A dexterous feature selection artificial immune system algorithm for keystroke dynamics

The main problem in security protecting the computer or resources from intruders. The password and username are the most common means to provide security. But this method has many loop holes such as password sharing, shoulder surfing, brute-force attack, dictionary attack, guessing, and many more. Keystroke dynamics is one popular and inexpensive behavioral biometric technology, which identifies the authenticity of a user when the user is working via a keyboard. Keystroke features like dwell time and flight time of every user are evaluated in this paper by preprocessing techniques such as Hausdroff timing, mean, median, and standard deviation. The artificial immune system is used for feature selection, and comparison between preprocessing techniques is shown.     

Magnetic interactions in supramolecular N-O...H-C[triple bond]C- type hydrogen-bonded nitronylnitroxide radical chains

Two paramagnetic building blocks, 2-(4-ethynyl-1-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl (3) and 2-(5-ethynyl-2-pyridyl)-4,4,5,5-tetramethylimidazoline-1-oxyl (4) were synthesized and crystallized. Single crystal X-ray studies of 3 and 4 show the formation of supramolecular head-to-tail one-dimensional H-bonded (N-O...H-C[triple bond]C- type) chain structures with O...C distances of 3.181 and 3.155 A, respectively. High-resolution isotropic liquid state (c相似文献   

JKR adhesion in cylindrical contacts

Planar JKR adhesive solutions use the half-plane assumption and do not permit calculation of indenter approach or visualization of adhesive force–displacement curves unless the contact is periodic. By considering a conforming cylindrical contact and using an arc crack analogy, we obtain closed-form indenter approach and load–contact size relations for a planar adhesive problem. The contact pressure distribution is also obtained in closed-form. The solutions reduce to known cases in both the adhesion-free and small-contact solution (Barquins, 1988) limits. The cylindrical system shows two distinct regimes of adhesive behavior; in particular, contact sizes exceeding the critical (maximum) size seen in adhesionless contacts are possible. The effects of contact confinement on adhesive behavior are investigated. Some special cases are considered, including contact with an initial neat-fit and the detachment of a rubbery cylinder from a rigid cradle. A comparison of the cylindrical solution with the half-plane adhesive solution is carried out, and it indicates that the latter typically underestimates the adherence force. The cylindrical adhesive system is novel in that it possesses stable contact states that may not be attained even on applying an infinite load in the absence of adhesion.     

Micropatterning of metallopolymers: syntheses of back-to-back coupled octylated 2,6-bis(pyrazolyl)pyridine ligands and their solution-processable coordination polymers

This paper presents a 10-step synthetic route for the preparation of a series of new back-to-back coupled 2,6-bis(pyrazol-1-yl)pyridine (bpp) ligands (L0-L3) decorated with tetraoctyl chains. Ligand L1 self-assembles with Zn(2+) ion to form a highly soluble metallo-supramolecular polymer 1 with M(n) ～ 9600 g/mol. To demonstrate the processability of polymer 1, by following a "top-down" approach periodic one-dimensional fluorescent microstripes were fabricated on a silica substrate.     

Tuning of Bistability,Thermal Stability of the Metastable States,and Application Prospects in the C3-Symmetric Designs of Multiple Azo(hetero)arenes Systems

Light-responsive molecular systems with multiple photoswitches in C₃-symmetric designs have enormous application potential. The design part of such molecular systems is critical due to its influence in several properties associated with the photoswitches. In order to tune, and in the evaluation of the design–property relationship, we synthesized 18 tripodal systems with variations in the core, linkers, connectivity, and azo(hetero)arene photoswitches. Through extensive spectroscopic and computational studies, we envisaged the factors controlling near-quantitative photoisomerization in both the directions (bistability) and the thermal stability of the metastable states. Furthermore, we also evaluated the impact of designs in obtaining reversible photo-responsive sol-gel phase transitions, solvatochromism, photo- and thermochromism.     

Exact likelihood inference based on Type-I and Type-II hybrid censored samples from the exponential distribution

Chen and Bhattacharyya (1988,Comm. Statist. Theory Methods,17, 1857–1870) derived the exact distribution of the maximum likelihood estimator of the mean of an exponential distribution and an exact lower confidence bound for the mean based on a hybrid censored sample. In this paper, an alternative simple form for the distribution is obtained and is shown to be equivalent to that of Chen and Bhattacharyya (1988). Noting that this scheme, which would guarantee the experiment to terminate by a fixed timeT, may result in few failures, we propose a new hybrid censoring scheme which guarantees at least a fixed number of failures in a life testing experiment. The exact distribution of the MLE as well as an exact lower confidence bound for the mean is also obtained for this case. Finally, three examples are presented to illustrate all the results developed here.     

Dirhodium tetraprolinate-catalyzed asymmetric cyclopropanations with high turnover numbers

The bridged dirhodium tetraprolinate Rh(2)(S-biTISP)(2) (2) catalyzes the asymmetric cyclopropanation reaction between methyl phenyldiazoacetate and styrene at room temperature with high turnover number (92 000) and turnover frequency (4000 per h). [reaction: see text]     

Kinetic resolution and double stereodifferentiation in catalytic asymmetric C-H activation of 2-substituted pyrrolidines

Dirhodium tetrakis(S-(N-dodecylbenzenesulfonyl)prolinate) (Rh(2)(S-DOSP)(4)) catalyzed decomposition of methyl aryldiazoacetates in the presence of 2-substituted pyrrolidines results in highly diastereoselective and enantioselective C-H insertions. These reactions can proceed with impressive levels of double stereodifferentiation and kinetic resolution, which allows for three stereocenters to be controlled during the C-H insertion step.     

Study on the heteroatom influence in pyridine-based nitronyl nitroxide biradicals with phenylethynyl spacers on the molecular ground state

Novel pyridine-based nitronyl nitroxide (NIT) biradicals, 3,5-bis[4-(1-oxyl-3-oxo-4,4,5,5-tetramethylimidazolin-2-yl)phenylethynyl)]pyridine (1) and 2,6-bis[4-(1-oxyl-3-oxo-4,4,5,5-tetramethylimidazolin-2-yl)phenylethynyl)]pyridine (2), and monoradicals, 4-(5-bromopyridine-3-ylethynyl)-1-(1-oxyl-3-oxo-4,4,5,5-tetramethylimidazolin-2-yl)benzene (3), 4-trimethylsilylethynyl-1-(1-oxyl-3-oxo-4,4,5,5-tetramethylimidazolin-2-yl)benzene (4), and 4-trimethylsilylethynyl-1-(1-oxyl-3-oxo-4,4,5,5-tetramethylimidazolin-2-yl)pyridine (5), were synthesized and investigated by ESR and UV-vis spectroscopy. The solution EPR measurements of the biradicals gave well-resolved, nine-line spectra with exact half line spacing as compared to monoradicals (giso = 2.0067) with isotropic line spacing /aN/= 7.36 G. This indicates strong, intramolecular exchange coupling (J > 7 x 10(-4) cm(-1); J/aN > 1) of the biradicals with in the limit of EPR. The temperature dependence on the Deltams = +/-2 signal intensity of biradicals follow Curie behavior down to 4 K ascertaining the triplet ground state or its near-degeneracy with the singlet state. UV-vis studies of 1-5 show characteristic differences in the extinctions of n-pi transitions around 600 nm. Both biradicals 1 and 2 were crystallized in monoclinic space groups C2/c and P2(1)/a with the intraradical distances 1.54 and 1.47 nm, respectively. Computational studies of the biradicals 1, 2, and 1,3-bis[4-(1-oxyl-3-oxo-4,4,5,5-tetramethylimidazolin-2-yl)phenylethynyl)]benzene (T) were performed by the AM1/CAS(8,8) method to calculate the singlet-triplet (DeltaEST) energy difference and the spin density distribution. Results show that the position of the pyridyl nitrogen in 1 and 2 in comparison with T does not alter the triplet ground-state spin multiplicities supporting the obtained experimental results.     

Cellulose functionalized with 8-hydroxyquinoline: new method of synthesis and applications as a solid phase extractant in the determination of metal ions by flame atomic absorption spectrometry

8-Hydroxyquinoline has been immobilized on cellulose via a moderate size NHCH₂CH₂NHSO₂C₆H₄NN linker and the resulting macromolecular chelator (and intermediates) characterized by infrared spectrometry, cross-polarization magic angle spinning (CPMAS) NMR spectrometry and thermogravimetric analysis (TGA). It has been used for enrichment of Cu(II), Zn(II), Fe(III), Ni(II), Co(II), Cd(II) and Pb(II) prior to their determination by flame atomic absorption spectrometry (FAAS), which are quantitatively sorbed (recoveries>97%) at pH 4.2-6.7, 4.2-7.5, 2.0-3.0, 5.3-6.7, 5.3-6.2, 6.2-9.0 and 4.2-5.3, respectively. The sorption capacity for the seven cations varies from 93.8 to 629.9 μmol g⁻¹. HCl or HNO₃ (1 mol dm⁻³) may be used to desorb all the cations. The optimum flow rate for sorption and desorption has been found to be 2-4 cm³ min⁻¹. The tolerance limits of electrolytes NaCl, NaBr, NaNO₃, Na₂SO₄, Na₃PO₄ and cations Ca²⁺ and Mg²⁺ (added as chloride and sulphate, respectively) in the sorption of all these metal ions are reported. The preconcentration factor is between 90 and 300. Simultaneous sorption of the cations other than iron(III) is possible if their total concentration does not exceed sorption capacity. The present matrix coupled with FAAS has been used to enrich and determine the seven metal ions in river water samples (R.S.D.<7.4%) and water samples having a composition similar to certified water sample SLRS-4 (NRC, Canada) with R.S.D. ∼2.3%.