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This study examines the factors that influence human vulnerability to natural disasters by focusing on the seismic evaluation of school buildings in Korea. Since natural disasters such as an earthquake often do not take people’s lives directly, but rather indirectly through the destruction of physical structures, seismic reinforcement of school buildings may reduce the vulnerability of their occupants by strengthening structures to withstand such disasters. Disaster mitigation measures are implemented within a state; however, little is known about how they are distributed when the physical properties of structures are taken into account. This paper analyzes a panel data based on the structural properties of school buildings in eight different provinces between 2011 and 2015 using a logistic regression model. The results show that factors identified in cross-country studies, such as economic capacity and political factors, still have influence on earthquake preparedness at the state level, even when the physical properties of structures or technical factors are considered.

The capacitive pressure sensor with ring mesa structure has been simulated and fabricated in order to replace the bulky and inaccurate mechanical pressure sensor which is currently used in laundry machines. A ring mesa structure has been adopted with the same 100 μm width and positioned at 250 μm distance from the substrate with 50 μm distance. The center displacement of diaphragm were measured with a good linearity and increased from 0.408 μm (M 6025) to 1.578 μm (M 6045) depending on the location of ring mesa structure with the same circular radius of diaphragm. When the ring mesa structure is located 250 μm distance from the substrate, the simulated capacitance according to the water pressure showed a good linearity with less than 1.3% best-fit nonlinearity error. However, as the location of ring mesa moved to the center of diaphragm, the characteristic curves of capacitance has been changed from quasi-linear to nonlinear curves with the best-fit nonlinearity errors, 3.8% (M 6030) and 11.2% (M 6035), respectively. Based upon the simulation and experiments, one candidate device has been chosen and will replace the current bulky sensor in the near future.

For producing high-quality recycled aggregates from waste concrete, the characteristics of waste concrete when subjected to breakage by impact were investigated under free-fall conditions at various heights. In general, a lump of waste concrete did not disintegrate by a single impact, but underwent abrasion and occasional chipping before eventually breaking into several pieces. Further, when the sample was pretreated by heat, the number of free falls required for disintegrative fracture reduced markedly. Moreover, the resulting recycled aggregates had less adherent cement mortar due to weakening of the bonding strength between the aggregates and the cement mortar. Therefore, the energy penalty resulting from preheating the sample could be partially compensated for by the production of high-quality recycled aggregates. These results suggest that preheating followed by gentle breakage through free fall is an efficient technique to produce high-quality recycled aggregates from waste concrete.

This paper describes a Non-Dispersive Infrared (NDIR) CO 2 gas sensor with auto-temperature compensation in order to apply HVAC systems. The developed gas sensor amplifies differentially both the output of thermopile and output of temperature sensor that has linear output characteristics. With differential amplification circuits, the output voltage of sensor module according to the CO 2 concentration shows the independent temperature output characteristics from 10 ∘ C to 40 ∘ C. The developed sensor module shows ±30 ppm error at 1,000 ppm and ±50 ppm error at 2,000 ppm CO 2 concentration regardless of temperature variations.

For the recovery of aggregates from construction waste, the principle process is a separation of aggregates by breakage from the cement paste. In this study, a model based on DEM (discrete element method) was used to simulate the breakage behaviour of a block of concrete waste in repeated free fall tests. With 3D DEM model, 73 mm × 53 mm concrete block was modelled with macro-particles formed by a group of 970 spherical sub-particles and the sample block free fell 30 times from a 2 m height. The results of simulation were used to analyze the breakage characteristics of bonds between particles according to the number of free fall impacts. And, liberation ratio showed that high-quality recycled aggregates from concrete waste can be produced.

In this study, the degree of the substitution of Cr3+ and Cr6+ into the ettringite structure has been investigated to extent the immobilization potential of ettringite in the field under specific conditions. Aqueous suspension containing calcium hydroxide, alumium sulfate, CrCl2(trivalent chromium) and CrO3(hexavalent chromium) was subjected to ultrasound irradiation under atmospheric pressure to investigate their effects on synthesis of Cr-ettringite. In the result, the substitution of Cr3+ into Al site takes place in ettringite structure in solution with Cr3+, and monosulfate/friedel’ salt phase is also formed by occurrence of extra Al ion in solution. However, in the case of Cr6+, owing to a higher affinity of sulfate anion to form ettringite than that of Cr6+,most of Cr6+ did not substituted into the crystal structure of ettringite.

Precipitated Calcium Carbonate (PCC) is obtained through three processes; that of calcination, hydration, and carbonation. Thus, changes in each process condition determine the particle size or morphology of the mediums (calcium oxide and calcium hydroxide) as well as the product (PCC). To date, studies concerning precipitated calcium carbonate have mainly focused on the carbonation process, aimed at the manufacturing of PCC. Thus far, few studies on calcination or hydration have been conducted. Calcium hydroxide is regarded as the most important factor during the carbonation process. It is obtained through a hydration process. Therefore, in order to create the valuable PCC studies that center on the hydration process should be carried out. The present study seeks to investigate the effect of the hydration condition, particularly the temperature, on the synthesis characteristics of calcium hydroxide and aragonite PCC. The results show that the particle size of calcium hydroxide changes with variations in the initial hydration temperature. In particular, a higher initial temperature resulted in a larger particle size of the calcium hydroxide used in the synthesis. The particle size and yield of aragonite also increased when calcium hydroxide created at high temperatures was used. However, the water/solid ratio or total amount at the hydration time had no effect on the manufacturing process of aragonite.

The characteristics of nucleation and the crystal growth of aragonite-precipitated calcium carbonate in Ca(OH)2 – MgCl2 – CO2 system by a carbonation process is investigated. MgCl2, in this study, was added in order to increase the formation yield of aragonite precipitated calcium carbonate. Optimum conditions of the concentration of the reactants, the temperature and the amount of additives were studied. The formation yield of calcite gradually decreased, and the formation yield of aragonite increased with the addition of MgCl2. A higher formation yield of above 98% for aragonite is obtained by the adding of the Mg2+ ion in a 0.2M Ca(OH)2 – 0.6M MgCl2 – CO2 system at 80. The nucleation rate increased as the temperature decreased and as the CO2 gas flow rate increased. The particle size and aspect ratio increased at a high temperature, a low flow rate of gas, and a high concentration of Ca(OH)2 slurry. Small-sized aragonite was obtained at a low temperature. The increase in crystal size with the decrease in the CO2 gas flow rate can be explained by the decrease in the nucleation rate, in addition to the increase in the crystal growth rate resulting from the decrease in the dissolution rate to CO3 2- ion.

Bottom ash generated from municipal solid waste incinerators in metropolitan areas contain calcium and aluminum compounds. As a result of a carbonation reaction, calcite and a calcium aluminum compound (Na6CaAl6Si6O24, Ca2Al2SiO7) as well as amorphous aluminum oxide can be found in bottom ash. Due to this, Cu and Pb leaching concentrations decrease via a carbonation process. Recently, the study of artificial carbonation reaction has been actively investigated, but most of these studies have been carried out utilizing an aqueous solution method with high water content. In this study, the carbonation reaction takes place in an aqueous environment, but does not occur on the surface of the particle. However, to cause the encapsulation of a particle with calcite, calcium aluminum compound and amorphous aluminum oxide, these must be formed on the surface of particle. Therefore in this study, a low water content encapsulation method of bottom ash from municipal solid waste incinerator was investigated with a view to immobilize Cu and Pb via a carbonation reaction. As seem in the results, the encapsulation effect appeared to be successful, with a water content of 20%.

Most carbonation processes utilizing municipal solid waste incineration bottom ash characteristically involve a high water content (over 100%). In this work, we developed an improved carbonation process, utilizing various water contents. In addition, we investigated the characteristics of a carbonation reaction using municipal solid waste incinerator bottom ash as a function of water content and their effects on the stabilization of copper and lead. As a result of such a carbonation reaction, the effect on the stabilization of heavy metals can be obtained. Due to this, the leaching concentrations of these were reduced. In a high water content, calcium aluminum compounds via carbonation reaction adsorbed Cu and Pb ions. Where a low water content (especially 30%) is present, particle surfaces are surrounded by calcium aluminum compounds of bottom ash as a result of the carbonation process. The leaching concentration of Cu and Pb were decreased through the carbonation process.

Bottom ash contains many ferrous materials (e.g. ferrous metals, Fe3O4, Fe2O3, FeS). In addition, ferrous metals include the heavy metals, as Ni and Cr have a chemical attraction to iron, with Cu used to coat with Ni and Cr metals for polishing or to prevent corrosion. For ferrous metals, the formation of a Fe3O4-Fe2O3 double layer (similar to pure Fe) was found during air-annealing in an incinerator (1000C). A strong thermal shock, such as that which takes place during water-cooling of bottom ash, leads to the breakdown of this oxidation layer, facilitating the degradation of ferrous metals and the formation of corrosion products. Therefore, Fe-ion (heavy metal) oxides can be formed on ferrous metals, and magnetic separation can separate it from bottom ash. Thus, in this study the objection is to investigate the separation ratio of heavy metals by magnetic separation along with the mineralogical formation of Fe-ion (a heavy metal).

This study focused on the synthesis of zeolite from coal bottom ash and the CEC assessment of synthesized products. To that end, zeolificaion tests were carried out at four temperature levels (80, 100, 120, 150oC) and five NaOH concentration levels (1, 2, 3, 4, 5M) by the alkali hydrothermal method. Consequently, NaP1, hydroxy-sodalite, and tobermorite were produced from coal bottom ash. NaP1 with an excellent cation exchange capability had a high crystallinity at below 2M NaOH and 120 oC; and the maximum CEC value was 160meq/100g at 2M NaOH and 120 oC under the given conditions.

This study has been carried out to use the waste sludges generated at Pohang Iron & Steel Co. Ltd. (POSCO) as the raw materials of Ordinary Portland Cement (OPC). The burnability index of the raw mixture and the hydration characteristics and compressive strength of clinker have been examined. The waste sludges were mainly composed of CaO, SiO 2 , Al 2 O 3 , and Fe 2 O 3 , the main component of OPC. The Burnability index of mixture was improved, according to the replacement content of POSCO sludge increase. POSCO sludge can be used as a raw material for cement because the state of mineral development and property of clinker produced from POSCO sludge are similar to the plain. Therefore, POSCO sludges can be used as the source materials of iron and calcium oxide.

It is known that gentle breakage in autogenous (AG) milling promotes preferential breakage along the grain boundaries. Therefore, in this study, AG milling of waste concrete was conducted for a better liberation of aggregate and cement mortar. Tests involved grinding of lumps of waste concrete with/without heat treatment at various conditions and examining the degree of liberation. Because of typical breakage mechanisms of AG milling, the breakage does not follow first-order relation, and it can make a better liberation of aggregate from cement matrix. The resistance to breakage was reduced considerably when a sample was pretreated with heat prior to AG milling. The degree of liberation increased as grinding time increased and the quality of recycled aggregate satisfied the Korea 1st grade specification after 30 min grinding in laboratory scale AG milling, 10 min grinding in semi-pilot scale AG milling.

A pneumatic triboelectrostatic beneficiation system of fly ash was studied using a continuous, bench-scale electroseparator composed of two vertical electrode plates and an ejector-tribocharger. Tests were conducted to evaluate the charge density and the separation efficiency at various operating conditions. It was found that the higher charge densities were obtained at [1] the air flow rate of 1.75 m3/min, [2] the feed rate of less than 50 kg/h, and [3] the relative humidity of less than 30% with use of a stainless ejector tribocharger. With these optimum conditions, the clean ash of less than LOI 3% was recovered with a yield over 75% when operated at the diffuser slit gap of 4 mm, the diffuser outlet velocity of 16.1–18.6 m/s, and the distance of 15 cm between diffuser slit and splitter. The optimum feed rate was found to be 740 kg/h per m2 of electrode surface area, which can be used as a scale-up factor of electroseparator.

Tests were conducted to investigate the triboelectrostatic process for separating unburned carbon from coal fly ash. Using a batch type separator composed of two parallel plates and an ejector‐tribocharger, the charge density and the separation efficiency were evaluated under various operating conditions. These included the air flow rate, the solids loading, the relative humidity and the temperature of the air, and the voltage between the two parallel electrodes. It was found that the relative humidity of the surrounding air was the most influencing factor of the charge density as well as the separation efficiency. The maximum charge density was obtained at the air flow rate of 326 l/min, and the air temperature of 74 °C when operated at solids loadings less than 290 g/m3 and at lower than 30% relative humidity. At the optimum conditions, a fly ash of 7.5% LOI could be processed into a 3.0% LOI product with a recovery over 80%.

This paper reports the performance improvement of micromachined piezoelectric microspeakers that are audible in open air according to the geometrical parameters. The sound pressure level (SPL) of the microspeaker fabricated with a piezoelectric ZnO film is even more enhanced due to the carefully designed process conditions and electrode shapes. The SPL of the fabricated microspeakers, which have a square electrode, shows more than 50 dB from 400 Hz to 20 kHz; the highest SPL is about 94 dB at 9.5 kHz with 5 Vpp sinusoidal input biases and 3 mm distances from the fabricated microspeakers to the reference microphone.

The efficiency of the air classification of fly ash was investigated. Due to the wide variations in the size consist of fly ash, it is commonly practiced to use more than techniques to measure the entire size range. Especially for fly ash, the sieving techniques are used to obtain information not only on the size distribution but also on the carbon distribution throughout the size. However, there is a substantial amount in the sub- sieve size range, and consequently, sub-sieve analyzer is used to obtain the information on the size distribution in the finer end. Since the size definitions differ depending on the measurement methods, it is necessary to convert one type of data to the other. Using a recently developed technique for inter-conversion of sizes, the separation efficiency of a commercial classifier was analyzed using the Tromp curve. The results showed that the cut size was about 55 mm and the bypass was 17%. Sharpness Index was calculated to be 0.25, which indicated an inefficient separ...