Journal of Engineering and Technological Sciences
Not a member yet
888 research outputs found
Sort by
Stiffness and Creep Properties of HRS-BC Powered by Palm Shell Gasification in Dryer Unit
Get PDFRoads are infrastructure that is very important in supporting people’s daily lives. With the high growth rate of traffic, the traffic load will cause damage to the road pavement in the form of deformation (rutting) and fatigue. The performance of an HRS-BC asphalt mixture was investigated to determine the asphalt’s resistance to damage. HRS-BC asphalt mixture specimens were produced by a palm shell AMP and by a diesel AMP. The performance of the HRS-BC asphalt mixture was tested in the laboratory with indirect tensile stiffness modulus (ITSM) and dynamic creep test. The results showed that the HRS-BC asphalt mixture sample produced by the palm shell AMP had better stiffness than the HRS-BC asphalt mixture produced by the diesel AMP. Both the samples of the HRS-BC asphalt mixture produced by the palm shell AMP and by the diesel AMP were not deformed when given a standard load of 100 kPa and 3,600 load repetitions
Risk Assessment and Fractionation of Cadmium Contamination in Sediment of Saguling Lake in West Java Indonesia
Get PDFThis research focused on the speciation and distribution patterns of cadmium in surface sediment from Saguling Lake, which is located in the Upper Citarum River. Organic compounds and heavy metals from anthropogenic activities in the watershed have contaminated the river. Sample from the upper layer of the sediment from Saguling Lake were taken from 12 locations, representing the dry and the rainy seasons in the period 2015-2018. Sediment cadmium (Cd) classification was conducted through a sequential extraction technique to determine Cd’s bioavailability and its risk to the water environment. During the rainy season, the total Cd concentration in the upper layer of the sediment was higher than during the dry season. The average dry and rainy season concentrations were 11.12 ± 2.16 mg/kg and 14.82 ± 1.48 mg/kgm in the sampling locations, distributed differently with the following order of the largest to the smallest concentration: 10B > 1A > 4 > 3 > 2 > 1B > 10A > 7 > 9 > 5 > 6 > 8 for the dry season, and 4 > 1A > 1B > 2 > 7 > 5 > 9 > 3 > 6 > 10A > 8 > 10B for the rainy season. All sampling locations (>60%) showed Cd in the resistant fraction, indicating no significant anthropogenic input of Cd into the surface sediment but more geological input due to high erosion. The values of RAC, ICF, and GFC indicate that the Cd in the surface sediment can be categorized as low risk
Experimental and Numerical Analysis of Carbon/Epoxy Composite Plate Subject to Low-Velocity Impact
Get PDFThe present work compared experimental and finite element analysis on the low-velocity impact response of a carbon/epoxy composite plate. Finite element analysis was based on the utilization of cohesive zone elements with the Benzeggagh-Kenane fracture criterion to predict the initiation and propagation of delamination. A Kirchhoff based formulation of a continuum shell element was used to model the stiffness of each lamina and the Hashim-Rotem damage mechanism to predict damages in every lamina. Five specimens of a 16-layer uni-directional carbon/epoxy composite plate with fiber orientation [+45°/90°/-45°/0°/+45°/90°/-45°/0°] s were subjected to low-velocity impact with a single energy value of 2.75 Joule/mm. The experimental results were then compared to the finite element results. Good agreement was achieved for the size and shape of the total projected delamination and visual damage to the top and bottom surface in the form of matrix and fiber failure. Slight differences were found for the dynamic response in the impact force history. Furthermore, a significant difference was found for the quantity of absorbed energy
Compensation of INS/LBL Navigation Errors in a Polynomial Sound-Speed-Profile
Get PDFThis paper presents an autonomous underwater vehicle (AUV) navigation scheme that pairs an inertial navigation system (INS) and a long baseline (LBL) acoustic positioning system. The INS is assigned to be the main navigation aid because of its faster rate. Meanwhile, the LBL provides position reference for compensation of the INS’ main inherent drawback, i.e., accumulating errors. However, the LBL has to deal with time-of-flight (ToF) measurements that may not be carried out under line-of-sight (LoS) circumstances. This is because the propagation speed of underwater acoustic waves is subject to the sound-speed-profile (SSP) of the area in question. This paper’s contribution is to consider the SSP in ToFs while addressing the above scheme. Specifically, the discrete approach to raytracing was implemented. For a given ToF, the Snell’s parameter of the wave is estimated and subsequently used to compute the horizontal range. The ToF results are then used to estimate the position of the AUV, while the position is obtained from a depth sensor. It was shown by simulation that the estimators can provide navigation with accuracy <0.5 m2, as it manages to compensate for errors. Since the estimation of Snell’s parameter is prone to exhibit imaginary numbers, future work should consider a more robust method to tackle this problem
The Effect of Filter Media Size and Loading Rate to Filter Performance of Removing Microplastics using Rapid Sand Filter
Get PDFMicroplastics (MP) can pose a serious threat to the environment and human health because of their tiny size and ability to spread easily in water. One of the alternative treatments to remove MP from water is the rapid sand filter (RSF). The objective of this study was to analyze the effects of filter media size and loading rate on RSF performance in removing MP. The applied filter media was silica sand with effective sizes (ES) of 0.39 and 0.68 mm. The loading rates of filtration were 4; 6; 8 and 10 m3/m2-h. The MP samples were made from plastic bags and torn tires (artificial samples: 10 to 800 µm). This study showed that the MP removal percentage was up to 96.6% (MP size larger than 200 µm). The head loss increment for loading rates 4; 6; 8; 10 m3/m2-h was 0.16; 0.35; 0.34; 0.25 m (ES 0.39 m) and 0.10; 0.18; 0.18; 0.19 m (ES 0.68 m)), respectively. Meanwhile, the filtration cycle for loading rates 4; 6; 8; and 10 m3/m2-h was 5, 2, 2, and 1 days (ES 0.39 mm) and 9, 4, 3, and 3 days (ES 0.68 mm), respectively. The result of this study showed that the smaller the filter media size, the higher the head loss of the filter media bed. Furthermore, there is an increased head loss of the filter media bed when the loading rate is greater
A Finite Element Approach to Conduct Machinability Studies on Age-Hardened AA6061 Matrix Hybrid Composites
Get PDFAA6061, a popular structural material, has found widespread usage in the automotive and aerospace domains. The current work explored the effect of the improvement of mechanical properties on the machinability of AA6061 through finite element analysis. Three compositions of AA6061 containing 2 wt.% graphite and 0, 2, 4 wt.% granite dust were fabricated by stir casting. In the current work, a finite element model of a slab milling cutter with eight teeth was designed with high-speed steel (HSS) as the tool material. The LS-DYNA module of ANSYS was used for simulation of the milling operation, selecting two peripheral speeds for the cutter during the machining of the workpiece. Surface milling was carried out on the cast slabs of the three compositions to study chip formation. At higher cutting speeds, there was an increase in the von Mises stress as well as material deformation. An increase in the weight fraction of the ceramic fillers led to a corresponding increase in the von Mises stress and material deformation. The experimental results from face milling of the three compositions showed that the surface roughness increased with an increase in the content of ceramic fillers and a decrease in chip size
A Low-Cost Laboratory Practice for Fundamental Learning of Wireless Digital Communication
Get PDFSeveral studies have shown that the main challenge in teaching complex systems involving many theoretical backgrounds to senior students is their lack of confidence. In this paper, we present an approach to the teaching methodology of an undergraduate course in a telecommunication study program. The first goal of this methodology is to help students understand the theoretical concepts behind wireless digital communication systems through direct practice to give them more exposure to a real system through affordable practice activities in an experiential context, utilizing an HF radio and a single-board computer (SBC). The second goal is to challenge senior students to understand the data link layer by using white box testing of the syntax of the programming language embedded in the SBC. This approach is ideally carried out based on offline and hands-on class activities, however, the pandemic condition made it unavoidable to do it online using a demonstration model. Feedback from students was collected through written comments, post-testing, including a facility index analysis, and a questionnaire that was distributed using the available e-learning system. The post-test results showed that the average score was 72 out of a maximum of 100