3,058 research outputs found
Relation between directed polymers in random media and random bond dimer models
We reassess the relation between classical lattice dimer models and the
continuum elastic description of a lattice of fluctuating polymers. In the
absence of randomness we determine the density and line tension of the polymers
in terms of the bond weights of hard-core dimers on the square and the
hexagonal lattice. For the latter, we demonstrate the equivalence of the
canonical ensemble for the dimer model and the grand-canonical description for
polymers by performing explicitly the continuum limit. Using this equivalence
for the random bond dimer model on a square lattice, we resolve a previously
observed discrepancy between numerical results for the random dimer model and a
replica approach for polymers in random media. Further potential applications
of the equivalence are briefly discussed.Comment: 6 pages, 3 figure
In Situ Structure Characterization in Slot-Die-Printed All-Polymer Solar Cells with Efficiency Over 9%
Herein, high-performance printed all-polymer solar cells (all-PSCs) based on a bulk-heterojunction (BHJ) blend film are demonstrated using PTzBI as the donor and N2200 as the acceptor. A slot-die process is used to prepare the BHJ blend, which is a cost-effective, high-throughput approach to achieve large-area photovoltaic devices. The real-time crystallization of polymers in the film drying process is investigated by in situ grazing incidence wide-angle X-ray scattering characterization. Printing is found to significantly improve the crystallinity of the polymer blend in comparison with spin coating. Moreover, printing with 1,8-diiodooctane as the solvent additive enhances the polymer aggregation and crystallization during solvent evaporation, eventually leading to multi-length-scale phase separation, with PTzBI-rich domains in-between the N2200 crystalline fibers. This unique morphology achieved by printing fabrication results in an impressively high power conversion efficiency of 9.10%, which is the highest efficiency reported for printed all-PSCs. These findings provide important guidelines for controlling film drying dynamics for processing all-PSCs
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Mixed Analog-Digital (MAD) Converters for High Power Density DC-DC Conversions
Conventional switched-mode power supplies (SMPSs) have intrinsic instantaneous power pulsation at the switching frequency thus require bulky filters. To improve the power density, this paper proposes a concept named the Mixed Analog-Digital (MAD) which can be applied as DC-DC converters. By inserting an analog voltage component between the load and source, the output voltage naturally has much smaller fluctuation thereby much smaller passive filter is required. Simulations and experiments validate that the proposed MAD concept can be applied as DC-DC converters to significantly increase the power density
A new topological aspect of the arbitrary dimensional topological defects
We present a new generalized topological current in terms of the order
parameter field to describe the arbitrary dimensional topological
defects. By virtue of the -mapping method, we show that the topological
defects are generated from the zero points of the order parameter field , and the topological charges of these topological defects are topological
quantized in terms of the Hopf indices and Brouwer degrees of -mapping
under the condition that the Jacobian . When , it is shown that there exist the crucial case of branch process.
Based on the implicit function theorem and the Taylor expansion, we detail the
bifurcation of generalized topological current and find different directions of
the bifurcation. The arbitrary dimensional topological defects are found
splitting or merging at the degenerate point of field function but
the total charge of the topological defects is still unchanged.Comment: 24 pages, 10 figures, Revte
NaMemo: Enhancing Lecturers' Interpersonal Competence of Remembering Students' Names
Addressing students by their names helps a teacher to start building rapport
with students and thus facilitates their classroom participation. However, this
basic yet effective skill has become rather challenging for university
lecturers, who have to handle large-sized (sometimes exceeding 100) groups in
their daily teaching. To enhance lecturers' competence in delivering
interpersonal interaction, we developed NaMemo, a real-time name-indicating
system based on a dedicated face-recognition pipeline. This paper presents the
system design, the pilot feasibility test, and our plan for the following
study, which aims to evaluate NaMemo's impacts on learning and teaching, as
well as to probe design implications including privacy considerations.Comment: DIS '20 Companio
HandPainter – 3D sketching in VR with hand-based physical proxy
3D sketching in virtual reality (VR) enables users to create 3D virtual objects intuitively and immersively. However, previous studies showed that mid-air drawing may lead to inaccurate sketches. To address this issue, we propose to use one hand as a canvas proxy and the index finger of the other hand as a 3D pen. To this end, we first perform a formative study to compare two-handed interaction with tablet-pen interaction for VR sketching. Based on the findings of this study, we design HandPainter, a VR sketching system which focuses on the direct use of two hands for 3D sketching without requesting any tablet, pen, or VR controller. Our implementation is based on a pair of VR gloves, which provide hand tracking and gesture capture. We devise a set of intuitive gestures to control various functionalities required during 3D sketching, such as canvas panning and drawing positioning. We show the effectiveness of HandPainter by presenting a number of sketching results and discussing the outcomes of a user study-based comparison with mid-air drawing and tablet-based sketching tools
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