Investigation of shape memory characteristics and production of HfZrTiFeMnSi high entropy alloy by mechanical alloying method

Güler Ömer,Şimşek Tuncay,Özkul İskender,Avar Barış,Canbay Canan A.,Chattopadhyay Arun K.,Güler Seval H. 한국물리학회 2022 Current Applied Physics Vol.33 No.-

High entropy alloy (HEA) with shape memory effect (SME) has been the subject of great interest for the past few decades. However, with the increased demands for new materials for high thermal applications, the research activities on the multi elemental high entropy shape memory alloys (HESMA) have been increased by many folds recently. The nano crystalline HEA powder with shape memory effect developed in this study, HfZrTiFeMnSi, was produced by mechanical alloying (MA) for the first time. In this method equiatomic ratio of Hf, Zr, Ti, Fe, Mn, and Si were mixed together and milled by MA process for 100 h. The powder formed was of amorphous in nature. Elemental mapping of the powder from SEM-EDS revealed homogeneity of the alloying elements confirming successful fabrication of HfZrTiFeMnSi HEA powder. The DSC studies from ambient to 500 ◦C of the annealed alloy powders showed reversible austenitic to martensitic (A↔M) transformations. The A↔M transformation hysteresis seemed to vary with the milling time and annealing temperature. The enthalpy values, ΔH, for the transformation were calculated from the DSC plots using tangent method for peak area calculation. Regardless of the annealing temperature, the thermal analysis revealed that the ΔH, equilibrium temperature (T0), and crystallization temperature values decreased with the increasing milling time.

Exploring critical behavioral differences in physical, structural, and nuclear radiation attenuation properties of produced High Entropy Alloy (HEA) and Refractory-High Entropy Alloy (RHEA) samples

Güler Seval Hale,Güler Ömer,Kavaz E.,Almisned Ghada,Issa Bashar,Tekin H.O. 한국물리학회 2024 Current Applied Physics Vol.58 No.-

Refractory-High entropy alloys (RHEAs) are known for their exceptional mechanical and radiation-resistant properties, making them promising materials for use in nuclear reactors. Their high entropy composition, which consists of multiple elements in roughly equal proportions, can create a stable microstructure that withstands high levels of radiation damage. The objective of this work is to further our comprehension of the unique behavioral, physical, structural, and nuclear radiation attenuation characteristics shown by High-Entropy Alloys (HEA) and Refractory-High entropy alloy (RHEA) materials. Accordingly, two high entropy alloy (HEA) samples through two different compositions were produced. The first composition under consideration is the typical high-entropy alloy (HEA) defined as MnCrFeNiCoMo0.5. The second composition under consideration is a refractory high entropy alloy (RHEA) characterized by the following elemental composition: TiZrNbHfVTa0.1. SEM and EDX analyses were conducted in terms of determining their physical and structural attributes. Next, a133Ba radioisotope together with a HPGe detector were utilized for gamma-ray transmission experiments. Finally, a241Am/Be source and a gas proportional detector were used for neutron absorption experiments for HEA and RHEA samples. The alloy structures displayed a unique degree of uniformity. Throughout the RHEA phase, the incorporation of refractory elements did not provide any discernible adverse impacts on the physical stability. The counting spectrum provided a clear explanation of the gamma ray absorption features shown by the RHEA (R) sample, highlighting its exceptional absorption properties. Regarding the absorption properties of neutrons, it was observed that RHEA had a comparatively reduced amount of absorption. Therefore, it can be concluded that the basic structure of RHEA grants it superior gamma-ray attenuation qualities compared to HEA. It can be concluded that RHEA demonstrates superior applicability as a material in comparison to HEA, especially in situations involving the use of fuel rods, where maintaining of neutron quantity has paramount importance for achieving optimum neutron activation.

Turkish prospective teachers’ professional goals, beliefs about the attainability of these goals, identities, and possible selves

Güler Çetin,Altay Eren 서울대학교 교육연구소 2019 Asia Pacific Education Review Vol.20 No.3

This study examined the relationships among prospective teachers’ (PTs) professional goals, their beliefs about the attainability of these goals, teacher identities, and teacher possible selves, with a particular focus on the mediating roles of teacher identities and teacher possible selves. A total of 2303 PTs from three large universities located in different regions of Turkey voluntarily participated in the study. Using an explanatory correlational research design, PTs were asked to complete various quantitative measures. Correlation, hierarchical regression, and structural equation modelling analyses were conducted to analyse the data in a comprehensive manner. The results showed that PTs’ professional goals, their beliefs about the attainability of these goals, teacher identities, and expected teacher possible selves (ETPS) were significantly and selectively related to each other. The results also showed that PTs’ teacher identities and expectations of learning to teach played significant mediating roles in the relationships between their professional goals and beliefs about the attainability of these goals. Overall, the results of the study suggest that, by considering the roles of teacher identity and ETPS, teacher educators and policy makers may better understand the factors potentially bridging the gap between professional goals and beliefs about the attainability of these goals.

A case report of furosemide extravasation in the hand: a rare cause of compartment syndrome

Güler Sertaç,Kocaşaban Dilber Üçöz 대한응급의학회 2023 Clinical and Experimental Emergency Medicine Vol.10 No.4

In emergency departments, many drugs, fluids, and materials for medical examinations and treatment are typically administered to patients intravenously. One of the most common complications of the intravenous bolus or infusion of drugs is extravasation injuries. These injuries may cause certain morbidities for the patient, increase the cost of treatment, and prolong hospital stays. At the same time, these injuries also carry medicolegal risks for health personnel. Furosemide is a potent diuretic that is commonly used in emergency departments for volume overload conditions. To the best of our knowledge, there have been no cases reported in the literature of furosemide-induced extravasation injury with subsequent compartment syndrome that has required surgical intervention. Presented herein is the case of a 70-year-old female patient who was administered intravenous furosemide from the dorsum of the left hand and whose extravasation injury progressed to compartment syndrome requiring an emergency fasciotomy.

Load Frequency Control of Single-Area Power System with PI–PD Controller Design for Performance Improvement

Güler Yavuz,Kaya Ibrahim 대한전기학회 2023 Journal of Electrical Engineering & Technology Vol.18 No.4

Load frequency control (LFC) is an important control problem as it determines the quality of power generation by controlling the system frequency and inter-area tie-line power. To maintain a good quality power supply, LFC must be robust against unknown external disturbances and parameter variations of the power system. Therefore, this paper presents the design of PI–PD controllers, which are robust against parameter changes and have good disturbance suppression capability, for load frequency control of a single-area single- or multi-source power system. PI–PD controller parameters were obtained by applying the weighted geometric center method to the stability boundary locus of the closed-loop control system. The approach was applied to both the inner and outer loops of the PI–PD control system structure, sequentially. Performance and robustness of the proposed PI–PD control system are evaluated using some well-known integral error criteria values, settling time, and peak value (overshoot) in the analysis of the power system with both nominal values and ± 50% changes in the system parameters. The simulation results show that the designed PI–PD controller effectively limits the effect of load disturbance and variations in system parameters.

SOME SPECTRAL AND SCATTERING PROPERTIES OF GENERALIZED EIGENPARAMETER DEPENDENT DISCRETE TRANSMISSION STURM-LIOUVILLE EQUATION

( Güher Gülçehre Özbey ),( Güler Başak Öznur ),( Yelda Aygar ),( Turhan Köprübaşi ) 호남수학회 2023 호남수학학술지 Vol.45 No.3

In this study, we set a boundary value problem (BVP) consisting of a discrete Sturm-Liouville equation with transmission condition and boundary conditions depending on generalized eigenvalue parameter. Discussing the Jost and scattering solutions of this BVP, we present scattering function and find some properties of this function. Furthermore, we obtain resolvent operator, continuous and discrete spectrum of this problem and we give an valuable asymptotic equation to get the properties of eigenvalues. Finally, we give an example to compare our results with other studies.

Usage of complementary and alternative medicine in women with urinary incontinence at a hospital in Turkey

İlknur Gökşin,Güler Duru Aşiret,Cemile Kütmeç Yılmaz 한국한의학연구원 2020 Integrative Medicine Research Vol.9 No.2

Background: Urinary incontinence (UI) is a health problem that is common in women of all ages. Besides pharmacological and surgical treatments, there are lifestyle changes and complementary and alternative medicine (CAM) to relieve UI symptoms. This study aimed to examine lifestyle arrangements and CAM use by women with UI. Methods: We conducted a cross-sectional study using data from 352 women with UI. The study sample consisted of female patients that were aged 18 and above. We asked patients whether they experienced urine leakage, and included all patients with UI in the sample regardless of UI type or severity. We collected the study data by using the personal information form and Incontinence Severity Index (ISI). Results: In this study, 7.1% of women with UI used CAM while 92.9% did not. We found that only the women with mixed incontinence used CAM more (p < 0.05). The CAM techniques commonly preferred by women included prayer (48.0%), hot application (36.0%) and herbal teas (24%). While 52.2% of women stated that they benefited from CAM use, all of them (100%) stated that they experienced no side effects of CAM. The most common lifestyle changes was losing weight. Conclusion: Turkish women with UI had a low rate of CAM use in this study. The use of CAM was related to age and education, and women with mixed UI used CAM more.

Effects of the Rotary Embossing Process on Mechanical Properties in Aluminum Alloy 1050 Sheet

H. Güler,R. Özcan 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.2

Heat shields are designed to protect components from heat damage, and one method of producing heat shields is with the embossing process. The embossing process is a sheet metal–forming method that is uti-lised in strengthening sheet metals. This method also increases the surface area useful for heat transfer. In this paper, the effect of this technique on the yield load, tensile load, bending strength and buckling strength for different sheet thicknesses of aluminium alloy 1050 sheets is investigated. Furthermore, the efficacy of this forming technique as a method for strengthening the sheets is discussed.

The association between pain, balance, fall, and disability in patients with lumbar spinal stenosis with vascular claudication

( Musa Güneş ),( Tarık Özmen ),( Tuğba Moralı Güler ) 대한통증학회 2021 The Korean Journal of Pain Vol.34 No.4

Background: The effect of lumbar spinal stenosis (LSS) and peripheral vascular disease (PVD), which occurs with similar degenerative conditions, when seen together, has not been studied. The aim of this study is to examine and compare the relationship between pain, balance, disability, fear of falling, and kinesiophobia in LSS patients with intermittent vascular claudication (IVC). Methods: Seventy-two patients diagnosed with LSS using magnetic resonance imaging participated in this study. Thirty-five patients with IVC symptoms and showing vascular lesions by lower extremity venous and arterial Doppler ultrasonography imaging were included in the IVC-LSS group. The pain, static balance, dynamic balance, disability, fear of falling, and kinesiophobia were evaluated using the numeric rating scale, single leg stance test, Time Up and Go (TUG), the Oswestry Disability Index (ODI), Fall Efficacy Scale-International (FES-I), and Tampa Scale for Kinesiophobia (TSK), respectively. Results: Age and female sex were found to be higher in the IVC-LSS group (P = 0.024; P = 0.012). The IVC-LSS group had a shorter single leg stance time and TUG test duration, pain intensity, ODI, FES-I, and TSK scores were higher than patients with LSS (P = 0.001). Pain, fear of falling, and kinesiophobia were moderately correlated with disability in the IVC-LSS group. No relationship was found between pain and dynamic balance. Also, the pain was not related to kinesiophobia. Conclusions: The findings indicated that IVC causes loss of balance and an increase in pain, disability, fear of falling, and kinesophobia in patients with LSS.

Assessment of Patient Pain Experience during Intravitreal 27-Gauge Bevacizumab and 30-Gauge Ranibizumab Injection

Mete Güler,Burak Bilgin,Musa Çapkın,Ali Şimşek,Şemsettin Bilak 대한안과학회 2015 Korean Journal of Ophthalmology Vol.29 No.3

Purpose: To compare pain scores of patients during intravitreal 27-gauge bevacizumab and 30-gauge ranibizumab injection procedures. Methods: Seventy eyes of 70 patients who had not previously undergone intravitreal anti-vascular endothelial growth factor therapy were included in this study. Thirty-five patients received ranibizumab and 35 patients received bevacizumab. The diagnoses of the patients were: 27 age related macular degeneration, 15 diabetic macular edema, 9 diabetic vitreous hemorrhage, 6 central retinal vein occlusion, 11 branch retinal vein occlusion and 2 central serous chorioretinopathy. Bevacizumab (1.25 mg/0.05 mL) was injected into the vitreous cavity using a 27-gauge needle, and ranibizumab (0.5 mg/0.05 mL) was injected with 30-gauge needle. Patients were asked just after the injection to rate their perceived pain during the injection using the visual analogue scale (VAS) of 0 (no pain) to 10 (unbearable/ worst pain). The average of these scores was used as the primary outcome. Results: The VAS pain scores in the ranibizumab and bevacizumab groups were 1.06 ± 0.91 (range, 0 to 3) and 1.94 ± 1.55 (range, 0 to 7), respectively, a significant difference (p = 0.005). Patients <65 and ≥65 years of age in both the ranibizumab and bevacizumab groups were then compared. For patients <65, there was a significant difference in the average VAS pain scores between groups (p = 0.003). However, for patients ≥65 years, there was not a significant difference in the average VAS pain scores between groups (p = 0.238). Female and male patients in both ranibizumab and bevacizumab groups were also compared. For female patients, there was a significant difference in the average VAS pain scores between groups (p = 0.016), although not for male patients (p = 0.078). Conclusions: Thirty-gauge intravitreal injection is more comfortable than 27-gauge injection. Injection of bevacizumab with 30-gauge needle syringes may be more tolerable for patients.