4,187 research outputs found
Practical Fine-grained Privilege Separation in Multithreaded Applications
An inherent security limitation with the classic multithreaded programming
model is that all the threads share the same address space and, therefore, are
implicitly assumed to be mutually trusted. This assumption, however, does not
take into consideration of many modern multithreaded applications that involve
multiple principals which do not fully trust each other. It remains challenging
to retrofit the classic multithreaded programming model so that the security
and privilege separation in multi-principal applications can be resolved.
This paper proposes ARBITER, a run-time system and a set of security
primitives, aimed at fine-grained and data-centric privilege separation in
multithreaded applications. While enforcing effective isolation among
principals, ARBITER still allows flexible sharing and communication between
threads so that the multithreaded programming paradigm can be preserved. To
realize controlled sharing in a fine-grained manner, we created a novel
abstraction named ARBITER Secure Memory Segment (ASMS) and corresponding OS
support. Programmers express security policies by labeling data and principals
via ARBITER's API following a unified model. We ported a widely-used, in-memory
database application (memcached) to ARBITER system, changing only around 100
LOC. Experiments indicate that only an average runtime overhead of 5.6% is
induced to this security enhanced version of application
Computer-based tracking, analysis, and visualization of linguistically significant nonmanual events in American Sign Language (ASL)
Our linguistically annotated American Sign Language (ASL) corpora have formed a basis for research to automate detection by
computer of essential linguistic information conveyed through facial expressions and head movements. We have tracked head position
and facial deformations, and used computational learning to discern specific grammatical markings. Our ability to detect, identify, and
temporally localize the occurrence of such markings in ASL videos has recently been improved by incorporation of (1) new techniques
for deformable model-based 3D tracking of head position and facial expressions, which provide significantly better tracking accuracy
and recover quickly from temporary loss of track due to occlusion; and (2) a computational learning approach incorporating 2-level
Conditional Random Fields (CRFs), suited to the multi-scale spatio-temporal characteristics of the data, which analyses not only
low-level appearance characteristics, but also the patterns that enable identification of significant gestural components, such as
periodic head movements and raised or lowered eyebrows. Here we summarize our linguistically motivated computational approach
and the results for detection and recognition of nonmanual grammatical markings; demonstrate our data visualizations, and discuss the
relevance for linguistic research; and describe work underway to enable such visualizations to be produced over large corpora and
shared publicly on the Web
A Generative Adversarial Approach for Zero-Shot Learning from Noisy Texts
Most existing zero-shot learning methods consider the problem as a visual
semantic embedding one. Given the demonstrated capability of Generative
Adversarial Networks(GANs) to generate images, we instead leverage GANs to
imagine unseen categories from text descriptions and hence recognize novel
classes with no examples being seen. Specifically, we propose a simple yet
effective generative model that takes as input noisy text descriptions about an
unseen class (e.g.Wikipedia articles) and generates synthesized visual features
for this class. With added pseudo data, zero-shot learning is naturally
converted to a traditional classification problem. Additionally, to preserve
the inter-class discrimination of the generated features, a visual pivot
regularization is proposed as an explicit supervision. Unlike previous methods
using complex engineered regularizers, our approach can suppress the noise well
without additional regularization. Empirically, we show that our method
consistently outperforms the state of the art on the largest available
benchmarks on Text-based Zero-shot Learning.Comment: To appear in CVPR1
Analytical description of high-aperture STED resolution with 0-2 vortex phase modulation
Stimulated emission depletion (STED) can achieve optical super-resolution,
with the optical diffraction limit broken by the suppression on the periphery
of the fluorescent focal spot. Previously, it is generally experimentally
accepted that there exists an inverse square root relationship with the STED
power and the resolution, yet without strict analytical description. In this
paper, we have analytically verified the relationship between the STED power
and the achievable resolution from vector optical theory for the widely used
0-2 vortex phase modulation. Electromagnetic fields of the focal region of
a high numerical aperture objective are calculated and approximated into
polynomials, and analytical expression of resolution as a function of the STED
intensity has been derived. As a result, the resolution can be estimated
directly from the measurement of the saturation power of the dye and the STED
power applied.Comment: (19 pages
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