直线与Bzier曲面求交的分割迭代综合法

本文所介绍的适合光线跟踪算法的直线与B(?)zier曲面求交的方法,采用了空间一般位置的圆柱和长方体作为曲面包围盒,并综合利用了分割法的稳定性和牛顿迭代法的效率,从而加快了用光线跟踪技术生成Bzier曲面的真实感图形的速度。     

Calculating the shading reduction coefficient of photovoltaic system efficiency using the anisotropic sky scattering model

The front-row shading reduction coefficient is a key parameter used to calculate the system efficiency of a photovoltaic(PV) power station. Based on the Hay anisotropic sky scattering model, the variation rule of solar radiation intensity on the surface of the PV array during the shaded period is simulated, combined with the voltage–current characteristics of the PV modules, and the shadow occlusion operating mode of the PV array is modeled. A method for calculating the loss coefficient of front...     

Influence of the type of forage supplied to ewes in pre- and post-partum periods on the meat fatty acids of suckling lambs

The aim of this study was to evaluate the use of forage diets (grazing vs. hay) around the time of ewe parturition, on the fatty acids profile of suckling lamb meat (10-12 kg body weight). Forty-eight multiparous single-bearing ewes were used. The experimental treatments were conducted during the last 5 weeks of pregnancy and the 5 weeks of lactation in a 2 × 2 factorial design. Ewes were fed ad libitum on pastures or hay in the autumn. Results showed that milk from grazing ewes during the pre-partum period had a higher content of PUFA and CLA (P < 0.05) and VA, CLA in their suckling lambs' meat (P < 0.05). The effect in post-partum feeding was greater, revealing higher CLA, PUFA/SFA, PUFA n-3 and PUFA n-6/n-3 in milk and meat (P < 0.05). The CLA, VA and PUFA n-6/n-3 ratios are those that are most affected by grazing. Pre-partum grazing, regardless of post-partum feeding, improves FA composition, increasing CLA content in both milk and meat.     

Fatty acid profile of milk from goats fed diets with different levels of conserved and fresh forages

Aim of the study was to evaluate the effect of different proportions of hay and fresh grass in goats’ diet on milk fatty acid profile. Nine Camosciata goats were fed a fixed amount of concentrate (30% of total diet) and different percentages (40% vs 30%, 50% vs 20% and 60% vs 10%) of hay and fresh grass, respectively. Diminishing amounts of fresh grass percentages in the diet led to significant increases of lauric, myristic and palmitic acids (P ≤ 0.001) and to significant decreases of C18:1 t6‐11, rumenic and α‐linolenic acids (P ≤ 0.001) in milk, thus determining a worsening of the health value of milk fat.     

Silent meadows: The uncertain decline and conservation of hay meadows in the british landscape

The environmental impacts of British agriculture have been a popular focus in recent years within Landscape Research. However, to date, little attention has been paid to the case of hay meadows, an important feature of the landscape in cultural, agricultural and ecological terms, and one which has been threatened with decline. The paper considers the factors which have marginalized hay meadows in the discussion of agri-environment relations, showing that the lack of definitive data on hay meadows, government funding for more intensive farming practices, and the ephemeral nature of hay meadows have contributed to their ‘silent’ decline. Drawing on a case study of the Peak District in the UK, the attempts of current agri-envrionment schemes to encourage ‘traditional’ management, and the problems associated with the use of this term and its connotations, are considered.     

Learning in Newbern: Rural Studio in Year Ten

Amidst the regulated and increasingly fraught business of architectural practice, particularly within its homestead of the town of Newbern, Hale County, Alabama, Rural Studio has entered its second decade as a force to contradict normative modes of architectural education and practice. In the coming years, we will see if the wider consequences triggered by this innovative organisation will take root elsewhere. In the meantime, John Forney 's reflective examination of its roots substantiates the condition that, in times of change, the periphery is a place that matters greatly. Copyright © 2005 John Wiley & Sons, Ltd.     

Interfacial Synthesis of Conjugated Crystalline 2D Fluorescent Polymer Film Containing Aggregation‐Induced Emission Unit

A fully conjugated 2D fluorescent film containing a tetraphenylethene (TPE) unit is constructed by Glaser–Hay coupling reaction on the surface of copper foil. A large‐area, freestanding fluorescent films with an average thickness 4.5 nm can be obtained through the strategy of solid–liquid interfacial synthesis. The film and the pore structure are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), X‐ray photoelectron spectroscopy (XPS). High‐resulution TEM and selected area electron diffraction (SAED) further confirm the dual pores structure with triangular‐ and hexagonal‐shaped pores. The as‐prepared 2D films exhibit excellent solid‐state fluorescence emission arising from the confinement of TPE units.     

Silent meadows: The uncertain decline and conservation of hay meadows in the british landscape

The environmental impacts of British agriculture have been a popular focus in recent years within Landscape Research. However, to date, little attention has been paid to the case of hay meadows, an important feature of the landscape in cultural, agricultural and ecological terms, and one which has been threatened with decline. The paper considers the factors which have marginalized hay meadows in the discussion of agri-environment relations, showing that the lack of definitive data on hay meadows, government funding for more intensive farming practices, and the ephemeral nature of hay meadows have contributed to their 'silent' decline. Drawing on a case study of the Peak District in the UK, the attempts of current agri-envrionment schemes to encourage 'traditional' management, and the problems associated with the use of this term and its connotations, are considered.     

Fishy and hay-like off-flavours of dry spinach

 Gas chromatography-olfactometry of headspace samples revealed that (Z)-3-hexenal, methanethiol, (Z)-1,5-octadien-3-one, dimethyl trisulphide, octanal, 2-isopropyl- and 2-sec-butyl-3-methoxypyrazine are potent odorants of raw spinach. Boiling the spinach led to a change, such that dimethyl sulphide, methanethiol, dimethyl trisulphide, methional and 2-acetyl-1-pyrroline became the most important odorants. A further change was observed after drying and storage of raw spinach: methylpropanal, 2- and 3-methylbutanal and propanal were identified as the odorants with higher odour activity values. It was also found that (Z)-1,5-octadien-3-one and methional, in a concentration ratio of about 1 : 100, are responsible for the fishy off-flavour as dry spinach stored at lower temperatures under nitrogen. The hay-like flavour was caused by oxidative degradation of furan fatty acids, yielding 3-methyl-2,4-nonanedione. Received: 24 July 1997     

Volatile composition of red clover (Trifolium pratense L.) forages in Portugal: The influence of ripening stage and ensilage

The volatile organic compounds (VOCs) of three different red clover (Trifolium pratense L.) forages, fresh plant, hay and silage, were analyzed using GC and GC/MS. Comparing the volatile composition of hay and silage forages of red clover with the corresponding green plant, the effects of ripening and postharvest secondary metabolism can be noticed in hay and in ensilage. In hay, reductions of the percentages of alcohols, such as 3-methylbutanol and 1-hexanol, of aldehydes and of low boiling point ketones are observed. A sesquiterpene (β-farnesene; ca. 10%) and a phytol degradation product (6,10,14-trimethyl-2-pentadecanone; ca. 12%) were the most abundant compounds detected in hay. In silage, as a result of the fermentation of fresh red clover, esters (ca. 46%) are a more representative class of compounds.