Point clouds captured by three dimensional scanner have been used in many fields, including modeling of digital cities, acquisition of three dimensional shapes, scene analysis and object measuring. However, due to the limitation of the sampling process and the complexity of scanned scenes, most traditional methods of surface modeling and three dimensional space analysis cannot work effectively when dealing with the point cloud data. Classification is therefore an important way for point cloud preprocess. Four features, namely the volume of a tetrahedron constructed by 4 neighboring points, the deviation of normal directions of neighboring points, the deviation of principal directions of neighboring points, and the values of principal curvature, are mixed with probabilities for semi-automatic classification of the three dimensional point cloud data. With the new method, a point cloud is to be divided into three classes:plane points, cylinder points and other points. The initial classification result is labeled according to its single shape feature value. The probability mixture is completed by estimating the probability of inferring a shape from a local point set with respect to each feature, generating a mixture with weighted sum, and maximizing the mixture probability function, while the probability is estimated with the average distance between a point and its neighbor points together with the consistency ratio of initial labels of the point to its neighbors. User interactions are invoked to make the choice of classification thresholds and the setting of weights, which is helpful when dealing with point cloud with different space scale and scanning point resolution. Experiments show that the proposed method works well for various kinds of point cloud data sets, including point clouds generated by simulation, and those corresponding to a single pine tree, a street scene, a country scene, and an airborne big scene.

A fast approach of generating a 2D offset curve from any polygonal curve is presented, which preserves sharp features and is self-intersection free. The basic idea is first to establish a local signed distance field on a uniform grid according to the input curve and then employ a contouring algorithm to extract the offset curve from the distance field. Three filters are conducted to generate a narrowband signed distance field around the offset curve in a very efficient way to reduce computation redundancies in regions far from the offset curves. The initial offset curve is derived by a traditional MS (Marching Square) method, the accurate intersections between the grid edges and the offset curve are computed quickly by a hybrid method employing the analytical solutions and the bisection search. Based on these closest points, an exact offset curve composed of line and arc segments is constructed by merging short line segments and reconstructing sharp features. The derived offset curve is intersection-free and retains the sharp features. The quality and performance of this approach are demonstrated by a number of experimental tests on various examples.

In CAGD, progressive iterative approximation (PIA) method is widely used to solve interpolation and approximation problems due to its perfect adaptability and convergence stability. Weighted progressive iterative approximation (WPIA) can accelerate the convergence rate by assigning an appropriate weight for each adjusting vectors. One new PIA method with mutually different weights is presented. It not only provides more flexibility in operation, but also achieves satisfactory iterative result for different control vertices. A set of weights with an adjustable parameter has also been put forward, which can be obtained without resorting to the eigenvalue of collocation matrices and can speed up the convergence rate compared with the WPIA method. Numerical examples of Bézier curves, tensor-product Bézier surfaces and triangular Bézier surfaces demonstrate the effectiveness of the method.

By employing the tree structure basis of coalgebra, an equivalent condition for coalgebra being isomorphic is achieved. The list of all isomorphism classes of 4-dimensional coalgebra is completed, and a general method for the classification of larger dimensional coalgebra is provided.

Firstly, the definition of anti-soft ideals is given, and we show that the restricted union and 'OR' operation of two anti-soft lattices are still anti-soft ideal. Then, we discuss the equivalent characterizations of anti-soft ideals based on the anti-dual of soft set. In addition, based on the anti-extension principle, the properties of their anti-image and inverse image are derived under the homomorphic mapping. Finally, we introduce the condition of chain over H which is composed of all the anti-soft ideals, and discuss the necessary and sufficient condition for that H is Artinian or Noetherian.

This paper studies the existence and uniqueness of time periodic solution for one type of fluid dynamics equation with inhomogeneous term. Firstly, the approximation sequence of time periodic solution is constructed using the Galerkin method. Next, the approximation sequence is verified to be convergent by means of a priori estimate and Leray-Schauder fixed point theorem. It is shown that there is a time periodic solution when the inhomogeneous term is periodic about time. We also prove that the solution is unique under certain conditions.

On the basis of local fractional calculus theory, inequalities of Hermite-Hadamard type are extended following the definition of generalized convex function on fractal sets. Some new Hadamard-type inequalities involving local fractional integrals on fractal sets R^α(0<α ≤ 1) are established. Finally, some applications of the new inequalities in special means and numerical integration are provided.

In the widely used optics textbooks for undergraduate students, the following conclusions and their derivation process are inconsistent, and even contradictory:(1)The wave function expression of the planar harmonic electromagnetic wave; (2)The relationship between the rotation direction of elliptically polarized light and the phase difference of two sub-waves; (3)The derivation and form of Jones vector of elliptically polarized light. These inconsistencies often make students confusing. Based on years of teaching experience in optics, we conduct a comparative analysis for these inconsistencies by proof and derivation, and draw clear conclusions for each of the above knowledge.

Rate control is crucial to rate distortion performance optimization in video coding design. In video coder, temporal prediction bring about distortion propagation along adjacent frames, and it is an efficient way to further improve the video coding efficiency by taking the temporal distortion dependency into consideration. The MBTree rate control is a typical temporal quantization control algorithm, in which the quantization parameter offset δ is employed for quantization adjustment according to the distortion propagation amount, i.e. the relative propagation cost ρ. An appropriate δ-ρ model is therefore the key for the MBTree-like adaptive quantization algorithm. Nevertheless, the current δ-ρ model in MBTree algorithm is designed in an empirical way with rough accuracy. This model has unsatisfactory universality to different video sequences, thus there is still room left to be improved. This paper focuses on this problem and applies the competitive decision mechanism in exploring the optimized δ-ρ model, and then proposes an improved δ-ρ model with rate distortion optimization. The simulation results show that the improved MBTree algorithm based on the proposed model can achieve up to 0.14 dB BD-PSNR improvement and 0.29 dB SSIM improvement. The proposed algorithm can also implement better bit allocation in temporal domain and reduce the temporal distortion fluctuation, achieving adaptive quantization control.

Based on the study the timing deviation of monostable circuit and physical unclonable function (PUF) circuit, a high recognition PUF circuit scheme was proposed. Firstly, by analyzing the self identity physical properties of monostable circuit, a long-range timing design method was presented. The monostable circuit is then used to generate a timing deviation signal, and two timing deviation signals were chosen by multiplexer through challenge signal. The arbiter circuit determined high recognition and unclonable response. The proposed PUF circuit was simulated under TSMC 65 nm CMOS technology by Monte Carlo test. With the Monte Carlo simulation results, its uniqueness and reliability under different circumstances were analyzed. Experimental results show that the recognition rate of PUF circuit is 99.82% with bit error rate of 2.7%.

Using poly(methacrylic acid) (PMAA) as the coelectrospinning agent, well-defined chitosan/poly(methacrylic acid) (CS/PMAA) fiber mat was fabricated by electrospinning and crosslinked at 180℃ for 2 h, then chemically modified with glutaraldehyde to immobilize palladium species. The fiber morphologies were observed by scanning electron microscopy (SEM) and the dispersion of palladium species were analyzed by SEM-energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The chemical modification of CS/PMAA fiber was characterized by fourier transform infrared spectroscopy (FT-IR) spectra. Density functional theory (DFT) calculation results demonstrate that the chemical modification can decrease the chelating strength between the CS/PMAA fiber and palladium species. The catalytic performances of these novel chitosan fiber supported Pd catalysts were evaluated by Sonogashira coupling reaction. It is found that the glutaraldehyde modification can improve the catalytic activity of CS/PMAA fiber supported palladium catalyst. Moreover, this novel catalyst can be reused at least nine times without obvious loss of initial activity.

Geometric algebra has advantages in solving problems of geometric object modeling and multidimensional data analysis. This paper conducts studies on the meaning, construction and application of its two operators:meet and join. By exploiting their merits of multidimensional consistency and high dimension adaptivity, we propose a spatio-temporal parcel meet algorithm. We also give definitions and representations of 3D and 4D spatio-temporal parcel within the domain of conformal geometric algebra and spatio-temporal algebra. The algorithm is successfully applied to conduct the topology computation of three dimension spatio-temporal parcels and achieves satisfactory results.. Experiment show that our approach provides a novel and effective way for the representation and topology computation of three dimensional spatio-temporal parcel and hopefully a new resolution for four dimensional spatio-temporal parcels.

Based on the 30 year data from 1981 to 2010 of the US National Centers for Environmental Prediction (NCEP), the process of seasonal temperature changes in Qinghai-Tibet plateau and its surrounding areas as well as the possible intrinsic mechanism are studied. The results show that the 24℃-isotherm of earth surface exhibits a sudden jump between the north and south about 18 latitudes in February-March and November, which is speculated to be the result of the joint effects of the solar radiation and the monsoon circulation. The seasonal temperature change on 200 hPa is earlier than on surface and 500 hPa, presumably due to the downward energy transfer from the sudden warming stratosphere. The surface temperature in Qinghai-Tibet plateau is closely related to lesser downward longwave radiation flux. The results will provide useful hints for further research on climate change in Qinghai-Tibet Plateau.

According to the monthly precipitation and temperature data of 49 sites in Yun-Gui area from 1960 to 2014, this paper uses standardized precipitation index, Mann-Kendall mutation test and wavelet analysis method to study the changes in seasonal scale and the year scale of temperature and precipitation characteristics, as well as the drought evolution trend. The results show that:(1)The temperature gradually increased from 1960 to 2014. The temperature rise rate of winter was the largest. The abrupt change of average annual temperature occurred in 1997. (2) The precipitation was decreasing; The fastest decline in autumn, and the slowest in winter; The precipitation presents 14 a and 28 a cycle.(3) Yun-Gui area presented a droughty trend from 1960 to 2014. The summer and autumn drought appeared as an obvious trend. (4)The climate of Yun-Gui area was becoming drought (SPI trend rate was less than 0), and is more seriously at the junction of Yunnan and Guizhou province, while, only the Northern Yunnan rigion becomes wetting. So the climate of Yun-Gui area was becoming warmer and drier in recent 55 years.

A matrix solid phase dispersion extraction-gas chromatography/mass spectrometric method has been developed for the determination of 13 polybrominated diphenyl ethers in soil. Parameters including species of solid-phase dispersant, ratios of sample to dispersant, elution species and amount have been optimized. The best pretreatment conditions are as follows:2 g sample was mixed with 4 g acidic silica, and then grinded for 10 min. The mixture was loaded into a glass column pre-filled with 4 g anhydrous sodium sulfate and 4 g acidic silica. Hexane/dichloromethane (v:v=1:1, 50 mL) mixture was used as eluent. The elution was concentrated to 0.5 mL prior to GC/MS analysis. 13 kinds of PBDEs all show good linear relationships (R²>0.992) in the range from 2 to 200 ng·g^-1. The average recoveries are 81% to 103% and the relative standard deviation is less than 15% (n=3). The method detection limits ranged from 75 to 950 pg·g^-1, which meets the need for the analysis of trace PBDEs in soil.

We collected 448 samples of PM_2.5 at urban area of Wenzhou from January to December, 2015. Water-soluble ionic constituents(SO₄^2-, NO₃^-, NH₄⁺, Cl^-, Na⁺, K⁺, Ca²⁺, Mg²⁺ and F^-)associated to PM_2.5 were detected by Ion Chromatogram (IC), chemical composition, variation characteristics, as well as the source apportionment were analyzed. The average mass concentration of the 9 ions was found to be 39.97 μg·m^-3. Secondary inorganic species SO₄^2-、NO₃^- and NH₄⁺were the major components of water-soluble ions in PM_2.5, with a contribution of (40.19±10.04)%. The order of total ions concentration was winter > spring > autumn > summer, showing obvious seasonal variations, and from the space, the concentrations of PM_2.5-bound water-soluble ions were lower in Shizhan in most of the seasons. The results of correlation analysis showed that PM_2.5 and NH₄⁺、Ca²⁺、Na⁺、K⁺、Cl^-、NO₃^-、SO₄^2- had a significant negative correlation, and most of SO₄^2- and NH₄⁺ existed as (NH₄)₂SO₄ in Wenzhou city. In addition, the sulfate oxidizing rate (SOR) and nitrate oxidizing rate (NOR) were (0.44±0.09) and (0.13±0.04), respectively. It indicated that SO₄^2- and NO₃^- in PM_2.5 were resulted by the secondary transformation. Principal component analysis (PCA) results suggested that water-soluble inorganic ions in PM_2.5 mainly came from coal combustion (thermal power generation and coal-fired industry), biomass combustion, vehicle exhaust emission, road and construction dust.

A questionnaire of "How the daily travels of urban families affect the nitrogen emission in 2015" was carried out in Hangzhou, including factors related to family members' age, income, education, occupation, type of family households and family cars ownership. Methods of correlation analysis and optimal scaling regression analysis were used in this study. The results obtained are as follows:(1) all the attributes of the family members have impact on the amount of nitrogen emission in daily travel, e.g.,families with both members aged between 31-50 incur the largest amount compared with other ages, and when the family income was in 15 001-20 000 yuan or above, the amount increased dramatically, the education level of the second member affects the amount more than that of the first member, and the amount of nitrogen emission also depends significantly on the occupations of both members, Furthermore, the total amount of nitrogen emission of urban households accounts for 2.6 times compared with rural households, and that of families with cars accounts for 16 times than otherwise; (2) influence factors in a descending order are as follows:family cars ownership, transportation manner, educational level of the second member, occupation and family members' age, respectively. This study could provide a useful reference for the construction of urban with low nitrogen emission.