Buckling of Bulk Structures With Finite Prebuckling Deformation

The prebuckling deformation of structures is neglected in most of the conventional buckling theory (CBT) and numerical method (CNM), because it is usually very small in conventional concepts. In the preceding paper (Su et al., 2019), we found a class of structures from the emerging field of stretchable electronics, of which the prebuckling deformation became large and essential for determining the critical buckling load, and developed a systematic buckling theory for 3D beams considering the effects of finite prebuckling deformation (FPD). For bulk structures that appear vastly in the advanced structures, a few buckling theories consider the effects of the prebuckling deformation in constitutive equations by energy method, which are significantly important but not straightforward and universal enough. In this paper, a systematic and straightforward theory for the FPD buckling of bulk structures is developed with the use of two constitutive models. The variables for the prebuckling deformation serve as the coefficients of the incremental displacements, deformation components, and stress in the buckling analysis. Four methods, including the CBT, CNM, DLU (disturbing-loading-unloading method) method and FPD buckling theory, are applied to the classic problems, including buckling of an elastic semi-plane solid and buckling of an elastic rectangular solid, respectively. Compared with the accurate buckling load from the DLU method, the FPD buckling theory is able to give a good prediction, while the CBT and CNM may yield unacceptable results (with 70% error for the buckling of an elastic semi-plane solid)

一种可拉伸的射频除皱面膜

本实用新型提供了一种便于家中使用的，柔性可拉伸的射频除皱面膜，能够与人脸完美贴合，并对皮肤发射均匀可控的射频能量，为皮肤真皮层加热从而达到改善甚至消除皱纹的美容效果。包括：面膜本体、弹性封装薄膜、用于封装导线的弹性密封胶层、连接器和控制单元；面膜本体为设有射频电极的可拉伸柔性电路板，用于发射射频电流；弹性封装薄膜，用于对面膜本体的背面进行封装，弹性密封胶层用于对面膜本体的正面上的导线进行封装并露出射频电极，实现射频电极与人脸友好紧密接触；连接器，用于为可拉伸柔性电路板提供电源与控制信号的接口；控制单元与连接器非固定连接，用于为可拉伸柔性电路板提供控制信号

一种三层柔性电池结构及制备方法

本发明公开了一种三层柔性电池结构，它包括柔性基底(1)、岛桥结构(2)、电池(3)。本发明将柔性基底之上的电池和导线设计为三层结构，中间一层为紧密排列的电池阵列，电池上下两侧为导电小圆柱以及使它们并联的铜导线，它们分别引出电池的正极与负极，每个小圆柱都对应与其共中心的正方形电池部分，电池之间紧密排列覆盖整个基底，整个结构具有很高的延展性，同时实现了电池覆盖率的最大化，极大地提升了电池单位面积容量

“有限初始变形”屈曲实验和理论研究（英文）

The initial deformation of structures before the onset of buckling is usually very small in conventional concepts, and is always neglected in the conventional buckling theory(CBT) and numerical method(CNM). In this work, we find a class of structures from the emerging field of stretchable electronics, of which the initial deformation becomes large and essential for determining the critical buckling load. The buckling of these structures is referred to as the ‘finite-initial-deformation buckling'(FID buckling). Although great progress has been made for the buckling theory in the past hundred years, it is still challenging to analyze the FID buckling behaviors. Here, experimental stretch of a series of serpentine interconnects was firstly conducted as a representative example to show the FID buckling behaviors and the inapplicability of the CBT and CNM. The CNM can yield a huge error of 50% on the critical buckling load for the case with thickness-to-width ratio of the cross section h/b=0.6. Most importantly, a systematic theory(FID buckling theory) is developed to analyze the FID buckling behaviors of beams, with the coupling of bending, twist and stretch/compression. As a comparison, various theoretical and numerical methods are applied to three classic problems, including lateral buckling of a three-point-bending beam, lateral buckling of a pure bending beam and Euler buckling. Our FID buckling theory is able to give a good prediction, while the CBT(by Timoshenko et al.) and CNM(by commercial program packages) yield unacceptable results(with 70% error for a three-point-bending beam with h/b=0.8, for example)

电动汽车智能动态无线充电系统的研究现状与展望

为了解决电动汽车的车载电池体积大和里程焦虑等问题，加速电动汽车的推广应用，动态无线充电系统（DWCS）应运而生。介绍了电动汽车智能DWCS的基本框架，从电路结构及系统建模、电动汽车定位、DWCS的控制策略以及与智能电网的相互影响等方面详细阐述了国内外学者在 DWCS 方面的研究工作，然后从系统结构及优化、与无人驾驶技术的融合以及电网和交通网的协同优化策略等方面对电动汽车智能 DWCS 未来的研究方向和发展趋势进行了展望

用于柔性可穿戴设备的薄膜式曲率传感器（英文）

Flexible and wearable electronics integrated with various sensors have great potential for applications in monitoring human activities and personal health.Bending and tension/compression dominate the deformation modes yielded by flexure of joints and diverse body gestures.A key challenge now is to sense the curvature/bending angle,while much research has been focused on the strain sensors for tension/compression.Alternative approaches by strain sensors or non-contact optical methods for curvature sensing are not practical for wearable electronics,because the former demands perfect adhesion of the sensors to target surfaces(e.g.,the human skin) and the latter requires complicated and bulky measurement systems that hinder their portability.Here,a novel adhesion-free thin-film-like curvature sensor that can monitor bending activities is introduced for flexible and wearable electronics.We present comprehensive design,fabrication,mechanism,structural analysis,performance characterization,and device-level demonstrations for bending of joints,gesture recognition,and real-time sitting posture correction.The most prominent advantage of the present sensor is that the measurement is independent of the strain of the target surface and the interfacial slippage,thus the perfect adhesion between the sensor and the surface is unnecessary.The features of adhesion-free,simple mechanical principle,low cost,and satisfactory monitoring results highlight the superiority of the present curvature sensors for practical applications to flexible and wearable electronics

基于噪声辅助快速多维经验模式分解的运动想象脑电信号分类方法

脑机接口是一项新兴的技术，它可以处理分析采集到的运动想象脑电信号，从而实现对外部辅助设备的控制。针对目前运动想象脑电信号处理方法计算效率低、分类准确率不高等问题，提出了一种新的基于噪声辅助快速多维经验模式分解（NA-FMEMD）的运动想象脑电信号分类方法。该方法首先利用 NA-FMEMD 得到全部的多维本征模式函数和趋势项；接着，根据平均频率选取特定的信号层，构建出新的多维信号；然后，通过共空间模式提取出脑电信号的特征向量；最后，将特征向量输入支持向量机分类器中进行分类。分别采用仿真数据和BCI Competition IV数据进行测试，并与基于噪声辅助多维经验模式分解（NA-MEMD）的方法进行比较，验证了所提方法的有效性和优势

Stretchable Electronic Facial Masks for Radiofrequency Therapy

Acne, the most prevalent chronic inflammatory skin condition, significantly impacts patients' quality of life and mental health. Radiofrequency (RF) therapy offers a deep heating effect, devoid of antibiotic resistance, and side effects in pharmacological treatments, while avoiding the skin-type limitations in phototherapy. However, conventional RF devices face challenges associated with long-time hand-held use and short effective treatment-duration due to small sizes and continuous movement of the probe. Consequently, the stretchable electronic facial mask for radiofrequency therapy (SEFM-RFT) is presented for large-area treatment and hands-free operation. A radiofrequency-array heating model is proposed to ensure the therapeutic efficacy and safety, and an adsorption hot-pressing packaging technique is developed to maintain close skin contact. Animal experiments demonstrate that SEFM-RFT reduces the number of lesions by 78%, while the effect on acne recovery is proved through bacterial and histochemical experiments. The development of SEFM-RFT represents a significant advancement in flexible electrical therapy devices

长期围栏封育对中天山三种类型草地土壤酶活性的影响[C]

本研究以新疆具有代表性的三种类型草地围栏年限为25年的土壤为研究对象,对围栏内外土壤酶活性以及与土壤环境因子之间的关系进行了相关性分析,结果表明:长期围栏封育可使围栏内的土壤酶活性高于围栏外,围栏可明显改善0～10cm土层中脲酶的活性和明显影响除亚高山草甸化草原土壤外的两类草地0～30cm土壤中蔗糖酶的活性;围栏内外土壤过氧化氢酶和碱性磷酸酶活性都较低,四种酶活性均随土壤深度增加,酶活性逐渐降低;在亚高山草原,酶活性与土壤含水量呈现出极显著的相关水平(P<0.01),而在亚高山草甸化草原,脲酶、碱性磷酸酶、蔗糖酶活性与土壤含水量也呈显著相关性(P<0.05)。酶活性与土壤有机质、速效磷、速效氮..