Off-line Instruments Research Articles

Particles Emission from an Industrial Spray Coating Process Using Nano-Materials.

Industrial spray coating processes are known to produce excellent coatings on large surfaces and are thus often used for in-line production. However, they could be one of the most critical sources of worker exposure to ultrafine particles (UFPs). A monitoring campaign at the Witek s.r.l. (Florence, Italy) was deployed to characterize the release of TiO2 NPs doped with nitrogen (TiO2-N) and Ag capped with hydroxyethyl cellulose (AgHEC) during automatic industrial spray-coating of polymethyl methacrylate (PMMA) and polyester. Aerosol particles were characterized inside the spray chamber at near field (NF) and far field (FF) locations using on-line and off-line instruments. Results showed that TiO2-N suspension produced higher particle number concentrations than AgHEC in the size range 0.3–1 µm (on average 1.9 102 p/cm3 and 2.5 101 p/cm3, respectively) after background removing. At FF, especially at worst case scenario (4 nozzles, 800 mL/min flow rate) for TiO2-N, the spray spikes were correlated with NF, with an observed time lag of 1 minute corresponding to a diffusion speed of 0.1 m/s. The averaged ratio between particles mass concentrations in the NF position and inside the spray chamber was 1.7% and 1.5% for TiO2-N and for AgHEC suspensions, respectively. The released particles’ number concentration of TiO2-N in the size particles range 0.3–1 µm was comparable for both PMMA and polyester substrates, about 1.5 and 1.6 102 p/cm3. In the size range 0.01–30 µm, the aerosol number concentration at NF for both suspensions was lower than the nano reference values (NRVs) of 16·103 p/cm-3.

Athletes' exposure to air pollution during World Athletics Relays: A pilot study

Potential adverse consequences of exposure to air pollutants during exercise include decreased lung function, and exacerbation of asthma and exercise-induced bronchoconstriction. These effects are especially relevant for athletes and during international competitions, as they may impact athletic performance. Thus, assessing and mitigating exposure to air pollutants during exercising should be encouraged in sports venues. A comprehensive air quality assessment was carried out during the World Relays Yokohama 2019, in the stadium and the warm-up track. The pilot included on-line and off-line instrumentation for gaseous and particulate pollutants and meteorological parameters, and the comparison with local reference data. Air quality perception and exacerbation of symptoms of already-diagnosed diseases (mainly respiratory and cardiovascular) were assessed by athletes by means of questionnaires during training sessions. Median NO2 concentrations inside the stadium (25.6–31.9 μgm−3) were in the range of the Yokohama urban background, evidencing the impact of urban sources (e.g., traffic) on athletes' exposure during training and competition. The assessment of hourly air pollutant trends was identified as a valuable tool to provide guidance to reduce atheletes' exposure, by identifying the periods of the day with lowest ambient concentrations. This strategy could be adopted to define training and competition schedules, and would have special added value for athletes with respiratory conditions. Personal exposure to polycyclic aromatic hydrocarbons was quantified through wearable silicone wristbands, and showed highly variability across volunteers. The wristbands are a simple approach to assess personal exposure to potentially toxic organic compounds. Further research would be necessary with regard to specific air pollutants that may trigger or exacerbate respiratory conditions typical of the athlete community. The availability of high time-resolved exposure data in the stadiums opens up the possibility to calculate doses of specific pollutants for individual athletes in future athletics events, to understand the impact of environmental factors on athletic performance.

Measuring metacognitive skills for mathematics: students’ self-reports versus on-line assessment methods

Various instruments for assessing metacognitive skills and strategy use exist. Off-line self-reports are questionnaires and interviews administered either before or after task performance, while on-line measures are gathered during task performance through thinking aloud or observation. Multi-method studies in reading have shown that off-line methods suffer from serious validity problems, whereas the validity of on-line methods is adequate. Little is known, however, about the validity of methods for assessing metacognition in mathematics. Five instruments were administered to 30 secondary-school students: two prospective questionnaires (MSLQ and ILS) before a mathematics task, two on-line methods (observation and thinking aloud) concurrent to the mathematics task, and a task-specific retrospective questionnaire after the mathematics task. Mathematics performance was assessed by a posttest and GPA. Results confirm that prospective questionnaires have poor convergent and predictive validity in mathematics. Although the retrospective questionnaire does slightly better than prospective questionnaires, the validity of both on-line methods stands out. It is concluded that on-line instruments should be preferred over off-line instruments for the assessment of metacognitive skillfulness in mathematics.

Thermal annealing induced enhancement of electrical properties of a co-continuous polymer blend filled with carbon nanotubes

In the current study, it is found that the electrical properties of a co-continuous polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend containing with conductive multi-wall carbon nanotubes (MWCNTs) can be remarkably improved via the thermal annealing treatment. Utilizing the on-line (rheometer and optical microscope) and off-line (transmission electron microscopy) instruments, the evolution of the morphology and microstructure of PS/PMMA/MWCNTs composites are visualized. It is observed that thermal annealing can induce the coalescence of small phases into the more perfect co-continuous phase structure, which can significantly improve the electrical properties of the composites. Moreover, the re-aggregation of MWCNTs under thermal annealing also helps to improve the electrical properties of the composites. Furthermore, it is worth to note that parts of MWCNTs can be enriched at the interface of a co-continuous PS/PMMA blend to build up the conductive network during the thermal annealing, which further enhances the electrical properties of the composites.

Design and evaluation of an in-line system for gas sensing in flow-packed products

Abstract A method for the in-line application of Tunable Diode Laser Absorption Spectroscopy (TDLAS) for headspace oxygen sensing in flow-packed products is presented. This is one of the first automated, industrial application on food packaging samples of a well known spectroscopic technique.The developed instrument is discussed starting from its sensor design with details on the optical working principles to point out the peculiarities and application issues linked with this particular technique. A production line implementation of the sensor is then presented, based on a conveyor belt for automatic sampling. This device was also integrated with line automation in order to enable measurement on the full production. Both in-line and off-line instruments were validated against traditional, industry-standard invasive measurement techniques. The accuracy of the measurement applied to regular samples from production line was found better than 0.4% vol. O2.

RAMMS - A High-Throughput Membrane Measurement System for Fuel Cell Manufacturing

The objective of this work was to develop a high-throughput polymer electrolyte membrane (PEM) resistance measurement device to enhance manufacturing quality control (QC). The principal outcome was the Rapid Membrane Measurement System (RAMMS), an automated, off-line instrument that can be used by membrane manufacturers for QC during production and by membrane users for lost acceptance of a critical component of PEM fuel cell systems. Principal components of the RAMMS were a novel humidification and environmental control system; integrated sample chamber, electrode and actuator system; impedance-based membrane resistance measurement instrumentation, and custom software. Testing and evaluation revealed that electrode durability was the most significant technical challenge and performance limitation of the RAMMS. Acceptable durability was unobtainable with any of the platinum deposition methods and post-deposition treatments designed to improve coating adhesion. Porous platinum electrodes exhibited acceptable durability. The prototype unit came close to achieving all performance criteria and specifications.

Heterogeneous nucleation of ice in the atmosphere

The occurrence of ice-nucleating aerosols in the atmosphere has a profound impact on the properties of clouds, and in turn, influences our understanding on weather and climate. Research on this topic has grown constantly over the last decades, driven by advances in online and offline instruments capable of measuring the characteristics of these cloud-modifying aerosol particles. This article presents different aspects to the understanding of how aerosol particles can trigger the nucleation of ice in clouds. In addition, we present some experimental results obtained with the Dynamic Filter Processing Chamber, an off-line instrument that has been applied extensively in the last years and that circumvents some of the problems related to the measurement of Ice Nucleating Particles properties.

Use of Raman spectroscopy to identify carbon nanotube contamination at an analytical balance workstation

ABSTRACTCarbon nanotubes (CNTs) are cylindrical molecules of carbon with diverse commercial applications. CNTs are also lightweight, easily airborne, and have been shown to be released during various phases of production and use. Therefore, as global CNT production increases, so do concerns that CNTs could pose a safety threat to those who are exposed to them. This makes it imperative to fully understand CNT release scenarios to make accurate risk assessments and to implement effective control measures. However, the current suite of direct-reading and off-line instrumentation used to monitor the release of CNTs in workplaces lack high chemical specificity, which complicates risk assessments when the sampling and/or measurements are performed at a single site where multiple CNT types are handled in the presence of naturally occurring background particles, or dust. Herein, we demonstrate the utility of Raman spectroscopy to unequivocally identify whether particulate matter collected from a multi-user analytical balance workstation comprised CNTs, as well as, whether the contamination included CNTs that were synthesized by a Ni/Y-catalyzed electric-arc method or a Co/Mo-catalyzed chemical vapor deposition method. Identifying the exact CNT type generated a more accurate risk assessment by knowing the metallic impurities involved, and it also led to the identification of the users who handled these CNTs, a review of their handling techniques, and an improved protocol for safely weighing CNTs.

Development of a sensitive long path absorption photometer to quantify peroxides in aerosol particles (Peroxide-LOPAP)

Abstract. A new off-line instrument to quantify peroxides in aerosol particles using iodometry in long path absorption spectroscopy has been developed and is called peroxide long path absorption photometer (Peroxide-LOPAP). The new analytical setup features important technical innovations compared to hitherto published iodometric peroxide measurements. Firstly, the extraction, chemical conversion and measurement of the aerosol samples are performed in a closed oxygen-free (~ 1 ppb) environment. Secondly, a 50-cm optical detection cell is used for an increased photometric sensitivity. The limit of detection was 0.1 μM peroxide in solution or 0.25 nmol m−3 with respect to an aerosol sample volume of 1 m3. The test reaction was done at a constant elevated temperature of 40 °C and the reaction time was 60 min. Calibration experiments showed that the test reaction with all reactive peroxides, i.e. hydrogen peroxide (H2O2), peracids and peroxides with vicinal carbonyl groups (e.g. lauroyl peroxide) goes to completion and their sensitivity (slope of calibration curve) varies by only ±5%. However, very inert peroxides have a lower sensitivity. For example, tert-butyl hydroperoxide shows only 37% sensitivity compared to H2O2 after 1 h. A kinetic study revealed that even after 5 h only 85% of this inert compound had reacted. The time trends of the peroxide content in secondary organic aerosol (SOA) from the ozonolysis and photo-oxidation of α-pinene in smog chamber experiments were measured. The highest mass fraction of peroxides with 34% (assuming a molecular weight of 300 g mol−1) was found in freshly generated SOA from α-pinene ozonolysis. Mass fractions decreased with increasing NO levels in the photo-oxidation experiments. A decrease of the peroxide content was also observed with aging of the aerosol, indicating a decomposition of peroxides in the particles.

Development of instrumentation systems as a base for control of digestion process stability in full-scale agricultural and industrial biogas plants

This article deals with the analysis of instrumentation from three modern German full-scale biogas plants with different inputs and typical process engineering concepts for German conditions. The measured results from each plant and the suitability of the instrumentation used are evaluated and assessed. Conclusions are also made about improving the use and architecture of the instrumentation. The analysis results show which benefits and optimum combination of on-line and off-line instrumentation could result for the control and automation of industrial and agricultural biogas plants.

New off-line aircraft instrumentation for non-methane hydrocarbon measurements

New off-line instrumentation was developed to implement measurements of non-methane hydrocarbons (NMHC) on (French) research aircraft. NMHC are collected on multisorbent tubes by AMOVOC (Airborne Measurements Of Volatile Organic Compounds), a new automatic sampler. AMOVOC is a versatile and portable sampler targeting a wide range of NMHC at high frequency (sampling time of 10 min). Multisorbent tubes are analyzed on the ground by short-path thermal desorption coupled with gas chromatography and mass spectrometry. The development and optimization of both NMHC sampling and analysis are reported here. On the one hand, the paper points out technical choices that were made according to aircraft constraints and avoiding sample loss or contamination. On the other hand, it describes analytical optimization, tube storage stability, and moisture removal. The method shows high selectivity, sensitivity (limit of detection less than 10 ppt) and precision (less than 24%). Finally, NMHC data collected on French aircraft during the African Monsoon Multidisciplinary Analysis campaign are reported for the first time. The results highlight instrumentation validity and protocol efficiency for NMHC measurements in the lower and upper troposphere.

Mach–Zehnder Interferometer for Real-TimeIn SituMonitoring of Refractive Microlens Characteristics at the Fabrication Level

We present a Mach-Zehnder interferometer to monitor in situ and in real-time the geometrical and optical characteristics of refractive microlenses during their fabrication process to increase the fabrication accuracy as well as the sample-to-sample reproducibility. We demonstrate for one test case that the deviation of our developed interferometric system against commercial instrumentation is smaller than 5 % while its repeatability error is smaller than 1.5% after calibration against dedicated off-line instrumentation. To conclude, we demonstrate the practical usefulness of this interferometer by applying it to the fabrication of microlenses by deep proton writing.

Secondary Organic Carbon and Aerosol Yields from the Irradiations of Isoprene and α-Pinene in the Presence of NOx and SO2

A laboratory study was carried out to investigate the secondary organic carbon (SOC) yields of alpha-pinene and isoprene in the presence of SO2, which produces acidic aerosol in the system. Experiments were based on irradiating each hydrocarbon (HC) with NOx in a 14.5 m3 smog chamber operated in the dynamic mode. The experimental design consisted of several multi-part experiments for each HC. In the first part of each experiment, an HC/NOx irradiation was conducted in the absence of SO2 and was followed by irradiations with the addition of SO2 in subsequent parts. Filter-based analyses for organic carbon were made using a thermal-optical approach either with an off-line instrument or in situ with an automated instrument. For isoprene in the absence of SO2, the SOC yield was approximately 0.001, a value consistent with earlier work from this laboratory. With the addition of up to 200 ppb SO2, the yield increased by a factor of 7. For alpha-pinene in the absence of SO2, the SOC yield of the irradiated mixture was found to average 0.096 from two experiments. With SO2 in the system, the SOC yield increased on average to 0.132. These results suggest that SO2, and by inference acidic aerosol, may play a role in increasing the yield of SOC from the photooxidation products of biogenic hydrocarbons or by the direct uptake of biogenic hydrocarbons onto acidic aerosol.

IN-LINE CONSISTENCY MONITORING OF TOMATO BASED PRODUCTS USING VIBRATIONAL PROCESS VISCOMETRY

A vibrational process viscometer was evaluated as an in-line consistency monitoring technique for tomato based products. This sensor was installed in both pilot and industry scale production processes. Accuracy of the sensor and its ability to distinguish between varying concentrations of non-Newtonian fluids was evaluated with flowrate and temperature closely controlled. The sensor was shown to have the least inherent variability when compared to off-line techniques. However it was found to be flowrate dependent for the tomato based products. Good correlations between the sensor and off-line techniques were developed for the pilot scale trials. Plant trials revealed a number of problems in developing such correlations under industrial process conditions, however the instrument proved capable of tracking out of specification sauce as determined by the off-line Brookfield viscometer. It was concluded that use of the sensor would result in increased measurement precision over the off-line instruments coupled with the benefits of in-line monitoring.

Instrument for the measurement of the instantaneous frequency

This paper describes the design and implementation of an instrument for the measurement of the instantaneous frequency of a signal. It is based on the extensive use of signal processing techniques and their implementation on efficient processors (digital signal processors). The concept of instantaneous frequency is first reviewed and some procedures for its estimation are evaluated with an off-line virtual instrument. The most promising techniques were then implemented on a PC-based instrument, achieving a real-time operation for audio ranges.

Heat transfer in a plate exchanger during pasteurization of orange juice

The heat transfer film coefficient of orange juice (OJ) during pasteurization using a plate heat exchanger with intermating 316 SS plates was studied. Mathematical models to predict OJ heat transfer film coefficient are presented. The OJ density was measured using an in-line density sensor at pasteurization temperature and also measured off-line by hygrometer at different temperatures. The OJ viscosity was measured by an off-line instrument, in the temperature range from 5–90°C. The mean values of OJ density and OJ viscosity at 20°C were 1046.0 ± 3.6 kg/m 3 and 14.17 ± 4.75 mPa s, respectively. The values of heat transfer film coefficient for OJ varied from 983 to 6500 W/m 2 °C, whereas the water heat transfer film coefficient varied from 8387 to 24245 W/m 2 °C. This study has provided a suitable heat transfer correlation to predict the OJ heat transfer film coefficient as a function of its viscosity and the channel velocity, that is, this correlation is independent of the plate geometry, for varied conditions of OJ pasteurization process.

Photoacoustic response of unburnt carbon in fly ash to infrared radiation

The photoacoustic response of unburnt carbon in fly ash to infrared radiation was investigated. The photoacoustic effect is the conversion of modulated electromagnetic radiation absorbed by gaseous, liquid or solid media into an acoustic wave, which can be detected by a sensitive microphone. The goal of this work was to develop an off-line instrument to measure unburnt carbon in fly ash. Twenty-four fly ashes from several pulverized coal and fluidized bed boilers burning a variety of coals were used. The photoacoustic effect generated by 1.315 μm infrared radiation from a 1.5 mW diode laser proved capable of measuring unburnt carbon in fly ash in the range 0.1–7.0 wt%. Compression and grinding of fly ash samples prior to measurement proved effective in improving the correlation between photoacoustic signal and carbon content. Such sample preparation reduces differences in powder voidage and particle size, both of which can affect photoacoustic response. The photoacoustic response was inversely proportional to the excitation modulation frequency, a result expected for photoacoustic saturation; however, the relatively large linear range observed for the photoacoustic signal as a function of fly ash carbon content is inconsistent with saturation. Therefore the photoacoustic response of unburnt carbon in bulk fly ash appears to be a blend of both solid-sample and single-particle effects.

A complete computer monitoring and control system using commercially available, configurable software for laboratory and pilot plant Escherichia coli fermentations.

The advent of inexpensive computers and associated control and data acquisition software makes possible the development of sophisticated, configurable, integrated monitoring and control systems for small-scale laboratory and pilot-scale fermentors at low cost. We describe here the implementation of such a system, the interfacing of off-line instruments to enhance real time data analysis, low level process control and several substrate feeding protocols.