bluuebunny/crossref_metadata_2025 huggingface dataset:
N‐Substituted Glutamyl Sulfonamides as Inhibitors of Glutamate Carboxypeptidase II (GCP2)
Authors: Blank Brian R. , Alayoglu Pinar , Engen William , Choi Joseph K. , Berkman Clifford E. , Anderson Marc O.
Published: January 2011

Glutamate carboxypeptidase II (GCP2) is a membrane‐bound cell‐surface peptidase which is implicated in several neurological disorders and is also over‐expressed in prostate tumor cells. There is a significant interest in the inhibition of GCP2 as a means of neuroprotection, while GCP2 inhibition as a method to treat prostate cancer remains a topic of further investigation. The key zinc‐binding functional group of the well‐characterized classes of GCP2 inhibitors (phosphonates and phosphoramidates) is tetrahedral and negatively charged at neutral pH, while glutamyl urea class of inhibitors possesses a planar and neutral zinc‐binding group. This study introduces a new class of GCP2 inhibitors, N‐substituted glutamyl sulfonamides, which possess a neutral tetrahedral zinc‐binding motif. A library containing 15 secondary sulfonamides and 4 tertiary (N‐methyl) sulfonamides was prepared and evaluated for inhibitory potency against purified GCP2 enzyme activity. While most inhibitors lacked potency at 100 μm, short alkyl sulfonamides exhibited promising low micromolar potency, with the optimal inhibitor in this series being glutamyl N‐(propylsulfonamide) (2g). Lastly, molecular docking was used to develop a model to formulate an explanation for the relative inhibitory potencies employed for this class of inhibitors.
The Changing Face of Neurosyphilis
Authors: Chahine Lama M. , Khoriaty Rami N. , Tomford Walton J. , Hussain Muhammad S.
Published: January 2011

The incidence of syphilis has increased over the past decade, particularly among HIV-positive patients, and the presenting clinical features have changed since the beginning of the HIV epidemic. The clinical manifestations of neurosyphilis are protean, and include acute stroke. In patients with HIV, the diagnosis and treatment of neurosyphilis is challenging. We review the clinical presentation, pathophysiology, and treatment of neurosyphilis, with emphasis on neurosyphilis in the HIV population, and neurosyphilis as a cause of acute stroke.
GGR Biennial Review: Atomic Absorption, Inductively Coupled Plasma‐Atomic Emission Spectrometry, Neutron Activation Analysis and X‐Ray Fluorescence Spectrometry Review for 2008–2009
Authors: Bédard L. Paul , Linge Kathryn L.
Published: January 2011

This review describes developments major and in trace element determination using atomic absorption spectroscopy (AAS), inductively coupled plasma‐atomic emission spectrometry (ICP‐AES), instrumental neutron activation analysis (INAA), and X‐ray fluorescence (XRF) spectrometry that were reported in 2008 and 2009. Publication levels were comparable to those of previous years, except for XRF which showed an increase in the number of articles published in the past 2 years. In terms of number of publications and impact, the most active field was AAS, while INAA was the least active. As expected for well‐established and mature methods, novel developments for all four analytical techniques were relatively sparse. For AAS, the most notable publications concerned developments in sample introduction, particularly focussing on solid samples, increasing analyte sensitivity, and higher sample throughput. For ICP‐AES, publication of developments in sample introduction, remediation of matrix effects and calibration continues. Compared with past years, there was a clear focus on sample preconcentration methods, but very few publications reporting new hyphenated speciation methods. For INAA, there were several publications exploring the accuracy and robustness of the method, as well as the requirements for INAA to meet criteria for a primary method of measurement. Two other related techniques, delayed neutron activation analysis, and prompt gamma activation analysis, were also described. Hyphenated XRF techniques showed interesting developments in enabling XRF and XRD analysis on the same spot, and further work characterising and calibrating three‐dimensional micro‐XRF shows promising results for investigating sample heterogeneity.
A Neural Model of Rule Generation in Inductive Reasoning
Authors: Rasmussen Daniel , Eliasmith Chris
Published: January 2011

Inductive reasoning is a fundamental and complex aspect of human intelligence. In particular, how do subjects, given a set of particular examples, generate general descriptions of the rules governing that set? We present a biologically plausible method for accomplishing this task and implement it in a spiking neuron model. We demonstrate the success of this model by applying it to the problem domain of Raven's Progressive Matrices, a widely used tool in the field of intelligence testing. The model is able to generate the rules necessary to correctly solve Raven's items, as well as recreate many of the experimental effects observed in human subjects.
Revenue and Cost Management for Remanufactured Products
Authors: Ovchinnikov Anton
Published: January 2011

This paper considers pricing and remanufacturing strategy of a firm that decides to offer both new and remanufactured versions of its product in the market and is concerned with demand cannibalization. We present a model of demand cannibalization and a behavioral study that estimates a key modeling parameter: a fraction of consumers who switch from new to remanufactured product. As we show, this fraction has an inverted‐U shape, and, thus, the underlying consumer behavior cannot be modeled using the standard methodologies that rely on consumers' willingness to pay (WTP). We find that by incorporating the inverted‐U‐shaped consumer behavior, the firm remanufactures under broader conditions, charges a much lower price, and typically remanufactures more units—leading to an increase of profits from remanufacturing by up to a factor of two as compared with making decisions based on the WTP only. Lastly, we find that the behavior of the low‐price market segment plays an important role because the firm reacts to it differently than the WTP‐based logic would suggest.
Optimal Enhancement and Lifetime of Software Systems: A Control Theoretic Analysis
Authors: Ji Yonghua , Kumar Subodha , Mookerjee Vijay S. , Sethi Suresh P. , Yeh Denny
Published: January 2011

We develop an optimal control model to maximize the net value provided by a software system over its useful life. The model determines the initial number of features in the system, the level of dynamic enhancement effort, and the lifetime of the system. The various factors affecting these optimal choices are systems characteristics (e.g., complexity, age, quality), user learning, and process maturity. We also consider that there is a time lag between the addition of a feature and the realization of its benefit to users. The basic model is extended to consider the decision of replacing the existing system by a new one.
Pricing Decisions During Inter‐Generational Product Transition
Authors: Li Hongmin , Graves Stephen C.
Published: January 2011

How should companies price products during an inter‐generational transition? High uncertainty in a new product introduction often leads to extreme cases of demand and supply mismatches. Pricing is an effective tool to either prevent or alleviate these problems. We study the optimal pricing decisions in the context of a product transition in which a new‐generation product replaces an old one. We formulate the dynamic pricing problem and derive the optimal prices for both the old and new products. Our analysis sheds light on the pattern of the optimal prices for the two products during the transition and on how product replacement, along with several other dynamics including substitution, external competition, scarcity, and inventory, affect the optimal prices. We also determine the optimal initial inventory for each product and discuss a heuristic method.
Pharmacy clients' attitudes to expanded pharmacist prescribing and the role of agency theory on involved stakeholders
Authors: Hoti Kreshnik , Hughes Jeffery , Sunderland Bruce
Published: January 2011

Objective

To examine the views of regular pharmacy clients on pharmacist prescribing and employ agency theory in considering the relationship between the stakeholders involved.

Methods

Computer assisted telephone interviews were conducted with 400 pharmacy clients recruited around Australia. Potential respondents were identified using a random number generation function in Microsoft Excel. Data were analysed with SPSS version 17 using one-way analysis of variance, principal component analysis and linear regression. The relationships between the main stakeholders involved were explored using agency theory.

Key findings

A total of 1153 answered calls recruited 400 consenting pharmacy clients. Most respondents (71%) trusted pharmacists adopting an expanded role in prescribing, however the majority (66%) supported this only after a diagnosis had been made by a doctor. Those who accepted pharmacist diagnosing and prescribing preferred that this was limited to pain management and antibiotics. Most respondents (64%) considered that expanded pharmacist prescribing would improve their access to prescription medicines, although those over 65 years of age were less supportive than younger respondents. Factors which contributed positively to clients' perception of trust in an expanded prescribing role for pharmacists were identified, and improved access to medicines was found to be the strongest predictor (P < 0.0001).

Conclusion

Most pharmacy clients trusted pharmacists adopting an expanded prescribing role, but preferred that this was limited to doctors performing the initial diagnosis. Agency theory would conceptualize the introduction of pharmacist prescribers, as disrupting the principal (patient) agent (doctor) relationship. Its introduction would best be facilitated by careful change management.
Numerical Simulation of Dynamics and Heat Transfer Associated With a Single Bubble in Subcooled Boiling and in the Presence of Noncondensables
Authors: Wu Jinfeng , Dhir Vijay K.
Published: January 2011

During phase change at the bubble-liquid interface, under subcooled boiling conditions, noncondensable gases dissolved in the liquid will be injected into the bubble along with vapor. Due to heat transfer into subcooled liquid, vapor will condense in the upper regions of the bubble while noncondensables will continue to accumulate. Subsequently, thermocapillary convection caused by nonuniform saturation temperature at the interface may occur. The aim of this work is to investigate the effects of noncondensables on heat transfer and bubble dynamics. The numerical results show that the effects of noncondensables on 5°C subcooled boiling of water are minor in terms of the equilibrium bubble diameter and overall Nusselt number. However, induced flow pattern around the bubble is altered, especially under reduced gravity conditions.
Review of Heat Conduction in Nanofluids
Authors: Fan Jing , Wang Liqiu
Published: January 2011

Nanofluids—fluid suspensions of nanometer-sized particles—are a very important area of emerging technology and are playing an increasingly important role in the continuing advances of nanotechnology and biotechnology worldwide. They have enormously exciting potential applications and may revolutionize the field of heat transfer. This review is on the advances in our understanding of heat-conduction process in nanofluids. The emphasis centers on the thermal conductivity of nanofluids: its experimental data, proposed mechanisms responsible for its enhancement, and its predicting models. A relatively intensified effort has been made on determining thermal conductivity of nanofluids from experiments. While the detailed microstructure-conductivity relationship is still unknown, the data from these experiments have enabled some trends to be identified. Suggested microscopic reasons for the experimental finding of significant conductivity enhancement include the nanoparticle Brownian motion, the Brownian-motion-induced convection, the liquid layering at the liquid-particle interface, and the nanoparticle cluster/aggregate. Although there is a lack of agreement regarding the role of the first three effects, the last effect is generally accepted to be responsible for the reported conductivity enhancement. The available models of predicting conductivity of nanofluids all involve some empirical parameters that negate their predicting ability and application. The recently developed first-principles theory of thermal waves offers not only a macroscopic reason for experimental observations but also a model governing the microstructure-conductivity relationship without involving any empirical parameter.
Waukesha 275GL Series NOx Control System Development and Performance Testing
Authors: Wentz Jared J.
Published: January 2011

Dresser Waukesha’s 275GL engine series, released in 2009, included an Engine System Manager (ESM) to manage and control critical engine operations. These engines are typically used in mechanical drive applications for natural gas compression as well as power generation at 2500 to 3300 kWb (3400–4500 bhp). The 275GL is now being offered in a low NOx configuration designated the 275GL+, that features a NOx based Air/Fuel Ratio (AFR) control. Market analysis determined that an engine with lower NOx output emissions while maintaining peak performance is of high importance. Utilizing a traditional oxygen based AFR system has limitations when controlling emissions at extreme low NOx values. In order to meet these needs and maintain a consistent low NOx level, development of a control system that allows an engine to achieve these requirements was essential. A NOx sensor based control system was developed to control extremely low NOx values while accounting for engine wear, humidity and fuel changes. An oxygen based AFR system has limitations that make it difficult, if not impossible, to use this approach for extremely low NOx levels. Some of these limitations can be attributed to sensor signal masking due to exhaust gases and having to correlate O2 to NOx for the specific application. This new NOx sensing functionality enables robust control of specific NOx emissions at varying engine and environmental conditions, yielding a powerful addition to the ESM engine control system applied on the 275GL engine. The NOx control running with ESM allows for the engine to achieve 0.5 g/bhp-hr NOx levels while maintaining fuel efficiency, fuel tolerance, and turndown range. This paper discusses the key testing, results and performance of this development when implemented on the 275GL+ engine.
An Experimental Investigation of Low Octane Gasoline in Diesel Engines
Authors: Ciatti Stephen , Subramanian Swami Nathan
Published: January 2011

Conventional combustion techniques struggle to meet the current emissions norms. In particular, oxides of nitrogen (NOx) and particulate matter (PM) emissions have limited the utilization of diesel fuel in compression ignition engines. Advance combustion concepts have proved the potential to combine fuel efficiency and improved emissions performance. Low Temperature Combustion (LTC) offers reduced NOx and PM emissions with comparable modern diesel engine efficiencies. The ability of premixed, low-temperature compression ignition to deliver low PM and NOx emissions is dependent on achieving optimal combustion phasing. Diesel operated LTC is limited by early knocking combustion whereas conventional gasoline operated LTC is limited by misfiring. So the concept of using an unconventional fuel with the properties in between those two boundary fuels has been experimented in this paper. Low octane (84 RON) gasoline has shown comparable diesel efficiencies with lowest NOx emissions at reasonable high power densities (NOx emission were 1 g/kW-hr at 12 bar BMEP and 2750 rpm).
Development of an Advanced Retrofit Aftertreatment System Targeting Toxic Air Contaminants and Particulate Matter Emissions From HD-CNG Engines
Authors: Kappanna Hemanth , Besch Marc C. , Carder Daniel K. , Gautam Mridul , Oshinuga Adewale , Miyasato Matt
Published: January 2011

Increasing urban pollution levels have led to the imposition of evermore stringent emissions regulations on heavy-duty engines used in transit buses. This has made compressed natural gas (CNG) a promising fuel for reducing emissions, particularly particulate matter (PM) from heavy-duty transit buses. Indeed, research studies performed at West Virginia University (WVU) and elsewhere have shown that pre-2010 compliant natural gas engines emit an order of magnitude lower PM emissions, on a mass basis, when compared to diesel engines without any exhaust aftertreatment devices. However, on a number basis, particle emissions in the nanoparticulate range were an order of magnitude higher for natural gas fueled buses than their diesel counterparts. There exists a significant number of pre-2007 CNG powered buses in transit agencies in the US and elsewhere in the world. Therefore, an exhaust aftertreatment device was designed and developed by WVU, in association with Lubrizol, to retrofit urban transit buses powered by MY2000 Cummins Westport C8.3G+ heavy-duty CNG engines, and effectively reduce Toxic Air Contaminants (TAC) and PM (mass and number count) exhaust emissions. The speciation results showed that the new exhaust aftertreatment device reduced emissions of metallic elements such as iron, zinc, nonmetallic minerals such as calcium, phosphorus and sulfur derived from lube oil additives to non-detectable levels, which otherwise could contribute to an increase in number count of nanoparticles. The carbonyl compounds were reduced effectively by the oxidation catalyst to levels below what were found in the dilution air. Also, hydrocarbons identified as TAC’s by California Air Resource Board (CARB) [1] were reduced to non-detectable levels. This ultimately reduced the number of nanoparticles to levels equal to that found in the dilution air.
Optimal Combustion Positioning Methodology Based on MFB50 On-Board Estimation
Authors: Ponti Fabrizio , Ravaglioli Vittorio , Serra Gabriele
Published: January 2011

As a result of the increasing request to reduce pollutant emissions and improve efficiency in modern Internal Combustion Engines, it is important to know a high number of quantities that are representative of the combustion process. One of the most important parameters to estimate on-board is the angular position where 50% of fuel mass injected over an engine cycle is burned (MFB50), because it provides information about the effectiveness of combustion (useful, for example, in HCCI combustion control). MFB50 can be evaluated using in-cylinder pressure sensors, nevertheless they would cause engine control systems cost to rise. The MFB50 estimation algorithm presented in this work is based on engine speed measurement, that can be performed using the same 60-2 toothed wheel already present on-board for other control purposes. For the above reason, this approach is not only compatible with on-board applications, it also requires no additional costs. The developed method mainly consists of 2 parts. The first one is to determine the relationship between the engine speed harmonic components and the corresponding indicated torque harmonic components, expressed as a Frequency Response Function representative of the engine-load system’s torsional behavior. After having estimated the indicated torque harmonic component, the following step is to estimate the value of MFB50 cycle by cycle. This is done analyzing the relationships between the indicated torque harmonic components phase and the angular position where 50% of the fuel injected over the engine cycle is burned. The procedure has been applied to an L4 turbocharged Diesel engine mounted on-board a vehicle, obtaining an estimation accuracy adequate enough to feedback a control algorithm for optimal combustion positioning over an engine cycle.
Development of a Cycle-Resolved Mechanism for Carbon Monoxide Formation
Authors: McFarland Jacob J. , Grauer Diana K. , Chapman Kirby S.
Published: January 2011

This paper presents an investigation into CO formation in large-bore two-stroke cycle (2SC) lean-burn engines. On March 5, 2009, the Environmental Protection Agency (EPA) proposed a new rule to addressing National Emission Standards for Hazardous Air Pollutants (HAP) for existing stationary reciprocating internal combustion engines. Specifically, the 2009 Proposed Rule identifies carbon monoxide (CO) as a surrogate for HAP and requires reductions in CO for 2SC lean-burn engines. This future promulgation has created the need for a comprehensive kinetic CO formation model. The CO model itself integrates equilibrium concentration values of CO with the CO concentration created later in the cycle from the dissociation of equilibrium CO2. The previously developed variable-geometry multi-cylinder Turbocharged-Reciprocating Engine Compressor Simulation (T-RECS) has been modified with a mechanism to model cycle-resolved CO formation using a calibrated kinetic reaction scheme. The simplified chemical kinetic CO reaction scheme has been tuned and validated with exhaust concentration data collected on a Cooper GMVC large-bore two-stroke cycle engine, and directly relates the impact of engine operating conditions and in-cylinder geometry.
Exhaust Emissions of a H2-Enriched Heavy-Duty Diesel Engine Equipped With Cooled EGR and Variable Geometry Turbocharger
Authors: Liew C. , Li H. , Liu S. , Besch M. C. , Ralston B. , Clark N. , Huang Y.
Published: January 2011

This paper investigated the effect of hydrogen (H2) addition on the exhaust emissions of a 2004 Mack MP7 355E diesel engine. As expected, the addition of H2 substantially reduced the emissions of particulate matter (PM), unburned hydrocarbon (HC), and carbon dioxide (CO2). However, the effect of H2 addition on the emissions of carbon monoxide (CO) and nitrogen oxide (NOx) depended on the amount of H2 added and the engine load. When preliminarily measured using the 13-mode European Stationary Cycle (ESC), the addition of 2% and 4% (vol. % in intake mixture) H2 significantly increased nitrogen dioxide (NO2) emissions and slightly reduced nitric oxide (NO) emissions. In comparison, the H2 addition only minimally affected NOx emissions. The detailed effects of H2 addition on the exhaust emissions were investigated for various loads at 1200 rpm. The addition of H2 at low load mildly influenced NOx emissions, with the exception of 10% load operation. Adding over 4% H2 at 10% load began to reduce NOx emissions. When operated at medium to high load, the addition of a relatively small amount of H2 slightly reduced NOx emissions. The expected increase in NOx emissions was observed only with the addition of a large amount of H2. When operated at full load, the addition of H2 had negligible effect on NOx emissions. In a few cases, a minor change in H2 flow rate suddenly increased the emissions of NOx. By further increasing or reducing the amount of H2 added, NOx emissions resumed to their expected values. This discrepancy was attributed to the unexpected change in EGR flow rate. Based on the data obtained, it seems infeasible to substantially reduce the exhaust emissions of diesel engine through the addition of a small amount of H2 such as that produced on-board using a small H2O electrolyzer.
Evaluation of Thermal Contact Resistance at the Interface Composed of Dissimilar Materials
Authors: Fukuoka Toshimichi , Nomura Masataka
Published: January 2011

When jointed portions of structures and machines are subjected to thermal loads, various problems and troubles occur due to the difference in thermal expansions between mating parts. In order to accurately analyze thermal and mechanical behaviors of the joints, the effect of thermal contact resistance must be taken into account. In this paper, thermal contact coefficient, which is the reciprocal of thermal contact resistance, at the interface composed of dissimilar materials is quantitatively measured by infrared thermography. The target materials are common engineering materials such as carbon steel, stainless steel and aluminum alloy. It has been shown in the previous papers that there exits a significant directional effect in thermal contact coefficients when the mating surface is composed of different materials. That is, thermal contact coefficient has a larger value when the heat flows from the material with lower thermal conductivity to the one with higher thermal conductivity. The effects of contact pressure and surface roughness on the coefficient are also evaluated in this work. Using the measured data, an empirical equation to estimate thermal contact coefficient is proposed, for the purpose of engineering applications, which correlates closely with the experimental data.
Time-Dependent Risk Control of Crucial Tube Furnace With SIL Requirement Considered
Authors: Zhu Jianxin , Chen Xuedong , Ai Zhibin , Guan Weihe
Published: January 2011

Hydrogenator feed tube furnace is of great safety concern due to its rigorous operation condition (up to 550°C, 17MPa) and flammable/explosive materials (H2, crude oil) involved in refining installations. Unlike instruments where the failure may not necessarily cause direct hazards, the failure of tubes in high temperature furnace always cause severe damage and downtime-caused economic loss. Normally the main cause of tube failure is time-dependent material degradation mechanism (such as creep, fatigue and oxidation). The occurrence of two tube rupture accidents gives birth to the consideration whether it is necessary to add a new isolation/mitigation layer in tube furnace in order to control time dependent risks. Taking advantage of the progress of life and probability prediction techniques (such as API581), the time-dependent risk of high pressure tube furnace was studied by taking into account of contributions provided by control system and safety instrumented functions (SIF). The frequency of severe initial events (leakage or rupture) of furnace tube was studied and fault tree analysis method was used to analyze the combined failure probability of time-dependent tube failure rate, basic process control system (BPCS) as well as safety instrumented system (SIS). The necessity of adding a mitigation function to reduce consequence caused by tube failure (leakage or rupture) was studied in order to control time dependent risks. A mitigation SIF at tube’s late service stage to reduce risks was proposed, which is of great significance for furnace safety.
Development of LBB Assessment Method for Japanese Sodium Cooled Fast Reactor (JSFR) Pipes: 3—Fracture Assessment Methods Considering Compliance at a Crack Part
Authors: Wakai Takashi , Machida Hideo , Yoshida Shinji , Enuma Yasuhiro , Asayama Tai
Published: January 2011

This paper presents a fracture assessment methods used in leak before break (LBB) assessment of sodium piping system in the Japanese sodium cooled fast reactor (JSFR). Use of thin wall pipes and compact layout of piping system are features of the design in JSFR. Since the internal pressure of piping of JSFR is low, the critical load is thermal expansion. Supposing a through wall crack (TWC) in such piping, the stiffness of the crack part will decrease, the load balance of the piping system will change from the condition without crack. The fracture assessment methods paying attention to this stiffness change at the crack part were proposed and these methods enabled rational LBB assessment. The proposed methods are much effective to loosen LBB conditions for the piping system of which the compliance is low. These methods applied to the LBB assessment of the piping system of JSFR which has the compact layout, and it was checked that the validity of these methods to loosen the LBB conditions.
Validation of the K and J Parameters in a Compact Tension Specimen Containing Intergranular and Straight Crack Paths
Authors: Mehmanparast A. N. , Davies C. M. , Nikbin K. M.
Published: January 2011

Methods have been examined to evaluate the fracture mechanics parameters J and K in finite element (FE) analyses on a compact tension, C(T), geometry using a mesh appropriate for the evaluation of both intergranular and transgranular microstructural damage processes. Realistic grain and grain boundary microstructures were modelled using ABAQUS. Both straight and deviating crack profiles were considered, representing transgranular and intergranular crack growth processes, respectively. Elastic and elastic-plastic finite element analyses were performed on a C(T) specimen model with a standard straight and deviating crack profile to derive and compare the stress intensity factor, K, and J parameter values under plane stress and plane strain conditions. Considerations as to the validity of the J domain integral calculations that ABAQUS computes are discussed. It has been found that the values of K and J obtained from FE simulations are consistent with theoretical solutions and the stress distribution ahead of the crack tip is very close to that of expected from analytical studies for the case of a straight fronted transgranular crack. Reasonable values of K and J parameters could also be achieved from the FE contour integral values of a deviating crack when the contours selected were adequately far from the crack tip. However, significant differences were found between the analytical and FE contour integral values of a deviating crack when the crack growth direction was considered to continue at the angle defined by its grain boundary. The values of J obtained by from the load line displacement measurements were uninfluenced by the crack profile and in good agreement with other analytical solutions.
Analysis of Residual Stresses in Three-Pass Slot Weld (NeT-TG4): Finite Element Modelling and Neutron Diffraction
Authors: Mura´nsky Ondrej , Bendeich Philip J. , Smith Mike C. , Kirstein Oliver , Edwards Lyndon , Holden Tom M.
Published: January 2011

In this paper finite element simulation and neutron diffraction measurements are employed to assess the residual stresses in an AISI 316LN austenitic stainless steel plate containing a three-pass finite length weld in a machined slot. This work forms a part of the Task Group 4 (TG4) measurement and simulation round robin being undertaken by the NeT European network. Finite element (FE) simulations were carried out using the FEAT-WMT and ABAQUS commercial finite element packages. The welding process was modelled both using a 3D moving-heat source (MHS) which is spatially correct but computationally expensive and using a simplified “block-dumped” methodology (BD) in which an entire weld bead is deposited simultaneously. This does not reproduce the effects of welding torch movement, but is computationally less expensive. The mechanical analyses used combined isotropic-kinematic material constitutive models with a two-stage annealing functionality to remove plastic strain accumulated at high temperatures. The finite element predictions of weld residual stress are compared with neutron diffraction measurements obtained on the KOWARI diffractometer at the OPAL reactor at ANSTO.
The Typical Steels for Pressure Equipment in China
Authors: Zuo Shangzhi , Shou Binan , Yang Guoyi
Published: January 2011

In this paper, the typical steels for Pressure Equipment in China are briefly introduced. On the basis of China, ASME and EN material standards, the general requirements, the relevant properties of the steels for Pressure Equipment are compared. The quality condition of the typical steels for Pressure Equipment in China is analyzed. And the development tendency of Chinese typical steels for Pressure Equipment is forecasted.
Growth Behavior of Two Interacting Surface Cracks of Dissimilar Size (Comparison for Tensile and Bending Load)
Authors: Kamaya Masayuki , Kikuchi Masanori , Miyokawa Eiichi
Published: January 2011

When multiple cracks approach one another, the stress intensity factor is likely to change due to the interaction of the stress field. This causes change in growth rate and shape of cracks. In particular, when cracks are in parallel position to the loading direction, the shape of cracks becomes non-planar. In this study, the complex growth of interacting cracks is evaluated by using the S-Version finite element method, in which local detailed finite element mesh (local mesh) is superposed on cores finite element model (global mesh) representing the global structure. In this study, two parallel surface cracks are subjected to two types of loading; tensile and bending load. Comparisons are made on the growth behavior under two types of loading. It is shown that the smaller crack stop growing due to the interaction when the difference in size of two cracks is large. This tendency is more significant for the bending load. The procedure for evaluating crack growth for Fitness-for-Service assessment is discussed.
Damage Observations of the Straight Pipes Subjected to Cyclic Load Amplitudes of Various Levels
Authors: Nakamura Izumi , Otani Akihito , Shiratori Masaki
Published: January 2011

Fatigue failure accompanied by ratchet deformation is well known as one of the failure modes of pressurized pipes under high-stress level cyclic load. In this research, the process of failure of such pipes was investigated based on the experimental result in which a straight pipe failed by increasing cyclic input of displacement amplitude step-by-step. The strain behavior, moment-deflection relationship, and observed damage were compared with the stress levels prescribed in the seismic design of the piping system in Japan. As a result, no significant damage was observed and the moment-deflection relationship remained almost linear within the primary stress limit of 3Sm, although the strains at some measurement points reached to the plastic region. In the experiment, damage was observed at the applied load level of approximately 5Sm of the primary stress level, and 0.15 and more of the fatigue damage index, i.e., the usage factor based on the design. The test results showed that there is several times as much margin as its designed stress limitation before failure occurs to actual piping systems.
The Future of the BS 7910 Flaw Assessment Procedures
Authors: Hadley Isabel , Ainsworth Bob , Budden Peter , Sharples John
Published: January 2011

BS 7910, the UK procedure for the assessment of flaws in metallic structures, was first published some 30 years ago in the form of a fracture/fatigue assessment procedure, PD6493. Since then it has been regularly maintained and expanded, taking in elements of other publications such as the UK power industry’s ‘R6’ procedure (in particular the Failure Assessment Diagram or FAD approach), the creep assessment procedure PD6539 and the UK gas transmission industry’s approach to corrosion assessment of locally thinned areas in pipelines. Work is currently underway to prepare another major revision, this time incorporating many elements of the European flaw assessment procedure FITNET. Like its predecessor, the new BS 7910 is intended for use by a range of industry sectors for virtually any type of metallic structure or component. The procedures will cover damage and failure by fatigue crack growth, fracture, creep and corrosion, including Environmentally Assisted Corrosion. The objective in revising the procedures is to support the use of more advanced assessment methods, whilst preserving compatibility with previous editions of BS 7910 and retaining methods for preliminary analyses based on simple, conservative inputs. Features of the new BS 7910 will include adoption of new advanced fracture assessment procedures (taking account of crack tip constraint and weld strength mismatch where appropriate), revision of the residual stress annex, preparation of a new annex covering guidance on NDE, an enhanced library of K-solutions and reference stress solutions and greater compatibility with procedures such as R6 and FITNET.
Method to Estimate the Bolt Loads to Satisfy Tightness Criteria for Gasketed Bolted Flanged Connections
Authors: Kobayashi Takashi , Masui Kiichi , Nishiura Kengou , Shibata Hideshi
Published: January 2011

With the recent increase of a safety and environmental concern, the tightness of gasketed flanged connections becomes an important issue. In estimating the tightness of gasketed flanged connections, the sealing behavior of gaskets must be known. Currently, methods to test the sealing behaviors have been established in the North America, Europe and Japan. However, the relationships between the gasket data and the tightness of gasketed flanged connections have not been examined systematically. This paper consists of two parts: gasket data concerning sealing behavior and tightness of gasketed flanged connections. Firstly, several sheet gaskets were tested based on the test method JIS B 2490 in order to grasp tightness characteristics of gaskets. Secondly, tightness tests are carried out using blind flanges with the gaskets used in the gasket test. Both the results are compared and discussed to highlight the relationship between them. It is shown that the tightness of bolted flanged connections is largely affected by the sealing behavior of gaskets. Finally, based on the results, a simplified method to estimate the tightness of flanged connections is proposed and applied bolting load.
Single Phase CFD Inside a Water Safety Valve
Authors: Vallet Christophe , Ferrari Je´roˆme , Rit Jean-Franc¸ois , Dehoux Fe´de´ric
Published: January 2011

In this paper, Computational Fluid Dynamics (CFD) modeling is used to improve the understanding of the liquid flow inside a safety valve and to predict both the hydraulic force acting on the disk and the flow coefficient Cv. The three-dimensional simulations are performed on a realistic geometry and with an unstructured hybrid mesh. Independent calculations are performed for several valve openings. Turbulence is simulated using the Reynolds-Averaged Navier-Stokes (RANS) model k – ω SST, and a single-phase flow is considered for simplification. First, sensitivity of results with boundary conditions and mesh fineness is analysed. The dependence of hydraulic parameters with the valve opening is then investigated and numerical results are compared to experimental data coming from a test rig reproducing industrial conditions. Results indicate firstly that the flow inside the valve is stationary and axisymmetric. Quantitative comparison with the experiment must account for cavitation which is not simulated. We show, however, the adequacy of our results with experimental data and that single phase CFD can provide valuable insights on cavitating relief valve flow.
Elastic-Plastic Shakedown Evaluation Using ASME Code Section III and Section VIII Methods
Authors: Molitoris David P. , Gregg John V. , Heald Edward E. , Roarty David H. , Heald Benjamin E.
Published: January 2011

Section III, Division 1 and Section VIII, Division 2 of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code provide procedures for demonstrating shakedown using elastic-plastic analysis. While these procedures may be used in place of elastic analysis procedures, they are typically employed after the elastic analysis and simplified elastic-plastic analysis limits have been exceeded. In using the Section III, Division 1 and Section VIII, Division 2 procedures for elastic-plastic shakedown analyses, three concerns are raised. First, the Section III, Division 1 procedure is vague, which can result in inconsistent results between analysts. Second, the acceptance criteria contained in both procedures are vague, which can also result in inconsistent results between analysts. Lastly, differences in the procedures and acceptance criteria can result in demonstration of component elastic-plastic shakedown under Section III, Division 1 but not under Section VIII, Division 2. The authors presume that the ASME Code intends to provide similar design and analysis conclusions, which may not be a correct assumption. To demonstrate these concerns, a nozzle benchmark design subject to a representative thermal and pressure transient was evaluated using the two Code elastic-plastic shakedown procedures. Shakedown was successfully demonstrated using the Section III, Division 1 procedure. However, shakedown could not be demonstrated using the Section VIII, Division 2 procedure. The conflicting results seem to indicate that, for the nozzle design evaluated, the Section VIII, Division 2 procedure is considerably more conservative than the Section III, Division 1 procedure. To further assess the conservative nature of the Section VIII, Division 2 procedure, the nozzle benchmark design was evaluated using the same thermal transient, but without a pressure load. While shakedown was technically not observed using the Section VIII, Division 2 acceptance criteria, engineering judgment concluded that shakedown was demonstrated. Based on the results of all the evaluations, recommendations for modifications to both procedures were presented for consideration.
Evolution of Plasticity in Relation to Ductile Tearing in 304(L) Stainless Steel
Authors: Wasylyk Andrew P. , Sherry Andrew H.
Published: January 2011

In the structural integrity assessment of structures containing defects, ductile tearing and plastic collapse are treated as competing failure mechanisms. The validity of fracture toughness measurements in test specimens is limited by the development of plasticity ahead of the crack tip. Compact Tension (CT) specimens are commonly used to characterise the ductile fracture toughness. Two sizes of CT specimens (thickness 25 and 15mm) were tested using the unloading compliance technique and the J-Resistance curve characterised. Concurrently, the development of the plastic zone was monitored on the surface of specimens using digital image correlation. This enabled the plastic zone size to be correlated with the evolution of crack growth. It was found that in both specimens no crack growth had occurred prior to plastic yielding of the un-cracked ligament on the specimen surface.
Failure of a Seamless 2-1/4Cr-1Mo Hot-Reheat Pipe Bend: Acoustic Emission Testing and Fitness for Service of Other Steam Pipe Bends
Authors: White G. A. , Klug M. T. , Gorman J. A. , Rodgers J. M. , Griffin R.
Published: January 2011

In April 2008, after 113,230 hours of operation at Belledune Generating Station Unit #2 in New Brunswick, Canada, a seamless ASME SA-335 grade P22 (2 1/4Cr-1Mo) steel hot-reheat steam pipe was found to be cracked longitudinally through the presence of a steam leak. The crack, shown in Figure 1, was about 760 mm (30 inches) long and on the extrados of a long-radius bend. No catastrophic rupture occurred of the pipe, which had an outside diameter of about 950 mm (37.5 in.). The particular bend in question was made by hot bending after furnace heating and slowly cooling in air. Prior to the unit being returned to operation, the cracked bend was replaced with a newly fabricated bend. As reported in a companion paper [1], a detailed root cause failure evaluation indicated that overheating the pipe in the furnace at the time the bending was performed produced an extremely large grain structure and was likely a key factor in the creep cracking degradation observed. Further, the failure evaluation indicated exceptionally low creep ductility for the material in the failed bend. Metallurgical examinations of the other 16 hot-reheat and main steam pipe bends in the unit showed a range of atypically large grain sizes, although not as large as for the failed bend. This paper describes the methods and findings of a study to assess the suitability for continued service of the other primary steam pipe bends at the station; and to determine the appropriate actions, such as additional inspections, for maintaining safe operation of these piping systems. This study included detailed assessments of the hot operating stresses in the bends (including those due to pipe moment loads and ovalization effects), creep crack growth assessments using the EPRI BLESS software, and acoustic emission (AE) testing on four bends remaining in service.
What’s New in the PCC-1-2010 Update “Guidelines for Pressure Boundary Bolted Joint Assembly”
Authors: Neely Clyde , Rodery Clay
Published: January 2011

ASME PCC-1 “Guidelines for Pressure Boundary Bolted Joint Assembly” was first published in 2000 [1]. Since that time, there have been advances in bolted joint technology and industry practices that necessitated an update of the original document. The new revision of PCC-1 [2] is over twice the length of the original document and contains many new and updated guidelines. Significant additional detail has been added to the document in an effort to provide the broadest possible array of bolted joint assembly considerations to cover situations commonly encountered in industry, and thereby improve the overall safety and performance of bolted joints. This paper identifies some of the notable changes/additions that are included in the updated document.
Comparison of Thermo-Mechanical Fatigue Life Assessment Methods for Coke Drums
Authors: Penso Jorge A. , Hazime Radwan
Published: January 2011

Assessing the life of coke drums is a challenge many refineries have faced since the delayed coking process was introduced in oil refineries. Delayed coking units are among the refinery units that have higher economical yields. Welds play an important role in the life of these vessels. Cracking and bulging occurrences in the coke drums, most often at the weld areas, characterize the history of the operation of delayed coking units. Thermo-mechanical fatigue is the most common cause for cracking in coke drums. Although coke drums constitutes a classical example of thermo-mechanical fatigue there are several other oil processes that are affected by this mechanism. Hence the findings from this work could be useful for other applications. Other possible application examples include mixing points of hot and cold streams, coal gasifiers, and steam generating equipment. There are a vast number of models and methods for estimating the thermo-mechanical fatigue life of engineering components subjected to thermal and mechanical loads. In this work, focus is placed on comparing some of the commonly used methods including: • API 579 methods: - Elastic stress analysis and equivalent stress; - Elastic-plastic stress analysis and equivalent strain; - Elastic stress analysis and structural stress. • Creep-fatigue crack initiation using R5 Volume 2/3. • Non-linear isothermal fatigue analysis using maximum shear strain amplitude with Morrow mean stress correction. In this study, a Finite Element (FEA) model is used to estimate the cyclic stresses and strains for the skirt-to-bottom head attachment weld. The model includes details of the geometry, material properties, boundary conditions, and loads. The results from the FEA are post-processed using the fatigue methods listed above. Lastly, a parametric study on the most important process variables is performed. The results of this work indicate that the predictions of the number of cycles to crack initiation are not significantly different between various crack initiation methods, but they are significantly different when compared with the structural stress method (a through-thickness crack). Thus, the thermo-mechanical fatigue algorithm selection should be based on the assessment goals and service conditions. The parametric analysis showed that the life of the drum is strongly influenced by the switch temperature and quench rates with lower switch temperatures and faster quench rates negatively impacting the life of the drum.