吡咯伯克霍尔德氏菌B1213产葡聚糖酶条件的优化

以吡咯伯克霍尔德氏菌B1213为研究对象,优化其发酵产葡聚糖酶条件。首先,通过单因素实验对其培养条件（碳源种类、碳源粒度、碳源质量浓度、氮源种类、氮源质量浓度、转速、温度、装液量、接种量、初始pH值、表面活性剂种类、表面活性剂质量浓度和时间）进行初步优化,然后通过Plackett-Burman试验,筛选出4个显著影响B1213产葡聚糖酶的因素,再利用最陡爬坡试验确定其产葡聚糖酶的最大响应区域,最后通过Box-Behnken试验设计确定其最优产葡聚糖酶条件为：40～60目麦麸质量浓度50 g/L,酵母浸粉质量浓度8 g/L,初始pH 6.6,装液量30 mL/250 mL,接种量0.15%,曲拉通100质量浓度25 g/L,温度30℃,转速160 r/min和培养时间83 h。在此培养条件下B1213产葡聚糖酶活力达到1 230 U/mL。研究结果为细菌B1213在白酒酿造中的应用提供理论基础。     

ZIF-67原位负载纳米纤维素基锂离子电池隔膜的制备及性能研究

本研究以纳米纤维素（CNF）为原料,经乙酰化、原位负载ZIF-67和浸渍电解液制备出一种新型ZIF-67@乙酰化纳米纤维素（ZIF-67@ACNF）锂离子电池隔膜,系统探讨了ZIF-67的粒径对隔膜结构及性能的影响。结果表明,当ZIF-67的粒径从0.46 μm（ZIF-67₄@ACNF隔膜）减小至0.25 μm（ZIF-67₈@ACNF隔膜）时,隔膜的孔隙率从74.2%减小至52.1%,离子电导率从0.75 mS/cm下降至0.22 mS/cm,界面电阻从112.5 Ω增加至1 115.7 Ω,锂离子迁移数从0.41减小至0.31,电化学稳定窗口从5.1 V减小至4.5 V。采用ZIF-67₄@ACNF隔膜组装电池,在室温、0.5 C的条件下进行电池充/放电测试,初始容量达到159.6 mAh/g,循环200圈后容量保持率达到90%。     

新能源极端出力特性及典型电力电量平衡场景研究

随着新能源发电占比的增加,电力系统的电力电量平衡呈现不确定性强、电力过剩/短缺交替出现等特征,给电力系统的供电可靠性带来了严重的影响。基于新能源出力实际运行特性和未来电源发展趋势,研究了含水电的新型电力系统的典型电源结构场景,并以此为基础,建立了电力电量平衡量化分析模型。通过算例结果量化了未来新能源发展场景下的典型电力电量平衡场景及系统灵活调节能力的需求,分析了新能源极端低/高出力对电力平衡的影响。研究可为我国新型电力系统构建提供决策参考。     

1000 – 1100 °C下多弧离子镀Cr涂层Zr-4合金的高温蒸气氧化行为

Cr涂层锆合金包壳是提高轻水反应堆燃料组件抗高温氧化性能的重要方法。本文旨在研究Cr涂层Zr-4合金在水蒸气环境中的高温氧化行为,采用多弧离子镀工艺制备Cr涂层Zr-4合金样品,在1000 °C和1100 °C水蒸气环境中开展高温氧化实验,采用高精度天平获得样品氧化增重,采用扫描电子显微镜(SEM)、能量色散谱仪(EDS)和X射线衍射仪(XRD)测试分析样品的表面与截面微观形貌、元素分布、物相及Cr-Zr扩散层厚度。结果显示,多弧离子镀制备的Cr涂层Zr-4合金样品表面存在大量尺寸不等的大颗粒,Cr涂层沿着(1 1 0)晶面择优生长。高温蒸气单位面积氧化增重与时间近似遵循抛物线规律,1100 °C的蒸气氧化速率明显高于1000 °C,相同温度下Cr涂层Zr-4合金的氧化速率低于无涂层Zr-4合金。高温蒸气氧化后,样品表面生成针须状氧化物,且氧化物间存在大量微孔。在1100 °C高温蒸气氧化3h和4h后,样品表面被氧化生成蠕虫状的团状物。样品截面呈层状结构,由外向内分别为Cr₂O₃层,Cr涂层,Cr-Zr扩散层,Zr-4合金层。但表面Cr₂O₃层的厚度并不是随着氧化时间的增加而同步增加的,而Cr-Zr扩散层的厚度随氧化温度和氧化时间的增加而增大,且与氧化时间基本呈线性关系。因此,采用多弧离子镀制备的Cr涂层Zr-4合金在1000 °C和1100 °C下表现出良好的抗高温蒸气氧化性能。     

Addition of hydrogen refueling for fuel cell bus fleet to existing natural gas stations: A case study in Wuhan,China

Hydrogen refueling is an essential infrastructure for fuel cell vehicles, and currently, it appears to be a critical service needed to initiate the highly anticipated hydrogen economy in China. A practical selecting procedure of adding hydrogen refueling service to existing natural gas (NG) stations is proposed in this study. A case study in Wuhan, China, is established to assess the feasibility and future planning. The demand for hydrogen fuel and initial supply chain of hydrogen in Wuhan are estimated based on the deployment objective of fuel cell buses. The existing NG stations are evaluated based on 300 kg/day to determine whether they meet the hydrogen safety requirement using Google map or field investigation. The safety space requirement of the hydrogen refueling area on existing NG station is determined as 25.9 × 27.1 m². The optimal hydrogen refueling plan for fuel cell buses is calculated with multi‐objective analysis in economic, environmental, and safety aspects from the view of the hydrogen refueling supply chain. It is shown that adding hydrogen refueling stations to existing NG stations is feasible in technology, economics, regulation, and operation considerations. This study provides guidelines for building the hydrogen infrastructure for fuel cell buses at their early stage of commercial operation.     

Catalytic conversion of Kraft lignin to bio-multilayer graphene materials under different atmospheres

Kraft lignin was catalytic graphitized by iron at 1000 °C in argon, hydrogen, CO₂, methane, and natural gas atmospheres, respectively. The effect of atmospheric agent types on product distribution (gas, liquid, and solid carbon yields) was analyzed. The solid products were characterized by scanning electron microscopy, Raman, high-resolution transmission electron microscopy, and X-ray diffraction. Experimental results have shown that the degree of graphitization of Kraft lignin depends not only on the highest temperature, but also the type of ambient gas phase during heat treatment. Methane and natural gas in the ambient gas phase seem to accelerate the formation of multilayer graphene materials with a range of 2–30 layers, and hydrogen and carbon dioxide have an etching effect on solid carbon species during the catalytic graphitization process, while multilayer graphene-encapsulated iron nanoparticles were the main products in the case of argon.     

Strategies in Structure and Electrolyte Design for High-Performance Lithium Metal Batteries

Lithium metal is the “holy grail” anode for next-generation high-energy rechargeable batteries due to its high capacity and lowest redox potential among all reported anodes. However, the practical application of lithium metal batteries (LMBs) is hindered by safety concerns arising from uncontrollable Li dendrite growth and infinite volume change during the lithium plating and stripping process. The formation of stable solid electrolyte interphase (SEI) and the construction of robust 3D porous current collectors are effective approaches to overcoming the challenges of Li metal anode and promoting the practical application of LMBs. In this review, four strategies in structure and electrolyte design for high-performance Li metal anode, including surface coating, porous current collector, liquid electrolyte, and solid-state electrolyte are summarized. The challenges, opportunities, perspectives on future directions, and outlook for practical applications of Li metal anode, are also discussed.     

A method for measuring the thermal geometric parameters of large hot rectangular forgings based on projection feature lines

The online dimensional measurement of large hot forging is an important procedure in the forging process. Because of different production demands, the final geometrical shapes of large forgings are usually different (e.g. cylindrical columns, rectangular prisms). Forgings of different geometric shapes need to be measured along different dimensions. For rectangular forgings, the lengths primarily need to be measured. A generalized measurement system for different geometric shapes of forgings cannot provide the accuracy of measurement systems targeted at measuring a known shape. Based on the characteristics of the rectangular forgings, a thermal dimensional measurement system is proposed in this paper. The localization, rapid extraction of feature points and method for measuring the dimensions of rectangular forgings are presented. The proposed methods can easily and efficiently extract the feature points of the forging. The experiment results show that the method proposed in this paper has the advantages of high precision and high efficiency, which is appropriate for online measurement.     

一种基于改进粒子群的无线传感器网络层次化聚类协议

延长网络的生存周期是无线传感器网络路由设计的主要目标之一。簇头的高能耗是网络快速死亡的一个重要原因。提出一种基于改进粒子群PSO( Particle Swarm Optimation)的无线传感器网络聚类路由协议IPSOCH。利用中继节点来分担簇头数据转发的任务,减轻簇头节点的负载,并利用改进的粒子群算法通过节点的剩余能量信息和位置信息来选择簇头和中继节点。仿真实验表明,IPSOCH协议比起现有的几种路由协议,能有效提高能量使用率,延长网络生存周期。     

多机系统超低频振荡稳定分析与调速器参数优化

云南电网与南方电网实施异步联网后出现了长时间的超低频振荡。基于奈奎斯特矢量裕度对超低频振荡的机理进行了分析。结果表明,水轮机传递函数存在右半平面零点使水电机组相位在振荡频率附近大幅滞后是引起超低频振荡的主要原因。为了避免切除调速器使跟踪性能下降,提出了一个考虑鲁棒稳定约束下最大化跟踪性能的调速器参数频域优化方法。该方法同时满足了多个方式的稳定需求,且可同时对多个机组调速器进行优化。分析与优化方法的有效性通过云南电网算例得到了验证。