Spark-based Advanced Ignition Control for Future Diluted Gasoline Engines

To meet the mandatory CO2 emissions regulations in the future, current gasoline engines require significant work for efficiency improvement. One critical part of combustion optimization is to improve the spark ignition process, especially for the engines that utilize charge dilution concept incorporated with strong cylinder flow. Such high efficiency combustion process requires the ignition systems to effectively ignite the mixture and secure the flame kernel until developing to self-sustainable propagation. In this paper, the extent of spark stretching and the ability to withhold from restrike in high-speed flow are investigated for various sparking strategies. A thick plasma channel that is generated by boosted glow current is less prone to be blown off by the strong flow, consequently, the restrike frequency is lowered. In comparison with a low current long lasting spark generated by the dual-coil continuous discharge strategy, the boosted current strategy can lead to a faster flame kernel growth. Single-cylinder engine experiments indicate that the combustion phasing controllability and the stability of lean/diluted engine operation can be improved by using the boosted current ignition strategies with conventional spark plug. Extensive engine test results indicate that the multi-core ignition can better control the gasoline combustion and extend the operable limits of lean/diluted engine combustion, compared with single-pole ignition for low to medium engine loads. Experimental results indicate that the multi-core ignition strategy, even with lower current on each pole, have clear advantages over the high current single-pole strategies such as the multi-coil ignition and the boosted current ignition, with respect to the combustion phasing controllability of super lean gasoline combustion. Multiple-cylinder production gasoline engine test results show that the multi-core ignition can improve the stability of gasoline engine at high levels of dilution, thereby leading to improvement of indicated specific fuel consumption

Individual and Joint Effects of Early-Life Ambient PM2.5 Exposure and Maternal Prepregnancy Obesity on Childhood Overweight or Obesity

Background: Although previous studies suggest that exposure to traffic-related pollution during childhood increases the risk of childhood overweight or obesity (COWO), the role of early life exposure to fine particulate matter (aerodynamic diameter <2.5μm; PM2.5) and its joint effect with the mother's prepregnancy body mass index (MPBMI) on COWO remain unclear. Objectives: The present study was conducted to examine the individual and joint effects of ambient PM2.5 exposures and MPBMI on the risk of COWO. Methods: We estimated exposures to ambient PM2.5 in utero and during the first 2 y of life (F2YL), using data from the U.S. Environmental Protection Agency’s (EPA's) Air Quality System matched to residential address, in 1,446 mother–infant pairs who were recruited at birth from 1998 and followed up prospectively through 2012 at the Boston Medical Center in Massachusetts. We quantified the individual and joint effects of PM2.5 exposure with MPBMI on COWO, defined as the child's age- and sex-specific BMI z-score ≥85th percentile at the last well-child care visit between 2 and 9 y of age. Additivity was assessed by estimating the reduced excess risk due to interaction. Results: Comparing the highest and lowest quartiles of PM2.5, the adjusted relative risks (RRs) [95% confidence intervals (CIs)] of COWO were 1.3 (95% CI: 1.1, 1.5), 1.2 (95% CI: 1.0, 1.4), 1.2 (95% CI: 1.0, 1.4), 1.3 (95% CI: 1.1, 1.6), 1.3 (95% CI: 1.1, 1.5) and 1.3 (1.1, 1.5) during preconception; the first, second, and third trimesters; the entire period of pregnancy; and F2YL, respectively. Spline regression showed a dose–response relationship between PM2.5 levels and COWO after a threshold near the median exposure (10.46μg/m3–10.89μg/m3). Compared with their counterparts, children of obese mothers exposed to high levels of PM2.5 had the highest risk of COWO [RR≥2.0, relative excess risk due to interaction (RERI) not significant]. Conclusions: In the present study, we observed that early life exposure to PM2.5 may play an important role in the early life origins of COWO and may increase the risk of COWO in children of mothers who were overweight or obese before pregnancy beyond the risk that can be attributed to MPBMI alone. Our findings emphasize the clinical and public health policy relevance of early life PM2.5 exposure. https://doi.org/10.1289/EHP26

SV2 Mediates Entry of Tetanus Neurotoxin into Central Neurons

Tetanus neurotoxin causes the disease tetanus, which is characterized by rigid paralysis. The toxin acts by inhibiting the release of neurotransmitters from inhibitory neurons in the spinal cord that innervate motor neurons and is unique among the clostridial neurotoxins due to its ability to shuttle from the periphery to the central nervous system. Tetanus neurotoxin is thought to interact with a high affinity receptor complex that is composed of lipid and protein components; however, the identity of the protein receptor remains elusive. In the current study, we demonstrate that toxin binding, to dissociated hippocampal and spinal cord neurons, is greatly enhanced by driving synaptic vesicle exocytosis. Moreover, tetanus neurotoxin entry and subsequent cleavage of synaptobrevin II, the substrate for this toxin, was also dependent on synaptic vesicle recycling. Next, we identified the potential synaptic vesicle binding protein for the toxin and found that it corresponded to SV2; tetanus neurotoxin was unable to cleave synaptobrevin II in SV2 knockout neurons. Toxin entry into knockout neurons was rescued by infecting with viruses that express SV2A or SV2B. Tetanus toxin elicited the hyper excitability in dissociated spinal cord neurons - due to preferential loss of inhibitory transmission - that is characteristic of the disease. Surprisingly, in dissociated cortical cultures, low concentrations of the toxin preferentially acted on excitatory neurons. Further examination of the distribution of SV2A and SV2B in both spinal cord and cortical neurons revealed that SV2B is to a large extent localized to excitatory terminals, while SV2A is localized to inhibitory terminals. Therefore, the distinct effects of tetanus toxin on cortical and spinal cord neurons are not due to differential expression of SV2 isoforms. In summary, the findings reported here indicate that SV2A and SV2B mediate binding and entry of tetanus neurotoxin into central neurons

Three-dimensional nonlinear analysis of seismic ground response of soft soils in Shanghai

Reduced order bounding surface model was employed to study 3-D seismic ground response of site considering the nonlinearity of soft soils in Shanghai. A nonlinear procedure for response analysis of horizontal layered sites subjected to multidirectional earthquake loading was used to study vertical and horizontal ground responses, respectively, under unidirectional and multidirectional base excitations (Taft). Also, the development of ratio of vertical and horizontal peak acceleration and the effects of the variation of groundwater table on the characteristics of seismic responses were studied. The study results show that the characteristics of vertical seismic ground response are much different from those of horizontal seismic ground response; the amplification effect is greatly increased under multidirectional base excitations compared with that under unidirectional base excitations; greatly difference is induced by the rise of groundwater table between vertical and horizontal seismic response, as result of the rise of groundwater table, seismic amplification effect at ground surface increases in horizontal direction, but decreases in vertical direction，which are important for geotechnical engineering aseismic design in Shanghai region

What if the Irresponsible Teachers Are Dominating?

As the Internet-based crowdsourcing services become more and more popular, learning from multiple teachers or sources has received more attention of the researchers in the machine learning area. In this setting, the learning system is dealing with samples and labels provided by multiple teachers, who in common cases, are non-expert. Their labeling styles and behaviors are usually diverse, some of which are even detrimental to the learning system. Thus, simply putting them together and utilizing the algorithms designed for single-teacher scenario would be not only improper, but also damaging. The problem calls for more specific methods. Our work focuses on a case where the teachers are composed of good ones and irresponsible ones. By irresponsible, we mean the teacher who takes the labeling task not seriously and label the sample at random without inspecting the sample itself. This behavior is quite common when the task is not attractive enough and the teacher just wants to finish it as soon as possible. Sometimes, the irresponsible teachers could take a considerable part among all the teachers. If we do not take out their effects, our learning system would be ruined with no doubt. In this paper, we propose a method for picking out the good teachers with promising experimental results. It works even when the irresponsible teachers are dominating in numbers

Field measurement and numerical analysis of ground vibration caused by metro

This paper presents the field measurement of ground vibration at the section of Long-Yang station along the Metro line 2 in Pudong of Shanghai. With the loading data for calculation from the measurement, the ground vibration caused by metro is simulated by the finite element method (FEM). Then the characteristic of wave propagation is obtained along the ground. The influences of the embedded depth of tunnel on vibration are discussed. Finally, the main causes of the differences between calculation and measurement are analyzed

Ground vibration analysis caused by China railway high- speed with track geometric irregularities

A semi-analytical approach, considering the effects of track geometric irregularities on the wheel/rail force, is presented in this paper to simulate the ground vibration induced by moving train loading. The; train is studied as a secondary suspension mechanical system. The track and the attached sleepers are simplified as Euler beams resting on infinite half-space. Based on the compatibility condition of deformation, combining with the 2.51) FEM for layered soil, the semi-analytical solutions of dynamic wheel/rail forces are obtained implicitly. Detailed analyses and discussions of the wheel/rail forces and ground vibration are carried out. The results show that the track geometric irregularities exert an important influence on dynamic wheel/rail forces and ground vibration. With the track geometric irregularity unchanged, the wheel/rail forces linearly increase with the increasing train speed; With the wavelength of the track geometric irregularities unchanged, the wheel/rail forces and ground vibration acceleration increases with the increasing track irregularity amplitude; With the track irregularity amplitude unchanged, the wheel/rail forces and ground vibration acceleration decreases with the increasing wave length of track irregularities

Effect of rise of ground water table on seismicground response of soft soil in Shanghai

A dynamic model is developed based on the results of geological investigations as well as laboratory and field tests in Shanghai. The Biot\u27s dynamic consolidation theory and reduced order bounding surface model are coupled to study the effect of the rise of groundwater table on the seismic ground response of soft soil undergoing 3-D seismic base excitations (which are obtained from Taft). The effect of the rise of groundwater table on the horizontal and vertical amplification factors, the ratio of vertical to horizontal peak acceleration, the characteristics of acceleration and response spectrum at ground surface as well as the maximum pore water pressure and pore water pressure ratio along the depth of soil layer are studied. The results show that the rise of groundwater table has dramatically different influences on the horizontal and vertical amplification effect as well as the characteristics of acceleration andresponse spectrum at ground surface. As the result of the rise of groundwater table, the amplification effect increases in horizontal direction but decreases in vertical direction. The ratio of vertical to horizontal acceleration decreases. The filtering effect on the acceleration with high frequency and the amplification effect on the acceleration with long period increase. The range of liquefiable soil near ground surface extends and hazard risk increases