甲醇/汽油混合燃料发动机非常规排放成分测量方法研究

对使用气相色谱仪检测甲醇／汽油混合燃料发动机排气中醇醛类排放方法进行了研究，优化选择了采样方法、载气流速、柱温等参数，证明安装PEG色谱柱的GC2010完全可以对甲醇／汽油混合燃料发动机排气中的醇、醛进行精确的检测分析。发动机尾气测试结果表明，汽油机燃用M10混合燃料时，排气中的甲醛中低负荷高达0．2mg／L。此外，发动机燃用市售汽油和M10两种燃料时，排气中的甲醇、乙醇和乙醛量相差在10％左右，经三效催化转化器后，可以被控制到接近零排放的水平。     

Single versus Multiple Prime Contracting

Policies regarding public building construction affect the interests of taxpayers, construction authorities, general contractors, specialty contractors, and other stakeholders. At the state level, the debate as to the optimal form such policies should take has become an ongoing struggle among competing interests. This study presents a systematic analysis of the main issues regarding single versus multiple prime contracting with the purpose of providing objective data to illuminate the debate. A statistical analysis of project bids and final costs from a national sample of state construction projects reveals that public construction projects organized with multiple prime contracts tend to have 5% less direct costs than projects using a single prime contractor. Moreover, approximately 80% of these savings are attributable to lower bid costs for multiple prime projects. The results of this study are in agreement with theoretical bidding models and efficient risk allocation models. Theoretical bidding models suggest that, in the absence of disruptions, multiple prime projects should have lower direct costs than single prime jobs. Efficient cost allocation models suggest that when specialty contractors do not bear the risks associated with the single prime contracting method (e.g., bid shopping and payment delays) they are willing to lower their bids, and forego the premium they would normally charge in response to such risks, as seems to be the case in multiple prime jobs.     

Borate Distribution in Stabilized Stainless-Steel Slag

Disintegration of stainless-steel slag during cooling is caused by the β→γ transformation of dicalcium silicate (2CaO·SiO₂ or C₂S). It is well established that disintegration can be avoided by borate additions, which are commonly believed to stabilize the high-temperature polymorphs by forming a solid solution with C₂S. In this study, the borate distributions in slowly cooled synthetic and industrial slag samples are determined. The slag microstructures are characterized using electron probe microanalysis (EPMA), quantitative X-ray diffraction (QXRD), and wavelength dispersive spectroscopy (WDS). The results show that only a limited fraction of the added borates forms a solid solution with the C₂S phase, while the main fraction is found in a calcium borosilicate phase. In combination with literature data, this suggests that slag stabilization involves more than the chemical stabilization of the high-temperature C₂S polymorphs.     

Time trends of polybrominated diphenyl ethers in sediment cores from the Pearl River Estuary, South China

The present study provides information on the time trend of PBDEs in three sediment cores from the Pearl River Estuary (PRE), South China, using 210Pb dating technique. The sigmaPBDEs (except for BDE 209) concentrations in all sediment cores increased gradually from the bottom (mid-1970s) to the middle layer (later 1980s and early 1990s) followed by different temporal trends in different locations to the surface sediments, reflecting the variations in the consumption of commercial penta-BDEs mixture in different regions of the Pearl River Delta. The BDE 209 concentrations remained constant until 1990 and thereafter increased exponentially to the present, with doubling times of 2.6 +/- 0.5-6.4 +/- 1.6 years, suggesting the increasing market demands for deca-BDE mixture after 1990 in China. The inventories of sigmaPBDEs and BDE 209 in sediments of the PRE were 56.0 and 368.2 ng cm(-2), respectively, and the total burden of PBDEs in the PRE were estimated at 8.6 metric tons. The current sigmaPBDEs and BDE 209 fluxes to the PRE were 2.1 and 29.7 ng cm(-2) yr(-1), respectively. The concurrent increase of BDE 209 fluxes and the annual gross industrial output values of electronics manufacturing revealed that the rapid growth of electronics manufacturing in this region since the early 1990s was responsible for the sharp rise of BDE 209 fluxes in the past decade. The PBDE congener compositions of the cores indicated the various input pathways for PBDEs transport to different locations of the estuary.     

Parallel Algorithm for SWFFT Using 3D Data Structure

Sliding-Window Fast Fourier Transform (SWFFT) is a very important and widely used time-frequency representation of a signal. In the paper, we mainly focus on the problem of how to implement non-recursive SWFFT in parallel programming. To avoid repeated calculations, non-recursive SWFFT algorithms always save the calculated results and use for later calculations. So the current calculations need the results from the earlier calculations, and this leads to the main obstacle of implementing SWFFT in parallel programming.     

Mesoporous Silica Preparation Using Sodium Bicarbonate as Template and Application of the Silica for Hydrocracking of Used Cooking Oil into Biofuel

Silicon - The hydrocracking of used cooking oil into biofuel over mesoporous silica was systematically studied. This research aims to induce the silica pores using NaHCO3 and employ the heteropore...