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As an attractive alternative to traditional porous materials, micro-perforated panel (MPP) absorbers have been widely used in room acoustics, environmental noise remediation and duct noise control. In the previous works, the MPP i...
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As an attractive alternative to traditional porous materials, micro-perforated panel (MPP) absorbers have been widely used in room acoustics, environmental noise remediation and duct noise control. In the previous works, the MPP is usually assumed to be a flat panel perforated with sub-millimeter orifices, and that is also the most common form of MPPs used in practice. In practice, however, corrugated panels are widely used in architecture as roofs, ceilings and walls not only for decoration but also for greater rigidity in comparison to the plane plates. For noisy environments such as swimming pools, perforated corrugated panels with a back sound absorption layer or corrugated micro-perforated panels (corrugated MPPs) can be conveniently used to achieve a favourable acoustic environment and reduce the noise level. So far, however, almost all reported studies on MPP absorbers are based on flat MPPs, and a comprehensive investigation on corrugated MPP absorbers is seldom seen. The main purpose of the present work is to investigate the sound absorption performance of corrugated MPP absorbers, with emphasis on comparison with that of flat MPP absorbers. To this end, a three-dimensional (3D) finite element model is established to simulate the sound absorption performance of the corrugated MPP absorber. The corrugated profile is assumed to be sinusoidal and other possible shapes such as triangle and trapezoid are excluded at the current stage. Results show that, replacing the flat MPP with a corrugated one modify the coupling mode in the air-mass system, resulting in different sound absorption performance in comparison with the conventional flat MPP absorbers.
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Imaging spectroscopic technique has been used for the mineral and rock geological mapping and alteration information extraction successfully with many reasonable results, but it is mainly used in arid and semi-arid land with low v...
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Imaging spectroscopic technique has been used for the mineral and rock geological mapping and alteration information extraction successfully with many reasonable results, but it is mainly used in arid and semi-arid land with low vegetation covering. In the case of the high vegetation covering, the outcrop of the altered rocks is small and distributes sparsely, the altered rocks is difficult to be identified directly. The target detection technique using imaging spectroscopic data should be introduced to the extraction of small geological targets under high vegetation covering area. In the paper, we take Ding-Ma gold deposit as the study area which located in Zhenan country, Shanxi province, the spectral features of the targets and the backgrounds are studied and analyzed using the field reflectance spectra, in addition to the study of the principle of the algorithms, some target detection algorithms which is appropriate to the small geological target detection are introduced. At last, the small altered rock targets under the covering of vegetation in forest are detected and discriminated in imaging spectroscopy data with the methods of spectral angle mapper (SAM), Constrained Energy Minimization (CEM) and Adaptive Cosine Estimator (ACE). The detection results are reasonable and indicate the ability of target detection algorithms in geological target detection in the forest area.
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摘要 :
Imaging spectroscopic technique has been used for the mineral and rock geological mapping andalteration information extraction successfully with many reasonable results, but it is mainly used in aridand semi-arid land with low veg...
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Imaging spectroscopic technique has been used for the mineral and rock geological mapping andalteration information extraction successfully with many reasonable results, but it is mainly used in aridand semi-arid land with low vegetation covering. In the case of the high vegetation covering, theoutcrop of the altered rocks is small and distributes sparsely, the altered rocks is difficult to beidentified directly. The target detection technique using imaging spectroscopic data should beintroduced to the extraction of small geological targets under high vegetation covering area. In thepaper, we take Ding-Ma gold deposit as the study area which located in Zhenan country, Shanxiprovince, the spectral features of the targets and the backgrounds are studied and analyzed using thefield reflectance spectra, in addition to the study of the principle of the algorithms, some targetdetection algorithms which is appropriate to the small geological target detection are introduced. At last,the small altered rock targets under the covering of vegetation in forest are detected and discriminatedin imaging spectroscopy data with the methods of spectral angle mapper (SAM), Constrained EnergyMinimization (CEM) and Adaptive Cosine Estimator (ACE). The detection results are reasonable andindicate the ability of target detection algorithms in geological target detection in the forest area.
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Traffic along the route is an important ecotone between humans and nature. With the development of the transportation industry, the road network continues to extend into the natural hinterland, and the traffic noise is increasingl...
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Traffic along the route is an important ecotone between humans and nature. With the development of the transportation industry, the road network continues to extend into the natural hinterland, and the traffic noise is increasingly disturbing the biological habitat. Therefore, it is of great significance to study the influence factors and adaptive strategies of traffic noise on animals to protect biodiversity. This article selects Xiamen Egret Park as the research object, analyzes the characteristics of traffic noise around the park and the spatial distribution characteristics of animals. Through the simulation, it reveals the logical relationship between the two, and proposes to mitigate traffic noise and improve Specific strategies for animal adaptability.
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Visible and near infrared (Vis-NIR) reflectance spectroscopy technology, which is rapid, cost-effective, in-situ and non-destructive, is getting more and more widely used in improving the prediction and digital mapping for soil pr...
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Visible and near infrared (Vis-NIR) reflectance spectroscopy technology, which is rapid, cost-effective, in-situ and non-destructive, is getting more and more widely used in improving the prediction and digital mapping for soil properties. Soil available nitrogen (AN) is closely related to soil fertility and quality, assessing its content and mapping the spatial variability greatly satisfies precision agriculture. In this study, the Vis-NIR diffuse reflectance spectra collected by ASD FieldSpec Pro FR spectrometer with a performance of spectral range from 350 nm to 2500 nm, 1 nm resampling intervals, was used to model and characterize the spatial variability of available nitrogen. Firstly, the raw soil spectra was pre-processing by reducing to 400 nm - 2450 nm with transformation into apparent absorbance spectral using Log(l/R) and Savitzky-Golay smoothing. Secondly, spectral indices (normalized spectral index-NDI; difference index-DI; ratio index-RI) were convinced for seeking further relationship between AN. Afterwards, Partial Least Squares Regression (PLSR) method was employed to predict AN. The results indicated good predictions with RPD more than 1.4. Finally, the spatial variability of AN was mapped by (co)kriging method, digital mapping of the measured and predicted AN showed similar patterns and value ranges, though there are some minor differences. The resultant prediction and mapping demonstrated a promotion of assessing and mapping of soil properties by a rapid and reliable approach from lab to field in-situ.
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摘要 :
Visible and near infrared (Vis-NIR) reflectance spectroscopy technology, which is rapid, cost-effective, in-situ and non-destructive, is getting more and more widely used in improving the prediction and digital mapping for soil pr...
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Visible and near infrared (Vis-NIR) reflectance spectroscopy technology, which is rapid, cost-effective, in-situ and non-destructive, is getting more and more widely used in improving the prediction and digital mapping for soil properties. Soil available nitrogen (AN) is closely related to soil fertility and quality, assessing its content and mapping the spatial variability greatly satisfies precision agriculture. In this study, the Vis-NIR diffuse reflectance spectra collected by ASD FieldSpec Pro FR spectrometer with a performance of spectral range from 350 nm to 2500 nm, 1 nm resampling intervals, was used to model and characterize the spatial variability of available nitrogen. Firstly, the raw soil spectra was pre-processing by reducing to 400 nm - 2450 nm with transformation into apparent absorbance spectral using Log(1/R) and Savitzky-Golay smoothing. Secondly, spectral indices (normalized spectral index-NDI; difference index-DI; ratio index-RI) were convinced for seeking further relationship between AN. Afterwards, Partial Least Squares Regression (PLSR) method was employed to predict AN. The results indicated good predictions with RPD more than 1.4. Finally, the spatial variability of AN was mapped by (co)kriging method, digital mapping of the measured and predicted AN showed similar patterns and value ranges, though there are some minor differences. The resultant prediction and mapping demonstrated a promotion of assessing and mapping of soil properties by a rapid and reliable approach from lab to field in-situ.
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Electro-optical stabilization and tracking system is critical and difficult issue in satellite laser communication. Moreover, line-of-sight stabilized system is the kernel of implementing electro-optical stabilization and tracking...
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Electro-optical stabilization and tracking system is critical and difficult issue in satellite laser communication. Moreover, line-of-sight stabilized system is the kernel of implementing electro-optical stabilization and tracking system, which can be used to isolate the vibration of the moving platform of the satellite and the disturbance of the space environment. In this paper, we propose a new method, which using H _∞ mix sensitivity based on generalized internal model controller (GIMC), to design the control system of the electro-optical stabilized platform. It is well known that there is an intrinsic conflict between performance and robustness in the standard feedback framework. Generalized internal model controller is a new architecture which can separate the performance and robustness design in controller design. This architecture has two parts: a high performance controller, say K0,which is designed by PI controller in this paper, and then a robustification controller, say Q, which is designed to improve the ability of the anti disturbance by using H _∞ mix sensitivity controller design method. In this paper, we also present the steps of controller design by using this method to make it easier to use. Based on the proposed method, numerical simulation and experiment are both carried out for a gyro stabilized platform of electro-optical tacking system. Both the numerical simulated and the experimental results show that the electro-optical stabilized platform using the H _∞ mix sensitivity controller design method based on GIMC is accurate and effective. Comparing with the same PI controller in standard feedback framework, the proposed method can guarantee the high tracking performance as same as the PI controller and improve the external disturbance restraining ability a lot. In conclusion, H _∞ mix sensitivity controller design method based on GIMC is a new approach for gyro stabilized platform of electro-optical stabilization and tracking system and might be used easily in practical.
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Electro-optical stabilization and tracking system is critical and difficult issue in satellite laser communication. Moreover, line-of-sight stabilized system is the kernel of implementing electro-optical stabilization and tracking...
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Electro-optical stabilization and tracking system is critical and difficult issue in satellite laser communication. Moreover, line-of-sight stabilized system is the kernel of implementing electro-optical stabilization and tracking system, which can be used to isolate the vibration of the moving platform of the satellite and the disturbance of the space environment. In this paper, we propose a new method, which using H_∞ mix sensitivity based on generalized internal model controller (GIMC), to design the control system of the electro-optical stabilized platform. It is well known that there is an intrinsic conflict between performance and robustness in the standard feedback framework. Generalized internal model controller is a new architecture which can separate the performance and robustness design in controller design. This architecture has two parts: a high performance controller, say K_0, which is designed by PI controller in this paper, and then a robustification controller, say Q, which is designed to improve the ability of the anti disturbance by using H_∞ mix sensitivity controller design method. In this paper, we also present the steps of controller design by using this method to make it easier to use. Based on the proposed method, numerical simulation and experiment are both carried out for a gyro stabilized platform of electro-optical tacking system. Both the numerical simulated and the experimental results show that the electro-optical stabilized platform using the H_∞ mix sensitivity controller design method based on GIMC is accurate and effective. Comparing with the same PI controller in standard feedback framework, the proposed method can guarantee the high tracking performance as same as the PI controller and improve the external disturbance restraining ability a lot. In conclusion, H_∞ mix sensitivity controller design method based on GIMC is a new approach for gyro stabilized platform of electro-optical stabilization and tracking system and might be used easily in practical.
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Wireless Sensor Networks (WSNs) have acquired new features recently, i.e.. both the sensor and the antenna of a node can be directional. This brings new challenges to the Connected Coverage (CoCo) problem, where a finite set of ta...
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Wireless Sensor Networks (WSNs) have acquired new features recently, i.e.. both the sensor and the antenna of a node can be directional. This brings new challenges to the Connected Coverage (CoCo) problem, where a finite set of targets needs to be monitored by some active sensor nodes, and the connectivity of these active nodes with the sink must be retained at the same time. In this paper, we study the Minimum-Enetgy Connected Coverage (MeCoCo) problem in WSNs with Omni-directional (O) and Directional (D) features, aiming at minimizing the total energy cost of both sensing and connectivity. Considering different combinations of O and D features, we study the MeCoCo problem under four cases, namely: O-Antenna and O-Sensor (OAOS), O-Antenna and D-Sensor (OADS), D-Antenna and D-Sensor (DADS), as well as D-Antenna and O-Sensor (DAOS). We prove that the MeCoCo problem is NP-hard under all these cases, and present approximation algorithms with provable approximation ratios. In particular, we propose a constant-approximation for OAOS, and polylogarithmic approximations for all other cases. Finally, we conduct extensive; simulations and the results strongly confirm the effectiveness of our approach.
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摘要 :
Wireless Sensor Networks (WSNs) have acquired new features recently, i.e.. both the sensor and the antenna of a node can be directional. This brings new challenges to the Connected Coverage (CoCo) problem, where a finite set of ta...
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Wireless Sensor Networks (WSNs) have acquired new features recently, i.e.. both the sensor and the antenna of a node can be directional. This brings new challenges to the Connected Coverage (CoCo) problem, where a finite set of targets needs to be monitored by some active sensor nodes, and the connectivity of these active nodes with the sink must be retained at the same time. In this paper, we study the Minimum-Enetgy Connected Coverage (MeCoCo) problem in WSNs with Omni-directional (O) and Directional (D) features, aiming at minimizing the total energy cost of both sensing and connectivity. Considering different combinations of O and D features, we study the MeCoCo problem under four cases, namely: O-Antenna and O-Sensor (OAOS), O-Antenna and D-Sensor (OADS), D-Antenna and D-Sensor (DADS), as well as D-Antenna and O-Sensor (DAOS). We prove that the MeCoCo problem is NP-hard under all these cases, and present approximation algorithms with provable approximation ratios. In particular, we propose a constant-approximation for OAOS, and polylogarithmic approximations for all other cases. Finally, we conduct extensive; simulations and the results strongly confirm the effectiveness of our approach.
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