Equivalence of robust stabilization and robust performance via feedback

One approach to robust control for linear plants with structured uncertainty as well as for linear parameter-varying (LPV) plants (where the controller has on-line access to the varying plant parameters) is through linear-fractional-transformation (LFT) models. Control issues to be addressed by controller design in this formalism include robust stability and robust performance. Here robust performance is defined as the achievement of a uniform specified $L^{2}$-gain tolerance for a disturbance-to-error map combined with robust stability. By setting the disturbance and error channels equal to zero, it is clear that any criterion for robust performance also produces a criterion for robust stability. Counter-intuitively, as a consequence of the so-called Main Loop Theorem, application of a result on robust stability to a feedback configuration with an artificial full-block uncertainty operator added in feedback connection between the error and disturbance signals produces a result on robust performance. The main result here is that this performance-to-stabilization reduction principle must be handled with care for the case of dynamic feedback compensation: casual application of this principle leads to the solution of a physically uninteresting problem, where the controller is assumed to have access to the states in the artificially-added feedback loop. Application of the principle using a known more refined dynamic-control robust stability criterion, where the user is allowed to specify controller partial-state dimensions, leads to correct robust-performance results. These latter results involve rank conditions in addition to Linear Matrix Inequality (LMI) conditions.Comment: 20 page

Die vroeg-Christelike doop as kultureelrituele simbool

Early Christian baptism as a cultural, ritual symbol This article describes baptism as a cultural, ritual symbol. Baptism is seen as a symbol consisting of reason, value and meaning. The reason why baptism functions as a symbol has a historical basis in the death and resurrection of Jesus. For the first Jesus followers the value of being baptized was that they became part of a new value system. This value system gave meaning to the lives of the baptized and others who stood in relationship with them. The initiation into this alternative lifestyle (through baptism) was made possible by an altered state of consciousness

THE POTENTIAL USE OF POLLUTION INSURANCE AS ENVIRONMENTAL POLICY: AN EMPIRICAL ANALYSIS

Market-based environmental policies have been forwarded as alternatives to current pollution control policies. Implementation of the "polluter pays" principle and governmental enforcement of pollution clean-up have led to astronomical environmental liabilities and clean-up costs, which may threaten the survival of many productive ventures, unless producers can spread pollution risk through insurance. An emission constrained target MOTAD LP (TMLP) model showed that pollution insurance for irrigation farmers can be a feasible and efficient solution to agricultural salinization problems in the Loskop Valley, and fairly low salinity standards with pollution insurance will still be reconcilable with profitable farming. Pollution insurance appears to hold promise for applying the "polluter pays" principles also to non-point pollution. Site specific studies are needed for pollution policy, and more research is needed on pollution standards.Environmental Economics and Policy,

Strategic Marketing Insights For Small Business Meat Retailers

Branded meat of consistently high quality has earned a reputation worldwide as a means to increase beef consumption. The feedlot industry is the main beef producer in South Africa and falls in the category of ‘Small Businesses.’ For these small business meat retailers to be successful in an industry subjected to fierce competition, it is necessary to be innovative in a market where high quality beef serves as just another commodity. This study explored the marketing efforts of meat producers in Middelburg, Mpumalanga, by drawing tangent planes between effective marketing and the knowledgeable consumer. The research approach that was used included both quantitative and qualitative research. The population consisted of consumers buying meat products at three different retailers in Middelburg, Mpumalanga. A sample of 612 was conveniently selected for the study. A total of 588 questionnaires were completed. The results of the study provide insights into the measures that influence brand equity for branded meat products. The importance to establish a link between brand variables and consumers’ perception regarding the importance of these variables is thus critical in the success of branded meat products. These marketing insights make a significant contribution to the competitive marketing strategies of small business meat retailers

The performance and meat quality of Bonsmara steers raised in a feedlot, on conventional pastures or on organic pastures

The effects of production system (feeding regime and time on feed) on growth performance, yield and economics and the effects of feeding regime, pre-slaughter treatment and electrical stimulation on meat quality were evaluated. Sixty Bonsmara steers were divided into three treatment groups, viz. feedlot, organic pasture and conventional pasture feeding. The feedlot and conventional pasture groups received a diet consisting of the same components, while the organic group received a diet with approved organic components. Initial weight, final live weight, warm carcass weight, cold carcass weight, warm and cold dressing percentage, average daily gain (ADG), pH at one and 24 hours post mortem, intramuscular fat content of the loin and subcutaneous back fat thickness were measured. The effects of electrical stimulation, feeding regime and pre-slaughter rest (recovery days at the abattoir) on meat tenderness were also investigated. Feedlot cattle had significantly higher final weights, warm and cold carcass weights, warm and cold dressing percentage, ADG, intramuscular fat content and back fat thickness measurements than organic and conventional pasture cattle. Pre-slaughter resting of animals for a week at the abattoir had no effect on meat tenderness, but electrical stimulation showed a significant positive response. Growth and carcass results were used to calculate price and feed margin for the different production systems. Feedlot cattle showed a higher profit than conventional and organic pasture groups, mainly due to faster and more efficient growth. The organic pasture cattle showed higher profit than the conventional pasture cattle as a result of the premium paid for the organically produced meat. Keywords: Production system, organic, meat quality, profit margins, feedlot, beef cattle South African Journal of Animal Science Vol. 38 (4) 2008: pp. 303-31

The Bezout equation on the right half plane in a Wiener space setting

This paper deals with the Bezout equation $G(s)X(s)=I_m$, $\Re s \geq 0$, in the Wiener space of analytic matrix-valued functions on the right half plane. In particular, $G$ is an $m\times p$ matrix-valued analytic Wiener function, where $p\geq m$, and the solution $X$ is required to be an analytic Wiener function of size $p\times m$. The set of all solutions is described explicitly in terms of a $p\times p$ matrix-valued analytic Wiener function $Y$, which has an inverse in the analytic Wiener space, and an associated inner function $\Theta$ defined by $Y$ and the value of $G$ at infinity. Among the solutions, one is identified that minimizes the $H^2$-norm. A Wiener space version of Tolokonnikov's lemma plays an important role in the proofs. The results presented are natural analogs of those obtained for the discrete case in [11].Comment: 15 page