Robust Control Design for Large Space Structures

The control design problem for the class of future spacecraft referred to as large space structures (LSS) is by now well known. The issue is the reduced order control of a very high order, lightly damped system with uncertain system parameters, particularly in the high frequency modes. A design methodology which incorporates robustness considerations as part of the design process is presented. Combining pertinent results from multivariable systems theory and optimal control and estimation, LQG eigenstructure assignment and LQG frequency shaping, were used to improve singular value robustness measures in the presence of control and observation spillover

Transforming Normal Programs by Replacement

The replacement transformation operation, already defined in [28], is studied wrt normal programs. We give applicability conditions able to ensure the correctness of the operation wrt Fitting's and Kunen's semantics. We show how replacement can mimic other transformation operations such as thinning, fattening and folding, thus producing applicability conditions for them too. Furthermore we characterize a transformation sequence for which the preservation of Fitting's and Kunen's semantics is ensured

Crew emergency return vehicle autoland feasibility study

The crew emergency return vehicle (CERV) autoland feasibility study focused on determining the controllability of the NASA Langley high lift over drag CERV for performing an automatic landing at a prescribed runway. An autoland system was developed using integral linear quadratic Gaussian (LQG) design techniques. The design was verified using a nonlinear 6 DOF simulation. Simulation results demonstrate that the CERV configuration is a very flyable configuration for performing an autoland mission. Adequate stability and control was demonstrated for wind turbulence and wind shear. Control surface actuator requirements were developed

“Building Louder”: An Assessment of Habitat for Humanity, International’s Government Relations and Advocacy Efforts

This paper examines the role that advocacy and lobbying has in nonprofit organizations and, specifically, makes an assessment of how well Habitat for Humanity, International is utilizing advocacy. This paper reviews the role of nonprofits in the United States, the barriers that keep some nonprofits from utilizing advocacy methods, and the advocacy methods that Habitat for Humanity, International has in place, as well as the methods of other nonprofits of similar size. Recommendations to Habitat for Humanity, International to increase their advocacy capacity are provided

Personnel launch system autoland development study

The Personnel Launch System (PLS) Autoland Development Study focused on development of the guidance and control system for the approach and landing (A/L) phase and the terminal area energy management (TAEM) phase. In the A/L phase, a straight-in trajectory profile was developed with an initial high glide slope, a pull-up and flare to lower glide slope, and the final flare touchdown. The TAEM system consisted of using a heading alignment cone spiral profile. The PLS autopilot was developed using integral LQG design techniques. The guidance and control design was verified using a nonlinear 6 DOF simulation. Simulation results demonstrated accurate steering during the TAEM phase and adequate autoland performance in the presence of wind turbulence and wind shear

On Safe Folding

In [3] a general fold operation has been introduced for definite programs wrt computed answer substitution semantics. It differs from the fold operation defined by Tamaki and Sato in [26,25] because its application does not depend on the transformation history. This paper extends the results in [3] by giving a more powerful sufficient condition for the preservation of computed answer substitutions. Such a condition is meant to deal with the critical case when the atom introduced by folding depends on the clause to which the fold applies. The condition compares the dependency degree between the fonding atom and the folded clause, with the semantic delay between the folding atom and the ones to be folded. The result is also extended to a more general replacement operation, by showing that it can be decomposed into a sequence of definition, general folding and unfolding operations

Integrated control-structure design

A new approach for the design and control of flexible space structures is described. The approach integrates the structure and controller design processes thereby providing extra opportunities for avoiding some of the disastrous effects of control-structures interaction and for discovering new, unexpected avenues of future structural design. A control formulation based on Boyd's implementation of Youla parameterization is employed. Control design parameters are coupled with structural design variables to produce a set of integrated-design variables which are selected through optimization-based methodology. A performance index reflecting spacecraft mission goals and constraints is formulated and optimized with respect to the integrated design variables. Initial studies have been concerned with achieving mission requirements with a lighter, more flexible space structure. Details of the formulation of the integrated-design approach are presented and results are given from a study involving the integrated redesign of a flexible geostationary platform

The Laser in Implantology

Danomice je sve veća uporaba lasera u stomatologiji, a samim tim i u oralnoj kirurgiji. Na području implantologije laserskom se terapijom postižu izvrsni rezultati u fazi postoperativne boli i oteklina, te se bitno skraćuje vrijeme zaraštanja rana. Koristeći s pozitivnim učinkom laserske terapije na koštanu regeneraciju, ubrzavamo i oseointegraciju titanske slitine s kosti. Postopertivne komplikacije, npr. periimplantitisi i periimplantni mukozitisi, minimalne su zbog potpune dekontaminacije područja. Osim toga moguće je vrlo uspješno modelirati meka i tvrda tkiva u potpunoj sterilonosti, bez krvarenja, uz minimalnu traumu i uporabu anestezije. Dakle, laser u kombinaciji s konvencionalnim metodama omogućuje znatno veći postotak uspješnosti terapije. Izazov svakog kliničara u svim granama stomatologije, pa tako i u implantologiji, jest znati kako, kada i gdje upotrijebiti određenu tehniku. Zato je važno znati načelo rada pojedinoga tipa lasera, vrijeme ekspozicije tkiva, te učinak različitih valnih duljina na tkivo kako bi se postignuli optimalni rezultati.Everyday increasing application is found for the laser in dentistry, and thus also in oral surgery. In the field of implantology, excellent results have been achieved by laser therapy in the phase of postoperative pain and swelling and greatly reduced period of wound healing. By utilising the positive effect of laser therapy on bone regeneration we can also accelerate osseointegration of titanium alloy with bone. Postoperative complications, e.g. periimplantitis and periimplant mucositis are minimal because of complete decontamination of the area. Furthermore, it is possible to very successfully model the soft and hard tissue in complete sterility, without bleeding, and with minimal trauma and use of anaesthesia. Thus, the laser in combination with conventional methods enables a significantly greater percentage of successful therapy outcomes. A challenge for every clinician in all branches of dentistry, and thus in implantology, is to know how, when and where to use a certain technique. Consequently it is important to learn the principle of work for each type of laser, period of tissue exposure, and the effect of different wavelengths on tissue in order to achieve optimal results