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1.
During the solidification of a liquid containing insoluble particles, the particles can be instantaneously engulfed, or continuously
pushed, or pushed and subsequently engulfed. A critical velocity for the pushing-engulfment transition is observed experimentally.
Most models proposed to date ignore the complications arising from the liquid convection ahead of the solid-liquid interface.
They simply solve the balance between the attractive drag force exercised by the liquid on the particle and the repulsive
interfacial force. This work is an effort to calculate analytically the lift forces (Saffman and Magnus forces) under certain
assumptions regarding the nature of fluid flow ahead of the solid/liquid interface. This makes possible the quantitative evaluation
of the three experimentally observed regimes occurring during particle-interface interaction: (1) at low convection—no effect
on the critical velocity for the particle engulfment transition; (2) at intermediate convection—increased critical velocity;
(3) at high convection—no particle-interface interaction.
The model was applied to evaluate the gravity level required for microgravity experimental work on particle pushing where
the effect of liquid convection during solidification is negligible. This is necessary to validate existing theoretical models
that do not take into account fluid flow parallel to the solidification interface. 相似文献
2.
Abstract The use of information technology (IT) in developing countries has attracted a considerable amount of attention in recent years. However, the research in this area is largely fragmented, and there is a need to consolidate efforts in order to make research more effective. Theory can provide a basis for this consolidation process by allowing communication between different researchers and also between researchers and practitioners. The primary objective of this paper is to describe aspects of the state of existing theory in the field of IT in developing countries, and discuss possible research directions for the future. A total of 199 articles were analyzed to describe existing research themes, and future directions are discussed in terms of level of analysis, research methods, and research reports. 相似文献
3.
Venkata Sundeep Seesala Santanu Dhara 《Journal of the American Ceramic Society》2022,105(8):5131-5139
For successful osseointegration of load-bearing implants, an improved bone–implant contact area through a trabecular porous surface resulting in minimized stress shielding effect is highly desirable. We propose a novel strategy of green net shaping a ceramic dough, combined with a reticular foam replica method and gradient coating, to fabricate biomimetic porosity in a customizable ceramic dental implant for the first time. About 85 vol% porosity and 300–600-μm pore size were evident in microCT and electron microscopy of the sintered samples, suitable for bone ingrowth. Excellent integrity at the interface along with homogeneous distribution of secondary alumina phase in zirconia matrix was achieved, despite the difference in the green state powder loading between the dough and the slurry. 相似文献
4.
5.
In this article we provide a theoretically informed empirical analysis of the introduction and use of information and communication technology (ICT) within the primary health care (PHC) sector of Mozambique. The theoretical lens for this analysis is developed from Manuel Castells' (1996, 1997, 2001) ideas on the network society and counter domination. These ideas help us to conceptualize the communicative action required to strengthen the PHC sector as a “counter network,” which has the normative aim to strengthen the health information system (HIS) as a key strategy to improve health care delivery. Taking an informational perspective, the role of communication is highlighted as playing an important constitutive basis in the strengthening of this network. These conceptual ideas are applied to the empirical analysis of an ongoing project (the Health Information Systems Programme or HISP), and to analyze some key constraints and strategies for strengthening these networks. This study makes key contributions to both the theoretical and practical domains of HIS in developing countries. © 2005 Wiley Periodicals, Inc. 相似文献
6.
Murodillo Abdusamadovich Latifov Sundeep Sahay 《Information Technology for Development》2013,19(3):215-229
Health information systems (HIS) in developing countries are mainly characterized as being “data led,” with vast amounts of data being routinely collected, but with limited evidence of them being used “for action.” While past research and practice have made significant progress in understanding issues contributing to this situation, limited advancement has been made as to how to redress the situation. Further, infrastructure issues impeding data use have also not been significantly highlighted in existing research. Drawing on a longitudinal case of the design, development and implementation of HIS in Tajikistan, we argue that a reason for this weak progress has been the rather narrow focus on technology, ignoring the broader issues that influence its uptake and use. We explore this through an “infrastructure” lens to enable a more holistic perspective to understand complex socio-technical networks with a multiplicity of interests, actors and technologies in play which need to be aligned. A key contribution of this paper is the identification of facets of a health information infrastructure which helps to identify both the constraints and opportunities in making a transition from a data-led to an action-led system. 相似文献
7.
8.
Sundeep Sahay 《Information Technology for Development》2016,22(1):168-176
As social scientists engaged in Information Technologies for Development (IT4D), a question we need to necessarily engage with is “are we building a better world with Information and Communication Technologies (ICTs)?” This question, first posed by Professor Geoff Walsham in the IS field, was the topic of my plenary discussion at the IFIP 9.4 meeting in Jamaica 2014, and had now been further developed to this “view from practice” paper for this journal. A first step in this paper has been the reformulation of the question which Professor Walsham raised: “What distortions and obstacles are created by the historical, material, and institutional conditions, and how these shape our efforts of ICTs creating a better world?” This reformulation is done to bring in more explicitly the political dimension into the question, and to nuance the technological deterministic argument implied in the question of technology (always) creating a better world. Taking an empirical example of an ICT intervention from the public health sector in India, deliberately chosen to emphasize distortions typically seen is similar Information and Communication Technologies for Development (ICT4D) projects, the analysis focuses on understanding the conditions of distortions, why they occur, and what can be done differently to contribute to our notion of a better world. 相似文献
9.
Electrocatalysts: Guided Evolution of Bulk Metallic Glass Nanostructures: A Platform for Designing 3D Electrocatalytic Surfaces (Adv. Mater. 10/2016) 下载免费PDF全文
Gustavo Doubek Ryan C. Sekol Jinyang Li Won‐Hee Ryu Forrest S. Gittleson Siamak Nejati Eric Moy Candy Reid Marcelo Carmo Marcelo Linardi Punnathat Bordeenithikasem Emily Kinser Yanhui Liu Xiao Tong Chinedum O. Osuji Jan Schroers Sundeep Mukherjee André D. Taylor 《Advanced materials (Deerfield Beach, Fla.)》2016,28(10):1902-1902
10.
Hema Bhandari Vineet Bansal Veena Choudhary Sundeep K Dhawan 《Polymer International》2009,58(5):489-502
BACKGROUND: Poly(1‐amino‐2‐naphthol‐4‐sulfonic acid) and its copolymers with aniline are a new class of conducting polymers which can acquire intrinsic protonic doping ability, leading to the formation of highly soluble self‐doped homopolymers and copolymers. Free ? OH and ? NH2 groups in the polymer chain can combine with other functional groups that could be present in protective paints which can thus be successfully used as antistatic materials. RESULTS: This paper reports the formation of nanotubes of polyaniline on carrying out oxidative polymerization of aniline in the presence of 1‐amino‐2‐naphthol‐4‐sulfonic acid (ANSA) in p‐toluenesulfonic acid (PTSA) as an external dopant. The presence of ? SO3H groups in the ANSA comonomer allows the copolymer to acquire intrinsic protonic doping ability. The polymerization mechanism was investigated by analysing the 1H NMR, 13C NMR, Fourier transform infrared and X‐ray photoelectron spectra of the copolymers and homopolymers, which revealed the involvement of ? OH/? NH2 in the reaction mechanism. Scanning and transmission electron microscopy showed how the reaction route and the presence of a dopant can affect the morphology and size of the polymers. Static decay time measurements were also carried out on conducting copolymer films prepared by blending of 1 wt% of copolymers of ANSA and aniline with low‐density polyethylene (LDPE) which showed a static decay time of 0.1 to 0.31 s on dissipating a charge from 5000 to 500 V. CONCLUSION: Copolymers of ANSA with aniline were synthesized in different reaction media, leading to the formation of nanotubes and nanoparticles of copolymer. Blends of 1 wt% of PTSA‐ and self‐doped copolymers of ANSA and aniline with LDPE can be formulated into films with effective antistatic properties. Copyright © 2009 Society of Chemical Industry 相似文献