High‐yield synthesis of multi‐walled carbon nanotube by hydrothermal method

The evolution of multi‐walled carbon nanotubes (MWCNTs) under hydrothermal condition was investigated, because the hydrothermal method (HTM) has been utilised for commercial production of advanced engineering materials. To synthesise MWCNTs by hydrothermal process using mixed aqueous solution diethylenetriamine, polyethyleneglycol (PEG) and NaOH were used as starting materials. We investigated the effect of hydrothermal temperature, time, and amount of formative compounds. Hydrothermal reaction temperature was in the range from 150 to 180°C. The aim of the present work is to presentation hydrothermal synthesis as a new processing method for fabrication of MWCNTs, without the addition of metal catalyst. The homogeneity of hydrothermal processes, cheapness, and availability of amorphous carbon materials, without the need of catalyst, are advantages favouring the scaling‐up of the new method. The treatment of higher volumes would only require autoclaves with increasing load‐bearing capacity. Synthesised MWCNTs were analysed with a scanning electron microscope (SEM), a high resolution transmission electron microscope (HRTEM), thermo‐gravimetric analysis (TGA), and Raman spectroscopy. This result also presented a controllable way to synthesise MWCNTs with high purity. Indeed, present work will introduce new chapter in synthesising MWCNTs for scientific and engineering.     

Performance analysis of the distributed queuing collision avoidance (DQCA) protocol with link adaptation

DQCA is a near-optimum Medium Access Control (MAC) protocol designed for Wireless Local Access Networks (WLANs). The protocol operates as a random access scheme under low traffic load and switches smoothly and automatically to a reservation scheme as the traffic grows. The inherent feedback mechanism of DQCA facilitates the implementation of a link adaptation algorithm that properly selects the best transmission rate taking into account the state of the wireless channel. This paper presents an analytical model for the evaluation of the performance in terms of throughput and mean message delay in the presence of a time-variant channel response.     

Separation of some light monocarboxylic acids from water inbinary solutions in a reverse osmosis pilot plant

The separation of formic (C₁), acetic (C₂), propionic (C₃), and n-valeric (C₅) acids in binary water solutions has been studied using a reverse osmosis (RO) membrane pilot plant operating at different temperatures and pressures (usually 21 °C and 1.72 MPa). The RO membrane, which is composite, polyamide and spiral-wound, having a surface area of 2.6 m², was fed by a solution of 0.5 M of C₁, C₂ and C₃ acids and 0.146 M of C₅. The pilot plant was used to simulate a cascade series of RO modules by recycling the permeate flux at the end of each semi-batch run. The influence on the retention coefficient, R, of molecular weight and molar volume, pK_a of the different acids was determined. For acetic acid the influence of temperature (T) and transmembrane pressure (ΔP) was also studied, obtaining an inverse and direct good linear correlation for R vs. T and R vs. ΔP, respectively. The results are particularly interesting for acetic acid-water separation, which is an open question in industrial applications.     

Zinc Oxide Sheath Voltage Limiter for HV and EHV Power Cable: Field Experience and Laboratory Tests

This paper deals with laboratory tests in order to qualify a new type of sheath voltage limiter (SVL) based on Zinc oxide non linear resistor (ZnO). The aim of the tests was to determine the maximum performance of the SVL and to investigate the possibility of ageing phenomena. The research was based on several years of field experience gained on silicon carbide (SiC) SVL. The high performance and the better reliability of the ZnO SVL, compared with the traditional SiC one, allow greater freedom in the project design of cable installations, making possible an increase in cable length and in the permissible short circuit current. The new SVL is now being installed to protect special bonding connections of high power cables.     

Towards Formalised Guidelines for Migrating Structured Designs to UML: A Case Study

This paper provides evidence that it is possible to migrate structured system designs to UML models. Legacy structured designs can be converted to object-oriented systems without losing data or functionality. The reason for choosing UML is that it is the new standard notation, which tries to build on and integrate object-oriented notations. Extracts from a case study are presented together with the proposed guidelines for the re-engineering process.     

Alternative storage options for solar thermal systems

The efficient implementation of solar systems in buildings depends on the storage of energy yielded, as it can both increase the solar system's autonomy and make it a feasible solution for zero energy buildings, and make storage vessels more compact, reducing precious space requirements. This is of particular important in places with reduced time of sunshine, where solar systems are less effective, because of the deviation between solar radiation and the demand. The traditional storage options use water, which is practical, safe and low‐cost, especially when the storage requirements are small. However, when larger storage is needed, limits concerning the use of water exist, mainly due to the need for larger installation space and the increased thermal losses. The use of phase change materials (PCM) for thermal energy storage seems an upcoming technology. The main idea is the substitution of water with PCM, which feature larger specific energy storage capacity compared to other conventional materials. In the context of the specific paper, a combined solar thermal system used for the preparation of domestic hot water (DHW) and space heating (Solar Combi System) with two different types of storage is studied, for two Greek cities. The aim is to find out which is the most efficient way of storing energy with respect to the autonomy of the system, for a solar combi system. This is being achieved by determining the comparative autonomy of PCM and water storage system for various climates. It was proven that using PCM is advantageous, as it can extend the autonomy duration of the solar system for 2 to 8 hours, depending on the season and the climatic conditions. However, it was also seen that in solar combi systems used throughout the whole year, PCM are inefficient during summer period.     

Towards Certificate-Based Authentication for Future Mobile Communications

Certificate-based authentication of parties provides a powerful means for verifying claimed identities, since communicating partners do not have to exchange secrets in advance for authentication. This is especially valuable for roaming scenarios in future mobile communications where users authenticate to obtain network access—service access may potentially be based thereon in integrated approaches—and where the number of access network providers and Internet service providers is expected to increase considerably. When dealing with certificates, one must cope with the verification of complete certificate paths for security reasons. In mobile communications, additional constraints exist under which this verification work is performed. These constraints make verification more difficult when compared to non-mobile contexts. Mobile devices may have limited capacity for computation and mobile communication links may have limited bandwidth. In this paper, we propose to apply PKI servers—such as implemented at FhG-SIT—that allow the delegation of certificate path validation in order to speed up verification. Furthermore, we propose a special structure for PKI components and specific cooperation models that force certificate paths to be short, i.e., the lenghts of certificate paths are upper-bounded to certain small values depending on the conditions of specific cases. Additionally, we deal with the problem of users who do not have Internet access during the authentication phase. We explain how we solved this problem and show a gap in existing standards.     

Neurological and cytogenetic study in early-onset ataxia-telangiectasia patients

The clinical diagnosis of ataxia-telangiectasia (AT) is difficult before the age of 4 years. We report clinical and cytogenetic data on three early-onset, early-diagnosed AT patients at the age of 12, 18 and 22 months, respectively. Postural instability of the trunk, characterized by motor impersistence, was the earliest neurological sign detected as early as 1 year of life. Dystonic movements and postures of arms and trunk and a subtle disorder of eye movement (blinking before gaze changing, increased latency and dysmetry of saccades) were observed during the 2nd year of life. All patients exhibited an unusual temper tantrum. We also observed an increased bleomycin-induced chromosomal instability in patient's cells in the early stages of the disease before all the clinical hallmarks were apparent. Our data suggest that detection of clinical indications, leading to early laboratory confirmation of AT, can reduce the age at diagnosis.     

Clinical, ultrasonographic and tomographic features on the natural evolution of primary mesenteric fibromatosis: a case report

Primary mesenteric fibromatosis is a rare, histologically benign, pathology which is characterized by fibrous proliferation in the mesentery and made more serious by biological malignancy as it has a high inclination towards involving the visceral abdominal structures in its growth. While the cases reported in the literature describe the attempts to cure and reduce the tumor growth, this report describes the clinical, ultrasonographic and tomographic features during the natural growth rate of a case of inoperable primary mesenteric fibromatosis during a 20 month follow-up.     

Pilot study to assess increased dialysis efficiency in patients with limited blood flow rates due to vascular access problems

In the last few years, the number of hemodialysis patients with inadequate blood flow (Qb) rates has increased due to vascular access problems. To avoid a clinical status of underdialysis, these patients need long-lasting dialysis sessions. However, other factors aimed to optimize the dialysis dose have to be considered. High-efficiency convective therapies, such as online hemodiafiltration (HDF), are claimed to be superior to high-flux hemodialysis (HF-HD) in improving the dialysis efficacy, but treatment efficacy is strongly related to blood flow rate and infusion volumes. Online mid-dilution (HDF-MD) with the Nephros OL-pure MD190 represents a new HDF concept to increase the removal of middle molecules. In a cross-over clinical trial, 8 patients, with Qb eff <300 mL/min, received either online HDF-MD or HF-HD; Qd was 700 mL/min, the time duration was 240 min, and the filtration volume in HDF-MD was 112+/-7 mL/min. No differences were found for Kt/V, urea, and creatinine clearances. Clearance of both small phosphate (P) large beta(2)-microglobulin (beta(2)m), and leptin (L) solutes was significantly greater for MD (P 217+/-32, beta(2)m 85.5+/-10, L 42.6+/-18 mL/min) than for HF-HD (P 178+/-32, beta(2)m 71.9+/-13, L 32.1+/-12 mL/min). The results of this study indicate that HDF remains the best means of providing increased removal of large-molecular weight solutes even in patients with vascular access problems.