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Zhang, Jianfeng

Publications and source records attributed to Zhang, Jianfeng.

6 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Structure and magnetic properties of Ba 9 ⁢V 3 ⁢Te 15 with ferromagnetic spin chains

Here we report a ferromagnetic compound Ba9⁢V3⁢Te15 with quasi-one-dimensional (1D) spin chains. It was synthesized at high-temperature and high-pressure conditions and systematically investigated via structural, transport, magnetic and heat capacity measurements. Ba9⁢V3⁢Te15 mainly consists of trimerized face-sharing V⁢Te6 octahedral chains running along the 𝑐 axis, which are separated by a distance of 10.184⁢(8)⁢Å, thus demonstrating a strong 1D structural character. Ba9⁢V3⁢Te15 is a semiconductor with a band gap ∼128meV and undergoes a ferromagnetic transition with 𝑇C∼3.6K. Far above 𝑇C, the short-range spin orders due to the intrachain spin coupling have developed, which leads to a negative magnetoresistance effect, the deviation of magnetic susceptibility from the Curie-Weiss law and 𝑇1/2 dependence of magnetic heat capacity. Our results reveal that Ba9⁢V3⁢Te15 provides a good opportunity to study the intrinsic properties of a system with quasi-1D ferromagnetic spin chains.

1-dimensional spin chains↗
DOE OSTI2022

Public Health Response and Medical Management of Internal Contamination in Past Radiological or Nuclear Incidents: A Review

Following a radiological or nuclear emergency, workers, responders and the public may be internally contaminated with radionuclides. Screening, monitoring and assessing any internal contamination and providing necessary medical treatment, especially when a large number of individuals are involved, is challenging. Experience gained and lessons learned from the management of previous incidents would help to identify gaps in knowledge and capabilities on preparedness for and response to radiation emergencies. In this paper, eight largescale and five workplace radiological and nuclear incidents are reviewed cross 14 technical areas, under the broader topics of emergency preparedness, emergency response and recovery processes. The review findings suggest that 1) new strategies, algorithms and technologies are explored for rapid screening of large populations; 2) exposure assessment and dose estimation in emergency response and dose reconstruction in recovery process are supported by complementary sources of information, including ‘citizen science’; 3) surge capacity for monitoring and dose assessment is coordinated through national and international laboratory networks; 4) evidence-based guidelines for medical management and follow-up of internal contamination are urgently needed; 5) mechanisms for international and regional access to medical countermeasures are investigated and implemented; 6) long-term health and medical follow up programs are designed and justified; and 7) capabilities and capacity developed for emergency response are sustained through adequate resource allocation, routine nonemergency use of technical skills in regular exercises, training, and continuous improvement.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2021

A Method of Ground-Based Cloud Motion Predict: CCLSTM + SR-Net

Ground-based cloud images can provide information on weather and cloud conditions, which play an important role in cloud cover monitoring and photovoltaic power generation forecasting. However, the cloud motion prediction of ground-based cloud images still lacks advanced and complete methods, and traditional technologies based on image processing and motion vector calculation are difficult to predict cloud morphological changes. In this paper, we propose a cloud motion prediction method based on Cascade Causal Long Short-Term Memory (CCLSTM) and Super-Resolution Network (SR-Net). Firstly, CCLSTM is used to estimate the shape and speed of cloud motion. Secondly, the Super-Resolution Network is built based on perceptual losses to reconstruct the result of CCLSTM and, finally, make it clearer. We tested our method on Atmospheric Radiation Measurement (ARM) Climate Research Facility TSI (total sky imager) images. The experiments showed that the method is able to predict the sky cloud changes in the next few steps.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Quantization of the band at the surface of charge density wave material 2H-TaSe 2

By using angle-resolved photoemission spectroscopy combined with the first-principles electronics atructure calculations, we report the quantum well states at the surface of a single crystal 2H-TaSe 2 . We observed sub-bands at the three-dimensional Brillouin zone center forming the quantized states due to its highly dispersive nature and light effective mass along k z direction. The quantized sub-bands shift upward towards E F with the decrease of temperature across TCDW. The band shift could not be explained by two-dimensional Fermi-surface nesting-driven charge density waves(CDW), nor by purely strong electron-phonon coupling only. The CDW in 2H-TaSe 2 is likely related to the bands at higher binding energy, and the CDW mechanism could be explained by the excitons, and our observation gives support to this scenario.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗