Spatial Analysis of Distributions and Habitat Conditions of Fallopia japonica (Japanese Knotweed) Invasive Species Applying Unmanned Helicopter Remote Sensing

Abstract: Fallopia japonica (Japanese knotweed) is a perennial herbaceous plant that is native to East Asia. It is considered as one of the worst invasive species worldwide because of its serious impact on biological diversity and human activities (Lowe et al., 2001). Once established, Japanese knotweed forms dense stands that shade and crowd out native plant species. The objectives of this research were to verify and confirm the distribution of Japanese knotweed as published online by the New York Department of Environmental Conservation (DEC) – iMap and to identify the geographic areas of spreading and the local habitat conditions. In this research, we apply an unmanned helicopter with multiple sensors including digital camera, thermometer and relative humidity sensor to survey the patches of F.japonica and its three-dimensional (3D) habitat conditions. The areas of each of the patch surveyed were identified and delineated in polygons applying ERDAS Imagine and ArcGIS software. To identify the local habitat conditions, the shade cover and distance to nearest water body were analyzed by using traditional statistical methods. And the distributions of temperature and relative humidity were analyzed in three-dimensional (3D) method in GIS environment

Optical characterization and device application of the semiconductors ZnSe and ZnS

We have presented evidence that the blue emission band, which is dominant at room temperature in ZnSe made under a wide variety of conditions, arises from a transition between a free hole and an electron bound to a donor, but not all donors contribute. There is a cutoff energy within the spread of donor levels above which there is negligible contribution to the emission. It is suggested that the cutoff corresponds to a localization edge of the same nature as the mobility edge. The line shape calculation based on a simple model agrees well with the experimental data. The origin of the blue emission seen at room temperature in the electroluminescence is examined to be the same. We have also discussed the injection mechanism of minority carriers in the ZnSe MIS diodes. It has been shown that annealing as-grown MOCVD ZnSe in the temperature range 300-400 °C can lead to large increases in resistivity. The effect is large for annealing in air or selenium and smaller for annealing in vacuum or zinc vapour. The process involved has an activation energy of only 0.26 eV and appears to be caused by a lattice defect acting as an acceptor. The photocapacitance spectra show that the acceptor is likely to be the so-called M-centre in ZnSe. We have shown that the attribution of the M-centre to copper-red centre is by no means conclusive. The possibility is still open that the M-centre is a lattice defect. We have made double light source steady-state photocapacitance measurements on ZnS single crystals. The Schottky diodes were made by evaporating a metal contact onto a chemically cleaned ZnS surface. Levels were found at 0.9 eV and 2.0 eV below the conduction band and 0.8 eV above the valence band in both melt-grown and iodine-transported material. These centres might be due to lattice defects. An additional level at 1.6 eV below the conduction band occurred in the iodine-transported material

MOOCs Meet Measurement Theory: A Topic-Modelling Approach

This paper adapts topic models to the psychometric testing of MOOC students based on their online forum postings. Measurement theory from education and psychology provides statistical models for quantifying a person's attainment of intangible attributes such as attitudes, abilities or intelligence. Such models infer latent skill levels by relating them to individuals' observed responses on a series of items such as quiz questions. The set of items can be used to measure a latent skill if individuals' responses on them conform to a Guttman scale. Such well-scaled items differentiate between individuals and inferred levels span the entire range from most basic to the advanced. In practice, education researchers manually devise items (quiz questions) while optimising well-scaled conformance. Due to the costly nature and expert requirements of this process, psychometric testing has found limited use in everyday teaching. We aim to develop usable measurement models for highly-instrumented MOOC delivery platforms, by using participation in automatically-extracted online forum topics as items. The challenge is to formalise the Guttman scale educational constraint and incorporate it into topic models. To favour topics that automatically conform to a Guttman scale, we introduce a novel regularisation into non-negative matrix factorisation-based topic modelling. We demonstrate the suitability of our approach with both quantitative experiments on three Coursera MOOCs, and with a qualitative survey of topic interpretability on two MOOCs by domain expert interviews.Comment: 12 pages, 9 figures; accepted into AAAI'201

Numerical Investigation of Two-stage Vapor Compression System with Simultaneous Vapor and Liquid Injection

Two-stage vapor compression systems can be advantageous over single-stage systems by providing improved system performance, lower discharge temperature and reduced throttling losses. These systems employ various intermediate configurations, such as liquid injection and vapor injection. This paper presents a configuration for a R1234ze(E) two-stage air-conditioning system using a turbo compressor with two injection ports, one for vapor injection and the second for liquid injection. The liquid injection is used to cool the motor and electronics. A component-based representation and solution approach was used to simulate the two-stage compression system with simultaneous vapor and liquid injection at steady state. The turbo compressor was represented using a customized performance map. The condenser and the evaporator were modeled using finite-volume approach. A parametric study was conducted to assess the impact of the following three variables on the system performance: vapor injection ratio, condenser air flow rate, and discharge pipe pressure drop. The simulation results show that as the vapor injection ratio increased, the system performance undergoes a tradeoff between an enhanced subcooling effect (and thus enhanced unit refrigeration capacity) and a decreased suction mass flow rate. Maximum COP occurs when the vapor injection ratio was 0.1. The results also show that as the condenser air flow rate increased, both the capacity and power consumption (including fan power) increased monotonically, and COP increased first and then decreased. At 75% load, the COP improvement at the optimum flow rate was marginally less than 0.5%. Lastly, higher discharge pipe pressure drop increased the discharge pressure. It showed very small effect on the overall system performance at the condition selected for the current study

EFFECTS OF TWO TYPES OF CONTROLLABLE DEFORMATION ON ENERGY EXTRACTION OF A FLEXIBLE HYDROFOIL

Energy extraction capacity of controllably flexible hydrofoil was studied under two identified deformation modes. Deformation modes, flexure parameters (flexure amplitude and flexure coefficient ) and motion parameters (reduced frequency f* and pitching amplitude 0) were investigated to understand the effects of controllably flexible deformation on energy extraction. The results reveal that deformation modes affect the effective angle of attack and vortex structure, which influence hydrodynamic performance. The energy extraction capacity improves from the deformation mode 2 to the rigid hydrofoil and then to the deformation mode 1. Under the deformation mode 1, lift, moment and power coefficients are increased obviously with the increase of , while they increase slightly with . Power coefficients and efficiency are sensitive to , which influences the development of leading-edge vortices. The flexible coefficient affects the wake structure, which has less impact on variation of force coefficient. As the increase in f*, averaged power coefficients firstly increase and then decrease. Further, the optimal f* is subjected to 0. Interestingly, a critical reduced frequency f*s, which is generally increase with increasing 0, was found under three modes. The condition that f* > f*s. is a prerequisite for subsequent adjustments of flexure modes and parameters according to different requirement of power coefficient under different tidal currents. The range of high efficiency () is: deformation mode 1 (36.1% rigid hydrofoils (34.2% deformation mode 2 (26.9%<<30.3%)

Fatigue Analysis of a High-Performance Heat Exchanger

Air-to-refrigerant heat exchangers (HX) are key components in Heating, Ventilation, Air Conditioning, and Refrigeration (HVAC&R) systems. For such HXs, the air-side convective resistance is the dominant factor which limits the heat transfer performance. Using non-round shape-optimized tubes and headers can successfully solve the problem leading to high performance HXs. However, the non-round shape tubes and headers may cause some fatigue issues in practices causing the failure during use. Therefore, it is desired to conduct fatigue analysis of such HXs designs to seek designs which can provide both high performance and high strength simultaneously. In present work, a framework of fatigue analysis of high-performance HXs has been developed and implemented. In the framework, the HXs were modeled using commercial Finite Element Analysis (FEA) software, SIMULIATM Abaqus FEA. Based on the stress analysis results, a fatigue analysis was conducted using fe-safe software for multiple metal materials to estimate the HX lifetime before failure occurs

The effect of Cu content on corrosion, wear and tribocorrosion resistance of Ti-Mo-Cu alloy for load-bearing bone implants

In this study, the effects of Cu content on wear, corrosion, and tribocorrosion resistance of Ti-10Mo-xCu alloy were investigated. Results revealed that hardness of Ti-10Mo-xCu alloy increased from 355.1 ± 15.2 HV to 390.8 ± 17.6 HV by increasing Cu content from 0 % to 5 %, much higher than CP Ti (106.6 ± 15.1 HV) and comparable to Ti64 (389.7 ± 13.9 HV). With a higher Cu content, wear and tribocorrosion resistance of Ti-10Mo-xCu alloys were enhanced, and corrosion resistance showed an initial increase with a subsequent decrease. Wear mechanisms under pure mechanical wear and tribocorrosion conditions of Ti-10Mo-xCu alloys were a combination of delamination, abrasion and adhesion wear