Search

In this paper, we solve the variable-coefficient fractional diffusion-wave equation in a bounded domain by the Legendre spectral method. The time fractional derivative is in the Caputo sense of order $\gamma \in (1,2)$ γ ∈ ( 1 , 2 ) . We propose two fully discrete schemes based on finite difference in temporal and Legendre spectral approximations in spatial discretization. For the first scheme, we discretize the time fractional derivative directly by the $L_{1}$ L 1 approximation coupled with the Crank–Nicolson technique. For the second scheme, we transform the equation into an equivalent form with respect to the Riemann–Liouville fractional integral operator. We give a rigorous analysis of the stability and convergence of the two fully discrete schemes. Numerical examples are carried out to verify the theoretical results.

As a promising technology to achieve perpetual operation of battery-powered wireless sensor devices, wireless power transfer has attracted much attention recently. In wireless power transfer, the charger enables the energy to be wirelessly transmitted to the rechargeable sensor devices that are hungry for energy. Previous works mainly focus on maximizing the charging utility or minimizing the charging delay. This paper concerns a more practical issue of placing wireless chargers, which aims at minimizing the deployment cost of chargers while satisfying the overall requirement for charging utility. We investigate the above cost-minimum charger placement problem under two typical scenarios in which omni chargers and directional chargers are used, respectively. To resolve this problem under the two charging models, we first prove its NP-hardness and then propose two approximation algorithms with proven performance guarantees. Finally, we conduct extensive simulation experiments to validate our designs, and the experimental results demonstrate that the proposed algorithms significantly outperform the baselines.

Unmanned Aerial Vehicles (UAVs) are expected to be an important component in the upcoming wireless communication field, which are increasingly used as data collectors to gather sensing data from Wireless Sensor Networks (WSNs) due to their high mobility. Since the storage capacity and lifetime of sensors are increasing with the development of science and technology, sensors can store more and more sensing data about the monitoring area. However, due to the energy limitation of UAVs, we can not collect all data from WSN in limited time. Therefore, in this paper, we investigate the Maximizing Data Collection Proportion (MDCP) problem: given the limited budget of UAV, the objective is to find the trajectory of UAV such that the minimum data collection proportion of collected data to the stored data among all sensors is maximized. We first prove that the MDCP problem is NP-hard. Then we propose two approximation algorithms to design the trajectory of UAV, and give the theoretical analysis for the algorithms. Finally, we present numerical results in different scenarios to evaluate the effectiveness of the proposed algorithms.

Over years, barrier coverage problems in wireless camera sensor networks have received an amount of attention for their important applications such as intrusion detection and battlefield surveillance. Though much work has been done in this field, few works focus on providing high surveillance quality efficiently. Recently, Cheng and Tsai pointed out the breadth of barrier-coverage of camera sensor network was significant to guarantee high quality of monitoring (QoM), and they proposed a β-breadth belt-barrier problem under 2D circumstances whose goal was to select camera sensors as few as possible to construct a β-breadth belt-barrier. In this paper, we study the problem of constructing a β-breadth belt-barrier with the minimum number of sensors thoroughly, both under 2D circumstances and 3D circumstances. Besides, we extend this problem and study how to build up k disjoint β-breadth belt-barriers under both 2D and 3D circumstances. We set many application scenarios in simulation and thoroughly study how our algorithms' performances are affected by different environmental parameters, including the number of sensors and the breadth of a barrier.

In this paper, we consider the numerical approximation of the time fractional diffusion equation with variable coefficients on a semi-infinite spatial domain. A fully discrete scheme based on finite difference method in time and spectral approximation using Laguerre functions in space is proposed. Stability and convergence of the proposed scheme are rigorously established. The scheme is unconditionally stable and convergent with order O ( ? 2 + N ( 1 - m ) / 2 ) , where ? , N , and m are the time-step size, polynomial degree, and regularity in the space variable of the exact solution, respectively. A pseudospectral scheme is also proposed and analysed. Some numerical examples are presented to demonstrate the theoretical results.

In camera sensor networks (CSNs), the target coverage problem is of special importance since a sensor with different viewing directions captures distinct views for the same target. Furthermore, mission-driven monitoring applications in CSNs usually have special network lifetime requirements in which the limited battery lifetime of sensors probably can not sustain for full coverage. In this paper, based on effective-sensing model, we address three new coverage problems in mission-driven camera sensor networks, namely the target-temporal effective-sensing coverage with non-adjustable cameras (TEC-NC) problem, the target-temporal effective-sensing coverage with adjustable cameras (TEC-AC) problem, and the target-temporal effective-sensing coverage with fully-adjustable cameras (TEC-FAC) problem. Given a mission period, the common objective of the problems is to find a sleep-wakeup schedule such that the overall target-temporal coverage is maximized. For TEC-NC, we propose a 2-approximation algorithm and two new heuristics. We also design two greedy strategies, each of which can be combined with our solutions for TEC-NC to deal with TEC-AC and TEC-FAC, respectively. We finally conduct extensive experiments to evaluate the performance of the proposed algorithms, whose results indicate the proposed algorithms outperform the existing alternatives as well as are close to the theoretical optimum on average under certain conditions.

The numerical approximation of the distributed order time fractional reaction-diffusion equation on a semi-infinite spatial domain is discussed in this paper. A fully discrete scheme based on finite difference method in time and spectral approximation using Laguerre functions in space is proposed. The scheme is unconditionally stable and convergent with order O ( ? 2 + Δ α 2 + N ( 1 - m ) / 2 ) , where ?, Δα, N, and m are the time-step size, step size in distributed-order variable, polynomial degree, and regularity in the space variable of the exact solution, respectively. A pseudospectral scheme is also proposed and analyzed. Some numerical examples are presented to demonstrate the efficiency of the proposed scheme.

In this paper, we consider the numerical approximation of the time fractional diffusion-wave equation in a semi-infinite channel. The time fractional derivative is described in Caputo sense with order γ ? ( 1 < γ < 2 ) . A fully discrete spectral scheme based on a finite difference method in the time direction and a Laguerre-Legendre spectral method in the space direction is proposed. We also propose an alternating direction implicit (ADI) spectral scheme in order to reduce the amount of computation. The stability and convergence of both schemes are rigorously established. Numerical results are presented to support our theoretical analysis.

Towards rapid development of lightweight, flexible, and even wearable electronics, a highly efficient energy-storage device is required for their energy supply management. Graphene fiber-based supercapacitor is considered as one of the promising candidates because of the remarkable mechanical and electrical properties of graphene fibers. However, supercapacitors based on bare graphene fibers generally suffer a low capacitance, which certainly restricts their potentially wide applications. In this work, hierarchically structured MnO 2 nanowire/graphene hybrid fibers are fabricated through a simple, scalable wet-spinning method. The hybrid fibers form mesoporous structure with large specific surface area of 139.9 m 2 g −1 . The mass loading of MnO 2 can be as high as 40 wt%. Due to the synergistic effect between MnO 2 nanowires and graphene, the main pseudocapacitance of MnO 2 and the electric double-layer capacitance of graphene are improved simultaneously. In view of the practical demonstration, a highly flexible solid-state supercapacitor is fabricated by twisting of two MnO 2 /graphene fibers coated by polyvinyl alcohol/H 3 PO 4 electrolyte. The supercapacitor exhibits a high volumetric capacitance (66.1 F cm −3 , normalized by the total volume of two fiber electrodes), excellent cycling stability (96% capacitance retention over 10,000 cycles), high energy and power density (5.8 mWh cm −3 and 0.51 W cm −3 , respectively).

The impacts of black tea infusion on physicochemical properties, antioxidant capacity and microstructure of stirred acidified dairy gel (ADG) system have not been fully explored. These impacts were studied during a 28-day cold storage (4 &deg, C) period to explore the feasibility and technical boundaries of making acidified dairy gels in which black tea infusion (BTI) is incorporated. Reconstituted skim milks containing different proportions of BTI were acidified by GDL (glucono-&delta, lactone) at 35 &deg, C for making ADG systems. Both textural properties and structural features were characterized, antioxidant capacity was determined through three assays. They are (1) free radical scavenging ability by DPPH (2,2-diphenyl-1-picrylhydrazyl) assay, (2) ABTS [2,2&prime, azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid)] assay and (3) ferric reducing antioxidant power (FRAP) assay. The microstructure of the ADGs was observed using SEM (scanning electron microscopy) and CLSM (confocal laser scanning microscopy). Results showed that BTI significantly increased the antioxidant capacity of the gel systems and the gel containing 15% BTI was as stable as the control gel in terms of syneresis rate. However lower phase stability (higher syneresis rate) was observed in the ADG with a higher portion of BTI (30% to 60%). The microstructure of the ADGs observed may explain to the phase stability and textural attributes. The results suggested that tea polyphenols (TPs) improved antioxidant capacity in all samples and the interactions between BTI and dairy components significantly altered the texture of ADGs. Such alterations were more pronounced in the samples with higher proportion of BTI (60%) and/or longer storage time (28 days).

Microbubbles have attracted widespread attention within the academic community, owing to their great potential for applications in microsystems. Considering practical applications, it is critical to use a simple method to generate a controllable microbubble without contaminating the target environment. In this paper, we propose a convenient and controllable method to generate a vapor microbubble using a monolayer graphene-assisted microfiber (GMF). When the light beam at a wavelength of 1.55 μm is coupled to GMF immersed in liquid, light energy can be converted into heat energy due to the photothermal effect of graphene, and thus a stable and controllable microbubble can be generated due to the existence of a temperature gradient around the GMF. This microbubble is used to capture microsphere particles such as polystyrene particles by means of the Marangoni Convection around it. Compared with bare microfiber, GMF has a higher fabrication tolerance for the purposes of generating microbubbles, and a lower threshold optical power due to the strong photothermal effect of graphene. Our proposed device, which demonstrates advantages such as ease of manufacture, simple structure, and biocompatibility, is a promising candidate for future applications in the fields of directional transport of drugs, biomedicine, biochemistry, microfluidics, etc.

In a Wireless Sensor Network (WSN), when a large amount of sensors are randomly deployed into a detection area, an efficient sleep/active scheduling for sensors to maximize the network lifetime of target (or detection area) coverage, which is called the coverage problem, is an important issue. The problem was proved NP-complete. Recently, many methods were proposed for solving the coverage problem, each of which can be divided into two phases: the first is to find as many as possible coverage sets from the sensors and the other is to schedule the coverage sets got from the first phase. Therefore, all coverage problems involve the scheduling process of the coverage sets to maximize the network lifetime. In this paper, we investigate the Maximum Coverage Sets Scheduling (MCSS) problem: given a coverage set collection in which each coverage set covers all targets (or the whole detection area) in WSN, the problem is to find a feasible scheduling for the coverage set collection to maximize the network lifetime. Firstly, we prove the MCSS problem is NP-hard. Secondly, we formulate the problem as an integer linear programming problem. Thirdly, we first propose a greedy algorithm, called Greedy-MCSS, to solve the MCSS problem. Then based on the Greedy-MCSS algorithm, we propose an approximation algorithm, MCSS Algorithm (MCSSA) for solving the MCSS problem, which gives the theoretical performance guarantee. Finally, extensive simulation results are shown to further verify the performance of our algorithms.

The particles in the population of the firefly algorithm learn from each other using an all-attractive model, and the algorithm has a strong ability of social learning and global detection. However, the algorithm ignores the role of the global optimal particle, resulting in weak self-learning and local development ability of the algorithm. Therefore, this paper proposes an intelligent single-particle learning firefly algorithm. The algorithm divides the iterative process into two stages, the first stage adopts the standard firefly algorithm to evolve; in the second stage, the intelligent single particle optimisation algorithm is used to optimise the global optimal particle. The iterative process in the first stage ensures the sociality and global detection ability of the particle, and the second stage enhances the ability of self-learning and local development of the algorithm. The experimental results show that the algorithm in this paper has better performance.

One significant problem in exchange networks is finding the equilibrium. To solve this problem, the concept of stable outcome has been developed. However, there are few effective methods to solve it from the point of graph theory. In this paper, we propose a minimum cost stable outcome (MCSO) problem, which is to find a stable outcome whose total transaction cost is minimized. Two algorithms have been designed to solve this problem on unit and general profit networks respectively. For unit profit networks, we use minimum cost edge cover based method to give the optimal solution. For general profit networks, we develop an approximate algorithm and prove that performance ratio is no more than twice the optimal value. Moreover, we provide the probabilistic analysis. At last, extensive experiments have been conducted on synthetic and real-life datasets. Experimental results validate the performance of the proposed algorithms.

Accurate and robust localization is crucial for wireless ad-hoc and sensor networks. Among the localization techniques, component-based methods advance themselves for conquering network sparseness and anchor sparseness. But component-based methods are sensitive to ranging noises, which may cause a huge accumulated error either in component realization or merging process. This paper presents three results for robust component-based localization under ranging noises. (1) For a rigid graph component, a novel method is proposed to evaluate the graph's possible number of flip ambiguities under noises. In particular, graph's \emph{MInimal sepaRators that are neaRly cOllineaR (MIRROR)} is presented as the cause of flip ambiguity, and the number of MIRRORs indicates the possible number of flip ambiguities under noise. (2) Then the sensitivity of a graph's local deforming regarding ranging noises is investigated by perturbation analysis. A novel Ranging Sensitivity Matrix (RSM) is proposed to estimate the node location perturbations due to ranging noises. (3) By evaluating component robustness via the flipping and the local deforming risks, a Robust Component Generation and Realization (RCGR) algorithm is developed, which generates components based on the robustness metrics. RCGR was evaluated by simulations, which showed much better noise resistance and locating accuracy improvements than state-of-the-art of component-based localization algorithms., Comment: 9 pages, 15 figures, ICCCN 2018, Hangzhou, China

Placing relay nodes in wireless sensor networks is a widely-used approach to construct connected network topology. Previous works mainly focus on the relay node minimization while achieving network connectivity but pay less attention on the path performance guarantee. In this paper we first investigate the hop-constrained relay node placement optimization which aims at using as few relays as possible to construct sensor-to-sink paths meeting the hop constraint given by the end user. We present a heuristic-based algorithm to solve the above optimization problem and evaluate its performance by extensive simulation. The experimental results demonstrate that the efficiency of our designs in comparison with two baselines.

The sensors in wireless sensor network (WSN) are vulnerable to malicious attacks due to the transmission nature of wireless media. Secure and authenticated message delivery with low energy consumption is one of the major aims in WSN. The identity-based key authentication scheme is more suitable for the WSN. In this paper, the Hierarchical Matrix Decomposition-based Signcryption (HMDS) algorithm was proposed, which is a kind of identity-based authentication scheme. In HMDS scheme, three-layer architecture, base station (BS), cluster head, and intracluster, is employed to adapt to the common structure of WSN. As the key generation center (KGC), the BS adopts matrix decomposition to generate the identification information and public key for cluster head, which not only reduces the cost of calculation and storage but also avoids the collusion attack. Experiments show that the HMDS algorithm has more advantages over other algorithms and is very suitable for the large-scale WSN.

The sensors in UWSN are vulnerable to malicious attack due to the transmission nature of wireless media under the water. Secure message delivery with low energy consumption is one of major aims in UWSN. In this paper, a Hierarchical Identity-based Signcryption (HIS) scheme is proposed for UWSN. Signcryption mechanism, which completes the signature and encryption in a single logical step, is adopted in the HIS scheme to decrease the communication and computation cost. The private keys of nodes are generated based on the node’s identity to decrease the communication cost. Two-layer architecture, cluster head layer and intra-cluster layer, is employed in the HIS scheme. Taking the difference on capacity between the cluster heads and ordinary nodes into account, we perform encrypting operations with different computation complexity in the two layers. The simulation results show that the HIS scheme outperforms ECC-CA, GLKM and AVM algorithm on energy consumption and time cost.

Natural Science Foundation of China [51273040]; Program for Changjiang Scholars and Innovative Research Team in University [T2011079, IRT1221]; National Natural Science Foundation for Distinguished Young Scholar of China [50925312]; Shanghai Nano Special Projects [11nm0500100]; Program of Introducing Talents of Discipline to Universities in China [111-2-04]

In this paper, two efficient numerical algorithms for the distributed order time fractional reaction-diffusion equation with Neumann boundary conditions are proposed, combining the finite difference method in time with Legendre spectral and Gauss-Lobatto-Legendre-Birkhoff (GLLB) pseudospectral method in space, respectively. It is proved that both of the schemes are unconditionally stable and have the same convergent order O(τ2 + Δα2 + N1-m), where τ, Δα, N and m are the temporal step, step size in distributed-order variable, polynomial degree and spatial regularity of the exact solution. Numerical results are presented to support the theoretical analysis.

Circular RNAs (circRNAs) are recognized as functional non-coding transcripts in eukaryotic cells. Recent evidence has indicated that even though circRNAs are generally expressed at low levels, they may be involved in many physiological or pathological processes, such as gene regulation, tissue development and carcinogenesis. Although the ‘microRNA sponge’ function is well characterized, most circRNAs do not contain perfect trapping sites for microRNAs, which suggests the possibility that circRNAs have functions that have not yet been defined. In this study, we show that a circRNA containing an open reading frame (ORF) driven by the internal ribosome entry site (IRES) can translate a functional protein. The circular form of the SNF2 histone linker PHD RING helicase (SHPRH) gene encodes a novel protein that we termed SHPRH-146aa. Circular SHPRH (circ-SHPRH) uses overlapping genetic codes to generate a ‘UGA’ stop codon, which results in the translation of the 17 kDa SHPRH-146aa. Both circ-SHPRH and SHPRH-146aa are abundantly expressed in normal human brains and are down-regulated in glioblastoma. The overexpression of SHPRH-146aa in U251 and U373 glioblastoma cells reduces their malignant behavior and tumorigenicity in vitro and in vivo. Mechanistically, SHPRH-146aa protects full-length SHPRH from degradation by the ubiquitin proteasome. Stabilized SHPRH sequentially ubiquitinates proliferating cell nuclear antigen (PCNA) as an E3 ligase, leading to inhibited cell proliferation and tumorigenicity. Our findings provide a novel perspective regarding circRNA function in physiological and pathological processes. Specifically, SHPRH-146aa generated from overlapping genetic codes of circ-SHPRH is a tumor suppressor in human glioblastoma.

The numerical approximation of the nonlinear time fractional Klein-Gordon equation in a bounded domain is considered. The time fractional derivative is described in the Caputo sense with the order $\gamma$ ($1 \lt \gamma \lt 2$). A fully discrete spectral scheme is proposed on the basis of finite difference discretization in time and Legendre spectral approximation in space. The stability and convergence of the fully discrete scheme are rigorously established. The convergence rate of the fully discrete scheme in $H^1$ norm is $\mathrm{O}(\tau^{3-\gamma} + N^{1-m})$, where $\tau$, $N$ and $m$ are the time-step size, polynomial degree and regularity in the space variable of the exact solution, respectively. Numerical examples are presented to support the theoretical results.

A camera sensor network is a sensor network of a group of camera sensors and is being deployed for various surveillance and monitoring applications. In this paper, we propose a new surveillance model for camera sensor network, namely half-view model, which requires a camera sensor network to capture the face image of any object if it moves forward to pass over an area of interest. Based on this new surveillance model, we introduce a new sleep-wakeup scheduling problem in camera sensor network, namely the maximum lifetime half-view barrier-coverage (MaxL-HV-BC) problem, whose goal is to find an on-off schedule of battery-operated camera sensors such that the continuous time duration providing half-view barrier-coverage over an area of interest is maximized. We develop a strategy to check if a region is half-view covered by a given set of camera sensors, and use this strategy to design two new heuristic algorithms for MaxL-HV-BC. We also conduct simulations to compare the average performance of the proposed algorithms with a trivial solution as well as the theoretical upper bound.

The preparation of granular X-type zeolite/activated carbon composites from a locally available elutrilithe by adding pitch powder and solid SiO2 was studied, and the variations in the synthesis process of zeolite X were investigated. The preparation steps of the composite involved (1) calcination of pre-shaped mixture (2) activation of the carbonaceous material from elutrilithe and pitch to prepare activated carbon and (3) hydrothermal conversion (zeolitisation) of aluminosilicate in elutrilithe and additional SiO2 to zeolite X in alkaline medium. The adding of additional SiO2 in the reaction system to adjust SiO2/Al2O3 ratio of the reaction mixture was necessary for the formation of zeolite X. The characterization of XRD, SEM and N2 adsorption of the resulting composites had a hierarchical pore structure, which shows that pure X-type zeolite phase with high crystallinity could be obtained regardless of the content of carbon in the composites.

In this study, polyamide 6 (PA6) with various contents of halloysite nanotubes (HNTs) and melamine cyanurate (MCA) were prepared by a twin-screw extruder. The flame retardant and physical properties of PA6 composites were examined. X-ray diffraction (XRD) patterns of PA6/HNTs and PA6/MCA/HNTs composites showed that HNTs as a nanoscale material dispersed in PA6 whether with MCA or not. Thermo gravimetric analyzer (TGA) results showed the presence of HNTs can improve thermal stability of PA6 and PA6/MCA composites. The incorporation of HNTs seemed to result the increase of crystallinity of PA6 and PA6/MCA composites from the differential scanning calorimetry (DSC) results. The combined of HNTs and MCA that leads to further improvements limiting oxygen index (LOI) value of PA6 to 31.7% exerted a positive effect on flame retardancy of PA6. What's more, some mechanical enhancements of PA6 with adding of HNTs were achieved and HNTs also made the tensile properties of PA6/MCA composites improved. POLYM. COMPOS., 36:892–896, 2015. © 2014 Society of Plastics Engineers

Mobile phones with embedded sensors have been applied in various collaborative sensing applications. To encourage mobile phone users to perform collaborative sensing, the data demanders usually pay mobile phone users for required data. In this paper, we study the Minimum Payment of Attaining the Required Data with mobile phones (MPARD) problem in collaborative sensing network: given sensing regions $$R = \{R_1, R_2, \ldots , R_m\}$$ R = { R 1 , R 2 , ? , R m } , the set of requisite data $$D_i$$ D i for each sensing region $$R_i$$ R i and a set of mobile phones $$M$$ M , the $$MPARD$$ M P A R D problem studies how to select mobile phones to obtain all the required data such that the data demanders' total payment to mobile phone users is minimized. In reality, some systems need the fresh sensing data from mobile phones at each pre-determined time slot, and others don't require the real-time data and the sensing data from previous time slots is also deemed useful. Based on the above two different requirements of data timeliness, we first define two subproblems derived from $$MPARD$$ M P A R D problem: $$MPARD_t$$ M P A R D t and $$MPARD_p$$ M P A R D p . After that, for each subproblem, we propose an approximation algorithm for the situation where the trajectories of mobile phones are determinate and a heuristic for the situation where trajectories are unknown. Simulation results demonstrate that our algorithms are efficient.

Tin mud ore separation is always the key to improve the utilization of tin resources. In view of the tin mud ore in Gejiu Yunnan province, the circulating fluidized bed is used for preconcentration. And reasonable separation parameters were determined based on the ore properties. When the tin grade in the feed is 0.3%, we can obtain the rough concentrate whose tin grade is 0.492% and recovery is 67.35%, and 60% of ore as tailings can be discarded. Then desulfurization and flotation was used, and YP-6 as collector, P86 as auxiliary collector and oxalic acid as regulator, a tin concentrate with grade of 4.38% and recovery of 77.18% was obtained by closed circuit test. The tin recovery of original mud ore was 51.02%, and the separation effect was improved.

The mode-order converter is a building block in a multimode optical transmission and switching system. It can be used for switching signals carried on different mode channels. However, such devices constructed by conventional structures can commonly accomplish one mode-order conversion process. It is because the phase-matching condition, which is utilized by a majority of designs, can usually be fulfilled between only one mode pair for specific device geometry. In this Letter, we propose a dual-polarization mode-order converter referring to the concept of a silicon planar metasurface. It can realize mode-order conversions on transverse electrical and transverse magnetic polarizations in parallel. In order to verify our concept, we design and experimentally demonstrate a prototype that can realize conversions from TE0 to TE1 and from TM0 to TM1 simultaneously. The footprint is 4 μm×1.6 μm. The measured insertion losses for both polarizations are smaller than 2.3 dB, and the crosstalk is lower than −11.5 dB within the wavelength range of 1525–1565 nm. We envision that the device can be a building block in polarization and mode multiplexed optical switching systems and endow the systems with simpler structure and a more compact footprint.

A mode-filtered light fiber-optic sucrose sensor was constructed from an annular column consisting of a bare optical fiber inserted into a capillary tube. A series of standard solutions with different concentrations of sucrose were measured by the sensor. The response range of the sucrose solution is 0%–60% (w/w). A linear relationship was found between the strength of the mode-filtered light and the sucrose concentration, with a correlation coefficient of 0.9994. The sensor exhibits good reproducibility and reversibility, as well as good standardized recovery for real samples. Thus, a real-time, fast, and sensitive determination method for sucrose concentration has been established.

In this paper, we study the minimum energy multicast/broadcast problem with reception cost in wireless sensor networks. Suppose there are n sensors in the network. Each node v has l(v) transmission power levels to choose and its reception cost is B(v) if it receives a message. The problem of our concern is: given a multicast (broadcast) request, how to find a multicast (broadcast) tree such that the total energy cost of the multicast tree including transmitting cost and reception cost is minimized. There are two cases for reception cost: one is that for any node v, the reception cost of v only relies on v itself and is irrelevant with its transmitting node, the other is that the reception cost of v relies on not only itself but also its transmitting node. For the first case, we firstly propose a general approximation algorithm MEB-R-G for the broadcast problem. Moreover, for the multicast problem, we propose a general algorithm MEM-R-G and prove its approximation ratio, we also present a greedy algorithm. For the second case, we also propose a general approximation algorithm MEM-RT-G, and prove its approximation ratio.

Activated carbon (AC) is the most extensively used electrode material for commercial electric double layer capacitors (EDLC) given its high specific surface area (SSA) and moderate cost. However, AC is primarily used in the forms of powders, which remains a big challenge in developing AC powders into continuous fibers. If AC powders can be processed into fiber, then they may be scaled up for practical applications to supercapacitors (SCs) and satisfy the rapid development of flexible electronics. Herein, we report a bottom-up method to fabricate AC fiber employing graphene oxide (GO) as both dispersant and binder. After chemical reduction, the fiber has high electrical conductivity (185 S m(-1)), high specific surface area (1476.5 m(2) g(-1)), and good mechanical flexibility. An all solid-state flexible SC was constructed using the prepared fiber as electrode, which is free of binder, conducting additive, and additional current collector. The fiber-shaped SC shows high capacitance (27.6 F cm(-3) or 43.8 F g(-1), normalized to the two-electrode volume), superior cyclability (90.4% retention after 10 000 cycles), and good bendability (96.8% retention after bending 1000 times).

High expression of Chemokine receptor 4 (CXCR4) is important in tumor invasion, metastasis, drug-resistance and maintenance of stemness in non-small cell lung cancer (NSCLC). We therefore studied the molecular characteristics of drug-resistant CXCR4-positive cells on epithelial-mesenchymal transition (EMT) for the future identification of the tumor cells with the properties of both EMT and stemness. EMT RT2 Profier PCR Array was performed to determine the expression levels of mRNA genes in A549 with TGF-β1 induced EMT (A549/TGF-β1) and gefitinib-resistant CXCR4-positive cells (A549/GR). TCGA database on the cBio Cancer Genomics Portal website and Gene Network Central (GNC) Pro Tutorial were used to analyze their clinical relevance and pathway interactions. CXCR4 was up-regulated both in TGF-β induced EMT cells and in gefitinib-resistant cells. In 84 mRNA genes related to EMT, 17 mRNA genes were up-regulated in CXCR4-positive population of A549/GR when compared to those in CXCR4 negative fraction, while 66 mRNA genes were up-regulated during TGF-β induced EMT. ITGA5, BMP7, MMP3, VIM, RGS2, ZEB2, TCF3, SNAI2, VCAN, PLEK2, WNT5A, COL3A1, SPARC and FOXC2 were doubly up-regulated during the two biological processes. Kaplan-Meier analysis indicated that the doubly up-regulated ITGA5, RGS2, SNAI2 and PLEK2 mRNA genes were related to poor overall survival in lung adenocarcinoma patients (P=9.291e-6, 0.0090, 3.81e-7 and 0.0013, respectively). In GNC analysis, SNAI2 mRNA gene but not ITGA5, RGS2 and PLEK2 was dependent on the signaling pathway of CXCR4. The molecular characteristics of drug-resistant CXCR4-positive cells have a crosstalk with EMT, which has the potential to find the marker with prognostic value on multiple signaling pathways in NSCLC.

One important problem of recommender system is rating prediction. In this paper, we use the movie rating data from MovieLens as an example to show how to use users’ attributes to improve the accuracy of rating prediction. Through data analysis, we observe that users having similar attributes tend to share more similar preferences and users with a special attribute have their own preferred items. Based on the two observations, we assume that a user’s rating to an item is determined by both the user intrinsic characteristics and the user common characteristics. Using the widely adopted latent factor model for rating prediction, in our proposed solution, we use two kinds of latent factors to model a user: one for the user intrinsic characteristics and the other for the user common characteristics. The latter encodes the influence of users’ attributes which include user age, gender and occupation. On the other hand, we jointly use user attributes or item category information and rating data for calculating similarity of users or items. The similarity calculating results are used in our proposed latent factor model as a regularization term to regularize users or items latent factors gap. Experimental results on MovieLens show that by incorporating users’ attributes influences, much lower prediction error is achieved than the state-of-the-art models. The prediction error is further reduced by incorporating influences from item category popularity and item popularity.

Energy cost and reliability are two main concerns in barrier coverage for wireless sensor networks. In this paper, we take the energy cost and reliability as objectives respectively to study two problems of k-barrier coverage: the minimum energy cost k-barrier coverage problem in static wireless sensor networks and the maximum k-barrier coverage problem in limited mobile wireless sensor networks. For the minimum energy cost k-barrier coverage problem, all sensors are stationary, and each sensor has l+1 sensing power levels in the network, the objective of the problem is to find a sensing level assignment to form k-barrier coverage such that the total power consumed by the k-barrier is minimized. We firstly transform it into a minimum cost flow problem with side constraints and use Lagrangian relaxation technique to solve the minimum cost flow problem. Then, we also propose a heuristic algorithm. For the maximum k-barrier coverage problem, each sensor can move within the limited range, the objective of the problem is to form more barriers while some sensors can move within limited range. We formulate the problem into an integer linear programming (ILP), then propose two heuristic algorithms based on the linear programming (LP) relaxation. The simulation results demonstrate our algorithms are efficient.

To assess systematically whether potentially functional polymorphisms in DNA repair genes influence the clinical behavior of non-small-cell lung cancer (NSCLC), we examined the impact of a comprehensive panel of 218 signal nucleotide polymorphisms (SNP) in 50 candidate DNA repair genes on overall survival of NSCLC in a case-cohort of 568 lung cancer patients. SNPs associated with lung cancer prognosis primarily mapped to 14 genes in different repair pathways, and 6 SNPs were remained in the final model after multivariate stepwise Cox regression analysis: ATM rs189037; MRE11A rs11020802; ERCC2 rs1799793; MBD4 rs140693; XRCC1 rs25487, and PMS1 rs5742933. In the combined analysis of these 6 SNPs, an increasing number of unfavorable loci was associated with a poorer prognosis (P for trend

Two mesogen-jacketed liquid crystalline polyelectrolytes, poly{sodium 2,5-bis[(4-sulfophenyl)aminocarbonyl]styrene} and poly{sodium 2.5-bis[(4-sulfophenyl)oxycarbonyl]styrene}, with rigid cores containing different linkages at the center and sulfonate groups on the two ends in the side chains were designed and successfully synthesized via conventional radical polymerization. X-ray scattering experiments revealed that the two polymers exhibited smectic A phases in bulk. Comb-shaped nonstoichiometric polymer–surfactant complexes were obtained by mixing the anionic sulfonated polyelectrolytes and cationic lipids of different lengths and shapes. The formation of ordered structures of the complexes depended on the length and shape of the lipids. Lamellar phases were observed when the two polyelectrolytes complexed with cetyltrimethylammonium bromide and fan-shaped 3,4,5-tris(dodecyloxy)benzenamine. Owing to the stronger bond strength of electrostatic interactions, the types of mesophases of the complexes based...

The effect of multi-walled carbon nanotubes on the crystallization behavior of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) has been investigated. The results have shown that carbon nanotubes (CNTs) act as an effective heterogeneous nucleation agent, inducing an increase in crystallinity and crystallite sizes. Comparing with the double melting peaks in pure PHBV, there is only one peak in the melting curves of nanocomposites. The isothermal crystallization kinetics of PHBV and its nanocomposite containing 0.5% CNTs were examined based on Avrami equation, indicating that the crystallization half-time decreases while the overall crystallization rate k increases dramatically with CNTs addition. The spherulitic nucleation and growth kinetics were also discussed grounded on Lauritzen–Hoffman equation. It is found that there is a spherulitic growth rates (G) maximum within selected temperature range in our study. Also, the temperatures corresponding to G maximum shift to a high level with addition of CNTs. The parameters of the equilibrium melting temperature $$ T_m^0 $$ , the nucleation parameter K g , the lateral surface free energy σ, the fold surface free energy σ e , and the work of chain folding q of PHBV and its composite containing 0.5% CNTs were all calculated. The reductions of K g , σ e and q values of nanocomposite are in agreement with the fact that the crystallization rate of PHBV increases greatly by addition of CNTs.

A series of mesogen-jacketed liquid crystalline polymers, poly{2,5-bis[(4-alkoxyphenyl)aminocarbonyl]styrene} (P-Cm, where m is the number of carbon atoms in the alkoxy groups, and m = 1, 4, 8, 12), with an amide core and flexible tails of varying lengths on the two ends in the side chain were designed and successfully synthesized via conventional radical polymerization. The mesophase structures of these polymers were dependent on the number of carbon atoms in the peripheral chains. Wide-angle X-ray diffraction and polarized light microscopy results revealed that the polymers with m ≥ 4 could form smectic A phases, while a columnar nematic phase could be formed for the polymer with methoxy end groups (P-C1). The hydrogen bonding among the side-chain amide groups might play an important role in forming and stabilizing these liquid crystalline phases, which was suggested by the results from variable-temperature FTIR and 2D IR analyses.

Over the last decades, combined chemotherapies that inhibit different signalling pathways together have been demonstrated to be more effective to treat the non-small-cell lung cancer (NSCLC). The epidermal growth factor receptor (EGFR) and the vascular endothelium growth factor (VEGF) are two key targets. Polymorphisms in EGFR and VEGF genes have been identified to be associated with therapy-response and cancer survival. In this study, we hypothesized that single-nucleotide polymorphisms (SNPs) of EGFR and VEGF genes are associated with NSCLC patients' survival in Chinese. Therefore, we screened and genotyped 54 potentially functional SNPs as well as tagging SNPs in these two genes using Illumina Golden Gate platform in 568 NSCLC patients. We found that subjects carrying EGFR rs3735061AA and rs6958497AG/GG genotypes survived significantly shorter time [median survival time (MST): 22.2 and 19.4 months, respectively] than those carrying rs3735061AG/GG (MST: 25.1 months) and rs6958497AA (MST: 25.9 months) (log-rank P = 0.015 for rs3735061 and log-rank P = 0.028 for rs6958497). However, subjects carrying EGFR rs759165AG/AA genotypes survived significantly longer (MST: 38.7 months) than those carrying rs759165GG genotype (MST: 24.7 months) (log-rank P = 0.024). Multivariate Cox regression analyses showed that the genotypes of rs3735061AA and rs6958497AG/GG were associated with a significantly increased risk of death for NSCLC [hazard ratio (HR) = 2.82, 95% confidence interval (CI) = 1.66-4.78 for rs3735061AA and HR = 1.69, 95% CI = 1.26-2.28 for rs6958497AG/GG], whereas the rs759165AG/AA were associated with a 44% significantly decreased risk of death of NSCLC (HR = 0.56, 95% CI = 0.39-0.83). Stepwise COX regression analyses suggested that EGFR rs373506, rs759165 and rs6958497 may be independent candidate biomarkers to predict NSCLC survival in this population.

Underwater Wireless Sensor Networks (UWSNs) are vulnerable to attack because of the broadcast nature of the transmission. The sensor nodes in UWSN are highly constrained in terms of computational capabilities and communication bandwidth. Authentication schemes for ground WSNs might not be applicable for UWSNs due to their less computation and communication capacity. Thus, it is necessary to design special schemes tailored to underwater environments. In this paper, a low computational complexity authentication scheme is proposed. By using Vandermonde matrix, we replace the matrix multiplication by matrix addition to greatly reduce the computation overhead. Moreover, our scheme is self-correctable and irreversible which further enhances the security of the UWSNs. Experiment results indicate our algorithm has advantages in energy and time consumption over traditional RSA and Blom's scheme.

Background It has been considered that the detection methods for circulating tumor cells (CTCs) based on epithelial cell adhesion molecule (EpCAM) underestimate the number of CTCs and may miss a metastatic subpopulation with cancer stem cell (CSC) properties. Therefore, we investigated EpCAM-positive and -negative CTCs in non-small cell lung cancer (NSCLC) patients at different stages, assessed the clinical value of these CTCs and explored their capacity in the following CSC model. Methods CTCs were enriched by the depletion of leukocytes with bi-antibodies using a magnetic bead separation technique and then identified by the expression of EpCAM and cytokeratin 7 and 8 using multi-parameter flow cytometry. We determined the distribution of CTCs classified by the expression of EpCAM in 46 NSCLC patients with stages I to IV, assessed the diagnostic value of these CTCs by longitudinal monitoring in 4 index patients during adjuvant therapy and characterized the stemness of these CTCs by the expression of CXCR4 and CD133 in 10 patients. Results EpCAM-negative (E-) CTCs were detected to be significantly higher than EpCAM-positive (E+) CTCs in stage IV (p = 0.003). The patients with the percentage of E-CTCs more than 95% (r > 95%) were detected to be significantly increased from 13.3% in stage I-II to 61.1% in stage IV (p = 0.006). Kaplan–Meier analysis indicated that the patients with r > 95% had significantly shorter survival time than those with r ≤ 0.95 (p = 0.041). Longitudinal monitoring of CTCs indicated that the patients with a high percentage of E-CTCs in the blood were not responsive to either chemotherapy or targeted therapy. Further characterization of CTCs revealed that a stem-like subpopulation of CXCR4+CD133+ CTCs were detected to be significantly more prevalent in E-CTCs than that in E+CTCs (p = 0.005). Conclusions The enrichment of CTCs by the depletion of leukocytes with bi-antibodies is a valuable method for estimating the number of CTCs, which can be potentially applied in predicting the prognosis, monitoring the therapeutic effect of NSCLC patients and further analyzing the biology of CTCs.

It is necessary to use a selective staining agent to enhance image contrast for transmission electron microscopy (TEM) morphological characterization of polymer composite particles. However, the typical selective staining agents osmium tetraoxide and ruthenium tetraoxide are neither suitable for poly(methyl methacrylate) (PMMA)/polyacrylonitrile (PAN) composite particles. In this study, it was found that phosphotungstic acid (PTA) solution with 6.4 pH value is unsuitable for PMMA, but it can stain PAN. Therefore, it can be a selective staining agent in the TEM for PMMA/PAN composite particles. By controlling different thermodynamic and kinetic polymerization parameters, PMMA/PAN and PMMA/P(AN-MMA) composite particles with nano to submicro sizes having different morphological structures were synthesized. TEM micrographs of all these composite particles with their predicted morphology have been compared, and the experimental results are completely consistent with the predictions.

We simulate and experimentally observe a tunable Fano resonance in a mutual coupling micro-ring resonator (MRR) system which is comprised of two cascaded micro-ring resonators. The scattering matrix model is employed to analyze the modulating characterization of the Fano resonance by changing the effective refractive index of MRRs, and the simulation results indicate that the Fano resonance is the sharpest when two MRRs' resonances are coincident. The Fano resonance device is fabricated on a silicon-on-insulator substrate using the standard complementary metal-oxide-semiconductor (CMOS) fabrication process. The experimental results show that the spectrum of the Fano resonance can be periodically tuned and flipped by applying forward-bias voltages to integrated micro-heaters above the MRRs. The proposed device has unique merits such as compact size, simple structure, CMOS compatible fabrication process, and large-scale integration, which is a promising candidate for high-sensitivity biochemical sensing and...