Logarithmic Frequency Research Articles

Temperature and Frequency Dependence of the Dynamic Viscoelastic Properties of Silicone Rubber.

Temperature-frequency sweep tests were performed on silicone rubber to investigate the dynamic viscoelastic properties. The test results show that the viscoelasticity of silicone rubber presents significant temperature dependence and frequency dependence. The dynamic viscoelastic test curves at different temperatures can be shifted along the logarithmic frequency coordinate axis to construct smooth master curves at the reference temperature of 20 °C, covering a frequency range of 10 decades, which indicates thermorheological simplicity on a macro level and frequency temperature equivalence of the silicone rubber material in the experimental temperature range. The van Gurp-Palmen plot and Cole-Cole plot for the test data at various temperatures merge into a common curve, which further validates thermorheological simplicity. The temperature dependent shift factors of silicone rubber material were well characterized by the Williams-Landel-Ferry equation. Moreover, the fractional-order differential Kelvin (FDK) model, the fractional-order differential Zener (FDZ) model, and the improved fractional-order differential Zener (iFDZ) model were used to model the asymmetric loss factor master curve. The result shows that the iFDZ model is in good agreement with the test results, indicating that this model is suitable for describing the asymmetry of dynamic viscoelastic properties of silicone rubber.

Petrophysical parameters inversion for heavy oil reservoir based on a laboratory-calibrated frequency-variant rock-physics model

Heavy oil has high density and viscosity, and exhibits viscoelasticity. Gassmann's theory is not suitable for materials saturated with viscoelastic fluids. Directly applying such model leads to unreliable results for seismic inversion of heavy oil reservoir. To describe the viscoelastic behavior of heavy oil, we modeled the elastic properties of heavy oil with varying viscosity and frequency using the Cole-Cole-Maxwell (CCM) model. Then, we used a CCoherent Potential Approximation (CPA) instead of the Gassmann equations to account for the fluid effect, by extending the single-phase fluid condition to two-phase fluid (heavy oil and water) condition, so that partial saturation of heavy oil can be considered. This rock physics model establishes the relationship between the elastic modulus of reservoir rock and viscosity, frequency and saturation. The viscosity of the heavy oil and the elastic moduli and porosity of typical reservoir rock samples were measured in laboratory, which were used for calibration of the rock physics model. The well-calibrated frequency-variant CPA model was applied to the prediction of the P- and S-wave velocities in the seismic frequency range (1–100 Hz) and the inversion of petrophysical parameters for a heavy oil reservoir. The pre-stack inversion results of elastic parameters are improved compared with those results using the CPA model in the sonic logging frequency (∼10 kHz), or conventional rock physics model such as the Xu-Payne model. In addition, the inversion of the porosity of the reservoir was conducted with the simulated annealing method, and the result fits reasonably well with the logging curve and depicts the location of the heavy oil reservoir on the time slice. The application of the laboratory-calibrated CPA model provides better results with the velocity dispersion correction, suggesting the important role of accurate frequency dependent rock physics models in the seismic prediction of heavy oil reservoirs.

고등학교 1학년 전국연합학력평가 영어 지문의 언어적 특성 및 난이도 분석

This study examines the linguistic characteristics and the text difficulty of the National Assessment of Academic Achievement (NAAA). First, the linguistic features of NAAA conducted in June, September, and November were compared to examine the difference among the tests by the scope of the assessment. Second, the linguistic features of NAAA and the reading texts in six high school English textbooks were compared. Lastly, the correlation between the linguistic features of NAAA and the correct answer rate for each question was analyzed. Corpus analysis was conducted by using Coh-Metrix 3.0. The indices were selected for descriptive analysis, lexical diversity, connectives, syntactic complexity, and readability. One-way ANOVA, Kruskal-Wallis H test, independent t-test, Mann-Whitney U test, and correlation analysis were conducted to investigate the Coh-Metrix data. The result revealed the statistical differences among NAAA tests held in June, September, and November regarding the differences in ‘mean number of words of sentences and readability score.’ In addition, discrepancies in linguistic features between the text in NAAA and the English textbooks were found. Lastly, it was found that ‘number of words, mean number of words, CELEX Log frequency for all words, argument overlap, and readability score' had a correlation with the correct answer rate. Implications and the limitations of the study were discussed.

Experimental Investigation into the Influence of LED Bias Setup on VLC Frequency Domain Characteristics: Beyond Non-Negativity

Different from the radio frequency bipolar complex signalling, LED-based visible light communication (LED-VLC) meets the non-negativity requirement by adding a bias component (BC) to a bipolar real-valued signal. Although many people know that there is a relationship between BC and LED characteristics, unfortunately, most of them chose to ignore it, and thus there has been little exploration of its impact on VLC. In this paper, we have experimentally measured the frequency domain characteristics of several LEDs commonly used in home and business applications. The numerical calculations show that the logarithmic domain absolute frequency response is approximately linear, where the corresponding intercepts and slopes can be quadratically expressed with respect to BC with a very low fitting error. This experimental investigation reveals that the BC value will remarkably influence the VLC system performance beyond non-negativity, and the LED-VLC transceiver designs should jointly take the BC and LED communication characteristic into consideration.

715-P: How Frequently Do People with Diabetes Use a Digital Diabetes Logbook and How Satisfied Are They with It?

A randomized controlled trial (RCT) was conducted to evaluate the efficacy of a digital diabetes logbook (mySugr) to help with diabetes self-management. Frequency of use as well as satisfaction with the app were assessed. A total of 424 people were included in the RCT with 282 being randomized to the intervention group using the app for 3 months (2:1 randomization) (age: 51.2±14.6 years; 13.1% type 1, 66.7% type 2, 20.2% gestational diabetes). Frequency of use was assessed with user data from the pseudonymized study server. Satisfaction with mySugr was assessed with an adapted version of the Mobile App Rating Scale (MARS). Mean MARS scores were calculated (range: 1-5) with higher scores indicating higher satisfaction. User data from 249 participants of the intervention group (88.3%) were analyzable. The app was used on a median of 92.6% (IQR: 57.7 - 100%) of the study days (median study duration: 91 [IQR: 84-96] days). Over the study duration, participants logged 3.1±2.5 blood glucose values. Satisfaction was very high with a mean MARS score of 4.3±0.7. 64.7% of participants agreed that the app is appealing for people with diabetes and 82.5% agreed that the app is easy to use. Satisfaction was highest in women with gestational diabetes, followed by people with type 1 and people with type 2 diabetes (4.5±0.5 vs. 4.3±0.6 vs. 4.2±0.7; p=0.037). Higher satisfaction was associated with higher percentage of days with app use (r=0.23, p<0.001), higher logging frequency (r=0.20, p=0.002) and less problems with the app (r=-0.20, p=0.001). Those who contacted mySugr support when they had problems were significantly more satisfied than those who did not contact support when they had problems (4.6±0.4 vs. 3.8±0.7, p=0.023). Participants randomized to using mySugr for 3 months (no prior app use) were highly satisfied with the app. Frequency of use of the app across the study period was very high. Satisfaction was high in all diabetes types with women with gestational diabetes having the highest satisfaction. Disclosure N.Hermanns: Advisory Panel; Insulet Corporation, Research Support; Sanofi-Aventis Deutschland GmbH, Roche Diagnostics, Becton, Dickinson and Company, Speaker's Bureau; Dexcom, Inc., Berlin-Chemie AG. D.Ehrmann: Advisory Panel; Roche Diabetes Care, mySugr, Dexcom, Inc., Speaker's Bureau; Berlin-Chemie AG, Dexcom, Inc. S.Silbermann: Employee; Roche Diabetes Care. J.Kober: Employee; mySugr. I.Vesper: None. K.Finke-gröne: None. T.Roos: None. E.Bingol: Employee; Roche Diabetes Care. B.Kulzer: Advisory Panel; Berlin-Chemie AG, Abbott Diabetes, Bayer Inc., Dexcom, Inc., Novo Nordisk, Insulet Corporation, embecta, Research Support; Sanofi, Roche Diabetes Care. Funding Roche Diabetes Care GmbH (DC000097)

Analysis of the influence of the discrete period of the zero-order hold of the digital automatic control system on dynamic indicators of control quality

The issue of increasing the accuracy of reproduction of the master signal in a digital system for automatic control of an electric drive in the presence of a zero-order extrapolator in the block diagram is considered. The formation of discreteness in a control system with a zero-order extrapolator is considered. The analysis of the influence of the extrapolator discreteness on the dynamic indicators of the system control quality is carried out. As indicators of the quality of control direct indicators: overshoot and time of the transition process. The necessary relationship between the zero-order extrapolator quantization frequency and the bandwidth frequency of the linear part of the system is shown, which ensures the approximation of the above indicators of the quality of control of a discrete system to those of an analog prototype. The bandwidth of the analog part of the system is determined from the logarithmic frequency response. The article provides a recommendation for choosing the quantization frequency of digital controllers with zero-order extrapolators for multi-loop control systems, for example, built on the principle of slave control systems.

Electron-phonon coupling in La3In under pressure

Conventional superconducting parameters Eliashberg spectral function, phonon DOS, average electron-phonon coupling constant & superconducting transition temperature of La3In were calculated at ambient and applied positive hydrostatic pressure. Ambient pressure electron-phonon coupling constant was found to be 1.43 and superconducting transition temperature was calculated to be 8.7 K which is close to the experimental reported value of 9.5 K. Logarithmic average phonon frequency at ambient pressure was found to be 6.21 × 10−3 eV. Phonon dispersion relations for the ambient and applied positive hydrostatic pressure were calculated to confirm the dynamical stability of La3In under positive pressure. Acoustic modes of vibrations were found to mediate most of the electron-phonon-electron interaction with a very small contribution from optical modes of vibrations. Fermi surface at ambient pressure was also calculated and employed in explaining the large value of the calculated electron-phonon coupling constant. The effect of spin–orbit coupling on electronic, phonon and superconducting properties of La3In was also studied.

Hilbert transform of unequally sampled data: Application to dispersion relations in magnetotellurics

The real and imaginary parts of the Fourier transform of a causal signal can be estimated from one another using the Hilbert transform. The numerical computation can be carried out by a fast Fourier transform or the convolution of the data with an appropriate Hilbert kernel. However, magnetotelluric (MT) data are unequally sampled because logarithmic frequency axes are conventionally used. A method has been developed for the Hilbert transformation of unequally sampled data and applied to the real and imaginary parts of the frequency normalized impedance to examine if the dispersion relations are satisfied for a given impedance tensor. A version of the Shannon sampling theory is generalized for the unequally sampled data. The method involves the reconstruction of the measured data by a linear combination of an analytic interpolation function distributed along the horizontal axis. Then, the decomposition coefficients that provide a fit between the measured and reconstructed data are solved using the linear least-squares method with singular-value decomposition. Finally, the discrete Hilbert transformed data are constructed at any desired abscissa values by the sum of the analytic Hilbert transform of the interpolation function using the decomposition coefficients solved in the previous step. Examples from the MT synthetic and field data, including out-of-quadrant phase cases, are given. In principle, the method also can be applied to other integral transforms.

Efficiency of Applying the Nyquist and V.M. Popov Criteria for Stability Analysis of Linearized Automatic Control Systems in Electromechanics and Power Engineering

It is well known that all real automatic control systems (ACS) are significantly nonlinear systems. Along with this, in engineering analysis the simplifications of their mathematic description, that is, linearization, are inevitable. These simplifications naturally introduce errors into engineering calculations. For the most complicated calculation of stability conditions, these errors can be very significant, since they lead to not only incorrect forecast of the ACS condition but also to the operating inability of the designed ACS. Most often, engineers simplify nonlinear structures in their calculations. In other words, they linearize these structures according to one of the numerous approaches which have been developed over 100 years. Calculation methods for linear ACS, in particular the Nyquist criterion, can be applied to the already linearized structure for the calculation of ACS stability condition. In this article, the authors suppose that for electromechanical and power ACS it would be more effective to widely use the absolute stability criterions or hyperstability which were developed when solving the “Aizerman problem” by V.M. Popov in the 1960s of the 20th century. This solution is not used as widely as the Nyquist criterion despite its outstanding qualities. In this article, the assumption was made that it is effective to apply the stability criterion of nonlinear ACS for the linearized models of nonlinear systems. Otherwise speaking, it is effective to use the criterion of V.M. Popov and its interpretation according to the logarithmic frequency characteristics of the ACS proposed earlier by the authors of the article. The authors provide simple and illustrative examples and give the results of the simulation.

Study on Seismic Attenuation Based on Wave-Induced Pore Fluid Dissolution and Its Application

Seismic wave attenuation is affected by wave-induced pore fluid dissolution. The mechanism of wave-induced pore fluid dissolution is the mutual dissolution between different fluids caused by pore fluid pressure. Compared with the traditional WIFF (wave-induced fluid flow) mechanism, the wave-induced pore fluid dissolution mechanism can predict the attenuation of the seismic frequency band and can be used in well-to-seismic calibration. Conventional methods neglect the velocity dispersion caused by the interaction between pore fluids, which will lead to errors in attenuation prediction. In this paper, we focus on accurately predicting the velocity dispersion at low porosity and permeability, which can be used in multi-scale data matching. The stretch between the synthetic data by using logging data and seismic data needs to be calibrated for more accurate interpretation. The kernel of well-to-seismic calibration is the knowledge of the velocity dispersion between the logging frequency band and seismic frequency band. We calibrate the difference between the two kinds of data by using the rock physical model. Both the model test and field data application prove the feasibility and accuracy of the proposed strategy.

Borehole radiation and reception responses for azimuthal shear-wave reflection imaging with an off-centred dipole acoustic tool

Abstract Radiation and reception responses of a dipole acoustic logging tool placed eccentrically in borehole fluid are an interesting and important topic in acoustic reflection imaging. Herein, we present a thorough research study on these responses. We treat the wave incidence from the reflector as the radiation from a virtual source and use the cylindrical-wave expansion method to solve both the wave radiation and reception problems for the off-centred tool, which, by using the steepest-descent method, yields asymptotic solutions for modelling the radiation and reception wavefield characteristics. The modelling results from the analytical solution and the 3D finite-difference method were in good agreement. Specifically, we analysed the radiation directivity of an eccentric dipole source in a fluid-filled borehole. The results revealed that the radiation pattern was asymmetric with respect to the borehole, and the asymmetry was determined by the eccentric distance, source frequency and formation properties. In particular, for the typical 3 kHz dipole logging frequency, the radiation was stronger in the off-centred direction than in the opposite direction. The asymmetry of the eccentric radiation resulted in a significant amplitude difference relative to its centred counterpart, which provided a potential method for addressing the 180° azimuth ambiguity of the dipole source. We used a theoretical waveform modelling example to demonstrate this advantage. Therefore, the results of this study provide a theoretical foundation for the development and application of dipole shear-wave imaging technology.

Crest Factor Optimization for Multisine Excitation Signals with Logarithmic Frequency Distribution Based on a Hybrid Stochastic-Deterministic Optimization Algorithm

For diagnosis of batteries and fuel cells based on impedance spectroscopy, excitation signals are required, including low frequencies down to the mHz range. This leads to a long measurement time and compromises the stability condition for impedance spectroscopy. Multisine excitation signals with logarithmic frequency distribution can significantly reduce the measurement time but need optimization of the crest factor to realize a high signal-to-noise ratio at all excitation frequencies and maintain at the same time the linearity and stability conditions of impedance spectroscopy. Crest factor optimization is challenging, as the obtained results strongly depend on the initial phase values and many trials are necessary. It takes a very long time and can not be easily performed automatically up to now. In this paper, we propose a time-efficient hybrid stochastic-deterministic crest factor optimization method for multisine signals with logarithmic frequency distribution. A sigmoid transform on the multisine signal gradually transforms the multi-frequency signal into a binary-alike signal. The crest factor is significantly decreased, but the phases of the singular frequency signals remain sub-optimal. Further optimization based on the Gauss-Newton algorithm can determine the final phases, realizing a lower crest factor. The proposed method is less sensitive to initial phase values and provides more reasonable results in a reasonable time. The validation on a Samsung INR-18650-25R Lithium-ion battery cell shows that the crest factor of the optimized multisine signals has a median of 3.62 ± 0.7 within 6 min of run time, which is significantly better than the best previous work in the state-of-the-art of 3.85 ± 0.11 for the same run time.

Association of Autonomic Activation with traumatic reminder challenges in posttraumatic stress disorder: A co-twin control study.

Post-traumatic stress disorder (PTSD) has been associated with cardiovascular disease (CVD), but the mechanisms remain unclear. Autonomic dysfunction, associated with higher CVD risk, may be triggered by acute PTSD symptoms. We hypothesized that a laboratory-based trauma reminder challenge, which induces acute PTSD symptoms, provokes autonomic dysfunction in a cohort of veteran twins. We investigated PTSD-associated real-time physiologic changes with a simulation of traumatic experiences in which the twins listened to audio recordings of a one-minute neutral script followed by a one-minute trauma script. We examined two heart rate variability metrics: deceleration capacity (DC) and logarithmic low frequency (log-LF) power from beat-to-beat intervals extracted from ambulatory electrocardiograms. We assessed longitudinal PTSD status with a structured clinical interview and the severity with the PTSD Symptoms Scale. We used linear mixed-effects models to examine twin dyads and account for cardiovascular and behavioral risk factors. We examined 238 male Veteran twins (age 68 ± 3 years old, 4% black). PTSD status and acute PTSD symptom severity were not associated with DC or log-LF measured during the neutral session, but were significantly associated with lower DC and log-LF during the traumatic script listening session. Long-standing PTSD was associated with a 0.38 (95% confidence interval, -0.83,-0.08) and 0.79 (-1.30,-0.29) standardized unit lower DC and log-LF, respectively, compared to no history of PTSD. Traumatic reminders in patients with PTSD lead to real-time autonomic dysregulation and suggest a potential causal mechanism for increased CVD risk, based on the well-known relationships between autonomic dysfunction and CVD mortality.

Rock Physics Modeling of Acoustic Properties in Gas Hydrate-Bearing Sediment

Gas hydrates (GH) are well known to have an influential effect on the velocity and attenuation of gas hydrate-bearing sediments (GHBS). Based on rock physics modeling, sediment velocity has been extensively used to characterize the distribution of gas hydrate. However, the results obtained from different models show a significant variation. In this study, we firstly review and compare the existing rock physics modeling for velocity and attenuation. The assumption, characteristics, theoretical basis, and workflow of the modeling are briefly introduced. The feasibility and limitations of the published models are then discussed and compared. This study provides insight into how to select a suitable rock physics model and how to conduct modeling in the application of the rock physics model to field data. Then, we introduce how to predict hydrate saturation, hydrate morphology, the dip angle of fracture, sediment permeability, and attenuation mechanisms from the comparison between the modeled and measured acoustic properties. The most important application of rock physics modeling is predicting the hydrate saturation and we discuss the uncertainties of the predicted saturation caused by the errors related to the velocity measurements or rock physics modeling. Finally, we discuss the current challenges in rock physics modeling related to optimizing the input parameters, choice of a suitable model, and upscaling problems from ultrasonic to seismic and well log frequencies.

Investigation of ACS image stabilization of on-board optoelectronic guidance and tracking devices

Introduction. The movement of the carrier and external factors (the effects of the atmosphere, temperature and pressure) degrade significantly the image quality of the servo optoelectronic systems (OES) and the positioning accuracy of the emitting OES. The issues of image quality improvement and the probability of keeping the image of the observation object (OO) on the optical axis of the servo EOS are considered.Materials and Methods. The development of an automatic control system for an optoelectronic device (ACS OED) involved solving a multi-criteria optimization problem taking into account a number of conflicting technical-andeconomic (TE) requirements. The determination of tolerated dynamic errors (TDE) of image stabilization was a key issue in the development of on-board optoelectronic devices (OOED). Lagrange equations of the second kind and the mixed Gilbert method made it possible to obtain a mathematical model of the CO OED. Then, the decomposition of a two-link ACS with nonlinear cross-couplings in the CO was performed. A functional diagram of the image formation model of the OOED was presented. The parameters of the matrix photodetector and the requirements for the dynamic error of the ACS OED, taking into account the permissible MTF of the OED, were listed. The functions of transferring modulation, as well as linear, harmonic and vibrational shift of the image corresponding to the permissible and achieved TDE were visualized. Logarithmic frequency characteristics were created in the Mathcad environment. The two-link control system of the OED with the specified parameters of the CO for the considered movement was presented as two independent azimuth and elevation control channels.Results. The processes of control of the on-board optoelectronic system in the stabilization and tracking modes were described. To study the dynamics of spatial control of the OOEP in accordance with the ACS methodology, a computer simulation model (CSM) of the digital automatic control systems (DACS) of the OED was developed. It was implemented in the Matlab environment and consisted of CSM CO, drives, proportional-integral-derivative (PID) controllers taking into account non-linearities, a central computing device (CCD), a guidance software device, a CSMcarrier that implemented the equations of motion. Harmonic vibrations of the carrier were described. The errors of tracking and stabilization in the tracking mode with an additional control action introduced in the form of a constant speed were determined. The dynamics of spatial control of the OOED was investigated. A computer simulation model of a digital automatic control system of an optoelectronic device, the results of modeling the DACS OED without considering the board movement, and the processes of OED control subject to movement were visualized.Discussion and Conclusions. The stabilization accuracy was calculated for the studied cases. It was established that the stabilization tens of times exceeded the previously stated indicators, and it tens of times reduced the requirements for the convergence of the laser beam and the laser radiation power when developing the optical path of the product in question. The proposed CSM can be used in the development of the on-board optoelectronic systems. In this case, the application of the presented methodology and CSM will help to reduce labor costs and minimize errors.

Semantic Pattern Detection in Covid-19 using Contextual Clustering and Intelligent Topic Modeling

The Covid-19 pandemic is the deadliest outbreak in our living memory. So, it is need of hour, to prepare the world with strategies to prevent and control the impact of the epidemics. In this paper, a novel semantic pattern detection approach in the Covid-19 literature using contextual clustering and intelligent topic modeling is presented. For contextual clustering, three level weights at term level, document level, and corpus level are used with latent semantic analysis. For intelligent topic modeling, semantic collocations using pointwise mutual information(PMI) and log frequency biased mutual dependency(LBMD) are selected and latent dirichlet allocation is applied. Contextual clustering with latent semantic analysis presents semantic spaces with high correlation in terms at corpus level. Through intelligent topic modeling, topics are improved in the form of lower perplexity and highly coherent. This research helps in finding the knowledge gap in the area of Covid-19 research and offered direction for future research.

A Real-Time Implementation of Air Audit System for Compressors towards Energy Conservation: An Industrial Case Study

The air audit system is designed for enabling sales engineers to capture customer’s requirement of the compressed air system. This system is required to create quick audit solution to support customers by estimating air consumption. It also educates the customers with potential improvement areas after understanding their existing demand pattern. At present, many industries and manufacturers are using third-party air audit tools. Many leading manufacturers of air compressors in accordance with the core values of the company intend to develop their own air audit system. The problem statement is to understand the air demand pattern with respect to flow and pressure, capture the existing power consumption details, and select the optimum compressor size based on the demand pattern. The air audit methodology involves data logging process, data transfer, and report generation. The data logging process includes measuring current, voltage, and true power of each compressor, tank pressure with logging frequency of minimum 5s, and data logging period of minimum seven days. The data will be transmitted to a mobile or tab over WiFi. A mobile GUI (graphical user interface) will be developed to generate the report and graph. All received data will be stored in a cloud database. The paper presents a proof of concept for the air audit system by tapping signals from the existing power quality analyzer, feeding it to a microcontroller, processing it, performing data logging, transferring the bulk data through WiFi upon request to the company or consumer, graphically presenting the data through a mobile app, and report generation. This work can also be extended by developing a battery-operated standalone module for air auditing which will be provided for the sales engineer and the customers. The overall need for the study is to conduct air audit in an industry indigenously without involving the third party. With aid of advanced tools and applications as described in the paper, the proposed system will certainly help the industries to understand the need and nuances of air audit system for compressors.

Understanding occupants’ behaviour, engagement, emotion, and comfort indoors with heterogeneous sensors and wearables

We conducted a field study at a K-12 private school in the suburbs of Melbourne, Australia. The data capture contained two elements: First, a 5-month longitudinal field study In-Gauge using two outdoor weather stations, as well as indoor weather stations in 17 classrooms and temperature sensors on the vents of occupant-controlled room air-conditioners; these were collated into individual datasets for each classroom at a 5-minute logging frequency, including additional data on occupant presence. The dataset was used to derive predictive models of how occupants operate room air-conditioning units. Second, we tracked 23 students and 6 teachers in a 4-week cross-sectional study En-Gage, using wearable sensors to log physiological data, as well as daily surveys to query the occupants’ thermal comfort, learning engagement, emotions and seating behaviours. Overall, the combined dataset could be used to analyse the relationships between indoor/outdoor climates and students’ behaviours/mental states on campus, which provide opportunities for the future design of intelligent feedback systems to benefit both students and staff.

Dilute carbon in H3S under pressure

Recently, room temperature superconductivity was measured in a carbonaceous sulfur hydride material whose identity remains unknown. Herein, first-principles calculations are performed to provide a chemical basis for structural candidates derived by doping H3S with low levels of carbon. Pressure stabilizes unusual bonding configurations about the carbon atoms, which can be six-fold coordinated as CH6 entities within the cubic H3S framework, or four-fold coordinated as methane intercalated into the H-S lattice, with or without an additional hydrogen in the framework. The doping breaks degenerate bands, lowering the density of states at the Fermi level (NF), and localizing electrons in C-H bonds. Low levels of CH4 doping do not increase NF to values as high as those calculated for Imbar{3}m-H3S, but they can yield a larger logarithmic average phonon frequency, and an electron–phonon coupling parameter comparable to that of R3m-H3S. The implications of carbon doping on the superconducting properties are discussed.

I CrossFit; Do You? Cross-Sectional Peer Similarity of Physical Activity Behavior in a Group High Intensity Functional Training Setting.

Physical activity (PA) is essential for physical, mental, and emotional health; however, few adults engage in enough PA. Group exercise environments such as CrossFit can promote sustained exercise habits through social influence, support, and norms. This cross-sectional study aims to provide evidence for PA social influence at CrossFit. CrossFit members (n = 62) reported PA, workout logging frequency, and members at their gym they: (1) work out with and (2) go to with personal matters. Separate linear network autocorrelation models (LNAMs) determined if individuals reported similar PA scores as those of their social ties at CrossFit that they work out with and/or those they go to for personal matters. Participants reported a mean of 2740.55 MET minutes/week (SD = 1847.08), working out with a mean of 9.89 members (SD = 6.26), and speaking to a mean of 2.66 members about personal matters (SD = 3.68). A person’s PA was significantly associated with that of their ties they go to with personal matters (PEp = 0.08, SEp = 0.02), but was not associated with the PA of their ties they work out with (PEw = 0.02, SEw = 0.01). Social influence on PA levels was present when a deeper connection is made between members. Fostering and promoting deeper connections between members may help promote PA and continued exercise habits.