Microfluidic fabrication of water-in-water (w/w) jets and emulsions

We demonstrate the generation of water-in-water (w/w) jets and emulsions by combining droplet microfluidics and aqueous two-phase systems (ATPS). The application of ATPS in microfluidics has been hampered by the low interfacial tension between typical aqueous phases. The low tension makes it difficult to form w/w droplets with conventional droplet microfluidic approaches. We show that by mechanically perturbing a stable w/w jet, w/w emulsions can be prepared in a controlled and reproducible fashion. We also characterize the encapsulation ability of w/w emulsions and demonstrate that their encapsulation efficiency can be significantly enhanced by inducing formation of precipitates and gels at the w/w interfaces. Our work suggests a biologically and environmentally friendly platform for droplet microfluidics and establishes the potential of w/w droplet microfluidics for encapsulation-related applications.     

Correspondence of document file structures to discipline structures

Online data bases might be more valuable to users if their structures more closely matched those of the disciplines represented by the data bases. To explore this concept, a structure for the field of tropical medicine was derived from the interrelationships of signs and symptoms of 37 tropical diseases. A similar structure was derived for the interrelationships of sign and symptom index terms applied to articles on these topical diseases in the MEDLINE data base. The poor correlation of the two structures led to the suggestion that rigorous indexing of articles with sign and symptom index terms or check tags would enhance the usefulness of the data base. Similar studies could be envisioned for other disciplines and data bases.     

Essential gyrators and reciprocity in junction structures

This paper proposes an extended definition of reciprocity for a multiport junction structure based on the concept of essential gyrator coupling. Two theorems are given for junction structures containing gyrators and an algorithm is presented for identifying essential gyrators. The results are useful both theoretically and for designing efficient computation procedures for junction structures.     

Travelling-wave-induced instability of structures

The effect of transmission time of propagating disturbances on the dynamic instability of structures is discussed in this paper. Through a parametric study it is shown that for certain values of transmission time and wave frequency parameters, the structure may become dynamically unstable. An example is worked out, and graphical results depicting the regions of instability are presented.     

Tuning bubbly structures in microchannels

Foams have many useful applications that arise from the structure and size distribution of the bubbles within them. Microfluidics allows for the rapid formation of uniform bubbles, where bubble size and volume fraction are functions of the input gas pressure, liquid flow rate, and device geometry. After formation, the microchannel confines the bubbles and determines the resulting foam structure. Bubbly structures can vary from a single row ("dripping"), to multiple rows ("alternating"), to densely packed bubbles ("bamboo" and dry foams). We show that each configuration arises in a distinct region of the operating space defined by bubble volume and volume fraction. We describe the boundaries between these regions using geometric arguments and show that the boundaries are functions of the channel aspect ratio. We compare these geometric arguments with foam structures observed in experiments using flow-focusing, T-junction, and co-flow designs to generate stable nitrogen bubbles in aqueous surfactant solution and stable droplets in oil containing dissolved surfactant. The outcome of this work is a set of design parameters that can be used to achieve desired foam structures as a function of device geometry and experimental control parameters.     

港口供应链概念及结构研究综述

为了解决港口的竞争,供应链思想被应用到港口研究中,港口供应链得到了学者们的关注。阐述了港口供应链的产生的背景,综述了学者们对港口供应链概念和港口供应链结构的理解,为港口供应链应用研究奠定理论基础,并提出未来港口供应链的研究方向。     

Correlating the electronic structures of metallic/semiconducting MoTe2 interface to its atomic structures

Contact interface properties are important in determining the performances of devices that are based on atomically thin two-dimensional (2D) materials, especially for those with short channels. Understanding the contact interface is therefore important to design better devices. Herein, we use scanning transmission electron microscopy, electron energy loss spectroscopy, and first-principles calculations to reveal the electronic structures within the metallic (1T^′)-semiconducting (2H) MoTe₂ coplanar phase boundary across a wide spectral range and correlate its properties to atomic structures. We find that the 2H-MoTe₂ excitonic peaks cross the phase boundary into the 1T^′ phase within a range of approximately 150 nm. The 1T^′-MoTe₂ crystal field can penetrate the boundary and extend into the 2H phase by approximately two unit-cells. The plasmonic oscillations exhibit strong angle dependence, that is a red-shift of π+σ (approximately 0.3–1.2 eV) occurs within 4 nm at 1T^′/2H-MoTe₂ boundaries with large tilt angles, but there is no shift at zero-tilted boundaries. These atomic-scale measurements reveal the structure–property relationships of the 1T^′/2H-MoTe₂ boundary, providing useful information for phase boundary engineering and device development based on 2D materials.     

基于位移的结构抗震设计方法研究

近几年来,直接以位移为设计参数的抗震设计方法越来越受到重视并且得到了很大的发展,逐渐成为了实现基于性能抗震设计思想的一条有效途径.本文将对基于位移的结构抗震设计方法进行评述.     

Discovering authorities and hubs in different topological web graph structures

This research is a part of ongoing study to better understand citation analysis on the Web. It builds on Kleinberg's research (J. Kleinberg, R. Kumar, P. Raghavan, P. Rajagopalan, A. Tomkins, Invited survey at the International Conference on Combinatorics and Computing, 1999) that hyperlinks between web pages constitute a web graph structure and tries to classify different web graphs in the new coordinate space: out-degree, in-degree. The out-degree coordinate is defined as the number of outgoing web pages from a given web page. The in-degree coordinate is the number of web pages that point to a given web page. In this new coordinate space a metric is built to classify how close or far are different web graphs. Kleinberg's web algorithm (J. Kleinberg, Proceedings of the ACM-SIAM Symposium on Discrete Algorithms, 1998, pp. 668–677) on discovering “hub web pages” and “authorities web pages” is applied in this new coordinate space. Some very uncommon phenomenon has been discovered and new interesting results interpreted. This study does not look at enhancing web retrieval by adding context information. It only considers web hyperlinks as a source to analyze citations on the web. The author believes that understanding the underlying web page as a graph will help design better web algorithms, enhance retrieval and web performance, and recommends using graphs as a part of visual aid for search engine designers.     

Data compression producing structures—Discoveries

This paper describes a formalism to construct some kinds of algorithms useful to represent one structure about a set of data. It proves that if we do not take into account cost considerations of one algorithm, one can partialy replace the memory by an algorithm. It also proves that the remaining memory part is independant of the construction process. It then evaluate the affects of algorithms representation cost and gives the resulting memory gain obtained in two particular examples.     

Optimal complexity of deployable compressive structures

The usual use of fractals involves self-similar geometrical objects to fill a space, where the self-similar iterations may continue ad infinitum. This is the first paper to propose the use of self-similar mechanical objects that fill an alloted space, while achieving an invariance property as the self-similar iterations continue (e.g. invariant strength). Moreover, for compressive loads, this paper shows how to achieve minimal mass and invariant strength from self-similar structures. The topology optimization procedure uses self-similar iteration until minimal mass is achieved, and this problem is completely solved, with global optimal solutions given in closed form. The optimal topology remains independent of the magnitude of the load. Mass is minimized subject to yield and/or buckling constraints. Formulas are also given to optimize the complexity of the structure, and the optimal complexity turns out to be finite. That is, a continuum is never the optimal structural for a compressive load under any constraints on the physical dimension (diameter). After each additional self-similar iteration, the number of bars and strings increase, but, for a certain choice of unit topology shown, the total mass of bars and strings decreases. For certain structures, the string mass monotonically increases with iteration, while the bar mass monotonically reduces, leading to minimal total mass in a finite number of iterations, and hence a finite optimal complexity for the structure. The number of iterations required to achieve minimal mass is given explicitly in closed form by a formula relating the chosen unit geometry and the material properties. It runs out that the optimal structures produced by our theory fall in the category of structures we call tensegrity. Hence our self-similar algorithms can generate tensegrity fractals.