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Metal-thermoplastic hybrid structures have proven their effectiveness to achieve lightweight design concepts in both primary and secondary structural components of advanced aircraft. However, the drastic differences in physical and chemical properties between metal and thermoplastic make it challenging to fabricate high-reliability hybrid structures. Here, a simple and universal strategy to obtain strong hybrid structures thermoplastics is reported by regulating the bonding behavior at metal/thermoplastic interfaces. To achieve such, we first researched and uncovered the bonding mechanism at metal/thermoplastic interfaces by experimental methods and density functional theory (DFT) calculations. The results suggest that the interfacial covalency, which is formed due to the interfacial reaction between high-electronegativity elements of thermoplastics and metallic elements at metal surfaces, dominates the interfacial bonding interaction of metal-thermoplastic hybrid structures. The differences in electronegativity and atomic size between bonding atoms influence the covalent-bond strength and finally control the interfacial reliability of hybrid structures. Based on our covalent-bonding mechanism, the carboxyl functional group (COOH) is specifically grafted on polyetheretherketone (PEEK) by plasma polymerization to increase the density and strength of interfacial covalency and thus fabricate high-reliability hybrid structures between PEEK and A6061-T6 aluminum alloy. Current work provides an in-depth understanding of the bonding mechanism at metal-thermoplastics interfaces, which opens a fascinating direction toward high-reliability metal-thermoplastic hybrid structures.

The linear motor feeding system is a typical electromechanical coupling system. Conventional characteristic analyses of electromechanical coupling often overlook the influence of flexible deformation in critical components of the linear motor feeding system. Moreover, when employing genetic algorithms to optimize servo system PID control parameters, slow convergence, nonconvergence, or premature convergence problems may arise. To address these issues, this paper proposes a new performance optimization method for a linear motor feeding system. The method uses a combination of “multi-body theory + finite element” to accurately account for the flexible deformation of critical components of the feeding system, establishes a rigid–flexible electromechanical coupling model of the linear motor feeding system, and optimizes the PID parameters of the established model with an improved adaptive genetic algorithm. Simulation results demonstrate that, when utilizing an adaptive genetic algorithm to optimize the rigid–flexible electromechanical coupling model and a control system model that disregards flexible body deformation, the system achieves stability in 0.02 s and 0.027 s with overshoots of 13% and 27%, respectively. These outcomes confirm the accuracy and importance of considering flexible body deformation in the optimization performance of a linear motor feeding system. At the same time, the time required to reach the steady state of the rigid–flexible electromechanical coupling model optimized by the adaptive genetic algorithm is shortened from 0.035 s to 0.02 s. The sinusoidal signal response curve of the optimized system does not exhibit any peak overshoot compared with that of the nonoptimized system, and the response speed is also faster. These results demonstrate the effectiveness of the rigid–flexible electromechanical coupling model optimized by the nonlinear adaptive genetic algorithm. The displacement response curves of the linear motor feeding system under different workbench loads are obtained through experiments and compared with those obtained from simulations to verify the established model and the correctness of the proposed method.

Although excellent progress has been made recently in powertrain fault diagnosis based on vibration signals, most of them are based on the assumption that the fault features of the training and test data are drawn from the same probability distribution. Due to the limitation of the domain shift phenomenon, the performance of the current intelligent fault diagnosis methods is significantly reduced. Even many existing transfer learning methods have the problem of low generalization ability. Inspired by sparse representation theory, a novel cross-domain fault diagnosis method based on K-means singular value decomposition (K-SVD) and long short-term memory network (LSTM) is proposed in this study. First, K-SVD can convert source domain data into a sparse dictionary and sparse coefficient. The domain-invariant features are explored in the sparse dictionary, which contains redundant features. The sparse coefficients are input into the LSTM to obtain a primary classifier. Then, the sparse coefficients of the target domain are solved by using the sparse dictionary of the source domain. It is input into the primary classifier for fine-tuning training, and the final diagnostic classification model is obtained. The proposed method establishes knowledge transfer from the source domain to the target domain by exploring domain-invariant features in the sparse domain and bridging the distribution discrepancy. It is evaluated using powertrain operating data acquired on cross-speed, cross-load and cross-sensor working conditions. It is demonstrated that the proposed method has superior performance in dealing with data imbalance and different distributions. It offers a promising approach for industrial applications on cross-domain fault diagnosis.

Because the surface corrosion damage could susceptibly occur in metallic structures for the corrosive environment and fatigue loads, it essential to detect the corrosion timely and precisely before the loss of life and property caused by corrosion. Based on low-frequency Lamb wave technique, the low-frequency A0 Lamb wave, the low-frequency S0 Lamb wave and one-way S0-A0 Lamb mixing wave are experimentally investigated in the thin plates with the early stage damage caused by the surface corrosion, which were made by different times of hydrochloric corrosion. Firstly, it verified that the damage degree of the surface corrosion region increases with the number of corrosion times by the Scanning Electron Microscopy (SEM). Secondly, the linear and nonlinear effect caused by corrosion had been investigated, and the relationship between the characters of the different Lamb waves and the different corrosion damage levels were qualitatively discussed. Especially, the length and the location of the corrosion region were located successfully by one-way S0-A0 Lamb mixing wave. This paper explores experimentally the propagation mechanism of low frequency linear and nonlinear Lamb wave in thin plates with corrosion damage, which can provide an experimental basis for Lamb-wave detection techniques used in the evaluation and location of damages.

BACKGROUND Berberine is a herbicidal chemical that we isolated from Coptis chinensis. In continuation of our program aimed at discovering and developing natural botanical herbicides, we evaluated the herbicidal activities of 39 berberine analogues and developed a three-dimensional quantitative structure-activity relationship (3D-QSAR) model. RESULTS Among these 39 analogs, the most active compounds were determined to be worenine chloride and coptisine chloride, with median inhibitory concentration (IC50 ) values on all eight tested weed species of

Berberine is a plant-derived herbicidal alkaloid. The herbicidal mechanism of berberine is still not clear. In this study, our aim is to clarify the mechanism of berberine inhibiting the root growth of Arabidopsis thaliana, aiming at providing new insight into identifying the molecular targets of berberine.The whole-genome RNA sequencing had revealed that 403 genes were down-regulated, and 422 genes were up-regulated in Arabidopsis roots with berberine treatment. According to KEGG and GO analysis, the expression of two genes AT5G48010 (Thas) and AT5G42600 (MRN1) which are in the sesquiterpenoid and triterpenoid biosynthesis pathway were affected most. These two genes belong to thalianol and marneral gene clusters. RT-PCR showed that Arabidopsis responds to berberine by inhibiting root growth through repressing the expression of thalianol and marneral gene clusters, which was independent of the upstream effectors ARP6 and HTA9-1. GC-MS analysis showed that berberine could inhibit THAH in the biosynthetic network of triterpenoid gene cluster in Arabidopsis and thus cause the accumulation of thalianol.Our study indicated the repression of the thalianol and marneral gene clusters as the primary mechanism of action of berberine in Arabidopsis, which may result in plant growth defects by interrupting the thalianol metabolic pathway. This provides novel clues as to the possible molecular herbicidal mechanism of berberine. © 2022 Society of Chemical Industry.

Background Tetranychus urticae (T. urticae) Koch is an important pest of vegetable crops worldwide. In this study, bioassays were carried out to analyze the resistance risk, multi-resistance and management of T. urticae Koch to bifenthrin, bifenazate and cyflumetofen on cowpea. Results The resistance ratios of the adult T. urticae population to bifenthrin (G16), bifenazate (G12) and cyflumetofen (G12) were 31.29, 9.38 and 5.81, respectively. Realized heritability (h 2 ) analysis showed that, under a selection pressure of 50-90% mortality, the generations needed to increase 10-fold LC50 values of bifenthrin, bifenazate and cyflumetofen were 3.64-8.05, 5.75-12.71, and 10.93-24.15, respectively. No obvious multi-resistance among these three acaricides was observed. Synergist bioassay results showed that microsomal multifunctional oxidase (MFO) was involved in bifenthrin resistance of T. urticae, with a synergistic ratio of 22.38. However, MFO and GSTs were not the main factors conferring the resistance to bifenazate. MFO, glutathione S-transferases(GSTs), together with esterase contributed to the development of the resistance to cyflumetofen. Additionally, the toxicity selection index test showed that bifenazate was safe to the natural enemy Neoseiulus barkeri (N. barkeri) with a toxicity selection index (TSI) >484.85, while bifenthrin was the least safe (TSI = 0.92). Conclusions These results demonstrated the T. urticae developed higher resistance risk to bifenthrin compared to bifenazate and cyflumetofen and no obvious multi-resistance among these three acaricides, providing guidance for designing appropriate strategies for the effective application of bifenthrin, bifenazate and cyflumetofen in the field and delaying the development of insecticide resistance. © 2019 Society of Chemical Industry.

Phononic crystals (PCs) and metamaterials are artificially structured materials with the unprecedented property of the existence of complete stop-bands. However, the generally narrow width of the stop-bands in such materials severely limits their applicability. Here, a particular kind of gradient zigzag metamaterial beams exclusively with flat bands within a broad frequency range is proposed based upon our previously proposed uniform counterparts. The calculated band structures by the Finite Element Method (FEM) and the Spectral Element Method (SEM) show the distinctly different characteristics of the gradient zigzag metamaterial beams from the conventional PCs and metamaterials, where the band structures are totally filled with flat bands within a broad frequency range without the normal pass bands. These flat bands are caused by the local resonance of certain parts in the gradient zigzag metamaterial beams, and the elastic waves with the frequencies at these flat bands are trapped in the resonant parts and cannot propagate. As a result, our proposed gradient zigzag metamaterial beams can be used as broadband vibration isolators for beam-like structures, which is verified by both numerical simulations and experiments conducted on the 3D-printed samples. This design strategy opens a new avenue for designing and constructing novel broadband vibration isolators.

The effects of aging time and temperature on the formation and growth behavior of interfacial intermetallic compound (IMC) of Sn-16Sb/Cu(wt%) solder joints prepared by using dip soldering were investigated. The results show that the major IMCs between Sn-16Sb solder and Cu substrate after thermal aging are Cu3Sn and Cu6Sn5. The thickness of the interfacial IMC in Sn-16Sb/Cu is linearly against the square root of aging time, which indicates that the growth of IMC is mainly controlled by diffusion between Cu and Sn atoms. By using linear regression method, the growth rate constants of interfacial IMC layers are 1.254×10-18, 8.821×10-18 and 1.22×10-17 m2s-1 for Sn-16Sb/Cu joints aged at 120, 150 and 170 °C, respectively. Besides, the activation energy of the interfacial IMC growth was also calculated to be 68.27 kJ/mol. The IMC grain diameters after aging treatment increase with the increasing aging time, with i e, d = 0.492t0.106, d = 0.543t0.143 and d = 0.290t0.263 for aging temperatures of 120, 150 and 170 °C, respectively. Besides, by using nanoindentation, the softening of Sn-16Sb solder was found during aging treatment. Moreover, the U-shape evolution of the values in hardness and Young's moduli was found in this work.

The (Ni,Cu)3Sn4 phase as intermetallic compounds (IMCs) plays an important role in evaluating reliability of solder joints. The first-principles calculations were performed to investigate the phase stability, mechanical properties and electronic structures of Ni3Sn4 and Ni2.5Cu0.5Sn4 IMCs. The results shows that the doping of Cu atom not only reduced the phase stability but also weakened the mechanical properties of Ni3Sn4 crystal structure. Meanwhile, all studied Ni3Sn4-based structures were structural stability. Moreover, the anisotropy of Ni2.5Cu0.5Sn4 (2a site) was strongest while that of Ni2.5Cu0.5Sn4 (4i site) was the weakest. Based on analysis of electronic structures, it indicated that the ionic bonding of Ni Cu in Ni2.5Cu0.5Sn4 structure was weaker than covalent bonding of nearest-neighbor Ni in Ni3Sn4, which led to an energy reduction with the formation of banding states. By means of nano-indentation measurements, the young's modulus and hardness were measured to be 135.3 ± 8.4 GPa and 5.0 ± 0.63 GPa for Ni3Sn4 while 126.3 ± 7.6 GPa and 4.7 ± 0.72 GPa for (Ni,Cu)3Sn4, respectively, which were close to the value of calculated results.

Instantaneous angular speed (IAS) measurement using zebra tape has been presented as an advantageous tool for rotating machinery surveillance. Unfortunately, both butt joint and mounting imperfection of the zebra tape result in stripes with different widths, which cause the outliers appear in the acquired signal. This paper proposed a solution to accurately identify the outliers and define the angular displacement values represented by outliers in the condition of periodic fluctuation of speed. The procedure is based on K-means clustering method and Fourier series model. Specially, a series of algorithms take K-means clustering partitioning method as core, and is used for outliers identification; the Fourier series fitting model is used to analyze the angular displacement values represented by outliers. Experimental study was performed on a test rig to validate the method under different measurement conditions. The result of error analysis shows the effectiveness of the algorithm.

As one kind of current main power sources, internal combustion engines require high-reliability to ensure mechanical systems working well in normal operation. This paper studies vibration signals in order to detect multiple types of faults by a single channel signal. First, for the decomposition level of variational mode decomposition (VMD) which needs to be chosen non-automatically, this paper analyzes the features of various faults and optimizes the iteration initial values of center frequency so as to reduce the adverse effect of inappropriate decomposition level. Moreover, considering that VMD cannot decompose different signal sources in the same frequency, robust independent component analysis (ICA) is an excellent method to overcome this challenge. Then, the fourth-order cumulant of restructured signals from VMD and robust ICA is taken as fault indexes. Finally, because of the high error rate of original fuzzy C-Mean clustering, Euclidean distance between test points and cluster center of fuel injection failure is taken as a fault detection threshold in order to achieve high-recognition rate. In conclusion, through optimizing several algorithms, the purpose of detecting multiple types of faults by single channel signal is achieved in the current research.

Background Pancreatic ductal adenocarcinoma (PDAC) exhibits the poorest prognosis of all solid tumors with a 5‐year survival rate of less than 10% and a median survival of 6 months after diagnosis. Numerous targeted agents have been developed and evaluated to improve the survival benefit in patients with PDAC. Unfortunately, most agents have been proven futile mainly owing to the dense stroma and the sophisticated signaling pathways of PDAC. Here, we show the potent effectiveness of Aptamer‐SH2 superbinder‐(Arg)9 conjugate on the treatment of PDAC. In this conjugate, DNA aptamer selected against PDAC cell line confers the function of specifically recognizing and binding to the PDAC cells and activated pancreatic stellate cells (PSCs) in stroma; cell penetrating peptide (Arg)9 facilitates the intracellular delivery of fused proteins; SH2 superbinder conducts the drastic blockade of multiple phosphotyrosines (pY)‐based signaling pathways in tumor cells. Methods PDAC‐associated pY were reanalyzed by bioinformatics screen. XQ‐2d and SH2 superbinder‐(Arg)9 were crosslinked with BMH to form XQ‐2d‐SH2 CM‐(Arg)9 conjugate. Immunofluorescence was utilized to assess the potency of the conjugate entering cells. MTT and wound healing assays were performed to evaluate the proliferation or migration of PANC‐1 and BxPC‐3 cells, respectively. Western blot and Pulldown assays revealed that conjugate influenced several pY‐based signaling pathways. Tumor‐bearing mice were used to validate XQ‐2d‐SH2 CM‐(Arg)9, which restrained the growth and metastasis of cancer cells. Results XQ‐2d‐His‐SH2 CM‐(Arg)9 conjugate restrained proliferation, invasion, and metastasis of PDAC cells with potent efficacy via blocking the activity of several pY‐related signaling cascades. XQ‐2d‐His‐SH2 CM‐(Arg)9 could eliminate the dense stroma of PDAC and then arrive at tumor tissues. Conclusions XQ‐2d‐SH2 CM‐(Arg)9 conjugate may efficiently destroy the pancreatic stroma and show potent antitumor efficacy with minimal toxic effect by regulating tumor cell proliferation and metastasis in vitro and in vivo, which makes it to be a promising targeted therapy of PDAC., Schematic diagram of XQ‐2d‐His‐SH2 CM‐(Arg)9 in PDAC cells and PSCs. XQ‐2d‐His‐SH2 CM‐(Arg)9 could bind and penetrate into PSCs, inactivate PSCs, and decrease ECM secretion. XQ‐2d‐His‐SH2 CM‐(Arg)9 could reach tumor tissues, recognize, and enter into the PDAC cells. XQ‐2d‐His‐SH2 CM‐(Arg)9 could function as a broad‐spectrum inhibitor via capturing pY‐containing proteins and blocking multitude pY‐based signaling pathways in PDAC cells.

Background: Identification of accurate targets is essential for a successful development of targeted therapy in cancer. Studies have shown that matrine has antitumor activity against many types of cancers, including lung cancer, breast cancer, liver cancer, pancreatic cancer, ovarian cancer and leukemia, etc. However, the direct target in cancer cells of its anticancer effect has not been identified. The purpose of this study was to find the molecular target of matrine to inhibit the proliferation of cancer cells and explore its mechanism of action. Methods: The effect of matrine on the proliferation of cancer cells were examined by MTT assay. Pull-down assay with matrine-amino coupling resins (MA beads) and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) were performed to explore the target of matrine. The target of matrine was further validated by competitive binding assay, cellular thermal shift assay (CETSA) and drug affinity responsive target stability (DARTS). A series of in vitro and in vivo experiments were conducted to reveal the mechanisms by which matrine targeted Src to regulate the downstream signaling pathways of Src in cancer cells. Results: Herein we showed that matrine inhibited the proliferation of cancer in vitro and in vivo. Pull-down assay with MA beads and LC-MS/MS identified Src as the target of matrine. The findings provided solid evidences that matrine directly bound to Src and Src kinase domain is required for its interaction with matrine and Ala392 in the kinase domain participated in matrine-Src interaction. Intriguingly, matrine was proven to inhibit Src kinase activity in a non-ATP-competitive manner by blocking the autophosphorylation of Tyr419 in Src kinase domain. Matrine down-regulated the phosphorylation levels of MAPK/ERK, JAK2/STAT3 and PI3K/Akt signaling pathways via targeting Src.Conclusions: Collectively, matrine targeted Src, inhibited its kinase activity and down-regulated its downstream MAPK/ERK, JAK2/STAT3 and PI3K/Akt phosphorylation signaling pathways to inhibit the proliferation of cancer cells.

CBP bromodomain could recognize acetylated lysine and function as transcription coactivator to regulate transcription and downstream gene expression. Furthermore, CBP has been shown to be related to many human malignancies including acute myeloid leukemia. Herein, we identified DC-CPin734 as a potent CBP bromodomain inhibitor with a TR-FRET IC50 value of 19.5 ± 1.1 nM and over 400-fold of selectivity against BRD4 bromodomains through structure based rational drug design guided iterative chemical modification endeavoring to discover optimal tail-substituted tetrahydroquinolin derivatives. Moreover, DC-CPin734 showed potent inhibitory activity to AML cell line MV4-11 with an IC50 value of 0.55 ± 0.04 μM, and its cellular on-target effects were further evidenced by c-Myc downregulation results. In summary, DC-CPin734 showing good potency, selectivity and anti AML activity could serve as a potent and selective in vitro and in vivo probe of CBP bromodomain and a promising lead compound for future drug development.

There are two severe limitations of current flexural wave metasurface based on local resonance mechanism or modal conversion method: low transmittance and only a single manipulation parameter. Inspired by the interaction between notches and flexural waves, we propose a high transmittance and multi-parameter independent manipulation metasurface composed of an array notches. Firstly, based on the phase shift accumulation method, a full 2π phase shift is achieved by modulating four notch parameters independently. Secondly, the refraction and focusing metasurfaces are designed based on the generalized Snell's law and compared with the simulation results. Finally, the designed focusing metasurfaces is validated by corresponding experiments. The four metasurfaces have a good performance for broadband flexural wave focusing, and the numerical and experimental focal lengths are in great agreement with the theoretical values. The notched metasurface provides an innovative way to manipulate flexural waves without resonators, which can be used in the applications of energy harvesting, waveguide design and ultrasonic detection.

The low-temperature α-CoSn3 intermetallic compound (IMC) doped with Ni is an important component at the interface between Sn-based solder and printed circuit boards, which largely controls the mechanical properties of solder joints. However, the structure and elastic properties of α-CoSn3 doped with Ni are not well understood. In this work, first-principle calculations and nano-indentation have been performed to explore the influences of additional Ni on elastic properties of α-CoSn3 IMC. By means of nano-indentation, the Young’s modulus and hardness were recorded for α-CoSn3 and α-(Co,Ni)Sn3 to be 149.9 ± 8.6 GPa and 6.14 ± 0.96 GPa, and 142.5 ± 7.6 GPa and 5.84 ± 0.76 GPa, respectively. Systematic works of first-principle calculations indicated that the doped Ni weakened the mechanical properties while strengthened the ductility and elastic anisotropy of α-CoSn3. The calculated electronic structures demonstrated that the bonding energies of α-CoSn3 were obviously decreased with the doping of Ni, which led to the degeneration of mechanical properties. Keywords: Intermetallic compound, Nano-indentation, First-principles calculations, Mechanical properties

This paper experimentally investigates the early stage damage caused by the surface corrosion in thin plates based on two nonlinear Lamb wave methods, which are the low-frequency S0 mode Lamb wave method and one-way S0-A0 Lamb mixing wave method. The experimental results show that the significant second/third harmonics and the resonant waves from these methods can be caused by the surface corrosion damage. Meanwhile, it is found that the normalized acoustic nonlinearity parameters in these methods increase monotonically with the number of corrosion times before the generation of the distinct cavities. Moreover, the position and the length of the surface corrosion region can be characterized by the resonant waves from one-way S0-A0 Lamb mixing wave method. This study reveals that the low-frequency S0 mode Lamb wave method and one-way S0-A0 Lamb mixing wave method are feasible to evaluate early stage damage caused by the surface corrosion.

The metal-thermoplastic hybrid structure has been widely employed in the aviation and aerospace industry. In this work, we developed a feasible way of laser surface texturing to address the poor adhesion between PEEK and 6061-T6 aluminum alloy. With the laser surface modification on 6061-T6 aluminum alloy, the PEEK/6061-T6 friction lap joining strength was improved significantly. The experimental results showed that the tensile shear strength between PEEK and 6061-T6 with laser textured surfaces achieved the maximum of 48.14 MPa. The enhanced bonding strength was attributed to the mechanical interlocking at the interface between PEEK and 6061-T6 caused by periodic micro-pores and nano-particles. After the progress of laser surface texturing, the double-scale hierarchical structures were produced on the surface of modified 6061-T6 alloy, leading to the formation of superhydrophobic or hydrophobic surfaces. Besides, quantitative fractal analysis of 6061-T6 surfaces was performed to study the relation between the morphology of 6061-T6 surface and the adhesion property of PEEK and 6061-T6. The results indicated that the superhydrophobic surface of 6061-T6 exhibited higher adhesion property with PEEK than the hydrophobic surface. A flawless interface was observed in the joint of PEEK and 6061-T6 with the superhydrophobic surface, compared to the voids observed at the interface of PEEK and 6061-T6 with the hydrophobic surface.

Numerous vibration-based techniques are rarely used in diesel engines fault diagnosis in a direct way, due to the surface vibration signals of diesel engines with the complex non-stationary and nonlinear time-varying features. To investigate the fault diagnosis of diesel engines, fractal correlation dimension, wavelet energy and entropy as features reflecting the diesel engine fault fractal and energy characteristics are extracted from the decomposed signals through analyzing vibration acceleration signals derived from the cylinder head in seven different states of valve train. An intelligent fault detector FastICA-SVM is applied for diesel engine fault diagnosis and classification. The results demonstrate that FastICA-SVM achieves higher classification accuracy and makes better generalization performance in small samples recognition. Besides, the fractal correlation dimension and wavelet energy and entropy as the special features of diesel engine vibration signal are considered as input vectors of classifier FastICA-SVM and could produce the excellent classification results. The proposed methodology improves the accuracy of feature extraction and the fault diagnosis of diesel engines.

The effects of Ni element on mechanical properties of CoSn2 phase were investigated by means of first-principles calculations and nano-indentation measurements in this work. Theoretical models of Co1−xNixSn2 (x = 0, 0.25, 0.5, 0.75 and 1) were built to research the phase stability, elastic constants and electronic structures of Ni-free and Ni-doped CoSn2 structures. Analyses about phase stability indicated that the Ni solubility in (Co,Ni)Sn2 phase could reach to 33.33 at.%. The calculated results showed that the additional Ni atoms weakened the mechanical properties of CoSn2 and the Young’s modulus decreased from 149.70 to 107.55 GPa. Besides, the ductility of CoSn2-based structures was improved after the doping of Ni. All studied crystal structures were anisotropic. The results of electronic structures demonstrated that the bonding energy of (Co,Ni)Sn2 phase decreased with the adding of Ni, which was the determinant of the decrement of mechanical properties. The experimental results obtained from nano-indentation showed that the Young’s modulus and hardness were 159.9 ± 11.3 GPa and 6.91 ± 0.65 GPa for CoSn2 while 140.5 ± 9.3 GPa and 6.23 ± 0.82 GPa for (Co,Ni)Sn2. By combining theoretical and experimental methods, it was certainly concluded that the introduced Ni element weakened the mechanical properties of CoSn2. Keywords: Intermetallic compounds, Ni additions, Nano-indentation, First-principles calculations, Mechanical properties

The evaluation and fault diagnosis of a diesel engine&rsquo, s health conditions without disassembly are very important for diesel engine safe operation. Currently, the research on fault diagnosis has focused on the time domain or frequency domain processing of vibration signals. However, early fault signals are mostly weak energy signals, and the fault information cannot be completely extracted by time domain and frequency domain analysis. Thus, in this article, a novel fault diagnosis method of diesel engine valve clearance using the improved variational mode decomposition (VMD) and bispectrum algorithm is proposed. First, the experimental study was designed to obtain fault vibration signals. The improved VMD method by choosing the optimal decomposition layers is applied to denoise vibration signals. Then the bispectrum analysis of the reconstructed signal after VMD decomposition is carried out. The results show that bispectrum image under different working conditions exhibits obviously different characteristics respectively. At last, the diagonal projection method proposed in this paper was used to process the bispectrum image, and the fourth order cumulant is calculated. The calculation results show that three states of the valve clearance are successfully distinguished.

Depositing Ni-based films on Cu pads has been accepted as an effective strategy to address the reliability challenges due to the development of plastic ball grid array (PBGA) in electronic packaging technology. Modification mechanisms of Co on Ni film and Sn-37 wt%Pb/Ni/Cu solder joints were researched from experimental and theoretical methods in this work. Experimental results suggested the additional minor Co element (12.46 at.%) led to the formation of Ni–Co solid solution. After reflowing, Ni3Sn4 intermetallic compound (IMC) was formed within Sn–37Pb/Ni/Cu system while (Ni,Co)3Sn4 IMC was produced at solder/Ni–Co interface. Nano-indentation tests indicated that the doping of Co enhanced the mechanical properties of Ni film and Ni3Sn4 IMC. Our single-lap shear tests demonstrated that the shear strength of Sn–37Pb/Ni/Cu reflowing joints increased from 24.68 to 29.72 MPa with the addition of Co. Moreover, theoretical investigations based on first-principles calculations were carried out to uncover the Co strengthening mechanism. The calculated results noted that the improved stability of coating/IMC interface and mechanical properties of coating and IMC phases were the main reasons for the enhanced shear strength of Sn–37Pb/Ni–Co/Cu solder joints.

In this paper a novel method for de-noising nonstationary vibration signal and diagnosing diesel engine faults is presented. The method is based on the adaptive wavelet threshold (AWT) de-noising, ensemble empirical mode decomposition (EEMD) and correlation dimension (CD). A new adaptive wavelet packet (WP) thresholding function for vibration signal de-noising is used in this paper. To alleviate the mode mixing problem occurring in EMD, ensemble empirical mode decomposition (EEMD) is presented. With EEMD, the components with truly physical meaning can be extracted from the signal. Utilizing the advantage of EEMD, this paper proposes a new AWT–EEMD-based method for fault diagnosis of diesel engine. A study of correlation dimension in engine condition monitoring is reported also. Some important influencing factors relating directly to the computational precision of correlation dimension are discussed. Industrial engine normal and fault vibration signals measured from different operating conditions are analyzed using the above method. These techniques have integrated with our proposed adaptive wavelet threshold de-noising to form a new AWT–EEMD–CD method. The advantage of combining of EEMD and fractal dimension is that it does not require the classifiers to recognize the diesel engine fault types, also the method can solve the difficulty of recognizing fault states when two or more fractal dimensions are close to each other. To verify the effectiveness of the EEMD–CD in detecting the faults, their induced vibrations are collected from a series of generators under normal and faulty engine conditions after de-noising. The results show that this method is capable of extracting the impact signal features induced by vibrations and is able to determine their types of fault accurately even when the impacts have been overwhelmed by other unrelated vibration signals.