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Strain dependence of critical current in internal tin process Nb<sub>3</sub>Sn strands
Oh, Sangjun,Park, Soo Hyeon,Lee, Chulhee,Chang, Yongbok,Kim, Keeman,Park, Pyeong-Yeol IEEE 2005 IEEE transactions on applied superconductivity Vol.15 No.2
The development of a high performance superconducting magnet requires a thorough understanding of the strain effect in the critical current density (J<SUB>c</SUB>) of Nb<SUB>3</SUB>Sn strands. A modified version of the WASP device is used for the investigation of the strain effect. The spring is made of BeCu alloy and is capable of applying strain up to 0.7% reversibly at 4.2 K. Several types of high performance Nb<SUB>3</SUB>Sn strands (J<SUB>c</SUB>>1000 A/mm<SUP>2</SUP> at 12 T and 4.2 K) have been developed using internal tin process. A comparative study on the axial strain dependence of the critical current is performed.
Sangjun Oh,Oh, D.K.,Bae, C.J.,Kim, H.C.,Keeman Kim Institute of Electrical and Electronics Engineers 2007 IEEE transactions on applied superconductivity Vol.17 No.2
<P>We report detailed magnetization measurement results for two internal-tin Nb<SUB>3</SUB>Sn strands. The paramagnetic background of a Mitsubishi strand is about 4 times larger than that of a KAT strand below the transition temperature, which can be understood as combined effects of Pauli and Langevin paramagnetism. From magnetic relaxation measurement for the KAT strand, a possibility of surface barrier effect is discussed. After subtracting the paramagnetic background, reversible magnetization data are analysed using the Hao-Clem model and the Ginzburg-Landau parameters (kappa), the thermodynamic and the upper critical fields (B<SUB>c</SUB>,B<SUB>c2</SUB>) at various temperatures are obtained. The temperature dependences of kappa, B<SUB>c</SUB> and B<SUB>c2</SUB> are compared with the recent theoretical calculation results for Nb<SUB>3</SUB>Sn and also with widely used empirical formulas.</P>
Oh, Sangjun,Lee, Chulhee,Cho, K W,Kim, Keeman,Uglietti, D,Flü,kiger, R IOP Publishing Ltd 2007 Superconductor science & technology Vol.20 No.8
<P>We find a simple expression for the field dependences of the <I>n</I>-value for Nb<SUB>3</SUB>Sn strands which gives reasonable fits to empirical data. It is also found that a relationship between the <I>n</I>-value and the critical current, which is obtained from an assumed reduction of the flux line lattice shearing pinning force due to thermal activation, can describe the field dependence of the critical current. Using the relation between the <I>n</I>-value and the critical current, we propose a scaling law which we have called the Kramer model including thermal activation. It is shown that the proposed scaling law can explain the critical current data at 4.2 K, even at high field near the upper critical field. It is also compared with Ekin’s strain scaling law.</P>
Sangjun Oh,Chulhee Lee,Heekyung Choi,Kyungmo Moon,Keeman Kim,Jiman Kim,Pyeong-Yeol Park IEEE 2008 IEEE transactions on applied superconductivity Vol.18 No.2
<P>We have developed a probe for the critical current measurements of low temperature superconducting strands at various field, temperature and strain. A 30 cm-long strand sample is soldered on a Walters spiral made of beryllium copper alloy and compressive or tensile axial strain can be applied up to 0.7%. Temperature control ability was tested using a MgB<SUB>2</SUB> wire up to 30 K. Three cernox sensors are attached on a spiral adjacent to the strand and the temperature of the spiral is controlled within plusmn50 mK of target temperature during the critical current measurement up to 80 A. Extensive critical current measurements have been carried out for an internal-tin processed Nb<SUB>3</SUB>Sn strand. It was found that the measured field, temperature and strain dependence of the critical current for the internal-tin Nb<SUB>3</SUB>Sn strand is in agreement with the recent scaling law based on strong coupling theory of superconductivity.</P>
Sangjun Oh,Soo-Hyeon Park,Chulhee Lee,Heekyung Choi,Wonwoo Park,Keeman Kim IEEE 2010 IEEE transactions on applied superconductivity Vol.20 No.3
<P>We have developed an apparatus to investigate the effect of transverse stress under axial strain on the critical current of superconducting strands. An internal tin Nb<SUB>3</SUB>Sn wire is soldered on a C-shape ring (called Pacman) made of 2% beryllium doped copper alloy and axial strain from -0.7 to 0.7% can be applied. The actual strain on a sample was estimated from a comparison with the critical current measurement results using a Walter spiral probe. Reversible transverse stress effects on the critical current were studied in this work and the transverse pressure was applied up to 40 MPa under ±0.5% axial strain. The critical current was initially increased about 3% as transverse load was applied and then decreased almost linearly under compressive axial strain. Similar behavior is observed under tensile axial strain but the critical current decreases rather sharply at higher load. A unified description based on 3 dimensional deviatoric strain was difficult for the sample studied in this work.</P>
Cranial Vena Cava Syndrome in a Retriever Dog Receiving CPN through Central Venous Catheter
Sangjun Oh,Jinsu Kang,Bumseok Kim,Nam Soo Kim,허수영 한국임상수의학회 2022 한국임상수의학회지 Vol.39 No.5
A 5-year-old castrated male Golden Retriever dog weighing 15 kg presented with evidence of intestinal intussusception. The patient had cachexia and severe dehydration before being referred to our department. Ultrasound imaging revealed a target sign indicative of intestinal intussusception. Emergen- cy surgery was performed shortly after diagnosis. After a successful surgery, the patient was hospitalised for postoperative care. Initial treatment was aimed at the reversion of dehydration and the provision of adequate nutrition. Fluid ther- apy and central parenteral nutrition were administered via the peripheral and central venous catheters, respectively. Ten days postoperatively, swelling and edema were observed in the head and neck. Ultrasound and computed tomog- raphy confirmed complete blockage of the cranial vena cava due to thrombosis, which consequently obstructed both the left and right jugular veins. For treat- ment, dalteparin and tissue plasminogen activator were administered. However, the patient lost all of its vital function on the daybreak of postoperative day 11. Venous thrombus formation secondary to central parenteral nutrition applica- tion via the central line is a rare but possible complication. Veterinarians who are concerned about taking care of patients receiving CPN through the central line should keep the possibility of venous thrombus formation in mind.