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The main technical challenge of the medium-voltage motor drives with modular multilevel converter (MMC) is the serious low-frequency fluctuation on the capacitor voltages, and the existing suppression methods inevitably inject high-frequency circulating currents in MMC. However, the output currents are evidently distorted by the large injected components, while little research has been done to study and solve this problem. This paper analyzes and proves the essential interactions between the output current distortion and the injected components, and the specific dominant output harmonic groups are derived and summarized, revealing the nature of the problem, and it can be taken as a favorable reference for the controller designing. Based on the derivations, this paper proposes a novel suppression method for the greatly improved harmonic characteristics of the output currents during the low-frequency operation. The output harmonics can be accurately measured by the proposed control and effectively suppressed for much lower current total harmonic distortion, benefiting for the superior output control performances with improved efficiency. The simulation results on PSCAD/EMTDC and experimental verifications on a 2.2 kW MMC-based motor drive prototype prove the validity of the presented harmonic analysis and suppression method.

The low-frequency fluctuation over the capacitor voltages seriously limits the development of medium-voltage variable-speed drives with a modular multilevel converter (MMC). Therefore, this paper presents an effective strategy of the low-speed and start-up operation for an MMC-based motor drive. The proposed strategy properly coordinates the improved injection and the reduced average capacitor voltage with high applicability. The specific interactions between the control parameters and the system metrics are analyzed to give the detailed steps of the parameters designing. Hence, based on the derivations, the proposed method enables the low-frequency operation under the nominal load torque with decreased injected components and reduced peak capacitor voltages. What is more, two start-up strategies that, respectively, aim at different objectives for the coordinated strategy are proposed, indicating satisfying control performances for the practical applications. The injected common-mode voltage and circulating current in the proposed method are designed to have a great reduction. Thus, the unfavorable risks for the motor are evidently decreased for better stability. The reduced peak current also lessens the high stress on switching devices with desirable reliability. The simulation and experiment results of an MMC-based motor drive prototype prove the effectiveness and superiority of the proposed method.

In this study, we investigated the effects of zinc threonine supplementation on growth, immunity-related genes, antioxidative stress, and resistance to heat stress (HS) in Nile tilapia. A total of 300 Nile tilapia ( 76.69 ± 0.11 g) were randomly allocated into five zinc treatments, with three replicates of 20 fish in each treatment. Based on the control group with zinc-free feeds, dietary zinc levels of 20 or 40 mg/kg diet were added in the form of zinc sulfate (ZnSO4) and zinc threonine (Thr-Zn). After 45 days of feeding, part of the fish was exposed to HS. The highest performance of growth and feed intake was found in fish fed with zinc (ZnSO4 or Thr-Zn) at 40 mg/kg, which also significantly elevated the villus length and absorption area. Additionally, significantly higher values of superoxide dismutase, catalase, and glutathione peroxidase activity but lower value of malondialdehyde both before and after the heat stress were documented in fish fed with zinc at 40 mg/kg in diets. After HS, dietary supplementation with zinc threonine significantly reduced the expression of HSP 70 in the liver but increased the expression of IL-10 and TNF-α. Our study demonstrated that zinc threonine supplementation at 40 mg/kg facilitated the coping of tilapia with HS by improving the growth, intestinal morphology, antioxidative resistance, and immune responses.

In recent years, with the rapid development of robotics, indoor mobile robots have gradually penetrated many aspects of human production and life. High accuracy localization is important for mobile robots in a variety of scenarios, including domestic and public places. In this paper, we present a fusion approach for indoor localization of a smartphone-based robot, which fuses the information of inertial sensors, encoder and indoor maps. In our approach, we first propose a dead reckoning model to obtain the position and attitude of the robot. Secondly, the information obtained by the encoder is used to identify the turning area. The difference between the turning position by our proposed algorithm and the known turning position is compared with a preset threshold. The estimated position converge on its true position. Finally, we design an Extended Kalman Filter (EKF)based fusion algorithm to fuse the inertial data, encoder data and map information. We evaluate our proposed method in an office building. The results show that the mean positioning error of the proposed method on the two routes is 0.7220m and 0.7150m respectively, which is a 60.4% and 68.3% reduction compared with the fusion of DR/Encoder approach.

Background: A very serious new type of coronavirus infection has recently erupted in China. For new viruses, data and information in all aspects need to be improved.Case Presentations: During the early COVID-19 outbreak, a 38-year-old man experienced COVID-19 infection in Shenzhen (nonendemic area-related personnel) and underwent SARS-CoV-2 nucleic acid screening multiple times due to an initial positive COVID-19 screening at the beginning of the disease. The results of these additional tests were negative, and the initial SARS-CoV-2 nucleic acid screening result for this patient was suspected as being a false positive.Diagnosis: After nearly 17 days of hospitalization in two hospitals, a variety of tests were performed to diagnosis this new coronavirus infection (due to the positive results of the initial screening).Intervention: Early in the onset of the disease, treatment was given to maintain water and electrolyte balance, and antibiotics and proprietary Chinese medicines were given as the treatment. The symptoms were controlled at an early stage.Outcomes: The patient developed symptoms on the first day and had pneumonia in the lungs, as shown by a chest CT examination on the 7th day of onset. The subsequent prognosis was good. The family members living with this patient did not show similar symptoms.Conclusion: The diagnostic process of COVID-19 needs to be improved, and the development of SARS-CoV-2 diagnostic reagents needs to be strengthened under certain conditions. Screening should be performed at an early stage when a COVID-19 infection is suspected and should distinguish between patients with a COVID-19 infection and with a non-COVID-19 infection. Patients are more conducive to controlling the COVID-19 epidemic.

As one of the most important transition-metal dichalcogenides (TMDs) materials, molybdenum disulfide (MoS2) has gained extensive attention for its marvelous optoelectronic properties. In this study, nanocomposites of two-dimensional (2D) molybdenum disulfide (MoS2) with plasmonic noble metal nanoparticles were synthesized by a one-step green process. Under irradiation, 2D MoS2 in the nanocomposites absorbed photons and generated carriers in a wide spectrum. Then MoS2 coupled to gold nanoparticles and produced the enhanced electromagnetic field in the nanosturctures, leading to outstanding optical properties. In virtue of bio-compatibilities of the particles, the nanocomposites were chemically modified with specific peptides to construct an optical biosensor for explosive detection. When exposed to 2,4,6-trinitrotoluene (TNT), the biosensor showed significant absorption peak changes in visible spectra with a concentration-dependent behavior. The biosensor could detect TNT at the concentration as low as 2 × 10−7 M. For selectivity, the biosensor could differentiate TNT from other nitroaromatic explosives that have extremely similar structures to TNT, such as 4-nitrotoluene (4-NT) and 2,6-dinitrotoluene (DNT). All the results suggested that the biosensor based on the nanocomposites of 2D MoS2 coupling to plasmonic nanoparticles exhibited remarkable optical performance, which provided a promising approach to design versatile biosensors to detect biochemical molecules.

A type of broadband (325−980 nm) self-powered photodetector based on graphene/GaAs van der Waals heterojunction is reported. By simply spinning a layer of Ag nano-particles (Ag NPs) onto graphene/GaAs heterostructure, the responsivity and detectivity of our devices for the whole spectrum range are enhanced significantly. The maximum photocurrent responsivity of 210 mA W−1 (increased by 38%) and detectivity of 2.98 × 1013 Jones (increased by 202%) are achieved at 405 nm, which is about two or three orders of magnitude larger than other graphene based self-powered photodetectors. The mechanism of the improvement originates from the overlap the depletion region of graphene/GaAs heterostructure, the surface plasmon enhanced light field region below the surface and the light absorption region of the GaAs layer. The external quantum efficiency (EQE) measurement, transient photoluminescence (PL) test and the comparative theoretical simulation show that the surface plasmon enhancement should only be applicable for graphene/direct band gap semiconductor heterostructure, where the semiconductor should have a high optical absorption coefficient. The obtained high performance broadband photodetector with excellent detectivity is a promising candidate for many important optoelectronic applications, such as ultrasensitive image sensor in charge coupled displayer field, which requires colour sensors not only with high photo responsivity but also in a wide spectral range.

Near-infrared photodetectors (NIRPDs) have attracted great attention because of their wide range of applications in many fields. Herein, a novel self-driven NIRPD at the wavelength of 980 nm is reported based on the graphene/GaAs heterostructure. Extraordinarily, its sensitivity to light illumination (980 nm) is far beyond the absorption limitation of GaAs (874 nm). This means that the photocurrent originates from the separation of photo-induced carriers in graphene, which is caused by the vertically built-in electric field formed through the high quality van der Waals contact between graphene and GaAs. Moreover, after introducing NaYF4:Yb3+/Er3+ upconversion nanoparticles (UCNPs) onto the graphene/GaAs heterojunction, the responsivity increases to be as superior as 5.97 mA W-1 and the corresponding detectivity is 1.1 × 1011 cm Hz0.5 W-1 under self-driven conditions. This dramatic improvement is mainly ascribed to the radiative energy transfer from UCNPs to the graphene/GaAs heterostructure. The high-quality and self-driven UCNPs/graphene/GaAs heterostructure NIRPD holds significant potential for practical application in low-consumption and large-scale optoelectronic devices.

The Oscillating Water Column Type is currently the most widely used wave energy generation device. The impulse turbine with fixed guide vanes has the advantages of high peak efficiency and excellent aerodynamic performance. Using three-dimensional numerical simulation methods to analyze the impulse turbine, construct and optimize the design of the turbine prototype, and provide suggestions for the subsequent innovation and improvement of the performance and structure of the impulse turbine with fixed guide vanes.

A viable approach to enhance the photovoltaic performance of graphene (Gr)/semiconductor solar cells has been demonstrated. In order to take full advantage of the solar energy in the range of visible and ultraviolet light, InP and ZnO quantum dots (QDs) with band gaps of 2.4 eV and 3.3 eV, respectively, are simultaneously introduced to dope Gr by a photo-induced doping mechanism. Raman and photoluminescence measurements indicate that the photo-induced holes diffuse into Gr, leading to p-doping of Gr. As a result, the power conversion efficiency (PCE) of the Gr/GaAs heterostructure solar cell with good stability can be improved from 8.57% to 11.50%. Although this process is simple and feasible, we emphasize that the mixed semiconductor QDs enhanced Gr/semiconductor heterostructure solar cell is similar to the band gap engineering of traditional multi-junction bulk semiconductor solar cells.

Putting a piece of graphene over p-GaN can form shallow P-N junction near the surface, which can act as light emitting diodes (LEDs) and promise many kinds of light manipulation methods. Herein, we introduce high performance surface plasmon enhanced graphene/p-GaN LEDs by inserting Ag nano-particles (Ag NPs) into the graphene/p-GaN interface. Bidirectional LEDs have been realized with a broad band emission from 550 nm to 650 nm at a forward bias of graphene side and a sharp emission of ~400 nm at a reversed bias of graphene. The emission intensity of graphene/Ag NPs/p-GaN is largely enhanced in both forward and reverse bias situation when compared with the bare graphene/p-GaN heterostructure, which is attributed to the surface plasmon resonance of Ag NPs. These results indicate that graphene/Ag NPs/p-GaN heterojunction is a promising candidate for high brightness LEDs.

Harvesting energy from multiple sources in our living environment is highly demanded, not only to cope with the increasing energy crises, but also to realize the self-powered electronics. Here we propose a graphene based two dimensional (2D) hybrid nanogenerator which can generate electricity through capturing sunlight as well as water flow. This 2D nanogenerator is mainly based on a graphene/silicon van der Waals Schottky diode. Two different metal electrodes are employed to build an asymmetric internal potential profile in the graphene channel, allowing for harvesting energy from sunlight in the 2D graphene plane with a maximum output power of 49.3 μW. When water flows over the graphene surface under illumination, an additional voltage can be generated simultaneously. This flow-induced voltage arises from an additional charge transfer in the graphene channel induced by a continuous doping and dedoping of the graphene, owing to a reversible wetting and dewetting effect of water during the water flowing process. The results show a physical picture of dynamic adjusting the charge transfer characteristic of graphene/silicon Schottky diode through water flow when under illumination, which may open prospects for practical applications for graphene nanogenerator.

The rectifying behavior between graphene and semiconductors makes novel type of solar cells, photo-detectors and light emitting diodes (LEDs). The interface between graphene and ZnO is the key for the performance of the optoelectronic devices. Herein, we find that green light emission is very strong for the forward biased graphene/ZnO nanowire van derWaals heterostructure.We correlated the green light emission with the surface defects locating at the ZnO nanowire surface through the detailed high resolution transmission electron microscopy and photoluminescence measurements. We pointed out engineering the surface of ZnO nanowires could bring a dimension of designing graphene/ZnO LEDs, which could be extended to other types of graphene/semiconductor heterostructure based optoelectronic devices.

Modular multilevel converter (MMC) has developed into an attractive topology for the variable-speed motor drives. However, the main challenge for the applications is the large low-frequency capacitor voltage fluctuation. This paper proposes a novel control strategy that is able to reduce the average capacitor voltages in a satisfying range when the motor operates below the base speed. Thus, the capacitor voltages can be well controlled under the nominal voltage for much better safety and reliability, and in the meantime the motor is able to operate with lower speed, larger load torque, and lower circulating current in the MMC for the wider range of operation conditions and greater control performances. The effectiveness of the proposed control strategy are demonstrated by the simulation results in PSCAD/EMTDC.

High efficient solar cell is highly demanded for sustainable development of human society, leading to the cutting-edge research on various types of solar cells. The physical picture of graphene/semiconductor van der Waals Schottky diode is unique as Fermi level of graphene can be tuned by gate structure relatively independent of semiconductor substrate. However, the reported gated graphene/semiconductor heterostructure has power conversion efficiency ( PCE ) normally less than 10%. Herein, utilizing a designed graphene-dielectric-graphene gating structure for graphene/GaAs heterojunction, we have achieved solar cell with PCE of 18.5% and open circuit voltage of 0.96 V. Drift-diffusion simulation results agree well with the experimental data and predict this device structure can work with a PCE above 23.8%. This research opens a door of high efficient solar cell utilizing the graphene/semiconductor heterostructure.

Graphene based van der Waals heterostructure has attracted wide attention recently, especially for graphene/semiconductor Schottky junction. Herein, through delicately designing and engineering the van der Waals heterostructure between graphene and indium phosphide (InP), which has a suitable bandgap of 1.34 eV for solar energy conversion, we have achieved graphene/p-InP solar cells with power conversion efficiency (PCE) of 3.3% under AM 1.5G illumination. The chemical doping or electrical field modulation has been used to tune the Fermi level of graphene, which leads to a PCE of 5.6% for the device under gating effect. Furthermore, the interface recombination rate could be reduced while graphene is doped or gated, as evidenced by transient photoluminescence measurements. Considering the stability of cell performance under illumination and the high resistance to space irradiation damage of InP, graphene/InP heterojunction may be promising for special applications such as space solar cells.

In this chapter we have reviewed side effects reported for Vitamin A (carotenoids), vitamins of the B group (cobalamins, folic acid and folinic acid, hopantenic acid, pyridoxine, riboflavin, tetrahydrobiopterin and sapropterin and thiamine), vitamin C (ascorbic acid), vitamin D analogues, vitamin E (tocopherol), vitamin K analogues, amino acids (arginine and glutamine), and eternal and parental nutrition. Our Search was restricted from January 2015 to January 2016. PUBMED, EMBASE and International Pharmaceutical Abstracts (IPA) were used as our search engines.

2D materials hold great potential for designing novel electronic and optoelectronic devices. However, 2D material can only absorb limited incident light. As a representative 2D semiconductor, monolayer MoS2 can only absorb up to 10% of the incident light in the visible, which is not sufficient to achieve a high optical-to-electrical conversion efficiency. To overcome this shortcoming, a "gap-mode" plasmon-enhanced monolayer MoS2 fluorescent emitter and photodetector is designed by squeezing the light-field into Ag shell-isolated nanoparticles-Au film gap, where the confined electromagnetic field can interact with monolayer MoS2 . With this gap-mode plasmon-enhanced configuration, a 110-fold enhancement of photoluminescence intensity is achieved, exceeding values reached by other plasmon-enhanced MoS2 fluorescent emitters. In addition, a gap-mode plasmon-enhanced monolayer MoS2 photodetector with an 880% enhancement in photocurrent and a responsivity of 287.5 A W-1 is demonstrated, exceeding previously reported plasmon-enhanced monolayer MoS2 photodetectors.

Two dimensional material/semiconductor heterostructures offer alternative platforms for optoelectronic devices other than conventional Schottky and p–n junction devices. Herein, we use MoS 2 /GaAs heterojunction as a self-driven photodetector with wide response band width from ultraviolet to visible light, which exhibits high sensitivity to the incident light of 635 nm with responsivity as 321 mA/W and detectivity as 3.5×10 13 Jones (Jones=cm Hz 1/2 W −1 ), respectively. Employing interface design by inserting h-BN and photo-induced doping by covering Si quantum dots on the device, the responsivity is increased to 419 mA/W for incident light of 635 nm. Distinctly, attributing to the low dark current of the MoS 2 /h-BN/GaAs sandwich structure based on the self-driven operation condition, the detectivity shows extremely high value of 1.9×10 14 Jones for incident light of 635 nm, which is higher than all the reported values of the MoS 2 based photodetectors. Further investigations reveal that the MoS 2 /GaAs based photodetectors have response speed with the typical rise/fall time as 17/31 μs. The photodetectors are stable while sealed with polymethyl methacrylate after storage in air for one month. These results imply that monolayer MoS 2 /GaAs heterojunction may have great potential for practical applications as high performance self-driven photodetectors.

Graphene has attracted increasing interest due to its remarkable properties. However, the zero band gap of monolayered graphene limits it's further electronic and optoelectronic applications. Herein, we have synthesized monolayered silicon-doped graphene (SiG) with large surface area using a chemical vapor deposition method. Raman and X-ray photoelectron spectroscopy measurements demonstrate that the silicon atoms are doped into graphene lattice at a doping level of 2.7-4.5 at%. Electrical measurements based on a field effect transistor indicate that the band gap of graphene has been opened via silicon doping without a clear degradation in carrier mobility, and the work function of SiG, deduced from ultraviolet photoelectron spectroscopy, was 0.13-0.25 eV larger than that of graphene. Moreover, when compared with the graphene/GaAs heterostructure, SiG/GaAs exhibits an enhanced performance. The performance of 3.4% silicon doped SiG/GaAs solar cell has been improved by 33.7% on average, which was attributed to the increased barrier height and improved interface quality. Our results suggest that silicon doping can effectively engineer the band gap of monolayered graphene and SiG has great potential in optoelectronic device applications.

MoS2 is a layered two-dimensional semiconductor with a direct band gap of 1.8 eV. The MoS2/bulk semiconductor system offers a new platform for solar cell device design. Different from the conventional bulk p-n junctions, in the MoS2/bulk semiconductor heterostructure, static charge transfer shifts the Fermi level of MoS2 toward that of bulk semiconductor, lowering the barrier height of the formed junction. Herein, we introduce hexagonal boron nitride (h-BN) into MoS2/GaAs heterostructure to suppress the static charge transfer and the obtained MoS2/h-BN/GaAs solar cell exhibits an improved power conversion efficiency of 5.42%. More importantly, the sandwiched h-BN makes the Fermi level tuning of MoS2 more effective. By employing chemical doping and electrical gating into the solar cell device, PCE of 9.03% is achieved, which is the highest among all the reported monolayer transition metal dichalcogenide based solar cells.

Astrocytes have a robust and dynamic intracellular Ca activity in response to stimulation by various neurotransmitters and neuromodulators such as angiotensin II, glutamate, and ATP [1-4]. ATP evokes Ca bursts in astrocytes by activation of purinergic receptors [4] and angiotensin II (AngII) by stimulation of AT1 receptors [2]. Intracellular Ca mobilization by the peptide and high energy purine signaling molecules enhances astrocyte cycling excitatory neurotransmitter glutamate, which governs the social behavior and cognitive ability [5-7]. Acute alcohol overdose alters users’ social behavior and affects abusers’ cognition [8,9]. We hypothesize that alcohol impairs the intracellular Ca handling in astrocytes particularly in response to neurotransmitter/neuromodulator stimulation, which may play an important role in understanding alcohol intoxication. The impairment may relate to the development of alcohol addiction, dependence and tolerance. In this work, we studied the alteration of intracellular Ca signaling by alcohol treatment in cultured rat hippocampal astrocytes. The findings of this study enrich our understanding of ethanol intoxication and may lead to a new treatment target for alcoholism.

A ZnO quantum dot photo-doped graphene/h-BN/GaN-heterostructure ultraviolet photodetector with extremely high responsivity of more than 1915 A W−1 and detectivity of more than 1.02 × 1013 Jones (Jones = cm Hz1/2 W−1) has been demonstrated. The interfaced h-BN layer increases the barrier height at the graphene/GaN heterojunction, which decreases the dark current and improves the on/off current ratio of the device. The photo-doping effect increases the barrier height and carrier concentration at the graphene/h-BN/GaN heterojunction, thus the responsivity is improved from 1473 A W−1 to 1915 A W−1 and the detectivity is improved from 5.8 × 1012 to 1.0 × 1013 Jones. Moreover, all of the responsivity and detectivity values are the highest values among all the graphene-based ultraviolet photodetectors.

We demonstrate significantly improved photovoltaic response of monolayer molybdenum disulfide (MoS2)/indium phosphide (InP) van der Waals heterostructure induced by graphene quantum dots (GQDs). Raman and photoluminescence measurements indicate that effective charge transfer takes place between GQDs and MoS2, which results in n-type doping of MoS2. The doping effect increases the barrier height at the MoS2/InP heterojunction, thus the averaged power conversion efficiency of MoS2/InP solar cells is improved from 2.1% to 4.1%. The light induced doping by GQD provides a feasible way for developing more efficient MoS2 based heterostructure solar cells.

In graphene/semiconductor heterojunction, the statistic charge transfer between graphene and semiconductor leads to decreased junction barrier height and limits the Fermi level tuning effect in graphene, which greatly affects the final performance of the device. In this work, we have designed a sandwich diode for solar cells and photodetectors through inserting 2D hexagonal boron nitride (h-BN) into graphene/GaAs heterostructure to suppress the static charge transfer. The barrier height of graphene/GaAs heterojunction can be increased from 0.88 eV to 1.02 eV by inserting h-BN. Based on the enhanced Fermi level tuning effect with interface h-BN, through adopting photo-induced doping into the device, power conversion efficiency (PCE) of 10.18% has been achieved for graphene/h-BN/GaAs compared with 8.63% of graphene/GaAs structure. The performance of graphene/h-BN/GaAs based photodetector is also improved with on/off ratio increased by one magnitude compared with graphene/GaAs structure.

We report a type of solar cell based on graphene/CdTe Schottky heterostructure, which can be improved by surface engineering as graphene is atomic thin. By coating a layer of ultrathin CdSe quantum dots onto graphene/CdTe heterostructure, the power conversion efficiency is increased from 2.08% to 3.10%. Photo-induced doping is mainly accounted for this enhancement, as evidenced by field effect transport, Raman, photoluminescence, and quantum efficiency measurements. This work demonstrates a feasible way of improving the performance of graphene/semiconductor heterostructure solar cells by combining one dimensional with two dimensional materials.

We demonstrate monolayer molybdenum disulfide (MoS2)/indium phosphide (InP) van der Waals heterostructure with remarkable photovoltaic response. Furthermore, benefiting from the atomically thin and semiconductor nature of MoS2, we have designed the gate tunable MoS2/InP heterostructure. Applied with a top gate voltage, the Fermi level of MoS2 is effectively tuned, and the barrier height at the MoS2/InP heterojunction correspondingly changes. The power conversion efficiency of MoS2/InP solar cells has reached a value of 7.1% under AM 1.5G illumination with a gate voltage of +6 V. The tunable MoS2/InP heterostructure may be promising for highly efficient solar cells.

Harvesting energy from environment is the current focus of scientific community. Here, we demonstrate a graphene nanogenerator, which is based on moving van der Waals heterostructure formed between graphene and two dimensional (2D) graphene oxide (GO). This nanogenerator can convert mechanical energy into electricity with a voltage output of around 10 mV. Systematic experiments reveal the generated electricity originates from the coulomb interaction induced momentum transfer between 2D GO and holes in graphene. 2D boron nitride was also demonstrated to be effective in the framework of moving van der Waals heterostructure nanogenerator. This investigation of nanogenerator based on the interaction between 2D macromolecule materials will be important to understand the origin of the flow-induced potential in nanomaterials and may have great potential in practical applications.