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We apply a Peak Shrinking and Interpolating (PSI) scheme to improve the Peak-to-Pverage Power Ratio (PAPR) performance in Multiple Intermediate-Frequency-over-Fiber (M-IFoF) based mobile fronthaul. The key idea is to detect the high peaks of the signal and shrink them, and then the shrunk peak values are interpolated into the original signal to reduce the PAPR. We also compare the PSI technique with the previous Tone-Reservation (TR) technique and Phase Pre-Distortion (PDP) technique in both PAPR reduction effect and computational complexity. The simulation results indicate that the PSI scheme can reduce the PAPR by more than 4.3 ​dB at 0.1% CCDF, which outperforms the two previous schemes with lower computational complexity. Furthermore, we find that the altering of the M-IFoF system parameters has little effect on the performance of the PSI technique.

Data deduplication technique has been widely adopted by commercial cloud storage providers, which is important in coping with the explosive growth of data. To further protect the security of users' sensitive data in the outsourced storage mode, many secure data deduplication schemes have been designed and applied in various scenarios. Among these schemes, secure and efficient re-encryption for encrypted data deduplication attracted the attention of many scholars, and many solutions have been designed to support dynamic ownership management. In this paper, we focus on the re-encryption deduplication storage system and show that the recently designed lightweight rekeying-aware encrypted deduplication scheme is vulnerable to the stub-reserved attack. Furthermore, we propose a secure data deduplication scheme with efficient re-encryption based on the convergent all-or-nothing-transform (CAONT) and randomly sampled bits from the Bloom filter. Due to the property of hash function, our scheme can resist the stub-reserved attack and guarantee the data privacy of data owners' sensitive data. Moreover, instead of re-encrypting the entire package, data owners are only required to re-encrypt a small part of it through the CAONT, thereby effectively reducing the computation overhead. Finally, security analysis and experimental results show that our scheme is secure and efficient in re-encryption.

As a key part of elliptical vibration cutting (EVC) technology, a two-dimensional ultrasonic elliptical vibration cutting (UEVC) device has become a prevalent area of importance and research interest. This paper dissects through the conventional structural design and creatively proposes the UEVC device with flexible guided wave propagation. The device resolves the problems of poor coupling efficiency of two-way excitation signal, complex structure design, non-orthogonal, and the difficulty in controlling the ellipse trajectories of the tool tip. It has been confirmed that a flexible guided wave exhibits an effective unidirectional propagation and lateral load decoupling ability via establishing its system dynamic response and frequency impedance characteristics. Here, we explain the coupling mechanism of the two-way flexible guided wave in the UEVC device. Results suggested that the experimental measurement of the impedance for the cutting device and the individual transducer shows that the cutting device with the transducer and the tool bar connected by the flexible guided wave has a lower impedance increase ratio compared to the individual transducer, and hardly influence the tool bar mode of the cutting device. At the same time, the tool tip trajectory of the cutting device having a phase difference of 90° showed a satisfactory “elliptical” shape, while the microstructure processed by the tool tip ellipse trajectory with a phase difference of 60° reached a burr-free state. Theoretical and experimental findings reveal that the flexible guided waves exhibit excellent weak coupling characteristics in the non-transmitting direction. This is convenient to the independent, orthogonal and stable propagation of signals in the two directions. Based on flexible guided wave propagation technology, our findings provide theoretical foundation and application value for the design of a two-dimensional UEVC device.

Detail-and-geometry richness is essential to bas-relief modelling. However, existing image-based and model-based bas-relief modelling techniques commonly suffer from detail monotony or geometry loss. In this paper, we introduce a new bas-relief modelling framework for detail abundance with visual attention based mask generation and geometry preservation, which benefits from our two key contributions. For detail richness, we propose a novel semantic neural network of normal transfer to enrich the texture styles on bas-reliefs. For geometry preservation, we introduce a normal decomposition scheme based on Domain Transfer Recursive Filter (DTRF). Experimental results demonstrate that our approach is advantageous on producing bas-relief modellings with both fine details and geometry preservation.

In this article, we propose a novel waveform with low cyclic prefix (CP) overhead for narrow-band Internet-of-things (NB-IoT) systems. Compared with the classical orthogonal frequency-division multiplexing (OFDM), the proposed waveform employs the concept of symbol repetition on multiple successive OFDM symbols (SR-OFDMs) and only one CP is occupied by multiple SR-OFDM symbols; hence, the CP overhead is reduced significantly, improving the spectral and energy efficiencies in NB-IoT systems. It is proved that the proposed SR-OFDM can effectively fight against the multipath fading channels by a simple single-tap equalization, avoiding the mutual interference among symbols. In addition, it is shown that the proposed SR-OFDM and classical OFDM have the same size of the inverse discrete Fourier transform (IDFT) at the transmitter, which indicates the same subcarrier spacing. Especially, it is demonstrated that the signals of multiple symbols are separated at the receiver, and the demodulation of each symbol can be performed independently, which is helpful to reduce the complexity of symbol demodulation. To evaluate the proposed SR-OFDM, simulations have been done by considering the Stanford university interim (SUI) channels, which have large channel delay spread and exhibit high frequency selectivity.

In this study, the anti-penetration performance of polyurea/ASTM1405-steel composite plate subjected to high velocity projectile was analyzed. Two kinds of modified polyurea material (AMMT-053 and AMMT-055) were selected and a ballistic impact testing system including speed measuring target system and high-speed camera was designed. This experiment was conducted with a rifle and 5.8 mm projectile to explore the effects by the polyurea coating thickness, the polyurea coating position and the glass-fiber cloth on the anti-penetration performance of polyurea/ASTM1405-steel composite plate. The result showed that the effects of polyurea coating position were different between two types of polyurea, and that the effects of glass-fiber position were disparate between two types of polyurea as well. For AMMT-053 polyurea material, it was better to be on front face than on rear face; whereas for AMMT-055 polyurea, it was better to be on rear surface although the difference was very subtle. Additionally, formulas had been given to describe the relationship between the effectiveness of polyurea and the thickness of polyurea coating. In general, AMMT-055 had better anti-penetration performance than AMMT-053. Furthermore, five typical damage modes including self-healing, crack, local bulge, spallation and local fragmentation were defined and the failure mechanism was analyzed with the results of SHPB test. Additionally, the bonding strength played an important role in the anti-penetration performance of polyurea/steel composite plate.

Aiming at the privacy protection of lightweight nodes based on Bloom filters in blockchain, this paper proposes a new privacy protection method. Considering the superimposition effect of query information, node and Bloom filter are regarded as the two parties of the game. A privacy protection mechanism based on the mixed strategy Nash equilibrium is proposed to judge the information query. On this basis, a Bloom filter privacy protection algorithm is proposed when the probability of information query and privacy, not being leaked, is less than the node privacy protection. It is based on variable factor disturbance, adjusting the number of bits’ set to 1 in the Bloom filter to improve the privacy protection performance in different scenarios. The experiment uses Bitcoin transaction data from 2009 to 2019 as the test data to verify the effectiveness, reliability, and superiority of the method.

With the maturity of the most advanced technology and virtual reality, the application of digital media technology in various fields has become more and more extensive. Digital media technology has greatly promoted the development of all classes of society. Therefore, how to develop digital media technology applications has become a major issue. This article aims to study the digital media application technology of mobile terminals based on edge computing and virtual reality. In this paper, we use edge computing and virtual reality methods to study the digital media application technology of mobile terminals. We used the SD-CEN architecture and FWA in edge computing to conduct simulation experiments and compared the delay time performance of the FWA with that of the PSO-CO algorithm, WRR algorithm, and Pick-KX algorithm. The results of this paper show that it can effectively reduce the response delay of real-time face recognition services and improve user experience. Compared with the traditional cloud computing architecture and a single MEC device, the SD-CEN network architecture based on FWA strategy has more advantages. The latency of the FWA is increased by 61%, 46%, and 17%, respectively, compared with that of the WRR, Pick-KX, and PSO-CO algorithms.

By virtue of their high uniformity and stability, metal oxide-based surface-enhanced Raman spectroscopy (SERS) substrates have attracted enormous attention for molecular trace detection. However, strategies for further enhancing the SERS sensitivity are still desired. Herein, MoOx/WOx nano-heterojunctions are constructed by mixing MoOx and WOx together (MoOx/WOx hybrid) with diverse weight ratios. Using a 532 nm laser as the excitation source and R6G as the Raman reporter, it is shown that the Raman signal intensity (for the peak @ 1360 cm-1) obtained on the optimal MoOx/WOx hybrid (MoOx/WOx = 1:1/3) is twice that observed on a pure MoOx or WOx substrate. Moreover, a limit of detection of 10-8 M and an enhancement factor of 108 are achieved. In the SERS enhancement mechanism investigation, it is revealed that MoOx and WOx form a staggered band structure. During the SERS measurement, electron-hole pairs are generated in the nano-heterojunction using the incident laser. They are then separated by the built-in potential with the electrons moving toward WOx. The accumulated electrons on WOx are further transferred to the R6G molecules through the coupling of orbitals. Consequently, the molecular polarizability is amplified, and SERS performance is enhanced. The abovementioned explanation is supported by the evidence that the contribution of the chemical enhancement mechanism in the optimal MoOx/WOx hybrid substrate is about 2.5 times or 5.9 times that in the pure WOx or MoOx substrate.

The as-extruded Mg-10Al2Y master alloy was chosen as a novel grain refiner for as-cast Mg-3Y alloy. Contrast samples of cast Mg-3Y alloy added with pure Al and Mg-Zr master alloy grain refiners were prepared under the same conditions. In this study, the influence of addition amounts of Al2Y and holding time on grain refinement efficiency as well as tensile properties was investigated. And the grain refining ability of the Al2Y particles was systematically evaluated in terms of the addition amounts, number density of the Al2Y particles and holding time. The finest grains are achieved at 2 wt% Al2Y addition amount, which corresponds to number density of the polygonal Al2Y particles of 420–460 mm–2. The Mg-10Al2Y master alloy has significant refinement performance and no refining recession occurs at the holding time within 60 min, or the settling time up to 180 min. Grain refinement and the second phase strengthening of uniformly distributed Al2Y particles contribute to the simultaneous enhancement on both strength and elongation of Mg-3Y alloy.

Distribution-level electricity market provides a platform for trading energy and grid services from large-amount of small-scale distributed energy resources (DERs) located on distribution grids. The behavior of the DERs in the distribution electricity market may ultimately impact the market-clearing and locational marginal prices (LMPs) in the wholesale market. This paper proposes a bi-level optimization model for distribution market clearing and distribution locational marginal pricing (DLMP) considering the interactions between distribution and transmission wholesale markets. In the proposed model, the upper-level model represents the distribution system operator (DSO) market-clearing and the lower-level model represents the wholesale market-clearing by the independent system operator (ISO). The LMP at the substation will impact the DER dispatch and power demands of the DSO as well as the DLMP. In turn, the power demands of the DSO will further impact the ISO market and its LMPs. The equilibrium problem with equilibrium constraints (EPEC) approach is applied to find the equilibria of multiple DSOs and the ISO. The EPEC problem is transformed into a single-level mixed-integer convex problem in order to allow for efficient solving. The effectiveness of the proposed model and solution method are demonstrated through case studies.

Laser cladding with SiC nanoparticles was performed on a Ti-6Al-4V substrate in an air environment. In this process, the oxide and reinforcement phases formed together in the coating layer and, consequently, the hardness and friction characteristics of the titanium surface were improved simultaneously. Specifically, the oxide phases such as SiO2 and TiO2 were formed on the top region of the coating layer through a reaction with oxygen. The reinforcement phases such as TiC and Ti5Si3, a eutectic structure, and martensite occurred in the lower region of the coating below the oxide phases. The reinforcement phases helped increase the hardness of the titanium surface by up to three times. Moreover, due to the influence of the oxide phases, the friction coefficient was reduced by up to 88% after the laser cladding. When the laser scanning speed decreased, the cooling rate decreased; therefore, the crystal size increased, and hardness value decreased. In addition, the friction coefficient decreased as the laser scanning speed decreased due to the increase in the TiO2 content and decrease in the agglomerated SiO2 at low laser scanning speeds. The amount of wear of the specimen reduced considerably after the laser cladding, and only light abrasive wear and fatigue wear were observed on the laser clad surface.

The penetration damaging behavior of ATI425 titanium alloy was studied by 7.62 mm diameter armor piercing projectiles. The damage characteristics and the mechanism were analyzed by observing and analyzing the craters of ATI425 titanium alloy target. It can be found that local temperature-rise of the target plate occurred, even sputtering phenomenon in the opening stage. The shear bands extended upward along the cater wall could be seen in the stable stage. The large non-homogeneous deformation in adiabatic shear bands caused microcracks and micropores. A large number of macro-cracks were observed on the side wall and at the bottom of the crater.

Industrial Internet of Things (IIoT) is an emerging area that fifth-generation (5G) mobile communication system penetrates industrial manufacturing applications. The indoor factory has larger space and there are a lot of metal machine tools distributed in it, which makes its radio propagation characteristics and corresponding channel models significantly different from those of the indoor office and indoor hotspot. To support the design and the evaluation of the IIoT techniques, the 3rd Generation Partnership Project (3GPP) released the first 5G IIoT standard model in October 2019. In this article, we give a detailed explanation of this IIoT model and compare it with other indoor models. First, we introduce the standardization of 3GPP IIoT channel model and its motivation. Second, four IIoT subscenarios, which are classified according to the clutter density and antenna height, are described. Third, the potential frequency bands of 5G IIoT are summarized. Fourth, the models of channel parameters, including the path loss and the line-of-sight (LOS) probability, the root mean-square (RMS) delay spread, and the angular spread, are given. Among them, the models of path loss and LOS probability take the antenna height and clutter density into consideration. The model of RMS delay spread changes from frequency-dependent to volume-dependent in order to catch the size variation of factories. Finally, two newly added key channel characteristics, dual mobility and absolute time of arrival, which help to describe the robot movement and positioning, are also presented.

Lncosh cost function is regarded as a natural logarithm obtaining from a hyperbolic cosine function, which has drawn growing attention due to its robust to impulsive noise. In this brief, a nonnegative adaptive algorithm is proposed based on lncosh function, named as NNLlncosh, which is derived by incorporating the nonnegativity constraint into lncosh cost function to deal with a nonnegativity constraint optimization problem under impulsive system noises. The steady-state excess mean square error (EMSE) for the newly constructed NNLlncosh algorithm is presented. Obtained results from the computer simulation validate the theoretical analysis and verify the excellent characteristics of the NNLlncosh over various non-Gaussian system noises.

We propose a recursive constrained least lncosh (RCLL) adaptive algorithm to combat the impulsive noises. In general, the lncosh function is used to develop a new algorithm within the context of constrained adaptive filtering via solving a linear constrained optimization problem, where the lncosh function is a natural logarithm of hyperbolic cosine function, which can be regarded as a combination of mean-square-error (MSE) and mean-absolute-error (MAE) criteria. Compared with other typical recursive methods, the proposed RCLL algorithm can obtain superior steady state behavior and better robustness for combating impulsive noises. Besides, the mean-square convergence condition and theoretical transient mean-square-deviation of the RCLL algorithm is presented. Simulation results verified the theoretical analysis in non-Gaussian noises and shown the superior performance of the proposed RCLL algorithm.

In this paper, we propose a distribution line fitting (DLF) based channel estimation method for offset quadrature amplitude modulation based filter-bank multicarrier (OQAM/FBMC) systems. Specifically, we firstly analyze the distribution characteristics of demodulated OQAM symbols at the receiver, and derive an intrinsic interference free relation between the real and imaginary parts of demodulated OQAM symbols. Then, based on the above derivation, we design a pilot structure of arbitrary columns of pilot symbols without guard symbols between pilot symbols and data symbols. Finally, the distribution lines can be fitted by utilizing the distribution characteristics of demodulated OQAM symbols and the channel frequency response can be estimated. Simulation results demonstrate that the proposed method with one column of pilot symbols outperforms the interference approximation method (IAM) in high signal-to-noise (SNR) regions and outperforms the pair of pilots (POP) method in all SNR regions in terms of bit error ratio (BER), and the proposed method with two columns of pilot symbols outperforms both IAM and POP in all SNR regions in terms of both BER and complexity.

Organic pores play an important role in shale reservoirs. Organic pores occur where shale gas was produced and accumulated. However, there is little scientific understanding of the distribution and connectivity of organic pores. Organic pore types and their structural characteristics were studied using a total organic carbon (TOC), thin section, focused ion beam scanning electron microscope (FIB-SEM), and nano-CT. The samples were from the Wufeng Formation in the Upper Ordovician and Longmaxi Formations from the lower Silurian. The results show that organic matter is mainly concentrated in the Wufeng Formation and the bottom of the Longmaxi Formation and that the middle and upper parts of the Longmaxi Formation contain a low amount of organic matter. The shale of the Wufeng-Longmaxi Formation has high maturity, and its organic pores are well developed. There are three types of organic pores: algae, graptolite, and pyrobitumen pores. The pore connectivity of shale with a high organic content is better than that of shale with a low organic content. The volume of the organic pores accounts for more than 50% of the volume of the organic matter. Majority of the organic pores have an aperture smaller than 100 nm and are round, nearly circular, and elliptical in morphology. Most of the organic pores in a shale formation are developed in pyrobitumen, and most of the larger organic pores are concentrated at the center of solid pyrobitumen. The organic pores in pyrobitumen have the best connectivity and are the most favorable reservoir spaces and migration channels for shale gas, which is a crucial point of reference for future research of shale gas.

Transition metal–nitrogen–carbon (M–N–C) catalysts have attracted significant attention for catalyzing oxygen reduction reactions (ORR). In this study, a porous Cr2O3@Cr–N–C catalyst with a small amount of Cr2O3 nanoparticles loaded on the surface of Cr–N4–C nanomaterials was prepared using synergistic heat treatment (SHT) method with zeolite imidazole frameworks (ZIFs) as precursors. TEM and spherical aberration-corrected TEM results demonstrated the presence of hollow morphologies, Cr2O3 nanoparticles and atomic-level Cr distribution in Cr2O3@Cr–N–C. XPS, XRD and XAFS analysis indicated the coexistence of Cr2O3 nanoparticles and Cr–N4 sites which were believed to act as active centers for ORR. In 0.1 M HClO4, this material showed outstanding ORR catalytic activity with a half-wave potential of 0.78 V that was 40 mV higher than the traditional heat treatment derived Cr–N–C. It also revealed relatively low Tafel slope of 52.2 mV dec−1; 4-electron pathway; remarkable stability and long-term durability. The improved ORR performance is mainly attributed to the synergy between Cr–N4 active center and Cr2O3 nanoparticle. The SHT strategy reported here provides a new route to prepare highly efficient non-precious metal M−N–C catalysts with greater ORR activity and stability in acidic environments.

With respect to the application of powdered graphene sheets, agglomeration is a troublesome problem. Another problem is that the conventional production method generates a huge amount of harmful wastewater, which brings about unbearable environmental and cost problems. It is thus of great significance to explore novel structure and massive production methods of powdered graphene. Here, we report growth of vertical graphene sheets (VGSs) on carbon black (CB) by thermal chemical vapor deposition, which forms a novel three-dimensional graphene powders (3DGPs). High yield growth of the VGSs at kilograms scale is achieved by increasing the substrate area. As a demonstration, the 3DGPs are used as conductive additive of lithium ion battery electrodes, which show excellent electrochemical performance. The rate performance of LiFePO4 electrode with 1.0 wt% 3DGPs is even better than that with 10.0 wt% CB measured in half-cells. The soft-pack full cells assembled using commercial LiFePO4 and graphite electrodes with 1.3 wt% 3DGPs possess 542.8 mAh with 93.3% retention after 400 cycles at 0.2C, and 85.4% retention after 1000 cycles at 1C. The novel 3DGPs also hold high promise in many other applications such as various composite materials, coatings, and electrochemical electrodes.

This article presents an indoor pose estimation system for microaerial vehicles (MAVs) with a single Wi-Fi access point. Conventional approaches based on computer vision are limited by illumination conditions and environmental texture. Our system is free of visual limitations and instantly deployable, working upon existing Wi-Fi infrastructure without any deployment cost. Our system consists of two coupled modules. First, we propose an angle-of-arrival (AoA) estimation algorithm to estimate MAV attitudes and disentangle the AoA for positioning. Second, we formulate a Wi-Fi-inertial sensor fusion model that fuses the AoA and the odometry measured by inertial sensors to optimize MAV poses. Considering the practicality of MAVs, our system is designed to be real-time and initialization-free for the need of agile flight in unknown environments. The indoor experiments show that our system achieves the accuracy of pose estimation with the position error of 61.7 cm and the attitude error of $0.92^{\circ }$ .

This study reports treatment of low-zinc EAF dust for obtaining high-grade metallized product with a focus on multiple valuable elements via microwave reduction followed by magnetic separation. In reduction, the conversions of components of iron, zinc, lead, manganese and chromium, mainly in the form of spinel phases, to Fe, Zn, PbCl2, MnO and Cr2O3, respectively, were partially restrained by the formation of complex silicates, e.g., Ca3Al0.84Fe1.16Si3O12. After microwave reduction under the conditions of C/Fe mass ratio of 0.25, temperature of 1323 K, dwell time of 15 min, heating rate of 25 K/min and microwave power of 2200 W, the reduced briquette had the iron metallization degree of 96.20%, with volatilization of 98.38% of Zn and 80.22% of Pb. By magnetic separation, a high-grade metallized product containing 81.77 wt% Fe (79.97 wt% metallic iron) and 0.04 wt% Zn, satisfying the Chinese standard (YB/T 4272–2012) of the first-grade metallized product from dust, was obtained.

Massive MIMO system yields significant improvements in spectral and energy efficiency for future wireless communication systems. The regularized zero-forcing (RZF) beamforming is able to provide good performance with the capability of achieving numerical stability and robustness to the channel uncertainty. However, in massive MIMO systems, the matrix inversion operation in RZF beamforming becomes computationally expensive. To address this computational issue, we shall propose a novel randomized sketching based RZF beamforming approach with low computational complexity. This is achieved by solving a linear system via randomized sketching based on the preconditioned Richard iteration, which guarantees high quality approximations to the optimal solution. We theoretically prove that the sequence of approximations obtained iteratively converges to the exact RZF beamforming matrix linearly fast as the number of iterations increases. Also, it turns out that the system sum-rate for such sequence of approximations converges to the exact one at a linear convergence rate. Our simulation results verify our theoretical findings.

In this paper, a regret-based risk-averse stochastic production task and energy management (PTEM) model for industrial microgrid is proposed, which is applied to a battery manufacturing plant (BMP) microgrid. We incorporate production task scheduling with production constraints in the energy management of industrial microgrid. The general PTEM of industrial microgrids is analyzed and the production processes and energy requirements of a BMP multi-energy microgrid prosumer are presented, in which thermostatically controlled loads (TCLs) in buildings are considered. Then, the regret-based risk-averse PTEM model is formulated as a mixed-integer linear programming (MILP) problem based on stochastic programming considering uncertainties of day-ahead electricity market price and photovoltaic (PV) power output. Conditional value-at-risk (CVaR) is introduced for risk control and utilized for minimizing the expected regret. Numerical studies are carried out to validate the proposed model by comparing with risk-neutral approach and deterministic model based on real market prices from PJM electricity market. The results show that the proposed PTEM approach is effectively risk-averse. In addition, the impacts of total target production task and risk-control parameter on expected cost and regret are analyzed.

In this work, the physicochemical properties of palm oil fuel ash (POFA) based geopolymers with the addition of graphene oxide (GO) were investigated. Geopolymer composites were prepared by mixing the treated POFA, sand, NaOH, Na2SiO3, and GO. The mixtures were then cast in mortar molds to form the geopolymer composites, with different GO proportions and curing temperatures applied to the composites. Compressive strength, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) analyses, as well as density functional theory (DFT) calculations, have been performed. The compressive test results showed that the compressive strength increased proportionally with the increase of GO content and decreased when there was an excess of GO. The excessive GO and the limited amount of NaOH activator solution inhibited the formation of reduced graphene oxide (rGO) via an in-situ reduction mechanism. The FTIR and SEM analyses revealed that the excess GO tended to promote the formation of epoxy groups on the GO, which eventually confined the formation of dense agglomeration and led to a decrease in compressive strength. The DFT calculations confirmed the significance of the epoxy group stretching. Overall, the ratio of NaOH to GO is a crucial factor in determining the mechanical properties of geopolymers-GO composites.

ZTC4 alloy prepared by electron beam melting was hot isostatically pressed, the macro-and microstructure were characterized by stereo microscopy and optical microscopy, the tensile properties were tested and the fracture profiles were characterized using scanning electron microscopy. The results show that: The vertical deposition samples exhibit coarsen epitaxial columnar grains and the parallel samples show equiaxed grains, and microstructure are basket-weave α+β phase. The vertical deposition samples exhibit very high ultimate tensile strength and yield strength but poor ductility with elongation and shrinkage, and show generally more planar and faceted fracture morphology. The anisotropy in tensile properties is mainly due to the difference in the orientation of the columnar grains with respect to the tensile test direction, and the characteristics of the minor fracture plane are mainly related to the α colonies.

Electric vehicles (EVs) are being introduced by different manufacturers, thanks to their environment-friendly perspective to alleviate CO2 pollution. In this paper, the proposed EV charging management scheme enables pre-empted charging service for heterogeneous EVs ( depends on different charging capabilities, brands, etc. ). Particularly, the anticipated EVs’ charging reservations information, including their arrival time and expected charging time at charging stations (CSs), are brought for planning CS-selection (where to charge). Along with applying ubiquitous cellular network communication to deliver ( delay tolerant ) EVs’ charging reservations, we further study the feasibility of applying opportunistic vehicle-to-vehicle (V2V) communication with delay/disruption tolerant networking (DTN) nature, due primarily to its flexibility and cost-efficiency in vehicular ad hoc networks (VANETs). Evaluation results under the realistic Helsinki city scenario show that applying the V2V-based charging reservation is promisingly cost-efficient in terms of communication overhead, while achieving a comparable charging performance to apply cellular network communication.

Poor permeability and low sintering productivity restrict the development of high-bed sintering. An efficient method of the double-layer sintering process (DLSP) was proposed to achieve high-bed sintering and solve the aforementioned problems. Theoretical calculation and sintering pot experiments were implemented to investigate the double-layer sintering process. Traditional sintering process and DLSP were compared in terms of sintering indices, metallurgical properties and morphology characterization. Under the condition of traditional sintering process, DLSP successfully realized fast velocity and highly productive sintering of 1000-mm high bed. After the sintering bed is charged and ignited twice, the air permeability of the bed has been greatly improved. Sintering time is shortened significantly by simultaneous sintering of the upper and lower feed layers. Under the condition of bed height proportion of 350/650 mm and pre-sintering time of 20 min, the yield, tumbler strength, productivity and solid fuel consumption are 69.96%, 65.87%, 1.71 t (m2 h)−1 and 56.71 kg/t, respectively. Magnetite, hematite, calcium ferrite and complex calcium ferrite are the main phases of DLSP products. The metallurgical properties of DSLP products meet the requirement of ironmaking. It indicates that DLSP is an effective method to solve the disadvantages of bad permeability and low sintering productivity in high-bed sintering.

Topological materials with robust topological surface states appear to be well-suited as electrochemical catalysts. However, few studies have been published on the development of non-noble metal topological catalysts, most likely because the topological properties tend to be attributed to the s and p orbital electrons, while transition-metal catalysis mainly involves d orbital electrons. Herein, we proposed a topological semimetallic (TSM) compound, VAl3, with a surface state consisting mainly of d orbital electrons, as an electrocatalyst for the hydrogen evolution reaction (HER). Density functional theory (DFT) calculations showed that the surface state electrons enhanced the adsorption of H atoms. Moreover, the transfer of surface state electrons between the surface and adsorbed H atoms was optimized through nickel doping. We experimentally prepared single-crystals VAl3 and V0.75Ni0.25Al3 alloys. Electrochemical analysis showed that not only did V0.75Ni0.25Al3 outperform VAl3 but also it was among the best non-noble metal topological HER electrocatalysts currently available.

In this paper, we study the synchronization of a new fractional-order neural network with multiple delays. Based on the control theory of linear systems with multiple delays, we get the controller to analyse the synchronization of the system. In addition, a suitable Lyapunov function is constructed by using the theory of delay differential inequality, and some criteria ensuring the synchronization of delay fractional neural networks with Caputo derivatives are obtained. Finally, the accuracy of the method is verified by a numerical example.

Due to the openness of wireless medium, robotic networks that consist of many miniaturized robots are susceptible to Sybil attackers, who can fabricate myriads of fictitious robots. Such detrimental attacks can overturn the fundamental trust assumption in robotic collaboration and thus impede widespread deployments of robotic networks in many collaborative tasks. Existing solutions rely on bulky multi-antenna systems to passively obtain fine-grained physical layer signatures, making them unaffordable to miniaturized robots. To overcome this limitation, we present ScatterID, a lightweight system that attaches featherlight and batteryless backscatter tags to single-antenna robots for Sybil attack mitigation. Instead of passively "observing" signatures, ScatterID actively "manipulates" multipath propagation by exploiting backscatter tags to intentionally create rich multipath signatures obtainable to single-antenna robots. Particularly, these signatures are used to carefully construct similarity vectors to thwart advanced Sybil attackers, who further trigger power-scaling and colluding attacks to generate dissimilar signatures. Then, a customized random forest model is developed to accurately infer the identity legitimacy of each robot. We implement ScatterID on the iRobot Create platform and evaluate it under various Sybil attacks in real-world environments. The experimental results show that ScatterID achieves a high AUROC of 0.987 and obtains an overall accuracy of 95.4% under basic and advanced Sybil attacks. Specifically, it can successfully detect 96.1% of fake robots while mistakenly rejecting just 5.7% of legitimate ones., Comment: To appear in ACM/IEEE Transactions on Networking. arXiv admin note: substantial text overlap with arXiv:1912.04613

The chromium-promoted preparation of forsterite refractory materials from ferronickel slag was investigated by microwave sintering of the slag with the additions of sintered magnesia and 0–10 wt% chromium oxide (Cr2O3). The thermodynamic calculations revealed that the addition of Cr2O3 can promote the formations of spinel and liquid phase and maintain high content of forsterite below 1500 °C. The experimental results showed that there existed a stronger promoting effect of Cr2O3 additive on the properties of refractory materials in the microwave field than that in conventional sintering. It was attributed to the preferential formation and growth of spinel with stronger microwave absorption than other phases (e.g., enstatite), the existence of more forsterite, and the enhanced densification in association with the presence of more liquid phase at the same temperature. By microwave sintering of the mixture of ferronickel slag, 25 wt% sintered magnesia, and 4 wt% Cr2O3 at 1350 °C for 20 min, a superior refractory material with refractoriness of 1801 °C, thermal shock resistance of 6 times, bulk density of 2.97 g/cm3, apparent porosity of 1.4%, and compressive strength of 197 MPa was obtained. Compared with that prepared by conventional sintering at 1350 °C for 2 h, the refractoriness and thermal shock resistance were increased by 175 °C and 100%, respectively. The present study provided a novel method for preparing high-quality refractory materials from ferronickel slag and relevant industrial wastes.

This article analyzes the channel estimation performance of massive multiple-input–multiple-output (MIMO) Internet-of-Things (IoT) systems with Ricean fading. First, by utilizing the least squares (LSs) and minimum mean squared error (MMSE) estimation methods, we consider the relative channel estimation error (RCEE) between the IoT device and base-station, and provide the approximations of the expectation of RCEE ( ${\text {Exp}}_{\textrm {rcee}}$ ). Then, it is found that when the number of antennas $M$ becomes infinite, pilot contamination (PC) exists in both cases. However, for MMSE case, ${\text {Exp}}_{\textrm {rcee}}$ scales down by the inverse of Ricean $K$ -factor, and hence PC phenomenon disappears with a large Ricean $K$ -factor. Moreover, as $M\rightarrow \infty $ , the power scaling laws show that the pilot sequence power can be scaled down proportionally to $1/M^{\alpha }$ ( $\alpha >0$ ) with the MMSE case, where the performance is determined only by the Ricean $K$ -factor. Next, the channel hardening and favorable propagation effects are examined via analyzing the approximations of the variance of RCEE ( ${\text {Var}}_{\textrm {rcee}}$ ). Analysis implies that ${\text {Var}}_{\textrm {rcee}}$ decreases by $1/M$ when $M\rightarrow \infty $ . For a large Ricean $K$ -factor, ${\text {Var}}_{\textrm {rcee}}$ approaches a nonzero constant for the LS case and scales down by the inverse of the square of Ricean $K$ -factor for the MMSE case. Finally, all results are verified via Monte Carlo simulations.

To dispose the problem of ferronickel slag for its value-added application, it was used for preparing thermal insulation materials by sintering of the slag in the presence of another waste, fly ash cenosphere (FAC), as pore former. The thermodynamic and experimental analyses revealed that the original phase of the slag, olivine, could be transformed to thermal insulation phases, including enstatite and cordierite, by optimizing sintering temperature in the range 1100–1300 °C. Specifically, after initial decomposition of ferronickel slag, there existed a low-iron olivine phase and cordierite and enstatite became the dominant phases when the sintering temperature increased from 1100 °C to 1300 °C. Except for the phase transformation, the microstructural evolution with proper pore features (porosity and size) contributed to a resulting material with desirable thermal and mechanical properties. It was shown that the ferronickel slag sintered at 1200 °C for 2 h with the addition of 25 wt % FAC exhibited the optimal thermal and mechanical performance. Additionally, it possessed good acid and alkali resistances. The results confirmed the feasibility of co-utilization of ferronickel slag and FAC for producing superior thermal insulation materials at a proper temperature, making efficient utilization of both wastes.

This paper presents an empirical study of the uplink and downlink azimuth angle of arrival (AoA) in an urban micro (UMi) scenario at 28 GHz. At present, most UMi measurements are conducted in the downlink and then the uplink situation is inferred assuming channel reciprocity. Although the channel correlation coefficient of the uplink and downlink can be as high as 0.8, this does not mean that they are the same. Only a real uplink measurement can accurately describe its channel conditions, and this is what this study does. A receiver equipped with a rotatable horn antenna is mounted at the base station and the user terminal, respectively, in simulating the uplink and downlink. To improve the angular resolution, we extract the multipath components (MPCs) using the space-alternating generalized expectation-maximization algorithm. Also, a spatial lobe approach is used to cluster the MPCs in the power angular spectrum. By matching MPCs with objects in the environment, we find that direct propagation and first-order reflections are dominant in line-of-sight and non-line-of-sight cases. By comparing our measurement with those in standard channel models, we verify that the AoA of clusters follows a Gaussian distribution in the uplink and downlink. In addition, a two-dimensional Gaussian distribution for ray AoA and power is established to reflect their correlation.

In this letter, we propose a novel complex-valued offset quadrature amplitude modulation based filter bank multicarrier (OQAM/FBMC) system with interference cancellation. Specifically, we construct the frame structure of OQAM/FBMC in a frequency-reversal form, where complex-valued symbols are transmitted repeatedly at paired symmetric subcarriers, with appropriate sign changes being inserted to achieve a complete self-cancellation of the intrinsic interference. Besides, we further present a block-wise preamble design method with frequency reversal to reduce the pilot overhead. The whole preamble is divided into multiple subblocks of equal size, each of which is optimally designed to provide a virtual boost of the pseudo-pilot power. Simulation results validate the effectiveness of the proposed complex-valued OQAM/FBMC and significant performance gains are demonstrated against conventional methods with the block-wise preamble design method.

With the development of demand-side management in the smart grid, load-serving entity (LSE) plays a more important role for consumers, which purchases energy from the electricity market and sells it to consumers. Moreover, aggregated thermostatically controlled loads (TCLs) in smart buildings can provide additional demand response capacities and require efficient energy management methods. This article proposes a stochastic optimal energy management and pricing model for LSE with aggregated TCLs and energy storage based on the Stackelberg game and stochastic programming. The energy management and pricing problem are formulated as a bilevel optimization model. The upper level model aims to maximize LSE's expected profit under market price uncertainties and determines the offering prices to consumers. According to the offering price from upper level model, the lower level model optimizes the power purchasing pattern for consumers of two types of buildings with TCLs: factory and office buildings. The nonlinear bilevel model is reformulated and converted into mixed-integer linear programming using a strong duality theory. The proposed model is validated by numerical studies based on real market prices from the PJM electricity market. In addition, the impacts of energy storage, number of buildings, comfortable indoor temperature limits, and offering price limits on LSE's profit are analyzed.

In this letter, we propose an improved pairs of pilots (POP) design method for channel estimation in offset quadrature amplitude modulation based filter bank multicarrier (OQAM/FBMC) systems. Based on an error analysis of the conventional POP channel estimation method, we first develop a heuristic pilot design in which each pilot pair is inserted at two consecutive subcarriers. Besides, we further propose to build a preamble by quartet of subcarriers and conduct a pilot optimization subject to a pilot power constraint, aiming to suppress the noise effect as much as possible. To obtain its optimal solution, we convert the original non-convex pilot optimization problem into a convex semidefinite programming problem, which is shown to be computationally efficient and readily solvable. Numerical simulations validate the effectiveness and superiority of the proposed pilot design method compared to the conventional POP and interference approximation methods.

In order to alleviate the dust pollution in the fully mechanized mining face, the novel negative pressure entrainment dust collector was optimized by the method of orthogonal experimental design and numerical simulation. The influences of nozzle distance, throat diameter and diffusion angle on the atomization efficiency of the proposed dust collector was investigated. The obtained results showed that the optimum ejection dust removal performance of the developed negative pressure entrainment dust collector was obtained for throat diameter 80 mm, throat distance 60 mm and diffusion angle 20 degrees. Under these conditions, air suction rate at the entrance of contraction section was 17.48 m3/min and the average droplet size and mass concentration were 62.99 μm and 0.034 kg/m3, respectively. Here, we have proposed a local closed atomization control dust removal technology for hydraulic support areas based on the optimized negative pressure entrainment dust collector. After the application of the developed system in 2307 fully mechanized mining face in Tangkou Coal Mine, the average total dust of measuring points was decreased from 337.90 to 49.53 mg/m3 and average exhaust dust was decreased from 271.80 to 41.40 mg/m3. The average dust removal rates of total dust and exhaled dust were 85.17% and 84.74% respectively, and dust removal efficiency of the proposed system was obviously confirmed.

Three new pyridine-cored alkyl-substituted carbazole derivatives of 2,6-bis(2,7-dimethyl-9H-carbazol-9-yl)pyridine (2,7-MeCzPy), 2,6-bis(3,6-dimethyl-9H-carbazol-9-yl) pyridine (3,6-MeCzPy) and 2,6-bis(3,6-di-tert-butyl-9H-carbazol-9-yl)pyridine (3,6-tBuCzPy) were synthesized by means of connecting methyl or tert-butyl substituents on the 3,6 or 2,7 positions of carbazole with pyridine ring as the core. The influence of different alkyl and linkages mode on the thermal, photophysical, electrochemical properties and devices electrolumiescent (EL) performances of the compounds were comprehensively studied. In solution-processed blue or green phosphorescent organic light-emitting diodes (PHOLEDs) with bis[2-(4,6-difluorophenyl)-pyridinato-N,C2] picolinate iridium(III) (FIrpic) or fac-tris(2-phenylpyridine)iridium (Ir(ppy)3) as phosphorescent dopants, EL performances follow the same sequence of 2,7-MeCzPy > 3,6-tBuCzPy > 3,6-MeCzPy, the trend is consistent with the value of triplet energies (ET). Devices hosted by 2,7-MeCzPy achieving the best EL performance, exhibited maxima 13.6 cd A−1 and 7.0 lm W−1 for current efficiency (CE) and power efficiency (PE) in blue PHOLEDs, maxima 26.2 cd A−1 and 16.2 lm W−1 for CE and PE in green PHOLEDs.

The hydrogenation of waste gas carbon dioxide into value added molecules could reduce greenhouse gas emissions and our dependence on nonrenewable energy sources. Catalytic paths toward this goal typically involve high pressures and low abundance transition metal catalysts. Here, we have found that vacancies induced in defect-laden hexagonal boron nitride (dh-BN) can effectively activate the CO₂ molecule for hydrogenation. Subsequent hydrogenation to formic acid (HCOOH) and methanol (CH₃OH) occur through vacancy facilitated coadsorption of hydrogen and CO₂. More importantly, we find that dh-BN catalyzes formic acid formation observable at reaction temperatures above 160 °C and pressures of 583 kPa, while methanol formation is observed at lower temperatures (as low as 20 °C). Methanol formation occurs with a TOF of 1.52 × 10–² s–¹ and TON of 289 at 20 °C. Carbon dioxide (CO₂) is a major greenhouse gas and the main component of all combustion products produced in power generation and transportation. In addition, boron and nitrogen are abundant elements and thus, catalysts prepared from h-BN would allow catalytic recovery of value-added molecules facilitating efforts to reduce the emissions of this gas.

Antenna array is one of the methods which can generate Orbital Angular Momentum (OAM) waves. However, OAM waves generated by different antenna arrays have different characteristics of Electric-field (E-field) components’ distribution and radiation patterns. In order to solve this problem, we derive E-field formulas of OAM waves generated by different kinds of dipole antenna array in this paper. The dipole antenna arrays are arranged by three methods: 1) antenna elements are in the same direction of y axis, 2) antenna elements are in the radial direction and 3) antenna elements are in the azimuthal direction. Results show that x components, y components and z components carry different OAM modes under the three conditions. Simulation results show that the same direction antenna array produces the best OAM waves because the y component is dominated by OAM mode l and RHCP/LHCP waves are negligible in energy, while the pure OAM waves carried by the z components generated by the other two antenna arrays have little energy. In addition, only the radiation pattern of l = 0 produced by the same direction antenna array does not have a null zone in the propagation direction. Radiation patterns of l = ± 1 do not have null zones in the propagation direction generated by other two antenna arrays.

In this paper, an efficient compressive sensing detector is proposed for uplink grant-free non-orthogonal multiple access (NOMA), where the indices and symbols of the active users are detected separately by using efficient matching pursuit (MP) based algorithms. Specifically, a low-complexity subspace MP (SMP) algorithm is designed for detecting the active user's indices, which is helpful for obtaining an initial estimated symbol vector. Then an efficient MP based symbol correcting mechanism (SCM) is designed for finding and correcting the erroneous results encountered in the initial result. Simulation results indicate that our proposed SMP based SCM (SMP-SCM) algorithm is capable of exhibiting better bit error rate (BER) performance over the oracle least squares (OLS) counterpart in the high SNR regime, which is always taken as a benchmark in conventional multi-user detection of grant-free NOMA system.

In this work, Nb5+ and Cu2+ were selected to partially substitute Zr4+ in Gd2Zr2O7 for studying the phase structure, microscopic morphology and thermal properties. Gd2(Zr1-3x/2NbxCux/2)2O7 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.25) ceramic materials were synthesized by high-temperature solid-state reaction method. The results show that the Gd2(Zr1-3x/2NbxCux/2)2O7 ceramics present cubic pyrochlore structure with clear grain boundaries and dense cell structure. And the thermal expansion coefficient of Gd2(Zr1-3x/2NbxCux/2)2O7 ceramics gradually decreases because of the incorporation of Nb5+ and Cu2+ into Zr-site in Gd2Zr2O7. Meanwhile, its thermal conductivity decreases firstly and then increases with the doping of Nb5+ and Cu2+, which reaches the lowest value for the composition of Gd2(Zr0.85Nb0.1Cu0.05)2O7.

In distributed passive radar, optimization of the receiver placement attracts much attention recently to improve the performance. Whereas most research optimizes receiver placement for best coverage or localization performance, the effect of one performance optimization on the other is ignored. In this article, the theoretical analysis on the conflict between the coverage and localization performance optimization is presented. Then, a joint coverage and localization-based receiver placement optimization is formulated, in which the detection probability and the localization accuracy are chosen as the corresponding metrics. To solve this optimization problem, a multiobjective neighborhood search algorithm with multineighborhood structure is proposed, by which a set of Pareto solutions corresponding to the optimal receiver placements is obtained. Compared with the traditional neighborhood search algorithms, the proposed algorithm is able to provide better receiver placements approaching the global Pareto optimum, which is validated by the simulations.

Novel MgO-doped CaO sorbent pellets were prepared by gel-casting and wet impregnation. The effect of Na+ and MgO on the structure and CO2 adsorption performance of CaO sorbent pellets was elucidated. MgO-doped CaO sorbent pellets with the diameter range of 0.5–1.5 mm exhibited an excellent capacity for CO2 adsorption and adsorption rate due to the homogeneous dispersion of MgO in the sorbent pellets and its effects on the physical structure of sorbents. The results show that MgO can effectively inhibit the sintering of CaO and retain the adsorption capacity of sorbents during multiple adsorption-desorption cycles. The presence of mesopores and macropores resulted in appreciable change of volume from CaO (16.7 cm3·mol−1) to CaCO3 (36.9 cm3·mol−1) over repeated operation cycles. Ca2Mg1 sorbent pellets exhibited favorable CO2 capture capacity (9.49 mmol·g−1), average adsorption rate (0.32 mmol·g−1·min−1) and conversion rate of CaO (74.83%) after 30 cycles.

Driven by the soaring traffic demand and the growing diversity of mobile services, wireless networks are evolving to be increasingly dense and heterogeneous. Accordingly, in such large-scale and complicated wireless networks, optimal controlling is reaching unprecedented levels of complexity while its traditional solutions of handcrafted offline algorithms become inefficient due to high complexity, low robustness, and high overhead. Therefore, reinforcement learning (RL), which enables network entities to learn from their actions and consequences in the interactive network environment, attracts significant attention. In this article, we comprehensively review the applications of RL in wireless networks from a layering perspective. First, we present an overview of the principle, fundamentals, and several advanced models of RL. Then, we review the up-to-date applications of RL in various functionality blocks of different network layers, ranging from the low-level physical layer to the high-level application layer. Finally, we outline a broad spectrum of challenges, open issues, and future research directions of RL-empowered wireless networks.

The classification of remote sensing images with high spatial resolution requires considerable training samples, but the process of sample making is slow and laborious. How to guarantee the accuracy of supervised classification under the condition of limited samples is an urgent problem to be solved in the field of supervised classification. For addressing this problem, we propose an improved conditional generative adversarial network with edge feature (ECGAN) to augment limited training data for the classification of remote sensing images with high spatial resolution in this article. On the basis of conditional generative adversarial network, feature factors of interclass boundaries and intraclass edges are added to networks, and an objective function with multiscale and multilevel features is constructed. The ISPRS potsdam and Vaihingen remote sensing datasets are regarded as examples. Results indicate that the high-resolution remote sensing images generated by using the network proposed in this article have abundant texture, accurate edges, and are highly similar to real images. The generated images are used to augment training samples, and an experiment for classifying high-resolution remote sensing images is conducted. The classification results of the proposed augmentation method perform better than that of the traditional sample augmentation method. We prove that ECGAN as a means of sample augmentation can effectively solves the problem that the classification effect is unideal when the supervised classification sample is insufficient.

In the sintering of iron ores, the partial substitution of anthracite for coke breeze has been considered to be an effective way of reducing pollutant emissions and production cost. In this study, the basic characteristics of anthracite and coke breeze were compared and the sintering performance at different substitution ratios of anthracite for coke breeze was investigated. The porosity of anthracite is lower than that of coke breeze, but its density and combustion reactivity are higher. The substitution of anthracite for coke breeze has no influence on the granulation effect of the sintering blend. As the anthracite proportion increased, the sintering speed and productivity increased and the sintering yield and tumbler index decreased. As the substitution ratio increased from 0 to 60%, the melting temperature duration and the melt quantity index decreased from 2.59 to 2.03 min and from 3218.28 to 2405.75 °C·min, respectively, leading to insufficient sintering mineralization and bad sintering indexes. For an anthracite substitution ratio of 40%, the sintering speed, sintering productivity, sintering yield and tumbler index were 22.34 mm min−1, 1.49 t·(m2 h)−1, 71.65% and 63.59%, respectively, which entirely satisfies the production requirements. Furthermore, hematite (Fe2O3), calcium ferrite (CaO–Fe2O3), and compound calcium ferrite (CaO–SiO2–Fe2O3) were the major mineral phases, which were embedded with an interwoven structure.

Due to the poor situation of water-flooding mechanism research on Chang 4 + 5 reservoir of Ordos basin, the authors quantitatively studied the influence factors of water-flooding characteristics by sedimentology, casting thin sections, constant-speed mercury injection, scanning electron microscope as well as production records. The size and distribution of pore-throat were also found closely related with the water-flooding seepage law. The results show that the microscopic seepage paths of Chang 4 + 5 reservoir include uniform displacement, finger displacement and peak displacement, and their correspondent oil displacement efficiency reduces in turn under the same conditions. Reservoir heterogeneity, reservoir properties, distribution of pore structure and wettability play a decisive role in water-flooding efficiency. Generally, When the intra-layer range is greater than 4.65, the breakthrough coefficient is greater than 3.54, the coefficient of variation is greater than 0.7, the distribution frequency of inter-layer is greater than 0.5 per meter, and the distribution density is greater than 0.435%, the range between layers is greater than 6.86, the breakthrough coefficient is greater than 2.58, the coefficient of variation is greater than 0.51, and the thickness of inter-layer is greater than 7.54 m. the increasing trend of oil displacement efficiency will be obviously weakened.