负载型Pt-Fe/SiO_2催化剂催化环己烷一步氧化制己二酸

己二酸是合成尼龙-66和尼龙-46纤维的重要原料,并进一步用于生产许多重要的化工产品。工业上的己二酸多采用以硝酸为氧化剂的两步法合成,该工艺不仅工艺复杂,而且对设备有腐蚀作用,还会释放大量的温室气体N_2O。本文以负载型Pt/SiO_2、Fe/SiO_2和Pt-Fe/SiO_2为催化剂,采用过氧化氢和氧气为氧源,研究了环己烷一步氧化制己二酸的绿色合成路线。对催化剂进行ICP、BET比表面积、XRD、TEM等表征,结果表明,Pt-Fe/SiO_2催化剂中不存在与Pt或Fe对应的衍射峰。在最佳反应条件下,用高压釜进行了催化剂性能评价,结果表明,Pt-Fe/SiO_2催化活性略优于Pt/SiO_2和Fe/SiO_2。在环己烷转化率为28%的情况下,己二酸选择性达到33%。     

Facile high yield synthesis of MgCo2O4 and investigation of its role as anode material for lithium ion batteries

In this article, we have reported a one-step scalable synthesis of MgCo₂O₄ nanostructures as efficient anode material for Li-ion batteries and investigated the role of post-synthesis calcination temperature (400, 600 and 800 °C) on its physiochemical properties and electrochemical performances. The XRD pattern of the calcinated sample at 400 °C (MC 400) indicates a pure phase of MgCo₂O₄. However, on increasing the calcination temperature to 600 °C (MC 600), an additional phase corresponding to MgO was detected and the corresponding XRD peak intensity further increased on increasing the calcination temperature to 800 °C (MC 800 °C). This was accompanied by a morphological transformation from flake and rod-like nanostructures, to an agglomerated dense flake-like morphology. Electrochemical studies revealed that the calcination temperature plays an important role in determining the electrochemical performance of the MgCo₂O₄ as anode material. In a half cell, the MC 600 showed the best electrochemical performance with high discharge capacity of 980 mA h g⁻¹ (2nd discharge at 60 mA g⁻¹) and a reversible discharge capacity of 886 mA h g⁻¹ at the end of 50 cycles with high coulombic efficiency of 98%. Long term stability was carried out at 0.5C which showed a capacity retention of 358 mA h g⁻¹ at the end of 500 cycles. The superior electrochemical performance of the MC600 can be attributed to the presence of the small amount of MgO, which is believed to provide the anode materials better structural stability during cycling. The claim was further supported by ex-situ TEM analysis of the anode material of a cycled cell (50 cycles).     

Comparison of joint angle,velocity and acceleration estimators for hydraulically actuated manipulators to a novel dynamical approach

Excavators are used for a wide range of applications like earthworks and material handling. Assistance systems are becoming more common to support the operator. For monitoring and control based assistance functions the angular position, velocity and acceleration of the joints from the working implement are required. Commercial systems often use inertial measurement units, consisting of triaxial accelerometers and gyroscopes, to accomplish an estimation of those states. A novel joint angle, velocity and acceleration estimation for hydraulic manipulators is proposed and compared to state of the art methods. A decentralized kinematic filter using no information about the underlying system and a centralized kinematic filter taking the system kinematics into account are implemented as state of the art approaches. Both filters only use inertial measurement units to obtain information about the current state of the system. The novel centralized dynamic filter uses the same information as the centralized kinematic filter and extends it by a dynamic model containing additional information about the angular acceleration due to pressure readings of the hydraulic cylinders. Kalman filtering is used to combine the derived system and measurement models with the sensor information. The methods are evaluated on a material handling excavator for single and coupled movements of the working implement. The novel centralized dynamic filter enables improvements for the angular acceleration estimation compared to the decentralized and centralized kinematic filter. Less noise of the acceleration estimation and a better tracking of the actual acceleration are shown.     

响应面法优化α-淀粉酶的酶反应体系

目的:采用单因素实验及响应面法优化α-淀粉酶的反应体系。方法:以淀粉为底物对象，以可溶性淀粉浓度、α-淀粉酶浓度、反应时间为考察因素，在单因素实验基础上，运用Box-behnken实验设计方法研究各因素及其交互作用对α-淀粉酶作用底物时的反应速度的影响。结果:建立α-淀粉酶酶反应体系的最佳反应条件为12.0 mg/mL可溶性淀粉、1.50 U/mL α-淀粉酶、10.0 min反应时间，在此条件下，α-淀粉酶表现出的反应速度达到（19.53±1.74） mmol/（L·min），接近模型中的预测数值18.75 mmol/（L·min）。结论:此优化α-淀粉酶酶反应体系的方法可行，能够使α-淀粉酶在反应过程中发挥的酶活最大化，为日后在此体系下进行糖苷酶抑制剂的研究奠定了基础，具有一定的指导意义。     

肉类解冻工艺研究进展

解冻是肉类加工或烹饪前的重要步骤，不恰当的解冻工艺会导致肉类品质的劣变，因此，开发高效益的解冻工艺是十分必要的。解冻工艺的发展在经历了传统工艺、新型工艺后，近年又涌现了一些独特且具有创新性的解冻工艺。本文除简要概括肉品解冻过程及常见解冻工艺之外，综述这些独特的解冻工艺，介绍其开发思路、解冻原理和相关研究内容，并对未来解冻工艺的发展提出建议，旨在为肉及肉制品解冻工艺的选择和优化提供参考。     

Predictions of frame compliance and apex morphology in sharp nanoindentations

If all components in a nanoindentation system are well calibrated and a reference material has unique hardness, H and reduced modulus, E_r independent of the indentation depths, the load, L and the penetration depth, h in the indentation loading curve of the reference material can be correlated by L=Kh². Here the constant K is expressed by H, E_r and indenter geometry constants. By using H and E_r of a fused silica and the Berkovich geometry, an analytical expression for the indentation loading curve could be derived. To compare with this analytical loading curve, experimental indentation data were measured with two commercial nanoindenters. The experimental loading curves shifted leftward or rightward from the analytical loading curve and this depth deviation was attributed to improper calibration of the nanoindenters. Quantitative calibrations of frame compliance and indenter bluntness were tried for the raw nanoindentation data and this resulted in consistent nanoindentation data regardless of the used nanoindenters.     

The impact of recrystallisation on the freeze-thaw cycles of red seabream (Pagrus major) fillets

Recrystallisation often occurs in the freeze-thaw cycles and results in poor food quality. This study was undertaken to analyse the effects of recrystallisation on the changes of protein conformation and moisture migration within red seabream fillets after the freeze-thaw cycles. The UV second-derivative spectroscopy, intrinsic fluorescence measurement and Raman spectroscopy were employed to evaluate the protein conformational changes. The Low-field NMR spectra analysis was used to evaluate moisture migration. The results indicated that the freeze-thaw cycles altered the secondary and tertiary structure of proteins. It was noticed that interactions between water and protein molecules were decreased gradually and eventually induced the thermal instability of the myosin molecules. The immobilised water content declined and the free water content increased. There were significant destructions in fillet muscle microstructure. These observations unambiguously reflect how the recrystallisations affect the protein conformation and moisture migration patterns of red seabream fillets during freeze-thaw cycles.     

Event-triggered controller design of nonlinear discrete-time networked control systems in T-S fuzzy model

This article is concerned with event-triggered fuzzy control design for a class of discrete-time nonlinear networked control systems (NCSs) with time-varying communication delays. Firstly, a more general mixed event-triggering scheme (ETS) is proposed. Secondly, considering the effects of the ETS and communication delays, based on the T-S fuzzy model scheme and time delay system approach, the original nonlinear NCSs is reformulated as a new event-triggered networked T-S fuzzy systems with interval time-varying delays. Sufficient conditions for uniform ultimately bound (UUB) stability are established in terms of linear matrix inequalities (LMIs). In particular, the quantitative relation between the boundness of the stability region and the triggering parameters are studied in detail. Thirdly, a relative ETS is also provided, which can be seen as a special case of the above proposed mixed ETS. As a difference from the preceding results, sufficient conditions on the existence of desired fuzzy controller are derived to ensure the asymptotic stability of the closed-loop system with reduced communication frequency between sensors and controllers. Moreover, a co-design algorithm for simultaneously determining the gain matrices of the fuzzy controller and the triggering parameters is developed. Finally, two illustrative examples are presented to demonstrate the advantage of the proposed ETS and the effectiveness of the controller design method.     

Iron-filled multiwalled carbon nanotubes surface-functionalized with paramagnetic Gd (III): A candidate dual-functioning MRI contrast agent and magnetic hyperthermia structure

A simple wet chemical method involving only sonication in aqueous GdCl₃ solution was used for surface functionalization of iron-filled multiwalled carbon nanotubes with gadolinium. Functional groups on the sidewalls produced by the sonication provide active nucleation sites for the loading of Gd³⁺ ions. Characterization by EPR, EELS, and HRTEM confirmed the presence of Gd³⁺ ions on the sidewall surface. The room temperature ferromagnetic properties of the encapsulated iron nanowire, saturation magnetization of 40 emu/g and coercivity 600 Oe, were maintained after surface functionalization. Heating functionality in an alternating applied magnetic field was quantified through the measurement of specific absorption rate: 50 W/g_Fe at magnetic field strength 8 kA/m and frequency of 696 kHz. These results point to candidacy for dual-functioning MRI imaging and magnetic hyperthermia structures for cancer therapy.     

Extended state observer for uncertain lower triangular nonlinear systems

The extended state observer (ESO) is a key part of the active disturbance rejection control approach, a new control strategy in dealing with large uncertainty. In this paper, a nonlinear ESO is designed for a kind of lower triangular nonlinear systems with large uncertainty. The uncertainty may come from unmodeled system dynamics and external disturbance. We first investigate a nonlinear ESO with high constant gain and present a practical convergence. Two types of ESO are constructed with explicit error estimations. Secondly, a time varying gain ESO is proposed for reducing peaking value near the initial time caused by constant high gain approach. The numerical simulations are presented to show visually the peaking value reduction. The mechanism of peaking value reduction by time varying gain approach is analyzed.