Showing papers by "Xi'an Jiaotong University published in 2009"
TL;DR: It is predicted that the single-crystal form of the MPB composition of the present system may reach a giant d(33) = 1500-2000 pC/N, which may provide a new recipe for designing highly piezoelectric materials (both Pb-free and P b-containing) by searching MPBs starting from a TCP.
Abstract: We report a non-Pb piezoelectric ceramic system Ba(Ti(0.8)Zr(0.2))O(3)-(Ba(0.7)Ca(0.3))TiO(3) which shows a surprisingly high piezoelectric coefficient of d(33) approximately 620 pC/N at optimal composition. Its phase diagram shows a morphotropic phase boundary (MPB) starting from a tricritical triple point of a cubic paraelectric phase (C), ferroelectric rhombohedral (R), and tetragonal (T) phases. The high piezoelectricity of the MPB compositions stems from the composition proximity of the MPB to the tricritical triple point, which leads to a nearly vanishing polarization anisotropy and thus facilitates polarization rotation between 001T and 111R states. We predict that the single-crystal form of the MPB composition of the present system may reach a giant d(33) = 1500-2000 pC/N. Our work may provide a new recipe for designing highly piezoelectric materials (both Pb-free and Pb-containing) by searching MPBs starting from a TCP.
2,197 citations
TL;DR: In this paper, the authors summarize recent development in research on synthesis and characterization of stationary nanofluids and try to find some challenging issues that need to be solved for future research.
732 citations
TL;DR: In this article, the authors investigated the role of transactional and relational mechanisms in hindering opportunism and improving relationship performance in an emerging economy, and found that transactional mechanisms are more effective in restraining opportunism while relational mechanisms were more powerful in improving the relationship performance.
652 citations
TL;DR: Wang et al. as discussed by the authors proposed a new EEMD-based method for fault diagnosis of rotating machinery, which can reveal the signal characteristic information accurately because of the problem of mode mixing.
473 citations
TL;DR: In this article, an experimental and numerical study on laminar burning characteristics of premixed premixed methane-hydrogen-air flames was conducted at room temperature and atmospheric pressure.
443 citations
15 May 2009
TL;DR: A novel algorithm called Regularized Extreme Learning Machine is proposed, based on structural risk minimization principle and weighted least square, which was improved significantly in most cases without increasing training time.
Abstract: Extreme Learning Machine proposed by Huang G-B has attracted many attentions for its extremely fast training speed and good generalization performance. But it still can be considered as empirical risk minimization theme and tends to generate over-fitting model. Additionally, since ELM doesn't considering heteroskedasticity in real applications, its performance will be affected seriously when outliers exist in the dataset. In order to address these drawbacks, we propose a novel algorithm called Regularized Extreme Learning Machine based on structural risk minimization principle and weighted least square. The generalization performance of the proposed algorithm was improved significantly in most cases without increasing training time.
404 citations
379 citations
04 Nov 2009
TL;DR: GreenOrbs is presented, a wireless sensor network system and its application for canopy closure estimates that outperforms the conventional approaches for canopyclosure estimates by incorporating a pre-deployment training process as well as a distributed calibration method.
Abstract: Motivated by the needs of precise forest inventory and real-time surveillance for ecosystem management, in this paper we present GreenOrbs [2], a wireless sensor network system and its application for canopy closure estimates. Both the hardware and software designs of GreenOrbs are tailored for sensing in wild environments without human supervision, including a firm weatherproof enclosure of sensor motes and a light-weight mechanism for node state monitoring and data collection. By incorporating a pre-deployment training process as well as a distributed calibration method, the estimates of canopy closure stay accurate and consistent against uncertain sensory data and dynamic environments. We have implemented a prototype system of GreenOrbs and carried out multiple rounds of deployments. The evaluation results demonstrate that GreenOrbs outperforms the conventional approaches for canopy closure estimates. Some early experiences are reported in this paper.
352 citations
TL;DR: This paper proposes a novel learning method, called improved balanced random forests (IBRF), and demonstrates its application to churn prediction, and finds it to improve prediction accuracy significantly compared with other algorithms, such as artificial neural networks, decision trees, and class-weighted core support vector machines.
Abstract: Churn prediction is becoming a major focus of banks in China who wish to retain customers by satisfying their needs under resource constraints. In churn prediction, an important yet challenging problem is the imbalance in the data distribution. In this paper, we propose a novel learning method, called improved balanced random forests (IBRF), and demonstrate its application to churn prediction. We investigate the effectiveness of the standard random forests approach in predicting customer churn, while also integrating sampling techniques and cost-sensitive learning into the approach to achieve a better performance than most existing algorithms. The nature of IBRF is that the best features are iteratively learned by altering the class distribution and by putting higher penalties on misclassification of the minority class. We apply the method to a real bank customer churn data set. It is found to improve prediction accuracy significantly compared with other algorithms, such as artificial neural networks, decision trees, and class-weighted core support vector machines (CWC-SVM). Moreover, IBRF also produces better prediction results than other random forests algorithms such as balanced random forests and weighted random forests.
349 citations
TL;DR: Wang et al. as mentioned in this paper investigated the relationship among three factors: IT implementation, supply chain integration (SCI), and SCP, and found that IT implementation has no direct effect on SCP, but instead enhances SCP through its positive effect on SCI.
346 citations
TL;DR: In this article, an experimental thermoelectric generator unit incorporating commercially available Tefas with the parallel-plate heat exchanger has been constructed to examine the influences of the main operating conditions, the hot and cold fluid inlet temperatures, flow rates and the load resistance, on the power output and conversion efficiency.
TL;DR: In this article, Li et al. collected samples at Xi'an, China during dust storms (DSs) and several types of pollution events, including haze, biomass burning, and firework displays.
TL;DR: In this article, a review on air-conditioning systems and indoor air quality control for human health is presented, where the problems in the existing research are summarized and a further study is suggested.
Abstract: With the improvement of standard of living, air-conditioning has widely been applied. However, health problems associated with air-conditioning systems and indoor air quality appear more frequently. In this paper, recent research is reviewed on air-conditioning systems and indoor air quality control for human health. The problems in the existing research are summarized. A further study is suggested on air-conditioning systems and indoor air quality control for healthy indoor air environment.
TL;DR: Wang et al. as mentioned in this paper investigated trust, coercive power and their interaction and their impact on internal and supplier integration, based on data collected in Chinese supply chains, and they found that coercive power improves supplier integration and with or without the presence of trust.
TL;DR: The results show that microRNAs are de-regulated in GC, suggesting the involvement of these genes in the development and progression of gastric cancer.
Abstract: MicroRNAs are a group of small non-coding RNAs that modulate gene expression. The de-regulation of microRNA expression has been found in several types of cancer. To study the role of microRNAs in gastric cancer (GC), we analyzed the expression profile of 847 microRNAs in GC from Chinese patients. Total RNA was used for hybridization on the miRCURY LNA Array (v. 11.0), which contains probes specific for 847 human microRNAs. The results from the miRNA microarray analysis were validated by real-time RT-PCR. A total of 24 miRNAs with a more than 2-fold change were differentially expressed between normal gastric tissue and GC. Of these, 22 miRNAs (miR-223, miR-106b, miR-147, miR-34a, miR-130b*, miR-106a, miR-18a, miR-17, miR-98, miR-616*, miR-181a-2*, miR-185, miR-1259, miR-601, miR-196a*, miR-221*, miR-302f, miR-340*, miR-337-3p, miR-520c-3p, miR-575 and miR-138) were significantly up-regulated in GC (P<0.05), whereas only miR-638 and miR-378 were significantly down-regulated in GC (P<0.05) compared to normal gastric tissue. The expression of miR-185 and miR-638, as measured by miRNA microarray analysis, was in agreement with the expression level of these microRNAs found by real-time RT-PCR in the same samples. Our results show that microRNAs are de-regulated in GC, suggesting the involvement of these genes in the development and progression of gastric cancer.
TL;DR: In this article, an exergy analysis for each cogeneration system is examined, and a parameter optimization for each system is achieved by means of GA to reach the maximum exergy efficiency.
TL;DR: By defining the concept of the transitive calibration matrix and its consistent index, this paper develops an optimization model to compute the numerical scale of the linguistic term set and the desired properties of the optimization model are presented.
Abstract: When using linguistic approaches to solve decision problems, we need the techniques for computing with words (CW). Together with the 2-tuple fuzzy linguistic representation models (i.e., the Herrera and Martinez model and the Wang and Hao model), some computational techniques for CW are also developed. In this paper, we define the concept of numerical scale and extend the 2-tuple fuzzy linguistic representation models under the numerical scale. We find that the key of computational techniques based on linguistic 2-tuples is to set suitable numerical scale with the purpose of making transformations between linguistic 2-tuples and numerical values. By defining the concept of the transitive calibration matrix and its consistent index, this paper develops an optimization model to compute the numerical scale of the linguistic term set. The desired properties of the optimization model are also presented. Furthermore, we discuss how to construct the transitive calibration matrix for decision problems using linguistic preference relations and analyze the linkage between the consistent index of the transitive calibration matrix and one of the linguistic preference relations. The results in this paper are pretty helpful to complete the fuzzy 2-tuple representation models for CW.
TL;DR: Special and closer attention should be paid in university freshmen with depression, anxiety, and other influential factors associated with Internet addiction at the beginning of their university life to guarantee the fulfillment of their academic study and graduation.
Abstract: The prevalence of Internet addiction and influential factors associated with Internet addiction among freshmen college students were investigated in this study. A total of 3557 first-year university students from a university in northwest China were surveyed with Young's 20-item Internet Addiction Test (IAT) questionnaire, a Self-Rating Depression scale (SDS), a Self-Rating Anxiety scale (SAS), and a basic information questionnaire. A rate of 6.44% of the participants surveyed showed Internet addiction. The students with Internet addiction had higher scores of SDS and SAS compared with those without Internet addiction (p < 0.01). There were significant positive correlations between SDS and SAS scores and Internet addiction (p < 0.001). Multiple logistic regression analyses showed that a single-parent family, the age of first exposure to Internet use, the age of the student, city residence, and homesickness were significantly associated with Internet addiction (p < 0.01). Special and closer attent...
TL;DR: In this paper, the effects of two important ejector geometry parameters, the primary Nozzle Exit Position (NXP) and the mixing section converging angle θ, on its performance were investigated.
TL;DR: In this article, a thermally conductive plastic composite was prepared from a mixture of silicon nitride (Si 3 N 4 ) filler particles and an ultrahigh molecular weight polyethylene-linear low density (PLD) blend.
Abstract: A novel thermally conductive plastic composite was prepared from a mixture of silicon nitride (Si 3 N 4 ) filler particles and an ultrahigh molecular weight polyethylene–linear low density polyethylene blend. The effects of Si 3 N 4 particle sizes, concentration, and dispersion on the thermal conductivity and relevant dielectric properties were investigated. With proper fabrication the Si 3 N 4 particles could form a continuously connected dispersion that acted as the dominant thermally conductive pathway through the plastic matrix. By adding 0–20% Si 3 N 4 filler particles, the composite thermal conductivity was increased from 0.2 to ∼1.0 W m −1 K −1 . Also, the composite thermal conductivity was further enhanced to 1.8 W m −1 K −1 by decreasing the Si 3 N 4 particle sizes from 35, 3 and 0.2 μm, and using coupling agent, for the composites with higher filler content. Alumina short fibers were then added to improve the overall composite toughness and strength. Optimum thermal, dielectric and mechanical properties were obtained for a fiber-reinforced polyethylene composite with 20% total alumina–Si 3 N 4 (0.2 μm size) filler particles.
TL;DR: In this article, surface effects on the axial buckling and the transverse vibration of nanowires are examined by using the refined Timoshenko beam theory, in which the impacts of surface elasticity, residual surface stress, transverse shear deformation and rotary inertia have been included.
Abstract: In this paper, surface effects on the axial buckling and the transverse vibration of nanowires are examined by using the refined Timoshenko beam theory. The critical compression force of axial buckling and the natural frequency of nanowires are obtained analytically, in which the impacts of surface elasticity, residual surface stress, transverse shear deformation and rotary inertia have been included. The buckling and vibration behaviour of a nanowire is demonstrated to be size dependent, especially when its cross-sectional dimension reduces to nanometres. The surface effects with positive elastic constants tend to increase the critical compression force and the natural frequency, especially for slender nanowires, while the shear deformation lowers these values for stubby nanowires. This study may be helpful to accurately measure the mechanical properties of nanowires and to design nanowire-based devices and systems.
TL;DR: In this paper, the effects of channel dimensions, channel wall thickness, bottom thickness and inlet velocity on the pressure drop, thermal resistance and the maximum allowable heat flux are presented.
TL;DR: An experimental study on the effect of hydrogen fraction and EGR rate on the combustion characteristics of a spark-ignition engine fueled with natural gas-hydrogen blends was investigated in this article.
TL;DR: In this article, a new combined power and refrigeration cycle is proposed, which combines the Rankine cycle and the ejector refrigeration cycles, and an exergy analysis is performed to guide the thermodynamic improvement for this cycle.
TL;DR: The experimental result demonstrates that the method combining WPT, EMD, the distance evaluation technique and the RBF network may accurately extract fault information and select sensitive features, and therefore it may correctly diagnose the different fault categories occurring in the bearings.
Abstract: A new method for intelligent fault diagnosis of rotating machinery based on wavelet packet transform (WPT), empirical mode decomposition (EMD), dimensionless parameters, a distance evaluation technique and radial basis function (RBF) network is proposed in this paper. In this method, WPT and EMD are, respectively, used to preprocess vibration signals to mine fault characteristic information more accurately. Then, dimensionless parameters in time domain are extracted from each of the original vibration signals and preprocessed signals to form a combined feature set. Moreover, the distance evaluation technique is utilised to calculate evaluation factors of the combined feature set. Finally, according to the evaluation factors, the corresponding sensitive features are selected and input into the RBF network to automatically identify different machine operation conditions. An experiment of rolling element bearings is carried out to test the performance of the proposed method. The experimental result demonstrates that the method combining WPT, EMD, the distance evaluation technique and the RBF network may accurately extract fault information and select sensitive features, and therefore it may correctly diagnose the different fault categories occurring in the bearings. Furthermore, this method is applied to slight rub fault diagnosis of a heavy oil catalytic cracking unit, the actual result shows the method may be applied to fault diagnosis of rotating machinery effectively.
TL;DR: In this article, the fracture characteristics of the reinforcing particles were rationalized using a proposed fracture criterion, and the yield strength and the elastoplastic deformation of such composites containing a high volume fraction of glassy particles were accurately modeled using a shear lag model and a self-consistent effective medium approach.
TL;DR: By combining living trees and archaeological wood, the annual mean temperatures were reconstructed based on ring-width indices of the mid-eastern Tibetan Plateau for the past 2485 years as discussed by the authors.
Abstract: By combining living trees and archaeological wood, the annual mean temperatures were reconstructed based on ring-width indices of the mid-eastern Tibetan Plateau for the past 2485 years. The climate variations revealed by the reconstruction indicate that there were four periods to have average temperatures similar to or even higher than that mean of 1970 to 2000 AD. A particularly notable rapid shift from cold to warm, we call it the “Eastern Jin Event”, occurred from 348 AD to 413 AD. Calculation results show that the temperature variations over the mid-eastern Tibetan Plateau are not only representative for large parts of north-central China, but also closely correspond to those of the entire Northern Hemisphere over long time scales. During the last 2485 years, the downfall of most major dynasties in China coincides with intervals of low temperature. Compared with the temperature records in other regions of China during the last 1000 years, this reconstruction from the Tibetan Plateau shows a significant warming trend after the 1950s.
TL;DR: Based on microstructural investigations, a solidification mechanism is proposed for these bulk metallic glass (BMG) composites in this article, which enhances the compressive plasticity (plastic strain up to 14%) and both plastic strain as well as yield strength scale with the crystalline volume fraction.
TL;DR: In this article, an experimental investigation on the influence of different hydrogen fractions and EGR rates on the performance and emissions of a spark-ignition engine was conducted, and the results showed that large EGR introduction decreases the engine power output.
TL;DR: In this article, a stoichiometric methane-hydrogen-air freely propagated laminar premixed flames at normal temperature and pressure were calculated by using PREMIX code of CHEMKIN II program with GRI-Mech 3.0 mechanism.