The Effect of Off-Farm Employment on Forestland Transfers in China : A Simultaneous-Equation Tobit Model Estimation

China's new round tenure reform has devolved collective forests to individuals on an egalitarian basis. To balance the equity-efficiency dilemma, forestland transfers are highly advocated by policymakers. However, the forestland rental market is still inactive after the reform. To examine the role of off-farm employment in forestland transfers, a simultaneous Tobit system of equations was employed to account for the endogeneity, interdependency, and censoring issues. Accordingly, the Nelson-Olson two-stage procedure, embedded with a multivariate Tobit estimator, was applied to a nationally representative dataset. The estimation results showed that off-farm employment plays a significantly negative role in forestland rent-in, at the 5% risk level. However, off-farm activities had no significant effect on forestland rent-out. Considering China's specific situation, a reasonable explanation is that households hold forestland as a crucial means of social security against the risk of unemployment. In both rent-in and rent-out equations, high transaction costs are one of the main obstacles impeding forestland transfer. A remarkable finding was that forestland transactions occurred with a statistically significant factor equalization effect, which would be helpful to adjust the mismatched labor-land ratio and improve the land-use efficiency.Peer reviewe

Impulsive rotational Raman scattering of N2 by a remote "air laser" in femtosecond laser filament

We report on experimental realization of impulsive rotational Raman scattering from neutral nitrogen molecules in a femtosecond laser filament using an intense self-induced white-light seeding "air laser" generated during the filamentation of an 800 nm Ti: Sapphire laser in nitrogen gas. The impulsive rotational Raman fingerprint signals are observed with a maximum conversion efficiency of ~0.8%. Our observation provides a promising way of remote identification and location of chemical species in atmosphere by rotational Raman scattering of molecules.Comment: 4 pages, 4 figure

Effect of polarization sensitivity on ultrasmall SOI-based AWG for FBG sensor interrogation

Polarization sensitivity is an important factor that affects the interrogation of ultrasmall arrayed waveguide grating (AWG) for fiber Bragg grating (FBG) sensor. An ultrasmall 1  ×  8 silicon-on-insulator (SoI) AWG with a core size of less than 530  μm  ×  480  μm is proposed in this study. This ultrasmall SoI AWG exhibits good transmission spectra and high polarization sensitivity. The increased channel numbers and tight structure increase the polarization sensitivity of AWG. Temperature interrogation experiments show that the FBG sensor interrogation is drastically affected when the effect of polarization sensitivity on the ultrasmall AWG is sufficiently large

Population Redistribution among Multiple Electronic States of Molecular Nitrogen Ions in Strong Laser Fields

We carry out a combined theoretical and experimental investigation on the population distributions in the ground and excited states of tunnel ionized N2 molecules at various driver wavelengths in the near- and mid-infrared range. Our results reveal that efficient couplings (i.e., population exchanges) between the ground state and the excited states occur in strong laser fields. The couplings result in the population inversion between the ground and the excited states at the wavelengths near 800 nm, which is verified by our experiment by observing the amplification of a seed at ~391 nm. The result provides insight into the mechanism of free-space nitrogen ion lasers generated in remote air with strong femtosecond laser pulses.Comment: 18 pages, 4 figure

Remote creation of strong and coherent emissions in air with two-color ultrafast laser pulses

We experimentally demonstrate generation of strong narrow-bandwidth emissions with excellent coherent properties at ~391 nm and ~428 nm from molecular ions of nitrogen inside a femtosecond filament in air by an orthogonally polarized two-color driver field (i. e., 800 nm laser pulse and its second harmonic). The durations of the coherent emissions at 391 nm and 428 nm are measured to be ~2.4 ps and ~7.8 ps respectively, both of which are much longer than the duration of the pump and its second harmonic pulses. Furthermore, the measured temporal decay characteristics of the excited molecular systems suggest an "instantaneous" population inversion mechanism that may be achieved in molecular nitrogen ions at an ultrafast time scale comparable to the 800 nm pump pulse.Comment: 19 pages, 4 figure