The Hydrodynamic Limit of Nonlinear Fokker-Planck Equation

The non-linear Fokker-Planck equation arises in describing the evolution of stochastic system, which is a variant of the Boltzmann equation modeling the evolution of the random system with Brownian motion, where the collision term is replaced by a drift-diffusion operator. This model conserves mass, momentum and energy;the dissipation is much weaker than that in a simplified model we considered before which conserved only mass, thus more difficult to analyze. The macro-micro decomposition of the solution around the local Maxwellian introduced by T.-P. Liu, T. Yang and S.-H. Yu for Boltzmann equation is used, to reformulate the model into a fluid-type system incorporate viscosity and heat diffusion terms, coupled with an equation of the microscopic part. The viscosity and heat diffusion terms can give dissipative mechanism for the analysis of the model.

Non-Maxwellian Kinetic Modelling of City Size Distribution

To extend the kinetic formulation of city size distribution introduced in [1], the non-Maxwellian kinetic modeling is introduced in the present study, in which a variable collision kernel is used in the underlying kinetic equation of Boltzmann type. By resorting to the well-known grazing asymptotic, a kinetic Fokker-Planck counterpart is obtained. The equilibrium of the Fokker-Planck equation belongs to the class of generalized Gamma distributions. Numerical test shows good fit of the generalized Gamma distribution with the city size distribution of China.

Dietary host-associated Bacillus subtilis supplementation improves intestinal microbiota,health and disease resistance in Chinese perch(Siniperca chuatsi)

The purpose of this study was to evaluate the potential of a host-associated Bacillus subtilis 1-C-7 as a probiotic for Chinese perch(Siniperca chuatsi).Four test diets were formulated to contain graded levels of B.subtilis 1-C-7 at 0(CY),0.85×10^(8)(Y1),0.95×10^(9)(Y2)and 0.91×10^(10)(Y3)CFU/kg diet.The test fish with initial weight 30.0±1.2 g were fed the 4 test diets with 3 replicates in an indoor water-flow aquaculture system with 12 net cages(40 fish/cage)for 10 wk.At the conclusion of the feeding trial,the probiotic effects of B.subtilis on Chinese perch were analyzed based on growth performance,serum biochemical indices,histologic morphology of liver and gut,gut microbiota and the resistance to Aero-monas hydrophila.The results showed that the percentage of weight gain had no significant change in the Y1 and Y2 groups(P>0.05)but decreased in the Y3 group compared to that in the CY group(P<0.05).The fish in the Y3 group displayed the highest activity of serum alanine aminotransferase(ALT)and aspartate aminotransferase(AST)among these 4 groups(P<0.05).The fish in the CY group had the highest value of malondialdehyde in the liver(P<0.05)and showed severe nuclear migration and vacuolization of hepatocytes.The morphology indicated that all test fish had poor intestinal health.However,the fish in the Y1 group had a relatively normal intestinal histologic structure.The mid gut microbial diversity analysis showed that dietary B.subtilis supplementation increased the abundance of probiotics such as Tenericutes and Bacteroides,whereas it reduced the abundance of pernicious bacteria such as Proteobacteria,Actinobacteria,Thermophilia and Spirochaetes.The challenge test showed that dietary B.subtilis supplementation increased the resistance to A.hydrophila in Chinese perch.In conclusion,dietary supplementation of 0.85×10^(8)CFU/kg B.subtilis 1-C-7 could improve the intestinal microbiota,intestinal health and disease resistance in Chinese perch,but more or excessive supple-mentation could reduce growth performance and have negative effects on health.

Information acquisition system of multipoint soil surface height variation for profiling mechanism of seeding unit of precision corn planter

The emergence rate and vitality of maize are directly affected by the sowing depth,and the uniformity of this depth is an important performance indicator of a planter,while the effective soil surface height information acquisition is the prerequisite for ensuring the accuracy of sowing depth control.The soil surface height variation acquisition system of a precision corn planter often produces profiling errors when performing active profiling due to interference from ground debris.In this study,a multipoint soil surface height variation information acquisition system was investigated,which consists of a ranging sensor group and a microcontroller unit(MCU)using a data comparison and screening method.The structure and specifications of the ranging sensors were determined according to the soil surface height variation and debris size,and a nonessential profiling control program was developed.Performed tests on the information acquisition system indicated that the measurement accuracy of the system was 3 mm,and when advancing at a speed of 8 km/h,the accuracy of the profiling decision and the system stability were 97.1%and 94.1%,respectively,indicating that the system was capable of nonessential profile control.The designed ranging system could provide a reference for the design of a ground information acquisition system of precision planters with an active profiling mechanism.

The Fabrication and Characterization of Polarization Insensitive Semiconductor Optical Amplifier

An angled facet strained bulk InGaAs SOA has been designed and fabricated. A device with double-layer antireflection coatings had <2dB polarization sensitivity and <0.5dB gain ripple.

Influences of Meteorological Conditions on Interannual Variations of Particulate Matter Pollution during Winter in the Beijing–Tianjin–Hebei Area

To investigate the interannual variations of particulate matter （PM） pollution in winter, this paper examines the pollution characteristics of PM with aerodynamic diameters of less than 2.5 and 10 μm （i.e., PM2.5 and PM10）, and their relationship to meteorological conditions over the Beijing municipality, Tianjin municipality, and Hebei Province--an area called Jing-Jin-Ji （JJJ, hereinafter）-in December 2013-16. The meteorological conditions during this period are also analyzed. The regional average concentrations of PM2.5 （PM10） over the JJJ area during this period were 148.6 （236.4）, 100.1 （166.4）, 140.5 （204.5）, and 141.7 （203.1） μg m^-3, respectively. The high occurrence frequencies of cold air outbreaks, a strong Siberian high, high wind speeds and boundary layer height, and low temperature and relative humidity, were direct meteorological causes of the low PM concentration in December 2014. A combined analysis of PM pollution and meteorological conditions implied that control measures have resulted in an effective improvement in air quality. Using the same emissions inventory in December 2013-16, a modeling analysis showed emissions of PM2.5 to decrease by 12.7%, 8.6%, and 8.3% in December 2014, 2015, and 2016, respectively, each compared with the previous year, over the JJJ area.

Few-mode vertical-cavity surface-emitting lasers for space-division multiplexing

In order to choose the proper radius of oxide aperture for few-mode vertical-cavity surface-emitting lasers （VCSELs）, the influences of oxide aperture size on the multi-transverse-mode behaviors are investigated in detail. By establishing the effective refractive index model to simulate VCSELs with different radii of oxide apertures, the wavelength and corresponding order of different modes are obtained. VCSELs with three kinds of oxide apertures are manufactured. Then the multi-transverse-mode spectra and near-field are measured. It is found that when the radius is between 1.5 and 4.5μm, few-mode VCSELs can be implemented. The 2.5μm VCSEL manufactured in this paper only emits LP01 mode and LP21 mode. Since the space distance between the two modes is 2μm, it is expected to realize direct-modulation few-mode VCSELs by channel etching or ion implantation between the two modes.