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Fatigue Crack Arrest in Mild Steel via Iron Electroplating

Materials Sciences and Applications 2021年第11期12卷 484-503页

作者： Jiaming Huang henry cardenas Taiji Group USA Inc. Hickory USA Louisiana Tech University Ruston USA

In this work, electrochemical plating treatments were applied to ASTM A36 steel specimens to study the efficiency and limitations of this method for arresting fatigue crack propagation. Electroplated iron was deposited onto the crack surfaces using a circuit in which Swedish Iron served as the anode in a solution of Ammonium Iron(II) Sulfate Hexahydrate. The iron ions were driven into fatigue cracks that were formed within ASTM E399 compact tension specimens. This work showed that an iron-plating treatment operated at 20°C can arrest fatigue crack propagation for a significant period of cycles. The propagation re-initiation lives that resulted ranged from 11,000 to 230,000 cycles. As observed in prior work, the propagation re-initiation life correlated strongly to the magnitude of the stress intensity factor range that was applied during cycling. As this stress intensity increased, the propagation re-initiation life decreased. Repeated treatments on the same crack provided extended service lives by as much as 370,000 cycles or 60% of the entire fatigue life of the component. Future work may show that re-application of the treatment, when conducted prior to crack re-initiation, could further extend the service life indefinitely. The Correia crack closure model was modified to provide an empirical expression for predicting the crack re-initiation life of the treated component. Interestingly, highly effective arrest behavior was still observed for cracks that were loaded to stress intensity factors of only 3 - 6 during the treatment but then subjected to 20 during cyclic loading. Galvanic corrosion of the plated material exposed to simulated seawater was estimated to be 3 mpy. Future work will examine the use of less active plating alloys and the possibility of applying effective treatments into cracks that are in an unloaded state.

关键词： Fatigue Crack Closure Crack Propagation Iron Plating Electrochemical Treatment Galvanic Corrosion

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Electrokinetic Nanoparticle Treatment Success Factors

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Materials Sciences and Applications 2020年第11期11卷 767-786页

作者： henry E. cardenas Huayuan Zhong College of Engineering and Science Louisiana Tech University Ruston LA USA

Electrokinetic pozzolanic nanoparticle treatments have been reported in the literature to achieve rapid porosity reductions and deeply penetrating strength enhancement of cement and concrete. The high electric fields required to achieve these results have tended to be accompanied by particle suspension instability. Coagulation is an instability that can limit the efficiency and effectiveness of a treatment by removing particles from suspension. The current study examines how electro-coagulation impacts electrokinetic treatment effectiveness. The nano-pozzolan suspension used in this study was Nalco 1056, alumina-coated silica (24-nm). A threshold electric field strength of 0.4 V/cm was identified for avoiding direct electro-coagulation. Treatments conducted at this threshold value exhibited a 50% strength increase. Treatments conducted above this threshold value exhibited significant particle electro-coagulation losses and strength increases of only 25%. This study found that electro-coagulation was influenced by the electric field strength, through a combination of particle crowding at pore entrances and pH shifts as driven by electrolysis.

关键词： Hardening Cement Electrokinetic Treatment Nanoparticle Stability Suspension Porosity Strength

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Crack Prediction Model for Concrete Affected by Reinforcement Corrosion

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Materials Sciences and Applications 2019年第6期10卷 475-495页

作者： Jeb M. Stefan Luz M. Calle Sven E. Eklund Mark R. Kolody Kunal Kupwade-Patil Eliza L. Montgomery henry E. cardenas University of Texas in Austin Austin USA NASA John F. Kennedy Space Center Kennedy Space Center Merritt Island USA Louisiana Tech University Ruston USA Department of Civil and Environmental Engineering Massachusetts Institute of Technology Cambridge USA

The purpose of this study was to develop an analytical model to predict the time required for cracking of concrete due to corrosion of the iron reinforcement. The concrete and cement specimens used for this study were batched with cover material ranging from 0.75 to 1.3 in (1.91 to 3.30 cm). The extent of cover material was not formulated into the model under the assumption that crack initiation would tend to produce visible cracking within a relatively short time period. The model was derived using both Hooke’s Law and the volume expansion induced by the corrosion oxides. Correlation achieved with specimen cracking data from the literature was relatively good with a 95% level of confidence. This model presents a key benefit to facility and infrastructure managers by enabling them to plan the time when corrosion mitigating actions are required. It also provides a significant convenience as the condition of the concrete structure or its environment changes over time. The only parameter that needs to be updated over time is the corrosion rate measurement. This single parameter captures the most influential impact that stems from several other parameters which tend to be required in models that are more mechanistically definitive.

关键词： Cracking Model Concrete Corrosion Marine Pore Band Green Rust

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Diversity and host assemblage of avian haemosporidians in different terrestrial ecoregions of Peru

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Current Zoology 2022年第1期68卷 27-40页

作者： Luz GARCIA-LONGORIA Jaime MURIEL Sergio MAGALLANES Zaira Hellen VILLA-GALARCE Leonila RICOPA Wilson Giancarlo INGA-DIAZ Esteban FONG Daniel VECCO Cesar GUERRA-SALDANA Teresa SALAS-RENGIFO Wendy FLORES-SAAVEDRA Kathya ESPINOZA Carlos MENDOZA Blanca SALDANA Manuel GONZALEZ-BLAZQUEZ henry GONZALES-PINEDO Charlene LUJAN-VEGA Carlos Alberto Del AGUILA Yessica VILCA-HERRERA Carlos Alberto PINEDA Carmen REATEGUI Jorge Manuel cardenas-CALLIRGOS JoseAlberto IANNACONE Jorge Luis MENDOZA Ravinder NMSEHGAL Alfonso MARZAL Departamento de Anatomia Biologia Celular y ZoologiaUniversidad de ExtremaduraBadajoz E-506071Spain Molecular Ecology and Evolution Lab Department of BiologyLund UniversitySolvegatan 37SE-22362 LundSweden Instituto Pirenaico de Ecologıa-IPE(CSIC) Avda.Nuestra Senora de la Victoria 16Jaca 22700Spain DIRESA Direccion Regional de SaludLoreto 16001Peru Departamento Academico de Microbiologia y Parasitologia.Facultad de Ciencias Biologicas Universidad Nacional de la Amazonia PeruanaIquitos 16001Peru Facultad de Ciencias Agropecuarias Universidad Alas PeruanasLima 15823Peru EverGreen Institute-San Rafael Distrito de IndianaLoreto 16200Peru Observatorio de Aves Loreto(LBO) Distrito de San JuanLoreto 16008Peru Centro Urku de Estudios Amazonicos Tarapoto 22200Peru Servicio Nacional de Areas Naturales Protegidas por el Estado 15036Peru Sanidad Animal-Facultad de Zootecnia Universidad Nacional Agraria La MolinaLima 15012Peru Laboratorio de Microbiologia Facultad de Medicina Veterinaria y ZootecniaUniversidad CientUfica del SurLima 15067Peru Laboratorio de Analisis Clinico Moraleslab SAC MoralesSan Martin 22201Peru Asociacion Ecosistemas Andinos(ECOAN) Cuzco 08002Peru Pharmacology and Toxicology Graduate Group University of CaliforniaDavisDA 95616USA Global Health Initiative Wabash CollegeCrawfordsvilleIN 47933USA Facultad de Ciencias Biologicas Universidad Nacional Mayor de San MarcosLima 15081Peru Facultad de Medicina Veterinaria Universidad Nacional Hermilio ValdizanHuanuco10160Peru Asociacion Peruana de Helmintologia e Invertebrados Afines Lima 15054Peru Laboratorio de Ecologia y Biodiversidad Animal Universidad Nacional Federico VillarrealEl AgustinoLima 15007Peru Laboratorio de Invertebrados Universidad Ricardo Palma-Santiago de SurcoLima 15537Peru Department of Biology San Francisco State UniversitySan FranciscoCA 94132USA

Characterizing the diversity and structure of host–parasite communities is crucial to understandingtheir eco-evolutionary *** and related haemosporidian parasites are responsible forfitness loss and mortality in bird species ***,despite exhibiting the greatest ornithologicalbiodiversity,avian haemosporidians from Neotropical regions are quite ***,we analyze the genetic diversity of bird haemosporidian parasites(Plasmodium andHaemoproteus)in 1,336 individuals belonging to 206 bird species to explore for differences in diversityof parasite lineages and bird species across 5 well-differentiated Peruvian *** 70 different haemosporidian lineages infecting 74 bird *** showed that 25 out ofthe 70 haplotypes had not been previously ***,we also identified 81 new host–parasite interactions representing new host records for these haemosporidian *** outcomesrevealed that the effective diversity(as well as the richness,abundance,and Shannon–Weaver index)for both birds and parasite lineages was higher in Amazon basin ***,we also showed that ecoregions with greater diversity of bird species also had highparasite richness,hence suggesting that host community is crucial in explaining parasite *** parasites were found in ecoregions with lower bird diversity,implying that the abundanceand richness of hosts may shape the exploitation strategy followed by haemosporidian *** outcomes reveal that Neotropical region is a major reservoir of unidentified *** studies analyzing host distribution and specificity of these parasites inthe tropics will provide important knowledge about phylogenetic relationships,phylogeography,and patterns of evolution and distribution of haemosporidian parasites.

关键词： Amazonia avian malaria generalist parasite habitat specificity Haemoproteus Plasmodium specialist parasite

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使用表皮肌电监测来检测全面强直-阵挛发作

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癫痫杂志 2018年第3期4卷 249-256页

作者： Jonathan J Halford Michael R Sperling Dileep R Nair 童馨高慧慕洁 Dlugos DJ Tatum WO Harvey J French JA Pollard JR Faught E Noe KH henry TR Jetter GM Lie OV Morgan LC Girouard MR cardenas DP Whitmire LE Cavazos JE

该前瞻性多中心Ⅲ期临床试验的目的在于评估在癫痫监测单元(Epilepsy monitoring unit,EMU)中使用可穿戴的表皮肌电图(surface electromyographic,s EMG)监测系统来检测全面强直-阵挛发作(Generalized tonic–clonic seizures,GTCS)的性能和耐受性。199例有GTCS病史的患者被收入11个Ⅳ级癫痫中心的EMU中,在进行临床视频脑电图(VEEG)监测的同时,也通过在肱二头肌上佩戴可穿戴设备接受了s EMG监测。所有s EMG数据记录都使用先前开发的检测算法在中心站点处理。将s EMG检测到的GTCS与3名评审专家验证的发作事件进行比较。在所有受试者中,检测算法共检测到了46次GTCS中的35次[76%,95%CI(0.61,0.87)],阳性预测值(Positive predictive value,PPV)为0.03,平均误报率(False alarm rate,FAR)为2.52/24 h。对于在肱二头肌中线上方记录到的数据,系统检测到了全部的29例GTCS[100%,95%CI(0.88,1.00)],检测时间平均延迟7.70 s,PPV为6.2%,平均FAR为1.44/24 h。28%(55/199)报告了轻至中度的不良事件,并导致9%的研究中止(17/199)。这些不良事件主要是电极贴片引起的皮肤刺激反应,这种情况未经治疗即可缓解。研究中无严重不良事件报告。在肱二头肌上使用s EMG监测装置来检测GTCS是可行的。正确放置该装置对于检测准确性至关重要,但是对于一些患者而言,减少误报数仍有一定难度。

关键词：临床试验癫痫监测全面性癫痫发作痉挛大发作可穿戴

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