Opto-VLSI-based tunable single-mode fiber laser

Xiao, Feng,Alameh, Kamal,Lee, TongTak The Optical Society 2009 Optics express Vol.17 No.21

<P>A new tunable fiber ring laser structure employing an Opto-VLSI processor and an erbium-doped fiber amplifier (EDFA) is reported. The Opto-VLSI processor is able to dynamically select and couple a waveband from the gain spectrum of the EDFA into a fiber ring, leading to a narrow-linewidth high-quality tunable laser output. Experimental results demonstrate a tunable fiber laser of linewidth 0.05 nm and centre wavelength tuned over the C-band with a 0.05 nm step. The measured side mode suppression ratio (SMSR) is greater than 35 dB and the laser output power uniformity is better than 0.25 dB. The laser output is very stable at room temperature.</P>

Electro-transport studies of electrodeposited (Bi_1−<i>x</i>Sb_<i>x</i>)₂Te₃ nanowires

Xiao, Feng,Yoo, Bongyoung,Lee, Kyu-Hwan,Myung, Nosang V IOP Pub 2007 Nanotechnology Vol.18 No.33

<P>A wide range of (Bi<SUB>1−<I>x</I></SUB>Sb<SUB><I>x</I></SUB>)<SUB>2</SUB>Te<SUB>3</SUB> thin films and nanowires were electrodeposited from acidic tartaric–nitric baths. Initially, (Bi<SUB>1−<I>x</I></SUB>Sb<SUB><I>x</I></SUB>)<SUB>2</SUB>Te<SUB>3</SUB> thin films were electrodeposited on gold substrates to investigate the effect of the deposition potential and electrolyte composition on film composition. After these investigations, (Bi<SUB>1−<I>x</I></SUB>Sb<SUB><I>x</I></SUB>)<SUB>2</SUB>Te<SUB>3</SUB> nanowires were potentiostatically electrodeposited using polycarbonate templates as scaffolds. The deposition conditions strongly influenced the deposit composition, crystal structures, and electrical properties of the nanowires. The preferential crystal orientation of the nanowires shifted from a {110} orientation at −20 mV to a {015} orientation at −100 mV. The temperature dependent <I>I–V</I> characteristics of bundle nanowires indicated that the nanowires were semiconductors with negative temperature coefficient of resistivity. The thermal activation energies were 0.20 eV for Bi<SUB>1.8</SUB>Sb<SUB>0.1</SUB>Te<SUB>3.1</SUB> and 0.49 eV for (Bi<SUB>0.3</SUB>Sb<SUB>0.7</SUB>)<SUB>2</SUB>Te<SUB>3</SUB> nanowires, respectively.</P>

A Study on Future Design using Scenario Planning Methods

Xiao, Feng 한국디자인학회 2018 한국디자인학회 학술발표대회 논문집 Vol.2018 No.11

Far-infrared Drying Characteristics and Quality Assessment of Ligularia fischeri

Xiaofeng Ning,한충수,조성찬,이준수,윤성수 한국식품과학회 2013 Food Science and Biotechnology Vol.22 No.suppl1

The purpose of this study was to investigate drying models and drying characteristics of Ligularia fischeri by using far-infrared drying. The far-infrared drying tests on L. fischeri were performed at air velocities of 0.6and 0.8 m/s, and drying chamber temperatures of 40, 45,and 50oC. Four thin layer drying models were used to estimate drying curves. Drying characteristics were analyzed on the basis of drying rate, color, antioxidant activity, and contents of polyphenolics and flavonoids. The goodness of the models was estimated using the coefficient of determination, the root mean square error, and the reduced chi-square. The results revealed that increases in drying temperature and air velocity caused a decrease in drying time. The Page and Thompson models were considered suitable for the far-infrared drying of L. fischeri. After drying, the antioxidant properties of L. fischeri were decreased under all drying conditions.

Experimental Study of Coffee Ring Effect with Ag Nanowire

Xiaofeng Wang(왕효풍),Hadi Teguh Yudistira(하디 테구 유디스티라),Baekhoon Seong(성백훈),Marten Darmawan(마튼 달마완),Doyoung Byun(변도영) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11

Modeling and Input-Output Decoupling of Hypersonic Vehicles

Xiaofeng Su,Yingmin Jia,Junping Du,Jun Zhang 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.1

This paper studies the problems of modeling and input-output decoupling of generic hyper-sonic vehicles. Dynamical equations of hypersonic vehicles are derived using Lagrangian approach, which capture the dominating characteristics and primary interactions. Then, based on the simplified model, the original decoupling problem is reformulated as an asymptotical stability problem of the cor-responding error system. The popular dynamic inversion is employed to design the decoupling controller, which can achieve steady-state decoupling. However, external disturbance will greatly destroy the effect of decoupling before the system reaches steady state. To this end, based on the error system, ro-bust H∞ theorem can be easily used to address this issue by reducing the impact of disturbance on error system outputs, which ultimately results in approximate decoupling. Moreover, the degree of approximate decoupling can be enhanced by choosing a small performance index γ. Simulations verify the effectiveness of proposed controllers.

Flow ripple analysis and structural parametric design of a piston pump

Xiaofeng Wu,Chihkeng Chen,Chihwei Hong,Yafeng He 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.9

The ripple in the outlet flow from a high-pressure piston pump is caused by pressure pulses in the piston cavity when it rotates through the transition region of the valve plate. We propose a parametric design that optimizes the transition region structure of a piston pump valve plate to reduce the ripple in the outlet flow. For a high- pressure piston pump, a theoretical model of the piston cavity is developed that includes fluid compression properties and leakages. The piston pump parametric model is built using AMESIM software and a simulation is conducted. The results show that the ripple in the outlet flow is affected by the outlet pressure and the pump’s speed and by the structure of the pre-compression region of the valve plate. To minimize the ripple in the outlet flow from the piston pump, the structural parameters in the pre-compression region are optimized as the design variables using the software, ISIGHT, which integrates the piston pump parametric model in AMESIM. After optimization, the ripple in the outlet flow rate is, respectively, reduced by 37.05 %, 38.54 % and 41.04 % for outlet pressures of 200 bar, 300 bar and 400 bar. Finally, a flow ripple test experiment is performed to verify the simulation results.

The effect of viscosity ratio on drop pinch-off dynamics in two-fluid flow

Xiaofeng Jiang,Enle Xu,Xianliang Meng,Huai Z. Li 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.91 No.-

Drop pinch-off draws a lot of interest from scientists and engineers because of widely practical applications as well as the fascinating mechanism of finite-time singularities and self-similar behavior. This work experimentally investigates the effect of viscosity ratio on the local pinch-off mechanism of liquid drops in both air and viscous fluids, with a high-speed camera. The results show that for 56 ≤ λ ≤ 6.3 × 103 and 0.009 ≤ λ ≤ 0.061, drop pinch-off exhibits self-similar profile which is asymmetric and conical away from hmin. Drop pinch-off in air with low viscosity ratios shows either in inertial regime (I) or transition from inertial to viscous regime (I→V). But the kinetics undergoes the inertial regime (I) to inertial-viscous regime (IV) through an intermediate viscous regime (V) when the viscosity ratio becomes larger. Drop pinch-off in viscous fluids displays the transition from inertial to viscous regime (I→V). These results agree well with Eggers’s universal solution until it becomes unstable and the previous literature. The viscosity ratio indeed affects the drop pinch-off dynamics as well as interface deformation. Our experiments enrich the understanding of the interaction between the internal and external fluids on drop pinch-off behavior near the singularity point.

Fuzzy Adaptive Control for Generic Hypersonic Vehicles with Non-Affine Aerodynamic Characteristics and Output Con-straints

Xiaofeng Zhang,Kang Chen,Wenxing Fu 제어로봇시스템학회 2019 제어로봇시스템학회 국제학술대회 논문집 Vol.2019 No.10

In this paper, a fuzzy adaptive control scheme is developed for a class of generic Hypersonic Vehicles (GHVs) subjected to non-affine aerodynamics. With the aid of the nonlinear mapping, the dynamics of the attitude tracking errors are transformed to a stochastic uncertain control system. By utilizing several specific smooth function vectors and estimating the boundaries of the uncertainties, the unknown changing uncertainties can be handled. Based on the mean-value theorem, the difficulties caused by non-affine aerodynamics can be circumvented. Meanwhile, two fuzzy logic systems (FLSs) are introduced for dealing with the aerodynamic nonlinearities. The constraints of the attitude angular tracking errors can be ensured simultaneously. Finally, simulation results demonstrated the effectiveness of the proposed algorithm.

Physical properties of tetragonal transition-metal borides Nb2MB2 (M = Mo, W, Re or Os) with a new superstructure

Xiaofeng Li,Yaping Tao,Ziyu Hu,Shengli Zhang 한국물리학회 2015 Current Applied Physics Vol.15 No.9

The mechanical and thermodynamic properties, chemical bonding characteristics and electronic structure of Nb2MB2 (M = Mo, W, Re or Os) with a new tetragonal U3Si2-type superstructure (space group P4/ mnc, no. 128) were studied by means of density functional theory calculations. All Nb2MB2 structures studied were demonstrated to be thermodynamically and mechanically stable. The bulk, shear and Young's moduli, Poisson's ratio, Debye temperature and anisotropy factors were derived for ideal polycrystalline Nb2MB2 aggregates. Among these compounds, Nb2WB2 was found to have the highest shear modulus and hardness. The electronic densities of state and electronic localization function analysis revealed the metallicity and strong covalent BeB, NbeB and MB bonding in Nb2MB2. Moreover, these results reveal that the covalence between Nb 4d, M nd (n = 4 for Mo and 5 for W, Re and Os) and B 2p states is the cause of the relatively higher elastic modulus and hardness of the Nb-based compounds. Finally, thermodynamic properties, including the bulk modulus, heat capacity and thermal expansion coefficient of Nb2WB2 were obtained systematically under high temperature and pressure.