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Accurate localization of a low-activity moving radiation source plays an important role in nuclear security and safety. The coded-aperture gamma camera is generally applied to detect a radiation source, but its reconstruction methods may have some limitations when the radiation source is motional and weak. The purpose of this paper is to improve the quality of the reconstruction images and the localization accuracy when detecting a low-activity moving radiation source with a gamma camera. The CLSTM-KF method consists of the CLSTM network and the Kalman filter. The CLSTM network is applied to improve the CNR of reconstruction images by making an adaptive superposition for sequential reconstruction images decoded by the correlation analysis method. After the CLSTM network, a series of sequential positions would be filtered by the Kalman filter. By comparing with the traditional methods of the gamma camera, the CLSTM-KF method performs well in improving both the CNR of reconstruction images and the localization accuracy. Moreover, the computation time of the CLSTM-KF method can also meet the application requirements. In summary, the CLSTM-KF method provides a better choice than the traditional methods in locating and tracking a low-activity moving radiation source.

Robotic CTs can achieve customized trajectory scanning with x-ray tube and detector held by flexible robotic arms rather than fixed rails or gantry. However, the motion errors of the robotic arms cannot be neglected. Hence, the reconstruction method of Robotic CTs should be suitable for arbitrary trajectory and should take motion errors into full consideration. In this paper, we present an iterative reconstruction method for robotic CT systems. Unlike the analytical algorithms, such as FDK, this method makes no assumption about the scan trajectory. The projection and backprojection operations are modeled by 3D distance-driven algorithm using the coordinates of x-ray source and detector center fed back from the robotic arm’s positioning system directly. Both numerical simulations and practical experiments are conducted to verify the effectiveness of this method in arbitrary trajectory reconstruction and motion errors correction for robotic CT systems. For our non-circular and non-planar trajectory scan, this proposed method could easily handle the reconstruction and obtain a result comparable to reference. In addition, for 0.1% motion errors, using the proposed method could improve the reconstruction quality, and the RMSE could be reduced by 30%. This iterative reconstruction method is suitable for arbitrary trajectory scans and can decrease the degradation of image quality caused by motion errors of robotic arm.

Fast neutrons and gamma-ray imaging detection is an effective way to detect and identify radioactive material in the field of nuclear security. A compact coded aperture imaging (CAI) camera was designed to be sensitive to both gamma and neutron radiation based on plastic scintillators and multi-pixel photon counters (MPPC). MPPCs coupling with the 13 × 13 pixelated plastic scintillators one-to-one were utilized to reduce the scale of the CAI system while maintaining good positional performance. The symmetric charge division (SCD) circuit was adopted to reduce the 169 signals output from the MPPC array to 26. Each waveform was collected and processed with four Domino Ring Sampler 4 (DRS4) chips and two 16-channel analog-to-digital converter (ADC) modules. As the pulse shapes of fast neutrons would be broadened after elastic scattering multiple times in the scintillators, the Anger-Logic method was applied to eliminate multiple elastic scattering events so that good pulse shape discrimination (PSD) performance can be achieved. The imaging and detection ability of the camera was evaluated using the 241Am-Be (5.9 × 105 n/s) neutron source and 137Cs (370 MBq) gamma source. The camera can be used to detect fast neutrons (0.5–10 MeV) and gamma rays (0.2–2.5 MeV). Furthermore, it can implement efficient neutron/gamma PSD capabilities in the mixed-field environment. The figure of merit (FOM) of the camera calculated at 400keVee energy cut is 0.93. A compact MPPC-based CAI camera was designed to detect and discriminate fast neutrons and gamma rays. Its good PSD performance was well suited to distinguish fast neutrons from gamma rays in a dual-particle environment. The portable design makes it promising for complex monitoring scenarios in nuclear security.

Compared to pixelated crystal detectors, monolithic crystal detectors present more advantages. Without reflective layer between crystal pixel, monolithic crystal detectors provide higher detection efficiency while being cheaper. Another important feature is that monolithic crystal detectors can provide depth of interaction (DOI) information, which can improve image quality in nuclear imaging systems. In this article, we aim to study a new positioning scheme of this kind of detector in order to push its applications in nuclear imaging systems. Fan-beam collimation and convolutional neural network are combined to reconstruct interaction points in crystal. Firstly, we built a monolithic detector model based on Geant4 and validated this positioning scheme with simulation data. Then, we constructed a monolithic GAGG(Ce) detector and evaluated its performance with experimental data. With proposed positioning scheme, in experiment, we obtained ~ 1.7 mm FWHM resolution on average in x-/y-direction, while ~ 2.5 mm FWHM resolution on average in DOI direction for a 33 × 33 × 10 mm3 monolithic GAGG(Ce) crystal coupled with 8 × 8 SiPM array. Through simulations and experiments, we validated our positioning scheme, i.e., fan-beam collimation and convolutional neural network. Convolutional neural network can reconstruct 3D positions of gamma-rays interaction points in a high resolution, and fan-beam collimation can provide high calibration efficiency; with combination of them, we established a high position resolution and high calibration efficiency positioning scheme for monolithic crystal detector.

This paper proposes an innovative procedure to improve an initial hydropower schedule by minimizing spillages in the short-term operation of multiple reservoir systems. This procedure is named as the field levelling (FL), which tries to eliminate scheduled spillages as much as possible by pushing forward and pulling backward the spillages in turn to explore spaces so as to absorb them, emulating the flied-levelling practice that pushes and pulls the protruding dirt in turn to find valleys to take it in. Even for a large-scale reservoir system, the procedure solves the problem very fast attributable to its stage-by-stage property. The procedure has the ability to handle the water travelling time between reservoirs and the nonlinearity in the optimization, and it is very useful in locally modifying an either feasible or infeasible scheduling solution to a feasible and satisfactory one. The model and procedure are applied to deal with the Yunnan provincial hydropower system that consists of 45 reservoirs. Start with a very good initial solution derived in our previous work, the present FL improves the solution by 0.58% and 1.34% reduction in water and energy spillages respectively.

This paper presents the technical measures used in the Yunnan electricity market to facilitate the trading mechanisms in ensuring energy trading and minimizing deviations from market contracts. A stochastic generation optimization model is proposed to tackle the generation variability of variable renewable energy in the market. A time-rolling model for checking consuming capability is presented to prevent energy imbalances induced by arbitrage from fictitious transactions by consumers from impeding system operation. Moreover, a set of congestion management methods accounting for transmission constraints in the interconnected grid and hydraulic coupling among cascade hydroplants are proposed to ensure safe grid operation and avoid unnecessary water spillages in cascade hydroplants. Furthermore, a series of measures related to contract deviations handling are presented to hedge market participants from much exposure to contract deviations and minimize deviation costs caused by failures to deliver the contracted energy in markets based on medium- and long-term transactions. Through three years of applications and improvements, the proposed measures are verified to be feasible and effective in improving market efficiency for ensuring energy trading, reducing deviation costs, promoting renewable energy integration, and facilitating low-carbon electricity development.

The Sulige gas field is the largest natural gas field in China so far. Using traditional mode to manage ten thousand wells is difficult. To meet the production requirement of intermittent and to implement fine management, technologies of remote well opening under pressure control based on electric needle valve in Sulige gas field are proposed in this paper. The existing manual operation needle valve at the wellhead was replaced with remote control equipment which had the function of opening or shutting in the well. Parameters can be pushed remotely via wireless system or set on-site. The built-in programs of the controller could simulate the manual operation of the well. Simultaneously, a system of data acquisition and transmission was installed at the well site. By the wireless communication system, data of the wells were uploaded to the upper computer of administration section, and the instruction of automatic intermittent could be issued there. Application and tests showed that the equipment and system of gas well automatic intermittent based on digital technology had a good applicability to the gas wells of Sulige gas field. The mode of manual intermittent could be substituted, and fine management of the gas well could be achieved.

Uranium enrichment measurement is an essential quality inspection for fuel rods before delivery to users. Generally, compared with active neutron assay (ANA) equipment, passive gamma-ray assay (PGA) equipment is more economical and safer. However, the current PGA equipment based on photomultipliers is too slow (1 m/min) to meet the growing needs in China. Recently, we have developed a set of compact high-speed PGA equipment including four detection modules (128 units in total), a 128-channel data acquisition system (DAS), a power supply, special software, and an automatic loading and unloading mechanism. The detection unit is based on silicon photomultipliers in virtue of its compact size and good performance. The DAS processes signals of all units in parallel into a sequence of data packets carrying the energy information and the corresponding unit ID. The software integrates the data packets into a fluctuating count curve in a time-delay superposition method and identifies possible abnormal pellets. After calibrations, our equipment can locate abnormal pellets accurately at a speed of 6 m/min. In addition, it can directly measure the enrichment of fresh pellets not in secular equilibrium without waiting for two months. So far, the equipment has been successfully run for one year on the assembly line of China North Nuclear Fuel Co. and shows good potential to replace the traditional ANA equipment.

A self-supporting, 2-D, time-encoded aperture system was developed for both gamma and neutron imaging. The system achieved high sensitivity for imaging due to the use of an M–P array which has flat sidelobes of cross-correlation reconstruction and is self-supporting. It is demonstrated that a 24.4 μ Ci 137 Cs radiological point source could be detected within 10 min when the source-to-background ratio is 1:1. Several radiation scenes support that the system has an imaging capability of multipoint, extended, and gamma/neutron discrimination sources. The features of good cross-correlation decoding properties, panoramic imaging, and rapid reconstruction make such a system design attractive and prospective for the localization of radioactive hot spots.

Because of the intermittent, volatility and randomness features of wind power, the flexibility of integrated energy system and the energy conversion ability between power system and natural gas system is an essential condition to consume large scale wind power. Since CHP (combined heat and power) unit and GF (gas furnace) are widely used and P2G (power to gas) technology is introduced, it had a great effect on different types of energy services, including electricity, gas, and heat. This paper puts forward an integrated energy system expansion planning model considering the coupling of power system, gas system and thermal system during the planning period. Based on the curve of load duration and wind intensities, by using scenario method to illustrate the uncertainty of wind power and load, then a mathematical model for dynamic coupling between gas and electricity of integrated energy planning that can consider wind power, P2G and CHP unit at the same time is built. The model minimize the investment cost and operation cost during planning period, which is constrained by operation safety and coupling relationship of power system and gas system, determining the optimal planning scheme for wind turbines, coal-fired units, transmission lines, gas transmission lines, CHP, GF, P2G. In order to achieve a balance between efficiency and precision, a series of linearization method is adopted to solve the model. Simplified mathematical model is a mixed integer linear programming model, which is programmed on GAMS software and call on CPLEX solver to solve the model. 6 nodes gas and electricity coupling test system is utilized to analyze and compare the cases. Case studies validate the effectiveness and superiority of the model in the paper.

To promote the orderly development and full utilization of hydro and wind power under the market competition circumstances, this paper presents an analysis study conducted on the complementary operation characteristic of hydro and wind power in Yunnan electricity market. First, the features of hydro and wind power resources in Yunnan are described. Then, according to the power source structure and supply and demand situation in Yunnan electricity market, hydro and wind power output characteristic, wind power generation cluster effect, complementary operation characteristic of hydro and wind power as well as the problems of renewable energies integration and development planning are further studied. The result of the analysis study not only demonstrates that hydro and wind power have considerable complementarities annually and monthly and joint operation could smooth the wind power output for the power grid to promote the renewable energies integration, but offers consults for electricity industry restructuring and market reform, power grid planning and operation, and the coordinated development of power producers and grids as well.

Aiming at the problems such as unclear price signals and insufficient competition in the current power market, a deep game bidding model for supply and demand sides is proposed based on the listing trading mechanism. Supply and demand sides both list and delist within the limits of price through three stages including information publicity, power plants listing and power consumers delisting, power consumers listing and power plants delisting, then electricity prices are cleared according to the delisting price. The accumulated delisting capacity limit is unconstrained. By optimizing the order of transactions in the two trading phases, the publicity volume of market participants is taken as the upper limit of the transaction volume of the entire two-way listing transaction. Flow charts of the transaction organization and the market clearing calculation method are also given. Not only can the bidding model stimulate the reasonable offer of both supply and demand, but also it can realize the organic cooperation of trading price and amount, reduce trading risk, expand trading power and improve the efficiency of resource allocation. The operation of the Yunnan electricity market has confirmed the rationality, effectiveness and practicability of the bidding model.

In this paper, we present a descent image based extraterrestrial terrain reconstruction technology, which has been successfully applied in China's first soft landing Chang'E-3 mission on moon. When scouting on the moon surface, the lunar rover (Jade Rabbit rover) requires reliable terrain information for navigation and positioning tasks. The descent image sequence acts as a link between the orbital images and the surface images. The proposed approach collects multilevel descent images, as well as inertial information from an inertial measurement unit and surface stereo vision information, to generalise a consistent surface model. A data fusion strategy is proposed to track the camera trajectory, and refined plane sweep stereo matching and 3D alignment technologies are analysed in this article. The onboard result, as well as on-earth simulation experiments, has shown that the discussed techniques are reliable to reconstruct the terrain information for the lunar rover's localisation and navigation.

This paper reviews the electricity market reforms improving resource allocation and renewable energy integration in Yunnan. Given the predominance of hydropower and the importance of energy exports in Yunnan, the province presents a challenging case study of electricity market reforms. The experience of and lessons from Yunnan provide a reference for other provinces in China engaged in the growing adoption of renewable energy. The main contributions of this paper lie in the extension of the existing understanding of electricity reforms in Yunnan and China. Based on extensive data previously unreported in the literature, this paper shows how the Yunnan electricity market functions in practice and indicates where the practice is deficient in terms of the theory of how electricity markets should function. Finally, this paper suggests how market reforms should be adopted toward a scientifically designed electricity market.

A PET module that comprises a pair of compact, high-resolution and large-area detectors based on silicon photomultipliers (SiPM) was developed and evaluated. The detector's effective area was 24 mm x 24 mm. LYSO crystals measuring 1.9 mm x 1.9 mm x 10 mm and charge division circuit were employed to obtain high spatial resolution with relatively concise Front-end electronics (FEE). Initial results showed the detector to be compatible with 1.5 T magnetic fields. The system's intrinsic FWHM spatial resolution is 1.50 mm. The average energy resolution is 18.5% and the coincidence timing resolution is 2.6 ns. (C) 2011 Elsevier B.V. All rights reserved.

In this work we studied the feasibility of detecting the depth of interaction (DOI) with two layers of crystal arrays of LYSO and BGO scintillators coupled to a position-sensitive photomultiplier tube (PS-PMT) R8900-C12. A front-end electronics was designed, with which we got different pulse shapes for different crystals to obtain depth information. With the double integration method, we got the DOI histogram of a divided integration ratio of two crystals as the standard to determine the layer-of-interaction. The DOI accuracy, measured by scanning a 22Na slit source along the side of the module, was 98% for the LYSO layer and 95% for the BGO layer. The energy resolution at 511keV was 13.1% for LYSO and 17.1% for BGO. We obtained good crystal separation in 2D position histograms of both layers. These results could be useful in the manufacture of PET scanners with high spatial resolutions.

We report on tests of combined positron emission tomography (PET) and fluorescence molecular tomography (FMT) imaging system for in vivo investigation on small animals. A nude mouse was inoculated with MD-MB-231 breast cancer cells which expressed red fluorescent protein (RFP). For FMT system, reflective illumination mode was adopted with full-angle data acquisition. [18F]-Fluorodeoxyglucose ([18F]-FDG) was used as radioactive tracer for PET. Both data were acquired simultaneously and then reconstructed separately before fusion. Fluorescent tomography results showed exactly where the tumor was located while PET results offered more metabolic information. Results confirmed feasibility for tumor detection and showed superiority to single modality imaging.

PET/MR is a new multi-modality imaging system which provide both structural and functional information with good soft tissue imaging ability and no ionizing radiation. In recent years, PET/MR is under major progress because of the development of silicon photomultipliers (SiPM). The goal of this study is to develop a MRI compatible PET insert based on SiPM and LYSO scintillator. The PET system was constituted by the detector ring, electronics and software. The detector ring consists of 16 detector module. The inner diameter of the ring was 151 mm, the external diameter was 216 mm, which was big enough for small animal research, e.g. rat, rabbit and tupaia. The sensor of each module was 2*2 SensL SPMArraySL, coupled with an array of 14 x 14 LYSO crystals, each crystal measuring 2 mm x 2 mm 10 mm. The detector was encapsulated in a copper box for light and magnetic shielding. Resister charge multiplexing circuit was used in the front end electronics. Each detector output 8X and 8Y position signals. One summed timing signal was extracted from the common cathode of all 64 channels. All these signals were transmitted to digital electronic board by a 3 m long coaxial cable from inside of the MR to the outside. Each digital electronic board handled 8 detector modules based on FPGA to obtain the timing, position and energy information of a single event. And then these single events were sent to the coincidence processing board to produce coincidence packets which are prepared for further processing. A 0.2mCi 68Ge line source was used to do the preliminary imaging test. The image was reconstructed by 3D-OSEM algorithm. The initial result proved the system to be feasible as a PET. FDG phantom imaging and simultaneous PET/MR imaging are in progress.

Gas well head pressure sensors are the important front-end equipments of digitalizatio n construction of Changqing oil field. Foreign pressure sensors are once relied on for a long time there. A problem urgent to be solved of digitalizatio n construction is to develope pressure sensors with independent intellectual property and with integrated advantages of high precision, high stability, high reliability and wide temperature range. This paper introduced the development of a kind of pressure sensor based on technology of sputtered thin film and method of micro-machini ng. Design and manufacture of the pressure-sensitive element are introduced, which are comprised of elastic body, insulating film, wire grid etc. Meanwhile, tests and experiments are developed. The pressure sensors this paper developed possess the merits of high precision, high stability, and could meet the long term pressure testing requirements of oil and gas field.

Purpose To automatically extract regions of interest (ROIs) and simultaneously preserve the anatomical characteristics of each individual, we developed a new atlas-based method utilizing a pair of coregistered brain template and digital atlas. Materials and Methods Unlike the previous atlas-based method, this method treats each individual as the target image, and the template and atlas are each transformed to register with the individual. To evaluate the accuracy of this method we implemented it in extracting the hippocampus from two groups of T2-weighted structural images with different spatial resolutions and a group of T2*-weighted functional images. Furthermore, the results were compared against a manually segmented hippocampus and an atlas-derived hippocampus. Results Jaccard similarity (JS) reached 84.7%–90.5%, and relative error in volume (RV) was 4.8%–12.7%. The consistency observed between the results of the proposed method and manual drawing was therefore considerable. Conclusion We developed a new atlas-based method for ROI extraction that can automatically extract ROI and simultaneously preserve each individual's unique anatomical characteristics. J. Magn. Reson. Imaging 2010;32:830–835. © 2010 Wiley-Liss, Inc.

Simultaneous positron emission tomography (PET) and fluorescence tomography (FT) for in vivo imaging of small animals is proposed by a dual-modality system. This system combines a charge-coupled device-based near-infrared fluorescence imaging with a planar detector pair-based PET. With [18F]-2-fluoro-2-deoxy-d-glucose radioactive tracer and the protease activated fluorescence probe, on the one hand, the simultaneous metabolic activity and protease activity in tumor region are revealed by the PET and FT, respectively. On the other hand, the protease activity both on the surface layer and the deep tissue of the tumor is provided by the fluorescence reflection imaging and FT, respectively.