一种航空发动机风扇叶片的强度分析

航空发动机是一种具有严格气动负荷、机械负荷,且要求强耐久性的热动力机械,它是由许多零部件和附件组成的复杂系统,其可靠性和寿命直接影响着飞行的安全性,而航空发动机的寿命,很大程度上取决于主要零部件的寿命。本文对国内B737民航班机CFM56发动机的风扇叶片的强度展开了一系列研究,为提高发动机可靠性提供了参考价值。利用CATIA自带的有限元软件建立了发动机风扇的有限元模型,分别计算了风扇在不同转速下的离心应力分布和不同转速下扭矩对风扇的影响,并对其静强度进行了强度校核。

飑线系统中的闪电活动与雷达回波特征的相关性研究

基于北京宽频带闪电网(Beijing Broadband Lightning Network,简称BLNet)获得的全闪三维定位和多普勒天气雷达等资料,详细分析了2015~2017年北京暖季7次强飑线过程的闪电活动与雷达回波强度之间的关系。结果表明,闪电主要发生于前部线状对流云区内且集中分布在30 d BZ以上的强回波区域,少部分的闪电分布在后部的层状云区域内。从闪电辐射源三维分布结构可以发现,闪电活动大部分处在6~11 km的高度范围。将能够同时反映强回波深度和面积的0~-30°C温度区域内大于30 d BZ雷达回波体积(V)作为强回波指标,并与闪电活动进行统计分析发现,整体上在7次飑线过程中,总闪频数和V存在较好的相关性,其中5次过程的闪电频数峰值同时或提前于V的峰值出现,二者的时滞相关系数超过0.61,提前时间为0~96 min。另外两次过程中闪电峰值落后于V峰值,落后时间分别为30 min和60 min。研究结果不仅对认识闪电与对流活动的关系有重要的科学意义,也可为闪电资料在数值模式中的同化应用提供科学依据。

Analysis of ground surface settlement in anisotropic clays using extreme gradient boosting and random forest regression models

Excessive ground surface settlement induced by pit excavation(i.e.braced excavation) can potentially result in damage to the nearby buildings and facilities.In this paper,extensive finite element analyses have been carried out to evaluate the effects of various structural,soil and geometric properties on the maximum ground surface settlement induced by braced excavation in anisotropic clays.The anisotropic soil properties considered include the plane strain shear strength ratio(i.e.the ratio of the passive undrained shear strength to the active one) and the unloading shear modulus ratio.Other parameters considered include the support system stiffness,the excavation width to excavation depth ratio,and the wall penetration depth to excavation depth ratio.Subsequently,the maximum ground surface settlement of a total of 1479 hypothetical cases were analyzed by various machine learning algorithms including the ensemble learning methods(extreme gradient boosting(XGBoost) and random forest regression(RFR)algorithms).The prediction models developed by the XGBoost and RFR are compared with that of two conventional regression methods,and the predictive accuracy of these models are assessed.This study aims to highlight the technical feasibility and applicability of advanced ensemble learning methods in geotechnical engineering practice.

Regulation of non-classical immune parameters in immune thrombocytopenic purpura mice by a spleen-invigorating,qi-replenishing and blood-containing formula

Objective:This study investigated the regulatory effect of non-classical immune parameters on immune thrombocytopenic purpura(ITP)mice by a spleen-invigorating,qi-replenishing and blood-containing formula(SQBF).Method:A total of 80 BALB/c mice were randomly divided into four equal groups(20 mice each):control group,model group,prednisone group and spleen-invigorating,qi-replenishing and blood-containing(SQBF)group.Mice in the model group,prednisone group,and SQBF group were administered anti-platelet serum to induce ITP.The dynamic variations of platelet counts in ITP mice were measured with an automatic blood analyzer before modeling and 48 h,and 8,12 and 15 days following APS injection.Levels of b-endorphin(b-EP),vasoactive intestinal peptide(VIP)and salivary IgA(SIgA)were detected by enzyme-linked immunosorbent assay(ELISA)on 15th day of experiment.Results:SQBF enhanced peripheral blood platelet counts in ITP mice similar to that of prednisone,and both groups showed a statistically significant response compared with the model group(P<.01).The SQBF significantly decreased b-EP levels compared with the model and prednisone intervention groups(P<.05),significantly increased the levels of VIP and SIgA in ITP mice compared with the model group(P<.05)and had significant protective effects on the thymus of ITP mice compared with the model group(P<.01).Conclusions:The SQBF had a similar effect to prednisone with regards to enhancing peripheral blood platelet counts in ITP mice.Furthermore,it decreased b-EP levels and increased VIP and SIgA,and protected the thymus.This shows that,on base of the brain-gut axis functions,some non-classical immune vascular active factors or neurotransmitters are also involved in immune responses,and also have relationship with the onset of ITP and bleeding and/or hemostasis.It needs further study to determine whether a change in these active factors is related to immediate hemostasis.

Lightning Nowcasting with an Algorithm of Thunderstorm Tracking Based on Lightning Location Data over the Beijing Area

A thunderstorm tracking algorithm is proposed to nowcast the possibility of lightning activity over an area of concern by using the total lightning data and neighborhood technique.The lightning radiation sources observed from the Beijing Lightning Network(BLNET)were used to obtain information about the thunderstorm cells,which are significantly valuable in real-time.The boundaries of thunderstorm cells were obtained through the neighborhood technique.After smoothing,these boundaries were used to track the movement of thunderstorms and then extrapolated to nowcast the lightning approaching in an area of concern.The algorithm can deliver creditable results prior to a thunderstorm arriving at the area of concern,with accuracies of 63%,80%,and 91%for lead times of 30,15,and 5 minutes,respectively.The real-time observations of total lightning appear to be significant for thunderstorm tracking and lightning nowcasting,as total lightning tracking could help to fill the observational gaps in radar reflectivity due to the attenuation by hills or other obstacles.The lightning data used in the algorithm performs well in tracking the active thunderstorm cells associated with lightning activities.

Joint Optimization of Task Caching,Computation Offloading and Resource Allocation for Mobile Edge Computing

Applications with sensitive delay and sizeable data volumes,such as interactive gaming and augmented reality,have become popular in recent years.These applications pose a huge challenge for mobile users with limited resources.Computation offloading is a mainstream technique to reduce execution delay and save energy for mobile users.However,computation offloading requires communication between mobile users and mobile edge computing(MEC) servers.Such a mechanism would difficultly meet users’ demand in some data-hungry and computation-intensive applications because the energy consumption and delay caused by transmissions are considerable expenses for users.Caching task data can effectively reduce the data transmissions when users offload their tasks to the MEC server.The limited caching space at the MEC server calls for judiciously decide which tasks should be cached.Motivated by this,we consider the joint optimization of computation offloading and task caching in a cellular network.In particular,it allows users to proactively cache or offload their tasks at the MEC server.The objective of this paper is to minimize the system cost,which is defined as the weighted sum of task execution delay and energy consumption for all users.Aiming at establishing optimal performance bound for the system design,we formulate an optimization problem by jointly optimizing the task caching,computation offloading,and resource allocation.The problem is a challenging mixed-integer non-linear programming problem and is NP-hard in general.To solve it efficiently,by using convex optimization,Karmarkar ’s algorithm and the proposed fast search algorithm,we obtain an optimal solution of the formulated problem with manageable computational complexity.Extensive simulation results show that in comparison to some representative benchmark methods,the proposed solution can effectively reduce the system cost.

An MAC Layer Algorithm Based on Power Line-Wireless Dual Media Channels and Multiplexing

Hybrid networking of power line and wireless communication can complement each other,save construction costs,improve network robustness,and has important value on the Internet of Things and smart grid.For power line and wireless dual-interface devices,a media access control(MAC)layer algorithm for hybrid communication is proposed,in which the stations can compete for two channels simultaneously.When a station obtains two channels at the same time,the station will randomly select a channel for transmission to ensure fairness,and reset the counters when the transmission is successful.In this paper,the performance of the unsaturated traffic model and counter spatial division is considered,and the throughput under coupling conditions is obtained.Finally,the simulation results show that the MAC layer algorithm based on the hybrid communication network can make full use of the advantages of the two channels,improve system throughput,and reduce transmission delay.

Three-Dimensional M-Shaped Resection for Nasal Alar Hypertrophy in Asian Patients

Background Nasal alarplasty is an important component of esthetic rhinoplasty in Asians.The two main surgical techniques that correct alar hypertrophy by reducing the height or length often leave external scars and are associated with a high relapse rate.Methods We developed a new technique,called three-dimensional(3D)M-shaped resection,which corrects both the nasal alar height and length and simultaneously minimizes external scarring.We performed this procedure from January 2013 to September 2016 in 49 consecutive female patients diagnosed with saddle nose and nasal alar hypertrophy.Their mean age was 28.6(range,18–40)years.All patients had previously undergone simple rhinoplasty.Nasal alar length and height,nostril length and width,and maximal nose width were analyzed preoperatively and postoperatively from photographs.Results After a mean of 9(range,3–24)months of follow-up,surgery was considered successful in 46 women(94%)with good cosmetic effects.In three patients,nasal alar hypertrophy recurred(6 months postoperatively).There were no early complications such as hematomas,infections,skin or mucosal necrosis,or wound dehiscence.The mean reductions postoperatively were 1.7 mm and 0.9 mm for nasal alar length and height,respectively,1.6 mm for both nostril length and width,and 3.5 mm for nose width.Conclusion The 3D M-shaped resection for nasal alar hypertrophy effectively reduced hypertrophy in 94%of patients for up to 24 months,producing minimal external scars and good cosmetic effects.It is a simple and convenient technique that is an effective and safe option for nasal alarplasty.

Concurrence of high dust aerosol and stratosphere-intruded ozone pollution in super sandstorms

The air quality in China has substantially improved in recent years,as indicated by the declining trends in SO_(2),NO_(2),PM_(2.5)and PM_(10)concentrations.Despite the reduced anthropogenic pollutant emissions;however,sustained increases in surface ozone(O_(3))that may impair the effectiveness of clean air actions have been observed.Moreover,complex heavy pollution episodes can still occur,and some of these episodes are closely linked with weather.For example,two severe sandstorms occurred successively in the early spring of 2021 in North China,despite the sandstorm frequency in China having significantly decreased in recent years[1-3].

(非)弱正则p值bent函数的间接构造

Bent函数在对称密码、序列设计、组合理论和编码理论等领域都有着重要的应用.基于已有的非直和与半直和构造研究方法,本文给出一类bent函数的间接构造.利用所得构造,通过选取合适的初始(向量)bent函数及其组合构造出高代数次数的(非)弱正则bent函数.更准确地,本文借助向量M-M(Maiorana-McFarland)类和PS(partial spread)类bent函数,给出了一些(弱)正则bent函数.特别地,给出了这些bent函数的对偶函数的显式表达式.进一步地,应用向量完美非线性(perfect nonlinear,PN)函数,生成了无限类非弱正则bent函数.

Anti-obesity and hypolipidemic effects of"Jinhua Xiangyuan"tea infusion in high-fat diet-induced obese rats

"Jinhua Xiangyuan"(JHXY)is a unique type of Chinese tea made from roasted oolong tea and subsequently fermented by Eurotium cristatum.In this study,we investigated the potential benefits of JHXY on obese rats induced by a high-sucrose high-fat diet.JHXY infusion was administered orally at 1.6 g/kg·bw(HI),0.8 g/kg·bw(MI),and 0.4 g/kg·bw(LI)per day for 10 weeks.Weight gain was significantly suppressed without affecting appetite.In the MI and HI groups,JHXY led to a significant reduction in triglycerides(TG),total cholesterol(TC),and low-density lipoprotein cholesterol(LDL-C),accompanied by an increase in high-density lipoprotein cholesterol(HDL-C)levels.A significant reduction in white adipose tissue(WAT)index and an increase in brown adipose tissue(BAT)index were observed.In MI group,the morphology of hepatocytes was restored.The abundance of Bifidobacterium was elevated,whereas the abundance of Desulfovibrio was significantly reduced.Correlation analysis revealed that the ratio of Ruminococcus to Bifidobacterium was positively correlated with HDL-C;the abundance of the Christensenellaceae_R-7_group was negatively correlated with TC and LDL-C,while positively correlated with HDL-C;the abundance of Lactobacillus was positively correlated with BAT/WAT ratio.In the MI group,the lipopolysaccharide biosynthesis pathway was predicted to be significantly weakened(p<0.05);in the HI group,the sulfur relay system pathway was attenuated,whereas the bacterial toxins pathway was augmented(p<0.05).Our research showed that JHXY has the potential to enhance metabolic health and maintain intestinal homeostasis.Optimal dosage should be a focal point in future research.

Identification and characterization of rice blast resistance gene Pid4 by a combination of transcriptomic profiling and genome analysis

Map-based cloning of plant disease resistance (R) genes is time-consuming. Here, we reported the isolation of blast R gene Pid4 using comparative transcriptomic profiling and genome-wide sequence analysis. Pid4 encodes a coiled-coil nucleotide-binding site leucine-rich repeat(CC-NBS-LRR) protein and is constitutively expressed at diverse developmental stages in the rice variety Digu. The Pid4 protein is localized in both the nucleus and cytoplasm. Introduction of Pid4 into susceptible rice cultivars confers race-specific resistance to leaf and neck blast. Amino acid sequence comparison and blast resistance spectrum tests showed that Pid4 is a novel R gene, different from the previously reported R genes located in the same gene cluster. A Pid4 Indel marker was developed to facilitate the identification of Pid4 in different rice varieties. We demonstrated that a plant R gene can be quickly isolated using transcriptomic profiling coupled with genome-wide sequence analysis.

Seismic behaviors of utility tunnel-soil system: With and without joint connections

Seismic responses of utility tunnel-soil system were studied via shaking table model tests with considerations of two kinds of double box utility tunnels:with and without joint connections.These two testing utility tunnel models were made of galvanized iron wire and micro-concrete,and the ground was simulated by the dry standard sand through layered tamping treatment.The utility tunnel-soil system was subjected to horizontal vibration in uniaxial direction perpendicular to the longitudinal direction of tunnel model.Via instrumentations of earth pressure gauges,accelerometers and strain gauges,the earth pressure response,acceleration response and bending moment response were measured.The testing results show that the joint connections in the utility tunnel along the longitudinal direction play an important role in determining the characteristic of earth pressure response and bending moment response,whereas the effect of joint connections on acceleration response is less significant.In addition,the partition wall exhibits the consistent acceleration response with the side-wall of double box utility tunnel model under seismic condition.Based on the testing results,it is suggested that the joint connection should be taken reasonably into consideration during design and construction for engineering practice.

Understanding the dynamical-microphysical-electrical processes associated with severe thunderstorms over the Beijing metropolitan region

The Dynamical-microphysical-electrical Processes in Severe Thunderstorms and Lightning Hazards(STORM973)project conducted coordinated comprehensive field observations of thunderstorms in the Beijing metropolitan region(BMR)during the warm season from 2014 to 2018.The aim of the project was to understand how dynamical,microphysical and electrical processes interact in severe thunderstorms in the BMR,and how to assimilate lightning data in numerical weather prediction models to improve severe thunderstorm forecasts.The platforms used in the field campaign included the Beijing Lightning Network(BLNET,consisting of 16 stations),2 X-band dual linear polarimetric Doppler radars,and 4 laser raindrop spectrometers.The collaboration also made use of the China Meteorological Administration’s mesoscale meteorological observation network in the Beijing-Tianjin-Hebei region.Although diverse thunderstorm types were documented,it was found that squall lines and multicell storms were the two major categories of severe thunderstorms with frequent lightning activity and extreme rainfall or unexpected local short-duration heavy rainfall resulting in inundations in the central urban area,influenced by the terrain and environmental conditions.The flash density maximums were found in eastern Changping District,central and eastern Shunyi District,and the central urban area of Beijing,suggesting that the urban heat island effect has a crucial role in the intensification of thunderstorms over Beijing.In addition,the flash rate associated with super thunderstorms can reach hundreds of flashes per minute in the central city regions.The super(5%of the total),strong(35%),and weak(60%)thunderstorms contributed about 37%,56%,and 7%to the total flashes in the BMR,respectively.Owing to the close connection between lightning activity and the thermodynamic and microphysical characteristics of the thunderstorms,the lightning flash rate can be used as an indicator of severe weather events,such as hail and short-duration heavy rainfall.Lightning data can also be assimilated into numerical weather prediction models to help improve the forecasting of severe convection and precipitation at the cloud-resolved scale,through adjusting or correcting the thermodynamic and microphysical parameters of the model.

Deletion of a Dna K protein gene causes seedling green-revertible albino by retarding chloroplast development in rice

Green-revertible albino mutants are important sources for studying chloroplast structure, chloroplast development, chlorophyll biosynthesis, and plant photo- synthesis. In the present study, we characterized a green- revertible albino mutant gra（k）, which was obtained from the tissue-cultured rice Kitaake. The mutant gra（k） exhib- ited albino on its first three leaves. The leaf color started to turn green at the four-leaf stage. The chlorophyll contents were deeply reduced at the seedling stage, and the chloroplast development was delayed in gra（k）. The green- revertible albino （gra） phenotype of the mutant gra（k） was temperature dependent. The main agronomic traits, including plant height, tilling number per plant, seed set- ting rate, and thousand-grain weight, slightly decreased in gra（k） comparing to those in the wild-type Kitaake. Genetic analysis showed that the gra phenotype was con- trolled by a single recessive nucleic gene. By using 5,168 recessive F2 individuals derived from the cross of gra（k） × Jodan, the locus of the gene Gra（k） was delimited in a DNA region of 200 kb between the makers B-31 and P11 on chromosome 5. Sequencing analysis indicated that the three functionally annotated genes, LOC_Os05g23700, LOC_Os05g23720, and LOC_Os05g23740, were all deleted in the 200 kb region in the mutant gra（k）. Trans- genic test revealed that the gra（k） plants over-expressing LOC_Os05g23740CDS were restored to normal green as the wild-type Kitaake. Our results proved that the deletion of the DnaK protein gene LOC_Os05g23740 （encoding the chaperon protein OsHsp70CP1） led to the gra phenotype in the mutant gra（k）.

Two theorems on QF rings

It is proved that a left QF-2 ring R is QF if R is either an artinian strongly right bounded ring, or a finite strongly left bounded and left Kasch ring with Soc(RR) = Soc( RR).