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Found 6278 publications

Equitable Economic Development in Global South through Sustainable Mineral Policy: Role of Political and Governance Factors

Gagan Deep Sharma Umer Shahzad

Publication Name: Politicka Ekonomie

Publication Date: 2025-01-01

Volume: 73

Issue: 5

Page Range: 769-777

Description:

No description provided

Open Access: Yes

DOI: 10.18267/j.polek.1514

Selection of Heat Transfer Enhancement Technique for Compact Mini and Micro Heat Exchangers Design

Olga Arsenyeva Petro Kapustenko Andrea Nemet Leonid Tovazhnyanskyy Leonid Tovazhnyanskyy Igor Plazl Petar Sabev Varbanov Zdravko Kravanja

Publication Name: Chemical Engineering Transactions

Publication Date: 2025-01-01

Volume: 120

Issue: Unknown

Page Range: 475-480

Description:

The need to decrease the sizes and masses of heat exchangers while preserving their performance has stipulated the development of compact heat exchangers with mini and micro channels (MCHE). It is supported by the need for increased recuperation of heat energy, facilitating better energy efficiency with strict limitations for space, material and cost. The adequate substitution of conventional heat exchangers with MCHE requires maintaining the same heat load, not exceeding the allowable pressure losses. The different ways to increase the compactness are analysed, including the change of hydraulic diameter, and the use of various methods of heat transfer intensification by changing the channel geometry and flow structure. The Nusselt numbers and friction factors correlations for plane tubes and criss-cross flow channels of plate heat exchangers are compared. A newer form of the core velocity equation has been developed, which allows comparison of the performance of MCHE heating surfaces with different enhancement techniques in specific process conditions. The results of the calculations illustrate the influence of the channel's hydraulic diameter and length on the MCHE performance for channels with the considered methods of heat transfer intensification. The ways to decrease channel size to mini and micro scales are determined. The recommendations on choosing the best channel geometry and size, depending on specified process conditions and stream nature, are formulated.

Open Access: Yes

DOI: 10.3303/CET25120080

Effect of the energy, carbohydrate, protein, and amino acid profile on the quality of ovum and embryo in cattle

Toth Tarnas Papp Peter

Publication Name: Magyar Allatorvosok Lapja

Publication Date: 2021-03-01

Volume: 143

Issue: 3

Page Range: 145-159

Description:

In the present review, the authors summarize the potential effects of energy, carbohydrate, protein, and amino acid supplementation on the reproductive performance of dairy and beef cattle, focusing on the development and quality of the ovum and the preimplantation embryo. Excess dry matter and energy intake can have a positive or negative effect on the development of the preovulatory follicle and embryo, depending on the body condition, the physiological status and the actual milk production of the cows. In this review, the importance of hormones (e.g. insulin, insulin-like growth factor and leptin) were taken into consideration regarding their role in the reproductive performance of the dairy and beef cattle. Feeding high levels of non-fibre car-bohydrates (NFC) can lead to hyperinsulinaemia and deteriorating results in embryo production. It is well-known that the type and composition of carbohydrates in the diet alter several physiological processes, but there is no exact information about the effects of carbohydrate-composition on the follicular development and embryo quality. High protein intake, particularly the rumen degradable protein (RDP), increases plasma urea concentration. High urea levels can lead to poor reproductive performance in cattle. Urea has a direct negative effect on the final stages of follicular development and indirectly alters embryonic development by decreasing pH in the uterine fluid. The levels of certain amino acids in the lumen of the pregnant uterus are significantly higher than before pregnancy. Methionine, lysine and histidine have the greatest rise at the presence of the preimplantation embryo. Feeding rumen-protected forms of these amino acids can positively alter embryo production, but further investigation is needed in this field. The authors deem that more research is needed to lay effective feeding strategies for the success of embryo production.

Open Access: Yes

DOI: DOI not available

A rule-based expert system for automatic question classification in mathematics adaptive assessment on indonesian elementary school environment

Siti Rochimah Umi Laili Yuhana A. Tormási Eko Mulyanto Yuniarno Aliia Rysbekova Mauridhi Hery Purnomo László T. Kóczy

Publication Name: International Journal of Innovative Computing Information and Control

Publication Date: 2019-02-01

Volume: 15

Issue: 1

Page Range: 143-161

Description:

This paper is part of research in developing a competency-based assessment system for mathematics in Indonesian elementary school environment. An essential task is to accurately classify questions based on competency and difficulty level. Thus, an expert system is needed to classify those questions since competency information is often manually defined by experts. The objectives of this work are replacing a human expert’s role in the related knowledge engineering process and providing a rule-based expert system to supersede an expert to classify the questions. Five types of the rule-based algorithm: OneR, RIPPER, PART, FURIA, and J48, were applied to the dataset, which is comprised of 9454 real mathematics examination questions collected from several Indonesian elementary schools. Following the knowledge engineering principles, these algorithms generated the classification rules based on a pattern of the data. The rules of the best performing algorithm were utilized by a knowledge base for inference. Finally, to be able to fully measure the system performance, ten expert teachers were involved in the question classification step. The results confirm that the system meets the stated objectives in classifying the competency and the difficulty level of a question automatically.

Open Access: Yes

DOI: 10.24507/ijicic.15.01.143

On stateform of Hungary between 1920 and 1944: Applicability of the term „monarchy without a king”

Péter Takács

Publication Name: Journal on European History of Law

Publication Date: 2019-01-01

Volume: 10

Issue: 2

Page Range: 139-148

Description:

The official stateform of Hungary between 1920 and 1944 was „monarchy”. Since she did not have a king for a long time, however, it is often interpreted, even in academic analyses, in a way that it was, in fact, a kingdom with an unspecified monarch, viz without a king that could have been determined. At the level of stateforms, this ambivalent situation of a „kingless kingdom” is expressed by the category „monarchy without a king”. Some legal scholars consider this category to be one of the particular variants of monarchy, while others argue that it might be conceived at a certain point on the scale between the two main types of stateforms, namely between monarchy and republic. This paper analyzes the origin of the term „monarchy without a king”, its meaning in public law and its interpretation within the framework of Hungarian legal history. In the latter respect, it raises the questions whether the term can be used to define and characterize the Hungarian stateform in the Horthy era, and if so, what specific meaning it conveys.

Open Access: Yes

DOI: DOI not available

Tempering effects in steel parts produced by additive fabrication using laser powder deposition

Lino Costa Augusto Moita De Deus R. Colaço Tamás Réti R. Vilar

Publication Name: Virtual Modelling and Rapid Manufacturing Advanced Research in Virtual and Rapid Prototyping

Publication Date: 2003-12-01

Volume: Unknown

Issue: Unknown

Page Range: Unknown

Description:

Laser processed tool steels present a metastable structure generally containing martensite and an extremely large proportion of retained austenite as compared to conventionally treated steel, which affects considerably the properties of the material. In rapid tooling by laser powder deposition, as consecutive layers of material are deposited to generate a 3D object, the material in previously deposited layers is submitted to successive thermal cycles, which destabilise retained austenite, leading to its transformation to martensite. Also, the martensite present in these layers will progressively decompose by tempering when the material is reheated. As a result, the properties of the material are progressively modified as the object is built-up. The evolution of the microstructure and properties of tool steels during laser freeform manufacturing is extremely difficult to study experimentally, due to the complexity of the transformations involved and the heterogeneity of the material and of the applied thermal field, hence modelling presents clear advantages in the optimization of part build-up strategy. In the present work, a model of the phase transformations resulting from the successive overlap of clad layers based on the coupling of finite element calculations of the time-dependent temperature distribution with transformation kinetics is described. The model was used to predict the evolution of properties and final property distribution in a martensitic stainless steel component produced by laser powder deposition.

Open Access: Yes

DOI: DOI not available

Balancing Performance and Health in Elite Hungarian Athletes: The Relationship Among Disordered Eating Risk, Body Composition, and Nutrition Knowledge

Andrea Petróczi Gusztáv J. Tornóczky Merve Alpay Réka Erika Kovács Szilvia Boros István Karsai

Publication Name: Nutrients

Publication Date: 2025-01-01

Volume: 17

Issue: 2

Page Range: Unknown

Description:

Background: disordered eating (DE) and eating disorders (ED) can negatively impact athletes’ health, wellbeing, and athletic performance. Objective: this cross-sectional study aims to assess DE risk, body composition, and nutrition knowledge among elite Hungarian athletes. Methods: DE risk was assessed using DESA-6H and EAT-26 scales, nutrition knowledge through the Abridged Nutrition for Sport Knowledge Questionnaire (A-NSKQ), and body composition with the OMRON BF511 device. The data were analyzed using Kendall’s tau correlations, Mann–Whitney U tests, and ROC analysis. Results: a total of 71 athletes participated (39.4% males, mean age = 24.8 years, SD = 4.8 years and 60.6% females, mean age = 24.3 years, SD = 4.3 years). At-risk scores on the DESA-6H scale were recorded for nine athletes (12.7%), while 32.4% scored in the risk zone on the EAT-26, with female athletes in aesthetic, endurance and weight-dependent sports being most affected. Low BF was observed in four males and four females. Nutrition knowledge (49.1%) was below the acceptable threshold. DESA-6H significantly correlated with EAT-26 scores, BMI, sports nutrition knowledge, and A-NSKQ total scores. A statistically significant difference by gender was found in the EAT-26 total score (p = 0.019, d = 0.65). Risk groups significantly differed in A-NSKQ scores (p = 0.026, d = 0.511) and sport nutrition knowledge, specifically (p = 0.016, d = 0.491). Using EAT-26 to identify at-risk athletes and the DESA-6H recommended cut-off, the ROC analysis showed a sensitivity of 29.1% and a specificity of 95.7%. Conclusions: insufficient nutrition knowledge plays a role in being at-risk for DE and ED. These results underscore the need for early detection, early sport nutrition education across all elite athletes, with particular attention to female athletes in aesthetic, endurance and weight-dependent sports, and for monitoring these athletes to prevent DE. Further work is warranted to optimize screening tools such as EAT-26 and DESA-6H for elite athletes.

Open Access: Yes

DOI: 10.3390/nu17020231

Atomic Beam Probe diagnostic for plasma edge current measurements at COMPASS

M. Berta G. Anda D. Dunai P. Hacek D. Réfy M. Aradi M. Lampert J. Krbec M. Palánkai S. Hegedus B. Leskó J. Kádi D. Nagy R. Pánek S. Zoletnik A. Bencze V. Weinzettl

Publication Name: 45th Eps Conference on Plasma Physics Eps 2018

Publication Date: 2018-01-01

Volume: 2018-July

Issue: Unknown

Page Range: 1028-1031

Description:

No description provided

Open Access: Yes

DOI: DOI not available

Digital image analysis of sheet metal testing and forming

Szabolcs Szalai Imre Czinege

Publication Name: 15th Imeko Tc10 Workshop on Technical Diagnostics 2017 Technical Diagnostics in Cyber Physical Era

Publication Date: 2017-01-01

Volume: Unknown

Issue: Unknown

Page Range: 176-180

Description:

Digital image analysing methods are widely used for evaluating local deformations in sheet metal tests and forming processes. The paper is focusing on tensile tests of uniform and non-uniform width flat specimens made of aluminum alloys, which are suitable for demonstrating Löders strain, Portevin-Le Chatelier (PLC) effect and for determination of Forming Limit Curve. Tests were carried out using GOM-ARAMIS® digital image analysis hardware and software. Observation of local deformations during tensile tests showed that initiation and evolution of local strains depend on the position of specimens related to rolling direction of sheet. Using non-uniform width specimens the local deformations are concentrated on the smallest cross-section in the final stage of tensile test. The measured major and minor strains give points of FLC.

Open Access: Yes

DOI: DOI not available