Comparison of four different programs for the analysis of hemispherical photographs using parameters of canopy structure and solar radiation transmittance

There have been many studies involving the use of hemispherical photographs to indirectly estimate canopy structures and forest light environments. A variety of commercial and free software packages are available for the analysis of hemispherical photographs. The costs of investment might represent an advantage of the free programmes over the commercial, but as yet little has been documented about the differences in their outputs and in the technical applications from a user (ecologist and forester) perspective. The objective of the study was to compare the canopy structure variables (canopy openness and effective plant area index) and solar radiation transmission estimates (direct, diffuse and global solar radiation transmittances) from digital hemispherical photographs taken under two forest canopy conditions (gap and closed canopy) in three different broadleaf forest regions (Chile, Germany, Venezuela) and calculated using four different programmes. The hemispherical photographs were analysed using one commercial (HemiView) and three free programmes (Gap Light Analyzer, hemIMAGE and Winphot). The results obtained revealed that all of the programmes computed similar estimates of both canopy structures and below-canopy solar radiation. Only the results relating to the effective plant area index with an ellipsoidal leaf angle distribution made with HemiView and Winphot deviated significantly. Other user aspects are also discussed, such as costs, image formats, computer system requirements, etc.In vielen Studien werden Hemisphärenphotos genutzt um indirekt die Kronenstruktur und die Belichtungsverhältnisse zu schätzen. Verschiedene kommerzielle und kostenfreie Softwarepakete sind zu Analyse von Hemisphärenphotos verfügbar. Es gibt bisher keine umfassende Vergleichsstudie zu Ergebnissen oder technischer Handhabung aus Sicht der Nutzer dieser Programme (Ökologen und Forstwissenschaftler). Das Ziel dieser Studie war der Vergleich der Schätzungen von Kronenstrukturvariablen (Kronenöffnung und effektiver Pflanzenflächenindex) Solartransmission (direkte, diffuse und Global-Strahlung) aus digitalen Hemisphärenphotos berechnet mit vier verschiedenen Programmen (kostenpflichtig: Hemi- View und frei: Gap Light Analyzer, hemIMAGE and Winphot). Die verwendeten Photos stammen aus drei verschiedenen Laubwaldregionen (Chile, Deutschland und Venezuela) und repräsentieren jeweils Verhältnisse unter geschlossenem Kronendach und in Lücken. Die ermittelten Schätzungen für die verschiedenen Strukturvariablen und Einstrahlungsverhältnisse zeigten eine sehr hohe Übereinstimmung. Einzig der effektive Pflanzenflächenindex basierend auf ellipsoider Blattwinkelverteilung unterschied sich signifikant zwischen den Programmen. Weitere für Nutzer interessante Aspekte wie Kosten, Bildformate, Systemvoraussetzungen und mehr wurden verglichen und diskutiert

Parametrisierte Algorithmen für Ganzzahlige Lineare Programme und deren Anwendungen für Zuweisungsprobleme

This thesis is concerned with solving NP-hard problems. We consider two prominent strategies of coping with such computationally hard questions efficiently. The first approach aims to design approximation algorithms, that is, we are content to find good, but non-optimal solutions in polynomial time. The second strategy is called Fixed-Parameter Tractability (FPT) and considers parameters of the instance to capture the hardness of the problem and by that, obtain efficient algorithms with respect to the remaining input. This thesis employs both strategies jointly to develop efficient approximation and exact algorithms using parameterization and modeling the problem as structured integer linear programs (ILPs), which can be solved in FPT. In the first part of this work, we concentrate on these well-structured ILPs. On the one hand, we develop an efficient algorithm for block-structured integer linear programs called n-fold ILPs. On the other hand, we investigate the similarly block-structured 2-stage stochastic ILPs and prove conditional lower bounds regarding the running time of any algorithm solving them that match the best known upper bounds. We also prove the tightness of certain structural parameters called sensitivity and proximity for ILPs which arise from combinatorial questions such as allocation problems. The second part utilizes n-fold ILPs and structural properties to add to and improve upon known results for Scheduling and Bin Packing problems. We design exact FPT algorithms for the Scheduling With Clique Incompatibilities, Bin Packing, and Multiple Knapsack problems. Further, we provide constant-factor approximation algorithms and polynomial time approximation schemes (PTAS) for the Class Constraint Scheduling problems. Broadening our scope, we also investigate this problem and the closely related Cardinality Constraint Scheduling problem in the online setting and derive lower bounds for the approximation ratios as well as a PTAS for them. Altogether, this thesis contributes to the knowledge about structured ILPs, proves their limits and reaffirms their usefulness for a plethora of allocation problems. In doing so, various new and improved algorithms with respect to the running time or approximation quality emerge

Spielen in virtuellen Welten: Übertragung von Inhalten und Handlungsmustern aus Bildschirmspielen

Bildschirmspiele wurden seit jeher als problematischer Aspekt des jugendlichen Umgangs mit dem Computer angesehen. Durch die fortschreitende Entwicklung werden sie auch spielerisch umfangreicher, komplexer und kommen der Realität immer näher. Der Artikel entwirft ein Schema zur Kategorisierung von Bildschirmspielen aus dem sich erschliessen lässt, wo die Schwerpunkte der Übertragung von Inhalten aus der virtuellen Welt der Bildschirmspiele in die Alltagswelt liegen. Dabei werden nicht nur die kritischen Seiten dieser Thematik besprochen, wie die Übernahme aggressiver Verhaltensweisen und emotionale Abstumpfung. Es werden auch die pädagogischen Möglichkeiten von Bildschirmspielen als Lernmedium aufgezeigt, durch den Aufbau einer Erlebniswelt am Bildschirm

Entscheidungstheoretische Grundlagen der Stochastischen Optimierung

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Testate amoebae (Protozoa: Testacea) as bioindicators in the Late Quaternary deposits of the Bykovsky Peninsula, Laptev Sea, Russia

Testate amoebae (Protozoa: Testacea) were studied in the Late Quaternary permafrost depositsin the Siberian Arctic (Bykovsky Peninsula of the Laptev Sea coast, 71º40'-71º80'N and 129º-129º30'E). The studied Testacea associations reflect specific environmental conditions in paleocryosols,which were controlled by the local micro-relief as well as regional climate conditions. Totally, 86species, varieties, and forms of testate amoebae were found in 38 Pleistocene and Holocenesamples. The rhizopods indicate that soil conditions at ca 53,000 14C yr BP were probably rathersimilar to the modern cold and wet arctic tundra environment. More moisture and warmer soilconditions were relatively favourable for rhizopods ca 45,300-43,000 14C yr BP, but significantlydrier at about 42,000 14C yr BP. Drier and colder environmental conditions were also presentabout 39,300-35,000 14C yr BP. The Late Pleistocene samples, radiocarbon dated to 33,000-12,000 yr BP, are characterized by a low species diversity and density. This period may have beenextremely cold and dry, which is also supported by the polymorphism of some species.Hydrophilic Difflugia species (mostly obligate hydrobiotes) are broadly represented in theHolocene samples. The species composition and density of rhizopods in the majority of Holocenesamples suggest wet and relatively warm conditions. Changes in rhizopod assemblages during thelast 53,000 years were not very dramatic, mostly consisting of rare species and changes in thedominant species complexes during the Pleistocene and Holocene. However, these changes weremore drastic during the Pleistocene. They, probably, were at least partly responsible for thedisappearance of some rare testacean species such as Argynnia sp

Do neural networks revolutionize our prediction abilities?

Diese Arbeit plädiert für eine rationale Behandlung von Patientendaten und untersucht dazu die Analyse der Daten mit Hilfe neuronale Netze etwas näher. Erfolgreiche Beispielanwendungen zeigen, daß die menschlichen Diagnosefähigkeiten deutlich schlechter sind als neuronale Diagnosesysteme. Für das Beispiel der neueren Architektur mit RBF-Netzen wird die Funktionalität näher erläutert und gezeigt, wie menschliche und neuronale Expertise miteinander gekoppelt werden kann. Der Ausblick deutet Anwendungen und Praxisproblematik derartiger Systeme an.Do Neural Networks Revolutionize our Prediction Abilities? This paper claims for a rational treatment of patient data. It investigates data analysis with the aid of artificial neural networks. Successful example applications show that human diagnosis abilities are significantly worse than those of neural diagnosis systems. For the example of the newer architecture using RBF nets the basic functionality is explained and it is shown how human and neural expertise can be coupled. Finally, the applications and problems of this kind of systems are discussed