基于灰色-神经网络的民机需求组合预测

民机数量是反映民航运输能力的重要标志,而对民机数量进行预测,能够研究分析未来民航业的发展趋势。本文重点研究了民机需求预测的模型架构和实施方法,首先以2013年到2020年民机数量和其他关键因素作为原始样本,然后把2021年的数据作为检验样本,最后通过构建灰色神经网络组合预测模型对未来的民机需求进行预测。从预测结果来看,灰色模型GM(1,1)与反向传播(back propagation,BP)神经网络模型结合效果较好,组合模型预测精度高,充分证明了该模型的有效性和可行性,同时预测结果对分析未来航空运输情况也具有一定的参考意义。

超临界CFB锅炉深度调峰跨临界过程中水冷壁动态特性的试验研究

为了保证超临界循环流化床(CFB)锅炉具有良好的宽负荷运行特性及深度调峰的能力,对跨临界压力变化时工质与水冷壁间的动态特性进行试验研究。采用Φ25.0 mm×3.5 mm的垂直上升光管,在压力20.0~23.0 MPa,质量流速400~800 kg/(m^(2)·s)试验工况范围内开展了近临界稳态传热试验和跨临界压力阶跃动态特性试验。结果表明:近临界压力下,增大质量流速、减小内壁热负荷、降低压力都能使传热恶化发生时的干度减小,对应的流体焓值增大,使传热恶化推迟发生;跨临界压力阶跃变化时,受热管内流体可能发生传热恶化导致壁温飞升,但随着质量流速的增大温度又回落到正常值;壁温飞升点与内壁面的传热随时间依次经历传热恶化阶段,过冷沸腾传热强化阶段和单液相换热阶段;各参数对跨临界压力阶跃变化时传热恶化的影响与对近临界稳态试验的传热恶化的影响相同,质量流速减小和内壁热负荷增大会使传热恶化发生的位置提前,同时壁温飞升的数值更大。

莲子心总黄酮多元醇提取工艺筛选及其性能研究

莲子心作为一种药食同源的植物,极具开发潜力。该研究通过单因素实验和响应面Box-Behnken设计实验筛选并优化莲子心总黄酮的多元醇超声辅助提取工艺,对该工艺获得的莲子心提取物进行了安全性及体外抗氧化、抑菌和抗敏活性的测定。结果表明,在提取溶剂为1,2-己二醇,溶剂体积分数87%,料液比3.6∶100(g∶mL),提取时间39 min的条件下,莲子心总黄酮得率为1.80%±0.08%,且其质量浓度在1.2 g/L以下时无刺激性,对DPPH和ABTS自由基的半数抑制质量浓度分别为0.76和0.69 g/L,对大肠杆菌、金黄色葡萄球菌和铜绿假单胞菌的最小抑菌质量浓度分别为0.56,1.12和0.14 g/L;且其对透明质酸酶的半数抑制质量浓度为0.35 g/L。该研究提供了一种简单、安全、高效的莲子心总黄酮提取工艺,在保证较高总黄酮得率的基础上兼顾其提取物的生物活性,为莲子心资源的开发提供了理论依据。

Combined genome-wide association studies and expression quantitative trait locus analysis uncovers a genetic regulatory network of floral organ number in a tree peony (Paeonia suffruticosa Andrews) breeding population

Great progress has been made in our understanding of floral organ identity determination and its regulatory network in many species;however,the quantitative genetic basis of floral organ number variation is far less well understood for species-specific traits from the perspective of population variation.Here,using a tree peony(Paeonia suffruticosa Andrews,Paeoniaceae)cultivar population as a model,the phenotypic polymorphism and genetic variation based on genome-wide association studies(GWAS)and expression quantitative trait locus(eQTL)analysis were analyzed.Based on 24 phenotypic traits of 271 representative cultivars,the transcript profiles of 119 cultivars were obtained,which indicated abundant genetic variation in tree peony.In total,86 GWAS-related cis-eQTLs and 3188 trans-eQTL gene pairs were found to be associated with the numbers of petals,stamens,and carpels.In addition,19 floral organ number-related hub genes with 121 cis-eQTLs were obtained by weighted gene co-expression network analysis,among which five hub genes belonging to the ABCE genes of the MADS-box family and their spatial–temporal co-expression and regulatory network were constructed.These results not only help our understanding of the genetic basis of floral organ number variation during domestication,but also pave the way to studying the quantitative genetics and evolution of flower organ number and their regulatory network within populations.

256排多层螺旋CT行头颈血管联合主动脉“一站式”扫描

目的:探讨头颈部血管联合主动脉一站式扫描的可行性。方法:回顾性分析临床检查头颈血管和胸腹血管患者40例,根据检查方法分为A、B两组,A组进行CT头颈血管和胸腹部血管的一站式扫描;B组分别行头颈血管CT扫描和胸腹部血管CT扫描。对两组图像进行主观评分和客观统计分析。结果:A组与B组CT血管图像均能满足诊断要求。A、B 2组血管的CT值差异均无统计学意义(P>0.05);主动脉弓、腹主动脉以及髂总动脉的CNR及SD差异均无统计学意义(P>0.05);大脑中动脉、椎动脉及颈总动脉CNR和SD差异有统计学意义(P<0.05),B组CNR均高于A组,B组SD均低于A组;2组主动脉弓、腹主动脉及髂总动脉SD差异均无统计学意义(P>0.05);A组[(104.70±10.62)m L]对比剂使用剂量和B组[(146.10±12.48)m L]对比剂使用剂量差异有统计学意义(t=-11.297,P=0.000)。结论:头颈血管联合胸腹部血管扫描图像能够满足诊断的需求,减少患者检查次数和对比剂的使用量,优化检查流程。

AMB转子系统动力学分析与控制研究

在主动磁悬浮轴承(active magnetic bearing,AMB)转子系统的静态稳定悬浮阶段,为了减缓传统PID控制带来的转子过冲碰壁现象,提出一种基于动力学分析的控制策略。对磁轴承转子系统进行理论动力学分析;将实测运动相关量与理论推导的运动量进行对比,修正理论动力学分析存在的不足;基于修正后的动力学分析推导出减缓过冲控制预测条件,结合不完全微分PID控制,形成基于动力学分析的带预测条件的控制策略。系统仿真及样机实验结果均表明该研究方法和控制理论能有效减少AMB转子过冲碰壁现象,实现AMB转子系统的静态稳定悬浮。

Thermodynamic modeling and phase diagram prediction of salt lake brine systemsⅡ.Aqueous Li^(+)-Na^(+)-K^(+)-SO_(4)^(2-) and its subsystems

It is still a challenging task to accurately and temperature-continuously express the thermodynamic properties and phase equilibrium behaviors of the salt-lake brine with multi-component,multitemperature and high concentration.The essential subsystem of sulfate type brine,aqueous Li^(+)-Na^(+)-K^(+)-SO_(4)^(2-) and its subsystems across a temperature range from 250 K to 643 K are investigated with the improved comprehensive thermodynamic model.Liquid parameters(Δg_(IJ),Δh_(IJ),and ΔC_(p,IJ))associated with the contributions of Gibbs energy,enthalpy,and heat capacity to the binary interaction parameters,i.e.the temperature coefficients of eNRTL parameters formulated with a Gibbs Helmholtz expression,are determined via multi-objective optimization method.The solid constantsΔ_(f)G_(k)°^((298.15))andΔ_(f)H_(k)°^((298.15))of11 solid species occurred in the quaternary system are rebuilt from multi-temperature solubilities.The modeling results show the accurate representation of(1)solution properties and binary phase diagram at temperature ranges from eutectic points to 643 K;(2)isothermal phase diagrams for Li_(2)SO_(4)-Na_(2)SO_(4)-H_(2)O,Li_(2)SO_(4)-K_(2)SO_(4)-H_(2)O and Na_(2)SO_(4)-K_(2)SO_(4)-H_(2)O ternary systems.The predicted results of complete structure and polythermal phase diagram of ternary systems and the isothermal phase diagrams of quaternary system excellently match with the experimental data.

倾斜管内汽水两相流动不稳定特性的数值分析

为对倾斜管道内的流动不稳定特性进行研究,建立了适用于不同工况条件的数学模型和本构关系。以频域法为基础,对守恒方程进行小扰动线性化和拉氏变换可得到用于描述流体流动稳定性的传递函数。使用尼奎斯特稳定性判据,绘制不同工况参数下的尼奎斯特图来判断流动的稳定性。对线性化模型的可靠性进行验证,在可靠性验证的基础上,对各种工况参数下的流动不稳定性进行研究,得到不同工况下的流动不稳定边界图。验证结果表明:模型的计算结果与实验数据的误差在10%以内。增大质量流速使流体的进口和出口密度差减小,有利于流动的稳定;相反,增大对流体施加的热流密度,使流体的进口和出口密度差增大,不利于流动的稳定,因此临界热流密度随质量流速的增大而增大;增大入口节流系数,可以抑制入口处流量的脉动,有利于流动的稳定,但是临界入口节流系数随质量流速的增大而减小;此外,增大入口过冷度在所研究的参数范围内有利于流动的稳定,得到的热流密度和入口过冷度不稳定边界线是单调的。

Co含量对旋转喷涂法制备的NiZn铁氧体薄膜的影响

采用旋转喷涂法低温沉积制备主配方为Ni_(0.17)Zn_(0.52)Co_(y)Fe_(2.31−y)O_(4)(y=0~_(0.09))的铁氧体薄膜,研究了Co含量对NiZn铁氧体薄膜相结构、显微形貌和磁性能的影响。结果表明,随Co含量增加,晶粒发生团聚,(222)择优取向减弱,三角形形貌不明显,晶粒均匀性变差。由于Co离子加入引起薄膜各向异性增强,矫顽力Hc增大至3.03 kA/m,且饱和磁化场逐渐增大,饱和磁化强度Ms单调递减,磁导率μ′单调递减截止频率fr单调递增。当主配方为Ni_(0.17)Zn_(0.52)Co_(0.09)Fe_(2.22)O_(4)时,截止频率fr可达最大值1.0 GHz。

Zn含量对NiZn铁氧体薄膜结构和磁性能的影响

采用旋转喷涂法低温沉积制备NiZn铁氧体薄膜,研究了Zn含量对NiZn铁氧体薄膜相结构、显微形貌和磁性能的影响。结果表明,随Zn含量增加,薄膜平均晶粒尺寸增大,其结晶度和饱和磁化强度M_(s)先增大后减小,矫顽力H_(c)减小至0.57 kA/m,薄膜起始磁导率μ′增大,截止频率f_(r)降低。EDS测试结果可知旋转喷涂法制备NiZn铁氧体薄膜中Zn含量越高时成分中Ni的缺失越严重。当主配方为Ni_(0.09)Zn_(0.68)Fe^(2.23)O_(4)时,频率在100 MHz的起始磁导率μ′可达最大值96。

沉积时间对旋转喷涂法制备的NiZn铁氧体薄膜的影响

采用旋转喷涂法低温沉积制备NiZn铁氧体薄膜,研究了沉积时间对薄膜相结构、显微形貌和磁性能的影响。结果表明,随着沉积时间延长,平均晶粒尺寸逐渐增大,(222)方向择优取向先增强后减弱,沉积速率先减小后稳定,随着薄膜厚度逐渐增大,晶粒的柱状结构也越发明显,结晶性能提高。NiZn铁氧体薄膜的饱和磁化强度M_(s)增高,矫顽力H_(c)降低,100 MHz的磁导率μ′增大,截止频率f_(r)从0.32 GHz降低至0.23 GHz。但是无论沉积时间长短,各薄膜均存在磁损耗角正切(μ"/μ′)过高的问题。

Ultrastable graphene isolated Au Ag nanoalloy for SERS biosensing and photothermal therapy of bacterial infection

Plasmonic metal nanomaterials with intrinsic surface–enhanced Raman scattering(SERS)and photothermal properties,especially AuAg nanoalloys with both the outstanding merits of Au and Ag nanocrystals,show huge application prospects in bacterial theranostics.However,the direct exposure of AuAg nanoalloys in external conditions probably cause undesirable reactions and poisonous metal ion leakage during SERS detection and photothermal antibacterial therapy process,which severely hinder bacterial theranostics applications.Herein,we report an ultrastable graphene–isolated AuAg nanoalloy(GAA)with AuAg core confined in few–layer graphitic shell as a versatile platform for bacterial detection and therapy.The encapsulation of graphene ensures the good stability of AuAg core,that its superior SERS and photothermal properties are therefore further guaranteed.GAA is used for SERS detection of two vital bacterial biomarkers(including corrosive cyanide and pyocyanin),exhibiting good SERS quantitative and multiplexing ability.GAA is further used for photothermal antibacterial therapy application,and ultrahigh antibacterial efficacies for both Gram–negative Escherichia coli and Gram–positive Staphylococcus aureus are achieved under 808 nm laser irradiation.This work proposes a valuable method to develop robust bacterial theranostic platform.

Experimental and Theoretical Study on CHF of a Ultra-Supercritical Circulating Fluidized Bed Boiler Water-Wall Tube at near-Critical Pressures

The experimental and theoretical research on the critical heat flux(CHF)in a uniformly heated water-wall tube of the efficient ultra-supercritical circulating fluidized bed(USCFB)boiler has been conducted.In particular,the experimental pressure varies from 18 MPa to 21 MPa,which is from 0.814Pcr–0.95Pcr(Pcr:critical pressure).The mass flux varies from 310 kg·m^(–2)·s^(–1)to 550 kg·m^(–2)·s^(–1).The inlet sub-cooling temperatures vary from 5°C to 10°C.The material of the tube is 12Cr1MoVg.From experimental investigation,the near critical pressure CHF test data of water are obtained.We find that the CHF mainly occurs when the vapor qualities are less than 0.4,and it occurs earlier(at lower vapor quality)when the pressure is closer to 22.115 MPa or the mass flux is smaller.From the experimental data,a correlation function for the CHF is established via regression and machine learning.Correlations established via machine learning greatly improved the regression accuracy.To study the CHF phenomenon mechanically,a theoretical model is established based on the near-surface bubble crowding model describing the DNB-type CHF.In the development of the CHF model,the friction resistance coefficient is determined according to our test results.By comparison with different experimental results,the near-surface bubble crowding model is well suited to describe DNB-type CHF.The calculation results of the model can provide reference for the optimal design of the USCFB boiler.

Porous organic polymers: a progress report in China

Porous organic polymers(POPs) are porous materials composed of light elements such as C, H, N, and O. The benign characters,including large surface area, good physical and chemical stability, well-defined chemical composition, wide ranges of monomer selection, and strong designability, have made POPs one of the frontiers in materials research. In this review, we discussed the design and synthesis of various POP materials that mainly led by Chinese scientists, including conjugated microporous polymers(CMPs), porous aromatic frameworks(PAFs), and hypercrosslinked porous polymers(HCPs), as well as crystalline POPs comprised of covalent organic frameworks(COFs) and a special class of COFs with triazine rings, covalent triazine frameworks(CTFs), and supramolecular organic frameworks(SOFs), and sorted out their main applications in adsorption, separation,catalysis, and electrochemistry fields.

Determination of Anthocyanins and Exploration of Relationship between Their Composition and Petal Coloration in Crape Myrtle (Lagerstroemia hybrid)

Petal coloration and pigment components in 12 American crape myrtle cultivars （Lagerstroemia indica x Lagerstroemia fauriei） and five Chinese crape myrtle cuItivars （L. indica hybrids） were studied. Color was measured by CIEL^＊a^＊b^＊ scale and anthocyanin composition of crape myrtle was determined using high-performance liquid chromatography coupled to photodiode array detection and electrospray ionization mass spectrometry. The presence of the previously reported delphinidin 3-O-glucoside, petunidin 3-O-glucoside and malvidin 3-O-glucoside were confirmed. Cyanidin 3-O-glucoside was identified in crape myrtle for the first time. We explored the relationship between petal color and anthocyanin contents by multiple linear regression analyses. The results indicated that total fiavones and fiavonols were important variables and contributed to blue-enhancing in crape myrtle. Based on anthocyanins and co-pigments analysis, flower color breeding in crape myrtle towards true-red and blue were discussed.

Redistribution of Li-ions using covalent organic frameworks towards dendrite-free lithium anodes:a mechanism based on a Galton Board

Because of its high theoretical specific capacity and low reduction potential,Li metal is considered to be key to reaching high energy density in rechargeable batteries.In this context,most of the research has focused on suppressing dendrite formation during Li deposition to improve the cycling reversibility and safety of the batteries.Here,covalent organic framework(COF)film coating on a commercial polypropylene separator is applied as an ion redistributor to eliminate Li dendrites.The COF crystallites consist of ordered nanochannels that hinder the movement of anions while allowing Li-ions to transport across,leading to a high Li-ion transference number of 0.77±0.01.The transport of Li-ions across the COF film can be considered to be analogous to beads passing through a Galton Board,a model that demonstrates a statistical concept of a normal distribution.Thus,an even distribution of Li-ions is obtained at the COF/Li metal interface.The controlled Li-ion flux yields a smooth Li metal surface after 1,000 h(500 times)of cycling,leading to a significantly improved cycling stability and reversibility,as demonstrated by Cu||Li half cells,Li||Li symmetric cells,and Li Fe PO4||Li full cells.These results suggest that,following the principle of a Galton Board,nanopore insulators such as COF-based materials are effective ion distributors for the different energy storage or conversion systems.

Versatile Graphene-Isolated AuAg-Nanocrystal for Multiphase Analysis and Multimodal Cellular Raman Imaging

Surface-enhanced Raman spectroscopy(SERS)-based bioanalytical technique involves the interaction of SERS-active substrate with complex environment,which has aroused intensive research interests.Compared to the commonly used Au SERS substrates,Ag nanocrystals have larger optical absorption cross section and acceptable price,but they possess poor oxidation resistance and potential biotoxicity,and the occurrence of unnecessary chemical reactions is inevitable due to the direct contact with probe molecules.Herein,we report a graphene-isolated AuAg nanocrystal(GIAAN)with the SERS-active AuAg core confined in a nanospace of few-layer graphene shell,which possesses unique Raman peaks,high SERS activity,excellent stability,superior fluorescence quenching performance and good biocompatibility.Based on the limited solubility of GIAAN in water and organic solvents,it is able to spontaneously generate interfacial self-assembled GIAAN(ISA-GIAAN)film at immiscible two-phase interfaces without any inducer,and multiphase Raman analysis of both water-and lipid-soluble drug model molecules is further achieved.Moreover,the GIAAN is further non-covalently functionalized with polyoxyethylenestearyl ether(C18-PEG)to acquire GIAAN@PEG with good water-solubility for SERS quantitative analysis in homogeneous system and multimodal Raman imaging of MCF-7 cells.We expect the versatile GIAAN holds great potential to monitor drug metabolism and guide intended drug delivery in clinic trials.

Toripalimab in advanced biliary tract cancer

Gemcitabine combined with platinum/fluorouracil drugs is the standard firstline treatment for advanced biliary tract cancers(BTCs).We explored the safety and efficacy of toripalimab plus gemcitabine and S-1(GS)as the first-line treatment for advanced BTCs.At a one-sided significance level of 0.025,a total of 50 patients could provide 80%power to show the efficacy at targeted progression-free survival(PFS)rate at 6 months of 70%versus 40%for the combined treatment.This single-arm,phase II study enrolled 50 patients with advanced BTCs who previously received no systemic treatment.The regimen was as follows:toripalimab(240 mg,i.v.,d1),gemcitabine(1,000 mg/m2,i.v.,d1 and d8),and S-1(40–60 mg bid p.o.,d1–14,Q21d).The primary endpoint was progression-free survival.The secondary endpoints included overall survival(OS),objective response rate(ORR),duration of response(DOR),and safety.The associations between response with PDL1 expression,tumor mutational burden(TMB),and genetic variations were explored.Patients were enrolled from January 2019 to August 2020,with a median follow-up time of 24.0 months(IQR:4.3–31.0 months).

Largely reduced cross-plane thermal conductivity of nanoporous In0.1Ga0.9N thin films directly grown by metal organic chemical vapor deposition

In recent year, nanoporous Si thin films have been widely studied for their potential applications in thermoelectrics, in which high thermoelectric performance can be obtained by combining both the dramatically reduced lattice thermal conductivity and bulk-like elec- trical properties. Along this line, a high thermoelectric figure of merit （ZT） is also anticipated for other nanoporous thin films, whose bulk counterparts possess superior electrical properties but also high lattice thermal conductivities. Numerous thermoelectric studies have been carried out on Si-based nanoporous thin fills, whereas cost-effective nitrides and oxides are not systematically studied for similar thermoelectric benefits. In this work, the cross-plane thermal conductivities of nanoporous Ino.lGao.9N thin films with varied porous patterns were measured with the time-domain thermoreflectance techni- que. These alloys are suggested to have better electrical properties than conventional SixGel x alloys; however, a high ZT is hindered by their intrinsically high lattice thermal conductivity, which can be addressed by introdu- cing nanopores to scatter phonons. In contrast to previous studies using dry-etched nanopores with amorphous poreedges, the measured nanoporous thin films of this work are directly grown on a patterned sapphire substrate to minimize the structural damage by dry etching. This removes the uncertainty in the phonon transport analysis due to amorphous pore edges. Based on the measurement results, remarkable phonon size effects can be found for a thin film with periodic 300-nm-diameter pores of different patterns. This indicates that a significant amount of heat inside these alloys is still carried by phonons with -300 nm or longer mean flee paths. Our studies provide important guidance for ZT enhancement in alloys of nitrides and similar oxides.

Thermal studies of individual Si/Ge heterojunctions--The influence of the alloy layer on the heterojunction

Phonon transport across an interface is of fundamental importance to applications ranging from electronic and optical devices to thermoelectric materials.The phonon scattering by an interface can dramatically suppress the thermal transport,which can benefit thermoelectric applications but create problems for the thermal management of electronic/optical devices.In this aspect,existing molecular dynamics simulations on phonon transport across various interfaces are often based on estimates of atomic structures and are seldom compared with measurements on real interfaces.In this work,planar Si/Ge heterojunctions formed by film-wafer bonding are measured for the interfacial thermal resistance (R_(K)) that is further compared with predictions from existing simulations and analytical models.The twist angle between a 70-nm-thick Si film and a Ge wafer is varied to check the influence of the crystal misorientation.Detailed transmission electron microscopy studies are carried out to better understand the interfacial atomic structure.It is found that the alloyed interfacial layer with mixed Si and Ge atoms dominates the measured thermal resistance(R_(K)).Some oxygen impurities may also help to increase RK due to the formation of glassy structures.Following this,RK reduction should be focused on how to minimize the interdiffusion of Si and Ge atoms during the formation of a Si/Ge heterojunction.