Economic time series;fuzzy forecasting;sparse representation;clustering
This paper addresses the problem of economic time series forecasting, and a new prediction method is proposed. The method fully capitalizes on the two key technologies, sparse representation, and fuzzy set theory, to handle the stock time series forecasting problems. First, sparse representation is applied to smooth the time series. Then, the fuzzy technology is used to convert time series into fuzzy series. Based on the number of the occurrence of fuzzy sets, the weights are calculated. Finally, the future value of the time series can be forecasted using the weights and inverse transformation of sparse representation. The experimental results show that the proposed method produces more accurate forecasted results.
This paper presents an integrated multi-attribute decision-making (MADM) approach to aid selection of commercially available materials in the context of sustainable design. The MADM couples grey relational analysis (GRA) with an analytic hierarchy process (AHP) to rank alternative materials in terms of their economic, environmental, and social performance. AHP is used to determine the corresponding weighting values for the selected indicators. In addition, a case example is used to verify the proposed MADM method and demonstrate its practical application. Three alternative polymer materials, i.e., poly(vinyl chloride) (PVC), polypropylene (PP), and polyethylene (PE), are examined to determine their sustainability for plastic pipe design. The associated MADM result and the limitations of the approach are discussed to lay the foundation for further improvement.
3-vehicle crashes;2-vehicle crashes;injury severity;continuation ratio logit
OBJECTIVE AND METHODS: In traditional injury severity-related studies, 2-vehicle and 3-vehicle crashes are typically considered in a combinatory manner and thus the injury casual factors for these 2 crash types are implicitly assumed to be the same. This article attempts to investigate the potential discrepancy between 2- and 3-vehicle crash severities with the aid of a continuation ratio logit model with the property of partial proportional odds. RESULTS: The modeling results show that there are a number of significant differences between 2- and 3-vehicle crash injury severities in terms of the contributing factors, the magnitude of impact, and even the direction of effects. CONCLUSIONS: The research illustrates that a series of environmental and crash factors (e.g., rear-end straight crashes, urban roadways, alcohol usage, and different driving cohorts) are statistically significant in interpreting the disparity of coefficients between 2- and 3-vehicle crash injury severity models. It raises awareness that the combined analysis of 2- and 3-vehicle crashes should be exercised with caution, particularly when safety research targets crashes with less severe injuries.
JOURNAL OF MATERIALS CHEMISTRY A,2019年7(4):1810-1823 ISSN：2050-7488
Yang, Weiqing;Meng, Fanbin;Lu, Jun
[Wang, Chuanfeng; Meng, Fanbin; Jin, Long; Xu, Yali; Xie, Meilin; Huang, Xi; Yang, Weiqing; Meng, FB; Lu, Jun; He, Xuebing] Southwest Jiaotong Univ, Sch Mat Sci & Engn, Key Lab Adv Technol Mat, Minist Educ, Chengdu 610031, Sichuan, Peoples R China.;[Lu, Jun] Sichuan Univ, State Key Lab Polymer Mat Engn, Chengdu 610065, Sichuan, Peoples R China.;[Zhang, Chaoliang] Sichuan Univ, West China Hosp Stomatol, State Key Lab Oral Dis, Chengdu 610041, Sichuan, Peoples R China.
[Yang, WQ; Meng, FB; Lu, J] Southwest Jiaotong Univ, Sch Mat Sci & Engn, Key Lab Adv Technol Mat, Minist Educ, Chengdu 610031, Sichuan, Peoples R China.;[Lu, Jun] Sichuan Univ, State Key Lab Polymer Mat Engn, Chengdu 610065, Sichuan, Peoples R China.
We report the design and fabrication of novel biodegradable hybrid polymeric nanofibers with the combined advantages of high shear piezoelectricity, multicolor photoluminescence and simultaneously improved heat resistance. The multifunctional flexible nanofibers, with uniform diameters and smooth surfaces, were fabricated through the electrospinning of poly(d-lactide) (PDLA)/poly(l-lactic acid) (PLLA)/carbon quantum dots (CQDs) with dichloromethane and alcohol as the mixed spinning solvent. The electrospinning at a high voltage enhanced the orientation and formation of stereocomplexed polylactide crystals, and at the same time remarkably suppressed the growth of homocrystallites in the ternary composite nanofibers. With the amplitude and/or frequency increase of stimulated dynamic loads, the electrical outputs of the stereocomplex PDLA/PLLA/CQD nanofibers increased, and the maximum open-circuit voltage and short-circuit current output density achieved were 74.2 V cm(-3) and 4.9 A cm(-3), respectively. Also, the stereocomplexed nanofiber based nanogenerator, during continuous operation of electromechanical conversion, demonstrated good stability and durability as a power source to operate LEDs, and no electrical output decay was observed for more than 10000 consecutive working cycles. Moreover, the electrospun hybridized nanofibers emitted different fluorescence colors under laser excitation at different wavelengths. The as-developed ecologically friendly bionanofibers may diversify niche applications in future transient electronics and implantable medical devices as self-powered bio-sensors, bio-piezoelectric nanogenerators, and so on.