Abstract: Robotic construction using 3D concrete printing (3DCP) offers significant potential to transform Kuwait’s construction industry, particularly in reducing waste. This study explores the feasibility of integrating 3DCP into Kuwait's construction waste management practices by examining the perspectives of key stakeholders. Through a mixed method approach of a comprehensive literature review, a survey of 87 industry professionals, and 33 in-depth interviews with representatives from the Public Authority for Housing Welfare (PAHW), Municipality, private sector, and the general public, the study identifies both the benefits and challenges of 3DCP adoption. The findings highlight key advantages of 3DCP, including increased construction efficiency, cost savings, enhanced design flexibility, and reduced material waste. However, several barriers such as regulatory limitations, technical challenges in adapting 3DCP to local project scales, and cultural resistance must be addressed. Results also indicate varying levels of stakeholder familiarity with 3DCP and existing waste management practices, underscoring the need for awareness and educational initiatives. This study makes two significant contributions: first, by providing a detailed analysis of the technical and regulatory challenges specific to Kuwait’s construction sector; and second, by offering a strategic roadmap for 3DCP integration, including regulatory reform, research into sustainable materials, and cross-sector collaboration. These recommendations aim to enhance waste management practices by promoting more sustainable and efficient construction methods by achieving SDGs 9, 11, 12, and 13. The study concludes that government support and policy development will be essential in driving the adoption of 3DCP and achieving long-term environmental benefits in Kuwait’s construction industry.

Abstract: Space structures are perhaps the most complicated man-made structures due to their extremely harsh and complex operational environments. For these structures, materials serve as crucial technology drivers. Composite materials are increasingly used in space structures due to their specific mechanical properties, customizability, and ability to easily acquire multifunctional and smart characteristics. This review critically examines the state-of-the-art in composite materials application and the computational models used to design and analyze composite space structures.

Abstract: This article investigated Ta-Cu and Nb-Cu coatings deposited via magnetron sputtering from metal targets with varying copper content. Scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS) revealed that the coatings had an average thickness of 2.5 μm, with a Cu composition of approximately 10 wt.% and Ta exceeding 86%, with the remaining percentages attributed to carbon and oxygen from the residual vacuum chamber atmosphere. It was observed that increasing the coating thickness from 2.5 μm to 8.5 μm did not result in a significant change in nanohardness (3.29 GPa) in Nb-Cu coatings, although the elastic modulus increased by 15% (from 81 to 95 GPa). Ta-Cu coatings demonstrated superior antibacterial properties compared to Nb-Cu coatings. Consequently, Ta-Cu coatings exhibit considerable potential for further applications due to their favorable structural properties and enhanced antibacterial efficacy.

Abstract: Small Autonomous Surface/Underwater Vehicles (S-ASUV) are gradually attracting attention from related fields due to their small size, low energy consumption, and flexible motion. Existing dynamic positioning(DP) control approaches suffer from chronic restrictions that hinder adaptability to varying practical conditions, rendering performance poor. A new three-dimensional (3D) dynamic positioning control method for S-ASUV is proposed to tackle this issue. Firstly, the dynamic model for the DP control problem considering the thrust allocation is established by deriving from the dynamic models of S-ASUV. A novel Lyapunov-based model predictive control (LBMPC) method is then designed. Unlike the conventional LMPC, this study uses multi-variable PID as the secondary control law, improving the accuracy and rapidity of the control performance significantly. Both the feasibility and stability are proved rigorously. A series of digital experiments using S-ASUV’s model under diverse conditions demonstrate the proposed method's advantages over existing controllers, affirming satisfactory performances for 3D dynamic positioning in complex environments.

Abstract: The construction industry faces persistent inefficiencies, with projects often failing to meet time, cost, quality and other conditions of satisfaction. This study investigates real estate owners’ early perceptions of Lean Integrated Project Delivery (Lean IPD) as a potential solution, analysing the acceptance of principles such as early stakeholder involvement, risk-reward compensation, and open-book accounting among other key features in Lean IPD. A survey of 62 professionals in Real Estate development compa-nies in Spain was conducted, analyzing their experience with collaborative contracts and Lean techniques, including Last Planner System and Target Value Design. Statis-tical methods such as hierarchical clustering and PLS-SEM modeling revealed two dis-tinct groups: those receptive to Lean IPD’s economic mechanisms and those less in-clined. While governance principles like early collaboration and team co-responsibility received widespread support, skepticism was noted toward economic transparency practices due to cultural and structural barriers. Additionally, the findings indicate a significant gap in formal training for Lean IPD. Despite challenges, there is strong in-terest in adopting Lean IPD, driven by its potential to address critical project ineffi-ciencies. The study concludes that successful Lean IPD implementation requires stra-tegic leadership from owners, targeted training programs, and a cultural shift within the industry to embrace collaborative and transparent practices.

Abstract: NiOx is a p-type semiconductor with excellent stability, which make it interesting for a wide range of applications. Broadband photodetectors with high responsivity (R) were fabricated by depositing r.f. sputtered NiOx layers on n-Si at room temperature (RT), 50 oC and 100 oC. In self-powered mode the RT diodes have R between 0.95 and 0.39 A/W for wavelengths between 365 and 635 nm, while at a reverse bias of -4V the responsivity increases to values between 22 A/W and 10.7 A/W for wavelengths in the same range. The increase of the deposition temperature leads to a decrease of R but also to a smaller reverse dark current. Thus, the 100 oC photodiodes might be more appropriate for applications where high responsivity is required, because of their smaller power consumption compared to the RT diodes. In addition, it was found that the increase of the deposition temperature leads to an increase of the diodes series resistance and the resistivity of NiOx. The effect of Rapid Thermal Annealing (RTA) on the properties of the photodiodes was studied. Annealing at 550 oC for 6 min leads to much higher responsivity compared to R of diodes with as-deposited NiOx. However, a disadvantage of the annealed diode is that the reverse current depends on the amplitude and polarity of previously applied bias voltage. The very high responsivity of the RTA photodiodes makes them useful as light sensors.

Abstract: The research of this paper was carried out on the low-temperature (100 ± 2 ◦C) pressure leaching of pyrite and chalcopyrite in their mixture. The resulting mathematical models of chalcopyrite and pyrite dissolution in their mixture, depending on the effect of oxygen pressure, initial concentration of sulfuric acid, concentrations of iron (III) and copper (II) ions and duration are obtained. According to kinetic analysis the oxidation process of chalcopyrite and pyrite proceeds with intra-diffusion limitations. The process is limited by the diffusion of reagents through the solid reaction product layer. According to the SEM and EDX mappings, the surface of chalcopyrite and pyrite particles is passivated by an elemental sulfur film. Analysis of the data allows us to conclude that the oxidation mechanism of chalcopyrite and pyrite in their mixture has changed. This is evidenced by the increase in the activation energy values: from 51.2 up to 59.0 kJ/mol for chalcopyrite and from 50.6 up to 74.6 kJ/mol for pyrite, respectively. The oxidation degree of pyrite in its mixture with chalcopyrite increased significantly from 54.5 up to 80.3% in 0–230 min. The increase in the dissolution degree of pyrite with the addition of chalcopyrite is not associated with an increase in the concentration of copper (II) and iron (III) ions during oxidation, since their effect on the degree of opening of minerals was insignificant, including for the mixture. The positive effect on the oxidation degree of pyrite in its mixture with chalcopyrite can be explained by the formation of an electrochemical bond between the minerals. The positive effect of the chalcopyrite additive is associated with a decrease in elemental sulfur formation on the pyrite surface, which is confirmed by the data of microphotographs and EDX mapping. The elemental sulfur distribution on minerals becomes more uniform with no formation of conglomerates, which also confirms their interaction with each other.

Abstract: The aim of this study was to clarify the impact of thickness of Pd/Cu membrane on the characteristics of biogas dry reforming (BDR) using Ni/Cr/Ru catalyst. In addition, this study also clarified the impact of reaction temperature, the molar ratio of CH4:CO2, the differential pressure between the reaction chamber and the sweep chamber, and the introduction of a sweep gas on the characteristics of BDR reactor using Pd/Cu membrane and Ni/Cr/Ru catalyst. As a result, this study revealed that the concentration of H2 in the reaction chamber and that in the sweep chamber increased with the increase in the reaction temperature. In addition, this study revealed that the highest concentration of H2 in the reaction chamber and that in the sweep chamber were obtained for the molar ratio of CH4:CO2 = 1.5:1. This study also clarified that the highest concentration of H2 was obtained for the thickness of 40 m, the molar ratio of CH4:CO2 = 1.5:1 and the differential pressure between the reaction chamber and the sweep chamber of 0 MPa without a sweep gas, which was 4890 ppmV in the reaction chamber and 38 ppmV in the sweep chamber, respectively. Under this condition, CH4 conversion, H2 yield and thermal efficiency were 75.0 %, 0.214 % and 2.92 %, respectively.

Abstract: Energy optimization of historic buildings is often perceived as a threat to their cultural values. This paper examines this assumption. Firstly, we assess the actual energy performance of historic apartment buildings in Denmark using a register-based approach with 20,000 historic apartment buildings of high preservation value. Secondly, we explore the potential for energy improvements in historic buildings by analyzing typical interventions that have been implemented to achieve an EPC label C. Thirdly, we discuss whether these interventions pose a threat to the preservation values of historic buildings and how local authorities might address this challenge. We present three examples of energy optimization in historic apartment buildings, ranging from step-by-step renovations to larger renovations and transformations of historic buildings. The study finds that historic apartment buildings perform at least as well as traditional buildings from the same period in terms of energy efficiency, and there is significant potential for further improvements. However, there are large variations across different types of municipalities. Finally, we observe that most interventions are based on conventional solutions with limited impact on preservation values. We discuss how more radical interventions can be managed through dialogue between local authorities, building owners, and consultants.

Abstract:

Double-helical gear is combined with the left and right-handed helical gears with the same twist angle, which smoothly transmits power between two parallel shafts on heavy loads for reduced noise and vibration operation. The helix angles influence the stress and deformation of double-helical gears before structural failures or breakdowns. Thus, variations in helix angles can result in wear, fatigue, increased stress, misalignment, and uneven load distributions. In this study, we modelled double-helical gear using SolidWorks software. By applying ANSYS 23.0, the effcets of helix angles on the stress distribution and overall performance were investigated. The evaluated data from both the ANSYS and AGMA (American Gears Manufacturing Association) approaches were compared, and this comparison achieved the result of a decrease in stress and strain with an increase in helix angle along the wider face width. At a helix angle of 30° and a constant value of face width, the stresses were found to be 1.4491 MPa and 1.5346 MPa for pressure angles of 20° and 14.5°, respectively, in ANSYS. After the comparison, discrepancies of 0.287% and 6.204% were identified between the evaluated stresses from the ANSYS and AGMA standards.