Search Results (172)

During the excavation of the underground cavern at the Baihetan hydropower station, significant time-dependent deformation of the surrounding rock was observed, posing a serious challenge to the long-term stability control of the caverns. In this study, numerical models of the layered excavation for typical monitoring sections in the main and auxiliary powerhouses on both banks of the Baihetan hydropower station were established using a viscoplastic damage model. The time-dependent deformation responses of the surrounding rock during the entire underground cavern excavation process were successfully simulated, and the deformation and failure mechanisms of the surrounding rock during layered excavation were analyzed in combination with field monitoring data. The results demonstrate that the maximum stress trajectories at the right-bank powerhouse under higher stress conditions exceeded those at the left-bank powerhouse by 6 MPa after the powerhouse excavation. A larger stress difference caused stress trajectories to move closer to the rock strength surface, therefore making creep failure more likely to occur in the right bank. Targeted reinforcement in high-disturbance zones of the right-bank powerhouse reduced the damage progression rate at borehole openings from 0.295 per month to 0.0015 per month, effectively suppressing abrupt deformations caused by cumulative damage. These findings provide a basis for optimizing the excavation design of deep underground caverns. Full article

This paper suggests an extensive inferential method for the Power Pratibha Distribution (PPD) under Unified Hybrid Censoring Schemes (UHCSs), since there is a growing interest in flexible models in both reliability and service operations. This work studies the PPD model using standard Maximum Likelihood Estimation methods and modern Bayesian approaches too. Using a complex architecture, UHCS simulates tests more closely to what is done in practice than by using more basic censoring schemes. Using analysis, the probability and statistical ranges are carefully calculated for the parameters. Tests demonstrate that Bayesian estimation gives better results than many other methods for estimation, especially when the dataset is not very large and when a lot of data is missing. Real-world tests of electromigration failure data and banking service times help to test the methods. In both situations, the PPD shows it can be used successfully in different reliability settings. By joining advanced censoring models and reliable statistical methods, this research gives a helpful toolset to experts in reliability analysis and statistics. Full article

This study investigates the excavation of the cataclastic loose rock slope at the mixing plant on the right bank of the BDa Hydropower Station, which is situated in the upper reaches of Lancang River. The dominant structural plane of the cataclastic loose rock mass was obtained using unmanned aerial vehicle tilt photography and 3D point cloud technology. The actual 3D numerical model of the study area was developed using the 3DEC discrete element numerical simulation software. The excavation response characteristics and overall stability of the cataclastic loose rock slope were analyzed. The support effect was evaluated considering the preliminary shaft micropile and Macintosh reinforced mat as slope support measures, and the stability was assessed by applying seismic waves. The results showed the main deformation and failure area after slope cleaning excavation at the junction of the cataclastic loose rock mass and Q^edl deposits in the shallow surface of the excavation face. Moreover, the maximum total displacement could reach 18.3 cm. Subsequently, the overall displacement of the slope was significantly reduced, and the maximum total displacement decreased to 2.78 cm. The support effect was significant. Under an earthquake load, the slope with support exhibited considerable displacement in the shallow surface of the excavation slope, with collapse deformation primarily occurring through shear failure. Full article

In the design of military, automotive, medical, space, and professional equipment, it is essential to demonstrate that devices can operate for a specific duration with a given level of confidence. Reliability must be considered in the design process, which can involve component selection, component testing, and mitigation techniques such as redundancy and forward error correction (FEC). In modern DC–DC converters, a higher level of reliability is now a mandatory requirement—the ISO 26262, for example, acts as the guidance to provide the appropriate standardized requirements, processes and risk based approach, and it determines integrity levels (known as automotive safety integrity levels or ASILs). The purpose is to reduce risks caused by systematic and random failures to an appropriate level of acceptance. Since the release of MIL-HDBK-217F Notice 2 in 1995, newer standards for predicting failure rates have emerged in the electronic systems reliability market. These updated standards were introduced to address the limitations of the older standards, particularly in relation to advanced component technologies. Numerous studies have shown that the output capacitor bank is one of the most critical components concerning reliability. This work focuses on calculating the failure rates of an output capacitor bank and a MOSFET transistor pair used in a high-current, low-voltage buck converter. The failure rates are calculated using both the latest prediction standard, SN 29500, and the previous MIL-HDBK standard. This comparison serves as a valuable tool for selecting the output capacitor during the early stages of design. Both simulations and experimental setups were employed to measure the temperatures of the components. The SN 29500 standard is particularly beneficial for components operating in harsh environments, as it provides up-to-date failure rate data and stress models. The environmental conditions for the components were defined using a standard point of load (PoL) buck converter for both calculation methods. Results are compared by considering the impact of component temperature and by applying specific parameters such as reference and operating conditions. This kind of comparison is useful for circuit designers, especially in the field of Power electronics when the concept of designing with reliability in mind is adopted. Full article

Climate changes have increased heavy rainfall, intensifying flood damage, especially along small streams with steep slopes, fast flows, and narrow widths. In Korea, nearly half of flood-related casualties occur in these regions, underscoring the need for effective flood early warning systems. However, predicting flood depths is challenging due to the complex channels and rapid flood wave propagation in small streams. This study developed a flood early warning framework (FEWF) tailored for small streams in Korea, optimizing rainfall–discharge nomographs using hydro-informatic data from four streams. The FEWF integrates a four-parameter logistic model with real-time updates with a nomograph using a robust constrained nonlinear optimization algorithm. A simplified two-level early warning system (attention and severe) is based on field-verified thresholds. Discharge predictions estimate the water depth in unmeasured cross-sections using the Manning formula, with real-time data updates allowing for the dynamic identification of the flood depth. The framework was validated during the 2022 flood event, where no inundation or bank failures were observed. By improving flood prediction and adaptive management, this framework can significantly enhance disaster response and reduce casualties in vulnerable small stream areas. Full article

This study investigates how the quality of engagement auditors, assessed using the auditor’s industry expertise and size at both national and state levels, influences the likelihood of going concern opinion (GCO) issuance for U.S. banks from 2002 to 2023. We also examine how auditor quality affects the accuracy of GCOs, specifically regarding Type I (false positive) and Type II (false negative) errors in GCO issuance. Using a dataset of 4992 bank-year observations from 414 unique banks, we analyze the correlations between auditor characteristics and these error types. We find that state-level audit industry experts issue significantly more accurate GCOs, demonstrating lower rates of both Type I and Type II errors compared to their counterparts. National-level experts and larger audit firms primarily show a reduced likelihood of Type II errors, indicating a more conservative approach. Our findings underscore the importance of localized auditor expertise in assessing bank financial health and suggest that enhanced collaboration between auditors and regulators could improve the predictive power of GCOs. These results offer important implications for regulatory policy and emphasize the need for improved audit standards to bolster financial system stability. Full article

The rapid worldwide transmission of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to severe cases of hypoxia, acute respiratory distress syndrome, multi-organ failure, and ultimately death. Small-scale molecular interactions have been analyzed by focusing on several genes/single genes, providing important insights; however, genome-wide multi-omics comprehensive molecular interactions have not yet been well investigated with the exception of GWAS and eQTLm, both of which show genetic risks. From April of 2020 until now, we have created a Japan-wide system, initially named the Japan COVID-19 Task Force. This system has collected more than 6500 COVID-19 patients’ peripheral blood and as much associated clinical information as possible from a network of more than 120 hospitals. DNA, RNA, serum, and plasma were extracted and stored in this bank. This study unravels the interplay of inflammatory gene networks that induce different COVID-19 severity levels (mild, moderate, severe, and critical) by using multi-omics data from the Japan COVID-19 Task Force. We analyze RNA and protein expressions to estimate severity-specific inflammation networks that uncover the interplay between RNA and protein networks via ligand–receptor pairs. Our large-scale RNA/protein expression data analysis reveals that the atypical chemokine receptor 2 (ACKR2) acts as a key broker linking RNA and protein inflammation networks to induce COVID-19 critical severity. ACKR2 emerges in RNA and protein inflammation networks, showing active interplay in high-severity cases and weak interactions in mild cases. The results also show severity-specific molecular interactions between interleukin (IL), cytokine receptor activity, cell adhesion, and interactions involving the CC chemokine ligand (CCL) gene family and ACKR2. Full article

(1) Background: The survival and growth of startups in their early stages are negatively impacted by the lack of financial sustainability and scarce resources that entrepreneurs face during the first 5 years. This is known as the Valley of Death (VoD). This study seeks to identify key factors that influence the financial sustainability of startups during the VoD, which demands a significant amount of funding and government support. (2) Methods: A quantitative methodology was employed, based on a worldwide literature review that pointed out the variables of the object of study; the information collection process was conducted through a questionnaire applied to 352 entrepreneurs in an innovative ecosystem. This study empirically applies a structural equation model to determine the relationship between constructs. (3) Results: A comprehensive analysis of the results indicates that indicators such as positive sales performance, sufficient financial solvency to meet short- and long-term commitments, accurate pricing policies, and access to government and banking support are the primary factors affecting the sustainability of startups in the early stages. (4) Originality: This study provides original and relevant insights into the indicators that affect the financial sustainability of startups during the VoD and offers interesting insights for governments, institutions, and entrepreneurs to foster innovative ecosystems; it also contributes to the extant literature on early-stage entrepreneurial failures. Full article

Transformers are essential in electrical networks, and their failure can lead to the shutdown of a section or the entire grid. This study proposes a combination of techniques for early fault detection, distinguishing between small load imbalances and incipient interturn short circuits. An experimental setup was developed using a three-phase transformer bank with three single-phase dry-type transformers. One transformer was modified to create controlled short circuits of two and four turns and to simulate a load imbalance by reducing the winding by four turns. The main contribution of this research is the development of a combined diagnostic approach using instantaneous space phasor (ISP) spectral analysis and infrared thermal imaging to differentiate between load imbalances and incipient interturn short circuits in transformers. This method enhances early fault detection by identifying distinctive electrical and thermal signatures associated with each condition. The results could improve transformer monitoring, reducing the risk of failure and enhancing grid reliability. Full article

The submarine canyons system is the most widely distributed geomorphic unit on the global continental margin. It is an important concept in the field of deep-water sedimentation and geohazards. Based on high-resolution multibeam bathymetry and two-dimensional seismic data, the dendritic canyon system north of Dongdao island is studied at the eastern Xisha area of the South China Sea. The Dongdaobei submarine canyon is distributed in water depths between 1000 and 3150 m. The main source area in the upper course of the canyon originates from the northwest of Dongdao platform and the Yongxing platform. The sediments from the source area are transported to the main canyon in the form of various gravity flows. Landslides on the slope significantly impact canyon evolution by delivering sediment to the canyon head and causing channel deflection through substrate failure and flow-path reorganization. A large number of pockmarks are distributed around the north slope of the main canyon. The small-scale channels, which are formed as a result of the continuous erosion of the pockmark chains, are connected to the canyon sidewalls. The seamounts are distributed along the south bank of the canyon, exerting a controlling influence on the directional changes in the main canyon’s downstream segment. The formation and evolution of the Dongdaobei submarine canyon are primarily influenced by several factors, including tectonic activity and inherited negative topography, erosion by sedimentary gravity flows, sediment instability, and the shielding effect of seamounts. Full article

The study aims to examine the enterprise risk management (ERM) practices of Ethiopian commercial banks. This approach is undertaken to examine the current approach to enterprise risk management within the Ethiopian banking context. A mixed-methods research design is employed which comprises content analysis and a survey study. The study found that the prevailing emphasis of risk management functions in Ethiopian commercial banks revolves on ensuring compliance with regulatory reporting standards. A significant number of the banks have implemented ERM programs primarily to meet regulatory obligations, rather than leveraging ERM to generate firm value. The study identified several gaps in the risk management function of Ethiopian commercial banks, including lack of integration of risk management with the banks’ mission and core values, failure to assess the resources required for effective risk management and to prioritise resource allocation accordingly, inadequate coverage of relevant activities and functional areas by both risk management and internal audit activities, and limitations on the assignment of chief risk officers (CROs) to oversee the risk management function within the banks. Overall, the maturity level of ERM implementation among Ethiopian commercial banks is moderate and requires further enhancement. Full article

This article describes the Heritage Sustainability Index (HSI), a benchmarking tool that draws on a series of key indicators to rate company actions as they relate to the protection of cultural heritage. The purpose of the HSI is to provide an independent framework for lenders, borrowers, and civil society, including Indigenous Peoples, to evaluate corporate safeguard policies and practices related to cultural heritage, enabling informed decision making. Given their importance and influence, the HSI focuses on the practices of Global Systemically Important Banks (G-SIBs), which were chosen to represent a baseline for comparison across all industry sectors. The HSI’s indicators (n = 12) and sub-indicators (n = 48) were successful in illustrating the variability that exists among the G-SIBs. Corporations with an HSI value below the upper quartile of the distribution should take steps to enhance their cultural heritage safeguard practices. This is crucial because scores below this value reflect weak practices, indicating higher financial and reputational risk exposures and poor outcomes for cultural heritage. By focusing on improving their HSI values, these corporations can better mitigate potential risks and enhance their overall sustainability profile. The success and longevity of the HSI will depend on industry goodwill and the perceived risk that cultural heritage poses to corporate financial performance and reputation. Given the potential financial and reputational damage from a significant failure in cultural heritage stewardship, corporations are expected to recognize these advantages and find it an easy decision to support the adoption of the HSI. Full article

In this study, statistical analysis was conducted to categorize a large number of actual typical cases and analyze the formation conditions of toppling deformation in bedding rock slopes. Based on geological prototypes and similarity theory, a bottom friction test was conducted on the toppling deformable body while considering the excavation process. Based on the deformation and failure phenomena observed in the bottom friction test model, along with the displacement curves at key points, the deformation process in steep bedding rock slopes can be divided into the following five distinct stages: the initial phase, the unloading–rebound phase, the tensile failure phase, the bending creep phase, and the bending–toppling damage phase. To evaluate the stability, a new constitutive model of the nonlinear viscoelastic–plastic rheology of rock masses was developed. This model is based on a nonlinear function derived from analyzing the creep test data of rock masses under fractional loading. Furthermore, a mechanical equilibrium differential equation for rock slabs was formulated to quantitatively describe the aging deformation and failure processes of slopes with delayed instability. Finally, a stability criterion and a quantitative evaluation model for toppling deformation slopes that considered time-varying factors were established. The stability of the model was calculated using a hydropower station slope case, and the results were found to be in good agreement with the actual situation. Full article

This article concerns the connection process of a squirrel-cage induction generator to the grid/microgrid. Typically, the generator is unexcited, and its connection to the grid is made directly via a switch. This connection causes a high inrush current and grid voltage drop, which local consumers notice. This article proposes a robust power system consisting of the squirrel-cage induction generator, a power electronic converter, and a capacitor bank, all connected in parallel. The proposed configuration and a dedicated control system eliminate the inrush current and compensate for the generator’s reactive power during grid-tied operation. The converter controls the generator voltage build-up to adjust the generator voltage to the grid voltage (controlled excitation) and connects the generator to the grid, minimising distortions. Moreover, the system is robust because the failure of the converter does not stop the power generation, unlike a system with a back-to-back converter, where the converter links the generator and the grid. Furthermore, the parallel-connected converter has a significantly reduced power rating because it is only rated for a part of the reactive generator power. The rest of the reactive generator power is delivered by the fixed capacitor bank. The article presents the system configuration, the control method, and laboratory results confirming the system’s effectiveness in maintaining high-quality grid voltage during generator-to-grid connection and high-quality power supplied to the grid. Full article

Rising levels of antibiotic-resistant bacteria have led to increasing interest in the use of phage therapy as an alternative treatment. While phage therapy is conceptually simple, and numerous semi-anecdotal data suggest that it could be effective if properly managed, there have been only a few randomized, double-blind clinical trials of phage therapy so far. These trials unequivocally showed that phage therapy is safe, but there is still a paucity of data on its efficacy for managing various bacterial infections. One common response to this situation is that there is a mismatch between the regulations that govern the testing of new drugs, that is, chemical agents, and biological agents like bacteriophages. Another response has been to sidestep clinical trial testing and to use phages to treat infected patients on an individual basis, sometimes called the magistral phage approach. In this paper, we argue that regulations are not the true barrier to approval of phage therapy as drugs but rather it is the lack of efficacy data. There is no one reason behind the failures of recent clinical trials. Instead, these demonstrate the complexity of implementing a therapy where both the treatment and disease are living entities interacting within another living entity, the patient. Phage banks can have an impact by monitoring these complexities during phage therapy. Importantly, phage therapy clinical trials are continuing under existing regulatory frameworks and with products manufactured under GMP (Good Manufacturing Practices). Full article