Determination of the minimum sampling frequency in bandpass sampling by geometric approach and geometric programming

This paper presents a simple and fast approach to find a minimum sampling frequency for multi-band signals. Instead of neighbor and boundary conditions, constraints on the sampling frequency were derived by using the geometric approach to the bandpass sampling theorem. Reformulation of the constraints on the minimum sampling frequency enabled to represent the problem as an optimization problem which was structured by the geometric programming and mixed-integer nonlinear programming methods. The convex optimization problem was then solved by the proposed algorithm applying interior point approach in the line search framework. It was demonstrated that this unified structure directly linked the geometric approach of the bandpass sampling theorem to the optimization problem. The proposed method was verified through numerical simulations in terms of the minimum sampling frequency and the computational efficiency. Results illustrated the feasibility of the geometric approach and the proposed algorithm in the determination of the minimum sampling frequency by providing the savings in the number of iterations and the decrease in the valid minimum sampling frequency.     

A Huffman compression based text steganography method

In this study, capacity and security issues of text steganography have been considered by proposing a compression based approach. Because of using textual data in steganography, firstly, the employed data compression algorithm has to be lossless. Accordingly, Huffmann coding has been chosen due to its frequent use in the literature and significant compression ratio. Besides, the proposed method constructs and uses stego-keys in order to increase security. Secret information has been hidden in the chosen text from the previously constructed text base that consists of naturally generated texts. Email has been chosen as communication channel between the two parties, so the stego cover has been arranged as a forward mail platform. As the result of performed experiments, average capacity has been computed as 7.962 % for the secret message with 300 characters (or 300?8 bits). Finally, comparison of the proposed method with the other contemporary methods in the literature has been carried out in Section 5.     

Synthesis and phosphorescence properties of Mn, La and Ho in MgAl2Si2O8

Mn⁴⁺, La³⁺ and Ho³⁺ doped MgAl₂Si₂O₈-based phosphors were first synthesized by solid state reaction. They were characterized by thermogravimetry (TG), differential thermal analysis (DTA), X-ray powder diffraction (XRD), photoluminescence (PL) and scanning electron microscopy (SEM). The phosphors were obtained at about 1300 °C. They showed broad red and fuchsia-pink emission bands in the range of 610-715 nm and had a different maximum intensity when activated by UV illumination. Such a fuchsia-pink emission can be attributed to the intrinsic d-d transitions of Mn⁴⁺.     

Effects of cavity disinfectants on bond strength of an etch-and-rinse adhesive to water- or ethanol-saturated sound and caries-affected dentin

Objective: To evaluate the effect of cavity disinfectants on the immediate microtensile bond strength (μTBS) of an etch-and-rinse adhesive to water- and ethanol-saturated sound and caries-affected dentin (CAD). Material and Methods: Thirty-six human molars were sectioned to expose 1/3 of the mid-coronal dentin surface. Sound (n = 18) and CAD (n = 18) specimens were divided into six groups each (n = 3): one positive control (sound), one negative control (CAD), and five experimental groups each. In the control group, dentin surfaces were bonded using an etch-and-rinse adhesive with a traditional water-wet bonding technique. In the experimental groups, ozone was applied before etching and chlorhexidine after etching. In the ethanol-wet bonding groups, acid-etched dentin surfaces were treated with ethanol. Following adhesive application and composite buildups, bonded specimens were sectioned to form sticks. Failure modes were analyzed using a stereomicroscope. Results: The water-wet bonded sound control group yielded the highest μTBS among all groups (p < 0.001). The lowest μTBS values were observed in the ozone groups (p < 0.05). The ethanol-wet bonded CAD group exhibited a higher μTBS than the water-wet bonded negative controls. Although compared to the positive control, chlorhexidine decreased the μTBS (p < 0.05), an increase with no significant difference was observed in the negative control (p > 0.05). Conclusions: The μTBS values of CAD were lower than those of sound dentin. Ethanol-wet bonding improved the μTBS of CAD. Ozone application reduced the μTBS in both sound and CAD; chlorhexidine improved the immediate μTBS after etching in CAD.     

Designing Approach of Fiber-Reinforced Polymer Composite by Combination of Fibrillated Olive Pomace and Marble Powder

The development of effective methods to utilize industrial and agricultural wastes is crucial from the perspective of a circular economy. Marble powder and olive pomace (OP), byproducts of olive oil production and marble processing, are considered one of the major sources causing severe environmental pollution, especially in Mediterranean countries. Herein, marble powder and OP are aimed to use as fillers in polypropylene (PP)-based polymer composite. In addition, fractionated OP is further fibrillated by a combination of mechanical grinding and ionic liquid treatment to enhance its performance as a reinforcement. After treatment for 24 h, the particle size decreases from about 2.1 to 1.1 µm, and the lignocellulosic composition also varies due to the partial removal of hemicellulose. Finally, the compounding ratio of polymer composites consisting of PP, marble powder, fibrillated OP, and compatibilizer is optimized using response surface methodology (RSM) to achieve both high mechanical properties and high filler contents. Mechanical properties of polymer composite fabricated with optimum ratio are in excellent agreement with those predicted by RSM. Furthermore, the yield strength and Young's modulus of polymer composite are 33.9 MPa and 1.89 GPa, accordingly, which are higher than those of PP.     

Fabrication,characterization, and performance of YbDSB ternary compounds for IT‐SOFC applications

(Yb₂O₃)_x(Dy₂O₃)_y(Bi₂O₃)_1?x?y (0.04≤x+y≤0.20) powders (xYbyDSB) were synthesized by modified sol‐gel Pecchini method. The powders were characterized for structural, surface morphological, thermal, and electrical properties and power density measurements by means of X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis/thermal gravimetry (DTA/TG), and impedance spectroscopy, respectively. Lattice parameters and crystalline size of δ‐phase of Yb₂O₃‐ and Dy₂O₃‐doped Bi₂O₃ samples were calculated from the X‐ray diffraction data. Surface and grain properties of the related phases were determined by SEM analysis. In the investigated system, the maximum electrical conductivity was observed as σ=0.954 S cm^?1 for 6% mol Yb₂O₃ and 6% mol Dy₂O₃ at 800°C among all δ‐YbDSB systems. Cathode supported electrochemical cell was fabricated and 6Yb6DSB was used as the electrolyte. Maximum power density of single cell with an active area of 1.5 cm² is 72.50 mW/cm² at 700°C.     

Production of the biomimetic small diameter blood vessels for cardiovascular tissue engineering

A novel biomimetic vascular graft scaffolds were produced by electrospinning method with the most superior characteristics to be a proper biomimetic small diameter blood vessel using Polycaprolactone(PCL), Ethyl Cellulose(EC) and Collagen Type-1 were used to create the most convenient synergy of a natural and synthetic polymer to achieve similarity to native small diameter blood vessels. Scanning Electron Microscopy(SEM), Fourier Transform Infrared Spectroscopy(FTIR), Differential Scanning Calorimetry Analysis(DSC), tensile measurement tests, and in-vitro and in-vivo applications were performed. Results indicated significant properties such as having 39.33?nm minimum, 104.98?nm average fiber diameter, 3.2?MPa young modulus and 135% relative cell viability.     

The Production and Characterization of Ytterbium‐Stabilized Zirconia Films for SOFC Applications

(ZrO₂)_1–x(Yb₂O₃)_x binary systems were investigated in the doping range of 0.02 ≤ x ≤ 0.12. Ytterbium‐doped zirconia powders were synthesized using the Pechini method. X‐ray diffraction (XRD) measurements showed that fcc ZrO₂ was stabilized for 8–12 mol% Yb‐doping rate. The produced Yb‐stabilized Zr (YbSZ) films were characterized; their thickness and homogeneity properties depended on the nature of the YbSZ slurry. All coating parameters were optimized and determined with precoating treatments. The samples were characterized by differential thermal analysis/thermal gravimetry (DTA/TG), scanning electron microscopy (SEM) and ac impedance measurements.     

A general framework of a Reference Model for Intelligent Integrated Manufacturing Systems (REMIMS)

Today's highly competitive business environment forces the managers to continuously make the best decisions in the shortest possible time. The ability to provide concurrency among manufacturing functions is a critical need for modern organizations as, especially, distributed environment requires synchronization of manufacturing functions. Moreover, manufacturing companies need to have strong capability of adaptation (agility) mainly because of the dynamic relationships that must be established between manufacturing units. To achieve these, there is a need for an integrated manufacturing system that will handle all interactions and interrelationships which will then be affected by the changes and create maximum gain under limited resources. In order to create and effectively manage such an integrated manufacturing system there is a need for a reference model. In this paper, such a reference model called REference Model for intelligent Integrated Manufacturing System (REMIMS) is introduced. REMIMS has hierarchical architecture with several agents responsible for different manufacturing functions. To facilitate REMIMS and allow interaction among the agents to share their knowledge, a specific knowledge exchange protocol in a knowledge network is being developed.