One of the common treatments in orthopedic surgery is machining of knee joints to attach the artificial joint. In this surgery preparation of tibia and femur surfaces is necessary to obtain proper joint kinematics and ligament balancing. For this purpose milling is involved in surgery requiring accurate machining of bone surfaces and creation of accurate slots. In this paper, milling process was carried out on Polymethylmethacrylate as workpiece and suitable substitute for bone and for the first time, it is focused on modeling and optimizing the effective parameters in milling namely cutting speed, feed rate, tool diameter and cutting depth for analyzing the surface roughness using the surface response methodology. The second-order regression equation governing the model is drived and the influence of the input parameters and their interaction on the surface roughness as the output parameter is carefully investigated. Also, sobol statistical sensitivity analysis is used to ascertain the effect of process input parameters quantitatively. The results show that in order to achieve the desirable surface quality, minimum of feed, minimum rotational speed, smaller tool diameter and low cutting depth should be considered. Results show that among all effective input parameters tool rotational speed, feed rate, tool diameter and ctting depth have the highest influence on process roughness respectively. The behavior of each output parameters with variation in each input parameter is further investigated.

Polymethylmethacrylate-silver (pMMA/Ag) nanocomposite is synthesized by irradiating the solution of silver ions in methylmethacrylate monomer by g-ray. In this method, polymerization of the methylmethacrylate monomer and the silver ion reduction occurred simultaneously. Optical properties of the PMMA/Ag solutions are investigated using UV-Vis spectroscopy. The structural characterizations of the PMMA/Ag nanocomposite are determined by FTIR spectroscopy XRD, and SEM measurements. The SEM image shows that the Ag nanoparticles disperse in the PMMA matrix with a relatively uniform distribution. The antibacterial studies show that the PMMA/Ag nanocomposite is antibacterial against E. coli, as a model for gram-negative bacteria.

Background: Incorporation of extra fillers into dental resins might enhance their physical properties. In this study, the tensile and impact strengths of modified heat‑ curing acrylic resin reinforced with nanoclay were investigated. Materials and Methods: In this experimental study, nanoclay-acrylic resin composite was prepared by mixing 0. 5, 1, and 2 wt% of nanoclay with methacrylate monomer in an ultrasonic probe, followed by mixing with the Polymethylmethacrylate (PMMA) powder. 24 cubic 20 mm × 20 mm × 200‑ mm specimens for each test, 18 samples containing nanoclay and 6 samples for the control group and a total of 48 samples were prepared. The tensile and impact strengths of the samples were tested according to ISO 527 and 179, respectively. One‑ way ANOVA was used for statistical analysis, followed by multiple comparison tests (Scheffé ’ s test). Statistical significance was set at P < 0. 05. Results: The maximum mean tensile and impact strengths were recorded in the control group, and an acrylic resin containing 2% of nanoclay demonstrated the minimum mean in all the tests. Increasing the percentage of nanoclay in PMMA compromised the tensile strength (P < 0. 05) with no effect on its impact strength. Conclusion: Incorporation of nanoclay particles into acrylic resins can adversely affect the mechanical properties of the final products, and this effect is directly correlated with the concentration of nanoparticles.

Whitening as one of the stages in rice processing is performed following dehusking. Studies on performance of milling machines prevailent in Mazandaran province, as the biggest rice producer province in Iran, are essential and helpful in reducing rice losses. A research was undertaken to examine the effects of variety (Tarom, Hibrid, and Fajr), milling machine (frictional and abrasive baed milling machines) as well as milling time duration (25, 35, 45, 55, 65 and 75 seconds) on some such rice qualitative, and quantitative parameters as broken rice, degree of milling, as well as whiteness index. Statistical design was a randomized complete block design one 36 treatments and in three replications. Results indicated that increasing milling duration increased the degree of rice whitening up to 53.39 %due to a more stay time of brown rice in the milling chamber. Among the treatments, Hibrid and Fajr varieties devoted the highest and the lowest degree of milling to themselves, respectively. Based on statistical analysis, Tarom variety scored the highest whiteness index of 0.360, whereas Hibrid variety showed the lowest one namely 0.247. Results indicated that milling machine type, rice variety and milling time duration as well as interaction effect of milling machine type and rice variety exert significant effects on all parameters studied. Amount of broken rice for Fajr variety and for the two types of milling machines was found to be equal, whereas, that figure for Tarom variety was almost 10.23% lower for abrasive type machine as compared with the frictional one.

Background and Aim: One of the main reasons for the failure of metal-ceramic restorations is insufficient bond strength between porcelain and metal, which depends on various factors, including the manufacturing method. The purpose of this study was to evaluate the effect of manufacturing method on bond strength of porcelain to titanium substructure made by EBM or milling method. Materials and methods: In this in-vitro study two groups comprised of twenty metal bars each were prepared with EBM or milling method. first a resin bar was molded into standard ISO: 9693 dimensions of 25 mm × 3 mm × 0. 5 mm. then it scanned and Ten bars from each group were manufactured using milling device from titanium disks or from an EBM device from Ti-6Al-4Va titanium alloy. bars were sandblasted with 110 μ, m aluminum oxide particles and were impregnated with bonding agent before the application of 1/1 mm of porcelain onto 8 mm × 3 mm rectangular area in the center of each bar porcelain. Afterwards, bond strengths of the samples were assessed using 3-point bending test with a Universal Testing Machine. Statistical analysis was performed using T-test and a significant level of 0. 05 was considered Results: The mean bond strength of EBM group (34. 36±, 3. 67MPa) was lower than milling group (46. 52±, 4. 34 MPa) and there was statistically significant difference between groups (p-value<0. 001). Conclusion: Bond strength of EBM-manufactured samples were lower than milled group while both groups exceed the minimum requirement of bond strength for metal-ceramic restoration according to ISO9693.

Archaeological buildings form the urban core of historical cities as a sign of urban life in society. Nanotechnology started to preserve heritage buildings. This study aimed to synthesize an optimal N: Ni: TiO2 photocatalyst, from TiO2 nanoparticles, as a nanofilm on chromatic tile surface and the N: Ni: TiO2/Polymethyl methacrylate as nanocomposite film on bricks for respiration functionality. The nanofilm and nanocomposite were synthesized and coated on historical samples to reduce the impact of Volatile Organic Components (VOC) and water penetration. The nanocatalyst was characterized using different techniques. The Fourier-transform infrared spectroscopy showed the Ti-O-Ti stretching vibration absorption mode and N and Ni ions in the TiO2 lattice. The X-ray diffraction analysis patterns exposed the anatase main peak and signs of dopants. The Scanning electron microscopy analysis was carried out N: Ni: TiO2 (0.024:0.024:0.27 with 0.8 M nitric acid and retention time of 20s) (E), nanoparticles with an average size of 48.48 nm. The energy dispersive X-ray analysis spectrometer confirmed Ti, O, N, and Ni bonding in a N: Ni: TiO2(E) photocatalyst. The co-dopants and single-bond dopants were found to be uniformly distributed in TiO2 matrix. The UV–Vis diffuse reflectance spectroscopy showed, an increase in visible light absorption by N: Ni: TiO2(E) when the wavelength was >400 nm. It was mainly due to the change in electron trap ability using N/Ni. In addition, Ni-N-TiO2 nanoparticles show enhanced activity compared with Ni-TiO2. Also, results show Ni and N co-doped TiO2 is a promising photocatalyst to degrade methylene blue under visible light. For N: Ni: TiO2 (E)= (0.024: 0.0099:0.27 M loading), with 0.8 M nitric acid and retention time of 10s films, Methylene blue degradation on white and violet chromatic tiles were 63% and 30% respectively. The antibacterial degradation test showed cut off of E. coli colonies’ growth on the tile surface.

Open circuit thermally stimulated current (TSC) and surface charge decay measurements have been carried out on the 30 mm thickness samples of pristine and iodine doped Polymethylmethacrylate (PMMA) to understand the nature of decaying charge. The samples are thermally charged at different temperatures with different polarizing fields. Both types of charges, hetero- and homo-charges are present in iodine doped PMMA samples, however, only hetero-charges are observed in pristine PMMA samples. A double charge reversal from hetero- to homo-charges and homo- to hetero-charges is observed in few cases of iodine doped PMMA samples. A single anomalous TSC peak is appeared in iodine doped PMMA when polarized at high field and temperature. The appearance of anomalous current in the high temperature region is in agreement with the double charge reversals (i.e., hetero- to homo-charges and homo- to hetero-charges) observed in surface charge decay study and TSC measurments. This could be explained on the basis of high return rate of the charge carriers released from the traps. However, this behaviour of TSC is inherent in pristine PMMA samples. The observed behaviour of surface charge decay and TSC have been explained in terms of the existence of hetero-charge due to dipole orientation and ionic space charge drift, together with an injection of charge carriers from an electrode and subsequent localization in surface and bulk trap.

The PMMA electrets were prepared by thermal polarization method. UV-vis absorption and thermally stimulated discharge current (TSDC) spectra have been recorded in PMMA electrets of 10 mm thickness. The PMMA electrets are polarized at 333 K with different polarizing fields. The observed TSDC and UV-visspectra are the function of polarizing field. It has been found that absorption decreases with increasing field. The TSDC peak (a peak obtained at high temperature) is shifted towards lower temperature region with increasing field. The observed activation energy with the low temperature peak (b peak) is found to be varied between 0.21-0.55 eV, while for a peak it varies from 0.50 to 0.91 eV. The TSDC peaks are explained on the basis of theoretical predictions; however, the decrease in band gap energy of PMMA electret could be explained on the basis of UV-vis absorption peak. The configuration of UV-vis absorption in the region 200-900 nm gives the method of characterizing band gap energy. The dipolar and space charge polarizations are possible mechanisms to explain the TSDC in PMMA electrets. The optical micrographs distinguish the molecular structure of polarized and unpolarized (i.e., pristine) samples.