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71.
H.C. Ji P.K.J. Park Hoon Kim J.H. Lee Y.C. Chung 《Photonics Technology Letters, IEEE》2006,18(8):950-952
We propose and demonstrate a novel technique to monitor the frequency offset between the optical source and delay interferometer (DI) for direct-detection differential phase-shift-keying (DPSK) systems. In this scheme, a phase-modulated tone is applied to DPSK signals at the transmitter and then detected after being converted into an amplitude-modulated tone at the DI to be used for the monitoring signal. Our experimental demonstration shows that the monitoring range and sensitivity of the proposed scheme are measured to be /spl plusmn/2 GHz and /spl sim/10 MHz, respectively, which we believe are good enough to be used either to generate alarm signals for the frequency offset monitoring or to control the feedback loop of the DI. 相似文献
72.
In this paper, by capturing the atomic information and reflecting the behaviour governed by the nonlinear potential function,
an analytical molecular mechanics approach is proposed. A constitutive relation for single-walled carbon nanotubes (SWCNT’s)
is established to describe the nonlinear stress-strain curve of SWCNT’s and to predict both the elastic properties and breaking
strain of SWCNT’s during tensile deformation. An analysis based on the virtual internal bond (VIB) model proposed by P. Zhang
et al. is also presented for comparison. The results indicate that the proposed molecular mechanics approach is indeed an
acceptable analytical method for analyzing the mechanical behavior of SWCNT’s.
The project supported by the National Natural Science Foundation of China (10121202, 90305015 and 10328203), the Key Grant
Project of Chinese Ministry of Education (0306) and the Research Grants Council of the Hong Kong Special Administrative Region,
China (HKU 7195/04E). 相似文献
73.
Comprehensive study on novel Linear-Dispersion Division Multiple-Access(LDDMA) for multi-user uplink Multiple-Input Multiple-Output(MIMO)systems is proposed.In the new multiplexing scheme,each user’s information symbol is dispersed by a User-Specific Matrix(USM)both in space and time domain and linearly combined at base-station side.And a simple random search algorithm,based on capacity maximization criteria,is developed to generate a bank of USMs.Simulation results are presented to demonstrate the advantages of LDDMA.When the Bit Error Rate(BER) reaches 10^–3,the performance gains are 3dB and 5dB,compared with Time-Division Linear Dispersion Codes(TD-LDC)and BLAST,respectively. 相似文献
74.
In Hwang Min Lee Sang Lee 《Quantum Electronics, IEEE Journal of》1982,18(2):148-151
As the cavity length of the iodine photodissociation laser (iodine PDL) is varied, the number of neighboring coherent modes increases and the time-dependent mode-competition effect gives rise to typical changes in the pulse shape. The ratio of the number of all coherent modes to that of all oscillating modes is found to be as high as 80 percent when the cavity length is 450 cm. The frequency width in which the neighboring modes are coherent is approximately 0.1 GHz for all cavity lengths used. The effect of a BDN absorber placed in the cavity is distinct in the shorter cavities. 相似文献
75.
Boris Kapilevich Yosef Pinhasi Ruth Arusi Michael Anisimov Danny Hardon Boris Litvak Yan Wool 《Journal of Infrared, Millimeter and Terahertz Waves》2010,31(11):1370-1381
A single-pixel imaging remote sensor operating at 330 GHz is described. It is based on a frequency modulated continuous wave
(FMCW) and aimed at detection of concealed objects for ranges up to 40 m. The system consists of 2 horn-lens antennas integrated
with a homodyne transceiver. The synthesized linear FMCW signal at X-band is multiplied by a factor of 32 to generate the
transmitted signal. An intermediate frequency (IF) signal obtained in the output port of the 2-nd harmonic mixer is employed
for image processing. Distance measurements were made by performing data acquisition unit based on LabView interface and resulting
in a range resolution about 1 cm. Examples of 2D and 3D images reconstructed with this sensor are presented. 相似文献
76.
In this paper, a paradigm is developed to design the linear-phase FIR multiple-notch filters with variable notch frequencies. The design procedure can be proceeded through two steps: First, a linear-phase narrow-band low-pass filter met the given bandwidth and stopband ripple specifications is designed. Second, a tuning procedure is applied to the computed low-pass filter to yield the desired multiple-notch filter. When the notch frequencies are varied, the same tuning procedure can be employed to render the multiple-notch filter with the new set of the notch frequencies. The tuning procedure employed reduces the computational complexity of designing the multiple-notch filter with the new set of the notch frequencies. The simulation results demonstrate the effectiveness of our scheme. 相似文献
77.
Xueyu Qiu Yadong Han Xiuli Zhuang Xuesi Chen Yuesheng Li Xiabin Jing 《Journal of nanoparticle research》2007,9(5):901-908
Nano-hydroxyapatite (HA)/poly(l-lactide) (PLLA) composite microspheres with relatively uniform size distribution were prepared by a solid-in-oil-in-water
(s/o/w) emusion solvent evaporation method. The encapsulation of the HA nanopaticles in microshperes was significantly improved
by grafting PLLA on the surface of the HA nanoparticles (p-HA) during emulsion process. This procedure gave a possibility
to obtain p-HA/PLLA composite microspheres with uniform morphology and the encapsulated p-HA nanoparticle loading reached
up to 40 wt% (33 wt% of pure HA) in the p-HA/PLLA composite microspheres. The microstructure of composite microspheres from
core-shell to single phase changed with the variation of p-HA to PLLA ratios. p-HA/PLLA composite microspheres with the diameter
range of 2–3 μm were obtained. The entrapment efficiency of p-HA in microspheres could high up to 90 wt% and that of HA was
only 13 wt%. Surface and bulk characterizations of the composite microspheres were performed by measurements such as wide
angle X-ray diffraction (WAXD), thermal gravimetric analysis (TGA), environmental scanning electron microscope (ESEM) and
transmission electron microscopy (TEM). 相似文献
78.
79.
Sang‐Mi Park Kyoung‐Soo Yook Woo‐Hyung Lee Yongtaek Hong Jun‐Yeob Lee In‐Nam Kang 《Journal of polymer science. Part A, Polymer chemistry》2013,51(23):5111-5117
Two new thermally crosslinkable hole‐transporting polymers, X‐PTPA and X‐PCz, were synthesized via Yamamoto coupling reactions. The number‐averaged molecular weights (Mn) of X‐PTPA and X‐PCz were found to be 45,000 and 48,000, respectively, and therewith, polydispersity indices were of 1.8 and 1.7, respectively. Thermally crosslinked X‐PTPA and X‐PCz exhibit excellent solvent resistance and stable optoelectronic properties. The UV–visible maximum absorption peaks of X‐PTPA and X‐PCz in the thin film state are at 389 and 322 nm, respectively. The HOMO levels of X‐PTPA and X‐PCz are estimated to be ?5.27 and ?5.39 eV, respectively. Multilayered devices (ITO/crosslinked X‐PTPA or X‐PCz/SY‐PPV/LiF/Al) were fabricated with SY (SuperYellow) as the emitting layer. The maximum efficiency of the multilayered device with a crosslinked X‐PTPA layer is approximately three times higher than that of the device without a crosslinked X‐PTPA layer and much higher than that of the crosslinked X‐PCz device. This result can be explained by the observations that crosslinked X‐PTPA produces increased electron accumulation within the emitter, SY, and also efficient exciton formation due to improved charge balance. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5111–5117 相似文献
80.
Xuqiu Yang Lisheng Liu Qingjie Zhang Pengcheng Zhai 《Journal of Electronic Materials》2011,40(5):489-492
Molecular dynamics simulations of the structural and mechanical properties of single-crystalline CoSb3 have been carried out at room temperature. Special emphasis was given to the surface effect. Four different boundary conditions were applied to represent a wide range of surface-atom fractions. The LAMMPS program in conjunction with a multibody potential was employed. First, free relaxation was performed to obtain the corresponding stable configurations. The atomic rearrangements and energy distributions were observed. Then, uniaxial tensile deformation was simulated at a constant strain rate. The stress–strain responses and structural evolutions were examined during the process. Comparison of simulation results between different boundary conditions was carefully made. It was found that, when the scale of the single-crystalline CoSb3 model becomes nanometric and the fraction of the surface atoms increases, the mechanical performance becomes substantially worse. Nonetheless, the deformation mechanism and intrinsic mechanical nature are very similar. 相似文献