Search Results (1,738)

The self-starting capability of straight-bladed H-type Darrieus Vertical Axis Wind Turbines (VAWTs) remains a major constraint for deployment, particularly in urban, low speed, and turbulent environments. We conducted a systematic review of technological strategies to improve self-starting, grouped into five categories: (1) aerodynamic airfoil design, (2) rotor configuration, (3) passive flow control, (4) active flow control, and (5) incident flow augmentation. Searches in Scopus and IEEE Xplore (last search 20 August 2025) covered the period from 2019 to 2026 and included peer-reviewed journal articles in English reporting experimental or numerical interventions on H-type Darrieus VAWTs with at least one start-up metric. From 1212 records, 53 studies met the eligibility after title/abstract screening and full-text assessment. Data were synthesized qualitatively using a comparative thematic approach, highlighting design parameters, operating conditions, and performance metrics (torque and power coefficients) during start-up. Quantitatively, studies reported typical start-up torque gains of 20–30% for airfoil optimization and passive devices, about 25% for incident-flow augmentation, and larger but less certain improvements (around 30%) for active control. Among the strategies, airfoil optimization and passive devices consistently improved start-up torque at low TSR with minimal added systems; rotor-configuration tuning and incident-flow devices further reduced start-up time where structural or siting constraints allowed; and active control showed the largest laboratory gains but with uncertain regarding energy and durability. However, limitations included heterogeneity in designs and metrics, predominance of 2D-Computational Fluid Dynamics (CFDs), and limited 3D/field validation restricted quantitative pooling. Risk of bias was assessed using an ad hoc matrix; overall certainty was rated as low to moderate due to limited validation and inconsistent uncertainty reporting. In conclusions, no single solution is universally optimal; hybrid strategies, combining optimized airfoils with targeted passive or active control, appear most promising. Future work should standardize start-up metrics, adopt validated 3D Fluid–Structure Interaction (FSI) models, and expand wind-tunnel/field trials. Full article

To contribute to the emerging knowledge on the sustainability impacts of small, circular clothing reuse businesses in the US, we employed a case study research methodology to empirically test the case of Circular Thrift, an innovative, community-based startup business model with potential to create a circular fashion ecosystem on the firm level. Primary data on circular activities were collected on site within the first year of business operation. The Life Cycle Assessment methodology was conducted to assess environmental impact avoidance. The social impact of reused products was assessed to contribute to a more comprehensive understanding of the benefits of born circular business models. Tangible environmental benefits accounted for the collection of 10,772 apparel units and resulted in the diversion of 2311.05 kg (approximately 5095 pounds) of clothing from the local landfill. Social impact accounted for 45.86% of the collected items that were given back to the local community. Empirical testing of the environmental benefits of a Circular Thrift business model makes a strong case for scaling up reusable efforts as a means to address post-consumer textile waste at the local community level within the US, where formal and government-regulated resource collection and recovery systems still do not exist. Full article

The rapid development of marine recirculating aquaculture systems (RASs) worldwide offers an efficient and sustainable approach to aquaculture. However, the slow start-up of the nitrification process under low-temperature conditions remains a significant challenge. This study evaluated multiple start-up strategies for moving bed biofilm reactors (MBBRs) operating at 13–15 °C. Among them, the salinity-gradient (SG) strategy exhibited the best performance, reducing the start-up time by 38 days compared to the control, with microbial richness (Chao1 index) reaching 396 and diversity (Shannon index) of 4.89. Inoculation with mature biofilm (MBI) also showed excellent results, shortening the start-up period by 26 days and achieving a stable total ammonia nitrogen (TAN) effluent concentration below 0.5 mg/L within 132 days. MBI exhibited the highest microbial richness (Chao1 index = 808) and diversity (Shannon index = 5.55), significantly higher than those of the control (Chao1 index = 279, Shannon index = 3.90) and other treatments. The hydraulic retention time-gradient (HRT) strategy contributed to performance improvement as well, with a 24-day reduction in start-up time and a Chao1 index of 663 and a Shannon index is 4.69. In contrast, nitrifying bacteria addition (NBA) and carrier adhesion layer modification (CALM) had limited effects on start-up efficiency or microbial diversity, with Chao1 indices of only 255 and 228, and Shannon indices were both 3.24, respectively. Overall, the results indicate that salinity acclimation, mature biofilm inoculation, and extended HRT are effective approaches for promoting microbial community adaptation and enhancing MBBR start-up under low-temperature marine conditions. Full article

Malicious actors often exploit persistence mechanisms, such as unauthorized modifications to Windows startup directories or registry keys, to achieve privilege escalation and maintain access on compromised systems. While information technology (IT) teams legitimately use these AutoStart Extension Points (ASEPs), adversaries frequently deploy malicious binaries with non-standard naming conventions or execute files from transient directories (e.g., Temp or Public folders). This study proposes a threat-hunting framework using a custom Elasticsearch Security Information and Event Management (SIEM) system to detect such persistence tactics. Two hypothesis-driven investigations were conducted: the first focused on identifying unauthorized ASEP registry key modifications during user logon events, while the second targeted malicious Dynamic Link Library (DLL) injections within temporary directories. By correlating Sysmon event logs (e.g., registry key creation/modification and process creation events), the researchers identified attack chains involving sequential registry edits and malicious file executions. Analysis confirmed that Sysmon Event ID 12 (registry object creation) and Event ID 7 (DLL loading) provided critical forensic evidence for detecting these tactics. The findings underscore the efficacy of real-time event correlation in SIEM systems in disrupting adversarial workflows, enabling rapid mitigation through the removal of malicious entries. This approach advances proactive defense strategies against privilege escalation and persistence, emphasizing the need for granular monitoring of registry and filesystem activities in enterprise environments. Full article

Regulatory changes related to the policy of reducing CO₂ emissions from natural gas are leading to an increase in the share of hydrogen in gas transmission and utilization systems. In this context, the impact of the change in composition on thermal radiation zones should be assessed for flaring during startups, scheduled shutdowns, maintenance, and emergency operations. Most existing models are calibrated for hydrocarbon flare gases. This study assesses how the CH₄–H₂ blends affect thermal radiation zones using a developed solver based on the Brzustowski–Sommer methodology with composition-dependent fraction of heat radiated (F) and range-dependent atmospheric transmissivity. Five blends, 0–50% (v/v) H₂, were analyzed for a 90 m stack at wind speeds of 3 and 5 m·s⁻¹. Comparisons were performed at constant molar (standard volumetric) throughput to isolate composition effects. Adding H2 contracted the radiation zones and reduced peak ground loads. Superposition analysis for a multi-flare layout indicated that replacing one 100% (v/v) CH₄ flare with a 10% (v/v) H₂ blend reduced peak ground radiation. Emission-factor analysis (energy basis) showed reductions of 3.24/3.45% at 10% (v/v) H₂ and 7.01/7.44% at 20% (v/v) H₂ (LHV/HHV); at 50% (v/v) H₂, the decrease reached 22.18/24.32%. Hydrogen blending provides coupled safety and emissions co-benefits, and the developed framework supports screening of flare designs and operating strategies as blends become more prevalent. Full article

Vertical axis wind turbines (VAWTs) are increasingly utilized for decentralized power generation in urban and low-wind settings because of their omnidirectional wind capture and compact form. This study numerically investigates the aerodynamic performance of Darrieus-type VAWT blades as their curvature varies systematically from deeply convex (−50 mm) to strongly concave (+50 mm) across seven configurations. Using steady-state computational fluid dynamics (CFD) with the frozen rotor method, simulations were conducted over a low Reynolds number range of 25 to 300, representative of small-scale and rooftop wind scenarios. The results indicate that deeply convex blades achieve the highest lift-to-drag ratio (Cl/Cd), peaking at 1.65 at Re = 25 and decreasing to 0.76 at Re = 300, whereas strongly concave blades show lower and more stable values ranging from 0.95 to 0.86. The power coefficient (Cp) and torque coefficient (Ct) similarly favor convex shapes, with Cp starting at 0.040 and remaining above 0.030, and Ct sustaining a robust 0.067 at low Re. Convex blades also maintain higher tip speed ratios (TSR), exceeding 1.30 at Re = 300. Velocity and pressure analyses reveal that convex profiles promote stable laminar flows and compact wakes, whereas concave geometries experience early flow separation and fluctuating torque. These findings demonstrate that optimizing the blade curvature toward convexity enhances the start-up, torque stability, and power output, providing essential design guidance for urban VAWTs operating under low Reynolds number conditions. Full article

Low-permeability oil reservoirs, due to their weak seepage capacity and high start-up pressure, have limited yield-increasing effects through conventional water injection development methods. High-pressure water injection can significantly change the seepage environment around the well and within the reservoir, expand the effective swept volume of injected water, and thereby greatly enhance the oil recovery rate of water flooding. However, there is still a relative lack of research on the mechanism of high-pressure water injection stimulation and its influencing factors. This paper systematically analyzes the effectiveness mechanism of high-pressure water injection technology in the exploitation of low-permeability reservoirs. The internal mechanism of high-pressure water injection for effective fluid drive and production increase is explained from the aspects of low-permeability reservoir seepage characteristics, capacity expansion and permeability enhancement by high-pressure water injection, and the dynamic induction of micro-fractures. Based on geological and engineering factors, the main factors affecting the efficiency enhancement of high-pressure water injection are studied, including formation deficit, reservoir heterogeneity, dominant channel development and fracturing stimulation measures, injection displacement and micro-fractures, etc. The results of numerical simulation showed the following: (1) formation depletion, reservoir heterogeneity, and the formation of dominant channels significantly affected the effect of water flooding development and (2) engineering factors such as the fracture direction of hydraulic fracturing, water injection rate, and the development of micro-fractures under high-pressure water injection directly determined the propagation path of reservoir pressure, the breakthrough speed of the water drive front, and the ultimate recovery factor. Therefore, during the actual development process, the construction design parameters of high-pressure water injection should be reasonably determined based on the geological reservoir conditions to maximize the oil production increase effect of high-pressure water injection. This study can successfully provide theoretical guidance and practical support for the development of low-permeability oil reservoirs. Full article

This study examines the intersection of artificial intelligence-driven personal branding strategies and female entrepreneurship within Indonesia’s unique hijabi startup ecosystem. Through a mixed-methods approach combining sentiment analysis of 2847 social media posts, in-depth interviews with 35 hijabi entrepreneurs, and machine learning analysis of branding patterns, this research reveals how AI technologies can be leveraged to create culturally sensitive personal branding frameworks for Muslim female entrepreneurs. The findings demonstrate that successful hijabi entrepreneurs employ distinct AI-enhanced communication strategies that balance religious identity, professional credibility, and market positioning. The study introduces the “Halal Personal Branding Framework,” a novel theoretical model that integrates Islamic values with contemporary digital marketing practices. Results indicate that AI-driven personal branding increases startup funding success rates by 34% and market reach by 58% among hijabi entrepreneurs when culturally appropriate algorithms are employed. This research contributes to entrepreneurship communication theory while providing practical guidelines for developing inclusive AI systems that respect religious and cultural diversity in the digital economy. Full article

To support NASA’s mission to use nuclear thermal rockets for future Mars missions, an instrumentation and control test bed has been built at Oak Ridge National Laboratory. The system is designed as a hardware-in-the-loop test bed for testing control elements and autonomous control algorithms for nuclear thermal propulsion rockets. The mock reactor system consists of a modular and scalable framework, using inexpensive components and open-source software. The hardware system consists of a two-phase flow loop and a mock reactor with six control drums. A single-board computer (NVIDIA Jetson) handles reactor core emulation and hosts a message queuing telemetry transport broker that allows user-deployed control algorithms to interact with the system hardware. The reactor emulator receives sensor data from the hardware and provides the simulated performance of the reactor under steady-state, transient, and fault conditions. The emulator uses a reactivity lookup table and the point kinetics equations to solve for the reactor dynamics in real time. Emulated reactor dynamics and sensor input inform the autonomous control algorithm’s decision-making in a closed-loop manner. The current system is capable of operating at 10 Hz, but faster cycle rates are an area of ongoing research. This test bed will enable NASA and other space vendors to rigorously test their autonomous control systems for NTP rockets under transient (reactor startup and shutdown), steady-state, and fault conditions to reduce development time and risk for autonomous control systems in future missions. Full article

Abrupt speed variations and motor start-ups have been pointed out as critical challenges in the framework of fault diagnostics in induction motor drives, namely inter-turn short circuit faults. Generally, abrupt accelerations influence the typical symptoms of the fault, and consequently, the fault detection becomes ambiguous, impacting prompt and effective decision-making. To overcome this issue, this study proposes an inter-turn short-circuit fault diagnostic technique for asymmetrical six-phase induction motor drives operating under both smooth and abrupt motor accelerations. A time–frequency domain spectrogram of the AC component extracted from the q-axis reference current signal serves as a reliable fault indicator. This technique stands out for the compromise between robustness and computational effort using only one control variable accessible in the model predictive control algorithm, thus discarding both voltage and current signals. Experimental tests involving various load torques and fault severities, in transient regimes, were performed to validate the proposed methodology’s effectiveness thoroughly. Full article

This paper presents a literature review of low-power hybrid wind–photovoltaic (PV) systems and introduces a 3 m diameter prototype rotor featuring twelve PV-coated pivoting blades stiffened by a peripheral rim. Existing solutions—foldable umbrella concepts, Darrieus rotors with PV-integrated blades, and morphing blades—are surveyed, and current gaps in simultaneous wind + PV co-generation on a single moving structure are highlighted. Key performance indicators such as power coefficient (C_p), DC ripple, cell temperature difference (ΔT), and levelised cost of energy (LCOE) are defined, and an integrated assessment methodology is proposed based on blade element momentum (BEM) and computational fluid dynamics (CFD) modelling, dynamic current–voltage (I–V) testing, and failure modes and effects analysis (FMEA) to evaluate system performance and reliability. Preliminary results point to moderate aerodynamic penalties (ΔC_p ≈ 5–8%), PV output during rotation equal to 15–25% of the nominal PV power (P_PV), and an estimated 70–75% reduction in blade–root bending moment when the peripheral ring converts each blade from a cantilever to a simply supported member, resulting in increased blade stiffness. Major challenges include the collective pitch mechanism, dynamic shading, and wear of rotating components (slip rings); however, the suggested technical measures—maximum power point tracking (MPPT), string segmentation, and redundant braking—keep performance within acceptable limits. This study concludes that the concept shows promise for distributed microgeneration, provided extensive experimental validation and IEC 61400-2-compliant standardisation are pursued. This paper has a dual scope: (i) a concise literature review relevant to low-Re flat-blade aerodynamics and ring-stiffened rotor structures and (ii) a multi-fidelity aero-structural study that culminates in a 3 m prototype proposal. We present the first evaluation of a hybrid wind–PV rotor employing untwisted flat-plate blades stiffened by a peripheral ring. Using low-Re BEM for preliminary loading, steady-state RANS-CFD (k-ω SST) for validation, and elastic FEM for sizing, we assemble a coherent load/performance dataset. After upsizing the hub pins (Ø 30 mm), ring (50 × 50 mm), and spokes (Ø 40 mm), von Mises stresses remain < 25% of the 6061-T6 yield limit and tip deflection ≤ 0.5%·R acrosscut-in (3 m s⁻¹), nominal (5 m s⁻¹), and extreme (25 m s⁻¹) cases. CFD confirms a broad efficiency plateau at λ = 2.4–2.8 for β ≈ 10° and near-zero shaft torque at β = 90°, supporting a three-step pitch schedule (20° start-up → 10° nominal → 90° storm). Cross-model deviations for C_p, torque, and pressure/force distributions remain within ± 10%. This study addresses only the rotor; off-the-shelf generator, brake, screw-pitch, and azimuth/tilt drives are intended for later integration. The results provide a low-cost manufacturable architecture and a validated baseline for full-scale testing and future transient CFD/FEM iterations. Full article

The increasing demand for high-performance power converters for electric vehicle (EV) applications places a significant emphasis on developing effective and robust control strategies for DC-DC converter operation. This paper deals with the development, simulation, and experimental validation of an adaptive Lyapunov-type Nonlinear Sliding Mode Control (L-SMC) strategy for a DC–DC boost converter, addressing significant uncertainties caused by large variations in system parameters (R and L) and ensuring the tracking of a voltage reference. The proposed control strategy employs the Lyapunov stability theory to build an adaptive law to update the parameters of the sliding surface so the system can achieve global asymptotic stability in the presence of uncertainty in inductance, capacitance, load resistance, and input voltage. The nonlinear sliding manifold is also considered, which contributes to a more robust and faster convergence in the controller. In addition, a logic optimization technique was implemented that minimizes switching (chattering) operations significantly, and as a result of this, increases ease of implementation. The proposed L-SMC is validated through both simulation and experimental tests under various conditions, including abrupt increases in input voltage and load disturbances. Simulation results demonstrate that, whether under nominal parameters (R = 320 Ω, L = 2.7 mH) or with parameter variations, the voltage overshoot in all cases remains below 0.5%, while the steady-state error stays under 0.4 V except during the startup, which is a transitional phase lasting a very short time. The current responds smoothly to voltage reference and parameter variations, with very insignificant chattering and overshoot. The current remains stable and constant, with a noticeable presence of a peak with each change in the reference voltage, accompanied by relatively small chattering. The simulation and experimental results demonstrate that adaptive L-SMC achieves accurate voltage regulation, a rapid transient response, and reduces chattering, and the simulation and experimental testing show that the proposed controller has a significantly lower steady-state error, which ensures precise and stable voltage regulation with time. Additionally, the system converges faster for the proposed controller at conversion and is stabilized quickly to the adaptation reference state after the drastic and dynamic change in either the input voltage or load, thus minimizing the settling time. The proposed control approach also contributes to saving energy for the application at hand, all in consideration of minimizing losses. Full article

Background: The human body’s exposure to high levels of endogenous estrogens and their metabolites, such as estradiol, estriol, 2-hydroxyestradiol, and 4-hydroxyestradiol, is implicated in the development and complications of breast cancers (BCs). Besides endogenous estrogen production, the human body is also exposed to environmental sources of estrogen and estrogen-like compounds, which include pharmaceutical estrogens, xenoestrogens, and phytoestrogens. Females consume pharmaceutical estrogens as a constituent of postmenopausal hormone replacement therapy (HRT) and oral contraceptive pills, either alone or in combination with progestins. Additionally, humans, including females, are exposed to estrogen-resembling non-native compounds called xenoestrogens, prevailing in pesticides, plastics, and personal care items via inhalation, dermal contact, and oral consumption. Several phytoestrogens, such as isoflavones and lignans, are consumed by humans as food ingredients. Methods and Results: Emerging cellular and molecular experimental evidence indicates that when binding to estrogen receptors (ERs), various pharmaceutical estrogens, including equine/synthetic forms, progestin combinations, and xenoestrogens, promote BC development and complications by triggering survival, proliferation, angiogenesis, and invasion of these cells. Conversely, other experimental observations reveal the protective and beneficial effects of phytoestrogens like genistein from soy products on BC development and complications. Conclusions: This comprehensive review article describes the implications of exposure to exogenous estrogens, such as pharmaceutical estrogens, xenoestrogens, and phytoestrogens, as risk factors in the prevention or development of BC and its complications. Full article

The purpose of the current research study was to identify appropriate educators for teaching entrepreneurship at the university level and to explore the best teaching methods for developing entrepreneurial knowledge and skills among students. The study aims to address two key questions in entrepreneurship education: (1) Who should teach entrepreneurship in universities? and (2) What methods are effective in teaching entrepreneurship in universities? The study was conducted using an interpretative phenomenological qualitative research approach. Data were collected from a purposive sample of eight (8) entrepreneurship educators from a South African university. Data collection spanned three months, from November 2024 to January 2025. The key findings of the study suggest that entrepreneurship should be taught by academics with practical experience, academics with at least a Master’s degree, entrepreneurs invited as guest lecturers, incubator professionals, and technology professionals. Additionally, the research revealed teaching methods that can be used to effectively teach entrepreneurship in universities: Universities need to prioritise hiring and training entrepreneurship educators with both academic and real-world experience and facilitate collaborations with incubators and real-world entrepreneurs. Teaching methods need to incorporate experiential learning methods such as startup simulations, case studies, and partnerships with innovation hubs. The study offers valuable insights into who should teach entrepreneurship and how it should be taught, emphasising the need for a multidisciplinary approach and practical orientation to develop entrepreneurial capabilities and mindsets among students. Full article

In this study, the effects of speed and red-light cameras (SRLCs) and traffic signal countdown timers (TSCTs) on the operation of pre-timed signalized intersections were studied through startup lost times (SLTs) and saturation time headways (STHs). The study used the beanplots package version 1.3.1 in R statistical software to graph and find the first STH that occurred in a queue. Then, one-way analysis of variance was used twice to explore the effects of the separate and joint use of SRLCs and TSCTs on the operation of pre-timed signalized intersections. The results show that SRLC use does not have a significant direct impact on the operation of pre-timed signalized intersections, but SRLC interacts negatively with TSCT use. In addition, TSCT use was shown to improve the operation of pre-timed signalized intersections by decreasing the SLT and STH. For SLT, the effect size of TSCT use depends on the presence or absence of SRLC use, and its reduction ranges from 0.5 to 1.25 s per queue. As for STH, the effect size of TSCT use does not depend on the presence or absence of SRLC use, and its reduction ranges from 0.08 to 0.12 s per vehicle, corresponding to 0.8–1.2 s per queue, given that there are 10 vehicles in the queue. Full article