Optical pulling force on nanoparticle clusters with gain due to Fano-like resonance

We demonstrate that,in a simple linearly-polarized plane wave,the optical pulling forces on nanoparticle clusters with gain can be induced by the Fano-like resonance.The numerical results based on the full-wave calculation show that the optical pulling forces can be attributed to the recoil forces for the nanoparticle clusters composed of dipolar nanoparticles with three different configurations.Interestingly,the recoil forces giving rise to optical pulling forces are exactly dominated by the coupling term between the electric and magnetic dipoles excited in the nanoparticle clusters,while other higherorder terms have a negligible contribution.In addition,the optical pulling force can be tailored by modulating the Fano-like resonance via either the particle size or the gain magnitude,offering an alternative freedom degree for optical manipulations of particle clusters.

Theoretical and experimental study of the pulling force of jet bits in radial drilling technology

Radial drilling technology, of which the jet bit is the key device, is a research focus in the field of oil drilling and production. This paper establishes mechanical equations for jet bits and analyzes the hydroseal of backward jets in bottom holes. Meanwhile this paper establishes a mechanical equation for a high pressure hose and analyzes the axial force distribution. Laboratory experiments indicate that the flow rate, the angle between the backward nozzle axis and the jet bit axis, and the hole diameter are the major influencing factors; the generation of the pulling force is mainly due to the inlet pressure of the jet bit; the backward jets can significantly increase not only the pulling force but also the stability of jet bits. The pulling force would reach 8,376 N under experimental conditions, which can steadily pull the high-pressure hose forward.

Pulling force of acoustic-vortex beams on centered elastic spheres based on the annular transducer model

To solve the difficulty of generating an ideal Bessel beam,an simplified annular transducer model is proposed to study the axial acoustic radiation force(ARF)and the corresponding negative ARF(pulling force)exerted on centered elastic spheres for acoustic-vortex(AV)beams of arbitrary orders.Based on the theory of acoustic scattering,the axial distributions of the velocity potential and the ARF for AV beams of different orders generated by the annular transducers with different physical sizes are simulated.It is proved that the pulling force can be generated by AV beams of arbitrary orders with multiple axial regions.The pulling force is more likely to exert on the sphere with a smaller k0a(product of the wave number and the radius)for the AV beam with a bigger topological charge due to the strengthened off-axis acoustic scattering.The pulling force decreases with the increase of the axial distance for the sphere with a bigger k0a.More pulling force areas with wider axial regions can be formed by AV beams using a bigger-sized annular transducer.The theoretical results demonstrate the feasibility of generating the pulling force along the axes of AV beams using the experimentally applicable circular array of planar transducers,and suggest application potentials for multi-position stable object manipulations in biomedical engineering.

Graphene-tuned threshold gain to achieve optical pulling force on microparticle

We investigate optical force on a graphene-coated gain microparticle by adopting the Maxwell's stress tensor method.It is found that there exists a threshold gain in obtaining the Fano-profile optical force which indicates the reversal of optical pushing and pulling force. And giant pushing/pulling force can be achieved if the gain value of the material is in the proximity of the threshold gain. Our results show that the threshold gain is more sensitive to the relaxation time than to the Fermi energy of the graphene. We further study the optical force on larger microparticle to demonstrate the pulling force occurring at octupole resonance with small gain value and then it will appear at quadrupole resonance by increasing gain value. Our work provides an in-depth insight into the interaction between light and gain material and gives the additional degree of freedom to optical manipulation of microparticle.

Effect of micro-dimple patterns on capillary pull-off force and friction force of silicon surface

A microtribometer is used to measure and compare pull-off forces and friction forces exerted on （a） micro-dimpled silicon surfaces, （b） bare silicon surfaces, and （c） octadecyltrichlorosilane （OTS） treated silicon surfaces at different relative humidity （RH） levels separately. It is found that above a critical RH level, the capillary pull-off force increases abruptly and that the micro-dimple textured surface has a lower critical RH value as well as a higher pull-off force value than the other two surfaces. A micro topography parameter, namely sidewall area ratio, is found to play a major role in controlling the capillary pull-off force. Furthermore, micro-dimpled silicon surface is also proved to be not sensitive to variation in RH level, and can realize a stable and decreased friction coefficient compared with un-textured silicon surfaces. The reservoir-like function of micro dimples is considered to weaken or avoid the breakage effect of liquid bridges at different RH levels, thereby maintaining a stable frictional behaviour.

Study on Ultimate Pullout Force of Grouting Anchors of the Anchor-Pull Retaining Wall

Determination of the grouting anchor pullout force is a key step during the design of anchor-pull retaining wall, but it is mostly determined relied on empirical formula at present, and the rationality and the safety cannot be effectively guaranteed. Based on the engineering case of the gravity retaining wall of Qinglin Freeway, the model test was designed, and combined with the results of the ABAQUS finite element numerical analysis, it was analyzed that how the anchor axial pulling force distributes. The results showed that the force of the anchor near the wall bolt was large and which far from the wall was small and the ultimate pullout force was proportional to the length, diameter and shear strength. When the end tension of the anchor was small, the top load played a leading role on the anchor tension. This conclusion confirmed the calculation formula of ultimate pullout force was and provided a theoretical basis for anchor-pull retaining wall design and calculation.

Anharmonic 1D actuator model including electrostatic and Casimir forces with fractional damping perturbed by an external force

We modeled a one-dimensional actuator including the Casimir and electrostatic forces perturbed by an external force with fractional damping. The movable electrode was assumed to oscillate by an anharmonic elastic force originated from Murrell- Mottram or Lippincott potential. The nonlinear equations have been solved via the Adomian decomposition method. The behavior of the displacement of the electrode from equilibrium position, its velocity and acceleration were described versus time. Also, the changes of the displacement have been investigated according to the frequency of the external force and the voltage of the electrostatic force. The convergence of the Adomian method and the effect of the orders of expansion on the displacement versus time, frequency, and voltage were discussed. The pull-in parameter was obtained and compared with the other models in the literature. This parameter was described versus the equilibrium position and anharmonicity constant.

Analytical modeling of static behavior of electrostatically actuatednano/micromirrors considering van der Waals forces

In this paper, the effect of van der Waals （vdW） force on the pull-in behavior of electrostatically actuated nano/micromirrors is investigated. First, the minimum po- tential energy principle is utilized to find the equation gov- erning the static behavior of nano/micromirror under electro- static and vdW forces. Then, the stability of static equilib- rium points is analyzed using the energy method. It is found that when there exist two equilibrium points, the smaller one is stable and the larger one is unstable. The effects of dif- ferent design parameters on the mirror＇s pull-in angle and pull-in voltage are studied and it is found that vdW force can considerably reduce the stability limit of the mirror. At the end, the nonlinear equilibrium equation is solved numer- ically and analytically using homotopy perturbation method （HPM）. It is observed that a sixth order perturbation approx- imation can precisely model the mirror＇s behavior. The re- suits of this paper can be used for stable operation design and safe fabrication of torsional nano/micro actuators.

Monitoring film coalescence from aqueous polymeric dispersions using atomic force microscopy: Surface topographic and nano-adhesion studies

The aim of the investigation was to develop the use of topographic and nano-adhesion atomic force microscopy(AFM) studies as a means of monitoring the coalescence of latex particles within films produced from a pharmaceutically relevant aqueous dispersion(Eudragit~?NE30 D). Films were prepared via spin coating and analysed using AFM, initially via tapping mode for topographic assessment followed by force-distance measurements which allowed assessment of site-specific adhesion. The results showed that colloidal particles were clearly observed topographically in freshly prepared samples, with coalescence detected on curing via the disappearance of discernible surface features and a decrease in roughness indices. The effects of temperature and humidity on film curing were also studied, with the former having the most pronounced effect. AFM force measurements showed that the variation in adhesive force reduced with increasing curing time, suggesting a novel method of quantifying the rate of film formation upon curing. It was concluded that the AFM methods outlined in this study may be used as a means of qualitatively and quantitatively monitoring the curing of pharmaceutical films as a function of time and other variables, thereby facilitating rational design of curing protocols.

Robot Application and Labor Force Employment:Substitution or Complementation?——An Empirical Analysis Based on the Data from 22 Economies

The rise of robotics has brought great uncertainty to the labor market.Based on the sectoral data from 22 economies during 2008-2019,this paper explores the impact of robot application on employment.The results show that,on the whole,robot application will have complementary effects on labor force employment,and the grouped regression by economic development level and demographic characteristics supports this conclusion,while the effect of robot application on labor force employment is significantly different by industry.Further research shows that the degree of robot use is the key factor that determines the effect of robots on employment,and the complementary effect is dominant in economies with low degree of robot application,and the subtitution effect is dominant in economies with high degree of robot application.In addition,obvious spillover effects are observed in robotic application.On the one hand,robot application will have a forward crowdingout effect and a reverse siphon effect,which drive the labor force moving from the primary industry to the secondary and tertiary industries.On the other hand,robot application will also have heterogeneous effects on the labor force employment of economies in the upstream and downstream position along the value chain through the transmission effect of the Global Value Chains(GVC).The conclusions of this paper provide some practical implications for the rational formulation of artificial intelligence plans in the context of“stabilizing employment”.

基于推拉理论的苏北大学生返乡就业意愿影响因素分析

切实发挥好人才在乡村振兴战略实施中的作用,是我国全面推进中国式现代化新实践的应然选择,如何更好地引导农村大学生返乡就业、投身三农已成为社会各界广泛热议的话题。以苏北地区大学生为研究对象,运用推拉理论对其返乡就业意愿及影响因素进行问卷调研与实证分析。研究结果显示,苏北地区对于乡村振兴的宣传力度不够,学校职业规划教育不足,家庭支持力度不大,个人就业择业观念尚未转变。政府加大政策宣传力度,学校加强对毕业生就业观的教育引导,家庭理性看待大学生返乡就业,以及学生自身合理规划职业生涯是促进大学生返乡就业、增强返乡就业意识的有效路径。

新就业形态就业规模测度研究——基于某市住户端调查及平台端大数据的综合分析

新就业形态创造了大量就业岗位已成为社会共识,但其就业规模和占就业人口比例一直未得到系统回答,导致相关政策出台缺乏依据。本研究构建了依托住户端调查数据和平台端大数据两个数据维度的新就业形态从业者就业规模测度方法。在此基础上,以W市劳动力调查数据为基础,结合职业伤害保障制度数据,对该市新就业形态从业者比例和就业规模进行了测算。研究结果显示,在未修正前,2023年上半年新就业形态从业者规模达61.42万人,占全市就业人口比例为4.97%;使用职业伤害保障等数据修正后,该市新就业形态从业者规模为100.38万人,占全市就业人口比例为8.13%。2019—2023年上半年,W市新就业形态从业者比例不断波动。2020年初,受到新冠疫情影响,新就业形态就业比例出现快速下降。2023年开始,新就业形态就业比例又重新开始上升。具体类别中,用车服务、物流服务、生活服务、网络直播、中介服务等新就业形态就业比例上升;而金融服务,商品交易,承接生产订单,知识、技能、娱乐、广告等线上服务新就业形态类别比例下降。本研究构建的依托住户端调查数据和平台端大数据相结合的测度方法避免了新就业形态就业规模的低估和高估。

ChatGPT对程序员职业的双重影响

ChatGPT的诞生开启了一场波及各行业的技术革命,人工智能在机械性的工作中展示了巨大的潜能,以至于威胁到一些工作岗位的存续,也引发了各行各业和学者们的热烈讨论。软件开发者--—大众口中的程序员,正站在这场技术革命的十字路口,ChatGPT得天独厚的能力既完美地匹配了程序员的工作,同时也威胁到本属于人类的工作岗位。但是这些威胁并非来自技术本身,而是技术的所有者在规范不健全的当下,对他人权利的侵犯。以ChatGPT为代表的人工智能技术不会夺走全部人类的工作,而是会对这些工作加以改变、改善,然而这一切的前提是对人工智能的发展进行正确的引导和规范。如何提升对这种尖端技术的监管能力,如何在发展技术的同时保障人们的权利,将是决定人工智能未来的关键。

竹集成材握钉性能试验研究

为研究单调加载下的竹集成材(LBL)握钉性能,对260个LBL钉节点试件进行拔出试验,以钉种类、钉直径、有效锚固长度以及作用力方向与LBL顺纹方向的夹角为参数,研究其破坏模式和握钉性能。结果表明:破坏模式与钉种有关,与钉直径、锚固长度和角度无关,光圆钉试件无可见破坏,而螺钉和麻花钉试件的破坏模式主要表现为钉杆环向的竹纤维发生剪切破坏,LBL内部竹纤维被环向肋纹切断并拉出试件表面。极限抗拔承载力随钉直径和有效锚固长度的增大而增加,顺纹向的承载力略低于横纹向。对于相同直径的钉而言,顺纹向螺钉和麻花钉的极限承载力分别为光圆钉的2.6倍和1.3倍,而横纹向的螺钉和麻花钉的抗拔承载力分别为光圆钉的2.3倍和1.2倍。LBL握钉力理论计算值和试验值吻合良好,误差不超过13%。

电磁吸盘-摩擦摆复合隔震支座理论分析与试验研究

为解决摩擦摆支座在外部荷载激励下不具备抗拔性的缺点,基于电磁原理和半主动控制思想,提出了一种以电磁力为基础,结合传统摩擦摆的电磁吸盘-摩擦摆复合隔震支座(Electromagnetic Chuck-Friction Pendulum System,ECFPS)。介绍了该复合隔震支座的构造特点和耗能机制,并基于电磁原理推导出电磁吸盘吸力以及ECFPS的等效刚度、周期和等效阻尼比等理论公式,建立了ECFPS计算模型。设计并制作了一个缩尺比为1∶3的ECFPS试件,对不同输入电流、竖向荷载和不同位移幅值下的滞回性能进行了试验研究,探究了不同输入电流对抗拔性能的影响。试验结果表明:理论值与试验值吻合度较高,验证了理论公式推导的正确性;等效刚度和单位循环耗能变化明显,两者最大变化幅度分别为19.81%和28.16%;随着电磁吸盘输入电流的增大,ECFPS支座的抗拔性能提高,实现了支座竖向抗拔的功能。

企业数字化对劳动力市场就业风险的影响

企业数字化是数字经济的微观形态,对劳动力市场将产生深刻影响。在劳动力价格不断上涨的背景下,探讨企业数字化如何影响就业风险具有重要意义。采用劳动力需求弹性衡量劳动力市场就业风险,基于2010—2020年中国A股上市企业数据考察企业数字化对就业风险的影响,发现企业数字化能够降低劳动力市场的就业风险,总体上具有积极的就业效应。从作用机制来看,企业数字化通过生产力机制与资源机制对劳动力市场就业风险产生影响,前者表现为替代效应与规模效应,后者表现为融资效应,其中替代效应深化就业风险,而规模效应与融资效应缓解就业风险。实证结果表明,生产力机制的规模效应与资源机制的融资效应占据主导地位,这两个效应均显著存在。在数字经济所催生的企业数字化过程中,借助数字化转型推动企业发展,进而改善经营状况,对化解劳动者就业风险,实现更加充分更高质量就业具有积极意义。

空间扭曲的导光条注塑模具设计

导光条的重要特征是导光齿,针对导光齿呈空间扭曲状态分布的长条形导光条模具的开模方向设计难点,提出了基于特征面的法向集合选择模具Z向的方法。先分析零件特征,进行特征面归类,整理归类好的特征面的法向集合,寻找法向的分布规律,根据分布规律确定模具的开模方向范围,再借助零件上其他特征缩小开模方向范围,直至选定合适的开模方向和模具坐标系。在模具结构设计过程中,充分考虑模具受力平衡,设计了瓣合分型+空间大角度抽芯的多层组合式分型机构,最终成功设计了一套一模两件带组合抽芯机构的热流道模具。模具受力平衡,产品质量好。

新型农村集体经济发展对劳动力回流的影响:“安居”与“乐业”

基于中国劳动力动态调查数据库(CLDS)2016年和2018年两期面板数据,利用双向固定效应模型和工具变量法,分析新型农村集体经济发展对劳动力回流的影响及其作用机理。结果表明:新型农村集体经济发展对劳动力回流具有显著正向影响;在进行替换变量、控制遗漏变量及测量误差等检验后,研究结论依然保持不变。机制分析表明,新型农村集体经济发展主要通过改善和优化农村人居环境与就业环境来促进劳动力回流。同时,新型农村集体经济发展吸引的回流劳动力具有年龄大、学历低的特征。此外,农村劳动力回流后更倾向于非农就业。因此,建议进一步推动新型农村集体经济高质量发展,为外出劳动力回流后的“安居”和“乐业”创造更为有利的环境和基础,进而更好地吸引高素质劳动力适度回流,推进乡村全面振兴。

稳定就业如何影响技能形成——基于我国企业雇佣制度的历史考察

技能,尤其是专有技能的形成,需要个体扎根某一岗位长时间的耕耘和摸索,这就需要为劳动者提供相对稳定的工作环境和就业保障。计划经济时期,我国国有企业执行统包统配的计划式就业,企业采取劳动竞赛、厂内师徒制、技术协作等方法促进个体的技能形成;社会主义市场经济时期,公有制企业以编制制度,为部分技术技能人才提供了就业稳定的制度保障,同时进一步延续和创新了技能竞赛、基于专家工作室的师徒制、职称评定等制度促进员工的技能形成,而非公有制企业则通过签订长期合同、竞业禁止等给予雇员稳定雇佣的可信承诺,并通过强化员工忠诚教育、建立内部人才上升和流动通道、建立内部人才培养体系和劳动力市场等措施,提升员工专有技能的形成效率。本质上,这是社会主义市场经济环境下,企业内劳动力商品化和去商品化之间的一次再平衡。企业以稳定的雇佣承诺尊重和保护劳动者作为人的特质和需求,并通过师徒传承、生涯发展、锦标赛和内培内招四大机制,发挥劳动力作为生产要素的价值。这一机制还受到国家经济体制以及规范有序的行业内部劳动力市场的宏观影响。未来我国的就业政策、教育政策、社会保障政策应重点促进社会群体的稳定就业,通过积极创设稳定就业的制度环境、提升中小微企业的人力资源开发与技能形成能力、提升职业院校校企合作人才培养的结构性与合规性,协助企业构筑健康稳定、可预期的劳资合作关系。

Estimation,analysis of China's labor force 2000-08

The author estimated and analyzed China's urban and rural economically active,employed and unemployed populations as well as the labor-force participation ratio and employment and unemployment rates from 2000-2008 by referring to population census data and establishing estimation models in this paper.The research results indicate changing trends in China's urban and rural economically active population from 2000-2008.