Efficiency of a blue organic light-emitting diode enhanced by inserting charge control layers into the emission region

We demonstrate high current efficiency of a blue fluorescent organic light-emitting diode （OLED） by using the charge control layers （CCLs） based on Alq3 . The CCLs that are inserted into the emitting layers （EMLs） could impede the hole injection and facilitate the electron transport, which can improve the carrier balance and further expand the exciton generation region. The maximal current efficiency of the optimal device is 5.89 cd/A at 1.81 mA/cm2 , which is about 2.19 times higher than that of the control device （CD） without the CCL, and the maximal luminance is 19.660 cd/m2 at 12V. The device shows a good color stability though the green light emitting material Alq3 is introduced as the CCL in the EML, but it has a poor lifetime due to the formation of cationic Alq3 species.

Design of a P-&-O algorithm based MPPT charge controller for a stand-alone 200W PV system

Solar cells convert sun light into electricity,but have the major drawbacks of high initial cost,low photo-conversion efficiency and intermittency.The current-voltage characteristics of the solar cells depend on solar insolation level and temperature,which lead to the variation of the maximum power point(MPP).Herein,to improve photovoltaic(PV)system efficiency,and increase the lifetime of the battery,a microcontroller-based battery charge controller with maximum power point tracker(MPPT)is designed for harvesting the maximum power available from the PV system under given insolation and temperature conditions.Among different MPPT techniques,perturb and observe(P&O)technique gives excellent results and thus is used.This work involves the design of MPPT charge controller using DC/DC buck converter and microcontroller.A prototype MPPT charge controller is tested with a 200 W PV panel and lead acid battery.The results show that the designed MPPT controller improves the efficiency of the PV panel when compared to conventional charge controllers.

Analytical charge control model for AlGaN/GaN MIS-HFETs including an undepleted barrier layer

An analytical charge control model considering the insulator/AlGaN interface charge and undepleted Al-GaN barrier layer is presented for AlGaN/GaN metal-insulator-semiconductor heterostructure field effect transistors （MIS-HFETs） over the entire operation range of gate voltage.The whole process of charge control is analyzed in detail and partitioned into four regions：Ⅰ—full depletion,Ⅱ—partial depletion,Ⅲ—neutral region andⅣ—electron accumulation at the insulator/AlGaN interface.The results show that two-dimensional electron gas（2DEG） saturates at the boundary of regionⅡ/Ⅲand the gate voltage should not exceed the 2DEG saturation voltage in order to keep the channel in control.In addition,the span of regionⅡaccounts for about 50%of the range of gate voltage before 2DEG saturates.The good agreement of the calculated transfer characteristic with the measured data confirms the validity of the proposed model.

Controllably Coupling Superconducting Charge and Flux Qubits by Using Nanomechanical Resonator

We propose an effective mechanism to couple superconducting charge and flux qubits by using a quantized nanomechanical resonator. The coupling between the charge and flux qubits can be controlled by the external flux of the charge qubit. Under the strong coupling limR, an iSWAP gate can be generated by this scheme. The experimental feasibility in our scheme is also presented.

Space Charges Effect of Static Induction Transistor

The space charge effect (SCE) of static induction transistor (SIT) that occurs in high current region is systematically studied.The I V equations are deduced and well agree with experimental results.Two kinds of barriers are presented in SIT,corresponding to channel voltage barrier control (CVBC) mechanism and space charge limited control (SCLC) mechanism respectively.With the increase of drain voltage,the gradual transferring of operational mechanism from CVBC to SCLC is demonstrated.It points out that CVBC mechanism and its contest relationship with space charge barrier makes the SIT distinctly differentiated from JFET and triode devices,etc.The contest relationship of the two potential barriers also results in three different working regions,which are distinctly marked and analyzed.Furthermore,the extreme importance of grid voltage on SCE is illustrated.

A control model for hysteresis based on microscopic polarization mechanisms in piezoelectric actuator

Aiming at the limitation of control accuracy caused by hysteresis and creep for a piezoelectric actuator, the hysteresis phenomenon is explained based on the microscopic polarization mechanism and domain wall theory. Then a control model based on polarization is established, which can reduce the hysteresis and creep remarkablely. The experimental results show that the polarization control method is with more linearity and less hysteresis compared with the voltage control method.

Optimal Control Strategy for Buck Converter Under Successive Load Current Change

A new control algorithm is presented for digitally controlled dc-dc converters to achieve a fast response under a successive load-change.Under the steady-state condition,the tight voltage regulation is processed by the conventional digital PID compensator.If the load disturbance is significant,the controller switches to an optimal control scheme.With the integration of the capacitor current,the proposed algorithm predicts the optimal switch over time based on the charge balance control,and the minimal voltage derivation and recovery time are thus achieved when the load current has a successive load-change.The method for calculating the optimal switch over time is described,and the implementation of the proposed algorithm with a digital controller is treated in detail.Furthermore,the simulation and experiment results are provided to validate the effectiveness of the approaches.

Management of Charging Load of Electric Vehicles for Optimal Capacity Utilisation of Distribution Transformers

A de-centralised load management technique exploiting the flexibility in the charging of Electric Vehicles (EVs) is presented. Two charging regimes are assumed. The Controlled Charging Regime (CCR) between 16:30 hours and 06:00 hours of the next day and the Uncontrolled Charging Regime (UCR) between 06:00 hours and 16:30 hours of the same day. During the CCR, the charging of EVs is coordinated and controlled by means of a wireless two-way communication link between EV Smart Charge Controllers (EVSCCs) at EV owners’ premises and the EV Load Controller (EVLC) at the local LV distribution substation. The EVLC sorts the EVs batteries in ascending order of their states of charge (SoC) and sends command signals for charging to as many EVs as the transformer could allow at that interval based on the condition of the transformer as analysed by the Distribution Transformer Monitor (DTM). A real and typical urban LV area distribution network in Great Britain (GB) is used as the case study. The technique is applied on the LV area when its transformer is carrying the future load demand of the area on a typical winter weekday in the year 2050. To achieve the load management, load demand of the LV area network is decomposed into Non-EV load and EV load. The load on the transformer is managed by varying the EV load in an optimisation objective function which maximises the capacity utilisation of the transformer subject to operational constraints and non-disruption of daily trips of EV owners. Results show that with the proposed load management technique, LV distribution networks could accommodate high uptake of EVs without compromising the useful normal life expectancy of distribution transformers before the need for capacity reinforcement.

Single‑Photon Sources Based on Novel Color Centers in Silicon Carbide P–I–N Diodes: Combining Theory and Experiment

Point defects in the crystal lattice of SiC,known as color centers,have recently emerged as one of the most promising single-photon emitters for non-classical light sources.However,the search for the best color center that satisfies all the requirements of practical applications has only just begun.Many color centers in SiC have been recently discovered but not yet identified.Therefore,it is extremely challenging to understand their optoelectronic properties and evaluate their potential for use in practical single-photon sources.Here,we present a theoretical approach that explains the experiments on single-photon electroluminescence(SPEL)of novel color centers in SiC p-i-n diodes and gives the possibility to engineer highly efficient single-photon emitting diodes based on them.Moreover,we develop a novel method of determining the electron and hole capture cross sections by the color center from experimental measurements of the SPEL rate and second-order coherence.Unlike other methods,the developed approach uses the experimental results at the single defect level that can be easily obtained as soon as a single-color center is identified in the i-type region of the SiC p-i-n diode.

Requirements and Architecture Concept for a Data Processing System in Local Area Smart Grid

WINNER, a German research project, integrates local photovoltaic systems, charging infrastructure for electric vehicles and tenant households, focusing devices with and without smart grid abilities. The project＇s goal is to manage the local power grid operations in a way that allows locally produced energy to be consumed locally. This local optimised consumption is done by using currently available devices. Further, we want to analyse accruing data streams and optimise the usage of local devices to manage this time-base shifted consumption scenario by implementing a non-hard real-time processing system. In this paper, we outline the project＇s primary objectives from a technical point of view. First, we present ＂Wohnnngswirtschaftlich integrierte netzneutrale Elektromobilitat in Quartier und Region＂ （WINNER） and some related research projects. We describe the integration tasks, the data sources, and sinks. So, a project overview can be given. Afterwards, we compare our approach and already developed technologies. Requirements are derived from the system overview. According to them, we can outline an architectural View of the core component of data stream processing within this scenario. Finally, the results are discussed, and consequences are drawn.

Wind-integration benefits of controlled plug-in electric vehicle charging

Flexibility in plug-in electric vehicle(PEV) charging can reduce the ancillary cost effects of wind variability and uncertainty on electric power systems. In this paper, we study these benefits of PEV charging, demonstrating that controlled PEV charging can reduce costs associated with wind uncertainty and variability. Interestingly, we show that the system does not require complete control of PEV-charging loads to mitigate the negative cost impacts of wind variability and uncertainty. Rather, PEV owners giving the system a two-hour window of flexibility in which to recharge their vehicles provides much of the benefits that giving full charging control does.

An optimization strategy of controlled electric vehicle charging considering demand side response and regional wind and photovoltaic

Renewable energy,such as wind and photovoltaic(PV),produces intermittent and variable power output.When superimposed on the load curve,it transforms the load curve into a‘load belt’,i.e.a range.Furthermore,the large scale development of electric vehicle(EV)will also have a significant impact on power grid in general and load characteristics in particular.This paper aims to develop a controlled EV charging strategy to optimize the peak-valley difference of the grid when considering the regional wind and PV power outputs.The probabilistic model of wind and PV power outputs is developed.Based on the probabilistic model,the method of assessing the peak-valley difference of the stochastic load curve is put forward,and a two-stage peak-valley price model is built for controlled EV charging.On this basis,an optimization model is built,in which genetic algorithms are used to determine the start and end time of the valley price,as well as the peak-valley price.Finally,the effectiveness and rationality of the method are proved by the calculation result of the example.

Rational design of a novel two-dimensional porous metal-organic framework material for efficient benzene sensor

As a common volatile organic compound,benzene(C_(6)H_(6)) exists in home decoration pollution gas widely,which causes great harm to the environment and human health.Therefore,it is necessary to rationally design advanced materials with high selectivity to detect and capture C_(6)H_(6).Herein,combined with the d-band center theory and cohesive energy,a new two-dimensional metal-organic framework material,Ni-doped hexaaminobenzene-based coordination polymer(Ni-HAB-CP)is designed,and its application potential as a C_(6)H_(6) sensor are systematically investigated by using first principles calculation.The result shows that Ni-HAB-CP has a strong adsorption for C_(6)H_(6) without any additional method.In addition,NiHAB-CP can maintain good conductivity before and after adsorption,and C_(6)H_(6) can be easily desorbed from the surface of Ni-HAB-CP by charge control.Moreover,the I-V curve calculated by Atomistix Toolkit(ATK)reveals that Ni-HAB-CP has high sensitivity and selectivity to C_(6)H_(6).Hence,Ni-HAB-CP is expected to be used as a potential material for a highly efficient and recyclable C_(6)H_(6) sensor in the future.The calculation and analysis methods used in this paper could provide a certain theoretical basis and reference for the future research of gas sensors.