• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.43-48
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• 2022

In order to evaluate the seismic performance of the modular expansion joint known for its large expansion allowance and remarkable durability, this study conducts seismic response analysis and seismic simulation test. The bridge selected for the seismic response analysis is a cable stayed bridge with main span length of 1,000m. Three artificial earthquake were generated with respect to the design response spectra of the Korean Standards (KS), AASHTO LRFD and Eurocode, and applied to the selected bridge. The seismic simulation tests reproduced the artificial earthquakes using dynamic hydraulic actuators in the longitudinal and transverse directions. The test results verified the durability and safety of the expansion joint in view of its seismic behavior since abnormal behavior or failure of the expansion joint was not observed when the artificial earthquake waves were applied in the longitudinal direction, transverse direction and both directions.

• Journal of the Korean Geotechnical Society
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• v.22 no.3
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• pp.37-43
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• 2006

An analytical solution method capable of determining the geometric configuration and developed tensile forces of mooring lines associated with fixed plate/pile or drag anchors has been developed. The solution method, satisfying complete equilibrium conditions, is capable of analyzing multi-segmented mooring lines that can consist of either chains, cables, or synthetic wires embedded in layered seafloor soils. The solution method utilizes a systematic iterative search method based on specific boundary conditions. This paper describes the principles associated with the development of the solution for the mooring line analysis. Comparisons of predictions with results from a series of field tests of mooring lines on various types of drag anchors are also described. Comparisons include the tension in anchor, the length of mooring line on the bottom, and the angle of mooring line at the water surface buoy. The results indicate that the analytical solution method is capable of predicting the behavior of mooring lines with high degree of accuracy.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.38 no.3
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• pp.209-216
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• 2002

How to estimate the shape of trawl net and ropes of a midwater trawl on full scale was described by implementing a three-dimensional semi-analytic treatment of a towing cable system with the field experiments obtained with the Scanmar system. The shape of trawl net from wingend to the beginning of codend was assumed to be of form $\chi$$^2$/ae$^2$+ y$^2$/be$^2$=(z - c)$^2$/c$^2$, and that of the ropes attached behind otter boards be of form yr = $A\chi$rB. In case of warp length 300m long, the volume of trawl net, the ratio of net height to net width at the mouth of the trawl net, and the inclination angle of float rope were estimated according to the change of towing speed. The volume and the distance between wingtips were increased with increasing towing speed. And the inclination angle of float (or ground) rope was slightly decreased with increasing towing speed.

• Journal of the Korean Association of Geographic Information Studies
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• v.6 no.1
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• pp.85-97
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• 2003

This study was aimed at suggest a proper logging method of mountain forest using geographic information system(GIS) based on digital terrain model(DTM) in the National Forest at Mt. Kumsan in Namhae-gun, Gyungsangnam-do, which has about 2,948 ha in area. The areal percentage of 201 to 250m in the elevation was about 15.5%, elevation of 251 to 300m was 14.5%, and 78.75% for higher than 400m. The accumulated areal percentage of below 30% in the gradient was 17.2%, and 81.0% for steeper than 60%. The area for tractor skidding was 17.2%(511.7ha), the area for tractor attached winch skidding was 63.8%(1,896.3ha) and 18.4%(545.5ha) for cable yarding. It is important to choose the proper logging machines for timber harvesting. In general, the selection of logging operation system was affected several major environmental factors like as terrain conditions(slope gradient, slope length) and stand factors. The rate of middle slope gradients in terrain conditions showed higher than that of steep slope gradients in this area. Therefore, it considered that the logging operation system in this area could apply to tractor+winch operating machine according to terrain conditions.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.4
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• pp.457-471
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• 2015

A domestic cutterhead with the diameter of 3.6 m was designed and manufactured in this study. Then, it was attached to an existing earth-pressure balanced shield TBM to excavate a cable tunnel with the length of 1,275 m. Especially, the procedures for TBM cutterhead design and its corresponding performance prediction were also summarized. From field data analyses of the refurbished shield TBM, its maximum advance rate was recorded as 14.4 m/day. Penetration depths of disc cutters were found to be approximately 4 mm/rev, which is equal to the maximum penetration depth designed for the strongest rock strength condition in the target tunnel. Every TBM operating thrust and cutter normal force during TBM driving was much smaller than their corresponding maximum capacities. When cutter acting forces recorded in the field were analyzed, their prediction errors by the CSM model were very high for weak rock conditions. In addition, rock strength showed very close relationships with cutter normal force and penetration depth.

• Journal of Korean Society of Forest Science
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• v.106 no.2
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• pp.204-212
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• 2017

Soil disturbance caused by timber harvesting is widely recognized as a potential threat to forest utilization. The degree and extent of soil disturbance is believed to vary with respect to harvesting methods and logging machines. This study has conducted to assess the degree of soil disturbance associated with ground-based cut-to-length (GC) and cable yarding with whole tree (CW) harvesting methods. Soil disturbance was classified using a visual assessment of harvest unit. The properties of soils in different disturbance levels were also evaluated to understand the influence of timber harvesting on soil structure with soil core sampling method. The deep disturbance and soil compaction were observed in sites by 48% and 23% through harvesting areas for GC and CW logging methods, respectively. The results showed that logging machine and number of machine passage had significant influences on soil bulk density and porosity. Soil disturbance types such as rutted, slash cover, and compact were influenced by equipment travel trends in a GC method.

• Progress in Medical Physics
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• v.14 no.2
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• pp.81-89
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• 2003

The dose distributions of designed Ir-192 micro-source were investigated by dose computations which were accomplished by employing shape of encapsule material and thickness of the source for self-absorption. The computation dose derived from air-kerma rate (S$_{k}$ ) and dose rate constant (Λ) includes the anisotropy of dose distribution around the source. We got the dose rate constants in a water medium is 1.154 cGy h$^{-1}$ U$^{-1}$ . The size of the source was 0.5 mm in diameter and 3.5 mm in length and it was encapsuled in 1.1 mm$\Phi$${\times}$5.5 mm of stainless steel sealed with 0.3 mm of filter thickness. The tissue dose of reference point at 1.0 cm radial distance of the source axis was delivered 1.154 Uh$^{-1}$ (1.3167${\times}$10$^{-3}$ cGy/mCi-sec) from the S$_{k}$ 4.108U/mCi of Ir-192 source. The filtration effect contributed to air-kerma strength as exponential filtering effect of 86.2% in total attenuation, but self-absorption was 88.4% from radial dose distributions. In particular, the dose attenuations showed a rapid anisotropic distributions as 56% of reference dose along to $\pm$10 degrees from the tip of source axis and 50% for of that to source-cable direction. We persist in use the large diameter of applicator will avoid the dose anisotropy by the filtered attenuation effects along the axis of Ir-192 micro-source.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1040-1049
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• 2006

A design method for minimizing transmission loss of a broadband right-angle transition from a coaxial cable to a microstrip line is presented. The right-angle transition has been widely used where printed circuit applications need to be fed from behind the ground plane using coaxial line. To obtain the minimized transmission loss over the whole operating frequency range of the transition, design parameters such as ground aperture and probe diameters, ground aperture offset, and stub length are optimized using a commercial electromagnetic simulation software. Results are presented for the optimum right-angle transition from an SMA connector to a microstrip line on common reinforced 0.787 mm thick PTFE substrates. Measurements of a fabricated transition show that reflection coefficient is less than -22 dB and insertion loss is less than 0.45 dB over $0.05{\sim}20GHz$.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.1
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• pp.1-8
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• 2002

The high frequency ultrasonic transducers using polyvinyliden fluoride(PVDF) and polyvinylidene fluoride trifluorethyylene(P(VDF-TrFE)) were developed. The characteristics of fabricated high frequency ultrasonic transducer such as beam diameter, high frequency ultrasonic detection field and amplitude of the first pulse echo signal from the test target in the water were analyzed. The high frequency ultrasonic detection field was affected by the length of coaxial cable between high frequency transducer and ultrasonic pulser/receiver. As the size of the test target increased, the high frequency detection field decreased and the amplitude of a reflection signal increased. The peak amplitude of the first pulse echo signal of P(VDF-TrFE) transducer was higher than that of PVDF transducer. The high frequency ultrasonic detection field of PVDF transducer was wider than that of P(VDF-TrFE) transducer. With C-scan testing, the developed high frequency ultrasonic transducer could detect the 30 to $100{\mu}m$ of hydrogen induced crack of steel specimen by C-scan testing.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.4
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• pp.474-482
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• 2021

An average of two to three typhoons that occur in the Philippines or Taiwan pass through Korea each year owing to the influence of the geographical location and western winds. Because Jinhae Bay is known as Korea's representative typhoon refuge, it is filled with ships during typhoons and later becomes saturated with ships anchored to the surrounding routes. If a strong wind drags an anchored ship, a collision accident may occur because of the short distance between the ships. Therefore, a systematic anchoring safety management of Jinhae Bay is required. In this study, the minimum wind speeds of a dragging anchor based on the water depths of Jinhae Bay anchorages were investigated. When 7-9 shackles were given, the minimum wind speeds were 48-63, 46-61, and 39-54 knots at depths of 20, 35, and 50 m, respectively. As the water depth increased, the length of the cable laid on the sea bed became shorter than 5 m owing to the external force, and the minimum wind speed showed a significant difference of 4-8 knots. In addition, ships with high holding power anchors (AC-14 type) had higher minimum wind speeds than ships with conventional anchors (ASS type). Finally, it was confirmed that at a depth of 50 m, dragging easily occurred even when a high holding power anchor was applied.