bluuebunny/crossref_metadata_2025 huggingface dataset:
Prospective mathematics teachers’ understanding of pedagogical knowledge: what and where it came from
Authors: Solekhah P , Retnawati H
Published: November 2019

Pedagogical Knowledge (PK) is one of teachers’ knowledge that important in teaching and learning process. Prospective mathematics teachers’ development in the PK is the key to its successful implementation. This research aims to describe prospective mathematics teachers’ understanding about PK and their opinions about university mathematics education courses that contribute. The research was a qualitative research using phenomenological approach. Data were collected through in-depth interview followed by focus group discussion (FGD) that involved 6 final-years mathematics education students and 5 professional teacher program students in Yogyakarta State University, both have done micro-teaching practice. The data were analysed by means of Cresswell’s step. The result of the study showed that prospective mathematics teachers have been able to explain PK and has mentioned the elements of PK. However, they had various opinions about which courses contribute to the development of their own PK. But, the implementation of these lectures still needs to be improved, such as advice from the prospective mathematics teacher, which is to expand teaching practices and update information about the system that applies in the school.
Implementation of Numbered Heads Together (NHT) type of cooperative learning to improve mathematical communication skills of eighth grade students of YKWI Pekanbaru MTs based on mathematical communication capability indicators
Authors: Wahyuni P
Published: November 2019

This study aims to improve students’ mathematical communication skills through the Implementation of Numbered Heads Together (NHT) Cooperative Learning. This research was a classroom action research with the subject of 20 eighth grade students. Data collection techniques in this study are using observation sheets and mathematical communication test questions. The results of this study indicate that there is an increase in students’ mathematical communication skills from the basic score to Cycle I, from cycle I to cycle II. The percentage of students’ mathematical communication ability on the baseline score was 36.87%, at cycle I was 47.5% and at cycle II was 72.81%. Based on the results of this study, it can be concluded that the application of Numbered Heads Together (NHT) cooperative learning can improve the mathematical communication skills of the eighth grade students.
Analysis of students’ financial literacy skills on mathematics teaching and learning
Authors: Mahmudi A , Listiyani D H
Published: November 2019

Life success requires a number of strategic skills, one of which is literacy skills, including financial literacy skills. Financial literacy skills is the possession of the set of skills and knowledge that allows an individual to make informed and effective decisions with all of their financial resources. Financial literacy skill is one of the basic skills to achieve a better life and avoid financial problems. Financial literacy consists of aspects of knowledge, skills and attitudes. This study describes the financial literacy of junior high school students in Gunung Kidul Regency Yogyakarta. The results of the study show that students’ financial attitudes for each aspect, namely confidence in financial planning and the tendency to save and not consumptive are categorized as good. Meanwhile, financial knowledge and skills in mathematics learning are also categorized as good. Students who have good financial knowledge tend to have good financial attitudes too.
How to Design Worked Examples for Learning Patterns in Mathematics
Authors: Rodiawati A , Retnowati E
Published: November 2019

Students will understand how to solve problems more meaningfully by instructions that reduce unproductive cognitive load. A worked example instruction has been proved by numerous research, to be effective for increasing novice student’s skills in solving problems. However, there might be different ways to design worked examples as it may depend on the learning topic. Also less is known on how to implement the instruction in real classroom since most of worked example research uses rigid experiment procedures. This study attempts to study how to create worked examples on the topic of patterns, which is learned at senior high school, including contextual problems related to arithmetic or geometric sequence patterns such as growth, decaying, compound interest, and annuity. These are considered difficult topics for students. Designs of worked examples for learning applications of patterns in mathematics as well as the lesson plan is explained using the perspective of the cognitive load theory. The result of the study provides examples to teachers that it is possible to apply the worked example instruction in a real classroom.
A study of junior high school students reasoning skill in mathematics
Authors: Wulandari S Y , Wutsqa D U
Published: November 2019

Mathematical reasoning skill is an ability that must be possessed by each student because it involves the ability to think logically and systematically. There are two types of tests to measure students’ skills in mathematics TIMSS and PISA. The purpose of this study is to investigate students reasoning skills to solve the tests that are similar to TIMSS and PISA model. The data were collected using 6 questions similar to TIMSS and PISA test from 27 Junior High School students. The data were analyzed through data reduction, data presentation, and data verification, to comprehensively measure students’ abilities for analyzing, generalizing, synthesizing, justifying, and solving a non-routine problem. The results show that there are students have good reasoning skills to analyze, to generalize, to synthesize, to justify, and to solve a non-routine problem (62.69%, 66.67%, 48.15%, 24.07%, and 3.70 respectively). There are some factors influence the different level of students reasoning skills including their ability to identify information in the question, use mathematical arguments to explain the answer and identify the strategy to solve problems.
Difficulties in learning algebra: An analysis of students’ errors
Authors: Pramesti T I , Retnawati H
Published: November 2019

Algebra is an important domain that first studied at the junior high school. This domain will be useful in obtaining the concept of another domain. However, learning algebra in the early grades has some challenges for students. This study aims to describe students’ difficulties when learning algebra in the early grade. This study is a qualitative research with phenomenology approach. Participants in this study are 65 students from junior high schools in Bantul Regency, Province of Special Region of Yogyakarta, Indonesia. The data collected used test. Data are analyzed using Milles & Huberman Model, with reduction, data display and verification. The results of the analysis show that students’ difficulties in learning algebra are (1) understanding the problem;(2) understanding meaning of variables and;(3) operation algebra. Therefore, the teachers’ strategy to teach algebra material have to developed to minimize students’ difficulties in learning algebra.
LSESC and Achievement Based Students’ Learning Outcome, Is There Any Different?
Authors: Maulina Y , Retnawati H
Published: November 2019

Student who have low socioeconomic status will get certificate that named LSESC (or SKTM in Bahasa). In the admission of high school student in Indonesia, there is student acceptance using LSESC that will be prioritized to be accepted. A high school accept students from LSESC and achievement based who will get same learning process. Because there are LSESC and achievement based, learning outcomes research is needed. This study aims to show the difference of LSESC and achievement based students’ learning outcome. This study is a descriptive explorative research using qualitative approach. Data were collected using learning outcome test and interview. Participants of this study were 18 LSESC based students, and 50 achievement based students. The result of the study showed that achievement based students’ learning outcome is higher than LSESC based students’ learning outcome.
Students’ Thinking in Solving Geometric Problems Based on PISA Levels
Authors: Murtiyasa B , Rejeki S , Setyaningsih R , Merdekawati A
Published: November 2019

The latest results of Programme for International Students assessment (PISA) shows that Indonesia is still on the bottom place among all participating countries. Therefore, this study aims at analysing students’ thinking in solving geometric problems based on PISA levels. This is a qualitative descriptive study involving 25 8thgraders of a private junior high school in Surakarta, Indonesia. The data collection is conducted using test and documentation. The data analysis is conducted in three stages namely data reduction, data display, and conclusion drawing/verification. Based on the analysis, it can be concluded that most students’ are categorizing in medium level of thinking (about 72%), less students are categorizing in high level of thinking (20%), and least students are categorizing in high level of thinking (8%). PISA level 1 and 2 are levels which are easily achieved by students. Whereas, PISA level 3-6 are levels which are difficultly achieved by students. This implies the importance of increasing students’ levels of thinking in solving mathematics problems, particularly geometric problems.
The Analysis of Correlation between Anxiety and Students’ Positive Attitudes toward Mathematic Using fuzzy Interval data and fuzzy correlation
Authors: Susanto H P , Sutarti T , Hafidah A S
Published: November 2019

In the present paper, we suggest the dimension that the statistical concept is based on uncertainty, in this case, the analysis of the correlation between anxiety and positive attitude towards Mathematics should employ a correlation analysis based on the fuzzy concept. However, far too little attention has been paid to this issue. Over past years, the anxiety and positive attitudes toward mathematics are usually explained using a crisp data. Both are usually using a correlation analysis based on statistical concepts. In certain conditions, a crisp data cannot expound a condition of a student; therefore the fuzzy interval data is used to overcome this problem. Fuzzy interval data is obtained from the data collection process using a fuzzy scale of mathematical anxiety and students’ positive attitudes toward mathematics. Moreover, the participants were recruited from 132 Vocational High School students. This research has shown that: (1) fuzzy interval data can expound the flexible and real variables of mathematical anxiety and positive attitude instead of the crisp data; (2) mathematical anxiety has a negative correlation at a moderate level with students’ positive attitudes toward mathematics; (3) the fuzzy correlation coefficients in the form of intervals provides benefits for researchers to determine the subjectivity of data analysis results, when compared to the correlation coefficient of Pearson correlation.
Scaffolding for international students in statistics lecture
Authors: Retnawati H , Apino E , Djidu H , Ningrum W P , Anazifa R D , Kartianom K
Published: November 2019

Statistics is one of the tools to draw generalization in conducting a research. However, university students still face various obstacles during statistics lectures. This study aimed to describe the students’ difficulties in learning statistics and strategies for scaffolding them. It was conducted with 12 international students from different majors who were enrolled in statistics lectures in Graduate School, Yogyakarta State University, Indonesia. It employed qualitative phenomenological research. The Cresswell’s model was used in data analysis covering data reduction, presentation, and verification. The data were collected through interviews and observations during 8 meetings of extra statistics lectures. The results indicated that the students’ obstacles in learning statistics were caused by several factors; they were not enrolled in Mathematics and Statistics lectures during their undergraduate study, and they found it hard to perform computation, run the software, understand mathematical symbols, relate one concept to others in hypothesis testing, and present analysis results in Bahasa. Various scaffolding can be taken by lecturers to overcome these problems.
Teachers’ Readiness in Implementing Lesson Study
Authors: Marsigit  , Retnawati H , Sugiman  , Ningrum R K
Published: November 2019

Improving educational quality by improving learning quality might be afforded through several initiatives and one of the initiatives is benefitting lesson study. With regards to the statement, the present study would like to describe the junior high school teachers’ readiness in implementing the lesson study in order to improve the learning quality of Mathematics. The study was a qualitative research that involved phenomenological approach. The data were gathered using open questionnaire and involving 12 junior high school teachers of Mathematics from the low, the moderate, and the high category in both the private and the public schools as the participants. The results of the study show that the teachers’ understanding toward the lesson study has still been partial. Most of the Mathematics teachers have theoretically understood the activities of the lesson study and some of these teachers have implemented the activities of the lesson study. Several obstacles that appear within the implementation of the lesson study are related to the teachers, the participants, and the availability of the facilities. Despite these obstacles, basically the teachers seek to implement the lesson study as one of the efforts for improving the learning quality and the learning results of Mathematics in the school Start your abstract here...
Teacher’s and prospective-teacher’s perceptions of mobile math game “Proadventure” implementation in mathematics learning
Authors: Bahauddin A , Setyaningrum W
Published: November 2019

Teaching mathematics through mobile games has been praised because of its potential as a motivating and engaging learning strategy. Yet, it is still a debatable issue in education and has received several criticisms. Modern teaching methods believe that involves student actively in the learning process may improve learning outcome. Although the current curriculum has design learning process to make students to be active in the classroom, but it does not adjust to the character of students in the 21st century. They are familiar with smartphones, internet, and mobile games. Mobile games are among the most popular application for student in primary schools and junior high schools. Student learning activities tend to be less because students are more interested in using their time to play games than to study from books. Theoretically, well designed gamification can improve learning, but qualitative investigations are required to disclose how a mobile game should be from teacher’s perceptions. This qualitative research aims to describe teacher’s and prospective-teacher’s perceptions on the use of mobile game “Proadventure”. Based on data collected via online questionnaires, the study acquires the possibility of the influence from the use of mobile games edutainment to support the process of learning mathematics.
Validity assessment of a multimedia based on cognitive load theory for undergraduate plane geometry learning
Authors: Triono M , Retnowati E
Published: November 2019

This paper discusses in particular how to assess the validity an android-based learning multimedia developed based on the Cognitive Load Theory (CLT) for a multimedia for learning plane geometry. The validation assessment uses two kinds of validation sheet. The first is for assessing the content of the learning material that includes three aspects; (1) The feasibility of content/material, (2) The feasibility of presentation, and (3) The compatibility with CLT in which the three of these aspects are divided into eleven indicators. These concern with how the multimedia manage intrinsic, extraneous and germane cognitive load. The second is for assessing the multimedia construction by android-based media experts, which also includes three aspects, namely (1) The feasibility of visual/display, (2) The feasibility of programming, and (3) The compatibility with CLT, these three aspects are divided into thirteen indicators for assessing the cognitive load factors. The validation was conducated by lecturers in the area of geometry and multiedia The quantitative data acquired from the experts (validators) assessment results then converted into qualitative data by referencing to the value conversion table. The test results of the developed learning multimedia validity are: the average total score by the material expert is 4.07 with “Very Good” validity criteria. The average total score by a media expert is 3.66 with “Good” validity criteria.
Multimedia: an alternative to improve self-regulated learning and mathematical problem-solving skills
Authors: Aadzaar R M , Widjajanti D B
Published: November 2019

A question is said to be a problem if it can’t be solved by routinely procedures and if it is not too challenging enough for the learners. Problem-solving skills are useful in finding answers and solutions to phenomena. One way to solve problems is through critical thinking. Students must learn how to think beyond their knowledge and it will serve as training in order to provide a solution in solving problems based on an appropriate and rational basis. Some problem-solving strategies can be used in solving mathematical problems such as self-regulated learning. Self-regulated learning can make students be more creative, responsible and have their own initiative in solving a problem without direct teacher assistance. With the progress of time, education seems to shift into a more advanced era. Education can be done anywhere and anytime to develop students’ potential. One of them is by using multimedia that will showcase the appearance of material by using sound, image, video, and animation to encourage students’ critical thinking skills for mathematical problem-solving. This article will discuss multimedia as an alternative to increase self-regulated learning in mathematical problem-solving.
Does the use of e-learning media with guided discovery method affect students’ understanding of mathematics concept?
Authors: Lu’luilmaknun U , Wutsqa D U
Published: November 2019

This study aims to discover whether the use of e-learning media with guided discovery method can affect students’ understanding of mathematics concept. The design of this study is quasi-experiment using two classes, namely the experimental class and the control class. The research subjects in this study were 79 eighth grade students. The instrument used is multiple choice tests of understanding mathematical concept. Learning in the experimental class uses e-learning media with guided discovery method while learning in the control class used guided discovery method only. The test results reveal that the understanding of students in mathematics concepts in the experimental class was better than that of the control class. Thus, it could be concluded that the use of e-learning media with guided discovery method does affects the understanding of students’ mathematics concept.
Flipped classroom in mathematics instruction: Teachers’ perception
Authors: Rachmawati V , Setyaningrum W , Retnawati H
Published: November 2019

Student-centered learning paradigm requires a learning model which is able to facilitate the students constructing their knowledge actively. The flipped classroom is a student-centered learning model that integrates technology in its implementation. This study aims to describe the teachers’ perception about the use of the flipped classroom model in mathematics instruction. The data were collected through an interview and were analyzed using qualitative methods. The subject of this study were five teachers from public and private schools in Yogyakarta. The result showed that the flipped classroom: (i) can motivate and make students active in learning mathematics; (ii) can train students’ critical thinking skill; (iii) can train students’ problem-solving skill. Besides, the use of the flipped classroom in mathematics instruction would be optimal when it is combined with the other learning methods, especially for the new learning topics that require a prior conceptual understanding.
Modules and their endomorphism rings
Authors: Susanto H , Irawati S , Hidayah I N , Irawati
Published: November 2019

Let R and S be a pair of equivalent rings. We will prove that if R has property that a pair of modules over R are isomorphic if and only if their endomorphism rings are isomorphic than S has same property, i.e. a pair of modules over S are isomorphic if and only if their endomorphism rings are isomorphic.
Ethnomathematics: humanistic learning to manage math anxiety
Authors: Nugroho Darwis Cahyo , Widjajanti Djamilah Bondan
Published: November 2019

Anxiety is one of someone emotion. Math anxiety will make a negative effect on student personality. Of course, this problem should not be left, because it will make a bad impact for next generation. One of learning approach that can manage math anxiety is by learning which regard the human side. Mathematical learning that regarding the human side of the student is called humanistic mathematical learning. This learning is recommended to make students enjoy in learning and pay more attention to their existence as humans in their learning environment. The school with strong tribal customs has problems in delivering material. Language is a major obstacle in delivering material. Furthermore, educators must use the local language to teach mathematics, it’s called ethnomathematics. Ethnomathematics appear as a bridge between formal mathematics and concrete mathematics around student culture. With ethnomathematics, students will be easier and more enjoyable when learning mathematics because the material is directly related to their culture in daily life. Therefore, ethnomathematics learning can help the teacher to manage math anxiety.
Making mathematics classes more humanistic
Authors: Widjajanti D B
Published: November 2019

Humanistic mathematics class is a class that can make each student learn mathematics enthusiastically. Such classes respect individual differences and pay attention to students’ psychology in learning mathematics, such as motivation, math-anxiety, and belief toward mathematics. Such classes underline the students’ human aspects to be considered in the learning process, such as students’ mind, hearts, feelings, and emotions. Such classes are needed to create a harmonious relationship between teacher-students and students. This harmonious relationship has the potential to help each student achieve their optimal achievement. From the study of several references it can be concluded that to make mathematics classes more humanist, the teachers need to: (1) motivating the students by demonstrating the usefulness or beauty of mathematics at the beginning of learning; (2) do not start learning by providing definitions or formulas; (3) controlling their emotion and full of enthusiasm throughout the lesson; (4) giving fair attention to all students; (5) giving a respect for every student’s learning progress; and (6) making varied learning activities, including discussion, singing, poetry reading, watching videos or outdoor activities such as playing games, doing mini research, or buying and selling in shops/markets.
Is it difficult to teach higher order thinking skills?
Authors: Afifah I R N , Retnawati H
Published: November 2019

A teacher must be aware of the importance of teaching higher order thinking skills (HOTS) to prepare young generations in 21st Century. But in reality, many teachers find difficulties in teaching HOTS. This research aims to describe teachers’ difficulties in teaching HOTS in the classroom. The research is a descriptive explorative research by means of qualitative approach. The data were collected from questionnare. This research involved 10 high school mathematics teachers in Yogyakarta, Indonesia. The result of the research shows that the teachers still find difficulties in teaching HOTS in the classroom, those are (1) teachers’ knowledge about HOTS is still low, (2) teachers’ difficulty in delivering apperception to students, (3) teachers’ difficulty in designing and applying the assessment based on HOTS, (4) teacher’s difficulty in delivering HOTS based learning materials, (5) teacher’s difficulty in making learning media based on HOTS, and (6) teachers’ difficulty in preparing learning tools based on HOTS.
Analyzing vocational school students’ error in solving mathematics problems involving higher order thinking skills
Authors: Baskoro I , Retnawati H
Published: November 2019

Higher-order thinking skill is conceived as the top end of Bloom’s cognitive taxonomy. Cognitive domain of higher order thinking skill consists of analyzing, evaluating, and creating. The study aimed to describe the type of error made by vocational school students in solving problems involving higher order thinking skills based on Newman, Lai, Subanji & Mulyoto. This study employed a qualitative descriptive approach with a test as data collecting technique. The respondents are 12 students of vocational school. The skill domain of analyzing contributes reading & decoding error, comprehension error, conceptual error, process skills error, and encoding error. The highest percentage of students’ error in this domain is conceptual error (33%). The skill domain of evaluating contributes decoding & reading error, comprehension error, language interpretation error, process skills error, and encoding error. The highest percentage of students’ error in this domain is encoding error (25%). The skill domain of creating contributes conceptual error, comprehension error, and process skill error. The highest percentage of students’ error in this domain is conceptual error (42%). The results suggest mathematics teacher to explore deeply about their students’ skill of analyzing, skill of evaluating, and skill of creating.
Numerical study on air-core vortex in a dual port cylindrical tank for lower speed of rotations
Authors: Sooraj PV , Joshy PJ
Published: November 2019

Rotating cylindrical tank filled with liquid engendered an air core during draining. The extension of the air-core into the drain port reduces the flow area and consequently the flow rate. The ongoing study focuses on the numerical simulation results of such vortex formation in a rotating cylindrical tank with dual ports in which speed of rotation as the variable parameter here by keeping centre to centre distance fixed.
Simulation of effect of bed temperature over producer gas composition using ASPEN PLUS, its experimental validation and emission characteristics of an IC engine
Authors: Vishnu A R , Kodakkattu Saijal Kizhakke , Fahd Syed Muhammed
Published: November 2019

Biomass is the source of energy that is generated from organic materials, which has the capacity to generate power in different means. Gasification is the technique that converts biomass materials into combustible gas by undergoing chemical reactions at high temperature with a controlled oxygen availability. The objective of this study is to determine the performance of downdraft gasifier and emission characteristics of IC engine using producer gases at various bed temperatures. The satisfactory performance of gasification, is theoretically attaining at a gasification temperature range of 500°c to 750°c. The temperature dependency of gasification process in the performance of downdraft gasifier is studied for different types of feed stocks. The downdraft gasifier is simulated using process simulation software ASPEN PLUS. PLUS. It is found that at higher gasification temperatures the quality of producer gas increases considerably. The exhaust emission characteristics and efficiencies of engine with producer gas are comparable with normal gasoline exhaust characteristics.
Numerical investigations on the heat transfer characteristics of tube in tube helical coil heat exchanger
Authors: Sheeba A , Mathew P , Jose Prakash M
Published: November 2019

Heat transfer characteristics of a tube in tube helical heat exchanger in the laminar flow regime is analysed numerically. Numerical scheme is validated with the experimental results reported in literature. The effect of helix angle on the overall heat transfer coefficient is analysed. The overall heat transfer coefficient increases with Dean number and its rate of increase at higher Dean number is low. The rate of heat transfer is maximum at a helix angle of 27°. Simulation studies show that the secondary flows that originate in a coiled tube due to curvature and torsion produce an additional transport of the fluid over the cross section of the pipe. The overall heat transfer coefficient increases with increase in inner diameter.
CFD analysis of the performance of different airfoils in ground effect
Authors: Zaheer Zubin , Roy K E Reby , Nair Gopakumar S , Ragipathi Vineeth , Niranjan U V
Published: November 2019

Ground effect is a phenomenon caused by the presence of a fixed boundary layer below the wing when it moves close to a fixed surface. This results in an effective increase in lift to drag ratio of the airfoil. In this paper, the performance of three airfoils used in general aviation is analysed in ground effect using ANSYS FLUENT at different operating conditions namely, the angle of attack and the height above the fixed surface. The main objectives are to are evaluate the performance of these airfoils in ground effect at different ground clearances and angles of attack and find the most suitable airfoil which can be used to exploit the advantages of ground effect. It was found that all the airfoils experienced an increase in lift and decrease in drag as distance from the ground reduced thus validating ground effect. The aerodynamic efficiency increases, reaches a maximum, and then decreased as the angle of attack increased due to the onset of flow separation at the top surface of the airfoil. It was also noted that the symmetric airfoil experienced negative lift at very low ground clearances which was attributed to the formation of a venturi effect between the airfoil and ground
Memory Effect in Methane Hydrate Formation
Authors: Pallipurath Mohamed Iqbal , Nagarajan Nandakishore , Vahid Yahiya
Published: November 2019

Memory effect of formation water in methane hydrate formation and reformation is investigated in a high pressure reactor. Methane hydrate formation rates in fresh water and reacted water are measured at different pressures and temperatures. A significant reduction in formation time and incubation period is found with reused water. In the context of transportation of natural gas from distant gas fields as hydrate, this information can be utilized to reduce reduce the transportation cost of natural gas.
Experimental and Numerical Investigations of Synthetic Jet Used for Electronic Cooling
Authors: Jacob Arun , Anandhu R , Leena R , Shafi K A
Published: November 2019

Cooling of electronics and micro-electronics devices is an important task in our present world. Synthetic jet is a relatively new technique for electronic chip cooling which synthesizes stagnant air to form a jet resulted from periodic oscillations of a diaphragm in a cavity. Synthetic jet cooling increases the rate of heat transfer as compared to other cooling techniques. The impingement heat transfer characteristics of a synthetic jet is studying in this work. Synthetic jet is driven by a piston-cylinder arrangement a through circular nozzle for the impingement of jet on the heated surface. Air is considered as the cooling medium. Heat flux is taken as 8000W/m2. Numerical simulations and experimental methods are conducted to study the effect of various distance between the orifice and the heated plated(Z). A circular orifice is used to study the characteristics of convective heat transfer. The results are verified by the time history of convective heat transfer characteristic and validated with experimental results. The model was simulated to investigate the dispersion of heat flow on the walls using a mathematical turbulent model of k- ω SST. The Reynolds number (Re) is in the range of 4000-8000 based on average velocity, while the normalized impinging distance varies between 2D to 10 D The results shows the significant influence of Z/D ratio and sinusoidal wave frequencies to the heat transfer rate obtained. Experimental and numerical investigations is carried out to study the variation of Nusselt number with jet velocity. It is found that the Z/D ratio at 6 gives the maximum amount of cooling for a flat plate.
Simulation of Stratified Two-phase Flow Regime using Air-Water Model in ANSYS Fluent®
Authors: Monachan Binet , Thomas Rijo J. , Steaphen Deepak , Skaria Mathew , Shafi K.A.
Published: November 2019

Two-phase flow has widely grown in importance in various fields of science and engineering system such as nuclear reactors, heat exchangers, transport system, chemical processing plants etc. One of the major issues faced by these sectors is the development of an accurate and reliable multiphase flow measurement system. At present there is no single system which could measure the two phase flow parameters irrespective of its incoming conditions. Characterization of the single phase flow parameter is easier when compared with two phase flow as the velocity distribution, mass flow rate and void fraction of each component phases are not easily measurable. The other factors that add to these difficulties are the prediction of flow regimes and the effect of pipe or channel orientation on the flow properties in the two phase flow. The hold-up of the individual phases and their relative velocity along with pressure drop needs to be taken care while dealing with these flows. Various researches have clearly shown that no correlation can be used for predicting the flow regimes in a two phase flow satisfactorily. By using volume of fluid multiphase flow model air water two phase flow was simulated for inlet velocities of water and air as 0.121 m/s and 6.56 m/s respectively. Stratified laminar flow was obtained from the CFD simulation. Variation in volume fraction of both air and water, mass flow rate and pressure drop with respect to change in time are investigated using the simulation.
A study of factors affecting supply chain performance
Authors: George Joby , Pillai V. Madhusudanan
Published: November 2019

In the present global market, the competition is not between the companies but between the supply chains. The comparison of performance measures of supply chains helps to identify a good supply chain. The best performing supply chains may survive over a long period. The performance of a supply chain is affected by various internal and external factors. The objective of this paper is to identify and conduct a detailed study of the major factors affecting the supply chain performance. The factors are identified by reviewing various literature in the supply chain field. In this respect, a total of 54 literature are reviewed. The major factors identified as supply chain structure, inventory control policy, information sharing, customer demand, forecasting method, lead time and review period length. The optimum selection of parameters of these factors improves the supply chain performance.
POGO Stability Analysis of a typical Launch vehicle for studying the effectiveness of POGO corrector in cryo stage
Authors: Raji R , Jancy Rose K , Murali P R , Neetha R
Published: November 2019

POGO is the longitudinal instability of liquid propellant launch vehicles due to the interaction of structural dynamics with the propulsion system. This interaction may give rise to the initiation of vibrations of large magnitudes when the propulsion and structural frequencies are nearer. This can be avoided by the separation of structural and propulsion frequencies by means of a POGO corrector. The present paper describes the propulsion structural interaction studies for the cryo stage of a typical launch vehicle to avoid POGO oscillations. The propulsion systems are represented as discrete elements described by a set of second order equation and the structure is represented by the normal mode parameters. Assembly of propulsion elements along with structural equations will define the structure propulsion system. Stability of system is studied by evaluating the roots of the assembled equation. The analysis showed that there will not be any POGO oscillations during the flight.
Managing Iterations in Product Development Process Using Dependency Structure Matrix
Authors: Shajahan C A , Firoz N , Sadhikh Mohammed , Pramod N V R , Ashim
Published: November 2019

The market is highly challenging with customers demanding a variety of products at competitive prices. To make a product competitive, it needs to be introduced quickly without compromising on its performance or quality. Thus, reduction of product development cycle time has become essential for companies to thrive and sustain in the market. Product Development (PD) is the set of activities beginning with the perception of a market opportunity and ending in the production, sale and delivery of a product. Companies are forced to develop a well-coordinated development plan to organize their processes and resources to develop competitive products. Today PD confronts complex development challenges. The difficulties in developing complex engineering products do not only arise from their technical complexity but also from the managerial complexity necessary to coordinate the interactions between the different engineering disciplines, which impose additional challenges on the development process. Traditional Project Management techniques are limited in application. Researchers and design managers are constantly searching for the effective and efficient methods for managing PD process. To address the limitations of traditional project management tools, Design Structure Matrix (DSM) has been identified as a sensible tool to represent PD process. In this work, the capability of DSM is demonstrated with a real life case example .The necessity of reducing iterations in PD process using PSM 32 software is also demonstrated
Effect of Strut thickness on the Inflation Behaviour of Coronary Artery Stent using FEM
Authors: Hashim V. , Resmi S.L. , Dr. Dileep P.N.
Published: November 2019

Stent implantation is one of the most accepted method in treating coronary artery diseases due to their simplicity and faster patient recovery. Coronary stents are highly patient specific and the implantation success greatly relies on the design and clinical procedure. Studies confirm that, performance characteristics like radial strength, maximum expansion, stress concentration, recoil etc. are highly governed by the physical design of the stent. This paper focuses on finite element analysis using ABAQUS package to investigate the effect of varying strut thickness on the expansion behavior of a commercially available coronary stent. Envision Scientific Coronary Stent was adopted for this study. Total of five stent designs, one with actual size, two models with a strut thickness lesser than actual thickness and two with higher values were considered. The expansion behavior of the models under consideration was compared to the model with original dimensions. It may be noted that the thickness is one of important design parameter that affects the expansion and stress directly. With 15% reduction in thickness, the expansion increases by 10%. While, for an increase of 15% in thickness resulted in decrease in expansion by 10%. It may be noted that the percentage of increment in stress is linear and inversely proportional. Whereas, the increment in expansion is non linear and is minimal for low thickness. The present approach can be used for selecting the design parameters of stent to arrive in an optimum design.
Design Process Sequencing in Product Development Process Using Design Structure Matrix and Particle Swarm Optimisation Techniques
Authors: Shajahan C A , Subramanyan Embranthiri E , Kumanan S , Firoz N
Published: November 2019

Product development (PD) is a complex business process of transforming new ideas into marketable new products, processes or services. PD process is characterized by information flow and iteration. Traditional project management techniques are limited in representing interdependent activities. Design Structure Matrix (DSM) is a powerful tool for identifying and managing information exchange and iterations. In this work the process is modeled with DSM and the design activities are optimally sequenced using a Particle Swarm Optimization (PSO) technique. The methodology is exemplified with a case example
Experimental study on the influence of hydrophilicity on bacterial adhesion in bioimplants
Authors: Shiju V P , Abhijith N V , Sudeep U
Published: November 2019

Titanium and its alloys are widely used as dental and orthopaedic implants because of their desirable mechanical properties and biocompatibility. However, implant failures due to bacterial infections occur in many cases unexpectedly. Formation of a biofilm on the implant surfaces facilitates growth of colony of bacteria which in turn reduces the effectiveness of antibacterial drugs. Hydrophilicity of implant surfaces diminishes the chances of biofilm formation. Micro surface features are created on the Ti6Al4V implant surface using a pulsed Nd-YAG laser and its influence on water wettability (and thus on hydrophilicity) has been studied and compared with a polished surface. Strains of Staphylococcus aureus have been inoculated on the test specimens and the bacterial adherence have been compared. The results show that micro-textured surfaces of Ti6Al4V have improved water wettability and thus are more hydrophilic than polished surface. This has reduced the formation of biofilm and bacterial growth.
Effect of heat treatment on mechanical and tribological characteristics of Electroless Ni-P deposits
Authors: Arora Abhishek , Kiran K Uday Venkat , Ramakrishnan Bijoy , Sunil B. Ratna , Dumpala Ravikumar
Published: November 2019

In the present paper, mechanical and tribological characteristics of as-deposited and heat-treated Electroless Ni-P coatings were investigated. Medium phosphorus Ni-P coatings were deposited on mild steel substrate using an acidic bath and subjected to heat treatment at 400°C in a tubular furnace. Surface morphology and elemental analysis of the coatings were carried out using Scanning electron microscope (SEM) and Energy dispersive X-ray spectroscopy (EDS) analysis respectively. Dry sliding wear characteristics of the coatings were investigated by linear reciprocating ball on flat tribometer using AISI E52100 Steel ball as a counter body at room (25±2°C) and elevated temperature (300°C). Hardness results showed significant improvement in the surface hardness of coatings on heat treatment. Low friction coefficient and high wear rate were observed at elevated temperature in comparison of those of tests conducted at room temperature for both as-deposited and heat-treated coatings. Best tribological performance is observed for heat-treated coating tested at room temperature.
Investigation of Magnetostriction in Second Generation High Temperature Superconductors
Authors: Ashok K.B. , Thomas R. J. , Prakash M. Jose
Published: November 2019

Superconductors help to drastically improve the efficiency in every field by making the transmission losses of electrical energy to minimum. Superconductors show special properties only when their parameters like temperature, magnetic field, current density, mechanical strain are within their critical limits. Effect of magnetic field on second generation high temperature superconducting compounds have been studied in past few years. In this paper, the numerical simulation of the magnetostriction effect of second generation superconductor REBCO is discussed. The results obtained from numerical studies is compared with the experimental results reported in literature. The findings show that there is good agreement and all the three samples are showing rapid change in magnetostriction when the magnetic field is above 106 A/m.
Homogenization of Mechanical Properties of Unidirectional Fibre Reinforced Composites with Matrix and Interface Defects: A Finite Element Approach
Authors: Siddharth S , Ramesh Ajith
Published: November 2019

Fiber Reinforced Composites find increasing applications in the areas of Aerospace, Military Armours, Bullet-proof vests, etc. As the composites are composed of two different constituents, there arises a need to determine the effective properties of the homogenous composites. Experimental determination of the effective properties is very expensive considering the amount of experiments that are required to be conducted, the time and cost to be incurred for each experiment, and the permutations and combinations of the optimal fiber volume fraction. The effective properties are essential for modeling of composites with reference to real-time applications. The micro-mechanics approach reduces most of the above mentioned complexities and helps in accurately evaluating the effective properties. In the presented paper, the properties like Young’s Modulus, Poisson Ratio, and Shear modulus of a healthy (defect free) composite is obtained by modeling a Representative Volume Element (RVE) using the commercial Finite Element Analysis (FEA) solver – Abaqus, with application of Periodic Boundary Conditions (PBC). The presented research focuses on Fiber-Reinforced Metal-Matrix composites like AA2024-Al2O3 and the Ceramic-Matrix composites like ZrB2-SiC. In general, defects in composites arise during the manufacturing process. Matrix Crack, Interfacial De-bonding and Fiber Crack are the major defects which degrade the mechanical properties of composites. This paper presents the modeling of Interfacial de-bonding using the Cohesive-Zone Modelling (CZM) technique for every 90° variation in the fiber-matrix interface and the subsequent evaluation of the corresponding homogenous properties. Matrix Crack is modelled as a matrix defect with a ‘V’ notch for varying a/w ratios. For every variation in matrix crack, the corresponding properties are estimated. Numerical evaluation of the individual effects of interfacial de-bonding and fully grown matrix cracks are followed by the modelling of the coupled effects.
High-end sensors: challenges for the future
Authors: Yurish Sergey Y.
Published: November 2019

The paper describes the coming challenges in high-end sensors and transducers design. These challenges are coming from the recent technological limitations in microelectronics. The proposed approach to overcome such limitations is based on programmable parameter-to-frequency converters as a digital sensor’s core and advanced method of measurement in order to move from a traditional analog-to-digital conversion to alternative frequency (period, duty-cycle, time interval)-to-digital conversion. Working in the frequency-time signal domain simplifies design, and obviates some technical and technological problems, due to the properties of frequency as informative parameter of sensors and transducers. The major benefits offered by such approach are high reliability, high metrological performance, wide functionality, cost effectiveness and scalability. The perspectives, which will bring such approach to various sensors and transducers for physical and chemical, electrical and non-electrical quantities are illustrated by examples of multivariable sensors, sensors for smart health care and wearable sensors.