Characterization of Security Notions for Probabilistic Private-Key Encryption

The development of precise definitions of security for encryption, as well as a detailed understanding of their relationships, has been a major area of research in modern cryptography. Here, we focus on the case of private-key encryption. Extending security notions from the public-key setting, we define security in the sense of both indistinguishability and non-malleability against chosen-plaintext and chosen-ciphertext attacks, considering both non-adaptive (i.e., ``lunchtime') and adaptive oracle access (adaptive here refers to an adversary's ability to interact with a given oracle even after viewing the challenge ciphertext). We then characterize the 18 resulting security notions in two ways. First, we construct a complete hierarchy of security notions; that is, for every pair of definitions we show whether one definition is stronger than the other, whether the definitions are equivalent, or whether they are incomparable. Second, we partition these notions of security into two classes (computational or information-theoretic) depending on whether one-way functions are necessary in order for encryption schemes satisfying the definition to exist. Perhaps our most surprising result is that security against adaptive chosen-plaintext attack is (polynomially) equivalent to security against non-adaptive chosen-plaintext attack. On the other hand, the ability of an adversary to mount a (non-adaptive) chosen-plaintext attack is the key feature distinguishing computational and information-theoretic notions of security. These results hold for all security notions considered here.     

Oral absorption and pharmacokinetics of rebamipide and rebamipide lysinate in rats

Rebamipide is an anti-ulcer agent exhibiting a low aqueous solubility and a poor oral bioavailability. This study was conducted to examine if the rebamipide lysinate salt form would exhibit improved solubility profiles and higher oral bioavailability compared with rebamipide free acid. Both compounds showed pH-dependent solubility profiles, with the solubility of rebamipide lysinate dramatically improved at a median pH of 5.1 (17-fold increases) over free acid, but the improvement in the solubility was not as pronounced in artificial gastric and intestinal fluids (1.4- and 1.9-fold increases, respectively). The Cl, V_ss and t_1/2 in rats after i.v. injection of rebamipide (0.5 mg/kg) averaged 21.0 ± 3.2 ml/min/kg, 0.3 ± 0.0 L/kg, and 0.4 ± 0.1 hr, respectively. No significant difference was observed in these parameters between rebamipide and rebamipide lysinate. Despite improved solubility profiles, the absolute oral bioavailability of rebamipide lysinate was not increased (5.1 vs. 4.8%) nor did AUC (407.8 vs. 383.6 ng^.hr/ml) and C_max (87.4 vs.77.0 ng/ml) compared with rebamipide free acid. Rebamipide lysinate, however, showed a more rapid absorption, and initial serum drug concentrations were higher than those found for rebamipide free acid.     

Evaluation of radiation exposure upon visual organs during a head CT scan

In order to analyze and compare the absorbed radiation dose and dose rate of visual organs (eyes, corneas, and lenses) of the head with the surrounding areas of the head during CT scans, a mathematical head phantom was created. In addition, the amount of radiation exposure reduced when using an eye shield was also analyzed. According to the results, it was found that the absorbed dose was highest when using 120 kV (as compared to 80 kV and 100 kV) and the absorbed dose rate of the visual organs compared to the head was about 1.35% for the eyes, 0.9% for the corneas, and 0.095% for the lenses. Finally, it was shown that the dose reduction rate of each organ when using an eye shield was about 24% for the eyes, about 22% for the corneas, and more than 40% for the lenses.     

A case study on detection and sizing of defects in steam generator tubes using eddy current testing

Eddy current testing (ECT) method is widely used to detect various types of defects occurring in nuclear steam generator tubes. Therefore, the reliability of its detection and sizing accuracy for defects should be validated. For this purpose, two tubes with defect signals were pulled from an operating steam generator and destructively examined. The defect type was a circumferential crack for one tube and an intergranular attack (IGA) for the other tube. The plus point coil probe showed a better capability to detect and size both a circumferential crack and a volumetric IGA than pancake and bobbin coil probe. The destructive results are correlated with the ECT results obtained during the in-service inspection.     

Hierarchical VP restoration management system for a reliable ATM backbone network

This paper proposes a distributed ATM VP PVC restoration framework with the dynamic rerouting schemes in a hierarchical transport network. The rerouting algorithm aims to provide rapid ATM VP PVC restoration in the case of fault or performance degradation in terms of maximization of network resource utilization and satisfaction of the end user's QoS requirement. Copyright © 2002 John Wiley & Sons, Ltd.     

Measurement of the heat transfer coefficient in the dimpled channel: effects of dimple arrangement and channel height

Heat transfer coefficients were measured in a channel with one side dimpled surface. The sphere type dimples were fabricated, and the diameter (D) and the depth of dimple was 16 mm and 4 mm, respectively. Two channel heights of about 0.6D and 1.2D, two dimple configurations were tested. The Reynolds number based on the channel hydraulic diameter was varied from 30000 to 50000. The improved hue detection based transient liquid crystal technique was used in the heat transfer measurement. Heat transfer measurement results showed that high heat transfer was induced downstream of the dimples due to flow reattachment. Due to the flow recirculation on the upstream side in the dimple, the heat transfer coefficient was very low. As the Reynolds increased, the overall heat transfer coefficients also increased. With the same dimple arrangement, the heat transfer coefficients and the thermal performance factors were higher for the lower channel height. As the distance between the dimples became smaller, the overall heat transfer coefficient and the thermal performance factors increased. This paper was recommended for publication in revised form by Associate Editor Yong Tae Kang Jae Su Kwak received his B.S. and M.S. degrees in Mechanical Engineering from Korea University in 1996 and 1998, respectively. He then received his Ph.D. from Texas A&M University in 2002. Dr. Kwak is currently an Assistant Professor at the School of Aerospace and Mechanical Engineering at Korea Aerospace University in Goyang-City, Korea. His main research interests include gas turbine heat transfer, compact heat exchanger, and enhancement of heat transfer.     

Synthesis and nonlinear optical properties of a novel polyurethane containing cyanovinylthiophene with enhanced thermal stability of dipole alignment for electro‐optic applications

Stabilization of electrically induced dipole alignment is one of the important criteria in the development of nonlinear optical (NLO) polymers for electro‐optic device applications. Polyurethanes for NLO applications have attracted attention because of their high thermal stability due to hydrogen bonding. In the work reported here, we designed and synthesized a new type of NLO polyurethane, in which the pendant NLO chromophores are part of the polymer backbone. This mid‐type NLO polymer is expected to have the merits of both main‐chain and side‐chain NLO polymers, namely stable dipole alignment and good solubility. 1‐[3,4‐Di‐(2‐hydroxyethoxy)phenyl]‐2‐(2‐thienyl)ethene was prepared and condensed with 3,3′‐dimethoxy‐4,4′‐biphenylenediisocyanate to yield a polyurethane. This polyurethane was reacted with tetracyanoethylene to give a novel Y‐type polyurethane (7) containing 1‐(3,4‐dioxyphenyl)‐2‐[5‐(1,2,2‐tricyanovinyl)‐2‐thienyl]ethenes as NLO chromophores, which constitute part of the polymer backbone. Polyurethane 7 is soluble in common organic solvents such as N,N‐dimethylformamide and dimethylsulfoxide. It shows a thermal stability up to 280 °C from thermogravimetric analysis with a glass transition temperature obtained from differential scanning calorimetry of ca 162 °C. The second harmonic generation (SHG) coefficient (d₃₃) of a poled polymer film of he polyurethane at 1560 nm fundamental wavelength is ca 1.11 × 10^?18 C. Polymer 7 exhibits an enhanced thermal stability and no significant SHG decay is observed below 150 °C, which is acceptable for NLO device applications. Copyright © 2009 Society of Chemical Industry