539 research outputs found
Graph Regularized Tensor Sparse Coding for Image Representation
Sparse coding (SC) is an unsupervised learning scheme that has received an
increasing amount of interests in recent years. However, conventional SC
vectorizes the input images, which destructs the intrinsic spatial structures
of the images. In this paper, we propose a novel graph regularized tensor
sparse coding (GTSC) for image representation. GTSC preserves the local
proximity of elementary structures in the image by adopting the newly proposed
tubal-tensor representation. Simultaneously, it considers the intrinsic
geometric properties by imposing graph regularization that has been
successfully applied to uncover the geometric distribution for the image data.
Moreover, the returned sparse representations by GTSC have better physical
explanations as the key operation (i.e., circular convolution) in the
tubal-tensor model preserves the shifting invariance property. Experimental
results on image clustering demonstrate the effectiveness of the proposed
scheme
Linear electro-optic effect due to the built-in electric field in InGaN/GaN quantum wells
A strong piezoelectric effect and large lattice mismatch allow one to incorporate high built-in electric fields in InGaN/GaN quantum wells. This letter examines the implications of these fields on the absorption spectra and refractive index changes induced by an external perpendicular electric field. We find that InGaN/GaN quantum wells show linear electro-optic effect due to quantum confined Stark effect. Our results suggest application of InGaN/GaN quantum wells in Mach–Zehnder type modulators and in electroabsorption modulators in the blue light region. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70668/2/APPLAB-75-13-1932-1.pd
Nonequilibrium distribution in quantum dots lasers and influence on laser spectral output
Self-assembled quantum dot structures used for lasers have shown significant variation in the dot size distribution. In this article, we address the issues related to carrier occupation of these dots as a function of temperature in the absence and presence of lasing. The carrier distributions among different dots are derived in this paper through detailed balance. It is found that at low temperatures the carrier occupation is highly nonequilibrium but with increased temperature it tends towards an equilibrium distribution. Based on this distribution, the threshold current density versus temperature has been calculated. Multimode operation of lasers at different injection levels and temperatures is also examined. The theoretical results are compared with published experimental results. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69377/2/JAPIAU-85-10-7438-1.pd
Shallow depth of the tunnel excavation response research based on CRD method
AbstractMost bids of Dalian Metro are carried out with shallow tunneling method. However, for the section of Xianggong Street Station of Line 2, the geologic condition, which is mainly composed of strong-weathered rock, is so poor that it brings great difficulties in tunnel excavation. To solve the problem of stability of surrounding rock, numerical simulation and field monitoring are used to analysis the displacement field, stress field and plastic zone in every step of construction which use CRD method and also though the contrast of both consequence, The safety of the construction process has been studied and analyzed. The result not only has important guiding meaning after the construction of the tunnel, but also provides the reference for the design and construction of similar projects
Body-Part Joint Detection and Association via Extended Object Representation
The detection of human body and its related parts (e.g., face, head or hands)
have been intensively studied and greatly improved since the breakthrough of
deep CNNs. However, most of these detectors are trained independently, making
it a challenging task to associate detected body parts with people. This paper
focuses on the problem of joint detection of human body and its corresponding
parts. Specifically, we propose a novel extended object representation that
integrates the center location offsets of body or its parts, and construct a
dense single-stage anchor-based Body-Part Joint Detector (BPJDet). Body-part
associations in BPJDet are embedded into the unified representation which
contains both the semantic and geometric information. Therefore, BPJDet does
not suffer from error-prone association post-matching, and has a better
accuracy-speed trade-off. Furthermore, BPJDet can be seamlessly generalized to
jointly detect any body part. To verify the effectiveness and superiority of
our method, we conduct extensive experiments on the CityPersons, CrowdHuman and
BodyHands datasets. The proposed BPJDet detector achieves state-of-the-art
association performance on these three benchmarks while maintains high accuracy
of detection. Code is in https://github.com/hnuzhy/BPJDet.Comment: accepted by ICME202
High power laser semiconductor interactions: A Monte Carlo study for silicon
In this article, we use Monte Carlo methods to study the interaction of high power laser pulses with electrons in the conduction band of semiconductors. The laser field is represented by a sinusoidal electric field which tends to cause an oscillatory motion in the electrons. The scattering of electrons from the lattice force the electrons to lose phase coherence with the field. The approach is applied to silicon. We use the approach to examine the carrier energy distribution and material breakdown due to the transfer of energy from the laser to the electrons followed by impact ionization. The impact ionization coefficient, α, and its dependence on the laser frequency and field strength is examined and compared to the values in a dc field. In general, the ac value is smaller than the dc value, but at low frequencies and high field strengths, the ac impact ionization coefficient approaches the dc value at the same rms field value. The importance of collisions in the energy transfer process is elucidated. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70199/2/JAPIAU-81-4-1807-1.pd
SSDA-YOLO: Semi-supervised Domain Adaptive YOLO for Cross-Domain Object Detection
Domain adaptive object detection (DAOD) aims to alleviate transfer
performance degradation caused by the cross-domain discrepancy. However, most
existing DAOD methods are dominated by outdated and computationally intensive
two-stage Faster R-CNN, which is not the first choice for industrial
applications. In this paper, we propose a novel semi-supervised domain adaptive
YOLO (SSDA-YOLO) based method to improve cross-domain detection performance by
integrating the compact one-stage stronger detector YOLOv5 with domain
adaptation. Specifically, we adapt the knowledge distillation framework with
the Mean Teacher model to assist the student model in obtaining instance-level
features of the unlabeled target domain. We also utilize the scene style
transfer to cross-generate pseudo images in different domains for remedying
image-level differences. In addition, an intuitive consistency loss is proposed
to further align cross-domain predictions. We evaluate SSDA-YOLO on public
benchmarks including PascalVOC, Clipart1k, Cityscapes, and Foggy Cityscapes.
Moreover, to verify its generalization, we conduct experiments on yawning
detection datasets collected from various real classrooms. The results show
considerable improvements of our method in these DAOD tasks, which reveals both
the effectiveness of proposed adaptive modules and the urgency of applying more
advanced detectors in DAOD. Our code is available on
\url{https://github.com/hnuzhy/SSDA-YOLO}.Comment: submitted to CVI
DirectMHP: Direct 2D Multi-Person Head Pose Estimation with Full-range Angles
Existing head pose estimation (HPE) mainly focuses on single person with
pre-detected frontal heads, which limits their applications in real complex
scenarios with multi-persons. We argue that these single HPE methods are
fragile and inefficient for Multi-Person Head Pose Estimation (MPHPE) since
they rely on the separately trained face detector that cannot generalize well
to full viewpoints, especially for heads with invisible face areas. In this
paper, we focus on the full-range MPHPE problem, and propose a direct
end-to-end simple baseline named DirectMHP. Due to the lack of datasets
applicable to the full-range MPHPE, we firstly construct two benchmarks by
extracting ground-truth labels for head detection and head orientation from
public datasets AGORA and CMU Panoptic. They are rather challenging for having
many truncated, occluded, tiny and unevenly illuminated human heads. Then, we
design a novel end-to-end trainable one-stage network architecture by joint
regressing locations and orientations of multi-head to address the MPHPE
problem. Specifically, we regard pose as an auxiliary attribute of the head,
and append it after the traditional object prediction. Arbitrary pose
representation such as Euler angles is acceptable by this flexible design.
Then, we jointly optimize these two tasks by sharing features and utilizing
appropriate multiple losses. In this way, our method can implicitly benefit
from more surroundings to improve HPE accuracy while maintaining head detection
performance. We present comprehensive comparisons with state-of-the-art single
HPE methods on public benchmarks, as well as superior baseline results on our
constructed MPHPE datasets. Datasets and code are released in
https://github.com/hnuzhy/DirectMHP.Comment: 13 page
Free carrier absorption as a probe of carrier dynamics: A Monte Carlo based study for silicon
The Monte Carlo method normally used for transport studies in semiconductors is extended and used to study free carrier absorption of subband gap radiation in semiconductors. The approach is applied to nn-type silicon where we find very good agreement with experimental results and calculations based on quantum electrodynamics. This method also allows us to study free carrier absorption in semiconductors with a dc bias. With a dc bias, the absorption coefficient has a strong dependence on the polarization of the ac field. We show that the absorption coefficient can be directly related to the carrier temperature as well as the momentum and energy relaxation times. Thus important carrier dynamics information can be obtained from free carrier absorption measurements in the presence of a dc field. © 1997 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69768/2/APPLAB-70-14-1834-1.pd
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