Synergy effect of hybrid fillers on the positive temperature coefficient behavior of polypropylene/ultra-high molecular weight polyethylene composites

Li, Qi,Basavarajaiah, Siddaramaiah,Kim, Nam Hoon,Heo, Seok-Bong,Lee, Joong Hee Wiley Subscription Services, Inc., A Wiley Company 2010 Journal of applied polymer science Vol.116 No.1

<P>Hybrid nanocomposites of polypropylene/ultra-high molecular weight polyethylene (PP/UHMWPE, 70/30) with various amounts of carbon black (CB) and carboxylated multiwalled carbon nanotubes (c-MWNTs) were prepared by the solution mixing and melt blending techniques. The effects of the mixture of CB and c-MWNTs on the positive-temperature-coefficient (PTC) behavior and the negative-temperature-coefficient (NTC) behavior, as well as the room temperature resistivity, were studied. The transmission electron microscopy (TEM) images showed that the CB particles were aggregated at the interface, between PP and UHMWPE. This selective localization of the CB particles at the interface along with the formation of continuous conducting media leads to the formation of additional conducting networks, resulting in a percolation threshold at a low CB content. A synergy effect of the hybrid conducting fillers of CB and c-MWNTs on the PTC behavior of the hybrid blends was also observed. The room temperature resistivity was reduced significantly by the incorporation of the c-MWNTs into the PP/UHMWPE/CB composite. The intensity and repeatability of the PTC effect in the nanocomposites were improved and the NTC effect weakened by incorporating a small amount (0.5 wt %) of c-MWNTs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010</P>

Optimization of an organic photovoltaic device via modulation of thickness of photoactive and optical spacer layers

Li, Qi,Yoon, Won Jung,Ju, Heongkyu Springer 2014 NANOSCALE RESEARCH LETTERS Vol.9 No.1

<P>We examine the modulation effects of thicknesses of both a photoactive layer (a bulk-heterojunction (BHJ) of poly(3-hexylthiophene) and [6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM)) and an optical spacer of a transparent metal oxide, for power conversion efficiency optimization of organic photovoltaic devices. The redistribution of the optical intensity at the photoactive layer via the thickness modulation of both layers is taken into account, to produce three-dimensional (3D) plots as a function of both layer thicknesses of 0 to 400 nm range (5 nm step), for the device efficiency optimization. The modulation pattern of absorption is produced in the 3D plot as scanning the thicknesses of both layers as a result of modulation of interference between incoming and reflected light, which can be secured by changing the effective optical path length between two electrodes of a photovoltaic device. It is also seen that the case of inserting the spacer of the higher refractive index demands finer adjustment of the spacer layer thickness to achieve the optimum device efficiency.</P><P>In addition, the series resistance of the photoactive layer of the thickness range of 0 to 70 nm is taken into account to provide the 3D plots as a function of the scanned thicknesses of both layers. Inclusion of the series resistance of the photoactive layer, which is also the function of its thickness, in the simulation, indicates that the series resistance can influence qualitatively the dependence of power conversion efficiency (PCE) on the thicknesses of both layers. We also find that minimization of series resistance, e.g., by device annealing, allows not only the relevant voltage to increase but also the optimum thickness of the photoactive layer to increase, leading to more absorption of light.</P>

Meaning in absence: The case of tampon use among Chinese women

Liqi Ren,Denis Simon,Jianfeng Wu 이화여자대학교 아시아여성학센터 2018 Asian Journal of Women's Studies(AJWS) Vol.24 No.1

While the tampon is a popular female hygiene product that is used in most western countries, within the Chinese market, around 98 percent of women use sanitary napkins and only 1.9 percent use tampons. The culture is changing rapidly in China today, but tampons have not been accepted by many women. What do Chinese women think about using tampons? How do culture and objects interact with each other in terms of rejection and receptivity? This paper tries to answer these questions by discussing the relationship between culture and objects, Chinese sexual culture, and the perceptions of women regarding tampons. It is possible to gain extensive cultural knowledge about Chinese society and values by exploring what the absence of this object means, which in turn provides a glimpse into the socio-cultural fabric of a society and the operational values of the community.

Experimental investigation on the dielectric and impedance properties of indium doped titanium dioxide ceramics

Liqi Cui,Ruifeng Niu,Depeng Wang,Weitian Wang 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.2

Single-phased indium doped titanium dioxide (Ti1-xInxO2, x=0~5%) ceramics were synthesized by using solid-state reactionmethod in this study. The doping effect on the dielectric and impedance properties was investigated in a broad frequency rangefrom 102 Hz to 106 Hz. The observed dielectric behavior can be ascribed to the Universal Dielectric Response. In higherfrequency field, the dielectric permittivity varies slightly with the doping concentration x. However, the measured dielectricconstant increases significantly with the increase of doping concentration within lower frequency range. The charged grainboundarycores originated from the doping trivalent ion can be used to explain the results.

Thesaurus-Based Semantic Smoothing in Language Modeling for Chinese Document Retrieval

Liqi Gao,Ting Liu,Ru Chen,Yu Zhang 한국어정보학회 2006 한국어정보학 Vol.8 No.1

Language modeling for Information Retrieval proposed a few years ago has been attractive and improved the performance of IR systems effectively comparing to classic models and approaches. Smoothing technology in parameter estimations is one of main problems in carrying out language models. The performance of IR system will be enhanced by effective smoothing methods. Semantic smoothing has been developed recently for language modeling with some knowledge of language. This paper presents a modification to a smoothing approach in general language model combining with translation modeling, which is taking synonyms in documents and the collection into account for semantic smoothing and performance improving in Chinese document retrieval. The synonym knowledge is from a well‐known thesaurus in Chinese NLP, called Tongyici Cilin (Extended). A comparison shows that the semantic smoothed approach brings approximately 1.33% improvement on average.

Effects of sintering temperature on the dielectric and impedance properties of phase-pure titanium dioxide ceramics

Liqi Cui, Ruifeng Niu,Weitian Wang 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.1

In this study, phase-pure titanium dioxide TiO2 ceramics were sintered at different temperatures (1,000, 1,100, 1,200, 1,300,1,400 oC). The effects of sintering temperature on the compaction, dielectric and impedance properties were investigated. Frequency and temperature dependencies of dielectric permittivity and dielectric loss were revealed by using dielectricmeasurements. When the TiO2 ceramics sintered at 1,400 oC, it exhibits the larger dielectric constant and the smaller dielectricloss as a result of increased density and decreased porosity. The analysis of complex impedance in the frequency range 100Hz-10 MHz indicated that the TiO2 ceramics were dielectrically combinations of bulk grains and grain boundaries. Theseresults suggest that the sintering temperatures have effects on the microstructure, leading to the variations in dielectric andimpedance properties of TiO2 ceramics.

Impedance Properties of Phase-Pure Titanium Dioxide Ceramics Sintered at Different Temperatures

Liqi Cui,Ruifeng Niu,Weitian Wang 한국재료학회 2022 한국재료학회지 Vol.32 No.4

In this study, phase-pure titanium dioxide TiO2 ceramics are sintered using standard high-temperature solid-state reaction technique at different temperatures (1,000, 1,100, 1,200, 1,300, 1,400 oC). The effect of sintering temperature on the densification and impedance properties of TiO2 ceramics is investigated. The bulk density and average grain size increase with the increase of sintering temperature. Impedance spectroscopy analysis (complex impedance Z * and complex modulus M *), performed in a broad frequency range from 100 Hz to 10 MHz, indicates that the TiO2 ceramics are dielectrically heterogeneous, consisting of grains and grain boundaries. The complex impedance Z *-plane indicates the resistance of grains of the TiO2 ceramics increases with increasing sintering temperature, while that of grain boundaries develops in the opposing direction. The complex modulus M *-plane shows a grain capacitance that seems to be independent of the sintering temperature, while that of the grain boundaries decreases with increasing sintering temperature. These results suggest that different sintering temperatures have effects on the microstructure, leading to changes in the impedance properties of TiO2 ceramics.

Trends in Venous Thromboembolism Readmission Rates after Ischemic Stroke and Intracerebral Hemorrhage

Liqi Shu,Adam de Havenon,Ava L. Liberman,Nils Henninger,Eric Goldstein,Michael E. Reznik,Ali Mahta,Fawaz Al-Mufti,Jennifer Frontera,Karen Furie,Shadi Yaghi 대한뇌졸중학회 2023 Journal of stroke Vol.25 No.1

Background and Purpose Venous thromboembolism (VTE) is a life-threatening complication of stroke. We evaluated nationwide rates and risk factors for hospital readmissions with VTE after an intracerebral hemorrhage (ICH) or acute ischemic stroke (AIS) hospitalization. Methods Using the Healthcare Cost and Utilization Project (HCUP) Nationwide Readmission Database, we included patients with a principal discharge diagnosis of ICH or AIS from 2016 to 2019. Patients who had VTE diagnosis or history of VTE during the index admission were excluded. We performed Cox regression models to determine factors associated with VTE readmission, compared rates between AIS and ICH and developed post-stroke VTE risk score. We estimated VTE readmission rates per day over a 90-day time window post-discharge using linear splines. Results Of the total 1,459,865 patients with stroke, readmission with VTE as the principal diagnosis within 90 days occurred in 0.26% (3,407/1,330,584) AIS and 0.65% (843/129,281) ICH patients. The rate of VTE readmission decreased within first 4–6 weeks (P<0.001). In AIS, cancer, obesity, higher National Institutes of Health Stroke Scale (NIHSS) score, longer hospital stay, home or rehabilitation disposition, and absence of atrial fibrillation were associated with VTE readmission. In ICH, longer hospital stay and rehabilitation disposition were associated with VTE readmission. The VTE rate was higher in ICH compared to AIS (adjusted hazard ratio 2.86, 95% confidence interval 1.93–4.25, P<0.001). Conclusions After stroke, VTE readmission risk is highest within the first 4–6 weeks and nearly three-fold higher after ICH vs. AIS. VTE risk is linked to decreased mobility and hypercoagulability. Studies are needed to test short-term VTE prophylaxis beyond hospitalization in high-risk patients.

Optical properties of transition-metal oxide thin films deposited using a pulsed laser

Cui Liqi,Wang Ruiteng,Wang Weitian 한국물리학회 2021 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.79 No.2

Transition-metal oxide thin films of V2O5, ZrO2, and CeO2 were fabricated on MgO single-crystal substrates using a pulsedlaser deposition technique. The linear optical transmission spectra were measured at room temperature, and the data showing a fringe pattern in the transparent spectral region were used to determine the linear refractive indices of the films. The values of the linear refractive indices decrease with increasing wavelength, and the relationship could be well explained using Wemple’s theory. The third-order nonlinear optical properties of the films were determined using a single-beam z-scan method at a wavelength of 532 nm. The results showed that the prepared V2O5 film exhibited a fast third-order nonlinear optical response, with the nonlinear absorption coefficient and the nonlinear refractive index being 3.97 × 10–10 m/W and 4.55 × 10–17 m2/ W, respectively, which are larger than those for the ZrO2 and the CeO2 films. The metal–oxygen bond lengths based on the bond-orbital theory could be used to explain these results.

Linear and Nonlinear Optical Properties of Vanadium Pentoxide Films Prepared by Pulsed-Laser Deposition

Cui, Liqi,Wang, Ruiteng,Wang, Weitian Materials Research Society of Korea 2021 한국재료학회지 Vol.31 No.7

Well-crystallized vanadium pentoxide V₂O₅ thin films are fabricated on MgO single crystal substrates by using pulsed-laser deposition technique. The linear optical transmission spectra are measured and found to be in a wavelength range from 300 to 800 nm; the data are used to determine the linear refractive index of the V₂O₅ films. The value of linear refractive index decreases with increasing wavelength, and the relationship can be well explained by Wemple's theory. The third-order nonlinear optical properties of the films are determined by a single beam z-scan method at a wavelength of 532 nm. The results show that the prepared V₂O₅ films exhibit a fast third-order nonlinear optical response with nonlinear absorption coefficient and nonlinear refractive index of 2.13 × 10^-10 m/W and 2.07 × 10^-15 cm²/kW, respectively. The real and imaginary parts of the nonlinear susceptibility are determined to be 3.03 × 10^-11 esu and 1.12 × 10^-11 esu, respectively. The enhancement of the nonlinear optical properties is discussed.