scholarly journals Effect of different thermocouple constructions on heat-level vapour phase soldering profiles

2020 ◽  
Vol 32 (4) ◽  
pp. 253-259 ◽  
Author(s):  
Mohamed Amine Alaya ◽  
Viktória Megyeri ◽  
David Bušek ◽  
Gábor Harsányi ◽  
Attila Geczy
Keyword(s):  
Heat Transfer ◽  
Design Methodology ◽  
Vapour Phase ◽  
Considerable Effect ◽  
Significant Alteration ◽  
Thermal Mass ◽  
Reflow Soldering ◽  
Content Type ◽  
Significant Difference ◽  
Heating Profiles

Purpose To improve productivity and reach better quality in assembling, measurements and proper process controlling are a necessary factor. This study aims to focus on the monitoring heat-level-based vapour phase reflow soldering (VPS), where – as it was found – different thermocouple constructions can affect the set parameters of the oven and resulting soldering profiles significantly. Design/methodology/approach The study experiments showed significant alteration of the heating profiles during the process of the reflowing using different construction of k-type thermocouples. In a heat-level-based VPS oven, polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA) gas and water-resistant, fibreglass, thin PFA and ultrathin PFA-covered thermocouples were tested with ±1 °C precision. The oven parameters were swept according to the heating power; the length of the introduced thermocouple cables was also taken into account. An FR4-based sample PCB was used for monitoring the temperature. Findings According to the results, due to the mass and volume of the thermocouples’ wires, different transients were observed on the resulting soldering profiles on the same sample PCB. The thermocouples with lower thermal mass result in faster profiles and significantly different heating factor values compared to the thermocouples that have larger thermal mass. Consequently, the length of the thermocouple wires put in the oven has also considerable effect on the heat transfer of the PCB inside the oven as well. Originality/value The paper shows that the thermocouple construction must be taken into account when setting up a required soldering profile, while the thermal mass of the wires might cause a significant difference in the prediction of the actual and expected soldering temperatures.

The effect of chia (Salvia hispanic L.) flour as a substitute for fat in gluten-free bread

2019 ◽  
Vol 49 (4) ◽  
pp. 517-527 ◽  
Author(s):  
Katira da Mota Huerta ◽  
Caroline Pagnossim Boeira ◽  
Marcela Bromberger Soquetta ◽  
Jamila dos Santos Alves ◽  
Ernesto Hashime Kubota ◽  
...  
Keyword(s):  
Design Methodology ◽  
Nutritional Assessment ◽  
Sensory Properties ◽  
Gluten Free ◽  
Main Ingredient ◽  
Sensorial Analysis ◽  
Content Type ◽  
Significant Difference ◽  
Nutritional Characteristics ◽  
Sensorial Analyses

Purpose The preparation of gluten-free bread is a challenge because the gluten in wheat is the main ingredient responsible for the retention of the gases which cause the bread to rise. This paper aims to develop breads without gluten and fat, and to evaluate the effect of the use of chia (Salvia hispanic L.) flour on the physical, nutritional and sensory properties of the breads that were developed. Design/methodology/approach Three formulations were developed with different proportions of chia flour (2.5, 5 and 7.5%), fat-free. Physiochemical, sensorial analyses were performed out in three repetitions (p-value = 0.05). Findings In the nutritional assessment, the results demonstrated that 7.5% chia showed higher levels of protein (15.1%), lipid (3.43%), total fiber (7.04%) and lower levels of carbohydrates (22.49%), with significant nutrient enrichment (p-value = 0.05). The specific volume and the elevation of the dough decreased with the addition of chia flour. In the sensorial analysis, the treatments with chia flour showed no significant difference regarding flavor and texture when compared to the standard. The addition of chia improved the nutritional and sensory properties (p-value = 0.05). Originality/value The chia flour improved the nutritional characteristics of the breads, in the reduction of carbohydrate content and the increase in the content of protein, minerals and fiber. It presented good acceptability and good nutritional characteristics, providing a healthy and differentiated variation in this segment.

Algebraic solutions of flow and heat for some nanofluids over deformable and permeable surfaces

2017 ◽  
Vol 27 (10) ◽  
pp. 2259-2267 ◽  
Author(s):  
Mustafa Turkyilmazoglu
Keyword(s):  
Heat Transfer ◽  
Design Methodology ◽  
Temperature Jump ◽  
Volume Fraction ◽  
Velocity Slip ◽  
Jump Conditions ◽  
Content Type ◽  
Layer Flow ◽  
Working Out ◽  
Algebraic Solutions

Purpose This paper aims to working out exact solutions for the boundary layer flow of some nanofluids over porous stretching/shrinking surfaces with different configurations. To serve to this aim, five types of nanoparticles together with the water as base fluid are under consideration, namely, Ag, Cu, CuO, Al2O3 and TiO2. Design/methodology/approach The physical flow is affected by the presence of velocity slip as well as temperature jump conditions. Findings The knowledge on the influences of nanoparticle volume fraction on the practically significant parameters, such as the skin friction and the rate of heat transfer, for the above considered nanofluids, is easy to gain from the extracted explicit formulas. Originality/value Particularly, formulas clearly point that the heat transfer rate is not only dependent on the thermal conductivity of the material but it also highly relies on the heat capacitance as well as the density of the nanofluid under consideration.

X-ray inspection and Six-Sigma in analysis of LED thermal pad coverage

2017 ◽  
Vol 29 (1) ◽  
pp. 28-33 ◽  
Author(s):  
Barbara Dziurdzia ◽  
Janusz Mikolajek
Keyword(s):  
Six Sigma ◽  
Vapour Phase ◽  
Inspection System ◽  
Solder Paste ◽  
Process Variables ◽  
Reflow Soldering ◽  
Content Type ◽  
X Ray ◽  
Solder Pastes ◽  
Free Solder

Purpose The purpose of this paper is to evaluate selected methods of reduction voidings in lead-free solder joints underneath thermal pads of light-emitting diodes (LEDs), using X-ray inspection and Six Sigma methodology. Design/methodology/approach On the basis of cause and effect diagram for solder voiding, the potential causes of voids and influence of process variables on void formation were found. Three process variables were chosen: the type of reflow soldering, vacuum incorporation and the type of solder paste. Samples of LEDs were mounted with convection and vapour phase reflow soldering. Vacuum was incorporated into vapour phase soldering. Two types of solder pastes OM338PT and LFS-216LT were used. Algorithm incorporated into X-ray inspection system enabled to calculate the statistical distribution of LED thermal pad coverage and to find the process capability index (Cpk) of applied soldering techniques. Findings The evaluation of selected soldering processes of LEDs in respect of their thermal pad coverage and statistical Cpk indices is presented. Vapour-phase soldering with vacuum is capable (Cpk > 1) for OM338PT and LFS-216LT paste. Convection reflow without vacuum with LFS-216LT paste is also capable (Cpk = 1.1). Other technological soldering processes require improvements. Vacuum improves radically the capability of a reflow soldering for an LED assembly. When vacuum is not accessible, some improvement of capability to a lower extent is possible by an application of void-free solder pastes. Originality/value Six Sigma statistical methodology combined with X-ray diagnosis was used to check whether applied methods of void reduction underneath LED thermal pads are capable processes.

scholarly journals Social exclusion: re-examining its conceptual relevance to tackling inequality and social injustice

2015 ◽  
Vol 35 (9/10) ◽  
pp. 600-617 ◽  
Author(s):  
Clive Sealey
Keyword(s):  
Social Justice ◽  
Social Policy ◽  
Social Exclusion ◽  
Design Methodology ◽  
Value Added ◽  
Social Injustice ◽  
Critical Approach ◽  
Content Type ◽  
It Value ◽  
Significant Difference

Purpose – The purpose of this paper is to rationalise the continued conceptual utility of social exclusion, and in so doing addresses the prevailing question of what to do with it. This is relevant from social exclusion’s declining relevance in contemporary UK social policy and academia, where its consideration as a concept to explain disadvantage is being usurped by other concepts, both old and new. Design/methodology/approach – The paper analyses criticisms of limitations of social exclusion which have typically centred on the operationalisation of the concept, but the author will argue that there are distinctive operationalisation and conceptual strengths within social exclusion which make it value-added as a concept to explain disadvantage. Specifically, there will be an analysis of both New Labour’s and the present Coalition government’s conceptualisation of the term in policy in relation to work. Findings – The analysis highlights the significant difference that a focus on processes rather than outcomes of social exclusion can make to our understanding of inequality and social injustice, and locates this difference within an argument that social exclusion’s true applied capabilities for social justice requires a shift to a conceptualisation built on the processes that cause it in the first place. Originality/value – The paper acts as a rejoinder to prevailing theoretical and political thinking of the limited and diminishing value of social exclusion for tackling disadvantage. In particular, the paper shows how social exclusion can be conceptualised to provide a critical approach to tackling inequality and social injustice, and in doing so foregrounds the truly applied capabilities of social exclusion for transforming social justice.

A study of consumers’ pre-purchase evaluation of apparel products in Ethiopia

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Berihun Bizuneh ◽  
Shalemu Sharew Hailemariam ◽  
Selam Tsegaye
Keyword(s):  
Factor Analysis ◽  
Developing Country ◽  
Social Factors ◽  
Design Methodology ◽  
Online Survey ◽  
Educational Background ◽  
Demographic Variables ◽  
Content Type ◽  
Significant Difference ◽  
Garment Fit

PurposeThe purpose of this paper is to explore pre-purchase apparel evaluation cues and examine the effect of demographic variables empirically in the context of a developing country. The initiation for the study was driven by the absence of such prior research and supplemented by the big market opportunity for clothing products in the country under investigation.Design/methodology/approachA self-administered online survey was used for data collection. Demographic questions, 23 apparel measurement items composed of 17 product-based and 6 sustainability-based items, and an open-ended question were included in the questionnaire. Factor analysis was used for dimension reduction and one-way multivariate analysis of variance (MANOVA) for hypotheses testing.FindingsGarment fit, design features, colour, fabric type and seasonality are the five important characteristics most Ethiopian consumers consider while buying apparel products. Factor analysis resulted in five important factors used for pre-purchase apparel evaluation amongst which the design and extrinsic cue is found to be the most important. Environmental factors in the apparel industry got higher emphasis than social factors. While age and educational background made differences in apparel evaluation, gender did not show a significant difference.Originality/valueThe paper provides a founding insight in exploring apparel evaluation cues by considering product- and sustainability-based cues in a developing country context. It also examines the effect of three demographic variables which are rarely studied in such combination.

Offline vs online problem-based learning: a case study of student engagement and learning outcomes

2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hans Kristianto ◽  
Linda Gandajaya
Keyword(s):  
Student Engagement ◽  
Learning Outcomes ◽  
Teaching And Learning ◽  
Design Methodology ◽  
Problem Based Learning ◽  
Student Learning Outcomes ◽  
Content Type ◽  
Significant Difference ◽  
Health Related

Purpose Furthermore, the purpose of this study is to compare the student engagement and the learning outcomes in offline and online PBL in the aforementioned course. The COVID-19 pandemic has caused disruption in various sectors, including education. Since it was first announced in mid-March 2020 in Indonesia, teaching and learning activities have been carried out online. In this study, a comparison of the offline (Spring 2019, prior to the pandemic) and online (Spring 2021, during the pandemic) problem-based learning (PBL) method in the sustainable chemical industry course is investigated. Design/methodology/approach A quantitative analysis was conducted by measuring the students’ engagement, course-learning outcomes (CLOs) and student learning outcomes (SLOs). Difference tests of engagement score, CLOs and SLOs were investigated by using the t-test or Mann–Whitney U-test. Furthermore, the perceived students’ stressors were measured. Findings It is found that the students’ engagement in offline and online PBL gives similar scores with no significant difference. This is possible because of the PBL structure that demands students to be actively engaged in gaining knowledge, collaboratively working in teams and interacting with other students and lecturers. Although similarly engaged, the CLOs and SLOs of online PBL are significantly lower than offline PBL, except for SLO related to oral and written communication skills and affective aspect. The decrease in CLOs and SLOs could be influenced by students’ academic, psychological and health-related stressors during the COVID-19 pandemic time. Originality/value This study provides a recommendation to apply online PBL during the COVID-19 pandemic time and beyond, although some efforts to improve CLOs and SLOs are needed.

Unsteady separated stagnation-point flow and heat transfer past a stretching/shrinking sheet in a copper-water nanofluid

2019 ◽  
Vol 29 (8) ◽  
pp. 2588-2605 ◽  
Author(s):  
Natalia C. Roşca ◽  
Alin V. Roşca ◽  
Ioan Pop
Keyword(s):  
Heat Transfer ◽  
Partial Differential Equations ◽  
Differential Equations ◽  
Stagnation Point ◽  
Design Methodology ◽  
Similarity Transformation ◽  
Stagnation Point Flow ◽  
Shrinking Sheet ◽  
Content Type ◽  
Flow And Heat Transfer

Purpose The purpose of this paper is to theoretically investigate the unsteady separated stagnation-point flow and heat transfer past an impermeable stretching/shrinking sheet in a copper (Cu)-water nanofluid using the mathematical nanofluid model proposed by Tiwari and Das. Design/methodology/approach A similarity transformation is used to reduce the governing partial differential equations to a set of nonlinear ordinary (similarity) differential equations which are then solved numerically using the function bvp4c from Matlab for different values of the governing parameters. Findings It is found that the solution is unique for stretching case; however, multiple (dual) solutions exist for the shrinking case. Originality/value The authors believe that all numerical results are new and original, and have not been published elsewhere.

scholarly journals Heat transfer aspects of condensation during vapour phase soldering on aligned PCB-based surfaces

2020 ◽  
Vol 32 (4) ◽  
pp. 247-252 ◽  
Author(s):  
Daniel Straubinger ◽  
István Bozsóki ◽  
Balazs Illes ◽  
Oliver Krammer ◽  
David Bušek ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Vertical Wall ◽  
Initial Pressure ◽  
Vapour Phase ◽  
Circuit Board ◽  
Pressure Measurements ◽  
Transfer Coefficients ◽  
Content Type

Purpose The paper aims to present an investigation on heat transfer in a vapour phase soldering (VPS) oven, focusing on the differences of horizontally and vertically aligned Printed Circuit Board (PCB) surfaces. The investigation can help develop a better understanding of the process and provide information for future modelling of the process. Design/methodology/approach For the investigations, flame retardant grade 4 (FR4) PCB plates and sealed plate–based boxes were immersed into saturated vapour of an experimental oven. The temperature and resulting heat transfer coefficients were analysed according to the sample boxes and the surface orientations. In addition, the boxes’ vapour consumption was investigated with pressure measurements. Findings The horizontal top- and bottom-side heating shows very similar results. In addition, the sides of a box were heated in a manner similar to the top and the bottom sides, but there was a slight increase in the heat transfer coefficient because of the vertical wall alignment. The pressure measurements reveal the dynamic changes in vapour after immersion of the boxes. Practical implications The findings may help to show differences on different surface orientations, pointing to more precise, explicit and multiphysics simulation results. Originality/value The experiments present an aspect of heat transfer coefficient differences in VPS ovens, also highlighting the effect of initial pressure drop inside the workspace of an oven.

Controversial product advertisements in Lebanon

2015 ◽  
Vol 6 (1) ◽  
pp. 22-43 ◽  
Author(s):  
Maya F. Farah ◽  
Lamis El Samad
Keyword(s):  
Representative Sample ◽  
Design Methodology ◽  
Content Type ◽  
Significant Difference ◽  
Religious Sect ◽  
Religious Sects ◽  
The Impact ◽  
Consumer's Perception ◽  
Minimal Research ◽  
Practical Implications

Purpose – The purpose of this paper is to examine the impact of religious sect on the Lebanese consumer’s perception of controversial product advertisements. Design/methodology/approach – The study used a quantitative survey that was administered to a purposive representative sample of respondents from the two main Muslim sects in the country, namely, Sunni and Shiite Muslims. Findings – The results indicated significant differences in perceptions between Sunni and Shiite Muslims with regards to the offensiveness of the advertising of controversial products. Briefly, Sunni Muslims found the advertising of social and political as well as health and care products more offensive, whereas Shiite Muslims found the advertising of gender and sex-related products more offensive, and no significant difference in offensiveness perception between the two sects was found with regards to the advertising of addictive products. Research limitations/implications – Two main limitations faced the researchers: the fact that the respondents were not shown examples of offensive product advertisements; and that religiosity was not measured for the respondents, which could also be a factor in offensiveness perception. Practical implications – The study indicates that a consumer’s religious sect can play a determining role in how he/she perceives product advertisement, thus encouraging marketers to consider the differences between these sects while advertising to ensure no potential consumers are alienated. Originality/value – Although research has looked into the impact of religiosity and religion on the perception of offensive product advertisements, minimal research exists on the impact of religious sects on the perception of offensive product advertisement. The results of this study provide some insights into the consumer behavior differences between the two sects.

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