Transfer of Ultrafine Particles and Air in Multi-storey Buildings

An emerging issue in Denmark is passive smoking in residential buildings where non-smokers are exposed to smoke from their neighbours. There are various ways that smoke is transferred from one flat to another. The air transfer rate between two flats in a multi-storey building depends on its construction, tightness and age. This paper presents results of a study on the transfer of ultrafine particles and tracer gas in an older multi-storey building in Copenhagen. The aim of the study was to quantify the transfer ofultrafine particles and gases from one flat to another fiat before and after sealing the floor. A new floor-sealing method was applied to seal the floor between the two flats. The sealing method was developed by a firm specialising in sealing. Indoor ultrafine particle concentrations and tracer gas were measured continuously in the two fiats during the measuring periods. In the unoccupied fiat, the gas source was N20 and the particle source was burning cigarettes. Reduction of the concentration of ultrafine particles and tracer gas by sealing the floor with polyethylene and joint filler made of bitumen was studied. It was evaluated how the sealing performed with regard to decreasing the amount of ultrafine particles and a tracer gas transferred between two fiats separated by a floor. When the floor between the flats was not sealed, the results showed that about 4% of the ultraflne particles and 14% of the tracer gas were transferred. After sealing, the amount transferred was reduced to 1.6% and 5%, respectively.     

半加成工艺:溅镀作为种子层在FR-4的初步研究简

文章就溅镀作为种子层在FR-4（高Tg）材料上进行了初步的研究，发现：不同的溅镀条件对线路剥离强度较大的影响，只有在适当的溅镀条件时才能达到良好的结合力。     

Influence of hydrogen content and microstructure on the fatigue behaviour of steel SAE 52100 in the VHCF regime

The fatigue life of the bearing steel 52100 (100Cr6) in bainite and martensite conditions was investigated up to 2 × 10⁹ cycles. The tests were performed under cycling tension (R = 0.1) and tension–compression (R = −1) on a piezo-electric ultrasonic testing equipment. The specimens are designed with a cylindrical part in the highly stressed centre. Due to grinding, compressive residual stresses are found at the surface, hence crack initiation solely occurs subsurface. Prior testing half of the specimens was charged with hydrogen. The hydrogen content varies from 0.6 as initial condition to 3 ppm after charging. The increased hydrogen content decreased the endurance limit to nearly half of the value of uncharged conditions and crack initiation changed: Conditions with low hydrogen content failed from chromium carbides, titanium nitrides or slag agglomerations. Conditions with 3 ppm hydrogen failed from slag agglomerations, often in combination with aluminium magnesium oxides, and manganese sulphides. Next to the inclusions a fine granular area (FGA) could be observed in some cases, and nearly all fractured surfaces showed a fisheye surrounded by an Optically Bright Zone (OBZ) with the crack initiating inclusion in its centre. Furthermore, selected specimens where analysed using secondary ion mass spectroscopy in a time of flight setup (ToF-SIMS) to ascertain the local hydrogen content. From the results it is assumed that hydrogen accumulates in the cavity at inclusions or bonds to the inclusion if it contains silicon.     

Elimination mechanism of micropores on bonding interface during solid-state crystal growth method

A pure yttrium aluminum garnet (YAG) ceramic/YAG single crystal composite material is prepared using the optimized solid-state crystal growth (SSCG) method. The micropores on the bonding interface of the composite sample are eliminated for the first time during the SSCG process and the transmittance is very close to the theoretical value, which reached 83.14% at 1064 nm. Meanwhile, the mechanism of elimination and migration of the pores under high temperature is studied. Additionally, the single crystal growth rate has significantly improved and the time of composite sample preparation has also significantly reduced proving that the SSCG method is an effective method for producing high quality composite material.     

In-process estimation of fracture surface morphology during wheel scribing of a glass sheet by high-speed photoelastic observation

Defect-free glass separation techniques are in strong demand in glass processing industries. In this study, we intended to observe the internal stress field during/after wheel scribing of a glass sheet using the photoelastic method. First, we visualized the crack propagation behavior in a 0.7-mm-thick non-alkali glass sheet during mechanical scribing with a 2.0-mm-diameter serrated diamond wheel using high-speed imaging techniques. The observation results under various applied load conditions showed that the crack propagation behavior changed dramatically at a load of approximately 9–10 N; the generated crack hardly propagated in the thickness direction under lower load conditions, in contrast to the rapid propagation under higher load conditions. The fracture surface morphology that was observed after cleavage also changed, from damaged to defect-free surfaces with increments in the applied load around the transition point (9–10 N). This result indicated that the fracture surface morphology was determined by the crack propagation behavior. Second, the birefringence phase difference was measured from the upper side of the glass sheet to enable understanding of the stress fields induced by scribing wheel indentations. As a result, the phase differences that were distributed along the scribe line were shown to differ depending on the applied loads; the phase difference changed little under lower load conditions, but vanished immediately under higher load conditions. Therefore, these differences were dependent on whether or not rapid crack propagation occurred. The measured phase difference distribution thus included information about the crack propagation behavior, and this information could be used as a criterion for estimation of the fracture surface morphology. An in-process estimation method for the fracture surface morphology during mechanical wheel scribing was therefore developed based on high-speed polarization imaging techniques.     

Effect of pulp rheology on flotation of nickel sulphide ore with fibrous gangue particles

Abstract

Tests are carried out with suspensions of fibrous chrysotile particles and nickel sulphide ore containing chrysotile as a gangue. They corroborate published results, and indicate a very strong effect of particle shape on slurry rheology. Such suspensions exhibit time dependent properties. The flotation tests revealed that the viscosity of this system strongly affects flotation performance. At a solids concentration of 15–20% (w/w), the concentrate yield increases and the concentrate grade dramatically declines. This deterioration is observed when the Casson yield stress exceeds 1·5–2 Pa. The tests imply that the rheological properties of the investigated system are mainly determined by fibrous components. However, because of the presence of anisotropic mineral particles, the effect of particle–particle interactions cannot be separated from the effect of particle shape in this system.

On effectue des essais avec des suspensions de particules fibreuses de serpentine et de minerai de sulfure de nickel contenant de la serpentine comme gangue. Ces essais confirment les résultats publiés et indiquent un effet très prononcé de la forme des particules sur la rhéologie de la boue. De telles suspensions exhibent des propriétés dépendantes du temps. Les essais de flottation ont révélé que la viscosité de ce système affecte grandement le rendement de la flottation. À une concentration en solides de 15 à 20% (poids/poids), la production de concentré augmente et la qualité du concentré décline dramatiquement. Cette détérioration est observée lorsque la contrainte de Casson excède 1·5 à 2 Pa. Les essais impliquent que les propriétés rhéologiques du système étudié sont déterminées principalement par les composantes fibreuses. Cependant, à cause de la présence de particules minérales anisotropes, on ne peut pas séparer l’effet des interactions particule-particule de l’effet de la forme des particules dans ce système.     

Online-review analysis based large-scale group decision-making for determining passenger demands and evaluating passenger satisfaction: Case study of high-speed rail system in China

High-speed rail (HSR) has become an essential mode of public transportation in China and is likely to remain so for the foreseeable future. To promote the development of the HSR industry, a high level of passenger satisfaction must be ensured, which means that passenger satisfaction must be assured. Focusing on HSR in-cabin factors that affect the travel experience of HSR passengers, this study aims to determine passenger demands (PDs) and to evaluate passenger satisfaction by using a combination of online review analysis and large-scale group decision-making (LSGDM). By using web crawler technology, online reviews related to HSR were harvested from a microblogging platform to extract PD data and information. The six PDs that reflect the most frequent concerns of passengers were identified by analyzing the online reviews. The level of satisfaction of passengers with respect to these PDs was analyzed based on the online responses from 100 HSR passengers and by adopting the interval-valued two-tuple linguistic representation model. The final degrees of satisfaction and rankings of the PDs were then determined by using the LSGDM approach with the k-means clustering method and a consensus-reaching process. This research thus constructs an index system of HSR passenger satisfaction evaluation based on online-review analysis and evaluates the process by using LSGDM approaches. The conclusions provide insights into the improvements desired by HSR passengers for in-cabin services and to improve passenger satisfaction.     

Position computation models for high-speed train based on support vector machine approach

High-accuracy positioning is not only an essential issue for efficient running of high-speed train (HST), but also an important guarantee for the safe operation of high-speed train. Positioning error is zero when the train is passing through a balise. However, positioning error between adjacent balises is going up as the train is moving away from the previous balise. Although average speed method (ASM) is commonly used to compute the position of train in engineering, its positioning error is somewhat large by analyzing the field data. In this paper, we firstly establish a mathematical model for computing position of HST after analyzing wireless message from the train control system. Then, we propose three position computation models based on least square method (LSM), support vector machine (SVM) and least square support vector machine (LSSVM). Finally, the proposed models are trained and tested by the field data collected in Wuhan-Guangzhou high-speed railway. The results show that: (1) compared with ASM, the three models proposed are capable of reducing positioning error; (2) compared with ASM, the percentage error of LSM model is reduced by 50.2% in training and 53.9% in testing; (3) compared with LSM model, the percentage error of SVM model is further reduced by 38.8% in training and 14.3% in testing; (4) although LSSVM model performs almost the same with SVM model, LSSVM model has advantages over SVM model in terms of running time. We also put forward some online learning methods to update the parameters in the three models and better positioning accuracy is obtained. With the three position computation models we proposed, we can improve the positioning accuracy for HST and potentially reduce the number of balises to achieve the same positioning accuracy.     

Estimation of the Risk Associated to Marketing of Swine Meat Contaminated with Salmonella spp., Employing the William T. Fine Method

Swine meat is a growing market in Colombia, reaching 3.1 million of carcasses sold in 2014. However, it is estimated that the proportion of hogs illegally marketed can be up to 50%, which exposes the population to foodborne pathogens such as Salmonella. The aim of this study was to estimate the risk associated to the marketing of swine meat contaminated with Salmonella, using the William T. Fine method in Tolima Department. The risk scenarios applied to four municipalities positive for Salmonella showed a medium and low level of risk, and an exposed population of 114,000 people, representing 8.7% of the Department's population. In the worst-case scenario, costs for hospitalization and compensation could represent more than US$ 145 billion for the biggest municipality. It can be concluded that the William T. Fine method is applicable for biological risk analysis focused on foodborne pathogen outbreaks.     

GPS技术下的露天矿山爆破设计及布孔

针对某露天铁矿布孔方式及弊端，该矿山引进GPS技术并将其应用到矿山爆破设计和布孔中，在现场进行实验研究。结果表明，使用了GPS技术进行布孔，可以极大地提高孔位的布设精度，且操作简便，工作效率较之前也有较大的提高，满足了矿山精细化爆破要求，使得最终的爆破效果得到改善。据现场统计，最终爆破大块率降低40%，减少了处理大块等待时间，满足露天矿山采装的要求，获得了良好的经济效益。