Remaining Useful Life Model and Assessment of Mechanical Products: A Brief Review and a Note on the State Space Model Method

The remaining useful life(RUL) prediction of mechanical products has been widely studied for online system performance reliability, device remanufacturing, and product safety(safety awareness and safety improvement). These studies incorporated many di erent models, algorithms, and techniques for modeling and assessment. In this paper, methods of RUL assessment are summarized and expounded upon using two major methods: physics model based and data driven based methods. The advantages and disadvantages of each of these methods are deliberated and compared as well. Due to the intricacy of failure mechanism in system, and di culty in physics degradation observation, RUL assessment based on observations of performance variables turns into a science in evaluating the degradation. A modeling method from control systems, the state space model(SSM), as a first order hidden Markov, is presented. In the context of non-linear and non-Gaussian systems, the SSM methodology is capable of performing remaining life assessment by using Bayesian estimation(sequential Monte Carlo). Being e ective for non-linear and non-Gaussian dynamics, the methodology can perform the assessment recursively online for applications in CBM(condition based maintenance), PHM(prognostics and health management), remanufacturing, and system performance reliability. Finally, the discussion raises concerns regarding online sensing data for SSM modeling and assessment of RUL.

Progress in Neural NLP:Modeling,Learning,and Reasoning

Natural language processing(NLP)is a subfield of artificial intelligence that focuses on enabling computers to understand and process human languages.In the last five years,we have witnessed the rapid development of NLP in tasks such as machine translation,question-answering,and machine reading comprehension based on deep learning and an enormous volume of annotated and unannotated data.In this paper,we will review the latest progress in the neural network-based NLP framework(neural NLP)from three perspectives:modeling,learning,and reasoning.In the modeling section,we will describe several fundamental neural network-based modeling paradigms,such as word embedding,sentence embedding,and sequence-to-sequence modeling,which are widely used in modern NLP engines.In the learning section,we will introduce widely used learning methods for NLP models,including supervised,semi-supervised,and unsupervised learning;multitask learning;transfer learning;and active learning.We view reasoning as a new and exciting direction for neural NLP,but it has yet to be well addressed.In the reasoning section,we will review reasoning mechanisms,including the knowledge,existing non-neural inference methods,and new neural inference methods.We emphasize the importance of reasoning in this paper because it is important for building interpretable and knowledgedriven neural NLP models to handle complex tasks.At the end of this paper,we will briefly outline our thoughts on the future directions of neural NLP.

电极插入深度的控制及其对冶炼的影响

电极插入渣池的深度对电渣重熔过程的熔炼速度有很大影响,而熔炼速度又是决定电渣钢锭质量的关键因素,本文主要叙述了在电渣重熔过程中对电极插入深度的控制方法及其对熔炼的影响。

Evaluation of freezing state of sandstone using ultrasonic time-frequency characteristics

Common problems in engineering projects that involve artificial ground freezing of soil or rock include inadequate thickness,strength and continuity of artificial frozen walls.It is difficult to evaluate the freezing state using only a few thermometer holes at fixed positions or with other existing approaches.Here we report a novel experimental design that investigates changes in ultrasonic properties(received waveform,wave velocity V_(p),wave amplitude,frequency spectrum,centroid frequency f_(c),kurtosis of the frequency spectrum KFS,and quality factor Q)measured during upward freezing,compared with those during uniform freezing,in order to determine the freezing state in 150 mm cubic blocks of Ardingly sandstone.Water content,porosity and density were estimated during upward freezing to ascertain water migration and changes of porosity and density at different stages.The period of receiving the wave increased substantially and coda waves changed from loose to compact during both upward and uniform freezing.The trend of increasing V_(p) can be divided into three stages during uniform freezing.During upward freezing,V_(p) increased more or less uniformly.The frequency spectrum could be used as a convenient and rapid method to identify different freezing states of sandstone(unfrozen,upward frozen,and uniformly frozen).The continuous changes in reflection coefficient r_(φ),refraction coefficient t_(φ) and acoustic impedance field are the major reason for larger reflection and refraction during upward freezing compared with uniform freezing.Wave velocity V_(p),wave amplitude A_(h),centroid frequency f_(c) and quality factor Q were adopted as ultrasonic parameters to evaluate quantitatively the temperature T of uniformly frozen sandstone,and their application within a radar chart is recommended.Determination of V_(p) provides a convenient method to evaluate the freezing state and calculate the cryofront height and frozen section thickness of upward frozen sandstone,with accuracies of 73.37%-99.23%.

Active straining engineering on self-assembled stacked Ni-based hybrid electrode for ultra-low overpotential

Generating sufficient strains on metal surfaces are highly challenging owing to that most metals can deform plastically to relax the strains on the surfaces.In this work,we developed a facile but highly efficient stacked deposition strategy to in situ activation and reconstruction of NiO/NiOOH on Ni matrix,following with the migration of Fe ions to NiOOH.The Fe sites on the Ni/NiO/NiOOH facilitate the formation of the stable*OH oxygenated intermediates,and the Ni matrix in the catalyst provides the catalyst excellent stability.The oxygen evolution reaction(OER)performance of the stacked NiFe-5 with compressive strain displays the strengthened binding to oxygenated intermediates and superior OER activity,the ultralow overpotentials of 162 versus reversible hydrogen electrode at 10 mA cm^(-2).On the other hand,the Ni-5 without the incorporation of Fe has shown an outstanding hydrogen evolution reaction(HER)activity,affording an overpotential of 47 mV at 10 mA cm^(-2).The NiFe-5‖Ni-5 enables the overall water splitting at a voltage of 1.508 V to achieve 20 mA cm^(-2) with remarkable durability.The stacked deposition strategy improves binding strength of Ni-based catalysts to oxygenated intermediates via generating compressive strain,causing high catalytic activities on OER and HER.

Analysis of the Microstructure of a Failed Cement Sheath Subjected to Complex Temperature and Pressure Conditions

One of the main obstacles hindering the exploitation of high-temperature and high-pressure oil and gas is the sealing integrity of the cement sheath.Analyzing the microstructure of the cement sheath is therefore an important task.In this study,the microstructure of the cement sheath is determined using a CT scanner under different temperature and pressure conditions.The results suggest that the major cause of micro-cracks in the cement is the increase in the casing pressure.When the micro-cracks accumulate to a certain extent,the overall structure of the cement sheath is weakened,resulting in gas channeling,which poses a direct threat to the safe production of oil and gas.A change in the casing temperature has a limited effect on the microstructure of the cement sheath.

Exploration on Reform of Ideological and Political Theory Examination in College

The ideological and political theory course exam in new era is an important part of the ideological and political theory teaching and important means to improve the effectiveness of teaching. In this paper, the author took a careful analysis of drawbacks and its causes of Universities traditional test, made a systematical summary of the combination of our school programs and 05 teaching practice of ideological and political theory course examinations of the Reform and effectiveness, and pointed out the problems of the Examination Reform and Development direction.

Reducing the Rate of Unplanned Extubation of Venous Access in Perioperative Patients

Objective:To investigate the application effect of quality control circle activities in reducing the rate of unplanned extubation of venous access in perioperative patients.Methods:The quality control circle method was used to analyze the causes,identify the actual causes of unplanned out-of-control,take corresponding measures,formulate corresponding countermeasures,implement standardized management,and carry out continuous improvement.Results:Following the implementation of quality control circle activities,the rate of unplanned extubation of venous access in perioperative patients decreased from 27.35%before improvement to 3.42%after improvement.Conclusion:The use of quality control circle activities in the safety management of venous access in perioperative patients is conducive to reducing the rate of unplanned extubation of venous access in perioperative patients.

Toward Human-centered XAIin Practice:A survey

Human adoption of artificial intelligence(AI)technique is largely hampered because of the increasing complexity and opacity of AI development.Explainable AI(XAI)techniques with various methods and tools have been developed to bridge this gap between high-performance black-box AI models and human understanding.However,the current adoption of XAI technique stil lacks"human-centered"guidance for designing proper solutions to meet different stakeholders'needs in XAI practice.We first summarize a human-centered demand framework to categorize different stakeholders into five key roles with specific demands by reviewing existing research and then extract six commonly used human-centered XAI evaluation measures which are helpful for validating the effect of XAI.In addition,a taxonomy of XAI methods is developed for visual computing with analysis of method properties.Holding clearer human demands and XAI methods in mind,we take a medical image diagnosis scenario as an example to present an overview of how extant XAI approaches for visual computing fulfil stakeholders'human-centered demands in practice.And we check the availability of open-source XAI tools for stakeholders'use.This survey provides further guidance for matching diverse human demands with appropriate XAI methods or tools in specific applications with a summary of main challenges and future work toward human-centered XAI in practice.

Development and application of wellbore heat transfer model considering variable mass flow

Dual-gradient drilling technology is being increasingly used in formations with narrow pressure margins.For dual-gradient drilling based on downhole separation,hollow spheres are separated into the annulus at the separator position,resulting in variable mass flow in the wellbore.Thus,existing heat transfer models are no longer suitable for describing wellbore temperature profiles in dual-gradient drilling.This study focused on developing a wellbore heat transfer model that fully considers separated hollow spheres entering the annulus,complex casing programs,and heat sources,for dual-gradient drilling based on downhole separation.The model was solved using an iterative method.Then,the accuracy of the model was verified using temperature data measured from two wells.Finally,the difference in the annular temperature distributions between dual-gradient drilling and conventional single-gradient drilling were investigated,as were the wellbore heat transfer characteristics for dual-gradient drilling.The following major conclusions were drawn:(1)for dualgradient drilling based on downhole separation,at the separator location,the annular fluid temperature does not decrease,but rather increase in the flow direction because of the inflow of hollow spheres;(2)a clear inflection point exists in the annular fluid temperature curve at the location where the separator would be;(3)the magnitude of the mutation of the temperature curve at the inflection point is considerably affected by the heat capacities of the hollow spheres and the pure drilling fluid;(4)under the same change in separation efficiency,distance between the bit and separator,flow rate,and thermal conductivity of formation,the variation range of the fluid temperature at the bottom hole is greater than that at the wellhead.

High-density/efficient surface active sites on modified separators to boost Li-S batteries via atomic Co^(3+)-Se termination

Various and critical electrocatalytic processes are involved during the redox reactions in the Li-S batteries,which extremely depend on the surface structure and chemical state.Recently,single-atom concept unlocks a route to maximize the use of surface-active atoms,however,further increasing the density of active site is still strictly limited by the inherent structure that single-atoms are only highly-dispersed on substrate.Herein,we provide a viewpoint that an elaborate facet design with singlecrystalline structure engineering can harvest high-density surface active sites,which can significantly boost the electrocatalyst performance for excellent Li-S batteries.Specifically,the single-crystal CoSe_(2)(scCS)exhibits three-types of terminated(011)facet,efficiently obtaining the surface with a high-rich Co^(3+)–Se bond termination,in contrast with lots of surface grain boundaries and dangling bonds in polycrystalline CoSe_(2).Surprisingly,the surface active sites concentration can reach more than 69%.As anticipated,it can provide high-density and high-efficient active sites,enormously suppressing the shuttle effect and improving the reaction kinetics via accelerating the conversion and deposition of polysulfides and Li2S.This surface lattice strategy with element terminated mode is a promising approach for designing electrocatalyst effect-based energy system,not merely for Li-S batteries.

The uniqueness and superiority of energy utilization in yaks compared with cattle in the highlands:A review

Yaks living on the Qinghai-Tibetan Plateau for a long time have evolved a series of mechanisms to adapt to the unique geographical environment and climate characteristics of the plateau.Compared with other ruminants,yaks have higher energy utilization and metabolic efficiency.This paper presents possible mechanisms responsible for the efficient energy utilization,absorption and metabolism resulting from the unique evolutionary process of yaks.It is hoped that the information discussed in this review will give a better insight into the uniqueness and superiority of yaks in regards to energy metabolism and utilization compared with cattle and open new avenues for the targeted regulation of energy utilization pathways of other ruminants.

Diagnosing the Dynamic and Thermodynamic Effects for the Exceptional 2020 Summer Rainy Season in the Yangtze River Valley

An exceptional rainy season occurred in the Yangtze River valley of eastern China in June-July 2020.The relative importance of the dynamic and thermodynamic effects on this unusual event is evaluated through the budget equations of moisture and moist static energy(MSE).The moisture budget analysis suggests that the thermodynamic effect contributes to the precipitation anomaly by 8.5%through the advection of abnormal water vapor by mean vertical motion,while the dynamic effect,related to water vapor advection by anomalous vertical motion,has the dominant contribution.The MSE budget analysis further reveals that the anomalous vertical motion is both constrained by the dynamic effect related to changes in atmospheric circulation and the thermodynamic effect related to changes of the atmospheric thermal state,with a ratio of thermodynamic versus total effects estimated at 45.3%.The dynamic effect is linked to the advection of warm and humid air by the abnormal southwesterly wind,which is related with an anomalous anticyclone over the Philippine Sea.The thermodynamic effect is partly induced by the positive advection of anomalous MSE(mainly latent energy)by the mean vertical motion.This analysis of the dynamic and thermodynamic effects is useful to understand the underlying physical mechanisms leading to the unusual rainy season in the Yangtze River valley in summer 2020.It is also helpful to put forward a few speculations on the potential role of global warming whose primary effect is,after all,to change the thermal state of the atmosphere.

放射敏感的纳米调节剂重新编程肿瘤-免疫细胞通讯用于免疫治疗

目前,将肿瘤相关巨噬细胞从促肿瘤生长的M2表型调节为抑制肿瘤生长的M1表型已成为一种有前途的肿瘤免疫治疗策略,但仍然具有挑战性,而且以可控的方式实现显得尤为困难.在此,我们报道了一种用于可时空激活免疫反应的放射敏感型纳米调节剂(AuDAP).AuDAP可通过多价相互作用同时识别和结合M2巨噬细胞与肿瘤细胞.在低剂量医用X射线照射下,纳米调节剂可介导产生大量活性氧(ROS),激活NF-κB信号通路,使M2型巨噬细胞复极化为M1型,从而原位激活巨噬细胞的免疫功能.一系列体外和体内实验结果表明,纳米调节剂可以有效重塑肿瘤细胞和巨噬细胞之间的通讯,并特异性地激活抗肿瘤免疫治疗.通过长时间观察发现,治疗组小鼠的原位肿瘤被明显抑制且未观察到肺部转移瘤的形成.该纳米调节剂可作为一种有潜力的纳米药物用于精确的肿瘤治疗,并能为可控的免疫治疗提供新的见解.

Nanozymes for biomedical applications in orthopaedics

As the next generation of artificial enzymes,nanozymes have attracted increasing attention in biomedical applications due to their multienzyme-like characteristics,multifunctionalities,low cost,and high stability.By taking advantage of their diverse activities,a growing number of nanozyme-mediated therapeutic strategies have been developed for various diseases.Herein,we provide a brief review of the representative studies of nanozymes,especially in orthopaedic diseases over the past decade,which include arthritis,osteoporosis,bone regeneration,bacteria-associated infections,and osteosarcoma.Moreover,the future potential applications and some major challenges are also discussed.This review would not only provide some instructive views of nanozymes but also promote the development of enzyme-mimetic strategies in orthopaedics.

Pancreatic steatosis and its correlation with clinicopathological features in patients with pancreatic neuroendocrine neoplasms

Background and objective:The incidence of pancreatic neuroendocrine neoplasms(pNENs)has been increasing year by year,and pancreatic steatosis has been paid more and more attention to by clinicians.Our study aims to reveal the correlation between pancreatic steatosis,clinicopathological parameters,and the prognosis of patients with pNENs.Methods:The clinicopathological data of patients with pNENs who underwent surgical resections in our institution from January 2013 to May 2022 were retrospectively analyzed.The mean computed tomography(CT)values of the pancreas and spleen were used to assess the severity of the pancreatic steatosis.Pearson Chi-square test,T test,Mann Whitney U test,Univariate Cox re-gression,and Multivariate Cox regression were used to explore the relationship between pancreatic steatosis and age,sex,body mass index,tumor type,tumor location,tumor stage,blood lipid,prognosis,and other factors.Results:A total of 122 patients were included in our study,and 19.67%have pancreatic steatosis.The incidence of pancreatic steatosis was significantly higher in patients with fatty liver than in patients without fatty liver(36.8%vs 16.5%,P=.04).In insu-linoma,the incidence of pancreatic steatosis in elderly patients was significantly higher than in young and middle-aged patients(41.7%vs 9.3%,P=.025).There was no significant difference in lipid levels between the pancreatic steatosis group and the non-pancreatic steatosis group(P>.05).Kaplan-Meier curves show that the prognosis of stage III/IV patients was significantly worse than that of stage I/II patients(P<.001).However,there was no significant difference in prognosis between patients with and without pancreatic steatosis(P=.404).Conclusion:The incidence of pancreatic steatosis was significantly higher in those with fatty liver than those without fatty liver.There is a high incidence of pancreatic steatosis in elderly patients with insulinoma.American Joint Committee on Cancer(AJCC)stage,but not pancreatic steatosis,significantly affected the prognosis of patients with pNENs.