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The Subarachnoid Hemorrhage Early Brain Edema Score (SEBES) is a radiographic marker for early brain injury after aneurysmal subarachnoid hemorrhage (aSAH). We evaluated the role of the SEBES in performing decompressive craniectomy (DC) for poor-grade aSAH.We retrospectively analyzed all cases of poor-grade (World Federation of Neurosurgical Societies [WFNS] grade IV and V) aSAH in adults who underwent microsurgery at our center between April 2017 and March 2021. Patient demographics, clinical presentation, imaging findings, and surgical data were obtained. The study endpoints of DC rate, complications, and functional outcomes (modified Rankin Scale score3) were compared between the traditional surgery and SEBES-informed groups. A survival analysis was performed to estimate 180-day survival and hazard ratios for death.The study included 116 patients (mean age, 60.8 ± 9.5 years, DCs [n = 63, 54.3%]). In the univariate analysis, age, intracranial pressure, midline shift, pupil changes, SEBES grade III-IV, traditional group, and WFNS grade Ⅴ were associated with DC. DC (46.4% vs. 67.4%) and in-hospital mortality rates (9.6% vs. 25.6%) were significantly lower in the SEBES-informed group. At day 180 after admission, modified Rankin Scale scores did not significantly differ between the 2 groups, but 180-day survival was significantly higher in the SEBES-informed group (78.1% vs. 53.5%). In the multivariable analysis, age, pupil changes, being in the traditional group, and delayed cerebral ischemia were independently associated with 180-day postadmission mortality.The SEBES provides good imaging support for preoperative and intraoperative intracranial pressure management in poor-grade aSAH, allowing for improved DC-related decision-making and better 180-day survival.

BACKGROUND: Posterior communicating artery (PcomA) aneurysms are more likely to recanalize than anterior communicating artery (AcomA) aneurysms. However, it is still unclear whether the recanalization rate of these aneurysms is a result of involvement from the fetal posterior cerebral artery (fPCA) in PcomA aneurysms and variation of the unilateral A1 segment in AcomA aneurysms. The purpose of this study is to retrospectively evaluate the different recanalization rates between PcomA aneurysms with fPCA and AcomA aneurysms with a variation of the unilateral A1 segment. METHODS: We retrospectively collected information regarding 214 patients, each with communicating segment aneurysms between January 2013 and January 2020. Follow-up documentation on clinical and imaging data was comparatively analyzed between variant types, and recanalization rates of the variant and normal types were analyzed by stratification. RESULTS: Of the 84 variant-type aneurysms (PcomA with fPCA and AcomA with a variation of the unilateral A1 segment, 41/43), complete recanalization occurred in 23 patients (27.4%), and it was significantly more likely to occur in PcomA aneurysms with fPCA (39.1%) than in AcomA aneurysms with a variation of the unilateral A1 segment (16.3%). Stent-assisted coil embolization (SACE) has been shown to reduce recanalization (OR =0.092, 95% CI: 0.011 to 0.790, P=0.03). Additionally, variant types and the normal type (non-fetal, 106, and bilateral A1 symmetry, 24) have different odds ratios (OR) of recanalization (P=0.04), and the OR of the variant subtypes was significant, unlike the normal type (P=0.49). CONCLUSIONS: This study suggests that PcomA aneurysms with fPCA are more likely to recanalize than AcomA aneurysms with a variation of the unilateral A1 segment.

Background: Symptomatic vertebral artery dissecting aneurysm (VADA) is a challenging disease with controversy on treatment strategy due to anatomic configuration and their nature. Moreover, the outcomes of reconstructive treatment have not been well established. Objective: To evaluate the safety and efficacy of reconstructive endovascular treatment (EVT) for symptomatic VADAs with Willis covered stent. Methods: We evaluated retrospectively 13 patients with symptomatic VADAs who treated with Willis covered stent, compared with stent-assisted coiling (SAC) on the characteristics, posttreatment course, angiographic and clinical follow-up outcomes at an average of 14.4 months (range, 3–48 months). Results: A total of 33 patients with symptomatic VADAs were reviewed, 23 of these patients with ruptured VADAs. The technical successful rate is 100% respectively in Willis covered stent (Group A) and SAC (Group B, n ​= ​20). The initial complete occlusion rate was significant higher in group A (100%) than group B (30%) (p ​ ​0.05). No obvious in-stent stenosis and no re-hemorrhage and delayed ischemic symptoms during the follow-up period. The final angiograms of all survived patients demonstrated the complete occlusion rate was higher in group A (100%) than group B (80%), but no significant statistical difference (p ​> ​0.05). Clinical outcomes were favorable in 31 (93.9%), severe disability occurred in one in group B, and only one death in group A. The final clinical outcomes were also not significant difference in the two groups (p ​> ​0.05). Conclusions: Our initial result demonstrated reconstructive EVT with Willis covered stent provides a viable approach for selected symptomatic VADAs involving the intracranial and extracranial segments, which is similar to favorable results with SAC. However, an expanded clinical experiences and larger cohort studies are needed.

We investigated lipidomic features from healthy controls (HCs), patients with unruptured cerebral aneurysms (UCAs) and ruptured CAs (RCAs) to analyze their lipidomic profiles and identify a lipid signature associated with CAs. Patients (n = 540) were enrolled from two centers. We identified significantly altered plasma lipids in 2 cohort with the total lipid intensity decreasing from HC to UCA to RCA. Triglycerides comprised the distinct profile of lipids in CAs. A four-lipid signatures showed good calibration and diagnostic prediction for CA vs. HC and UCA vs. RCA, but independent discriminate CA from HC, UCA from RCA, and RCA (RI and RII) or UCA (UI and UII) subtypes, in training and validation cohorts. Comprehensive lipidomic profiles identified decreased lipids as a prominent feature of CA development, and a four-lipid signature could not only better diagnose and predict UCAs/RCAs from HCs, but also predicted patients subtypes with severe RCA or high-risk UCA.

Purpose: To evaluate the safety and the clinical efficacy of percutaneous vertebroplasty (PVP) in treating malignant spinal tumors and malignant vertebral compression fractures with epidural involvement.Materials and methods: 43 patients with spinal metastatic tumors and malignant vertebral compression fractures with epidural involvement were treated using PVP. American Spinal Injury Association (ASIA) impairment scale results at presentation were used to divide patients into 2 groups. Patients in group A had no symptoms of neurological compression (n = 25); and patients in group B had symptoms of neurological compression (n = 28). A 13G bone puncture needle was placed across the pedicle of the fractured vertebra, and polymethyl methacrylate (PMMA) was injected into the fractured vertebral body under fluoroscopic control. Patients were seen in follow-up at 1, 3, and 6 months after the procedure and every six months thereafter.Results: PVP was technically successful and well-tolerated in all patients. Clinical assessment at the final follow-up found complete pain relief (n = 19) or good pain relief (n = 14) in 33 patients (62.3%, 95% CI: 49%, 76%). ASIA impairment scale assessment at the final follow-up demonstrated symptoms of neurologic compression in 31 patients and no symptoms of neurologic compression in 22 patients. Symptoms of neurologic compression were found in five group A patients and eight group B patients.Conclusions: PVP was a safe and moderately effective procedure in the treatment of malignant vertebral compression fractures with epidural involvement. Keywords: percutaneous vertebroplasty, pain, malignant spinal tumor, metastasis

DC collection network offers an attractive alternative to AC network for photovoltaic, as it avoids the charging current issues and reduces the size and weight. Variable voltage gain DC/DC converters play an important role in DC collection network. Two topologies suitable for photovoltaic DC collection are studied. Boost and LLC converter and active clamp isolated full-bridge boost converter are two converters with high and variable voltage conversion ratio suitable for the photovoltaic system. This work investigates the two converters comprehensively. The topologies are analysed so as to summarise and compare the characteristic of the converters. Soft switching condition is compared to help extend the zero voltage switching range. Voltage and current stress of the two converters are calculated. Loss comparison is made with the theoretical analysis. Advantages and disadvantages are summarised to get a deep insight into their application field.

Quasicrystals are a kind of new materials that exhibit a number of unique mechanical behaviors such as the coexistence of the phonon and phason fields. However, they are brittle and susceptible to the failure of fracture. As is known, both phonon and phason fields may contribute to fracture, but which one has more contribution? This is an open question that is of both scientific and engineering significance. The main purpose of the present paper is to answer this question. For this purpose, the axial shear fracture analysis is performed for a cylindrical composite that is made of 1D piezoelectric quasicrystals. Because of material symmetry (i.e. transverse isotropy), the problem is formulated in the cross section of the cylinder by using the polar coordinate system. The solution of the governing equation is expressed as an infinite series and the generalized dislocations are introduced to derive the singular integral equation, which is numerically solved. The computation is first verified by considering an existing example. Parametric studies then reveal that the fracture is dominated by the phason field when the phonon-phason loading ratio is below a critical point, but it is governed by the phonon field instead if the critical point is passed. In addition, the position of the critical point may be shifted by changing the values of a part of material properties only.

With the development of NEMSs (nano-electro-mechanical systems), the size-dependent behavior has been an active topic. The scale parameter seems an essential factor dominating mechanical behavior at nanoscale. However, is it always dominant? This is a question deserving careful investigation. For this reason, the buckling of a bi-layered PE (piezoelectric) nanobeam is analyzed. The main purpose is to reveal and compare the effects of the nonlocal scale, imperfect interface, interlaminar van der Waals force and loading ratio. The imperfect interface is modeled by normal and shear springs, and the van der Waals force is represented by the Hamaker formula. Based on the principle of virtual work, the analytical solution of the critical buckling loading is derived by using the trigonometric shear deformation theory. After the verification in some degenerated cases, parametric studies are conducted. It is indicated that if the nonlocal parameter varies in the typical range [0, 4 nm^2], it only has quite limited effect on the buckling behavior, as compared with the other three factors. In this case, although the buckling relies on the nonlocal scale, it is far more dependent on the conventional non-nanoscale factors. The conclusions can provide references for optimal design of NEMSs.

Mg-based stent is a promising candidate of the next generation fully degradable vascular stents. The latest progress includes the CE approval of the Magmaris ® WE43 based drug eluting stent. However, so far, the long term (more than 1 year implantation) in vivo degradation and the physiological effects caused by the degradation products were still unclear. In this study, a 20 month observation was carried out after the bare Mg-Nd-Zn-Zr (abbr. JDBM) stent prototype was implanted into the common carotid artery of New Zealand white rabbit in order to evaluate its safety, efficacy and especially degradation behavior. The degradation of the main second phase Mg12Nd was also studied. Results showed that the bare JDBM stent had good safety and efficacy with a complete re-endothelialization within 28 days. The JDBM stent struts were mostly replaced in situ by degradation products in 4 month. The important finding was that the volume and Ca concentration of the degradation products decreased in the long term, eliminating the clinicians’ concern of possible vessel calcification. In addition, the alloying elements Mg and Zn in the stent could be safely metabolized as continuous enrichment in any of the main organs were not detected although Nd and Zr showed an abrupt increase in spleen and liver after 1 month implantation. Collectively, the long term in vivo results showed the rapid re-endothelialization of JDBM stent and the long term safety of the degradation products, indicating its great potential as the backbone of the fully degradable vascular stent. Statement of significance Mg-based stent is a promising candidate of the next generation fully degradable stents, especially after the recent market launch of one of its kind (Magmaris). However the fundamental question about the long term degradation and metabolic mechanism of Mg-based stent and its degradation products remain unanswered. We implanted our patented Mg-Nd-Zn-Zr bare stent into the common carotid artery of rabbits and conducted a 20 months observation. We found that the Ca containing degradation products could be further degraded in vivo. All the alloying elements showed no continuous enrichment in the main organs of rabbits. These findings eliminate the clinicians’ concern of possible vessel calcification and element enrichment after the implantation of Mg alloy based stents to some extent.

Although the cracking problems of multiferroic structures have been widely investigated, concentrated force-induced fracture still remains as an un-fully explored failure mode that has considerable significance in this field. The present article analyzes the interfacial crack in a layered multiferroic cylinder subjected to a concentrated axial shear force on its outer surface. The methods of infinite trigonometric-series and Cauchy singular integral equation are applied to solve the problem. The convergence behaviors of the dimensionless infinite trigonometric-series functions are clarified, and the numerical results of stress intensity factor (SIF) are verified by the analytical solution in a special case. Parametric studies are conducted, and the effects of structural parameters on the fracture behavior are revealed. Two structural optimization ways are suggested for reducing the harmful peak value of SIF. One is to decrease the radius of the interface when the total thickness is given, and the other is to increase the layer thickness when the radius of the interface is specified. The obtained conclusions can provide references for anti-fracture optimization of cylindrical multiferroic devices under a concentrated force.

Swarm robots have been an active topic in the field of intelligent machines in recent years. Self-assembly is an important function of swarm robots that provides an effective way for building different kinds of configurations by autonomous docking. For a self-assembly process, the path planning control is a key technique. The present paper proposes a CVT (Centroidal Voronoi Tessellation) based intelligent control algorithm for the self-assembly path planning. It can enable swarm robots to move from an initial virtual region into the target virtual region by a synchronous collaborative scheduling method. Matlab simulations are performed on the self-assembly control of three typical configurations including the line-shape, cross-shape and H-shape. The time consumption is compared under different error conditions, the effectiveness of the new algorithm is validated and its limitation is also pointed out. Overall, this algorithm provides a promising way for the intelligent control of self-assembly path planning of swarm robots.

Irregular interfaces may be formed between the neighboring ferromagnetic and ferroelectric layers of multiferroic composites during the hot-pressing process. They undoubtedly affects the mechanical behavior of multiferroic composites and this is a scientific problem deserving studying. In addition, phase velocity will be a function of coordinate if the interface is irregular, and this makes the governing equation so complicated that direct analytical solution is unobtainable. The present article proposes an approximate approach for analyzing SH waves in a cylindrical multiferroic composite with interfacial irregularity. The dispersion equation is analytically derived and numerically solved. After the validity range of the approximate treatment is clarified, parametric studies reveals that interfacial corrugations can give rise to an oscillatory distribution of phase velocity along the propagation direction. Because such oscillation can lead to unstable signal transmission, it should be avoided in engineering. Further discussion suggests three possible ways for suppressing the oscillation of phase velocity. The research results can provide references for optimizing the design, manufacture and application of multiferroic devices.

The high temperature and pressure of the hot-pressing process of layered ferromagnetic/ferroelectric (FM/FE) composites inevitably give rise to magneto-electro-elastic (MEE) interfacial regions, where defects such as cracks often aggregate and definitely affect the performance of the composite. Fracture analysis is performed on an MEE interfacial region between an FM layer and an FE layer by the methods of Fourier integral transform and Cauchy singular integral equations. After the numerical computation is verified by the exact solution in a special case and the numerical solutions in existing literature, numerical results of MSERR (mechanical strain energy release rate) and COD (crack opening displacement) are provided to discuss the fracture behavior. The effect of FE volume fraction of the interfacial region on the fracture behavior is demonstrated from three different perspectives. Both material stiffness and constraint effect are used to explain the physical mechanisms. The obtained results may serve as guidelines for the anti-fracture design of FM/FE multiferroic composites. Because the existence of such MEE interfacial regions has been scarcely considered by existing papers, the main novelty of the present work is the incorporation of the MEE interfacial region into the mechanical model of the FM/FE composite.

Magnetic resonance angiography (MRA) is an important diagnosis method for the detection of intracranial aneurysms (IAs), but it is not useful for differentiating between IA and infundibular dilatation (ID) in patients in whom imaging shows an intracranial protrusion with a branch artery at its top. The objective of this study was to introduce a new approach—measurement of the outflow angle (OA)—for differentiating between IA and ID in such cases. The study included 7 patients with a total of 9 protrusions. The protrusions were separately reviewed on MRA and DSA images. We first diagnosed the protrusions using OA approach. An OA ≥90° was considered indicative of an IA and an OA

Multiferroic devices often serve under harmonic vibration. Resonance induced cracking is a common failure of them. The present work studies the resonant fracture of a multiferroic cylindrical structure by the combined methods of variable separation, infinite series, singular integral equation and Lobatto–Chebyshev collocation. It is found that complex modulus and residual stress are two important factors governing the resonant fracture behavior. Generally, the loss factors only affect the resonant amplitude of the fracture parameter, but the residual stress affects both the resonant amplitude and frequency. The obtained conclusions can provide guidelines for the anti-fracture optimal designs of multiferroic devices.

Yi-Feng Gu,1 Qing-Hua Tian,1 Yong-Dong Li,1 Chun-Gen Wu,1 Yan Su,2 Hong-Mei Song,1 Cheng-Jian He,1 Dong Chen,2 1Institute of Diagnostic and Interventional Radiology, 2Department of Orthopaedics, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, Shanghai, People’s Republic of China Objective: The aim of this study was to compare the efficacy of percutaneous vertebroplasty (PVP) and interventional tumor removal (ITR), with PVP alone for malignant vertebral compression fractures and/or spinal metastatic tumor with epidural involvement. Patients and methods: A total of 124 patients were selected for PVP and ITR (n = 71, group A) and PVP alone (n = 53, group B). A 14G needle and guide wire were inserted into the vertebral body, followed by sequential dilatation of the tract until the last cannula reached the anterior portion of the pedicle. Tumors were then ablated with a radiofrequency probe. ITR was performed with marrow nucleus rongeurs, and then cement was injected into the extirpated vertebra. Outcomes were collected preoperatively and at 1, 3 and 6months and every subsequent 6months. Results: The rates of pain relief and increased mobility at the last follow-up were higher in group A than those in group B (P < 0.05). There were significant differences in visual analog scale (VAS) score and Oswestry disability index (ODI) score at 1, 3 and 6months, 1year and >1year in group A than in group B (P < 0.05). The rates of paraplegia recovery and vertebral stability in group A were higher than those in group B (P < 0.05). Conclusion: PVP and ITR proved to be an effective approach for patients with malignant vertebral compression fractures and/or spinal metastatic tumor and provided distinct advantages in pain relief, function recovery and vertebral stability that are comparable to that obtained with PVP alone. Keywords: percutaneous vertebroplasty, pain, malignant spinal tumor, removal, metastasis

Magneto-electro-elastic (MEE) interfacial regions may be formed in multiferroic composites consisting of alternate piezoelectric (PE) and piezomagnetic layers during the hot-pressing process. The existence of such an MEE region may have effects on the mechanical behavior of the composite, which is an interesting problem deserving studying. The present article proposes an interfacial fracture model for a multiferroic composite that contains an MEE interfacial region. The methods of Fourier integral transform and Green’s functions are employed to convert the crack problem with mixed boundary conditions into Cauchy singular integral equations, which are further numerically solved by the Lobatto–Chebyshev collocation method to determine the stress intensity factors. In the numerical computation, the PE volume fraction is chosen as the only characteristic parameter to calculate the material properties of the MEE interfacial region based on the linear rule of mixture. Finally, parametric studies are conducted to reveal the effects of the volume fraction on the fracture behavior, and two main conclusions are drawn: (a) The effects of the PE volume fraction reflect the effects of the material-property jumps across the interfaces, and (b) the interfacial fracture behavior is mainly dominated by the competition between the property jumps across the interfaces and the thickness of the interfacial region.

The ability to diagnose sidewall cerebral aneurysms (SCAs) on an angle measurement basis may be useful in clinical practice. A study was undertaken to evaluate the effect of an outflow angle (OA)-assisted approach.MR angiography (MRA) images of 438 patients with suspected SCAs and other cerebrovascular diseases were separately evaluated using the subjective approach and the OA approach. The approaches were then exchanged for confirmation of unclear cases. An OA of ≥90° was considered to represent SCA positivity. The accuracy, sensitivity, and specificity of the OA-assisted approach were determined using patient-based, aneurysm-based, and size-based evaluations.Digital subtraction angiography (DSA) detected 301 SCAs in 267 patients and no SCAs in 171. An OA of ≥90° was observed for 271 aneurysms in 244 patients (true positives); the OA approach misinterpreted OA as90° for 29 aneurysms in 29 patients (false negatives) and missed one aneurysm. The subjective approach detected 309 SCAs in 273 patients. This approach misdiagnosed 10 patients (false positives) and missed two aneurysms in two patients (false negatives). The OA-assisted approach detected 300 SCAs in 267 patients and no SCAs in 171, overlooking one aneurysm. Patient-based evaluation yielded high accuracy, sensitivity, specificity, and positive and negative predictive values for the OA-assisted approach.The OA-assisted approach for SCA diagnosis effectively reduced the false-positive rate obtained with the subjective approach with high accuracy, sensitivity, and specificity, suggesting that MRA based on this approach can be a reliable alternative to DSA in SCA screening and diagnosis.

The problem of dispersive SH wave in a piezoelectric/piezomagnetic plate that contains an imperfect interface is considered in the present work. An imperfection coupling model is adopted to describe the magnetic, electric and mechanical imperfections on the interface. A transcendental dispersion equation is derived and numerically solved to get the phase velocity. The validity of the numerical procedure is verified in a degenerated case. The effects of the coupled interfacial imperfections on the dispersion behavior of SH waves are discussed in detail and the related underlying physical mechanisms are explained.

Essentially speaking, both crack and interfacial imperfection can be regarded as continuously distributed dislocations. Therefore, the fracture behavior of composites containing imperfect interfaces may be explained by the interactions of different distributed dislocations. The purpose of this paper is to make a try on such explanation. For this purpose, in-plane fracture analysis is performed on two bonded multiferroic half-planes with coupled interfacial imperfections by the methods of Fourier integral transform and Green's functions. Numerical results of the mechanical strain energy release rate are obtained by numerically solving the Cauchy singular integral equations of the crack problem. The effects of the three kinds of interfacial imperfections and their inter-couplings on the fracture behavior are discussed based on the variations of mechanical strain energy release rate versus the interface parameters, and the fracture behavior including shielding, anti-shielding, interference and anti-interference are revealed, respectively. Finally, the cracks and the imperfect interface are simulated as continuously distributed dislocations to construct two types of dislocation distribution models, which are then, for the first time, employed to explain the mechanisms of the fracture behavior.

The problems of periodic cracks have been widely solved in existing literature of fracture mechanics. Although the assumption of periodicity facilitates the theoretical derivation, practical multiple cracks in most cases are not periodically distributed in materials and structures. The present article performs fracture analysis on a piezoelectric/piezomagnetic/piezoelectric (PE/PM/PE) tri-layered smart structure containing nonperiodic interfacial cracks under magnetic/electric and mechanical loadings. The methods of dislocation simulation, Green's function and Cauchy singular integral equations are employed to solve the problem. Stress intensity factors (SIFs) are numerically calculated, and parametric studies are conducted to demonstrate the variation laws of SIFs versus geometrical parameters. The obtained conclusions may provide references for the optimal design of PE/PM/PE smart structures.

ObjectiveTo evaluate whether the aneurysm outflow angle (OA) at MR angiography (MRA) might serve as discriminant for accurate diagnosis of, and differentiation between, small sidewall cerebral aneurysms (SCAs) and infundibula.MethodsBetween June 2007 and July 2015, 426 consecutive patients with SCAs completed both an MRA and DSA examination. Of these, 156 patients with small SCAs and 52 patients with infundibula were included in this study. A patient with an OA ≥90° was defined as having a SCA, while those with OA ResultsDSA identified 172 SCAs in 156 patients and 55 infundibula in 52 patients. The average OA on MRA was 102.96°±13.36° (range 60°–151°) in 172 SCAs of 156 patients. An OA of ≥90° was seen for 159 (92.4%) small SCAs in 147 patients, while an OA of ConclusionsThe OA at MRA could serve as discriminant for accurate diagnosis of, and differentiation between, small SCAs and infundibula.

The effect of rotation around the central C–C bond on the electronic and photophysical properties of biphenyl and 4,4′-bis(phenylsulfonyl) biphenyl is investigated theoretically using the density functional theory (DFT) method in this work. The sulfonyl groups () act as effective breaking points of π-conjugation between the biphenyl core group and the outer phenyl rings. As a result, the electronic structure of these compounds are consistently observed to be very similar to these be controlled by the central moiety. Attributed to the lowered conjugation induced by twist, rotation around the single bond between two phenyl rings leads to an evolution to a more benzenoid structure for the biphenyl core. A linear relationship between the frontier MOs (HOMOs and LUMOs) energies and twisted angles of the biphenyl core in SO1 was observed. Moreover, both HOMO and LUMO are stabilized when the twisted angle is increased, and the HOMO–LUMO energy gap is enlarged. Correspondingly, the AE/VE will be increased by the rotation of the central C–C bond in biphenyl and SO1. This is confirmed by further excitation energies obtained from TD-DFT analysis based on the S0 or T1 states optimized geometries.

Crack interaction may give rise to local upward pulse of fracture parameter, which is harmful to structural safety. The method to be adopted to remove such pulse is significant but remains unclear. In addition, piezoelectric (PE) stiffening exists in multiferroic composites, but does its counterpart, PE softening, also exist? If yes, when do they occur? These problems deserve study. In the present article, a fracture analysis is performed on a multiferroic semicylinder consisting of a PE inner layer, a magnetoelectroelastic (MEE) interlayer, and a piezomagnetic (PM) outer one. This is the first study to consider the MEE interlayer in multiferroic composites. The combined methods of Green's functions, dislocation simulation, and Cauchy singular integral equations are used for solving the problem. Numerical results are provided for parametric studies, yielding two main conclusions: (a) bilateral clamping is an effective way for removing the upward pulse of the local SIF oscillation induced by crack interaction. (b) Besides the conventional PE stiffening effect, its counterpart effect of PE softening is also noted, both of which depend on the piling way of the PM, PE, and MEE layers. Specifically, PE stiffening always occurs on the PM–MEE interface, while PE softening invariably appears on the PE–MEE interface.

Sliding is a typical failure mode of composite interfaces. According to traditional theory, interfacial sliding can be represented by the linear shear-spring model (LSSM). Although the required driving interfacial shear stress has been characterized by LSSM, the relation between interfacial normal stress and sliding is not yet reflected by it. The present paper proposes an interfacial sliding-prevention/promotion model to consider the effect of interfacial normal stress on interfacial sliding. As an example of application, the intra-layer fracture problem is analyzed on a bi-layered multiferroic ceramics. Green’s functions are derived to construct the Cauchy singular integral equations, which are further numerically solved to get mechanical strain energy release rate (MSERR) and interfacial normal stress. Parametric studies yield a new finding that non-zero normal stress may be produced in local interfacial regions by intra-layer cracks under pure in-plane shear. Local positive normal stress gives rise to local sliding-promotion effect, while local negative normal stress leads to local sliding-prevention effect. The interfacial shear imperfection and local sliding-prevention/promotion constitute the mechanisms for the variation of MSERRs of the two intra-layer cracks.

The matching relationship between bolt diameter and borehole diameter determines the bolt supporting effect in the mining roadway. In this paper, the failure modes of the anchorage body under different diameter matching were studied by the pullout test. When the anchorage agent was pulled out completely with bolt, the anchoring effect was ideal. Whereas, when the bolt was pulled out smoothly with only a thin layer of anchorage agent, the anchoring effect was relatively worse. Through multiple pullout tests, the suitable diameter matching difference can be defined with a range of 6–11 mm. Based on the interface sliding failure mode between anchorage agent and rock-like mass, a mechanical model of diameter matching was established. Both equations of tensile force and interfacial shear stress along with the anchorage direction in perfectly elastic state were derived. FLAC 3D was applied to analyze the distribution of interfacial shear stress and axial stress under different diameter matching between the bolt and the borehole. As a result, a 4–11 mm diameter difference shows the best anchoring effect. According to both experimental and simulation results, the optimal diameter matching difference is 6–11 mm. Refereed/Peer-reviewed

The across-interface diffusion and permeation of the ingredients in the manufacturing process inevitably induce magneto-electro-mechanical couplings in the interfacial regions of multiferroic composites that consist of alternate ferromagnetic (FM) and ferroelectric (FE) layers. Therefore, it is impossible for the mechanical, the magnetic and the electric interfacial imperfections to occur and grow independently. Up till now, the imperfection couplings have not been investigated. By extending the classical spring model, this article presents a new one to formulate these three kinds of imperfections and their inter-couplings in the anti-plane deformation case. Six coefficients are proposed to construct the model, three representing the imperfections and the other three characterizing the inter-couplings. On this basis, fracture analysis is further performed on a bi-layered multiferroic composite with two groups of cracks parallel to the imperfect interfacial region and each in a layer. Numerical results of the stress intensity factor (SIF) are obtained from the Cauchy singular integral equations derived by the methods of Fourier integral transform and Green's function. The effects of the imperfections and their inter-couplings on the SIFs are surveyed, yielding three main conclusions: (a) the mechanical imperfection can enhance the SIFs independently; (b) the magnetic or electric imperfection can reduce the SIFs only if it is coupled with the mechanical one; (c) the magneto/electro-mechanical imperfection coupling can help to lower down the SIFs, but the magneto-electric imperfection coupling always has no effect on the SIFs. These conclusions can serves as theoretical references for the optimal design against intra-layer fracture of the multiferroic composites.

Based on B-spline wavelets, the present work proposes the concept of fairness degree for the first time, via which a quantitative criterion is established to evaluate the fairness of curves and surfaces. Further, a new fairing algorithm is presented for B-spline curves. Finally, the effectiveness and efficiency of our approach are demonstrated by several examples.

A coupling model is proposed to characterize interfacial imperfections by generalizing the spring model and referring to the magneto-electro-elastic constitutive relations. As an application, in-plane fracture analysis is performed on a multiferroic composite, which consists of a ferromagnetic layer, a ferroelectric layer and an imperfect interfacial region. The methods of Fourier integral transform and Green’s function are employed to derive the Cauchy singular integral equations for the cracks. Numerical results of the mechanical strain energy release rate are provided to survey the effects of interfacial imperfections and their couplings. It is found that imperfection couplings affect the fracture behavior remarkably and so it is necessary to consider them in the mechanical problems of this kind of smart structures.

When interphases between ferromagnetic and ferroelectric layers become imperfect, the magnetic, electric, and mechanical imperfections may have inter-couplings. A coupled generalized linear spring model is proposed to formulate such inter-couplings. As an application, fracture analysis is performed on a multiferroic cylindrical shell containing an imperfect interphase. Parametric studies are made on the numerical results of the stress intensity factor to reveal the effects of the three kinds of imperfections and their inter-couplings. Three conclusions are drawn: (a) the mechanical imperfection can enhance the stress intensity factors and meanwhile weaken and even prevent the crack interaction across the interphase; (b) the magnetic/electric imperfection cannot affect the cracks independently, and only when it is coupled with the mechanical one can it reduce the stress intensity factor; and (c) the magneto-mechanical and electro-mechanical imperfection couplings are beneficial to reducing the stress intensity factor, but the magneto-electric imperfection coupling cannot affect the cracks.