Bond Strength of a Silicone Soft Lining Material to Poly(methyl methacrylate) Resin Treated with Maleic Anhydride and its Terpolymers

This study investigated the effectiveness of surface treatment of Poly (methyl methacrylate) (PMMA) denture base resin on tensile bond strength between PMMA/silicone-based soft liner. A total of 25 specimens were fabricated and assigned into five groups (n = 5). The surfaces of PMMA were treated with maleic anhydride, maleic anhydride-styrene-vinyl-acetate, n-butylmaleate-styrene-vinyl-acetate, or n-pentamaleate-styrene-vinyl-acetate prior to Primo adhesive primer application and silicone liner placement. The Primo adhesive primer on applied group untreated dentuse base resin served as control. The tensile test was performed using a universal testing machine. Fractured surfaces were observed under Scanning Electron Microscopy (SEM) and spectroscopic interpretation of the interfaces was done by Fourier Transform Infrared (FTIR). Test results showed that surface treatment increased interfacial strength giving the highest value for n-butylmaleate-styrene-vinyl acetate treated group. SEM micrographs revealed that the specimens with n-butylmaleate-styrene-vinyl-acetate and n-penta maleate-styrene-vinyl-acetate terpolymers underwent cohesive failure. FTIR analysis indicated secondary interactions such as hydrogen bonding, possibly on acrylic resin surfaces, caused by the use of maleic anhydride and its terpolymers, and the adhesive.     

KINETICS OF PAHS LOSSES AND RELATIONSHIPS BETWEEN PAHS PROPERTIES AND PROPERTIES OF SOIL IN SEWAGE SLUDGE-AMENDED SOIL

Abstract

The properties of soil determine the activity of its microflora which is responsible for the degradation of polycyclic aromatic hydrocarbons (PAHs). Moreover, soil properties influence the strength of the interactions between the PAHs and individual soil components. The introduction of sewage sludge into the soil changes these properties which, in turn, changes environmental conditions. In the present studies, relationships between the PAH content and changes in selected soil properties (pH, CEC, TEB, BS, N _t ) have been evaluated. The present experiment was carried out in two blocks of experimental plots divided according to the type of plants grown. In the first block, the following field plants were grown in specific sequence, (maize, spring barley, winter rape, potatoes and cereal mixture) while in the other block a perennial, i.e. willow, was grown. Plant cultivation was carried out for 54 months, whereas the cultivation of the willow was conducted over 42 months. Each block consisted of 6 plots with a surface area of 15 m² into which sewage sludge had been introduced in the following doses: soil without fertilization – control, sludge 30, 75, 150, 300, 600 t/ha. Both the disappearance rate and the scope of the individual polycyclic aromatic hydrocarbons as determined by their respective half-lives showed that losses of these compounds depended on the sewage sludge properties (among other things, the pollutant content) as well as the sludge dose and the type of area used. The correlation coefficients determined depended on the sludge dose and the experimental variant. The highest frequency of their occurrence was found in the case of the total sum of nitrogen and cation exchange capacity for the highest sludge doses (in the experimental with willow).     

公路盐渍土路基处理与病害防治策略

盐渍土在我国的分布区域非常广泛,尤其是在沿海地区,盐渍土由于自身的盐胀性和腐蚀性会对公路路基造成很大的破坏.因此,公路盐渍土路基的防腐蚀处理和病害防治对保证公路工程的建设质量具有重要意义.基于此,本文对公路盐渍土路基的病害成因进行了简要的分析,并提出了相应的防治策略.     

降补固态软启动装置在我公司的应用

大型高压电机的启动是一个令人棘手的问题。从启动方式的确定、启动装置的选型、降补固态软启动装置的特点、启动数据和效果评价等方面人手,介绍了甘肃刘化（集团）有限责任公司利用有限的供电系统容量启动大型高压电机的成功经验。     

深厚软土地区搅拌桩复合地基的沉降计算与实测分析

通过工程实例,介绍了深厚软土地区搅拌桩复合地基以不同的计算模式计算的沉降结果与实测沉降量的差异性,以及复合地基静载荷试验检测的沉降量与建筑物实际沉降量的差异性;分析了建筑物沉降与区域地面沉降,建筑物基础尺寸及基础埋深等因素的关系;论证了类似条件下复合地基沉降计算模式选择的合理性。     

土工合成材料在库岸防护中的应用

鞍子坝库岸的主要破坏形式是由于库水位消涨而使岸坡产生的塌岸。应用土工格栅加筋土护坡和土工石笼护脚相结合的方法进行库岸防护设计,且对于多级斜坡式加筋土挡墙的稳定性验算作了一些初步的探讨。     

Effect of slaked lime and gypsum on acidity alleviation and nutrient leaching in an acid soil from Southern China

A soil column experiment was made to study the effects of slaked lime (Ca(OH)₂) and gypsum (CaSO₄·2H₂O) on soil acidity, soil solution chemistry and nutrient leaching in an acid soil from Southern China. Results showed that application of sufficient slaked lime to initially increase the pH of the topsoil by 1 unit caused an increase in pH to 5 cm deeper than the layer of application as a result of bicarbonate leaching. With leaching of Ca from slaked lime or gypsum from the topsoil to the subsoil there was a decrease in exchangeable Al in the subsoil. Surface application of slaked lime or gypsum or both decreased the activity of toxic Al and increased AlSO₄⁺ activity in the subsoil solution. The Ca added in slaked lime or gypsum was accounted for by the increase in exchangeable Ca over the soil profile and the leaching loss. By contrast there was a negative balance of extractable sulfate and aluminum in the soil, indicating the formation of precipitates. There was little mineralisation of N and formation of NO₃^- under the conditions of the experiment. The leaching of cations in this soil treated with slaked lime or gypsum was driven by the dynamics of sulfate.     

多年冻土地区路基温度场和水分迁移场耦合问题研究

基于冻土路基特殊的工程性质,对水分迁移结果即含水量变化对温度场的影响特别是对热物理参数的影响进行了研究,考虑温度变化对土体水分迁移机理及计算方法进行了研究,提出了冻土路基水热耦合计算模型,并给出了水热耦合计算的总体流程图,实例计算揭示了冻土路基温度场和含水状态的横向差异。