基于差速耦合的混合动力汽车传递特性分析与控制

通过分析传统对称式汽车差速器的传递特性,建立了其作为动力耦合器的数学模型,开发了基于差速耦合的整车控制策略,并嵌入到ADVISOR与整车模型进行集成。以某混合动力轿车为例进行性能仿真,结果表明:应用此对称式锥齿轮差速器除具有节能优势外,取消变速器与离合器,并具有电控无级自动变速的功能(ECVT),从而达到了整车混联式传递灵活、多自由度可控制的目的。     

Problems of spatial linkage of a geo-referenced Demographic and Health Survey (DHS) dataset to a population census: A case study of Egypt

GPS coordinates are increasingly available as spatial references on population surveys in the developing world, where high-resolution address and street mapping are absent. This potentially offers opportunities to enhance national census data by spatial linkage with survey sources. The paper explores the use of GPS-referenced Demographic and Health Survey (DHS) data in combination with census data in Egypt and identifies errors in coordinate referencing. The study develops a practical approach to the measurement of spatial uncertainty in this situation and assessment of its impact on data linkage. The analysis specifically addresses the analytical implications at three different spatial scales and is internationally relevant to the handling of GPS-referenced DHS data in GIS.     

用单纯形模拟退火混合算法反演地声参数

提出了一种基于下降的单纯形算法和模拟退火算法的混合优化算法用于反演地声参数。下降的单纯形方法对于目标函数的梯度信息相当敏感,因此在参数空间中能迅速地移向极小点,但由于它只能向下移动,因而往往易陷入局部极小且依赖初始条件。而模拟退火算法使用随机选取的目标函数值在参数空间中搜索最佳答案,其结构有利于从局部极小中跳出,但是由于它不能利用目标函数的梯度信息因而对参数空间的搜索效率很低。混合方法结合了下降的单纯形方法与快速模拟退火方法这二者的优点,能更有效、更迅速地获得全局最优点。     

Development of a quantitative method for headspace analysis of methylsulfanyl-volatiles from kiwifruit tissue

Minor fruit volatiles are likely to be missed using sampling techniques optimized for the extraction of major compounds. This can be a disadvantage if these minor compounds contribute to characteristic fruit flavors. In this comparative study, headspace solid-phase microextraction (HS-SPME) and dynamic headspace sampling (DHS) parameters were systematically optimized to ensure highest extraction yields of methylsulfanyl-volatiles from kiwifruit tissue samples. A significant “salting-out” effect from the fruit matrix was observed using both sampling techniques after (NH₄)₂SO₄ saturation. HS-SPME at optimized conditions (polydimethylsiloxane-divinylbenzene-coated fiber, (NH₄)₂SO₄ saturation, 5 min equilibration and 20 min sampling at 40 °C) was faster and more convenient to use than DHS for qualitative purposes. Despite this, the qualitative and quantitative methylsulfanyl-volatile profile was improved using optimized DHS ((NH₄)₂SO₄ saturation; sampling time 20 h; flow rate 30 mL min^− 1) compared with HS-SPME, making this the more sensitive and preferred method for quantitative studies. The optimization strategies for increasing headspace extraction yields of trace compounds presented in this study can easily be applied to tissue samples from other fruit.     

The influence of physical-chemical and biological factors on the removal of faecal coliform through down-flow hanging sponge (DHS) system treating UASB reactor effluent

The mechanism of faecal coliform removal in down-flow hanging sponge (DHS) system treating up-flow anaerobic sludge blanket (UASB) reactor effluent was the subject of this study. The results obtained revealed that the most important removal mechanism of faecal coliform in the DHS system is adsorption, followed by predation. Die-off is a relatively minor removal mechanism in the DHS system. The impact of physical and chemical factors such as contact time, effective sponge bulk volume and pH values on faecal coliform removal has been investigated. Increasing the contact time and sponge bulk volume exerted positive effect on the removal of faecal coliform. Changing the pH values between 6.5 and 9.0 did not show significant impact. Reducing sponge pore size from 1.92 to 0.56 mm, increased faecal coliform removal by a value of 1.3 log10.     

Active metal-based corrosion protective coating systems for aircraft requiring no-chromate pretreatment

There has been much R&D effort expended to develop pretreatments and coatings that allow the replacement of toxic, carcinogenic, mutagenic, environmentally hazardous chromates used as pretreatments and pigments in aircraft coating systems. There have been many claims for chromate replacement in primer and pretreatment systems for aircraft, but no systems presently are in use that can function and meet specifications without some form of chromate used in the pretreatment and/or primer. The Mg-rich primer technology developed at North Dakota State University and now in final commercial development at AKZO Nobel Aerospace Coatings shows that finally aerospace Al alloys can be protected against corrosion. With simple cleaning only or a non-chromate pretreatment, the Mg-rich primer (MgRP) + aerospace topcoat provides an aircraft protection system that give corrosion protection that equals or exceeds any system using chromate in any form. About 18 peer reviewed papers have been published and at least twice that many presentations at technical meetings describing this new aircraft primer technology. There are an extensive number of samples in outdoor exposure, and in exposure on small parts of aircraft like port-hole covers and doors, and the coating system has been in accelerated exposure cabinets of all sorts. In the first versions of the magnesium primer premature blistering was noted during immersion or B117 continuous salt spray testing which may be due to hydrogen generation from water contact at a particle. Efforts to control the level of activity of the magnesium have been successfully accomplished since the testing reported in this paper which controls this phenomenon. Current formulations meet and exceed the ASTM B117 test results of full chromate primer systems. Open circuit potential (OCP) measurements indicate an extended period of cathodic protection of the Al aircraft alloys such as AA 2024 T-3 and AA 7075 T-6. After this stage of protection, a combination of Mg oxide, hydroxide and carbonate compounds seem to give protection to the system, as we have seen corrosion protection given to samples for greater than 10,000 h of cyclic exposure for Mg-rich primers with good aerospace topcoats. Preliminary data are presented for other Mg alloys as pigments in metal-rich coating systems. All data indicates that the Mg-rich (or Mg-alloy pigment-rich) primer + aircraft topcoat system gives excellent corrosion protection by mechanisms entirely different from the modes of protection for aircraft alloys given by the toxic, carcinogenic chromate compounds now in use in all corrosion protection systems for aircraft. In most cases thus far examined, the protection, especially in cyclic exposure, exceeds the present chromate-based systems.     

Comparison of Three Methods for Extraction of Volatile Lipid Oxidation Products from Food Matrices for GC–MS Analysis

The aim of this study was to compare three different collection methods; purge and trap, solid phase micro extraction and automated dynamic headspace/thermal desorption, all followed by GC–MS analysis used for the measurements of concentrations of volatile oxidation products in three different food matrices, namely oil, emulsion and milk. The linearity ranges of calibration curves obtained by the three different methods were compared for oil samples. Overall, the results showed that the three collection methods were comparable, although there were large differences in the linearity range of the calibration curves depending on the collection method. However, some challenges were observed for solid phase micro extraction and automated dynamic headspace/thermal desorption, namely, competition problems and overestimation of concentration by calibration curves, respectively. Based on the results, we suggest mainly to apply solid phase micro extraction on simple matrices and to be cautious with more complex matrices such as enriched milk and highly oxidized oils. Thereby, the study confirmed some challenges observed by other authors regarding competition problems on the fiber when using solid phase micro extraction. Furthermore, we observed that purge and trap, and automated dynamic headspace/thermal desorption were excellent for extraction of volatile compounds in all three matrices. However, automated dynamic headspace/thermal desorption calibration curves did provide an overestimation for oil samples so results must be interpreted with caution.     

Performance comparison of a pilot-scale UASB and DHS system and activated sludge process for the treatment of municipal wastewater

This study compares the performance of a pilot-scale combination of UASB and DHS system to that of activated sludge process (ASP) for the treatment of municipal sewage. Both systems were operated in parallel with the same sewage as influent. The study was conducted for more than 300 days, which revealed that organic removal efficiency of UASB+DHS system was comparable to that of ASP. Unfiltered BOD removal by both systems was more than 90%. However, UASB+DHS system outperformed ASP for pathogen removal. In addition, volume of excess sludge production from UASB+DHS was 15 times smaller than that from ASP. Moreover, unlike ASP, there is no requirement of aeration for the operation of UASB+DHS system, which makes it an economical treatment system. Considering the above observations, it was concluded that UASB+DHS system can be a cost-effective and viable option for the treatment of municipal sewage over ASP, especially for low-income countries.     

Biological oxidation of dissolved methane in effluents from anaerobic reactors using a down-flow hanging sponge reactor

Anaerobic wastewater treatment plants discharge dissolved methane, which is usually not recovered. To prevent emission of methane, which is a greenhouse gas, we utilized an encapsulated down-flow hanging sponge reactor as a post-treatment to biologically oxidize dissolved methane. Within 3 weeks after reactor start-up, methane removal efficiency of up to 95% was achieved with a methane removal rate of 0.8 kg COD m⁻³ day⁻¹ at an HRT of 2 h. After increasing the methane-loading rate, the maximum methane removal rate reached 2.2 kg COD m⁻³ day⁻¹ at an HRT of 0.5 h. On the other hand, only about 10% of influent ammonium was oxidized to nitrate during the first period, but as airflow was increased to 2.5 L day⁻¹, nitrification efficiency increased to approximately 70%. However, the ammonia oxidation rate then decreased with an increase in the methane-loading rate. These results indicate that methane oxidation occurred preferentially over ammonium oxidation in the reactor. Cloning of the 16S rRNA and pmoA genes as well as phylogenetic and T-RFLP analyses revealed that type I methanotrophs were the dominant methane oxidizers, whereas type II methanotrophs were detected only in minor portion of the reactor.