Low Cost, Good Accuracy - Attitude Determination using Magnetometer and Simple Sun Sensor

A low cost, robust Attitude Determination System with good accuracy for small satellites can be achieved by using a combination of magnetometer and Coarse Sun Sensor. The Coarse Sun Sensor consists of solar cells placed on each of the six outside surfaces of the satellite. The main measurement error of the Coarse Sun Sensor occurs due to the Earth\u27s albedo which can cause an angular deviation of more than 20 degrees. By modeling the albedo and applying state estimation methods for attitude determination the error can be reduced drastically to less than 1 degree, depending on the conditions. In the _rst part of this paper the development of the albedo model is presented. It is used to correct the measurements of the Coarse Sun Sensor as well as to have a realistic simulation of the sensor. The albedo model of the Earth is created using existing re_ectivity data. The variation of the re_ectivity is analyzed statistically and parametric functions are derived to describe the albedo light vector received by a satellite in its orbit. In the second part an Extended Kalman Filter for attitude determination is presented which is using the two vectors provided by the magnetometer and the Coarse Sun Sensor. A model of the total light vector - the sum of sunlight and Earth albedo light - and the magnetic _eld vector taken from the IGRF model are utilized as the measurement model. The paper will present simulation results showing the accuracy of the attitude determination system for various types of orbits

Costate Convergence with Legendre-Lobatto Collocation for Trajectory Optimization

This paper introduces a new method of discretization that collocates both endpoints of the domain and enables the complete convergence of the costate variables associated with the Hamilton boundary-value problem. This is achieved through the inclusion of an \emph{exceptional sample} to the roots of the Legendre-Lobatto polynomial, thus promoting the associated differentiation matrix to be full-rank. We study the location of the new sample such that the differentiation matrix is the most robust to perturbations and we prove that this location is also the choice that mitigates the Runge phenomenon associated with polynomial interpolation. Two benchmark problems are successfully implemented in support of our theoretical findings. The new method is observed to converge exponentially with the number of discretization points used

Sensor fault detection and isolation for electro-mechanical actuators in a reusable launch vehicle TVC system

This paper introduces a model-based Fault Detection and Isolation (FDI) approach for a Reusable Launch Vehicle (RLV) Thrust Vector Control (TVC) system operated by Electro-Mechanical Actuators (EMAs). The focus is on the sensors required for the EMA embedded control system to track the on-board computer control commands. The nullspace FDI method is considered and applied to detect and isolate additive faults affecting the mentioned sensors. A detailed formulation of the problem and the EMA-based TVC system modelling for FDI synthesis is provided, including the mechanical load exerted by the rocket nozzle. The FDI synthesis framework is introduced and the application of the nullspace-based strategy is described, including considerations about isolability of the faults. Vehicle-induced loads can potentially disrupt the fault detection process, therefore they are included in the problem formulation to achieve decoupling from the residual generator output and not incur into false alarms. The generator performance is then assessed in fault-free and faulty scenarios using a high-fidelity TVC physical model, and successively benchmarked at the example of an RLV mission scenario

Infant mortality in mid-19th century Amsterdam:Religion, social class, and space

This study uses a unique historical GIS dataset compiled from birth, death, and population register records for infants born in the city of Amsterdam in 1851 linked to micro‐level spatial data on housing, infrastructure, and health care. Cox's proportional hazards models and the concept of egocentric neighbourhoods were used to analyse the effects of various sociodemographic characteristics, residential environment, water supply, and health‐care variables on infant mortality and stillbirth. The analyses confirm the favourable position of the Jewish population with respect to infant mortality as found in other studies and show the unfavourable position of orthodox Protestant minorities. Infant mortality rate differences are much smaller between social classes than between religions. The exact role of housing and neighbourhood conditions vis‐a‐vis infant mortality is still unclear; however, we ascertained that effects of environmental conditions are more pronounced in later stages of infancy and less important in the early stages of infancy

A triple helix model of medical innovation: supply, demand, and technological capabilities in terms of medical subject headings

We develop a model of innovation that enables us to trace the interplay among three key dimensions of the innovation process: (i) demand of and (ii) supply for innovation, and (iii) technological capabilities available to generate innovation in the forms of products, processes, and services. Building on triple helix research, we use entropy statistics to elaborate an indicator of mutual information among these dimensions that can provide indication of reduction of uncertainty. To do so, we focus on the medical context, where uncertainty poses significant challenges to the governance of innovation. We use the Medical Subject Headings (MeSH) of MEDLINE/PubMed to identify publications classified within the categories “Diseases" (C), "Drugs and Chemicals" (D), "Analytic, Diagnostic, and Therapeutic Techniques and Equipment" (E) and use these as knowledge representations of demand, supply, and technological capabilities, respectively. Three case-studies of medical research areas are used as representative 'entry perspectives' of the medical innovation process. These are: (i) human papilloma virus, (ii) RNA interference, and (iii) magnetic resonance imaging. We find statistically significant periods of synergy among demand, supply, and technological capabilities (C-D-E) that point to three-dimensional interactions as a fundamental perspective for the understanding and governance of the uncertainty associated with medical innovation. Among the pairwise configurations in these contexts, the demand-technological capabilities (C-E) provided the strongest link, followed by the supply-demand (D-C) and the supply-technological capabilities (D-E) channels

Evaluating Forecasting Methods

Ideally, forecasting methods should be evaluated in the situations for which they will be used. Underlying the evaluation procedure is the need to test methods against reasonable alternatives. Evaluation consists of four steps: testing assumptions, testing data and methods, replicating outputs, and assessing outputs. Most principles for testing forecasting methods are based on commonly accepted methodological procedures, such as to prespecify criteria or to obtain a large sample of forecast errors. However, forecasters often violate such principles, even in academic studies. Some principles might be surprising, such as do not use R-square, do not use Mean Square Error, and do not use the within-sample fit of the model to select the most accurate time-series model. A checklist of 32 principles is provided to help in systematically evaluating forecasting methods

Perspectives on Immunoglobulins in Colostrum and Milk

Immunoglobulins form an important component of the immunological activity found in milk and colostrum. They are central to the immunological link that occurs when the mother transfers passive immunity to the offspring. The mechanism of transfer varies among mammalian species. Cattle provide a readily available immune rich colostrum and milk in large quantities, making those secretions important potential sources of immune products that may benefit humans. Immune milk is a term used to describe a range of products of the bovine mammary gland that have been tested against several human diseases. The use of colostrum or milk as a source of immunoglobulins, whether intended for the neonate of the species producing the secretion or for a different species, can be viewed in the context of the types of immunoglobulins in the secretion, the mechanisms by which the immunoglobulins are secreted, and the mechanisms by which the neonate or adult consuming the milk then gains immunological benefit. The stability of immunoglobulins as they undergo processing in the milk, or undergo digestion in the intestine, is an additional consideration for evaluating the value of milk immunoglobulins. This review summarizes the fundamental knowledge of immunoglobulins found in colostrum, milk, and immune milk

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead