bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of bend stiffeners of a suspended inter-array power cable between two floating offshore wind turbines
Authors: Liu D , Ahmad I , Janocha M J , Nystrøm P , Ong M C
Published: December 2023

The concept of a suspended inter-array power cable assumes that the cable floats within the water column instead of being laid on the seabed. This setup requires additional equipment, such as buoyancy modules or buoys, to achieve the desired cable configuration. The implementation of buoyancy modules introduces abrupt changes in stiffness between the cable sections with clamped-on buoyancy modules and bare cable sections. Large stiffness variations can negatively impact cable bending, causing excessive curvature and fatigue damage. In order to form a smooth transition in stiffness between the buoyancy sections and the bare cable, bend stiffeners can be equipped. The study aims to optimize the bend stiffener design for a representative suspended power cable between two floating offshore wind turbines (FOWTs). The inter-array power cable system is simulated in OrcaFlex. Two parameters, including the outer diameter and the length of the bend stiffener, are adjusted to generate different cases. Eight environmental conditions are applied to the dynamic analysis of the cases. The fitness factor approach is used as a criterion to assess the overall performance of different bend stiffener designs. Adjusting the outer diameter of bend stiffeners clearly influences the maximum effective tension and the minimum bending radius by changing the stiffness profile of the bend stiffener and its submerged weight. In the investigated range of parameters, increasing the overall length of bend stiffeners is found to be less effective than adjusting the outer diameter of the bend stiffener.
Effect of a rotational damper on a moored and articulated multibody offshore system in waves
Authors: Zhang Qi , Moctar Ould el , Jiang Changqing
Published: December 2023

Motions and loads of an articulated and moored floating platform consisting of multiple bodies in waves are investigated through numerical analysis. The wave–structure interaction (WSI) problem is solved using a high-fidelity viscous–flow solver that couples nonlinear rigid body motions, multibody interactions with an internal connection, and mooring dynamics. The study focuses on two modular floating structures (MFSs) connected by a flexible joint, with and without a rotational damper, and positioned using four symmetrical mooring lines. Multibody responses and the corresponding loads acting on the mooring lines and hinged joints are analyzed. Our results reveal that the influence of the damper on heave motions is less significant. Notably, the presence of the rotational damper has a noticeable impact on pitch motions between the two hinged MFSs. Introducing a rotational damper on the flexible joint effectively dampens the highly dynamic pitch motions while not imposing additional loads on the flexible joints.
A parametric study on the initial transverse stability of suspension ships
Authors: Han J , Murai M
Published: December 2023

Suspension ships are a novel type of ships that utilize a suspension system as an integral part of their structure. One critical aspect of a suspension ship is its stability characteristics. The parameters that affect the initial transverse stability of these ships include the ship’s mass ratio, loaded height of suspension, placement location height of suspension, and beam. It is found that designing a suspension ship in monohull configuration is more difficult than in a catamaran configuration. Special attention is required when the static mass ratio is below 2 for both monohulls and catamarans.
Numerical analysis of centrifugal water pump impeller under varying loads
Authors: Yadeta L , Lemu H G , Tadese A K/M
Published: December 2023

Centrifugal pumps are widely used to move liquids from one place to another at varying pressure and flow rate, and to an elevated height for irrigation, water supply plants, and steam power plants. The load variations often lead to unpredictable performance of the impeller. The objective of this study is to investigate the performance of a three-stage centrifugal water pump impeller under varying loads using numerical methods. To conduct the investigation, a water pump used by Jimma town water treatment station, which operates with head of 191 m and discharges 439.2 m3/hr water was used as a case study. Computational fluid dynamics analysis of the pump was conducted using ANSYS 19.0 CFX to get the pressure distribution at different flow rates (60%, 100% and 140% of the design flow rate). The fluid pressure was then used to make static stress analysis of the impeller employing one way fluid structural interaction analysis for three different materials. The finding of the study shows that the fluid pressure on the impeller has great impact on the impeller performance causing high stress and deformation of the impeller.
Design optimization of small fishing vessel structures: A case study
Authors: Putra G L , Rizqillah F , Yatim A , Liu Y
Published: December 2023

The cost of vessel operations poses a significant challenge for fishermen in Indonesia, with 60% - 70% of their operational expenses being allocated to fuel. To address this issue and decrease fuel consumption in fishing vessels, one possible solution is to construct lighter boat designs. Through careful optimization of the construction process and the selection of suitable materials, it becomes feasible to achieve such a lighter design, leading to reduced operational and construction costs. The optimization process involves considering various frame spacing variations, like 400 mm, 500 mm, and 600 mm, and utilizing materials such as mild steel and AH32. Additionally, optimizing the plate thickness ensures that the vessel’s stress and deformation remain within the limits set by the rules. As a result of this optimization, a weight reduction of up to 20% is observed.
Non-linear buckling analysis of ship hull stiffened panels
Authors: Hacihamud E , Dahl K , Gabrielsen O , Lemu H G , Siriwardane S C
Published: December 2023

Stiffened panels are crucial in maritime applications, where buckling is a primary structural failure concern. Typically, assessing the buckling capacity of these panels relies on established guidelines like DNV-RP-C201 and NS-EN 1993-1-5. Alternatively, non-linear finite element methods, guided by DNV-RP-C208, can be used. However, there’s a significant research gap in calibrating buckling capacities for large ship-hull stiffened panels. This paper bridges that gap by employing non-linear finite element analysis to evaluate the buckling capacity of ship hull stiffened panels and compare the results with DNV-RP-C201. It establishes a capacity benchmark by thoroughly comparing results for a plated panel. Subsequently, it develops a validated model using ABAQUS, introducing material and geometric nonlinearities, including a mid-stiffener span imperfection ranging from 0.06% to 1% of the stiffener span length for 99.7% calibration. The validated non-linear model then assesses the impact of holes on buckling capacity under uniaxial and gravity loads, revealing a clear correlation between reduced buckling capacity.
Spatial and temporal crack initiation prediction in steels based on residual stress tensor distribution monitoring
Authors: Mangiorou E , Damatopoulou T , Angelopoulos S , Vourna P , Ktena A , Hristoforou E
Published: December 2023

We have developed a method and the corresponding instruments, able to provide the spatial and temporal determination of crack initiation in ferromagnetic steels and their welds. The method is based on the monitoring of the differential magnetic permeability µr along the length of the steel, since a sigmoid monotonical dependence of µr on residual stresses has been determined in the past. Thus, the magnetic stress calibration (MASC) curves can inform on the localized residual stresses. Therefore, the temporal stress monitoring at different areas of interest can inform about the status of residual stresses. Then, the tendency of the residual stress value can inform about reaching the positive (tensile) or negative (compressive) yield point of the steel. As an example, a quasi-parabolic temporal dependence of µr offers the tendency to determine the time, or the time window, required to reach yield point. This way, the temporal prediction of the crack initiation is provided for the given point in space, since reaching the yield point results in crack initiation.
Experimental assessment of cracked tubular joints repaired with crack-deflecting holes and weld-toe grinding
Authors: Riise S , Atteya M , Mikkelsen O , Ersdal G
Published: December 2023

Tubular joints in offshore structures for energy production are exposed to cyclic loading and may experience fatigue cracking. Presently, the inspection method commonly used for such structures will primarily detect whether a member is flooded, which is an indication of through thickness cracks. As a result, repair methods suitable for repairing through thickness cracks that are cost-effective and quick to implement are needed. One such repair method could be crack arrest by hole drilling. However, the validity of such a repair method is at present not sufficiently proven. Hence, this paper presents the results of an experimental fatigue test of pre-cracked tubular joint repaired with crack-deflecting holes combined weld-toe grinding. One tubular double T joint was tested and underwent three-phases comprising of a pre-cracking phase, a repair phase and a post-repair testing phase. The through-thickness fatigue crack was achieved by subjecting the intact test joint to cyclic axial loading within the high-cycle fatigue domain. In the repair phase, crack-deflecting holes were drilled in front of each crack tip to arrest the crack ends. In addition, the weld-toe behind these holes were grinded to enhance the fatigue life of the repaired joint. The performances of the repaired test joint were then investigated in the last phase by subjecting it to further cyclic loading within the high cycles fatigue domain. In the test, the crack was successfully arrested in the crack-deflecting holes. Furthermore, the repair method indicated an apparent enhancement of the fatigue endurance of the cracked tubular joint when subjected to stress ranges within the high-cycle fatigue domain.
Optimization of the routing problem using the physics-based electromagnetism-like algorithm
Authors: Jao J R , Vallar E A
Published: December 2023

Waste collection is considered as a first objective in planning a sustainable waste management, and provision of substantial collection coverage in urban and rural areas should be satisfied before investing in more sophisticated infrastructure. Therefore, good waste collection service is essential to upgrade further the next levels of a municipal solid waste system. One of the ways to enhance performance on waste collection is to plan effective routing of trucks. The study formulated a Waste Collection Arc Routing Problem to model the waste collection routing problem of Parang, Marikina City. The study revealed that the EM-like with local search and selection strategy mechanism displayed significant minimization abilities of distance values, and the capacity consideration of truck is important to attain better efficiency and cost savings of route.
Bio-inspired design trends for sustainable energy structures
Authors: Regassa Y , Dabasa T , Amare G , Lemu H G.
Published: December 2023

Researchers and engineers are constantly looking to nature for design inspiration as they work to create novel and effective energy conversion structures. Engineers are developing durable and resilient materials to survive extreme weather conditions and environmental issues using inspiration from the Nenuphar’s durability in adverse aquatic environments and the Sunflower’s adaptation to vary climatic situations. The analysis of new design ideas in renewable energy systems in this research was inspired by the Nenuphar (Water Lily) and the Sunflower. The Nenuphar’s exceptional capacity to float and large leaf surface make it a model for enhanced water-based energy conversion systems. Researchers have been looking into novel concepts like floating solar farms and wave energy collecting platforms after being inspired by the Nenuphar’s buoyancy and ability to efficiently use sunlight. Solar panel integration with water features can boost overall energy output while preserving precious land resources. The Sunflower, known for its phototropism and effective sun-tracking mechanism, offers suggestions for improving solar energy harvesting. Advanced heliotropic solar panels have demonstrated promising results in boosting energy production throughout the day by mimicking the Sunflower’s ability to follow the trajectory of the Sun. These designs maximize energy outputs and boost overall system efficiency by maximizing solar exposure. Embracing these bio-inspired concepts can lead to the development of sustainable and efficient energy solutions, contributing to a greener and more sustainable future. Furthermore, the integration of smart technology and artificial intelligence is on the rise to optimize energy conversion structures.
Process parameter modelling and optimization techniques applied to fused deposition modelling: A review
Authors: Batu T , Lemu H G , Shimels H G , Zebenay M
Published: December 2023

Manufacturing is the foundation of any industrialized country and involves making products from raw materials using various processes. Additive manufacturing (AM) was originally created as a method for swift prototyping, allowing the visualization, testing, and validation of a design prior to final production for end-users. FDM is the most commonly used additive manufacturing process for constructing products and prototypes. It encompasses numerous process parameters that impact the quality of manufactured products. Properly selecting these process parameters is crucial for producing products at a lower cost while enhancing mechanical properties, build time, and part quality, among other factors. Therefore, in the past, researchers have optimized the process parameters to achieve the desired product outcomes. In the present study, we provide an overview of FDM process parameters and review various design optimization methods. We present several experimental designs, such as the Taguchi method, response surface methodology, and design of experiments, as well as computational approaches like artificial intelligence, and machine learning.
The influences of international standards on structural performance and fracture behaviour of 3D printed long fiber composite structures
Authors: Akessa A D , Adugna Y W , Tucho W M
Published: December 2023

The material properties of the additive manufactured composite structures are usually done following international standards, that show some difference dimensionally. This study focuses on the impact-induced on the tensile properties of the 3D printed continuous carbon fiber reinforced composite part due to the standards applied for sample preparation. The specimens were fabricated by Markforged® Mark two 3D printing machine using carbon fiber as reinforcement and Onyx® as matrix material based on ASTM D638 and ASTM D3039-D3039M standards. The experimental results revealed that the specimens fabricated based on ASTM D638 showed a premature failure at the location where the straight gauge section of the specimen ends, and the curved transition regions begin due to stress concentration. The tests based on ASTM D3039-3039M standard showed better tensile strength and less stress concentration compared to ASTM D638. Fracture test with SEM reveals fiber breakage, debonding, and fiber pullout, which created cavities and voids between layers as the reasons for the tensile failure.
Triply periodic minimal surfaces based functionally graded biomimetic scaffold fabrication via stereolithography
Authors: Adugna Y W , Lemu H G , Hagland H R
Published: December 2023

Triply Periodic Minimal Surfaces (TPMS), a class of intricate mathematical surfaces, have emerged as a promising framework for scaffold design due to their ability to replicate the complex geometries found in biological structures. Four TPMS structures, the Schwarz Diamond (D), Schwarz Primitive (P), Gyroid, and IWP (I-wrapped package) were designed for both uniform and graded density and additively manufactured through Stereolithography based additive manufacturing (AM) techniques using biomedical graded material. Two different mechanical tests, tensile and compression tests were examined on the TPMS structure to study their mechanical properties. The results showed that Schwarz D and IWP TPMS show greater tensile strength for both uniform and graded structures with 18.22 MPa and 14.41 MPa in uniform structures and 9.89 MPa and 9.23 MPa in graded structures of Schwarz D and IWP respectively. Uniform TPMSs show overall tensile strength over the graded TPMS. Compressive properties also show that Schwarz D and IWP TPMS have greater compressive strength in both uniform and graded TPMS, where overall graded structures show better strength over the uniform. Graded Schwarz D observed to have 100.68 MPa, and IWP TPMS has 99.57 MPa, and uniform Schwarz D has 33.94 MPa, whereas IWP TPMS shows 31.82 MPa compressive strength. Results reinforce the structure’s suitability for scaffold applications, particularly in contexts demanding robust mechanical integrity. The application of SLA AM with biomedical-graded material strengthens the viability in areas like tissue engineering and regenerative medicine.
Fracture toughness analysis of a woven sisal-glass fiber hybrid composite
Authors: Gudeta O K , Tolcha M A , Badasa T D , Koricho E G
Published: December 2023

This experimental work’s goal was to investigate the mode-I fracture toughness behavior of a hybrid composite material made of woven sisal and glass fibers under mode-I loading circumstances to gauge the material’s resistance to fracture behavior. The sisal plant was painstakingly stripped of its fibers. For the sisal fiber surface treatment, 5% NaOH was utilized. Next, treated fibers were weaved by hand to create the woven sisal fiber. Using the hand lay-up technique and the ASTM D5045-99 standard, compact tension specimens were created. The findings indicated that, under mode I loading circumstances, the mode I fracture toughness value of a specimen with a thickness of 5 mm has a (KIC) of 18.34 MPa. m. By determining a material’s resistance to fracture under mode I stress conditions—a condition that is employed in a variety of engineering applications—it is a valuable parameter for developing and establishing preconditions for engineering applications. The manufactured hybrid specimens’ performance and applications for various engineering materials for construction (such as tables, ceilings, and partitions), lightweight vehicle parts (like boards), and replacing synthetic materials with natural fibers in engineering applications were demonstrated by the results of the fracture toughness test.
Assessing impact of borehole field data’s input parameters on hybrid deep learning models for heating and cooling forecasting: A local and global explainable AI analysis
Authors: Ahmed N , Assadi M , Zhang Q , Ahmed A A
Published: December 2023

Achieving accurate performance forecasting of borehole heat exchanger is essential for optimizing ground source heat pump systems, enabling optimal control, and facilitating energy-efficient operations with enhanced sustainability of the built environment. This study aims to investigate and quantify the impact of model architecture, the number of input data sensors, and their accurate identification on multivariate hybrid deep learning models. Moreover, the significance of incorporating a recent development in deep learning to pay selective attention to the input data i.e., attention-based mechanisms in LSTM-CNN and CNN-LSTM architectures is also investigated. The significance of input parameters for the data-driven AI models is assessed through a significance interpretability analysis utilizing Explainable-AI local-method, namely Shapley Additive Explanations and global-explanation methods i.e., permutation feature importance method and Friedman statistical test. The findings highlight the efficacy of attention mechanisms in capturing temporal dependencies in LSTM-CNN-At and spatial patterns in CNN-LSTM-At, may not necessarily enhance their multistep forecasting capabilities for the borehole field data in comparison to LSTM-CNN architecture. The 24 hours ahead forecasting results show that the order of accuracy is LSTM-CNN> LSTM-CNN-At> CNN-LSTM> CNN-LSTM-At. The findings emphasize that by carefully designing the model layers, it is feasible to remove redundant borehole field sensors for data measurement while maintaining the forecasting accuracy of the hybrid data-driven models.
Numerical modelling of a high temperature borehole thermal energy storage system: Norway case study
Authors: Ahmed A A , Assadi M , Gholami R , Ahmed N
Published: December 2023

Global warming is threatening life on earth. Utilising renewable energy is considered as the most effective measure to minimise anthropogenic CO2 emissions. High-temperature borehole thermal energy storage (BTES) systems have a world-wide potential to reduce energy consumption, increase energy utilisation of waste heat and provide efficient seasonal heat storage. Hybrid application of BTES and solar energy leads to net zero emissions. In this study HT-BTES is evaluated for seasonal thermal heat storage and recovery. To this end, a CMG STARS model was built and validated using the existing 100-wells BTES system in Norway. Then, the model was used to evaluate BTES thermal performance and thermal recovery efficiency. Sensitivity analysis was also conducted to study the dynamics of storage temperature in the BTES under different operating conditions, such as heat carrier flow rate, injection temperature, and charging period. Results of this case study show that the model-predicted temperatures during charging and discharging are in good agreement with the existing BTES system. In 5 years of operation, 35.5% of the heat injected into the BTES system was recovered, while the significant heat remained in the borehole region and lost to surrounding rock (64.5%). BTES was found very sensitive to flow rate, the charging period and injection temperature. Borehole depth has a minimal effect on BTES storage temperature at constant studied injection temperature.
Modeling of Stainless Steel Bending Force on CNC Press Brake
Authors: Cinac Hasan , Gredelj Sanel
Published: December 2023

Bending processing is one of the most common plastic deformation processing procedures. It is widely represented in the metal processing industry. In this paper, sheet metal bending on a CNC press with a tool that has two basic parts is analysed: the lower-die and the upper-punch. The sheet metal material is stainless steel, which is one of the most commonly used materials. During the bending process on presses, one of the main challenges is the experimental determination of the bending force. The methodology used in this work is based on the experimental stochastic method, that is, design of experiment. A rotatable plan for three input parameters: material thickness, bending angle and bending line length, are varied at five levels. The output parameter is precisely the bending force. No special devices are needed to measure the bending force as an output parameter, because the bending force is measured and registered on the CNC press via the control panel. After the experiment, using the experimental design matrix, the coefficients of an adequate nonlinear mathematical model were determined. Such a mathematical model is suitable for analysis and optimization of the bending force.
Instrumented microindentation – a versatile technique in the field of wood science and technology
Authors: Petrič Marko
Published: December 2023

Hardness is an important mechanical property of wood or other wood-based materials and it is also very important in the case of wood coatings. Different indentation methods for measurements of hardness and other mechanical properties have been utilised already for a long time. In the last 50 years the instrumented indentation was developed. Here, an indenter tests the surface of a specimen with a controlled load and movement, in order to assess its mechanical properties. Three ranges of instrumented indentation tests are distinguished. In the macro range, the force is higher than 2 N, in the micro range it is below 2 N and the depth of indentation must exceed 0.2 μm. When the indentation depth is lower than 0.2 μm, the indentation technique is called nanoindentation. There can be found thousands of scientific papers about applications of instrumented nanoindentation in research of a large variety of materials. Instrumented microindentation remained somehow in the shadow of nanoindentation, but yet, it is a highly versatile technique with potentials to study various (micro)mechanical properties. In this review, examples of possible applications of instrumented microindentation are presented, with a focus on investigations of wood, wood-based composites, surface coated wood and polymeric films. In the second part of this paper, as an illustration, investigations of a self-healing wood paint are shown. The cyclic method and a single-load indentation confirmed the different mechanical properties and good scratch resistance of the self-healing paint.
Eco-friendly adhesives for wood-based composite production
Authors: Ćehić Minka , Talić Hasan , Eldien Omer Salah
Published: December 2023

In the process of creating composites, especially if we talk about wood-based composites, great attention should be paid on a variety of factors which affect the final composite properties.One of the essential elements is proper adhesive selection. Most common used are synthetic formaldehyde adhesives. We are aware how dangerous emission of free formaldehyde can be; we tend to minimize its usage. Using adhesives which are safe for the environment and humans as well, we tend to find safer composites which are ecologically acceptable and recognized as a better option.The paper briefly describes the adhesives used so far and their dangers, and selects several types of adhesives with basic characteristics that can meet the requirements for the production of ecologically acceptable composite panels, with an emphasis on wood-based composites. Certain tests and achievements in the development of these adhesives are also presented.
Performance of Coconut Wood in Timber Structures: A Review of Its Properties and Applications
Authors: Fathi Leila , Hasanagić Redžo , Bjelić Aldin , Bahmani Mohsen
Published: December 2023

Timber structures have been a popular choice for construction due to their natural and aesthetic appeal. However, with the increasing focus on sustainability and eco-friendliness, alternative building materials are gaining popularity. One such material that has gained attention is coconut wood. Coconut wood is a by-product of the coconut industry and has several unique properties that make it an excellent choice for timber structures. This paper reviews the properties and applications of coconut wood in timber structures and discusses its advantages, limitations, and challenges. We discussed the physical and chemical properties and durability of coconut wood. The average density of coconut palm wood ranges from 0.41-1.11g/cm3, while its moisture content ranges from 50% to 400%. Coconut wood has low shrinkage and swelling rates, reducing the risk of cracking or warping. The holocellulose content is about 67% while the lignin content is approximately 25%. Chemical and natural products, are effective in protecting coconut wood against decay and insect attack. Understanding such characteristics of coconut wood is critical for its optimal utilization in various industries. By employing appropriate preservation techniques and utilizing this versatile and sustainable resource, coconut wood can continue to provide significant benefits for communities and industries around the world.
Numerical analysis of wood beam bending with verification of breaking force
Authors: Kulenović Fatka , Hurem Nedim , Talić-Čikmiš Amra
Published: December 2023

The work represents the continuation of the research of the maximum bending stress force of a wooden beam up to the moment of failure, which is defined experimentally and with a corresponding mathematical model. The goal was to confirm the accuracy of the mathematical model of the breaking force using numerical simulation and the Solid Works software. Five different types of wood and five different beam thicknesses were used as input parameters whose influence was monitored trough the simulation. The stress deformation state and deflection for the calculated fracture forces were analysed separately for each variant. The breaking force model, which is defined depending on the density of the wood and the thickness of the board, proved to be adequate for defining the maximum stresses and deflections when bending beams.
Use of the Lagrange interpolation polynomial to estimate the bending strength value of plywood
Authors: Talić Hasan , Haurdić Melisa , Kulenović Fatka
Published: December 2023

In order to determine the bending strength of wood or wood-based panels, an experimental method is typically used to test samples of different sizes that involves bending or compression. However, such tests are expensive and time-consuming, so mathematical models are often applied that allow predicting the bending strength based on a smaller number of obtained test results. One such model is the Lagrange interpolation polynomial. The study discusses Lagrange’s interpolation model. Using the results of tests done on plywood of various thicknesses, approximates the bending strength of plywood for values that could not be tested directly and provides an estimate of strength for particular values.
Design and FPGA Implementation of Compensator for Sharpening CIC Filter
Authors: Jovanovic Dolecek Gordana , Alejandro Martinez Novelo Gabriel
Published: December 2023

This paper presents a novel compensator design for sharpened CIC (cascade-integrator-comb) proposed in the literature. Sharpened CIC provides higher aliasing attenuation than the CIC filter. However, its passband droop is higher than the corresponding CIC filter and must be compensated. Our motivation was to design a decimator with better compensation than the one proposed in the literature. The proposed decimation filter has two coefficients and six adders. The coefficients are determined using particle swarm optimization (PSO) in MATLAB. Two designs are presented. The first one has two multipliers and six adders. The second is a multiplierless design obtained by presenting optimal coefficients in the signed power-of-two (SPT) form. The proposed design is compared with the design from the literature. The designed compensator is implemented in a field-programmable gate array (FPGA). Details of the implementation are described in the paper.
Adaptive Fuzzy PID Car Control using a Bilateral Teleoperator
Authors: Toroman Amel , Mujčić Aljo
Published: December 2023

This paper investigates the application of Adaptive Fuzzy PID Control in the context of car control using a bilateral teleoperator. A bilateral teleoperator allows the operator to operate a remote car using his own controls and at the same time receive feedback on the car’s condition. The goal of the research is the analysis and comparison of different control methods, including PID controller, Adaptive Fuzzy PID controller, and the use of energy and wave variables of the bilateral teleoperator. The paper presents a car control model by means of a bilateral teleoperator, which was implemented in a simulation environment. Then performance comparisons of different control methods were made. The PID controller was used as the basic method, while the Adaptive Fuzzy PID controller was additionally included to achieve system adaptivity. Also, the use of energy and wave variables of the bilateral teleoperator was additionally investigated. The results of the comparison show that the use of bilateral teleoperator wave variables gave the best response of the control system. The analysis of signal waveforms and frequencies enabled more precise monitoring of the car’s condition and the detection of possible problems or instability in the system. This knowledge can be of great importance for improving the performance of car control by means of a bilateral teleoperator.
How fragile are buildings in Bosnia and Herzegovina once exposed to earthquake motion?
Authors: Ademović Naida
Published: December 2023

The 2020 earthquakes that hit the Croatian capital city Zagreb and Petrinja revealed the (un)preparedness of the country once exposed to strong earthquake motion. Three years after, numerous buildings out of 25,000 that have been heavily damaged and destroyed still have not been reconstructed. The effect of the earthquake was felt as well in the bordering cities and towns in Bosnia and Herzegovina (BIH). Seismic assessment of the existing buildings in BIH is done by individual researchers and there is no defined methodology not policy for such activities. This paper aims to present the work that has been done in this field up to now and to give guidelines for the further work that needs to be conducted. The starting point was the calculation of the earthquake risk for the entire Bosnia and Herzegovina based on the rapid assessment taking into account the vulnerability of buildings, seismic hazard, and population exposure. A more detailed assessment was conducted for the three largest cities in BIH, specifically Sarajevo, Banja Luka, and Tuzla. Typical residential masonry structures were identified, and detailed calculations were conducted, leading to the need for their strengthening. To have a more detailed picture much work has to be conducted.
Spalling of concrete caused by ASR – a review
Authors: Džidić Sanin , Bidžević Irfan
Published: December 2023

A very well-known fact is that cracks in concrete members can allow water to enter the member, thus jeopardizing the concrete member integrity by changing the chemical composition of concrete and causing the aggregates to expand. This initiates the consequent chemical reactions that may evoke spalling of concrete thus creating a cycle of undesirable occurrences in concrete. As a final result, the concrete member can be deteriorated affecting the serviceability, but sometimes even leading the reduction of its load bearing capacity. An overlooked cause of concrete spalling of a chemical nature is the spalling caused by the Alkali-aggregate reaction. This is colloquially known as “concrete cancer”. It is a specific type of a reaction between alkali hydroxides and specific types of aggregate that occurs in concrete. Two main types of alkali-aggregate reactions are the alkali-silica reaction (ASR) and the alkali-carbonate reaction (ACR). The main goal of this research was to review the alkali-silica reaction in concrete as well as the mechanism of aggregate expansion it causes, which ultimately results in concrete spalling. Finally, the ways of prevention the alkali-silica reaction were reviewed and discussed.
Estimation of channel and flood plain roughness using HEC-RAS model: A case study of the Veseočica River, Bosnia and Herzegovina
Authors: Milišić Hata , Hadžić Emina
Published: December 2023

Modeling flow in open channels is essential for determining channel capacity and predicting flood events. The key segment for creating flood hazard and risk maps is a high-quality hydraulic model of the flow in the main bed with its tributaries. Several software packages have been developed for hydrodynamic simulations of flood events. In addition to the geometric characteristics of the watercourse, the equations of a one-dimensional flow model include a parameter that connects all influences that provide resistance to the flow of water. Determining the roughness of a natural channel is one of the most demanding procedures for the development of hydraulic models. Therefore, it is necessary to calibrate and validate the Manning coefficients of the channel roughness using simulation models. In the present study, the estimation of channel and floodplain roughness for the Veseočica River in Bosnia and Herzegovina was performed using the HEC-RAS hydrodynamic model. After calibration and verification of the model, flood hazard maps were created for flood waves with return periods of 20, 100, and 500 years. ArcGIS and HEC-GeoRAS software tools were used to create the flood risk maps.
Cell viability prediction and optimization in extrusion-based bioprinting via neural network-based Bayesian optimization models
Authors: Mohammadrezaei Dorsa , Podina Lena , Silva Johanna De , Kohandel Mohammad
Published: December 2023

The fields of regenerative medicine and cancer modeling have witnessed tremendous growth in the application of 3D bioprinting. Maintaining high cell viability throughout the bioprinting process is crucial for the success of this technology, as it directly affects the accuracy of the 3D bioprinted models, the validity of experimental results, and the discovery of new therapeutic approaches. Therefore, optimizing bioprinting conditions, which include numerous variables influencing cell viability during and after the procedure, is of utmost importance to achieve desirable results. So far, these optimizations have been accomplished primarily through trial and error and repeating multiple time-consuming and costly experiments. To address this challenge, we initiated the process by creating a dataset of these parameters for gelatin and alginate-based bioinks and the corresponding cell viability by integrating data obtained in our laboratory and those derived from the literature. Then, we developed machine learning models to predict cell viability based on different bioprinting variables. The trained neural network yielded regression

R
2

value of 0.71 and classification accuracy of 0.86. Compared to models that have been developed so far, the performance of our models is superior and shows great prediction results. The study further introduces a novel optimization strategy that employs the Bayesian optimization model in combination with the developed regression neural network to determine the optimal combination of the selected bioprinting parameters to maximize cell viability and eliminate trial-and-error experiments. Finally, we experimentally validated the optimization model’s performance.
A vascularized 3D model of the human pancreatic islet for ex vivo study of immune cell-islet interaction
Authors: Bender R Hugh F , O’Donnell Benjamen T , Shergill Bhupinder , Pham Brittany Q , Tahmouresie Sima , Sanchez Celeste N , Juat Damie J , Hatch Michaela M S , Shirure Venktesh S , Wortham Matthew , Nguyen-Ngoc Kim-Vy , Jun Yesl , Gaetani Roberto , Christman Karen L , Teyton Luc , George Steven C , Sander Maike , Hughes Christopher C W
Published: December 2023

Insulin is an essential regulator of blood glucose homeostasis that is produced exclusively by β cells within the pancreatic islets of healthy individuals. In those affected by diabetes, immune inflammation, damage, and destruction of islet β cells leads to insulin deficiency and hyperglycemia. Current efforts to understand the mechanisms underlying β cell damage in diabetes rely on in vitro-cultured cadaveric islets. However, isolation of these islets involves removal of crucial matrix and vasculature that supports islets in the intact pancreas. Unsurprisingly, these islets demonstrate reduced functionality over time in standard culture conditions, thereby limiting their value for understanding native islet biology. Leveraging a novel, vascularized micro-organ (VMO) approach, we have recapitulated elements of the native pancreas by incorporating isolated human islets within a three-dimensional matrix nourished by living, perfusable blood vessels. Importantly, these islets show long-term viability and maintain robust glucose-stimulated insulin responses. Furthermore, vessel-mediated delivery of immune cells to these tissues provides a model to assess islet-immune cell interactions and subsequent islet killing—key steps in type 1 diabetes pathogenesis. Together, these results establish the islet-VMO as a novel, ex vivo platform for studying human islet biology in both health and disease.
Exploration of Cd1−xZnxSe as a window layer for CIGS based solar cell with PEDOT: PSS as back surface field layer
Authors: Islam Md Samiul , Rashid Mohammad Junaebur , Akhtaruzzaman Md , Takashi Suemasu , Kazmi Jamal , Karim Mohammad R , Alnaser Ibrahim A , Sobayel K
Published: December 2023

This research investigates the potential of Cd1−xZnxSe thin film for photovoltaic applications. The electrical behavior of CIGS based solar cell is examined with the novel Cd1−xZnxSe as buffer layer material by Solar Cell Capacitance Simulator (SCAPS). The tunability of Cd1−xZnxSe facilities to reduce the defects between absorber and buffer layer by determining the ideal conduction band offset. It is revealed that cross-over occurs between the p-type absorber and the metal back contact if the metal work function is below 4.6 eV. In this research, a thin PEDOT: PSS back surface (BSF) layer was integrated which enhances the device efficiency from 22.5 percent to 28.32% while retaining the metal work function at 5.1 eV. The trade-off between the use of metal having higher work function and inclusion of heavily doped BSF layer is one of the important findings of this research. These findings pave the way for Cd1−xZnxSe to be commercially used as a buffer layer material for CIGS solar cell.
Comparative performance of machine learning models for the classification of human gait
Authors: Thakur Divya , Lalwani Praveen
Published: December 2023

The efficacy of human activity recognition (HAR) models mostly relies on the characteristics derived from domain expertise. The input of the classification algorithm consists of many characteristics that are utilized to accurately and effectively classify human physical activities. In contemporary research, machine learning techniques have been increasingly employed to automatically extract characteristics from unprocessed sensory input to develop models for Human Activity Recognition (HAR) and classify various activities. The primary objective of this research is to compare and contrast several machine learning models and determine a reliable and precise classification model for classifying activities. This study does a comparison analysis in order to assess the efficacy of 10 distinct machine learning models using frequently used datasets in the field of HAR. In this work, three benchmark public human walking datasets are being used. The research is conducted based on eight evaluating parameters. Based on the study conducted, it was seen that the machine learning classification models Random Forest, Extra Tree, and Light Gradient Boosting Machine had superior performance in all the eight evaluating parameters compared to specific datasets. Consequently, it can be inferred that machine learning significantly enhances performance within the area of Human Activity Recognition (HAR). This study can be utilized to provide suitable model selection for HAR-based datasets. Furthermore, this research can be utilized to facilitate the identification of various walking patterns for bipedal robotic systems.
Renewable energy planning in Africa: robustness of mean and extreme multi-model climate change patterns in solar PV and wind energy potentials
Authors: Larsen Morten Andreas Dahl , Bournhonesque Jean , Thiery Wim , Halsnæs Kirsten , Hattermann Fred F , Hoff Holger , Salack Seyni , Adenle Ademola , Liersch Stefan
Published: December 2023

Increasing renewable sources in the energy mix is essential to mitigate climate change, not least in countries where the energy demand is likely to rise over the coming decades to reduce or even skip durations of time where fossils dominate. For Africa, solar photovoltaic (PV) and inland wind energy, combined with hydropower, provide significant and untapped potentials, whereas trends and robustness measures need further investigation. This study aims to gain insight into distributed trends in solar PV and wind energy potentials over Africa. This study employs relevant metrics, including relative change, model agreement, robustness, bias, and absolute levels for every available model combination and two climate scenarios, with energy planning purposes in mind. The study finds that regional climate models were the primary control of spatio-temporal patterns over their driving global climate model. Solar PV potentials show more coherence between models, a lower bias and general high potentials in most African regions than wind potentials. Favourable locations for inland wind energy include mainly the regions of greater Sahara and the Horn region. For wind and solar potentials combined, scattered locations within Sahara stand out as the most favourable across scenarios and periods. The analysis of minimum energy potentials shows stable conditions despite low potentials in certain regions. The results demonstrate a potential for solar and wind power in most of the African regions and highlight why solar and wind power or synergies of energy mix should be considered for local energy planning and storage solutions.
Building-Integrated Concentrating Photovoltaics based on a low-toxicity photopolymer
Authors: Lloret Tomás , Morales-Vidal Marta , Nieto-Rodríguez Belén , Carlos García-Vázquez José , Beléndez Augusto , Pascual Inmaculada
Published: December 2023

Low-toxicity solar concentrator systems represent an important challenge for outstanding photovoltaic (PV) applications. Particularly, multiplexed holographic lenses (MHL) as Holographic Solar Concentrators (HSC) provide insight into promising possibilities for Building-Integrated Concentrating PVs. This technology does not affect crucial ecosystems, and can convert buildings from energy consumers into energy suppliers. They can be used in windows, roofs, or walls, and a high diffraction efficiency and wide acceptance angle are desired. In this work, we presented several designs of MHL of low spatial frequency 525 lines mm−1, based on a low-toxicity photopolymer and supported on a window glass. The average diffraction efficiency of these HSC was evaluated at 633 nm, whereas the acceptance angle was evaluated by measuring the short-circuit current under solar illumination at different incident angles. Versatile and high-efficiency holographic elements have been used to concentrate sunlight from different relative positions during the day, avoiding the need for expensive tracking systems. To the best of our knowledge, this is the best trade-off between high diffraction efficiency (85

%

) and wide acceptance angle (104∘) in a low-toxicity holographic solar concentrator.