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21.
Cheating in Visual Cryptography 总被引:3,自引:0,他引:3
A secret sharing scheme allows a secret to be shared among a set of participants, P, such that only authorized subsets of P can recover the secret, but any unauthorized subset cannot recover the secret. In 1995, Naor and Shamir proposed a variant
of secret sharing, called visual cryptography, where the shares given to participants are xeroxed onto transparencies. If
X is an authorized subset of P, then the participants in X can visually recover the secret image by stacking their transparencies together without performing any computation. In this
paper, we address the issue of cheating by dishonest participants, called cheaters, in visual cryptography. The experimental
results demonstrate that cheating is possible when the cheaters form a coalition in order to deceive honest participants.
We also propose two simple cheating prevention visual cryptographic schemes. 相似文献
22.
Aryne‐Induced Novel Tandem 1,2‐Addition/(3+2) Cycloaddition to Generate Imidazolidines and Pyrrolidines 下载免费PDF全文
Dr. Sharada P. Swain Yi‐Chun Shih Dr. Shwu‐Chen Tsay Joby Jacob Dr. Chun‐Cheng Lin Dr. Kuo Chu Hwang Dr. Jia‐Cherng Horng Prof. Dr. Jih Ru Hwu 《Angewandte Chemie (International ed. in English)》2015,54(34):9926-9930
A new “single‐flask” method was developed for the synthesis of imidazolidines and pyrrolidines with high stereoselectivity. First, a Schiff base was arylated with an aryne. Second, an intramolecular proton transfer took place from the methylene position to the anionic aryne ring. Third, the resultant ylide reacted with a second equivalent of the same Schiff base in situ or an electron‐deficient alkene through a (3+2) cycloaddition. These sequential tandem 1,2‐addition/(3+2) cycloaddition reactions led to the desired heterocycles in 63–88 % yields. 相似文献
23.
This work prepared poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate) (PETG)/organoclay nanocomposites via a melt intercalation process and investigated the influences of organoclay aspect ratio and organoclay content on the dispersed state, mechanical, thermal, gas barrier, and heat recovery properties of PETG/organoclay nanocomposites. X‐ray diffraction (XRD) and transmission electron microscopic analyses showed that the organoclay dispersed in the polymer matrix with intercalation in the nanometer scale range. Differential scanning calorimetry (DSC) analysis demonstrated that all of the obtained nanocomposites were amorphous, indicating that the addition of organoclay did not affect the amorphous nature of PETG. The gas barrier properties of the nanocomposites improved with organoclay content and the properties were also affected by the organoclay aspect ratio. Water vapor and oxygen transmission rates (OTRs) of PETG/organoclay nanocomposites containing 3 phr Cloisite 15A, and 3 phr modified polymer grade Na‐montmorillonites (MPGN) were the lowest among the samples tested, and were 41.7 and 44.3%, respectively, of those of neat PETG. Similar organoclay content‐ and aspect ratio‐related effects were observed in the mechanical and heat recovery properties of the tested nanocomposites. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
24.
Shing Horng Lee Christina F. Jou Chien Ping Lee Cheng Chi Hu 《International Journal of Infrared and Millimeter Waves》1997,18(10):2001-2017
A simple varactor tuned X-band Gunn diode VCO antenna array which is strongly coupled has been demonstrated. These arrays
have the advantages of simple biasing circuit, no resistors required to eliminate multimode problem and suitable for monolithic
integration circuit. Preliminary results show a maximum tuning range of 47MHz for 1×1 array and 170MHz for 2×2 array. In order
to solve power combining heating problem, we move the backside metal forward and it becomes a microstrip form. The measured
frequency and radiation patterns of these grid arrays agree very well with theoretical calculations. 相似文献
25.
26.
The initial stages of epitaxial growth in the (111)Ag/Cu and (111)Au/Cu systems were investigated using UHV-RHEED and TEM on the same specimens. Flat, monocrystalline (111)Cu substrates, 1100 Å thick, were formed in situ in the RHEED system on (111)NaCl/mica bilayers. The latter consisted of air-cleaved mica on which 150 Å of NaCl was vacuum-evaporated to form a (111)NaCl monocrystalline film. The NaCl layer allowed easy removal in water of the subsequently deposited bilayer metal film. RHEED showed that these Cu films grew with extremely flat surfaces at 400°C and 10 Å/sec deposition rates. They were then annealed at 500°C for 15 min to reduce their dislocation content and finally used as substrates for subsequent deposition of thin Ag or Au superlayers. The average Ag and Au superlayer thicknesses were varied from fractions of an Angstrom to approximately 20 Å. It was shown that despite the elongated streaks in the RHEED patterns, film growth occurred by an island mechanism, the islands having flat top surfaces. In the initial growth processes, the islands merely thickened. After a few average monolayers were deposited, the islands began to widen, often by means of much thinner islands, finally coalescing into a continuous film. The Au overgrowths became continuous in the 6–11 Å thickness range. In the case of Ag, there still were some open areas in the overgrowth at 20 Å. In both cases the continuous regions of the Ag and Au overgrowths consisted of sharply delineated thick and thin areas that gave rise to steps on the otherwise flat surface. 相似文献
27.
A series of lanthanide porphyrin dimers have been synthesized and investigated with IR spectroscopic techniques. The spectra of the porphyrin dimers are compared not only with each other but also with those of their component monomer units. The experimental results exhibit that the IR spectra of the porphyrin dimers are closely related to those of their corresponding monomers. A detailed analysis of the IR spectra between the porphyrin dimers and monomers suggest that the dimer molecules can be treated as regular derivatives of metalloporphyrin monomers despite the symmetries of these two systems being different. The dimerization of the porphyrin rings only result in frequency shifts and intensity changes of the IR spectra. These shifts are attributed to the induced π–π interactions between these two macrocycles. The downshifts of the frequencies observed in Ce(OEP)2 further indicate that the π–π interactions intrinsically decrease the bond strength of the entire molecule. Additionally, only the relative intensities instead of the frequencies of the ethyl vibrations in the region 2800–3000 cm−1 are observed to be sensitive to the types and the positions of the substituent groups. These observations suggest that these ethyl vibrational modes of the OEP moiety can be used as characteristic bands to monitor subtle deformations of the porphyrin rings caused by the substituent groups in the dimer complexes. 相似文献
28.
W L Pearn Y-C Hsu J-J Horng Shiau 《The Journal of the Operational Research Society》2007,58(8):1075-1083
In most manufacturing industries, tool replacement policy is essential for minimizing the fraction defective and the manufacturing cost. Tool wear is caused by the action of sliding chips in the shear zone, and the friction generated between the tool flank and workpiece. This wear, apparently, is a dominant and irremovable component of variability in many machining processes, which is a systematic assignable cause. As the tool wear occurs in the machining processes, the fraction of defectives would gradually become significant. When the fraction defective reaches a certain level, the tool must be replaced. Therefore, detecting suitable time for tool replacement operation becomes essential. In this paper, we present an analytical approach for unilateral processes based on the one-sided process capability index C PU (or C PL ) to find the appropriate time for tool replacement. Accurate process capability must be calculated, particularly, when the data contains assignable cause variation. By calculating the index C PU (or C PL ) in a dynamical environment, we propose estimators of C PU (or C PL ) and obtain exact form of the sampling distribution in the presence of systematic assignable cause. The proposed procedure is then applied to a real manufacturing process involving tool wear problem, to demonstrate the applicability of the proposed approach. 相似文献
29.
Mei‐Ing Chung Horng‐Huey Ko Ming‐Hong Yen Chun‐Nan Lin Sheng‐Zehn Yang Lo‐Ti Tsao Jih‐Pyang Wang 《Helvetica chimica acta》2000,83(6):1200-1204
A novel phenolic compound, artocarpol A ( 1 ), was isolated from the root bark of Artocarpus rigida and its structure determined by spectroscopic methods and by comparison with its diacetate derivative. Compound 1 strongly inhibited superoxide formation in phorbol 12‐myristate 13‐acetate (PMA) stimulated rat neutrophils in a concentration‐dependent manner with an IC50 value of 13.7±0.7 μM . Compound 1 also showed a significant inhibitory effect on tumor necrosis factor‐α (TNF‐α) formation in lipopolysaccharide(LPS)‐stimulated RAW 264.7 cells. 相似文献
30.
Yi‐Huang Lu Chun‐Nan Lin Horng‐Huey Ko Sheng‐Zehn Yang Lo‐Ti Tsao Jih‐Pyang Wang 《Helvetica chimica acta》2002,85(6):1626-1632
With the scope of our search for biologically active compounds, two new phenolic compounds, artocarpols G ( 1 ) and H ( 2 ), and two known compounds, rubraflavone C ( 3 ) and trans‐stilbene‐2,4,3′,5′‐tetrol, were isolated from the root bark of Artocarpus rigida. Their structures were determined by spectroscopic methods and comparison with data reported in the literature. Compound 4 , previously isolated from this plant, strongly inhibited in a concentration‐dependent manner the release of β‐glucuronidase and histamine from mast cell degranulation caused by compound 48/80, with IC50 values of 10.9±1.4 and 13.2±0.6 μM , respectively. Compound 4 also showed a concentration‐dependent inhibitory effect on the formyl‐peptide‐stimulated superoxide anion formation in neutrophils with an IC50 value of 26.0±5.6 μM . 相似文献