波谱法在纸质文物科学分析中的应用进展

作为我国古代四大发明之一,造纸术在推动世界文明进程中发挥了重要作用。纸质文物是人类文明的传承载体,促进了知识的传播。纸质文物的保护修复是历史文化传承和研究的关键所在。利用现代仪器分析技术研究古代纸质文物和现代修复用纸对于了解其制作工艺、保存状况、真伪鉴别和制定保护修复方案等具有指导作用。本文重点讨论了X射线衍射、红外光谱、拉曼光谱和气相色谱-质谱联用等技术在纸质文物分析和评价方面的进展,并展望其未来发展,以期为纸质文物的科学认知和保护修复提供更多借鉴。     

Investigation of multiphase hydrogenation in a catalyst‐trap microreactor

BACKGROUND: Multiphase hydrogenation plays a critical role in the pharmaceutical industry. A significant portion of the reaction steps in a typical fine chemical synthesis are catalytic hydrogenations, generally limited by resistances to mass and heat transport. To this end, the small‐scale and large surface‐to‐volume ratios of microreactor technology would greatly benefit chemical processing in the pharmaceutical and other industries. A silicon microreactor has been developed to investigate mass transfer in a catalytic hydrogenation reaction. The reactor design is such that solid catalyst is suspended in the reaction channel by an arrangement of catalyst traps. The design supports the use of commercial catalyst and allows control of pressure drop across the bed by engineering the packing density. RESULTS: This paper discusses the design and operation of the reactor in the context of the liquid‐phase hydrogenation of o‐nitroanisole to o‐anisidine. A two‐phase ‘flow map’ is generated across a range of conditions depicting three flow regimes, termed gas‐dominated, liquid‐dominated, and transitional, all with distinctly different mass transfer behavior. Conversion is measured across the flow map and then reconciled against the mass transfer characteristics of the prevailing flow regime. The highest conversion is achieved in the transitional flow regime, where competition between phases induces the most favorable gas–liquid mass transfer. CONCLUSION: The results are used to associate a mass transfer coefficient with each flow regime to quantify differences in performance. This reactor architecture may be useful for catalyst evaluation through rapid screening, or in large numbers as an alternative to macro‐scale production reactors. Copyright © 2008 Society of Chemical Industry     

Smart,connected open architecture product: an IT-driven co-creation paradigm with lifecycle personalization concerns

Nowadays, the emphasis on manufacturing has shifted from a manufacturer-dominating to a customer-centric manner by actively involving users into the co-creation process to realise individual satisfaction. In such era, the rapid development of information and communication technology (e.g. wireless sensor network, and cyber-physical systems) enables a promising market of IT-driven product, i.e. smart, connected product, and also changes the way of user–manufacturer interaction in the product development process. However, to the best of authors’ knowledge, co-creation manner in such context is scarcely reported. Meanwhile, there is a lack of any paradigms given to enable such product open innovation along the lifecycle for personalisation concerns. Aiming to fill this gap, this paper, as an explorative research, proposes a new product development paradigm, i.e. smart, connected open architecture product (SCOAP). It follows the adaptable design principles for product extendibility and lifecycle consideration. Moreover, it enlarges the scope of existing open architecture product by involving IT-driven innovation consideration as well. Hence, the definitions, characteristics, evaluation criteria, development method, and lifecycle co-creation context of SCOAP are presented in details. To make it more concrete, a demo project of a smart, connected open architecture bicycle is given at last.     

Novel ceramic substrates for high Tc superconductors

A group of complex perovskite oxides REBa₂NbO₆ (RE=La and Dy) have been synthesized and developed for their use as substrates for both YBa₂Cu₃O_7-δ and Bi(2223) superconductors. These materials have a complex cubic perovskite (A₂BB′O₆) structure with lattice constants,a=8·48?8·60 Å. REBa₂NbO₆ did not show any phase transition in the temperature range 30–1300°C. The thermal expansion coefficient, thermal diffusivity and thermal conductivity values of REBa₂NbO₆ are favourable for their use as substrates for highT _c superconductors. The dielectric constant and loss factor of REBa₂NbO₆ are in a range suitable for their use as substrates for microwave applications. Both YBa₂Cu₃O_7-δ and Bi(2223) superconductors did not show any detectable chemical reaction with REBa₂NbO₆ even under extreme processing conditions. Dip coated YBa₂Cu₃O_7-δ thick films on polycrystalline REBa₂NbO₆ substrate gave aT _c(0) of 92 K and a current density of ～1·1×10⁴ A/cm² and Bi(2223) thick film on polycrystalline REBa₂NbO₆ substrate gave aT _c(0) of 110 K and a current density of ～ 4×10³ A/cm² at 77 K and zero magnetic field. A laser ablated YBa₂Cu₃O_7-δ thin film deposited on polycrystalline REBa₂NbO₆ substrate gave aT _c(0) of 90 K and a current density of ～5×10⁵ A/cm².     

Intelligent molecular orientation transformation in 3D printing system

Microsystem Technologies - Proper orientation of a molecular structure in three-dimensional (3D) printing could increase successful printing rates, reduce the amount of supporting material...     

Relationships between voltage and angle stability of power systems

This paper discusses modelling and theoretical issues associated with voltage and angle stability of power systems. A time-scale decomposition is performed to illustrate how the critical modes can be identified with reduced-order models and the bifurcation phenomena can be explained with these low order models. Examples are given for single and multi-machine systems.     

Some Observations on Sublimation and Decomposition of Ammonium Perchlorate

Ammoniumperchlorate (AP) was aged at 100 °C and 150 °C. Depending on the aging time, AP shows different decomposition characteristics. By a special experimental arrangement sublimation and thermal decomposition could be separated.     

Is ammonium perchlorate in composite solid propellant under strain?

Thermal decomposition of ammonium perchlorate-polystyrene propellant as a function of oxidizer loading has been found to behave in a fashion analogous to the thermal decomposition of ammonium perchlorate as a function of precompression pressure. It has been argued that the above behaviour of the propellant is due to the strain caused by the binder film on ammonium perchlorate contained in the propellant matrix. The presence of strain has been demonstrated independently by x-ray diffraction peak and infrared peak broadening and strain energy measurements.