the Institution of Mechanical Engineers Part B 1, 185) provides results in good agreement with those obtained using the KR model. Furthermore, it has been verified that the values are insensitive to the model used for the density distribution. [Copyright &y& Elsevier]

In this paper the application of X-ray computed tomography (CT) to measure the material density distribution in pharmaceutical tablets is discussed. X-ray CT is a non-destructive inspection technique which provides cross-sectional images in different planes through a component. The CT image values provide information on the local X-ray attenuation coefficients. For a particular material and X-ray energy, X-ray attenuation is approximately proportional to material density. Determination of quantitative density distributions requires consideration of non-linear instrumental effects including scatter and “beam hardening”. Density maps in tablets manufactured under controlled conditions are presented. The results are discussed with reference to the local properties of the material within the tablet and the tablet design features. [Copyright &y& Elsevier]

The distribution of voltage, temperature and titanium-compact density in the spark sintering was investigated for clarification of phenomena in the sintering stage governed by plastic deformation mechanism. The largest heat source in a punch–die-two step cylindrical compact system was in the punch with a smaller sectional area. The heat flow was mainly from the smaller punch to the compact. The sintering was mainly promoted by the mechanisms of plastic deformation and power law creep during the continuous current discharge. The effect of the plastic deformation mechanism on the final relative density of compacts was large in the press method and flanged compact used in this study. A procedure, particularly the press method, was proposed on the basis of this result for the production of homogeneously perfect sintered products. This proposed procedure could produce perfectly sintered complex compacts with their designed final dimension. [Copyright &y& Elsevier]

The size and density distributions of two commercial media, that is, Streamline particles and 6% agarose coated steel beads (6AS), in an expanded bed system has been studied with a glass column (26 mm I.D.) modified by side ports. The Streamline particles have a broad size distribution but a relatively uniform density, while the 6AS beads have both broad size and density distributions. The effect of liquid-phase flow velocity, liquid viscosity and settled bed height on the particle size and density distributions is investigated. It is found that the radial mean particle size and density of the two matrices are uniform, while axial classifications are obvious in the expanded beds. For the Streamline, the volume-weighted mean particle size decreases linearly with increasing expanded bed height. For the 6AS beads, however, the mean particle size is even in the axial direction, but the particle density decreases exponentially with the increase of bed height. Moreover, the mean particle size of the Streamline or the density of the 6AS beads is well expressed as a function of the normalized bed height (that is, the ratio of the distance from bed bottom to the expanded bed height). The liquid flow-rate, liquid viscosity and settled bed height influence the mean axial size or density distribution by affecting the expanded bed height. [Copyright &y& Elsevier]