Optimisation of the ultrasound-assisted extraction of betalains and polyphenols from Amaranthus hypochondriacus var. Nutrisol

The present study optimised the ultrasound-assisted extraction (UAE) of bioactive compounds from Amaranthus hypochondriacus var. Nutrisol. Influence of temperature (25.86–54.14 °C) and ultrasonic power densities (UPD) (76.01–273.99 mW/mL) on total betalains (BT), betacyanins (BC), betaxanthins (BX), total polyphenols (TP), antioxidant activity (AA), colour parameters (L*, a*, and b*), amaranthine (A), and isoamaranthine (IA) were evaluated using response surface methodology. Moreover, betalain extraction kinetics and mass transfer coefficients (K_La) were determined for each experimental condition. BT, BC, BX, TP, AA, b*, K_La, and A were significantly affected (p < 0.05) by temperature extraction and UPD, whereas L*, a*, and IA were only affected (p < 0.05) by temperature. All response models were significantly validated with regression coefficients (R²) ranging from 87.46 to 99.29%. BT, A, IA, and K_La in UAE were 1.38, 1.65, 1.50, and 29.93 times higher than determined using conventional extraction, respectively. Optimal UAE conditions were obtained at 41.80 °C and 188.84 mW/mL using the desired function methodology. Under these conditions, the experimental values for BC, BX, BT, TP, AA, L*, a*, b*, K_La, A, and IA were closely related to the predicted values, indicating the suitability of the developed quadratic models. This study proposes a simple and efficient UAE method to obtain betalains and polyphenols with high antioxidant activity, which can be used in several applications within the food industry.     

Measurement of dense plasma temperature of the shock-compressed silicon

Measurements of the brightness temperature and compressibility of a dense silicon plasma formed by powerful shock waves (SWs) passing through a single-crystal sample have been carried out. Plane SWs were created using an explosive technique: the traditional plane acceleration of a steel driver plate made it possible to obtain pressures in silicon up to 133 GPa, and the use of “Mach” cumulative generators realized the pressures up to 510 GPa. The shock Hugoniot of silicon was determined by the impedance matching with α-quartz as the reference. The intensity of emitted thermal radiation was measured in the infrared range λ ∼ 1.5 μm, where silicon is optically transparent, and in the visible range of the spectrum. A significant (up to five times) understatement of the measured values of the brightness temperature in comparison with the values calculated by the equation of state was found. Taking into account the reflective properties of the SW in silicon does not lead to an agreement with the experiment. The estimates of relaxation processes behind the shock front suggest the presence of a zone of the establishment of ionization equilibrium with a width of ∼10 μm.     

HL-2M 装置扫频 ECE 测量系统研制

为了测量 HL-2M 装置中的电子温度剖面分布,研制了一套扫频电子回旋辐射(SECE)系统。该系统 能够测量装置中心纵场大小在 1.4~2.2T 时的等离子体电子温度。采用扫频外差接收的方式,径向空间分辨达到 2.5cm,时间分辨达到 1ms。接收机前端的准光学系统采用两级金属反射镜的配置,系统能够接收的最小极向光 斑的直径为 1.5cm（波数 k_θ<4.2rad·cm^-1）。系统的频带范围覆盖 33~110GHz,采用 VCO 作为本振源,双边带混频 输出中频信号。后端首次采用高性能对数检波器解调中频,能直接对-70dBm 的微弱信号进行检测,输入-输出工 作区间的动态范围达到 45dB 以上。在实验期间,成功测量到了等离子体中电子逃逸以及回旋辐射产生的信号。     

Experimental Study of Effect of Temperature Variations on the Impedance Signature of PZT Sensors for Fatigue Crack Detection

Structural health monitoring (SHM) is recognized as an efficient tool to interpret the reliability of a wide variety of infrastructures. To identify the structural abnormality by utilizing the electromechanical coupling property of piezoelectric transducers, the electromechanical impedance (EMI) approach is preferred. However, in real-time SHM applications, the monitored structure is exposed to several varying environmental and operating conditions (EOCs). The previous study has recognized the temperature variations as one of the serious EOCs that affect the optimal performance of the damage inspection process. In this framework, an experimental setup is developed in current research to identify the presence of fatigue crack in stainless steel (304) beam using EMI approach and estimate the effect of temperature variations on the electrical impedance of the piezoelectric sensors. A regular series of experiments are executed in a controlled temperature environment (25°C–160°C) using 202 V1 Constant Temperature Drying Oven Chamber (Q/TBXR20-2005). It has been observed that the dielectric constant ε₃₃^T which is recognized as the temperature-dependent constant of PZT sensor has sufficiently influenced the electrical impedance signature. Moreover, the effective frequency shift (EFS) approach is optimized in term of significant temperature compensation for the current impedance signature of PZT sensor relative to the reference signature at the extended frequency bandwidth of the developed measurement system with better outcomes as compared to the previous literature work. Hence, the current study also deals efficiently with the critical issue of the width of the frequency band for temperature compensation based on the frequency shift in SHM. The results of the experimental study demonstrate that the proposed methodology is qualified for the damage inspection in real-time monitoring applications under the temperature variations. It is capable to exclude one of the major reasons of false fault diagnosis by compensating the consequence of elevated temperature at extended frequency bandwidth in SHM.     

Prediction of Liner Metal Temperature of an Aeroengine Combustor with Multi-Physics Scale-Resolving CFD

Computational Fluid Dynamics is a fundamental tool to simulate the flow field and the multi-physics nature of the phenomena involved in gas turbine combustors, supporting their design since the very preliminary phases. Standard steady state RANS turbulence models provide a reasonable prediction, despite some well-known limitations in reproducing the turbulent mixing in highly unsteady flows. Their affordable cost is ideal in the preliminary design steps, whereas, in the detailed phase of the design process, turbulence scale-resolving methods (such as LES or similar approaches) can be preferred to significantly improve the accuracy. Despite that, in dealing with multi-physics and multi-scale problems, as for Conjugate Heat Transfer (CHT) in presence of radiation, transient approaches are not always affordable and appropriate numerical treatments are necessary to properly account for the huge range of characteristics scales in space and time that occur when turbulence is resolved and heat conduction is simulated contextually. The present work describes an innovative methodology to perform CHT simulations accounting for multi-physics and multi-scale problems. Such methodology, named U-THERM3D, is applied for the metal temperature prediction of an annular aeroengine lean burn combustor. The theoretical formulations of the tool are described, together with its numerical implementation in the commercial CFD code ANSYS Fluent. The proposed approach is based on a time de-synchronization of the involved time dependent physics permitting to significantly speed up the calculation with respect to fully coupled strategy, preserving at the same time the effect of unsteady heat transfer on the final time averaged predicted metal temperature. The results of some preliminary assessment tests of its consistency and accuracy are reported before showing its exploitation on the real combustor. The results are compared against steady-state calculations and experimental data obtained by full annular tests at real scale conditions. The work confirms the importance of high-fidelity CFD approaches for the aerothermal prediction of liner metal temperature.     

Research on the ions' axial temperature of a sympathetically-cooled 113Cd+ ion crystal

Molecular dynamics simulation of a sympathetically-cooled ¹¹³Cd⁺ ion crystal system is achieved. Moreover, the relationship between ions' axial temperature and different electric parameters, including radio frequency voltage and end-cap voltage is depicted. Under stable trapping condition, optimum radio frequency voltage, corresponding to minimum temperature and the highest cooling efficiency, is obtained. The temperature is positively correlated with end-cap voltage. The relationship is also confirmed by a sympathetically-cooled ¹¹³Cd⁺ microwave clock. The pseudo-potential model is used to illustrate the relationship and influence mechanism. A reasonable index, indicating ions' temperature, is proposed to quickly estimate the relative ions' temperature. The investigation is helpful for ion crystal investigation, such as spatial configuration manipulation, sympathetic cooling efficiency enhancement, and temporal evolution.     

Ultra-longer fiber cantilever taper for simultaneous measurement of temperature and relative humidity

An ultra-longer fiber cantilever taper for simultaneous measurement of the temperature and relative humidity (RH) with high sensitivities was proposed. The structure was fabricated by using the simple and cost-effective method only including fiber cleaving, splicing, and tapering. The length of the cantilever taper is about 1.5 mm. The dip A and dip B were measured simultaneously, owing to the ultra-long length and super-fine size, the temperature sensitivities of the dip A and dip B reached as high as 127.3 pm/℃ and 0 pm/℃ between 25 ℃ and 50 ℃, and the RH sensitivities are -31.2 pm/% RH and -29.2 pm/% RH with a broad RH interval ranging from 20% RH to 70% RH. Besides, the proposed structure showed good linearity in the sensing process and small temperature crosstalk. It will be found in wide applications in environmental monitoring, food processing, and industries.     

Tunable and highly sensitive temperature sensor based on graphene photonic crystal fiber

Optical fiber temperature sensors have been widely employed in enormous areas ranging from electric power industry, medical treatment, ocean dynamics to aerospace. Recently, graphene optical fiber temperature sensors attract tremendous attention for their merits of simple structure and direct power detecting ability. However, these sensors based on transfer techniques still have limitations in the relatively low sensitivity or distortion of the transmission characteristics, due to the unsuitable Fermi level of graphene and the destruction of fiber structure, respectively. Here, we propose a tunable and highly sensitive temperature sensor based on graphene photonic crystal fiber (Gr-PCF) with the non-destructive integration of graphene into the holes of PCF. This hybrid structure promises the intact fiber structure and transmission mode, which efficiently enhances the temperature detection ability of graphene. From our simulation, we find that the temperature sensitivity can be electrically tuned over four orders of magnitude and achieve up to ～ 3.34×10^-3 dB/(cm·℃) when the graphene Fermi level is ～ 35 meV higher than half the incident photon energy. Additionally, this sensitivity can be further improved by ～ 10 times through optimizing the PCF structure (such as the fiber hole diameter) to enhance the light-matter interaction. Our results provide a new way for the design of the highly sensitive temperature sensors and broaden applications in all-fiber optoelectronic devices.     

The effects of pre-equilibrium emission and secondary decay on the determination of freeze-out volume at intermediate energies

The effects of pre-equilibrium emission and secondary decay on the determination of the freeze-out volume are investigated using the isospin-dependent quantum molecular dynamics model accompanied by the statistical decay model GEMINI. Small-mass projectiles and large-mass targets with central collisions are studied at intermediate energies. It is revealed that the proton yields of pre-equilibrium emission are smaller than those of secondary decay. However, the determination of the freeze-out volume from the proton yields is more easily affected by pre-equilibrium emission. Moreover, the percentage of proton yields in the freeze-out stage is found to be approximately 50%.     

二甲醚低温低压自点火行为的实验和理论研究

针对二甲醚(DME)低温低压数据缺乏和反应机理认识不统一问题,利用高压激波管进行点火延迟期测量实验,实验工况完整覆盖负温度系数(NTC:Negative Temperature Coefficient)区域.使用Aramco Mech 3.0机理对实验结果进行了数值仿真,发现与实验数据相比存在两个差异较大的典型区域:N...