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Hao Chen

Publications and source records attributed to Hao Chen.

At least 1,423 records · Page 79Linked to original sources

3D Deeply Supervised Network for Automatic Liver Segmentation from CT Volumes

Automatic liver segmentation from CT volumes is a crucial prerequisite yet challenging task for computer-aided hepatic disease diagnosis and treatment. In this paper, we present a novel 3D deeply supervised network (3D DSN) to address this challenging task. The proposed 3D DSN takes advantage of a fully convolutional architecture which performs efficient end-to-end learning and inference. More importantly, we introduce a deep supervision mechanism during the learning process to combat potential optimization difficulties, and thus the model can acquire a much faster convergence rate and more powerful discrimination capability. On top of the high-quality score map produced by the 3D DSN, a conditional random field model is further employed to obtain refined segmentation results. We evaluated our framework on the public MICCAI-SLiver07 dataset. Extensive experiments demonstrated that our method achieves competitive segmentation results to state-of-the-art approaches with a much faster processing speed.

cs.CV↗

Measurement device independent quantum key distribution over 404 km optical fibre

Quantum key distribution (QKD) can provide unconditional secure communication between two distant parties. Although the significance of QKD is undisputed, its feasibility has been questioned because of certain limitations in the practical application of real-life QKD systems. It is a common belief the lack of perfect single-photon source and the existence of detection loss will handicap the feasibility of QKD by creating security loopholes and distance limitations. The measurement device independent QKD (MDIQKD) with decoy-state method removes the security threats from both the imperfect single-photon source and the detection loss. Lengthening the distance and improving the key rate of QKD with such a superior method is thus the central issue in the practical application of QKD. Here, we report the results of MDIQKD over 404 km of ultralow-loss optical fibre and 311 km of standard optical fibre by employing an optimized four-intensity decoy-state method. This record-breaking implementation of MDIQKD method not only provides a new distance record for both MDIQKD and all types of QKD systems, more significantly, it achieves a distance that the traditional BB84 QKD would not be able to achieve with the same detection devices even with ideal single-phone sources. For the first time, our work demonstrates that with the MDIQKD method, imperfect devices can achieve better results than what ideal sources could have achieved. This work represents a significant step towards proving and developing a feasible long-distance QKD.

quant-ph↗

Ball packings with high chromatic numbers from strongly regular graphs

Inspired by Bondarenko's counter-example to Borsuk's conjecture, we notice some strongly regular graphs that provide examples of ball packings whose chromatic numbers are significantly higher than the dimensions. In particular, from generalized quadrangles we obtain unit ball packings in dimension $q^3-q^2+q$ with chromatic number $q^3+1$, where $q$ is a prime power. This improves the previous lower bound for the chromatic number of ball packings.

math.CO↗

A weighted edge-count two-sample test for multivariate and object data

Two-sample tests for multivariate data and non-Euclidean data are widely used in many fields. Parametric tests are mostly restrained to certain types of data that meets the assumptions of the parametric models. In this paper, we study a nonparametric testing procedure that utilizes graphs representing the similarity among observations. It can be applied to any data types as long as an informative similarity measure on the sample space can be defined. The classic test based on a similarity graph has a problem when the two sample sizes are different. We solve the problem by applying appropriate weights to different components of the classic test statistic. The new test exhibits substantial power gains in simulation studies. Its asymptotic permutation null distribution is derived and shown to work well under finite samples, facilitating its application to large datasets. The new test is illustrated through an analysis on a real dataset of network data.

stat.ME↗

DCAN: Deep Contour-Aware Networks for Accurate Gland Segmentation

The morphology of glands has been used routinely by pathologists to assess the malignancy degree of adenocarcinomas. Accurate segmentation of glands from histology images is a crucial step to obtain reliable morphological statistics for quantitative diagnosis. In this paper, we proposed an efficient deep contour-aware network (DCAN) to solve this challenging problem under a unified multi-task learning framework. In the proposed network, multi-level contextual features from the hierarchical architecture are explored with auxiliary supervision for accurate gland segmentation. When incorporated with multi-task regularization during the training, the discriminative capability of intermediate features can be further improved. Moreover, our network can not only output accurate probability maps of glands, but also depict clear contours simultaneously for separating clustered objects, which further boosts the gland segmentation performance. This unified framework can be efficient when applied to large-scale histopathological data without resorting to additional steps to generate contours based on low-level cues for post-separating. Our method won the 2015 MICCAI Gland Segmentation Challenge out of 13 competitive teams, surpassing all the other methods by a significant margin.

cs.CV↗

Optimizing Energy Storage Participation in Emerging Power Markets

The growing amount of intermittent renewables in power generation creates challenges for real-time matching of supply and demand in the power grid. Emerging ancillary power markets provide new incentives to consumers (e.g., electrical vehicles, data centers, and others) to perform demand response to help stabilize the electricity grid. A promising class of potential demand response providers includes energy storage systems (ESSs). This paper evaluates the benefits of using various types of novel ESS technologies for a variety of emerging smart grid demand response programs, such as regulation services reserves (RSRs), contingency reserves, and peak shaving. We model, formulate and solve optimization problems to maximize the net profit of ESSs in providing each demand response. Our solution selects the optimal power and energy capacities of the ESS, determines the optimal reserve value to provide as well as the ESS real-time operational policy for program participation. Our results highlight that applying ultra-capacitors and flywheels in RSR has the potential to be up to 30 times more profitable than using common battery technologies such as LI and LA batteries for peak shaving.

eess.SY↗

Space-variant polarized Airy beam

We experimentally generate an Airy beam with polarization structure while keeping its original amplitude and phase profile intact. This class of Airy beam preserves the acceleration properties. By monitoring their initial polarization structure we have provided insight concerning the self-healing mechanism of Airy beams. We investigate both theoretically and experimentally the self-healing polarization properties of the space-variant polarized Airy beams. Amplitude as well as the polarization structure tends to reform during propagation in spite of the severe truncation of the beam by finite apertures.

physics.optics↗

Energy flow structuring in the focused field

We propose an iterative method of energy flow shaping in the focal region with the amplitude, phase and polarization modulation of incident light. By using an iterative optimization based on the diffraction calculation with help of the fast Fourier transform, we can tailor the polarization and phase structure in the focal plane. By appropriate design of the polarization and phase gradients, arbitrary energy flow including spin and orbital parts can be designed and tailored independently. The capability of energy flow structuring is demonstrated by the measurement of the Stokes parameters and self-interference pattern. This provides a novel method to control the vectorial feature of the focal volume.

physics.optics↗

A novel exact solution to transmission problem of electron wave in a nonlinear Kronig-Penney superlattice

Nonlinear Kronig-Penney model has been frequently employed to study transmission problem of electron wave in a nonlinear electrified chain or in a doped semiconductor superlattice. Here from an integral equation we derive a novel exact solution of the problem, which contains a simple nonlinear map connecting transmission coefficient with system parameters. Consequently, we suggest a scheme for manipulating electronic distribution and transmission by adjusting the system parameters. A new effect of quantum coherence is evidenced in the strict expression of transmission coefficient by which for some different system parameters we obtain the similar aperiodic distributions and arbitrary transmission coefficients including the approximate zero transmission and total transmission, and the multiple transmissions. The method based on the concise exact solution can be applied directly to some nonlinear cold atomic systems and a lot of linear Kronig-Penney systems, and also can be extended to investigate electron transport in different discrete nonlinear systems.

quant-ph↗

Independent and simultaneous tailoring of amplitude, phase, and complete polarization of vector beams

We present an approach that enables complete control over the amplitude, phase and arbitrary polarization state on the Poincaré sphere of an optical beam in a 4-f system with a spatial light modulator (SLM). The beams can be constructed from a coaxial superposition of x- and y-linearly polarized light, each carrying structured amplitude profile and phase distributions by using an amplitude-modulated mask imposed on the SLM. The amplitude, phase and polarization distribution of vector beams with four free parameters can be tailored independently and simultaneously by the SLM.

physics.optics↗

New $q$-ary Quantum MDS Codes with Distances Bigger than $\frac{q}{2}$

Constructions of quantum MDS codes have been studied by many authors. We refer to the table in page 1482 of [3] for known constructions. However there are only few $q$-ary quantum MDS $[[n,n-2d+2,d]]_q$ codes with minimum distances $d>\frac{q}{2}$ for sparse lengths $n>q+1$. In the case $n=\frac{q^2-1}{m}$ where $m|q+1$ or $m|q-1$ there are complete results. In the case $n=\frac{q^2-1}{m}$ where $m|q^2-1$ is not a factor of $q-1$ or $q+1$, there is no $q$-ary quantum MDS code with $d> \frac{q}{2}$ has been constructed. In this paper we propose a direct approch to construct Hermitian self-orthogonal codes over ${\bf F}_{q^2}$. Thus we give some new $q$-ary quantum codes in this case. Moreover we present many new $q$-ary quantum MDS codes with lengths of the form $\frac{w(q^2-1)}{u}$ and minimum distances $d > \frac{q}{2}$.

cs.IT↗

Unidirectional dissipative soliton operation in an-normal-dispersion bidirectional Yb-doped fiber laser without an isolator

We demonstrate self-started unidirectional dissipative soliton operation and noise-like pulse operation in an all-normal-dispersion bidirectional Yb-doped fiber laser mode-locked by nonlinear polarization rotation. The laser works unidirectional once mode locking was achieved due to the cavity directional nonlinearity asymmetry along with the nonlinear polarization rotation mode locking mechanism.

physics.optics↗

Even More Infinite Ball Packings from Lorentzian Root Systems

Boyd (1974) proposed a class of infinite ball packings that are generated by inversions. Later, Maxwell (1983) interpreted Boyd's construction in terms of root systems in Lorentz space. In particular, he showed that the space-like weight vectors correspond to a ball packing if and only if the associated Coxeter graph is of "level $2$." In Maxwell's work, the simple roots form a basis of the representations space of the Coxeter group. In several recent studies, the more general based root system is considered, where the simple roots are only required to be positively independent. In this paper, we propose a geometric version of "level" for the root system to replace Maxwell's graph theoretical "level." Then we show that Maxwell's results naturally extend to the more general root systems with positively independent simple roots. In particular, the space-like extreme rays of the Tits cone correspond to a ball packing if and only if the root system is of level $2$. We also present a partial classification of level-$2$ root systems, namely the Coxeter $d$-polytopes of level-$2$ with $d+2$ facets.

math.GR↗

New Explicit Binary Constant Weight Codes from Reed-Solomon Codes

Binary constant weight codes have important applications and have been studied for many years. Optimal or near-optimal binary constant weight codes of small lengths have been determined. In this paper we propose a new construction of explicit binary constant weight codes from $q$-ary Reed-Solomon codes. Some of our binary constant weight codes are optimal or new. In particular new binary constant weight codes $A(64, 10, 8) \geq 4108$ and $A(64, 12, 8) \geq 522$ are constructed. We also give explicitly constructed binary constant weight codes which improve Gilbert and Graham-Sloane lower bounds in some range of parameters. An extension to algebraic geometric codes is also presented.

cs.IT↗

Spatially-Resolved Dense Molecular Gas and Star Formation Rate in M51

We present the spatially-resolved observations of HCN J = 1 -- 0 emission in the nearby spiral galaxy M51 using the IRAM 30 m telescope. The HCN map covers an extent of $4\arcmin\times5\arcmin$ with spatial resolution of $28\arcsec$, which is, so far, the largest in M51. There is a correlation between infrared emission (star formation rate indicator) and HCN (1--0) emission (dense gas tracer) at kpc scale in M51, a natural extension of the proportionality between the star formation rate (SFR) and the dense gas mass established globally in galaxies. Within M51, the relation appears to be sub-linear (with a slope of 0.74$\pm$0.16) as $L_{\rm IR}$ rises less quickly than $L_{\rm HCN}$. We attribute this to a difference between center and outer disk such that the central regions have stronger HCN (1--0) emission per unit star formation. The IR-HCN correlation in M51 is further compared with global one from Milky Way to high-z galaxies and bridges the gap between giant molecular clouds (GMCs) and galaxies. Like the centers of nearby galaxies, the $L_{\rm IR}$/$L_{\rm HCN}$ ratio measured in M51 (particularly in the central regions), is slightly lower than what is measured globally in galaxies, yet is still within the scatter. This implies that though the $L_{\rm IR}$/$L_{\rm HCN}$ ratio varies as a function of physical environment in the different positions of M51, IR and HCN indeed show a linear correlation over 10 orders of magnitude.

astro-ph.GA↗

Raman-scattering-assistant broadband noise-like pulse generation in all-normal-dispersion fiber lasers

We report on the observation of both stable dissipative solitons and noise-like pulses with the presence of strong Raman scattering in a relatively short all-normal-dispersion Yb-doped fiber laser. We show that Raman scattering can be filtered out by intracavity filter. Furthermore, by appropriate intracavity polarization control, the Raman effect can be utilized to generate broadband noise-like pulses (NLPs) with bandwidth up to 61.4 nm. To the best of our knowledge, this is the broadest NLP achieved in all-normal-dispersion fiber lasers

physics.optics↗

Deterministic Construction of RIP Matrices in Compressed Sensing from Constant Weight Codes

The expicit restricted isometry property (RIP) measurement matrices are needed in practical application of compressed sensing in signal processing. RIP matrices from Reed-Solomon codes, BCH codes, orthogonal codes, expander graphs have been proposed and analysised. On the other hand binary constant weight codes have been studied for many years and many optimal or near-optimal small weight and ditance constant weight codes have been determined. In this paper we propose a new deterministic construction of RIP measurement matrices in compressed sensing from binary and ternary contant weight codes. The sparse orders and the number of budged rows in the new constant-weight-code-based RIP matrices can be arbitrary. These contant-weight-code based RIP matrices have better parameters compared with the DeVore RIP matrices when the sizes are small.

cs.IT↗

Explicit RIP Matrices in Compressed Sensing from Algebraic Geometry

Compressed sensing was proposed by E. J. Candés, J. Romberg, T. Tao, and D. Donoho for efficient sampling of sparse signals in 2006 and has vast applications in signal processing. The expicit restricted isometry property (RIP) measurement matrices are needed in practice. Since 2007 R. DeVore, J. Bourgain et al and R. Calderbank et al have given several deterministic cosntrcutions of RIP matrices from various mathematical objects. On the other hand the strong coherence property of a measurement matrix was introduced by Bajwa and Calderbank et al for the recovery of signals under the noisy measuremnt. In this paper we propose new explicit construction of real valued RIP measurement matrices in compressed sensing from algebraic geometry. Our construction indicates that using more general algebraic-geometric objects rather than curves (AG codes), RIP measurement matrices in compressed sensing can be constructed with much smaller coherence and much bigger sparsity orders. The RIP matrices from algebraic geometry also have a nice asymptotic bound matching the bound from the previous constructions of Bourgain et al and the small-bias sets. On the negative side, we prove that the RIP matrices from DeVore's construction, its direct algebraic geometric generalization and one of our new construction do not satisfy the strong coherence property. However we give a modified version of AG-RIP matrices which satisfies the strong coherence property. Therefore the new RIP matrices in compressed sensing from our modified algebraic geometric construction can be used for the recovery of signals from the noisy measurement.

cs.IT↗