桉树木材干燥特性与工艺及其皱缩研究现状

本文回顾和分析了桉树木材与干燥有关的材性和干燥特性 ,指出桉木的密度、含水率和干缩率变异性大、渗透性差 ,在干燥过程中易产生皱缩、开裂等干燥缺陷 ,若采用预冻处理和前后期调湿处理可减少木材的皱缩 ;同时建议研究各种桉木不同规格板材的干燥基准和两段式干燥工艺     

Retrospective evaluation of sildenafil citrate as a therapy for pulmonary hypertension in dogs

Pulmonary arterial hypertension (PH) is a pathologic condition in dogs characterized by abnormally high pressures in the pulmonary circulation and has been associated with a poor outcome. Sildenafil is a type V phosphodiesterase inhibitor that produces nitric oxide mediated vasodilatation. Sildenafil treatment decreases pulmonary arterial pressure and pulmonary vascular resistance in people with PH. The purpose of this study was to describe the clinical characteristics and outcome of dogs with PH treated with sildenafil. The cardiology database was searched for dogs with PH treated with sildenafil. PH was defined as systolic pulmonary arterial pressure (PAPs) > or = 25 mmHg at rest. Medical records were reviewed for the following information: signalment, duration and type of clinical signs before treatment, underlying disease, estimated or measured PAPs, dosage and dosing interval of sildenafil, and the effect of treatment on clinical signs and pulmonary arterial pressure and survival time. Thirteen affected dogs were identified. Clinical signs included collapse, syncope, respiratory distress, and cough. Duration of clinical signs before presentation ranged from 3 days to 5 months. An underlying cause was identified in 8 dogs. The median sildenafil dosage was 1.9 mg/kg. Ten dogs received concurrent medications. Median PAPs was 90 mmHg; 8 dogs were reevaluated after therapy, and the median decrease in PAPs was 16.5 mmHg. The median survival time of all dogs was 91 days. Sildenafil appeared to be well tolerated in dogs with PH and was associated with decreased PAPs and amelioration of clinical signs in most. Sildenafil represents a reasonable treatment option for dogs with pulmonary hypertension.     

Characterization of viscoelastic,shrinkage and transverse anatomy properties of four Australian hardwood species

Abstract

Several key wood properties of four Australian hardwood species: Corymbia citriodora, Eucalyptus pilularis, Eucalyptus marginata and Eucalyptus obliqua, were characterized using state-of-the-art equipment at AgroParisTech, ENGREF, France. The wood properties were measured for input into microscopic (cellular level) and macroscopic (board level) vacuum-drying models currently under development. Morphological characterization was completed using a combination of environmental scanning electron microscopy and image analysis software. A clear difference in fibre porosity, size, wall thickness and orientation was evident between species. Viscoelastic properties were measured in the tangential and radial directions using dynamic mechanical analysis instrumentation. The glass transition temperature was markedly different for each species owing to anatomical and chemical variations. The radial direction showed higher stiffness, internal friction and glass transition temperature than the tangential direction. A highly sensitive microbalance and laser technology were used to measure loss of moisture content in conjunction with directional shrinkage on microsamples. Collapse shrinkage was clearly evident with this method for E. obliqua, but not with other species, consistent with industrial seasoning experience. To characterize the wood–water relations of E. obliqua, free of collapse, thinner sample sections (in the radial–tangential plane) are recommended.     

闽西南崩岗侵蚀区芒萁叶片生态化学计量特征

为了阐明极度退化的崩岗生态系统内芒萁的生长状态和养分储存特征,对闽西南3处不同侵蚀强度的典型崩岗内芒萁叶片C、N、P含量及C/N、C/P、N/P特征进行研究,对比分析不同侵蚀强度下崩壁部位和崩岗不同侵蚀部位中芒萁叶片的生态化学计量特征。结果表明:崩岗内芒萁叶片的C、N、P平均含量分别为477.10 g·kg~(-1)、6.45 g·kg~(-1)、0.25 g·kg~(-1),芒萁叶片的N、P养分含量极低;而C/N、C/P、N/P平均值分别为96.82、2 097.20、27.67,芒萁生长受P限制。不同侵蚀强度下的崩壁内芒萁叶片的C、N、P含量及C/P、N/P均存在显著差异(P0.05),C含量、C/P和N/P均随着侵蚀强度的增强而减小,N含量在中度侵蚀的崩壁内较高,而P含量则随着侵蚀强度的增强而增加,表明芒萁对土壤侵蚀严重的崩岗生态系统具有很强的适应能力。在崩岗的不同侵蚀部位中芒萁叶片的P含量、C/P和N/P均存在显著差异(P0.05),P含量在集水坡面最高,在崩壁最低;而C/P、N/P均表现为崩壁显著大于其他各侵蚀部位。可见,在崩岗的不同侵蚀部位,崩壁中芒萁对C的同化能力强于其他侵蚀部位,且对P利用效率也显著高于其他侵蚀部位。综上,在侵蚀严重的崩岗生态系统中,芒萁有较强的同化C能力和较高的对P利用效率,能通过调节自身C、N、P元素含量很好地适应土壤侵蚀严重、养分极度贫瘠的生境。     

Improvement of water-stability of clay aggregates admixed with aqueous polymer soil stabilizers

Aqueous soil stabilizers improve soil properties. Water-stability of soil aggregates was determined using two different soil stabilizers: S-type and E-type. Various concentrations of the two soil stabilizers were tested in soil aggregates that were bigger than 5 mm but smaller than 10 mm. Testing the aggregates using the static water-measure method showed that the water-stability index, K, increased with the concentrations of soil stabilizers. S-type soil stabilizer in concentrations ranging between 20% and 40% resulted in K-values between 64.0% and 83.8%, and E-type polymer emulsions in concentrations between 3% and 7% resulted in K-values between 90.1% and 99.7% respectively. The soil aggregates admixed with water resulted in a K-value of 11.5%, which was tested as a control. Two aggregate collapse models were found and discussed based on the collapse characteristics of the modified aggregates: S-type soil stabilizer in low concentrations follows a gradual collapse pattern, while S-type stabilizer in high concentrations and E-type stabilizer in low concentrations follow an explosive collapse pattern. These patterns depend on the formation of a membrane structure on the surface of the aggregates through physicochemical bonding. By identifying the mechanisms of the membrane structure and calculating the K-values, significant information on the improvement of soil properties can be determined.     

采煤塌陷裂缝对降雨后坡面土壤水分的影响

为探究采煤塌陷裂缝对坡面储蓄降水的影响,本文对降雨后不同坡向上裂缝两侧的不同土层水分动态变化特征进行了研究。结果表明:降雨主要补充坡面地表0~20 cm土层土壤水分,且在雨后0~20 cm土层土壤水分散失也较为严重;雨后阴坡土壤含水率最高,0~10cm、10~20cm和20~40 cm土层土壤水分差异显著(p0.05)。降雨结束8 d后,裂缝附近的土壤水分变化幅度较大,尤以坡面裂缝上部边缘处最为明显,裂缝处与远离裂缝的土壤水分之间差异显著(p0.05);阳坡土壤水分损失最高,阳坡裂缝周边土壤水分平均损失量高达3.31%。可见,裂缝的出现会在一定程度上打破坡面储蓄降水的格局,加剧坡面局部土壤水分散失,这一点在植被恢复与建设过程中不容忽视。     

陕西商南金丝峡地质公园崩塌地质灾害机理与防治研究

分析了陕西商南金丝峡地质公园崩塌地质灾害的形成机理,并有针对性地提出了防治措施。该地质公园崩塌地质灾害的形成主要与地形地貌、岩性条件、地质构造、气象因素、河流冲蚀以及人类活动等因素密切相关;其崩塌灾害主要为倾倒式崩塌和滑移式崩塌两大类型,分别主要分布于该地质公园的中部及南部;提出危岩加固、旅游线路设计避让、建设监测系统及危险期闭园等对策。     

热处理对桉材皱缩的作用

多枝桉、细叶桉、赤桉采用恒温调湿干燥法测绘含水率－收缩曲线，探求热处理对改善桉材皱缩的效果。结果多枝桉、细叶桉是否热处理均具典型的“皱缩”型含水率－收缩曲线，但热处理材少有“二段”皱缩，“肩点”处收缩率和全收缩率比未热处理材小，处理效果明显；赤桉则无区别。同时，论述了“皱缩”型曲线出现“肩点”的必然性；提出了“二阶段”皱缩理论；并对寺尺＾［１］等的“导管二次皱缩”论的局部性进行了探讨。     

Simulation of Collapse by Discrete Element Method for Diversion Tunnel under Complex Geological Conditions

Geological conditions of Jinping I Hydropower diversion tunnel is very complicated, it has the following characteristics, such as high geostress and developmental faults and joints, several collapse occurred in the construction process. A brief introduction is given to the geological conditions of Jinping I Hydropower diversion tunnel, based on discrete element method, Major joints and faults were simulated, and calculation models were built. By calculation and analysis, Rules and characteristics of deformation and failure for rock diversion tunnel has been obtained. After the diversion tunnel was excavated, high geostress were released, structural surface relaxation and slip. Side wall generated vertical cracks, vault take place chipping. With deformation increasing, the structural plane was further slip and open, dome support weakened, leading to collapse.     

山杨小径木皱缩材组织结构的变化及其皱缩机理的探讨

目前,关于木材皱缩的机理各说不一,一种认为皱缩是由于受到过量的压应力,而压应力又归因于木材的干缩力,这种力的产生是当细胞腔内的自由水蒸发完毕后在细胞腔内产生真空而使细胞溃陷;另一种认为,由于细胞腔内的自由水流过纹孔时,产生的静水压力使细胞破坏而致。此种理论的建立要求细胞腔里充满水分而没有空汽泡存在。因为半径大于弯月面半径的空气泡膨胀时会降低应力,所以要完全不含汽泡。日本学者服部芳明利用后一种理论测定了水分传导过程中的渗透压,用测定渗透压的方法确定细胞