Measurement and modeling of crank train friction in light-duty diesel engines

Journal of Mechanical Science and Technology - In this study, we present measurements and calculations of friction energy loss in the crank train of a light-duty vehicle diesel engine. The main...     

An integrated adaptive bandwidth-management framework for QoS-sensitive multimedia cellular networks

Bandwidth is an extremely valuable and scarce resource in a wireless network. Therefore, efficient bandwidth management is necessary in order to provide high-quality service to users in a multimedia wireless/mobile network. In this paper, we propose new online bandwidth-management algorithms for bandwidth reservation, call admission, bandwidth migration, and call-preemption strategies. These techniques are combined in an integrated framework that is able to balance the traffic load among cells accommodating heterogeneous multimedia services while ensuring efficient bandwidth utilization. In addition, our online framework to adaptively control bandwidth is a cell-oriented approach that has low complexity, which makes it practical for real cellular networks. Simulation results indicate the superior performance of our bandwidth-management framework to strike the appropriate performance balance between contradictory quality-of-service requirements.     

An Online Buffer Management Algorithm for QoS‐Sensitive Multimedia Networks

In this letter, we propose a new online buffer management algorithm to simultaneously provide diverse multimedia traffic services and enhance network performance. Our online approach exhibits dynamic adaptability and responsiveness to the current traffic conditions in multimedia networks. This approach can provide high buffer utilization and thereby improve packet loss performance at the time of congestion.     

Fast reference frame and inter-mode selection method for H.264/AVC

This paper presents an efficient method for selecting the best reference frame (RF) and the best inter-mode in H.264/AVC. The proposed method employs a different examination order compared to conventional methods and examines the most important RF for all inter-modes in the first step. Then, in the second step, it further examines the best mode from the first step for all available RFs. Finally, in the third step, it additionally examines the remaining modes for the best RF determined in the second step. Based on the intermediate results after the first and second steps, the proposed method skips many less important RFs in each inter-mode and significantly reduces the coding complexity. However, the proposed method also shows very good performance in terms of the peak signal-to-noise ratio and bit rate, as it does not skip important RFs in each inter-mode. Simulation results show that the proposed method greatly reduces the encoding time while significantly improving the encoding performance of conventional methods.     

Multi-leader multi-follower Stackelberg model for cognitive radio spectrum sharing scheme

Radio spectrum is one of the most scarce and variable resources for wireless communications. Therefore, the proliferation of devices and rapid growth of wireless services continue to strain the limited radio spectrum resource. Cognitive Radio (CR) paradigm is a promising technology to solve the problem of spectrum scarcity. In this paper, a new fair-efficient spectrum sharing scheme is proposed for cognitive radio networks. Based on the multiple-leader multiple-follower Stackelberg game model, the proposed scheme increases opportunistic use of the licensed radio spectrum. To adaptively use the spectrum resource, control decisions are coupled with one another; the result of the each user’s decisions is the input back to the other user’s decision process. Under widely diverse network environments, this adaptive feedback process approach can provide an effective way of finding a suitable solution. The simulation results demonstrate that the proposed scheme has excellent network performance, while other schemes cannot offer such an attractive performance balance.     

An Adaptive Smart Grid Management Scheme Based on the Coopetition Game Model

Recently, the idea of the smart grid has been gaining significant attention and has become a hot research topic. The purpose of this paper is to present a novel smart grid management scheme that uses game theory principles. In our proposed scheme, power appliances in the smart grid adaptively form groups according to the non‐cooperative hedonic game model. By exploiting multi‐appliance diversity, appliances in each group are dynamically scheduled in a cooperative manner. For efficient smart grid management, the proposed coopetition game approach is dynamic and flexible to adaptively respond to current system conditions. The main feature is to maximize the overall system performance while satisfying the requirements of individual appliances. Simulation results indicate that our proposed scheme achieves higher energy efficiency and better system performance than other existing schemes.     

A mission management system for complex aerial logistics by multiple unmanned aerial vehicles in MBZIRC 2017

In this study, we present a system that manages multiple unmanned aerial vehicles (UAVs) for a search, pickup, and drop mission in the 2017 Mohamed Bin Zayed International Robotics Challenge (MBZIRC). Three UAVs picked up and dropped 23 circular and rectangular targets into a designated drop box. To control the operation of three UAVs flying over an arena of 90 × 60 m, we designed and integrated a set of technologies into our system: airspace allocation, communication framework among UAVs, anticollision based on geofencing, and a token‐based prioritization for coordination. The proposed UAV system uses a single GPS and its error of a few meters is solved by means of the following component technologies: (a) flight path generator based on one reference point, (b) vision‐based redefinition of a reference point for GPS correction, and (c) calibration of flight path to update the reference point. The pickup‐and‐drop mission is conducted via color‐ and shape‐based vision processing and a magnetic gripper to pickup and drop‐off the targets. Our proposed system is able to successfully manage three UAVs, recognize targets on the ground, and drop the targets into a drop box in the drop zone. Finally, we achieved fourth place among 18 teams in Challenge 3.     

Shape control of cadmium hydroxides (Cd(OH)2) sensitive to pH quenching depth and massive production of CdSe nanocrystals by their chemical transformation

This study demonstrates that the structure of cadmium hydroxides (Cd(OH)(2)) precipitated from a basic cadmium nitrate solution can be finely controlled by adjusting the pH of the precursor solution. The synthesis process involves only pouring the saturated solution into pure water to quench the pH and the total process is finished within 30 s. At a shallow pH quenching, the unstable nanoparticles turned into microparticles via a ripening process. Cd(OH)(2) was precipitated in the form of one-dimensional nanowires and then two-dimensional plates as the pH quenching was increased. At a large pH quenching, porous aggregates of Cd(OH)(2) were obtained due to the too fast precipitation. The ultrafine Cd(OH)(2) nanowires were readily transformed into CdSe chain-like nanocrystals. The transformation was quick and gave 100% yield, facilitating massive production of CdSe nanocrystals in an aqueous condition. The Cd(OH)(2) nanowires were directly grown on Si nanowires and transformed into CdSe chain-like nanocrystals, decorating the surface of each Si nanowire.     

Ni-Fe2O4 nanoparticles as contrast agents for magnetic resonance imaging

Reported herein is the synthesis of a dextran coating on nickel ferrite (Ni-Fe2O4) nanoparticles via chemical coprecipitation. The aqueous solution of the synthesized nanoparticles showed good colloidal stability, and no precipitate was observed 20 months after the synthesis. The coated nanoparticles were found to be cylindrical in shape in the TEM images, and showed a uniform size distribution with an average length and diameter of 17 and 4 nm, respectively. The coated particles were evaluated as potential T1 and T2 contrast agents for MRI. The T1 and T2 relaxations of the hydrogen protons in the water molecules in an aqueous solution of dextran-coated Ni-Fe2O4 nanoparticles were studied. It was found that the T1 relaxivity for the aqueous solution of dextran-coated nanoparticles was slightly greater than that of a commercial Gd-DTPA-BMA contrast agent. The T2 relaxivity, however, was almost twice that of the commercial Gd-DTPA-BMA contrast agent. Animal experimentation also demonstrated that the dextran-coated Ni-Fe2O4 nanoparticles are suitable for use as either T1 or T2 contrast agents in MRI.