Orthopantomographic X-ray findings, not due to jaws or teeth, and their interpretation

An attempt was made to make an early diagnosis of intrauterine growth retardation due to chronic placental insufficiency using ultrasound cephalometry and biochemical tests of placental function. We examined 83 hospitalised patients in whom there was a risk or suspicion of chronic placental insufficiency. For each patient an average of 4 determinations were made of head diameter, 10 of estriol and 3 of pregnandiol urinary excretion, 6 serum HPL and 7 of heat stable alkaline phosphatase (HSAP). Fetal growth retardation was assumed if the last 2 determined head diameters were below the normal curve with the same tendency and with term being well predicted. Biochemical parameters were considered to indicate pathological changes if they were 95% below normal values, with 2 below this range or 3 continuously falling below the normal level. Infants were assessed after birth both neurologically and somatically according to DUBOWITZ. Small for date infants were those whose birth weight was below the 10th percentile (LUBCHENKO). This was found to be the case in 15 out of 83 newborns five of whom were younger than 37 weeks. These 15 could be diagnosed before birth with various degrees of certainty. For estriol and HPL this was 67% or 53% and these two parameters were found to be the most valuable. Cephalometry was found to be less valuable with 20%, pregnandiol levels with 9% and placental HSAP with 33%. Hence it is recommended to perform serial determinations of estriol and HPL in the third trimester of pregnancy in all patients with histories indicative of fetal growth retardation and in those in whom the uterus appears small for date.     

Comments on “Mixed L∞/H∞suboptimal controllers for SISO continuous time systems”

The authors state that they have no serious criticism of the original paper but make certain remarks. An example in the original illustrates a method to do tradeoffs between two design goals: H_∞ and L^∞. To make a fair comparison, they authors say that the optimal H_∞ norm should have been presented. The also point out misprints, and make remarks on the cancellation of the integrator pole and the tending to ∞ of the settling time     

Mechanical behaviour of Zn–Fe alloy coated mild steel

Zinc alloy coatings containing various amounts of Fe were deposited by electrodeposition technique on a mild steel substrate. The concentration of Fe in the produced alloy coatings ranged from 0 to 14 wt.%, whereas the thickness of the coatings was about 50 μm. Structural and metallurgical characterization of the produced coatings was performed with the aid of X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. This study aims in investigating the mechanical behaviour of Zn–Fe coated mild steel specimens, as no research investigation concerning the tensile behaviour of Zn alloy coated ferrous alloys has been reported in the past. The experimental results indicated that the ultimate tensile strength of the Zn–Fe coated mild steel was lower than the bare mild steel. In addition, the ductility of the Zn–Fe coated mild steel was found to decrease significantly with increasing Fe content in the coating.     

Process simulation and techno-economic assessment of a zero liquid discharge/multi-effect desalination/thermal vapor compression (ZLD/MED/TVC) system

Brine from desalination plants is an upcoming environmental threat to aquatic ecosystems. Multi-effect distillation with thermal vapor compression (MED-TVC) is proposed to treat desalination brine solutions of more than 70 000 mg/L of total dissolved solids (TDS). To achieve this, an integrated techno-economic model consisting of three submodels (scaling prediction, mathematical, and economic) is developed and a techno-economic assessment of a 10 m³/d MED-TVC system is presented under two different scenarios. In this respect, various sensitivity analyses were performed, revealing that the 4-effect MED-TVC system operating at 120°C feed steam presents the lowest freshwater cost (US$3.00/m³) and the lowest payback period (3.04 years) under the first scenario, whereas the 2-effect MED-TVC system operating at 120°C feed steam presents the lowest freshwater cost (US$1.69/m³) and the lowest payback period (1.71 years) under the second scenario of waste heat utilization. Exergy analysis for these optimal systems revealed that the exergy efficiency of the optimal system in the second scenario (4.36%) is higher than in the first scenario (4.21%). For both optimal systems, the exergy destruction in the TVC unit and in the effects accounts for more than 79% of the total exergy destruction. Moreover, it was found that thermal energy costs contribute significantly to the costs and affect the design procedure. Scaling up the optimal systems for freshwater production by more than 190 m³/d, freshwater cost becomes constant and can be reduced by up to 50% with waste heat integration. Considering the high quality of the freshwater produced, MED-TVC process can be profitable due to the revenue from the sale of the freshwater. Overall, the results suggest that the MED-TVC process for brine treatment is economically feasible.     

Time varying interference statistical distribution for direct-to-user satellite applications

Adjacent co-channel satellite systems might lead to unacceptable mutual radio interference levels due to their close spacing in orbit and to the reduced antenna sizes at the user?s reception. Tropospheric propagation impairments along with the interference effects are of utmost importance for the reliable design of modern satellite communication systems operating at Ku (14/12 GHz) and Ka(30/20GHz) frequency bands and above. The objective of this Letter is the presentation of a novel analytical and accurate methodology for the prediction of the time varying carrier-to-interference ratio (CIR) statistical distribution under rain fading conditions. Appropriate physical space-time structure is employed for the correlation between the rain-induced attenuations on the two converging slant paths. The analysis proposed is flexible and incorporates various operational and geometrical parameters of the interference scenario. Numerical results illustrating the impact of those parameters on the space-time varying CIR statistics are presented and useful conclusions are drawn.     

Optimization in differentiable manifolds in order to determine the method of construction of prehistoric wall paintings

In this paper, a general methodology is introduced for the determination of potential prototype curves used for the drawing of prehistoric wall paintings. The approach includes 1) preprocessing of the wall-paintings contours to properly partition them, according to their curvature, 2) choice of prototype curves families, 3) analysis and optimization in 4-manifold for a first estimation of the form of these prototypes, 4) clustering of the contour parts and the prototypes to determine a minimal number of potential guides, and 5) further optimization in 4-manifold, applied to each cluster separately, in order to determine the exact functional form of the potential guides, together with the corresponding drawn contour parts. The methodology introduced simultaneously deals with two problems: 1) the arbitrariness in data-points orientation and 2) the determination of one proper form for a prototype curve that optimally fits the corresponding contour data. Arbitrariness in orientation has been dealt with a novel curvature based error, while the proper forms of curve prototypes have been exhaustively determined by embedding curvature deformations of the prototypes into 4-manifolds. Application of this methodology to celebrated wall paintings excavated at Tyrins, Greece, and the Greek island of Thera manifests that it is highly probable that these wall paintings were drawn by means of geometric guides that correspond to linear spirals and hyperbolae. These geometric forms fit the drawings’ lines with an exceptionally low average error, less than 0.39 mm. Hence, the approach suggests the existence of accurate realizations of complicated geometric entities more than 1,000 years before their axiomatic formulation in the Classical Ages.     

QoS-Driven Power Allocation Under Peak and Average Interference Constraints in Cognitive Radio Networks

Efficient radio spectrum utilization can be improved using cognitive radio technology. In this work, we consider a spectrum underlay cognitive radio system operating in a fading environment. We propose an efficient power control scheme that maximizes the effective capacity of the secondary user, provisioning quality of service while on the same time the communication of the primary user is guaranteed through interference constraints. The specific power allocation scheme uses a policy in which the outage events of the primary user are exploited leading to a significant increase of the secondary user’s effective capacity. Moreover, the interference of the primary link to the secondary is taken into account so as to study a more realistic scenario. In order to safeguard primary user’s communication, two types of restrictions are considered: the traditional interference power constraint and the proposed inverse signal to interference plus noise ratio constraint. Different scenarios depending on the nature of the constraints (peak/average) are studied and their impact on the performance of the primary and secondary users is investigated. The superiority of the proposed schemes is demonstrated through their comparison with two reference power control schemes. Finally, numerical calculations, validated with simulation results, confirm the theoretical analysis and evaluate the performance of the proposed scheme for all the different scenarios.     

Interference Studies Between Adjacent Satellite Communications Systems operating Above 10 GHz and Using Power Control as Fade Mitigation Technique

Interference problems are arising from the spectral coexistence between satellite communication networks that operate at frequencies above 10 GHz and particularly when they employ power control as fade mitigation technique. This situation is aggravated due to tropospheric propagation phenomena. In this frequency range, rain attenuation is considered to be the dominant tropospheric fading mechanism. The conditional acceptable intersystem interference probability of the Carrier-to-Interference Ratio of a satellite terminal interfered by an adjacent satellite network is defined as a figure of merit and analytically calculated taking into account a physical-mathematical model for the rainfall medium. The correlated propagation fading phenomena over multiple slant paths are accurately incorporated. The proposed model is flexible and can be applied on a global scale since it incorporates the local climatic conditions concerning the point rainfall rate and the spatial rainfall inhomogeneity. Useful numerical results of the proposed model are obtained and the impact of various crucial operational and geometrical parameters of satellite networks’ coexistence is examined. The numerical results have been also verified through simulations using a multi-dimensional rain attenuation synthesizer. Finally, simple and easy-calculated formulas for the satellite communication designers for back of the envelope computations are given.     

ZnO thin films prepared by pulsed laser deposition

Zinc oxide (ZnO) thin films were deposited on soda lime glass substrates by pulsed laser deposition (PLD) in an oxygen-reactive atmosphere. The structural, optical, and electrical properties of the as-prepared thin films were studied in dependence of substrate temperature and oxygen pressure. High quality polycrystalline ZnO films with hexagonal wurtzite structure were deposited at substrate temperatures of 100 and 300 °C. The RMS roughness of the deposited oxide films was found to be in the range 2-9 nm and was only slightly dependent on substrate temperature and oxygen pressure. Electrical measurements indicated a decrease of film resistivity with the increase of substrate temperature and the decrease of oxygen pressure. The ZnO films exhibited high transmittance of 90% and their energy band gap and thickness were in the range 3.26-3.30 eV and 256-627 nm, respectively.     

Total CNIDR degradation during rain fade conditions of a dual polarized satellite link suffering from double adjacent satellite interference

Atmospheric impairments have a significant influence on the performance of modern satellite communication networks, working at Ku, Ka and potentially Q/V frequency bands. Both differential rain attenuation from an adjacent satellite system, operating at the same frequency range, and cross‐polarization phenomena on dual polarized satellite systems due to rain and ice crystals, induce a further aggravation on the already limited signal‐to‐noise‐plus‐total‐interference ratio (CNIDR), due to the frequency and orbital congestion of today's global communication satellite constellation. In the present paper, a new statistical methodology, towards the modelling of CNIDR under rain fade conditions, is proposed to include interference effects by two adjacent satellites, incorporating the impact of correlated fading channels (spatial rainfall inhomogeneity) of multiple slant paths. The method is based on a convective raincell model and the lognormal assumption for both the point rain‐rate statistics and the slant‐path rain attenuation. The obtained numerical results indicate the significant impact of the second interfering satellite on the aggravation of total interference effects. Some simple mathematical formulas for the prediction of the CNIDR, based on the derived theoretical results, and demonstrating the influence of various link parameters on the total link availability statistics, are also presented. Copyright © 2009 John Wiley & Sons, Ltd.