Robust Multivariable Microgrid Control Synthesis and Analysis

AbstractIn this paper, an islanded microgrid is modelled as a linear multivariable dynamic system. Then, the multivariable analysis tools are employed. The generalized Nyquist diagram and the relative gain array are used respectively for the stability assessment and solving the paring problem among the inputs and outputs. Droop control dependency on the X/R ratio of the microgrid DERs is recognized and its type is proposed using the relative gain array concept. Robust stability, nominal performance and robust performance requirements are evaluated in order to a better understanding of the system dynamics. Finally, three different controllers including H∞, H2 and sequential proportional-integral-derivative controls are designed and compared

Influence of phonons on exciton-photon interaction and photon statistics of a quantum dot

In this paper, we investigate, phonon effects on the optical properties of a spherical quantum dot. For this purpose, we consider the interaction of a spherical quantum dot with classical and quantum fields while the exciton of quantum dot interacts with a solid state reservoir. We show that phonons strongly affect the Rabi oscillations and optical coherence on first picoseconds of dynamics. We consider the quantum statistics of emitted photons by quantum dot and we show that these photons are anti-bunched and obey the sub-Poissonian statistics. In addition, we examine the effects of detuning and interaction of quantum dot with the cavity mode on optical coherence of energy levels. The effects of detuning and interaction of quantum dot with cavity mode on optical coherence of energy levels are compared to the effects of its interaction with classical pulse

Two-scale modelling of fracture of magnesium phosphate cement under bending using X-ray computed tomography characterisation

This paper presents an efficient experimental-numerical analysis of fracture mechanics in magnesium phosphate cement (MPC) based on the structural and mechanical properties of its constituents including potassium magnesium phosphate hexahydrate (MKP), magnesium oxide (MgO) and pores. At micro-scale, the fracture energy and material strength of solid phases were obtained relying on the combination of nanoindentation experiments and simulation. The X-ray computed tomography (XCT) image-based 3D meso-structure model of MPC beam was generated and incorporated with the finite element cohesive zone model to analyse the fracture process of MPC beam under three-point bending. The unknown fracture parameters of cohesive elements at the interface between MKP and MgO were determined via the model calibration process conditional to the experimental data in terms of relationship between macro-load and crack mouth opening displacement. The cohesive strengths obtained for MKP, MgO and MKP-MgO were found to be 5.8, 106 and 24 MPa, respectively. In the same order, the fracture energies were0.02, 0.08 and 0.04 N/mm, respectively

Optical feedback instabilities in a monolithic InAs/GaAs quantum dot passively mode-locked laser

International audienceThe impact of optical feedback on the direct performance of a monolithic InAs/GaAs quantum dot passively mode-locked laser intended for applications such as multigigahertz interchip/intrachip clock distribution is experimentally investigated. Evaluation of the feedback resistance is an important feature, as the laser is to be monolithically integrated on chip with other devices, in which case optical isolation is difficult. This work shows that a feedback level on the order of −24 dB is detrimental for mode-locking operation, enhancing noise in the rf electrical signal, strongly narrowing the useful mode-locking region as well as causing central frequency shift, and severe instabilities

Effect of Ursodeoxycholic Acid on Pentylenetetrazole Kindling and Kindling Induced Memory Impairment in Rat

BACKGROUND AND OBJECTIVE: Epilepsy is one of the common diseases of the brain that about 30-40% of patients with epilepsy experience recurent attacks due to drug resistance. Recently, the beneficial effects of Ursodeoxycholic acid on brain disorders have been considered. The aim of this study was to evaluate the effect of Ursodeoxycholic acid(UDCA)on the Pentylenetetrazole (PTZ) induced kindling, and related learning and memory impairments on Morris water maze. METHODS: This experimental study was done on 32 male Winstar rats divided into 4 groups. The first(n=7)and the second(n=9)groups have received three injections of 0.5 ml NaCl or 50 mg/kg of UDCA respectively and third(n=7) and fourth(n=9) groups have received fifteen injections of 0.5 ml NaCl or 50 mg/kg of UDCA respectively. All injections were given intraperitoneally(ip)(every 48 hours). In all groups, chemical kindling were started after third injections. Twenty-four hour after the last injection, spatial memory was investigated in the Morris water maze. FINDING: Fifteen injections of UDCA significantly reduced the seizure stage from 3.5±0.17 to 3.08±0.11 and duration of stages five from 12.37±1.21 to 8.43±1.09 and increased time to reach the stage five seizures from 1021.65±72.07 to 1252.41±49.63 as compared to control group. However, three injections of UDCA have no effect on the kindling process. However, three time administration of UDCA significantly increased reference memory from 18.72±1.2 s to 26.11±1.8 s. CONCLUSION: Ursodeoxycholic acid inhibits chemical kindling and improves kindling induced memory impairment

A developed asymmetric mulitlevel inverter with lower number of components

In this paper, a new configuration for symmetrical and asymmetrical multilevel inverters is proposed. In asymmetric mode, different algorithms are suggested in order to determine the magnitudes of DC voltage sources. The merit of this topology to the conventional symmetric and asymmetric inverters is verified by the provided comparisons. This topology uses a lower number of power electronic devices such as switches, IGBTs, diodes, related gate driver circuits and DC voltage sources. Owing the lower amount of requirements, it has lower total costs and needs less installation area. Also the control strategy has less complexity. The proposed converter can generate all the desired output voltage levels with positive and negative values. To confirm the practicability of the proposed inverter, simulation and experimental results are provided which are in good agreements

Increased entropy of signal transduction in the cancer metastasis phenotype

Studies into the statistical properties of biological networks have led to important biological insights, such as the presence of hubs and hierarchical modularity. There is also a growing interest in studying the statistical properties of networks in the context of cancer genomics. However, relatively little is known as to what network features differ between the cancer and normal cell physiologies, or between different cancer cell phenotypes. Based on the observation that frequent genomic alterations underlie a more aggressive cancer phenotype, we asked if such an effect could be detectable as an increase in the randomness of local gene expression patterns. Using a breast cancer gene expression data set and a model network of protein interactions we derive constrained weighted networks defined by a stochastic information flux matrix reflecting expression correlations between interacting proteins. Based on this stochastic matrix we propose and compute an entropy measure that quantifies the degree of randomness in the local pattern of information flux around single genes. By comparing the local entropies in the non-metastatic versus metastatic breast cancer networks, we here show that breast cancers that metastasize are characterised by a small yet significant increase in the degree of randomness of local expression patterns. We validate this result in three additional breast cancer expression data sets and demonstrate that local entropy better characterises the metastatic phenotype than other non-entropy based measures. We show that increases in entropy can be used to identify genes and signalling pathways implicated in breast cancer metastasis. Further exploration of such integrated cancer expression and protein interaction networks will therefore be a fruitful endeavour.Comment: 5 figures, 2 Supplementary Figures and Table

Synergy between inhibitors of androgen receptor and MEK has therapeutic implications in estrogen receptor-negative breast cancer

Introduction: Estrogen receptor-negative (ER-) breast cancer is a heterogeneous disease with limited therapeutic options. The molecular apocrine subtype constitutes 50% of ER-tumors and is characterized by overexpression of steroid response genes including androgen receptor (AR). We have recently identified a positive feedback loop between the AR and extracellular signal-regulated kinase (ERK) signaling pathways in the molecular apocrine subtype. In this feedback loop, AR regulates ERK phosphorylation through the mediation of ErbB2 and, in turn, ERK-CREB1 signaling regulates the transcription of AR in molecular apocrine cells. In this study, we investigated the therapeutic implications of the AR-ERK feedback loop in molecular apocrine breast cancer.Methods: We examined a synergy between the AR inhibitor flutamide and the MEK inhibitor CI-1040 in the molecular apocrine cell lines MDA-MB-453, HCC-1954 and HCC-202 using MTT cell viability and annexin V apoptosis assays. Synergy was measured using the combination index (CI) method. Furthermore, we examined in vivo synergy between flutamide and the MEK inhibitor PD0325901 in a xenograft model of the molecular apocrine subtype. The effects of in vivo therapies on tumor growth, cell proliferation and angiogenesis were assessed.Results: We demonstrate synergistic CI values for combination therapy with flutamide and CI-1040 across three molecular apocrine cell lines at four dose combinations using both cell viability and apoptosis assays. Furthermore, we show in vivo that combination therapy with flutamide and MEK inhibitor PD0325901 has a significantly higher therapeutic efficacy in reducing tumor growth, cellular proliferation and angiogenesis than monotherapy with these agents. Moreover, our data suggested that flutamide and CI-1040 have synergy in trastuzumab resistance models of the molecular apocrine subtype. Notably, the therapeutic effect of combination therapy in trastuzumab-resistant cells was associated with the abrogation of an increased level of ERK phosphorylation that was developed in the process of trastuzumab resistance.Conclusions: In this study, we demonstrate in vitro and in vivo synergies between AR and MEK inhibitors in molecular apocrine breast cancer. Furthermore, we show that combination therapy with these inhibitors can overcome trastuzumab resistance in molecular apocrine cells. Therefore, a combination therapy strategy with AR and MEK inhibitors may provide an attractive therapeutic option for the ER-/AR+ subtype of breast cancer

Effect of Weld Schedule on the Residual Stress Distribution of Boron Steel Spot Welds

Press-hardened boron steel has been utilized in anti-intrusion systems in automobiles, providing high strength and weight-saving potential through gage reduction. Boron steel spot welds exhibit a soft heat-affected zone which is surrounded by a hard nugget and outlying base material. This soft zone reduces the strength of the weld and makes it susceptible to failure. Additionally, different welding regimes lead to significantly different hardness distributions, making failure prediction difficult. Boron steel sheets, welded with fixed and adaptive schedules, were characterized. These are the first experimentally determined residual stress distributions for boron steel resistance spot welds which have been reported. Residual strains were measured using neutron diffraction, and the hardness distributions were measured on the same welds. Additionally, similar measurements were performed on spot welded DP600 steel as a reference material. A correspondence between residual stress and hardness profiles was observed for all welds. A significant difference in material properties was observed between the fixed schedule and adaptively welded boron steel samples, which could potentially lead to a difference in failure loads between the two boron steel welds