Institut za istrazivanja i projektovanja u privredi / Institute for Research and Design in Industry
Autori koji objavljuju u ovom časopisu pristaju na sledeće uslove: Autori zadržavaju autorska prava i pružaju časopisu pravo prvog objavljivanja rada i licenciraju ga Creative Commons licencom koja omogućava drugima da dele rad uz uslov navođenja autorstva i izvornog objavljivanja u ovom časopisu. Autori mogu izraditi zasebne, ugovorne aranžmane za neekskluzivnu distribuciju rada objavljenog u časopisu (npr. postavljanje u institucionalni repozitorijum ili objavljivanje u knjizi), uz navođenje da je rad izvorno objavljen u ovom časopisu. Autorima je dozvoljeno i podstiču se da postave objavljeni rad onlajn (npr. u institucionalnom repozitorijumu ili na svojim internet stranicama) pre i tokom postupka prijave priloga, s obzirom da takav postupak može voditi produktivnoj razmeni ideja i ranijoj i većoj citiranosti objavljenog rada (up. Efekat otvorenog pristupa).
A REVIEW OF FAILURE MODES IN DYNAMIC POSITIONING VESSEL OPERATIONS
Dynamic positioning (DP) is a key enabling technology for offshore drilling, subsea construction, and renewable energy operations, yet loss-of-position incidents continue to pose significant safety, environmental, and financial risks. This paper reviews failure modes in DP vessel operations over the 2015–2024 period by integrating a structured literature review, bibliometric co-occurrence analysis, and content analysis of incident and reliability studies. A PRISMA-style screening applied to Scopus and complementary databases identifies 26 relevant publications, of which 10 are selected as core analytical studies addressing DP failure mechanisms and reliability modelling. The synthesis indicates that technical failures in power generation and distribution, thruster and propulsion systems, and sensor and reference subsystems dominate DP incidents in drilling and construction operations. In addition, human and organisational factors are directly involved in approximately 20% of reported incidents based on a dataset of 311 DP cases, with higher proportions (up to 29.5%) observed in drilling and diving operations where human involvement is more direct. The variation across studies reflects differences in operational context, incident classification methodology, and dataset scope. Incident-based risk analyses further show that power generation failures and adverse environmental conditions disproportionately contribute to expected economic losses. Quantitative reliability and RAM studies consistently report lower failure probabilities for DP3 architectures compared with DP2, while identifying components such as busbars and wind sensors as critical risk contributors. Recent advances, including Bayesian networks, Monte Carlo–based RAM modelling, and the Dynamic Positioning Reliability Index (DP-RI), as well as LSTM-based real-time reliability prediction, demonstrate the potential of data-driven methods to combine incident statistics, equipment failure data, and operational conditions into dynamic risk indicators. Building on these insights, this paper proposes a hybrid framework integrating incident analytics, RAM modelling, and AI-enabled condition monitoring to support more resilient DP operations and to inform future research on human reliability, predictive maintenance, and decision-support integration with class and industry guidance.
Copyright (c) 2026 Journal of Applied Engineering Science
ENERGY RETROFIT AND RENEWABLE ENERGY INTEGRATION FOR RESILIENT PUBLIC SCHOOL BUILDINGS: A VALIDATED CASE STUDY USING BUILDING ENERGY SIMULATION
Jordan places a high priority on improving energy security by lowering energy costs and CO2 emissions through enhanced energy efficiency, boosting investment in renewable energy sources, and diversifying the energy mix. Upgrading public facilities in the area, such as schools, has recently attracted a lot of interest. This study uses carrier HAP and related computations to examine the energy-retrofitting saving potentials model of a local public school, which is driven by the retrofit framework. Five passive and active solutions were evaluated, including the installation of an 84-kWp photovoltaic system. Investment in a PV system, which has a payback period of less than five years, secured a break-even outcome for the expected energy expenses of the resilient school pilot project along with its associated energy demands when strategically paired with other measurements, such as the use of 5cm XPS and 10cm CMU to existing walls and 5cm XPS and other insulative materials to roofs when adhering to local energy code requirements for building envelope retrofits.
SURFACE ROUGHNESS ANALYSIS OF SLM-PRODUCED TI-6AL-4V MILLING USING TAGUCHI DOE
Selective Laser Melting (SLM) is an advanced additive manufacturing technique widely used to produce Ti-6Al-4V components with complex geometries and high material efficiency. However, SLM-produced Ti-6Al-4V commonly exhibits surface irregularities and a hardened microstructure, which necessitate post-processing by machining to achieve the required surface quality. Surface roughness is a critical parameter that influences the functional performance, fatigue life, and reliability of machined components, particularly in high-precision applications such as biomedical and aerospace engineering. This study investigates the surface roughness behaviour during milling of SLM-produced Ti-6Al-4V using a Taguchi-based Design of Experiments (DOE) approach. An L9 orthogonal array was employed to evaluate the effects of three machining parameters—spindle speed, feed rate, and depth of cut—each at three different levels. Surface roughness was assessed using the arithmetic mean roughness (Ra), measured with a contact-type surface profilometer. The experimental data were analysed using signal-to-noise (S/N) ratio analysis, supported by analysis of variance (ANOVA) to determine the contribution of each parameter. The results indicate that spindle speed is the most influential factor affecting surface roughness, contributing approximately 83.66% to the total variation. The optimal machining parameters for minimizing surface roughness were identified as a spindle speed of 7000 rpm, a depth of cut of 0.1 mm, and a feed rate of 1200 mm/min. These findings demonstrate the effectiveness of the Taguchi DOE method and provide practical guidance for optimizing milling parameters in post-processing of SLM-produced Ti-6Al-4V components.
METHODS AND TECHNIQUES FOR ESTIMATING CONCEPTUAL COSTS IN PUBLIC HIGHWAY PROJECTS: A SYSTEMATIC LITERATURE REVIEW
Accurate cost estimation during the conceptual phase of public highway construction is essential for effective transportation planning and budgeting. This paper reviews techniques and methods for initial cost estimation in highway projects, focusing on accuracy, trends, and key cost drivers. The research methodology involved selecting relevant papers by reviewing titles, abstracts, keywords, and full texts during the final stage. This process yielded 87 relevant publications and 33 cost estimation methods and techniques spanning the period from 1980 to 2025. The study found that artificial neural networks, machine learning, and regression analysis are the most used methods for predicting costs early in projects, with machine learning techniques showing the highest accuracy. Among the 184 cost drivers reviewed, 50 were grouped into five categories, providing a basis for selecting critical inputs during the planning phase of cost estimation for highway projects. A thorough review of the research literature highlights gaps and provides recommendations for future studies to focus on the use of advanced technologies to improve cost estimation. Specifically, employing GIS and 3D terrain models, along with geomechanical data, can help accurately calculate the quantities of all items in the bill of quantities. Such advancements are expected to enhance the precision of conceptual cost estimation in highway construction.
TEMPERATURE-DEPENDENT RELATIONSHIP BETWEEN INDIRECT TENSILE STRENGTH AND STIFFNESS MODULUS OF SBS-MODIFIED ASPHALT MIXTURES
This study investigated the temperature-dependent relationship between indirect tensile strength (ITS) and indirect tensile stiffness modulus (ITSM) in styrene–butadiene–styrene (SBS) polymer-modified asphalt mixtures using a PG 76-22 binder. Cylindrical specimens were tested at four temperatures (20, 30, 40, and 50°C) to evaluate their tensile resistance and stiffness. The results show that both ITS and ITSM decrease markedly with increasing temperature, reflecting a reduction in binder viscosity and a weakening of aggregate interlock. Statistical analysis confirmed a strong positive correlation (r = 0.914, p < 0.001) between ITS and ITSM, with linear regression (R² = 0.9045) indicating that ITS is a reliable predictor of ITSM. An analysis of variance showed that temperature had significant effects on ITS and ITSM. These findings highlight the coupled mechanical behavior of ITS and ITSM, supporting their integration into mechanistic-empirical pavement design and performance-based mix evaluation. The study reinforces the role of SBS modification in enhancing thermal resilience and provides a practical framework for predicting stiffness modulus from tensile strength under varying thermal conditions.
CRITICAL FAILURE MODE ANALYSIS OF PROTON EXCHANGE MEMBRANE FUEL CELL USING FUZZY RISK PRIORITY CALCULATION AND PARETO RANKING
Fuel cell systems experience continuous performance degradation due to harsh operating conditions, which limits their durability and reliability. This paper therefore aims to examine the main causes and mechanisms of degradation affecting fuel cells, and in particular Proton Exchange Membrane Fuel Cells (PEMFCs), by conducting a detailed Failure Mode, Effects, and Criticality Analysis (FMECA). Each failure mode is assessed through the Fuzzy Risk Priority Number (FRPN), enabling the identification of the most critical degradation pathways. A Pareto-based classification is then applied to rank failure causes according to their contribution to system performance loss. The combined FMECA and Pareto approach makes it possible to highlight the dominant defects related to auxiliary components, flow regulation, sensor inaccuracies and the aging of the membrane and electrodes. Based on the critical causes identified, specific recommendations are proposed to improve reliability, including improved energy management and operating strategies, optimized control of pressure and humidity, and improved monitoring of auxiliary subsystems. The results provide a structured methodology for prioritizing degradation sources and guiding preventive maintenance and design improvements in fuel cell systems.
CAUSES OF TIME OVERRUN IN ROAD CONSTRUCTION PROJECTS
Time overrun is a situation in which construction project exceeds the specified completion date or the period agreed upon by the parties for handover. The concept is also known as overtime and has become a major problem for most construction projects worldwide due to significant waste and missed opportunities for several relevant stakeholders. Therefore, this study aimed to determine the causes of time overrun and mitigate time overrun in road construction projects. The method used includes interviews and questionnaires, which were subjected to focus group discussions (FGDs) with several experts before distribution to competent parties in construction sector. The data collected were analyzed using exploratory factor analysis to ensure accuracy and for optimization. A total of 132 questionnaires were answered correctly and returned. The results identified 7 factors affecting time overrun, which included (1) politics and government, (2) finance and planning, (3) management, (4) resources, (5) delays and errors, (6) projects, and (7) others. A total of 17 causes were also observed including political situations, political interference, economic determinants, land disputes, and late payments for additional work by the owner, followed by 12 other causes. Moreover, mitigation efforts were recommended to prevent and reduce the causes of project time overrun.
MULTI-OBJECTIVE OPTIMIZATION WITH GENETIC ALGORITHM OF AIR SUSPENSION SYSTEM FOR ENHANCING RIDE COMFORT AND ROAD-HOLDING PERFORMANCES
This study presents a systematic investigation of air suspension control strategies for vehicular applications, employing computational optimization techniques to enhance both ride comfort and road holding performances. A comprehensive simulation framework was developed, incorporating a quarter-truck model with nonlinear air spring dynamics subjected to spectrally rich road excitations. The research methodology integrates conventional PID control with multi-objective genetic algorithm optimization to determine Pareto-optimal solutions for conflicting performance criteria. Extensive numerical simulations reveal that the optimized controller achieves significant improvements in vibration attenuation (58.4% reduction in sprung mass displacement) while maintaining superior road contact characteristics (41.5% enhancement in tire-road contact force) compared to a passive system. The analysis provides quantitative insights into the fundamental trade-space between ride comfort-oriented and stability-focused control objectives, demonstrating that intelligent optimization approaches can effectively navigate these design compromises. Furthermore, the results establish practical boundaries for control system performance under realistic operating conditions, offering valuable guidelines for automotive suspension system design. The technical contributions include novel control architectures, advanced performance evaluation metrics, and a rigorous methodology for controller optimization in nonlinear air suspension systems. These findings advance the state-of-the-art in vehicle dynamics control and identify several promising avenues for future research in adaptive control systems and hybrid optimization algorithms.
SHEAR STRESSES OF HOLLOW CYLINDRICAL CONCRETE BEAMS MADE WITH RECYCLED CERAMICS AGGREGATES
The main focus of the study presented in the work is an experimental investigation into the effects related to recycled ceramic coarse aggregates from the industrial brick waste on reinforced concrete beams (RCBs) shear behavior. For such an aim, a total of twelve concrete beams with 250mm height, 1200mm length, and 140mm width have been employed. A total of six Normal Concrete Beams (NCB) models made up of three Solid Normal Concrete Beams (SNCB) and Hollow Normal Concrete Beams (HNCB). Of the six models of Recycled Ceramic Concrete Beams (RCCB), there are also three Solid Recycled Ceramic Concrete Beams (SRCCB) and three Hollow Recycled Ceramic Concrete Beams (HRCCB). At such percentages of 0% and 30%, the weight related to coarse aggregate in concrete mixes is replaced with crushed ceramic that is acquired from building demolition wastes. A total of four points on the samples were examined for bending. The mid-span of the beam had the most deflection. The test evaluated the behavior related to beam concrete with the waste material by measuring the ultimate shear strength and diagonal cracking load. The experiment was designed to determine the impact of crushed ceramic on mechanical characteristics of RCBs. Additionally, the results show that, when compared to control samples, adding crushed ceramic improved the properties of the samples in shear behavior with reference to crushed ceramic concrete beams. Results have shown that the use of recycled ceramic aggregates caused a reduction in ultimate shear capacity of approximately 10–15% compared with conventional beams, while reducing stirrup spacing significantly enhanced shear resistance and crack control. Results have confirmed that recycled ceramic aggregates can be effectively used in reinforced concrete beams without significantly compromising structural performance. This study is limited to a 30% replacement ratio and monotonic static loading conditions. To the best of the authors’ knowledge, limited studies investigated combined effect of recycled ceramic aggregates and longitudinal hollow sections on shear behavior of reinforced concrete beams. This study provides additional information about the feasibility of utilizing ceramic waste in structural applications, thereby supporting sustainable construction practices and reducing environmental impacts associated with construction waste.
MULTI-OBJECTIVE OPTIMIZATION OF TWO-STAGE HELICAL GEARBOXES USING NSGA-II AND MCDM METHODS: MINIMIZING MASS AND MAXIMIZING EFFICIENCY
This study presents a multi-criteria design approach for two-stage helical gearboxes using the Non-dominated Sorting Genetic Algorithm II (NSGA-II) in combination with MCDM methods. The optimization problem was formulated with two conflicting objectives: minimizing gearbox mass and maximizing transmission efficiency. NSGA-II was employed to generate a set of Pareto-optimal solutions, while three different MCDM methods—MARCOS (the Measurement of Alternatives and Ranking according to Compromise Solution (MARCOS), TOPSIS (Technique for Order Preference by Similarity to Ideal Solution), and SAW (Simple Additive Weighting)— was applied to identify the most preferred compromise design among them. Regression analysis revealed a strong linear relationship between the stage-one gear ratio (u1) and the overall transmission ratio (uh), ensuring practical feasibility of the optimized gear allocation. Numerical results demonstrated that gearboxes designed with transmission ratios in the range of uh=15–25 achieved the most balanced trade-off between reduced mass and high efficiency. The proposed hybrid NSGA-II–MCDM framework thus provides a powerful decision-support tool for gearbox designers, enabling both lightweight and energy-efficient configurations. In addition, the findings have clear practical implications, as the proposed framework can support the development of more compact and efficient gearboxes in automotive and industrial applications, where reducing mass and improving efficiency are critical design requirements.
OPTIMIZATION OF UNMANNED AERIAL VEHICLE STRUCTURES USING CARBON PLASTIC MATERIALS
This research explores the potential of using carbon plastic composite materials to optimize the structure of unmanned aerial vehicles (UAVs). The main issue addressed is reducing the weight of drones while increasing their strength and aerodynamic stability. The study found that the specific strength of carbon composites is 1500 MPa/g/cm³, which is three times higher than that of conventional materials. Additionally, the structural vibration resistance increased by 25-30%, and the weight was reduced by 25%. These results are explained by the low density of the material (1.55 – 1.65 g/cm³) and optimal distribution of stresses in the structure. A key feature of the research is the use of a method based on actual CAD modeling and numerical simulations, and the assessment of the efficiency of 3D printing and Out-of-Autoclave technologies, which supports its industrial potential. The findings can be applied in the construction of lightweight, reliable, and energy-efficient drones. Practical applications of these materials include military, agricultural, and emergency rescue systems, with usage conditions in environments with moderate temperatures and vibrational loads.
MODIFICATION OF SIZE EFFECT FORMULA FOR CONCRETE BEAMS WITHOUT SHEAR REINFORCEMENT
The current state of engineering science and practice has been concluded that the size effect cannot be overlooked, especially in the calculation of the shear capacity. Models based entirely on fracture mechanics have led to complex formulations inconvenient for practical use. Models based on simple theories, are resulting in a formula for determining the shear capacity of reinforced concrete. They are practically convenient, but multiple empirical parameters without a clear physical meaning are involved in their formulation. In the present study one modification of a size effect formula is presented. The purpose of this modification is to replace an empirical coefficient with a fracture mechanic’s parameter with a clear physical meaning.
ELASTOHYDRODYNAMIC ANALYSIS OF MULTISTEP TEXTURED JOURNAL BEARINGS WITH GROOVE DEPTH VARIATIONS USING CFD–FSI
Journal bearings are widely employed in numerous industrial machines such as compressors, pumps, turbines, and generators, primarily to support rotating shafts. Compared with other surface texturing geometries, multistep journal bearing represents a geometric modification of conventional designs and is increasingly adopted because of its simple configuration, low manufacturing cost, and ease of fabrication. The stepped profile also facilitates greater lubricant flow, thereby enhancing the bearing’s operational performance. Extensive research has been devoted to evaluating parameters such as pressure distribution, load-carrying capacity, frictional forces and elastic deformation to improve tribological characteristics of journal bearings. This work investigates the influence of groove geometry—specifically groove height and width on the performance of multistep journal bearings in order to develop an optimized configuration. Three-dimensional computational fluid dynamics (CFD) simulations coupled with fluid-structure interaction (FSI) analysis, including cavitation effects, were performed. The results reveal that increasing the number of steps reduces frictional forces, while the load-carrying capacity decreases slightly. For instance, at a groove width of 35°, the load-carrying capacity was 6.96 % lower than at 15°, yet the frictional performance improved by 14.5 %.
MECHANICAL DAMAGE ASSESSMENT IN CONCRETE BEAMS REINFORCED WITH STEEL AND POLYPROPYLENE FIBERS USING ULTRASONIC PULSE VELOCITY TESTING
Concrete beams are structural elements primarily subjected to vertical loads, including self-weight (dead load) and externally applied actions (live load). The sustained interaction of these loads induces bending deformations. As with all structural materials, concrete beams experience mechanical damage when the applied stresses exceed their ultimate capacity, typically manifested through cracking, which occurs on the tensile face opposite the load application. For several decades, fiber reinforcement has been employed worldwide to enhance the physical and mechanical properties of concrete, particularly its residual strength and crack control. In this study, concrete specimens were reinforced with two types of fibers—steel and polypropylene—and evaluated using ultrasonic pulse velocity (UPV) testing to characterize mechanical damage. After curing time, UPV measurements were taken to assess internal damage development under flexural loading. Based on the experimental data, predictive equations are proposed to estimate mechanical damage as a function of pulse velocity, allowing for improved evaluation of reinforced concrete behavior under stress.
VALIDATION OF THE PERFORMANCE OF HDPE-CONCRETE AS AN ALTERNATIVE FOR SUSTAINABLE CONSTRUCTION
Concrete is the most widely used material in global construction, which generates high demand for natural resources and a significant carbon footprint. In response to these challenges, incorporating plastic waste, such as high-density polyethylene (HDPE), has been proposed as a sustainable alternative to reduce dependence on natural aggregates and mitigate plastic pollution. This study evaluates the mechanical performance of concrete with partial replacements of HDPE at 2.5%, 5%, 7.5%, 10%, 15%, 20%, and 30% in sand to produce HDPE-concrete, which is compared against a control mix with 0% replacement. Optimal replacement percentages have been identified in the literature, and 64 specimens were prepared and tested to determine the concrete's behavior, including its strength and flexural performance, to validate the advantages and disadvantages of each replacement in the search for the optimal configuration of sustainable concrete. Results showed that 5% and 7.5% replacement levels achieved optimal compressive (409 kg/cm²) and flexural (49 kg/cm²) strengths, respectively. Although these mixes exhibit slower strength gain reaching peak values at 28 days, lower replacement rates showed superior 7-day strength. Conversely, higher replacement levels increased recycling volume, reduced unit weight and slump, and raised air content without compromising the paste-aggregate bond. The findings suggest that HDPE-concrete is a promising solution for the construction industry, as it not only promotes the circular economy of plastic waste but also offers adequate mechanical performance, making it a viable and eco-friendly alternative for building material production.
CALCULATION OF NONLINEAR VIBRATION ISOLATION SYSTEMS UNDER HARMONIC ACTION
The aim of the study is to develop a methodology for calculating the dynamic characteristics of nonlinear vibration isolators and to evaluate the influence of the type of dissipative forces on the vibration protection efficiency. The paper addresses the calculation of vibration isolators with nonlinear elastic and dissipative properties under harmonic force and kinematic excitations. Using the harmonic linearization method, general expressions were derived for the amplitude-frequency response and the vibration isolation efficiency coefficient. The analysis of these expressions determined the conditions for suppressing large-amplitude vibrations. Specific analytical relationships were obtained for vibration isolators possessing the most common nonlinear elastic characteristics. These include isolators with odd cubic stiffness characteristics, preloaded systems, systems with symmetric linear elastic stops, and systems with a nonlinear elastic element and symmetric rigid stops. It was established that the efficiency of vibration protection systems depends significantly on the type of dissipative forces present in the isolator. Analytical relationships were derived, and the performance of vibration isolators with viscous, dry, and internal friction was analyzed. A comparison of the performance efficiency of vibration isolators with different dissipative characteristics was conducted. The possibility of achieving vibration protection goals by combining different forms of damping is highlighted.
DEVELOPMENT OF SIMILARITY CRITERIA FOR PHYSICAL MODELING OF THE PROCESS OF ROADBED COMPACTION
This paper focuses on developing criteria for the physical modeling of roadbed compaction using a vibration roller. A rheological model of the process was employed to establish the relationship between stresses and strains in soils with elastic-viscoplastic properties. Additional similarity criteria were utilized to characterize the design and technological specifications, as well as the initial and boundary conditions of the process. Based on these similarity criteria, a physical model of the working element of a vibration roller was created. A series of experiments was conducted to identify the key parameters of this working element. By analyzing the inverse relationships that define these key design and technological parameters, it is possible to determine optimal values for the essential parameters of the vibration roller.
VIBRATION PROTECTION OF PUMPS ON THE FOUNDATION WITH A DAMPING PLATE MADE OF ELASTOMER
This paper examines the decrease in pump efficiency under off-design operating conditions, where vibrations and dynamic loads cause bearing failures, overloading of pump–foundation connections, rotor displacement, and runout. These effects also deteriorate the performance of end and slot seals, leading to increased fluid leakage. To address this issue, the use of damping devices in the form of polyurethane elastomer plates is proposed. These materials provide high damping capacity, dynamic modulus of elasticity, tensile strength, and acoustic vibration isolation efficiency. They are also characterized by exceptional abrasion resistance, significantly exceeding that of rubber and low-carbon alloys, as well as resistance to environmental influences, water, oils, and most chemically active substances. The application of elastomer damping deviceАs significantly reduces vibration levels, decreases dynamic loads on foundations, and enhances the overall reliability of pumping equipment.
THERMODYNAMICS ANALYSIS TO EVALUATE THE COMBUSTION PROCESS OF E50 FUEL WITH INJECTION VOLUME VARIATION
The study is based on the first and second laws of thermodynamics to investigate and analyze the performance of spark ignition engines with varying injection durations of the gasoline and bioethanol fuel blend (E50). Experiments were conducted using standard parameters of engines, including an 11:1 compression ratio and 12 bTDC of ignition timing. The injection volume of the fuel blend was set at 100% to 200% (increment of 25%) of the injection volume of gasoline. The effect of the injection volume of E50 is evident in various performance indicators, including brake-specific fuel consumption (BSFC), thermal efficiency, and brake power, as observed in both energy and exergy analyses. The most important conclusion of this study is that the performance of the engine using E50 would be similar to gasoline (E0), both in energy and exergy analyses, when the injection volume of E50 increased by 25% compared to gasoline.
HYBRID AI-BASED PREDICTIVE QUALITY CONTROL FOR AUTOMOTIVE CUTTING PROCESSES: A SMART MANUFACTURING APPROACH UNDER IATF 16949
Ensuring product quality in the automotive industry becomes a technical strategic challenge in the era of digital and networked supply chains. Traditional final inspection methods, often reactive, are not sufficient to attempt the rigorous expectations of IATF 16949. The case of covers seating industry must be at the forefront of industrial excellence. Evoking comfort, functionality, and aesthetics for customer, taking into account that the cutting area in such industry is the focal point to loop considered as internal supplier in the covers supply chain, cutting output is the input for all assembly lines, which means that an uncontrolled quality KPI will disturb the manufacturing process. A hybrid AI –based predictive quality control modeling in cutting process is used combines expert-based validation through the Fuzzy Delphi Method to define the factors affecting the quality of cut products. The integration of data driven prediction (AI and IoT) represented in a linear-regression-based supervised learning model trained and learned with a simulated dataset from real production conditions according to literature review and experts feedback to detect and prevent failures in the early stage of production. The analysis shows the three variates (cutting speed, cutting temperature, vibration intensity) predefined from the literature review were validated as input data. The results indicate a high predictive quality accuracy since the coefficient of determination R2 =0.87 and the model statistically very significant ANOVA results. Concluding that the vibration factor have the most significant impact on quality cutting defect. This hybrid AI-based predictive approach provides an improvement lever of the smart automotive manufacturing chains supporting data driven decisions under the IATF 16949.
FLEXURAL PERFORMANCE AND DESIGN EVALUATION OF REINFORCED CONCRETE BEAMS WITH STEEL REINFORCEMENT AND BASALT FIBER-REINFORCED POLYMER LONGITUDINAL BARS
This study experimentally and analytically investigates the flexural behaviour of RC beams reinforced with either conventional steel longitudinal bars or basalt fibre-reinforced polymer (BFRP) longitudinal bars in combination with steel stirrups. Eight simply supported beam specimens were tested under monotonic static loading, comprising two distinct reinforcement systems: steel-reinforced control beams and BFRP-reinforced beams. The experimental program evaluated reinforcement and concrete strains, mid-span deflections, cracking behaviour, ultimate load capacity, and elastic energy storage prior to failure. The results indicate that steel-reinforced beams exhibited ductile flexural failure characterized by steel yielding followed by gradual concrete crushing, enabling controlled crack development and deformation. In contrast, beams reinforced with BFRP longitudinal bars failed in a more brittle manner governed by concrete crushing, reflecting the linear-elastic response of BFRP reinforcement, while exhibiting larger deflections and higher concrete strain levels. Despite these differences in failure mode and ductility, BFRP-reinforced beams achieved comparable or higher ultimate load capacities relative to their steel-reinforced counterparts. Analytical predictions based on ACI 440.2R-08 showed good agreement with experimental results, with conservative underestimations of ultimate capacity (ACI/Exp ratios ranging from 0.93 to 0.97), confirming the reliability of current design provisions. The findings highlight the inherent trade-offs between stiffness, ductility, and load-carrying capacity associated with steel and BFRP reinforcement systems and emphasize the importance of serviceability considerations in BFRP-reinforced RC beam design.
NUMERICAL STUDY OF DROPLET LENGTH AND BREAKUP TIME FOR GEOMETRY AND FLOW PARAMETERS IN A T-JUNCTION MICROFLUIDICS
Droplet microfluidics finds its application in medical, chemical and biological research as well as in the field of medical device manufacturing. This paper studies the T-junction microfluidics and its parameters, such as droplet length and breakup time, as they vary with the channel width and phase velocities. The study reveals that droplet length rises with an increase in either of the channel width and time taken for breakup reduces and attains a steady value when dispersed phase width is increased. The droplets are smaller in size and form very quickly when the velocity of continuous phase is increased and vice versa. The study can be utilized as a part of a larger study of droplets and their particle encapsulations, and its utilization to generate more efficient and economical medical devices.
EVALUATING AND RANKING SERVICE QUALITY ATTRIBUTES FOR OPTIMIZING METRO RAIL TRANSIT SRVICES IN DHAKA USING ADVANCED ANALYTICS
As Dhaka embraces its first Mass Rapid Transit (MRT) system, understanding what drives users’ satisfaction has become crucial for shaping its success. This study examines the service quality (SQ) of MRT Line-6, identifying and prioritizing the factors that influence user perceptions of this transformative transit solution. Using advanced machine learning models such as Random Forest Classifier, Support Vector Machine, and CART, alongside statistical methods like Probit, Ordered and Multiple Linear Regression, the research provides a robust analysis of twenty-nine (29) SQ indicators. Random Forest Classifier emerged as the most effective model, achieving 88.21% accuracy and offering valuable insights into the interrelationships of key attributes, including inclusive service performance, customer loyalty, switching cost from other transportation mode, ticket affordability, performance of ticketing system, and feeder service costs. Survey results highlight that most users around 60% switched from buses to MRT for its comfort and reliability. The findings emphasize the need to enhance affordability, accessibility, overall comfort and feeder services while promoting digital ticketing through options like Rapid Pass and online platforms. These actionable insights offer a roadmap for policymakers and urban planners to optimize MRT services, aligning with global best practices to support sustainable urban mobility in Dhaka and beyond.
Copyright (c) 2025 Journal of Applied Engineering Science
PARAMETRIC MODELING OF BOLTED ASSEMBLY AND ITS COMPONENTS FOR INDUSTRIAL DESIGN AND APPLICATION
In the present work is proposed a methodology for parametric modeling of a bolted joint including four separate components, each of which is described with tabular dimensions according to current standard. The parametric model can automatically create a bolted assembly unit with a selected fastening size used for creating metal construction and bigger assemblies. Solutions are performed for the bolted joints used mostly in the industry.
COMPREHENSIVE EVALUATION OF INDIAN STANDARD CODES AND CURING APPROACHES FOR GEOPOLYMER CONCRETE
Geopolymer Concrete (GPC) is a sustainable alternative to Ordinary Portland Cement (OPC), reducing global CO₂ emissions by 8-10% using industrial by-products such as fly ash, slag, metakaolin and silica fume. This approach not only reduces landfill waste and environmental pollution but also aligns with global sustainability goals. Extensive research highlights the increased sustainability of GPC, which includes excellent resistance to chemical corrosion, fire and elevated temperatures, rapid strength development and long-term structural stability. This study undertakes a comprehensive review of the existing literature on GPC, with a special focus on the applicability of Indian Standard (IS) codes for mix design and optimization of curing methods. However, despite significant research progress, GPC remains excluded from building codes in many regions. Given the absence of a dedicated design code for GPC, the review evaluates standardized test protocols for fresh and hard properties tailored to India's climatic conditions. The data for this analysis were systematically extracted from the Scopus database and non-Scopus journals, providing a solid foundation for critical evaluation, presented in a consolidated way to give a clear and focused context. This study validates GPC as a sustainable alternative to conventional concrete in India. However, optimization of mix design parameters, curing methods and durability performance, along with standardized guidelines, is required for widespread adoption. These findings provide important insights for researchers and practitioners to develop environmentally friendly construction technologies.
LQR-BASED ACTIVE SEAT SUSPENSION DESIGN TO IMPROVE BUS DRIVER RIDE COMFORT
Bus drivers are exposed to vibrations generated by the road surface affecting their fatigue, comfort and health. Vibrations are transmitted from bus wheels to the driver’s body through bus suspension system, bus floor and the seat suspension system. Active and semi-active seat suspensions have been developed to alleviate vibrational negative effects. This paper investigated bus driver ride comfort as a function of bus speeds and road quality considering linear quadratic regulator for active seat suspension system. A 3-degree-of-freedom intercity bus model had been defined for simulation. Bus modelling, controller design and simulations were performed by MATLAB/Simulink software. Results showed that active seat suspension significantly reduces the vertical acceleration transmitted to the driver’s body compared to the passive system. Improvements were particularly noticeable on rough roads and at higher bus speeds.
DEVELOPMENT OF A DEVICE FOR COOLING LADLE LINERS FOR CASTING LADLES
This article focuses on the controlled cooling process of the linings of ferroalloy production ladles. Analysis of the operating conditions of the linings revealed that temperature stresses during heating and cooling are the main cause of damage to the linings of high-temperature units. At the enterprise in question, the cooling process is uncontrolled when the lining is exposed to the workshop atmosphere. This leads to cracks forming in the lining and its subsequent destruction. Cooling schedules have been developed for the ladles under consideration, during which the resulting thermal stresses do not damage the lining. A device has been developed for the ladle liners to ensure the cooling process is kept on schedule. Incomplete liner replacement involves cooling the ladle by supplying a mixture of combustion gases from the ladle heating booth and air. The liner is cooled using a mixture of three media: ambient air from the workshop, combustion products from the ladle heating stand, and combustion products from the ferroalloy gas burnt in the burner. A cooling schedule for casting ladle liners has been developed to ensure that thermal stresses do not exceed the strength limit of the refractory materials. At the same time, the cooling time is reduced from 19 hours 30 minutes to 6 hours 50 minutes. The developed device enables the outer and inner walls of the lining to be cooled, secondary resources (ferroalloy gas and combustion products from the ladle heating stand) to be used.
SIMPLE EQUATION FOR WALL-COLUMN CONTACT LENGTH TO ESTIMATE THE LATERAL STRENGTH OF REINFORCED CONCRETE FRAMES WITH MASONRY INFILL WALLS
This work introduces an analytical approach for assessing the seismic capacity of brick masonry infills within reinforced concrete frame structures by the use of a diagonal strut model. The model demonstrates that when the column experiences flexural displacement and the masonry wall endures shear deformation, separation or contact transpires between the masonry infill and the column. The contact height between the masonry infill and column was determined based on the compatibility of lateral displacements of both elements. As a result, a simple equation of contact length between infill and column to determine the lateral strength of masonry infill was employed to calculate the strut width of the masonry infill. The lateral strength for several reinforced concrete frame structures with brick masonry infills was determined using the simplified contact length equation. Furthermore, the analytical results were validated using lateral strength of structure models as outcomes of the pushover method. The results showed that the lateral forces of the structures were relatively similar between the analytical and pushover methods. It suggests that the strut model and the simplified wall-column contact height can be used to estimate the lateral strength of masonry infill in reinforced concrete structures.
APPLICATION OF ANALYTIC HIERARCHY PROCESS IN SITE SELECTION OF URBAN CONSOLIDATION CENTERS
The Analytic Hierarchy Process (AHP) is a structured and widely-used multi-criteria decision-making (MCDM) method. This study applies AHP to evaluate and rank five potential sites for establishing an Urban Consolidation Center (UCC). UCCs serve as logistics hubs that aggregate deliveries in urban areas, aiming to reduce traffic congestion, emissions, and inefficiencies. The evaluation framework was developed using seven main criteria categories, each containing detailed sub-criteria. A hierarchy was constructed, and pairwise comparisons were conducted to derive weights. The consistency of judgments was verified using the Consistency Ratio (CR). The results yielded a final ranking of the locations, offering a rational and transparent approach to support urban logistics planning.
PERFORMANCE INVESTIGATION OF SPLIT-WALL AIR CONDITIONING: AN EXPERIMENTAL ANALYSIS OF COP AND EER WITH A CUSTOM DATA LOGGER
This investigation presents a comparative performance analysis of inverter and non-inverter air conditioning configurations under tropical climatic conditions, employing a custom-developed data logger system for real-time monitoring. The experimental investigation employed coefficient of performance (COP) and energy efficiency ratio (EER) as primary performance indicators. Both air conditioning configurations were evaluated at a standardized cooling capacity of 2.5 kW to ensure consistent comparative conditions. The experimental setup incorporated a custom-built data logger utilizing an ATmega 2560 microcontroller as the central processing unit, enabling real-time acquisition of thermal and electrical parameters critical for performance evaluation. Comprehensive sensor calibration procedures were conducted to ensure measurement reliability. The DS18B20 temperature sensors underwent rigorous calibration, yielding a mean absolute error (MAE) of ±0.75°C. This result demonstrates a high level of measurement accuracy and complies with established standard calibration acceptance criteria. Quantitative analysis revealed that the inverter system achieved a COP of 4.06, demonstrating 8.6% improvement over the non-inverter system's COP of 3.74. Moreover, the energy efficiency ratio measurements showed the inverter system achieved an EER of 13.8, while the conventional system recorded 12.7, indicating 8.7% improvement. Additionally, the custom data logger demonstrated consistent reliability with multi-parameter measurement capabilities, enabling comprehensive monitoring of essential parameters for HVAC performance.