Institut za istrazivanja i projektovanja u privredi / Institute for Research and Design in Industry
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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.
Copyright (c) 2026 Journal of Applied Engineering Science
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.
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 %.
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.
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.
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.
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.
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
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.
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.
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.
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.
EXPERIMENTAL AND NUMERICAL STUDY OF TUNNEL VARIATIONS EFFECTS ON BLAST WAVE TRANSMISSION MECHANISM
This study investigates the effects of tunnel configuration changes on blast pressure transmission under near-field explosion conditions using both experimental and numerical approaches. Small-scale models were employed to conduct explosion tests, including near-surface detonations and variations in tunnel patterns. Numerical simulations utilizing ALE (Arbitrary Lagrangian-Eulerian) fluid-structure interaction were performed to evaluate blast pressure transmission. The analysis revealed that elbow-type, T-type, and branched tunnels exhibited varying effects on blast pressure transmission, with significant differences in pressure between the inner and outer walls of the tunnels' bend sections. In elbow-type tunnels, the inner wall experienced greater blast pressure than the outer wall, whereas the opposite was observed in T-type and branched tunnels. The findings demonstrate that the numerical model accurately reflects experimental blast pressure transmission patterns.
CORAL ROCK ASH AS A SUPPLEMENTARY FILLER IN ASPHALT CONCRETE WEARING COURSE: LABORATORY PERFORMANCE AND MECHANISTIC–EMPIRICAL SERVICE-LIFE PREDICTION
Flexible pavements with hot-mix asphalt (HMA) may underperform when conventional mineral filler provides insufficient mastic stiffness and moisture resistance. This study evaluates coral rock ash (CRA) as a partial replacement of conventional mineral filler in an asphalt concrete wearing course (AC–WC) mixture to improve laboratory performance and predicted service life. CRA was introduced at 0–10% of the total mixture mass, replacing an equivalent portion of filler in the gradation. Marshall stability/flow and indirect tensile strength (ITS, tensile strength) were measured at an optimum asphalt content of 6%. To link mixture-scale changes to structural performance, layer responses were computed using KENPAVE multilayer elastic analysis, where the HMA elastic modulus was derived from the ITS-based stiffness correlation used in the study (with Poisson’s ratio held constant), enabling mechanistic–empirical estimation of critical strains and allowable load repetitions. Regression analysis identified 4.8% CRA as optimal, yielding peak Marshall stability (1060.7 kg) and the smallest 7-day strength loss after 60 °C conditioning. Relative to the control, ITS increased by 22.6% (11.62→14.25, unit-consistent with the original dataset). In the mechanistic analysis, the improved mixture stiffness led to a reduction in bottom-HMA tensile strain (εt) and a corresponding increase in predicted allowable repetitions, extending the design life of the reference pavement section from 5 to 7 years. These findings indicate that CRA is a feasible, locally available supplementary filler for improving HMA performance and extending service life in coastal regions, provided that sourcing uses non-living, naturally stranded coral debris and complies with environmental regulations.
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.
EXPERIMENTAL ENHANCEMENT OF SOLAR WATER HEATER FOR USING IN A LOW TEMPERATURE WITH HEAT EXCHANGER VERTICAL COLLECTOR BY CONCENTRATOR AND ACETONE
This study presents an innovative solar water heating system that integrates a condenser with water or acetone as the working fluid, offering a promising solution to key challenges in solar energy utilization, like cost efficiency, optimal angle alignment, and material limitations. The proposed design significantly improves thermal performance, making it a viable alternative to conventional flat-plate solar collectors. Experimental results demonstrate a significant efficiency improvement of 80% compared to conventional systems. This improvement is referred to two main factors: First, advanced collector geometry: The utilize of a spiral-coil tube design enhances radiation absorption in all directions, reducing dependence on precise solar angle alignment. Second, improved heat transfer fluid. where the acetone used as the working fluid due to its superior thermophysical properties significantly improves heat transfer rates within a thermosyphon-based natural circulation system. The efficiency of acetone was found to be higher in both the single- and double-loop cases by 77.66% and 70.78%, respectively, compared to water. The combination of these innovations ensures consistent energy capture and heat production, even under suboptimal conditions. Furthermore, the system's scalability and adaptability suggest it could be widely applied in engineering contexts, including residential, industrial, and agricultural heating. By addressing cost constraints and efficiency limitations, this spiral solar collector emerges as a revolutionary alternative to conventional solar thermal technologies, accelerating the adoption of renewable energy solutions.
ANALYSIS OF CYLINDER HEAD REPAIR OF MAIN ENGINE: A CASE STUDY OF PASSENGER SHIP KM GD IN INDONESIA
KM GD a passenger ship operated by PT. PELNI. Playing an important role as a transportation link between regions in Indonesia, especially given the country’s archipelagic geography. The reliability of the main engine as the main driver of the ship is a crucial factor in ensuring smooth operations. One of the vital components in a master engine system is the cylinder head at KM GD was found to have repeated damage to the cylinder head shortly, although repairs have been made. Damage to the cylinder head has a high presentation on engine operation. Repeated damage is interesting for research to discover more details about the causes of cylinder head cracks. This study identified the root cause of damage using the Root Cause Analysis method with the 5 Whys approach and the Fishbone diagram. The results of the study show that many factors are the cause of cracks. The main factor of damage is a non-standard reconditioning procedure. Repairs to standards provide significant savings and improve engine reliability. Research using the RCA method effectively analyses technical issues and supports efficient and sustainable treatment decision-making. Recommendations are given to improve the working performance of the machine after reconditioning, among others, through the implementation of strict technical procedures according to the manufacturer's standards and increased quality control during the repair process. With a thorough improvement in this technical and managerial aspect, it is hoped that the damage frequency can be reduced and the reliability of the main's engine can be optimally maintained to support operations KM GD.
REGRESSION ANALYSIS ALGORITHM FOR THE RESULTS OF REINFORCED CONCRETE SLABS TECHNICAL INSPECTION
The paper presents an algorithm for calculating key statistical parameters, including correlation dependences, correlation coefficients, and a method of checking the presence of a linear dependence. A quadratic regression equation is obtained, regression curve graphs are constructed, distribution functions and probability densities with the procedure for their normalization are calculated. The main statistical parameters of random variables are also calculated: mathematical expectation, variance, standard deviation, and quantiles of various levels. The proposed regression analysis algorithm can be used to assess safety and reliability of building structures, which allows analyzing their operation in a probabilistic form. Based on the theoretical and applied results of the work, prospects are opened for further development of probabilistic analysis methods for safety of construction projects as a whole, taking into account their complex structure and interaction of various structural elements.
ANALYSIS OF THE IMPACT OF INSTALLING CAI AND IMS ON A MOTORCYCLE ENGINE
Engine performance and fuel efficiency are very important in a motor vehicle, so many studies aim to improve the performance of motor vehicles. The Intake Manifold Spacer (IMS) is placed on the intake manifold channel before the air and fuel mixture enters the combustion chamber, while the Cyclonic Air Injector (CAI) is placed on the air channel that will enter the carburettor chamber. With the addition of IMS and CAI, it is expected to increase the homogeneity of the fuel-air mixture and provide a turbulent flow effect (swirling) on the air entering the carburettor and the air-fuel mixture entering the combustion chamber. The method used in this study is to manufacture IMS and CAI with variations in the number of blades: 3 and 4 and the angle of inclination of the blades 35o and 45o. Testing was conducted on a 110cc 4-stroke motorcycle, where a dyno test was used to determine power, torque, and fuel consumption. The results of this study show that the addition of IMS and CAI can improve performance and increase fuel efficiency compared to standard motor vehicle conditions. The largest increase in motor power was in the variation of adding IMS and CAI with 4 blades and a blade angle of 35o, which was 3.9%. Meanwhile, the maximum torque increased by 3.9 in the variation of adding IMS and CAI with 4 blades and a blade angle of 45o. Fuel consumption also experienced savings or decreased compared to the standard conditions of all test variations. The highest efficiency of 9.36% occurred in the variation of adding IMS. Based on this research, it can be one of the considerations to improve the performance of combustion engines for the automotive industry. It can also serve as a reference for other researchers who wish to conduct research on combustion engine performance.
ASSESSMENT OF PROCESSING CAPACITY OF RAILWAY STATIONS BASED ON STATISTICAL ANALYSIS METHODS
The purpose of the study is to improve the methods of assessing the processing capacity of railway stations based on scientific observation data. The paper considers a large private station that provides transport services to port terminals when performing railway and water transportation. The research is performed based on methods of analysis of time series and theory of operation of railways. The study established the maximum permissible volume of work for the port station and also assessed the impact of the combination of diverse types of goods on the amount of its processing capacity. The scientific novelty of the work is to improve the methods of evaluating the processing capacity of railway stations based on the methods of statistical data analysis. Unlike the existing method, the method allows you to more accurately consider local features of stations. The practical value of the results obtained is that they allow to predict the work of the station in the conditions of accidental flow of port terminals requests for servicing and avoid overload. This enables the station management to develop more efficient strategies for managing its work.
DESIGN AND IMPLEMENTATION OF A REMOTELY SURFACE VEHICLE (RSV EMAS) POWERED BY RENEWABLE ENERGY FOR AUTOMATED WATER QUALITY MONITORING
This paper presents the design, implementation, and field evaluation of RSV Emas, a compact, solar-powered, remotely operated surface vehicle (RSV) developed for autonomous water quality monitoring. The system introduces a novel integration of three key technologies: renewable energy harvesting for extended mission endurance, a fuzzy-PID hybrid control algorithm for adaptive navigation, and embedded piezoelectric actuators for real-time stabilization in dynamic aquatic conditions. RSV Emas is equipped with a multi-sensor suite capable of measuring temperature, pH, turbidity, and total dissolved solids, with data transmitted wirelessly to a remote dashboard. Field experiments in a controlled freshwater pond demonstrate that the vehicle can operate autonomously for over six hours under moderate sunlight, maintain stable trajectory with less than 0.5 m path deviation, and reduce tilt oscillations by up to 38% through smart material-based stabilization. These results confirm that RSV Emas offers a cost-effective, energy-efficient, and scalable platform for real-time water quality assessment, with potential applicability in environmental management and early pollution detection.
PREDICTIVE MODELING OF TRACK QUALITY INDEX WITH NEURAL NETWORKS
The Track Quality Index (TQI) was used as a primary metric to assess the structural and geometric condition of railway track infrastructure, which is directly related to traffic safety, ride comfort, and maintenance prioritization. This paper presents a predictive modeling approach aimed at forecasting future TQI values by incorporating historical measurements, geometric characteristics, and operational parameters. The analyzed dataset consisted of 821 observations of track sections collected over several measurement cycles. It included explanatory variables such as previous TQI levels, train operating speed, traffic volume, and infrastructure elements like tunnels, bridges, and records of ballast tamping. A General Regression Neural Network (GRNN) was trained using 657 data samples and validated on 164 samples, achieving a coefficient of determination (R²) of 0.699, a root mean square error (RMSE) of 4.70, and a mean absolute error (MAE) of 3.55. The results confirmed that neural networks are suitable for short-term predictions of track conditions, facilitating more effective planning and optimization of maintenance interventions. The proposed framework supports engineering decision-making related to condition-based maintenance of railways.