• Geomechanics and Engineering
• /
• v.9 no.1
• /
• pp.1-14
• /
• 2015

Piezovibrocones have been developed to evaluate the liquefaction potential of onshore soils, but have not yet been utilized to evaluate the in-situ liquefaction behavior of offshore marine and volcanoclastic sediments. Two static and vibratory CPTu (Cone Penetration Tests) were performed at Tauranga Harbor, New Zealand. The lithology is known from nearby drillholes and the influence of vibration on different types of marine soils is evaluated using the reduction ratio (RR) calculated from static and vibratory CPTu. A sediment layer with high potential for liquefaction and one with a slight reaction to cyclic loading are identified. In addition to the reduction ratio, the liquefaction potential of sediment is analyzed using classic correlations for static CPTu data, but no liquefaction potential was determined. This points to an underestimation of liquefaction potential with the classic static CPTu correlations in marine soil. Results show that piezovibrocone tests are a sensitive tool for liquefaction analysis in offshore marine and volcanoclastic soil.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2007.05a
• /
• pp.361-363
• /
• 2007

The light weight aluminum subframe for automobile chassis part was developed using hybrid process, i.e. extruforming, press stamping and MIG welding. To achieve a 30 % weight reduction compared with conventional steel subframe keeping satisfactory performance, the design of cross-section of extruforming part was introduced, then forming simulation was performed and the final design was determined. In addition, we tried to estibilish optimun aluminum welding conditions for good penetration depth and few pore defact, finally the prototype of aluminum subframe was assembled using MIG welding method.

• 한국연소학회:학술대회논문집
• /
• 2004.11a
• /
• pp.117-123
• /
• 2004

The burning characteristics of interacting coal particles in a convective flow are numerically investigated at various Reynolds numbers. The transient combustion of 2-dimensionally arranged particles, both the fixed particle distances of 5 radii to 20 radii horizontally and 3 radii to 24 radii vertically, is studied. The results obtained from the present numerical analysis reveal that the transient flame configuration and retardation of particle temperature augmentation with the horizontal or vertical particle spacing substantially influence devolatilization process and carbon conversion ratio of interacting particles. Volatile release and carbon conversion ratio of the second particle with decreasing horizontal and vertical particle spacing decrease gradually, whereas those of the first particle with decreasing vertical particle spacing increases due to flow acceleration. When the vertical particle spacing is smaller than $6R_{o}$, volatile release and carbon conversion ratio of the second particle decrease greatly due to reduction of flame penetration depth.

• Journal of the Korea Safety Management & Science
• /
• v.15 no.4
• /
• pp.73-80
• /
• 2013

Because the damages of corrosion resulting from the chloride ion are very serious, many research studies have been performed to measure the penetration depth of the chloride ion. However, there is a problem with data selection obtained from collection during experiments. In this study, it appears that the collected data are not conformed to a normal distribution. The result of this study will play a very important role, as a first step for the development and construction of a forecasting system to help determine a reliable service lifetime of marine structures.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.159-162
• /
• 1999

The paper presents results of an investigation on the permeability characteristics and pore structure of concrete containing different levels of fly ash, silica fume, or blast furnace slag. The total cementitious content was 351kg/㎥, and the water/cementitious materials ratio was 0.55. The porosity and pore structure of representative pastes of the matrix were measured using mercury intrusion porosimetry, and the permeability characteristics of concrete were also determined by water and oxygen permeability, chloride ion penetration. The results show that significant reduction in permeability of concrete containing pozzolanic materials due to formation of a discontinuous macro-pore system which inhibits flow. And, the permeability of concrete and pore structure(capillary porosity or total porosity) shows linear relationship.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1997.10a
• /
• pp.19-36
• /
• 1997

This paper discusses the reduction and subsequent recovery and increase of shear strength of clay in the vicinity of soil-cement column. Laboratory and field tests were conducted to investigate the effects on surrounding clay during and after soil-cement column installation in soft Ariake clay. Discussions were made on the mechanism of strength changes of clay by considering the thixotropic recovery, reconsolidation effect, penetration of cement slurry and diffusion of exchangeable cations. On the basis of field and laboratory observations, 10 days after column installation, the decreased shear strength of surrounding clay during mixing was recovered and 30 days later, shear strength of surrounding clay increased 30% by average. Therefore, it is recommended that the increase of shear strength of clay can be taken into consideration in the bearing capacity and stability analysis of the composite ground.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.33 no.1
• /
• pp.53-61
• /
• 2001

This study was carried out to evaluate the effect of coating pigments on the printability by investigating the pore structure of casting layer such as the number, size and distribution of pores and the pore rate. The coating structure was mainly determined by the interaction between pigment and binder. It means that the structure of pores was chiefly affected by the shape and size distribution of pigments and their packing rate. The physical properties of pore have close relationships with ink set-off, the speed of ink penetration and printing gloss. The results suggested that the rate and number of pores were greatly affected by the particle size distribution and shape of pigments. The rate of pore increased with the reduction of particle size distribution of pigments. Calcite was effective to improve greatly the printability of coated paper.

• Journal of the Korean Society of Safety
• /
• v.28 no.5
• /
• pp.83-89
• /
• 2013

Occupational Safety and Health Act provides that industrial safety helmets are personal protective equipment(PPE) to protect heads against falls from a height. Relevant domestic regulations are distinguished and different from other countries' cases. This study investigated industrial safety helmet's protective purposes and characteristics related to falls and the notion of fall prevention. A comparative analysis of regulations on safety helmets and fall prevention as well as standards on safety helmet's impact test requirements is followed by a literature review. It is also suggested that the term "fall" related to safety helmets should be changed to "impact on the upper part of head" in domestic regulations and standards.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2005.05a
• /
• pp.66-68
• /
• 2005

This paper presents the reduction characteristics of penetrated electromagnetic fields through a narrow slot aperture in a planar conducting screen of infinite extent. When a plane wave is excited to the narrow slot, the aperture electric field is controlled by the parallel plate connected on the slot. The magnitude of penetrated electromagnetic fields through a narrow slot is controlled by electric field distributions on the slot aperture. An integral equation for the aperture electric field on narrow slots is derived and solved by applying Galerkin's method of moments. The results show that the magnitude of the penetrated electromagnetic field can be effectively reduced by installing the parallel plate on the slot aperture.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.26 no.4
• /
• pp.430-435
• /
• 2017

The effect of the surface profile on CFRP and aluminum metal bonding was studied. A small number of steps were made on the aluminum surface, and the shear stress and elongation were measured using a shear test after bonding with an autoclave method. As the number of surface steps increased, the shear stress and elongation increased. The surface bonding strength increased because of the effect of the mechanical and chemical bonding. When the number of effective stages was exceeded, the shear strength decreased again due to the aspect ratio of the step and the reduction of the penetration effect of the resin into the groove.