Thermal properties of glass-ceramic bonded thermal barrier coating system

The thermal properties of a thermal barrier coating （TBC） system comprised of BaO-MgO-SiO_2 based glass-ceramic bond coating, 8% （mass fraction） yttria stabilized zirconia （8YSZ） top coating and nimonic alloy substrate were evaluated. The thermal diffusivity and thermal conductivity of the TBC coated substrate were lower than those of bare substrate and glass-ceramic coated substrate under identical conditions. The specific heat capacity, thermal diffusivity and thermal conductivity of the TBC coated substrate increase with the increase of the temperature. Further, it is observed that the thermal conductivity of the TBC system decreases with the increase in the top coating thickness.

Development of non-shrinkable ceramic composites for use in high-power microwave tubes

Al_2O_3–CaO–SiC-based ceramic composites with four different compositions were sintered at 1700℃ for 3 h in an air furnace. The phase analysis, microstructural characterization, and elemental composition determination of the developed composites were performed by X-ray diffraction(XRD), field-emission scanning electron microscopy(FESEM), and energy-dispersive X-ray(EDAX) analysis, respectively. The shrinkage, thermal properties, and electrical resistivity of the composites were also studied. The experimental results showed the effects of adding silicon carbide and calcia to alumina on the thermal, electrical, and shrinkage properties of the resultant composites. Among the four investigated ceramic composites, the one composed of 99 wt% alumina, 0.5 wt% CaO, and 0.5 wt% SiC exhibited the best characteristics for use as a potting material in a dispenser cathode of a microwave tube. The material exhibited slight expansion instead of shrinkage during drying or firing. Other properties of the composite powder, such as its thermal properties and electrical resistivity, were comparable to those of a commercial alumina powder.

Oblique Wave Trapping by a Surface-Piercing Flexible Porous Barrier in the Presence of Step-Type Bottoms

The present study deals with the oblique wave trapping by a surface-piercing flexible porous barrier near a rigid wall in the presence of step-type bottoms under the assumptions of small amplitude water waves and the structural response theory in finite water depth.The modified mild-slope equation along with suitable jump conditions and the least squares approximation method are used to handle the mathematical boundary value problem.Four types of edge conditions,i.e.,clamped-moored,clamped-free,moored-free,and moored-moored,are considered to keep the barrier at a desired position of interest.The role of the flexible porous barrier is studied by analyzing the reflection coefficient,surface elevation,and wave forces on the barrier and the rigid wall.The effects of step-type bottoms,incidence angle,barrier length,structural rigidity,porosity,and mooring angle are discussed.The study reveals that in the presence of a step bottom,full reflection can be found periodically with an increase in(i)wave number and(ii)distance between the barrier and the rigid wall.Moreover,nearly zero reflection can be found with a suitable combination of wave and structural parameters,which is desirable for creating a calm region near a rigid wall in the presence of a step bottom.

棉纤维表面还原糖的近红外定量分析

1.引言棉的粘性早已成为一个影响成纱生产效率的阵发性问题。梳棉机、细纱机的罗拉及其它部件上出现积聚物使问题变得突出了。遇到不良天气条件,这种情况还会恶化。在梳棉机、并条机、精梳机和细纱机上最易看到这种积聚现象。此外,缠卷罗拉更是屡见不鲜。众所周知,棉的粘性是由白蝇和蚜虫分泌物所致,通常称为蜜露。其它的植物糖和棉籽油也会产生粘性。

高速拉伸变形中的热传递

对高速拉伸变形加工中的短程高温加热器用集总容量方法建立了热传递数学模型,可预测变形加工中的纱线温度.

A model to determine soiling,shading and thermal losses from PV yield data

Apart from being a clean source of energy,photovoltaic(PV)power plants are also a source of income generation for its investors and lenders.Therefore,mitigation of system losses is crucial for economic operation of PV plants.Combined losses due to soiling,shading and temperature in PV plants go as high as 50%.Much of these losses are unaccounted initially,which can jeopardize the economic viability of PV projects.This paper aims to provide a model to determine losses due to soiling,shading and temperature using quantities like irradiance,cell temperature,DC power and current,which are readily available in PV yield data captured by the remote monitoring system,without involving any additional sensors or equipment.In this study,soiling,shading and thermal losses were calculated using PV yield data obtained from a 30-kWp PV plant located in Kharagpur,India.The results showed soiling and shading losses as high as 25.7%and 9.7%,respectively,in the month of December.Soiling loss was verified by measuring transmittance loss of coupon glasses installed in the vicinity of the plant.Shading loss was verified by shadow simulation using an architectural tool(SketchUp).Array thermal loss obtained using the proposed methodology was found to be in line with the estimated value obtained from PVsyst simulation.Additionally,using time-series data,the energy losses corresponding to soiling,shading and temperature effects were calculated by a numerical-integration technique.The monetary loss due to these energy losses thus obtained provides criteria for deciding when to mitigate the sources of these losses.