无环境风险含氟残液充装技术应用

介绍了含氟残液充装过程中管道余气的处理方法,减少了有毒余气对人和环境的影响,大大降低了充装过程中的环境风险。     

A tribute to D.B. Spalding and his contributions in science and engineering

This paper presents a summary of some of the scientific and engineering contributions of Prof. D.B. Spalding up to the present time. Starting from early work on combustion, and his unique work in mass transfer theory, Spalding’s unpublished “unified theory” is described briefly. Subsequent to this, developments in algorithms by the Imperial College group led to the birth of modern computational fluid dynamics, including the well-known SIMPLE algorithm. Developments in combustion, multi-phase flow and turbulence modelling are also described. Finally, a number of academic and industrial applications of computational fluid dynamics and heat transfer applications considered in subsequent years are mentioned.     

Photographic Image Intensification and Reduction: A Unified Optical Approach

A simple, non-destructive method of image intensification and reduction is described which can be applied to continuous-tone negative materials. The method employs a commercially available direct copy (reversal) film whose contrast (γ) can be continuously varied by pre-exposure from 0.8 to ~ 10.0. This film is then used with a difTuse-light contact printer to extract images from negatives which have been severely under- or over-exposed. Examples of images extracted from Plus-X negatives which have received from eight SlOps over- to seven stops underexposure are shown. This same process can be used to retrieve usable images from exposures where the chemical or image fog levels approach developed densities of 5.0. The technique compares favourably with the complicated autoradiographic procedures recently introduced for thin negative enhancement but is not affected by high levels of chemical fog. It appears that the process is versatile enough to replace traditional chemical methods of photographic intcnsification and reduction.     

Development and malignant progression of astrocytomas in GFAP-v-src transgenic mice

We have generated a transgenic mouse model for astrocytoma by expressing the v-src kinase under control of the glial fibrillary acidic protein (GFAP) gene regulatory elements in astrocytes. Abnormal astrogliosis was observed in all transgenic animals already at 2 weeks postnatally, frequently followed by the development of dysplastic changes. Later, small proliferative foci arose, and overt astrocytoma developed in the brain and spinal cord in 14.4% of mice after a follow up time of 65 weeks. While early lesions were histologically consistent with low-grade astrocytoma, at later stages most tumors were highly mitotic and frankly malignant. Vascular endothelial growth factor (VEGF) was expressed by tumor cells already at early stages, suggesting induction by v-src, and it was most pronounced in pseudopalisading cells surrounding necrotic areas, implying additional upregulation by hypoxia. In larger lesions, mitotic activity and expression of flk-1, the cognate receptor of VEGF were induced in endothelial cells. Therefore, end-stage tumors mimicked the morphological and molecular characteristics of human glioblastoma multiforme. Time course and stochastic nature of the process indicate that v-src did not suffice for malignant transformation, and that astrocytomas were the result of a multistep process necessitating co-operation of additional genetic events.     

The Ven Te Chow Memorial Lecture: Environment and Development: Urgent Need for a Water Perspective

ABSTRACT

This paper contains the text of the Chow Memorial Lecture, delivered at the VIIth World Congress on Water Resources Rabat, Morocco, May 13–18, 1991.

The paper addresses water-cycle related environmental problems. Three essential water functions are crucial for the disturbances introduced by the interventions in life-support systems known as “environmental problems”: water as a necessity of life on all scales from the cell to the planet: water as a solvent continuously moving above and below the ground surface, and the water-wetting of the landscape due to partitioning disturbances.

The second part of the paper analyzes water-cycle related development problems, demonstrating that drought-proneness is today at the core of the problems in the most poverty-stricken countries. There, development is equivalent to challenging water scarcity (seasonal, interannual, or local), and environmental vulnerability. Particularly fatal is rapid population growth, especially as there are few models dealing with high population pressure on a finite, scarce, and highly seasonal water resource that may be copied from the industrialized world.

The paper concludes that water is at the core of both the dominating environmental problems of today and of the development problems. Consequently, it is urgent to bridge the gap between the environmental lobby, preparing for the Brazil Conference, and the water specialists acting from on inherited platform of water knowledge to which Ven Te Chow skillfully and abundantly contributed, but which he also completely summarized and described in classical works.     

Realization of Wurtzite GaSb Using InAs Nanowire Templates

The crystal structure of a material has a large impact on the electronic and material properties such as band alignment, bandgap energy, and surface energies. Au‐seeded III–V nanowires are promising structures for exploring these effects, since for most III–V materials they readily grow in either wurtzite or zinc blende crystal structure. In III–Sb nanowires however, wurtzite crystal structure growth has proven difficult. Therefore, other methods must be developed to achieve wurtzite antimonides. For GaSb, theoretical predictions of the band structure diverge significantly, but the absence of wurtzite GaSb material has prevented any experimental verification of the properties. Having access to this material is a critical step toward clearing the uncertainty in the electronic properties, improving the theoretical band structure models and potentially opening doors toward application of this material. This work demonstrates the use of InAs wurtzite nanowires as templates for realizing GaSb wurtzite shell layers with varying thicknesses. The properties of the axial and radial heterointerfaces are studied at the atomic scale by means of aberration‐corrected scanning transmission electron microscopy, revealing their sharpness and structural quality. The transport characterizations point toward a positive offset in the valence bandedge of wurtzite compared to zinc blende.     

Radiation enhancement in doped AlGaN-structures upon optical pumping

Spectral characteristics of spontaneous and stimulated luminescence have been studied for molecular beam epitaxy synthesized Al _x Ga_1–x N/AlN solid solutions with x = 0.5 and 0.74 upon optical pumping by pulse laser radiation with λ = 266 nm. Broadband radiation spectra with a width of ~260 THz for Al_0.5Ga_0.5N and ~360 THz for Al_0.74Ga_0.26N have been obtained. The measured enhancement factors are g ≈ 70 cm^–1 for Al_0.5Ga_0.5N at λ ≈ 528 nm and g ≈ 20 cm^–1 for Al_0.74Ga_0.26N at λ ≈ 468 nm.     

Dual layer SiC coating on matrix graphite sphere prepared by pack cementation and fluidized‐bed chemical vapor deposition

A dual layer silicon carbide (SiC) coating including inner porous SiC (p‐SiC) layer and outer dense SiC (d‐SiC) layer was fabricated on the matrix graphite (MG) spheres of high‐temperature gas‐cooled reactor fuel elements by pack cementation and fluidized‐bed chemical vapor deposition process to improve the oxidation‐resistant property. Microstructure of the coating demonstrates different density and structure of the two SiC layers with no obvious boundaries between them. Weight gain curves of oxidation tests at 1773 K for 200 hours show that the coating could effectively protected the MG sphere by isolating the air infiltration with p‐SiC layer as the main functional layer and d‐SiC layer as the transition layer to improve the bond strength. Due to the transition function of p‐SiC layer, the coated spheres could understand more than 50 times thermal shocking tests from 1773 K to room temperature with no stress cracking.     

Novel hydroperoxides as primary autoxidation products of a model ethoxylated surfactant

Ethoxylated alcohols, widely used as surfactants, are susceptible to oxidation when exposed to air. A complex mixture is formed, in which alkylated aldehydes, alkylated formates, hydroxyaldehydes, and formaldehyde have previously been identified by our group. The compounds identified so fat are all secondary oxidation products, some of which have been shown to be skin sensitizers and irritants. The primary oxidation products from ethoxylated surfactants have been described as peroxides and hydroperoxides, but their structures have not been elucidated more closely. Hydroperoxides are reactive species and can be suspected to be biologically active as skin sensitizers and irritants. In the present study we used a small model compound, diethylenglycol monoethylether (C₂E₂), to facilitate the identification of primary oxidation products formed at autoxidation of ethoxylated surfactants. By performing NMR and HPLC-MS analyses, we found that at least four different hydroperoxides were formed at autoxidation of C₂E₂, one of them dominating in concentration over the others. The hydroperoxide present in the highest concentration was identified as 2-[2-(1-hydroperoxyethoxy)ethoxy]ethanol.