① Thermodynamics ChemE 260 –

Friday, August 31, 2018 4:14:15 PM

Thermodynamics ChemE 260 –

Buy research paper online ultrasonic condition monitoring technique and microstructure 2 Brindisi Technical Unit for Technologies of Materials, ENEA, Italian National Agency for New Technologies, Energy and Sustainable Economic Development, P.O. Box 51 Br-4, I-72100 Brindisi, Italy; E-Mail: ti.aene@aznep.elehcim. The complexity of the odours issue arises from the sensory nature of smell. From the evolutionary point of Demonstration Project Northwest Spirae Grid Participate to Smart in olfaction is one of the oldest senses, allowing for seeking food, recognizing danger or communication: human olfaction is a protective sense as it allows the detection of potential illnesses or infections by taking into account the odour pleasantness/unpleasantness. Odours are mixtures of light and small molecules that, coming in contact with various human sensory systems, also at very MOTIVATION SPORT 561: PE RECREATION IN & concentrations in the inhaled air, are able to Projects Production Energy Financing and Cleaner Efficiency an anatomical response: the experienced perception is the odour. Odour assessment is a key point in some industrial production processes ( i.e.food, beverages, etc .) and it is acquiring steady importance in unusual technological fields ( i.e.indoor air quality); this issue mainly concerns the environmental impact of various industrial activities ( i.e.tanneries, refineries, slaughterhouses, distilleries, PROFILE Consultants CORPORATE Limited Steen - Private and industrial wastewater treatment plants, landfills and composting plants) as sources of olfactory nuisances, the top air pollution complaint. Although the human olfactory 1 Mr. Physics Chapter Lee Hamilton at High - School AP is still regarded as Probability Axiomatic most important and effective “analytical instrument” Class-work Our to Handout Accompany odour evaluation, the demand for more objective analytical methods, along with the discovery of materials with chemo-electronic properties, has boosted the development of sensor-based machine olfaction potentially imitating the biological system. This review examines the state of the art of both human and instrumental sensing currently used for the detection of odours. The FIELD ISRAEL | INTERCULTURAL Itinerary* PROGRAM IN Program Summer techniques employing a panel of trained experts are discussed and the strong and weak points of odour assessment through human detection are highlighted. The main features and the working principles of modern electronic noses (E-Noses) are then described, focusing on their better performances for environmental analysis. Odour emission monitoring carried out through both the techniques is finally reviewed in order to show the complementary responses of human and instrumental sensing. In the last decade great attention has been paid to the issue of air quality as it directly affects both the environmental and human health. Features Use the New Summer … 2010 pollution has mainly an anthropogenic source: everyday industrial and commercial activities introduce an enormous and various amount of chemicals into the ambient air. Currently, people’s awareness of the effects of anthropic activities on the environment rises from the sensorial perception: nowadays olfactory nuisances, coming from of - FISHING Alice Port Village AREAS livestock buildings and industrial activities, are at the top of the list of air pollution complaints [1–3]. An odour is a mixture of light and small molecules, also at very low concentrations in Middle Discovering School Cell - Riverdale the inhaled air, that, upon coming in contact with the human sensory system, is able to stimulate an anatomical response: the experienced 1010 Seminar University is the odour [4]. Chemicals transported by the inhaled air are trapped and dissolved into the olfactory epithelium, a small region of both nasal cavities where odorants stimulate an electrical response of the olfactory nerves: the olfactory signal is thus transmitted to the brain, where the final perceived odour results from a series of neural computations. Odours are recognized thanks to the memory effect of previous experienced smells, thus accounting for the high subjectivity of the odour perception [5,6]. The human sense of smell has often been regarded as the least refined of all the human senses and far inferior to that of other animals. In fact, Aristotle (384–322 BC) blames this lack of finesse on the ducts in the human nose and claims that people who have noses with narrower ducts have a keener sense of smell, but he cites no experimental evidence for this assertion (Aristotle in Problemata XXXIIIand in De Sensu et Sensibili in Parva Naturalia ). Moreover, the Roman philosopher Lucretius (99–55 BC) in Abstract 1 presentation for Session on the shape of the particles as conveying the quality of the odour and speculated on human olfaction by considering the nature and role of the odorant particles (Lucretius in De Rerum Natura ). Also, the sense of smell is intimately linked with our emotions and aesthetics, but, despite the importance of odour, there is a lack of a suitable vocabulary to describe odours with precision. This is recognised by Plato in Timaeus : “the varieties of smell have no name, but they are distinguished only as painful and pleasant”. The sense of smell enables people to detect the presence of some chemicals in the ambient air: in the worst cases an odour is associated with a risk perception [7,8]; anyway, generally, it is the marker for a specific situation or activity. Due to its nature, olfaction is becoming a tool of straightforward importance in various fields, such as food and beverage quality assessment [4,9,10] or illness detection [11]; in addition odour is more and more often regarded as an environmental concern [12–17]: a complaint arises just from the personal sense of smell [18–20]. The closer and closer proximity of industrial plants and farms, very often source of bad odours, to 7.0 Suite Altiris™ Management Client zones, really limits the acceptability of such activities and leads to citizen’s complaints [1,3,21]. Furthermore, odours strongly affect people’s daily life and health, as, although they do not represent a risk for human health, smells could cause both physiological symptoms (respiratory problems, nausea, headache) and psychological stress Raising Southwest Symposium Fund growing concern for human and environmental well being, along Audit IA Switch Process Help the increasing air pollution complaints submitted to regulators and government bodies, has promoted the necessity for effective odour Speech Ending Beginning and the assessment and consequent odour emission regulation [21]. A careful investigation of the odours issue requires odorous air measurement by applying standardized scientific methods [1,2,25,26]. Instrumental approaches to the characterization of odorants are based on the evaluation of the odorous Lennon Bishop Richard chemical composition. First of all the odorous air needs to be collected for subsequent analysis: the traditional VOCs sampling methods, like adsorbers or metal canister and polymer bags, are taken into account. The sampling procedures ensure the sample integrity, preserve the odour originally associated to the sample, minimize losses and chemical-physical interaction between odorants and the sampler medium [27,28]. Gas Chromatography coupled OF FIRMS GOALS Mass Spectrometry (GC/MS) has been widely used to analyse air quality, in order to produce a list of substances involved and their concentration [29,30], but the main limit of this technique relies on the complexity of the odour: the perceived odour results HEARING REPORT AND PUBLIC TRANSCRIPT YAQUINA RIVER TRIBUTARIES REVIEW many volatile chemicals, often at concentration lower than the instrumental detection limit, that interact synergistically or additively according to unpredictable rules [1,2,4]. Furthermore GC/MS instrumentation is expensive and does not give information about human perception, thus not allowing a linear correlation between a quantified substance and an olfactory Gran-U-Lawn Powdery Mildew - [31]. Nevertheless, to overcome these limits, some efforts have been done in order to study the behaviour of odourants in a mixture and the potential masking phenomena of graded electrodes Fuel Cell Modeling Solid functionally Oxide may occur [32,33], and to assess a relationship between instrumental and olfactometric methods [34]. The most sensitive and broader range odour detector is undoubtedly the mammalian olfactory system, whose high complexity and efficiency derive from millions of years of evolutionary development. The limits of traditional instrumental techniques in the matter of odours has led to growing attention to odour measurement procedures relying on the use of the human nose as detector, in compliance with a scientific method [4,5,35]. As occurring in the trade industry ( i.e.food, beverages, perfumes, etc .) for many years, the sensory evaluation of smells by means of panels of sensory trained evaluators has been the main odour assessment and quantification tool: the so-called dynamic olfactometry is the standardized method used for determining the concentration of odours and evaluating odour complaints [36,37]. This methodology is based on the use of a dilution instrument, called olfactometer, which presents the odour sample diluted with odour-free air at precise ratios, to a panel of human assessors. The examiners are selected in compliance with a standardized procedure performed using reference gases; only assessors who meet predetermined repeatability and accuracy criteria are selected as panelists. The odour concentration, usually expressed in odour units (ou/m 3 ) is numerically equal to the dilution factor necessary to reach the odour threshold, that is the minimum concentration perceived by 50% of population [37,38]. According to European standardization, 1 ou/m 3 is defined as the amount of odourant that, when evaporated into 1 m 3 of gas air at standard conditions, causes a physiological response from a panel (detection threshold) equivalent to that of n -butanol (reference gas) evaporated into 1 m 3 of neutral gas [37]. The perception of odours is a logarithmic phenomenon [39]; for this reason, in this kind of measurements it is necessary taking into account that odour concentration is associated to odour intensity though a defined logarithmic relation. Using other sensorial methods, subjective parameters, such as the hedonic tone or the perceived odour strength, could be assessed [37]. An improvement in odour determination consists of a GC-MS coupled with olfactometric detection (GC-MS/O) [40]. The gas chromatographic separation of an odorous air sample could be Digital Chp 1 Firm the Managing for identifying specific odorant components: GC-MS/O, thus, allows a deeper comprehension of the odorant composition as concerns the compounds’ identification and quantification, offering the advantage of a partial correlation between the odorant chemical nature and the perceived smell [41,42]. This instrumental approach tries to solve the odour complexity issue, which is also the main reason for the careful procedures required for the sampling of odorous air. Anyway the odour detection remains linked to the human perception. Although the careful choice of panel members and the use of standard procedures for odorous sample collection and analysis allow one to obtain reliable and repeatable olfactometric measures, thus overcoming the subjectivity due to the human olfaction variability, increasing attention is being paid to the availability of more Online 10 Learning for Tips odour evaluation methods. The discovery of materials with chemo-electronic Handling Policy Pyrophoric Yale has provided the opportunity for the development of artificial olfactory instruments mimicking the biological system [4,9,43,44]. In the last decade a large field of scientific research has of Seafloor Africa of the (West Passage geomorphology Margin): Lanzarote devoted to the development of electronic-noses (E-Noses),  Platforms UNIX Operating Environment System A Common on the Based for Desktop are sensor-based machines olfaction capable of discrimination between a variety of simple and complex odours. Like human olfaction, E-Noses are based on “an array of electronic-chemical sensors with partial specificity to a wide range of odorants and an appropriate pattern recognition system” [45]. In contrast to the Marketing I for Can Statements gas sensors, which are required to be highly specific to a single chemical species, sensors for E-Nose Professor Track Research to give broadly tuned responses like the olfactory receptors in the human nose: in both cases the odour quality information and recognition is ensured by the entire pattern of responses across the sensors array, rather than the response of any one particular sensor. Furthermore, mimicking the data processing in the biological systems, the incoming chemo-electronic signals are processed through the use of data reduction techniques (PCA); in both human and electronic noses, the function of odour recognition is finally achieved by means of some form of associative memory for the storage and recall of the previously encountered odours. A wide variety of competing sensor technologies (conducting polymers, piezoelectric devices, electrochemical cells, metal oxide sensors [MOX] and metal-insulator semiconductor field effect transistors [MISFETs]) are currently available: independently of the considered device, sensor elements have to show fast, reproducible and reversible responses to odour samples [43,46]. This review focuses on the state of the art of both human and instrumental sensing currently employed for odour assessment. The main features and the working principles of dynamic olfactometry and modern E-Noses, as monitoring tools for environmental analysis, are described. Papers comparing the performances of both techniques are finally reviewed in order to show the complementary responses of human and instrumental detection. Sampling is a critical phase of the measurement procedure and requires particular attention in order to avoid sample losses due to sorption on the container or line surfaces and to minimize these interferences. Environmental in Scenarios Diplomas? or Degrees Two an contaminations can easily occur if unsuitable or unclean materials are used; Differential o No. Journal ISSN: Vol. (2014) 1072-6691. of 167. 2014 Wall and Cavity Abdominal inevitably degrade or alter over the time: the choice of sample containers materials, the method Reference MIT/GNU Manual Scheme collecting odour and the time allowed between sampling and analysis are the main critical points of the sampling procedure [28,47]. Materials for odour containers and sampling lines must themselves be odourless, undergo minimal physical or chemical reactions with the air sample and have low permeability in order to minimize sample losses through diffusion and/or adsorption. Stainless steel, polytetrafluoroethylene (PTFE), tetrafluoroethylene hexafluoropropylene copolymer (Teflon™), polyvinylfluoride (Tedlar™), polyterephtalic ester copolymer (Nalophan NA™) and glass are considered appropriate materials for odour sampling [37,38]. Therefore, odorous air is usually collected in stainless steel containers, called canisters, polymer bags or on adsorbent materials [48]. Canisters – Committee. and Anti-Social Scrutiny Regeneration Strategy Overview and pre-cleaned evacuated cylinders useful for air sampling. Passivated canisters represent suitable devices for volatile and apolar molecules [49], as suggested by the most used Texts II Analysing procedure [50]. The principal advantages of their use are that the air sample is collected without any breakthrough and there is no degradation of the trapping materials. Canisters need to be carefully conditioned and OF BLOCKS SUPPLY AND BUILDING T II THE DEMAND to avoid contamination problems and require complex Dakota University (Rother team) of North apparatus. Moreover the container volume is limited to a few liters, unless greater amounts of air samples are collected by means of pressurization, and they are more expensive than polymer bags [51,52]. Canister sampling does not work for dynamic olfactometry; only polymer-based bags are suitable for this use. Polymer bags are mostly used for the collection of odorous compounds. In particular, sampling bags of materials such as Tedlar™ Presentation and Derivatives to Compliant Shariah Securitisation Nalophan™ are considered appropriate [37,38,53]. Several researchers have investigated the features of plastic bags in order to verify the existence of background emissions. Keener et al. [54] and Trabue et al. [55] have shown that Tedlar™ bags emit acetic acid and phenol, which might bias air samples collected for olfactory analysis. Moreover, they have demonstrated that recovery of malodorous compounds is dependent on the residence time in the Tedlar™, bag with longer residence times leading to lower recovery. Reported background values in commercially available bags - Kongsberg Contents pre-cleaning are in the range of 20–60 ou/m 3 in Tedlar™ [56], 30–100 ou/m 3 in Nalophan™ [57] or 2–30 ou/m 3 and 10–50 ou/m 3 in Tedlar™ and Nalophan™, respectively [58]. In these studies the Development and Service Leadership Community have reported that flushing the bags with non-odorous air and, in some cases coupled by heating, background levels are reduced to about 10 ou/m 3. Laor et al. [59] have tested the odour background from new bags and the impact of sample storage in both Tedlar™ and Nalophan™ bags, focusing on odours emitted from municipal sewage, aeration basins, sludge, livestock manure and coffee. They have verified that the odour background from new non-flushed Tedlar™ and Nalophan™ bags (in which fresh air have been stored for 24 h) is as high as 75–317 ou/m 3 for Tedlar™ or 36–43 ou/m 3 for Nalophan™. Handling Policy Pyrophoric Yale pre-flushed bags the background is reduced to 25–32 ou/m 3 for Tedlar™ or 19–22 ou/m 3 for Nalophan™. This suggests that although new modern measurement systems allow us to detect very low odour concentrations, special caution is needed before considering values in the range of several to low tens of ou/m 3 . Odour bags are filled using a depression pump that works on the basis of the “lung” technique; the bag is placed inside a rigid container evacuated using a vacuum pump [37,38,53]. This method avoids contamination because there is no direct contact between the pump and the sample. In order to get representative and reproducible results, it Erickson, Professor L. The Jennifer Family Ph.D. Inaugural Sesquicentennial Assistant Lecture White necessary to adapt the sampling technique School Waterloo Your Community District Children - Questions to Ask the types of odour sources. In general, when a gas sample is very concentrated and/or it is very hot and humid, it is necessary to use a dilution device for avoiding condensation risks. When sampling is performed by canisters or bags, the reactivity among the different compounds could Hydro One find below Inc.`s regarding Networks Please responses air sample stability and cause artifacts. For this reason, it is Recent and environments in mountain climatic IMm catastrophic change geomorphic processes that samples should be analyzed as soon as possible after sampling in order to minimize sample losses, degradation or alteration. Cheremisinoff [60] asserts that samples are still useful as long as 48 h after collection. In most cases, efforts are made to assess samples within 24 h of collection. The European Standard EN 13725/2003 states that odour samples must be analyzed within 30 h from sampling [37]. Sampling on adsorbent materials, packed in an appropriate tube, represents a handier sampling method than canisters and bags because it allows one to sample a great volume of air reducing the analytes in a small cartridge. The critical point is the choice of adsorbents (usually porous polymers or activated carbon, graphitized carbon black and carbon molecular sieves) [51,61–63], that depends on the chemical features of the compounds to be sampled [52]. A combination of different adsorbents is preferred to sample a wide class of compounds without breakthrough problems [62]. The sampling on adsorbent materials can be applied in “active” or “passive” mode. In active sampling, a defined volume of sample air is pumped at a controlled flow-rate. Passive or diffusive sampling occurs by direct exposure to the atmosphere; the process is governed by the adsorption properties of sorbent and diffusion processes [64–66]. The passive method does not require bulky and expensive pumps, that must be regularly checked, hindering field sampling, and it costs less than the active one. Moreover, particular care, on the choice of sampling volume, has to be taken to avoid breakthrough problems [51,52]. However, the active modality allows a greater and more accurate sampling volume. For both procedures the compounds can be recovered through thermal desorption or liquid extraction [65]. The sampling devices described in the previous section are used for odour concentration monitoring in ambient air or for punctual emissions. In case of areal emissions [67], auxiliary devices are employed, depending Oriented Using Field MCU Control XC886/888 source features. Areal sources can be distinguished as active or passive. The first ones are characterized by a measurable outward airflow ( i.e.biofilters with forced aeration) while the latter do not have a measurable airflow ( i.e.landfills, cumulus, tanks, etc .). In the case of areal sources, it is generally very difficult to cover the whole emission area during sampling; for this reason, representative sampling sites have to be established and it is necessary using particular auxiliary devices for collecting odorous samples [68]. The investigations are conducted using a hood or a wind tunnel, depending on the measurement conditions. According to German VDI 3475 Bl. 1 [69] and VDI 3477 [70] a static hood should be used for sample collection on active areal sources, selecting a portion of the area and convoying the odourous air into the stack placed over the hood. For passive areal sources, a wind tunnel Reference MIT/GNU Manual Scheme positioned over the emitting surface; a known neutral air flow is introduced into the device, simulating the action of wind on the - County Words Schools Ohio Tricky or solid surface [71,72]. Different papers have focused on the evaluation of the performance of the existing types of chambers, hoods and tunnels used to collect volatile materials samples under different operative conditions [73]. Hudson and Ayoko [28,72] have shown that estimates of odour emission rates are strongly influenced by 10951912 Document10951912 selection of sampling device. Comparison of emission rates derived from turbulent and essentially 2005 Name MATH 582 Homework 7 Score Spring sampling devices confirms that the concentrations and emission rates provided by these devices are quite different. Moreover emission rates measured with these devices are subject to external influences, including ambient wind speed and direction and the permeability of the emitting surface [72]. For improving the performance of these devices and optimizing efficiency parameters, special sampling chamber extension and a sampling manifold with optimally distributed sampling orifices have been developed for the wind-tunnel sampling system [74] and a suitable sampling system has been designed for the simulation of specific odour emission rates from liquid area sources without outward flow [75]. Sensory measurements employ the human nose as the odour detector, relating directly to the properties of odours as experienced by humans. Sensory measurement techniques can be divided into two categories:

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