High improvement in the properties of exfoliated PU/clay nanocomposites by the alternative swelling process

In this work, a stable de-aggregated solvent-swollen organic modified clay, ALA-MMT, suspension is prepared by an efficient solvent swelling process using a home-made shaking mixer. It is found that the estimated average size of the as-prepared organoclay particles in the suspension is reduced to about 155 nm, which has not been reported before. The X-ray diffraction (XRD) patterns confirm that the d-spacing of the silicate layers of the solvent-swollen ALA-MMT expands from 1.4 nm to about 2.1 nm. The de-aggregated solvent-swollen ALA-MMT suspension is then used with polyurethane (PU) to prepare a series of highly exfoliated and high-organoclay-loading nanocomposites, PU/ALA-MMT. Both the XRD patterns and the TEM photographs of the as-prepared PU/ALA-MMT nanocomposites indicate that the organoclay is uniformly dispersed in the PU matrix with a highly exfoliated morphology structure of up to 7 wt% loading. Meanwhile, the TEM photographs give the first report for PU/clay nanocomposites which are almost completely exfoliated, and ∼1-nm thin silicate nanolayers are homogeneously dispersed in the polymer matrix with a high aspect ratio of 30-100. The thermal, mechanical, and anti-corrosion properties are all tremendously enhanced for the as-prepared nanocomposites. The results obtained for the PU nanocomposite with 7 wt% ALA-MMT loading (PUC7) reveal a 19 °C increment in T_g, a 48 °C increment in T_5%, a 248% increase in the tensile strength, and a 123% increase in the elongation. The stainless steel disk (SSD) coated with PUC7 shows the lowest corrosion rate of 2.01 × 10⁻⁶ mm/year, which is 469% lower than that of the SSD coated with pure PU. The reinforcements are much greater than the previously reported PU/clay nanocomposites with comparable clay loadings ascribed to the exceptional homogeneity of as-prepared nanocomposites, which are accredited largely to the stable de-aggregated solvent-swollen organoclay suspension generated by the efficient solvent swelling process.     

硅微仿生矢量水声传感器研制

根据鱼类侧线听觉仿生学原理,设计出硅微仿生矢量水声传感器结构.该传感器结构包括高精度压阻式硅微换能单元结构和空芯光子晶体光纤柱体.讨论了水声传感器结构的仿生学原理和声学原理.用有限元软件Ansys分析传感器的应力分布,讨论了传感器的加工工艺,并采用气流静态加载法测试出传感器的矢量指向性图,测试结果表明,仿生水声传感微结构具有“8字型“矢量指向性.     

HAO打卡系统：以组织智能成就智能组织

打卡可能出于私人目的, 没有组织关联, 比如记录个人的旅行日志; 也可能是公事需求, 属于组织考勤的一部分, 有时还会与多个组织关联. 因此, 打卡数据的保存、分享和分析需要精细化管理. HAO打卡是一个移动式轻量级打卡平台, 以个人和组织为两个抓手, 以人类智能(HI)、人工智能(AI)和组织智能(OI)相结合的HAO智能为技术驱动, 构建HAO打卡知识图谱, 通过提出HAO打卡闭环权限管理架构, 并辅以从粗粒度到细粒度的隐私权限管理办法, 在进行精细化考勤管理的同时保护用户的隐私, 从而推动新一代打卡系统的智能化变革. 在组织考勤分析方面, 提出四要素得分法和四要素考勤报表法, 通过打卡数据计算员工考勤得分, 生成精准全面的考勤报表, 为组织提供决策支持, 激发组织和个人的活力, 以组织智能成就智能组织.     

Structural, magnetic and dielectric properties of La2−xCaxNiO4+δ (x = 0, 0.1, 0.2, 0.3)

The synthesis, structural, magnetic and dielectric properties of a new type of high permittivity materials La_2−xCa_xNiO_4+δ (x = 0, 0.1, 0.2, 0.3) (abbreviated as LCNs) were reported. The samples were prepared through conventional solid state reaction route. Detailed structural information was retrieved by Rietveld refinement; normalized bond length and bond valence was calculated to investigate the compression/dilation effect of bonds and atoms in unit cell. It can be found all samples belong to K₂NiF₄ structure with space group I4/mmm. Doping of Ca in La₂NiO_4+δ shrinks the unit cell and makes the structure tend to become instable. Three types of (La, Ca)-O bonds, and two kinds of Ni-O bonds exist in LCNs. Along c axis there are alternately compressed (La,Ca)O₉ dodecahedra and lengthened NiO₆ octahedra. Room temperature magnetic measurements show that the materials are paramagnetic and Ca doping can improve the spontaneous magnetization. Furthermore, all samples have colossal values of the dielectric constant (?) at frequencies lower than 1 kHz. Interestingly, La_1.8Ca_0.2NiO_4+δ maintains its high permittivity at frequencies up to 1 MHz while La_1.7Ca_0.3NiO_4+δ has the lowest dielectric loss (tan δ). Calcium doping can effectively enhance ? and inhibit tan δ. The distortion of (La,Ca)O₉ dodecahedra can well explain their dielectric properties.     

An improved localization algorithm with wireless heartbeat monitoring system for patient safety in psychiatric wards

Psychiatric patients often require continuous monitoring to keep them out of dangerous situations. Accordingly, hospitals hire additional staff to monitor patients' vital signs, maintain patient safety, and ensure that patients do not leave the hospital without notice. However, ward staff have difficulty knowing whenever a psychiatric patient is stepping into potential danger zones or encountering any safety threat. This paper reports the development of a wireless monitoring system to improve patient safety in psychiatric wards and reduce avoidable risks. The proposed system can ease the workload of nurses, help locate patients, and monitor patients' heartbeats. A two-step clustering localization algorithm is proposed for use in tracking patients' locations. This study marks for the first time that heartbeat detection using a ZigBee-based platform with localization function has been proposed. A proof-of-concept system is developed to understand the current hardware challenges and to enable functional analysis of the proposed ZigBee-based patient localization system. The error distance of the proposed localization algorithm is approximately 1 m. Its location accuracy is 90% with the error distance of up to 3 m. The proposed system is expected to improve patient safety significantly in psychiatric wards at low cost.     

An approach for research and training in enterprise information system with RFID technology

Successful implementation of Radio Frequency Identification (RFID) in Enterprise Information System (EIS) depends on exploring the knowledge of RFID technology and providing EIS software training to potential users. The restriction of RFID technology and huge amount item-level data collection via RFID potentially increases the complexity of integrating with EIS. It raises several concerns such as reduced data accuracy, and increased exceptions leading to processes requiring more time to be developed, tested and maintained. However, this approach has not been entirely investigated so far. This paper proposes an integrated research on EIS and a training approach for students and employees who intend to integrate RFID with EIS software in an organization. This integrated research approach applies a typical EIS project workflow from automatic shop floor data collection to customer order fulfillment. This research identifies these stages as transaction, planning and scheduling, integration, execution and control, and automatic identification and data collection. For training and demonstration purpose, this research proposes prototype information systems that emulate the systems used in any organization. This ensures that the logic of the proposed methodology of integrating RFID and EIS software is consistent with that in the business organization. This paper discusses some of the important case studies that were conducted with the suggested prototype systems.     

Preparation of UV-filter encapsulated mesoporous silica with high sunscreen ability

In this study, a UV-filter encapsulated in a mesoporous silica, MCX-MS, was prepared by the in-situ sol-gel polymerization of tetraethyl orthosilicate (TEOS) with an ionic liquid (IL) as solvent and pore-forming agent and octal methoxycinnamate (MCX) as an additive. MCX-MS was characterized by Fourier transformation infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The result of the thermogravimetric analysis (TGA) showed that the amount of MCX encapsulated in MS was about 65 wt.% of MCX-MS. Comparing with that of the free MCX, the SPF value of the MCX-MS-containing sunscreen cream increased by about 57%, indicating significant enhancement of the UV protection ability of MCX by encapsulation in the mesoporous silica matrix. Furthermore, because the average particle size of MCX-MS emulsion droplets was big enough, damage by penetration through the skin is expected to be prevented.     

Novel single-layer gas diffusion layer based on PTFE/carbon black composite for proton exchange membrane fuel cell

A series of poly(tetrafluoroethylene)/carbon black composite-based single-layer gas diffusion layers (PTFE/CB-GDLs) for proton exchange membrane fuel cell (PEMFC) was successfully prepared from carbon black and un-sintered PTFE, which included powder resin and colloidal dispersion, by a simple inexpensive method. The scanning electron micrographs of PTFE/CB-GDLs indicated that the PTFE resins were homogeneously dispersed in the carbon black matrix and showed a microporous layer (MPL)-like structure. The as-prepared PTFE/CB-GDLs exhibited good mechanical property, high gas permeability, and sufficient water repellency. The best current density obtained from the PEMFC with the single-layer PTFE/CB-GDL was 1.27 and 0.42 A cm⁻² for H₂/O₂ and H₂/air system, respectively.     

Influence of polymer concentration and dyes on photovoltaic performance of dye-sensitized solar cell with P(VdF-HFP)-based gel polymer electrolyte

A series of gel polymer electrolytes (GPEs) is synthesized using Poly(vinylidenefluoride-hexafluoropropylene) P(VdF-HFP) as the host matrix and propylene carbonate (PC)–diethyl carbonate (DEC) as plasticizers to fabricate dye-sensitized solar cells. Equal amounts of PC and DEC are used to comprehend high dielectric constant and low viscosity of the electrolyte. The as-prepared GPEs are characterized by XRD, FTIR and SEM. Their thermal properties and ionic conductivities are investigated by TGA/DSC analyses and AC impedance measurements, respectively. The optimized gel polymer electrolyte gives a maximum ionic conductivity of 5.25 × 10⁻³ S cm⁻¹ at room temperature. The formation of porous structure in the electrolyte film supports the entrapment of large volumes of liquid electrolyte inside its cavities. The role of N3 and N719 dyes are also investigated for better photovoltaic performance of DSSC. The overall light-to-electrical-energy conversion efficiencies of 3.95% and 4.41% are obtained for N3 and N719 dyes, respectively, under 100 mW cm⁻² irradiation, which are comparable to those obtained from the corresponding liquid electrolyte cell.     

Low-complexity centralized joint power and admission control in cognitive radio networks

This letter introduces a centralized joint power and admission control algorithm for cognitive radio networks. Its novelty lies in the proposed admission metric. Unlike those in existing algorithms, our metric predetermines the admission order of N secondary users which intend to access the network. This allows us to search a group of admitted secondary users with the bisection method. The proposed algorithm is shown by simulation to achieve a comparable performance to existing algorithms, and the computational complexity is reduced from O(N³) to O(N² log₂ N).