MAKING BETTER USE OF NATURAL LIGHT WITH A LIGHT-REDIRECTING DOUBLE-GLAZING SYSTEM

The subject of the present paper is a fixed daylighting system known as the LIF light guide. The system consists of a fixed arrangement for capturing sunlight incident at various angles and re-directing it by means of an optical wave-guide which provides diffuse ceiling illumination. The light guide is generally sandwiched between two glass panes and mounted above the windows to avoid obstructing visibility. Its intended function is to furnish offices and other working areas with a uniform level of natural illumination while avoiding glare.     

Ultra High Pressure Tribometer for Testing CO2 Refrigerant at Chamber Pressures up to 2000 psi to Simulate Compressor Conditions

Abstract

The growing interest for using the natural refrigerant carbon dioxide (CO₂) in refrigeration and air-conditioning applications instead of HFC refrigerants, due to environmental concerns, has led to the development of an ultra high pressure tribometer (UHPT) specifically tailored for testing in CO₂ environment. The existing research on tribology related to CO₂ environment has focused on investigations at relatively low chamber pressures due to equipment restrictions. The UHPT is a unique tribometer that has been custom designed and manufactured to allow testing under CO₂ refrigerant at environmental pressures comparable to those found in compressors. A special housing, which surrounds the tribological surfaces subject to testing, is capable of withstanding chamber pressures up to 13.8 MPa (2000 psi) and can be temperature controlled from 0°C to 100°C via a thermal control system. A multi-axis strain gauge force transducer measures the applied load, frictional forces, and moments during friction testing, and computer control permits different loading profiles. Using this machine, experiments were performed at a range of pressures between 1.4 MPa (200 psi) and 6.9 MPa (1000 psi) of CO₂ refrigerant. The results suggest a slightly better tribological performance at higher pressures compared to lower pressures.     

Tribological Studies on Scuffing Due to the Influence of Carbon Dioxide Used as a Refrigerant in Compressors

Because hydrofluorocarbon (HFC) refrigerants in air-conditioning systems are known to have a negative effect on the environment, carbon dioxide (CO₂) is a candidate as a replacement refrigerant. Research work related to CO₂ as a refrigerant has been focused primarily on its thermodynamic performance, whereas work in the area of tribology related to carbon dioxide is absent. In this study, the effects of CO₂ used as a refrigerant on the tribological behavior of surf aces in contact in such systems were investigated. Controlled experiments were performed at constant loads in environments of CO₂ and the conventional HFC refrigerant, R134a, as well as under conditions of step-increasing loads in the presence of refrigerant (CO₂ or R134a) and polyalkylene glycol lubricant. The experiments were performed on a high-pressure tribometer that is particularly suited for tribological testing of compressor contact interfaces. The tribological behavior of contacting surfaces in a CO₂ environment was nearly identical to that in an R134a environment when tested under the same operating conditions.     

Detection of cheese packaging containment failures using reversible optical oxygen sensors

This study investigated the capacity of optical oxygen sensors to nondestructively detect containment packaging failures in commercial vacuum packed cheddar cheese. Unacceptable oxygen levels in packs lead to product deterioration and can significantly reduce shelf life. Vacuum packed cheddar cheese was monitored for oxygen levels over time at 4 °C with optical sensors prefitted to packaging laminates polyethyleneterephthalate/polypropylene. Oxygen levels present in packs immediately after packaging were 3% on average. Further ingress of oxygen into all packs occurred over storage time and levels ranged from 3.6% to 8.2% after 6 days. Information obtained using oxygen sensors led to further assessments and identification of the causes of packaging containment failure.     

The Development of Corporate Concentration in the Western World Gold Mining Industry between 1975 and 1984

This paper describes some trends in the development of corporate concentration in the gold mining industry in the Western world. The main source of information is a data base on corporate control of the production of non-fuel minerals, which has been established by the Raw Materials Group in Sweden. The data base contains data on production, ownership and management of about 1000 companies engaged in the non-fuel minerals industry in the Western world. Reference years arc 1975 and 1984. The data base is updated continuously.     

用于钢板中氧化镁夹杂物分析的显微洁净度测量装置的联合应用

生产用于石油和天然气工业的厚钢板需要最高质量等级的半成品,如钢坯。炼钢过程结束时的钙处理是非常必要的。在此生产过程中,非金属夹杂物的成分会发生变化。直读光谱仪的脉冲鉴别分析技术（OES-PDA）使所有钢铁样品的统计研究成为可能。采用OES-PDA检测基本的显微洁净度参数,例如含量和组成。采用定向、自动的光栅电子显微镜-能量色散X射线荧光光谱法（REM-EDX）为非金属夹杂物提供更详细的信息,并验证OES-PDA的数据集。研究表明,两种方法测得结果的组合可以为过程提供一些新的、更细节的信息,尤其是钢坯凝固过程中含氧化镁夹杂物的信息。     

Missing wedge computed tomography by iterative algorithm DIRECTT

A strategy to mitigate typical reconstruction artefacts in missing wedge computed tomography is presented. These artefacts appear as elongations of reconstructed details along the mean direction (i.e. the symmetry centre of the projections). Although absent in standard computed tomography applications, they are most prominent in advanced electron tomography and also in special topics of X‐ray and neutron tomography under restricted geometric boundary conditions. We investigate the performance of the DIRECTT (Direct Iterative Reconstruction of Computed Tomography Trajectories) algorithm to reduce the directional artefacts in standard procedures. In order to be sensitive to the anisotropic nature of missing wedge artefacts, we investigate isotropic substructures of metal foam as well as circular disc models. Comparison is drawn to filtered backprojection and algebraic techniques. Reference is made to reconstructions of complete data sets. For the purpose of assessing the reconstruction quality, Fourier transforms are employed to visualize the missing wedge directly. Deficient reconstructions of disc models are evaluated by a length‐weighted kernel density estimation, which yields the probabilities of boundary orientations. The DIRECTT results are assessed at different signal‐to‐noise ratios by means of local and integral evaluation parameters.