Aditya Medury

Pilot Models for Estimating Bicycle Intersection Volumes

Bicycle volume data are useful for practitioners and researchers to understand safety, travel behavior, and development impacts. Several simple models of bicycle intersection volumes were developed for Alameda County, California. The models were based on 2-h bicycle counts performed at a sample of 81 intersections in the spring of 2008 and 2009. Study sites represented areas with a wide range of population density, employment density, proximity to commercial property, neighborhood income, and street network characteristics. The explanatory variables considered for the models included intersection site, land use, transportation system, and socioeconomic characteristics of the areas surrounding each intersection. Four alternative models were developed with adjusted R2 values ranging from .39 to .60. The models showed that bicycle volumes tended to be higher at intersections surrounded by more commercial retail properties within1 .10mi, closer to a major university, with a marked bicycle facility on at least one leg of the intersection, surrounded by less hilly terrain within1 .2mi, or surrounded by a more connected roadway network. The models also showed several important differences between weekday and weekend intersection volumes. The positive association between bicycle volume and proximity to retail properties or a large university was greater on weekdays than on weekends, whereas bicycle facilities had a stronger positive association and hilly terrain had a weaker negative association with bicycle volume on weekends than on weekdays. The study found that further testing and refinement was necessary before accurate count predictions could be made in Alameda County or other communities.

Simultaneous Network Optimization Approach for Pavement Management Systems

AbstractIn the context of sequential decision making under uncertainty, the Markov decision process (MDP) is a widely used mathematical framework. The MDP-based approaches in the infrastructure management literature can be broadly categorized as either top-down or bottom-up. The former, while efficient in incorporating system-level budget constraints, provide randomized policies, which must be mapped to individual facilities using additional subroutines. Conversely, although state-of-the-art bottom-up approaches provide facility-specific decisions, the disjointed nature of their problem formulation does not account for budget constraints in the future years. In this paper, a simultaneous network-level optimization framework is proposed, which seeks to bridge the gap between the top-down and bottom-up MDP-based approaches in infrastructure management. The salient feature of the approach is that it provides facility-specific policies for the current year of decision making while utilizing the randomized pol...

Unified Compact Model Covering Drift-Diffusion to Ballistic Carrier Transport

In this letter, we present a unified compact model, which accurately captures carrier transport from the drift-diffusion to ballistic regime. This is a single unified model, which accounts for carrier degeneracy effects in ballistic transport. The model is implemented into the industry standard compact models for FinFETs, fully depleted silicon-on-insulator (FDSOI) devices and bulk MOSFETs: 1) Berkeley Spice model for common multi-gate; 2) Berkeley Spice model for independent multi-gate; and 3) BSIM6. The model is validated with experimental data and TCAD simulations for FDSOI devices, FinFETs, and bulk MOSFETs.

New industry standard FinFET compact model for future technology nodes

A new production ready compact model for future FinFETs is presented. This single unified model can model FinFETs with realistic fin shapes including rectangle, triangle, circle and any shape in between. New mobility models support Ge p-FinFETs and InGaAs n-FinFETs. A new quantum effects model enables accurate modeling of III-V FinFETs. Special attention is paid to shape agnostic short-channel effect model for aggressive Lg scaling and body bias model for FinFETs on bulk substrates. With its accuracy verified with experimental data and TCAD, this computationally efficient model is an ideal turn-key solution for simulation and design of future heterogeneous circuits.

BSIM-IMG: Compact model for RF-SOI MOSFETs

Emerging market of RFSOI applications has motivated us to come up with the robust compact model for RFSOI MOSFETs. In this work, we have validated the RF capabilities of BSIM-IMG model which is the latest industry standard compact model for independent double gate MOSFETs. Results are validated with the experimental S-parameter data measured. Model shows good agreement for different biases over wide frequency range from 100KHz-8.5GHz.

Crashes on and near college campuses: : a comparative analysis of pedestrian and bicyclist safety

Problem, research strategy, and findings: College campuses are multimodal settings with very high levels of walking and biking in conjunction with high levels of vehicular traffic, which increases risks for bicyclists and pedestrians. In this study, we examine crash data (both police reported and self-reported) and urban form data from three U.S. campuses to understand the spatial and temporal distribution of crashes on the campuses and their immediate periphery. To account for underreporting of pedestrian and bicycle crashes, we developed and circulated an online survey, which helped identify collision hotspots across the three campuses. We then studied these locations to determine their characteristics, generate a typology of campus danger zones, and recommend design and policy changes that could improve pedestrian and cycling safety. We find a significant underreporting of crashes, and unequal spatial and temporal distributions of campus crashes. We identify three particular types of danger zones for pedestrians and cyclists: campus activity hubs, campus access hubs, and through traffic hubs. Injuries tended to be more serious for those crashes taking place on campus peripheries. Takeaway for practice: The intermingling of motorized and non-motorized modes creates significant opportunities for crashes. Planners should be aware of the existing underreporting and give special attention to the three types of danger zones. In addition to the recommendations of the literature for the creation of campus master plans for walking and biking, campuses should conduct safety audits and surveys to identify hotspots and consider specific design improvements for each of the three danger zones to lessen modal conflict.

Modeling of Subsurface Leakage Current in Low

We present a phenomenological model for subsurface leakage current in MOSFETs biased in accumulation. The subsurface leakage current is mainly caused by source-drain coupling, leading to carriers surmounting the barrier between the source and the drain. The developed model successfully takes drain-to-source voltage (VDS), gate-to-source voltage (VGS), gate length (LG), substrate doping concentration (Nsub), and temperature (T) dependence into account. The presented analytical model is implemented into the BSIM6 bulk MOSFET model and is in good agreement with technology-CAD simulation data.

V_{\mathrm {TH}}

This work presents new compact models that capture advanced physical effects presented in industry FinFETs. The presented models are introduced into the industry standard compact model BSIM-CMG. The core model is updated with a new unified FinFET model, which calculates charges and currents of transistors with complex fin cross-sections. In addition, threshold voltage modulation from bulk-bias effects and bias dependent quantum mechanical confinement effects are incorporated into the new core model. Short channel effects, affecting threshold voltage and subhtreshold swing, are modeled with a new unified field penetration length, enabling accurate 14nm node FinFET modeling. The new proposed models further assure the BSIM-CMG models capabilities for circuit design using FinFET transistors for advanced technology nodes.

Short Channel MOSFET at Accumulation Bias

In this letter, we model future generation SiGe FinFETs using the industry standard compact model BSIM-CMG. BSIM-CMG is enhanced to model these aggressively scaled devices. It is found that in these narrow fin (fin width Wfin = 12 nm) devices spacer region resistance behaves nonlinearly with drain-current. This nonlinear resistance behavior arises due to the saturation of carrier velocity in the spacer region. Accurate modeling of spacer region nonlinearity is important to predict the drain-current and the device transconductance. The developed model captures this phenomenon very well and produces excellent agreement with experimental data.

BSIM-CMG: Standard FinFET compact model for advanced circuit design

In this paper, the non-motorized traffic safety concerns in and around three university campuses are evaluated by comparing police-reported crash data with traffic safety information sourced from the campus communities themselves. The crowdsourced traffic safety data comprise of both self-reported crashes as well as perceived hazardous locations. The results of the crash data analysis reveal that police-reported crashes underrepresent non-motorized safety concerns in and around the campus regions. The spatial distribution of police-reported crashes shows that police-reported crashes are predominantly unavailable inside the main campus areas, and the off-campus crashes over-represent automobile involvement. In comparison, the self-reported crash results report a wide variety of off-campus collisions not involving automobiles, while also highlighting the issue of high crash concentrations along campus boundaries. An assessment of the perceived hazardous locations (PHLs) reveals that high concentrations of such observations at/near a given location have statistically significant association with both survey-reported crashes as well as future police-reported crashes. Moreover, the results indicate the presence of a saturation point in the relationship between crashes and PHLs wherein beyond a certain limit, an increasing number of traffic safety concerns may not necessarily correlate with a proportional increase in the number of crashes. These findings suggests that augmenting our existing knowledge of traffic safety through crowdsourcing techniques can potentially help in better estimating both existing as well as emerging traffic safety concerns.