An Efficient Mechanism for UMTS Multicast Routing

In this paper, we present a novel scheme for the multicast transmission of data over Universal Mobile Telecommunications System (UMTS) networks. Apart from the normal multicast transmission over UMTS, we consider the handling of exceptional cases caused by user mobility scenarios. The proposed scheme is in accordance with the current specifications of the Multimedia Multicast/Broadcast Service (MBMS) defined by the 3rd Generation Partnership Project (3GPP) and introduces minor modifications in the UMTS architecture and the mobility management mechanisms. The proposed scheme is implemented as an ns-2 network simulator module. The performance of the proposed scheme is validated and analyzed through ns-2 simulation experiments. This new module can be employed to investigate various aspects of UMTS multicast. Furthermore, in order to further highlight the contribution of our mechanism, we have implemented two multicast congestion control mechanisms for UMTS and we have measured their performance for MBMS transmissions.     

Architectural Alternatives for Information Filtering in Structured Overlays

Content providers are naturally distributed and produce large amounts of new information every day. Peer-to-peer information filtering is a promising approach that offers scalability, adaptivity to high dynamics, and failure resilience. The authors developed two approaches that utilize the chord distributed hash table as the routing substrate, but one stresses retrieval effectiveness, whereas the other relaxes recall guarantees to achieve lower message traffic and thus better scalability. This article highlights the two approaches' main characteristics, presents the issues and trade-offs involved in their design, and compares them in terms of scalability, efficiency, and filtering effectiveness.     

Efficiency limits of concentrating spectral-splitting hybrid photovoltaic-thermal(PV-T)solar collectors and systems

Spectral splitting is an approach to the design of hybrid photovoltaic-thermal(PVT)collectors that promises significant performance benefits.However,the ultimate efficiency limits,optimal PV cell materials and optical filters of spectral-splitting PVT(SSPVT)collectors remain unclear,with a lack of consensus in the literature.We develop an idealized model of SSPVT collectors and use this to determine their electrical and thermal efficiency limits,and to uncover how these limits can be approached through the selection of optimal PV cell materials and spectral-splitting filters.Assuming that thermal losses can be minimized,the efficiency limit,optimal PV material and optimal filter all depend strongly on a coefficient w,which quantifies the value of the delivered thermal energy relative to that of the generated electricity.The total(electrical plus thermal)efficiency limit of SSPVT collectors increases at higher w and at higher optical concentrations.The optimal spectral-splitting filter is defined by sharp lower-and upper-bound energies;the former always coincides with the bandgap of the cell,whereas the latter decreases at higher w.The total effective efficiency limit of SSPVT collectors is over 20%higher than those of either standalone PV modules or standalone ST collectors when w is in the range from 0.35 to 0.50 and up to 30%higher at w~0.4.This study provides a method for identifying the efficiency limits of ideal SSPVT collectors and reports these limits,along with guidance for selecting optimal PV materials and spectral-splitting filters under different conditions and in different applications.     

Dominant Role of PI3K p110α over p110β in Insulin and β-Adrenergic Receptor Signalling

Attribution of specific roles to the two ubiquitously expressed PI 3-kinase (PI3K) isoforms p110α and p110β in biological functions they have been implicated, such as in insulin signalling, has been challenging. While p110α has been demonstrated to be the principal isoform activated downstream of the insulin receptor, several studies have provided evidence for a role of p110β. Here we have used isoform-selective inhibitors to estimate the relative contribution of each of these isoforms in insulin signalling in adipocytes, which are a cell type with essential roles in regulation of metabolism at the systemic level. Consistent with previous genetic and pharmacological studies, we found that p110α is the principal isoform activated downstream of the insulin receptor under physiological conditions. p110α interaction with Ras enhanced the strength of p110α activation by insulin. However, this interaction did not account for the selectivity for p110α over p110β in insulin signalling. We also demonstrate that p110α is the principal isoform activated downstream of the β-adrenergic receptor (β-AR), another important signalling pathway in metabolic regulation, through a mechanism involving activation of the cAMP effector molecule EPAC1. This study offers further insights in the role of PI3K isoforms in the regulation of energy metabolism with implications for the therapeutic application of selective inhibitors of these isoforms.     

Modelling of a thermosyphon solar water heating system and simple model validation

A thermosyphon solar water heater consisting of two flat plate collectors of total aperture area of 2.7 m² and 150 l storage tank is modelled using TRNSYS. Simple experiments were conducted in order to validate the model. During the experiments weather conditions were measured every 10 min and integrated over an hour. The temperature of the water in the storage tank was also measured at the beginning and at the end of the day. The storage tank temperature rise was used to validate the model by using the actual weather data as input to the program. Validation tests were performed for 25 days spread over 6 months and the mean deviation between the predicted and the actual values of water temperature rise is 4.7% which is very satisfactory. Subsequently, long term system performance is estimated by using TRNSYS model run with the weather values of TMY file for Nicosia, Cyprus. The annual solar fraction obtained was 79% and the system could cover all the hot water needs of a house of four people during the three summer months. The maximum auxiliary energy was needed during the months of December and January (about 280 MJ/month). In addition, an economic analysis of the system was carried out. The pay-back time of the system was found to be 8 years and the present worth of life cycle savings was found equal to C£ 161.     

An in silico evaluation of data‐driven optimization of biopharmaceutical processes

Two methodological improvements of the design of dynamic experiments (C. Georgakis, Ind Eng Chem Res. 2013) for the modeling and optimization of (semi‐) batch processes are proposed. Their effectiveness is evaluated in two representative classes of biopharmaceutical processes. First, we incorporate prior process knowledge in the design of the experiments. Many batch processes and, in particular, biopharmaceutical processes are usually not understood completely to enable the development of an accurate knowledge‐driven model. However, partial process knowledge is often available and should not be ignored. We demonstrate here how to incorporate such knowledge. Second, we introduce an evolutionary modeling and optimization approach to minimize the initial number of experiments in the face of budgetary and time constraints. The proposed approach starts with the estimation of only a linear Response Surface Model, which requires the minimum number of experiments. Accounting for the model's uncertainty, the proposed approach calculates a process optimum that meets a maximum uncertainty constraint. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2796–2805, 2017     

Investigation of the Pt/YSZ interface at low oxygen partial pressure by solid electrochemical mass spectroscopy under high vacuum conditions

The Pt/YSZ interface was investigated at low oxygen partial pressure under high vacuum (HV) conditions at 400 °C. Two different electrochemical techniques were coupled to mass spectrometric gas analysis using a new solid electrochemical mass spectrometric monitoring device. Under cathodic polarization, the lack of oxygen in the gas phase induces the reduction of the YSZ solid electrolyte which acts as oxygen source for the formation of O²⁻ ions migrating to the anode. Under anodic polarization, both platinum oxidation and oxygen evolution reaction are identified. PtO _x is formed at both the Pt/YSZ and the Pt/gas interface according to two different mechanisms. At the Pt/YSZ interface, PtO _x formation is an electrochemical process following a parabolic growth law, while the presence of PtO _x at the Pt/gas interface is related to the diffusion of PtO _x formed at the triple phase boundary towards the Pt/gas interface. It is proposed that the side oxygen evolution reaction stabilizes thermodynamically the PtO _x diffusion toward the gas exposed interface during the anodic polarization.