一种新型的膏体充填工艺技术

膏体充填技术作为一种将选矿尾砂排放坑内采空区并形成坚固支承体的充填技术,从20世纪80年代初期就已经在加拿大地下矿山开始使用.然而,早期的膏体充填系统设备昂贵、能耗较高,使得地下矿山最近几年来开始探求一种更经济有效的充填技术.针对这个问题,现在已经研发出一种相应的技术,它能将选矿尾砂通过沉淀、浓缩和流态化过程制出膏体.加拿大矿物能源工艺中心(CANMET)在这种新工艺的研究中所取得的成果表明,选矿尾砂能在一个尾砂仓内通过浓缩和流态过程而制成膏体用于矿山充填.     

A solar pond-assisted heat pump for greenhouses

A solar pond for annual cycle solar energy collection and storage was studied at The Ohio Agricultural Research and Development Center (OARDC), Wooster. It has been used as a thermal energy source for greenhouse heating. A brine-source electric-power-driven heat pump was incorporated into the heat extraction system. Initial results of the field studies indicated that the combined system improved the effectiveness of both the heat pump and the solar pond by enabling a larger temperature cycle within the solar pond.

To study the operation of such a system, a computer simulation model for the heating system was developed. The results of simulations were used to establish a relationship between the system performance and the present design and for sizing the solar energy collection and storage system. Also, the effect of a polystyrene pellet nighttime insulation for the greenhouse was simulated. Increasing the surface area of the OARDC pond was found to be less effective than changing its depth. Thr results showed that a 5 m deep pond with 1.0 m gradient zone significantly improved the overall performance of the system when used as a heat source for a heat pump. Based on the detailed experimental and computer simulation performance analysis, the solar pond-assisted heat pump system has the potential of improved performance compared with convential air source heat pumps.     

A model for phase noise generation in amplifiers

In this paper, a model is presented for predicting the phase modulation (PM) and amplitude modulation (AM) noise in bipolar junction transistor (BJT) amplifiers. The model correctly predicts the dependence of phase noise on the signal frequency (at a particular carrier offset frequency), explains the noise shaping of the phase noise about the signal frequency, and shows the functional dependence on the transistor parameters and the circuit parameters. Experimental studies on common emitter (CE) amplifiers have been used to validate the PM noise model at carrier frequencies between 10 and 100 MHz     

Modeling and testing a salt gradient solar pond in northeast Ohio

A dynamic computer model of a salt gradient solar pond as an annual-cycle solar energy collection and storage system was developed. The model was validated using experimental results of a solar pond located at the Ohio Agricultural Research and Development Center (OARDC), Wooster, Ohio. The model was then used to analyze the transient energy phenomena which occurred within the storage zone of the pond. Generalized daily weather functions used were the incident solar radiation upon a horizontal surface, the daylight length and the daily maximum and minimum ambient air temperatures.Various simulations were performed to evaluate the OARDC solar pond and to improve its overall effective capacity of heat storage. It was found that 4–6 weeks variation in start-up time and 5–10°C variation in start-up temperature had no effect on late summer peak storage temperature. The pond operated at a 20 per cent collection efficiency with a 1.5-m deep gradient. Insulating the pond in the winter would be beneficial if no heat was removed during the fall. Reducing the gradient zone thickness to 1 m and enlarging the storage zone could improve the performance of a 3-m deep pond. The model could be used to predict and analyze the transient thermal response of large storages associated with solar heating system for a variety of purposes and climatic conditions.     

Oligodendrocyte-Specific Deletion of FGFR1 Reduces Cerebellar Inflammation and Neurodegeneration in MOG35-55-Induced EAE

Multiple sclerosis (MS) is a chronic inflammatory and degenerative disease of the central nervous system (CNS). MS commonly affects the cerebellum causing acute and chronic symptoms. Cerebellar signs significantly contribute to clinical disability, and symptoms such as tremor, ataxia, and dysarthria are difficult to treat. Fibroblast growth factors (FGFs) and their receptors (FGFRs) are involved in demyelinating pathologies such as MS. In autopsy tissue from patients with MS, increased expression of FGF1, FGF2, FGF9, and FGFR1 was found in lesion areas. Recent research using mouse models has focused on regions such as the spinal cord, and data on the expression of FGF/FGFR in the cerebellum are not available. In recent EAE studies, we detected that oligodendrocyte-specific deletion of FGFRs results in a milder disease course, less cellular infiltrates, and reduced neurodegeneration in the spinal cord. The objective of this study was to characterize the role of FGFR1 in oligodendrocytes in the cerebellum. Conditional deletion of FGFR1 in oligodendrocytes (Fgfr1^ind−/−) was achieved by tamoxifen application, EAE was induced using the MOG_35-55 peptide. The cerebellum was analyzed by histology, immunohistochemistry, and western blot. At day 62 p.i., Fgfr1^ind−/− mice showed less myelin and axonal degeneration compared to FGFR1-competent mice. Infiltration of CD3(+) T cells, Mac3(+) cells, B220(+) B cells and IgG(+) plasma cells in cerebellar white matter lesions (WML) was less in Fgfr1^ind−/−mice. There were no effects on the number of OPC or mature oligodendrocytes in white matter lesion (WML). Expression of FGF2 and FGF9 associated with less myelin and axonal degeneration, and of the pro-inflammatory cytokines IL-1β, IL-6, and CD200 was downregulated in Fgfr1^ind−/− mice. The FGF/FGFR signaling protein pAkt, BDNF, and TrkB were increased in Fgfr1^ind−/− mice. These data suggest that cell-specific deletion of FGFR1 in oligodendrocytes has anti-inflammatory and neuroprotective effects in the cerebellum in the EAE disease model of MS.     

Defektfreie Mixed‐Matrix‐Membranen aus Matrimid® und Aktivkohle für die Gastrennung

In this work the fabrication of new mixed‐matrix membranes (MMMs) of Matrimid® and activated carbon (AC) for gas separation is reported. The aim is the fabrication of membranes that have better gas permeation properties compared to the pristine Matrimid® membranes. The membranes were thermally and morphologically characterized, and the gas transport properties of single gases were estimated by a variety of methods. It has been found that with an increase of the AC content the selectivity remained stable for the different gases despite the marked increase in the effective permeability of the pure gases.     

A discrete element model of laser beam induced current (LBIC) due to the lateral photovoltaic effect in open-circuit HgCdTe photodiodes

The non-destructive optical characterization technique of Laser-Beam-Induced-Current (LBIC) imaging has proven useful in qualitatively assessing electrically active defects and localized non-uniformities in HgCdTe materials and devices used for infrared photovoltaic arrays. To further the development of a quantitative working model for LBIC, this paper focuses on the application of the technique to photovoltaic structures that are represented by a discrete element equivalent circuit. For this particular case the LBIC signal arises due to the lateral photovoltaic effect in non-uniformly illuminated open-circuit photodiodes. The outcomes of the model predict all of the experimentally observed geometrical features of the LBIC image and signal. Furthermore, the model indicates that the LBIC signal has an extremely weak dependence on the p-n junction reverse saturation current, and shows a linear dependence with laser power. This latter feature map be useful for non-contact measurement of the quantum efficiency of individual photodiodes within a large two-dimensional focal plane array. The decay of the LBIC signal outside the physical boundary of the p-n junction is of the same form as the roll-off in the short circuit photoresponse and, therefore, can be used to extract the diffusion length of minority carriers. Experimental data is obtained from an arsenic implanted p-on-n junction fabricated on MBE grown Hg/sub 1-x/Cd/sub x/Te material with an x-value of 0.3. The p-on-n diode is shown to be uniform and of high quality with an R/sub 0/A product of 1/spl times/10/sup 8/ /spl Omega//spl middot/cm/sup 2/ at 77 K. The validity of the simple model developed in this paper, is confirmed by the excellent agreement with experimental results. Consequently, the LBIC technique is shown to be an appropriate diagnostic tool for non-contact quantitative analysis of semiconductor materials and devices.<>