996 research outputs found
MIMO Beamforming for Secure and Energy-Efficient Wireless Communication
Considering a multiple-user multiple-input multiple-output (MIMO) channel
with an eavesdropper, this letter develops a beamformer design to optimize the
energy efficiency in terms of secrecy bits per Joule under secrecy
quality-of-service constraints. This is a very difficult design problem with no
available exact solution techniques. A path-following procedure, which
iteratively improves its feasible points by using a simple quadratic program of
moderate dimension, is proposed. Under any fixed computational tolerance the
procedure terminates after finitely many iterations, yielding at least a
locally optimal solution. Simulation results show the superior performance of
the obtained algorithm over other existing methods.Comment: 12 pages, 2 figure
Study of the Correlation Between Bronchial Hyperresponsiveness and Exhaled Nitric Oxide in Subjects with Suspected Symptoms of Asthma
Background: Bronchial hyperresponsiveness (BHR) is one of main features of asthma within chronic inflammation and reversible bronchoconstriction. Actually, methacholine challenge is useful method to detect BHR in subjects with suspected asthma symptoms. However, this method has some limitations due to its safety and side effects. The measure of exhaled nitric oxide (NO) demonstrates currently as the alternative method for methacholine challenge.
Methods: Ninety-five subjects had at least one of the following symptoms were included in this study: wheezing or chest tightness during exercise, chronic cough, or nocturnal coughing. They were divided into two groups depending on the positivity or negativity of BHR. Lung function test, exhaled NO measurement, and methacholine challenge were done for each study subject.
Results: There were no significant differences between two groups for age and male/female ratio (41 ± 22 vs 38 ± 23 years old and 0.9 vs 1.1; P > 0.05 and P > 0.05; respectively). The percentage of wheezing and nocturnal coughing in subjects with positive BHR (BHR+) was significantly higher than that in subjects with negative BHR (BHR-: 70.9% and 64.5% vs 31.2% and 45.1%; P<0.001 and P<0.01; respectively). FENO measured at 50 mL/s in subjects with BHR+ was significantly higher subjects with BHR- (36 ± 10 ppb vs 11 ± 9 ppb; P<0.001). There was a significant correlation between FENO-50 mL/s and methacholine dose in subjects with BHR+ (R= -0.695; P<0.001). FENO-50 mL/s at 35 ppb had 86.7% of sensibility and 82.9% of specificity for diagnosis of BHR. Conclusion: FENO is a useful biomarker for diagnosis of asthma in subjects with suspected symptoms of asthma. FENO level has a high sensitivity and specificity for screening out subjects with BHR. The measurement of exhaled NO may be an alternative method for detecting BHR in diagnosis of asthma in clinical practice
Review of potential and actual penetration of solar power in Vietnam
With the average solar radiation reaching up to 5 kWh/m2, Vietnam is considered as a country showing an excellent potential for solar power production. Since the year 2000, there have been a lot of studies about the potential of this source in Vietnam. So far, many applications of solar power have been implemented on small, medium, and large scales. In fact, the total capacity of current grid-connected solar power plants has exceeded the planned capacity by 2020 nearly 6 times. However, the studies of solar potential in Vietnam are still incomplete. The policies and mechanisms for developing solar power projects have received attention from the authorities but have not been really satisfactory. The infrastructure is still poor and the power system does not keep up with the development of modern grids. This paper reviewed the potential and actual implementation stage of photovoltaic projects in Vietnam. Moreover, the barriers and challenges of institution, technique, economy, and finance have been considered explicitly for the future development of solar energy in Vietnam
Calculation of the micromaser spectrum. I. Green's-function approach and approximate analytical techniques
We first calculate the "exact" micromaser spectrum by solving numerically for the Green's function of the approximate master equation for the one-atom (micro-) maser. We then proceed to calculate approximate analytical expressions for the maser linewidth using (i) a phase-operator approach, (ii) an ansatz similar to the standard quantum theory of the laser, and (iii) a linear expansion of the correlation function. Novel features, quite distinct from the familiar Schawlow-Townes linewidth, are found, e.g., the linewidth decreases as the number of thermal photons increases
Synthesis and Photocatalytic Activity for Toluene Removal of CDs/TiO2 - Zeolite Y
Hydrothermally synthesized carbon nanodots (CDs) were impregnated on TiO2. The product (CDs/TiO2) was mechanically mixed with zeolite Y for application in toluene photocatalytic oxidation reaction under UV radiation. Material properties of the samples were investigated by different methods. Toluene vapor was chosen as a typical volatile organic compound to investigate the performance of CDs/TiO2 – zeolite Y photocatalyst when these technological parameters were changed: toluene concentration, gas flow rate, humidity and UV light intensity. In each reaction, only one parameter was changed and the remaining conditions were fixed. The toluene concentrations at the beginning and the end of each reaction were analyzed with the use of gas chromatography (GC). The results of different reaction conditions show the trends for toluene treatment of the CDs/TiO2 – zeolite Y catalyst, thereby providing specific explanations for these trends. The experiments also show that toluene removal is highest when the toluene concentration in the inlet gas is 314 ppmv, the flow rate is 3 L/h, the humidity is 60%, and the catalyst (CDs/TiO2 – zeolite Y composite with 70% zeolite in weight) is illuminated by 4 UV lamps. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).
Интеллектуальная радиосеть с нечеткой конфигурацией
В статье обсуждаются возможности применения одноранговой радиосети стандарта IEEE 802.15.4 (ZigBee) диапазона 2,4 ГГц для работы системы, состоящей из группы малогабаритных мобильных роботов и одного командного пункта. Основная задача группы роботов – проведение разведки во время спасательных операций после техногенных и природных катастроф и аварий. Для сохранения управляемости отдельными роботами и системой в целом предлагается повысить «интеллект» системы связи за счет гибкой маршрутизации каналов между командным пунктом и конкретным мобильным роботом с тем, чтобы иметь систему с автоматическим, интеллектуальным восстановлением канала обмена данных.У статті обговорюються можливості застосування однорангової радіомережі стандарту ІЕЕ 802.15.4 (ZigBee) діапазону 2,4 Ггу для роботи системи, що складається з групи малогабаритних мобільних роботів та одного командного пункту. Основна задача групи роботів – проведення розвідки під час рятувальних операцій після техногенних та природних катастроф і аварій. Для збереження керованості окремими ротами та системою в цілому пропонується підвищити інтелект системи зв’язку за рахунок гнучкої маршрутитизації каналів між командним пунктом та конкретним мобільним роботом з тим, щоб мати систему з автоматичним, інтелектуальним відновлюванням каналу обміну даних.In the article the possibilities of application peer-to-peer radio networks of standard IEEE 802.15.4 (ZigBee) a range of 2,4 GHz for work of the system consisting of small-sized mobile robots group and one command point are discussed. The primary goal of group of robots – is carrying out of investigation during rescue operations after technogenic and natural accidents and failures. For controllability preservation by separate robots and system as a whole, it is offered to raise “intelligence” of a communication system at the expense of flexible routeing of channels between command point and the concrete mobile robot to have system with automatic, intellectual restoration of the channel of data exchange
Kaluza-Klein Structure Associated With Fat Brane
It is known that the imposition of orbifold boundary conditions on background
scalar field can give rise to a non-trivial vacuum expectation value (VEV)
along extra dimensions, which in turn generates fat branes and associated
unconventional Kaluza-Klein (KK) towers of fermions. We study the structure of
these KK towers in the limit of one large extra dimension and show that
normalizable (bound) states of massless and massive fermions can exist at both
orbifold fixed points. Closer look however indicates that orbifold boundary
conditions act to suppress at least half of bound KK modes, while periodic
boundary conditions tend to drive the high-lying modes to the conventional
structure. By investigating the scattering of fermions on branes, we
analytically compute masses and wavefunctions of KK spectra in the presence of
these boundary conditions up to one-loop level. Implication of KK-number
non-conservation couplings on the Coulomb potential is also examined.Comment: RevTex4, 29 pages, 7 ps figures, new references adde
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