热喷涂用送粉器国内外现状及发展

本文归纳介绍了几种常用热喷涂送粉器的结构原理,分析比较了不同类型送粉器间的差异和适用范围,收集了近年来国内外商品化设备的信息,提出了国内热喷涂送粉器的发展趋势。     

Vacancy-ordered yttria stabilized zirconia as a low-temperature electronic conductor achieved by laser melting

Laser melting is known to be capable in initiating thorough evolution in microstructure and bringing novel functional performance in metals. But realization of this potential in ceramics only reaches a preliminary stage that needs further investigation. Here we demonstrate zirconia, traditionally an insulative ceramic at low temperature, could be transformed into an electronic conductor with the conductivity on order of 10⁻³ S⋅cm^-1 at room temperature by a simple laser melting process without inducing metallic phases. Transmission electron microscopy and ab-initio simulation show that oversaturated oxygen vacancies, together with their ordered metastable distribution along <001 > , are introduced during this non-equilibrium process, and result in a clear defect level significantly narrowing bandgap to less than 1 eV, leading to the considerable electronic conductivity. These results identify a strategy of utilizing this non-equilibrium method in oxide ceramics to realize some unconventional performances determined by metastable structure thoroughly altered down to atomic level.     

大型开沟铺管机自动控制系统的研制

为了解决1KPZ-250型开沟铺管机自动控制系统中的关键问题,在分析其工作原理和基本结构的基础上,将液压驱动技术、电液调控技术、传感器技术、GPS技术、人机环境工程模块化技术等应用到机器中,提出了车体姿态、自动行走和开沟深度的自动控制方法,并总体设计了开沟铺管机的车体自动调平控制系统、自动导航控制系统和激光高程控制系统。研究结果表明,该系统的动态品质较好,当车体倾斜时能自动将其调节到水平位置;机器能够按照预定的路径实现自动导航,偏航误差控制在±10 cm以内;开沟铺管的高程误差可控制在±20 mm以内,能够满足控制系统的要求。     

降解南瓜纤维素菌株的分离筛选及酶活测定

目的:筛选出能高效降解南瓜纤维素的菌株,以制备南瓜可溶性膳食纤维。方法:从土壤、腐烂的树叶和水果上分离出具有降解南瓜纤维素的菌株,用刚果红染色透明水解圈进行初筛,然后用CMC-Na、滤纸和南瓜渣为碳源测所有菌株及混合菌株的羧甲基纤维素酶活力,最终选出1株酶活力较高菌株进行下一步实验。结果:共分离到能够有效降解纤维素的共有5株细菌和7株真菌,通过测单菌株和混合菌株的酶活力,表明混合菌株的酶活力最大值比单菌株的酶活力最大值要高3倍之多。结论:混合菌株的酶活力比单株菌酶活力值高,发酵培养72h南瓜渣可溶性多糖降解力最强。     

辊式磨粉机轧距稳定影响因素的研究

辊式磨粉机轧距系统是否稳定直接关系到物料的粉碎效果,磨粉机制造厂家和设计者一直在探索和改进。结合多年对磨粉机的研究和学习,探讨了辊式磨粉机轧距稳定的关键因素与解决措施。     

Effects of layer arrangement on heating uniformity and product quality after hot air assisted radio frequency drying of carrot

The conventional drying technology prolongs the shelf life of carrots but may cause the serious loss of nutrients. The aim of this study was to investigate the effects of intermittently rearranging layers on the heating uniformity, drying characteristics and quality of carrot slices under the hot air assisted radio frequency (RF) heating. The carrot slices were dried for 270 min using hot air (60 °C) assisted RF heating at the electrode gap of 100 mm firstly, and then followed hot air drying to achieve the final moisture level (0.11 kg/kg (d.b.)). The results showed that the selected hot air assisted RF drying protocol for the carrot slices reduced 30% of the duration compared to the single hot air drying. The carrot slices dried by the combined drying method had the highest total carotenoid value (P ≤ 0.05) except for possessing accepted color and rehydration. Therefore, the combined drying method could improve the drying rate and maintain heat sensitive substances in carrot slices.     

Improving radio frequency heating uniformity using a novel rotator for microorganism control and its effect on physiochemical properties of raisins

In the present study, a novel material rotator was designed to evaluate the possibilities to improve radio frequency (RF) heating uniformity in raisins. The rotator provided a means to rotate materials when subjected to RF heating. The results showed that RF heating uniformity was significantly (p < 0.05) improved with the rotation of raisins. The relative heating uniformity parameter (λ) reduced to less than 15% at rotational speed of 40 and 60 rpm. No significant (p > 0.05) influence on heating rate was observed. Pasteurization experiments showed the total bacterial (4.88 log) count was reduced by 2.55 log CFU/g and the molds (4.83 log) were completely inactivated when raisins were heated to 80 °C and maintained for 10 min, which indicated a great disinfection efficiency of RF heating. Quality evaluation showed the physiochemical property changes of raisins were satisfied with acceptable color and nutrients loss. Therefore, the method used in this experiment could be expanded to develop an effective treatment protocol for controlling microorganisms in raisins.     

Hot corrosion behavior of NdYbZr2O7 exposed to V2O5 and Na2SO4 + V2O5 molten salts

In order to evaluate the application prospects of NdYbZr₂O₇ as a novel TBC material, NdYbZr₂O₇ ceramic was synthesized via a solid-state reaction sintering method, and its hot corrosion behavior exposed to V₂O₅ and Na₂SO₄ + V₂O₅ molten salts at 900 °C, 1000 °C, and 1100 °C was comparatively investigated. For the V₂O₅ salt, the primary corrosion products were granular (Nd,Yb)VO₄ as well as cube-like m-ZrO₂. The corrosion layer consisted of two distinct layers, one of which was Zr-rich layer and another was V-rich layer. In the case of Na₂SO₄ + V₂O₅, NaVO₃, as an intermediate product, played an important role in dissolving the NdYbZr₂O₇ ceramic. Herein, the (Nd,Yb)VO₄ exhibited a rod/plate-like morphology, which could be attributed to the synergistic effect of low driving force and low nucleation rate. Since the molten salt infiltration rate was superior to the pore filling rate throughout the hot corrosion, the thickness of corrosion layer increased with the rise of temperature. The hot corrosion mechanisms of NdYbZr₂O₇ ceramic in various molten salts were discussed based on the phase diagram, Lewis acid-base rule and chemical thermodynamics. On this basis, the NdYbZr₂O₇ coating was prepared by atmospheric plasma spray (APS) and it exhibits a higher corrosion resistance compared to YSZ coating.     

Thin layer modeling of drying kinetics,rehydration kinetics and color changes of osmotic pre-treated pineapple (Ananas comosus) slices during drying: Development of a mechanistic model for mass transfer

This study aimed to develop an effective and safe drying protocol for pineapple fruits. The combination of different osmotic pre-treatments and drying temperatures were used to evolve a novel method that can reduce drying associated changes in pineapple fruits. The pre-treatment was accomplished by soaking fresh pineapple slices in four osmotic solutions (1% trehalose, 2% NaCl, 10% sucrose, and 10% fructose) for 30 min. A hot air convection dryer carried out the drying at 50, 55, and 60 °C temperatures maintaining a constant 30% relative humidity (RH). During the drying experiment, moisture content data were taken and transformed into moisture ratio (MR) and then fitted to the four thin layer models viz. Page, Logarithmic, Newton (Exponential model), and Henderson and Pabi's Model. The impact of pre-treatments and drying temperature on drying kinetics, mass transfer rate, moisture diffusion, rehydration capacity, and color changes of pineapple slices were observed. The drying process was affected by both osmotic pre-treatments and temperature. A satisfactory curve with good fitting as anticipated by the Page and Logarithmic models, with the Logarithmic model fitting best during the drying of pineapple slices. The ideal drying temperature integrated with pre-treatments was 55 °C at 30% RH based on maintaining the color and rehydration. The Page equation provided an excellent statistical fit to experimental rehydration data, with low mean percentage error values of 2.188–7.479%. The pre-treatment of dried pineapples, particularly with trehalose, improved structural retention as seen by increased rehydration capacity and lower color changes after reconstitution. The mechanistic model, which describes activation energy for the increase of moisture diffusion coefficient and mass transfer coefficient, and their correlation to drying conditions (temperature and time), showed a better fit for mass transfer and diffusion. Weibull's distribution model gave a better fit for the water loss model during drying at various temperatures. As a result, the combination of dipping in 1% trehalose solution and hot air drying at 55 °C appears to be a promising procedure for producing high-quality, nutritious dried pineapple products for consumers. This work will assist future researchers in understanding the influence of osmotic pre-treatments on plant foods and improve the existing literature.