scholarly journals GENERAL ANALYSIS OF STRESS AND DEFORMATION OF PARTS MOVING WITH HIGH VELOCITY IN A LIQUID OR GAS (REVIEW ARTICLE)

2021 ◽  
pp. 71-76
Author(s):  
Mykola Prokopenko
Keyword(s):  
Working Conditions ◽  
Thermal Fatigue ◽  
Uniaxial Stress ◽  
Material Strength ◽  
High Speeds ◽  
Analytical Review ◽  
Stress And Deformation ◽  
The Relationship

The article provides an analytical review and analysis of stresses and deformations of parts moving at high speeds in a liquid or gas. The working conditions of materials and parts of turbines (blades, rotor and casing) operating at high temperatures and loads are analyzed. The main ways of solving the problem of ensuring the strength of such parts are presented. The main ways to solve the problem of reliability of parts or the product as a whole are given: mathematical modeling (calculated determination of strength, durability and reliability); physical modeling (model testing); testing of full-scale products in reproducible real or operational conditions.It is impossible to speak about the strength of a part only from the calculation of deformations and stresses, even taking into account their change over time, so it is necessary to have strength criteria that establish the relationship between the strength parameters. It is emphasized that in the general case, the criterion of strength should answer the question: will the part collapse or not with the known laws of change in time of stresses, strains and temperatures It is shown that the considered standard characteristics of creep and long-term strength can be directly used in calculations only for those parts in which the uniaxial stress state at constant stresses and temperature is realized, when the working conditions of the material fully meet the test conditions of materials.An analytical view of deformation diagrams is considered as the main means of carrying out practical calculations of material strength. It is shown that in order to determine the stresses and strains in parts that move at high speeds in a liquid or gas, it is necessary to take into account the model of parts exploitation, the processes of creep and thermal fatigue of the material, and the unsteadiness of load processes. Keywords: stresses and deformations of turbine parts; deformation diagram; operating model of turbine parts; creep and thermal fatigue; nonstationarity of loading processes  

An Experimental Investigation of the Feasibility of “Self-Sensing” Shape Memory Alloy Based Actuators

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
K. Malukhin ◽  
K. F. Ehmann
Keyword(s):  
Shape Memory ◽  
Working Conditions ◽  
Voltage Drop ◽  
The Self ◽  
Order System ◽  
System Response ◽  
Crystallographic Structure ◽  
The Relationship ◽  
Insulation Condition

Shape memory alloys (SMAs) change their crystallographic structure and shape during heating/cooling and, as a consequence, their electrical resistance also changes. This allows the determination of the location of a SMA-based structure in space without separate sensors by suitably measuring this change. In this paper, this “self-sensing” concept is explored in SMA wire-type actuators. Step responses, expressed in terms of resistance (voltage drop) across the wire, and the corresponding displacement changes during heating/cooling, were measured. It was shown that the relationship between the displacement and the voltage drop can be approximated by a linear regression with a correlation coefficient close to 1. System identification has shown that SMA wire actuator performance can be best approximated by first or by second order system response depending on the thermal insulation condition of the actuator. The resolution and the sensitivity of the self-sensing method were evaluated based on experimental data and it was shown that their minimal values were less than 1.7μm and 0.7μm, respectively, thus supporting the feasibility of the “self-sensing concept.” Both values exponentially increase with the increase in the range of the measured displacements whose magnitudes vary under different working conditions.

scholarly journals Evaluation of diagnostic thresholds dependability for tribologic signals received in the environment disturbed by vibroacoustic and functional signals

2015 ◽  
Vol 36 (1) ◽  
pp. 17-32
Author(s):  
Paweł Lindstedt ◽  
Marek Zboiński ◽  
Maciej Deliś ◽  
Jerzy Manerowski
Keyword(s):  
Working Conditions ◽  
Operation Time ◽  
Working Environment ◽  
Cauchy Product ◽  
Diagnostic Thresholds ◽  
Diagnostic Threshold ◽  
Complete Set ◽  
The Relationship ◽  
Insufficient Number

Abstract Determination of dependable diagnostic thresholds for tribologic signals received e.g. from antifriction bearings (in particular for insufficient number of measurements, only 4÷5) is a really difficult task due to complexity of working environment where such bearings are operated. Typical working environment for such objects must take account for operation time under various working conditions and accompanying (and disturbing) signals, e.g. vibroacoustic ones. The sought assessment of the relationship between diagnostic signals and environmental noise can be determined from convolution of both diagnostic and environments signals that make up the complete set of received information. The convolution of these two series of signals can be obtained from an algorithm based on the Cauchy product. Then one has to find the coherence factor and the square of amplitude gain for the set of diagnostic signals with reference to various sets of signals received from environment, which makes it possible to evaluate cohesion of the investigated series of signals, thus their suitability to determine diagnostic threshold for tribologic signals intended for the analysis.

scholarly journals PROFILING OF ISLAMIC CALLIGRAPHY SCRIPTS USED FOR ARCHITECTURAL DECORATION OF MASJID IN PENINSULAR MALAYSIA

2020 ◽  
Vol 18 (14) ◽  
Author(s):  
Zumahiran Kamarudin ◽  
Ziad Baydoun ◽  
Nik Ahmed Mazlan Nik Mahidin
Keyword(s):  
Peninsular Malaysia ◽  
Kuala Lumpur ◽  
Face To Face ◽  
Decorative Art ◽  
The Past ◽  
Analytical Review ◽  
Architecture Style ◽  
The Relationship ◽  
Further Development

In Malaysia, the introduction of the Islamic calligraphy, especially after the spread of Islam in the 14th century has impacted on the further development of decorative art in the built environment. While Islamic calligraphy has witnessed significant developments in the past decades, it still lacks a profiling classification system of calligraphy scripts that give impact to the contemporary mosque. The objectives of the study are to analyse the visual qualities of the calligraphy scripts in the mosque components and its compositional categories and to determine the relationship between the calligraphy placement and the mosque architecture within the interior and exterior fabrics of the buildings. This research involved an analytical review of the Islamic calligraphy found in the 10 selected mosques in Selangor and Kuala Lumpur, Malaysia and their depiction in various components. Face-to-face interviews with the mosque authorities and local calligraphers on the types and styles of scripts used in the mosque components were conducted as a complementary measure to the analytical method. The analysis reveals the application of cursive and angular style of scripts, fabricated in specified shapes, sizes and dimensions of the mosque components. Selection and depiction of calligraphy, especially in Thuluth and Kufi scripts suggest their strong preference to the traditional major styles ranging from its composition to the determination of its positional layout regardless of differences in the mosque architecture style.

Rubidium Sulfate Flame Detector: Effect of Design of Alkali Source and Anode on Sensitivity and Stability

1969 ◽  
Vol 52 (3) ◽  
pp. 533-541
Author(s):  
Hiroko K DeLoach ◽  
D D Hemphill
Keyword(s):  
Detection System ◽  
Physical Stability ◽  
Optimum Conditions ◽  
Flame Detector ◽  
Short And Long Term ◽  
Rubidium Sulfate ◽  
Relationship Of ◽  
The Relationship

Abstract An improved alkali-flame detector using pure rubidium sulfate and an anode of new design were optimized for the quantitative determination of organophosphate pesticides. The performance of this detection system was evaluated for response to organophosphate standards, noise level, fluctuation of baseline, short- and long-term reproducibility at low pesticides levels, conditioning time of instrument, life and physical stability of alkali source, and required frequency of detector cleaning. Under optimum conditions the detector was sensitive to 1 pg pesticide standard. To define the parameters of the alkali flame detector, studies were made of different designs of the alkali source which influence flame configuration and the relationship of the position and shape of the anode to the flame. The most important parameter appears to be the method of introducing alkali vapor.

scholarly journals Experimental Determination of CO2 Diffusion Coefficient in a Brine-Saturated Core Simulating Reservoir Condition

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 540
Author(s):  
Zerong Li ◽  
Lei Yuan ◽  
Guodong Sun ◽  
Junchen Lv ◽  
Yi Zhang
Keyword(s):  
Diffusion Coefficient ◽  
Co2 Storage ◽  
Co2 Diffusion ◽  
Nacl Concentration ◽  
Reservoir Conditions ◽  
Temperature And Pressure ◽  
The Relationship ◽  
Crucial Part

CO2 diffusion coefficient plays a crucial part in saline aquifers for the CO2 storage and the safety of long-term sequestration. Therefore, it is particularly important to measure the diffusion coefficient accurately. As far as we know, there are currently no CO2 brine diffusion data in real cores under reservoir temperature and pressure conditions. In this paper, a study on the CO2 diffusion coefficient diffused in a brine-saturated Berea core along the radial direction was conducted at temperatures of 313.15 K to 373.15 K and pressures of 8 MPa to 30 MPa. On account of the experimental results, the effect of permeability, NaCl concentration, temperature and pressure on the CO2 diffusivity is analyzed. The results in this study indicate that the diffusion coefficient increases with increasing permeability, pressure and temperature and decreases with increasing NaCl concentration. However, the relationship between pressure and the diffusion coefficient is not linear. As the pressure gradually increases, the effect of pressure will become weak. In addition, an empirical correlation of the relationship between temperature–pressure and the CO2 diffusion coefficient could be obtained based on the experimental data. The data in this paper fill the blank on the study of the CO2 diffusivity in brine under reservoir conditions, which has positive significance for the study of supercritical CO2 diffusion in a brine-saturated core.

scholarly journals Impact of selected parameters on the loading process with cutting screw heads

2019 ◽  
Vol 2 (1) ◽  
pp. 249-256
Author(s):  
Tomasz Wydro
Keyword(s):  
Working Conditions ◽  
Cutting Process ◽  
Kinematic Parameters ◽  
Loading Process ◽  
Cutting Machine ◽  
Auxiliary Process ◽  
The Relationship

Abstract The article presents the influence of selected constructional and kinematic parameters of cutting screw heads on the loading process. The loading process is often referred to as an auxiliary process, because in the entire operation of the head the cutting process is considered dominant. Proper determination of the relationship between the cutting process and the loading process allows to understand how individual constructional and kinematic parameters of cutting heads and the cutting machine on which they are installed have an impact on each other. This knowledge gives potential users an opportunity to determine a reason for the lack of effective loading in the working conditions of a given wall. Besides construction and kinematic parameters, shielded loaders also have an impact on the loading process. The use of a shielded loader allows for improving the efficiency of the loading process, i.e. increasing the percentage of output loaded in the whole of the output transferred by the head.

Hubungan antara Lama Tidur dengan Akumulasi Kelelahan Kerja pada Dosen

1970 ◽  
Vol 2 (1) ◽  
Author(s):  
Gurdani Yogisutanti ◽  
Hari Kusnanto ◽  
Lientje Setyawati Maurits
Keyword(s):  
Sleep Duration ◽  
Working Conditions ◽  
Health And Safety ◽  
Job Burnout ◽  
Check List ◽  
Cross Sectional ◽  
Cross Sectional Design ◽  
The Relationship

Fatigue merupakan fenomena normal bagi setiap orang sehat, yang dapat dikurangi dengan istirahat maupun tidur. Kurang tidur (sleepiness) telah menjadi fokus masalah dalam isu kesehatan kerja. Penelitian kelelahan kerja pada dosen masih sangat terbatas dan belum menjadi perhatian. Tujuan penelitian untuk mengetahui hubungan lama waktu tidur dengan akumulasi kelelahan kerja pada dosen. Desain potong lintang digunakan dalam penelitian terhadap 236 partisipan berasal dari delapan sekolah tinggi ilmu kesehatan swasta di Jawa Barat. Lama waktu tidur per hari diukur menggunakan kuesioner dan akumulasi kelelahan kerja diukur menggunakan instrumen self-diagnosis check list for assessment of worker’s accumulated fatigue. Rerata waktu tidur adalah 6,23±1,1 jam per hari. Hasil uji statistik menggunakan uji korelasi product moment didapatkan lama waktu tidur berkorelasi negatif dengan gejala kelelahan subjektif (r=-0.132; p<0.05), kondisi kerja (r=-0.169; p<0.05), dan akumulasi kerja (r=-0.173; p<0.05). Semakin tinggi lama tidur, maka semakin rendah kelelahan kerja yang terjadi. Kurangnya waktu tidur dalam jangka waktu yang lama dapat berakibat pada kualitas hidup dosen dan dapat menyebabkan sakit. Perlunya mengurangi akumulasi kelelahan kerja agar cukup waktu tidur dan beristirahat bagi dosen. Kata kunci:Dosen, fatigue, kelelahan kerja, makan pagi, waktu tidur AbstractFatigue is a normal phenomenon for everybody, it can be reduced by rest and sleep. Sleepiness is a health issue in the occupational health and safety. However, a study related to job burnout in the lecturer community is limited. The aims of this study was to uncover the relationship between lecturers’ sleep duration and their job burnout. The cross sectional design was applied to 236 participants who came from eight different private Health Sciences School in West Java. Sleep durations were measured by a questionnaire and Self-diagnosis Check List for Assessment of Worker’s accumulated fatigue was used to measure lecturers’ job burnout. Results have shown that rates of the sleep duration in a day were around 6,23±1,1 hours. Product moment test has shown that the sleep duration had negative correlation with subjective fatigue (r=-0.132; p<0.05), working conditions (r=-0.169; p<0.05), and working accumulation (r=-0.173; p<0.05). The more sleep duration the lower job burnout. Long term sleepiness can be affected to lecturers’ quality of live. Enough rest and sleep are the best way to deal with job burnout problems.Key words:Breakfast, fatigue, job burnout, lecturer, sleep duration

Physics and Metrology

2017 ◽  
Author(s):  
Kathryn M. Olesko
Keyword(s):  
Electrical Resistance ◽  
Moral Values ◽  
Thomas Kuhn ◽  
History Of ◽  
Historical Issues ◽  
The Relationship

This article traces the history of the relationship between physics and metrology, or physical metrology. It first examines how metrology became a part of the concerns of historians of science, and particularly physics, citing the work of Alexandre Koyré, Thomas Kuhn, and Witold Kula. It then describes various approaches to physics and metrology, focusing on the construction of a standard of length based on the seconds pendulum and the determination of the unit of electrical resistance. It also discusses broader historical issues in physics and metrology, including labour practices in physics, physics pedagogy, long-term processes of modernity (bureaucratization, industrialization, and the construction of empires), and the moral and ethical connotations of standards of measure. It shows that moral values became intertwined with metrology, especially in the British context.

scholarly journals 2.2.3 The Long Term Population of Interplanetary Micrometeoroids

1976 ◽  
Vol 31 ◽  
pp. 232-232
Author(s):  
G. Poupeau ◽  
R.M. Walker ◽  
E. Zinner ◽  
D. Morrison
Keyword(s):  
Solar Flare ◽  
Free Space ◽  
Lunar Regolith ◽  
Lunar Soil ◽  
The Past ◽  
Ion Probe ◽  
Space Data ◽  
The Relationship

Three problems will be discussed: A) The relationship between mlcro-meteoroids and solar flare particles averaged over the recent geologic past (~1 my); B) the past record of this relationship as measured in lunar soils and lunar and meteoritic breccias; C) the determination of the time at which different extraterrestrial samples were exposed to free space. Data bearing on these points obtained from studies of special lunar rocks and from measurements on individual crystals removed from lunar cores will be presented. Progress in using ion-probe mass spectrometry to link measurements of micro-impact craters with the past properties of the solar wind will also be discussed. Comparing microcraters and solar flare tracks in individual crystals from lunar cores, we find no evidence of any extraordinary variations for a time span covering an interval of ~109 yrs. Crystals 100µ to 400µ in size in mature lunar soil samples appear to have been exposed 3 to free space at the top of the lunar regolith for times from 103 to 104 yrs.

scholarly journals The Relationship between Hope and Perceived Stress in Teacher Candidates

2019 ◽  
Vol 8 (2) ◽  
pp. 1
Author(s):  
Serdar Sucan
Keyword(s):  
Perceived Stress ◽  
Personnel Selection ◽  
Teacher Candidates ◽  
Negative Effects ◽  
Positive Effects ◽  
Preparatory Course ◽  
High Level ◽  
The Relationship

The long-term and uncontrollable stress of KPSS (Personnel Selection Examination) candidates disrupts their psychology, weakens thinking and decision-making, and thus decreases academic achievement. The aim of this study is; It is the determination of the relationship between the level of hope and perceived stress of teacher candidates prepared for KPSS.A total of 382 teacher candidates participated in a special KPSS preparatory course in Kayseri. Candidate teachers who graduated from different departments and universities are between the ages of 21-25 in 41.6%. When we look at socio-demographic characteristics; 68.4% male; 59.9% single and 51.5% were at medium income level. Perceived Stress Scale (PSS-10) and Adult Hope Scale (AHS) were administered to the participants. The mean AHS score of the teacher candidates was 27.73±1.92. This shows the high level of hope of the participants. Perceived Stress level was found to be medium at 53.6%. As a result of the analysis, a significant a negative correlation was found between level of hope and perceived stress (p <0.01). According to regression analysis, level of hope in teacher candidates showed a statistically significant positive effect on perceived stress (p <0.01).As a result, negative relationships were found between hope and perceived stress. It is thought that highly hopeful people perceive stress lower and life satisfaction increases. Therefore, in order to increase the level of hope and to reduce the negative effects of stress, educators should support KPSS candidates. Programs related to the high level of hope to be implemented in schools may have positive effects on individuals' low stress and examinations.

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