Impact of Compression Force on Mechanical, Textural, Release and Chewing Perception Properties of Compressible Medicated Chewing Gums

Medicated chewing gums (MCGs) represent a beneficial platform for realizing drugs intended for dental prophylaxis and treatment. The present study aimed to investigate the impact of compression force on the mechanical, textural, release, and chewing perception characteristics of compressible MCGs with the combination of lysozyme hydrochloride (LH) and ascorbic acid (AsA). Four batches of MCGs were obtained on a laboratory single-punch tablet machine applying different forces, i.e., 5, 7, 10, and 15 kN, and evaluated by their geometrical parameters, mechanical resistance, surface and internal structure characteristics, texture profile, release behavior, and perception attributes during mastication. It was found that increasing compression force slightly affected resistance to crushing and friability of MCGs, but resulted in surface smoothing and formation of a thicker layer with highly compacted particle arrangement. According to the texture analysis, increasing compression force led to harder and more adhesive gums, indicating possible difficulties in chewing and, therefore, impairment of their consumer properties. Lower compression forces were also found to be preferable in terms of better drug release from the obtained chewing gums. The volunteers’ assessment showed that an increase of compression force led to significantly raising the initial hardness and crumbliness as well as to decreasing the rate of the integral gum mass formation during mastication, which may negatively affect perceptive sensations when using MCGs. Based on the results obtained, the optimal compressing force was selected to be 7 kN, which allows obtaining MCGs with good organoleptic, mechanical, textural, and release properties.

PENGARUH PEMBERIAN LARUTAN SARI KURMA (PHOENIX DACTYLIFERA L.) DAN LARUTAN FLUOR TERHADAP KEKERASAN EMAIL GIGI SETELAH DIRENDAM DALAM MINUMAN RINGAN BERKARBONASI

Soft drink with low pH (5,5) causes tooth erosion. Erosion may result in a decrease in surface hardness of tooth enamel. This research will be used a solution of palm juice and solution of fluoride to increase the surface hardness of tooth enamel. The purpose of this study was to evaluate effect of using a solution of palm juice 100%, 75%, 50%, 25% and APF 1,23% to the surface hardness of tooth enamel. The methode used in this research is the experimental laboratory and were tested for their hardness using Vicker Hardness Tester.Measurement performed three times, initial hardness, after all specimens was soaked in soft drink for 25 hours and were then applied with 100%, 75%, 50%, 25% solution of palm juice dan APF 1,23%. Data was analyzed by using SPSS with Repeated ANOVA.The result showed that a significant decrease in tooth enamel hardness on immersion in carbonated soft drink (p<0,05) and increased hardness of surface enamel after application with 100% solution of palm juice with a mean increase of microhardness 42,91VHN, 38,46 VHN with 75% solution of palm juice, 35,836 VHN with 50% solution of palm juice,29,41 VHN with 25% solution of palm juice dan 23,94 VHN in APF 1,23%.The result of this study is there is no significant difference enamel hardness after applied with 100%, 75%, 50%, 25% solution of palm juice and APF 1,23%.

Method of Ultrasonic Nanocrystal Surface Modification for Improvement of Surface Characteristics of Aisi D2 Heat-Treated With Different Tempering Conditions

AISI D2, an alloy tool steel, has been widely used as a cold-work die steel because of its excellent wear resistance, toughness, and machinability. However, when it is used as a mold or tool under a high load, high hardness and wear resistance are required to improve its service life. This study aimed to apply ultrasonic nanocrystal surface modification (UNSM), a local surface hardening technology, to the surface of D2 steel. To maximize the surface improvement effect achievable through UNSM, it is important to select the optimal process conditions according to the characteristics of the base metal. Therefore, the effects of UNSM were compared for different initial hardness values of D2 in this study. To this end, the base metal was subjected to different heat treatment conditions to exhibit different hardness values (approximately 40, 45, 50, and 55 HRc). Changes in the surface of the base metal were observed according to the three main parameters of the UNSM process: the load, inter-pass interval, and feed rate. No significant changes in the surface roughness and hardness was caused by the feed rate. As the inter-pass interval of UNSM decreased and the static load increased, the surface roughness of the base metal increased. However, the specimen with low initial hardness (D2-H40), the roughness improvement decreased as the load increased. On the other hand, the surface hardness improvement increased as the inter-pass interval decreased and the load increased regardless of the initial hardness of the base metal. It also was found that the specimen with the highest initial hardness (D2-H55) exhibited the greatest hardness improvement rate of 8.7 % and smallest hardened layer thickness of 220 μm. In addition, the largest compressive residual stress (-1,130.6 MPa) was formed on the surface of D2-H55 after UNSM, which occurred because the base metal with high initial hardness had limited plastic flow due to fine grains and low ductility, causing thus the energy repeatedly delivered by UNSM to be concentrated in a limited area. Consequently, reducing the inter-pass interval is effective on improving the surface roughness and hardness regardless of the material hardness. However, the load must be applied at an appropriate level, depending on the material hardness. Therefore, when D2 is heat-treated and used according to the product requirements, it will be effective to consider the changes after UNSM treatment based on hardness after heat treatment that were derived in this study.

Hardness Prediction in Quenched and Tempered Nodular Cast Iron Using the Hollomon-Jaffe Parameter

The Hollomon-Jaffe parameter is usually used to stablish a equivalence between time and temperature in a tempering treatment, but not to predict the harness of the alloy after the treatment. In this paper this last possibility has been studied. A group of cast iron samples was annealed and cooled at different rates in order to obtain samples with three different hardness values. These samples were tempered using different times and temperatures. The Hollomon-Jaffe parameter was calculated for each case and a relationship based on a logistic function between that parameter and the final hardness was stablished. This relationship was found to depend on the initial hardness and the lowest hardness achievable.

Retrofitting Steel Moment Frames by Using the Cable Bracing

In this paper, the behavior of retrofitted steel moment frames with bracing has been investigated. Braces include double-channel cross brace, cross braces with cable and brace with two cables passed through a cylindrical steel sheath at the location of the cables. Nonlinear analysis of frames has been carried out under cyclic loading with increasing amplitudes. Comparison of numerical analysis results with laboratory data shows the accuracy of finite element models. By determining the hysteresis and plasticity behavior of the frames, advantages and disadvantages of each of the retrofitting methods have been examined. The results have shown the use of double channels and cables to retrofit the frame increases the initial hardness and final load of the frame considerably compared to the moment frames and reduces its ductility. In frame with sheathed cable brace, the initial hardness was the same with the moment frames and the frame has been shown to have ductile behavior.

Drastic corrosive coliation of petroleum oils and the decay of metals

In the industry of petroleum oil refining industry the term of corrosion is frequently applicable regarding the several incidents because of the corrosiveness of petroleum oils due to the presence of trace corrosive compounds in such petroleum oils since the occurrences. Usually the corrosion is the results of chemical or electrochemical process of metals when it is exposing to the corrosive environment. The investigations of the impact of the organic acids, salts, elemental sulfur and the Mercaptans on the corrosion rates of seven different types of ferrous metals and the analysis of the nature of the corrosion between these materials were the objectives of the existing research. The relevant corrosive properties of two different types of selected crude oils and the chemical compositions of selected seven different types of ferrous metals were tested by the standard methods and instruments. A batch of similar sized metal coupons was immersed in both crude oil samples separately as three homogeneous metal coupons per each crude oil container. In order of after 15, 30 and 45 days from the immersion the corrosion rates of such metal coupons were determined by the weight loss method as three sets of samples while observing the corroded metal surfaces through an optical microscope. In addition, the decay of ferrous and copper from metals into crude oils while the interaction and the deductions of the initial hardness of metals were tested. As the basic investigations there were observed the relatively lower corrosion rates from stainless steels, relatively higher impact from salts on the metallic corrosion at lower temperatures, formations of FeS, Fe2O3, corrosion cracks and pitting, significant decays of ferrous and copper from some metals and the slight reductions of the initial hardness of metals after the interaction with the petroleum oils.

Preliminaries of the Decay of Metals versus Petroleum Oils

Petroleum oils are predominantly made of various hydrocarbons with trace compounds including corrosive aided compounds that basically known as the salts, organic acids and various forms of sulfur. The scope of the current research was based on the investigations of the effect of salts, organic, elemental sulfur and Mercaptans of crude oils on the corrosion rates of seven different types of ferrous metals that important in the industry of crude oil refining. As the procedure the important corrosive properties of two different selected crude oils and the chemical compositions of the selected ferrous metals were analyzed by the standard instruments and methods. There were determined the corrosion rates of prepared metal coupons from selected ferrous metals with the similar dimensions after certain immersion time periods with respect to both crude oils by the weight loss method while analyzing the corroded metal surfaces through the microscope also simultaneously analyzed the decayed metallic elemental concentrations from metals into crude oils and the variations of initial hardness of the metals. As the foremost outcomes of the existing analysis there were obtained the significantly lower corrosion rates from stainless steels which are having at least 12% of chromium with sufficient amount if nickel, relatively higher corrosive impact from salts especially at the lower temperatures, formations of ferrous sulfides, ferrous oxides, corrosion cracks and pitting corrosion, significantly decay of copper from Monel metal, higher decay of ferrous from some of carbon steels and slight reductions of the initial hardness of metals after the formations of the corrosion on the metal surfaces.

Retrofitting steel moment frames by using the cable bracing

In this paper, the behavior of retrofitted steel moment frames with bracing has been investigated. Braces include double-channel cross brace, cross braces with cable and brace with two cables passed through a cylindrical steel sheath at the location of the cables. Nonlinear analysis of frames has been carried out under cyclic loading with increasing amplitudes. Comparison of numerical analysis results with laboratory data shows the accuracy of finite element models. By determining the hysteresis and plasticity behavior of the frames, advantages and disadvantages of each of the retrofitting methods have been examined. The results have shown the use of double channels and cables to retrofit the frame increases the initial hardness and final load of the frame considerably compared to the moment frames and reduces its ductility. In frame with sheathed cable brace, the initial hardness was the same with the moment frames and the frame has been shown to have ductile behavior.

Coating of 1.4404 stainless steel by a combination of brazing and nitriding

In the current research, surface hardening of 1.4404 stainless steel was investigated. A hard Ni-containing coating was prepared by brazing at 1150 °C using a Ni foil with Si powder. The hardness behavior was increased by nitriding as well. The nitriding experiments were performed at low and high temperatures (460 and 640 °C) for a different period (3 and 6 h). The microstructure and material properties were characterized using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and Micro Vickers hardness testing. Results show that the hard phase and the binding Ni foil were well distributed into the hard layer. The hard coating material was composed of a Si-phases and Ni-containing compound dispersion.After the nitriding, the hardness of the samples was increased with increasing the nitriding time and temperature and increasing the brazing time. The 10 min brazing and 6h nitriding at 640°C resulted in 32% higher hardness than the non-nitride sample.Strong metallurgical bonding is formed between the stainless steel substrate and the coating layer, as well as between the binding Ni foil and the hard phase; because of the mutual diffusion of alloying elements, the hardness of this hard coating was 2 to 3 times higher than the initial hardness of steel substrate.