Microwave-assisted biosynthesis of glycerol monolaurate in reverse microemulsion system: key parameters and mechanism

This study highlights the microwave-assisted biosynthesis of glycerol monolaurate catalyzed by Novozym 435 in reverse microemulsion system dispersed by Aerosol-OT. Optimization of key parameters including catalyst/surfactant loading and temperature showed that under microwave irradiation, 125.9 mol L⁻¹ (36 wt%) of glycerol monolaurate was achieved within 30 min, which had improved 150% compared with that of water bath under the same conditions (60 °C, 1 wt% enzyme, 5 wt% AOT). Also, a synergistic effect of microwave irradiation and Aerosol-OT on reaction and a decline of optimum temperature (from 70 to 60 °C) were observed in comparison with traditional heating. More importantly, further comparative studies on morphology and chemicophysical profiles of reaction system heated by different thermal modes revealed the following: (1) due to the volumetric and selective heating character of molecular heating, superiorly larger interface of reaction system was formed under microwave irradiation, directly accelerating the reaction course investigated; and (2) microwave irradiation more favored a less compact state of enzyme. And faster mobilities of lid structure of enzyme were evident under microwave irradiation. This enhancement might facilitate the transition of conformational states, which is of key importance for the activation of bioactivity of Novozym 435. Moreover, the stepwise changes in steady-state fluorescent profiles demonstrated that the thermal-induced variation was not two-state transition but involves intermediate states, which was further supported by activity measurements reflected in glycerol monolaurate yield.     

太阳能热气流发电系统辅助加热与塔囟高度研究

对太阳能塔囱热气流发电系统中辅助加热与塔囱高度的关系进行了分析研究,提出了在塔囱内对上升热气流进行二次辅助加热的设想,以增加气流速度,提高塔囱抽力,降低塔囱高度.以乌海沙漠太阳能热风气流发电系统为例,在塔囱压差和底部入口气流速度不变的情况下,最佳辅助加热气流温度为90℃;塔囱高度为80 m时,辅助加热位置设在塔囱内距地面50 m处较为合适.     

城市水系统控制与规划原理

城市水资源的开发利用和保护涉及自然科学、社会科学和工程技术的许多领域,是一项非常复杂的系统工程。本文试图以系统科学理论为指导,构建城市水系统的理论框架,对城市水系统的内涵、要素、结构、功能和特征等进行分析,对城市水系统控制的依据、途径、类型和战略等进行探讨,并提出了加强城市水系统规划的建议。     

Applications of static and dynamic iterated rippled noise to evaluate pitch encoding in the human auditory brainstem

This paper presents a new application of the dynamic iterated rippled noise (IRN) algorithm by generating dynamic pitch contours representative of those that occur in natural speech in the context of EEG and the frequency following response (FFR). Besides IRN steady state and linear rising stimuli, curvilinear rising stimuli were modeled after pitch contours of natural productions of Mandarin Tone 2. Electrophysiological data on pitch representation at the level of the brainstem, as reflected in FFR, were evaluated for all stimuli, static or dynamic. Autocorrelation peaks were observed corresponding to the fundamental period (tau) as well as spectral bands at the fundamental and its harmonics for both a low and a high iteration step. At the higher iteration step, both spectral and temporal FFR representations were more robust, indicating that both acoustic properties may be utilized for pitch extraction at the level of the brainstem. By applying curvilinear IRN stimuli to elicit FFRs, we can evaluate the effects of temporal degradation on 1) the neural representation of linguistically-relevant pitch features in a target population (e.g., cochlear implant) and 2) the efficacy of signal processing schemes in conventional hearing aids and cochlear implants to recover these features.     

Robust Tracking Controller Design for a Class of Block Lower‐Triangular Systems

A class of multi‐input multi‐output (MIMO) block lower‐triangular systems are considered with the dynamic and static uncertainties related to the states of the former subsystems. A design procedure of robust tracking controller is presented, which avoids the problem of the “explosion of complexity” and can be implemented very simply. The closed‐loop system possesses robust properties that, 1) all signals involved are semi‐global uniformly ultimately bounded for bounded differentiable reference inputs; 2) for given initial tracking errors and uncertainty boundary, controller parameters can be found to guarantee that the tracking errors can be smaller than a specific positive constant after a limited time. Two numerical instances are given at last.     

Vertical manoeuvring and rotor speed robust control for mini-helicopter

A robust control approach is presented for vertical manoeuvring helicopters with aerodynamics acting on the main rotor. An induced inflow observer is applied which only requires the measured values of the vertical accelerator in the body frame. The controller consists of three parts: a feedback linearisation controller, a nominal controller and a robust compensator. Feedback linearisation is applied to decouple the vertical motion dynamics and the rotor speed dynamics; the nominal controller aims to achieve desired performances for the nominal system without external disturbances or uncertainties; and the robust compensator is designed to restrain the effect of the external disturbance and the uncertainties. It is proven that all the states involved are bounded and the tracking error of the actual system can converge into an arbitrary specified boundary in a finite time for any given initial state. The results of outdoor flight experiments show that the robust tracking performances are consistent with the theory analysis conclusions.     

一种基于FPGA的OQPSK软解调简化算法

采用对数似然比 LLR 算法进行软解调不仅运算量大,而且比较耗费硬件资源,并不适合在可编程逻辑门阵列 FPGA 硬件平台实现。针对该问题,本文提出了一种最大值 MAX 软解调简化算法,该方法降低了 LLR 算法复杂度,并且对系统接收性能影响不大。最后利用 Matlab 进行 OQPSK 软解调仿真验证,测试结果表明该算法与传统算法相比性能损失非常小,适合应用于硬件平台实现。     

ANSYS中强度折减法等效DP-MC准则二次开发

在ANSYS有限元软件中,用有限元强度折减法进行边坡稳定分析时,操作比较复杂,且关于岩土材料,ANSYS软件只有一种屈服准则,计算结果偏于安全。首先对二次开发的理论依据进行说明,然后基于ANSYS的二次开发工具APDL和UIDL,对不同的等效DP-MC准则的有限元强度折减法进行二次开发,最后通过标准边坡模型的分析,证明了二次开发程序的合理性和实用性。     

NHD溶济在化肥石脱硫脱碳中的应用

通过MHD溶剂在上海吴泾、浙江巨化、安徽淮化等厂的应用实践,介绍了采用NHD脱硫脱碳工艺对原工艺的改造情况,分析了改造后的生产运行数据,对比了改造前后的工艺能耗,对改造产生的经济效益和改造成本进行了估算。