14 research outputs found
Impact Investing Handbook: An Implementation Guide for Practitioners
No full textRockefeller Philanthropy Advisors published the "Impact Investing Handbook: An Implementation Guide for Practitioners"—180 pages of helping asset owners turn interest into action. Two years in the making, this practical publication features case studies and detailed guidance for individuals, families, foundations, and corporations. Written by Steven Godeke of Godeke Consulting and Patrick Briaud of RPA, it features input from over fifty experts and practitioners.The Handbook comes at a pivotal moment. In the midst of urgent social, economic and environmental challenges including COVID-19, a rapidly changing climate, growing economic inequity, and broader realization of systemic impacts of racism, more investors are seeking to better understand the positive and negative consequences of how they deploy capital. There is a growing realization among those who seek to influence society that they can use more of their assets to complement and even accelerate their social impact goals.The Handbook covers:The Why – Developing a theory of change by merging impact goals with investment goals.The How – Building or shifting a portfolio using the full range of impact tools and structures.The So What – Measuring success through leading principles, frameworks, and standards.The Now What – Crafting a realistic implementation plan by following best practices
Analysis of a database of open pit mine slope failures to predict travel distance, setback distance, and geometric properties
No full textIn mining, open pits have slopes cut as steep as possible to ensure efficient mining yet not too steep to jeopardize safety. Building on existing contributions, the Texas A University Mine Slope database (TAMU-MineSlope) was created to provide global-scale insights into the runout mechanics of open pit slope failures and offer the database to engineers for further study. The database includes 134 cases of open pit slope failures that occurred at 76 mines worldwide. Based on energy principles and an analysis of the TAMU-MineSlope data, an equation to predict the travel distance of the slope failure mass is presented in this paper. Furthermore, based on the case histories analysis, an equation to predict the setback distance is proposed. Finally, the TAMU-MineSlope database shows that the average width to height ratio of the failing slope mass is 2.7 and that, for this ratio, the 3D factor of safety (FS) can reach a value 15% higher than the 2D FS. The database has been released in the public domain.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
STABILITY OF SLOPE CORNERS: A DISPLACEMENT BASED FEM STUDY
No full textThe stability of slopes is typically evaluated by two-dimensional plane strain analysis. However, many slopes exhibit three-dimensional geometries, including slope corners. Several researchers have studied the stability of slope corners but found that the factor of safety (FS) was close to the FS for the plane strain case. The results of a new series of 3D Finite Element Method (FEM) simulating slope corners including slope angle, plan view angle, radius of curvature, and slope height are presented. They confirm that the FS does not vary much for corners compared to the plane strain case. However, 220 cases using an elastic-perfectly plastic soil model together with the FEM shear strength reduction method show that the displacement field is very different at the corners compared to plane strain with differences reaching over 100%. The displacement ratio between corners and plane strain is presented as a function of the plan view angle of the corner. Often failure is defined at a chosen large displacement, as in the ultimate load of foundation elements. If this concept is carried over to slope stability, it would indicate that the FS of corners should be very different from the plane strain case. A possible explanation is discussed.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
System and method for testing the compaction of soil
No full textA device for determining soil compaction includes a control member fitted with one or more sensors that measure the response of the control member during co-action between the control member and a soil surface. In one embodiment, this response can be flexure as characterized by a measurable parameter such as strain. A measurement module in communication with the sensor or sensors determines a soil modulus for the soil based on the strain measurement from the sensor or sensors. In one arrangement, the control member includes one set of sensors that measure radial strain and another set of sensors that measures hoop strain. The device can also include a load sensor for measuring the load applied to the control member. In one embodiment the measurement module includes a processor that determines soil modulus based the strain measurements and the measured load.U
MEANDER MIGRATION: THE OBSERVATION METHOD
No full textRiver meanders migrate over time and the consequences of this migration can create a problem for bridges and embankments near the river. This is why it is important to predict the lateral extent of future migration over the life of neighboring infrastructure. In the observation method for meander migration (OMM), the past movement and velocity history of the meander are used to back-calculate site specific erosion parameters. Those parameters serve as input to predict the meander migration for a chosen future velocity hydrograph. In this article and after a review of existing knowledge, the analytical steps leading to the development of the OMM are described, then the field and laboratory work at 4 full scale meander migration case histories are presented, and then the 4 full scale meander migration case histories are used to evaluate the OMM. The OMM has been automated in an Excel spreadsheet.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
On the Soundness of Algebraic Attacks against Code-based Assumptions
No full textWe study recent algebraic attacks (Briaud-Øygarden EC\u2723) on the Regular Syndrome Decoding (RSD) problem and the assumptions underlying the correctness of their attacks\u27 complexity estimates. By relating these assumptions to interesting algebraic-combinatorial problems, we prove that they do not hold in full generality. However, we show that they are (asymptotically) true for most parameter sets, supporting the soundness of algebraic attacks on RSD. Further, we prove—without any heuristics or assumptions—that RSD can be broken in polynomial time whenever the number of error blocks times the square of the size of error blocks is larger than 2 times the square of the dimension of the code.
Additionally, we use our methodology to attack a variant of the Learning With Errors problem where each error term lies in a fixed set of constant size. We prove that this problem can be broken in polynomial time, given a sufficient number of samples. This result improves on the seminal work by Arora and Ge (ICALP\u2711), as the attack\u27s time complexity is independent of the LWE modulus
LNCS
No full textWe study recent algebraic attacks (Briaud-Øygarden EC’23) on the Regular Syndrome Decoding (RSD) problem and the assumptions underlying the correctness of their attacks’ complexity estimates. By relating these assumptions to interesting algebraic-combinatorial problems, we prove that they do not hold in full generality. However, we show that they are (asymptotically) true for most parameter sets, supporting the soundness of algebraic attacks on RSD. Further, we prove—without any heuristics or assumptions—that RSD can be broken in polynomial time whenever the number of error blocks times the square of the size of error blocks is larger than 2 times the square of the dimension of the code.
Additionally, we use our methodology to attack a variant of the Learning With Errors problem where each error term lies in a fixed set of constant size. We prove that this problem can be broken in polynomial time, given a sufficient number of samples. This result improves on the seminal work by Arora and Ge (ICALP’11), as the attack’s time complexity is independent of the LWE modulus
Sensitivity analysis of polar orbiter motion to lunar viscoelastic tidal deformation
No full textWe investigate the impact of viscoelastic tidal deformation of the Moon on the motion of a polar orbiter. The dissipative effects in the Moon’s interior, i.e., tidal phase lags, are modeled as Fourier series sampled at given frequencies associated with linear combinations of Delaunay arguments, the fundamental parameters describing the lunar motion around the Earth and the Sun. We implement the tidal model to evaluate the temporal lunar gravity field and the induced perturbation on the orbiter. We validate the numerical scheme via a frequency analysis of the perturbed orbital motion. We show that, in the case of the Lunar Reconnaissance Orbiter at a low altitude of less than 200 km, the main lunar tides and hence the potential Love numbers around the monthly and some multiple frequencies are dynamically separable. The omission of those effects in practice introduces a position error at the level of a few decimeters within 10 days.</p
A holistic model for coastal flooding using system diagrams and the Source–Pathway–Receptor (SPR) concept
No full textCoastal flooding is a problem of increasing relevance in low-lying coastal regions worldwide. In addition to the anticipated increase in likelihood and magnitude of coastal floods due to climate change, there is rapid growth in coastal assets and infrastructure. Sustainable and integrated coastal flood management over large areas and varying coastline types cannot be simply treated as local combinations of flood defences and floodplains. Rather, a system level analysis of floodplains is required to structure the problem as a first step before applying quantitative models. In this paper such a model is developed using system diagrams and the Source–Pathway–Receptor (SPR) concept, to structure our understanding of large and complex coastal flood systems. A graphical systems model is proposed for the assessment of coastal flood systems with regard to individual elements and their topological relationships. Two examples are discussed – a unidirectional model for a large-scale flood system, and a multi-directional model for a smaller-scale system, both based on the Western Scheldt estuary. The models help to develop a comprehensive understanding of system elements and their relationships and provide a holistic overview of the coastal flood system. The approach shows that a system level analysis of floodplains is more effective than simple topographic maps when conveying complex information. The models are shown to be useful as an a-priori approach to making assumptions about flood mechanisms explicit and informing inputs to numerical models
Development of an Erosion Function Apparatus for the assessment of the erosion resistance of compacted clay
No full textThe erosion resistance of clay is an important aspect when assessing the integrity of a levee. This is because the clay layer of a dike must resist the forces that are imposed in the case of overflow or overtopping. Currently, the erosion resistance of clay in the Netherlands is being assessed based on the sand content, the liquid limit and the plasticity index. The quality of compaction is assessed by a density requirement. However, the effect of compaction on the erosion resistance of clay is not well understood and although its importance has been widely acknowledged by multiple literature sources, it has never been quantified. Therefore the goal of this thesis is to investigate what the are of compaction on the erosion resistance of clay and how large. To do this first of all a set-up has been designed and built, resembling the Erosion Function Apparatus as suggested by Briaud with some differences. Then 3 types of clay have been tested with differing initial erosion characteristics: one kind which fully complies with the current Dutch guidelines, 1 which does not quite suffice and 1 which does not suffice in any way. These 3 types of clay have been compacted at various energy levels (Modified Proctor, Proctor and 0.5*Proctor density). Also samples with differing water contents have been produced at each energy level and each clay. These samples were subsequently tested in the Erosion Function Apparatus at several flow-velocities in order to establish an erosion curve from which several erosion parameters were determined. \bigskip Having performed the erosion tests and determined the accompanying erosion parameters the results were interpreted in the Proctor curve. Plotting the results in the Proctor curve show that samples compacted at the optimum water content in the Proctor plane perform best, whereas they perform poorer the farther the water content is off from the optimum. Also it shows an increase in the compaction effort will generally result in a lower amount of erosion occurring. This result has been obtained by determining the critical shear stress, critical erosion velocity, the detachment coefficient and the velocity detachment coefficient and plotting these results in the Proctor curve. The first two parameters are measures of the amount of strength the soil has before it starts eroding at all, whereas the latter two are an increment meant to predict how much a soil might erode if the force imposed on the soil is above the erosion threshold. The results consistently showed the detachment coefficients were lowest with the samples compacted at an optimum water content and/or undergone a higher compaction effort (i.e. the soils erode less). On the other hand the critical shear stress/critical erosion velocity was highest at the optimum water content (i.e the soil erodes less), but did not necessarily increase with an increasing compaction effort. This is attributed to the loss of suction. Further, all tested soils showed their optimum erosion characteristics at or close to a degree of saturation of 85 \%. Several other methods were tried, but to no avail unfortunately. Also the rates of erosion were compared between the different types of clay. The clay which is in compliance with the Dutch codes showed the least amount of erosion, the one that did not quite suffice showed some more erosion and the clay that did not comply with the erosion guidelines at all showed the most erosion. However, it was also proved that the clay which did not quite suffice the requirements was (if compacted at optimum water content and at a sufficient energy level) only slightly more erodible than the clay which fully complied with the current Dutch regulations. Finally, the results of the tests carried out in this study were also compared to similar tests performed in the United States and the show consistent similar results. Overall, this study concludes that the use of (currently perceived) unsuitable clay as dike cover can be possible if compacted at or very close to the optimum water content and at a sufficient energy level. Also it can be concluded that compaction at the optimum water content can dramatically reduce the erodibility of a soil or even stop the erosion process. Increasing the compaction effort also reduces erodibility of a soil, although it must be kept in mind that the optimum water content also changes and thus if it is wise to do so. Finally this thesis leaves some suggestions for further research. These mainly concern the effects of cyclic wetting/drying cycles on the erodibility of the soil as well as trying to better understand the effects of the erosion process happening in the field versus the erosion process that is happening in the laboratory.Civil Engineerin
