Increase of critical current density with doping carbon nano-tubes in YBa₂Cu₃O₇₋<i>_δ</i>

Dadras, S.,Liu, Y.,Chai, Y.S.,Daadmehr, V.,Kim, K.H. Elsevier 2009 Physica. C, Superconductivity Vol.469 No.1

<P><B>Abstract</B></P><P>The effects of carbon nano-tubes (CNTs) on the crystal structure and superconducting properties of YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7−</SUB><I><SUB>δ</SUB></I> (Y-123) compound were studied. Samples were synthesized using standard solid-state reaction technique by adding CNT up to 1wt% and X-ray diffraction data confirm the single phase orthorhombic structure for all the samples. Current–voltage measurements in magnetic fields up to 9T were used to study the pinning energy <I>U<SUB>J</SUB></I> and critical current density <I>J</I><SUB>c</SUB> as a function of magnetic field at fixed temperature. We find that while <I>T</I><SUB>c</SUB> does not change much with the CNT doping (91–92K), both <I>U<SUB>J</SUB></I> and <I>J</I><SUB>c</SUB> increase systematically up to 0.7wt% CNT doping in a broad magnetic field ranges between 0.1 and 9T and <I>J</I><SUB>c</SUB> in the 0.7wt% CNT doped sample is at least 10 times larger than that of the pure Y-123. The scanning electron microscope image shows that CNTs are forming an electrical-network between grains. These observations suggest that the CNT addition to the Y-123-compounds improve the electrical connection between superconducting grains to result in the <I>J</I><SUB>c</SUB> increase.</P>

Liposuction in the Treatment of Lipedema: A Longitudinal Study

Dadras, Mehran,Mallinger, Peter Joachim,Corterier, Cord Christian,Theodosiadi, Sotiria,Ghods, Mojtaba Korean Society of Plastic and Reconstructive Surge 2017 Archives of Plastic Surgery Vol.44 No.4

Background Lipedema is a condition consisting of painful bilateral increases in subcutaneous fat and interstitial fluid in the limbs with secondary lymphedema and fibrosis during later stages. Combined decongestive therapy (CDT) is the standard of care in most countries. Since the introduction of tumescent technique, liposuction has been used as a surgical treatment option. The aim of this study was to determine the outcome of liposuction used as treatment for lipedema. Methods Twenty-five patients who received 72 liposuction procedures for the treatment of lipedema completed a standardized questionnaire. Lipedema-associated complaints and the need for CDT were assessed for the preoperative period and during 2 separate postoperative follow-ups using a visual analog scale and a composite CDT score. The mean follow-up times for the first postoperative follow-up and the second postoperative follow-up were 16 months and 37 months, respectively. Results Patients showed significant reductions in spontaneous pain, sensitivity to pressure, feeling of tension, bruising, cosmetic impairment, and general impairment to quality of life from the preoperative period to the first postoperative follow-up, and these results remained consistent until the second postoperative follow-up. A comparison of the preoperative period to the last postoperative follow-up, after 4 patients without full preoperative CDT were excluded from the analysis, indicated that the need for CDT was reduced significantly. An analysis of the different stages of the disease also indicated that better and more sustainable results could be achieved if patients were treated in earlier stages. Conclusions Liposuction is effective in the treatment of lipedema and leads to an improvement in quality of life and a decrease in the need for conservative therapy.

Hall anomaly in CNT-doped Y-123 high temperature superconductor

Dadras, S.,Manivannan, N.,Kim, K.H.,Daadmehr, V.,Akhavan, M. North-Holland 2010 Physica. C, Superconductivity Vol.470 No.5

In order to study the Hall effect in pure and CNT-doped Y-123 polycrystalline samples, we have measured the longitudinal and transverse voltages at different magnetic field (0-9T) in the normal and vortex states. In the normal state, the Hall coefficient is positive and decreases with increasing temperature, and can be approximately fitted to R<SUB>H</SUB>=a+bT<SUP>-1</SUP>. We have found a sign reversal in the pure sample for the magnetic field of about 3T, and double sign reversal of the Hall coefficient in the 0.7wt% CNT-doped sample at about 3 and 5T. The Hall resistivity in our samples depends on the pinning.

Liposuction in the Treatment of Lipedema: A Longitudinal Study

Mehran Dadras,Peter Joachim Mallinger,Cord Christian Corterier,Sotiria Theodosiadi,Mojtaba Ghods 대한성형외과학회 2017 Archives of Plastic Surgery Vol.44 No.4

Background Lipedema is a condition consisting of painful bilateral increases in subcutaneous fat and interstitial fluid in the limbs with secondary lymphedema and fibrosis during later stages. Combined decongestive therapy (CDT) is the standard of care in most countries. Since the introduction of tumescent technique, liposuction has been used as a surgical treatment option. The aim of this study was to determine the outcome of liposuction used as treatment for lipedema. Methods Twenty-five patients who received 72 liposuction procedures for the treatment of lipedema completed a standardized questionnaire. Lipedema-associated complaints and the need for CDT were assessed for the preoperative period and during 2 separate postoperative follow-ups using a visual analog scale and a composite CDT score. The mean follow-up times for the first postoperative follow-up and the second postoperative follow-up were 16 months and 37 months, respectively. Results Patients showed significant reductions in spontaneous pain, sensitivity to pressure, feeling of tension, bruising, cosmetic impairment, and general impairment to quality of life from the preoperative period to the first postoperative follow-up, and these results remained consistent until the second postoperative follow-up. A comparison of the preoperative period to the last postoperative follow-up, after 4 patients without full preoperative CDT were excluded from the analysis, indicated that the need for CDT was reduced significantly. An analysis of the different stages of the disease also indicated that better and more sustainable results could be achieved if patients were treated in earlier stages. Conclusions Liposuction is effective in the treatment of lipedema and leads to an improvement in quality of life and a decrease in the need for conservative therapy.

Control of Uncertain Butterfly-Shaped Chaotic System: Sliding-mode Approach

Sara Dadras,Hamid Reza Momeni,Vahid Johari Majd 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10

A sliding mode control scheme for an uncertain Butterfly-shaped chaotic dynamical system is proposes in this paper. A sliding surface is determined according to the sliding mode control technique and the control law is established. Stability of the sliding control law is determined using Lyapunov stability theory. The chattering phenomenon, which deteriorates the system performance and may cause unforeseen instabilities, is attenuated due to this control law. The effectiveness of the presented sliding mode control design is confirmed through numerical simulations.

Improvement of the Electrospinnability of Silk Fibroin Solution by Atmospheric Pressure Plasma Treatment

Masoud Dadras Chomachayi,Atefeh Solouk,Hamid Mirzadeh 한국섬유공학회 2019 Fibers and polymers Vol.20 No.8

In this study, silk fibroin (SF) was extracted from the silkworm cocoon and fabricated to form a nonwoven mat byelectrospinning process. In order to improve the electrospinnability of SF, the polymer solution was treated with atmosphericpressure plasma. Conductivity and viscosity of SF-formic acid solution increased after the plasma treatment. Themorphology of SF electrospun scaffolds before and after treatment was investigated by scanning electron microscope (SEM). The results showed that plasma treatment significantly improved the electrospinnability of SF solution and the morphologybecame fine and bead-less. Furthermore, the results of the fourier-transform infrared spectroscopy (FT-IR) and differentialscanning calorimetry (DSC) showed that the plasma treatment increased the crystallinity of SF scaffolds and changed somepart of polymer conformation from random coil to β-sheet crystals. Additionally, this method increased the mechanicalproperties and biodegradation resistance of SF scaffolds.

Fuzzy Surface-Based Control for Uncertain Unified Chaotic Systems

Sara Dadras,Hamid Reza Momeni,Vahid Johari Majd 제어로봇시스템학회 2008 제어로봇시스템학회 국제학술대회 논문집 Vol.2008 No.10

This paper proposes a fuzzy sliding mode control strategy for an uncertain unified chaotic system with input nonlinearity. Using the sliding mode control technique, a sliding surface is determined and the control law is established. A fuzzy system is used instead of sign function in the sliding mode control to reduce the chattering phenomenon on the sliding surface. Based on Lyapunov stability theory, stability of the fuzzy sliding control law is determined. Chattering in the system with nonlinearity input is also damped due to this control law. The illustrative simulation results are given to demonstrate the effectiveness of the proposed fuzzy sliding mode control design.

Improved thermal exchange optimization algorithm for optimal design of skeletal structures

Kaveh, A.,Dadras, A.,Bakhshpoori, T. Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.21 No.3

Thermal Exchange Optimization (TEO) is a newly developed algorithm which mimics the thermal exchange between a solid object and its surrounding fluid. In this paper, an improved version of the TEO is developed to fix the shortcomings of the standard version. To demonstrate the viability of the new algorithm, the CEC 2016's single objective problems are considered along with the discrete size optimization of benchmark skeletal structures. Problem specific constraints are handled using a fly-back mechanism. The results show the validity of the improved TEO method compared to its standard version and a number of well-known algorithms.

Improved thermal exchange optimization algorithm for optimal design of skeletal structures

A. Kaveh,A. Dadras,T. Bakhshpoori 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.21 No.3

Thermal Exchange Optimization (TEO) is a newly developed algorithm which mimics the thermal exchange between a solid object and its surrounding fluid. In this paper, an improved version of the TEO is developed to fix the shortcomings of the standard version. To demonstrate the viability of the new algorithm, the CEC 2016\'s single objective problems are considered along with the discrete size optimization of benchmark skeletal structures. Problem specific constraints are handled using a fly-back mechanism. The results show the validity of the improved TEO method compared to its standard version and a number of well-known algorithms.