Search results for: frequency of fatigue

Authors: Hamed Alizadeh Dashagholi, Hossein Yousefi-Banaem, Mina Naeimi

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Current study established for EEG signal analysis in patients with language disorder. Language disorder can be defined as meaningful delay in the use or understanding of spoken or written language. The disorder can include the content or meaning of language, its form, or its use. Here we applied Z-score, power spectrum, and coherence methods to discriminate the language disorder data from healthy ones. Power spectrum of each channel in alpha, beta, gamma, delta, and theta frequency bands was measured. In addition, intra hemispheric Z-score obtained by scoring algorithm. Obtained results showed high Z-score and power spectrum in posterior regions. Therefore, we can conclude that peoples with language disorder have high brain activity in frontal region of brain in comparison with healthy peoples. Results showed that high coherence correlates with irregularities in the ERP and is often found during complex task, whereas low coherence is often found in pathological conditions. The results of the Z-score analysis of the brain dynamics showed higher Z-score peak frequency in delta, theta and beta sub bands of Language Disorder patients. In this analysis there were activity signs in both hemispheres and the left-dominant hemisphere was more active than the right.

Keywords: EEG, electroencephalography, coherence methods, language disorder, power spectrum, z-score

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Authors: A. A. Vasin, N. V. Klassen, A. M. Likhter

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Water suspensions of in-organic (metals and oxides) and organic nano-objects (chitozan and collagen) were subjected to the treatment of direct and alternative electrical fields. In addition to quasi-periodical spatial patterning resonance-like performance of spatial distributions of these suspensions has been found at low frequencies of alternating electrical field. These resonances are explained as the result of creation of equilibrium states of groups of charged nano-objects with opposite signs of charges at the interparticle distances where the forces of Coulomb attraction are compensated by the repulsion forces induced by relatively negative polarization of hydrated regions surrounding the nanoparticles with respect to pure water. The low frequencies of these resonances are explained by comparatively big distances between the particles and their big masses with t\respect to masses of atoms constituting molecules with high resonance frequencies. These new resonances open a new approach to detailed modeling and understanding of mechanisms of the influence of electrical fields on the functioning of internal organs of living organisms at the level of cells and neurons.

Keywords: bio-polymers, chitosan, collagen, nanoparticles, coulomb attraction, polarization repulsion, periodical patterning, electrical low frequency resonances, transformations

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Authors: Samson Mil'shtein, Dhawal N. Asthana

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The presented heterostructure n-p-n bipolar transistor is comprised of Ge/GaAs heterojunctions consisting of 0.15µm thick emitter and 0.65µm collector junctions. High diffusivity of carriers in GaAs base was major motivation of current design. We avoided grading of the base which is common in heterojunction bipolar transistors, in order to keep the electron diffusivity as high as possible. The electrons injected into the 0.25µm thick p-type GaAs base with not very high doping (1017cm-3). The designed HBT enables cut off frequency on the order of 150GHz. The Ge/GaAs heterojunctions presented in our paper have proved to work better than comparable HBTs having GaAs bases and emitter/collector junctions made, for example, of AlGaAs/GaAs or other III-V compound semiconductors. The difference in lattice constants between Ge and GaAs is less than 2%. Therefore, there is no need of transition layers between Ge emitter and GaAs base. Significant difference in energy gap of these two materials presents new scope for improving performance of the emitter. With the complete structure being modelled and simulated using TCAD SILVACO, the collector/ emitter offset voltage of the device has been limited to a reasonable value of 63 millivolts by the dint of low energy band gap value associated with Ge emitter. The efficiency of the emitter in our HBT is 86%. Use of Germanium in the emitter and collector regions presents new opportunities for integration of this vertical device structure into silicon substrate.

Keywords: Germanium, Gallium Arsenide, heterojunction bipolar transistor, high cut-off frequency

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Authors: Cíntia Martins Sanches

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In the first part of Phoenissae of Seneca, Antigone is a guide to Oedipus, and they leave Thebes: he is blind searching for death (inflicting the punishment himself wished on the killer of Laius, ie exile and death); she is trying to convince him to give up such punishment and bring him back to Thebes. Concerning Oedipus lines, we observed a high frequency of Latin neuter in the treatment the protagonist gave to his daughter Antigone. We considered in this study that such frequency may be related to the sanctification of the daughter, who is seen by him as an enlightened being and without defects, free of the human condition (which takes on the existence of failures by essence). This study, thus, puts forward an analysis of the passages the said feature is present, relating them to the effect of meaning found in each occurrence. As part of a doctorate, this study investigates the stylistic idiom of Seneca in the Oedipus and Phoenissae tragedies, aiming at translating both tragedies expressively. The concept of stylistic idiom concerns the stylistic affinity required for a translation to be equivalent to the source text. In this wise, this study inquires into how the Latin text is organized poetically, pointing out the expressive features frequently appearing in both dramas. The method we used is based on the Semiotics theory — observing how connotation, ie a language use in which prevails the poetic function, naturally polysemous, acts to achieve each expressive effect.

Keywords: antigone, neuter, Oedipus, Phoenissae, Seneca

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Authors: Can Mungan, Gokhan Kilic

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Structural engineers and tunnel owners have good reason to attach importance to the assessment and inspection of tunnels. Regular inspection is necessary to maintain and monitor the health of the structure not only at the present time but throughout its life cycle. Detection of flaws within the structure, such as corrosion and the formation of cracks within the internal elements of the structure, can go a long way to ensuring that the structure maintains its integrity over the course of its life. Other issues that may be detected earlier through regular assessment include tunnel surface delamination and the corrosion of the rebar. One advantage of new technology such as the ground penetrating radar (GPR) is the early detection of imperfections. This study will aim to discuss and present the effectiveness of GPR as a tool for assessing the structural integrity of the heavily used tunnel. GPR is used with various antennae in frequency and application method (2 GHz and 500 MHz GPR antennae). The paper will attempt to produce a greater understanding of structural defects and identify the correct tool for such purposes. Conquest View with 3D scanning capabilities was involved throughout the analysis, reporting, and interpretation of the results. This study will illustrate GPR mapping and its effectiveness in providing information of value when it comes to rebar position (lower and upper reinforcement). It will also show how such techniques can detect structural features that would otherwise remain unseen, as well as moisture ingress.

Keywords: tunnel, GPR, health monitoring, moisture ingress, rebar position

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Authors: Aman Patidar, Dipankar Sarkar, Manish Pal

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Due to rapid development, increase in the traffic load, higher traffic volume and seasonal variation in temperature, asphalt pavement shows distresses like rutting, fatigue and thermal cracking etc. because of this pavement fails during service life so that bitumen needs to be modified with some additive. In this study VG30 grade bitumen modify with addition of nanosilica with 1% to 5% (increment of 1%) by weight of bitumen. Hot mix asphalt (HMA) have higher mixing, laying and rolling temperatures which leads to higher consumption of fuel. To address this issue, a nano material named ZycoTherm which is chemical warm mix asphalt (WMA) additive is added to bitumen. Nanosilica modification (NSMB) results in the increase in stability compared to unmodified bitumen (UMB). WMA modified mix shows slightly higher stability than UMB and NSMB in a lower bitumen content. The Retained stability and tensile strength ratio (TSR) is more than 75% and 80% respectively for both mixes. Nanosilica with WMA has more resistant to temperature susceptibility, moisture susceptibility and short term aging than NSMB.

Keywords: HMA, nanosilica, NSMB, temperature, TSR, UMB, WMA

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Authors: Hussain Al-Baghli

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In comparison to hot mix asphalt (HMAs) composed of non-modified bitumens, the superior performance of rubberized HMAs is very well documented, and numerous trials in the USA and elsewhere have demonstrated excellent performance in terms of creep, fatigue, and durability. In this investigation, rubberized HMA technology was examined to address the most critical forms of pavement distresses in the State of Kuwait, namely, high-temperature rutting and moisture-induced raveling. Pelletpave additive was selected as the preferred technology since it offered a convenient method of directly modifying the exiting local HMA recipe without having to polymer modify the bitumen. Experimental work using various Pelletpave contents was carried out at Kuwait Institute for Scientific Research (KISR) to design an optimum rubberized HMA formulation prior to conducting a pilot-scale road trial. With the aid of a gyratory compactor, the compaction and volumetric properties of HMAs containing 2.5% and 3.0% Pelletpave additive were investigated at a range of bitumen contents, all by mass of total mix.

Keywords: modified bitumen, rubberized hot mix asphalt, gyratory compaction, volumetric properties

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Authors: John Tolentino, Yong Seok Park

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There are currently many people living with limb loss in the USA. The main causes for amputation can range from vascular disease, to trauma, or cancer. This number is expected increase over the next decade. Many patients have a single prosthetic for the first year but end up getting a second one to accommodate their changing physique. Afterwards, the prosthesis gets replaced every three to five years depending on how often it is used. This could cost the patient up to $500,000 throughout their lifetime. Complications do not end there, however. Due to the absence of nerves, it becomes more difficult to traverse terrain with a prosthetic. Moving on an incline or decline becomes difficult, thus curbs and stairs can be a challenge. Certain physical activities, such as cycling, could be even more strenuous. It will need to be relearned to accommodate for the change in weight, center of gravity, and transfer of energy from the leg to the pedal. The purpose of this research project is to develop a new, alternate below-knee cycling prosthetic using Dieter & Schmidt’s design process approach. It will be subjected to fatigue analysis under dynamic loading to observe the limitations as well as the strengths and weaknesses of the prosthetic. Benchmark comparisons will be made between existing prosthetics and the proposed one, examining the benefits and disadvantages. The resulting prosthetic will be 3D printed using acrylonitrile butadiene styrene (ABS) or polycarbonate (PC) plastic.

Keywords: 3D Printing, Cycling, Prosthetic design, Synthetic design.

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Authors: Isil Kerti, Onur Okur, Sibel Daglilar, Recep Calin

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Particulate reinforced aluminium matrix composites have gained more importance in automotive, aeronautical and defense industries due to their specific properties like as low density, high strength and stiffness, good fatigue strength, dimensional stability at high temperature and acceptable tribological properties. In this study, 2014 Aluminium alloy used as a matrix material and B₄C and SiC were selected as reinforcements components. For production of composites materials, vacuum infiltration method was used. In the experimental studies, the reinforcement volume ratios were defined by mixing as totally 10% B₄C and SiC. Aging treatment (T6) was applied to the specimens. The effect of T6 treatment on hardness was determined by using Brinell hardness test method. The effects of the aging treatment on microstructure and chemical structure were analysed by making XRD, SEM and EDS analysis on the specimens.

Keywords: metal matrix composite, vacumm infiltration method, aluminum metal matrix, mechanical feature

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Authors: Jinu Phonamontham

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Coronavirus, also referred to as COVID-19, is a virus caused by the SARS-Cov-2 virus. The pandemic has caused over 10 million cases and 500,000 deaths worldwide through the end of June 2020. In a previous study, HLA-DQA1*01:02 allele was associated with COVID-19 disease (p-value = 0.0121). Furthermore, there was a statistical significance between HLA- DQB1*06:02 and COVID-19 in the Italian population by Bonferroni’s correction (p-value = 0.0016). Nevertheless, there is no data describing the distribution of HLA alleles as a valid marker for prediction of COVID-19 in the Thai population. We want to investigate the prevalence of HLA-DQA1*01:02 and HLA-DQB1*06:02 alleles that are associated with severe COVID-19 in the Thai population. In this study, we recruited 200 healthy Thai individuals. Genomic DNA samples were isolated from EDTA blood using Genomic DNA Mini Kit. HLA genotyping was conducted using the Lifecodes HLA SSO typing kits (Immucor, West Avenue, Stamford, USA). The frequency of HLA-DQA1 alleles in Thai population, consisting of HLA-DQA1*01:01 (27.75%), HLA-DQA1*01:02 (24.50%), HLA-DQA1*03:03 (13.00%), HLA-DQA1*06:01 (10.25%) and HLA-DQA1*02:01 (6.75%). Furthermore, the distributions of HLA-DQB1 alleles were HLA-DQB1*05:02 (21.50%), HLA-DQB1*03:01 (15.75%), HLA-DQB1*05:01 (14.50%), HLA-DQB1*03:03 (11.00%) and HLA-DQB1*02:02 (8.25%). Particularly, HLA- DQA1*01:02 (29.00%) allele was the highest frequency in the NorthEast group, but there was not significant difference when compared with the other regions in Thais (p-value = 0.4202). HLA-DQB1*06:02 allele was similarly distributed in Thai population and there was no significant difference between Thais and China (3.8%) and South Korea (6.4%) and Japan (8.2%) with p-value > 0.05. Whereas, South Africa (15.7%) has a significance with Thais by p-value of 0.0013. This study supports the specific genotyping of the HLA-DQA1*01:02 and HLA-DQB1*06:02 alleles to screen severe COVID-19 in Thai and many populations.

Keywords: HLA-DQA1*01:02, HLA-DQB1*06:02, Asian, Thai population

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Authors: Adnan Z. Mkhelif

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Grammatical collocations (GCs) are word combinations containing a preposition or a grammatical structure, such as an infinitive (e.g. smile at, interested in, easy to learn, etc.). Such collocations tend to be difficult for Iraqi EFL university students (IUS) to master. To help address this problem, it is important to identify the factors causing it. This study aims at investigating the effects of L2 proficiency, frequency of GCs and their transparency on IUSs’ productive knowledge of GCs. The study involves 112 undergraduate participants with different proficiency levels, learning English in formal contexts in Iraq. The data collection instruments include (but not limited to) a productive knowledge test (designed by the researcher using the British National Corpus (BNC)), as well as the grammar part of the Oxford Placement Test (OPT). The study findings have shown that all the above-mentioned factors have significant effects on IUSs’ productive knowledge of GCs. In addition to establishing evidence of which factors of L2 learning might be relevant to learning GCs, it is hoped that the findings of the present study will contribute to more effective methods of teaching that can better address and help overcome the problems IUSs encounter in learning GCs. The study is thus hoped to have significant theoretical and pedagogical implications for researchers, syllabus designers as well as teachers of English as a foreign/second language.

Keywords: corpus linguistics, frequency, grammatical collocations, L2 vocabulary learning, productive knowledge, proficiency, transparency

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Authors: M. Vadivel, R. Ramesh Babu

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Spinel ferrite magnetic nanomaterials have received a great deal of attention in recent years due to their wide range of potential applications in various fields such as magnetic data storage and microwave device applications. Among the family of spinel ferrites, cobalt ferrite (CoFe2O4) has been widely used in the field of high-frequency applications because of its remarkable material qualities such as moderate saturation magnetization, high coercivity, large permeability at higher frequency and high electrical resistivity. For aforementioned applications, the materials should have an improved electrical property, especially enhancement in the dielectric properties. It is well known that the substitution of rare earth metal cations in Fe3+ site of CoFe2O4 nanoparticles leads to structural distortion and thus significantly influences the structural and morphological properties whereas greatly modifies the electrical and magnetic properties of a material. In the present investigation, we report on the influence of lanthanum (La3+) ion substitution on the structural, morphological, dielectric and magnetic properties of CoFe2O4 magnetic nanoparticles prepared by co-precipitation method. Powder X-ray diffraction patterns reveal the formation of inverse cubic spinel structure with the signature of LaFeO3 phase at higher La3+ ion concentrations. Raman and Fourier transform infrared spectral analysis also confirms the formation of inverse cubic spinel structure and Fe-O symmetrical stretching vibrations of CoFe2O4 nanoparticles, respectively. Transmission electron microscopy study reveals that the size of the particles gradually increases with increasing La3+ ion concentrations whereas the agglomeration gets slightly reduced for La3+ ion substituted CoFe2O4 nanoparticles than that of undoped CoFe2O4 nanoparticles. Dielectric properties such as dielectric constant and dielectric loss were recorded as a function of frequency and temperature which reveals that the dielectric constant gradually increases with increasing temperatures as well as La3+ ion concentrations. The increased dielectric constant might be the reason that the formation of LaFeO3 secondary phase at higher La3+ ion concentrations. Magnetic measurement demonstrates that the saturation magnetization gradually decreases from 61.45 to 25.13 emu/g with increasing La3+ ion concentrations which is due to the nonmagnetic nature of La3+ ions substitution.

Keywords: cobalt ferrite, co-precipitation, dielectric properties, saturation magnetization

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Authors: El Miloudi Djelloul

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Based on analysis on applications by perception control technology in computer network security status and security protection measures, from the angles of network physical environment and network software system environmental security, this paper provides network security system perception control solution using Internet of Things (IOT), telecom and other perception technologies. Security Perception Control System is in the computer network environment, utilizing Radio Frequency Identification (RFID) of IOT and telecom integration technology to carry out integration design for systems. In the network physical security environment, RFID temperature, humidity, gas and perception technologies are used to do surveillance on environmental data, dynamic perception technology is used for network system security environment, user-defined security parameters, security log are used for quick data analysis, extends control on I/O interface, by development of API and AT command, Computer Network Security Perception Control based on Internet and GSM/GPRS is achieved, which enables users to carry out interactive perception and control for network security environment by WEB, E-MAIL as well as PDA, mobile phone short message and Internet. In the system testing, through middle ware server, security information data perception in real time with deviation of 3-5% was achieved; it proves the feasibility of Computer Network Security Perception Control System.

Keywords: computer network, perception control system security strategy, Radio Frequency Identification (RFID)

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Authors: Jonida Hasanaj

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Abstract: Four years after the pandemic, numerous studies discuss the long-term effects of COVID-19 on patients, with chronic fatigue syndrome being a prominent concern. Understanding the mechanisms behind this syndrome is crucial for developing prevention, treatment, and rehabilitation strategies. The appropriateness of physiotherapeutic treatment in covid 19 and post-COVID-19 patients has remained uncertain due to inconsistent diagnostic criteria, highlighting the need for further research. This paper intends to offer guidelines and specific suggestions for hospital-based physical therapists managing COVID-19 hospitalized patients at ‘’Expert Physiotherapy’ and ’American Hospital’ in Albania using a national approach in accordance with worldwide initiatives. Several studies indicate that chronic tiredness syndrome and high intracranial pressure could result from failure of the post-Covid-19 lymphatic system. Enabling the patient to intensify their physical activity and enhance their ability to move, exercise, and even resume a regular life cycle is the aim of physiotherapy treatment.

Keywords: mobility, physiotherapy, post-covid 19, rehabilitation, results

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Authors: Renato Morbidelli, Carla Saltalippi, Alessia Flammini, Marco Cifrodelli, Corrado Corradini

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The trend of magnitude and frequency of extreme rainfalls seems to be different depending on the investigated area of the world. In this work, the impact of climate change on extreme rainfalls in Umbria, an inland region of central Italy, is examined using data recorded during the period 1921-2015 by 10 representative rain gauge stations. The study area is characterized by a complex orography, with altitude ranging from 200 to more than 2000 m asl. The climate is very different from zone to zone, with mean annual rainfall ranging from 650 to 1450 mm and mean annual air temperature from 3.3 to 14.2°C. Over the past 15 years, this region has been affected by four significant droughts as well as by six dangerous flood events, all with very large impact in economic terms. A least-squares linear trend analysis of annual maximums over 60 time series selected considering 6 different durations (1 h, 3 h, 6 h, 12 h, 24 h, 48 h) showed about 50% of positive and 50% of negative cases. For the same time series the non-parametrical Mann-Kendall test with a significance level 0.05 evidenced only 3% of cases characterized by a negative trend and no positive case. Further investigations have also demonstrated that the variance and covariance of each time series can be considered almost stationary. Therefore, the analysis on the magnitude of extreme rainfalls supplies the indication that an evident trend in the change of values in the Umbria region does not exist. However, also the frequency of rainfall events, with particularly high rainfall depths values, occurred during a fixed period has also to be considered. For all selected stations the 2-day rainfall events that exceed 50 mm were counted for each year, starting from the first monitored year to the end of 2015. Also, this analysis did not show predominant trends. Specifically, for all selected rain gauge stations the annual number of 2-day rainfall events that exceed the threshold value (50 mm) was slowly decreasing in time, while the annual cumulated rainfall depths corresponding to the same events evidenced trends that were not statistically significant. Overall, by using a wide available dataset and adopting simple methods, the influence of climate change on the heavy rainfalls in the Umbria region is not detected.

Keywords: climate changes, rainfall extremes, rainfall magnitude and frequency, central Italy

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Authors: Ching-Yuan Huang, Rhay-Hung Weng, Yi-Ting Chen

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Mentoring functions will improve new nurses' job performance, provide support with new nurses, and then reduce the turnover rate of them. This study explored the impact of transformational leadership and interpersonal interaction on mentoring functions. We employed a questionnaire survey to collect data and selected a sample of new nurses from three hospitals in Taiwan. A total of 306 valid surveys were obtained. Multiple regression model analysis was conducted to test the study hypothesis. Inspirational motivation, idealized influence, and individualized consideration had a positive influence on overall mentoring function, but intellectual stimulation had a positive influence on career development function only. Perceived similarity and interaction frequency also had positive influences on mentoring functions. When the shift overlap rate exceeded 80%, mentoring function experienced a negative result. The transformational leadership of mentors actually would improve the mentoring functions among new staff nurses. Perceived similarity and interaction frequency between mentees and mentors also had a positive influence on mentoring functions. Managers should enhance the transformational leadership of mentors by designing leadership training and motivation programs. Furthermore, nursing managers should promote the interaction between new staff nurses and their mentors, but the shift overlap rate should not exceed 80%.

Keywords: interpersonal interaction, mentoring function, mentor, new nurse, transformational leadership

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Authors: Svetlana Guryeva, Inna Kornienko, Andrey Usanov, Dmitry Usanov, Elena Petersen

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Every day cells in our organism are exposed to various factors: chemical agents, reactive oxygen species, ionizing radiation, and others. These factors can cause damage to DNA, cellular membrane, intracellular compartments, and proteins. The fate of cells depends on the exposure intensity and duration. The prolonged and intense exposure causes the irreversible damage accumulation, which triggers the permanent cell cycle arrest (cellular senescence) or cell death programs. In the case of low dose of impacts, it can lead to cell renovation and to cell functional state improvement. Therefore, it is a pivotal question to investigate the factors and doses that result in described positive effects. In order to estimate the influence of different agents, the proliferation index and levels of cell death markers (annexin V/propidium iodide), senescence-associated β-galactosidase, and lipofuscin were measured. The experiments were conducted on primary human fibroblasts of the 8th passage. According to the levels of mentioned markers, these cells were defined as senescent cells. The effect of low-frequency magnetic field was investigated. Different modes of magnetic field exposure were tested. The physical agents were compared with chemical agents: metformin (10 mM) and taurine (0.8 mM and 1.6 mM). Cells were incubating with chemicals for 5 days. The highest decrease in the level of senescence-associated β-galactosidase (21%) and lipofuscin (17%) was observed in the primary senescent fibroblasts after 5 days after double treatments with 48 h intervals with low-frequency magnetic field. There were no significant changes in the proliferation index after magnetic field application. The cytotoxic effect of magnetic field was not observed. The chemical agent taurine (1.6 mM) decreased the level of senescence-associated β-galactosidase (23%) and lipofuscin (22%). Metformin improved the activity of senescence-associated β-galactosidase on 15% and the level of lipofuscin on 19% in this experiment. According to these results, the effect of double treatment with 48 h interval with low-frequency magnetic field and the effect of taurine (1.6 mM) were comparable to the effect of metformin, for which anti-aging properties are proved. In conclusion, this study can become the first step towards creation of the standardized system for the investigation of different effects on senescent cells.

Keywords: biomarkers, magnetic field, metformin, primary fibroblasts, senescence, taurine

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Authors: Bharat Kumar, Deepak Kumar, Vijay Chaudhry

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Zirconium alloys are used as core components of nuclear reactors due to their high wear resistance, good corrosion properties, and good mechanical stability at high temperatures. Water flows inside the pressure tube through fuel claddings, which produces vibration of these core components and results in the wear of some components. Some components are subjected to the environment of coolant water containing LiOH which results in the corrosion of these components. The present work simulates some of these conditions to determine the failure mechanisms under these conditions and the effect of various parameters on them. Friction and wear experiments were performed varying the surrounding environment (room temperature, high temperature, and water submerged), duration, frequency, and displacement amplitude. Electrochemical corrosion experiments were performed by varying the concentration of LiOH in water. The worn and corroded surfaces were analyzed using scanning electron microscopy (SEM) to analyze the wear and corrosion mechanism and energy dispersive x-ray spectroscopy (EDS) and Raman spectroscopy to analyze the tribo-oxide layer formed during the wear and oxide layer formed during the corrosion. Wear increases with frequency and amplitude, and corrosion increases with LiOH concentration in water.

Keywords: zirconium alloys, wear, oxide layer, corrosion, EIS, linear polarization

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Authors: Liliia N. Butymova, Vladimir Ya Modorskii

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To ensure the gas transmittal GCU's efficient operation, leakages through the labyrinth packings (LP) should be minimized. Leakages can be minimized by decreasing the LP gap, which in turn depends on thermal processes and possible rotor vibrations and is designed to ensure absence of mechanical contact. Vibration mitigation allows to minimize the LP gap. It is advantageous to research influence of processes in the dynamic gas-structure system on LP vibrations. This paper considers influence of rotor vibrations on LP gas dynamics and influence of the latter on the rotor structure within the FSI unidirectional dynamical coupled problem. Dependences of nonstationary parameters of gas-dynamic process in LP on rotor vibrations under various gas speeds and pressures, shaft rotation speeds and vibration amplitudes, and working medium features were studied. The programmed multi-processor ANSYS CFX was chosen as a numerical computation tool. The problem was solved using PNRPU high-capacity computer complex. Deformed shaft vibrations are replaced with an unyielding profile that moves in the fixed annulus "up-and-down" according to set harmonic rule. This solves a nonstationary gas-dynamic problem and determines time dependence of total gas-dynamic force value influencing the shaft. Pressure increase from 0.1 to 10 MPa causes growth of gas-dynamic force oscillation amplitude and frequency. The phase shift angle between gas-dynamic force oscillations and those of shaft displacement decreases from 3π/4 to π/2. Damping constant has maximum value under 1 MPa pressure in the gap. Increase of shaft oscillation frequency from 50 to 150 Hz under P=10 MPa causes growth of gas-dynamic force oscillation amplitude. Damping constant has maximum value at 50 Hz equaling 1.012. Increase of shaft vibration amplitude from 20 to 80 µm under P=10 MPa causes the rise of gas-dynamic force amplitude up to 20 times. Damping constant increases from 0.092 to 0.251. Calculations for various working substances (methane, perfect gas, air at 25 ˚С) prove the minimum gas-dynamic force persistent oscillating amplitude under P=0.1 MPa being observed in methane, and maximum in the air. Frequency remains almost unchanged and the phase shift in the air changes from 3π/4 to π/2. Calculations for various working substances (methane, perfect gas, air at 25 ˚С) prove the maximum gas-dynamic force oscillating amplitude under P=10 MPa being observed in methane, and minimum in the air. Air demonstrates surging. Increase of leakage speed from 0 to 20 m/s through LP under P=0.1 MPa causes the gas-dynamic force oscillating amplitude to decrease by 3 orders and oscillation frequency and the phase shift to increase 2 times and stabilize. Increase of leakage speed from 0 to 20 m/s in LP under P=1 MPa causes gas-dynamic force oscillating amplitude to decrease by almost 4 orders. The phase shift angle increases from π/72 to π/2. Oscillations become persistent. Flow rate proved to influence greatly on pressure oscillations amplitude and a phase shift angle. Work medium influence depends on operation conditions. At pressure growth, vibrations are mostly affected in methane (of working substances list considered), and at pressure decrease, in the air at 25 ˚С.

Keywords: aeroelasticity, labyrinth packings, oscillation phase shift, vibration

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Authors: Theresa Veach, Erin Crisp

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It has been shown that traditional students flourish as a function of several factors including level of academic challenge, student/faculty interactions, active/collaborative learning, enriching educational experiences, and supportive campus environment. With the increase in demand for remote or online courses, factors that result in academic flourishing in the virtual classroom have become more crucial to understand than ever before. This study seeks to give insight into those factors that impact student learning, overall student wellbeing, and flourishing among college students enrolled in an online program. 4160 unique students participated in the completion of End of Course Survey (EOC) before final grades were released. Quantitative results from the survey are used by program directors as a measure of student satisfaction with both the curriculum and the faculty. In addition, students also submitted narrative comments in an open comment field. No prompts were given for the comment field on the survey. The purpose of this analysis was to report on the qualitative data available with the goal of gaining insight into what matters to students. Survey results from July 1st, 2016 to December 1st, 2016 were compiled into spreadsheet data sets. The analysis approach used involved both key word and phrase searches and reading results to identify patterns in responses and to tally the frequency of those patterns. In total, just over 25,000 comments were included in the analysis. Preliminary results indicate that it is the professor-student relationship, frequency of feedback and overall engagement of both instructors and students that are indicators of flourishing in college programs offered in an online format. This qualitative study supports the notion that college students flourish with regard to 1) education, 2) overall student well-being and 3) program satisfaction when overall engagement of both the instructor and the student is high. Ways to increase engagement in the online college environment were also explored. These include 1) increasing student participation by providing more project-based assignments, 2) interacting with students in meaningful ways that are both high in frequency and in personal content, and 3) allowing students to apply newly acquired knowledge in ways that are meaningful to current life circumstances and future goals.

Keywords: college, engagement, flourishing, online

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Authors: Chih-Hua Wu, Bang-Fuh Chen, Keryea Soong

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Midges can move on the surface of the water at speeds of approximately 340 body-lengths/s and can move continuously for >90 min. Their wings periodically scull the sea surface to push water backward and thus generate thrust; their other body parts, including their three pairs of legs, touch the water only occasionally. The aim of this study was to investigate the locomotion mechanism of marine midges with a size of 2 mm and living in shallow reefs in Wanliton, southern Taiwan. We assumed that midges generate lift through two mechanisms: by sculling the surface of seawater to leverage the generated tension for thrust and by retracting their wings to generate aerodynamic lift at a suitable angle of attack. We performed computational fluid dynamic simulations to determine the mechanism of midge locomotion above the surface of the water. The simulations indicated that ground effects are essential and that both the midge trunk and wing tips must be very close to the water surface to produce sufficient lift to keep the midge airborne. Furthermore, a high wing-beat frequency is crucial for the midge to produce sufficient lift during wing retraction. Accordingly, ground effects, forward speed, and high wing-beat frequency are major factors influencing the ability of midges to generate sufficient lift and remain airborne above the water surface.

Keywords: ground effect, water locomotion, CFD, aerodynamic lift

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Authors: Pawel Martynowicz

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Vibrations are a crucial problem for slender structures such as towers, masts, chimneys, wind turbines, bridges, high buildings, etc., that is why most of them are equipped with vibration attenuation or fatigue reduction solutions. In this work, a slender structure (i.e., wind turbine tower-nacelle model) equipped with nonlinear, semiactive tuned vibration absorber(s) is analyzed. For this study purposes, magnetorheological (MR) dampers are used as semiactive actuators. Several optimal-based approaches to structural vibration attenuation are investigated against the standard ‘ground-hook’ law and passive tuned vibration absorber(s) implementations. The common approach to optimal control of nonlinear systems is offline computation of the optimal solution, however, so determined open loop control suffers from lack of robustness to uncertainties (e.g., unmodelled dynamics, perturbations of external forces or initial conditions), and thus perturbation control techniques are often used. However, proper linearization may be an issue for highly nonlinear systems with implicit relations between state, co-state, and control. The main contribution of the author is the development as well as numerical and experimental verification of the Pontriagin maximum-principle-based vibration control concepts that produce directly actuator control input (not the demanded force), thus force tracking algorithm that results in control inaccuracy is entirely omitted. These concepts, including one-step optimal control, quasi-optimal control, and optimal-based modified ‘ground-hook’ law, can be directly implemented in online and real-time feedback control for periodic (or semi-periodic) disturbances with invariant or time-varying parameters, as well as for non-periodic, transient or random disturbances, what is a limitation for some other known solutions. No offline calculation, excitations/disturbances assumption or vibration frequency determination is necessary, moreover, all of the nonlinear actuator (MR damper) force constraints, i.e., no active forces, lower and upper saturation limits, hysteresis-type dynamics, etc., are embedded in the control technique, thus the solution is optimal or suboptimal for the assumed actuator, respecting its limitations. Depending on the selected method variant, a moderate or decisive reduction in the computational load is possible compared to other methods of nonlinear optimal control, while assuring the quality and robustness of the vibration reduction system, as well as considering multi-pronged operational aspects, such as possible minimization of the amplitude of the deflection and acceleration of the vibrating structure, its potential and/or kinetic energy, required actuator force, control input (e.g. electric current in the MR damper coil) and/or stroke amplitude. The developed solutions are characterized by high vibration reduction efficiency – the obtained maximum values of the dynamic amplification factor are close to 2.0, while for the best of the passive systems, these values exceed 3.5.

Keywords: magnetorheological damper, nonlinear tuned vibration absorber, optimal control, real-time structural vibration attenuation, wind turbines

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Authors: M. Münch, R. Brandt

Abstract:

Martensitic steels with an ultimate tensile strength beyond 2000 MPa are applied in the powertrain of vehicles due to their excellent fatigue strength and high creep resistance. However, the creep controlling mechanism in martensitic steels at ambient temperatures up to 423 K is not evident. The purpose of this study is to review the low temperature creep (LTC) behavior of martensitic steels at temperatures from 363 K to 523 K. Thus, the validity of a logarithmic creep law is reviewed and the stress and temperature dependence of the creep parameters α and β are revealed. Furthermore, creep tests are carried out, which include stepped changes in temperature or stress, respectively. On one hand, the change of the creep rate due to a temperature step provides information on the magnitude of the activation energy of the LTC controlling mechanism and on the other hand, the stress step approach provides information on the magnitude of the activation volume. The magnitude, the temperature dependency, and the stress dependency of both material specific activation parameters may deliver a significant contribution to the disclosure of the nature of the LTC rate controlling mechanism.

Keywords: activation parameters, creep mechanisms, high strength steels, low temperature creep

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Authors: Zoran Herceg, Višnja Stulić, Tomislava Vukušić, Anet Režek Jambrak

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High voltage electrical discharge is a new technology used for inactivation of pathogen microorganisms. Pathogen yeasts can cause diseases in humans if they are ingested. Nowadays new technologies have become the focus of researching all over the world. Rhodotorula is known as yeast that can cause diseases in humans. The aim of this study was to examine whether the high voltage electrical discharge treatment generated in gas phase has an influence on yeast reduction and recovery of Rhodotorula spp 74 in pure culture. Rhodotorula spp. 74 was treated in 200 mL of model solution. Treatment time (5 and 10 min), frequency (60 and 90 Hz) and injected gas (air or argon 99,99%) were changed. Titanium high voltage needle was used as high voltage electrode (positive polarity) through which air or argon was injected at the gas flow of 0.6 L/min. Experimental design and statistical analyses were obtained by Statgraphics Centurion software (StatPoint Technologies, Inc., VA, USA). The best inactivation rate 1.7 log10 reduction was observed after the 10 min of treatment, frequency of 90 Hz and injected air. Also with a longer treatment time inactivation rate was higher. After the 24 h recovery of treated samples was observed. Therefore the further optimization of method is needed to understand the mechanism of yeasts inactivation and cells recovery after the treatment. Acknowledgements: The authors would like to acknowledge the support by Croatian Science Foundation and research project ‘Application of electrical discharge plasma for preservation of liquid foods’.

Keywords: rhodotorula spp. 74, electrical discharge plasma, inactivation, stress response

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Authors: M. J. Suriani, F. Mansor, W. Siti Maizurah, I. Nurizwani

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Silicon Carbide (SiC) is one of the Silicon-based materials, which get interested by the researcher. SiC is an emerging semiconductor material, which has received a great deal of attention due to their application in high frequency and high power systems. Although its superior characteristic for a semiconductor material, its outstanding mechanical properties, chemical inertness and thermal stability has gained important aspect for a surface coating for deployment in extreme environments. Very high frequency (VHF)-PECVD technique utilized to deposit nano ns-SiC film in which variation in chamber pressure, substrate temperature, RF power and precursor gases flow rate will be investigated in order to get a good quality of thin film coating. Characterization of the coating performed in order to study the surface morphology, structural information. This performance of coating evaluated through corrosion test to determine the effectiveness of the coating for corrosion prevention. Ns-SiC film expected to possess better corrosion resistance and optical properties, as well as preserving the metal from the marine environment. Through this research project, corrosion protection performance by applying coating will be explored to obtain a great corrosion prevention method to the shipping and oil and gas industry in Malaysia. Besides, the cost of repair and maintenance spending by the government of Malaysia can be reduced through practicing this method.

Keywords: composite materials, marine corrosion, nano-composite, nano structure–coating

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Authors: Ali Siami, Masoud Asayesh, Asghar Najafi, Amirhosein Hamedanian

Abstract:

There are so many noise sources in power generation units that these sources can produce high-level sound noise. Therefore, sound noise reduction methods can assist these industries, especially in these days that laws related to environmental issues become more strict. In a typical power plant, so many machines and devices with high-level sound noise are arranged beside of each others. Therefore, the sound source identification and reducing the noise level can be very vital. In this paper, the procedure for designing, manufacturing and testing of a silencer-muffler used for a power plant steam vent is mentioned. This unit is placed near the residential area and so it is very important to reduce the noise emission. For this purpose, in the first step, measurements have done to identify the sound source and the frequency content of noise. The overall level of noise was so high and it was more than 120dB. Then, the appropriate noise control device is designed according to the measurement results and operational conditions. In the next step, the designed silencer-muffler has been manufactured and installed on the steam discharge of the ejector. For validation of the silencer-muffler effect, the acoustic test was done again in operating mode. Finally, the measurement results before and after the installation are compared. The results have confirmed a considerable reduction in noise level resultant of using silencer-muffler in the designed frequency range.

Keywords: silencer-muffler, sound noise control, sound measurement, steam ejector

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Authors: Barbosa M. L. S., von Ancken A. C. B., Coelho C. P.

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In order to improve the treatment of epileptic dogs, this case report aims toobjective todescribe the use of the homeopathic medicine Cicuta virosa for the treatmentof seizuresin dogs that already use allopathy to control them. Howeach patient presents symptoms individually, the choice of medicationhomeopathic treatment must also be individualized. He was treated in the municipality of RibeirãoPires, São Paulo - Brazil, an animal of the canine species, female, 7 years old, SRD, with a history of seizuregeneralized tonic-clonic for two years, with a variable frequency of 1-2 seizures perday. With no identifiable etiology, the patient used phenobarbital daily, and the dose ofmedication was increased according to the frequency of seizures. The serum concentration of phenobarbital within 12 hours of itsadministration via blood sample was within the range ofreference. The patient experienced weight gain and intermittent sedation. the choice ofhomeopathic medicine Cicuta virosa 6 cH, prepared according to the PharmacopoeiaBrazilian Homeopathic Medicine, occurred due to its characteristic action on the nervous system, especially in epileptic animals that present with seizures, spasmodic contractions of the muscles of the whole body starting from the head, mouth, extremely violent, with rigidity and opisthotonos, extreme agitation, contortionsmultiple. The animal was submitted to treatment with 2 globules orally twicea day for 30 days. The treatment resulted in a clinical cure as there was no moreseizures, being effective to control this symptom.

Keywords: homeopathy, cicuta virosa, epilepsy, veterinary medicine

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Authors: Roghieh A. Biroon, Zoleikha Abdollahi

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The recent growth of renewables, e.g., solar panels, batteries, and electric vehicles (EVs) in residential and small commercial sectors, has potential impacts on the stability and operation of power grids. Considering approximately 50 percent share of the residential and the commercial sectors in the electricity demand market, the significance of these impacts, and the necessity of addressing them are more highlighted. Utilities and power system operators should manage the renewable electricity sources integration with power systems in such a way to extract the most possible advantages for the power systems. The most common effect of high penetration level of the renewables is the reverse power flow in the distribution feeders when the customers generate more power than their needs. The reverse power flow causes voltage rise and thermal issues in the power grids. To overcome the voltage rise issues in the distribution system, several techniques have been proposed including reducing transformers short circuit resistance and feeder impedance, installing autotransformers/voltage regulators along the line, absorbing the reactive power by distributed generators (DGs), and limiting the PV and battery sizes. In this study, we consider a medium-scale battery energy storage to manage the power energy and address the aforementioned issues on voltage deviation and power loss increase. We propose an optimization algorithm to find the optimum size and location for the battery. The optimization for the battery location and size is so that the battery maintains the feeder voltage deviation and power loss at a certain desired level. Moreover, the proposed optimization algorithm controls the charging/discharging profile of the battery to absorb the negative power flow from residential and commercial customers in the feeder during the peak time and sell the power back to the system during the off-peak time. The proposed battery regulates the voltage problem in the distribution system while it also can play frequency regulation role in islanded microgrids. This battery can be regulated and controlled by the utilities or a third-party ancillary service provider for the utilities to reduce the power system loss and regulate the distribution feeder voltage and frequency in standard level.

Keywords: ancillary services, battery, distribution system and optimization

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Authors: Zhi Hao Chow, Cian Mulligan, Jack Walsh, Antonio Garzon Vico, Dimitar Krastev

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Drug development is resource-intensive, time-consuming, and increasingly expensive with each developmental stage. The success rates of drug development are also relatively low, and the resources committed are wasted with each failed candidate. As such, a reliable method of predicting the success of drug development is in demand. The hypothesis was that some examples of failed drug candidates are pushed through developmental pipelines based on false confidence and may possess common linguistic features identifiable through sentiment analysis. Here, the concept of using text analysis to discover such features in research publications and investor reports as predictors of success was explored. R studios were used to perform text mining and lexicon-based sentiment analysis to identify affective phrases and determine their frequency in each document, then using SPSS to determine the relationship between our defined variables and the accuracy of predicting outcomes. A total of 161 publications were collected and categorised into 4 groups: (i) Cancer treatment, (ii) Neurodegenerative disease treatment, (iii) Vaccines, and (iv) Others (containing all other drugs that do not fit into the 3 categories). Text analysis was then performed on each document using 2 separate datasets (BING and AFINN) in R within the category of drugs to determine the frequency of positive or negative phrases in each document. A relative positivity and negativity value were then calculated by dividing the frequency of phrases with the word count of each document. Regression analysis was then performed with SPSS statistical software on each dataset (values from using BING or AFINN dataset during text analysis) using a random selection of 61 documents to construct a model. The remaining documents were then used to determine the predictive power of the models. Model constructed from BING predicts the outcome of drug performance in clinical trials with an overall percentage of 65.3%. AFINN model had a lower accuracy at predicting outcomes compared to the BING model at 62.5% but was not effective at predicting the failure of drugs in clinical trials. Overall, the study did not show significant efficacy of the model at predicting outcomes of drugs in development. Many improvements may need to be made to later iterations of the model to sufficiently increase the accuracy.

Keywords: data analysis, drug development, sentiment analysis, text-mining

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Authors: Zayd Parekh, Amish Prasad, Baraa Souman

Abstract:

Postural orthostatic tachycardia syndrome (POTS) is characterized by orthostatic intolerance due to an exaggerated tachycardia in response to standing upright. This exaggerated orthostatic tachycardia is defined as the heart rate (HR) rising 30 beats above a baseline value while supine or seated within ten minutes. The tachycardia can lead to symptoms of orthostatic intolerance such as palpitations, lightheadedness, exercise intolerance, fatigue, and anxiety. POTS can go undiagnosed for many years due to its similarities with other cardiac and psychiatric conditions and nonspecific presentation, making it crucial to raise awareness for it in the medical field. The following case study discusses a 30-year-old female who was evaluated in the emergency room several times before being referred to the clinic for POTS. An overview of what tests are performed with this patient is also provided, highlighting the diagnostic work-up for POTS and the process of ruling out other differentials being considered. Finally, the epidemiology, the various theories regarding its pathophysiology, the diagnostic process, and pharmacological and non-pharmacological management for POTS are reviewed.

Keywords: orthostatic intolerance, postural orthostatic tachycardia syndrome, syncope, tachycardia

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