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Transition to Film Boiling in microgravity： Influence of Subcooling

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Chinese Physics Letters 2010年第7期27卷 198-201页

作者：赵建福李晶闫娜王双峰 Key laboratory of microgravity (national microgravity laboratory) Institute of Mechanics Chinese Academy of Sciences Beijing 100190

The transition process to film pool boiling in microgravity is studied experimentally aboard the Chinese recoverable satellite S J-8. A quasi-steady heating method is adopted, in which the heating voltage is controlled to increase exponentially with time. Small, primary bubbles are formed and slid on the surface, which coalesce with each other to form a large coalesced bubble. Two ways are observed for the transition from nucleate to film boiling at different subcoolings. At high subcooling, the coalesced bubble with a smooth surface grows slowly. It is then difficult for the coalesced bubble to cover the whole heater surface, resulting in a special region of transition boiling in which nucleate boiling and local dry areas can coexist. In contrast, strong oscillation of the coalesced bubble surface at low subcooling may cause rewetting of local dry areas and activation of more nucleate sites, resulting in an abrupt transition to film boiling.

关键词： Boiling Packaging materials Films Heat Heating Methods Dry period Water depletion Drying

The impact of N-terminal phosphorylation on LHCII conformation in state transition

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Acta Mechanica Sinica 2014年第3期30卷 447-456页

作者： Jin-Hong Ding Ning Li Man-Liu Wang Yan Zhang Shou-Qin Lü Mian Long Key laboratory of microgravity(national microgravity laboratory)and Center of Biomechanics and Bioengineering Institute of MechanicsChinese Academy of Sciences

State transition is an important protection mechanism of plants for maintaining optimal efficiency through redistributing unbalanced excitation energy between photosystem II （PSII） and photosystem I （PSI）. This process depends on the reversible phosphorylation/dephosphorylation of the major light-harvesting complex II （LHCII） and its bi-directional migration between PSII and PSI. But it remains unclear how phosphorylation/dephosphorylation modulates the LHCII conformation and further regulates its reversible migration. Here molecular dynamics simulations （MDS） were employed to elucidate the impact of phosphorylation on LHCII conformation. The results indicated that N-terminal phosphorylation loosened LHCII trimer with decreased hydrogen bond （H-bond） interactions and extended the distances between neighboring monomers, which stemmed from the conformational ad- justment of each monomer itself. Global conformational change of LHCII monomer started from its stromal N- terminal （including the phosphorylation sites） by enhancing its interaction to lipid membrane and by adjusting the interaction network with surrounded inter-monomer andintra-monomer transmembrane helixes of B, C, and A, and finally triggered the reorientation of transmembrane helixes and transferred the conformational change to luminal side helixes and loops. These results further our understanding in molecular mechanism of LHCII migration during state transition from the phosphorylation-induced microstructural feature of LHCII.

关键词： State transition LHCII Phosphorylation Conformation

An experimental research on surface oscillation of buoyant-thermocapillary convection in open cylindrical annuli

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Acta Mechanica Sinica 2014年第5期30卷 681-686页

作者： Li Zhang Li Duan Qi Kang national microgravity laboratory Institute of Mechanics Chinese Academy of Sciences

An experiment is carried out on the surface oscillation of buoyant-thermocapillary convection in an open cylindrical annulus. When the radial temperature difference AT reaches a critical value △Tc, a regular oscillation appears and soon disappears on the open surface, which varies when the liquid layer＇s thickness h and temperature difference △T are varied. With growth of △T, dominant frequency of the visible oscillation will grow too but is found within certain frequencies. Driving forces, buoyance and thermocapillarity, are responsible for this phenomanon and the ＂balance＂ point is considered to exist when h is between 4.5-5.0 mm. Surface oscillation region is also found restricted within a narrow gap when Bo is smaller than 3.7.

关键词： Cylindrical annulus Buoyant-thermocapillary convection Surface oscillation Critical temperature differ- ence

Instability of thermocapillary flow in liquid layers under microgravity

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Science China(Physics,Mechanics & Astronomy) 2012年第4期55卷 684-692页

作者： XUN Bo LI Kai HU WenRui Key laboratory of microgravity(national microgravity laboratory) Institute of MechanicsChinese Academy of SciencesBeijing 100190China

The instability of the thermocapillary flow in liquid layers is studied in the present paper using the linear stability *** on the two-dimensional steady flow state,the three-dimensional disturbance with a wave number in the spanwise direction is *** effects of the aspect ratio and free surface shape of the liquid layer on the flow instability are studied,and the results are compared with the case with the two-dimensional disturbance.

关键词： thermocapillary convection flow instability numerical simulations of chaotic systems

Numerical study on onset of oscillatory thermocapillary flow in rectangular liquid pool

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Science China(Technological Sciences) 2010年第4期53卷 1069-1076页

作者： HU WenRui,TANG ZeMei & LI Kai Key laboratory of microgravity(national microgravity laboratory),Institute of Mechanics,Chinese Academy of Sciences,Beijing10090,China Key laboratory of microgravity (national microgravity laboratory) Institute of Mechanics Chinese Academy of Sciences Beijing China

Thermocapillary flow in a rectangular liquid pool of large Prandtl fluid(Pr=105.6) is numerically studied in *** thermocapillary flow arises when the imposed temperature difference between the sidewalls exceeds a critical *** fluctuations of the oscillatory flow,accompanied by the propagation of the hydrothermal wave from the cold sidewall to the hot one,are much smaller than the time-averaged velocity and temperature *** corresponding disturbance cells arise in the centre of the liquid pool initially,and extend to the whole region with the increasing imposed temperature *** present study reveals the different characteristics of the oscillatory themocapillary flow in the rectangular liquid pool as compared to the cases in other configurations.

关键词： hydrothermal wave bifurcation numerical simulation microgravity

Competitive Adsorption between Bovine Serum Albumin and Collagen Observed by Atomic Force Microscope

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Chinese Chemical Letters 2004年第12期15卷 1465-1468页

作者： Yong YU Pei Qing YING Gang JIN national microgravity lab,Institute of Mechanics,Chinese Academy of Sciences, Beijing 100080 national microgravity lab. Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China

Atomic force microscopy (AFM) was used to study the competitive adsorption betweenbovine serum albumin (BSA) and type Ⅰ collagen on hydrophilic and hydrophobic silicon wafers.BSA showed a grain shape and the type Ⅰ collagen displayed fibril-like molecules with relativelyhomogeneous height and width, characterized with clear twisting (helical formation). These AFMimages illustrated that quite a lot of type Ⅰ collagen appeared in the adsorption layer on hydrophilicsurface in a competitive adsorption state, but the adsorption of BSA was more preponderant than thatof type Ⅰ collagen on hydrophobic silicon wafer surface. The experiments showed that theinfluence of BSA on type Ⅰ collagen adsorption on hydrophilic surface was less than that onhydrophobic surface.

关键词： Atomic force microscope protein competitive adsorption collagen bovine serum albumin.

Transition to Chaos in the Floating Half Zone Convection

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Chinese Physics Letters 2007年第2期24卷 475-478页

作者：阿燕曹重华胡文瑞 national microgravity laboratory Institute of Mechanics Chinese Academy of Sciences Beijing 100080

The transition process from steady convection to chaos is experimentally studied in thermocapillary convections of floating half zone. The onset of temperature oscillations in the liquid bridge of floating half zone and further transitions of the temporal convective behaviour are detected by measuring the temperature in the liquid bridge. The fast Fourier transform reveals the frequency and amplitude characteristics of the flow transition. The experimental results indicate the existence of a sequence of period-doubling bifurcations that culminate in chaos. The measured Feigenbaum numbers are δ2 =4.69 and δ4 = 4.6, which are comparable with the theoretical asymptotic value δ=4.669.

关键词： FLOW

An in-situ Observation on Initial Aggregation Process of Colloidal Particles near Three-Phase Contact Line of Air, Water and Vertical Substrate

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Chinese Physics Letters 2008年第10期25卷 3811-3814页

作者：姚灿王育人蓝鼎段俐康琦 national microgravity laboratory Institute of Mechanics Chinese Academy of Sciences Beijing 100190

The self-assembling process near the three-phase contact line of air, water and vertical substrate is widely used to produce various kinds of nanostructured materials and devices. We perform an in-situ observation on the selfassembling process in the vicinity of the three phase contact line. Three kinds of aggregations, i.e. particle-particle aggregation, particle-chain aggregation and chain-chain aggregation, in the initial stage of vertical deposition process are revealed by our experiments. It is found that the particle particle aggregation and the particle-chain aggregation can be qualitatively explained by the theory of the capillary immersion force and mirror image force, while the chain-chain aggregation leaves an opening question for the further studies. The present study may provide more deep insight into the self-assembling process of colloidal particles.

关键词： the power-law exponents precipitation durative abrupt precipitation change

Gas-liquid phase coexistence and finite-size effects in a two-dimensional Lennard-Jones system

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Chinese Science Bulletin 2011年第26期56卷 2773-2779页

作者： OUYANG WenZe XU ShengHua SUN ZhiWei Key laboratory of microgravity (national microgravity laboratory) Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

The gas-liquid phase coexistence in a two-dimensional Lennard-Jones system is investigated using Maxwell construction method together with molecular dynamics *** results of phase coexistence in different truncations of the potential are compared with data obtained from the literature,and the corresponding critical properties *** crossover from Ising-like to mean field behavior is observed and confirmed as the temperature approaches the critical point from *** simulations on systems with different sizes,we find that a finite size effect is more significant than those shown in most of the previous results,and a lower critical temperature is obtained when the full extent of this finite size effect is considered.

关键词：有限尺寸效应气液相系统二维共存分子动力学模拟规模效应临界温度