Evaluating the Use of Humidification Systems During Heat Treatment of MPB Lumber

Lumber produced from lodgepole pine logs attacked by the mountain pine beetle (MPB) infestation in British Columbia, Canada, exhibits very low initial moisture content (MC). Depending on the time elapsed since attack, the initial MC can be significantly lower than the fiber saturation point (FSP ～30%). Lumber exhibiting 19% MC or less is considered ready for the dimension lumber market and does not necessarily need to be kiln dried. However, phytosanitary regulations require that lumber products be heat treated before delivery to customers. For lumber already quite dry, the Canadian Food Inspection Agency (CFIA) kiln drying/heat treatment schedules may be too long and can result in overdrying. For the significant volume of MPB lumber with an initial MC below 19%, the use of low-pressure steam or cold water spray could allow this lumber to be heat treated without causing further drying. This approach should result in improved lumber quality because overdrying would certainly be minimized and probably eliminated.

In this study, two sorts (dry and wet sort) of MPB lumber were dried in a pilot laboratory kiln humidified with low-pressure steam or cold water spray. Twelve drying runs were carried out. The experimental results indicated that the times to reach the temperature of 56°C in the core of the lumber were shortened and warp for the dry-sort lumber group was reduced when the low-pressure steam or cold water spray system was used. Thus, for MPB lumber with a low initial MC, the utilization of lower pressure steam or cold water spray during heat treatment represents an attractive alternative to reduce kiln residence time, minimize or eliminate overdrying, and improve lumber quality.     

Phase transition-induced high electromechanical activity in [(K0.5Na0.5)1−xLix](Nb0.8Ta0.2)O3 lead-free ceramic system

A high electromechanical activity is observed in the [(K_0.5Na_0.5)_1−xLi_x](Nb_0.8Ta_0.2)O₃ (x = 0, 0.02, and 0.03) lead-free ceramic system at and around the orthorhombic (O)–tetragonal (T) phase transition temperature (T_O–T). This activity is found to originate from an O–T phase transition region at ambient temperature rather than a classical morphotropic phase boundary (MPB) region intrinsic in the Pb(Zr_1−xTi_x)O₃ (PZT) lead-based ceramic system. Li modification enables a large decrease in T_O–T instead of constituting a classical MPB. In contrast to the nearly temperature-independent classical MPB behavior in the PZT system, the strong temperature-dependent phase transition behavior in the system may impose a challenge to temperature demanding applications.     

合成工艺对五元系压电陶瓷性能的影响

固相法合成0.03PZN-0.03PSN-0.04PMS-0.09PZT五元系压电陶瓷,锆钛比为变量。研究了一、二次合成工艺对压电性能的影响。当采用一次合成工艺时,系统准同型相界在Zr/Ti为0.445/0.455~0.44/0.46附近;采用二次合成工艺后,系统的准同型相界向富Zr的方向发生了移动。采用二次合成工艺比一次合成工艺效果好,在烧结温度为1 260℃,Zr/Ti=0.435/0.465时,性能最好,其介电损耗tanδ=0.30%;rTε3=1 143;d33=303 pC/N;Qm=1 233;kp=55.1%;TC=309℃。二次合成使d33、kp、rTε3及矫顽场强Ec和剩余极化强度Pr都要比一次合成的试样的高。     

The decrease of depolarization temperature and the improvement of pyroelectric properties by doping Ta in lead-free 0.94Na0.5Bi0.5TiO3-0.06BaTiO3 ceramics

Ta-doped lead-free 0.94NBT-0.06BT-xTa (x=0.0–1.0%) ceramics were synthesized by a conventional solid-state route. XRD shows that the compositions are at a morphotropic phase boundary where rhombohedral and tetragonal phases coexist. The depolarization temperature (T_d) shifted to lower temperature with the increase of Ta content. The pyroelectric coefficient (p) of doped ceramics greatly enhanced compared with undoped material and reached a maximum of 7.14×10⁻⁴ C m⁻² °C⁻¹ at room temperature (RT) and 146.1×10⁻⁴ C m⁻² °C⁻¹ at T_d at x=0.2%. The figure of merits, F_i and F_v, also showed a great improvement from 1.12×10⁻¹⁰ m v⁻¹ and 0.021 m² C⁻¹ at x=0.0 to 2.55×10⁻¹⁰ m v⁻¹ and 0.033 m² C⁻¹ at x=0.2% at RT. Furthermore, F_i and F_v show the huge improvement to 52.2×10⁻¹⁰ m v⁻¹ and 0.48×10⁻¹⁰ m v⁻¹ respectively at T_d at x=0.2%. F_C shows a value between 2.26 and 2.42 ×10⁻⁹ C cm⁻² °C⁻¹ at RT at x=0.2%. The improved pyroelectric properties make NBT-0.06BT-0.002Ta ceramics a promising infrared detector material.     

MMM柔性调节式电动作动系统

磁粉离合器和磁粉制动器是性能优异的自动控制和自动调节元件。在电动作动系统中应用分离合器伺服机构是提高快速性的有效途径。将驱动部分的电动机，磁粉离合器组及具有制动阻尼功能的磁粉制动器复合调节能很好地实现快速驱动和精确控制。本文阐述了此三种元素均能调节的ＭＭＭ柔性调节电动作动系统的构成，原理，特点及应用前景。     

Discovery of ordered tetragonal and cubic phases in the morphotropic phase boundary region of (1-x)Bi(Mg3/4W1/4)O3-xPbTiO3 piezoceramics

Studies on (1-x)[Bi(Mg_3/4W_1/4)O₃]-xPbTiO₃ ceramics across morphotropic phase boundary have been done to investigate the crystal structure and structure-property correlations. Rietveld structure refinement reveals that the structure of the morphotropic phase boundary compositions consists of coexisting ordered tetragonal and cubic phases for 0.55 < x < 0.72, not reported earlier. The structure is B-site ordered cubic (space group Fm-3m) for the compositions with x ≤ 0.55, B-site ordered tetragonal (space group I4/m) for x ≥ 0.72. The structure gradually transforms into disordered tetragonal phase (space group P4mm) for higher concentrations (x) of PbTiO₃. Raman studies also confirm the B-site ordered structure for the compositions close to morphotropic phase boundary. For all the compositions investigated, two peaks are observed in the temperature dependence of the permittivity, originating due to dielectric relaxation and structural transition from tetragonal (I4/m) to cubic (Fm-3m) phase. A new phase diagram of the solid solution is established.     

Sn2P2S6 films for memory devices with nondestructive readout

The polarization switching processes of ferroelectric polycrystalline Sn₂P₂S₆ films on Al substrates were studied. The effect of full reverse spontaneous switching after the influence of a repolarizing pulse on the prepoled sample was investigated. This opens the way for making the ferroelectric memory devices with rapid nondestructive readout.     

关于硫化物抑制厌氧消化的新探讨

采用间歇试验的方法研究了硫化物对厌氧消化的影响。试验结果表明，投加量小于４０ｍｇ／Ｌ时，硫化物促进产气，中量大于８０ｍｇ／Ｌ时，硫化物抑制产气，并且随硫化物投加量增加抑制增强。硫化物在发酵过程中能以Ｈ２Ｓ的形式随生物气排出，抑制随发酵时间延长逐渐减轻。     

相组成对PMN-PT陶瓷压电性能的影响

研究了ＰＭＮ－ＰＴ陶瓷在准同型相界（ＭＰＢ）区域、不同烧结温度下,化学组成、相组成对陶瓷压电性能的影响．发现对于同一化学组成的陶瓷,随着烧结温度的上升,发生了菱方相→四方相的相转变,同时随着菱方相、四方相相比例的接近,陶瓷的压电性能有显著的提高．而在不同烧结温度下,最佳压电性能所对应的化学组成有微小的变化．据此认为,陶瓷的压电性能不仅与化学组成有关,而且与相组成也密切相关,随着烧结温度的变化,发生了准同型相界的微小移动     

铌镁酸铋-钛酸铅压电陶瓷准同型相界附近的性能和相变温度研究

利用传统固相烧结法制备了Bi(Mg_2/3Nb_1/3)O₃-PbTiO₃(BMN-PT)压电陶瓷, 分析了不同PbTiO₃含量对BMN-PT压电陶瓷的晶体结构、介电、压电及铁电性能的影响. XRD结果表明: 合成的BMN-PT陶瓷具有纯钙钛矿结构, 并且在PbTiO₃含量为x=0.60时, 其组分的XRD图谱在衍射角2θ=45°出现明显的分峰, 说明该组分相结构中存在三方和四方相的共存. 压电铁电性能显示, BMN-0.60PT有最大的压电常数d₃₃(~170pC/N)和平面机电耦合系数k_p(0.35), 最小的矫顽场E_c(29.4 kV/cm)及最大的剩余极化P_r(31.4 μC/cm²). 确定了BMN-PT压电陶瓷的准同型相界(MPB)为PbTiO₃含量x=0.60的组分. 介电系数温谱表明介电系数峰值温度(Tm)随着PbTiO₃含量的增大而升高, MPB组分的Tm约为276℃.