Adaptive turning force control with optimal robustness and constrained feed rate

In rough cutting operations, the typical economic objective is to maximize the metal removal rate by the highest possible feed rate under the constraint of tool breakage. This type of control strategy is called adaptive constraint control. However, the strategy has a poor industrial acceptance record because of the potential problems of controller instability and tool breakage resulting from the sudden change of cutting depth or spindle speed. In this paper, an adaptive turning force controller that has optimal robustness under the constraint of feed rate is presented. The experimental results for the sudden change of cutting depth are demonstrated. The proposed controller may be a promising method for the industrial application of turning force control.     

Simulation of large bubble/molten steel interaction for gas-injected ladle

A mathematical model has been developed to simulate numerically the interactions between gas bubbles and molten steel during the gas-injection treatment in secondary refining of steel and to experimentally verify the reliability of the model. A marker-and-cell (MAC) technique is employed to simulate the motions of gas bubbles and molten steel. Photographic observation is used to evaluate the reliability of the mathematical model. A two-dimensional ladle with only one bubble was used to test the capability of the model to handle the interaction between the relatively large bubble and the molten steel. The shape of the bubble is initially round. Then it gradually becomes flattened and eventually evolves into a spherical-cap bubble. Molten steel is induced to flow and forms two circulations. The model was then tested on the same ladle with bubbles continuously released. The first bubble rises in a similar way as the previous case. The second bubble is affected by the first bubble and becomes slightly elongated in the vertical direction rather than in the horizontal direction. It also rises faster and later collides with the first bubble. The released bubbles can be grouped in clusters and are repeated cluster after cluster. Water-model experimental observations are consistent with the predicted results.     

A study of the mechanism of in vitro cytotoxicity of metal oxide nanoparticles using catfish primary hepatocytes and human HepG2 cells

Nanoparticles (NPs), including nanometal oxides, are being used in diverse applications such as medicine, clothing, cosmetics and food. In order to promote the safe development of nanotechnology, it is essential to assess the potential adverse health consequences associated with human exposure. The liver is a target site for NP toxicity, due to NP accumulation within it after ingestion, inhalation or absorption. The toxicity of nano-ZnO, TiO₂, CuO and Co₃O₄ was investigated using a primary culture of channel catfish hepatocytes and human HepG2 cells as in vitro model systems for assessing the impact of metal oxide NPs on human and environmental health. Some mechanisms of nanotoxicity were determined by using phase contrast inverted microscopy, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, reactive oxygen species (ROS) assays, and flow cytometric assays. Nano-CuO and ZnO showed significant toxicity in both HepG2 cells and catfish primary hepatocytes. The results demonstrate that HepG2 cells are more sensitive than catfish primary hepatocytes to the toxicity of metal oxide NPs. The overall ranking of the toxicity of metal oxides to the test cells is as follows: TiO₂ < Co₃O₄ < ZnO < CuO. The toxicity is due not only to ROS-induced cell death, but also to damages to cell and mitochondrial membranes.     

Reactions of free chlorine with substituted anilines in aqueous solution and on granular activated carbon

Aqueous HOCl reacted with substituted anilines to form chlorinated derivatives. Some debromination and bromination products were also detected from two brominated anilines. When granular activated carbon was present, many additional products were formed. These compounds fall into several different groups: (1) N-acylation products, (2) N-carbomethoxylation products, (3) N=N dimerization products and (4) deamination and hydroxylation products.     

Project management knowledge and skills for green construction: Overcoming challenges

A competent project manager is vital to project success. While many studies have examined competency of project managers, few have done so in the context of green construction. Therefore, this study aims to identify challenges faced by project managers who execute green construction projects and to determine the critical knowledge areas and skills that are necessary to respond to such challenges. Through literature review, surveys and interviews with project managers, this study will help establish a knowledge base for project managers to be competitive and to effectively execute sustainable projects.     

Identifying the critical risks in underground rail international construction joint ventures: Case study of Singapore

Since the 1980s, Singapore has experienced the widespread use of international construction joint ventures (ICJVs), which are associated with a variety of risks. This study aims to assess the risks associated with the underground rail ICJVs in Singapore. To achieve this objective, a comprehensive literature review was carried out and a questionnaire survey was conducted with 33 contractors. The survey results reported “disagreement on some conditions in contract” as the most critical risk. Although the risk criticalities of some risks significantly differed according to multiple company characteristics, there was strong agreement on the risk rankings. With the help of this study, ICJV partners can identify the most critical risks and thus develop mitigation measures. Also, the findings from this study provide a comprehensive picture of risks for the companies that intend to participate in ICJVs in Singapore.     

Bacterial communities in commercial aircraft high‐efficiency particulate air (HEPA) filters assessed by PhyloChip analysis

Abstract  Air travel can rapidly transport infectious diseases globally. To facilitate the design of biosensors for infectious organisms in commercial aircraft, we characterized bacterial diversity in aircraft air. Samples from 61 aircraft high‐efficiency particulate air (HEPA) filters were analyzed with a custom microarray of 16S rRNA gene sequences (PhyloChip), representing bacterial lineages. A total of 606 subfamilies from 41 phyla were detected. The most abundant bacterial subfamilies included bacteria associated with humans, especially skin, gastrointestinal and respiratory tracts, and with water and soil habitats. Operational taxonomic units that contain important human pathogens as well as their close, more benign relatives were detected. When compared to 43 samples of urban outdoor air, aircraft samples differed in composition, with higher relative abundance of Firmicutes and Gammaproteobacteria lineages in aircraft samples, and higher relative abundance of Actinobacteria and Betaproteobacteria lineages in outdoor air samples. In addition, aircraft and outdoor air samples differed in the incidence of taxa containing human pathogens. Overall, these results demonstrate that HEPA filter samples can be used to deeply characterize bacterial diversity in aircraft air and suggest that the presence of close relatives of certain pathogens must be taken into account in probe design for aircraft biosensors.

Practical Implications

A biosensor that could be deployed in commercial aircraft would be required to function at an extremely low false alarm rate, making an understanding of microbial background important. This study reveals a diverse bacterial background present on aircraft, including bacteria closely related to pathogens of public health concern. Furthermore, this aircraft background is different from outdoor air, suggesting different probes may be needed to detect airborne contaminants to achieve minimal false alarm rates. This study also indicates that aircraft HEPA filters could be used with other molecular techniques to further characterize background bacteria and in investigations in the wake of a disease outbreak.

     

Capture of CO2 from flue gas via multiwalled carbon nanotubes

Carbon nanotubes (CNTs) were modified by 3-aminopropyl-triethoxysilane (APTS) solution and were tested for its CO₂ adsorption potential at multiple temperatures (20-100 °C). The physicochemical properties of CNTs were changed after the modification, which makes CNTs adsorb more CO₂ gases. The adsorption capacities of CO₂ via CNTs and CNTs(APTS) decreased with temperature indicating the exothermic nature of adsorption process and increased with water content in air at 0-7%. The mechanism of CO₂ adsorption on CNTs and CNTs(APTS) appears mainly attributable to physical force regardless of temperature change, which makes regeneration of spent CNTs at a relatively low temperature become feasible. The CNTs(APTS) have good adsorption performance of CO₂ at 20 °C as compared to many types of modified carbon or silica adsorbents documented in the literature. This suggests that the CNTs(APTS) are promising low-temperature adsorbents for CO₂ capture from flue gas.     

Performance prediction of a hybrid ventilation system in an apartment house

The performance of a hybrid ventilation system, composed of a natural supply inlet and mechanical exhaust, was predicted numerically for a South Korean apartment. Analysis was performed using Computational Fluid Dynamics (CFD) for three ventilating flow rates: 30, 60, and 120 m³/h. The heating period chosen in this study reflects how residents are usually exposed to poorer indoor environments in winter. An effort was made to create acceptable residential comforts regarding air current, temperature and CO₂ concentration distributions. The results show that ventilating flow rates are identified as an important parameter, not only in residential comfort, but also in energy savings. An ACH of 0.7 or greater seems to be a reasonable value for the permissible minimum ventilation flow rate in occupied zones. The results also show that for a ventilating flow rate of 60 m³/h, some acceptable criteria are satisfied and residents achieve comfort. In the 30 and 120 m³/h cases, however, residents no longer feel as comfortable with regard to thermal conditions and air currents. Lastly, when a whole apartment has a flow rate of 180 m³/h, and the living room-kitchen region has a flow rate of 120 m³/h, energy losses occur.