High area-to-mass ratio hybrid propulsion Earth to Moon transfers

This paper examines the design of transfers that are useful to micro or nano spacecraft with high area-to-mass ratio, propelled by a simple propulsion engine (such as chemical with a specifc impulse ca. 100 to 300 s or arcjet/resistojet), and possessing relatively small solar reflective panels to provide power and a small thrust due to solar radiation pressure. This type of transfer is becoming of greater interest as advances in structures, materials, and small spacecraft design & propulsion are made. Such a hybrid design especially offers possibilities of cheaply exploring the Moon using multiple vehicles. With this small hybrid design, interior transfers in the circular restricted 3-body problem between the pair of primary and secondary masses (e.g. the Earth and Moon) are attempted using solar radiation pressure and multiple small impulses. The source of the outside solar radiation pressure is modeled using an external source rotating about – and in the plane of – the co-rotating set of primary and secondary masses. Starting from a GTO about the primary mass a basic optimization method of sequences of manoeuvres is used to achieve the transfer, where the segments are patched together using ideally small maneuvers. The spacecraft coasting arc is controlled by a number of locally optimal control laws to optimize performance while minimizing computational cost. The spacecraft hops onto a stable invariant manifold leading to the system’s Lagrange L1 point after successive small maneuvers and coasting arcs. Following connection with a manifold and subsequent arrival at a periodic orbit at L1, temporary or permanent capture around the Moon can be performed using the remaining resources at hand

Domain-oriented architecture design for production control software

this paper, we present domain-oriented architectural design heuristics for production control software. Our approach is based upon the following premisses. First, software design, like all other forms of design, consists of the reduction of uncertainty about a final product by making design decisions. These decisions should as much as possible be based upon information that is certain, either because they represent laws of nature or because they represent previously made design decisions. An import class of information concerns the domain of the software. The domain of control software is the part of the world monitored and controlled by the software; it is the larger system into which the software is embedded. The software engineer should exploit system-level domain knowledge in order to make software design decisions. Second, in the case of production control software, using system-level knowledge is not only justified, it is also imposed on the software engineer by the necessity to cooperate with hardware engineers. These represent their designs by means of Process and Instrumentation Diagrams (PIDs) and Input-Output (IO) lists. They do not want to spend time, nor do they see the need, to duplicate the information represented by these diagrams by means of diagrams from software engineering methods. Such a duplication would be an occasion to introduce errors of omission (information lost during the translation process) or commission (misinterpretation, misguided but invisible design decisions made during the translation) anyway. We think it is up to the software engineer to adapt his or her notations to those of the system engineers he or she must work with. Third, work in patterns and software architectures started from the programminglanguage level and is now moving..

A monoclonal antibody recognizing very late activation antigen-4 inhibits eosinophil accumulation in vivo.

Using an in vivo test system, the role of the β1 integrin very late activation antigen-4 (VLA-4) in eosinophil accumulation in allergic and nonallergic inflammatory reactions was investigated. Eosinophil infiltration and edema formation were measured as the local accumulation of intravenously injected 111In-labeled eosinophils and 125I-human serum albumin. The inflammatory reactions investigated were a passive cutaneous anaphylaxis (PCA) reaction and responses elicited by intradermal soluble inflammatory mediators (platelet-activating factor, leukotriene B4, C5a des Arg), arachidonic acid, and zymosan particles. The in vitro pretreatment of 111In-eosinophils with the anti-VLA-4 monoclonal antibody (mAb) HP1/2, which crossreacts with guinea pig eosinophils, suppressed eosinophil accumulation in all the inflammatory reactions investigated. Eosinophil accumulation was inhibited to the same extent when mAb HP1/2 was administered intravenously. It is interesting that HP1/2 had no effect on stimulated edema formation. These results suggest a role for VLA-4 in eosinophil accumulation in vivo and indicate a dissociation between the inflammatory events of eosinophil accumulation and edema formation

Searching for interacting QTL in related populations of an outbreeding species

Many important crop species are outbreeding. In outbreeding species the search for genes affecting traits is complicated by the fact that in a single cross up to four alleles may be present at each locus. This paper is concerned with the search for interacting quantitative trait loci (QTL) in populations which have been obtained by crossing a number of parents. It will be assumed that the parents are unrelated, but the methods can be extended easily to allow a pedigree structure. The approach has two goals: (1) finding QTL that are interacting with other loci and also loci which behave additively; (2) finding parents which segregate at two or more interacting QTL. Large populations obtained by crossing these parents can be used to study interactions in detail. QTL analysis is carried out by means of regression on predictions of QTL genotypes

The influence of conceptual user models on the creation and interpretation of diagrams representing reactive systems

In system design, many diagrams of many different types are used. Diagrams communicate design aspects between members of the development team, and between these experts and the non-expert customers and future users. Mastering the creation of diagrams is often a challenging task, judging by particular errors persistently found in diagrams created by undergraduate computer science students. We assume a possible misalignment between human perception and cognition on the one hand and the diagrams’ structure and syntax on the other. This article presents the results of an investigation of such a misalignment. We focus on the deployment of so-called 'conceptual user models' (mental models, created by users in their mind) at the creation of diagrams. We propose a taxonomy for mental mappings, used for categorization of representations. We describe an experiment where naive and novice subjects created one or several diagrams of a familiar task. We use our taxonomy for analysing these diagrams, both for the represented task structure and the symbols used. The results indeed show a mismatch between mental models and currently used diagram techniques

Wahrhaftiger Glaube

Plädoyer für einen kritischen Agnostizismus.\ud In dem philosophischen Essay wird versucht, von erkenntnistheoretischen Überlegungen (radikale Konstruktivisten, Popper, Descartes, Putnam u. a.) ausgehend einen Bogen zu ethischen und gesellschaftspolitischen Positionen zu spannen

Collective Intentionality and Individual Action

People often do things together and form groups in order to get things done that they cannot do alone. In short they form a collectivity of some kind or a group, for short. But if we consider a group on the one hand and the persons that constitute the group on the other hand, how does it happen that these persons work together and finish a common task with a common goal? In the philosophy of action this problem is often solved by saying that there is a kind of collective intention that the group members have in mind and that guides their actions. Does such a collective intention really exist? In this article I’ll show that the answer is “no”. In order to substantiate my view I’ll discuss the approaches of Bratman, Gilbert and Searle on collective intention. I’ll put forward four kinds of criticism that undermine the idea of collective intention. They apply mainly to Bratman and Gilbert. First, it is basically difficult to mark off smaller groups from bigger unities. Second, most groups change in membership composition over time. Third, as a rule, on the one hand groups are internally structured and on the other hand they belong to a larger structure. It makes that generally it cannot be a collective intention that moves the actions of the members of a group. Fourth, conversely, most individual actions cannot be performed without the existence of a wider context of agents who support these actions and make them possible. My critique on Searle mainly involves that in his approach his idea of collective intention is superfluous and that he is not radical enough in his idea that collective action is based on coordinated individual intentions and actions. However, it is a good starting point for showing how collective action actually functions, especially when combined with Giddens’s structuration theory. Every agent in a group executes his or her own individual intentions, relying on what the group offers to this agent and asks from him or her. In this way individual actions of the members of a group are coordinated and it makes that the group can function and that its goals can be performed. And in this way the group is produced and reproduced by fitting individual actions together. An individual agent who belongs to a group only needs to know what s/he wants and what s/he has to do in the group, even if s/he has no knowledge of the intentions and commitments of the other members. Then he or she can do things together with others in a group without supposing that there is something like a collective intention