ASSESSING FOREST BIOMASS AND MONITORING CHANGES FROM DISTURBANCE AND RECOVERY WITH LIDAR AND SAR

This dissertation research investigated LiDAR and SAR remote sensing for assessing aboveground biomass and monitoring changes from anthropogenic forest disturbance and post-disturbance recovery. First, waveform LiDAR data were applied to map forest biomass and its changes at different key map scales for the two study sites: Howland Forest and Penobscot Experimental Forest. Results indicated that the prediction model at the scale of individual LVIS footprints is reliable when the geolocation errors are minimized. The evaluation showed that the predictions were improved markedly (20% R2 and 10% RMSE) with the increase of plot sizes from 0.25 ha to 1.0 ha. The effect of disturbance on the prediction model was strong at the footprint level but weak at the 1.0 ha plot-level. Errors reached minimum when footprint coverage approached about 50% of the area of 1.0 ha plots (16 footprints) with no improvement beyond that. Then, a sensitivity analysis was conducted for multi-source L-band SAR signatures, to change in forest biomass and related factors such as incidence angle, soil moisture, and disturbance type. The effect of incidence angle on SAR backscatter was reduced by an empirical model. A cross-image normalization was used to reduce the radiometric distortions due to changes in acquisition conditions such as soil moisture. Results demonstrated that the normalization ensured that the derived biomass of regrowth forests was cross-calibrated, and thus made the detection of biomass change possible. Further, the forest biomass was mapped for 1989, 1994 and 2009 using multi-source SAR data, and changes in biomass were derived for a 15- and a 20-year period. Results improved our understanding of issues concerning the mapping of biomass dynamic using L-ban SAR data. With the increase of plot sizes, the speckle noise and geolocations errors were reduced. Multivariable models were found to outperform the single-term models developed for biomass estimation. The main contribution of this research was an improved knowledge concerning waveform LiDAR and L-band SAR’s ability in monitoring the changes in biomass in a temperate forest. Results from this study provide calibration and validation methods as a foundation for improving the performance of current and future spaceborne systems

VENTURE CAPITAL AND CORPORATE INNOVATION INPUT FROM THE PERSPECTIVE OF SYNDICATED INVESTMENT

Using data for 341 enterprises listed on the Growth Enterprise Market (GEM) of the Shenzhen Stock Exchange and taking R&D expenditure as an indicator of innovation investment, this paper implements multiple linear regression to test whether venture capital promotes corporate innovation input. It also considers the relationship between the syndicated investment of venture capital and innovation input. The results showthat venture capital indeed promotes R&D in the invested enterprises. The innovation input of syndicated investment enterprises is significantly higher than that of sole investment enterprises. Under syndicated investment, the higher the number of syndicated investment members and the greater the heterogeneity of the shareholding ratio among the members, the higher is the innovation input. The reputation of the syndicated investment team, however, has no significant impact on innovation input.Using data for 341 enterprises listed on the Growth Enterprise Market (GEM) of the Shenzhen Stock Exchange and taking R&D expenditure as an indicator of innovation investment, this paper implements multiple linear regression to test whether venture capital promotes corporate innovation input. It also considers the relationship between the syndicated investment of venture capital and innovation input. The results showthat venture capital indeed promotes R&D in the invested enterprises. The innovation input of syndicated investment enterprises is significantly higher than that of sole investment enterprises. Under syndicated investment, the higher the number of syndicated investment members and the greater the heterogeneity of the shareholding ratio among the members, the higher is the innovation input. The reputation of the syndicated investment team, however, has no significant impact on innovation input

CHARACTERISTICS OF BOARD OF DIRECTORS AND PERFORMANCE OF GEM LISTED COMPANIES FROM THE PERSPECTIVE OF VENTURE CAPITAL PARTICIPATION

Using the difference-in-differences (DID) model and taking the sample of companies listed from 2009 to 2014 on the Growth Enterprises Market (GEM) of the Shenzhen Stock Exchange in China, this paper studies the impact of Venture Capital (VC) participation on board characteristics, which is measured by the chief executive officer (CEO) duality, the scale of the board of directors and the proportion of independent directors, and it also studies how the board characteristics influence the company performance. The findings are as follows: VC-backed GEM listed companies are more inclined to choose the mode of CEO duality and to have a larger board of directors and a higher proportion of independent directors, all of which are conducive to improving company performance

Weak Signal Detection Technology Based on Holmes Duffing Oscillator

AbstractIn this paper, the principle and application of weak signal detection based on Holmes Duffing oscillator is introduced. The relationship between the state equation of Duffing oscillator and the control of signal by scanning is analyzed and the signal is detected. The simulation and design the circuit of weak signal detection are researched based on Duffing oscillator. Control experiments are carried out on the circuit with sine signal of different frequencies. We achieve the purpose of detecting weak period signal from noise background by scanning. This study is a useful exploration in Chaos control using engineering signal detection

Synthesis and biological evaluation of 1, 3-dihydroxyxanthone mannich base derivatives as anticholinesterase agents

BACKGROUND: Alzheimer’s disease (AD), a progressive and degenerative disorder, has become one of the severe problems among the aged population all over the world. To use cholinesterase inhibitor drugs has become the most predominant treatment strategy for AD. RESULTS: A series of novel 1, 3-dihydroxyxanthone Mannich bases derivatives (1a ~ 4e) were synthesized, structure elucidated and evaluated for anti-cholinesterase activity. The result showed that most of the target compounds exhibited moderate to good inhibitory activities with the IC(50) values at micromole level concentration against both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). The preliminary structure-activity indicated that: (i) The alkoxy or alkenoxy substituents in the position 3 of xanthone have a positive influence on the inhibition potency; (ii) types of dialkylamine methyl in position 2 of xanthone affected cholinesterase activities and AChE/BuChE selectivity. Among them, 2-((diethylamino)methyl)-1-hydroxy-3-(3-methylbut-2-enyloxy)-9H-xanthen-9-one showed potent inhibitory activity against AChE with the IC(50) value of 2.61 ± 0.13 μM and the best inhibitory activity against BuChE with the IC(50) value of 0.51 ± 0.01 μM. The results of a mixed-type manner in enzyme kinetic experiment and molecular docking study for 2-((diethylamino)methyl)-1-hydroxy-3-(3-methylbut-2-enyloxy)-9H-xanthen-9-one demonstrated that the Mannich base derivatives were likely to bind to the active site (AS) and the peripheral anionic site (PAS) of cholinesterases. CONCLUSIONS: This study suggested that 1, 3-dihydroxyxanthone Mannich base derivatives were potential dual inhibitors of both AChE and BuChE, which may be considered as a kind of novel drug candidates for treatment of AD

Identification of Two Vulnerability Features: A New Framework for Electrical Networks Based on the Load Redistribution Mechanism of Complex Networks

This paper proposes a new framework to analyze two vulnerability features, impactability and susceptibility, in electrical networks under deliberate attacks based on complex network theory: these two features are overlooked but vital in vulnerability analyses. To analyze these features, metrics are proposed based on correlation graphs constructed via critical paths, which replace the original physical network. Moreover, we analyze the relationship between the proposed metrics according to degree from the perspective of load redistribution mechanisms by adjusting parameters associated with the metrics, which can change the load redistribution rules. Finally, IEEE 118- and 300-bus systems and a realistic large-scale French grid are used to validate the effectiveness of the proposed metrics

下水汚泥および好気性汚泥顆粒中におけるリンの種類、分布及びその生物学的利用性

筑波大学 (University of Tsukuba)201