| 1. |
- Sattari, Amir, 1980-, et al.
(author)
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INDUSTRIAL NANOPARTICLES HEALTH RISKS AND ADVANTAGES OF A DECENT INDUSTRIAL VENTILATION SYSTEM IN REDUCING THE RELATED RISKS
- 2012
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In: INDUSTRIAL NANOPARTICLES HEALTH RISKS AND ADVANTAGES OF A DECENT INDUSTRIAL VENTILATION SYSTEM IN REDUCING THE RELATED RISKS. ; , s. -6
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Conference paper (peer-reviewed)abstract
- With the fast-growing use of nanoparticles (NPs) in a wide range of production and manufacturing processes, and great health and environmental risks associated to NPs, it is important to treat the industry-produced NPs in a proper way. Ventilation of industrial workplaces lies within the concept of sustainability challenges for the development of nanoproducts. Due to the decreased grain size of material to nano limits and thus the appearance of either new or changed properties, health risk of workers in such environments is critical concerning the complicated and unknown characteristics of nanoparticles. There is great evidence over the past few years that ultrafine particles and especially NPs in the breathing air are strong toxins. Different mitigation measures for air-borne nanoparticles in industrial workplaces are substitution, engineering controls such as ventilation and provision of personal protective equipment. In this paper selection criteria for ventilation systems and different ventilation methods (hood ventilation and global enclosure/room ventilation systems) as engineering controls of nanoparticles within industrial enclosures will be reviewed. Novel methods for improvement of ventilation efficiency in general and industrial work places with an eye on ventilation of nanoparticles will be presented.
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| 2. |
- Sattari, Amir, 1980-
(author)
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Investigations of Flow Patterns in Ventilated Rooms Using Particle Image Velocimetry : Applications in a Scaled Room with Rapidly Varying Inflow and over a Wall-Mounted Radiator
- 2015
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Artistic work (other academic/artistic)abstract
- This thesis introduces and describes a new experimental setup for examining the effects of pulsating inflow to a ventilated enclosure. The study aimed to test the hypothesis that a pulsating inflow has potential to improve ventilation quality by reducing the stagnation zones through enhanced mixing. The experimental setup, which was a small-scale, two-dimensional (2D), water-filled room model, was successfully designed and manufactured to be able to capture two-dimensional velocity vectors of the entire field using Particle Image Velocimetry (PIV). Using in-house software, it was possible to conclude that for an increase in pulsation frequency or alternatively in the flow rate, the stagnation zones were reduced in size, the distribution of vortices became more homogeneous over the considered domain, and the number of vortices in all scales had increased. Considering the occupied region, the stagnation zones were moved away in a favorable direction from a mixing point of view. In addition, statistical analysis unveiled that in the far-field occupied region of the room model, stronger eddies were developed that we could expect to give rise to improved mixing. As a fundamental experimental study performed in a 2D, small-scale room model with water as operating fluid, we can logically conclude that the positive effect of enhanced mixing through increasing the flow rate could equally be accomplished through applying a pulsating inflow.In addition, this thesis introduces and describes an experimental setup for study of air flow over a wall-mounted radiator in a mockup of a real room, which has been successfully designed and manufactured. In this experimental study, the airflow over an electric radiator without forced convection, a common room-heating technique, was measured and visualized using the 2D PIV technique. Surface blackening due to particle deposition calls for monitoring in detail the local climate over a heating radiator. One mechanism causing particle deposition is turbophoresis, which occurs when the flow is turbulent. Because turbulence plays a role in particle deposition, it is important to identify where the laminar flow over radiator becomes turbulent. The results from several visualization techniques and PIV measurements indicated that for a room with typical radiator heating, the flow over the radiator became agitated after a dimensionless length, 5.0–6.25, based on the radiator thickness.Surface properties are among the influencing factors in particle deposition; therefore, the geometrical properties of different finishing techniques were investigated experimentally using a structured light 3D scanner that revealed differences in roughness among different surface finishing techniques. To investigate the resistance to airflow along the surface and the turbulence generated by the surfaces, we recorded the boundary layer flow over the surfaces in a special flow rig, which revealed that the types of surface finishing methods differed very little in their resistance and therefore their influence on the deposition velocity is probably small.
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| 3. |
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| 4. |
- Sattari, Ämir
(author)
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Particle image velocimetry visualization and measurement of airflow over a wall-mounted radiator
- 2015
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In: The International Journal of Ventilation. - : Veetech. - 1473-3315 .- 2044-4044. ; 14:3, s. 289-302
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Journal article (peer-reviewed)abstract
- A common room-heating technique involves the use of a wall-mounted radiator without forced convection. The cold surrounding air passes adjacent to the warm surfaces of the radiator where it absorbs heat and gains momentum to rise along the wall surface and finally circulate in the entire room. Understanding the properties of heated airflows is important for several purposes. To understand the flow process it is important to identify where the transition from laminar to turbulent flow occurs and to quantify the turbulent fluctuations. With the objective to characterize the airflow in the vicinity of wall surfaces, the local climate over the radiator was visualized and measured using a two-dimensional particle image velocimetry technique. The PIV technique yields 2D vector fields of the flow. The resulting vector maps were properly validated and post-processed using in-house software to provide the average streamlines and other statistical information such as standard deviation, average velocity, and covariance of the entire vector field. The results show that, for a room with a typical heating power, the airflow over the radiator becomes agitated after an ordinate of N = 5 - 6.25 over the radiator upper level, in which N is the dimensionless length based on the thickness of the radiator. Practical problems encountered in near-wall PIV measurements include generating a homogeneous global seeding that makes it possible to study both plume and entraining region, as well as optical problems due to near-surface laser reflection that makes the measurement process more complicated.
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| 5. |
- Sattari, Amir, 1980-, et al.
(author)
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Plaster finishes in historical buildings – Measurements of surface structure, roughness parameters and air flow characteristics
- 2013
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In: Plaster finishes in historical buildings. - 9788888307268 ; , s. 69-75
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Conference paper (peer-reviewed)abstract
- Soiling of surfaces in historical buildings by deposition of particles is a common problem. Minimizing soiling is an important goal for conservation of structures and objects. The surfaces give rise to an interference with the air motions along the surfaces. Properties of surfaces may therefore influence the particle deposition. It is well known that with increasing roughness of the surfaces the particle deposition rate increases. The properties of surfaces in historical buildings are not well documented. We have investigated samples of surfaces finished by wood float finish, steel float finish and brushed finish. As a reference we have used an MDF board. The geometrical properties of the surfaces have been documented by using the stripe projection method. The resistance to airflow along the surface and the turbulence generated by the surfaces have been investigated by recording the boundary layer flow over the surfaces in a special flow rig. The work reported is part of a project where the process of soiling is studied both in laboratory and in field studies. The air velocity adjacent to the surfaces will be recorded with both PIV (Particle Image Velocimetry) and hot-wire technique. The temperature gradient close to the walls will be recorded with cold-wire technique.
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| 6. |
- Feng, X. M., et al.
(author)
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Image analysis for monitoring the barley tempeh fermentation process
- 2007
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In: Journal of Applied Microbiology. - Oxon, United Kingdom : Oxford University Press (OUP). - 1364-5072 .- 1365-2672. ; 103:4, s. 1113-1121
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Journal article (peer-reviewed)abstract
- Aims: To develop a fast, accurate, objective and nondestructive method for monitoring barley tempeh fermentation. Methods and Results: Barley tempeh is a food made from pearled barley grains fermented with Rhizopus oligosporus. Rhizopus oligosporus growth is important for tempeh quality, but quantifying its growth is difficult and laborious. A system was developed for analysing digital images of fermentation stages using two image processing methods. The first employed statistical measures sensitive to image colour and surface structure, and these statistical measures were highly correlated (r = 0.92, n = 75, P < 0.001) with ergosterol content of tempeh fermented with R. oligosporus and lactic acid bacteria (LAB). In the second method, an image-processing algorithm optimized to changes in images of final tempeh products was developed to measure number of visible barley grains. A threshold of 5 visible grains per Petri dish indicated complete tempeh fermentation. When images of tempeh cakes fermented with different inoculation levels of R. oligosporus were analysed the results from the two image processing methods were in good agreement. Conclusion: Image processing proved suitable for monitoring barley tempeh fermentation. The method avoids sampling, is nonintrusive, and only requires a digital camera with good resolution and image analysis software. Significance and Impact of the Study: The system provides a rapid visualization of tempeh product maturation and qualities during fermentation. Automated online monitoring of tempeh fermentation by coupling automated image acquisition with image processing software could be further developed for process control.
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| 7. |
- Sattari, Amir, 1980-, et al.
(author)
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PIV Study of Ventilation Quality in Certain Occupied Regions of a Two-Dimensional Room Model with Rapidly Varying Flow Rates
- 2013
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In: The International Journal of Ventilation. - : Veetech Ltd. - 1473-3315 .- 2044-4044. ; 12:2, s. 187-194
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Journal article (peer-reviewed)abstract
- The use of supply jet flows is the most common type of air distribution for general ventilation. Usually the supply flow rate is constant or slowly varying (VAV-systems) to cope with a varying load. A novel air distribution method, with the potential to reduce stagnation and to increase the ventilation efficiency, is to introduce rapid flow variations (pulsations). This paper reports on a fundamental study of this type of air distribution. The purpose of the study was to explore the effect of flow variations on stagnant zones and the levels of the turbulent kinetic energy and the relative turbulence intensity. A small scale room model is used that consists of an enclosure with a ventilation supply at the bottom and an extract at the top of the opposite wall. Water was used as an operating fluid and the model had a design which mainly generated a two-dimensional flow. The size of the model made it possible to investigate the two-dimensional velocity vector field using the Particle Image Velocimetry (PIV) method in regions corresponding to occupied regions. Further post processing was conducted from the resulting vector fields. The comparison between cases of constant inflow and pulsated inflow (flow variations with frequency of 0.5 Hz) was conducted for three domains: two belonging to the far-field occupied zone and one belonging to the near-field, downstream of the supply wall jet.
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| 8. |
- Elcadi, Guilherme H., 1966-, et al.
(author)
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Shoulder and forearm oxygenation and myoelectric activity in patients with work related muscle pain and healthy subjects
- 2013
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In: European Journal of Applied Physiology. - New York : Springer. - 1439-6319 .- 1439-6327. ; 113:5, s. 1103-1115
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Journal article (peer-reviewed)abstract
- We tested hypotheses of (i) reduced oxygen usage, oxygen recovery, blood flow and oxygen consumption; and (ii) increased muscle activity for patients diagnosed with work related muscle pain in comparison to healthy controls. Oxygenation was measured with near infrared spectroscopy (NIRS), and muscle activity with EMG for the extensor carpi radialis (ECR) and trapezius descendens (TD) muscles. Eighteen patients with diffuse neck-shoulder-arm pain and seventeen controls (matched in age and sex) were equipped with NIRS and EMG probes. After determining an individual’s maximum voluntary contraction (MVC) force, short term (20 sec) isometric contractions for the ECR and TD of 10%, 30%, 50% and 70% MVC generated ∆StO2% and StO2% recovery (Rslope) from NIRS, and RMS%max from EMG signals. In addition, upper arm venous (VO) and arterial (AO) occlusions generated slopes of total hemoglobin (HbTslope) and deoxyhemoglobin (HHbslope) for the resting ECR as surrogates of blood flow and oxygen consumption, respectively. Mixed Model analyses, t-tests, and Mann-Whitney test were used to assess differences between groups. There was no significant difference in MVC between groups for either muscle. Also, ∆StO2%, Rslope for either muscle, and ECR-HbTslope were not different between groups, thus our hypotheses of reduced oxygen use, recovery, and blood flow for patients were not confirmed. However, patients had a significantly lower ECR-HHbslope confirming our hypothesis of reduced consumption. Further, there was no difference in RMS%max during contractions meaning that the hypothesis of increased activity for patients was not confirmed. When taking into account the number of NIRS variables studied, differences we found between our patient group and healthy controls (i.e. in forearm oxygen consumption and shoulder oxygen saturation level) may be considered modest. Overall our findings may have been impacted by the fact that our patients and controls were similar in muscle strength, which is in contrast to previous studies.
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| 9. |
- Fallenius, Bengt E. G., et al.
(author)
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Experimental study on the effect of pulsating inflow to an enclosure for improved mixing
- 2013
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In: International Journal of Heat and Fluid Flow. - : Elsevier. - 0142-727X .- 1879-2278. ; 44, s. 108-119
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Journal article (peer-reviewed)abstract
- Optimal control of inlet jet flows is of broad interest for enhanced mixing in ventilated rooms. The general approach in mechanical ventilation is forced convection by means of a constant flow rate supply. However, this type of ventilation may cause several problems such as draught and appearance of stagnation zones, which reduces the ventilation efficiency. A potential way to improve the ventilation quality is to apply a pulsating inflow, which has been hypothesised to reduce the stagnation zones due to enhanced mixing. The present study aims at testing this hypothesis, experimentally, in a small-scale two-dimensional water model using Particle Image Velocimetry with an in-house vortex detection program. We are able to show that for an increase in pulsation frequency or alternatively in the flow rate the stagnation zones are reduced in size and the distribution of vortices becomes more homogeneous over the considered domain. The number of vortices (all scales) increases by a factor of four and the swirl-strength by about 50% simply by turning on the inflow pulsation. Furthermore, the vortices are well balanced in terms of their rotational direction, which is validated by the symmetric Probability Density Functions of vortex circulation (Γ) around Γ= 0. There are two dominating vortex length scales in the flow, namely 0.6 and 0.8 inlet diameters and the spectrum of vortex diameters become broader by turning on the inflow pulsation. We conclude that the positive effect for enhanced mixing by increasing the flow rate can equally be accomplished by applying a pulsating inflow.
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| 10. |
- Kjellberg, Anders, 1942-, et al.
(author)
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Stress, energy and psychosocial conditions in different types of call centres
- 2010
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In: Work. - 1051-9815 .- 1875-9270. ; 36:1, s. 9-25
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Journal article (peer-reviewed)abstract
- Objective: To identify risk indicators for high stress and low mental energy as well as to describe psychosocial working conditions at different types of call centres. Participants: 1183 operators from 28 call centres in Sweden, both external and internal, with different levels of task complexity, ownership and geographical location. Method: A cross sectional questionnaire study. Results: The stress level was moderately high and the energy level fairly high. Stress levels tended to be lower and psychosocial conditions better with increasing level of task complexity. Fourteen per cent of the operators were in a state of high stress/low energy ("worn out") and 47% in high stress/high energy ("committed under pressure"). Operators in a state of low stress/high energy ("committed without pressure") were most likely to report a better health status. High stress and lack of energy was mainly associated with time pressure, low decision latitude, and lack of social and supervisor support. Conclusions: Time pressure in combination with lack of support and influence should be seen as a potential high risk situation for the development of a "worn-out" state among call centre operators. Management should make use of this knowledge in order to promote a long lasting efficient and healthy call centre work.
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