A noncontact NDE method using a laser generated focused-Lamb wave with enhanced defect-detection ability and spatial resolution

The laser generation method of a focused Lamb wave is expected to have high defect-detection abilities and spatial resolution, with the added advantage of noncontact testing. In this method, the laser beam is illuminated on the surface of an object through an arrayed arc slit. The energy of the generated Lamb wave is then concentrated at a focus of an arc. This focusing effect improves the NDE (nondestructive evaluation) performance, which is dependent on the geometries of an arrayed arc slit. In this paper, the relationships between the parameters determining the slit geometry and the focusing effect of the generated Lamb wave was investigated using a parametric study, and appropriate values of the parameters were obtained to maximize the focusing ability. In order to validate the performance of this method, an NDE system was constructed and experiments were performed to detect through-hole defects in a plate. The results showed that the proposed system could clearly detect defects as small as 0.3 mm in diameter, while the conventional line array method failed to detect defects smaller than 1 mm in diameter. Moreover, this method showed possible detection of defects much smaller than 0.3 mm, and great improvements in the spatial resolution as compared with the line array method.     

Physical properties of transition to chaos in RF-driven Josephson junction analog

An analog circuit is used to investigate the behavior of the transition to chaos in the rf-driven Josephson junction under the variation of excitation amplitude and frequency with McCumber parameter >1. A series of transitions is observed, including a hysteretic jump, symmetry breaking, period doubling, and intermittency prior to chaos, and the transition boundaries are given in a state diagram in the vs. parameter space. Thus, the sequence of transitions to chaos can be inferred from this diagram. Based on these results, the harmonic balance method and Floquet theory are applied to study the instability of the transition series. It is suggested that all these transitions to chaos can be explained as parametric excitations. In addition, the transition boundaries in the state diagram can be satisfactorily computed from the conditions with a Floquet multiplier =±1.     

A User‐Centric Evaluation Procedure for the Design of Child‐Resistant Medicine Bottles

Recently, people have begun to realize the importance of child‐resistant (CR) medicine packaging. However, most manufacturers and designers have not been able to effectively provide prevention strategies or design criteria to protect consumers. This research proposes a systematic approach to analyze CR packaging design problems and experiments to evaluate the identified design parameters and to generate the most suitable CR medicine packaging design. The design of a CR packaging bottle is used as an example to help explain the development procedure. During the development procedure, user trials, questionnaires, and children's anthropometric data on bottle opening and hand operations are analyzed. Five design parameters, specifically the cap diameter, cap height, bottle height, bottle diameter, and torsion, are identified and used to perform a Taguchi orthogonal array experimental analysis. A computer‐aided design system is also built to help generate the most suitable design alternatives. The results should assist designers in determining the most important CR design parameters and their most suitable combinations for bottle and related CR medicine packaging design.     

Evaluation of fracture toughness degradation of CrMoV rotor steels based on ultrasonic nonlinearity measurements

The objective of this paper is to develop a nondestructive method for estimating the fracture toughness (K _IC) of CrMoV steels used as the rotor material of steam turbines in power plants. To achieve this objective, a number of CrMoV steel samples were heat-treated, and the fracture appearance transition temperature (FATT) was determined as a function of aging time. Nonlinear ultrasonics was employed as the theoretical basis to explain the harmonic generation in a damaged material, and the nonlinearity parameter of the second harmonic wave was the experimental measure used to be correlated to the fracture toughness of the rotor steel. The nondestructive procedure for estimating theK _IC consists of two steps. First, the correlations between the nonlinearity parameter and the FATT are sought. The FATT values are then used to estimateK _IC, using theK _IC versus excess temperature (i.e.,T-FATT) correlation that is available in the literature for CrMoV rotor steel.     

Renal Protective Effects of Low Molecular Weight of Inonotus obliquus Polysaccharide (LIOP) on HFD/STZ-Induced Nephropathy in Mice

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease in diabetes mellitus. Oxidative stress, insulin resistance and pro-inflammatory cytokines have been shown to play an important role in pathogeneses of renal damage on type 2 diabetes mellitus (DM). Inonotus obliquus (IO) is a white rot fungus that belongs to the family Hymenochaetaceae; it has been used as an edible mushroom and exhibits many biological activities including anti-tumor, anti-oxidant, anti-inflammatory and anti-hyperglycemic properties. Especially the water-soluble Inonotus obliquus polysaccharides (IOPs) have been previously reported to significantly inhibit LPS-induced inflammatory cytokines in mice and protect from streptozotocin (STZ)-induced diabetic rats. In order to identify the nephroprotective effects of low molecular weight of IOP fraction (LIOP), from the fruiting bodies of Inonotus obliquus, high-fat diet (HFD) plus STZ-induced type 2-like diabetic nephropathy C57BL/6 mice were investigated in this study. Our data showed that eight weeks of administration of 10–100 kDa, LIOP (300 mg/kg) had progressively increased their sensitivity to glucose (less insulin tolerance), reduced triglyceride levels, elevated the HDL/LDL ratio and decreased urinary albumin/creatinine ratio(ACR) compared to the control group. By pathological and immunohistochemical examinations, it was indicated that LIOP can restore the integrity of the glomerular capsules and increase the numbers of glomerular mesangial cells, associated with decreased expression of TGF-β on renal cortex in mice. Consistently, three days of LIOP (100 μg/mL) incubation also provided protection against STZ + AGEs-induced glucotoxicity in renal tubular cells (LLC-PK1), while the levels of NF-κB and TGF-β expression significantly decreased in a dose-dependent manner. Our findings demonstrate that LIOP treatment could ameliorate glucolipotoxicity-induced renal fibrosis, possibly partly via the inhibition of NF-κB/TGF-β1 signaling pathway in diabetic nephropathy mice.     

The triterpenoids of Ganoderma tsugae prevent stress‐induced myocardial injury in mice

Ganoderma mushrooms (Lingzhi in Chinese) have well‐documented health benefits. Ganoderma tsugae (G. tsugae), one of the ganoderma species, has been commercially cultivated as a dietary supplement. Because G. tsugae has high antioxidant activity and because oxidative stress is often associated with cardiac injury, we hypothesized that G. tsugae protects against cardiac injury by alleviating oxidative stress. We tested the hypothesis using a work‐overload‐induced myocardial injury model created by challenging mice with isoproterenol (ISO). Remarkably, oral G. tsugae protected the mice from ISO‐induced myocardial injury. Moreover, the triterpenoid fraction of G. tsugae, composed of a mixture of nine structurally related ganoderic acids (GAs), provided cardioprotection by inhibiting the ISO‐induced expression of Fas/Fas ligand, oxidative stress, and apoptosis. The antioxidant activity of GAs was tested in cultured cardio‐myoblast H9c2 cells against the insult of H₂O₂. GAs dissipated the cellular reactive oxygen species imposed by H₂O₂ and prevented cell death. Our findings uncovered the cardioprotective activity of G. tsugae and identified GAs as the bioactive components against cardiac insults.     

The optimal used period of repairable product with leadtime after the warranty expiry

This paper considers the two-phase warranty models for repairable products. It defines the time-interval [0,?W] as the first phase (warranty period) and the time interval (W,?T?+?W) as the second phase (buyer survival period). The products have two types of failures: type I failures (minor failures) and type II failures (catastrophic failures). In the model, type I failures are also removed by minimal repairs in the first and the second phases, and type II failures are removed by replacements in the first phase. If type II failures take place in the second phase, then it is supposed the life of products will be ended. To buy a new product is conducted at time T+W or upon the type II failure. Whenever each replacement takes place, the spare unit is ordered and then delivered. Therefore, the lead-time is considered. This thesis considers three warranty and maintenance models for seller, buyer and the society. The objective is to obtain the optimal T?*. Finally, a numerical example is provided.     

A generalized age replacement policy with random delivery time and inspection

This paper is concerned with an age replacement policy that is more general because spare part random delivery time, age-dependent minimal repair and inspection are considered. Introducing the cost due to ordering, repairs, shortage, holding and inspection, we derive the expected cost per unit time in the long run as a criterion of optimality and seek the optimum age replacement policy by minimizing that cost. Various special cases are discussed and a numerical example is finally given to illustrate the method.     

Cooperative and Opportunistic Channel Access for Vehicle to Roadside (V2R) Communications

This paper focuses on vehicle to roadside (V2R) communications in vehicular networks based on the IEEE 802.11 DCF MAC protocol. In vehicular networks, roadside units (RSUs) are typically spaced apart along the road and each vehicle can be connected to an RSU only when the vehicle is within its transmission range. Due to the high relative speed between a moving vehicle and a stationary RSU, the residence time of the vehicle within the coverage of each RSU is very short. Thus it is hard for the system to reach a steady state. With multi-hop forwarding, in which a vehicle may be connected to an RSU through relaying over other vehicles, the connection time of each V2R access may be extended. But this is at the expense of introducing wireless interference among vehicles, which may dramatically degrade the system performance. To tackle these challenges, we propose a new mechanism called Proxy-based Vehicle to RSU access (PVR) for V2R communications. This protocol is designed to exploit cooperative and opportunistic forwarding between any two distant RSUs and to emulate back-to-back transmissions within the coverage of an RSU. As a result, it can shorten the access delay by taking advantage of opportunistic forwarding and mitigate the interference problem during the short residence time within the coverage of an RSU. The simulation results show that PVR achieves excellent performance and outperforms all existing solutions for V2R communications in vehicular networks.     

Efficient three‐party password‐based key exchange scheme

In three‐party password‐based key exchange protocol, a client is allowed to share a human‐memorable password with a trusted server such that two clients can negotiate a session key to communicate with each other secretly. Recently, many three‐party password‐based key exchange protocols have been developed. However, these proposed schemes cannot simultaneously achieve security and efficiency. Based on elliptic curve cryptography (ECC), this paper will propose a new simple three‐party password‐based authenticated key exchange scheme. The proposed method not only reduces computation cost for remote users and a trusted server but also is more efficient than previously proposed schemes. It is better suited for resource constrained devices, such as smart cards or mobile units. Copyright © 2010 John Wiley & Sons, Ltd.