Mesoscale soil moisture survey by mobile cosmic-ray neutron sensor across various landscapes in the Heihe River Basin

The cosmic-ray neutron technology is a novel method for upscaling soil moisture,holding significant importance in drought monitoring,soil water storage estimation,calibration of remote sensing products,and data assimilation of land surface models.However,most studies conducted soil moisture measurement experiments using static Cosmic-Ray Neutron Sensors(CRNS)and are often limited to a single landscape,lacking in-situ measurement for the cosmic-ray neutron rover across various landscapes.This study carried out soil moisture observation experiments using a cosmic-ray neutron rover in nine grassland plots,nine farmland plots,and nine desert plots of the Heihe River Basin,Northwest China.The neutron counts displayed clear variations among different plots,and an equation could represent the relationship between neutron intensity and multiple variables near the ground.The parameter N0 was the smallest for grassland and greatest for desert,and there was a significant negative correlation between Normalized Difference Vegetation Index and N0(P<0.05).Furthermore,the performance of CRNS notably improved after considering soil lattice water and soil organic matter.The Root Mean Square Error(RMSE)between the measured and oven-dried soil moisture increased with radius.Soil moisture measured by CRNS strongly supported the 100 m diameter footprint assumption(RMSE<0.044 g/g).The study offers valuable insights into the application and promotion of cosmic-ray neutron technology across various landscapes within a basin.

Impacts of hydrogen annealing on the carrier lifetimes in p-type 4H-SiC after thermal oxidation

Thermal oxidation and hydrogen annealing were applied on a 100μm thick Al-doped p-type 4H-Si C epitaxial wafer to modulate the minority carrier lifetime,which was investigated by microwave photoconductive decay(μ-PCD).The minority carrier lifetime decreased after each thermal oxidation.On the contrary,with the hydrogen annealing time increasing to3 hours,the minority carrier lifetime increased from 1.1μs(as-grown)to 3.14μs and then saturated after the annealing time reached 4 hours.The increase of surface roughness from 0.236 nm to 0.316 nm may also be one of the reasons for limiting the further improvement of the minority carrier lifetimes.Moreover,the whole wafer mappings of minority carrier lifetimes before and after hydrogen annealing were measured and discussed.The average minority carrier lifetime was up to 1.94μs and non-uniformity of carrier lifetime reached 38%after 4-hour hydrogen annealing.The increasing minority carrier lifetimes could be attributed to the double mechanisms of excess carbon atoms diffusion caused by selective etching of Si atoms and passivation of deep-level defects by hydrogen atoms.

A 4H-SiC semi-super-junction shielded trench MOSFET: p-pillar is grounded to optimize the electric field characteristics

A 4H-SiC trench gate metal-oxide-semiconductor field-effect transistor(UMOSFET)with semi-super-junction shiel-ded structure(SS-UMOS)is proposed and compared with conventional trench MOSFET(CT-UMOS)in this work.The advantage of the proposed structure is given by comprehensive study of the mechanism of the local semi-super-junction structure at the bottom of the trench MOSFET.In particular,the influence of the bias condition of the p-pillar at the bottom of the trench on the static and dynamic performances of the device is compared and revealed.The on-resistance of SS-UMOS with grounded(G)and ungrounded(NG)p-pillar is reduced by 52%(G)and 71%(NG)compared to CT-UMOS,respectively.Additionally,gate ox-ide in the GSS-UMOS is fully protected by the p-shield layer as well as semi-super-junction structure under the trench and p-base regions.Thus,a reduced electric-field of 2 MV/cm can be achieved at the corner of the p-shield layer.However,the quasi-intrinsic protective layer cannot be formed in NGSS-UMOS due to the charge storage effect in the floating p-pillar,resulting in a large electric field of 2.7 MV/cm at the gate oxide layer.Moreover,the total switching loss of GSS-UMOS is 1.95 mJ/cm2 and is reduced by 18%compared with CT-UMOS.On the contrary,the NGSS-UMOS has the slowest overall switching speed due to the weakened shielding effect of the p-pillar and the largest gate-to-drain capacitance among the three.The proposed GSS-UMOS plays an important role in high-voltage and high-frequency applications,and will provide a valuable idea for device design and circuit applications.

Analysis of the Prognosis for Patients with Stage T3N0-1M0 Nasopharyngeal Carcinoma Treated by Chemotherapy Combined with Radiotherapy

OBJECTIVE To investigate the relationship between the therapeutic modality and prognostic factors for the patients with T3N0-1M0 nasopharyngeal carcinoma. METHODS The clinical data from 127 cases of T3N0-1M0 nasopharyngeal carcinoma patients with initial treatment, during the period from January 4th, 2000 to November 12th, 2001, were retrospectively analyzed. The cases were divided into Group A with simple radiotherapy (90) and Group B with the radiation therapy combined with chemotherapy (37), based on various patients' conditions. In group B, inductive chemotherapy was conducted for 18 cases, inductive chemotherapy plus homochronous chemotherapy for 5 and homochronous chemotherapy for 14. RESULTS The 5-year overall survival (OS) in the groups A and B was 73.4% and 72.3% respectively (P>0.05); the cancer-correlated survival (CCS) in the 2 groups was 76.4% and 72.3% respectively (P>0.05); the disease-free survival (DFS) in group A and B was 65.5% and 71.7% respectively (P<0.05). A multiple analysis showed that the mode of radiation therapy plus chemotherapy was a favorable independent impact factor for DFS. CONCLUSION Chemotherapy plus radiotherapy can improve the DFS of patients with T3N0-1M0 nasopharyngeal carcinoma, but fails to prolong the survival time of the patients. The modality of chemotherapy plus radiotherapy is not the necessary choice in treatment of patients with T3N0-1M0 nasopharyngeal carcinoma.

The High Surface Ratio Micro-MoS₂Grain Composed of MoS₂Nanosheet Prepared with One-Step Hydrothermal Synthesis

Micro molybdenum disulfide was prepared with one-step hydrothermal method;the influence of reactant concentration and temperature on the surface ratio of micro-MoS2 grain was investigated. Raman spectroscopy (Raman), X-ray diffraction (XRD), and Scanning electron microscopy (SEM) were used to characterize the structure, composition and morphology of MoS2. The results show that micro-MoS2 grains were synthesized with one-step hydrothermal synthesis, and the morphology of micro-MoS2 grains is like flower and sphere. The SEM figures indicate that the surface ratio of micro-MoS2 grains is different and also show that the surface ratio of micro-MoS2 grains can be improved by regulating reactant concentration and temperature. This research showed a method to improve the surface ratio of micro-MoS2 grains.

Simulation and Optimization Characteristic of Novel MoS₂/c-Si HIT Solar Cell

Monolayer MoS2 has excellent optoelectronic properties, which is a potential material for solar cell. Though MoS2/c-Si heterojunction solar cell has been researched by many groups, little study of MoS2/c-Si solar cell physics is reported. In this paper, MoS2/c-Si heterojunction solar cells have been designed and optimized by AFORS-HET simulation program. The various factors affecting the performance of the cells were studied in details using TCO/n-type MoS2/i-layer/p-type c-Si/BSF/Al structure. Due to the important role of intrinsic layer in HIT solar cell, the effect of different intrinsic layers including a-Si:H, nc-Si:H, a-SiGe:H, on the performance of TCO/n-type MoS2/i-layer/p-type c-Si/Al cell, was studied in this paper. The results show that the TCO/n-type MoS2/i-layer/p-type c-Si/Al cell has the highest efficiency with a-SiGe:H as intrinsic layer, efficiency up to 21.85%. The back surface field effects on the properties of solar cells were studied with p + μc-Si and Al as BSF layers. And the effect of various factors such as thickness and band gap of intrinsic layer, thickness of MoS2, density of defect state and the energy band offset of MoS2/c-Si interface of TCO/n-type MoS2/i-layer nc-Si:H/p-type c-Si/Al cells, on the characteristics of solar cells, have been discussed for this kind of MoS2 heterojunction cells. The optimal solar cell with structure of TCO/n-type MoS2/i-type nc-Si:H/p-type c-Si/BSF/Al, has the best efficiency of 27.22%.

Plasmon resonance-enhanced graphene nanofilmbased dual-band infrared silicon photodetector

Graphene-based photodetectors have attracted much attention due to their unique properties,such as high-speed and wide-band detection capability.However,they suffer from very low external quantum efficiency in the infrared(IR)region and lack spectral selectivity.Here,we construct a plasmon-enhanced macro-assembled graphene nanofilm(nMAG)based dual-band infrared silicon photodetector.The Au plasmonic nanostructures improve the absorption of long-wavelength photons with energy levels below the Schottky barrier(between metal and Si)and enhance the interface transport of electrons.Combined with the strong photo-thermionic emission(PTI)effect of nMAG,the n MAG–Au–Si heterojunctions show strong dual-band detection capability with responsivities of52.9 mA/W at 1342 nm and 10.72 mA/W at 1850 nm,outperforming IR detectors without plasmonic nanostructures by 58–4562 times.The synergy between plasmon–exciton resonance enhancement and the PTI effect opens a new avenue for invisible light detection.