Sharif Digital Repository

In this work, two important opioid antagonists, naltrexone and oxycodone, were prepared from thebaine and were characterized by IR, 1H NMR and 13C NMR spectroscopy. Moreover, computational NMR and IR parameters were obtained using density functional theory (DFT) at B3LYP/6-311++G* * level of theory. Complete NMR and vibrational assignment were carried out using the observed and calculated spectra. The IR frequencies and NMR chemical shifts, determined experimentally, were compared with those obtained theoretically from DFT calculations, showed good agreements. The RMS errors observed between experimental and calculated data for the IR absorptions are 85 and 105 cm-1, for the 1H NMR peaks are... 

Carbide morphologies of white cast iron containing 22% Cr and 10-12% tungsten with different carbon contents (2.34-3.20. wt.%) were investigated. Results indicated that for the as-cast alloys with no heat treatments, the addition of carbon changes the morphology of carbides during air-cooling in the presence of tungsten. Light microscopy analysis revealed that for an alloy with 2.3. wt% carbon, chromium carbides possess coarse gray appearance (GA). Increasing the carbon content reduced the coarse GA zones volume fraction while a finer GA zones emerged. The coexistence of coarse and fine GA phases came to an end at 2.8. wt% carbon, at which only fine GA zones spread throughout the chromium... 

In the present study, oblique low-velocity impact (OLVI) on GLARE fiber-metal laminates (FMLs) has been modeled using finite element analysis (FEA) for the first time. Two types of boundary conditions (BCs) can be considered for impactor in the low-velocity impact: constrained (if the impact angle between the impactor and target remains constant during and after the contact) and free (if rotation of the impactor and change in angle with respect to the target is likely) BCs. The more details of these BCs are described in the paper. The OLVI is numerically modeled for four different impact angles. Effect of BC types and impact angle on energy absorption, as well as maximum contact force, is... 

In the present study, oblique low-velocity impact (OLVI) on GLARE fiber-metal laminates (FMLs) has been modeled using finite element analysis (FEA) for the first time. Two types of boundary conditions (BCs) can be considered for impactor in the low-velocity impact: constrained (if the impact angle between the impactor and target remains constant during and after the contact) and free (if rotation of the impactor and change in angle with respect to the target is likely) BCs. The more details of these BCs are described in the paper. The OLVI is numerically modeled for four different impact angles. Effect of BC types and impact angle on energy absorption, as well as maximum contact force, is... 

Let (Formula presented.) be a signed graph, where G is the underlying simple graph and (Formula presented.) is the sign function on the edges of G. The adjacency matrix of a signed graph has (Formula presented.) or (Formula presented.) for adjacent vertices, depending on the sign of the connecting edges. In this paper, the eigenvalues of signed complete graphs are investigated. We prove that (Formula presented.) and 1 are the eigenvalues of the signed complete graph with the multiplicity at least t if there are (Formula presented.) vertices whose all incident edges are positive or negative, respectively. We study the spectrum of a signed complete graph whose negative edges induce an... 

Let Γ = (G, σ) be a signed graph, where G is the underlying simple graph and σ E(G) → {-, +} is the sign function on the edges of G. The adjacency matrix of a signed graph has-1 or +1 for adjacent vertices, depending on the sign of the edges. It was conjectured that if is a signed complete graph of order n with k negative edges, k-lt-n-1 and has maximum index, then negative edges form K1 ,k. In this paper, we prove this conjecture if we confine ourselves to all signed complete graphs of order n whose negative edges form a tree of order k + 1. A [1, 2]-subgraph of G is a graph whose components are paths and cycles. Let Γ be a signed complete graph whose negative edges form a [1, 2]-subgraph.... 

In this study, a thermal method was used to synthesize spinel NiCo2O4 and carbon nanotubes (CNTs)@NiCo2O4 with an average size 50 nm and 20 nm, respectively. Addition of CNTs into NiCo2O4 noticeably increases the active surface area compared to pure spinel NiCo2O4. SEM analyses showed that the morphologies are spherical in both pure and composite samples. Uniform CNTs@NiCo2O4 nanoparticles exhibit high specific capacitance of 210 F g−1 at 2 A g−1 and a good retention capacity of 92.70% after 2500 cycles, which shows a considerable improvement compared to NiCo2O4. Additionally, an exceptional rate capability of about 73.2% was obtained at 50 A g−1. Such remarkable electrochemical performance... 

A new approach, based on Adaptive-Network-based Fuzzy Inference System (ANFIS), is presented for the classification of arthrometric data of normal/ACL-ruptured knees, considering the insufficiency of existing criteria. An ANFIS classifier was developed and tested on a total of 4800 arthrometric data points collected from 40 normal and 40 injured subjects. The system consisted of 5 layers and 8 rules, based on the results of subtractive data clustering, and trained using the hybrid algorithm method. The performance of the system was evaluated in four runs, in the framework of a 4-fold cross validation algorithm. The results indicated a definite correct diagnosis for typical injured and normal... 

Ceramic-matrix composites containing TiC-TiN have been used in a variety of application because of their superior properties such as high hardness, good wear resistance and high chemical stability. In this research, effect of coke and coke/calcium beds in synthesis of Al2O3-Ti(C, N) composites using alumino-carbothermic reduction ofTiO2 has been investigated. Al, TiO2 and active carbon with additives of extra carbon and NaCl and without additives, in separate procedures, have been mixed. Afterwards, mixtures were pressed and synthesized in 1200°C for 4hrs, in coke and coke/calcium beds, separately. Al2O3-Ti(C,N) composite was synthesized in ternary system of Al-TiO2-C with excess carbon and... 

In this paper, we propose a fuzzification method for clusters produced from a clustering process, based on Active Learning Method (ALM). ALM is a soft computing methodology which is based on a hypothesis claiming that human brain interprets information in pattern-like images. The proposed fuzzification method is applicable to all non-fuzzy clustering algorithms as a post process. The most outstanding advantage of this method is the ability to determine the membership degrees of each data to all clusters based on the density and shape of the clusters. It is worth mentioning that for existing fuzzy clustering algorithms such as FCM the membership degree is usually determined as a function of... 

Due to unique advantages, the development of high-performance supercapacitors has stimulated a great deal of scientific research over the past decade. The electrochemical performance of a supercapacitor is strongly affected by the surface and structural properties of its electrode materials. Herein, we report a facile synthesis of high-performance supercapacitor electrode material based on CuS nano-hollow spheres with nanoporous structures, large specific surface area (97 m2 g−1) and nanoscale shell thickness (<20 nm). This interesting electrode structure plays a key role in providing more active sites for electrochemical reactions, short ion and electron diffusion pathways and facilitated... 

In recent years, development of high-performance supercapacitor electrode materials has stimulated a great deal of scientific research. The electrochemical performance of a supercapacitor strongly depends on its material structures. Herein, we report a simple strategy for high-performance supercapacitors by building pseudocapacitive CuS nanospheres with nanoporous structures, nanosized walls (<10 nm) and relatively large specific surface area of 65 m2/g. This electrode demonstrates excellent electrochemical performance including a maximum specific capacitance of 814 F/g at 1 A/g, significant rate capability of 42% capacitance retention at an ultrafast rate of 50 A/g, and outstanding... 

Proper thermal treatment of metals in metal processing plants is important both in terms of quality and economy of the final product. Addition of a highly soluble gas such as carbon dioxide to water has been shown to create an excellent quenching medium for metal objects in metal working processes. It causes slower rate of cooling due to the insulating effect of carbon dioxide on the surface of immersed metal objects which as a result hinders residual stress build up and warpage commonly observed in quenching metal objects in cold water. Additionally, absence of carbon dioxide-filled bubbles on the surface of quenching metal object causes cold water-like cooling of the surface, producing...