Existence of Universal Phase Diagrams for Describing General Pore Shape Resulting From an Entrapped Bubble During Solidification

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
P. S. Wei ◽  
C. C. Chang
Keyword(s):  
Climate Change ◽  
Contact Angle ◽  
Phase Diagrams ◽  
Pore Formation ◽  
Solidification Rate ◽  
Pore Shape ◽  
Coordinate Systems ◽  
General Development ◽  
Base Radius ◽  
Dimensionless Coordinate

This study shows that there exist a pair of universal and unique phase diagrams to describe general development of the pore shape in solid, resulting from a bubble captured by a solidification front. Like thermodynamics, phase diagrams have advantages to generally identify the states and design processes of a system. Pore formation and its shape in solids influence not only microstructure of materials but also contemporary issues of biology, engineering, foods, geophysics, and climate change, etc. In this study, a pair of phase diagrams is thus found to be under dimensionless coordinate systems of dimensionless apex radius, contact angle, and base radius of the bubble cap, as well as solidification rate, contact angle, and growth rate of base radius. The computed results of the development of the pore shape agree with experimental data. The pore shape in solid thus can be optimistically predicted and controlled by choosing a desired path on phase diagrams.

Effects of Bubble Growth and Solidification Rate on Pore Formation in Solid

2012 ◽  
Author(s):  
P. S. Wei ◽  
S. Y. Hsiao
Keyword(s):  
Growth Rate ◽  
Contact Angle ◽  
Solidification Front ◽  
Bubble Growth ◽  
Pore Formation ◽  
Solidification Rate ◽  
Bubble Radius ◽  
Abel Equation ◽  
Spherical Cap ◽  
Factors Affecting

The shapes of a pore in solid resulted from entrapment of a tiny bubble by a solidification front are predicted in this work. Pore formation and its shape in solid are one of the most critical factors affecting properties and microstructure, in materials. For simplicity without loss of generality, the tiny bubble is considered to have a spherical cap. From a geometrical analysis, the contact angle of the bubble cap on the solidification front or the pore shape in solid is found to be governed by the Abel equation of the first kind. The pore becomes closed by imposing a finite bubble growth rate-to-solidification rate ratio which can produce a minimal bubble radius at the contact angle of 90 degrees. Closure of a pore resulted from a greater solidification rate than bubble growth rate, as accepted in the literature, is incorrect.

Zanzibari Seaweed

2015 ◽  
pp. 132-158
Author(s):  
Nadra Hashim
Keyword(s):  
Climate Change ◽  
Water Resources ◽  
Global Climate Change ◽  
Global Climate ◽  
Dar Es Salaam ◽  
Economic Empowerment ◽  
General Development ◽  
Environmentally Responsible ◽  
History Of

Well before island nations began to consider rising ocean levels, a feature of global climate change (GCC), they have been concerned with the allocation of water resources. The purpose of this chapter is to examine the efforts of universities, in the Tanzanian cities of Zanzibar and Dar-Es-Salaam, to promote environmentally responsible entrepreneurial projects, which sustain women's economic empowerment, while advancing the general development of the broader community, in which they live. The object of this discussion is to examine the history of sea-weed production, and to examine how Zanzibar's seaweed farmers, who are largely women, have responded to adversity, and what, if anything, they can do to address current difficulties.

Zanzibari Seaweed

2017 ◽  
pp. 365-391
Author(s):  
Nadra Hashim
Keyword(s):  
Climate Change ◽  
Water Resources ◽  
Global Climate Change ◽  
Global Climate ◽  
Dar Es Salaam ◽  
Economic Empowerment ◽  
General Development ◽  
Environmentally Responsible ◽  
History Of

Well before island nations began to consider rising ocean levels, a feature of global climate change (GCC), they have been concerned with the allocation of water resources. The purpose of this chapter is to examine the efforts of universities, in the Tanzanian cities of Zanzibar and Dar-Es-Salaam, to promote environmentally responsible entrepreneurial projects, which sustain women's economic empowerment, while advancing the general development of the broader community, in which they live. The object of this discussion is to examine the history of sea-weed production, and to examine how Zanzibar's seaweed farmers, who are largely women, have responded to adversity, and what, if anything, they can do to address current difficulties.

Atomistic Simulation of Pore Formation in Lipid Bilayers in the Presence of Dimethylsulfoxide: Further Evidence for Entropic Driven Pore Formation

2008 ◽  
Author(s):  
Raghava Alapati ◽  
Dorel Moldovan ◽  
Ram Devireddy
Keyword(s):  
Lipid Bilayer ◽  
Lipid Bilayers ◽  
Pore Formation ◽  
Configurational Entropy ◽  
Line Tension ◽  
Nucleation Theory ◽  
Classical Nucleation Theory ◽  
Pore Shape ◽  
Dmso Concentration ◽  
Pore Nucleation

In a recent study, Moldovan et al [1] have demonstrated that in the presence of 11.3 mol% dimethylsulfoxide (DMSO) a pore can nucleate and grow spontaneously in a lipid bilayer even in the absence of an externally applied stresses or electric field. The authors rationalized the spontaneous pore nucleation, in the absence of any external driving force, by considering the combined effect of the entropy of pore shape fluctuation and the significant decrease of the bilayer line tension in the presence of DMSO. Building on the classical nucleation theory developed three decades ago by Lister [2] the authors propose a new formulation for the bilayer free energy that incorporates the pore shape configurational entropy. According to this study, in the presence of DMSO, the pore nucleates spontaneously and grows provided the bilayer line tension decreases below a threshold value, λ. In this study we report our recent simulation results on the effect of DMSO concentration on both bilayer line tension and bilayer structural stability with respect to pore nucleation. The lipid bilayer systems investigated in this study by molecular dynamics (MD) consists of 96 molecules (48 in each leaflet) of dimyristoylphosphatidylcholine (DMPC) immersed in DMSO-water solutions at various concentrations. In all MD simulations reported the bilayer systems were followed over 100 ns. Our simulations results indicate the existence of a critical DMSO concentration below which there are no pores nucleated in the lipid bilayers. Our findings corroborate and complement the entropy-based pore nucleation model proposed earlier by Moldovan et al. [1].

scholarly journals Understanding the Abrupt Climate Change in the Mid-1970s from a Phase-Space Transform Perspective

2018 ◽  
Vol 57 (11) ◽  
pp. 2551-2560 ◽  
Author(s):  
Tanlong Dai ◽  
Wenjie Dong ◽  
Yan Guo ◽  
Tao Hong ◽  
Dong Ji ◽  
...  
Keyword(s):  
Climate Change ◽  
Phase Space ◽  
Coordinate System ◽  
Abrupt Change ◽  
The Arctic ◽  
Abrupt Climate Change ◽  
Coordinate Systems ◽  
Dimensional Phase Space ◽  
Increasing Trend ◽  
Space Coordinate

AbstractAbrupt climate change may cause heat, drought, and flood disasters. In this study, we find that many climate factors [e.g., the East Asian summer monsoon (EASM), the Arctic Oscillation (AO) and the Pacific decadal oscillation (PDO)] show a decadal-scale abrupt change in the 1970s. To analyze this phenomenon thoroughly, a new method of pedigree clustering combined with phase-space analysis (PCPSA) is used to establish two-dimensional phase-space coordinate systems of EASM–AO, EASM–PDO, and AO–PDO and the three-dimensional phase-space coordinate system of EASM–AO–PDO. By using the PCPSA method, it is found that all of the phase-space coordinate systems have a significant abrupt change in the mid-1970s, with a transition period, and the fit to the abrupt change of the phase-space coordinate system is better than 80%, which indicates excellent fit. By analyzing the correlation of EASM, AO, and PDO with sea level pressure (SLP) and sea surface temperature (SST), it is found that SLP has an obvious weakening trend in the high latitudes and an increasing trend in the tropics while SST has an increasing trend in most of the Southern Hemisphere waters and a minor weakening trend in the North Pacific Ocean waters between 30° and 40°N. Therefore, the abrupt climate change of the 1970s may well be a global abrupt change of the climatic system.

Trail of pore shape and temperature-sensitivity of poly(N-isopropylacrylamide) hydrogels before and after removing Brij-58 template and pore formation mechanism

RSC Advances ◽  
2014 ◽  
Vol 4 (65) ◽  
pp. 34460-34469 ◽  
Author(s):  
Wenjun Gao ◽  
Qingsong Zhang ◽  
Pengfei Liu ◽  
Shuhua Zhang ◽  
Juan Zhang ◽  
...  
Keyword(s):  
Formation Mechanism ◽  
Temperature Sensitivity ◽  
Pore Formation ◽  
Liquid Crystalline ◽  
Pore Shape ◽  
Brij 58 ◽  
Before And After ◽  
Thermosensitive Hydrogels ◽  
Porous Morphology

Modulate porous morphology and properties of thermosensitive hydrogels by containing different contents of lyotropic liquid crystalline.

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