A novel design of high performance multilayered cylindrical dielectric lens antenna using 3D printing technology

In this work, design and realization of high performance, low‐cost X‐band multilayered cylindrical dielectric lens antenna (MLCDLA) is presented using 3D printing technology. Firstly, MLCDLA is designed and simulated in the complete 3D CST microwave studio (MWS) within the X‐ band as consisting of six layers and being fed through a conventional rectangular waveguide (WR90). These layers are in the form of cylindrical discs having different radii, thicknesses and made of a cheap polylactic acid material. These layers have also varying dielectric constant from 1.2 to 2.7 that are compatible for fused deposition modeling (FDM) based 3D‐printing process. Secondly, a prototype of MLCDLA is produced by using a FDM based 3D‐printer. 3D printed dielectric lens antenna is measured and a good return loss of almost more than 10 dB within the X‐band with a high gain of 16‐18 dBi are achieved as compared with the counterpart alternative designs. Thus, it can be concluded that the proposed novel design and prototyping method not only achieves the high radiation performance characteristics along X‐band but also is a fast, low‐cost, and effective method for prototyping dielectric lens structures for the microwave applications.     

Determination of antioxidant activities of various extracts and essential oil compositions of Thymus praecox subsp. skorpilii var. skorpilii

The aim of this work is to examine the chemical composition and antioxidant activity of separated essential oils and different solvent extracts of Thymus praecox subsp. skorpilii var. skorpilii (TPS). The ethanol, acetone, methanol, hexane, aqueous extracts and separated essential oils of TPS were assessed for their antioxidant activities. Antioxidant activities were evaluated by reduction of Mo(VI) to Mo(V), reducing power, superoxide scavenging activity, free radical-scavenging activity, metal chelating activity, linoleic acid peroxidation, hydrogen peroxide scavenging activity and peroxide scavenging activity. Essential oils were characterized in total to be 41 components, whereas 9 components were isolated by column chromatography for antioxidant activity. TPS essential oil was found to contain thymol (40.31%) and o-cymene (13.66%) as the major components. The ethanol, methanol and water extracts exerted significant free radical-scavenging activity. The methanol and water extracts displayed highest superoxide scavenging activity. The water extract has the highest total phenolics (6.211 mg gallic acid (GAE)/g DW) and flavonoids (0.809 mg quercetin/g DW).     

Investigation of a new heart contractility power parameter

First derivative of arterial blood pressure, dp/dt is known to reflect the contractility power of the heart. We hypothesize that the calculated area under each cardiac cycle of the blood pressure curve is also another practical tool in revealing the heart contractility power. Of the 84 subjects, 61 patients were found to have adequate contractility power (high dp/dt) and their mean area calculation resulted in 64.2 mmHg s with a standard deviation of 2.9 mmHg s. The remaining 23 patients have indicated poor heart contractility power (low dp/dt) and stayed in serious condition for long time. This group had mean area of 41.4 +/- 3.1 mmHg s. Patients with poor contractility power had areas below 45 mmHg s, while all area calculations for patients with high contractility power stayed over 60 mmHg s. Therefore, small area of the arterial blood pressure curves seems to be a good indicator of a poor heart contractility power and the area calculation may be an adjunct parameter to the dp/dt that has been employed for the assessment of heart contractility.     

Highly dependable concurrent programming using design for verification

There has been significant progress in automated verification techniques based on model checking. However, scalable software model checking remains a challenging problem. We believe that this problem can be addressed using a design for verification approach based on design patterns that facilitate scalable automated verification. In this paper, we present a design for verification approach for highly dependable concurrent programming using a design pattern for concurrency controllers. A concurrency controller class consists of a set of guarded commands defining a synchronization policy, and a stateful interface describing the correct usage of the synchronization policy. We present an assume-guarantee style modular verification strategy which separates the verification of the controller behavior from the verification of the conformance to its interface. This allows us to execute the interface and behavior verification tasks separately using specialized verification techniques. We present a case study demonstrating the effectiveness of the presented approach.     

Microstrip tapered traveling wave antenna for wide range of beam scanning in X‐ and Ku‐bands

In this work, a broadband traveling wave antenna (TWA) is presented as a microstrip design that is capable of a wide range of beam scanning by changing the operation frequency within 8 to 14 GHz. For this purpose, a rhombus shaped microstrip patch is used as a unit element and TWA is built as a tapered microstrip line consisting of the cascaded rhombus shaped unit elements and terminated by a rectangular antenna instead of traditional resistive termination which can be called patch loaded traveling wave antenna (PLTWA). Optimization and simulation of the PLTWA is carried out using 3‐D Microwave simulation software CST and its dimensions are resulted as 130 × 30 mm. From the simulations, it should be noted that the patch termination increases the maximum gain almost 3 dB and the total efficiency up to 90% compared to the traditional resistive load over the operation band at the expanse of a small distortion on S₁₁ characteristics. Then the PLTWA is fabricated and measured along its operation band 8 to 14 GHz and it exhibits a peak gain of 9.5 dBi at 11 GHz. The measured gain of the proposed antenna is found between 9 dB and 12 dB and its beam direction is steerable with the range of 80° (?65°‐15°) over the operation band 8 to 14°GHz.     

Automata-based symbolic string analysis for vulnerability detection

Verifying string manipulating programs is a crucial problem in computer security. String operations are used extensively within web applications to manipulate user input, and their erroneous use is the most common cause of security vulnerabilities in web applications. We present an automata-based approach for symbolic analysis of string manipulating programs. We use deterministic finite automata (DFAs) to represent possible values of string variables. Using forward reachability analysis we compute an over-approximation of all possible values that string variables can take at each program point. Intersecting these with a given attack pattern yields the potential attack strings if the program is vulnerable. Based on the presented techniques, we have implemented Stranger, an automata-based string analysis tool for detecting string-related security vulnerabilities in PHP applications. We evaluated Stranger on several open-source Web applications including one with 350,000+ lines of code. Stranger is able to detect known/unknown vulnerabilities, and, after inserting proper sanitization routines, prove the absence of vulnerabilities with respect to given attack patterns.     

Gel casting of mullite for radome applications

Gel-casting method was used to fabricate mullite ceramics because this method has not been applied to fabricate dense mullite in literature. Gel-casting parameters such as monomer types (acrylamide and metyhlenebisacrylamide), effect of initiator (ammonium persulfate), and catalyst (tetramethylenediamine) were studied. All samples reached to relative densities of 97% to 98.2% after sintering at 1540°C for 2 hours. Backscattered SEM images revealed anisotropically grown mullite grains, glassy phase located at triple junctions, hexagonally-shaped and faceted Al₂O₃ grains, and white-color grains consisting of ZrO₂ and undissolved TiO₂. A Weibull modulus of 12.33 (ie, indicating tough ceramics) and characteristic strength of 186 MPa were calculated, below which no failure was expected. A critical quenching temperature was found as about 400°C (ΔT ~ 380°C) by indentation-quench method. In addition, a thermal shock resistance parameter (eg, R in °C) of 142.4°C was calculated, which was higher than commonly used Al₂O₃ ceramics. Lower dielectric constant and loss are desired for wide frequency band application and shorter signal transmission delay time in radomes. The dielectric constant was found as nearly 7.5 up to 10 GHz and loss tangent was 0.0031 at 5 MHz. Dielectric and thermomechanical results suggest that mullite is a suitable candidate ceramic for radome applications.     

Catalytic effects of borax and iron(III) chloride on supercritical liquefaction of Anchusa azurea with methanol and isopropanol

Anchusa azurea is a lignocellulosic gramineous plant, and it has been selected as a renewable feedstock to be used in a liquefaction process to obtain biofuel. Milled Anchusa azurea stalks were converted to liquid products in methanol and isopropanol with (borax or iron(III) chloride) and without catalyst in an autoclave at temperatures of 260, 280, and 300°C. The liquefaction parameter effects such as catalyst, solvents, and temperature were investigated. The highest percentages of liquid yields from methanol and isopropanol conversions were 64.70% (with borax) and 29.20% (with borax) at 300°C in the catalytic runs, respectively. The highest conversion (73.80%) was obtained in methanol with borax catalyst at the same temperature. The obtained liquid products at 300°C were analyzed and characterized by elemental, Fourier transform infrared spectroscopy and gas chromatography–mass spectrometry (GC-MS). Seventy-three different compounds have been identified by GC-MS in the liquid products obtained in methanol at 300°C.     

Correction to: 3D SASHA myocardial T1 mapping with high accuracy and improved precision

Purpose

To improve the precision of a free-breathing 3D saturation-recovery-based myocardial T1 mapping sequence using a post-processing 3D denoising technique.

Methods

A T1 phantom and 15 healthy subjects were scanned on a 1.5 T MRI scanner using 3D saturation-recovery single-shot acquisition (SASHA) for myocardial T1 mapping. A 3D denoising technique was applied to the native T1-weighted images before pixel-wise T1 fitting. The denoising technique imposes edge-preserving regularity and exploits the co-occurrence of 3D spatial gradients in the native T1-weighted images by incorporating a multi-contrast Beltrami regularization. Additionally, 2D modified Look-Locker inversion recovery (MOLLI) acquisitions were performed for comparison purposes. Accuracy and precision were measured in the myocardial septum of 2D MOLLI and 3D SASHA T1 maps and then compared. Furthermore, the accuracy and precision of the proposed approach were evaluated in a standardized phantom in comparison to an inversion-recovery spin-echo sequence (IRSE).

Results

For the phantom study, Bland–Altman plots showed good agreement in terms of accuracy between IRSE and 3D SASHA, both on non-denoised and denoised T1 maps (mean difference −1.4 ± 18.9 ms and −4.4 ± 21.2 ms, respectively), while 2D MOLLI generally underestimated the T1 values (69.4 ± 48.4 ms). For the in vivo study, there was a statistical difference between the precision measured on 2D MOLLI and on non-denoised 3D SASHA T1 maps (P = 0.005), while there was no statistical difference after denoising (P = 0.95).

Conclusion

The precision of 3D SASHA myocardial T1 mapping was substantially improved using a 3D Beltrami regularization based denoising technique and was similar to that of 2D MOLLI T1 mapping, while preserving the higher accuracy and whole-heart coverage of 3D SASHA.