Tuning Martensitic Phase Transition by Non-Magnetic Atom Vacancy in MnCoGe Alloys and Related Giant Magnetocaloric Effect

The effects of non-magnetic atom vacancy on structural, martensitic phase transitions and the corresponding magnetocMoric effect in MnCoGel-x alloys are investigated using x-ray diffraction and magnetic measurements. The introduction of non-magnetic atom vacancy leads to the decrease of the martensitic transition temperature and realizes a temperature window where magnetic and martensitic phase transitions can be tuned together. Moreover, the giant magnetocaloric effect accompanied with the coupled magnetic-structural transition is ob- tained. It is observed that the peak values of magnetic entropy change of MnCoGeo.97 are about -13.9, -35.1 and -47.4J.kg-1K-1 for △H = 2, 5, 7T, respectively.

Optimize two-phase distribution of lithium-rich materials to stabilize structure and suppress voltage attenuation

Lithium-rich materials possess the ultra-high specific capacity,but the redox of oxygen is not completely reversible,resulting in voltage attenuation and structural instability.A stepwise co-precipitation method is used for the first time in this paper to achieve the control of the two-phase distribution through controlling the distribution of transition metal elements and realize the modification of particle surface structure without the aid of heterologous ions.The results of characterization tests show that the content of LiMO_(2) phase inside the particles and the content of Li_(2)MnO_(3) phase on the surface of the particles are successfully increased,and the surface induced formation of Li_(4)Mn_(5)O_(12) spinel phase or some disorderly ternary.The electrochemical performance of the modified sample is as follows:LR(pristine)shows specific discharge capacity of 72.7 mA·h·g^(−1)after 500 cycles at 1 C,while GR(modified sample)shows specific discharge capacity of 137.5 mA·h·g^(−1) at 1 C,and the discharge mid-voltage of GR still remains above 3 V when cycling to 220 cycles at 1 C(mid-voltage of LR remains above 3 V when cycling to 160 cycles at 1 C).Therefore,deliberately regulating the local state of the two phases is a successful way to reinforced the material structure and inhibition the voltage attenuation.

Design of a CMOS multi-mode GNSS receiver VCO

A voltage-controlled oscillator（VCO） with dual stages of accumulation mode varactors for a multimode global navigation satellite system（GNSS） application,which adopts sigma-delta fractional-N technology in the synthesizer,is presented.The structure is selected to optimize the frequency coverage and tuning linearity, based on a general analysis of the parasitic capacitance in the coarse tuning switch bank cells,which cover the global positioning system（GPS） and Beidou（BD） bands.The VCO implemented in the 0.18μm CMOS process can cover the GPS L1,BD B1,B2 and B3 bands with sufficient margin,and exhibits low phase noise by using this tuning curve linearization technique.The equalized K_（vco）,characteristic behavior further offers a wide voltage tuning range and improves the stability of the closed loop.