Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 25
Filtrar
1.
Risk Anal ; 43(5): 994-1010, 2023 May.
Artigo em Inglês | MEDLINE | ID: mdl-35725023

RESUMO

Environmental impact assessment (EIA) procedures required in the United States and many other countries are often highlighted as a major hindrance to timely and efficient deployment of critical infrastructure projects. Under the U.S. National Environmental Policy Act, a more extensive environmental impact statement (EIS) review can take several more years and cost much more than a succinct environmental assessment (EA). This not only affects the project in question, but also likely informs how-or whether-additional projects are pursued. Thus, understanding key predictors of the EA versus EIS choice sheds light on supply-side considerations affecting infrastructure deficits. Using the case of NEPA reviews conducted for 244 transmission line projects between 2005 and 2018 by two U.S. federal agencies in the western United States, the Bureau of Land Management (BLM) and Department of Energy (DOE), this addresses the following question: What project features most predict whether EA or an EIS is used to assess a transmission line project? Drawing upon NEPA assessment guidance and agency NEPA records, we use a regression classification tree to analyze how protocols and project attributes relate to assessment choice. The result is essentially a null finding: transmission line length is by far the most important predictor of whether a project receives an extensive EIS or a shorter EA, with little predictive value provided by other attributes. While absolute project size undoubtedly influences impacts, the lack of further differentiation in what predicts use of EISs versus EAs suggests assessment does not simply respond to project details but also shapes proposal and design choices beforehand.

2.
Risk Anal ; 41(2): 273-288, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-32822075

RESUMO

In Pakistan, annual poliovirus investment decisions drive quantities of supplemental immunization campaigns districts receive. In this article, we assess whether increased spending on poliovirus surveillance is associated with greater likelihood of correctly identifying districts at high risk of polio with assignment of an elevated "risk ranking." We reviewed programmatic documents from Pakistan for the period from 2012-2017, recording whether districts had been classified as "high risk" or "low risk" in each year. Through document review, we developed a decision tree to describe the ranking decisions. Then, integrating data from the World Health Organization and Global Polio Eradication Initiative, we constructed a Bayesian decision network reflecting investments in polio surveillance and immunization campaigns, surveillance metrics, disease incidence, immunization rates, and occurrence of polio cases. We test these factors for statistical association with the outcome of interest-a change in risk rank between the beginning and the end of the one-year time period. We simulate different spending scenarios and predict their impact on district risk ranking in future time periods. We find that per district spending increases are associated with increased identification of cases of acute flaccid paralysis (AFP). However, the low specificity of AFP investment and the largely invariant ranking of district risk means that even large increases in surveillance spending are unlikely to promote major changes in risk rankings at the current stage of the Pakistan polio eradication campaign.


Assuntos
Viroses do Sistema Nervoso Central/diagnóstico , Viroses do Sistema Nervoso Central/virologia , Erradicação de Doenças/métodos , Programas de Imunização/economia , Mielite/diagnóstico , Mielite/virologia , Doenças Neuromusculares/diagnóstico , Doenças Neuromusculares/virologia , Poliomielite/epidemiologia , Poliomielite/prevenção & controle , Poliomielite/transmissão , Vigilância da População , Medição de Risco/métodos , Teorema de Bayes , Simulação por Computador , Tomada de Decisões , Árvores de Decisões , Geografia , Custos de Cuidados de Saúde , Humanos , Incidência , Poliovirus , Risco , Vacinação , Organização Mundial da Saúde
3.
Energy Policy ; 1332019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32863530

RESUMO

The performance of energy service providers has important environmental and safety consequences in local communities. This paper uses a novel dataset compiled from operator reports and infrastructure monitoring data obtained from three different US federal agencies to assess the performance of retail gas utilities nationwide in terms of addressing gas leaks and minimizing leak volumes. Our panel data set includes yearly observations for 727 retail gas utilities from 2009 to 2017. We show that safety hazards and environmental costs of gas leaks are widespread across providers that vary in terms of ownership, size, and region. We then use series of Bayesian hierarchical models to regress four outcome variables--hazardous leaks, end-year unfixed leaks, total gas volume leaked, and significant incidents--on infrastructure conditions, regional service context, and socio-economic service population characteristics. Unlike what is observed in other critical infrastructure cases such as drinking water, socioeconomic conditions are not strongly predictive of service outcomes. Public utilities exhibit better environmental performance on average, and no difference in maintenance backlogs. Because the environmental costs of poor performance--primarily in terms of methane greenhouse gas emissions--are predominantly social, policy tools such as consolidation and privatization are unlikely to improve environmental outcomes.

4.
Opt Express ; 25(11): 12653-12665, 2017 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-28786620

RESUMO

This paper reports design, fabrication, and demonstration of a silica photonic integrated circuit (PIC) capable of conducting interferometric imaging with multiple baselines around λ = 1550 nm. The PIC consists of four sets of five waveguides (total of twenty waveguides), each leading to a three-band spectrometer (total of sixty waveguides), after which a tunable Mach-Zehnder interferometer (MZI) constructs interferograms from each pair of the waveguides. A total of thirty sets of interferograms (ten pairs of three spectral bands) is collected by the detector array at the output of the PIC. The optical path difference (OPD) of each interferometer baseline is kept to within 1 µm to maximize the visibility of the interference measurement. We constructed an experiment to utilize the two baselines for complex visibility measurement on a point source and a variable width slit. We used the point source to demonstrate near unity value of the PIC instrumental visibility, and used the variable slit to demonstrate visibility measurement for a simple extended object. The experimental result demonstrates the visibility of baseline 5 and 20 mm for a slit width of 0 to 500 µm in good agreement with theoretical predictions.

5.
Opt Express ; 25(8): 8872-8885, 2017 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-28437962

RESUMO

This paper demonstrates rapidly reconfigurable, high-fidelity optical arbitrary waveform generation (OAWG) in a heterogeneous photonic integrated circuit (PIC). The heterogeneous PIC combines advantages of high-speed indium phosphide (InP) modulators and low-loss, high-contrast silicon nitride (Si3N4) arrayed waveguide gratings (AWGs) so that high-fidelity optical waveform syntheses with rapid waveform updates are possible. The generated optical waveforms spanned a 160 GHz spectral bandwidth starting from an optical frequency comb consisting of eight comb lines separated by 20 GHz channel spacing. The Error Vector Magnitude (EVM) values of the generated waveforms were approximately 16.4%. The OAWG module can rapidly and arbitrarily reconfigure waveforms upon every pulse arriving at 2 ns repetition time. The result of this work indicates the feasibility of truly dynamic optical arbitrary waveform generation where the reconfiguration rate or the modulator bandwidth must exceed the channel spacing of the AWG and the optical frequency comb.

6.
Risk Anal ; 36(10): 1916-1935, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26800227

RESUMO

In emergent photovoltaics, nanoscale materials hold promise for optimizing device characteristics; however, the related impacts remain uncertain, resulting in challenges to decisions on strategic investment in technology innovation. We integrate multi-criteria decision analysis (MCDA) and life-cycle assessment (LCA) results (LCA-MCDA) as a method of incorporating values of a hypothetical federal acquisition manager into the assessment of risks and benefits of emerging photovoltaic materials. Specifically, we compare adoption of copper zinc tin sulfide (CZTS) devices with molybdenum back contacts to alternative devices employing graphite or graphene instead of molybdenum. LCA impact results are interpreted alongside benefits of substitution including cost reductions and performance improvements through application of multi-attribute utility theory. To assess the role of uncertainty we apply Monte Carlo simulation and sensitivity analysis. We find that graphene or graphite back contacts outperform molybdenum under most scenarios and assumptions. The use of decision analysis clarifies potential advantages of adopting graphite as a back contact while emphasizing the importance of mitigating conventional impacts of graphene production processes if graphene is used in emerging CZTS devices. Our research further demonstrates that a combination of LCA and MCDA increases the usability of LCA in assessing product sustainability. In particular, this approach identifies the most influential assumptions and data gaps in the analysis and the areas in which either engineering controls or further data collection may be necessary.


Assuntos
Conservação dos Recursos Naturais/métodos , Técnicas de Apoio para a Decisão , Nanotubos de Carbono/química , Simulação por Computador , Custos e Análise de Custo , Desenho de Equipamento , Grafite/química , Luz , Militares , Molibdênio , Método de Monte Carlo , Medição de Risco , Incerteza , Estados Unidos
7.
Opt Express ; 22(23): 27942-57, 2014 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-25402035

RESUMO

We describe a technique for dynamic quantum optical arbitrary-waveform generation and manipulation, which is capable of mode selectively operating on quantum signals without inducing significant loss or decoherence. It is built upon combining the developed tools of quantum frequency conversion and optical arbitrary waveform generation. Considering realistic parameters, we propose and analyze applications such as programmable reshaping of picosecond-scale temporal modes, selective frequency conversion of any one or superposition of those modes, and mode-resolved photon counting. We also report on experimental progress to distinguish two overlapping, orthogonal temporal modes, demonstrating over 8 dB extinction between picosecond-scale time-frequency modes, which agrees well with our theory. Our theoretical and experimental progress, as a whole, points to an enabling optical technique for various applications such as ultradense quantum coding, unity-efficiency cavity-atom quantum memories, and high-speed quantum computing.


Assuntos
Óptica e Fotônica/instrumentação , Teoria Quântica , Desenho de Equipamento , Fótons
8.
Opt Express ; 22(1): 145-56, 2014 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-24514976

RESUMO

We demonstrate free-space space-division-multiplexing (SDM) with 15 orbital angular momentum (OAM) states using a three-dimensional (3D) photonic integrated circuit (PIC). The hybrid device consists of a silica planar lightwave circuit (PLC) coupled to a 3D waveguide circuit to multiplex/demultiplex OAM states. The low excess loss hybrid device is used in individual and two simultaneous OAM states multiplexing and demultiplexing link experiments with a 20 Gb/s, 1.67 b/s/Hz quadrature phase shift keyed (QPSK) signal, which shows error-free performance for 379,960 tested bits for all OAM states.

9.
Opt Express ; 20(24): 26958-68, 2012 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-23187551

RESUMO

This paper demonstrates a rapid and full hitless defragmentation method in elastic optical networks exploiting a new technique for fast wavelength tracking in coherent receivers. This technique can be applied to a single-carrier connection or each of the subcarriers forming a super-channel. A proof-of-concept demonstration shows hitless defragmentation of a 10 Gb/s QPSK single-carrier connection from 1547.75 nm to 1550.1 nm in less than 1 µs. This was obtained using a small (0.625 kB) link-layer transmitter buffer without the need for any additional transponder. We also demonstrated that the proposed defragmentation technique is capable of hopping over an existing connection, i.e. 10 Gb/s OOK at 1548.5 nm, without causing any degradation of its real-time Bit Error Rate (BER) value. The proposed scheme gives advantages in terms of overall network blocking probability reduction up to a factor of 40.


Assuntos
Algoritmos , Tecnologia de Fibra Óptica/instrumentação , Fibras Ópticas , Processamento de Sinais Assistido por Computador , Telecomunicações/instrumentação , Desenho de Equipamento , Humanos , Informática Médica
10.
Opt Express ; 20(9): 9396-402, 2012 Apr 23.
Artigo em Inglês | MEDLINE | ID: mdl-22535028

RESUMO

We propose and demonstrate silicon photonic integrated circuits (PICs) for free-space spatial-division-multiplexing (SDM) optical transmission with multiplexed orbital angular momentum (OAM) states over a topological charge range of -2 to +2. The silicon PIC fabricated using a CMOS-compatible process exploits tunable-phase arrayed waveguides with vertical grating couplers to achieve space division multiplexing and demultiplexing. The experimental results utilizing two silicon PICs achieve SDM mux/demux bit-error-rate performance for 1­b/s/Hz, 10-Gb/s binary phase shifted keying (BPSK) data and 2-b/s/Hz, 20-Gb/s quadrature phase shifted keying (QPSK) data for individual and two simultaneous OAM states.


Assuntos
Semicondutores , Processamento de Sinais Assistido por Computador/instrumentação , Silício/química , Ressonância de Plasmônio de Superfície/instrumentação , Telecomunicações/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento , Integração de Sistemas
11.
Opt Lett ; 37(3): 341-3, 2012 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-22297346

RESUMO

This Letter demonstrates a measurement technique based on frequency-to-time mapping and coherent detection, which enables the complete (i.e., amplitude and phase) characterization of dynamically reconfigurable photonic filters. We apply this technique to a unit cell from a silicon CMOS-compatible photonic lattice filter that has a rapidly changing transfer function with an 8.33 ns update time, 120 MHz spectral resolution, and 12 GHz bandwidth. These dynamic measurements allow characterization of transients, thermal effects, filter fidelity, and other time-dependent phenomena during switching.

12.
Opt Express ; 19(9): 8242-53, 2011 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-21643074

RESUMO

We demonstrate an optical transmitter based on dynamic optical arbitrary waveform generation (OAWG) which is capable of creating high-bandwidth (THz) data waveforms in any modulation format using the parallel synthesis of multiple coherent spectral slices. As an initial demonstration, the transmitter uses only 5.5 GHz of electrical bandwidth and two 10-GHz-wide spectral slices to create 100-ns duration, 20-GHz optical waveforms in various modulation formats including differential phase-shift keying (DPSK), quaternary phase-shift keying (QPSK), and eight phase-shift keying (8PSK) with only changes in software. The experimentally generated waveforms showed clear eye openings and separated constellation points when measured using a real-time digital coherent receiver. Bit-error-rate (BER) performance analysis resulted in a BER < 9.8 × 10(-6) for DPSK and QPSK waveforms. Additionally, we experimentally demonstrate three-slice, 4-ns long waveforms that highlight the bandwidth scalable nature of the optical transmitter. The various generated waveforms show that the key transmitter properties (i.e., packet length, modulation format, data rate, and modulation filter shape) are software definable, and that the optical transmitter is capable of acting as a flexible bandwidth transmitter.


Assuntos
Refratometria/instrumentação , Processamento de Sinais Assistido por Computador/instrumentação , Telecomunicações/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento
13.
Opt Express ; 19(26): B736-45, 2011 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-22274096

RESUMO

We demonstrate a flexible-bandwidth network testbed with a real-time, adaptive control plane that adjusts modulation format and spectrum-positioning to maintain quality of service (QoS) and high spectral efficiency. Here, low-speed supervisory channels and field-programmable gate arrays (FPGAs) enabled real-time impairment detection of high-speed flexible bandwidth channels (flexpaths). Using premeasured correlation data between the supervisory channel quality of transmission (QoT) and flexpath QoT, the control plane adapted flexpath spectral efficiency and spectral location based on link quality. Experimental demonstrations show a back-to-back link with a 360-Gb/s flexpath in which the control plane adapts to varying link optical signal to noise ratio (OSNR) by adjusting the flexpath's spectral efficiency (i.e., changing the flexpath modulation format) between binary phase-shift keying (BPSK), quaternary phase-shift keying (QPSK), and eight phase-shift keying (8PSK). This enables maintaining the data rate while using only the minimum necessary bandwidth and extending the OSNR range over which the bit error rate in the flexpath meets the quality of service (QoS) requirement (e.g. the forward error correction (FEC) limit). Further experimental demonstrations with two flexpaths show a control plane adapting to changes in OSNR on one link by changing the modulation format of the affected flexpath (220 Gb/s), and adjusting the spectral location of the other flexpath (120 Gb/s) to maintain a defragmented spectrum.

14.
Opt Express ; 19(14): 13245-56, 2011 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-21747479

RESUMO

We demonstrate a fully-reconfigurable fourth-order optical lattice filter built by cascading identical unit cells consisting of a Mach-Zehnder interferometer (MZI) and a ring resonator. The filter is fabricated using a commercial silicon complementary metal oxide semiconductor (CMOS) process and reconfigured by current injection into p-i-n diodes with a reconfiguration time of less than 10 ns. The experimental results show full control over the single unit cell pole and zero, switching the unit cell transfer function between a notch filter and a bandpass filter, narrowing the notch width down to 400 MHz, and tuning the center wavelength over the full free spectral range (FSR) of 10 GHz. Theoretical and experimental results show tuning dynamics and associated optical losses in the reconfigurable filters. The full-control of each of the four cascaded single unit cells resulted in demonstrations of a number of fourth-order transfer functions. The multimedia experimental data show live tuning and reconfiguration of optical lattice filters.


Assuntos
Filtração/instrumentação , Interferometria/instrumentação , Refratometria/instrumentação , Silício/química , Transistores Eletrônicos , Desenho Assistido por Computador , Desenho de Equipamento , Análise de Falha de Equipamento
15.
J Transp Health ; 21: 101075, 2021 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36567867

RESUMO

Introduction: During the COVID-19 pandemic many municipalities closed or limited access to parks. A few also added new shared streets for citizens to recreate. This large and unprecedented change in the ability of residents to use green space provides an important case for assessing how emergency planning processes might differentially impact minority groups. Methods: Using the case of park closures and shared streets expansion in Denver, Colorado in March and April of 2020, this analysis evaluates how walking time and density of use at parks changed for different minority and income groups based on estimating park visits for residential blocks. Results: The analysis demonstrates that minority and low income groups were not disproportionately impacted by initial closures. Shared streets provide net decreases across the city in terms of travel time and density for recreational space usage, though there is some indication benefits were not equally distributed. Conclusion: The result emphasizes the importance of modern planning efforts and community engagement in ensuring equitable urban resilience while highlighting the potential for shared streets to provide more recreational accessibility if they can be equitably located.

16.
Opt Express ; 18(18): 18655-70, 2010 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-20940758

RESUMO

We introduce a dynamic optical arbitrary waveform generation (OAWG) technique that produces bandwidth scalable, continuous waveforms of near perfect fidelity. Additionally, OAWG's complement, real-time arbitrary optical waveform measurement (OAWM) is discussed. These approaches utilize gigahertz-bandwidth electronics to generate, or measure, truly arbitrary and dynamic optical waveforms scalable to terahertz bandwidths and infinite record lengths. We describe the theory, algorithms and enabling technologies necessary to calculate and produce a set of spectral modulations that create continuous, high-fidelity waveforms in the presence of spectral filtering from multiplexers.


Assuntos
Óptica e Fotônica , Algoritmos , Desenho de Equipamento , Luz , Espectroscopia Terahertz/métodos , Fatores de Tempo
17.
Opt Express ; 18(22): 22988-95, 2010 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-21164638

RESUMO

We experimentally demonstrate a dynamic line-by-line optical arbitrary waveform generation technique capable of generating continuous and bandwidth scalable high-fidelity waveforms without update rate limitations. Two quadrature modulators are used to create up to three spectral slices that are coherently combined by a passband-shaped multiplexer into a single contiguous spectrum to form complex optical waveforms with up to 30 GHz of bandwidth and 6 ns record lengths.

18.
Opt Express ; 17(15): 12332-44, 2009 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-19654635

RESUMO

Four-quadrature spectral interferometry using balanced coherent detection enables single-shot full-field characterization of complex-shaped optical waveforms with near quantum-limited sensitivity. A 90 degrees optical hybrid places a waveform in four-quadrature-phases with a stronger, well-characterized reference pulse. Measurement of the four spectra with an integrating two-dimensional detector array followed by balanced detection uniquely determines the signal field. Balanced coherent detection provides common-mode noise rejection and coherent gain enabling near quantum-limited sensitivity. The single-shot waveform was temporally gated from a 100 ps periodic train of arbitrary optical waveforms generated using line-by-line pulse shaping on a 10 GHz optical frequency comb. The measurements show arbitrary waveforms with 200-ps record lengths, 500 GHz optical bandwidths and only 1200 detected photons.


Assuntos
Óptica e Fotônica , Algoritmos , Desenho de Equipamento , Processamento de Imagem Assistida por Computador , Fótons , Teoria Quântica , Fatores de Tempo
19.
Opt Express ; 17(18): 15911-25, 2009 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-19724590

RESUMO

This paper presents the concept of an optical transmitter based on optical arbitrary waveform generation (OAWG) capable of synthesizing Tb/s optical signals of arbitrary modulation format. Experimental and theoretical demonstrations in this paper include generation of data packet waveforms focusing on (a) achieving high spectral efficiencies in quadrature phase-shift keying (QPSK) and 16 quadrature amplitude modulation (16QAM) modulation formats, (b) generation of complex data waveform packets used for optical-label switching (OLS) consisting of a data payload and label on a carrier and subcarrier, and (c) repeatability and accuracy of duobinary (DB) data packet waveforms with BER measurements. These initial demonstrations are based on static OAWG, or line-by-line pulse shaping, to generate repeated waveforms of arbitrary shape. In addition to experimental and theoretical demonstrations of static OAWG, simulated results show dynamic OAWG, which involves encoding continuous data streams of arbitrary symbol sequence on data packet waveforms of arbitrary length.

20.
Perspect Public Manag Gov ; 2(2): 155-165, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-31548995

RESUMO

Thin participatory processes are designed for information exchange. But complaint processes, message boards, and hotlines sometimes facilitate thick, meaningful engagement. Can policy design leverage factors driving engagement to enable values-based responses to complex policy problems, while allowing information exchange to continue as-needed for most participants? Using place-based case studies from oil and gas drilling and community complaints in three regions of Colorado, I make propositions about how the drivers of collaboration are related to the practice of engagement within participatory programs. Based on the case studies, presence of coercive policy actors, inclusion of multiple governmental authorities, and transparency in participatory communication are likely to facilitate thickening. Meanwhile, measurement-based responses to participation are likely to propagate thin participation only. Accordingly, in designing thin processes, policy makers should recognize the nature of engagement will depend on the type of knowledge exchanged and the suite of institutions that might use or leverage the participatory action.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA