Comparison of satellite-derived and in-situ observations of ice and snow surface temperatures over Greenland

The most practical way to get spatially broad and continuous measurements of the surface temperature in the data-sparse cryosphere is by satellite remote sensing. The uncertainties in satellite-derived LSTs must be understood to develop internally-consistent decade-scale land surface temperature (LST) records needed for climate studies. In this work we assess satellite-derived “clear-sky” LST products from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), and LSTs derived from the Enhanced Thematic Mapper Plus (ETM+) over snow and ice on Greenland. When possible, we compare satellite-derived LSTs with in-situ air temperature observations from Greenland Climate Network (GC-Net) automatic weather stations (AWS). We find that MODIS, ASTER and ETM+ provide reliable and consistent LSTs under clear-sky conditions and relatively-flat terrain over snow and ice targets over a range of temperatures from ? 40 to 0 °C. The satellite-derived LSTs agree within a relative RMS uncertainty of ~ 0.5 °C. The good agreement among the LSTs derived from the various satellite instruments is especially notable since different spectral channels and different retrieval algorithms are used to calculate LST from the raw satellite data. The AWS record in-situ data at a “point” while the satellite instruments record data over an area varying in size from: 57 × 57 m (ETM+), 90 × 90 m (ASTER), or to 1 × 1 km (MODIS). Surface topography and other factors contribute to variability of LST within a pixel, thus the AWS measurements may not be representative of the LST of the pixel. Without more information on the local spatial patterns of LST, the AWS LST cannot be considered valid ground truth for the satellite measurements, with RMS uncertainty ~ 2 °C. Despite the relatively large AWS-derived uncertainty, we find LST data are characterized by high accuracy but have uncertain absolute precision.     

A linear-time model-checking algorithm for the alternation-free modal mu-calculus

We develop a model-checking algorithm for a logic that permits propositions to be defined using greatest and least fixed points of mutually recursive systems of equations. This logic is as expressive as the alternation-free fragment of the modal mu-calculus identified by Emerson and Lei, and it may therefore be used to encode a number of temporal logics and behavioral preorders. Our algorithm determines whether a process satisfies a formula in time proportional to the product of the sizes of the process and the formula; this improves on the best known algorithm for similar fixed-point logics.     

Service Engineering: Linking Business and IT

With its strong emphasis on modularization, service-oriented computing radically alters the way business processes are modeled, realized, and maintained. Domain-specific services virtualize complex functions of the underlying business applications so that they can be loosely coupled to form transorganizational processes. This level of abstraction fosters agility and lessens traditional provider dependence. Service-oriented design has long driven the development of the telecommunications infrastructure and applications, especially intelligent network services. Applying the same principles of domain specificity, visualization, loose coupling, and seamless vertical integration to business processes has the potential to lead to a new generation of personalized, secure, and highly available Web services     

Advertising an event

The paper considers a problem of how to minimize advertising costs to sell seats for a particular event, for instance, a sports game, a rock concert or a ballet performance. We take into consideration a word-of-mouth effect, which means that people buying a ticket tell their friends about it, so that advertising is unnecessary to inform those people.The problem is one of optimal control and the number of seats sold and the advertising effort of the organizers are the state and control variables, respectively. We show that, besides being dependent on the cost and revenue parameters, the optimal advertising policy is also affected by the length of the planning period and the relation between the number of seats and the total number of potential attendees.     

Lightweight coarse-grained coordination: a scalable system-level approach

In this paper, our solution to the problem of modelling functionally complex communication systems at the application level, based on lightweight coordination, is extended to seamlessly capture system-level testing as well. This extension could be realized simply by self-application: the bulk of the work for integrating system-level testing into our development environment, the ABC, concerned domain modelling, which can be done using the ABC. Therefore, the extension of the ABC to cover system-level testing was merely an application development on the basis of the ABC, illustrated here in the domain of Computer Telephony Integration. Here the adoption of a coarse-grained approach to test design, which is central to the scalability of the overall testing environment, is the enabling aspect for system-level test automation. Together with our lightweight coordination approach this induces an understandable modelling paradigm of system-wide test cases that is adequate for the needs and requirements of industrial test engineers. In particular, it enables test engineers to graphically design complex test cases that, in addition, can even be automatically checked for their intended purposes via model checking.     

A Nyström-based finite element method on polygonal elements

We consider families of finite elements on polygonal meshes, that are defined implicitly on each mesh cell as solutions of local Poisson problems with polynomial data. Functions in the local space on each mesh cell are evaluated via Nyström discretizations of associated integral equations, allowing for curvilinear polygons and non-polynomial boundary data. Several experiments demonstrate the approximation quality of interpolated functions in these spaces.     

Process development and accurate low‐cost characterization for OLED sealants by using a calcium test

Abstract— A calcium measurement setup was built for testing encapsulation especially for OLED applications. This setup is able to measure both reflective and transmissive cells. For the characterization of sealants, a method to compare them with other sealing products will be described. This includes the use of spacers, a homogeneous surface energy, and the geometry of the sealant line. The effects of different geometries will be discussed. The setup was designed to achieve good accuracy at a very reasonable component cost, which will allow other facilities to replicate this setup. Therefore, the construction plan as well as the list of components can be downloaded from our website (Ref. 3).     

Interactive faceted search and exploration of open social media data on a touchscreen mobile phone

A central challenge of semantic ambient media applications is designing smart user interfaces that are able to dynamically deal with an a-priori unknown number of data categories and data instances received live from different Linked Open Data sources while at the same time being intuitive and easy to use. In the mobile world, this challenge is even more difficult as the mobile devices have limited interaction possibilities and smaller display size. In this paper, we tackle this challenge and present the user-centered, iterative design of a mobile application for faceted search and exploration of a large, multi-dimensional data set of open social media on a touchscreen mobile phone. The application is called Mobile Facets and provides live retrieval and interactive search and exploration of resources like places, persons, organizations, and events originating from different, integrated social media sources like DBpedia, Eventful, Upcoming, Flickr, and GeoNames. In contrast to existing work, we do not know in advance the number and type of data categories and data instances that will be received as the data is queried live from the sources. While developing Mobile Facets, we have applied a participatory design with a small group of five users. For the final prototype we have conducted a task-based, formative evaluation with 12 additional subjects to investigate the applicability and usability of our Mobile Facets application.     

A constraint-based variability modeling framework

Constraint-based variability modeling is a flexible, declarative approach to managing solution-space variability. Product variants are defined in a top-down manner by successively restricting the admissible combinations of product artifacts until a specific product variant is determined. In this paper, we illustrate the range of constraint-based variability modeling by discussing two of its extreme flavors: constraint-guarded variability modeling and constraint-driven variability modeling. The former applies model checking to establish the global consistency of product variants which are built by manual specification of variations points, whereas the latter uses synthesis technology to fully automatically generate product variants that satisfy all given constraints. Each flavor is illustrated by means of a concrete case study.     

Aggregation dynamics of particles in a microchannel due to an applied magnetic field

Functionalized magnetic microspheres have promising applications in different microfluidic devices including MEMS-scale biosensors. These particles exhibit magnetic field-induced aggregation, which can be harnessed to achieve several practical tasks in microfluidic devices. For this, the particle aggregation needs to be well characterized. Herein, a numerical simulation and experimental validation of particle-chaining is presented. Simulations show that the particle aggregation time scales linearly with a group parameter. The predicted growth of one- two- and three-particle chains with time shows a similar trend as that found in the experiments. The results of the study could help predicting the performance of magnetic aggregate-based lab-on-a-chip devices.