Jet-Driven Mixing Regimes Identified In The Unsteady Isothermal Filling Of Rectangular Municipal Water Storage Tanks

Poor mixing of old and new water in municipal water storage vessels is a well-documented basis for potentially harmful water quality degradation in drinking water distribution systems. This numerical study investigates the effects of inflow and operational variables on mixing in the jet-driven filling process, with a particular focus on the transition from inadequate to sufficient mixing levels. An isothermal unsteady reynolds-averaged-navier-stokes volume-of-fluid (RANS-VOF) simulation is used to model the variable-volume filling process, accounting for the moving free surface following a draw-down in the stored water volume. A low diffusivity tracer is used to mark the old-water volume, and a coefficient of variation (CoV) quantifying the departure from a uniform tracer distribution is used to monitor the time-dependent mixing. The results indicate that adequate mixing does not necessarily follow refills from common draw-down levels. Three distinct mixing regimes are identified by unique CoV transients. Introducing consideration of the mean-flow kinetic energy, the observed mixing behaviors are readily explained by the jet inlet power and the distribution of the mean-flow kinetic energy in the tank. Extending the simulations to periods after cessation of the inflow and to partial refills, the role of residual mean-flow kinetic energy is further highlighted, especially its limited vertical reach. For cases in which a sufficiently mixed condition is achieved, the time-to-mix results are well described by a mixing-time correlation closely matching previously published results

Dielectric Properties Of Polycrystalline And Single Crystal (100) Strontium Titanate From 4 To 295 K

The dielectric properties of single crystal and polycrystalline SrTiO3 (ST) were investigated from 295 to 4 K. Relative permittivity (εr) and loss tangent (tan(δ)) were measured systematically as a function of direct current (DC) voltage (0 V/cm to 800 V/cm), frequency (100 Hz to 1 MHz), and temperature (295 K to 4 K) for type (100) single crystal SrTiO3 (SC-ST) and for polycrystalline SrTiO3 (PC-ST). Calculated equivalent series resistance (ESR) data are also reported. Overall, the permittivity of ST showed a dependence on temperature, DC voltage, and frequency. Dependences on voltage and frequency were only observed at temperatures below about 40 K. Curie–Weiss temperature (Tcw) was found to be independent of measurement frequency and applied DC field for SC-ST and PC-ST. Two frequency-dependent ESR peaks were observed for the SC-ST. There were five such peaks for PC-ST including the same two peaks displayed by SC-ST. All loss peaks were found to follow an Arrhenius type behavior. While certain peaks might be related to structural phase transitions, the additional peaks observed for PC-ST were attributed to the presence of grain boundaries, domains, residual porosity, impurities, or their combined effects. The results provide a good prediction of the dielectric performance of SrTiO3 based capacitors towards optimizing the design of circuits used for cryogenic electronic applications

Multilayer Ceramic Capacitor Vibration Source Model Library Development

When a Multilayer Ceramic Capacitor (MLCC) is Soldered on a Printed Circuit Board (PCB), the Capacitor Deformation Generates a Force on the PCB, Which Serves as a Source to Excite PCB Vibration and Generate Unwanted Acoustic Noise. a MLCC Can Be Used under Any Loading Conditions as Long as the Power Supply Voltage Remains Below its Rated Voltage; Thus, the MLCC Source Mode Can Be Extremely Complicated Because of Different Combinations Including Direct Current Voltage Levels, Alternating Current Noise Amplitudes, and Related Frequencies. When the Power Rail is under Different Loading Conditions, the PCB Vibration Amplitude Can Differ; However, the MLCC Vibration Source Model Should Remain the Same under a Given Condition. in This Article, the MLCC Equivalent Source Models Are Developed with a Simplified Method, and a Source Model Library for the Six MLCCs is Constructed. a Method for Simplifying the MLCC Equivalent Source Model is Addressed from Three Aspects: Frequency, Power Supply Dc Voltage, and Ac Noise Amplitude. the Developed Source Model Library is Validated by Comparing the Simulated and Measured System Vibration Velocity. the Proposed Simplification Method Can Significantly Reduce Model Development Efforts and Enable the Creation of a Comprehensive Source Model Library for MLCCs

Prompt, Accurate, and Noncontact Material Identification using a Single Microwave Sensor with Machine Learning Analysis

In This Article, a Novel Approach to Microwave Sensors is Proposed and Demonstrated that Allows for Prompt, Accurate, and Noncontact Material Identification Even with Arbitrary Lift-Off Distances between the Sensor and the Material under Test (MUT). a Multilayer Perceptron (MLP) is Trained to Directly Learn the Relation of the Measured Reflection Spectra of a Homemade Open-Ended Coaxial Cable Resonator Probe with Respect to Different MUTs and Then Achieve One-To-One Mapping between a Measured Spectrum and the MUT. as a Proof-Of-Concept Demonstration, the Performance of the MLP Model is Tested using Easily Accessible Materials, Including Wood, Glass, Water, and Metal. Reflection Spectra of the Probe for Different MUTs with Different Lift-Off Distances Are Acquired using a Vector Network Analyzer (VNA) and Are Utilized to Train and Test the MLP Model. High Classification Accuracy is Realized. More Importantly, the MUT Can Be Identified using the Well-Trained Model with an Arbitrary Lift-Off Distance and Even a Tilt Angle with Respect to the Probe End Face, as Long as the Lift-Off Distance is within the Model Calibration Range. This Preliminary Work is Expected to Inspire Researchers in the Field of Microwave Sensors and Instrumentation to Develop a New Generation of Intelligent Systems with Expanded Functionalities that Could Find Potential Applications in Diverse Fields

Designing a Ppb-level Fiber-optic Microphone for Photoacoustic Spectroscopy of Trace Gases

We Report Our Progress on the Design of a Highly Sensitive Photoacoustic Spectroscopy Sensor using an Extrinsic Fabry-Perot Interferometer Fiber-Optic Microphone for Detecting Parts-Per-Billion-Level Trace Gas Concentrations. a Theoretical Model is Set Up to Predict the Mechanical Behavior of the Sensor and Extended with a Mathematical Framework for Detecting Gas Concentration from the Generated Acoustic Modes in a Photoacoustic Gas Cell. a Detection Limit Up to 1.55ppb for Nitric Oxide is Predicted based on the Model for a Minimum Detectable Pressure of 2.1μpa√Hz. We Also Investigated Different Frequency Response of Two Different Gas Cells with the Finite Element Method (FEM) using COMSOL for the Fiber-Optic Acoustic Sensor

Synergetic Kinetics Of High-Temperature Surface Degradation Processes In Austenitic Heat-Resistant Cast Steels

When the severity of high-temperature environments increases, the oxidation mode changes from a normal oxidation mode, when a formed oxide layer protects the surface of austenitic heat-resistant cast steels, to an extreme mode, when scale spallation and partial vaporization intensify surface degradation. These processes can also influence each other. On the example of two oxidized austenitic heat-resistant steels with different alloying levels, we show how the described simulation/experimental methodology may be applied to analyze and quantify the synergetic kinetics of the extreme surface degradation processes. The surface degradation processes were formulated using diffusion-controlled parabolic oxidation, time-dependent vaporization, and spallation with an intensity cross-linked to the instantaneous thickness of the oxide layer. The 400 h tests were performed in air and water vapor-containing combustion gases at upper working temperatures. Three experimentally obtained surface degradation quantities included changing the weight of the specimen with adherent oxide, the weight of the spalled scale, and the thickness of the formed adherent oxide. These experimental quantities were used to compute the values of oxidation, vaporization, and spallation kinetic constants for each uninterrupted oxidation test. An additional interrupt every 100-h test was also performed to verify the model-predicted trends. It was shown that the alloying level in austenitic heat-resistant cast steel determines its ability to withstand surface degradation at extreme oxidation mode by the synergetic effects of oxidation, vaporization, and spallation. The described approach can be used for the metallic component lifetime prediction in severe gaseous environments

Geomechanical Monitoring of an Underground Bulk Mining Operation using a Novel Distributed Optical Fiber Strain Sensing Method

As Mines Continue to Deepen and Become More Expansive, Active Monitoring of Larger Volumes of Rock Mass Will Become More Critical to Calibrate Numerical Simulations and to Ensure the Safety of Underground Workers. Monitoring Larger Volumes of Rock Mass Requires Low-Cost Sensors Which Are Simple in Construction and Installation. in This Study, a Novel Hybrid Optical Fiber Cable (HOFC) Designed for Use in Distributed Optical Fiber Sensing (DOFS) Via Grouted Boreholes Was Employed to Monitor a Bulk Mining Operation in an Underground Metal Mine. the HOFC Was Successfully Used to Monitor Approximately 2.7 X 103 M3 of Rock Mass above Excavations Surrounding a Pillar Removal Area in Which Six Large Pillars Were Removed Simultaneously. a Total of Six Measurement Boreholes (Maximum Depth of 22 M) Were Used to Measure Strain Along the Optical Fiber during the Pillar Removal Operation using the HOFC, Allowing for 70 Individual Strain Measurement Points, Which Were Constructed for under One US Dollar Each. Monitoring of the Excavation Area Took Place over a 44-Day Period after Pillar Removal. Extensional Strains Were Noted in the Areas Closest to the Removed Pillars, While Areas of Compression Were Noted Directly above the Remaining Pillar in the Area. the Results of the Case Study Demonstrate that a Low-Cost Optical Fiber Strain Sensing Network Can Be Rapidly Installed in a Large Excavation Area and Can Provide Highly Sensitive Strain Measurements in a Manner that Would Be Cost-Prohibitive Via Other Methods

Circular Economy Strategies For Reducing Embodied Carbon In US Commercial Building Stocks: A System Dynamics Modeling Approach

Environmental concerns over embodied carbon - which is generated during the extraction, transportation, manufacturing, construction, and disposal of building materials - have been increasing as the industry shifts to renewable energy and grid decarbonization efforts prevail. Commercial buildings, a rapidly growing sector and a major source of embodied carbon, can contribute immensely to the national climate goals by transitioning into a circular economy (CE). Nevertheless, embodied carbon research is rather dispersed, with sparse data on the actual impact of different CE strategies and how they scale on nationwide commercial building stocks. To address this research need, the goal of this paper is to provide policymakers with a conceptual model that depicts the potential of CE strategy portfolios on embodied carbon reduction of commercial building stocks. Using US commercial buildings data from the Energy Information Administration, the authors (1) developed a systems dynamics model to conceptualize and serve as a baseline for calculating existing embodied emissions; and (2) evaluated the influence of various policy packages in terms of their overall emissions reduction potential over a planning horizon between the years 2022 and 2050. Findings of the study highlight the effectiveness of early design and construction CE interventions as compared to end-of-life strategies such as recycling, as well as traditional and business-as-usual approaches. Ultimately, results of the developed model can aid decision-makers to create multiple what-if scenarios for their policies, in addition to capitalizing on the most effective strategies for narrowing material loops and curbing embodied carbon emissions

Monitoring Residual Solvents in Pharmaceutical Products using a Portable Pre-Concentration Gc-Pid

Pharmaceutical manufacturing utilizes solvents at different stages of production. Some of the harmful solvent residuals may be retained in the final product; therefore, they need to be monitored for quality control and to meet the regulation requirement. Here, a novel method capable of rapidly analyzing residual solvents in pharmaceutical products was developed using a compact-portable gas chromatography with a photoionization detector (GC-PID). The method consists of modified Tedlar® bag sampling, online pre-concentration, separation of volatiles by miniaturized GC, and micro-PID detection. The method detection limits of selected residual solvents were in the range of 26.00 – 52.03 pg/mL which is much lower than the pharmaceutical compliance concentration limits. Limits of detection \u3e 520 pg of analyte per grams of sample was also determined for the over-the-counter drugs. The method performance showed rapid speed (5 min), linear calibration (r2 \u3c 0.99), and repeatable retention time (RSD \u3c 0.4 %). Direct analysis of residual solvents in solid samples was conducted without the need for complex sample preparation. The method validation using over-the-counter pharmaceutical products yielded excellent accuracy (recovery \u3e 91.2 %) and precision (RSD \u3c 6.5 %) for the selected residual solvents, including 1,4-dioxane, benzene, chlorobenzene, cyclohexane, xylenes, and toluene. This portable and rapid method could be deployed during the pharmaceutical drug manufacturing processes for quality control

Angle-Dependent Photoinduced Changes of Near-Infrared Transmission in Amorphous Selenium Films

Amorphous selenium (a-Se) is a promising semiconductor for a variety of photoconductive applications, predominantly in X-ray detection. In addition, material properties introduce several other potential applications in nonlinear optics. Photodarkening (PD) presents an interesting area of study; when exposed to band-region light, metastable structural changes induce a shift in the band edge and increase tail absorption. In this work, we investigate these effects utilizing a near-infrared (NIR) probe to avoid generating any darkening during beam transmission. We observe an unexpected result; here, we present the effects of band region exposure in NIR transmission (1570 nm). We observe a shift from darkening to lightening as the angle of incidence changes and compare PD with a red probe (633 nm), which does not exhibit this same phenomenon. We discuss the possible mechanisms and the next steps in delving into the physics underlying this behavior. These effects have strong implications for applications in nonlinear optics, memory, and sensing in the NIR