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More and more enterprises are migrating services and data into virtual machine (VM) using base and increment, and the files in the VM may contain critical data. Therefore, it is necessary to build a trusted environment to enhance the security of the files in VM by the integrity measurement methods (IMMs). In order to simplify the management of the files in integrity measurement, the security manager needs to put these files into one region and then to measures the integrity of the region. If the region is integrity, the files in that region are integrity too. Currently, the traditional IMMs are all based on the message digest algorithms that use too much amount of data, spend much time, and make the performance of VMs degraded. Aiming to address those problems, we propose a novel IMM based on copy-on-write for the region, called RIMM. The method puts the region into the base image, gets the integrity information of the region from the base image by the structures of image and region, and periodically measures the integrity of the region in the increment image by the structure of image and copy-on-write. It is transparent for VM and can eliminate the semantic gap. The evaluation shows that the RIMM can significantly reduce the amount of data and time in the process of integrity measurement. For example, (1) when the region size is 100MB, the amount of data used by RIMM is about 400 times smaller than that used by IMMs based on MD5; the time spent by RIMM is about 600 times less than that used by IMMs based on MD5. (2) when the region size is 9GB, the amount of data used by RIMM is about 29000 times smaller than that used by IMMs based on MD5; the time spent by RIMM is about 3864 times less than that used by IMMs based on MD5.

In this work, BCN-TiO2(A+R) heterojunctions were constructed via a simple one-step calcination method as efficient photocatalysts for H2 evolution. Simultaneously, an anatase/rutile phase-junction was also obtained due to the crystalline phase transformation that occurred during high-temperature calcination. The unique heterojunction and phase-junction lead to the formation of an intimate interface and large contact area between two semiconductors and extended the visible-light absorption range. Therefore, BCN-TiO2(A+R) heterojunctions with a mixed anatase and rutile phase exhibit enhanced photocarrier separation efficiency, realizing an eleven-fold increase in the electron lifetime compared to that of pure TiO2 and yielding a remarkable visible-light-driven H2 evolution rate nearly 7.5 and 12.2 times higher than that of TiO2(A+R) and pure BCN, respectively. This work provides a new strategy for designing efficient water-splitting photocatalysts with highly efficient charge separation and transfer.

The development of the cloud and data centers alike has caused users to increasingly share storage systems, and storage systems have adopted SSDs to improve performance. The number of users is growing sharply and causing resource competition, so the throughput allocation of a hybrid storage system has an important effect on users’ performance. A hybrid storage architect faces a challenge: sharing I/O throughput resources between SSDs and HDDs fairly with high resource utilization. Drawing on economic game-theory, many methods based on Leontief preference have been proposed to determine fair throughput allocation in a hybrid storage system with having the properties of Sharing Incentive (SI), Envy Freeness (EF) and Pareto Optimality (PO). However, users’ workload characteristics vary because of the adoption of SSDs, so there is heterogeneity among the storage media. The heterogeneity of storage media and the diversity of user workloads together create more constraints on fairness, which imposes restrictions to improve the resource utilization. To improve the resource utilization, some researchers have proposed relaxing the limitation of fairness properties by adjusting users’ allocations. However, when adjusting the allocation between users, some users’ allocations are reduced but others’ are improved, with the goal of increasing the resource utilization of the whole system, this will pose a problem because of the Leontief preference restriction: some users’ performance is degraded, while other users’ performance is improved. In this paper, we first propose one variant of the Cobb–Douglas preference based on users’ workloads and allocations, and then present a throughput allocation model based on this variant named TACD that can capture the effects of diminishing returns and substitutability in throughput allocation for hybrid storage. By making use of these effects, TACD can improve some users’ performance while providing the same performance for other users and achieving higher resource utilization in the whole system, and it can provide a fair allocation while enjoying SI, EF and PO properties. The variant of the Cobb–Douglas preference proposed in this paper has taken consideration of users’ workloads, so TACD can conduct the throughput allocation based on these workloads for meeting the performance requirements of users reasonably. Extensive experiments are conducted to prove the effectiveness of TACD. The simulation results show that TACD can fit the throughput allocation of hybrid storage system very well. The Linux results show that compared with the allocation method based on Leontief preference, TACD can provide a higher resource utilization and performance for users throughout the system, it can improve some users’ performance when maintaining comparable performance for other users, in contrast to the Leontief method based on weaker fairness under the same resource utilization, and its allocation result enjoys SI, EF and PO properties.

Background Endoscopic endonasal clipping of intracranial aneurysms may use microsurgical techniques as an alternative to the transcranial approach. Here we report a series of patients who underwent microsurgical clipping of anterior circulation aneurysms via an endoscopic endonasal approach (EEA). Methods This retrospective chart review included all the patients who underwent standard binostril EEA for aneurysm clipping. Surgical outcomes and complications are noted. The rationality and limitations of this procedure are discussed. Results Seven patients with 12 aneurysms of the anterior circulation underwent EEA for clipping. These 12 aneurysms consisted of 5 anterior communicating artery (AComA) aneurysms, 4 paraclinoid aneurysms, 1 ophthalmic artery aneurysm, and 2 aneurysm located in the cavernous segment of internal carotid artery (ICA). Nine of the 12 aneurysms were successfully clipped. One giant paraclinoid aneurysm could not be clipped during operation and was coiled in second endovascular stage. The 2 aneurysms located in the cavernous segment of ICA were not clipped intentionally in a single-stage procedure, after weighing the surgical benefit against the difficulty of surgical exposure and feasibility. The proximal control of ICA was achieved in all cases. There was no death, no cerebrospinal fluid leak, or other complications. All patients recovered completely. Conclusions EEA can provide direct access for microsurgical clipping of strictly selected anterior circulation aneurysms. All the principles of cerebrovascular surgery must be followed. These procedures require a long learning curve. Only teams with adequate experience in microvascular and endoscopic skull base surgeries should attempt this approach for treating aneurysms.

An oxygen-vacancy-rich Z-scheme g-C3N4/Pd/TiO2 ternary nanocomposite was fabricated using nanotubular titanic acid as precursors via a simple photo-deposition of Pd nanoparticles and calcination process. The prepared nanocomposites were investigated by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and UV-visible diffuse reflectance spectroscopy, respectively. For g-C3N4/TiO2 binary nanocomposites, at the optimal content of g-C3N4 (2%), the apparent photocatalytic activity of 2%g-C3N4/TiO2 was 9 times higher than that of pure TiO2 under visible-light illumination. After deposition of Pd (1 wt%) at the contact interface between g-C3N4 and TiO2, the 2%g-C3N4/Pd/TiO2 ternary nanocomposites demonstrated the highest visible-light-driven photocatalytic activity for the degradation of gaseous propylene, which was 16- and 2-fold higher activities than pure TiO2 and 2%g-C3N4/TiO2, respectively. The mechanism for the enhanced photocatalytic performance of the g-C3N4/Pd/TiO2 photo-catalyst is proposed to be based on the efficient separation of photo-generated electron-hole pairs through Z-scheme system, in which uniform dispersity of Pd nanoparticles at contact interface between g-C3N4 and TiO2 and oxygen vacancies promote charge separation.

Objectives Removal of recurrent or residual symptomatic craniopharyngiomas is more challenging than the primary surgery. The extended endoscopic endonasal (EEE) approach has been proposed an alternative surgical route for removal of various suprasellar tumors including craniopharyngiomas currently. In this study, we summarized the operative experience and described the feasibility and advantages of this technique in recurrent or residual symptomatic craniopharyngiomas. Patients and methods A retrospective review of 15 patients (9 males and 6 females) whom underwent EEE approach between April 2012 and February 2017, were included in this study. The lesions included 8 purely suprasellar craniopharyngiomas (2 extraventricular, 6 intraextraventricular), 3 both intra- and suprasellar craniopharyngiomas, and 4 intrasellar craniopharyngiomas. The mean preoperative (that is, EEE approach) tumor volume was 10.54 cm3. The mean follow-up period was 23.1 months (range, 8–54). All patients were analyzed in terms of the treatment effect, complictions and follow-up results. Results Total removal of tumors was achieved in 12 patients (80.0%) and subtotal removal in 3 cases (20.0%). The pituitary stalks were identified in 11 patients during operations and secured in 8 patients. Postoperative visual acuity was improved in 10 cases, and normalization of the impairment was achieved in 3 patients. There were no significant differences between pre and postoperative endocrine function, except in one patient with normal preoperative pituitary hormone function who suffered postoperative hypopituitarism. Postoperative diabetes insipidus (DI) occurred in 14 patients including 6 patients who had long-term DI and others reporting transient postoperative DI. No cerebrospinal fluid (CSF) leak was identified. There were no deaths or major complications. Obesity developed in 2 patients, with no deaths and recurrent cases during follow-up period. Conclusion The pure EEE approach is a safe, effective alternative for treatment of recurrent or residual symptomatic craniopharyngiomas owing to its advantages including wide-angle view, close observation and elimination of brain retraction. Larger studies with further follow-up is needed to assess the long-term efficacy of this minimal access approach.

The inherent structure and connectivity of a group are important features of social networks. Finding the densest subgraphs of a graph directly maps to revealing the densest communities of a social network. Various techniques, e.g., edge density, k-core, near-cliques and k-cliques, have been developed to characterize graphs and extract the densest subgraphs of the graphs. However, as extraction of subgraphs with constraints is NP-hard, these techniques face a major difficulty of processing big and/or streaming data sets from social networks. This demands new methods from the expert and intelligent systems perspective for computation of the densest subgraph problem (DSP) with big and/or streaming data. The most recent method for this purpose is the “Sampling” method. It samples the big data sets, thus reducing the data space and consequently speeding up the DSP computation. But the sampled data inevitably miss out many useful data items. A new approach is presented in this paper for accelerated DSP computation with big and/or steaming data through data space reduction without loss of useful information. It uses a sliding window of small graphs with a fixed number of edges. Then, it filters out the least connected edges for each small graph. While the small graphs are processed, subgraphs are incrementally put together to reveal the densest subgraphs. Finally, the data space previously filtered out is checked for recovery of globally important edges. The approach is incorporated with existing subgraph extraction techniques for scalable and efficient DSP computation with improved accuracy. It is demonstrated for four subgraph extraction techniques over four Twitter data sets, and is shown to outperform the “sampling” method.

A hybrid self-growing polymer microtip is firstly proposed and fabricated as an ultracompact fiber-tip Fabry-Perot interferometer (FPI) with enhanced figure of merit (FoM). The hybrid microtip FPI is based on a sharp polymer microtip grown on an ultraviolet (UV) cured polymer film at the fiber end, which has exhibited significant interferometric visibility with high fringe contrast up to 30 dB in the reflection spectra. Using this tiny FPI, an optical fiber relative humidity (RH) sensor with the enhanced FoM of ∼ 0.95/%RH was demonstrated, which is ∼30 times higher than the previous optical fiber-based humidity sensors, and the achieved sensitivity is high enough to perform real-time human breath observation. Furthermore, the humidity sensor exhibited excellent performance in monitoring human breath with fast response time of ∼ 0.6 s. This new type of photonic microtip RH sensing element has shown advantages of compactness, flexibility, fast-response and high sensitivity, which provides a promising platform for potential applications in environmental and biological RH sensing, especially in a restricted space environment.

Logic minimization is one of the most crucial steps in combinational logic synthesis. The minimization for ternary fixed polarity Reed–Muller (FPRM) expressions aims to find a polarity that produces a ternary FPRM expression with as few operation terms as possible. However, the size of the ternary FPRM optimization space is much larger than that of binary FPRM optimization space, and the minimization for ternary FPRM expressions is a computationally hard problem. In this paper, we first propose a ternary quantum shuffled frog leaping algorithm (TQSFL) to solve the three-valued combinatorial optimization problem. The TQSFL divides frog individuals into three subpopulations: a subpopulation with a global updating strategy, a subpopulation with a local updating strategy, and a subpopulation with a random updating strategy, and performs local depth search on the three subpopulations based on the proposed ternary quantum rotation gate, ternary quantum correction mechanism, and ternary quantum crossover operator. Moreover, based on the TQSFL, we propose a minimization algorithm (MA) for ternary FPRM expressions, which searches for a polarity that produces a ternary FPRM expression with as few operation terms as possible by using the TQSFL. Experimental results demonstrated the effectiveness of the MA in minimizing ternary FPRM expressions.

Area optimization is one of the most important contents of circuit logic synthesis. In logical function expressions, mixed polarity Reed–Muller (MPRM) expansion produces a smaller area than Boolean expansion and fixed polarity Reed–Muller (FPRM) expansion. However, the area optimization for MPRM logic circuits is a combinatorial optimization problem, and the existing area optimization effect of MPRM logic circuits is poor. In this paper, an improved multiple disturbances fireworks algorithm is proposed to solve the combinatorial optimization problem of three-valued variables. Based on the ordinary fireworks algorithm, the algorithm we proposed initializes the individual of the fireworks population by introducing the Latin hypercube sampling model and introduces multiple disturbances in the process of iterative optimization of the population, so that the algorithm takes the global and local search into account, and achieves a good result. Moreover, we propose an MPRM logic circuits area optimization method, which uses the proposed improved multiple disturbances fireworks algorithm to search for the optimal polarity corresponding to MPRM logic circuits with minimum area. An adequate comparative analysis based on different MCNC benchmark circuits has been presented. The results of the experiment show that the method we proposed has a good effect on MPRM logic circuits area optimization.

BCN-TiO 2 nanocomposites are obtained by a simple calcination method using a hexagonal boron carbon nitride (BCN) semiconductor and nanotubular titanic acid (NTA) as precursors. The BCN-TiO 2 nanocomposites are characterized systematically by XRD, TEM, XPS, DRS, ESR, BET, I-t and PL techniques. Compared with the novel TiO 2 or single BCN sample, the BCN-TiO 2 nanocomposites prepared by a calcination method show the highest photocatalytic activity for hydrogen production under visible-light irradiation. The photocatalytic activity of BCN-TiO 2 nanocomposites is optimized by changing the amount of BCN. Characterization results confirm that a large amount of single electron oxygen vacancies can be formed when NTA was calcined at the higher temperature, which is beneficial to the enhancement of visible light absorption and the transfer of photogenerated carriers due to the formation of ohmic contact at the interface between BCN and novel TiO 2 . Therefore, the visible light photocatalytic activity for H 2 production of BCN-TiO 2 nanocomposites has been improved significantly by the formation of BCN-TiO 2 Z-scheme photocatalyst, which results in efficient space separation of photo-induced charge carriers.

Communication exacerbates the performance for parallel applications with thousands of CPU cores and quantities of data to exchange. The high communication cost is usually attributed to the mismatch between the communication patterns of parallel applications and the physical topology graphs of the computing resources (or the underlying network topologies). The topology-aware process mapping method can usually obtain a better embedding scheme with the aim to improve communication performance. Many existing heuristic-search based mapping methods have high execution time for large-scale applications. Some low-cost graph-partitioning based mapping methods depend on that the allocated resources form a regular structure, which is usually impractical in most high performance computing systems shared by multiple users and applications. This weakens their performance. Other graph-partitioning based mapping methods come at a high cost or require users to provide the network structure information. To address these issues, a quadratic time complexity topology-aware process mapping method is presented in this paper. The experimental results show that the proposed method often achieves a better application communication performance than several state-of-the-art mapping methods on a shared HPC system, while maintaining a significantly lower execution cost. Moreover, the real-world scientific application proxies gain an execution time reduction as large as 14.60% in the 512 process-scale compared to the system default process placement on the TianHe-2 HPC systems.

We demonstrated the sensitive CO detection in a novel hollow-core negative curvature fiber (HC-NCF) with infrared laser absorption at 2.3 μm. The HC-NCF consists of a single ring of eight nontouching silica capillaries around the air core, providing a single-mode light delivery of the 2.3-μm distributed feedback laser. A high coupling efficiency of 90% was achieved with the aid of optimal free-space coupling optics. The hollow-core fiber was used as a gas cell for gas absorption measurement of a total path length of 85 cm. Both direct absorption spectroscopy (DAS) and wavelength modulation spectroscopy (WMS) were adopted to demonstrate the sensor performance by detecting the CO line R(10) at 4297.7 cm−1. In scanned-wavelength DAS, we obtained a minimum detection limit (MDL) of 13 ppm CO, which was limited mainly by the existing mode noise in the HC-NCF. By applying a pressure difference of 0.8 bar between the two ends of the fiber, we demonstrated a very short gas loading time of only 5 s. Finally, we achieved a MDL of 0.4 ppm CO using the WMS technique, corresponding to a noise equivalent absorption of 1.6 × 10-7 cm−1.

Graphical abstractThis tile assembly system computes 01102mod 10011 over finite field GF(2n). Parameter a and the module f are encoded on the bottom DNA tiles, and the top row reads the final result 0111. Display Omitted Two major advantages of DNA computing - huge memory capacity and high parallelism - are being explored for large-scale parallel computing, mass data storage and cryptography. Tile assembly model is a highly distributed parallel model of DNA computing. Finite field GF(2n) is one of the most commonly used mathematic sets for constructing public-key cryptosystem. It is still an open question that how to implement the basic operations over finite field GF(2n) using DNA tiles. This paper proposes how the parallel tile assembly process could be used for computing the modular-square, modular-multiplication with two same inputs, over finite field GF(2n). This system could obtain the final result within less steps than another molecular computing system designed in our previous study, because square and reduction are executed simultaneously and the previous system computes reduction after calculating square. Rigorous theoretical proofs are described and specific computing instance is given after defining the basic tiles and the assembly rules. Time complexity of this system is 3n-1 and space complexity is 2n2.

Existing template matching based visual object tracking algorithms usually require to manually update the template and have high execution cost on general embedded systems. To address these issues, an adaptive template matching-based single object tracking algorithm with parallel acceleration is proposed in this paper. In this algorithm, we propose an adaptive single object tracking algorithm framework to achieve template update online. Based on the Faster-RCNN model, we design a single object capture method to update the template. Meanwhile, we present a parallel strategy to accelerate the process of template matching. To evaluate the proposed algorithm, we use OTB benchmark to compare the performance with several state-of-the-art trackers on TX2 embedded platform. Experimental results show that the proposed method achieves a 5.9 times execution speed and 71.9% accuracy improvement over the comparison methods.

With the scale expansion of high performance computer systems, efficient power management has developed into an important issue. To strive to balance power consumption and performance, this paper proposes an adaptive workload-driven dynamic power management policy for homogeneous clusters, which dynamically adjusts the power mode of computing nodes according to workload variation. The proposed policy combines the pre-wakeup method and the feedback mechanism to reduce performance degradation due to the wakeup delay. The experimental results demonstrate that, as compared with two existing timeout policies, adaptive workload-driven dynamic power management effectively reduced the performance loss with a slight increase in power consumption.

Many solutions have been proposed to tackle the load imbalance issue of parallel file systems. However, all these solutions either adopt centralized algorithms, or lack considerations for both the network transmission and the tradeoff between benefits and side-effects of each dynamic file migration. Therefore, existing solutions will be prohibitively inefficient in large-scale parallel file systems. To address this problem, this paper presents SALB, a dynamic and adaptive load balancing algorithm which is totally based on a distributed architecture. To be also aware of the network transmission, SALB on the one hand adopts an adaptively adjusted load collection threshold in order to reduce the message exchanges for load collection, and on the other hand it employs an on-line load prediction model with a view to reducing the decision delay caused by the network transmission latency. Moreover, SALB employs an optimization model for selecting the migration candidates so as to balance the benefits and the side-effects of each dynamic file migration. Extensive experiments are conducted to prove the effectiveness of SALB. The results show that SALB achieves an optimal performance not only on the mean response time but also on the resource utilization among the schemes for comparison. The simulation results also indicate that SALB is able to deliver high scalability.

Plasmonic aerogel containing 50 nm gold nanoparticles is made using a modified 2-step method that maintains control over the gel time while preventing nanoparticle aggregation. Strong narrow surface plasmon resonances verify that the nanoparticles are well dispersed within the silica matrix, and enable applications in sensing, SERS, nonlinear optics or plasmonic gain. Discrepancies between measured and simulated resonance wavelengths are attributed to the breakdown of the effective index approximation, due to the short-scale penetration of the resonance electric field into the host medium.

With the increase of the computing demand, cluster is becoming one of the most important computing infrastructures. Most of cluster systems use central air conditioning to remove heat. Therefore, the hot spot is unavoidable. Motivated by alleviating the hot spot issue and optimizing workload distribution, we propose a thermal-aware workload distribution policy. It ranks the nodes according to the thermal characteristics of racks layout and dispatches the workloads based on the ranked node queue. We analyze the saving power trend and validate that this policy can reduce power consumption to some extent with no impact on quality of service (QoS).

The effects of loading Fe(3+), Mg(2+), Cu(2+) or Ag(+) on activated carbons (ACs) on interaction of the carbon surfaces with dichloromethane (DCM) and trichloromethane (TCM) were investigated. Temperature-programmed desorption (TPD) experiments were conducted to measure the desorption activation energy of DCM/TCM on the ACs separately doped with ions Fe(3+), Mg(2+), Cu(2+) and Ag(+). The absolute hardness and electronegativity of DCM and TCM were estimated on the basis of density functional theory. The influence of loading the metal ions on the ACs on the interaction of its surfaces with DCM/TCM was discussed. Results showed that the desorption activation energy of DCM and TCM on the modified ACs followed the order: Fe(III)/AC>Mg(II)/AC>Cu(II)/AC>AC>Ag(I)/AC. Both DCM and TCM were hard base. The loading of ion Fe(3+) or Mg(2+) on the surface of the ACs enhanced the interaction between DCM/TCM and the surfaces due to Fe(3+) and Mg(2+) being hard acid, while the loading of ion Ag(+) on the surface of the AC weakened the interaction between DCM/TCM and the carbon surfaces due to Ag(+) being soft acid.

Refractive index (RI) sensing based on the anti-guiding property of a depressed-index core photonic crystal fiber (PCF) is studied. A new type of RI sensor is formed by adding a hole to the core of a conventional index guiding PCF for the purpose of measurand filling and the depressed-index core formation. The dependencies of measurement resolution and dynamic range on the structural parameters of the RI sensor are investigated. RI sensors filled with the measurand covering a refractive index range from 1.328 to 1.445 are numerically simulated. Simulation results show that the measurement resolution from 9.32 × 10 −7 to 1.23 × 10 −7 can be achieved by means of wavelength measurement with an optical spectrum analyzer with 0.01 nm resolution. Also, problem caused by the existence of the photonic bandgap (PBG) mode which may influence the feasibility of the RI sensing mechanism is considered.

A whole temperature sensor in one package utilizing a fiber Bragg grating (FBG) made in a conventional single-mode fiber and which uses a long-period grating (LPG) made in a photonic crystal fiber is proposed and experimentally demonstrated. The function of the interrogation is that the wavelength change of the FBG with environmental temperature is transferred to the intensity of the output via the LPG. Utilizing the temperature-insensitivity of the LPG in the PCF, the interrogation is stable and enables a cheap and practical temperature measurement system with a wide dynamic range.

A theoretical analysis of strongly pumped Yb-doped double-clad fiber lasers is presented and an approximate analytic function of distributed laser along the whole fiber with the scattering loss is obtained for the first time. A comparison is made between the analytic solution and the exact numerical solution. The results have shown that the analytic function of distributed laser within the fiber is accurate and explicit. With the analytic solution the losses caused by laser scattering are shown in three different pump modes. The results verify that the backward pumping can get the highest output power in strongly pumped fiber lasers.