3,074 research outputs found
Beyond domain-specific expertise: Neural signatures of face and spatial working memory in Baduk (Go game) experts
Generalized gravity model for human migration
The gravity model (GM) analogous to Newton's law of universal gravitation has
successfully described the flow between different spatial regions, such as
human migration, traffic flows, international economic trades, etc. This simple
but powerful approach relies only on the 'mass' factor represented by the scale
of the regions and the 'geometrical' factor represented by the geographical
distance. However, when the population has a subpopulation structure
distinguished by different attributes, the estimation of the flow solely from
the coarse-grained geographical factors in the GM causes the loss of
differential geographical information for each attribute. To exploit the full
information contained in the geographical information of subpopulation
structure, we generalize the GM for population flow by explicitly harnessing
the subpopulation properties characterized by both attributes and geography. As
a concrete example, we examine the marriage patterns between the bride and the
groom clans of Korea in the past. By exploiting more refined geographical and
clan information, our generalized GM properly describes the real data, a part
of which could not be explained by the conventional GM. Therefore, we would
like to emphasize the necessity of using our generalized version of the GM,
when the information on such nongeographical subpopulation structures is
available.Comment: 14 pages, 6 figures, 2 table
6.4 GHz Acoustic Sensor for In-situ Monitoring of AFM Tip Wear
This paper demonstrates an acoustic sensor that can resolve atomic force microscopy (AFM) tip blunting with a frequency sensitivity of 0.007%. The AFM tip is fabricated on a thin film piezoelectric aluminum nitride (AlN) membrane that is excited as a film bulk acoustic resonator (FBAR). We demonstrate that cutting 0.98 μm off of the tip apex results in a resonance frequency change of 0.4MHz at 6.387GHz. This work demonstrates the potential for in-situ monitoring of AFM tip wear
Progressive Processing of Continuous Range Queries in Hierarchical Wireless Sensor Networks
In this paper, we study the problem of processing continuous range queries in
a hierarchical wireless sensor network. Contrasted with the traditional
approach of building networks in a "flat" structure using sensor devices of the
same capability, the hierarchical approach deploys devices of higher capability
in a higher tier, i.e., a tier closer to the server. While query processing in
flat sensor networks has been widely studied, the study on query processing in
hierarchical sensor networks has been inadequate. In wireless sensor networks,
the main costs that should be considered are the energy for sending data and
the storage for storing queries. There is a trade-off between these two costs.
Based on this, we first propose a progressive processing method that
effectively processes a large number of continuous range queries in
hierarchical sensor networks. The proposed method uses the query merging
technique proposed by Xiang et al. as the basis and additionally considers the
trade-off between the two costs. More specifically, it works toward reducing
the storage cost at lower-tier nodes by merging more queries, and toward
reducing the energy cost at higher-tier nodes by merging fewer queries (thereby
reducing "false alarms"). We then present how to build a hierarchical sensor
network that is optimal with respect to the weighted sum of the two costs. It
allows for a cost-based systematic control of the trade-off based on the
relative importance between the storage and energy in a given network
environment and application. Experimental results show that the proposed method
achieves a near-optimal control between the storage and energy and reduces the
cost by 0.989~84.995 times compared with the cost achieved using the flat
(i.e., non-hierarchical) setup as in the work by Xiang et al.Comment: 41 pages, 20 figure
A Suspended Nanogap Formed by Field-Induced Atomically Sharp Tips
A sub-nanometer scale suspended gap (nanogap) defined by electric field-induced atomically sharp metallic tips is presented. A strong local electric field (\u3e109 V=m) across micro/nanomachined tips facing each other causes the metal ion migration in the form of dendrite-like growth at the cathode. The nanogap is fully isolated from the substrate eliminating growth mechanisms that involve substrate interactions. The proposed mechanism of ion transportation is verified using real-time imaging of the metal ion transportation using an in situ biasing in transmission electron microscope (TEM). The configuration of the micro/nanomachined suspended tips allows nanostructure growth of a wide variety of materials including metals, metal-oxides, and polymers. VC 2012 American Institute of Physics
Matchmaker, Matchmaker, Make Me a Match: Migration of Populations via Marriages in the Past
The study of human mobility is both of fundamental importance and of great
potential value. For example, it can be leveraged to facilitate efficient city
planning and improve prevention strategies when faced with epidemics. The
newfound wealth of rich sources of data---including banknote flows, mobile
phone records, and transportation data---has led to an explosion of attempts to
characterize modern human mobility. Unfortunately, the dearth of comparable
historical data makes it much more difficult to study human mobility patterns
from the past. In this paper, we present an analysis of long-term human
migration, which is important for processes such as urbanization and the spread
of ideas. We demonstrate that the data record from Korean family books (called
"jokbo") can be used to estimate migration patterns via marriages from the past
750 years. We apply two generative models of long-term human mobility to
quantify the relevance of geographical information to human marriage records in
the data, and we find that the wide variety in the geographical distributions
of the clans poses interesting challenges for the direct application of these
models. Using the different geographical distributions of clans, we quantify
the "ergodicity" of clans in terms of how widely and uniformly they have spread
across Korea, and we compare these results to those obtained using surname data
from the Czech Republic. To examine population flow in more detail, we also
construct and examine a population-flow network between regions. Based on the
correlation between ergodicity and migration in Korea, we identify two
different types of migration patterns: diffusive and convective. We expect the
analysis of diffusive versus convective effects in population flows to be
widely applicable to the study of mobility and migration patterns across
different cultures.Comment: 24 pages, 23 figures, 5 table
Intraosseous Hemangioma of the Middle Turbinate Misdiagnosed As a Nasal Polyp
Intraosseous hemangiomas account for 1% of all bone tumors and primarily originate from the vertebral column and skull bones. However, intraosseous hemangiomas of the nasal cavity are extremely rare. Here, we report a case of intraosseous hemangioma with a cavernous pattern arising from the middle turbinate that was preoperatively misdiagnosed as chronic rhinosinusitis with polyps. Except for nasal obstruction, there were no specific rhinologic symptoms. The tumor was excised en bloc by the endoscopic endonasal approach without preoperative embolization
A Novel Batch-Processing Method for Accurate Crystallographic Axis Alignment
A new method for the accurate alignment of lithographically-defined patterns to the crystallographic axes of substrates is presented. We provide a lower (worst-case) limit of the achievable high aspect ratio using anisotropic wet chemical silicon etch for deep trenches. The method uses the fact that the intensity of light reflected from two sets of gratings, one on the photomask and the other on the substrate, is a sharp function of their relative angular misalignment. By using pre-etched gratings on the substrate formed by wet anisotropic etching, alignment accuracies better than 50 millidegrees with respect to silicon crystallographic axes have been demonstrated. Two types of microstructures—trenches with an aspect ratio \u3e90:1 and silicon nanowires with widthsfacets—have been fabricated using i-line lithography to illustrate some applications of this alignment method. This all-optical method is readily applicable to industry-standard optical lithography and avoids the need for any individualized process steps, enabling cost-effective micro/nanostructure manufacturing
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