Power-Optimal Feedback-Based Random Spectrum Access for an Energy Harvesting Cognitive User

In this paper, we study and analyze cognitive radio networks in which secondary users (SUs) are equipped with Energy Harvesting (EH) capability. We design a random spectrum sensing and access protocol for the SU that exploits the primary link's feedback and requires less average sensing time. Unlike previous works proposed earlier in literature, we do not assume perfect feedback. Instead, we take into account the more practical possibilities of overhearing unreliable feedback signals and accommodate spectrum sensing errors. Moreover, we assume an interference-based channel model where the receivers are equipped with multi-packet reception (MPR) capability. Furthermore, we perform power allocation at the SU with the objective of maximizing the secondary throughput under constraints that maintain certain quality-of-service (QoS) measures for the primary user (PU)

On Spectrum Sharing Between Energy Harvesting Cognitive Radio Users and Primary Users

This paper investigates the maximum secondary throughput for a rechargeable secondary user (SU) sharing the spectrum with a primary user (PU) plugged to a reliable power supply. The SU maintains a finite energy queue and harvests energy from natural resources and primary radio frequency (RF) transmissions. We propose a power allocation policy at the PU and analyze its effect on the throughput of both the PU and SU. Furthermore, we study the impact of the bursty arrivals at the PU on the energy harvested by the SU from RF transmissions. Moreover, we investigate the impact of the rate of energy harvesting from natural resources on the SU throughput. We assume fading channels and compute exact closed-form expressions for the energy harvested by the SU under fading. Results reveal that the proposed power allocation policy along with the implemented RF energy harvesting at the SU enhance the throughput of both primary and secondary links

Optimal Spectrum Access for a Rechargeable Cognitive Radio User Based on Energy Buffer State

This paper investigates the maximum throughput for a rechargeable secondary user (SU) sharing the spectrum with a primary user (PU) plugged to a reliable power supply. The SU maintains a finite energy queue and harvests energy from natural resources, e.g., solar, wind and acoustic noise. We propose a probabilistic access strategy by the SU based on the number of packets at its energy queue. We investigate the effect of the energy arrival rate, the amount of energy per energy packet, and the capacity of the energy queue on the SU throughput under fading channels. Results reveal that the proposed access strategy can enhance the performance of the SU.Comment: arXiv admin note: text overlap with arXiv:1407.726

Cooperative Access in Cognitive Radio Networks: Stable Throughput and Delay Tradeoffs

In this paper, we study and analyze fundamental throughput-delay tradeoffs in cooperative multiple access for cognitive radio systems. We focus on the class of randomized cooperative policies, whereby the secondary user (SU) serves either the queue of its own data or the queue of the primary user (PU) relayed data with certain service probabilities. The proposed policy opens room for trading the PU delay for enhanced SU delay. Towards this objective, stability conditions for the queues involved in the system are derived. Furthermore, a moment generating function approach is employed to derive closed-form expressions for the average delay encountered by the packets of both users. Results reveal that cooperation expands the stable throughput region of the system and significantly reduces the delay at both users. Moreover, we quantify the gain obtained in terms of the SU delay under the proposed policy, over conventional relaying that gives strict priority to the relay queue.Comment: accepted for publication in IEEE 12th Intl. Symposium on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt), 201

Energy-aware cooperative wireless networks with multiple cognitive users

In this paper, we study and analyze cooperative cognitive radio networks with arbitrary number of secondary users (SUs). Each SU is considered a prospective relay for the primary user (PU) besides having its own data transmission demand. We consider a multi-packet transmission framework that allows multiple SUs to transmit simultaneously because of dirty-paper coding. We propose power allocation and scheduling policies that optimize the throughput for both PU and SU with minimum energy expenditure. The performance of the system is evaluated in terms of throughput and delay under different opportunistic relay selection policies. Toward this objective, we present a mathematical framework for deriving stability conditions for all queues in the system. Consequently, the throughput of both primary and secondary links is quantified. Furthermore, a moment generating function approach is employed to derive a closed-form expression for the average delay encountered by the PU packets. Results reveal that we achieve better performance in terms of throughput and delay at lower energy cost as compared with equal power allocation schemes proposed earlier in the literature. Extensive simulations are conducted to validate our theoretical findings

Evaluation of pediatric bradycardia: A single center experience

Background: Heart rate is an integral part of the clinical assessment of the children with acute illness and is commonly used in pediatric early warning scores. Objective: The aim of this study was to assess our current practice for evaluation and management of bradycardia in children. Patients and methods: The study was conducted in Pediatric Arrhythmia Clinic, Neonatal Intensive Care Unit and Pediatric Intensive Care Unit from March 2020 to August 2021. 61 Neonates and children aged from 1 day to 18 years presenting with bradycardia were included in this study. Predeath bradycardia was excluded. Full medical history, physical examination, basic investigations, 12 leads ECG and echocardiography were performed to all patients. Thyroid function tests, 24 hours Holter monitoring, and stress ECG were done if indicated. Results: 61 patients were included in the study. Heart rate ranged from 44 to 94 beat/minute with mean 69.44 beat/minute, the most common form of presentation was abnormal echocardiography. Hypocalcemia was present in 85.2% of patients. 70.5% of patients had sinus bradycardia, 13% had complete heart block (CHB),10% of patients had long QTc Syndrome with sinus bradycardia, 3.3% had 1st and 2nd degree heart block, 1.6% had ECG changes of ALCAPA with sinus bradycardia and 1.6% had ventricular ectopic. Conclusion: It could be concluded that bradycardia in children needs accurate assessment to rule out the need of acute intervention and to decrease the risk of life-threatening conditions

A New Approach for Optimal Sizing of Standalone Photovoltaic Systems

This paper presents a new method for determining the optimal sizing of standalone photovoltaic (PV) system in terms of optimal sizing of PV array and battery storage. A standalone PV system energy flow is first analysed, and the MATLAB fitting tool is used to fit the resultant sizing curves in order to derive general formulas for optimal sizing of PV array and battery. In deriving the formulas for optimal sizing of PV array and battery, the data considered are based on five sites in Malaysia, which are Kuala Lumpur, Johor Bharu, Ipoh, Kuching, and Alor Setar. Based on the results of the designed example for a PV system installed in Kuala Lumpur, the proposed method gives satisfactory optimal sizing results

The relationship between tolerance of ambiguity and creativity in architectural design studio

Creativity is a cognitive ability that enables individuals to come up with both original and functional ideas and products. As architectural design requires producing aesthetic and practically useful solutions, it is a primary concern to enhance creativity in design disciplines. Many theorists argued that design is a non-linear process and many components of design problems are not clear at the beginning. At the start of the process, designers are always working at the periphery of a solution space where there is less coherence and more ambiguity. Thus, they must deal with a lot of ambiguity in every design situation. These states of uncertainty and confusion can be annoying for architecture students. On the other hand, tolerance of ambiguity is a personality trait that has been linked to creative thinking. Therefore, this paper attempts to investigate the correlation between tolerance of ambiguity of architectural students and their creativity via a qualitative study. The researchers implemented a mixed-method approach and recruited 18 architecture students. The results from this study revealed that there is a significant correlation between students’ creative thinking abilities and their tolerance for ambiguity. Our results also indicated that there is no statistically significant correlation between students’ tolerance of ambiguity and their design creativity. Article in English. Santykis tarp tolerancijos dviprasmiškumui ir kūrybiškumo architektūrinio projektavimo studijoje Santrauka Kūrybiškumas kaip kognityvinis gebėjimas sudaro sąlygas asmenims sukurti originalių ir funkcionalių idėjų bei produktų. Kadangi architektūrinis projektavimas reikalauja priimti estetinius ir praktine prasme naudingus sprendimus, todėl pirmiausia reikia rūpintis kūrybiškumo stiprinimu su projektavimu susijusiose disciplinose. Dauguma teoretikų įrodinėja, kad projektavimas yra nelinijinis procesas, o didžioji dalis projektavimo problemų sudedamųjų dalių nuo pat pradžių sudaro neaiškumų. Prasidedant procesui, projektuotojai bet kuriuo atveju darbuojasi sprendimo erdvės paribyje, kuriame yra mažai darnumo, tačiau kur kas daugiau – dviprasmiškumo. Tad jiems tenka spręsti klausimus, susijusius su dideliu dviprasmiškumu bet kurioje projektavimo situacijoje. Šios netikrumo ir painiavos būsenos gali erzinti architektūros studentus. Kita vertus, tolerancija dviprasmiškumui – tai asmenybės bruožas, siejamas su kūrybiniu mąstymu. Todėl šiame straipsnyje siekiama išnagrinėti koreliaciją tarp architektūros studentų tolerancijos dviprasmiškumui ir jų kūrybiškumo, atliekant kokybinį tyrimą. Tyrėjai taikė mišrų metodą, o jų tyrimo objektu tapo 18 architektūros studentų. Šio tyrimo rezultatai atskleidė, kad yra reikšminga koreliacija tarp studentų kūrybinio mąstymo gebėjimų ir jų tolerancijos dviprasmiškumui. Rezultatai, kuriuos gavome, taip pat parodė, kad nėra statistiškai reikšmingos koreliacijos tarp studentų tolerancijos dviprasmiškumui ir to, ar jų atliekamas projektavimas yra kūrybiškas. Reikšminiai žodžiai: architektūros studentai, kūrybiškumas, projektavimo problemos, projektavimo procesas, tolerancija dviprasmiškumui

Lupine as a potential agent against diet-induced obesity through adenosine monophosphateactivated protein kinase pathway: crude oil versus nanoemulsion formulations

Obesity represents a major challenge to the pharmaceutical community due to the minimal availability of anti-obesity drugs and the drawbacks of current weight-loss agents. The study described herein presents lupine oil, in two pharmaceutical formulations, as a potential anti-obesity agent via its effect on different physiological, biochemical, and hormonal parameters. Rats were divided into two groups; one group was continued on a standard commercial rodent diet and served as the non-obese control. The other group was fed a high-fat diet for 7 weeks to prepare an obese rat model. Then, the obese rats were divided into groups to receive 100 mg/kg of the crude lupine oil or nanoemulsion for 10 or 20 days. Lupine oil showed a potent body weight-reducing effect and improved insulin resistance. The oil altered obesity-induced hyperlipidemia and it enhanced the leptin/adiponectin/AMPK hormonal system in epididymal fat, serum, and liver, to which all the above physiological activities could be attributed. The nanoemulsion formulation of lupine oil significantly amplified the activity for all the above physiological and hormonal parameters when compared to the crude oil formulation. Lupine oil nanoemulsion could be used as a potential drug against diet-induced obesity