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      • Krill-Herd-Based Investigation for Energy Saving Opportunities in Offshore Liquefied Natural Gas Processes

        Qadeer, Kinza,Qyyum, Muhammad Abdul,Lee, Moonyong American Chemical Society 2018 INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH - Vol.57 No.42

        <P>For offshore natural gas liquefaction operation, the single mixed refrigerant process is considered as one of the best and most suitable processes. However, multivariable nonlinear thermodynamic interactions among operating conditions and flow rates of mixed refrigerant ingredients lead to energy losses, which ultimately contributes to high energy consumption for liquefied natural gas production. The present work investigates the energy saving opportunities in the single mixed refrigerant liquefaction process through “krill-herd” strategy which is based on the biological flocking (herding) behavior of individual krill. To find the energy saving opportunities, the krill-herd approach effectively reduced the exergy losses of the compression units and cryogenic heat exchanger up to 18.6 and 41.1%, respectively, as compared to the published liquefaction process. The figure of merit was found as 27.0% in the krill-herd-optimized single mixed refrigerant process, whereas it was 22.2% in the base case.</P> [FIG OMISSION]</BR>

      • KCI등재

        Preventive Gabapentin versus Pregabalin to Decrease Postoperative Pain after Lumbar Microdiscectomy: A Randomized Controlled Trial

        Mohsin Qadeer,Muhammad Waqas,Muhammad Jawad Rashid,Syed Ather Enam,Salman Sharif,Ghulam Murtaza 대한척추외과학회 2017 Asian Spine Journal Vol.11 No.1

        Study Design: Randomized controlled trial. Purpose: The purpose of this study was to compare pregabalin and gabapentin for mean postoperative visual analog score (VAS) for pain in patients undergoing single-level lumbar microdiscectomy for intervertebral disc prolapse at a tertiary care hospital. Overview of Literature: Pregabalin has a superior pharmacokinetic profile and analgesic effect at lower doses than gabapentin; however, analgesic efficacy must be established during the perioperative period after lumbar spine surgery. Methods: This randomized controlled trial was carried out at our institute from February to October 2011 on 78 patients, with 39 participants in each study group. Patients undergoing lumbar microdiscectomy were randomized to group A (gabapentin) or group B (pregabalin) and started on trial medicines one week before surgery. The VAS for pain was recorded at 24 hours and one week postoperatively. Results: Both groups had similar baseline variables, with mean ages of 42 and 39 years in groups A and B, respectively, and a majority of male patients in each group. The mean VAS values for pain at 24 hours for gabapentin vs. pregabalin were comparable (1.97±0.84 vs. 1.6±0.87, respectively; p =0.087) as were the results at one week after surgery (0.27±0.45 vs. 0.3±0.46, respectively; p =0.79). None of the patients required additional analgesia postoperatively. After adjusting for age and sex, the VAS value for group B patients was 0.028 points lower than for group A patients, but this difference was not statistically significant (p =0.817, R2=0.018). Conclusions: Pregabalin is equivalent to gabapentin for the relief of postoperative pain at a lower dose in patients undergoing lumbar microdiscectomy. Therefore, other factors, such as dose, frequency, cost, pharmacokinetics, and side effects of these medicines, should be taken into account whenever it is prescribed.

      • KCI등재

        Relationship between articulation paper mark size and percentage of force measured with computerized occlusal analysis

        Sarah Qadeer,Robert Kerstein,Ryan Jin Yung Kim,Jung-Bo Huh,Sang-Wan Shin 대한치과보철학회 2012 The Journal of Advanced Prosthodontics Vol.4 No.1

        PURPOSE: Articulation paper mark size is widely accepted as an indicator of forceful tooth contacts. However, mark size is indicative of contact location and surface area only, and does not quantify occlusal force. The purpose of this study is to determine if a relationship exists between the size of paper marks and the percentage of force applied to the same tooth. MATERIALS AND METHODS: Thirty dentate female subjects intercuspated into articulation paper strips to mark occlusal contacts on their maxillary posterior teeth, followed by taking photographs. Then each subject made a multi-bite digital occlusal force percentage recording. The surface area of the largest and darkest articulation paper mark (n = 240 marks) in each quadrant (n = 60 quadrants) was calculated in photographic pixels, and compared with the force percentage present on the same tooth. RESULTS: Regression analysis shows a bi-variant fit of force % on tooth (P<.05). The correlation coefficient between the mark area and the percentage of force indicated a low positive correlation. The coefficient of determination showed a low causative relationship between mark area and force (r2 = 0.067). The largest paper mark in each quadrant was matched with the most forceful tooth in that same quadrant only 38.3% of time. Only 6 2/3% of mark surface area could be explained by applied occlusal force, while most of the mark area results from other factors unrelated to the applied occlusal force. CONCLUSION: The findings of this study indicate that size of articulation paper mark is an unreliable indicator of applied occlusal force, to guide treatment occlusal adjustments.

      • KCI등재

        Computed Tomography-Guided Biopsy for Potts Disease: An Institutional Experience from an Endemic Developing Country

        Muhammad Waqas,Mohsin Qadeer,Faizuddin Faiz,Mohammad Ali Alvi,Muhammad Ehsan Bari 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.3

        Study Design: A retrospective chart review. Purpose: In endemic resource poor countries like Pakistan, most patients are diagnosed and treated for Potts disease on clinical and radiological grounds without a routine biopsy. The purpose of this study was to evaluate the use and effect of computed tomography (CT)-guided biopsy in the management of Potts disease since the technique is becoming increasingly available. Overview of Literature: CT-guided biopsy of spinal lesions is routinely performed. Literature on the utility of the technique in endemic resource poor countries is little. Methods: This study was conducted at the Neurosurgery section of Aga Khan University Hospital Karachi. All the patients with suspected Potts disease who underwent CT-guided biopsy during the 7 year period from 2007 to 2013 were included in this study. Details of the procedure, histopathology and microbiology were recorded. Results: One hundred and seventy-eight patients were treated for suspected Potts disease during the study period. CT-guided biopsies of the spinal lesions were performed in 91 patients (51.12%). Of the 91 procedures, 22 (24.2%) were inconclusive because of inadequate sample (10), normal tissue (6) or reactive tissue (6). Sixty-nine biopsies were positive (75.8%). Granulomatous inflammation was seen in 58 patients (84.05%), positive acid-fast bacillus (AFB) smear in 4 (5.7%) and positive AFB culture in 12 patients (17.3%). All 91 cases in which CT-guided biopsy was performed responded positively to antituberculosis therapy (ATT). Conclusions: 75.8% of the specimens yielded positive diagnoses. Granulomatous inflammation on histopathology was the commonest diagnostic feature. In this series, the rates of positive AFB smear and culture were low compared to previous literature.

      • KCI등재

        Variation in Outcome in Tethered Cord Syndrome

        Noorulain Iqbal,Mohsin Qadeer,Salman Yousuf Sharif 대한척추외과학회 2016 Asian Spine Journal Vol.10 No.4

        Study Design: Fifty patients surgically treated for tethered cord syndrome (TCS) were retrospectively studied at Liaquat National Hospital, Karachi from 2010 until 2014. Purpose: To assess the common presentations of TCS in our part of the world and the surgical outcome of the different presentations. Overview of Literature: TCS is a stretch-induced functional disorder of the spinal cord with its caudal part anchored by an inelastic structure, which results in characteristic symptoms and signs. Due to the variety of lesions and clinical presentations and the absence of high-quality clinical outcome data, the decision regarding treatment is difficult. Methods: Fifty consecutive patients with TCS were reviewed retrospectively with a follow-up period of 12–48 months. The majority of the patients were 0-15 years of age with the mean age of 4 years. The presenting complaints and the associated pathologies were documented, and the patients were assessed using the new Karachi TCS severity scale for clinical assessment. Results: Eighty five percent of the patients with thickened filum terminale improved. Sixty six percent of the patients with diastematomyelia, 60% with lipoma and only 46% with myelomeningocele showed clinical improvement postoperatively. Sixty two percent of the patients who presented with paraperesis improved following surgery while 37% remained stable and only one patient deteriorated. Back and leg pain improved in 93% of patients and 50% of patients with urinary impairment improved. Conclusions: Outcome of patients with TCS varies according to pathology and severity of symptoms. Diastematomyelia and thickened filum had the best outcome. The Karachi TCS severity scale is a valid tool for future studies.

      • Nitrogen self-recuperation expansion-based process for offshore coproduction of liquefied natural gas, liquefied petroleum gas, and pentane plus

        Qyyum, Muhammad Abdul,Qadeer, Kinza,Minh, Le Quang,Haider, Junaid,Lee, Moonyong Elsevier 2019 APPLIED ENERGY Vol.235 No.-

        <P><B>Abstract</B></P> <P>In the current scenario of energy challenges, natural gas (NG) and associated liquids such as liquefied petroleum gas (LPG) are considered to be clean energy sources compared with coal and oil. Liquefaction is one of the most feasible and safe approaches for transporting NG from the site of production to the site of consumption. However, NG processing to produce liquefied natural gas (LNG) and LPG is extremely costly in terms of both operating and capital expenses because it requires a tremendous amount of energy, particularly at offshore sites. We have developed a new liquefaction process that uses N<SUB>2</SUB> self-recuperation rather than external precooling with 80% less energy consumption than that required by existing single N<SUB>2</SUB> expander processes. In this work, we evaluate the use of an innovative self-recuperative expander-based integrated process to produce LNG–LPG–pentane plus (condensate) at an offshore site in an energy-efficient manner with minimal capital expenditure. Thermodynamic and economic analyses were performed to evaluate the commercial feasibility of the proposed process. Furthermore, the environmental impact in terms of CO<SUB>2</SUB> emissions was calculated. This study reveals that LNG–LPG can be produced at a specific energy expense of 0.2362 kW with a payback period of 1.38 years.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An innovative self-recuperative expander-based integrated process. </LI> <LI> Offshore coproduction of LNG, LPG, and Pentane-plus. </LI> <LI> Commercial feasibility of integrated LNG-LPG-condensate production process. </LI> <LI> Energy and exergy analysis are performed. </LI> <LI> Environmental impact in terms of CO<SUB>2</SUB> emissions was also calculated. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

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