It was aimed to simultaneously study standardized ileal digestible (SID) tryptophan (Trp) and lysine (Lys) for gilts. A digestibility assay was previously conducted to determine the SID amino acid in the basal diet (low levels of SID Trp and Lys). Sixty-four gilts (15.04 ± 1.44 kg) were allotted to 16 diets in a 4 × 4 factorial arrangement (1.55, 1.85, 2.15 and 2.45 g/kg SID Trp and 9.72, 11.12, 12.52 and 13.92 g/kg SID Lys) with four replicates per treatment. Performance, longissimus muscle (LM), backfat thickness (BF) and blood variables were evaluated. An interaction was observed for G:F, and by response surface model, the optimum Trp level was achieved at 2.15 g/kg (0.159 g/MJ of ME). A quadratic effect of Trp was observed on body weight (BW) and average daily gain (ADG); the daily feed intake increased linearly as Trp increased. The optimum Trp levels of 2.25 and 2.24 g/kg were estimated for BW and ADG, respectively. The BF increased with increasing levels of Trp. There was a quadratic and linear effect of Trp and Lys, respectively, on the LM, in which the optimum Trp level was determined as 2.05 g/kg in the diet. Plasma urea nitrogen decreased as Trp and Lys levels increased. Using estimates provided by response surface, maximized G:F ratio was obtained at 2.15 g SID Trp/kg of diet and at least 13.92 g SID Lys/kg of diet is necessary to optimize the G:F for 15–30 kg gilts, providing a Trp:Lys ratio of 15.4:100.

Surrogate models are widely used for dataset correlation. A popular application very frequently shown in public literature is in the field of engineering design where a large number of design parameters are correlated with performance indices of a complex system based on existing numerical or experimental information. Such an approach allows the identification of the key design parameters and their impact on the system’s performance. The generated surrogate model can become part of wider computational platforms and enable optimisation of the complex system without the need to run expensive simulations.

In this paper, a number of design point simulations for a combined gas-steam cycle are used to generate a response surface. The generated response surface correlates a range of cycle’s key design parameters with its thermal efficiency while it also enables identification of the optimum overall pressure ratio and the high pressure level of the raised steam across a range of recuperator effectiveness, pinch temperature difference across the heat recovery steam generator and the pressure at the condenser. The accuracy of a range of surrogate models to capture the design space is evaluated using root mean square statistical metrics.

The design and analysis of competition experiments should be based on an unambiguous objective. Recent criticisms of particular designs have been made without reference to objectives and may be misleading. Three common designs are discussed: additive, replacement series, and response surface. Additive designs are well suited to agronomic objectives; replacement series are useful for comparing pairs of species; response surface designs can be used for most objectives but may be unnecessarily complex. The published criticisms of additive and replacement series designs are argued to be acceptable limitations within the bounds of the objectives for which they are used. Concerns about these designs confounding density and proportion are irrelevant to the objectives for which they are most suited. The continued use of multiple comparison tests is argued to be illogical. Regression approaches to analysis are more relevant, many non-linear equations are now easy to fit to data and these can be used without the need for linearization. However, there are various pitfalls not adequately reported to date. In particular, error structures need to be checked carefully and over-elaborate equations should be avoided.

Economic assessment of weed management strategies in rice is dependent upon a quantitative estimate of the yield impact of a given weed population. To assist rice producers in making such assessments, a mathematical model was developed to predict rice yield reduction as a function of weed density and duration of interference. The nonlinear empirical model was a unique 3-dimensional adaptation of the Richards equation with 4 parameters. Using published data, individual parameter values were fitted for each of 6 weed species interfering with either conventional or semi-dwarf statured rice cultivars. The functional form of the equation produced surfaces that were qualitatively consistent with available data and experience regarding rice-weed biology. Hence, predictions from the model should be useful and reliable in assessing the economic impact of weeds and in determining the feasibility of alternative weed control treatments for various field scenarios.

In crop/weed interactions a method is needed to reduce the complex data derived from interference research to a simple form which can be utilized immediately. A response surface technique was utilized in analyses involving densities, duration of interference, interference abilities of different species, and weed growth rates. At high weed densities interfering for long durations, multispecies interference is not additive but at low densities additiveness is approached. Soybean [Glycine max (L.) Merr.] yield loss from multispecies weed interference was calculated by subtracting the percent yield loss from the most competitive weed and then repeating the same procedure for remaining weeds. Interference data for weed species in which fewer data were available were determined by linear interpolation for densities of more comprehensively researched, closely related species. Polynominal regression curves were utilized to predict weed age and future weed size from weed height. These analyses can produce information to assist soybean producers in recognizing economically detrimental threshold levels of weed infestations which require the initiation of control measures.

Produced as a joint product, economic theory suggests that manure value could influence livestock management decisions such as herd size and optimal market weights. This study examines the concept of manure value and its connection with optimal replacement age or market weight. A model of a swine finishing operation representative of North Carolina conditions is developed. Over the range of conditions considered, manure value is negative and does not affect market weights. The marginal per head change in manure value is small relative to the marginal per head change in net returns from pork production. Further, economies of scale with respect to irrigation cause manure value to increase with herd size.

The focus of the review is to show how the Box-Behnken Design (BBD) could be applied in poultry nutrition research. BBD is a multivariate experimental design which uses less treatment combinations and allows researchers to estimate and optimise processes. Box-Behnken design was used in an experiment to estimate growing broiler requirements for total sulphur amino acids (TSAA), lysine (Lys) and threonine (Thr). In the experiment BBD has shown to be a useful tool in estimating and optimizing nutrient requirements in growing broilers.

Lors de la fabrication, à l’aide d’un procédé d’emboutissage, de pièces en tôles minces telles que les carrosseries automobiles ou les composants d’électroménager, certaines surfaces doivent être ajoutées à la pièce désirée afin d’éviter des défauts comme la rupture, le plissement et la rayure. Ces surfaces additionnelles sont constituées de murs de protection et de surfaces sous serre-flan. L’objectif principal de cette étude est de proposer une méthodologie d’aide à la conception des surfaces additionnelles s’appuyant sur le développement d’une procédure numérique automatique de conception et d’optimisation de ces surfaces additionnelles dans le cadre d’un procédé d’emboutissage de tôles minces. La conception automatique des surfaces additionnelles s’appuie sur la création des courbes de profil et de surfaces de COONS. Ces surfaces sont ensuite maillées automatiquement et la simulation du problème d’emboutissage est résolue avec l’Approche Inverse. Enfin, les paramètres géométriques nécessaires à la création des surfaces sont optimisés afin de satisfaire des critères mécaniques propres au procédé d’emboutissage. Ces outils paramétriques de conception-simulation-optimisation permettent d’aboutir rapidement à des surfaces additionnelles optimales.

Les outils numériques actuels permettent de prendre en compte la majorité des paramètres prévisibles et quantifiables intervenant dans la conception, la fabrication et la mise au point d'un produit et permettent de mettre en place des modèles numériques tridimensionnels très précis. Ce travail présente une étude de faisabilité dans le cadre d'une démarche d'optimisation de forme des pièces de sécurité automobiles obtenues à partir de tôle à Haute Limite Élastique (H.L.E). La méthode proposée repose sur un algorithme d'optimisation utilisant des plans d'expériences. Elle permet de déterminer l'influence de la forme des pièces sur leur comportement statique en traction afin de simuler la résistance au choc de l'attache lors de son dépliage. La méthodologie des surfaces de réponse est utilisée dans un contexte d'optimisation pour l'exploitation des résultats. La technique numérique adoptée est basée sur la théorie de l'élastoplasticité couplée au dommage et avec écrouissage isotrope. La formulation de l'endommagement ductile isotrope de Lemaître utilisée permet une simulation fiable dans le cadre de la méthode des éléments finis à travers une étude paramétrique et comparative de trois formes géométriques d'attaches. Les calculs qui sont effectués sur le code ABAQUS/standard ont montré que le rayon du trou oblong permettant l'accrochage de la ceinture, est le paramètre géométrique qui a l'effet le plus prononcé sur les résultats de l'étude. L'analyse par surfaces de réponse montre que l'état de contrainte de von Mises n'évolue que très peu en fonction des autres variables considérées, mais par contre que les valeurs des contraintes sont beaucoup plus importantes quand le rayon du trou oblong augmente.