Angular response of ‘pin-hole’ imaging structure measured by collimated β source

The pitch-angle distribution of energetic particles is important for space physics studies on magnetic storm and particle acceleration.A‘pin-hole’imaging structure is built with the‘pin-hole’technique and a position sensitive detector,which can be used to measure the pitch angle distribution of energetic particles.To calibrate the angular response of the‘pin-hole’imaging structure,special experiment facilities are needed,such as the particle accelerator with special design.The features of this kind of particle accelerator are:1)The energy range of the outgoing particles should be mid-energy particles(tens keV to several hundred keV);2)the particle flux should be consistent in time-scale;3)the directions of the outgoing particles should be the same and 4)the particle number within the spot should be low enough.In this paper,a method to calibrate the angular response of the‘pin-hole’imaging structure by the90Sr/90Y β source with a collimator is introduced and simulated by Geant4 software.The result of the calibration with the collimated β source is in accord with the Geant4 simulations,which verifies the validity of this method.     

Allocation of congestion relief cost based on flow change on the congested facilities

Electric utilities have experienced a period of rap-id changes especially in market structure and regulatorypolicies in many parts of the world. In a deregulatedenvironment, considerable attention has been focusedon a variety of issues, with transmission congestion be-ing an important one.Congestion management means not only solving thetransmission constraints but also pricing congestion re-lief cost reasonably. As for pricing, there are two kindsof approaches-nodal prices based approaches and…     

Variations of the relativistic electron flux after a magnetospheric compression event

On January 21, 2015, a sharp increase of the solar wind dynamic pressure impacted the magnetosphere. The magnetopause moved inward to the region L 8 without causing a geomagnetic storm. The flux of the relativistic electrons in the outer radiation belt decreased by half during this event based on the observations of the particle radiation monitor(PRM) of the fourth of the China-Brazil Earth Resource Satellites(CBERS-4). The flux remained low for approximately 11 d; it did not recover after a small magnetic storm on January 26 but after a small magnetic storm on February 2. The loss and recovery of the relativistic electrons during this event are investigated using the PRM data, medium-and high-energy electron observations of NOAA-15 and the Van Allen Probes, medium-energy electron observations of GOES-13, and wave observations of the Van Allen Probes. This study shows that the loss of energetic electrons in this event is related to magnetospheric compression. The chorus waves accelerate the medium-energy electrons, which causes the recovery of relativistic electrons. The Van Allen Probes detected strong chorus waves in the region L =3–6 from January 21 to February 2. However, the flux of medium-energy electrons was low in the region. This implies that the long-lasting lack of recovery of the relativistic electrons after this event is due to the lack of the medium-energy"seed" electrons. The medium-energy electrons in the outer radiation belt may be a clue to predict the recovery of relativistic electrons.     

Polyvinylpyrrolidone/graphene oxide thin films coated on quartz crystal microbalance electrode for NH3 detection at room temperature

In this paper, composite film based on polyvinylpyrrolidone (PVP)/graphene oxide (GO) was fabricated by spray method on AT-cut 9.986 MHz quartz crystal microbalance (QCM) for NH₃ sensing. The thin films were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-VIS) to investigate the morphologies and the composition contents, respectively. The experimental results reveal that PVP/GO based sensor holds higher sensitivity, larger responsiveness and smaller baseline drift than those based on pure PVP at room temperature. Besides, the prepared sensor exhibits greater response to NH₃ than other gases such as CO, CO₂ and NO₂ at the same concentration. The good linearity, reproducibility and stability demonstrate the practicability of PVP/GO hybrid film in detecting NH₃.     

The mobility improvement of organic thin film transistors by introducing ZnO-nanrods as an zctive layer

Organic thin film transistors (OTFTs) based on poly(3-hexylthiophene) (P3HT)/Zinc oxide (ZnO) nanorods composite films as the active layers were prepared by spray-coating process. The OTFTs with P3HT/ZnO-nanorods composite films owned higher carriers mobility than the OTFT based on pure P3HT. It can be found that the mobility of OTFTs increased by 135% due to ZnO-nanorods doping. This was attributed to the improvement of the P3HT crystallinity and the optimization of polymer chains orientation. Meanwhile, because of the distinction of work function between P3HT and ZnO, the majority carriers would accumulate on either side of the P3HT-ZnO interface which benefited carrier transfer. The influence on the mobility of composite film was studied. In addition, the threshold voltage of devices changed positively with the increase of ZnO-nanorods due to the decrease of electrostatic potential for P3HT/ZnO-nanorods composite films. The effect could be explained by the energy level theory of semiconductor.     

An analysis of the correlation between the fluxes of high-energy electrons and low-middle-energy electrons in the magnetosphere

The variation of the flux of energetic electrons in the magnetosphere has been proven to be strongly related to the solar wind speed. Observations of GEO orbit show that the flux of low-energy electrons is not only modulated by the solar wind speed, but, if a time delay is added, is also positively correlated to the flux of high-energy electrons. This feature provides a possible method to forecast the flux of high-energy electrons in GEO orbit. In this study, the correlations of the fluxes between the high-energy electrons and low-middle-energy electrons obtained at different L values and in different orbits are investigated to develop the application of this feature. Based on the analysis of long–term data observed by NOAA POES and GOES, the correlations between the fluxes of high-energy electrons and low–middle–energy electrons are good enough at different L values and in different orbits in quiet time, but this correlation is strongly affected by CME–driven geomagnetic storms.     

High-efficiency pipeline design of binary arithmetic encoder

This paper focuses on the pipeline design of context-based adaptive binary arithmetic coding(CABAC).CABAC is a well-known bottleneck in very large scale integration circuit design of H.264/AVC encoder.Despite its high performance,the tight feedback loops of CABAC make parallelization difficult.Most researchers are concerned about multi-bin processing regardless of pipeline design.However,without pipeline,the overall performance becomes significantly limited.In this paper,the critical path for the hardware implementation of binary arithmetic encoder(BAE)was analyzed in detail.We break down the computing steps to the best extent,and rearrange such steps to the appropriate pipeline to achieve a balanced latency at each stage.Moreover,a new BAE architecture with a five-stage pipeline and one bin per cycle is proposed,the latency of critical path is substantially reduced,and the frequency and throughput rate are improved.An field-programmable gate array implementation of the proposed pipelined architecture in our H.264 encoder is capable of a 190 Mbps encoding rate.A maximum 483 MHz could be achieved on SMIC 0.13μm technology,which meets the requirements of quad full high-definition encoding at 30fps.The proposed architecture can be utilized in other designs to achieve improved performance.     

高温热电偶保护套管材料的研究

热电偶在工业生产和科学研究等领域中已成为应用最广泛的感温元件。热电偶保护套管材料的性能影响热电偶长期稳定性、使用寿命等各项性能指标。在高温下工作的热电偶,对其套管材料有更严格的要求。本文综述了高温热电偶保护套管材料的性能、分类及应用,阐述了高温熔体和高温流动粉体温度测量的难点和研究现状。     

基于Duolateral PSD的高精度光位置检测系统

精密机械加工业的发展对位置检测提出了更高的要求.Duolateral PSD(Position Sensitive Detector)克服了lateral PSD的测量错误率高、非线性严重等不足.系统实验的测量不确定度评定结果表明:基于Duolateral PSD的光位置测量系统具有位置分辨率高、测量精度高、性能稳定等特点,有广泛的应用前景.     

Experimental study of a micro-scale solar organic Rankine cycle system based on compound cylindrical Fresnel lens solar concentrator

In the present study, a micro-scale solar organic Rankine cycle power generation system was developed. The system comprises of a solar collection system based on compound cylindrical Fresnel lens concentrator and an organic Rankine cycle power generation system integrated with a scroll expander. YD320 and R245 fa were used as the heat transfer fluid and the working fluid, respectively. The effects of the evaporation pressure, the degree of superheat, and the mass flow rate of the working fluid were analyzed to evaluate the solar collection efficiency, the electric power output, the thermal efficiency and exergy efficiency of the system. The results illustrate that both the increasing evaporation pressure and decreasing superheat degree have positive impacts on solar collection efficiency. The electric power increases as the evaporation pressure increases, while the thermal efficiency and the exergy efficiency decrease. However, the system overall efficiency decreases slowly due to the increase of solar collection efficiency. The electric power increases with the increment of the working fluid mass flow rate. The increasing mass flow rate has no visible impact on the thermal and exergy efficiencies of organic Rankine cycle subsystem, whereas a slightly increase of the thermal and exergy efficiencies of the integrated system. The electric power decreases with the increase of the superheat degree, whereas the thermal and the exergy efficiencies of the system increase. The system works more suitably with a higher degree of superheat for the small mass flow rate condition.