Static Tension Research Articles

Study on the influence mechanism of polypropylene fiber on crack propagation of concrete with existing cracks under uniaxial compression

In the process of long-term service of concrete, cracks are inevitable, especially in the state of tension and compression, the crack expansion speed is accelerating, which seriously affects the service performance of concrete, and even causes major disasters. While polypropylene fiber has remarkable cracking resistance, there is a lack of theoretical analysis on crack initiation and path expansion of concrete cracks with existing cracks during the compression process. In order to analyze the inhibitory effect of fiber on the propagation of pre-existing cracks, we performed uniaxial compression tests on concrete prisms containing pre-existing cracks. Acoustic emission technology was used to monitor each test group and obtain relevant data on the cracking process of the specimens. GDEM software was used to simulate typical test conditions, and the results were compared with the test results to further explain the mechanism of crack propagation and fiber suppression. The results show that: (1) fiber can inhibit the initiation and propagation of tension wing cracks at the existing crack tip. The higher the fiber content, the shorter the symmetrical wing cracks become. (2) With the increase of fiber content (0 ∼ 4 kg/m3), the failure mode of polypropylene fiber-reinforced concrete prismatic specimens changes from tensile failure to tensile-shear failure, and finally shear failure. (3) The crack initiation stress and peak strength of prismatic specimens first increase and then decrease with the increase of fiber content. (4) The increase of fiber content delays the crack initiation time, prolongs the time to the disappearance of the peak of the acoustic emission signal, and prolongs the total time of the failure process.

Effect of Combined Laser Thermal and Shock Wave Effects on the Mechanical and Tribological Properties of Steels.

Herein, we present the results of an experimental study on the mechanical properties of Fe-C alloys with different carbon contents (0.2, 0.45, and 0.8%) in a wide range of deformation rates (10-3-103 s-1) and abrasive wear resistance, which underwent combined laser thermal (laser surface hardening-LSH) and laser shock wave (Laser Shock Peening-LSP) processing. The combined treatment modes included a different sequence of exposure to laser thermal and laser-induced shock pulses on the material. The amplitude and duration of laser-induced shock waves were measured using a laser Michelson interferometer. The mechanical properties of steel samples were studied under conditions of uniaxial tension under static loads on a standard universal testing machine, the LR5KPlus, and under dynamic loading, tests were carried out on a specialized experimental complex according to the H. Kolsky method using a split Hopkinson rod. The abrasive wear resistance of hardened surfaces was studied using the Brinell-Haworth method. Studies have shown that the use of a combination of LSH and LSP treatments leads to an increase in both the mechanical properties of steels and abrasive wear resistance compared to traditional laser hardening. It has been established that in the combinations considered, the most effective is laser treatment, in which LSP treatment is applied twice: before and after LSH. Thus, after processing steels using this mode, an increase in the depth of the hardened layer was recorded-by 1.53 times for steel 20, by 1.41 times for steel 45, and by 1.29 times for steel U8-as well as a maximum increase in microhardness values by 22% for steel 20, by 27% for steel 45, and by 13% for U8 steel. The use of this mode made it possible to obtain the maximum strength properties of the studied materials under static and dynamic loading, which is associated with an increase in the volume fraction of the strengthened metal and high microhardness values of the strengthened layer of traditional LSH. The dependences of abrasive wear of the studied steels after various combinations of LSP and LSH impacts were established. It is shown that the greatest wear resistance of the studied steels is observed in the case when the LSH pulse is located between two LSP pulses. In this case, abrasive wear resistance increases by 1.5-2 times compared to traditional LSH.

Anxiety, Stress and Depression in Overseas Medical Students and its Associated Factors: A Descriptive Cross-Sectional Study at Jalalabad State University, Jalalabad, Kyrgyzstan

Background: Stress can be described as a mental state of tension or be concerned brought on by an unpleasant circumstance. Stress is an ordinary human reaction that encourages us to face challenges and dangers in life. According to the WHO, four out of every five college students are contemplating or have attempted suicide. Medical education is considered as demanding because students undergo several psychological transformations. It is estimated that half of all significant adult psychiatric illnesses, including depression, begin before the age of fourteen. 75 % of college students do not seek help for mental health issues. (1)  Materials and Methods: A cross-sectional study was conducted in three months period of time from the month September till November 2023, among 150 students of various years at Jalalabad State Medical University using online Google forms. The study was conducted using DASS 21-item questionnaire to assess the level of stress, anxiety, and depression among students. The data were analyzed using the Statistical Package for Social Sciences (SPSS) version 22.0 software. Ethical approval was taken from the University.  Result: In the study 9% of people reported having a moderate to extremely severe degree of stress, anxiety 27.3% and depression was found among 4% respectively in students. Stress and study of year were substantially correlated. (p = 0.007). Anxiety and extracurricular activities were found to be significiant (p = 0.004). Extracurricular activities and depression were linked. (p = 0.029) and the type of family they belong to (p = 0.015). While stress and depression were shown to be uncommon among medical students, anxiety was found to be more common, which might be related to a variety of factors such as new environments, difficult subjects, complex terminology, etc.  Conclusion: It is important to highlight the points like financial issues, home sick, behaviour of teachers and friends etc would be the stressful elements that might lead to increase the psychological problem among medical student. Following research endeavors in this domain ought to endeavor to address these constraints. In any event, we believe that our results emphasize the necessity of putting policies in place to protect and, where appropriate, improve the mental health and general wellbeing of medical students.

Implications of the jihadist terrorism in cyberspace

The terrorist attack on the 11th of September, 2001, marked the change in the West’s perception of the Middle East and vice versa. Followed by the US military presence in the Middle East, this event contributed to the development of the means of terrorist actions around the world and the popularization of jihad. The hostile attitude of the West thus succeeded in maintaining the state of tension between the two spaces. Over time, jihadist and terrorist groups have been joined by members originating from the West who were convinced by the importance of the “missions” they later undertook. In the present paper, we will focus on the transposition and continuation of hostilities in both geographic and cyber spaces, with reference even to the current Israeli-Palestinian conflict

Investigation on the flexural–tensile behaviour of CFRP tendon composite anchorage system

The cable at the anchorage end is in a bending–tension condition in service due to the variable loads. A new composite anchorage system was proposed to study the flexural–tensile behaviour of the anchorage system with CFRP tendon. Four groups of single-tendon composite anchorage and three groups of five-tendon composite anchorage with bend restrictor were tested. Besides, one group of five-tendon composite anchorage without bend restrictor was tested as a control group. The effects of the bending angle, inner cone angle of the steel barrel and pre-tension force on the flexural–tensile behaviour of the anchorage system were investigated. The internal force state of the tendon inducing different failure modes was analysed. A finite element method was used to analyse the failure mechanism of the anchorage system under the bending–tension condition. Moreover, the flexural–tensile behaviours of the anchorage systems with different elastic moduli of the bonding medium were compared. Results showed that the efficiency coefficients of the composite anchorage with multi-tendon exceeded 0.9 when the end bending angle was less than 4.2°. The setting of the bending restrictor improves the flexural–tensile bearing capacity of the anchorage system and increases the maximum allowable bending angle. A larger bending angle will lead to a faster increase in the transverse shear stress at the loading end. Furthermore, increasing the pre-tension force can prompt the cooperation ability of the tendons and reduce the ultimate slips, thus improving the ultimate load-bearing capacity of the anchorage. The increase in the elastic modulus remarkably reduces the slip of the tendon, but increases the shear stress at the loading end under the bending–tension condition.

Evaluation of the strength performance of the steering system of hybrid off-road vehicles

In response to the strength performance requirements of the new energy Off road Vehicle steering system, this article analyzes and studies the strength performance and failure modes of the new energy Off road Vehicle steering rod based on a certain new energy Off road Vehicle model through simulation, bench experiments, and vehicle strength testing teams. Based on various vehicle misuse conditions, the force law of the steering rod under different vehicle driving conditions was analyzed, and a load spectrum for the steering rod strength bench test was developed to meet the actual vehicle usage conditions. The results indicate that the steering rod strength failure is mainly manifested as bending failure of the compression rod under alternating tension and compression conditions. Finally, based on the stability principle of the compression rod, the requirements for the strength performance index of the steering rod are proposed. The research results can provide certain technical support for the strength assessment of the vehicle steering rod.

WORK STRESS AND ITS INFLUENCE ON THE EMPLOYEES OF A SERVICE COMPANY IN THE CITY OF MANIZALES

Objective: The study seeks to determine the levels of work stress in the employees of a service company, describing the causes and their financial impact.
 
 Theoretical Framework: The concepts of work stress defined as a general state of tension that triggers different emotional, cognitive, physiological and behavioral reactions are addressed, as well as some causing factors such as: Physical Environment, Job Demand, Knowing the tasks and interpersonal relationships.
 
 Method: The study has a mixed approach, where qualitative categories were given quantitative management of the data, to find numerical evidence and be able to explain in more detail the presence of the event. The ILO-WHO Work Stress scale was used as an instrument, which was applied to 33 employees of a Contact Center company in the city of Manizales.
 
 Results and Discussion: The results obtained revealed that work stress is below the limit of the intermediate stress range (81.09 / 90.02) and that due to Absenteeism and Turnover, the company has had costs of $43,995,586 COP according to approximate calculations.
 
 Research Implications: The evidence from the study showed information that allows companies in the service sector to generate strategies for stress management and contribute to reducing costs due to absenteeism and turnover, the above could be used in other sectors or companies in the region.
 
 Originality/Value: The value lies in contributing to the development of the state of the art on the subject and as a reference for future studies since the state of the art shows little research in Contact Center companies in Latin America, likewise for companies generating well-being strategies and the management of the stress.

Effects of the second-order hydrodynamics on the dynamic behavior of the platform among the wind-wave hybrid systems

This paper presents three different wind-wave hybrid systems (HSs) with multiple point-absorption wave energy converters (WECs) integrated onto a floating semi-submersible wind turbine (WT). The focus of the present study is to explore the effects of the second-order wave forces on the dynamic behavior of the platform in the HS, including the platform motion and the mooring line tension, under both operational and extreme sea states. ANSYS/AQWA based on 3D diffraction/radiation potential theory is used to conduct numerical investigation on the second-order hydrodynamics of the HS. To ensure the reliability of the investigation, the validations of the semi-submersible platform and point-absorption WEC are done based on the available experimental data. Additionally, two models, "1st-order" and "1st&2nd-order", are set up for comparative analysis, to highlight the significance of the second-order forces. The simulation results show that the second-order hydrodynamics have a significant influence on the surge and pitch responses of the platform, but almost no effects on the heave response. In addition to this, ignoring the second-order hydrodynamics will significantly underestimate the mooring line tension response. Overall, this study suggests that the second-order hydrodynamics should be considered in the design of wind-wave HSs, in order to ensure their performance and safety, especially under the severe sea states.

RECOVERY IN THE INTERNATIONAL TRADE OF UKRAINIAN TOURIST SERVICES AT POST-WAR CONDITION

Article highlights several issues of recovery and develop in international tourism after the Covid-19 pandemic in conditions of growth war tension in the world. Considered main economic and geopolitical factors what brakes growth of international tourism up to positions, which loss after 2019. Reviewed importance of reducing the negative impact of rising prices for fossil energy due to the overall dynamics of global economic recovery after the Covid-19 pandemic through the diversification of energy sources and increased investment in renewable energy. Highlighted are several issues of disinformation and vaccine-related fake news as negatively impacting factors on the recovery of the tourism sector due to obstacles to successful vaccination in various regions of the world, particularly in China and other countries in the Asia-Pacific region. The analysis conducted reveals weaknesses in protecting the economies of different countries against global economic and geopolitical challenges, regardless of their level of development.

Performance analysis of fiber-reinforced polypropylene composite laminates under quasi-static and super-sonic shock loading conditions for impact application

In the present research, glass and basalt fiber-reinforced polypropylene composites’ behaviour in quasi-static and dynamic conditions is studied. Composites were fabricated by vacuum assisted Compression molding method. Composites failure under quasi-static tension and compressive conditions was studied along with its failure behaviour under low-velocity impact and super-sonic shock loading under dynamic conditions. The study results showed that basalt fiber-reinforced polypropylene (Basalt/PP) composite’s tensile and compressive strength is higher than glass fiber-reinforced polypropylene (Glass/PP). The Basalt/PP showed no penetration against low velocity impact (LVI) with negligible deformations till 50 J. However, the Glass/PP perforated at 50 J with various failure patterns occurring at back side. The fiber-matrix interface adhesion plays an important role in super-sonic shock loading by absorbing shock wave energy due to ductile nature of polypropylene and the two composites absorbed energy via matrix and fibers failure, no brittle failure of laminates occurred under shock loading.

Deformation characterization of multi-morphology composite cellular hyperelastic structure under biaxial tension: Analytic approaches for sensor applications

As a preliminary study to develop an effective stretchable sensor, we implemented multi-morphology cellular structures in the gauge area of a biaxial tensile specimen to obtain the desired biaxial mechanical behaviour. A numerical parametric study was conducted by considering the unit cell geometries, four biaxial tension conditions, and three groups of unit cells. The parametric study reveals that a multi-morphology composite cellular (M2C2) specimen with compliant unit cells near the centre and stiff unit cells along the border of the gauge area shows high linearity between the force and displacement relationships and high compliance. M2C2 specimens optimised using the Bayesian optimisation process share similar geometric patterns found in the parametric study and show enhancements in linearity and compliance up to 40.4 % and 65.6 %, respectively, compared with those of a conventional solid specimen.

UNEMPLOYMENT LEVEL AS A TRIGGER FOR THREATS TO THE NATIONAL SECURITY OF COUNTRIES (ОN THE EXAMPLE OF RUSSIA AND EUROPEAN COUNTRIES)

The phenomenon of unemployment is characteristic of almost all developed countries, and the issues of unemployment regulation remain the most important at the macro and micro levels of public policy. Unemployment is one of the most important indicators of the general state of a country's economy. The authors of the article drew a connection between the unemployment rate in Russia and European countries and the state of economic and national security of the states. Pyramids of the security levels of Russia and the EU countries are proposed. The characteristics of the labour market of the European countries and the Russian Federation are considered with an emphasis on the diversity of the regions. It has been established that the unemployment rate in the developed countries is connected with the processes of globalisation and digitalisation, with the geopolitical situation, and can be an economic trigger that has provoked fundamental changes in the modern labour market, the state of human capital and social tensions in the world countries. A number of universal measures are proposed to strengthen the national and economic security of countries.

Features of mental states in representatives of different types of sports

The article analyzes the problem of finding psychological properties that determine high sports results in various types of sports activities, far from unequivocal conclusions. The analysis of literary data and the results of one's own research provide grounds for asserting that the endogenous factors of influence on mental states are the properties of nervous processes and temperament, and the exogenous factors of influence can be, in the case of a transactional process, the process of the subject's interaction with the environment. In the structure of the transactional process of a stressful episode, several elements can be distinguished: awareness of the stressor and its assessment; disruption of homeostasis, stress-related emotions and cognitive processes; coping reaction; the result of coping and a new assessment of the situation; personal factors. The analysis of the results of the own research of groups of athletes from various sports provides a basis for asserting that statistically significant differences in indicators of the state of mental tension, as well as reactive and personal anxiety, were not found in athletes - relievers. Research into the study of psychological mechanisms that determine the performance of top-level athletes and their evaluation criteria is considered promising in the future.

ANALYSIS OF SKIN SCARRING WITH PRE-, INTRA- AND DELAYED SURGICAL INJECTION THERAPY: THE PRECLINICAL RESEARCH

Purpose: Experimental testing of injection therapy in the area of the upcoming skin incision in order to improve the quality of achieving the aesthetic appearance of the skin scarring process. Materials and methods: The study was carried out on the skin of the sternum and anterior abdominal wall on 2 closely related minipigs.3 series of operations were carried out synchronously on two individuals in a surgical operating room with preliminary specific markings in the form of rectangles and trapezoids, respectively; the nipple-areolar complexes served as a guide for drawing the figures. At each stage, the same type of geometric marking of the surgical field was used and repeated interventions were performed in the same areas of injection therapy and biopsy sampling. In the postoperative period, on the 30th and 120th days, biopsy specimens were taken to verify the ongoing reparative processes based on clinical, photometric and histological analysis. Results: Preoperative injection therapy contributed to the formation of a normotrophic scar in structure closer to normal skin compared to a scar during normal tissue healing, which allows it to be recommended for preoperative preparation and for research in humans. The selected technique allows for assessment of the classic primary wound, with the introduction of saline and botulinum toxin intraoperatively and delayed at 1 and 4 months with histological analysis of the results. At each stage of the experiment, the team achieved long-term survival of minipigs without compromising their vital functions. The same type of geometric marking of the surgical field was used and repeated interventions were performed in the same areas of injection therapy and biopsy sampling. Conclusion: The methodology allows to assess different methods of linear scar formation with or without the use of injection therapy during surgical access, as well as comparing tissue adhesion histologically and optimal scar formation. When the effectiveness of BTA therapy is achieved, injection therapy requires further research under conditions of tissue deficit or tension during wound closure.

Unmasking Sentiments: A Comprehensive Review on Emotion Detection Technologies

Stress is a state of tension, either physical or emotional, that can be brought on by any idea or incident that leaves you feeling anxious, irate, or disappointed. It is a basic human reaction that drives us to confront obstacles and dangers in our lives. Stress can elicit a variety of emotions, such as worry and irritation, and makes it difficult for us to unwind. This paper reviews many techniques [ECG, EMG, EDA, EEG, etc..,] for identifying stress.

Anomalous buckling of odd elastic plates

Buckling of thin-walled structures such as plates and shells is a consequence of in-plane stress being released through out-of-plane displacements. Generally, thin-walled structures that are subjected to tension or zero stress conditions remain stable. In this article, the anomalous tension buckling and stress-free active buckling of odd elastic plates are reported, which are a novel instability caused by odd elastic effects. The latter can only occur in the form of left- or right-handed chiral deformation and it does not involve external loads or internal active stress in a critical state. We demonstrate that the chiral rotation angle deformation is responsible for the active buckling of the plates, because the energy required for instability can be obtained based on the odd elastic effect. These findings can serve as an interpretation in a novel way for the occurrence of surface morphologies with biological activities, as well as provide references for buckling designs and applications of active structures.

The design, fabrication and analysis of a cantilever-based tensile-mode nonlinear piezoelectric energy harvester

In this paper, a cantilever-based tensile-mode piezoelectric energy harvester is proposed. In contrast to a bending mode, the tensile mode enables a uniform strain distribution within the piezoelectric material. This stands in contrast to the strain concentration at the fixed end of a typical cantilevered design. The proposed design comprises a two-segment cantilever beam and an elastic PVDF film that are interconnected. The PVDF film undergoes pre-stretching to guarantee that the harvester maintains a state of tension rather than compression during excitations, as the film is not capable of withstanding compressive forces. The theoretical model of the proposed harvester is derived and validated via experiments. Due to the geometric nonlinearity of this mechanism, a highly nonlinear hardening effect is observed in the simulation and experiments. The effects of different parameters, including preload, dimensions of the elastic beam, tip mass, and excitation accelerations, are explored. The optimal configuration can provide a maximum peak power output of 1827 μW.

A generalized nonlinear three-dimensional Hoek‒Brown failure criterion

To understand the strengths of rocks under complex stress states, a generalized nonlinear three-dimensional (3D) Hoek‒Brown failure (NGHB) criterion was proposed in this study. This criterion shares the same parameters with the generalized HB (GHB) criterion and inherits the parameter advantages of GHB. Two new parameters, β, and n, were introduced into the NGHB criterion that primarily controls the deviatoric plane shape of the NGHB criterion under triaxial tension and compression, respectively. The NGHB criterion can consider the influence of intermediate principal stress (IPS), where the deviatoric plane shape satisfies the smoothness requirements, while the HB criterion not. This criterion can degenerate into the two modified 3D HB criteria, the Priest criterion under triaxial compression condition and the HB criterion under triaxial compression and tension condition. This criterion was verified using true triaxial test data for different parameters, six types of rocks, and two kinds of in situ rock masses. For comparison, three existing 3D HB criteria were selected for performance comparison research. The result showed that the NGHB criterion gave better prediction performance than other criteria. The prediction errors of the strength of six types of rocks and two kinds of in situ rock masses were in the range of 2.0724%–3.5091% and 1.0144%–3.2321%, respectively. The proposed criterion lays a preliminary theoretical foundation for prediction of engineering rock mass strength under complex in situ stress conditions.

Breaking the institutional logic or going under - Controllers and sustainability

PurposeThe present paper aims to focus on the role which German controllers play so far in the process of sustainable transformation in for-profit organizations, the current obstacles to a wider engagement here and ways to overcome these obstacles.Design/methodology/approachThe analysis combines two qualitative study designs. Empirical data is generated via a job advertisement analysis and an explorative survey with 107 subjects from management accounting/controlling and sustainability management. The generated data is interpreted against the background of the theory of institutional logics and Abbott’s (1988) theory of professional jurisdiction.FindingsWe find that controllers are in a state of tension. On the one hand, the pressure to integrate sustainability into companies is increasing. On the other hand, they seem to be rather reluctant to get involved. The institutional logics that shape their profession play an important role here, as does an unclear relationship with the sustainability department, which has its own claims here. Based on these observations, we identify the core obstacles to the transformation of the controllers’ profession and discuss solutions which can guide the transformation of this profession.Originality/valueThe present paper provides insights from a unique combination of different quantitative study designs and different perspectives on the possible role that controllers can play in advancing sustainable transformation in companies.

Psychological Stress and Role Management on Construction Technology Industry: Post-Pandemic Challenges

Psychological stress is an unpleasant feeling and emotion for a person who is in a state of restlessness, anxiety, and tension because of the mental or physical stress that occurs. The purpose of this study was to find out the level and factors of psychological stress faced by employees in terms of barriers to the role of company management, particularly in the context of construction technology industry. This study was conducted on construction workers in the district of Hulu Selangor affected by the Covid-19 pandemic. This study uses random sampling referring to the population of selected companies. The study sample was 70 people from a total target population of 70 people. The researcher used the method of distributing questionnaires from google forms medium which contains five-section, namely Part A (demographics of respondents), Part B (psychological stress factors among workers) and Part C (aspects of company management role) is the content for the research instrument. The data collected will be analysed using the Statistical Package for School Science (SPSS) program. Descriptive methods were used to obtain the mean, percentage, frequency, and standard deviation in this study. According to the study's findings, the level of psychological stress among worker’s was a moderate and employees also perceived the psychological stress associated with their managerial responsibilities in the context of construction technology sector. To foster a healthier and more productive workplace, this discovery can offer all parties involved with useful information they can use as a guide to leverage technological solutions and structural adjustments to prevent employees from experiencing psychological stress in the future.