Data-driven design of fault diagnosis for three-phase PWM rectifier using random forests technique with transient synthetic features

A three-phase pulse-width modulation (PWM) rectifier can usually maintain operation when open-circuit faults occur in insulated-gate bipolar transistors (IGBTs), which will lead the system to be unstable and unsafe. Aiming at this problem, based on random forests with transient synthetic features, a data-driven online fault diagnosis method is proposed to locate the open-circuit faults of IGBTs timely and effectively in this study. Firstly, by analysing the open-circuit fault features of IGBTs in the three-phase PWM rectifier, it is found that the occurrence of the fault features is related to the fault location and time, and the fault features do not always appear immediately with the occurrence of the fault. Secondly, different data-driven fault diagnosis methods are compared and evaluated, the performance of random forests algorithm is better than that of support vector machine or artificial neural networks. Meanwhile, the accuracy of fault diagnosis classifier trained by transient synthetic features is higher than that trained by original features. Also, the random forests fault diagnosis classifier trained by multiplicative features is the best with fault diagnosis accuracy can reach 98.32%. Finally, the online fault diagnosis experiments are carried out and the results demonstrate the effectiveness of the proposed method, which can accurately locate the open-circuit faults in IGBTs while ensuring system safety.Comment: IET Power Electronic

Clinical outcomes of microincision vitrectomy for high myopia patient with macular hole retinal detachment

AIM: To observe the clinical effects of microincision vitrectomy combined with internal limiting membrane(ILM)peeling for high myopia patient with macular hole retinal detachment(MHRD). METHODS: This was a retrospective non-randomized controlled clinical study. A total of 26 eyes of 26 patients with high myopic MHRD from January 2011 to December 2016 were included. All eyes underwent 23G pars plana microincision vitrectomy combined with ILM peeling. The preoperative and postoperative best corrected visual acuity(BCVA), intraocular pressure, ocular anterior segment and fundus examination were observed, and the anatomical closure of macular hole was checked by optical coherence tomography(OCT). The relationships between final BCVA and these parameters(age, GASS stage, onset time, OCT pattern of MH closure, initial vision)were examined by regression analysis. RESULTS: The postoperative MH closure rate of high myopia MHRD was 58%. OCT images of the repaired MH in high myopia were categorized into 3 patterns: U-type(3 eyes)with relative normal foveal contour; V-type(4 eyes)with steep foveal contour; W-type(8 eyes)with foveal defect od neruosensory retina, but without warped hem of retinal hole or cystic formation. Multivariate Logistic regression analysis showed that postoperative BCVA was correlated with the OCT patternts of closed MH and initial vision(PCONCLUSION: Microincision vitrectomy combined with ILM peeling is a safe and effective surgical treatment for high myopia patient with macular hole retinal detachment. The postoperative visual acuity was correlated with the OCT patterns of closed MH and initial vision

Scalable and controllable synthesis of atomic metal electrocatalysts assisted by an egg-box in alginate

Herein, a general strategy is developed to synthesize atomic metal catalysts using sustainable and earth-abundant sodium alginate (Na-Alg), a common seaweed extract, as a precursor. The “egg-box” structure in Na-Alg after ion-exchange with metal cations (Zn2+, Co2+, Ni2+, Cu2+, etc.) is the key to achieve a scalable and controllable synthesis of highly dispersed atomic metals. For instance, atomic Co, Ni and Cu have been successfully synthesized using this method. As a representative, the as-synthesized atomically dispersed Co on reduced graphene oxide (A-Co/r-GO) can reach a maximum metal loading of 3.6 wt%, showing outstanding catalytic activity and stability for the oxygen reduction reaction (ORR) with a half-wave potential (E1/2) of 0.842 V vs. RHE that is more positive than that of 20 wt% Pt/C (0.827 V vs. RHE) in alkaline solutions. The A-Co/r-GO catalyzed zinc-air batteries (ZABs) outperform Pt/C-based ZABs in the aspects of discharge voltage and specific zinc capacity, and can work robustly for more than 250 h with negligible voltage loss with refueling the Zn anode and KOH electrolyte periodically. This work opens up a new strategy for a general, practical and scalable synthesis of atomic metal catalysts at very low cost.No Full Tex

Atomically Dispersed Pd on Nanodiamond/Graphene Hybrid for Selective Hydrogenation of Acetylene

An atomically dispersed palladium (Pd) catalyst supported onto a defective nanodiamond-graphene (ND@G) is reported here for selective hydrogenation of acetylene in the presence of abundant ethylene. The catalyst exhibits remarkable performance for the selective conversion of acetylene to ethylene: high conversion (100%), ethylene selectivity (90%), and good stability (i.e., steady for at least 30 hours). The unique struc-ture of the catalyst (i.e., atomically dispersion of Pd atoms on graphene through Pd-C bond anchoring) ensure the facile desorption of ethylene against the over-hydrogenation of ethylene to undesired ethane, which is the key for the outstanding selectivity of the catalyst

Dense network of one-dimensional mid-gap metallic modes in monolayer MoSe2 and their spatial undulations

We report the observation of a dense triangular network of one-dimensional (1D) metallic modes in a continuous and uniform monolayer of MoSe2 grown by molecular-beam epitaxy. High-resolution transmission electron microscopy and scanning tunneling microscopy and spectroscopy (STM/STS) studies show these 1D modes are mid-gap states at inversion domain boundaries. STM/STS measurements further reveal intensity undulations of the metallic modes, presumably arising from the superlattice potentials due to moire pattern and the quantum confinement effect. A dense network of the metallic modes with high density of states is of great potential for heterocatalysis applications. The interconnection of such mid-gap 1D conducting channels may also imply new transport behaviors distinct from the 2D bulk

Prevalence and treatment gap of active convulsive epilepsy: A large community-based survey in rural West China

AbstractPurposeActive convulsive epilepsy (ACE) impacts patients greatly, especially in low-income countries where patients do not receive appropriate treatment. In the present study, we measured the prevalence and treatment gap (TG) of ACE in rural West China.MethodsSix rural areas in West China that have a total population of 3,541,319 were selected to conduct prevalence and TG estimates of ACE via a clue survey from 2007 to 2009. Clue survey here is a community-based screening strategy among defined population which requires employed well-trained local physicians//health workers to collect all clues available to discover/identify/recruit patients within a study period. Questionnaire-based interviews were used for the identification of ACE patients, and information was obtained during the survey. Prevalence and TG of ACE were calculated.ResultsA total of 6547 patients with ACE were identified. The estimated prevalence of ACE was 1.8 per 1000 in the general population, with the prevalences in males and females determined to be 2.0 and 1.7, respectively (p<0.001). The TG in the general population was 66.3%, and it was 66.6% and 66.0% in males and females, respectively (p>0.05). The TG figures dropped with advancing age and increased above 30 years of age. Patients aged 60 years or older had the largest TG (77.8%); those with disease course less than 10 years showed a larger TG and those who experienced two to five seizures annually had a significantly larger TG (70.6%). Additionally, only 63.9% of the ACE patients included in the study were aware of the disease and had consulted a doctor.ConclusionsThere exists a large TG of ACE in West China rural areas. Majority of those ever consulted a doctor but failed to receive or adhere to an appropriate treatment program. Management including public education as well as training of local physicians were necessary to fill that gap

Anchoring Cu 1 species over nanodiamond-graphene for semi-hydrogenation of acetylene

The design of cheap, non-toxic, and earth-abundant transition metal catalysts for selective hydrogenation of alkynes remains a challenge in both industry and academia. Here, we report a new atomically dispersed copper (Cu) catalyst supported on a defective nanodiamondgraphene (ND@G), which exhibits excellent catalytic performance for the selective conversion of acetylene to ethylene, i.e., with high conversion (95%), high selectivity (98%), and good stability (for more than 60 h). The unique structural feature of the Cu atoms anchored over graphene through Cu-C bonds ensures the effective activation of acetylene and easy desorption of ethylene, which is the key for the outstanding activity and selectivity of the catalyst

Recent advances in optical aptasensors for biomarkers in early diagnosis and prognosis monitoring of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) accounts for approximately 90% of all primary liver cancers and is one of the main malignant tumor types globally. It is essential to develop rapid, ultrasensitive, and accurate strategies for the diagnosis and surveillance of HCC. In recent years, aptasensors have attracted particular attention owing to their high sensitivity, excellent selectivity, and low production costs. Optical analysis, as a potential analytical tool, offers the advantages of a wide range of targets, rapid response, and simple instrumentation. In this review, recent progress in several types of optical aptasensors for biomarkers in early diagnosis and prognosis monitoring of HCC is summarized. Furthermore, we evaluate the strengths and limitations of these sensors and discuss the challenges and future perspectives for their use in HCC diagnosis and surveillance

Tin Assisted Fully Exposed Platinum Clusters Stabilized on Defect-Rich Graphene for Dehydrogenation Reaction

Tin assisted fully exposed Pt clusters are fabricated on the core-shell nanodiamond@graphene (ND@G) hybrid support (a-PtSn/ND@G). The obtained atomically dispersed Pt clusters, with an average Pt atom number of 3, were anchored over the ND@Gsupport by the assistance of Sn atoms as a partition agent and through the Pt-C bond between Pt clusters and defect-rich graphene nanoshell. The atomically dispersed Pt clusters guaranteed a full metal availability to the reactants, a high thermal stability, and an optimized adsorption/desorption behavior. It inhibits the side reactions and enhances catalytic performance in direct dehydrogenation of n-butane at a low temperature of 450 °C, leading to \u3e98% selectivity toward olefin products, and the turnover frequency (TOF) of a-PtSn/ND@G is approximately 3.9 times higher than that of the traditional Pt3Sn alloy catalyst supported on Al2O3 (Pt3Sn/Al2O3)