An exploratory study of the corrosion of Mg alloys during interrupted salt spray testing

A first systematic investigation was carried out to understand the corrosion of common Mg alloys (Pure Mg, AZ31, AZ91, AM30, AM60, ZE41) exposed to interrupted salt spray. The corrosion rates were also evaluated for these alloys immersed in 3 wt.% NaCl by measuring hydrogen evolution and an attempt was made to estimate the corrosion rate using Tafel extrapolation of the cathodic branch of the polarisation curve. The corrosion of these alloys immersed in the 3 wt.% NaCl solution was controlled by the following factors: (i) the composition of the alpha-Mg matrix, (ii) the volume fraction of second phase and (iii) the electrochemical properties of the second phase. The Mg(OH)₂ surface film on Mg alloys is probably formed by a precipitation reaction when the Mg²⁺ ion concentration at the corroding surface exceeds the solubility limit. Improvements are suggested to the interrupted salt spray testing; the ideal test cycle would be a salt spray of duration X min followed by a drying period of (120-X) min. Appropriate apparatus changes are suggested to achieve 20% RH rapidly within several minutes after the end of the salt spray and to maintain the RH at this level during the non-spray part of the cycle. The electrochemical measurements of the corrosion rate, based on the “corrosion current” at the free corrosion potential, did not agree with direct measurements evaluated from the evolved hydrogen, in agreement with other observations for Mg.     

Calculated phase diagrams and the corrosion of die-cast Mg-Al alloys

The corrosion of commercial die-cast Mg-Al alloys was elucidated by a study, of the corrosion in 3% NaCl, of (i) high-pressure die-cast (HPDC) model Mg-Al alloys, (ii) low-purity Mg, (iii) high-purity (HP) Mg and (iv) HP Mg heat treated at 550 °C. HPDC is the most important route for the production of Mg components. The corrosion of the model alloys was dominated by the Fe impurity element. The present research identified the appearance of the Fe-rich particles in the microstructure. In high magnification (∼1000× to 5000×) secondary electron images, they appear as small white features, typically less than 1 μm in diameter. In order to understand the impurity tolerance limits, (i) the appropriate corrosion literature was summarised and reviewed and (ii) Mg phase diagrams were calculated using the Pandat software package. Calculated phase diagrams can explain (i) the tolerance levels for Fe and Cu and (ii) the production of high-purity castings by means of control of melt conditions; this has high significance for the production of quality castings from recycled Mg. A full analysis requires that the Mg database be extended to include Ni, Co and some RE. The Fe tolerance limit is ∼5-10 ppm for cast HP Mg heat treated at 550 °C. Analysis of the Mg corrosion literature indicates that several studies have been dominated by the Fe impurity content and have not dealt with the stated aims; it means that the full chemical composition should be reported in all studies of the corrosion of Mg alloys.     

Thin film measurement system for moving objects based on a laterally distributed linear variable filter spectrometer

Instantaneous measurement of optical or geometrical parameters of thin layers is an ambitious aim in many industrial applications. These layers have a variety of use-cases, such as optical bandpassing, dielectric permittivity, or lubrication. Mostly, these layers are in motion due to the production process. In order to observe process parameters, the motion usually has to be disrupted. Thus, the increase of production time due to control purposes is an undesirable drawback of this otherwise suitable technique. In this publication, we present a solution to this particular drawback of most production process monitoring systems exemplarily for film thickness measurement. We show the realization of a measurement principle which has, to our knowledge, never been published before in this application. Therefore, we exploit the advantages of the combination of a linear variable filter with a complementary metal oxide semiconductor sensor array. By an apt readout sequence, this measurement system is able to measure transmission spectra while the target is in motion. We show that this measurement system is able to measure film thicknesses of objects in the range of several 100 nm thickness at up to a velocity of 4 m/s. A reproducibility below 2 nm was acquired.     

Progress in SIFT‐MS: Breath analysis and other applications

The development of selected ion flow tube mass spectrometry, SIFT‐MS, is described from its inception as the modified very large SIFT instruments used to demonstrate the feasibility of SIFT‐MS as an analytical technique, towards the smaller but bulky transportable instruments and finally to the current smallest Profile 3 instruments that have been located in various places, including hospitals and schools to obtain on‐line breath analyses. The essential physics and engineering principles are discussed, which must be appreciated to design and construct a SIFT‐MS instrument. The versatility and sensitivity of the Profile 3 instrument is illustrated by typical mass spectra obtained using the three precursor ions H₃O⁺, NO⁺ and ${\rm O}_{{\rm 2}}^{{\rm + } \cdot }$ , and the need to account for differential ionic diffusion and mass discrimination in the analytical algorithms is emphasized to obtain accurate trace gas analyses. The performance of the Profile 3 instrument is illustrated by the results of several pilot studies, including (i) on‐line real time quantification of several breath metabolites for cohorts of healthy adults and children, which have provided representative concentration/population distributions, and the comparative analyses of breath exhaled via the mouth and nose that identify systemic and orally‐generated compounds, (ii) the enhancement of breath metabolites by drug ingestion, (iii) the identification of HCN as a marker of Pseudomonas colonization of the airways and (iv) emission of volatile compounds from urine, especially ketone bodies, and from skin. Some very recent developments are discussed, including the quantification of carbon dioxide in breath and the combination of SIFT‐MS with GC and ATD, and their significance. Finally, prospects for future SIFT‐MS developments are alluded to. © 2010 Wiley Periodicals, Inc., Mass Spec Rev 30:236–267, 2011     

A Comparison of Leisure Time Spent in a Garden with Leisure Time Spent Indoors: On Measures of Restoration in Residents in Geriatric Care

During the past 20 years, findings have indicated that nature plays an active role in helping people recover from stress and fatigue. Two of the most cited theories in this field are Rachel and Stephen Kaplan's theory of recovery from Directed Attention Fatigue in nature and Roger Ulrich's theory of aesthetic and affective responses to natural environments and stress recovery. One aim of the present study is to test whether being outdoors in a green recreational environment causes people to be more focused, compared to being in a room indoors (in line with hypotheses suggested by the Kaplans). Another aim is to test whether people experience stress reduction, i.e. as evidenced by changes in blood pressure and heart rate, if they are placed in an environment with many green elements (in line with hypotheses suggested by Ulrich). The overall study design is that of an intervention study. Fifteen elderly persons living at a home for very elderly people participated. Their powers of concentration, blood pressure and heart rate were measured before and after an hour of rest in a garden or in an indoor setting. Seven elderly people were randomly chosen to have their first series of tests in a garden, while eight elderly people had their first series of tests indoors. The results indicate that powers of concentration increase for very elderly people after a visit to a garden outside the geriatric home in which they live, compared to that after resting indoors in their favourite room. The results did not show any effects on blood pressure or heart rate. It is suggested that having a one-hour rest outdoors in a garden setting plays a role in elderly people's powers of concentration, and could thereby affect their performance of activities of daily living. One important factor in this study was that both the outdoor environment and the indoor environment at the home were highly valued by participants.     

A Comparison of Leisure Time Spent in a Garden with Leisure Time Spent Indoors: On Measures of Restoration in Residents in Geriatric Care

During the past 20 years, findings have indicated that nature plays an active role in helping people recover from stress and fatigue. Two of the most cited theories in this field are Rachel and Stephen Kaplan's theory of recovery from Directed Attention Fatigue in nature and Roger Ulrich's theory of aesthetic and affective responses to natural environments and stress recovery. One aim of the present study is to test whether being outdoors in a green recreational environment causes people to be more focused, compared to being in a room indoors (in line with hypotheses suggested by the Kaplans). Another aim is to test whether people experience stress reduction, i.e. as evidenced by changes in blood pressure and heart rate, if they are placed in an environment with many green elements (in line with hypotheses suggested by Ulrich). The overall study design is that of an intervention study. Fifteen elderly persons living at a home for very elderly people participated. Their powers of concentration, blood pressure and heart rate were measured before and after an hour of rest in a garden or in an indoor setting. Seven elderly people were randomly chosen to have their first series of tests in a garden, while eight elderly people had their first series of tests indoors. The results indicate that powers of concentration increase for very elderly people after a visit to a garden outside the geriatric home in which they live, compared to that after resting indoors in their favourite room. The results did not show any effects on blood pressure or heart rate. It is suggested that having a one-hour rest outdoors in a garden setting plays a role in elderly people's powers of concentration, and could thereby affect their performance of activities of daily living. One important factor in this study was that both the outdoor environment and the indoor environment at the home were highly valued by participants.     

Tectonic Articulation: Making Engineering Logics Speak

As much of the responsibility of a building's physical design and fabrication has increasingly shifted to engineers, spatial communication has remained the sole and significant preserve of architects. Patrik Schumacher , Partner at Zaha Hadid Architects (ZHA), explains how tectonic articulation through architectural design – the selection and employment of technically engineered forms and details – enables the legible enunciation of a building's forms in a manner that has the potential to give it social meaning and expression.     

Urban qualities and residents’ strategies in compact global south cities: the case of Havana

Research and policy argue for more compact cities to respond to sustainable development challenges. However, what actually needs to be made more compact and how, is under examined, particularly in global South cities where north notions of urban qualities are adopted without being questioned. Informed by a qualitative study in informal and compact neighborhoods in Havana, this paper explores which qualities are important to deliver more just cities, and what strategies are developed by residents to strengthen beneficial qualities and address detrimental qualities in contexts of informal urbanization and compactness. It shows how the street, human capital, neighborhood, housing affordability, citizenship and vibrancy are significant compact city qualities neglected in the literature. Finally, the paper shows how diverse strategies are developed by residents to draw upon these qualities, such as self-help urbanism, learning and innovation, economic entrepreneurship, networks of solidarity, economies of reciprocity, local imaginaries and active citizenship.

     

The relation between perceived sensory dimensions of urban green space and stress restoration

Research indicates a relationship between sensory perception of natural environments and human health. Our hypothesis is that people perceive green spaces in terms of certain dimensions, where some dimensions are more important and preferred than others with respect to restoring people from stress.The aims are to: identify and describe the perceived dimensions in nature; identify which dimensions people in general prefer; identify the dimensions people reporting stress prefer; and identify a combination of the dimensions people reporting stress prefer.A total of 953 randomly selected informants from nine Swedish cities (representative of the Swedish population) answered a postal questionnaire with pre-coded questions. The questionnaire consisted of three parts: personal data, preferences for natural qualities and self-estimations of health status. The data were analyzed using factor analysis and regression analyses.The results identify and describe eight perceived sensory dimensions. People in general prefer the dimension Serene, followed by Space, Nature, Rich in Species, Refuge, Culture, Prospect and Social. The dimensions Refuge and Nature are most strongly correlated with stress, indicating a need to find the most restorative environments. A combination of Refuge, Nature and Rich in Species, and a low or no presence of Social, could be interpreted as the most restorative environment for stressed individuals.From a city planning perspective, the results indicate how urban green spaces can be viewed as elements of importance to public mental health. However, before the dimensions can be used by practitioners as tools to promote health through city planning, more research is needed.