Constructing interpretable principal curve using Neural ODEs

The study of high dimensional data sets often rely on their low dimensional projections that preserve the local geometry of the original space. While numerous methods have been developed to summarize this space as variations of tree-like structures, they are usually non-parametric and "static" in nature. As data may come from systems that are dynamical such as a differentiating cell, a static, non-parametric characterization of the space may not be the most appropriate. Here, we developed a framework, the principal flow, that is capable of characterizing the space in a dynamical manner. The principal flow, defined using neural ODEs, directs motion of a particle through the space, where the trajectory of the particle resembles the principal curve of the dataset. We illustrate that our framework can be used to characterize shapes of various complexities, and is flexible to incorporate summaries of relaxation dynamics

Paste Backfill Corrosion Mechanisms in Chloride and Sulfate Environments

To study paste backfill corrosion mechanisms in chloride and sulfate environments, we studied the effect of chloride and sulfate on the strength of paste backfill after 7, 14, 28, and 40 days. The chloride solutions and sulfate solutions in concentrations are 0 g/L, 0.5 g/L, 1.5 g/L, 4.5 g/L, or 15 g/L. The obtained specimens were analyzed by performing uniaxial compressive strength tests, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results show that chloride and sulfate significantly increased the uniaxial compressive strength of the specimen at a very fast speed in the early stage of the test, and the original structure of the specimen was destroyed and its uniaxial compressive strength decreased with the gradual corrosion. The reason for this characteristic is because the chloride reacts with the paste backfill to form calcium chloroamine hydrate (Ca4Al2O6Cl2·10H2O), and the sulfate reacts with the paste backfill to form dihydrate gypsum (CaSO4·2H2O), mirabilite, and ettringite. In the early stage, these substances can fill the pores to improve the compressive strength, and then expand to damage the structure of the backfill and reduce its compressive strength. In addition, sulfate can enhance the decomposition of C-S-H, which results in a faster destruction of specimens than in chloride environments

Enhanced axial mixing of rotating drums with alternately arranged baffles

Traditional rotating drums are a popular type of tumbling mixer; however, they generally suffer from poor axial mixing with granular materials. To overcome this weakness, a system of alternately arranged baffles is presented, and its effect on particle mixing is numerically assessed using a GPU-based discrete element method. It is found that this arrangement of baffles displays better axial mixing performance than drums with (or without) traditional baffles, and that maximum mixing efficiency can be obtained through a suitable choice of baffle dimension and number. Essentially, this novel arrangement promotes the bulk movement of particles in the axial direction because of the combined radial scattering and axial guiding effects of the baffles. Together with the enhanced dispersive mixing, axial convective mixing serves to increase the axial mixing efficiency. Moreover, it is found that alternately arranged baffles produce good performance in various granular systems of rotating drums. Thus, the proposed system is a promising approach for industrial applications in more complicated mixers. (C) 2015 Elsevier B.V. All rights reserved

Extended Gersgorin Theorem-Based Parameter Feasible Domain to Prevent Harmonic Resonance in Power Grid

Harmonic resonance may cause abnormal operation and even damage of power facilities, further threatening normal and safe operation of power systems. For renewable energy generations, controlled loads and parallel reactive power compensating equipment, their operating statuses can vary frequently. Therefore, the parameters of equivalent fundamental and harmonic admittance/impedance of these components exist in uncertainty, which will change the elements and eigenvalues of harmonic network admittance matrix. Consequently, harmonic resonance in power grid is becoming increasingly more complex. Hence, intense research about prevention and suppression of harmonic resonance, particularly the parameter feasible domain (PFD) which can keep away from harmonic resonance, are needed. For rapid online evaluation of PFD, a novel method without time-consuming pointwise precise eigenvalue computations is proposed. By analyzing the singularity of harmonic network admittance matrix, the explicit sufficient condition that the matrix elements should meet to prevent harmonic resonance is derived by the extended Gersgorin theorem. Further, via the non-uniqueness of similar transformation matrix (STM), a strategy to determine the appropriate STM is proposed to minimize the conservation of the obtained PFD. Eventually, the availability and advantages in computation efficiency and conservation of the method, are demonstrated through four different scale benchmarks

Numerical analysis of enhanced mixing in a Gallay tote blender

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Numerical analysis of enhanced mixing in a Gallay tote blender

The mixing performance of a multi-bladed baffle inserted into a traditional Gallay tote blender is explored by graphic processing unit-based discrete element method software. The mixing patterns and rates are investigated for a binary mixture, represented by two different colors, under several loading profiles. The baffle effectively enhances the convective mixing both in the axial and radial directions, because of the disturbance it causes to the initial flowing layer and solid-body zone, compared with a blender without a baffle. The axial mixing rate is affected by the gap between the baffle and the wall on the left and right sides, and an optimal blade length corresponds to the maximum mixing rate. However, the radial mixing rate increases with the blade length almost monotonically. (C) 2016 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.</p

Dominoes with interlocking consequences triggered by zinc: involvement of microelement-stimulated MSC-derived exosomes in senile osteogenesis and osteoclast dialogue

Abstract As societal aging intensifies, senile osteoporosis has become a global public health concern. Bone microdamage is mainly caused by processes such as enhancing osteoclast activity or reducing bone formation by osteoblast-lineage cells. Compared with young individuals, extracellular vesicles derived from senescent bone marrow mesenchymal stem cells(BMSCs) increase the transient differentiation of bone marrow monocytes (BMMs) to osteoclasts, ultimately leading to osteoporosis and metal implant failure. To address this daunting problem, an exosome-targeted orthopedic implant composed of a nutrient coating was developed. A high-zinc atmosphere used as a local microenvironmental cue not only could inhibit the bone resorption by inhibiting osteoclasts but also could induce the reprogramming of senile osteogenesis and osteoclast dialogue by exosome modification. Bidirectional regulation of intercellular communication via cargoes, including microRNAs carried by exosomes, was detected. Loss- and gain-of-function experiments demonstrated that the key regulator miR-146b-5p regulates the protein kinase B/mammalian target of rapamycin pathway by targeting the catalytic subunit gene of PI3K–PIK3CB. In vivo evaluation using a naturally-aged osteoporotic rat femoral defect model further confirmed that a nutrient coating substantially augments cancellous bone remodeling and osseointegration by regulating local BMMs differentiation. Altogether, this study not only reveals the close link between senescent stem cell communication and age-related osteoporosis but also provides a novel orthopedic implant for elderly patients with exosome modulation capability

Study of micro-mesoscopic creep damage on mudstone based on stress corrosion model

To study the creep minor damage evolution process and creep damage mechanism of mudstone, this paper establishes a numerical model of a two-media triple cementation particle flow procedure of mudstone, reproduces the tender damage destruction process of mudstone under creep based on a parallel bonded stress corrosion model, and explores the macroscopic creep characteristics and minor damage mechanism of mudstone specimens under different stress levels and surrounding pressure conditions. The results show that the intrinsic driving force for creep damage in mudstone is the micro-tensile force generated between non-homogeneous particles of mudstone, and the inter-particle cementation is continuously damaged and deteriorated with increasing time; the stable creep rate of mudstone specimens increases with increasing stress level and decreases with increasing surrounding pressure; high-stress levels diffuse microscopic damage in mudstone by increasing the magnitude of inter-particle microtension and the number of particles generating microtension, manifesting as multiple extensions of microcracks; the enclosing pressure dramatically reduces the creep characteristics by limiting the development of inter-particle micro-tensile forces; the microcrack distribution is more uniform and dispersed under the enclosing pressure conditions. The amount of mutual slip between particles increases