Elastic-plastic fracture mechanics assessment for steam generator tubes with through-wall cracks

The present work provides an elastic‐plastic fracture mechanics (EPFM) assessment scheme for a steam generator tube with a through‐wall crack under internal pressure. Noting that the geometry and material are rather uniform for steam generator tubes, and furthermore the only loading to be considered is internal pressure, an engineering EPFM analysis method is proposed to assess through‐wall cracks in steam generator tubes. Important outcomes of the present work are closed‐form approximations for J and crack opening displacement (COD). Sufficient confidence in the proposed J and COD estimates is gained from good agreements with the finite element results over a wide range of the crack length and pressure magnitude. Another important element of the EPFM assessment is to determine relevant J‐resistance curve for steam generator tubes. To improve the accuracy of predicting tube failure, the present paper also proposes a new method to determine fracture toughness using an actual tubular specimen instead of using a standard specimen, from which J‐resistance curves of steam generator tubes are obtained. Using the proposed J and toughness estimates, maximum pressures of steam generator tubes with through‐wall crack are estimated based on EPFM analysis, which is compared with experimental results and predicted ones based on limit load approach.     

The long range distributed fiber raman photon temperature sensor

A 31 km long range distributed optical fiber Raman photon temperature sensor (DOFRPTS) system have been developed based on temperature effect of the amplified spontaneous Raman scattering in fiber, and using fiber laser as a pumped source. The results show that temperature measuring uncertainty is ±2 ℃, temperature resolution is 0.1 ℃, measurement time is 432 s, spatial resolution is less than 4 m.     

A LOGIC PROGRAMMING APPROACH TO HYBRID KNOWLEDGE REPRESENTATION

A new hybrid system called Sphinx is presented which combines classification-based reasoning with logic programming technique. It consists of two major components: a terminological component and an assertional one. The former uses a frame-based knowledge representation scheme based on classification and the latter is a theorem prover based on Horn logic. The assertional component can also handle a first-order query language and wh-questions. A new knowledge base maintenance mechanism based on the negation as failure inference rule enables Sphinx to support incremental assertions and retractions. In addition, Sphinx provides explanation capability to help the user in developing and debugging knowledge bases.     

EFFECTIVE DIFFUSIVITY ASSOCIATED WITH AXIAL TRANSPORT IN INSULATED OPEN-ENDED GORTER-MELLINK DUCTS

Steady, single-phase transport characterized by high eddy diffusivity in axial direction is a special case of vessel transport phenomena which has not been studied systematically so far. In the present paper, experiments are reported for a Gorter-Mellink duct, at zero net mass flow, covering turbulent eddy transport in cold He⁴ pressurized beyond its thermodynamic critical pressure above 4 K. Axial transport in vertical direction is induced by gravitational buoyancy. A new phenomenological equation is proposed on the basis of quantum fluid convection postulated originally for He II below the lambda point (Goner and Mellink, 1949). Our data agree reasonably with the equation.     

High-Temperature Electrical Conductivity of Aluminum Oxynitride Spinel

The electrical conductivity of pure aluminum oxynitride spinel was measured at 1300° to 1500°C under flowing nitrogen gas. The re sults for two nonstoichiometric spinel compositions can be fitted by exponential expressions with an activation energy of 116± I Wlmol. The mobilities calculated from aluminum vacancy concentrations and conductivities, 8.07x cm'/V-s, are reasonable for ionic conduction. The complex impedance plot suggests electrode double-layer effects being damped out at higher frequencies in the range 10'to lo4 Hz.     

EFFECTS OF OIL DROPLET AND AGAR CONCENTRATION ON GEL STRENGTH AND MICROSTRUCTURE OF O/W EMULSION GEL

The effects of oil droplet size and agar concentration on gel strength and microstructure of emulsion gels were investigated by compression test and cryoscanning electron microscope (Cryo-SEM). At all agar concentrations, the compressive stress values of emulsion gels were lower than those of the oil-free gels. Compressive stress and energy were significantly affected by oil droplet size and agar concentration, but compressive strain was not. SEM observation revealed that the overall volume of void spaces decreased and strand compactness increased with increasing agar concentration. Gels containing oil droplets had some void spaces between the gel network and the oil droplets. The strands of emulsion gels did not cover the oil globules completely, a phenomenon which was also observed for the gel with high agar concentration.     

Formation of interfacial brittle phases sigma phase and IMC in hybrid titanium-to-stainless steel joint

The microstructures of the brazed joints for commercially pure Ti and stainless steel were investigated by the applications of various filler alloys including Ag-, Ti-, Zr- and Ni-based alloys. Generally, the dissimilar joints between Ti and stainless steel were dominated by the Ti-based intermetallic compounds (IMCs), e.g. (Ti, Zr)2(Fe, Ni), TiFe, TiCu, and Ti2(Fe, Ni), due to a significant dissolution of Ti from the base metal. The (Fe-Cr) σ phase was also observed near the stainless steel due to a segregation of Cr into the interface region. This research demonstrates empirically that the brittleness of the Ti and stainless steel joint can not be avoided only by applying single braze alloy or single insert metal, and thus an introduction of additional suitable interlayer between the filler alloy and the base metal is necessary to prevent the brittleness of the joint.     

Economic analysis of inventory systems: a clarifying analysis

In a recent study by Gurnani (1983), ‘Economic analysis of inventory systems’, three main conclusions were presented. (1) The inventory models analysed in his paper demonstrate that the inventory policy derived from the discounted (PW) coat differs substantially from that given by the traditional undiscounted inventory analysis. (2) The difference between the two depends upon the discounting rate. The discounting causes the optimum order quantity and correspondingly the period length to vary monotonically with the discounting rate. (3) However, it is not influenced by the inventory system planning horizon. This paper first examines each conclusion and demonstrates why his conclusions are either unfounded or irrelevant to his analysis. Next, some crucial derivational errors in his exposition are demonstrated via corrected formulations. Finally, a net present value maximizing framework that is consistent with modern theory of financial analysis, is suggested for the economic analysis of inventory systems.     

EXPERIMENTAL AND NUMERICAL STUDY FOR HYDRODYNAMIC CHARACTERISTICS OF AN OSCILLATING HYDROFOIL

The present article reports the experimental Particle Image Velocimetry （PIV） investigation and the corresponding numerical simulation results about the water flow over the oscillating hydrofoil and its unsteady dynamic characters. The experimental study focuses on the effect of mean angles of attack. The comparison between the PIV results and numerical prediction about the flow field using Fluent well demonstrates the capability of CFD on the simulation of the water flow around the pitching hydrofoil. The numerical results indicate that the forced oscillating frequencies have evident effects on the flow separation and vortex shedding. The simulations about the hydrodynamic drag and lift coefficients were also performed.     

Characterization and Identification of Raw Beef, Pork, Chicken and Turkey Meats by Electrophoretic Patterns of Their Sarcoplasmic Proteins

Electrophoretic patterns of fresh beef, pork, chicken, and turkey sarcoplasmic proteins were studied using thin layer agarose gel electro-phoresis. Creatine kinase isozyme MM and myoglobin bands were used to identify the species. Binary mixtures (5/95, 25175, 50150, 751 25, 9515, % by weight of each species) were also examined by their electrophoretic and densitometric patterns. Electrophoretic patterns remained stable at elevated pH (7.5), but were affected by low pH (4.7). The relative ratios of the bands which characterized each species changed in proportion to the species content in each binary mixture. These ratios make it possible to predict the approximate fraction of each species present in such mixtures.