BNT-based ferroelectric ceramics: Electrical properties modification by Ta2O5 oxide addition

Due to their superior piezo-responses (strain S > 0.3%), bismuth sodium titanate (BNT)-based relaxor ferroelectrics have received much attention. Compared to other chemical elements, tantalum (Ta) doping provides superior electro-strain for these ferroelectrics, while the effect of Ta₂O₅ as oxide additive has been rarely reported. Herein, lead-free piezoceramics of Bi_0.5(Na_0.72K_0.22Li_0.06)_0.5TiO₃-xTa₂O₅ (BNKLT-xTa₂O₅, x = 0-0.015) are synthesized. We study the effects of Ta₂O₅ addition on the crystal structure, piezoelectric responses, dielectric properties, and ferroelectric properties of BNKLT ceramics. All of the ceramics exhibit a typical perovskite structure, and Ta₂O₅ diffuses into the BNKLT lattice to form a uniform solid solution. The addition of Ta₂O₅ can make the grains more regular and uniform, while excess Ta₂O₅ result in finer grains. The undoped BNKLT ceramics show good ferroelectric and piezoelectric properties (remnant polarization P_r = 22.5 μC/cm² and piezoelectric coefficient d₃₃ = 250 pC/N); however, the addition of Ta₂O₅ leads to an clear degradation in d₃₃ and P_r. Meanwhile, the addition of an appropriate Ta₂O₅ amount leads to an increase in the electro-strain, and the unipolar strain reaches 0.385% under 60 kV/cm for x = 0.003, together with a higher normalized strain (d₃₃^*=S_max/E_max) of 633 pm/V (x = 0.003). The enhanced strain behaviors can be attributed to the coexistence of the ferroelectric and relaxor states, and an excellent electrostriction coefficient Q₃₃ (Q₃₃ = S/P²) value of 0.038 m⁴C⁻² is obtained under 60 kV/cm for x = 0.003.     

1-MCP 结合PE 包装处理对带壳茭白贮藏品质的影响

为探究低温贮藏条件下1-甲基环丙烯（1-methylcyclopropene,1-MCP）结合聚乙烯（polyethylene,PE）保鲜袋包装处理对带壳茭白采后贮藏品质和木质化进程的影响,以新鲜带壳茭白为原料,将其分别用0.07 mm PE 袋、0.14 mm PE 袋、0.07 mm 纳米复合PE 袋、1-MCP 结合0.07 mm PE 袋、1-MCP 结合0.14 mm PE 袋包装。各处理组于（1±1）℃条件下贮藏,定期检测分析各组原料的理化指标。结果表明：1-MCP 结合不同厚度的PE 袋处理均能有效减缓茭白硬度和L* 值的降低,维持果实中总糖和还原糖的含量,并且通过抑制丙二醛含量的升高和过氧化物酶活性的增加,减缓茭白中纤维素和木质素的合成和积累。其中1-MCP 结合0.14 mm PE 袋对带壳茭白的保鲜效果最好,能够有效延缓茭白的采后衰老,延长贮藏期并改善其贮藏品质。     

中原油田注水管线PIG清洗实例

中原油田注水管线结垢严重,影响注水量,经研究分析清洗工艺技术,决定选用PIG清洗,清洗效果达到预期目的.     

Microstructure and Electrical Properties of [(K0.50Na0.50)0.95−xLi0.05Agx](Nb0.95Ta0.05)O3 Lead-Free Ceramics

[(K_0.50Na_0.50)_{0.95− x} Li_0.05Ag _x ](Nb_0.95Ta_0.05)O₃ (KNLNANT- x ) lead-free piezoelectric ceramics were prepared by normal sintering. Effects of the Ag content on the microstructure and electrical properties of KNLNANT- x ceramics were systematically investigated. It is found that the ceramics with x =0.03 exhibit relatively good electrical properties along with high Curie temperature: ( d ₃₃∼252 pC/N, T _c∼438°C, k _p∼45.4%, P _r∼30.1 μC/cm², E _c∼13.8 kV/cm, ɛ_r∼1030, and tan δ∼2.6%). The related mechanism for enhanced electrical properties of the ceramics was also discussed. These results show that KNLNANT-0.03 ceramic is a promising candidate material for high temperature lead-free piezoelectric ceramics.     

丙烷压缩装置循环水系统清洗

选择和设计了一种复配清洗剂和清洗工艺.将复配的清洗剂和相应的复合缓蚀剂应用于该设备的清洗,取得了很好的效果.     

Construction of new morphotropic phase boundary in 0.94(K0.4?xNa0.6BaxNb1?xZrx)O3–0.06LiSbO3 lead-free piezoelectric ceramics

0.94(K_0.4−x Na_0.6Ba _x Nb_1−x Zr _x )O₃–0.06LiSbO₃ ceramics were prepared by conventional technique, and the effect of BaZrO₃ on the phase transitions, dielectric, ferroelectric, and piezoelectric properties of the ceramics were investigated. The phase transitions for the ceramics were determined by the temperature dependence of dielectric properties and X-ray diffraction patterns. BaZrO₃ changes the symmetry of the ceramics from tetragonal dominant phase with x = 0–0.06 to rhombohedral phase with x = 0.07–0.09. The phase transition near room temperature for the composition with x ~ 0.06 is different from previously reported phase transition between orthorhombic and tetragonal phases. It is suggested that a new morphotropic phase boundary (MPB) is constructed with both rhombohedral–orthorhombic and orthorhombic–tetragonal phase transitions near room temperature, and the enhanced piezoelectric properties (d ₃₃ = 344 pC/N and k _P = 32.4% with x = 0.06) are obtained. The results indicate that the construction of new MPB is of significance for further development of KNN-based ceramics.     

Enhanced pyroelectric performance in potassium sodium niobate-based ceramics via multisymmetries coexistence design

Achieving excellent pyroelectric performance remains a challenge for lead-free piezoelectric ceramics. To meet the requirements of both an enhanced pyroelectric coefficient at room temperature and good thermal stability during the encapsulation of pyroelectric devices, (1–x)K_0.48Na_0.52NbO₃–xBi_0.5Ag_0.5ZrO₃–0.2%Fe₂O₃ (KNN–BAZ–Fe) lead-free ferroelectric ceramics with high Curie temperatures were prepared to obtain improved pyroelectric performance via the coexistence of multiple symmetries. The variation of BAZ content led to the formation of rhombohedral–orthorhombic–tetragonal phase boundary and promoted grain growth, resulting in the best pyroelectric coefficient (p = 5.09 × 10⁻⁴ C m⁻²°C⁻¹) and enhanced figures of merit (F_i = 0.2084 × 10⁻⁹ (m V⁻¹), F_v = 0.0142 m² C⁻¹, F_d = 0.0947 × 10⁻⁴ Pa^−1/2, and F_e = 17.66 J m⁻³ K⁻²) for infrared (IR) detection when x = 0.05. The room-temperature pyroelectric coefficient obtained in this study is approximately four times that of the pure KNN ceramic and is the maximum value reported for niobate-based piezoelectric ceramics. Moreover, compared with the poor thermal stability of barium titanate- and bismuth sodium titanate-based ceramics because of their ultralow Curie temperature or thermal depolarization temperature, the ceramics investigated here exhibit much better thermal stability because of their high Curie temperature (T_C > 300°C) and diffused phase-transition behavior, making them more adaptable for practical applications. These results suggest that KNN–xBAZ–Fe ceramics are attractive candidates for applications in the field of IR sensors.     

SMO算法的简化及其在非正定核条件下的应用

SMO算法是求解大型支持向量机(SVM)的有效算法.已有的算法都必须判定4个Lagrange乘子位于哪个象限,从而使算法的实现更为复杂.此外,现有算法都假定核矩阵是正定的或半正定的,因此使其应用受到了限制.考虑到传统算法的不足,提出了一种用于ε-SVR的简化SMO算法,进而将其用于求解非正定核的ε-SVR.与已有的算法不同,通过将ε-SVR的原始规划问题进行展开并求解其KKT条件,提出的算法只需考虑2个Lagrange乘子,从而有效地简化了算法的实现,并能方便地应用于非正定核SVR的求解.采用一个常用于衡量预测误差的函数对算法进行了测试,实验表明,与ε-SVR现有的SMO算法相比,在不增加空间复杂度和时间复杂度的前提下避免了大量繁琐的判别条件,简化了算法的实现,这就为不同的损失函数所对应的SVR提供了一个通用的SMO算法,从而有利于SVR的推广应用.另外,提出的求解非正定核的ε-SVR的方法也为求解其他的非正定核SVR提供了一个思路.     

指针的学习与应用

指针是C程序设计的重点和难点，也是软件界的讨论热点：、正确而灵活地运用指针，可以有效地表示复杂的数据结构，能动态分配内存，直接处理内存地址等。在学习和应用指针过程中，传统的指针概念和用法常常使人感到困惑。文中提出了单星指针、双星指针等新概念，比较全面地介绍了指针的理论和应用．