SAR-derived wind fields at the coastal region in the East/Japan Sea and relation to coastal upwelling

The relationship between the modification of synthetic aperture radar (SAR) wind field and coastal upwelling was investigated using high-resolution wind fields from Advanced Land Observing Satellite (ALOS) Phased Array type L-band synthetic aperture radar (PALSAR) imagery and sea-surface temperature (SST) from National Oceanic and Atmospheric Administration/Advanced Very-High-Resolution Radiometer (NOAA/AVHRR) data. The retrieved SAR wind speeds seem to agree well with in situ buoy measurements with only a relatively small error of 0.7 m s^?1. The SAR wind fields retrieved from the east coast of Korea in August 2007 revealed a spatial distinction between near and offshore regions. Low wind speeds of less than 3 m s^?1 were associated with cold water regions with dominant coastal upwelling. Time series of in situ measurements of both wind speed and water temperature indicated that the upwelling was induced by the wind field. The low wind field from SAR was mainly induced by changes in atmospheric stability due to air–sea temperature differences. In addition, wind speed magnitude showed a positive correlation with the difference between SST and air temperature (R² = 0.63). The dependence of viscosity of water on radar backscattering at the present upwelling region was negligible since SAR data showed a relatively large backscattering attenuation to an SST ratio of 1.2 dB °C^?1. This study also addressed the important role of coastal upwelling on biological bloom under oligotrophic environments during summer.     

Friction losses modeling of piston rings for various combustion pressures in diesel engine

Journal of Mechanical Science and Technology - This paper describes a numerical simulation of the lubrication between the first compression piston ring and the cylinder liner in a typical diesel...     

Carbon-coated iron oxide nanoparticles as contrast agents in magnetic resonance imaging

Coprecipitated ferrite nanoparticles were coated with carbon using a hydrothermal method. From transmission electron microscope pictures, we could see that the coated iron oxide nanoparticles were spherical in shape with an average diameter of 90 nm. The strong bonding of carbon on the nanoparticle surfaces was checked by noting the C = O and C = C vibrations in Fourier transform infrared spectra. The spin-lattice relaxation process [T ₁] and spin-spin relaxation process [T ₂] relaxivities of hydrogen protons in the aqueous solution of coated nanoparticles were determined to be 1.139 (mM·s)^-1 and 1.115 (mM·s)^-1, respectively. These results showed that the carbon-coated iron oxide nanoparticles are applicable as both T ₁ and T ₂ contrast agents in magnetic resonance imaging.     

Timed strategic machine type communications for dual-level future wireless networks

For the next generation wireless networks, machine type communication (MTC) is gaining an enormous interest as a new communication paradigm. MTC is expected to become a cost-effective solution for improving the wireless communication performance. In MTC, one of the most critical issues is to support data transfers among devices without human interaction. In this study, we introduce a new MTC control scheme for the future network infrastructure. To effectively support a large number of MTC devices, we investigate a dual-level interaction mechanism by employing the timed strategy game model. In dynamic wireless network environments, our timed strategic game approach can practically adapt current system conditions while maximizing system performance. Main contribution of this research is to show a way of MTC system modeling based on the competitive and cooperative manner. Finally, numerical simulations illustrate the validity of our game-based approach. Our solution enables a better network resource utilization for heterogeneous traffic services in contrast to existing schemes.

     

Multi-hop Network Bandwidth Management Scheme Based on Cooperative Bargaining Models

Multi-hop cellular network (MCN) can preserve the advantages of traditional single-hop cellular networks and ad hoc relaying networks. In multi-hop network, efficient bandwidth management plays an important role in determining network performance. In this paper, a new bandwidth management scheme is proposed for MCNs. By integrating the Nash and Kalai–Smorodinsky bargaining models, the proposed scheme adaptively controls the wireless bandwidth to maximize network efficiency. In the proposed Nash and Kalai–Smorodinsky bargaining models, bargaining powers are decided according to the real-time negotiation process. It is a powerful method for resolving conflicts and enables the system to fairly and effectively control the bandwidth management problem. With a simulation study, it is demonstrated that the proposed scheme approximates an optimized solution under widely diverse traffic load intensities.     

Electrical properties of ultra-thin oxynitrided layer using N2O plasma in inductively coupled plasma chemical vapor deposition for non-volatile memory on glass

In this work, the silicon oxynitride layer was studied as a tunneling layer for non-volatile memory application by fabricating low temperature polysilicon thin film transistors on glass. Silicon wafers were oxynitrided by only nitrous oxide plasma under different radio frequency powers and plasma treatment times. Plasma oxynitridation was performed in RF plasma using inductively coupled plasma chemical vapor deposition. The X-ray energy dispersive spectroscopy was employed to analyze the atomic concentration ratio of nitrogen/oxygen in oxynitride layer. The oxynitrided layer formed under radio frequency power of 150 W and substrate temperature of 623 K was found to contain the atomic concentration ratio of nitrogen/oxygen as high as 1.57. The advantage of high nitrogen concentration in silicon oxide layer formed by using nitrous oxide plasma was investigated by capacitance-voltage measurement. The analysis of capacitance-voltage characteristics demonstrated that the ultra-thin oxynitride layers of 2 nm thickness formed by only nitrous oxide plasma have good properties as tunneling layer for non-volatile memory device.     

Surface roughness and polarization ratio in microwave remote sensing

The characteristics of the polarization ratio in the case of rough surfaces are investigated. In addition, an inversion method is also proposed for retrieving the surface roughness over land and sea. The proposed method was effective for angles of incidence near the Brewster angles close to the view angles of many satellite microwave sensors. This new method retrieves the sea surface roughness within a reasonable range of bias. Consequently, this study provides insight into the polarization ratio and an inversion method to estimate the surface roughness by using the characteristics of the polarization ratio from passive microwave remote sensing.     

Decomposition of unpolarized emissivity

Many satellite remote sensors perform unpolarized measurements. A systematic procedure to decompose measured unpolarized emissivity is proposed using the definition of total reflectivity and the relationship between vertically and horizontally polarized reflectivity. Two polarizations are retrieved for various view angles with mixed emissivity simulated using the refractive index of water for ultraviolet, visible, infrared and microwave wavelengths. The results indicate that the absolute bias errors are small and consistent within Brewster angles, irrespective of the wavelengths. However, the relative bias is less than 4% and 5% for vertical and horizontal polarization, respectively, for any instrument working at infrared and microwave wavelengths. The relative bias for horizontal polarization is 20–30% for ultraviolet and visible wavelengths due to small absolute reflectivity values. Consequently, the method proposed in this study is applicable to specular surfaces for various view angles without the dielectric properties of a medium being required.     

Adaptive Online Voltage Scaling Scheme Based on the Nash Bargaining Solution

In an effort to reduce energy consumption, research into adaptive power management in real‐time systems has become widespread. In this paper, a novel dynamic voltage scaling scheme is proposed for multiprocessor systems. Based on the concept of the Nash bargaining solution, a processor's clock speed and supply voltage are dynamically adjusted to satisfy these conflicting performance metrics. In addition, the proposed algorithm is implemented to react adaptively to the current system conditions by using an adaptive online approach. Simulation results clearly indicate that the superior performance of the proposed scheme can strike the appropriate performance balance between contradictory requirements.