Failure Analysis of a Ruptured Trunkline

This article reports a detailed analysis of a failure observed in a petroleum trunkline in the Niger Delta region of southwestern Nigeria. The study was carried out using various techniques including metallurgical, chemical, and x-ray analysis. Leakage was observed along a petroleum trunkline route, and excavation of the trunkline revealed that the trunkline had actually fractured along the 6 o’clock position. The pipeline material was found to conform to the API specification for low carbon steel of X52 grade. Wormwood-like interconnecting pits typical of microbial-induced corrosion were noticed at the 6 o’clock position. Scale deposits composed of corrosion products and debris from the crude oil transported by the trunkline were also noticed. The liquid analysis result showed that the produced water was corrosive, and it has a high bacteria count. The failure of the trunkline was found to be due to the thinning of the pipeline at the 6 o’clock position by the combined effect of abrading by debris, erosion, and corrosion aided by bacteria activities, i.e., microbial-induced corrosion (MIC) and eventual rupture.     

Effect of grain size on the strength characteristics of cement-stabilized lateritic soils

Lateritic soils are readily available all over Nigeria and as such have attracterd several research studies in recent times, the obvious aim being its utilization in the construction industry. This paper gives an account of the work done to further classify the usefulness and limitations of lateritic soils.Cement was used as the stabilizer and the lateritic soils used were obtained from the Ifewara deposits located about 10 km along Ife-Ifewara Road. A sieve analysis of the sample was made. Five different grain size ranges, from coarse to fine, were extracted from the samples. Cubes were moulded by mixing each grain size range with cement in five different proportions, the optimum water/cement ratio of each mix proportion being determined beforehand. The compressive strengths of the cubes were determined after 7, 21, and 28 days of curing in water, respectively. It was established that the higher the laterite/cement ratio, the lesser the compressive strength, and that the finer the grain size range, the higher the compressive strength. Finally, it was observed that cubes made using laterite/cement mix proportions 1:1 and 3:1 kept gaining strength with age while the others were losing strength.     

Light and Electron Microscopy Studies of the Visible Diffusion Zone of Mild Steel Pack Cyanided in Processed Cassava Leaves

This study investigates the microstructure of the processed cassava leaves. Standard parts machined from low visible diffusion zone formed in low carbon steel pack cyanided using carbon steel were pack cyanided by high temperature in-situ diffusion of nascent carbon and nitrogen into austenite. Formation of a visible diffusion zone was confirmed after observation with a Reichert-Jung Polyval optical microscope coupled with Zeiss AxioCam ICc 1 camera. High magnification Scanning Electron Microscope （SEM） imaging of the visible diffusion zone was done with a CamScan Series 2 scanning electron microscope. The zone was found variable in depth as measured from a representative position. The structure of all samples consists of ferrite and pearlite as determined by optical and SEM examination. Resulting products were thus both tough and hard suitable for service environments requiring high resistance to both wear and impact failure.     

False‐Name Manipulation in Weighted Voting Games: Empirical and Theoretical Analysis

Weighted voting games are important in multiagent systems because of their usage in automated decision making. However, they are not immune from the vulnerability of false‐name manipulation by strategic agents that may be present in the games. False‐name manipulation involves an agent splitting its weight among several false identities in anticipation of power increase. Previous works have considered false‐name manipulation using the well‐known Shapley–Shubik and Banzhaf power indices. Bounds on the extent of power that a manipulator may gain exist when it splits into k = 2 false identities for both the Shapley–Shubik and Banzhaf indices. The bounds when an agent splits into k > 2 false identities, until now, have remained open for the two indices. This article answers this open problem by providing four nontrivial bounds when an agent splits into k > 2 false identities for the two indices. Furthermore, we propose a new bound on the extent of power that a manipulator may gain when it splits into several false identities in a class of games referred to as excess unanimity weighted voting games. Finally, we complement our theoretical results with empirical evaluation. Results from our experiments confirm the existence of beneficial splits into several false identities for the two indices, and also establish that splitting into more than two false identities is qualitatively different than the previously known splitting into exactly two false identities.     

A behavioral change-based approach to energy efficiency in a manufacturing plant

In the realm of industrial energy efficiency studies, very little research has been done to understand the barriers and opportunities to influence behavior of production workers and the corresponding energy-saving potentials. This paper analyzes a case study of Volvo Construction Equipment AB in Braås, Sweden (VCE Braås), that has reduced its relative idle electricity use by more than 10 percentage points during 2013–2016 by implementing a strategy of changing everyday behavior of production workers. The results based on interviews with actors involved in the energy efficiency project showed that a concrete goal, the employment of a fulltime operational leader who earlier worked as a production worker at VCE Braås, and the involvement of both the leadership and employees in project management were key to the success of the project.     

Strength Evaluation of Concrete Made with Dug-up Gravel from Southwestern Nigeria

Large expanses of natural deposits of gravel and sand are known to be available in many parts of the Southwestern Nigeria, which are being used for concrete production but with no standards. This study investigates the effects of using raw and washed dug-up gravel on the strength properties of concrete with a view to provide some standards for their usage. Field survey of quarry sites around Ile-Ife identified two commonly used dug-up gravel (Tiwantiwa), gravel A and (Majeroku), gravel B, which were selected for investigation. Prescribed mix proportions (measurements by weight) of 1:2:4 (cement:fine aggregate:washed/raw gravel) and 1:6 (cement:raw gravel) were used to produce the concrete cubes and beams for compressive and flexural strength tests. The results showed that using gravel A in raw form without sand and in washed form with sand have almost the same compressive strength (CS), while washing gravel B before use and with sand improved the CS of concrete. At 28 days, the CSs of concretes made from raw with no sand (RNS) of gravels A and B were 17.07 and 12.47 N/mm², while those of raw with sand (RWS) and washed with sand (WWS) were 14.73 and 16.80 N/mm² for gravel A and 11.93 and 16.00 N/mm² for gravel B, respectively. Characteristic strength of 15 N/mm² is recommended for concrete made with RNS and WWS of gravel A, while 11 and 14 N/mm² are recommended for those of gravel B, respectively.     

Metallographic Studies of Pack Cyanided Mild Steel Using Cassava Leaves

Cassava has been found to contain cyanogenic glucoside, which is hydrolyzed to cyanide as a waste product during cassava processing. This cyanide content is found to vary in the various parts of the cassava plant. Powdered cassava leaf has been utilized to pack cyanide mild steel specimens using BaCO₃ and BaCl₂ as energizers. The microstructures of the treated specimens were examined; these revealed a case formation resulting from the diffusion of C into the specimen. The diffusion proceeded from the case to the core of the specimen with increase in treatment temperature and time. The cutting time of the case-hardened steels was investigated and correlated with pack cyaniding heat treatment. The specimens were found to be more resistant to sectioning with increasing temperature and time.     

Factors affecting the strength and creep properties of laterized concrete

Many factors are known to affect the strength and creep properties of laterized concrete prisms. Those considered in this report include: mix proportion, water/cement ratio, curing ages, grain size ranges, stress level, lateritic soils-river sand variation. Moulds of 50 × 50 × 250 mm high were used for making prism specimens. Four different mix proportions were selected while prism specimens were cast using four different water/cement ratios which were kept constant for each mix proportion. Prism specimen were also made using a constant water/cement ratio with different river sand lateritic soils proportions forming the fine aggregate component of the selected 1:2:4 mix proportion. The results have shown that increase in cement content and decrease in water/cement ratio of laterized concrete prisms bring about increase in the compressive strength obtained. The mix ratio of 1 part lateritic soils plus $\text{1}\text{1}\text{2}$ parts river sand produced a slightly higher strength than the conventional concrete grade 20. There is also a corresponding increase in the creep of laterized concrete prisms due to different curing ages and different imposed loads. Both the mix proportion and the grain size ranges affect the creep of laterized concrete prisms differently. Unlike the creep of concrete which shows some definite recovery after unloading, laterized concrete prisms did not show any form of recovery, and there was drastic reduction in the compressive strength of the specimens after unloading.     

A Cuckoo Search Detector Generation-based Negative Selection Algorithm

The negative selection algorithm (NSA) is an adaptive technique inspired by how the biological immune system discriminates the self from non-self. It asserts itself as one of the most important algorithms of the artificial immune system. A key element of the NSA is its great dependency on the random detectors in monitoring for any abnormalities. However, these detectors have limited performance. Redundant detectors are generated, leading to difficulties for detectors to effectively occupy the non-self space. To alleviate this problem, we propose the nature-inspired metaheuristic cuckoo search (CS), a stochastic global search algorithm, which improves the random generation of detectors in the NSA. Inbuilt characteristics such as mutation, crossover, and selection operators make the CS attain global convergence. With the use of Lévy flight and a distance measure, efficient detectors are produced. Experimental results show that integrating CS into the negative selection algorithm elevated the detection performance of the NSA, with an average increase of 3.52% detection rate on the tested datasets. The proposed method shows superiority over other models, and detection rates of 98% and 99.29% on Fisher’s IRIS and Breast Cancer datasets, respectively. Thus, the generation of highest detection rates and lowest false alarm rates can be achieved.     

Characteristics and composition of the pulp oil and cake of the African pear,Dacryodes edulis (G. don)

The pulp of the African pear, Dacryodes edulis, was investigated for its nutritional quality and oil characteristics. The crude protein, fat, fibre and carbohydrate contents were 25.9, 31.9, 17.9 and 13.5%, respectively. The pulp was found to contain significant levels of Ca, Mg, K and P. The fatty acid profiles showed a saturated fatty acid content of 50.85% and an unsaturated fatty acid content of 49.14%. The predominant fatty acids were palmitic and oleic acids. The saponification value and iodine value were 201.4 and 59.6. The amino acid profiles showed high contents of the essential amino acids lysine, leucine and threonine.