Experimental study of the damage characteristics of rocks containing non-penetrating cracks under cyclic loading

The damage evolution process of non-penetrating cracks often causes some unexpected engineering disasters.Gypsum specimens containing non-penetrating crack(s)are used to study the damage evolution and characteristics under cyclic loading.The results show that under cyclic loading,the relationship between the number of non-penetrating crack(s)and the characteristic parameters(cyclic number,peak stress,peak strain,failure stress,and failure strain)of the pre-cracked specimens can be represented by a decreasing linear function.The damage evolution equation is fitted by calibrating the accumulative plastic strain for each cycle,and the damage constitutive equation is proposed by the concept of effective stress.Additionally,non-penetrating cracks are more likely to cause uneven stress distribution,damage accumulation,and local failure of specimen.The local failure can change the stress distribution and relieve the inhibition of non-penetrating crack extension and eventually cause a dramatic destruction of the specimen.Therefore,the evolution process caused by non-penetrating cracks can be regarded as one of the important reasons for inducing rockburst.These results are expected to improve the understanding of the process of spalling formation and rockburst and can be used to analyze the stability of rocks or rock structures.

Oxygen-coordinated low-nucleus cluster catalysts for enhanced electrocatalytic water oxidation

The oxygen evolution reaction(OER)activity of single-atom catalysts(SACs)is closely related to the coordination environment of the active site.Oxygencoordinated atomic metal species bring about unique features beyond nitrogen-coordinated atomic metal species due to the fact that the M-O bond is weaker than the M-N bond.Herein,a series of metal-oxygen-carbon structured low-nucleus clusters(LNCs)are successfully anchored on the surface of multiwalled carbon nanotubes(M-MWCNTs,M=Ni,Co,or Fe)through a foolproof low-temperature gas transfer(300℃)method without any further treatment.The morphology and coordination configuration of the LNCs at the atomic level were confirmed by comprehensive characterizations.The synthetic Ni-MWCNTs electrocatalyst features excellent OER activity and stability under alkaline conditions,transcending the performances of Co-MWCNTs,Fe-MWCNTs and RuO_(2).Density functional theory calculations reveal that the moderate oxidation of low-nucleus Ni clusters changes the unoccupied orbital of Ni atoms,thereby lowering the energy barrier of the OER rate-limiting step and making the OER process more energy-efficient.This study demonstrates a novel versatile platform for large-scale manufacturing of oxygen-coordinated LNC catalysts.

Detection of EEG signals in normal and epileptic seizures with multiscale multifractal analysis approach via weighted horizontal visibility graph

Electroencephalogram(EEG) signals contain important information about the regulation of brain system. Thus, automatic detection of epilepsy by analyzing the characteristics obtained from EEG signals has important research implications in the field of clinical medicine. In this paper, the horizontal visibility graph(HVG) algorithm is used to map multifractal EEG signals into complex networks. Then, we study the structure of the networks and explore the nonlinear dynamics properties of the EEG signals inherited from these networks. In order to better describe complex brain behaviors, we use the angle between two connected nodes as the edge weight of the network and construct the weighted horizontal visibility graph(WHVG). In our studies, fractality and multifractality of WHVG are innovatively used to analyze the structure of related networks. However, these methods only analyze the reconstructed dynamical system in general characterizations,they are not sufficient to describe the complex behavior and cannot provide a comprehensive picture of the system. To this effect, we propose an improved multiscale multifractal analysis(MMA) for network, which extends the description of the network dynamics features by focusing on the relationship between the multifractality and the measured scale-free intervals.Furthermore, neural networks are applied to train the above-mentioned parameters for the classification and identification of three kinds of EEG signals, i.e., health, interictal phase, and ictal phase. By evaluating our experimental results, the classification accuracy is 99.0%, reflecting the effectiveness of the WHVG algorithm in extracting the potential dynamic characteristics of EEG signals.

Early brainstem hemorrhage progression:multi-sequence magnetic resonance imaging and histopathology

According to clinical statistics,the mortality of patients with early brainstem hemorrhage is high.In this study,we established rat models of brainstem hemorrhage by injecting type Ⅶ collagenase into the right basotegmental pontine and investigated the pathological changes of early brainstem hemorrhage using multi-sequence magnetic resonance imaging and histopathological methods.We found that brainstem hematoma gradually formed in the injured rats over the first 3 days and then reduced after 7 days.The edema that occurred was mainly of the vasogenic type.No complete myelin sheath structure was found around the focus of the brainstem hemorrhage.The integrity and continuity of nerve fibers gradually deteriorated over the first 7 days.Neuronal degeneration was mild in the first 3 days and then obviously aggravated on the 7^(th)day.Inflammatory cytokines,interleukin-1β,and tumor necrosis factorαappeared on the 1st day after intracerebral hemorrhage,reached peak levels on the 3^(rd)day,and decreased from the 7^(th)day.Our findings show the characteristics of the progression of early brainstem hemorrhage.

Association between body mass index and body fat measured by dual-energy X-ray absorptiometry (DXA) in China: a systematic review and meta-analysis

Objective:We examined the association between body mass index(BMI)and body fat percentage(BF%)measured by dual-energy X-ray absorptiometry(DXA)among adults and children in China.Methods:We searched four databases-PubMed,China National Knowledge Infrastructure,Wanfang,and Vip for studies published in the past 22 years.Meta-analysis was conducted using random-or fixed-effect models.Results:In total of 21 studies met inclusion criteria and were included in review,and 17 ot them in meta-analysis.They were conducted across China.Their sample size ranged from 62 to 5726,and participants'age ranged from 6-80 years.Meta-analysis revealed strong associations between BMI and BF% measured by DXA in adults(pooled r=0.71,95% CI:0.66 to 0.74)and children(pooled r=0.60,95% CI:0.52 to 0.68).The association was stronger in Northern China than in East China in children(β=-0.40,95%CI:-0.65 to-0.14)and in Central China in adults(β=-0.25;95% CI:-0.51 to-0.01).Urban children's BMI was strongly associated with BF%than rural(β=0.19;95%CI:0.04 to 0.35),whereas it was stronger in adults living in rural than in urban(β=-0.35;95% CI:-0.66 to-0.05).Conclusions:BMI was strongly associated with BF%measured by DXA,and the association in children and adults in China varied by residence and region.

An SDN/NFV Based Framework for Management and Deployment of Service Based 5G Core Network

The traffic explosion and the rising of diverse requirements lead to many challenges for traditional mobile network architecture on flexibility, scalability, and deployability. To meet new requirements in the 5 G era, service based architecture is introduced into mobile networks. The monolithic network elements(e.g., MME, PGW, etc.) are split into smaller network functions to provide customized services. However, the management and deployment of network functions in service based 5 G core network are still big challenges. In this paper, we propose a novel management architecture for 5 G service based core network based on NFV and SDN. Combined with SDN, NFV and edge computing, the proposed framework can provide distributed and on-demand deployment of network functions, service guaranteed network slicing, flexible orchestration of network functions and optimal workload allocation. Simulations are conducted to show that the proposed framework and algorithm are effective in terms of reducing network operating cost.

Heat stress impacts the multi-domain ruminal microbiota and some of the functional features independent of its effect on feed intake in lactating dairy cows

Background:Heat stress(HS)affects the ruminal microbiota and decreases the lactation performance of dairy cows.Because HS decreases feed intake,the results of previous studies were confounded by the effect of HS on feed intake.This study examined the direct effect of HS on the ruminal microbiota using lactating Holstein cows that were pair-fed and housed in environmental chambers in a 2×2 crossover design.The cows were pair-fed the same amount of identical total mixed ration to eliminate the effect of feed or feed intake.The composition and structure of the microbiota of prokaryotes,fungi,and protozoa were analyzed using metataxonomics and compared between two thermal conditions:pair-fed thermoneutrality(PFTN,thermal humidity index:65.5)and HS(87.2 for daytime and 81.8 for nighttime).Results:The HS conditions altered the structure of the prokaryotic microbiota and the protozoal microbiota,but not the fungal microbiota.Heat stress significantly increased the relative abundance of Bacteroidetes(primarily Gram-negative bacteria)while decreasing that of Firmicutes(primarily Gram-positive bacteria)and the Firmicutes-toBacteroidetes ratio.Some genera were exclusively found in the heat-stressed cows and thermal control cows.Some co-occurrence and mutual exclusion between some genera were also found exclusively for each thermal condition.Heat stress did not significantly affect the overall functional features predicted using the 16S rRNA gene sequences and ITS1 sequences,but some enzyme-coding genes altered their relative abundance in response to HS.Conclusions:Overall,HS affected the prokaryotes,fungi,and protozoa of the ruminal microbiota in lactating Holstein cows to a different extent,but the effect on the structure of ruminal microbiota and functional profiles was limited when not confounded by the effect on feed intake.However,some genera and co-occurrence were exclusively found in the rumen of heat-stressed cows.These effects should be attributed to the direct effect of heat stress on the host metabolism,physiology,and behavior.Some of the“heat-stress resistant”microbes may be useful as potential probiotics for cows under heat stress.

Effect of DBD plasma excitation characteristics on turbulent separation over a hump model

In this paper, the effect of dielectric-barrier discharge plasma excitation characteristics on turbulent boundary layer separation over a hump is investigated using computational fluid dynamics. Four different turbulence models were used for verification. The Reynolds stress model showed the best agreement with the experimental data, in general. Based on the verification and validation, the effect of duty cycle and excitation frequency on the turbulent flow separation were investigated. The results showed that the pulsed plasma excitation could effectively suppress the flow separation by mixing augmentation. With increasing duty cycle and excitation frequency, the flow separation first increased, then decreased again. The optimal duty cycle was 0.75 and the optimal excitation frequency was 50 Hz.

A study of variable stars in the open cluster NGC 1582 and its surrounding field

This paper presents Charge-Coupled Device time-series photometric observations of the open cluster NGC 1582 and its surrounding field with Johnson B, V and R filters by using the Nanshan 1 m telescope administered by Xinjiang Astronomical Observatory. 19 variable stars and three variable candi- dates were detected in a 45＇ - 48.75＇ field around the cluster. 12 of the variable stars are newly-discovered variable objects. The physical properties, classifications and memberships of these 22 objects are studied through their light curves, their positions on the color-magnitude diagram and with archival data from the Naval Observatory Merged Astrometric Dataset. Among these objects, five are eclipsing binary systems, six are pulsating variable stars including one known 6 Scuti star and one newly-discovered RR Lyrae star. The distance to the RR Lyrae star is estimated to be 7.9 - 0.3 kpc, indicating that the star is located far behind the cluster. Four variable stars are probable members of the cluster, and 13 of the 22 objects are confirmed to be field stars.

Space-to-Ground Quantum Key Distribution Using a Small-Sized Payload on Tiangong-2 Space Lab

Quantum technology establishes a foundation for secure communication via quantum key distribution （QKD）. In the last two decades, the rapid development of QKD makes a global quantum communication network feasible. In order to construct this network, it is economical to consider small-sized and low-cost QKD payloads, which can be assembled on satellites with different sizes, such as space stations. Here we report an experimental demonstration of space-to-ground QKD using a small-sized payload, from Tiangong-2 space lab to Nanshan ground station. The 57.9-kg payload integrates a tracking system, a QKD transmitter along with modules for synchronization, and a laser communication transmitter. In the space lab, a 50MHz vacuum＋weak decoy-state optical source is sent through a reflective telescope with an aperture of 200mm. On the ground station, a telescope with an aperture of 1200mm collects the signal photons. A stable and high-transmittance communication channel is set up with a high-precision bidirectional tracking system, a polarization compensation module, and a synchronization system. When the quantum link is successfully established, we obtain a key rate over 100bps with a communication distance up to 719km. Together with our recent development of QKD in daylight, the present demonstration paves the way towards a practical satellite-constellation-based global quantum secure network with small-sized QKD payloads.

Switching CO_(2) Electroreduction Selectivity Between C_(1) and C_(2) Hydrocarbons on Cu Gas-Diffusion Electrodes

Regulating the selectivity toward a target hydrocarbon product is still the focus of CO_(2)electroreduction.Here,we discover that the original surface Cu species in Cu gas-diffusion electrodes plays a more important role than the surface roughness,local pH,and facet in governing the selectivity toward C_(1)or C_(2)hydrocarbons.The selectivity toward C_(2)H_(4) progressively increases,while CH_(4) decreases steadily upon lowering the Cu oxidation species fraction.At a relatively low electrodeposition voltage of 1.5 V,the Cu gas-diffusion electrode with the highest Cu^(δ+)/Cu^(0)ratio favors the pathways of∗CO hydrogenation to form CH_(4) with maximum Faradaic efficiency of 65.4%and partial current density of 228 mA cm^(−2)at−0.83 V vs RHE.At 2.0 V,the Cu gas-diffusion electrode with the lowest Cu^(δ+)/Cu^(0)ratio prefers C-C coupling to form C_(2)+products with Faradaic efficiency topping 80.1%at−0.75 V vs RHE,where the Faradaic efficiency of C_(2)H_(4) accounts for 46.4%and the partial current density of C_(2)H_(4) achieves 279 mA cm^(−2).This work demonstrates that the selectivity from CH_(4) to C_(2)H_(4) is switchable by tuning surface Cu species composition of Cu gas-diffusion electrodes.

Detection of healthy and pathological heartbeat dynamics in ECG signals using multivariate recurrence networks with multiple scale factors

The electrocardiogram(ECG)is one of the physiological signals applied in medical clinics to determine health status.The physiological complexity of the cardiac system is related to age,disease,etc.For the investigation of the effects of age and cardiovascular disease on the cardiac system,we then construct multivariate recurrence networks with multiple scale factors from multivariate time series.We propose a new concept of cross-clustering coefficient entropy to construct a weighted network,and calculate the average weighted path length and the graph energy of the weighted network to quantitatively probe the topological properties.The obtained results suggest that these two network measures show distinct changes between different subjects.This is because,with aging or cardiovascular disease,a reduction in the conductivity or structural changes in the myocardium of the heart contributes to a reduction in the complexity of the cardiac system.Consequently,the complexity of the cardiac system is reduced.After that,the support vector machine(SVM)classifier is adopted to evaluate the performance of the proposed approach.Accuracy of 94.1%and 95.58%between healthy and myocardial infarction is achieved on two datasets.Therefore,this method can be adopted for the development of a noninvasive and low-cost clinical prognostic system to identify heart-related diseases and detect hidden state changes in the cardiac system.

A Taint Analysis Framework Applied to Android Applications in the Packed State

In recent years,Android applications have caused personal privacy leaks frequently.In order to analyze the malicious behavior,taint analysis technology can be used to track the API call chain,build a control-flow graph of function,and determine whether there is a security risk.However,with the continuous escalation of offensive and defensive confrontation of source code,more and more applications use reinforcement technology to prevent security practitioners from performing reverse analysis,therefore it is impossible to analyze function-behavior from the source code.Thus,we design a framework of taint analysis that applied to the Android applications,which automatically unpacks the Android APKs,restores the real source code of the App,performs taint analysis,and generates a control-flow graph of function.Experimental tests showed that the system can cope with the current mainstream reinforcement technology and restore the real Dex file quickly.Simultaneously,compared with the number of nodes before packing,the generated control-flow graph had an explosive increase,which effectively assisted manual analysis of App with the privacy leakage behaviors.

Supplementation with sodium butyrate improves growth and antioxidant function in dairy calves before weaning

Background: There is increasing research interest in using short-chain fatty acids(SCFAs) including butyrate as potential alternatives to antibiotic growth promoters in animal production. This study was conducted to evaluate the effects of supplementation of sodium butyrate(SB) in liquid feeds(milk, milk replacer, and the mixture of both)on the growth performance, rumen fermentation, and serum antioxidant capacity and immunoglobins in dairy calves before weaning. Forty healthy female Holstein calves(4-day-old, 40 ± 5 kg of body weight) were housed in individual hutches and randomly allocated to 1 of 4 treatment groups(n = 10 per group) using the RAND function in Excel. The control group was fed no SB(SB0), while the other three groups were supplemented with 15(SB15),30(SB30), or 45(SB45) g/d of SB mixed into liquid feeds offered. The calves were initially fed milk only(days 2 to 20), then a mixture of milk and milk replacer(days 21 to 23), and finally milk replacer only(days 24 to 60).Results: The SB supplementation enhanced growth and improved feed conversion into body weight gain compared with the SB0 group, and the average daily gain increased quadratically with increasing SB supplementation. No significant effect on rumen pH;concentrations of NH_3-N, individual and total VFAs;or acetate:propionate(A:P) ratio was found during the whole experimental period. Serum glutathione peroxidase activity increased linearly with the increased SB supplementation, while the serum concentration of maleic dialdehyde linearly decreased. Serum concentrations of immunoglobulin A, immunoglobulin G, or immunoglobulin M were not affected by the SB supplementation during the whole experimental period.Conclusions: Under the conditions of this study, SB supplementation improved growth performance and antioxidant function in pre-weaned dairy calves. We recommended 45 g/d as the optimal level of SB supplementation mixed into liquid feeds(milk or milk replacer) to improve the growth and antioxidant function of dairy calves before weaning.

Dietary energy sources and levels shift the multi-kingdom microbiota and functions in the rumen of lactating dairy cows

Background: Dietary energy source and level in lactation diets can profoundly affect milk yield and composition.Such dietary effects on lactation performance are underpinned by alteration of the rumen microbiota, of which bacteria, archaea, fungi, and protozoa may vary differently. However, few studies have examined all the four groups of rumen microbes. This study investigated the effect of both the level and source of dietary energy on rumen bacteria, archaea, fungi, and protozoa in the rumen of lactating dairy cows. A 2 × 2 factorial design resulted in four dietary treatments: low and high dietary energy levels(LE: 1.52–1.53;and HE: 1.71–1.72 Mcal/kg dry matter) and two dietary energy sources(GC: finely ground corn;and SFC: steam-flaked corn). We used a replicated 4 × 4 Latin square design using eight primiparous Chinese Holstein cows with each period lasting for 21 d. The rumen microbiota was analyzed using metataxonomics based on kingdom-specific phylogenetic markers [16 S r RNA gene for bacteria and archaea, 18 S r RNA gene for protozoa, and internally transcribed spacer 1(ITS1) for fungi] followed with subsequent functional prediction using PICRUSt2.Results: The GC resulted in a higher prokaryotic(bacterial and archaeal) species richness and Faith's phylogenetic diversity than SFC. For the eukaryotic(fungi and protozoa) microbiota, the LE diets led to significantly higher values of the above measurements than the HE diets. Among the major classified taxa, 23 genera across all the kingdoms differed in relative abundance between the two dietary energy levels, while only six genera(none being protozoal)were differentially abundant between the two energy sources. Based on prokaryotic amplicon sequence variants(ASVs) from all the samples, overall functional profiles predicted using PICRUSt2 differed significantly between LE and HE but not between the two energy sources. Fish Taco analysis identified Ruminococcus and Coprococcus as the taxa potentially contributing to the enriched KEGG pathways for biosynthesis of amino acids and to the metabolisms of pyruvate, glycerophospholipid, and nicotinate and nicotinamide in the rumen of HE-fed cows. The co-occurrence networks were also affected by the dietary treatments, especially the LE and GC diets, resulting in distinct co-occurrence networks. Several microbial genera appeared to be strongly correlated with one or more lactation traits.Conclusions: Dietary energy level affected the overall rumen multi-kingdom microbiota while little difference was noted between ground corn and steam-flaked corn. Some genera were also affected differently by the four dietary treatments, including genera that had been shown to be correlated with lactation performance or feed efficiency.The co-occurrence patterns among the genera exclusively found for each dietary treatment may suggest possible metabolic interactions specifically affected by the dietary treatment. Some of the major taxa were positively correlated to milk properties and may potentially serve as biomarkers of one or more lactation traits.

Uniformly dispersed FeOx atomic clusters by pulsed arc plasma deposition： An efficient electrocatalyst for improving the performance of Li-O2 battery

The present study explored a new method to improve the catalytic activity of non-precious metals, especially in electrochemical reactions. Highly ionized Fe plasma produced by arc discharge was uniformly deposited on a porous carbon substrate and formed atomic clusters on the carbon surface. The as-prepared FeO~/C material was tested as a cathode material in a rechargeable Li-02 battery under different current rates. The results showed significant improvement in battery performance in terms of both cycle life and reaction rate. Furthermore, X-ray diffraction （XRD） and scanning electron microscopy （SEM） results showed that the as-prepared cathode material stabilized the cathode and reduced side reactions and that the current rate was a critical factor in the nucleation of the discharge products.

Site-testing at Muztagh-ata site Ⅰ:ground meteorology and sky brightness

Site-testing is crucial for achieving the goal of scientific research and analysis of meteorological and optical observing conditions,one of the associated basic tasks.As one of three potential sites to host the 12-meter Large Optical/infrared Telescope(LOT),the Muztagh-ata site,which is located on the Pamir Plateau in Xinjiang,in west China,began its site-testing task in the spring of 2017.In this paper,we firstly start with an introduction to the site and then present a statistical analysis of the ground-level meteorological properties such as air temperature,barometric pressure,relative humidity,and wind speed and direction,recorded by an automatic weather station with standard meteorological sensors for a two-year duration.We also show the monitoring results of sky brightness during this period.

Site-testing at Muztagh-ata site Ⅲ:temperature inversion in surface-layer atmosphere

In this article,we present detailed seasonal,monthly and daily statistics of temperature difference in the surface layer at the Muztagh-ata site based on the temperature measurements at two heights of 2 m and6 m.We find that temperature inversion occurs frequently at our site during nighttime,especially during the cold season.Strong temperature inversion always represents stable atmospheric turbulence,which is crucial for an optical observatory.By analyzing the behavior of temperature inversion and its correlation with wind and cloud amount,one conclusion can be made that radiation inversion is the main reason for the existence of temperature inversion in the surface-layer at the Muztagh-ata site.

Site testing campaign for the Large Optical/infrared Telescope of China:overview

The Large Optical/infrared Telescope(LOT)is a ground-based 12 m diameter optical/infrared telescope which is proposed to be built in the western part of China in the next decade.Based on satellite remote sensing data,along with geographical,logistical and political considerations,three candidate sites were chosen for ground-based astronomical performance monitoring.These sites include:Ali in Tibet,Daocheng in Sichuan and Muztagh-ata in Xinjiang.Up until now,all three sites have continuously collected data for two years.In this paper,we will introduce this site testing campaign,and present its monitoring results obtained during the period between March 2017 and March 2019.

The wide-field photometric system of the Nanshan One-meter Telescope

The Nanshan One-meter Wide-field Telescope is a prime focus system that is located at Nanshan Station of Xinjiang Astronomical Observatories.The field of view was designed to 1.5°× 1.5°,and the Johnson-Cousins UBVRI system was chosen as the main filter set.The telescope has been providing observation services for astronomers since September 2013.Variable source searching and time-domain surveys are the main scientific goals.The system’s test results are reported including linearity,dark current,bias,readout noise and gain of the CCD camera.The accurate instrumental calibration coefficients in UBVRI bands were driven with Landolt standard stars during photometric nights.Finally,the limiting magnitudes are given with signal-to-noise ratios and various exposure times for observers.