bluuebunny/crossref_metadata_2025 huggingface dataset:
The analysis of olympic tutors problem-solving skill of the national science olympic for elementary school level
Authors: Rufaida S , Nurdiyanti
Published: March 2021

This study aims to describe the olympic tutors problem-solving skill of the National Science Olympic for elementary school level and analyze based on the type of problem-solving skill. In a National Science Olympic competition, the selection is made based on the ability of students to solve questions, so that the teacher as olympic tutors need to apply correct problemsolving skills as the main key to solving olympic questions. This research was a qualitative descriptive study that aimed to determine the condition of an object through a case study for olympic tutors of the National Science Olympics for elementary school level in Barru Regency, South Sulawesi. The data collection methods were tests and interview. This study showed the olympic tutors problem-solving skill of the National Science Olympic for elementary school level in Barru Regency at the moderate category which revolved around the score 25 - 49. Based on the result of the analysis, in terms of the types and stages of problem-solving, most of the olympic tutors of the National Science Olympic for elementary school level did not understand systematic problem solving and still needed accuracy in choosing the most appropriate equations to use when solving problems.
Mathematical literacy of prospective mathematics teachers in solving social arithmetic problems in the context of the wetland environment
Authors: Zulkarnain I , Hidayanto T
Published: March 2021

Mathematical literacy is an individual’s ability to formulate, use, and interpret mathematics in various contexts. However, the achievement of Indonesian students’mathematical literacy is low, according to the PISA study. Therefore, it is necessary to have a mapping of the mathematical literacy abilities of mathematics education students who are prepared as prospective mathematics teachers. The research describes the mathematical literacy of prospective mathematics teachers in solving social arithmetic problems in the context of the wetland environment. This research used the descriptive method. The participants were 87 students in the second year of mathematics education study program at Universitas Lambung Mangkurat. The students were tested with social arithmetic problems in the context of the wetland environment. The results showed that there are five categorizations of mathematical literacy of prospective mathematics teachers in solving social arithmetic problems in the context of a wetland environment. These categories are 6% of subjects did not solve problems, 3% of subjects only identified problems, 60% of subjects solved problems but did not fit the given context, 3% of subjects solved problems, but the procedure or the final answer is wrong, and 28% of subjects can solve the problem correctly both in the procedure and in the final answer. Based on these findings, prospective mathematics teachers need to be prepared to be familiar with problems related to the context of their environment to improve their mathematical literacy skills.
Analyzing the online assessment using the expert system in fashion making practices of fashion design students in Universitas Negeri Malang
Authors: Irianti A H S , Sunandar A , Smaradigna A A , Aris A , Muhartiningsih R , Irzatul T
Published: March 2021

Online assessment using the expert system in fashion making practice was a new assessment as a result of developmental research. Online assessment using the expert system was made to avoid subjective assessment in evaluating the practice results. During the evaluation, there was a fitting process where students’ posture and face could give individual influences. The practice results from slim and pretty students would provide better effects than students who were fat and less beautiful, even using the practice assessment indicators. The physical appearance of the participants or models such as body shape, face, and others would psychologically affect the lecturers’ subjectivity during evaluation. Conducting practice evaluations using the expert system allowed students to report the practice results by answering online questions related to the fashion making results. Online assessment using the expert system facilitated the students to upload their practice results progress complete with answers following the issue in the online assessment software. Online evaluation with the expert system also assisted lecturers in monitoring the practice progress online that they could access everywhere and anywhere. This research aimed to analyze the online assessment of women fashion making practice using the expert system, to find the ease of use from the online system software, assessment content suitability, and assessment objectivity. For the methodology, this research used a quantitative descriptive method in a population of 28 Fashion Education students’ class of 2018. The sampling technique in this research was total sampling. This research used the close questionnaire as the research instrument and analyzed the data using the percentage technique. The results showed that first, software easiness such as followings instruction, operational, filling and uploading the progress, indicated that 25 of 28 respondents, or 89.28%, were in favour of the ‘easy’ category. Second, assessment content analysis, such as assessment indicator, content from each index, and assessment aspect, demonstrated that 26 of 28 respondents or 92.85% was in favour of the ‘relevant’ category. And third, the assessment objectivity such as definite measuring instruments and objective assessment presented 27 of 28 respondents in support of the ‘objective’ category. The conclusion of this research using the expert system was overall in the excellent grade. This report was accurate because, in direct practicum assessment, the fitting session used model, and thus the physical condition of the models who were pretty and slim often gave subjective final results.
E-Comic mathematics based on STEAM-CC and its effect on students creative thinking ability
Authors: Hobri  , Adeliyanti S , Fatekurrahman M , Wijaya H T , Oktavianingtyas E , Putri I W S , Ridlo Z R
Published: March 2021

This research aims to create an e-comic mathematics based on Science, Technology, Engineering, Arts, and Mathematics – Caring Community (STEAM-CC) concept as well as to know its effect on the students’ creative thinking ability. Creative thinking is heavily influenced by approaching the students’ during the teaching and learning process. Moreover, it can be done through conducting small group students as a medium to collaborate, learn, and care each other along Caring Community (CC) in Lesson Study for Learning Community (LSLC). This study was used mixed method, 4D development method by Thiagarajan and experimental researcch. The result of this study showed that the developed e-comic was valid according to the material and media experts, while STEAM-CC concept was effective and practical way by looking at the students were able to achieve the standard minimun score on the test and observation. This research also found that the media can effect the studens’ creative thinking ability.
Eigenvalues of Adjacency and Laplacian Matrices of Bracelet—Kn
Graph
Authors: Albirri E R , Fatahillah A , Hussen S , Sugeng K A
Published: March 2021

Let G be an undirected simple graph. Adjacency matrix of a graph G, denoted by (A(G)), is defined as a matrix which has entry-(i, j) is equal 1 if vertex i and vertex j are adjacent and 0 if otherwise. Let D(G) be the diagonal matrix of vertex degree and J(G) be the matrix which has entry all ones. Laplacian matrix (L(G)) can be defined by L(G) = D(G) – A(G). This study discusses eigenvalues of adjacency and Laplacian matrices of the Bracelet—Kn
graph. The results of this study indicate that the Bracelet—Kn
graph for n ≥ 4, n even has four different eigenvalues of adjacency and Laplacian matrices.
Corrections for photons attenuation and scattering for the extrapolation chamber for measurement of air-kerma strength of 125I brachytherapy source
Authors: Liu C. , Song M. , Liu Y. , Wang H. , Wei K. , Hang Z.
Published: March 2021

A type of extrapolation chamber was designed in China Institute of Atomic Energy, CIAE. The chamber was used for the measurement of the air-kerma strength of the medical radiation 125I source on primary standard level. In order to obtain the air-krema strength with a low uncertainty, some correction factors such as photon attenuation and scattering are needed to calculate. Correction factors for different types of 125I seeds were estimated with increasing chamber depth. Based on the relation between ionization current and average photon fluence, attenuation correction factors were calculated with the analytical solution. Additionally, the scattering correction factors were estimated by a suitable method of Monte Carlo simulation. Photon attenuation includes four components. katt-volume, katt-foil, katt-sf, and katt-Al. The differences of correction factors are concerned, mainly due to the variation of chamer depths and 125I seed types. katt-volume increases from 1.001 to 1.005. katt-foil varies between 1.0012 and 1.0014. katt-sf changes from 1.015 to 1.018. katt-Al varies between 1.038 and 1.048, which largely depend on the photon spectrum from the source. Meanwhile, the geometric dimension of the ionization chamber has a great influence on the scattering correction factors. The ksca values vary from 0.9960 to 0.9964 with different chamber depths, which only has 0.04% fluctuation.
Automatic segmentation of fish midlines for optimizing robot design
Authors: Fetherstonhaugh Samuel E A W , Shen Qiang , Akanyeti Otar
Published: March 2021

While fish use continuous and flexible bodies to propel themselves, fish robots are often made from interconnected segments. How many segments do robots need to represent fish movements accurately? We propose a new method to automatically determine parsimonious robot models from actual fish data. We first identify key bending points (i.e., joint positions) along the body and then study the concerted movement of the segments so that the difference between actual fish and modelled bending kinematics is minimized. To demonstrate the utility of our method, we analyse the steady swimming kinematics of 10 morphologically distinct fish species. Broadly classified as sub-carangiform (e.g., rainbow trout) and carangiform (e.g., crevalle jack) swimmers, these species exhibit variations in the way they undulate when traditional parameters (including head and tail beat amplitudes, body wavelength and maximum curvature along the body) are considered. We show that five segments are sufficient to describe the kinematics with at least 99% accuracy. For optimal performance, segments should progressively get shorter towards the tail. We also show that locations where bending moments are applied vary among species, possibly because of differences in morphology. More specifically, we find that wider fish have shorter head segments. We discover that once bending points are factored in, the kinematics differences observed in these species collapse into a single undulatory pattern. The amplitude and timing of how body segments move entirely depend on their respective joint positions along the body. Head and body segments are also coupled in a timely manner, which depends on the position of the most anterior joint. Our findings provide a mechanistic understanding of how morphology relates to kinematics and highlight the importance of head control, which is often overlooked in current robot designs.
Multi-decadal improvement in US Lake water clarity
Authors: Topp Simon N , Pavelsky Tamlin M , Stanley Emily H , Yang Xiao , Griffin Claire G , Ross Matthew R V
Published: March 2021

Across the globe, recent work examining the state of freshwater resources paints an increasingly dire picture of degraded water quality. However, much of this work either focuses on a small subset of large waterbodies or uses in situ water quality datasets that contain biases in when and where sampling occurred. Using these unrepresentative samples limits our understanding of landscape level changes in aquatic systems. In lakes, overall water clarity provides a strong proxy for water quality because it responds to surrounding atmospheric and terrestrial processes. Here, we use satellite remote sensing of over 14 000 lakes to show that lake water clarity in the U.S. has increased by an average of 0.52 cm yr−1 since 1984. The largest increases occurred prior to 2000 in densely populated catchments and within smaller waterbodies. This is consistent with observed improvements in water quality in U.S. streams and lakes stemming from sweeping environmental reforms in the 1970s and 1980s that prioritized point-source pollution in largely urban areas. The comprehensive, long-term trends presented here emphasize the need for representative sampling of freshwater resources when examining macroscale trends and are consistent with the idea that extensive U.S. freshwater pollution abatement measures have been effective and enduring, at least for point-source pollution controls.
Generalised Airy polynomials
Authors: Clarkson Peter A , Jordaan Kerstin
Published: March 2021

We consider properties of semi-classical orthogonal polynomials with respect to the generalised Airy weight

ω

(

x
;
t
,
λ

)

=

x

λ

exp

−

1

3

x

3

+
t
x

,

x
∈

R

+

with parameters λ > −1 and

t
∈
R

. We also investigate the zeros and recurrence coefficients of the polynomials. The generalised sextic Freud weight

ω

(

x
;
t
,
λ

)

=
|
x

|

2
λ
+
1

exp

−

x

6

+
t

x

2

,

x
∈
R

arises from a symmetrisation of the generalised Airy weight and we study analogous properties of the polynomials orthogonal with respect to this weight.
Influence of asymmetric factor on spur gears to dynamic bending stress
Authors: Pramono Agus Sigit , Rizal Mohamad Zainulloh
Published: March 2021

Asymmetric spur gear is used in one-way rotation transmission. This spur gear has a higher bending strength than symmetric spur gear. In this research, the effect of asymmetrical spur gear level on bending stresses is studied dynamically. The asymmetric spur gear level is expressed as asymmetric factor (K). Asymmetric factors K = 1, K = 1.05, K = 1.06, K = 1.07 and K = 1.08 are used. Dynamic analysis is performed by explicit dynamics numerical modeling. Material used for five asymmetric factor is AISI 1045. Two variables applied on this spur gears are torque loads and rotational speeds to investigate that effect on bending stress. Torque loads varied from 100 Nm to 250 Nm with 50 Nm increment and rotational speeds varied from 1000 rpm to 2500 rpm with 500 rpm increment. The results of this study show that the asymmetric factor can reduce more significantly bending stress cause of torque loads than cause of rotational speeds.
Kijang LGX camshaft’s failure analysis using the finite element method approach
Authors: Prasetya Riduwan , Andoko
Published: March 2021

The camshaft on the Kijang LGX was broken after 14 years of use. This study aims to determine causes of camshaft fracture using finite element approach. The software used is Solidworks and ANSYS 17.0 for FEM simulation. The results to be obtained from the simulation results are stress, strain, and deformation which are then analyzed. The results showed that the greatest stress occurred in the fillet section where the area with highest stress concentration was 168.93 MPa. This value is smaller than the compressive strength so that the applied stress is within the limits of the strength of the material. Maximum stress location is 7 mm away from the fracture site (53.17 MPa), therefore the stress is not the main cause of the camshaft fracture and it can be assumed that there is a defect. The maximum strain is located at the same location as the maximum stress which is 0.0015361 mm/mm. The maximum deformation value is 0.016741 which is far from the fracture (located at the end of the cam). This value is included in the elastic deformation of the material so that the load applied to the camshaft does not change shape / does not lead to plastic deformation that triggers the appearance of cracks.
Strength consideration on car body of light rail transit making from aluminum extrusion
Authors: Syaifudin Achmad , Nurfadillah Egy Meirarizka , Farid Abdul Rohman , Windharto Agus
Published: March 2021

There are two common series of aluminum alloy that used to construct car body of light rail transit (LRT), i.e. Al 6061 and Al 6005a. Type of Al 6005a has lower strength but cheaper rather than Al 6061. In this numerical study, their extrusion characteristics based on strength consideration are analyzed using ANSYS Workbench 18. The 3D solid model is extracted from interior-exterior facet models of LRT. To save computational time, the car body model is simplified by removing fillets and then generating a symmetrical model. Anyhow, the effect of fillet removal is also studied by introducing a correction factor. Four cases of static loading are given to observe actual loading phenomena that could occur. The simulation results indicated that Al 6005a has better characteristics to be used for constructing the car body of LRT. In addition, simplifying the model in the FEM simulation of a rail-based car body using a shell element type and applying a correction factor to the simulation results is a breakthrough simulation method that could improve the accuracy of the results.
Experimental study of thermoelectric cooler box using heat sink with u-shape heat pipe and methanol working fluid
Authors: Winarta Adi , Made Rasta I , Ike Midiani Luh Putu , Wayan Adi Subagia I , Gde Sapteka Anak Agung Ngurah
Published: March 2021

Thermoelectric refrigeration system is considered environmentally friendly because it does not use refrigerants which have huge potential damaging the ozone layer. In this experimental work, u-shape heat pipe with heat sink was charged with methanol working fluid with different filling ratios to observe its effect on the thermoelectric performance. The cooler box has 240 mm x 180 mm x 130 mm of inner dimension. 37.3 watt DC power supply supplied constantly to the thermoelectric module to performed cooling action. The result shows that methanol with 45% and 55% filling ratios has the maximum COP about 0.03881 and 0.03885 respectively. This filling ratio also provides for a lower cabin temperature and temperature difference between the cold and hot thermoelectric sides.
Droplet combustion behavior of crude palm oil-carbon nanoparticles blends
Authors: Marlina Ena , Nanlohy Hendry Y. , Gusti Ketut Puja I , Riupassa Helen
Published: March 2021

Research on the combustion behavior of a mixture of palm oil and carbon nanoparticles has been carried out. The burning phenomenon is observed through oil droplets that are ignited at the thermocouple junction, and the evolution of the droplets is recorded with a high-speed camera. The results indicate that the addition of carbon nanoparticles increases the molecular density of the fuel. This has the potential to produce effective collisions that weaken the strength of carbon chain bonds and increase the reactivity of fuel molecules. The increased motion of fuel molecules makes it easy for molecules to absorb heat and burn. This analysis was proven because the results showed that the addition of carbon nanoparticles succeeded in increasing the temperature and burning rate.
Effect of performance generator set 1.5 PK 4 stroke with variations in load and type of spark plugs
Authors: Paristiawan Permana Andi , Simanullang Bantu Hotsan , Saefudin
Published: March 2021

Energy is one of the most important needs for humans, and electricity is one of the energy needs needed to support various human activities both day and night. One source of electrical energy is obtained by using a generator as a power plant. The generator set is used as a backup when the electricity supply from PLN is cut off.Efforts to get a good performance generator set are made by improving the combustion quality to increase efficiency. Tests carried out on a four-stroke one cylinder generator capacity of 1.5 PK with variations in load and type of spark plugs are standard, platinum, and iridium, which at 3000 rpm engine speed with a load of 350, 700 and 1050 Watt pertalite fuel with a volume of 10 ml. The value of Torque and power has increased along with the increased engine load. The optimum generator performance is obtained at a load of 700 watts when using this type of platinum spark plug. The maximum engine power generated is 1,092 HP. Torque of 2.59 Nm and the lowest fuel consumption (SFC) of 0.484 kg/hp.hour.
Experimental investigation on the effect of carbon chain length to the droplet combustion characteristic of fatty acid methyl ester
Authors: Ibadurrohman Ibrahim Ahmad , Hamidi Nurkholis , Yuliati Lilis , Valentino Benedict Amadeus
Published: March 2021

Biodiesel which produces from vegetable oil consists of various fatty acids as fatty acid methyl ester constituent. Each fatty acid has a specific combustion characteristic due to the difference in physicochemical characteristics. This study was done with a single fatty acid methyl ester from various saturated fatty acids to analyze the effects of carbon chain length on the droplet combustion during the evaporation and combustion stages in ambient temperature and atmospheric pressure. Results show that the ignition delay time increase with the longer carbon chain due to the higher viscosity and boiling point. The higher oxygen content in the fatty acid methyl ester molecule promotes the faster combustion, gives a higher burning rate, and cause the flame dimension shorter. Furthermore, oxygen content results in higher radiation caused a brighter flame. The high droplet temperature occurs in the long carbon chain due to the higher of combustible matter gives an increase to the heating value. Low radiation heat loss in a long carbon chain which indicates by the flameless bright also causes the droplet temperature higher. The higher droplet temperature gives the lower gas density which causes the flame dimension higher due to the natural convection.
Performance of diesel engine using cooking oil biodiesel (B20) with additional bioaditive essential oils (Eucalyptus)
Authors: Permanasari Avita Ayu , Sukarni Sukarni , Wulandari Retno , Hamidi Nurkholis , Ramadani Ramadani , Mauludi Muhammad Najib
Published: March 2021

This research is geared by the depletion of the availability of fossil fuels in nature. This is inversely proportional to the level of fossil fuel consumption, which is getting higher from year to year. Thus, there is a need for alternative fuels. One of which is biodiesel. The existence of an assessment in preparing biodiesel as an alternative fuel is significant. This study aims to determine the effect of the addition of bioaditive essential oil (eucalyptus) on the performance of diesel engines. The method used in this research was the manufacture of biodiesel through esterification and transesterification steps, then testing the diesel engine to determine the performance and gas emissions were also carried out. The results show that brake torque has decreased along with the loading at each engine speed. The value of brake power increases from 1700 rpm to 1900 rpm and then decreases to 2300 rpm. Brake fuel consumption increases with increasing engine speed, and thermal brake efficiency decrease with increasing engine speed. The CO emission is constant, but in the B20 biodiesel sample with 0.1% eucalyptus oil additive, the CO emission increases to 2100 rpm. CO2 and HC emissions fluctuate with an increasing trend with increasing engine speed. O2 emissions fluctuate with a decreasing trend along with the increase in engine speed, the O2 content produced by pure biodiesel B20 is lower than B20 with additives
Identification of gradient temperature and heat flow area of geothermal Ijen Volcano Indonesia
Authors: Afandi Akhmad , Lusi Nuraini , Catrawedarma IGNB , Badarus Zaman M. , Subono
Published: March 2021

A researcher carried out a study about gradient temperature and heat flow in the field of regional area of solfatara Ijen Banyuwangi Regency, East Java province, Indonesia. It is according to the temperature from the surface to about 100 cm deep, while making use of thermocouples with the accuracy of ± 0.5 % and ± 1 °C. Coordinate position measurements using a Garmin GPS device. This research aims to study the distribution of the temperature at any given depth, which is the gradient of temperature at a depth of 2000 m and the value of heat transfer through conduction. Temperature distribution of the depth contour, there are zones with high-temperature, and they increase along with the increase in depth. The gradient of temperature is 35 °C m−1 at a depth of 2000 meters generates 175.6 °C. The maximum heat flow value is always obtained in the presence of sulfur, while the average heat flow of solfatara on the field is 21.08 W m−2.
Adding the activated carbon of rice husk to increase hydrogen production on water electrolysis
Authors: Purnami  , Wardana ING. , Sudjito  , Widhiyanuriyawan Denny , Hamidi Nurkholis
Published: March 2021

Water electrolysis is decomposing water (H2O) into Oxygen and Hydrogen with the help of electric current. At present, the conventional electrolysis efficiency is around 50%. The use of catalysts is partly engineered to increase the hydrogen production. In this paper, activated carbons from rice husk (RHAC) of 50 ppm and 100 ppm were added as the catalyst to increase Hydrogen production. FTIR tests showed that RHAC had an aromatic ring functional group with magnetic field. By the help of ImageJ software, it was proven that RHAC surface has an electric charge dominated by a positive charge. The magnetic field weakens the hydrogen bonding, while the electric charge increases the solution acidity, and makes it a good electrical conductor. As a result, greater addition of RHAC increases Hydrogen production. The largest hydrogen production of 8.2 ml for 10 minutes was obtained by the addition of 100 ppm.
Preliminary study of FCC design for palm-based biofuel production through heat balance analysis
Authors: Hilman Gumelar Syafei M. , Siswantara Ahmad Indra , Budiarso  , Widiawaty Candra Damis , Farhan Tanwir Ahmad , Pujowidodo Hariyotejo , Ramdlan Gunadi Gun Gun
Published: March 2021

Fluid Catalytic Cracking (FCC] is playing a big role in oil refinery industries and it has been used for producing most of the fuel around the world. FCC has also a great potential for producing biofuel derived from palm-based bio oil. However, it takes a complex calculation to design the overall FCC system. This paper offers the design simplification of FCC through heat balance analysis in two main components, that is riser section and regenerator section. The objective of this study is to estimate the appropriate amount of fuel for a given amount of feed. It is obtained that the required amount of fuel is greater as amount of the given feed increased.
Effect of natural zeolite on biomass pyrolysis
Authors: Bahri Mokh. Hairul
Published: March 2021

Study the pyrolysis of biomass with the addition of natural zeolite to determine the enthalpy required to become gas, oil, and char. The materials used were Sengon (S) sawdust and natural zeolite type Clipnotilolite (Z). The pyrolysis process used STA Iliensies PTA 1600. The test samples S, S + Z1, S + Z2, and S + Z3 were heated at a heating rate of 20 °C min−1 and an air flowrate (Argon) of 0.5 liters min−1. The result shows that the enthalpy of pyrolysis S decreases with the increase of Z. The greater the percentage of Z the decrease in enthalpy is getting sharper, while the decrease in mass is relatively small.
The influence of increased carbon content on the number of electrons in dye-sensitized solar cell (DSSC)
Authors: Trihutomo Prihanto , Marji
Published: March 2021

Dye-Sensitized Solar Cell (DSSC) is a solar cell that uses sensitive dye toward visible light to convert light into electricity. The sensitive dye that are commonly used are chlorophyll which contains many elements of carbon. The carbon element in chlorophyll contains electrons which can generate an electric current in the DSSC. This research has proven that increasing the carbon content of dye can increase the number of electrons generated in the DSSC. The method used in this study was to vary the dye content of TiO2, namely dye concentrations of 25%, 50%, 75% and 100%. The results showed that increasing the dye content would increase the carbon content and the number of electrons generated by the DSSC, namely that the 100% dye content had a carbon content of 1.414% and the number of electrons was 0.22 x 1019.
Waste analysis in aircraft production process
Authors: Lustyana Astuteryanti Tri , Widiyawati Sri , Lukodono Rio Prasetyo , Fanani Angga Akbar , Puspita Feby
Published: March 2021

Waste is any type of work activity that does not provide added value and it is eliminated, because it can have a negative impact on the company. During the production process, waste can occur due to the operator, the machine, nature, etc. In the production process of aircraft manufacturing at one of Indonesian-aircraft Industries, there are many factors that influence the occurrence of waste; therefore, there is a need to minimize or even eliminate the waste, one of them by using lean manufacturing. In this company, there are three of the biggest waste that occurs during the production process of aircraft, namely Defects, Inventory and Motion waste. From those three wastes, they will be identified which causes the greatest impact on other waste using the Waste Relationship Matrix (WRM) method. The results of the calculation of WRM, found that defect waste has a considerable impact when compared to inventory waste and motion waste, with an average value of 44.02%. So, the company needs to focus on eliminating these wastes, by improving the condition of the production floor, both from the people, methods, machines, or even from the environment.
The effect of layer height on the surface roughness in 3D Printed Polylactic Acid (PLA) using FDM 3D printing
Authors: Bintara Redyarsa Dharma , Lubis Didin Zakariya , Aji Pradana Yanuar Rohmat
Published: March 2021

This study aims to investigate the surface roughness and the time consume printing on PLA material using FDM 3D printing on differences in layer height. A 3D printer machine, Creality Ender 3 was involved to manufacture the specimen. Furthermore, they tested with the SurftestSJ-301 Mitutoyo device to determine the roughness of surface object. The height of the test specimen layer varies from 0.05 mm to 0.25 mm with the increment of 0.5 mm for each variation, while the layer angle keep constant at zero degree (0°). Surface roughness and print time are analysed to determine the best design parameters. The test results show that, the greater of layer height has the rougher of the surface. In addition, the printing time is inversely proportional to surface roughness. The smallest of surface roughness occurs on the 0.05 mm of layer height, whereas the lowest occurs on the 0.25 mm of layer height. In addition, the optimize parameter occurs on 0.15 mm and 0.2 mm of layer height which surface roughness and printing time are 9.11 μm and 158 min respectively (Lh 0.15 mm), while the layer height of 0.20 mm for 120 min and 10.48 μm.
Performance of TiAlN PVD coated carbide tool in machining AISI 4340 with Minimum Quantity Lubrication (MQL) condition
Authors: Darsin Mahros , Hidayatul Qoryah Rika Dwi , Sidartawan Robertus , Luviandy Allen , Muttaqin Aris Zainul , Djumhariyanto Dwi
Published: March 2021

There are several ways to assess machinability, viz. forces that are working during machining, the surface roughness of machined part, chip formation, and tool performance. This article aims to observe the machinability from the tool performance perspective when machining with minimum quantity lubrication (MQL). The MQL device can either be time-controlled or temperature-controlled using an Arduino. The machining was carried out on a conventional lathe toward a bar of AISI 4330 using carbide coated insert tools. The experiments were carried out using Taguchi design L9, by the varying depth of cut, coolant composition and method of applying the coolant. Tool performance was evaluated by tool deterioration value. There are four levels of tool deterioration according to its severities after machining. Analysis of variance shows that depth of cut more influence to the tool performance than the coolant application method by 32.69% and 12.82% each, respectively. However, it is proof that MQL with temperature-controlled would contribute to the minimum tool deterioration.
Taguchi-grey-fuzzy method for optimization of turning process parameters with environmentally friendly cooling
Authors: Pamuji Dian Ridlo , Lusi Nuraini
Published: March 2021

Surface roughness is an indicator of the quality of workpieces produced by machining processes. Whereas, the indicator of the productivity of the machining process is the metal removal rate. Surface roughness and metal removal rate have different characteristics. Setting the combination of turning parameters results is essential to get optimal responses. This research has been carried out of determining the parameters of the turning process to produce an optimal response with the use of environmentally friendly coolant. The turning process parameters that are varied are the cutting fluids, spindle rotation, feeding motion, and cutting depth while the tool used is the CNMG insert tool. The optimization method used is Taguchi, combined with grey and fuzzy logic. The results showed that to obtain the optimum arithmetic surface roughness, average total surface roughness and metal removal rate, the cutting fluids is set at level 1, which is soluble cold water + air pressure, level 3 spindle rotation with a value of 1200 rpm, level 3 feeding with an amount of 0.161 mm rev−1, and cutting depth level 3 of 0.5 mm.
Improvement of DEET level of product X using Deming cycle (PDCA Method) in PT Z
Authors: Nurzaki Alfi , Santoso Arga , Benawan Chano , Wahyudin Didin , Santoso Sugeng
Published: March 2021

DEET is a complex compound that is used as an active ingredient in the manufacture of insect repellent products. PT Z is one of the sub-contracting companies that manufacture mosquito coils from PT XYZ with product X. PT Z received complaints from PT XYZ claiming that DEET levels in a tested batch were below the specified specifications. PT Z needs to conduct an internal assessment and investigation to find the cause of the release of DEET levels from the specification range. The research was carried out with a Deming cycle, namely the sub-stage PDCA method. Based on the results of the investigation, the decrease in DEET levels is caused by the inhomogeneity of DEET in the product because the mixing process is only done in 5 minutes, so it is necessary to optimize the mixing time. Both parties have agreed on corrective and preventive actions in the form of a revalidation process by determining the best mixing time, which is 20 minutes, which produces a DEET level of 32.58%. Validation is carried out for three consecutive batches with all batches showing DEET results that meet the specified product specifications.
Phase identification and morphology of CaCO3/CaO from Achatina Fulica snail shell as the base material for Hydroxyapatite
Authors: Puspitasari Poppy , Fauzi Andre Faiz , Susanto Hendra , Permanasari Avita Ayu , Gayatri Rara Warih , Razak Jeefferie Abdul , Abdillah Pratama Muhammad Mirza
Published: March 2021

Snail shell is an abundance of waste in Indonesia, particularly from snail or Achatina fulica snail. Snail shell has high calcium content; thus, it can be used as an alternative replacement for CaO/CaCO3. This research aimed to make CaCO3 and CaO from the Achatina fulica snail shell waste as the base material of hydroxyapatite. The synthesis process of CaO/CaCO3 used the ball milling method for 6 hours in various sintering temperature of 850 °C, 950 °C, 1050 °C. The synthesised samples were then characterized using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM-EDX) and Fourier transform infrared (FTIR). The XRD results showed the successful synthesis of snail shell waste into CaCO3 and CaO with the smallest particle size from each temperature variation were 17.60 nm, 30.16 nm, and 53.30 nm. The SEM images showed agglomeration and porosity in all samples. The EDX test results displayed the highest Ca (calcium) was found in the sample with 1050°C sintering temperature, and the highest O (oxygen) level was found in the sample with 850 °C sintering temperature. The FTIR test results presented the functional group transformation from CaCO3 into higher CaO along with the increase of the sintering temperature.
Analysis of tensile strength, microstructure, and fractograph of Al-Si with snail shell powder as reinforce agent
Authors: Puspitasari Poppy , Susilo Galy Dwi , Aminnudin  , Aji Pradana Yanuar Rohmat , Rahma Putra Andika Bagus Nur , Abdillah Pratama Muhammad Mirza
Published: March 2021

This research aimed to increase the mechanical property of Al-Si alloy by adding snail shell powder reinforcement using the stir casting method. This research used 1 minute, 2 minutes, and 3 minutes variations of stirring time. The snail shell powder percentage in this research was 0.05 wt% from the total 1.5 kg Al-Si alloy. The stir casting method was performed by melting the Al-Si in the furnace then was stirred at 500 rpm speed in 850°C temperature before sprinkled with snail shell powder. After the stir casting process, the Al-Si alloy was poured into permanent cylindric mould according to the tensile test specimen. The specimens then tested with the mechanical test to find the tensile strength and microstructure. The results showed increases of the mechanical property with the best result was found in the specimen with a stirring time of 3 minutes with the value of 21.04 kg/mm2.
Quality improvement of SS 304 with variations in feed rate and spraying distance in semi-automatic sandblasting
Authors: Raharjo Rudianto , Ardiyanto Mochamad Tio , Widodo Teguh Dwi , Kusumaningsih Haslinda , Bintarto Redi , Alamsyah Fikrul Akbar , Ali Mukhlis
Published: March 2021

Roughness and flatness are things to consider in metal coating and painting. Sandblasting is one method to get certain roughness on the surface of the material. Blasting that occurs in the process affects roughness, flatness, and deflection of the workpiece. The purpose of this study was to determine the effect of the sandblasting process on surface roughness and flatness in SS 304 stainless steels material using variations in feed rate and distance by applying a semi-automatic sandblasting process by controlling the nozzle motion. The spray feed rate variations were 20, 40, and 60 mm min−1 and the distance variations were 100, 200, and 300 mm. The results of the test show that the smaller the feed rate and the closer the spraying distance, the higher the roughness value and the greater the deflection that affects surface flatness. The highest value occurs at a feed rate variation of 20 mm/min and a distance of 10 cm with a surface roughness value of 1.268 µm and flatness with a deflection angle formed of 1.184° one-sided treatment. In spraying experiments on two sided, improved the surface flatness with the highest deflection angle that occurs at a feed rate of 20 mm/min and a distance of 10 cm with a value of 0.737°.
Optimization for tensile strength of polyester composites reinforced by waru bark fiber with rice husk filler using response surface method
Authors: Pandiatmi Pandri , Kasogi Adnan
Published: March 2021

This research on the composite of Waru (Hibiscus tiliaceus) bark fibers aims to determine the optimum conditions for the tensile strength of polyester composites reinforced by Waru bark fiber with rice husk filler using the response surface method. The method used is to alkalize Waru bark by 5% NaOH soaking per 1 liter of water for 2 hours. The test object was made using the Hand Lay-Up and Compaction method, the ratio of fibers was 35.86%, 40%, 50%, 60% and 64.14% with filler 2.93%, 5%, 10%, 15% and 17.071 %. Tensile testing using standard ASTM D3039 and data analysis using response surface method. The test results show that the best conditions are at 57.131% fiber fraction and 10.73% filler volume fraction with a tensile strength value of 123.59 N mm−2. The response surface method is an efficient method used to determine levels of independent variables that can optimize response.
ZrOX insertion layer enhanced switching and synaptic performances of TiOX-based memristive devices
Authors: Chang Lung-Yu , Simanjuntak Firman Mangasa , Gapsari Femiana , Prodromakis Themis , Tseng Tseung-Yuen
Published: March 2021

The impact of ZrOx material serving as an electro-thermal modulation layer (ETML) in the TiN/Ti/TiOx/TiN memristive device structure is investigated. Although the introduction of the ETML increases the total thickness of the device resulting in the increase of forming voltage, it helps to generate weak filaments. The formation of weak filaments in analog memristive devices is preferable to ensure stable switching cycles and epoch training. The device made with ETML performs stable endurance for more than 600 cycles with an On/Off ratio of approximately one order of magnitude; moreover, the device exhibits uniform potentiation and depression with low nonlinearity.
The effect of epoxy/hardener composition ratio on the young’s modulus of bulk adhesive at high strain rate
Authors: Yohanes  , Sidharta Indra , Pramono Agus S. , Varian Kenny
Published: March 2021

This research investigated the effects of resin/hardener ratio to the mechanical behaviors of bulk epoxy adhesive at high strain rate loading using split Hopkinson pressure bar (SHPB) test. The variation of resin/hardener ratio are 2:1, 2:3, 1:1, 3:2, and 1:2 by weight. The results show that the bulk adhesive become more ductile as the ratio deviates from the manufacturer recommendation of ratio 1:1. The adhesive exhibits lower modulus but longer elongation as compared to the baseline. In contrast, at ratio of 3:2 where epoxy resin is slightly excessive, the modulus increases, and the elongation is shorter which indicates a brittle nature. The results facilitate the engineer to design adhesive of gradational modulus to improve joint performances.
Effect of addition elemental Sulfur as additive in the selective reduction process of limonite nickel ore with the presents of sodium sulfate
Authors: Pratama Adiyaksa , Ananda Rizky , Nurjaman Fajar , Ferdian Deni , Suharno Bambang
Published: March 2021

High temperatures in the smelting nickel ore increases the energy costs. The use of sulphur or sulphate as additives can optimize the reduction process at low temperatures through the formation of FeS compound. Biomass waste, which is palm shell charcoal, has potential as a reducing agent in the process of reducing laterite nickel ore because it has a fixed carbon value and a high heating value, besides that palm shell charcoal waste is more abundant as Indonesia’s palm oil industry develops. This research was carried out to investigate the effect of addition elemental sulphur as additives and palm shell charcoal as reducing agent in the selective reduction process of limonite nickel ore. This research used limonite ore with 1.38% Ni and 38.2% Fe content. The reduction of nickel ore was conducted at a reduction in temperature variations (950°C, 1050°C, 1150°C) with the presents of 10 wt.% additive sodium sulfate (Na2SO4) and addition 0%, 2.68% and 5% of elemental sulphur. The amount of reducing agent was stoichiometric variations (0.5, 1.0, 1.5). This research shows that the reduction process with 0% sulphur addition produced the most optimal grade and nickel recovery.
Characteristic of friction welding weld joint of AA6061 on elevated environmental temperature
Authors: Sugiarto  , Syamsul Ma’arif M. , Darmadi Djarot B. , Ikram Kido M.
Published: March 2021

Rotary Friction Welding is a solution in addressing the poblems in welding of material difficult to weld by fusion welding, such as AA6061 aluminium alloy. Fusion welding is difficult to apply to aluminium alloy because of porosity and crack which often occur during solidification. From the research on friction welding of AA6061, it can be conclude that excessive welding temperature of friction welding may result in thermal softening in weld zone and HAZ. The excessive cooling rate after friction welding run will affect to formation of hard and brittle of weld zone. Increase of environmental temperature above room temperature will accelerate workpiece to achieve solid state condition and lowering difference between weld peak temperature and inital weld temperature (ΔT) which mean decreasing of coooling rate. In this research, environmental temperature were varied of 27 °C (room temperature), 50 °C, 75 °C, 100 °C, 125 °C dan 150 °C. Some parameters are set constant such as rotation speed of 1600 rpm, friction pressure of 65 bar or 65 kg.cm−2, friction time (tf) of 6 seconds, forging pressure of 325 bar or 325 kg.cm−2, forging time of 60 seconds, contact diameter of workpiece of 15 mm and the workpiece chamfer angle of 15°. The contact area is divided into three zones, which are the plastic deformation zone (Zpl), the partial deformation zone (Zpd) and the non-deformed zone (Zud). The higher the environmental temperature will produces the wider plastic zone and plastic deformation zone (Zpl + Zpd). The higher the environmental temperature will causes the yield strength of the AA 6061 friction weld joint to increase which modelled as y = 3E-05x2 + 0.0033x + 16.582. Likewise, the tensile strength of the AA 6061 friction weld joint also increases which modelled as y = 3E-05x2 + 0.0026x + 18.119. When comparing the hardness of rotating workpiece side (spin) with workpiece side pressing (press), the previous one is higher at all variations of the temperature. From the photograph of the microstructure of base metal of Al 6061, dark particles (Mg2Si) and gray particles (Fe3SiAl12) are present in the Al matrix. The grain structure of Zud is bigger than Zpd and Zpl. Zpd microstructures at all environmental temperatures form smaller granular structures than base metal grains. Zpl microstructure in workpieces with environmental temperature of 27 °C, 50 °C, 75 °C and 100 °C were formed in small granular structure with Mg2Si (black) and Fe3SiAl12 (gray) structure which spread evenly. However Zpl microstructure with environmental temperature of 125 °C and 150 °C seems to enlarge, especially the structure of Fe3SiAl12 (gray), due to overheat and excessive softening.
A robust approach for people counting in dense crowd images using deep neural networks
Authors: Sri Harsha K , Shoba Bindu C , Sudheer Kumar E
Published: March 2021

People counting in dense crowd images with deep neural networks are proved to be effective. The models like RCNN are able to predict the crowd count by head detection, using the CNN and selective search algorithm, but these approaches are very slow, as they involve computing convolutional operation for 2k regional proposals, involving no shared computations, besides the selective search algorithm itself is slow. In this approach a Faster R-CNN for head detection which uses a Regional Proposal Network (RPN) has been used. The region proposal network is a Fully Convolutional Neural Networks that generates region proposals, these regional proposal were fed in to RoI pooling layer and subsequently classified and localized, Thus Faster-RCNN reduces computation cost of convolutional operations by passing a image only once, sharing the convolutional operations and also using RPN for regional Proposals. Using the Faster R-CNN MAE and MSE are reduced compared to R-CNN.