• Journal of Ocean Engineering and Technology
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• v.38 no.1
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• pp.30-42
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• 2024

This study examined the jack-up spudcan penetration for a new type of offshore wind substructure newly proposed using the jack-up concept to reduce construction costs. The jack-up spudcan for offshore wind turbines should be designed to penetrate a stable soil layer capable of supporting operational loads. This study evaluated multi-layered soil conditions using centrifuge tests: loose sand over clay and loose sand-clay-dense sand. The penetration resistance profiles of spudcan recorded at the centrifuge tests were compared with the ISO and InSafeJIP methods. In the tests, a spudcan punch-through effect slightly emerged under the sand-over-clay condition, and a spudcan squeezing effect occurred in the clay-over-sand layer. On the other hand, these two effects were not critically predicted using the ISO method, and the InSafeJIP result predicted only punch-through failure. Nevertheless, ISO and InSafeJIP methods were well-matched under the conditions of the clay layer beneath the sand and the penetration resistance profiles at the clay layer of centrifuge tests. Therefore, the ISO and InSafeJIP methods well predict the punch-through effect at the clay layer but have limitations for penetration resistance predictions at shallow depths and strong stratum soil below a weak layer.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• v.4 no.1
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• pp.44-50
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• 2001

Existing surface defects in structural members often act as sites of fatigue crack initiation, and if undetected, these cracks may grow through the thickness of the member, leading to catastrophic failure of the structure. Thus, in-service monitoring of fatigue cracks through reliable and effective nondestructive techniques is an important ingredient in the leak-before-break (LBB) design and safe operation of defects critical structures. An advanced, waveform-based, acoustic emission (AE) technique has been used in this paper to study the characteristics of the signals emanating from the initiation, growth and through-the -thickness penetration of surface fatigue crack in a 6061 aluminum plate. The goal of this experimental study is to determine whether the evolution of the fatigue crocks could be identified from the properties of the waveforms produced during the tests. The AE waveform signals detected at different stages of crack growth was found to have different temporal and spectral characteristics. The data analysis technique presented here can be applied to real-time monitoring of the initiation and propagation of fatigue cracks in structural components.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.90-99
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• 2002

The main purpose of this study lies on the development of micro dilution tunnel based on the Sierra Dilution chamber model. As a primary examination, characteristics of flow and temperature distributions during the steady dilution process in dilution chamber are observed with numerical analysis. The penetration of dilution air through porous tube as well as wall temperature and temperature gradient inside porous tube are examined. The thermophoretic velocity in terms of temperature behavior inside porous tube are defined and examined. Based on the ratio of penetration and thermophoretic velocities, all part of porous tube are shown to be safe from the particulate depositions. However, The inlet portion of porous tube in addition to the portion of impinging of dilution air are marginally safe from the particulate depositions. Generally the safer design against particulate deposition is required in provision f3r steady dilution process and for transient process as well.

• Korean Journal of Food Science and Technology
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• v.30 no.6
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• pp.1327-1332
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• 1998

The optimum thermal condition of retort Biji product was determined by heat penetration curve, aerobic bacteria count and sensory test. Retort Biji showed a simple logarithmic heating curve regardless of solid content. Heating time was a $26{\sim}27$ min until Fo value reached 9 min and the amount of microorganism in the Biji product sterilized for 26 min at $121^{\circ}C$ were decreased to $10^{-4}\;CFU/g$, indicating the safe range for retort product. The rate of heat penetration was reduced as solid content and size of product were increased, whereas sterilization temperature and initial temperature of product influenced the heat penetration curve. Sensory scare indicated that there was no significant difference in color, flavor, and appearance among different thermal processes. However, Biji product sterilized at $121^{\circ}C$ showed the highest score in overall preference value.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.71-74
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• 2008

For reinforcing the overturn of concrete pole instituted in slope ground and weak ground, in this paper, develop the reinforcing installation. The installation increase penetration depth and effect of increasing the penetration depth is verified by experimental paper of Lim, jong suk(2004). In this research, through the experiment of bending test using the reinforcing installation, evaluate the performance. In the result of experiment, concrete pole behave elastically in design load and all sample are safe up to failure load.

• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.19-25
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• 2013

The joining methods of steel structures of gas facilities, bridges, ships etc. by welding are composed mostly of T-type or cruciform fillet welding and full penetration or partial penetration according to the uses and the shape of the structures. In this study, it was examined the characteristics of fatigue crack according to penetration depth in relation to material thickness in the cruciform fillet welded joints. From the results, it was investigated the safe design stresses within the range of infinite life. When the LOP length is long the range of infinite life is small with root failure and when the LOP length is short the range of infinite life is large with teo failure. For the specimen of material thickness, 20mm welded by 3 pass compared with 10mm, 15mm welded by 2 pass, the fatigue strength and the range of infinite life was more improved by increasing of notch toughness from formation of micro-ferrite acicular structure.

• Journal of Ocean Engineering and Technology
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• v.31 no.6
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• pp.397-404
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• 2017

In this study, an anchor dragging simulation was performed using the CEL method to design a rock-berm, which is a protection method for submarine cables. In order to simulate an anchor drag, preliminary simulations were first performed to determine the initial anchor penetration depth, anchor drag velocity, drag angle, and distance between the anchor and rock-berm. Based on the preceding simulation results, a safe rock-berm design for protecting the submarine cables was simulated to calculate the anchor penetration depth by the anchor dragging. As a result, the penetration depth of the anchor was found to be shallower in a hard seabed, and the penetration depth was deeper in a soft seabed, the height of the rock-berm was determined according to the physical properties of the seabed.

• Proceedings of the Korean Geotechical Society Conference
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• 2007.09a
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• pp.611-622
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• 2007

In the design and construction of the coastal/offshore structures, it is very important to evaluate the geotechnical characteristics of marine soils, which support the structures. Although the offshore site investigation is much more difficult than onshore, safe and precise jobs have not been accomplished in Korea because of the insufficiency of the test equipments especially for the site with deep water depth. The main objective of this study is to develop a new type of marine cone penetration testing(CPT) system, which can be utilized to even deep sea and high depth of soil layer. The system is one of seabed types and employs the conventional cone, which shows more reliable results than miniature cone. The most important parts of the marine CPT including continuous rod system, cone penetration system with wheel drive, automatic cone rod assembly/dissembly system etc., were designed and manufactured. Some tests to verify the developed marine CPT system were performed at both onshore and offshore sites as well as mechanical test in laboratory. The test results show the consistent and promising performance of the new equipment, and thereafter the system would be applicable to various sites with practical/economical advantages.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.6
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• pp.1051-1057
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• 2010

Database for the damage reference by armor piercing bullet test was established for both tube and plate specimens having a range of thickness. As the inclined angles of hit are increasing, it has been found that penetration damage diameter tends to increases accordingly in both specimen of the tube and plate, and such penetration damage diameter on the rear side becomes bigger than those on the front side. The tube specimen showed that the damage becomes bigger when central areas rather than the peripheral were hit. Through the plate test, it also has been found that the penetration ballistic limit for Al alloy is about 25.4mm and that of stainless steel about 12.7mm. From the fatigue analysis results using the database for damage reference, it has been identified whether the safety requirements of military aircraft could be met.

• International Journal of Advanced Culture Technology
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• v.7 no.3
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• pp.10-24
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• 2019

This study aimed to investigate the effects and epidermis penetration system with polymer micelle of Red Pinus densiflora extract. In the antioxidant test, the total concentration of polyphenol compounds was determined to be $137.5163{\pm}7.70mg/g$ in ethanol extract, $133.956{\pm}1.57mg/g$ in hydrothermal extract. The DPPH radical scavenging effects were $95.29{\pm}0.15%$ in ethanol extract at 1,000 mg/L. Elastase inhibition rates were $100.00{\pm}2.85%$ in ethanol extract at 2,000 mg/L. The antimicrobial effect of the ethanol extraction was higher than that of hydrothermal extractions. In the epidermal permeability experiment, it was confirmed that the permeation of the polymer micelle containing the Red Pinus densiflora's ethanol extract and cell penetrating peptides was remarkable. Here, we confirmed that ethanol extract of Red Pinus densiflora displayed excellent the effects in antioxidant test and epidermis penetration system with polymer micelle. As a result, Red Pinus densiflora extract has potential to be used as a safe and natural cosmetic material in the future.