Against the backdrop of high-quality development in the new era, the expanding scale of Chinese college graduates, coupled with economic slowdown and industrial restructuring, has led to structural employment pressure. Flexible employment, though a key transitional choice for new graduates, lacks a sound supporting system. This paper focuses on college students' employment policies, screening 18 authoritative documents via keywords "college students," "employment," and "policies," and categorizes them into four types: policy issue analysis, orientation & countermeasures, situation & evolution, and research in special periods/new perspectives. A policy focus, government-market roles, and research methods. Existing studies contribute significantly through interdisciplinary frameworks, scientific methods, structural problem diagnosis, and multi-level countermeasures. However, they have shortcomings: insufficient discussion on adapting to emerging occupations, lack of group need subdivision, over-reliance on Western models disconnected from China's reality, and inadequate policy dynamic adjustment and long-term evaluation. Accordingly, it proposes research directions on labor relations identification, skill training, social security connection, and inter-departmental collaboration in college students' gig and flexible employment, designing a framework including literature review, policy analysis, and mixed research. Future research should consider emerging technologies, regional differences, and long-term tracking, with theoretical significance in enriching policy research and promoting interdisciplinary integration, and practical significance in guiding policy optimization, supporting employment/entrepreneurship, and boosting social harmony.
No abstract is provided for this article.
With advancements in material properties and reduced costs, carbon fibre reinforced polymer (CFRP) cables are gaining popularity in engineering applications due to their superior strength-to-mass ratio and durability. However, the tensile strength of large-scale parallel CFRP cables remains a critical issue, warranting further research and engineering expertise. To address this issue, this paper proposes a method to rapidly predict and adaptively correct the tensile strength of large-scale parallel CFRP cables using multi-source experimental data and an integrated approach that incorporates Monte Carlo simulations, Neural Network algorithms, and Genetic algorithms. This comprehensive method takes into account the influence of various factors including small-scale material strength and its coefficient of variation, cable length, the number of parallel wires, installation errors, and anchorage errors. Validated by reported experimental data, the method demonstrates its effectiveness in accurately predicting the tensile strength of parallel CFRP cables. Moreover, a design method for large-scale parallel CFRP cables is proposed based on the reliability theory. Lastly, the efficiency and effectiveness of the proposed method are validated through the design and optimization of a cable-stayed bridge featuring a main span of 1984 m, utilising both parallel steel and CFRP cables.
The use of seawater coral aggregate concrete (SCAC) instead of ordinary aggregate concrete (OAC) in concrete-filled FRP tube (CFFT) members is highly attractive due to the beneficial effect of fiber-reinforced polymer (FRP), which has good resistance to salt and can effectively counteract the greatest shortcomings of the chloride-containing ions in SCAC. In the development of marine construction, SCAC-filled FRP tubes are a potential attractive alternative for pile and column applications in corrosive marine environments. The axial compressive behavior of SCAC-filled FRP tube (SCFFT) was first experimentally investigated and compared with OAC-filled FRP tube (OCFFT) in this study. The chosen coral aggregates (CAs) and SCAC were systematically prepared and tested, including classification and materials testing on CAs, uniaxial load testing on SCAC and microstructure analysis of SCAC. The porous nature and low strength of CAs led to a different and brittle failure mechanism of SCAC under uniaxial loading, and result in SCAC experiencing a compacting behavior before the development of its rapid expansion and the activation of confinement in SCFFT. As a consequence, the axial loading of SCFFT displayed a slight drop in the transition zone for the range of axial strains between approximately 0.002 and 0.004. The non-homogeneity and brittleness of SCAC led to a non-uniform hoop strain distribution in SCFFT under compression and thus discounted the effect of confinement. The ultimate load of SCFFT was approximately 60% of that of its OCFFT counterpart. The key elements and basic framework used to develop a detailed analysis-oriented model for predicting FRP-confined SCAC under axial compression was illustrated. Furthermore, the model developed originally for FRP-confined lightweight concrete with ceramsite aggregates was extended to cover FRP-confined SCAC, and the extended model was confirmed to be capable of producing reliable predictions.
A novel prestressed carbon fiber reinforced polymer (CFRP) plate strengthening method for signal towers was proposed. The proposed strengthening system incorporates a circumferential anchorage system, a support system, a column system, and CFRP plates. These elements synergistically interact with the tower, forming a self-balancing system. This integrated system can provide exceptional flexural capacity and reduce the lateral displacement of the tower under wind load. To validate this novel method, a series of four static load tests were conducted. The results showed that the initial stiffness of the strengthened tower with CFRP plate prestresses of 0, 200, and 400 MPa increased by 71.0 %, 113.8 %, and 113.8 % compared with the unstrengthened tower, respectively. Moreover, the CFRP plate slacking occurred later for the strengthened tower with higher CFRP plate prestress, and the stiffness of the tower after the CFRP plate slacking kept increasing as CFRP plate prestress increases. The results indicate that the prestressed CFRP plate strengthening method effectively improved the behavior of the tower under wind load. Moreover, the finite element method (FEM) was utilized to analyze the influence of the ratio of the circumferential anchorage system height to tower height, the ratio of the support system height to tower height, the ratio of the column height to tower height, the ratio of steel support length to tower diameter, the elastic modulus of the CFRP plate and CFRP plate prestress on the strengthening effect. Finally, a strengthening procedure was proposed according to FEM results and sensitivity analysis. The analysis findings can serve as a guide for designing the strengthening system.
Curvilinear architecture and structures are becoming a worldwide trend for its streamlined appearance and synchronicity with the surroundings. Nonetheless, the conventional construction materials might not be able to achieve the desired curvilinear geometries in an effective and economic manner. In this regard, glass fiber-reinforced polymer (GFRP) curved sandwich panel with polyurethane foam core is able to meet the requirement of the construction efficiency and economy as well as satisfy the need for a lower energy consumption. However, few studies are available on the mechanical behavior of such panels. In this regard, this work was to conduct an experimental and numerical investigation on the singly curved GFRP sandwich panels to evaluate the flexural performance. In particular, the effect of the foam density, inclined angle, core thickness and stacking sequence of face sheet on the load-carrying capacity and failure mode was addressed. Four failure modes were identified. The singly curved GFRP sandwich panel showed an improved stiffness when compared to the flat panel, but showed more complicated failure mechanism. The stiffness of the curved panel with inclined angle 30° was 250 % higher than that of the flat panel in the test results. It was shown that the strength and stiffness increased as the density and thickness of the foam core increased. In addition, a finite element analysis was conducted via MSC.Marc and validated by the experimental results. A parametric study was performed to address the design parameters. It was found that the specimens with inclined angles of 30° and 45° showed the greatest stiffness.
Concrete confined using fiber-reinforced polymer (FRP) composites experience significant enhancements in strength and strain. For the seismic retrofitting of existing reinforced concrete (RC) structures, a large rupture strain (LRS) FRP (i.e., polyethylene terephthalate and naphthalate, denoted as PET and PEN respectively), with a larger rupture strain of more than 5%, is a promising alternative to conventional FRPs with a rupture strain of less than 3%. The majority of analytical models on the stress–strain behavior of FRP-confined concrete under axial compression have focused largely on concrete confined with the traditional FRP material. Analytical research on LRS FRP-confined concrete is, however, limited. Moreover, all existed stress–strain models were determined based on theoretical analysis and test data fitting. In this paper, the artificial neural networks (ANN) method is employed to build a confinement model directly from experimental data to predict the different components of the stress–strain response. A test database consisting of 226 axial compression tests on LRS FRP-confined concrete specimens is used. The test results, in terms of full confined stress–strain response, strength, strain, FRP rupture strain, and dilation response were investigated. Predictive expressions and practical ANN models for the strength, strain, and shape of an axial stress–strain response are provided. Existing models for LRS FRP-confined concrete were also evaluated. The results of the existing and proposed models report that the proposed methods achieve significantly better results.
郭雍是程颐再传弟子，南宋兼山学派的代表人物，有易学及医学等著作传世。本文以其《郭氏传家易说》为研究对象，集中探讨了两个问题：其一，郭雍的易道观；其二，《郭氏传家易说》的用《易》方法。在易道观上，郭雍继承了北宋义理易学的传统，主张《易》为明道之书，并通过对《易》文本形成过程的思考，一方面将《周易》理解为圣人阐释“太板之道”的工具，另一方面又区分了《易》文本形成的不同阶段之间易道主旨的变化，即“包羲画三画以象三才”，“文王著六爻以明人道”等，主张“《易》以人道为主”。在用《易》方法上，郭雍强调“《易》者，用也，用之之书也”的观念，将易学诠释的重点从理解文本提升到运用文本的层面，认为学《易》的终极目的在于“返诸其身”而用《易》的诠轻则在干“拟议爻象”。
A FRP curve sandwich panels with varied thickness is studied.The stress distribution of the FPR curve sandwich panel is analyzed in tension,shear and flexure,which shows the maximum of stress happens in the support and decreases with panel length.Based on the failure standard of Tsai-Wu and the first、third principal stress,the material properties such as the thickness of facing sheet,the thickness of core,and the paving angle of facing sheet are considered in the load combination.The result indicates the strength performance is improved by the increment of the thickness of facing sheet,and the thickness of core;and paving angle of 0/90/0/90.
No abstract is provided for this article.
The use of sea sand in engineering construction is an effective solution to solve the problem of shortage of building sand in the coastal area not only,and is also reduces environmental impact. Upon review of the existing reinforced sea sand concrete applications,it is clear that there have been many substandard outcomes,primarily due to steel corrosion. Although these problems can be largely avoided by thoroughly washing sea sands with fresh water,the process is extremely water intensive,meaning that its overall usefulness is limited. However,fiber reinforced polymer( FRP) materials have both excellent mechanical performance and resistance to chloride-induced corrosion. Using FRP reinforcement and sea sand concrete in concert can avoid corrosion problems entirely. There are already many potential applications for this type of composite structure,and the prospects of further future development are equally good. An innovative FRP-concrete hybrid structural system for use in seaborne engineering is proposed herein. Specifically,this structure aims to fulfill an increasing demand for seaborne and coastal development. Meanwhile,it is also hoped to promote the application of sea sand concrete and FRP in engineering structures.
As numerous impressive large-scale 3D printed concrete structures have been built with 3D concrete printing (3DCP) technology, more attention has been given to the automation, accuracy and reliability of this technology. The concept of Brain-Eyes-Hands Loop (BEH Loop) is defined for use in automatic construction, describing the relationships among design, evaluation, and construction. In this paper, an innovative continuous reinforcement method with fiber reinforced polymer (FRP) flexible textile and Engineered Cementitious Composite (ECC) is presented, that offers an effective solution for the lack of tensile reinforcement and corrosion of steel bars in 3D printed concrete structures. The reinforced 3D printed concrete walls were constructed, evaluated, and tested under quasi-static cyclic loading. By digital rebuilding and geometric evaluation, the printing quality of wall specimens was accessed and ensured. Based on the mechanical tests, the seismic performances of the wall specimens were obtained and found to be mainly bending failure. The proposed reinforcement method was demonstrated for delaying crushing and improving mechanical behaviors. The end column and smaller height-width ratio also showed much improvement in mechanical performance. Compared with the conventional cast concrete wall, the 3DCP wall specimens reinforced by the proposed reinforcement method showed better material utilization efficiency and mechanical properties. Therefore, the 3DCP structures reinforced with flexible FRP textile show great potential for the future use in fully automatic construction of large-scale complex architectures according to the frame of the BEH Loop.
