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Search Results: 1 - 10 of 33100 matches for " Minggang Feng "
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The Application of a New Neutron Induced Gamma Ray Spectroscopy Tool in Evaluation the Shale Gas in Fuling Shale Gas Field  [PDF]
Wei Yan, Minggang Feng, Yue Wang, Shuai Liu, Kaixuan Li, Xianran Zhao, Wenjun Liang
Open Journal of Yangtze Oil and Gas (OJOGas) , 2018, DOI: 10.4236/ojogas.2018.32008
Abstract: Shale gas reservoir is characterized by complex lithology with ultra-low porosity and permeability, which brings many challenges in the formation evaluation. Elemental Capture Spectroscopy Sonde (ECS) can be used to measure the elements and get the formation of the mineralogy. LithoScanner is a newly-generated spectroscopy tool, which can be used to measure both inelastic and capture spectra, providing estimation of more elements, including silicon, calcium, iron, sulfur, titanium, gadolinium, aluminum, potassium, sodium, magnesium, manganese, carbon, etc. LithoScanner can be directly used to measure the total organic carbon content (TOC) in the formation, and provide solutions to the lithology classification and heterogeneous rock analysis (HRA). The changing lithology and borehole rugosity have little influence on the direct measurement of TOC by LithoScanner. LithoScanner shows great advantage in accuracy when comparing with other methods using triple-combo. The systematic lithology classification method in shale gas reservoir using LithoScanner is correlatable in multi-wells. The brittleness index from mineralogy can be applied to hydraulic stimulation. HRA results offered guides in both the coring sample selection and the experiment. The advantages of LithoScanner in shale gas formation evaluation were presented in this paper, and the workflow can also be applied to other reservoirs.
Improved method for analyzing the degradation of estrogens in water by solid-phase extraction coupled with ultra performance liquid chromatography-ultraviolet detection

Minggang Zheng,Ling Wang,Yuandui Bi,Feng Liu,

环境科学学报(英文版) , 2011,
Abstract: We established an improved method for the determination of four estrogens including estriol (E3), 17β-estradiol (E2), 17α-ethynyl-estrodiol (EE2) and estrone (E1) in water. The method consisted of solid-phase extraction (0.5 L water) and subsequent analysis of analytes by ultra-performance liquid chromatography (UPLC) with an ultraviolet detector (UVD). Base-line separation was achieved for all studied estrogens using a column (50 nm × 2.1 mm) packed with 1.7 μm particle size stationary phase. Recovery was higher than 88% and detection limits ranged between 12.5-23.7 ng/L for the four estrogens, with the RSD ranging from 7% to 11%. The method was successfully applied to determine E2 and EE2 in simulated natural water, which found that about 70% of E2 was degraded (with a half-life of about 30 hr) within 48 hr and about 55% of EE2 was degraded (with a half-life of about 36 hr). Low levels of El were found, however E3 was undetectable during the process.
Common model analysis and improvement of particle swarm optimizer

Feng PAN,Jie CHEN,Minggang GAN,Guanghui WANG,Tao CAI,

控制理论与应用 , 2007,
Abstract: Particle swarm optimizer (PSO), a new evolutionary computation algorithm, exhibits good performance for optimization problems, although PSO can not guarantee convergence of a global minimum, even a local minimum. However, there are some adjustable parameters and restrictive conditions which can affect performance of the algorithm. In this paper, the algorithm are analyzed as a time-varying dynamic system, and the sufficient conditions for asymptotic stability of acceleration factors, increment of acceleration factors and inertia weight are deduced. The value of the inertia weight is enhanced to (?1, 1). Based on the deduced principle of acceleration factors, a new adaptive PSO algorithmharmonious PSO (HPSO) is proposed. Furthermore it is proved that HPSO is a global search algorithm. In the experiments, HPSO are used to the model identification of a linear motor driving servo system. An Akaike information criteria based fitness function is designed and the algorithms can not only estimate the parameters, but also determine the order of the model simultaneously. The results demonstrate the effectiveness of HPSO.
Adsorbate and defect effects on electronic and transport properties of gold nanotubes
Yongqing Cai,Miao Zhou,Minggang Zeng,Chun Zhang,Yuan Ping Feng
Physics , 2011, DOI: 10.1088/0957-4484/22/21/215702
Abstract: First-principles calculations have been performed to study the effects of adsorbates (CO molecules and O atoms) and defects on electronic structures and transport properties of Au nanotubes (Au(5, 3) and Au(5, 5)). For CO adsorption, various adsorption sites of CO on the Au tubes were considered. The vibrational frequency of the CO molecule was found to be very different for two nearly degenerate stable adsorption configurations of Au(5, 3), implying the possibility of distinguishing these two configurations via measuring the vibrational frequency of CO in experiments. After CO adsorption, the conductance of Au(5, 3) decreases by 0.9G0 and the conductance of Au(5, 5) decreases by approximately 0.5G0. For O-adsorbed Au tubes, O atoms strongly interact with Au tubes, leading to around 2G0 of drop in conductance for both Au tubes. These results may have implications for Au-tube-based chemical sensing. When a monovacancy defect is present, we found that, for both tubes, the conductance decreases by around 1G0. Another type of defect arising from the adhesion of one Au atom is also considered. For this case, it is found that, for the Au(5, 3) tube, the defect decreases the conductance by nearly 1G0, whereas for Au(5, 5), the decrease in conductance is only 0.3G0.
Thermal Stability and Electrical Control of Magnetization of Heusler/Oxide Interface and Non-collinear Spin Transport of Its Junction
Zhaoqiang Bai,Lei Shen,Yongqing Cai,Qingyun Wu,Minggang Zeng,Guchang Han,Yuan Ping Feng
Physics , 2013, DOI: 10.1088/1367-2630/16/10/103033
Abstract: Towards next-generation spintronics devices, such as computer memories and logic chips, it is necessary to satisfy high thermal stability, low-power consumption and high spin-polarization simultaneously. Here, from first-principles, we investigate thermal stability (both structure and magnetization) and the electric field control of magnetic anisotropy on Co2FeAl (CFA)/MgO. A phase diagram of structural thermal stability of the CFA/MgO interface is illustrated. An interfacial perpendicular-anisotropy, coming from the Fe-O orbital hybridization, provides high magnetic thermal stability and a low stray field. We find an electric-field-induced giant modification of such perpendicular-anisotropy via a great magnetoelectric effect (the anisotropy energy coefficient beta~10-7 erg/V cm). Our spin electronic-structure and non-collinear transport calculations indicate high spin-polarized interfacial states and good magnetoresistance properties of CFA/MgO/CFA perpendicular magnetic tunnel junctions.
Simultaneous Magnetic and Charge Doping of Topological Insulators with Carbon
Lei Shen,Minggang Zeng,Yunhao Lu,Ming Yang,Yuan Ping Feng
Physics , 2013, DOI: 10.1103/PhysRevLett.111.236803
Abstract: A two-step doping process, magnetic followed by charge or vice versa, is required to produce insulating massive surface states in topological insulators for many physics and device applications. Using first-principles calculations, we demonstrate here simultaneous magnetic and hole doping achieved with a single dopant, carbon, in Bi2Se3. Carbon substitution for Se (CSe) results in an opening of a sizable surface Dirac gap (53-85 meV), while the Fermi level (EF) remains inside the bulk gap and close to the Dirac point at moderate doping concentrations. The strong localization of 2p states of CSe favors spontaneous spin polarization via a p-p interaction and formation of ordered magnetic moments mediated by the surface state. Meanwhile, holes are introduced into the system by CSe. This dual function of carbon doping suggests a simple way to realize insulating massive topological surface states.
Graphene-based spintronic components
Minggang Zeng,Lei Shen,Haibin Su,Miao Zhou,Chun Zhang,Yuanping Feng
Physics , 2010, DOI: 10.1103/PhysRevB.83.115427
Abstract: A major challenge of spintronics is in generating, controlling and detecting spin-polarized current. Manipulation of spin-polarized current, in particular, is difficult. We demonstrate here, based on calculated transport properties of graphene nanoribbons, that nearly +-100% spin-polarized current can be generated in zigzag graphene nanoribbons (ZGNRs) and tuned by a source-drain voltage in the bipolar spin diode, in addition to magnetic configurations of the electrodes. This unusual transport property is attributed to the intrinsic transmission selection rule of the spin subbands near the Fermi level in ZGNRs. The simultaneous control of spin current by the bias voltage and the magnetic configurations of the electrodes provides an opportunity to implement a whole range of spintronics devices. We propose theoretical designs for a complete set of basic spintronic devices, including bipolar spin diode, transistor and logic gates, based on ZGNRs.
Mn-doped Thiolated Au$_{25}$ Nanoclusters: Atomic Configuration, Magnetic Properties, and A Possible High-performance Spin Filter
Miao Zhou,Yongqin Cai,Minggang Zeng,Chun Zhang,Yuan Ping Feng
Physics , 2013, DOI: 10.1063/1.3575203
Abstract: We report an \emph{ab inito} investigation on the ground-state atomic configuration, electronic structures, magnetic and spin-dependent transport properties of Mn-doped Au$_{25}$ nanoclusters protected by thiolate. It is found that the most stable dopant sites are near surfaces, rather than the center positions of the nanoparticles. Transport calculations show that high-performance spin filters can be achieved by sandwiching these doped clusters between two nonmagnetic Au electrodes. The nearly perfect spin filtering originates from localized magnetic moments of these clusters that are well protected by ligands from the presence of electrodes.
Efficient spin injection into graphene through a tunnel barrier: overcoming the spin conductance mismatch
Qingyun Wu,Lei Shen,Zhaoqiang Bai,Minggang Zeng,Ming Yang,Zhigao Huang,Yuan Ping Feng
Physics , 2014, DOI: 10.1103/PhysRevApplied.2.044008
Abstract: Employing first-principles calculations, we investigate efficiency of spin injection from a ferromagnetic (FM) electrode (Ni) into graphene and possible enhancement by using a barrier between the electrode and graphene. Three types of barriers, h-BN, Cu(111), and graphite, of various thickness (0-3 layers) are considered and the electrically biased conductance of the Ni/Barrier/Graphene junction are calculated. It is found that the minority spin transport channel of graphene can be strongly suppressed by the insulating h-BN barrier, resulting in a high spin injection efficiency. On the other hand, the calculated spin injection efficiencies of Ni/Cu/Graphene and Ni/Graphite/Graphene junctions are low, due to the spin conductance mismatch. Further examination on the electronic structure of the system reveals that the high spin injection efficiency in the presence of a tunnel barrier is due to its asymmetric effects on the two spin states of graphene.
Non-wandering Operator in Bargmann Space
Minggang Wang,Hua Xu
Journal of Mathematics Research , 2010, DOI: 10.5539/jmr.v2n2p34
Abstract: In this paper the Bargmann space is denoted by F. This space’s roots can be found in mathematical problem of relativistic physics or in quantum optics. In physics the Bargmann space contains the canonical coherent states, so it is the main tool for studying the bosonic coherent state theory of radiation field and for other application .This paper deals with the unilateral backward shift operator T on a Bargmann space F. We provide a sufficient condition for an unbounded operator to be non-wandering operator, and then apply the condition to give a necessary and sufficient condition in order that T be a non-wandering operator.
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