Dynamical Models of Extreme Rolling of Vessels in Head Waves

Rolling of a ship is a swinging motion around its length axis. In particular vessels transporting containers may show large amplitude roll when sailing in seas with large head waves. The dynamics of the ship is such that rolling interacts with heave being the motion of the mass point of the ship in vertical direction. Due to the shape of the hull of the vessel its heave is influenced considerably by the phase of the wave as it passes the ship. The interaction of heave and roll can be modeled by a mass-spring-pendulum system. The effect of waves is then included in the system by a periodic forcing term. In first instance the damping of the spring can be taken infinitely large making the system a pendulum with an in vertical direction periodically moving suspension. For a small angular deflection the roll motion is then described by the Mathieu equation containing a periodic forcing. If the period of the solution of the equation without forcing is about twice the period of the forcing then the oscillation gets unstable and the amplitude starts to grow. After describing this model we turn to situation that the ship is not anymore statically fixed at the fluctuating water level. It may move up and down showing a motion modeled by a damped spring. One step further we also allow for pitch, a swinging motion around a horizontal axis perpendicular to the ship. It is recommended to investigate the way waves may directly drive this mode and to determine the amount of energy that flows along this path towards the roll mode. Since at sea waves are a superposition of waves with different wavelengths, we also pay attention to the properties of such a type of forcing containing stochastic elements. It is recommended that as a measure for the occurrence of large deflections of the roll angle one should take the expected time for which a given large deflection may occur instead of the mean amplitude of the deflection

Rubidazone vs adriamycin: an evaluation of their differential toxicity in the spleen colony assay system.

Rubidazone, the new semi-synthetic benzol hydrazone hydrochloride derivative of dauorubicin, has proved on a molecular weight basis to be less toxic than adriamycin and similar to daunorubicin in cardiac toxicity studies in the hamster as well as in other in vivo and in vitro test systems. It has proven effectiveness against several animal tumours and human acute leukaemias. We have compared the inhibitory effect of rubidazone to that of adriamycin on P388 leukaemia and normal bone marrow colony-forming units (CFU) using the spleen colony assay system in male DBA2 mice. The efficacy ratios (i.e., the ratio of the slopes of the normal bone marrow CFU to leukaemic CFU dose-survival curves) in the spleen colony assay system for rubidazone and adriamycin were 7-8 and 7-5 respectively. This near identity of efficacy ratios fro rubidazone and adriamycin correlated with the results of median survival time studies in the leukaemic mice. Their dose-median survival time curves were almost parallel, having nearly identical slopes. Rubidazone's equal therapeutic index as compared to adriamycin in the spleen colony assay system together with its known decreased toxicity to cardiac muscle cells makes it an extremely promising new anthracycline derivative to study in comparison to adriamycin in human malignancies

Individual stochasticity in the life history strategies of animals and plants

The life histories of organisms are expressed as rates of development, reproduction, andsurvival. However, individuals may experience differential outcomes for the same set ofrates. Such individual stochasticity generates variance around familiar mean measures oflife history traits, such as life expectancy and the reproductive number R0. By writing lifecycles as Markov chains, we calculate variance and other indices of variability for longevity,lifetime reproductive output (LRO), age at offspring production, and age at maturity for 83animal and 332 plant populations from the COMADRE and COMPADRE matrix databases. Wefind that the magnitude within and variability between populations in variance indices inLRO, especially, are surprisingly high. We furthermore use principal components analysis toassess how the inclusion of variance indices of different demographic outcomes affects lifehistory constraints. We find that these indices, to a similar or greater degree than the mean,explain the variation in life history strategies among plants and animals

Efficient approximations of the multi-sensor labelled multi-Bernoulli filter

In this paper, we propose two efficient, approximate formulations of the multi-sensor labelled multi-Bernoulli (LMB) filter, which both allow the sensors' measurement updates to be computed in parallel. Our first filter is based on the direct mathematical manipulation of the multi-sensor, multi-object Bayes filter's posterior distribution. Unfortunately, it requires the division of probability distributions and its extension beyond linear Gaussian applications is not obvious. Our second filter is based on covariance intersection and it approximates the multi-sensor, multi-object Bayes filter's posterior distribution using the geometric mean of each sensor's measurement-updated distribution. This filter can be used for distributed fusion under non-linear conditions; however, it is not as accurate as our first filter. In both cases, we approximate the LMB filter's measurement update using an existing loopy belief propagation algorithm, which we adapt to account for object existence. Both filters have a constant complexity in the number of sensors, and linear complexity in both number of measurements and objects. This is an improvement on an iterated-corrector LMB filter, which has linear complexity in the number of sensors. We evaluate both filters' performances on simulated data and the results indicate that the filters are accurate

Incorporating stakeholder perspectives into model-based scenarios: Exploring the futures of the Dutch gas sector

Several model-based, analytical approaches have been developed recently to deal with the deep uncertainty present in situations for which futures studies are conducted. These approaches focus on covering a wide variety of scenarios and searching for robust strategies. However, they generally do not take the multiplicity of stakeholder perspectives into account in analytic terms, which could bring in diverse opinions and views, not only on possible futures but also on values and interests. In this study, we present an approach to incorporate stakeholder perspectives into model-based scenarios for exploring the future dynamics of the Dutch gas sector. The results demonstrate that the scenario space can be demarcated according to the perspectives. This allows for a systematic comparison of the perspectives and provides a basis for identification of robust strategies. Also, the analysis shows that incompatible elements between the model and perspectives, or within perspectives can be identified. This provides insights about the problem complexity and potential barriers to the futures envisioned by the perspectives. Future research can strengthen this approach by involving stakeholders in modelling and in the model-based representation of the perspective narratives to enhance learning and credibility, and can extend the analysis to identify (socially) robust policies