SUMMARY / RELATED TOPICS

Gasoline direct injection

Gasoline direct injection known as petrol direct injection, is a mixture formation system for internal combustion engines that run on gasoline, where fuel is injected into the combustion chamber. This is distinct from manifold fuel injection systems; the use of GDI can help increase engine efficiency and specific power output as well as reduce exhaust emissions. The first GDI engine to reach production was introduced in 1925 for a low-compression truck engine. Several German cars used a Bosch mechanical GDI system in the 1950s, however usage of the technology remained rare until an electronic GDI system was introduced in 1996 by Mitsubishi for mass-produced cars. GDI has seen rapid adoption by the automotive industry in recent years, increasing in the United States from 2.3% of production for model year 2008 vehicles to 50% for model year 2016. The'charge mode' of a direct-injected engine refers to how the fuel is distributed throughout the combustion chamber:'Homogeneous charge mode' has the fuel mixed evenly with the air throughout the combustion chamber, as per manifold injection.

Stratified charge mode has a zone with a higher density of fuel around the spark plug, a leaner mixture further away from the spark plug. In the homogeneous charge mode, the engine operates on a homogeneous air/fuel mixture, that there is an mixture of fuel and air in the cylinder; the fuel is injected at the beginning of the intake stroke in order to give the fuel much time to mix up with the air, so that a good homogeneous air/fuel mixture is formed. This mode allows using a conventional three-way catalyst for exhaust gas treatment. Compared with manifold injection, the fuel efficiency is only slightly increased, but the specific power output is better, why the homogeneous mode is useful for so-called engine downsizing. Most direct-injected passenger car petrol engines use the homogeneous charge mode; the stratified charge mode creates a small zone of fuel/air mixture around the spark plug, surrounded by air in the rest of the cylinder. This results in less fuel being injected into the cylinder, leading to high overall air-fuel ratios of λ > 8, with mean air-fuel ratios of λ = 3...5 at medium load, λ = 1 at full load.

Ideally, the throttle valve remains open as much as possible to avoid throttling losses. The torque is set by means of quality torque controlling, meaning that only the amount of injected fuel, but not the amount of intake air is manipulated in order to set the engine's torque. Stratified charge mode keeps the flame away from the cylinder walls, reducing the thermal losses. Since mixtures too lean cannot be ignited with a spark-plug, the charge needs to be stratified. To achieve a stratified charge, a stratified charge engine injects the fuel during the latter stages of the compression stroke. A "swirl cavity" in the top of the piston is used to direct the fuel into the zone surrounding the spark plug; this technique enables the use of ultra-lean mixtures that would be impossible with carburetors or conventional manifold fuel injection. The stratified charge mode is used at low loads, in order to reduce fuel consumption and exhaust emissions. However, the stratified charge mode is disabled for higher loads, with the engine switching to the homogeneuos mode with a stoichiometric air-fuel ratio of λ = 1 for moderate loads and a richer air-fuel ratio at higher loads.

In theory, a stratified charge mode can further improve fuel efficiency and reduce exhaust emissions, however, in practice, the stratified charge concept has not proved to have significant efficiency advantages over a conventional homogeneous charge concept, but due to its inherent lean burn, more nitrogen oxides are formed, which sometimes require a NOx adsorber in the exhaust system to meet emissions regulations. The use of NOx adsorbers can require low sulphur fuels, since sulphur prevents NOx adsorbers from functioning properly. GDI engines with stratified fuel injection can produce higher quantities of particulate matter than manifold injected engines, sometimes requiring particulate filters in the exhaust in order to meet vehicle emissions regulations; therefore several European car manufacturers have abandoned the stratified charge concept or never used it in the first place, such as the 2000 Renault 2.0 IDE petrol engine, which never came with a stratified charge mode, or the 2009 BMW N55 and 2017 Mercedes-Benz M256 engines dropping the statified charge mode used by their predecessors.

The Volkswagen Group had used fuel stratified injection in aspirated engines labelled FSI, these engines have received an engine control unit update to disable the stratified charge mode. Turbocharged Volkswagen engines labelled TSI have always used the homogeneous mode. Like the latter VW engines, newer direct injected petrol engines also use the more conventional homogeneous charge mode, in conjunction with variable valve timing, to obtain good efficiency. Stratified charge concepts have been abandoned. Common techniques for creating the desired distribution of fuel throughout the combustion chamber are either spray-guided, air-guided, or wall-guided injection; the trend in recent years is tow

Extracellular polymeric substance

Extracellular polymeric substances are natural polymers of high molecular weight secreted by microorganisms into their environment. EPSs establish the functional and structural integrity of biofilms, are considered the fundamental component that determines the physiochemical properties of a biofilm. EPSs are composed of polysaccharides and proteins, but include other macro-molecules such as DNA, lipids and humic substances. EPSs are the construction material of bacterial settlements and either remain attached to the cell's outer surface, or are secreted into its growth medium; these compounds are important in biofilm formation and cells attachment to surfaces. EPSs constitute 50% to 90% of a biofilm's total organic matter. Exopolysaccharides are high-molecular-weight polymers that are composed of sugar residues and are secreted by a microorganism into the surrounding environment. Microorganisms synthesize a wide spectrum of multifunctional polysaccharides including intracellular polysaccharides, structural polysaccharides and extracellular polysaccharides or exopolysaccharides.

Exopolysaccharides consist of monosaccharides and some non-carbohydrate substituents. Owing to the wide diversity in composition, exopolysaccharides have found multifarious applications in various food and pharmaceutical industries. Many microbial EPSs provide properties that are identical to the gums in use. With innovative approaches, efforts are underway to supersede the traditionally used plant and algal gums by their microbial counterparts. Moreover, considerable progress has been made in discovering and developing new microbial EPSs that possess novel industrial significance. Capsular exopolysaccharides can protect pathogenic bacteria against desiccation and predation, contribute to their pathogenicity. Bacteria existing in biofilms are less vulnerable compared to planktonic bacteria, as the EPS matrix is able to act as a protective diffusion barrier; the physical and chemical characteristics of bacterial cells can be affected by EPS composition, influencing factors such as cellular recognition and adhesion in their natural environments.

Furthermore, the EPS layer acts as a nutrient trap. The exopolysaccharides of some strains of lactic acid bacteria, e.g. Lactococcus lactis subsp. Cremoris, contribute a gelatinous texture to fermented milk products, these polysaccharides are digestible. An example of the industrial use of exopolysaccharides is the application of dextran in panettone and other breads in the bakery industry. Exopolysaccharides can facilitate the attachment of nitrogen-fixing bacteria to plant roots and soil particles, which mediates a symbiotic relationship; this is important for colonization of roots and the rhizosphere, a key component of soil food webs and nutrient cycling in ecosystems. It allows for successful invasion and infection of the host plant. Bacterial extracellular polymeric substances can aid in bioremediation of heavy metals as they have the capacity to adsorb metal cations, among other dissolved substances; this can be useful in the treatment of wastewater systems, as biofilms are able to bind to and remove metals such as copper, lead and cadmium.

The binding affinity and metal specificity of EPS varies depending on polymer composition, as well as environmental factors such as concentration and pH. In a geomicrobiological context, EPS has been observed to affect precipitation of minerals carbonates. EPS may bind to and trap particles in biofilm suspensions, which can restrict dispersion and element cycling. Sediment stability can be increased by EPS, as it influences cohesion and erosion of the sediment. There is evidence that the adhesion and metal-binding ability of EPS affects mineral leaching rates in both environmental and industrial contexts; these interactions between EPS and the abiotic environment allow for EPS to have a large impact on biogeochemical cycling. Due to the growing need to find a more efficient and environmentally friendly alternative to conventional waste removal methods, industries are paying more attention to the function of bacteria and their EPSs in bioremediation. Researchers found that adding EPSs from cyanobacteria to wastewaters removes heavy metals such as copper and lead.

EPSs alone can take them in through biosorption. The efficiency of removal can be optimized by treating the EPSs with different acids or bases first before adding them to the wastewaters. Contaminated soils contain high levels of polycyclic aromatic hydrocarbons. EPSs contain enzymes such as hydrolase, which are capable of degrading PAHs; the amount of PAHs degradation depends on the concentration of EPSs added to the soil. This method proves to be low cost and efficient. In recent years, EPSs from marine bacteria have been found to speed up the cleanup of oil spills. During the Deepwater Horizon oil spill in 2010, these EPS-producing bacteria were able to grow and multiply rapidly, it was found that their EPSs dissolved the oil and formed oil aggregates on the ocean surface, which sped up the cleaning process. These oil aggregates provided a valuable source of nutrients for other marine microbial communities; this let scientists optimize the use of EPSs to clean up oil spills. Acetan alginate cellulose chitosan curdlan cyclosophorans (Agr

Simeon Deming House

The Simeon Deming House is a historic residence in western Washington County, United States. Located along Willis Road northeast of the community of Watertown, the house was built in 1815 as the residence of a veteran of the American Revolution. A native of Sandisfield, Deming enlisted in the Continental Army in 1780 and was promoted to an officer's rank; the present structure is one of Ohio's oldest extant Federal houses, featuring brick walls that rest on a foundation of sandstone with a full basement. Two-and-a-half stories tall, topped with a metal roof, the walls are built in Flemish bond. Central to the four-bay symmetrical facade is a rounded-arch main doorway with a transom and the original fanlight. Deming remained in Washington County for only a short time. Despite living in Washington County for only a few years, Deming is seen as holding an important place in the area's history. In 1980, the Simeon Deming House was listed on the National Register of Historic Places. Spread out around the 4 acres surrounding the house itself are seven related buildings that were added to the Register together with the house as contributing properties.

The house qualified for inclusion on the Register for two different reasons: because of its association with Deming and because of its locally significant historic architecture