再生水回用于景观水体氮营养盐对叶绿素a和藻密度的影响研究

再生水回用于景观水体是否会带来严重的生态风险,尚需广泛而深入的研究。以北京市某再生水厂出水为研究对象,人工配制各浓度梯度的营养盐,试验研究补给再生水后景观水体水质指标的变化,重点考察氮营养盐(氨氮、硝酸盐氮)对叶绿素a和藻密度的影响情况。试验结果表明叶绿素a和藻密度主要受水体中氮磷比和磷酸盐浓度的影响,与单独的硝酸盐氮浓度增加并无直接的关系。当磷酸盐浓度保持在1mg/L以下,氨氮浓度在4mg/L以下,硝酸盐氮浓度在16mg/L以下,将再生水一次性补给景观水体是可行的,不会产生藻类暴发。     

基于CCCⅡ的多功能滤波器及其仿真研究

提出了由电流控制传输器 (CCC )实现的新型电流模式和电压模式多功能滤波器电路 ,该滤波器由CCC 和两个接地电容构成。电路具有以下特点 :可实现多种滤波功能 ;易于集成 ;能独立调节中心频率 ω0 和品质因数 Q;灵敏度较低     

Formation of porous PLGA scaffolds by a combining method of thermally induced phase separation and porogen leaching

A novel method for the fabrication of porous poly(L -lactide-co-glycolide) (PLGA) scaffolds by combining thermally induced phase separation and porogen leaching is presented in this article. Big pores with about 75–400 μm diameters in the obtained scaffolds were generated by the porogen, sucrose particles, while small pores with diameters less than 20 μm induced via phase separation. Extraction of the solvent, chloroform by ethanol at cool temperatures could reduce the scaffold toxicity. Effects of PLGA concentration, freezing temperature, volume fraction of porogen, and introduction of β-tricalcium phosphate (β-TCP) on morphology, porosity, and compressive properties of the scaffolds were systematically discussed. Results showed that the size of small pores decreased by decreasing the polymer concentration and reducing the freezing temperature, whereas the interconnectivity of the scaffolds was improved by increasing the porogen fraction. The compressive modulus and strength were significantly lowered by increasing the scaffold porosity, that is, by increasing porogen fraction, or decreasing the polymer concentration, or reducing the freezing temperature. Addition of β-TCP into the scaffolds did not influence the compressive modulus significantly but tended to decrease the compressive strength. The obtained scaffolds with diverse pore sizes would be potentially used in bone tissue engineering. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

粉煤灰用量和早期养护温度对EGC拉伸性能的影响EI北大核心CSCD

研究了粉煤灰用量、早期养护温度对工程地质聚合物复合材料(EGC)拉伸性能及微观结构的影响,并从细观力学角度对其纤维-基体界面的力学性能进行了分析.结果表明:降低粉煤灰用量不利于EGC拉伸延性的提高,适当提高早期养护温度有利于EGC拉伸性能的提高;粉煤灰用量为80%、早期养护温度为60℃或80℃时,EGC的拉伸应变可达到3.5%以上;纤维拉拔过程中较长的滑移硬化阶段有助于EGC拉伸性能的提升.     

虾壳活性肽对斑马鱼氧化应激损伤的保护作用

目的:探究虾壳活性肽(PCSBP)对机体氧化应激损伤的保护作用。方法:采用碱性蛋白酶水解制备虾壳活性肽,测定其体外抗氧化活性,并分析PCSBP对禁食胁迫下斑马鱼氧化应激损伤的保护作用。结果:PCSBP在体外表现出潜在的抗氧化能力,其对DPPH自由基和羟自由基的清除率分别为(46.35±1.32)%和(75.22±2.18)%。禁食胁迫下斑马鱼的终末体重、体长和肌肉氨基酸含量均有所降低,而摄入PCSBP后能有效提高其生长性能和肌肉氨基酸含量;肌肉组织结构显示,禁食后斑马鱼肌纤维间隙增宽,出现断裂现象,摄入PCSBP后肌纤维排列整齐,形态结构完整,未见明显断裂;在抗氧化应激方面,PCSBP显著增强了斑马鱼肌肉超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GSH-PX)活性和谷胱甘肽(GSH)含量,同时还减少了氧化损伤指标丙二醛(MDA)和蛋白质羰基(PC)的生成量;进一步分析发现,PCSBP显著上调抗氧化信号分子nrf2基因表达,下调keap1表达,并增加其下游抗氧化酶基因转录表达,有效改善了斑马鱼肌肉氧化应激损伤。结论:虾壳活性肽对斑马鱼的氧化应激损伤有一定保护作用...     

Ni Single Atoms on Hollow Nanosheet Assembled Carbon Flowers Optimizing Polysulfides Conversion for Li−S Batteries

The sluggish conversion kinetics and shuttling behavior of lithium polysulfides (LiPSs) seriously deteriorate the practical application of lithium–sulfur (Li–S) batteries. Herein, Ni single atoms on hollow carbon nanosheet-assembled flowers (Ni-NC) are synthesized via a facile pyrolysis-adsorption process to address these challenges. The as-designed Ni-NC with enhanced mesoporosity and accessible surface area can expose more catalytic sites and facilitate electron/ion transfer. These advantages enable the Ni-NC-modified separator to exhibit both enhanced confinement-catalysis ability and suppressed shuttling of LiPSs. Consequently, the Li−S battery with Ni-NC-modified separator shows an initial capacity of 1167 mAh g⁻¹ with a low capacity decay ratio (0.033% per cycle) over 700 cycles at 1 C. Even at the sulfur loading of 6.17 mg cm⁻², a high areal capacity of 5.17 mAh cm⁻² is realized at 0.1 C, together with superior cycling stability over 300 cycles. This work provides a facile catalyst design strategy for the development of high-performance Li−S batteries.     

Fuzzy rule-based models via space partition and information granulation

Neural Computing and Applications - Fuzzy rule-based model (FRBM) has attracted significant attention in various fields due to its accuracy and high level of interpretability. In this study, two...     

A first-principles study of Li and Na co-decorated T4,4,4-graphyne for hydrogen storage

To obtain high hydrogen storage performance, Li and Na co-decorated T4,4,4-graphyne have been studied by the method of first-principles calculations in this paper. Li and Na atoms are bound on hexagonal ring and acetylenic ring included in T4,4,4-graphyne, with the average adsorption energy of 1.73 and 2.38 eV, respectively. Our calculations show that the maximum gravimetric density of H₂ uptake is 10.46 wt%, and an appropriate adsorption energy is reached. Moreover, by plotting charge density differences, it is found that the induced electric field between Li/Na and T4,4,4-graphyne can enhance the adsorption for hydrogen molecule. Furthermore, this complex is thermodynamic stable at room temperature, which is certificated by molecule dynamics simulation. Our results demonstrate that Li and Na co-decorated T4,4,4-graphyne is an alternative material for hydrogen storage.     

环形永磁悬浮的控制仿真

为了实现环形偶极磁体的稳定性悬浮,基于环形永磁悬浮装置的设计,利用Simulink进行控制系统的建立和仿真.通过Routh-Hurwitz稳定判据,判断PID控制策略是否存在稳定控制的可能,以及稳定控制参数选取的范围.为了优化控制过程分别讨论了控制系统电源的启动方式对电源的性能要求,以及不同PID系数的取值进行迭代优化.结果 表明,PID控制策略能够实现环形永磁体的稳定悬浮,且kp、kd参数取值区域分别为5.43×10-5＜kd＜119.2、0.0412＜kp＜757.6kd-6.356kd2;斜坡信号启动系统可以有效降低电源的性能要求,将电流峰值从25 A降低到22 A;优化的PID参数取值(kp=5.4、ki=8.3、kd=1.2)能够极大的缩短控制收敛时间实现1.3 s内将悬浮体稳定在预定位置.基于PID控制设计反馈控制系统能够在短时间内将永磁环稳定在预设工作位置,实现长时间稳定悬浮.     

Improved breakdown strength and energy density of polyimide composites by interface engineering between BN and BaTiO3 fibers

Conventionally,interface effects between polymers and fillers are essential for determining the breakdown strength and energy storage density of polymer-based dielectric composites.In this study,we found that interface effects between different fillers have similar behavior.BN and BaTi03 fiber composite fillers with three different interface bonding strengths were successfully achieved by controlling composite processes (BT-fiber/BN ＜ BT-fiber@BN ＜ BT-fiber&BN),and introduced into a polyimide (PI)matrix to form composite films.Considerably enhanced breakdown strength and energy storage density were obtained in BT-fiber&BN/PI composites owing to strong interface bonding,compared to other two composite fillers,which are well supported by the data from the finite element simulation.Specifically,PI composites with only 3 wt％ BT-fiber&BN possess an optimized energy storage density of approximately 4.25 J/cm3 at 4343 kV/cm.These results provide an effective way for adjusting and improving the energy storage properties of polymer-based composites.