ISTRAŽIVANJE UTJECAJA TEKUĆINA ZA HLAĐENJE/PODMAZIVANJE NA VELIČINU STRUJE REZNIH STROJEVA S DISKOM ZA TVRDE STIJENE

One of the most crucial steps in producing dimension rocks is the rock cutting process, which incurs a high cost. The amperage draw of rock cutting machines is a major cost factor of this production process. Determining the effect of factors, such as the machine’s operating configurations, mechanical and physical characteristics of the rock, and type of cooling/lubricant fluid, on the cutting machine’s performance can significantly reduce operational costs. This study evaluates the electrical current consumption of a disc cutting machine during the cutting of hard rocks for producing dimension rocks under different operating conditions and using different fluids for cooling/lubrication. For this purpose, a number of cutting tests were performed under different operating conditions (cutting depths of 0.5, 0.7, 1, and 1.3 cm and feed rates of 45, 60, 75, and 90 cm/min) with five cooling/lubrication fluids, including tap water, soap water with a ratio of 1:40 and 1:20, and a commercial cutting power (Abtarash) with a ratio of 30:10 and 15:10. After examining the relationship between operating parameters and the amperage draw of the cutting machine in the presence of five fluids, several linear and nonlinear multivariate statistical models were developed to predict the amperage draw of the cutting machine. The developed models were evaluated using the t-test and F-test statistical methods. The results showed that using the developed models, the amperage draw of the cutting machine can be accurately predicted from the properties of the cooling/lubrication fluid, including viscosity and pH.Jedan od najvažnijih koraka u obradi arhitektonsko-građevnoga kamena jest proces rezanja, koji uzrokuje visoku cijenu proizvodnje. Veličina električne struje kod strojeva za rezanje glavni je faktor troškova ovoga proizvodnog procesa. Određivanje radnih čimbenika, kao što su radne konfiguracije stroja, mehaničke i fizičke karakteristike stijene te vrsta tekućine za hlađenje/podmazivanje, na performanse stroja za rezanje može znatno smanjiti operativne troškove. Ovo istraživanje procijenilo je potrošnju električne struje reznoga stroja s diskom tijekom rezanja tvrdih stijena pri obradi arhitektonsko-građevnoga kamena u različitim radnim uvjetima i pri korištenju različitih tekućina za hlađenje/podmazivanje. Proveden je niz ispitivanja rezanja u različitim radnim uvjetima (dubine rezanja od 0,5, 0,7, 1 i 1,3 cm te brzine rezanje od 45, 60, 75 i 90 cm/min) s pet tekućina za hlađenje/podmazivanje, uključujući vodu iz slavine, sapunicu omjera 1 : 40 i 1 : 20 te komercijalni prah za rezanje (Abtarash) u omjeru 30 : 10 i 15 : 10. Nakon ispitivanja odnosa između radnih parametara i veličine struje reznoga stroja uz upotrebu pet tekućina razvijeno je nekoliko linearnih i nelinearnih multivarijantnih statističkih modela kako bi se predvidjela veličina struje reznoga stroja. Razvijeni modeli procijenjeni su statističkim metodama t-testa i F-testa. Rezultati su pokazali kako se pomoću razvijenih modela može točno procijeniti veličina struje stroja za rezanje iz svojstava tekućine za hlađenje/podmazivanje, uključujući viskoznost i PH

Design and cognitive evaluation of 6 dynamic lane departure warning symbols

<p><b>Objective</b>: Lane departure, caused by inattention, distraction, drowsiness, or any unusual driver behavior, is a typical risk threatening the driver as well as other road users. Accurate perception of such situations through effective warnings would help drivers to avoid serious consequences. With regard to critical functions of warning symbols for risk communication, the present study focused on providing effective and easily perceivable symbols, compatible with human cognitive capabilities. Thus, the main purpose of the present study was to design and cognitively appraise 6 newly designed dynamic symbols, candidates for a new type of lane departure warning system.</p> <p><b>Methods</b>: Simplicity, familiarity, concreteness, meaningfulness, and semantic closeness were the major assessment criteria, defining cognitive features by the earlier researchers in the field. A total number of 187 driving license applicants, with a mean age of 20.58 years (SD = 3.20), participated in the present survey. The participants rated cognitive features of the 6 dynamic symbols along a 0–100 scale.</p> <p><b>Results</b>: Significant main effect of the element factor type of the designed symbols on rating cognitive features revealed that the existence of car element was the best predictor for illustrating lane departure. The interaction of both element factor and location of element factor significantly affected the ratings. However, the location of element factor did not solely have any strong effect on the ratings. The results also demonstrated that semantic closeness received the highest overall mean score across symbols (M = 61.80), especially within the symbols that include the car element (M = 75.67). Moreover, a significant difference was observed between the average ratings of the cognitive features, despite the fact that a significant correlation was found between cognitive features.</p> <p><b>Conclusion</b>: The most considerable result of the current study was the match between the symbol with the highest ratings and the International Organization for Standardization (ISO)-related icon in appearance. Because previous studies demonstrated a strong correlation between comprehension scores of the symbol and both semantic closeness and meaningfulness, high-level comprehensibility of the best ranked symbol is expected.</p

Evaluation of the educational environments of undergraduate medicine and pharmacy programmes at the University of Zambia

Background:A Based on the World Health Organization’s reporting, over 1.25 million people die annually in traffic accidents worldwide. Traffic accidents are the ninth main cause of death worldwide, with an average age range of victims of 15 to 29. Broadly speaking, 90% of traffic accidents happen in the lowand middle-income countries that comprise 82% of the global population, and these countries account for half of the world’s vehicles. One of the goals of the National Road Traffic Knowledge Development Trustee is to plan and implement training courses (content design, design and implementation and evaluation) for target groups. To achieve this goal and due to the lack of academic programs on traffic safety in Iran, a single-credit course, “Safety and Traffic,” was developed to be run as a compulsory academic course in all universities across the country. Methods: This course was administered as a national pilot study in four phases and in 17 medical universities across the country. All experts and national authorities in the Ministry of Science and the Ministry of Health and Medical Education were requested to provide feedback. Afterwards, the results and comments were forwarded to the Supreme Council of Cultural Revolution for further investigation. Upon approval of the Council, the course will be implemented in all universities across the country. Results: Results from the pre-test showed that the level of students’ knowledge was low before attending the training courses. Surveys also revealed that the two items of “pedestrian safety” and “first aids in RTCs” were the most useful and applicable subjects. The percentage of wrong answers ranged from 61 to 98%. Conclusion: Considering the importance of traffic accidents and people’s role in traffic-related issues, it seems that it is necessary to provide university courses for traffic safety education