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A pulsed optical parametric oscillator (OPO) was demonstrated for the purpose of wavelength-tunable yellow output with narrow spectral line width. The OPO pumped by the green output of an acousto-optic Q-switched Nd:YAG used a type II phase-matched KTiOPO4 (KTP) crystal as the nonlinear gain medium and a folded cavity arrangement. The OPO was designed to have the idler wave tunable in near infrared oscillated in the cavity, which was further frequency doubled to generate the wavelength-tunable yellow output by using a LiB3O5 (LBO) crystal with type I non-critical phase matching scheme. A fused silica etalon was inserted in the idler wave cavity to narrow the idler wave and the resultant yellow spectral line width. The wavelength of the yellow output obtained could be tuned over 587.2-595.2 nm, within which the maximum average output power of 2.89 W was obtained at 591.2 nm, under an incident average green pump power of 24.0 W. The beam quality factor M2 was 3.4. The conversion efficiency from the green pump to the yellow output was 12.0%. The pulse width at the maximum output power was 37 ns, and the peak power was 7.8 kW. The spectral line width of the yellow output was 0.15 nm, which was narrowed effectively compared with that without etalon in the OPO cavity.

A novel method for computing kinoform of 3D object based on traditional iterative Fourier transform algorithm is described.The method divides three-dimensional object into many object planes by tomographic technique and treat every object plane as a target image,then iterative computation is carried out between one input plane(kinoform) and several output planes(reconstruction images).A space phase factor is added into iterative process to represent depth characters of 3D object.The experimental result shows that this algorithm computational and convergent velocity is fast.At last,the influences of object planes number and distance to reconstruction quality of kinoform are analyzed,and time-division multiplexing technique is used to reconstruct several object planes based on spatial light modulator.

In order to obtain the whole lens′precision surface information and reduce its errors transfer and accumulation,a new global optimization stitching algorithm based on weight coefficient is presented.The common region of the two neighborhood sub-aperture can reach the optimal match and the stitching error is minimized by using this algorithm.The multi-apertures stitching simulation is carried out,and an actual experiment is carried to the flat lens of 150mm.A new sub-aperture position method based on the image edge contour feature extraction is introduced and the error factors are analyzed for stitching.Both the simulation and the experiment results show that this global optimization stitching algorithm is good for reducing the transfer and accumulation error,which exist in the traditional method,and realizing the high precision sub-aperture stitching measurement.

The rapid development of social media has had a profound impact on how people access and share information in China. Some researchers suggest that the new social media has broken through the monolithic propaganda of traditional Chinese media and brought a diversity of topics and perspectives into view. Others argue that platforms such as Weibo (microblogging) largely privilege the opinions of well-educated, middle class individuals, keeping working class industrial and rural workers' voices on the margins. The question remains: has the development of social media bridged or deepened the "digital divide"? In an effort to address this question, this paper explores the appearance of members of a "new generation" of migrant workers on Sina Weibo, the most popular microblogging service in China. Drawing on the results a study of Sina Weibo posts, reposts, and authors, this paper offers three main arguments: (1) Weibo is not only a means for sharing information and expressing opinions, it is also a platform where users mobilize to improve the lives of migrant workers in cities; (2) Weibo provides an emotional outlet, offering members of the "new generation" of migrant workers the opportunity to express dissatisfaction with the bitter reality of their lives and a longing for a better life; and (3) The most influential users of this microblogging platform tend to be media figures, scholars, government officials, and other individuals from outside the community. The author concludes that more effort needs to be made so that, instead of creating new inequalities, social media technology can be of assistance to members of socially marginalized groups.

On the basis of error propagation characteristics of an Inertial Navigation System(INS) and the effect of axial Ring Laser Gyroscope(RLG) on the errors of longitude and latitude,a calibrating method for the RLG drift was proposed to solve the problems that single-axis rotation could compensate the vertical RLG errors automatically,but could not compensate the axial RLG errors in a single-axis rotation INS.First,the auto-compensation principle of the single-axis rotation INS was introduced briefly.Then,the effect of the axial RLG drift,initial heading and attitude error,and initial velocity error on the longitude and the latitude was analyzed on the stationary base.Depending on the errors of longitude and latitude,a new method based on the least squares was proposed to calibrate the RLD drift precisely.Finally,the static and vehicle navigation experiments were performed.The results show that the identification precision reaches 0.000 5(°)/h and radial position error of the INS is less than 1 nm/72 h.The axial RLG drift can be calibrated precisely by the least square method proposed and the experiment result of navigation meets practical demands.

Serials of chalcogenide glasses based on composition of 72GeS(2)-18Ga(2)S(3)-10CsI (in mol%) and doped with high Tm3+ content (up to 10,000 ppm) were prepared, and their luminescence properties were investigated under excitation with 800 nm laser. The influences of doping concentration on Judd-Ofelt intensity parameter Omega(i) spontaneous transition probability A, fluorescence branching ratio beta, and radiative lifetime tau(rad) of Tm3+ in the samples were studied. Four infrared emission bands observed were centered at 1.48, 1.8, 2.3, and 3.8 mu m, corresponding to optical transitions H-3(4) -> F-3(4), F-3(4) -> H-3(6), H-3(4) -> H-3(5) and H-3(5) -> F-3(4), respectively. For 1.0 wt.% Tm3+: doped sample, no concentration quenching was observed and its emission cross-sections at 2.3 and 3.8 mu m calculated by using Fuchtbauer-Ladenburg equation were 6.85 x 10(-21) and 7.66 x 10(-21) cm(-2), respectively. (C) 2010 Elsevier B.V. All rights reserved.