On-road heavy-duty diesel particulate matter emissions modeled using chassis dynamometer data

This study presents a model, derived from chassis dynamometer test data, for factors (operational correction factors, or OCFs) that correct (g/mi) heavy-duty diesel particle emission rates measured on standard test cycles for real-world conditions. Using a random effects mixed regression model with data from 531 tests of 34 heavy-duty vehicles from the Coordinating Research Council's E55/E59 research project, we specify a model with covariates that characterize high power transient driving, time spent idling, and average speed. Gram per mile particle emissions rates were negatively correlated with high power transient driving, average speed, and time idling. The new model is capable of predicting relative changes in g/mi on-road heavy-duty diesel particle emission rates for real-world driving conditions that are not reflected in the driving cycles used to test heavy-duty vehicles.     

Evaluation and comparison of portable emissions measurement systems and federal reference methods for emissions from a back-up generator and a diesel truck operated on a chassis dynamometer

There is considerable interest in portable emissions measurement systems (PEMS) for emission inventory and regulatory applications. For this study, four commercial PEMS were compared with a Federal Reference Method (FRM) for measuring emissions from a back-up generator (BUG) over steady-state loads and a diesel truck on transient and steady-state chassis dynamometer tests. The agreement between the PEMS and the FRM varied depending on the pollutant and the particular PEMS tested for both the BUG and chassis dynamometer testing. The best performing PEMS for both the BUG and chassis testing was within approximately 12% for NOx of the FRM. For the BUG testing, several PEMS showed agreement with the FRM within approximately 5% for CO2. For the chassis dynamometer testing, the best PEMS showed agreement typically within approximately 5% for CO2. PM measurements for the BUG testing were low compared to the FRM, with the best measurements approximately 20% lower. For the chassis testing, two PM PEMS showed a good correlation but a high bias, while the correlation was worse for the other two PEMS. For each emissions component, some PEMS under different test conditions showed considerably larger deviations than those for the best performing PEMS.     

Size-dependent mixing characteristics of volatile and nonvolatile components in diesel exhaust aerosols

Mixing characteristics of particles of different volatilities from a diesel engine were studied with two tandem differential mobility analyzers (TDMAs) and an aerosol particle mass analyzer (APM). In both TDMA systems, a heater was located in the aerosol path between the first and second DMAs. Diesel exhaust particles that were size-selected in the first DMA were passed through the heater, and the change in particle size due to loss of volatile components was determined by the second DMA. On the basis of the volatility measurements, the particles could be separated into two overlapping modes that varied in peak diameter and magnitude depending on the engine operating conditions. Particles in the smaller size mode were almost completely volatile, while those in the larger size mode contained a nonvolatile core. The TDMA data inversion technique used here allowed accurate determination of the mixing ratios of the two types of particles. These data were in turn used to validate a simple fitting method that uses two log-normal curves to obtain the mixing ratios. In some experiments, the APM was used downstream of a TDMA to directly measure the particle mass loss due to evaporation. The loss determined bythe TDMA-APM system was significantly greater than that calculated from mobility size changes measured solely with the TDMA. The TDMA-APM results were used to calculate the size-dependent mass concentrations of volatile and nonvolatile components for particles in the size range from 70 to 200 nm.     

Effect of lubricant on the formation of heavy-duty diesel exhaust nanoparticles

The effect of lubricants on nanoparticle formation in heavy-duty diesel exhaust with and without a continuously regenerating diesel particulate filter (CRDPF) is studied. A partial flow sampling system with a particle size distribution measurement starting from 3 nm, approximately, is used. Tests are conducted using four different lubricant formulations, a very low sulfur content fuel, and four steady-state driving modes. A well-documented test procedure was followed for each test. Two different kinds of nanoparticle formation were observed, and both were found to be affected bythe lubricant but in differentway. Without CRDPF, nanoparticles were observed at low loads. No correlation between lubricant sulfur and these nanoparticles was found. These nanoparticles are suggested to form mainly from hydrocarbons. With CRDPF, installed nanoparticles were formed only at high load. The formation correlated positively with the lubricant (and fuel) sulfur level, suggesting that sulfuric compounds are the main nucleating species in this situation. Storage effects of CRDPF had an effect on nanoparticle concentration as the emissions of nanoparticles decreased over time.     

Characterization of diesel particles: effects of fuel reformulation, exhaust aftertreatment, and engine operation on particle carbon composition and volatility

Diesel exhaust particles are the major constituent of urban carbonaceous aerosol being linked to a large range of adverse environmental and health effects. In this work, the effects of fuel reformulation, oxidation catalyst, engine type, and engine operation parameters on diesel particle emission characteristics were investigated. Particle emissions from an indirect injection (IDI) and a direct injection (DI) engine car operating under steady-state conditions with a reformulated low-sulfur, low-aromatic fuel and a standard-grade fuel were analyzed. Organic (OC) and elemental (EC) carbon fractions of the particles were quantified by a thermal-optical transmission analysis method and particle size distributions measured with a scanning mobility particle sizer (SMPS). The particle volatility characteristics were studied with a configuration that consisted of a thermal desorption unit and an SMPS. In addition, the volatility of size-selected particles was determined with a tandem differential mobility analyzer technique. The reformulated fuel was found to produce 10-40% less particulate carbon mass compared to the standard fuel. On the basis of the carbon analysis, the organic carbon contributed 27-61% to the carbon mass of the IDI engine particle emissions, depending on the fuel and engine operation parameters. The fuel reformulation reduced the particulate organic carbon emissions by 10-55%. In the particles of the DI engine, the organic carbon contributed 14-26% to the total carbon emissions, the advanced engine technology, and the oxidation catalyst, thus reducing the OC/EC ratio of particles considerably. A relatively good consistency between the particulate organic fraction quantified with the thermal optical method and the volatile fraction measured with the thermal desorption unit and SMPS was found.     

Understanding the difference in oxidative properties between flame and diesel soot nanoparticles: the role of metals

The purpose of this paper is to address the differences observed in the oxidative kinetics between flame and diesel derived soots. In particular, it has been observed that flame soot has a significantly higher activation energy for oxidation than does diesel soot. The hypothesis tested in this paper is that metals, possibly coming from lubricating oils, within diesel generated soot particles may be responsible for this effect. This is supported by the fact that addition of metal additives to diesel fuel is shown to have no effect on the activation energy of soot oxidation. The subject of this paper lies in testing the hypothesis by adding metal directly to a flame and extracting oxidation kinetics. Using a high temperature oxidation tandem differential mobility analyzer (HTO-TDMA) we extract particle size dependent kinetics for the oxidation of flame-derived soot doped with and without iron. We found that indeed addition of iron to a flame reduced the activation energy significantly from approximately 162 +/- 3 kJ/mol to approximately 116 +/- 3 kJ/mol, comparable with diesel engine generated soot with an activation energy approximately 110 kJ/mol. These results are consistent with the idea that small quantities of metals during diesel combustion may play an important role in soot abatement.     

Ternary nucleation as a mechanism for the production of diesel nanoparticles: experimental analysis of the volatile and hygroscopic properties of diesel exhaust using the volatilization and humidification tandem differential mobility analyzer

The volatile and hygroscopic properties of diesel nanoparticles were simultaneously determined under a range of engine loads using the volatilization and humidification tandem differential mobility analyzer (VH-TDMA). Additionally, the VH-TDMA was used to measure changes in the hygroscopic behavior of the heterogeneously nucleated diesel nanoparticles as one or more semivolatile species were removed via thermal evaporation or decomposition. Particles produced at high loads exhibited high, dual-step volatility, while those particles produced at low loads were less volatile and exhibited continuous volatilization curves. The hygroscopic growth factor of the particles was shown to be load dependent with high-load particles exhibiting growth factors similar to that of ammonium sulfate. At 85% relative humidity, particles produced at moderate loads exhibited growth factors of approximately 1.1 while low-load particles were shown to be hydrophobic. Growth factors and volatilization temperatures measured for high-load particles clearly indicate that ternary nucleation is involved in particle formation.     

Evaluation of udder firmness by palpation and a dynamometer

Swelling of the mammary gland is an important health status sign for clinical exploration and palpation is a routine diagnostic tool for mastitis detection in dairy cows. Data on repeatability or validity of specific methods of udder palpation are rare. The overall objective was to study the validity of estimates of udder firmness generated by palpation and by using a validated dynamometer. Specifically, we set out to determine within-observer repeatability and between-observer repeatability in 2 specific experiments. Additionally, we compared a 4-point palpation scoring system with estimates obtained with a dynamometer in this study. In a pilot trial, we determined the range of udder firmness of 25 cows and developed an in vitro model for udder firmness. This model enabled training of the observers and allowed investigating a 4-point palpation scoring system. In vivo, udder firmness was determined before and after milking by palpation and by using a dynamometer. Within-observer repeatability based on estimates of udder firmness of 25 cows obtained by 3 observers on a single day by palpation was 0.968. Within-observer repeatability of estimates of udder firmness of 25 cows obtained with the dynamometer by a single observer was 0.997. The coefficient of variation of the same measures was 9.1%. To determine between-observer repeatability (palpation: 0.932; dynamometer: 0.898), udder firmness of 100 cows was measured on 4 different days by 9 observers in experiment 2. Udder firmness in dairy cows could be measured repeatably with the dynamometer and by palpation, especially when performed by a single observer. Estimates of udder firmness generated by palpation and with the dynamometer were moderately related (correlation coefficient = 0.54). Training of observers through the pilot trial or practical experience in the 4 d of the study in experiment 2 did not improve the correlation. Further research is warranted to understand how udder firmness develops in infected udders.     

三维异型整体编织底盘装置的设计

为提高三维异型整体编织的自动化程度进而提高编织效率,通过分析现有的三维异型预制件通用法和混合式样法编织工艺以及可实现异型编织的底盘设备,提出了一种利用步进电动机作为固定式导轨的驱动装置,并结合直流电磁铁在导轨两端中的定位功能,利用DMC5400A 四轴轨迹卡、IOC1280 IO 扩展卡与STM32F103 型微控制器控制实现了多种异型预制件自动编织的底盘装置。通过对编织底盘的结构组成和异型编织的工作过程进行分析测试,结果表明,利用这种底盘装置并结合其控制系统所进行的编织工艺,可实现异型预制件的柔性化织造,具有较好的应用前景。     

高地隙通用作业底盘的设计与试验

设计一种高地隙全液压四轮驱动通用作业底盘。通过前期调研数据确立设计初始目标值,对底盘的结构原理、液压系统进行总体设计;结合通过性参数目标值,计算确定行走泵与行走马达型号,完成转向支腿与车架结构设计并进行有限元分析;在该基础上开展底盘通过性能研究,确定轴距与结构参数的关系;最后试制样机并进行通过性试验。试验结果表明:作业底盘在爬坡时液压系统的压力与流量特性曲线均在理论设计范围内。在满载的情况下,通用底盘能通过的最高陡坡为41°,最大台阶高度为490 mm,可实现原位转向,水泥路面行驶速度范围为0~13km/h,水田作业速度范围为0~11km/h。试验结果满足通用作业底盘通过性设计目标要求,具备较好的通过性能,适用于水田和果园不同作用环境。     

Research Watch: A diesel exhaust-cancer link?

Health.     

Effect of diesel oxidation catalysts on the diesel particulate filter regeneration process

A Diesel Particulate Filter (DPF) regeneration process was investigated during aftertreatment exhaust of a simulated diesel engine under the influence of a Diesel Oxidation Catalyst (DOC). Aerosol mass spectrometry analysis showed that the presence of the DOC decreases the Organic Carbon (OC) fraction adsorbed to soot particles. The activation energy values determined for soot nanoparticles oxidation were 97 ± 5 and 101 ± 8 kJ mol(-1) with and without the DOC, respectively; suggesting that the DOC does not facilitate elementary carbon oxidation. The minimum temperature necessary for DPF regeneration was strongly affected by the presence of the DOC in the aftertreatment. The conversion of NO to NO(2) inside the DOC induced the DPF regeneration process at a lower temperature than O(2) (ΔT = 30 K). Also, it was verified that the OC fraction, which decreases in the presence of the DOC, plays an important role to ignite soot combustion.     

Airborne brake wear debris: size distributions, composition, and a comparison of dynamometer and vehicle tests

Particle size distributions of light-duty vehicle brake wear debris are reported with careful attention paid to avoid sampling biases. Electrical low-pressure impactor and micro-orifice uniform deposit impactor measurements yield consistent size distributions, and the net particulate matter mass from each method is in good agreement with gravimetric filter measurements. The mass mean diameter of wear debris from braking events representative of urban driving is 6 microm, and the number-weighted mean is 1-2 microm for three currently used classes of lining materials: low metallic, semimetallic, and non-asbestos organic (NAO). In contrast, the wear rates are very material dependent, both in number and mass of particles, with 3-4 times higher emissions observed from the low metallic linings as compared to the semimetallic and NAO linings. Wind tunnel and test track measurements demonstrate the appearance of micron size particles that correlate with braking events, with approximately 50% of the wear debris being airborne for the test vehicle in this study. Elemental analysis of the wear debris reveals a consistent presence of the elements Fe, Cu, and Ba in both dynamometer and test track samples.     

三维异型整体编织底盘控制系统的设计

为提高三维异型整体编织技术的自动化程度,进而提高编织效率,通过介绍编织底盘装置的工作原理,提出了一种底盘控制系统。该控制系统利用DMC5400A型四轴轨迹卡控制4组步进电动机驱动整行(列)携纱器纵横步进循环运动,并结合STM32F103型微控制器控制直流电磁铁定位机构完成异型编织动作实现可控增减纱携纱器工作。选用IOC1280 10型扩展卡控制位置传感器实现底盘运动状态检测,利用MFC中基于对话框的应用程序开发的操作界面实现对多种异型预制件自动编织。对底盘控制系统的硬件组成和异型编织的工作过程进行试验验证。结果表明,利用这种底盘控制系统结合人机交互界面所进行的编织工艺,可实现异型预制件的自动编织具有较高的应用价值。     

Size-dependent toxicity of nano-C60 aggregates: more sensitive indication by apoptosis-related Bax translocation in cultured human cells

The toxicity of NPs is not well characterized in terms of their size. In particular, the size-based toxicity of fullerene (C(60)) remains an issue because of a lack of C(60) NPs with a well-controlled size. In this work, six fractions of the nano-C(60) aggregates (nC(60)) with different size distribution were prepared by a simple differential centrifugation. By using these nC(60) fractions, we demonstrate the size-dependent inhibition of DNA polymerase and reduced-size enhanced cytotoxicity. Above all, we found that nC(60) NPs with smaller size may have higher toxicity potency. These size-dependent effects were observed at the high exposure doses (4-6 mg/L). Interestingly, at 20-times lower and noncytotoxic doses, the size-dependent effect can be indicated by apoptosis-related fluorescent protein fused Bax translocation. Considering the toxicity of NPs is often ignored in the traditional end-point analysis for cytotoxicity when the exposure dose is low, the findings presented here will assist in the evaluation of the size-dependent cytotoxicity and dose-response relationships of toxicity mediated by nC(60) NPs at low doses.     

Short communication: Diagnosis and classification of clinical and subclinical mastitis utilizing a dynamometer and a handheld infrared thermometer

In times of ongoing automatization of dairy cow husbandry, objective and reliable tools for mastitis diagnostic are highly in demand. The objective of this study was to investigate the diagnostic value of a handheld dynamometer and an infrared thermometer to diagnose and score clinical and subclinical mastitis and to compare those values with results from palpation of the udder tissue. Overall, 218 cows with clinical mastitis (i.e., 46 mild, 106 moderate, and 66 severe cases), 142 with subclinical mastitis, and 68 healthy cows were enrolled. Our data provide evidence that the dynamometer is an accurate diagnostic tool to differentiate between healthy udder quarters, and those with subclinical and clinical mastitis. Furthermore, the severity score of clinical mastitis can be estimated by dynamometer. The firmness threshold for the detection of clinical mastitis was 1.002 kg. Using a threshold of 1.175 kg in clinical mastitis quarters, it was possible to differentiate between negative and positive bacteriological results. A differentiation between healthy and clinical mastitis quarters with the infrared thermometer was possible, albeit udder surface temperatures were highly influenced by ambient temperature. Udder surface temperature increased by 0.15 to 0.18°C for each degree of ambient temperature. In conclusion, the utility of an infrared thermometer to estimate the udder health status of dairy cows is limited, whereas the handheld dynamometer appeared to be an accurate and objective method.     

孜然挥发油稳定性的研究

对孜然挥发油的稳定性进行了初步研究.研究结果显示,光照、温度和pH值影响孜然挥发油的稳定性,自然光照60 d后挥发油光吸收值下降了29%,37℃保存60 d后挥发油光吸收值下降了41%,在pH10的碱性条件下(保存30 min)孜然挥发油光吸收值下降17%;另外,Na 、Al3 、Fe3 对孜然挥发油的稳定性也有不同程度的影响,其中Fe3 对孜然挥发油的稳定性影响较大,加入Fe3 浓度为0.4%时,溶液变混浊.因此,为保证挥发油的品质,应在低温、避光以及偏酸性条件下保存孜然挥发油,同时应避免与重金属离子接触.     

Kinetics of diesel nanoparticle oxidation

The technique of high-temperature oxidation tandem differential mobility analysis has been applied to the study of diesel nanoparticle oxidation. The oxidation rates in air of diesel nanoparticles sampled directly from the exhaust stream of a medium-duty diesel engine were measured over the temperature range of 800-1140 degrees C using online aerosol techniques. Three particle sizes (40, 90, and 130 nm mobility diameter) generated under engine load conditions of 10, 50, and 75% were investigated. The results show significant differences in the behavior of the 10% load particles as compared to the 50 and 75% load particles. The 10% load particles show greater size decrease at temperatures below 500 degrees C and significant size decrease at temperatures between 500 and 1000 degrees C in a non-oxidative environment, indicating release of adsorbed volatile material or thermally induced rearrangement of the agglomerate structure. Activation energies determined are 114, 109, and 108 kJ mol(-1) for the 10, 50, and 75% load particles, respectively. These activation energies are lower than for flame soot (Higgins et al. J. Phys. Chem. A 2002, 106, 96), but the preexponential factors are lower by 3 orders of magnitude, and the overall oxidation rates are slower by up to a factor of 4 over the temperature range studied. Possible reasons for the differences are discussed in the text.     

Size-dependent dry deposition of airborne polybrominated diphenyl ethers in urban Guangzhou, China

Gaseous and size-segregated particulate PBDEs (specifically BDE-47, -99, -183, -207, and -209) in the air were measured in urban Guangzhou at 100 and 150 m above the ground in daytime and at night in August and December 2010, to assess dry deposition of these contaminants accurately with regards to influences of meteorological factors but without confounding surface effects. Particulate PBDEs were more abundant at night than in daytime, and slightly higher in winter than in summer, likely from varying meteorological conditions and atmospheric boundary layers. More than 60% of particulate-phase PBDEs was contained in particles with an aerodynamic diameter (D(p)) below 1.8 μm, indicating long-range transport potential. The average daily particle dry deposition fluxes of PBDEs in August ranged from 2.6 (BDE-47) to 88.6 (BDE-209) ng m(-2) d(-1), while those in winter ranged from 2.0 (BDE-47) to 122 (BDE-209) ng m(-2) d(-1). Deposition fluxes of all PBDE congeners were significantly higher in daytime than at night for both months, due to the effect of diurnal variability of meteorological factors. In addition, mean overall particle deposition velocities of individual BDE congeners ranged from 0.11 to 0.28 cm s(-1). These values were within a factor of 2 of assumed values previously used in southern China and the Laurentian Great Lakes, suggesting that such assumptions were reasonable for sites with similar particulate size distributions and PBDE sources. Dry deposition velocities of PBDEs were lower at night than those in the daytime, probably reflecting higher mechanical and thermal turbulence during daytime. Dry deposition of particulate-bound PBDEs is influenced by short-term temporal variability from meteorological factors, and also by particulate size fractions.