Journal of the Nigerian Society of Engineers
The NSE Technical Transactions (ISSN: 1119-5363) is the flagship, peer-reviewed scientific journal of the Nigerian Society of Engineers (NSE) , serving as the definitive academic and professional repository for engineering research and technical innovation in Nigeria. Published out of the NSE National Headquarters at the National Engineering Centre in Abuja, this authoritative publication spans the entire spectrum of the profession by covering all 25 specialized engineering divisions of the society, including Civil, Mechanical, Electrical, Chemical, Structural, Aeronautical, and Agricultural engineering, among others. The journal publishes high-quality original research papers, technical reports, and pioneering case studies that advance engineering education, theory, and local practice. Managed through the office of the Editor-in-Chief (editorinchief@nse.org.ng ), the publication enforces rigorous technical review standards, making contribution to or publication within its volumes a critical milestone for professionals seeking to fulfill the requirements for corporate membership registration and career advancement within the society.
OPTIMUM STABILIZATION REQUIREMENT OF IMO CLAYSHALE
Clayshale is one of the problematic soils often encountered in civil engineering construction and is notable for its low shear strength when wet and rapid deterioration on exposure to weather. The geo-technical and engineering properties of samples of Imo clayshale collected from Nsugbe Omo (along Onitsha - Nsukka road in the eastern part of Nigeria) were investigated. When the existing standards in civil engineering practice such as Road Note 29, Western Nigeria Road specification, Nigeria Board of Road Research Institute, (NBRRI), the soil proves highly inadequate for road construction from strength criteria. Also index properties suggest that the sample is a potentially high swelling clay. In order to reduce the expansiveness of this sample and also increase the strength, stabilization by additives was employed. Cement, Lime and flyash were utilized at various percentages. Stabilized samples were tested in accordance with BS 1924 (1975). It was observed that flyash stabilization Imo clayshale is inadequate for civil engineering construction both from strength criteria and index properties. It was also observed from the results that 8% lime, 15% lime, mixture of 6% lime and 8% flyash, and 15% cement are suitable for road construction on the basis of strength criterion.
PERFORMANCE ANALYSIS OF A SINGLE-PHASE LINEAR INDUCTION MOTOR USING SYMMETRICAL COMPONENTS
The paper presents the circuital approach and performance calculation for a shaded-pole single-sided linear induction motor using symmetrical components for a two-phase system. The physical model has been built. Results obtained from the circuital approach and experimental tests are compared and discussed.
INVESTIGATION OF CASTING DEFECTS IN NIGERIAN FOUNDRY INDUSTRY (A Case Study of Lagos and Ogun States)
Casting that does not meet the quality standard or agree with the laid down technical specifications is said to contain Cast Defect since it cannot be used directly without necessary corrections. In this work, attempt is made to study the level of cast defects in foundries in Lagos and Ogun States. The study revealed that 35.7% of defects recorded are blow holes; 31% short run, shrinkage 7% and porosity 6% other various types of defects are less than 20%. This high percent of blow holes, which is caused by high moisture content, improper drying and inadequate vent and permeability of the moulding materials, can be attributed to the fact that a large number of our foundries employ sand casting process. Majority of casting without defect are obtained from non-ferrous metals using permanent moulds. Most casting defects are recorded in ferrous metals and alloys (steel and cast iron).
EFFECTS OF AUMINA AND BAUXITE ON THE PHYSICAL PROPERTIES OF SUPERFLUXED NIGERIA IRON ORE SINTERS
An attempt has been made to examine the effects of alumina and bauxite on the strength characteristics of superfluxed sinters. The results of the experiments indicate that alumina and bauxite superfluxed sinters are stronger than normal iron ore sinter. The strength minimum reportedly experienced at basicity 1.0-1.8 for normal sinter was absent for superfluxed bauxite and alumina sinters. A mixture of alkaline and bauxite gave even stronger sinter.
THE DESIGN AND INSTALLATION OF A DISSIPATION ARRAY SYSTEM FOR LIGHTNING PREVENTION
In this paper, a device known as the Dissipation Array System (DAS), acclaimed to prevent lightning strikes within its immediate vicinity, is presented. The design and installation specifications of the system are presented. Though the system functions effectively, the principies behind its operation is not well-developed. However, the electrostatic field theory behind the operation of the DAS is developed in mathematical equations and presented in this paper.
STABILITY OF EMBANKMENTS IN THE YENAGOA AREA OF THE NIGER DELTA
This paper presents case records of embankment failures, while the computed safety factors were higher than unity. A modified method of stability analysis is therefore adopted in a programme of research into the problem of embankment stability in the Yenagoa area of the Niger Delta. Good results are obtained with the modified method. A brief outline is also given of some construction expedients for countering problems of settlement and stability.
BINARY ILP FORMULATION FOR THE SIMULTANEOUS MACHINE LOADING PROBLEMS OF TARAKU MILLS LIMITED
The integer linear programming (ILP) in production scheduling provides optimal solutions for the desired objective function in sequential scenario. A similar formulation for Taraku Mills Limited is presented where processors are capable of accommodating more than one job (Products) at the same time. The algorithm used in the computation, utilizes two other algorithms, the Cambell, Dudex and Smith algorithms and the nearest neighbour method of the assignment problems. The simultaneous approach performs extremely better than the sequential approach. There is great reduction in the total flow time of products considered. The solution to the Taraku Mills Limited formulation is presented in three parts with the objective of minimizing the total flow time. The first part schedules the jobs (products) unto the first processor. The second part finds the total flow time of the four products while the third part schedules the production times of these jobs unto a ganth chart. The simultaneous approach performs entirely better than the sequential approach and the method like other operations research models can be applied to real life problems.
LABORATORY TRIAL OF SOIL STABILIZATION USING PULVERIZED COAL BOTTOM ASH
A low calcium pulverized coal bottom ash (PCВА) is evaluated for use as a stabilizer for a residual lateritic soil. The laboratory study consisted of the following tests conducted on soil PCBA mixtures compacted at the energy level of the standard Proctor: moisture - density relationship, unconfined compressive strength (UCS), California bearing ratio (CBR) and durability by immersion in water. Moderate increases in strength and durability were recorded on treating the lateritic soil with an optimum 6% PCBA content. Testing methods and recommendations for mix design of PCBA stabilized pavement subgrade are presented and the mechanism of PCBA cementation is discussed.
THE USE OF SELECTED BIOMATERIALS AS ENERGISER IN SURFACE HARDENING OF MILD STEEL
Surface hardening is an essential heat treatment given to gears, shafts, cutting tools and other machine components to impact on them a good wear resistance surface. The kinetics of the depth of diffusion of carbon in mild steel is usually enhanced by the addition of an energizer such as barium carbonate (BaCO,) in the hardening mix. Barium carbonate is not locally available in Nigeria. Investigation were therefore carried out to appraise some agricultural waste: cow bones, coconut shells and sea shells for use as energizers in surface hardening of mild steel. Packed-carburization technique was used and various compositions of the carburizing mixture were investigated. At 900°C, optimal values of surface hardness were obtained at 20% cow bone and 30% sea shell additions. Coconut shell did not seem to significantly influence the hardening process at any level of addition. The results showed that cow bone was 65.5% as efficient as BaCO,, while sea shell was 82.5% efficient. This paper presents the effects of energizer concentration, chemical compositions and holding time on the kinetics and quality of the hardened products.
STRENGTH OF CONCRETE COLUMN CONFINED BY PLASTIC (PVC) PIPE
This experimental investigation was carried out to determine the strength of concrete column confined by plastic pipe and the effect of slenderness ratio on the strength. Pipes of 75.0mm and 100.0mm diameters and of varied lengths were used. Two different concrete mixes were tested. The first had a 1.5 sand cement ratio and 3.0 coarse aggregate cement ratio, while the second a 1.0 sand-cement ratio and 7.0 course aggregate. cement ratio was used. The samples were made into three groups and one of these groups was reinforced with 6.0mm diameter bars. All tests were carried out in uniaxial compression under monotonic loading. The results showed appreciable increase in concrete strength when confined by plastic pipe. Increase in strength of about two times the strength of unconfined concrete was recorded. The reinforcement bars were of no significance in terms of strength Increase particularly in the case of short columns. The ultimate strength of the confined columns decreased with increasing slenderness ratio.
APPLICATION OF THE METHODS OF INITIAL PARAMETERS AND SUBSTITUTE CANTILEVER TO DYNAMIC ANALYSIS OF A MULTI - STOREY STEEL FRAMED BUILDING
Although Africa i largely within the earthquake-free zone of the World, recent events have shown that dangerous earth tremors were caused by earthquakes with epicenters at different locations in Africa. In this paper, a dynamic analysis of a 10-Storey building is discussed using a combination of: 1. The static method of P-delta analysis 2. Energy method of determining the minimum Eigenfrequency of the substitute cantiliver and 3. The method of initial parameters. It discusses the use of structural steel, through the application of deformations obtained from the static method of P-Delta analysis with a virtual force P =1.0 KN varied linearly from the top, to zero at the base as input or initial load. This, combined with the use of energy method for determining the minimum Eigenfrequency of the substitute cantilever and the method of initial parameters was used in a dynamic analysis of a ten-Storey building. The result of the analysis shows that the maximum deformation (top drift) caused by the siesmic load at the highest point of the building falls within conventionally acceptable limit recommended as a adequate. The minimum total equivalent flexural rigidity, the frequency of oscilliation, period and the frist normal mode of characteristic shape were also deterimined before computing the design of a seismic loading corresponding to the seventh Richter scale.
A USEFUL APPROACH TO MAINTENANCE SCHEDULING
A five-step approach to facility routine maintenance scheduling is presented. The approach involves parts segmentation, identification of maintenance activities and frequencies, time and material analysis, compilation of schedules, and implementation and control, in that order. The application of the method is illustrated with examples. The method is particularly useful in organizations where expertise in detailed industrial engineering techniques, and relevant information on technical specifications and maintenance requirements are limited or absent. This situation is prevalent in developing countries.
PERFORMANCE OF INDUCTION MOTOR DRIVE UNDER LIAPUNOV STABILITY DESIGN CRITERIA
For an optimal linear regulator design, a performance function of the quadratic form must be chosen. The question arises of how to decide the weighting matrix Q of the performance function. A method is developed in this paper based on liapunov stability design. The method begins by linearizing the system equation about an equilibriums point. The system considered is an induction motor driver. The equilibrium points were selected so as to have stable closed loop system. Several cases are investigated. It is found that emphases on control of rectifier current and stator voltage result in a more stable system. This is shown from the non-linear test conducted on the system.
THE MECHANISM OF FORMATION AND DEVELOPMENT OF DEFECTS IN HADFIELD STEEL
This paper is directed at solving the problem metallurgists and material engineers face during the application of hadfield steel. It was established that fast cooling of this steel should be undertaken at a temperature range of 600-800°C so as to eliminate the intensive process of carbide formation. A relationship between the amount of precipitated carbides and hardness was numerically developed to allow for the correct assessment of the structural state of this steel using the hardness value.
THE USE OF LOCALLY FABRICATED INSTRUMENTS FOR MEASUREMENT OF UNDRAINED SHEAR STRENGTH OF MUDS
A literature review of submarine mudslides has shown that six methods exist to measure the undrained shear strength, Cu, of muds. Instruments for two of these methods, namely: the pull out test instrument, using a cylinder, and the laboratory cone penetration test instrument, were fabricated locally. Test results for deltaic mangrove mud sample locally known as 'chikoko' mud, using the locally fabricated instruments gave similar results with standard vane shear tests for Cu and therefore compare well.
STRATEGIES FOR IMPROVING INTRA URBAN MASS TRANSIT OPERATION IN NIGERIA: A CASE STUDY OF KWARA STATE
This paper examines the nature and conditions of the existing road network systems in Kwara State. It also discusses the public transportation needs and operating agencies. It highlights the nature and causes of the transport problems. Four factors namely the poor conditions of the roads, the vehicles, the Drivers/Mechanics and the Economy have been seen as factors responsible for the problems. These factors are discussed with reference to their magnitude, trends and severity. Solutions considered as appropriate to reduce the negative influence of these factors are proposed as strategies for improved performance. It is concluded that adopting these solutions would result to improvement in the level of safety, quality of vehicles, haulage capacity, level of pollution, economy of operation and commuter satisfaction.
LABORATORY INVESTIGATION OF CHIKOKO MUD AS A POZZOLANA
The need for economic use of cement in soil stabilization arises from consideration of the trend in the cost of cement. This paper presents a laboratory investigation of the engineering characteristics of soil-cement and soil-pozzolana made from a lateritic soil and pozzalana made from a silty clay (locally known as chikoko mud) respectively. The results show that less than 50% of the cement requirement given by the Portland Cement Associa-tion is required for efficient stabilization of a lateritic soil; and that up to 30% of this cement requirement can be replaced by calcined and ground chikoko mud (otherwise referred to in this paper, as Chikoko Pozzolana) without adversely affecting the performance of the soil cement. It is therefore concluded that the Chikoko Pozzolana be commercially produced to supplement the fly ash (most common pozzolana) that is presently produced from only one power station in Nigeria.
MODELLING THE NIGERIAN POWER SYSTEM FOR AUTOMATIC GENERATION CONTROL PART II: SIMULATION STUDIES OF THE POWER PLANT RESPONSE
In this second part of the two part serial experimentation on the derived models with standard test signals is carried out. The aim is to compare the plant response under different operating conditions. The effects of the non-linearities mentioned in part one on the plant response are exposed. Finally integral control action is imposed on the model and several operating conditions simulated to show the inadequacy of the integral controller especially under wide variations of frequency.
THE PERFORMANCE EVALUATIONS OF LOCALLY AVAILABLE FLUORESCENT BALLAST/LAMP SYSTEMS
The electrical and photometric characteristics of locally available 20W and 40W compact energy saving fluorescent lamps with a number of core - coil ballasts have been compared under the same laboratory conditions. Particular attention was paid to the active, reactive power consumption, power factor, and watt per ampere under varying voltage levels. A total of forty-five ballast/lamp combinations were involved in the study. The study revealed that for the locally available samples of 20W ballast/lamp system tested, the Newclime/lamptan fixture recorded the best starting characteristics. Its watt, power factor, var., and watt per ampere were respectively 18W, 0.41, 39.86 var., and 66.69. This was followed by Newcline/EPI and Sartra/Jecon combination. For the twenty-five samples of 40W ballast/lamp combinations, it was found that Philips/Maspion fixture showed a remarkable starting characteristics, with input starting voltage of 159V followed by Philips/Osram system with 164V and Philips/SiBalec, 166V. The result of the study also revealed that the 40W ballast/lamp energy saving systems require lower rms starting voltage, result in lower input currents, higher power factor, higher watt per ampere, better luminaries characteristics, and lower Var consumption. These qualities compared favourably with the 20W ballast/lamp combinations. The results of the experimental data obtained from this study will be of importance to designers, Engineers and Architects involved with the lighting design and specification process.
CASTOR OIL: A BIODEGRADABLE EXTREME PRESSURE AND ANTIWEAR LUBRICANT
Castor oil, extracted from natural castor seed and mineral extreme pressure and antiwear lubricant, HD-90 gear oil were tested on a four ball machine. The test modes include: load, temperature, wear and seizure tests in sixty (60) seconds duration. The assessment criteria are: friction transients, surface temperature, flash temperature, wear scar diameter, and load capacity. The results showed that natural castor oil apart from being biodegradable possessed extreme pressure and antiwear properties superior to one mineral gear oil HD 90 (A), though inferior to HD 90 (B). Also, the results suggests that the lubricant film in castor oil consisted of jelly brush-like polar molecules of fatty-acid (mainly recinoleic acid) oriented vertically to the surface - giving rise to static friction values which decreased with increasing load unlike the mineral gear oil, In the latter, lubricity is derived from the extreme pressure and antiwear additives in the mineral oil adhering to and/or reacting with the surface to form a protective laminar independent of the load, except transition is attained.
STRENGTH CHARACTERISTICS OF REGROUND CAKED CEMENT
The construction climate in Nigeria is fraught with so many problems that lead to projects not being executed as scheduled or eventual abandonment of site. These lead to the storage of purchased cement for times longer than necessary, resulting in their getting caked. Compounding this problem is the activities of some cement traders who re-bag cement after long periods of exposure and the importation of cement, which may have lost their properties due to long period of shipment. Various tests were conducted on normal and reground-caked ordinary Portland cement (Elephant brand) with a view to determining the effect of long period of storage. The tests included mineralogical composition, consistence, fineness, soundness, setting times and strength performance of mortar and concrete cubes at different ages. The results of the investigation showed a reduction in the Tricalcium Silicate (CS) as well as increase in Dicalcium Silicate (C₂S) contents of the reground-caked cement thus resulting in low strength capacity. The various strengths of mortar and concrete cubes cast with the reground-caked cement were about 10-28% those of the corresponding normal cement. The reground-caked cement is therefore recommended for use in non-load bearing elements and sandcrete blocks for partitions.
CARBON REDUCTION WITH THE AID OF GRANULATED MILLSCALE (FeO) DURING STEEL PRODUCTION VIA THE ELECTRIC ARC FURNACE PROCESS
In Nigeria and the Third Countries generally, conventional carbon reduction mechanism using 02 lance during steelmaking is usually plagued with a lot of hitches which bother on irregular supply of gaseous oxygen coupled with a rather exorbitant cost regime. This has resulted in high cost of production which invariably renders steels produced in Nigeria not being competitive in the market. The above necessitates a concerted effort geared towards finding functional alternative for 0,- Lance. This was achieved, as revealed by the results of the experiments using granulated iron-oxide otherwise called millscale. The scope of its application for carbon reduction during steelmaking was found to be between 0.50% and 0.90% of the initial carbon content. The optimum charging sequence of the millscale was obtained at 70kg with respect to a range of furnace liquid steel capacities from 10-20 tons per heat. With the application of millscale, the desirable carbon reduction value was achieved within a time frame which compared favourably with that of the conventional 0, Lance. Other advantages of the millscale application for carbon reduction in steelmak-ing include:- Consistency in production as the supply of the material (millscale) is not hampered by any constraint. Reduction in production cost. Self reliance since the materialis sourced within the factory. Improved environmental condition on the factory floor. Low down-time hours.
STRENGTH ASSESSMENT OF CONCRETE SUBJECTED TO ALKALINE MEDIA
The aim of any structural design is to achieve an acceptable probability that structures being designed will perform satisfactorily during their intended life with an appropriate degree of safety. They should sustain all loads and deformation of normal construction and use, and have adequate durability and resistance to the effect of misuse. The durability of concrete can be defined as its resistance to deterioration resulting from external and internal causes. The external causes include the effects of environmental and service conditions to which concrete is subjected, such as weathering, chemical actions and wear. The internal causes are the effect of interaction between the constituent materials such as alkali aggregate reaction, volume change, absorption and permeability. This research work is to assess the structural strength of concrete cubes cured in varying concentration of a number of alkali solutions. Two grades of concrete, 30 and 40 were used. The concrete cubes were cured in aqueous solutions of Sodium hydroxide (NaOH), Potassium hydroxide (KOH) and Calcium hydroxide (Ca(OH)2) of 20, 40, 60 and 80 percent concentrations. Compressive strength test was conducted on the cubes at the end of 7, 14 and 28 days immersion period. The compressive strength of concrete cubes immersed in water (control cubes) increased steadily from 30.96 N/mm² to 35.26 N/mm² at the end of 28 days of immersion for grade 30 concrete and from 40.07 N/mm² to 42.52 N/mm² at the end of 28 days of immersion for grade 40 concrete Generally, the compressive strength increased steadily for cubes in 0 percent concentration of alkali solution up to 40 percent concentration of alkali solution beyond which it started falling, irrespective of the immersion periods for the two grades of concrete. The influence of alkaline media on concrete is such that the higher the grade of concrete, the more aggressive is the attack on the concrete.
ANALYTICAL PROCEDURES IN THE DESIGN OF UNDERGROUND MINE OPENING OF A PRPOPOSED URANIUM DEPOSIT IN NIGERIA
In this paper the necessary factors to be considered while designing an underground mine opening for a proposed uranium deposit were outlined. Its scope include the assessment of various state of stresses existing in the rock before mine opening and the distribution of stresses at a depth very close to the opening. This eventually will lead to the control of rock failure within the shaft opening and also provide optimum pattern in the design of a mine opening with different diameter of openings for the proposed uranium deposit in Nigeria.
THE EFFECTS OF SILICON CARBIDE ON SOME REFRACTORY PROPERTIES OF BAUCHI CLAY
Some refractory properties of Bauchi clay, found in abundant in Alkaleri area of Bauchi State, Nigeria blended with silicon carbide, for the production of refractory bricks for furnace lining has been Investigated. 525% silicon carbide was used as blend to enhance some refractory properties such as porosity and thermal shock resistance of the clay. Refractory properties measured included: Linear shrinkage, apparent porosity, bulk density, thermal shock resistance and cold crushing strength. Linear shrinkage and apparent porosity of the bricks made from the blend decreased with the percentage of silicon carbide added. These properties decreased from 5.66 to 2.49% and from 33.02 to 16.31% at 25% silicon carbide level respectively. The cold crushing strength and thermal shock resistance of the bricks increased as the percentage of silicon carbide added increased.
EFFECTS OF REDUCTION, SQUARE ROOT OF THICKNESS AND SPREAD CONSTANT ON SPREAD FOR HOT FLAT ROLLED STEEL (HC SS316)
The increasing tendency towards automation of the rolling process together with the trend towards more stringent specifications for hot rolled products, particularly wide strip for subsequent cold rolling, makes it highly desirable to assess the effects reduction, square root of thickness and spread constant have on spread for steels (HC SS316) hot flat rolled at low strain rates. The spread coefficient (SPECO 1, SPECO 2 and SPECO 3) increased gradually as reduction increased from 8% to 25% with average values of 0.065, 0.057 and 0.039 respectively for both low and high speeds of 9.32mm/s and 133mm/s. For square root of thickness (SRTHS) varying between 1.04 1.16, spread coefficient, SPECO 1 was 0.057 0.076; SPECO 2 was 0.0480.069 and SPECO 3 was 0.025-0.056 for low and high speeds of 9.32mm/s and 133mm/s. The effect of spread constant, Z1 on spread coefficient (SPECO 1, SPECO 2 and SPECO 3) is contrary to that of reduction and that of square root of thickness (SRTHS). As spread constant, Z1 increased, spread coefficient decreased for both low and high speeds of 9.32mm/s and 133mm/s.
SIMULATION OF FOUNDATION STABILITY OF A JACK-UP RIG
The procedure for assessing foundation stability of jack-up rig (self-elevating drilling unit) on offshore soil has become increasing important as a result of the frequent incidence of rig damage and in some cases total collapse of the rig. In this investigation, computer simulation in assessing the foundation stability during a preload check of production jack-up rig is presented. Predicted results of two analytical methods are compared to establish the reliability of an initial theoretical assessment of the procedure. The methods used gave good agreement. A framework for these assessments ensures the safe operation of jack-up rigs in deeper waters.
Coupled Polyphase Reluctance Machines Without Rotating Windings
This paper discusses asynchronous electromechanical energy conversion of coupled polyphase reluctance machines without rotating windings. The scheme comprises two identical salient pole synchronous machines without rotating windings that are mechanically coupled together and electrically interconnected in parallel. The mechanism of torque production of the coupled set is uniquely presented in terms of the interaction between the stator mmf and the rotor permeance distribution.
Direct measurement of power angle of synchronous machines
In this paper, a novel method of measuring load angle of synchronous machines is presented. The load angle of the synchronous machine is directly related to the emf induced in the auxiliary winding of a load angle meter that is attached to the shaft of the main machine. The meter consists of a round rotor half and a salient pole half, which are coupled together and suitably interconnected. When the axis of the rotating stator excitation mmf coincides with the d-axis of the salient pole half of the device, the output voltage from its auxiliary winding will be zero and when it coincides with the q-axis, the induced emf will be a maximum. In general, the emf is proportional to the sine of the load angle.
ENCRYPTION TECHNIQUES IN DATA COMMUNICATION NETWORKS
Electronic messaging and data transfers are the main features of most communication networks. Electronic messaging (e-Mail) in a network environment for example has grown, providing features from simple correspondence, broadcasting (message distribution) and scheduling/calendering to on-line conferences with network users. Because these features are provided through a global data communication highway, confidentiality and data security is not always assured. In most communication systems, the solution uses different methods to scramble the data to be transmitted thus providing secrecy to every correspondence. This paper presents some techniques suitable for data encryption in any computer network. The presentation is very detailed and the techniques are described further using procedures written in a structured language.