The sensitivity of landscape evolution models to spatial and temporal rainfall resolution

© Author(s) 2016. Climate is one of the main drivers for landscape evolution models (LEMs), yet its representation is often basic with values averaged over long time periods and frequently lumped to the same value for the whole basin. Clearly, this hides the heterogeneity of precipitation - but what impact does this averaging have on erosion and deposition, topography, and the final shape of LEM landscapes? This paper presents results from the first systematic investigation into how the spatial and temporal resolution of precipitation affects LEM simulations of sediment yields and patterns of erosion and deposition. This is carried out by assessing the sensitivity of the CAESAR-Lisflood LEM to different spatial and temporal precipitation resolutions - as well as how this interacts with different-size drainage basins over short and long timescales. A range of simulations were carried out, varying rainfall from 0.25 h × 5 km to 24 h × Lump resolution over three different-sized basins for 30-year durations. Results showed that there was a sensitivity to temporal and spatial resolution, with the finest leading to & gt; 100 % increases in basin sediment yields. To look at how these interactions manifested over longer timescales, several simulations were carried out to model a 1000-year period. These showed a systematic bias towards greater erosion in uplands and deposition in valley floors with the finest spatial- and temporal-resolution data. Further tests showed that this effect was due solely to the data resolution, not orographic factors. Additional research indicated that these differences in sediment yield could be accounted for by adding a compensation factor to the model sediment transport law. However, this resulted in notable differences in the topographies generated, especially in third-order and higher streams. The implications of these findings are that uncalibrated past and present LEMs using lumped and time-averaged climate inputs may be under-predicting basin sediment yields as well as introducing spatial biases through under-predicting erosion in first-order streams but over-predicting erosion in second- and third-order streams and valley floor areas. Calibrated LEMs may give correct sediment yields, but patterns of erosion and deposition will be different and the calibration may not be correct for changing climates. This may have significant impacts on the modelled basin profile and shape from long-timescale simulations

Overview of environmental test plans for Space Station Freedom work package 4

The generation and distribution of electric power for Space Station Freedom (SSF) is critical to the station's success. Work Package 4 (WP-04) has the responsibility for the design, development, test, and delivery of the Electric Power System (EPS) for the SSF. During launch, assembly, and operation, the EPS will be subjected to various environments. A test and verification approach has been developed to assure that the EPS will function in these environments. An overview of that test program is presented with emphasis on environmental testing of hardware. Two key areas of the test program are highlighted in the overview. One area is the verification of the Solar Power Module (SPM) and associated cargo element hardware. This area includes detailing the plans for development and qualification testing of the SPM hardware. One series of tests, including modal and acoustic, has been completed on a development cargo element. Another area highlighted is the acceptance testing of high-power Orbital Replacement Units (ORU). The environmental test equipment plans are presented and reviewed in light of an aggressive production rate, which delivers ORU's to the WP-04 and other Space Station Work Packages. Through implementing the test program as outlined, the EPS hardware will be certified for flight and operation on the Space Station Freedom

The Missing Monitor in Corporate Governance: The Directors\u27 & Officers\u27 Liability Insurer

This article reports the results of empirical research on the monitoring role of directors\u27 and officers\u27 liability insurance (D&O insurance) companies in American corporate governance. Economic theory provides three reasons to expect D&O insurers to serve as corporate governance monitors: first, monitoring provides insurers with a way to manage moral hazard; second, monitoring provides benefits to shareholders who might not otherwise need the risk distribution that D&O insurance provides; and third, the bonding provided by risk distribution gives insurers a comparative advantage in monitoring. Nevertheless, we find that D&O insurers neither monitor corporate governance during the life of the insurance contract nor manage litigation defense costs once claims arise. Our findings raise significant questions about the value of D&O insurance for shareholders as well as the deterrent effect of corporate and securities liability. After exploring various explanations for these findings, we conclude that the absence of monitoring is due, at least in part, to the agency problem in the corporate context. Our analysis thus suggests that the existing form of corporate D&O insurance both results from and contributes to the relatively weak constraints on corporate managers. Corporate managers buy D&O coverage for self-serving reasons, and the coverage itself because it does not control moral hazard, reduces the extent to which shareholder litigation aligns managers\u27and shareholders\u27 incentives

The Missing Monitor in Corporate Governance: The Directors\u27 & Officers\u27 Liability Insurer

This article reports the results of empirical research on the monitoring role of directors\u27 and officers\u27 liability insurance (D&O insurance) companies in American corporate governance. Economic theory provides three reasons to expect D&O insurers to serve as corporate governance monitors: first, monitoring provides insurers with a way to manage moral hazard; second, monitoring provides benefits to shareholders who might not otherwise need the risk distribution that D&O insurance provides; and third, the bonding provided by risk distribution gives insurers a comparative advantage in monitoring. Nevertheless, we find that D&O insurers neither monitor corporate governance during the life of the insurance contract nor manage litigation defense costs once claims arise. Our findings raise significant questions about the value of D&O insurance for shareholders as well as the deterrent effect of corporate and securities liability. After exploring various explanations for these findings, we conclude that the absence of monitoring is due, at least in part, to the agency problem in the corporate context. Our analysis thus suggests that the existing form of corporate D&O insurance both results from and contributes to the relatively weak constraints on corporate managers. Corporate managers buy D&O coverage for self-serving reasons, and the coverage itself because it does not control moral hazard, reduces the extent to which shareholder litigation aligns managers\u27and shareholders\u27 incentives