Combinatorial Assortment Optimization

Assortment optimization refers to the problem of designing a slate of products to offer potential customers, such as stocking the shelves in a convenience store. The price of each product is fixed in advance, and a probabilistic choice function describes which product a customer will choose from any given subset. We introduce the combinatorial assortment problem, where each customer may select a bundle of products. We consider a model of consumer choice where the relative value of different bundles is described by a valuation function, while individual customers may differ in their absolute willingness to pay, and study the complexity of the resulting optimization problem. We show that any sub-polynomial approximation to the problem requires exponentially many demand queries when the valuation function is XOS, and that no FPTAS exists even for succinctly-representable submodular valuations. On the positive side, we show how to obtain constant approximations under a "well-priced" condition, where each product's price is sufficiently high. We also provide an exact algorithm for $k$-additive valuations, and show how to extend our results to a learning setting where the seller must infer the customers' preferences from their purchasing behavior

Protein metabolism, feed energy partitioning, behavior patterns and plasma cortisol in Nellore steers with high and low residual feed intake.

The objective was to evaluate protein turnover, nitrogen balance, feed energy partitioning, behavior patterns and plasma cortisol in Nellore (B. indicus) cattle with high and low residual feed intake (RFI = actual minus expected dry matter intake). Seventy-two Nellore steers (16 to 21 months-old, 334±19 kg initial body weight) were fed a feedlot diet for 70 days ad libitum. Daily dry matter intake (DMI) and average daily gain (ADG) were recorded individually and RFI was calculated. The 12 steers of lowest (Low-RFI, most efficient) RFI and the 12 ones of highest RFI (High-RFI, least efficient) were evaluated with respect to their behavior patterns and plasma cortisol concentration. Urine was collected for determination of daily 3-methylhistidine excretion (3MH) and myofibrillar protein breakdown rates. Urinary, gaseous and fecal energy losses were determined as well as the N retention and excretion. High-RFI steers tended to have shorter lying and idle periods and greater feeding time and plasma cortisol levels than low-RFI cattle. No RFI effects were seen for urine 3MH excretion and for rates of protein degradation and synthesis. No effects of efficiency class were observed for N excretion or N retention. No RFI effects were observed for dry matter digestibility, digestible energy (DE) and metabolizable energy (ME) content and DE/ME ratio. Methane energy losses were lower for low- compared with high-RFI steers. Protein turnover seems not to affect feed efficiency in Nellore steers. Improved RFI in Nellore steers is probably associated with lower degrees of activity and responsiveness to stress and lower losses of dietary energy as methane

Effect of substrate bias voltage on amorphous Si–C–N films produced by PVD techniques

SixCyNz thin films were deposited by reactive magnetron sputtering in glass and steel substrates. The films were grown in a rotation mode over a carbon and a silicon targets in a mixed Ar/N2 atmosphere. The substrates were held at a substrate temperature of 573 K. The argon flow was kept constant (100 sccm) and the nitrogen flow was 20 sccm or 25 sccm, in each one of the two series of produced films, resulting in a working pressure around 0.5 Pa. The substrate bias varied between grounded and -100 V. The films were analysed with respect to microstructure, state of chemical bonding and optical properties by X-Ray Diffraction (XRD), Raman Spectroscopy (RS), optical reflectance and transmittance. Raman spectroscopy was used as a probe of microstructural modifications induced by deposition conditions. The main features observed in RS spectra are the well-known D- and G-bands characteristic of amorphous carbon materials. The position, widths and intensity ratio of these bands are found to be dependent of the films deposition conditions. The refractive index, absorption coefficient, optical band gap and also the thickness were calculated from transmittance spectra obtained between 200 nm and 2500 nm.The residual stress of the coatings depends on deposition conditions and was calculated by measuring the substrate curvature before and after film deposition. The curvature of the samples was measured by laser triangulation in two series of two orthogonal directions. All coatings were in a state of compressive residual stress. The average hardness and Young’s modulus of the produced coatings is about 16 GPa and 170 GPa, respectively. The nano-hardness of the grounded produced samples presented values about 30% lower

PHYSIOLOGICAL RESPONSES OF HOLSTEIN COW’S FACE TO RESOURCE OF FAN IN FREE-STALL

Este estudo teve como objetivo avaliar a influência do recurso de ventilação sobre a fisiologia de vacas Holandesas alojadas em free-stall, durante o verão do sudeste brasileiro. Foram utilizadas 20 vacas Holandesas submetidas a dois tratamentos: controle e ventilação. Os parâmetros ambientais registrados foram temperatura e umidade relativa do ar e temperatura de globo negro. As variáveis fisiológicas avaliadas foram temperatura retal e frequência respiratória. Para obtenção das estatísticas descritivas utilizou-se a metodologia de quadrados mínimos. Apesar das diferenças estatísticas obtidas para as variáveis fisiológicas, as mesmas não foram biologicamente efetivas e indicaram que os animais se encontravam em conforto térmico

Influence of pre-slaughter management on cortisol level in lambs

This study aimed to verify the influence of the transport in open or closed compartments, followed by two resting periods (1 and 3 hours) for the slaughter process on the levels of cortisol as a indicative of stress level in lambs. The slaughterhouse was located 85 km away from the place of confinement and the transportation of the lambs was carried out in a cage truck type, each cage had a divider in the middle making the front without external visual access to the environment, and the back portion of the cages with visual access to the road. At the slaughterhouse, blood samples were taken from 86 lambs after the transport and before slaughter (1 or 3 hours of resting) for plasma cortisol analysis. Variables were evaluated through the PROC GLM procedure from the Statistical Analysis System ©, version 9.1.3 software.The method of transport influenced in the cortisol concentration (P<0.01), the animals transported in the closed compartment had a lower level. After the resting period in the slaughterhouse, there was a decline in the plasmatic cortisol concentration, with the animals subjected to three hours of rest presenting the lower average cortisol value (P<0.05). It can be inferred that the lambs that remained three hours in standby before slaughter had more time to recover from the stress of the transportation than those that waited just one hour. Visual access to the external environment during the transport of the lambs is a stressful factor changing the level of plasmatic cortisol, and the resting period before slaughter was effective in lowering stress, reducing the plasmatic cortisol in the lambs

Correlations of visual scores and ultrasound carcass traits with economically relevant traits in Nellore cattle.

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Banco de dados geográfico sobre a cafeicultura mineira: organização lógica e inserção de dados.

Os sistemas de informações geográficas (SIG) foram desenvolvidos com o objetivo de facilitar o tratamento de um volume cada vez maior e mais preciso de informações sobre a superfície terrestre e suas questões ambientais. Na utilização para a cafeicultura o SIG integra softwares para tratamento e armazenamento de dados segundo um modelo conceitual predefinido. A partir da definição deste modelo iniciou-se o armazenamento dos dados, em um Sistema de Gerenciamento de Banco de Dados (SGBD). A ferramenta escolhida para o gerenciamento dos dados foi o PostgreSQL pois este é um SGBD objeto-relacional e de código aberto, mantido em constantes atualizações gratuitas pela Comunidade Brasileira do PostgreSQL 1. Devido ao grande número de atualizações, o PostgreSQL é extensível, sendo utilizado para dar suporte à diversos tipos de aplicações desde dados simples à aplicações mais complexas, bem como seus metadados. Para a integração e o armazenamento dos dados foi utilizado o sistema de informação geográfico SPRING 2. O SPRING é um software gratuito para criação e gerenciamento de banco de dados geográficos, possuí funções para processamento de imagens, análises espaciais, modelagem numérica de terreno e consulta a banco de dados espaciais. No acesso aos dados geográficos foi utilizado um tipo de arquitetura conhecida como ?Arquitetura Dual?. A principal vantagem desta arquitetura consiste na separação das funcionalidades na qual o gerenciamento dos metadados é feita pelo SGBD, pois os mecanismos de transação, recuperação a falhas, concorrência, integridade dos dados e indexação podem ser usados para a parte não espacial dos dados, enquanto que a responsabilidade do gerenciamento dos dados geográficos é realizada pelo SPRING. Portanto, o objetivo principal deste trabalho foi inserir e organizar dados geográfico sobre pesquisas realizadas pela EPAMIG relacionadas á cafeicultura mineira