• Fire Science and Engineering
• /
• v.32 no.5
• /
• pp.15-21
• /
• 2018

This study examined the growth characteristics and carbonization pattern when a fire occurs due to a flammable liquid sprinkled on a vinyl floor. When acetone was sprinkled on a floor, the flame reached its peak in approximately 0.2 s after it was ignited. The lower part of the flame showed a laminar pattern while the upper part showed a turbulent pattern. The pattern showed a turbulent pattern and generated white smoke. The combustion completed floor surface showed carbonization of a dim pore pattern. In the case of benzene, an intense flame was formed in approximately 0.6 s after ignition. The flame length was measured to be approximately 50 mm. When the flame became weak, a significant amount of black smoke was generated due to incomplete combustion. The combustion completed floor surface showed carbonization of a pour pattern and splash pattern. In the case of alcohol, an intense flame was formed in approximately 1.1 s after ignition. In addition, the depth of carbonization was significant where the flammable liquid was collected and a trace of carbonization was observed at the boundary of the flow path of the flammable liquid.

• Journal of the Korean Geosynthetics Society
• /
• v.8 no.1
• /
• pp.25-32
• /
• 2009

In reclaimed loose sandy layer with dredged soil, liquefaction by the small scale earthquake coud be occurred easily. A study has been carried out to investigate the Liquefaction characteristic on Saemangeum dredged sandy soil, and compared with other results from the literature investigation. A series of undrained cyclic triaxial compression tests were performed on dredged sandy soil of Seamangeum area. The tests were performed at the three different initial relative densities(namely 30%, 50%, 70%), different cyclic stress ratio and different consolidation stress condition. The results of this study showed that cyclic stresses (${\sigma}_d$) increased linearly with increase of consolidation ratio, but the stress ratios (${\sigma}_d/2{\sigma}^{\prime}{_c}$) were almost same. The stress ratios were increased almost linearly with increase of relative density. Compared with other sandy soil, Saemangeum dredged sandy soil showed relatively weak liquifaction characteristics.

• The Journal of Korean Academy of Prosthodontics
• /
• v.43 no.5
• /
• pp.684-693
• /
• 2005

Statement of problem: Ti-6Al-7Nb alloy is used instead of Ti-6Al-4V alloy that was known to have toxicity. Purpose: This study was performed to investigate the effect of electrolyte concentration on the surface characteristics of anodized and hydrothermally-treated Ti-6Al-7Nb alloy Materials and methods: Discs of Ti-6Al-7Nb alloy of 20 mm in diameter and 2 mm in thickness were polished sequentially from #300 to 1,000 SiC paper ultrasonically washed with acetone and distilled water for 5 min, and dried in an oven at $50^{\circ}C$ for 24 hours. Anodizing was performed at current density $30mA/cm^2$ up to 300 V in electrolyte solutions containing $\beta-glycerophosphate$ disodium salt hydrate $(\beta-GP)$ and calcium acetate (CA). Hydrothermal treatment was conducted by high pressure steam at $300^{\circ}C$ for 2 hours using a autoclave. All samples were soaked in the Hanks' solution with pH 7.4 at $36.5^{\circ}C$ for 30 days. Results and conclusion: The results obtained were summarized as follows: 1. After hydrothermal treatment, the precipitated HA crystals showed the dense fine needle shape. However, with increasing the concentration of electrolyte they showed the shape of thick and short rod. 2. When the dense fine needle shape crystals was appeared after hydrothermal treatment, the precipitation of HA crystals in Hanks' solution was highly accelerated. 3. The crystal structures of $TiO_2$ in anodic oxide film were composed of strong anatase peak and weak rutile peak as analyzed with thin-film X-ray diffractometery. 4. The Ca/P ratio of the precipitated HA layer was equivalent to that of HA crystal in Hanks' solution.

• Journal of the Korean Wood Science and Technology
• /
• v.13 no.4
• /
• pp.67-72
• /
• 1985

To improve the bending strength of sawdustboard, verious resin contents of 10, 13, 16, and 19% were applied to the thin shell (face layer) composed with wire net or not. The shell effect of sawdust and wire net composition formed with core sawdustboard were evaluated. Forcusing on the effects of wire net composition and noncomposition including a comparison with chipboard and veneer complyboard, bending properties (Modulus of rupture (MOR), Modulus of elasticity (MOE), Stress at proportional limit ($S_{pl}$). Work to maximum load ($W_{ml}$))were analyzed and discussed. 1. In modulus of rutpute, veneer comply was the highest (621.5 kg/$cm^2$), and next decreasing order was wire net composition (159.1 kg/$cm^2$), chipboard (81.75 kg/$cm^2$), and wire net noncomposition (76.21 kg/$cm^2$) as in modulus of elasticity, work to maximum load, except for stress at proportional limit. 2. The highly significant effects were shown in both wire net composition and noncomposition, at the same time wire net composition exceeded two times of noncomposition throughout resin contents in bending properties. Chipboard was similar to the mean or 16% resin content in noncomposirion. 3. Every board in wire net composition above 10% resin content was beyond 100 kg/$cm^2$ in MOR, minimum allowable strength for structural use according to KS F 3104. In conclusion, the feasibility for improving the bending strength of weak sawdustboard by wire net composed shell was offered.

• Membrane Journal
• /
• v.9 no.4
• /
• pp.202-208
• /
• 1999

The car washing effluent containing various oils and detergent was treated by ultrafiltration membranes. Dead-end type stirred cell (Amicon 8050) with 10, 30 and lOOk dalton membranes was used to determine permeation and rejection characteristics for the car washing effluent. In case of low molecular weight cut-off membranes, the effect of membrane fouling was weak under the applied pressures. However, the permeation flux for YM100 membrane(look dalton) may be affected by oil layer formation on the membrane surface as well as oil particle plugging for a part of membrane pores due to compressible and deformable oil properties. Oil and particle rejections in the permeates were over 95%, but detergent was passed easily through the membranes. Hence, the permeates containing detergent can be recycled to the system, and may reduce water pollution. Also, the car washing effluent was treated continuously by a capillary type ultrafiltration membrane of MWCO 50k dalton. The experimental data were fitted suitably to the cake filtration model.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2009.09a
• /
• pp.1372-1377
• /
• 2009

For the remediation of the subsurface contaminated by nonaqueous phase liquids(NAPLs), it is important to characterize the NAPL zone properly. Conventional characterization methods provide data at discrete points. To overcome the weak points of conventional characterization methods, the partitioning tracer method has been developed and studied. The average saturation of NAPL($S_n$), which is the representative and continuous saturation value within contaminated site, can be calculated by comparing the transport of the partitioning tracers to that of the conservative tracer in the partitioning tracer method. In this study, the application of the partitioning tracer method in heterogeneous media was investigated. To represent the heterogeneous condition of subsurface, a two-dimensional soil box was divided into four layers and each layer contained different sized soils. Soils in the soil box were contaminated by the mixture of kerosene and diesel, and partitioning tracer tests were conducted before and after the contamination using methanol as conservative tracer and 4-methyl-2-pentanol, 2-ethyl-1-butanol, and hexanol as partitioning tracers. The response curves of partitioning tracers from contaminated soils were separated and retarded in comparison with those from non-contaminated soils. The contamination of soils by NAPLs, therefore, can be detected by partitioning tracer method considering these retardations of tracers. From our experiment condition, the average saturation of NAPLs calculated by partitioning tracer method using the methanol as conservative tracer and hexanol as partitioning tracer showed the highest accuracy, though all results were underestimated. Further studies, therefore, were needed for improving the accuracy using the partitioning tracer test in heterogeneous media.

• Geomechanics and Engineering
• /
• v.5 no.4
• /
• pp.363-377
• /
• 2013

Any structure constructed on the earth is supported by the underlying soil. Foundation is an interfacing element between superstructure and the underlying soil that transmits the loads supported by the foundation including its self weight. Foundation design requires evaluation of safe bearing capacity along with both immediate and long term settlements. Weak and compressible soils are subjected to problems related to bearing capacity and settlement. The conventional method of design of footing requires sufficient safety against failure and the settlement must be kept within the allowable limit. These requirements are dependent on the bearing capacity of soil. Thus, the estimation of load carrying capacity of footing is the most important step in the design of foundation. A number of theoretical approaches, in-situ tests and laboratory model tests are available to find out the bearing capacity of footings. The reliability of any theory can be demonstrated by comparing it with the experimental results. Results from laboratory model tests on square footings resting on sand are presented in this paper. The variation of bearing capacity of sand below a model plate footing of square shape with variation in size, depth and the effect of permissible settlement are evaluated. A steel tank of size $900mm{\times}1200mm{\times}1000mm$ is used for conducting model tests. Bearing capacity factor $N_{\gamma}$ is evaluated and is compared with Terzaghi, Meyerhof, Hansen and Vesic's $N_{\gamma}$ values. From the experimental investigations it is found that, as the depth of sand cushion below the footing ($D_{sc}$) increases, ultimate bearing capacity and settlement values show an increasing trend up to a certain depth of sand cushion.

• Korean Journal of Materials Research
• /
• v.5 no.6
• /
• pp.732-742
• /
• 1995

Effects of the substrate pretreatment on uncleation density of the diamond thin films have been investigated. The film was prepared using the hot-filament CVD reactor with the mixture of methane and hydrogen. The substrate pretreatment was done in three different ways: predeposition of carbon on the substrate, soot on the substrate, and graphite on the substrate. All three cases enhanced the nucleation density of diamond. And the effect was more marked in the first and the second cases than in the third one. In the first case where the substrate was predeposited by the carbon phase, a very smooth and uniform film of diamond could be obtained. Since the bound strength between the substrate and the predeposited carbon phase is relatively weak, separation of the diamond film layer from the substrate was found to be easy.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.09c
• /
• pp.3-10
• /
• 2010

Case study was carried out on the interpretation of the mechanical behavior of a severely damaged reinforced earth wall comprising geotextile with the concrete panel facing. In this part I, the outline of the damaged reinforced earth wall is in detail described. The background and cause of the damage are discussed based on the results of site investigation. The engineering properties of the fill were examined by performing various in-situ and laboratory tests, including the surface wave survey (SWS), PS-logging, RI-logging, soaking test, the direct shear box (DSB) test, bender element (BE) test, etc. The background as well as the cause for the damage of the wall may be described such that i) a considerable amount of settlement took place over a 3m thick weak soil layer in the lower part of the reinforced earth due to seepage of rainfall water, ii) the weight of the upper fill was partially supported by the geo-textile hooked on the concrete panels (n.b., named conveniently "hammock state" in this paper), and iii) the concrete panels to form the hammock were severely damaged by the unexpectedly large downwards compression force triggered by the tension force of the geotextile. The numerical simulation for the hammock state of the wall, together with counter-measures to re- stabilize the wall is subsequently described in Part II.

• Journal of Korean Society of Forest Science
• /
• v.99 no.4
• /
• pp.590-596
• /
• 2010

To investigate and to compare the structure of Picea jezoensis forests at Chunwangbong area in the Jirisan National Park, 33 plots(400) were set up by a random sampling method. Dead individuals of Picea jezoensis trees were 15.6%, these were observed mainly in the upper-layer trees. A few seedlings of Picea jezoensis were found in this investigation area. This result indicates that Picea jezoensis might be gradually decreased in the future. Picea jezoensis stands were classified into two major groups by cluster analysis. There were strong positive correlations between Syringa reticulata and Acer pseudosieboldianum, Tripterygium regelii, Quercus serrata; Betula ermani and Lonicera maackii; Euonymus macropterus and Acer ukurunduense; Acer pseudosieboldianum and Tripterygium regelii, and relatively weak negative correlations were showed between Picea jezoensis and Abies koreana; Betula ermani and Acer ukurunduense; Acer pseudosieboldianum and Tripterygium regelii. Species diversity index(H') of investigated groups ranged from 1.0000 to 1.3010.