Effect of spark advance and fuel on knocking tendency of spark ignited engine

Knock, in spark ignition engine is the combustion caused by the autoignition of the fuel-air mixture. It is the phenomenon that limits engine performance and thermal efficiency. Knock also has an adverse effect on emissions and fuel economy. Engine designers target engines with maximum power and torque output without compromising on fuel economy. Engine downsizing is the method generally adopted. The main goal of engine downsizing is to achieve better fuel economy while increasing the power and torque output of the engine. Better fuel economy is achieved by reducing the displaced volume which in turn means a much higher brake mean effective pressure. It is common for downsized engines to have BMEP values higher than 20 bar. As a comparison, this value reduces to about 15 bar without downsizing for the same power output. To compensate for the reduced volume, boosting devices like turbochargers or superchargers are incorporated. This increased pressure leads to a higher temperature of the compressed mixture. As a result, the self-ignition temperature is attained quicker than expected which promotes the occurrence of knock. When targeting high engine outputs at lower speeds, sustained knocking events can prove to cause catastrophic engine damage. The need to understand the phenomenon of knock as completely as possible is extremely important. Elimination of knock will prove to be vital for further engine development. The major factors affecting knock are the octane rating of the fuel, spark timing, compression ratio of the engine, the percentage of exhaust gas re-circulation employed and lambda value. This report studies the effect of changing the fuel octane rating and spark timing on intensity of knock. The report briefly introduces knock, theories of its occurrence, detection methods and control techniques. Three fuels, E10 87, E0 91 and E15 91 were tested on a spark ignited, liquid cooled, two-cylinder carbureted engine. The fuels were selected as they represent a range of octane ratings usually available for daily use. In-cylinder pressure and crankcase vibrations are the two parameters used for knock detection. Each fuel was tested for a set of three spark timings set 10 CAD apart. With an increase in spark advance, the knocking intensity increases when all other engine operating parameters are maintained constant. From the comparison of results for E0 91 and E15 91 fuels it can be concluded that the knock intensity decreases with an increase in ethanol content when all other engine operating conditions, including fuel octane rating and spark advance, were kept unchanged. Finally, the comparison of results from E0 91 and E10 87 fuels exhibit mixed effects of rise in ethanol levels and drop in octane rating on the knock intensity. While, for lower loads, the effect of increase in octane rating dominates resulting in lower knock intensity for E0 91, for higher loads the increase in ethanol content seems to have an upper hand resulting in lower knock intensity for E10 87 fuel

Low-Noise Large-Area Photoreceivers with Low Capacitance Photodiodes

A quad photoreceiver includes a low capacitance quad InGaAs p-i-n photodiode structure formed on an InP (100) substrate. The photodiode includes a substrate providing a buffer layer having a metal contact on its bottom portion serving as a common cathode for receiving a bias voltage, and successive layers deposited on its top portion, the first layer being drift layer, the second being an absorption layer, the third being a cap layer divided into four quarter pie shaped sections spaced apart, with metal contacts being deposited on outermost top portions of each section to provide output terminals, the top portions being active regions for detecting light. Four transimpedance amplifiers have input terminals electrically connected to individual output terminals of each p-i-n photodiode

Study of instabilities and outbursts in luminous blue variables AF And &\& R 127

Luminous blue variables (LBVs) are evolved massive stars close to the Eddington limit, with a distinct spectroscopic and photometric variability having unsteady mass-loss rates. These stars show a considerable change in their surface temperature from quiescent to outbursts phase. The cause of irregular variability and unsteady mass-loss rate is not properly understood. Here we present the result of linear stability analysis in two LBVs AF And and R 127 during their quiescent and outburst phase. We note that several modes are unstable in the models of the considered LBVs. Mode interaction is frequent in the modal diagrams for the models of both LBVs. For AF And, number of instabilities increase in models having temperature below 15000 K. The found instabilities may be linked with the observed irregular variabilities and surface eruptions. Observational facilities of Belgo-Indian Network for Astronomy and Astrophysics (BINA) will be very beneficial to study the spectroscopic and photometric behavior of the considered LBVs.Comment: 7 pages, 3 figures, Proceedings paper of the third Belgo-Indian Network for Astronomy and Astrophysics (BINA) workshop, Accepted for publication in the Bulletin of Li\`ege Royal Society of Science

Successful Space Flight of High-Speed InGaAs Photodiode Onboard the International Space Station

Photonic systems are required for several space applications, including satellite communication links and lidar sensors. Although such systems are ubiquitous in terrestrial applications, deployment in space requires the constituent components to withstand extreme environmental conditions, including wide operating temperature range, mechanical shock and vibration, and radiation. These conditions are significantly more stringent than alternative standards, namely Bellcore GR-468 and MIL-STD 883, which may be satisfied by typical, commercially available, photonic components. Furthermore, it is very difficult to simultaneously reproduce several aspects of space environment, including exposure to galactic cosmic rays (GCR), in a laboratory. Therefore, it is necessary to operate key photonic components in space to achieve a technology readiness level of 7 and beyond. Accordingly, the International Space Station (ISS) provides an invaluable test bed for qualifying such components for space missions. We present a fiber-pigtailed photodiode module, having a -3 dB bandwidth of 16.8 GHz, that survived 18 months on the ISS as part of the Materials International Space Station Experiment (MISSE) 7 mission. This module was launched by NASA Langley Research Center on November 16, 2009 on the Space Shuttle Atlantis (STS-129), as part of their lidar transceiver components. While orbiting on the ISS in a passive experiment container, the photodiode module was exposed to extreme temperature cycling from -157 degrees Celsius to +121 degrees Celsius 16 times a day, proton radiation from the inner Van Allen belt at the South Atlantic Anomaly, and galactic cosmic rays. The module returned to Earth on the Space Shuttle Endeavor (STS-134) on June 1, 2011 for further characterization. The post flight test of the photodiode module, shown in Fig. 1a, demonstrates no change in the module's performance, thus proving its survivability during launch and in space environment

Instabilities in models of supergiants MWC 137 and MWC 314

In several B-type supergiants photometric and spectroscopic variabilities together with episodes of enhanced mass-loss have been observed. Here we present the preliminary results of linear stability analysis followed by nonlinear numerical simulations in two B-type supergiants MWC 137 and MWC 314. All the considered models of MWC 137 having mass in the range of 30 M$_{\odot}$ to 70 M$_{\odot}$ are unstable while for the case of MWC 314 models with mass below 31 M$_{\odot}$ are unstable. The instabilities have been followed into nonlinear regime for selected models of these two supergiants. During the nonlinear numerical simulations, instabilities lead to finite amplitude pulsation with a well defined saturation level in the considered models of MWC 137 with mass greater than 42 M$_{\odot}$. The model of MWC 314 with mass of 40 M$_{\odot}$ - the suggested mass for the primary star - does not show any instabilities both in linear stability analysis and nonlinear numerical simulations. Velocity amplitude reaches to 10$^7$ cm/s in the nonlinear regime for the model of MWC 314 with mass of 30 M$_{\odot}$. Further extensive numerical simulations and observations are required to understand the origin of the observed variabilities in these stars.Comment: 8 pages, 4 figures, Accepted for publication in the Bulletin of Li\`ege Royal Society of Science

Electron Beam Irradiation of Sliced Fresh Cucumber (Cucumis sativus)

A healthy and balance diet includes consumption of fresh fruits and vegetables. Cucumber (Cucumis sativus) is one of the most cultivated vegetable in the world and is mostly consumed raw. Raw products are recognized as important vehicles for the transmission of human pathogens which causes foodborne illness. According to the Center of Disease Control and Prevention (CDC) Foodborne Outbreak Online Database, there were nine outbreaks due to Salmonella Poona associated with consumption of contaminated food between 1998 and 2008. From July 2015 until February 2016, multistate Salmonella Poona outbreak in the USA was reported due to the consumption of contaminated and imported Californian cucumbers. Hence, measures to decontaminate fresh produce are necessary. Electron-beam irradiation is an effective nonthermal method of decontamination against pathogens such as Salmonella Poona. However, irradiation of fresh produce such as cucumbers could produce negative quality effects such as loss of texture, flavor, and nutrients. Therefore, the process must be characterized. The main objective of this study was to (1) determine the radiation D10-value of Salmonella Poona on sliced cucumber; (2) quantify the effect of electron-beam irradiation on the product quality attributes (texture and color) throughout storage at refrigeration temperature (4-5°C); and (3) optimize irradiation treatment of sliced cucumbers to ensure proper decontamination (5D) while maintaining produce quality. Five (± 2) grams of fresh cucumber was inoculated with 0.5 ml of a 10^8 CFU/mL of the bacterial culture of Salmonella Poona in sterile bags (18-oz). Samples were irradiated at room temperature with up to 1 kGy with an increment of 0.2 kGy using a low energy electron beam to find the D10-value of the pathogens. Samples were also be irradiated at a 5D dose for decontamination of the pathogen. Irradiated samples were stored at 4-5°C and analyzed for product quality in terms of texture, color, water activity, moisture content, pH, and sensory characteristics for 3 days. All tests were performed in three replications. Non-irradiated samples served as controls. The D10-value of the Salmonella Poona strain used in this study was found 0.38 ± 0.03 kGy. Firmness (texture) of irradiated samples was significantly (P 0.05) in the other quality parameters of sliced cucumbers. Therefore, application of an e-beam irradiation decontamination step can significantly improve the microbiological safety of fresh sliced cucumbers

Effect of Psoralea corylifolia on dexamethasone-induced insulin resistance in mice

AbstractThe whole plant of Psoralea corylifolia (PC) is traditionally used in the treatment of diabetes. Mice were treated with prestandardised dose of dexamethasone for 22days and effect of PC at the doses of 100, 200 and 300mg/kg, p.o. on plasma blood glucose level, serum triglyceride level, glucose uptake in skeletal muscle, levels of hepatic antioxidant enzymes (GSH, SOD, catalase and LPO), and body weight were observed. PC showed significant decrease in plasma glucose and serum triglyceride levels (p<0.01) at the dose of 100 and 200mg/kg, p.o. and also stimulated glucose uptake in skeletal muscle. The levels of antioxidant enzymes GSH, SOD, and catalase were significantly increased (p<0.01) and there was significant decrease (p<0.01) in level of LPO.Hence it can be concluded that Psoralea carylifolia may prove to be effective in the treatment of Type-II Diabetes mellitus owing to its ability to decrease insulin resistance

Floristic Diversity and Indigenous Uses of Forest Vegetation of Dabka Watershed in Indian Central Himalaya

A species check list of flora is presented in and around Dabka watershed, District Nainital of Uttarakhand, together with preliminary Phytosociological data for the major species of communities. A total of 45 tree species, 09 shrubs and 32 species of grasses and herbs recorded. Results of quantitative sampling indicate that Adina cordifolia (IVI 66.26) species dominated in the watershed area. Other important woody associates include Quercus incana (IVI 26.74), Pinus roxburghii (IVI 14.64). The diversity range for tree layer was 3.16 followed by herbs (2.92) and then shrubs (1.84); all of the tree species were contagious distribution. Analysis of use diversity showed that the recorded species provide 8 Different uses to local communities. About 56% of the species are used for more than one use categories. Although some species have multiple uses, the average number of uses per species is three. The uses were placed under three major use categories, which had highest contribution of the total uses. These include food, medicinal and fuel/fodder/timber/ dye etc. use value of species shows that about 38% species use in medicinal purposes, 32% species used for edible purposes and 33% use as various purposes. The current work provide the baseline floristic and ecological data and documents the structure and composition of vegetation and also collect information about ethno-botanic used to explore the conservation status and folk medicinal knowledge of the surrounding peoples of the study area, for managers planners and policy makers to understand such simple method assessing the biodiversity of any potential area for conservation in any region. The finding suggest that, public awareness and community based management need to be encouraged at all levels in order to overcome the threats; further investigation into nutritional properties of all the species reported; study on the pharmacological attributes would help to understand their medicinal application. Furthermore urgent collection of germplasm from areas under human pressure is recommended