Approaching Collaborative Modeling as an Uncertainty Reduction Process

ABSTRACT Model-Driven Engineering (MDE) technologies aim to support the growing complexity of software systems. Models are increasingly becoming large and unmanageable, and hence difficult to be understood by humans and processed by machines. As a consequence, multi-user environments are necessary to enable designers to create and refine large models in a collaborative manner enabling the engineering, modularization and reuse. In this paper, we propose a model-driven approach to represent, manage and manipulate models edited in a collaborative manner. In particular, we propose to represent the solutions space (i.e, model versions) in an intensional manner by adopting a model with uncertainty. We define a plan to manage the uncertainty by selecting the desired design, to manipulate their collaborative models in manually or automatic way, and to exploit a collaborative environment for real time multi-user editing. The approach is showed by means of a motivating example that involves business models demonstrating the advantages of the proposed approach

Exploring the Way to Approach the Efficiency Limit of Perovskite Solar Cells by Drift-Diffusion Model

Drift-diffusion model is an indispensable modeling tool to understand the carrier dynamics (transport, recombination, and collection) and simulate practical-efficiency of solar cells (SCs) through taking into account various carrier recombination losses existing in multilayered device structures. Exploring the way to predict and approach the SC efficiency limit by using the drift-diffusion model will enable us to gain more physical insights and design guidelines for emerging photovoltaics, particularly perovskite solar cells. Our work finds out that two procedures are the prerequisites for predicting and approaching the SC efficiency limit. Firstly, the intrinsic radiative recombination needs to be corrected after adopting optical designs which will significantly affect the open-circuit voltage at its Shockley-Queisser limit. Through considering a detailed balance between emission and absorption of semiconductor materials at the thermal equilibrium, and the Boltzmann statistics at the non-equilibrium, we offer a different approach to derive the accurate expression of intrinsic radiative recombination with the optical corrections for semiconductor materials. The new expression captures light trapping of the absorbed photons and angular restriction of the emitted photons simultaneously, which are ignored in the traditional Roosbroeck-Shockley expression. Secondly, the contact characteristics of the electrodes need to be carefully engineered to eliminate the charge accumulation and surface recombination at the electrodes. The selective contact or blocking layer incorporated nonselective contact that inhibits the surface recombination at the electrode is another important prerequisite. With the two procedures, the accurate prediction of efficiency limit and precise evaluation of efficiency degradation for perovskite solar cells are attainable by the drift-diffusion model.Comment: 32 pages, 11 figure

Between Scylla and Charybdis: Environmental governance and illegibility in the American West

In The Odyssey, Odysseus and his crew must navigate the Strait of Messina between two great hazards: the six-headed monster Scylla on one side, and the whirlpool Charybdis on the other. This conceit here guides a critical engagement with scientific knowledge and state power, grounded in the positionality and practices of government agents charged with the management of controversial species and processes in the American West. Based in ethnographic and archival research on wolf-livestock conflict and public lands grazing in Central Idaho, I relate how agents with the U.S. Forest Service and Idaho Department of Fish and Game navigate conditions not of their own choosing. Sailing the “choppy seas” of complex systems and multiple-use mandates, with the “whirlpool” of cuts to capacity on one side and the “monster” of political controversy and litigation on the other, agents appear to collect less or more ambiguous information on their charges, resulting in a partial “blindness” or illegibility. Although a rational adaptation to unrealistic expectations, this ignorance is not bliss but rather symptom and source of dysfunction, limiting agents’ ability to carry out monitoring, collaboration, and effectively conduct on-the-ground management. Understanding patterns of illegibility requires that we attend both to broader contextual pressures and situated motivations. In so doing, we might account for the seeming disconnect between agencies’ stated aims and practices, complicate traditional assumptions of evidence-based scientific management and analyses of bureaucratic rationality and state power, and make sense of the apparent dysfunction around environmental governance in the American West today

Foreword: Making Sense of Information for Environmental Protection

Despite the ubiquity of information, no one has proposed calling the present era the Knowledge Age. Knowledge depends not only on access to reliable information, but also on sound judgment regarding which information to access and how to situate that information in relation to the values and purposes that comprise the individual\u27s or the social group\u27s larger projects. This is certainly the case for wise and effective environmental governance. A regulator needs accurate information to understand the nature of a problem and the consequences of potential responses. Likewise, the regulated community needs information to decide how best to comply with adopted rules, and the public needs information in order to accept the credibility and legitimacy of the regulatory regime. But governance also requires judgment regarding how to manage information itself - how to structure burdens of proof in light of goals such as public safety or promotion of economic growth, how to balance the public\u27s interest in disclosure against competing aims such as national security or the protection of trade secrets, whether to withhold information in the belief that it may actually be harmful to the recipient, and so on. This paper, written as a foreword for the Texas Law Review\u27s symposium issue, Harnessing the Power of Information for the Next Generation of Environmental Law, provides a model to understand the role of information in environmental law - how it is generated, utilized, and disseminated within regulatory processes. Drawing on the diverse and significant insights of the symposium articles, the paper attempts both to make sense of the role of information in environmental protection and to highlight significant questions and concerns

Influence of Source Propagation Direction and Shear Flow Profile in Impedance Eduction of Acoustic Liners

The acoustic impedance of liners is a key parameter for their design, and depends on the flow conditions, i.e., the sound pressure level and the presence of a grazing flow. The surface impedance of a locally reacting liner is defined as a local intrinsic property relating the acoustic pressure to the normal acoustic particle velocity at the liner surface. Impedance eduction techniques are now widely used to retrieve the impedance of liners in aeroacoustic facilities in the presence of a shear grazing flow. While surface impedance is intrinsic by definition, the educed impedance has recently been shown to depend on the direction of the incident waves relative to the mean flow. Different studies have investigated this issue by considering different acoustic propagation models used in the education process in the hope of matching the educed values. The purpose of the present work is to continue the previous investigations by evaluating the influence of the shear flow profile on the educed impedance, while considering a Bayesian inference process in order to evaluate the uncertainty on the educed values. The identified uncertainties were not able to totally account for the observed discrepancies between educed impedances

The Spring 1985 high precision baseline test of the JPL GPS-based geodetic system

The Spring 1985 High Precision Baseline Test (HPBT) was conducted. The HPBT was designed to meet a number of objectives. Foremost among these was the demonstration of a level of accuracy of 1 to 2:10 to the 7th power, or better, for baselines ranging in length up to several hundred kilometers. These objectives were all met with a high degree of success, with respect to the demonstration of system accuracy in particular. The results from six baselines ranging in length from 70 to 729 km were examined for repeatability and, in the case of three baselines, were compared to results from colocated VLBI systems. Repeatability was found to be 5:10 to the 8th power (RMS) for the north baseline coordinate, independent of baseline length, while for the east coordinate RMS repeatability was found to be larger than this by factors of 2 to 4. The GPS-based results were found to be in agreement with those from colocated VLBI measurements, when corrected for the physical separations of the VLBI and CPG antennas, at the level of 1 to 2:10 to the 7th power in all coordinates, independent of baseline length. The results for baseline repeatability are consistent with the current GPA error budget, but the GPS-VLBI intercomparisons disagree at a somewhat larger level than expected. It is hypothesized that these differences may result from errors in the local survey measurements used to correct for the separations of the GPS and VLBI antenna reference centers