Compaction and Other Sources of Error in Obtaining Sea-Level Data: Some Results and Consequences

Diese Arbeit beschreibt Beobachtungen und Ergebnisse zu Radiocarbon-Altersbestimmungen, die mit der Auswirkung verschiedener Fehlerquellen auf die Zeit/Tiefenposition von Datenpunkten zusammenhängen. Es wird (u. a.) gezeigt, daß die Vergleichbarkeit setzungsfreier Zeit/Tiefen-Datenpunkte von der Unterfläche von Torflagen, die das Einsetzen von Moorwachstum in verschiedenen Höhenlagen anzeigen, durch Setzung des beprobten Torfes, durch Wurzelkontamination und durch Kontamination mit älterem Material negativ beeinflußt werden kann.researc

Time-Limit Assessment of some Holocene Transgressive and Regressive Periods in the Northern Netherlands

Die Arbeit diskutiert die Bedeutung von sechs Zeitgrenzen der gegenwärtigen Chronologie holozäner transgressiver und regressiver Perioden in den nördlichen Niederlanden. Der Schluß wird gezogen, daß (1) die Zeitgrenzen für die regressive Periode Holland III noch festgelegt werden muß; (2) die Zeitgrenze 3525 v. h. wohlbegründet ist, jedoch nicht den Beginn einer Subphase des Calais IVB, sondern den Beginn der transgressiven Periode des Dunkerque 0 markiert; (3) die Zeitgrenze 3325 v. h. ein Kunstprodukt ist; (4) die Zeitgrenze 3000 v. h. einem transgressivem Moorwachstum zuzuordnen ist, das in der ersten Hälfte des transgressiven Intervalls Dunkerque IA liegt und nicht am Beginn einer regressiven Phase, und daß (5) die Zeitgrenze 2650 v. h. wahrscheinlich eher den Beginn des transgressiven Intervalls Dunkerque IB markiert als das Ende der Periode Dunkerque IA.researc

Coupling instrumental and geological records of sea-level change : evidence from southern New England of an increase in the rate of sea-level rise in the late 19th century

Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 31 (2004): L05203, doi:10.1029/2003GL018933.We construct a high-resolution relative sea-level record for the past 700 years by dating basal salt-marsh peat samples above a glacial erratic in an eastern Connecticut salt marsh, to test whether or not the apparent recent acceleration in the rate of sea-level rise (SLR) is coeval with climate warming. The data reveal an average SLR rate of 1.0 ± 0.2 mm/year from about 1300 to 1850 A.D. Coupling of the regional tide-gauge data (1856 to present) with this marsh-based record indicates that the nearly three-fold increase in the regional rate of SLR to modern levels likely occurred in the later half of the 19th century. Thus the timing of the observed SLR rate increase is coincident with the onset of climate warming, indicating a possible link between historic SLR increases and recent temperature increases.A Research Initiative Grant from the NOSAMS facility at WHOI funded the C-14 analysis. The Postdoctoral Scholar Program at WHOI (with funding provided by the U.S.G.S.), The John E. and Anne W. Sawyer Endowed Fund, and The J. Lamar Worzel Assistant Scientist Fund provided support to J. Donnelly

Evaluating a formal KBS specification language

In recent years, the knowledge engineering community has begun to explore formal specification languages as a tool in the development of knowledge-based systems. These formal knowledge modelling languages have a number of advantages over informal languages, such as their precise meaning and the possibility to derive properties through formal proofs. However, these formal languages also suffer from problems which limit their practical usefulness: they are often not expressive enough to deal with real world applications, formal models are complex and hard to read, and constructing a formal model is a difficult, error prone and expensive process. The goal of the study presented in this paper is to investigate the usability of one such formal {KBS} modelling language, called (ML)^2. (ML)^2 is strongly based on the structure of the knowledge-models used in the KADS KBS development method. We first designed a set of evaluation criteria. We then applied (ML)^2 in two case-studies and scored the language on our evaluation criteria. (ML)^2 scored well on most of our criteria. This leads us to conjecture that the close correspondence between the informal KADS models and the formal (ML)^2 models avoids some of the problems that traditionally plague formal specification languages

Climate related sea-level variations over the past two millennia

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of National Academy of Sciences for personal use, not for redistribution. The definitive version was published in Proceedings of the National Academy of Sciences of the United States of America 108 (2011): 11017-11022, doi:10.1073/pnas.1015619108.We present new sea-level reconstructions for the past 2100 years based on salt-marsh sedimentary sequences from the US Atlantic coast. The data from North Carolina reveal four phases of persistent sea-level change after correction for glacial isostatic adjustment. Sea level was stable from at least BC 100 until AD 950. It then increased for 400 years at a rate of 0.6 mm/yr, followed by a further period of stable, or slightly falling, sea level that persisted until the late 19th century. Since then, sea level has risen at an average rate of 2.1 mm/yr, representing the steepest, century-scale increase of the past two millennia. This rate was initiated between AD 1865 and 1892. Using an extended semi-empirical modeling approach, we show that these sea-level changes are consistent with global temperature for at least the past millennium.Research was supported by NSF grants (EAR-0951686) to BPH and JPD. ACK thanks a NOSAMS internship, UPenn paleontology stipend and grants from GSA and NAMS. North Carolina sea-level research was funded by NOAA (NA05NOS4781182), USGS (02ERAG0044) and NSF (EAR-0717364) grants to BPH with S. Culver and R. Corbett (East Carolina University). JPD (EAR-0309129) and MEM (ATM-0542356) acknowledge NSF support. MV acknowledges Academy of Finland Project 123113 and COST Action ES0701

Performance analysis of a palletizing system

When designing the layout of the material handling system for a warehouse there is a need for the analysis of overall system performance. Since warehouses are typically very large and complex systems it is infeasible to build a simulation model for the entire system. Our approach is to divide the system into subsystems that are small enough to be captured in simulation models. These models can then later be assembled to acquire a simulation model of the entire system. In this case study we assess the feasibility of this approach by creating a simulation model of a part of a warehouse and verify whether it can be used to embed it in a larger simulation model. The subsystem we use for our case study is a container unloading and automatic palletizing system. This system is chosen because it has already been studied extensively using another simulation tool. We also do a performance analysis of this system in order to come to an optimal layout for this subsystem as well as to reproduce the results of the earlier study for validation. For our performance analysis we created a chi model of the unloading and palletizing area. The process algebra chi has been extensively used for modeling and simulation of real-time manufacturing systems. Our case study is also used as a means to assess the suitability of chi for modeling and simulation in a logistics environment. Our experiments resulted in roughly the same outcomes as the earlier study. It turns out that for the required throughput the layout chosen in that study is optimal. We also concluded that chi is perfectly suitable for modeling logistic systems. Considering the extensive time it takes to run simulations of a rather small part of a warehouse using chi, we conclude that it is infeasible to perform simulations of entire warehousing systems by integrating the simulation models of all subsystems into one simulation model. To overcome this problem, aggregate modeling can be used