Effects of heat input on metallurgical behavior in HAZ of multi-pass and multi-layer welded IN-939 superalloy

The hot components of a gas turbine are susceptible to damage in the high-temperature environment of turbine engine operation. Given that these components are relatively costly to manufacture, they are often repaired than replaced when damaged. Fusion welding is an economical method for repairing the damaged components of a gas turbine. This research examines the roles of heat input, pass number and layer number on the intergranular liquation cracking of the Inconel-939 (IN-939) precipitate nickel base superalloy during tungsten arc welding. Several specimens were welded with IN-625 filler alloy under argon gas by following the Taguchi method and an L8 array. These specimens were then characterized via metallographic investigations and hardness measurements. Results show that, during welding, the IN-939 heat-affected zone (HAZ) is acutely prone to cracks that propagate along the grain boundaries. Moreover, layer number, heat input and pass number significantly influence the microstructure and liquation cracking of HAZs with impact percentages of 72.37%, 22.17% and 4.84%, respectively

Brazing Polycrystalline Diamonds (PCDs) in Applications of Cutting Tools: A review

This article surveys all researches which have conducted on polycrystalline diamond (PCDs) cutting tools, with particular consideration to the characteristics and performance of diamond-metal interface. There has been a revolution in industry over the fifty years or so, due to the usage of diamond in numerous applications, because of the special properties of diamond, joining diamonds to various materials by brazing requires much more precision than traditional brazing. Diamond is frequently utilized in cutting tools and workpieces because of its great hardness and wear resistance. Copper base filler & nickel base filler are the two materials that are most frequently used as brazing fillers in diamond brazing. This review describes the properties of diamond, how it interacts with metals and alloys, how it wets them, what influences these interactions, and how practical aspects of diamond joining is. Additionally, an analysis is done on a number of new brazing alloys, including amorphous Ni-based brazing filler metals

The effectiveness of web-based training for parents on post-traumatic stress disorder in children

IntroductionPost-traumatic stress disorder (PTSD) after an injury such as accidents is common in children and can affect their overall physical and mental functioning and quality of life. Early intervention can have significant health benefits for children. This study aimed to investigate the effectiveness of web-based training for parents on post-traumatic stress disorder in children.MethodThis was a quasi-experimental study with intervention and control group. 110 parents of children aged 10–18 years with PTSD after a traumatic event were selected through available sampling and assigned to intervention and control groups. Data was collected by a researcher-made demographic questionnaire and the Child Revised Impact of Events Scale (CRIES-8). Parents in the intervention group received a 4-week training course through a researcher-designed website, but the control group received routine care by the clinical team, which the main focus of care and training was on the physical aspects of the disease, and no intervention was done for PTSD. Two weeks after the intervention, the level of child stress was measured and compared in both groups. Data were analyzed using SPSS V.22.ResultsThe difference between the mean score of total traumatic stress and its subscales before intervention was not statistically significant (p = 0.23). But after intervention, the mean score of total traumatic stress and its subscales decreased in the intervention group and increased in the control group and this difference was statistically significant (p < 0.001).ConclusionE-learning parent training has the potential to support children with PTSD. This available and cost-effective procedure can be recommended to help children with PTSD and possibly increase recovery in these patients

Comparison of Psychopathologic Characteristics between Individuals Undergoing Methadone Maintenance Treatment, Opioid Dependents, and Control Group

Background: Methadone maintenance treatment (MMT) can theoretically reduce the psychosocial harms of opioid dependency. The increasing number of MMT clinics in Iran during the last two decades was not accompanied by a reduction in addiction rates. Therefore, this study was conducted to compare the psychopathological characteristics of individuals on MMT, opioid dependents, and a control group in the Iranian population. Methods: This cross-sectional study was conducted in Mashhad to evaluate the psychopathological profile of 99 participants (33 opioid-dependent individuals [ODI], 33 MMT clients, and 33 controls) using the Symptom Checklist-90-Revised (SCL-90-R) questionnaire and demographic form. Parametric and non-parametric tests were used to compare the mean score of symptoms between the three groups. The Spearman correlation test was used to test the correlation of psychological features with age anddependency duration.  Findings: There was no significant difference between MMT clients and ODI regarding the Global Severity Index (GSI) and nine items of the SCL-90-R questionnaire. However, a significant difference was found between the controls and two other groups (P<0.001). Paranoid ideation in the ODI was more frequent compared to MMT clients significantly (P=0.015). Psychological characteristics had a direct correlation with dependency duration and an inverse correlation with age (P<0.05). Conclusion: Psychopathologic features observed in the dependent patients and MMT clients were significantly higher than in the control group. It seems that the psychopathology profile in MMT clients was not better than dependent individuals in Ira

An innovative method to assess clinical reasoning skills: Clinical reasoning tests in the second national medical science Olympiad in Iran

BACKGROUND: Clinical reasoning plays a major role in the ability of doctors to make a diagnosis and reach treatment decisions. This paper describes the use of four clinical reasoning tests in the second National Medical Science Olympiad in Iran: key features (KF), script concordance (SCT), clinical reasoning problems (CRP) and comprehensive integrative puzzles (CIP). The purpose of the study was to design a multi instrument for multiple roles approach in clinical reasoning field based on the theoretical framework, KF was used to measure data gathering, CRP was used to measure hypothesis formation, SCT and CIP were used to measure hypothesis evaluation and investigating the combined use of these tests in the Olympiad. A bank of clinical reasoning test items was developed for emergency medicine by a scientific expert committee representing all the medical schools in the country. These items were pretested by a reference group and the results were analyzed to select items that could be omitted. Then 135 top-ranked medical students from 45 medical universities in Iran participated in the clinical domain of the Olympiad. The reliability of each test was calculated by Cronbach's alpha. Item difficulty and the correlation between each item and the total score were measured. The correlation between the students' final grade and each of the clinical reasoning tests was calculated, as was the correlation between final grades and another measure of knowledge, i.e., the students' grade point average. RESULTS: The combined reliability for all four clinical reasoning tests was 0.91. Of the four clinical reasoning tests we compared, reliability was highest for CIP (0.91). The reliability was 0.83 for KF, 0.78 for SCT and 0.71 for CRP. Most of the tests had an acceptable item difficulty level between 0.2 and 0.8. The correlation between the score for each item and the total test score for each of the four tests was positive. The correlations between scores for each test and total score were highest for KF and CIP. The correlation between scores for each test and grade point average was low to intermediate for all four of the tests. CONCLUSION: The combination of these four clinical reasoning tests is a reliable evaluation tool that can be implemented to assess clinical reasoning skills in talented undergraduate medical students, however these data may not generalizable to whole medical students population. The CIP and KF tests showed the greatest potential to measure clinical reasoning skills. Grade point averages did not necessarily predict performance in the clinical domain of the national competitive examination for medical school students

Films composites de nickel et de cuivre à base de graphite et PTFE, élaborés par la technique de dépôt chimique dynamique

Le procédé de dépôt chimique dynamique est une technique nouvelle qui consiste à métalliser un substrat en projetant simultanément par un aérosol, 2 phases aqueuses dispersées ; l une contenant un réducteur l autre un ou plusieurs sels métalliques. Le mélange de ces deux solutions forme un film liquide thermodynamiquement instable. La réaction d oxydo réduction se déclenche alors à la surface du substrat. Des films de nickel-bore ou de cuivre sont ainsi réalisés, à température ambiante. Ce travail montre la faisabilité d élaborer par cette technique, des films composites de NiB, NiBP et de cuivre incorporant des micro ou nano particules de graphite ou de PTFE. Les résultats présentés dans ce mémoire concernent d une part, les caractéristiques d élaboration (composition des solutions, cinétique de croissance est de 6 mh-1 ) de films composites NiB avec graphite ou PTFE, de ternaire NiBP avec graphite ou PTFE, et des films de cuivre-graphite et cuivre-PTFE. D autre part, nous présentons les résultats concernant les taux d incorporation des particules dans les matrices métalliques et qui peuvent atteindre, pour le graphite et le PTFE, respectivement, en moyenne12% et 24%. Ces films fonctionnels possèdent des coefficients de frottement de l ordre de 0.1. Avec des films minces de 2 m d épaisseur, il est possible de réaliser pour les films composites NiB et NiBP, des lubrifiants solides et,dans le cas d un film composite de cuivre, un film fonctionnel anti-usure.The technique of dynamic chemical plating is a new method which consists in direct metallization of a substrate. This technique is based on projection of a reducing agent and of a metal salts at the same time but separately onto a conductor or non-conductor substrate. Thus a very thin liquid film is formed and is adsorbed on the surface. This film, containing the active species, is also thermodynamically unstable which means that the oxidation-reduction reaction will occur spontaneously onto the substrate. The NiB and the Copper dynamic deposition were elaborated at room temperature. This work consists of the realization and caracterization of Ni and Cu composite coatings by this technique. This research outlines the development of the codeposition of micro or nano particles of graphite or PTFE in the NiB, NiBP and Cu matrix. The deposition rate under the optimum operating conditions is approximately 6 mh-1, while the amount of the graphite and PTFE codeposited are about 12% and 24%, respectively. The coefficient of friction of these composites was determined by about 0.1. With regard to the low coefficient of friction, it is possible to realize the thin films of NiB and NiBP composite with the thickness of 2 m for the applications of the solid lubricants on the one hand and the copper composite coating in order to the anti-wear functional films on the other hand.LYON-Ecole Centrale (690812301) / SudocSudocFranceF

EFFECTS OF IMPREGNATION WITH STYRENE AND NANO-ZINC OXIDE ON FIRE-RETARDING, PHYSICAL, AND MECHANICAL PROPERTIES OF POPLAR WOOD

Nanoparticles have been vastly applied in wood polymer composites (WPCs) in the recent years to improve some of the drawbacks of solid wood species. In the present study, the effects of ZnO nanoparticles on fire retarding, physical, and mechanical properties of polymerized poplar wood were investigated. Poplar specimens were impregnated with styrene monomer, containing four different contents of nano-zinc oxide (ZnO) (0, 0.5, 1 and 1.5%, based on the dry weight of monomer). Results of the scanning electron microscopy (SEM) showed homogeneous dispersion of ZnO nanoparticles in the WPC matrix. Nano-zinc oxide improved physical properties such as dimensional stability and water absorption. Moreover, mechanical properties increased in comparison to the control specimens. The impregnation process also significantly improved some of the fire-retarding properties, including the ignition time; however, the flammability nature of styrene aggravated some others, such as carbonized area. It was concluded that, although most of the properties were improved, the final application of WPC should be taken in to consideration before making decision on whether or not to impregnate populus wood with styrene

In-service welding of X70 steel gas pipeline: Numerical and experimental investigations

The in-service welding process is widely used to repair defective gas pipelines, which allows the damaged section to be repaired without interrupting gas flow. In this way, consumers and gas transportation companies will be able to minimize losses. In this study, a thermomechanical finite element analysis model was developed to examine the effects of pipe pressure, thickness, diameters, and welding heat input on temperature history and residual stress. The results were analyzed using the design of the experiment method (DOE). According to the results, these parameters significantly affect the thermal distribution and pipe yield stress at the welding point by 48.8%, 29.4%, 15.1 and 6.9%, respectively. On the basis of optimal conditions, in-service welding is conducted. Investigations were conducted on the microstructure, temperature distribution, and residual stresses induced during the in-service welding of API 5L X70 steel pipelines. As a result, it was determined that the HAZ microstructure consists primarily of ferrite, bainite, and M/A constituents, whereas the pipe microstructure undergoes fewer phase transformations. In order to validate the numerical model, mechanical tests, as well as hole drilling, were conducted to gather data, and a combination of equivalent carbon and T8/5 was used to determine hardness at various locations in the HAZ in order to determine which areas are susceptible to cold cracking. The numerical results and the experimental results were highly concordant

Investigating the effective factors on electronic trade by viral marketing

This paper performs an investigation to explore a number of strategies underpinning virtual marketing. The study also provides several suggestions for marketers seeking to use viral marketing to position brands or to change a brand’s image, to encourage new product trials and to increase product uptake rates. In this article, we investigate the effect of external factors such as capturing the imagination, targeting credible sources, leveraging combinations of technology and easy to use product on virtual marketing. In addition, the study considers internal factors such as inclusion (the need to be part of a group, the need to be different) and affection on viral marketing. The survey has been accomplished among 140 Iranian people, who were familiar with virtual marketing and they are selected, randomly. Using Pearson correlation as well as regression analysis, the study provides some evidences that there were some positive and meaningful relationship between some internal/external factors and virtual marketing

Effect of Welding Parameters on the Liquation Cracking Behavior of High-Chromium Ni-Based Superalloy

Gas turbine blades working under extremely harsh operating conditions are made of superalloys. These superalloys are exposed to various damage mechanisms, which wear them out gradually. Welding is often preferred to repair the damaged components for cost minimization. This study aimed to investigate the effects of flexural load, heat input, and welding speed on the weldability and intergranular liquation cracking of high-chromium Ni-based superalloy. For this purpose, a series of Sigmajig tests designed based on the Taguchi method with L4 array, as well as microstructure investigations and residual stress measurements, were performed. The results showed that the microstructures of heat-affected zones (HAZs) were highly susceptible to cracking during the welding process, and all of these cracks appeared in the HAZ and grew perpendicular to the melting zone along grain boundaries. Flexural load contributed the most substantial impact (82%) on crack propagation compared with the 9.7 and 9.2% impacts of welding speed and welding heat input, respectively. We found that the lowest flexural load, welding speed, and heat input are the best welding parameters to reduce the total crack lengths at the welded area of high-chromium Ni-based superalloy