Evolution of Anisotropy in Granular Materials: Effect of Particle Rolling and Particle Crushing

The effect of particle rolling and crushing on the evolutions of the two types of anisotropy, i.e., anisotropy of particle packing (microstructure) and anisotropy of force chains, is investigated numerically using the discrete element method. To this end, the classical fabric tensor is adopted to describe the anisotropy of microstructure, while two similar orientation tensors defined by the directions of contact forces are used to characterize the anisotropy of force chains. Numerical results show that the evolutions of anisotropy follows the same tendency as the stress–strain curve, and the anisotropy of force chains is more intense than that of the microstructure. In addition, particle rolling exerts different effect on anisotropy before and after the peak stress state, and particle crushing decreases the anisotropy of granular materials.Представлено чисельне дослідження за допомогою методу дискретних елементів впливу скочування і дроблення частинок на еволюцію анізотропій скочування частинок (мікроструктура) і силового ланцюжка. Для опису анізотропії мікроструктури використовується структурний класичний тензор, а два аналогічних тензора орієнтації, що характеризуються напрямком контактних зусиль, – для визначення анізотропії силового ланцюжка. Результати чисельного дослідження показали, що еволюція анізотропій має той же характер, що і залежність деформації від напруження, однак анізотропія силового ланцюжка є більш інтенсивною порівняно з анізотропією мікроструктури. Більш того, скочування частинок по-різному впливає на анізотропію до і після досягнення максимального значення напруження, в той час як дроблення частинок зменшує анізотропію гранульованих матеріалів.Представлено численное исследование с помощью метода дискретных элементов влияния скатывания и дробления частиц на эволюцию анизотропий скатывания частиц (микроструктура) и силовой цепочки. Для описания анизотропии микроструктуры используется структурный классический тензор, а два аналогичных тензора ориентации, характеризующихся направлением контактных усилий, – для определения анизотропии силовой цепочки. Результаты численного исследования показали, что эволюция анизотропий имеет тот же характер, что и зависимость деформации от напряжения, однако анизотропия силовой цепочки является более интенсивной по сравнению с анизотропией микроструктуры. Более того, скатывание частиц по-разному влияет на анизотропию до и после достижения максимального значения напряжения, тогда как дробление частиц уменьшает анизотропию гранулированных материалов

Fermionic Casimir effect with helix boundary condition

In this paper, we consider the fermionic Casimir effect under a new type of space-time topology using the concept of quotient topology. The relation between the new topology and that in Ref. \cite{Feng,Zhai3} is something like that between a M\"obius strip and a cylindric. We obtain the exact results of the Casimir energy and force for the massless and massive Dirac fields in the ($D+1$)-dimensional space-time. For both massless and massive cases, there is a $Z_2$ symmetry for the Casimir energy. To see the effect of the mass, we compare the result with that of the massless one and we found that the Casimir force approaches the result of the force in the massless case when the mass tends to zero and vanishes when the mass tends to infinity.Comment: 7 pages, 4 figures, published in Eur. Phys. J.

Efficiency evaluation of a novel supercapattery stack with a power electronic interface for energy storage systems

The increase of renewable energy generation seen as the only way to ensure clean and sustainable development, is under scrutiny due to its intermittent nature and an insufficient development of com-plementary technologies such as electrical energy storage. There are quite a few energy storage devices available such as super/ultracapacitors that can address the high specific power applications compared to batteries, but have quite large size for same energy installed. Batteries on the other hand have much higher specific energy but cannot accommodate that easily the requirement to deliver quickly high power. This paper reports on the evaluation of a newly developed device, the supercapattery, that is a single device in which the core material is chemically engineered carbon nanotubes that can store similar amount of energy as a battery but release it faster

Cardiorenal syndrome: emerging role of medical imaging for clinical diagnosis and management

Cardiorenal syndrome (CRS) concerns the interconnection between heart and kidneys in which the dysfunction of one organ leads to abnormalities of the other. The main clinical challenges associated with cardiorenal syndrome are the lack of tools for early diagnosis, prognosis, and evaluation of therapeutic effects. Ultrasound, computed tomography, nuclear medicine, and magnetic resonance imaging are increasingly used for clinical management of cardiovascular and renal diseases. In the last decade, rapid development of imaging techniques provides a number of promising biomarkers for functional evaluation and tissue characterization. This review summarizes the applicability as well as the future technological potential of each imaging modality in the assessment of CRS. Furthermore, opportunities for a comprehensive imaging approach for the evaluation of CRS are defined.Cardiovascular Aspects of Radiolog

Efficiency evaluation of a novel supercapattery stack with a power electronic interface for energy storage systems

The increase of renewable energy generation seen as the only way to ensure clean and sustainable development, is under scrutiny due to its intermittent nature and an insufficient development of com-plementary technologies such as electrical energy storage. There are quite a few energy storage devices available such as super/ultracapacitors that can address the high specific power applications compared to batteries, but have quite large size for same energy installed. Batteries on the other hand have much higher specific energy but cannot accommodate that easily the requirement to deliver quickly high power. This paper reports on the evaluation of a newly developed device, the supercapattery, that is a single device in which the core material is chemically engineered carbon nanotubes that can store similar amount of energy as a battery but release it faster

Ferromagnetism and giant magnetoresistance in the rare earth fullerides Eu6-xSrxC60

We have studied crystal structure, magnetism and electric transport properties of a europium fulleride Eu6C60 and its Sr-substituted compounds, Eu6-xSrxC60. They have a bcc structure, which is an isostructure of other M6C60 (M represents an alkali atom or an alkaline earth atom). Magnetic measurements revealed that magnetic moment is ascribed to the divalent europium atom with S = 7/2 spin, and a ferromagnetic transition was observed at TC = 10 - 14 K. In Eu6C60, we also confirm the ferromagnetic transition by heat capacity measurement. The striking feature in Eu6-xSrxC60} is very large negative magnetoresistance at low temperature; the resistivity ratio \rho(H = 9 T)/\rho(H = 0 T) reaches almost 10^{-3} at 1 K in Eu6C60. Such large magnetoresistance is the manifestation of a strong pi-f interaction between conduction carriers on C60 and 4f electrons of Eu.Comment: 5 pages, 4 figure

Probing the nature of the conjectured low-spin wobbling bands in atomic nuclei

The precession of an atomic nucleus can be approximately described as wobbling motion, arising from the coupling of a rotation and a harmonic vibration. Recently, a number of wobbling bands were reported at low spin, which violate the wobbling approximation that can be valid only at high spin. In the present work, we explore the nature of the reported low-spin wobbling bands. Via a new experiment including both angular correlation and linear polarization measurements, we demonstrate that one such band in 187Au is generated by dominant single-particle excitation rather than by the excitation of a wobbling phonon. Assessing the experimental proofs and discussions to assign the reported low-spin wobbling bands, we further point out that the imperfect research paradigm used previously would lead to unreliable identification of low-spin wobbling bands

Properties and Performance of Two Wide Field of View Cherenkov/Fluorescence Telescope Array Prototypes

A wide field of view Cherenkov/fluorescence telescope array is one of the main components of the Large High Altitude Air Shower Observatory project. To serve as Cherenkov and fluorescence detectors, a flexible and mobile design is adopted for easy reconfiguring of the telescope array. Two prototype telescopes have been constructed and successfully run at the site of the ARGO-YBJ experiment in Tibet. The features and performance of the telescopes are presented

Structure and properties of a novel fulleride Sm6C60

A novel fulleride Sm6C60 has been synthesized using high temperature solid state reaction. The Rietveld refinement on high resolution synchrotron X-ray powder diffraction data shows that Sm6C60 is isostructural with body-centered cubic A6C60 (A=K, Ba). Raman spectrum of Sm6C60 is similar to that of Ba6C60, and the frequencies of two Ag modes in Sm6C60 are nearly the same as that of Ba6C60, suggesting that Sm is divalent and hybridization between C60 molecules and the Sm atom could exist in Sm6C60. Resistivity measurement shows a weak T-linear behavior above 180 K, the transport at low temperature is mainly dominated by granular-metal theory.Comment: 9 pages, 3 figures, submitted to Phys. Rev. B (March 12, 1999

Polyamine plays key role in different osmotic stress responses of wheat-rye 1BL/1RS translocation lines

It is well demonstrated that wheat-rye 1BL/1RS translocated chromosome leads to some valuable novel traits such as disease resistance, high yield and functional stay-green after anthesis. To understand the physiological mechanism of 1BL/1RS translocation responsible for osmotic stress, two wheat cultivars, CN12 and CN17, carrying the translocated chromosome and MY11 without the translocated chromosome were employed in the study. During 5-day osmotic stress, fresh weight inhibition, chlorophyll content, soluble protein content, MDA concentration, antioxidant enzymes activity and free polyamines content were examined. CN12 and CN17, especially cultivar CN17, registered greater biomass and minor oxidative damage compared with their wheat parent. Meanwhile, the concentration of Spd and Spm in CN17 was significantly higher than the others. In addition, we found a positive correlation of fresh weight inhibition (FWI) and Put concentration, and a negative one with the parameters (Spd + Spm): Put ratio, indicating the importance of higher polyamine (Spd and Spm) accumulation on the adaptation to osmotic stress. Therefore, we proposed that the accumulation of higher polyamines (Spd and Spm) should play an important role on the adaptation of 1BL/1RS translocation lines to osmotic stress and might be important factors for the origin of novel traits introduced by 1BL/1RS