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In this study, the effects of curing white Portland cement (WPC) and hydroxyapatite mixed with white Portland cement (HAp/WPC) pastes in water and the in vitro biological environment on the compressive strength and bone-like apatite formation were examined. The compressive strength of both WPC and HAp/WPC pastes increased with longer curing periods in water. The compressive strength of WPC and HAp/WPC pastes was 51.88 and 25.67 MPa, respectively, after curing in water for 28 days. The compressive strength of both samples continuously increased during in vitro testing in a simulated body fluid (SBF). After 4 weeks of immersion in a SBF, the strengths of cured WPC and HAp/WPC samples were 59.01 and 28.06 MPa, respectively. It is due to continued hydration of WPC. The addition of HAp to WPC decreased the compressive strength of the sample. Alternatively, it enhanced bone-like apatite formation on the surface of the samples.

The present research was aimed to investigate the carbide distribution and hardness in A356-SiC composite produced by stir casting. The particle size of reinforcingphase was 37 μm silicon carbide with loading content of 5, 10, 15 and 20 percent by weight. In the casting process, molten composite was stirred by the rotor blades with a stirring speed of 300 rpm. Molten A356 was continuously stirred during cooling from superheated liquid state to a semi-solidtemperature of 615°C. During stirring the SiC powder was slowly added into the melt and continuouslystirred for another 15 min. The melt was then poured into a stainless moldat the pouring temperature of 680°C. The results showed that silicon carbide was uniformly distributed in the A356 in all conditions. SEM micrographs showed that the interface between the matrix and reinforced particles of 5, 10 and 15percent SiC exhibited well bonding. However, at a composition of 20 percent SiCby weight, small cracks were found at the interface between a reinforced phase and the matrix phase. Hardness values of composite material of 5, 10, 15 and 20 percent were 69.87, 71.09, 74.05 and 71.01 HB, respectively.

Biomaterials containing calcium phosphate ceramics have been used as bone substitute materials. In this study, the compressive strength and in vitro bioactivity tests of hydroxyapatite (HAp) from golden apple snail shell mixed with calcined kaolin (CK) were investigated for used as bone substitute materials. Mixed paste samples were cured at 23°C and 60°C for 2 days and curing continued at 23°C for 7 days. The effects of HAp:CK weight ratio on compressive strength and apatite formation in simulated body fluid (SBF) were investigated. The good compressive strength was 32.93 MPa at 25 % hydroxyapatite with 75% calcined kaolin at curing temperature of 60°C. Apatite formation was observed on sample surfaces after soaking in SBF for 28 days using SEM, EDS and XRD analyses. It was found that apatite formation took place on the surface of samples, consisting of HAp, after immersion in SBF.

The highly pure and crystalline calcium carbonate (CaCO3) and calcium oxide (CaO) with small amounts of As, Cd, Hg, and Pb were prepared by calcinating shells of a golden apple snail. Solid-state reaction and mechanical activation between the CaCO3 and CaO from calcined golden apple snail shells and dibasic calcium phosphate dihydrate (CaHPO4•2H2O, DCPD) were performed to develop calcium phosphate powders. The effects of the milling media used on the mechanical activation were examined. A solid-state reaction of manually mixed CaCO3 or CaO with DCPD powders at a temperature of 1100 °C produced mostly β-tricalcium phosphate (β-TCP). Hydroxyapatite (HAp) with a small quantity of β-TCP could be produced from a mixed CaCO3 + DCPD powder using dry and wet mechanical activations with distilled water, alcohol and acetone and from a mixed CaO + DCPD powder using dry mechanical activation combined with a solid-state reaction at a temperature of 1100 °C. A phase change of milled powders to β-TCP was clearly observed from a wet mechanical activation of CaO + DCPD powder with distilled water or alcohol in a solid-state reaction. The thermal instability of HAp powders from a combined mechanical activation with solid-state reaction of CaCO3 or CaO and DCPD powders could result from two factors. The first is that the pollution was released from the balls and pot mill materials during the mechanical process. Another factor is a reduced level of calcium in the CaO + DCPD mixed powder due to a reaction between CaO and water or alcohol during mechanical milling.

The highly pure and crystalline calcium carbonate (CaCO

In this study, artificial neural network with a supervised learning algorithm called vector-quantized temporal associative memory (VQTAM) is proposed to estimate chilled weight loss during chilling process of pig slaughtering plant. Four models based on carcass weights are developed. The results show that the proposed algorithms can accurately predict chilled weight loss with an error rate of less than 5% on average. The models are also employed to determine the suitable chilling times for each weight class.

The use of biogenic materials to produce naturally based biomaterials has been widely studied. In this study, heavy metal content, phase transformation and physical characterization of Golden Apple Snail shell were investigated for use as a calcium source in the production of naturally based biomaterials. In order to investigate phase transformation, Golden Apple Snail shell was calcined at 600 °C, 700 °C, 800 °C and 900 °C. Small amounts of As and Pb were found in raw Golden Apple Snail shell. Calcium carbonate (CaCO3, calcite) and calcium oxide (CaO) phases were observed in Golden Apple Snail shells after calcination at 600 °C and 800 °C. Fine white CaCO3 (calcite) and CaO powders were prepared after calcination of Golden Apple Snail shells. The CaCO3 (calcite phase) was completely transformed into a CaO phase at 800 °C. Phase transformation depended on calcination temperature and time.

In order to improve the adhesive strength of hydroxyapatite (HAp) coatings, grit blasting with Al 2 O 3 powder and then wet blasting with HAp/Ti mixed powders was carried out on a commercially pure Ti (cp-Ti) substrate. Subsequently, an HAp/Ti bond coat layer and HAp top coat layer were deposited by plasma spraying. Fatigue tests of the HAp-coated specimens were carried out under four-point bending. Acoustic emission (AE) signals during the entire fatigue test were monitored to investigate the fatigue cracking behavior of the HAp-coated specimens. The HAp-coated specimens could survive up to 10 7 cycles without spallation of the HAp coating layers at the stress amplitude of 120 MPa. The HAp-coated specimens without HAp/Ti bond coat layer showed shorter fatigue life and easy crack nucleation compared to the HAp-coated specimens with HAp/Ti bond coat layer. The delamination and spallation of the HAp top coat with HAp/Ti bond coat on cp-Ti was not observed until the crack propagated into the cp-Ti during the final fracture stage of the fatigue cycle. Therefore, the HAp/Ti bond coat layer was found to greatly improve the fatigue damage resistance of the HAp coating layer. Three stages of the fatigue failure behavior of the HAp top coat with HAp/Ti bond coat on a cp-Ti substrate can be clearly estimated by the AE monitoring technique. These stages are cracks nucleating and propagating in the coating layer, cracks propagating in the substrate, and cracks propagating unstably to final fracture.

This study aims to investigate patient waiting time in General Practice Clinic and identify the main cause of the problem through patient satisfaction survey. 9,232 Patients were randomly observed and quantitative data such as arrival time and waiting time were recorded. Other 1,200 patients were randomly selected for satisfaction survey which is considered as qualitative data. The result indicated that average waiting time of patients was 175.87 minutes with standard deviation of 68.66 minutes. Waiting time at GP clinic appeared to be the longest with an average of 92.9 minutes and standard deviation of 43.4 minutes. Also, based on the obtained data, patients remained positive until their waiting time exceeded 2 hours.

Four point bending tests with acoustic emission (AE) monitoring were conducted for evaluating failure behavior of the plasma-sprayed hydroxyapatite (HAp) top coat on commercially pure titanium (cp-Ti) plate with and without mixed HAp/Ti bond coat. Effect of immersion in simulated body fluid (SBF) on failure behavior of the coated specimen was also investigated by immersing the specimen in SBF. The AE patterns obtained from the bending test of the HAp coating specimens after a week immersion in SBF clearly showed the earlier stage of delamination and spallation of the coating layer compared to those without immersion in SBF. It was also found that the bond coating improved failure resistance of the HAp coating specimen compared to that without the bond coat. Four point bend fatigue tests under ambient and SBF environments were also conducted with AE monitoring during the entire fatigue test for investigating the influence of SBF environment on fatigue failure behavior of the HAp coating specimen with the mixed HAp/Ti bond coat. The specimens tested at a stress amplitude of 120 MPa under both ambient and SBF environments could survive up to 10⁷ cycles without spallation of HAp coating layer. The specimens tested under SBF environment and those tested under ambient environment after immersion in SBF showed shorter fatigue life compared to those tested under ambient environment without SBF immersion. Micro-cracks nucleated in the coating layer in the early stage of fatigue life and then propagated into the cp-Ti substrate in the intermediate stage, which unstably propagated to failure in the final stage. It was found from the XRD analysis that the dissolution of the co-existing phases and the precipitation of the HAp phase were taken place during immersion in SBF. During this process, the co-existing phases disappeared from the coating layer and the HAp phase fully occupied the coating layer. The degradation of bending strength and fatigue life of the HAp coating specimens tested under SBF environment would be induced by dissolution of the co-existing phases from the coating layer during immersion in SBF.