Polishing Of Materials Research Articles

Surface roughness of acrylic denture base resins polished with different abrasive agents: an in-vitrostudy

Background: Excessive surface roughness on the denture base can adversely impact the oral health of the patient. Therefore, it is necessary to polish the denture before they are delivered to the patient. The abrasive and polishing agents should provide a smoother surface without affecting the physical and mechanical properties of denture bases. Aim: This study aims to examine and understand the potential of different polishing materials on surface roughness of acrylic denture base resins. Materials and methods: A total of 60 Heat-cure acrylic specimens (acrylic bars) were made and grouped into six groups. Control (no abrasive), Pumice (Micro-white), Eggshell powder, Seashell powder, Black sand powder, White sand powder are used as abrasive materials for polishing these specimens. These polished specimens were subjected to profilometer surface roughness analysis. Results: The acrylic specimens polished with eggshell powder on acrylic specimens showed the least surface roughness followed by black sand, white sand, pumice and seashell powders. Tukey HSD showed significant differences (p=0.000) between unpolished and polished specimens. Conclusion: Eggshell powder effectively reduced the surface roughness of denture base resin material. However, the surface roughness demonstrated by all the abrasive materials used was within the threshold limit (2 µm). Therefore, all the materials can be used as abrasives.

THEONYMS AND MYTHONYMS IN EARLY LATIN-SLAVIC DICTIONARIES

The interpretation of the onyms and mythonyms in the early printed dictionaries of Europe, including Slavic (Czech, and then Polish) material, deserves close attention. Latin-Czech dictionary of 1511 and subsequent dictionaries of the XVI cent. sometimes give unexpected links and definitions in the Slavic part. These peculiarities in the presented material allow us to reconstruct some details in the concepts of the past concerning the analyzed phenomena. In addition, like other proper names, theonyms and mythonyms do not have special marks in the common alphabetical order or thematic subsections; the last complicates their detection and analysis.

Prediction Model of Material Removal for Polishing Single Crystal Silicon by Cluster Magnetorheological Finishing with Dynamic Magnetic Fields Based on BP Neural Network

Magnetorheological Finishing (MRF) is a new optical surface processing method, which has the advantages that good polishing effect, no subsurface damage, and suitable for complex surface processing. However, the interaction mechanism between the MRF pad and the workpiece is very complicated, so that the existing MRF material removal theoretical model is not accurate enough to establish the relationship between polishing parameters and material removal. In order to improve the processing efficiency and explore the material removal mechanism, a cluster magnetorheological finishing (CMRF) with dynamic magnetic fields method was proposed. Studying CMRF with dynamic magnetic fields material removal model is helpful to explain the removal mechanism more deeply, and improve the processing efficiency. In this study, the CMRF method was used to conduct a multi-factor orthogonal test on 2-inch single crystal silicon wafers. Based on the empirical Preston equation, the relationship between the machining gap and the polishing pressure was explained. Orthogonal experiments were done for a series of speeds, and obtaining the order of the influence of various factors on the average surface roughness <i>Ra</i> of the workpiece was: workpiece rotation speed > polishing disk speed > magnetic poles rotation speed > oscillating speed; the material removal rate (<i>MRR</i>) was: polishing disk speed > workpiece rotation speed > magnetic poles rotation speed > oscillating speed. Then combining with the orthogonal experimental data, and taking the surface roughness <i>Ra</i> and <i>MRR</i> as evaluation criteria, using Adam (Adaptive momentum) optimization algorithm to build a prediction model of <i>Ra</i> and <i>MRR</i> for polishing single crystal silicon by CMRF with dynamic magnetic fields based on BP neural network. For the prediction result, <i>Ra</i> of the maximum error was 7.05%, the minimum was 0.31%; <i>MRR</i> of the maximum error was 10.22%, the minimum was 1.32%. Therefore, the feasibility of this model for predicting the results of CMRF was verified, and it laid a good foundation for the development of CMRF technology and its industrial application.

Optimal parameter ranges of material removal depth of abrasive cloth wheel polishing based on sensitivity analysis

Uniform material removal depth has an important influence on the profile accuracy and surface quality of the blisk blades in polishing. In order to guarantee the consistence of the polishing removal depth, a preferred method of polishing process parameter range based on sensitivity analysis is proposed. Firstly, the sensitive process parameters of polishing material removal depth were determined by four-factor three-level orthogonal experiments. Then, the three-factor central composite sequential (CCD) design experiment in the response surface method is used to obtain the quadratic regression empirical prediction model of polishing depth by multilinear regression through Minitab software, and the polishing material removal depth prediction model is analyzed significantly. Secondly, a mathematical model of relative sensitivity is established to determine the method of dividing the stable and unsteady domains of the process parameters, and the stable domain of each polishing process parameter and the sensitivity to the polishing removal depth were obtained. Finally, the comparative experiment verification was carried out by blisk polishing. Abrasive cloth wheel which is 12 mm in diameter and P600# in abrasive size and has abrasive of Green Sic is used to the polishing of TC4 titanium alloy blade. The results show that the optimal stability ranges of significant parameters through sensitivity analysis are as follows: compression amount within [0.6 mm, 0.8 mm], rotation speed within [5000 r/min, 6000 r/min] and feed speed within [200 mm/min, 400 mm/min]. The depth of polishing in the stable domain is the most sensitive to the compression amount, followed by the speed, and the feed speed sensitivity is the lowest. The optimized polishing process parameters effectively reduce the fluctuation of the removal depth, and the surface quality has greatly improved by using the optimized polishing parameters.

Estimation of Energy Savings When Adopting Ultrasonic Vibration-Assisted Magnetic Compound Fluid Polishing

Reducing energy use is a major consideration in green manufacturing. Ultrasonic vibration has the advantage of improving machining performance. This work presents an experimental investigation on magnetic compound fluid (MCF) polishing with and without ultrasonic vibration and estimates reductions in polishing energy consumption and surface roughness due to ultrasonic vibration during the machining process. A series of ultrasonic vibration-assisted MCF polishing (UVAMP) tests was carried out for brass H62, and the normal and tangential polishing forces, surface roughness and material removal rate of the traditional MCF polishing (MP) and UVAMP of brass were investigated for various machining parameters. The polishing energy consumptions during traditional MCF polishing and UVAMP were calculated and analyzed from the perspective of the energy of the polishing process. Results indicate that the use of UVAMP considerably reduces energy consumption and surface roughness during the polishing of brass. The adoption of UVAMP therefore has the potential to improve the efficiency and quality of polishing processes and offers a practical solution for the greener manufacturing of brass.

Preliminary Genetic Map of a New Recombinant Inbred Line Population for Narrow-leafed Lupin (Lupinus angustifolius L.)

Genetic maps are an essential tool for investigating molecular markers’ linkage with traits of agronomic importance. Breeders put a lot of emphasis on this type of markers, which are used in breeding programs implementation and speed up the process of a new variety development. In this paper, we construct a new, high-density linkage genetic map for Polish material on narrow-leafed lupin. The mapping population originated from crossing the Polish variety ‘Emir’ and the Belarusian breeding line ‘LAE-1’. A new map was constructed based on DArTseq markers—a new type of marker generated with the next-generation sequencing (NGS) technique. The map was built with 4602 markers, which are divided into 20 linkage groups, corresponding with the number of gametic chromosomes in narrow-leafed lupin. On the new map there are 1174 unique loci. The total length of all linkage group is 3042 cM. This map was compared to the reference genome of narrow-leafed lupin and the CDS sequence for model legume species: emphMedicago truncatula, emphLotus japonicus and Glycine max. Analysis revealed the presence of the DArTseq marker common for all investigated species. We were able to map 38 new, unplaced scaffolds on the new genetic map of narrow-leafed lupin. The high-density genetic map we received can be used for quantitative trait locus (QTL) mapping, genome-wide association study analysis and assembly of the reference genome for the whole genome sequencing (WGS) method

Evaluation of in vitro Streptococcus mutans and Actinomyces naeslundii attachment and growth on restorative materials surfaces.

Restorative materials have varying surface characteristics from natural tooth, which may affect oral-bacterial surface attachment/growth. This study examined 48-h Streptococcus mutans (Sm) or Actinomyces naeslundii (An) growth on various restorative materials and tooth surfaces. The quantity and viability of 48-hour-old Sm and An growth on polished (180- or 1200-grits), saliva-coated resin composite (RC), glass ionomer cements (GIC), resin-modified GIC (R-GIC), GIC containing casein phosphopeptide-amorphous calcium phosphate (3% (w/w), CPP-ACP GIC), amalgam or tooth blocks (5×5×1mm3 ) were examined. Rough-polished (arithmetical mean deviation of the assessed surface roughness profile (Ra): 1.50-1.75µm) material surfaces revealed relatively higher proportion of inorganic, positively charged surface components ((Si+Al)/C) and greater quantity of surface attached bacteria than smooth polished (Ra: 0.20-0.35µm) material groups (P<0.001). Less Sm and An were observed on tooth, and smooth polished GIC and CPP-ACP GIC surfaces than on resin-based materials (RC, R-GIC) and amalgam (P≤0.003). Viability of Sm was found to belower on amalgam surfaces (P<0.001), whereas that of An appeared lower on both amalgam surfaces and rough CPP-ACP GIC surfaces (P≤0.033). Surface roughness exerted a pronounced effect on in vitro growth/attached Sm/An quantity but may not have animpact on bacteria viability. Interestingly, despite smoother surfaces of various materials tested, fewer Sm/An were observed attaching on tooth surfaces.

Influence of Different Composites and Polishing Techniques on Periodontal Tissues near Noncarious Cervical Lesions: A Controlled, Randomized, Blinded Clinical Trial.

Objectives This study evaluated the long-term effect on gingival tissues near noncarious cervical lesions after restoration with different composites in association with two different polishing techniques. Materials and Methods This study was conducted on 60 patients as a randomized, split-mouth, single-blind clinical trial and divided into four groups ( n = 15) and restored using different composites (Tetric N-Ceram nanohibride or Z350 XT nanoparticles) and polishing materials (Astropol or Sof-Lex). The periodontal parameters analyzed were Silness–Löe plaque index; Silness–Löe gingival index; probing depth, clinical insertion level; and bleeding on probing. Periodontal analysis was performed before scaling and root planing at 30, 60, 120, and 180 days after restoration. Statistical Analysis The data submitted to the Friedman’s test were employed for comparison between groups ( p < 0.05). Results Statistically significant differences between Z350/Astropol and other groups were observed for visible plaque and probing depth. Gingival index Tetric/Sof-Lex, the time factor did not influence the results. All experiment groups exhibited statistically significant differences in the clinical level of insertion when the follow-up time was considered. Percentage of bleeding on probing, in which there was a difference only with regard to group Tetric/Sof-Lex when the time factor was considered. Conclusion The evaluated composites and polishing techniques did not exhibit differences in performance in the periodontal parameters analyzed at the end of 6 months of evaluation.

Atomistic simulation of influence of laser nano-structured diamond abrasive on the polishing behavior of silicon

Micro/nano-structured surfaces often present many interesting behaviors and lend themselves to advanced functions. To further improve the polishing performance of diamond abrasives, large scale MD (molecular dynamics) simulations are employed to investigate the ultra-precision mechanical polishing of monocrystalline silicon with laser-fabricated nano-structured diamond abrasive. The material removal mechanism during polishing using structured diamond abrasive is studied in detail. The effects of the structured depth, structured width, structured factor, and structured pattern on the material deformation are studied in detail by analyzing the surface morphologies of the polished surface, normal stresses, shear stress, polishing temperature, atomic coordination numbers, von Mises stress, hydrostatic stress, polishing force, and dislocation extraction algorithm (DXA). The simulation results show that a bigger structured width abrasive, smaller structured depth abrasive，higher structured factor abrasive, or rectangle pattern abrasive would cause a larger material removal rate. Moreover, the abrasive with a smaller structured width, smaller structured depth, or higher structured factor tends to polish silicon materials in a more ductile mode. The abrasive with a bigger structured width has a lower hydrostatic stress, better polished surface, and less defect atoms. However, the abrasive with a bigger structured width, smaller structured depth, or higher structured factor results in a larger normal polishing force. Polishing using an abrasive with a higher structured factor leads to more polishing heat. In addition, the abrasive with 33.3% structured factor polishing can reduce the tangential polishing forces.

Influence of the surface properties of the connector material on the reliable and reproducible contacting of battery cells with a laser beam welding process

The increasing electrification of the automotive industry leads to a growing demand for high-performance energy storage systems. Three different cell types are used for the construction and production of battery modules or packs. These include, for example 18650 round cells, prismatic cells or pouch cells. For the electrical interconnection of prismatic energy storage devices or round cells, the laser bonding method can be used as a particularly flexible connection technology. This method combines the technique of a conventional wire bonder with laser beam welding. Compared to wire bonding, wider and thicker connectors can be contacted, and thus higher currents can be transmitted. During the production of wires/ribbons for wire bonding, sometimes complicated and costly process steps are necessary in order to ensure a consistently high quality of the produced material and consequently obtain a reproducible wire bonding process. Unfortunately, a polished and hence highly reflective surface of an aluminium or copper ribbon adversely affects the reliability of the laser beam welding process. A rough or oxidised ribbon surface however can favour the coupling of the laser radiation into the copper material and thus contribute to a stable process sequence. In this work, the influence of the surface properties of pure copper ribbons regarding the process reliability is investigated. Therefore, ribbons produced for a wire bonding process are thermally oxidised or mechanically roughened, and their optical properties are compared with a polished reference material. The sample ribbons are welded with a continuous wave fibre laser, and the mechanical properties of the resulting connection are investigated. Due to a more stable interaction of the laser radiation, a mechanically and electrically improved connection is expected.

Study of Surface Structure Changes for Selected Ceramics Used in the CAD/CAM System on the Degree of Microbial Colonization, In Vitro Tests.

In the article has been presented an analysis of susceptibility of selected dental materials, made in the CAD/CAM technology. The morphology and structural properties of selected dental materials and their composites were determined by using XRPD (X-ray powder diffraction) techniques, as well as the IR (infrared) spectroscopy. Moreover, an adhesion as well as development of biofilm by oral microorganisms has been studied. It has been shown that a degree of the biofilm development on the tested dental materials depended on microorganism genus and species. Streptococcus mutans has demonstrated the best adhesion to the tested materials in comparison with Candida albicans and Lactobacillus rhamnosus. However, the sintered materials such as IPS e.max® and the polished IPS e.max® have showed the best “anti-adhesive properties” in relation to S. mutans and L. rhamnosus that have not formed the biofilm on the polished IPS e.max® sample. Furthermore, S. mutans have not formed the biofilm on both surfaces. On the contrary to S. mutans and L. rhamnosus, C. albicans has demonstrated the adhesive properties in relation to the above-mentioned surfaces. Moreover, in contrast to S. mutans and C. albicans, L. rhamnosus has not formed the biofilm on the polished IPS Empress material.

МУЗИЧНО-ПЕДАГОГІЧНІ ПОСІБНИКИ СХІДНОЇ ГАЛИЧИНИ ПЕРШОЇ ПОЛОВИНИ ХХ СТ.

In the first half of the twentieth century, a number of textbooks on major musical disciplines, such as solfeggio, the theory of music, and the history of music, appear. Most of them are written for the needs of the M. Lysenko Higher Music Institute (including solfeggio textbooks and the theory of music by S. Lyudkevych). The manuals of S.Lyudkevych are innovative in their approach to solving their tasks. The teacher and composer, S. Lyudkevych, in detail studies the available English, German, Czech, Polish materials and on this basis creates his own methodology. Composite talent helps him to develop constructive exercises that are not devoid of musicality. Also, as a musical material, many melodies from Ukrainian and world music literature have been used. In this way, Lyudkevych introduces Ukrainian music into the auditory memory of the younger generation. Three different approaches to filing the history of music are shown by V. Barvinskiy, B. Kudrick, F. Steshko. Using the historical approach, each of them chooses another way of disclosing the material through different goals of their work. The “Review of the History of Ukrainian Church Music” is based on a detailed review of the historical situation, composer biographies and a deep comprehensive analysis of musical works, as it is a textbook. “Music” by V. Barvinskiy is a section “The History of Ukrainian Art”, edited by I. Krypyakevych, and a generalizing approach is chosen here. “Music” in, a concise form, allows us to trace the ways of developing Ukrainian music from ancient times to the present in the context of world music. F.Steshko focuses on comparing the works of Ukrainian composers with their contemporaries (for example, Berezovskiy and Mozart). Their value is in combination with proven long-standing practice of European techniques with Ukrainian musical material. Today, these textbooks, which undoubtedly can and must be part of the Ukraine, need to return to scientific circulation and educational practice.

Different polishing methods for zirconia: impact on surface, optical, and mechanical properties.

To test the impact of polishing strategies on zirconia properties. One hundred eight zirconia specimens were divided into nine groups (n= 12/group). Seven groups were polished in the white-stage with either (1) a felt wheel (FW), (2) a felt wheel combined with a polishing paste (FWP), (3) a goat hair brush (GB), (4) a goat hair brush combined with a polishing paste (GBP), (5) a green-state finishing kit (FK), (6) a universal polisher (UP), or (7) with SiC polishing paper (PP), and sintered. Thereafter, the seven groups were divided into two subgroups each and polished using (1) a fine polisher (one-step, n= 6) or (2) a rough and fine polisher (two-steps, n= 6). The positive control group (polish-lab-kit, PLK) was sintered and polished in two-steps. The no polished group (NP) acted as negative control group. Translucency (T%) was measured after white-stage polishing and sintering, and after sintered-stage polishing. Surface free energy (SFE), surface roughness (SR), and flexural strength (FS) were determined. Data were analyzed using one-way ANOVA with Tukey-B post-hoc, t test, and Wilcoxon-test (p< 0.05). FWP, GB, FK, UP, and PP presented decreased T% after one-step, while FWP, GB, GBP, FK, and UP presented decreased T% following two-steps polishing. FW showed the highest T% after white-stage, one-, and two-steps polishing. PP presented the lowest SFE. Two-steps polishing resulted in a lower SR for FW, FWP, GB, FK, UP, and PP and increased FS in all groups. White-stage polishing improved zirconia properties. Two-steps polishing in the sintered stage, especially when combined with a polishing paste, can decrease SR and increase T% and FS. With polishing in the sintered-stage impairing the polishing material and being time consuming, alternatives such as white-stage polishing should be investigated.

Low-temperature direct bonding of Si and quartz glass using the APTES modification

Abstract Low-temperature direct bonding is an attractive technique for joining mirror polished dissimilar materials with large mismatch in the coefficient of thermal expansion or/and lattice constant. In this paper, we proposed a method for the direct bonding of Si and quartz glass using the 3-aminopropyltriethoxysilane (APTES) modification. Strong bonding strength which was equal to or stronger than the fracture strength of the quartz glass substrate has been achieved after the Si/quartz glass pre-bonded pair was annealed at 150 °C. Based on the analyses of the wettability and surface chemical states, grafting of APTES and substitution of ethoxy groups have been studied in detail. Additionally, the tight and nanoscale bonding interface observed by scanning electron microscopy and transmission electron microscopy also ensured the excellent sealability, as well as, facilitated the device miniaturization.

One-shot recording of the instantaneous change in the refractive index of bulk semiconductors exposed to pulsed radiation by a Fabry-Perot-like interferometer.

An interferometer, directly coupling a single-mode fiber with a bulk semiconductor, was used to one-shot record the instantaneous change in the refractive index of bulk semiconductors. A practical contrast level can be achieved in the interferometer with different types of polished bulk materials several hundred micrometers in thickness. The temporal resolution was approximately 50 ps and can be improved by using thinner materials or higher bandwidth detection. This interferometer can also be used to study the fast recording technology based on pulsed radiation-induced changes in optical characteristics.

Ultra-smooth Cu surface fabricated by hydrodynamic suspension polishing technique

Hydrodynamic suspension polishing technique is proposed to prepare an ultra-smooth surface by designing a setup with a particular polishing disk. The novel polishing technique involves two preceding steps of mechanical polishing and chemical erosion processes. They are introduced to deal with the as-received Cu surface before the hydrodynamic suspension polishing for the polishing efficiency. Surface roughness, surface deformation layer and crystalline structures of the mechanically polished surface and the surface polished by the novel technique proposed here are characterized to show the advantages of the proposed technology. Results show that chemical erosion process efficiently removes surface deformation layer and the novel polishing process decreases the surface roughness significantly. The minimum surface roughness (Ra) is only 0.81 nm. Furthermore, there are no apparent surface deformation layers and crystalline defects on the surface after hydrodynamic suspension polishing. The relationship between the kinetic energy of abrasive and bonding energy of Cu atom is established to provide a clear understanding of the two typical planarization mechanisms, i.e., removing and filling. Both the scientific design of non-contact polishing and appropriate processing parameters are bases of preparation of the atomic-scale smooth surface. This study provides a new strategy to polish metal material with an atomic scale surface roughness and high efficiency.

Preparation and characterization of magnetorheological elastic polishing composites

Magnetorheological elastic polishing composites, a new type of polishing material using magnetorheological elastomers as a binder, were developed to solve the problems of low processing efficiency and difficulty controlling the machining process in current polishing technology. A set of heat–magnet–force-coupled devices was designed and used to prepare isotropic and anisotropic silicon rubber–based magnetorheological elastic polishing composites by magnetic field–assisted compression molding technology. Then, the microstructure and properties of magnetorheological elastic polishing composites were characterized by X-ray diffraction, optical microscope, electronic universal testing machine, and microscratch tester. The results show that magnetorheological elastic polishing composite is a polymer-based composite composed of rubber and micro/nanoparticles, and the magnetic field applied during the preparation process causes the interior of the magnetorheological elastic polishing composites to appear as chains and columns formed by iron particles. The compressive elastic modulus and scratch resistance of magnetorheological elastic polishing composites increase with the increase in the surrounding magnetic field strength. The main reason for the above phenomena is related to the change in the microstructure of magnetorheological elastic polishing composites induced by an external magnetic field. Finally, a simple application of magnetorheological elastic polishing composites in polishing proves that magnetorheological elastic polishing composites can be applied to mechanical processing to achieve magnetically controlled polishing.

Pamiętniki jako źródło wiedzy o kształtowaniu się kompetencji leksykalnej (na przykładzie XVII-wiecznych Les anecdotes de Pologne… F. P. Dalairaca)

W artykule podjęto próbę opisu kompetencji leksykalnej w XVII-wiecznym, francuskojęzycznym pamiętniku F. P. Dalairaca Les anecdotes de Pologne…. Autor, który był poddanym Ludwika XIV, przebywał na dworze króla Jana III Sobieskiego. W diariuszu dokumentującym wydarzenia związane z wyprawą wojenną w 1683 roku zamieścił bogaty polski materiał leksykalny. Na podstawie obserwacji słownictwa specjalistycznego i ogólnego, które zostało wplecione w tekst francuski, można sądzić, że autor posiadał zaawansowaną kompetencję językową w zakresie języka polskiego, był więc osobą dwujęzyczną. Poddany ekscerpcji pamiętnik stanowi ciekawe źródło do badań charakterystycznych dla mowy biblingwalnej zachowań językowych, które były konsekwencją dawnych kontaktów językowych.

Levels and trends of PCDD/Fs and DL-PCBs in Polish animal feeds, 2004–2017

ABSTRACTFeed control is essential for the safety of animal-origin food. It is estimated that more than 80% of human exposure to dioxins and related compounds comes from the consumption of animal-origin food, and farm animals are exposed to dioxins mainly through the feed. A monitoring programme for dioxins (polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs)) and dioxin-like polychlorinated biphenyls (DL-PCBs) was conducted in the Polish feed market between 2004 and 2017. Using two complementary ISO 17025-accredited analytical methods (bioassay and high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS)), 2919 samples of plant, animal and minerals origin were analysed. The total number of samples exceeding the maximum limit (ML) was 52, which is 1.8% of all tested samples. They all contained PCDD/Fs in concentrations over the ML, and in 16 samples the limit for the sum of PCDD/F/DL-PCBs was also exceeded. The highest dioxins level was found in feedstuffs derived from Baltic fish; the fish oil was followed by fish meal. Low-chlorinated furans (2.3,7,8 TCDF, 2,3,4,7,8-PCDF and 1,2,3,7,8-PeCDF) were dominant and these congeners accounted for the toxicity expressed in WHO toxic equivalents (WHO-TEQ). In this category, 155 out of the 498 samples (32%) exceeded the action threshold (AT) for PCDD/Fs and in 10 samples (2.0%) for DL-PCBs. Non-compliant fish meals were found in 34 (5.6%) of the tested samples, in 0.7% of compound feeds, and in 1.5% of plant-origin materials. Seven dried plant-derived materials contained PCDD/F level above ML, including alfalfa, maize, apple, basil and beet pulp pellets containing molasses. The dry vegetable materials were mostly contaminated by the 2,3,7,8-furans, the congeners arising from a faulty drying process. No significant time trend can be seen. From the obtained results, it can be concluded that concentrations of PCDD/Fs and DL-PCBs in Polish feed materials were sufficiently low to ensure low concentrations in animal-derived products.

Optimization of Ultrasonic-Assisted Polishing SiC Through CFD Simulation

In this paper, a detailed simulation about ultrasonic-assisted polishing was conducted, which is helpful to understand the contribution of the ultrasonic vibration to polishing. The influence of ultrasonic vibration on flow field parameters and optimal ultrasonic parameters was investigated. Results indicate that ultrasonic vibration can produce a cavitation phenomenon, which can contribute to improving the polishing quality and material removal rate (MRR). Optimal ultrasonic frequency, amplitude and film thickness were 42 μm, 25 kHz and 14 mm, respectively. Furthermore, the required minimum film thickness was 1.5 mm, at which cavitation could occur normally. At last, contrast experiment indicated that polishing quality and MRR were much improved when using ultrasonic-assisted polishing. After polishing, there were only a few scratches and MRR was 0.68 μm/h compared with many scratches and 0.32 μm/h MRR of traditional polishing.