Nickel-based superalloy architectures with surface mechanical attrition treatment: Compressive properties and collapse behaviour

Surface modifications can introduce natural gradients or structural hierarchy into human-made microlattices,making them simultaneously strong and tough.Herein,we describe our investigations of the mechanical properties and the underlying mechanisms of additively manufactured nickel–chromium superalloy(IN625)microlattices after surface mechanical attrition treatment(SMAT).Our results demonstrated that SMAT increased the yielding strength of these microlattices by more than 64.71%and also triggered a transition in their mechanical behaviour.Two primary failure modes were distinguished:weak global deformation,and layer-by-layer collapse,with the latter enhanced by SMAT.The significantly improved mechanical performance was attributable to the ultrafine and hard graded-nanograin layer induced by SMAT,which effectively leveraged the material and structural effects.These results were further validated by finite element analysis.This work provides insight into collapse behaviour and should facilitate the design of ultralight yet buckling-resistant cellular materials.

Employee Attrition Classification Model Based on Stacking Algorithm

This paper aims to build an employee attrition classification model based on the Stacking algorithm.Oversampling algorithm is applied to address the issue of data imbalance and the Randomforest feature importance ranking method is used to resolve the overfitting problem after data cleaning and preprocessing.Then,different algorithms are used to establish classification models as control experiments,and R-squared indicators are used to compare.Finally,the Stacking algorithm is used to establish the final classification model.This model has practical and significant implications for both human resource management and employee attrition analysis.

Effect of mechanical attrition on microstructure and property of electroplated Ni coating

Ni coating was deposited on carbon steel by a mechanical attrition enhanced electroplating （MAEE） process. During the electroplating, the mechanical attrition（MA） was introduced by impact of glass balls on the sample surface with a special vibrating frequency. The surface and cross-sectional images of Ni coating were observed with SEM. The microstructure and crystallinity of coating were examined with TEM and XRD. The electrochemical performance of coating was measured with polarization curves and electrochemical impedance spectroscopy （EIS） and its mechanical behaviours, such as tensile strength and hardness, were studied. The results show that the MA has significant effects on the microstructure and property of the electroplated Ni coating. By MA, the coating becomes smooth, compact, thin and has refined grains and is free of cracks and pores. Consequently, the adhesion, tensile strength, hardness and corrosion resistance of coating are improved significantly.

English Language Attrition Among EFL Learners in Terms of Writing Skills

This study aims to identify if participants experience attrition in writing skills after two years' nonuse of English.70 participants took the tests of writing.A questionnaire was administered to the 70 participants and it included numerous variables that relate to language attrition such as motivation and social activities.The data collected from the tests and questionnaire were analyzed via SPSS.Cronbach's alpha and Many Facets Rasch Model were used to validate the construct and external reliability.The findings showed that participants experienced an overall statistically significant level of attrition in writing skills.Additionally,the specific skills of pertinence,coherence,clarity but excluding grammar,were seen to experience significant attrition over the two years' period.Participants showed a lower level of positive motivation and less social activities for learning English language during the two years' nonuse than before the two years' nonuse of English and this could have contributed to the writing attrition.

Implications of language attrition theory to vocabulary teaching strategies

As the reverse of language acquisition, language attrition refers to the loss of language ability resulting from little or no use of certain languages over a period of time. Among the three factors of language, vocabulary tends to be more vulnerable to attrition compared with syntax and phoneme. Therefore, a study based on vocabulary attrition is of greater importance. By reviewing the literatures on language attrition and outlining the influencing factors of language attrition, the paper tends to figure out the corresponding strategies which are effective in college English vocabulary teaching.

Investigation into Phonological Attrition among Beginner Chinese Mandarin Language Learners

Studying foreign language attrition is important in the context of Chinese language learning because, in light of a growing worldwide interest in learning Chinese languages, language professionals need to understand the complexities of Chinese language acquisition. However, little research exists to date on foreign language attrition among Chinese language learners. In this study, we examined the features of language attrition,especially phonological attrition, among Mandarin learners in a higher educational institution in Brunei Darussalam. Additionally, we sought to test, in a Bruneian context,prominent theories and hypotheses about language attrition, including markedness theory and functional load theory. Our sample consisted of 86 beginner Mandarin students who spoke Malay as their native language and English as the academic language. Participants were 18-20 years old and studied Mandarin formally 4 hours per week for 14 consecutive weeks, during which they were also required to study for 8 hours per week on their own.Subsequently, they took a 3-month break from studying. We tested participants before and after the break and computed descriptive statistics to compare the results of the two tests. Our results showed the greatest attrition rates in tones and special structures of Mandarin, with less attrition in final and initial sounds. We discuss specific phonological findings as they relate to native Malay speakers, and we describe how our findings confirm or contradict,within the Bruneian context, existing theories. We conclude that markedness theory is applicable in our research context, but our findings failed to support functional load theory.

Attrition resistant catalyst for dimethyl ether synthesis in fluidized-bed reactor

Fluidized-bed reactor is a candidate for dimethyl ether （DME） synthesis from syngas because of its excellent heat removal capability. In order to improve the attrition resistance of catalyst, an amount of silica sol as binder was added to the catalyst composed of methanol synthesis component CuO/ZnO/Al2O3 and methanol dehydration component HZSM-5, which was prepared by coprecipitation and shaped by spray drying to get spherical particles. The effect of silica sol on the catalytic activity was investigated in a fixed-bed flow microreactor. Based on the experiment results, silica sol in the range of 0-20wt% had small effect on the catalytic activity. Generally, the CO conversion and DME yield decreased with the increase in concentration of silica sol, while the attrition resistance of catalysts increased with increasing silica sol, indicating that it was feasible to improve the attrition resistance without greatly sacrificing the activity of catalyst. In addition, the characterizations of catalysts were carried out using Brunauer-Emmett-Teller （BET）, X-ray powder diffraction （XRD） and temperature programmed reduction （TPR）.

Study on attrition of spherical-shaped Mo/HZSM-5 catalyst for methane dehydro-aromatization in a gas–solid fluidized bed

As a potential methane efficient conversion process,non-oxidative aromatization of methane in fluidized bed requires a catalyst with good attrition resistance,especially in the states of high temperature,longtime rapid movement and chemical reaction.Existing evaluation methods for attrition resistance,such as ASTM D5757 and Jet Cup test,are targeted for fresh catalysts at ambient temperature,which cannot well reflect the real process.In this study,spherical-shaped Mo/HZSM-5 catalyst prepared by dipping and spray drying was placed in a self-made apparatus for attrition testing,in which the catalyst attrition under different system temperatures,running time and process factors was investigated with percent mass loss(PML),particle size-mass distribution(PSMD)and scanning electron microscope(SEM).Carbon deposition on the catalyst before and after activation,aromatization and regeneration was analyzed by thermogravimetry(TG),and the attrited catalysts were evaluated for methane dehydro-aromatization(MDA).The results show that the surface abrasion and body breakage of catalyst particles occur continuously,with the increase of system temperature and running time,and make the PML rise gradually.The process factors of activation,aromatization and regeneration can cause the catalyst attrition and carbon deposits,which broaden the PSMD in varying degrees,and the carbon-substances on catalysts greatly improve their attrition resistance at high temperature.Catalyst attrition has a certain influence on its catalytic performance,and the main reasons point to particle breakage and fine powder escape.

Improved Fatigue Behavior of Pipeline Steel Welded Joint by Surface Mechanical Attrition Treatment(SMAT)

A pipeline steel X80 with welded joint was subjected to surface mechanical attrition treatment （SMAT）. After SMAT, a nanostructure surface layer with an average grain size of about 10 nm was formed in the treated sample, and the fatigue limit of the welded joint was elevated by about 13% relative to the untreated joints. In the low and the high amplitude stress regimes, both fatigue strength and fatigue life were enhanced. Formation of the nanostructured surface layer played more important role in the enhanced fatigue behavior than that of residual stress induced by the SMAT.

Thermal stability of nanocrystalline layer prepared by surface mechanical attrition in 0Cr18Ni9Ti stainless steel

By means of surface mechanical attrition (SMA), a nanostructured surface layer was formed on a 0Cr18Ni9Ti austenite stainless steel plate. A strain-induced martensite transformation was observed during SMA treatment, and a single magnetic martensite phase layer with thickness of about 30 μm was gotten. The grain growth and phase transformations in the nanocrystalline layer are investigated during heating. The grain growth exponent for nanocrystalline polycrystalline steel is estimated. The kinetics mechanism governing the grain growth in the nanocrystalline layer is discussed. The martensite in the surface layer is quite stable and the temperature at which the reverse transformation of martensite to austenite starts during heating is about 500 ℃.

Study on the friction and wear properties of the surface nanocrystallized 1.0C-1.5Cr steel induced by the surface mechanical attrition treatment

Nano-structured layers are fabricated on the surface of 1.0C-1.5Cr steel by using the surface mechanical attrition treatment(SMAT)technology,and the microstructures of the surface nano-crystallization layers are characterized by means of X-ray diffraction(XRD)and transmission electron microscopy(TEM).The friction and wear properties are also investigated by a UMT-2 friction and wear tester.Experimental research has indicated that the average diameter of nanocrystalline grains in the surface layer after being treated for 15 min is in the range of 10-20 nm,and ferrite and cementite grains can not be identified by their morphologies.The wear-resistance of the specimen treated for 15 min has been doubled,compared with that of the matrix due to the grain refinement to a nano-sized scale.The lowest friction coefficient is 0.27,which is for the specimen treated for 30 min,resulting from the dissolution of the cementite phase and the formation of a relative homogenous structure.The SMAT technique for enhancing the wear-resistance of the 1.0C-1.5Cr steel has an optimum processing time,which is in the range of 15-30 min.The dominant wear mechanism of the specimen treated for 15 min changes from adhesive wear into particle wear.

A Tentative Study of Foreign Language Attrition over the Period of Winter Vacation—A Survey of College Students in Yanshan University

This paper first presents a review of language attrition research with its defi nition and classifi cation. Then, through a survey of college students, the infl uence of shortterm language attrition over the learners' cognition and affection is identifi ed. To decrease the negative factors, some pedagogical implications and suggestions are discussed and provided in the end.

The Influence of Second Language Attrition on Foreign Language Teaching

Besides the sessions of teaching and learning in language learning activities, language attrition, as the concomitant product of language acquisition, exerts significant impact on language teaching, especially on foreign language teaching. By exploring this phenomenon, some effective ways against language attrition can be found in order to maximize foreign language teaching. This paper is about to illustrate the relevant theories from scholars at home and abroad, and providing some ways to help foreign language learners maintain the language proficiency.

AUTORADIOGRAPHIC STUDY OF THE ATTRITION OF MIGRATING SCHISTOSOMULA IN THE SKIN OF MICE II.MICE CHALLENGED WITH NORMAL S.MANSONI CERCARIAE AFTER IMMUNIZATION WITH HIGHLY IRRADIATED CERCARIAE

The migratory pattern and attrition of75Se-labelled S.mansoni challenge cercariae in CF1mice immunized 0,1,3, or 5 times with 12kR-or 48kR-irradiated cercariae were investigatedby compressed organ autoradiography.Mice were percutaneously inoculated with 500-1000 cer-cariae for each immunization and with a known count of approximately 90 cercariae at adifferent site for challenge.The skin,lungs,liver,other organs,and catrcass were processedfor autoradiography.Hepatic and mesenteric perfusions for worm collection were alsosampled from day 19 through 34.In naive tnice,25% of challenge cercariae died in theskin.Skin attrition of challenge cercariae in mice immunized with 12kR-irradiated cercariaewas 43% with 1 immunization,54% with 3,and 58% with 5,whereas in mice immunized with48kR-irradiated cercariae,skin,attrition was48% with 1,63% with 3,and 76% with 5 immunni-zations.In all immunized mice,a high percentage of migrating sehistosomula died in the skinwithin 24 hours of a challenge infection.Utilizing autoradiography,it was found that thesilver foci created by single labelled worms were difficult to differentiate from those of pairedworms.This study documents the induction of acquired resistance against a challenge infectionin the skin by vaccination with highly irradiated cercariae,with the degree of attemtation ofimmunizing cercariae and the number of immunizations being closely related to the attritiotn.rate in the skin.Finally,we discuss the contradictory views concerning the site of attritiotn ofchallenge cercariae.

Real-world treatment attrition rates in advanced esophagogastric cancer

BACKGROUND Over the last decade,multiple agents have demonstrated efficacy for advanced esophagogastric cancer(EGC).Despite the availability of later lines of therapy,there remains limited real-world data about the treatment attrition rates between lines of therapy.AIM To characterize the use and attrition rates between lines of therapy for patients with advanced EGC.METHODS We identified patients who received at least one cycle of chemotherapy for advanced EGC between July 1,2017 and July 31,2018 across six regional centers in British Columbia(BC),Canada.Clinicopathologic,treatment,and outcomes data were extracted.RESULTS Of 245 patients who received at least one line of therapy,median age was 66 years(IQR 58.2-72.3)and 186(76%)were male,Eastern Cooperative Oncology Group(ECOG)performance status 0/1(80%),gastric vs GEJ(36%vs 64%).Histologies included adenocarcinoma(78%),squamous cell carcinoma(8%),and signet ring(14%),with 31%HER2 positive.72%presented with de novo disease,and 25%had received previous chemoradiation.There was a high level of treatment attrition,with patients receiving only one line of therapy n=122,50%),two lines n=83,34%),three lines n=34,14%),and four lines n=6,2%).Kaplan-Meier analysis demonstrated improved survival with increasing lines of therapy(median overall survival 7.7 vs 16.6 vs 22.8 vs 40.4 mo,P<0.05).On multivariable Cox regression,improved survival was associated with better baseline ECOG and increased lines of therapy(P<0.05).CONCLUSION The steep attrition rates between therapies highlight the unmet need for more efficacious early-line treatment options for patients with advanced EGC.

Attrition from care after the critical phase of severe pre-eclampsia and eclampsia: Insights from an intervention with magnesium sulphate in a primary care setting in northern Nigeria

Background: Evidence has shown that Magnesium Sulphate (MgSo4) is the gold standard for treating severe pre-eclampsia and eclampsia (SPE/E), and calls for its widespread use at all levels of health service delivery, including the primary care level. Objective: To determine if administering loading dose of MgSo4 on pregnant women with severe preeclampsia and eclampsia at primary care level would improve maternal and fetal outcomes. Method: Two sets of Primary Health Care (PHC) facilities were identified;one served as experimental one and the other as control. The community health extension workers (CHEWs) and the community health officers (CHOs) at the experimental PHCs were trained to administer the loading dose of MgSo4 for patients with SPE/E, in addition to other supportive treatments, before making a referral while the control PHCs did not give MgSo4, and neither administered diazepam as an alternative or no anti-convulsant at all, before making a referral to higher centers. Patients from the experimental and control facilities were prospectively monitored for fetal and maternal outcomes, namely maternal and fetal deaths, and for toxic effects of MgSo4 in the experimental arm. Results: Of the 150 patients recruited, 82 (55%) were in the experimental group and 68 (45%) were in the control group. 90% of the patients in the experimental group defaulted after receiving the loading dose of MgSo4 while the remaining 10% completed the referral process. 44% of those in the control group completed the referral process. There were 3 maternal and 3 perinatal deaths, all in the control group. No adverse outcome (maternal or fetal death) or toxic effect was recorded among the recipients of MgSo4. Conclusion: This study suggests that lower-cadre health care professionals at PHCs can administer the loading dose of MgSo4 to SPE/E patients to improve maternal and fetal survival in critical states, without significant risk of adverse effects. However, the lack of compliance with referral processes remains a huge challenge.

Magnitude and associated factors of health professionals’ attrition from public health sectors in Bahir Dar City, Ethiopia

Background: Attrition of health professionals from public health sectors is found to be a barrier to effectiveness of health systems and to provide essential health service to population. In Ethiopia, the public health system is the major provider of health care service to the people. In particular, the poor segment of community uses public hospital, health centers and clinic, since the private health facilities are inaccessible and unaffordable to them. The aim of this study was to determine the magnitude and factors associated with health professionals’ attrition from public health sectors in Bahir Dar city. Methods: A Facility based cross-sectional study was conducted in September-October 2012. All inclusive sampling techniques of five years document reviews were used to select 727 health professional documents. Quantitative and qualitative data were collected using structured questionnaires and indepth-interview guides respectively, by trained data collectors. Descriptive statistics (frequencies, proportion and chi square test) were used to describe the study population in relation to relevant variables. To identify independent predictors of attrition, only variables that were statistically significant during bivariate analysis were entered into multiple logistic regression models to control the effects of confounders. Pvalues sex, marital status, educational status, workplace, current salary, professional category and work experience were the main factors associated with health professionals’ attrition from public health sectors. Conclusion: The findings showed that the level of health professionals’ attrition is high in the study area. Policy makers and health mangers should design appropriate retention strategies for health professionals at public health sectors in terms of most associated factors with attritions of health professionals to reduce the prevalence of health professionals’ attrition from public health sectors in collaboration with development partners and concerned body.

Surgical Resident Attrition and the Menninger Morale Curve

BACKGROUND: Attrition in surgical residency programs continues to be a significant challenge. Ap-proximately 20% of residents who begin a categorical surgery residency fail to complete it. A number of studies speculated reasons for this including work hours, life style, family pressures, and resident feelings of inadequacy including fear of termination. To date no research has been conducted investigating the relation-ship between resident morale and attrition. This study sought to determine if this linkage exists in surgery residents. METHODS: The Morale Assessment in General Practice Index (MAGPI) was administered to 21 PGY 1, 2, 3, and 5 surgical residents to assess level of morale. Non-parametric methods were carried out to assess if there were differences in morale among the four PGY groups. Additionally, analyses of the four factors comprising the MAGPI were also conducted. RESULTS: Although differences did not reach statis-tical significance, analysis of the data reveals that residents demonstrate different trends in their levels of morale based on the amount of time they spend in a residency and in a way that approximates the morale curve described by W. Walter Menninger, M.D. Additionally, two of the four factors comprising the MAGPI also indicate trends similar to that described by the Menninger morale curve. CONCLUSIONS: Although no statistically significant results were achieved, the data reveal trends that approximate shifts in morale similar to those described by the Menninger morale curve, with residents at the PGY 2 and 3 levels present-ing lower morale levels than at the PGY 1 and 5 levels. This may be due in part to the size of the population studied. Future research should be continued in this area with a larger sample size.

Use or Lose On Second Language Vocabulary Attrition

The author tries to find how well the students master the new words the teachers teach in class. The result is some disappointing since many words are undergoing partial or complete attrition. The survey suggests that words of high frequency are not easily forgotten.