bluuebunny/crossref_metadata_2025 huggingface dataset:
Crack Detection and Monitoring Crack Growth in Fastener Holes Using the DMI Optical SR-2 Strain Measurement Technology
Authors: Ranson William F. , Vachon Reginald I. , Hovis Gregory L. , Nardiello Jerrell A. , Fidnarick Robert D. , Christ Robert J.
Published: May 2009

Results are presented for crack initiation detection and crack growth monitoring using DMI SR-1 Strain Gages and DMI SR-2 Reader in two Northrop Grumman aluminum test coupons subjected to cyclic loading. Results demonstrate the utility of the technology to detect cracks and crack growth in holes. The DMI SR-1 strain gage is applied so that it frames the hole in the test coupon. This results in strain measurements at tangents to hole and associated shear strains. A differential strain reading between gage lengths on parallel and opposing sides of a hole, resulting from discontinuities in the material surrounding a hole, indicates crack initiation and as the crack grows the differential reading increases.
Experimental and Analytical Studies on Frictional Pressure Drops of Gas-Liquid Two-Phase Flow in Mini-Micro Pipes and at Vena Contract and Expansion
Authors: Ohtake Hiroyasu , Ohtaki Hideyasu , Hagiwara Masato , Koizumi Yasuo
Published: May 2009

The frictional pressure drops of gas-liquid two-phase flow in mini-micro pipes and at vena contract and expansion were investigated experimentally and analytically. Pressure drops of straight pipe, sudden enlargement and sudden contraction of gas-liquid two-phase flow in mini-pipes were measured. Test liquid was water at room temperature; test gas was argon. The diameter of the test mini-pipe was 0.5, 0.25 and 0.12 mm, respectively; the length was 500, 250 and 50 mm, respectively. The cross-sectional ratio of the contraction was about 1000; the ratio of the enlargement was about 0.001. The pressure drop data and the flow pattern were collected over 3.0 < UG < 130 m/s for the superficial gas velocity and 0.02 < UL < 6.0 m/s for the superficial liquid velocity. The two-phase friction multiplier data for D > 0.5 mm showed to be in good agreement with the conventional correlations. On the other hand, the two-phase friction multiplier data for D < 0.25 mm differed from the calculated values by the conventional correlations. Then, thickness of liquid film around a gas plug and size of gas core were estimated and the effect of frictional pressure drop on channel size was discussed through Knudsen Number of gas and instability on liquid-gas interface. Namely, the effect of mini-pipe was rarefaction effects, Kn<0.1. New correlation of frictional pressure drop of gas-liquid two-phase flow is proposed for mini pipes. The coefficients of sudden enlargement and sudden contraction in mini-pipes for the gas-water two-phase flow were modified from the present experimental results. The experimental results were also examined through numerical simulation by a commercial code.
Design and Analysis of Ultrasonic Assisted Friction Stir Welding
Authors: Park Kwanghyun , Kim Gap-Yong , Ni Jun
Published: May 2009

This paper presents ultrasonic assisted friction stir welding (UaFSW), which is suggested to improve the weld quality and efficiency as a hybrid welding system. Ultrasonic-assisted processes have been coupled with tooling in various manufacturing processes to enhance the performance of conventional machining and bonding processes. For successful and effective implementation of the UaFSW, we must first consider how to integrate ultrasonics into the friction stir welding equipment. To solve this problem, we designed an ultrasonic horn to vibrate the FSW tool and transmit ultrasonic energy into the workpiece. Using a numerical modal and harmonic analysis, we fabricated and analyzed the ultrasonic horn under specific design considerations. Force was measured and compared during ultrasonic assisted and conventional friction stir welding. The mechanical properties of the workpieces were also investigated.
An Investigation on Tensile, Compression and Flexural Properties of Natural Fibre Reinforced Polyester Composites
Authors: Yousif B. F. , Wong K. J. , El-Tayeb N. S. M.
Published: May 2009

In the present work, effects of two types of natural fibres on mechanical properties of polyester composites were investigated at different volume fractions of fibre. Tensile, compression, and flexural properties of oil palm bunch and oil palm fruit fibres reinforced polyester composites were investigated. Additionally, tensile strength of the selected composites was calculated theoretically. Scanning electron microscope was used to observe the fracture mechanism of the specimens. Single fiber pull-out tests were carried out to determine the interfacial shear strength between polyester resin and both types of oil palm fibre. As results, it was found that both types of oil palm fibre enhanced the mechanical performance of polyester composites. At higher volume fraction (≈41%), tensile strength was improved, when polyester reinforced with oil palm fruit fibres, i.e. 2.5 folds improvement in the tensile strength value. Further, experimental tensile strength values of oil palm bunch/polyester composites was found to be less varied compared to theoretical results. Flexural strength of polyester was worsened with oil palm fibres at all of fibre volume fraction.
Measurement Methods of Pad Properties for Chemical Mechanical Polishing
Authors: Zhang X. H. , Pei Z. J. , Fisher Graham R.
Published: May 2009

Silicon wafers are the fundamental building blocks for most integrated circuits. Chemical mechanical polishing is used to manufacture silicon wafers as the final material removal process to meet the ever-increasing demand for flatter wafers and lower prices. The polishing pad is one of the critical factors in planarizing wafer surfaces and its properties play critical roles in polishing. However, pad properties change during the process. This paper reviews the measurement methods for thickness, hardness, and Young’s modulus of polishing pads.
Stability Control of an Amphibious Single Wheel Robot
Authors: Marzban Mostapha , Alasty Aria
Published: May 2009

Single wheel robots are typically those kinds of robots which contain all the necessary mechanizations, namely the stabilization and driving mechanizations, within a shell-liked housing appearing analogous to a wheel. These robots have proved to be useful in various fields of industry due to their advantages of giving high instant acceleration and maintaining high cruise speeds for considerable amount of time in addition to being compact and small. It is a sharp-edged wheel actuated by a spinning flywheel for steering and a drive motor for propulsion. The spinning flywheel acts as a gyroscope to stabilize the robot and it can be tilted to achieve steering. In this paper first the kinematics of a single wheel robot, like Gyrover, in water is considered and then a simple mechanism for its movement in water is proposed. After hydrodynamic analysis of the robot a complete dynamics model is designed with Lagrange energy method. Then a stabilizer controller is designed to balance the robot with nonlinear control approach. For simplicity the added mass effect in hydrodynamic analysis, has been neglected. This complete model can be used for examining the behavior of the robot in designing a controller.
Probabilistic Interactions of Vehicles With Surroundings: Modeling for Dynamic Control
Authors: Vantsevich Vladimir V. , Stuart Charles
Published: May 2009

A deterministic approach is usually used to describe a vehicle’s motion mathematically when developing controls for vehicle dynamics. This paper presents a methodology for modeling the interaction between a vehicle and its surroundings based on the probabilistic characteristics of a vehicle and roads. The latter effects include distributions of the rolling resistance and the friction coefficient between a tire and the road surface; micro- and macro-profiles in the longitudinal direction of various road surfaces are also embedded in a vehicle model which is built on the inverse dynamics approach. A quality functional of the vehicle running gear efficiency is maximized to obtain optimal power distributions to the drive wheels when implementing a program of motion. Based on such developments, fundamentals for designing control algorithms are discussed. This includes probabilistic variations of the optimal wheel torques; time delays between road conditions of the front and rear wheels; correlations between the time thresholds and the wheel torque and wheel angular velocity variations; and others. These fundamentals are needed to develop and to verify more accurate control algorithms for vehicle dynamics control based on controlling mechatronic power dividing units of vehicle driveline systems. Examples are discussed.
Generation and Propagation of Thermally Induced Acoustic Waves in Supercritical Carbon Dioxide
Authors: Lei Zhiheng , Farouk Bakhtier
Published: May 2009

The generation and propagation of thermally induced acoustic waves in a confined layer of supercritical carbon dioxide are investigated by solving the fully compressible unsteady Navier-Stokes equations. These waves are generated by rapidly heating/cooling a sidewall. Due to the high compressibility, thermally induced acoustic waves are generated along any heated/cooled surface. The acoustic wave reflects from the opposing sidewall and continues to reverberate between the opposing walls. Even though supercritical fluids have high thermal conductivity, heat diffusion is slow. However, the temperature of the layer of the supercritical carbon dioxide is found to increase due to the dissipation of the acoustic energy. Ideal-gas law does not apply to supercritical fluids. Furthermore the internal energy is also not a function of temperature only. The above property variation effects are considered in the present paper.
Miniature Piezo Composite Bimorph Actuator for Elevated Temperature Operation
Authors: Seeley Charles E. , Delgado Eladio , Kunzman Jan , Bellamy Dirk
Published: May 2009

Development of a new, miniature actuator with large stroke and enhanced thermal stability could provide an improved capability for useful applications. This paper investigates the design, fabrication and testing of a macro fiber composite (MFC) based bimorph actuator to meet stringent requirements such as size, stroke and thermal stability. Results indicate that a d33/d31 MFC configuration was compact and provided sufficient stroke while avoiding issues related to depolarization at elevated temperature. A compact, high voltage power supply that runs off of a 3 volt battery was also developed as part of this effort.
A Simple and Practical Solution for Characterization of Adhesively Bonded Joints in Dissimilar Materials
Authors: Shahin Khaled , Taheri Farid
Published: May 2009

Fiber-reinforced polymer (FRP) composites are increasingly used in structural systems, replacing structural steel and aluminum. It is now well established that adhesive bonding is the most efficient mean of joining composites. Unfortunately, analytical models available in the literature offer design equations mainly applicable to balanced adhesive joints; where the two adherends are identical. In many practical applications, however, FRP composites are used (joined) in conjunction with other materials. This paper presents a simplified model that accurately predicts the behaviour of adhesive joints between different adherends. In this model, exponentially small terms are removed from the analytical solution, greatly simplifying the solution. The resulting design equations provide an accurate method of the design and analyzing of adhesive joints. The model applies to single-lap, single-strap and stiffener-plate joints, where shear and peel stresses are present. Furthermore, the model is easily extended to determine the energy release rate in adhesive joints. Results from the analytical model closely agree with finite element results, which are obtained in a fraction of the time and effort required for a non-linear finite element analysis.
Development of an Automotive Magnetorheological Brake Via Optimization of Magnetic Circuit
Authors: Karakoc Kerem , Suleman Afzal , Park Edward J.
Published: May 2009

In this paper, the development of a novel electromechanical brake is presented for automotive applications. The proposed brake consists of multiple rotating disks immersed into a magnetorheological (MR) fluid, and an enclosed electromagnet. When current is applied to the electromagnet, the MR fluid solidifies as its yield stress varies as a function of the magnetic field applied by the electromagnet. This controllable yield stress produces shear friction on the rotating disks, generating the braking torque. An electromagnetic finite element analysis was performed to optimize the magnetic circuit within the MR brake and obtain its design parameters. With these parameters, a prototype MR brake was built; and the experimental results were compared to the finite element simulation results.
Distributed Modeling and Decentralized H∞ Control of a Segmented Telescope Mirror
Authors: Kerley Daniel , Park Edward J. , Dunn Jennifer
Published: May 2009

In this paper a distributed dynamic model for a segmented primary mirror of an optical telescope is presented, based on the distributed modeling framework for spatially interconnected systems. The next generation of optical telescopes will employ highly segmented primary mirrors, which leads to a large-scale control problem. The distributed modeling technique allows for the design of scalable decentralized controllers that are better suited for such systems. A numerical seven segment mirror surface model is used as the benchmark system for comparing the performance between a scalable decentralized H∞ controller and a global H∞ controller. The closed-loop control simulation results show that both controllers perform comparably for the benchmark case. However when the number of the segments increases significantly (e.g. > 100) the scalable decentralized control will allow for a more tractable solution than the monolithic global control.
Criterion-related validity of functional capacity evaluation lifting tests on future work disability risk and return to work in the construction industry
Authors: Gouttebarge V , Kuijer P P F M , Wind H , van Duivenbooden C , Sluiter J K , Frings-Dresen M H W
Published: May 2009

Objectives:

To assess the criterion-related validity of the five Ergo-Kit (EK) functional capacity evaluation (FCE) lifting tests in construction workers on sick leave due to musculoskeletal disorders (MSDs).

Methods:

Six weeks, 6 months and 1 year after the first sick leave day due to MSDs, construction workers underwent two isometric and three dynamic EK FCE lifting tests, and completed the Instrument for Disability Risk (IDR) for future work disability risk. Concurrent and predictive validity were assessed by the associations between the scores of the EK FCE lifting tests and the IDR outcomes (Pearson Correlation coefficients (r) and associated proportions of variance (PV) and area under receiver operating characteristic curve (AUC)). Predictive validity of the EK FCE lifting tests on the total number of days on sick leave until full durable return to work (RTW) was also evaluated (Cox regression analysis).

Results:

Concurrent validity with future work disability risk was poor for the two isometric EK FCE lifting tests (−0.15⩽r⩽0.04) and moderate for the three dynamic EK FCE lifting tests (−0.47⩽r⩽−0.31). Only the carrying lifting strength test showed moderate and acceptable predictive validity on future work disability risk (r = −0.39; AUC = 0.72). Cox regression analyses revealed that two out of the five EK FCE lifting tests predicted durable RTW significantly, but only weakly.

Conclusions:

Criterion-related validity with future work disability risk was poor for the two isometric EK lifting tests and moderate for the three dynamic lifting tests, especially the carrying lifting strength test. Predictive validity on durable RTW was poor, although weakly significant in two dynamic EK FCE tests, of which one was the carrying lifting strength test.
Freshwater and marine migration and survival of endangered Cultus Lake sockeye salmon (Oncorhynchus nerka) smolts using POST, a large-scale acoustic telemetry array
Authors: Welch David W. , Melnychuk Michael C. , Rechisky Erin R. , Porter Aswea D. , Jacobs Melinda C. , Ladouceur Adrian , McKinley R. Scott , Jackson George D.
Published: May 2009

Freshwater and early marine migration and survival of endangered Cultus Lake sockeye ( Oncorhynchus nerka ) salmon were studied using the Pacific Ocean Shelf Tracking (POST) array. Smolts were acoustically tagged in 2004–2007, and their migration was recorded within the lower Fraser River and coastal southern British Columbia waters. Most smolts showed rapid directional movement (swimming speeds of ~15–30 km·day–1). Average exit time from the Fraser River was 4.0–5.6 days after release, and average residence time within the Strait of Georgia was 25.6–34.1 days. Most individuals migrated northward, generally close to the mainland coast. Survival rates, assessed using standard mark–recapture methods, were generally high during the downstream migration (50%–70%), except in 2005 when survival was <20%, possibly because of a late release. Marine survival rates were stable among years, between 10%–30% at a subarray sited 500 km away from the release site. Movement rates were similar to those of previously published work, but the POST array provided direct measurements of movement and estimates of survival and demonstrated the feasibility of establishing continental-scale acoustic arrays for management and conservation of marine species.
Evidence of density- and size-dependent mortality in hatchery-reared juvenile white sturgeon (Acipenser transmontanus) in the Kootenai River
Authors: Justice Casey , Pyper Brian J. , Beamesderfer Raymond C.P. , Paragamian Vaughn L. , Rust Pete J. , Neufeld Matthew D. , Ireland Susan C.
Published: May 2009

We evaluated effects of stocking level and size-at-release on survival rates of hatchery-reared juvenile white sturgeon ( Acipenser transmontanus ) in the Kootenai River using Cormack–Jolly–Seber and related models implemented in Program MARK. A total of 119 768 marked and unmarked hatchery juveniles were released from 1992 to 2006, of which 2938 passive integrated transponder (PIT)-tagged fish were subsequently recaptured. Annual survival rates of marked groups ranged from 0.01 to 0.84 (mean = 0.45) during the first year at large, from 0.48 to 1.0 (mean = 0.84) in the second year, and averaged 1.0 during all subsequent years. First year survival rates declined substantially in recent years, particularly for small fish (<25 cm fork length). Approximately 59% of the variation in first year survival was explained by a negative relationship with estimated juvenile abundance (linear regression, P < 0.01). Length-at-release of individuals explained a substantial proportion of the within-year variation in survival during the first year at large. Our results provide strong evidence of density- and size-dependent mortality in hatchery-reared juvenile white sturgeon in the Kootenai River. Management actions that prioritize the release of fewer, larger-sized fish will likely improve first year survival rates and subsequent recruitment to the spawning-age population.
Bacteria associated with the mucus layer of Merlangius merlangus (whiting) as biological tags to determine harvest location
Authors: Smith Cindy J. , Danilowicz Bret S. , Meijer Wim G.
Published: May 2009

We describe a new technique to determine the harvest location of Merlangius merlangus (whiting) based on exploiting the natural bacterial populations associated with the mucus layer of fish and surrounding seawater as biological tags. Bacterial community profiles from the outer and mouth mucus and the surrounding seawater were characterized by terminal restriction fragment length polymorphism (T-RFLP), and fish harvest location was predicted based on T-RFLP profile comparisons between fish and water and between individual fish. Fish harvest location was not resolved reliably based on analysis of the shared seawater and outer-mucus markers. However, comparisons based on shared seawater and mouth-mucus markers placed fish within 1.92 (± standard error (SE) of 0.31) stations (p < 0.002), equivalent to 153.0 km, of their known harvest location. Fish placement resolution was further increased when fish-to-fish bacterial assemblage comparisons were made. Based on outer-mucus, mouth-mucus, and combined outer- and mouth-mucus analysis, fish were placed within 1.00 (±SE 0.27), 1.55 (±SE 0.28), and 0.71 (±SE 0.24) (p < 0.04) stations, equivalent to 79.7, 123.5, and 57.3 km, respectively, of their known harvest location.
Recent shifts in the crustacean zooplankton community of Lake Huron
Authors: Barbiero Richard P. , Balcer Mary , Rockwell David C. , Tuchman Marc L.
Published: May 2009

Cladoceran populations in the open waters of Lake Huron declined abruptly in 2003 and have since remained at historically low levels. The two dominant cladocerans, Daphnia mendotae and Bosmina longirostris , have been nearly extirpated from the northern region of the lake and are present in only slightly greater numbers in the south. Average nonpredatory cladoceran biomass in the lake has declined over 90% between 1998–2002 and 2003–2006. In addition, historically unprecedented declines in cyclopoid copepods were seen in the lake in 2005. These changes have occurred against the backdrop of declining nutrient levels in the lake and have coincided closely with declines in the amphipod Diporeia . We speculate that a combination of reduced primary production in the open waters and intensified planktivory due to the continuing disappearance of Diporeia has accounted for the losses in crustacean biomass seen in recent years.
Influences of prey- and predator-dependent processes on cadmium and methylmercury trophic transfer to mummichogs (Fundulus heteroclitus)
Authors: Goto Daisuke , Wallace William G.
Published: May 2009

Factors affecting CH3Hg and Cd trophic transfer from six invertebrates and a juvenile fish prey to mummichogs ( Fundulus heteroclitus ) were investigated using prey-dependent and predator-dependent approaches. Prey-specific trophic availability of metals to mummichogs was estimated using a subcellular partitioning approach (i.e., trophically available metals (TAM), as originally proposed by Wallace and Luoma (2003) ). The proportions of CH3Hg partitioned to TAM (CH3Hg-TAM%) ranged from 39.7% to 82.7%, while the proportions of Cd partitioned to TAM (Cd-TAM%) ranged from 51.8% to 67.4%. CH3Hg-TAM% and Cd-TAM% were significantly correlated with the proportions of metals released from prey by in vitro solubilization with mummichog gut fluid (i.e., gut solubilizable metals (GSM)), CH3Hg-GSM% and Cd-GSM%, respectively. This relationship suggests that the majority of CH3Hg and Cd partitioned as TAM in prey were solubilized in the digestive tract of mummichogs. Mummichogs retained 52.7% to 73.7% of the ingested CH3Hg, which was comparable with prey-specific CH3Hg-TAM% and CH3Hg-GSM%. However, mummichogs retained only 3.2%–11.0% of ingested Cd, which was substantially lower than Cd-TAM% or Cd-GSM%. These results suggest that solubilizable, prey-associated CH3Hg was transported through the gut membrane of mummichogs, whereas the majority of prey-associated Cd was excluded and subsequently eliminated, regardless of its subcellular partitioning.
Reproductive behavior and relative reproductive success of natural- and hatchery-origin Hood Canal summer chum salmon (Oncorhynchus keta)
Authors: Berejikian Barry A. , Van Doornik Donald M. , Scheurer Julie A. , Bush Richard
Published: May 2009

Estimates of the relative fitness of hatchery- and natural-origin salmon can help determine the value of hatchery stocks in contributing to recovery efforts. This study compared the adult to fry reproductive success of natural-origin summer chum salmon ( Oncorhynchus keta ) with that of first- to third-generation hatchery-origin salmon in an experiment that included four replicate breeding groups. Hatchery- and natural-origin chum salmon exhibited similar reproductive success. Hatchery- and natural-origin males obtained similar access to nesting females, and females of both types exhibited similar breeding behaviors and durations. Male body size was positively correlated with access to nesting females and reproductive success. The estimates of relative reproductive success (hatchery/natural = 0.83) in this study were similar to those in other studies of other anadromous salmonids in which the hatchery population was founded from the local natural population and much higher than those in studies that evaluated the lifetime relative reproductive success of nonlocal hatchery populations.
Underground gas storage project at Welton oilfield, Lincolnshire: Local perspectives and responses to planning, environmental and community safety issues
Authors: Davidson Meg
Published: May 2009

This paper describes the research undertaken by two local councillors to assess the proposed underground gas storage (UGS) scheme at Welton oilfield, Lincolnshire and the implications for the local community. Compared to the US, where over 300 operational gas storage facilities in onshore depleted fields exist, this form of gas storage is in its infancy in the UK. This has proved to be a challenge for the various agencies involved in the planning process.

The councillors have identified a number of planning and safety issues which merit further consideration, including the applicability of the control of major accident hazards (COMAH) regulations, well integrity and the effects of re-pressurization of the oilfield.

The proposed UGS facility is in close proximity to residential areas and concern amongst local residents is considerable. The councillors believe that their research has shown that insufficient attention has so far been given to community safety issues. A full and thorough assessment of all potential risks associated with this particular type of UGS needs to be undertaken and appropriate safeguards put in place to protect the local community.
A review of underground fuel storage events and putting risk into perspective with other areas of the energy supply chain
Authors: Evans D. J.
Published: May 2009

The UK became a net importer of gas during 2004 and faces an increasing dependency on imports, yet has very little gas storage capacity. The UKs capacity to import, transport and store gas and liquid natural gas (LNG) has to be improved, requiring greater investment in new gas supply infrastructure. Construction of appropriately sited onshore underground gas storage (UGS) facilities is needed. However, local groups oppose most proposed UGS sites on the grounds of safety, citing the dangers of gas migration and rare fatal events, mostly in America.

This paper summarizes 228 reported events of widely varying cause, nature and severity at underground fuel storage (UFS) facilities; the majority at USA SPR facilities. Since UGS was first undertaken in 1915, reports of 13 fatalities, around 72 injured and the evacuation of at least 6700 people are found at UFS sites. Some communities have experienced multiple evacuations. In the context of the danger posed to the general public, three of those killed were staff at two UFS facilities. UGS (including LPG) has led to 10 civilian deaths, 25 injured and
c.
1250 evacuated.

In other areas of the energy supply chain, casualties are orders of magnitude greater, with at least 1525 dead, 6826 injured and the evacuation of over 7000 at incidents involving above ground fuel storage tanks since 1951. When considering UK UGS applications, the risk of UGS and wider UFS experiences should be put into context. Worldwide, over 90 years experience in UGS now exists, with around 630 facilities of different types currently operational. Technologies used are often those of, or derived from, a well-regulated oil and gas exploration industry. In contrast to public perception, industry and academia recognize that UGS has an excellent health, safety and environmental record. Although it should not be claimed that gas will never be found outside the intended well or storage facility area, UFS casualty figures appear to corroborate claims by supporters of the technologies that salt caverns provide one of the safest answers to the problem of storing large amounts of hydrocarbons and that even in urban areas underground gas storage, oil and gas production can be conducted safely if proper procedures are followed. If gas is found outside the intended system, then after recognition of the problem, mitigation and safe operating procedures can and have been developed.
Gas storage: An onshore operator's perspective
Authors: Fernando A. , Raman A.
Published: May 2009

Operating 28 onshore oil and gas fields, Star Energy Group plc is the leading onshore operator in terms of fields. The company believes that with the decline in flexible gas production facilities close to market in the North Sea and Irish Sea, Great Britain (GB) will need a significant expansion in gas storage capacity. To meet these demands, Star Energy aims to construct underground gas storage (UGS) facilities by converting depleted onshore hydrocarbon reservoirs both on- and offshore GB. This paper provides an overview of the UK position with respect to UGS, Star Energy's strategy and their planned developments.
Underground gas storage: Why and how
Authors: Plaat Hans
Published: May 2009

Although it appears surprising that gas is put back into the ground after expending so much time, effort and money on extracting it in the first place, underground gas storage (UGS) plays an important role in the management of the gas supply chain. UGS has been used effectively for nearly a century to balance the mismatch in gas supply and demand. Its use continues to grow and with the advent of gas market liberalization, additional uses of UGS have been introduced. In several countries some 20–30% of the annual gas consumption is supplied through the use of UGS. This paper provides an overview of the most common use of UGS, the current status of UGS in the world and the main characteristics of the various types of facility: such as gas fields, aquifers and salt caverns. Aspects related to the planning and performance of gas storage facilities are also discussed.
A review of onshore UK salt deposits and their potential for underground gas storage
Authors: Evans D. J. , Holloway S.
Published: May 2009

The UK faces a major change in the nature of its gas supply as North Sea production declines and the country becomes increasingly reliant upon gas imports. As a result the UK Government recognizes that significant investment in gas supply infrastructure is required to maintain security of supply and manage the gas market. Part of that infrastructure will be additional underground gas storage capacity in specially designed and engineered salt caverns. This paper summarizes the distribution and nature of halite (rock salt) deposits in England and Northern Ireland, and reviews the details of existing and planned storage sites in salt caverns. There is considerable potential for further salt cavern development. However, not all of the UK salt fields are suitable, with the halite beds being too shallow, thin or impure.
New procedure for tightness tests (MIT) of salt cavern storage wells: Continuous high accuracy determination of relevant parameters, without the need to use radioactive tools
Authors: Von Tryller Hartmut , Reitze Andreas , Crotogino Fritz
Published: May 2009

In performing the mechanical integrity test (MIT) on salt cavern storage wells the most used method worldwide is the
In-Situ
Balance method (ISB). The principal sources of errors in the execution and evaluation of the test are the depth change of the gas/liquid interface and the surface area of the interface.

In the past, the interface depth has been predominantly determined using radioactive methods, i.e. gamma-gamma, neutron-gamma and neutron-neutron tools. The disadvantages of these methods are the low measurement accuracy and the need to perform several tool runs during the test period, which introduces an additional source of error, because cost factors normally prevent continuous measurements.

A new method (SoMIT) is presented based on ultrasonic techniques in which the interface depth, the temperature and the differential pressure at the interface depth can be measured continuously during the tightness test while achieving much greater levels of accuracy than was previously the case. In the SoMIT method a tool is fixed in place throughout the entire test period such that the problems associated with several tool runs are also avoided. The advantages for users are to be found in the greater accuracy available to verify the tightness of the well and also in the reduced test period.
Environmental issues in permitting gas storage: The Wild Goose case history
Authors: Hietter Laurie McClenahan
Published: May 2009

With recent fires and explosions at Moss Bluff, Texas (2004) and Hutchinson, Kansas (2001), initial environmental review is becoming more critical for public acceptance of new underground gas storage facilities; the environmental review is especially important for gas storage fields that use depleted oil and gas fields. Components of successful environmental review and permitting include an experienced and capable project manager and technical team, sufficient and thorough data for use in understanding affected resources, monitoring data for analysing well conditions and a holistic approach to public relations.

The Wild Goose Gas Storage Field, located in Butte County, California, was developed originally in 1999, using a depleted gas field. Its initial storage capacity was 396.5 million cubic metres (Mcm, or 14 billion cubic feet, bcf). A subsequent expansion to 821.3 Mcm (29 bcf) and construction of a 41.8 km long gas pipeline were subject to a thorough environmental review and permits were approved without opposition.

An interdisciplinary team experienced in environmental review of oil and gas fields successfully completed a comprehensive environmental review of the Wild Goose Gas Storage Field expansion. Keys to successful environmental review and permitting for the Wild Goose expansion project included assembling a qualified and independent technical team, identifying potential local emission sources, understanding well integrity, defining vertical and lateral containment of the gas field and developing a thorough understanding of affected parties' concerns and the affected local environment.

The thorough approach to environmental review undertaken in the Wild Goose Gas Storage Field project can be used as a model for the permitting process applied to other gas storage fields, serving to shorten schedules, reduce project costs and lessen risk when considering new underground storage facilities.
Program transformations using temporal logic side conditions
Authors: Kalvala Sara , Warburton Richard , Lacey David
Published: May 2009

This article describes an approach to program optimization based on transformations, where temporal logic is used to specify side conditions, and strategies are created which expand the repertoire of transformations and provide a suitable level of abstraction. We demonstrate the power of this approach by developing a set of optimizations using our transformation language and showing how the transformations can be converted into a form which makes it easier to apply them, while maintaining trust in the resulting optimizing steps. The approach is illustrated through a transformational case study where we apply several optimizations to a small program.
Term transformers
Authors: Morris Joseph M. , Bunkenburg Alexander , Tyrrell Malcolm
Published: May 2009

We present a new approach to adding state and state-changing commands to a term language. As a formal semantics it can be seen as a generalization of predicate transformer semantics, but beyond that it brings additional opportunities for specifying and verifying programs. It is based on a construct called a
phrase
, which is a term of the form
C
▹
t
, where
C
stands for a command and
t
stands for a term of any type. If
R
is boolean,
C
▹
R
is closely related to the weakest precondition
wp
(
C
,
R
). The new theory draws together functional and imperative programming in a simple way. In particular, imperative procedures and functions are seen to be governed by the same laws as classical functions. We get new techniques for reasoning about programs, including the ability to dispense with logical variables and their attendant complexities. The theory covers both programming and specification languages, and supports unbounded demonic and angelic nondeterminacy in both commands and terms.
Isolation points
Authors: Mansour Mohamed S. , Schwan Karsten , Abdelaziz Sameh
Published: May 2009

This article explores a performance isolation-based approach to creating robust distributed applications. For each application, the approach is to understand the performance dependencies that pervade it and then impose constraints on the possible ‘spread’ of such dependencies through the application. The mechanisms used for this purpose, termed isolation points, are software abstractions inserted at key program locations: (1) in application interfaces, (2) in middleware implementations for making remote requests, and (3) in the system interfaces used by middleware and applications. This article demonstrates the utility of isolation points by using them to implement higher level abstractions that improve the performance-robustness of representative enterprise applications. The I-Queue abstraction uses isolation points to implement performance-robust messaging, targeting the message queues used in distributed enterprise codes. By appropriately orchestrating message dispatching, I-Queue can achieve an improvement of 16--32% in dispatched message locality based on traces obtained from the large-scale e-Pricing® search engine operated by Worldspan L.P.
Semantics-based context-aware dynamic service composition
Authors: Fujii Keita , Suda Tatsuya
Published: May 2009

This article presents a semantics-based context-aware dynamic service composition framework that composes an application through combining distributed components based on the semantics of components and contexts of users. The proposed framework consists of Component Service Model with Semantics (CoSMoS), Component Runtime Environment (CoRE), and Semantic Graph based Service Composition (SeGSeC). CoSMoS models the semantics of components and contexts of users. CoRE is a middleware to support CoSMoS on various distributed computing technologies. SeGSeC is a mechanism to compose an application by synthesizing its workflow based on the semantics of components and contexts of users. The proposed framework is capable of composing applications requested in a natural language by leveraging the semantic information of components. The proposed framework composes applications differently to individual users based on their contexts and preferences. The proposed framework acquires user preferences from user-specified rules and also via learning. The proposed framework also adapts to dynamic environments by autonomously composing a new application upon detecting context change. This article describes the design and mechanism of the proposed framework, and also presents simulation experiments to evaluate the proposed framework.
Exploiting user location for load balancing WLANs and improving wireless QoS
Authors: Alyfantis George , Hadjiefthymiades Stathes , Merakos Lazaros
Published: May 2009

A “Smart Spaces System”, called MITOS, for improved user connectivity in large wireless LAN installations is proposed. MITOS extends the scope of resource management to the dynamic relocation of nomadic users: the system suggests to a user the best location to move to for obtaining a satisfactory quality of service level, when the controlling access point of its current location becomes congested. The system monitors the traffic and user location across the network, and formulates the appropriate relocation proposal urging specific users to move to better locations at reasonable distances. Two enhancements to the basic MITOS system are introduced for maintaining an almost uniform load level across the considered infrastructure: the first uses microeconomic concepts, while the second borrows game theoretic mechanisms from the Santa Fe Bar problem. Simulation results on the efficiency of the proposed schemes are provided.
Self-adaptive software
Authors: Salehie Mazeiar , Tahvildari Ladan
Published: May 2009

Software systems dealing with distributed applications in changing environments normally require human supervision to continue operation in all conditions. These (re-)configuring, troubleshooting, and in general maintenance tasks lead to costly and time-consuming procedures during the operating phase. These problems are primarily due to the open-loop structure often followed in software development. Therefore, there is a high demand for management complexity reduction, management automation, robustness, and achieving all of the desired quality requirements within a reasonable cost and time range during operation. Self-adaptive software is a response to these demands; it is a closed-loop system with a feedback loop aiming to adjust itself to changes during its operation. These changes may stem from the software system'sself(internal causes, e.g., failure) orcontext(external events, e.g., increasing requests from users). Such a system is required tomonitoritself and its context,detectsignificant changes,decidehow to react, andactto execute such decisions. These processes depend on adaptation properties (called self-* properties), domain characteristics (context information or models), and preferences of stakeholders. Noting these requirements, it is widely believed that new models and frameworks are needed to design self-adaptive software. This survey article presents a taxonomy, based on concerns of adaptation, that is,how,what,whenandwhere, towards providing a unified view of this emerging area. Moreover, as adaptive systems are encountered in many disciplines, it is imperative to learn from the theories and models developed in these other areas. This survey article presents a landscape of research in self-adaptive software by highlighting relevant disciplines and some prominent research projects. This landscape helps to identify the underlying research gaps and elaborates on the corresponding challenges.
Gem #23
Authors: Duff Bob
Published: May 2009

Ada Gem #23 --- The "not null" syntax allows an Ada 2005 program to prevent access values from being null in cases where the null value is undesirable. This new syntax helps provide useful documentation.
Gem #24
Authors: Duff Bob
Published: May 2009

Ada Gem #24 --- The "not null" syntax can make programs more efficient by removing the need for implicit run-time checks.
Gem #25
Authors: Briot Emmanuel
Published: May 2009

Ada Gem #25 --- The Ada standard defines several subprograms related to searching text in a string. In addition, GNAT provides additional packages to search. This gem will cover the various possibilities.
Gem #28
Authors: Dewar Robert
Published: May 2009

Ada Gem #28 --- Part 2, Efficiency Considerations.
Gem #29
Authors: Obry Pascal
Published: May 2009

Ada Gem #29 --- Introduction to Ada Web Server (AWS).
Gem #32
Authors: Barnes John
Published: May 2009

This week's gem is the first chapter of John Barnes' new booklet: Safe and Secure Software: An Introduction to Ada 2005.

Over the coming months, we will be publishing all thirteen chapters of the booklet. In the attachment at the bottom of Gem #30 you can access the contents and bibliography for the entire booklet. We hope you will enjoy the read!
Gem # 33
Authors: Fernández-Marina Ramón
Published: May 2009

Ada Gem #33 --- The existence of dangling references (pointers to objects that no longer exist) in a program can have catastrophic results. Ada incorporates a set of "accessibility rules" that help the programmer prevent dangling references, making programs more secure.
Gem #35
Authors: Rogers Pat
Published: May 2009

Ada Gem #35 --- Ada 95 introduced "protected types" as a fundamental building block for efficient concurrent programming and interrupt handling. In this Gem we examine the use of protected types in the implementation of the classic asynchronous bounded buffer abstraction provided by the GNAT hierarchy of library units. This Gem assumes the reader is somewhat familiar with protected types and will, therefore, explain some, but by no means all, of their semantics.
Gem #38
Authors: Barnes John
Published: May 2009

This week's gem is the fourth chapter of John Barnes' new booklet: Safe and Secure Software: An Introduction to Ada 2005.

Over the coming months, we will be publishing all thirteen chapters of the booklet. In the attachment at the bottom of Gem #30 you can access the contents and bibliography for the entire booklet. We hope you will enjoy the read!
Gem #44
Authors: Duff Bob
Published: May 2009

Ada Gem #44 --- 'Unchecked_Access can be used to bypass the accessibility rules, and controlled types can be used to rein in this dangerous feature.
Pregnancy modifies the large conductance Ca2+-activated K+ channel and cGMP-dependent signaling pathway in uterine vascular smooth muscle
Authors: Rosenfeld Charles R. , Liu Xiao-tie , DeSpain Kevin
Published: May 2009

Regulation of uteroplacental blood flow (UPBF) during pregnancy remains unclear. Large conductance, Ca2+-activated K+ channels (BKCa), consisting of α- and regulatory β-subunits, are expressed in uterine vascular smooth muscle (UVSM) and contribute to the maintenance of UPBF in the last third of ovine pregnancy, but their expression pattern and activation pathways are unclear. We examined BKCa subunit expression, the cGMP-dependent signaling pathway, and the functional role of BKCa in uterine arteries (UA) from nonpregnant ( n = 7), pregnant ( n = 38; 56–145 days gestation; term, ∼150 days), and postpartum ( n = 15; 2–56 days) sheep. The α-subunit protein switched from 83–87 and 105 kDa forms in nonpregnant UVSM to 100 kDa throughout pregnancy, reversal occurring >30 days postpartum. The 39-kDa β1-subunit was the primary regulatory subunit. Levels of 100-kDa α-subunit rose ∼70% during placentation ( P < 0.05) and were unchanged in the last two-thirds of pregnancy; in contrast, β1-protein rose throughout pregnancy (R2 = 0.996; P < 0.001; n = 13), increasing 50% during placentation and approximately twofold in the remainder of gestation. Although UVSM soluble guanylyl cyclase was unchanged, cGMP and protein kinase G1α increased ( P < 0.02), paralleling the rise and fall in β1-protein during pregnancy and the puerperium. BKCa inhibition not only decreased UA nitric oxide (NO)-induced relaxation but also enhanced α-agonist-induced vasoconstriction. UVSM BKCa modify relaxation-contraction responses in the last two-thirds of ovine pregnancy, and this is associated with alterations in α-subunit composition, α:β1-subunit stoichiometry, and upregulation of the cGMP-dependent pathway, suggesting that BKCa activation via NO-cGMP and β1 augmentation may contribute to the regulation of UPBF.