Implementation of Thermite Reactions in the Production of Advanced Intermetallic-Matrix Composites: The Case of Nb2O5/Al Thermite Mixture

Arman Ahmadi‑Binahri,Mandana Adeli,M. Reza Aboutalebi,Sergey Krasikov 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.6

In this study, the application of thermite reactions in Nb2O5–Al system in the fabrication of novel NbAl3/Al2O3 compositeswas investigated. Combining the thermite reactions with self-propagating high-temperature synthesis (SHS) techniquein compressed powder mixtures of Nb2O5+ Al resulted in layer-by-layer progress of the exothermic reaction, controlledformation of the desired products and their coexistence in each reacted layer. Characterization of the products using X-raydiffraction (XRD), scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS) techniques showedthat all samples were composed of a metallic matrix including NbAl3as the main compound, along with Al2O3as ceramicreinforcing phase. Differential thermal analysis (DTA) analysis was used to study the mechanism of reaction using bothstoichiometric and over-stoichiometric amounts of aluminum. The effect of such parameters as stoichiometry and greendensity of the samples on the combustion temperature, formed phases, microstructure, and hardness of the obtained compositeswas investigated using samples with stoichiometric as well 20 wt% and 40 wt% excess aluminum, and samples withgreen densities of 75%, 85%, and 95% of theoretical maximum density (TMD). The presence of excess aluminum resultedin prolonged reaction times, lower combustion temperatures, and lower mean values of hardness. While the variations ingreen density had no remarkable effect on the microstructural features of products within the density range under study, themost intensive reactions, highest combustion temperature, and highest mean value of hardness were encountered in sampleswith green density of 85%TMD.

Effect of Synthesis Mode and Ni Particle Size on Microstructural Aspects and Hardness Properties of Combustion-Synthesized NiTi

Arman Khobzi,Mandana Adeli,Ashkan Sabour‑Bagherzadeh,Ashkan Arab,Hooman Abedi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.5

NiTi intermetallic compound was fabricated via two modes of the combustion synthesis process, namely, thermal explosion(TE) and self-propagating synthesis (SHS). The effect of combustion synthesis mode as well as Ni particle size on themicrostructure and microhardness of the final products was investigated. The phases in the products were determined usingXRD technique, and microstructural investigations were performed using optical as well as SEM-EDS in order to make acomparison between microstructural evolutions in each mode, other conditions being constant. The analyses showed thatthe desired B2(NiTi) was successfully formed as the primary phase in all samples, and no unreacted Ni or Ti powders werepresent. The main secondary phase was NiTi2which was invariably present in all samples; however, the percentage as wellas the morphology of the detrimental NiTi2phase was found out to be controllable by the mode of combustion as well asNi particle size. A comparison between the two modes revealed that samples produced by TE showed coarse dendritesin the microstructure; they also presented higher average microhardness values. The SHS-synthesized samples exhibitedmicrostructures similar to those observed in heat-treated and homogenized NiTi obtained from methods such as vacuum arcremelting and vacuum induction melting, and contained finely dispersed NiTi2particles. It was shown that a decrease in Niparticle size presented a grain refining effect on NiTi2in both modes.

ABOUT THE ANCIENT RITUAL OF DAMAGE TO ITEMS PLACED IN THE GRAVE

Arman Beisenov,Gulnar Jumabekova 가천대학교 아시아문화연구소 2016 아시아문화연구 Vol.41 No.-

The archaeologists have many facts stating that the ancient graves had objects that were intentionally spoiled before putting them into the grave. This tradition was widespread both chronologically and geographically, and, therefore, it is not associated with certain cultures or regions. A new fact about this ritual was recorded in 2015 in the study of the burial ground of the middle Sarmatian period Borsyk which is located in West Kazakhstan. The central grave of the kurgan 6 had badly damaged bronze cauldron. The grave was robbed in antiquity. Some scattered bones of a human skeleton, small ornaments of gold foil from the full dress of a nobleman were found in the grave. The diameter of the kurgan 50 m, height – 1,7 m .Dimensions of graves at the top - 4,5x3,8 m. Its depth - 2.3 m. The parameters of the kurgan and the grave, the nature of the findings show that this monument was the burial place of the representative of the Sarmatian elite. The cauldron is located in the northern corner of the grave and is strongly deformed. It has been bent and folded double. Along the edges, there are numerous destructions, traces of numerous blows by metal tool on the surface. As a result there are deep dents, cracks. Around the cauldron its small fragments were found. Thus, it is quite obvious that the boiler has been intentionally deformed by participants of the ancient ritual. Currently, the researchers have not expressed their unequivocal opinion about the essence of the ritual. The main hypothesis of the scientists is to ensure that the damage of ritual objects was associated with the idea of enduing the subjects with ‘other’, unearthly qualities that are originated from the owner’s death. Cauldrons have played an important role in the life of steppe leaders. It is assumed that the sacred nature of the use of them (bowls) in the culture of the steppe peoples is associated with the feast, the battle, the sacred hunting. Perhaps there was a tradition to bury the cauldrons with their owners, after making a damage of the subject in connection with the concept of the other world and the role of the leader-hero in it.

INVESTIGATION OF PARTICLE MOTIONS IN THREE-DIMENSIONAL LID DRIVEN CAVITY

Arman Safdari,Kyung Chun Kim 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.5-2

A reliability-based approach to investigate the challenges of using international building design codes in developing countries

Arman Kakaie,Azad Yazdani,Mohammad-Rashid Salimi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.6

The building design codes and standards in many countries usually are either fully or partially adopted from the international codes. However, regional conditions like the quality of construction industry and different statistical parameters of load and resistance have essential roles in the code calibration of building design codes. This paper presents a probabilistic approach to assess the reliability level of adopted national building codes by simulating design situations and considering all load combinations. The impact of the uncertainty of wind and earthquake loads, which are entirely regional condition dependent and have a high degree of uncertainty, are quantified. In this study, the design situation is modeled by generating thousands of numbers for load effect ratios, and the reliability level of steel elements for all load combinations and different load ratios is established and compared to the target reliability. This approach is applied to the Iranian structural steel code as a case study. The results indicate that the Iranian structural steel code lacks safety in some load combinations, such as gravity and earthquake load combinations, and is conservative for other load combinations. The present procedure can be applied to the assessment of the reliability level of other national codes.

Loss Evaluation for Modular Multilevel Converters with Different Switching Strategies

Arman Hassanpoor,Staffan Norrga,Alireza Nami 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

Apparently, modular multilevel converter (MMC) has been extensively used in high voltage direct current (HVDC) transmission links in recent years. The efficiency of MMC stations are highly related to the switching methods and semiconductor devices. So, various switching methods and semiconductor devices have been investigated and introduced in the field. This paper settles a benchmark for an HVDC link, based on a real project, and investigates the impact of six different switching methods on the converter loss, utilizing a commercial semiconductor device. The evaluation indicates that switching methods which consider the current level at switching instants are more efficient in comparison with the other methods which only consider the number of switching events. The result of this study is essential for more efficient converter stations.

Status of the Concordance Model of Cosmology

Arman Shafieloo 한국천문학회 2020 天文學會報 Vol.45 No.1

Early outcomes of cleft and palatal width following anterior palate repair (vomerine flap) in infants with wide cleft lip and palate

Arman Zaharil Mat Saad,Koh Siang Chai,Wan Azman Wan Sulaiman,Siti Fatimah Noor Mat Johar,Ahmad Sukari Halim 대한성형외과학회 2019 Archives of Plastic Surgery Vol.46 No.6

Background Anterior palatal repair performed during cleft lip repair using a vomerine flapmay assist in recruiting additional soft tissue for subsequent completion of palatoplasty, especiallyin patients with a wide cleft. We present our early results in the hope of triggering are-evaluation of this technique regarding its advantages for maxillary growth through furtherstudies of patients with a wide cleft. Methods A retrospective analysis of patients with complete unilateral and bilateral cleft lipand palate was performed, including cleft and palatal measurements taken during initial surgery(lip repair together with anterior palate repair) and upon completion of palatoplasty. Results In total, 14 patients were included in this study, of whom nine (63.3%) had unilateralcleft lip and palate and five (37.5%) had bilateral cleft. All patients had a wide cleft palate. Lip and anterior palate repair was done at a median age of 3 months, while completion ofpalatoplasty was done at a median age of 10.5 months. Measurements taken upon completionof palatoplasty showed significant cleft width reduction in the mid-palate and intertubercleregions; however, the palatal arch distances at nearby landmarks showed non-significantmarginal changes. Conclusions Anterior palate repair using a vomerine flap significantly reduced the remainingcleft width, while the palatal width remained. Further research is warranted to explore thelong-term effects of this technique in wide cleft patients in terms of facial growth.

A Study on the Multi-level RRAM behavior of TaOx and TiOx devices

Arman Kadyrov,Jungho Bae(배정호),Youngsu Choi(최용수),Batyrbek Alimkhanuli,Gihwan Hyun(현기환),Hyeyoon Ryu(유혜윤),Kyesan Lee(이계산),Seunghyun Lee(이승현) 한국통신학회 2021 한국통신학회 학술대회논문집 Vol.2021 No.2

Artificial Intelligence (AI) has achieved a lot of breakthroughs in recent years. The areas include but are not limited to face and speech recognition, machine translation, classification, etc. To carry out the AI tasks, Deep Neural Networks (DNNs) are trained in software using significant amounts of datasets. To improve the efficiency of these networks novel processing methods in the category of analog memory and computations in non-von Neumann architectures have been under development. Among the modern concepts for accelerating a neural network, few emerging technologies attract special attention, namely phase-change memory (PCM) and resistive-switching random access memory (RRAM). PCM and RRAM facilitate the ability to store multiple states in a single cell, which is necessary for the precise measurements during the update of synaptic weights with analog behavior. This study is aiming to compare the behaviors of two different RRAM structures. One of them is using titanium oxide as an active layer and the second one is using tantalum oxide. As a result of the comparative advantages of the tantalum oxide have been highlighted.

Authors’ Reply to Letter to the Editor: Commentary on In-Fracture Pedicular Screw Placement During Ligamentotaxis Following Traumatic Spine Injuries, a Randomized Clinical Trial on Outcomes (Korean J Neurotrauma 2023;19:90–102)

Arman Sourani,Majid Rezvani,Jamalodin Asadi,Mina Foroughi,Donya Sheibani Tehrani 대한신경손상학회 2023 Korean Journal of Neurotrauma Vol.19 No.4

Dr. Lee questioned multiple topics that needs to be addressed for better clearance. As provided the commentary they asked about the pedicle status of our cases. To equal the severity indices in both groups, before group allocation, we did not include obvious and dislocated bilateral pedicular fractures to prevent selection biases. However, it is worth mentioning pedicular fracture has no prognostic role in Thoracolumbar Injury Classification and Severity Score (TLICS)/Arbeitsgemeinschaft für Osteosynthesefragen (AO) classifications.