Biography:

In the past J.X. Wang has collaborated on articles with I. Brissaud and H. An. One of their most recent publications is Analysis of Gaulish coins by proton induced X-ray emission, synchrotron radiation X-ray fluorescence and neutron activation analysis. Which was published in journal Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms.

More information about J.X. Wang research including statistics on their citations can be found on their Copernicus Academic profile page.

J.X. Wang's Articles: (23)

Analysis of Gaulish coins by proton induced X-ray emission, synchrotron radiation X-ray fluorescence and neutron activation analysis

AbstractRecent diggings in Brittany provide us with new Gaulish coins for a further study about their value and dating. The elemental analysis gives a good idea of the great variety in the monetary alloys used in Gallia in the second part of the first century B.C. Each coin was analyzed by surface and volume techniques. For some samples the discrepancy between the two types of analysis is large for Ag-rich alloys: a surface enrichment in silver is observed.

Numerical investigation on the combustion and emission characteristics of a hydrogen assisted biodiesel combustion in a diesel engine

Highlights•Skeletal kinetics was constructed for biodiesel and hydrogen combustion.•The developed mechanism contains the CO, NOx and soot formation kinetics.•Engine performance is improved with the increase of H2 addition.•CO and soot emissions significantly decrease with the H2 addition.

Short communicationThe occurrence of barium in a Jurassic coal in the Huangling 2 Mine, Ordos Basin, northern China

AbstractThis paper describes the modes of occurrence of significantly-enriched barium in a Jurassic coal in the Ordos Basin, northern China. A total of 14 bench samples were taken from a mining face in the Huangling 2 Mine, situated southeastern of the Ordos Basin, China. The coal investigated in this study is characterized by high volatile matter, low ash yield, and low sulfur content. The average content of barium (5728 μg/g) is about 36 times higher than that of common Chinese coals. SEM–EDS data show that the carriers of barium are witherite and strontianite, both of which are of epigenetic origin. It is inferred that the barium was originated from the Ba-ore deposits in the black shales in the Qinling Mountains, located to the south of the Ordos Basin.

Growth and characterization of axially periodic Zn2SnO4 (ZTO) nanostructures

AbstractTransparent semiconductor Zn2SnO4 nanowires were synthesized for the first time by the thermal evaporation method. The nanowires show a unique periodic structure along the axis of the nanowire. By varying the Zn ratio in the reactants, ZTO nanowires with different morphologies can be achieved. High-resolution transmission microscopy (HRTEM) characterization confirms that the ZTO nanowires are crystalline. PL (photoluminescence) measurement of the ZTO nanowires reveals a green emission band centered at ∼493 nm. Our method provides a simple approach for assembling nanocrystals into one-dimensional periodic nanostructures. These nanostructures may have potential applications for opto-electronic nanodevices and nanosystems.

Adsorption of bromide at the Ag(100) electrode surface

AbstractThe adsorption and phase formation of bromide on Ag(100) has been studied by chronocoulometry and surface X-ray scattering (SXS). With increasing electrode potential, bromide undergoes a phase transition from a lattice gas to an ordered c(2×2) structure (θ=0.5). The degree of lateral disorder was estimated by comparing the SXS- and the electrochemical measurements. Based on chronocoulometric experiments, a thermodynamic analysis of charge density data was performed to describe the bromide adsorption at the Ag(100) electrode. The Gibbs surfaces excess, electrosorption valencies, Esin–Markov coefficients, and the Gibbs energy of adsorption, lateral interaction energies as well as surface dipole moments have been estimated. The experimental θ versus E- isotherms are modeled employing (i) a quasi-chemical approximation as well as (ii) the results of a recent Monte Carlo simulation. An attempt is made to discuss the structure data and thermodynamic quantities of bromide adsorption on Ag(100) on the basis of the Grahame–Parsons model of the Helmholtz layer.

Raman and FTIR spectra of iron phosphate glasses containing cerium

AbstractIn the present work, cerium iron phosphate glasses were studied to examine the effect of the CeO2 composition on the structure of the iron phosphate glasses system. Cerium iron phosphate samples with the compositions, I: xCeO2(40 − x)Fe2O360P2O5 and II: xCeO2(100 − x)(40Fe2O360P2O5) (x = 0–30 mol%) have been prepared. The structure of glasses has been studied using X-ray diffraction (XRD), Raman spectrum, Fourier transform infrared spectrum (FT-IR) and differential thermal analysis (DTA), especially focusing on the structure dependence on the CeO2 content. The glass formation occurs at series I; at series II, the crystalline phases are detected in the samples. The Q1 groups are the predominant structural units in glasses with the cerium-free and 10 mol% CeO2 content. With increasing CeO2 content in glass compositions, the POP network get extensively depolymerised, resulting in the systematic conversion of Q1 to Q2 structural units. The Q0 units can be detected in the all glasses compositions. The glass transition temperature (Tg) linearly increase with the addition of CeO2 content, indicating an increase in thermal stability tendency with increasing CeO2 content. The change of Tg is consistent with structural modification of glass.

Reducibility study of oxide-ion conductors La2−xBaxMo2−yAyO9−δ (A = W, Al, Ga) assessed by impedance spectroscopy

AbstractThe reducibility of oxide-ion conductors La2−xBaxMo2−yWyO9−δ (x = 0, 0.06; y = 0, 0.1, 0.5, 1.0) and La2Mo1.9A0.1O9−δ (A = Al, Ga) were studied in the reducing atmosphere of 5%H2 + Ar by means of impedance spectroscopy measurement. The introduction of Ba at La site in La2Mo2−yWyO9 can lower the sintering temperature by about 100 K in comparison with the La2Mo2−yWyO9 samples. All substitutions can enhance the conductivity and improve the reducibility in the temperature range from 548 to 923 K. The double substitution of Ba and W as well as substitution of Al or Ga at Mo sites has a better stabilizing effect than the single tungsten substitution. Among these substitutions the introduction of Al has the best stabilizing effect.

Growth of SnO2 nanowires with uniform branched structures

AbstractSnO2 nanowires have been prepared using the active carbon reaction with the fine SnO2 powder at low temperature (700 °C). These nanowires show rectangular cross-section, with their widths ranging from 10 to 50 nm. Branched nanowires with definite included angle are also observed in these products. The morphology and microstructure of the single crystalline SnO2 nanowires and the branched nanowires are characterized by means of scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selective area electron diffraction (SAED) and Raman spectrum. In addition, the possible growth mechanism of the SnO2 nanowires and branched nanowires is also discussed.

Improved DC and RF performance of AlGaN/GaN HEMTs grown by MOCVD on sapphire substrates

AbstractHigh-quality AlGaN/GaN high electron mobility transistor (HEMT) structures were grown by metalorganic chemical vapor deposition (MOCVD) on 2-in. sapphire substrates. Two-dimensional electron gas (2DEG) mobility of 1410 cm2/V s and concentration of 1.0 × 1013 cm−2 are obtained at 295 K from the HEMT structures, whose average sheet resistance and sheet resistance uniformity are measured to be about 395 Ω/sq and 96.65% on 2-in. wafers, respectively. AlGaN/GaN HEMTs with 0.8 μm gate length and 0.2 mm gate width were fabricated and characterized using the grown HEMT structures. Maximum current density of 0.9 A/mm, peak extrinsic transconductance of 290 mS/mm, unity cutoff frequency (fT) of 20 GHz and maximum oscillation frequency (fmax) of 46 GHz are achieved. These results represent significant improvements over the previously fabricated devices with the same gate length, which are attributed to the improved performances of the MOCVD-grown HEMT structures.

Perfluorinated compounds in the Pearl River and Yangtze River of China

AbstractA total of 14 perfluorinated compounds (PFCs) were quantified in river water samples collected from tributaries of the Pearl River (Guangzhou Province, south China) and the Yangtze River (central China). Among the PFCs analyzed, perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) were the two compounds with the highest concentrations. PFOS concentrations ranged from 0.90 to 99 ng/l and <0.01–14 ng/l in samples from the Pearl River and Yangtze River, respectively; whereas those for PFOA ranged from 0.85 to 13 ng/l and 2.0–260 ng/l. Lower concentrations were measured for perfluorobutane sulfonate (PFBS), perfluorohexane sulfonate (PFHxS), perfluorooctanesulfoamide (PFOSA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorononaoic acid (PFNA), perfluorodecanoic acid (PFDA), and perfluoroundecanoic acid (PFUnDA). Concentrations of several perfluorocarboxylic acids, including perfluorododecanoic acid (PFDoDA), perfluorotetradecanoic acid (PFTeDA), perfluorohexadecanoic acid (PFHxDA) and perfluorooctadecanoic acid (PFOcDA) were lower than the limits of quantification in all the samples analyzed. The highest concentrations of most PFCs were observed in water samples from the Yangtze River near Shanghai, the major industrial and financial centre in China. In addition, sampling locations in the lower reaches of the Yangtze River with a reduced flow rate might serve as a final sink for contaminants from the upstream river runoffs. Generally, PFOS was the dominant PFC found in samples from the Pearl River, while PFOA was the predominant PFC in water from the Yangtze River. Specifically, a considerable amount of PFBS (22.9–26.1% of total PFC analyzed) was measured in water collected near Nanjing, which indicates the presence of potential sources of PFBS in this part of China. Completely different PFC composition profiles were observed for samples from the Pearl River and the Yangtze River. This indicates the presence of dissimilar sources in these two regions.

Distribution and developmental changes in ghrelin-immunopositive cells in the gastrointestinal tract of African ostrich chicks

AbstractGhrelin, the endogenous ligand for the growth hormone secretagogue receptor (GHS-R), has been found in the gastrointestinal tract of many vertebrates, but little is known about its distribution in the gastrointestinal tract of African ostrich chicks. In the present study, the distribution, morphological characteristics, and developmental changes of ghrelin-producing cells in the gastrointestinal tract of African ostrich chicks were investigated using immunohistochemistry. Ghrelin-immunopositive (ghrelin-ip) cells were found to be localized in the mucous membrane of the entire gastrointestinal tract, but not in the myenteric plexus. The greatest number of ghrelin-ip cells was found in the proventriculus, and the ghrelin-ip cell density gradually decreased from the proventriculus to the rectum. Interestingly, from postnatal day 1 to day 45 in the proventriculus, and from postnatal day 1 to day 90 in the gizzard and small intestine, there was a steady increase in the number of ghrelin-ip cells. By day 45 in the proventriculus and day 90 in the gizzard and small intestine, the number of cells reached a plateau and remained steady. These results clearly demonstrate that ghrelin-ip cells exist and the number of ghrelin-ip cells increases with age in the African ostrich gastrointestinal tract from postnatal day 1 to day 90; ghrelin may be involved in gastrointestinal tract development.

cDNA cloning of ghrelin and ontogeny of ghrelin mRNA expression in the gastrointestinal tract of African ostrich chicks

AbstractGhrelin is the endogenous ligand for the growth hormone secretagogue receptor (GHS-R). The sequence of ghrelin has been determined in many species ranging from fish to mammals. The ostrich is the largest herbivorous bird in the world. Although the distribution, morphological characteristics, and developmental changes of ghrelin-producing cells in the gastrointestinal tract of African ostrich chicks have recently been determined, the sequence and structure of ghrelin and its expression in the gastrointestinal tract of African ostrich chicks have not been studied. In the present study, the sequence and structure of ghrelin and its expression in the gastrointestinal tract of African ostrich chicks were investigated by reverse-transcriptase polymerase chain reaction (RT-PCR). Results of cDNA cloning revealed that African ostrich ghrelin is composed of 28 amino acid residues and the sequence of the 7 amino acids of the N-terminal region of African ostrich ghrelin was identical with that of other birds. Ninety-day-old female African ostriches were used to investigate the expression of ghrelin in the gastrointestinal tract. The results showed that ghrelin mRNA existed in the proventriculus, gizzard, duodenum, ileum, cecum, and rectum; there was no expression in the jejunum and colon. We observed developmental changes in the ghrelin mRNA expression in the stomach and small intestine of African ostriches. The results of the present study showed that ghrelin mRNA existed on day 1 in the proventriculus, but there was no expression in other tissues. On day 45, ghrelin mRNA existed in the proventriculus, gizzard, and ileum; however, there was no expression in the duodenum and jejunum. On day 90 and 334, we detected ghrelin mRNA in the proventriculus, gizzard, duodenum, and ileum, but there was no expression in the jejunum. The results of the present study clearly demonstrate that ghrelin mRNA exists and the distribution of ghrelin mRNA in the gastrointestinal tract of African ostriches changes with age (from postnatal day 1 to day 334).

Fabrication of porous titanium implants with biomechanical compatibility

AbstractBy using H2O2 as foaming reagent, porous titanium with open and interconnected pore morphology was obtained. The morphology, pore structure and elemental composition were observed by SEM–EDX. The mechanical property was determined by compressive test. The results show that the compressive strength and Young's modulus of porous titanium with 64% porosity were 102 ± 10 MPa and 3.3 ± 0.8 GPa, respectively, and for 76% porosity porous titanium, the values were 23 ± 10 MPa and 2.1 ± 0.5 GPa. These results suggest that the former has sufficient mechanical properties for clinical use under load-bearing conditions and the latter has the potential application for tissue engineering scaffolds.

Wavelet analysis of photospheric magnetic flux

AbstractWe link 342 NSO/Kitt Peak synoptic charts during 1978 to 2003 one by one in time order and reconstruct a daily sequence of photospheric magnetic flux (PMF). By using wavelet transform (WT) some typical mid-term periodicities of PMF are identified, such as 1.38-year, 332-, 275- and 158-day periods. We discuss briefly their temporal evolutions and mutual relations in this paper. For a comparison with another solar general index, we also analyze the periodicities of total solar irradiance (TSI) with the same method. We find the wavelet power spectra of such two sequences are very similar. Therefore, we think PMF and TSI may have some common physical origins.

Fluorinated photoinitiators: Synthesis and photochemical behaviors

Highlights•Two fluorinated photoinitiators with carbamate 2959-IPDI-F and 2959-IPDI-F-HDDA have been synthesized and characterized.•The fluorinated photoinitiators have higher reactivity and good anti-oxygen inhibition than Irgacure 2959 with or without PFEA.•The fluorinated photoinitiators can migrate to top layer and the liquid-air interface in the gradient distribution, resulting in anti-oxygen inhibition and unique surface morphology. The migration was verified by XPS, SEM and EDS.

Mechanism of electron violent acceleration by extra-intense lasers in vacuum

AbstractThe mechanism underlying the electron capture acceleration (Phys. Rev. E 58 (1998) 6575) is studied. It is found that the longitudinal electric field, resulting from the transverse spatial gradient of the laser fields, is responsible for the violent electron acceleration while the transverse fields play the role of confining the electron inside the laser beam.

Violent acceleration of electrons by an ultra-intense pulsed laser beam☆

AbstractWe present a novel phenomenon of electron dynamics in an ultra-intense pulsed laser beam. When the field intensity is sufficiently strong (Q ≡ eE0meωc ≳ 100, Q is a dimensionless parameter measuring the field intensity), the electron can be captured by the laser beam and thus violently accelerated by the laser field.

Catalytic combustion of toluene on Cu-Mn/MCM-41 catalysts: Influence of calcination temperature and operating conditions on the catalytic activity

AbstractCatalytic combustion of toluene on Cu-Mn/MCM-41 catalyst was performed in tubular flow reactor operated at atmospheric pressure. The effect of catalyst pre-treatment temperatures on the catalytic activity and stability was investigated. Some reaction variables, such as inlet concentration of toluene and oxygen, reaction temperatures and space velocities were varied over wide ranges, and the influence of different reaction conditions on toluene conversion was discussed. It is showed that the catalytic activity was significantly affected by calcination temperatures between 300 and 800 °C, and oxygen concentration, toluene concentration and space velocity are all key experimental factors to optimize the toluene combustion activities. The objective of this study was to investigate catalytic properties of Cu-Mn/MCM-41 catalysts prepared at different calcination temperatures, in order to obtain additional information to prepare an efficient and highly active catalyst at low temperature.

Study on inductive high-Tc superconducting fault current limiters☆

AbstractAn inductive superconducting fault current limiter based on Bi-2212 tubes has been built. In this paper, we present the experimental results of static impedance tests and dynamic short circuit tests. The dynamic short circuit tests show the limiter can limit the fault current to a few times the nominal current. We evaluate the performance of the limiter and compare the differences between the closed-iron core and the open-core. Using the equivalent circuit of inductive superconducting fault current limiter (SCFCL), we calculate the effective permeability, (μ(H)), of the magnetic circuit during fault conditions. Results show that the resistance of superconducting tubes is the primary limiting factor of the SCFCL during the fault condition, and the open-core is more suitable for the distribution networks than the closed-core.

The high voltage problem in the saturated core HTS fault current limiter

AbstractA small model of a one-phase saturated core HTS fault current limiter was developed. It consists of an iron core, an AC coil and a DC HTS coil. The HTS coil comprised six 126 turns double-pancakes (ID 70 mm), wound after heat treatment from Bi-2223 multifilamentary tape in Ag matrix. A fault simulation circuit was set up to characterize the dynamic properties of the model limiter. The voltages and currents of the AC coil and the DC HTS coil were measured through a computer-based data acquisition system. The tests have shown that the limiter has a fast response and the first current peak can be easily limited, but a high voltage will be induced on the DC HTS coil side during the fault state. This high voltage can badly affect the DC current equipment on the DC HTS coil side. The origin and value of the high voltage can be explained using a transformer model. For a limiter with n1 turns AC coil and n2 turns DC coil, the largest induced voltage will be roughly close to (n2/n1)U, where U is the rated voltage of the limiter. To commercialize this kind of limiter, the high voltage problem must be solved. Some different designs were introduced to lower the induced voltage.

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