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Found 6319 publications

Scheduling a forge with due dates and die deterioration

Máté Hegyháti Olivér Osz Balázs Ferenczi

Publication Name: Annals of Operations Research

Publication Date: 2020-02-01

Volume: 285

Issue: 1-2

Page Range: 353-367

Description:

In this paper a new scheduling problem is presented, which originates from the steel processing industry. The optimal scheduling of a steel forge is investigated with the goal of minimizing setup and storage costs under strict deadlines and special resource constraints. The main distinctive feature of the problem is the deterioration of some equipment, in this case, the so-called forging dies. While the aging effect has been widely investigated in scheduling approaches, where production speed decreases through time, durability deterioration caused by equipment setup has not been addressed yet. In this paper a mixed-integer linear programming model is proposed for solving the problem. The model uses a uniform discrete time representation and resource-balance constraints based on the resource–task network model formulation method. The proposed method was tested on 3-week long schedules based on real industrial scenarios. Computational results show that the approach is able to provide optimal short-term schedules in reasonable time.

Open Access: Yes

DOI: 10.1007/s10479-019-03336-6

Short-term cognitive fatigue effect on auditory temporal order judgments

Gábor Orosz Endre Takács Júlia Simon Borbála Berki István Winkler

Publication Name: Experimental Brain Research

Publication Date: 2020-02-01

Volume: 238

Issue: 2

Page Range: 305-319

Description:

Fatigue is a core symptom in many psychological disorders and it can strongly influence everyday productivity. As fatigue effects have been typically demonstrated after long hours of time on task, it was surprising that in a previous study, we accidentally found a decline of temporal order judgment (TOJ) performance within 5–8 min. After replicating prior relevant findings we tested whether pauses and/or feedback relating the participant’s performance to some “standard” can eliminate or reduce this short-term performance decline. We also assessed whether the performance decline is specific to the processes evoked by the TOJ task or it is a product of either general inattentiveness or the lack of willingness to thoroughly follow the task instructions. We found that both feedback and introducing pauses between successive measurements can largely reduce the performance decline, and that these two manipulations likely mobilize overlapping capacities. Performance decline was not present in a similar task when controlling for the TOJ threshold and it was not a result of uncooperative behavior. Therefore, we conclude that the TOJ threshold decline is either specific to temporal processing in general or to the TOJ task employed in the study. Overall, the results are compatible with the notion that the decline of TOJ threshold with repeated measures represents a short-term cognitive fatigue effect. This objective fatigue measure did not correlate with subjective fatigue. The latter was rather related to perceived difficulty/effort, the reduction of positive affectivity, heightened sensitivity to criticism, and the best TOJ threshold.

Open Access: Yes

DOI: 10.1007/s00221-019-05712-x

Vibration levels of stacked automotive engine rack in truck shipments as a function of vehicle speed and road condition

Péter Böröcz

Publication Name: Journal of Testing and Evaluation

Publication Date: 2020-01-29

Volume: 49

Issue: 1

Page Range: Unknown

Description:

In the past three decades, there has been a tremendous global shift in the use of returnable or reusable packaging in the automotive industry. This article focuses on the physical vibration forces that occur in a very important type of package system designed for engines and transmissions, namely the steel racks that have vertical posts on the four vertical edges that allow higher return ratios when empty. Engines and transmissions require zero damage acceptance levels today, as they are mated at the end of the assembly process, and they need to function 100 % of the time as the vehicle rolls off the finish line. They also are the most expensive components of the vehicle. This study was conducted to investigate the vibration environment of the stacked engine rack during truck transportation with various truck speeds, road conditions, and other road characteristics, such as speed bumps and railway crossings. Triaxial acceleration data were collected both on the truck floor as well as on the stacked racks themselves to determine the differences of vibration levels from truck floor to the stacked rack where vibration intensity increased. This study found that there were significant vibration severities in the stacked racks in all three orientations.

Open Access: Yes

DOI: 10.1520/JTE20180782

Effect of cell disruption methods on the extraction of bioactive metabolites from microalgal biomass

Péter Bálint Csaba Lovász Zoltán Molnár McMaster Vambe Vince Ördög Wendy A. Stirk Johannes van Staden

Publication Name: Journal of Biotechnology

Publication Date: 2020-01-10

Volume: 307

Issue: Unknown

Page Range: 35-43

Description:

Microalgae synthesize a variety of potentially high-value compounds. Due to their robust cell wall, cell disruption is necessary to improve extraction of these compounds. While cell disruption methods have been optimized for lipid and protein extraction, there are limited studies for other bioactive compounds. The present study investigated the effect of freeze-drying combined with sonication or ball-milling on the extraction of antioxidant and plant biostimulating compounds from Chlorella sp., Chlorella vulgaris and Scenedesmus acutus. Both cell disruption methods resulted in higher extract yields from the biomass compared to freeze-dried biomass using 50% methanol as a solvent. Antioxidant activity of Chlorella extracts was generally higher than freeze-dried extracts based on the diphenylpicrylhydrazyl (DPPH) and β-carotene linoleic acid assays. However, the effectiveness of each treatment varied between microalgae strains. Sonication resulted in the highest antioxidant activity in Chlorella sp. extracts. Ball-milling gave the best results for C. vulgaris extracts in the DPPH assay. Both cell disruption methods decreased antioxidant activity in S. acutus extracts. Plant biostimulating activity was tested using the mung bean rooting assay. Damaging the membrane by freeze-drying was sufficient to release the active compounds using water extracts. In contrast, both cell disruption methods negatively affected the biological activity of the extracts. These results indicate that bioactive compounds in microalgae are sensitive to post-harvest processes and their biological activity can be negatively affected by cell disruption methods. Care must be taken to not only optimize yield but to also preserve the biological activity of the target compounds.

Open Access: Yes

DOI: 10.1016/j.jbiotec.2019.10.012

Experiencing the sense of presence within an educational desktop virtual reality

Borbála Berki

Publication Name: Acta Polytechnica Hungarica

Publication Date: 2020-01-01

Volume: 17

Issue: 2

Page Range: 255-265

Description:

This study examines the sense of presence in MaxWhere desktop virtual reality. Thirty-one people participated in the research. The participants spend about fifteen minutes in the virtual environment. For measuring presence, the Igroup Presence Questionnaire (IPQ) was used. The results showed that more automatic navigation positively relates to spatial presence. This research also measured the participants' level of experience with the VR software. A significant difference was found in the spatial presence and experienced realism: the more experienced users gave higher ratings on both subscales. At the same time, the involvement and the general presence scores were similar in the two groups, which is advantageous in education as the presence is positively related to the learning outcome.

Open Access: Yes

DOI: 10.12700/APH.17.2.2020.2.14

Purification of model dairy wastewaters by Ozone, Fenton pre-treatment and membrane filtration

Zsuzsanna László E. Lakatos Mihály Zakar Gábor Keszthelyi-Szabó Dániel Imre Farkas

Publication Name: Periodica Polytechnica Chemical Engineering

Publication Date: 2020-01-01

Volume: 64

Issue: 3

Page Range: 357-363

Description:

This study aimed to investigate the effect of ozone and Fenton-reaction as a pre-treatment before ultrafiltration of model dairy waste waters containing sodium caseinate. Filtration resistances and pollutant retentions were determined and compared. It was found, that both pre-treatment increased the retention, achieving almost 100 % pollutant elimination efficiency after short term pre-oxidation. The effect of Fe-ion concentration on Fenton pretreatment efficiency also was examined, and it was found that higher concentration resulted in decreased filtration resistances, revealing that coagulation-flocculation effect of reactants has dominant role in the protein separation efficiency. The presence of lactose also affects the pollutant removal efficiency, it promotes fouling in presence of Fenton reagents.

Open Access: Yes

DOI: 10.3311/PPch.15046

On the Python programming language for statisticians

Attila Sóti

Publication Name: Statisztikai Szemle

Publication Date: 2020-01-01

Volume: 98

Issue: 4

Page Range: 324-352

Description:

This study provides easily accessible introduction to the Python programming language for readers who are beginners in software development but proficient in statistics. The tutorial presents the beauty of Python programming, outlines a path to an easily executable code and also highlights pitfalls of Python. Most of the statistical methods used as an example are deliberately basic, with the exception of cluster analysis. As a final step, the importance of data visualization is highlighted and examples of the possible use of Python in this area are given

Open Access: Yes

DOI: 10.20311/stat2020.4.hu0324

Three level fuzzy signature based decision methodology for packaging system design

Peter Foldesi Adrienn Buruzs Kata Vöröskoi Gergő Fogarasi Ĺaszĺo T. Ḱoczy

Publication Name: Journal of Automation Mobile Robotics and Intelligent Systems

Publication Date: 2020-01-01

Volume: 14

Issue: 2

Page Range: 99-105

Description:

In the field of logistics packaging, companies have to take decisions on determining the optimal packaging solutions and expenses. The decisions often involve a choice between one-way (disposable) and reusable (returnable) packaging solutions. Even nowadays, in most cases the decisions are made based on traditions and mainly consider the material and investment costs. Although cost is an important factor, it might not be sufficient for finding the optimal solution. Traditional (two-valued) logic is not suitable for modelling this problem, so here the application of a fuzzy approach, because of the metrical aspects, a fuzzy signature approach is considered. In this paper three different fuzzy signatures connected by fuzzy rules modelling the packaging decision are suggested, based on logistics expert opinions, in order to support the decision making process of choosing the right packaging system. Two real life examples are also given, one in the field of customer packaging and one in industrial packaging.

Open Access: Yes

DOI: 10.14313/JAMRIS/2-2020/25

Challenges of Corporate Ecological Footprint Calculations in the SME Sector in Hungary: Case Study Evidence from Six Hungarian Small Enterprises

Cecília Szigeti Áron Szennay L. Radácsi J. Lisányi Endréné Beke J. R.Polák Weldon

Publication Name: Agroecological Footprints Management for Sustainable Food System

Publication Date: 2020-01-01

Volume: Unknown

Issue: Unknown

Page Range: 345-363

Description:

Scientific and social discourse examines primarily the environmental performance of large enterprise actors. Although these large enterprises usually operate on an international level, over half of the added value created in the European Union and thus over half of the environmental damage are generated by small- and medium-sized enterprises (SME). Nevertheless, while the tools and expertise required to measure environmental performance are available for large enterprises, the SME sector has only limited access to these tools. s part of our research, we have developed an ecological footprint (EF) calculator applicable to the specificities of the SME sector, which has been tested on six Hungarian companies operating in different sectors and organisational frameworks. The test results indicate that the managerial information system of partnerships includes all the main inputs that are necessary to estimate a company’s EF. However, in the case of sole proprietorships, most of the required data can only be acquired by estimation. Our EF calculations on analysed firms cannot be considered as representative data. But on the base of the case studies, we can suggest that our EF calculator for SMEs is suitable to take a more comprehensive survey on EF of Hungarian and international firms, in order to generate sectoral benchmarks. Ecological footprint among analysed enterprises ranged between 5102 and 263,589 global square metres. It is caused mainly by (1) the sector (e.g. constructions have generally larger footprints than office activities) and (2) the size, expressed in number of employees or value added. To increase transparency of the environmental performance of the SME sector, we recommend that the supplementary annex of partnerships includes the main input data necessary for the calculation of the EF in a comparable and consistent way, in natural units of measurement. With such information and our calculator, it would be possible to determine the average environmental impact of the individual sectors, which would provide an appropriate starting point for the environmental investments of enterprises.

Open Access: Yes

DOI: 10.1007/978-981-15-9496-0_11