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Circular RNAs (circRNAs) are closed back-splicing products of precursor mRNA in eukaryotes. Compared with linear mRNAs, circRNAs have a special structure and stable expression. A large number of studies have provided different regulatory mechanisms of circRNAs in tumors. Challenges exist in understanding the control of circRNAs because of their sequence overlap with linear mRNA. Here, we survey the most recent progress regarding the regulation of circRNA biogenesis by RNA-binding proteins, one of the vital functional proteins. Furthermore, substantial circRNAs exert compelling biological roles by acting as protein sponges, by being translated themselves or regulating posttranslational modifications of proteins. This review will help further explore more types of functional proteins that interact with circRNA in cancer and reveal other unknown mechanisms of circRNA regulation.

Owing to its superior durability, good biocompatibility, and high recycling capability, high-density polyethylene (HDPE) has been widely applied into making prosthetic implants, liquid permeable membranes, corrosion-resistant pipes, etc., and gains its popularity in packaging, consumer goods, and chemical industries. Injection molding and blow molding are two most common conventional processes of making HDPE products. These conventional processes, however, are considered time-consuming and labor-intensive since molds are usually needed prior to fabricating parts. Moreover, manufacturing complex-structured parts (such as lattice and cellular structures) is a challenge for these conventional manufacturing processes. Facing these problems, it is crucial to find a time- and labor-saving process, which can be used to manufacture complicated structures in a cost-effective way. Additive manufacturing (AM) is such a process that needs no mold and is more affordable to create complex and highly customized parts. Among all types of AM processes, fused deposition modeling (FDM), which is primarily designed for thermoplastic materials, seemed to be a benevolent process for fabricating HDPE parts. Based on reported publications, however, it is difficult to print HDPE materials using FDM due to the problems of warping, shrinking, and weak bonding between printed HDPE parts and the substrate. In addition, the FDM-printed HDPE parts can demonstrate defects of porosities and delamination. To improve the printability of FDM, we conducted preliminary experiments and optimized processing parameters. For the first time, we added carbon fiber (CF) into HDPE to make CF-reinforced HDPE composites (CF-HDPE) using FDM and investigated the effects of CF on part quality, microstructure characteristics, and mechanical properties (including tensile properties and dynamic mechanical properties) of CF-reinforced HDPE composites. Experimental results show that the addition of CF was beneficial for not only improving the printability of FDM and quality of printed composite parts, but also for enhancing mechanical properties (such as Young’s Modulus and ultimate tensile strength) of the parts.

Hepatic fibrosis is a reversible scaring response to chronic liver injury. MicroRNA (miR)-129-5p might regulate fibrosis-related gene expression. This study is performed to decipher, potential of miR-129-5p to influence the progression of hepatic fibrosis in a carbon tetrachloride (CCl4) rat model. Rat hepatic fibrosis was successfully established by subcutaneous injection of 50% CCl4. RT-qPCR revealed that miR-129-5p was poorly expressed and PEG3 was highly expressed in hepatic fibrosis tissues. As reflected by dual-luciferase reporter gene assay, miR-129-5p targeted and reduced the expression of PEG3. Thereafter, miR-129-5p antagomir or short hairpin RNA against paternally expressed gene 3 (PEG3) was adopted for gain- and loss-of-function assay to determine the molecular regulatory mechanism of miR-129-5p. Moreover, we detected the expression of nuclear factor kappa B (NF-κB) signaling pathway-related proteins and apoptosis-related factors, and made a serological analysis of the rat serum samples. Results showed that upregulated miR-129-5p or downregulated PEG3 led to reduction of the histological changes of liver cirrhosis and lowered the apoptosis rate, via downstream effects on the NF-κB signaling pathway. Thus, the hepatic fibrosis induced by CCl4 can be rescued by upregulated miR-129-5p or downregulated PEG3 expression.

Colorectal cancer (CRC) is one of the most common malignant tumors worldwide. In terms of cancer-related death, colon cancer ranks second and third among men and women, respectively, and the incidence is increasing annually. Accumulating evidence have indicated that long noncoding RNA (lncRNA) plays an important role in tumorigenesis. In this study, we found that lncRNA EPB41L4A-AS1 was highly expressed in CRC tissues and was associated with poor prognosis and tumor metastasis in patients with CRC. In vitro studies showed that the knockdown of EPB41L4A-AS1 inhibited the proliferation, migration, invasion, and epithelial-mesenchymal transition of CRC cells. Mechanically, we found that EPB41L4A-AS1 may participate in the development of CRC by activating the Rho/Rho-associated protein kinase signaling pathway. Collectively, these results demonstrated that EPB41L4A-AS1 can promote the proliferation, invasion, and migration of CRC, and it may be a novel biomarker for the diagnosis and targeted treatment of CRC.

Carbon fiber reinforced plastic (CFRP) composites were attractive in lots of applications, in which surface machining processes were always needed after molding fabrication processes to achieve the final functional surface geometry with desired accuracy. To improve the effectiveness and efficiency, rotary ultrasonic surface machining (RUSM) had been applied in processing CFRP composites. With the assistance of vertical ultrasonic vibration in RUSM, cutting forces were significantly reduced, but the surface roughness was increased. To improve the surface conditions and additionally reduce the cutting force for RUSM, the applied ultrasonic vibration should be aligned with surface generation direction (namely horizontal feeding direction). Up till now, there were no reported investigations on RUSM with horizontal vibration and 3D elliptical ultrasonic vibration, formed from the combination of horizontal and vertical ultrasonic vibrations. In this investigation, the horizontal and 3D elliptical ultrasonic vibrations were applied in RUSM. The comparisons among RUSM with 3D elliptical ultrasonic vibration, RUSM with horizontal ultrasonic vibration, and the surface machining without ultrasonic vibration on machining performance and surface quality were conducted. Experimental results showed that RUSM with horizontal ultrasonic vibration reduced both cutting force and surface roughness. With the application of 3D elliptical ultrasonic vibration, both cutting force and surface roughness can be further decreased. The critical horizontal ultrasonic frequency for the overlapping of abrasive grains’ trajectories was analyzed. The mechanisms of RUSM with both horizontal and 3D elliptical ultrasonic vibrations and the reasons for both cutting force decreasing and surface roughness decreasing were also investigated.

Owing to its advantages of freedom to design, improved material utilization, and shortened lead time, additive manufacturing (AM) has the potential to redefine manufacturing after years of evolvement and opens new avenues to produce customized and complex-shaped products. Despite these benefits, AM still suffers problems stemmed from limited material selection, anisotropic material property, low production speed, coarse resolution, etc. In response to these problems, extensive attention has been drawn on integrating AM with fields, which mainly include magnetic field (MF), electric field (EF), and acoustic field (AF). These fields have been proved to be effective in tailoring microstructures, enhancing mechanical properties, focusing and sorting cells, serving as stimuli, etc., thus providing new opportunities to address existing problems and enable new functionalities of AM technologies. This paper presents a review on recent developments and major advances in MF-, EF-, and AF-assisted AM technologies and 4D printing method from aspects of materials, methodologies, and applications. In addition, current challenges and future trends of field-assisted AM technologies and 4D printing method are also outlined and discussed.

This paper aims to present innovative modifications of the contents and delivery mode of “Manufacturing Processes” laboratory for Mechanical and Manufacturing Engineering students during the global pandemic due to coronavirus (COVID-19). The objective was to maintain high level of student engagement and academic rigor, while minimizing face-to-face activities in the lab and ensuring social distancing when performing lab activities. Modifications are done in the lab to replace some of the previous activities heavily focused on machining processes with additive manufacturing, as activities focusing on machining processes need more face-to-face interactions. Out of three labs and one final project, the major modifications have been done to casting lab to make it fully online and to final project to make it about 90% online. Students were allowed for face-to-face activities that are very critical to students’ learning, and all other activities were performed virtually either by synchronous or asynchronous classes. In the other two labs (bulk deformation, i.e., forging and rolling, lab and the machining lab), students were divided into groups and they took turn to take face-to-face instructions in order to maintain social distancing and safety in the lab. Students were surveyed at the end of the semester to assess their perceptions on the modifications done in the lab and level of engagement in the course, and whether learning outcomes were achieved. Students found the level of engagement appropriate and agree that they have learned new and key concepts of various manufacturing processes and will be able to apply knowledge in the real-life applications. However, the students also reported that hybrid-mode lab instruction cannot completely replace in-person lab instruction, as many of them faced challenges to keep themselves engaged and motivated in all online lab activities.

In recent years, more and more attentions have been attracted on integrating three-dimensional (3D) printing with fields (such as magnetic field) or innovating new methods to reap the full potential of 3D printing in manufacturing high-quality parts and processing nano-scaled composites. Among all of newly innovated methods, four-dimensional (4D) printing has been proved to be an effective way of creating dynamic components from simple structures. Common feeding materials in 4D printing include shape memory hydrogels, shape memory polymers, and shape memory alloys. However, few attempts have been made on 4D printing of ceramic materials to shape ceramics into intricate structures, owing to ceramics’ inherent brittleness nature. Facing this problem, this investigation aims at filling the gap between 4D printing and fabrication of complex ceramic structures. Inspired by swelling-and-shrinking-induced self-folding, a 4D printing method is innovated to add an additional shape change of ceramic structures by controlling ZrO2 contents and patterns. Experimental results evidenced that by deliberately controlling ZrO2 contents and patterns, 3D-printed ceramic parts would undergo bending and twisting during the sintering process. To demonstrate the capabilities of this method, more complex structures (such as a flower-like structure) were fabricated. In addition, functional parts with magnetic behaviors were 4D-printed by incorporating iron into the PDMS-ZrO2 ink.

A new unified polynomial chaos expansion method, named as fuzzy and random moment-based arbitrary polynomial chaos method (FRMAPCM), is proposed for the response analysis of the composite structural–acoustic system with multi-scale fuzzy/bounded random uncertainties. In the FRMAPCM, the moment-based arbitrary polynomial chaos (MAPC) is adopted to construct the polynomial basis according to the moment of the bounded random variable. The coefficient of MAPC is calculated by using the Gauss integration method. For the fuzzy variable, the weight function of the Chebyshev polynomial is assumed as the probability density function (PDF) to yield the moment matrix. Compared with the conventional polynomial based method which constructs the polynomial basis according to the PDF of the random variable, the proposed FRMAPCM can avoid the error produced by the process of approximating the PDF. A numerical example is given to validate the proposed method, and two engineering examples are presented to demonstrate its efficiency and accuracy.

Rotary ultrasonic machining has been successfully explored in surface machining of carbon fiber reinforced plastic (CFRP) composites. It has been proven to be an effective and efficient CFRP machining method. Both theoretical and experimental investigations have been conducted with the assumption that the CFRP is removed by brittle fracture removal mode. However, in brittle material machining, ductile flow phenomenon still exists. Ductile scratching marks are also observed on the machined CFRP surfaces. It is still unknown that what actual material removal modes are under different machining variables. To investigate the material removal mechanisms in rotary ultrasonic surface machining (RUSM) of CFRP, single abrasive scratching tests were conducted. The scratching induced characteristics and scratching forces were analyzed. Both the ductile removal mode and the brittle fracture removal mode were observed and identified in both carbon fiber layers and epoxy resin layers on the machined marks by using scanning electron microscopy (SEM) imaging. With the increase of scratching depth, the material removal mode of CFRP was changed from the ductile removal mode to the brittle fracture mode. From the analysis of kinematic trajectory of diamond grain, the scratching cutting forces were decreased in the tests with the assistance of ultrasonic vibration under the same machining variables. The generation mechanisms of the delamination were analyzed and discussed.

Rotary ultrasonic machining (RUM) is effective and efficient in cutting carbon fiber–reinforced plastic (CFRP) composites. With ultrasonic vibration assistance, both machining efficiency and machining effectiveness can be improved. Ultrasonic vibration has two major variables (including ultrasonic amplitude and ultrasonic frequency), which play important roles in RUM processes. Other intermediate variables, such as ultrasonic power and indentation depth, are directly related to these two variables. Effects of ultrasonic vibration amplitude have been extensively investigated in RUM hole making and surface machining processes. However, the effects of ultrasonic frequency in RUM have not been reported. The effects of ultrasonic frequency under different combinations of tool rotation speed, feed rate, and depth of cut on output variables, including cutting forces, surface roughness, and machined surface characteristics, are investigated, for the first time, in this study. The critical frequency is analyzed for the RUM process. Three different levels of ultrasonic frequencies are generated and applied to the RUM process. The kinematic motions of abrasive grains in RUM with different frequencies are analyzed and discussed. The results show that RUM with higher frequency of ultrasonic vibration is a more effective machining process, leading to cutting force reduction and the machined surface quality improvement.

In surface grinding of carbon fiber reinforced plastic (CFRP) composites, cutting force is a key factor that controls surface damage, tool wear, cutting temperature, delamination, etc. Surface grinding of CFRP composites using rotary ultrasonic machining (RUM) with vertical ultrasonic vibration has been proven to be an effective method to reduce cutting force. However, the machined surface quality is lowered due to the knocking effects on the machined surface resulted from up-and-down vertical vibration. It has been proven that to decrease cutting force and simultaneously improve surface quality, ultrasonic vibration aligning with surface generation direction (feeding direction) is needed. However, there are limited investigations on RUM surface grinding of CFRP composites with horizontal ultrasonic vibration, and the mechanistic model on cutting force in such a process is not explored. This paper, for the first time, establishes a mechanistic model on feeding-directional cutting force in RUM surface grinding of CFRP composites with horizontal ultrasonic vibration. This modeling development is based on the assumption of brittle fracture material removal mechanism, which is the dominant removal mechanism in such a process. The predicted trends in this model agree well with those in experimentally measured results. This modeling will provide a guidance for the mechanistic modeling development to predict other output variables through the cutting force in RUM surface grinding of CFRP composites.

As one of the ceramic matrix composites (CMCs), carbon fiber-reinforced silicon carbide matrix (C/SiC) composites are promising materials used in various engineering applications owing to their superior properties. Precision surface grinding has been widely applied in the machining of CMC composites; however, the material removal mechanisms of C/SiC composites have not been fully elucidated yet. To reveal the material removal mechanisms in the grinding of chemical vapor infiltration-fabricated C/SiC composites, novel single-abrasive scratch tests were designed and conducted in two typical cutting directions. The experimental parameters, especially the cutting speed, conformed to the actual grinding process. The results show that the grinding parameters (feed rate, spindle speed, depth of cut, and cutting direction) have significant influences on the grinding forces, surface integrity, and affected subsurface region. The tangential force is in general larger than the normal force at the same cutting depth. Furthermore, both the tangential and normal forces in the longitudinal cutting direction are larger than those in the transverse cutting direction. The impacts and abrasive actions at the tool tip mainly caused the material removal. The predominant material removal mode is brittle fracture in the grinding of unidirectional C/SiC composites, because the damage behaviors of the C/SiC composites are mainly the syntheses of matrix cracking, fiber breakage, and fiber/matrix interfacial debonding. These results are rationalized based on the composite properties and microstructural damage features.

Carbon fiber reinforced plastic (CFRP) composites are popular in many industries due to their superior properties. However, many problems, including high cutting forces, high tool wear, high surface roughness, etc., are generated in conventional surface grinding (CSG) processes, due to the carbon fibers’ abrasive property as well as the inhomogeneous and anisotropic properties of CFRPs. Rotary ultrasonic surface machining (RUSM) with vertical ultrasonic vibration has been proven to be effective to reduce cutting forces. However, this process produces larger surface roughness than CSG because of vertical ultrasonic vibration. To solve this issue, RUSM with horizontal ultrasonic vibration is developed in this investigation. The comparisons between CSG and RUSM with horizontal ultrasonic vibration are conducted. The kinematic motions of abrasive grains in both processes are discussed and analyzed. Effects of input variables (including tool rotation speed, feedrate, and depth of cut) on output variables (including cutting forces and surface roughness) are also investigated in both CSG and RUSM processes. RUSM with horizontal ultrasonic vibration is proven to be an effective machining method for reducing cutting forces and simultaneously improving machined surface quality.

It is universally acknowledged that long non-coding RNAs (lncRNAs) involved in tumorigenesis in human cancers. However, the function and mechanism of many lncRNAs in colorectal cancer (CRC) remain unclear. By analyzing the two sets of CRC-related gene microarrays data, downloaded from the Gene Expression Omnibus (GEO) database and the lncRNA expression in a set of RNA sequencing data, we found that lncRNA SLCO4A1-AS1 was significantly upregulated in CRC tissues. We then collected CRC tissue samples and verified that SLCO4A1-AS1 is highly expressed in CRC tissues. Furthermore, SLCO4A1-AS1 was also upregulated in the CRC cell line. In situ hybridization results showed that high expression of SLCO4A1-AS1 was associated with poor prognosis in patients with CRC. Next, we found that SLCO4A1-AS1 promoted CRC cell proliferation, migration, and invasion. Results of western blotting assays show that its mechanism may relate to the epidermal growth factor receptor (EGFR)/mitogen-activated protein kinase (MAPK) pathway. Therefore, SLCO4A1-AS1 may be a potential biomarker for CRC prognosis and a new target for colorectal cancer therapy.

The role of long non-coding RNA ACTA2 antisense RNA 1 (LncRNA ACTA2-AS1) in colorectal cancer (CRC) was awaited to be elucidated. Clinical specimen and data on ACTA2-AS1 expression in colon adenocarcinoma (COAD) were collected, followed by in situ hybridization. Transfected CRC cell viability, proliferation, migration, and invasion were determined with Cell Counting Kit-8, colony formation, Scratch, and Transwell assays, respectively. Relative expressions of ACTA2-AS1, PCNA, Bcl-2, MMP-2 and MMP-9 were quantified by quantitative real-time polymerase chain reaction (qRT-PCR) and western blot. ACTA2-AS1 expression was downregulated in CRC. Overexpressed ACTA2-AS1 repressed the cell viability, proliferation, migration and invasion, increased cleaved caspase-3 level yet decreased PCNA, Bcl-2, MMP-2 and MMP-9 levels. ACTA2-AS1 silencing, however, did oppositely. Collectively, ACTA2-AS1 inhibits the viability, proliferation, migration and invasion of CRC cells to effectively suppress the progression of CRC.

Ceramics and ceramic reinforced metal matrix composites (MMCs) are widely used in severe working conditions and have been applied in biomedical, aerospace, electronic, and other high-end engineering industries owing to their superior properties of high wear resistance, outstanding chemical inertness, and excellent properties at elevated temperatures. These superior properties, on the other hand, make it difficult to process these materials with conventional manufacturing methods, posing problems of high cost and energy consumptions. In response to this problem, direct additive manufacturing (AM), which is equipped with a high-power-density laser beam as heat source, has been developed and extensively employed for processing ceramics and ceramic reinforced MMCs. Compared with other direct AM processes, laser deposition-additive manufacturing (LD-AM) process excels in several aspects, such as lower labor intensity, higher fabrication efficiency, and capabilities of parts remanufacturing and functionally gradient composite materials fabrication. Besides these benefits, problems of poor bonding, cracking, lowered toughness, etc. still exist in LD-AM fabricated parts. This paper reviews developments on LD-AM of ceramics and ceramic reinforced MMCs in both bulk parts fabrication and cladding. Main issues to be solved, corresponding solutions, and the trend of development are summarized and discussed.

To explore the correlation between cytosine-phosphoric-guanylic (CpG) site of Septin 9 gene and colorectal cancer, and to develop a real-time PCR detection system in plasma in patients with colorectal cancer.The methylation of training samples was detected by high-throughput sequencing technology, and the sites highly consistent with the clinical information of colorectal cancer were identified. Then the detection system of real-time PCR was designed to analyze the consistency of plasma and tissue based on methylationa sensitive enzyme digestion. Finally, 100 clinical trials were conducted to evaluate the performance of the detection system with the methylation sensitive enzyme digestion-real-time PCR.The highly consistent sites, which were selected by high-throughput sequencing from 71 training set samples, was the 38th CpG. Based on the detection region, the screened methylation sensitive enzymes wereThe 38th CpG site of Septin 9 detected by the detection system of methylation sensitive enzyme digestion-real-time PCR can highly predict the occurrence of colorectal cancer with great clinical application value.

ObjectiveTo establish and validate a radiomics nomogram based on the features of the primary tumor for predicting preoperative pathological extramural venous invasion (EMVI) in rectal cancer using machine learning.MethodsThe clinical and imaging data of 281 patients with primary rectal cancer from April 2012 to May 2018 were retrospectively analyzed. All the patients were divided into a training set (n = 198) and a test set (n = 83) respectively. The radiomics features of the primary tumor were extracted from the enhanced computed tomography (CT), the T2-weighted imaging (T2WI) and the gadolinium contrast-enhanced T1-weighted imaging (CE-TIWI) of each patient. One optimal radiomics signature extracted from each modal image was generated by receiver operating characteristic (ROC) curve analysis after dimensionality reduction. Three kinds of models were constructed based on training set, including the clinical model (the optimal radiomics signature combining with the clinical features), the magnetic resonance imaging model (the optimal radiomics signature combining with the mrEMVI status) and the integrated model (the optimal radiomics signature combining with both the clinical features and the mrEMVI status). Finally, the optimal model was selected to create a radiomics nomogram. The performance of the nomogram to evaluate clinical efficacy was verified by ROC curves and decision curve analysis curves.ResultsThe radiomics signature constructed based on T2WI showed the best performance, with an AUC value of 0.717, a sensitivity of 0.742 and a specificity of 0.621. The radiomics nomogram had the highest prediction efficiency, of which the AUC was 0.863, the sensitivity was 0.774 and the specificity was 0.801.ConclusionThe radiomics nomogram had the highest efficiency in predicting EMVI. This may help patients choose the best treatment strategy and may strengthen personalized treatment methods to further optimize the treatment effect.

Hepatic fibrosis is a reversible scaring response to chronic liver injury. MicroRNA (miR)-129-5p might regulate fibrosis-related gene expression. This study is performed to decipher, potential of miR-129-5p to influence the progression of hepatic fibrosis in a carbon tetrachloride (CCl

Titanium is widely used in many industry areas (such as automotive industry, aerospace industry, and medical industry) due to its superior properties of low density, high strength to weight ratio, strong corrosion-resistance, etc. However, commercial pure titanium (CP-Ti) parts still have some disadvantages (such as relatively low hardness, and wear resistance) which limit their further applications. In order to reduce these disadvantages, some reinforcement materials (such as ceramics and nanomaterials) are involved to fabricate titanium-based parts Compared with ceramics, low content of nanomaterials could significantly improve the mechanical properties and reduce disadvantages of ceramics (such as poor wettability and low interfacial bonding between reinforcement materials and Ti). Graphene oxide (GO) is a preferable candidate of nanomaterial due to its excellent mechanical properties and low density. The GO reinforced Ti parts have been fabricated by the selective laser sintering (SLS) process. Laser additive manufacturing (LAM) process includes directed energy deposition method and powder bed fusion method. Compared with powder bed fusion method (such as the SLS and selective laser melting (SLM)), directed energy deposition method (e.g. laser engineered net shaping (LENS)) has advantages of parts repairing and gradient parts fabrication capabilities. There are no studies on the fabrication of GO-Ti parts by LENS process. In this study, GO-Ti parts are fabricated by the LENS process. The effects of GO and laser power on fabricating defects of porosity, microstructure, and mechanical properties (including microhardness, elastic modulus, wear rate) were studied, for the first time.

Purpose The purpose of this paper is to identify if the implementation of ultrasonic vibration in laser engineered net shaping (LENS) process can help to reduce internal weaknesses such as porosity, coarse primary TiB whisker and heterogeneous distribution of TiB reinforcement in the LENS-fabricated TiB reinforced Ti matrix composites (TiB-TMC) parts. Design/methodology/approach An experimental investigation is performed to achieve the results for comparative studies under different fabrication conditions through quantitative data analysis. An approach of microstructural characterization and mechanical testing is conducted to obtain the output attributes. In addition, the theoretical analysis of the physics of ultrasonic vibration in the melting materials is presented to explain the influences of ultrasonic vibration on the microstructural evolution occurred in the part fabrication. Findings Because of the nonlinear effects of acoustic streaming and cavitation induced by ultrasonic vibration, porosity is significantly reduced and a relatively small variation of pore sizes is achieved. Ultrasonic vibration also causes the formation of smaller TiB whiskers that distribute along grain boundaries with a homogeneous dispersion. Additionally, a quasi-continuous network (QCN) microstructure is considerably finer than that produced by LENS process without ultrasonic vibration. The refinements of both reinforcing TiB whiskers and QCN microstructural grains further improve the microhardness of TiB-TMC parts. Originality/value The novel ultrasonic vibration-assisted (UV-A) LENS process of TiB-TMC is conducted in this work for the first time to improve the process performance and part quality.

Edge surface grinding has been widely applied in achieving functional surfaces and repairing the damage surfaces of carbon fiber–reinforced plastic (CFRP) composites especially with complex three-dimensional features. The conventional surface grinding (CSG) usually generates surface damages, leading to reduced service life and load-carrying capability of the parts. Therefore, there is a critical need to develop a surface grinding process of CFRP composites in a high-quality and high-efficiency way. Rotary ultrasonic machining (RUM) surface grinding has been proven to be such a process. In addition, RUM edge surface grinding can be conducted by up surface grinding or down surface grinding. However, the difference between up surface grinding and down surface grinding with RUM has not been reported. In this paper, the comparison between up surface grinding and down surface grinding with RUM is studied for the first time. The effects of the grinding parameters on machining performance, including cutting force, surface roughness, and surface morphology characteristics, are experimentally studied. The results show that the cutting forces in up grinding are obviously larger than those in down grinding. Lower surface roughness is generated by down grinding when grinding parameters are kept unchanged. The reasons for the differences of cutting forces and surface integrity are discussed. Surface morphologies suggest clearly that brittle fracture is the predominant material removal mode in grinding of CFRP composites. The chip size of the resin, the fracture size of the carbon fiber, and the material removal scale are smaller in down grinding. Furthermore, compared with CSG, the advantages of RUM surface grinding are presented. This investigation will provide useful guidance for surface grinding of CFRP composites.

Laser engineered net shaping (LENS), developed from laser cladding and rapid prototyping, has different promising applications such as aerospace, automotive, marine, tool manufacturing, etc. Due to the features of LENS process, the capability of overhang structure deposition was limited and some geometrical structures cannot be perfectly built. Investigating overhang building mechanisms and angle accuracy are crucial. In this study, the effects of scanning patterns (reciprocating and unidirectional deposition way) and vertical increment (z-increment) on overhang structures in LENS have been investigated. It was found that the overhang deposited in a reciprocating way exhibited higher geometry accuracy than that deposited in a unidirectional way. By optimizing z-increment, the discrepancy between the designed and experimental inclined angles of overhangs greatly decreased. The effects of processing parameters, including laser power, scanning speed, and powder feed rate, on the optimal z-increment were also investigated.