A methodology for the integration of stiff chemical kinetics on GPUs

Numerical schemes for reacting flows typically invoke the method of fractional steps in order to isolate the chemical kinetics model from diffusion/convection phenomena. Here, the reaction fractional step requires the solution of a collection of independent ODE systems which may be severely stiff. Recently, researchers have begun to explore the highly parallel structure of graphics processing units (GPUs) in order to accelerate integration schemes for these ODE systems. However, much of the existing work concentrates on explicit integration algorithms which may fall short in the presence of stiffness. In this light, we have carefully reimplemented in OpenCL C the Fortran 77 program of the 3-stage/5th order implicit Runge–Kutta method Radau5 by Hairer and Wanner (1991) and tested it extensively in the context of a transient equilibrium scheme for the flamelet model. Our implementation can easily be integrated with any existing reactive flow software in order to solve the reaction fractional step on an OpenCL-enabled GPU. Moreover, it is suited for any Chemkin-format reaction mechanism with ≲200≲200 species without incurring a loss in occupancy and it reaches its limit speedup (which is largely independent of the mechanism size) at a small problem size (≈500 ODE systems). In view of memory constraints, we include an optimized scheme for splitting the ODE systems across several kernel invocations and overlapping the kernel execution with data transfers. An in-depth evaluation is based upon runtime measurements of the CPU and the GPU implementation on a user level and a high-end CPU/GPU for an increasing number of ODE systems, reduced and detailed reaction mechanisms and a range of time step sizes

Reviewing A&Is and Aggregators in a Large Research Library Collection

To facilitate discovery, libraries have traditionally subscribed to many specialized subject abstracting and indexing databases (A&Is), as well as aggregator packages with A&I function and full-text content. Library collection staff must continue to demonstrate effective and responsible stewardship of the library’s acquisitions budget by using evidence to inform collection development decisions. Using COUNTER statistics, title lists, the Gold Rush overlap review tool, and feedback from colleagues, review teams at University of Toronto Libraries analyzed a select list of A&Is and aggregators to confirm if subscription renewal is necessary. Involving staff from various departments resulted in a deeper understanding of database use and assisted in deciding not to renew. The review methodology will be used in future reviews, and analysis tools will be shared for future collection development decisions. Discontinuing subscriptions allows us to redirect funds for new resources

The role of actors in the policy design process: introducing design coalitions to explain policy output

Despite a renaissance of policy design thinking in public policy literature and a renewed interest in agency in the policy process literature, agency in the policy design process has, so far, not received systematic attention. Understanding the agency at play when designing policy, however, is crucial for better comprehension of policy design choices and varia- tion in policy design across cases. Here, we build on the hierarchical structure of design elements that constitute each policy and analyse how actors position themselves during a policy design process in relation to individual design elements. Our aim is to establish dif- ferent actors’ roles in shaping the policy output in an inductive, single-case study using the empirical case of the Swiss renewable energy feed-in tariff. Notably, we find agency in the form of coalitions which emerge around particular design elements. Based on our repre- sentative analysis, we derive the generalisable concept of design coalitions that we define as relational structures of actors who gather around and advocate for specific policy design elements during the policy design process. Policy design coalitions are dynamic through- out the design process and strategic and constitute the determinants in translating policy problems into final policy designs during policy designing. Our approach allows us to shed light on the role of agency in the policy design process in general

Comparative Climate Politics : Patterns of Climate Policy Performance in Western Democracies

Although the comparative study of environmental politics and policy dates back well into the 1970s, it has never featured prominently within comparative politics generally. Against a background of mounting environmental pressures, most notably climate change, this low profile seems puzzling. As Steinberg and VanDeveer (2012) point out, building bridges between comparative environmental politics and the broader field of comparative politics is an important task for current research. This dissertation seeks to contribute to this linkage by revisiting the issue of cross-national environmental performance, focusing on climate performance. By addressing both the outcome and the output dimension of national climate performance, this thesis engages with two central issues of comparative politics: (i) the effect of political institutions on performance and (ii) policy change. Thus, it also contributes to broader research into the capacity of political systems to deal with complex longterm political problems. This dissertation attempts to make six major conceptual, methodological, and analytical contributions: 1) the thesis presents a conceptualization of general environmental performance based on the “planetary boundaries” approach; 2) it provides a theoretical framework for policy output and develops a measurement for its assessment; 3) it argues that actor constellations of specific environmental problems need to be considered to strengthen theoretical arguments about the effects of political institutions; 4) it argues that entire policy portfolios rather than (a set of) individual policy instruments need to be considered for assessing policy change; 5) it analyses the effect of political institutions on climate performance; 6) and it analyses policy change in climate mitigation and the role of policy innovations in altering policy portfolios

Curve shortening and the three geodesics theorem

The three geodesics theorem of Lusternik and Schnirelmann asserts that for every Riemannian metric on the 2-sphere, there exist at least three embedded closed geodesics. In the process of determining the geodesics as critical points of the energy or length functional, a suitable method of curve shortening is needed. It has been suggested to use the so-called curve shortening flow as it continuously deforms smooth embedded curves while naturally preserving their embeddedness. In the 1980s, the investigation of the curve shortening flow began and a proof of the Lusternik-Schnirelmann theorem using the flow was sketched. We build upon these results. After introducing the curve shortening flow, we prove the well-known result that the geodesic curvature of a smooth embedded closed curve on a smooth closed two-dimensional Riemannian manifold decreases smoothly to zero, provided the curve evolves forever under the flow. From this, we prove subconvergence to an embedded closed geodesic, using mainly local arguments. After introducing, in the form of Lusternik-Schnirelmann theory, the topological machinery employed in the process of determining critical points of certain functions, we turn to the three geodesics theorem which we prove under a few assumptions. For the round metric on the 2-sphere, we deformation retract a suitable space of unparametrized curves onto a simpler space of which we determine the homology groups relative to a subspace which deformation retracts onto the subspace of point curves. As this yields three subordinate homology classes, proving the validity of Lusternik-Schnirelmann theory for the curve shortening flow and the length functional on our space of curves completes the proof

Monitoring of the accelerator beam distributions for internal target facilities

We describe a direct method for monitoring the geometrical dimensions of a synchrotron beam at the target position for internal target installations. The method allows for the observation of the proton beam size as well as the position of the beam relative to the target. As a first demonstration of the technique, we present results obtained by means of the COSY-11 detection system installed at the cooler synchrotron COSY. The influence of the stochastic cooling on the COSY proton beam dimensions is also investigated.Comment: 7 pages, 8 figures, Submitted to Nucl. Inst. & Meth.

The measurement of the pp->K+ n Sigma+ reaction near threshold

It is shown that a recent extraction of the total cross section for pp->K+ n Sigma+ from inclusive K+ production data is in conflict with experimental data on the exclusive pp->K+ p Lambda reaction. The result may be interpreted as an upper bound which is not inconsistent with the much lower values that already exist in the literature.Comment: Submitted to PL

Enhancing the effect of repetitive I-wave paired-pulse TMS (iTMS) by adjusting for the individual I-wave periodicity

<p>Abstract</p> <p>Background</p> <p>Repeated application of paired-pulse TMS over the primary motor cortex (M1) in human subjects with an inter-pulse interval (IPI) of 1.5 ms (iTMS_{1.5 ms}) has been shown to significantly increase paired-pulse MEP (ppMEP) amplitudes during the stimulation period and increased single-pulse MEP amplitudes for up to 10 minutes after termination of iTMS.</p> <p>Results</p> <p>Here we show in a cross-over design that a modified version of the iTMS_{1.5 ms}protocol with an I-wave periodicity adjusted to the individual I1-peak wave latency (iTMS_adj) resulted in a stronger effect on ppMEPs relative to iTMS_{1.5 ms}.</p> <p>Conclusions</p> <p>Based on these findings, our results indicate that the efficiency of iTMS strongly depends on the individual choice of the IPI and that parameter optimization of the conventional iTMS_{1.5 ms}protocol might improve the outcome of this novel non-invasive brain stimulation technique.</p