Bubble Behavior and Heat Transfer in Quasi-Steady Pool Boiling in Microgravity

Pool boiling of degassed FC-72 on a plane plate heater has been studied experimentally in microgravity. A quasi-steady heating method is adopted, in which the heating voltage is controlled to increase exponentially with time. Compared with terrestrial experiments, bubble behaviors are very different, and have direct effect on heat transfer. Small, primary bubbles attached on the surface seem to be able to suppress the activation of the cavities in the neighborhoods, resulting in a slow increase of the wall temperature with the heat flux. For the high subcooling, the coalesced bubble has a smooth surface and a small size. It is difficult to cover the whole heater surface, resulting in a special region of gradual transitional boiling in which nucleate boiling and local dry area can co-exist. No turning point corresponding to the transition from nucleate boiling to film boiling can be observed. On the contrary, the surface oscillation of the coalesced bubble at low subcooling may cause more activated nucleate sites, and then the surface temperature may keep constant or even fall down with the increasing heat flux. Furthermore, an abrupt transition to film boiling can also be observed. It is shown that heat transfer coefficient and CHF increase with the subcooling or pressure in microgravity, as observed in normal gravity

Experimental study of subcooled flow boiling heat transfer on micro-pin-finned surfaces in short-term microgravity

The flow boiling heat transfer of subcooled air-dissolved FC-72 on micro-pin-finned surfaces was studied in microgravity by utilizing the drop tower facility in Beijing. The micro-pin-fins with the dimension of 30 x 30 x 60 mu m(3) (width x thickness x height), named PF30-60, were fabricated on a silicon chip by using the dry etching technique. For comparison, experiments of flow boiling heat transfer in terrestrial gravity were also conducted. The effects of inlet velocity on both flow boiling heat transfer and bubble behavior were explored. It was found that gravity has nearly no effect on flow boiling heat transfer for the departure of the inertial-force dominant bubbles in the low and moderate heat fluxes regions. In contrast, in the high-heat-flux region, the flow boiling heat transfer deteriorates and the critical heat flux (CHF) decreases due to the bubble accumulation in the channel. For PF30-60 at V = 0.5 m/s, the CHF point can be inferred to be between 20.8 and 24.5 W/cm(2), which is 63.0-74.2% of that in normal gravity. Regarding PF30-60 at V = 1.0 m/s, the CHF point can be inferred to be between 25.4 and 31.6 W/cm(2), which is 67.6-84.0% of that in normal gravity. The impact of gravity on CHF is closely linked to the channel geometry parameter and surface modification. The dimensionless numbers, Ch (Channel number) and Sf (Surface number), were proposed to describe the effect of the channel geometry and surface modification on the ratio of CHF in microgravity to that in normal gravity (CHF mu g/CHF1g). An empirical correlation based on We (Weber number), Ch and Sf was proposed to predict the value of CHF mu g/CHF1g ratio in good agreement with the experimental data. This study provides a new perspective to determine the threshold inlet velocity of inertial-force-dominant flow boiling under different experimental conditions at different gravity levels

Effects of Retinoic Acid on Proliferation and Associated Gene Expression of Human Osteosarcoma MG-63 Cells

目的:研究维甲酸对人成骨肉瘤Mg-63细胞增殖和相关基因表达的影响,以探索其对成骨肉瘤细胞的生物学效应。方法:以1μMOl/l维甲酸处理人成骨肉瘤Mg-63细胞,生长曲线测定,流式细胞仪分析、光镜观察和免疫细胞化学检测等研究维甲酸对Mg-63细胞的生长曲线、细胞周期和相关癌基因、抑癌基因表达的影响,并对其作用机理进行初步分析。结果:维甲酸处理7天后,Mg-63细胞生长抑制率达到42.2%,g0/g1期比例达到61.8%,细胞形态铺展,排列趋于规则,癌基因C-MyC、C-fOS的表达降低,而抑癌基因rb、P27表达上调。结论:1μMOl/l维甲酸可以有效抑制细胞的增殖活动,改变细胞恶性形态特征,下调癌基因C-MyC、C-fOS和上调抑癌基因rb、P27的表达,从而对人成骨肉瘤细胞分化具有诱导作用。Objective:To explore effect of Retinoic Acid(RA) on proliferation of human osteosarcoma MG-63 cells and its mech-anism of antitumor.Methods:The MG-63 cells treated by 1μmol/L RA were subjected to growth curve counts,flow sytometry,im-muncocytochemical assay and light microscopy.We investigated the influence of RA on proliferation,cell cycle,expression of associated oncogene and tumor suppressor gene of MG-63 cells.Then we analyzed the mechanism of RA in inducing differentiation primarily.Re-sults:Seven days after treated by 1 μmol/L RA,the inhibition rate of proliferation of MG-63 cells amounted to 42.2 % and RA reduced the rate of progression from G1 to S phase.The cells tend to be flat and spread.Meanwhile,the expression level of oncogene was down-regulated and the expression level of tumor suppressor gene was upregulated.Conclusions:1μmol/L RA could inhibit proliferation of MG-63 cells,reverse the malignant phenotype characters,downregulate expression of Oncogene c-Myc,c-fos and upregulate expression of Tumor Suppressor Gene Rb,p27,as a result,induce MG-63 cells into differentiation effectively.国家自然科学基金资助项目(30470877

微重力池沸腾中的气泡行为实验研究

采用图像分析方法,对实践十号返回式科学实验卫星沸腾气泡实验项目获得的微重力单气泡过冷沸腾实验图像进行研究,提取并分析了微重力条件下单个气泡的生长过程.实验中观察到气泡激发形成、稳定黏附生长和滑移三个阶段,其中气泡稳定黏附生长又可分为底部扩张与回退两个子阶段.在气泡稳定黏附生长的底部扩张子阶段,气泡半径可以表示为时间的指数函数,时间指数从初期小气泡时的0.42减小到中期的0.28,最终趋于0.气泡尺寸在气泡底部收缩之初略有回调,随后再次缓慢增大,直到过冷液体完全侵入气泡底部,使气泡与加热面脱离,并在外界扰动作用下在加热面上滑移.相关数据可以作为沸腾现象中气泡热动力学分析的依据

Expression and Localization of hnRNP A2/B1 during Differentiation of Human Osteosarcoma MG-63 Cells Induced by HMBA

背景与目的:核基质蛋白的差异表达与细胞癌变和增殖分化调控关系密切。本研究观察了hnRNP A2/B1在诱导分化处理前后人成骨肉瘤MG-63细胞核基质中的存在和分布,及其与Actin、Prohibitin的共定位关系。方法:选择性抽提经环六亚甲基双乙酰胺(hexamethylene bisacetamide,HMBA)诱导处理前后的MG-63细胞核基质,并运用双向电泳、质谱分析、蛋白质印记杂交、免疫荧光、激光共聚焦等技术检测hnRNP A2/B1在核基质中的表达与定位变化,及其与相关蛋白的共定位关系。结果:双向电泳及蛋白质印迹杂交结果证实了hnRNP A2/B1存在于MG-63细胞核基质蛋白组分中,并在HMBA处理后细胞核基质中表达下调;免疫荧光显微镜观察显示hnRNP A2/B1定位在核基质上,经HMBA处理后hnRNP A2/B1表达减弱。激光共聚焦显微镜观察结果显示,hnRNP A2/B1与细胞核基质蛋白组分Actin、细胞增殖相关调控因子Prohibitin具有共定位关系,但在诱导处理后细胞内的共定位关系减弱。结论:hnRNP A2/B1在MG-63细胞诱导分化过程中的表达分布,及其与Actin、Prohibitin的共定位关系的改变对MG-63细胞分化具有重要影响,值得进一步探索和研究。BACKGROUND & OBJECTIVE: The differentially expressed nuclear matrix proteins have great effects on canceration and regulation of cell differentiation. This study was to explore the existence and distribution of ribonucleoprotein hnRNP A2/B1 in nuclear matrix and its co-localization with Actin and Prohibitin in human osteosarcoma MG-63 cells before and after hexamethylene bisacetamide (HMBA) treatment. METHODS: The nuclear matrix of MG-63 cells before and after treatment of HMBA were selectively extracted. The expression and localization of hnRNP A2/B1 in nuclear matrix were detected by 2-D PAGE, MALDI-TOF-MS, Western blot, and immunofluorescent staining. The co-localization of hnRNP A2/B1 with Actin and Prohibitin was observed under laser scanning confocal microscope (LSCM). RESULTS: hnRNP A2/B1 was detected in the component of nuclear matrix proteins of MG-63 cells by Western blot and immunogold staining and its expression was decreased after treatment of HMBA. hnRNP A2/B1 was located in the nuclear matrix, and its expression was weakened after HMBA treatment. hnRNP A2/B1 was co-localized with Actin or Prohibitin in MG-63 cells, while the co-localization relationship was weakened during differentiation of MG-63 cells. CONCLUSIONS: hnRNP A2/B1 is a kind of nuclear matrix protein, and localizes in the nuclear matrix. The distribution and expression of hnRNP A2/B1 and its co-localization with Actin and Prohibitin play important roles during the differentiation of MG-63 cells.国家自然科学基金项目(No.30470877)~

Topological structure evolvement of flow and temperature fields in deformable drop Marangoni migration in microgravity

Using the level-set method and the continuum interface model, the axisymmetric thermocapillary migration of a deformable liquid drop immerged in an immiscible bulk liquid with a temperature gradient is simulated numerically with constant material properties of the two phases. Steady terminal state of the motion can always be reached. The dimensionless terminal migration velocity decreases monotonously with the increase of the Marangoni number. Good agreements with space experimental data and most of previous numerical studies in the literature are evident. The terminal topological structure of flow field, in which a recirculation identical to Hill's vortex exists inside the drop, does not change with the Marangoni number. Only slight movement of the location of vortex center can be observed. On the contrary, bifurcations of the terminal topological structure of temperature field occur twice with increasing Marangoni number. At first, the uniform and straight layer-type structure of temperature field at infinitesimal Reynolds and Marangoni numbers wraps inside of the drop due to convective transport of heat as the Marangoni number increases, resulting in the emergence of an onion-type local cooler zone around the center of the drop beyond a lower critical Marangoni number. Expanding of this zone, particularly in the transverse direction, with the increasing of the Marangoni number leads to a cap- or even shell-type structure. The coldest point within the liquid drop locates on the axis. There is a middle critical Marangoni number, beyond which the coldest point will jump from the rear stagnation into the drop, though the topological structure of the temperature field does not change. The second bifurcation occurs at an upper critical Marangoni number, where the shell-type cooler zone inside drops ruptures from the central point and then a torus-type one emerges. The coldest point departs from the axis, and the so-called "cold-eye" appears in the meridian. It is also found that the inner and outer thermal boundary layers along the interface may exist both inside and outside the drop if Ma > 70. But the thickness decreases with the increasing Marangoni number more slowly than the prediction of potential flow at large Marangoni and Reynolds numbers. A velocity shear layer outside the drop is also introduced formally, of which modality may be affected by the convective transports of heat and/or momentum. (C) 2011 Elsevier Ltd. All rights reserved

Influences of wake-effects on bubble dynamics by utilizing micro-pin-finned surfaces under microgravity

The influences of wake on bubble dynamics under various heat fluxes have been studied in microgravity. Nucleate pool boiling experiments of FC-72 on silicon chips fabricated with micro-pin-fins were conducted in 10(-3) gravitational acceleration for 3.6 s. Experimental results indicated that wake field had little influence on bubble dynamics at low heat flux, q = 12.53 W/cm(2), but its effects on bubble dynamics became very great at moderate heat flux, q = 27.89 W/cm(2), and high heat flux, q = 39.54 W/cm(2). More importantly, wake-effects appeared even more significant in microgravity. In the wake field, the horizontal flow of the liquid on micro-pin-finned silicon chips promoted the collision, coalescence and movement of bubbles, and the vertical flow of liquid phase exerted an upward force on bubbles, which can effectively shorten the growth cycle and decrease the departure radius of bubbles. Furthermore, fresh liquid could easily be inhaled into the micro-pin-finned structure owning to the negative pressure in wake region, which can supply sufficient liquid for the growth of bubble, avoiding film boiling. The interaction between the micro-pin-finned structure and the wake effect promoted the process of bubble coalescence and departure effectively, so the process of heat transfer was significantly improved on micro-pin-finned surface. In addition, the flow field and bubble behavior in wake region were also briefly analyzed based on some reasonable simplifications and hypotheses. The theoretical analyses showed that the durations of wake-effects lasted longer than the time periods of the bubble in next generation, and the bubble diameters were also smaller than the thickness of Wake region. Therefore, the dominant bubble of next generation was influenced by the wake field during its ebullition cycle, which is consistent with the experimental phenomenon. (C) 2016 Elsevier Ltd. All rights reserved

浦城县大口窑调查勘探报告

浦城县大口窑是宋元时期闽北地区一处著名的窑场,以烧造青白瓷为主,此外还兼烧部分酱釉瓷、少量绿釉瓷等。器型种类丰富,质量较高,窑业技术与江西景德镇窑关系密切。其产品在东亚、东南亚等地有发现,是福建一处重要的外销瓷生产地

Numerical simulation of bubble dynamics and heat transfer with transient thermal response of solid wall during pool boiling of FC-72

Using the Ghost Fluid Method for sharp interface representation, bubble dynamics and heat transfer during single bubble pool boiling of saturated FC-72 are simulated numerically with transient thermal response of the heated SiO2 solid wall. A constant and uniform temperature is fixed on to the bottom surface of the solid wall in the simulations, and thus, both the spatio-temporal averaged heat flux and superheat on the top surface, which contacts the working fluid directly, are dependent variables instead of controllable ones. Multi-cycle simulations are carried out to eliminate the influence of unreal initial conditions. Steady periodical processes of single bubble pool boiling can be reached on the wall with a thickness of 1 mm, while only quasi-steady ones on the wall with a thickness of 5 mm due to the limited simulation time, which results in a smaller thermal penetration depth inside the solid wall compared with its thickness. Comparing with the prediction of the correlation by Zuber for the discrete bubble region and experimental data of single bubble pool boiling, the numerical results of boiling curves in both steady and quasi-steady cases exhibit the same trend. Transient heat conduction inside the solid wall is analyzed in detail. A sharp drop of the wall temperature is evident in the vicinity of the contact line due to violent evaporation in this tiny region. The area of the temperature drop moves with the contact line, resulting in a pseudo-periodical process of heat storage and release inside the solid wall, which exhibits a coupling effect with bubble dynamics and heat transfer. The thermal penetration depth caused by the processes of bubble growth and departure in a single bubble cycle is about 0.5 mm in both steady and quasi-steady cases, which is much small than the heater thickness. (C) 2014 Elsevier Ltd. All rights reserved

中国物理海洋学研究70年：发展历程、学术成就概览

本文概略评述新中国成立70年来物理海洋学各分支研究领域的发展历程和若干学术成就。中国物理海洋学研究起步于海浪、潮汐、近海环流与水团,以及以风暴潮为主的海洋气象灾害的研究。随着国力的增强,研究领域不断拓展,涌现了大量具有广泛影响力的研究成果,其中包括:提出了被国际广泛采用的"普遍风浪谱"和"涌浪谱",发展了第三代海浪数值模式;提出了"准调和分析方法"和"潮汐潮流永久预报"等潮汐潮流的分析和预报方法;发现并命名了"棉兰老潜流",揭示了东海黑潮的多核结构及其多尺度变异机理等,系统描述了太平洋西边界流系;提出了印度尼西亚贯穿流的南海分支(或称南海贯穿流);不断完善了中国近海陆架环流系统,在南海环流、黑潮及其分支、台湾暖流、闽浙沿岸流、黄海冷水团环流、黄海暖流、渤海环流,以及陆架波方面均取得了深刻的认识;从大气桥和海洋桥两个方面对太平洋–印度洋–大西洋洋际相互作用进行了系统的总结;发展了浅海水团的研究方法,基本摸清了中国近海水团的分布和消长特征与机制,在大洋和极地水团分布及运动研究方面也做出了重要贡献;阐明了南海中尺度涡的宏观特征和生成机制,揭示了中尺度涡的三维结构,定量评估了其全球物质与能量输运能力;基本摸清了中国近海海洋锋的空间分布和季节变化特征,提出了地形、正压不稳定和斜压不稳定等锋面动力学机制;构建了"南海内波潜标观测网",实现了对内波生成–演变–消亡全过程机理的系统认识;发展了湍流的剪切不稳定理论,提出了海流"边缘不稳定"的概念,开发了海洋湍流模式,提出了湍流混合参数化的新方法等;在海洋内部混合机制和能量来源方面取得了新的认识,并阐述了混合对海洋深层环流、营养物质输运等过程的影响;研发了全球浪–潮–流耦合模式,推出一系列海洋与气候模式;发展了可同化主要海洋观测数据的海洋数据同化系统和用于ENSO预报的耦合同化系统;建立了达到国际水准的非地转(水槽/水池)和地转(旋转平台)物理模型实验平台;发展了ENSO预报的误差分析方法,建立了海洋和气候系统年代际变化的理论体系,揭示了中深层海洋对全球气候变化的响应;初步建成了中国近海海洋观测网;持续开展南北极调查研究;建立了台风、风暴潮、巨浪和海啸的业务化预报系统,为中国气象减灾提供保障;突破了国外的海洋技术封锁,研发了万米水深的深水水听器和海洋光学特性系列测量仪器;建立了溢油、危险化学品漂移扩散等预测模型,为伴随海洋资源开发所带来的风险事故的应急处理和预警预报提供科学支撑。文中引用的大量学术成果文献(每位第一作者优选不超过3篇)显示,经过70年的发展,中国物理海洋学研究培养了一支实力雄厚的科研队伍,这是最宝贵的成果。这支队伍必将成为中国物理海洋学研究攀登新高峰的主力军