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Live delivery of goods is a novel type of marketing model that has injected new vitality into the development of agricultural e-commerce. It is only in the last few years that live streaming has become a popular e-commerce marketing approach. Agriculture e-commerce in China has a new lease on life thanks to the advent of a new marketing model. This article comprehensively surveys the live broadcast delivery models in the e-commerce era. The comprehensive survey includes the significance and current state of the live broadcast delivery models and identifies the factors impeding the integration and development of agricultural products. The review includes the new marketing model of live broadcast delivery and makes pertinent recommendations. The article presents a novel model for precise marketing classification of agricultural products for e-commerce live broadcast platforms using clustering. Moreover, this article uses customer development space to achieve precise marketing for the e-commerce live broadcast platform. The article enhances K-means with local density and information entropy and proposes an improved TFA customer segmentation method. The results demonstrate that the proposed method is capable of efficiently classifying customers, accurately reflecting their value, and optimizing the algorithm’s efficiency by optimizing the clustering technique.

A Nd:CNGG laser operated at 935 nm and 1061 nm pumped at 885 nm and 808 nm, respectively, is demonstrated. The 885 nm direct pumping scheme shows some advantages over the 808 nm traditional pumping scheme. It includes higher slope efficiency, lower threshold, and better beam quality at high output power. With the direct pumping, the slope efficiency increases by 43% and the threshold decreases by 10% compared with traditional pumping in the Nd:CNGG laser operated at 935 nm. When the Nd:CNGG laser operates at 1061 nm, the direct pumping increases the slope efficiency by 14% with a 20% reduction in the oscillation threshold.

We report the generation of high-peak power multi-wavelength picosecond laser pulses using optical parametric amplification (OPA) in BBO seeded with pulses generated in a 5-mm length BaWO4 Crystal by stimulated Raman scattering of 18-ps laser pulses at 532 nm. The maximum output energy of the amplified first-Stokes component at 559.7 nm was about 1.76 mJ. The corresponding maximum peak power, pulse duration and spectral line width were measured to be 117.3 MW, 15 ps and 18.0 cm(-1), respectively. The multi-wavelength picosecond laser pulses were in the visible and near infrared ranges. Using this Raman-seeded OPA technique, the beam quality of the stimulated Raman scattering pulses can be improved. (C) 2009 Elsevier B.V. All rights reserved.

We report a technique for characterization of ultra-weak fluorescence based on a 355-nm pumped pico-second non-collinear optical parametric amplifier (OPA). In the experiment, we effectively reduced the strong super-fluorescence background by using a series of methods. With the picosecond OPA as the pre-amplifier and the gating pulse, the decay of the fluorescence of Rhodamine 6G dye in ethanol was measured and the fluorescence lifetime was found to be about 941 ps. The gain factor of this parametric fluorescence amplifier was measured to be similar to 4.2 x 10(6), while the energy detection limit was similar to 160 aJ per pulse within a 15-ps gating pulse. (C) 2009 Elsevier B.V. All rights reserved.

A LD-pumped self-Q-switched 946 nm laser by using a co-doped Cr,Nd:YAG crystal as a gain medium as well as a saturable absorber is studied. The 946 nm self-Q-switched rate equations of co-doped crystal are solved numerically by Runge-Kutta method directly. The important parameters of lasers, such as average output power, threshold pump power, pulse width, pulses repetition rate, and optimal transmission of output coupler are obtained numerically. Experimentally, the maximum average output power up to 2.61 W, corresponding to a slope efficiency of 23.43%, was obtained in a simple and compact linear cavity. The optical-to-optical efficiency is 17.3% and the peak power is 7.57 kW with repetition rate of 23.78 kHz and pulse width of 14.5 ns. In the experiments, a high-quality fundamental transverse mode can be preserved in a large range of incident pump power. The numerical results of the 946 nm self-Q-switched Cr,Nd:YAG laser are in good agreement with the experimental results.

We report the characteristics of the amplified stimulated Raman scattering (SRS) pulses generated in liquid benzene by a picosecond (ps) beta-barium, borate (BBO) optical parametric amplifier (OPA). When the OPA system was used as an energy amplifier for SRS pulses, with a pump energy of 2.4 mJ at 355 nm for the OPA, the maximum output energy of the amplified SRS was about 0.73 mJ for the signal and 0.18 mJ for the idler, the energy conversion efficiency was 30.4% from the pump beam to the amplified third order Stokes component at 635.1 nm. The total efficiency would be as high as 37.9% if the output of the idler is also included. The corresponding spectral line width of the amplified Raman pulse was 11.8 cm(-1) with a pulse width of similar to 10.9 ps and a peak power of 67 MW. The OPA system was also used as an amplifier for very weak Raman signal, the slope gain factor of this amplifier was found to be as high as similar to 4.1 x 10(7) and the energy detection limit was as low as 14.8 aJ per pulse, or 48 photons at 635.1 nm, in particular. Such a detection limit corresponds to approximately 0.5 photons per pulse if the time-gate of the OPA is reduced to 150 fs and it is about the same as or even better than a recently report on the 0.75 photons detection limit for a 150-fs OPA of coherent signal at 800 nm. (c) 2008 Elsevier B.V. All rights reserved.

We report a technique for detecting weak scattered light pulses based on a 532 nm pumped picosecond beta-barium-borate collinear optical parametric amplifier. The measured maximum slope gain factor of the amplifier was found to be around 107, and the energy detection limit was of the order of fJ/pulse for the signal of 730 nm and the idler of 1.5 mu m at a pumping intensity of 2.83 GW/cm(2). The linearity of the gain for this amplifier was found to be excellent for a seeding level of lower than 420 fJ per pulse. The maximum gains and the energy detection limits for the scattered light pulses from various scattering targets were found to be poorer than that from the reflective mirror, owing to the degraded beam quality and the depolarization of the scattered light. A reduction of the maximum gain for the scattered light with the increase of the angle of incidence, which causes pulse broadening and reduces the photon flux of the signal, was investigated. The feasibility of detecting weak scattered light in the infrared by using idler-to-signal frequency up-conversion was also demonstrated, in which the infrared seeder located in the idler branch of the amplifier was injected as the seeding beam and was then parametrically up-converted into the visible signal branch, with an even higher gain. (c) 2007 Elsevier B.V. All rights reserved.

Bloom syndrome (BS) is an autosomal recessive disorder characterized by genomic instability and the early development of many types of cancer. Missense mutations have been identified in the BLM gene (encoding a RecQ helicase) in affected individuals, but the molecular mechanism and the structural basis of the effects of these mutations remain to be elucidated. We analysed five disease-causing missense mutations that are localized in the BLM helicase core region: Q672R, I841T, C878R, G891E and C901Y. The disease-causing mutants had low ATPase and helicase activities but their ATP binding abilities were normal, except for Q672, whose ATP binding activity was lower than that of the intact BLM helicase. Mutants C878R, mapping near motif IV, and G891E and C901Y, mapping in motif IV, displayed severe DNA-binding defects. We used molecular modelling to analyse these mutations. Our work provides insights into the molecular basis of BLM pathology, and reveals structural elements implicated in coupling DNA binding to ATP hydrolysis and DNA unwinding. Our findings will help to explain the mechanism underlying BLM catalysis and interpreting new BLM causing mutations identified in the future.

We report a diode-pumped self-Q-switched 1064-nm Cr,Nd:YAG laser with pulse duration in the range of 16?18 ns. The maximum average output power up to 7 W, corresponding to a slope efficiency of 33%, is obtained in a simple and compact linear cavity by using a plane-concave output coupler with a transmittance of 15%. The laser operates at TEM00 mode with a pump power of 14.2 W.