INVESTIGATION ON STABILITY OF PZT/EPOXY PIEZOCOMPOSITE WITH PRESSURE AND TEMPERATURE

With the universal test machine and temperature test chamber, the effect of pressure and temperature on the behavior of 1-3 and 1-3-2 piezocomposites prepared with PZT/epoxy in our lab has been investigated through electrical impedance and dielectric analysis. The permittivity, resonant frequency and dielectric loss of the composites have been measured under vertical stress and temperature, and the variety of the material properties under pressure and temperature could also be obtained. The pressure and temperature stability of the composites have been assessed through experiments. The data of these two types of composites indicated that the stability of 1-342 composite with pressure was better than that of 1-3 composite, and two composites have almost the same dielectric stability with temperature. However, 1-3-2 composite showed slower frequency variation than 1-3 composite.

The Artist in Henry James An Appreciation of The Portrait of a Lady

The Jamesian style of poise and exquisiteness, and his notion of structural balance and his superb craftsmanship, is bril-liantly exemplified by The Portrait of a Lady, a work to be appreciated endlessly. This paper studies the artistic genius of HenryJames, as it attains a great height in this early masterpiece.

Exploration and Reflection on College Online English Teaching in Henan Police College

Under the background of the Internet Plus,the research on the online and offline integrated teaching mode is particularly important.Therefore,based on the teaching of Henan Police College and taking the college English course as an example,this paper investigates and analyzes the online teaching situation.The results show that there are significant differences between gender and grade in students’online English learning;the biggest difficulty for students in online English learning is the lack of learning materials like textbooks and the simultaneous use of multiple equipment in class;the biggest problem in the ideological and political integration of English course is that the way of ideological and political integration in English class lacks of variety.Through this research,it is hoped to help teachers in HNP college improve the online teaching mode,improve the online teaching quality,and promote the normalization of online and offline teaching mode.

A Discourse Analysis on Problem-Solution Pattern of Cosmetic Advertisements

Based on Winter's and Hoey's theories on discourse analysis, the Problem-Solution Pattern in cosmetic advertising from the perspective of text patterns and lexical signaling is discussed by analyzing thirty pieces of advertisements on cosmetic products. Findings suggest text patterns of cosmetic advertisements display in various forms and the components of Problem-Solution Pattern are signaled by lexical items as emotive vocabulary with positive or negative meanings and repetition of the brand names. Possible implications are offered for cosmetic advertising industry in writing effective advertisements both in English and Chinese.

The HY5 transcription factor negatively regulates ethylene production by inhibiting ACS1 expression under blue light conditions in pear

Ethylene is the main factor controlling fruit ripening of pear(Pyrus ussuriensis).Ethylene production rate is negatively correlated with fruit shelf life;therefore,it is important to decrease the ethylene levels for optimal fruit storage.Here,we observed that blue light treatment could inhibit ethylene production and promote the expression of ELONGATED HYPOCOTYL 5(PuHY5),a basic leucine zipper domain(bZIP)transcription factor.The following studies showed that PuHY5 could bind to the promoter of ACC synthase 1(PuACS1),a rate-limiting enzyme in ethylene biosynthesis,and inhibit its expression.For pears in which Pu HY5 was silenced,the ethylene production and PuACS1 expression were much higher than those in the control fruit.These results demonstrated that blue light inhibited ethylene production through the induction of Pu HY5 in pear.Our finding provides a new method for prolonging fruit shelf life.

Analysis on Cooperative Principle in Chinese Context

Some examples of flouting Cooperative Principle (CP) in Chinese people's greeting, requesting, and accepting compliment are presented and the cultural reasons for these violations are explained in this article. By analyzing the Chinese way of flouting CP, the author explores the unique characteristics of CP in Chinese context.

Chinese Keyword Search by Indexing in Relational Databases

In this paper, we propose a new method based on index to realize IR-style Chinese keyword search with ranking strategies in relational databases. This method creates an index by using the related information of tuple words and presents a ranking strategy in terms of the nature of Chinese words. For a Chinese keyword query, the index is used to match query search words and the tuple words in index quickly, and to compute similarities between the query and tuples by the ranking strategy, and then the set of identifiers of candidate tuples is generated. Thus, we retrieve top-N results of the query using SQL selection statements and output the ranked answers according to the similarities. The experimental results show that our method is efficient and effective.

Evaluating Relational Ranking Queries Involving both Text Attributes and Numeric Attributes

In many database applications, ranking queries may reference both text and numeric attributes, where the ranking functions are based on both semantic distances/similarities for text attributes and numeric distances for numeric attributes. In this paper, we propose a new method for evaluating such type of ranking queries over a relational database. By statistics and training, this method builds a mechanism that combines the semantic and numeric distances, and the mechanism can be used to balance the effects of text attributes and numeric attributes on matching a given query and tuples in database search. The basic idea of the method is to create an index based on WordNet to expand the tuple words semantically for text attributes and on the information of numeric attributes. The candidate results for a query are retrieved by the index and a simple SQL selection statement, and then top-N answers are obtained. The results of extensive experiments indicate that the performance of this new strategy is efficient and effective.

Luminescence and energy transfer of white emitting phosphor YAl_3(BO_3)_4:Ce^(3+), Dy^(3+)

A white emitting phosphor of YAl33(BO3)4:Ce+,Dy3+is synthesized by a solid state reaction,and its luminescent properties are investigated.Its phase formation is carried out with X-ray powder diffraction analysis,and there is no crystalline phase other than YAl3(BO3)4.YAl3(BO3)4:Ce3+can produce 422 nm blue emission under 367 nm excitation.The emission spectrum of YAl33(BO3)4:Dy+shows several emission peaks under 350 nm excitation,and the peaks locate at485 nm,575 nm and 668 nm,respectively.Emission intensities of Ce3+and Dy3+in YAl3(BO3)4 are influenced by their concentrations,and the concentration quenching effect is observed.Energy transfer from Ce3+to Dy3+in YAl3(BO3)4 is validated and proved to be a resonant type via a quadrupole-quadrupole interaction,and the emission color can be tuned from blue to white by tuning the ratio of Ce3+/Dy3+.Moreover,the critical distance(Rc)of Ce3+to Dy3+in YAl3(BO3)4 is calculated to be 1.904 nm.

Luminescent properties of blue emitting phosphor SrZn_2(PO_4)_2:Eu^(2+) for white LEDs

Blue emitting phosphor SrZn_2(PO_4)_2:Eu^(2+) is synthesized by a high temperature solid state method,and the luminescent properties are investigated.At the 330 nm radiation excitation,SrZn_2(PO_4)_2:Eu^(2+) presents an emission band at 416 nm,which is assigned to the 4f^65d^1→4f^7 transition of Eu^(2+) ion.The concentration quenching effect of Eu^(2+) in SrZn_2(PO_4)_2has been validated and proved to be a resonant type via a dipole-dipole interaction.The critical distance(R_c) of Eu^(2+) in SrZn_2(PO_4)_2 is calculated to be 3.244 nm.The Commission International de I'Eclairage(CIE) chromaticity coordinates of SrZn_2(PO_4)_2:Eu^(2+) locate at the blue region,such as(0.150,0.072).The results indicate that the SrZn_2(PO_4)_2:Eu^(2+)phosphor may have potential applications in white light emitting diodes(LEDs).

Luminescence,Concentration Quenching and Thermal Stability of White Emitting Phosphor Ba_2Ca(BO_3)_2:Dy^(3+)

A white emitting phosphor Ba2Ca(BO3)2:Dy3+ was synthesized via a high temperature solid state reaction at 1000℃ for 5 h. The luminescence, mole fraction quenching and thermal stability of Ba2Ca(BO3)2:Dy3+ were investigated. According to the phase composition analyzed by X-ray powder diffraction, there is no crystalline phase except Ba2Ca(BO3)2 in the sample. Ba2Ca(BO3)2:Dy3+ can produce white emission under 348 nm excitation. The emission intensities of Ba2Ca(BO3)2:Dy3+ are affected by Dy3+ concentration. The concentration quenching effect was analyzed, and the concentration quenching mechanism was verified as dipole-dipole interaction. The critical distance(R c) obtained based on the crystal structure data is 2.911 nm. At 150℃, the emission intensity of Ba2Ca(BO3)2:Dy3+ is 68.0% of the initial value at room temperature. The activation energy for the thermal quenching calculated is 0.202 e V. Moreover, the CIE chromaticity coordinates of Ba2Ca(BO3)2:Dy3+ locate in the white region of(0.319, 0.356).

Tunable emission, concentration quenching and crystallographic sites of Eu^(2+) in Sr_3Y(PO_4)_3

A series of Sr3Y(PO4)3:Eu2+ samples are synthesized by the high temperature solid-state method. Sr3Y(PO4)3:Eu2+shows an asymmetrical emission band under excitation of 350 nm. The emission peaks at 426 nm and 497 nm are assigned to the nine-coordination Eu2+ and six-coordination Eu2+, respectively. The effects of Eu2+ doping content on the emission intensity and color are observed, and the concentration quenching effect is also observed. For two different Eu2+ luminescence centers, the quenching mechanisms are dipole-dipole interaction and quadrupole-quadrupole interaction, respectively. And the critical distance of energy transfer is calculated by concentration quenching and turns out to be about 3.67 nm. The results above show that the asymmetrical emission band of Sr3Y(PO4)3:Eu2+ comes from two different Eu2+ luminescence centers in the lattice.

Luminescence and energy transfer of Ce^(3+)-Eu^(2+) in Ca_9Al(PO_4)_7

A series of Ce^(3+),Eu^(2+) and Ce^(3+)-Eu^(2+) doped Ca_9Al(PO_4)_7 phosphors are synthesized by a high temperature solid-state method.Under 291 nm excitation,Ca_9Al(PO_4)_7:Ce^(3+) has one emission band at 356 nm,which is attributed to4f°5d^1→4f^1 transition of Ce^(3+).Under 305 nm excitation,Ca_9Al(PO_4)_7:Eu^(2+) presents one emission band at 445 nm,which is assigned to 4f^65d^1→4f^7 transition of Eu^(2+).Energy transfer from Ce^(3+) to Eu^(2+) in Ca_9Al(PO_4)_7 is validated and proved to be a resonant type via a quadrupole-quadrupole interaction.Critical distance(R_c) of Ce^(3+) to Eu^(2+) in Ca_9Al(PO_4)_7 is calculated to be 1.264 nm.Moreover,the emission intensity of Ca_9Al(PO_4)_7:Ce^(3+),Eu^(2+) can be tuned by properly adjusting the relative doping composition of Ce^(3+)/Eu^(2+).

Luminescence properties of tunable red-green emitting phosphor Ba2Ca(BO3)2：Eu3＋,Tb3＋

A series of Eu^(3+) or Tb^(3+) doped Ba_2Ca(BO_3)_2 phosphors were synthesized by a high temperature solid state method, and the luminescence properties are investigated. Ba_2Ca(BO_3)_2:Tb^(3+) can show an obvious green emission, and the peak locates at 551 nm, which corresponds to the 5D34→7F5 transition of Tb^(3+). Ba_2Ca(BO_3)_2:Eu+ can present the characteristic emission of Eu^(3+), and the peak locates at 600 nm, which is ascribed to the 5D70→F2 transition of Eu^(3+). In order to achieve the emission-tunable phosphors, the Eu^(3+)/Tb^(3+) co-doped Ba_2Ca(BO_3)_2 are synthesized. When tuning the Eu^(3+) or Tb^(3+) concentration, Ba_2Ca(BO_3)_2:Eu^(3+), Tb^(3+) can both show the tunable emission, which may be induced by the energy transfer from Tb^(3+) to Eu^(3+).

Photoluminescence properties of solid-state Tb^(3+) doped NaY(MoO_4)_2

A series of Tb3+ doped Na Y(Mo O4)2 are synthesized by a solid-state reaction at 550 °C for 4 h, and their luminescent properties are investigated. The phase formation is carried out with X-ray powder diffraction analysis, and there is no other crystalline phase except Na Y(Mo O4)2. Na Y(Mo O4)2:Tb3+ can produce the green emission under 290 nm radiation excitation, and the luminescence emission peak at 545 nm corresponds to the 5D4→7F5 transition of Tb3+. The emission intensity of Tb3+ in Na Y(Mo O4)2 is enhanced with the increase of Tb3+ concentration, and there is no concentration quenching effect. The phenomena are proved by the decay curves of Tb3+. Moreover, the Commission International de I'Eclairage(CIE) chromaticity coordinates of Na Y(Mo O4)2:Tb3+ locate in the green region.

A novel white-bluish emitting phosphor of (Ba_(0.49)Sr_(0.49))_2B_2P_2O_(10):0.02Eu^(2+) for white LEDs

A novel white-bluish emitting phosphor of (Ba0.49Sr0.49)2B2P2O10:0.02Eu2+ is synthesized by the solid state reaction. (Ba0.49Sr0.49)2B2P2O10:0.02Eu2+ can be effectively excited by 370 nm ultraviolet (UV) light, and exhibits two emission bands at 430 nm and 522 nm which are attributed to the d-f transitions of the Eu2+ ions in two different cation sites in the host lattices. And the chromaticity coordinate of (Ba0.49Sr0.49)2B2P2O10:0.02Eu2+ phosphor is (0.29, 0.25).

Improved luminescent properties of SrZn_2(PO_4)_2:Sm^(3+) doped with Li^+, Na^+ and K^+ ions

SrZn2(PO4)2:Sm3+ phosphor was synthesized by a high temperature solid-state reaction in atmosphere. SrZn2(PO4)2:Sm3+ phosphor is efficiently excited by ultraviolet(UV) and blue light, and the emission peaks are assigned to the transitions of 4G5/2-6H5/2(563 nm), 4G5/2-6H7/2(597 nm and 605 nm) and 4G5/2-6H9/2(644 nm and 653 nm). The emission intensities of SrZn2(PO4)2:Sm3+ are influenced by Sm3+ concentration, and the concentration quenching effect of SrZn2(PO4)2:Sm3+ is also observed. When doping A+(A=Li, Na and K) ions, the emission intensity of SrZn2(PO4)2:Sm3+ can be obviously enhanced. The Commission Internationale de l'Eclairage(CIE) color coordinates of SrZn2(PO4)2:Sm3+ locate in the orange-red region. The results indicate that the phosphor has a potential application in white light emitting diodes(LEDs).

Improving the luminescence properties of Ba_3Eu(PO_4)_3 by doping Sm^(3+) as sensitizer

For enhancing the emission intensity and broadening the excitation region of Ba_3Eu(PO_4)_3(BEP),Sm^(3+) is doped as sensitizer in this paper.BEP:Sm^(3+) can produce an obvious red emission at near ultraviolet(n-UV) radiation.An effective energy transfer from Sm^(3+) to Eu^(3+) is proved.The commission international de I'Eclairage(CIE) chromaticity coordinates of BEP:Sm^(3+) locate at red region.When the environment temperature is 150℃,the emission intensity of BEP:0.10Sm^(3+) is decreased to 76%of the initial one at room temperature,and the activation energy is calculated to be0.164 eV,which can prove the good thermal stability of BEP:Sm^(3+).The results indicate that BEP:Sm^(3+) may have potential applications in white light emitting diodes(LEDs).