Tracing DDoS Floods: An Automated Approach

We propose a Controller-Agent model that would greatly minimize distributed denial-of-service (DDoS) attacks on the Internet. We introduce a new packet marking technique and agent design that enables us to identify the approximate source of attack (nearest router) with a single packet even in the case of attacks with spoofed source addresses. Our model is invoked only during attack times, and is able to process the victims traffic separately without disturbing other traffic, it is also able to establish different attack signatures for different attacking sources and can prevent the attack traffic at the nearest router to the attacking system. It is simple in its implementation, it has fast response for any changes in attack traffic pattern, and can be incrementally deployed. Hence we believe that the model proposed in this paper seems to be a promising approach to prevent distributed denial-of-service attacks.     

Effect of Retrogression Heat Treatment Time on Microstructure and Mechanical Properties of AA7010

The effect of retrogression time during retrogression and re-aging (RRA) treatment of AA7010 is evaluated by performing tensile tests and characterizing the microchemistry of the grain boundary precipitates (GBPs) using transmission electron microscope coupled with the energy-dispersive spectroscopy. Retrogression time is evaluated so that the ultimate tensile strength of the RRA-treated sample is equal to that of the T6-treated sample and the grain boundary microstructure similar to that of the over-aged (T7451) condition. The investigation reveals that the sample retrogressed at 200 °C for 20 min has UTS of 586 MPa which is equivalent to that of the T6 sample and 11.5% higher than that of the T7451 condition. The fracture toughness of the RRA-treated sample was 41 MPa√m. Microstructure of the RRA-treated sample is similar to T7451, along the grain boundaries and in the grain interior similar to that of the T6-treated sample. Energy-dispersive spectroscopy confirmed the increment of Cu content on the GBP’s with increase in the retrogression time, which is expected to improve the stress corrosion cracking resistance of the alloy.     

Syntheses and characterization of blend membranes of sodium alginate and poly(vinyl alcohol) for the pervaporation separation of water + isopropanol mixtures

The blend membranes of sodium alginate and poly(vinyl alcohol) have been prepared by physical mixing in different ratios (75, 50, and 25%) of sodium alginate with poly(vinyl alcohol). The membranes were crosslinked with glutaraldehyde and used in the pervaporation separation of water + isopropanol mixtures at 30°C. The crosslinking reaction was confirmed by Fourier transform infrared spectra. Permeation flux increased with an increase in mass % of water in the feed mixture as well as with an increase in the amount of poly(vinyl alcohol) in the blend, but separation selectivity decreased. Diffusion coefficients of water + isopropanol mixtures have been calculated using the Fick's equation from the sorption data. Arrhenius activation parameters were calculated for 10 mass % of water in the feed mixture using the values of flux and diffusion coefficients obtained at 30, 40, and 50°C. The diffusion and pervaporation results have been explained on the basis of solution‐diffusion principles. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3642–3651, 2002     

Response surfaces for solubility of crude soylecithin lipid in super critical carbon dioxide

 The solubility of soy lecithin lipids in supercritical CO₂ was measured at pressures of 120, 200 and 280 bar and at temperatures of 40, 50 and 60  °C. The effects of temperature and pressure on the solubility of total lipids were studied by response surface methodology. The response surface equation to predict the solubility of total lipids in the above range of pressure and temperature is: Y=–3.237+0.0431* P–7.3×10^–5 P ²–0.00011 P*T where Y is the total lipid solubility in g/kg CO₂, P is the pressure in bar and T is the temperature in   °C. The total lipids solubility increased with pressure at constant temperature, but decreased with increasing temperature. The total lipids consisted of a very small phospholipid content compared to neutral lipids and glycolipids at all the pressures and temperatures studied. Optimum search indicated a maximum solubility of total lipids of 1.829 g/kg CO₂ at 263 bar and 40  °C. Received: 1 April 1999     

The Potential of Genome Editing for Improving Seed Oil Content and Fatty Acid Composition in Oilseed Crops

A continuous rise in demand for vegetable oils, which comprise mainly the storage lipid triacylglycerol, is fueling a surge in research efforts to increase seed oil content and improve fatty acid composition in oilseed crops. Progress in this area has been achieved using both conventional breeding and transgenic approaches to date. However, further advancements using traditional breeding methods will be complicated by the polyploid nature of many oilseed crops and associated time constraints, while public perception and the prohibitive cost of regulatory processes hinders the commercialization of transgenic oilseed crops. As such, genome editing using CRISPR/Cas is emerging as a breakthrough breeding tool that could provide a platform to keep pace with escalating demand while potentially minimizing regulatory burden. In this review, we discuss the technology itself and progress that has been made thus far with respect to its use in oilseed crops to improve seed oil content and quality. Furthermore, we examine a number of genes that may provide ideal targets for genome editing in this context, as well as new CRISPR-related tools that have the potential to be applied to oilseed plants and may allow additional gains to be made in the future.     

Supercritical CO2 extraction of Mortierella alpina single cell oil: Comparison with organic solvent extraction

Analysis of supercritical fluid extracted (SFE) and organic solvent extracted lipids from freeze dried Mortierella alpina biomass was carried out. The effect of biomass pre-treatment on effectual lipid recovery was also investigated. Results indicated that the methods employed viz., SFE and organic solvent (Sox Tec™) exhibited significant variation in lipid extraction efficacy. Efficacy of SFE on lipid recovery (38.73%) was significantly lower when compared to that of Sox Tec™ method (51.47%) because the organic solvent can also extract polar lipids. Biomass pretreatment by enzymatic method resulted in a substantial increase in lipid recovery. Maximum disruption of cell wall evidenced by scanning electron microscopy of treated cells warranted their higher mass transfer and efficient extraction. Characterisation of the extracted lipids by GC and GC–MS revealed considerable variation in the fatty acid profile. The FT-IR spectrum indicated a prominent cis-stretching vibration, no evident trans- stretching vibration and no major discrepancies between the SFE and Sox Tec™ extracts.     

Prediction of solubility of <Emphasis Type="Italic">Psoralea corylifolia</Emphasis> L. Seed extract in supercritical carbon dioxide by equation of state models

Solubility of bakuchiol and psoralen, key components of Psoralea corylifolia L. seed extract, in supercritical carbon dioxide was predicted by employing well known Peng-Robinson and Soave-modified Redlich-Kwong equations of state. Solubility (in mole fraction) of both bakuchiol and psoralen was in the range 10⁻⁶–10⁻⁴ for the pressure 22 to 30 MPa. Both the models were found to agree with the experimental solubilities of psoralen very well with average deviation less than 9%. If the extract was assumed as a single pseudo-component having average critical properties of main components, the model predicted solubility of the extract well with average deviation less than 17%. Critical properties necessary for the solubility prediction such as critical temperature, critical pressure, and critical volume were predicted for the key components following group contribution methods proposed by Ambrose, Lydersen, Joback and Klincewicz-Reid. Vapor pressure of the components was also predicted based on Riedel equation. Depending on the temperature, vapor pressure of Psoralen is higher by a factor of 10 to 2 × 10¹¹ compared to vapor pressure of bakuchiol.     

Rheology of lecithin dispersions

Dispersions of lecithin (1–25% solids, dry basis) in soybean oil or water were subjected to rheological measurement in a coaxial-cylinder viscometer. The different rheological characteristics determined included yield stress, flow behavior index, consistency index, and apparent viscosity. Pseudoplastic behavior was observed for all lecithin emulsions in oil and for dispersions in water. The flow behavior indices for lecithin-oil emulsions (0.855–0.875) were higher than for lecithin-water dispersions (0.472–0.584). Yield stresses were observed only for lecithin-water dispersions. An increase in the concentration of lecithin in oil or water increased yield stress, consistency index, and apparent viscosity. The apparent viscosities of the lecithin-oil emulsions were higher than those for corresponding lecithin-water dispersions. The power law model can adequately fit (r≥0.988, p≤0.01) the shear-rate vs. shear-stress data for lecithin-oil emulsions, whereas the Herschel-Bulkley model was suitable (r≥0.988, p≤0.01) for lecithin-water dispersions.     

Enhancement of Surface Flashover Performance of High Voltage Ceramic Disc Insulators

In this paper, an effort is made to study accurately the field distribution for various types of ceramic insulators used for high-voltage transmission. The surface charge simulation method (SCSM) is employed for the field computation. With the help of SCSM program, a Novel field reduction electrode is designed and developed to reduce the maximum field around the pin region. In order to experimentally analyze the performance of discs with field reduction electrode, special artificial pollution test facility was built and utilized. The experimental results show better surface flashover performance of ceramic insulators used in high-voltage transmission and distribution systems.     

New p-ary sequence family with low correlation and large linear span

In this paper, for an odd prime p and positive integers n, m, and e such that n = me, a new family S{\mathcal{S}} of p-ary sequences of period p ⁿ − 1 with low correlation and large linear span is constructed. It is shown that S{\mathcal{S}} has maximum correlation 1+p^[(n+2e)/2]{1+p^{n+2e\over 2}}, family size p ⁿ , and maximal linear span [((m+3)n)/2]{{(m+3)n\over 2}}. When m is even, the proposed family S{\mathcal{S}} contains Tang, Udaya, and Fan’s construction as a subset. Furthermore, when n is even and e=1, S{e=1, \mathcal{S}} has the same correlation and family size, but larger linear span compared with the construction by Seo, Kim, No, and Shin.