scholarly journals CONDITIONAL OPTIMIZATION MATHEMATICAL MODEL OF THE ASPHALT CONCRETE MIXTURE GRADING

2002 ◽  
Vol 8 (2) ◽  
pp. 125-132
Author(s):  
Henrikas Sivilevičius ◽  
Valentinas Podviezko
Keyword(s):  
Mathematical Model ◽  
Asphalt Concrete ◽  
Optimization Method ◽  
Concrete Mixture ◽  
Mass Ratio ◽  
First Time ◽  
Model Algorithm ◽  
Purification Equipment ◽  
Conditional Optimization

A new partial conditional optimization method which enables to select the best ratio of imported fillers not only while designing the composition of asphalt concrete mixture but also while adjusting the composition of the produced asphalt concrete mixture according to the actual quality of hot fractions is presented. The constructed mathematical model, algorithm and the solved task prove that irrespective of the number of fillers (from 2 to 7 and more) the ratio of their mass can be selected which enables to produce an asphalt concrete mixture which meets the requirements of the composition project best. The mass ratio λ of imported fillers A 1 and reclaimed dust A 2, which settled and accumulated in the dry purification equipment of an asphalt concrete plant presented in Regulations DAT.AD-96 was taken into account for the first time. Methodological scientific novelty and a possibility to apply it in practice can improve the control of asphalt concrete mixture production.

scholarly journals Karakteristik Marshall Pada Campuran Asphalt Concrete – Wearing Course (AC-WC) Dengan Penambahan Styrofoam

2019 ◽  
Vol 8 (2) ◽  
pp. 51-62
Author(s):  
Ika Sulianti ◽  
Ibrahim Ibrahim ◽  
Agus Subrianto ◽  
Adelia Monita ◽  
Medici Medici
Keyword(s):  
Asphalt Concrete ◽  
Asphalt Pavement ◽  
Flexible Pavement ◽  
Asphalt Mixtures ◽  
Concrete Mixture ◽  
Pavement Performance ◽  
Food Container ◽  
Optimum Stability ◽  
Marshall Test

Styrofoam waste presents the environment issue because it is difficult to decompose. As an effort to recycle this pollutant, styrofoam can be utilized as an additive in asphalt concrete mixture. The use of additives aims to create a flexible pavement layer having good performance and meet the requirements. The purpose of this study is to find out whether the addition of styrofoam can improve the quality of asphalt mixtures, and look for alternative additives that can increase asphalt pavement performance. In this study, researchers used food container styrofoam as an addition and incorforated into Asphalt Concrete Wearing Course (AC-WC) mixture. The styrofoam content was 6.5%; 6.75%; 7% ; 7.25%; and 7.5% of asphalt weight. The optimum asphalt contentused is 5.5%. The value of the optimum stability was 3126,002 kg, found at 7.25% of styrofoam content. The best results of Marshall test was obtained at 6.5% of styrofoam content  with stability value  1362,045 kg, VIM value 4,96%, VMA 15,025%, VFA 67,800%, flow 3,44 mm, and MQ 416,338 kg / mm.

Study of the Effect of Hot Gas on Atomization Quality of Spray Forming

2013 ◽  
Vol 774-776 ◽  
pp. 1190-1193
Author(s):  
Qing Yang ◽  
Ying Dong Qu ◽  
Rui Ming Su ◽  
Bing Kun Zheng ◽  
Yu Sheng Wu
Keyword(s):  
Mathematical Model ◽  
Grain Size ◽  
Grain Shape ◽  
Spray Forming ◽  
Forming Process ◽  
Hot Gas ◽  
Average Grain Size ◽  
Calculation Results ◽  
First Time

In the spray forming process, the atomizing quality is not very good under the low pressure. This article attempts to improve the quality of atomization through heating the gas. A mathematical model is built and calculated according to the existing knowledge, and then the influence of airflow temperature in the spray forming is theoretical calculated and analyzed. The experimental results show that the average grain size is 54μm when the gas is not heated; the average grain size is 39 μm which decreases by 27.7% than airflow unheated when the gas is heated to 150 °C. The calculation results show that when the gas is not heated, the first time atomization grain size is 201 μm, the second time atomization grain size is 15 μm, the total atomization time is 92 μs. And the velocity of atomization droplets is 80 m/s; when the airflow temperature is 150°C, the above results are 131 μm, 10 μm, 76 μs and 127 m/s respectively, the atomization quality has a certain improvement compared to the unheated condition. At the same time, the grain shape becomes more round as the temperature of airflow increases, and the holes between the grains also become smaller.

scholarly journals THEORETICAL PRINCIPLES AND EXPERIMENTAL DATA TO IDENTIFY STABILITY OF ASPHALT CONCRETE COMPONENTS IN FINALLY DOSED MINERAL MATERIALS

Transport ◽  
2002 ◽  
Vol 17 (1) ◽  
pp. 19-29 ◽  
Author(s):  
Henrikas Sivilevičius
Keyword(s):  
Experimental Data ◽  
Asphalt Concrete ◽  
Concrete Mixture ◽  
Sand Particle ◽  
Regression Equations ◽  
Mineral Component ◽  
Mineral Components ◽  
Concrete Mixer ◽  
Mineral Powder

The duration of asphalt concrete functioning depends on the quality of the asphalt concrete mixture used to pave the road. Grading of hot fractions sieved through technological sieves of asphalt concrete mixture, their pollution with particles of different size as well as stability influence on the quality of an asphalt concrete mixture. Each j - (j = 1...., m) aggregate mineral material or mixture is made up of two (mineral powder, particle of size less than 0,09 or 0,071 mm, and sand, particle of size from 2 to 0,09 mm or 5-0,071 mm) or three (crushed stone, particle size is larger than 2 or 5 mm) mineral components (i = 1, ..., k) . When required technological operations of asphalt concrete mixture production are carried out, the quantity and stability of any i - component in mineral materials change when they move through an asphalt concrete mixer. The more stable the quantity of mineral components in mineral materials (especially in finally dosed) is, the more uniform the composition of asphalt concrete mixture is produced. The experiments showed that when asphalt concrete mixture is produced applying a traditional technology in an asphalt concrete mixer of model D-597, D-508-2A, D-645-3 andD-590, sieved hot fractions of 0–5 mm and 5–15 are polluted with particles of different size by more than 10 per cent; and this pollution is neither uniform nor stable. Following a well-known theory, an average quadratic deviation σ of arithmetic undersized particles sieved through laboratory sieves ~aggregate mineral materials is the greatest when their mean X makes up 50 per cent; therefore, hot fractions of 0–5 mm and 5–15 mm were produced on the experimental data obtained from production as well as regression equations σ = ƒ( X )of statistical indeces of cold mineral powder. The values of average quadratic deviations σ µij of mineral component quantities in those finally dosed mineral materials are obtained from curves drawn according to the regression equations. They can be used to estimate dispersion σ2 Gi of mineral component i in asphalt concrete mixture which depends on the accuracy and stability of technological factors of an asphalt concrete mixer.

scholarly journals CRITERIA AND METHODOLOGY OF COMPLEX EVALUATION OF BITUMINOUS CONCRETE MIXER QUALITY/ASFALTBETONIO MAIŠYTUVO KOKYBĖS KOMPLEKSINIO VERTINIMO KRITERIJAI IR METODIKA

2001 ◽  
Vol 7 (3) ◽  
pp. 213-223
Author(s):  
Henrikas Sivilevičius
Keyword(s):  
Mathematical Model ◽  
Concrete Mixture ◽  
Significance Level ◽  
Environmental Care ◽  
Expert Opinions ◽  
Complex Evaluation ◽  
Concrete Mixer ◽  
Care Economy ◽  
Bituminous Concrete

The structure and sequence of technological operations of mixers for bituminous concrete mixtures, functioning in Lithuanian bituminous concrete mixing plants have been analyzed. The problems, which are subject to interest by the owners of bituminous concrete mixers, have been systematized. The necessity and objectives of quality evaluation of the functioning bituminous concrete mixers have been proved. A new multi-criteria mathematical model for determining quality of bituminous concrete—consisting of the sum of 4 group indicators, which evaluate quality of bituminous concrete mixture production in the mixer, environmental care, economy and technological universality—has been provided. The following 9 criteria make up the mathematical model, which can be used for calculation of quality indicator K of the working bituminous concrete mixer: accuracy of the bituminous concrete mixture content, produced in the mixer, ie the conformity of its component quantity with the project requirements (s); its temperature conformity with the temperature determined (t); its homogeneity in the batch, described by the mixing quality of batched components (h); environmental care, when the air is polluted by pollutants, thrown out from bituminous concrete (aa); bituminous concrete mixture production expenses as for one ton of (gi); level of physical and moral wear of the mixer (nl); expenses, needed for its maintenance and reconstruction (rr); use of its capacity when producing bituminous concrete mixture (pn); as well as technological universality of bituminous concrete mixer, ie ability to produce mixtures of different types and marks (tu). Coefficients of significance (importance) of all criteria are determined, using expert research methods. For this purpose a questionnaire for respondents (experts) has been prepared, which was filled by 43 scientists and production specialists, who have good knowledge of technology of bituminous concrete mixture production. The high value of concordation coefficient (W = 0,719) has shown good coordination of expert opinions, because X 2 = 247,5 is much higher than critical X 2 kr value with ε = 8 freedom level and 1% of accepted significance level, which makes up only 20,09. The experts believe that the most important criteria, reflecting the quality of bituminous concrete mixture are S([Xbar] j = 8,60), H([Xbar] j = 7,58), t(Xj = 7,3o), following in the range is the criterion AA (Xmac;j = 4,95), TU([Xbar]j = 4,56), GI([Xbar]j= 3,91), NL([Xbar]j = 3,47), and at the end least important RR([Xbar]j = 2,44) and PN([Xbar]j = 2,19). total sum of criteria is 45. The bituminous concrete mixer quality change when using it has been provided. The relation of its quality coefficient K reduction rhythm and level of conformity with the requirements imposed and constantly getting stricter has been analyzed.

DETERMINATION OF THE OPTIMAL ORDER PORTFOLIO FROM THE MANY OF POSSIBLE

2021 ◽  
Vol 1 ◽  
pp. 98-104
Author(s):  
Maria V. Dykha ◽  
◽  
Nadezhda V. Gripinskaya ◽  
Maria Ya. Marko ◽  
Grigory G. Tsegelik ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Optimal Portfolio ◽  
Optimal Order ◽  
Government Programs ◽  
Manufactured Products ◽  
The Many ◽  
The Cost ◽  
First Time

The problem of optimal portfolio of purchase of products (services) at the enterprises from many possible ones is considered. In this setting, the problem is explored and solved for the first time using a simulation tool. A mathematical model of the problem is built and an algorithm for its solution is developed. When building a mathematical model, the following parameters are taken into account: the number of types of products / services purchased; the number of enterprises that produce the required products; the need for products of a certain type; the cost of manufacturing a unit of production of each type at each enterprise; generalized indicator of quality of manufactured products of each type at each enterprise; index of identified comparative advantages in the manufacture of products j-th enterprise; the general budget of funds allocated for the purchase of products (financing the manufacture of products). The developed mathematical model makes it possible to find the optimal result of distribution of the required volume of orders (purchases) of each type of products at different enterprises (or at one enterprise), which provides the maximum offered level of product quality, and product purchase costs do not exceed the planned level. To illustrate the results of the developed algorithm, the example shows the search for the best option for purchasing products of four types (meeting a specific need) at each of the five companies offering these types of products. The proposed algorithm is of interest for practical application, makes it possible to determine the optimal portfolio of purchases of products (semi-finished products, parts), to solve the problem of optimal "package" purchases / orders. It is advisable to use it in private business, in enterprises of various spheres of activity and forms of ownership, as well as at the macro level of the economy, in particular, in the process of finding optimal options for government programs.

scholarly journals Experimental investigation of an asphalt concrete mixture cooling characteristics with the aim of reducing heat loss during transportation from the asphalt plant to the roadbed construction site

2018 ◽  
Vol 5 (4) ◽  
Author(s):  
Khizar Dzhabrailov ◽  
Magomed-Emi Soltamuradov ◽  
Salam Gaziev
Keyword(s):  
Asphalt Concrete ◽  
Federal Budget ◽  
Concrete Mixture ◽  
Concrete Pavements ◽  
Existing Building ◽  
The Road ◽  
Existing Structures ◽  
Strict Compliance ◽  
Positive Effect

In connection with the sharp increase in the traffic flow, the problem of the durability of asphalt concrete pavements comes to the fore – their ability to maintain their properties within a certain period of time within certain limits. In many respects, the quality of future coverage is laid by the adaptability of the laying process, strict compliance with the requirements of project documentation and existing building codes and regulations (SNiP, GOST, ISO, etc.). However, the technology itself of the process of making asphalt concrete pavements is constantly evolving – new complexes are emerging, changes are being introduced to existing structures of machines for building coatings. Addition, reduction and combination of operations of the technological process, including, against the background of improving the quality and, as a result, the durability of the coating, reduce the complexity of the work performed, reduce the number of necessary staff – all of this has a positive effect on the economic component of construction, frees up additional funds. And, as you know, there is already enough evidence that the main factor hindering the development of the road network in the Russian Federation is, just the same, the need to spend huge budget funds (in 2016, about 30 billion rubles were allocated from the federal budget to repair existing roads due to their poor condition). In turn, the road-building industry, which is developing at a high pace, sets stringent requirements to ensure the required level of quality throughout the entire process, starting from the places of production of asphalt-concrete mixture (ABZ).

Communication Sciences and Disorders PhD Graduates' Perceptions of Their PhD Program

2020 ◽  
Vol 5 (2) ◽  
pp. 463-478
Author(s):  
Elizabeth Crais ◽  
Melody Harrison Savage
Keyword(s):  
Detailed Examination ◽  
Career Expectations ◽  
Doctoral Preparation ◽  
Creative Solutions ◽  
Phd Education ◽  
Doctor Of Philosophy ◽  
First Time ◽  
Students Success ◽  
Phd Program

Purpose The shortage of doctor of philosophy (PhD)–level applicants to fill academic and research positions in communication sciences and disorders (CSD) programs calls for a detailed examination of current CSD PhD educational practices and the generation of creative solutions. The intended purposes of the article are to encourage CSD faculty to examine their own PhD program practices and consider the perspectives of recent CSD PhD graduates in determining the need for possible modifications. Method The article describes the results of a survey of 240 CSD PhD graduates and their perceptions of the challenges and facilitators to completing a PhD degree; the quality of their preparation in research, teaching, and job readiness; and ways to improve PhD education. Results Two primary themes emerged from the data highlighting the need for “matchmaking.” The first time point of needed matchmaking is prior to entry among students, mentors, and expectations as well as between aspects of the program that can lead to students' success and graduation. The second important matchmaking need is between the actual PhD preparation and the realities of the graduates' career expectations, and those placed on graduates by their employers. Conclusions Within both themes, graduate's perspectives and suggestions to help guide future doctoral preparation are highlighted. The graduates' recommendations could be used by CSD PhD program faculty to enhance the quality of their program and the likelihood of student success and completion. Supplemental Material https://doi.org/10.23641/asha.11991480

Multifactor mathematical model of criticality of welding process of products from aluminum- magnesium alloys

2020 ◽  
pp. 12-18
Author(s):  
F.A. Urazbahtin ◽  
A.YU. Urazbahtina
Keyword(s):  
Mathematical Model ◽  
Magnesium Alloy ◽  
Magnesium Alloys ◽  
Welding Process ◽  
Welding Equipment ◽  
Equipment Operation ◽  
Aluminum Magnesium Alloys ◽  
Aluminum Magnesium Alloy ◽  
Welding Materials

A multifactor mathematical model of the welding process of products from aluminum-magnesium alloys, consisting of 71 indicators that assess the quality of the weld, the welding process, costs, equipment operation and quality of the welded material. The model can be used to control and optimize the welding process of products from aluminum-magnesium alloys. Keywords welding, products, aluminum-magnesium alloy, indicators, process parameters, welding equipment, welding materials, electrode sharpening, lining [email protected]

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