• Journal of the Microelectronics and Packaging Society
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• v.21 no.4
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• pp.111-115
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• 2014

Effect of dynamic electric fields on dielectric breakdown behavior in Cu damascene interconnects was investigated. Among the DC, unipolar, and bipolar pulse conditions, the longest dielectric lifetime is observed under the bipolar condition because backward Cu ion drift occurs when the direction of electric field is changed by 180 degrees and Cu contamination is prohibited as a results. Under the unipolar pulse condition, the dielectric lifetime increases as pulse frequency increases and it exceed the lifetime under DC condition. It suggests that the intrinsic breakdown of dielectrics significantly affect the dielectric breakdown in addition to Cu contamination. As the unipolar pulse width decreases, dielectric bond breakdown is more difficult to occur.

• Korean Journal of Digital Imaging in Medicine
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• v.8 no.1
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• pp.51-55
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• 2006

The effects of Asaddition in amorphous selenium(a-Se) films for digital X-ray conversion material have been studied using the moving photocarrier grating(MPG) technique. This method utilizes the moving interference pattern generated by the superposition of the two frequency shifted laser beams for the illumination of the sample. This moving intensity grating induces a short circuit current, j$_{sc}$ in a-Se:As film. The transport parameters of the sample are extracted from the grating-velocity dependent short circuit current induced in the sample along the modulation direction. The electron and hole mobility, and recombination lifetime of a-Se films with arsenic(As) additions have been obtained. We have found an Increase in hole drift mobility and recombination lifetime, especially when 0.3% As is added into a-Se film, whereas electron mobility decreases with As addition due to the defect density. The transport properties for As doped a-Se films obtained by using MPG technique have been compared with X-ray sensitivity for a-Se:As device. The fabricated a-Se(0.3% As) device film exhibited the highest X-ray sensitivity out of 5 samples.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.2
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• pp.18-22
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• 2008

The pitch and orthogonality of two-dimensional (2-D) gratings were measured using a metrological atomic force microscope (MAFM), and the measurement uncertainty was analyzed. Gratings are typical standard devices for the calibration of precision microscopes, Since the magnification and orthogonality in two perpendicular axes of microscopes can be calibrated simultaneously using 2-D gratings, it is important to certify the pitch and orthogonality of such gratings accurately for nanometrology. In the measurement of 2-D gratings, the MAFM can be used effectively for its nanometric resolution and uncertainty, but a new measurement scheme is required to overcome limitations such as thermal drift and slow scan speed. Two types of 2-D gratings with nominal pitches of 300 and 1000 nm were measured using line scans to determine the pitch measurement in each direction. The expanded uncertainties (k = 2) of the measured pitch values were less than 0.2 and 0.4 nm for each specimen, and the measured orthogonality values were less than $0.09^{\circ}$ and $0.05^{\circ}$, respectively. The experimental results measured using the MAFM and optical diffractometer agreed closely within the expanded uncertainty of the MAFM. We also propose an additional scheme for measuring 2-D gratings to increase the accuracy of calculated peak positions, which will be the subject of future study.

• Earthquakes and Structures
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• v.1 no.4
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• pp.371-390
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• 2010

Historical buildings in seismically active regions are severely damaged by earthquakes, since they certainly were not designed by the original builders to withstand seismic effects. In particular the reports after major ground motions indicate that earthquake-induced pounding between buildings may lead to substantial damage or even collapse of colliding structures. The research on structural pounding during earthquakes has been recently much advanced, although most of the studies are conducted on simplified single degree of freedom systems. In this paper a detailed pounding-involved response analysis of three adjacent structures is performed, concerning the main bodies of the "Quinto Orazio Flacco" school. The construction includes a main masonry building, with an M-shaped plan, and a reinforced concrete building, separated from the masonry one and realized along its free perimeter. By the analysis of the capacity curves obtained by suitable pushover procedures performed separately for each building, it emerges that masonry and reinforced concrete buildings are vulnerable to earthquake-induced structural pounding in the longitudinal direction. In particular, due to the geometric configuration of the school, a special case of impact between the reinforced concrete structure and two parts of the masonry building occurs. In order to evaluate the pounding-involved response of three adjacent structures, in this paper a numerical procedure is proposed, programmed using MATLAB software. Both a non-linear viscoelastic model to simulate impact and an elastic-perfectly plastic approximation of the storey shear force-drift relation are assumed, differently from many commercial softwares which admit just one non-linearity.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.4
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• pp.66-72
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• 1994

For the reliable prediction of maneuverability of a ship, lots of captive model tests have been carried out for over 10 years. But the parameters appearing in the mathematical model are so versatile and showing complex characteristics, and it is still hard to establish the useful formulae that we can adopt directly in the design stage. In this paper, the most important parameters in the mathematical model. i.e.($1-\omega_P$) the effective wake fraction at propeller, and $\delta_R(\beta_R)$), the effective rudder inflow angles are investigated by the captive model tests at the circulating water channel. The model is tested at designed speed and at low speed, and the drafts at both full load and ballast load conditions are taken. Propeller thrusts and rudder normal forces are measured at the given drift angle and propeller revolution. These forces are used for the analysis of the effective flow velocity or flow direction, to the propeller or rudder.

• Journal of Astronomy and Space Sciences
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• v.36 no.2
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• pp.61-68
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• 2019

We have investigated the variations of sporadic E (Es) layer using the measurements of digisondes at Icheon ($37.14^{\circ}N$, $127.54^{\circ}E$, IC) and Jeju ($33.4^{\circ}N$, $126.30^{\circ}E$, JJ) in 2011-2018. The Es occurrence rate and its critical frequency (foEs) have peak values in summer at both IC and JJ in consistent with their known seasonal variations at mid-latitudes. The virtual height of the Es layer (h'Es) during equinox months is greater than that in other months. It may be related to the similar variation of meteor peak heights. The h'Es shows the semidiurnal variations with two peaks at early in the morning and late in the afternoon during equinoxes and summer. However, the semi-diurnal variation is not obvious in winter. The semi-diurnal variation is generally thought to be caused by the semi-diurnal tidal variation in the neutral wind shear, whose measurements, however, are rare and not available in the region of interest. To investigate the formation mechanism of Es, we have derived the vertical ion drift velocity using the Horizontal Wind Model (HWM) 14, International Geomagnetic Reference Field, and Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Radar-00 models. Our results show that h'Es preferentially occur at the altitudes where the direction of the vertical ion velocity changes. This result indicates the significant role of ion convergence in the creation of Es.

• Journal of Ocean Engineering and Technology
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• v.34 no.6
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• pp.394-405
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• 2020

To assess the station-keeping performance of floating structures in the Arctic region, the ice load should be considered along with other environmental loads induced by waves, wind, and currents. However, present methods for performance evaluation in the time domain are not effective in terms of time and cost. An ice load generation module is proposed based on the experimental data measured at the KRISO ice model basin. The developed module was applied to a time domain simulation. Using the results of a captive model test conducted in multiple directions, the statistical characteristics of ice loads were analyzed and processed so that an ice load corresponding to an arbitrary angle of the structure could be generated. The developed module is connected to commercial dynamic analysis software (OrcaFlex) as an external force input. Station-keeping simulation in the time domain was conducted for the same floating structure used in the model test. The mooring system was modeled and included to reflect the designed operation scenario. Simulation results show the effectiveness of the proposed ice generation module and its application to station-keeping performance evaluation. Considering the generated ice load, the designed structure can maintain a heading angle relative to ice up to 4°. Station-keeping performance is enhanced as the heading angle conforms to the drift direction. It is expected that the developed module will be used as a platform to verify station-keeping algorithms for Arctic floating structures with a dynamic positioning system.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.208-222
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• 2021

Managing with the presence of sea ice is the primary challenge in the operation of floating platforms in the Arctic region. It is widely accepted that offshore structures operating in Arctic conditions need station-keeping methods as well as ice management by icebreakers. Dynamic Positioning (DP) is one of the station-keeping methods that can provide mobility and flexibility in marine operations. The presence of sea ice generates complex external forces and moments acting on the vessel, which need to be counteracted by the DP system. In this paper, an icevaning control algorithm is proposed that enables Arctic offshore vessels to perform DP operations. The proposed icevaning control enables each vessel to be oriented toward the direction of the mean environmental force induced by ice drifting so as to improve the operational safety and reduce the overall thruster power consumption by having minimum external disturbances naturally. A mathematical model of an Arctic offshore vessel is summarized for the development of the new icevaning control algorithm. To determine the icevaning action of the Arctic offshore vessel without any measurements and estimation of ice conditions including ice drift, task and null space are defined in the vessel model, and the control law is formulated in the task space. A backstepping technique is utilized to handle the nonlinearity of the Arctic offshore vessel's dynamic model, and the Lyapunov stability theory is applied to guarantee the stability of the proposed icevaning control algorithm. Experiments are conducted in the ice tank of the Korea Research Institute of Ships and Ocean Engineering to demonstrate the feasibility of the proposed approach.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4D
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• pp.561-567
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• 2008

In this study, shoreline change was analyzed by RTK-GPS and advanced airborne LiDAR survey. For extraction of coastline, first of all, tide correction was conducted at all RTK-GPS points through the comparing with the corresponding tidal height, and cross section providing coastline was produced using Autocad Civil3D program. Comparing with two results of RTK-GPS (first, 29 Aug 2007; second, 6 Oct 2007) surveys, coastline of the first result had been decreased about 21m compare with that of the second. And it was also demonstrated that the length of coastline by the first RTK-GPS was 15m shorter than that by the airborne LiDAR survey (Dec. 2006). In addition, we recoquized that the erosion appeared in the top right-hand (dock area); the sediment in the bottom left-hand (Chosun beach area) of the Haeundae beach. As a result, therefore, it was learned that artificial sand filling for beach open and natural effects such as a typhoon, current drift, wind direction gave cause for area changes and coastline.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.5
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• pp.320-331
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• 2023

In this study, a model test was conducted using the soft-mooring technique to evaluate the added resistance of the ship in waves. The study also examined the specific factors that should be considered during the soft-mooring test. The main purpose of soft-mooring is to prevent drifting caused by waves by providing horizontal restoring forces. However, it can also create undesired restoring forces in the vertical direction. Therefore, we examined the restoring force of the ship's 6-DOF motion based on the arrangement of the soft-mooring and the height of the mooring connection point. We also checked the corresponding resonance period and drift distance. The soft-mooring test was conducted twice, once with self-propulsion and once without self-propulsion, allowing us to review the advantages and disadvantages of each test technique. The main parameters measured in these model tests were 6DOF motion and added resistance on the ship. We compared these measurements obtained from two different techniques (with and without self-propulsion). Additionally, we also compared the measurements based on the types of measuring sensors used (2D load cells on FP, AP, and 1D load cells on each mooring line) as well as the height of the mooring connection point.