• Composites Research
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• v.28 no.6
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• pp.348-355
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• 2015

NDT (Non Destructive Test) of the adhesive joints is very important because their strengths have greatly affected by the worker's skill and environmental condition. Recently, the electric impedance method in which 1-2 wt% CNT was dispersed in the adhesive and the electric resistance of the adhesive joint was measured was suggested for the defect detection of the adhesive joint. The uniform dispersion of CNT in the electric impedance method is very important to make a constant electric resistance of the adhesive joint and the accuracy of defect detection depends on the uniform dispersion. In this paper, the adhesive joints in which CNT was dispersed in the adhesive by the four dispersion methods were made and their electric resistance were measured. The pre-process and evaporation process of CNT using the ultrasonic method and agitation method was used and the effective dispersion method was suggested. Also, the criteria to evaluate the dispersivity was proposed.

• Nuclear Engineering and Technology
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• v.55 no.11
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• pp.4066-4076
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• 2023

Pressure resistance welding is usually used to seal the connection between the cladding tube and the end plug made of zirconium alloy. The seal welded joint has a direct effect on the service performance of the fuel rod cladding structure. In this paper, the pressure resistance welded joints of zirconium alloy tube-plug structure were obtained by thermal-mechanical simulation experiments. The microstructure and microhardness of the joints were both analyzed. The effect of processing parameters on the microstructure was studied in detail. The results showed that there was no β-Zr phase observed in the joint, and no obvious element segregation. There were different types of Widmanstätten structure in the thermo-mechanically affected zone (TMAZ) and heat affected zone (HAZ) of the cladding tube and the end plug joint because of the low cooling rate. Some part of the grains in the joint grew up due to overheating. Its size was about 2.8 times that of the base metal grains. Due to the high dislocation density and texture evolution, the microhardnesses of TMAZ and HAZ were both significantly higher than that of the base metal, and the microhardness of the TMAZ was the highest. With the increasing of welding temperature, the proportion of recrystallization in TMAZ decreased, which was caused by the increasing of strain rate and dislocation annihilation.

• Structural Engineering and Mechanics
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• v.67 no.1
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• pp.1-8
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• 2018

Shake table tests performed on five 1:3 reduced scale two story RC moment resisting frames having construction defects, have shown severe joint damageability in deficient RC frames, resulting in joint panels' cover spalling and core concrete crushing. Haunch retrofitting technique was adopted herein to upgrade the seismic resistance of the deficient RC frames. Additional four deficient RC frames were built and retrofitted with steel haunch; both axially stiffer and deformable with energy dissipation, fixed to the beam-column connections to reduce shear demand on joint panels. The as-built and retrofitted frames' seismic response parameters are calculated and compared to evaluate the viability of haunch retrofitting technique. The haunch retrofitting technique increased the lateral stiffness and strength of the structure, resulting in the increase of structure's overstrength. The retrofitting increased response modification factor R by 60% to 100%. Further, the input excitation PGA was correlated with the lateral roof displacement to derive structure response curve that have shown significant resistance of retrofitted models against input excitations. The technique can significantly enhance the seismic performance of deficient RC frames, particularly against the frequent and rare earthquake events, hence, promising for seismic risk mitigation.

• Progress in Superconductivity and Cryogenics
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• v.24 no.4
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• pp.16-24
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• 2022

Applications of REBa₂Cu₃O_7-δ tapes require joints with a simple manufacturing process, low resistance and good mechanical properties. In the present study, we successfully developed a copper diffusion joint between Cu-stabilized REBa₂Cu₃O_7-δ tapes that meets the above requirements without solder simply by applying flux, heat and pressurization. After a 3 min thermocompression process at approximately 150 δ and 336 MPa in air, two tapes were directly connected between Cu stabilizers by copper diffusion, which was proven by microstructure analysis. The specific resistivity of the copper diffusion joint reached 5.8 nΩ·cm² (resistance of 0.4 nΩ for a 306 mm splicing length) at 77 K in the self-field. The axial tensile stress reached 200 N without critical current degradation. The results show promise for the preparation of copper diffusion joints to be used in coils, attached tapes, and wire/cable terminals.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.7
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• pp.799-804
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• 2011

A thermal cycling test was conducted on a chip resistor solder joint with real-time failure monitoring. In order to study the failure mechanism of the chip resistor solder joint during the test, the resistance between both ends of the resistor was monitored until the occurrence of failure. It was observed that the monitored resistance first fluctuated linearly according to the temperature change. The initial variation in the resistance occurred at the time during the cycle when there was a decrease in temperature. A more significant change in the resistance followed after a certain number of cycles, during the time when there was an increase in the temperature. In order to explain the failure patterns of the solder joint, a mechanism for the solder failure was suggested, and its validity was proved through FE simulations. Based on the explained failure mechanism, it was shown that prognostics for the solder failure can be implemented by monitoring the resistance change in a thermal cycle condition.

• International Journal of Internet, Broadcasting and Communication
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• v.12 no.1
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• pp.81-89
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• 2020

The purpose of this study is to investigation the effects of functional compression clothing on muscle function by comparing the iEMG response of muscle during exercise according to the wearing of taping applied functional clothing. Six men in their twenties in Chungcheongnam-do were selected for the study. Resistance exercise was performed by cross-distributing the conditions of wearing and not wearing functional clothing. Resistance exercises for iEMG measurements are biceps curl, wrist curl, reverse wrist curl, kickback and push-up. iEMG measurement muscles were the biceps brachii, triceps brachii, extensor carpi ulnaris, flexor carpi radialis. During biceps curl exercise, the iEMG of triceps brachii, biceps brachii wearing condition was lower than the non-wearing condition. During kickback exercise, the iEMG of triceps brachii, extensor carpi ulnaris wearing condition was lower than the non-wearing condition. During reverse wrist curl exercise, the iEMG of extensor carpi ulnaris wearing condition was lower than the non-wearing condition. During wrist curl exercise, the iEMG of flexsor biceps brachii, carpi radialis wearing condition was lower than the non-wearing condition. During push-up exercise, the iEMG of triceps flexsor biceps brachii, carpi radialis, brachii, biceps brachii non-wearing condition was lower than the wearing condition.

• Korean journal of applied entomology
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• v.31 no.3
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• pp.314-327
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• 1992

Insecticide resistance is a serious is a serious threat to IPM, resulting in various adverse effects not to mention the loss of yield in agriculture. One approach to counter the problem is the disruption of resistance mechanisms. This can be achieved by (1) compounds which show a negative correlation with resistance at the site of action, (2) specific metabolic inhibitors which serve as synergists, or (3) a certain combination of two insecticides producing a joint action. This approach, however, requires certain precautions for the side effects may cause an increase in toxicity to mammals. Owing to the recent advances in theoretical studies on resistance management employing computer simulation and mathematical models, a few principles to reduce the risk of development of resistance have been clarified. They are helpful in designing operational strategies with regard to, for instance, insecticide doses to be applied, mode of application, and choice and nature of the insecticide(s) to be used. For restoration of insecticide susceptibility of a resistant population, reintroduction of susceptible individuals to the resistant population is feasible when certain conditions are met. Natural enemies which developed resistance to insecticides can be an important component of IPM as has been shown in the pest management in apple orchards. After all, the implementation of a successful resistance management program depends upon cooperation between different sigments of the agricutural community. Although resistance is a preadaptive phenomenon, in some cases spontaneous loss of resistance does occur without contamination by susceptible individuals. The instability of resistance in these insects implies the possible existence of a switch machanism controlling the expression of resistance gene(s). Elucidation of such a mechanism may eventually provide us with a new technical approach with which we can combat the problem of insecticide resistance.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.3
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• pp.247-253
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• 2000

We evaluated the electric properties of Bi-2223 jointed tapes processed by both resistive-and superconducting-joint methods. For resistive-joint. filler materials of wood metal Pb/Sn. In and silver paste were used whereas for superconductive-joint lap joint method was used. In the resistive joint tape. critical transport property(CCR) n-value and contact resistance were observed to be in the range of 10-85% 1-8,9. and 0.71x10$\^$-6/-0.13x10$\^$-6/Ω, respectively. depending on their filler materials. Specifically it is believed that the electrical properties of resistive joint tape are significantly related to the resistivity of filler materials. On the other hand the CCR of superconductin joint type was varied 55 to 85% with uniaxial pressure probably due to the irregular microstructure in the transition region.

• International journal of steel structures
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• v.18 no.4
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• pp.1373-1383
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• 2018

Experimental study was conducted to investigate the seismic behavior of roof joint. Eight full-scale specimens were tested considering the effects of axial force, joint height, hole shape of base plate and edge distance of concrete on the failure mode and resistance capacity of roof joint. With the increase of axial force, the hysteretic curves were fuller. The mechanical model of roof joint change from bending to shear. With the increase of joint height, the ultimate strength of roof joint decreased. If the hole shape of base plate changed from circle to loose, the slip behavior of roof joint appeared and the ultimate strength of roof joint decreased. The damage of edge concrete may occur if the edge distance of concrete was not big enough.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.217-217
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• 2009

In this study, the effect of bending strain on the transport property and critical current of lap and butt-jointed BSCCO tapes have been investigated. The samples were joined using a mechanically controlled jointing procedure. In order to ensure a uniform pressure application at the joint part, a single point contact has been devised and also to achieve a uniform thickness at the joint interface.