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        • KCI등재SCIESCOPUS

          Dielectric and Electromechanical Properties of Zr-Doped BNT-ST Lead-Free Piezoelectric Ceramics

          Amir,Ullah,Mateen,Ullah,Aman,Ullah,A.,V.,Trukhanov,Ghulam,Saddiq,Burhan,Ullah,Aurang,Zeb,Saeed,Ullah,Jan,김일원 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.74 No.6

          0.72(Bi$_{0.5}$Na$_{0.5}$)Ti$_{(1-x)}$Zr$_x$O$_3$-0.28SrTiO$_3$ (BNTZ-ST) with $x$ = 0.00, 0.01, 0.02 and 0.03 were produced using a solid solution reaction procedure. Results from the X-ray diffraction (XRD) analysis showed the presence of a perovskite structure with cubic symmetry for all samples. Surface analysis was completed using field emission scanning electron microscopy (FE-SEM), and the grain size was found to decrease slightly with increasing Zr doping. The grain morphology was primarily rectangular, but morphed into a rounder shape with increases in Zr. In a dielectric constant study, the depolarization temperature was found to decrease with increasing Zr$^{+4}$ content and increasing frequency. The strain was found to be 0.34\% for the undoped samples with an equivalent dynamic strain ($S_{max}/E_{max}$) of 618 pm/V, without negative strain. However, the strain decreased slightly and hysteresis loops become slim and more symmetric, attaining a relaxor ferroelectric behavior with increasing Zr content.

        • KCI등재

          The ex-ante Effect of Law and Judicial Efficiency on Borrower Discouragement: An International Evidence

          Safi,Ullah,Khan,Naimat,Ullah,Khan,Asad,Ullah 한국증권학회 2021 Asia-Pacific Journal of Financial Studies Vol.50 No.2

          We investigate whether cross-country differences in the legal system influence demand-side credit constraints. We explore the notion of discouraged borrowers — firms that choose not to apply for bank credit because they anticipate rejection. Employing survey data from 46 economies, we find that rapid and less costly court proceedings, lower procedural complexity in court processes, and higher recovery rates under bankruptcy lead to the lower likelihood of borrower discouragement. These results are more pronounced in countries with strong creditor protections in relation to company reorganization and liquidation. The results corroborate the supply-side view that strong creditor rights and their efficient enforceability alleviate banks' participation constraints in the loan market, thereby encouraging small and medium-sized enterprises to apply for credit in the first place. We also find that differences in institutional settings, such as higher regulatory quality, better control of corruption, and the rule of law, lead to lower rates of credit self-rationing in the loan market.

        • KCI등재SCOPUS

          Integrated Tracking and Accident Avoidance System for Mobile Robots

          Irfan,Ullah,Furqan,Ullah,Qurban,Ullah,신서용 제어·로봇·시스템학회 2013 International Journal of Control, Automation, and Vol.11 No.6

          In the intelligent transportation field, various accident avoidance techniques have been applied. One of the most common issues with these is the collision, which remains an unsolved problem. To this end, we developed a Collision Warning and Avoidance System (CWAS), which was implemented in the wheeled mobile robot. Path planning is crucial for a mobile robot to perform a given task correctly. Here, a tracking system for mobile robots that follow an object is presented. Thus, we implemented an integrated tracking system and CWAS in a mobile robot. Both systems can be activated independently. Using the CWAS, the robot is controlled through a remotely controlled device, and collision warning and avoidance functions are performed. Using the tracking system, the robot performs tasks autonomously and maintains a constant distance from the followed object. Information on the surroundings is obtained through range sensors, and the control functions are performed through the microcontroller. The front, left, and right sensors are activated to track the object, and all the sensors are used for the CWAS. The proposed system was tested using the binary logic controller and the Fuzzy Logic Controller (FLC). The efficiency of the robot was improved by increasing the smoothness of motion via the FLC, achieving accuracy in tracking and increasing the safety of the CWAS. Finally, simulations and experimental outcomes have shown the usefulness of the system.

        • KCI등재SCIESCOPUS

          Dielectric, Ferroelectric and Strain Properties of (Bi0.5Na0.5)0.935Ba0.065Ti1-x(Al0.5Nb0.5)xO3 Lead-free Piezoelectric Ceramics

          Mateen,Ullah,Amir,Ullah,Hidayat,Ullah,Khan,Imtiaz,Ahmad,Ill,Won,Kim 한국물리학회 2020 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.76 No.2

          Piezoelectric ceramics (Bi0.5Na0.5)0.935Ba0.065Ti1-x(Al0.5Nb0.5)xO3 (BNBT-AN) have been synthesized for x = 0, 0.010, 0.015, 0.020, 0.025, and 0.030 through simple solid state reaction technique. Synthesis and sintering of all the systems were successful as single phase was obtained through out. This work explains the influence of AN on morphology, phase structure, electrical and electromechanical characteristics of the parent BNBT matrix. All compositions were single phase perovskites by X-ray diffraction (XRD), that could be confirmed as the tetragonal, P4/m, and rhombohedral, R3c, mixed structures. Tetragonality was increased with increase in the AN content. With similar modification, dynamic piezoelectric constant d*33 (= Smax/Emax) was increased monotonically gaining a highest value of 354 pm/V corresponding to x = 0.030. The overall increase was found in remnant polarization (Pr) for all the systems except for the one with x = 0.030. Maximum Pr, 30.6 μC/cm^2, was noted for x = 0.025. This phenomenon was also accompanied by a persistent decrease in coercive field Ec, from 28.0 kV/cm for undoped to 14.5 kV/cm for 3 mol%. The ceramics were signified with encouraging electrical properties.

        • KCI등재SCOPUS

          An Experimental Study on Modelling the Physical Properties of Composite Psyllium, Alginate and Chitosan Fibers Using Box-Behnken Technique

          Azeem,Ullah,Sana,Ullah,Tanzeel,Areeb,Muhammad,Umar,Phan,Duy,Nam,Rashid,Masood,Soonjee,Park,김익수 한국섬유공학회 2020 Fibers and polymers Vol.21 No.11

          Polysaccharides from different sources have found their applications in the wound care for their inherent abilitiesof gelling, biocompatibility, biodegradability, and antibacterial activity. Considering the low cost, ease of processing,abundance in nature and therapeutic benefits of the polysaccharides we developed psyllium, alginate and chitosan (PAC)composite fibers and modelled their physical properties namely; tenacity, linear density and absorption in both distilled waterand saline solution; using Box-Behnken (BB) technique of Response Surface Methodology (RSM). The PAC fibers wereproduced using an in house developed wet spinning module; briefly the dope solutions containing psyllium and alginate wereextruded into a hydrolyzed chitosan and CaCl2. The produced fibers were acetone washed to remove the polar solvent; in thiscase water; and later dried in air. The present work aimed at the development of statistical models for physical properties:linear density, tenacity, antibacterial efficacy and liquid absorption; of the composite PAC fibers. The factors underconsideration were the raw material concentration namely; alginate and psyllium in dope solution and calcium chloride(CaCl2) and hydrolysed chitosan in the coagulation bath. The experimental work was designed and analyzed using Minitab®17 statistical software. Regression models using the under consideration factors were successfully developed.

        • KCI등재SCOPUS

          Dynamic numerical simulation of plastic deformation and residual stress in shot peening of aluminium alloy

          Himayat,Ullah,Baseer,Ullah,Riaz,Muhammad 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.63 No.1

          Shot peening is a cold surface treatment employed to induce residual stress field in a metallic component beneficial for increasing its fatigue strength. The experimental investigation of parameters involved in shot peening process is very complex as well as costly. The most attractive alternative is the explicit dynamics finite element (FE) analysis capable of determining the shot peening process parameters subject to the selection of a proper material´s constitutive model and numerical technique. In this study, Ansys / LS-Dyna software was used to simulate the impact of steel shots of various sizes on an aluminium alloy plate described with strain rate dependent elasto-plastic material model. The impacts were carried out at various incident velocities. The influence of shot velocity and size on the plastic deformation, compressive residual stress and force-time response were investigated. The results exhibited that increasing the shot velocity and size resulted in an increase in plastic deformation of the aluminium target. However, a little effect of the shot velocity and size was observed on the magnitude of target´s subsurface compressive residual stress. The obtained results were close to the published ones, and the numerical models demonstrated the capability of the method to capture the pattern of residual stress and plastic deformation observed experimentally in aluminium alloys. The study can be quite helpful in determining and selecting the optimal shot peening parameters to achieve specific level of plastic deformation and compressive residual stress in the aluminium alloy parts especially compressor blades.

        • KCI등재SCIESCOPUS

          Frequency-dependent Impedance Spectroscopy on the 0.925(Bi0.5Na0.40K0.10)TiO3-0.075(Ba0.70Sr0.30)TiO3 Ceramic

          Amir,Ullah,Muneeb-ur-Rahman,Muhammad,Javid,Iqbal,Chang,Won,Ahn,Ill,Won,Kim,Aman,Ullah 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.12

          The electrical properties of the 0.925(Bi0.5(Na0.40K0.10)TiO3-0.075(Ba0.70Sr0.30)TiO3 (0.925BNKT-0.075BST) ceramic were investigated by using AC impedance spectroscopy over a wide range of frequencies (10−2 105 Hz). The X-ray diffraction patterns confirmed the formation of a single-phase compound. A single semicircular arc in the impedance spectrum indicates that the main contribution of the bulk resistance (Rb) were due to grain effects, with Rb decreasing with increasing temperature. The conductivity of the ceramics increased with increasing temperature, and the activation energy resulting from the DC conductivity was 0.86 eV. The ceramic displayed a typical negative temperature coefficient of resistance (NTCR) behavior, like that of a semiconductor.

        • KCI등재

          Post-Crisis Behavior of Banks in Asia: A Case of Chronic Over-Capitalization

          Khalil,Ullah,MOHAMMAD,Affan,MUHAMMAD,Kaleem,Ullah,MUHAMMAD 한국유통과학회 2021 The Journal of Asian Finance, Economics and Busine Vol.8 No.3

          The study investigates the behavior of Asian banks in response to the subprime mortgage crisis and examines how countries that have experimented with a mix of conventional and Islamic banking managed their balance sheet during that period. The study carries out an independent mean t-test comparing the difference of leverage of 464 conventional commercial Asian banks pre- and post-crisis from the largest twenty-five Asian economies based on GDP (2007). The analysis uses 10-year unbalanced panel data of conventional banks and employs the generalized least squares estimation using a dummy variable event window method to capture the response of Asian banks. The study finds evidence of a structural change in the capital structure of Asian commercial banks in response to the financial crisis. Findings suggest that conventional banks increased their capital position more in countries that have both Islamic and conventional banking than those countries without Islamic banking services. By having Islamic banking in their product portfolio, countries can exert market discipline on conventional banks. The study identifies a significant role of global macroeconomic shocks on banks liability structure decision-making. Evidence shows that this increase in capital positioning by banks was a permanent rather than a temporary response.

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