Pressure Dependence of Wall Relaxation in Polarized 3^3He Gaseous Cells

We have observed a linear pressure dependence of longitudinal relaxation time ($T_1$) at 4.2 K and 295 K in gaseous $^3$He cells made of either bare pyrex glass or Cs/Rb-coated pyrex due to paramagnetic sites in the cell wall. The paramagnetic wall relaxation is previously thought to be independent of $^3$He pressure. We develop a model to interpret the observed wall relaxation by taking into account the diffusion process, and our model gives a good description of the data

Kinematics and Performance Analysis of 2R2T Parallel Manipulator with Partially Decoupled Motion

© 2019, Chinese Society of Agricultural Machinery. All right reserved. A novel parallel manipulator with two rotations and two translations was proposed. The moving platform of the parallel manipulator was connected to the fixed base through four kinematic limbs. Four prismatic joints can be used as actuations to fully control the motion of manipulator. The mobility and motion characteristic of the manipulator were analyzed by using Lie Group theory. Position model of the parallel manipulator was established. Inverse and forward position solutions were analyzed. It was demonstrated that the analytical expressions can be obtained for the inverse and forward position solutions. Partially decoupled motion characteristic of the manipulator was analyzed. Position of the moving platform can be determined by two limbs. Singularity analysis was conducted based on Jacobian matrix. Singular configurations, including inverse kinematic singularity, forward kinematic singularity and combined singularity were analyzed. Workspace and singularity curves were determined. It was found that the singularities located near the boundary of the workspace and the parallel manipulator had relatively high rotational capability. The rotational ranges in two directions were -44°~60° and -35°~52°, respectively. Performance analysis was carried out by using the method of motion/force transmission. Performance distribution over the orientation workspace was sketched. Global performance index was used in optimal design of the manipulator. The proposed parallel manipulator can be used in many fields such as five axis machine and motion simulator

A review of net zero energy buildings in hot and humid climates: Experience learned from 34 case study buildings

Sustainable development in the building sector requires the integration of energy efficiency and renewable energy utilization in buildings. In recent years, the concept of net zero energy buildings (NZEBs) has become a potential plausible solution to improve efficiency and reduce energy consumption in buildings. To achieve an NZEB goal, building systems and design strategies must be integrated and optimized based on local climatic conditions. This paper provides a comprehensive review of NZEBs and their current development in hot and humid regions. Through investigating 34 NZEB cases around the world, this study summarized NZEB key design strategies, technology choices and energy performance. The study found that passive design and technologies such as daylighting and natural ventilation are often adopted for NZEBs in hot and humid climates, together with other energy efficient and renewable energy technologies. Most NZEB cases demonstrated site annual energy consumption intensity less than 100 kW-hours (kWh) per square meter of floor space, and some buildings even achieved “net-positive energy” (that is, they generate more energy locally than they consume). However, the analysis also shows that not all NZEBs are energy efficient buildings, and buildings with ample renewable energy adoption can still achieve NZEB status even with high energy use intensity. This paper provides in-depth case-study-driven analysis to evaluate NZEB energy performance and summarize best practices for high performance NZEBs. This review provides critical technical information as well as policy recommendations for net zero energy building development in hot and humid climates

Effect of Vortex Generators on NREL Wind Turbine: Aerodynamic Performance and Far-Field Noise

Passive flow separation control with vortex generators (VG) is actively used over the wind turbine blade. In this paper, the effect of vortex generators is simulated on a full-scale 2-blade wind-turbine tested at the National Renewable Energy Laboratory. The simulation is performed using Very-Large-Eddy/Lattice-Boltzmann method (VLES/LBM). The analysis focuses on the effect of vortex generators on the aerodynamic performance and far-field noise. The simulation results without vortex generators are compared with the experimental results, reaching good agreement. The vortex generators produce counter-rotating vortices in the wake which effectively delay flow separation, leading to better aerodynamic performance. The acoustic analysis indicates that the dominant noise sources are the tonal noise produced by the flow separation and the turbulent-boundary-layer trailing-edge noise. Similar noise levels are obtained for the configurations with and without vortex generators

Enzymatic cross-linking of pea and whey proteins to enhance emulsifying and encapsulation properties

Improving the functionality of commercial plant proteins is essential for food application. Here an alternative strategy is provided to modify the structure of pea protein by microbial transglutaminase-induced cross-linking with whey protein for enhancing emulsifying and encapsulation properties. The protein structures and the physicochemical stability of β-carotene-loaded emulsions were investigated subject to protein ratio and cross-linking. Formation of disulphide and isopeptide bonds between heteroproteins according to cross-linking changed protein structures by exposing the hydrophobic sites of proteins with stiffer network. The cross-linked pea/whey protein complexes at protein ratio of 2:1 formed a stable emulsion with a droplet size of 0.10 µm, showing no phase separation for 30 days of storage and high encapsulation efficiency of 92%. These findings provided a novel strategy to design plant/dairy protein networks to protect lipophilic bioactive compounds by replacing half or more dairy protein with plant protein, leading to gradual change towards plant-based diets

What Drives Wind and Solar Energy Investment in India and China?

This research is motivated by the need to transform the basis of energy systems from fossil fuels to renewable sources. As well as the imperative of climate change, this transformation is needed to create development trajectories for economies that are genuinely sustainable over the long term. Our objectives are therefore both environmental and developmental. Understanding what drove low-carbon investments in the past is the key to identifying the drivers of investment in the future. In this regard, low-carbon investment decisions are not technical questions of optimal asset allocation. Rather, understanding these decisions requires an approach rooted in political economy, which assesses the motivations and incentives of the different actors involved, and how these interact. Understanding the dynamics of this process is the first step in shaping it. This research concentrates on private investment. Of the US$45 trillion of investments that the International Energy Agency (IEA) estimates are required by 2050 to reduce global carbon emissions by half, it is assumed that 85 per cent will need to come from the private sector. Annually, this averages at a little over US$1 trillion, half of which will fund the replacement of existing technologies, largely in developed countries. The remaining US$530bn is investment in new capacity, the bulk of which (US$400bn pa) will be in developing countries (IEA 2008). Our focus is on the determinants of low-carbon investment in the world’s two largest emerging economies: China and India. While these countries are responsible for the biggest growth in carbon emissions, China is now the largest global investor in renewable energy and India saw the highest growth rate in recent times between 2010 and 2011 (BNEF 2012).UK Department for International Developmen