Self-organized criticality of power system faults and its application in adaptation to extreme climate

This paper analyzes the statistics of faults in a transmission and distribution networks in central China, unveils long-term autocorrelation and power law distribution of power system faults, which indicates that power system fault has self-organized criticality (SOC) feature. The conclusion is consistent with the power systems data in 2008 with ice storm present. Since power systems cover large areas, climate is the key factor to its safety and stability. In-depth analysis shows that the SOC of atmosphere system contributes much to that of power system faults. Extreme climate will be more intense and frequent with global warming, it will have more and more impact upon power systems. The SOC feature of power system faults is utilized to develop approaches to facilitate power systems adaptation to climate variation in an economical and efficient way. Supported by the National Basic Research Program of China (Grant No. 2009CB219701), National Natural Science Foundation of China (Grant No. 50595414), and Youth Scientific & Technological Innovation Project of CSEE     

Ultrahigh resolution optical coherence tomography with femtosecond Ti:sapphire laser and photonic crystal fiber

Optical coherence tomography （OCT） with ultrahigh axial resolution was achieved by the super-continuum generated by coupling femtosecond pulses from a commercial Ti：sapphire laser into an air-silica microstructure fiber. The visible spectrum of the super-continuum from 450 to 700 nm centered at 540 nm can be generated. A free-space axial OCT resolution of 0.64 pm was achieved. The sensitivity of OCT system was 108 dB with incident light power 3 mW at sample, only 7dB below the theoretical limit. Subcellular OCT imaging was also demonstrated, showing great potential for biomedical application.     

Process modeling of fuel cell vehicle power system

Constructed here is a mathematic model of PEM Fuel Cell Vehicle Power System which is composed of fuel supply model, fuel cell stack model and water-heat management model. The model was developed by Matlab/Simulink to evaluate how the major operating variables affect the output performances. It shows that the constructed model can represent characteristics of the power system closely by comparing modeling results with experimental data, and it can be used in the study and design of fuel cell vehicle power system. Supported by the National High Technology Research and Development Program of China (Grant No. 2007AA05Z145), State Key Development Program for Basic Research of China (Grant No. 2007cb209707) and Shanghai Science and Technology Project (Grant Nos. 06SN07115 and 07JC14024)     

Crack spacing of unsaturated soils in the critical state

The cracking mechanism of unsaturated soils due to evaporation is poorly understood, and the magnitude of crack spacing is usually hard to estimate. In this work, cracks were postulated to occur succedently rather than simultaneously, that is, secondary cracks appear after primary cracks as evaporation continues. Formulae of the secondary crack spacing and secondary trend crack spacing were then derived after stress analysis. The calculated spacing values were consistent with the published experimental data. Meanwhile, the effect of the Poisson ratio on the crack spacing was analyzed, which showed that the magnitude of crack spacing was proportional to the Poisson ratio in the range of [0.30, 0.35].     

Arbitrarily long distance quantum communication using inspection and power insertion

The biggest obstacle for long distance quantum communication is the channel loss and the channel noise on photons. In this paper, a method to solve this problem was analyzed using inspection and power insertion (IPI). It is proved that quantum communication may be established over arbitrarily long distance using this technology. The amount of resources required is a polynomial function of the distance. IPI is proposed as a general technique to prolong quantum secure direct communication where secret messages are transmitted directly over a quantum channel. Supported by the National Basic Research Program of China (Grant No. 2006CB921106), National Natural Science Foundation of China (Grant No. 10325521) and Key Project of Ministry of Education of China (Grant No. 306020)     

Design and demonstration of a 0.22 THz gyrotron oscillator

Gyrotrons are the most powerful terahertz sources and have potential applications in many areas. A terahertz gyrotron oscillator with a pulsed solenoid producing up to an 8 T magnetic field has been designed, constructed and tested. In a 7.96 T magnetic field, 3 kW output power radiations at 0.22 THz frequency have been generated. Supported by the State Key Development Program of Basic Research of China (Grant No. 2007CB310400) and National Natural Science Foundation of China (Grant No. 1067611)     

New research advancement in electrical engineering field of China-Reviews on special issue of Science in China Series E:Technological Sciences

Based on,but not limited to the research results of electrical engineering published in the special issue of Science in China Series E,June 2008,this essay gives a brief review on a wide range of state-of-art advancement in electrical engineering field of China,which includes power system modeling,analysis and control,risk assessments in power system,etc.     

Coexistence of normal, super-, and hyper-deformation in nuclei: A study with angular momentum projection method

Angular-momentum-projected energy surface calculations for A ≈ 110 nuclei indicate three distinct energy minima occurring at different angular-momenta. These correspond to normal, super-, and hy- per-deformed shapes coexisting in one nucleus. 110Pd is studied in detail, with a quantitative prediction on super- and hyper-deformed spectra by the Projected Shell Model calculation. It is found that several other neighboring nuclei in the A-110 mass region, with the neutron number around 64, also exhibit clear s...     

Near-infrared spectroscopy-based quantification of substrate and aqueous products in wastewater anaerobic fermentation processes

In this study, a Fourier transform near-infrared （FT-NIR） technique was used for process monitoring of anaerobic fermentation. Orthogonal signal correction （OSC） method was used as NIR spectral pre- processing options. Calibration models were established and the validation of the method was per- formed with the sucrose, ethanol and volatile fatty acids （VFAs） contents determined by the anthrone and gas chromatography methods, respectively. Spectral range and the number of internal latent variables were optimized for the best correlation coefficient. Test set validation of sucrose resulted in excellent measurement of prediction performance and the correlation coefficient of determination is 0.930. Similar prediction statistics for individual VFA and total VFA contents were obtained. These re- sults proved that the NIR spectroscopy technology is able to quantify the contents of both volatile fatty acids and sucrose in wastewater anaerobic fermentation process.     

Influence of location-dependent protuberance damage on cell viability

The influence of femtosecond laser-induced damages on viability of olfactory ensheathing cells (OECs) is investigated. Several cytokinetic processes including cellular damage, recovery and death are discussed. Using femtosecond laser with the power of 100 μW and cutting speed of 2 μm/s, we cut the cellular protuberance with smaller diameter twice in different locations, and then observe the viability of the damaged cells. Under the same conditions, the root of protuberance with larger diameter is cut six times to observe changes of cellular shape. Whether the damage is located in the end, middle or root of protuberance with smaller diameter, the cell viability can recover within 3 h. When the damage is located in the root of protuberance with larger diameter, the damaged cell will die in the way of oncosis. Cytokinetic phenomena including intracellular high Ca²⁺ concentration, cellular morphologic change, recovery and oncosis are discussed. Meanwhile, high Ca²⁺ concentration is observed after femtosecond laser surgery. Therefore, femtosecond laser surgery is an important tool for establishing cell damage model and studying cytokinetics. Supported by National High Technology Research & Development Program of China (Grant No. 2006AA04Z307), Author of National Excellent Doctoral Dissertation of PR China (Grant No. 2006039), National Natural Science Foundation of China (Grant No. 50775104), Natural Science Foundation of Jiangsu Province (Grant No. BK2006507) and Jiangsu Provincial Research Innovation Program for College Graduates (Grant No. CX07B_086z)     

Applications of membrane distillation technology in energy transformation process-basis and prospect

Membrane distillation technology is a new type of efficient separation technology that combines traditional distillation technology and membrane separation technology. In the study, applications of membrane distillation technology in thermal engineering and refrigerating engineering with typical energy transformation process were presented. Desorption and regeneration process of saline solution by vacuum membrane distillation was proposed on the basis of the concentration and separation properties of membrane distillation. Membrane distillation technology could be used in lithium bromide absorption refrigeration system, energy storage system, and the regeneration process of liquid desiccant solution in temperature-humidity independent control air-conditioning system. The aim of the applications was to use the low-grade energy such as waste heat, solar energy and geothermal energy adequately and to improve the available temperature difference of heat source. According to latent heat transfer and thermal conduction across the membrane in direct contact membrane distillation process, a novel membrane heat exchanger with both heat transfer and mass transfer processes was proposed. The heat exchanger could be used as the solution heat exchanger of lithium bromide absorption refrigeration system and as the special heat exchanger that recovered heat and pure water simultaneously. Some feasible process flows about the applications of membrane distillation technology to energy transformation process were listed and analyzed. Finally, future research emphases were indicated.     

Arctic dipole anomaly and summer rainfall in Northeast China

A dipole structure anomaly in summer Arctic atmospheric variability is identified in this study, which is characterized by the second mode of empirical orthogonal function （EOF） analysis of summer monthly mean sea level pressure （SLP） north of 70°N, accounting for 12.94% of the variance. The dipole anomaly shows a quasi-barotropic structure with opposite anomalous centers over the Canadian Arctic and the Beaufort Sea and between the Kara Sea and the Laptev Sea. The dipole anomaly reflects alternating variations in location of the polar vortex between the western and eastern Arctic regions. The positive phase of the dipole anomaly corresponds to the center of the polar vortex over the western Arctic, leading to an increase in summer mean rainfall in Northeast China. The dipole anomaly has a predominant 6-year periodicity, and shows interdecadal variations in recent decades.     

Improving analytic hierarchy process applied to fire risk analysis of public building

The structure importance in Fault Tree Analysis (FTA) reflects how important Basic Events are to Top Event. Attribute at alternative level in Analytic Hierarchy Process (AHP) also reflect its importance to general goal. Based on the coherence of these two methods, an improved AHP is put forward. Using this improved method, how important the attribute is to the fire safety of public building can be analyzed more credibly because of the reduction of subjective judgment. Olympic venues are very important public buildings in China. The fire safety evaluation of them will be a big issue to engineers. Improved AHP is a useful tool to the safety evaluation to these Olympic venues, and it will guide the evaluation in other areas. Support by the National Natural Science Foundation of China (Grant No. 50536030), National Project of Scientific and Technical Supporting Programs funded by Ministry of Science & Technology of China (Grant No. 2006BAK06B02) and China Postdoctoral Science Foundation (Grant No. 20070410220)     

Utilizing Chinese high-resolution satellite images for inspection of unauthorized constructions in Beijing

After Beijing wins the bit to host the 29th Olympic Games, in order to manifest the technical support advantages and capabilities of the autonomously-developed RS and GIS based change detection techniques in 2008 Beijing Olympic Games, and from the standpoints of executing new city planning, relieving the traffic congestion as well as maintaining the historic features, an automatic satellite monitoring system has been studied and established to accomplish the mission of unauthorized construction inspection within the Sixth Ring Road of Beijing city quarterly, by adopting the CBERS-2 satellite images and combining technologies of GIS, GPS, etc. This article discusses the applicable procedures and key issues when utilizing such Chinese satellite images and relevant techniques to discover the illegal constructions, and introduces the monitoring system from both the design and implementation aspects; additionally, some typical application cases in the practice of the system are also illustrated. The monitoring system can timely supply abundant information to facilitate the policy-making of relevant planning departments, thus providing consolidate technical support to eliminate the illegal constructing behaviors in the blossom. During the five years＇ excellent performance, it has helped China save large amounts of expenditures for processing of unauthorized constructed buildings.     

Field emission characteristics of ZnO nanotetrapods and the effect of thermal annealing in hydrogen

Large-scale tetrapod-like ZnO nanostructures have been synthesized using a thermal chemical vapor deposition method on a silicon substrate. The high-purity nanotetrapods show sharp tips geometry with a wurtzite structure. The field emission properties of the uniform ZnO nanostructural material are investigated at different anode-cathode distances. The turn-on field for the ZnO nanotetrapods is found to be about 3.7 V/μm at a current density of 1 μA/cm^2. The field emission behavior obeys Fowler-Nordheim relationship. More importantly, the field emission properties are improved after annearing in hydrogen, and therefore high emission current and low turn-on field are obtained. These results indicate that tetrapod-like ZnO nanostructures are a promising candidate for cold cathode emitters.     

Biomimetic coupling effect of non-smooth mechanical property and microstructural features on thermal fatigue behavior of medium carbon steel

Some kinds of particular functions possessed by natural organisms are often formed by coupling up the multiple typical features on their body surfaces. Inspired by the coupling phenomenon in biological system, the medium carbon steel specimens with the coupling effect of non-smooth mechanical property and microstructural features were fabricated by laser processing. Thermal fatigue behavior of specimens with biomimetic coupling surface was investigated and compared. The results confirmed that such a biomimetic method has the beneficial effect on improving the thermal fatigue property of medium carbon steel specimens. The related mechanisms behind the biomimetic coupling effect for explaining the enhanced thermal fatigue resistance were discussed preliminarily. Supported by the Key Program of National Natural Science Foundation of China (Grant No. 50635030), Project 985-Automotive Engineering of Jilin University, International Cooperation key Project (Grant No. 2005DFA00850) and Transfer Foundation of Scientific and Technical Fruits in Agriculture (Grant No. 2007GB23600467) of Ministry of Science and Technology of China     

A bionic artificial joint system and investigation of tribological performance

Joint replacement is one of the most common and successful operations in orthopaedic surgery. It consists of replacing painful, arthritic, worn or cancerous parts of the joint with artificial surfaces shaped in such a way as to allow joint movement. The polyethylene component has been implicated as the key factor affecting the lifetime of these prostheses. This paper introduces a bionic artificial joint system which aims to prolong the lifetime of such prostheses. Included are bionic system design, investigation of bionic therapeutic lubricants and analysis of the mechanical properties of hip prostheses. Possible future developments which might improve artificial joints are also discussed. Supported by the National Natural Science Foundation of China (Grant No. 50105014), Science and Technology Committee of Shanghai (Grant No. 04 QMX1442), Shanghai Leading Academic Discipline Project (Grant No. Y0102) and Graduate Innovation Fund of Shanghai University (Grant No. A.16-0109-07-002)     

Combining docking and comparative molecular similarity indices analysis （COMSIA） to predict estrogen activity and probe molecular mechanisms of estrogen activity for estrogen compounds

Estrogen compounds are suspected of disrupting endocrine functions by mimicking natural hormones, and such compounds may pose a serious threat to the health of humans and wildlife. Close attention has been paid to the prediction and molecular mechanisms of estrogen activity for estrogen com- pounds. In this article, estrogen receptor a subtype （ERa） -based comparative molecular similarity indices analysis （COMSIA） was performed on 44 estrogen compounds with structural diversity to find out the structural relationship with the activity and to predict the activity. The model with the significant correlation and the best predictive power （R^2= 0.965, Q^2 LOO： 0.599, R^2 pred ： 0.825） was achieved. The COMSIA and docking results revealed the structural features for estrogen activity and key amino acid residues in binding pocket, and provided an insight into the interaction between the ligands and these amino acid residues.     

Stable dislocation configuration in the surface layer of metals

The stable dislocation configuration in the surface layer of metals was calculated according to dislo-cation energy theory. It was shown that the stable dislocation configuration was only influenced by Burger's vector, while dislocation line could fluctuate closely around the direction vertical to free sur-face in a limited range.     

Estimating divergence times among subfamilies in Nymphalidae

The mitochondrial cytochrome oxidase subunit Ⅰ （COⅠ） gene and the nuclear elongation factor 1α （EF-1α） gene were sequenced from 13 species of Nymphalidae. Phylogenetic trees of Nymphalidae, which is the largest family in butterflies, were constructed based on the sequences determined from 13 species sequenced in our laboratory and an additional 43 species obtained from GenBank using the maximum likelihood （ML） and Bayesian methods. Relative-rate tests between lineages in these phylogenetic trees were performed. On the basis of the results of the relative-rate tests and fossil information of Satyrinae, Nymphalinae and Biblidinae, the average divergence times among the subfamilies are estimated as 44.2-87.1 million years ago （Ma）. These results will be helpful for better understanding of the origin and evolution of this family, as well as the divergence time of butterflies and other complex taxa.