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Loess areas, such as the Loess Plateau, are characterized by a fragile ecological environment, high soil erosion, and frequent geological disasters due to the unique hydrological properties of loess (e.g., collapsibility and permeability). Therefore, the loess must be stabilized for use in engineering construction. Traditional stabilizers (lime, cement, and fly ash) cause environmental problems, such as soil salinization and greenhouse gas emissions. Therefore, this study investigated the effect of nanosilica on the hydrological properties of loess and the microscopic mechanism. Different nanosilica contents (0.2%, 0.4%, 0.8%, 1%, and 3%) were added to loess sample, and the particle size distribution, Atterberg limits, collapsibility, and soil water characteristics were analyzed. The results revealed the following. The addition of nanosilica changed the particle size distribution, liquid limit, plastic limit, and plasticity index of loess. After the addition of nanosilica with different contents, the loess collapsibility coefficient curve shifted downward, the soil water retention curve shifted upward, and the unsaturated permeability coefficient curve shifted downward. The pores between particles were filled, and the number of large and medium pores and the pore connectivity were lower after the nanosilica addition. The surface of the coarse particles adsorbed more fine particles, and a large number of micro-aggregates or clay aggregates were present in the pores between particles. In conclusion, the environmentally friendly material nanosilica can be used to improve the hydrological properties of loess, which is applicable to alleviating soil erosion and preventing geological disasters on the Loess Plateau. [ABSTRACT FROM AUTHOR]

Malan loess is a wind-deposited sediment that is loose and porous and has high water permeability. It has experienced many dry–wet cycles during tens of thousands of years, resulting in unique engineering properties. The unique properties of loess are closely related to its texture and microstructure formed during dry–wet cycles. This paper investigates the influence of dry–wet cycles on the microstructure of Malan loess and its formation mechanism. The results show the following. (1) In an open environment, the ion content of the loess samples decreased after the dry–wet cycles, indicating that the cementation of the loess particles had weakened and the structural strength of the loess has decreased due to the loss of cementation materials as the cycle number increased. (2) The ion content of the soil samples did not change significantly after dry–wet cycles in a closed environment. However, after several cycles, the clay and colloid particles migrated and were adsorbed around the skeleton particles, and soluble salt ions were enriched in the form of cementation, with a slight increase in structural strength. The proposed dry–wet cycle model in this paper showed that the loess structure property was weaker in an open environment and stronger in a closed environment, revealing the formation and evolution of loess structure at the microscale. The results of this study provide very important theoretical and practical engineering significance for deep understanding of the mechanical and hydraulic properties of loess and the prediction and prevention of geological disasters. [ABSTRACT FROM AUTHOR]

Most of the current methods for the synthesis of two-dimensional materials (2DMs) require temperatures not compatible with traditional back-end-of-line (BEOL) processes in semiconductor industry (450 °C). Here, we report a general BiOCl-assisted chemical vapor deposition (CVD) approach for the low-temperature synthesis of 27 ultrathin 2DMs. In particular, by mixing BiOCl with selected metal powders to produce volatile intermediates, we show that ultrathin 2DMs can be produced at 280–500 °C, which are ~200–300 °C lower than the temperatures required for salt-assisted CVD processes. In-depth characterizations and theoretical calculations reveal the low-temperature processes promoting 2D growth and the oxygen-inhibited synthetic mechanism ensuring the formation of ultrathin nonlayered 2DMs. We demonstrate that the resulting 2DMs exhibit electrical, magnetic and optoelectronic properties comparable to those of 2DMs grown at much higher temperatures. The general low-temperature preparation of ultrathin 2DMs defines a rich material platform for exploring exotic physics and facile BEOL integration in semiconductor industry. Chemical vapor deposition (CVD) is a versatile method to synthesize 2D materials, but usually requires high growth temperatures. Here, the authors report a BiOCl-assisted CVD approach to grow 2D nanosheets from 27 different layered and nonlayered materials at temperatures <500 °C, which are compatible with back-end-of-the-line industrial processes. [ABSTRACT FROM AUTHOR]

Small fused silica components with complex structure, such as hemispherical shell resonator in inertial navigation system, are the core components of the equipment in precision optics, aerospace, and other fields. Due to the hard and brittle characteristics of fused silica, these components easily form surface defects in grinding process. This restricts the improvement of equipment performance. The small ball-end permanent-magnet magnetorheological polishing can remove the surface defects of these workpieces. However, due to the high hardness of fused silica, the material removal rate in the polishing process is low. This makes it difficult to increase production and reduce costs. In this research, a method to improve the polishing efficiency by the promoting effect of water-bath heating and NaOH addition on polishing velocity and chemical reaction is proposed. The promotion mechanism is studied. It is found that adding NaOH to magnetorheological fluid can not only promote the chemical removal of fused silica by abrasive particles, but also soften the surface and subsurface of workpiece through chemical reaction to improve the mechanical removal of abrasive particles. Meanwhile, adding NaOH can reduce the zero-field viscosity of magnetorheological fluid. This can increase the polishing velocity of abrasive particles and the number of abrasive particles participating in material removal per unit time. Moreover, increasing the temperature of alkaline magnetorheological fluid by water-bath heating can not only improve the chemical reaction rate to generate more reaction product per unit time, but also further reduce the zero-field viscosity of magnetorheological fluid to increase the polishing velocity. The experimental result shows that when the magnetorheological fluid temperature is 60 °C and the pH value is 14, the material removal rate can be increased by 287%, and the polished surface roughness Sa can be reduced from 208.4 to 12.3 nm. [ABSTRACT FROM AUTHOR]

The designation of the cluster number K and the initial centroids is essential for K-modes clustering algorithm. However, most of the improved methods based on K-modes specify the K value manually and generate the initial centroids randomly, which makes the clustering algorithm significantly dependent on human-based decisions and unstable on the iteration time. To overcome this limitation, we propose a cohesive K-modes (CK-modes) algorithm to generate the cluster number K and the initial centroids automatically. Explicitly, we construct a labeled property graph based on index-free adjacency to capture both global and local cohesion of the node in the sample of the input datasets. The cohesive node calculated based on the property similarity is exploited to split the graph to a K-node tree that determines the K value, and then the initial centroids are selected from the split subtrees. Since the property graph construction and the cohesion calculation are only performed once, they account for a small amount of execution time of the clustering operation with multiple iterations, but significantly accelerate the clustering convergence. Experimental validation in both real-world and synthetic datasets shows that the CK-modes algorithm outperforms the state-of-the-art algorithms. [ABSTRACT FROM AUTHOR]

A facile heterogeneous photocatalyst system that consists of a nickel complex and cadmium sulfide (CdS), which act as the catalyst and light antenna, respectively, was developed to the efficiency photocatalytic activation and conversion of CO2. Ni(bpy)3Cl2 was firstly found to be an active material for photocatalytic CO2 reduction. Besides, promoting the photo-generated electrons transfer from CdS to CO2 through such nickel complex further enhanced the catalytic activity. 5.2 µmol of CO has been obtained in acetonitrile solution containing Ni(bpy)3Cl2 under 2 h visible-light irradiation, which is approximately sixfold more than that system without Ni(bpy)3Cl2 complex. The different amount of Ni(bpy)3Cl2 used reveals the relationship of active center and photocatalytic performance. The use of a suitable amount of Ni(bpy)3Cl2 resulting in an apparent quantum yield of 1.68% at 420 nm. Electrochemical measurement and photochemical observation suggest a possible mechanistic detail of charge carrier transfer and information of key intermediates during CO2 reduction, which broadens the perspective of reaction mechanism.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Data uncertainty are common in real-world applications and it can be caused by many factors such as imprecise measurements, network latency, outdated sources and sampling errors. When mining knowledge from these applications, data uncertainty need to be handled with caution. Otherwise, unreliable or even wrong mining results would be obtained. In this paper, we propose a rule induction algorithm, called uRule, to learn rules from uncertain data. The key problem in learning rules is to efficiently identify the optimal cut points from training data. For uncertain numerical data, we propose an optimization mechanism which merges adjacent bins that have equal classifying class distribution and prove its soundness. For the uncertain categorical data, we also propose a new method to select cut points based on possible world semantics. We then present the uRule algorithm in detail. Our experimental results show that the uRule algorithm can generate rules from uncertain numerical data with potentially higher accuracies, and the proposed optimization method is effective in the cut point selection for both certain and uncertain numerical data. Furthermore, uRule has quite stable performance when mining uncertain categorical data. [ABSTRACT FROM AUTHOR]

A new equivalent map projection called the parallels plane projection is proposed in this paper. The transverse axis of the parallels plane projection is the expansion of the equator and its vertical axis equals half the length of the central meridian. On the parallels plane projection, meridians are projected as sine curves and parallels are a series of straight, parallel lines. No distortion of length occurs along the central meridian or on any parallels of this projection. Angular distortion and the proportion of length along meridians (except the central meridian) introduced by the projection transformation increase with increasing longitude and latitude. A potential application of the parallels plane projection is that it can provide an efficient projection transformation for global discrete grid systems. [ABSTRACT FROM AUTHOR]

Vector-raster conversion is one of the classic research topics in the field of Geographical Information Systems (GIS). The algorithms commonly used in GIS are devoted to maintaining the vector polygons’ shape characteristics, but neglect the gain and loss of a polygon’s area, which is another important attribute. This paper proposes an equal-area conversion model based on an area compensation optimization principle. According to the topological relationship among polygons and boundary grids, a neighborhood compensation principle was adopted to assign the attributes of boundary grids and a global optimization algorithm was developed to minimize area distortion in the whole data set. Two experiments were designed and the results indicated that this algorithm not only guaranteed the area error is as small as possible, but also has the advantage as being adaptive to polygon shape and spatial structure. [ABSTRACT FROM AUTHOR]

Ramamritham gives three common types of constraints for the execution history of concurrent transactions. This paper extends the constraints and gives the fourth type of constraint. Then the weak commit dependency and abort dependency between transactions, because of data access conflicts, are analyzed. Based on the analysis, an optimistic commit protocol 2LC (two-Level Commit) is proposed, which is specially designed for the distributed real-time domain. It allows transactions to optimistically access the locked data in a controlled manner, which reduces the data inaccessibility and priority inversion inherent and undesirable in distributed real-time database systems. Furthermore, if the prepared transaction is aborted, the transactions in its weak commit dependency set will execute as normal according to 2LC. Extensive simulation experiments have been performed to compare the performance of 2LC with that of the base protocol, the permits reading of modified prepared-data for timeliness (PROMPT) and the deadline-driven conflict resolution (DDCR). The simulation results show that 2LC is effective in reducing the number of missed transaction deadlines. Furthermore, it is easy to be incorporated with the existing concurrency control protocols. [ABSTRACT FROM AUTHOR]

The conventional lock scheme tends to suffer from a cascade of blockings, while the optimistic concurrency control (OCC) scheme may suffer from wasting resources. To overcome these problems, some researchers have proposed a combination of OCC and lock in transaction processing. Using this method, Thomasian proposed the hybrid method for conventional distributed transaction processing, and Lam proposed the DOCC-DA protocol for distributed realtime database system based on forward validation. This paper proposes a new protocol, called Hybrid Distributed Optimistic Concurrency Control Embedded in two-Phase Commit, which is based on back validation. The new protocol makes use of access invariance and runtime information which can guarantee a rerun transaction to meet its deadline and abort the fruitless run transactions as early as possible. A series of simulation experiments have been done to investigate the performance of the new protocol. The results show that its performance is consistently better than that of other protocols. [ABSTRACT FROM AUTHOR]