Relative Chemical Shifts for Obtaining Accurate Chemical Shifts of Hydrogen Atoms in CH Groups

Accurate chemical shifts of hydrogen atoms in CH groups are difficult to obtain. To solve this problem, relative chemical shifts are introduced. Internal and external standard methods were used to measure the chemical shifts in a whole-concentration of N-methylacetamide- water system. Determination of the chemical shifts of hydrogen atoms, especially those of CH groups, according to the two methods yielded significant differences. Relative chemical shifts were proven to be independent of the reference and may be applied to other systems.

China-Africa Relations Shift

PRESIDENT Xi Jinping＇s trip to Africa was as refreshing as it was reinforcing. Considering the significant effort and financial commitments of China＇s foreign policy toward Africa under Hu Jintao＇s administration, there are concerns as to whether or not Beijing＇s generous policies will change with the new government. While there was less mention of sizeable multi-billion dollar deals during Xi＇s time in Africa, this probably reflects the China-Africa relationship as it matures.

Nanoscale mass sensing based on vibration of single-layered graphene sheet in thermal environments

Based on vibration analysis, single-layered graphene sheet （SLGS） with multiple attached nanoparticles is developed as nanoscale mass sensor in thermal environments. Graphene sensors are assumed to be in simplysupported configuration. Based on the nonlocal plate the- ory which incorporates size effects into the classical theory, closed-form expressions lot the frequencies and relative fre- quency shills of SLGS-based mass sensor are derived using the Galerkin method. The suggested model is justified by a good agreement between the results given by the present model and available data in literature. The effects of tem- perature difference, nonlocal parameter, the location of the nanoparticle and the number of nanoparticles on the relative frequency shift of the mass sensor are also elucidated. The obtained results show that the sensitivity of the SLGS- based mass sensor increases with increasing temperature difference.

A New Method For Mitigation Of Cross Correlation In GPS Receiver

An algorithm for GPS receiver performing to mitigate cross correlations between weak satellite signal and strong satellite signals is presented.By using the tracking result of strong signal,the cross-correlation and cross correlation sequence between weak signals and strong signal can be computed,further modifying the local generate C/A code to drive the cross correlation to zero. The advantage of this method is that it does not require estimation of the strong signal amplitude and it partially independent of the data bit value.Simulation result shows it can eliminate the interference of 75%,and this method is at the cost of sensitivity loss of 0.28dB.

Enhanced high gain harmonic generation scheme with negative dispersion

The enhanced high gain harmonic generation （EHGHG） scheme has been proposed and shown to be able to significantly enhance the performance of HGHG FEL. In this paper we investigate the EHGHG scheme with negative dispersion. The bunching factor at the entrance of the radiator is analyzed, which indicates that the scheme with negative dispersion can further weaken the negative effect of the dispersive strength on the energy spread correction factor. The numerical results from GENESIS （3D-code） are presented, and are in good agreement with our analysis. Then we comparatively study the effects of the initial beam energy spread and the relative phase shift on the radiation power. The results show that the EHGHG scheme with negative dispersion has a larger tolerance on the initial beam energy spread and a nearly equal wide good region of the relative phase shift compared with the case of positive dispersion.