Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Mechanical Properties of Cement-Clay Interlocking (CCI) Hollow Bricks
Get PDFIn this paper, an investigative study on mechanical properties of CCI hollow bricks, for example, compressive strength, modulus of rupture, splitting tensile strength, water absorption capacity and heat transfer is conducted. The experimental program is divided into two parts. In the 1st part, bricks from three different regions (A, B and C having different soil stratum) of Thailand were collected and their mechanical properties were investigated. The mechanical properties of CCI hollow bricks of region A were observed relatively very low as compared to other regions. The compressive strength values of region A bricks were found even below the standard values required by Thai Community Product Standards (TCPS). Then, in the 2nd part, change in three mix design ratios followed by sand, cement and fly ash for region A have been exercised to observe their effects on mechanical properties of bricks from said region. Results showed significant improvements as compared with previous results obtained in first part of the experimental program. Also, a cost-benefit analysis was performed to observe the effect of the manufacturing cost on the mechanical properties of CCI hollow bricks in Thailand. It has been investigated that the brick samples with more cement content (from region C, Mix – 2 & Mix – 3) are relatively expensive as compared with other brick samples with less cement content (from region A, region B & Mix – 1)
Experimental and Analytical Study on Reinforcing Steels with Threaded Mechanical Couplers under Monotonic and Cyclic Loadings
Get PDFThis study performs the experimental and analytical investigation on the effect of mechanical couplers on the axial behavior of spliced reinforcing bars. The effect of unsupported-length-to-bar-diameter (L/D) ratios on the monotonic and cyclic behavior was observed. The test configurations in monotonic tension, compression, and cyclic tests included reinforcing bars with and without threaded mechanical couplers. Specimens with mechanical couplers have higher strength in compression than the bars without couplers, especially when L/D is less than 10. The procedure for determining the effective unsupported length for bars with a mechanical splice was proposed. And the observation on the energy dissipation confirmed the proposed method. The calculated hysteretic loops using the modified unsupported length model of the bar with mechanical splice agreed well with the test result
Consensus Synthesis of Robust Cooperative Control for Homogeneous Leader-Follower Multi-Agent Systems Subject to Parametric Uncertainty
Get PDFThis paper presents a design of robust consensus for homogeneous leader-follower multiagent systems (MAS). Each agent of MAS is described by a linear time-invariant dynamic model subject to parametric uncertainty. The agents are interconnected through a static interconnection matrix over an undirected graph to cooperate and share information with their neighbours. The consensus design of MAS can be transformed to stability analysis by using decomposition technique. We apply Lyapunov theorem to derive the sufficient condition to ensure the consensus of all independent subsystems. In addition, we design a robust distributed state feedback gain based on linear quadratic regulator (LQR) setting. Controller gain is computed via solving a linear matrix inequality. As a result, we provide a robust design procedure of a cooperative LQR control to achieve consensus objective and maximize the admissible bound of the uncertainty. Finally, we give numerical examples to illustrate the effectiveness of the proposed consensus design. The results show that the response for MAS in presence of uncertainty using robust consensus design follows the response of the leader and is better than that of the existingnominal consensus design
Land Value Capture Modeling in Residential Area Using Big Data Approach Method
Get PDFThe increase in the number of train ridership in Jakarta induced the government in constructing more rail infrastructures for example Light Rail Transit as a new option. However, this project is not supported by sufficient funds. Therefor new funding sources are needed to include all process which comprises of development, operation, and maintenance. Land Value Capture modeling is one of such solutions because it refers to the idea that all portions of land which arises from the presence of public infrastructure need to be returned. This research was carried out to obtain hedonic price modeling as a basic reference in capturing land values, by identifying variables that affect the increase of residential property prices obtained using big data approach and web scraping techniques. The result acquired from scraping Lamudi.co.id and Rumah.com websites was 1,237 properties located in South Jakarta. Furthermore, by plotting ArcGIS, 105 data located in catchment areas about 1 km from LRT line Dukuh Atas-Cawang station were obtained following Transit-Oriented Development (TOD) standard. According to the calculated SPSS, the increase in residential property value was approximate to the mall and CBD area with significant values of 0.845 and 0.819, which indicate a highly potent correlation
Simulation and Levelized Cost Analysis of Direct use Geothermal Energy for Enhanced Oil Recovery
Get PDFTo meet the demand for crude oil, which has a limited reserve; efforts are needed to maximize proven potentials. One of the solutions is the use of steam flooding as the most widely used Enhanced Oil Recovery (EOR) technology. However, the challenge that must be faced is the high production cost of steam which strongly depend on fuel cost. Meanwhile, the geothermal utilization in Indonesia is still low, only 9.3%. Seeing these problems and potential, it could be possible to utilize the geothermal heat for steam flooding. However, at present no research has been conducted related to geothermal utilization for steam flooding, only for water flooding. Therefore, this study is aimed to evaluate geothermal heat utilization for steam flooding by evaluating the maximum distance between geothermal and oil field, evaluating the technical aspect by using Honeywell UniSim Design and CMG Star and reviewing the levelized cost of steam. The results that geothermal heat can be used economically and technically possible as a pre-heating system before the boiler and it reduces the cost of steam production by 12% with a maximum distance between geothermal and oil field of 30.1 km
Sol–Gel Spin Coating Growth of Magnesium-Doped Indium Nitride Thin Films on Different Substrates
Get PDFWe report on the growth of p-type indium nitride (InN) thin films on different substrates using a relatively simple and cost-effective sol-gel spin coating method. The precursors for the indium source and p-type dopant were indium nitrate hydrate and magnesium chloride 6-hydrate powders, respectively. The structural, morphology, and optical properties of p-type InN thin films grown on different substrates were investigated. X-ray diffraction patterns revealed that the deposited Mg-doped InN thin film on GaN/AlN/Si(111) template show polycrystalline wurtzite structure with a strong InN(002) orientation and have a good crystallinity. Field emission scanning electron microscopy images and energy dispersive X-ray results showed that all the films exhibit densely packed surface morphology with hexagonal-like grains shape and low oxygen percentage with almost 1:1 ratio of indium to nitrogen. Moreover, two Raman-active modes of E2(High) and A1(LO) of the wurtzite InN were clearly observed for all samples. The ultraviolet-visible-near infrared spectroscopy results showed that the energy bandgap of the Mg-doped InN thin films was in the range of 1.62-1.66 eV. From all the results, it can be concluded that the Mg doped InN film on GaN/AlN/Si(111) substrate has better crystalline quality as compared to that of other substrates
Groundwater and River Interaction Impact to Aquifer System in Saigon River Basin, Vietnam
Get PDFSince the 1990s, under the pressure of socio-economic growth in the Ho Chi Minh City and nearby provinces, the heavy-extraction of groundwater of this area has dramatically increased to meet high water demand for domestic and industrial purposes. Although the groundwater – Saigon River interaction significantly contributes to groundwater reserves, researchers have been less attentive to fully describe and understand the river recharge. This study attempts to explore the impact of groundwater-river interaction to aquifer system due to pumping increase via field seepage and (O18, H2) isotopic measurements in the Saigon River Basin, South East of Vietnam. The analysis showed that river bed conductance at 0 km, 30 km, 60 km, 80 km, and 120 km were 4.5 m2/day/m, 4.2 m2/day/m, 2.5 m2/day/m, 1.7 m2/day/m, and 0.25 m2/day/m respectively. The riverbed conductance relies on the sand percentage of sediment. The composition δO18 in groundwater, river, and precipitation indicates that river recharge to groundwater exists mainly in the lower part of the basin. In contrast to downstream, the composition of δO18 was signified that the river primarily gains water from groundwater upstream. Under pressure of developing economies, the groundwater pumping in the Saigon river basin increased from 175,000 m3/day in 1995 to 880,000 m3/day in 2017. As a consequence of the increased pumping rate, the groundwater discharge to the river decreases from 1.6 to 0.7 times of groundwater pumping in upstream, while the amount of Saigon river recharge increases by 33% to 50% of the total groundwater pumping downstream. Under the exceedance pumping rate, the aquifers in the Saigon River Basin release less water to the Saigon river and it tends to gain more water through the river - groundwater interaction process. Therefore, groundwater management in downstream aquifers needs better joint planning with surface water development plans, particularly for surface water supply utilities which still struggle to satisfy the water demand of the development plan
Research Trends and Outlooks in Assembly Line Balancing Problems
Get PDFThis paper presents the findings from the survey of articles published on the assembly line balancing problems (ALBPs) during 2014-2018. Before proceeding a comprehensive literature review, the ineffectiveness of the previous ALBP classification structures is discussed and a new classification scheme based on the layout configurations of assembly lines is subsequently proposed. The research trend in each layout of assembly lines is highlighted through the graphical presentations. The challenges in the ALBPs are also pinpointed as a technical guideline for future research works
A Dynamic Model for Simulating Elephant-Lifting by Using a Tilting Frame
Get PDFA rigid multi-body dynamic model of an elephant was developed for motion analysis during tilt-lifting. The elephant lifting to standing position is required by veterinarians to perform surgery and bedsores treatment. The elephant mechanism dynamic model (EMDM) was developed by simplifying the skeleton to simple straight linkages connected by joints. The model consisted of 10 bones and 9 joints. A mechanical harness model (MHM) was developed. Two harnesses were attached to the tilt-frame mechanism model (FMM) and the EMDM; this assembly became the elephant dynamic during tilt-lifting model (EDTM). The developed EDTM permitted us to observe the displacement, velocity, and acceleration responses at any location on the elephant. The model allowed the virtual study of the motion, and avoided the real elephant testing; thus, the cost, time, and resources were reduced and no conflict with the animal experimental ethics. The simulation was found to be a valuable tool for engineers to design a suitable elephant bed. It permitted us to observe the operation, safety, and precaution of the equipment
Evaluation of AISC 360-16 and Eurocode 4 Compressive Strength Equations for Concrete-Filled Steel Tube Columns.
Get PDFThis paper presents a review and evaluation of the AISC 360-16 and Eurocode 4 strength prediction equations for concrete-filled steel tube (CFST) columns subjected to axial compression. A new experimental database of CFST column test results is compiled from the published technical literature from year 1988 to present. The database includes up-to-date research data of which column properties are outside the specification or code limitations. A total of 335 and 257 columns of different properties regarding the material strength, column size and slenderness, confinement factor, and steel tube fabrication method (only for square CFST) are used to evaluate the accuracy and conservativeness of the predictions for circular and square CFST columns. It is found that the AISC 360-16 strength equations conservatively predict the compressive strength of circular CFST columns even the tube slenderness exceeds the current specification limit, while the simplified method of Eurocode 4 is not recommended for square CFST columns when the yield strength of steel tube or tube slenderness ratio exceeds the code limits. Based on the strength prediction equations, the effectiveness of circular over square CFST columns is more realized in Eurocode 4 than AISC360-16. The predicted circular-to-square column strength ratio increases as confinement factor increases, while it decreases as column length-to-depth ratio increases. Based on the experimental database, the effect of column sizes on the normalized strength of circular CFST columns is also investigated. The different tendency of the size effect is found when the confinement factor changes