Classical Mode Research Articles

Evaluation of Graphene Oxide as a Thermal Ionization Enhancer for Plutonium in TIMS Measurement.

Thermal ionization mass spectrometry (TIMS) has been extensively employed for the assessment of plutonium (Pu) isotopes in nuclear forensics and environmental monitoring. Recently, great efforts have been made to improve the ionization efficiency (IE) of Pu to achieve better accuracy and precision for trace-level analysis. Herein, the thermal ionization enhancement effect for plutonium of graphene oxide (GO) was investigated and the corresponding mechanism was discussed. The GO layers were homogeneously mounted on the filament's central surface to promote pg-level Pu ion emission. With the excellent structural property of GO, a greatly promoted ionization efficiency of 0.44% for Pu was obtained, and the initial ionization temperature for Pu was remarkably reduced from 1610 to 1390 °C. Average boosts in IE compared to the classical double-filament mode and graphite-loaded single-filament mode were 1640 and 520%, respectively. The analytical accuracy and precision based on the GO-loaded single-filament mode were validated using Pu isotopic certified reference materials. This work demonstrates the excellent property of GO as an ion source additive for Pu ionization, as it provided an interface for the promotion of energy transfer and Pu carbide formation. The operation of GO loading is quite simple and can be finished within 5 min. This rapid filament carburization approach has great potential for improving the measurement precision of trace-level plutonium isotopes and can be applied in nuclear safeguards, nuclear forensics, and environmental monitoring.

Shining light on halogen-bonding complexes: a catalyst-free activation mode of carbon-halogen bonds for the generation of carbon-centered radicals.

The discovery of new activation modes for the creation of carbon-centered radicals is a task of great interest in organic chemistry. Classical activation modes for the generation of highly reactive radical carbon-centered intermediates typically relied on thermal activation of radical initiators or irradiation with unsafe energetic UV light of adequate reaction precursors. In recent years, photoredox chemistry has emerged as a leading strategy towards the catalytic generation of C-centered radicals, which enabled their participation in novel synthetic organic transformations which is otherwise very challenging or even impossible to take place. As an alternative to these activation modes for the generation of C-centered radicals, the pursuit of greener, visible-light initiated reactions that do not necessitate a photoredox/metal catalyst has recently caught the attention of chemists. In this review, we covered recent transformations, which rely on photoactivation with low-energy light of a class of EDA complexes, known as halogen-bonding adducts, for the creation of C-centered radicals.

Expert knowledge-based peak current mode control of electrosurgical generators for improved output power regulation.

Electrosurgical generators (ESG) are widely used in medical procedures to cut and coagulate tissue. Accurate control of the output power is crucial for surgical success, but can be challenging to achieve. In this paper, a novel expert knowledge-based peak current mode controller (EK-PCMC) is proposed to regulate the output power of an ESG. The EK-PCMC leverages expert knowledge to adapt to changes in tissue impedance during surgical procedures. We compared the performance of the EK-PCMC with the classical peak current mode controller (PCMC) and fuzzy PID controller. The results demonstrate that the EK-PCMC significantly outperformed the PCMC, reducing the integral square error (ISE) and integral absolute error (IAE) by a factor of 3.88 and 4.86, respectively. In addition, the EK-PCMC outperformed the fuzzy PID controller in terms of transient response and steady-state performance. Our study highlights the effectiveness of the proposed EK-PCMC in improving the regulation of the output power of an ESG and improving surgical outcomes.

Vortex Speckles with Customized Symmetry and Spatial Correlations

A family of optical speckles with propagation-invariant annular morphology are generated via a phase-only mask and free-space evolution, termed vortex speckles, for which phase design is inspired by the vortex beam's helical wave front carrying orbital angular momentum. Vortex beams' graceful symmetry (central and/or axial) can be naturally inherited into vortex speckles by adjusting the parity of the topological value $\ensuremath{\ell}$ and the consistency of the initial phase angle ${\ensuremath{\phi}}_{0}$. By sequentially imprinting such a series of phase profiles onto a spatial light modulator, the resultant stochastically fluctuating vortex speckles naturally constitute an annular pseudothermal light field, and the customized symmetry in intensity profiles leads to spatial correlations, which are exploited for Hanbury Brown and Twiss interferometry and beam-splitter-free lensless ghost imaging and diffraction experiments. Symmetric annular pseudothermal light also has diverse phase correlations, so in a proposed vortex self-interferometer, we can manipulate photon correlations (parity-induced anticorrelation) and observe intriguing correlation states (spatially varying photon correlation oscillations). This work not only presents a flexible light-source option for applications requiring ring-shaped speckle illumination, but it also paves the way for the customization of nontrivial classical correlation modes.

Effective Production of Selected Dioxolanes by Sequential Bio- and Chemocatalysis Enabled by Adapted Solvent Switching.

Most combinations of chemo- and biocatalysis take place in aqueous media or require a solvent change with complex intermediate processing. Using enzymes in the same organic solvent as the chemocatalyst eliminates this need. Here, it was shown that a complete chemoenzymatic cascade to form dioxolanes could be carried out in a purely organic environment. The result, including downstream processing, was compared with a classical mode, shifting solvent. First, a two-step enzyme cascade starting from aliphatic aldehydes to chiral diols (3,4-hexanediol and 4,5-octanediol) was run either in an aqueous buffer or in the potentially biobased solvent cyclopentyl methyl ether. Subsequently, a ruthenium molecular catalyst enabled the conversion to dioxolanes [e. g., (4S,5S)-dipropyl-1,3-dioxolane]. Importantly, the total synthesis of this product was not only highly stereoselective but also based on the combination of biomass, CO2 , and hydrogen, thus providing an important example of a bio-hybrid chemical.

Dominant role of Atlantic multidecadal oscillation in the tipping point of maximum and minimum temperatures over inner East Asia

AbstractDespite unprecedented heatwave events reported in the past two decades over inner East Asia, the maximum and minimum temperatures of Tmax and Tmin do not always exhibit continuous increasing. After drastic increases in Tmax and Tmin appeared over inner East Asia from 1982, a decreasing trend occurred around 1998, which was closely associated with the Atlantic multidecadal oscillation (AMO). During 1950–2014, the correlation between Tmax (Tmin) and AMO at the decadal time scale reached 0.70 (0.83); and 65% (79%) variance of the decadal variability in Tmax (Tmin) was explained by the AMO and three other classic oceanic modes; the contribution of the AMO was up to 82% (91%) in the decadal modulated oscillation. The declines of Tmin and Tmax synchronized with the downward swing of the AMO since the late‐1990 s, which was because the AMO could affect the vertical motion and wind anomalies of inner East Asia through the cyclonic‐anticyclonic teleconnection wave train in the mid‐latitudes of the Northern Hemisphere. The results of composite analysis show that during the positive phase of the AMO, a local ascending motion was enhanced over inner East Asia and a large‐scale abnormal high was found north of East Asia in favour of cold air intrusion. Meanwhile, the start of growing season was delayed by the positive phase of the AMO over the northern part of inner East Asia due to the high sensitivity of spring phenology to the Tmin controlled by the AMO.

Validation of a Classical Sliding Mode Control Applied to a Physical Robotic Arm with Six Degrees of Freedom

The control of robotic manipulators has become increasingly difficult over recent years due to their high accuracy, performance, speed, and reliability in a variety of applications, such as industry, medicine, research, etc. These serial manipulator systems are extremely complex because their dynamic models include perturbations, parametric variations, coupled nonlinear dynamics, and non-modular dynamics, all of which require robust control for trajectory tracking. This paper compares two control techniques: computational torque control (CTC) and sliding mode control (SMC). In this study, the latter was used for a physical robotic arm with six degrees of freedom (DOF) and online experiments were conducted, which have received little attention in the literature. As a result, the contribution of this work was based on the real-time application of this controller via a self-developing interface. The great resilience of sliding mode controllers to disturbances was also demonstrated in this study.

The content of VEGF, COX-2 and PGE-2 in the blood serum of patients with non-small cell lung cancer with different schemes of conformal radiotherapy in the dynamics of treatment

Background. Overcoming radioresistance is an important problem in radiation oncology. Therefore, the development of new approaches to modeling the radiosensitivity of tumors in cancer patients becomes relevant and important. Cyclooxygenase-2 (COX-2) inhibitors are new agents for radiomodification in various radiation therapy schemes, the use of which slows down angiogenesis by suppressing the activity of the COX-2 enzyme.
 Purpose. To determine the content of indicators of radioresistance: vascular endothelial growth factor (VEGF), COX-2, prostaglandin E-2 (PGE-2) in the blood serum of patients with non-small cell lung cancer (NSCLC) and changes in their levels with different schemes of radiation therapy (RT).
 Materials and methods. 36 patients with NSCLC were examined and treated, who were divided into four groups: RT (the first group – 16 patients), RT with the COX-2 inhibitor – ranselex (the second group – 9 patients), RT with ranselex and cisplatin (the third group – 5 patients ) and RT with cisplatin (fourth group – 6 patients). The patients received a course of radiation treatment using a Clinac 600C linear accelerator. The classical fractionation mode was used, the total focal doses were 60–66 Gy. Cisplatin was prescribed at 30 mg/m2 per week up to a total dose (SD) of 200 mg, the COX-2 inhibitor Rancelex® at a dose of 100 mg per day (active substance – celecoxib). The levels of VEGF, COX-2, and PGE-2 in the blood serum of patients with NSCLC were determined by enzyme-linked immunosorbent assay (ELISA) before and after treatment.
 Results. The level of the angiogenesis marker VEGF after treatment in the group with RT decreases by 1.46 times, in the group with the combined action of RT and ranselex – 2.4 times, in the group with the combined action of PT, ranselex and cisplatin – by 3.7 times, and in the group with the combined effect of RT and cisplatin, it decreases by 1.1 times. The greatest decrease in the level of VEGF is observed with RT in combination with ranselex and cisplatin, which indicates a more effective enhancement of the antiangiogenic effect.
 Conclusions. It has been proven that with various schemes of RT using the COX-2 inhibitor – ranselex and cisplatin in patients with NSCLC, there is a decrease in the radioresistance markers PGE-2 and COX-2, the angiogenesis marker – VEGF, which indicates that the effect of radiomodification on the angiogenesis process is most pronounced in the combined actions of RT and both radio modifiers. The use of COX-2 inhibitors as radiosensitizers in combination with RT provides a new opportunity to increase tumor radiosensitivity.

VLF/LF Lightning Location Based on LWPC and IRI Models: A Quantitative Study

The group velocity of lightning electromagnetic signals plays an important role in lightning location systems using the time difference of arrival (TDOA) method. Accurate estimation of group velocity is difficult due to the space- and time-varying properties of the Earth-ionosphere waveguide. Besides, the analytical solution of the group velocity is difficult to obtain from the classic mode theory, especially when higher-order modes, anisotropic geomagnetic background, diffuse ionosphere profile, and propagation path segmentation are all taken into consideration. To overcome these challenges, a novel numerical method is proposed in this paper to estimate the group velocity of the lightning signal during ionospheric quiet periods. The well-known Long Wavelength Propagation Capability (LWPC) code is used to model the propagation of VLF/LF radio waves. Since LWPC uses a simplified ionospheric model which is unable to describe the subtle variations of ionospheric parameters over time and space, the IRI-2016 model is incorporated into the numerical modeling process to provide more accurate ionosphere parameters. Experimental results of a VLF/LF lightning location network are demonstrated and analyzed to show the effectiveness of our method. The proposed method is also applicable when there is a sudden ionospheric disturbance as long as the parameters of the ionosphere are obtained in real time by remote sensing methods.

Magnetohydrodynamic instabilities in a self-gravitating rotating cosmic plasma

The generation of magnetohydrodynamic (MHD) waves and their instabilities are studied in galactic gaseous rotating plasmas with the effects of the magnetic field, the self gravity, the diffusion-convection of cosmic rays as well as the gas and cosmic-ray pressures. The coupling of the Jeans, Alfvén and magnetosonic waves, and the conditions of damping or instability are studied in three different cases, namely when the propagation direction is perpendicular, parallel and oblique to the static magnetic field, and are shown to be significantly modified by the effects of the Coriolis force due to the rotation of cosmic fluids and the cosmic-ray diffusion. The coupled modes can be damped or anti-damped depending on the wave number is above or below the Jeans critical wave number that is reduced by the effects of the Coriolis force and the cosmic-ray pressure. It is found that the deviation of the axis of rotation from the direction of the static magnetic field gives rise to the coupling between the Alfvén wave and the classical Jeans mode which otherwise results into the modified slow and fast Alfvén waves as well as the modified classical Jeans modes. Furthermore, due to the effects of the cosmic rays diffusion, there appears a new wave mode (may be called the fast Jeans mode) in the intermediate frequency regimes of the slow and fast Alfvén waves, which seems to be dispersionless in the long-wavelength propagation and has a lower growth rate of instability in the high density regimes of galaxies. The dispersion properties and the instabilities of different kinds of MHD waves reported here can play pivotal roles in the formation of various galactic structures at different length scales.

The analysis and validation of natural frequencies and mode shapes of 3D plates in the framework of the generalized thermoelastic theory

This article considers thermal effects that induce thermoelastic damping and, which, consequently, because of the absorbed thermal energy, cause thermal stresses. The problem is stated in the framework of the generalized thermoelastic theory. The natural frequency and mode shape analyzes of 3D plates are presented under uniform and nonuniform heating. From the modeling point of view, this results in the quadratic eigenvalue problem where complex frequencies and modes are obtained. Moreover, the quality factor related to the thermoelastic damping is also calculated in terms of the imaginary and the real parts of the frequencies for both the uniform and nonuniform thermal distributions. The variation of natural frequencies with temperature is investigated and compared with the experimental results for the plates with free boundary conditions. The first two mode shapes are also examined for all clamped edges for the uniform and nonuniform cases. Complex frequencies and complex modes are observed due to the thermal effects. For the uniform case, the real part of the modes decreases and the complex part increases, while the mode’s norm remains the same as in the classical modes as temperature increases. For the nonuniform case, the mode shape analysis is performed under the assumption that the elasticity modulus, thermal expansion, and specific heat parameters are functions of temperature. The peak point of the out-of-plane displacement is shown to be shifted toward the warm zone. The obtained outcomes may help design thermal structures and allow for future extensions.

Maximizing the selectivity to triacetin in glycerol acetylation through a plastic waste-derived carbon catalyst development and selection of a reaction unit

Carbon catalysts derived from poly(ethylene terephthalate), PET, enriched with surface acidic sites were prepared and used in glycerol acetylation to increase the glycerol conversion and formation of higher acetins, i.e., diacetins and triacetin (DA and TA, respectively). Two approaches of carbon functionalization were applied – treatment with concentrated sulfuric acid or modification with benzenediazonium sulfonate (BDS) generated in-situ. The as-prepared carbons were characterized applying different techniques (e.g., elemental analysis, potentiometric titration, TG method, or XPS studies), and used as catalysts in glycerol esterification with acetic acid under different conditions. Using the synthesized carbons in the process carried out in a classical reaction mode (i.e., batch and reflux conditions, no water removal) enabled us to significantly increase the reaction rate and yields of the produced di- and triacetins compared to the reaction without a catalyst. The most active sample showed a high content of sulfonic groups and gave about 95 % conversion of glycerol and 55 and 20 % selectivity to DA and TA, respectively, just within 1 h of the process at 110 °C. Moreover, the used catalyst caused a significant increase in the TA yield when the reaction was performed with the addition of toluene compared to the toluene-free process. This was related to the continuous removal of water from the reactor and shifting the reaction equilibrium toward the higher esters as well as due to the perfectly-tailored properties of the obtained carbon sample.

Structure-function studies can improve binding affinity of cohesin-dockerin interactions for multi-protein assemblies

The cellulosome is an elaborate multi-enzyme structure secreted by many anaerobic microorganisms for the efficient degradation of lignocellulosic substrates. It is composed of multiple catalytic and non-catalytic components that are assembled through high-affinity protein-protein interactions between the enzyme-borne dockerin (Doc) modules and the repeated cohesin (Coh) modules present in primary scaffoldins. In some cellulosomes, primary scaffoldins can interact with adaptor and cell-anchoring scaffoldins to create structures of increasing complexity. The cellulosomal system of the ruminal bacterium, Ruminococcus flavefaciens, is one of the most intricate described to date. An unprecedent number of different Doc specificities results in an elaborate architecture, assembled exclusively through single-binding-mode type-III Coh-Doc interactions. However, a set of type-III Docs exhibits certain features associated with the classic dual-binding mode Coh-Doc interaction. Here, the structure of the adaptor scaffoldin-borne ScaH Doc in complex with the Coh from anchoring scaffoldin ScaE is described. This complex, unlike previously described type-III interactions in R. flavefaciens, was found to interact in a dual-binding mode. The key residues determining Coh recognition were also identified. This information was used to perform structure-informed protein engineering to change the electrostatic profile of the binding surface and to improve the affinity between the two modules. The results show that the nature of the residues in the ligand-binding surface plays a major role in Coh recognition and that Coh-Doc affinity can be manipulated through rational design, a key feature for the creation of designer cellulosomes or other affinity-based technologies using tailored Coh-Doc interactions.

Asymmetric Interfacet Adatom Migration as a Mode of Anisotropic Nanocrystal Growth.

Crystals are known to grow nonclassically or via four classical modes (the layer-by-layer, dislocation-driven, dendritic, and normal modes, which generally involve minimal interfacet surface diffusion). The field of nanoscience considers this framework to interpret how nanocrystals grow; yet, the growth of many anisotropic nanocrystals remains enigmatic, suggesting that the framework may be incomplete. Here, we study the solution-phase growth of pentatwinned Au nanorods without Br, Ag, or surfactants. Lower supersaturation conditions favored anisotropic growth, which appeared at variance with the known modes. Temporal electron microscopy revealed kinetically limited adatom funneling, as adatoms diffused asymmetrically along the vicinal facets (situated inbetween the {100} side-facets and {111} end-facets) of our nanorods. These vicinal facets were perpetuated throughout the synthesis and, especially at lower supersaturation, facilitated {100}-to-vicinal-to-{111} adatom diffusion. We derived a growth model from classical theory in view of our findings, which showed that our experimental growth kinetics were consistent with nanorods growing via two modes simultaneously: radial growth occurred via the layer-by-layer mode on {100} side-facets, whereas the asymmetric interfacet diffusion of adatoms to {111} end-facets mediated longitudinal growth. Thus, shape anisotropy was not driven by modulating the relative rates of monomer deposition on different facets, as conventionally thought, but rather by modulating the relative rates of monomer integration via interfacet diffusion. This work shows how controlling supersaturation, a thermodynamic parameter, can uncover distinct kinetic phenomena on nanocrystals, such as asymmetric interfacet surface diffusion and a fundamental growth mode for which monomer deposition and integration occur on different facets.

A molecular dynamics study of evaporation mode transition of hydrocarbon fuels under supercritical conditions

The mode transition of evaporation for single- and multi-component hydrocarbon fuels is investigated at the molecular level. This study scrutinizes first the subcritical and supercritical evaporation of n-hexadecane droplets and liquid films by molecular dynamics (MD) simulations. The mode regime map of n-hexadecane droplets is obtained. Then the mode transition of evaporation of a three-component droplet and a six-component droplet is studied. A critical dimensionless number τ0.9P of 0.5 based on the average displacement increment (ADI) of fuel atoms is used to identify the evaporation mode transition of fuels with any type and number of components. It is found that in the diffusion mode of evaporation, the entropy becomes the dominant factor in the evaporation of fuels, and the disorder of the fuel molecules increases significantly compared with that in the classic evaporation mode. Compared with the case of the quiescent droplet, with increasing relative velocity between the droplet and the ambient gas, the mode transition becomes easier, although this is a non-linear process. Fuel droplets and liquid films with different initial sizes are investigated to understand the size effect. In addition, for the same ambient temperature and pressure, the smaller the normalized specific heat transfer surface area of the fuel is, the easier the mode transition of evaporation is. A correlation was proposed to compare the possibility of mode transition of evaporation for single- and multi-component fuels.

Oxygen-boosted biomimetic nanoplatform for synergetic phototherapy/ferroptosis activation and reversal of immune-suppressed tumor microenvironment

Photodynamic therapy (PDT) induces apoptosis of cancer cells by generating cytotoxic reactive oxygen species, the therapeutic effect of which, however, is impeded by intrinsic/inducible apoptosis-resistant mechanisms in cancer cells and hypoxia of tumor microenvironment (TME); also, PDT-induced anti-tumor immunity activation is insufficient. To deal with these obstacles, a novel biomimetic nanoplatform is fabricated for the precise delivery of photosensitizer chlorin e6 (Ce6), hemin and PEP20 (CD47 inhibitory peptide), integrating oxygen-boosted PDT, ferroptosis activation and CD47-SIRPα blockade. Hemin's catalase-mimetic activity alleviates TME hypoxia and enhances PDT. The nanoplatform activates ferroptosis via both classical (down-regulating glutathione peroxidase 4 pathway) and non-classical (inducing Fe2+ overload) modes. Besides the role of hemin in consuming glutathione and up-regulating heme oxygenase-1 expression, interestingly, we observe that Ce6 enhance ferroptosis activation via both classical and non-classical modes. The anti-cancer immunity is reinforced by combining PEP20-mediated CD47-SIRPα blockade and PDT-mediated T cell activation, efficiently suppressing primary tumor growth and metastasis. PEP20 has been revealed for the first time to sensitize ferroptosis by down-regulating system Xc−. This work sheds new light on the mechanisms of PDT-ferroptosis activation interplay and bridges immunotherapy and ferroptosis activation, laying the theoretical foundation for novel combinational modes of cancer treatment.

Effective interfacial energy band engineering strategy toward high-performance triboelectric nanogenerator

Provided that electron transition ascribed to overlapping electron dominates the mechanism of contact electrification of triboelectric nanogenerators (TENGs), the electron transfer process occurs due to the built-up electric field between the triboelectrification surface and bottom electrode. In this work, we embed a solution-processed high-permittivity electron blocking layer (HPEBL) of LaZrO into the classical contact-separation mode TENG to build an energy barrier (ΔE > 1.3 eV) between ITO and PDMS, which could effectively block the transportation of electrons towards the bottom electrode. The surface potential decline rate of PDMS is obviously suppressed, extending the half-charge decay time by ∼3.1 times. A La0.1Zr0.9Ox HPEBL based TENG (H-TENG) demonstrates the electrical outputs with 215 V, 96.3 mA m−2 and 243.3 μC/m−2. Under the external load of 100 MΩ, the average gravimetric/volumetric power density and energy conversion efficiency can be calculated to be 59.34 μW g−1, 152.5 μW cm−3 and 39.2%, respectively. Furthermore, the dielectric behaviors of LaZrO thin films are investigated by metal–insulator-metal (MIM) devices. The Poole-Frenkel (PF) emission is found to dominate the leakage mechanism of LaZrO during operation. Consequently, increasing the relative permittivity and reducing the trap density could be indicated as the optimization orientation of HPEBL.

Use of multifractal parameters to determine soil particle size distribution and erodibility of a physical soil crust in the Loess Plateau, China

Understanding the knowledge of multifractal analysis on particle size distribution (PSD) of soil physical crusts is indispensable for progressing soil surface erosion mode. In this study, hoeing tillage (20 cm long × 15 cm wide × 5 cm deep) were conducted to simulate classic tillage mode in Yangling, China to obtain physical crusts under artificial rainfall (60 mm h−1 intensity with three durations (5, 15, and 30 min)). We defined crusts formed in ridges as structural crust (Cst), formed by infiltration of runoff in hoes as sediment-containing depositional crust (Cscd), and formed by the extraction of runoff as sediment-free depositional crust (Csfd). Soil stratification methods were used to explore physical crust particle sorting. Results represented that the sand content of Cst, Cscd, and Csfd decreased, whereas clay and silt contents increased after rainfall compared to undisturbed soil. There was no significant difference between Cscd and Csfd under short rainfall duration. Three crust types became gradually concentrated in areas with higher density with increasing rainfall duration according to six common parameters in the generalised dimension spectrum (D0, D1, D2, D1/D0, Dv(D-10–D0), and Ds(D0–D10)). Multifractal singularity spectrum (α0, Av, Fv) showed that PSD was most symmetrical in Csfd, followed by Cscd and Cst. Erodibility index KEPIC was largest for Cst, followed by Csfd then Cscd. The relationship between KEPIC and multifractal parameters were significant. Spatial difference caused by tillage activities and rainfall events determine the heterogeneous formation mode, particle size distribution and erodibility of physical crust.

Regional operating patterns of world container shipping network: A perspective from motif identification

The operation of liner shipping services follows some typical patterns as Hub and Spoke (H&S), End-to-End (ETE), Round-The-World (RTW), Pendulum (PDM), which reveals the operating mechanism of the world container transport. Different with analytic lens on the technical and economic elements, this paper explored the regional operational patterns of liner shipping services from the perspective of the network, aiming to provide reference for regional cooperations of liner shipping companies (LSC). The concept of motif detection is introduced in verifying the classic patterns and discover the new ones. Through the identification of motifs, the recognition of basic unit in motif study is proved to be applicable in the container shipping network. The (route) connection modes of 3 to 4 ports are discovered which could help to explain the formation of network. Findings show that complying with motifs in biological and technological network, the maritime network motifs have a strong nature of hub configuration in connecting with each other. Since motifs with 3 vertices are the basic structure of the network, we proposed two regional connecting modes as‘Branching’ and‘Circling’. In comparison with the classic modes obtained from empirical analysis, we argue that these two modes are more favored by shipping companies on a regional scale in contributing to the feeder service and local trade development.

Bearing Fault Diagnosis Using Piecewise Aggregate Approximation and Complete Ensemble Empirical Mode Decomposition with Adaptive Noise.

Complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) effectively separates the fault vibration signals of rolling bearings and improves the diagnosis of rolling bearing faults. However, CEEMDAN has high memory requirements and low computational efficiency. In each iteration of CEEMDAN, fault vibration signals are added with noises, both the vibration signals added with noises and the added noises are decomposed with classical empirical mode decomposition (EMD). This paper proposes a rolling bearing fault diagnosis method that combines piecewise aggregate approximation (PAA) with CEEMDAN. PAA enables CEEMDAN to decompose long signals and to achieve enhanced diagnosis. In particular, the method first yields the vibration envelope using bandpass filtering and demodulation, then compresses the envelope using PAA, and finally decomposes the compressed signal with CEEMDAN. Test data verification results show that the proposed method is more effective and more efficient than CEEMDAN.