• Proceedings of the KSME Conference
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• 2001.11a
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• pp.174-179
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• 2001

In order to investigate the fracture behaviors(perforation modes) and resistance to perforation during ballistic impact of aluminum alloy plate, ballistic tests were conducted. Depth of penetration experiments with 5.56mm-diameter ball projectile launched into 25mm-thickness Al 5052-H34 targets were conducted. A powder gun launched the 3.55g projectiles at striking velocities between 0.6 and 1.0 km/s. radiography of the damaged targets showed different penetration modes as striking velocities increased. Resistance to perforation is determined by the protection ballistic limit($V_{50}$), a statistical velocity with 50% probability for complete perforation. Fracture behaviors and ballistic tolerance, described by perforation modes, are respectfully observed at and above ballistic limit velocities, as a result of $V_{50}$ test and Projectile Through Plates (PTP) test methods. PTP tests were conducted with $0^{\circ}$ obliquity at room temperature using 5.56mm ball projectile. $V_{50}$ tests with $0^{\circ}$ obliquity at room temperature were conducted with projectiles that were able to achieve near or complete perforation during PTP tests. The effect of various impact velocity are studied with depth of penetration.

• Journal of KSNVE
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• v.7 no.5
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• pp.861-869
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• 1997

An approximate analytical method has been developed for estimating hydrodynamic forces acting on oscillating inner cylinder in concentric annulus. When the rigid inner cylinder executes translational oscillation, fluid inertia and damping forces on the oscillating cylinder are generated by unsteady pressure and viscous skin friction. Considering the dynamic-characteristics of unsteady viscous flow and the added mass coefficient of inviscid fluid, these hydrodynamic forces including viscous effect are dramatically simplified and expressed in terms of oscillatory Reynolds number and the geometry of annular configuration. Thus, the viscous effect on the forces can be estimated very easily compared to an existing theory. The forces are calculated by two models developed for relatively high and low oscillatory Reynolds numbers. The model for low oscillatory Reynolds number is suitable for relatively high ratio of the penetration depth to annular space while the model for high oscillatory Reynolds number is applicable to the case of relatively low ratio. It is found that the transient ratio between two models is approximately 0.2~0.25 and the forcea are expressed in terms of oscillatory Reynolds number, explicity. The present results show good agreements with an existing numerical results, especially for high and low penetration ratios to annular gap.

• Journal of Welding and Joining
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• v.33 no.4
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• pp.7-16
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• 2015

New lasers such as high power, high brightness and short wavelength laser are using diverse industry. Also new technologies are developing actively to solve various issues such as spattering, process monitoring, deep penetration and key-hole stability. ICALEO is the international congress where recent technology for laser material processing and laser system are present. At 2014, it was held at San Diego in USA and more than 260 papers were presented from 28 country. The effect of the laser beam shape such as Gaussian like and top-hat was investigated on acoustic emission signal and pore formation in welding. Inline penetration depth was measured with ICI(Inline Coherent Imaging) technique and the data was verified with real time X-ray image on laser welding. The laser welding performance at low pressure environment was evaluated for the thick plate alloy steel. UV laser was used to weld various metals such as Cu, Aluminum, steel and stainless steel. The effect of the wavelength of the laser on the formation of the wave at the wall of the key-hole front and the absorptivity was investigated.

• Journal of the Korean Wood Science and Technology
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• v.10 no.3
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• pp.135-151
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• 1982

In order to investigate the effectiveness of Osmose process for the practical treatment of wood this study has been made using water soluble preservatives such as Malenit and chromated zinc chloride. The results obtained in this investigation are as follows: 1. The penetration of Malenit in sapwood has been observed deeper than that of chromated zinc chloride for all species tested in this investigation. 2. The penetration of preservatives applied in soft wood, ie. Pinus densiflora and Larix leptolepis has been observed better results than that of hard wood, i.e., Quercus accutissima and Carpinus laxiflora. 3. The longer stack covering, despite of preservatives applied and size of wood tested, has given better penetration for all species tested, and the fastest diffusion has been occured in 15 days from they day started. Following after 15 days diffusion had gradualy become slower. 4. The length of time needed for effective penetration has taken 45 days for all species tested, reaching twenty millimeters (20mm) in depth in case of Malnit, that means also more than 50% of penetration into sapwood portion. However it has taken 45 days fer Pinus densiflora and Larix leptolepis, reaching fifteen millimeters (15mm) and 60 days for Quercus accutissima and Carpinus laxiflora, reaching same fifteen millimeters in case of chromated zinc chloride, that means also less than 50% (except 50% for Larix) of penetration into sapwood portion. 5. Deeper penetration of preservatives from the wood surface has been observed in the larger wood than the smaller wood for all species tested, although the penetration ratio between the width of sapwood and the length penetrated has been observed smaller in larger wood than smaller wood. 6. The relation between moisture content of wood and the penetration of preservatives into wood tested has shown the linear regression, that is, the more moisture content brought the deeper penetration. 7. Following the result obtained at this investigation osmose process with Malenit applied has indicated as a useable process for the none pressure treatment of wood.

• Journal of Soil and Groundwater Environment
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• v.15 no.6
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• pp.107-113
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• 2010

This paper presents the prediction of shear strength of oil contaminated clay using fall cone test used to determine the liquid limit of soil. The penetration depth of fall cone is related to water content of soil. Laboratory vane shear can also be related to water content. To explore the relative correlation between penetration depth of fall cone and laboratory vane shear, both fall cone tests and laboratory vane shear test were carried out with water contents of soil. The developed empirical relationships in this studys showed that the shear strength is reduced to 3.9% with 1% increase of oil content. And, the lesser initial water content of contaminated clay, the more shear strength of contaminated clay is affected by oil content.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.537-544
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• 2005

We find out many soft ground deep excavation cases where results of careless overexcavation accelerate the advance of loosening zone of adjacent ground, bucklings of struts and bottom heaves happen due to delayed supporting time. This article introduces a soft ground deep excavation case where steel pipe sheet piles were used with struts as an earth retaining system. There were 2 times of buckling in the supporting system and heaving of bottom ground due to overexcavation and insufficient penetration depth of the steel pipe sheet piles. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• Carbon letters
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• v.15 no.1
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• pp.15-24
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• 2014

As a part of the electromagnetic spectrum, microwaves heat materials fast and efficiently via direct energy transfer, while conventional heating methods rely on conduction and convection. To date, the use of microwave heating in the research of carbon-based materials has been mainly limited to liquid solutions. However, more rapid and efficient heating is possible in electron-rich solid materials, because the target materials absorb the energy of microwaves effectively and exclusively. Carbon-based solid materials are suitable for microwave-heating due to the delocalized pi electrons from sp2-hybridized carbon networks. In this perspective review, research on the microwave heating of carbon-based solid materials is extensively investigated. This review includes basic theories of microwave heating, and applications in carbon nanotubes, graphite and other carbon-based materials. Finally, priority issues are discussed for the advanced use of microwave heating, which have been poorly understood so far: heating mechanism, temperature control, and penetration depth.

• Journal of the Optical Society of Korea
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• v.18 no.2
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• pp.151-155
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• 2014

Although various ophthalmic imaging methods, including fundus photography and optical coherence tomography, have been applied for effective diagnosis of ocular diseases with high spatial resolution, most of them are limited by shallow imaging penetration depth and a narrow field of view. Also, many of those imaging modalities are optimized to provide microscopic anatomical information, while functional or cellular information is lacking. Compared to other ocular imaging modalities, photoacoustic imaging can achieve relatively deep penetration depth and provide more detailed functional and cellular data based on photoacoustic signal generation from endogenous contrast agents such as hemoglobin and melanin. In this paper, array-based ultrasound and photoacoustic imaging was demonstrated to visualize pigmentation in the eye as well as overall ocular structure. Fresh porcine eyes were visualized using a real-time ultrasound micro-imaging system and an imaging probe supporting laser pulse delivery. In addition, limited photoacoustic imaging field of view was improved by an imaging probe tilting method, enabling visualization of most regions of the retina covered in the ultrasound imaging.

• Computers and Concrete
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• v.21 no.3
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• pp.345-353
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• 2018

This paper approaches to improve the mechanical and durability properties of low calcium fly ash geopolymer concrete with the addition of Alccofine as a mineral admixture. The mechanical and durability performance of GPC was assessed by means of compressive strength, flexural strength, permeability, water absorption and permeable voids tests. The correlation between compressive strength and flexural strength, depth of water penetration and percentage permeable voids are also reported. Test results show that addition of Alccofine significantly improves the mechanical as well as permeation properties of low calcium fly ash geopolymer concrete. Very good correlations were noted between the depth of water penetration and compressive strength, percentage permeable voids and compressive strength as well as between compressive strength and flexural strength.

• Laser Solutions
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• v.12 no.2
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• pp.17-25
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• 2009

Two methodologies for predicting thermal relaxation time of tissue subjected to pulsed laser irradiation is introduced by the calculation the optical penetration depth and by the investigation of the temperature diffusion behavior. First approach is that both x-axial and y-axial thermal relaxation times are predicted and they are superposed to achieve the thermal relaxation time (${\tau}_1$) for two-dimensional square tissue model. Another approach to achieve thermal relaxation time (${\tau}_2$) is measuring the time required for local temperature drop until $e^{-1}$ of the maximum laser induced heating.