In recent years, the heavy metal pollution incidents in China were frequently reported. However, studies on pollution, sources, and control strategies of atmospheric heavy metals in China are rare. We summarize the research results reported in recent years. The features of pollution level, seasonal variation, regional differences, size distribution of the atmospheric heavy metal elements including Pb, V, As, Mn, Ni, Cr, and Cd in China are analyzed. The main sources, current control status, and control technologies of atmospheric heavy metals are discussed. Comprehensive suggestions for China's heavy metal pollution control are put forward based on the summarization of the progress and experience of the atmospheric heavy metal pollution control in other countries and regions.
We give a boundary estimate of Poincaré metric on C-{0, 1} using a simple direct method, which does not involve Ahlfors's Schwarz lemma about ultrahyperbolic metrics, harmonic analysis, or modular functions.
A Hilbert space operator T has the single-valued extension property if the only analytic function f which satisfies (T-λI)f(λ)=0 is f≡0. Obviously the point spectrum of any operator which has empty interior must have the single-valued extension property. Using the spectrum derived from "generalized Kato decomposition", we investigate stability of the single-valued extension property under compact perturbations. Also, we characterize the 2×2 upper triangular operator matrix for which the single-valued extension property is stable under compact perturbations.
Dynamical responses of the first-wall in ITER are studied. The uniformly distributed lateral and longitudinal loads are exerted to a rectangular thin plate, which is located in a transverse steady uniform magnetic field. By considering finite deformation, the motion equations are derived. The partial differential equations are transferred to differential dynamical system by Galerkin method. Runge-Kutta method is employed to simulate the dynamical behaviors of the plate. The motions are analyzed by using time-displacement diagrams, phase trajectories, and Poincare map.
The relativistic configuration interaction method is employed to investigate the resonant transfer excitation (RTE) processes of Kr34+ colliding with CH4, NH3, H2O, and HF targets under the impulse approximation. Compared to the case of CH4, the RTE cross sections of NH3, H2O, and HF targets reduce by 10.7%, 23.3%, and 33.6% in the first peak position and by 6.0%, 12.3%, and 18.9% in the second peak position, respectively, due to the decrease in Compton profiles in the small momentum region. On the other hand, the width of the peaks increases from CH4 to HF, which indicates that strong Coulomb effect leads to the broader momentum distribution.
The discrete-time hidden Markov model is employed to model the probabilistic relation between the network states and the controller-to-actuator (C-A) delays in networked control systems (NCSs). The NCS is modeled as a Markovian jump linear system and the C-A delay in the current sampling period is predicted. By taking the prediction into account, a state-feedback controller is designed to compensate for the stochastic C-A delays. The superiority of the proposed method is demonstrated by the comparative simulation experiments.
DFT B3LYP calculations with the 6-31G(d, p) and 6-311+G(d, p) basis sets were carried out to investigate the mechanisms of intramolecular cycloaddition of six-carbon tethers phenyl-substituent bis(enone). Both the hetero-Diels-Alder cycloaddult (da-P-) and the cis-cyclobutanation are predicted to be possible products of the reactions via radical anion. Our calculations also indicate that the da-P- is the dominant product both dynamically and thermodynamically, via a six-membered ring intermediate and two transition states.
Dissolution of cornstalk in 1-butyl-3-methylimidazolium chloride (BmimCl) and 1-ethyl-3-methylimidazolium acetate (EmimOAc) was studied. Chemical structure and crystalline form of cornstalk before and after dissolution were analyzed by means of FT-IR, TGA, SEM, and XRD. The results show that the crystallinity and thermostability of the regenerated cellulose-rich material slightly decreased after dissolution. Cornstalk directly dissolved in ionic liquids, and no derivatization reaction occurred.
Glycol chitosan-graft-carboxymethyl β-cyclodextrin (GCH-g-CM β-CD) was synthesized by a simple cross-linking reaction, and the products were characterized by FT-IR,13C-NMR, and H2SO4-phenol degradation method. Interaction between GCH-g-CM β-CD and hydrophobic anticancer drug methotrexate (MTX) was studied by surface plasmon resonance (SPR) in real time and in situ. UV-vis spectroscopy analysis indicated that each CM β-CD unit binds one MTX molecule, which showed that MTX can be successfully loaded into the hydrophobic cavities of grafted CM β-CDs. The results indicated that the newly synthesized GCH-g-CM β-CD can be used as hydrophobic anticancer drug carrier.
A full length cDNA encoding a type Ⅲ PKS (PcCHS1) was isolated from Polygonum cuspidatum Sieb. et Zucc. Functional and enzymatic assays biochemically confirmed that PcCHS1 was a chalcone synthase. When incubated with p-coumaroyl-CoA and malonyl-CoA at pH 7-8, PcCHS1 catalyzed the formation of chalcone as the major product. However, at pH 9 both p-hydroxybenzalacetone and chalcone were detected. Site-directed mutagenesis of Phe216 into Leu caused reduction of enzyme activity. Another mutation N333K performed activity of releasing some common derailment products, CTAL and BNY, of many CHSs in vitro.
Activated alumina (AA) is widely used for defluoridation. Batch experiments were carried out to investigate the influence of Cl- (1000 mg·L-1) and HCO3- (2000 mg·L-1) on adsorption kinetics of F- (10 mg·L-1) on AA in coalbed methane co-produced water (CBMW). The results show that in the presence of Cl- the adsorption rate and the equilibrium absorption capacity increase, but in the presence of HCO3- both the quantities decrease. These effects should be considered when one treats CBMW.
The Yellow River delta is rich in land resource, but serious soil salinization affects local agricultural production and poses a threat to stability of ecological environment. The traditional multiple linear regression model and the BP artificial neural network model were both used to derive the soil salinity in the Yellow River delta based on the home-made CBERS-02B multispectral images. It is found that the BP artificial neural network model performs much better than the multiple linear regression model in inversing soil salinity, especially for heavy saline soil area.
Along-track interferometric synthetic aperture radar (ATI-SAR) detects ground moving objects and measures their velocities. Phase center error is a major error source of ATI-SAR. Not only does the constant offset need external calibration, but also the rigidity of antennas should prohibit the drifting errors. We analyzed the drifting errors caused by antenna's mechanical deformation and proposed requirements for structural design of antenna to meet the velocity measuring requirements, providing theoretical foundation for airborne ATI-SAR antenna structure design.
A single-stage variable gain amplifier for WiMAX receiver is implemented. By adopting current squaring technique, the VGA provides a large variable gain range compared to other single-stage VGAs. As a result, the proposed structure can achieve a given variable gain range with less stages and the whole power consumption is reduced. The chip is fabricated in 0.13 μm CMOS process, occupies 0.6×0.4 mm2, and consumes 3.6 mW power from 1.2 V supply. Experimental results show that a continuous gain range from -20 dB to 25 dB is achieved when the control voltage varies from 0.5 V to 1 V. Furthermore, the VGA provides a 3 dB bandwidth greater than 15 MHz and the measured IIP3 value is in the range -21 dBm to 5 dBm.
We present a new method which integrates fuzzy c-means cluttering and region-based level set evolution for SAR image segmentation. Benefited by spatial fuzzy clustering, the initial level set segmentation approximates the component of interest. The controlling parameters are also estimated on the basis of the results of the spatial fuzzy clustering. The proposed method was evaluated on synthetic and real SAR images, and the results show that the new method is more robust, fast, and accurate in segmentation and does not need manual intervention.
A probabilistic model named MUGG (mixture of unilateral generalized Gaussians) is designed for modeling the distribution of trajectories in visual scene. Information of trajectory is calculated to determine whether the trajectory is abnormal. This method is unsupervised and independent of prior knowledge.It is fit for time-varying environment with the real-time updated model. Its availability and robustness shown by experiments proves the application value.
Sleep scheduling is a widely-used mechanism for saving energy and prolonging network lifetime. However, in extremely low duty-cycled wireless sensor networks, achieving high performance of end-to-end packet delivery delay requires a carefully-designed routing method. We first present an implementation of random duty cycling, and then design a distributed routing method. We consider both forwarding progresses and transmission delay in the selection of next hop node when making forwarding decisions. Theoretical analyses and simulation results show that our routing method has advantages in terms of latency and hop distances, compared to the existing methods.
Nowadays, most chip multiprocessor (CMP) designs face the challenge of how to keep the balance between on-chip parallelism, communication overhead, program performance, and resource utilization. By using the conception of physical core and logical processor, flexible-core CMPs(FCMPs) provide more optimization space. We propose a novel FCMP architecture named FTPA (flexible tiled processor architecture), which provides an efficient platform for single thread execution. The evaluation demonstrates that FTPA outperforms the state-of-art FCMP design, TFlex, by 19.2% on average.
In STOC 2003, based on the existence of one-way function, a non-interactive and reusable statistically binding non-malleable commitment in the common reference string (CRS) model was proposed. There the CRS contains four parts: a public key to a commitment, a public key to a signature scheme, a universal one-way hash function, and a commitment to string 0. In this paper, we use two signature schemes to construct such a scheme. Here the CRS has only two parts: a public parameter of an equivocable commitment and a public key to a signature scheme. Therefore, the new scheme has a much shorter CRS.
Asynchrony of short messages(SMS) brings inconvenience to the key distribution. We propose an SMS encryption system based on the dynamic key. The dynamic encryption key increases difficulty in cryptanalysis. The dynamic authentication key resists the replay attack. The scheme uses only hash function and symmetric encryption which are more suitable to the resource-limited mobile system. Experimental results on Android platform show good realization performance of the scheme.
Fuzzing is an efficient method for ensuring software security. However, when one tests network-based software using this method, one may obtain unsatisfied results because of lacking the protocol format. To solve this problem, we propose a new protocol analysis technique based on symbolic expression. We use this technique to translate the crucial code into symbolic expressions and accelerate protocol analysis. In addition, we develop a translation framework which contains the function of automatic protocol format analysis and could export the protocol format to Peach platform. Finally, we apply our framework to analyze one target (eyou client) and obtain good results.
Contradiction between supply and demand for construction land has become the main bottleneck in economic and social sustainable development, and in this paper we attempt to crack this contradiction. Regional differentiation and industrial differentiation are both considered as industrial land-consuming indicator and construction land use intensity indicators. The former is used to judge the admittance of industry, and the latter to assess land use efficiencies of the provincial governments.