Physics of spontaneous ignition of high-pressure hydrogen release and transition to jet fire

The aim of this study is to gain an insight into the physical phenomena underlying the spontaneous ignition of hydrogen following a sudden release from high-pressure storage and transition to sustained jet fire. The modelling and large-eddy simulation (LES) of the spontaneous ignition dynamics in a tube with a non-inertial rupture disk separating the high-pressure hydrogen storage and the atmosphere is described. Numerical experiments confirmed that due to the stagnation conditions a chemical reaction first commences in the tube boundary layer, and subsequently propagates throughout the tube cross-section. The dynamics of flame formation outside the tube, simulated by the LES model, has reproduced the combustion patterns, including vortex induced “flame separation”, which have been experimentally observed by high-speed photography. It is concluded that the LES model can be applied for hydrogen safety engineering, e.g. for the development of innovative pressure relief devices.     

Efficient Oxygen Evolution and Gas Bubble Release Achieved by a Low Gas Bubble Adhesive Iron–Nickel Vanadate Electrocatalyst

Surface chemistry is a pivotal prerequisite besides catalyst composition toward advanced water electrolysis. Here, an evident enhancement of the oxygen evolution reaction (OER) is demonstrated on a vanadate‐modified iron–nickel catalyst synthesized by a successive ionic layer adsorption and reaction method, which demonstrates ultralow overpotentials of 274 and 310 mV for delivering large current densities of 100 and 400 mA cm^?2, respectively, in 1 m KOH, where vigorous gas bubble evolution occurs. Vanadate modification augments the OER activity by i) increasing the electrochemical surface area and intrinsic activity of the active sites, ii) having an electronic interplay with Fe and Ni catalytic centers, and iii) inducing a high surface wettability and a low‐gas bubble‐adhesion for accelerated mass transport and gas bubble dissipation at large current densities. Ex situ and operando Raman study reveals the structural evolution of β‐NiOOH and γ‐FeOOH phases during the OER through vanadate‐active site synergistic interactions. Operando dynamic specific resistance measurement evidences an accelerated gas bubble dissipation by a significant decrease in the variation of the interfacial resistance during the OER for the vanadate‐modified surface. Achievement of a high catalytic turnover of 0.12 s^?1 suggests metallic oxo‐anion modification as a versatile catalyst design strategy for advanced water oxidation.     

活性包装薄膜中活性物质缓释技术研究进展

综述了活性包装薄膜中活性物质缓释技术的国内外研究进展,着重从活性物质释放速率的调控技术、影响因素以及释放动力学模型三方面进行了归纳,并对其未来发展趋势进行了展望。     

Multilayer‐coated NPK compound fertilizer hydrogel with controlled nutrient release and water absorbency

A novel trilayered controlled‐release nitrogen, phosphorous, and potassium (NPK) fertilizer hydrogel was prepared by dipping the NPK fertilizer granules sequentially in 7% w v^?1 poly(vinyl alcohol) (PVA) and 2% w v^?1 chitosan (CS) solutions and then cross‐linking the CS layer (cross‐CS) via glutaraldehyde vapor deposition. Different NPK fertilizer hydrogels were then synthesized by inverse suspension polymerization of the dried PVA/cross‐CS bilayer‐coated fertilizer granules in various molar ratios of acrylamide (AM) and acrylic acid (AA) monomers, and polymerization with varying molar ratios of ammonium persulfate, N,N,N′,N′‐tetramethylethylenediamine and N,N′‐methylenebisacrylamide (N‐MBA). The water dissolution time of the obtained PVA/cross‐CS/poly (AA‐co‐AM) trilayer‐coated NPK fertilizer hydrogel granules was prolonged, while the water absorbency increased with increasing AA contents, and decreased with increasing N‐MBA contents in the outer poly(AA‐co‐AM) coating. The optimal trilayer‐coated NPK fertilizer hydrogel obtained released 84 ± 18, 63 ± 12, and 36 ± 15% of the N, P, and K nutrients, respectively, after a 30‐day immersion in water. The release phenomena of the N, P, and K nutrients of the fertilizer hydrogel obeyed both the Korsmeyer‐Peppas and Ritger‐Peppas models with a pseudo‐Fickian diffusion mechanism. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41249.     

Characterising the release of flavour compounds from chewing gum through HS-SPME analysis and mathematical modelling

The headspace solid-phase microextraction (HS-SPME) technique combined with GC–MS was evaluated to study 33 selected flavour compounds released from chewing gum. The operating conditions of SPME were optimised, including different fibres (PDMS, DVB/CAR/PDMS, PA and PDMS/DVB), sample size, extraction time and temperature. The results indicated that while HS-SPME was a rapid and valuable technique, poor reproducibility occurred under all conditions. It was found that this deficiency could be alleviated by utilising mathematical modelling techniques, an approach which had not been previously used in the analysis of flavour compounds in chewing gum by HS-SPME. Compared to the instrumental analysis data themselves, the models provided more insights to the release behaviour of flavour compounds from chewing gum and the more reproducible kinetic rate constants might be used for comparing the release of different compounds or the same compound under different conditions.     

Interaction between an electrically permeable crack and the imperfect interface in a functionally graded piezoelectric sensor

For a cracked piezoelectric sensor with an imperfect interface, the interaction between the crack and the imperfect interface is a problem of practical significance. Such a problem is investigated by the method of singular integral equation in the present work. The interface is assumed to be mechanically compliant and weakly conducting. Parametric studies on stress intensity factors (SIFs) indicate that when the crack is near to the interface SIFs increase as the interface change from perfection to imperfection, and the mechanical imperfection generally has more remarkable influence on SIFs than the dielectric imperfection does. For a crack in the piezoelectric layer and near to the interface, the SIF gets less sensitive to the variation of the substrate thickness if the interface becomes imperfect. The interfacial imperfection has less influence on the fracture behavior of a stiffer piezoelectric layer.     

-50℃用20MnMoD钢锻件及其焊接接头性能

研究了-50℃的20MnMoD钢锻件及其焊接接头在不同热处理状态时的综合力学性能。结果表明,-50℃的20MnMoD钢锻件具有良好的低温韧性,可与-50℃级正火型低温压力容器钢15MnNiNbDR配套使用。     

Sustainable Stabilizer-Free Nanoparticle Formulations of Valsartan Using Eudragit® RLPO

The bioavailability of the antihypertensive drug valsartan can be enhanced by various microencapsulation methods. In the present investigation, valsartan-loaded polymeric nanoparticles were manufactured from Eudragit^® RLPO using an emulsion–solvent evaporation method. Polyvinyl alcohol (PVA) was found to be a suitable stabilizer for the nanoparticles, resulting in a monodisperse colloid system ranging in size between 148 nm and 162 nm. Additionally, a high encapsulation efficiency (96.4%) was observed. However, due to the quaternary ammonium groups of Eudragit^® RLPO, the stabilization of the dispersion could be achieved in the absence of PVA as well. The nanoparticles were reduced in size (by 22%) and exhibited similar encapsulation efficiencies (96.4%). This more cost-effective and sustainable production method reduces the use of excipients and their expected emission into the environment. The drug release from valsartan-loaded nanoparticles was evaluated in a two-stage biorelevant dissolution set-up, leading to the rapid dissolution of valsartan in a simulated intestinal medium. In silico simulations using a model validated previously indicate a potential dose reduction of 60–70% compared to existing drug products. This further reduces the expected emission of the ecotoxic compound into the environment.     

双氯芬酸钠速缓双释口腔膜剂的制备及质量评价

目的 制备可用于口腔局部用药的双氯芬酸钠速缓双释膜剂,并考察其质量特性.方法 以喷雾干燥法制备速缓双释口腔膜剂,单因素法优化制备工艺条件,评价工艺优化后口腔膜剂的外观、厚度和耐折度,采用紫外分光光度法和桨碟法分别对口腔膜剂的药物含量和药物释放度进行评价.结果 双氯芬酸钠速缓双释膜剂光滑透明,无明显气泡,平均厚度为0.0...     

含铁低镍白色金合金镍渗出及抗变色性能

研究Fe元素部分取代镍对白色金合金镍渗出以及抗变色性能影响.指出当Fe等元素取代合金中的部分Ni元素后,由于镍含量降低,合金的镍释放率出现下降,镍降低导致表面镍钝化膜的破坏.当镍质量分数低于2.5%时,合金的镍释放量反而升高.Fe对合金的漂白效果弱于镍,Fe的加入会导致合金抗变色性能降低.均匀化退火热处理对该实验系列金合金材料的抗变色性能影响不大,但可减少合金成分的偏析,有效降低合金的镍渗出量.