Molybdenum disilicide-silicon nitride bushing nozzles tailor-made for basalt fibers production

A carefully comparative study of several ceramics compounds allowed the identification of MoSi₂ blended with Si₃N₄ as a suitable material for the realization of bushing nozzles, specifically designed for basalt fibers production. Degradation static tests were developed and performed to demonstrate the high resistance to oxidation at operating temperature of MoSi₂-Si₃N₄ composites with respect to alumina, zirconia stabilized with magnesia or yttria, pure MoSi₂, pure Si₃N₄, and MoSi₂ englobing SiC. Moreover, the MoSi₂-Si₃N₄ composites resulted resistant to corrosion and chemical inert with respect to oxidizing components present in basalt melts.Bushings in MoSi₂-Si₃N₄ were obtained by using hot isostatic pressing and were processed through mechanical drilling. The basalt fibers produced with the MoSi₂-Si₃N₄ bushing showed a constant diameter and a regular surface morphology. The bushing was recovered intact without defects or fractures demonstrating the efficiency of the selected material. Replacing platinum-rhodium bushings with ceramic ones could greatly reduce costs of basaltic fibers production and could encourage the use of these eco-friendly, natural fibers as reinforcement in lightweight polymer composites.     

STRUCTURAL TYPES IN PETROLEUM ASPHALTENES AS DEDUCED FROM PYROLYSIS/GAS CHROMATOGRAPHY/MASS SPECTROMETRY

ABSTRACT

An integrated technique has been developed for the study of the thermal chemistry of petroleum fractions—particularly the asphaltenes. The procedure involves the integrated use of a pyroprobe/gas chroma-tographic/mass spectrometric technique which offers information about the structuraI-types and distribution within the volatile products from the thermal decomposition of asphaltenes. The technique offers itself as an attractive on-line analytical method for the study of structural types that occur in asphaltenes as well as a technique for studying the parameters that can influence asphaltene decomposition. The concept of deducing “average” structures of asphaltenes is briefly discussed in terms of the observance of the lower molecular weight species in the volatile products of the thermal decomposition.     

Mass balance and kinetic analysis of anaerobic microbial dechlorination of pentachlorophenol in a continuous flow column

A mass balance and kinetic investigation of anaerobic dechlorination of pentachlorophenol (PCP) was undertaken using an enriched microbial consortium in a laboratory scale continuous flow column, as a model microbial permeable reactive barrier. The chlorine balance showed that 50 µM PCP was largely dechlorinated to phenol with the formation of a small quantity of 3-chlorophenol as an intermediate metabolite (hydraulic retention time 7.6 days), and the chlorine removal efficiency reached 36 µM d^-1. When the initial PCP concentration was increased to 100 µM the chlorine removal efficiency increased 1.5 times. However, the dechlorination activity disappeared after 7.4 pore volumes (58 days), demonstrating the susceptibility of the dechlorination culture to high concentrations of PCP. Lactate released hydrogen as an electron donor during PCP dechlorination, with acetate, propionate, CO₂ and CH₄ as byproducts. The carbon balance showed that some of the organic carbon source (PCP, lactate) in the influent was converted to gas and utilized for biomass growth in addition to organic metabolites. The kinetic study was conducted in a batch culture and yielded 1.99 mg l^-1 biomass growth per unit of chlorine consumption (µM). The Monod equation was well fitted to the specific growth rate of 1.38 d^-1 and a half saturation constant of 0.29 µM. The organic chlorine removal rate in the batch culture was consistent with the results in the flow column, indicating the feasibility of and potential for in situ estimation and prediction through batch culture studies.     

A novel automatic suspicious mass regions identification using Havrda & Charvat entropy and Otsu's N thresholding

Mass detection is a very important process for breast cancer diagnosis and computer aided systems. It can be very complex when the mass is small or invisible because of dense breast tissue. Therefore, the extraction of suspicious mass region can be very challenging. This paper proposes a novel segmentation algorithm to identify mass candidate regions in mammograms. The proposed system includes three parts: breast region and pectoral muscle segmentation, image enhancement and suspicious mass regions identification. The first two parts have been examined in previous studies. In this study, we focused on suspicious mass regions identification using a combination of Havrda & Charvat entropy method and Otsu's N thresholding method. An open access Mammographic Image Analysis Society (MIAS) database, which contains 59 masses, was used for the study. The proposed system obtained a 93% sensitivity rate for suspicious mass regions identification in 56 abnormal and 40 normal images.     

Recursive least square vehicle mass estimation based on acceleration partition

Vehicle mass is an important parameter in vehicle dynamics control systems. Although many algorithms have been developed for the estimation of mass, none of them have yet taken into account the different types of resistance that occur under different conditions. This paper proposes a vehicle mass estimator. The estimator incorporates road gradient information in the longitudinal accelerometer signal, and it removes the road grade from the longitudinal dynamics of the vehicle. Then, two different recursive least square method （RLSM） schemes are proposed to estimate the driving resistance and the mass independently based on the acceleration partition under different conditions. A 6 DOF dynamic model of four In-wheel Motor Vehicle is built to assist in the design of the algorithm and in the setting of the parameters. The acceleration limits are determined to not only reduce the estimated error but also ensure enough data for the resistance estimation and mass estimation in some critical situations. The modification of the algorithm is also discussed to improve the result of the mass estimation. Experiment data on asphalt road, plastic runway, and gravel road and on sloping roads are used to validate the estimation algorithm. The adaptability of the algorithm is improved by using data collected under several critical operating conditions. The experimental results show the error of the estimation process to be within 2.6%, which indicates that the algorithm can estimate mass with great accuracy regardless of the road surface and gradient changes and that it may be valuable in engineering applications. This paper proposes a recursive least square vehicle mass estimation method based on acceleration partition.     

Improving design and technological properties of the means of mechanization of assembling joints in plating of metal structures

The design and operation principle of existing portable mechanization means and technological features of their application in assembling joints in plating are investigated; structural and technological features of tooling and assembly equipment are described, the physiology of labour in assembling plating joints is analysed, including static and dynamic loading of the hands when carrying over, holding and application of assembling means on different levels in relation to the height of the worker body, the maximum allowable weight and size parameters of portable mechanization means for assembling plating joints are determined and the results of development of new specialized equipment for mechanization of assembling of joints’ pneumohydraulic operating mode are described.     

浅论大体积混凝土施工质量控制

近年来，新建铁路设计必须以双线铁路为主。本文主从裂缝的分类、产生的原因、控制方法等方面入手，对混凝土原材料的控制直至施工完成后的养护和成品保护等问题进行了探讨，力争保证大体积混凝土的施工质量。