针对252Cf自发裂变中子源构成的核信息系统，以实际所测随机中子脉冲数据的自相关函数为研究对象，借助仿真实验， 利用Elman神经网络对不同质量核材料进行识别。在实测数据的基础上，通过叠加随机抖动，模拟产生了不同质量核材料的相关函数样本，并将其用于神经网络的训练与测试，实验结果表明，训练过的Elman神经网络能够较好地识别相关函数的特征，分辨不同质量的核材料，平均识别率达到85%，综合平均误差为0.04，且具有较高的鲁棒性。
As a pivotal anti-corrosion structure in the wet flue gas desulfurization system, the huge filament-wound GFRP (glass fiber-reinforced polymer) tube is often employed as the chimney liner. However, the study on its mechanical properties is rare. Three large-scale stiffened cylindrical GFRP chimney liner segments were tested under the axial compression, including an integrated filament-wound chimney liner specimen with two ring stiffeners, a specimen with two ring stiffeners cut into two segments and joined by a hand-wound technique, and a specimen with an outside ring bracket. The failure modes, load-displacement relationships, variation of strains during the loading process, were acquired by test. The effects of ring stiffeners on the mechanical behavior, service reliability of the joint between the two segments of the chimney liner, and the reliability of the ring bracket were examined. Comparisons between theoretically calculated stiffness and experimentally measured stiffness were discussed. Finally, finite element analysis was performed to examine the failure modes and axial load-displacement behavior of the investigated chimney liners. Different ranges of diameter to thickness ratios and load eccentricity values were selected to examine their effects on the mechanical behavior of chimney liners. Finally, suggestions on the design of chimney liner structure were given.
This study investigates the impact of long-term water immersion on the mechanical and hydrochemical properties of cemented calcareous soil, emphasizing the critical role of carbonate content in mechanical performance. Utilizing hydrochemical analysis and triaxial testing, the research revealed that prolonged immersion disrupts the acid-base balance of the solution, resulting in an increased concentration of ions and chemicals. Significant dissolution of carbonates and soluble minerals occurs, which reacts with carbon dioxide to generate bicarbonate ions, thereby elevating the alkalinity of the soaking solution. Additionally, the gradual dissolution of clay minerals compromises the cementitious structure, leading to particle reorientation and interlocking. The study quantitatively assesses the changes in soil properties, demonstrating a substantial reduction in soil cohesion by up to 86.1% and an increase in the internal friction angle by 37.5%. Furthermore, the gradual dissolution of clay minerals compromises the cementitious structure, resulting in particle reorientation and interlocking that contribute to the observed mechanical changes. The findings underscore the importance of understanding the effects of extended immersion on the stability and engineering applicability of cemented calcareous soils.
With the core idea of controlling the advance core deformation around the tunnel,ADECO-RS approach is an instructional design and construction method for soft-rock tunnels.Combining with the actual construction conditions of a soft-rock tunnel project with large section(Taoshuping tunnel),the reasonable reinforcement parameters of soft-rock tunnel with large section based on ADECO-RS approach are obtained by numerical simulation of pre-support around tunnel,reinforcement of the core rock at tunnel face and strengthening of arch springing.The reinforcement parameters of Taoshuping tunnel are evaluated and analyzed with the monitoring data and comparison between the monitoring data and the simulation result.The results show that(1) it is difficult to make the pre-support play the role as the beam and arch to control the stability and deformation of the tunnel face if only reinforcing the rock around the tunnel arch;(2) the reinforcement of soft-rock tunnel face requires long advanced support and the effect will be significant after the reinforcement density reaches a certain value;(3) compared to the tunnel face anchor bolts,the horizontal churning piles and the advance core soil can be mixed together and turn into a complex with higher strength which can significantly increase the bearing capacity of the core soil;(4) feet-lock churning piles can achieve better closed-structure result than the feet-lock bolts.
西汉《周易》经学经孟喜、焦延寿、京房等人的努力，发生了阴阳灾异化的转向。这一转向肇端于宣帝时的魏相、孟喜，至元帝朝京氏《易》立于学官，始成就经学的地位。而之前立于学官的孟喜《易》仍然保持汉初儒门易学的宗旨，与京房假托的孟京之学并存。京氏《易》的官方化，得益于彼时阴阳灾异说的盛行。同时，它又反过来改变了西汉《周易》经学的格局，造成了《易》与律历之学的杂糅，导致《易》在五经之中地位的提升，最终经刘歆等人的努力而推出《易》为五经之原的新观念。
In this work, the rotational stiffness of flange-web junctions of pultruded GFRP I-sections is investigated through an experimental program. Flange-web junctions of GFRP profiles are found to be non-rigid, contradicting typical design assumptions. Accounting for flange-web rotational stiffness reduces the rotational restraint of the flange/web junction; often by 15% or more, although more modest reductions were observed in this study. A discussion of different test methods for assessing flange/web junction stiffness is provided. A simple method that mitigates unfavorable effects is recommended. The effectiveness of the selected test method is demonstrated through 25 experimental tests which also serve to augment the limited data available in this area. Finite element modeling is conducted to simulate the experimental test and investigate parameters impacting the experimentally-determined rotational stiffness. Recommendations are made to standardize test parameters. Findings from this study directly support the developments of evaluation criterion for flange-web junctions and design equations; particularly those intended to capture the local buckling behavior of pultruded GFRP beams.
Multi-layered materials are everywhere, from fiber-reinforced polymer composites (FRPCs) to plywood sheets to layered rocks. When in service, these materials are often exposed to long-term environmental factors, like moisture, temperature, salinity, etc. Moisture, in particular, is known to cause significant degradation of materials like polymers, often resulting in loss of material durability. Hence, it is critical to determine the total diffusion coefficient of multi-layered materials given the coefficients of individual layers. However, the relationship between a multi-layered material’s total diffusion coefficient and the individual layers’ diffusion coefficients is not well established. Existing parallel and series models to determine the total diffusion coefficient do not account for the order of layer stacking. In this paper, we introduce three parameters influencing the diffusion behavior of multi-layered materials: the ratio of diffusion coefficients of individual layers, the volume fraction of individual layers, and the stacking order of individual layers. Computational models are developed within a finite element method framework to conduct parametric analysis considering the proposed parameters. We propose a new model to calculate the total diffusion coefficient of multi-layered materials more accurately than current models. We verify this parametric study by performing moisture immersion experiments on multi-layered materials. Finally, we propose a methodology for designing and optimizing the cross-section of multi-layered materials considering long-term moisture resistance. This study gives new insights into the diffusion behavior of multi-layered materials, focusing on polymer composites.
No abstract is provided for this article.
As an economical and eco-friendly construction material, coral aggregate concrete (CAC) plays an increasingly important role in emerging marine engineering applications. CAC fully utilizes local raw materials on remote islands. Due to the porous structure and low-strength characteristics of coral aggregates, CAC exhibits unique characteristics compared to ordinary concrete. This paper presents a state-of-the-art review of the properties of CAC, including (1) the physical properties of coral aggregates; (2) the mechanical properties of CAC under uniaxial and multiaxial compression; and (3) the durability of CAC especially its chloride ion resistance and performance under drying-wetting cycles. To overcome the challenges of steel corrosion in marine environments, fiber-reinforced polymer (FRP) has been indicated to be a promising material for applications in CAC construction. The latest studies on the combination of FRP and CAC are reviewed, including the use of FRP tubes and bars.
No abstract is provided for this article.
This paper reports on axial compression experiments on 18 specimens that were strengthened using fiber-reinforced polymer (FRP) fabric and bamboo sticks to improve buckling resistance. The core steel members were first bundled with bamboo sticks longitudinally using steel wire and were then wrapped longitudinally and laterally with FRP fabric. The bending stiffness and load-bearing capacity of the members were increased by the strengthening system, and the bamboo sticks acted as lightweight and free-shaped filling between the steel and FRP. Three major parameters were examined: (1) the cross-sectional shape; (2) the nominal slenderness ratio of the steel members; (3) the number of FRP fabric layers. Although global buckling that is analogous to that in unstrengthened specimens was observed, the strengthened specimens exhibited significant local deformation at the end of the steel member and rupture of the FRP fabric at midheight. The load-displacement results demonstrated an increase of 25–114% for load-bearing capacity and a maximum increase of up to 6.7 times for ductility. The load-strain developments also evidenced a reduced effective compression stiffness of the strengthened section. Based on the test results, a calculation method for the load-bearing capacity of the strengthened specimens was proposed.
