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47 results on '"Liu, Xiaomeng"'

23. Design of Thermal Insulated Transmission Section for 2.4mm Coaxial Microcalorimeter

Author

Liu Xiaomeng, Xiangjun Li, Jianxin Ding, Sheng Ding, Xiaohai Cui, and Wenze Yuan

Subjects
Optics, Materials science, Transmission (telecommunications), Physics::Instrumentation and Detectors, business.industry, Transmission line, Thermal insulation, Coplanar waveguide, Thermal, Insertion loss, Coaxial, business, Microwave
Abstract

The 2.4mm coaxial microcalorimeter is a system used to calibrate the effective efficiency of coaxial microwave power sensors. The frequency range of DC~50 GHz is of great significance for microwave precision measurement and applications. The system requires a thermal insulated transmission line. In this paper, a section of grounded coplanar waveguide transmission line with vias is designed, which has good thermal insulation effect confirmed by experiment results.

Published
2020
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24. Study on Effective Efficiency Measurement of a Type N Thermistor Mount at 10MHz

Author

Yong Li, Liu Xiaomeng, Wenze Yuan, Sheng Ding, Jianxin Ding, Xiaohai Cui, and Susu Ma

Subjects
Materials science, business.industry, Electricity meter, Broadband, Thermistor, Optoelectronics, Coaxial, business, Power sensor, Signal, Power (physics)
Abstract

When calibrating the Type N power sensor, HP 8478B thermistor mount, with the broadband (0.01~18GHz) coaxial primary power standard, the effective efficiency at the 10MHz was investigated, and we found that the Agilent 34420A nanovoltmeter could not measure floating signal. To weaken the effect of 34420A on the effective efficiency measurement, we modified the power meter.

Published
2020
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33. Proximity-Based Sensor Fusion of Depth Cameras and Isotropic Rad-Detectors.

Author

Henderson, Kristofer, Liu, Xiaomeng, Stadnikia, Kelsey, Martin, Allan, Enqvist, Andreas, and Koppal, Sanjeev J.

Subjects
*GAMMA ray detectors, *PROXIMITY detectors, *DETECTORS, *NUCLEAR counters, *KALMAN filtering
Abstract

Finding and tracking radioactive sources have numerous security applications in civilian energy installations, military facilities, and ports of entry. The price of radiological sensors varies proportionally to size and imaging characteristics such as angular resolution, and the cheapest devices are nearly isotropic–i.e., they integrate radiation from a sphere of directions centered at the sensor. While many radiation sensors have high aspect ratios or odd shapes, the sensors used here are right cylinders, with a near identical directional efficiency such that for analysis purposes, other aspects, such as counting statistics, would make nonisotropy of the sensor negligible. In this article, we propose a simple and robust way to integrate measurements from both isotropic radiological sensors and depth sensors, whose reliability and resolution benefit from recent advances in computer vision and imaging. Our key idea is to convert all sensor measurements into proximity signals based on radial distance variations over time. Based on this sensor fusion model, we show that for moving radiological sources even a simple Kalman filter can trade-off the complementary strength of high-resolution depth sensors and isotropic radiological sensors. We show novel results with a LIDAR sensor and a thermal stereo pair, and demonstrate applications such as tracking and rendering non-line-of-sight imagery behind obstacles and detecting multiple radiological sources in the same scene. [ABSTRACT FROM AUTHOR]

Published
2020
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39. A Fast Method to Analyze the Fiber Amplifier With the GTWave Pumping Configuration.

Author

Liu, Qinyong, Liu, Xiaomeng, and Ke, Weiwei

Abstract

The pump propagation in the GTWave pumping structure is studied with analytical method and the beam propagation method (BPM). The power distribution function $f(\xi)=P_0(z)/[P_0(z)+P_1(z)]$ is proved to be independent of the fiber core size and the doping content. Based on this $f(\xi)$ function, the propagation of the pump power and the signal power in the fiber amplifier is quickly calculated. With our method, a BPM calculation on a long fiber can be simulated with a highly doped short fiber; thus, the total calculation time is greatly reduced. The analysis of a fiber amplifier with very complicated GTWave pumping configuration is greatly simplified and the calculation speed is accelerated without losing too much accuracy. [ABSTRACT FROM AUTHOR]

Published
2018
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40. China's oil vulnerability and economic growth: An empirical study

Author

Feng Tian-tian, Liu Lu, Liu Xiaomeng, Zhao Xin-gang, and Liu Pingkuo

Subjects
Government, Index (economics), Empirical research, Economic indicator, Petroleum industry, business.industry, Natural resource economics, Vulnerability, Economics, Duration (project management), business, China
Abstract

Economic growth relies on energy. Accompany with the enhancement of oil vulnerability, it's crucial for China's government to research the relationship between oil security and economic growth. This paper selects eight quantifiable individual indicators to comprehensively measure oil vulnerability of China for the duration of 1997–2008 by means of principal component analysis, and a comparison between the index and China's real growth rate of GDP is conducted through the adoption of grey relational analysis, then demonstrates the following: (1) China's oil vulnerability has been generally increased in recent years. (2) There is a comparatively high consistency between China's oil vulnerability and economic growth. As China's economy develops stably and rapidly, oil vulnerability is increasing invisibly. Therefore, attention should be paid to easing China's oil vulnerability when the goal of stable and rapid economic growth is guaranteed.

Published
2011
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