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A novel approach to enhancing the efficacy and surface quality of magnetic polishing involves the incorporation of a magnetic liquid circulation system for abrasive particle regeneration in conjunction with a circular Halbach array. The continuous renewal of abrasive particles within the polishing zone is realised through a conveyor belt that transports new abrasive particles into the polishing liquid solution. This formation of a continuously circulating polishing system ensures uninterrupted magnetic finishing processes and maintains stability throughout the polishing operation. This study extensively explores polishing force distribution, magnetic field distribution and abrasive grain behaviour in the polishing area facilitated by the magnetic liquid solution. The application of the proposed polishing processes to polymethyl methacrylate, an optical lens material, aims to comprehend the characteristics and validate the feasibility of the polishing method. Key influencing factors in the magnetic polishing process, including abrasive grain size, magnetic particle, polishing distance and conveyor speed to surface quantity, are examined through experimental analysis. Results of the experimental polishing processes demonstrate that the utilisation of circular Halbach arrays with circulating abrasives produces a nanometric surface finish. Even in the polishing of polymethyl methacrylate with an initial rough surface (Ra = 464.895 nm), the process achieves an ultra-fine level with Ra below 9 nmwithout disruption in the material polishing processes of optical lenses. [ABSTRACT FROM AUTHOR]

As an important indicator of the surface quality of workpieces, surface roughness has a great impact on production costs and the quality performance of the finished components. Effective surface roughness prediction can not only increase productivity but also reduce costs. However, the current methods for surface roughness prediction have some limitations. On the one hand, the prediction accuracy of classical experimental and statistical-based surface roughness prediction methods is low. On the other hand, the results of deep learning-based surface roughness prediction methods are uninterpretable due to their black-box learning mechanism. Therefore, this paper presents an ensemble learning with a differential evolution algorithm, applies it to the prediction of surface roughness of abrasive water jet polishing (AWJP), and conducts an interpretability analysis to identify key factors contributing to the prediction accuracy of surface roughness. First, we proposed automatically constructing features by an Evolution Forest algorithm to train the base regression models. The differential evolution algorithm with a simplified encoding mechanism was then used to search for the best weighted-ensemble to integrate the base regression models for obtaining highly accurate prediction results. Extensive experiments have been conducted on AWJP to validate the effectiveness of our proposed methods. The results show that the prediction accuracy of our proposed method is higher than the existing machine learning algorithms. In addition, this is the first of its time for the contributions of machining parameters (i.e., features) on surface roughness prediction by using interpretable analysis methods. The analysis results can provide a reference basis for subsequent experiments and studies. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate how two different polishing techniques affect the color stability, surface roughness, and changes in surface morphology of aged and coffee-stained bulk-fill resin composites. A total of 112 disc-shaped samples were prepared using Omnichroma Flow Bulk (OB), Charisma Bulk Flow One (CB), Estelite Bulk Fill Flow (EB), and Estelite Sigma Quick (control). Samples were divided into two subgroups (n = 16) and aged using thermocycling. A profilometer was used to measure the surface roughness (Ra) and a spectrophotometer was used for color stability (ΔE00). The EB group had the highest Ra values both before aging (disc: 0.23 ± 0.05, twist: 0.42 ± 0.05) and after aging (discs: 0.28 ± 0.04, twist: 0.46 ± 0.05). The OB group had the highest ΔE00 values before and after aging (discs: 3.06 ± 0.54, twist 3.05 ± 0.41) and the highest after coffee-staining (discs: 3.75 ± 0.70, twist: 3.91 ± 0.57). Re-polishing reduced the ΔE00 values in all materials but did not restore all to clinically acceptable levels. According to the results of this study, it can be concluded that the surface roughness and color stability of resin composites are notably influenced by the polishing technique, aging process, and coffee staining. Specimens that were polished using the multi-stage Super-Snap discs consistently exhibited smoother surfaces across all bulk-fill resin composites compared to those polished with the two-stage Diacomp plus Twist. [ABSTRACT FROM AUTHOR]

Nanofinishing of blind-hole cavities is important to produce high quality products without any surface irregularities. The commonly used methods such as grinding or honing are not efficient because of the uncontrolled forces and direct contact of the solid abrasive tool with the workpiece. Magnetorheological (MR) polishing process using smart fluid has proved its effectiveness in achieving the nano-finished surface. The existing tool design uses two different operations for nano-scale finishing of a blind-hole cavity, resulting into a higher production cost. In this present work, a novel tool that can vary its dimensions during finishing operation was developed for enhancing the surface finishing of blind-hole cavities. Distribution of magnetic fields within the entire tool and blind-hole cavity surface was found appropriate and also revealed that the tool surface has maximum magnetic field for stiffening the MR polishing fluid over its surface. After 90 minutes of finishing, it was concluded that the roughness (Ra) change on the blind-hole cavity were reduced by 75.12% (on inner vertical) and 74.21% (on inner bottom). [ABSTRACT FROM AUTHOR]

During the polishing process of complex curved PMMA parts, the polishing force is an important factor affecting the surface quality and optical performance. In this paper, a force-controlled polishing device integrated into a machining center to maintain the polishing force is investigated. In order to achieve the real-time active control of the polishing force, the linear voice coil motor and force sensors are used for motion and measurement. A compact structure was designed to couple the linear motion of the voice coil motor with the rotation for polishing. The force-controlled polishing system with a high real-time hardware architecture was developed to perform complex curved polishing path movement with precise force control. Next, the polishing force between the device and the workpiece was analyzed to obtain the mathematical model of the device. Considering the impact during the approaching phase of polishing, a fuzzy PI controller was proposed to reduce the overshoot and response time. To implement the control method, the controller model was established on Simulink and the control system was developed based on TwinCAT 3 software with real-time computing capability. Finally, a polishing experiment involving a complex curved PMMA part was conducted by a force-controlled polishing device integrated into a five-axis machining center. The results show that the device can effectively maintain the polishing force to improve surface quality and optical performance. [ABSTRACT FROM AUTHOR]

Polishing torque holds significance in monitoring the chemical mechanical polishing (CMP) process due to its close correlation with material removal. This study introduces a new model-based technique for estimating the material removal rate (MRR) using in-process data from CMP machines. The proposed method employs either the sequential least squares method or Kalman filter for real-time state estimation. Real-time estimation of MRR enables material removal control without relying on conventional endpoint detection (EDP) technologies. The accuracy of the proposed approach is validated through oxide CMP experiments, demonstrating precise estimation of the center-slowed MRR profile towards the end of the pad life. [ABSTRACT FROM AUTHOR]

Electrorheological polishing (ERP) is an important field-assisted polishing method, which can reduce abrasive loss and improve machining efficiency by using the electric field-induced electrorheological (ER) effect to help the abrasive to overcome the centrifugal force caused by high rotating speed during polishing. ERP has many advantages, including high efficiency, high precision, facile polishing for a small object, and a good application prospect in polishing optical devices and hard molds. This review describes the research progress in ERP in the past two decades. The mechanism of electrorheological polishing is analyzed from two aspects of electrorheological effect and dielectrophoresis. According to the time sequence of electrorheological polishing development, two kinds of ERP materials including the simple mixing system and composite particle system are introduced. ERP electrodes including off-axis bipolar electrode, needle-ring electrode, needle-like single electrode, one-sided patterned electrode, and one-sided simple composite electrode are described. From the two characterization quantities of removal rate and surface quality, the industrial factors affecting the ERP effect are discussed. The advantages and disadvantages of ERP and other polishing processes are compared. Finally, the remaining challenges and possible development trends in ERP technology for the future outlook are proposed. [ABSTRACT FROM AUTHOR]

In this paper, the influence of miscut-angle on the processing of β-Ga2 O3 (100) plane substrates was studied. The morphology changes of (100) plane substrates during the processing were analyzed when the miscut-angles were 0°, 1° and 6°, respectively. Furthermore, the influence of different parameters on the polishing of the substrate was analyzed. The experimental results show that with the increase of the miscut-angle, the cleavage damage of (100) plane substrate reduces, the surface roughness reduces after machining, and the way of material removal transformed from brittle removal to brittle plastic mixed removal to plastic removal. Low polishing pressure can effectively suppress the cleavage damage and improve the surface quality. When the miscut-angle is 6°, the polishing efficiency of (100) plane substrate is high, and the surface roughness after polishing can reach Ra≤0.2nm. [ABSTRACT FROM AUTHOR]

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A slight alteration of the enamel surface is inevitable upon debonding of orthodontic brackets, adhesive removal, and finishing/polishing. The aim of this in vitro study was to compare two adhesives and three polishing methods by measuring enamel surface roughness using confocal laser scanning microscopy (CLSM). Brackets were bonded on 42 extracted human premolars using Transbond XT (Transbond group) or Fuji Ortho (Fuji group). After debracketing, adhesives were removed with a tungsten carbide bur, and surfaces were polished using Sof-Lex discs, a rotary brush with a prophylactic paste (Depural), or a prophylactic cup with two polishing pastes (n = 7 in each subgroup). Surface roughness (Sa, Sku, Sq, and Sz) was measured using CLSM and compared before treatment (T1), after debracketing and adhesive removal (T2), and after polishing (T3). The data were statistically analyzed using the Mann–Whitney U and Kruskal–Wallis tests with Bonferroni correction. The time required for adhesive removal was measured and compared using a two-sample t-test. Surface roughness at T2 increased compared to T1, but the difference was significant only for the Fuji group (p < 0.01). The time required to remove Transbond XT (94.1 ± 6.8 s) was significantly higher compared to Fuji (72.1 ± 5.9 s, p < 0.0001). Polishing with Sof-Lex discs resulted in lower surface roughness compared to T1 (p = 0.018). Using Depural and polishing pastes showed no significant difference in surface roughness compared to T1, except for a significant decrease in Sa and Sq for Transbond (p = 0.043) and in Sku for Fuji (p = 0.018) after polishing with Depural. In conclusion, the removal of Transbond took significantly longer, but there were fewer residues of composite resin on the enamel surface. Sof-Lex discs decreased enamel roughness, whereas enamel morphology and roughness were similar to the pre-treatment state after polishing with polishing pastes. [ABSTRACT FROM AUTHOR]

Three-dimensional printing has become incorporated into various aspects of everyday life, including dentistry. Novel materials are being introduced rapidly. One such material is Dental LT Clear by Formlabs, a resin used for manufacturing occlusal splints, aligners, and orthodontic retainers. In this study, a total of 240 specimens, comprising two shapes (dumbbell and rectangular), were evaluated through compression and tensile tests. The compression tests revealed that the specimens were neither polished nor aged. However, after polishing, the compression modulus values decreased significantly. Specifically, the unpolished and nonaged specimens measured 0.87 ± 0.02, whereas the polished group measured 0.086 ± 0.03. The results were significantly affected by artificial aging. The polished group measured 0.73 ± 0.05, while the unpolished group measured 0.73 ± 0.03. In contrast, the tensile test proved that the specimens showed the highest resistance when the polishing was applied. The artificial aging influenced the tensile test and reduced the force needed to damage the specimens. The tensile modulus had the highest value when polishing was applied (3.00 ± 0.11). The conclusions drawn from these findings are as follows: 1. Polishing does not change the properties of the examined resin. 2. Artificial aging reduces resistance in both compression and tensile tests. 3. Polishing reduces the damage to the specimens in the aging process. [ABSTRACT FROM AUTHOR]

Roughness down to atomic and close-to-atomic scale is receiving an increasing attention in recent studies of manufacturing development, which can be realized by high-precision polishing processes. This review presents polishing approaches at atomic and close-to-atomic scale on planar and curved surfaces, including chemical mechanical polishing, plasma-assisted polishing, catalyst-referred etching, bonnet polishing, elastic emission machining, ion beam figuring, magnetorheological finishing, and fluid jet polishing. These polishing approaches are discussed in detail in terms of removal mechanisms, polishing systems, and industrial applications. The authors also offer perspectives for future studies to address existing and potential challenges and promote technological progress. [ABSTRACT FROM AUTHOR]

Magnetic particles (Fe 3 O 4 /CIP) in magnetorheological elastomer (MRE) were used as solid-phase catalysts in the heterogeneous Fenton reaction for chemical mechanical polishing (CMP) of single-crystal SiC. The polishing effect and polishing mechanism were investigated by experiments and polishing debris analysis. The results show that when using H 2 O 2 polishing solution the material removal rate (MRR) was higher and the surface roughness (Ra) was lower at all stages of polishing than using deionized water polishing solution. The MRRs when polishing for 60 min with the deionized water and the H 2 O 2 polishing debris were, respectively, 636.94 nm/h and 1194.27 nm/h (an increase by 87.5%), and the corresponding Ra values were, respectively, 12.445 nm and 4.420 nm (a decrease by 64.5%). From the analysis of the polishing debris after 60 min of polishing, it was found that the H 2 O 2 polishing solution was polished with laminated loose chips, and the main elements of the chips were C, O, and Si, with O element accounting for 38.585 wt%. This indicates that a chemical reaction has occurred on the SiC surface during polishing, generating low hardness and low binding strength SiO 2 , and thus resulting in increased material removal; this phenomenon is confirmed by the profile morphology of SiC wafer by fixed-point polishing. It is shown that the use of Fe 3 O 4 /CIP in MRE as a solid-phase catalyst for the heterogeneous Fenton reaction of polishing SiC can substantially increase the material removal capacity of MRE polishing pads and improve the polishing quality at the same time. • A MRE polishing pad with heterogeneous Fenton reaction was provided. • Magnetic particles in MRE were used as solid-phase catalysts in the heterogeneous Fenton reaction for CMP. • The material removal model for polishing single-crystal SiC with MRE polishing pads was proposed. [ABSTRACT FROM AUTHOR]

Due to the inevitable, nonuniform relative speed distribution between a workpiece and polishing pads, double-sided polishing (DSP) faces the challenge of nonuniform removal distributions. Hence, maintaining workpiece flatness while perfecting surface finishing remains a challenge in the DSP process. This study controlled the pressure distribution on a workpiece using a polishing pad design to compensate for the nonuniformity. An analytical model of the removal distribution was proposed considering the impact of pressure distribution. Experiments confirmed the proposed model's capability to evaluate the compensating effect of the polishing pad design. Finally, design guidelines for uniform removal distributions were established. [ABSTRACT FROM AUTHOR]

Extensive research has been conducted on Bonnet polishing for its ability to manufacture freeform surfaces with nano-scale precision. However, surface ripples are easy to introduce under regular motion, and the underlying principle to address this problem remains unclear. In this study, a novel methodology based on frequency domain characterization is proposed, connecting the spatial process parameters and frequency domain evaluation index directly. Bessel function and single pulse convolution are introduced for model establishment. Tool radius, tool tilt angle, and contact radius are correlated with surface ripple mitigation. Polishing parameters optimization case study was conducted and verified using self-designed polishing robot. [ABSTRACT FROM AUTHOR]

Mirror-polishing processes have recently been required to add high quality, high-precision precision and multifunctionality to industrial products. However, this requires skilled manual work, making it difficult to improve productivity. Automatic polishing of these products is also very difficult. Furthermore, mirror-polishing process of stainless steel, titanium and glass, which are often used in high-value-added medical products, is also difficult. Therefore, in this study, a technology for high-precision, automatic mirror polishing of three difficult-to-polish materials - stainless steel, titanium and glass - was developed and evaluated. First, the difficult-to-polish properties of different materials were considered, and then tools were developed to improve these properties and enable suitable mirror-polishing processes. Next, a polishing slurry was developed to improve the surface roughness (Rz = 0.1 µm or less). Finally, the optimum polishing conditions for the proposed mirror-polishing process were determined by design of experiment and then evaluated. It was concluded that; (1) In order to perform mirrorpolishing processes of three types of workpieces, stainless steel (SUS304), titanium (pure titanium) and glass (quartz glass), new polishing tool and slurries corresponding to each material were developed and the optimum polishing processing conditions were clarified, (2) Using (1), mirror-polishing processes of each material with a surface roughness of Rz = 0.1 µm has been achieved. [ABSTRACT FROM AUTHOR]

Magnetic field-assisted magnetic compound fluid (MCF) ultra-precision machining technology is regarded as an effective method to obtain a smooth surface. However, due to the evaporation and splashing of water in the polishing fluid during processing, the service life of the MCF slurry is reduced. This paper presents a material removal model for MCF polishing, and a novel experimental apparatus is proposed to extend the service life by supplying MCF components into the MCF slurry. Firstly, in order to obtain the ideal polishing tool, the appearance morphologies and the formation process of the MCF slurry were observed by an industrial camera. On this basis, the optimum parameters were determined by multi-factor and multi-level orthogonal experiments. Finally, the investigation of the MCF service life was carried out under the optimal processing parameters. The main findings are summarized as follows. (1) Excellent MCF polishing tools are obtained when the eccentric distance r is 4 mm and the MCF slurry supply V is 1 mL. (2) When the eccentric distance increases from 2 mm to 4 mm, the forming time of the MCF tool decreases sharply, but when the eccentricity exceeds 4 mm, the decreasing trend becomes slow. The molding time grows steadily as the supply is increased. (3) When the machining gap Δ, the MCF carrier speed nc, the eccentricity r, and the revolution speed of magnetic nm are 1 mm, 500 rpm, 4 mm, and 600 rpm, respectively, the ideal machining effect can be obtained. (4) It could be proven that the polishing device is feasible to extend the service time of the MCF slurry by adding MCF components. [ABSTRACT FROM AUTHOR]

On a single-cylinder gasoline engine test bench, the experimental study of the effects of polishing the combustion chamber wall and piston top surface on the indicated thermal efficiency and combustion characteristics were carried out, and the mutual influence of combustion phase, combustion duration and indicated thermal efficiency before and after polishing the wall of combustion system was systematically analyzed. The results show that when the single-cylinder gasoline engine operates at stoichiometric air-fuel ratio, low load and low compression ratio, the heat transfer loss of the polished combustion chamber is reduced and the fuel economy is improved, and the indicated thermal efficiency is increased from 40.8 to 42.2 %. With the increasing of load and compression ratio, the knock effect caused by the reduction of heat transfer loss after polishing is enhanced, and the combustion phase is delayed and the combustion duration is prolonged, which eventually leads to the decrease of the indicated thermal efficiency. After combustion chamber polishing, HC and NOx decrease by up to 70 %. With the increase of compression ratio, HC emission gradually increases, while NOx emission gradually decreases. There is no obvious change trend of CO emission before and after polishing. When the gasoline engine operates in lean combustion mode, the indicated thermal efficiency increases effectively, and the highest thermal efficiency exceeds 45 %; When the gasoline engine operates at indicated mean effective pressure of 1.05 MPa, the reduction of heat transfer loss in the combustion chamber after polishing enhances the knocking tendency, resulting in the overall decrease of the gross indicated thermal efficiency compared with that before polishing. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is an advanced near net shape manufacturing technology that facilitates the formation of complex shaped products from a digital 3D design. Freedom of design, minimal scrap formation, and mass customization make AM technology dominant over conventional methods. Recently, metal additive manufacturing (MAM) gained ambience owing to the ever-increasing demand for complex and customized metallic parts/components in aerospace, biomedical, automotive and marine industries. However, the parts/components produced by MAM cannot be directly employed in practical applications due to the poor surface integrity and loss of dimensional accuracy. Metallic AM surfaces are characterized by staircase effect, balling phenomena, lack of fusion defects, porosities and cracks. In order to overcome the aforementioned problems, several post-processing methods have been introduced by researchers over the years. These include laser polishing, abrasive finishing, chemical and electrochemical polishing, conventional finishing, electrical discharge polishing, and some other hybrid methods. The principle of operation, significant outcomes in terms of surface modification as well as pros and cons of each of these methods are discussed in detail in this review article. The comprehensive outlook of the paper establishes a foundation of reference for future research works in the area of post-processing metallic AM components. Moreover, the future path of research ahead in the domain of post-processing methods has been discussed with special attention on automation of finishing methods using machine learning and artificial intelligence. [ABSTRACT FROM AUTHOR]

The increasing demand of the superfinished three-dimensional (3D) surfaces has stimulated the development and upgrade of the precision polishing technology. However, current ultra-precision polishing methods usually polish the workpiece one-by-one, leading to low production efficiency and high polishing cost. Even though some batch polishing methods have been developed for polishing a number of workpieces simultaneously, it is difficult for them to obtain high form accuracy, as well as nanometre scale surface roughness. Hence, this paper presents a shape-adaptive magnetic field-assisted batch polishing (SAMABP) method which not only implements nanometre scale batch polishing of 3D surfaces, but also achieves high form maintainability. Firstly, the effect of surface shape on the material removal in magnetic field-assisted batch polishing (MABP) is revealed. Secondly, the shape-adaptive optimization (SAO) algorithm is developed to cater for the effect of the material removal variation on different kinds of surface shapes, based on the kinematic analysis of the magnetic brush in MABP, as well as modelling of the material removal distribution. At last, a series of verification experiments are designed and conducted on convex, concave and structured surfaces to validate the proposed method. The surface roughness of 3D surface was significantly reduced from larger than 100 nm to less than 10 nm or even less than 5 nm in arithmetic surface roughness (Sa) after 20 min of polishing. Meanwhile, the surface forms were maintained well, and the deviation of them after polishing were all less than 4 μm in peak-to-valley (PV). These results show that the SAMABP method is effective to obtain nanometric surface roughness together with micrometric form accuracy in the batch polishing of 3D surfaces. This study sheds the light for the applications of SAMABP in batch polishing of optical components and moulds, functional structured surfaces, turbine blades, dental crowns, surgical knives, high-end jewelleries, etc. [Display omitted] • The effect of surface shape on surface quality in magnetic field-assisted batch polishing (MABP) is revealed. • Material removal model and shape adaptive optimization algorithm are developed to cater for the shape effect. • A novel shape adaptive magnetic field-assisted batch polishing (SAMABP) method is developed. • The SAMABP method is validated on different kinds of 3D surfaces including freeform surfaces. • The SAMABP is found to achieve nanometric surface roughness and micrometre scale form accuracy. [ABSTRACT FROM AUTHOR]

The long-term success of a composite restoration largely depends on its smoothness, which can be achieved by the appropriate polishing tools and material selection. The purpose of this study was to evaluate the surface roughness of two composite materials after the application of selected polishing systems. Filtek Ultimate (FU) and Filtek Z250 (FZ) were tested. Forty specimens of each material were prepared. After polymerization under a Mylar strip, the surface roughness of five samples from each group was measured. Subsequently, all specimens were ground by 600 grit sandpaper. The surface roughness of five samples per group was tested again. The samples from each group were randomly assigned to eight subgroups, and polished by Sof-Lex, Sof-Lex Diamond Polishing System, Super Snap, One Gloss, Astrobrush, Stainbuster, Enamel Shiny, and Jiffy Polishing System. The collected data were analyzed using the Shapiro–Wilk and Kruskal–Wallis tests. The lowest Ra coefficient after polishing is found in the Super Snap groups (FU—0.077 μm, FZ—0.085 μm). The lowest Rlr coefficient is measured in the Enamel Shiny group for FU (1.000), and for Sof-Lex, Sof-Lex Diamond Polishing System, and Jiffy Polishing Kit for FZ (1.001), and only slightly higher for Super Snap (FU—1.001, FZ—1.002). The roughest-measured surface is in the One Gloss group for FU (Ra—0.657 µm, Rlr—1.009), and Astrobrush group for FZ (Ra—0.525 μm, Rlr—0.011). Additionally, it was not confirmed that the nanoparticle material (FU) demonstrates better results than the microhybrid one (FZ). Different polishing systems produce varying surface roughness. The most effective polishing system is Super Snap. The structure of composites does not significantly affect their surface roughness after polishing. [ABSTRACT FROM AUTHOR]

To solve the problems of the low use rate of magnetic fields and weak magnetic field intensity caused by the use of only a one-sided magnetic pole in the design of the magnetic field device based on permanent magnets in the usual magnetorheological polishing process, a design method and a mathematical model of the dynamic magnetic field device based on the Halbach array are set up in this paper. Through the simulation and experimental research of two different array forms, the ideal magnetic field layout scheme is determined in the form of a circularly symmetrical array, and the effects of process parameters such as the magnetic field speed, the workpiece speed, and the workpiece immersion depth in the polishing pad on the surface roughness of the workpiece after polishing are studied. The orthogonal experimental results show that when the magnetic field is at a low speed of 40r/min, the workpiece is at a medium speed of 650r/min, and the workpiece is immersed in the upper and middle depth of the polishing pad, in which the workpiece can obtain better surface roughness. The research results also show that the dynamic magnetic field device based on the Halbach array can achieve greater changes in magnetic field intensity and gradient with fewer magnets, which provides a reference method for the small and lightweight design of magnetic field devices in magnetorheological polishing. [ABSTRACT FROM AUTHOR]

A new polishing pad based on the sol-gel (SG) technique is fabricated and can polish the single crystal diamond (SCD) substrate at high speed. In this work, the base material, fillers, and coating height of the polishing pad are selected. Pressed polymer fiber is used as the base material, talcum powder is chosen as filler, and the coating height of the gel formulation system on the surface of the base material is between 20 and 40 $\mu \text{m}$. The surface morphology of SCD substrate was observed with a 3D optical surface profiler. The surface roughness decreased from 78.024 nm to 6.126 nm in 2 h and the material removal rate of the SCD (100) was about 135 nm/h. The Raman spectroscopy result shows that there was phase transformation on the surface of the SCD substrate after polishing. The material removal mechanism was proposed based on the result. During the scratch of the diamond abrasive, the diamond on the surface of the SCD substrate was transformed into amorphous carbon. Then the amorphous carbon was removed mechanically. The new gel polishing pad can polish the SCD substrate with high efficiency. [ABSTRACT FROM AUTHOR]

Air-abrasion is a popular prophylactic procedure to maintain oral hygiene. However, depending on the applied air-abrasive powder, it can damage the surface of the tooth and restorations, making it susceptible to plaque accumulation. The purpose of this study was to investigate the effect of 5 s and 10 s air-abrasion of calcium carbonate on surface roughness (Ra) of enamel, nanofill, and microhybrid resin-composites and the effect of post-polishing with two-step rubber- (RP) or one-step brush polisher (BP) to re-establish the surface smoothness. Surface topography was visualized by scanning-electron-microscopy. The quantitative measurement of the Ra was carried out with atomic-force-microscopy. Air-abrasion for 10 s decreased the Ra of enamel as a result of abrasion of the natural surface texture. Post-polishing with RP after 10 s air-abrasion did not change the Ra or BP; however, Ra was increased significantly by scratching the surface. Air-abrasion increased the Ra of resin composites significantly, irrespective of the application time. While RP provided a similarly smooth surface to the control in the case of microhybrid resin composite, BP increased the Ra significantly. The Ra for the control group of the nanofill-resin composite was initially high, which was further increased by air-abrasion. RP and BP re-established the initial Ra with deeper and shallower scratches after BP. Both the material and treatment type showed a large effect on Ra. [ABSTRACT FROM AUTHOR]

New manufacturing technologies, such as Sheet-Bulk Metal Forming, are facing the challenges of highly stressed tool surfaces which are limiting their service life. For this reason, the load-adapted design of surfaces and the subsurface region as well as the application of wear-resistant coatings for forming dies and molds made of high-speed steel has been subject to many research activities. Existing approaches in the form of grinding and conventional milling processes do not achieve the surface quality desired for the forming operations and therefore often require manual polishing strategies afterward. This might lead to an unfavorable constitution for subsequent PVD coating processes causing delamination effects or poor adhesion of the wear-resistant coatings. To overcome these restrictions, meso- and micromilling are presented as promising approaches to polishing strategies with varying grain sizes. The processed topographies are correlated with the tribological properties determined in an adapted ring compression test using the deep drawing steel DC04. Additionally, the influence of the roughness profile as well as the induced residual stresses in the subsurface region are examined with respect to their influence on the adhesion of a wear-resistant CrAlN PVD coating. The results prove the benefits of micromilling in terms of a reduced friction factor in the load spectrum of Sheet-Bulk Metal Forming as well as an improved coating adhesion in comparison to metallographic finishing strategies, which can be correlated to the processed roughness profile and induced compressive residual stresses in the subsurface region. [ABSTRACT FROM AUTHOR]

Sheet metal parts with high-quality surface have wide applications in many manufacturing procedures. However, polishing these parts are challenging due to occurrence of deformations at contact area between the polishing tool and part. This stems from the thinness of these parts, making them susceptible to deformations, compared to thick solid parts. To address the above challenge, this study proposes a new robotic polishing path planing method that accounts for such deformations. The proposed method starts by estimating the contact area between the tool head, and the free-form surface of the sheet metal part is estimated using Hertz theory and differential geometry. Next, it uses a polynomial equation—that is derived from FEM-based contact analysis of the part—to calculate the true tool-part contact area under deformations. Then, it combines the contact-area information with a new constant speed robot path planing technique to ensure high-quality robot polishing. Numerical studies on several sample geometries verify the effectiveness of the method. [ABSTRACT FROM AUTHOR]

Diamond offers great potential for use as a thermal spreader in various applications, including power electronics and radio-frequency (RF) applications. However, to be used as an efficient thermal spreader, the atomically smooth surface of the diamond is critical to be bonded with chips. Herein, a polishing technique for a 2-inch diameter wafer-scale bulk polycrystalline diamond substrate is proposed. In this work, 350 μ m thick polycrystalline diamond is grown by the microwave plasma-assisted chemical vapor deposition (MPACVD) technique on a Si substrate at a growth rate of 8 µm/h. Thereafter, a three-step polishing process was applied to achieve an atomically smooth surface, consisting of grinding using a diamond slurry with an iron plate, ICP etching using the SF6 gas, and final mechanical polishing using a resin-bonded diamond wheel. Surface roughness of diamond characterized by atomic force microscopy showed the significantly reduced from 900 nm to 0.3 nm. Hence, this study provide the practical methods for obtaining atomically smooth diamond films suitable for thermal management in various areas including power electronics and RF devices. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) has been a promising the third-generation semiconductor power device material for high-power, high-temperature, and substrate applications. However, under certain surface quality requirement, its current processing efficiency is the bottleneck. Therefore, it aims to improve the material removal rate (MRR), on the premise of ensuring the surface roughness requirements. To obtain the relationship between any point on SiC substrate and polishing pads, the model about double-faced mechanical polishing has been established, and the kinematics equations have been created. Best optimized material removal rate parameters were obtained. MRR reached the maximum when speed rate of the outside ring gear to the inside sun gear m = − 1, speed rate of lower plate to the inside sun gear n = 5, and SiC substrate distribution radius RB = 75. The primary and secondary order of MRR (n>m>RB) was obtained. An accurate mathematical model of orthogonal rotary regression test of Tri-factor quadratic of MRR was established, and the regression model was significant. Surface quality of SiC substrate was observed and characterized with SEM and AFM. It greatly provides a key guarantee for the next process of CMP, confirms the importance of MRR to ultra-smooth polishing, and provides a guarantee for its application in semiconductor equipment and technology. [ABSTRACT FROM AUTHOR]

AASHTO has provisionally endorsed the use of a three-wheel polishing device (TWPD) for polishing and the dynamic friction tester (DFT) for measuring the friction of the coarse aggregates used in hot mix asphalt (HMA). Despite ample studies showing the feasibility of such a system for HMA specimens, research efforts related to quantifying the coarse aggregates that are used in those mixes have been less common. The results of a study to accelerate the test and to decrease the tedium of specimen preparation for aggregates are reported here. Three identical TWPD devices that complied with the AASHTO provisional specification were fabricated. A new specimen preparation method was introduced to reduce the associated time and cost. Several operational parameters that can impact the repeatability and reproducibility of the process, such as tire type and tread condition, specimen preparation, and DFT rubber pad thickness, were investigated. This study verified that the TWPD/DFT test method can delineate the polishing/friction performance of different aggregates with acceptable repeatability and reproducibility. The TWPD/DFT test time and cost can potentially be decreased considerably by using the proposed practical and analysis modifications. [ABSTRACT FROM AUTHOR]

Nanoscale roughness with ultra-precise form control can be readily achieved using compliant finishing methods such as bonnet polishing. However, their weak point lies in the difficulty of removing mid-spatial-frequency (MSF) waviness in the typical range from 0.1 to 5.0 mm wavelength. To overcome this shortcoming, a bonnet tool filled with viscoelastic fluid is developed and a comprehensive model is established to disclose its distinct removal behavior in the MSF range. The model considers tool viscoelasticity, stress distribution and workpiece topography. Experiments show high consistency with theoretical predictions, and show that MSF waviness can be effectively reduced using the proposed method. [ABSTRACT FROM AUTHOR]

A new polishing process for metallic parts has been developed by simultaneously coupling drag finishing and electrochemical polishing. This new hybrid process, called PEMEC, enables an improvement in the surface roughness within some minutes, and at the same time, preserves the shape of the edges. This hybrid process is based on a synergistic effect between abrasive and chemical mechanisms. It has confirmed its suitability to be applied on complex and rough surfaces produced by additive manufacturing SLM parts. [ABSTRACT FROM AUTHOR]

A mirror-like reflecting surface is an important characteristic in many industrial metallic parts. Polishing is done to form a mirror surface on metals. However, the effect of the grain size of metals on surface roughness through polishing processes is not clear. Specifically, mirror surface formation of ultrafine grained materials is still unknown. Ultrafine grained steels and coarse grained steels with 0.02, 0.10, and 0.60 wt% carbon contents were prepared by warm caliber rolling and annealing. Average grain sizes were 1–2 μm and 4–40 μm. The changes in surface roughness, Sa, were measured with an atomic force microscope (AFM) via eight polishing steps, using emery papers of type #600, #1000, #1500, #2000, #2500, #4000, and free abrasive grains of 3 μm and 1 μm diamond. As the polishing process progressed, the surface unevenness was removed and the surface roughness, Sa, decreased in all steels. The differences of Sa at each polishing step were analyzed from the point of carbon content, Vickers hardness, and grain size. Carbon contents and Vickers hardness have little effect on Sa. However, grain size has a considerable effect on Sa in all steels. Ultrafine grained steels have smaller Sa in all polishing steps in all steels. This is because ultrafine grained steels have very small work hardening rate. After final polishing, Sa is 2.5–3.6 nm in coarse grained steels and 2.0–2.6 nm in ultrafine grained steels. To obtain a mirror surface with smaller Sa, grain size control is important. [ABSTRACT FROM AUTHOR]

This study investigates the development of an ultrasonic vibration-assisted magnetic compound fluid (MCF) polishing technology for final polishing. The fabrication of an experimental apparatus entails an ultrasonic polishing unit, and the experimental investigation of its performance in surface polishing is described. In addition, ultrasonic vibration-assisted MCF polishing under different applied methods of ultrasonic vibration is studied. The experimental results indicate that applying ultrasonic vibration to the workpiece improves the surface roughness and material removal rate when the ultrasonic vibrations are changed. In addition, across the range of polishing conditions employed in this study, the precision surface roughness and high material removal rate can be easily obtained on the acrylic plate by applying an elliptical vibration to the ultrasonic vibration. [ABSTRACT FROM AUTHOR]

In this study, a naturally sourced cutting oil mixture using for the magnetorheological finishing (MRF) as an environmentally friendly carrier liquid. In addition, fuzzy grey relation analysis has been developed to predict and give optimal cutting parameters, the main factors affecting surface quality and material removal rate (MRR) identified. Experimental polishing procedures Ti-6Al-4V alloy were performed to confirm the availability of MRF models of the surface quality and MRR proposed. The fuzzy grey levels of elements to the polishing surface quality, namely the workpiece speed (nw), working distances (K), MRF carrier speed (nMRF) and feed rate (F), were 0.6983, 0.8057, 0.7818, and 0.7817, respectively. The analysis showed that the working distances (K) showed the most remarkable influence on the polishing effect, while the effect of workpiece speed (nw) was the least important. Microscopic observations significantly minimize scratches on the surface. This observation provides an excellent reference value for high surface quality and material removal rate when polishing Ti-6Al-4V alloys. [ABSTRACT FROM AUTHOR]

In the robotic polishing process, the tool and the blisk interfere easily because of the narrow operation space and seriously twisted curved surfaces. Algorithms are proposed to detect and avoid collisions with high efficiency and accuracy. First, the curved surface of the blade is discretized into a set of points, and the collision detection between the tool and the blisk is converted into the calculation of distances between the tool and points on blade surface. Then, the tool axial vector is adjusted with the minimum rotation angle to avoid collision, which reduces the impact on surface profile accuracy after changing the tool postures. The machining quality is finally guaranteed by controlling the material removal depth of the polishing process. The proposed method realizes the collision detection and interference avoidance of the blisk polishing effectively, while it also ensures the surface quality of workpiece when adjusting the tool posture. Simulation and experiments are carried out to verify the feasibility and advantages of the proposed method. [ABSTRACT FROM AUTHOR]

This paper proposes a method of quality for the uneven removal caused by the change of the radius of curvature in the aspheric surface polishing and finishing. This method uses a polishing disk and a bonnet as polishing devices, two kinds of aspheric parts as workpieces with a concave surface and a convex surface respectively. By deriving the model of pressure and velocity at different positions, the equation between dwell time and curvature radius on the elliptical generatrix of aspheric workpiece could be obtained from the famous Preston equation on polishing material removal. According to the dwell time on the different path points, the movement of the robot could be controlled. In this way, only the dwell time of the path points on the elliptical generatrix needs to be calculated, rather than the entire aspheric surface. By measuring the values of surface roughness in the polishing of concave and convex aspheric surfaces, the experimental results verify that the method could improve the processing efficiency. [ABSTRACT FROM AUTHOR]

For the highly efficient and versatile polishing of metals, isotropic etching polishing (IEP), which is based on the merging of isotropic etching holes, has been developed. In this study, the feasibility and mechanism of isotropic etching polishing of nickel-based superalloy Inconel 718 (IN718) and the polishing characteristics have been studied. The potentiodynamic experiments revealed similar trends of the cathodic, passive, second passivation, and transpassive regions in all the electrolytes, while the corrosion susceptibility of IN718 successively decreased with the increasing H 2 SO 4 concentration in the electrolyte. The etching anisotropy of the IN718 precipitated with different phases can be experimentally transmuted to isotropic etching by modulating the electrolyte concentration and keeping electrolyte temperature equal or above the room temperature. Because of the positive correlation of the etching current with isotropic holes density and diameter, etching at higher currents is promoted for the rapid and proficient polishing. The surface evolution mechanism during IEP has been confirmed. The surface roughness initially increased due to the formation of etching holes, then decreased abruptly owing to the rapid merging of etching holes and finally achieved a smooth surface. The wet grounded surface of IN718 with a roughness of Sa 62.7 nm has been transformed into a mirror-like smooth surface with a roughness of Sa 0.86 nm within 300 s of IEP at optimized conditions and a high MRR of 2.73 mm3/min has been achieved. • Electrochemical-based isotropic etching polishing mechanism of Inconel 718. • Electrolyte concentration and temperature control etching anisotropy of Inconel 718. • Two phase Inconel 718 with MC carbides was polished by isotropic etching polishing. • Inconel 718 surface roughness first increased and then decreased during polishing. • Isotropic etching polishing achieved mirror-like shining Inconel 718 surface. [ABSTRACT FROM AUTHOR]

The aim of this study was the morphological evaluation of root surfaces subjected to manual (curette) and ultrasonic (conventional and diamond tips) scaling. The surface was then polished with a rubber cup and three medium-sized pastes. Ninety teeth were randomly divided into three groups of 30 and subjected to three different root instrumentation: (1) manual instrumentation with a Gracey® curette; (2) ultrasonic instrumentation with a standard steel tip (Universal Perio S-SERIES: USU, Hu-Friedy, Chicago, IL, USA) at a power equal to 50%; and (3) with a diamond tip (Punta Piezo Serie E Scaling, Hu-Friedy, Chicago, IL, USA) at a power of 20%. Each group of the instrumented teeth was then divided in three subgroups of 10 and subjected to 30 s of rubber polishing with three different polishing pastes with medium grain sizes in single-dose cups: (1) Ultrapro Tx cool mint medium®; (2) Stomyprox media®; and (3) Nupro medium orange®. Polyether root surface replicas were then taken from all 90 samples and analyzed by SEM to evaluate surface morphology after scaling and polishing procedures. All scaling techniques caused an alteration of the root surface without statistically significant difference, whereas polishing resulted in maintenance or improvement of the surface texture. [ABSTRACT FROM AUTHOR]

Aluminum nitride (AlN) is a semiconductor material with the wide band gap. The requirement of the substrate for the semiconductor device is no surface damage. In this paper, based on the principle of the hydration reaction of aluminum nitride, the single crystal aluminum nitride was polished under dry conditions and wet conditions using a sol-gel (SG) tool. The abrasive used in the SG polishing tool was diamond with a particle size of 5 μm. Surface morphology of single crystal aluminum nitride was observed by scanning electron microscopy (SEM). Surface damage to the polished single crystal aluminum nitride was detected by 3D optical surface profiler, and the wear debris were analyzed by high resolution transmission electron microscopy (TEM). The product of the hydration reaction remaining on the aluminum nitride surface after polishing was studied by X-ray photoelectron spectroscopy. The results demonstrate that the removal rate of single crystal aluminum nitride by wet polishing is higher than that of dry polishing. The final roughness Sa of workpiece by dry polishing is 1.8–2.2 nm, and the final roughness Sa of workpiece by wet polishing is 1.1–1.2 nm. In addition, wear debris of workpiece by two polishing methods are amorphous. [ABSTRACT FROM AUTHOR]

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With the development of mould manufacturing industry, the high precision polishing technologies of Ni–P-coated SKD11 steel are in high demand. In this work, the factors influencing the magnetic material polishing process were determined by investigating the force distribution of carbonyl iron (CIPs) and abrasive particles (APs) in the working surface of magnetorheological fluid (MRF). The influence of certain factors, such as the diameters of the CIPs and the APs and the current and working distance (K), on the polishing surface quality, was assessed by fuzzy grey and Taguchi analysis. Results showed that the values of the fuzzy grey relationships with the surface quality of the factors were 0.4914, 0.7797, 0.6686 and 0.7461. Result showed that the fuzzy grey relationship point of factors known as diameters of the AGs had the most remarkable influence on the polishing effect, and the effect of CIP diameter was insignificant. The MRF contained commercially available CIPs that had been successfully applied for polishing the surface of magnetic materials with extremely high accuracy (surface roughness Ra = 0.561 nm) without leaving scratches on the surface after polishing. [ABSTRACT FROM AUTHOR]

Pad asperities in chemical-mechanical polishing (CMP) provide necessary forces for mechanical abrasion. This article investigates the abrasive behaviour of polishing pads at the asperity contact scale. A contact mechanics model predicts that compliant and soft asperities or rigid and hard asperities may solely achieve either large contact area or high indentation depth respectively, whereas bi-layered asperities can enable both the enlarged contact and deep abrasion. Hemispherical pad micro-asperities with precise dimensions, including the new bi-layered design, were fabricated using thermal reflow and micro-replica molding techniques and their polishing behaviours were experimentally compared using a pin-on-disk polishing setup. [ABSTRACT FROM AUTHOR]

A method of dielectrophoresis abrasive flow polishing was proposed for internal surface polishing of thin-walled ceramic workpieces. A nonuniform electric field was arranged on outer surfaces of the ceramic workpieces to be polished, and the abrasive particles were polarized to implement efficient polishing of the ceramic workpiece miner surfaces. Simulation results show that when electrode gap ratio is as 2, SiC abrasive particles have the best dielectrophoresis effectiveness and the most abrasive particles involved in polishing. When initial internal surface roughness value of workpiece Ra is as (208 + 5)nm, after 10 h polishing, the internal surface roughness value Ra of the workpiecess is as 51nm without dielectrophoresis effectiveness, and that of the workpieces is as 23 nm with dielectrophoresis effectiveness. [ABSTRACT FROM AUTHOR]

Sapphire has been the most widely used substrate material in LEDs, and the demand for non-C-planes crystal is increasing. In this paper, four crystal planes of the A-, C-, M- and R-plane were selected as the research objects. Nanoindentation technology and chemical mechanical polishing technology were used to study the effect of anisotropy on material properties and processing results. The consequence showed that the C-plane was the easiest crystal plane to process with the material removal rate of 5.93 nm/min, while the R-plane was the most difficult with the material removal rate of 2.47 nm/min. Moreover, the research results have great guiding significance for the processing of sapphire with different crystal orientations. [ABSTRACT FROM AUTHOR]

Tooth polishing is a procedure that is performed in most of the dental practices. It is an act to even out the rough surfaces of the tooth to make it aesthetically appealing and smoothening of tooth surface after restoration prevents deposition of plaque. Polishing typically refers to both cleaning and polishing, cleaning is the ability to remove the deposits on the tooth surface and extrinsic stains by making the tooth surface lustrous and smooth. However routine polishing is not recommended as it causes damage to the enamel. Use of proper technique, selection of least abrasive polishing agent, controlled working time, pressure during procedure are to be taken care during the process of tooth polishing. A questionnaire pertaining to the polishing systems in dentistry is prepared and administered through an online portal forum, survey planet link to 50 dental professionals who volunteered for the study. The responses were tabulated using Microsoft Excel and the data is coded for statistical analysis. Statistical analysis is performed with the help of SPSS software. Chi square tests were performed by setting p value as .05 which is considered to be statistically significant. From the results, general practitioners had good insight and practical knowledge on the polishing systems, different instruments used for polishing, and effects of tooth polishing when compared to interns. [ABSTRACT FROM AUTHOR]

The blade profile of a milled aeroengine blisk is a spatial free-form surface with significant curvature changes, which seriously restrict the quality uniformity of the polished surface. To investigate the geometric characteristics of the flexible contact of an elastic grinding tool–polished complex surface, a polishing process equipment integrating "CNC machine tool + flexible grinding head + elastic grinding tool" was used in this study. Through an analysis of the geometric theory, a mathematical model for the boundary between the sanding wheel and polished surface in the contact zone, a mathematical model for the compression amount in the contact zone, and a mathematical model for the removal depth were established to conduct simulation and polishing tests. The results show that both the compression amount of the sanding wheel and curvature radius on workpiece surface have remarkable effects on the boundary and removal depth in the contact zone; the feed speed, rotation speed, and particle size of the sanding wheel have no bearing on the boundary in the contact zone, but they can influence the removal depth markedly. The simulation results are basically consistent with the test results, proving that the established models are reliable and applicable to geometric characteristic prediction of the elastic grinding tool–polished complex surface. [ABSTRACT FROM AUTHOR]

When applied to blisk blade profile polishing of aero-engines, "five-axis NC + flexible grinding head + elastic grindstone" polishing technological equipment has advantages of high precision, minor interference, favorable adaptivity, etc. In order to improve the polishing quality and polishing efficiency, a mathematical calculation formula of polishing efficiency was established according to the polishing principles of elastic grindstone (sanding wheel). The optimized combination of technological parameters (ω = 6000 r/min, a p = 0.9 mm, v f = 320 mm/min) was obtained through the range method of orthogonal test results with double optimization objectives—surface roughness and polishing efficiency. Based on the relationship between number of polishing times and surface roughness, a technological program was put forward, that is, polishing is firstly conducted using 320# sanding wheel for 6 times and then 400# sanding wheel for 9 times (totally 15 times) under the optimized combination of technological parameters, then surface roughness less 0.4 μm can be achieved. Blade polishing test results indicate that: efficiency-optimized technological parameters can not only significantly shorten polishing time but also acquire qualified blade surface roughness less 0.4 μm, thus verifying reliability of the optimization method and results. [ABSTRACT FROM AUTHOR]

There were used the spherical lenses in industry conventional for long time, but new types of lenses were created during innovation processes. One type of lenses is aspherical. Two main parameters describing the quality of aspherical lenses are accuracy of the form shape and surface roughness. These parameters can be obtained after the last operation - polishing. The technical parameters that have the biggest influence on the form shape and surface roughness were investigated in this experiment, and optimal technical parameters for the polishing process were established. Melted quartz "UVFS" was used in this research, the investigations were carried out according to full factorial design. The five-axis CNC machine Schneider SCPA100 was used for polishing and the profilometer Nanoscan 855 was used for measurements. After the analysis of the results, it was found out that the speed of rotation and penetration depth are the most important factors in the polishing process. To obtain the best shape, it is necessary to use the smallest chosen values of rotation speed and penetration depth, whereas the parameters for surface roughness polishing change conversely. The smallest value of surface roughness Rz was 0.06 µm, and shape deviation was 2.6 µm. Optimal polishing parameters for the best quality of aspherical lenses are provided. [ABSTRACT FROM AUTHOR]

The surface profile roughness (Ra), surface area roughness (Sa), and surface topography of newly developed as-prepared, ground, and polished self-glazed zirconia (SGZ) were evaluated using a profilometer, 3D optical surface profiler, and SEM, with conventional dry-milled zirconia (CZ) as a reference. A statistical analysis was conducted using repeated measures analysis of variance (ANOVA) and the Bonferroni test (α =.05). Results revealed that the material (p =.005), clinical adjustment procedure (p <.001), and interaction between factors (p <.001) had statistically significant effects on the Ra values. SGZ showed lower Sa values than CZ during the same period. Ten patient cases involving the restoration of the monolithic anatomic contour SGZ crowns were investigated. All crowns remained functional until the latest clinical follow-up and no further antagonist wear was observed. Thus, SGZ had relatively lower surface roughness, which was also more easily altered than that of CZ. [ABSTRACT FROM AUTHOR]