A DDoS Attack Detection Method Based on Natural Selection of Features and Models

Distributed Denial of Service (DDoS) is still one of the main threats to network security today. Attackers are able to run DDoS in simple steps and with high efficiency to slow down or block users’ access to services. In this paper, we propose a framework based on feature and model selection (FAMS), which is used for detecting DDoS attacks with the aim of identifying the features and models with a high generalization capability, high prediction accuracy, and short prediction time. The FAMS framework is divided into four main phases. The first phase is data pre-processing, including operations such as feature coding, outlier processing, duplicate elimination, data balancing, and normalization. In the second stage, 79 features are extracted from the dataset and selected by the feature selection algorithms filter, wrapper, embedded, variance, mutual information, backward elimination, Lasso.L1, and random forest. The purpose of feature selection is to simplify the model, avoid dimensional disasters, reduce computational costs, and reduce the prediction time. The third stage is model selection, which aims to select the most ideal algorithm from GD, SVM, LR, RF, HVG, SVG, HVR, and SVR using a model selection algorithm for the selected 21 features, and the results show that RF is far ahead in all evaluation indexes compared to the other models. The fourth stage is model optimization, which aims to further improve the performance of the RF algorithm in detecting DDoS attacks by optimizing the parameters max_samples, max_depth, n_estimators for the initially selected RF by the RF optimization algorithm. Finally, by testing the 100,000 CIC-IDS2018, CIC-IDS2017, and CIC-DoS2016 synthetic datasets, the results show that all the results have achieved excellent performance in the same category. Moreover, the framework also shows an excellent generalization performance by testing over 1 million synthetic datasets and over 330,000 CIC-DDoS2019 datasets

A metal-free "black dye" for panchromatic dye-sensitized solar cells

A novel metal-free "black dye" was designed and synthesized for panchromatic dye-sensitized solar cells. Based on this dye, the broader incident photon-to-current conversion efficiency spectrum was obtained over the whole visible range extending into the near-IR region up to 920 nm

Effect of Different Dye Baths and Dye-Structures on the Performance of Dye-Sensitized Solar Cells Based on Triphenylamine Dyes

Triphenylamine dyes were designed and synthesized as photosensitizers for dye-sensitized solar cells (DSSCs). Different substituted phenylene units, 2,2';5',2''-ter-thiophene (TT) and dithieno[3,2-b;2',3'-d]thiophene (DTT) serve as the π-spacers - the electron acceptors use cyanoacrylic acid or rhodanine-3-acetic acid units. A detailed study on the relation between the dye structure, and photophys., photoelectrochem. properties and performance of DSSCs is described here. By substituting the phenylene group with electron-withdrawing units as π-spacers or replacing the cyanoacrylic acid with rhodanine-3-acetic acid units as electron acceptors, bathochromic shift of absorption spectra is achieved. Significant differences in the redox potential of these dyes are due to small structure changes. The different dye baths for semiconductor sensitization have a crucial effect on the performance of the DSSCs due to the different absorbed amt., absorption spectra and binding modes of anchored dyes on the TiO2 surface in various solvents. From optimized dye bath and mol. structure, TPC1 shows a prominent solar-to-electricity conversion efficiency (η), 5.33% (JSC = 9.7 mA/cm2, VOC = 760 mV, ff = 0.72), under simulated AM 1.5 G irradn. (100 mW/cm2). DFT showed the electron distribution and the intramol. charge transfer (HOMO→LUMO) of the dyes. From the calcn. results of the selected dyes, the authors can also find the cyanoacrylic acid unit better than the rhodanine-3-acetic acid unit as electron acceptor. Also, the electron-withdrawing groups on phenylene units as π-spacers show the neg. effect on the performance of the org. DSSCs

Effect of Tetrahydroquinoline Dyes Structure on the Performance of Organic Dye-Sensitized Solar Cells

Eleven novel donor acceptor π-conjugated (D-π-A) org. dyes were engineered and synthesized as sensitizers for the application in dye-sensitized solar cells (DSSCs). The electron-donating moieties are substituted tetrahydroquinoline, and the electron-withdrawing parts are cyanoacrylic acid group or cyanovinylphosphonic acid group. Different lengths of thiophene-contg. conjugation moieties (thienyl, thienylvinyl, and dithieno[3,2-b;2',3'-d]thienyl) are introduced to the mols. and serve as electron spacers. Detailed study on the relation between the dye structure, photophys. and photoelectrochem. properties, and performance of DSSCs is described here. The bathochromic shift and increase of the molar absorptivity of the absorption spectrum are achieved by introduction of larger conjugation moiety. Even small structural changes of dyes result in significant changes in redox energies and adsorption manner of the dyes on TiO2 surface, affecting dramatically the performance of DSSCs based on these dyes. The higher performances are obtained by DSSCs based on the rigid dye mols., C2 series dyes (Figure 1), although these dyes have lower light absorption abilities relative to other dyes. A max. solar-to-elec. energy conversion efficiency (η) of 4.53% is achieved under simulated AM 1.5 irradn. (100 mW/cm2) with a DSSC based on C2-2 dye (Voc = 597 mV, Jsc = 12.00 mA/cm2, ff = 0.63). D. functional theory (DFT) calcns. were performed on the dyes, and electron distribution from the whole mols. to the anchoring moieties occurred during the HOMO-LUMO excitation. The cyanoacrylic acid groups or cyanovinylphosphonic acid group are essentially coplanar with respect to the thiophene units, reflecting the strong conjugation across the thiophene-anchoring groups

Phenothiazine derivatives for efficient organic dye-sensitized solar cells

Novel org. dyes based on the phenothiazine (PTZ) chromophore were designed and synthesized for dye-sensitized solar cells, which give solar energy-to-electricity conversion efficiency (η)of up to 5.5% in comparison with the ref. Ru-complex (N3 dye) with an η value of 6.2% under similar exptl. conditions

Influence of π-Conjugation Units in Organic Dyes for Dye-Sensitized Solar Cells

Two org. dyes with the general structure donor-conjugated chain-acceptor (D-π-A) were studied as sensitizers for nanocryst. TiO2 solar cells. The electron donor and acceptor groups were pyrrolidine and cyano acrylic acid, resp. The conjugated chain of 2-cyano-3-{5-[2-(4-pyrrolidin-1-ylphenyl)vinyl]thiophen-2-yl}acrylic acid contains one Ph ring and a thiophene unit and is therefore denoted PT, while for 2-cyano-3-{5-[2-(5-pyrrolidin-1-ylthiophen-2-yl)vinyl]thiophen-2-yl}acrylic acid the Ph ring is replaced by a 2nd thiophene unit (TT). Solar-to-elec. energy conversion efficiencies under simulated AM 1.5 irradn. (1000 W m-2) of 2.3% were obtained for solar cells based on PT but of <0.05% for those based on TT. The reasons for the dramatic difference of the efficiencies were analyzed. Photoinduced absorption measurements revealed that the TT dye was not properly regenerated by redox electrolyte after electron injection. This sluggish regeneration is probably due to the 0.3 V less pos. HOMO level for TT dye compared to the PT dye, resulting in a lower driving force for regeneration of the oxidized dye by iodide in the electrolyte. Regeneration of the oxidized TT dye and electron injection from the excited TT dye may be poor due to formation of dye aggregates/complexes, as FTIR measurements show an excess of not properly and/or unidentate bound TT dye mols. instead of bidentate bound PT dye mols. The results highlight that small structural change of dyes results in significant changes in redox energies and binding features, affecting dramatically the performance of these dyes in dye-sensitized solar cells

Tuning of phenoxazine chromophores for efficient organic dye-sensitized solar cells

Through introducing an energy antenna system into a simple phenoxazine dye (TH301), a novel and efficient dye TH305 was designed and synthesized for application in a dye sensitized solar cell with prominent overall conversion efficiency of 7.7%

Anthraquinone dyes as photosensitizers for dye-sensitized solar cells

Three anthraquinone dyes with carboxylic acid as anchoring group are designed and synthesized as sensitizers for dye-sensitized solar cells (DSSCs). Preliminary photophys. and photoelectrochem. measurements show that these anthraquinone dyes have very low performance on DSSC applications, although they have broad and intense absorption spectra in the visible region (up to 800 nm). Transient absorption kinetics, fluorescence lifetime measurements and d. functional theory (DFT) calcns. are conducted to investigate the cause of such low DSSC performance for these dyes. The strong electron-withdrawing character of the two carbonyl groups on anthraquinone framework may lie behind the low performance by suppressing the efficient electron injection from the dye to the conduction band of TiO2