bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Multilane Median Openings Zone on Travel Speed
Authors: R Rahman , J Ben-Edigbe
Published: April 2015

Thispaperaims to assess the impact of median openings zone of travel speed. Median openings or Midblock U-turn facilities are often constructed to provide motorists with detour option in circumstances where traffic conflict manoeuvres are eminent and prevalent. In previous studies, it has been shown that median openings will reduce the number of conflicts at relevant intersection.Hence median openings were built on multilane highways in Malaysia.Theirconstruction provoked debate on safety and traffic flow impediment issues. Based on the hypothesis that multilane median openings would cause travel speed reduction; an impact study was carried out at selected sites in Johor, Malaysia during daylight and dry weather conditions. Traffic volume, speed, and vehicle types were collected per road section for two directions continuously for eight weeks. The survey data were supplemented with highway design information culled from the Malaysian Public Works Departments manual. Travel speeds at median opening zone were estimated for both directional traffic flows. Results show significant decrease in travel speed of up to54.2% at the diverging section of the median openings zone. A slight drop of about 5% resulted from median openings zone at the merging section. The paper concluded that median openings zone facilities irrespective of their traffic conflicts minimisation merits will trigger significant travel speed reduction.
Steel Slag as A Road Construction Material
Authors: Hainin Mohd. Rosli , A. Aziz Md. Maniruzzaman , Ali Zulfiqar , Putra Jaya Ramadhansyah , El-Sergany Moetaz M. , Yaacob Haryati
Published: April 2015

Steel slag is a byproduct obtained from steel industry. It is generated as a residue during the production of steel. Because of the high disposal cost as a waste material and the overall positive features of steel slag, it has been declared a useful construction material, not an industrial waste by most of the developed countries. Successively, it is recycled as an aggregate for the construction of roads, soil stabilization, and base and for the surfacing of flexible pavement.  Despite this, a large amount of steel slag generated from steel industries is disposed of in stockpiles to date. As a result, a large area of land is being sacrificed for the disposal of this useful resource. Many researchers have investigated the use of steel slag as an aggregate in the design of asphalt concrete for the road construction. The best management option for this by product is its recycling. This leads to reduction of landfills reserved for its disposal, saving the natural resources and attaining a potential environment. The purpose of this paper is to review the engineering properties of steel slag and its utilization for road construction in different ways.
Evaluation Of Major Causes Of Road Accidents Along North–East Highway, Nigeria
Authors: Yero Arafat Suleiman , Y Ahmed Tijanni , Hainin Mohd Rosli
Published: April 2015

A major road link in the North-Eastern region of Nigeria is the Bauchi – Maiduguri highway that is a 425 km road that links a section of the north east region to other regions of Nigeria. The goods and services to the region are basically transported by road.  This has increased vehicular traffic that resulted in increased road accident rates over the years.  It is paramount to investigate the major causes of vehicle accidents on this highway as much has not been done to investigate accident cases on the route. The five year accident record on that route was obtained from the Federal Road Safety Corp of Nigeria,   the Nigeria Police traffic unit, and the Nigeria union of road traffic workers. The study indicated that speed violation by drivers and bad road conditions contributes greatly in the rate of accidents along the route. Hence the study recommends better road maintenance culture and more sensitization of the road users and enforcement of speed limits.
Pedestrian’s Behaviour on Road Crossing Facilities
Authors: Pasha Md. Mosabbir , Mohammad Rifaat Dr. Shakil , Hasnat Abul , Rahman Istiakur
Published: April 2015

Walking is a major mode of transportation in developing countries where most road users are pedestrians who spend significant time on roads and using the road system. Walking almost inevitably involves crossing a road, where the chances of conflict between pedestrian and motor vehicle is much higher. In Dhaka, the capital of a developing country Bangladesh, pedestrians increase their accident risk when they decide to cross the road way without using the road crossing facilities. When a relatively unsafe choice is made, the pedestrian increases his accident risk and faces casualties. However, in Dhaka, it was not explored in the past about what percentage of people cross the road by pedestrian foot over bridge/ underpass or by jaywalking. Therefore, It is found that 40.2% of the pedestrians do not use road crossing facilities and 71% pedestrians prefer underpass rather than using foot over bridge. The reasons pedestrians are not using road crossing facilities are insufficient security, time consuming, poor entrance, hawker’s problem, discomfort, takes a long walk etc. To improve this situation several steps should be taken, such as: Enhance lighting facilities, prohibit commercial activities, adequate usage of roadside and median barrier, construct more underpass rather than foot over bridge etc.
Aggregate Angularity Effect on Porous Asphalt Engineering Properties and Performance
Authors: Ahmad Tarmuzi Nadhir , Putra Jaya Ramadhansyah , Yaacob Haryati , Abdul Hassan Norhidayah , A. Aziz Md. Maniruzzaman
Published: April 2015

Porous asphalt is a flexible pavement layer with highly interconnected air voids constructed using an open-graded type of aggregate. The aggregate shape and surface texture serve a vital function in determining the engineering properties and performance of porous asphalt. The angular aggregates with clearly defined fracture faces and sharp edges encourage better interlocking between the aggregates' skeleton structures, which makes them preferable to use in asphalt mixtures. This study evaluates the effect of aggregate angularity on the engineering properties and performance of porous asphalt using both conventional and empirical particle index test methods. The term “engineering properties” refers to the experimental works determining resilient modulus and stability, whereas “performance” deals with the porosity and durability characteristics of porous asphalt caused by variations in the particle index number (Ia). A laboratory data analysis shows that angular particles provide a larger Ia number than non-angular particles. Furthermore, resilient modulus and stability properties significantly improve when angular aggregates are applied. The angular particles provide high mixture porosity but cause poor durability performance of porous asphalt against abrasion loss. Some improvements are suggested to enhance the strength properties and performance of porous asphalt on the basis of engineering applications.
Improvement in Properties of Expansive Clay by Stabilizing with Buton Rock Asphalt
Authors: Rusbintardjo Gatot , Hainin Mohd. Rosli , Md. Yusoff Nur Izzi
Published: April 2015

Subgrade is a soil layer underneath a constructed road pavement, airport runway or railway track. It is essential to make the layer stable and has sufficient shearing strength to withstand the traffic induced stresses without excessive deformation. If the subgrade soil is weak, it may need to be stabilized to improve its properties. This paper investigates the suitability of Buton Rock Asphalt (BRA) and natural sand in stabilizing expansive clay in order to be used as subgrade soil. Amount of 2%, 4%, 6%, and 8% of BRA by weight of soil were added while 5 to 25% of natural sand in increments of 5% by weight of soil was added to compare the effects of using natural sand and BRA in stabilizing expansive clay.  Tests such as Atteberg Limit, California Bearing Ratio, and direct shear were conducted on both natural clay soil and clay stabilized BRA. From the study, it was found that BRA can improve bearing capacity of expansive clay soil better than the natural sand.
Environmental Hostility Contingencies on the Relationship between Knowledge Management Strategy and Firm Performance
Authors: Hasan Alizar , Mohammed Abdul Hakim , Wardi Wardi , Yulius Nursyaifi , Heldi Heldi , Abdullah Mat Naim
Published: April 2015

This study aims to investigate the environmental hostility contingencies on the relationship between knowledge management strategy and firm performance. Knowledge management strategies are classified into two dimensions: Codification and Personalization. These studies cover the 192 completed and usable questionnaires were received from respondents which comprises of large size Indonesian manufacturing firms. The result via smartPLS revealed that knowledge management strategies positively and significantly influence the Indonesian manufacturing firm’s performance. Other findings display that environmental turbulences has only the contingency effect (the moderating effect) on the relationship between knowledge management strategy and manufacturing firm performance. Based on findings, the implications and future research also be discussed in this paper.
Service Level Agreements: Governance in Outsourcing Facility Management
Authors: Mohamed Armai , Mohammed Abdul Hakim , Abdullah Mat Naim
Published: April 2015

Governance mechanism is playing vital role in service performance. Service level agreement is a governance mechanism to facilitate the performance management of the facility management services outsourced. Service level agreement is indispensable document to be referred to ensure that the facility management services delivery comply the quality standard stipulated in the agreement. The service level agreement elements represent the required service performance. Previous research indicates that one of the reasons for the agreement failure is due to unclear and confusing service level agreement elements. The aim of this study is to develop the service level agreement fundamental elements for facilities management services in outsourcing contract.
GeoPackage as Future Ubiquitous GIS Data Format: A Review
Authors: Rashidan Muhammad Hanis , Musliman Ivin Amri
Published: April 2015

The emerging geospatial technologies in earth and space science informatics have led to the advancement in developing international standards for geospatial interoperability. In the last few years, two main trends are making disruptions in geospatial applications; mobile and context sharing. Geospatial data format used in mobile GIS to support advance mobile application is challenged. This is due to the lack of interoperability, open-standard, cross platform and standard APIs for access and management. For instance, most mobile GIS developments are application-dependent, contains redundant geospatial data, consume large storage capacity, and require custom applications for data translation. Based on these issues, new OGC file format named GeoPackage will enable greater geospatial data sharing on mobile and web platform. This data format is an open standard, non-proprietary, platform-independent, container for distribution, and direct use of all kinds of geospatial data will increase cross-platform interoperability, geospatial applications and web services. This presents a comprehensive review of mobile GIS hence, the concept of GeoPackage as a modern geospatial tool was discussed, while its relevance in contemporary geospatial technology are highlighted.
Comparing Shoppers’ Perception in Image Dimensions: A Retail Case Study
Authors: YM Lee Janice , Zhao Yuan Wee , Abdullah @ Mohd Asmoni Mat Naim , Abdul Jalil Rohaya , Baba Maizan
Published: April 2015

In the highly competitive retail industry, an understanding on the perceptions of shoppers is important in attracting and retaining loyal customers. This study compares the shoppers’ perceptions on various image dimensions using KSL City and Plaza Pelangi in Johor Bahru, Malaysia as case studies. Plaza Pelangi is more established but faces high vacancy rate and competition from KSL City. The latter is relatively new and needs to capture the shoppers market from Plaza Pelangi. A total 200 questionnaires were distributed using random sampling. Wilcoxon Signed Ranks Test, Paired-Samples T Test, Chi Square Test, One Way ANOVA were used. There was no significant difference between the overall preferences towards both shopping centers. However, there were significant differences according to demographic groups (race, age and marital status). Majority of the image dimension attributes were rated higher in KSL City compared to Plaza Pelangi. KSL City needs to improve the ease in locating merchandise and appoint higher quality tenants.  KSL should strive for more inclusive shopper demographic groups. Plaza Pelangi needs to improve its physical dimension in terms of layout and facility dimension by undergoing upgrading works. Plaza Pelangi also needs to recruit more food and beverage outlets as well as entertainment outlets.
Evaluation Criteria of Safety and Health Induction for Construction Worker (SICW) in Malaysia
Authors: Pui Teck Alfred Goh , Abdullah @ Mohd Asmoni Mat Naim , Abdul Hamid Hamdi , Misnan Mohd Saidin , YM Lee Janice , Jaafar Mohd Nadzri
Published: April 2015

Workplace safety is one the main concern by facilities managers due to high fatality rates in Malaysia construction industry. Occupational Safety and Health (OSH) training is an important effort to reduce workplace accident and improve employees’ safety and health in construction industry by enhancing the workers’ safety knowledge and awareness on workplace. In Malaysia, Safety and Health Induction for Construction Worker (SICW) or commonly known as Green Card Training, a mandatory safety training, has been introduced by Construction Industry Development Board (CIDB) to the construction related workers in order to enhance the workers’ safety knowledge and awareness on workplace. However, SICW has never been evaluated in term of its effectiveness in delivering safety knowledge and awareness to the workers since it has been introduced. Therefore, an evaluation is needed to be carried out to evaluate the safety knowledge and awareness gain by the workers from SICW. This paper will show the evaluation criteria for SICW based on the topics covered by standardized materials provided by CIDB. The evaluation criteria will serve as a guideline for evaluation of SICW in future research.
Local Authorities Challenges in the Implementation of Maintenance and Operation Blueprint
Authors: M. Y. Norhidayah, , H. Khadijah, , M. R. Maryanti, , Z. Ainur Zaireen, , A. L. Maslinda , M. N. Razali, , M. N. Noorsidi Aizuddin, , M. Abdul Hakim, , Z. Siti Radiaton Adawiyah,
Published: April 2015

Maintenance and Operation Blueprint for Iskandar Malaysia was established to ensure local authority immovable asset maintenance management is in line with Government Asset Management Policy 2009. This paper deals with investigation on the challenges in the implementation of Maintenance and Operation Blueprint Plan for Iskandar Malaysia among five local authorities in Iskandar Malaysia. A total of 25 respondents have been selected and interviewed. The data have been analyzed qualitatively. Base on the interview, the results show that there are challenges to implement maintenance and operation blueprint in local authority immovable asset maintenance management which are no clear direction from the top management to implement the Maintenance and Operation Blueprint for Iskandar Malaysia, lack of staff to implement the Maintenance and Operation Blueprint for Iskandar Malaysia, did not have enough time to implement the Maintenance and Operation Blueprint for Iskandar Malaysia and the high cost required to implement the Maintenance and Operation Blueprint for Iskandar Malaysia. This article can serve as a foundation for future studies in critical success factors to implement immovable asset maintenance and operation blueprint. A future study investigating critical success factors to implement immovable asset maintenance and operation blueprint would be very interesting to produce a new approach for successful blueprint implementation.
The Need for Land Use Assessment in Enhancing the Implementation of Integrated Water Resource Management (IWRM)
Authors: Sukereman Anis Syazwani , Suratman Robiah , Wai Sin Chang
Published: April 2015

Over 20 years, there has been an explosive growth of interest in the application of Integrated Water Resource Management among majority of developing and developed countries in settling various type of water issue. Unfortunately, the effective implementation of this approach still remains in doubt. Fragmented water resources legislation, complexity of constitutional framework on water resources management, lack of coordination among stakeholders and overlapping of authorities in managing water resources are among the issues that challenge the Integrated Water Resource Management implementation. Therefore, this paper attempts to review the broad literature regarding what is still wrong with this approach and propose the solution on how to enhance the current implementation. Since, there is still no authorized framework available to be used by the stakeholders involved in assessing land use practice and comparing the effectiveness of the implementation progress between states in Malaysia, this paper briefly concludes that there is a need to develop a framework for Land Use Assessment as a work performance guideline especially to the various stakeholders involved. Therefore, it is hope that this finding would offer better improvement to water resource management through effective, good governance and practical ways.
Performance Determinants of Malaysian Real Estate Investment Trusts
Authors: Abdul Jalil Rohaya , Mohd Ali Hishamuddin
Published: April 2015

The aim of this paper is to identify determinants of Malaysian real estate investment trust (REITs). By identifying the correct combination of these determinants, it able to assist the REITs companies to construct their property allocation strategy (PAS). However, studies on REITs’ performance in Malaysia showed few arguments on Malaysian REITs. Despite the evidence on potential for diversification, Malaysian REITs received inadequate response from institutional investors. Meanwhile the development of REITs in United States (US) started in early 1960s and it underwent significant cyclical performance and structure changes. Therefore, understanding of the literature review on the weaknesses and strengths of US REITs industry is essential. Furthermore, the lack of local study on these determinants, it is a research gap which can be explored in Malaysian REITs. The correct combination of determinants component contribute toward superior performance on REITs. Based on these reasons, REITs determinants that trigger the performance of Malaysian REITs warrant special attention and investigation. Through the literature review done on REITs determinants, this study manage to design the property allocation strategy for Malaysian.  This beneficial for both REITs firm to construct their own PAS to maximize distribution as well as institutional investor to evaluate REITs investment. All in all, ramification of Malaysian REITs determinants helps to improve Malaysian REITs industry.
On the Extraction of Elastic–Plastic Constitutive Properties From Three-Dimensional Deformation Measurements
Authors: Gross A. J. , Ravi-Chandar K.
Published: April 2015

In this article, a coupled experimental and numerical method is utilized for characterizing the elastic–plastic constitutive properties of ductile materials. Three-dimensional digital image correlation (DIC) is used to measure the full field deformation on two mutually orthogonal surfaces of a uniaxial tensile test specimen. The material’s constitutive model, whose parameters are unknown a priori, is determined through an optimization process that compares these experimental measurements with finite element simulations in which the constitutive model is implemented. The optimization procedure utilizes the robust dataset of locally observed deformation measurements from DIC in addition to the standard measurements of boundary load and displacement data. When the difference between the experiment and simulations is reduced sufficiently, a set of parameters is found for the material model that is suitable to large strain levels. This method of material characterization is applied to a tensile specimen fabricated from a sheet of 15-5 PH stainless steel. This method proves to be a powerful tool for calibration of material models. The final parameters produce a simulation that tracks the local experimental displacement field to within a couple percent of error. Simultaneously, the percent error in the simulation for the load carried by the specimen throughout the test is less than 1%. Additionally, half of the parameters for Hill’s yield criterion, describing anisotropy of the normal stresses, are found from a single tensile test. This method will find even greater utility in calibrating more complex material models by greatly reducing the experimental effort required to identify the appropriate model parameters.
Guidelines for Constructing Strain Gradient Plasticity Theories
Authors: Fleck N. A. , Hutchinson J. W. , Willis J. R.
Published: April 2015

Issues related to the construction of continuum theories of strain gradient plasticity which have emerged in recent years are reviewed and brought to bear on the formulation of the most basic theories. Elastic loading gaps which can arise at initial yield or under imposition of nonproportional incremental boundary conditions are documented and analytical methods for dealing with them are illustrated. The distinction between unrecoverable (dissipative) and recoverable (energetic) stress quantities is highlighted with respect to elastic loading gaps, and guidelines for eliminating the gaps are presented. An attractive gap-free formulation that generalizes the classical J2 flow theory is identified and illustrated.
On Void Coalescence Under Combined Tension and Shear
Authors: Torki M. E. , Benzerga A. A. , Leblond J.-B.
Published: April 2015

A micromechanics-based yield criterion is developed for a porous ductile material deforming by localized plasticity in combined tension and shear. The new criterion is primarily intended to model void coalescence by internal necking or internal shearing. The model is obtained by limit analysis and homogenization of a cylindrical cell containing a coaxial cylindrical void of finite height. Plasticity in parts of the matrix is modeled using rate-independent J2 flow theory. It is shown that for the discontinuous, yet kinematically admissible trial velocity fields used in the limit analysis procedure, the overall yield domain exhibits curved parts and flat parts with no vertices. Model predictions are compared with available finite-element (FE) based estimates of limit loads on cubic cells. In addition, a heuristic modification to the model is proposed in the limit case of penny-shape cracks to enable its application to materials failing after limited void growth as well as to situations of shear-induced void closure.
Scaling Laws in the Ductile Fracture of Metallic Crystals
Authors: Baskes M. I. , Ortiz M.
Published: April 2015

We explore whether the continuum scaling behavior of the fracture energy of metals extends down to the atomistic level. We use an embedded atom method (EAM) model of Ni, thus bypassing the need to model strain-gradient plasticity at the continuum level. The calculations are performed with a number of different 3D periodic size cells using standard molecular dynamics (MD) techniques. A void nucleus of a single vacancy is placed in each cell and the cell is then expanded through repeated NVT MD increments. For each displacement, we then determine which cell size has the lowest energy. The optimal cell size and energy bear a power-law relation to the opening displacement that is consistent with continuum estimates based on strain-gradient plasticity (Fokoua et al., 2014, “Optimal Scaling in Solids Undergoing Ductile Fracture by Void Sheet Formation,” Arch. Ration. Mech. Anal. (in press); Fokoua et al., 2014, “Optimal Scaling Laws for Ductile Fracture Derived From Strain-Gradient Microplasticity,” J. Mech. Phys. Solids, 62, pp. 295–311). The persistence of power-law scaling of the fracture energy down to the atomistic level is remarkable.
Purification of Single-Walled Carbon Nanotubes Based on Thermocapillary Flow
Authors: Song Jizhou , Lu Chaofeng , Hun Jin Sung , Dunham Simon N. , Xie Xu , Rogers John A. , Huang Yonggang
Published: April 2015

Single-walled carbon nanotubes (SWNTs) are of significant interest in the electronic materials research community due to their excellent electrical properties and many promising applications. However, SWNTs grow as mixture of both metallic and semiconducting tubes and this heterogeneity frustrates their practical use in high performance electronics. Recently developed purification techniques based on nanoscale thermocapillary flow of thin film overcoats enables complete elimination of metallic SWNTs from as-grown arrays. We studied the thermocapillary flow to purify SWNTs analytically and established a simple scaling law for the film thickness profile in terms of the geometry (e.g., film thickness), material (e.g., thermal conductivity and viscosity), and loading (e.g., power density) parameters. The results show that the normalized thickness profile only depends on one nondimensional parameter: the normalized power density. These findings may serve as useful design guidelines for process optimization.
Cloud-Based Intelligent User Interface for Cloud Manufacturing: Model, Technology, and Application
Authors: Ren Lei , Cui Jin , Li Ni , Wu Qiong , Ma Cuixia , Teng Dongxing , Zhang Lin
Published: April 2015

Cloud manufacturing is gradually transforming the way enterprises do business from traditional production-oriented manufacturing to service-oriented manufacturing. The development of cloud manufacturing in industry practice is closely related to domain-specific user experience. The huge amount of users with diverse roles and various requirements in manufacturing industry are facing great challenges of cloud system usability problems. Thus, user interface issues play a significant role in pushing this new area forward. In this paper, we discuss the key characteristics of intelligent user interface (IUI) for cloud manufacturing, i.e., naturality, smart mobility, self-configuration, and flexible customization. Further, a cloud-plus-IUI model for cloud end-users is presented. Then we discuss the enabling technologies, i.e., automatic configuration based on virtualization, context-aware adaption and recommendation, and multimodal interaction. Finally, we present SketchPart, a sketch-based pad system prototype for searching part drawings in the cloud, to show the advantages of the proposed cloud-plus-IUI solution.
Influence of Weld Defects and Postweld Heat Treatment of Gas Tungsten Arc-Welded AA-6061-T651 Aluminum Alloy
Authors: Dewan Mohammad W. , Wahab M. A. , Okeil Ayman M.
Published: April 2015

Welding defects and the reduction of mechanical performances are the foremost problems for fusion welded aluminum alloys joints. The influences of weld defects and postweld heat treatment (PWHT) on tensile properties of gas tungsten arc (GTA) welded aluminum alloy AA-6061-T651 joints are investigated in this current study. All welded specimens are nondestructively inspected with phased array ultrasonic testing (PAUT) to classify weld defect and measure the projected defects area-ratio (AR). Ultimate tensile strength (UTS) decreased linearly with the increase of the size of weld defect but tensile toughness behaved nonlinearly with defect size. Depending on defect size, defective samples' joint efficiency (JE) varied from 35% to 48% of base metal's (BM) UTS. Defect-free as-welded (AW) specimens observed to have 53% and 34% JE based on UTS and yield strength (YS) of BM, respectively. PWHT was applied on defect-free welded specimens to improve tensile properties by precipitation hardening, microstructures refining, and removal of postweld residual stresses. Solution treatment (ST) (at 540 °C) followed by varying levels of artificial age-hardening (AH) time was investigated to obtain optimum tensile properties. For GTA-welded AA-6061-T651, peak aging time was 5 hr at 180 °C. PWHT specimens showed 85% JE based on UTS and up to a 71% JE based on YS of BM. However, toughness values decreased about 29% due to the presence of precipitate-free fusion zones. The experimental investigations can be used to establish weld acceptance/rejection criteria and for the design of welded aluminum alloy structures.
Forming of Al 5182-O in a Servo Press at Room and Elevated Temperatures
Authors: Ju Long , Patil Shrinivas , Dykeman Jim , Altan Taylan
Published: April 2015

Aluminum alloys are increasingly used in automotive manufacturing to save weight. The drawability of Al 5182-O has been proven at room temperature (RT) and it is also shown that formability is further enhanced at elevated temperatures (ETs) in the range of 250–350 °C. A cost effective application of ET forming of Al alloys can be achieved using heated blank and cold dies (HB–CD). In this study, the material behavior of Al 5182-O is characterized using tensile test and viscous bulge test at RT. The nonisothermal finite element model (FEM) of deep drawing is developed using the commercial software pamstamp. Initially, deep drawing simulations and tests were carried out at RT using a 300 ton servo press, with a hydraulic cushion. The predictions with flow stress curves obtained from tensile and bulge tests were compared with experimental data. The effect of punch speed and temperature rise during forming at RT is investigated. The warm forming simulations were carried out by combining material data at ETs obtained from the literature. The coupled effects of sheet temperatures and punch speeds are investigated through the finite element analysis (FEA) to provide guidelines for ET stamping of Al 5182-O.
Automated Diagnostic System for Engine Maintenance
Authors: Fanuele Frank , Rio Richard A.
Published: April 2015

The rapidly increasing costs of maintenance, the demand for increased equipment utilization, fuel costs and the difficulty of correctly diagnosing internal mechanical problems in operating gas turbine engines has stressed the requirement for more effective monitoring and diagnostic equipment. Such equipment must be capable of performing three functions:

1. Acquiring condition data from operating gas turbines,

2. Analyzing the acquired data, and

3. Associating the cause and effect relationship to an incipient malfunction.

This paper describes the MTI Automated Vibration Diagnostic System (AVID) developed for the U. S. Air Force jet engine overhaul centers. The AVID concept is to automate troubleshooting procedures for fully assembled gas turbine engines. The System extracts high-frequency vibration data from existing, standard instrumentation to provide input to a specialized Symptom/Fault Matrix. This Symptom/Fault Matrix is configured to analyze the incoming data and assign a particular malfunction (or malfunctions) to a specified data set. This diagnosis is then printed out to provide maintenance personnel with exact knowledge of what the problem is and how to correct it.

This System, plus the growing awareness on the part of personnel of the capabilities of such automated equipment, will enable the Air Force to significantly reduce expenses at their jet engine overhaul facilities.
Automotive Gas Turbine Ceramic Component Testing
Authors: Carruthers W. D. , Boyd G. L.
Published: April 2015

Development of ceramic components for the Garrett/Ford AGT101, Advanced Gas Turbine Powertrain System Development Project, authorized under NASA Contract DEN3-167 is an iterative process involving current and advanced NDE inspection techniques, visual/dimensional inspection, and mechanical and thermal screening tests. Analytically predicted peak thermal and/or mechanical component stresses have been defined for engine operation and are closely simulated during rig testing. As development testing continues steady state strain and transient thermal data is continually fed back to the analytical models to aid in the design/development process. As part of the ceramic development task for the AGT101 a set of ceramic parts (49), constituting a complete assembly of engine structural hardware has been successfully rig tested to 1144K (1600°F) without incident, qualifying this assembly for subsequent engine testing. During the course of testing approximately 7.5 hours of 1144K (1600°F) operation has been accumulated on the assembly.
Spray Characteristics of Plain-Jet Airblast Atomizers
Authors: Rizk N. K. , Lefebvre A. H.
Published: April 2015

The effects of air and liquid properties, and atomizer dimensions, on the spray characteristics of plain-jet airblast atomizers are examined. Mean drop size and drop-size distribution are measured using an improved form of light scattering technique. The test range includes wide variations in air velocity, air pressure, air/liquid ratio, and liquid viscosity.

The experimental data generally confirm the results of previous studies on prefilming types of airblast atomizers. They show that increases in air velocity, air pressure and air/liquid ratio all tend to produce a more uniform spray and a lower mean drop size. It is also observed that any change in air properties, liquid properties and atomizer geometry that lowers the mean drop size also produces a more uniform distribution of drop sizes in the spray.
Finite Element Results of Possible CAES Tube to Tubesheet Joints
Authors: Lukas Holger , Montgomery Michael E.
Published: April 2015

Recuperators are required to improve the thermal efficiency of compressed air energy storage (CAES) plants. The duty of these recuperators is severe from a thermal cycling standpoint. To determine relative life expectancies of standard and nonstandard tube to tubesheet joints, the Electric Power Research Institute (EPRI) instituted a project to quantify the life. A finite element computer model was used to evaluate eight different tube to tubesheet joints under a variety of conditions. The study determined that successful tube to tubesheet joints can be made.
Water-Cooled Gas Turbine Nozzle Technology Demonstration at Ultra-High Firing Temperature
Authors: Geiling D. W. , Klompas N. , Zeman K. P.
Published: April 2015

During Phase II of the Department of Energy (DOE) funded High Temperature Turbine Technology (HTTT) Program, critical technology development and component verification testing related to the design of an advanced water-cooled gas turbine, firing at 2600°F (1427°C) on low-Btu gas, are being performed by General Electric. A composite construction first stage nozzle was chosen so that low surface temperature [1000°F (538°C)], necessary to control corrosion and high heat flux induced strain, would result. This paper discusses the prototype testing of a three throat segment of this design. The segment consists of two test vanes and a pressure and suction side slave. Hot gas conditions exceeded the design point conditions of 2600°F (1427°C) firing temperature, 166 psia (1.14 MPa) and 6.37 lbm/s (2.89 kg/s) per throat. Nozzle temperatures are presented as a function of firing temperature. Discussion of boiling phenomena which occurred during coolant flow reduction is included. Results are discussed as they relate to verification of the design method and to establishing the “technology readiness” of this design.
Installation of a Waste Heat Recovery System at a Gas Turbine-Driven Compressor Station
Authors: Tateosian Charles J. , Roland George K.
Published: April 2015

A waste heat recovery system for generation of electricity has been added to a natural gas pipeline compressor station. The heat recovery system, utilizing a dual pressure Rankine cycle with water/steam as the working fluid, increases the overall thermal efficiency of the 12,500 hp simple cycle gas turbine from 25.3% to 36.1%. The system will generate power for the local electric distribution system.
State-of-the-Art Review of Closed Cycle Gas Turbines Burning Dirty Fuels
Authors: Provenzale G. E.
Published: April 2015

The Closed Cycle Gas Turbine (CCGT) offers potential savings in operating costs due to high system efficiency and the ability to direct fire coal. However, for the full potential of CCGT to be realized, more competitive cost information must be generated, correlated, and compared with conventional steam power systems. Current development programs are intended to resolve many of the remaining uncertainties in design, performance, and cost by detailed examination and testing of critical components of CCGT coal-fired power systems. This paper reviews current technology developments and economic considerations of the closed cycle gas turbine burning dirty fuels versus conventional steam power systems.
A Coal Fired Gas Turbine Using an Air Cooled Fluidized Bed Combustor
Authors: Moskowitz S. , Mullen J. , Vanderlinden S.
Published: April 2015

A gas turbine cogeneration system using a coal fired atmospheric fluid bed (AFB) combustor represents an environmentally clean and less costly alternative to the oil or gas fired electric power generators, process steam boilers and process heaters that are necessary for the operations of both small and large industrial energy users.

This paper describes a cogeneration system which uses an air-to-gas heat exchanger tube assembly immersed in an AFB combustor to indirectly heat the compressor airflow from a gas turbine. This AFB combustor replaces the conventional direct fired oil or gas combustor. The flue gas from the AFB is used to produce steam and the waste energy from the gas turbine exhaust is used to provide additional steam or clean hot process air. By appropriate selection of components, AFB cogeneration systems can provide electrical-to-thermal ratios of 30 to 150 kilowatts per 1000 pounds of steam for a range of applications.

The paper presents the key design features of this type of system. The selection of materials and mechanical configurations are presented. The status of the technology and the R&D supporting test results are discussed. Cogeneration applications are discussed.
High Efficiency Pressurized Fluid Bed Systems
Authors: Berman Paul A. , Dille Joseph C.
Published: April 2015

The development of pressurized fluidized bed combustors (PFB) as an efficient, economical, and enviromentally acceptable means of utilizing the nation’s coal reserves has been underway for a short time. Although at least a dozen PFB facilities are in existence or under construction, and other PFB plants (1) are being designed, the technology is not fully developed.

This paper presents the results of an investigation into achieving high efficiency with a PFB system. The base case was a novel cycle, with the PFB combustor is located at an intermediate pressure between the maximum cycle pressure and atmospheric pressure. This configuration eliminates many of the technical problems associated with conventional PFB systems, and has a higher heating value net efficiency of 38 percent. Gas reheat, topping combustion, carbonizer systems, and compressor intercooling are added to the base system to yield a cycle efficiency of 45 percent.
On the Importance of Shear Deformation, Rotatory Inertia and Coriolis Forces in Turbine Blade Vibrations
Authors: Ansari Khyruddin Akbar
Published: April 2015

This paper is concerned with the significance of the effects of shear deformation, rotatory inertia and Coriolis forces in the analysis of turbine blade vibrations. Since these are quite pronounced at the high frequency ranges encountered in turbine blade vibration problems, they should not be overlooked although their inclusion paves the way for a complicated nonlinear analysis. An approximate analysis technique is presented which involves an application of the stationary functional method using the normal modes of a discretized model. Numerical results are obtained and discussed. It is noted that a definite advantage of applying this technique to a lumped parameter model is that nonlinear modes higher than the fundamental can also be easily generated.
Field Test of the W501D, a 100 MW Combustion Turbine
Authors: Scalzo A. J. , Howard G. S. , Holden P. C.
Published: April 2015

The field test of the current production W501D combustion turbine shows the engine to be an outstanding success. The engine meets power and exceeds efficiency expectations. Metal temperatures are at or below expected levels throughout the engine. In particular the test data demonstrates low temperatures provided by improved design concepts for the combustion chamber and first stage turbine vane, which are critical components because of their severe environment. Other design improvements for performance and reliability were also verified during the test.
An Investigation Into the Effect of Side-Plate Clearance in an Uncentralized Squeeze-Film Damper
Authors: Cookson R. A. , Dainton L. J.
Published: April 2015

An experimental investigation has been carried out into the influence of side-plate flow restrictors on the performance of a squeeze-film damper bearing. The experimental rig used was a flexible rotor with a disc positioned mid-way between two squeeze-film damper bearings. One of the squeeze-film dampers was fitted with side-plates which could be adjusted and accurately located with respect to the squeeze-film damper journal.

It has been found that the influence of the side-plate clearance on the ability of the squeeze-film damper to reduce the amplitude of the central disc can be considerable if the side-plate clearance is less than the radial clearance. As the side-plate clearance reduces towards zero, the effectiveness of the squeeze-film damper diminishes until the amplitudes obtained are the same as those measured when the rolling-contact bearing is rigidly supported.

An interesting type of precessing elliptical orbit was discovered for conditions where the ‘jump’ phenomenon was operating.
A Coal Fired air Turbine Cogeneration System
Authors: Foster-Pegg R. W. , Davis J. S.
Published: April 2015

This paper describes coal-fired, indirectly heated, air turbine combined cycle cogeneration plants that employ atmospheric pressure external combustion of coal, an open cycle gas (air) turbine, and a steam turbine. Air to operate the air turbine is heated indirectly, by hot fluidized solids contained inside tubes. The result is a high efficiency system that burns coal (or almost anything that will burn), does not require extensive operator training or support facilities, and emits low quantities of sulfur, NOx and particulates. The plant is capable of supplying electrical power, process heat, steam, and clean hot air in varying quantities, depending on the application. Uses exist in the chemical, petroleum, mining, metallurgical, paper, and textile industries and in enhanced oil recovery.
Corrosion and Deposition Results From Pressurized Passage Tests With Heavy Ash Bearing Fuels From the SRC-II Process
Authors: Spengler C. J. , Whitlow G. A. , Lee S. Y. , Wenglarz R. A. , Mulik P. R. , Cohn A.
Published: April 2015

A program is in progress to detect possible deposition and corrosion in combustion turbines that may use coal-derived liquid (CDL) fuels. Four tests in a turbine simulator (pressurized test passage) were made with CDL from the SRC-II process. The CDL was a pilot plant product with about a one-third heavy distillate fraction added to middle distillate to accelerate possible corrosion and deposition effects. At the temperature levels of current operating turbines (about 1366 K, 2000°F) there was no excessive deposition from the CDL fuels tested. Possible excessive deposition at high (1533 K, 2300°F) temperatures occurred but may be reduced significantly by use of CDL with low ash content.
Emergency Power for the F-16 Aircraft
Authors: Allen Dale V. , Stancliffe A. Colin , White Opie W.
Published: April 2015

The emergency power unit (EPU) for the General Dynamics F-16 “Fighting Falcon” aircraft provides electrical and hydraulic power in the event of main engine generator or hydraulic pump failure or an engine-out condition. The unit is powered by main engine bleed air, or by the decomposition products of H-70 fuel (a hydrazine-water mixture), or a combination of both. This paper describes the emergency power unit and discusses the use of H-70 on the flight line.
Royal Naval Marine Gas Turbines in the South Atlantic in 1982
Authors: Ridley P. W. W.
Published: April 2015

The Royal Navy has now over 20 operational gas turbine powered warships, the majority with a two Olympus/two Tyne COGOG main propulsion fit. Many of these were deployed in the South Atlantic during the Falklands crisis in the Spring of 1982. The paper analyses the lessons learnt during 4 months of strenuous operations in a hostile environment.
Modelling of Soot Formation in Spray Combustors
Authors: Koussa S. S.
Published: April 2015

A model for the prediction of the distribution of soot concentration in spray combustors is presented. Both gas-phase and liquid-phase soot formation have been considered. The methods have been developed within the constraints on detailed combustion modelling for practical application. Some predictions are assessed by comparison with published experimental data. It is concluded that predictions of the same quality as those of gaseous-fuelled combustors may be obtained neglecting liquid-phase soot formation in case of light fuels.
Emissions From Enclosed Swirl Stabilised Premixed Flames
Authors: Ahmad N. T. , Andrews G. E.
Published: April 2015

The premixed combustion efficiency and emissions characteristics of four axial vane swirlers are compared with a simple grid plate stabilised premixed flame. The four swirlers are designed to investigate the influence of Swirl Number, pressure loss and swirler design. The results show that efficient combustion of weak mixtures at simulated gas turbine combustion conditions is difficult with swirl systems, but relatively easily achieved with grid plate systems. High swirl numbers are shown to have the worst combustion efficiency with a major unburned hydrocarbon problem. NOx emissions are similar for all the stabilisers and they all exhibit a very high proportion of NO2 and NOx emissions for weak mixtures.
Experience With High Efficiency Aircraft Derivative Gas Turbine Units on a Gas Transmission System
Authors: Cataford G. F. , Najnar G.
Published: April 2015

This paper reviews the use of aero derivative gas turbine compressor units or pumping operations on a natural gas transmission system. The discussion spans the period from the installation of first generation machines to procurement of the latest., most modern units. Past developments and future directions are discussed together with installation and operation philosophy of the operating utility.
Torsional Analysis of Partially Closed Open Section
Authors: Mysore R. K.
Published: April 2015

The torsional stiffness of a thin walled closed section is many times greater than that of the corresponding open section. The structure consisting of a thin walled open section partially closed along its length by beams is an intermediate case and studies have been carried out to analyze the torsional behavior of such structures. The continuous medium method, in which the intermediate connecting beams are replaced by an equivalent continuous medium, is applied for the torsional analysis. Basically, Vlasov’s theory is applied for the torsional analysis and for the determination of axial warping stresses. Expressions to determine the angle of twist and warping stresses are obtained. Design charts are developed to determine the response for various stiffnesses of intermediate connecting beams. Comparisons between completely open and partially open sections are made for angle of twist and warping stresses. Also, the warping stresses are compared with bending stresses and it is shown that the warping stresses could be very significant.