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Optical metasurfaces for momentum exchange between light and matter
No full textLight carries energy and momentum that can be transferred to matter. Because of the conservation of total momentum, a change in light momentum due to interaction with an object must be compensated by an equal but opposite change in the momentum of that object. The resulting optical forces may in turn cause observable mechanical translation and rotation of the object, as a consequence of a change in linear and angular momentum of the light, respectively. These effects can be controlled by structuring the impinging light field and/or by engineering the optical properties of the object.Metasurfaces, flat structures with engineered subwavelength building blocks, provide various possibilities for tailoring optical forces and momentum exchange. A metasurface can be used as a compact replacement for conventional bulky optical elements used to shape light, such as lenses and spatial light modulators. An example of this is provided in the appended paper, where a cylindrical metalens with a linear phase gradient is used to optically trap and translate small particles along its line focus. But in the process of shaping a light beam, a metasurface is itself subject to momentum exchange and optical forces. This effect can be observed if a metasurface is incorporated into a micro-scale object allowed to move freely across a surface. Several examples of such meta-particles propelled by light are provided in the thesis.The thesis is organized as follows: The first part is devoted to studying the fundamentals and developments of optical metasurfaces by categorizing them based on aspects of material composition, working wavelength, and applications. Then a brief review of different actuation mechanisms used for the manipulation of micro and nano-objects is provided, with a focus on using optical fields as the external source of energy and momentum.The second part of the thesis is dedicated to results that highlight the versatility of stationary and movable metasurfaces in facilitating optical manipulation of objects. Finally, a description of the metasurface fabrication and characterization methods used is provided
Coal-exit alliance must confront freeriding sectors to propel Paris-aligned momentum
Get PDFThe global phase-out of coal by mid-century is considered vital to the Paris Agreement to limit warming well-below 2 \ub0C above pre-industrial levels. Since the inception of the Powering Past Coal Alliance (PPCA) at COP23, political ambitions to accelerate the decline of coal have mounted to become the foremost priority at COP26. However, mitigation research lacks the tools to assess whether this bottom-up momentum can self-propagate toward Paris alignment. Here, we introduce dynamic policy evaluation (DPE), an evidence-based approach for emulating real-world policy-making. Given empirical relationships established between energy-economic developments and policy adoption, we endogenize national political decision-making into the integrated assessment model REMIND via multistage feedback loops with a probabilistic coalition accession model. DPE finds global PPCA participation <5% likely against a current policies backdrop and, counterintuitively, foresees that intracoalition leakage risks may severely compromise sector-specific, demand-side action. DPE further enables policies to interact endogenously, demonstrated here by the PPCA’s path-dependence to COVID-19 recovery investments
Systems thinking and efficiency under emissions constraints: Addressing rebound effects in digital innovation and policy
Get PDFInnovations and efficiencies in digital technology have lately been depicted as paramount in the green transition to enable the reduction of greenhouse gas emissions, both in the information and communication technology (ICT) sector and the wider economy. This, however, fails to adequately account for rebound effects that can offset emission savings and, in the worst case, increase emissions. In this perspective, we draw on a transdisciplinary workshop with 19 experts from carbon accounting, digital sustainability research, ethics, sociology, public policy, and sustainable business to expose the challenges of addressing rebound effects in digital innovation processes and associated policy. We utilize a responsible innovation approach to uncover potential ways forward for incorporating rebound effects in these domains, concluding that addressing ICT-related rebound effects ultimately requires a shift from an ICT efficiency-centered perspective to a “systems thinking” model, which aims to understand efficiency as one solution among others that requires constraints on emissions for ICT environmental savings to be realized
Online Learning of Energy Consumption for Navigation of Electric Vehicles
Get PDFEnergy efficient navigation constitutes an important challenge in electric vehicles, due to their limited battery capacity. We employ a Bayesian approach to model the energy consumption at road segments for efficient navigation. In order to learn the model parameters, we develop an online learning framework and investigate several exploration strategies such as Thompson Sampling and Upper Confidence Bound. We then extend our online learning framework to the multi-agent setting, where multiple vehicles adaptively navigate and learn the parameters of the energy model. We analyze Thompson Sampling and establish rigorous regret bounds on its performance in the single-agent and multi-agent settings, through an analysis of the algorithm under batched feedback. Finally, we demonstrate the performance of our methods via experiments on several real-world city road networks
Energy Loss Savings Using Direct Current Distribution in a Residential Building with Solar Photovoltaic and Battery Storage
Get PDFThis work presents a comparison of alternating current (AC) and direct current (DC) distribution systems for a residential building equipped with solar photovoltaic (PV) generation and battery storage. Using measured PV and load data from a residential building in Sweden, the study evaluated the annual losses, PV utilization, and energy savings of the two topologies. The analysis considered the load-dependent efficiency characteristics of power electronic converters (PECs) and battery storage to account for variations in operating conditions. The results show that DC distribution, coupled with PV generation and battery storage, offered significant loss savings due to lower conversion losses than the AC case. Assuming fixed efficiency for conversion gave a 34% yearly loss discrepancy compared with the case of implementing load-dependent losses. The results also highlight the effect on annual system losses of adding PV and battery storage of varying sizes. A yearly loss reduction of 15.8% was achieved with DC operation for the studied residential building when adding PV and battery storage. Additionally, the analysis of daily and seasonal variations in performance revealed under what circumstances DC could outperform AC and how the magnitude of the savings could vary with time
Gas kinematics around filamentary structures in the Orion B cloud
Get PDFContext. Understanding the initial properties of star-forming material and how they affect the star formation process is key. From an observational point of view, the feedback from young high-mass stars on future star formation properties is still poorly constrained. Aims. In the framework of the IRAM 30m ORION-B large program, we obtained observations of the translucent (2 ≤ AV < 6 mag) and moderately dense gas (6 ≤ AV < 15 mag), which we used to analyze the kinematics over a field of 5 deg2 around the filamentary structures. Methods. We used the Regularized Optimization for Hyper-Spectral Analysis (ROHSA) algorithm to decompose and de-noise the C 18 O(1−0) and 13CO(1−0) signals by taking the spatial coherence of the emission into account. We produced gas column density and mean velocity maps to estimate the relative orientation of their spatial gradients. Results. We identified three cloud velocity layers at different systemic velocities and extracted the filaments in each velocity layer. The filaments are preferentially located in regions of low centroid velocity gradients. By comparing the relative orientation between the column density and velocity gradients of each layer from the ORION-B observations and synthetic observations from 3D kinematic toy models, we distinguish two types of behavior in the dynamics around filaments: (i) radial flows perpendicular to the filament axis that can be either inflows (increasing the filament mass) or outflows and (ii) longitudinal flows along the filament axis. The former case is seen in the Orion B data, while the latter is not identified. We have also identified asymmetrical flow patterns, usually associated with filaments located at the edge of an H II region. Conclusions. This is the first observational study to highlight feedback from H II regions on filament formation and, thus, on star formation in the Orion B cloud. This simple statistical method can be used for any molecular cloud to obtain coherent information on the kinematics
Caring for the monstrous algorithm: attending to wrinkly worlds and relationalities in an algorithmic society
No full textThis text proposes that we, social analysts of algorithms, need to develop a split vision for the algorithm-as-technological-object and the algorithm-as-assemblage in order to effectively attend to, analyze, and critique algorithms in society. The point of departure is that we need to distance ourselves from a simplified and reductive understanding of algorithms-as-objects, and care for them as part of a relational algorithmic assemblage. A simplified notion of algorithms is problematic for two reasons: First, as it produces a reductive notion of the world where decision makers point to algorithms-as-objects to make simplified decisions about the world. Second, by taking a simplified and delineated object called “algorithm” as the point of departure for analysis and critique in an algorithmic society, we risk producing technologically deterministic understandings of complex and composite problems. We illustrate this argument through two example drawn from the handling of Covid-19 pandemic, where we attend to a universalist mathematical epidemiology and the particularities of field epidemiology to problematize how we should care for, understand, and analyze algorithms in society
A 16 7 16 45\ub0 Slant-Polarized Gapwaveguide Phased Array With 65-dBm EIRP at 28 GHz
No full textA high equivalent isotropic radiated power (EIRP) active phased array antenna is proposed for fifth-generation (5G) communication systems at 28 GHz. The numerical design, measurements of a fabricated prototype, and performance analysis are presented. The antenna design is based on the gapwaveguide technology and consists of single 45\ub0 slant-polarized elements. The proposed design uses a low complexity printed circuit board (PCB) structure with only six layers, i.e., a half of the existing wideband solutions. The array antenna incorporates up/downconverter integrated circuits (UDCs) and transceiver beamformer integrated circuits (BFICs). Moreover, a compact and highly efficient transition at the end of each channel of the BFICs has been designed to interconnect the antenna elements with the PCB. The antenna\u27s front-end loss, which includes the feed line, mismatch, and ohmic losses, is only 1.3 dB. The array covers the scanning range of \ub160\ub0 in the azimuth plane and \ub110\ub0 in the elevation plane. The S_{11} < -10 dB frequency bandwidth is from 26.5 to 29.5 GHz. The maximum EIRP of the antenna is 65.5 dBm at saturation point. The presented design offers a compact, robust, and low-loss performance solution meeting the high transmission power requirements of 5G applications
From Sweden to the world: Analysis of future low-carbon electricity systems
Get PDFThe increasing urgency of addressing climate change, along with the sustained cost declines in wind and solar power, has led to a rapid expansion in their deployment to decarbonize the electricity sector. In cost-optimal scenarios for future low-carbon electricity systems, wind and solar often serve as the cornerstone of electricity supply. Although many studies have investigated a future low-carbon electricity system based on wind and solar, there are still several important aspects that are not well understood for such a future system, e.g., uncertainty in future electricity demand patterns, potential for trade in renewable energy, the spatial scope for resource sharing and the role of nuclear power. This thesis investigates these aspects and their potential impacts on developing a low-carbon electricity system.\ua0\ua0\ua0\ua0\ua0 This thesis reveals that varied electricity demand patterns affect only slightly the electricity system cost for Europe, except for the case of summer peak, where the system cost may increase by up to 8%. The change in demand pattern is generally more consequential to the electricity supply mix than the system cost. Notably, the increased electric cooling demand may change the demand pattern such that the hourly electricity demand is better correlated with the output of solar PV. Through analyzing seven different regions under various CO2 emission targets, this thesis shows that solar PV is the most cost-optimal generation technology for meeting the cooling demand. In addition, to have a more realistic assessment of renewable energy potential, this thesis introduces a new metric “Renewable levelized cost of electricity available for export”, which incorporates heterogeneous discount rates, electricity demand, and land-use requirements. By applying this metric to most of the countries in the world, this thesis shows that countries with significant potential for renewable energy export include the US, China, and Saudi Arabia. Furthermore, this thesis shows that the benefit of an intercontinental super grid, as suggested by the One Sun One World One Grid initiative, is rather limited. Allowing for long-distance intercontinental electricity trade reduces the electricity system cost by 0-5% compared to the case where the continents are isolated from each other. This thesis also shows that integrating different continents always reduces the integration of solar PV, which indicates that an intercontinental super grid is not a cost-effective variation management strategy for solar power. Finally, this thesis shows that including nuclear power in the electricity system reduces the nodal net average system cost by 4% for Sweden. This implies that the economic rationale for Sweden as a country to invest in nuclear power is limited if there is a transition towards a low-carbon electricity system in Europe. This thesis provides practical information about demand profile treatment for modeling practice, introduces a useful metric for renewable energy trade potential assessment, and generates valuable insights about deploying solar PV to power cooling, and investment in super grid and nuclear power
Making packaging more sustainable: Effects of resource embeddedness
Get PDFFirms involved in e-commerce distribution are faced with challenges due to the increasing volume of single shipments to consumers, including concerns regarding sustainability. For instance, the role of packaging has gained increased attention because of over-packed parcels and excessive air within those parcels, which frustrate retailers, logistics service providers, and consumers. E-commerce also challenges established structures for distribution to physical stores, when firms increasingly use multiple distribution channels to reach consumers. The design of e-commerce packaging affects other resources in retail distribution, and vice versa. In turn, such interdependence not only affects how packaging solutions can be developed but also highlights the importance of various firms developing resources in interaction. This thesis aims to explore how more sustainable packaging solutions are developed in a business network context. A single case study was conducted to examine how e-commerce packaging interacts with other resources and how this interaction affects various firms in their efforts to create more sustainable packaging solutions. In doing so, the thesis is theoretically grounded in the Industrial Network Approach and focuses on resource interaction and how a focal resource—e-commerce packaging—is embedded in a business network. The thesis contributes by highlighting the challenges involved in efforts to make individual resources more sustainable in various parts of a business network. The findings underscore the importance of identifying how resources are embedded in network settings. Regarding e-commerce packaging, three network settings are identified: product development, sorting, and packing. The implications for firms involved in these network settings are that interaction is required both within and across the network settings to develop more sustainable packaging solutions