Autonomous Control Strategy for Microgrid Operating Modes Smooth Transition

© 2013 IEEE. Microgrid transition between standalone and grid-connected modes is a promising alternative to provide the grid with increasing flexibility and availability. However, transition smoothness relies heavily on control topologies and corresponding parameters, which thus remains challengeable. Existing microgrid transition strategies have two major deficiencies: 1) Inverter control mode alters subjected to microgrid operating mode, for instance, the inverter in current control will switch to voltage control when microgrid disconnects to the utility grid; 2) Controller parameters are selected based on practice and experience, where a systematic and efficient approach does not exist. Motivated by these limitations, in this paper, an autonomous control strategy is proposed for microgrid smooth state transitions. It is highlighted in the following aspects: 1) The cascaded control strategy enables smooth state transition within a single control structure, which permits controller independent of mode switching; 2) Nonlinear-Simplex based algorithm is interfaced with electromagnetic transient simulations, searching for optimal controller parameters in order to minimize voltage deviation in a chain of microgrid events. The effectiveness of the control framework is validated with simulations in PSCAD/EMTDC and RTDS

Influence of C28H58 on the structure and phase change of C28H58/C22H46 n-alkane mixtures

This study adopted molecular dynamics to investigate the influence of C28H58 mass fraction on the structure and phase change of C28H58/C22H46 n-alkane mixtures at different temperatures; systematically analyzed the C–H and C–C bond lengths, changes in the H–C–H bond angle and C–C–C–C torsion angle, and energy conversions within the mixture during heating of C28H58/C22H46 n-alkane mixtures; calculated the self-diffusion coefficient (D) by combining the Einstein relation and mean squared displacement; and determined the phase change temperature of each mixture according to the relationship between D and temperature. The results show that, at 280 K, changing the mass fraction of C28H58 does not affect the C–H and C–C bond lengths and the H–C–H bond angle. At 350 K, the C–H bond length decreases with the increase in the mass fraction of C28H58, the C–C bond length increases slightly when the mass fraction is 65.2% and remains unchanged for other mass fractions, and the H–C–H bond angle slightly decreases. With an increase in temperature, the peak intensity of the stretched conformation at ±180° gradually decreases, while the peak of the twisted conformation appears around ±70°, and the degree of twist of the C–C–C–C dihedral angle in the mixture increases. The phase change temperature begins to increase slowly with the increase in the mass fraction of C28H58, and the phase change temperature increases rapidly when the mass fraction exceeds 65.2%. The kinetic and potential energies of the mixture tend to increase with the increasing mass fraction of C28H58

Somatic mutation landscape of a meningioma and its pulmonary metastasis

Abstract Background Extracranial metastasis (ENM) of meningiomas is extremely rare, and typically occurs several years after a primary tumor is diagnosed. However, the genetic changes underlying ENM events have not yet been investigated. Case presentation A 58-year-old male patient was sent to the emergency room of our hospital because of a sudden fall. Magnetic resonance imaging detected a mass at the right frontal sagittal sinus. He underwent tumor resection and recovered well, but post-operative computed tomography revealed three lumps on the right side of his chest. Thoracic surgery was performed to remove two of the lumps. Pathological findings revealed that the brain and lung tumors were grade I meningiomas. The patient received no additional radiation or chemotherapy post-surgery, and there was no sign of tumor recurrence in the brain or progression of the remaining lump in the chest 1 year after surgery. We performed whole exome sequencing of the patient’s blood, primary brain tumor, and lung metastatic tumor tissues to identify somatic genetic alterations that had occurred during ENM. This revealed that a frameshift deletion of the neurofibromin 2 gene likely drove formation of the meningioma. Surprisingly, we found that the brain tumor was relatively homogeneous and contained only one dominant clone; both the pulmonary metastasis and the original brain tumor were derived from the same clone, and no obvious additional driver mutations were detected in the metastatic tumor. Conclusion Although ENM of meningiomas is very rare, brain tumor cells appear to be more adaptable to tissue microenvironments outside of the central nervous system than was commonly thought

Highly Sensitive and Selective Sensing of Free Bilirubin Using Metal–Organic Frameworks-Based Energy Transfer Process

Free bilirubin, a key biomarker for jaundice, was detected with a newly designed fluorescent postsynthetically modified metal organic framework (MOF) (UIO-66-PSM) sensor. UiO-66-PSM was prepared based on the aldimine condensation reaction of UiO-66-NH₂ with 2,3,4-trihydroxybenzaldehyde. The fluorescence of UIO-66-PSM could be effectively quenched by free bilirubin via a fluorescent resonant energy transfer process, thus achieving its recognition of free bilirubin. It was the first attempt to design a MOF-based fluorescent probe for sensing free bilirubin. The probe exhibited fast response time, low detection limit, wide linear range, and high selectivity toward free bilirubin. The sensing system enabled the monitor of free bilirubin in real human serum. Hence, the reported free bilirubin sensing platform has potential applications for clinical diagnosis of jaundice

Effects of calcination and acid treatment on improving benzene adsorption performance of halloysite

In this paper, calcination and subsequent acid treatment were performed on halloysite to investigate their effects on dynamic benzene adsorption performance. Calcination at 800 degrees C had little effect on halloysite's tubular morphology, but it caused dehydroxylation and phase separation of amorphous SiO2 and Al2O3. The occurrence of dehydroxylation resulted in removal of hydroxyl groups, which reduced halloysite's hydrophilicity, leading to an improvement in the halloysite's affinity for hydrophobic benzene molecules. The dynamic benzene adsorption capacity increased from 68.1 mg/g in the original halloysite to 103.6 mg/g in the calcined halloysite. The acid treatment after pre-calcination preserved the halloysite's tubular morphology and introduced massive micropores as a result of the rapid dissolution of Al2O3 layers. The emergence of these massive micropores substantially improved the specific surface area and dynamic benzene adsorption capacity of the acid-treated calcined halloysite, which reached 472.3 m(2)/g and 204.2 mg/g, respectively. In addition, the recycling efficiency of the acid-treated calcined halloysite for benzene adsorption reached 92.5%, thus displaying good regeneration performance. These results demonstrate that calcination and subsequent acid treatment play important roles in promoting the halloysite's benzene adsorption performance, which makes the resulting halloysite a promising adsorbent for the treatment of volatile organic compounds

Tailoring Structure and Surface Chemistry of Hollow Allophane Nanospheres for Optimization of Aggregation by Facile Methyl Modification

International audienceAllophane, an earth-abundant and easy-to-be-synthesized hollow nanospherical material, readily loses its unique pore structure via irreversible aggregation of particles upon drying, which mainly results from capillary stress in the unsaturated inner cavity. To tackle this problem, we develop a strategy for tailoring the capillary stress and thus the aggregation state of allophane by introducing methyl moieties onto the inner surface during preparation. Combined spectroscopic results verified the formation of methyl-allophane with methyl groups only on its inner surface. The presence of a reflection at approximately 33 Å in the X-ray diffraction pattern, ascribed to the interference between particles, indicated an increased structural order in methyl-allophane. The thermal analysis data revealed a decrease of the inner-surface hydrophilcity. The Brunauer-Emmett-Teller (BET) specific surface area increased from 269 to 523 m$^2$/g after methyl modification. An aggregation model, in contrast with that of allophane, was proposed based on the microscopic and small-angle X-ray scattering results to explain these observed changes. This work exhibited that substitution of silanol by methyl on the inner surface of allophane leads to improvement of structural order by eliminating the presence of oligomeric silicates and decreases the hydrophilicity, resulting in the reduction of the capillary stress in the inner cavity and thus the inhibition of irreversible aggregation of particles during drying. The insight into the mechanisms underneath the above mentioned changes upon methyl modification unraveled in this work is helpful for addressing the common aggregation issue of other nanomaterials

Investigating the anti-inflammatory and bone repair-promoting effects of an injectable porous hydrogel containing magnesium ions in a rat periodontitis mode

Periodontitis is associated with several systemic diseases, and advanced periodontitis is often linked to an extensive inflammatory microenvironment and irregularly shaped alveolar bone defects. However, eliminating periodontal inflammation in a minimally invasive manner while repairing irregularly shaped bone defects is clinically challenging. In comparison to traditional bone grafts, a thermo-sensitive hydrogel can be injected into deep periodontal pockets, forming and filling the alveolar bone defects in situ. In this study, porous injectable thermo-sensitive hydrogels containing magnesium ions were prepared by adding magnesium particles (MPs) to a glycerophosphate solution and combining this mixture with a chitosan solution. The incorporation of MPs created interconnected pores in the hydrogel, exhibiting high cytocompatibility and maintaining cell viability, proliferation, spreading, and osteogenesis in vitro. Evaluation on an experimental periodontitis rat model, using micro-computed tomography and histological analyses, demonstrated that this Mg2+-containing hydrogel effectively reduced periodontal inflammation, inhibited osteoclast activity, and partially repaired inflammation-induced alveolar bone loss. These results suggest that Mg2+-containing thermo-sensitive porous hydrogels might be promising candidates for treating periodontitis

Constructing Hierarchically Porous Nestlike Al2O3-MnO2@Diatomite Composite with High Specific Surface Area for Efficient Phosphate Removal

In this work, Al2O3-MnO2@diatomite composite (AM-Dt) was prepared by a simple hydrothermal method. This composite was formed by using diatomite as a porous substrate to support Al2O3 and MnO, nanoparticles. It exhibited hierarchically porous structures and a high specific surface area (352 m(2)/g). The maximum phosphate adsorption capacity of AM-Dt was 63.7 mg of P/g of (Al2O3-MnO2), which is 6 times greater than those of Al2O3 coated diatomite, Al2O3, and Al2O3-MnO2. The composite also showed superior adsorption efficiency, high structural stability, and selectivity for phosphate in the presence of interfering anions (Cl-, NO3-, and CO32-). With the help of X-ray photoelectron spectroscopy and P K-edge X-ray absorption nearedge structure analysis, it can be concluded that electrostatic attraction and formation of surface complexes via phosphate bonding with Al2O3 and MnO2 were the main adsorption mechanisms. The facile preparation method, excellent adsorption performance, and cost effectiveness suggested that this composite possesses a promising potential for phosphate removal from contaminated water

Identification of the occurrence of minor elements in the structure of diatomaceous opal using FIB and TEM-EDS

The occurrence of minor elements in the structure of biogenic diatomaceous opal-A is an important issue because it is closely related to biogeochemical processes driven by the precipitation, sedimentation, and storage of diatoms, as well as to the properties and applications of diatomite, which is the sedimentary rock composed of diatomaceous opal-A. However, to date, there is no direct microscopic evidence for the existence of minor elements, such as Al, Fe, and Mg, in the structure of diatomaceous opal-A, because such evidence requires observation of the internal structure of frustules to exclude the disturbance of impurity minerals, which is technically challenging using conventional techniques. In this work, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS) mapping analysis were performed on diatomaceous opal-A from three typical diatomite specimens that were pretreated using focused ion beam (FIB) thinning. This technique produces a slice of a diatom frustule for direct TEM observation of the internal structure of the diatomaceous opal-A. The results of this work clearly indicate that minor elements, such as Al, Fe, Ca, and Mg, conclusively exist within the siliceous framework of diatomaceous opal-A. The contents of these minor elements are at atomic ratio levels of 1 (minor element)/10000 (Si) - 1/100, regardless of the genus of the diatoms. The occurrence of minor elements in the internal structure is likely through biological uptake during biosynthesis by living diatoms. Moreover, surface coatings composed of aluminosilicates on diatom frustules are common, and the contents of elements such as Al and Fe are tens or hundreds of times higher in the coatings than in the internal siliceous structure of diatomaceous opal-A. The discovery of the incorporation of the above-mentioned minor elements in the diatomaceous opal-A structure, both in the internal Si-O framework and on the surface, updates the knowledge about the properties of diatomite