Bottom Half Research Articles

Earnings Shocks and Stabilization During COVID-19

<ns3:p>This paper documents the magnitude and distribution of U.S. earnings changes during the COVID-19 pandemic and how fiscal relief offset lost earnings. We build panels from administrative tax data to measure annual earnings changes. The frequency of earnings declines during the pandemic were similar to the Great Recession, but the distribution was very different. In 2020, workers starting in the bottom half of the distribution were more likely to experience large annual earnings declines and a similar share of male and female workers had large earnings declines. While most workers experiencing large annual earnings declines do not receive unemployment insurance, over half of beneficiaries were made whole in 2020, as unemployment insurance replaced a median of 103 percent of their annual earnings declines. After incorporating unemployment insurance, the likelihood of large earnings declines among low-earning workers was not only smaller than during the Great Recession, but also smaller than in 2019.</ns3:p>

Residual stress distribution in thick double-V butt welds with varying groove configuration, restraints and mechanical tensioning

This paper aims to investigate the effect of different weld groove configurations on the residual stresses dispersed in 40 mm thick multipass high strength low alloy (HSLA) steel butt-welds. Two welded joints having double-V type groove geometry were prepared, one of which had an equal double-V groove, and the other had an unequal double-V groove appearance. The locked-in residual stresses present in the weld zone and heat-affected zone (HAZ) were evaluated using both computational and experimental approaches. Furthermore, the effect of restrained condition on the trend of residual stresses of the equal double-V groove weld was analyzed using computational modeling technique with varying weld pass sequence. Lastly, a feasibility study was conducted on the implementation of mechanical tensioning technique to mitigate the weld-induced residual stresses in thick multipass butt-welded joints. The findings show that using an unequal-V groove joint can effectively reduce residual stress levels in the bottom half of the weld. A restrained welding condition with a single directional weld pass sequence can adversely impact the intensity of residual stresses across the weldment. The transverse residual stress levels can be reduced in the weld zone and its vicinity by an amount equal to the corresponding applied mechanical lateral tensioning load.

Sedimentation effects on particle position and inertial deposition in 90° circular bends

Laminar fluid-particle flows in bend geometries are present in many industrial, pharmaceutical, and biomedical applications. Particle deposition has been studied extensively; however, little attention has been paid to the effect of particle sedimentation on particle position and deposition in different pipe geometry combinations. This study presented a comprehensive analysis of sedimentation effects on particle flow behaviour in 90° circular pipe bends of micron particles in laminar pipe flows. Pipe geometry combinations consisted of eight pipe diameters, nine bend radii, and 30 particle diameters in a range of 1 to 100 μm. The results demonstrated the locations of particles that sedimented to the bottom half of the straight pipe section, and the particle positions upstream from the pipe bend entrance, which was no longer in a fully developed profile. These new locations represent the effects of gravity, pulling the particles down. While obtaining these positions can be found through CFD analysis, we proposed an analytical solution to predict the particle trajectory from different release locations that would help to identify the initial particle distribution at locations upstream to the bend, to obviate the need for long upstream straight pipe sections in the CFD analysis.

Characteristics of natural convection in n-eicosane in a square cavity with discrete heat source

The natural convection of phase change material (PCM) in a two-dimensional square cavity is numerically analyzed. The cavity consists of heat surface with a constant total heated area and adiabatic wall. The Grashof and Prandtl numbers for the PCM (n-eicosane with the melting temperature, Tmelt=36°C) in basic LHS system are 9 × 10^5 and 62.7, respectively, at 350.15K. The mass, momentum and energy balance equations of the system were considered. Three basic heating surface strategies were considered (discrete heat sources): single, side-side and side-bottom heating surface. The results show that the transient Nusselt number, mean kinetic energy at the surface and energy storage rate of the fluid are effectively enhanced by proper arrangement of the discrete heat source location and heating from the bottom half of the left and right sides requires the least time for 300 kJ energy storage. The results indicate that optimally placed discrete heat sources in PCM could be a promising alternative for high-efficient thermal energy storage.

Holistic face processing is influenced by non-conscious visual information.

Holistic face processing has been widely implicated in conscious face perception. Yet, little is known about whether holistic face processing occurs when faces are processed unconsciously. The present study used the composite face task and continuous flash suppression (CFS) to inspect whether the processing of target facial information (the top half of a face) is influenced by irrelevant information (the bottom half) that is presented unconsciously. Results of multiple experiments showed that the composite effect was observed in both monocular and CFS conditions, providing the first evidence that the processing of top facial halves is influenced by the aligned bottom halves no matter whether they are presented consciously or unconsciously. However, much of the composite effect for faces without masking was disrupted when bottom facial parts were rendered with CFS. These results suggest that holistic face processing can occur unconsciously, but also highlight the significance of holistic processing of consciously presented faces.

Comprehensive Modified Latarjet Technique: What the Masters Taught Us.

The Latarjet technique can be performed via a cosmetic axillary-based approach. The subscapularis is split horizontally without detachment as described by Neer5. The capsule is released like in a medially based T-plasty as described by Altchek et al.6. The coracoid osteotomy is performed with a 90° oscillating saw and prepared for en-face implantation as described by Edwards and Walch7. The inferior surface of the coracoid is decorticated and prepared per Molé8. Coracoid fixation is performed with two 3.5-mm cortical screws. The soft-tissue reconstruction is selectively tensioned per Warner et al.9. The capsular shift is augmented with a pants-over-vest repair per Kim et al.10. Nonoperative treatment in young patients with glenohumeral instability and bone loss can lead to recurrence rates as high as 87%11. Arthroscopic management with anterior capsulolabral repair and a remplissage procedure can be beneficial for patients with instability. In the setting of bone loss, arthroscopic repair is associated with failure rates as high as 75%12. In the setting of glenoid and/or humeral bone loss, there is a loss of native osseous anatomy, leading to a higher risk of instability. Gerber and Nyffeler reported a >30% loss of compressive force when the vertical edge of the glenoid defect is greater than one-half of the glenoid diameter13. The Latarjet procedure is a reliable procedure that reconstructs the anterior osseous anatomy as well as the capsular laxity, restoring glenohumeral stability. When compared with arthroscopic labral repair, the Latarjet procedure is superior with more consistent improvements in functional outcomes with low risk of recurrence, even in high-risk populations of young, active athletes in contact sports2,3. At our institution, a total of 34 patients underwent Latarjet reconstruction as described in the present article and videos from 2013 to 2018, with a minimum follow-up of 1 year. Among these patients, the mean Single Assessment Numeric Evaluation score was 90.7 (range, 70 to 100). There were 4 cases of recurrent instability with graft fracture or resorption (11.8%). Zimmermann et al. presented a series of Latarjet reconstructions with similar functional outcomes and a recurrence rate of 11%4. Meta-analysis of long-term Latarjet studies show high rates of return to sports and successful outcomes in 86% of cases, with an 8.5% recurrence rate2. The Latarjet procedure can be consistently performed with a subscapularis-sparing approach, which minimizes adverse comorbidities.Splitting the subscapularis at the inferior one-third junction will position the surgical window directly over the bottom half of the glenoid, which optimizes coracoid implantation.A medially based T-plasty will maximize the glenoid exposure for direct coracoid implantation. Subsequently, the capsule may be shifted for capsular imbrication.Low-profile, non-bulky retractors will help to improve visualization.Adjusting the arm is a key technique in performing this surgical procedure. This adjustment will help to shift the surgical window, expose key anatomic structures, and allow a capsular shift without overtensioning. This cannot be overstated.

Interview-Rated Meaning and Survival Over 17 Years in People Living With HIV.

The primary purpose of this study was to determine whether meaning in life predicts survival in people living with HIV (PLWH) over 17 years. This study also examined whether interviewer- and transcript-rated meanings predict survival equivalently. A third purpose of the study was to investigate whether meaning in life adds to the prediction of survival over positive emotional expression. A diverse sample of people with HIV (n = 177) completed an interview on stress and coping at baseline and were followed up for survival up to 17 years. Meaning was measured by interviewer rating of four items (meaningful purpose, unfinished business, finding new meaning, and meaningful activities). Transcript-rated meaning was assessed by two independent raters. Cox proportional hazards regression was used to determine whether meaning predicted survival over 17 years. Meaning in life predicted significantly greater survival, adjusting for biomedical and sociodemographic variables whether assessed by interviewer or by transcript raters. Hazard ratios suggest that the effect is moderate to large (2.66-3.45 for top versus bottom third; 2.05-2.49 for top versus bottom half). Significance was maintained after adjusting for positive emotion. Meaning assessed by interview (by both interviewer and transcript ratings) predicted greater survival over 17 years in PLWH and did so above positive emotion. This adds to a literature that is primarily based on self-report questionnaires. Meaning may have beneficial effects for both psychological and physical health in PLWH.

Insight into the Effect of the Continuous Testing and Aging on the so2 Sensing Characteristics of a YSZ (Yttria-stabilized Zirconia)-Based Sensor Utilizing ZnGa2O4 and Pt Electrodes

IntroductionSO2 concentration detection in harsh environment is still a challenge because the present technology is based on large-scale instrument, which is expensive and can’t monitor in real time. Recently, gas sensor with low cost and the ability of in-situ measurement has been used to SO2 detection. Due to high sensing performance, reliable stability and acceptable humidity resistance, the mixed potential sensor based on YSZ was expected to achieve the real-time detection in harsh environment [1]. Method Fabrication and measurement of the gas sensor The sensor was fabricated utilizing 8mol% Y2O3-doped YSZ plate (2 mm×2 mm square, 0.3 mm thick, provided by Anpeisheng Corp. China). A point-shaped and a narrow stripe-shaped Pt electrode (PE) were formed on two ends of the YSZ plate using a commercial Pt paste (Sino-platinum Metals Co. Ltd.), and sintered at 950°C. The paste which was mixed by a minimum quantity of deionized water and the sensing materials ZnGa2O4. Next, the resultant paste was applied on the point-shade Pt to form stripe-shaped ZnGa2O4 electrode (ZE). Afterward, the device was annealed at 800°C to make a good contact between the sensing electrode and electrolyte. A Pt heater and a linear DC Power Supply were used to provide required heat to regulate the operating temperature of the sensor. Sulfuration process In order to further investigate the sensing mechanism of the sensor, we added a sulfuration experiment. The sulfuation process is as following: The sensor was put into a 1L chamber with a mixture of air and 100 ppm SO2 for 24 hrs, the temperature of the sensor maintain at 650°C during this process. When time is up, put the sensor into a 1L chamber with fresh air and begin to measure the sensing performance of the sensor after sulfuration. Results and Conclusions YSZ-based mixed potential sensor with ZnGa2O4 and Pt electrodes (ZE and PE) was developed for the SO2 detection. The effects of long-term aging and continuous test on various properties of the electrode materials had been investigated and characterized. Some interesting phenomenon were found that when the sensor exposed to the relative high concentration SO2 with air, the response direction was opposite to that exposing to low concentration SO2 as shown in Fig. 1. Moreover, with the last of the testing time, the responses of the sensor to all concentration SO2 were opposite to that in the original state. Hence, giving a reasonable explanation is one of the most important purposes in this paper. We have proved that the PtS was produced during the testing and aging process. According to the Y. shimizu’s work [2], most of metal mono-sulfides performed a high electrochemical catalytic activity to SO2. Hence, we speculated that the mono-sulfides PtS also has a high electrochemical catalytic activity to SO2. In this case, when measuring lower concentration SO2, the diffusion rate is a slow value. Due to the Pt’s high catalytic activity to SO2, SO2 react with Pt electrode and changed to PtS, which adhere to the Pt electrode surface. The process was clearly exhibited in the bottom half of Fig. 1. This process sharply decreased the SO2 concentration reaching TPB of PE, and then caused the ΔVPE approaching 0. On the other hand, ZnGa2O4 electrode had a response to SO2 and according to the mixed potential mechanism, the ΔVZE should be a negative value. However when measuring higher SO2 concentration, Pt has changed to PtS, which decreased the contact area, and then decreased the catalytic activity to SO2. Because of the much higher electrochemical catalytic activity of PtS at PE to SO2 than that of ZnGa2O4, the response at PE was much higher than that at ZE. Hence, the reversed response characteristics occurred as shown in the second response and recovery transient of Fig. 1. Furthermore, with continuous testing and aging, more and more sulfur element was deposited to the Pt electrode and the critical concentration deceased, finally, all of the ΔV were changed to the positive values as shown in the third of Fig. 1. Moreover, the sensor after sulfuration process (the detail of the sulfuration process was given in the last part) also performed similar sensing properties to the sensor with continuous testing and aging process, which indicated that the produced PtS should be the reason for that the sensor performed reversed sensing performances. In addition, the sensor after sulfuration can detect 0.05-500 ppm SO2 with the sensitivity being 5 mV/decade to 0.05-1 ppm and 41 mV/decade to 1-500 ppm. The sensor also had a reliable stability during the continuous measurement.

Investigation on wall thickness reduction of hydropower pipeline underwent to erosion-corrosion process

The present investigation was carried out to study the erosion-corrosion analysis in the hydropower pipeline of a Francis turbine. Testing was performed on a mild steel pipe having a diameter of 6 in.. An extensive set of experiments was carried out to test the properties of the erodent and the worn-out pipeline. Experiments were carried out using the sand-water suspension of concentration, ranging from 5000 to 20,000 ppm. The physical properties such as size and morphology of the sand particles as well as settling concentration of sand-water suspension were examined by the various bench-scale tests. The SEM-EDS techniques were used to study the morphological and chemical composition of the pipeline. Visual inspections depicted that the major deterioration occurred at the bottom half of the pipeline. Also, the lower surface of the pipeline seems underwent to high erosion and corrosion as compared to the upper surface of the pipeline. Results show that the erosion-corrosion process causes the wall thickness reduction of the horizontal pipeline. However, the properties of sand namely size, shape and static settled concentration of particles play a key role in the erosion wear of the pipeline. The solid particles of the sand eroded the pipeline material, which results in pits, craters, and cutting wear mechanisms on the pipeline surface. It can be said that the use of pipelines having an uneven hardness and lack of established inspection norms results in unexpected failures.

Role of buoyancy on the thermalhydraulic behavior of supercritical carbon dioxide flow through horizontal heated minichannel

With the growing demand of higher power density, at the expense of lesser environmental encroachment, use of supercritical carbon dioxide in miniature systems is becoming increasingly lucrative. However, concerned literature, particularly for horizontal geometry under heating condition, is relatively thin. Presently work, therefore, focuses on the numerical characterization of thermalhydraulics of supercritical carbon dioxide flowing through horizontal circular channel having diameter of 2 mm, with specific emphasis on the effect of local buoyancy. Three-dimensional turbulent simulations are performed over reasonably wide range of system pressure, heat flux and mass flux. Buoyancy-induced local recirculation, originating from density stratification, is found to have substantial influence on both azimuthal and axial profiles. Average heat transfer coefficient over the bottom half surface is noticeably higher than the same over top half surface because of thermal asymmetry, allowing delayed heat transfer deterioration there. Such disparity is amplified at higher heat fluxes, but reduces with increased pressure. The maxima in average heat transfer coefficient corresponds to the pseudocritical temperature. Larger mass flux augments heat transfer, with the peak moving downstream. Finally a buoyancy parameter is defined following literature on macrochannel, which is able characterize the loop performance satisfactorily.

Law firms’ preferences and willingness to pay for attributes of law school graduates: results from a choice experiment

ABSTRACT Preferences and willingness-to-pay for attributes of law school graduates are examined using a choice experiment. Results suggest preferences for candidates who graduate near the top of their class or from top ranked schools and an aversion to candidates from lower ranked schools and those graduating in the bottom half of their class. Despite the potential for significant economic gains from attending a top ranked school and graduating in the top of the class, students should consider the tradeoffs that hiring firms are willing to make between candidate attributes. Higher class rank can moderate the salary premium associated with university prestige.

Genes, Ideology, and Sophistication

AbstractTwin studies function as natural experiments that reveal political ideology’s substantial genetic roots, but how does that comport with research showing a largely nonideological public? This study integrates two important literatures and tests whether political sophistication – itself heritable – provides an “enriched environment” for genetic predispositions to actualize in political attitudes. Estimates from the Minnesota Twin Study show that sociopolitical conservatism is extraordinarily heritable (74%) for the most informed fifth of the public – much more so than population-level results (57%) – but with much lower heritability (29%) for the public’s bottom half. This heterogeneity is clearest in the Wilson–Patterson (W-P) index, with similar patterns for individual index items, an ideological constraint measure, and ideological identification. The results resolve tensions between two key fields by showing that political knowledge facilitates the expression of genetic predispositions in mass politics.

Can Low Retirement Savings Be Rationalized?

Simple presentations of the life cycle model often suggest a constant level of real consumption in retirement. Similarly, financial planners commonly suggest that people save for retirement in such a way as to enable them to maintain a level retirement standard of living equal to their standard of living while working. However, constant consumption with age is only optimal under the precise and unlikely condition that the subjective rate of time preference is equal to the real interest rate. Most people exhibit a positive rate of pure time preference, and additionally discount the future by both mortality and morbidity risks. In comparison, the real interest rate is roughly 0%—and the term structure of interest rates suggests this condition is likely to persist. These considerations suggest that optimal consumption in the life cycle model declines with age. This finding has major implications for optimal retirement saving. For instance, we find that for many, perhaps most, people in the bottom half of the lifetime earnings distribution, it is optimal to spend out their retirement wealth well before death and to live on Social Security alone after that. Very low earners may find it optimal to not engage in retirement saving at all. <b>TOPICS:</b>Long-term/retirement investing, portfolio theory <b>Key Findings</b> ▪ Under plausible assumptions, optimal consumption in the life cycle model declines with age. ▪ For many people in the bottom half of the lifetime earnings distribution, it is optimal to spend out retirement wealth well before death and live on Social Security alone after that. ▪ These results stand in contrast to standard financial planning advice that people save for retirement in such a way as to enable them to maintain a level retirement standard of living equal to their standard of living while working.

An alternative approach to estimation of the energy efficiency gap in food processing

This paper proposes an alternative approach to the estimation of the “practical” energy efficiency gap, using the US food processing industry as an empirical example. Starting with stochastic frontier energy demand functions estimates based on non-public, plant level data from the U.S. Census Bureau, the approach controls for plant level inputs and output, energy prices, and other observables including 6-digit NAICS industry designations. This approach generates an estimate of the cumulative distribution of energy efficiency across all plants in the industry. While the estimates of the distributions are sensitive to the methods, the analysis consistently shows that few plants come close to 100% efficiency. Defining a “practical level of energy efficiency” using the 95th percentile of the estimated efficiency distributions, instead of assuming 100% efficiency, results in an ~ 20% estimate of the efficiency gap. Most of the reductions in energy use from closing this practical efficiency gap are from plants that are “low hanging fruit,” i.e., plants in the bottom half of the efficiency distribution. Two-thirds of the estimated 20% practical efficiency gap can be achieved by bringing the lower half of the efficiency distribution up to just the median level of observed performance. New plants do exhibit higher energy efficiency than existing plants which is statistically significant, but the difference is small for most of the industries, ranging from a low of 0.4% to a high of 5.7%.

Influence of electrolytic and crevice corrosion on mechanical resistance of porcelain insulators

Porcelain insulators are widely used in transmission lines; however, their durability and considerable overall maintenance cost have become problems over the years. In this work, porcelain insulators were collected from various locations in South Korea and classified according to their length of service. Mechanical and electrical load tests were performed, and the failure load and damaged region were recorded for each specimen. The fast degradation of the pin in porcelain insulators exceeding 50 years in operation was notable because there was no pin breakage among the samples in service for less than 50 years. Moreover, the failure of 73.68% of all porcelain insulators in service for 54 years occurred in the pin. The average failure load of these samples was 14% lower than that of samples in use for 45 years. To confirm the pin’s deterioration mechanism over time, a mechanical analysis of the reduction in the pin cross-section was performed using the finite element analysis method. Applied loads of 45, 75, and 95 kN resulted in stresses of 170, 285, and 350 MPa, respectively, in the bottom half part of the pin exposed to air. To calculate the stresses due to corrosion, the model was redrawn considering diameter reductions of 0.6, 1.2, 1.8, and 2.4 mm. The stress fields were found to considerably affect the corroded zone even in the case of the sample with a 0.6-mm reduction in diameter. Accordingly, a novel degradation mechanism is proposed in this study. Previous studies that focused on the critical areas of the porcelain insulator found that the exposed pin side was easily damaged by the external load. The current findings revealing an unfamiliar porcelain deterioration mechanism may aid in the formulation of a better design to mitigate the problems described above.

Differences in decompression of a high-pressure unit: A case study from the Cycladic Blueschist Unit on Naxos Island, Greece

Determining the tectonic evolution and thermal structure of a tectonic unit that experiences a subduction-related pressure temperature (P-T) loop is challenging. Within a single unit, P-T conditions can vary from top to bottom which can only be revealed by detailed petrological work. We present micropetrological data from the middle section of the Cycladic Blueschist Unit (CBU) in Naxos, Greece, which indicates a different P-T loop than that for the top of the sequence. Using Zr-in-rutile and Ti-in-biotite thermometry coupled with quartz-in-garnet elastic barometry and phase equilibrium thermodynamic modeling, we identify a prograde path from 15.4 ± 0.8 kbar to 19.9 ± 0.6 kbar and from 496 ± 16 °C to 572 ± 7 °C (2σ uncertainty), equilibration during decompression at 8.3 ± 1.5 kbar and 519 ± 12 °C followed by near-isobaric heating to 9.2 ± 0.8 kbar and 550 ± 10 °C (or even 584 ± 19 °C), and a final greenschist-facies equilibration stage at 3.8 ± 0.3 kbar and 520 ± 4 °C. We compare these P-T estimates with published data from the top and also the bottom of the CBU section and find that the bottom half of the CBU on Naxos records higher peak high-pressure (HP) of about 4 kbar than the top of the unit, defining the thickness of the CBU section on Naxos to about 15 km in the Eocene. We determine that crustal thickening of up to ~15% occurs in the upper half of the CBU section during exhumation of the HP rocks in an extrusion wedge in a convergence setting. At about 30 Ma, the bottom half of the CBU was finally thrust onto the radiogenic Cycladic basement. Subsequently this bottom half of the CBU section underwent isobaric heating of 9–96 °C between c. 32–28 and 23–21 Ma. Isobaric heating occurred below the upper CBU section that thickened during decompression and commenced when HP metamorphism in the Cyclades ended. This suggests that thermal relaxation following tectonic accretion in the Cyclades controlled heating of the evolving Cycladic orogen during a tectonically quiescent period before lithospheric extension commenced by 23–20.5 Ma.

Origins of ‘the gap’: perspectives on the historical demography of aboriginal victorians

Australia enjoys ninth place out of 190 countries on the United Nations Life Expectancy Index. Aboriginal Australians—as a fourth-world people within a first-world society—rank in the bottom half of the Index, just below Guatemala and Bangladesh. Progress on closing ‘the gap’ in health and wellbeing has been slow, despite initial rapid gains in infant mortality. The barriers are inter-generational trauma, inherited disadvantage, poverty and systemic racism. This paper reports on the Koori Health Research Database, a cradle-to-grave dataset of Aboriginal Victorians from the 1840s. It finds that population recovery after the nadir reached at the end of the nineteenth century, was hindered by high acquired secondary infertility among women vulnerable to sexual abuse, violence and sexually transmitted infections. Improvements in survival and the health transition were ‘blocked’ by barriers to land acquisition and full citizenship, as has happened in New Zealand. The dramatic recovery of the population of people now identifying as Aboriginal in Victoria has come from out-marriage.

New Methodological Approach for Performance Assessment in the Bioenergy Field

Bioenergy, along with other renewables, has always played its part in the world’s energy transition. Tracking the progress to meet specific goals has long been tackled and led to performance evaluation in the field. The present study aims to contribute to this area with a performance assessment framework in the bioenergy field. It comprises 16 European countries and 30 indicators assigned to three dimensions: innovation, efficiency, and sustainability and it follows a well-established methodology. For enabling country-to-country comparison, five maps are designed for better illustration. The country performance ranking is one of the main outputs of the analysis, revealing the outperformers and the weakest countries from its bottom half, as well as the particularities of countries scoring on each of the three dimensions. The policy recommendations and study limitations represent the most relevant part of the conclusions.

An Empirical Analysis of COVID-19 Response: Comparison of US with the G7

We compare US policy response to COVID-19 with its G7 counterparts between March and September 2020. The G7 countries, while economically and ideologically aligned, have instituted vastly different policies to mitigate the spread of the disease with varying degrees of compliance. To quantify the effect of policy responses on the spread of infections, we estimate beta for each country which is the slope coefficient of daily new cases in each country regressed against world new cases. First we test for structural breaks in daily data for world new cases using the Bai Perron (1998, 2003a, 2003b) method which endogenously determines break points. We obtain five break dates that allow us to divide the time period into six windows and estimate betas separately for each window. Next we rank the G7 countries based on their beta values for each window. Our empirical findings suggest that countries that eased their lockdown measures moderately while enforcing nationwide mask mandate and comprehensive contact tracing generally performed better in mitigating the spread of new infections. Furthermore, countries with higher degree of compliance saw improvement in their rankings. US was ranked mostly in the bottom half of the G7 group but not always the worst.

Multimedia Communication Security in 5G/6G Coverless Steganography Based on Image Text Semantic Association

Recently, researchers have shown that coverless steganography is relatively safe. On this basis, to improve the payload of the coverless steganography, a novel semiconstruction coverless steganography algorithm is introduced in the paper. Firstly, web crawler technology is applied to crawl a wide range of small icons and hot news images from the Internet. These icons can be used as the training subset, and the hot news can be designed according to construction rules. Secondly, the Alex-Net network is introduced for training in the algorithm, and the adversarial samples are added to the training set. Thirdly, using the preset template, certain small icons and a hot news image are spliced into a secret carrier image according to the construction principle. The hot news image is in the top half of the carrier, and those small icons are in the bottom half. The image on the upper part of the carrier and the icons of the lower part can be connected by image and text semantics, and the semantic matching can be realized between image semantics and explanatory. The experimental results and analysis show that the proposed algorithm can resist steganalysis tools effectively and has good robustness against various image attacks. Meanwhile, the secret information payload has been greatly improved, the maximum payload can reach 180 bits of a single 512 × 512 image. This promising algorithm can be applied to build covert communications.