http://hdl.handle.net/123456789/122 Sat, 04 Apr 2026 11:49:18 GMT 2026-04-04T11:49:18Z http://hdl.handle.net/123456789/2173 DEVELOPMENT OF A SAFE WEIGHT OF LIFT MODEL FOR MANUAL WORKERS AT ARULOGUN, IBADAN, OYO STATE MUYIWA, Omotunde Alabi The Low Back Pain (LBP) problem is prevalent among construction workers involved in the Manual Load Handling (MLH) of sandcrete blocks. Studies have shown that human and environmental based factors affect the weight of lift appropriateness and may lead to musculoskeletal disorders such as low back pain. Ergonomic models that utilise compounded human characteristic factors and environmental temperature to estimate Safe Weight of Lift (SWL) for construction workers are sparse. This study was, therefore, designed to develop a model for determining SWL among manual labourers at varying workplace temperatures. A safe weight of lift model was developed with compounded human ergonomic factors of age, body weight, spinal shrinkage, spine length, lift frequency, and environmental temperature using the principle of strain energy. Subjective sampling technique was used in selecting fifty experienced male bricklayers involved in lifting sandcrete blocks of weight between 20.00 and 22.50 kg for 8-hours daily at Arulogun, Akinyele Local Government Area, Ibadan. For each subject, the compounded human ergonomic factors and environmental temperature were measured using the ZT-160 scale, stadiometer, measuring tape, clock timer and Extech RH/Temperature pen device. The obtained data were used as input into the developed model to estimate the SWL for each subject at varying temperature ranges of 26.00 – 27.90, 28.00 – 29.90, 30.00 – 31.90, 32.00 – 33.90, 34.00 – 35.90 and 36.00 – 37.00°C. These were compared with existing secondary SWL data at the temperature range of 27.00 – 32.00℃. Analysis was subsequently done to determine factors that were significant in estimating SWL. Data were analysed using ANOVA at ∝0.05. The model revealed that a non-linear relationship exists between the SWL and compounded ergonomic factors. The age, body weight, spinal shrinkage, spine length, lift frequency, and temperature were 33.26±7.22 years, 67.50±11.58 kg, 0.02±0.06 m, 0.47±0.03 m, 2.00±0.48 lifts/min, and 30.46±2.51℃, respectively. The safe weight of the lift at environmental temperature ranges of 26.00 – 27.90, 28.00 – 29.90, 30.00 – 31.90, 32.00 – 33.90, 34.00 – 35.90 and 36.00 – 37.00℃ were 6.23±0.82, 5.79±1.45, 7.20±1.84, 8.04±2.74, 5.96±0.00, and 5.87±0.00, respectively. The SWL, which ranged between 3.78 and 12.77 kg implied that sandcrete blocks in this weight range when lifted, were incapable of causing low back pain. The SWL from the model and that of the compared secondary data were 6.10±1.29 and 16.34±6.40. These indicated that there was a significant difference between the model and secondary data, which could be attributed to differences in the environmental temperature at which the secondary data were obtained as compared with those of the model. The model SWL was significantly influenced by the interaction between compounded human ergonomic factors and environmental temperature. An ergonomic model to estimate the safe weight of lifts for manual labourers was developed. The model is a useful tool for decision-making in the area of safety management of male labourers involved in the manual load handling. Thu, 01 Jun 2023 00:00:00 GMT http://hdl.handle.net/123456789/2173 2023-06-01T00:00:00Z http://hdl.handle.net/123456789/1020 DEVELOPMENT OF AN IMPROVED LOGISTIC MAPPINGFUNCTION FOR OBJECTIVE ASSESSMENT OF QUALITY OF RECEIVED SPEECH OVER MOBILE TELEPHONE NETWORKS PATRICK, OLANIYI OLABISI Users’ perspectives approach provides an unbiased assessment of Quality of Service (QoS) of voice offerings in telecommunication networks. This approach is implemented using subjective or objective technique. Though the subjective rating scale is the basis for all ratings, objective technique being computational, can effectively predict quality of degraded speeches. However, existing objective techniques’ mapping functions are unable to properly scale speech quality rating. This study was designed to develop a new logistic mapping function that can effectively predict quality of degraded speeches and provide improved quality rating scale. A speech database consisting of 64 original speeches was developed and transmitted over three mobile telephone networks (A, B and C). Psychoacoustic study was carried out using Zwicker loudness model to evaluate the maximum instantaneous loudness (Nmax) and maximum instantaneous loudness level (Lmax) of original and received speeches. The quality of received speeches relative to the transmitted speech was obtained using Nmax and Lmax values. Subjective quality test was carried out on the received speeches based on listening-only technique and Absolute Category Rating (ACR). Objective quality assessment was carried out using Perceptual Evaluation of Speech Quality (PESQ) model, and the scores obtained were mapped using the ITU-T P.862.1 mapping function. The mapped and subjective scores were compared to obtain the correlation coefficient (r), the prediction error (EP), and the Root Mean Square Error (RMSE). A new logistic mapping function for PESQ was developed by optimising the steepness of the logistic S-curve to obtain the growth rate that maximised the range of the quality score. The new mapping function was compared with two international standard mapping functions (ITU-T P.862.1 and Morfitt III–Cotanis). Data were analysed using ANOVA at α_0.05. The Nmax of 46.19 sone and Lmax of 95.29 phon were obtained for the transmitted speech, and Nmax of 19.65, 17.13, 16.46 sones and Lmax of 82.97, 80.98, 80.41 phons were obtained for the received speeches over A, B, and C networks, respectively. The relative quality of the received speeches for the Nmax and Lmax were 42.55, 37.08, 35.64% and 87.06, 84.98, 84.37%, respectively. The subjective test of received speeches over networks A, B, and C, resulted in 2.902±0.380, 2.952±0.447 and 2.983±0.612, respectively, while the objective mapped scores were 2.615±0.563, 2.589±0.594 and 2.693±0.730, respectively. Comparing the mapped and subjective scores produced r of 0.854, 0.871, and 0.848, EP of 0.4264, 0.4724 and 0.4825, and RMSE of 0.4230, 0.4687 and 0.4787, respectively. The optimised steepness resulted in growth rate of 2.2106 and quality coverage of about 1.005 to 4.950. Score coverages of 98.6, 86.8 and 93.7% of the subjective scale were obtained with the developed logistic mapping function, ITU-T P.862.1 and Morfitt III –Cotanis mapping functions, respectively. This indicates a significant improvement over the other two mapping functions. A new logistic mapping function that enhanced objective technique for users’ perspective approach in the assessment of speech quality over mobile telephone networks was developed. Sat, 01 Feb 2020 00:00:00 GMT http://hdl.handle.net/123456789/1020 2020-02-01T00:00:00Z http://hdl.handle.net/123456789/185 HARMONIC ANALYSIS AND MITIGATION IN SELECTED NIGERIAN 33KV DISTRIBUTION NETWORKS MUTALUB, ADESINA LAMBE ABSTRACT The non-linear characteristics of power electronic loads introduce harmonics, which may result in power distribution losses and reduction of the operational efficiency of equipment. Therefore, minimization of power harmonics is highly desirable in electrical power networks. Various techniques to mitigate against harmonics have been developed but do not meet the ultimate quality power supply and voltage level of 5% for total harmonic distortion (THD) and 3% for any individual harmonics, as specified by IEEE standard 519-1992. This study aimed at the development of an improved technique for minimisation of harmonic contents in distribution networks. Power flow analysis of a selected Nigerian 33 kV distribution network in Southwestern Nigeria was carried out to obtain its bus voltage and power characteristics (active and reactive power) using Newton-Raphson numerical technique. An algorithm was developed to induce power harmonics on the bus voltages resulting from the power flow analysis in order to obtain harmonic contents in each distribution line of network considered. Single and n-stage cascaded harmonic reduction networks were developed using standard procedure. The distribution network, with induced harmonics, was inserted into the developed harmonic reduction network. Effects of harmonics on distribution lines less than 1 km (short) and long lines of 7 km were observed. Data were analysed using Anova at p=0.05 Bus voltages at the 1st harmonic range from 32.553 to 32.997 kV, with percentage deviations varying from 0.01 to 1.35% of the nominal voltage of 33 kV. Reactive power (MVar) in the network was 61.97% of the active power supplied to the system at a given load. Unwanted harmonics generated in the network is in the frequency range of 100-1450Hz. Harmonic impedances for 2nd and 29th harmonics ranges from 101.962Ω to 102.118Ω and 101.556Ω to 102.007Ω respectively at different switching times. Mitigation, using single and 2nd stage cascaded harmonic reduction networks revealed that the peak harmonic impedance amplitude was reduced by 46.0% and 98.0% respectively. The number of harmonic components in the induced harmonics were reduced by single and 2nd stage reduction techniques, with 2nd stage reduction technique having much reduced harmonic amplitudes. The 2nd harmonic was completely removed in the single stage reduction technique, while the 2nd stage reduction technique eliminated the 2nd and 6th harmonics. The average impedance amplitudes of the remaining harmonics for single and 2nd stage reduction techniques were 102.1Ω and 102.0Ω, respectively. Harmonic impedance at the 2nd harmonic remained constant for short distribution line distance of less than 1 km. The 3rd harmonic and above were associated with distribution feeders of long distances of up to 7 km. Analysed data showed that the 2nd stage is significantly better than the single stage technique of harmonic reduction. The developed algorithm for harmonic analysis and its mitigation in power system resulted in improved supply voltage in short distribution feeders. Further mitigation in the 2nd stage technique enhanced power quality in the selected distribution network. Sun, 26 Jun 2016 00:00:00 GMT http://hdl.handle.net/123456789/185 2016-06-26T00:00:00Z