Motives for romantic relationships and the risk of heavy alcohol use, regular smoking and cannabis use during adolescence and early adulthood: A longitudinal study

Background: Engaging in sexual activities at a younger age is associated with higher risk of substance misuse among adolescents. It could be hypothesized that substance misuse and certain romantic relationship related behaviors may be influenced by similar hormone and other inner physiological factors that are affected by related motives. This study investigated the association between motives for romantic relationships and the risk of heavy alcohol use, regular smoking and cannabis use from adolescence through to early adulthood. Method: A population-based longitudinal study using data collected from Wave I and Wave III of the National Longitudinal Study of Adolescent Health. Characteristics of romantic relationship ideals (as the proxy of motives) measured in Wave I (mean age: 16 yrs) were applied to predict substance use indicated at Wave III (mean age: 22 yrs) using multivariate analyses. Results: Adolescents who included sexual activities as part of their romantic relationship ideals were at significantly higher risk of cannabis use among males and heavy alcohol use among females. Romantic ideals that included, gift giving (female) or receiving (male), declaration of love (male), marriage (male) and becoming pregnant (female) were associated with reduced risk of one or more types of substance use. Conclusion: In adolescence, sexual motives for romantic relationships were associated with higher risk of substance use and misuse, while motives related to intimacy and commitment in romantic relationships were associated with lower risk.

Longitudinal Relationship between Axial Length and Height in Chinese Children:Guangzhou Twin Eye Study

Purpose:.To understand the growth model of axial length(AL) and height, and to explore the relationship between the two with the passage of time.Methods:.We followed twins in the Guangzhou Twin Eye Study for five years..The AL of both eyes was measured by partial coherence interferometry, and height was measured by a standard scale during each visit..A multivariate multilevel mixed model was adopted for data analysis.Results:.A total of 1217 children were included in the study.Both AL and height increased, but the rate of growth slowed down with age..The mitigation rate of height growth was-0.34 cm / year;.while that of AL growth was-0.01 mm / year.AL was positively related to height,.with a relevant coefficient of R=0.22(Cov [height intercept, AL intercept] =1.56, 95%CI=1.14 to 1.99). The growth rates of AL and height were also positively related, with a relevant coefficient of R =0.18(Cov [height slope, AL slope] =0.03, 95%CI=0.01 to 0.05).However, taller children had slower rates of height increases,with a relevant coefficient of R=-0.12(Cov[height intercept,height slope]=-1.33,95%CI=-2.25 to-0.42); but had faster AL growth,.with a relevant coefficient of R =(Cov [height intercept, AL slope] =0.02, 95%CI=-0.05 to 0.08, R=0.02).AL and its growth rate were positively related to each other,with a relevant coefficient of R=(Cov [AL intercept,.AL slope]=0.04, 95%CI=0.03 to 0.05, R=0.3); while the growth rates of AL and height were negatively related to each other, with a relevant coefficient of R=(Cov [AL intercept, height slope]=--0.03 95%CI=-0.16 to 0.1, R=-0.02).Conclusion:.The increase in children's AL is relevant to their height increases..The faster their height increases,.the faster their AL increases.

Stress-Strain Relationship and Failure Criterion for Concrete after Freezing and Thawing Cycles

The research of the failure criterion and one-dimensional stress-strain relationship of deteriorated concrete were carried out. Based on the damage mechanics theory, the dsmage which reflects the alternation of internal state of material were introduced into the formula presented by Desayi and Krishman and the weighted twin-shear strength theory. As a nondestructive examination method in common use, the ultrasonic technique was adopted in the study, and the ultrasonic velocity was used to establish the damage variable. After that, the failure criterion and one-dimensional stress-strain relationship for deteriorated concrete were obtained. Eventually, tests were carried out to study the evolution laws on the damage. The results show that the more freezing and thawing cycles are, the more apparently the failure surface shrinks. Meanwhile, the comparison between theoretical data and experimental data verifies tile rationality of tile damage-based one-dimensional stress-strain relationship proposed.

Nonlinear model characterizing stress-strain relationship and permeability change of contact compression fracture at closing stage

Understanding the stress-strain relationship and permeability change for contact compression fracture at closing stage has been a hot issue for a long time.Previous investigations of this topic were mainly focused on experimental tests;however,theoretical approaches were rarely reported.Based on this,this paper focuses on the contact fracture at closing stage when rock is uniaxially loaded,and then a theoretical model is proposed.Based on the change of fracture elasticity modulus,it shows that as crack apertures are gradually reduced in the loading process,the permeability of rock sample will decrease progressively.This scenario shows that theoretical computation matches well with the experimental results.Finally,the effects of ratio of sample size to fracture aperture(n).pore pressure(P),and initial aperture(b) on stress-strain relationship and permeability change for contact compression fracture at closing stage are analyzed.

A novel binary effective medium model to describe the prepeak stressstrain relationship of combined bodies of rock-like material and rock

Combined bodies of rock-like material and rock are widely encountered in geotechnical engineering,such as tunnels and mines.The existing theoretical models describing the stress-strain relationship of a combined body lack a binary feature.Based on effective medium theory,this paper presents the governing equation of the“elastic modulus”for combined and single bodies under triaxial compressive tests.A binary effective medium model is then established.Based on the compressive experiment of concretegranite combined bodies,the feasibility of determining the stress threshold based on crack axial strain is discussed,and the model is verified.The model is further extended to coal-rock combined bodies of more diverse types,and the variation laws of the compressive mechanical parameters are then discussed.The results show that the fitting accuracy of the model with the experimental curves of the concretegranite combined bodies and various types of coal-rock combined bodies are over 95%.The crack axial strain method can replace the crack volumetric strain method,which clarifies the physical meanings of the model parameters.The variation laws of matrix parameters and crack parameters are discussed in depth and are expected to be more widely used in geotechnical engineering.

何以为家:分而不散的农民家庭

本文以云南省弥村四个农民家庭为例,分析了农民家庭“分而不散”的现象,进而回应“何以为家”的问题,在经验层面对家庭结构固定化的划分和家庭边界进行反思和拓展。研究发现,变化万千的家庭形态只是顺应社会变迁的方式,即当下的家庭形态是“权宜之计”。一旦农民家庭遭遇重大变故,家庭内部情境或外部条件的突变迫使具有责任的家庭成员在个人生活与经济功能的维度上妥协与改变,矛盾解决的过程表现为个人与家庭关系重新调试以达至新的平衡的过程。本文认为,家庭纵向主轴结构的存续和兴旺始终是目的,构成每个家庭成员最为根本的行动逻辑,这是将农民家庭凝聚在一起而“不散”的力量;而在当前城乡关系下,分散的家庭形态是农民迫于生计不得已而为之。家庭的核心意涵驱动了家庭形态上的分散,而家庭责任伦理跨越空间对分散在各地的家庭成员产生约束性力量。

Mechanical Properties and Stress Strain Relationship Models for Bamboo Scrimber

In order to investigate the basic mechanical properties and stress strain relationship model for bamboo scrimber manufactured based on a new technique,a large quantities of experiments have been carried out.Based on the analysis of the test results,the following conclusions can be drawn.Two main typical failure modes were classified for bamboo scrimber specimens both under tension parallel to grain and tension perpendicular to grain.Brittle failure happened for all tensile tests.The slope values for the elastic stages have bigger discreteness compared with those for the specimens under tensile parallel to grain.The failure modes for bamboo scrimber specimens under compression parallel to grain could be divided into four.Only one main failure mode happened both for the bending specimens and the shear specimens.With the COV values of 28.64 and 25.72 respectively,the values for the strength and elastic modulus under tensile perpendicular to grain have the largest discreteness for bamboo scrimber.From the point of CHV values,the relationship among the mechanical parameters for bamboo scrimber were proposed based on the test results.Compared with other green building materials,bamboo scrimber manufactured based on a new technique has better mechanical performance and could be used in construction area.Three stress strain relationship models which are four-linear model,quadratic function model,and cubic function model were proposed for bamboo scrimber specimens manufactured based on a new technique.The latter two models gives better prediction for stress strain relationship in elastic plastic stage.

居家/机构养老模式变化对老年人代际关系的影响——横断与纵向的比较

采用横断和纵向比较的范式对居家/机构养老模式变化对老年人代际关系的影响进行探讨,结果发现:①养老模式变化的老年人比无变化的老年人代际关系显著偏低.②养老模式变化的老年人初始代际关系显著低于无变化的老年人,且养老模式变化会抑制代际关系的上升速度.③随着时间的推移,老年人的代际关系总体呈上升趋势;年龄、配偶状况、自评生活质量可调节代际关系的变化速度.研究进一步拓展了机构养老对代际关系影响的研究,认为社会各界应重视机构养老老年人的初始代际关系,尽量减少距离等因素对代际关系的不利影响.

Strength and deformation behavior of the Yellow River silt under triaxial drained condition considering characteristic states

Currently,the application of the Yellow River silt in subgrade,especially in expressway subgrade,has not been widely promoted.The main reason is that the research on the mechanical characteristics of the Yellow River silt used for subgrade filling is extremely limited.In this study,the static shear test of the Yellow River silt under drained condition was carried out using Global Digital Systems(GDS)triaxial apparatus,and the effects of confining pressure,relative density and shear rate on the strength and deformation behavior of the Yellow River silt were investigated.The cohesive force of the Yellow River silt is low,and the friction angle is the main factor determining the shear strength.Friction angle at phase transformation stateφpt,friction angle at peak stateφps,friction angle at critical stateφcs,were obtained via the observation on the evolution law of mobilized friction angle during the whole shearing process.The friction angles corresponding to three different characteristic states have the following magnitude relationship,namelyφps>φcs>φpt.The strength parameters for low-grade subgrade and highgrade subgrade were chosen to be 29.33°and 33.75°.The critical state line(CSL),envelop of phase transformation(EOP),and envelop of dilatancy(EOD)for three different characteristic states were determined.The critical stress ratio M,the phase transformation stress ratio Mptand the dilatancy stress ratio Mdof the Yellow River silt are 1.199,1.235,1.152,respectively.These results provide a basis for the mechanical analysis of the Yellow River silt subgrades and the subsequent establishment of dynamic constitutive model of the Yellow River silt.

大型船舶上层建筑-主船体剪切耦合方法研究

对于大型客船、豪华邮轮等船舶,上层建筑参与总纵弯曲的程度较大,主船体与上层建筑之间的作用关系非常复杂。探究大型船舶上层建筑-主船体间的各向耦合关系对于改善大型船舶的力学性能、结构安全等具有十分重要的意义。本文基于双梁理论和耦合梁理论,重点研究上层建筑-转换层-主船体之间的纵向剪切耦合关系,提出一种适用于带有大型上建船体结构的简化耦合梁方法。通过建立耦合梁结构的控制方程,获得上建与主船体间的弯矩-曲率关系、剪切耦合关系以及耦合刚度-极限剪切位移之间的关系,从而有效表征大型上建与主船体间的相互作用。经实例分析,验证了该耦合梁方法的准确性和有效性,可以为带有大型上层建筑船舶的极限强度研究、设计优化等提供有益参考。

Influence of freeze-thaw damage gradient on stress-strain relationship of stressed concrete

Freeze-thaw damage gradients lead to non-uniform degradation of concrete mechanical properties at different depths.A study was conducted on the stress-strain relationship of stressed concrete with focus on the freeze-thaw damage gradient.The effects of relative freeze-thaw depths,number of freeze-thaw cycles(FTCs)and stress ratios on the stress-strain curves of concrete were analyzed.The test results demonstrated that freeze-thaw damage was more severe in the surface layers of concrete than in the deeper layers.The relative peak stress and strain of concrete degraded bilinearly with increasing depth.The stress-strain relationship of stressed concrete under FTC was established,and it was found to agree with the experimental results.

Tensile Properties and Prediction Model of Recombinant Bamboo at Different Temperatures

The destruction of recombinant bamboo depends on many factors,and the complex ambient temperature is an important factor affecting its basic mechanical properties.To investigate the failure mechanism and stress–strain relationship of recombinant bamboo at different temperatures,eighteen tensile specimens of recombinant bamboo were tested.The results showed that with increasing ambient temperature,the typical failure modes of recombinant bamboo were flush fracture,toothed failure,and serrated failure.The ultimate tensile strength,ultimate strain and elastic modulus of recombinant bamboo decreased with increasing temperature,and the ultimate tensile stress decreased from 154.07 to 96.55 MPa,a decrease of 37.33%,and the ultimate strain decreased from 0.011 to 0.008,a decrease of 26.57%.Based on the Ramberg-Osgood model and the pseudo‒elastic design method,a predictive model was established for the tensile stress–strain relationship of recombinant bamboo considering the temperature level.The model can accurately evaluate the tensile stress–strain relationship of recombinant bamboo under different temperature conditions.

Compressive Performance of Fiber Reinforced Recycled Aggregate Concrete by Basalt Fiber Reinforced Polymer-Polyvinyl Chloride Composite Jackets

The development of recycled aggregate concrete(RAC)provides a new approach to limiting the waste of natural resources.In the present study,the mechanical properties and deformability of RACs were improved by adding basalt fibers(BFs)and using external restraints,such as a fiber-reinforced polymer(FRP)jacket or a PVC pipe.Samples were tested under axial compression.The results showed that RAC(50%replacement of aggregate)containing 0.2%BFs had the best mechanical properties.Using either BFs or PVC reinforcement had a slight effect on the loadbearing capacity and mode of failure.With different levels of BFs,the compressive strengths of the specimens reinforced with 1-layer and 3-layer basalt fiber reinforced polymer(BFRP)increased by 6.7%–10.5%and 16.5%–23.7%,respectively,and the ultimate strains increased by 48.5%–80.7%and 97.1%–141.1%,respectively.The peak stress of the 3-layer BFRP-PVC increased by 42.2%,and the ultimate strain improved by 131.3%,relative to the control.This reinforcement combined the high tensile strength of BFRP,which improved the post-peak behavior,and PVC,which enhanced the structural durability.In addition,to investigate the influence of the various constraints on compressive behavior,the stress-strain response was analyzed.Based on the analysis of experimental results,a peak stress-strain model and an amended ultimate stress-strain model were proposed.The models were verified as well;the result showed that the predictions from calculations are generally consistent with the experimental data(error within 10%).The results of this study provide a theoretical basis and reference for future applications of fiber-reinforced recycled concrete.

同伴关系的发展研究

同伴关系因其在个体心理社会适应中的重要作用而受到研究者的广泛重视。本文介绍了作者及其团队在同伴关系领域基于13年的"中美儿童同伴关系数据库"开展的长期研究工作,主要包括儿童同伴关系的影响因素及影响后效、同伴关系的追踪研究、同伴关系的中美比较和网络同伴关系等主题,较为全面地阐述了儿童同伴关系领域的现有研究基础,概括了儿童同伴关系的童年期特点、发展趋势及其文化差异,总结了对儿童同伴关系及其发展的主要指标研究得到的结论,并从网络交往、同伴关系的社会网络分析和个体中心的分析等视角指出了同伴关系领域后续研究的可行方向。

酒店员工正面心理资本、敬业度与工作绩效的关系研究——基于师徒制的视角

酒店员工不仅要付出体力与智力劳动,更需要情绪投入。开发、培育员工的心理资本是酒店提升服务质量与竞争力的重要环节。对于新员工而言,帮带师傅是他们适应角色转换、学习知识与技能的重要途径。在频繁的接触中,师傅的心理状态与工作态度均会对新员工产生影响。文章采用纵断调研设计,3次收集酒店新员工及其指导师傅配对的心理资本、敬业度及工作绩效数据。研究结果表明,师傅的心理资本与敬业度对新员工均有积极的传递作用。同时,师傅的心理资本对自身的敬业度有显著正向影响,并通过敬业度间接正向影响工作绩效。新员工的心理资本、敬业度均与工作绩效显著正相关,心理资本正向预测敬业度,敬业度在心理资本与绩效之间起部分中介作用。

复杂地质条件下隧道三维变形规律分析

对乌鞘岭隧道岭脊F7断层和志留系地层的三维位移进行现场测试,并与三维数值计算结果进行对比分析;采用均值比较方法分析F7断层和板岩地段的三维变形规律,并与地应力场反演结果进行印证分析。结果表明,F7断层和千枚岩地段软岩隧道三维位移十分明显,具有隧道大变形特性,其纵向位移背离开挖面方向发展并在相距开挖面约2.0倍洞径时趋于稳定状态;F7断层地段隧道三维位移呈不均匀对称地发展变化,而板岩地段三维位移变化的一致性较好;隧道三维变形规律与隧道区域地应力场的分布存在相互印证关系。因此,在复杂地质条件下开展隧道三维位移测试并掌握其三维变形规律,对隧道工程的修建具有较大的指导作用。

扁管换热器内纵向涡强度与换热强度对应关系

纵向涡强化传热技术在管翅式换热器中得到了广泛的应用。但是一直以来对纵向涡强化传热的研究主要停留在涡产生器结构参数及布置方式对换热的影响方面,文献对纵向涡强度与换热强度之间定量关系的研究鲜有报道。建立了采用纵向涡强化传热的扁管管翅换热器数值模型,采用二次流强度参数Se分析了翅片及涡产生器结构参数变化时,通道内纵向涡强度与换热强度之间的定量关系;并定量分析了通道中涡产生器引起的纵向涡强度增量与传热强化量之间的定量关系。结果表明:翅片及涡产生器结构参数变化时,Nu、Se与Re之间,以及阻力系数f与Re及Se之间均不存在定量对应关系,但Se与Nu以及?Se与?Nu之间存在对应关系。这表明,在布置有纵向涡产生器的扁管管翅换热器翅侧通道内,纵向涡强度决定了通道内的换热强度。

工作压力与员工学习互惠关系纵贯研究——以研发人员为例

在Karasek动态模型的基础上,将员工学习细分为内化与外化两个阶段。以研发人员为样本,选取107份纵贯数据,实证检验了工作压力与员工学习之间的互惠关系。结果显示:两者存在互惠因果关系,且工作要求对学习与压力间的关系起部分中介作用。研究表明,在学习内化阶段,工作压力带来的差距感能激励员工学习并提升自身能力;在学习外化阶段,员工在习得知识和技能后将重新评估工作要求,认定自己有能力应对压力并采取积极策略。

考虑黏结滑移关系的连续道床板伸缩刚度计算方法

连续道床板在降温和自身收缩情况下容易出现裂缝,从而造成伸缩刚度的折减,不同裂缝间距时的伸缩刚度差别很大,而伸缩刚度又是连续道床板温度力计算的重要参数。考虑钢筋与混凝土间的黏结滑移关系,建立一种连续道床板伸缩刚度计算方法,对不同裂缝间距情况下的钢筋和混凝土应力、黏结阻力以及伸缩刚度进行研究,对黏结阻力型式、混凝土强度等级和配筋率对伸缩刚度的影响进行参数研究。研究结果表明:即使在一定的裂缝间距情况下,伸缩刚度也并非一定值,而是随荷载增大而逐渐降低的变量,混凝土强度等级对伸缩刚度折减的影响较小,配筋率影响较大,检算过程中可根据裂缝间距增加一定的边界条件即可得到不同温度条件下的应力与刚度分布。

压力与学习的互惠:对积极塑造者假说的纵贯实证检验

引入积极塑造者假说阐释工作压力与员工学习间的互惠关系,构建二者的良性循环,并据此提出两项中介假设;以研究院所、管理咨询机构的知识型员工为样本,采用两期107份纵贯样本进行回归分析;结果显示,员工学习中介工作压力与工作资源之间的正向关系,工作资源中介员工学习与工作压力之间的负向关系,压力与学习构成良性循环;研究表明,面对压力,积极塑造者将展开适应学习,习得知识后,积极塑造者将改变工作、获取资源以缓解压力,工作压力与员工学习良性互惠、员工福祉和技能螺旋上升。