耐低温露点腐蚀非金属空气预热器的性能及应用

从解决炼油厂加热炉空气预热器的低温露点腐蚀问题出发,分析讨论了耐腐蚀非金属材料(搪瓷、玻璃、氟塑料、石墨及陶瓷等)空气预热器的材料性能、结构形式、传热性能和工业应用效果.分析表明:石墨和陶瓷空气预热器具有优异的耐腐蚀性能和稳定的结构强度,可以在烟气酸露点以下温度安全使用.     

Sequential estimation of borehole resistance and ground thermal properties through thermal response test

Borehole thermal resistance and ground thermal properties (thermal conductivity and heat capacity) are the key parameters to implement the ground source heat pump (GSHP), usually obtained by thermal response test. In this study, a novel sequential parameters estimation method for the above three parameters is proposed, and the sensitivity analysis by using a special correlation method is performed to decide the best estimation sequences. At first, the Spearman partial rank correlation coefficient was used to represent the correlation between the estimated thermal properties and fluid temperature for the line source model (ILS), then the estimation sequence for the three parameters could be determined by the correlation results. Lastly, with the estimation step, Monte Carlo method was adopted to determine the parameters replacing conventional iterative algorithms. In addition, the effect of value bounds and initial inputs as well as random samples was investigated. The results showed that compared to the other estimation steps, the estimation sequence following borehole resistance firstly, then thermal conductivity, heat capacity lastly could get the best precision with 4.5%, 0.4%, 1% respectively. Specially, the estimation precision for ground heat capacity could be promoted by the sequential estimation. Also, the effect of value bounds on estimation precision was nearly eliminated by the proposed method.     

Microstructures and enhanced flexural properties of single-crystalline HfC nanowires in-situ modified carbon/carbon composites by electrophoresis-thermal evaporation using CNTs as the template

To improve the mechanical properties of carbon/carbon (C/C) composites, in-situ synthetized single-crystalline hafnium carbide nanowires (HfCnws) were introduced into the carbon fiber preforms by electrophoresis-thermal evaporation method. The Multi-walled carbon nanotubes (MWCNTs) were utilized as the carbon source and templates for forming HfCnws. The microstructure, chemical composition and mechanical properties of the HfCnws modified carbon/carbon (HfCnws-C/C) composites were characterized. Results reveal that HfC is produced preferentially in the inner nodular parts and end parts of MWCNTs. The raising heat-treatment temperature would influence the diffusion rate of Hf atoms and then the number of nucleation sites, which further changed the aspect ratio and morphology of HfCnws. The HfCnws have refined the grain size of pyrolytic carbon (PyC), and significantly improve the flexural strength of C/C composites by 79.3%.     

Electrical and photoluminescence properties of Sm3+ doped Na0.5La0.5Bi8-xSmxTi7O27 ceramics

In this study, Sm³⁺ doped Na_0.5La_0.5Bi_8-xSm_xTi₇O₂₇ (NBT-BITL-xSm, x = 0, 0.01, 0.015, 0.02, and 0.03) ceramics were synthesized via a conventional solid-state reaction process. The structural, electrical, and photoluminescence properties of NBT-BITL-xSm ceramics were systematically investigated. The crystal structure of NBT-BITL-xSm was refined using XRD Rietveld refinement and found to possess a single orthorhombic structure at room temperature. Raman spectroscopy revealed that Sm³⁺ ions preferred to substitute for Bi³⁺ located in the A-sites of pseudo-perovskite layers, inducing a slight decrease in orthorhombic distortion. Strong characteristic emission peaks of Sm³⁺ ions were observed in orange-red regions under a 407 nm laser source, and the sample with x = 0.015 achieved the optimal photoluminescent property. Dielectric measurements showed double anomaly permittivity peaks at the temperature of 589 and 600^°C (T_m and T_c, respectively). The complex impedance spectrum indicated that the electrical conductivities mainly originated from crystal grains at high temperature. The activation energy was calculated to be 1.37–1.44 eV from Arrhenius fitting results. After Sm³⁺ substitution, the activation energy for conductivity was increased as a result of reduced oxygen vacancies.     

Comprehensive Analysis of Secure Data Aggregation Scheme for Industrial Wireless Sensor Network

As an Industrial Wireless Sensor Network (IWSN) is usually deployed in a harsh or unattended environment, the privacy security of data aggregation is facing more and more challenges. Currently, the data aggregation protocols mainly focus on improving the efficiency of data transmitting and aggregating, alternately, the aim at enhancing the security of data. The performances of the secure data aggregation protocols are the trade-off of several metrics, which involves the transmission/fusion, the energy efficiency and the security in Wireless Sensor Network (WSN). Unfortunately, there is no paper in systematic analysis about the performance of the secure data aggregation protocols whether in IWSN or in WSN. In consideration of IWSN, we firstly review the security requirements and techniques in WSN data aggregation in this paper. Then, we give a holistic overview of the classical secure data aggregation protocols, which are divided into three categories: hop-by-hop encrypted data aggregation, end-to-end encrypted data aggregation and unencrypted secure data aggregation. Along this way, combining with the characteristics of industrial applications, we analyze the pros and cons of the existing security schemes in each category qualitatively, and realize that the security and the energy efficiency are suitable for IWSN. Finally, we make the conclusion about the techniques and approach in these categories, and highlight the future research directions of privacy preserving data aggregation in IWSN.     

Improving Ideality of P-Type Organic Field-Effect Transistors via Preventing Undesired Minority Carrier Injection

Electron injection plays a crucial role in arousing the double-slope characteristics for p-type organic field-effect transistors (OFETs) with narrow-bandgap organic semiconductors (OSCs). This issue will not only result in the misrepresentation of OFET performance but also may cause device instability, hence impeding their further development in real-world applications. A facile and highly efficient approach is developed to circumvent this issue by implementing modification on the electrode/organic semiconductor interface. An ultrathin layer of wide-bandgap OSC with suitable energy levels is introduced to block the undesirable electron injection. By this means, typical double-slope behaviors and bias stress stability in the p-type OFETs can be significantly improved. Using 2,8-difluoro-5,11-bis(triethylsilylethynyl) anthradithiophene-based OFETs the double-slope behaviors of as-fabricated devices are effectively converted to near-ideal behaviors after modification, leading to a dramatic improvement of average reliability from 65.11% to 91.76%. Furthermore, the positive drift of transfer curves under prolonged bias stress is also successfully suppressed. This strategy demonstrates good universality and can provide a new guideline for the fabrication of OFETs with ideal behaviors.     

聚能式逆流超声强化制备脂肪酸乙酯工艺研究

以大豆油脱臭馏出物为原料,通过聚能式逆流超声强化与乙醇反应制备脂肪酸乙酯。分析醇油体积比、反应温度、超声功率、催化剂用量和反应时间对脂肪酸乙酯转化率、得率、含量和生物柴油转化率的影响。通过正交实验优化得到:脂肪酸乙酯转化率最优工艺条件为醇油体积比20∶1,反应温度35℃,超声功率300 W,催化剂用量1.6%,反应时间30 min;脂肪酸乙酯得率最优工艺条件为醇油体积比30∶1,反应温度40℃,超声功率600 W,催化剂用量1%,反应时间30 min;脂肪酸乙酯含量最优工艺条件为醇油体积比20∶1,反应温度40℃,超声功率600 W,催化剂用量1%,反应时间60 min;生物柴油转化率最优工艺条件为醇油体积比25∶1,反应温度35℃,超声功率500 W,催化剂用量1%,反应时间30 min。     

Thermal-Disrupting Interface Mitigates Intercellular Cohesion Loss for Accurate Topical Antibacterial Therapy

Bacterial infections remain a leading threat to global health because of the misuse of antibiotics and the rise in drug-resistant pathogens. Although several strategies such as photothermal therapy and magneto-thermal therapy can suppress bacterial infections, excessive heat often damages host cells and lengthens the healing time. Here, a localized thermal managing strategy, thermal-disrupting interface induced mitigation (TRIM), is reported, to minimize intercellular cohesion loss for accurate antibacterial therapy. The TRIM dressing film is composed of alternative microscale arrangement of heat-responsive hydrogel regions and mechanical support regions, which enables the surface microtopography to have a significant effect on disrupting bacterial colonization upon infrared irradiation. The regulation of the interfacial contact to the attached skin confines the produced heat and minimizes the risk of skin damage during thermoablation. Quantitative mechanobiology studies demonstrate the TRIM dressing film with a critical dimension for surface features plays a critical role in maintaining intercellular cohesion of the epidermis during photothermal therapy. Finally, endowing wound dressing with the TRIM effect via in vivo studies in S. aureus infected mice demonstrates a promising strategy for mitigating the side effects of photothermal therapy against a wide spectrum of bacterial infections, promoting future biointerface design for antibacterial therapy.