Design of Highly Efficient Light-Trapping Structures for Thin-Film Crystalline Silicon Solar Cells

We present a design optimization of a highly efficient light-trapping structure to significantly increase the efficiency of thin-film crystalline silicon solar cells. The structure consists of an antireflection (AR) coating, a silicon active layer, and a back reflector that combines a diffractive reflection grating with a distributed Bragg reflector. We have demonstrated that with careful design optimization, the presented light-trapping structure can lead to a remarkable cell-efficiency enhancement for the cells with very thin silicon active layers (typically 2.0-10.0 mum) due to the significantly enhanced absorption in the wavelength range of 800-1100 nm. On the other hand, less enhancement has been predicted for much thicker cells (i.e.,>100 mum) due to the limited absorption increase in this wavelength range. According to our simulation, the overall cell efficiency can be doubled for a 2.0-mum-thick cell with light-trapping structure. It is found that the improvement is mainly contributed by the optimized AR coating and diffraction grating with the corresponding relative improvements of 36% and 54%, respectively. The simulation results show that the absolute cell efficiency of a 2.0-mum-thick cell with the optimal light-trapping structure can be as large as 12%.     

防御缓冲区溢出攻击的有效策略

缓冲区溢出攻击严重地危害着我们的网络安全,已经给人们带来了巨大的损失。在对现有防御技术和工具进行合理分类的基础上,文章总结其中存在的优缺点,探讨更有效防御工具的开发方向。同时针对日益增长的网络安全需求,从整个系统的角度提出了防御缓冲区溢出攻击的一种有效策略。     

太阳电池用直拉硅单晶中碳对氧沉淀的作用

主要通过单步退火、二步退火的方法，借助于红外光谱仪，研究了太阳电池用直拉硅单晶中碳对氧沉淀的作用，发现碳在单步退火过程中不参与氧沉淀；经过预处理的太阳电池用硅单晶尾部（高碳区）样片在950℃和1050℃第二步退火时碳参与了氧沉淀的长大。二步退火过程中尾部（高碳区）样片产生的氧沉淀较头部（低碳区）多（除了850℃以外），由此可以推断原生碳含量越高，就越能促进氧沉淀。     

黄瓜黑星病抗性鉴定分析

通过室内苗期人工接种抗病性鉴定的方法，对30个黄瓜品种进行了抗黑星病鉴定，从中初筛出黄瓜抗黑星病品种和品系：中农9号为高抗品种；中农5号、8608、中农11号和九月青为抗病品种；吉杂四号和叶三为中抗品种。     

丙酮／丁醇间歇萃取发酵

为了防止丙酮/丁醇发酵过程中代谢产物丁醇对丙酮/丁醇梭状芽孢杆菌(Closlridium acetobutylicum)的抑制作用,进行了萃取和发酵相结合过程的研究。从十三种有机化合物对丙酮/丁醇梭状芽孢杆菌的毒性以及它们的物理性能出发,选出了油醇和混合醇(油醇和硬脂醇的混合物)作为丙酮/丁醇萃取发酵的萃取剂。和用正交试验考察了以油醇作萃取剂时,发酵温度、初始葡萄糖浓度和油水比等三因素对游离细胞、固定化细胞的无搅拌间歇萃取发酵的影响。根据正交试验结果,研究了发酵温度41/35℃、油水比1∶2和不同初始葡萄糖浓度时的间歇搅拌萃取发酵。当初始葡萄糖浓度为110(g/1)时,发酵结束水相丁醇浓度5.12(g/1)、折合水相丁醇浓度16.27(g/1)、折合水相总溶剂浓度33.63(g/1),发酵过程的葡萄糖利用率98.0％。总浓剂产率0.312。研究结果表明:萃取发酵可以减轻产物丁醇对丙酮/丁醇梭状芽孢杆菌的抑制、提高初始葡萄糖浓度、减少生产过程的废水量,为降低产物分离的能耗和总溶剂的生产成本打下了基础。     

硅橡胶表面壳聚糖载铜凝胶涂层的制备及其抗菌功能

在硅橡胶表面制备一种具有抗感染功能的涂层—壳聚糖载铜凝胶涂层。为了克服硅橡胶的生物惰性,在其表面制备涂层,先用逐步化学接枝法对其表面进行活化预处理,然后化学接枝壳聚糖载铜凝胶涂层。对比浸泡前后涂层的形貌,研究了活化预处理对功能化涂层与硅橡胶基体之间结合性能的影响。结果表明,用化学接枝法可在硅橡胶表面生成丰富的活性官能团从而提高了功能化涂层与硅橡胶的结合强度。载铜功能化涂层使硅橡胶导管具有良好的抗菌功能。     

Preventive maintenance policy of single‐unit systems based on shot‐noise process

This paper develops reliability and maintenance models for a single‐unit system subject to hard failures under random environment of external shocks. Motivated by the observations of shot‐noise process in practice, the impact of shock damage on system failure behavior is characterized by random hazard rate increments. To remove such negative impact, imperfect preventive repair is performed periodically, and preventive replacement is performed after several repairs. Considering the joint effects of both random shocks and imperfect repair on the system hazard rate, we derive recursive equations for the system reliability function. Furthermore, we investigate the optimal maintenance policy that minimizes the expected cost per unit time of the system. The applicability of the reliability and maintenance model is validated by a case study on a wind turbine system.     

Well‐Dispersed Nickel‐ and Zinc‐Tailored Electronic Structure of a Transition Metal Oxide for Highly Active Alkaline Hydrogen Evolution Reaction

The practical scale‐up of renewable energy technologies will require catalysts that are more efficient and durable than present ones. This is, however, a formidable challenge that will demand a new capability to tailor the electronic structure. Here, an original electronic structure tailoring of CoO by Ni and Zn dual doping is reported. This changes it from an inert material into one that is highly active for the hydrogen evolution reaction (HER). Based on combined density functional theory calculations and cutting‐edge characterizations, it is shown that dual Ni and Zn doping is responsible for a highly significant increase in HER activity of the host oxide. That is, the Ni dopants cluster around surface oxygen vacancy of the host oxide and provide an ideal electronic surface structure for hydrogen intermediate binding, while the Zn dopants distribute inside the host oxide and modulate the bulk electronic structure to boost electrical conduction. As a result, the dual‐doped Ni, Zn CoO nanorods achieve current densities of 10 and 20 mA cm^?2 at overpotentials of, respectively, 53 and 79 mV. This outperforms reported state‐of‐the‐art metal oxide, metal oxide/metal, metal sulfide, and metal phosphide catalysts.     

Pd Single‐Atom Catalysts on Nitrogen‐Doped Graphene for the Highly Selective Photothermal Hydrogenation of Acetylene to Ethylene

The selective hydrogenation of acetylene to ethylene in an ethylene‐rich gas stream is an important process in the chemical industry. Pd‐based catalysts are widely used in this reaction due to their excellent hydrogenation activity, though their selectivity for acetylene hydrogenation and durability need improvement. Herein, the successful synthesis of atomically dispersed Pd single‐atom catalysts on nitrogen‐doped graphene (Pd₁/N‐graphene) by a freeze‐drying‐assisted method is reported. The Pd₁/N‐graphene catalyst exhibits outstanding activity and selectivity for the hydrogenation of C₂H₂ with H₂ in the presence of excess C₂H₄ under photothermal heating (UV and visible‐light irradiation from a Xe lamp), achieving 99% conversion of acetylene and 93.5% selectivity to ethylene at 125 °C. This remarkable catalytic performance is attributed to the high concentration of Pd active sites on the catalyst surface and the weak adsorption energy of ethylene on isolated Pd atoms, which prevents C₂H₄ hydrogenation. Importantly, the Pd₁/N‐graphene catalyst exhibits excellent durability at the optimal reaction temperature of 125 °C, which is explained by the strong local coordination of Pd atoms by nitrogen atoms, which suppresses the Pd aggregation. The results presented here encourage the wider pursuit of solar‐driven photothermal catalyst systems based on single‐atom active sites for selective hydrogenation reactions.