Assessment of Low-Cost Particulate Matter Sensor Systems against Optical and Gravimetric Methods in a Field Co-Location in Norway

The increased availability of commercially-available low-cost air quality sensors combined with increased interest in their use by citizen scientists, community groups, and professionals is resulting in rapid adoption, despite data quality concerns. We have characterized three out-the-box PM sensor systems under different environmental conditions, using field colocation against reference equipment. The sensor systems integrate Plantower 5003, Sensirion SPS30 and Alphasense OCP-N3 PM sensors. The first two use photometry as a measuring technique, while the third one is an optical particle counter. For the performance evaluation, we co-located 3 units of each manufacturer and compared the results against optical (FIDAS) and gravimetric (KFG) methods for a period of 7 weeks (28 August to 19 October 2020). During the period from 2nd and 5th October, unusually high PM concentrations were observed due to a long-range transport episode. The results show that the highest correlations between the sensor systems and the optical reference are observed for PM1, with coefficients of determination above 0.9, followed by PM2.5. All the sensor units struggle to correctly measure PM10, and the coefficients of determination vary between 0.45 and 0.64. This behavior is also corroborated when using the gravimetric method, where correlations are significantly higher for PM2.5 than for PM10, especially for the sensor systems based on photometry. During the long range transport event the performance of the photometric sensors was heavily affected, and PM10 was largely underestimated. The sensor systems evaluated in this study had good agreement with the reference instrumentation for PM1 and PM2.5; however, they struggled to correctly measure PM10. The sensors also showed a decrease in accuracy when the ambient size distribution was different from the one for which the manufacturer had calibrated the sensor, and during weather conditions with high relative humidity. When interpreting and communicating air quality data measured using low-cost sensor systems, it is important to consider such limitations in order not to risk misinterpretation of the resulting data.

Reducing the measurement error of signal propagation delays using an optical reflectometer with picosecond resolution

The problems requiring high-precision measurements of signal propagation delays in optical fibers are considered. Design features of a pulsed optical reflectometer with a picosecond resolution designed for measuring propagation delays of a signal are considered. It is shown that the error of such a reflectometer includes the additive and multiplicative components. A method for determining the additive component of the optical reflectometer error based on measurements of signal delays introduced by individual optical fiber coils and the total delay introduced by series-connected coils is proposed. The requirements to the measurement conditions are formulated and the results of the error estimation of the proposed method are presented. To exclude the multiplicative component of the reflectometer error, a method for determining corrections to the reflectometer readings is proposed. The method is based on measuring the propagation delays of the signal in the coils of the optical fiber, first using reference equipment (installation for measuring the propagation delay of the signal), and then using an optical reflectometer, and then calculating the differences of the obtained measurement results. The scheme of installation for measurements of a propagation delay of signal in a coil of optical fiber is presented, the principle of operation of measuring installation is described. The results of the estimation of the error in determining the corrections to the reflectometer readings by the proposed method are presented. It is shown that the exclusion of the additive and multiplicative components of the error will reduce the error of optical reflectometers to values less than ± 100 ps.

Device for Generating and Measuring Time Intervals

The article suggests a device that extends the functionality of the measuring devices such as generators and frequency meters. So these devices can be used as part of working standards in a complex for verification and calibrating stopwatches. The device consists of an electronic commutator and a component controlled by a microcontroller, which forms the required intervals of time and provides a necessary connection from the generator output to the frequency counter input, turned on in the pulse counting mode. The control signal simultaneously arrives at the commutator and the device for automatic start/stop of stopwatches. The circuit design of the device allows minimizing the device’s influence on the overall metrological characteristics of the complex through the use of a high-speed controlled M74HC125 buffer (high-speed CMOS QUAD BUFFER (3-STATE)) as a switch. The M74HC125 buffer in this device is the only metrologically significant node; the state switching time of which in the aspect of this task can be ignored (Fig. 3). A computer and standard software, such as HyperTerminal from the Windows XP or PuTTY distribution, are used to control and communicate with the device. The device can be connected to the computer via USB. For laboratories that have these instruments in operation, this approach can help to avoid acquisitions of the additional reference equipment, which helps to reduce the maintenance and calibration costs of reference equipment.

Employing correlation for wireless components and device characterization in reverberation chambers

Reverberation chambers are well-proven test environments for radio frequency (RF) measurements. Typically, mean values are taken from the measurements to characterize the equipment under test. In the novel approach presented in this paper, the correlation of measured sample sequences is utilized to detect deviations, in particular of the radiation characteristics, from reference equipment. This approach is exemplified by a measurement setup using several different antennas with the same housing. The complex correlation coefficient and the correlation coefficient with respect to the transferred power of two measured sample sequences are calculated and evaluated for a suitable frequency range to detect differences between the radiation characteristics.

Demonstrating the value of “library as place” with the MISO Survey

Purpose The purpose of this paper is twofold. It first examines cross-institutional benchmark data about “library as place” from 99 US schools in the Measuring Information Service Outcomes (MISO) Survey (www.misosurvey.org). The data demonstrate the value of “library as place” to students in particular. Second, the paper shares case studies of how two college libraries made MISO Survey “library as place” data actionable. Lafayette College (Easton, Pennsylvania) analyzed local MISO Survey data after a renovation to validate return on investment. Earlham College (Richmond, Indiana) analyzed MISO Survey data to help secure a science library renovation and to justify an architectural study for its main library. Design/methodology/approach The paper begins with an analysis of “library as place” using aggregate benchmarks derived from US college and university respondents between 2012 and 2015. Specifically, the paper contrasts student and faculty perceptions of “library as place” via national benchmarks about: library services importance, satisfaction, and use (three benchmarks); hybrid online/“place-based” library services importance, satisfaction, and use (three benchmarks). Pivoting from higher education to individual, local perspectives, two case studies reveal how academic libraries used MISO Survey findings to demonstrate the value of “library as place” for renovation purposes. Findings The findings include that undergraduates make more frequent use than faculty of place-based services such as reference, equipment loans, and physical course reserves. Undergraduates also find most of these services more important than faculty do. Faculty makes generally more frequent use than undergraduates of online services such as library databases and the catalog. They find that these services to be more important than undergraduates do. Faculty and undergraduates use newer library discovery systems with equal frequency and find them to be equally important. Undergraduates find comfortable library spaces to be very important, and faculty considers them to be only a bit less important. Originality/value This is the first paper using MISO Survey data to focus on the importance and satisfaction of place-based library services involving cross-institutional comparisons for students and faculty. Previously published research using MISO Survey data have compared the use of place-based library services. This is also the first paper to offer case studies about how institutions use MISO Survey data to demonstrate the value of “library as place.”

Rock Properties versus Blades and Grit Consumption in Granite Multi Blade Sawing Process

Among the dimensional stone production processes, block splitting into slabs is very important in terms of time, costs and quality of final products. The world’s leading reference equipment for granite block cutting is the multi blade gang saw, in which sawing is the consequence of the combined action of a set of steel blades settled in an oscillating frame and an abrasive slurry containing water, steel shot and lime or bentonite. As the blades enter the block, stone powder is added to the abrasive slurry and as commercial granites include very different rock types, slurry characteristics also depend on the rock nature. Consequently, parameters of the cutting process have great variability. Depending on those parameters, the steel blades and shot are worn out differently during this process having great influence on costs. Due to its complexity, stone cutting mechanisms are still not well understood but compression, abrasion, impact and stone characteristics seem to influence the most. Aiming to help with the understanding of that process and based on previous studies, this work intends to establish correlations between granite petrographic and technological characteristics and steel blades and shot consumption. Laboratorial studies that include petrographic analysis, physical indexes measurement, and abrasion, impact and compression standardized testing of a selected group of stones are being crossed over with steel blades and steel shot consumption measurements in gang saws from several Brazilian processing companies. Although it is a study in progress, preliminary results show a relationship between the characteristics of selected stones and steel blades and shot consumption within the sawing process. The higher the quartz contents of the rock the higher its abrasion resistance, which results in higher consumption of steel shot during sawing. It can be also pointed out that beyond quartz and k-feldspar contents, microfissures seem to have influence on compression strength of the stones and this strength is directly related to the steel blades consumption. This can allow not only a better understanding of slabs production in multi blade gang saws process, but also to improve that process control.