The Geometrical Structure of Disordered Sphere Packings

The three dimensional structure of large packings of monosized spheres with volume fractions ranging between 0.58 and 0.64 has been studied with X-ray Computed Tomography. We search for signatures of organization, we classify local arrangements and we explore the effects of local geometrical constrains on the global packing. This study is the largest and the most accurate empirical analysis of disordered packings at the grain-scale to date with over 140,000 sphere coordinates mapped. We discuss topological and geometrical ways to characterize and classify these systems, and discuss implications that local geometry can have on the mechanisms of formation of these amorphous structures.Comment: 15 pages; 16 figure

Investigating the Geometrical Structure of Disordered Sphere Packings

Bead packs of up to 150,000 mono-sized spheres with packing densities ranging from 0.58 to 0.64 have been studied by means of X-ray Computed Tomography. These studies represent the largest and the most accurate description of the structure of disordered packings at the grain-scale ever attempted. We investigate the geometrical structure of such packings looking for signatures of disorder. We discuss ways to characterize and classify these systems and the implications that local geometry can have on densification dynamics.Comment: 3 figures, 9 page

Crystallisation in a granular material

The athermal and dissipative nature of packings of grains is still challenging our understanding of their compaction as well as their crystallisation. For instance, some beads poured in a container get jammed in random disordered con gurations, which cannot be denser than 64%, the random closed packing (RCP) limit. Remarkably it has been suggested that the RCP bound is saturated with dense patterns of beads aggregated into polytetrahedral structures. Yet when a suitable vibration is applied, a packing of beads might start to order and some regular patterns appear. We present new experiments on the crystallisation of the packing of beads. By extending tapping techniques, we have obtained packings with volume fractions φ ranging from the RCP to the crystal (φ = 0.74). Computing tomography has been used to scan the internal structure of large packings (≈200,000 beads). Voronoi and Delaunay space partitions on the grain centres were performed to characterise the structural rearrangements during the crystallisation. This allows us to describe statistical properties of the local volume uctuations and the evolution of the densest patterns of beads. In terms of statistical description, a parameter based on the volume uctuations discloses different regimes during the transition. In terms of geometry, we con rm that polytetrahedral dense clusters are ubiquitous at the RCP. We describe some intrinsic features of these clusters such as rings of tetrahedra and show how they disappear as the crystal grows. This experiment enlightens how an athermal system jammed in a complex frustrated con guration is gradually converted into a periodic crystal

Local and Global relations between the number of contacts and density in monodisperse sphere packs

The topological structure resulting from the network of contacts between grains (\emph{contact network}) is studied for large samples of monosized spheres with densities (fraction of volume occupied by the spheres) ranging from 0.59 to 0.64. We retrieve the coordinates of each bead in the pack and we calculate the average coordination number by using three different methods. We show that, in the range of density investigated, the coordination number is larger than 4 and it increases with the packing fraction. At local level we also observe a positive correlation between local packing fraction and number of neighbors. We discover a dependence between the local densities of configurations with few neighbors in contact and the global sample-denities. This might indicate that local configurations with small number of neighbors are able to deform plastically when the sample is compactifying. PACS: 45.70.-n, Granular Systems; 45.70.Cc, Static sandpiles; Granular Compaction.Comment: 10 pages, 6 figure

Determination the values of employees based on Allport value system theory (Case study: Shahrekord University of Medical Sciences)

زمینه و هدف: ارزش های نهادینه شده زیر ساخت تحقق آرمان ها و اهداف سازمان می باشند. با توجه به وجود تفات های مختلف در بافت نیروهای دانشگاه های علوم پزشکی و رسالت آنها در تولید علم و درمان بیماری ها، این مطالعه با هدف استفاده از الگوی سیستم ارزشی آلپورت در شناخت ارزش های کارکنان دانشگاه علوم پزشکی شهرکرد برای حل برخی از مشکلات آن اجرا شده است. روش بررسی: این مطالعه توصیفی تحلیلی در پائیز 1391 در دانشگاه علوم پزشکی شهرکرد با جامعه آماری 6891 نفر و تعداد نمونه 385 نفر صورت گرفت. پس از تعیین حجم نمونه با استفاده از فرمول کوکران، از روش نمونه گیری تصادفی دو مرحله ای جهت تعیین حجم نمونه در هر واحد استفاده شد. از پرسشنامه ای شامل 36 سوال که بر اساس محتویات منابع شاخص های تحقیق تهیه شده بود، جهت جمع آوری داده ها استفاده گردید. داده ها با استفاده از آزمون های آماری تی و فریدمن در نرم افزار SPSS مورد تجزیه و تحلیل قرار گرفتند. یافته ها: مهمترین ارزش از دیدگاه کارکنان دانشگاه علوم پزشکی شهرکرد، ارزش اجتماعی با 86/23 مقبولیت و کمترین اهمیت مربوط به ارزش اقتصادی با 76/8 مقبولیت تعیین شد. همچنین در طبقه بندی جامعه آماری به چهار گروه، ارزش اجتماعی به عنوان ارزش برتر (27/22 کارکنان) در گروه کارکنان مراکز ستادی تعیین شد و کمترین اهمیت (08/10 کارکنان) به ارزش زیبایی شناختی تعلق گرفت. نتیجه گیری: با توجه به نتایج این مطالعه، ارزش اجتماعی مهمترین ارزش در بین کارکنان دانشگاه علوم پزشکی شهرکرد شناخته شد؛ لذا مدیران دانشگاه بایستی ضمن توجه به این مهم، در تصمیم گیری های خود، موضوع اقبال عمومی کارکنان به این ارزش را مدنظر داشته باشند

FCS-MBFLEACH: Designing an Energy-Aware Fault Detection System for Mobile Wireless Sensor Networks

Wireless sensor networks (WSNs) include large-scale sensor nodes that are densely distributed over a geographical region that is completely randomized for monitoring, identifying, and analyzing physical events. The crucial challenge in wireless sensor networks is the very high dependence of the sensor nodes on limited battery power to exchange information wirelessly as well as the non-rechargeable battery of the wireless sensor nodes, which makes the management and monitoring of these nodes in terms of abnormal changes very difficult. These anomalies appear under faults, including hardware, software, anomalies, and attacks by raiders, all of which affect the comprehensiveness of the data collected by wireless sensor networks. Hence, a crucial contraption should be taken to detect the early faults in the network, despite the limitations of the sensor nodes. Machine learning methods include solutions that can be used to detect the sensor node faults in the network. The purpose of this study is to use several classification methods to compute the fault detection accuracy with different densities under two scenarios in regions of interest such as MB-FLEACH, one-class support vector machine (SVM), fuzzy one-class, or a combination of SVM and FCS-MBFLEACH methods. It should be noted that in the study so far, no super cluster head (SCH) selection has been performed to detect node faults in the network. The simulation outcomes demonstrate that the FCS-MBFLEACH method has the best performance in terms of the accuracy of fault detection, false-positive rate (FPR), average remaining energy, and network lifetime compared to other classification methods

Experimental investigation of the mechanical stiffness of periodic framework-patterned elastomers

Recent advances in the cataloguing of three-dimensional nets mean a systematic search for framework structures with specific properties is now feasible. Theoretical arguments about the elastic deformation of frameworks suggest characteristics of mechanically isotropic networks. We explore these concepts on both isotropic and anisotropic networks by manufacturing porous elastomers with three different periodic net geometries. The blocks of patterned elastomers are subjected to a range of mechanical tests to determine the dependence of elastic moduli on geometric and topological parameters. We report results from axial compression experiments, three-dimensional X-ray computed tomography imaging and image-based finite-element simulations of elastic properties of framework-patterned elastomers

Measuring intergranular force in granular media

A new method is proposed to measure intergranular forces in granular geomaterial from time-lapsehigh-resolution X-ray computed tomographyimaging using a grain trackingapproachand discrete element metho

Chemoimmunotherapy Drugs with Antiviral Activity to Treat Patients with Lung Cancer and COVID-19; a Narrative Review

Every year lung cancer is a cause of high morbidity and mortality in the human population. However, since 31 December 2019, the coronavirus disease 2019 [COVID-19] had importantly affected various degrees of pulmonary regions. Therefore, patients with lung cancer must be the priority group for COVID-19 prevention, treatment, and vaccination during the COVID-19 pandemic. Until now, clinicians and patients know that most individuals with respiratory distress and/or those with a weakened immune system are more susceptible to COVID-19, however, the associations with lung cancer remain unclear. Here, we present the combination of common chemotherapeutic drugs with a historical antiviral activity that may be too immunosuppressive to eliminate COVID-19-infected cells in patients with lung cancer. This review will help understand the preferred chemoimmunotherapy drugs for severe forms of COVID-19 [SARS-CoV-2] in these patients