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The feature extraction and state recognition of vibration signals of hydroelectric generating units are of great significance for effectively ensuring the safety and lifespan of unit operation. This paper introduces a novel fault diagnosis approach that leverages a wavelet threshold algorithm for initial signal preprocessing and enhances the Radial Basis Function (RBF) neural network with an optimized Gravitational Search Algorithm (GSA). Initially, the Wavelet Transform (WT) algorithm is employed to denoise the raw signal, which is subsequently decomposed using Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN). Intrinsic Mode Function (IMF) components are then selected based on their correlation coefficients for sample entropy calculation. A GSA-optimized RBF neural network is constructed to diagnose faults in hydroelectric units. To further enhance the model’s convergence speed and accuracy, Lévy flight and chaotic sequence optimizations are integrated into the GSA, resulting in the development of the LCGSA-RBF diagnosis model. Experimental results demonstrate that this method achieves a 100% accuracy rate, outperforming other comparative models. Specifically, this approach enhances accuracy by 12.5% over the CEEMDAN-RBF method, showing the highest alignment with actual fault diagnosis results. This research significantly contributes to the advancement of safe and reliable operations in hydroelectric generating units.

Studies show that sediment erosion is one of the main factors attributing to hydraulic turbine failure. The present paper represents an investigation into acoustic vibration signals generated by the water flow impacting the hydraulic turbine runner under three different operating conditions. Collected signals were denoised using the ICEEMDAN-wavelet threshold method, and then the spectral characteristics and sample entropy characteristics of the signals for the three operating conditions were analyzed. The results show that when clean water flows through the hydraulic turbine, the sample entropy reaches its smallest values and the dominant frequency component in the spectrogram is 59.39 Hz. When transitioning from clean water to the flood flow containing 2–4 mm sediment particles, the sample entropy is increasing and a high-frequency component higher than 59.39 Hz becomes the prominent frequency of the spectrogram. Meanwhile, the formation of high-frequency components increases with the sand-containing particle size. Based on the spectral characteristics and sample entropy characteristics of the acoustic vibration signals under different operating conditions, it can provide a reference for the sand avoidance operation of the hydraulic turbine during flood season. In addition, it provides a supplement to the existing hydraulic turbine condition’s monitoring systems and a new avenue for subsequent research on early warning of hydraulic turbine failure.

The power oscillation induced by pressure fluctuation in the draft tube of the hydraulic turbine is one of the limiting factors preventing the Francis turbine from operating in the vibration zone. At the present power grid with a high proportion of renewable energy resources, we try to improve the load regulation ability of the hydropower units by extending the stable operation zone to the vibration zone. By the mathematical modelling of pressure fluctuation, this paper gives an analytical expression of the power oscillation. We derive the extended Hamiltonian model of the hydropower unit where power oscillation is external excitation. Secondly, the damping injection method introduces some desired interconnection and damping matrices as the Hamiltonian damping factor into the additional damping control. Finally, through theoretical analysis and experimental simulation, this research discusses the resonance characteristics of pressure fluctuation and power oscillation, the equivalent analysis between the damping factor and equivalent damping coefficient, and the control design of vibration zone crossing during the start-up. Simulation results show that when r25 = 1.3, the minimum power oscillation amplitude is 0.5466, which is equivalent to an increase in D by 20. The maximum oscillation amplitude decreases by 4.6%, and the operation limited zone is reduced by 10.1%. The proposed additional damping control can effectively suppress the power oscillation and expand the regulation range.

In this paper, a mixed $H_{2}/H_{\infty }$ robust control strategy that considers the weights of the $H_{2}$ and $H_{\infty }$ norm in the optimization process is proposed, and it is used to solve the load frequency control (LFC) problem of the micro-grid (MG). The MG load frequency model established in this paper includes battery energy storage system (BESS), fuel cell (FC), wind turbine (WT), photo-voltaic (PV), and diesel engine generator (DEG). The optimal mixed $H_{2}/H_{\infty }$ robust controller takes the minimum square integral of the system’s frequency fluctuation as the goal of control optimization by integrating the robust performance expressed by the $H_{2}/H_{\infty }$ two norms. The hybrid particle swarm optimization and gravitational search algorithm with chaotic map algorithm (CPSOGSA) is used to optimize the weight value reflecting the $H_{2}$ and $H_{\infty }$ performance of the system and the evaluation function’s weighting matrix of the output performance so that the controller can reach the optimum under the constraints. Simulation experiments show that the robust controller designed by the proposed method has better dynamic performance when compared with $H_{\infty }$ robust controller, $H_{2}$ robust controller, and traditional $H_{2}/H_{\infty }$ robust controller, and the results are very satisfactory.

The health of the hydroelectric generator determines the safe, stable, and reliable operation of the hydropower station. In order to keep the hydroelectric generator in a better state of health and avoid accidents, it is crucial to detect its faults. In recent years, fault detection methods based on sound and vibration signals have gradually become research hotspots due to their high sensitivity, achievable continuous dynamic monitoring, and easy adaptation to complex environments. Therefore, this paper is a supplement to the existing state monitoring and fault diagnosis system of the hydroelectric generator; it divides the hydroelectric generator into two significant parts: hydro-generator and hydro-turbine, and summarizes the research and application of fault detect technology based on sound signal vibration in hydroelectric generator and introduces some new technology developments in recent years, and puts forward the existing problems in the current research and future development directions, and it is expected to provides some reference for the research on fault diagnosis of the hydroelectric generator.

BackgroundThe incidence of liver cancer in Hmong Americans is 5 times higher than that of non-Hispanic whites, and there is a low hepatitis B screening rate (24%) among Hmong adults compared with other Asian American populations. The purpose of this study was to examine the Hmong's perceptions on social-cultural determinants, traditional health beliefs, and health care system barriers that influenced community-based hepatitis B screening interventions.MethodsA qualitative method was used, integrating a collective case study research design. In-depth interviews were used to collect data from 20 Hmong adults from the greater Sacramento area. A pattern matching analytic technique was used to analyze the data. The main core elements of Culture Care Theory were used to capture the key themes presented by the participants.ResultsProtecting a family's reputation; fear of doctors, medical procedures, and test results; lack of trust in medical doctors and medical care services; and using Hmong herbal medicines and practicing spiritual healing were identified as social-cultural and traditional health belief barriers to obtaining HBV screening. Health care costs, perceived discrimination, lack of transportation, linguistic discordance, and poor quality of care were identified as barriers to accessing high-quality health care services and obtaining hepatitis B screening.ConclusionProviders, health policy makers, researchers, and community-based organizations will need to work together to develop intervention strategies to address the social-cultural factors, traditional health beliefs, and health care challenges that influence obtaining hepatitis B screening in the Hmong community. Cancer 2018;124:1576-82. © 2018 American Cancer Society.

BackgroundAn exploratory study was performed to determine the prevalence of the patatin-like phospholipase domain-containing protein 3 (PNPLA3) rs78409 [G] allele among the Hmong as a risk factor for nonalcoholic fatty liver disease (NAFLD). NAFLD/nonalcoholic steatohepatitis is the world's most common chronic liver disease and is expected to replace viral hepatitis as the leading cause of cirrhosis and potential precursor to hepatocellular carcinoma (HCC). Of all populations in California, the Hmong experience the highest risk of death from HCC and the highest prevalence of metabolic syndrome risk factors among Asians that predispose them to NAFLD. Here a genetic explanation was sought for the high rates of chronic liver disease among the Hmong. The literature pointed to the PNPLA3 rs738409 [G] allele as a potential genetic culprit.MethodsCell-free DNA was isolated from 26 serum samples previously collected in community settings. Quantitative polymerase chain reaction-based single-nucleotide polymorphism (SNP) genotyping was performed with a validated TaqMan SNP genotyping assay, and results were analyzed with TaqMan Genotyper software.ResultsThe PNPLA3 rs738409 [C>G] variant occurred at a frequency of 0.46 (12 of 26; 95% confidence interval, 0.27-0.67). This carrier rate would rank the Hmong as the third highest population in the 1000 Genomes Project.ConclusionsAlthough this small sample size limits the generalizability, the high frequency rates of this allele along with the presence of metabolic syndrome risk factors warrant further studies into the etiology of NAFLD among the Hmong. Cancer 2018;124:1583-9. © 2018 American Cancer Society.

BackgroundHepatitis B-linked liver cancer disproportionately affects Hmong Americans. With an incidence rate of 18.9 per 100,000, Hmong Americans experience liver cancer at a rate that is 6 to 7 times more than that of non-Hispanic Whites. Serologic testing for the hepatitis B virus (HBV) is a principal means to prevent liver cancer-related deaths through earlier identification of those at risk.MethodsAcademic researchers and Hmong leaders collaborated in the design, conduct, and evaluation of a 5-year randomized controlled trial testing a lay health worker (LHW) intervention to promote HBV testing among 260 Hmong adults through in-home education and patient navigation.ResultsIntervention group participants were more likely to report receiving serologic testing for HBV (24% vs. 10%, P = 0.0056) and showed a greater mean increase in knowledge score (1.3 vs. 0.3 points, P = 0.0003) than control group participants. Multivariable modeling indicated that self-reported test receipt was associated with intervention group assignment [OR 3.5; 95% confidence interval (CI) 1.3-9.2], improvement in knowledge score (OR 1.3 per point; 95% CI 1.02-1.7), female gender (OR 5.3; 95% CI 1.7-16.6), and having seen a doctor in the past year at baseline (OR 4.8; 95% CI 1.3-17.6). The most often cited reason for testing was a doctor's recommendation.ConclusionsLHWs were effective in bringing about HBV screening. Doctor visits and adherence to doctors' recommendations were pivotal. Participation of health care providers is essential to increase HBV testing.ImpactLHWs can significantly increase HBV screening rates for Hmong but their doctors' recommendation is highly influential and should be pursued.

We aimed to investigate the diagnostic value of urinary Tamm-Horsfall protein (THP) and 24 h urine osmolality for recurrent calcium oxalate (CaOx) stones. Clinical data of 120 patients with upper urinary tract stones admitted to our hospital between January 2020 and January 2022 were retrospectively reviewed. Patients were divided into recurrence (53 patients) and non-recurrence (67 patients) groups based on postoperative stone recurrence. Meanwhile, 50 healthy patients were selected as the control group. Urinary THP levels, 24 h urine osmolality, and biochemical indices were compared between the three groups; their diagnostic values for stone recurrence were evaluated using receiver operating characteristic (ROC) curves. Urinary THP, 24 h urine osmolality, and biochemical indices were significantly higher in the recurrence group than in the non-recurrence and control groups (P < 0.05). The 24 h urine osmolality was positively correlated with urinary oxalic acid and calcium excretion. ROC curve analysis showed that optimal cutoff values of urinary THP and 24 h urine osmolality for the diagnosis of stone development were ≥27.01 mg/L and ≥577.69 mOsm/(kg H2O), respectively. Furthermore, these indices combined significantly improved the accuracy of diagnosis. Urinary THP and 24 h urine osmolality were higher in patients with recurrent CaOx stones. Detection of both parameters combined can accurately diagnose stone recurrence.