保持PC安全、安静和冷却的热管理技术

引言最新个人电脑的工作速度已经超过2GHz。伴随这惊人速度而来的是CPU和外围设备所产生的大量热量。降温风扇通常用来驱散这些过量的热量,但是风扇会增加音频噪声。降低CPU内核的电压和系统时钟能够减少热量耗散,但是这是以牺牲工作性能为代价的。最新的系统和热监视器件整合了复杂的温度监视器、电压监视器和风扇控制功能,使所有参数达到平衡并且保持个人电脑的冷、静和安全。图1是一个典型系统的配置方框图。温度测量测量温度最理想的地方是系统中的最热点。可以是CPU或者是电源、内存、硬盘、显卡这样的外围设备。某些热量监视器提…     

NICE’s Indirect Coal-to-Liquid Process for Producing Clean Transportation Fuels Using Fischer-Tropsch Synthesis

China is currently the world’s top coal consumer and the largest oil importer to sustain its rising economy and meet the mounting demand for transportation fuels. However, the increasing emissions due to the huge fossil fuels consumption, coupled with oil market instability, could derail China’s economic growth and jeopardize its national energy security. To face such a hurdle, China has been aggressively supporting low-carbon businesses opportunuties over the past decade, has recently announced several plans to cap coal utilization, and is currently the biggest investor in clean energy technologies. Coal-to-Liquid (CTL) is one of the most promising clean coal technologies, offering an ideal solution that can meet China’s energy demands and environmental expectations. It is widely known that the Shenhua Group has pioneered and is currently leading the commercialization of the Direct Coal Liquefaction (DCL) process in China. This paper highlights a part of the joint research effort undertaken by the National Institute of Clean-and-Low-Carbon Energy (NICE) and University of Pittsburgh in order to develop and commercialize the Indirect Coal Liquefaction (ICL) process. In this mission, NICE has built and operated an ICL plant including a large-scale (5.8-m ID and 30-m height) Slurry-Bubble-Column Reactor (SBCR) for Fischer-Tropsch synthesis using iron catalyst. The research, conducted at the University of Pittsburgh over the past few years, allowed building a user-friendly Simulator, based on a comprehensive SBCR model integrated with Aspen Plus and is validated using data from the NICE actual ICL plant. In this paper, the Simulator predictions of the performance of the NICE SBCR, operating with iron and cobalt catalysts under four different tail gas recycle strategies: (1) direct recycle; (2) using a Pressure Swing Adsorption (PSA) unit; (3) using a reformer; and (4) using a Chemical looping Combustion (CLC) process, are presented. It should be mentioned also that our joint research effort has laid the foundation for the design of a commercial-scale SBCR for producing one-million tons per annum of environmentally friendly and ultraclean (no sulfur, no nitrogen and virtually no aromatics) transportation fuels, which could greatly contribute to ensuring China’s national energy security while curbing its lingering emission problems.     

Impact of radiation attenuation and temperature evolution on monomer conversion of dimethacrylate‐based resins with a photobleaching photoinitiator

The photopolymerization process of a dimethacrylate copolymer system activated by the camphorquinone (CQ)/amine photoinitiator system (1 wt%), was experimentally studied under nonisothermal conditions in 1‐ and 2‐mm thick samples by measuring double bond conversion, temperature rise and radiation attenuation through the sample during polymerization. The peak temperature in 1‐ or 2‐mm thick samples irradiated at 5 mW/cm² was 29 and 38°C, respectively. The temperature evolution during polymerization was also predicted by solving the energy balance coupled with the kinetic expressions for the reaction rate. Radiation attenuation as a function of depth by the photobleachable CQ results in spatial and temporal variation in the local rates of the kinetic steps involved. General relationships for spatiotemporal variations in concentration of a photobleaching initiator, in systems where attenuation and initiator consumption are taken into account, were used to compute local polymerization rates. The effects of radiation attenuation, photobleaching of the photoinitiator and variation of cure temperature at different depths into the resin, all compete to determine the double bond consumption. The increased radiation attenuation in the 2‐mm thick sample was accompanied by a higher cure temperature compared with the 1‐mm thick sample, and as a result, the monomer conversion averaged over the sample thickness in the 1‐ and 2‐mm thick samples was the same. Results obtained in this research highlight the inherent interlinking of thermal and radiation attenuation effects in bulk photopolymerizing systems. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Renewable energy potential on brownfield sites: A case study of Michigan

Federal priorities are increasingly favoring the replacement of conventional sources of energy with renewable energy. With the potential for a federal Renewable Electricity Standard (RES) legislation, many states are seeking to intensify their renewable energy generation. The demand for wind, solar, geothermal and bio-fuels-based energy is likely to be rapidly expressed on the landscape. However, local zoning and NIMBYism constraints slow down the placement of renewable energy projects. One area where land constraints may be lower is brownfields; whose development is currently constrained by diminished housing, commercial, and industrial property demand. Brownfield sites have the potential for rapid renewable energy deployment if state and national interests in this area materialize. This study investigates the application of renewable energy production on brownfield sites using Michigan as a case study. Wind and solar resource maps of Michigan were overlaid with the brownfield locations based on estimates of brownfield land capacity. The total estimated energy potential available on Michigan’s brownfield sites is 4320 megawatts (MW) of plate capacity for wind and 1535for solar, equating to 43% of Michigan’s residential electricity consumption (using 30% capacity factor). Estimated economic impacts include over $15 billion in investments and 17,500 in construction and long-term jobs.     

Antimicrobial properties of the chelating agent EDTA on Streptococcal bovine mastitis isolates

To determine the efficacy of the chelating agent EDTA on microbial growth, separate cultures of two streptococcal bovine mastitis isolates, Streptococcus agalactiae and Streptococcus uberis, were exposed to known concentrations of EDTA. Bacterial cultures of 10(8) CFU/ml were exposed to concentrations of EDTA ranging from 30 to 100 mM in an in-vitro-milk environment. Multiple replications of cultures exposed to EDTA were plated during a two-hour time course. A concentration of 100 mM EDTA resulted in a 90% reduction of S. agalactiae and a 99% reduction of S. uberis. Under these experimental conditions, EDTA treatments in cultures of both isolates exhibited from 1 to 2 log reductions suggesting that EDTA is a potentially effective antimicrobial against streptococcal isolates implicated in causing bovine mastitis.     

Surface roughness of stainless-steel mirrors for focusing soft x rays

We have used polished stainless steel as a mirror substrate to provide focusing of soft x rays in grazing-incidence reflection. The critical issue of the quality of the steel surface, polished and coated with gold, is discussed in detail. A comparison is made to a polished, gold-coated, electroless nickel surface, which provides a smoother finish. We used the surface height distributions, measured with an interferometric microscope and complemented by atomic-force microscope measurements, to compute power spectral densities and then to evaluate the surface roughness. The effects of roughness in reducing the specular reflectivity were verified by soft-x-ray measurements.     

An investigation on the mechanism of the increased NO2 emissions from H2-diesel dual fuel engine

The addition of hydrogen (H₂) into the intake air of a diesel engine was found to significantly increase the emissions of nitrogen dioxide (NO₂). Previous research demonstrated a strong correlation between the emissions of NO₂ and unburned H₂ in exhaust gas. However, the mechanism whereby H₂ addition in increasing NO₂ formation in a H₂-diesel dual fuel engine. Previously has not been investigated.This research numerically verified the hypothesis that the increased NO₂ emissions observed with the addition of H₂ was formed through the conversion from NO to NO₂ during the post combustion oxidation process of the unburned H₂ when mixed with the hot NO-containing combustion products. A variable volume single zone model with detailed chemistry was applied to simulate post-combustion oxidation process of the unburned H₂ and its effect on NO₂ emissions. The mixing of the unburned H₂ with the NO-containing hot combustion products was found to convert NO to NO₂. Such a conversion is promoted by the hydroperoxyl (HO₂) radical formed during the oxidation process of the H₂. The factors affecting the NO₂ formation and its destruction include the concentration of NO, H₂, O₂, and the temperature of the bulk mixture. When H₂ and hot NO-containing combustion products mixed during the early stage of expansion stroke, the NO₂ formed during H₂ oxidation was later dissociated to NO after the complete consumption of H₂. The complete combustion of H₂ exhausted the source of HO₂ necessary for the conversion from NO to NO₂. The mixing of H₂ with combustion products during the last part of the expansion stroke was not able to convert NO to NO₂ since the temperature was too low for H₂ to oxidize and to provide the HO₂ needed. The bulk mixture temperature range suitable for meaningful conversion from NO to NO₂ aided by HO₂ produced during the oxidation of H₂ was examined and presented.     

Comparison of feeding diets diluted with sorghum-sudangrass silage or low-quality grass on nutrient intake and digestibility and growth performance of Holstein dairy heifers

This study was carried out to evaluate the nutrient intakes and growth of dairy heifers offered an alfalfa silage–corn silage diet (CON; 14.3% crude protein, 61.1% total digestible nutrients, 47.9% neutral detergent fiber) compared with diets containing 1 of 2 types of sorghum-sudangrass (SS) silages: conventional or photoperiod sensitive. The objective of the study was to determine the potential to use SS to control dry matter (DM) and nutrient intakes and weight gain. Both diets were similar in nutrient composition, with approximately 13% crude protein, 60 to 61% total digestible nutrients, and 55% neutral detergent fiber. Seventy-two Holstein heifers (16–18 mo at study initiation) were blocked by initial body weight (light = 422 ± 12.8 kg; medium = 455 ± 14.8 kg; heavy = 489 ± 16.7 kg) with 3 pens assigned to each weight block (8 heifers/pen; 24 heifers/block). The 3 diets were randomly allocated to the pens within each block and offered for 12 wk. Heifers offered the CON diet had greater DM, protein, and energy intakes compared with those offered the SS silage-based diets due to the greater neutral detergent fiber concentration of the SS diets. With lower DM and nutrient intakes, average daily gain was in the recommended range (0.8–1 kg/d for Holstein heifers) for heifers offered the SS silage-based diets (mean of 0.92 kg/d for both SS diets vs. 1.11 kg/d for CON). Sorting behaviors for heifers offered both SS diets were more aggressive against long, medium, and short particles compared with those of heifers offered the CON diet; however, heifers sorted large particles from photoperiod-sensitive silage more aggressively than those from conventional silage. Based on this study, SS silage-based diets can control the DM and energy intakes for heifers and maintain optimum growth rates, with harvesting at a shorter chop length likely helping to alleviate sorting issues.