Study on the Evolution Principles of Aircraft Engine Exhaust

Jingbo Zhao,Da Chen 한국대기환경학회 2021 한국대기환경학회 학술대회논문집 Vol.2021 No.10

Airport activities emit both particulate and gaseous emissions (Unal et al., 2005) and are a significant source of local gas- and particle-phase pollutants (Westerdahl et al., 2008). These emissions affect public health (Lin et al., 2008) and local air quality by increasing pollutant concentrations, e.g., ultrafine particulate matter (PM) number concentrations, at the surrounding residential areas (Hudda et al., 2016). Due to the influence of meteorological conditions, the atmospheric environment and background pollutants together with the physicochemical characteristics of aircraft exhaust varied significantly after emitted into the atmosphere. In this regard, we designed the exhaust monitoring system to monitor aircraft exhaust emissions. Based on the integrated exhaust monitoring system of the aircraft, sampling points are set at different distances (1 m, 10 m, 30 m) behind the engine. Meteorological parameters (including temperature and humidity), the concentration of various gaseous pollutants (including nitrogen oxides, sulfur oxides, carbon oxides, hydrocarbons, etc.) and physicochemical properties (such as particle size distribution, chemical composition, optical properties, etc.) of particulate matter are measured online, in order to analyze the characteristic changes of gaseous and particulate matters at different distances behind aircraft engines. The morphology evolution of particulate matter was investigated by scanning electron microscope (SEM). The evolution trend of engine exhaust near the engine area was summarized under different working conditions, and the main factors that affect these changes were identified, such as temperature gradient, pollutant concentration level, engine working conditions, etc. Based on the theory of gas-solid allocation of semi-volatile substances, the evolution of gas-solid allocation of semi-volatile pollutants emitted by aircraft was studied by using VBS and other volatile models. With the comprehensive three-dimensional detection of airport atmospheric environment, multi-point enhanced observations in downwind areas of aircraft emissions is designed to obtain the spatial distribution characteristics of air pollutants in airports with high time resolution. The evolution of aircraft exhaust pollutants in airports was determined by the temporal and spatial variations of the ratios of pollutant concentrations to CO₂ (e.g., particle concentration/DCO₂). The influence of meteorological factors, such as temperature, humidity, illumination, etc. on the evolution of aircraft exhaust characteristics was identified based on the airport micrometeorological field data. Above all, the on-line monitoring of aircraft exhausts could optimize the accuracy of airport quality model, thus providing a promising tool for future air governance.

Soil characteristics and new formation model of loess on the Chinese Loess Plateau

Jingbo Zhao,Xiaoqing Luo,Yandong Ma,Tianjie Shao,Yingli Yue 한국지질과학협의회 2017 Geosciences Journal Vol.21 No.4

In this paper characteristics of loess are discussed from a pedological perspective. A new model of loess formation is presented, developed in different soil formation processes according to its pedogenic characteristics, including soil structure, organic matter content and CaCO3 content. Loess has all the characteristics of typical soils and all five soil-forming factors have important roles in loess formation. In this regard, loess is a type soil and the previous concept of loess actually comprises various kinds of palaeosols developed in cold and arid climatic conditions. The loess-forming process is, in fact, equivalent to a pedogenic process and loess layers with different characteristics represent different pedogenic processes indicative of different environments, such as desert-steppe, steppe or forest-steppe climatic conditions. In contrast to red-brown palaeosol layers, which develop in warm and wet climates, loesses – more accurately called ‘loessial palaeosols’ – are grey-yellow palaeosols and can be regarded as a reliable indicator of cold and arid climate. The model of loess formation suggests that aeolian dust transfers to grey-yellow palaeosols via pedogenesis and the characteristics of loess are mainly a result of climatic conditions and diagenesis processes after its sedimentation. This new model of loess formation also suggests that traditional pedological theory has its limitations when explaining soil formation processes.

A monolithic silicon multi-sensor for measuring three-axis acceleration, pressure and temperature

Xu Jingbo,Zhao Yulong,Jiang Zhuangde,Sun Jian 대한기계학회 2008 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.22 No.4

A monolithic multi-sensor for small unmanned aerial vehicles is presented in the paper; it consists of a three-axis piezoresistive accelerometer, a piezoresistive absolute pressure sensor and a silicon thermistor temperature sensor. The accelerometer is designed with four silicon beams supporting the seismic mass and appropriate piezoresistors arrangement to detect three-axis acceleration and greatly reduce cross-axis sensitivities. For minimizing the effect of stress on the temperature sensor, the thermistor is designed along [100] and [010] crystal orientation. The multi-sensor is fabricated on SOI wafers by using MEMS bulk-micromachining technology. Some effective micromachining steps are applied in the fabrication. The two-step wet anisotropic etching process on the backside of the wafers can form the whole backside shape of the multi-sensor. The metal electrode sputtered on the Pyrex glass can avoid sticking between the Pyrex glass and the seismic mass in the process of anodic bonding. The die size of the multi-sensor is 4×6×0.9mm3. The measured results show that the multi-sensor is appropriate for its application field.

Research and Practice of Full Plugging Groundwater Technology in Water-Rich TBM Diversion Tunnel

Lichuan Wang,Shuai Zhang,Zongqing Zhou,Jian Wu,Tao Bai,Yunjuan Chen,Jingbo Zhao,Shuo Xu 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.2

To solve the problem of water discharge in the tunnel when the tunnel passes through the low-pressure water-rich fractured stratum, the grouting plugging technology of the low-pressure water-rich tunnel is studied. The grouting plugging scheme is optimized through the field test. The post-validation research is numerically simulated and the parameters of the complete sealing grouting ring are analyzed. The results show that: 1) Full plugging grouting can effectively improve the funnel effect of precipitation with good water plugging effect. With the decrease of the permeability coefficient and the increase of the thickness of the grouting ring, the flow velocity around the tunnel and the water discharge in the tunnel both decreased significantly, with a trend of “rapidly decreasing-slowly decreasing”. Considering various factors, an optimal grouting ring thickness between 1.5 m and 2.5 m and a reasonable range for permeability coefficient between 2.07 × 10−6 cm/s and 4.14 × 10−6 cm/s are considered appropriate. 2) The use of cement-water glass system full plugging grouting for water plugging, can significantly reduce the discharge of water, only partial dripping or even dripping state. Using polyurethane foam single point method to systematically block grouting and water plugging can only changes the discharge path and hardly attenuates water discharge.

Axial Movements and Length Changes of the Human Lower Esophageal Sphincter During Respiration and Distension-induced Secondary Peristalsis Using Functional Luminal Imaging Probe

( Donghua Liao ),( Christian Lottrup ),( Lotte Fynne ),( Barry P Mcmahon ),( Klaus Krogh ),( Asbjørn M Drewes ),( Jingbo Zhao ),( Hans Gregersen ) 대한소화기기능성질환·운동학회(구 대한소화관운동학회) 2018 Journal of Neurogastroenterology and Motility (JNM Vol.24 No.2

Background/Aims Efficient transport through the esophago-gastric junction (EGJ) requires synchronized circular and longitudinal muscle contraction of the esophagus including relaxation of the lower esophageal sphincter (LES). However, there is a scarcity of technology for measuring esophagus movements in the longitudinal (axial) direction. The aim of this study is to develop new analytical tools for dynamic evaluation of the length change and axial movement of the human LES based on the functional luminal imaging probe (FLIP) technology and to present normal signatures for the selected parameters. Methods Six healthy volunteers without hiatal hernia were included. Data were analyzed from stepwise LES distensions at 20, 30, and 40 mL bag volumes. The bag pressure and the diameter change were used for motion analysis in the LES. The cyclic bag pressure frequency was used to distinguish dynamic changes of the LES induced by respiration and secondary peristalsis. Results Cyclic fluctuations of the LES were evoked by respiration and isovolumetric distension, with phasic changes of bag pressure, diameter, length, and axial movement of the LES narrow zone. Compared to the respiration-induced LES fluctuations, peristaltic contractions increased the contraction pressure amplitude (P < 0.001), shortening (P < 0.001), axial movement (P < 0.001), and diameter change (P < 0.01) of the narrow zone. The length of the narrow zone shortened as function of the pressure increase. Conclusions FLIP can be used for evaluation of dynamic length changes and axial movement of the human LES. The method may shed light on abnormal longitudinal muscle activity in esophageal disorders. (J Neurogastroenterol Motil 2018;24:255-267)