Intrinsic Defect Limit to the Growth of Orthorhombic HfO2 and (Hf,Zr)O2 with Strong Ferroelectricity: First-Principles Insights

It is believed that promoting the fraction of ferroelectric orthorhombic phase (o-phase) through O-poor growth conditions can increase the spontaneous polarization of HfO₂ and (Hf,Zr)O₂ thin films. However, the first-principles calculations show that the growth may be limited by the easy formation of point defects in the orthorhombic and tetragonal phases of HfO₂, ZrO₂, and (Hf,Zr)O₂. Their dominant defects, O interstitial (O_i) under O-rich conditions and O vacancy (V_O) under O-poor condition, have low formation energies and quite high density (10¹⁶–10¹⁹ cm⁻³ for 800–1400 K growth temperature). Especially, O_i has negative formation energy in tetragonal HfO₂ under O-rich condition, causing non-stoichiometry and limiting the crystalline-seed formation during o-phase growth. High-density defects can cause disordering of dipole moments and increase leakage current, both diminishing the polarization. These results explain the experimental puzzle that the measured polarization is much lower than the ideal value even in O-poor thin films and highlight that controlling defects is as important as promoting the o-phase fraction for enhancing ferroelectricity. The O-intermediate condition (average of O-rich and O-poor conditions) and low growth temperature are proposed for fabricating HfO₂ and (Hf,Zr)O₂ with fewer defects, lower leakage current, and stronger ferroelectricity, which challenges the belief that O-poor condition is optimal.     

Study of Pb-based and Pb-free perovskite solar cells using Cu-doped Ni1-xO thin films as hole transport material

SCAPS solar cell simulation program was applied to model an inverted structure of perovskite solar cells using Cu-doped Ni_1-xO thin films as hole transport layer. The Cu-doped Ni_1-xO film were made by co-sputtering deposition under different deposition conditions. By increasing the amount of the Cu-dopant, the film crystallinity enhanced whereas the bandgap energy decreased. The transmittance of the thin films decreased significantly by increasing the sputtering power of copper. High quality, uniform, compact, and pin-hole free films with low surface roughness were achieved. The structural, chemical, surface morphology, optical, electrical, and electronic properties of the Cu doped Ni_1-xO films were used as input parameters in the simulation of Pb-based (MAPbI_3-xCl_x) and Pb-free (MAGeI₃) perovskite solar cells. Simulation results showed that the performance of both Pb-based and Pb-free perovskite solar cell devices significantly enhanced with Cu-doped Ni_1-xO film. The highest power conversion efficiency (PCE) for the Pb-free perovskite solar cell is 8.9% which is lower than the highest PCE of 17.5% for the Pb-based perovskite solar cell.     

Facile self-assembly approach to construct a novel MXene-decorated nano-sized phase change material emulsion for thermal energy storage

In recent years, phase change material emulsions (PCMEs) with enhanced energy storage capacities and good flow characteristics have drawn significant attention. However, due to the thermodynamically unstable nature and tiny particle confinement, the nanomaterial modification strategies at PCM/water interface to improve stabilities and reduce supercooling of nano-sized PCMEs (NPCMEs) are very limited and challenging. Herein, we report a facile strategy for constructing MXene-decorated NPCME with good stability, little supercooling, and high thermal conductivity by self-assembly of MXene nanosheets at PCM/water interface. The concentrations of MXene have great influences on the average droplet diameters, stabilities, and thermophysical properties of the NPCMEs. The results show that the PCMs have been well dispersed into the water in the form of quasi-spherical droplets, with average droplet diameters of 242–805 nm. The thermal conductivity of 10 wt% n-tetradecane/water NPCME containing 9 mg ml^-1 MXene is 0.693 W m^-1·K^-1, achieving an enhancement by 15.5%, as compared to that of water. Besides, the MXene-decorated paraffin/water NPCMEs exhibit little supercooling and enhanced heat storage capacities. More importantly, this facile self-assembly strategy opens a new platform for preparing high-performance NPCMEs, which can be used as novel heat transfer fluids for thermal energy storage systems.     

人造金刚石填充聚酰亚胺树脂基复合材料防刺性能

为研究树脂材料的防刺性能及防刺机制,利用手糊成型与热压法成型制备了手糊分层结构和均布结构层2种结构的人造金刚石填充聚酰亚胺树脂基复合树脂片,并探讨了人造金刚石粒径、填充体积分数对树脂片防刺性能的影响。研究结果表明:经过人造金刚石填充的聚酰亚胺树脂片的防刺性能得到提高,并且均布结构层分层复合结构的树脂片的防刺性能更好;随着人造金刚石粒径的减小,树脂片防刺性能出现先减小后增加的趋势,故防刺机制基本在于碰撞概率与树脂基的防挡;比较防刺力和消耗功发现,不同填充体积分数的单层防刺树脂片的防刺性能随人造金刚石填充体积分数的增加而逐渐降低,该趋势的成因在于复合树脂片的脆化与破坏;在颗粒等效粒径为300 μm、体积分数为10%时,其防刺性能最好。     

Interleukin-1β Modulation of the Mechanobiology of Primary Human Pulmonary Fibroblasts: Potential Implications in Lung Repair

Pro-inflammatory cytokines like interleukin-1β (IL-1β) are upregulated during early responses to tissue damage and are expected to transiently compromise the mechanical microenvironment. Fibroblasts are key regulators of tissue mechanics in the lungs and other organs. However, the effects of IL-1β on fibroblast mechanics and functions remain unclear. Here we treated human pulmonary fibroblasts from control donors with IL-1β and used Atomic Force Microscopy to unveil that IL-1β significantly reduces the stiffness of fibroblasts concomitantly with a downregulation of filamentous actin (F-actin) and alpha-smooth muscle (α-SMA). Likewise, COL1A1 mRNA was reduced, whereas that of collagenases MMP1 and MMP2 were upregulated, favoring a reduction of type-I collagen. These mechanobiology changes were functionally associated with reduced proliferation and enhanced migration upon IL-1β stimulation, which could facilitate lung repair by drawing fibroblasts to sites of tissue damage. Our observations reveal that IL-1β may reduce local tissue rigidity by acting both intracellularly and extracellularly through the downregulation of fibroblast contractility and type I collagen deposition, respectively. These IL-1β-dependent mechanical effects may enhance lung repair further by locally increasing pulmonary tissue compliance to preserve normal lung distension and function. Moreover, our results support that IL-1β provides innate anti-fibrotic protection that may be relevant during the early stages of lung repair.     

Traveling-wave Phenomena in a Model of Autocrine Signaling Coupled with Dynamics of the MAPK Cascade

Recently we have revealed a minimal reaction subnetwork in the MAPK (mitogen-activated protein kinase) cascade that is responsible for the emergence of bistable and oscillatory behavior. Here we examine a possible mechanism that provides for the propagation of increased MAPK activity in cell populations by interconnecting the intracellular MAPK subnetwork with the ligand-receptor signaling machinery. Such approach allows for significant reduction of the dimensionality of the parameter space on one hand and the conservation of dynamical complexity of the system on the other hand. The coupled model predicts coexistence of one, two or three different stable steady states, or the coexistence of a stable steady state and periodic solution. We found two robust and physiologically relevant characteristics of the proposed model: (i) There is a very large region of coexistence of at least one stable steady state with non-zero MAPK activity and one steady state with zero MAPK activity in the parameter space. (ii) Spontaneous traveling front waves always switching originally inactive cells into ligand releasing cells emerge in adjacent cell populations, e. g. in healthy and injured tissues. Moreover, the formation of composite traveling front waves and spatial oscillatory patterns of MAPK activity are predicted and discussed.     

大数据环境下基于K中心点优化算法的Web服务组合

在当前Web服务海量增加、现有Web服务选择算法低效、用户匹配度差的基础上，针对K中心点算法存在的质点偏移、准确率低和容易发生畸变等问题，提出一种大数据环境下基于K中心点优化算法的Web服务组合方法。该方法是在大数据环境下，根据不同用户需求满意度及Web服务QoS参数，对基于优化初始聚类中心的K中心点算法的Web服务选择及最优Web服务组合进行研究。同时针对不同的选择方法对服务动态选择及组合的准确度、迭代更新次数、候选集选择时间及选择总时间进行实验分析，验证了本文研究方法的有效性和可靠性。     

基于单片机C8051F500的无刷直流电机控制研究

永磁无刷直流电机是近些年发展起来的一种新型电机,具有效率高、调速性能好、启动转矩大等诸多优点,在运动控制领域中的应用日趋广泛。基于电机专用控制芯片MC33035,采用单片机C8051F500为主控芯片,设计一款无刷直流电机智能控制器,实现对无刷直流电机启动停止、正反转、调速、转速显示等控制。通过简要介绍无刷直流电机工作原理,使用MATLAB/Simulink对控制系统进行建模仿真,对无刷直流电机控制系统进行软、硬件设计。实验结果表明,该控制系统运行稳定,抗干扰性强,具有良好的市场应用价值。     

面向连续查询的敏感语义位置隐私保护方案

针对连续查询位置服务中构造匿名区域未考虑语义位置信息导致敏感隐私泄露问题，通过设计[(K,θ)]-隐私模型，提出一种路网环境下面向连续查询的敏感语义位置隐私保护方案。该方案利用Voronoi图将城市路网预先划分为独立的Voronoi单元，依据用户的移动路径和移动速度，选择具有相似特性的其他[K-1]个用户，构建匿名用户集；利用匿名用户集用户设定的敏感语义位置类型和语义安全阈值，以及用户所处语义位置的Voronoi单元，构建满足[(K,θ)]-隐私模型的语义安全匿名区域，可以同时防止连续查询追踪攻击和语义推断攻击。实验结果表明，与SCPA算法相比，该方案在隐私保护程度上提升约15%，系统开销上降低约20%。     

一种新的应用于5G中的自适应波束赋形优化算法

5G standard uses millimeter wave band to realize communication. In order to cover more reasonable in 5G communication system, beamforming technology must be adopted. To speed up the convergence, a novel algorithm based on the SWO criterion is proposed which can be applied in millimeter wave communication. The simulation results show that compared with other beamform- ing algorithms, the proposed algorithm can achieve higher convergence speed and is more realizable.