A study of fluid dynamics parameters for prediction of obstructive sleep apnea

Obstructive sleep apnea (OSA) is a syndrome characterized by the repetitive episodic collapse of the upper airway. The purpose of this study is to investigate the fluid dynamic parameters for the prediction of obstructive sleep apnea in the upper airway before and after setback surgery. Here, we analyzed the flow phenomena of inspiration and expiration in obstructive sleep apnea patients. The modeling of the upper airway was performed with facial 3 dimensional facial computed tomography images (3D facial CT). We used timedependent value for boundary conditions. The changes of pressure were studied with 3D facial CT taken both before and after the setback surgery. Further, it was found that the correlation between PSG data and non-dimensional pressure drop can be used to predict the severity of OSA. In all 6 patients except for patient 1, the average values of the non-dimensional pressure drops and PSG clinical data are inversely related. For each patient, the lower the pressure drop is, the higher the PSG values will be.     

Effect of Second Phase on the Deformation and Fracture Behavior of Multiphase Low-Density Steels

The effects of the second-phase characteristics on the deformation and fracture behavior in low-density steel are investigated in Fe-0.2C-(4, 8)Mn-5Al-1Si alloys, where the second phase can be retained austenite or a mixture of κ-carbide and ferrite depending on the processing condition. With austenite as second phase, the mechanical stability of the austenite is critical regarding ductility because the fracture is likely to occur before the onset of necking when the austenite transforms into martensite in the early stage of deformation. In the case of the mixture of ferrite and κ-carbide, the round shape of κ-carbide is more favorable than the dense lamellar structure. The prominent influence of the second phase on the deformation and fracture behavior is attributable to the propensity of matrix ferrite for cleavage fracture due to its large aluminum concentration.     

A multichannel relay MAC protocol for IEEE 802.11 wireless LANs

One of the challenging issues in wireless LANs (WLANs) is improving the network throughput. One of the possible solutions for the issue is maximizing the number of concurrent transmissions. Although some protocols have been proposed to exploit transmission concurrency in WLANs, their performance depends on the degree of the interference among links. Also, it is hard to obtain interference information because of their dynamics. In this paper, we propose an enhanced medium access control (MAC) protocol for WLANs, named multichannel relay MAC (MRMAC), which is able to transmit multiple frames simultaneously without considering interference. To enable concurrent transmissions, MRMAC adopts the concept of frame relaying. Furthermore, MRMAC utilizes several nonoverlapping channels to eliminate interferences. Through extensive simulations, we found that MRMAC shows better performance than existing well‐known MAC protocols. Copyright © 2013 John Wiley & Sons, Ltd.     

Retinal oximetry based on nonsimultaneous image acquisition using a conventional fundus camera

To measure the retinal arteriole and venule oxygen saturation (SO(2)) using a conventional fundus camera, retinal oximetry based on nonsimultaneous image acquisition was developed and evaluated. Two retinal images were sequentially acquired using a conventional fundus camera with two bandpass filters (568 nm: isobestic, 600 nm: nonisobestic wavelength), one after another, instead of a built-in green filter. The images were registered to compensate for the differences caused by eye movements during the image acquisition. Retinal SO(2) was measured using two wavelength oximetry. To evaluate sensitivity of the proposed method, SO(2) in the arterioles and venules before and after inhalation of 100% O(2) were compared, respectively, in 11 healthy subjects. After inhalation of 100% O(2), SO(2) increased from 96.0 ±6.0% to 98.8% ±7.1% in the arterioles (p=0.002) and from 54.0 ±8.0% to 66.7% ±7.2% in the venules (p=0.005) (paired t-test, n=11). Reproducibility of the method was 2.6% and 5.2% in the arterioles and venules, respectively (average standard deviation of five measurements, n=11).     

Widely tunable S/S+ band thulium-doped fiber laser locked to 50-GHz ITU-T grid

In this study, we demonstrate an S/S+ band discretely tunable thulium-doped fiber laser (TTDFL), locked to the 50-GHz ITU-T grid. By optimizing the inversion dynamics of the thulium-doped fiber while using a dual-wavelength (1.4 and 1.5 /spl mu/m) pumping scheme, 66.2 nm of tuning range (1452.2-1518.4 nm) that cover most of the thulium bandwidth, and more than 6.7 dBm of output power were obtained. By controlling the temperature of the fine grid filter, we also stabilized the output frequency of the TTDFL to within /spl plusmn/2 pm.     

Ultrathin gate oxide grown on nitrogen-implanted silicon for deepsubmicron CMOS transistors

Nitrogen implantation on the silicon substrate was performed before the gate oxidation at a fixed energy of 30 keV and with the split dose of 1.0×10¹⁴/cm² and 2.0×10¹⁴ /cm². Initial O₂ injection method was applied for gate oxidation. The method is composed of an O₂ injection/N₂ anneal/main oxidation, and the control process is composed of a N₂ anneal/main oxidation. CMOS transistors with gate oxide thickness of 2 nm and channel length of 0.13 μm have been fabricated by use of the method. Compared to the control process, the initial O₂ injection process increases the amount of nitrogen piled up at the Si/SiO₂ interface and suppresses the growth of gate oxide effectively. Using this method, the oxidation retarding effect of nitrogen was enhanced. Driving currents, hot carrier reliability, and time-zero dielectric breakdown (TZDB) characteristics were improved     

A Fiber Ring Laser Dilatometer for Measuring Thermal Expansion Coefficient of Ultralow Expansion Material

A new type of measuring system for coefficient of linear thermal expansion (CTE) of ultralow expansion (ULE) material by using a fiber ring laser is introduced in this letter. The lasing frequency of the laser is stabilized to one of the transmission peaks of the etalon filter by controlling the resonant frequency of the tunable filter. The spacer of the (Fabry-Perot type) etalon filter is made of ULE material. We could measure the CTE of ULE by measuring the optical frequency change caused by the temperature change of the etalon spacer. The combined standard uncertainty is estimated as the value of plusmn36.6 ppb/degC in the temperature range from 5degC to 60degC.     

A link contact duration-based routing protocol in delay-tolerant networks

Delay Tolerant Networks (DTNs) provide message delivery services to users via intermittently connected nodes. In DTNs, routing is one of the most challenging issues since end-to-end connectivity between nodes may not be available most of the time. Although many routing protocols for DTNs have been proposed, they do not achieve satisfactory performance, since they exploit only some of the network characteristics. In this paper, we present a new DTN routing protocol, called the Link Contact Duration-based Routing Protocol (LCD). Like existing protocols, LCD uses the disconnect duration of a link between two nodes to find the routing path with the shortest end-to-end delay. In addition, LCD uses the contact duration of a link and the number of buffered messages to deliver as many messages as possible in a short time. Our simulation results show that LCD has better performance than existing DTN routing protocols.