IEEE 802.11e standard is developed for QoS provisioning in WLANs. Admission Control is a mechanism that controls stations to be served in WLANs. In practice, evaluation of admission control plays an ...important role for QoS support. The goal of this paper is to calculate the WLAN delays with ACs. The delay calculation can be used to guarantee the QoS of the VoIP and video streams, which is divided into three parts. One is the propagation delay. Another is that packets queue up in stations or APs. Lastly, the delay is taken due to collisions. For VoIP and video streams, the second delay is more important than other two delays. Consequently, we will focus on the calculation of the second delay. Some simulations and numerical results are provided and discussed in detail. Experimental results show that the proposed method is more accurate in calculating the delay of packets in WLANs.
Lipid accumulation and carbon dioxide (CO sub(2)) utilization of Nannochloropsis oculata in response to CO sub(2) aeration were investigated. A direct microscopic count was performed with Brightline ...Hemocytometer. Determination of nitrate content in broth was followed by the spectrometric method. A fluorescent spectrometric method was applied for fast determination of lipid content. The microalgal cells from logarithmic, early stationary phase and stationary phase were collected to measure lipid content. The result showed that the lipid accumulation in microalgal cells was associated with growth phases. It was also concluded that the lipid accumulation of N. oculata NCTU-3 could be increased from logarithmic growth phase to stationary growth phase.
Background This study aimed to explore parameters which will predict good control of HbA.sub.1c after adding a second anti-diabetic drug in patients with type 2 diabetes mellitus (T2DM) inadequately ...controlled with metformin monotherapy. Methods Fifty-one patients (M/F: 25/26, mean age: 53.7 + or - 8.2 years, mean glycated hemoglobin HbA.sub.1c 8.4 + or - 1.2%) with T2DM inadequately controlled with metformin were randomized to add-on glibenclamide or acarbose for 16 weeks. Before and after combination therapy, the subjects underwent a 2-hour liquid mixed meal tolerance test to determine insulin secretion (HOMA-beta, insulinogenic index, and disposition index DI) and insulin sensitivity (HOMA-IR and Matsuda insulin sensitivity index). Results At baseline, there was a significant inverse relationship between DI.sub.120 and HbA.sub.1c (p = 0.001) in all subjects. The addition of glibenclamide and acarbose improved HbA.sub.1c significantly from 8.6 + or - 1.6% to 7.4 + or - 1.2% (p 0.001), and from 8.2 + or - 0.8% to 7.5 + or - 0.8% (p 0.001), respectively. In the glibenclamide group, DI.sub.120 significantly increased from 51.2 + or - 24.2 to 74.9 + or - 41.9 (p 0.05), and in the acarbose group, from 62.5 + or - 31.4 to 91.7 + or - 36.2 (p 0.05), respectively. Multiple regression analyses showed that both baseline HbA.sub.1c and DI.sub.120 independently predicted reduction of HbA.sub.1c as well as final HbA.sub.1c after combination therapy. Conclusions In patients with T2DM inadequately controlled with metformin, add-on oral anti-diabetic agent with glibenclamide or acarbose resulted in the significant HbA.sub.1c reduction and improvement of beta-cell function. Subjects with greater baseline beta-cell function reserve displayed better glycemic response in the combination therapy of metformin with glibenclamide or acarbose. Trial registration This study was registered in the ClinicalTrials.gov with registration number of NCT00417729. Keywords: Beta-cell function, Disposition index, Glycated hemoglobin, Glycemic control, Metformin
When the orbital altitude of a satellite is relatively low, for example, less than 500 km, the method of aerodynamic stabilization can be considered. In particular, this method is very effective when ...the satellite is small. The aerodynamic restoring torque can be provided by a very light tail stabilizer which is several meters downstream from the main body of the small satellite. An aerodynamic stabilization system has been installed in the Cosmos-149 and another one in the Cosmos-320. One of the disadvantages in using the aerodynamic stabilization is that no rolling stabilization can be achieved. The gravity gradient stabilization method has been used in many satellites. One of the examples is the Eole satellite. In the recent years, many small satellites have adopted this method owing to its long life and continuous Earth pointing characteristics. The main disadvantage is the poor pointing accuracy with respect to the orbiting reference coordinates. This disadvantage can be overcome with the aid of a small reaction wheel. Both pitch and roll orientations can be stabilized. However, no yawing motion stabilization can be achieved by using the pure passive gravity gradient method.
The purpose of this paper is to combine the aerodynamic and gravity gradient stabilization methods together so that all the three axes stabilizations can be obtained. We shall consider the attitude motion of a microsatellite under the action of both gravity gradient torque and aerodynamic torque. The set of nonlinear equations of motion will be solved numerically with specified initial condition. The satellite operates in a circular orbit with 500 km altitude. The history of the attitude stabilization will be investigated and discussed in detail.
The microalga incorporated photobioreactor is a highly efficient biological system for converting CO sub(2) into biomass. Using microalgal photobioreactor as CO sub(2) mitigation system is a ...practical approach for elimination of waste gas from the CO sub(2) emission. In this study, the marine microalga Chlorella sp. was cultured in a photobioreactor to assess biomass, lipid productivity and CO sub(2) reduction. We also determined the effects of cell density and CO sub(2) concentration on the growth of Chlorella sp. During an 8-day interval cultures in the semicontinuous cultivation, the specific growth rate and biomass of Chlorella sp. cultures in the conditions aerated 2-15% CO sub(2) were 0.58-0.66 d super(-1) and 0.76-0.87 g L super(-1), respectively. At CO sub(2) concentrations of 2%, 5%, 10% and 15%, the rate of CO sub(2) reduction was 0.261, 0.316, 0.466 and 0.573 g h super(-1), and efficiency of CO sub(2) removal was 58%, 27%, 20% and 16%, respectively. The efficiency of CO sub(2) removal was similar in the single photobioreactor and in the six-parallel photobioreactor. However, CO sub(2) reduction, production of biomass, and production of lipid were six times greater in the six-parallel photobioreactor than those in the single photobioreactor. In conclusion, inhibition of microalgal growth cultured in the system with high CO sub(2) (10-15%) aeration could be overcome via a high- density culture of microalgal inoculum that was adapted to 2% CO sub(2). Moreover, biological reduction of CO sub(2) in the established system could be parallely increased using the photobioreactor consisting of multiple units.
Due to the sheer size of software logs, developers rely on automated techniques for log analysis. One of the first and most important steps of automated log analysis is log abstraction, which parses ...the raw logs into a structured format. Prior log abstraction techniques aim to identify and abstract all the dynamic variables in logs and output a static log template for automated log analysis. However, these abstracted dynamic variables may also contain important information that is useful to different tasks in log analysis. In this paper, we investigate the characteristics of dynamic variables and their importance in practice, and explore the potential of a variable-aware log abstraction technique. Through manual investigations and surveys with practitioners, we find that different categories of dynamic variables record various information that can be important depending on the given tasks, the distinction of dynamic variables in log abstraction can further assist in log analysis. We then propose a deep learning based log abstraction approach, named VALB, which can identify different categories of dynamic variables and preserve the value of specified categories of dynamic variables along with the log templates (i.e., variable-aware log abstraction). Through the evaluation on a widely used log abstraction benchmark, we find that VALB outperforms other state-of-the-art log abstraction techniques on general log abstraction (i.e., when abstracting all the dynamic variables) and also achieves a high variable-aware log abstraction accuracy that further identifies the category of the dynamic variables. Our study highlights the potential of leveraging the important information recorded in the dynamic variables to further improve the process of log analysis.
The microalga incorporated photobioreactor is a highly efficient biological system for converting CO
2 into biomass. Using microalgal photobioreactor as CO
2 mitigation system is a practical approach ...for elimination of waste gas from the CO
2 emission. In this study, the marine microalga
Chlorella sp. was cultured in a photobioreactor to assess biomass, lipid productivity and CO
2 reduction. We also determined the effects of cell density and CO
2 concentration on the growth of
Chlorella sp. During an 8-day interval cultures in the semicontinuous cultivation, the specific growth rate and biomass of
Chlorella sp. cultures in the conditions aerated 2–15% CO
2 were 0.58–0.66
d
−1 and 0.76–0.87
g
L
−1, respectively. At CO
2 concentrations of 2%, 5%, 10% and 15%, the rate of CO
2 reduction was 0.261, 0.316, 0.466 and 0.573
g
h
−1, and efficiency of CO
2 removal was 58%, 27%, 20% and 16%, respectively. The efficiency of CO
2 removal was similar in the single photobioreactor and in the six-parallel photobioreactor. However, CO
2 reduction, production of biomass, and production of lipid were six times greater in the six-parallel photobioreactor than those in the single photobioreactor. In conclusion, inhibition of microalgal growth cultured in the system with high CO
2 (10–15%) aeration could be overcome via a high-density culture of microalgal inoculum that was adapted to 2% CO
2. Moreover, biological reduction of CO
2 in the established system could be parallely increased using the photobioreactor consisting of multiple units.
The emerging of renewable energy demands energy storage. Redox flow batteries are inherently suited for large-scale applications, but their market penetration is thwarted by the high materials cost. ...In contrast, membrane-less and single-flow soluble lead flow batteries (SLFBs) are more economical to scale up and free of expensive noble metals. However, lifespan of SLFBs reported so far is limited to approximately 200 cycles under normal flow conditions, which is insufficient for long-term operation in utility applications.
Failures of SLFBs are believed to be associated with PbO
2
deposition/dissolution at the positive electrode. Although failure mechanisms are not well understood, passivation and shedding of PbO
2
are suggested to decrease efficiency of SLFBs. Formation of a passivation layer of non-stoichiometric PbOx is found to be correlated to proton activities. PbO
2
deposits of poor adherence and low quality are also observed to occur when the electrolyte is high in acidity. We therefore employ sodium acetate (NaOAc) as electrolyte additive, and successfully extend the cycle life of SLFBs by over 50%.
In this study, effects of acetate additive on electroplating of PbO
2
are investigated. Surface morphology and mechanical strength of electroplated PbO
2
via electrolyte with and without NaOAc are examined by scanning electron microscopy (SEM) and nano-indentation, respectively. Acetate-assisted electrolyte is found to substantially enhance deposited film strength and leads to a more integrated and smoother surface. Crystal structures, grain sizes, and grain orientations of plated PbO
2
are analyzed via x-ray diffraction (XRD) and electron back scatter diffraction (EBSD), and very different phase distributions and grain orientations are observed for electrolyte with and without NaOAc. Electroplating and oxygen evolution kinetics are further investigated by rotating disk electrode (RDE) experiments. Our findings elucidate acetate additive effects on electroplating of PbO
2
in SLFB systems and shed lights on battery life extension.
![Post-meal [beta]-cell funct...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1758-5996/small "Post-meal [beta]-cell function predicts the efficacy of glycemic control in patients with type 2 diabetes inadequately controlled by metformin monotherapy after addition of glibenclamide or acarbose")
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