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The rhombohedral La0.8K0.175Li0.025MnO3 sample was elaborated using the sol–gel method at low temperature of 900 °C. The prepared sample exhibits a second-order paramagnetic-ferromagnetic transition with decreasing temperature. Based on the data of the magnetic measurements, the critical behavior analysis is investigated through various techniques such as modified Arrott plot, Kouvel–Fisher method and critical isotherm analysis. The critical exponents determined using the Kouvel-Fisher method are found to be β = 0.533 and γ = 1.114 at T C ~ 270 K. The critical exponent values obtained are in agreement with the values predicted by the mean field model, indicating the existence of long-range magnetic interaction in our synthesized sample. The maximum of the magnetic entropy change is about 3.51 J kg−1 K−1 under a magnetic applied field change of 5 T. The relative cooling power is found to be 320.5 J kg−1 at 5 T. This value represents about 78% of that of standard gadolinium. [ABSTRACT FROM AUTHOR]

The Internet of Things (IoT) plays a fundamental role in contemporary society, necessitating an in-depth comprehension of its application layer protocols, intertwined technologies, security issues, and effective countermeasures. This survey delivers an exhaustive analysis of these protocols, emphasizing the escalating significance of explainable artificial intelligence in IoT (XAIoT). To elucidate its practical implications, we conducted a case study examining a real-world scenario where XAIoT significantly bolstered IoT security. This case study demonstrated XAIoT's potential to enhance transparency and trustworthiness in IoT systems. Furthermore, the survey critically evaluates existing literature, pinpointing specific opportunities and gaps in the present state of IoT application layer security. For instance, our analysis revealed a pressing need for more robust security protocols and the integration of advanced machine-learning techniques for anomaly detection in IoT applications. This survey, designed to provide a comprehensive perspective, seeks to stimulate additional innovation and research in the realm of secure and intelligent IoT applications. In doing so, it contributes to the ongoing dialogue on improving IoT security, offering valuable insights for researchers and practitioners alike. [ABSTRACT FROM AUTHOR]

Background: Double congenital tracheoesophageal fistula (TEF) without esophageal atresia, known as double H-type fistula, is an extremely uncommon malformation. Due to its nonspecific symptoms and the small size of the fistula in infancy, H-type tracheoesophageal fistula is rarely diagnosed in the neonatal period and is also challenging to repair. Case presentation: We report a rare case of double H-type tracheoesophageal fistula in a 2-day-old newborn, identified with a time-lapse and repaired separately. The diagnosis was established through repeated bronchoscopy, with methylene blue injected through an esophagoscope. A right thoracotomy was performed to undertake the surgical repair after cannulating the fistula with a vascular guide wire. Five months later, the infant, who had a history of recurrent episodes of coughing and shortness of breath, was diagnosed with acute respiratory distress, and a second TEF was detected by bronchoscopy. A cervical incision was used to repair the second H-type fistula. Conclusions: Double H-type tracheoesophageal fistula should be considered while correcting a tracheoesophageal fistula, especially if the symptoms continue after the first operation. Repeated radiological contrast studies and bronchoscopy with methylene blue injected through an esophagoscope help the early diagnosis. [ABSTRACT FROM AUTHOR]

The design of an efficient routing algorithm for the Internet of Vehicles (IoV) poses several problems due to its special characteristics, including nodes high-speed mobility, frequent topology change, link instability, and the presence of radio obstacles. Geographic routing protocols are a promising solution for the IoV, since the main routing parameter used by these protocols is the location information accessible through a location-based service. However, location services and traffic status measurements generate high network overhead. In this paper, we first propose a novel proactive location service called ATLAS that utilizes smart mobile agents to avoid the traffic overhead of traditional services and reduce the location update latency. Then, we present an Agent-Based Proactive Geographic Routing Protocol called ARDENT to route data packets with reduced delay and higher delivery ratio. The proposed systems aim to benefit from the IoV environment and multiagent characteristics to adapt to high-speed mobility, reduce the communication interruptions and the number of control messages overhead generated by the location service, and produce a complete geographic routing protocol suitable for urban settings. The evaluation of ATLAS shows significant performance improvements in terms of query success ratio and location update delay. In addition, the results of ARDENT illustrate its superiority in terms of data packet delivery ratio and end-to-end delay as compared to similar routing protocols. [ABSTRACT FROM AUTHOR]

The structural, magnetic, and magnetocaloric properties of La0.7Sr0.3-xLixMnO3 (0 ≤ x ≤ 0.15) samples have been investigated. All our samples were synthesized using the sol–gel technique at low temperature. The Rietveld refinement of the X-ray powder diffraction shows that the La0.7Sr0.3-xLixMnO3 compounds crystallize in a rhombohedral system with R 3 ¯ c space group. Magnetization measurements versus temperature showed that all our investigated samples display a paramagnetic-ferromagnetic transition with decreasing temperature. The Curie temperature, TC, decreases with increasing Li content from 365 K for x = 0 to 194.4 K for x = 0.15. The maximum of the magnetic entropy change, Δ S M Max , under an applied magnetic field change of 2 T is found to be 1.97, 1.05, 1.07, and 1 J kg−1 K−1 for x = 0, 0.05, 0.1, and 0.15 respectively. The relative cooling power reaches 82.1, 80.6, 83.2, and 102.5 Jkg−1 for x = 0, 0.05, 0.1, and 0.15, respectively, under the same magnetic field change of 2 T. [ABSTRACT FROM AUTHOR]

Hard hexagonal barium ferrite BaFe12O19 (BaM), as well as core–shell structure BaFe12O19-TiO2 composite nanoparticles, was successfully prepared by solid state reaction. An interesting photocatalytic activity has been noticed for the first time in pure BaM and doped TiO2 nanopowders. The obtained powders can photodegrade organic pollutants in the dispersion system effectively and can be recycled easily using a magnetic field. The BaFe12O19-TiO2 magnetic photocatalyst is composed of two parts: (1) TiO2 shell used for photocatalysis and (2) BaFe12O19 core for separation by the magnetic field. The photocatalytic activity of the as-prepared magnetic photocatalyst is enhanced with BaFe12O19 doping. Besides, the saturation magnetizations of BaFe12O19-TiO2 nanoparticles decreased in comparison to pure hexaferrite, while the coercivity remains almost constant. [ABSTRACT FROM AUTHOR]

In the blockchain environment, smart contracts are computer programs that run on the blockchain platform. However, the development of smart contracts is a major challenge for developers, since blockchain platforms are still evolving. Owing to the inherited nature of blockchain, developing smart contracts without introducing vulnerabilities is not an easy task, as the deployed code is immutable and can be invoked by anyone with access to the network. Smart contracts have proved to be error-prone in practice due to the complexity of programming. Additionally, non-functional requirements, such as service cost, security, performance, authorization, and authentication, should be well implemented and defined in computer systems. In this paper, we aim to present a systematic literature review to outline in detail different approaches of smart contracts generation. Furthermore, we present a comparison of the existing approaches based on a classification according to automation paradigm and a set of defined criteria. Finally, we discuss the gaps in the literature, as well as identify a set of potential challenges which can significantly strengthen the existing work. The study shows that the examined works focused only on a limited number of specific features, such as authorization, asset control, and security. Additionally, formal verification of smart contracts and data privacy are poorly addressed. [ABSTRACT FROM AUTHOR]

Blockchain has the potential to improve sustainable food security due to its unique features like traceability, decentralized and immutable database, and smart contract mechanisms. However, blockchain technology is still in the early stages of adoption in particular in agricultural applications. In this context, this article aims to identify blockchain drivers to achieve sustainable food security in the Indian context and model them using an integrated MCDM (Multiple Criteria Decision Making) approach. The blockchain adoption drivers are identified through an exhaustive literature review and opinions from domain experts from industry, academia, and Agriculture Supply Chain (ASC) stakeholders. Subsequently, the integrated MCDM approach is developed by combining Total Interpretive Structural Modelling (TISM) and Fuzzy Decision-Making Trial and Evaluation Laboratory (DEMATEL), which does not only investigate the interrelation between the identified constructs and builds hierarchy but also determines the intensity of the causal interrelationships. At a later stage, Fuzzy Cross-Impact Matrix Multiplication Applied to Classification (MICMAC) is used to cluster the identified drivers to evaluate the importance of each driver. The results reveal that Traceability, Real-time information availability to agro-stakeholder, and Decentralized and immutable database are the most significant drivers. Policymakers, governmental organizations and other relevant stakeholders may utilize the information about the interrelationship between these drivers and their influential power, to frame suitable strategies for enhancing the adoption rate of blockchain in the Indian ASC. [ABSTRACT FROM AUTHOR]

The reverse logistics network (RLN) design for sustainable supply chain management is a strategic decision in network configuration, and is higher influenced by uncertainty. This paper applies a bi-level stochastic multi-objective model to design an RLN for a disposable product recycling management system. The goal is to balance the overall network cost against the associated environmental risks. An LP-metric based sample average approximation is formulated to solve the optimization problem. The model is validated numerically through a disposable product firm. [ABSTRACT FROM AUTHOR]

Currently, constant innovations in service-oriented architectures lead to extending the Cloud services with promising solutions such as Fog computing. As the Cloud-Fog environment still remains in its infancy stage, several issues remain among the considerable challenges to be handled. One of the key issues in a Cloud-Fog environment is the scheduling of business processes tasks, i. e. selecting the suitable Cloud-Fog resources to support the execution of the business processes tasks while considering budget and temporal constraints. Indeed, these constraints are generally contradictory. Indeed, the use of cheaper resources increases the execution time and vice versa. Furthermore, minimizing the energy consumption is among the prominent considerations when dealing with Cloud-Fog environment. Hence, finding out the trade-off set of optimal solutions is required considering minimizing cost, time and energy consumption. To address such an issue, we propose, in this paper, a Multi-Objectives Particle Swarm Optimization (MOPSO) algorithm based on a non-dominance sort to handle the scheduling problem of time-aware business processes with many conflicting objective functions. Our algorithm aims to optimize three conflicting objectives namely, the makespan (total execution time), the monetary cost and the energy consumption while taking into account budget and temporal constraints of the business process. The output of our MOPSO algorithm represents a set of Pareto optimal solutions from which the user can select the best one. The elaborated experimentation illustrates the good performance of the proposed algorithm. [ABSTRACT FROM AUTHOR]

This paper presents an approach for fragmenting business processes over 2 types of complementary platforms referred to as cloud resources and edge resources. Fragmentation caters to the separate needs and requirements of business processes' owners. Indeed, some owners prioritize the security of their fragmented processes over availability while others prioritize the reliability of their fragmented processes over performance. Despite its benefits, fragmentation raises many concerns like how to reduce communication delays between disparate fragments and how to maintain acceptable loads over all the distributed resources. To identify the necessary cloud and edge resources that would accommodate fragmented business processes, the approach resorts to Allen's time algebra allowing to simultaneously reason over both resources' availability-time intervals and processes' use-time intervals. This reasoning covers a good range of time relations like overlaps, during, and meets, is aware of resources' properties like limited-but-extensible, and satisfies business processes' requirements like data freshness. The fragmentation approach, in this paper, is illustrated with a banking case-study, validated through a system developed on top of Google Colaboratory, and evaluated through a set of real experiments. [ABSTRACT FROM AUTHOR]

Background: Intussusception is commonly idiopathic in children. Pathologic lead points (PLP) especially intestinal tumors (IT) are extremely rare. The diagnosis of intussusception secondary to pediatric IT is difficult due to the non-specific nature of symptoms. Its management remains a challenge. We report here four pediatric cases of intussusception secondary to IT lesions in order to analyze the clinical and therapeutic characteristics of this unusual condition. Case presentations: Four children were diagnosed and operated in our center for intussusception secondary to IT during the period from February 2017 to February 2021. Patients' demographics, clinical presentations, investigations, operative data, and postoperative outcome were recorded and analyzed. There were three girls and one boy. Ages ranged between 1 and 8 years (average of 5.5 years). Intermittent abdominal pain with acute exacerbation and vomiting were the main clinical signs. Radiologic investigations showed the intussusception in all cases but the tumor lead point was evident only during the surgical exploration in most cases. All patients underwent surgical treatment with intussusception reduction and mass removal. Pathological examination of these masses revealed: submucosal intestinal lipoma (1 case), hamartomatous polyposis (2 cases), and Burkitt's lymphoma (1 case). For this last case, adjuvant chemotherapy was also needed. The postoperative period was uneventful in all cases. Conclusion: Pediatric intussusception secondary to IT lesions is an unusual and challenging condition that requires high preoperative diagnostic suspicion, considerate intraoperative judgment, and appropriate postoperative follow-up for successful outcomes. These tumors should be considered by the pediatric surgeons as possible PLP for recurrent intussusception, especially in older children. Surgeons should be familiar with the various treatment options, because the real cause of the intussusception is often accurately diagnosed by laparotomy. [ABSTRACT FROM AUTHOR]

Localization is a crucial method applied in Wireless Sensor Networks (WSNs) to determine the geographic position of the sensor nodes in the sensing region. Many existing WSNs applications require location awareness of sensor nodes. Global Positioning System (GPS) is a well-known technique of localization. However, as a WSN is composed of thousands of sensor nodes, the installation of GPS is not available at every node. Nowadays, many localization algorithms are developed to solve the location awareness problem. The Distance Vector-Hop algorithm (DV-Hop) is a well-known technique thanks to its simplicity and its accurate localization results for WSNs. However, the DV-Hop presents some localization accuracy drawbacks. In this paper, we propose an improvement of the DV-Hop algorithm based on Tikhonov regularization method for wireless sensors networks. We verify the validity of the proposed method through experiments. Simulation results confirm that the proposed localization algorithm is better than the original DV-Hop algorithm and some of its improved algorithms with up to 60% in terms of localization accuracy. [ABSTRACT FROM AUTHOR]

In this research paper, our central focus is upon investigating structural and electrical properties of polycrystalline Ba0.9Ag0.1TiO3 powder which was fabricated through standard solid-state reaction technique. X-ray diffraction analysis at room temperature confirmed that the component crystallizes in both tetragonal and orthorhombic structures. The electrical response was explored by complex impedance spectroscopy in the temperature range of 540 K–620 K and frequency from 67. 5 Hz to 1 MHz. The findings demonstrated that the variation of the imaginary part of impedance (Z'') as a function of the real one (Z') at various temperatures presented semicircle arcs. An electrical similar circuit was set forward to interpret the impedance data. The results obtained from the temperature dependence of the exponent s suggest that the transport process of the charge carriers in the compound Ba0.9Ag0.1TiO3 follows the correlated barrier hopping (CBH) model. [ABSTRACT FROM AUTHOR]

The high-energy ball milling method has been used to synthesize the polycrystalline powders La0.5Ca0.5Mn1−xVxO3 (x = 0.05, x = 0.10). The Rietveld refinement technique shows that the samples crystallized in the orthorhombic structure with the Pbnm space group. The La0.5Ca0.5Mn0.95V0.05O3 exhibits a second-order phase transition from paramagnetic (PM) to ferromagnetic (FM) state at TC = 208 ± 1 K followed by a second one from FM to charge ordering–antiferromagnetic state at TN = 150.0 ± 0.1 K when decreasing temperature. The substituted sample with 10% amount of vanadium dopant corresponds to the disappearance of the charge-order phase; meanwhile, it was suppressed for 5% of the vanadium in the solid-state route. The Curie temperature TC increases with vanadium content from 208 ± 1 K for x = 0.05 to 255 ± 1 K for x = 0.10. The values of the maximum of the magnetic entropy change under a magnetic field change of 5 T are found to be 2.95 ± 0.04 J kg−1 K−1 and 5.42 ± 0.07 J kg−1 K−1 corresponding to a relative cooling power RCP = 128.4 ± 0.3 and 220.8 ± 0.7 for x = 0.05 and x = 0.10 respectively. The order of phase transition has been determined. The critical exponent study has been performed for La0.5Ca0.5Mn0.9V0.10O3 by using the Arrott plot, Kouvel–Fisher method, and critical isotherm analysis. The measured β, γ, and δ values are in agreement with those expected for the tricritical mean-field model. [ABSTRACT FROM AUTHOR]

The effects of atmospheric air plasma treatment based on dielectric barrier discharge (DBD) technology on the surface alteration of a woven polyester (PET) textile fabric were investigated. Chemical and physical surface modifications were characterized by specific wettability measurements (water contact angle-WCA and % capillarity), scanning electron microscopy (SEM), zeta potential assessments, Fourier transform infrared spectroscopy (FTIR) and chemical quantification analysis using ortho-toluidine blue (TBO) dye before and after the DBD processing. A striking enhancement of capillarity percentage from 1.6 % to 108 % was ensured by the plasma treatment suggesting that special chemical elements such as hydroxyl, carbonyl, and carboxyl groups were embedded on the polyester surface, thereby offering it a new hydrophilic behavior. The morphological analysis revealed that plasma treatment is a suitable mechanism to enhance the roughness of treated samples improving furthermore the water retention of the fabric and making the structure more adapted to further chemicals applications. The zeta potential and chemical quantification analysis were also of great interest since they reveal overall the same trend as do the wettability measurements and confirms that the extent of surface modification is in big dependency to the selected plasma parameters. Dyeability of untreated and plasma treated samples was also investigated in terms of color strength, in addition to wash and rub fastness. Sufficiently, higher dyeing performances were noted for plasma treated polyester when compared to the untreated fabric. Atmospheric air plasma treatment was found to be an effective approach to boost the technical reactivity of PET fabrics opening up new opportunities for surface modification under the growing environmental and energy-saving concerns. [ABSTRACT FROM AUTHOR]

Background: Ganglioneuroma (GN) is an uncommon tumor belonging to the neuroblastic tumors group and is often localized in the posterior mediastinum, retroperitoneum, and adrenal gland. Presacral (PS) location is extremely rare. Its management remains a challenge. Case presentation: A 4-year-old child presented to our department for an isolated abdominal mass. Para-clinical exams concluded to PSGN. Subtotal surgical excision was performed through an anterior transperitoneal approach. The size of the residual tumor did not progress after the 6-year follow-up period and the patients were asymptomatic. Conclusions: GN should be considered in the case of soft tissue presacral masses in pediatrics. Subtotal resection seems sufficient in case of an extension to the sacrum with low morbidity. The residual tumors are still stable and the prognosis seems conserved. Further, long-term follow-up in large studies is needed to confirm these findings. [ABSTRACT FROM AUTHOR]

Background: Intestinal lipomas are benign, non-epithelial, intestinal tumors with an exceptionally rare localization at the ileum. Lipomas in the small intestine occur mainly in elderly patients and seldom occur in childhood. They are frequently asymptomatic, possibly due to their slow growth. These tumors may act as a lead point of intussusception. Case presentation: We report a rare case of double compounded ileo-ileal intussusception due to a submucosal intestinal lipoma in an 8-year-old female. To our knowledge, this is only the seventh pediatric case to be reported in the medical literature. Conclusions: Small intestinal submucosal lipoma should be considered in case of intussusception in pediatric patients. Surgical resection seems sufficient in case of symptomatic intestinal lipoma with low morbidity. [ABSTRACT FROM AUTHOR]

The effect of substituting sodium by potassium on electrical and dielectric properties is investigated in details for the GdFeO3-type Pr0.8Na0.2-xKxMnO3 (x = 0.00, 0.05, 0.1, 0.15 and 0.2) manganites. The electrical measurements indicate that the parent compound exhibits a metal behavior. When introducing potassium, all samples show a metal–semiconductor transition. Then, the increase of K content reduces the resistivity in the whole temperature range but doesn't affect the metal–semiconductor temperature transition (TMS). At a specific temperature TS, a saturation region was marked in the resistivity curve. It is found that TS values shift toward lower temperatures when the potassium content rises. The TS value approaches to room temperature for x = 0.2. The temperature coefficient of resistance (TCR) of the investigated manganites shows significant value, especially for x = 0, indicating that these ceramics can be used for a specific application such as bolometer technology. The frequency dependence of conductance was investigated through Jonscher's universal power law and the electrical conduction mechanism well interpreted by the correlated barrier hopping (CBH) model. Impedance spectroscopy measurements indicate that the electrical behavior of these perovskites is primarily dominated by the grain boundary response. The dependence of the dielectric constant on the frequency and the temperature confirms that the investigated samples are of a classical dielectric type. [ABSTRACT FROM AUTHOR]

We report in this work the results of synthesis and characterization of La0.8Ca0.2−xNaxMnO3 (0 ≤ x ≤ 0.2) prepared by the Pechini sol–gel method. We have investigated different effects of replacing Ca by Na on the magnetic properties and magnetocaloric effect of La0.8Ca0.2MnO3 compounds using X-ray diffraction and magnetization measurements. We have observed an evolution from an orthorhombic to a rhombohedral symmetry caused by the addition of Na and that the rhombohedral phase is stable for x ≥ 0.1. The partial substitution of Ca by Na leads to a monotonic increase in the Curie temperature (TC) of the samples from 105 K for x = 0 to 330 K for x = 0.2. A second-order nature of the magnetic phase transition is established in all the prepared compounds with the help of the Banerjee criterion. At an applied field of 5T, the maximum magnetic entropy change (∆SMmax) shows an enhancement with increasing Na+ concentration. Moreover, the relative cooling power (RCP) values are found to vary between 203 and 300.5 J/kg in this series of materials. In order to compare the magnetocaloric performances of the prepared samples, we have used several figures of merit such as the temperature-averaged entropy change (TEC), refrigerant capacity (RC) and normalized refrigerant capacity (NRC). Accordingly, the addition of Na ion greatly increases TEC, RC and NRC and thereby improves the magnetocaloric performance in La0.8Ca0.2−xNaxMnO3 (0 ≤ x ≤ 0.2). These metrics can help in identifying materials with high performance and clearly suggest that the sol–gel-made samples with x ≥ 0.1 can be customized for use in magnetic cooling applications near room temperature. [ABSTRACT FROM AUTHOR]

Perovskite manganites have many prospective applications as magnetic solids, however, their synthesis remains challenging of a high purity and a high crystallinity. Herein, a solid state method has been successfully employed for the synthesis of the La0.65Dy0.05Sr0.3Mn1−xTixO3 (x = 0.05 and x = 0.10) materials. Moreover, the impact of the Mn by Ti ion substitution on the structural, magnetic and magnetocaloric properties has fully been looked into. The Rietveld refinement technique showed that all the compounds crystallize in the orthorhombic structure with Pbnm space group and that the Mn4+ by Ti4+ substitution causes the increase of the unit cell volume. Magnetization versus temperature measurements shows a large ferromagnetic–paramagnetic transition with decreasing temperature. The Curie temperature TC fall with the rise of titanium content from 175 K for x = 0.05 to 114 K for x = 0.10. An analysis of both Banerjee criteria and Landau theory revealed a second-order magnetic phase transition at TC for the current manganites. The magnetocaloric impact is calculated through the measurement of initial isothermal magnetization versus magnetic applied field at various temperatures. The maximum magnetic entropy change Δ S M max , which is calculated on the basis of isothermal magnetization curves under magnetic field change of 5 T is found to be 1.79 J kg−1 K−1 and 1.49 J kg−1 K−1 for x = 0.05 and 0.10, respectively. The relative cooling power (RCP) rose to 239 J kg−1 and 211 J kg−1 at 5 T for x = 0.05, 0.10, respectively. In fact, our results match those about some other doped manganites, which imply that these materials may be appropriate candidates as working substances in magnetic cooling applications. Furthermore, by normalizing the Δ S M (T , μ 0 H) curves to their respective Δ S ′ = Δ S M T / Δ S M Max values, we noticed that all the obtained curves drop to a universal master curve. The combination of experiment data and theory analysis is favorable for a better understanding of manganite properties. [ABSTRACT FROM AUTHOR]

Structural, magnetic, and magnetocaloric effect (MCE) properties and the critical behavior of the La0.45Pr0.2Sr0.35MnO3 sample prepared by the sol–gel method have been investigated. The X-ray diffraction characterization reveals that our sample crystallizes in the orthorhombic structure with Pnma space group. Magnetization versus temperature measurement shows that our compound exhibits a ferromagnetic–paramagnetic transition. The Curie temperature is found to be 348 K. Close to this temperature, the maximum values of the magnetic entropy change (ΔSM) and the relative cooling power (RCP) are found to be 2.84 J/kg/K and 230 J/K under µ0H = 5 T, respectively. The Arrott plots revealed that this compound exhibits a second-order magnetic phase transition at TC. The critical behavior has been investigated by several techniques which are the modified Arrott plot method, the Kouvel–Fisher method, and the critical isotherm analysis. The obtained critical exponents β, γ, and δ are consistent with those predictions of the mean-field model. Their reliability was confirmed by Widom's scaling relation, as well as the universal scaling hypothesis. [ABSTRACT FROM AUTHOR]

We report the structural, magnetic, and magnetocaloric properties of La0.67Ba0.33Mn0.95Ni0.05O3 (LBMNO) manganite, synthesized by sol-gel method. X-ray diffraction (XRD) analysis using Rietveld refinement showed that this sample crystallizes in the rhombohedral structure with R 3 ̄ c space group. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analysis were used to confirm the structure formation of the LBMNO material. The temperature dependent magnetization data revealed a transition from ferromagnetic (FM) to paramagnetic (PM) phase at T C = 308 K. Using Arrott plots, it was found that the transition is of a second order. From the measured magnetization data as a function of magnetic applied field, the magnetic entropy change (−ΔSM) and the relative cooling power RCP have been determined. In the vicinity of T C (−ΔSM) reached a maximum value of 2.15 J kg− 1 K− 1 and a large RCP value of about 299 J kg− 1 under 5 T− 1. This magnetocaloric effect has been analyzed by considering the Landau theory of magnetic phase transition. Consequently, our sample can be considered a promising material in room-temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

(1− x) Cr2O3/x MoS2 (x = 0.25, 0.5, 0.75) were synthesized using the powder solid-state route. The structural, morphological, vibrational, and magnetic properties of the as-prepared MoS2/Cr2O3 samples with different Cr2O3 contents have been studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared spectroscopy, Raman spectroscopy, and vibrating sample magnetometry (VSM), respectively. The X-ray diffraction results show the presence of the parent compounds (molybdenum disulfide (MoS2) and chromium oxide (Cr2O3)) in addition to a secondary phase corresponding to chromium molybdenite Cr2Mo3O12. Raman and IR spectra were recorded, and the observed modes were analyzed and assigned to different normal modes of vibration. Magnetic characterizations revealed that all the series MoS2/Cr2O3 composites possess paramagnetic characteristics both at room temperature and at 30 K. Further, the maximum of magnetization increased with the increase of Cr2O3 content. [ABSTRACT FROM AUTHOR]

Globalization pressure on organizations calls for new approaches to survive, grow, and compete. An approach is to allow inter-organizational business processes (IOBP) collaboration where each partner would expose its public know-how without putting its private know-how at-risk nor impeding this collaboration from happening. Private processes would be the result of running views over public processes. For a successful IOBP collaboration, constraints like temporal need to be satisfied. Organizations could have different time requirements. This paper presents an approach for generating views over collaborative IOBP along with satisfying the combined temporal constraints that would restrict these collaborative IOBP. The paper also details how the consistency of these constraints would be achieved. The approach is illustrated using an online shopping scenario and demonstrated through a system. [ABSTRACT FROM AUTHOR]

Internet of Things (IoT) comprises a plethora of networks of things that could be exemplified with devices like sensors and actuators. Although IoT is expected to play a major role in the development and provisioning of smart applications, things in IoT are still confined into silos making their collaboration in the context of complex composition scenarios quite challenging. This paper addresses the silo concern by allowing things to take part in orchestration- and choreography-based composition scenarios. Orchestration relies on a central component to regulate the progress of things' operations, while choreography relies on peer-to-peer interactions to guide this progress. Things' operations are specified according to a set of transactional properties that dictate when an operation's execution outcome could be canceled despite the success or retried until success. This execution consumes resources that are also specified according to a set of availability properties. Not all resources are constantly available and hence could impact the completion of composition scenarios. To demonstrate the technical feasibility of orchestration- and choreography-based composition of transactional things, 2 scenarios consisting of different use-cases are implemented allowing to benchmark orchestration versus choreography at design-time and run-time. Each use-case mixes transactional properties and availability properties, which ensures good coverage of the composition scenarios in which thing could participate. [ABSTRACT FROM AUTHOR]

The orthorhombic Pr0.7Ca0.3Mn0.95Fe0.05O3 manganite is subject to magnetic and impedance spectroscopy measurements. This sample shows a paramagnetic to ferromagnetic phase transition at about 90 K. According to the Banerjee criterion, the nature of the magnetic transition is found to be of second order.The conductance spectra for Pr0.7Ca0.3Mn0.95Fe0.05O3 ceramic obey the power law variation for characterizing the hopping dynamics of charge carriers. The activation energies extracted from the dc conductance and hopping frequency show a positive correlation. Using the scaling approach, the conductance spectra are merged into a single master curve, confirming the validity of the time–temperature superposition principle. Equally, a strong deviation from the Summerfield scaling is observed. The random barrier model (RBM) is applied to correct this anomaly and a single master curve is constructed with a positive value of the scaling parameter α. Such parameter indicates a coulomb exchange between the interacting particles. Impedance results confirm the contribution of the resistive grain boundary on the electrical properties and the appearance of multiple electrical relaxation phenomena in Pr0.7Ca0.3Mn0.95Fe0.05O3 sample. From the evolution of the derivative ANC with temperature, we confirm the presence of various conduction mechanisms. The Nyquist plots show that the increase in temperature is followed by a decrease in the grain resistance (Rg) and the grain boundary resistance (Rgb) values. Such monotonic decrease confirms a predominant role of grain boundary contribution in governing the transport properties of Pr0.7Ca0.3Mn0.95Fe0.05O3 compound. [ABSTRACT FROM AUTHOR]

Characterization of the electrical properties of Pr0.65Ca0.25Pb0.1MnO3 ceramic, prepared by the solid-state method, is conducted using the impedance spectroscopy technique. Ac-conductivity measurements reveal the presence of two electrical behaviors. A semiconductor character obtained at low-temperature ranges of 80–160 K, and a metallic behavior found at high-temperature ranges of 180–400 K. The temperature dependence of the exponent s confirms the contribution of two conduction processes in the transport mechanism. In the range of T < 140 K, the non-overlapping small polaron tunneling (NSPT) is the predominant mechanism. However, for T > 140 K, the conduction process is governed by the correlated barrier hopping (CBH) model. Finally, beyond T = 250 K, the dc-conductivity is characterized by the appearance of a saturation region. [ABSTRACT FROM AUTHOR]

Shipping logistics is one of the very important criteria which can directly and indirectly affect the economy and GDP of any country. Shipping logistics depends on various factors which have been addressed by several authors in their previous studies. Studies in this literature are focused on selecting the most impactful factors among all the criteria. Methods used in this literature are fuzzy Analytical hierarchy process (AHP) and fuzzy Technique for order of Preference by Similarity to Ideal Solution (TOPSIS) for multi-criteria decision analysis. These methods also helped in this literature to develop a new hybrid method "fuzzy TOPSIS AHP". There have been no studies involving maritime logistics with comparative analysis of multi-criteria decision making i.e., fuzzy AHP and fuzzy TOPSIS AHP. The literature involved large number of expert opinions on the factor prioritization of maritime logistics. Factors selected for prioritization are Environmental Sustainability, Supply and Demand, Operations and Port Selection. However, the research showed that the comparative analysis of the results was quite opposite to one another and proposed a new way for researchers to use the hybrid method of fuzzy TOPSIS AHP method in future research. The study aimed to improve the existing maritime model which can help professionals to get connected with the maritime logistics firms. The study also aims to contribute this model for researchers in their study related to maritime logistics. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel script-independent approach for word spotting in printed and handwritten multi-script documents. Since each writing type and script need to be processed using a specific spotting engine, the proposed system proceeds on two stages. The script identification is a preliminary stage that aims at recognizing on one level the writing type and the script of the input image document. Second, a specific word spotting method is used to spot query words in a large collection of documents. The proposed spotting system is based on deep bidirectional long short-term memory neural network and hidden Markov model (HMM) hybrid architecture. It takes advantage of DNN's strong representation learning power and HMM's sequential modeling ability. The global system has been evaluated on a mixed corpus of public databases such as KHATT, PKHATT for Arabic script and RIMES for Latin script. The experimental results on script identification and keyword spotting confirm the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

An exhaustive study of structural, magnetic and magnetocaloric properties on La1.95Sr0.05BMnO6 (B = Ni and Co) double perovskite were performed. The samples were prepared by the sol-gel method. The crystallographic structure was studied by the X-ray diffraction patterns and Rietveld refinement which revealed that all samples crystallize in a monoclinic structure with P21/n space group. The magnetic behaviors of these double perovskite have been studied in detail. For La1.95Sr0.05NiMnO6, the M(T) curves exhibit double magnetization transition temperature at 68 K and 266 K which can be ascribed to Ni3+-O-Mn3+ and Ni2+-O-Mn4+ superexchange interaction, respectively. However, unique magnetic transition has been observed for the La1.95Sr0.05CoMnO6 double perovskite at 210 K due to Co2+-O-Mn4+ superexchange interaction. A deep investigation based on the Landau Theory and Arrot analysis confirmed a second order ferromagnetic phase transition for both samples. Besides, the magnetocaloric behaviors of these new samples have been studied by analysis the magnetic entropy change. This latter reached maximum values of 1.01 and 1.35 J/kg/K for La1.95Sr0.05NiMnO6 and La1.95Sr0.05CoMnO6, respectively, under µ0H = 5 T. Moreover, the relative cooling power values for La1.95Sr0.05NiMnO6 and La1.95Sr0.05CoMnO6 are found to be 94 J/kg and 116 J/kg, respectively, under µ0H = 5 T. Based on the obtained ΔSM data, we have also described the universal master curve for (ΔSM/ΔSMmax) versus rescaled temperature to confirm the order magnetic phase transition. Interestingly, all the ΔSM(T, H) data points are collapsed into a universal curve in the whole temperature range. The significant values of relative cooling power for both samples suggest that they might be an interesting candidate for exploring a new kind of magnetic refrigerants. [ABSTRACT FROM AUTHOR]

In this paper, we report the structural, magnetic and magnetocaloric properties of Ni-doped La0.67Ba0.33Mn1−xNixO3 (x = 0, 0.025 and 0.075) manganites. Our compounds were synthesized using the sol-gel method. The structural analysis using Rietveld refinement shows that Ni-doped LaBaMnO3 system crystallizes in the rhombohedral symmetry with R3¯c space group. Magnetization measurements versus temperature in a magnetic applied field of 0.05 T reveal that all the compositions exhibit a transition from a ferromagnetic to paramagnetic phase with increasing temperature. A systematic decrease in the transition temperature is clearly observed upon Ni doping and a near room temperature TC (302 K) is achieved with x = 0.075 composition. The maximum magnetic entropy change -ΔSMmax in a magnetic field change of 5 T is found to be 2.12, 2.78 and 1.78 J/kg K for x = 0, 0.025 and 0.075, respectively. At this value of magnetic field, large relative cooling power values are obtained in our samples, especially for x = 0.075 (271 J/kg) making it a promising candidate for magnetic refrigeration near room temperature. [ABSTRACT FROM AUTHOR]

The La0.7Sr0.2Ca0.05Li0.05Mn1−xVxO3 [S1(x = 0) and S2(x = 0.05)] polycrystalline compounds are found to exhibit a ferromagnetic—paramagnetic transition (FM-PM) when temperature increases with a decrease of Curie temperature TC when substituting Mn with V from TC = 271 K to TC = 266 K. The Arrott plots near Curie temperature show positive slopes under an applied magnetic field varying from 0 to 5 T showing a second order magnetic transition for our samples. Basing on the magnetic-field dependences of magnetization measured around TC, maximum magnetic-entropy changes ΔSMmax, under the applied field of 5 T, are about 5.4 and 4.8 J kg−1 K−1 for S1 and S2 respectively. The efficiency of our samples for magnetic refrigeration application has been evaluated throw calculating the relative cooling power (RCP) values, which were equal to 211.5 J kg−1 for S1 and 195.5 J kg−1 for S2. The study of the universal curves show that the rescaled magnetic entropy change curves for different applied fields collapse onto a same curve confirming that both S1 and S2 reveal a second order transition. [ABSTRACT FROM AUTHOR]

In this paper, we report the magnetic properties of Ca vacancies in La0.65Ca0.35−x□xMnO3 (0 ≤ x ≤ 0.15) powder samples synthesized using the sol-gel reaction. Rietveld refinement of powder X-ray diffraction data reveals that all samples crystallize in the orthorhombic structure with Pbnm space group. Then, the magnetic properties of these compounds are discussed in detail, building on the magnetization and the susceptibility. The temperature dependence of magnetization reveals a magnetic transition from ferromagnetic to paramagnetic phase when increasing temperature. The inverse of magnetic susceptibility shows a downturn with decreasing temperature before the Curie temperature TC indicating the existence of Griffiths phase for the temperature range TC ≤ T ≤ TG, where TG is the Griffiths temperature, which proves the existence of ferromagnetic clusters in the paramagnetic domain. Furthermore, by investigating the magnetocaloric parameters, the field dependences of ΔSMMax and RCP can be expressed by the power laws, ΔSMmax ≈ a (µ0H)n and RCP ≈ b (µ0H)m, where a and b are coefficients, n and m are the field exponents, respectively. [ABSTRACT FROM AUTHOR]

In this work, we present the study of structural, magnetic and critical behavior of LaSrCoO ( x = 0.3 and 0.5) cobaltites. X-ray diffraction analysis using the Rietveld refinement shows that the sample LaSrCoO crystallizes in a rhombohedral distorted perovskite structure with $R\overline {3} c$ space group, while LaSrCoO exhibits both phases rhombohedric and cubic, with $R\overline {3} c$ and $Pm\overline {3} m$ space groups. Our samples exhibit thermo-magnetic irreversibility behavior in the magnetization data under a magnetic applied field of 0.05 T. The temperature dependence of magnetic susceptibility at higher temperatures for LaSrCoO sample reveals the presence of the Griffiths' phase above the Curie temperature, while it follows the Curie-Weiss law perfectly for LaSrCoO. Different techniques including the modified Arrott plot, the Kouvel-Fisher method and the critical isotherm analysis have been used to analyze the paramagnetic-ferromagnetic phase transition. The values of the critical exponents associated to this transition were close to those expected in the mean-field model. The validity of the calculated critical exponents has been confirmed by the scaling equation of state. The determined critical exponents using various methods are found to follow the scaling equation with the magnetization data scaled into two different curves below and above the critical temperature. [ABSTRACT FROM AUTHOR]

Improvement of magnetocaloric properties with tunable Curie temperature near room temperature is revealed to be possible by the mixture of both individual phases La CaMnO (phase 1) and LaCaSrMnO (phase 2). This work demonstrates the outstanding agreement between the experimental results and the continuous curves predicted by numerical calculations in a two phases composite system (1 − x)La CaMnO/xLaCaSrMnO (0 ≤ x ≤ 1). Our samples were synthesized using the sol-gel process and the solid-state reaction for phase 1 and phase 2, respectively. For both samples, a clear ferromagnetic (FM)-paramagnetic (PM) transition at the Curie temperature (T) is observed. Such a T is found to be 274.7 and 308 K for La CaMnO and LaCaSrMnO, respectively. Besides, the magnetic entropy change and the Relative Cooling Power (RCP) values were estimated for the biphasic system (1 − x)La CaMnO/xLaCaSrMnO with 0 ≤ x ≤ 1. We revealed that the optimum magnetocaloric effect at µH = 2 T has been found for the composition with x = 0.65, which displays a table-like ΔS curve with a peak value slightly lowered and strongly expanded around room temperature when compared with those of the parent compounds. Therefore, the obtained results will draw considerable attention in the field of research regarding the development of magnetic refrigeration devices. [ABSTRACT FROM AUTHOR]

LaDyCaMnO (x = 0.00, 0.01 and 0.03) compounds were prepared using sol-gel method. X- ray diffraction and magnetic measurements were used to investigate the effects of Dy doping on the physical properties of LaDyCaMnO. XRD data have been analyzed by Rietveld refinement technique. Moreover they crystallized in an orthorhombic structure with Pnma space group. Magnetization as a function of temperature has shown that these compounds exhibit a transition from a ferromagnetic to paramagnetic phase with increasing temperature. The $$\Delta {\text{S}}_{{\text{M}}}^{{{\text{max}}}}$$ in a magnetic field change of 5 T is found to be 6.79, 10.15 and 3.97 J Kg K for x = 0.00, 0.01 and 0.03, respectively. At this value of magnetic field, the relative cooling power (RCP) is found to be 191, 155 and 157 J Kg for x = 0.00, 0.01 and 0.03, respectively. Our result on magnetocaloric properties suggests that LaDyCaMnO (x = 0.00, 0.01 and 0.03) compounds are attractive as possible refrigerants for near room temperature magnetic refrigeration. [ABSTRACT FROM AUTHOR]

LaDyCaMnVO, prepared by solid-state route, was characterized using x-ray diffraction at room temperature. The Rietveld refinement shows that the sample crystallizes in orthorhombic structure with Pbnm space group. A secondary phase LaVO has been also detected. The temperature dependence of the magnetization was investigated to determine the characteristics of the magnetic transition. The sample exhibits a paramagnetic-ferromagnetic transition (PM-FM) at T = 81 ± 0.7 K when temperature decreases. The study of the inverse of susceptibility reveals the presence of ferromagnetic clusters in the paramagnetic region. A metamagnetic transition was observed from the M( H) curves and the magnetic entropy change was calculated from magnetization curves at different temperatures in order to evaluate the magnetocaloric effect. [ABSTRACT FROM AUTHOR]

Magnetic, magnetocaloric and critical behavior properties of LaDyCaMnO are studied. The Rietveld refinements of the X-ray diffraction patterns show that our sample crystallizes in the orthorhombic structure with Pnma space group. The Curie temperature is found to be 245 K. In the vicinity of T, |-ΔS| reached, in a magnetic applied field of 5T, maximum value of 14.94 J kg K. The critical exponents β, γ and δ have been determined using various techniques such as the modified Arrott plot, Kouvel-Fisher methods as well as the critical isotherm, and are found to be β = 0.25 at T = 246.74 K and γ = 0.87 at T = 246.2 K for LaDyCaMnO. The values of critical exponents are close to the tri-critical mean-field model. [ABSTRACT FROM AUTHOR]

The LaDyCaMnO (LDCMO) compound prepared via high-energy ball-milling (BM) presents a ferromagnetic-to-paramagnetic transition (FM-PM) and undergoes a second-order phase transition (SOFT). Based on a phenomenological model, magnetocaloric properties of the LDCMO compound have been studied. Thanks to this model, we can predict the values of the magnetic entropy change Δ S, the full width at half-maximum δ T , the relative cooling power (RCP), and the magnetic specific heat change Δ C for our compound. The significant results under 2 T indicate that our compound could be considered as a candidate for use in magnetic refrigeration at low temperatures. In order to further understand the FM-PM transition, the associated critical behavior has been investigated by magnetization isotherms. The critical exponents estimated by the modified Arrott plot, the Kouvel-Fisher plot, and the critical isotherm technique are very close to those corresponding to the 3D-Ising standard model ( β = 0.312 ± 0.07, γ = 1.28 ± 0.02, and δ = 4.80).Those results revealed a long-range ferromagnetic interaction between spins. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the field dependence of the magnetocaloric properties of LaCaSrMnO powder sample using a phenomenological model. Our compound was elaborated by the conventional solid state reaction. The model parameters were determined from the magnetization data and were used to give better fits to magnetic transition and to calculate the magnetocaloric quantities. The magnetocaloric parameters such as the maximum of the magnetic entropy change $$\Delta S_M^{max}$$ and the relative cooling power RCP, have been determined from the calculation of the magnetization as a function of temperature under several magnetic applied field. Thus, from the magnetocaloric results, such as RCP ≈ b(μH) and T − T ≈ b (µH), the critical exponents values related to the magnetic transition have been determined. The estimated results are close to those expected by the tricritical mean-field model. Furthermore, the values of the ferromagnetic transition temperature T, as well as the critical exponents β, γ and δ obtained by the theoretical model, are compared with those obtained by other various techniques (such as the modified Arrott plots, the Kouvel-Fisher method and the critical isotherm analysis). A good agreement has been found in the vicinity of the Curie temperature. [ABSTRACT FROM AUTHOR]

In this paper, we studied in detail the critical behavior of LaCaBaMnO manganite sample synthesized by the solid state reaction. The critical properties near the ferromagnetic-paramagnetic phase transition have been analyzed from the magnetic data, using various techniques such as the modified Arrott plots, the Kouvel fisher method, critical isotherm analysis and the field dependence of magnetocaloric results. Moreover, the validity of the critical exponents using the various methods has been confirmed by the scaling equation of state and all data fall on two distinct branches, one for T < T and the other for T > T, indicating that the critical exponents obtained in this work are accurate. The exponents determined in this study have revealed that the β value is in between the theoretically expected values for 3D-Ising and tricritical mean field model. While, the γ value is close to the mean field theory. The third exponent δ was determined independly from the critical isotherms satisfying the Widom scaling relation. Our systematic result reflects the coexistence of a long range and short range ferromagnetic order in our sample. The temperature variation in the effective exponents β and γ resemble with those for disordered ferromagnet around Curie temperature. [ABSTRACT FROM AUTHOR]

In this work, we studied in detail the magnetic and magnetocaloric properties of the LaCaBaMnO compound according to the phenomenological model. Based on this model, the magnetocaloric parameters such as the maximum of the magnetic entropy change Δ S and the relative cooling power (RCP) have been determined from the magnetization data as a function of temperature at several magnetic fields. The theoretical predictions are found to closely agree with the experimental measurements, which make our sample a suitable candidate for refrigeration near room temperature. In addition, field dependences of ${{\Delta } S}_{\mathrm {M}}^{\max }$ and RCP can be expressed by the power laws ${\Delta S}_{\mathrm {M}}^{\max }\approx a$ ( μ H) and RCP ≈ b( μ H), where a and b are coefficients and n and m are the field exponents, respectively. Moreover, phenomenological universal curves of entropy change confirm the second-order phase transition. [ABSTRACT FROM AUTHOR]

We have synthesized LaCaSrMnO sample using two different methods: the solid-state reaction (S1) and the sol-gel process (S2). Structural, morphological, infrared and magnetic properties were investigated by X-ray diffraction, scanning electron microscopy, Spectrum Two FT-IR Spectrometer and vibrating sample magnetometer. Despite the various conditions employed in the elaboration, the crystallographic study shows that our samples are single phase and crystallize in orthorhombic system with Pnma space group. A small difference appears in the microstructural and magnetic properties. The Curie temperature T is found to be 308-256 K for S1 and S2 respectively. A large magnetocaloric effect has been observed in both samples, besides; the relative cooling power for S2 is bigger than S1. It attains exactly 250.75 J kg under a magnetic applied field of 5 T. These results show that the elaboration process has an important impact on the magnetic and magnetocaloric properties. Furthermore, the importance of the magnetoelastic coupling and electron interaction in the magnetocaloric properties of manganite was confirmed by the analysis of Landau theory. [ABSTRACT FROM AUTHOR]

In this paper, a profound theoretical work has been conducted on magnetic and magnetocaloric properties of La CaMnO (0 ≤ x ≤ 0.15) perovskite manganites. Our work is based on a phenomenological model. The magnetization data as a function of temperature at several magnetic fields allows to determine the magnetocaloric parameters such as the maximum of the magnetic entropy change (Δ S ), the relative cooling power (RCP), and the magnetic specific heat change (Δ C ). The theoretical predictions nearly match with the experimental measurements. These materials present large magnetocaloric effect, suggesting their possible application in moderate magnetic fields. [ABSTRACT FROM AUTHOR]

Choosing the right professional that has to meet indeterminate requirements is a critical aspect in humanitarian development and implementation projects. This paper proposes a hybrid evaluation methodology for some non-governmental organizations enabling them to select the most competent expert who can properly and adequately develop and implement humanitarian projects. This methodology accommodates various stakeholders' perspectives in satisfying the unique requirements of humanitarian projects that are capable of handling a range of uncertain issues from both stakeholders and project requirements. The criteria weights are calculated using a two-step multi-criteria decision-making method: (1) fuzzy analytical hierarchy process for the evaluation of the decision maker weights coupled with (2) technique for order preference by similarity to ideal solution to rank the alternatives which provide the ability to take into account both quantitative and qualitative evaluations. Sensitivity analysis have been developed and discussed by means of a real case of expert selection problem for a non-profit organisation. The results show that the approach allows a decrease in the uncertainty associated with decision-making, which proves that the approach provides robust solutions in terms of sensitivity analysis. [ABSTRACT FROM AUTHOR]

La0.5Eu0.2Ba0.3−x□xMnO3 (x = 0.00, 0.05 and 0.15) samples were prepared using sol–gel method and annealed at Ts = 750 and 950 °C. The X-ray diffraction technique shows that all samples crystallize in the rhombohedral structure with R-3c space group. Electrical properties of the prepared compounds were investigated using impedance spectroscopy technique in a wide temperature range (80–440 K). The results show a semiconductor behavior for all samples. From dc-conductivity (σdc) analysis, it is observed that increasing barium-deficiency content and sintering temperature improves the electrical conductivity. It is also found that the conduction mechanism is governed by hopping process. Ba-deficiency and sintering temperature affects the activation energy (Ea). From σdc, in the temperature range of 250–480 K and at Ts = 750 °C, it is found that Ea1 decreases from 190 meV for x = 0.00 to 164 meV for x = 0.15. Also, for x = 0.00, Ea1 decreases from 165 meV at Ts = 750 °C to 145 meV at Ts = 950 °C. Complex impedance analysis indicates the presence of non-Debye type relaxation. Such analysis confirms the contribution of grain boundary on the conduction. The activation energy Ea2 deduced from dc-conductivity matches very well with the value estimated from relaxation time (Eaτ) indicating that relaxation and transport mechanisms are related to the same defect. [ABSTRACT FROM AUTHOR]

We have investigated gallium doping effect on magnetic and magnetocaloric properties of La0.65Bi0.05Sr0.3Mn1−xGaxO3 (x = 0 and 0.06) manganites. All compounds present a ferromagnetic–paramagnetic transition at Curie temperature (TC). A large magnetocaloric effect is observed near TC. The maximum value of the magnetic entropy change is Δ S M max = 4.45 J kg - 1 k - 1 at 4.5 T applied magnetic field for x = 0 compound which decreases to a lower value of Δ S M max = 3.44 J kg - 1 k - 1 at 4.5 T for x = 0.06. Gallium doping reduces TC and Δ S M max . The relative cooling power (RCP) reaches 40 J kg−1 (resp. 200 J kg−1) with 1 T (resp. 4.5 T) applied magnetic field for La0.65Bi0.05Sr0.3MnO3 manganites. For La0.65Bi0.05Sr0.3Mn0.94Ga0.06O3, the RCP value is 48 J kg−1 (resp. 220 J kg−1) with 1 T (resp. 4.5 T) applied magnetic field. These values are relatively high as compared with those generally reported for manganite, and our samples can be considered as a promising material to be used in ecologically friendly magnetic refrigeration technology. Obviously, the variations of EPR, as the Ga doping increases, giving a further confirmation for the decrease in the Curie temperature, were already observed in analogous magnetic results M(T) curves. [ABSTRACT FROM AUTHOR]

Our study was to determine the critical exponents of LaCaKNaMn0 compound near the Curie temperature ( T ). The experimental results reveal that our sample undergoes a second-order magnetic phase transition. The estimated critical exponents have been determined using different techniques, such as the modified Arrott plot (MAP), the Kouvel-Fisher (KF) method, and critical isotherm (CI) analysis. The obtained values using the MAP method ( β = 0.303 ± 0.013 with T = 292.24 K, γ = 1.236 ± 0.101 with T = 293.02 K) and KF method ( β = 0.341 ± 0.007 with T = 292.48 K, γ = 1.216 ± 0.024 with T = 293.13 K) are close to 3D Ising values and their T is near room temperature. These critical exponents fulfill the Widom scaling relation δ = 1 + γ/ β. Finally, based on the critical exponents, the magnetization-field-temperature data around T collapses into two curves obeying the single-scaling relation, implying the reliability of our values. [ABSTRACT FROM AUTHOR]

In this paper, the prediction of the magnetocaloric properties has been investigated in the LaCaBa $_{\mathrm {0.15}}\square _{\mathrm {0.05}}$MnO system near the ferromagnetic-paramagnetic phase transition as a function of temperature. The data indicate that the LaCaBa $_{\mathrm {0.15}}\square _{\mathrm {0.05}}$MnO system has potential application for magnetic refrigerants in an extended high-temperature range. In addition, the magnetic entropy change distribution is quite uniform, which is desirable for an Ericsson cycle magnetic refrigerator. [ABSTRACT FROM AUTHOR]