Effects of different planting configurations and clones on biomass and carbon storage of a 12-year-old poplar ecosystem in southern China

The main objective of this study was to compare the effects of two densities (278 stems·ha−1 with two spacings of 6 m × 6 m or 4.5 m × 8 m, 400 stems·ha−1 with two spacings of 5 m × 5 m or 3 m × 8 m) and three poplar clones (NL95, NL895, and NL797) on productivity and carbon (C) sequestration of poplar ecosystems. The results showed that planting density significantly affected the biomass of a single tree. The mean tree biomass of clone NL95 was higher in all spacings than that of the other clones, with a significant difference for the 6 m × 6 m spacing. The biomass of poplar trees ranged from 78.9 to 110.3 Mg·ha−1, with the highest tree biomass observed in the square configuration. Soil C concentration (0–100 cm) increased after 12 years of management. Soil C storage ranged from 138.1 to 164.3 Mg C·ha−1, and the highest soil C storage was in the NL797 poplar plantation with 6 m × 6 m spacing. Our results suggested that clones NL95 and NL797 should be chosen for planting, with a planting density of 278 stems·ha−1 and spacing of 6 m × 6 m.

Seven Conformations of the Macrocycle Cyclododecanone Unveiled by Microwave Spectroscopy

The physicochemical properties and reactivity of macrocycles are critically shaped by their conformations. In this work, we have identified seven conformations of the macrocyclic ketone cyclododecanone using chirped-pulse Fourier transform microwave spectroscopy in combination with ab initio and density functional theory calculations. Cyclododecanone is strongly biased towards adopting a square configuration of the heavy atom framework featuring three C–C bonds per side. The substitution and effective structures of this conformation have been determined through the observation of its 13C isotopologues. The minimisation of transannular interactions and, to a lesser extent, HCCH eclipsed configurations drive conformational preferences. Our results contribute to a better understanding of the intrinsic forces mediating structural choices in macrocycles.

A multirotor vehicle performance prediction method

A method has been developed to predict the performance of small multirotor vehicles. Using the vehicle geometry, rotor geometry and flight conditions as inputs, the aerodynamic performance is found through an interpolation method using tabulated rotor performance data. The model is able to predict performance in hover and forward flight, and can produce results quickly and easily, making the prediction model a powerful tool. The vehicle performance prediction model also includes a wake interference model that captures the effect of rotors and their shed wakes on others rotors in the vicinity. When compared to flight test data, the method shows good agreement when predicting the angle of attack, rotational velocity and power requirements of the vehicle. The effect of the vehicle orientation on the performance of the vehicle was investigated showing that during fast forward flight, the vehicle requires about 5% less power in a diamond configuration than in a square configuration.

A multirotor vehicle performance prediction method

A method has been developed to predict the performance of small multirotor vehicles. Using the vehicle geometry, rotor geometry and flight conditions as inputs, the aerodynamic performance is found through an interpolation method using tabulated rotor performance data. The model is able to predict performance in hover and forward flight, and can produce results quickly and easily, making the prediction model a powerful tool. The vehicle performance prediction model also includes a wake interference model that captures the effect of rotors and their shed wakes on others rotors in the vicinity. When compared to flight test data, the method shows good agreement when predicting the angle of attack, rotational velocity and power requirements of the vehicle. The effect of the vehicle orientation on the performance of the vehicle was investigated showing that during fast forward flight, the vehicle requires about 5% less power in a diamond configuration than in a square configuration.

Effect of Defects Part II: Multiscale Effect of Microvoids, Orientation of Rivet Holes on the Damage Propagation, and Ultimate Failure Strength of Composites

Material properties at the vicinity of the cut-outs in composites are not entirely defect-free. The nteraction of multiple cutouts like rivet holes, the repercussion of their configuration on crack propagation, and ultimate strength were predicted using Peridynamic method and the results are reported in this article. The effect of microscale defects at the vicinity of the cutouts on macroscale damage propagation were shown to have quantifiable manifestation. This study focused on two to four holes in unidirectional composite plates with 0°, 45°, and 90° fiber directions, while the vicinity of a hole was considered degraded. Numerical results were validated using quantitative ultrasonic image correlation (QUIC) and the tensile test. Both the experimental and numerical results confirmed that the strength of the horizontal configuration is higher than the vertical in the plates with two holes. Furthermore, the square configuration was found to be stronger than the diamond configuration with four holes. When the effect of microscale defects was considered, the prediction of ultimate strength was better compared to the experimental results. The predictive model could be reliably used for progressive damage analysis.

Effects of Module Spatial Distribution on the Energy Efficiency and Electrical Output of Automotive Thermoelectric Generators

Automotive thermoelectric generators (ATEGs) are devices used to harvest waste energy from the exhaust gases of internal combustion engines. An ATEG is essentially formed by three main elements: (1) heat absorber in contact with exhaust gases; (2) thermoelectric modules that directly convert heat into electricity; (3) heat sink to increase the heat transfer through the system. Thermoelectric modules (TEM) are commonly based on small-scale commercial units, with tenths of them needed to assemble a full ATEG device. Thus, several thermal and electrical connections between TEMs can be implemented. Previous studies focused on the implications on the output power. Here, we investigated the effects of using different module connections on the energy efficiency and on the electrical outputs (voltage and current). The study was carried out numerically with ATEGs that used from 4 to 100 individual TEMs. Series, parallel and square connections were investigated under two different engine operating points. The maximum output power was obtained with overall energy conversion efficiencies on the order of 3%. Though the series connection provided the highest output power, the square configuration was the best compromise between output power and electrical characteristics (voltage and current) to successfully integrate the ATEG into the vehicle management system.