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Malik, Rizwan Ahmed,Zaman, Arif,Hussain, Ali,Maqbool, Adnan,Song, Tae Kwon,Kim, Won-Jeong,Sung, Yeon Soo,Kim, Myong-Ho Elsevier 2018 Journal of the European Ceramic Society Vol.38 No.4
<P><B>Abstract</B></P> <P>Lead free piezoelectric ceramics (1–<I>x</I>) (0.67Bi<SUB>1.05</SUB>FeO<SUB>3</SUB>–0.33BaTiO<SUB>3</SUB>)–<I>x</I>LiNbO<SUB>3</SUB> with <I>x</I> =0.00, 0.015 and 0.030 were prepared by using conventional mixed oxide route. The incorporation of LiNbO<SUB>3</SUB> into BF–BT system caused no significant change in crystal structure. However, an obvious variation in electrical properties was observed. The <I>x</I> =0.015 composition showed enhanced ferroelectric and electric field-induced strain properties with dynamic piezoelectric constant <I>S</I> <SUB>max</SUB>/<I>E</I> <SUB>max</SUB> =440 pm/V at a relatively low field of 40kV/cm, along with a high working temperature upto <I>T</I> <SUB>m</SUB> =392°C. LiNbO<SUB>3</SUB> addition improved the temperature insensitivity of relative permittivity (ε<SUB>r</SUB>) at high temperatures. At <I>x</I> =0.030, a near-plateau ε<SUB>r</SUB> ∼5000, extended across the temperature range, 200°C–500°C was observed which is advantageous for temperature insensitive dielectric ceramics for high temperature capacitor applications. Large strain and almost temperature invariant ε<SUB>r</SUB> with high working temperature range makes this system suitable for high temperature electronic devices.</P>
Malik, Rizwan Ahmed,Hussain, Ali,Maqbool, Adnan,Zaman, Arif,Song, Tae Kwon,Kim, Won Jeong,Kim, Myong Ho Materials Research Society of Korea 2015 한국재료학회지 Vol.25 No.6
New lead-free piezoelectric ceramics $0.96[\{Bi_{0.5}(Na_{0.84}K_{0.16})_{0.5}\}_{1-x}La_x(Ti_{1-y}Nb_y)O_3]-0.04SrTiO_3$ (BNKT-ST-LN, where $x=y=0.00{\leq}(x=y){\leq}0.015)$ were synthesized using the conventional solid-state reaction method. Their crystal structure, microstructure, and electrical properties were investigated as a function of the La and Nb (LN) content. The X-ray diffraction patterns revealed the formation of a single-phase perovskite structure for all the LN-modified BNKT-ST ceramics in this study. The temperature dependence of the dielectric curves showed that the maximum dielectric constant temperature ($T_m$) shifted towards lower temperatures and the curves became more diffuse with an increasing LN content. At the optimum composition (LN 0.005), a maximum value of remnant polarization ($33C/cm^2$) with a relatively low coercive field (22 kV/cm) and high piezoelectric constant (215 pC/N) was observed. These results indicate that the LN co-modified BNKT-ST ceramic system is a promising candidate for lead-free piezoelectric materials.
DOMAINS WITH INVERTIBLE-RADICAL FACTORIZATION
Ahmed, Malik Tusif,Dumitrescu, Tiberiu Korean Mathematical Society 2018 대한수학회보 Vol.55 No.3
We study those integral domains in which every proper ideal can be written as an invertible ideal multiplied by a nonempty product of proper radical ideals.
Malik, Rizwan Ahmed,Hussain, Ali,Acosta, Matias,Daniels, John,Han, Hyoung-Su,Kim, Myong-Ho,Lee, Jae-Shin Elsevier 2018 Journal of the European Ceramic Society Vol.38 No.6
<P><B>Abstract</B></P> <P>In this work, the relationship between the structural mechanisms and macroscopic electrical properties of the Nb-modified 0.96(Bi<SUB>0.5</SUB>Na<SUB>0.84</SUB>K<SUB>0.16</SUB>TiO<SUB>3</SUB>)–0.04SrTiO<SUB>3</SUB> (BNKT–ST) system were elucidated by using temperature dependent and <I>in situ</I> synchrotron X-ray diffraction (XRD) techniques. For the composition <I>x</I> = 0.0175, a large-signal piezoelectric coefficient (<I>S</I> <SUB>max</SUB>/<I>E</I> <SUB>max</SUB> = <I>d</I> <SUB>33</SUB>*) of 735 pm V<SUP>−1</SUP> at 6 kV mm<SUP>−1</SUP> was observed at room temperature. Interestingly, at a higher temperature of 110 °C, the sample still showed a large <I>d</I> <SUB>33</SUB>* of 570 pm V<SUP>−1</SUP>. Furthermore, the temperature-invariant electrostrictive coefficient for this sample was found to be 0.0285 m<SUP>4</SUP> C<SUP>−2</SUP> over the temperature range of 25–170 °C. Moreover, the energy density for <I>x</I> = 0.030 sample was ∼1.0 J cm<SUP>−3</SUP> with an energy storage efficiency of ˃70% in the temperature range of 25–135 °C. These results suggest that the synthesized Nb-modified BNKT–ST system is promising for the design of ceramic actuators as well as capacitor applications.</P>
Ahmed Malik, R.,Hussain, A.,Kwon Song, T.,Kim, W.J.,Ahmed, R.,Soo Sung, Y.,Kim, M.H. Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.suppl1
A new lead-free piezoelectric ceramics (1-x) (0.67Bi<SUB>1.05</SUB>FeO<SUB>3</SUB> - 0.33BaTiO<SUB>3</SUB>)-x LiNbO<SUB>3</SUB>, abbreviated as BFBT-LNx (x = 0.00-0.030), were fabricated by conventional mixed oxide route following by quenching process and crystal structure and electromechanical properties were discussed. X-ray diffraction pattern showed that LiNbO<SUB>3</SUB> addition into 0.67Bi<SUB>1.05</SUB>FeO<SUB>3</SUB> - 0.33BaTiO<SUB>3</SUB> system did not caused any significant change in crystal structure. However, an obvious variation in electrical properties was observed. It is revealed from electrical properties that the modification of LiNbO<SUB>3</SUB> induces a phase transition from a ferroelectric to relaxor state in the 0.67Bi<SUB>1.05</SUB>FeO<SUB>3</SUB> - 0.33BaTiO<SUB>3</SUB> system. At optimum composition (x = 0.010), enhanced field-induced strain with large dynamic piezoelectric constant S<SUB>max</SUB>/E<SUB>max</SUB> = d<SUP>*</SUP><SUB>33</SUB> = 500pm / V at a relatively low field of 3.5kV / mm with lower hysteresis loss of 40% was recorded. For this composition, a high Curie temperature T<SUB>C</SUB> ~ 390<SUP>o</SUP>C was found. These properties suggests that the synthesized system is promising for high temperature actuator applications.
Domains with invertible-radical factorization
Malik Tusif Ahmed,Tiberiu Dumitrescu 대한수학회 2018 대한수학회보 Vol.55 No.3
We study those integral domains in which every proper ideal can be written as an invertible ideal multiplied by a nonempty product of proper radical ideals.
Antioxidant Activity with Flavonoidal Constituents from Aerva persica
Ahmed Ejaz,Imran Muhammad,Malik Abdul,Ashraf Muhammad The Pharmaceutical Society of Korea 2006 Archives of Pharmacal Research Vol.29 No.5
A new flavanone Persinol (1) and the new flavanone glucosides persinosides A (2) and B (3), along with known flavonoids (4 and 5) have been isolated from the ethyl acetate soluble fraction of the whole plants of Aerva persica. Their structures were elucidated on the basis of extensive analysis of nuclear magnetic resonance (1D & 2D-NMR) spectral data. All of them showed profound antioxidative activities by DPPH and cytochrome-c-reduction assays using the HL-60 cell culture system.
Malik Adeel Umer,Dongju Lee,Owais Ahmed Waseem,Ho Jin Ryu,Soon Hyung Hong 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.3
SiC reinforced tungsten matrix composites were fabricated via the spark plasma sintering process. In order to prevent an interfacial reaction between the SiC and tungsten during sintering, TiOx coated SiC particles were synthesized by a solution-based process. TiOx layer coated SiC particles were treated in high temperature nitriding conditions or annealed in a high temperature vacuum to form TiN or TiC coated SiC particles, respectively. The TiC layers coated on SiC particles successfully prevented tungsten from reacting with SiC; hence the proposed process resulted in successful fabrication of the SiC/W composites. The mechanical properties such as compressive strength and flexural strength of the composites were measured. Additionally, the effect of SiC on the high temperature oxidative ablation of tungsten was also investigated. The addition of SiC resulted in an improved oxidative ablation resistance of the tungsten-based composites.
Risk factors for intensive care unit admission and mortality in hospitalized COVID-19 patients
Ayaz Ahmed,Arshad Ainan,Malik Hajra,Ali Haris,Hussain Erfan,Jamil Bushra 대한중환자의학회 2020 Acute and Critical Care Vol.35 No.4
Background: This study investigated the clinical features and outcome of hospitalized coronavirus disease 2019 (COVID-19) patients admitted to our quaternary care hospital. Methods: In this retrospective cohort study, we included all adult patients with COVID-19 infection admitted to a quaternary care hospital in Pakistan from March 1 to April 15, 2020. The extracted variables included demographics, comorbidities, presenting symptoms, laboratory tests and radiological findings during admission. Outcome measures included in-hospital mortality and length of stay. Results: Sixty-six COVID-19 patients were hospitalized during the study period. Sixty-one percent were male and 39% female; mean age was 50.6±19.1 years. Fever and cough were the most common presenting symptoms. Serial chest X-rays showed bilateral pulmonary opacities in 33 (50%) patients. The overall mortality was 14% and mean length of stay was 8.4±8.9 days. Ten patients (15%) required intensive care unit (ICU) care during admission, of which six (9%) were intubated. Age ≥60 years, diabetes, ischemic heart disease, ICU admission, neutrophil to lymphocyte ratio ≥3.3, and international normalized ratio ≥1.2 were associated with increased risk of mortality. Conclusions: We found a mortality rate of 14% in hospitalized COVID-19 patients. COVID-19 cases are still increasing exponentially around the world and may overwhelm healthcare systems in many countries soon. Our findings can be used for early identification of patients who may require intensive care and aggressive management in order to improve outcomes.