Underlying Principles Of Operation Research Articles

Electromagnetic Properties of Aluminum-Based Bilayers for Kinetic Inductance Detectors

The complex conductivity of a superconducting thin film is related to the quasiparticle density, which depends on the physical temperature and can also be modified by external pair breaking with photons and phonons. This relationship forms the underlying operating principle of Kinetic Inductance Detectors (KIDs), where the detection threshold is governed by the superconducting energy gap. We investigate the electromagnetic properties of thin-film aluminum that is proximitized with either a normal metal layer of copper or a superconducting layer with a lower $T_C$, such as iridium, in order to extend the operating range of KIDs. Using the Usadel equations along with the Nam expressions for complex conductivity, we calculate the density of states and the complex conductivity of the resulting bilayers to understand the dependence of the pair breaking threshold, surface impedance, and intrinsic quality factor of superconducting bilayers on the relative film thicknesses. The calculations and analyses provide theoretical insights in designing aluminum-based bilayer kinetic inductance detectors for detection of microwave photons and athermal phonons at the frequencies well below the pair breaking threshold of a pure aluminum film.

Modal Expansion Analysis, Inverse Design, and Experimental Verification of a Broadband High-Aperture Efficiency Circular Short Backfire Antenna Loaded With Anisotropic Impedance Surfaces

In this paper, a broadband highly-efficient circular short backfire antenna (SBFA) loaded with cylindrical anisotropic impedance surfaces (AISs) is proposed. An efficient modal expansion method (MEM) is developed to facilitate the analysis of the AIS-loaded SBFA with a finite-sized flange, which considerably reduces the computational resources as compared to commercial full-wave solvers. By combining the MEM with a multi-objective genetic algorithm, the geometrical dimensions of the antenna and the dispersive properties of the AIS are optimized through an inverse design strategy. As a proof-of-concept example, an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -band AIS-loaded SBFA with a broad bandwidth and high aperture efficiency is demonstrated, showing a good agreement between measured results and simulation predictions. An aperture efficiency of greater than 83% is experimentally achieved over a broad <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> < -10 dB bandwidth of 35.3%, with a peak aperture efficiency of about 100%. Moreover, the underlying operating principle of the antenna is revealed by investigation of the main propagating modes in the SBFA. The extraordinary performance demonstrates that the proposed AIS-loaded SBFA represents a promising candidate for various wireless communication systems.

Heat-driven direct reverse osmosis for high-performance and robust ad hoc seawater desalination

This work presents an approach to using a low-grade thermal energy source to power seawater desalination at high performance ratios and with minimal complexity - important requirements for a system that can generate potable water off the grid. In the proposed process - called heat-driven direct reverse osmosis (HDRO) - heat is transferred to a piston containing a saturated working fluid, which in turn directly applies pressure to a feed water reservoir connected in series with a standard reverse osmosis membrane assembly. Presented here are the underlying operating principles and thermodynamics for a generalized HDRO device, including criteria for selecting a working fluid and the definition of several key performance metrics. An idealized HDRO device is analyzed and a theoretical upper bound on performance is computed. At low recovery ratios, a lossless device using ethanol as a working fluid can achieve a performance ratio of up to 49, with a first-law efficiency 5.7%, indicating the significant potential for using this approach for small-scale, thermally driven desalination.

Integrated Nonreciprocal Photonic Devices With Dynamic Modulation

Nonreciprocal components, such as isolators and circulators, are crucial components for photonic systems. In this article we review theoretical and experimental progress towards developing nonreciprocal photonic devices based on dynamic modulation. In particular, we focus on approaches that operate at optical wavelengths and device architectures that have the potential for chip-scale integration. We first discuss the requirements for constructing an isolator or circulator using dynamic modulation. We review a number of different isolator and circulator architectures, including waveguide and resonant devices, and describe their underlying operating principles. We then compare these device architectures from a system-level performance perspective, considering how their figures of merit, such as footprint, bandwidth, isolation, and insertion loss scale with respect to device parameters.

Electrically-Transduced Chemical Sensors Based on Two-Dimensional Nanomaterials.

Electrically-transduced sensors, with their simplicity and compatibility with standard electronic technologies, produce signals that can be efficiently acquired, processed, stored, and analyzed. Two dimensional (2D) nanomaterials, including graphene, phosphorene (BP), transition metal dichalcogenides (TMDCs), and others, have proven to be attractive for the fabrication of high-performance electrically-transduced chemical sensors due to their remarkable electronic and physical properties originating from their 2D structure. This review highlights the advances in electrically-transduced chemical sensing that rely on 2D materials. The structural components of such sensors are described, and the underlying operating principles for different types of architectures are discussed. The structural features, electronic properties, and surface chemistry of 2D nanostructures that dictate their sensing performance are reviewed. Key advances in the application of 2D materials, from both a historical and analytical perspective, are summarized for four different groups of analytes: gases, volatile compounds, ions, and biomolecules. The sensing performance is discussed in the context of the molecular design, structure-property relationships, and device fabrication technology. The outlook of challenges and opportunities for 2D nanomaterials for the future development of electrically-transduced sensors is also presented.

Design Parameters of Vortex Pumps: A Meta-Analysis of Experimental Studies

Vortex pumps can impel solid-containing fluids and are therefore widely applied, from wastewater transport to the food industry. Despite constant efforts to improve vortex pumps, however, they have remained relatively inefficient compared to conventional centrifugal pumps. To find an optimized design of vortex pumps, this paper provides a systematic analysis on experimental studies that investigated how variations in geometric parameters influence vortex pump characteristics, in particular the pump head, the pressure coefficient and the efficiency for best point operation. To this end, an extensive literature search was conducted, and eighteen articles with 53 primary investigations were identified and meta-integrated. This showed that it is not yet clarified how vortex pumps operate. Two different assumptions of the underlying operating principle of a vortex pump lead to diverging design principles. From the results of this meta-analysis, we deduce recommendations for a more efficient design of a vortex pump and emphasize further aspects on the underlying operating principle of a vortex pump.

Resources for Assignment of Phosphorylation Sites on Peptides and Proteins.

Reversible protein phosphorylation is a key regulatory posttranslational modification that plays a significant role in major cellular signaling processes. Phosphorylation events can be systematically identified, quantified, and localized on protein sequence using publicly available bioinformatic tools. Here we present the software tools commonly used by the phosphoproteomics community, discuss their underlying principles of operation, and provide a protocol for large-scale phosphoproteome data analysis using the MaxQuant software suite.

Forces of Agglomeration: Allen Scott's &lt;I&gt;The Cultural Economy of Cities&lt;/I&gt; Revisited

Sometime in the 1980s, it became obvious that cities in the West were undergoing some fundamental changes. Deindustrialization had more or less run its course in many cities in developed countries. In quite a few cases, however, urban economies were growing again - this time driven by a whole set of economic activities different from large-scale manufacturing. At first, researchers often focused on service activities, notably producer services (especially financial services) as drivers of the urban renaissance. In his book The Cultural Economy of Cities, Allen Scott, however, not only broadened the scope, but altered the way the new urban economy should be conceptualized by focusing on cultural industries: those economic activities in which the exchange value of their products are to a large extent determined by the aesthetic or semiotic content. In addition, he presented a firmly grounded analysis both of why these industries were emerging as engines of urban growth and why they were strongly oriented towards urban milieux. By posing that the underlying operating principles in cultural industries are quite similar to those in other knowledge-intensive industries and in financial industries, he could use a sophisticated theory of agglomeration economies in which small series, volatility of demand, vertical disintegration, innovation, knowledge exchange, and spatial proximity are woven seamlessly together. Allen Scott - from his vantage point in Los Angeles, a global cultural industries powerhouse - displayed not just a sensitivity and open-mindedness towards the social reality around him, but was also able to embed his observations within a much broader theoretical framework which aims to explain how changes in the economic structure of contemporary cities are related to certain spatial patterns, and how this is linked to the emerging global division of labour. He thus changed the way - certainly for me - cities should be looked at.

Constant energy calibration for permittivity based moisture probes

Summary Soil moisture or soil water content (SWC) is an important variable and its determination with an acceptable accuracy is an essential need for a variety of hydrological disciplines. Among the alternatives, permittivity based probes are gaining popularity and becoming established techniques. However, probes are affected by local soil conditions, requiring soil-specific calibrations for accurate and reliable measurements. Measurement errors associated with these probes can be classified in three groups as primary, secondary and tertiary. Primary errors are mostly associated with the underlying operating principles of a probe. Soil density variation is inherently the major source of secondary error as it can create a measurement error as much as 0.030 m3 m−3. The error associated with the secondary variables can be reduced by up to 0.015 m3 m−3 by targeting the half range of the density variations. Currently available techniques do not explicitly quantify/minimize the secondary errors. Tertiary errors arise mostly from user dependent factors associated with probe-soil contact discontinuities and unexpected small scale environmental variations in the vicinity of the measurement point. This study presents a unique approach in considering the natural variations of the dry density by proposing to conduct the soil specific calibrations on repacked samples under constant compaction/compression energy of 350 kN m/m3. A simple probe insertion procedure was also employed by using guides and predrilling for probe rods in order to minimize the tertiary variables. A comparative assessment of the proposed calibration approach was conducted, considering a time domain reflectometry (TDR) probe and two relatively affordable moisture probes with different operating principles (ThetaProbe ML2x and Wet-2 sensor). The findings of this study showed that accuracy levels of 0.012 m3 m−3, 0.015 m3 m−3 and 0.016 m3 m−3, through Root Mean Square Error (RMSE), were achieved for TDR, ThetaProbe and WET sensor, respectively, for a wide range of soil types including the clays and silts. It is concluded that the proposed constant energy calibration approach help contain the secondary effects due to density variation in a tight range and that the recommended probe installation procedure help minimize the tertiary effects associated with the probe-soil contact discontinuities.

Enabling healthcare services for the rural and semi‐urban segments in India: when shared value meets the bottom of the pyramid

PurposeThe access to high quality, a reliable and affordable basic healthcare service is one of the key challenges facing the rural and semi‐urban population lying at base of the pyramid (BoP) in India. Realizing this as a social challenge and an economic opportunity (shared value), there has been an emergence of healthcare service providers who have bundled entrepreneurial attitude and passion with available scarce resources to design and implement cost‐effective, reliable and scalable market solutions for the BoP. The purpose of this research paper is to understand the underlying operating principles of these self‐sustainable business models aimed at providing healthcare services to the BoP segment in India.Design/methodology/approachThe empirical context involves the use of case study research methodology, where the source of data is published case studies and the company websites of four healthcare organizations who have made a socio‐economic difference in the lives of the rural and semi‐urban population lying at the BoP in India.FindingsThe analysis and findings reflect the key operating principles for sustainable healthcare business ventures at the BoP. These include focus on 4A's (accessible, affordable, acceptable and awareness), local engagement, local skills building, learning by experiment, flexible organizational structure, dynamic leadership, technology integration and scalability.Research limitations/implicationsThis research study has focused mainly on the published case studies as source of data.Originality/valueThe intent is to understand and bring forth the learning and guiding principles, which act as a catalyst for the future researchers and business ventures engaged in BoP context.

(Keynote) In Quest of a Fast, Low-Voltage Digital Switch

In a recent survey of the exploratory device literature (1), Theis and Solomon studied proposed low-voltage digital devices, and identified the underlying operating principles which enable those devices to overcome the voltage-scaling limit of the conventional field effect transistor. Here, I briefly summarize the status of the ongoing device research, and argue that the operating principles exemplified by these devices are quite general, and can be applied in ways that have not yet been explored. It is therefore likely that we are still in the early stages of the quest for a fast, low-voltage digital switch.

Successfully merging architectural and electronic acoustical treatments

In enclosed volumes, the integration of electronic acoustical components with architectural surface treatments forms a hybrid system that produces the perceived acoustical conditions. Since the underlying operating principles for electro-acoustic enhancement systems differs considerably between manufacturers, the requirements for system infrastructure are not germane, nor is the optimum integration of architectural treatments. As a result, the nature of the work performed by the acoustical consultant changes to accommodate optimum performance of the specific “hybrid” system, which may also include other forms of variable treatments.

Commentary: Memristor and memristive switch mechanism

Many nanostructures exhibit electrically stimulated change of resistance and have been proposed as the basis for non-volatile random access memories (NVRAM), but progress toward implementation has been delayed by difficulties in understanding and controlling the resistive switching phenomena [1]. To design a device that can be reliably used for information processing, one needs (i) a mathematically consistent theory for modeling the circuit component, and (ii) knowledge of the underlying operating principles so that one might improve a device by fine tuning parameters such as doping and geometrical profile. Recent breakthrough occurred at Hewlett-Packard Laboratories has been receiving increasing attention in both fundamental researches and commercial applications. In May 2008, HP scientists announced the discovery of the missing circuit element memristor, acronym for memory resistor. The memristor concept gives a simple explanation for many puzzling voltage-current characteristics in nanoscale electronics [2]. Researchers also clarified coupled electron-ion dynamics responsible for memristive switch [3]. With the reported advance, HP is promising prototypes of ultradense memory chips in 2009.

Ultrasound cylindrical phased array for transoesophageal thermal therapy: initial studies

This work was undertaken to investigate the feasibility of constructing a cylindrical phased array composed of 64 elements spread around the periphery (OD 10.6 mm) for transoesophageal ultrasound thermotherapy. The underlying operating principle of this applicator is to rotate a plane ultrasound beam electronically. For this purpose, eight adjacent transducers were successively excited with appropriate delay times so as to generate a plane wave. The exposure direction was changed by exciting a different set of eight elements. For these feasibility studies, we used a cylindrical prototype (OD 10.6 mm) composed of 16 elementary transducers distributed over a quarter of the cylinder, all operating at 4.55 MHz. The active part was mechanically reinforced by a rigid damper structure behind the transducers. It was shown that an ultrasound field similar to that emitted by a plane transducer could be generated. Ex vivo experiments on pig's liver demonstrated that the ultrasound beam could be accurately rotated to generate sector-based lesions to a suitable depth (up to 19 mm). Throughout these experiments, exposures lasting 20 s were delivered at an acoustic intensity of 17 W cm−2. By varying the power from exposure to exposure, the depth of the lesion at different angles could be controlled.