PROPERTIES OF FOAMED CEMENT WITH ADDITIVES FOR ZONAL ISOLATION IN COAL BED METHANE (CBM) WELLS (A CASE STUDY ON MUKAH COALFIELD, SARAWAK)

Coal bed methane (CBM) generally has lower fracture gradient as compared to - - conventional oil or gas wells due to weak structures of coal. Therefore, CBM are more vulnerable to downhole problems faced such as lost circulation and formation fracture as the formation cannot withstand the cement densities of averagely above 11 ppg (1320kg/m3 ). Foam cement when used together with additives offers a versatile and - - economical means of cementing with low density (5-13 ppg) and high strength per unit volume. Foamed cement was first introduced in the application of light weight cement for - - use in constructions and site building, which later, similar theory were applied in the foamed cementin~ process for the oil and ~as industry. The objectives of this project are to determine properties of the foamed cement when used with Microsilica and BJ Ultra additives (density, compressive strength, fluid loss, porosity and permeability) to be compared and analyzed for their compatibility for the Mukah Coalfield, Sarawak. This thesis will discuss the characteristics of CBM reservoirs, foamed cement with additives sample preparation methods and data analysis. The various aspect of slurry design, including their method of determination is discussed. The properties of the conventional Class G cement can be determined directly with existing equipment which includes the curing chamber, compressive strength testers, and HPHT Filter Press. For the foamed cement, since these parameters are determined by the air quality and water to cement ratio and type of additive used, their relationships to density are focused

The Transactional Conflict Problem

The transactional conflict problem arises in transactional systems whenever two or more concurrent transactions clash on a data item. While the standard solution to such conflicts is to immediately abort one of the transactions, some practical systems consider the alternative of delaying conflict resolution for a short interval, which may allow one of the transactions to commit. The challenge in the transactional conflict problem is to choose the optimal length of this delay interval so as to minimize the overall running time penalty for the conflicting transactions. In this paper, we propose a family of optimal online algorithms for the transactional conflict problem. Specifically, we consider variants of this problem which arise in different implementations of transactional systems, namely "requestor wins" and "requestor aborts" implementations: in the former, the recipient of a coherence request is aborted, whereas in the latter, it is the requestor which has to abort. Both strategies are implemented by real systems. We show that the requestor aborts case can be reduced to a classic instance of the ski rental problem, while the requestor wins case leads to a new version of this classical problem, for which we derive optimal deterministic and randomized algorithms. Moreover, we prove that, under a simplified adversarial model, our algorithms are constant-competitive with the offline optimum in terms of throughput. We validate our algorithmic results empirically through a hardware simulation of hardware transactional memory (HTM), showing that our algorithms can lead to non-trivial performance improvements for classic concurrent data structures

Systematic Risk Factors and Stock Return Volatility

This study analyzes the transmission of systematic risk exhaling from macroeconomic fundamentals to volatility of stock market by using auto regressive generalized auto regressive conditional heteroskedastic (AR-GARCH) and vector auto regressive (VAR) models. Systematic risk factors used in this study are industrial production, real interest rate, inflation, money supply and exchange rate from 2000-2014. Results indicate that there exists relationship among the volatility of macroeconomic factors and that of stock returns in Pakistan. The relationship among the volatility of macroeconomic variables and that of stock returns is bidirectional; both affect each other in different dynamics

In-Built Customised Mechanical Failure of 316L Components Fabricated Using Selective Laser Melting

The layer-by-layer building methodology used within the powder bed process of Selective Laser Melting facilitates control over the degree of melting achieved at every layer. This control can be used to manipulate levels of porosity within each layer, effecting resultant mechanical properties. If specifically controlled, it has the potential to enable customisation of mechanical properties or design of in-built locations of mechanical fracture through strategic void placement across a component, enabling accurate location specific predictions of mechanical failure for fail-safe applications. This investigation examined the process parameter effects on porosity formation and mechanical properties of 316L samples whilst maintaining a constant laser energy density without manipulation of sample geometry. In order to understand the effects of customisation on mechanical properties, samples were manufactured with in-built porosity of up to 3% spanning across ~1.7% of a samples’ cross-section using a specially developed set of “hybrid” processing parameters. Through strategic placement of porous sections within samples, exact fracture location could be predicted. When mechanically loaded, these customised samples exhibited only ~2% reduction in yield strength compared to samples processed using single set parameters. As expected, microscopic analysis revealed that mechanical performance was closely tied to porosity variations in samples, with little or no variation in microstructure observed through parameter variation. The results indicate that there is potential to use SLM for customising mechanical performance over the cross-section of a componen

The role of greulich and pyle method in age estimation from left hand plain x-rays

Objective: To determine whether the Greulich and Pyle (G&P) atlas is applicable to populations of different ethnicity.Material and Methods: A cross sectional study was conducted at Department of Diagnostic Radiology, National Institute Rehabilitation Medicine during 2017.  Total 100 left hand and wrist radiographs were assessed using GP atlas for age estimation using non-probability consecutive sampling technique.ean Chronological age (CA) and Skeletal age (SA) were calculated for each group and any significant differences between the two were established through two- tailed, paired t-test. Data was analyzed using SPSS version 17.Results: Total of 100 patients with left hand and wrist x-rays were included (50 males, 50 females). Analysis showed a strong correlation between Chronological age (CA) and Estimated age (skeletal age) with a p <0.001. The mean difference between chronological age and skeletal age was .31050 years and std. Deviation 1.06866 respectively; p-values < 0.001. However, a strong significant positive correlation (r = .980; p-values, 0.001) was noted between chronological age and skeletal age in both the genders.Conclusion: GP atlas can be used for age estimation to Islamabad Rawalpindi population but would recommend that differences highlighted are to be taken in to consideration for over- and under-aging

PROPERTIES OF FOAMED CEMENT WITH ADDITIVES FOR ZONAL ISOLATION IN COAL BED METHANE (CBM) WELLS (A CASE STUDY ON MUKAH COALFIELD, SARAWAK)

Coal bed methane (CBM) generally has lower fracture gradient as compared to - - conventional oil or gas wells due to weak structures of coal. Therefore, CBM are more vulnerable to downhole problems faced such as lost circulation and formation fracture as the formation cannot withstand the cement densities of averagely above 11 ppg (1320kg/m3 ). Foam cement when used together with additives offers a versatile and - - economical means of cementing with low density (5-13 ppg) and high strength per unit volume. Foamed cement was first introduced in the application of light weight cement for - - use in constructions and site building, which later, similar theory were applied in the foamed cementin~ process for the oil and ~as industry. The objectives of this project are to determine properties of the foamed cement when used with Microsilica and BJ Ultra additives (density, compressive strength, fluid loss, porosity and permeability) to be compared and analyzed for their compatibility for the Mukah Coalfield, Sarawak. This thesis will discuss the characteristics of CBM reservoirs, foamed cement with additives sample preparation methods and data analysis. The various aspect of slurry design, including their method of determination is discussed. The properties of the conventional Class G cement can be determined directly with existing equipment which includes the curing chamber, compressive strength testers, and HPHT Filter Press. For the foamed cement, since these parameters are determined by the air quality and water to cement ratio and type of additive used, their relationships to density are focused

SURVIVAL OUTCOMES IN EARLY GLOTTIC CARCINOMA; A SINGLE INSTITUTION EXPERIENCE

Purpose: Laryngeal cancers are amongst the most common cancers affecting head and neck region. In this study, we analyse the overall survival (OS) following hypofractionated radiotherapy (RT) in early stage glottic carcinoma treated at Shaukat Khanum Memorial Cancer Hospital and Research Centre, Lahore. Methods: Between October 2003 and June 2009, 87 patients with early stage glottic carcinoma were treated with hypofractionated RT. All patients were included in the study. The ratio of male: female is 94%:6%. Mean age was 62 years (range 31–83 years). 66% of the patients were smokers. AJCC stage was T1a in 76%, T1b 20% and T2 in 4% of the patients. Histological distribution was; squamous cell carcinoma 97%, verrucous carcinoma 2% and squamous cell spindle variant 1%. Median follow-up time was 59 months (range 4–122 months). RT dose was 55 Gy in 20 fractions over a period of 4 weeks. Median RT treatment time was 28 days (range 23–35 days). Patients that lost to follow-up were contacted through telephone. Results: The 10-year OS was 83%. Patterns of failure was 7 local and 1 distant while 1 patient had persistent disease. 15 patients were dead at the time of study. Cause of death; 13 patients died due to Ischemic heart disease and 2 due to primary disease. Conclusion: Hypofractionated RT 55 Gy in 20 fractions seems to achieve good OS while offering potential for optimizing resources usage. Key words: Glottic carcinoma, hypofractionated, overall survival, radiotherapy

Effect of pre-emptive in situ parameter modification on residual stress distributions within selective laser-melted Ti6Al4V components

The effect of thermally induced residual stresses is not dynamically considered during a selective laser melting (SLM) build; instead, it processes using invariable parameters across the entire component’s cross-section. This lack of pre-emptive in situ parameter adjustment to reduce residual stresses during processing is a lost opportunity for the process with the potential to improve component mechanical properties. This investigation studied the residual stresses introduced during manufacturing of SLM Ti6Al4V benchmark components and adapted process parameters within a build (layer-to-layer specific modifications) to manage and redistribute stresses within these components. It was found that temporarily switching to an increased layer thickness during the build, directly below highly stressed regions within the component, redistributed stresses and reduced the overall stresses within the structure by 8.5% (within the 80–320-MPa residual stress range) compared to standard invariable SLM processing parameters. This work demonstrates the need for current SLM systems to focus on developing a more intelligent processing architecture with parameters that adapt on the fly during a build, in order to manage residual stresses within the built structure