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Estimation of the Lubricating Oil Rheology at High Pressure Based on Phase Diagram
MD. Z. RAHMAN,N. OHNO 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.2002 No.10
For rheology investigation of lubricating oils, first phase diagrams were made from determined free volume based on density measurements and the temperature-pressure relation was estimated using the expansion coefficient of free volume and the temperature-pressure relation of the viscoelastic transition point. Next, the authors proposed the density-pressure-temperature relation and the viscosity-pressure-temperature relation of the tested oils based on the free volume and the phase diagrams. Moreover, it was shown that the Ehrenfest equation or the gradient of the phase diagram is closely related to the expansion coefficient of free vol lime.
Md. Anamul Hoque,Md. Mofaqkharur Rahman,Shamim Mahbub,Mezbah Hossain,Mohammed Abdullah Khan,Md. Ruhul Amin,Ali S. Alqahtani,Mohammad Z. Ahmed,Mohammed S. Alqahtani,Omar M. Almarfadi 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.7
Surfactant is one of the most important chemical entities in drug formulation which can bind with drug molecules. Herein, the binding interaction of ciprofloxacin hydrochloride (CFH) drug with two different surfactants (sodium dodecyl sulfate (SDS) and Triton X-100 (TX-100)) has been investigated through UV-Visible spectroscopic and cloud point measurement techniques at different conditions. The absorption spectrum of CFH was found to be dependent on presence of additives/temperature change. The binding constant (Kb) of CFH+SDS/CFH+TX-100 was found to be increased primarily, reached a maximum value and then decreased with the increase of temperature, except in water medium (pH=2.0) and 30% (v/v) methanol. The Kb values for CFH+SDS were found to be higher in the aqueous medium than almost all medium studied herein, while better binding was observed in the alcoholic medium in the case of the CFH+TX-100 system. The Gibbs free energy of binding (Gb o) for both CFH+SDS and CFH+TX- 100 systems were attained negative in each case studied, inferring the spontaneous binding phenomenon. The cloud point (CP) value of CFH+TX-100 mixture was lessened in ZnSO4·7H2O solution and the CP values exhibited a gradual reduction through the upsurge of electrolyte concentration. The positive values of the Gibbs free energy of clouding indicated the nonspontaneous clouding phenomena. To disclose the interaction between drug and surfactant, other thermodynamic parameters, e.g., enthalpy (Hb o) and entropy (Sb o), different transfer energies as well as entropyenthalpy compensation parameters of binding/clouding were evaluated and clarified with proper explanation.
Selecting Tanker Steaming Speeds under Uncertainty: A Rule-Based Bayesian Reasoning Approach
N.S.F. ABDUL RAHMAN,R.MD. HANAFLAH,A.F. AHMAD NAJIB,W.M.Z. ABDUL HALIM 국제이네비해양경제학회 2015 International Journal of e-Navigation and Maritime Vol.2 No.1
In the tanker industry, there are a lot of uncertain conditions that tanker companies have to deal with.For example, the global financial crisis and economic recession, the increase of bunker fuel prices and global climate change. Such conditions have forced tanker companies to change tankers speed from full speed to slow speed, extra slow speed and super slow speed. Due to such conditions, the objective of this paper is to present a methodology for determining vessel speeds of tankers that minimize the cost of the vessels under such conditions. The four levels of vessel speed in the tanker industry will be investigated and will incorporate a number of uncertain conditions. This will be done by developing a scientific model using a rule-based Bayesian reasoning method. The proposed model has produced 96 rules that can be used as guidance in the decision making process. Such results help tanker companies to determine the appropriate vessel speed to be used in a dynamic operational environmental.
Effect of Chain Matching between Hydrocarbon and Fatty Acid on High Pressure Rheology
N. OHNO,R. MUKAI,Md. Z. RAHMAN,K. SHIBATA 한국트라이볼로지학회 2002 한국트라이볼로지학회 학술대회 Vol.2002 No.10
For estimation of chain-matching phenomena between normal paraffin as a solvent and straight-chain fatty acid as an additive, the density measurement of n-dodecane, n-tetradecane and n-hexadecane were-carried out at oil temperature 313K and pressure up to 1.3 ㎬. Their solidification pressure were easily determined by the appearance of molecular crystal, abrupt volumetric contraction and generation of heat of solidification and showed minima under the matching condition. The bulk modulus K of molecular crystal was evaluated using phase diagram. The bulk modulus showed maxima under the each matching condition. The chain matching effect on the bulk modulus beyond the scope of the interfacial phenomena are confirmed.
Sharmin Akter,A S M Bazlul Karim,Md Wahiduzzaman Mazumder,Md Rukunuzzaman,Khan Lamia Nahid,Bishnu Pada Dey,Maimuna Sayeed,A Z M Raihanur Rahman,Kaniz Fathema,Mukesh Khadga 대한소아소화기영양학회 2022 Pediatric gastroenterology, hepatology & nutrition Vol.25 No.5
Purpose: Perinatal cytomegalovirus (CMV) infection can lead to biliary atresia (BA) in different entities. This study aimed to compare the clinical, hematological, biochemical, and histological features of infants with BA based on their CMV immunoglobulin M (IgM) status at presentation. Methods: This cross-sectional descriptive study was carried out between January 2019 and June 2020 at the Department of Pediatric Gastroenterology and Nutrition at the Bangabandhu Sheikh Mujib Medical University (BSMMU) in Dhaka. Forty-three patients with BA were selected purposively and categorized into either the CMV IgM-positive or CMV IgM-negative BA group. Categorical variables were compared using Fisher’s exact test and chi-square tests, while the Student’s t-test and Mann–Whitney U-test were used to compare continuous variables. For all statistical tests, a p-value <0.05 was considered statistically significant. Results: Thirty-three (76.7%) of the cases were between 2 and 3 months of age on admission. The clinical, hematological, and biochemical parameters did not differ significantly between the CMV IgM-positive and CMV IgM-negative BA groups. Most (50.0%) of the CMV IgM-positive cases had fibrosis stage F2, while 43.5% of the CMV IgM-negative cases had fibrosis stage F3, with no significant difference between the groups (p=0.391). Conclusion: Our data shows no significant distinction between CMV IgM-positive and CMV IgM-negative BA, suggesting that CMV does not contribute to BA pathogenesis.