bluuebunny/crossref_metadata_2025 huggingface dataset:
How can we detect and analyze navigation-related low-frequency oscillations in human invasive recordings?
Authors: Liang Mingli , Ekstrom Arne
Published: July 2022

Theta oscillations are a prominent semi-periodic fluctuation in the local field potential of the human hippocampus and show important links to areas of cognition like episodic memory and navigation. In this chapter, we begin by characterizing the properties of human hippocampal theta oscillations, which are more bursty and less continuous compared with rodents. Next, we introduce the Better OSCillation Detection algorithm (Whitten et al., 2011) for detecting oscillations based on amplitude and temporal thresholding. We compare BOSC with other oscillatory detection methods, such as those based on dual-amplitude thresholding and hidden Markov models. Additionally, we provide tutorials and a practical guide for oscillation detection for the interested reader. All codes and examples are provided freely in open-source format. Together, these provide researchers with the tools to explore novel questions about the nature of hippocampal navigation-related theta oscillations. As we demonstrate in this chapter, oscillatory detection procedures are extremely helpful for characterizing oscillatory dynamics including burst frequency and burst duration, exceeding beyond the singular dimension provided by amplitude changes measured in the power spectra.
Police practitioner views on the challenges of analysing and responding to knife crime
Authors: Bullock Karen , Agar Iain , Ashby Matthew P J , Brennan Iain , Hales Gavin , Sidebottom Aiden , Tilley Nick
Published: July 2022

Knife crime remains a major concern in England and Wales. Problem-oriented and public health approaches to tackling knife crime have been widely advocated, but little is known about how these approaches are understood and implemented by police practitioners. To address this knowledge gap, this article draws on semi-structured interviews and focus groups with 44 police personnel to consider the processes and challenges of applying problem-oriented and public health approaches to knife crime. Our findings show that knife crime was seen as a complex social problem which would not be solved by ‘silver bullets’; prevention was prioritised and the limitations of enforcement were widely acknowledged; there was an emphasis on understanding and responding to vulnerability and risk; discussion of ‘holistic’ and ‘whole systems’ approaches was evident (but these concepts were rarely defined); and the problem of serious violence was viewed as a shared, multi-agency issue that the police could not tackle alone. Various challenges were also evident, most notably around the analysis of the drivers and patterns of knife crime and the evaluation of knife crime interventions. The article concludes by discussing the implications of the findings for knife crime prevention and the implementation and advancement of problem-oriented and public health approaches to policing.
The Cost of Widowhood: A Matching Study of Process and Event
Authors: Van Winkle Zachary , Leopold Thomas
Published: July 2022

Widowhood is a common life transition entailing far-reaching consequences. We examine the consequences of widowhood in a novel way by assessing the consequences of bereavement for meaningful comparison groups allowing us to evaluate the impact of bereavement before and after the event. The analysis of the cost of widowhood for mental health and economic wellbeing focuses on two scenarios: unexpected and expected widowhood. The first scenario models a two-period process in which effects of widowhood occur only after the event. The second models a three-period process in which effects of widowhood also occur before spousal loss. US Health and Retirement Study data and a combination of random-coefficient modelling, propensity score matching, and regressions are used to estimate the consequences of widowhood from ten years before to six years after spousal loss. Results on mental health show a slow but full recovery for unexpected widowhood, but larger and lasting declines for expected widowhood. Findings on economic wellbeing show sizable losses for expected widowhood due to the economic cost of the pre-widowhood period. In sum, the impact of widowhood is smaller for unexpected compared to expected events. Our approach advances knowledge about spousal loss, but also research on life events more generally.
Local Perception on the Climate Change in Nepali Society: A Spatial Comparison between Urban and Rural Area of Dharan and Bhojpur in Nepal
Authors: Sharma Bigyan , Subedi Shukra Raj
Published: July 2022

Climate change has become a global concern and debatable issue worldwide in the present era. It needs to be discussed from rural community and urban perspective in terms of the local understanding, experience, and knowledge in environmental discourse.  The local understanding on climate change in Nepali society is the spatial comparative analysis of understanding to the environment from the perspective of local people. Being spatial comparative studies, it compares the understanding of environmental change of people among rural and urban areas Province 1 of Nepal.  It underpins the interpretive research philosophy based on the qualitative research approach, employing the convenience sampling of non-probability sampling design with in-depth interview, and observation as the tools of data collection. The six research informants, three from the rural areas of Temkemaiyum of Bhojpur district and three from the urban areas of Dharan Sub-metropolitan City of Sunsari district have selected for the perception and experience collection for the comparative study. The finding has revealed that the both people of urban and rural areas are noticing the climate change. However, their understanding has varied based their knowledge, understanding, and experience. Though the study has focused on climate change, it has been recommended for researchers, policy makers, and policy implementers for environmental discourse in further research in Nepalese context.
Narrative Inquiry: An Alternative Tool to Recapitulate Teachers' Pedagogical Capital
Authors: Bastola Ganesh Kumar
Published: July 2022

In this paper, I examine how the interpretative prototype is undertaking its supremacy in the educational research model and how a narrative inquiry paradigm supported and helped me to explore different realities of teachers' pedagogical capital in the context of Nepal. It aims to relate how the perceptions of pedagogical capital affect teachers’ performance in the language classroom. Data for this study were collected from three participants purposively. The data, in this research, have been analyzed based on the framework of Stake (1995). The study uses Bourdieu's (1977) notion of cultural capital for theoretical substantiation and the findings indicate that teachers' pedagogic capital is an ability that can be employed for an effective teaching-learning process. More specifically, this paper pinpoints how narrative inquiry could be considered as an alternative tool to recapitulate teachers' pedagogical capital in educational research.
Transnational Characters in Bhattarai's Muglan
Authors: Timalsina Ramji
Published: July 2022

This article deals with the transnational characters used in Govinda Raj Bhattarai’s novel Muglan (1974). Based on the centuries long trend of Nepali people’s migration across the border and the pains they have been undergoing, the novel has presented three types of characters to show the types of Nepali transnational community living in India and Bhutan. The first type is that of transnational mobiles who leave Nepal for job and education, want to return to Nepal and cannot have any type of permanent settlement in the hostland. The main character Sutar is one of such characters. The highest number of characters in the novel is of this type. The second type of characters are diasporic ones who have left Nepal and have been permanently settled in Bhutan. Characters from the Nepali speaking community in Bhutan are of this type. The lowest number of characters in the novel are transnational outsiders who visit India from Nepal for a short time. The people who go for pilgrimage and cross-border purchase of everyday goods are the characters of this type. The discussion section of the article analyses the causes and effects of such migration resulting into the creation of such characters. The theoretical modality used for the analysis is Janine Dahinden and Steven Vertovec’s ideas of transnationalism. This article will be useful for the researchers and critics who want to study Nepali texts from transnational perspective.
Health Status of Ageing People A Case Study of Bisharanti Old Aged Home, Mulghat, Dhankuta
Authors: Poudel Tanka Mani
Published: July 2022

Health is a prime concern for the elderly people who reside in old age homes. Against this backdrop, this research has explored the condition of old aged people regarding their social and health-related issues in an old aged home. The research was carried out among the old-aged people residing at Bishranti Old Aged Home. Among the 40 participants of Bishranti Old Aged Home, 21 participants were selected purposively including 12 females and 9 males. The study concluded that the societal condition including racial, religious, familial and social-economic components were the prime reasons behind their residence in Bishranti Old Aged Home. Due to poor health of the ageing people living in the old aged home, they have been suffered from various physical, mental and social problems. More specifically, the research also indicated that the majority of the participants were victim of hypertension and severe joint pain. Moreover, many of the participants were the victims of diabetes, gastritis, depression, asthma, heart-diseases, chest pain, eye and ear problems etc.
Effects of Ganggangsullae on Self-Esteem in Severe-to-Profound Hearing Impaired Adolescents
Authors:   The Korean Society of Medicine & Therapy Science, An JungYoun , Heo Seung-Deok
Published: July 2022

Objective: Dance can achieve harmonious integration in mentally and physically while expressing oneself through creative and improvised artistic movements. For disabilities, dance is an important incentive to think positive and appreciate their value. The study aims to investigate the effect of dance rehabilitation using the dancing steps of Ganggangsullae, which develops balance, unity, sociality, and creativity for hearing impaired adolescents, on their self-esteem. Methods: 6 hearing impaired girls aging 11.8 to 17.6 years (14.7 ± 2.07) participated. Two of them had no dance class experiences, other two experiences, and the other two had aerobics exercise experiences. Rosenberg's Self-Esteem Scale (RSES) was used for self-esteem. These tools were investigated at 8-week pre-/post-Ganggangsullae activity, and then the mean scores of respective responses were compared. Results: The mean scores of RSES improved from 2.87 ± 0.46 to 3.27 ± 0.46. Conclusion: The dancing steps of Ganggangsullae improved the self-esteem of the hearing impaired.
Effect of Modified Bimanual Massed Practice on Hand Function and Occupational Performance in Patients with Incomplete Cervical Spinal Cord Injury: A Single-Subject Research Design
Authors:   The Korean Society of Medicine & Therapy Science, Han Byeo-Ri , Lee Sang-Heon
Published: July 2022

Objective: The purpose of this study is to investigate the effect of modified bimanual massed practice training on hand function and occupational performance of a incomplete tetraplegia patient. Methods: The participant was a 27 years old man diagnosed with C7/C7(s), C6/C6(m) incomplete tetraplegia ASIA-C. The patient performed developed modified bimanual massed practice with a total of 20 sessions, 30 minute 5 sessions per each week for 4 weeks modified according to domestic clinical setting. Results: The mean value of dynamometer on the right hand progressively improved through baseline A1(mean 2.96 kg), intervention B(mean 3.07 kg), baseline A2(mean 3.50 kg). And on the left hand, it also increased from B(mean 2.64 kg) to A2(mean 3.04 kg). In the Box and block test, the right hand improved from A1(47 unit) to B(52.55 unit) and maintained for A2, and the left hand improved through A1(46.4 unit), B(47.2 unit), and A2(49.8 unit). And the results of Assessment of Motor and Process skills showed that motor skills improved from before (0.0 logit) to after(0.7 logit), and process skills also improved from 0.7 logit to 1.0 logit. Conclusion: This study results support that the modified bimanual massed practice training is beneficial in improving hand function and occupational performance in a incomplete cervical spinal cord injury patient.
Situating the Kegalle Rebels of 1971: The Narrative Disconnect Between Michael Ondaatje and Those Who Took His Family Gun
Authors: Perera V.
Published: July 2022

The article uses Michael Ondaatje’s representation of the Kegalle rebels of the 1971 insurgence to examine the question of historical disconnect in the writer which has resulted in his reduction of an era-defining political event to an amusing anecdote. This anecdote – to do with a group of young rebels who came to collect the Ondaatjes’ family gun in Running in the Family – has been widely quoted in literature on Ondaatje’s work, but without sufficient emphasis on what appears to be a historical alienation of the writer. The present discussion attempts to reconstruct the fate of the Kegalle rebels who disappear from Ondaatje’s field of vision after the gun was collected. Through the association of narratives written by former insurgents in Kegalle who retreated to Wilpattu after the uprising failed, I attempt to reconstruct their story to offer an overview of the history Ondaatje misses out on. By interpolating work such as Raja Proctor’s Waiting for Surabiel the article also draws on the role of historical awareness and political empathy in representing a politically-turbulent era.
Psychological Factors Influencing Credit Card Usage of Employees in Colombo District, Sri Lanka
Authors: De Zoysa D. P. S. , Rathnayaka R. M. K. G. U.
Published: July 2022

Credit card is one of the trending cashless transaction methods used worldwide with the advancement of technology. Records in Central Bank of Sri Lanka (CBSL) show the demand and the number of credit cards issued are increasing day by day due to different reasons. Researchers have revealed that different demographic, socio-economic and credit card attributes were reasons for use of credit cards among different types of credit card holders. But the influence of psychological factors is also a subject of considerable research. Therefore, the objective of this research is to identify the influential psychological factors on credit card usage of employees in the Colombo district. With the aid of different sampling techniques where necessary, 385 respondents were selected for the sample. Required data were collected through a structured questionnaire and psychological variables were measured by ten-point Likert Scale Statements. Multiple linear regression analysis was carried out with the aid of Minitab 20. Results of the study revealed that the perceived financial cost, user pattern, social status and attitudes are highly influential psychological factors while convenience and financial optimism have not significantly influenced the credit card usage of employees in the Colombo district. Future research is suggested to identify the influence of similar factors for other districts and commercial banks separately, and apply advanced analysis to identify the latent factors that affect credit card usage of employees in the Colombo district.
“Something Is Happening”: Medical Realism and the Problem of Acting in Harold Pinter’sA Kind of Alaska
Authors: Brown Jeffrey M.
Published: July 2022

Harold Pinter’s A Kind of Alaska outlines and responds to a critical dilemma in the relationship between modern drama and medical practice. Focusing on a clinical encounter between a doctor and a patient, Pinter’s play was inspired by a real-life medical case history taken from neurologist Oliver Sacks’s Awakenings. Its engagement with medical reality, however, is disturbed by the aesthetic effects of Pinteresque dramaturgy, which subtly undermine the play’s presentation of bioethical dilemmas that are determined by authoritative acts of diagnosis and the control of doctor-patient communication. Reviewing the history of medical vision alongside theatrical realism reveals a paradoxical emphasis on pedagogy and unlearning within both traditions, wherein naïve acts of empiricism and a dutiful adherence to material presence are meant only to reinforce prescribed conclusions and extant structures of knowledge. A Kind of Alaska responds to this paradox by eliciting mutually exclusive attitudes toward narrative and acting, juxtaposing realist effects with those borrowed from the Brechtian Lehrstücke. As a result, the play challenges the kinds of closure implicit in both clinical vision and history, prioritizing instead the dialectical indeterminacies necessary to both the learning and the practice of medicine.
Hana Worthen, Humanism, Drama, and Performance: Unwriting Theatre
Authors: Ezell Brice
Published: July 2022

Hana Worthen’s Humanism, Drama, and Performance: Unwriting Theatre is a trans-historical and transnational survey of humanist conceptions of the theatre, of use to graduate students and researchers working on the intersections of theatre studies, performance studies, and philosophy.
Funciones de fluidez, flexibilidad cognoscitiva, planeación y organización en niños rurales mexicanos
Authors: Reyes Domínguez Genoveva Genyen , Reynosa-Alcántara Vicenta , Del-Callejo-Canal Diana , Canal-Martínez Margarita Edith , Núñez-de la Mora Alejandra
Published: July 2022

El desarrollo de las funciones ejecutivas, que tienen un papel importante en el aprendizaje y la adaptación de un individuo, ha sido descrito a partir de poblaciones urbanas; sin embargo, poco se sabe del desempeño de un niño o una niña que se desarrolla en un contexto rural con características socioeconómicas, culturales y ecológicas distintas. El propósito del estudio fue determinar si las subpruebas de funciones ejecutivas de la batería ENI 2 de Matute y colaboradores (2013) son aplicables a una población rural, describir el desempeño ejecutivo de esta población y conocer la distribución de los percentiles obtenidos por la población estudiada al usar los valores normativos estimados en contextos urbanos. Se aplicaron siete subpruebas a 54 niños de dos comunidades rurales en Veracruz, México. En todos los casos, los participantes ejecutaron las pruebas dentro de los parámetros establecidos. En general, registraron un bajo desempeño en los dominios de fluidez, algo menos contrastante en flexibilidad cognoscitiva, y un desempeño alto en planeación y organización. Los resultados destacan la relevancia de incluir poblaciones de contextos diversos para validar instrumentos neuropsicológicos estandarizados, así como reconocer la necesidad de replantear el currículo de acuerdo con las características y demandas del ámbito rural.
Innovation through Web 2.0 to support English language learning
Authors: Pineda Castillo Kristian Armando
Published: July 2022

This investigation had the purpose of understanding how the use of a website created by the teacher-researcher contributed to an improvement in the educational experience in English language teaching with Mexican high schoolers. The inquiry undertook a qualitative methodology following an action research design tied to the critical educational science paradigm. Results revealed that the online site encouraged a positive educational experience by attending to the learners’ interests and needs, offering support, an easy navigational interface, and a good experience in the study of English. Furthermore, the internet site was perceived as highly supportive as the subject’s contents were organized by levels and topics, where videos were available to explain each linguistic item clearly. In conclusion, it can be said that the intervention benefited the teenagers’ formation since the website favored their learning of the foreign language with the support that it provided, the simple navigation, the pedagogical approach, and the personal touch employed by the teacher.
Manufacturing Diamond Impregnated Tools for Stone Machining through Thermal Spraying
Authors: Tillmann W. , Vogli E. , Rechlin R. , Bach F.-W. , Möhwald K. , Babiak Z. , Rothardt Th.
Published: July 2022

The use of diamond-impregnated tools for the machining of any type of building material or natural stone is an established technology. Sintering and brazing are the key manufacturing technologies. The restricted flexibility of the geometry variation, the absence of the repair possibilities of damaged tool surfaces as well as difficulties in controlling the materials interfaces are some drawbacks. Therefore, manufacturing diamond tools through new technology concepts are required not only to avoid these restrictions mentioned but also to enhance the tools properties. In particular, thermal spraying technologies can act as a potential problem solver due to their special technological properties. Especially the new high-speed technologies such as the detonation-gun and high velocity oxygen fuel thermal spraying are promising approaches. Through these technologies, it is possible to control the kinetic energies of the diamond particles as well as their temperature during coating. In this report, a novel manufacturing technology of the diamond-impregnated tools based on these high-speed thermal spraying technologies will be reported. The layer properties will be evaluated with respect to the diamond quality after coating and with respect to the properties of the diamond composite coatings. Diamond spraying efficiency, diamond distribution in the layer as well as diamond-metal binder-interaction are analysed.
Composition Changes of Selected Alloys During their Plasma Spraying
Authors: Chráska P. , Kolman B. , Suchánek M. , Voleník K.
Published: July 2022

Atmospheric plasma spraying of alloys often results in their composition changes. The main source of the changes is usually preferential oxidation of some elements composing the alloy. As a rule, these are the alloying elements whose affinity to oxygen is high. Changes due to this effect are well known from metallurgy; however, they were scarcely studied from the point of view of plasma spraying. Preferential evaporation of some elements may also contribute to the alloy composition changes. The aim of the present paper is to give quantitative data on composition changes of selected alloys sprayed by a water-stabilized plasma gun. Two Ni-base alloys and one high-alloy Cr-Ni-steel were studied. The main tool for determining the sample composition was electron probe X-ray microanalysis. To quantify the results and to eliminate the systematic errors, the data obtained by this method were calibrated by repeated chemical analysis of feedstock powders. The alloy composition was determined after both stages of plasma spraying, i.e. after the inflight stage of molten particles and after the stage comprising particle impact, solidification, coating formation and cooling. To study the situation after the former stage, the flying particles were trapped and quenched in liquid nitrogen. In the Ni-Cr alloy containing 20%Cr, strong Cr depletion was observed. The Fe depletion in the Ni-Fe alloy (47%Fe), though unambiguous, was less significant. The high-alloy steel (Czech equivalent of AISI 316) was also Cr depleted, whereas the concentrations of other alloying elements (Mo, Ni) remained effectively unchanged. In all cases, the depletion occurred at the first spraying stage and became more pronounced during the second stage. Strong air entrainment occurs not only in a plasma jet produced by a water-stabilized plasma gun, but also if gas-stabilized plasma guns are used in atmospheric plasma spraying. It follows that the dominant mechanisms of composition changes during plasma spraying by both techniques are similar.
A Study of Adhesive Strength of Cold Spray Coatings
Authors: Fukanuma H. , Ohno N.
Published: July 2022

This paper presents the adhesive strength results of copper and titanium deposits produced by cold spray processes on steel, stainless steel, aluminum and copper substrates. We investigated how the combinations of the particles and the substrate, and the pressure in the cold spray nozzle chamber affect the adhesive strength between the deposits and substrates. We used nitrogen and helium as cold spray process and powder carrier gasses in the processes. We found that helium gas produced much higher adhesive strength than nitrogen and that the strength of the deposits produced by using both helium and nitrogen gases was almost proportional to the chamber pressure. The adhesion produced by cold spray processes appeared to be dependent on the combination of hardness of powder and substrate metals. We also present cross section micrographs of the deposits and substrate observed after tensile strength tests. They show the substrate which is soft or easily deformed by particle collisions generates strong adhesion.
Impact Fusion Phenomenon During Cold Spraying of Zinc
Authors: Li Chang-Jiu , Li Wen-Ya , Fukanuma H.
Published: July 2022

In the present study, the zinc powder (-48 µm) was used to deposit coating by cold spraying using nitrogen as driving gas at different operating temperatures. The microstructure of the deposited coating was characterized by optical microscopy, scanning electron microscopy and transmission electron microscopy (TEM) to reveal the occurrence of fusion during the impacting of spray particles. The selected area electron diffraction analysis was used to examine the microstructural feature at the near interface areas between the deposited particles in zinc coating. Numerical simulation was carried out to estimate the particle temperature increment during the impacting process. The simulation result suggests a possibility of the melting of zinc particles at the localized contact region on impact. The examination of the coating surface provided the evidence for the occurrence of the melting of spray particles on impact. The experimental results showed that the cold-sprayed zinc coating presented a dense microstructure. The nano-structural phase was formed at the near interface areas between deposited particles in zinc coating, while the grains in the size of micrometers similar to that in the powder were retained in the inside of the particles in the coating. Moreover, the TEM observation evidently showed that the amorphous phase was formed at the interface areas between the particles. It can be considered that the amorphous phase in the coating was formed through subsequent rapid solidification of the melted material on impact. This fact provided further evidence to the occurrence of localized melting during impacting of spray particles.
Microstructural and Electrochemical Characterization of Cold-Sprayed 1100 Aluminum Coating
Authors: Karthikeyan J. , Laha T. , Balani K. , Agarwal A. , Munroe N.
Published: July 2022

Cold spray is an effective technique to deposit pure metallic coatings on a variety of substrates. 1100 series aluminum-based coating has been deposited on similar aluminum substrate by cold spray technique using helium and a mixture of helium and nitrogen as powder carrying gases. The microstructural features of the coating were analyzed using optical micrography, Scanning Electron Microscopy (SEM) and Microhardness depth profiles. The electrochemical behavior of the materials was studied using 0.5 N H2SO4 as electrolyte. Tafel extrapolation experiments were carried out in order to calculate the corrosion rate, corrosion potential and the Tafel slopes, whereas, potentiodynamic polarization experiments were performed to understand the passivation behavior of the material under the experimental conditions. The electrochemical studies validate the use of cold sprayed aluminum coating for corrosion protection applications. SEM characterization of the coatings was also performed after the electrochemical experiments.
Influence of Substrate Conditions and Traverse Speed on Cold Sprayed Coatings
Authors: Sakaki K. , Tajima T. , Li H. , Shinkai S. , Shimizu Y.
Published: July 2022

In this study, experiments investigated the influence of substrate conditions such as substrate thickness, substrate surface conditions (blasted or polished), substrate temperature, number of overlaps and gun traverse speed on cold sprayed copper and titanium coatings. The influence of substrate thickness, substrate temperature and number of overlaps were different by materials of feedstock powder (copper and titanium). In another words, titanium deposition efficiency increase slightly while copper deposition efficiency decrease slightly with increasing the substrate thickness, the preheated substrate temperature and number of overlaps and gun traverse speed. On the other hands, both deposition efficiency of copper and titanium coating increase slightly with an increase in surface roughness from 0.2 μm Ra (polished surface) to 7 μm Ra (blasted surface). The deposition efficiency of titanium and copper decrease rapidly with increasing gun traverse speed.
Off-Line Programming for Spraying and Laser Cladding of Three-Dimensional Surfaces
Authors: Zieris R. , Schmidt A.
Published: July 2022

The economic efficiency of spraying a frequently changing spectrum of parts is strongly dependent on the costs of planning the spray process. In many cases, the robot program for coating a three-dimensional surface is generated directly on the control unit computer. Programming results in costly downtime. At IWS, a technology for off-line programming of robots and CNC systems for thermal spraying (TS) and laser cladding (LC) was developed. Coating programs are developed using CAD data from a workpiece and checked with simulation software. All steps are accomplished off-line without influencing ongoing production. Off-line programming of spray processes for three-dimensional surfaces enables substantial time savings to be realized, more so with increasing part complexity. These programs enable a constant spray distance and traverse speed as well as a permanent spray angle of 90° to the substrate to be achieved.
HVOF Ceramic Coatings
Authors: Morishita T. , Osawa S. , Itsukaichi T.
Published: July 2022

A secondary acetylene after burner attached with an HVOF gun has been developed to produce high quality coatings required of ceramics. The secondary burner adds heat energy, enough to make deposition, to fine ceramic particles heated and accelerated by an HVOF gun. The energized particles are still not fully melted but just softened or partially melted on the surface and accelerated at as high as jet flame velocity. The coatings produced by this way present extremely unique characteristics, quite unlike from plasma coatings or D-gun coatings. The phase transformation in coatings is very little observed. The porosity is negligible. The wear resistance and the density are very close to those of the bulk. This paper will present significant features of HVOF ceramic coatings in comparison with plasma coatings.
Wear Behavior of HVOF Sprayed WC-12%Co Coatings vs. Hard Chrome Plating
Authors: Sahraoui T. , Fenineche N.E. , Montavon G. , Coddet C.
Published: July 2022

Environmental protection and worker safety measures against hard chrome plating are increasing and leading many industries to adopt alternatives. HVOF thermal spray technology for applications of tungsten carbide based coatings have proved to be more environmentally friendly and effective than hard chrome. In this study, the results of wear tests for WC-12%Co sprayed coatings deposited onto AFNOR 25CD4 low carbon steel are compared to those for hard chrome. It was shown that WC-12%Co coatings exhibit the adequate tribological properties compared to those of electrodeposited hard chrome.
Phase Structure-Mechanical Property Relationships in HVOF-Sprayed WC-12Co Coatings
Authors: Bouaricha S. , Marple B.R.
Published: July 2022

Rietveld analysis was used to measure the phase content of twenty-four coatings sprayed with a multimodal WC-12Co feedstock using three HVOF spray guns. Different correlations were investigated involving, on the one hand, the thermal spray history (particle temperature and velocity) and the mechanical properties of the deposits (microhardness and abrasion resistance), and, on the other, the phase structure of the tested coatings. The results show an inherent effect of the spraying temperature, regardless of the HVOF process used, on the generation of sub-carbide species, mainly W2C, W and an amorphous-nanocrystalline phase. In particular, it was found that decarburization of the WC to produce the amorphous/nanocrystalline and tungsten phases is beneficial in enhancing the mechanical properties as long as there is no large amount of tungsten present in the coating. A linear relationship relates this phase with the presence of the amorphous-nanocrystalline phase, independently of the spraying process used in this study. It was also shown that metallic tungsten precipitated in a nanocrystalline structure only with the Diamond Jet HVOF process.
Fabrication of Aluminum Nitride Coating by Reactive RF Plasma Spray Process
Authors: Fukumoto M. , Yamada M. , Yasui T. , Takahashi K.
Published: July 2022

Aluminum nitride (AlN) is one of the attractive ceramics applicable to the surface modification because of its excellent properties in chemical stability and thermal conductivity. In this research AlN coating was fabricated by reactive RF (Radio Frequency) plasma spray process, a kind of thermal spraying techniques. Reactive plasma spraying, in which metal element reacts with surrounding active species in plasma, has been considered to be an useful process for the formation of non-oxide ceramics thick coatings. By increasing nitrogen content in plasma gas, AlN coating without pure Al part was attained while the coating microstructure was heterogeneous, brittle and quite porous. By decreasing nitrogen content in plasma gas, on the other hand, Al/AlN composite coating with more homogeneous, less porous microstructure could be attained. Changing nitrogen fraction in plasma gas may be effective for controlling AlN content in Al/AlN composite coating. Nitriding process of aluminum in reactive RF plasma spraying was also investigated in this study. It could be considered that nitridation process of Al was occured during the particle flight in plasma or after the particle deposited onto the substrate. Nitriding reaction process of Al in the reactive plasma spray process was verified in the study.
Ceramic Spraying using Electromagnetically Accelerated Plasma
Authors: Tahara H. , Moriyama M. , Fujiuchi K.
Published: July 2022

In magneto-plasma-dynamic (MPD) arcjet generators, plasma is accelerated by electromagnetic body forces. The MPD arcjet generator can produce higher-velocity, higher-temperature, higher-density and larger-area plasmas than those of conventional thermal plasma torches. Two types of MPD arcjet generator were developed for applications to ceramic spray coatings. One generator was installed with a cathode covered with mullite or zirconia ceramics and the other with a titanium cathode. The former was operated with Ar for mullite or zirconia coating by an ablation process of the cathode cover and the latter with N2 for titanium nitride coating by a reactive process between ablated titanium particles and nitrogen plasma. Silicon nitride reactive spraying was also carried out. The MPD spray process could successfully form dense, uniform and hard ceramic coatings. In titanium nitride reactive spraying, plasma diagnostic measurement and flowfield analysis were conducted. A large amount of N and N+ was expected to be exhausted with a high velocity from the MPD generator. Both the electron temperature and the electron number density were kept high at a substrate position compared with those for conventional low-pressure thermal sprayings. A chemically active plasma with excited particles of N+, Ti, Ti+ and Ti2+ was considered to contribute to better titanium nitride coatings. All coating characteristics showed that the MPD arcjet generators had high potentials for ceramic spray coatings.
Splat Formation in Wire Arc Spraying
Authors: Abedini A. , Pourmousa A. , Chandra S. , Mostaghimi J.
Published: July 2022

An experimental study was conducted to study the effect of impact velocity and substrate temperature on splat morphology using a wire arc spraying system. Aluminum was sprayed onto polished AISI304L substrates held at various temperatures. In-flight particle parameters (size, velocity, temperature) were measured using a DPV 2000 system. Individual splats deposited on the substrate were photographed. Comparisons between the in-flight particle size distribution and the final splat size distribution showed that increasing substrate temperature results in increased mean spread factor. A transition temperature from splash to disk splats was determined. Coatings were also produced at various substrate temperatures and porosity levels measured. The effect of substrate temperature on deposition efficiency and coating adhesion was measured. Increasing substrate temperature was found to improve both deposition efficiency and adhesion strength.
Investigation of AlSi Coatings Prepared by Laser-Assisted Atmospheric Plasma Spraying of Internal Surfaces of Tubes
Authors: Zieris R. , Langner G. , Berger L.-M. , Nowotny S. , Beyer E.
Published: July 2022

Laser-assisted atmospheric plasma spraying (LAAPS) is a new one-step coating process performed in air whereby the laser beam interacts with the plasma torch at the substrate or coating surface during deposition to generate a coating that is metallurgically bonded to the substrate. This hybrid process was developed in order to combine the specific advantages of APS and laser cladding. In this paper, the development of a hybrid gun for coating internal surfaces of tubes and cylinder bores by LAAPS is presented. The process was optimized for spraying AlSi30 coatings on internal surfaces of aluminum alloy cylinder bores. Single-pass coatings with thicknesses of 300-400 µm and metallurgical bonding to the substrates can be realized by applying an optimized parameter set. The dependence of coating microstructure on spray parameters was investigated by metallographic preparation and optical microscopy. Surface pretreatment must be performed to eliminate the strongly adhering oxide layer on the aluminum alloy substrate and to attain metallurgical bonding of coating to substrate.
An Advanced Ceramic Coating Buildup Model for Thermal Spray Processes
Authors: Wei Guanghua , Xiong Hongbing , Zheng Lili , Zhang Hui
Published: July 2022

To obtain good quality coatings, spray parameters must be carefully selected. Due to the large variety in process parameters, it is difficult to optimize the process for each specific coating and substrate combinations. In this paper, the process of particle in-flight, coating growth and pore formation has been analyzed by numerical simulation. Three sub-models, plasma-particle, splat formation and coating buildup, have been developed. A comprehensive three-dimensional computational code (LAVA3D-P) is used to predict the plasma flame formation, flame-particle interaction, and particle state and trajectory. Assuming each splat is disk-like shape and the flattening ratio, a ratio between the splat diameter and droplet diameter, can be calculated based on the interplay among particle kinetic energy, dissipation energy and solidification. A set of rules of coating buildup are proposed to predict the coating deposition and pore formation, considering the influences of particle size, velocity, temperature and location related to the substrate. Using this model we can obtain the porosity, surface roughness and thickness of the coating considering splat adhesion and quenching stresses. Although the current model has server restrictions which attributes to many assumptions, it however, forms a foundation for further improvement of an advanced ceramic coating buildup model.
Supersonic Plasma Jet Modelling at Low Pressure Using Recent Advances of the Enthalpy Probe Measurement Technique
Authors: Blais A. , Jodoin B. , Dorier J.-L. , Gindrat M. , Hollenstein C. , Barbezat G.
Published: July 2022

This paper describes the investigation of low pressure supersonic plasma jets as found in LPPS processes. The main objective is to develop and validate a two-dimensional axisymmetric mathematical model representing such flows. Due to the supersonic nature of the jet, insertion of a measurement probe leads to the appearance of a detached shock in front of the probe. Consequently plasma values are measured behind the probe-induced shock, namely the stagnation enthalpy (ho), the stagnation pressure (po) and the static pressure (p). The first two values are taken from enthalpy probe measurements while the third value comes from a new technique. Combining these measurements, a new interpretation method enables the calculation of the free-stream supersonic plasma jet properties. The mathematical model is validated using the enthalpy probe measurements and the free-stream properties from the new interpretation method. Results show that the model does not predict a static pressure as large as the new interpretation method. The principal cause for this discrepancy is attributed to the LTE assumption which is questionable for a 40 mbar plasma jet. The modelling effort reported here confirms the need to develop more detailed mathematical models for low pressure supersonic plasma jets in the future.
Heating and Impact Modeling of HVOF Sprayed Polymer Particles
Authors: Ivosevic M. , Cairncross R.A. , Knight R.
Published: July 2022

An initial stage of the current work including a preliminary comparative numerical analysis of molten polymer and metal droplets upon impact on a cold steel substrate was presented. A commercially available Volume-of-Fluid [VoF] code was used to model particle deformation and cooling of molten nylon-11 and zinc droplets on impact with a steel substrate. Comparison between polymer and metal splatting was chosen in order to better understand how large fundamental differences between the materials affected their spreading behavior under similar thermal spray conditions. It was found that the inertia is more strongly balanced by the viscous flow resistance in molten polymers while high surface tension of molten metals may lead to particle breakup onto rivulets and satellite during later stage of particle deformation. Spreading ratios of nylon-11 and zinc droplets were 0.53 and 0.34, respectively, owing to the zinc droplets being almost twice the size of the nylon. Zinc splats less than 5 ìm in thickness spread fully and solidified in less than 1.5 µs. Over the same time interval, 17 µm thick nylon-11 splats were also fully developed, however, only a thin boundary layer [<2 µm] was solidified owing to a significantly lower thermal conductivity.
Studies of the Photocatalytic Efficiency of Titanium Dioxide Powders and Coatings Obtained by Plasma Spraying
Authors: Toma F.-L. , Bertrand G. , Chwa S.-Ok , Coddet C. , Klein D. , Nardin P. , Ohmori A.
Published: July 2022

Titanium dioxide (TiO2) is one of the most important photocatalyst that allows the environmental purification of water and air by the decomposition of toxic organic compounds and removal of harmful gases. In the photocatalytic applications, TiO2 can be used in form of powder or coating. In this paper, two techniques of deposition were used to elaborate thin deposits starting from an agglomerated TiO2 anatase nanopowder: conventional plasma spraying in atmospheric conditions and suspension plasma spraying. The photocatalytic efficiency of the coatings was performed with respect to nitrogen oxides (NOx) and compared with the photocatalytic activity of the TiO2 Degussa P25 powder. Differences in the photocatalytic efficiencies of the nanocoatings obtained by the two techniques of plasma spraying were obtained. The coatings elaborated by suspension plasma spraying have poor mechanical properties but better photocatalytic efficiencies. This method is a promising technique to elaborate photocatalytic coatings for the removal of different air pollutants.
Improvement of Bond Strength of Thermal Barrier Coatings by a Laser Remelting Process
Authors: Tanno M. , Ogawa K. , Shoji T. , Chwa S.O. , Ohmori A.
Published: July 2022

In order to improve the efficiency of gas turbines, thermal barrier coatings (TBCs) have been applied to components in the hot sections of advanced gas turbines. During service, thermally grown oxide (TGO), which consists of an Al2O3 layer and a mixed oxide layer, forms at the interface between the top coating and bond coating. It is supposed that the reason for failures of TBCs, such as cracking, delamination or spalling, is due to decreased bond strength caused by TGO growth or due to the formation of stress concentration sites caused by porosities in the mixed oxide. In this study, to inhibit the growth of TGO, plasma sprayed CoNiCrAlY bond coating was remelted with a YAG laser prior to spraying the top coating. A thin Al2O3 layer formed at the top coating/bond coating interface, and the formation of porous mixed oxide during thermal aging tests was inhibited. Four-point bending tests showed that the bond strength of TBC with remelted CoNiCrAlY was superior to standard TBC.
The Effect of YSZ Microstructure on Young's Modulus
Authors: Michlik Petr , Racek Ondrej , Berndt Christopher C.
Published: July 2022

The mechanical behavior of nanostructured yttria stabilized zirconia (YSZ) thermal spray deposits was examined and compared to conventional zirconia coatings. Young’s modulus was measured using indentation techniques. The anisotropy of the deposits was estimated by indenting the deposits in the perpendicular and parallel directions to the substrate. Statistical distribution of the mechanical properties was correlated with the microstructure. The effective Young’s moduli of nanostructured and standard YSZ were also modeled by means of 2D eXtended FEM; whereby actual microstructures were assessed. The simulation was based on micrographs by employing a standard meshing program combined with an in-house developed XFEM package, which incorporates the crack structure into the model. The effect of nano-scale features on the effective Young’s modulus were predicted and compared to experimental observations.
Bridge and Open Circuit Defect Properties
Authors: Gattiker Anne , Soden Jerry , Hawkins Chuck
Published: July 2022

CMOS IC failure mechanisms are of three general types: bridge defects, open circuit defects, and parametric related failures. This article summarizes bridge and open-circuit defect properties and provides references for further self-study. Bridge defects are characterized based on location, their significance in terms of logic gates and transistors, and critical resistance for dc logic and timing failures. Open defects are more complex and diverse with six possible failure modes each of which are described in the article.
Design, Metrics, and Control of the Unpredictable–A Business Model for Failure Analysis Service (Part I)
Authors: Boit Christian , Scholtens Koos , Weiland Rainer , Görlich Siegfried , Brillert Christof , Burmer Christian , Egger Peter , Schlenker Dietmar
Published: July 2022

This article presents a complete business model for Failure Analysis (FA) as a high tech provider in the world of microelectronics. Part I introduces the fundamentals of such a model. It starts with the definitions of a business process, and then the analysis flows are presented. Finally, a Key Performance Indicator (KPI) based operation is developed. Part II of this article will appear in the next issue of EDFA, and it will address the implementation of such a model in an FA lab. It discusses the interdependencies of workload and cycle times—the pipeline management. This opens the path to quantitative target setting agreements with customers. A complete system builds a database that can calculate all the parameters for an FA lab tailored exactly to the demand of the customer. Such a database acts as a reference lab and represents best FA practice.