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排序方式: 共有143条查询结果,搜索用时 31 毫秒
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2.
Reliability analysis of TLP tethers under impulsive loading 总被引:1,自引:0,他引:1
R.A. Khan N.A. Siddiqui S.Q.A. Naqvi S. Ahmad 《Reliability Engineering & System Safety》2006,91(1):73-83
In the present study, reliability assessment of Tension Leg Platform (TLP) tethers against maximum tension (i.e. tension exceeding yield) has been carried out under combined action of extreme wave and impulsive forces. For this purpose, a nonlinear dynamic analysis of TLP has been carried out in time domain. A limit state function for maximum tension (i.e. tension exceeding yield) has been derived employing Von-Mises theory of failure. Using this derived limit state function and responses obtained after dynamic analysis under sinusoidal, half-triangular and triangular impulsive forces, reliability assessment of the TLP tethers has been carried out. Design point, important for probabilistic design of tethers, has been located on the failure surface after solving a constrained optimization problem. To study the influence of various random variables on tether reliability, sensitivity analysis has been carried out. Effects of angle of impact; effect of variable submergence; and effect of material yield strength on tether reliability have also been studied on parametric basis. Effect of uncertainty on overall tether reliability has also been discussed to show the importance of quality control in the various design parameters. 相似文献
3.
Asif Hussain Khoja Arslan Mazhar Faisal Saleem Muhammad Taqi Mehran Salman Raza Naqvi Mustafa Anwar Sehar Shakir Nor Aishah Saidina Amin Muhammad Bilal Sajid 《International Journal of Hydrogen Energy》2021,46(29):15367-15388
The catalyst has a significant role in gas processing applications such as reforming technologies for H2 and syngas production. The stable catalyst is requisite for any industrial catalysis application to make it commercially viable. Several methods are employed to synthesize the catalysts. However, there is still a challenge to achieve a controlled morphology and pure catalyst which majorly influences the catalytic activity in reforming applications. The conventional methods are expansive, and the removal of the impurities are major challenges. Nevertheless, it is not straightforward to achieve the desired structure and stability. Therefore, significant interest has been developed on the advanced techniques to take control of the physicochemical properties of the catalyst through non-thermal plasma (NTP) techniques. In this review, the systematic evolution of the catalyst synthesis using NTP technique is elucidated. The emerging DBD plasma to synthesized and effective surface treatment is reviewed. DBD plasma synthesized catalyst performance in reforming application for H2 and syngas production is summarised. Furthermore, the status of DBD plasma for catalyst synthesis and proposed future avenues to design environmentally suitable and cost-effective synthesis techniques are discussed. 相似文献
4.
Md. Sayem Alam Andleeb Z. Naqvi Kabir-ud-Din 《Journal of surfactants and detergents》2007,10(1):35-40
The effect of additives (surfactants and polymers) and pH on the clouding behavior of promethazine hydrochloride (PMT, a phenothiazine
drug) was investigated. Cloud point (CP) decreases with increase in pH due to deprotonation of drug molecules. The same trend
occurs in the presence of surfactants. However, at constant pH, and depending on their structure and nature, these additives
behave differently. Anionic surfactants show peaked behavior, whereas cationic (conventional as well as geminis) and non-ionic
surfactants increase the CP, although the mechanisms differ. Cationic surfactants hinder drug association (due to interaggregate
repulsion) resulting in an increase in CP, while non-ionic surfactants form mixed micelles with the drug, increasing micelle
hydration and CP. Polymers can cause both a decrease as well as an increase in CP, depending on their molecular weight. A
large CP increase (with the increase in surfactant concentration) for gemini surfactants suggests they are excellent candidates
for drug delivery.
相似文献
Kabir-ud-DinEmail: |
5.
Benzyl chloride has been used in a kinetic study of chlorine replacement by acetoxy groups to model the behaviour of allylic chlorine during the acetoxylation of poly(vinyl chloride). Chlorine substitution was carried out in tetrahydrofuran at 30°C using a potassium acetate-crown ether complex with methanol to ensure homogeneous solution. The process followed an SN2 mechanism. The orders of reaction with respect to benzyl chloride and potassium acetate were close to one, and the second order velocity constant was 4.2 x 10?5 litre mol?1 s?1 when the molar ratio of crown ether to potassium acetate was approximately unity. Higher ratios caused a slight increase in rate constant. Substitution was followed by NMR spectroscopy which also revealed a proton exchange between methanol and acetate anion with an equilibrium constant 9.4 x 10?2. This observation has suggested an explanation for the effect of some free-radical inhibitors on the rate of acetoxylation of poly(vinyl chloride) by potassium acetate in the presence of crown ether. 相似文献
6.
Fehmida Naqvi Abdul Rauf M. M. Siddiqui M. S. Ahmad Jr. S. M. Osman 《Journal of the American Oil Chemists' Society》1997,74(6):713-717
Pseudohalogenation of methyl 9-hydroxy-cis-12-octadecenoate (I) and methyl 12-hydroxy-cis-9-octadecenoate (II) has been carried out with N,N-dibromobenzenesulfonamide (NNDBS). Compounds I and II, on reaction with NNDBS, formed four and three products, respectively. The interesting feature of these reactions was the
formation of 1,4-epoxy compounds. The structures of individual compounds were established with the help of elemental and spectral
analysis. 相似文献
7.
8.
A new medium access protocol which exploits the physical layer capability of multiuser detection is proposed to help in improving
the throughput/delay performance of ad-hoc networks. When more than one node has packets buffered for a common node in the
neighborhood, all such nodes can simultaneously transmit their packets to the common receiver after reserving their surrounding
channel. This is achieved in our protocol by extending the (sender-initiated) CSMA/CA collision avoidance framework by the
receiver-initiated medium access technique and incorporating the transmission power control. We analyze the improvement in
the throughput that can be achieved over the basic sender-initiated collision avoidance protocol in the network. Since the
throughput improvement via multi-packet reception is influenced by the network layer activity as well, the performance of
our protocol rolls back to that of the basic sender-initiated protocol in case of no coordination from the network layer.
For the evaluation of performance of our protocol we simulate ad-hoc networks for different network topologies and traffic
configurations. We observe the scheme to be capable in significantly improving the throughput/delay performance of the network. 相似文献
9.
10.
This paper presents part-load evaluation of a natural gas-fired chemical looping combustion (CLC) combined cycle with CO2 capture. The novel combined cycle employs an air-based gas turbine, a CO2-turbine and a steam turbine cycle. In this combined cycle, the CLC reactors replace combustion chamber of the gas turbine. The proposed combined cycle has a net plant efficiency of about 52.2% at full-load, including CO2 compression to 200 bar. The part-load evaluation shows that reducing the load down to 60% results in an efficiency drop of 2.6%-points. However, the plant shows better relative part-load efficiency compared to conventional combined cycles. The pressure in CLC-reduction and -oxidation reactors is balanced by airflow control, using a compressor equipped with variable guide vanes. A combination of control strategies is discussed for plant start-up and shutdown and for part-load when airflow reduction is not practically possible with current generation of compressors. The results show that the combined cycle has a promising efficiency even at part-load; however, it requires an advanced control strategy. 相似文献