Biogenic coal bed methane (CBM) has been detected in various CBM fields in the world, and microorganisms are the key factors for its formation. Studies on the molecular microbial ecology associated with biogenic CBM are highly valuable, and will improve the understanding of the formation mechanism of biogenic CBM and promote the exploitation of CBM. We summarize the role of microorganisms in the formation of biogenic CBM and the latest developments of in situ microbial diversity in CBM fields worldwide. The present work is valuable for further studies on biogenic CBM and the sustainable development of CBM industry.
Value sets are of importance in implying properties of polynomials over a finite field. In this paper, we characterize polynomials over a finite field with value sets contained in the kernel of the trace functions, i.e., polynomials which have the whole finite field as zeros after incorporated in the trace function. In particular, simpler equivalent conditions about monomials, linearized polynomials,and DO polynomials are given based on their own properties.
Asian options are path dependent contingent claims whose terminal payoff depends on the average of underlying asset price over some period prior to maturity. Using change of numéraire as a tool, we illustrate how to derive price formulae for the discrete and continuous geometric average Asian options with floating strike price by risk-neutral valuation approach.
The domain name system (DNS) plays an important role in the internet, and maintaining its health and security is significant to the normal operation of the entire internet. To this end, we detect and shield the IP addresses that have potential threats to the name servers. We propose the generalized and regularized Mahalanobis distances to diagnose the threat degree of IP addresses. Both the methods efficiently solve the issue where the covariance matrix is singular. Real data analysis shows that the two proposed distances are very efficient in the diagnosis of threat degree of IP addresses.
In order to study the thermal transport process of liquid metal in micro scale, liquid metal flow and heat transfer process between two constant-temperature plates is simulated by using molecular dynamics simulation method. Cu atoms are used in the two plates as different constant-temperature solid walls, and liquid metal Pb is arranged in initial alignment as FCC structure between the two plates. The simulation results show that the liquid metal temperature has a linear distribution between two plates. At different temperatures, thermal transport processes of liquid metal show linear temperature distributions and thermal conductivity of the liquid metal linearly increases with temperature. By exerting gravity acceleration, liquid metal does not show obvious natural convection temperature distribution because boundary resistance and viscous force of liquid metal suppress the natural convection of liquid metal in micro scale.
A three-dimensional numerical analysis of the growth and collapse of a micro-bubble under pulsed heating is carried out in this work. Geometry reconstruction and interface tracking methods are used to trace the evolution of the free surface flow. Details of the velocity and temperature in the liquid and vapor phases during the growth and collapse of the vapor bubble are obtained. Numerical results for the growth and collapse of the micro-bubble are compared with those of experiments under similar conditions. Comparisons show that the volume evolution of the vapor bubble is well predicted by the numerical model.
Single screw water vapor compressor is applied in the mechanical vapor recompression heat pump (MVR) system. Analysis of the working process of the compressor is carried out. Experiments for the MVR systems with closed cycle and open cycle are performed under different evaporation temperature conditions. The results show that the volume efficiency of the compressor is larger than 0.73 and the adiabatic efficiency is larger than 0.5 when the evaporation temperature is higher than 80 ℃. The largest practical COP of the system reaches 12.5 and the highest actual SMER reaches 20 kg/(kW·h) in the present experiments. The high efficiency and energy-saving features of the MVR system driven by single screw water vapor compressor are fully shown in this study.
CoFe1.9Nb0.1O4 phase was synthesized through solid-state reaction. Rietveld refinement shows that it has cubic spinel structure in the Fd-3m space group. Nb replaces Fe mainly in B site, leading to significant effects on the magnetic and electronic properties. The substitution weakens the ferromagnetic property of CoFe2O4, but improves its dielectric characteristics. An obvious dielectric relaxor behavior is observed in CoFe1.9Nb0.1O4, which is mainly attributed to the mixed-valence of Fe induced by the Nb-doping. Because of high-leakage current of CoFe1.9Nb0.1O4, only a P-E loop of low-quality is recorded.
Carboxymethyl-β-cyclodextrin (CMβ-CD) modified glycol chitosan (GCS) polymers (GCSn-CMβ-CD) were synthesized in the presence of CMβ-CD and GCS. The degree of substitution of CMβ-CD was controllable. The products were characterized by MALDI-TOF MS, 1H nuclear magnetic resonance spectrum (1H-NMR), Fourier transform infrared spectrum (FT-IR), and H2SO4-pheno degradation method. 5-fluorouracil was used as a model drug to explore the interaction with GCSn-CMβ-CD. The results indicate that different GCSn-CMβ-CD polymers showed different drug loading capacities and the adsorption equilibrium was fitted to Langmuir equation. This study provides the basis for usage of GCSn-CMβ-CD as drug carrier.
Investigation on soil fauna was carried out in forest gap and under forest canopy of Cryptomeria fortune artificial stands. A total of 60 orders soil fauna, belonging to 10 phyla and 25 classes, were collected, and average density was 1.89×104 ind./m2. The group number of soil fauna in forest gap was higher than that under forest canopy, and both decreased when the soil layers increased. Densities in forest gap and under forest canopy were found to be significantly different in 0~5 cm layer (p<0.05). The guilds of soil fauna in forest gap and under forest canopy were dominated by the omnivorous, and followed by the saprozoic. H', J, and DG index were higher in forest gap than under forest canopy, but C index was lower in forest gap than under forest canopy, which showed that forest gap had influences on distribution and diversity of soil fauna in Cryptomeria fortune artificial stands.
Usually, atmospheric effects on microwave remote sensing are ignored because of the penetration of microwave. However, for quantitative inversion in which high precision inversion is required, atmospheric effects should be taken into account. Based on the radiative transfer model, three atmospheric parameters, upwelling and downwelling atmospheric brightness temperature and atmospheric transmissivity, were proved to be much influenced by precipitable water vapor. The MonoRTM and 946 global atmospheric profiles were used to simulate these atmospheric parameters. Then we got regression models for PWV(precipitable water vapor) and atmospheric brightness temperatures and for PWV and atmospheric transmissivity, respectively. Finally, Zhangye radiosonde data sets were used to validate the models, and verification results showed that the estimation models had high credibility.
Study on thermal decomposition kinetics of hydrous minerals is important to the exploration of the formation mechanisms of intermediate-deep earthquakes occurred in subduction zone. In the present work thermal decomposition of talc was studied by using thermogravimetric (TG) techniques under the condition of dynamical air atmosphere. The model-free methods including Friedman and FWO were employed to determine the activation energy (Ea) and the pre-exponential factor (A). Based on the initial values derived from Friedman method, the most probable kinetic model of the dehydration reaction was obtained by using the multivariate non-linear regression approach. The results showed that talc decomposed in the temperature range of 830~1 050℃ and the most probable kinetic model could be expressed as f(α)=(1-α)n and G(α)=(1-(1-α)(1-n))/(1-n), with the derived values of 1.7,344.2 kJ/mol, and 4.9E12 s-1 for n, Ea, and A, respectively.
A fundamental premise of the plate tectonics is that a relatively rigid lithosphere moves over a weaker asthenosphere. Howerer, the nature of the lithosphere-asthenosphere boundary (LAB) remains poorly understood, especially that beneath the continental lithosphere. At the present there are several definitions for the LAB based on different measurements. By defining the LAB as the depth where the effective viscosity has a weak minimum, a semi-analytical method to determine this bottom boundary is presented. This boundary is called thermal-rheological bottom boundary because it combines the thermal and rheological properties of the lithospheric mantle. Studies on the three famous cratons (Kaapvaal, Fennoscandia, Slave) show that the thermal-rheological LAB is at the depth of ~250 km, which is consistent with the results based on other geophysical methods (for example, magnetotelluric method). The thermal-rheological LAB is closer to the LAB in the plate tectonics, because it provides the possibility for the mechanical plates moving over the asthenosphere. At the thermal-rheological LAB and in its adjacent area, the deformation mechanism is predominant by diffuse creep, and the differential stress level is low while the strain rate is high.
Based on qualitative and quantitative analyses of organic and mineral in shales, the composition geological characteristics and adsorptivity of shales in coal-bearing strata were systematically studied in Huainan mining area. Results are given below, 1) TOC content of shale in study area varies between 0.13% and 8.58% with the average content of 1.98%; the organic matter type is mainly Ⅲ and a little Ⅱb; thermal maturity of organic matter ranges from 0.61% to 1.48% with the average of 0.93%; and mineral composition of shale mainly consists of clay minerals and quartz and kaolinite and mixed layer illite/smectite (I/S) are the staple clay types. 2) Adsorption capacity increases with TOC content, and the maximum adsorption amount per unit TOC increases with Ro value; and the adsorptivity of clay mineral is associated with its type. 3) Brittle deformed shale and brittle-ductile deformed shale have different adsorption isotherm characteristics.
A high efficiency processing method for mode switch is proposed based on the requirements of airborne synthetic aperture radar (SAR). The features of the mode switch from stripmap to spotlight are well analyzed, and the precise echo signal model during the mode switch is established. By combining the processing steps by means of motion compensation, the polar format algorithm (PFA) is used for the multi-mode imaging. The processing results before and after the mode switch can be shared.Hence the processing efficiency is improved and hardware memory is reduced, which makes the method highly suitable for real-time imaging. Simulation results confirm the validity of the proposed method and show high efficiency.
State-of-the-art speech recognition systems often depend on a lot of training data, but perform poorly when limited data is available. In this paper, we study speech recognition systems under low-resource condition. The subspace Gaussian mixture (SGMM) model is first applied to reduce the number of parameters. The model is further enhanced by discriminative training based on maximum mutual information criterion. The bottleneck features based on deep neural networks are then studied to make robust feature extraction. The SGMM model and the bottleneck features are finally combined to produce a novel speech recognition system under low-resource condition. On the standard OpenKWS 2013 evaluation corpus, experimental results show the combination of the two technologies brings substantial relative improvement of about 12% over the baseline system.
In order to provide a high-performance OGC-WPS (Open Geospatial Consortium, Web processing service) which supports high-concurrency of client requests, an extensible multi-process mode single WPS server is designed and implemented. On this basis, we build a scalable service cluster and implement an asynchronous processing mode based on thread pool and distributed cache. Experiments show that with this platform one can obtain good speed up and scalability in dealing with high concurrency tasks.
The problem of DSSS signal acquisition in presence of phase shift is analyzed and discussed. Firstly, our work focuses on the impact of the code phase and Doppler frequency estimation due to the modulated data. Then, two acquisition methods are discussed, and they can be used to overcome the impact of the phase shift. Compared to the sectional correlative accumulation algorithm, the approach of the delay and conjugate multiplication provides more stable performance. Simulation results show that the algorithms proposed here are able to capture the DSSS signal when the conventional algorithms fail due to the modulated data.
In view of the data extraction problems in large-capacity data curve plotting, the "data reading by-block" → "data join"→ "data extraction" achieving finally "full extraction" process is proposed, which can achieve the processing of the large-capacity data file over 4 GB. When the data quantity is large, conventional curve plotting methods may give rise to the low efficiency or the flicker problem in the plotting area. The "Polyline" function is employed to optimize the plotting program, and greatly improves the plotting efficiency. The dual-buffering method is adopted to eliminate the flicker in plotting area, and thus further shortens the drawing time.
We propose a new heterogeneous transfer learning method, which uses related heterogeneous feature dataset. We use translation invariant kernels(Euclidean kernels and RBF kernels) to map the target dataset and the related dataset to a new reproducing kernel Hilbert space, in which the two datasets have equal feature dimensions and similar distributions and reserve their topological property. The experimental results show that our method works well and the method based on the Euclidean kernel improves accuracy by more than 5%~10%.
Capability leak vulnerability on Android platform may lead to permission elevation and privacy disclosure, and it is often exploited by malicious applications to bypass Android security mechanism. However, so far there is no approach aiming at Android capability leak detection on the source code level comprehensively. In this paper, we propose a novel approach named CLDroid, which uses backward program slicing to abstract application logic from the Java source code, detects pattern violations based on predefined security rules, and reports the violations as capability leak vulnerability. Results show that our approach is effective in detecting capability leak vulnerability and has better scalability.
Based on kernel method and Gaussian mixture model, we analyze the distribution of the mobile network access time from a new view, the mobile model view. The analysis of real data suggests that the distribution of the mobile network has two peaks. We give some reasonable interpretations for such a phenomenon.
We propose a location-based multi-level-neighbor-assisted coding-aware routing protocol (LFCR) for wireless multi-hop networks. LFCR is based on the concept of inter-flow network coding and utilizes location information for establishing routes, which takes into account not only the potential network coding opportunities but also the positive progress brought by each transmission. Simulation results show that, compared to COPE, LFCR significantly improves performance of the network.