An experimental study of particulate matter emissions was conducted on a Direct Injection Gasoline (DIG) engine produced by a Chinese Original Equipment Manufacturer (OEM) to investigate the impacts ...of fuel properties from China market on particulate emissions of modern gasoline vehicles. The emissions include both the primary emissions and the secondary ones in the atmosphere. The objective of this work is to provide some experimental data and analysis on the impacts of fuel properties and vehicle technologies on Particulate Matter 2.5 (PM2.5) in China. On the basis of better understanding of those impacts, it is desired to provide some suggestions and guidelines on how to improve fuel quality and vehicle technology to help effectively reduce air pollution in China.
In this paper, six test fuels with different aromatics, olefin, sulfur, Methyl-cyclopentadienyl Manganese Tricarbonyl (MMT), ethanol content were blended and tested to research on the influences on primary particulate emission including mass, number, size distribution and compounds including Polycyclic Aromatic Hydrocarbons (PAHs) and the toxicity of PAHs emissions. The test results demonstrated that the fuel compositions impacted significantly on particulate emissions of DIG engine. Higher aromatics in gasoline resulted in much higher Particle Mass (PM), Particle Number (PN) and PAHs emission and much higher toxicity to human health. Reducing olefin content in gasoline showed benefits to a certain degree on reducing PM and PN emission especially under high load engine operation conditions, and did not show obvious improvement of PAHs emission factor, but reduced the toxicity of PAHs. 10% of Ethanol in gasoline showed limited improvement on particulate emissions comparing with the effect of reducing aromatics and olefin content in gasoline, moreover E10 increased PN emission under low load conditions. The test results also demonstrated that the typical China Phase V gasoline did not show benefits of reducing vehicle emissions the typical Phase IV gasoline with higher sulfur (<=50ppm) and manganese (<=8mgMn/l) in China market.
The particulate compounds of DIG engine mainly consisted Elemental Carbon (EC), Organic Matter (OM) and small amount of inorganic ions. The mass percentage of EC in total PM increased as the load of engine rose. Three-way Catalyst (TWC) is more effective in reducing OM than EC, with the overall OM reduction rate of 67–85%.
Energy transformation and environmental quality are now fundamental components of China’s economic development plans, which are being reorganized to ensure the dependability of the energy supply and ...protect environmental quality. Nonetheless, technical inefficiency is one of the most significant obstacles to achieving these overall objectives. Therefore, utilizing yearly data from 2000 to 2021 and the autoregressive distributed lag model, this article examines the implications of information and communication technology trade openness on China’s energy transformation and environmental quality. The findings indicate that information and communication technology trade openness has a favorable impact on environmental quality as a consequence of its negative impact on carbon dioxide emissions. Moreover, the findings indicate that information and communication technology trade openness has a beneficial impact on energy transformation due to its positive impact on renewable energy consumption and negative impact on energy intensity. In conclusion, our findings demonstrate the necessity of eliminating obstacles to information and communication technology trade in China in terms of guaranteeing energy transformation and environmental quality. Therefore, it is optimal for China’s government to progressively reduce trade barriers in order to increase cross-border flows of information and communication technology products.
Surface-layer defects of M-plane sapphire caused by ultrasonic vibration-assisted cutting were investigated in this paper through comparison cutting experiments. Topography analysis results indicate ...that when the cutting direction is not along a-axis or c-axis, the spalling defects of conventional cutting groove are asymmetric because the probabilities of activated cleavage/twinning systems vary with machining direction; however, the vibrational cutting groove presents better symmetry and less spalling owning to the propagation of stress wave. The cross-section of cutting groove was obtained by focus ion beam cutting. The cross-section analysis shows that the subsurface defects of conventional cutting groove involve median cracks and lateral cracks, and the main propagating path of cracks is towards downward, which is the cause of the generation of serious spalling; however, lateral cracks are the main defect in the subsurface of the vibrational cutting groove, and they mainly propagate towards the free surface and give rise to material removal. The subsurface quality of cutting groove with ultrasonic assistance is better than that of the conventional cutting groove. It is evident that ultrasonic vibration can prevent the median crack from extending towards bulk material and contribute to improve the uniformity of groove quality.
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•Crystal indices are considered in computing the probability of deformation system.•Subsurface defects are more serious in traditional cutting groove.•Vibration-assisted cutting improves the uniformity of groove quality.•Ultrasonic vibration can prevent median crack from extending in bulk material.
During peritectic steel continuous casting, mold flux properties and flux film structures play significant roles in controlling slab quality. In this study, mold fluxes and flux films for casting ...peritectic steel slab were obtained using mineral raw materials such as quartz, wollastonite, fluorite, soda ash and others. The effects of mineral raw materials on mold flux properties and flux film structures were investigated through the measurement of melting point, viscosity, crystallization temperature, critical cooling rate, crystallization ratio and crystalline phase content. The results indicated that with increasing the quartz addition (16 to 24 mass%) and the wollastonite addition (11 to 19 mass%) in mineral raw materials, the melting point, viscosity and wollastonite content of flux film increased, while the crystallization temperature, critical cooling rate, crystallization ratio and cuspidine content of flux film decreased. The melting point, viscosity and wollastonite content of flux film reduced with increasing the fluorite addition (8 to 16 mass%) and soda ash addition (10 to 18 mass%) in mineral raw materials. Furthermore, compared with soda ash, the fluorite predominantly enhanced the crystallization temperature, critical cooling rate, crystallization ratio, cuspidine content of flux film. In addition, it was showed that the heat transfer performance and the slab quality might be primarily attribute to the crystallization ratio and cuspidine content of flux film. These results provided a theoretical foundation for optimizing the mold flux of the peritectic steel and were vital to improving the slab quality.
Precast segmental girder bridges are threatened by impact loads during service, but there is currently little research on the impact behavior of such bridges. This study investigated the dynamic ...responses and failure modes of precast assembled segmental beams experimentally and numerically. 10 beam specimens were designed for static and impact tests, respectively. Numerical simulations were conducted in LS-DYNA and verified by comparing them with the test results. Failure mechanisms were analyzed by verified models. The results show that the local shear failure mechanism is prominent under impact loading. Two typical failure modes were obtained: oblique section failure and joint section direct shear failure, which are related to the relative positions of joint and impact point. Confining stress can effectively improve the static bearing capacity and impact resistance, but has little effect on the early response and final failure mode. The main failure cracks occur near the joint bottom in the initial stage of impact, when the impact force is resisted by the inertia force, resulting in a characteristic “N” shape in shear force distribution. Shear failure of the joints dominates the beam failure mode. A dynamic shear span ratio can evaluate the early force characteristics of the joint section.
A novel precast segmental barrier system was proposed to facilitate the connections between barriers and between the barrier and bridge deck by casting ultra-high-performance concrete joints in situ. ...To assess the performance of the barrier with this connection, a full-scale pseudo-static tests were conducted. At the same time, a comparative assessment was considered the failure mode and load capacity of the precast barrier for two different bridge deck stiffnesses. The results indicated that the ultimate capacity of the precast barrier was comparable to that of a traditional cast-in-place barrier and emphasised the critical role of the deck slab stiffness in the overall load capacity. Based on the damage patterns observed in the barrier and deck slab during the pseudo-static tests, a refined trapezoidal yield-line model considering the deck slab stiffness contribution was derived to more accurately evaluate the load capacity of a precast segmental barrier. Moreover, the calibrated numerical model of the barrier system was employed to investigate the structural dynamic performance under varying scenarios, specifically examining the effects of different impact masses and velocities. Numerical results demonstrated that upon impact by a high-mass, high-velocity object, the barrier experienced a shift in damage mode from flexural–shear to more critical punching shear. This transition concentrated the dynamic load exclusively on the impacted barrier segment, which in turn markedly diminished its dynamic load capacity.
Emissions from gasoline vehicles have recently become one of the main causes for urban air pollution. In this work, individual particles of particulate matter emitted from the gasoline engines on the ...test bench were characterised using transmission electron microscopy coupled with energy-dispersive X-ray spectrometry (TEM-EDX). Effects of the engine types (gasoline direct injection (GDI) engines and port fuel injection (PFI) engines), fuel components (F1–5), engine loads (25, 50, and 75%), and three-way catalyst (TWC) on particulate emissions were tested. The results show that there were six types of individual particles emitted from gasoline engines including soot, organic particles, Fe-rich particles, S-rich particles, Mn-rich particles, and Ca-rich particles, in which the organic, soot, and S-rich particles were predominant types. The particles emitted from GDI engines had a higher percentage of soot and lower percentage of organic particles compared to those from PFI engines. Fuel types also influenced compositions of the emitted particles. F1 produced a relatively high percentage of organic particles. Compared to F1, F2 containing more aromatics contributed a higher percentage of soot particles; F3 containing MMT (methylcyclopentadienyl manganese tricarbonyl) led to a considerably higher percentage of soot particles, and F4 gasoline (addition of 10% ethanol by volume) produced a lower percentage of soot particles. Compared to F1, F5 with a lower olefin content produced a lower percentage of organic particles. In addition, with increasing load, the relative percentages of soot increased, while the relative percentages of organic particles decreased. Finally, when TWC was used, the percentage of soot increased significantly in association with an increase in particle sizes.
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•Gasoline engines emit soot, organic, S-rich, Fe-rich, Ca-rich, and Mn-rich particles.•Engine types, loads, and fuel components impact relative proportions of individual particles.•The GDI engines emit an obviously higher number of particles than the PFI engines.•The GDI engines emit mainly soot, organic and S-rich particles, while the PFI engines emit mainly organic particles.
High-resolution and high-accuracy mapping products of the Lunar South Pole (LSP) will play a vital role in future lunar exploration missions. Existing lunar global mapping products cannot meet the ...needs of engineering tasks, such as landing site selection and rover trajectory planning, at the LSP. The Lunar Reconnaissance Orbiter (LRO)’s narrow-angle camera (NAC) can acquire submeter images and has returned a large amount of data covering the LSP. In this study, we combine stereo-photogrammetry and photoclinometry to generate high-resolution digital orthophoto maps (DOMs) and digital elevation models (DEMs) using LRO NAC images for a candidate landing site at the LSP. The special illumination and landscape characteristics of the LSP make the derivation of high-accuracy mapping products from orbiter images extremely difficult. We proposed an easy-to-implement shadow recognition and contrast stretching method based on the histograms of the LRO NAC images, which is beneficial for photogrammetric and photoclinometry processing. In order to automatically generate tie points, we designed an image matching method considering LRO NAC images’ features of long strips and large data volumes. The terrain and smoothness constraints were introduced into the cost function of photoclinometry adjustment, excluding pixels in shadow areas. We used 61 LRO NAC images to generate mapping products covering an area of 400 km2. The spatial resolution of the generated DOMs was 1 m/pixel, and the grid spacing of the derived DEMs was 1 m (close to the spatial resolution of the original images). The generated DOMs achieved a relative accuracy of better than 1 pixel. The geometric accuracy of the DEM derived from photoclinometry was consistent with the lunar orbiter laser altimeter (LOLA) DEM with a root mean square error of 0.97 m and an average error of 0.17 m.
Damage identification is a key issue in structural health monitoring and safety state assessment. Damage information extraction from measurements is difficult due to environmental noise and ambient ...excitation, which greatly reduce the accuracy of structural damage identification. In this study, a structural damage information amplification method based on Mahalanobis distance cumulant (MDC) and intrinsic mode function (IMF) was proposed. Firstly, the measurements of the structure were decomposed by the empirical mode decomposition (EMD) technology, and the relative energy change rate of each order IMF was used to screen the damage-sensitive component. By comparing the damage identification vectors constructed by MDC values from the raw measured parameters, the damage-sensitive component can obtain more damage information making damage detecting efficient. Meanwhile, the area difference of the probability density function of MDC values was used to assess the damage information amplification to determine the appropriate level of accumulation by using the cyclic analysis procedure. The model simulations and experiments were carried out to verify the method. The results showed that the selected damage-sensitive component used for constructing MDC values can amplify the damage information and make better accuracy for damage identification.
In the numerical analysis of electromagnetic scattering from random rough surfaces, the spectral acceleration (SA) algorithms proposed by Chou, Torrungrueng, and Johnson are very efficient in their ...capability of producing an O(N) iterative method of moment for 1-D lossless rough surfaces, where N is the number of surface unknowns. In this paper, we propose a method to extend the SA method to the lossy surfaces, where the magnitude of the complex radiation function may take noncanonical forms along the deformed integration path when evaluating the spectral representation of Green's function. The proposed method specifies ways on how the integration path in the complex angular plane should be deformed, how the domain of integration should be determined, and how the integration step size should be adjusted. It is shown to be very accurate through comparison with the exact results of Green's function. Its combination with the right-preconditioned generalized minimal residual (GMRES-RP) method renders an efficient and robust algorithm capable of handling both lossless and lossy rough surfaces. The predicted bistatic scattering coefficients agree almost perfectly with that of direct matrix inversion. The conservation of energy holds very well under a wide range of surface roughness and dielectric constant conditions. The proposed method thus provides a means for the analysis of scattering from rough surfaces, under realistic settings, and holds the potential for numerous important applications such as under surface target detection.
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