Taiwan Association of Engineering and Technology Innovation: E-Journals
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CPW-Fed Penta Band Monopole Antenna for Multiservice Wireless Applications
Get PDFA compact triple T-shaped stub with meander loaded strip antenna for penta band applications is proposed. The rectangular patch antenna with meandered and open-ended slot cuts is utilized to realize four operating bands at 2.45 GHz, 3.1 GHz, 5.3 GHz, and 6.5 GHz with an impedance bandwidth of 400 MHz (2.15-2.550 GHz), 1000 MHz (2.7-3.7 GHz), 200 MHz (5.4-5.6 GHz), and 200 MHz (6.4-6.6 GHz), respectively. For an additional resonance frequency, the length of the central T-shaped stub is slightly modified which causes the variation in the current distribution. As a result, the resonance frequency of 5.5 GHz is divided into two resonance frequency bands which are operating at 5.25 GHz and 5.85 GHz with an impedance bandwidth of 100 MHz (5.25-5.35 GHz) and 200 MHz (5.75-5.95 GHz), respectively. Furthermore, a parametric reflection coefficient and surface current distribution analysis is carried out to understand the strip and slot behavior at resonance frequency bands. Finally, a prototype is fabricated and its reflection coefficient, gain, and radiation pattern are measured. The experimental result shows that the proposed antenna is reliable for penta band applications
Effects of the Vibration Amplitude in Vibratory Stress Relief on the Fatigue Life of Structures
Get PDFThis research aims to investigate the effects of vibration amplitude in vibratory stress relief (VSR) on the fatigue strength of structures with residual stress. Experiments are carried out on specimens with residual stress generated by local heating. Flat specimens made of A36 steel are prepared to be suitable for setting up fatigue bending tests on a vibrating table. Several groups of samples are subjected to VSR at resonant frequencies with different acceleration amplitudes. The results show that VSR has an important influence on the residual stress and fatigue limit of steel specimens. The maximum residual stress in the samples is reduced about 73% when the amplitude of vibration acceleration is 57 m/s2. The VSR method can also improve the fatigue limit by up to 14% for steel samples with residual stress
Clustering Analysis with Embedding Vectors: An Application to Real Estate Market Delineation
Get PDFAlthough clustering analysis is a popular tool in unsupervised learning, it is inefficient for the datasets dominated by categorical variables, e.g., real estate datasets. To apply clustering analysis to real estate datasets, this study proposes an entity embedding approach that transforms categorical variables into vector representations. Three variants of a clustering algorithm, i.e., the clustering based on the traditional Euclidean distance, the Gower distance, and the embedding vectors, are applied to the land sales records to delineate the real estate market in Gwacheon-si, Gyeonggi province, South Korea. Then, the relevance of the resultant submarkets is evaluated using the root mean squared errors (RMSE) obtained from a hedonic pricing model. The results show that the RMSE in the embedding vector-based algorithm decreases substantially from 0.076-0.077 to 0.069. This study shows that the clustering algorithm empowered by embedding vectors outperforms the conventional algorithms, thereby enhancing the relevance of the delineated submarkets
Durability Study of Hybrid Fiber Reinforced Concrete
Get PDFSisal has been reported as one of the promising fibers for cement composite applications. The durability of sisal fiber reinforced concrete (SFRC) and steel sisal fiber reinforced concrete (SSFRC) have not been reported. Water absorption, rapid chloride permeability, and acid attack tests are conducted on fibrous cement composites. Steel, polypropylene, and sisal fibers with a total volume of 0.50%, 1.00%, 1.25%, and 1.50% were used. Sisal at a content of 1.50% in SFRC increases the water absorption by 76%, but it is reduced to 30% for SSFRC with 0.2% of sisal content. SFRC and SSFRC show the increased permeability of 1.69% and 2.09% respectively. SFRC experiences the highest volume loss of 6.52%. SSFRC illustrates the resistance to the mass loss and compressive strength loss. In conclusion, untreated sisal in any form is found to be not advantageous for durable fibrous concrete structures
Multi-Object Face Recognition Using Local Binary Pattern Histogram and Haar Cascade Classifier on Low-Resolution Images
Get PDFThis study aims to build a face recognition prototype that can recognize multiple face objects within one frame. The proposed method uses a local binary pattern histogram and Haar cascade classifier on low-resolution images. The lowest data resolution used in this study was 76 × 76 pixels and the highest was 156 × 156 pixels. The face images were preprocessed using the histogram equalization and median filtering. The face recognition prototype proposed successfully recognized four face objects in one frame. The results obtained were comparable for local and real-time stream video data for testing. The RR obtained with the local data test was 99.67%, which indicates better performance in recognizing 75 frames for each object, compared to the 92.67% RR for the real-time data stream. In comparison to the results obtained in previous works, it can be concluded that the proposed method yields the highest RR of 99.67%
Effect of Zeolite on the Compaction Properties and California Bearing Ratio (CBR) of Cemented Sand
Get PDFThis research investigates the impact of zeolite on the compaction properties and California Bearing Ratio (CBR) of cemented sand. For this purpose, firstly, sand, cement (2, 4, 6, and 8% by the sand dry weight), and zeolite (0%, 30%, 60%, and 90% of cement content, as a replacement material) are mixed. Then, various cylindrical samples with sizes of 101×116 mm and 119×152 mm are prepared for compaction and CBR tests, respectively. After curing for 28 days, the samples are tested according to the standards of compaction and CBR tests. The results depict that the use of zeolite reduces Maximum Dry Density (MDD) while it increases Optimum Moisture Content (OMC) of cemented sand. Furthermore, the inclusion of zeolite up to 30% of cement content contributes to the highest CBR values due to the pozzolanic and chemical reactions. Finally, some correlations with high correlation coefficients are proposed between the CBR and MDD of zeolite-cemented sand
Power Sharing and Control by Droop Controller with Advanced Filter Design: A Case Study in Lock-down Periods
Get PDFIn the lock-down period, the islanding mode of operation with droop controllers has several advantages in the alternating current grid. This study focuses on an improvised droop controller. It consists of an advanced filtering segment embedded with a conventional droop controller, which overcomes the drawback of droop controllers of the non-handling of non-linear loads in an ordinary situation. A selective harmonic elimination technique in grid-connected mode and lock-down mode and an advanced filter embedded with droop control are used so that the proposed controller can also work as an Active Harmonic Filter (AHF). The simulation results in different cases show that the proposed controller can control the active and reactive power in the lock-down period as well as the harmonics in the normal period up to an extent
Optimum Combinations of GGM and GDEM Models for Precise National Geoid Modelling
Get PDFThis study aims to develop a Local Geoid Model (LGM) for Egypt to determine the optimal combinations of global models with Global Navigation Satellite Systems (GNSS/Levelling) data. A precise national geodetic dataset, four Global Geopotential Models (GGMs), and three global Digital Elevation Models (DEMs) have been utilized. Hence, twelve gravimetric LGMs have been developed using the Least-Square Collocation (LSC) method fitted to GNSS/Levelling data and judged over 100 checkpoints. Results revealed that improvements in local geoid accuracy are attributed mainly to GGMs models representing the long wavelength of the Earth's gravitational field. Regarding DEMs, the accuracy of LGMs does not significantly depend on the utilized DEM. Based on the available data, the attained optimum geoid of Egypt has been developed with a standard deviation, equals 0.129 m
Instability Risk and Beam Profile Variation in Optical Ring Resonator due to Thin Gradient Index Lens
Get PDFIn this study, a simple ring resonator model in presence of thin gradient index (GRIN) lens is investigated to characterize the optical beam maginification quality beyond its traditional modalities. This model allow us to vary and control the limit of resonator stability more significantly.It consist of two folding arms and each arm can be realized by its cavity components. Insertation of thin GRIN lens ( thickness < 9.3mm) in ring resonator, mainly in between first folding range gives the magnified output beams and meets the beam expander feature for the laser. Variation of GRIN lens thickness (L) is an emphatic and influencing parameter than its refractive index (n) to disturb the resonator stability. Resonator stability in Tangential (T) plane is relatively more sensitive than sagittal (S) plane. Vigorous magnification in optical beam size at the end of output range in a cavity is the noticeable consequences because of GRIN lens
Enhancing Design Features of Asymmetric Spur Gears Operating on a Specified Center Distance Using Tooth Sum Altered Gear Geometry
Get PDFAsymmetric gears have evolved from the rising demand for power transmission drives with high load-carrying capacity, surface durability, and service life. Direct design and S± profile shifted system are the most common approaches used for enhancing design features by geometry modification in asymmetric gears. This paper aims at establishing asymmetric gear geometry modification using tooth sum alteration for a family of gears running on a specified center distance as a feasible design approach. A complete mathematical treatment of the design approach is provided, and an in-house developed computer program is used for numerical simulation. The paper explores the influence of dynamic load factors, location factors for bending, specific sliding on load-bearing capacity, and surface durability on different tooth sum alterations. The study concludes that tooth sum altered asymmetric gear geometry can be employed as an effective design technique that offers designers flexibility in designing gears for surface wear, load-bearing, and tooth life