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Traditional remote sensing observation can only derive chlorophyll-a concentration in surface water (Chlasurf), which is insufficient for water quality monitoring or biogeochemical applications. In this paper, a column-integrated biomass (CIB) estimation algorithm was established in Lake Dianchi, China, and the CIB was estimated by Ocean and Land Color Instrument (OLCI) data from 2016 to 2018. First, the results show that the method is applicable to CIB estimation in nonbloom conditions [mean absolute percentage error (MAPE) = 10.55%, mean ratio (MR) = 0.996]. On the one hand, Chlasurf could be estimated using a universal model of Chla (UMOC) estimation for case-II waters; on the other hand, CIB could be obtained from Chlasurf according to the linear relationship between the Chlasurf and CIB. Second, both the spatial and temporal variabilities of Chlasurf are larger than those of CIB, which indicates that the biomass of the whole lake is relatively stable from day to day. During algal bloom periods, the CIB at nonbloom areas tends to decrease, suggesting that algae from nonbloom regions have migrated to bloom regions. Third, wind speed (WS) is the most critical meteorological factor affecting the water surface biomass, compared with other parameters. The average percentage of surface-to-total biomass in nonbloom conditions is about 7% when the WS is less than 2 m/s. [ABSTRACT FROM AUTHOR]

Understanding and predicting cellular traffic at large-scale and fine-granularity is beneficial and valuable to mobile users, wireless carriers, and city authorities. Predicting cellular traffic in modern metropolis is particularly challenging because of the tremendous temporal and spatial dynamics introduced by diverse user Internet behaviors and frequent user mobility citywide. In this paper, we characterize and investigate the root causes of such dynamics in cellular traffic through a big cellular usage dataset covering 1.5 million users and 5,929 cell towers in a major city of China. We reveal intensive spatio-temporal dependency even among distant cell towers, which is largely overlooked in previous works. To explicitly characterize and effectively model the spatio-temporal dependency of urban cellular traffic, we propose a novel decomposition of in-cell and inter-cell data traffic, and apply a graph-based deep learning approach to accurate cellular traffic prediction. Experimental results demonstrate that our method consistently outperforms the state-of-the-art time-series based approaches and we also show through an example study how the decomposition of cellular traffic can be used for event inference. [ABSTRACT FROM AUTHOR]

After entering the big data era, a new term of 'big knowledge' has been coined to deal with challenges in mining a mass of knowledge from big data. While researchers used to explore the basic characteristics of big data, we have not seen any studies on the general and essential properties of big knowledge. To fill this gap, this paper studies the concepts of big knowledge, big-knowledge system, and big-knowledge engineering. Ten massiveness characteristics for big knowledge and big-knowledge systems, including massive concepts, connectedness, clean data resources, cases, confidence, capabilities, cumulativeness, concerns, consistency, and completeness, are defined and explored. Based on these characteristics, a comprehensive investigation is conducted on some large-scale knowledge engineering projects, including the Fifth Comprehensive Traffic Survey in Shanghai, the China's Xia-Shang-Zhou Chronology Project, the Troy and Trojan War Project, and the International Human Genome Project, as well as the online free encyclopedia Wikipedia. We also investigate the recent research efforts on knowledge graphs, where they are analyzed to determine which ones can be considered as big knowledge and big-knowledge systems. Further, a definition of big-knowledge engineering and its life cycle paradigm is presented. All of these projects are accordingly checked to determine whether they belong to big-knowledge engineering projects. Finally, the perspectives of big knowledge research are discussed. [ABSTRACT FROM AUTHOR]

In recent years, bike-sharing systems have been widely deployed in many big cities, which provide an economical and healthy lifestyle. With the prevalence of bike-sharing systems, a lot of companies join the bike-sharing market, leading to increasingly fierce competition. To be competitive, bike-sharing companies and app developers need to make strategic decisions and predict the popularity of bike-sharing apps. However, existing works mostly focus on predicting the popularity of a single app, the popularity contest among different apps has not been explored yet. In this paper, we aim to forecast the popularity contest between Mobike and Ofo, two most popular bike-sharing apps in China. We develop CompetitiveBike, a system to predict the popularity contest among bike-sharing apps leveraging multi-source data. We extract two novel types of features: coarse-grained and fine-grained competitive features, and utilize Random Forest model to forecast the future competitiveness. In addition, we view mobile apps competition as a long-term event and generate the event storyline to enrich our competitive analysis. We collect data about two bike-sharing apps and two food ordering & delivery apps from 11 app stores and Sina Weibo, implement extensive experimental studies, and the results demonstrate the effectiveness and generality of our approach. [ABSTRACT FROM AUTHOR]

This paper proposes a resilience enhancement strategy for power transmission system against ice storms by the optimal coordination of power system schedule with the pre-positioning and routing of mobile dc de-icing devices (MDIDs). A two-stage robust optimization model is established to accommodate the variable ice thickness on transmission lines. The first stage coordinates the pre-positioned MDIDs and unit commitment in day-ahead. These decisions, which are based on a robust approach, can accommodate the variable ice thickness in which the coordinated real-time schedule would always be feasible with respect to day-ahead decisions. At the second stage, the real-time operation, which integrates the power system dispatch, de-icing schedule, and MDID routing, is scheduled according to the real-time ice thickness. Auxiliary variables are adopted to convert the proposed nonconvex nonlinear model to a mixed-integer second-order cone programming (MISOCP) problem. The nested column-and-constraint generation algorithm is utilized to solve the two-stage robust MISOCP problem. Several computational enhancement strategies including Lagrangian relaxation are proposed to improve the performance of the proposed resilience enhancement strategy. Numerical results for an integrated 6-bus 6-node electricity-road network and a real-world example employed in China show the effectiveness of the proposed model and solution technique for enhancing the transmission grid resilience. [ABSTRACT FROM AUTHOR]

Convergence service (CS), which integrates broadband and broadcast services, is considered promising in bridging the gap between scarce bandwidth and user demands for real-time, immersive, and super high-quality service in a ubiquitous environment. However, many urgent issues remain to be tackled in media transport system (MTS) to support CS. In this paper, the challenges MTS would entail over a heterogeneous network to diverse users are first analyzed. The architecture and functionalities of the smart media transport (SMT) system are then advocated and reviewed. Several key technologies in the SMT system, including hierarchical media-aware data model for content encapsulation, context-aware data protection mechanism for reliable transmission, and media synchronization control based on network condition estimation, are discussed. Field trial results on campus for certain CS are provided to validate the system design and illustrate the performance of the SMT system. [ABSTRACT FROM AUTHOR]

Due to its brief form and growing popularity, microblogging is becoming people’s favorite choice for seeking information and expressing opinions. Messages received by a user mainly depend on whom the user follows. Thus, recommending users with similar interests may improve the experience quality for information receiving. Since messages posted by microblogging users reflect their interests, and the keywords in the messages indicate their main focus to a large extent, we can discover users’ preferences by analyzing the user-generated contents. Moreover, users’ interests are not static, on the contrary, they change as time goes by. Based on such intuitions, in this paper, we propose a temporal-topic model to analyze users’ possible behaviors and predict their potential friends in microblogging. The model learns users’ latent preferences by extracting keywords on aggregated messages over a period of time via a topic model, and then the impact of time is considered to deal with interest drifts. The experimental results of friend recommendations on Sina Weibo, one of the most popular microblogging sites in China, have demonstrated the effectiveness of our model. [ABSTRACT FROM AUTHOR]

Due to the uneven geographical distribution between load and wind power, currently it is difficult to integrate the large-scale wind power into the State Grid in China. There are significant wind curtailments for wind farms due to system restrictions. This paper proposes a new way of utilizing wind power, i.e., in-situ consumption, as an alternative to the costly development of long-distance transmission of large-scale wind power. Electrolytic aluminum load, which is one of the most typical high energy consuming loads, is employed to absorb the excess wind power in western China. An actual isolated industrial power system for aluminum production driven by wind power and coal-fired power is described. The penetration level of wind power in the isolated power system is up to 48.8%. The power imbalance between generation and load demand caused by wind power fluctuation or the tripping of coal-fired generators can dramatically impact the frequency stability of the isolated power system, which is of small inertia. An online identification method of power imbalance based on Wide Area Measurement System (WAMS) is presented. According to the characteristics of the electrolytic aluminum load, a system frequency control method by regulating the bus voltages of aluminum loads to eliminate the power imbalance is introduced. The simulation is done in Real Time Digital Simulator (RTDS) and the results verify the validity of the proposed frequency control method. [ABSTRACT FROM PUBLISHER]

High-frequency harmonic resonance has occurred frequently in the traction power-supply system (TPSS) when high-speed trains that are equipped with pulsewidth-modulation converters were serviced in the China High-Speed Railway (HSR). This phenomenon can result in serious voltage distortion, overheating of electrical components, and electromagnetic interference (EMI) of communication circuits. In order to address this issue, a complete mathematical model of the 2\,\times\,27.5-kV ac railway system, by means of the nodal admittance matrix, is presented to attain equal modeling of TPSS and modern train for harmonic studies in this paper. The impact of the train on resonance behavior of TPSS by employing resonance-mode assessment and modal sensitivity analysis are investigated. Finally, numerical simulation results using the presented model are compared to measurements results of the China HSR to verify the accuracy of the TPSS model and Norton model of the train, and proved that the method of resonance frequency shifts described is doable. The comparison results illustrate that the proposed model and harmonic resonance assessment can be useful for determining and mitigating the harmonic resonance problems in TPSS as well as the power system. [ABSTRACT FROM AUTHOR]

The IEEE Communications Society Harbin Chapter, PRC, was founded on 24 February, 2012. It has already been two years since approval. In the past year we have held many activities to make our community life much more colorful and acquire something that cannot be learned outside the activities at the same time. The activities are presented as follows. [ABSTRACT FROM AUTHOR]

This paper develops a methodology for optimizing the hydro unit commitment (HUC) for the Three Gorges Project (TGP) in China. The TGP is the world's largest and most complex hydropower system in operation. The objective is to minimize the total operational cost. The decision variables are the startup or shutdown of each of the available units in the system and the power releases from the online units. The mathematical formulation must take into account the head variation over the operation periods as the net head changes from hour to hour and affects power generation. Additionally, the formulation must consider the operation of 32 heterogeneous generating units and the nonlinear power generation function of each unit. A three-dimensional interpolation technique is used to accurately represent the nonlinear power generation function of each individual unit, taking into account the time-varying head as well as the non-smooth limitations for power output and power release. With the aid of integer variables that represent the on/off and operation partition statuses of a unit, the developed HUC model for the TGP conforms to a standard mixed integer linear programming (MILP) formulation. We demonstrate the performance and utility of the model by analyzing the results from several scenarios for the TGP. [ABSTRACT FROM PUBLISHER]

Train stations are one of the largest and most unavoidable obstructions for electromagnetic wave propagation on a high-speed railway. They can bring about severe extra propagation loss, and therefore, lead to poor coverage or handover failure. However, their influence has been rarely investigated before. Based on rich experimental results of 930 MHz measurements conducted on train stations of high-speed railway in China, this paper proposes two empirical models for the extra propagation loss owing to train stations for the first time. The extra loss depends on four conditions: the distance between the transmitter (Tx) and the train station, the type of the train station, the track carrying the train, and the propagation mechanism zones. Hence, the models are established for every case of all the combinations of these four conditions. The validation shows that the proposed models accurately predict the extra propagation loss and support an effective way to involve the influence of the train station in the simulation and design of the signaling and train control communications systems. [ABSTRACT FROM PUBLISHER]

This paper describes the evolution of picture archiving and communication systems (PACS) in China and identifies several obstacles to its development, including vendors' opportunism, hospital administrators' IT ignorance, mindlessness in IT adoption, lack of system integration, and misfits between foreign PACS and local hospitals. Lessons learned from these obstacles are provided, which are of value to developing countries where PACS has just started diffusing. [ABSTRACT FROM AUTHOR]

Drawing on new institutional economics and the innovation literature, this paper examines how subnational institutions can impact corporate research and development (R&D) investment in emerging economies. The study further investigates a key contingency of this institutional effect: a firm's country/ownership identity. Using China's pharmaceutical sector as the empirical context, we find that the quality of subnational institutions, such as the degree of government deregulation and the effectiveness of local contracting institutions, has a significantly positive impact on corporate R&D intensity. Moreover, this institutional effect is more salient in indigenous firms and international joint ventures than in wholly owned foreign subsidiaries. This study serves to shed light on future research on how multifaceted subnational institutions shape innovation activities across different types of business organizations in emerging economies. [ABSTRACT FROM AUTHOR]

A higher magnetic field can provide more opportunities to reveal new phenomena in a scientific research. Aiming to achieve a higher magnetic field, Wuhan National High Magnetic Field Center (WHMFC), Wuhan, China has designed a a power supply system for 100 T magnetic field under existing power supply conditions in April 2015. The 100 T magnet consisting of three coils is energized by a multipower supply system. The outer coil is energized by a pulsed generator-rectifier connected to battery bank in series. The middle coil and the inner coil are energized by two capacitor bank, respectively. To ensure safety and reliable operation, control sequence as well as protection system for the power system is designed and developed. A test system including the prototype of three-coil magnet is established at WHMFC. A series of tests are carried out on hybrid power supply systems. 73.3 T peak field has been achieved as the highest magnetic field in the test. The test results presented in this paper show the hybrid power supply system is feasible and operable. [ABSTRACT FROM AUTHOR]

With the largest installed capacity in the world, wind power in China is experiencing a ∼20% curtailment. The inflexible combined heat and power (CHP) has been recognized as the major barrier for integrating the wind source. The approach to reconcile the conflict between inflexible CHP units and variable wind power in Chinese energy system is yet unclear. This paper explores the technical and economic feasibility of deploying the heat storage tanks and electric boilers under typical power grids and practical operational regulations. A mixed integer linear optimization model is proposed to simulate an integrated power and heating energy systems, including a CHP model capable of accounting for the commitment decisions and nonconvex energy generation constraints. The model is applied to simulate a regional energy system (Jing–Jin–Tang) covering 100-million population, with hourly resolution over a year, incorporating actual data, and operational regulations. The results project an accelerating increase in wind curtailment rate at elevated wind penetration. Investment for wind breaks even at 14% wind penetration. At such penetration, the electric boiler (with heat storage) is effective in reducing wind curtailment. The investment in electric boilers is justified on a social economic basis, but the revenues for different stakeholders are not distributed evenly. [ABSTRACT FROM AUTHOR]

In order to solve the frequently occurring lightning flashover problems on ±500 kV dc transmission lines in China, the authors have conducted the research on the dc line arrester since 2011. In this paper, the structure and installation, technical parameters, and protection performances, as well as their deterministic processes of the arrester are presented and analyzed in detail. In 2013, the authors successfully developed the arrester products, and the type tests show that they have excellent performance parameters and can act effectively against the lightning impulse and cutoff the dc follow current. By now more than 500 dc line arresters have been installed and used on seven ±500 kV dc transmission lines in eight provinces of China. About four years of operating experience shows that the arresters work safely and reliably over a long period of time, and have been effectively reducing the lightning flashover rate of the ±500 kV dc lines. [ABSTRACT FROM PUBLISHER]

This paper presents a novel emergency damping control (EDC) to suppress inter-area oscillations occurred as anticipated low-probability cases in power system operations. The proposed EDC combines the event-driven and response-based control strategy. It is tested and evaluated in a standard power system and a real large-scale power system in China to compute the optimal location, amount and applying time of generator decreasing and load shedding in order to suppress inter-area oscillations. Test simulation results have demonstrated and validated the effectiveness of the proposed EDC scheme. [ABSTRACT FROM PUBLISHER]

In this paper, we aim to analyze the impact of dc transmission on self-organized criticality (SOC) of the East China power system (ECPS), which is a large-scale, ac–dc interconnected and classical receiving-end power system. To this end, a detailed ac–dc cascading failure analysis model is established to study the SOC of this system. In the proposed model, some important issues of dc transmission and several kinds of stochastic factors are considered. The corresponding algorithm realized on the platform of the PSS/E software is discussed as well. Simulation based on the 2010 East China ac–dc power system is performed and the following results are obtained: 1) the dc issues such as the operation modes and the control parameters have obvious effects on the SOC of the ac–dc system and 2) the risk of cascading failure and blackout can be decreased by deliberately choosing the dc operation modes and control parameters. [ABSTRACT FROM PUBLISHER]

The standard waveform of switching impulse is important for insulation tests of air gaps as well as external insulation and inner insulation of power apparatus in the power system, which should be consistent with the waveforms in actual power systems. Different definitions of waveform parameters of standard switching impulse are discussed in this paper, and a definition based on breakdown characteristics of air gaps is suggested to obtain the front times. Waveform parameters of switching overvoltages in two 1000-kV ultra-high voltage systems in China are studied and their statistical regularities under different operation conditions are analyzed. Based on the breakdown characteristics of air gaps and the concept of equivalent insulation performance, the typical front times in the system are obtained by a weighted average method. [ABSTRACT FROM PUBLISHER]

This paper reviews developments in high-altitude electromagnetic pulse (HEMP) research in China in recent decades. The main contents are obtained from a literature survey of technical papers published in the past years, which include HEMP simulators and test systems, coupling analysis methods and results, experimental research on the susceptibility of electronic equipment, time-domain measurement, and modeling technology. [ABSTRACT FROM AUTHOR]

This paper reports on a 10-year case study at a Chinese university of a faculty team's attempt to develop and disseminate a project-based computer-assisted language learning (CALL) program for professional communication. The discussion focuses on three main challenges (professional/academic values, pedagogical philosophy, and institutional culture) to expand a project-based CALL program at this university. Based on the findings, this paper discusses how the implementation of project-based CALL for professional communication needs to be founded upon a good understanding of China's sociocultural contexts and how it might be tailored in order to be more responsive to the local university context. This paper concludes by suggesting a path that practitioners might take in light of these circumstances and challenges. [ABSTRACT FROM PUBLISHER]

When adopting transmit diversity in the Chinese digital television terrestrial broadcasting (DTTB) system, there exists two kinds of interference: training sequences (TSs) from different transmit antennas are overlapped; and the TSs are interfered with OFDM data due to multipath fading. In order to distinguish different TSs, this paper proposes a method to design orthogonal TS set, which also have good correlation characteristic. Subsequently, an iterative algorithm to eliminate the interference between TSs and data is proposed and theoretically analyzed. Finally, simulations are performed and the results show that the system with the proposed scheme can achieve great diversity gain under acceptable computational complexity. [ABSTRACT FROM PUBLISHER]

University ties are an important innovation resource for both foreign direct investment (FDI) firms and local firms. Since these university connections involve local personal ties, which are established through long-term efforts that require social and cultural embeddedness, it is probably more difficult for FDI firms to establish such ties than it is for local firms. However, FDI firms, which have two advantages, size and R&D capacity, can possibly compensate for that disadvantage. This paper contributes to the current innovation and international business literature by comparing the effect of university ties on innovation between local firms and FDI firms due to their heterogeneous resources and capabilities. Specifically, this paper examines the joint influence of university ties, R&D capacity, and firm size in both FDI firms and local firms in China. The results show that R&D capacity and firm size have different moderating effects on FDI firms and local firms, suggesting that internal capability and external personal relationship with universities are substitutes in local firms but complementary in FDI firms. Our results are relevant for practicing managers because they show that acquiring the knowledge in universities is contingent on firm characteristics as well as ownership types. [ABSTRACT FROM PUBLISHER]

This paper describes a design method of a leaf spring using a genetic algorithm. To avoid disconnected shape, a novel genetic representation which contains travel points and their order is proposed. A two-stage search is performed to improve the convergence and compared with the single stage search. To demonstrate the proposed method, it is applied to a leaf spring for an optical disc drive (ODD) actuator. The final result of the genetic algorithm has unnecessary parts, and thus manual mending process is needed. The obtained design of the leaf spring satisfies the required specification. The proposed design method is very simple, and hence it is expected that the proposed design method can be easily applied to other applications. [ABSTRACT FROM AUTHOR]

With the decision to construct the smart grids around China, the power line communications (PLC) on the low-voltage (LV) distribution networks have become one of the potential technologies to commute the information between the end users and the power provider. In order to provide communications services with different priorities under the smart grids environment, it is a must to design a completely new PLC system with variable information rate, which means understanding of the LV PLC channel characteristics become vital. This paper presents the measurement results of channel properties of LV PLC systems after giving a general overview of the topologies for the typical LV distribution networks in China. The testing results show that the main reason influencing the reliable communication of high-speed data of power line is the attenuation of the high-frequency signal, which exhibits more obviously in the branch of power line. It is almost impossible to use the frequency range from 10 to 20 MHz for the reliable communications from distribution transformer to end user, so it must be solved with the aid of such means as the repeater and the modulation schemes. Considering the signal's attenuation, the lower frequency range from 2 to 10 MHz is more suitable for the high-speed data access system. Based on the general topologies of the LV distribution networks, a new method with the help of the reflection matrix based on the multiconductor transmission line theory is proposed to model the channel transfer functions, taking into account of the source inner impedance matrix. The simulation results fit the measured data quite well and verify the feasibility of the proposed modeling scheme. [ABSTRACT FROM AUTHOR]

The author provides information on the "Antenna Measurement Techniques Association Corner" column. He announces a new paper related to the NASA return-to-flight work, a topic of general interest to the AP-S Magazine readership. He also provides information on the Air Force Research Laboratory Mobile Diagnostic Laboratory deployed to China Lake to measure the dynamic scattering and signature contribution of the Booster Separation Motor rocket plumes.

According to the four spectra of a cloud-to-ground lightning discharge, channels have been captured by a slitless spectrograph in Qinghai and Tibet plateau, the electrical conductivities are calculated, and, for the first time, the electron thermal conductivities and the electron thermal diffusivities are calculated by applying the transport theory of air plasma to the lightning channels. The results are compared with existing values, and in general, they are in satisfactory agreement. These transport characteristic parameters have added important value for further research on the transport characteristic of the current and energy of the lightning discharge channel. [ABSTRACT FROM AUTHOR]

Existing literature argues, in general terms, that China has a growing need for technical communication and technical communication education. Following up on these studies, this paper more closely examines China's needs for technical communication education. Based on interviews with industry professionals and reviews of their writing samples, this paper seeks to find out who among the industry professionals in China needs technical communication, what their communication practices are, the areas in which they need education, and what US technical communication professionals can do to help develop this education. Preliminary findings and suggestions as well as topics for future research are presented. [ABSTRACT FROM AUTHOR]

CYCIAE-100, a 100 MeV H-cyclotron under construction at China Institute of Atomic Energy, is a compact H-cyclotron. Since its upper/bottom and return yokes are each made of a casting steel of large dimension (with final dimension of 6160 mm in diameter and weight of 140 tons each piece), special attention has to be paid to the annealing procedure to insure the magnetic properties of this kind of large scale casting steel pieces with high purity. First, this paper presents an overview of annealing strategies to improve the magnetic properties of large scale casting steel. Then an estimation of heating time during annealing procedure has been made by FEM simulation based on the current status of annealing facility in China and has been indirectly verified by a rule of thumb from the results in TRIUMF design note. Based on that as well as on a close collaboration with CITIC HMC, the manufacturer of large casting steel mill, an agreement on detailed annealing procedure has been reached and issued for production of large casting steel for CYCIAE-100. The results from the practice have been obtained and the detail procedure will be presented in this paper as well. [ABSTRACT FROM AUTHOR]

Climate change poses a huge threat to human welfare. Hence, developing a low-carbon economy has become a prevailing and inevitable trend. Decarbonization of power generation, especially converting the current power mix into a low-carbon structure, will be a critical option for CO2 emission mitigation. In this paper, an integrated power generation expansion (PGE) planning model towards low-carbon economy is proposed, which properly integrates and formulates the impacts of various low-carbon factors on PGE models. In order to adapt to the characteristics of PGE models based on low-carbon scenario, a compromised modeling approach is presented, which reasonably decreases complexities of the model, while properly keeping the significant elements and maintaining moderate precision degree. In order to illustrate the proposed model and approach, a numerical case is studied based on the background of China's power sector, making decisions on the optimal PGE plans and revealing the prospects and potentials for CO2 emission reduction. [ABSTRACT FROM AUTHOR]

Ice melting with dc is one of the key technologies to prevent the Chinese power grid from ice storms. Especially after the severe ice storm in the southern part of China in early 2008, dc ice-melting technology has drawn more attention than ever before. However, there are few satisfactory methods to select correct parameters so the ice-melting project rarely achieves desired effects in some cases when applied in Hunan, Guizhou, and other provinces in China. Therefore, it is of great significance to develop a method to estimate parameters which is applicable in the practical situation for dc ice melting. To handle this, the factors, such as wind velocity, ambient temperature, current density and ice-layer thickness were analyzed and then a dc ice-melting model is put forward in this paper. Both the results of simulations and experiments show that the ice-melting process can be divided into three stages composed of temperature rising, ice melting, and ice shedding, among which the ice melting is the key stage consuming most of the ice-melting time. In this stage, an elliptic airgap is formed and widened gradually with an influence on the ice-melting time and the temperature of the conductor. The experiments in the artificial climate chamber demonstrate that the results of the presented model are consistent with those of the experiments generally, so it can be employed to estimate the parameters of ice melting in practical engineering as reference. [ABSTRACT FROM AUTHOR]

The breakage of overhead covered conductors on distribution lines resulting from the short-circuit arcs caused by lightning flash becomes a challenge as the application of covered conductors increases on distribution lines. Based on various methodologies and devices developed to avoid the covered conductor breakage in the world, novel arc-guided devices, including arcing protection hardware with barbs, clamping post composite insulator, and barb electrode clamping post porcelain/composite insulator are presented in this paper. Experimental results are also presented to validate these new developed devices. Devices based on the developed technologies have been widely applied on the power grids in China successfully. [ABSTRACT FROM AUTHOR]

With the operation of long transmission lines, unknown severe vibration and noise in transformers have sometimes been observed at the Shanghe substation and at the Ling'ao nuclear power plant in China. This paper gives a comparison of magnetic-storm recordings and measured transformer neutral current data and confirms that the disturbances were caused by geomagnetically induced currents (GICs). On November 7 and 9, 2004, the maximum GIC at the Ling'ao nuclear power plant was 47.2 A and 75.5 A, respectively, which are both larger than the neutral dc current caused by the HVdc monopole operation. The analysis of GIC data indicates that the GIC level is mainly determined by the geomagnetic-field variation rate, but the earth conductivity and power grid parameters are also important factors affecting GIC values. The data show that the GIC level is higher at the Ling'ao nuclear power plant than at the Shanghe substation. The reason is considered to be related to the grid structure and to the coast effect. Furthermore, because of smaller resistances, longer transmission lines, a larger scale, and the adoption of single-phase transformers, the influences of GIC on the ultra-high voltage power grid being constructed in China need to be studied more urgently. [ABSTRACT FROM AUTHOR]

Intelligent transportation systems (ITSs) have become increasingly important for public transportation in Shanghai, China. In response, ShanghaiGrid (SG) aims to provide abundant intelligent transportation services to improve traffic conditions. A fundamental service in SG is to locate the nearest desirable vehicles for users. In this paper, we propose an innovative protocol called ANTS to locate a desirable vehicle close to the querying user. The protocol finely mimics the efficient searching strategy adopted by a lost ant searching for its nest. Taking query locality into account, ANTS can retrieve the closest vehicles satisfying the query with high probability but incurs small query latency and modest network traffic. ANTS is a fully distributed and robust protocol and, therefore, has good scalability. Extensive simulations based on the real road network and the trace data of vehicle movements in Shanghai demonstrate the efficacy of ANTS. [ABSTRACT FROM AUTHOR]

During the last decade, neural networks have emerged as one of the most powerful and accurate nonlinear models for load forecasting. However, using neural networks requires users to have in-depth knowledge to determine the model structure and parameters, which limits their wide application. To overcome this weakness, this paper proposes an integrated approach which combines a self-organizing fuzzy neural network (SOFNN) learning method with a bilevel optimization method. SOFNNs can automatically determine both the model structure and parameters, while the bilevel optimization method automatically selects the best pre-training parameters to ensure that the best fuzzy neural networks be identified. Therefore, the proposed approach is able to automatically identify the best fuzzy neural network for a given forecasting task and is much easier to use in practice. The proposed approach is tested on real-load data from the Southern Power Network of Hebei Province, China, and on the EUNITE competition data. Results show the proposed approach improves existing load forecasting models. [ABSTRACT FROM AUTHOR]

Vehicle-based sensors can be used for traffic monitoring. These sensors are usually set with long sampling intervals to save communication costs and to avoid network congestion. In this paper, we are interested in understanding the traffic-monitoring performance that we can expect from such vehicle-based mobile sensor networks, despite the incomplete information provided. This is a fundamental problem to be addressed. A performance evaluation has been carried out in Shanghai, China, by utilizing the vehicle-based sensors installed in about 4000 taxies. Two types of traffic status-estimation algorithms, i.e., the link-based and the vehicle-based, are introduced and analyzed. The results show that estimations of the traffic status based on these imperfect data are reasonably accurate. Therefore, the feasibility of such an application is demonstrated. [ABSTRACT FROM AUTHOR]

To effectively address the explosive growth of multi-media applications over the Internet, a large-scale media streaming system has to fully take into account the issues of security, quality of service (QoS), scalability, and heterogeneity. However, current streaming solutions do not address all these challenges simultaneously. To address this limitation, this paper proposes a secure and high-performance streaming system called TrustStream, which combines the best features of scalable coding, content distribution network (CDN) and peer-to-peer (P2P) networks to achieve unprecedented security, scalability, heterogeneity, and certain QoS simultaneously under a unified architecture. In this architecture, raw video is encoded into two layers, namely, the base layer, which contains the most critical media content and is transmitted through a CDN-featured single-source multi-receiver (S-M) P2P network to guarantee a minimal level of quality, and the enhancement layer, which is transmitted in a pure multi-source multi-receiver (M-M) P2P framework to achieve maximum scalability and bandwidth utilization. Heterogeneity is therefore addressed by delivering only the layers that a receiver is able to manage. Security is provided by combining our key distribution mechanism and key-embedding scheme under' our proposed S-M P2P topology. We have implemented TrustStream system over the Internet. Deployed by ChinaCache, the largest CDN provider in China, TrustStream has broadcasted several popular live video programs over the Internet. The experimental results demonstrate the advantages and effectiveness of our architecture and system. [ABSTRACT FROM AUTHOR]

Transmit diversity is especially important in broad-casting network. In this paper, a transmit diversity method is proposed for the Chinese National Digital Terrestrial Television Broadcasting (DTTB) Standard. The transmit diversity scheme is based on the design of orthogonal sequences which have perfect crosscorrelation and almost perfect autocorrelation characteristic. The characteristics of the proposed sequences can help for synchronization and channel estimation in time domain synchronous orthogonal frequency division multiplexing (TDS-OFDM) system. Simulations using space-time codes (STCs) in Digital Terrestrial/Television Multimedia Broadcasting (DTMB) system with low density parity check coding (LDPC) show that the proposed transmit diversity method has about 1-2 dB signal-to-noise ratio (SNR) gain comparing with no diversity for QPSK and 16 QAM constellations at BER = 10-4, and it can avoid the appearance of BER floor for 64QAM constellation. [ABSTRACT FROM AUTHOR]

Failure probability of system components may vary with the changes of weather, environment and other operation conditions. The time-varying or condition-based failure probability can be represented using a fuzzy model. Based on credibility theory, this paper presents a novel operation risk assessment method to handle the two-fold uncertainty combining randomness and fuzziness in power system operations. In the proposed method, a random fuzzy model is developed to accommodate impacts due to various operation conditions and other factors on the failure probability of system components. The WECC nine-bus system, IEEE 14-bus system and an actual power system in Northeast China were used to demonstrate feasibility and applicability of the presented method. The operation risk assessment module using the proposed method has been embedded in the EMS system in a district control center of a power company to perform real-time operation risk assessment. [ABSTRACT FROM AUTHOR]

In this paper, the design, fabrication and tests of a 1 MJ HTS magnet for SMES was presented. The magnet was fabricated by BSSCO tapes, it consisted of 44 pancakes, the inner diameter of the winding is 400 mm, the outer diameter is 568 mm and the height is 648 mm, the inductance is 6.38 H and the rated operation current is 560 A at 4.2 K. The tests show the magnet could be operated at the design parameters. The magnet will be used for the 1 MJ/500 kVA SMES unit which will be demonstrated at a 10 kV substation in Beijing. [ABSTRACT FROM AUTHOR]

In R&D project selection, experts (or external reviewers) always play a very important role because their opinions will have great influence on the outcome of the project selection. It is also undoubted that experts with high-expertise level will make useful and professional judgments on the projects to be selected. So, how to measure the expertise level of experts and select the most appropriate experts for project selection is a very significant issue. This paper presents a group decision support approach to evaluate experts for R&D project selection. Where the criteria and their attributes for evaluating experts are summarized mainly based on the experience with the National Natural Science Foundation of China (NSFC). A formal procedure that integrates both objective and subjective information on experts is also presented. It is mainly based on analytic hierarchy process (AHP), scoring method, and fuzzy linguistic processing. A group decision support system is designed and implemented for illustration of the proposed method. [ABSTRACT FROM AUTHOR]

This paper describes the principle of a new current differential relay developed for a 1000-kV UHV transmission line that is being constructed in China. The distributed capacitive current along the relatively long overhead line will have a significant effect on the relay performance and should be taken into account in the relay principle. The study results in a new current differential relay based on the steady state transmission line equations, in which the distributed capacitive current is inherently represented. Analysis is carried out for different practical situations where shunt reactors or series capacitors are present in the system for compensation. Laboratory tests show that the relay principle developed in this study can be used as a main protection scheme for the 1000-kV UHV transmission line. [ABSTRACT FROM AUTHOR]

Accurate forecast of citywide passenger demand helps online car-hailing service providers to better schedule driver supplies. Previous research either uses only passenger order history and fails to capture the deep dependency of passenger demand, or is restricted on grid region partition that loses physical context. Recent advance in mobile traffic analysis has fostered understanding of city functions. In this article, we propose FlowFlexDP, a demand prediction model that integrates regional crowd flow and applies to flexible region partition. Analysis on a cellular dataset covering 1.5 million users in a major city in China reveals strong correlation between passenger demand and crowd flow. FlowFlexDP extracts both order history and crowd flow from cellular data, and adopts Graph Convolutional Neural Network to adapt prediction for regions of arbitrary shapes and sizes in a city. Evaluation on a large scale data set of 6 online car-hailing applications from cellular data shows that FlowFlexDP accurately predicts passenger demand and outperforms the state-of-the-art demand prediction methods. [ABSTRACT FROM AUTHOR]

Since it is safer and less expensive to absorb delays on the ground, many models have been developed to assign ground holding delays optimally in the general network of airports, so that the total (ground plus airborne) delay costs of all fights are minimized. Still, the undeniable fact remains that airborne delays cannot be totally avoided. When there are airborne holds, such as when the local airspace capacity has a sudden decrease due to bad weather or other unpredicted disruptions, it is important to quickly minimize the costs of airborne holds. Much research has been conducted to explore ways to minimize airborne holds. Motivated by this, after analyzing the network structure of air traffic control areas and the dynamic nature of air traffic flow, this paper presents a model based on multicommodity dynamic network flow for short-term air traffic flow management. The model was validated by practical data from the Beijing ATC Center of the Civil Aviation Administration of China (CAAC). [ABSTRACT FROM AUTHOR]

Recently, sustained power oscillation at subsynchronous frequency was captured in direct-drive permanent magnetic synchronous generator (PMSG) based wind farms in Xinjiang Uygur Autonomous Region, China. This new type of subsynchronous interaction (SSI) detected in practical systems has never been reported and analyzed before. Therefore, its mechanism and characteristics are not yet clearly clarified. In this paper, a simplified but representative system model with multiple PMSGs interfaced with AC networks is established first based on the actual system and the PMSG model provided by the manufacturer. Then, small-signal eigenanalysis, time-domain simulation, and impedance model analysis are carried out to investigate the interactive dynamics between them. The results show that such interaction between direct-drive PMSG wind farms and weak ac grids characterized by low short-circuit ratio would cause negative-resistance effect for the SSI mode, leading to unstable oscillation. In such cases, the controller of PMSG would saturate soon, resulting in sustained power oscillation in the system. If unfortunately the oscillation frequency matches the torsional mode of any nearby turbogenerator, severe torsional vibration would be excited on the shaft of the latter. The analysis results are finally validated with field measurements of an actual SSI event. To address the problem, a supplementary subsynchronous damping control loop is attached to the controllers of PMSGs to reshape the impedance and thus to stabilize the SSI. [ABSTRACT FROM PUBLISHER]

This paper proposes a dc voltage incipient sensor fault isolation method for single-phase three-level rectifier devices in high-speed railway electrical traction systems. Different incipient fault modes characterizing locations and incipient fault types are parameterized nonlinearly by unknown fault parameters. A new incipient fault isolation method is developed by combining sliding mode technique with nonlinear parameterization adaptive estimation technique. A bank of particular adaptive sliding mode estimators is proposed, which facilitates to derive new isolation residuals and adaptive threshold intervals. The isolability is studied, and the isolable sufficient condition is derived using new functions. For the practical electrical traction system in China Railway High-Speed 2, simulation and experiment based on TDCS-FIB (a software) are presented to verify the effectiveness and feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

The fast development of mobile networks calls for the massive consumption of materials, land, and energy in building and maintaining infrastructures, which is always intensified by the repetitive constructions of competing network operators. To reduce the resource consumption for social benefit, one business solution, implemented in the Chinese telecom industry, is forming a joint venture responsible for building and maintaining common infrastructures. The novelty of this practice is that the joint venture is shared by the competing operators who also rent infrastructures from the joint venture. We note that such a solution can be potentially generalized to other industries for reducing resource consumption. However, before generalization, an understanding of the pros and cons from the economic perspective of the business model is urgently needed. In this paper, we study this business model from a game theoretic approach. Our results show that if we properly regulate the joint venture, the market can converge to equilibriums with desirable properties which cannot be achieved without the joint venture. Furthermore, we also study the investment reduction in the presence of the joint venture. Our numerical results show that under a moderate user density, the total investment on the infrastructures can be significantly reduced. [ABSTRACT FROM PUBLISHER]

In September 1961, the first ruby laser successfully debuted at Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP), Chinese Academy of Sciences (CAS), marking the beginning of laser science and technology in China. It operated with unique features about one year after T. H. Maiman’s first working model in the United States, and three months after the first laser in the former Soviet Union. It was unusual for China to achieve such an accomplishment given its technically backward state in the 1950s, and one cannot help but wonder how the Chinese scientists caught up with international trends in laser research. We want to answer some important questions about this historical event and explain the birth of the first ruby laser in China by examining the archives of the developmental process and interviewing some of the key members who pioneered China’s laser research. [ABSTRACT FROM AUTHOR]