Base Pressure Control with Semi-Circular Ribs at Critical Mach Number

When better fuel-air mixing in the combustion chamber or a reduction in base drag are required in vehicles,rockets,and aeroplanes,the base pressure control is activated.Controlling the base pressure and drag is necessary in both scenarios.In this work,semi-circular ribs with varying diameters(2,4,and 6 mm)positioned at six distinct positions(0.5D,1D,1.5D,2D,3D,and 4D)inside a square duct with a side of 15 mm are proposed as an efficient way to apply the passive control technique.In-depth research is done on optimising rib size for various rib sites.According to this study,the base pressure rises as rib height increases.Furthermore,the optimal location for the semi-circular ribs with a diameter of 2 mm is at 0.5D.The 1D location appears to be optimal for the 4 mm size as well.For the 6 mm size,however,the 4D position fills this function.

Form and Mechanism of Sulfate Attack on Cement-based Material Made of Limestone Powder at Low Water-binder Ratio under Low Temperature Conditions

The development of strength and the form of attack of cement-based material made of limestone powder at low water-binder ratio under low-temperature sulfate environment were studied. The results indicate that when water-binder ratio is lower than 0.40, the cement-based material with limestone powder has insignificant change in appearance after being soaked in 10% magnesium sulfate solution at low temperature for 120 d, and has significant change in appearance after being soaked at the age of 200 d. Expansion damage and exfoliation occur on the surface of concrete test cube at different levels. When limestone powder accounts for about 28 percent of cementitious material, with the decrease of water-binder ratio, the compressive strength loss has gradually decreased after the material is soaked in the magnesium sulfate solution at low temperature at the age of 200 d. After the specimen with the water-binder ratio of less than 0.4 and the limestone powder volume of greater than 20% is soaked in 10% magnesium sulfate solution at low temperature at the age of 200 d, gypsum attack-led destruction is caused to the concrete test cube, without thaumasite sulfate attack.

Signal Separation and Instantaneous Frequency Estimation Based on Multi-scale Chirplet Sparse Signal Decomposition

An approach based on multi-scale chirplet sparse signal decomposition is proposed to separate the multi-component polynomial phase signals,and estimate their instantaneous frequencies.In this paper,we have generated a family of multi-scale chirplet functions which provide good local correlations of chirps over shorter time interval.At every decomposition stage,we build the so-called family of chirplets and our idea is to use a structured algorithm which exploits information in the family to chain chirplets together adaptively as to form the polynomial phase signal component whose correlation with the current residue signal is largest.Simultaneously,the polynomial instantaneous frequency is estimated by connecting the linear frequency of the chirplet functions adopted in the current separation.Simulation experiment demonstrated that this method can separate the components of the multi-component polynomial phase signals effectively even in the low signal-to-noise ratio condition,and estimate its instantaneous frequency accurately.

Strategy of preparing SmCo based films with high coercivity and remanence ratio achieved by temperature and chemical optimization

SmCo based films with excellent intrinsic magnetic properties have promising applications in micro-electro-mechanical system(MEMS).However,due to the complexity of phase composition and uncontrollable crystallization degree of SmCo hard magnetic phase in the film,both the coercivity(Hc)and remanence(Mr)of films are difficult to enhance simultaneously.In this paper,SmCo based films were deposited with a Cr underlayer and capping layer on single crystal Si substrates via magnetron sputtering process.The effects of annealing parameters and Sm/Co atomic ratio on the phase structure and coercivity of films are discussed.By adjusting the Sm/Co atomic ratio from 1:5 to 1:4,Co soft magnetic phase disappears and the single phase SmCo5 is obtained,leading to the increase of coercivity of the films from 30 to 34 kOe.The influence of deposition temperature and Cu doping on magnetic properties of SmCo based films was investigated.When the deposition temperature increases from room temperature to 250℃,the coercivity will further increase from 34 to 51 kOe.However,a severe kink is observed in the demagnetization curves due to the poor exchanged coupling.An analysis of transmission electron microscopy(TEM)confirms that the average size of non-hard magnetic amorphous phase exceeds the effective exchanged coupling length of SmCo5,which contributes to the decoupling and low remanence ratio.Therefore,doping Cu and applying a post-annealing process can significantly improve the crystallization degree of the films.Both the coercivity and the remanence ratio of the demagnetization curves are greatly enhanced.We propose a plausible strategy to prepare the SmCo based films with high coercivity and remanence ratio by temperature and chemical optimization,which can be utilized in high performed MEMS devices.

Base cation concentrations in forest litter and topsoil have different responses to climate and tree species along elevational gradients

The forest litter is an essential reservoir of nutrients in forests, supplying a large part of absorbable base cations(BC) to topsoil, and facilitating plant growth within litter-soil system. To characterize elevational patterns of base cation concentrations in the forest litter and topsoil, and explore the effects of climate and tree species, we measured microclimate and collected the forest litter and topsoil(0-10 cm) samples across an elevational range of more than 2000 m(1243 ～ 3316 m a.s.l.),and analyzed the concentrations of BC in laboratory. Results showed that: 1) litter Ca concentration displayed a hump-shaped pattern along the elevational gradients, but litter K and Mg showed saddle-shaped patterns. Soil Ca concentration increased with elevation, while soil K and Mg had no significant changes. 2) Ca concentration in the forest litter under aspen(Populus davidiana) was significantly higher than that in all other species, but in topsoil, Ca concentration was higher under coniferous larch and fir(Larix chinensis and Abies fargesii). Litter K and Mg concentrations was higher under coniferous larch and fir, whereas there were nosignificant differences among tree species in the concentrations of K and Mg in topsoil. 3) Climatic factors including mean annual temperature(MAT), growing season precipitation(GSP) and non-growing season precipitation(NGSP) determined BC concentrations in the forest litter and topsoil. Soil C/N and C/P also influenced BC cycling between litter and soil. Observation along elevations within different tree species implies that above-ground tree species can redistribute below-ground cations, and this process is profoundly impacted by climate. Litter and soil Ca, K and Mg with different responses to environmental variables depend on their soluble capacity and mobile ability.

Inflammation-based factors and prognosis in patients with colorectal cancer

Several parameters for predicting survival in patients with colorectal cancer have been identified, including the performance status, age, gender and tumor-nodemetastasis(TNM) stage. Although the TNM stage is important and useful for predicting the prognosis and determining the appropriate treatment, it is well known that the survival time varies widely, even in patients with the same stage of disease. Therefore, the identification of new parameters capable of more precisely predicting patient survival is needed to help select the optimal treatment, especially in patients in the advanced stage of disease. Although the TNM stage reflects the tumor characteristics, cancer progression and survival are not determined solely based on the local characteristics of the tumor, but also the host systemic immune/inflammatory response. Therefore, using a combination of parameters that reflect both tumor characteristics and the host systemic inflammatory status is thought to be important for accurately predicting patient survival.

Spatial-temporal Pattern Evolution of Manufacturing Geographical Agglomeration and Influencing Factors of Old Industrial Base:A Case of Jilin Province,China

The primary object of this paper is to examine the spatial-temporal pattern evolution of manufacturing geographical agglomeration of the old industrial base.Industrial spatial agglomeration index and concentration ratio are used in this paper.Multiple linear regression models are also applied to try to explore the internal driving mechanisms on manufacturing geographical agglomeration.The results show that:1) the manufacturing agglomeration degree of Jilin Province is increasing gradually.The spatial polarization structure is visible;and the central region is the agglomeration area,in addition,the manufacturing industries of Changchun Proper present a trend of dispersion;2) the structure of manufacturing industries has changed,and the concentration ratio of labor-intensive manufacturing industry is declining,while the proportions of technology-intensive and capital-intensive manufacturing industry are relatively rising;3) marketing level,location accessibility,labor resources,capital,science and technology innovation capability,scale economy and the level of globalization affect manufacturing agglomeration with different degree.There are significant differences of the effects about employment,technology,the quality of residents and the export-oriented market on the industrial concentration ratio;4) in the future,the impact of policy and institution,export-oriented market and quality of resident on manufacturing geographical agglomeration pattern will be more profound.

Electrochemical Performance of Nickel Hydroxide/Activated Carbon Supercapacitors Using a Modified Polyvinyl Alcohol Based Alkaline Polymer Electrolyte

聚乙烯化合物的白酒(PVA ) 钠 polyacrylate (PAAS )-KOH-H2O 有高离子的电导率的碱的聚合物电解质电影被一个扔答案的方法准备。聚合物 Ni (哦) 有不同电极的 2/activated 碳(交流) hybridsupercapacitors 活跃材料团比率(对积极否定) 用这碱的聚合物电解质被制作，镍氢氧化物积极电极，和交流否定电极。Galvanostatic 控告 / 解除和电气化学的阻抗光谱学(EIS ) 方法被用来学习电容器的电气化学的表演，例如控告 / 解除特定的电容，率控告 / 解除能力，和控告 / 解除周期的稳定性。试验性的结果与活跃材料团比率 m 减少显示出那(Ni (哦)2)/m(AC), 特定的电容增加的控告 / 解除和控告 / 解除周期的稳定性减少。

Noise properties of multi-combination information in x-ray grating-based phase-contrast imaging

Grating-based x-ray phase contrast imaging has attracted increasing interest in recent decades as multimodal and laboratory source usable method.Specific efforts have been focused on establishing a new extraction method to perform practical applications.In this work,noise properties of multi-combination information of newly established information extraction method,so-called angular signal radiography method,are investigated to provide guidelines for targeted and specific applications.The results show that how multi-combination of images can be used in targeted practical applications to obtain a high-quality image in terms of signal-to-noise ratio.Our conclusions can also hold true for upcoming targeted practical applications such as biomedical imaging,non-destructive imaging,and materials science.

A new image watermarking framework based on levels-directions decomposition in contourlet representation

With the development of digital information technologies,robust watermarking framework is taken into real consideration as a challenging issue in the area of image processing,due to the large applicabilities and its utilities in a number of academic and real environments.There are a wide range of solutions to provide image watermarking frameworks,while each one of them is attempted to address an efficient and applicable idea.In reality,the traditional techniques do not have sufficient merit to realize an accurate application.Due to the fact that the main idea behind the approach is organized based on contourlet representation,the only state-of-the-art materials that are investigated along with an integration of the aforementioned contourlet representation in line with watermarking framework are concentrated to be able to propose the novel and skilled technique.In a word,the main process of the proposed robust watermarking framework is organized to deal with both new embedding and de-embedding processes in the area of contourlet transform to generate watermarked image and the corresponding extracted logo image with high accuracy.In fact,the motivation of the approach is that the suggested complexity can be of novelty,which consists of the contourlet representation,the embedding and the corresponding de-embedding modules and the performance monitoring including an analysis of the watermarked image as well as the extracted logo image.There is also a scrambling module that is working in association with levels-directions decomposition in contourlet embedding mechanism,while a decision maker system is designed to deal with the appropriate number of sub-bands to be embedded in the presence of a series of simulated attacks.The required performance is tangibly considered through an integration of the peak signal-to-noise ratio and the structural similarity indices that are related to watermarked image.And the bit error rate and the normal correlation are considered that are related to the extracted logo analysis,as well.Subsequently,the outcomes are fully analyzed to be competitive with respect to the potential techniques in the image colour models including hue or tint in terms of their shade,saturation or amount of gray and their brightness via value or luminance and also hue,saturation and intensity representations,as long as the performance of the whole of channels are concentrated to be presented.The performance monitoring outcomes indicate that the proposed framework is of significance to be verified.

高掺量磷石膏道路基层材料配比设计及性能研究

按传统矿质混合料设计掺磷石膏道路基层材料难以大规模消纳磷石膏,为实现磷石膏在道路基层材料中大规模利用,通过骨料替代法进行高掺量磷石膏道路基层材料配比设计,确定适宜的碎石比(5~10 mm粒级与10~25 mm粒级质量比39∶61)后以不同掺量替代磷石膏基胶凝材料体系,再击实然后得出最佳含水率及最大干密度。通过对设计好的配比进行性能试验筛选,得出适宜配比为P85S60,养护28 d的试件抗压强度最大达5.39 MPa,体积变化率较低,且养护7 d后试件的体积增长稳定,体积变化率最终维持在0.5%左右,有利于现场道路施工应用。所有配比浸出氟、磷均满足《污水综合排放标准》(GB 8978—1996)一级限值,相较于常规水泥稳定碎石材料,该道路基层材料浸出液的酸碱性不会额外增加不利影响。通过XRD和SEM分析可知,胶凝材料水化产生的钙矾石和水化硅酸钙包裹在未反应的二水石膏周围,另外针棒状钙矾石和水化硅酸钙填充微小孔隙,使得试件整体结构密实、强度增加、体积稳定性增强。

硅酸镁基胶凝材料的制备与性能研究进展

硅酸镁基胶凝材料是由活性氧化镁和硅质原材料及外加剂按照一定比例混合制得,具有低碳排放、轻质高强、隔热保温等优良特点,受到了国内外学者的广泛关注。主要从原料配比、水化机理及其性能的影响因素综述了硅酸镁基胶凝材料的研究进展,硅酸镁基胶凝材料的性能主要受MgO活性、养护温度、Mg/Si比和外加剂、掺合料掺量的影响。其中MgO活性与Mg/Si比对体系反应产物影响显著,养护温度对反应进程起到了控制作用。概述了当前硅酸镁基胶凝材料存在的问题,并提出了可行的改进措施。

矿渣水泥基复合材料在杂散电流作用下的抗软水溶蚀机理研究

在轨道交通工程运营期间,复杂的服役环境导致混凝土结构耐久性下降。本文主要研究了在杂散电流与软水溶蚀耦合作用下,矿渣掺量、水胶比和杂散电流电压强度对矿渣水泥基复合材料微观结构的影响。结合X射线衍射、热重、扫描电子显微镜和压汞等方法,分析了矿渣水泥基复合材料经溶蚀90 d后的物相组成、Ca(OH)_(2)含量、微观形貌以及孔结构变化。研究结果表明:矿渣掺量越大,矿渣水泥基复合材料内部的Ca(OH)_(2)含量越少,材料的孔隙率越低,结构更均匀致密;随着杂散电流电压强度的增加,矿渣水泥基复合材料内部的Ca(OH)_(2)和AFt含量变少,且AFt和Ca(OH)_(2)等物相边界变得模糊不清;矿渣水泥基复合材料中C-(A)-S-H的含量略有增多,孔隙率略有下降;随着水胶比的增大,矿渣水泥基复合材料内部的Ca(OH)_(2)含量变少,剩余物相含量变少,微观结构变得松散多孔,孔径结构整体粗化,孔隙率增大。

超音速火焰喷涂氧燃比对铁基非晶涂层性能的影响

非晶涂层具有优良的物理和化学性能,在工业中有广泛的应用。以FeCrMoCBSi非晶粉末为喷涂粉末,采用超音速火焰喷涂(HVOF)技术在不同喷涂参数下在Q235钢基板上沉积了铁基非晶涂层。通过X射线衍射仪(XRD)、差示扫描热仪(DSC)、扫描电子显微镜(SEM)、维氏显微硬度计等测试方法,探讨氧燃比对涂层显微组织、微观结构及耐磨性的影响。研究表明,随着喷涂氧燃比的减小,涂层的非晶相含量呈增加趋势。这是因为过量的氧气会降低喷涂过程中颗粒的熔化程度,并使颗粒氧化。涂层的显微硬度和耐磨性随氧燃比的减小而增加。这是因为在较小氧燃比下,颗粒熔化程度增加,与基板间润湿性增加,孔隙率减小。三种铁基非晶涂层相比于Q235钢基板均具有更加优良的耐磨性,有望成为碳钢表面保护和耐磨涂层的候选材料。

占空比传输机制下基于协同预测的时变不确定系统递推滤波

以工业互联网为背景,研究占空比传输机制下一类时变不确定系统的滤波问题,结合协同预测方法设计了新颖的递推滤波算法,解决了占空比传输机制下滤波性能降低的问题。首先给出描述占空比传输机制的数学模型,然后提出结合协同预测方法的递推滤波方案,设计基于占空比机制的递推滤波算法,推导了滤波误差协方差矩阵的一个上界,随后分析这个上界的有界性,实现了在稀疏数据情形下提高滤波性能的目的。仿真结果验证了所提算法的高效性和有效性。

扩底桩竖向承载特性及群桩效应研究

为探明扩底群桩竖向承载特性,采用扩底桩筏结构,开展单桩(扩径比分别为1.5、2.0、2.5、3.0)和桩筏(扩径比为2)基础静载模型试验,分析其荷载传递规律,并建立桩间距为3.75、4.00、4.50、5.00倍桩直径时扩底桩筏基础有限元模型,研究桩间距对群桩效应影响。结果表明:扩底单桩和扩底桩筏结构荷载沉降曲线均为缓变型;扩底桩极限承载力随扩径比增大而逐渐增大,扩径比2.5~3.0时极限承载力增幅变缓,建议扩底桩扩径比取2.5~3.0;由于桩土共同沉降,桩间土压缩,桩土作用更充分,扩底桩筏基础中心桩侧摩阻力荷载分担比比扩底单桩增大了17.71%;群桩效应系数随桩间距增大而逐渐增大,桩间距为4.5~5.0倍桩直径时群桩效应系数增幅较小,群桩效应较弱,建议扩底桩筏基础桩间距取值不小于4.5倍桩直径。

非酒精性脂肪性肝病患者C/RL-r、APRI、FIB-4水平与肝纤维化发生的相关性

目的分析非酒精性脂肪性肝病(NAFLD)患者改良肝尾状叶/右叶比值(C/RL-r)、天门冬氨酸氨基转移酶与血小板比值指数(APRI)、基于4因子的纤维化指数(FIB-4)与肝纤维化发生的相关性。方法选择2021年2月至2022年12月在保定市第一中心医院治疗的NAFLD患者153例,根据病理学结果,将患者分为无肝纤维化组81例、肝纤维化组72例。行MRI扫描检测C/RL-r;计算APRI、FIB-4水平;分析NAFLD患者实验室指标、C/RL-r、APRI、FIB-4水平与发生肝纤维化的相关性,发生肝纤维化的独立危险因素及C/RL-r、APRI、FIB-4对NAFLD患者发生肝纤维化的预测价值。结果肝纤维化组ALT、AST、TBil、GGT、TG、C/RL-r、APRI、FIB-4水平显著高于无肝纤维化组,分别为(42.32±10.21)U/L比(36.21±7.78)U/L、(45.36±8.72)U/L比(27.45±5.40)U/L、(13.52±3.65)μmol/L比(12.24±2.16)μmol/L、(60.53±13.41)U/L比(53.69±12.44)U/L、(1.99±0.53)mmol/L比(1.05±0.33)mmol/L、(1.15±0.12)比(0.92±0.09)、(0.52±0.15)比(0.32±0.10)、(1.47±0.47)比(0.94±0.30),高密度脂蛋白胆固醇(HDL-C)水平显著低于无肝纤维化组为(1.03±0.26)mmol/L比(1.32±0.45)mmol/L,(t=4.189、15.453、2.674、3.272、13.322、13.501、4.302、8.405、4.801,均P<0.05);NAFLD患者ALT、AST、TG、C/RL-r、APRI、FIB-4与发生肝纤维化呈正相关(r=0.531、0.435、0.571、0.605、0.771、0.716,均P<0.001);ALT、AST、TG、C/RL-r、APRI、FIB-4水平高是影响NAFLD患者发生肝纤维化的独立危险因素(P<0.05);C/RL-r、APRI、FIB-4、三者联合预测NAFLD患者发生肝纤维化的曲线下面积(AUC)分别为0.767、0.830、0.754、0.936;相较于C/RL-r、APRI、FIB-4单独预测的AUC,三者联合预测的AUC更高(Z=4.495、3.999、4.677,均P<0.001)。结论发生肝纤维化的NAFLD患者C/RL-r、APRI、FIB-4水平较高,三者联合检测对NAFLD患者发生肝纤维化具有较高预测价值。