Ca and Sr co-doping induced oxygen vacancies in 3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts for boosting low-temperature oxidative coupling of methane

It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.

Design and Implementation of an SDN-Enabled DNS Security Framework

The Domain Name System(DNS) is suffering from the vulnerabilities exploited to launch the cache poisoning attack. Inspired by biodiversity, we design and implement a non-intrusive and tolerant secure architecture Multi-DNS(MDNS) to deal with it. MDNS consists of Scheduling Proxy and DNS server pool with heterogeneous DNSs in it. And the Scheduling Proxy dynamically schedules m DNSs to provide service in parallel and adopts the vote results from majority of DNSs to decide valid replies. And benefit from the centralized control of software defined networking(SDN), we implement a proof of concept for it. Evaluation results prove the validity and availability of MDNS and its intrusion/fault tolerance, while the average delay can be controlled in 0.3s.

Orchestrating Network Functions in Software-Defined Networks

Software.defined networking(SDN) enables third.part companies to participate in the network function innovations. A number of instances for one network function will inevitably co.exist in the network. Although some orchestration architecture has been proposed to chain network functions, rare works are focused on how to optimize this process. In this paper, we propose an optimized model for network function orchestration, function combination model(FCM). Our main contributions are as following. First, network functions are featured with a new abstraction, and are open to external providers. And FCM identifies network functions using unique type, and organizes their instances distributed over the network with the appropriate way. Second, with the specialized demands, we can combine function instances under the global network views, and formulate it into the problem of Boolean linear program(BLP). A simulated annealing algorithm is designed to approach optimal solution for this BLP. Finally, the numerical experiment demonstrates that our model can create outstanding composite schemas efficiently.

Theoretical study of(e,2e) triple differential cross section of 1b3g orbital of ethylene by vibrational multi-center distorted-wave method

The vibrational motions are usually neglected when calculating(e,2e) triple differential cross sections(TDCSs) of molecules. Here, multi-center distorted-wave method(MCDW) has been modified by including molecular vibrations. This vibrational MCDW method is employed to calculate the TDCSs of 1b3gorbital of ethylene at low(100 eV) and medium(250 eV) incident electron energies in coplanar asymmetric kinematic condition. The results show that molecular vibrations significantly influence the angular distributions of the TDCSs, especially in the binary region along momentum transfer near the Bethe ridge.

Theoretical study of (e,2e) triple differential cross sections of pyrimidine and tetrahydrofurfuryl alcohol molecules using multi-center distorted-wave method

We report theoretical studies of electron impact triple differential cross sections of two bio-molecules,pyrimidine and tetrahydrofurfuryl alcohol,in the coplanar asymmetric kinematic conditions with the impact energy of 250 eV and ejected electron energy of 20 eV at three scattering angles of-5°,-10°,and-15°.Present multi-center distorted-wave method well describes the experimental data,which was obtained by performing(e,2e)experiment.The calculations show that the secondary electron produced by the primary impact electron is strongly influenced by the molecular ionic multi-center potential,which must be considered when the low energy electron interacts with DNA analogues.

Co-NC as adsorbent and matrix providing the ability of MALDI MS to analyze volatile compounds

Traditional matrix does not allow matrix-assisted laser desorption/ionization mass spectrometry(MALDI MS) to analyze volatile compounds,because volatile analytes may vaporize during the sample preparation process or in the high vacuum circumstance of ion source.Herein,we reported a Co and N doped porous carbon material(Co-NC) which were synthesized by pyrolysis of a Schiff base coordination compound.Co-NC could simultaneously act as adsorbent of volatile compounds and as matrix of MALDI MS,to provide the capability of MALDI MS to analyze volatile compounds.As adsorbent,Co-NC could stro ngly adsorb and enrich the volatile compounds in perfume and herbs,and hold them even in the high vacuum circumstance.On the other hand,Co-NC could absorb the energy of the laser,and then transfer the energy to the analyte for desorption and ionization of analyte in both negative and positive ionization modes.Additionally,the background interferences were avoided in the low-mass region(<500 Da) when using Co-NC as matrix,overcoming the challenges of MALDI MS analysis of small molecule compounds.In summary,Co-NC as matrix tremendously extended the application of MALDI MS.

Research on recognition for cotton spider mites’damage level based on deep learning

The changes in cotton leaf characteristics are closely related to the cotton spider mites’damage level.Extracting the distinguishable features of cotton leaves is an effective method to identify the level.However,it faces enormous challenges for the classification due to various factors,such as illumination intensity,background complexity,shooting angle and so on.A recognition model is proposed,which is trained through transfer learning with the two-stage learning rate from 0.01 to 0.001 based on MobileNetV1.The experiments demonstrate that the deep learning model attains the accuracy of 92.29%for the training set and 91.88%for the test set of the mixed data.For testifying the effectiveness of the two-stage training method,the models are trained with the two public datasets,CIFAR-10 and Flowers,and attain the accuracy of 95.46%and 95.57%for the test sets,respectively.The average recognition time for a single cotton leaf image is about 0.015 s.Furthermore,the mobile terminal application is developed with the model embedded,to realize the real-time recognition for cotton spider mites’damage level in the field.