다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Foreword 1. Prosperity Lost 2. The Age of Irresponsibility 3. Redefining Prosperity 4. The Dilemma of Growth 5. The Myth of Decoupling 6. The 'Iron Cage' of Consumerism 7. Keynesianism and the 'Green New Deal' 8. Ecological Macro-Economics 9. Flourishing - within Limits 10. Governance for Prosperity 11. The Transition to a Sustainable Economy 12. A Lasting Prosperity Appendices References Endnotes

Prosperity without growth : economics for a finite planet

Biodiesel is produced by the transesterification of oil triglycerides with methanol or ethanol, in the presence of a homogeneous or heterogeneous catalyst. This study aims to report the results of the transesterification of sunflower oil with methanol to produce biodiesel using CaO nanoparticles supported on NaX zeolite as catalyst. The effect of the CaO nanoparticles concentration on the NaX zeolite surface was studied in the range of 5−25 wt %. The transesterification reaction was carried out at reflux temperature of methanol, atmospheric pressure, a reaction time of 6 h, and with a 6:1 molar ratio of methanol to sunflower oil. Catalyst characterization was carried out by X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. It was concluded that methyl esters content is highly influenced by basicity and that the best catalyst was the one holding 16 wt % CaO nanoparticles. The produced biodiesel was 93.5% methyl esters and was found to fulfill the specifications of Europ...

Preparation and Characterization of CaO Nanoparticles/NaX Zeolite Catalysts for the Transesterification of Sunflower Oil

The world is confronted with the twin crises of fossil fuel depletion and environmental degradation. The indiscriminate extraction and consumption of fossil fuels have led to a reduction in petroleum reserves. Petroleum based fuels are obtained from limited reserves. These finite reserves are highly concentrated in certain region of the world. Therefore, those countries not having these resources are facing a foreign exchange crisis, mainly due to the import of crude petroleum oil. Hence it is necessary to look for alternative fuels, which can be produced from materials available within the country. Although vegetative oils can be fuel for diesel engines, but their high viscosities, low volatilities and poor cold flow properties have led to the investigation of its various derivatives. Among the different possible sources, fatty acid methyl esters, known as Biodiesel fuel derived from triglycerides (vegetable oil and animal fates) by transesterification with methanol, present the promising alternative substitute to diesel fuels and have received the most attention now a day. The main advantages of using Biodiesel are its renewability, better quality exhaust gas emission, its biodegradability and the organic carbon present in it is photosynthetic in origin. It does not contribute to a rise in the level of carbon dioxide in the atmosphere and consequently to the green house effect. This paper reviews the source of production and characterization of vegetable oils and their methyl ester as the substitute of the petroleum fuel and future possibilities of Biodiesel production.

Biodiesel production through the use of different sources and characterization of oils and their esters as the substitute of diesel: A review

The fluid flow and the transport of species in an intensified topology of oscillatory baffled reactors is analyzed here by means of CFD. The classic configuration with equidistant single orifice plate baffles has been replaced by multiple-orifice disks, of the same open cross-sectional area. The flow through these disks generates an array of parallel jets downstream and upstream, exhibiting various swirl structures that increase the radial mixing. Time-dependent flow patterns are presented here for configurations of disks with 1, 3, 7, 19 and 43 orifices. The evaluation of their mixing performance has been accomplished by injecting a pulse of a tracer, for a constant oscillatory Reynolds number of Reo = 800. The concentration-time profile of the tracer throughout the reactor was analyzed and an axial dispersion coefficient was derived on the basis of a 1D plug flow with dispersion model. It was clear that the quality of plug flow increased with increasing number of holes. Pressure-drop was reported by means of Fanning friction factor and power density dissipation.

Residence time distribution in multiorifice baffled tubes: A numerical study

To cope with the increasing cooling loads in power electronics especially in traction, a new heat sink based on the irregular aluminium foam/salt hydrate phase change material composite was proposed for the integration into liquid cooling or heat pipe systems to provide transient cooling during the traction stationary phase. This heat sink would also be applicable to accommodate power surges or thermal buffering-related conditions. The melting point of the salt hydrate PCM was 46 °C. The coolant water was heated up to 60 °C, similar to the inlet condition in traction liquid cooling systems. The vacuum impregnation method used to create the composite resulted in a 96% impregnation ratio. The heat sink absorbed a thermal load up to 0.092 kW h with increasing charging temperature from 50 to 60 °C (from ambient: 20 °C) within an hour of heating and the PCM was fully melted. This was a combination of latent and sensible heat storage methods. The thermal capacity value matched closely with the theoretical calculation of 0.103 kW h (11% deviation). An hour of complete melting would match the stopping period of intercity trains at the terminus and the sink would be able to cool a group of 4–5 IGBTs, rated at 20 W power dissipation for each IGBT, during this stopping period. The heat balance formulated was commendable due to the small mismatch (7% deviation) between the released and absorbed heat, from the coolant to the heat sink. Therefore, it could be used to further optimise the design with alternative PCMs, foam porosities, operational conditions, thermal masses, heat exchanger configurations and so on. The effective thermal conductivity (Keff) for the composite was calculated as 10.8 W/m K and the ratio of Keff/KPCM was 24, higher than many composites previously studied in literature. In general, the heat sink would benefit in providing a transient, compact and inexpensive solution.

The melting of salt hydrate phase change material in an irregular metal foam for the application of traction transient cooling

The oscillatory baffled reactor has been well-characterised in most areas of flow reactor performance (mixing, mass transfer, multi-phase operation etc.), with the exception of heat transfer, where comparatively few data exist in the literature. Here, a robust investigation of heat transfer in the “standard”, 26 mm diameter, oscillatory baffled reactor is presented which goes beyond the parametric limitations of previous studies. 5-fold Nusselt number increases over steady unbaffled flows are shown to be achievable. The maximum enhancement attributed to the oscillatory flow component alone compared to the steady-flow, baffled case is shown to be 1.7-fold. The degree of heat transfer enhancement is shown to plateau when the oscillatory flow Reynolds number exceeds 1300, indicating that a radial mixing limit has been reached. A new correlation for predicting heat transfer coefficients in oscillatory baffled reactors has been developed. Based on the data generated here, it is accurate to ±30% across the experimental range of the study. The correlation has been further validated using literature data, and shown to be the most robust correlation to date for predicting heat transfer performance in oscillatory baffled reactors.

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Development of a more robust correlation for predicting heat transfer performance in oscillatory baffled reactors

Abstract Synthesis of styrene carbonate (SC) via the fixation of CO2 with styrene oxide (SO) has been investigated using a combination of zinc bromide (ZnBr2) and tetrabutylammonium halides (TBAX) as acid-base binary homogeneous catalysts. The combination of ZnBr2 and TBAB had a synergistic effect, which led to about 6-fold enhancement in the rate of SC formation as compared to using TBAB alone as a catalyst. Propylene carbonate (PC) was chosen as a green solvent for a comprehensive study of reaction kinetics. The reaction followed a first-order kinetics with respect to SO, CO2, and TBAB, whereas a fractional order was observed for the ZnBr2 when used in combination with the TBAB. Arrhenius and Eyring’s expressions were applied to determine the kinetic and thermodynamic activation parameters, where activation energy (Ea) of 23.3 kJ mol−1 was obtained for the SC formation over the temperature range of 90-120°C. The thermodynamic analysis showed that positive values for enthalpy (ΔH‡ = 18.53 kJ mol−1), Gibbs free energy (ΔG‡ = 79.74 kJ mol−1), whereas a negative entropy (ΔS‡ = –162.88 J mol−1 K−1) was obtained. These thermodynamic parameters suggest that endergonic and kinetically controlled reactions were involved in the formation of SC from SO and CO2.

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A kinetic study of Zn halide/TBAB-catalysed fixation of CO2 with styrene oxide in propylene carbonate

The design of experiments response surface analysis was employed for the first time to study the effect of divinylbenzene (DVB) (20-80 wt. %), diluent (0-100 wt.%), and mixing (200-900 rpm) on the beads' physical properties and on swelling ability. The beads with the highest performances, in terms of mechanical stability, surface area, and swelling ability, were sulphated, and tested in converting glycerol to a valuable product "solketal." Process options for glycerol valorization to solketal using synthesized sulphonic acid-functionalized styrene-divinylbenzene (ST-DVB-SO3H) copolymer beads and techno-economic analysis of the processes have been investigated. Three processes were evaluated: two one-stage processes at 8.5 wt.% catalyst and 50°C, based on either 6:1 acetone to glycerol molar ratio (87% conversion) or 12:1 (98% glycerol to solketal conversion), and a two-stage route (two acetone additions), where ≥98% conversion can be achieved with lower overall acetone use (10:1 acetone to glycerol molar ratio and 50°C). Techno-economic analyses of the three solketal options were performed using Aspen (HYSYS), based on a fixed capacity of 100,000 te/y and 20-years lifetime. The techno-economic analyses showed that the net present values for the solketal process options were $707 M for the two-stage, $384 M for the one-stage at 6:1 acetone to glycerol molar ratio, and $703 M for the one-stage at 12:1 acetone to glycerol molar ratio. The break-even prices for these solketal processes were $2,058/ ton for the one-stage at 12:1 of acetone and two-stage and $2,088/ton for the one-stage at 6:1 of acetone, which is lower than the current price of solketal at $3,000/ton. The two-stage process was found to be the most effective method of glycerol valorization production to solketal.

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Adam Harvey

Papers

Residence time distribution in multiorifice baffled tubes: A numerical study

The melting of salt hydrate phase change material in an irregular metal foam for the application of traction transient cooling

Development of a more robust correlation for predicting heat transfer performance in oscillatory baffled reactors

A kinetic study of Zn halide/TBAB-catalysed fixation of CO2 with styrene oxide in propylene carbonate

Techno-Economic Analysis of Glycerol Valorization via Catalytic Applications of Sulphonic Acid-Functionalized Copolymer Beads.