Applied Mechanics and Materials Vols. 284-287

Abstract: Combining Short Message Service (SMS) and Global Position System (GPS), this paper proposes a novel method, called Location-based Delivering (LBD), and further develops a realistic system to tracking target's moving. LBD can reduce the number of short message transmissions while maintaining location accuracy within an acceptable range. LBD mainly adopts two proposed techniques: location prediction and dynamic threshold. Location prediction utilizes the current target's location, moving speed, bearing to predict its next location. When the distance between the predicted location and the actual location exceeds a threshold, the target sends a short message of the actual location to the tracker for updating. According to the target’s moving speed, dynamic threshold dynamically adjusts the threshold in order to balance the location accuracy and the amount of short messages. Experiment results show that LBD indeed outperforms other methods because it sends the least number of short messages and also maintains the satisfactory location accuracy.

Abstract: In this letter, we present a blind carrier frequency offset (CFO) estimator by exploiting the polynomial rooting technique for multicarrier-code division multiple access (MC-CDMA) systems. Relative high accuracy and low-complexity to the CFO estimation can be achieved by rooting a polynomial. Simulation results are provided for illustrating the effectiveness of the proposed blind polynomial rooting estimator.

Abstract: Wireless mesh networks (WMNs) have attracted much attention in recent years. The main problems in WMNs are the unfairness in bandwidth sharing and potential selfish behavior. In this paper, an incentive-based pricing model is designed which follows the concepts of mechanism design in game theory to encourage nodes to relay packets for other nodes and therefore achieve fairness. In the pricing model, we consider the packet transmitting amounts, idle conditions and the special need of border nodes in the margin area. The incentive is the main feature of the model. We also discuss the model using mathematical analysis from various perspectives. The analysis shows that this model is highly effective in eliminating unfairness in the multi-hop transmission topology. This is achieved by allowing border mesh routers to receive a fair profit. This flexible pricing model is capable of encouraging packet forwarding. With the issue of unfairness resolved, WMNs can be expected to have a broader range of applications.

Abstract: Cell planning problem is one of the most important issues in mobile communication networks. To tackle the problem, one should address the location management issue because it significantly affects the cost of cell planning in mobile networks. The partition of location areas is developed to minimize the total costs of considering user location and search operation simultaneously in cellular networks, which has been shown to be NP-complete and is commonly solved by metaheuristics in previous works. In this paper, we propose novel cell planning methods for base stations using genetic algorithms with initialization, local search, and particular mechanisms of area and cell crossovers. Several simulations are conducted on various cell networks with previous, random and real configurations. The simulation results reveal that our schemes are superior to the considered algorithms.

Abstract: LED gradually replaces light source in many fields, it becomes more and more important. For the purpose of letting LED more effective, people usually use secondary optical lens to improve the optical quality. In this research, reflector and lens are used to compose a LED light module. In this study, a LED module is designed to meet the specific requirement of the illumination. It was found that changing lens thickness and lens position can improve the uniformity and the size of light patch. As a result, we found parameters about lens for best results. In the design process, we realized that uniformity can be increased by decreasing D10 value of the light. The best result of simulation was found (which are in the form of point data). We used polynomials to fit the contour of LED module of point data and used it to extend the reflector contour of calculated results. The size of light patch of LED contour with reflector-masked and point data is much smaller than with polynomials.

Abstract: An optical mechanism composed of a movable part and a fixed part for the increment high-resolution optical displacement encoders is proposed in this paper. The parallel light emitted from the movable part passes through a double-concave lens and a specially designed optical grating; it is then projected onto a phototransistor array receiver to indicate the displacement of the movable part. The relationship equation of the lens is developed to design an optical mechanism which can enlarge the displacement so that it becomes observable. Based upon the simulation results, a specially designed optical grating is designed to compensate for the deviations on the detecting surface and to derive the increment movement of the light source. The simulation results indicated that the optical mechanism with 50 times magnification could make the 10 nm movement intervals of a light source be about 500 nm movement intervals in the detecting surface. Furthermore, an experimental system with a 200 nm resolution is established to verify the possibility of the proposed structure.

Abstract: The presented paper shows results from the mechanical design of lightweight mirrors for space applications, where demand for maximum weight loss goes together with demands for sufficient strength, shape accuracy, and surface quality of optical surfaces. The paper illustrates the material properties of different materials, which are often used for manufacturing precise optics. It compares three materials – e.g. optical glass such as NFS-15, optical ceramic such as Zerodur, and Silicon-infiltrated sintered Silicon Carbide – from the point of view of suitability for machining and their mechanical and thermal properties. It also shows the possibility of mass reduction by using different geometries of lightweight structure. Paper shows the results of numerical simulations of specified load-cases and comparison of different lightweight structures and different materials with respect to their strength and stiffness.

Abstract: The light-emitting diode (LED) has been applied extensively to various kinds of applications according to the advantages of its small dimension, low energy consumption and strong reliability. The projector headlamp system proposed in this study was composed of four main critical components including focused LED, asymmetric metal-based plate, freeform surface and condenser lens. It was designed, developed and simulated under low energy consumption to save more energy. Only five 3-Watt focused LEDs without a shield or baffle inside the projector headlamp system was designed to provide the low-beam cutoff in order to meet the requirements of international Economic Commission for Europe (ECE) R112 regulation. Eventually, the prototype of this LED vehicle projector headlamp system was also fabricated to perform the correct light pattern.

Abstract: Neural network optimal optical design and Roll to Roll (R2R) microfabrication has been integrated in the development of a light guide film (LGF) for liquid crystal display application in this study. TracePro software was used for optical simulation work for the light guide film. Back-propagation neural network (BPNN) was applied to establish a light guide film optical quality predictor. Combined with genetic algorithms (GA), global optimization of the optical quality was achieved. The optimal pattern radii of different zones range from 40 μm to 210 μm were first transferred to an 80 μm thick stainless steel sheet through lithograpgy and etching process. The patterned sheet was then wrapped around the stainless steel roller for R2R fabrication of the patterns on a 188 μm thick PET substrate with UV resin. When operated with imprinting pressure of 0.61 MPa and substrate speed of 0.251 m/min, the LGF measurement results showed that the replication rate is around 98% while the luminace uniformity reaches 74.9%.

Abstract: In this paper, we study the throughput optimization problem in wireless multi-hop networks. For this problem, we introduce a cross-layer formulation to accommodate routing, scheduling and stream control from different layers of network with relevant constraints. Specially, by using a Lagrangian approach and a Markov Chain Monte Carlo method, we extend the programming-based formulation to a distributed algorithm that can dynamically approximate the optimal solution without the overhead of centralization. Finally, through computational results, we discuss the insight that can be gained from the cross-layer optimization and the distributed algorithm.