• Journal of the Korean Geosynthetics Society
• /
• v.19 no.4
• /
• pp.33-40
• /
• 2020

It is now common to find the wastes buried in the past during the excavation process of soil for large scale housing and land development. Without proper treatment of the wastes environmentally, the excavation process is no longer able to proceed, and an action plan should be provided to treat the wastes with environmental and economic viability. In the study, the relationship between the apparent density of the wastes and the volume conversion factor, which is the basis in the estimation of waste treatment cost was investigated. From 10 sampling points of a landfill site, wastes were sampled, analyzed for physical characteristics, and the apparent density of mixed and sorted waste was assessed. Applying the empirical formula, and the formula we suggested here, the volume conversion factors were compared with that measured directly in the field using dump truck and excavator. Obviously there was a close relationship among the volume conversion factors resulting from the empirical formula, the formula we suggested and that measured in the field.

• Journal of Industrial Technology
• /
• v.7
• /
• pp.9-14
• /
• 1987

The maximum specific gravity of asphaltic concrete can be calculated based on the effective specific gravity of aggregates and the specific gravity of asphalt cement. The maximum specific gravity is sometimes obtained based on the apparent specific gravity of aggregates and specific gravity of asphalt concrete. However, the apparent specific gravity is in general greater than the effective specific gravity for most aggregates. This study showed, by comparing the results obtained based on two specific gravities, that application of the apparent specific gravity instead of the effective specific gravity resulted in discrepancies in the calculated values of effective asphalt content, air void and maximum density.

• Progress in Superconductivity and Cryogenics
• /
• v.16 no.1
• /
• pp.19-22
• /
• 2014

The effects of Mg content on the pore formation, density and critical properties were investigated in in-situ reacted $MgB_2$ superconductors. The $Mg_{1+x}B_2$, (x=-0.2, 0.0, 0.05, 0.3, 1.0) bulk samples with different Mg contents were heat-treated at $900^{\circ}C$ for 1 h in an Ar atmosphere. The dimensional changes of a pellet's mass and volume after heat-treatment were measured. After heat-treatment process, the sample mass was decreased by Mg evaporation, but the sample volume was expanded by pore formation at the Mg site; therefore, the apparent density was decreased. Spherical pores the same as Mg particles were developed after heat-treatment in all samples, and the pore density was increased with increasing Mg content. As the x of Mg content was increased to 1.0, the apparent density of $Mg_{1+x}B_2$ samples was decreased due to a relatively larger reduction in a mass change. The critical current density of Mg excessive sample of x=0.05 showed the highest values over the applied magnetic fields because the excessive Mg may compensate Mg loss and enhance grain connectivity.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.8 no.2
• /
• pp.324-331
• /
• 1998

After the addition of yttrium aluminum garnet of 2, 5, 10 mol% as a sintering aid, $\alpha$-silicon carbides were prepared by a liquid-phase sintering at $1850^{\circ}C$, and the microstructural evolution was investigated during sintering as functions of liquid-phase amount and sintering time. The highest apparent density in each compositions was obtained in specimens sintered for 2 h, and the percentage of weight loss increased with sintering time. By increasing the amount of sintering aid (yttrium aluminum garnet), the rate of grain growth during sintering decreased, but the apparent density of sintered body increased. The phase transformation from 6H-SiC to 4H-SiC was partially observed in specimens sintered for a long time, and so, a few rod-like grains were observed.

• Elastomers and Composites
• /
• v.58 no.4
• /
• pp.208-215
• /
• 2023

In this study, the properties of polyurethane-polydimethylsiloxane (PU-PDMS) hybrid foams containing different types and contents of physical blowing agents (PBAs) were investigated. Two types of blowing agents, namely physical blowing agents and thermally expandable microspheres (TEM), were applied. The apparent density was measured using precisely cut foam samples, and the pore size was measured using image software. In addition, the microstructure of the foam was confirmed via scanning electron microscopy and transmission electron microscopy. The thermal conductivities related to the microstructures of the different foams were compared. When 0.5 phr of the hydrocarbon-based PBA was added, the apparent density and pore size of the foam were minimal; however, the pore size was larger than that of neat foam. In contrast, the addition of 3 phr of TEM effectively reduced both the apparent density and pore size of the PBAs. The increase in resin viscosity owing to TEM could enhance bubble production stability, leading to the formation of more uniform and smaller pores. These results indicate that TEM is a highly efficient PBA that can be employed to decrease the weight and pore size of PU-PDMS hybrid foams.

• Proceedings of the KSME Conference
• /
• 2000.11a
• /
• pp.522-528
• /
• 2000

Dynamic characteristics of seated human body were investigated by measuring apparent masses of eight different seating subjects exposed to vertical vibration. Two types of vibration signals - one is random signals over 1 to 30Hz having flat spectral density and the other is signals measured on seat rail in passenger car under driving conditions - were employed. It was found that the apparent masses are highly dependent on vibration level rather than type of the vibration signals. Based on the apparent mass measurements, a mathematical model of the human body in seating posture was developed by using genetic algorithm. Three-degree-of-freedom model was satisfactory in describing apparent mass of seated human body.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.4
• /
• pp.400-406
• /
• 2023

In this study, the relationship between the material properties and air permeability characteristics was examined, an experimental method to analyze the air permeability characteristics was presented, and experimental results were derived. The effects of compressive strength and apparent density of hardened concrete on air permeability characteristics were evaluated experimentally. Focusing on the mix proportions used in nuclear power plant concrete structures, concrete test specimens were manufactured and air permeability characteristics were measured according to changes in binder, maximum aggregate size, and water-binder ratio. The apparent density was over 2,400 kg/m³ for the OPC mix and the FA-35 mix, and the air permeability for both mixes were low, in the range of 0.1-0.2 L/min. On the other hand, in the case of the combination of FA-40, FA-45, and FA-M, the apparent density was measured to be less than 2,400 kg/m³ and the air permeability was measured to be more than 0.3 L/min, experimentally verifying that the apparent density is an important factor in air permeability characteristics.

• Journal of the Korean Ceramic Society
• /
• v.21 no.2
• /
• pp.156-164
• /
• 1984

The characteristic of pyrolytic carbon deposited in a fluidized bed as measured by density apparent crystallite size and viewed metallographically under polarized light can be easily controlled by adjusting the deposition parameters such as deposition temperature and propane flow rate or silicon content. The density of isotopic pyrolytic carbons deposited from propane between 120$0^{\circ}C$ and 140$0^{\circ}C$ increases with increasing propane flow rate and decreasing deposition temperature from 1, 73g/cc to 2.08g/cc. The apparent crystallite size Lc parameter appears to depend only on deposition temperature being entirely independent of the propane flow rate. The carbon matrix density of the silicon-alloyed carbonds deposited from propane and methyltrichlorosil-ane from 2.05g/cc for a silicon content around 9wt% to 2.67g/cc for a silicon content of 36.7wt% The Lc parameter of the deposition temperature being entirely independent of the silicon content.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.35 no.2
• /
• pp.103-111
• /
• 2015

The present study investigated the influence of thick cortical endplates on the ultrasonic properties of trabecular bone in a femur with a high fracture risk. Twelve trabecular bone samples were prepared from bovine femurs, and acrylic plates with thicknesses of 1.25, 1.80, and 2.75 mm were manufactured to simulate the cortical endplates using acrylic with a density and a sound speed similar to cortical bone. Although the thickness of the acrylic plates attached to the two sides of the trabecular bone increased, high correlations were observed between the speed of sound and the apparent bone density of the trabecular bone, with Pearson's correlation coefficients of 0.80-0.86. High correlations were also observed between the attenuation coefficient at 0.5 MHz and the apparent bone density of the trabecular bone, with Pearson's correlation coefficients of 0.84-0.91. These results suggest that the speed of sound and attenuation coefficient at a specific frequency measured in a femur with relatively thick cortical endplates compared to the calcaneus could be used as indices for predicting the bone mineral density of the femur.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.07a
• /
• pp.365-368
• /
• 2000

We have studies on the Microstructures and densities as a function of forming pressures and the magnetic properties of the specimens with additive Bi$_2$O$_3$ that sintered at 95$0^{\circ}C$ for 4.5 hours for synthesizing optimal Ni-Cu-Zn ferrite. Green density rose generally as Forming pressure increased from 1.7 ton/cm$^2$to 2.5 ton/cm$^2$and Cold Isostatic Pressure(CIP) method was more effective than Die Pressure(DP) method to high green density. Forming pressure had no influence on apparent density but on the other hand Bi$_2$O$_3$contents were strongly dominant to appaernt density than forming pressure. Bi$_2$O$_3$liquid phases created during sintering process promoted sintering and grain growth so that apparent density, grain size and permeability increased compared to that of the specimens which were sintered with non-additive Bi$_2$O$_3$.