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Adaptive Priority-Based Downlink Scheduling for WiMAX Networks
Shih-Jung Wu,Shih-Yi Huang,Kuo-Feng Huang 한국통신학회 2012 Journal of communications and networks Vol.14 No.6
Supporting quality of service (QoS) guarantees for diverse multimedia services are the primary concerns for WiMAX (IEEE 802.16) networks. A scheduling scheme that satisfies QoS requirements has become more important for wireless communications. We propose a downlink scheduling scheme called adaptive priority-based downlink scheduling (APDS) for providing QoS guarantees in IEEE 802.16 networks. APDS comprises two major components: Priority assignment and resource allocation. Different service-type connections primarily depend on their QoS requirements to adjust priority assignments and dispatch bandwidth resources dynamically. We consider both starvation avoidance and resource management. Simulation results show that our APDS methodology outperforms the representative scheduling approaches in QoS satisfaction and maintains fairness in starvation prevention.
Numerical Simulation of High Power LED Heat-Dissipating System
Shih-Jeh Wu,Hsiang-Chen Hsu,Shen-Li Fu,Jiam-Nan Yeh 대한금속·재료학회 2014 ELECTRONIC MATERIALS LETTERS Vol.10 No.2
In this paper, thermal analysis of the heat dissipation under different heat sink for high-power white Light Emitting Diode (LED) is presented. Junction temperature of LED is elevated as the power of LED increases, which brings up deterioration of light efficiency and other side effects. Heat dissipation is another design concern other than material and illumination efficiency. The purpose of this paper is to investigate the cooling of high-power LED chips and modules for design of heat sinks. Three types of heat sinks are designed for a tandem 12-chip module and an extensive numerical investigation of the heat sink design performance is conducted by Computational Fluid Dynamics software Fluent. The effects of heat sink geometry and adhesive material are also investigated. Design variables are the thickness of sink base, number, thickness and length of fins. The total wetted area is the dominant factor to the junction temperature. The objective of design regarding the junction temperatures around 50°C is easily achieved. However, its effect is limited at high values of these parameters, furthermore an excessive number of fins incurs reverse consequence due to problem of ventilation also waste of material.
Development of Novel Tool Center Point Velocity Planning Algorithm for Five Axis Machine Tool
Shih-Kai Wu,Meng-Shiun Tsai,Ming-Tzong Lin,Hong-Wei Huang 한국정밀공학회 2018 International Journal of Precision Engineering and Vol.19 No.8
In this paper, a tool center point (TCP) feedrate scheduling algorithm for 5-axis machine tool is developed to generate the axes interpolation commands. The proposed algorithm considers not only the constraints of TCP velocity, acceleration and jerk, but also the velocity differences of each axes at the junction of each block. First, the proposed method determines the maximum speed for each block segment at the TCP coordinate based on the computed length. Then the kinematics of the five axis machine tool is employed to derive the five-axis corner velocity difference (FCVD) formulation. The FCVD utilizes the axis velocity difference at the junction of blocks as the designed variable. As the starting and end velocities of each block are determined, the S-shape acceleration/ deceleration (Acc/Dec) method is adopted to generate both smooth TCP and rotary axis profile based on the given interpolation parameters. The servo dynamics of the five axis machine tool are utilized to evaluate the performances of the FCVD. Simulation results demonstrate that the FCVD can achieve better contour accuracy with less machining time as compared to the five-axis feedrate regulation formulation (FFRF) algorithm. Furthermore, the FCVD are compared with Heidenhain CNC controller and the results show that the FCVD has similar behaviors as the Heidenhain controller, but it can achieve less machining time.
Wu Shih-Ching,Hsu Hsueh-Chuan,Liu Mei-Yi,Ho Wen-Fu 한국세라믹학회 2021 한국세라믹학회지 Vol.58 No.1
Hydroxyapatite (HA) has been vigorously studied for orthopedic and dental applications due to its excellent bioactivity, osteoconductivity, and osteoinductivity. This study aims to present a simple room-temperature aqueous precipitation method for obtaining carbonated HA nanoparticles of high purity from biowaste chicken eggshells. Biowaste chicken eggshells were used for preparing HA through aqueous precipitation method. Moreover, mulberry leaf extract was used as a template to regulate the morphology, size, and crystallinity of HA. All produced nanocrystalline HA powders exhibited rod-like particle agglomerates of a size below 100 nm. The HA particles synthesized with the mulberry leaf extract showed higher crystallinity and slightly decreased crystallite sizes compared to the samples prepared without adding the extract. Carbonate peaks observed for the specimens closely matched those of A- and B-type carbonates, which can contribute to the low crystallinity. Notably, the HA synthesized from the eggshell powders contains several important trace elements such as Mg and Sr, which are benefi cial to the overall biological performance as biomaterials. The morphology, size, structure, and composition of the obtained HA products are similar to those of natural bones, and consequently, the products show potential as a material for biomedical applications.
Adaptive Priority-Based Downlink Scheduling for WiMAX Networks
Wu, Shih-Jung,Huang, Shih-Yi,Huang, Kuo-Feng The Korea Institute of Information and Commucation 2012 Journal of communications and networks Vol.14 No.6
Supporting quality of service (QoS) guarantees for diverse multimedia services are the primary concerns for WiMAX (IEEE 802.16) networks. A scheduling scheme that satisfies QoS requirements has become more important for wireless communications. We propose a downlink scheduling scheme called adaptive priority-based downlink scheduling (APDS) for providing QoS guarantees in IEEE 802.16 networks. APDS comprises two major components: Priority assignment and resource allocation. Different service-type connections primarily depend on their QoS requirements to adjust priority assignments and dispatch bandwidth resources dynamically. We consider both starvation avoidance and resource management. Simulation results show that our APDS methodology outperforms the representative scheduling approaches in QoS satisfaction and maintains fairness in starvation prevention.
Hydroxyapatite prepared from eggshell and mulberry leaf extract by precipitation method
Wu, Shih-Ching,Hsu, Hsueh-Chuan,Hsu, Shih-Kuang,Liu, Mei-Yi,Ho, Wen-Fu Techno-Press 2019 Biomaterials and Biomechanics in Bioengineering Vol.4 No.1
Eggshell is a waste material after the usage of egg. In this work, biowaste chicken eggshells were used for preparing carbonated hydroxyapatite (HA) nanoparticles of high purity through aqueous precipitation method at room temperature. The eggshell-derived HA will be a cost-effective bioceramics for biomedical applications and an effective material-recycling technology. Additionally, mulberry leaf extract was used as a template to regulate the morphology, size and crystallinity of HA, and the effects of pH value were also examined. Characterization of the samples was performed by X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. Scanning electron microscopy (SEM) was used to determine the size, shape and morphology of HA. The results indicate that only one phase of HA were synthesized in the both absence and presence of mulberry leaf extract at pH of 7 and above, while DCPD or DCPA/DCPD phase was observed at pH 4 condition. The crystallite sizes of the HA samples obviously decreased when adding mulberry leaf extract as a template, while they decreased gradually as the solution pH levels increased. With increasing pH level from 7 to 14, the rod-like HA nanoparticles gradually changed to spherical shape at pH 14. Note that, the obtained product is Mg and Sr containing A- and B-type carbonate HA at alkaline pH and it can be a potential material for biomedical applications.
The effect of bending loads on the dynamic behaviors of a rolling guide
James Shih-Shyn Wu,Jyh-Cheng Chan,Gent-An Tsai,Ching-Yuan Lin,Feng-Ming Ou 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.3
Dynamic behaviors of ball-type contact surfaces under unbalanced bending loads are studied using point-to-point analysis, threedimensional finite element simulation based on the Hertz Contact Theory, and a modal test. Results derived from these models are very similar but the Finite Element Model provides the best results since it allows for more elements of study, such as the steel ball, carriage,rail etc. In the study, results also show that frequencies vary slightly, but there is an obvious change in shapes. Therefore, the contact stiffness in simulations must be properly selected with the conclusion that different external loadings may affect the dynamic characteristics of such structures significantly.
3D contact analysis of conjugate spur gears by a complete mating process
James Shih-Shyn Wu,Shu-Ling Xu,Yi-Tsung Lin,Wei-Hung Chen,Yuan-Lung Lai 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.12
Instead of applying fixed boundary conditions to constrain and simplify material behavior in 2D models, the point and line contact of tooth surfaces are substituted by a face-contact model of teeth in this study. The inaccurate prediction of load, deformation, and stress in 3D contacts are solved. Most research uses one pair to three pairs of meshing teeth to simulate the mating process. However, describing the entire process of three contact zones during each mating pair is insufficient. By implementing a combined 3D face contact and finite element method, the contact stress analyses between two spur gear teeth are conducted in 11 different contact positions during a full mating process. The proposed approach provides a complete and effective solution to the contact problem in a quasi-dynamic manner. This model not only determines the load-sharing prediction but also verifies the applied boundary conditions.