School of Infrastructure Process Engineering and Technology (SIPET)

Permanent URI for this communityhttp://197.211.34.35:4000/handle/123456789/46

School of Infrastructure Process Engineering and Technology (SIPET)

Browse

Filter results by year or month

Now showing 1 - 20 of 40

Thermal Stability, Transparency, and Water Sensitivity Properties of Bleached, Cross-Linked Cassava Starch Film
(Journal of Digital Food, Energy ans Water Systems (JD-FEWS), 0024) J. Y. JIYA; M. ABUBAKAR; I. A. JOSEPH; E. C. EGWIM; K. T. OBANIMOMO
This work investigates a novel study of the effect of bleaching and cross-linking cassava starch film. Native cassava starch was bleached with hydrogen peroxide (H2O2), cross-linking was carried out with oxidized sucrose, while glycerol was added to enhance the plasticity of the film. Operating temperature and time of 90 °C and 10 Minutes, respectively, adding 0.5 ml of glycerol gave the best bleached, cross-linked cassava starch film. UV-visible spectrophotometer analysis revealed that the cassava starch film produced at the above reaction conditions retained 88.2 % of its transparency at 96 hours of water immersion. The water solubility test shows that the film experienced 52.02 % weight loss after 96 hours of immersion in water. The thermo-gravimetric analysis (TGA) shows a significant improvement in the thermal stability with a Temperature peak (Tp) of 420.75 °C, compared to 374.13°C Tp of the control sample (unbleached, uncross-linked) of the cassava starch film.
Optimization of Operating Parameters in the Extraction of Caustic Potash (KOH) from Palm Kernel Bunch (An Agricultural By-Product) Ash
(Journal of Applied Science and Education (JASAE), 2001) Eterigho, E. J.
Triglyceride cracking for biofuel production using a directly synthesised sulphated zirconia catalyst
(Journal of Bioresource Technology, 2011-02-13) Eterigho, Elizabeth Jumoke; Lee, J. G. M.; Harvey, Philip A.
In this study, sulphated zirconia was directly synthesised and compared to the conventional wet method of preparation. The surface areas and pore sizes were 169 m2/g, 0.61 lm (directly synthesized) and 65 m2/g, 0.24 lm (conventional method), respectively. Directly synthesized sulphated zirconia was amorphous, whereas conventionally prepared sulphated zirconia is polycrystalline. Their IR spectra were broadly similar, although the area of the 1250 to 950 cmÿ1 band was larger for directly synthesised sulphated zirconia. Not only were conversions greater for directly synthesised sulphated zirconia (63% vs. 42% after 4 h), but it exhibited significantly greater yield for fatty acid methyl esters. The percentage yield (after 1 h) of methyl esters was 43% for the directly synthesised catalyst and 15% for the conventionally synthesised
Evaluation of Catalytic Activity of Synthesized Sulphated Zirconia for Triglyceride Cracking”
(8th European Congress of Chemical Engineering. Berlin, Germany, 2011-09-25) Eterigho, Elizabeth Jumoke; Lee, J. G. M.; Harvey, A. P
Conventional wet-precipitation method was used to synthesis sulphated zirconia using two different molar ratios of sulphating agents. (1) the first was using a molar ratio of 1: 45 of ZrOCl.8H20 impregnated with 1 M H2SO4 (wp) and (2) a molar ratio of 1: 6 was used for the modified conventional wet-precipitation method, (mwp).. The properties of both catalysts were examined by various techniques: EDX, XPS, FTIR, SEM, XRDP, Py-DRIFTS and BET nitrogen adsorption techniques. The variation in the molar ratio of the sulphating agent used during preparation led to sulphated zirconia that exhibited different properties in terms of specific surface areas, acid sites, thermal stability and surface sulphate. Both catalysts were catalytically active for triglycerides cracking for fatty acid methyl esters in a thermocatalytic reaction. The SZI not only exhibited higher conversion of triglycerides but higher FAMEs yield, approximately 50% after 3 h, as compared to SZ2 (39%). Interestingly, SZ1 was selective towards unsaturated esters whereas SZ2 was towards saturated esters.
Development and Preliminary Testing of an Electronic Pest Repeller with Automatic Frequency Variation
(International Journal of Environmental Science and Technology-Springer, 2013-01-01) Simeon, Meshack Imologie; Mohammed A.S.; Adebayo S. E.
This study presents the development and preliminary performance evaluation of an improved electronic pest repeller with automatic frequency variation. The study is aimed at developing a device that is capable of emitting ultrasonic energy of varied frequencies. These frequencies do affect the auditory senses of pests such as rodents, avian, and nocturnal insects by making them uncomfortable in their abode. However, these frequencies do not affect the hearing ability of humans. An Astable Multi-vibrator (AMV), timer NE555, was used to generate the required ultrasonic frequency and automatically varied in five steps by a pulse generating IC (CA3130) and a counter (CD4017). A D-type flip-flop IC (CD4013) was used to obtain a symmetrical output signal, which was amplified in push-pull mode by 2-NPN Transistors (BD-139) and 2-PNP transistors (BD140). Five variable resistors (each 100KΩ) were used to control the different frequencies. Two transducers (tweeters) were employed to produce an efficient sound. The unit was tested with three groups of white foot mice (Peromyscus leucopus) and a female house mouse Mus musculus which all responded positively from a distance of up to fifteen (15) meters from the source. The average designed efficiency was found to be 86.5%. The device can be utilized by both small and large-scale farmers for repelling pests. The performance of the device could be greatly improved with little modifications, for instance, using microcontrollers and ultrasonic sensors to transmit the ultrasonic sound in a special frequency band.
Effect of modification on conventional preparation method for Sulphated Zirconia on the production of Fatty Acid Methyl Ester
(The Nigerian Society of Chemical Engineers, 2014-11) Eterigho, Elizabeth Jumoke; Farrow, T. S.
Sulphated zirconia was synthesized using different volume of sulphating agent in order to optimise its catalytic property: (1) in the first case the "conventional" 15 ml H2SO4 to 1g of Zr(OH)4 for impregnation was used in wet-precipitation method and the catalyst designated 'wp' and (2) same procedure but with modification in volume of acid; 2 ml of H2SO4 was used for 1g of Zr(OH)4, 'mw'. The properties of the uncalcined and calcined catalysts were examined by various techniques: EDX, XPS, XRDP, Py-DRIFTS and BET nitrogen adsorption techniques. The sulphur content in the uncalcined ('mwp' and 'wp') catalysts was the s a m e ; 0.07 mol each whereas the calcined catalysts were 0.07 mol and 0.05 mol for 'mwp' and 'wp' respectively. BET surface area was determined to be 65.0 m2/g for wp and 101m2/g for 'mwp'. The effect of the variation of sulphating ageni on the catalyst activity was investigated in catalytic cracking of triglycerides for fatty acid methyl esters. Sulphated zirconia from the modified conventional method was found to perform better than the conventional wet-precipitated sulphated zirconia. Furthermore, 'mwp' retained approximately 74% of its sulphur content after 3 h reaction whereas 'wp' catalysi lost 100% during the reaction as indicated by SEM-EDX. Interesting the results show variation in characterization and in their selectivity to different types of fatty acid methyl esters under the same reaction conditions. The 'mp' catalysi showed higher catalytic activity for methy! ester yield of 40% as well as higher selectivity for saturated methyl esters
SECURITY MANAGEMENT: THE ENGINEERING PERSPECTIVE
(IEC, 2015) H. U. Ogboo; A. Nasir; J. Y. Jiya; H. T. Abdulkarim
Security management is a difficult task as everyone agrees that security is a problem. As such, this work aims at addressing the ever increasing security challenge confronting us as individuals from the engineering perspective. Throughout human history, engineering has driven the advance of civilization. This can be seen from the metallurgists who ended the Stone Age to the shipbuilders who united the world’s people through travels and trades; the past witnessed many marvels of engineering prowess. As civilization grew, it became pertinent that the world became confronted with the challenge of survival and relevance and hence, the desire not to be cut out from the basic necessities of life and existence gave rise to devices by humanity to remain relevance and hence, the field of engineering owes it a responsibility to the world to see that this issue is sorted out as usual as it has always provided respite to the world.
Effect of Cutting Speed and Feed Rate on Tool Wear Rate and Surface Roughness in Lathe Turning Process
(International Journal of Engineering Trends and Technology (IJETT), 2015) O. A. Olugboji; M. S. Abolarin; J. Y. Jiya; S. O. Popoola; C. K. Ajani
Machining is a vital part of the production process in the manufacturing industries. Turing operation was carried out on the mild steel to produce shaft of various diameters. The conditions applied during the turning operation include varying the cutting speed and feed rate while keeping other cutting variables like depth of cut constant. The results affirms that an increase in the cutting speed causes a decrease in the tool life, increase in the feed rate also affects the surface finish obtained.
Development of a Test Rig for the Determination of Headloss and Friction Factor of Polyvinyl Chloride (PVC) Pipes
(Journal of Energy Technologies and Policy, 2016) N. A. Musa; J. Y. Jiya; T. K. Aderoju
This paper reports the design, construction and performance evaluation of a test rig for determining the head loss and friction factor of PVC pipes of different diameters (13mm, 19mm and 25mm) transporting water. On performance evaluation, friction factors of 0.0121, 0.0396 , 0.0171 and head losses of 37.8mm, 25.2mm and 12.6mm for 13mm, 19mm, and 25mm diameter PVC pipes respectively were obtained. Keywords: Head loss, friction factor, PVC pipes, test rig, water
Assessment of Heavy Metal Contamination on Dumpsite in Kuyi Village, Niger State, Nigeria
(International Journal of Research in Chemical, Metallurgical and Civil Engineering. (IJRCMCE), 2016) Iyakwari, Joseph; Agbajelola, D. O.; Farrow, T. S.; Eterigho, Elizabeth Jumoke
Soil samples collected from the dumpsite located in Kuyi village, Minna, Niger State were analyzed for copper (Cu), iron (Fe2+) and manganese (Mn) using Atomic Absorption Spectrometer. Twenty-one (21) sample points both horizontally and vertically (depth) were studied. The results revealed that Mn had the highest concentration (11.6mg/kg) compared to Cu and Fe2+. However, it was observed that a minimal reduction in concentration of each metal along the surface of the dumpsite occurred. Interestingly, the concentration of Fe at all points was relatively high (5.54mg/kg, 4.67mg/kg, 3.99mg/kg and 3.78mg/kg). Based on the Federal Environmental Protection Agency and Land Disposal Restriction Standard Regulation, this metal could have adverse effect on human health, stream and agricultural activities of villagers around the dumpsite.
Harnessing Alternative Technology for the Sustainability of Biodiesel Production
(Iranica Journal of Energy and Environment, 2016-11-17) Eterigho Elizabeth J.; Farrow, T. S.; Agbajelola, D. O.; Ejejigbe, S. E.; Harvey, A.P.
Biofuel, a renewable energy is mainly produced by transesterification of fatty acids either in presence of enzyme or catalysts. The transesterification relies on the use of either strong base or strong acid homogeneous catalysts for effective performance; but, homogeneous catalysts are associated with a variety of technical hurdles that limit their use for biodiesel production. Although there have been recent developments in heterogeneous catalysts for biodiesel production via transesterification; the separation of methyl ester (FAMEs) from crude glycerol and alcohol recovery are still major hindrances. A possible alternative could be the use of solid acid catalysts in thermo-catalytic cracking of triglycerides. Sulphated zirconia catalyst was evaluated for thermo-catalytic cracking of triglycerides at a relatively low temperature (270oC) and atmospheric pressure. The catalyst was found to be active toward cracking vegetable oils to methyl esters. The catalyst at this temperature exhibited different selectivity towards formation of saturated and unsaturated methyl esters. The catalyst yield of methyl esters under these conditions was 58% while 80% of the product being unsaturated. This opens up the possibility of controlling the degree of saturation of the methyl ester product by catalyst choice, to produce more or less saturated fuels for different markets. The range of products from gases to middle distillates and the unique selectivity for saturated and unsaturated esters may be a significant process advantage of this form of catalytic cracking. An important long chain unsaturated alcohol (1- Heptatriacotanol) was also identified. The unsaturated alcohol is known as an industrial chemical.
The Effect of Surfactant Concentration on Crude Oil Removal from Contaminated Soil
(Nigerian Research Journal of Engineering and Environmental Sciences (RJEES), 2017) Farrow, T.S.; Ketebu, O.; Eterigho, E.J.
The extraction efficiencies of three non-ionic surfactants; Tween 80, Brij 35 and Triton X-100 at different concentrations of 0.1- 0.5% w/v were investigated. It was observed that for the three surfactants examined, the bulk oil removal increased with increasing surfactant concentration. The results of the investigation also revealed that Brij 35 was effective in the removal of aliphatics while low concentration of Tween 80 did not favour the removal of aromatic hydrocarbons. Triton X-100 seems to be the best amongst the surfactants investigated considering its capability for removing both aliphatic and aromatic hydrocarbons at relatively low concentrations. Concentration of 0.5% w/v for all the surfactants generally produced an appreciable increase in bulk oil removal, aliphatic and aromatic fractions. These results will provide a guideline for evaluating and selecting non-ionic surfactants for the remediation of crude oil contaminated soil
Biogas Production from the Co-digestion of Cow dung and poultry Droppings Using a Plastic Cylindrical Digester
(2017-07-13) Simeon, Meshack Imologie; Edache, Julius; Eyeowa, Adegoke
This study was carried out to compare the rate and amount of gas produced from the codigestion of two different substrates of cow dung and poultry droppings under anaerobic conditions. Biogas production from three(3) cylindrical bio-digesters containing cow dung, poultry droppings, and a mixture of cow dung and poultry droppings under an average temperature of 28 oc and a pH of 6.2 was examined. In each case, the feedstock was diluted with an equal volume of water to form a slurry. The digestion took place for 35 days. The biogas produced during this period was collected by the balloon method and subsequently measured and recorded. The results obtained from this study show that the co-digestion of cow dung and poultry droppings yielded a maximum volume of 2.62 cm³, while poultry droppings yielded 2.50 cm³ and cow dung yielded 1.78 cm³. Thus, the co-digestion of the feedstocks gave a better gas production, and the mean biogas yield was found to be significant (P<0.05) compared to each of the single substrates. This study has demonstrated that the co-digestion of cow dung and poultry droppings in a plastic cylinder could be a cheap method for locally producing biogas for domestic purposes. It is, however, recommended that gas production can be enhanced during hot seasons where higher temperature is easily attained.
Study of the Physical Properties and Biodegradability of Potato-Starch Based Plastics
(World Congress on Engineering and Computer Science (WCECS 2017) San Francisco, USA, 2017-10-25) Eterigho, Elizabeth J.; Farrow, T. S.; Ejejigbe, Silver E.; Gideon, O. Daniel
Due to the exceptional growth of environmental menace pollution caused by the disposal of used plastics in the world today, there exist the needs to produce biodegradable plastics from cheap and renewable feed stocks. This research work focuses on the synthesis and characterization of potato starch- based plastics (biodegradable) using polyvinyl alcohol (PVA) as cross linker. PVA was varied in mass ratios of 15, 30, 45 and 80% in the thermoplastic starch (TPS)/PVA blend. Mechanical properties (such as tensile strength, percentage elongation, young modulus) and specific gravity of the blends were studied. The results showed that 80% PVA plastic had the highest tensile strength, elongation and lowest young modulus of 384.47kPa, 347.27%, and 310.10kPa respectively. The specific gravity of the whole blends was 1.2. The elongation at break increases with increasing concentration of PVA, having the least value of 0% and highest value of 481.82% for 15 % and 80 % PVA plastic respectively. In addition, the results obtained showed increase in the values of the properties of the samples with respect to thermal conductivity, acid, base and water resistance with increase in composition of PVA. Biodegradability test was done via soil-burial method and the PVA/TPS blend was noted to be biodegradable
Analysis of Safety Performance in Nigerian Construction Industry
(Nigeria Journal of Engineering and Applied Sciences (NJEAS), 2018-02-22) Kolo, D. N.,; Tsado, T. Y.,; Abdullahi, M.,; Yakubu, D.M.,; Aguwa, J. I.
The quest for the provision of adequate housing for all has translated to the increase in activities of Building construction industry in Nigeria. This growth is accompanied however with cases of poor safety performancewhich at times leads to structural failure. This study investigates and analyses safety performance in Nigerian construction industry. Investigatory survey research method (work study) was adopted to appraise the aim and objectives of the study through field and questionnaire approach. Questionnaire survey consisting of a five point Likert scale was conducted to solicit information from the respondents, and a total of 120 questionnaires were issued to construction professionals and workers on the sites visited. 92 questionnaires representing 76.67% response rate were retrieved and analysed using Statistical Package for Social Sciences (SPSS) version 21. Communalities test, Principal Component Analysis along with ANOVA were utilised for data analysis. A total of thirty-two (32) factors influencing safety performance were identified from literature, subsequently principal component analysis was utilised to reduce the list to nine (9) significant principal factors. The top nine principal factors influencing safety performance determined from the research are: Relationship between Supervisors and Employees on site, Geographical Location (Environmental Factors: Natural and Working Environment), Working Procedure, Ear defenders not worn (while working under noisy equipment), Talk by Management on Safety, Tidy Site, Safety Communication, Operatives job experience and Ladders used without being tied secured. These factors were further incorporated into a regression model. The adjusted coefficient of determination of the model was 0.98; this shows that the model has the capability of explaining 98% of variability in the data under consideration. This implies that the model is adequate in evaluating safety performance. It is therefore recommended that key industry professionals and stakeholders should channel available resources to the determined nine (9) principal safety performance factors.
Evaluation of the physicochemical and thermal properties of honey samples from different floral locations in Enugu North senatorial zone, Nigeria.
(The proceedings 12th CIGR Section, 2018-10-25) Asoiro, Felix; Simeon, Meshack Imologie; Ugochukwu Christian Abada; Chukwuemeka Jude Ohagwu
This study was carried out to investigate the physicochemical and thermal properties of natural honey collected from different floral locations in Enugu North senatorial zone. The physicochemical and thermal parameters like moisture content, pH, sucrose, glucose, fructose, acidity, density, thermal conductivity, thermal heat diffusivity, specific heat capacity, viscosity, ash content, colour, and electrical conductivity were analyzed. The results obtained show that the pH values of the samples ranged from 4.7 to 5.7. The maximum and minimum moisture content were 22.5 and 16.59% (wb), respectively, with the sample from Igbo-Etiti having the lowest moisture content. The density value ranged from 820-1250 kg m-3, with honey samples from Igboeze-South recording the highest density. It was also observed that the sucrose content of the samples ranged from 1.037- 1.78g/100g, which is considered good and within the internationally acceptable value for honey. Electrical conductivity values for Igboeze-North, Udenu, Igboeze-South, Igbo-Etiti and Nsukka were 16.5, 6.0, 25.4, 3.5 and 11.4μS/cm, respectively, Fructose values were 34.339, 33.484, 34.515, 39.434 and 33.136 g/100g respectively and glucose contents were 31.361, 30.856, 31.639, 35.224 and 30.621 g/100g respectively It was also observed that honey from Igbo-Etiti is more viscous than all the samples. The honey samples from the different floral locations in Enugu North Senatorial zone were acidic. The colour of the sample is classified as Amber for samples from Igboeze-North, Igboeze-South, and Igbo-Etiti, while that of Udenu is Light Amber and that of Nsukka is Extra White. The thermal properties fell within the internationally acceptable range of values. Thermal heat conductivity ranged from 0.4358-0.4490 Wm-1K-1, specific heat capacity was from 1.3024-1.6355 kJkg-1K-1, and thermal heat diffusivity ranged from 2.4252× 10 -3.8313× 10 m2s-1. Honey is a promising source of food, raw material, and essential minerals. Knowledge of its physicochemical and thermal properties is essential to facilitate its postharvest processing.
Production of Biogas from Chicken and Goat Wastes
(2019) N. W. Okafor, O. Adedipe, F. J. Usman, J. Y. Jiya, and R. O. Mamman.
One of the problems facing the world today is waste management, particularly those generated from animals. Examples of such wastes include goat waste and chicken droppings. This paper presents the performance evaluation of five 32 litre capacity biogas digesters that were used to investigate the anaerobic digestion of chicken and goat wastes. Biogas was produced from chicken and goat wastes with different mixing ratios: 100:0 (Sample I), 30:70 (Sample II), 70:30 (Sample III), 50:50 (Sample IV) and 0:100 (Sample V) from digesters 1, 2, 3, 4 and 5 respectively. The digesters were charged differently with these wastes and the mesophilic ambient temperature range attained during the experiment were 26-38 oC and a slurry temperature of 25-32 oC. The result showed that the samples were capable of producing a total of 17.3, 44.3, 74.3, 86.2 and 113.2 litres of biogas respectively, using the 32 litre capacity digesters for 30 days. The result obtained from the gas production showed that sample IV produced the highest methane content of 63.3% followed by sample III with 59.4% and sample II with 59.2%. Sample I produced a methane content of 59.1% while sample V had the least methane content of 57.3%.
Application of urine as fuel in a soil-based membrane-less single chamber microbial fuel cell
(AgricEngInt: CIGR Journal, 2019-04-30) Simeon, Meshack Imologie; Otache, Matins Yusuf; Ewemoje, Temidayo Abayomi; Raji, Abdulganiy Olayinka
Microbial fuel cell (MFC) technology is a promising bio-technology that utilizes the microorganisms in organic wastes to generate electricity. Although human urine has been identified as a suitable substrate in MFCs, its possible utilization in a soil-based membrane-less single chamber microbial fuel cell (MSCMFC) for constant power generation has, hitherto, not been reported. In this study, an MFC was set up with mud as inoculum in a plastic cylindrical vessel using carbon felt electrodes. It was operated for 19 days (456 hours) without extra substrate. Then, the MFC was treated with human urine (as substrate) four times (Days 19, 24, 32, and 36), each time the MFC output stabilized across external loads. A control MFC (MFCcontrol) was made the same way and operated under the same conditions, but without the addition of urine. Both MFCs were operated for 40 days. The initial open circuit voltage (OCV) of the MFC treated with urine (MFCurine) was 227 mV, and that of the MFC control was 219 mV. Both MFCs produced overlapping OCVs to the point of adding urine. The maximum OCVs of MFC control and MFCurine prior to treatment were 729 mV and 740 mV, respectively. The OCV of MFCurine increased to a maximum value of 755 mV, four days after the initial treatment (day 23). At the final stage (Day 40), the OCV of MFCurine was 474.64 mV; whereas the corresponding value for MFCcontrol was 7.31 mV. A microchip was used to amplify the output of the MFCs to power a light-emitting diode. In addition, MFCurine was used to power a digital clock/thermometer. This study showed that human urine can be successfully utilized as fuel in a soil-based MSCMFC for the production of electrical energy, which can be boosted to power low-energy utility devices in farms or homes.
A Fundamental Review of Trends in Perovskite Solar Cells Based on Introduction of Buffer Layers to Enhance Stability
(JOURNAL OF SCIENCE TECHNOLOGY AND EDUCATION, 2020) J. Y. Jiya; J. S. Enaburekhan; M. T. Jimoh; E. C. Egwim
Perovskite solar cells (PSCs), as photo-electric conversion devices, exhibit adequate power conversion efficiency (PCE) and low processing cost and have thus become one of the most promising devices to replace conventional silicon-based solar cells thereby addressing current prevailing energy issues. Despite rapid progress in the perovskite solar cell efficiency, there have been concerns about issues which could affect the measurement accuracy and/or practical applications of these devices, amongst which are stability, scaling up (large area devices), and possible environmental effects related to the use of lead-based active material. Current PSCs use nonbiodegradable petroleum-based polymer substrates, discarding of which will aggravate environmental pollution. In this study, a review of the fundamentals and progress in the perovskite solar cell (PSC) is discussed. The processing cost of metal electrode deposition in PSC is very costly, hence, the replacement of the metal electrode by some other low-cost counter electrode is discussed.
Reliability studies on reinforced concrete beam subjected to bending forces with natural stone as coarse aggregate
(Asian Journal of Civil Engineering, 2020-01-12) Kolo, D. N.; Aguwa, J. I.; Tsado, T. Y.; Abdullahi, M.; Yusuf, A.; Oritola, S. F.
This paper presents the results of structural reliability analysis of a structural element (beam) in building using First-order reliability method (FORM) to ascertain the level of safety. The natural stone (NS) which is the by-product of Precambrian deposits of the Bida trough was used as coarse aggregate: unwashed and washed aggregates were used. A total of 80 concrete cubes of 150 mm × 150 mm × 150 mm were cast and used for this study, sensitivity analysis was conducted by varying the span, depth, effective depth, area of shear reinforcement and dead load of the beam in bending. The result of the sensitivity analysis revealed that the beam utilising unwashed and washed NS are both structurally safe at a span of 3000 mm with probabilities of failure of 9.20 × 10–5 and 2.06 × 10–8 and both safe at a depth of 600 mm with probabilities of failure of 4.19 × 10–4 and 2.602 × 10–4, respectively, in bending.