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Adaptive EY-NPMA: A Medium Access Protocol for Wireless LANs
Dimitriadis, Gerasimos,Pavlidou, Foteini-Niovi The Korea Institute of Information and Commucation 2004 Journal of communications and networks Vol.6 No.4
Wireless local area networks have known an increasing popularity during the past few years. However, as new user applications diverge from the traditional data-centric model, the introduction of efficient, QoS aware medium access methods becomes of utmost importance. EY-NPMA is a medium access protocol belonging to the contention paradigm that provides support for service differentiation and low collision rates. In this paper, we address a shortcoming of EY-NPMA as indicated by previous studies, namely the insensitivity of the protocol to different working conditions. In this work, we study and evaluate a mechanism that allows a network employing EY-NPMA to adapt its operating parameters according to the offered load. Simulation studies further document and confirm the positive characteristics of the proposed mechanism.
Dimitriadis, Konstantinos,Spyropoulos, Konstantinos,Papadopoulos, Triantafillos The Korean Academy of Prosthodonitics 2018 The Journal of Advanced Prosthodontics Vol.10 No.1
PURPOSE. The aim of the present study was to record the metal-ceramic bond strength of a feldspathic dental porcelain and a Co-Cr alloy, using the Direct Metal Laser Sintering technique (DMLS) for the fabrication of metal substrates. MATERIALS AND METHODS. Ten metal substrates were fabricated with powder of a dental Co-Cr alloy using DMLS technique (test group) in dimensions according to ISO 9693. Another ten substrates were fabricated with a casing dental Co-Cr alloy using classic casting technique (control group) for comparison. Another three substrates were fabricated using each technique to record the Modulus of Elasticity (E) of the used alloys. All substrates were examined to record external and internal porosity. Feldspathic porcelain was applied on the substrates. Specimens were tested using the three-point bending test. The failure mode was determined using optical and scanning electron microscopy. The statistical analysis was performed using t-test. RESULTS. Substrates prepared using DMLS technique did not show internal porosity as compared to those produced using the casting technique. The E of control and test group was $222{\pm}5.13GPa$ and $227{\pm}3GPa$, respectively. The bond strength was $51.87{\pm}7.50MPa$ for test group and $54.60{\pm}6.20MPa$ for control group. No statistically significant differences between the two groups were recorded. The mode of failure was mainly cohesive for all specimens. CONCLUSION. Specimens produced by the DMLS technique cover the lowest acceptable metal-ceramic bond strength of 25 MPa specified in ISO 9693 and present satisfactory bond strength for clinical use.
Fotios Dimitriadis,Maria Papaioannou,Ioannis Sokolakis,Aikaterini Fragou,Dimitrios Hatzichristou,Apostolos Apostolidis 대한배뇨장애요실금학회 2021 International Neurourology Journal Vol.25 No.1
Purpose: Preclinical data increasingly support an impact of low-intensity extracorporeal shockwave therapy (Li-ESWT) on the bladder. We investigated the molecular effects of Li-ESWT on the bladder of a streptozotocin-induced diabetic rat model. Methods: Fifteen 8-week-old male Wistar rats were randomized into 3 groups: a control group (n=5), a group of diabetic rats without treatment (diabetes mellitus [DM], n=5) and a group of diabetic rats treated with Li-ESWT (DM-ESWT, n=5). A single intraperitoneal dose of streptozotocin (60 mg/kg) was used to induce diabetes. Twenty days after diabetes induction, each rat in the DM-ESWT group received 300 shockwaves with an energy flux density of 0.09 mJ/mm2. Sessions were repeated 3 times/week for 2 weeks, followed by a 2-week washout period. Total RNA from bladder tissue was extracted, cDNA was synthesized, and quantitative real-time polymerase chain reaction was performed to analyze the expression pattern of transient receptor potential vanilloid 1 (Trpv1), interleukin-1β (Il1b), and the muscarinic receptors M1, M2, and M3 (Chrm1, Chrm2, and Chrm3). Results: The expression of Trpv1, Il1b, and Chrm2 genes was significantly different between the 3 groups (P=0.002, P<0.0001, and P=0.011, respectively; 1-way analysis of variance). In the DM group, the expression of all genes was higher than in the control group, but statistical significance was observed only for Trpv1 and Il1b (P=0.002 and P<0.0001, respectively). Li-ESWT significantly reduced the expression of Il1b and Chrm2 (P=0.001 and P=0.011, respectively), whereas a nonsignificant tendency for reduced expression was noted for Trpv1 (P=0.069). Conclusions: The induction of diabetes was associated with increased expression of genes related to mechanosensation, inflammation/ ischemia, and contraction in the rat bladder. Li-ESWT reduced the expression of IL1b, Chrm2, and to a lesser extent Trpv1 toward the control levels, suggesting the therapeutic potential of this treatment modality for diabetic cystopathy.
Konstantinos Dimitriadis,Athanasios Konstantinou Sfikas,Spyros Kamnis,Pepie Tsolka,Simeon Agathopoulos 대한치과보철학회 2022 The Journal of Advanced Prosthodontics Vol.14 No.2
PURPOSE. Microstructural and physico-mechanical characterization of highly translucent zirconia, prepared by milling technology (CAD-CAM) and repeated firing cycles, was the main aim of this in vitro study. MATERIALS AND METHODS. Two groups of samples of two commercial highly-translucent yttria-stabilized dental zirconia, VITA YZ-HTWhite (Group A) and Zolid HT + White (Group B), with dimensions according to the ISO 6872 “Dentistry - Ceramic materials”, were prepared. The specimens of each group were divided into two subgroups. The specimens of the first subgroups (Group A1 and Group B1) were merely the sintered specimens. The specimens of the second subgroups (Group A2 and Group B2) were subjected to 4 heat treatment cycles. The microstructural features (microstructure, density, grain size, crystalline phases, and crystallite size) and four mechanical properties (flexural strength, modulus of elasticity, Vickers hardness, and fracture toughness) of the subgroups (i.e. before and after heat treatment) were compared. The statistical significance between the subgroups (A1/A2, and B1/B2) was evaluated by the t-test. In all tests, P values smaller than 5% were considered statistically significant. RESULTS. A homogenous microstructure, with no residual porosity and grains sized between 500 and 450 nm for group A and B, respectively, was observed. Crystalline yttria-stabilized tetragonal zirconia was exclusively registered in the X-ray diffractograms. The mechanical properties decreased after the heat treatment procedure, but the differences were not statistically significant. CONCLUSION. The produced zirconia ceramic materials can be safely (i.e., according to the ISO 6872) used in extensive fixed prosthetic restorations, such as substructure ceramics for three-unit prostheses involving the molar restoration and substructure ceramics for prostheses involving four or more units. Consequently, milling technology is an effective manufacturing technology for producing zirconia substructures for dental fixed all-ceramic prosthetic restorations.
Malioris Apostolos,Dimitriadis Georgios,Kampantais Spyridon,Gkotsos Georgios,Vakalopoulos Ioannis,Ioannidis Stavros,Hatzimoutatidis Konstantinos,Hatzichristou Dimitrios 대한배뇨장애요실금학회 2015 International Neurourology Journal Vol.19 No.4
Purpose: The aim of the present study was to determine the diagnostic accuracy of conventional and ambulatory urodynamic studies (UDS) in estimating neobladder function. Methods: We evaluated 32 patients who underwent radical cystectomy and orthotopic Hautmann W neobladder with Abol- Enein-Ghoneim uretero-intestinal anastomosis for bladder cancer. The patients were initially examined by using both conventional and ambulatory UDS. Results: Conventional UDS detected a very high mean intravesical pressure at maximum capacity (53.7±17.5 cm H2O). By contrast, the mean intravesical pressure detected by using ambulatory UDS (which reflects the dominant pattern of pressure variation during filling) was significantly lower (34.4±5.2 cm H2O, P<0.001). The comparison between intravesical pressure at half of maximum capacity in conventional UDS and the mean value in ambulatory UDS did not show significant difference (P=0.152). The mean voided volume in conventional UDS was greater than both the mean voided volume (P<0.001) and the mean maximum voided volume in ambulatory UDS (P=0.001). However, this difference did not affect the postvoid residual urine volume measured in both studies (P=0.207). Moreover, incontinence episodes recorded in ambulatory UDS were more frequent but not statistically significantly different from those recorded in conventional UDS (P=0.332). Conclusions: The estimation of neobladder function by means of ambulatory UDS seems to provide interesting research data for the mode of lower urinary tract function in patients with orthotopic substitution after radical cystectomy. The great high value in ambulatory UDS, in cases in which conventional UDS had failed, is due to the exposure of daily and nocturnal incontinence episodes, confirming our patients’ complaints.
Surgical Reconstruction of Traumatic Pseudoaneurysm of Palmar Arch Caused by Blunt Trauma
Nikolaos Papatheodorou,Konstantinos Dimitriadis,Damianos Doukas,Christos Argyriou,George S. Georgiadis 대한혈관외과학회 2022 Vascular Specialist International Vol.38 No.4
Although rare, pseudoaneurysms (PAs) of the palmar arch are mostly considered benign. However, they can cause severe complications if left untreated or misdiagnosed. There are a few data on traumatic PAs of the palmar arch, particularly those most commonly caused by penetrating hand injuries. However, PAs caused by blunt trauma are more insidious in onset, presenting as a painful pulsatile mass in the palmar area of the hand, and require prompt diagnosis and management to avoid catastrophic sequelae. Our case is the first study to describe a patient with traumatic PA of the palmar arch caused by blunt trauma that was treated with surgical reconstruction and venous bypass interposition.
Arpatzanis, N.,Hastas, N. A.,Dimitriadis, C. A.,Konstantinidis, G.,Charitidis, C.,Song, J. D.,Choi, W. J.,Lee, J. I. WILEY-VCH Verlag 2009 Physica Status Solidi. B Vol.246 No.4
<P>The effect of rapid thermal annealing temperature on the trap properties of Au/n-GaAs Schottky diodes with embedded InAs quantum dots in asymmetric In<SUB>0.2</SUB>Ga<SUB>0.8</SUB>As wells have been investigated by capacitance–voltage (C –V) and low frequency noise (LFN) measurements in both reverse and forward bias regimes. The current noise spectra show 1/f behaviour and generation–recombination (g–r) noise, attributed to uniformly distributed traps in energy and to a discrete trap level in the energy band-gap of the GaAs capping layer, respectively. The experimental results show that the annealing temperature is closely related with the level of these noise sources. The apparent doping concentrations, calculated from the C –V characteristics, indicate that the density of trapping states near the buffer layer interface is increased as the annealing temperature increases. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Arpatzanis, N.,Hastas, N. A.,Dimitriadis, C. A.,Charitidis, C.,Song, J. D.,Choi, W. J.,Lee, J. I. WILEY-VCH Verlag 2008 Physica status solidi. PSS. C, Current topics in s Vol.5 No.12
<P>The trap properties of Au/n-GaAs Schottky diodes with embedded InAs quantum dots (QDs) and different ideality factors were studied by capacitance-voltage (C-V) and low-frequency noise (LFN) measurements in the reverse bias regime. The reverse current noise spectra show 1/f behaviour and g-r noise, attributed to uniformly distributed traps in energy or to a discrete trap level in the energy band-gap of the GaAs capping layer, respectively. The Schottky contact performance or characteristics is closely related with the level of these noise sources. The C-V characteristics indicate the existence of traps with Gaussian energy distribution in the GaAs capping layer and in the InAs QDs layer. From analysis of the C-V characteristics, the density and the activation energy of these trap distributions are determined. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>