Particle size distributions and concentrations above radiators in indoor environments: Exploratory results from Xi`an, China

Xi Chen,Angui Li 대한환경공학회 2015 Environmental Engineering Research Vol.20 No.3

Particulate matter in indoor environments has caused public concerns in recent years. The objective of this research is to explore the influence of radiators on particle size distributions and concentrations. The particle size distributions as well as concentrations above radiators and in the adjacent indoor air are monitored in forty-two indoor environments in Xi’an, China. The temperatures, relative humidity and air velocities are also measured. The particle size distributions above radiators at ten locations are analyzed. The results show that the functional difference of indoor environments has little impact on the particle size distributions above radiators. Then the effects of the environmental parameters (particle concentrations in the adjacent indoor air, temperatures, relative humidities and air velocities) on particle concentrations above radiators are assessed by applying multiple linear regression analysis. Three multiple linear regression models are established to predict the concentrations of PM10, PM2.5 and PM1 above radiators.

Efficient VaR and CVaR Measurement via Stochastic Kriging

Chen, Xi,Kim, Kyoung-Kuk Institute for Operations Research and the Manageme 2016 INFORMS journal on computing Vol.28 No.4

<P>In this paper, stochastic kriging (SK) is considered as a metamodeling tool to capture risk-related properties of complex stochastic system outputs. To better assess the tail behavior of the underlying distribution of a system output, we specifically focus on global prediction of value-at-risk and conditional value-at-risk. Going beyond the standard SK framework intended for metamodeling of mean response surfaces, we rethink the original formulation to allow for the flexibility of utilizing different estimation methods for metamodel construction. The resulting impact on the predictive performance of SK is examined in detail. In parallel with the study by Chen et al. [Chen X, Ankenman BE, Nelson BL (2013) Enhancing stochastic kriging metamodels with gradient estimators. Oper. Res. 61(2): 512-528], we further consider the situation in which noisy gradient information can be incorporated into SK metamodel construction and prediction. The theoretical results are illustrated by two numerical examples.</P>

Effects of macro-parameters on vibration and radiation noise for high speed wheel gear transmission in electric vehicles

Xi Chen,Chaosheng Song,Caichao Zhu,Jianjun Tan,Najeeb Ullah 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.9

Considering flexible shafts, a coupled dynamic model for the gear transmission system of wheel reducer used in electric vehicle was developed. By combining the acoustics finite element modal for housing in Virtual Lab and the coupled dynamic model for gear transmission system, a simulation method was proposed for the prediction of the radiation noise for the wheel reducer. Then, the effects of different macro geometry gear parameters including pressure angle and helical angle on the dynamic response and radiation noise were investigated under the rated working condition. Results show that the peak-peak value of the transmission error dramatically falls in the starting zone, followed by an upward trend with the increase of the pressure angle for the low speed stage gear pair. The minimum transmission error and vibration acceleration occur when the pressure angle is 17°. The increase of the pressure angle does not affect the sound pressure level at the field point obviously. The design case with 17° pressure angle shows the optimum radiation noise level, which is 4.41dB less than the original model. Compared to the pressure angle, the helix angle has a major influence on the transmission error, vibration acceleration and acoustic radiation noise. With the increase of the helix angle, the time-varying transmission error curve becomes more smooth with a lower peak-peak value. Besides, the increase of helix angle results in lowering the varying and fluctuating trend of both vibration acceleration and acoustic radiation noise. The design case with 24° helix angle shows the prime radiation noise level, which is 7 dB less than the original scheme.

A FORWARD-BACKWARD VQ CLUSTERING ALGORITHM FOR MULTISYLLABLE WORD RECOGNITION

Xi Xian Chen,Chang Nian Cai 대한전자공학회 1989 JTC-CSCC : Joint Technical Conference on Circuits Vol.- No.-

An Investigation of the Cross-border E-commerce Export Trade of Agricultural Products in Shandong Province

Xi Chen 한국무역연구원 2019 무역연구 Vol.15 No.1

This paper focuses on the cross-border e-commerce export trade of China’s agricultural products, and analyzes the current situation and problems of cross-border e-commerce export trade of agricultural products in the Shandong Province of China. It was found that there are some problems in the cross-border e-commerce export trade of agricultural products in Shandong Province, such as lagging construction of a cross-border e-commerce platform, high cost of cross-border logistics, shortage of compound cross-border e-commerce talents, quality certification, standardization issues of cross-border e-commerce agricultural products, and related service supervision of cross-border e-commerce of agricultural products. Countermeasures are put forward to promote the integration and development of cross-border e-commerce and traditional industries, establish an international logistics system adapted to the development of cross-border e-commerce, train and introduce high-end talents of cross-border e-commerce, strengthen the quality standardization and brand building of cross-border e-commerce agricultural products, and improve the mechanism of tax supervision, and rights and interests protection related to cross-border e-commerce agricultural products. This will provide a theoretical basis for future research on related topics, provide a theoretical basis for the export form of cross-border e-commerce of agricultural products in Shandong Province, and also provide a basis for cross-border e-commerce of agricultural products in other provinces of China.

Effect of windshields on the aerodynamic performance of a four-box bridge deck

Xi Chen,Elena Dragomirescu 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.31 No.1

A new type of bridge deck section consisting of four-box decks, two side decks for vehicular traffic lanes and two middle decks for railway traffic, has been experimentally investigated for determining its aerodynamic properties. The eight flutter derivatives were determined by the Iterative Least Squares (ILS) method for this new type of four-box deck model, with two windshields of 30 mm and 50 mm height respectively. Wind tunnel experiments were performed for angles of attack  = ±6°, ±4°, ±2° and 0° and Re numbers of 4.85×105 to 6.06×105 and it was found that the four-box deck with the 50 mm windshields had a better aerodynamic performance. Also, the results showed that the installation of the windshields reduced the values of the lift coefficient CL for the negative angles attack in the range of -6° to 0°, but the drag coefficient CD increased in the positive angle of attack range. However, galloping instability was not encountered for the tested reduced wind speeds, of up to 9.8. The aerodynamic force coefficients and the flutter derivatives for the four-box deck model were consistent with the results reported for the Messina triple-box bridge deck, but were different from those reported for the twin-box bridge decks.

The Top-K QoS-aware Paths Discovery for Source Routing in SDN

( Xi Chen ),( Junlei Wu ),( Tao Wu ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.6

Source routing is the routing scheme that arranges the whole path from source to target at the origin node that may suit the requirements from the upper layer applications’ perspective. The centralized control in SDN (Software-Defined Networking) networks enables the awareness of the global topology at the controller. Therefore, augmented source routing schemes can be designed to achieve various purposes. This paper proposes a source routing scheme that conducts the top-K QoS-aware paths discovery in SDN. First, the novel non-invasive QoS over LLDP scheme is designed to collect QoS information based on LLDP in a piggyback fashion. Then, variations of the KSP (K Shortest Paths) algorithm are derived to find the unconstrained/constrained top-K ranked paths with regard to individual/overall path costs, reflecting the Quality of Service. The experiment results show that the proposed scheme can efficiently collect the QoS information and find the top-K paths. Also, the performance of our scheme is applicable in QoS-sensitive application scenarios compared with previous works.

Dose-Dependent Associations between Wine Drinking and Breast Cancer Risk - Meta-Analysis Findings

Chen, Jia-Yan,Zhu, Hong-Cheng,Guo, Qing,Shu, Zheng,Bao, Xu-Hui,Sun, Feng,Qin, Qin,Yang, Xi,Zhang, Chi,Cheng, Hong-Yan,Sun, Xin-Chen Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.3

Purpose: To investigate any potential association between wine and breast cancer risk. Materials and Methods: We quantitatively assessed associations by conducting a meta-analysis based on evidence from observational studies. In May 2014, we performed electronic searches in PubMed, EmBase and the Cochrane Library to identify studies examining the effect of wine drinking on breast cancer incidence. The relative risk (RR) or odds ratio (OR) were used to measure any such association. Results: The analysis was further stratified by confounding factors that could influence the results. A total of twenty-six studies (eight case-control and eighteen cohort studies) involving 21,149 cases were included in our meta-analysis. Our study demonstrated that wine drinking was associated with breast cancer risk. A 36% increase in breast cancer risk was observed across overall studies based on the highest versus lowest model, with a combined RR of 1.0059 (95%CI 0.97-1.05) in dose-response analysis. However, 5 g/d ethanol from wine seemed to have protective value from our non-linear model. Conclusions: Our findings indicate that wine drinking is associated with breast cancer risk in a dose-dependent manner. High consumption of wine contributes to breast cancer risk with protection exerted by low doses. Further investigations are needed for clarification.

Thoughts on food experience design from the Perspective of Service Design

Chen Xi,Yonghwan Pan,Wansok Jang 한국서비스디자인학회 2021 한국서비스디자인학회 학술대회자료집 Vol.2021 No.-

Buckling patterns of thin films on curved compliant substrates with applications to morphogenesis and three-dimensional micro-fabrication

Chen, Xi,Yin, Jie Royal Society of Chemistry 2010 SOFT MATTER Vol.6 No.22

<P>Self-assembled buckling patterns of thin films on compliant substrates have been subjected to extensive studies and shown great promise in micro-fabrication. However, most previous studies were limited to planar substrates, and the study of buckling of films on curved substrates has not received sufficient attention. With the constraining effect from various types of substrate curvature, numerous new types of buckling morphologies may emerge which not only enable true three-dimensional (3D) fabrication of microstructures and microdevices, but also have important implications for the morphogenesis of quite a few natural and biological systems. We review the scientific aspects of elastic buckling of thin films on several representative curved substrates, emphasizing the critical effect of substrate curvature, its interaction with other material/system parameters, ways to control the buckles based on mechanical and physical principles, and bridge them with prospective applications in biology, biomedical engineering, and small-scale fabrication.</P> <P>Graphic Abstract</P><P>Mechanical self-assembly, underpinned by the spontaneous buckling patterns of thin films on curved compliant substrates, is highly relevant to the morphogenesis of some biological systems and fabrication of 2D/3D microstructures. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0sm00401d'> </P>