198,603 research outputs found
Hydrogen reduction of industrial iron ore pellets : a multi-scale study from surface to core
No full textAbstract
The transition towards sustainable ironmaking necessitates the replacement of carbon-based reduction processes with hydrogen-based alternatives to mitigate CO₂ emissions. This study investigates the reduction behavior of two types of industrial pellets utilized in direct reduction (DRI) and blast furnaces (BFs), using hydrogen (H₂) and carbon monoxide (CO) as reducing agents. The experimental analysis utilizes ambient pressure X-ray photoelectron spectroscopy (APXPS) to examine the surface reduction mechanisms and a thermogravimetric analysis (TGA) to evaluate kinetic parameters in bulk scale.
DRI pellets achieved a higher metallization degree during surface reduction by hydrogen due to their higher porosity. Although adding CO to the reducing gas hindered the formation of metallic iron in DRI pellet, BF pellet reached to 20% metallization degree by a mixture of 50:50 CO:H₂. However, subsequent reoxidation of the reduced iron to wüstite and magnetite occurred due to increasing partial pressure of H₂O and CO₂ on the surface of the pellets.
Investigating the effect of water vapor on the hydrogen reduction of pellets showed that although complete reduction is thermodynamically possible with 30% water vapor in the system, the reduction of wüstite to iron could not start, even at high temperatures, due to a kinetic barrier. The effect of 20% water vapor on the reduction degree was dependent on the reduction temperature. Although adding 10% water vapor decreased the rate of reduction, it did not affect the reduction degree. Original papers Heidari, A., Niknahad, N., Iljana, M., & Fabritius, T. (2021). A review on the kinetics of iron ore reduction by hydrogen. Materials, 14(24), 7540. https://doi.org/10.3390/ma14247540 https://doi.org/10.3390/ma14247540 Self-archived version Heidari, A., Ghosalya, M. K., Alaoui Mansouri, M., Heikkilä, A., Iljana, M., Kokkonen, E., Huttula, M., Fabritius, T., & Urpelainen, S. (2024). Hydrogen reduction of iron ore pellets: A surface study using ambient pressure X-ray photoelectron spectroscopy. International Journal of Hydrogen Energy, 83, 148–161. https://doi.org/10.1016/j.ijhydene.2024.08.094 https://doi.org/10.1016/j.ijhydene.2024.08.094 Self-archived version Heidari, A., Heikkilä, A., Iljana, M., & Fabritius, T. (2024). A comparison between the reduction behavior of DRI and BF pellets in H2 and CO atmospheres. Journal of Sustainable Metallurgy, 10(4), 2068–2084. https://doi.org/10.1007/s40831-024-00951-x https://doi.org/10.1007/s40831-024-00951-x Self-archived version Heidari, A., Ilmakangas, T., Pöyhtäri, S., Heikkinen, E. P., Sulasalmi, P., & Fabritius, T. (in press). The influence of water vapor on hydrogen reduction of iron ore pellets. Ironmaking & Steelmaking. Tiivistelmä
Siirtyminen kestävään raudanvalmistukseen edellyttää hiilipohjaisten pelkistysprosessien korvaamista vetyyn perustuvilla vaihtoehdoilla hiilidioksidipäästöjen vähentämiseksi. Tämä tutkimus tarkastelee kahden teollisen pellettityypin pelkistymiskäyttäytymistä suorapelkistyksessä (DRI) ja masuunissa (BF) käyttäen pelkistimenä vetyä (H₂) ja hiilimonoksidia (CO). Kokeellinen analyysi hyödyntää painetta kontrolloivaa röntgenfotoelektronispektroskopiaa (APXPS) pinnan pelkistysmekanismien tutkimiseen sekä termogravimetristä analyysia (TGA) kineettisten parametrien arviointiin suuremmassa mittakaavassa.
Tutkittaessa pinnan pelkistymistä vedyllä DRI-pelletti saavutti korkeamman metallisaatioasteen verrattuna BF-pellettiin, mikä johtui sen suuremmasta huokoisuudesta. Metallista rautaa ei muodostunut DRI-pelletissä, kun pelkistyskaasuun vedyn lisäksi lisättiin hiilimonoksidia. Kuitenkin BF-pelletti saavutti korkeamman metallisaatioasteen (20 %), kun pelkistyskaasujen suhde oli 50:50. Pelkistyneen raudan uudelleenhapettumista wüstiitiksi ja magnetiitiksi havaittiin tapahtuvan, kun H₂O- ja CO₂-osapaineet kasvoivat pelletin pinnalla.
Tutkittaessa vesihöyryn vaikutusta pelletin vetypelkistyksen aikana havaittiin, että vaikka täydellinen pelkistyminen on termodynaamisesti mahdollista vesihöyrypitoisuuden ollessa 30 %, wüstiitin pelkistyminen raudaksi ei tapahdu edes korkeissa lämpötiloissa kineettisten esteiden takia. Vesihöyrypitoisuuden ollessa 20 % pelkistymiseen vaikutti myös käytetty pelkistyslämpötila. Vaikka 10 prosentin vesihöyrypitoisuus hidasti pelkistysnopeutta, se ei vaikuttanut pelkistysasteeseen. Osajulkaisut Heidari, A., Niknahad, N., Iljana, M., & Fabritius, T. (2021). A review on the kinetics of iron ore reduction by hydrogen. Materials, 14(24), 7540. https://doi.org/10.3390/ma14247540 https://doi.org/10.3390/ma14247540 Rinnakkaistallennettu versio Heidari, A., Ghosalya, M. K., Alaoui Mansouri, M., Heikkilä, A., Iljana, M., Kokkonen, E., Huttula, M., Fabritius, T., & Urpelainen, S. (2024). Hydrogen reduction of iron ore pellets: A surface study using ambient pressure X-ray photoelectron spectroscopy. International Journal of Hydrogen Energy, 83, 148–161. https://doi.org/10.1016/j.ijhydene.2024.08.094 https://doi.org/10.1016/j.ijhydene.2024.08.094 Rinnakkaistallennettu versio Heidari, A., Heikkilä, A., Iljana, M., & Fabritius, T. (2024). A comparison between the reduction behavior of DRI and BF pellets in H2 and CO atmospheres. Journal of Sustainable Metallurgy, 10(4), 2068–2084. https://doi.org/10.1007/s40831-024-00951-x https://doi.org/10.1007/s40831-024-00951-x Rinnakkaistallennettu versio Heidari, A., Ilmakangas, T., Pöyhtäri, S., Heikkinen, E. P., Sulasalmi, P., & Fabritius, T. (in press). The influence of water vapor on hydrogen reduction of iron ore pellets. Ironmaking & Steelmaking. Academic dissertation to be presented with the assent of the Doctoral Programme Committee of Technology and Natural Sciences of the University of Oulu for public defence in the Oulun Puhelin auditorium (L5), Linnanmaa, on 29 August 2025, at 12 noonAbstract
The transition towards sustainable ironmaking necessitates the replacement of carbon-based reduction processes with hydrogen-based alternatives to mitigate CO₂ emissions. This study investigates the reduction behavior of two types of industrial pellets utilized in direct reduction (DRI) and blast furnaces (BFs), using hydrogen (H₂) and carbon monoxide (CO) as reducing agents. The experimental analysis utilizes ambient pressure X-ray photoelectron spectroscopy (APXPS) to examine the surface reduction mechanisms and a thermogravimetric analysis (TGA) to evaluate kinetic parameters in bulk scale.
DRI pellets achieved a higher metallization degree during surface reduction by hydrogen due to their higher porosity. Although adding CO to the reducing gas hindered the formation of metallic iron in DRI pellet, BF pellet reached to 20% metallization degree by a mixture of 50:50 CO:H₂. However, subsequent reoxidation of the reduced iron to wüstite and magnetite occurred due to increasing partial pressure of H₂O and CO₂ on the surface of the pellets.
Investigating the effect of water vapor on the hydrogen reduction of pellets showed that although complete reduction is thermodynamically possible with 30% water vapor in the system, the reduction of wüstite to iron could not start, even at high temperatures, due to a kinetic barrier. The effect of 20% water vapor on the reduction degree was dependent on the reduction temperature. Although adding 10% water vapor decreased the rate of reduction, it did not affect the reduction degree.Tiivistelmä
Siirtyminen kestävään raudanvalmistukseen edellyttää hiilipohjaisten pelkistysprosessien korvaamista vetyyn perustuvilla vaihtoehdoilla hiilidioksidipäästöjen vähentämiseksi. Tämä tutkimus tarkastelee kahden teollisen pellettityypin pelkistymiskäyttäytymistä suorapelkistyksessä (DRI) ja masuunissa (BF) käyttäen pelkistimenä vetyä (H₂) ja hiilimonoksidia (CO). Kokeellinen analyysi hyödyntää painetta kontrolloivaa röntgenfotoelektronispektroskopiaa (APXPS) pinnan pelkistysmekanismien tutkimiseen sekä termogravimetristä analyysia (TGA) kineettisten parametrien arviointiin suuremmassa mittakaavassa.
Tutkittaessa pinnan pelkistymistä vedyllä DRI-pelletti saavutti korkeamman metallisaatioasteen verrattuna BF-pellettiin, mikä johtui sen suuremmasta huokoisuudesta. Metallista rautaa ei muodostunut DRI-pelletissä, kun pelkistyskaasuun vedyn lisäksi lisättiin hiilimonoksidia. Kuitenkin BF-pelletti saavutti korkeamman metallisaatioasteen (20 %), kun pelkistyskaasujen suhde oli 50:50. Pelkistyneen raudan uudelleenhapettumista wüstiitiksi ja magnetiitiksi havaittiin tapahtuvan, kun H₂O- ja CO₂-osapaineet kasvoivat pelletin pinnalla.
Tutkittaessa vesihöyryn vaikutusta pelletin vetypelkistyksen aikana havaittiin, että vaikka täydellinen pelkistyminen on termodynaamisesti mahdollista vesihöyrypitoisuuden ollessa 30 %, wüstiitin pelkistyminen raudaksi ei tapahdu edes korkeissa lämpötiloissa kineettisten esteiden takia. Vesihöyrypitoisuuden ollessa 20 % pelkistymiseen vaikutti myös käytetty pelkistyslämpötila. Vaikka 10 prosentin vesihöyrypitoisuus hidasti pelkistysnopeutta, se ei vaikuttanut pelkistysasteeseen
Corrigendum
No full textBiazar E, Heidari M, Asefnezhad A, Montazeri N. The relationship between cellular adhesion and surface roughness in polystyrene modified by microwave plasma radiation. International Journal of Nanomedicine. 2011;6:631-639.The correct spelling of the third author's name is "Asefnejad."Original articl
Corrigendum
No full textHeidari S, Azhdadi SN, Asefnezhad A, Sadraeian M, Montazeri M, Biazar EThe relationship between cellular adhesion and surface roughness for polyurethane modified by microwave plasma radiation. International Journal of Nanomedicine. 2011;6:641-647.The correct spelling of the third author's name is "Asefnejad."Original Articl
Two new species of Niphargus (Crustacea: Amphipoda) from Iran
No full textHekmatara, M., Zakšek, V., Baladehi, M. Heidari, Fišer, C. (2013): Two new species of Niphargus (Crustacea: Amphipoda) from Iran. Journal of Natural History 47 (21-22): 1421-1449, DOI: 10.1080/00222933.2012.743616, URL: http://dx.doi.org/10.1080/00222933.2012.74361
A New Service Composition Method in the Cloud-Based Internet of Things Environment Using a Grey Wolf Optimization Algorithm and Mapreduce Framework
No full textAl-Khafaji, Hamza Mohammed Ridha/0000-0003-3620-581X; Heidari, Arash/0000-0003-4279-8551Cloud computing is quickly becoming a common commercial model for software delivery and services, enabling companies to save maintenance, infrastructure, and labor expenses. Also, Internet of Things (IoT) apps are designed to ease developers' and users' access to networks of smart services, devices, and data. Although cloud services give nearly infinite resources, their reach is constrained. Designing coherent and organized apps is made possible by integrating the cloud and IoT. Expanding facilities by combining services is a critical component of this technology. Various services may be presented in this environment based on the user's demands. Considering their Quality of Service (QoS) attributes, discovering the appropriate available atomic services to construct the needed composite service with their collaboration in an orchestration model is an NP-hard issue. This article suggests a service composition method using Grey Wolf Optimization (GWO) and MapReduce framework to compose services with optimized QoS. The simulation outcomes illustrate cost, availability, response time, and energy-saving improvements through the suggested approach. Comparing the suggested technique to three baseline algorithms, the average gain is a 40% improvement in energy savings, a 14% decrease in response time, an 11% increase in availability, and a 24% drop in cost. © 2024 John Wiley & Sons Ltd
Gammarus sirvannus Hekmatara, Sari & Heidari Baladehi 2011
No full textGammarus sirvannus Hekmatara, Sari & Heidari Baladehi, 2011 Gammarus sirvannus Hekmatara, Sari & Heidari Baladehi, 2011: 49 –56, Figs. 8–13. Locus typicus. Sirvan River-Paveh branch (N 35 º 0 7 ʹ, E 46 º 15 ʹ), 25 Km west of Paveh city, Kermanshah province, Iran. Material examined. Paratypes, September 2008, leg. M. Hekmatara (ZUTC amph. 2251). Distribution. This species was found only in locus typicus in north-west of the Zagros, in western Iran. Ecological notes. This cold mountainous region lies at an altitude of ca. 700 m asl. Taxonomic remarks. Long setation of antenna 2 makes G. sirvannus resembling a few other species present in the same region. However, in G. komareki, such setae are slightly curled, it has small eyes, lacks the distinctly projecting postero-distal corner lobe in bases of pereopods 6–7, and has few short setae on pereopod 5–7. Elongated eyes and setation of antenna 2 make G. sirvannus similar to G. loeffleri and to G. shirazinus, but the latter differ with highly setose pereopod 3–7. G. parthicus may be obviously told apart from G. sirvannus by the small eyes and lack of distinct projection in postero-distal corner of pereopod 6–7 bases in the former species. In a detailed examination, presence of a single long seta on the first article of mandible palp is a deciding criterion to differentiate G. sirvannus from all the other similar species.Published as part of Zamanpoore, Mehrdad, Grabowski, Michal, Poeckl, Manfred & Schiemer, Friedrich, 2011, Taxonomic review of freshwater Gammarus (Crustacea: Amphipoda) from Iran, pp. 1-14 in Zootaxa 3140 on page 11, DOI: 10.5281/zenodo.20563
Sustainable Tourism Governance: a systems thinking Triple Helix approach
No full textPurpose – Like any economic sector, the tourism industry encounters growing pressures to achieve a viable balance between economic growth, environmental preservation, and societal welfare. Contemporary strategies for tourism governance frequently place a greater emphasis on economic advancement, thereby overlooking the significance of environmental and social considerations. The objective of this study is to investigate how the multiple actors involved in tourism systems can effectively interact to co-create value by integrating the economic, social, and environmental dimensions of sustainability.
Design/Methodology/Approach – This paper introduces a comprehensive framework inspired by the Viable Systems Approach (vSa) for addressing the challenges of balancing economic progress with environmental and social well-being in the tourism sector. It adopts the VSA framework of the Triple Helix of Sustainability (THS) to highlight the main challenges for effective integrated governance of sustainable tourism systems.
Findings/Results – Maintaining profitability conditions while addressing challenging expectations at both environmental and social levels implies that tourism management addresses a variety of diverse requirements. This variety is further complicated by the involvement of multiple actors characterized by different interests and goals and the transitional and seasonal characteristics inherent to the tourism industry that introduce a certain variability to manage. In such a direction, the study highlights the contribution of the THS, a governance framework that integrates the Triple Bottom Line with the Triple Helix of Innovation, providing guidance for science, policy, and industry actors to make tourism sustainable.
Originality/Value – Developing long-term strategies for sustainable tourism is challenging because tourist systems are multi-actor and constantly changing. Strategic issues like an interplay of multiple different stakeholders, in addition to practical problems like seasonal changes in visitors’ numbers, changing consumer tastes, and global economic trends, can all make it very hard to converge toward sustainable tourism models. Through the THS, systems thinking could support key actors in better catching and understanding the multidimensionality of sustainability and the ways to harmonize the variety to manage.
Research/Practical/Social/Environmental Implications – Effectively integrating the Tourism and Hospitality Sector into the tourism industry requires a deep understanding of complex feedback mechanisms and adapting to dynamic conditions. This adaptation is necessary to ensure economic growth aligns with environmental and social considerations. This study offers guidance to policymakers and organizations responsible for overall governance. It also provides insights to academic institutions and scholars who play a crucial role in envisioning new scenarios.
Limits of the research/future directions – One limitation of this study is the reliance on theoretical literature without empirical studies to supplement it. A potential avenue for future research involves using empirical methods to explore how systems thinking and the THS can be practically applied in real-world tourism governance contexts
A shape preserving quasi-interpolation operator based on a new transcendental rbf
No full textIt is well-known that the univariate Multiquadric quasi-interpolation operator is constructed based on the piecewise linear interpolation by |x|. In this paper, we first introduce a new transcendental RBF based on the hyperbolic tangent function as a smooth approximant to φ(r) = r with higher accuracy and better convergence properties than the MQ RBF. Then the Wu-Schaback’s quasi-interpolation formula is rewritten using the proposed RBF. It preserves convexity and monotonicity. We prove that the proposed scheme converges with a rate of O(h^2). So it has a higher degree of smoothness. Some numerical experiments are given in order to demonstrate the efficiency and accuracy of the method
On a new class of positive definite RBFs by using Fourier cosine transform
No full textIn this article, we use Fourier cosine transform in order to introduce a new family of infinitely smooth positive definite radial basis functions from completely monotone functions. These bases are represented in terms of positive Borel measures and their Fourier transforms are also given. The proposed theory is used for reconstructing the well-known Matérn RBF and presenting a new positive definite RBF. Numerical results show an accurate reconstruction of the Franke’s function and also mitigating the Runge phenomenon as a key error mechanism
Challenges of Nutrition Department in a Selected Teaching Hospital: a qualitative study
No full textBackground & Objectives: Department of Nutrition is one of the most important parts of a hospital that has a significant role in patient's satisfaction. Managers' attention to the quality of nutrition services reduces hospital costs. This study was conducted to identify the challenges of the nutrition department of a selected teaching hospital.
Methods: The present study was a qualitative study done with phenomenological approach in 2018. Purposeful sampling and snowball sampling were used. Data collection was done through semi-structured interview. Participants were 25 individuals involved in the nutrition department of the selected teaching hospital in Kerman. Finally, data analysis was done using framework analysis.
Results: The identified challenges were classified into 7 main codes and 21 sub-codes. Main codes were the contracts and tenders, staff supervision, financing, operational line monitoring, human resources, quality of food and physical space.
Conclusion: Paying attention to the hospitals’ nutrition departments is one of the main factors in patients' recovery and an inseparable part of the treatment process. Therefore, hospital managers and policymakers should pay particular attention to this part and to improve the nutrition department status of the hospitals through reviewing and modifying contracts and tenders, staff supervision, financing, queue monitoring and providing sufficient human resources, high quality food and required physical space.
Keywords: Nutrition department, Line and staff, Quality, Teaching Hospital
Citation: Heidari N, Yazdanpanah M, Nekoui Moghadam M, Amiresmaili M, Heidari A, Heidari jamebozorgi M. Challenges of Nutrition Department in a Selected Teaching Hospital: a qualitative study. Journal of Health Based Research 2019; 5(2): 203-14. [In Persian
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