Aqueous sols and gels of tungstic acid were prepared from Na2WO4 with protonated cation-exchange resin. Nano-tungsten oxide of a microporous lamella was synthesized by means of washing of WO3· 2H2O with distilled...Aqueous sols and gels of tungstic acid were prepared from Na2WO4 with protonated cation-exchange resin. Nano-tungsten oxide of a microporous lamella was synthesized by means of washing of WO3· 2H2O with distilled water under ultrasonic wave agitation and centrifuging repeatedly, and the specific surface area tended to increase gradually with washing and centrifuging. The sample of centrifuged 7 h has more than 2 times highs specific surface area and more high photocatalytic activity . The mechanisms are also discussed.展开更多
为降低粗精煤泥水分,进行了吐温类表面活性剂(吐温20,吐温40,吐温60,吐温80,吐温85)对粗煤泥离心脱水促进作用的研究。通过测量这些药剂分别作用后离心脱水煤样的水分、接触角以及离心液的表面张力,发现吐温类表面活性剂对粗煤泥离心脱...为降低粗精煤泥水分,进行了吐温类表面活性剂(吐温20,吐温40,吐温60,吐温80,吐温85)对粗煤泥离心脱水促进作用的研究。通过测量这些药剂分别作用后离心脱水煤样的水分、接触角以及离心液的表面张力,发现吐温类表面活性剂对粗煤泥离心脱水均有促进效果,它们使煤颗粒的接触角变大;吐温20,吐温80和吐温85的脱水促进作用好于吐温40和吐温60;当离心液表面张力降至67 m N/m时,脱水效率最高。对效果较好的吐温85不同用量下作用后的煤表面水化膜厚度进行了测量,并对煤颗粒表面进行电镜扫描,结果发现,煤表面上的水化膜变薄,煤颗粒表面粘附的细泥也明显减少。可以认为,吐温类表面活性剂吸附在煤粒表面,通过疏水改性使水化膜变薄和对细泥的"洗涤"作用,是其助滤的主要机理;离心液的表面张力对脱水效果有指示作用。展开更多
An investigation of the hysteresis of vortex breakdown over pitching-up deltawings is presented. Based on experiments, there are two main reasons which can be usedto explain the hysteresis of vortex breakdown. One is ...An investigation of the hysteresis of vortex breakdown over pitching-up deltawings is presented. Based on experiments, there are two main reasons which can be usedto explain the hysteresis of vortex breakdown. One is the time or phase lag due to the ini-tial suPerPOsition of linearized small disturbance, which enlarges the range of the incidenceof keeping attached flow and postpones the initial incidence of vortex breakdown. Theother is the reduction of adverse pressure gradient due to the periphery centrifugal instabil-ity after the concentrated vortex has come into being, which is the key reason of hystere-sis of vortex breakdown- The structure of vortex over a pitching up delta wing can be di-vided into three layers, which is not a significant a1teration compared with that of vortexover a static delta wing.展开更多
文摘Aqueous sols and gels of tungstic acid were prepared from Na2WO4 with protonated cation-exchange resin. Nano-tungsten oxide of a microporous lamella was synthesized by means of washing of WO3· 2H2O with distilled water under ultrasonic wave agitation and centrifuging repeatedly, and the specific surface area tended to increase gradually with washing and centrifuging. The sample of centrifuged 7 h has more than 2 times highs specific surface area and more high photocatalytic activity . The mechanisms are also discussed.
文摘为降低粗精煤泥水分,进行了吐温类表面活性剂(吐温20,吐温40,吐温60,吐温80,吐温85)对粗煤泥离心脱水促进作用的研究。通过测量这些药剂分别作用后离心脱水煤样的水分、接触角以及离心液的表面张力,发现吐温类表面活性剂对粗煤泥离心脱水均有促进效果,它们使煤颗粒的接触角变大;吐温20,吐温80和吐温85的脱水促进作用好于吐温40和吐温60;当离心液表面张力降至67 m N/m时,脱水效率最高。对效果较好的吐温85不同用量下作用后的煤表面水化膜厚度进行了测量,并对煤颗粒表面进行电镜扫描,结果发现,煤表面上的水化膜变薄,煤颗粒表面粘附的细泥也明显减少。可以认为,吐温类表面活性剂吸附在煤粒表面,通过疏水改性使水化膜变薄和对细泥的"洗涤"作用,是其助滤的主要机理;离心液的表面张力对脱水效果有指示作用。
文摘An investigation of the hysteresis of vortex breakdown over pitching-up deltawings is presented. Based on experiments, there are two main reasons which can be usedto explain the hysteresis of vortex breakdown. One is the time or phase lag due to the ini-tial suPerPOsition of linearized small disturbance, which enlarges the range of the incidenceof keeping attached flow and postpones the initial incidence of vortex breakdown. Theother is the reduction of adverse pressure gradient due to the periphery centrifugal instabil-ity after the concentrated vortex has come into being, which is the key reason of hystere-sis of vortex breakdown- The structure of vortex over a pitching up delta wing can be di-vided into three layers, which is not a significant a1teration compared with that of vortexover a static delta wing.
