Honeycomb lattice Na2IrO3 at high pressures: A robust spin-orbit Mott insulator

The honeycomb iridate Na2IrO3 has received much attention as a candidate to realize a quantum spin liquid state, but the nature of its insulating state remains controversial. We found that the material exhibits structural transitions at 3 and 10 GPa. The former is accompanied by 166-meV suppression of the activation gap, but the energies for the low-lying interband transitions change by less than 10 meV. This can be reconciled in a picture in which the application of high pressure barely shifts the electronic bands, but rather merely broadens them. First-principles calculations uncover a strong correlation between the band gap and the β angle of the monoclinic structure, indicating non-negligible interlayer coupling. These results offer clear evidence for a spin-orbit Mott insulating state in Na2IrO3 and are inconsistent with the quasimolecular orbital model

The Effect of Environmental Information Disclosure on Green Total Factor Productivity: Evidence from Quasi-Natural Experiments on Cities in China

The relationship between environmental regulation and green economic growth has become a focal issue in China. This study utilizes the environmental information disclosure (EID) policy as a quasi-natural experiment in the Chinese context. Using a sample of 280 Chinese cities from 2003–2019 and measuring urban green total factor productivity (GTFP), the propensity score matching and difference-in-difference methods are applied to assess the impact mechanism of EID on urban GTFP in China. The results show that, first, the urban GTFP showed a decreasing trend from 2003 to 2008 and a general increasing trend from 2009 to 2019. The EID policy had a significantly positive impact on GTFP, and this finding remained robust after a series of tests. Second, the policy effect of EID was more pronounced in large and medium-sized cities than in small cities and eastern and central regions. The mechanism analysis shows that a positive effect from EID on GTFP in cities can be achieved through green technological innovation and industrial agglomeration

The Effect of Environmental Information Disclosure on Green Total Factor Productivity: Evidence from Quasi-Natural Experiments on Cities in China

The relationship between environmental regulation and green economic growth has become a focal issue in China. This study utilizes the environmental information disclosure (EID) policy as a quasi-natural experiment in the Chinese context. Using a sample of 280 Chinese cities from 2003–2019 and measuring urban green total factor productivity (GTFP), the propensity score matching and difference-in-difference methods are applied to assess the impact mechanism of EID on urban GTFP in China. The results show that, first, the urban GTFP showed a decreasing trend from 2003 to 2008 and a general increasing trend from 2009 to 2019. The EID policy had a significantly positive impact on GTFP, and this finding remained robust after a series of tests. Second, the policy effect of EID was more pronounced in large and medium-sized cities than in small cities and eastern and central regions. The mechanism analysis shows that a positive effect from EID on GTFP in cities can be achieved through green technological innovation and industrial agglomeration

Research on High-Resolution Miniaturized MEMS Accelerometer Interface ASIC

High-precision microelectromechanical system (MEMS) accelerometers have wide application in the military and civil fields. The closed-loop microaccelerometer interface circuit with switched capacitor topology has a high signal-to-noise ratio, wide bandwidth, good linearity, and easy implementation in complementary metal oxide semiconductor (CMOS) process. Aiming at the urgent need for high-precision MEMS accelerometers in geophones, we carried out relevant research on high-performance closed-loop application specific integrated circuit (ASIC) chips. According to the characteristics of the performance parameters and output signal of MEMS accelerometers used in geophones, a high-precision closed-loop interface ASIC chip based on electrostatic time-multiplexing feedback technology and proportion integration differentiation (PID) feedback control technology was designed and implemented. The interface circuit consisted of a low-noise charge-sensitive amplifier (CSA), a sampling and holding circuit, and a PID feedback circuit. We analyzed and optimized the noise characteristics of the interface circuit and used a capacitance compensation array method to eliminate misalignment of the sensitive element. The correlated double sampling (CDS) technology was used to eliminate low-frequency noise and offset of the interface circuit. The layout design and engineering batch chip were fabricated by a standard 0.35 μm CMOS process. The active area of the chip was 3.2 mm × 3 mm. We tested the performance of the accelerometer system with the following conditions: power dissipation of 7.7 mW with a 5 V power supply and noise density less than 0.5 μg/Hz1/2. The accelerometers had a sensitivity of 1.2 V/g and an input range of ±1.2 g. The nonlinearity was 0.15%, and the bias instability was about 50 μg

Can the Policy of National Urban Agglomeration Improve Economic and Environmental Gains? Evidence from Quasi-Natural Experiments with 280 Cities in China

Urban agglomerations are an important symbol in the development of modernization. In this paper, we utilize the National Urban Agglomeration (NUA) policy as a quasi-natural experiment in the Chinese context. Adopting data from 280 cities from 2005 to 2019 as research samples, we use difference-in-differences (DID) and spatial difference-in-differences models (SDID) to examine the effect and mechanism of the implementation of the NUA policy on economic development and environmental pollution in China. The result shows that the NUA policy can achieve urban economic and environmental gains, which still holds after the robustness test. The heterogeneity analysis showed that the effects of the NUA policy are more evident in large and medium-sized cities. The curbing effect of the NUA policy on pollution emissions is apparent in the eastern region. Considering spatial heterogeneity, the expected economic and environmental benefits of the NUA policy are partially borne out. In addition to the green technology innovation, the NUA policy also influences regional economic development and environmental pollution through industrial agglomeration and the upgrading of industrial structures, respectively. It is essential to strengthen regional cooperation and establish the development concept of community interests between cities

Neuromuscular Magnetic Field Measurement Based on Superconducting Bio-Sensors

These years, disease-causing and disabling diseases have caused great concern. Neurological musculoskeletal disorders are diverse and affect people of a wide range of ages. And the lack of comprehensive diagnostic methods places a huge burden on healthcare systems and social economies. In this paper, the current status of clinical research on neuromuscular diseases is introduced, and the advantages of magnetic field measurement compared with clinical diagnostic methods are illustrated. A comprehensive description of the related technology of superconducting quantum interference devices (SQUIDs), magnetic field detection noise suppression scheme, the development trend of the sensor detection system, and the application and model establishment of the neuromuscular magnetic field is also given in this paper. The current research and development trends worldwide are compared simultaneously, and finally the conclusions and outlook are put forward. Based on the description of the existing literature and the ideas of other researchers, the next development trends and my own research ideas are presented in this paper, that is, starting from the establishment of a neuromuscular model, combining medical and industrial work, designing a sensor system that meets clinical needs, and laying the foundation for the clinical application of a bio-magnetic system. This review promotes a combination between medicine and industry, and guides researchers on considering the challenges of sensor development in terms of clinical needs. In addition, in this paper, the development trends are described, including the establishment of the model, the clinical demand for sensors, and the challenges of system development so as to give certain guidance to researchers

High intrinsic noise and absence of hysteresis in superconducting quantum interference devices with large Steward-McCumber parameter

We investigated niobium thin film superconducting quantum interference devices (SQUIDs) with large Steward-McCumber parameter (βc > 1). No hysteresis was observed in the current-voltage (I-V) characteristics of the SQUIDs, even for βc ≈ 17. We attribute the absence of hysteresis to an excess voltage noise of the junctions which increases the SQUID intrinsic noise δΦs. It can be represented by an effective noise temperature T* of the SQUID which is higher than the bath temperature T. We simulated SQUID I-V characteristics using the measured device parameters and confirmed the absence of hysteresis