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The growth behavior of stress corrosion cracking (SCC) of Alloy 600 with different cold-work levels was investigated in simulated boiling water reactors water environments. In addition, a correlation of cold-work levels, grain boundary characteristic, and the SCC growth behavior of Alloy 600 were studied. The results show that grains with high residual strain caused by cold work provide transgranular crack growth paths. The SCC growth rates of the specimens also increase with an increase in the degree of cold work and decrease remarkably after switching to the hydrogen water chemistry environment. Grain boundary character proves to be a factor more important than the localized strain concentration at the grain boundary in terms of its role in the intergranular crack growth rate of the Alloy 600 with a cold-work degree from 20% to 30%.

Numerical investigations were carried out with special attentions on the inlet and outlet behaviors of foam flow process in a homogeneous porous media with confined entrance and exit boundaries. The Stochastic Bubble Population (SBP) balance model, which usually involves two parameters of the bubble generation rate Kg and the maximum bubble density n∞ for bubble number prediction, was employed to study the dynamic foam generation and development process in porous media. With introduction the Kfp parameter to take into account the foam phase relative permeability reduction effect, the control equations of the two-phase flow process in a two-dimensional computational domain were solved with the IMPES algorithm and the inlet and outlet behavior of the foam displacement process were scrutinized based on detailed analysis of the bubble density, water phase pressure and water phase saturation distributions in porous medium. Numerical results showed a clear entrance effect of higher water saturation, lower pressure gradient and developing bubble density in the inlet region of the porous media in the transient foam displacement process, whereas the confined exit results in elevating water saturation and decreasing pressure gradient towards the outlet of the core. Parametric studies on Kg, n∞, Kfp and inlet & outlet sizes D indicate higher bubble generation rate could remarkably suppress the entrance region in the foam seepage process, while the higher maximum bubble number did not lead to obvious change of the foam flow behavior in the inlet and outlet region, although it could produce higher absolute values of bubble density and pressure drop along the core. With lower Kfp values, the strong foam flooding behavior could be properly predicted with much higher pressure drop and lower water saturation. Two dimensional numerical results at various inlet and outlet sizes clearly show the confined geometry effect on foam flow characteristics with smaller sizes corresponding to longer inlet and outlet regions. Computational domain and numerical results were validated through comparisons with corresponding experimental setup and CT measurement results. It is observed that, the numerical simulation could reproduce not only qualitatively but also quantitatively the experimentally obtained water saturation distribution and pressure drop result. It is concluded that the mechanistic stochastic bubble population model could be reasonably employed on prediction of the inlet and outlet behavior in the transient foam flow process in the homogeneous porous media.

A coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) approach is used to investigate the hydrodynamic and mechanical behavior of multi-particle, which settle and horizontally transport between two parallel plates. The particle-fluid interaction is two-way coupled, while inter-particle and particles-walls interactions are calculated based on the soft-sphere model. The Joint Roughness Coefficient (JRC) is used to represent the roughness of planar walls, and its effect on particle transport is quantitatively studied. When particles transport between two parallel smooth plates, the planar walls exert extra hydrodynamic retardation, which causes particle transport velocity to decrease with the decrease in the aperture between two plates. In contrast, when particles transport between two parallel rough plates, due to frequent interaction between particles, the mechanical interaction-induced retardation starts to work and further decreases particle transport velocity. Particle longitudinal migration is frequent because of inter-particle interaction, which hinders its transverse transport and even causes particle agglomeration in a duct during horizontal transport. In addition, the mechanical retardation is significantly dependent of particle transport regimes, and its effect gradually increases and changes to be dominant at high particle Reynold number regime.

Effective ionic/electronic percolation, especially in a thick electrode, has a decisive influence on the electrochemical properties of rechargeable batteries, such as material usefulness, electrode reversibility and cell lifespan. Using low cost and highly safe rechargeable aqueous zinc ion batteries (RAZBs) as a model, in this paper a dense electrode architecture is presented which is constructed using silver vanadium oxide@water-pillared vanadium oxide core–shell (Ag0.333V2O5@V2O5·nH2O) coaxial nanocables that maintain optimal ion/electron percolation without admixing the additional inert component. This electrochemically robust architecture is composed of a highly electronic conductive phase of silver vanadate and a highly ionic conductive phase of the water-pillared V2O5·nH2O structure, which synergistically forms a coaxial nanocable structure benefiting ion/electron contact and penetration in a thick electrode. As expected, the Ag0.333V2O5@V2O5·nH2O coaxial nanocables deliver a high reversible capacity (312.1 mA h g−1 at 0.5 A g−1), excellent rate capability (196.7 mA h g−1 at 3.0 A g−1) and stable cycling performance (261.7 mA h g−1 at 0.5 A g−1 after 100 cycles). The investigation of the electrochemical reaction kinetics reveals a combinatorial fast pseudocapacitive reaction and a diffusion controlled intercalation reaction. The lower percolation threshold of both ions and electrons should be responsible for the better electrode kinetics and the improved zinc ion storage capacity of the Ag0.333V2O5@V2O5·nH2O coaxial nanocables compared to that of pristine Ag0.333V2O5 electrodes. It is anticipated that the as-proposed strategy of constructing effective ionic/electronic percolating thick electrodes to boost the reaction kinetics can be applied to other active materials for constructing practical multivalent batteries.

Stainless steels are used as canister materials for interim storage of spent fuel. Crevice corrosion has proved to be a safety concern of 304L stainless steel spent fuel canisters, when exposed to the saline environments of coastal sites. To study the effects of chloride concentration and test duration on the crevice corrosion behavior, and the effect of relative humidity on the initiation of discrete SCC cracks, a test program was conducted on the 304L steel specimens sprayed with synthetic sea water of 3.5 wt.%. The salt-deposited specimens, wrapped up with a crevice former to form a crevice configuration, were then exposed to an environment at 45 &deg, C with a pre-set 45%, 55%, and 70% relative humidity (RH), for 400 h and 10,000 h, respectively. The surface features and crack morphology of the tested 304L stainless-steel specimens were examined by energy-dispersive spectrometry (EDS) and electron back scatter diffraction (EBSD). For the specimens deposited with a chloride concentration of 1 g/m2, no cracks were found in the corroded regions after 400-h exposure, whereas SCC cracks were observed with the specimens tested for 10,000 h at all three pre-set relative humidity. The specimens tested at the pre-set relative humidity 45% are characterized with discrete SCC cracks, but, on the other hand, those exposed to the environments of 55% and 70% relative humidity show SCC cracks of distinct features. From the results of 10,000-h tests, it is inferred that the chloride concentration threshold for SCC initiation of 304L stainless steel at 45 &deg, C is between 0.1 g/m2 and 1 g/m2.

In the dry cask storage of spent nuclear fuels, a stainless-steel canister acts as an important barrier for encapsulating spent fuels. As a result, local corrosion behavior of 304L stainless steel has become an issue of concern in the wet coastal region and salt spray environment. The test was conducted after deposition of simulated sea salt particles on the 304L stainless-steel specimen. It was first covered with a crevice former, and then kept at 45 &deg, C with a relative humidity of 45%, 55%, and 70%, respectively. The surface morphologies and electron back scatter diffraction (EBSD) analysis of the corroded region for the 304L stainless-steel specimen are presented in this paper. The goal of this work was to investigate the crevice corrosion behavior of 304L stainless steel under different chloride concentrations and relative humidity conditions. From the experimental results, a threshold relative humidity for stress corrosion cracking (SCC) initiation of 304L stainless steel was proposed.

Information technology development leads to the data explosion in many industries. In the era of big data, telecom operator stores huge amount of data, namely telecom big data. Telecom operator can employ data mining and analysis to seek the valuable information from telecom big data. In this paper, we design a novel big data assisted analysis architecture for telecom operator. The proposed architecture collects operation support system data and business support system data of telecom operator. Based on these data, the architecture draws the portrait of each user. Then, the user trajectory is analyzed. Furthermore, the proposed architecture takes the service behavior analysis. Finally, we apply the proposed big data assisted analysis architecture to the local telecom operator.

In the past thirty years, China experiences fast development in terms of economic and technology. This leads to the frequent exchange and communication among different cities. Specifically, meetings, sports, and industry exchanges at various levels are becoming more frequent and popular. Above events have significant impact on the city, hence, government/organizer should quantitatively evaluate the impact of events. Based on the various data of telecom operators, this paper proposes an insight scheme for large-scale events of the city. The proposed scheme can analyze the changes of the users scale and the business volume. In addition, this scheme also analyzes the aggregation areas of users before and after events and other characteristics. Especially, for the characteristics of external users from other cities, the proposed scheme can provide the data analysis results, in this way to support both the organizer and the government of the host city. Finally, the organizer and the government can provide good services.

Rheological properties of supercritical CO 2 (ScCO 2 ) foam fluids are essential to understand foam displacement mechanisms in the research & development of efficient CO 2 -EOR and CO 2 geological storage technologies. In this paper, a systematic laboratory study concerning non-Newtonian ScCO 2 foam flow characteristics in a straight tube was carried out under different gas-liquid ratios. Through modifying experimental pressure and temperature conditions, comparative studies on liquid phase CO 2 and gaseous CO 2 foam rheology were also carried out. The experimental results show obvious shear-thickening behavior for the scCO 2 foam (45 °C and 8.0 MPa) with flow behavior index increasing from 1.03 to 1.76 with increasing foam quality. And the apparent viscosity of scCO 2 foam could reach up to 140 times of the single-phase water. The liquid phase CO 2 foam (25 °C and 8.0 MPa) also exhibits clearly the shear-thickening characteristics with flow behavior index ranging from 1.56 to 1.88. The gaseous CO 2 foam, on the other hand, behaves in a shear-thinning or pseudo-plastic manner with flow behavior index of 0.70 2 and liquid CO 2 bulk foam, which mainly contributes to the shear thickening behavior for ScCO 2 and liquid CO 2 foam fluid.

The hot cracking behavior of Ni-based Alloy 52M weld overlay with respective SS 307Si and SS 308L buffer layers was investigated. The dilution level of SS 307Si buffer layer is a little higher than that of SS 308L. However, the hot crack length of overlay with SS 307Si buffer layer is shorter and the SS 307Si layer has higher mechanical properties than that of SS 308L layer. As observed by SEM and EBSD, ferrites precipitated in SS 307Si buffer layer are in vermicular skeletons dotted with lathy precipitates, which have a little higher local stain than that of SS 308L weld. However, Alloy 52M weld around SS 307Si fusion boundary has a lower degree of local distortion. The results generalize that the SS 307Si buffer layer is marginally better for reducing hot cracking susceptibility, owing to its lower local stain and slightly higher mechanical strength.

In this study, Zn/15Al, Al and Inconel 625 coatings were applied on low carbon steel substrates by twin wire arc spray process as a corrosion and wear protection barrier against the marine atmosphere. The wear behavior of the coating layer was characterized by a pin-on-disk apparatus at a combination condition of three normal loads and two sliding speeds. The wear tests were conducted in a 3.5 wt.% NaCl solution to evaluate the wear resistance of the coatings in a corrosive environment. The results suggested that the Inconel 625 coating had a better wear resistance in a 3.5 wt.% NaCl solution as compared to the ZnAl and Al specimens. Zn/15Al coatings revealed less wear resistant in a corrosive environment due to the rupture of the oxide film on the coating surface during wear. For the sacrificial protection coatings of Zn/15Al and Al, the characteristics of surface oxide film play a vital role in the wear resistance of the coating materials.

The operation condition of wireless system directly impacts both the system performance and the quality of experience (QoE). On the basis of telecom operator data, this paper designs a comprehensive operation and revenue analysis (CORA) algorithm for LTE/5G wireless system. The objective of the proposed CORA algorithm is to analyze and evaluate both the operation state and the revenue of base station (BS) in the wireless system. The designed CORA algorithm is applied in the realistic 4G wireless system. The CORA algorithm can assist telecom operator to effectively analyze and evaluate the BS comprehensive state of operation and revenue.

The next-generation (5G) wireless networks have been evolving into very complex systems due to the diversified service requirements, heterogeneity in applications, devices, and networks. The network operators need to make the best use of the available resources, for example, power, spectrum, infrastructures, as well as data. Large amounts of data, generated from the network and the subscribers, would dramatically help make the system smart and efficient by advanced exploiting. Besides, the synergy of the 5G and the big data would create new services, which promotes a faster digital transformation of the vertical industries. In this paper, we first present the evolution of the big data in the uprising 5G era. Then, an overview of the interplay between the 5G and the big data is provided. Following gives the discussion on challenges and trends of the development of 5G and big data. To further illustrate the benefits, data-driven services are studied.

With the development of information technology, we are living in a society of data explosion. In precise marketing field, how to classify the population and identify the target users has attracted much concern. Based on telecom big data, this paper has proposed a precise user classification scheme using decision tree. According to the classification result, potential users can be identified and focused on, which can dramatically improve the marketing efficiency and effectiveness with limited marketing expense.

An interesting phenomenon, I D /I G intensity ratios between D mode and G mode increase around micro-wells, is observed in defective graphene sensors. A modified phenomenological model depicting the relation between I D /I G and the built-in stress is developed to reveal the physical mechanism of the above phenomenon. It is demonstrated that the initial defects in graphene gas sensors arising from fabrication processes can further propagate under the built-in tension resulting in increasing the defect density. The underlying mechanism is that the built-in stress provides the energy for the defect propagation of stretched graphene. The work could be helpful for applications of defective graphene-based devices.

This study investigated the effects of dendrite axis and fusion boundary (FB) on the stress corrosion cracking (SCC) of 308 L/304 L welds by using an alternating current potential drop (ACPD) technique to measure the SCC growth rates in a simulated boiling water reactor environment. The results show that the ferrite/austenite interfaces are more susceptible to SCC in the SS 308 L welds. Furthermore, the angle between the applied load and the dendrite axis affects the SCC growth rate, and as this angle approached 90°, the SCC crack growth rate increases. The SCC cracks in the heat affected zone (HAZ) are mainly intergranular and some cracks propagate transgranularly. Furthermore, the primary crack in the HAZ propagates along the FB; when reaching FB, some secondary cracks are arrested at the FB. The residual strain caused by weld shrinkage is the crucial factor for the increase in SCC susceptibility in HAZ.

Employee turnover indicates the staff decides to leave the company. Along with the fast development of economic and industries, employee turnover phenomenon becomes popular gradually in recent years. On one hand, the staff decides to leave the company due to various reasons. On the other hand, staff retention and job stability impact the normal operation of the company. Companies need to grasp the major factors of employee turnover, and then take relevant measures to deal with this problem. This paper employs machine learning technique to sort out the characteristics of employee turnover. Furthermore, we adopt GBDT algorithm and LR algorithm to fit the characteristic model which influences employee turnover. Finally, this paper implements the employee turnover prediction in realistic companies, which provides an effective reference for companies to reduce the turnover rate of employees.

With the popularity of 4G mobile networks, mobile video service becomes the key service in the 4G era. In order to improve users’ awareness and increase the network optimization efficiency, it is important to establish a scientific and accurate model to evaluate the video service from the user’s perception. In this paper, we focus on the video streaming traffic and propose a modelling approach to evaluate the video service performance. The essential characteristics of video traffic are taken into account. Based on the hierarchical clustering and the Pearson correlation coefficient method, key factors of video service perception are determined. Furthermore, the threshold values of key factors are obtained through extensive user surveys and simulation tests. The results of the application in the realistic network demonstrate the effectiveness of the proposed model. In addition, results show the proposed model enables the telecom operator to evaluate the video service quality of each user or user group, which helps improve the network optimization efficiency.

In the traditional marketing activities, the key to success is to identify the potential needs of target users. An excellent recommendation system can help improve the effectiveness and efficiency of the precision marketing. In this paper, an Apriori algorithm based recommendation scheme is proposed, and it’s then applied to the mobile APP marketing field. The scheme is realized through two processes, the frequent item sets generation process and the strong association rule generation process. Experimental results have shown that the scheme can achieve high advertising arrival rate, as well as superior exposure and click conversion rate. The effectiveness of the mobile APP product promotion has been improved dramatically.

Effective base station (BS) evaluation can assist telecom operators to find problematic cells and optimize the system performance. This paper proposes a data mining based joint BS evaluation (JBSE) algorithm in LTE cellular systems. Initially, the JBSE algorithm considers four key factors, including the cell energy consumption, the cell revenue, the cells distribution induced interference, the high BS induced cross-boundary coverage. Then, the expert judgement matrix is employed to rank the level of each factor. Finally, the JBSE algorithm evaluates each cell comprehensively. The JBSE algorithm is used in the LTE systems evaluation of a city in China. It can find problematic cells effectively.

The mobile advertising industry in China has developed rapidly in recent years. Many companies and brands tend to employ mobile advertising in order to reach the target customers accurately. However, the conversion rates associated with the advertising campaigns are usually quite low due to the low quality of the datasets and impropriate predictive model. In this paper, we propose a novel mobile advertising system architecture based on telecom big data analytics. The defined multi-dimensional user portrait is introduced for user label oriented ad display strategy or as the basic database for the further user classification algorithm. We also adopt the widely used logistic regression algorithm in this paper to improve the target accuracy. The result of use case, which is calculated from the real-time collected cellular network data, also shows the superior performance of the proposed mobile advertising system.

Traffic offloading is a widely used technique to address the unbalanced traffic distribution between pico cells and macro cells in heterogeneous cellular networks. However, the shifted users may result in the macro cell receiving large traffic from multiple pico cells and then becoming heavily loaded. This phenomenon is called the exacerbation problem in this paper. In order to address this problem and balance load effectively, this paper proposes a self-optimised joint traffic offloading (JTO) scheme. The JTO scheme jointly employs two traffic offloading techniques, including cell biasing technique to offload traffic between pico cell and macro cell, and mobility load balancing among macro cells. Simulation results show the JTO scheme can effectively deal with the cell exacerbation problem, in terms of handover failure and call dropping. The JTO scheme can also reduce the call blocking probability.

Telecom big data implies abundant user information. In this paper, it employs the telecom data and proposes a user clustering and influence power ranking scheme. The scheme is implemented through three stages, i.e. the user portrait analysis stage, the user clustering analysis stage and the ranking stage of user influence power. Experimental results have shown that, marketing promotion effectiveness based on this scheme has been improved significantly, while the advertising costs are also considerably reduced.

The transport of proppant-fracturing fluid mixture in a fracturing pipe can significantly affect the final proppant placement in a hydraulic fracture in horizontal well fracturing. To improve the understanding of the hydrodynamic performance of proppants in a curving fracturing pipe, a modified two-layer transport model was proposed by taking the viscoelastic properties of carrier fluid into consideration. Fluid temperature was determined by an energy equation in order to accurately characterize its rheological properties, and the Chang–Darby model was used to represent the viscosity-shear rate relationship. The flow pattern of particle-fluid mixture in a curving fracturing pipe was investigated, the effects of particle and fluid properties and injection parameters were analyzed, and a flow pattern map was established. Three transport stages are observed: (1) particles keep suspended in the carrier fluid at small inclined angle; (2) a small number of particles settle and accumulate on pipe bottom to form a particle bed load flow at intermediate inclined angle; (3) numerous particles settle out of carrier fluid and the particle bed quickly develops in an approximate horizontal pipe. The transition processes between different stages were observed, and the transition velocity from particle bed load flow to full suspension flow increases with the increase in inclined angle. However, an inverse transition phenomenon occurs at intermediate inclined angle, where the full suspension flow inversely turns into particle bed load flow with the increase in injected velocity.