Diesel engines are the main source of rapidly-growing energy consumption worldwide. Diesel consumption is responsible for serious air pollution, which includes nitrogen oxides (NOx), hydrocarbon ...(HC), carbon monoxide (CO) emissions and some particulate matter (PM) discharged from the combustion chamber. In the past few decades, alternative fuels, such as alcohol, biodiesel, natural gas, and Di Methyl Ether (DME), have been used in diesel engines to reduce energy costs and environmental pollution. As a result of alternative fuels directives, an increasing number of diesel engines have adapted dual fuel blends, and an enormous amount of research is focused on new and inadequately studied combustion and emission profiles. Compared to conventional diesel fuel, the application of dual fuels would add new parameters to combustion and emission profiles for diesel vehicles worldwide. This review aims to reveal (1) Known and anticipated combustion characteristics and emissions products from dual fuels. (2) Toxic properties and the expected influence on engine performance. (3) Identifying promising alternative fuels for emissions control in compression combustion engines. The results presented herein will show a significant reduction of regular gas and PM emissions by the use of alcohol/diesel dual fuel, while unregulated emissions such as methanol, ethanol, acetaldehyde, formaldehyde, ketone, have increased compared to those from diesel fuel. PM emissions decreased significantly with the increase of alternative fuels, such as alcohols, natural gas, biodiesel and DME, while regular gaseous emissions varied depending on the type alternative fuel and the engine conditions. As one new and cleaner substitute for diesel engines, DME operation has a longer injection delay, lower maximum cylinder pressure, a lower ratio of pressure rise, and shorter ignition delay in comparison with diesel operation--the opposite of alcohol/diesel and dual fuels. This review evaluates the effects of some alternative fuels (alcohol, biodiesel, natural gas and Di Methyl Ether (DME)) on combustion characteristics and emission products from diesel engines to meet future emission regulations using alternative fuel.
In this paper, we propose and demonstrate a gas pressure fiber probe with high sensitivity magnified by Vernier effect. The probe is composed of two cascaded Fabry-Perot interferometers based on a ...SMF-SOHST-OFC structure (SMF: single-mode fiber; SOHST: side-opened hollow silica tube; OFC: optical fiber column). The high-frequency CO 2 laser drilling method for hollow silica tube can effectively maintain the transient balance of the air pressure inside and outside the cavity without destroying the reflective ends of the optical fibers. Experimental results show that the prepared fiber probe with the SOHST length of 375.2 μm and column length of 247.3 μm has high gas pressure sensitivity of 80.3 pm/kPa by demodulating Vernier envelope, and it has relatively low temperature cross-sensitivity of -1.33 kPa/°C. This sensor is highly sensitive and of compact size, which not only can be applied in gas pressure sensing but also has the potential for application in microfluidic detection.
Fused deposition modeling (FDM) is a rapidly growing 3D printing technology. However, printing materials are restricted to acrylonitrile butadiene styrene (ABS) or poly (lactic acid) (PLA) in most ...Fused deposition modeling (FDM) equipment. Here, we report on a new high-performance printing material, polyether-ether-ketone (PEEK), which could surmount these shortcomings. This paper is devoted to studying the influence of layer thickness and raster angle on the mechanical properties of 3D-printed PEEK. Samples with three different layer thicknesses (200, 300 and 400 μm) and raster angles (0°, 30° and 45°) were built using a polyether-ether-ketone (PEEK) 3D printing system and their tensile, compressive and bending strengths were tested. The optimal mechanical properties of polyether-ether-ketone (PEEK) samples were found at a layer thickness of 300 μm and a raster angle of 0°. To evaluate the printing performance of polyether-ether-ketone (PEEK) samples, a comparison was made between the mechanical properties of 3D-printed polyether-ether-ketone (PEEK) and acrylonitrile butadiene styrene (ABS) parts. The results suggest that the average tensile strengths of polyether-ether-ketone (PEEK) parts were 108% higher than those for acrylonitrile butadiene styrene (ABS), and compressive strengths were 114% and bending strengths were 115%. However, the modulus of elasticity for both materials was similar. These results indicate that the mechanical properties of 3D-printed polyether-ether-ketone (PEEK) are superior to 3D-printed ABS.
Phagocyte oxidase plays an essential role in the first line of host defense against pathogens. It oxidizes intracellular NADPH to reduce extracellular oxygen to produce superoxide anions that ...participate in pathogen killing. The resting phagocyte oxidase is a heterodimeric complex formed by two transmembrane proteins NOX2 and p22. Despite the physiological importance of this complex, its structure remains elusive. Here, we reported the cryo-EM structure of the functional human NOX2-p22 complex in nanodisc in the resting state. NOX2 shows a canonical 6-TM architecture of NOX and p22 has four transmembrane helices. M3, M4, and M5 of NOX2, and M1 and M4 helices of p22 are involved in the heterodimer formation. Dehydrogenase (DH) domain of NOX2 in the resting state is not optimally docked onto the transmembrane domain, leading to inefficient electron transfer and NADPH binding. Structural analysis suggests that the cytosolic factors might activate the NOX2-p22 complex by stabilizing the DH in a productive docked conformation.
The development of maritime trade has greatly promoted the development of diesel engines. However, with the increasingly serious environmental problems, more and more attention has been paid to the ...exhaust emissions of high-power marine diesel engines. The restrictions on SO
x
have been implemented globally, and the limitation of the NO
x
will be the next priority. This paper illustrates (a) Principle and research progress of NO
x
emissions-reduction technology of marine diesel engine; (b) Summary of advantages and disadvantages among various reduction technologies and their reduction effects; (c) The application effect of mainstream technology on board. Firstly, since exhaust gas recirculation (EGR) can achieve Tier-III directly from Tier-I without considering the increased fuel consumption. It is deemed as the most promising technology to reduce emissions by controlling combustion condition. However, EGR has shortcomings of excessive increase in fuel consumption and generation of waste water, which need to be solved immediately. Secondly, selective catalytic reduction (SCR) is the most effective and straightforward means to achieve Tier-III. Despite of the continuous optimization of SCR unit volume, the problem of scrap catalyst seriously limits its wide application. How to match the supercharger more efficiently is a key factor in choosing between high and low pressure SCR. Thirdly, nature gas (NG) engines are capable of achieving a reduction in NO
x
, but in order to meet the requirements of Tier-III, it still needs to be assisted by other technologies. The emissions of hydrocarbon (HC) and CO in NG engines are huge defects that must be solved. Lastly, technologies such as the Miller cycle, Two-stage supercharging and mixed-water combustion can also reduce emissions but were rarely used alone. These technologies can be combined with EGR, SCR and NG engines to optimize the engines’ economy and emission characteristics.
In this study, aluminum-doped zinc oxide (Al:ZnO) thin films were grown by high-speed atmospheric atomic layer deposition (AALD), and the effects of air annealing on film properties are investigated. ...The experimental results show that the thermal annealing can significantly reduce the amount of oxygen vacancies defects as evidenced by X-ray photoelectron spectroscopy spectra due to the in-diffusion of oxygen from air to the films. As shown by X-ray diffraction, the annealing repairs the crystalline structure and releases the stress. The absorption coefficient of the films increases with the annealing temperature due to the increased density. The annealing temperature reaching 600 °C leads to relatively significant changes in grain size and band gap. From the results of band gap and Hall-effect measurements, the annealing temperature lower than 600 °C reduces the oxygen vacancies defects acting as shallow donors, while it is suspected that the annealing temperature higher than 600 °C can further remove the oxygen defects introduced mid-gap states.
Honey bees are essential pollinators threatened by colony losses linked to the spread of parasites and pathogens. Here, we report a new approach for manipulating bee gene expression and protecting ...bee health. We engineered a symbiotic bee gut bacterium,
, to induce eukaryotic RNA interference (RNAi) immune responses. We show that engineered
can stably recolonize bees and produce double-stranded RNA to activate RNAi and repress host gene expression, thereby altering bee physiology, behavior, and growth. We used this approach to improve bee survival after a viral challenge, and we show that engineered
can kill parasitic
mites by triggering the mite RNAi response. This symbiont-mediated RNAi approach is a tool for studying bee functional genomics and potentially for safeguarding bee health.
Information and communication technology (ICT) has broken the boundaries of traditional geographical space, and thus substantially promoted the development of the logistics industry. However, the ...effect of ICT on the carbon emissions of the logistics industry (CELI) has not been systematically explained. With Chinese provincial data from 2000 to 2018, this paper uses static and dynamic panel models and three robustness test methods to unveil the nonlinear impact of ICT (taking Internet usage as a proxy) on CELI. Some significant findings are concluded in this paper. (1) The relationship between Internet usage and CELI is inverted U-shaped, with the curve’s inflection point emerging in 2015. (2) The formation of the inverted U-shaped relationship is determined by the different roles of total factor productivity (TFP) and the express delivery business of the logistics industry. Specifically, Internet usage plays a positive role in TFP, which reduces carbon emissions but simultaneously increases carbon emissions by promoting the development of express delivery business. (3) The relationship between Internet usage and CELI is an inverted U-shape in the eastern and western regions, while in the central region, the relationship is linear. According to the findings, some policies at country, region and enterprise levels are highlighted in order for policymakers to utilize ICT to achieve reductions in carbon emissions.
Based on textual data mining methods and global English articles, we develop an index for measuring the uncertainty of international trade rules and evaluating the role of trade rule uncertainty in ...the relationship between international trade and carbon emissions, via a mediating effect model. The empirical results show that: (1) Increasing trade volume in developing countries contributes to a rise in trade rule uncertainty, which in turn triggers trade conflicts and even trade wars between countries. (2) There are significant correlations between international trade and carbon emissions, and international trade impacts carbon emissions in both direct and indirect ways. (3) Trade rule uncertainty plays a mediating role in the relationship between international trade and carbon emissions. (4) Trade rule uncertainty significantly impacts carbon emissions in most developed and developing countries, but the impact is not significant in the USA. Our work not only contributes to extending measurements of uncertainty but also helps to quantify the impacts of trade rule uncertainty on carbon emissions.
Abstract
In view of the problems of low straw decomposition rates and reduced soil fertility in southern Liaoning, China, we investigated the effects of no-tillage mode (NT), deep loosening + deep ...rotary tillage mode (PT), rotary tillage mode (RT) and the addition of decomposing agent (the next is called a decomposer) (NT + S, PT + S, RT + S) on the decomposition proportion of straw, respectively, by using the nylon net bag method in combination with 365-day field plot experiments. The decomposition rules of cellulose, hemicellulose and lignin as well as the dynamics of soil organic carbon (SOC), soil microbial biomass carbon (MBC) and soil dissolved organic carbon (DOC) in straw returned to the field for 15, 35, 55, 75, 95, 145 and 365 days were analyzed. The results showed that in the short term, the decomposition of straw was better in both the rotray tillage and deep loosening + deep rotary modes than in the no-tillage mode, and the addition of decomposer significantly promoted the decomposition of straw and the release of carbon from straw, among them, the RT + S treatment had the highest straw decomposition proportion and carbon release proportion in all sampling periods. After a one year experimental cycle, the RT + S treatment showed the highest proportion of cellulose, hemicellulose and lignin decomposition with 35.49%, 84.23% and 85.50%, respectively, and soil SOC, MBC and DOC contents were also higher than the other treatments with an increase of 2.30 g kg
−1
, 14.22 mg kg
−1
and 25.10 mg kg
−1
, respectively, compared to the pre-experimental soil. Our results show that in the short term, to accelerate the decomposition rate of returned straw and increase the content of various forms of carbon in soil, rotary tillage can be used to return the straw to the field, while also spraying straw decomposer on its surface. This experiment used a new straw decomposer rich in a variety of microorganisms, combined with the comparison of a variety of straw return modes, and in-depth study of straw decomposition effects of cellulose, hemicellulose and lignin. Thus, a scheme that can effectively improve the decomposition rate of straw and the content of various forms of organic carbon in soil within a short period of time was explored to provide theoretical support for the southern Liaoning.
PDF
