Magnetization mechanism in amorphous ferromagnetic wires

Çiftekararlılık için sınır uzunluğun üzerindeki bir amorf ferromanyetik telin üzerinde yaratılan eziğin ve küçük bobinler ile tele uygulanan yerel manyetik alanların telin DC manyetik histeresisine etkisi, deneysel olarak incelenmiş, sonuçlar bir model ile yorumlanmıştır. Bir grup amorf tel, ölçümden önce 0.75mm çaplı sert çelik iğneyle tele dik olarak ortadan değişik miktarlarda ezilmiştir. Diğer bir grup ölçüm de ortasından kesilip çeşitli aralıklar bırakılmış örneklerle yapılmıştır. Üçüncü bir grup deney de, tele 1.5mm uzunluğunda bobin(ler) sarılarak uygulanan manyetik alan(lar)ın telin manyetik histeresisi üzerindeki etkilerini incelemek üzere yapılmıştır. Birinci grup ölçümlerde kullanılan teller çiftekararlılık için sınır uzunluktan kısa olduğu halde ezik 20µm’yi aştıktan sonra histeresis döngülerinde iki aşamalı büyük Barkhausen sıçraması ile kademeli düşüş görülmüştür. İkinci grup deneylerden elde edilen histeresis döngüleri fark olarak birinci gruptakilerden sadece basamaklı gevşeyen kısımlarında daha büyük bir eğim göstermiştir. Aynı yerde tele sarılı küçük bir bobin ile tele artı yönlü manyetik alan uygulandığında ise, mıknatıslanma histeresis döngüsünde uzun, basamaklı bir gevşemeden sonra büyük bir Barkhausen sıçraması ile ters yönde doyuma gitmiştir. Döngünün çıkıcı kısmında ise ters mıknatıslanmanın, eksi bir dış alan değerinde büyük bir Barkhausen sıçraması ile başlayıp küçük basamaklarla doyuma gittiği görülmüştür. Bu çalışmada sunulan model, telin iç çekirdeğindeki manyetik bölge duvarı hareketi ve kapanma bölgelerindeki parçalanma sonucunda ortaya çıkan manyetik moment dağılımının bilgisayar yazılımları ile hesaplanması temeline dayanmaktadır. Hesap sonucu elde edilen histeresis döngüleri deneysel sonuçlarla uyum içindedir. Anahtar Kelimeler: Amorf tel, ezik, histeresis, ferromanyetik.Hysteresis loops in a ferromagnetic amorphous wire longer than the critical length are studied. Wires with a deformation in the middle are considered. Both theoretical and experimental studies using DC vibrating sample magnetometer were performed. Amorphous wires with compositions Fe-Si-B and with diameter 125µm of positive magnetostriction coefficient are used in the experiments. Samples have been deformed at the middle by pressing with a hard steel needle of 0.75mm diameter, perpendicular to the axis of the wire. Another group of measurements was carried out of the samples cut at the middle. A third group of experiments was intended to be a bridge to the hysteresis model proposed. 1.5mm coils were wound up at the middle of the wire under investigation to apply a local magnetic bias. An oppositely directed pair of local fields is applied with a pair of identical coils reversely connected is employed to investigate its effect on the hysteresis loop. The DC hysteresis loops were measured with a home made vibrating sample magnetometer. The sample vibrates sinusoidally along the axis of a long solenoid at the frequency of 23 Hz. The pick-up coils have been particularly designed to measure long samples. Magnetic field has been changed with a step of 0.3 A/m, and measured with a sensitivity of 0.01 A/m. In the first group of experiments, although the length of the wire is greater than the critical length for bistable behavior, after a threshold value of increasing, the hysteresis loop starts to narrow keeping its rectangular shape. Furthermore deformations more than 20 µm lead to two large Barkhausen jumps separated by a staircase relaxation. The only difference of the hysteresis loops yielded by the second group of experiments from the first is that the slope of the inclined parts is bigger than those in the first group. The unidirectional magnetic bias gave rise to a staircase relaxation, followed by a long Barkhausen jump in the descending branch of the loop. In the ascending branch, the domain wall completes its almost entire motion in a negative external field and the magnetization approaches saturation with staircase movements. As the current through the reversely connected pair of coils is increased, the hysteresis loop starts developing nearly horizontal tails first at the up right, and then at the bottom left corners. The model proposed in this work is based on the calculation of the magnetic moment distribution in the core of the wire by means of computer simulations. To simulate the magnetization process of the deformed wire, the total energy is taken as a function of five variables. Three of these correspond to the nucleation at two ends and at the middle of the wire while the remaining two represent the domain wall locations in the two regions. The simulation traces the gradient in the six dimensional energy landscape to find the set of coordinates, which, for a given value of external field, minimizes the total energy. Magnetization makes a jump to another stable position when the total energy loses its local minimum in the landscape. Since in general there are more than one energy minima along the entire process, a magnetic hysteresis occures. The total energy of the system is taken as the summation of mutual magnetostatic interactions along all the domains, Zeeman energy, and the anisotropy energies. Exchange interactions are taken into accound by assuming the domain wall motions along the wire. When the deformation created in the middle of the wire is represented by just an anisotropy field, but no nucleation allowed, the upper and lower halves of the calculated loop is shifted symmetrically to the right and to the left respectively, with horizontal stretch lines in the two directions. The horizontal lines result from the energy barrier created by the local anisotropy field in the middle. Although the great simplicity of this structure, it reveals the response mechanism of the wire beyond a certain threshold of deformation; no change in the hysteresis occurs before the threshold is reached. When the wall motion starts at a point around the deformation, and nucleation mechanism occurring at the deformed part and at the ends is taken into account, the same staircase character in the hysteresis loops is obtained as the experimental ones. The ends and the deformed part of the wire act as pinning sites.    Keywords: Amorphous wire, deformation, hysteresis, ferromagnetic

Electrical and mechanical properties of superconducting MgB2/Mg metal matrix composites

MgB2/Mg composites were prepared using a metal matrix composite fabrication method that offers the potential to produce superconducting wires as an alternative approach to the powder in tube process. To obtain composites, MgB2 and Mg powders were mixed at different weight fractions and uniaxially pressed in a cylindrical die under the pressure of 0.5 and 1.0GPa for two hours at various temperatures. The x-ray diffraction technique was used for phase identification. Temperature dependence of resistivity and magnetization measurements were carried out to determine superconducting properties. The effects of composite fabrication temperature and the addition of the Mg on the mechanical properties of MgB2/Mg composites were investigated. For this purpose, the compressive mechanical testing was performed to measure the elastic modulus and fracture strength values of the composites. It was found that the relative weight fraction of the Mg and the fabrication conditions of the composites have considerable effect on the superconducting and mechanical properties of the composites.TÜBİTAK: TBAG-2031 and LO/TUBA-GEBIP/2002-1-1

The effect of preoperative Lugol's iodine on intraoperative bleeding in patients with hyperthyroidism

Aim: To investigate the effect of preoperative Lugol's iodine on intraoperative bleeding in patients with hyperthyroidism. Material and methods: This controlled, randomized, prospective cohort was carried out on 40 patients who admitted for surgery due to hyperthyroidism. Cases were randomly assigned to receive either preoperative treatment with Lugol solution (Group 1) or no preoperative treatment with Lugol solution (Group 2). Group 3 (n = 10) consisted of healthy adults with no known history and signs of hyperthyroidism. Blood flow through the thyroid arteries of patients was measured by color flow Doppler ultrasonography. Free T3, free T4, TSH, thyroid volume and the resistance index of the four main thyroid arteries were measured in all patients. Results: There was not a significant difference between gender, preoperative serum thyroid hormone levels, or thyroid gland volumes between groups 1 and 2. The mean blood flow of the patients in Group 1 was significantly lower than values in Group 2. When age, gender, thyroid hormone, TSH, thyroid volume, blood flow, and Lugol solution treatment were included as independent variables, Lugol solution treatment (OR, 7.40; 95% CI, 1.02–58.46; p = 0.001) was found to be the only significant independent determinant of intraoperative blood loss. Lugol solution treatment resulted in a 7.40-fold decrease in the rate of intraoperative blood loss. Conclusion: Preoperative Lugol solution treatment was found to be a significant independent determinant of intraoperative blood loss. Moreover, preoperative Lugol solution treatment decreased the rate of blood flow, and intraoperative blood loss during thyroidectomy

Measurement of the double-differential inclusive jet cross section in proton-proton collisions at s\sqrt{s} = 5.02 TeV

International audienceThe inclusive jet cross section is measured as a function of jet transverse momentum $p_\mathrm{T}$ and rapidity $y$. The measurement is performed using proton-proton collision data at $\sqrt{s}$ = 5.02 TeV, recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 27.4 pb$^{-1}$. The jets are reconstructed with the anti-$k_\mathrm{T}$ algorithm using a distance parameter of $R$ = 0.4, within the rapidity interval $\lvert y\rvert$$\lt$ 2, and across the kinematic range 0.06 $\lt$$p_\mathrm{T}$$\lt$ 1 TeV. The jet cross section is unfolded from detector to particle level using the determined jet response and resolution. The results are compared to predictions of perturbative quantum chromodynamics, calculated at both next-to-leading order and next-to-next-to-leading order. The predictions are corrected for nonperturbative effects, and presented for a variety of parton distribution functions and choices of the renormalization/factorization scales and the strong coupling $\alpha_\mathrm{S}$

Two-particle Bose-Einstein correlations and their Lévy parameters in PbPb collisions at sNN\sqrt{s_\mathrm{NN}} = 5.02 TeV

Two-particle Bose-Einstein momentum correlation functions are studied for charged-hadron pairs in lead-lead collisions at a center-of-mass energy per nucleon pair of $\sqrt{s_\mathrm{NN}}$ = 5.02 TeV. The data sample, containing 4.27$\times10^{9}$ minimum bias events corresponding to an integrated luminosity of 0.607 nb$^{-1}$, was collected by the CMS experiment in 2018. The experimental results are discussed in terms of a L\'evy-type source distribution. The parameters of this distribution are extracted as functions of particle pair average transverse mass and collision centrality. These parameters include the L\'evy index or shape parameter ($\alpha$), the L\'evy scale parameter ($R$), and the correlation strength parameter ($\lambda$). The source shape, characterized by $\alpha$, is found to be neither Cauchy nor Gaussian, implying the need for a full L\'evy analysis. Similarly to what was previously found for systems characterized by Gaussian source radii, a hydrodynamical scaling is observed for the L\'evy $R$ parameter. The $\lambda$ parameter is studied in terms of the core-halo model.Comment: Submitted to Physical Review C. All figures and tables can be found at http://cms-results.web.cern.ch/cms-results/public-results/publications/HIN-21-011 (CMS Public Pages

Measurement of the double-differential inclusive jet cross section in proton-proton collisions at s= \sqrt{s} = 5.02 TeV

The inclusive jet cross section is measured as a function of jet transverse momentum $p_{\mathrm{T}}$ and rapidity $y$. The measurement is performed using proton-proton collision data at $\sqrt{s} =$ 5.02 TeV, recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 27.4$\,\text{pb}^{-1}$. The jets are reconstructed with the anti-$k_{\mathrm{T}}$ algorithm using a distance parameter of $R=$ 0.4, within the rapidity interval $|y| <$ 2, and across the kinematic range 0.06 $< p_{\mathrm{T}} <$ 1 TeV. The jet cross section is unfolded from detector to particle level using the determined jet response and resolution. The results are compared to predictions of perturbative quantum chromodynamics, calculated at both next-to-leading order and next-to-next-to-leading order. The predictions are corrected for nonperturbative effects, and presented for a variety of parton distribution functions and choices of the renormalization/factorization scales and the strong coupling $\alpha_\mathrm{S}$.The inclusive jet cross section is measured as a function of jet transverse momentum $p_\mathrm{T}$ and rapidity $y$. The measurement is performed using proton-proton collision data at $\sqrt{s}$ = 5.02 TeV, recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 27.4 pb$^{-1}$. The jets are reconstructed with the anti-$k_\mathrm{T}$ algorithm using a distance parameter of $R$ = 0.4, within the rapidity interval $\lvert y\rvert$$\lt$ 2, and across the kinematic range 0.06 $\lt$$p_\mathrm{T}$$\lt$ 1 TeV. The jet cross section is unfolded from detector to particle level using the determined jet response and resolution. The results are compared to predictions of perturbative quantum chromodynamics, calculated at both next-to-leading order and next-to-next-to-leading order. The predictions are corrected for nonperturbative effects, and presented for a variety of parton distribution functions and choices of the renormalization/factorization scales and the strong coupling $\alpha_\mathrm{S}$

Measurement of the double-differential inclusive jet cross section in proton-proton collisions at s\sqrt{s} = 5.02 TeV

International audienceThe inclusive jet cross section is measured as a function of jet transverse momentum $p_\mathrm{T}$ and rapidity $y$. The measurement is performed using proton-proton collision data at $\sqrt{s}$ = 5.02 TeV, recorded by the CMS experiment at the LHC, corresponding to an integrated luminosity of 27.4 pb$^{-1}$. The jets are reconstructed with the anti-$k_\mathrm{T}$ algorithm using a distance parameter of $R$ = 0.4, within the rapidity interval $\lvert y\rvert$$\lt$ 2, and across the kinematic range 0.06 $\lt$$p_\mathrm{T}$$\lt$ 1 TeV. The jet cross section is unfolded from detector to particle level using the determined jet response and resolution. The results are compared to predictions of perturbative quantum chromodynamics, calculated at both next-to-leading order and next-to-next-to-leading order. The predictions are corrected for nonperturbative effects, and presented for a variety of parton distribution functions and choices of the renormalization/factorization scales and the strong coupling $\alpha_\mathrm{S}$