National University of Civil Engineering

The impact of antibiotic residues on human health and the environment has become a serious global concern. Scientists are developing new technologies to remove antibiotic pollutants from water, wastewater, and soil. This study presents an effective method for removing antibiotic residues from sewage using Cu-doped TiO₂ photocatalyst (Cu-TiO₂). Ciprofloxacin antibiotic residue (CFA) was selected as the model pollutant for this investigation due to its common use in the healthcare system. The result showed that Cu-TiO₂ effectively removes 94.1% and 85.7% of CFA from wastewater under solar and visible light, respectively. According to the Langmuir-Hinshelwood model, Cu-TiO₂ degrades CFA faster than TiO₂, with a half-life of 14.7min, whereas TiO₂ has a half-life of over 69min. Besides, the doped photocatalyst also presented high reusability, retaining 74.6% CFA degradation efficiency after five cycles and releasing less than 1.8% of Cu ions. Furthermore, this study investigated the effectiveness of the Cu-TiO₂ photocatalyst in mitigating health risks associated with antibiotic-resistant bacteria and evaluated its practical application.

Bitumen, the primary binder in asphalt concrete, lacks sufficient resistance to prolonged mechanical and environmental stress. To improve its durability, styrene-butadiene polymers are commonly used, although they are prone to oxidative degradation and phase instability. This study proposes a nanostructured approach to enhancing the stability and performance of polymer-modified bitumen (PMB) through the synergistic use of multiwalled carbon nanotubes (MWCNTs) and hydrocarbon plasticizers-specifically, selective oil refining extracts (SORE) and vacuum distillates (VD). Short-term oxidative degradation was assessed using isothermal RTFOT aging at 153, 163, and 173 °C. A classical first-order Arrhenius kinetic model was applied, with dynamic viscosity serving as a rheological proxy for SBS network integrity. Nanomodified compositions exhibited a 6-7-fold reduction in degradation rate constant (from 13.97 × 10⁻⁵ to 1.98 × 10⁻⁵ s⁻¹) and a 25-60% decrease in the preexponential factor, indicating suppressed molecular mobility and enhanced network cohesion. Performance was validated on SMA-16 specimens, showing up to 240% improvement in shear adhesion at 50 °C and 27% higher water resistance. Rutting resistance also increased, with rut depth reduced to 1.6–1.8 mm after 20,000 loading cycles. To integrate physical, mechanical, and durability characteristics, a set of Partial Quality Criteria (PQC) was developed and used to calculate a Generalized Effectiveness Coefficient (GEC), supporting multi-criteria optimization of asphalt mixtures. These findings confirm that nanostructured dispersed systems based on MWCNTs and hydrocarbon carriers not only delay oxidative degradation but also ensure multifunctional performance gains critical for high-traffic pavement applications.

Purpose To enhance the efficiency of personnel assignment in layout operations, this study employs 0–1 integer programming optimization theory, integrated with practical layout operations in steel structure construction, to assign manpower under known constraints to find the optimal personnel assignment and minimal cost and to provide management decision-makers with an effective way to control operational costs. Design/methodology/approach The research considers constraints such as personnel availability and part types, constructing a mathematical model with one objective function and 11 constraints. By applying this model to a real-world project for constructing a technology factory and using LINGO 18.0 software, the study demonstrates that optimizing personnel assignment can reduce total costs by 12.82% and manual assignment time by 99%. Findings The findings also elucidate the following: (1) Sensitivity analysis indicates that decreasing the number of working days slightly increases total operational costs, whereas extending the duration to 30–40 days results in cost reductions. Furthermore, reducing high-efficiency and high-salary personnel has a minor impact on overall costs, while cutting low-efficiency and low-salary personnel leads to a substantial cost increase of approximately 50–52%. (2) Efficient and rapid personnel assignment contributes to achieving minimal operational costs, with a cost reduction of 12.82%, while also facilitating the attainment of project goals in the most effective manner. Originality/value The study developed a mathematical model featuring a single objective function and 11 practical constraints, providing practitioners with the flexibility to adapt it as needed to address empirical engineering challenges related to personnel layout assignments.

The advancement of concrete 3D printing in construction necessitates a thorough study of factors affecting interlayer adhesion, as it directly impacts the strength and durability of printed structures. The lack of sufficient data on the influence of mixture workability, aggregate type and ratio, and curing time limits the optimization of process parameters. Addressing these gaps will improve the quality of 3D-printed structures, expand their applications, and reduce defect risks. This study is crucial for the further development of additive manufacturing in construction, providing a scientific basis for refining printing methods. The aim of this work is to investigate the effects of fine-grained concrete mixture workability, sand fineness modulus, process interruption time, and curing duration on interlayer adhesion in additive construction. The results reveal key dependencies of interlayer bond strength on mix design and process factors: workability, sand fineness modulus, and curing duration under varying process interruptions. Optimal parameters for maximum interlayer bond strength in 3D-printed structures include a workability grade of Pk=3 and a sand fineness modulus of Mk=3. The observed effects are primarily attributed to chemical, diffusion, and adsorption adhesion mechanisms, with mechanical interlocking playing a secondary role. The findings indicate that the key approach to enhancing interlayer adhesion in additive construction lies in optimizing mixture composition, which governs hydration kinetics and material structure formation.

A calculation methodology and analytical model are presented for determining deformation parameters and crack width in eccentrically compressed reinforced concrete elements subjected to combined compression and torsion. The analytical relationships are derived using static equilibrium equations under the simultaneous action of torsional moment and eccentric loading, taking into account the deformation effect proposed by Vl.I. Kolchunov. The physical essence of this effect lies in the fact that upon failure of the tensile concrete and crack formation, the crack opening displacements are restrained by the reaction of the reinforcing bar, resulting in a nonlinear curvature of the crack profile. This phenomenon is accounted for in the analytical relationships when determining the relative mutual displacements of concrete and reinforcement between two adjacent cracks. Using the derived analytical relationships, the crack width in a lightly reinforced eccentrically compressed concrete element under combined compression and torsion is calculated. The computational results are compared with experimental data obtained from testing structural elements under the considered stress state, as well as with results from design methods specified in Russian and international standards. It is shown that the proposed analytical relationships satisfactorily reflect the quantitative values of experimentally measured crack widths in reinforced concrete elements under the given complex stress state.

This paper investigates approaches to mitigating staff shortage in maintenance of real estate properties of the urban economy. The role of the institute for vocational guidance of citizens is considered. Reasons for staff shortage on the labor market are discussed, including in the fields of the severely afflicted professions, including qualified workers, middle-ranking workers, and high university degree specialists corresponding to the present stage of economic development. The statement about the prestige of professions in the sphere of housing and communal services is proved to be unreasonable. The multidisciplinary nature of such an activity as derived from the use of buildings is discussed. The methods of vocational guidance to children, pupils, students, and adults as one of the priority areas of state policy are characterized. Best practices of vocational guidance, i.e., federal and regional projects and events contributing to the elimination of current staff shortage of workers in maintenance of real estate properties of the urban economy, are presented. In this paper, the authors set tasks for the professional community concerning prospects for the upcoming development of vocational guidance taking into account the technological, global, and social challenges.

This study presents the first comprehensive simulations of dynamic flows past a permeable semi-circular cylinder, exploring wide parameter space of porosity (10−4–0.8) and angle of attack (0°–180°) at a Reynolds number of 150. Employing lattice Boltzmann method with block-structured mesh refinement, we utilized a high-resolution Cartesian grid to correlate the complex vortex structures to fluid mechanics. Five distinct flow regimes were identified as overshoot (labeled as OS), overshoot-primary (OP), primary–meandering (PM), primary-two-layered (PT), and primary-two-layered-secondary (PTS). These regions are distributed within the variation of porosity and angle of attack, revealing a systematic transition in wake dynamics. The OS region occurs at high porosity, characterized by double elongating vortex structures. Otherwise, the PM region appears at moderate porosity and low or high angles of attack, indicating oscillatory behavior of wake vortex. In particular, the PTS region is observed at low or high angle of attack, indicating identical wake patterns to those of rigid semi-circular cylinder. The angle of attack significantly influences the time-averaged drag coefficient map, showing its symmetric distribution around the angle of attack of 90°, with the PTS regime having the highest drag coefficient. The Strouhal number peaks in the OP and PT regimes, signifying the angle of attack's role in the stretching of upper and lower shear layers, which leads to the highest frequency of primary vortex shedding. An increase in the porosity coefficient delays the transition of primary-two-layered-secondary vortex shedding modes.

Modular construction (MC) is increasingly recognised as a viable solution to the growing need for affordable, sustainable social housing, especially in rapidly urbanising countries like Vietnam. Despite its potential benefits in terms of construction speed, waste reduction, and quality control, the uptake of MC in Vietnam remains limited. This study identifies and evaluates 22 barriers and 12 drivers of MC adoption in the Vietnamese social housing sector, drawing on survey data from 256 construction professionals representing five key stakeholder groups: clients, contractors, consultants, policymakers, and academics. Statistical analyses, including reliability testing, mean score ranking, and ANOVA, reveal significant divergence in stakeholder perceptions. The results indicate that the most critical barriers, including the lack of experience among suppliers and designers, inflexible design processes, and high upfront investment costs. In addition, key drivers identified, including early design finalisation, dimensional standardisation, pilot projects, and international knowledge transfer. Based on the findings, the study proposes tailored policy implications for key stakeholders. Policymakers should mandate BIM for MC projects, offer financial incentives, and establish R&D centres to foster innovation. Contractors and consultants are encouraged to adopt BIM comprehensively and engage in pilot MC projects to strengthen technical capacity. Clients and developers would benefit from access to benchmarking data and international partnerships to reduce perceived risks. Educational and research institutions should introduce targeted training and innovation hubs to bridge skill gaps. These recommendations offer a practical roadmap for advancing MC in sustainable social housing development in Vietnam and similar contexts.

Hiện nay, việc thiết kế và thi công các công trình nhà bê tông cốt thép ven biển ở Việt Nam áp dụng các tiêu chuẩn TCVN 9346:2012, TCVN 12041:2017, và TCVN 12251:2020 để đáp ứng các yêu cầu về bảo vệ chống ăn mòn cốt thép, đồng thời sử dụng TCVN 5574:2018 để tính toán dự báo chiều rộng vết nứt. Tuy nhiên, một số quy định trong TCVN 9346:2012, TCVN 12041:2017, và TCVN 12251:2020 còn có nhiều vấn đề bất cập, khá khắt khe trong mối tương quan với các quy định của các tiêu chuẩn quốc tế. Do đó, bài báo này sẽ tổng hợp so sánh các quy định về bảo vệ chống ăn mòn cốt thép cho các công trình bê tông cốt thép ven biển theo các tiêu chuẩn Việt Nam, Mỹ, và Châu Âu nhằm làm rõ hơn sự tương đồng và khác biệt giữa các tiêu chuẩn. Trong bài báo cũng sẽ tổng hợp các các phương pháp tính toán và kiểm soát chiều rộng vết nứt giữa các tiêu chuẩn liên quan, từ đó thực hiện ví dụ tính toán để đưa ra nhận xét so sánh.

Quadruped robots are increasingly favored for their ability to handle uneven terrain where wheeled robots fall short. This study presents a compact, low-cost quadruped robot designed for educational and research purposes, featuring high-torque servo motors and joints optimized for flexibility and space efficiency. A dual-layer operating system integrating multithreading and multiprocessing enables smooth coordination. An experimental prototype confirms the design's practicality in teaching and integrated technology research.