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 Efficient Multiuser Scheduling: Statistical Guarantees on Bursty Packet Loss

In this paper, we consider energy efficient multiuser scheduling. Packet loss tolerance of the applications is exploited to minimize average system energy. There is a constraint on average packet drop rate and maximum number of packets dropped successively (bursty loss). A finite buffer size is assumed. We propose a scheme which schedules the users opportunistically according to the channel conditions, packet loss constraints and buffer size parameters. We assume imperfect channel state information at the transmitter side and analyze the scheme in large user limit using stochastic optimization techniques. First, we optimize system energy for a fixed buffer size which results in a corresponding statistical guarantee on successive packet drop. Then, we determine the minimum buffer size to achieve a target (improved) energy efficiency for the same (or better) statistical guarantee. We show that buffer size can be traded effectively to achieve system energy efficiency for target statistical guarantees on packet loss parameters.Comment: Proc. Physcomnet in conjunction with WIOPT 201

Conductometric and volumetric study of copper sulphate in aqueous ethanol solutions at different temperatures

AbstractAn Anton Par Model 55 densimeter was used to measure the densities of copper sulphate solutions in H2O and EtOH–H2O at 298.15K, 303.15K, 308.15K, and 313.15K. The acquired information was used to ascertain the apparent molar volumes, limiting partial molar volumes, and transfer partial molar volumes of copper sulphate. These computed parameters were utilized to decipher the solute–solute and solute–solvent interactions of copper sulphate in an aqueous ethanol solution. The ion solvation behavior of copper sulphate in water and aqueous ethanol over the range of 298.15–313.15K was studied using the electrical conductivity principle. The Kraus–Bray and Shedlovsky models of conductivity were used to analyze the obtained conductance data. From the obtained data, the limiting molar conductance λ°m, association constant KA, energy of activation of the rating process (Ea), and related thermodynamic parameters were determined. The Walden product (λ°mη0) was determined. The standard thermodynamic parameters of association (ΔG°A, ΔH°A) were calculated and discussed. Increased ion–solvent and solvent–solvent interactions are indicated by limiting molar conductance values with an increasing amount of ethanol. The negative ΔG°A values indicate that the association processes in all of the studied systems are spontaneous processes. The negative estimation of (ΔH°A) demonstrates that the association processes is exothermic in nature

Sacrococcygeal teratoma excision: a vertical rather than transverse wound closure

Background: The chevron incision has been the standard approach for sacrococcygeal teratoma (SCT) excision. Here, we are reporting our experience of shifting to the vertical posterior sagittal approach.Patients and methods: During the period 2011 through 2016, we operated on 17 (16 female and one male) cases of SCT. Their age at presentation ranged from day 1 to 26 months (mean=4.8 months, median=2 months). The chevron incision was used in five, whereas the vertical posterior sagittal approach was used in 12 patients.Results: In this series, we had one case of perioperative mortality, in addition to another case of perineal wound disruption (in the group of vertical wound closure), which was managed conservatively (to heal by secondary intention) with a very satisfactory hidden scar at 6-month follow-up. Overall, we did not find the vertical approach to add any extra limitations to the surgical exposure or dissection; meanwhile, it provided a well-recognized cosmetic advantage.Conclusion: The vertical posterior sagittal approach for excision of SCT is both feasible and advantageous in terms of the cosmetic outcome. It provides a well-hidden scar in the natal cleft and preserves normal contouring of the buttocks.Keywords: buttock, cosmesis, posterior sagittal, reconstruction, sacrococcygeal teratom

Novi steroidni derivati sintetizirani iz 3betha-hidroksiandrosten-17-ona

In this study, we synthesized some new substituted steroidal derivatives using 3betha-hydroxyandrosten-17-one (dehydroepiandrosterone) as starting material. The synthesized steroidal derivatives 1-11 were evaluated for their androgenic-anabolic activities compared to testosterone as positive control. Details of the synthesis, spectroscopic data and toxicity (LD50) of synthesized compounds are reported.U radu je opisana sinteza novih steroidnih derivata 1-11 koristeći 3betha-hidroksiandrosten-17-on (dehidroepiandrosteron) kao početnu supstanciju. Androgeno-anaboličko djelovanje tih spojeva uspoređivano je s djelovanjem testosterona kao pozitivnom kontrolom. Navode se detaljni sintetski postupci, spektroskopska karakterizacija i podaci o toksičnosti (LD50)

The effect of cold crystalloid versus warm blood cardioplegia on the myocardium during coronary artery bypass grafting

Background: The optimal cardioplegic solution is still debated. The objective of this study was to compare the effect of cold crystalloid versus warm blood cardioplegia on the myocardial injury during coronary artery bypass grafting. Methods: The study included 34 consecutive patients who underwent elective primary on-pump isolated coronary artery bypass grafting from 2016 to 2019. We randomly assigned the patients into two groups. Group (ICCC) (n= 17) received intermittent antegrade cold crystalloid cardioplegia and Group (IWBC) (n= 17) received intermittent antegrade warm blood cardioplegia. Results: There was no difference in the preoperative and operative variables between groups. The time taken by the heart to regain normal sinus rhythm was significantly longer in the cold crystalloid group (7.06 ± 1.8 vs. 2.17 ± 0.8 minutes, p<0.001) with a higher rate of reperfusion ventricular arrhythmia (35% versus 6%; p=0.03) compared to the warm blood cardioplegia group. Both coronary sinus acid production and lactate level were significantly higher in the warm blood group than in the cold crystalloid group (p< 0.001 and 0.043, respectively). The ischemic ECG changes and the severity of new segmental wall motion abnormalities were non-significantly different between both groups (p= 0.68 and 0.67, respectively). Postoperative CK-MB and cTnI levels in all-time points were not significantly different between groups (p= 0.46 and 0.37, respectively). ICU (2.29 ± 0.77 vs. 2.41 ± 0.87 days, p= 0.68) and hospital stay (9.28 ± 0.76 vs. 9.42 ± 0.88 days, p= 0.62) were non-significantly different between both groups. Conclusion: Intermittent antegrade cold crystalloid cardioplegia was associated with attenuated myocardial metabolism. However, it was associated with a longer time to regain normal sinus rhythm and more reperfusion ventricular arrhythmias. We did not find differences in the clinical and echocardiographic outcomes and cardiac enzymes between cold crystalloid and warm blood cardioplegia

Comprehensive platform for distribution transactiveenergy markets

Reducing the cost of distributed energy resources (DERs) such as renewables, storage,electric vehicles and smart loads is driving their increased connection to distributionsystems. Extracting maximum benefits from DERs require liberalising distribution sys-tems by allowing: (1) a distribution transactive energy market (DTEM) operated by alocal distribution operator (LDO) and (2) peer-to-peer (P2P), peer-to-LDO (P2LDO) andTransmission-to-LDO (T2LDO) type transactions. A DTEM will bring several benefitssuch as: (1) enhanced economic opportunity for DERs, making them more profitable and(2) increased social welfare benefiting both buyers and sellers. To achieve this objective, wedevelop a comprehensive three-phase DTEM platform that provides maximum economicopportunities for DERs and maximises social welfare that benefits all market participants,while considering P2P, P2LDO and T2LDO transactions, for both energy and ancillaryservices. Interaction between bulk electricity market independent system operator (ISO)and LDO controlled DTEM is presented. The DTEM model is implemented as a practi-cal mixed-integer linear programming formulation that includes a network reconfigurationfeature. The DTEM model is studied on three-phase 5-bus and 34-bus systems, demon-strating its effectiveness to settle energy and ancillary service transactions, while obtainingdistribution locational marginal prices. Results show that P2P transactions, when allowed,increase social welfare and increases profitability of DER