电力系统低频振荡的研究现状和展望

围绕电力系统低频振荡的产生机理、分析方法、影响因素和控制策略四个方面,综述了电力系统低频振荡的研究现状,分析了现有研究成果的主要优点和存在的不足然后。根据现实中电力系统低频振荡出现的新特点,提出了低频振荡的机制问题,即:低频振荡的研究需要解决五个问题,最后结合控制科学、结构动力学和电力电子技术等其它学科或领域已有研究成果,重点给出了电力系统低频振荡在分析方法和控制策略等研究方面的新思路,比如:模态分析法、同步相角测量法、储能法。

电力系统低频振荡的研究现状和展望

围绕电力系统低频振荡的产生机理、分析方法、影响因素和控制策略四个方面,综述了电力系统低频振荡的研究现状,分析了现有研究成果的主要优点和存在的不足,根据实际中电力系统低频振荡出现的新特点,提出了低频振荡的机制问题,即:低频振荡的研究需要解决五个问题,并且结合控制科学、结构动力学和电力电子技术等其它学科或领域的已有研究成果,重点给出了电力系统低频振荡在分析方法和控制策略等研究方面的新思路,比如:模态分析法、同步相角测量法、储能法。

A new method for reservoir fluid identification

The wavelet transform （WT） method has been employed to decompose an original geophysical signal into a series of components containing different information about reservoir features such as pore fluids, lithology, and pore structure. We have developed a new method based on WT energy spectra analysis, by which the signal component reflecting the reservoir fluid property is extracted. We have successfully processed real log data from an oil field in central China using this method. The results of the reservoir fluid identification agree with the results of well tests.

MXene quantum dots of Ti_(3)C_(2):Properties,synthesis,and energy-related applications

The emerging two-dimensional MXene-derived quantum dots(MQDs)have garnered considerable research interest owing to their abundant active edge atoms,excellent electrical conductivity,and remarkable optical properties.Compared with their two-dimensional(2D)counterpart MXene,MQDs with forceful size and quantum confinement effects exhibit more unparalleled properties and have considerably contributed to the advanced photocatalysis,detection,energy storage,and biomedicine fields.This critical review summarizes the fundamental properties of MQDs in terms of structure,electricity,and optics.The mechanism,characteristics,and comparisons of two typical synthesis strategies(traditional chemical method and novel fluorine-free or chemical-free method)are also presented.Furthermore,the similarities and differences between MQDs and 2D MXenes are introduced in terms of their functional groups,light absorption capacity,energy band structure,and other properties.Moreover,recent advances in the applications of MQD-based materials for energy conversion and storage(ECS)are discussed,including photocatalysis,batteries,and supercapacitors.Finally,current challenges and future opportunities for advancing MQD-based materials in the promising ECS field are presented.

A research on an energy-saving software for pumping units based on FNN intelligent control

An energy-saving scheme for pumping units via intermission start-stop performance is proposed. Because of the complexity of the oil extraction process, Fuzzy Neural Network (FNN) intelligent control is adopted. The structure of the Takagi-Sugeno (T-S) fuzzy neural network model is introduced and modified. FNNs are trained with sample information from oil fields and expert knowledge. Finally, pumping unit energy-saving FNN software, which cuts down power costs substantially, is presented.

Solar Desalination with Latent Heat Storage Materials and Solar Collector

Availability of clean water is going to become one of biggest demands of the country. Even though there arc various technologies available for purification of water harnessing solar energy fits the purpose for future problems. Distillation is one of many processes available for water purification, and solar energy is one of several forms of heat energy that can be used to energize this process. In this review a study is made to enhance the productivity of the solar stills by connecting solar still with latent heat storage and solar air heater in series and other factors like improving evaporation rate by maintaining Low depth, more exposure area, heat addition by solar collector and presence of latent heat storage material, which is a paraffin wax as a integral part of still. Latent heat storage is one of the most efficient ways of storing thermal energy. Unlike the sensible heat storage method, the latent heat storage method provides much higher storage density, with a smaller temperature difference between storing and releasing heat. Further augmentation of the yield by scraps, pebble, and sand are added.

Operating performance of novel reverse-cycle defrosting method based on thermal energy storage for air source heat pump

To solve the fundamental problem of insufficient heat available during defrosting while ensuring the efficient and safe system operation for air-source heat pumps (ASHPs). A novel reverse-cycle defrosting (NRCD) method based on thermal energy storage to eliminate frost off the outdoor coil surface was developed. Comparative experiments using both the stand reverse cycle defrosting (SRCD) method and the NRCD method were carried out on an experimental ASHP unit with a nominal 2.5 kW heating capacity. The results indicate that during defrosting operation, using the NRCD method improves discharge and suction pressures by 0.24 MPa and 0.19 MPa, respectively, shortens defrosting duration by 60%, and reduces the defrosting energy consumption by 48.1% in the experimental environment, compared with those by the use of SRCD method. Therefore, using the NRCD method can shorten the defrosting duration, improve the indoor thermal comfort, and reduce the defrosting energy consumption in defrosting.

激光通信信标激光器仿真与测试方法研究

介绍了激光通信中用于信标探测的大功率窄脉冲半导体激光器的驱动仿真方法和测试方法,原理仿真采用储能法在multisim中进行激光器驱动功能验证,然后利用器件的IBIS或者spice模型对核心器件功能进行了电源完整性和信号完整性仿真,最后介绍了输出光脉冲的峰值功率与平均功率的测试方法。最终设计结果表明,功能仿真和后端仿真结果与驱动电路的电流和脉宽设计参数一致。

Enhanced performance of CdS/CdSe quantum dotsensitized solar cells by long-persistence phosphors structural layer

Light absorption plays an important role in improving the power conversion efficiency(PCE)of quantum dot-sensitized solar cells(QDSSCs).In this study,a multifunctional long-persistence phosphor(LPP)layer was introduced into the CdS/CdSe QDSSCs via a simple doctor blade method.The LPP layer can simultaneously improve the light harvesting and photo charge transfer in CdS/CdSe QDSSCs.As a result,their short-circuit current and corresponding PCE are effectively enhanced.The PCE can reach up to 5.07%,which is about 24%larger than that of the conventional CdS/CdSe QDSSCs without LPP layer.The solar cells can work in dark for a while due to the long-lasting fluorescence of the LPP layer.This research provides an effective way to improve the PCE of QDSSCs,and finds the possibility for all-weather QDSSCs.

Realization of a non-markov chain in a single 2D mineral RRAM

The non-Markov process exists widely in thermodymanic process,while it usually requires the packing of many transistors and memories with great system complexity in a traditional device structure to minic such functions.Two-dimensional(2D)material-based resistive random access memory(RRAM)devices have the potential for next-generation computing systems with much-reduced complexity.Here,we achieve a non-Markov chain in an individual RRAM device based on 2D mineral material mica with a vertical metal/mica/metal structure.We find that the potassium ions(K+)in 2D mica gradually move in the direction of the applied electric field,making the initially insulating mica conductive.The accumulation of K+is changed by an electric field,and the 2D-mica RRAM has both single and double memory windows,a high on/off ratio,decent stability,and repeatability.This is the first time a non-Markov chain process has been established in a single RRAM,in which the movement of K+is dependent on the stimulated voltage as well as their past states.This work not only uncovers an intrinsic inner ionic conductivity of 2D mica,but also opens the door for the production of such RRAM devices with numerous functions and applications.

New synthetic procedure for Na NH_2(BH_3)_2 and evaluation of its hydrogen storage properties

Tremendous efforts have been devoted to the synthesis of new light element hydrides for hydrogen storage. Ammonia borane （AB） is a promising candidate possessing high hydrogen capacity and low dehydrogenation temperature. The step-wise dehydrogenation and release of by-products, however, are obstacles to its practical application. Chemical modifications of AB to synthesize new compounds or its derivatives are of practical and fundamental importance. Here we report an improved synthesis of sodium aminodiborane （NaNH2（BH3）2, NaABB）, a derivative of ammonia borane. This procedure leads to high purity NaABB by reacting NaNH2 and 2 eq. AB. The dehydrogenation properties have been investigated by means of temperature programmed desorption-mass spectrometry, volumetric release, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and X-ray diffraction. In a closed vessel, NaABB can release -2 eq. H2 when heated at 271 ℃, forming solid products of NaBH4 and highly condensed polyborazylene.