• The Journal of Korea Robotics Society
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• v.14 no.3
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• pp.221-227
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• 2019

This paper studies an effect of vibration on twisted string actuation inside conduit at high curvature angles. In our previous work. we have mentioned that twisted string actuators can be used to transmit power even at significant curvature angles of the conduit. However, several undesirable effects, namely pull-back, hysteresis, and chattering, were present during actuation due to friction between strings and the internal sheath of the conduit. This paper reports the results of experimental study on effects of vibration on twisted string actuation inside curved conduits. We have demonstrated that applying vibration generated near natural frequency of the system during the stages of twisting and untwisting cycles helped reduce pull-back and hysteresis and increase string contraction. In case when sheath was deflected by $180^{\circ}$ under a constant load of 3 kg, we were able to achieve over 40% decrease in pull-back and 30% decrease in hysteresis, compared with no vibration case.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.698-703
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• 2007

In this paper, a novel impedance tuner using a directional coupler is proposed. The design topology is analyzed by signal flow graph(SFG) and shows advantages compared with conventional single and double stub methods from the view points of easy implementation and wide tuning range, respectively. This impedance tuner consists of ten switches and its $2^{10}$ tuning points are distributed uniformly on the whole Smith chart. The measured maximum magnitude of the reflection coefficient is 0.9. And the fabricated impedance tuner has a wide bandwidth from 1.8 to 2.2 GHz. Using this impedance tuner, we did a load-pull measurement of a power transistor.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.687-691
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• 2011

In this paper, we design an 8-bit eSuse OTP (one-time programmable) memory in consideration of EM (electro-migration) and eFuse resistance variation based on a $0.18{\mu}m$ generic process, which is used for an analog trimming application. First, we use an external program voltage to increase the program power applied an eFuse. Secondly, we apply a scheme of precharging BL to VSS prior to RWL (read word line) activation and optimize read NMOS transistors to reduce the read current flowing through a non-programmed cell. Thirdly, we design a sensing margin test circuit with a variable pull-up load out of consideration for the eFuse resistance variation of a programmed eFuse. Finally, we increase program yield of eFuse OTP memory by splitting the length of an eFuse link.

• Journal of the Korean Geotechnical Society
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• v.33 no.11
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• pp.35-43
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• 2017

In this study, the pull-out resistance behavior of the anchor with the bump type resistors at the anchor body was experimentally investigated. In the model tests, the pull-out resistance was measured by pulling out the anchor at a constant speed. Anchor body was installed in the center of the circular sand tank. Pull-out tests were conducted for 10 conditions. The anchor type (existence of the resistor), the friction conditions of the anchor body surface ($1/3{\phi}$, $2/3{\phi}$, ${\phi}$), the bump type resistor set number (1set, 2set, 4set), and the height of resistors (0.05d, 0.10d, 0.20d) were varied. The load-displacement relationship for each conditions was measured during the pull-out tests at a constant speed (1 mm/min). Maximum pull-out length was 80 mm. As a result, the pull-out behavior of the friction type anchor and the expansion type anchor was different. As the number of resistor increased, the maximum pull-out resistance increased and the residual pull-out resistance ratio increased significantly, which were at 171~591 percent larger than that of the friction type anchor.

• Journal of Navigation and Port Research
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• v.28 no.1
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• pp.37-41
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• 2004

In this paper, a reflector type frequency doubler for local oscillator at 24GHz is designed and fabricated with ne71300-N MESFET. Optimum source and load impedances are decided through a multiharmonic load pull simulation technique. A conversion gain can be improved using the reflector and fundamental and third harmonics are well suppressed with open stub of $\lambda$/4 length Measured results show output power at 0dBm of input power is -3.776dBm, conversion gain 0.736dB, harmonic suppression 41.064dBc, respectively.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.896-901
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• 2009

A Soil Nail is a structural element which provides load-transfer to the ground in excavation reinforcement applications. The nail may simply consist of a steel tendon, but most commonly the tendon is encapsulated in a cement grouted body to provide corrosion protection and improved load- transfer to the ground. For temporary excavation support in a congested urban area, the steel bar of Soil Nails should be removed to get permission of the private land to install Soil Nails. Several removable nail systems were developed and evaluated by pull-out load tests. The Soil Nail pull-out tests were performed on five nails installed in soft and hard rock at a 00 housing-redevelopment area in seoul. Two nails are plastic socket type and two are complex socket type mixed steel and plastic. The nail was 0.1mm in diameter, 4m long. In this study verification tests, and steel bar removing tests of plastic socket type nails and complex socket type nails were performed and presented.

• Steel and Composite Structures
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• v.48 no.5
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• pp.531-545
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• 2023

Composite dowels are implemented as a powerful alternative to headed studs for the efficient combination of Ultra High-Performance Concrete (UHPC) with high-strength steel in novel composite structures. They are required to provide sufficient shear resistance and ensure the transmission of tensile forces in the composite connection in order to prevent lifting of the concrete slab. In this paper, the load bearing capacity of puzzle-shaped and clothoidal-shaped dowels encased in UHPC specimen were investigated based on validated experimental test data. Considering the influence of the embedment depth and the spacing width of shear dowels, the characteristics of UHPC square plate on the load bearing capacity of composite structure, 240 numeric models have been constructed and analyzed. Three artificial intelligence approaches have been implemented to learn the discipline from collected experimental data and then make prediction, which includes Artificial Neural Network-Particle Swarm Optimization (ANN-PSO), Adaptive Neuro-Fuzzy Inference System (ANFIS) and an Extreme Learning Machine (ELM). Among the factors, the embedment depth of composite dowel is proved to be the most influential parameter on the load bearing capacity. Furthermore, the results of the prediction models reveal that ELM is capable to achieve more accurate prediction.

• 전자공학회논문지 IE
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• v.44 no.3
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• pp.42-50
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• 2007

In this paper, elastic and plastic adhesion index was very important in deciding adhesive characteristics and varying elastic and plastic index, dimensionless load and pull-off force were analyzed and simulated. Finally, using AFM, experimental surface roughness parameters of substrates and pull-off force between tip and substrates were produced. Using these values, pull-off forces were calculated and were compared with experimental pull-off forces. Through simulation and experiment, it was found that interaction of asperity also had very important influence on adhesive contact.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.1324-1326
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• 2000

This paper proposes a Current-Fed Push Pull type DC-DC converter using LCCC Resonant circuit and Zero Voltage Switching function to reduce turn on and off loss at the switching instants. This paper have the advantage which is able to operating safely in load short, because of DC reactor is connected with resonance reactor in order to supply a fixed current with low ripple from DC Power supply. The capacitor ($C_1$, $C_2$) connected in switch are common using as resonance capacitor and ZVS capacitor. The analysis of the proposed Current-Fed Push Pull type DC-DC converter is generally described by using normalized parameter, and we have evaluated characteristic values which is needed to design a circuit. We confirm a rightfulness theoretical analysis by comparing a theoretical values and experimental values obtained from experiment using MOSFET as switching devices.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.11
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• pp.1034-1046
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• 2011

In this paper, a design and fabrication of 40 W power amplifier for the X-band using load-pull measurement of GaN HEMT chip are presented. The adopted active device for power amplifier is GaN HEMT chip of TriQuint company, which is recently released. Pre-matched fixtures are designed in test jig, because the impedance range of load-pull tuner is limited at measuring frequency. Essentially required 2-port S-parameters of the fixtures for extraction optimal input and output impedances is obtained by the presented newly method. The method is verified in comparison of the extracted optimal impedances with data sheet. The impedance matching circuit for power amplifier is designed based on EM co-simulation using the optimal impedances. The fabricated power amplifier with 15${\times}$17.8 $mm^2$ shows the efficiency above 35 %, the power gain of 8.7~8.3 dB and the output power of 46.7~46.3 dBm at 9~9.5 GHz with pulsed-driving width of 10 usec and duty of 10 %.