Contact Face Research Articles

A Ka-band high-isolation waveguide power divider with planar output ports and out-of-phase

AbstractA waveguide power divider based on ridge waveguide to microstrip line transition is presented in this paper. To improve the isolation performance, a probe insulator is inserted into the contact face from the center of the waveguide side wall, also two chip resistors are mounted on a planar substrate and connected with the probe to absorb the coupled energy. The impedance transformation is accomplished by ridge waveguide to microstrip line transition, which is hidden in the waveguide. This proposed power divider shows merits of waveguide power dividers and substrate-integrated waveguide power dividers simultaneously, i.e. planar output ports, compact size, and high isolation. For verification, a power divider operating at the Ka-band is simulated, fabricated, and measured. The obtained results show the return loss and isolation are better than 10 and 20 dB, respectively. The measured insertion loss is <1.5 dB, including the insertion loss of waveguide to microstrip line transitions at the output port in the range of 34.6–39 GHz.

Use of electrode displacement signals for electrode degradation assessment in resistance spot welding

In resistance spot welding, the quality of welds is not only affected by the correct design of the welding cycle, but also by the electrode degradation that occurs over time. This work proposes a novel approach to indirectly monitor the electrode degradation during welding by analyzing the electrode displacement signal from a non-contact sensor embedded in the welding machine and the electrode tip shape obtained from carbon imprint tests. As a result of an experimental campaign involving more than 1200 weld spots, the electrode speed during the final hold stage has been determined as the most explanatory feature describing the electrode displacement. Based on the mechanical strength of spot welds, the electrode contact face area has been defined as the most representative feature characterizing electrode degradation. A regression analysis has been carried out to infer a relationship between the electrode speed and the contact area representative of tool wear. A Neural Network has been built to use some features extracted from the electrode displacement signals to predict the contact area and thus indirectly the electrode degradation. The model has shown a good accuracy, with a mean error of the contact area about 1.61 mm2, and with a standard deviation of about 3.73 mm2. The data-driven approach proposed allows through the evaluation of the electrode contact area to have better real-time knowledge and control of the welding process.

Fundamental study on slip behavior and slip strength of the high strength bolted joints with adhesive for putty lining on the contact face

Fundamental study on slip behavior and slip strength of the high strength bolted joints with adhesive for putty lining on the contact face

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2 ) IgG-antibody seroprevalence among quarantined population, during the first wave of COVID-19 pandemic, In North West Ethiopia (from 30 April to 30 May 2020).

Objective:The spread of Severe Acute Respiratory Syndrome Corona Virus-2 (SARS-CoV-2) in Ethiopia is below par understood and to date has been poorly characterized by a lower number of confirmed cases and deaths as compared with other regions of the Sub-Saharan African (SSA) countries. We aimed to investigate the seroprevalence of SARS-CoV-2 specific IgG antibodies, using the Abbott anti-nucleocapsid IgG chemiluminescent microparticle immunoassay, in two COVID-19 diagnosed and treatment centers of quarantined population during the first wave of the COVID-19 pandemic (since 30 April–30 May 2020).Methods:We analyzed data of 446 quarantined individuals during the first wave of COVID-19 pandemic. The data were collected using both interviewed and blood sample collection. Participants asked about demographic characteristics, COVID-19 infection symptoms, and its practice of preventive measures. Seroprevalence was determined using the severe acute respiratory syndrome coronavirus 2 IgG test.Results:The mean (± standard deviation) age of the respondent was 37.5 (±18.5) years. The estimated SARS-CoV-2 infection seroprevalence was found 4.7% (95% confidence interval: 3.1–6.2) with no significant difference on age and gender of participants. Severe acute respiratory syndrome coronavirus 2 antibody seroprevalence was significantly associated with individuals who have been worked by moving from home to work area (adjusted odds ratio = 7.8, 95% confidence interval: 4.2–14.3, p < 0.019), not wearing masks (adjusted odds ratio = 2.4, 95% confidence interval: 1.9–3.8, p < 0.02), and baseline comorbidity (adjusted odds ratio = 6.3, 95% confidence interval: 2.3–17.1, p < 0.01) as compared to their counter groups, respectively.Conclusion:Our study concluded that lower coronavirus disease 2019 seroprevalence, yet the large population in the community to be infected and insignificant proportion of seroprevalence, was observed between age and sex of respondents. Protective measures like contact tracing, face covering, and social distancing are therefore vital to demote the risk of community—strengthening factors should be continued as effect modification of anticipation for severe course of coronavirus disease 2019.

Interfacial Crack with Frictionless and Frictional Contact of Faces in a Bimaterial under a Shear Wave

Interfacial Crack with Frictionless and Frictional Contact of Faces in a Bimaterial under a Shear Wave

From Facebook Toward the Metaverse – How the Future Educators Build Interpersonal Relationships Using Social Media

At the threshold of emerging parallel immersive environments and metaverse worlds, the use of social media to build interpersonal relationships is a common phenomenon. This study aimed to diagnose, describe, and compare the use of social media to build and sustain interpersonal contacts and to refer to the level of interpersonal competences among students of pedagogical courses in two selected universities in Poland and Portugal. The studies were quantitative and employed the Interpersonal Competence Questionnaire by D. Buhrmester, W. Furman, M.T. Wittenberg and H.T. Reis, as well as the author’s own questionnaire. The analyses show that social media play a major role in building interpersonal relationships for Polish and Portuguese students in areas such as establishing new contacts, maintaining offline relationships, mutual learning and self-presentation. Non-face-to-face relations may interfere with establishing contact face to face. The analyses also show that the level of interpersonal competences among the respondents in terms of the skills and readiness to provide emotional support to others is differentiated by the way and scope of social media usage in the area under consideration. It can be assumed that in the group of respondents, the more they are willing and able to provide emotional support to others, the more effective and balanced way they use social media in building interpersonal relationships.

Collecting Social Media Information in a Substance Use Intervention Trial With Adolescent Girls With Lifetime Substance Use History: Observational Study.

BackgroundAdolescents with juvenile legal system contact face numerous barriers to participation in behavioral health intervention research, including housing disruption, legal privacy concerns, and systems mistrust. Technology, such as social media, may be a novel and developmentally appropriate adolescent research study engagement and retention tool.ObjectiveWe examined data on social media information collected for study retention purposes from adolescents participating in a substance use intervention trial.MethodsData were collected as part of a randomized controlled trial determining efficacy of a group-based substance use intervention for girls and young women (12-24 years) with substance use histories referred from legal and school systems in the United States. Baseline demographic and social media information was analyzed from the subset of 114 adolescent girls (mean age 15.7 years; range 13-18 years), of whom 31.6% (36/114) were legally involved, 87.7% (100/114) belonged to minoritized racial/ethnic groups, and 32.5% (37/114) received public assistance.ResultsMost girls (74/114, 64.9%) provided at least one social media account (Instagram, 95% [70/74]; Facebook, 27% [20/74]; and Twitter, 11% [8/74]) during study enrollment. Legally involved girls were significantly less likely to provide social media information than school-referred girls (44% [16/36] versus 74% [58/78]; χ21 [N=114]=9.68, P=.002).ConclusionsObtaining social media information for study retention purposes from adolescent girls with lifetime substance use appears possible; however, particular subgroups (ie, legally involved girls) may be less likely to provide accounts. Factors shaping legally involved girls’ willingness to provide social media information, including mistrust and privacy concerns, and the impact of researcher’s access to social media information on study retention are critical directions for future research.Trial RegistrationClinicalTrials.gov NCT02293057; https://clinicaltrials.gov/ct2/show/NCT02293057

Occupational contact dermatitis in painters and varnishers: Data from the Information Network of Departments of Dermatology (IVDK), 2000 to 2019.

Painters and varnishers ("painters") are exposed to various contact allergens and skin irritants, and therefore, are at risk for developing occupational dermatitis (OD). To describe the spectrum of occupational sensitizations in painters and revise the corresponding current patch test recommendations. Retrospective analysis of Information Network of Departments of Dermatology (IVDK) data from 2000 to 2019 with focus on male painters with OD, ages 20-59 years (n=557) in comparison to age-matched male painters without OD (n=422) and male OD patients who have had never worked as painters (n=13 862). Male painters with OD have a significantly higher rate of allergic contact dermatitis and face dermatitis than male patients with OD who work in other professions. Positive patch tests to epoxy resin, methylisothiazolinone (MI), and methylchloroisothiazolinone (MCI)/MI were significantly more frequent in painters with OD than in the other groups. Epoxy resin sensitization was significantly associated with face dermatitis. Epoxy resin, MI, and MCI/MI represent the most important occupational sensitizers in painters. In addition to baseline, resins and glues, and industrial biocides series, the patients' own workplace materials should be tested in painters with suspected OD.

Mechanical evaluation of 3D printed biomimetic non-Euclidean saddle geometries mimicking the mantis shrimp

Engineering design has drawn inspiration from naturally occurring structures to advance manufacturing processes and products, termed biomimetics. For example, the mantis shrimp, order Stomatopoda, is capable of producing one of the fastest appendage strikes in the world with marginal musculoskeletal displacement. The extreme speed of the mantis shrimp’s raptorial appendage is due to the non-Euclidean hyperbolic paraboloid (i.e. saddle) shape within the dorsal region of the merus, which allows substantial energy storage through compression in the sagittal plane. Here, investigation of 3D printed synthetic geometries inspired by the mantis shrimp saddle geometry has revealed insights for elastic energy storage (i.e. spring-like) applications. Saddles composed of either a stiff or a flexible resin were investigated for spring response to explore the geometric effects. By modulating the saddle geometry and testing the spring response, it was found that, for the stiff resin, the spring constant was improved as the curvature of the contact and orthogonal faces were maximized and minimized, respectively. For the flexible resin, it was found that the spring constant increased by less than 250 N mm−1 as the saddle geometry changed, substantiating that the flexible component of mantis saddles does not contribute to energy storage capabilities. The geometries of two saddles from the mantis shrimp species O. scyllarus were estimated and exhibited similar trends to manufactured saddles, suggesting that modulating saddle geometry can be used for tailored energy storage moduli in spatially constrained engineering applications.

Simulation of the Operation of Contact Face Seals for Multimode Turbomachinery

Simulation of the Operation of Contact Face Seals for Multimode Turbomachinery

Seroprevalence of anti-SARS-CoV-2 IgG antibodies in the staff of a public school system in the midwestern United States.

Since March 2020, the United States has lost over 580,000 lives to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes COVID-19. A growing body of literature describes population-level SARS-CoV-2 exposure, but studies of antibody seroprevalence within school systems are critically lacking, hampering evidence-based discussions on school reopenings. The Lake Central School Corporation (LCSC), a public school system in suburban Indiana, USA, assessed SARS-CoV-2 seroprevalence in its staff and identified correlations between seropositivity and subjective histories and demographics. This study is a cross-sectional, population-based analysis of the seroprevalence of SARS-CoV-2 in LCSC staff measured in July 2020. We tested for seroprevalence with the Abbott Alinity™ SARS-CoV-2 IgG antibody test. The primary outcome was the total seroprevalence of SARS-CoV-2, and secondary outcomes included trends of antibody presence in relation to baseline attributes. 753 participants representative of the staff at large were enrolled. 22 participants (2.9%, 95% CI: 1.8% - 4.4%) tested positive for SARS-CoV-2 antibodies. Correcting for test performance parameters, the seroprevalence is estimated at 1.7% (90% Credible Interval: 0.27% - 3.3%). Multivariable logistic regression including mask wearing, travel history, symptom history, and contact history revealed a 48-fold increase in the odds of seropositivity if an individual previously tested positive for COVID-19 (OR: 48, 95% CI: 4-600). Amongst individuals with no previous positive test, exposure to a person diagnosed with COVID-19 increased the odds of seropositivity by 7-fold (OR: 7.2, 95% CI: 2.6-19). Assuming the presence of antibodies is associated with immunity against SARS-CoV-2 infection, these results demonstrate a broad lack of herd immunity amongst the school corporation's staff irrespective of employment role or location. Protective measures like contact tracing, face coverings, and social distancing are therefore vital to maintaining the safety of both students and staff as the school year progresses.

Molecular Dynamic Simulation of Micro-Structured Diamond Tool in Silicon Carbide Cutting

Abstract Silicon carbide (SiC) is an important material in many industrial applications. However, due to the hardness and brittleness nature, achieving ultra-precision machining of SiC is still challenging. In recent years, function surface with micro-structures has been introduced in cutting tool to suppress wear process. But the wear mechanism of the structured tool has not been revealed completely. Therefore, in present research, molecular dynamic simulations were conducted to investigate the cutting performance of the micro-structure on the nano scale cutting process of 3C-SiC. The simulation results showed that the dislocation propagation in workpiece can be suppressed with a structured tool. The micro-structures have a significant influence on the stress distribution in the workpiece subsurface. Furthermore, the abrasive wear of the structured tool is obvious smaller since the edges of the tool became blunt and the contact face between tool and workpiece changed to the close-packed plane of diamond. Moreover, the amorphization of the structured tool is effectively suppressed. This study contributes to the understanding of the material behavior involved in the ultra-precision cutting of SiC.

Evaluating the Impact of Intervention Strategies on the First Wave and Predicting the Second Wave of COVID-19 in Thailand: A Mathematical Modeling Study.

Simple SummaryThe world is currently experiencing the COVID-19 pandemic, consequently, we developed a compartmental model to describe the transmission dynamic of the disease, which can reproduce the incidence of COVID-19 first wave in Thailand. Screening incoming visitors, contact tracing, and case investigation were introduced from the beginning of the pandemic, while the rapid reduction of new cases was a result of the declaration of emergency decree in March 2020. The validated model was used to quantify the impacts of these intervention strategies. The model predicted that the daily reported incidence would have reached zero by the end of June if the on-going non-pharmaceutical interventions (NPIs) were strictly and widely implemented. Our study provides a better understanding of the first wave COVID-19 pandemic and the impacts of government interventions in a Thai setting, where data were still limited. The model further explored the use of these available interventions in the scenario analysis to control the emergence of a second wave of COVID-19 in Thailand. Continued good practice of social distancing to minimize the contact rates is still necessary while the vaccines are not fully available to all populations.Coronavirus disease 2019 (COVID-19) has spread rapidly worldwide. This study aimed to assess and predict the incidence of COVID-19 in Thailand, including the preparation and evaluation of intervention strategies. An SEIR (susceptible, exposed, infected, recovered) model was implemented with model parameters estimated using the Bayesian approach. The model’s projections showed that the highest daily reported incidence of COVID-19 would be approximately 140 cases (95% credible interval, CrI: 83–170 cases) by the end of March 2020. After Thailand declared an emergency decree, the numbers of new cases and case fatalities decreased, with no new imported cases. According to the model’s predictions, the incidence would be zero at the end of June if non-pharmaceutical interventions (NPIs) were strictly and widely implemented. These stringent NPIs reduced the effective reproductive number (Rt) to 0.73 per day (95% CrI: 0.53–0.93) during April and May. Sensitivity analysis showed that contact rate, hand washing, and face mask wearing effectiveness were the parameters that most influenced the number of reported daily new cases. Our evaluation shows that Thailand’s intervention strategies have been highly effective in mitigating disease propagation. Continuing with these strict disease prevention behaviors could minimize the risk of a new COVID-19 outbreak in Thailand.

A numerical finite element study on connections of SFRC offshore wind towers with prestressed CFRP reinforcement and steel connectors

The growing need for sustainable production of electricity highlights the importance and the necessity of having higher number and more effective offshore wind towers. The rapid growth of offshore wind towers is estimated to produce 4% of electricity demands in Europe by the end of 2020. The research described in this paper is part of a project dedicated for the development of innovative structural system using advanced materials for lightweight and durable offshore towers. Specifically, it discusses the nonlinear finite element modelling of the connection between representative prefabricated rings of offshore wind tower made by steel fibre reinforced concrete (SFRC), and prestressed by a hybrid system of carbon fibre reinforced polymers (CFRP) bars and steel strands. This connection is assured by post-tension high steel strength cables and concrete-concrete shear friction width an idealized geometric configuration of the faces in contact. The model takes into account the loads from the rotor, wind and water currents, by considering the critical loading conditions for the safety verifications of serviceability and ultimate limit states. The material nonlinear analyses are carried out with FEMIX V4.0 software, considering a 3D constitutive model capable of simulating the relevant nonlinear features of the SFRC, and interface finite elements for modelling the shear friction of the concrete-concrete surfaces in contact. The parametric analyses involve the influence on the relevant results of the SFRC fracture parameters, pre-stress level of the reinforcements, shape of interlock mechanism, friction angle and interface cohesion.

Influence of friction in a case of impact simulation

This paper presents an analysis of two cases, simulating the impact of a cylindical projectile on a perfectly rigid plate. One case is run without friction, the second one is run taking into account a friction coeficient between the plate and the projectile. The authors used for the projectile the same material constitutive model for both cases, based on experimental data and model developed by Johnson and Cook. Here, the comparing criteria were the maximum value of von Mises stress, the velocity and acceleration of the central point on the opposite face to the contact face of the projectile. Introducing friction, the simulation is more realistic. Taking into account friction, the projectile is less deformed and there was no edge breakage, at the same time moment.

A leakage model for a seal-on-seal structure based on porous media method

The main interface docking seal (MID seal) is one of the key components in the developing low impact docking systems for future space vehicles, and its sealing property is crucial to the spacecrafts docking in space. A seal-on-seal structure is one of the mainstream designs of the MID seal, and is generally made of rubber materials that can adapt to the complex space environment. For the MID seal of the seal-on-seal structure, it is further confirmed that the porous media theory is suitable to study the sealing property by investigating the micromorphology characteristics of seal contact faces, which based on a leakage model is proposed by this paper. In this model, both the primary seal and the secondary seal are considered as a whole, which is more consistent with the structure and the physical process of sealing face leakage. By comparison with the performed experiments, the leakage model was verified. Based on the proposed leakage model, some simulation results about the studied MID seal are presented and discussed, which mainly correspond with pressure distributions, compression levels, design parameters and operating temperatures. These analyses clearly present some intrinsic relationships implicated in the leakage model. This study is favorable for the mechanism researches, designs, assemblies, and applications of the MID seal, and other seals like that are also included.

THE EMOTIONAL INFECTION OF THE VIRTUAL INNOVATION PROJECT TEAM

Emotional infection is considered as a social and psychological mechanism of transferring the mental mood of the manager to the virtual project team and stakeholders of the projects. Emotional impact in the face of direct contact and the inclusion of the virtual team members in certain mental states have an impact on the effectiveness of project management. The main objective of emotional infection analysis is educated and creates the organization of new behavior in adverse, deadly, and aggressive external conditions the manager or virtual team. In times of global crisis and depression 2.0, the emotional behavior of the innovation project manager and his infection with the project team is exacerbated by external uncertainty. The stakeholder infection model is based on an understanding of the life cycle of the project manager, which is presented as a curve for personal changes of the manager of innovative communication projects and programs. Emotions are considered in content, reflecting the various aspects and meanings that caused them. To apply the psychophysiological formula for assessing the impact of the emotional state of the virtual team of innovative projects, these influences have been transformed into a competent model for managing these projects.

Early estimates of COVID-19 infections in small, medium and large population clusters

IntroductionSince its emergence in late December 2019, COVID-19 has rapidly developed into a pandemic in mid of March with many countries suffering heavy human loss and declaring emergency conditions to...

Mechanical behavior and constitutive model of shotcrete–rock interface subjected to heat damage and variable temperature curing conditions

The hydration of shotcrete under a high curing temperature is usually accompanied by the evolution of internal defects and microdamages. To study the physical and mechanical properties and the performance of the bond between shotcrete and rock in a high and changing temperature environment in tunnel construction, shear experiments on shotcrete-rock specimens under different initial curing conditions (60 ℃, 80 ℃, 100 ℃ with relative humidity of 55%) were conducted. The results indicated that the shotcrete used in a high geothermal tunnel was actually cured under high and variable temperature, which caused the damage in the micro-unit of shotcrete near the contact face and, to different extents, the reduction in strength of the interface. The main reason is that high temperatures have a significant impact on the quantity and distribution of the shotcrete hydrates, and they also lead to the formation and increase of micro cracks. However, the increase in normal stress had a certain inhibitoryeffect on the damage caused by the high temperature. Specimens under different normal stresses and initial curing temperatures exhibited two typical failure modes. Moreover, the stress–strain curves were also obtained and used to calibrate the parameters of the proposed thermal damage constitutive model. The research results may provide some supports for the design and analysis of underground engineering affected by high geothermal.

Evaluation of Thermal Contact Resistance Between Two Solid Surfaces Using Photoacoustic Technique

Thermal contact resistance is one of the factors that complicates heat transfer between the interfaces of different components. Because heat transfer is influenced by several factors, it is difficult to estimate all the influencing factors for practical applications. In this study, the thermal contact resistance between two solid surfaces was evaluated using the photoacoustic (PA) technique. The samples consisted of a metal foil and metal cylinders, which had various surface roughnesses at the contact faces measured at the same contact pressure. A one-dimensional analytical solution of the phase lag of the PA signal showed a similar trend with the experimental results. However, there were some quantitative differences between the two groups. By comparing the numerical calculation results for the developed heat conduction model of a cylindrical coordinate system with the experimental results, we found that the in-plane distribution of thermal contact resistance at the contact face contributed to the deviation between the experimental results and the numerical results. The thermal contact resistance was evaluated by considering the in-plane distribution of the thermal contact resistance, and reasonable values of thermal contact resistance were obtained.