• Land and Housing Review
• /
• v.12 no.3
• /
• pp.87-96
• /
• 2021

Korea has begun to use the Helical pile prevalent in Europe. Korea hasn't still set up the standard design criteria on Helical pile due to the lack of relevant researches. In this regard, this study carried out static and dynamic load tests on Helical pile and then performed reliability analysis including the previous research data. The results present that Road bridge design standard design criteia for pre-boring pile with regard to Modified Davisson method showed good reliability and consistency because Resistance bias factor of this design criteria approached '1.0' and Design C.O.V. showed 'low' level.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.6C
• /
• pp.367-377
• /
• 2008

As part of study to develop LRFD (Load and Resistance Factor Design) codes for foundation structures in Korea, resistance factors for static bearing capacity of driven steel pipe piles were calibrated in the framework of reliability theory. The 57 data sets of static load tests and soil property tests conducted in the whole domestic area were collected and these load test piles were sorted into two cases: SPT N at pile tip less than 50, SPT N at pile tip equal to or more than 50. The static bearing capacity formula and the Meyerhof method using N values were applied to calculate the expected design bearing capacities of the piles. The resistance bias factors were evaluated for the two static design methods by comparing the representative measured bearing capacities with the expected design values. Reliability analysis was performed by two types of advanced methods: the First Order Reliability Method (FORM), and the Monte Carlo Simulation (MCS) method using resistance bias factor statistics. The target reliability indices are selected as 2.0 and 2.33 for group pile case and 2.5 for single pile case, in consideration of the reliability level of the current design practice, redundancy of pile group, acceptable risk level, construction quality control, and significance of individual structure. Resistance factors of driven steel pipe piles were recommended based on the results derived from the First Order Reliability Method and the Monte Carlo Simulation method.

• Tribology and Lubricants
• /
• v.38 no.6
• /
• pp.274-280
• /
• 2022

There is a problem that semiconductor probe pin has a short lifespan. In order to solve this problem, Ti having excellent conductivity was doped to tetrahedral amorphous carbon (ta-C) having excellent hardness and abrasion resistance. This experiment was planned through the Taguchi robust design to determine the effect of the control factor of the ta-C:Ti coating film. The effect and contribution of control factors such as Unbalanced Magnetron Sputter(UBM) discharge current, arc discharge current, temperature, and bias voltage on ta-C:Ti characteristics were analyzed from the perspective of electrical and mechanical characteristics. The UBM discharge current was set to 4, 6, and 8 A. The main control factor of thickness and resistance is the UBM discharge current, and the thickness increased and the resistance decreased as the current increased. The decrease in resistance is due to the increase in the Ti content of the ta-C:Ti coating film. The arc discharge current was set to 60, 80, and 100 A. The main control factor of hardness and wear is the arc discharge current, and as the current rises, the hardness increases and the wear area decreases. This is due to the increased ta-C content of the ta-C:Ti coating film. Since resistance and wear are important for Probe Pin, the optimal level is set from the perspective of resistance and wear and a confirmation experiment is conducted.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.1C
• /
• pp.19-29
• /
• 2008

As a part of study to develop LRFD (Load and Resistance Factor Design) codes for foundation structures in Korea, reliability analyses for driven steel pipe piles are performed and the target reliability indices are selected carefully. The 58 data sets of static load tests and soil property tests conducted in the whole domestic area were collected and analyzed to determine the representative bearing capacities of the piles. The static bearing capacity formula and the Meyerhof method using N values are applied to calculate the expected design bearing capacity of the piles. The resistance bias factors were evaluated for the two static design methods by comparing the representative bearing capacities with the design values. Reliability analysis was performed by two types of advanced methods: First Order Reliability Method (FORM), and Monte Carlo Simulation (MCS) method using resistance bias factor statistics. The static bearing capacity formula exhibited relatively small variation, whereas the Meyerhof method showed relatively high inherent conservatism in the resistance bias factors. Reliability indices for safety factors in the range of 3 to 5 were evaluated respectively as 1.50~2.89 and 1.61~2.72 for both of the static bearing capacity formula and the Meyerhof method. The target reliability indices are selected as 2.0 and 2.33 for group pile case and 2.5 for single pile case, based on the reliability level of the current design practice and considering redundancy of pile group, acceptable risk level, construction quality control, and significance of individual structure.

• Progress in Superconductivity and Cryogenics
• /
• v.16 no.4
• /
• pp.17-20
• /
• 2014

We have investigated the effect of temperature and bias current on the stability of the inverse spin-switch effect in Permalloy(Py)/Nb/Permalloy pseudo spin-valves. The inverse spin-switch operates between two orientations of the ferromagnetic moments of Py layers; parallel (ON) and antiparallel-domain (OFF) state. Measuring time scans of the resistance changes between the ON and OFF state, ${\Delta}R_{ON-OFF}$, while alternating magnetic fields between the two states at various temperatures and bias currents, revealed that enhancement of ${\Delta}R_{ON-OFF}$ is a key factor to achieve successful operation of superconducting spin switch.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.59 no.11
• /
• pp.2038-2042
• /
• 2010

In this paper, we confirmed the thermal & optical properties for improving the heat transfer coefficient by changing the via hole size and in FR4 PCB with the same area. Osram 1W power LED Package (Golden Dragon) was used and the K-factor which is relative constant between LED junction temperature and forward bias was measured with power source meter(KEITHLEY 2430) to measure the thermal resistance from PCB configuration. As results, thermal resistance in metal PCB came out to the lowest as $26 [^{\circ}C/W]$ and thermal resistance in FR4 PCB without via-holes emerged as the highest as $69 [^{\circ}C/W]$. However thermal resistance of FR4 PCB could have decreased until $32[^{\circ}C/W]$ in 0.6 mm by using the via hole. Also, the luminous flux could have improved, too.

• Korean Journal of Materials Research
• /
• v.26 no.10
• /
• pp.556-560
• /
• 2016

Using current-voltage (I-V) and capacitance-voltage (C-V) measurements, the electrical properties of Au and Cu Schottky contacts to n-Ge were comparatively investigated. Lower values of barrier height, ideality factor and series resistance were obtained for the Au contact as compared to the Cu contact. The values of capacitance showed strong dependence on the bias voltage and the frequency. The presence of an inversion layer at the interface might reduce the intercept voltage at the voltage axis, lowering the barrier height for C-V measurements, especially at lower frequencies. In addition, a higher interface state density was observed for the Au contact. The generation of sputter deposition-induced defects might occur more severely for the Au contact; these defects affected both the I-V and C-V characteristics.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.3 no.1
• /
• pp.229-234
• /
• 1999

We analyzed the reliability characteristics in platinum schottky diodes with variations of n-type silicon substrates concentrations and temperature variations of measurements. The parameters of reliability measurement analysis are saturation current. turn-on voltage and ideality factor in the forward bias, the breakdown voltage in the reverse bias with device shapes. The shape of devices are square type and long rectangular type for edge effect. As a result, we analyzed that the forward turn-on voltage, barrier height, dynamic resistance and reverse breakdown voltage were decreased but ideality factor and saturation current were increased by increased concentration in platinum and n-silicon junction parts. In measurement temperature(RT, $50^{\circ}C$, $75^{\circ}C$), the extracted electrical parameter values of reliability characteristics were increased at the higher temperature under the forward and reverse bias. The long rectangular type devices were more decreased than the square type in reverse breakdown voltage by tunneling effects of edge part.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.11a
• /
• pp.65-65
• /
• 2009

High temperature silicon carbide Schottky diode was fabricated with Au deposited on poly 3C-SiC thin film grown on p-type Si(100) using atmospheric pressure chemical vapor deposition. The charge transport mechanism of the diode was studied in the temperature range of 300 K to 550 K. The forward and reverse bias currents of the diode increase strongly with temperature and diode shows a non-ideal behavior due to the series resistance and the interface states associated with 3C-SiC. The charge transport mechanism is a temperature activated process, in which, the electrons passes over of the low barriers and in turn, diode has a large ideality factor. The charge transport mechanism of the diode was analyzed by a Gaussian distribution of the Schottky barrier heights due to the Schottky barrier inhomogeneities at the metal-semiconductor interface and the mean barrier height and zero-bias standard deviation values for the diode was found to be 1.82 eV and $s_0$=0.233 V, respectively. The interface state density of the diode was determined using conductance-frequency and it was of order of $9.18{\times}10^{10}eV^{-1}cm^{-2}$.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.12
• /
• pp.61-73
• /
• 2007

As a part of Load and Resistance Factor Design(LRFD) code development in Korea, in this paper an intensive reliability analysis was performed to evaluate reliability levels of the two static bearing capacity methods for driven steel pipe piles adopted in Korean Standards for Structure Foundations by the representative reliability methods of First Order Reliability Method(FORM) and Monte Carlo Simulation(MCS). The resistance bias factors for the two static design methods were evaluated by comparing the representative measured bearing capacities with the design values. In determination of the representative bearing capacities of driven steel pipe piles, the 58 data sets of static load tests and soil property tests were collected and analyzed. The static bearing capacity formula and the Meyerhof method using N values were applied to the calculation of the expected design bearing capacity of the piles. The two representative reliability methods(FORM, MCS) based computer programs were developed to facilitate the reliability analysis in this study. Mean Value First Order Second Moment(MVFOSM) approach that provides a simple closed-form solution and two advanced methods of FORM and MCS were used to conduct the intensive reliability analysis using the resistance bias factor statistics obtained, and the results were then compared. In addition, a parametric study was conducted to identify the sensibility and the influence of the random variables on the reliability analysis under consideration.