Showing papers by "Tsinghua University published in 2005"

Borderline-SMOTE: a new over-sampling method in imbalanced data sets learning

Abstract: In recent years, mining with imbalanced data sets receives more and more attentions in both theoretical and practical aspects. This paper introduces the importance of imbalanced data sets and their broad application domains in data mining, and then summarizes the evaluation metrics and the existing methods to evaluate and solve the imbalance problem. Synthetic minority over-sampling technique (SMOTE) is one of the over-sampling methods addressing this problem. Based on SMOTE method, this paper presents two new minority over-sampling methods, borderline-SMOTE1 and borderline-SMOTE2, in which only the minority examples near the borderline are over-sampled. For the minority class, experiments show that our approaches achieve better TP rate and F-value than SMOTE and random over-sampling methods.

A general strategy for nanocrystal synthesis

Abstract: New strategies for materials fabrication are of fundamental importance in the advancement of science and technology. Organometallic and other organic solution phase synthetic routes have enabled the synthesis of functional inorganic quantum dots or nanocrystals. These nanomaterials form the building blocks for new bottom-up approaches to materials assembly for a range of uses; such materials also receive attention because of their intrinsic size-dependent properties and resulting applications. Here we report a unified approach to the synthesis of a large variety of nanocrystals with different chemistries and properties and with low dispersity; these include noble metal, magnetic/dielectric, semiconducting, rare-earth fluorescent, biomedical, organic optoelectronic semiconducting and conducting polymer nanoparticles. This strategy is based on a general phase transfer and separation mechanism occurring at the interfaces of the liquid, solid and solution phases present during the synthesis. We believe our methodology provides a simple and convenient route to a variety of building blocks for assembling materials with novel structure and function in nanotechnology.

Adjusting multiple testing in multilocus analyses using the eigenvalues of a correlation matrix.

Abstract: Correlated multiple testing is widely performed in genetic research, particularly in multilocus analyses of complex diseases. Failure to control appropriately for the effect of multiple testing will either result in a flood of false-positive claims or in true hits being overlooked. Cheverud proposed the idea of adjusting correlated tests as if they were independent, according to an ‘effective number’ (Meff) of independent tests. However, our experience has indicated that Cheverud's estimate of the Meff is overly large and will lead to excessively conservative results. We propose a more accurate estimate of the Meff, and design Meff-based procedures to control the experiment-wise significant level and the false discovery rate. In an evaluation, based on both real and simulated data, the Meff-based procedures were able to control the error rate accurately and consequently resulted in a power increase, especially in multilocus analyses. The results confirm that the Meff is a useful concept in the error-rate control of correlated tests. With its efficiency and accuracy, the Meff method provides an alternative to computationally intensive methods such as the permutation test.

Visible-light-induced degradation of rhodamine B by nanosized Bi2WO6.

Abstract: Visible-light-induced photodegradation of rhodamine B over nanosized Bi2WO6 has been observed. Bi2WO6 exhibited a high photoactivity to photodegrade rhodamine B in the central pH solution under visible irradiation (λ > 420 nm). After five recycles for the photodegradation of rhodamine B, the catalyst did not exhibit any significant loss of activity, confirming the photocatalyst is essentially stable. The total organic carbon measurement displayed that a high degree of mineralization was achieved in the present photochemical system. The results of density functional theory calculation illuminated that the visible-light absorption band in the Bi2WO6 catalyst is attributed to the band transition from the hybrid orbitals of Bi6s and O2p to the W5d orbitals. The Bi2WO6-assisted photocatalytic degradation of rhodamine occurs via two competitive processes: a photocatalytic process and a photosensitized process. The transformation of rhodamine is mainly via the photocatalytic process. Kinetic studies by using el...

Improved particle swarm optimization combined with chaos

Abstract: As a novel optimization technique, chaos has gained much attention and some applications during the past decade. For a given energy or cost function, by following chaotic ergodic orbits, a chaotic dynamic system may eventually reach the global optimum or its good approximation with high probability. To enhance the performance of particle swarm optimization (PSO), which is an evolutionary computation technique through individual improvement plus population cooperation and competition, hybrid particle swarm optimization algorithm is proposed by incorporating chaos. Firstly, adaptive inertia weight factor (AIWF) is introduced in PSO to efficiently balance the exploration and exploitation abilities. Secondly, PSO with AIWF and chaos are hybridized to form a chaotic PSO (CPSO), which reasonably combines the population-based evolutionary searching ability of PSO and chaotic searching behavior. Simulation results and comparisons with the standard PSO and several meta-heuristics show that the CPSO can effectively enhance the searching efficiency and greatly improve the searching quality.

Synthesis of Square Bi2WO6 Nanoplates as High-Activity Visible-Light-Driven Photocatalysts

Abstract: Square Bi2WO6 nanoplates have been successfully synthesized by simple hydrothermal process. The effects of hydrothermal temperature and reaction time on morphologies and sizes of the nanoplates were investigated. These nanoplates are square geometric shapes having their basal plane as the (001) plane of orthorhombic Bi2WO6. On the basis of results of morphologies observation and selected area electron diffraction of series samples, a possible growth mechanism of the nanoplates is revealed. The square laminar shape could be attributed to anisotropic growth along the (001) plane, which is parallel to their intrinsic layer structure. UV−visible diffuse reflection spectra of the prepared Bi2WO6 nanoplates indicate they had absorption in the visible region, but a blue shift appeared compared to their bulk counterparts. Their photocatalytic activities are determined by rhodamine B degradation under visible light irradiation (λ > 400 nm). The reaction constant (k) of the best quality Bi2WO6 nanoplates is three t...

Quantum secure direct communication with high-dimension quantum superdense coding

Abstract: A protocol for quantum secure direct communication with quantum superdense coding is proposed. It combines the ideas of block transmission, the ping-pong quantum secure direct communication protocol, and quantum superdense coding. It has the advantage of being secure and of high source capacity.

Design of Wide-Spectrum Inhibitors Targeting Coronavirus Main Proteases

Abstract: The genus Coronavirus contains about 25 species of coronaviruses (CoVs), which are important pathogens causing highly prevalent diseases and often severe or fatal in humans and animals. No licensed specific drugs are available to prevent their infection. Different host receptors for cellular entry, poorly conserved structural proteins (antigens), and the high mutation and recombination rates of CoVs pose a significant problem in the development of wide-spectrum anti-CoV drugs and vaccines. CoV main proteases (Mpros), which are key enzymes in viral gene expression and replication, were revealed to share a highly conservative substrate-recognition pocket by comparison of four crystal structures and a homology model representing all three genetic clusters of the genus Coronavirus. This conclusion was further supported by enzyme activity assays. Mechanism-based irreversible inhibitors were designed, based on this conserved structural region, and a uniform inhibition mechanism was elucidated from the structures of Mpro-inhibitor complexes from severe acute respiratory syndrome-CoV and porcine transmissible gastroenteritis virus. A structure-assisted optimization program has yielded compounds with fast in vitro inactivation of multiple CoV Mpros, potent antiviral activity, and extremely low cellular toxicity in cell-based assays. Further modification could rapidly lead to the discovery of a single agent with clinical potential against existing and possible future emerging CoV-related diseases.

Image completion with structure propagation

Abstract: In this paper, we introduce a novel approach to image completion, which we call structure propagation. In our system, the user manually specifies important missing structure information by extending a few curves or line segments from the known to the unknown regions. Our approach synthesizes image patches along these user-specified curves in the unknown region using patches selected around the curves in the known region. Structure propagation is formulated as a global optimization problem by enforcing structure and consistency constraints. If only a single curve is specified, structure propagation is solved using Dynamic Programming. When multiple intersecting curves are specified, we adopt the Belief Propagation algorithm to find the optimal patches. After completing structure propagation, we fill in the remaining unknown regions using patch-based texture synthesis. We show that our approach works well on a number of examples that are challenging to state-of-the-art techniques.

Classification of real and pseudo microRNA precursors using local structure-sequence features and support vector machine

Abstract: Background: MicroRNAs (miRNAs) are a group of short (similar to 22 nt) non-coding RNAs that play important regulatory roles. MiRNA precursors (pre-miRNAs) are characterized by their hairpin structures. However, a large amount of similar hairpins can be folded in many genomes. Almost all current methods for computational prediction of miRNAs use comparative genomic approaches to identify putative pre-miRNAs from candidate hairpins. Ab initio method for distinguishing pre-miRNAs from sequence segments with pre-miRNA-like hairpin structures is lacking. Being able to classify real vs. pseudo pre-miRNAs is important both for understanding of the nature of miRNAs and for developing ab initio prediction methods that can discovery new miRNAs without known homology.

Azimuthal anisotropy in Au+Au collisions at sNN=200GeV

Abstract: The results from the STAR Collaboration on directed flow (v(1)), elliptic flow (v(2)), and the fourth harmonic (v(4)) in the anisotropic azimuthal distribution of particles from Au+Au collisions at root s(NN) = 200 GeV are summarized and compared with results from other experiments and theoretical models. Results for identified particles are presented and fit with a blast-wave model. Different anisotropic flow analysis methods are compared and nonflow effects are extracted from the data. For v(2), scaling with the number of constituent quarks and parton coalescence are discussed. For v(4), scaling with v(2)(2) and quark coalescence are discussed.

A Highly Efficient Chemical Sensor Material for H2S: α-Fe2O3 Nanotubes Fabricated Using Carbon Nanotube Templates

Abstract: {alpha}-Fe{sub 2}O{sub 3} nanotubes that can be used as chemical sensors are fabricated by a novel carbon nanotube (CNT) templated synthesis. CNTs are coated with a continuous layer of Fe{sub 2}O{sub 3} nanoparticles by the decomposition of Fe(NO{sub 3}){sub 3} in a supercritical CO{sub 2}/ethanol solution. Subsequent removal of the CNTs gives {alpha}-Fe{sub 2}O{sub 3} nanotubes that are highly sensitive to H{sub 2}S, which makes them attractive materials for chemiluminescent H{sub 2}S sensors. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

Symmetric multiparty-controlled teleportation of an arbitrary two-particle entanglement

Abstract: We present a way for symmetric multiparty-controlled teleportation of an arbitrary two-particle entangled state based on Bell-basis measurements by using two Greenberger-Horne-Zeilinger states, i.e., a sender transmits an arbitrary two-particle entangled state to a distant receiver, an arbitrary one of the n+1 agents, via the control of the others in a network. It will be shown that the outcomes in the cases that n is odd or is even are different in principle as the receiver has to perform a controlled-NOT operation on his particles for reconstructing the original arbitrary entangled state in addition to some local unitary operations in the former. Also we discuss the applications of this controlled teleporation for quantum secret sharing of classical and quantum information. As all the instances can be used to carry useful information, its efficiency for qubit approaches the maximal value.