Search Results (13)

In recent years, increasing the proportion of quartz sand in the hydraulic fracturing of shale gas has become one of the primary approaches to reduce development costs. However, the lack of industry standards for evaluating quartz sand specifically for shale gas hydraulic fracturing has constrained its widespread application in this context. Therefore, based on indoor comparative experiments, statistical analysis of product indicators, and field production data of shale gas, this study experimentally analyzed the particle size, turbidity, density, crush rate, embedment depth, friction coefficient, and packing coefficient of quartz sand used in shale gas hydraulic fracturing to define performance criteria. Certain evaluation methods deviate from the practical application of shale fracturing, and it is necessary to carry out specific experimental methods and performance indicators. The results indicate that for quartz sand used in shale gas hydraulic fracturing, it is recommended to increase five particle size specifications, maintain turbidity values below 250 FTU (formazine turbidity unit), ensure visual density does not exceed 2.75 g/cm³, and limit the crush rate to below 18%, embedment depth to below 0.15, packing coefficient to below 0.8, and friction coefficient to below 0.5. This work establishes evaluation standards and performance requirements for the optimal selection of quartz sand, aiming to reduce fracturing costs and enhance production efficiency in shale gas reservoirs. Full article

This paper investigates whether the Job Content Questionnaire (JCQ) 2.0 composite scales for demand, control, and stability-support at the task and organizational level are related to health and work-related outcomes as hypothesized in the job demand–control and Associationalist Demand–Control models. Further, the relative improvement of the JCQ 2.0 instrument over the JCQ 1 scales in the prediction of health and work-related outcomes is tested. The JCQ 2.0 was applied among workers in Australia and Germany. Analyses of variance and Kruskal–Wallis tests were applied for mean score comparison. In addition, path modeling as well as regression analyses were used. JCQ 2.0 task and organizational level demand, control, and stability-support as well as job strain and organizational-level active work are related to health and work-related outcomes as expected. Associations with active work at the task level are limited. A multilevel framework whereby organizational demands relate to task demands and, in turn, depression and burnout, is found in both German and Australian data. A similar organization to task process is found for control and support in German data, but for Australia, there is only a direct organizational effect on both outcomes. The task- and organizational-level composites—demand, control, and stability-support—explain unique variances in health and work-related outcomes. The JCQ 2.0 composites explain substantially more variance in all outcomes than the classic JCQ 1 DC and DCS scales. The results underline the utility of the JCQ 2.0 to assess multilevel aspects of the psychosocial work environment with broad practical value as a psychosocial risk assessment tool. Full article

The Job Content Questionnaire JCQ 2.0 (JCQ 2.0) thoroughly revises the well-known JCQ 1, based on an expanded Demand/Control theory-consistent platform with new scales, the Associationalist Demand Control (ADC) theory. This study tests the JCQ 2.0 in an urban population in Germany (N = 2326) for concurrent validity of each specific task and organizational-level scale and the relative importance of the task and organizational-level scales, using burnout and commitment as outcome measures. Cross-sectional regression analyses in the test and validation samples were run after multiple imputation. Five JCQ 2.0 task-level scales explain 44% of burnout variance; three JCQ 2.0 task-level scales explain 25% of commitment variance. Adding organizational-level scales, organizational disorder and rewards, increases the explained variance for burnout by five percentage points; consideration of workers’ interests and reward add four percentage points of variance for commitment. Organizational-level scales alone explain 33% and 28% of the variance in burnout and commitment, respectively, due to three and five organizational-level scales for both outcomes. Thus, the JCQ 2.0 task and organizational-level scales show substantial relations to work- and health-related outcomes, with task level more relevant for burnout and organizational level more relevant for commitment. The most strongly related JCQ 2.0 scales have evolved from new ADC theory, confirming its utility. Full article

Salivary turbidity is a promising indicator for evaluating oral hygiene. This study proposed a wearable mouthguard-type sensor for continuous and unconstrained measurement of salivary turbidity. The sensor evaluated turbidity by measuring the light transmittance of saliva with an LED and a phototransistor sealed inside a double-layered mouthguard. The sensor was also embedded with a Bluetooth wireless module, enabling the wireless measurement of turbidity. The mouthguard materials (polyethylene terephthalate-glycol and ethylene-vinyl acetate) and the wavelength of the LED (405 nm) were experimentally determined to achieve high sensitivity in salivary turbidity measurement. The turbidity quantification characteristic of the proposed sensor was evaluated using a turbidity standard solution, and the sensor was capable of turbidity quantification over a wide dynamic range of 1–4000 FTU (formazine turbidity unit), including reported salivary turbidity (400–800 FTU). In vitro turbidity measurement using a saliva sample showed 553 FTU, which is equivalent to the same sample measured with a spectrophotometer (576 FTU). Moreover, in vivo experiments also showed results equivalent to that measured with a spectrophotometer, and wireless measurement of salivary turbidity was realized using the mouthguard-type sensor. Based on these results, the proposed mouthguard-type sensor has promising potential for the unconstrained continuous evaluation of oral hygiene. Full article

Turbidity is a commonly used indicator of water quality in continental and marine waters and is mostly caused by suspended and colloidal particles such as organic and inorganic particles. Many methods are available for the measurement of turbidity, ranging from the Secchi disk to infrared light-based benchtop or in situ turbidimeters as well as acoustic methods. The operational methodologies of the large majority of turbidity instruments involve the physics of light scattering and absorption by suspended particles when light is passed through a sample. As such, in the case of in situ monitoring in water bodies, the measurement of turbidity is highly influenced by external light and biofouling. Our motivation for this project is to propose an open-source, low-cost in situ turbidity sensor with a suitable sensitivity and operating range to operate in low-to-medium-turbidity natural waters. This prototype device combines two angular photodetectors and two infrared light sources with different positions, resulting in two different types of light detection, namely nephelometric (i.e., scattering) and attenuation light, according to the ISO 7027 method. The mechanical design involves 3D-printed parts by stereolithography, which are compatible with commercially available waterproof enclosures, thus ensuring easy integration for future users. An effort was made to rely on mostly off-the-shelf electronic components to encourage replication of the system, with the use of a highly integrated photometric front-end commonly used in portable photoplethysmography systems. The sensor was tested in laboratory conditions against a commercial benchtop turbidimeter with Formazin standards. The monitoring results were analyzed, obtaining a linear trendline from 0 to 50 Nephelometric Turbidity Unit (NTU) and an accuracy of +/−0.4 NTU in the 0 to 10 NTU range with a response time of less than 100 ms. Full article

Dredged material dumping is an activity that causes some of the greatest changes in coastal waters. It results in the need to regularly monitor the properties of seawater related to water quality. In this study, we present the first wide-ranging attempt to correlate seawater turbidity and suspended particulate matter (SPM) concentrations within dumping sites and adjacent waters on the basis of in situ measurements. In the years 2019–2020, we examined four dumping sites, namely Darłowo, Gdynia, Gdańsk, and DCT, located in Polish coastal waters of the Baltic Sea, in the course of four measurement campaigns conducted in the spring, summer, autumn, and winter. The measurements were conducted using a turbidity sensor to determine the turbidity, in formazin turbidity units (FTU), a spectrophotometer to determine the concentrations of nutrients (total phosphorus (P-tot), phosphate phosphorus (P-PO₄⁻³), total nitrogen (N-tot), ammonium nitrogen (N-NH₄⁺), and nitrate nitrogen (N-NO₃⁻)), as well as glass microfiber filters to determine the concentrations of SPM. The analysis of the relationship between the turbidity and SPM within the dumping sites in comparison to reference points showed that the dumping sites are very complex waters and that the issue must be approached locally. The highest turbidity values were registered in the spring, and they correlated linearly with the SPM concentrations (R² = 0.69). Moreover, we performed a statistical cluster analysis to illustrate the similarities between sampling points in the four dumpsites based on nutrient concentrations. We conclude that the influence of the dumping sites on the local bio-optical and chemical properties significantly exceeds their borders and spreads to the adjacent waters. Nutrient concentrations in many cases exceeded the legal policy limits. Full article

Testing assumptions of the widely used demand–control (DC) model in occupational psychosocial epidemiology, we investigated (a) interaction, i.e., whether the combined effect of low job control and high psychological demands on depressive symptoms was stronger than the sum of their single effects (i.e., superadditivity) and (b) whether subscales of psychological demands and job control had similar associations with depressive symptoms. Logistic longitudinal regression analyses of the 5-year cohort of the German Study of Mental Health at Work (S-MGA) 2011/12–2017 of 2212 employees were conducted. The observed combined effect of low job control and high psychological demands on depressive symptoms did not indicate interaction (RERI = −0.26, 95% CI = −0.91; 0.40). When dichotomizing subscales at the median, differential effects of subscales were not found. When dividing subscales into categories based on value ranges, differential effects for job control subscales (namely, decision authority and skill discretion) were found (p = 0.04). This study does not support all assumptions of the DC model: (1) it corroborates previous studies not finding an interaction of psychological demands and job control; and (2) signs of differential subscale effects were found regarding job control. Too few prospective studies have been carried out regarding differential subscale effects. Full article

Lithium has become an element of great relevance in recent times, because among its various applications is the manufacture of batteries, and it is a vital part of the growing development of new products such as electric vehicles. On the other hand, the geographical distribution of lithium reserves is very heterogeneous. Of the existing minerals, only some of them are important sources of exploitation, such as the salt in South America, while in other countries mineral deposits such as spodumene stand out. The process for obtaining lithium from spodumene consists of concentrating up to 3% lithium by flotation. Because other minerals associated with this mineral are mainly silicates (feldspar, clays, quartz and micas), great problems are generated in the thickening stage. This article seeks to study the effect of the addition of flocculants and KCl on the sedimentation rate, in addition to studying its effects on the turbidity of the supernatant in different types of water. This is done by Batch sedimentation tests with tailings pulps, to later characterize both the pulp and the supernatant by means of the turbidity of the clarified water. Magnafloc-338 flocculant is the most convenient to use with industrial water, since it reaches a high sedimentation rate of 34.2, 37.44, and 45.36 m/h, with doses of 5, 10, and 15 g/t respectively, and a low turbidity rate (31 Formazin Nephelometric Units (FNU)) at low flocculant dosages. Full article

A cost-effective optical instrument for continuous in-situ monitoring applications is presented. With a production cost in raw materials of 38 €, a power consumption of 300 A in sleep mode and 100 mA in active mode (5 ms reading), and a capacity to monitor turbidity and sedimentary displacement at eight different depths in the water column, the sensor was developed for sediment monitoring in coastal areas. Due to the extent and dynamics of the processes involved in these areas, observations require a wide spatial and temporal resolution. Each of the eight monitoring nodes uses one infrared backscatter channel, to estimate turbidity and sediment concentration, and one ultraviolet with one infrared transmitted light channels to distinguish organic/inorganic composition of the suspended material load. An in-lab calibration was conducted, using formazine to correlate turbidity with the electronic outputs of the instrument. An analysis of the influence of external light sources and correction techniques were performed. Moreover, an in-lab experiment was conducted to study the behaviour of the sensor-to-sediment transport, wash load and sediment accumulation. The device was deployed, with a water level sensor, in an estuarine area with high sediment dynamics. The monitoring data were analysed, showing the potential of the device to continuously monitor turbidity, sediment processes, and distinguish between organic and inorganic matter, at the different depths in the water column. Full article

Turbidity is a key environmental parameter that is used in the determination of water quality. The turbidity of a water body gives an indication of how much suspended sediment is present, which directly impacts the clarity of the water (i.e., whether it is cloudy or clear). Various commercial nephelometric and optical approaches and products exist for electronically measuring turbidity. However, most of these approaches are unsuitable or not viable for collecting data remotely. This paper investigates ways for incorporating a turbidity sensor into an existing remote aquatic environmental monitoring platform that delivers data in near real-time (i.e., 15-min intervals). First, we examine whether an off-the-shelf turbidity sensor can be modified to provide remote and accurate turbidity measurements. Next, we present an inexpensive design for a practical light attenuation turbidity sensor. We outline the sensor’s design rationale and how various technical and physical constraints were overcome. The turbidity sensor is calibrated against a commercial turbidimeter using a Formazin standard. Results indicate that the sensor readings are indicative of actual changes in turbidity, and a calibration curve for the sensor could be attained. The turbidity sensor was trialled in different types of water bodies over nine months to determine the system’s robustness and responsiveness to the environment. Full article

Water quality monitoring and predicting the changes in water characteristics require the collection of water samples in a timely manner. Water sample collection based on in situ measurable water quality indicators can increase the efficiency and precision of data collection while reducing the cost of laboratory analyses. The objective of this research was to develop an adaptive water sampling device for an aerial robot and demonstrate the accuracy of its functions in laboratory and field conditions. The prototype device consisted of a sensor node with dissolved oxygen, pH, electrical conductivity, temperature, turbidity, and depth sensors, a microcontroller, and a sampler with three cartridges. Activation of water capturing cartridges was based on in situ measurements from the sensor node. The activation mechanism of the prototype device was tested with standard solutions in the laboratory and with autonomous water sampling flights over the 11-ha section of a lake. A total of seven sampling locations were selected based on a grid system. Each cartridge collected 130 mL of water samples at a 3.5 m depth. Mean water quality parameters were measured as 8.47 mg/L of dissolved oxygen, pH of 5.34, 7 µS/cm of electrical conductivity, temperature of 18 °C, and 37 Formazin Nephelometric Unit (FNU) of turbidity. The dissolved oxygen was within allowable limits that were pre-set in the self-activation computer program while the pH, electrical conductivity, and temperature were outside of allowable limits that were specified by Environmental Protection Agency (EPA). Therefore, the activation mechanism of the device was triggered and water samples were collected from all the sampling locations successfully. The adaptive water sampling with Unmanned Aerial Vehicle-assisted water sampling device was proved to be a successful method for water quality evaluation. Full article

Turbidity sensing is very common in the control of drinking water. Furthermore, turbidity measurements are applied in the chemical (e.g., process monitoring), pharmaceutical (e.g., drug discovery), and food industries (e.g., the filtration of wine and beer). The most common measurement technique is nephelometric turbidimetry. A nephelometer is a device for measuring the amount of scattered light of suspended particles in a liquid by using a light source and a light detector orientated in 90° to each other. Commercially available nephelometers cost usually—depending on the measurable range, reliability, and precision—thousands of euros. In contrast, our new developed GRIN-lens-based nephelometer, called GRINephy, combines low costs with excellent reproducibility and precision, even at very low turbidity levels, which is achieved by its ability to rotate the sample. Thereby, many cuvette positions can be measured, which results in a more precise average value for the turbidity calculated by an algorithm, which also eliminates errors caused by scratches and contaminations on the cuvettes. With our compact and cheap Arduino-based sensor, we are able to measure in the range of 0.1–1000 NTU and confirm the ISO 7027-1:2016 for low turbidity values. Full article

Membrane hybrid processes—coagulation coupled with ultrafiltration (UF)—have become a common method to comply with the legal, chemical, and microbiological requirements for drinking water. The main advantages of integrating coagulation with membrane filtration are the enhanced removal of natural organic matter (NOM) and reduced membrane fouling. With in-line coagulation, coagulants are patched into the feed stream directly prior to the membrane process, without removing the coagulated solids. Compared with conventional coagulation/sedimentation, in-line coagulation/membrane reduces the treatment time and footprint. Coagulant dosing could be challenging in raw water of varying quality; however, with relatively stable specific ultraviolet absorbance (SUVA), dosing can be controlled. Recent studies indicate that UV absorbance correlates well with humic substances (HS), the major fraction to be removed during coagulation. This paper describes and evaluates a 30-month UF pilot trial on the surface water of Lake Neden (Sweden), providing drinking water to 60,000 residents. In this study, automatic coagulant dosing based on online measurement was successfully applied. Online sensor data were used to identify the current optimal aluminium coagulation conditions (0.5–0.7 mg L⁻¹) and the potential boundaries (0.9–1.2 mg L⁻¹) for efficient future (2040) NOM removal. The potential increase in NOM could affect the Al dose and drinking water quality significantly within 20 years, should the current trends in dissolved organic carbon (DOC) prevail. UV absorbance, the freshness index, and liquid chromatography-organic carbon detection (LC-OCD) measurements were used to optimise the process. Careful cross-calibration of raw and filtered samples is recommended when using online sensor data for process optimisation, even in low-turbidity water (formazin nephelometric unit (FNU) < 5). Full article