1.

2016-12-01

Efficient common mode noise suppression for fiber optic interferometric sensor using heterodyne demodulation

Min Zhang, et al.

Abstract:

Common-mode noises (CMNs) are frequently encountered in all types of fiber sensor systems. Through involving a reference interferometer, here we report the application of a differential delay heterodyne scheme to suppress CMNs in fiber optic interferometric sensor systems. The contributions of CMNs are shared by both sensing and reference interferometers and are further suppressed by heterodyne demodulation. For the first time we develop the full theoretical model describing this method and experimental results are also presented to confirm the theory. Theoretical analysis shows that the CMN suppression effect (SE, defined as the ratio of the noise floor of the sensing interferometer after and before suppression) is sensitive to several key paramters, including the mean phase difference, the ratio of the visibility and AC amplitude between the two interferometers. Experimental results show that the proposed method can suppress CMNs by 24 dB within the frequency range of 20 Hz to 1 kHz. The measured CMN SE agrees well with the theory. The CMN suppression method and the theory reported here can also be extended to other interferometric systems.

Reference:

Liu F, Xie S, Qiu X, et al. Efficient common-mode noise suppression for fiber-optic interferometric sensor using heterodyne demodulation[J]. Journal of Lightwave Technology, 2016, 34(23): 5453-5461.

2.

2016-11-23

Influence of stimulated Brillouin scattering on positioning accuracy of long-range dual Mach-Zehnder interferometric vibration sensors

Min Zhang, et al.

Abstract:

The properties of noise induced by stimulated Brillouin scattering (SBS) in long-range interferometers and their influences on the positioning accuracy of dual Mach-Zehnder interferometric (DMZI) vibration sensing systems are studied. The SBS noise is found to be white and incoherent between the two arms of the interferometer in a 1-MHz bandwidth range. Experiments on 25-km long fibers show that the root mean square error (RMSE) of the positioning accuracy is consistent with the additive noise model for the time delay estimation theory. A low-pass filter can be properly designed to suppress the SBS noise and further achieve a maximum RMSE reduction of 6.7 dB.

Reference:

He X, Xie S, Cao S, et al. Influence of stimulated Brillouin scattering on positioning accuracy of long-range dual Mach–Zehnder interferometric vibration sensors[J]. Optical Engineering, 2016, 55(11): 116111.

3.

2016-11

Versiquinazolines A-K, Fumiquinazoline-Type Alkaloids from the Gorgonian-Derived Fungus Aspergillus versicolor LZD-14-1

Lin Wenhan, et al.

Abstract:

Eleven fumiquinazoline-type alkaloids, namely, versiquinazolines A-K (1-11), along with cottoquinazolines B–D, were isolated from the gorgonian-derived fungus Aspergillus versicolor LZD-14-1. Their structures were determined by extensive analyses of the spectroscopic data (1D and 2D NMR, HRESIMS), in addition to the experimental and calculated ECD data and X-ray single-crystal diffraction analysis for the assignments of the absolute configurations. Versiquinazolines A, B, and F (1, 2, and 6), bearing a methanediamine or an aminomethanol unit and representing a unique subtype of fumiquinazolines, were found from nature for the first time. Possible biogenetic relationships of the versiquinazolines are postulated. In addition, the structures of cottoquinazolines B (12), D (13), and C (14) should be revised to the enantiomers. Compounds 1, 2, 7, and 11 exhibited inhibitory activities against thioredoxin reductase (IC50 values ranging from 12 to 20 μM).

Reference:

Cheng Z, Lou L, Liu D, et al. Versiquinazolines A–K, Fumiquinazoline-Type Alkaloids from the Gorgonian-Derived Fungus Aspergillus versicolor LZD-14-1[J]. Journal of natural products, 2016, 79(11): 2941-2952.

4.

2016-10-28

Heat Flux Estimation of a Flame Thermal Spray Process Using a Thermally Thin Composite Calorimeter

Yi Duo, et al.

Abstract:

Temperature measurements take on prime importance in the field of the thermal spray coating since the temperature variation greatly affects the formation of splat morphology and also the coating properties and qualities. The evaluation of the heat flux is therefore essential since temperature variation comes from the energy transfer and conduction of the thermal system. The aim of this study is to estimate the heat flux of a flame thermal spray by solving an inverse heat conduction problem. Firstly, the substrate material and geometry are well designed so that the Biot number is small enough to conform to the lumped capacitance conditions. A lumped capacitance model of a substrate with its coating subjected to a uniform echelon heat flux is evaluated by solving a heat balance equation in the Laplace domain. Then, a thermally thin calorimeter is designed and the experimental thermogram is obtained by embedding a thin-wire micro-thermocouple onto the front and rear faces of the substrate. The forced convective heat transfer coefficient as well as the net incident heat flux density brought to the substrate during the thermal spray process are estimated. The theoretical composite surface temperature is compared to the experimental recording, the result showing a good agreement.

Reference:

Yi D, Serio B, Lecler S, et al. Heat flux estimation of a flame thermal spray process using a thermally thin composite calorimeter[J]. Journal of Thermal Spray Technology, 2016, 25(8): 1650-1656.

5.

2016-10-15

On the modeling of viscous incompressible flows with smoothed particle hydrodynamics

Liu Moubin, et al.

Abstract:

Smoothed particle hydrodynamics (SPH) is a Lagrangian, meshfree particle method and has been widely applied to differrent areas in engineering and science. Since its original extension to modeling free surface flows by Monaghan in 1994, SPH has been gradually developed into an attractive approach for modeling viscous incompressible fluid flows. This paper presents an overview on the recent progresses of SPH in modeling viscous incompressible flows in four major aspects which are closely related to the computational accuracy of SPH simulations. The advantages and disadvantages of different SPH particle approximation schemes, pressure field solution approaches, solid boundary treatment algorithms and particle adapting algorithms are described and analyzed. Some new perspectives and future trends in SPH modeling of viscous incompressible flows are discussed.

Reference:

Liu M B, Li S. On the modeling of viscous incompressible flows with smoothed particle hydro-dynamics[J]. Journal of Hydrodynamics, 2016, 28(5): 731-745.

6.

2016-10-05

Global deepwater circulation between 2.4 and 1.7Ma and its connection to the onset of Northern Hemisphere Glaciation

Zhou Liping, et al.

Abstract:

We have generated an early Pleistocene benthic isotopic record for the Ocean Drilling Program (ODP) Site 807 (2804 m) from the western equatorial Pacific. Between 2.4 and 1.7 Ma, the benthic δ13C of this site and a few other deep Pacific sites was consistently higher than the Southern Ocean Site MV0502-4JC (4286 m), pointing to a reversal relative to the current gradient and hence implying a different circulation regime. We reconstructed the deep water mass distribution of this interval using a collection of benthic isotope records from 15 Pacific and 10 Atlantic sites and a δ13C-δ18O mixing model. A two-end-member mixing regime between the North Atlantic Deep Water (NADW) and the Antarctic Bottom Water (AABW), with properties very different from today, was identified. The Southern Ocean showed strong signs of stratification and AABW with low benthic δ13C but high δ18O values reached out to other basins only below ~4000 m. In contrast, NADW ventilated most of the ocean interior, contributing ~70% to the Pacific Deep Water (PDW) volumetrically. Our model results also reveal a strong remineralization effect at the bottom sites of the Pacific and the Atlantic, suggesting significant accumulation of respired carbon in the bottom water between 2.4 and 1.7 Ma. We propose that such a circulation pattern was initiated by the reversal of salinity gradient between AABW and NADW from 3.0 to 2.4 Ma, possibly linked to Antarctic sea ice expansion and reduced southward heat transport during the onset of Northern Hemisphere Glaciation (NHG).

Reference:

Du J, Huang B, Zhou L. Global deepwater circulation between 2.4 and 1.7 Ma and its connection to the onset of Northern Hemisphere Glaciation[J]. Paleoceanography, 2016, 31(11): 1480-1497.

7.

2016-09-15

Polarization Beat Length Estimation Based on the Statistical Properties of Brillouin Gain in SMF

Min Zhang, et al.

Abstract:

A simple method is proposed to estimate the average polarization beat length of single mode fiber (SMF) through the analysis of statistical characteristics of stimulated Brillouin amplified signals. Through launching a variety of pump wave polarizations, the standard deviation of the Brillouin gain is found linearly related with the fiber beat length, within the normal range of beat length values for SMFs. Both the numerical simulations and the experimental results are presented to test the validity of the method. The technique reported here offers a fast, convenient, and low-cost solution to estimate fiber average beat length.

Reference:

Cao S, Xie S, Zhang M. Polarization beat length estimation based on the statistical properties of Brillouin gain in SMF[J]. IEEE Photonics Technology Letters, 2016, 28(18): 1960-1963.

8.

2016-08-28

Initial Results of Microseismic Monitoring of SAGD well by Fiber-optic Seismometer Arrays in Fengcheng Oilfield

Min Zhang, et al.

Abstract:

In order to obtain the microseismic signals during steam-assisted gravity drainage (SAGD) production, especially at the stage of hydraulic fracture treatments, microseismic monitoring is one the of essential measurements. In the November of 2015, we have completed a two-week monitoring of a SAGD well by using fiber-optic seismometer arrays in Fengcheng Oilfield, Xinjiang. The initial results show that the monitoring system has captured numerous seismic signals which are confirmed to be yielded by the injection of vapor and water during the operation of SAGD well. Even more, the energy and quantity of valid signals per hour are analyzed and these two parameters correspond with actual field data basically.

Reference:

Zhang* C, Liu F, Xu G, et al. Initial Results of Microseismic Monitoring of SAGD well by Fiber-optic Seismometer Arrays in Fengcheng Oilfield[C]//2016 Workshop: Rock Physics and Borehole Geophysics, Beijing, China, 28-30 August 2016. Society of Exploration Geophysicists, 2016: 122-124.

9.

2016-05

Pregnane steroids from a gorgonian coral Subergorgia suberosa with anti-flu virus effects

Lin Wenhan, et al.

Abstract:

Five new pregnane-type steroids namely subergorgols T-X (1-5) and three known analogues (6-8) were isolated from a gorgonian coralSubergorgia suberosa. The structures of new compounds were determined on the basis of extensive spectroscopic (IR, MS, 1D and 2D NMR) data analyses, in association with photochemical transformation and ECD methods for the configurational assignment. Compounds1-8were evaluated for the inhibitory effects against H1N1 virus infected in MDCK cells, while subergorgols T-U and 1,2-dehydroprogesterone exerted potent inhibition against A/WSN/33 virus.

Reference:

Cheng W, Ren J, Huang Q, et al. Pregnane steroids from a gorgonian coral Subergorgia suberosa with anti-flu virus effects[J]. Steroids, 2016, 108: 99-104.

10.

2016-04

Eremophilane-Type Sesquiterpenoids from an Acremonium sp Fungus Isolated from Deep-Sea Sediments

Lin Wenhan, et al.

Abstract:

Chemical examination of an EtOAc extract of a cultured Acremonium sp. fungus from deep-sea sediments resulted in the isolation of 15 new eremophilane-type sesquiterpenoids, namely, acremeremophilanes A-O (1-15), together with seven known analogues. The structures of new compounds were determined through extensive spectroscopic analyses, in association with chemical conversions and ECD calculations for configurational assignments. The PKS-derived 4-hexenoic acid unit in 2-6 is rarely found in nature. All compounds were evaluated for inhibitory effects toward nitric oxide production induced by lipopolysaccharide in RAW 264.7 macrophage cells. Compounds 2-6 and 14 exhibited inhibitory effects with IC50 values ranging from 8 to 45 μM.

Reference:

Cheng Z, Zhao J, Liu D, et al. Eremophilane-type sesquiterpenoids from an Acremonium sp. fungus isolated from deep-sea sediments[J]. Journal of natural products, 2016, 79(4): 1035-1047.