Xinyu Li - Academia.edu (original) (raw)

Papers by Xinyu Li

Biosensors and Bioelectronics, 2015

A sensitive photoelectrochemical (PEC) biosensor for detection of organophosphorus pesticides (OP... more A sensitive photoelectrochemical (PEC) biosensor for detection of organophosphorus pesticides (OPs) using the nanocomposite of CdSe@ZnS quantum dots (QDs) and graphene deposited on the ITO coated glass electrode as a photoactive electrode is presented. The integration of CdSe@ZnS/graphene nanocomposite with biomolecules acetylcholinesterase (AChE) as a biorecognition element yields a novel biosensing platform. Under visible light irradiation, the AChE-CdSe@ZnS/graphene nanocomposite can generate a stable photocurrent and the photocurrent is found to be inversely dependent on the concentration of OPs. Under the optimal experimental conditions, the photocurrents were proportional to the logarithm of paraoxon and dichlorvos within the concentration range of 10(-12)-10(-6) M. The detection limits (LOD) of the proposed biosensor for paraoxon and dichlorvos are as low as 10(-14) M and 10(-12) M. The photoelectrochemical biosensor shows good sensitivity, reproducibility, stability, and could be successfully applied to detection of OPs in real fruit samples.

PloS one, 2014

To investigate the associations of single nucleotide polymorphisms (SNPs) of three genes (IL-12B,... more To investigate the associations of single nucleotide polymorphisms (SNPs) of three genes (IL-12B, IL-12Rβ1 and IL-12Rβ2) in Behcet's disease (BD) and Vogt-Koyanagi-Harada (VKH) syndrome in a Chinese Han population. A total of 806 BD cases, 820 VKH patients, and 1600 healthy controls were involved in this study. The first investigation included 400 BD patients, 400 VKH cases, and 600 healthy individuals. A second confirmatory study included a separate set of 406 BD patients, 420 VKH cases and another 1000 normal controls. Genotyping was carried out by PCR-restriction fragment length polymorphism assay and results were validated by using direct sequencing. The χ2 test was performed to compare the allele and genotype frequencies between cases and healthy controls. This study comprised two phases. In the first phase study, a significantly increased frequency of the rs3212227/IL-12B genotype CC and C allele was found in BD patients as compared to controls (Bonferroni corrected p valu...

Ferroelectric perovskite oxides possess large electrocaloric effect, but only at high temperature... more Ferroelectric perovskite oxides possess large electrocaloric effect, but only at high temperature, which limits their potential as next generation solid state cooling devices. Here, we demonstrate from phase field simulations that a giant adiabatic temperature change exhibits near room temperature in the strained ferroelectric PbTiO 3 nanotubes, which is several times in magnitude larger than that of PbTiO 3 thin films. Such giant adiabatic temperature change is attributed to the extrinsic contribution of unusual domain transition, which involves a dedicated interplay among the electric field, strain, temperature and polarization. Careful selection of external strain allows one to harness the extrinsic contribution to obtain large adiabatic temperature change in ferroelectric nanotubes near room temperature. Our finding provides a novel insight into the electrocaloric response of ferroelectric nanostructures and leads to a new strategy to tailor and improve the electrocaloric properties of ferroelectric materials through domain engineering.

ABSTRACT The entropy and/or temperature change of material with respect to electric fields is kno... more ABSTRACT The entropy and/or temperature change of material with respect to electric fields is known as electrocaloric effect (ECE). Giant ECE is discovered in P(VDF-TrFE) ferroelectric copolymers near ferroelectric-paraelectric (F-P) transition temperature. F-P transition is normally much higher than room temperature around which is preferred by working temperature of cooling device configuration. This paper presents the two defect-inducing methods to lower and broaden working temperature range of P(VDF-TrFE) based copolymers for ECE. Giant ECE is experimentally demonstrated in large temperature range (0-55°C). In addition, an electrocaloric oscillatory refrigerator (ECOR) was proposed and simulated by finite volume method and its high performance was theoretically demonstrated. Temperature gradient larger than 30 °C can be maintained across the two sides of a 1 cm device. For ΔT=20 °C cooling condition, a high cooling power (5.4 W/cm2) and significantly higher coefficient of performance (COP) can be achieved (50% of Carnot efficiency).

The electrocaloric effect (ECE) is the adiabatic temperature change or isothermal entropy change ... more The electrocaloric effect (ECE) is the adiabatic temperature change or isothermal entropy change caused by the polarization change of a dielectric material when subjected to a change of external electric field. The electrostrictive effect is a form of elastic deformation of a dielectric induced by an electric field, associated with those components of strain which are independent of reversal field direction. It was found that both the ECE, e.g., adiabatic temperature change, and the electrostrictive strain in poly (vinylidene fluorideÀtrifluoroethyleneÀchlorofluoroethylene) (P(VDFÀTrFEÀCFE)) terpolymers are proportional to the square of the electric field. The adiabatic temperature change ÁT of ECE versus electric field can be illustrated using a modified BelovÀGoryaga equation. ÁT is proportional to E 2 when E is small. For electrostrictive effect, the rigid-ion model assumes that the anharmonic movement of the ions leads to the quadratic strainÀelectric field relation. The quotient of electrostrictive coefficient Q over the phenomenological coefficient is empirically a constant, indicating that the larger the electrostrictive coefficient, the larger the ECE, which opens a new way to find out new electrocaloric materials.

ABSTRACT We report dielectric investigations of poly(vinylidene fluoride-trifluoroetylene), P(VDF... more ABSTRACT We report dielectric investigations of poly(vinylidene fluoride-trifluoroetylene), P(VDF-TrFE) copolymer, irradiated with high-energy electrons. While the ferroelectric copolymer is transformed into a relaxor system at high irradiation doses, our investigations, particularly nonlinear dielectric experiments, clearly evidence that at lower doses ferroelectric and relaxor states coexist in the P(VDF-TrFE). Nonlinear dielectric response furthermore reveals the nature of the ferroelectric phase transition, which is confirmed by the polarization measurements.

ABSTRACT Dielectric, thermal, and electrocaloric investigations of poly(vinylidene fluoride-trifl... more ABSTRACT Dielectric, thermal, and electrocaloric investigations of poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) copolymer, irradiated with high-energy electrons, are reported. While the ferroelectric copolymer is transformed into a relaxor system at high irradiation doses, dielectric investigations, particularly nonlinear dielectric experiments, i.e., temperature dependences of the second and the third harmonic dielectric response, clearly evidence that at lower doses ferroelectric and relaxor states coexist in the P(VDF-TrFE). This is confirmed by the differential scanning calorimetry, which further reveals the influence of irradiation on the copolymer crystallinity and melting point. Finally, it is shown that large electrocaloric response of VDF-TrFE-based polymers is further enhanced in systems with coexisting relaxor and normal ferroelectric states.

ABSTRACT Currently, sustainable manufacturing (SM) attracts more and more attentions due to the i... more ABSTRACT Currently, sustainable manufacturing (SM) attracts more and more attentions due to the increasing environmental pollution and energy shortage threat. Energy consumption is a fundamental element of SM for its valuable effect in the environmental impacts and business opportunities. Analyzing the relationship between process parameters and energy consumption is helpful to reduce production costs, eliminate negative environmental impacts, and increase business opportunities. Since energy consumption is impacted by the inherent uncertainties in the machining process, how to model energy consumption presents a significant challenge. Gene Expression Programming (GEP) combines the advantages of the Genetic Algorithm and Genetic Programming, and has been successfully applied in formula finding. In this paper, a Greedy Randomized Adaptive Search Procedure (GRASP)-based Gene Expression Programming, named GGEP, is proposed to predict the face milling energy consumption. In this proposed GGEP approach, a GRASP-based learning mechanism and an iterative re-start mechanism have been introduced into the basic GEP. At the basis of defining a GGEP environment for the energy consumption prediction, an explicit model has been constructed. To verify the effectiveness of the proposed approach, a case study has been conducted. The analysis of experiment results reveals that the proposed approach models and predicts the energy consumption with high accuracy and high-speed convergence. Moreover, in order to better study the mechanism of machining, the influence and contribution of different impact factors on energy consumption in face milling are analyzed.

ABSTRACT ABSTRACT The poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) based ferroelectr... more ABSTRACT ABSTRACT The poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) based ferroelectric and relaxor materials have been proved to be good electrocaloric (EC) materials. To further enhance the EC effect in ferroelectric relaxor terpolymer poly(vinylidene fluoride–trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)), composites such as polymer-polymer blends and nanocomposites filled with inorganic nanoparticles are fabricated and investigated. It is found that the addition of small amount of filler (such as P(VDF-TrFE) or nano-ZrO2) can increase terpolymer’s crystallinity and enhance its relaxor behavior through interface couplings. The increased crystallinity and enhanced relaxor behavior together result in enhanced electrocaloric effect. The results demonstrate the promise of composite approaches in tailoring and enhancing ECE in the relaxor terpolymers.

ABSTRACT Both the pyroelectric and electrocaloric effects originate from the cross-coupling betwe... more ABSTRACT Both the pyroelectric and electrocaloric effects originate from the cross-coupling between polarization and temperature in insulating dielectrics. Although both effects have been studied for many decades for various applications and large pyroelectric effect has been observed in many polar-dielectrics, it is only very recently that a large electrocaloric effect (ECE) was obtained in ferroelectric ceramic thin films and polymers, which revives the interest in the ECE. This review will summarize typical properties of pyroelectric and electrocaloric materials, present figures of merit for both phenomena, examine the relationship between the pyroelectric and electrocaloric effect. Moreover, we will also present theoretical works, experimental results, and material modifications to achieve large responses in electrocaloric materials.

ABSTRACT The recent finding of large electrocaloric effect in several ferroelectric polymers crea... more ABSTRACT The recent finding of large electrocaloric effect in several ferroelectric polymers creates unique opportunity for developing compact size solid state cooling cycles beyond the traditional mechanical vapor compression cycles. Here, we show that, by employing regeneration process with solid state regenerators, a chip scale Electrocaloric Oscillatory Refrigeration (ECOR) can be realized. A prototype ECOR is fabricated and characterized. More than 6 K temperature span is obtained near room temperature between the hot and cold sides of a 2 cm long device. Finite volume simulation validates the test results and shows the potential high performance of the ECOR.

ABSTRACT The electrocaloric effect (ECE) is enhanced in ferroelectric relaxor terpolymer poly(vin... more ABSTRACT The electrocaloric effect (ECE) is enhanced in ferroelectric relaxor terpolymer poly(vinylidene fluoride–trifluoroethylene–chlorofluoroethylene) (P(VDF–TrFE–CFE))/ZrO2 nanocomposites. It was observed that the interface effects between the polymer matrix and nano-fillers enhance the polarization response and provide additional electrocaloric entropy changes. As a consequence, the nanocomposites exhibit a larger ECE than that of the neat terpolymer, i.e., the adiabatic temperature change of the nanocomposite with 3 volume percent of nano-fillers is 120% of that of the neat terpolymer. The results, for the first time, demonstrate that ECE can be tailored and enhanced through nanocomposite approach in the ferroelectric polymers.

ABSTRACT In most real manufacturing environment, schedules are usually inevitable with the presen... more ABSTRACT In most real manufacturing environment, schedules are usually inevitable with the presence of various unexpected disruptions. In this study, a new rescheduling technique based on a hybrid intelligent algorithm is developed for solving job shop scheduling problems with random job arrivals and machine breakdowns. According to the dynamic feature of this problem, a new initialization method is proposed to improve the performance of the hybrid intelligent algorithm, which combines the advantage of genetic algorithm and tabu search. In order to solve the difficulty of using the mathematical model to express the unexpected disruptions, a simulator is designed to generate the disruptions. The performance measures investigated respectively are: mean flow time, maximum flow time, mean tardiness, maximum tardiness, and the number of tardy jobs. Moreover, many experiments have been designed to test and evaluate the effect of different initializations in several disruption scenarios. Finally, the performance of the new rescheduling technique is compared with other rescheduling technologies in various shop floor conditions. The experimental results show that the proposed rescheduling technique is superior to other rescheduling techniques with respect to five objectives, different shop load level, and different due date tightness. The results also illustrate that the proposed rescheduling technique has a good robustness in the dynamic manufacturing environment.

Biosensors and Bioelectronics, 2015

PloS one, 2014