This research aims to gain an overview of the evaluation results and the many challenges to implementing machining competency test certification (CTC) in Vocational High Schools (VHS). The research approach to evaluating this program is a qualitative method using the analysis of Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). The program evaluation design in this study uses the Assessment Evaluability and Performance Monitoring (AEPM) model, which has four evaluation components: Context, Inputs, Activities, and Performance Monitoring. The subjects involved in data collection through the distribution of questionnaires of five VHS in the Special Capital Region of Jakarta. The technique of determining all subjects using the Purposive Sampling technique. The results showed the level of effectiveness of the implementation of the machining CTC program. Some dimensions need to be strengthened, especially for the “less and “very lacking” category. Finally, the approach presented in this research using the AEPM model is a step forward in the analysis of the CTC program. This approach can easily be replicated in other countries with similar aims as this research.

A pressurized liquid extraction (PLE) technique was evaluated in this study and optimized using response surface methodology (RSM) for the determination of polycyclic aromatic hydrocarbons and their nitro derivatives from diesel particulate matter. A central composite design (CCD) was applied for the study of three parameters (temperature, nature of solvent and static time) and the optimal conditions were determined for a time of 9 min and a temperature of 145 °C and dichloromethane as extraction solvent. With the GC/MS analytical technique, the limits of detection (LOD) obtained range from 0.3 to 1.5 µg.L-1 for PAHs and from 4.6 to 8 µg.L-1 for nitrated PAHs. Also, this method allowed excellent recoveries of NPAH adsorbed on diesel soot particles (R ≥ 90%) using a mixture of solvents (1% acetic acid in pyridine). The PLE process developed in this research is quantitative and reproducible while using much less solvent than conventional extraction methods.

In this research, the photocatalytic effect was studied for sol-gel synthesized Mn/Mg co-doped metal oxide (TiO2) nanoparticles (NPs), which are encapsulated with anionic Gemini surfactant. The physicochemical properties of Mn/Mg co-doped TiO2 were investigated using a variety of characterization techniques, FT-IR, UV Vis-DRS, XRD, SEM, EDX, TEM, BET and PL. Characterization results reveal that Mn/Mg dopants stabilize TiO2 in the form of anatase phase and reduce the bandgap energy. Presence of strong chemical bonding and functional groups at the interface of dopant and TiO2 NPs was confirmed with FT-IR. The photocatalytic activity of these catalysts was assessed by the degradation of Orange II (AO7) using visible light irradiation. Of the variable nanomaterials MMT5-GS2 showed remarkable results. The photoluminescence studies revealed that OH radicals are the reactive species and responsible for oxidative photocatalytic degradation of Orange II.

This study focuses on developing a nano zinc oxide (ZnO) catalyst with fly ash (FA) as a support material for converting kapok seed oil (KSO) into biodiesel. This research aims to study the preparation of nano ZnO/FA solid catalysts and the catalyst's reactivity towards kapok seed oil biodiesel (KSOB) products. The catalysts were synthesized using a modification of the Stober process, which is the co-precipitation, impregnation, and precipitation step co-occurred. The catalyst is prepared on base condition using sodium hydroxide with a solvent of methanol and zinc chloride as a raw material. FA waste was effectively modified with zinc oxide particles to create a high-performance ZnO/FA composite catalyst. Under optimal stoichiometric NaOH and 60% ZnO, the resulting material achieved a remarkable specific surface area of 14.8 m²/gram, indicating its potential for enhanced catalytic activity. The prepared catalyst of nano ZnO/FA achieved successful methanolysis of KSO, with a maximum FAME yield of 61.09% attained at 65°C after 5 hours of reaction time, using a 3% catalyst dose and a KSO: methanol molar ratio of 1:15. The initial success of nano ZnO/FA with kapok seed oil paves the way for further development towards robust catalysts specifically tailored for low-grade oil conversion.

This study examines the impact of indentations on the strength of float glass. Using the Vickers indentation method with loads of 1N and 10N, we created defects at varying distances from the point of contact. Biaxial flexure tests revealed that indentations with 1N at 18mm decreased the strength, while those with 10N and shorter distances from the point of contact increased the strength. Weibull distribution analyses showed a correlation between the load, distance, and the Weibull modulus, highlighting the influence of defect size on the probability of rupture.

Many industries rely heavily on the availability and reliability of complex structural and functional components to execute operations efficiently. However, failure of components during service occurs due to exposure to unfavourable operating conditions, causing wear and tear of these components. The damage will result in costly downtime and potential safety hazards. Repairing, remanufacturing and refurbishing these complex parts is critical. Restoring broken structures into operation ensures the smooth operation of the industry, thus preventing losses. Conventionally, repairing parts poses a challenge. However, Wire-arc additive manufacturing (WAAM), which employs the welding principle, has revolutionised component repairing or remanufacturing. This paper reviews the literature on manufacturing complex parts, repair, remanufacture and refurbishment of broken structural and functional parts using WAAM technology. This paper also highlights the various strategies and techniques currently used to improve the quality of WAAM 3D printed parts. The study further covers the immense potential of WAAM in revolutionising the remanufacturing and repair of components. The review study has provided a roadmap for future research and development to take full advantage of this new cutting-edge manufacturing technology.

The effect of air injection into a coffee roasting chamber of a 2 kg rotary drum roaster is investigated on the temperature profiles and organoleptic properties of a Catuai coffee variety. In the experimental study, 1 kg of coffee beans were used and the air injection velocities were varied for the cases of 0 (standard roasting design), 1, 2 and 3 m/s; testing in triplicate and the two most representative were taken. In the coffee roaster, the temperature was monitored simultaneously in the air inlet duct, roasting chamber and gas outlet duct. The organoleptic properties were examined by a group of professionals from Negociaciones Agroindustrial Arévalo S.A. NARSA in the province of Chanchamayo - Peru, which has a G4 laboratory certified by the Specialty Coffee Association (SCA). In the organoleptic ratings, a maximum score of 83.21/100 was found for the 2 m/s test and a minimum of 80.63/100 for the 1 m/s test. For the numerical characterization, the principle of fluid mechanics such as turbulent regime flow and energy transport were used by the finite volume (FV) method using SolidWorks 2021 Flow Simulation software. The numerical results showed that for the 2 m/s test, the temperature of the bean reaches 195 oC at 500 s, indicating that the whole coffee bean reaches the cooking temperature required for the development time prior to eviction; while for the 1 m/s test, it did not exceed 190 oC. It is shown here that the effect of air injection in the roasting chamber, caused organoleptic changes with respect to the conventional design without air injection, due to a sustained cooking at different times and an adequate development time. However, there is a speed threshold where when exceeded, temperatures inside the chamber remain low, development time is extended (machine energy consumption is extended), and organoleptic properties should not improve. However, as the test speeds are exceeded, temperatures inside the chamber remain low, causing the development time to be extended with higher energy consumption and under these conditions the organoleptic properties are not improved.

Adhesive joints play a vital role in different industries owing to their advantages and ease of application compared to other joining methods. This research focuses on enhancing the mechanical properties of epoxy adhesives by incorporating graphene nanoplatelets (G) and iron-oxide nanofillers (Fe3O4). Single-lap adhesive joints, including both G and Fe3O4 nanoparticles, are fabricated at 2%, 3%, and 4% weight percentages and tested under tensile load at ambient, 45°C, and 88°C. The results reveal that adding G and Fe3O4 nanofillers enhances shear strength at elevated and room temperatures without altering the epoxy glass transition temperature (Tg). Furthermore, G nanofiller performs better in improving shear strength than Fe3O4. The optimal weight percentage is identified as 3 wt% for G and Fe3O4, as higher percentages lead to decreased shear strength due to agglomeration

Fatigue crack growth studies require models that accurately predict component life with low uncertainty. Despite the large number of proposed models, there is no clarity on their applicability, which justifies a comparative analysis between some of them. The dual boundary element method (DBEM) was applied for cracked bodies, whereby the stress intensity factors (SIF), the growth rate, and the number of cycles were computed. Three crack increment models were studied under constant amplitude fatigue loads: the Paris, the Klesnil-Lucas, and the Forman models. Results were validated with experimental literature and through the finite element method, indicating that each model represents a specific zone of the crack growth curve. Klesnil-Lucas model reproduces the region near the fracture threshold, Paris fits the controlled crack growth zone, whereas Forman’s model recreates the unstable fracture zone, i.e., when the stress intensity factor approaches the material’s fracture toughness. The J-integral with stress field decomposition gave errors below 0.8% for mode I. Results were similar for the propagation path and the number of cycles to those obtained with the finite element method, with errors of about 3% considering different K-effective approaches. Klesnil-Lucas accurately predicts the number of cycles with an error margin below 3%, considering the curved region in the growth rate at the propagation onset, while the Paris model becomes very conservative, predicting values up to 50% lower than experimental data. The Klesnil-Lukas model is advised for simulating the entire crack propagation.

A flat Aluminum specimen with a geometric discontinuity, which allows testing of the applicability of 2D and 3D Digital Image Correlation Strain measurements, has been considered for this research since it is prone to high stress concentration via Addis Ababa Institute of Technology research interest. Experimental strain using digital image correlation and geometry measurements should be measured with estimated material properties and compare the results with theoretical model predictions. Aluminum plate with central hole were subjected for far field stress in the Machine shop of School of Mechanical and Industrial Engineering at Addis Ababa University in order to test the agreement between DIC’s strain analysis, strain gauge strain analysis and calculated empirical formulas of strain analysis and for the stress distribution of the plate elastically deformed by using VIC-3D and strain gauge. The aim is to measure vertical strain field, Vertical strain along horizontal line through hole center as function of applied loading and vertical strain using theoretical formula along same line as measurements in a plate with central hole subjected to far field and near field tensile loading using visual image coloration (VIC-3D) software, Destensometere device and solid mechanics equations to compare strain results.