Search

Aiming at the problem that the standard RAW mechanism cannot adjust to changes in the network and the grouping depends on continuous AIDs,a RAW regrouping method based on a pseudo-random sequence was proposed.The AP assigned a pseudo-random sequence to the node as the address code during the association phase,and used compound code to carry groups information during the grouping phase.It implemented online regrouping of discontinuous AID nodes and reduced the overhead of regrouping.In order to rationally allocate resources in RAW and solve the problem of load imbalance between groups,a RAW regrouping method based on expected channel time was proposed.Based on channel utilization,the RAW groups,RAW duration,and numbers of RAW were optimized.NS3 simulation results show that the proposed method significantly improves the performance of IEEE 802.11ah protocol networks.

Experiments on surface-active polymer flooding for enhanced oil recovery were carried out by detection analysis and modern physical simulation technique based on reservoirs and fluids in Daqing placanticline oilfield. The experimental results show that the surface-active polymer is different from other common polymers and polymer-surfactant systems in molecular aggregation, viscosity and flow capacity, and it has larger molecular coil size, higher viscosity and viscosifying capacity, and poorer mobility. The surface-active polymer solution has good performance of viscosity-increasing and viscosity retention, and has good performance of viscoelasticity and deformability to exert positive effects of viscosifying and viscoelastic properties. Surface-active polymer can change the chemical property of interface and reduce interfacial tension, making the reservoir rock turn water-wet, also it can emulsify the oil into relatively stable oil-in-water emulsion, and emulsification capacity is an important property to enhance oil washing efficiency under non-ultralow interfacial tension. The surface-active polymer flooding enlarges swept volume in two ways: Microscopically, the surface-active polymer has mobility control effect and can enter oil-bearing pores not swept by water to drive residual oil, and its mobility control effect has more contribution than oil washing capacity in enhancing oil recovery. Macroscopically, it has plugging capacity, and can emulsify and plug the dominant channels in layers with high permeability, forcing the injected fluid to enter the layer with medium or low permeability and low flow resistance, and thus enlarging swept volume. Key words: high water-cut oilfield, reservoir, surface-active polymer, oil-washing efficiency, swept volume, plug by emulsification, enhanced oil recovery

It was difficult to meet the increasing demand of quality of service (QoS) for the best-effort IP network,so it was urgent to develop a kind of QoS control mechanism that was compatible with the existing IP software and hardware resources.Therefore,a priority-differentiated control mechanism based on the software defined networking called PriQoS was proposed.When the network resource was scarce,a multi-queue bandwidth allocation algorithm based on the inte-grated priority of service flow was used to meet the bandwidth requirement with high priority flows.PriQoS was deployed on the network edge,which was no need to modify applications in the end systems and routers in the core network.The mechanism has advantages such as easy to deploy and being compatible with the IP applications and devices.Experimental results show that the PriQoS mechanism can guarantee the QoS of higher priority services.

GIS technology can be used for all the services about spatial location,to improve the service efficiency and service quality of the OSS/BSS.The GIS technology development trend and OSS/BSS principle were introduced,the various applications of GIS technology in the OSS/BSS were summarized,the problems and evolutions in the GIS platform of telecommunications were analyzed,and GIS future trends forecast was made.

Cut flower chrysanthemum (Dendranthema grandiflora 'Jinba') plants were treated with 40 °C/35 °C or 33 °C/28 °C (day/night) for 11 days and then transferred to 23 °C/18 °C for 5 days to study the changes in their photosysnthesis and flourescence parameters under high temperature stress and normal temperature recovery. The results showed that on the 5th day of 33 °C/28 °C treatment, net photosynthesis (Pn) decreased gradually and stomatal conductance (Gs) decreased evidently; while after recovery for 5 days, both P n and G s resumed to 80% of the control. At 40 °C/35 °C, Pn and Gs decreased dramatically. The increase of intercellular CO2 concentration (Ci) at the early stage under given high temperatures that the photosynthesis inhibition by high temperature stress was resulted from non-stomatal limitations. However, 9 days later, stomatal limitation became the mainly cause of photosynthesis inhibition by high temperature stress was resulted from non-stomatal limitations. However, 9 days later, stomatal limitation became the mainly cause of photosynthesis inhibition. The intrinsic photochemical efficiency (Fv/Fm), quantum yields of PS II (Φ PS II), and the efficiency of excitation energy capture by open PS II reaction center (Fv'/Fm') at 33 °C/28 °C and 40 °C/35 °C all decreased light capture and efficiency of electron transfer through PS II. The photochemical quenching (qp) at 33 °C/28 °C descended first and turned to rise then, suggesting that the election transfer was firstly restrained by the stress. Contrastively, qp rose continuously at 40 °C/35 °C, indicating that oxygen-evolving complex (OEC) was the location in chrysanthemum photosynthesis apparatus most sensitive to extreme high temperature. [ABSTRACT FROM AUTHOR]

The arched rock bolt support plate is one of the key components in the rock bolting system, and its structural size and strength directly affect the rock bolting effect. In this paper, using the method of combining indoor experiments and numerical simulation, the diffusion evolution law of anchoring force in the interior of rock mass at different loading stages of arched rock bolt support plate is studied and analyzed, and secondly, the sensitivity of the diffusion evolution of anchoring force diffusion to the arch height and radius of arched rock bolt support plate is analyzed by using orthogonal experiment theory. The study found that: the anchoring force is transmitted to the rock mass through the tray, and the diffusion forms a “stress bubble” type secondary stress field; if the anchoring force is less than the bearing strength of the rock bolt support plate, the secondary stress field range increases with the increase of the anchoring force, and vice versa; factors such as the arch radius and arch height of the arched rock bolt support plate have a significant impact on the secondary stress field range, but the primary and secondary order of sensitivity is the arch radius > the arch height.

Objective To examine serum C-reactive protein (CRP), tumor necrosis factor-α(TNF-α), tumor necrosis factor-β(TNF-β), E-cadherin (E-cad), human interferon-γ (IFN-γ) and cluster of differentiation 8 (CD8) in patients with vitiligo. Methods From May 2017 to December 2018, 60 patients with vitiligo (30 cases in active phase group and 30 cases in stable stage group) and 30 cases as control group collected from physical examination center joined the research program. The content of serum CRP, TNF-α, TNF-β, E-cad, IFN-γ and CD8 were compared among the three groups by enzyme-linked immunosorbent assay (ELISA). Results The content of serum CRP, TNF-α, TNF-β and IFN-γ in patients with active and stable vitiligo were significantly higher(P＜0.05). The content of serum IFN-γ in patients with active vitiligo was significantly higher than that in patients with stable vitiligo(P＜0.05)and significantly decreased after 6 months of treatment(P＜0.05). Conclusions The content of serum IFN-γ might be used as a biomarker in laboratory to evaluate the activity of vitiligo.

Nuclear data are fundamental data for nuclear energy, nuclear engineering, nuclear technology applications and nuclear science research, and have always received national attention. In particular, the importance of neutroninduced fission nuclear reaction data is unquestionable and the theoretical evaluation of nuclear data is required for a long period of time. The reaction mechanism of neutron induced fission reaction is very complicated and needs to be described by several different nuclear reaction models, such as optical potential model and compound nuclei model and so on. Nowadays, the most famous international nuclear reaction program systems are TALYS and EMPIRE. In China, the program FUNF is a fission nuclear reaction program system with our own independent intellectual property rights, which was developed by Prof. Zhang Jingshang of the China Nuclear Data Center. Each of these program systems need more than 40 parameters to be adjusted. Therefore, it is necessary to optimize a large number of parameters at the same time in order to correctly describe the nuclear fission reaction data. In this work, the FUNF program system was used to calculate the fission reaction data of neutron induced 238U. The fast neutron reaction data of fissile materials with incident energy from about 1 keV up to 20 MeV were calculated by FUNF code. It consists of the spherical optical model, the HauserFeshbach model, and the angular momentum dependent exciton model to describe the emission from compound nucleus to the discrete levels of the residual nuclei in preequilibrium process, meanwhile equilibrium reaction process was described by the HauserFeshbach model with width fluctuation correction. Based on the FUNF nuclear fission reaction model, the parameters of the FUNF program system was adjusted by the advanced optimization method MINUIT. MINUIT is a numerical minimization software library in the Fortron by CERN staff Fred James in the 1970 s. Then, combined with the parallel calculation method of MPI (message passing interface), preliminary calculations for the neutron induced fission reaction of 238U were performed. The results show that the FUNF parameters obtained by the MINUIT optimization method can well describe the fission reaction data of 238U. Next, the procedure will continue to be optimized to further improve the efficiency of the tuning parameters and the accuracy of the parameters. And the application to the relevant fission nuclear reactions will be developed to improve the accuracy of our fission nuclear reaction data.

Neutron induced reaction cross sections play an important role in nuclear science and technology research, such as national defense, nuclear energy construction and development, nuclear medicine, radiation protection and nuclear safety. With the rapid development of nuclear technology, there are increasing demand for the variety and accuracy of neutron data. As an important structure material nuclide, the accuracy of neutron induced reaction cross section on 56Fe is directly related to the design and operation of reactors, spent fuel disposal and miniaturization design, and also of great significance to nuclear physics basic research. The 56Fe(n,p)56Mn reaction is usually used as the standard to monitor the neutron field flux in the experiment. It greatly influences the results of nuclear data measurement, and also has guiding significance for upon carry the determination of the parameters in the nuclear reaction model. Due to the obvious differences existing in the previous experimental data and inconsistency between the evaluation databases, the experimental measurement data evaluation and covariance analysis were carried out for the 56Fe(n,p)56Mn reaction cross section in this paper. Firstly, the existing experimental measurement data of 56Fe(n,p)56Mn reaction cross section in EXFOR and literature were downloaded and systematically collected, then summarized, contrasted, and classified in terms of neutron source, measurement method, detector kinds, etc. Secondly, the data with low reliability were discarded with checking the original papers, and the uncertainty mentioned in these papers was also analyzed. Additionally, previous experimental results which using the imprecise values were adjusted and modified with the more accurate data such as recently ratios, supervised reaction standard cross sections, and isotopic abundances. The data with significant divergence near 14 MeV were normalized, which made it more concentrated and less divergent. The polynomial curve fitting was applied to obtain the excitation curve of 56Fe(n,p)56Mn reaction between 29535 MeV which was derived from the corrected and normalized results. Following that, the correlation covariance matrix was calculated for the suggested experimental data after evaluation. Meanwhile, the energy density, optical potential parameters, energy level density parameters, and other parameters of 56Fe(n,p)56Mn reaction were adjusted within the physical model calculated by the nuclear reaction simulation program TALYS. Finally, the reaction cross section of 56Fe(n,p)56Mn was computed theoretically, compared with experimental data and evaluation databases. This paper broadened the existing evaluation method of neutron activation reaction cross section experimental data, and also improved the accuracy of the assessment data for neutroninduced 56Fe(n,p)56Mn reaction cross section measured data below 35 MeV. The recommended assessment value and its covariance of the 56Fe(n,p)56Mn reaction excitation function were given based on the evaluted results of experimental data. Excitation function input file for 56Fe(n,p)56Mn reaction derived by adjusting the TALYS parameters agree well with the experimental and evaluation data. A set of standard assessment techniques were constructed, which serves as a guide for theoretical calculation and database construction of related nuclear data.

Objective To study the impact of comprehensive teaching mode and trainer experience on teaching effect of surgical basic technique training. Methods The present study adopted 2×2 factorial design. Seventy surgical interns were randomly assigned to the control group adapting lecture-based learning and the experimental group was trained with the comprehensive teaching mode integrating lecture-based, problem-based and case-based learning. Each study group was further randomly divided into two subgroups with either resident or attending surgeon as trainers. Results The comprehensive teaching mode was superior to the control group in terms of quantitative subjectobject assessment and operation time consumption, especially for “willingness to pursue a career in surgery” “clinical reasoning” and “direction of future development”. Furthermore, except for “clinical reasoning”, the teaching effect of resident didn't show statistically significant difference with attending surgeon. Conclusions The comprehensive teaching mode exhibits better teaching effect as compared with the classoc lecture-based learning. The surgical resident is fully competent to serve as the trainer for surgical basic technique training program.

In some scenarios of opportunistic network,energy could not be replenished.It was prone to flooding attacks in opportunistic network.The energy consumption of nodes and the effect on the network lifetime caused by flooding at-tacks under the mechanism of the Epidemic routing was analyzed.The analysis showed that the increase of malicious nodes had significant effects on network lifetime,and the number of packets from malicious nodes can only had effects in particular scenarios,and had minimal effects.ONE to simulate flooding attacks was used,the simulation results are same as the theoretical analysis.