Engineering Journal (Faculty of Engineering, Chulalongkorn University, Bangkok)
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Performance Comparison of Two-phase LP-based Heuristic Methods for Capacitated Vehicle Routing Problem with Three Objectives
Get PDFThis paper develops a two-phase LP-based heuristic for the Capacitated Vehicle Routing Problem (CVRP). It considers three objectives: (1) minimizing the total costs of fuel consumption and overtime, (2) maximizing the total personal relationships between customers and drivers, and (3) balancing the delivery weights of vehicles. The two-phase LP-based heuristic (cluster-first route-second) is proposed. First, in the clustering stage, three LP-based clustering models (denoted by C1, C2, and C3) are developed. Customers are grouped into clusters based on real distances between the customers for C1, personal relationships between the customers and drivers for C2, and the delivery weights of vehicles for C3. Second, in the routing stage, an LP-based traveling salesman problem model is used to form a route for each cluster, to minimize the total costs of fuel consumption and overtime labor. The experimental results from a case study of Thai SMEs show that when the C2 clustering model is applied, the performances are the best. Significant contributions of this paper include: (1) it is an original paper that proposes the C2 clustering model, and it has the best performances based on the experimental results, and (2) the proposed two-phase LP-based heuristic methods are suitable for practical use by SMEs since the required computational time is short, and it has multiple models with different objectives that can be selected to match a user's requirements
Vendor Managed Inventory for Multi-Vendor Single-Manufacturer Supply Chain: A Case Study of Instant Noodle Industry
Get PDFThis paper develops a vendor-managed inventory (VMI) model for a multiple-vendor, single-manufacturer supply chain, in which the first stage members can be traders and/or producers and the second stage member is a manufacturer. The model utilizes a realistic transportation cost which is dependent on the sizes (small- or medium-sized) of trucks. It can determine suitable sizes and numbers of trucks that minimize the transportation cost. A genetic algorithm (GA) technique, implemented in MATLAB software, is used to determine the best solution to the problem. A case study in the instant noodle industry is conducted to demonstrate the usefulness of the proposed model. Based on the experimental results, the VMI model has reasonable behaviors using sensitivity analysis. To reduce the inventory level of raw materials, the penalty cost may be set at a relatively high level or the upper inventory limits may be set at relatively low levels, without significantly affecting the average total cost per period of the entire supply chain. When the vendors are allowed to make decision independently, the solution is still the same as the solution from the proposed VMI model, which means that the manufacture does not take advantage of the vendors
Influence of Type and Compositions of SCMs on Expansion of Mortar Bars from Alkali Silica Reaction
Get PDFThe effect of different local pozzolans, as a supplementary cementitious material (SCM), on the expansion of mortar bar due to Alkali Silica Reaction (ASR) were reported in this paper. Accelerated test on specimens using local volcanic aggregates, rhyolite, was used to investigate and to compare the effects of fly ash (FA) and metakaolin (MK) on the suppression of the length change. In this study, three different percentages of FA, namely, 20, 35 and 50 and three of MK, namely, 10, 15 and 20 were used in cement replacement. The results showed the lowest expansions at 14 days were -0.036% and -0.001%, respectively for 35% FA and 10% MK, compared to 0.176 % of the control mix. Results from 28 days acceleration registered a slight increase in expansion for both FA and MK mixes. Increase the SCMs to 50% FA and 15-20% MK yielded reduction of expansion to the innocuous level for both short and long term expansion. Chemical composition analysis revealed decrease in CaO/SiO2 and CaO/Al2O3 of the cementitious systems. This could affect the expansion reduction. But alumina in Al2O3/SiO2 show the dominant effect on ASR suppression. Microstructures of all materials and casted specimens were also studied in detail. Considering all aspects, these SCMs were considered good candidates for ASR prevention in new concrete structures
Chemical Modification of Cotton Fabric Using Chitosan and Hydrolyzed Silk Fibroin
Get PDFA cotton fabric modified with chitosan (CS) and hydrolyzed fibroin (HF) was prepared by using glyoxal as crosslinker. Fixation of CS and HF on cotton fabric was confirmed by Scanning electron microscopy (SEM) and Fourier transform infrared spectrometer (FTIR) and color depth (K/S) of finished fabrics which was dyed with acid dye. %Water absorption, tensile strength as well as %elongation and crease recovery angle were evaluated. Results of SEM micrograph and FTIR spectra clearly confirmed fixation of CS and HF on cotton fabric surface by using glyoxal as crosslinker. %Water absorption and %elongation of the finished fabrics increased with increased concentration of HF in finishing solution. However, decreases in tensile strength and % crease recovery were observed when increased concentration of HF was used. This work demonstrated that the surface properties of cotton fabrics was changed by HF modification, fixation of CS and HF placed onto cotton fabric changed the fabric surface properties, which facilitated more uptake of chemicals such as water and anionic acid dye. The cotton fabrics finished with hydrolyzed fibroin exhibited antibacterial activity against the growth of S.aureus and E.coli which facilitated the finished cotton fabric as a functional materials, for example in a medical application
Weighted-Probability Random Number Generator for PLC Channel Transfer Function Generation
Get PDFThe concept of randomization shows many realistic scenarios and has enormous applications in everyday life. However, existing random number generators have poor adaptability when representing some of the actual occurrences in natural environment, such as in biology, mobile communications, and even electrical behavior. For PLC channel transfer function generation, biased sampling of the channel is more applicable. This paper proposes a weighted-probability method to generate random numbers to emulate the real-world variations of a power line communications channel. Existing PLC channel emulator can mimic the random behavior of the channel, altered by several parameters such as cable length, cable type, presence of loads, and ejecting different noises. However, the scenario of integrating the effect of changing the state of the loads and channel variation due to time is not well represented in the normal random channel generation. The best concept for this scenario is the weighted random number generator (WRNG). This work developed an algorithm in Matlab and VHDL, implemented it in FPGA and integrated it with an existing PLC channel emulator. The emulator is implemented using Kintex-7 FPGA. In this study, ten different weights corresponding to the probability of occurrence of the actual household appliances and eighty transfer functions were used as inputs to the program. The randomness and periodicity of the WRNG are tested and passed the Runs test. Autocorrelation and histograms are used to determine the correct implementation of the weights
Automatic Assessment of Seed Germination Percentage
Get PDFThis research was designed to investigate an automatic seed germination rate for the top of paper germination method. Chili and guinea were adopted to be used in the experiment with a 4-time repetition and 2 sets of the germination group (4-separated plates with 50 seeds per plate, 2 sets per seed type, totally 400 seeds of chili and 400 seeds of quinea). Two detection methods were proposed binary thresholding and maximum likelihood; based on color analysis. An uncontrolled environment image taking was the way to collect image data. The results were compared to a hand-labeling groundtruth. Both methods achieved accuracy rate higher than 93% which was promising to implement this system. The binary thresholding was a lightweight method suitable for a very limited resource software environment system. The maximum likelihood was more complex. The method had more potential than the binary thresholding, it was flexible to the light condition, returned few false alarms per image (less than 3 false alarms per image). Maximum likelihood could be adopted to implement in a proper environment which still could be in a mobile device
The Acceptance of Using Information Technology for Disaster Risk Management: A Systematic Review
Get PDFThe numbers of natural disaster events are continuously affecting human and the world economics. For coping with disaster, several sectors try to develop the frameworks, systems, technologies and so on. However, there are little researches focusing on the usage behavior of Information Technology (IT) for disaster risk management (DRM). Therefore, this study investigates the affecting factors on the intention to use IT for mitigating disaster’s impacts. This study conducted a systematic review with the academic researches during 2011-2018. Two important factors from the Technology Acceptance Model (TAM) and others are used in describing individual behavior. In order to investigate the potential factors, the technology platforms are divided into nine types. According to the findings, computer software such as GIS applications are frequently used for simulation and spatial data analysis. Social media is preferred among the first choices during disaster events in order to communicate about situations and damages. Finally, we found five major potential factors which are Perceived Usefulness (PU), Perceived Ease of Use (PEOU), information accessibility, social influence, and disaster knowledge. Among them, the most essential one of using IT for disaster management is PU, while PEOU and information accessibility are more important in the web platforms
Sizing and Positioning of Cylindrical Object Based on the Millimeter-Wave Radar System
Get PDFIn this article, we propose an algorithm to estimate the size and position of an object with the millimeter wave radar system. With the proposed algorithm, the size and position of objects is represented by cylinders with a single IWR1443 radar sensor module. From the estimated cylinder, the radius and center of the cross-sectional circle shows the approximate size and position. Raw data from IWR1443 show scanningof objects in the form of data points which cannot be directly used to determine the exact size or shape of the object. The data in one frame of the sensor provides many data points. With K-mean and selection of K, we can group the number of data points to each object and find the size and position by circle-fitting. The results of the algorithm show that the mean of a position of the object is close to the actual value, but the mean of the radius is rather smaller than the actual value
State Estimation Filtering using Recent Finite Measurements and Inputs for Active Suspension System with Temporary Uncertainties
Get PDFIn this paper, the finite memory structure(FMS) filter using most recent finite measured outputs and control inputs is applied for the state estimation filtering of automotive suspension systems to verify intrinsic robustness of FMS filter. Firstly, the single-corner model for the automotive suspension system and its state-space model are described. Secondly, FMS as well as infinite memory structure(IMS) filters are briefly introduced and represented by the summation form. Thirdly, a couple of temporary uncertainties, model uncertainty and unknown input, are discussed. Finally, extensive computer simulations are performed for both nominal system and temporarily uncertain system. It is shown that the FMS filter can be better than the IMS filter for both temporary uncertainties. In addition, the FMS filter can be shown to be comparable to the IMS filter after the effects of a couple of temporary uncertainties have completely disappeared
Concentration Optimization of Sodium Percarbonate as Buffering Catholyte on Stacked Microbial Desalination Cell by Utilizing Tofu Wastewater as a Substrate
Get PDFThe objective of this research is to obtain the optimum concentration of Sodium percarbonate (SP) as catholyte which gives the best desalination performance in Stacked Microbial Desalination Cell (SMDC) system using tofu wastewater as a substrate. SMDC is a promising technology for wastewater treatment and water desalination to overcome the problem of water crisis and the use of Sodium percarbonate will prevent pH imbalance which is one of the major issues in SMDC technology. Four Sodium percarbonate concentration variations of 0.05, 0.1, 0.15 and 0.2M were examined at 50 hours operating time. The optimum performance of Sodium percarbonate is then compared with other commercial catholyte Potassium permanganate. The result of this research is the optimum concentration of sodium percarbonate as a catholyte is at concentration equal to 0.15 M with 1.77% salt removal in Desalination-Cathode Chamber and 0.82% salt removal in Desalination-Anode Chamber. Also, the best catholyte is SP in comparison to KMnO4 because it acts as a better electron acceptor (oxidation agent) as well as buffering catholyte with higher value of SDR and TDR equal to 1.2469 g/(L.h) and 1.8704 g/h respectively