The combustion properties of 2,6,10-trimethyl dodecane and a chemical functional group analysis

The global combustion characteristics of 2,6,10-trimethyl dodecane (trimethyl dodecane), a synthetic fuel candidate species, have been experimentally investigated by measuring extinction limits for strained laminar diffusion flames at 1 atm and reflected shock ignition delays at 20 atm. The Derived Cetane Number (DCN) of trimethyl dodecane, (59.1) and Hydrogen/Carbon (H/C) ratio (2.133) are very close to the DCN and H/C ratio of a previously studied synthetic aviation fuel, S-8 POSF 4734 (S-8) and its surrogate mixture composed of n-dodecane/iso-octane (58.9 and 2.19, respectively). Identical high temperature global kinetic reactivities are observed in all experiments involving the aforementioned compounds. However, at temperatures below ∼870 K, the S-8 surrogate mixture has ignition delay times approximately a factor of two faster. A chemical functional group analysis identifies that the methylene (CH₂) to methyl (CH₃) ratio globally correlates the low temperature alkylperoxy radical reactivity for these large paraffinic fuels. This result is further supported experimentally, by comparing observations using a surrogate fuel mixture of n-hexadecane (n-cetane) and 2,2,4,4,6,8,8-heptamethyl nonane (iso-cetane) that shares the same methylene-to-methyl ratio as trimethyl dodecane, in addition to the same DCN and H/C ratio. Measurements of both diffusion flame extinction and reflected shock ignition delays show that the n-cetane/iso-cetane model fuel has very similar combustion behavior to trimethyl dodecane at all conditions studied. A kinetic modeling analysis on the model fuel suggests the formation of alkylhydroperoxy radicals (QOOH) to be strongly influenced by the absence or presence of the methyl and methylene functional groups in the fuel chemical structure. The experimental observations and analyses suggest that paraffinic based fuels having high DCN values may be more appropriately emulated by further including the CH₂ to CH₃ ratio as an additional combustion property target, as DCN alone fails to fully distinguish the relative reaction characteristics of low temperature kinetic phenomena.     

Indoxylsulfate in milk

Indoxylsulfate in 27 individual milk samples ranged from 25.4 to 111 μg/l (average 52.3 μg/l); pooled milk samples from 12 farms contained 81.1 μg/l (46.4–146 μg/l); the variation in indoxylsulfate concentration of dried skimmed milk over a period of one year amounted to 23%. This variability is likely attributable to regional and seasonal, and hence to feeding effects. The indoxylsulfate content of milk seems also to be dependent upon the degree of fermentation during processing of milk; yoghurt contained very low amounts of this component (6.4 μg/kg). On the other hand, heat treatment of the milk (HTST, UHT, sterilization) apparently does not affect its indoxylsulfate content. Indoxylsulfate concentrations in milk correlated positively with blood-serum indoxylsulfate content (r=0.752,n=20) and with the urea content of milk (r=0.61,n=12 pooled milks). Further research is suggested on the use of indoxylsulfate determinations as an aid to determine sweet whey added to dried skimmed milk, also as an analytical tool to differentiate bovine and sheep milks.     

Farfield tracing of a point source discharge plume in the coastal ocean using sulfur hexafluoride

Pathways and dilution of a point source ocean discharge in the farfield (approximately to 10-66 km) were measured using the deliberate tracer sulfur hexafluoride (SF6). The injection of SF6 was performed by bubbling the gas over a period of 6 days into an ocean outfall pipe discharging into the southeast Florida coastal ocean. The surface SF6 concentrations show that the discharged water flowed northward parallel to the coast with a broadening of the width of the plume to about 3 km at the farthest point sampled, 66 km from the outfall. The discharge was fully mixed throughout the water column within 13 km of the outfall terminus. In the first 20 km from the outfall, SF6 surface concentrations were highly variable, while beyond this the SF6 concentrations decreased monotonically going northward. The currents were measured during the study with a bottom-mounted acoustic Doppler current profiler (ADCP) located 5.5 km from the outfall. Velocities were variable in magnitude and direction but showed a net northward flow during the 6-day study. Maximum concentrations decreased by about 200-fold per kilometer from the outfall to the northern end of the study area. The study shows that SF6 is an effective method to trace point source releases far from their origin.     

Identification and quantitative determination of the lipids of Alocasia macrorrhiza tubers

The identity, composition and concentration of each of the major lipids found in Alocasia tubers were investigated using a combination of chromatographic procedures. On a weight to weight basis, the neutral lipids, glycolipids and phospholipids comprised 60.5, 19.0 and 20.5% respectively while the total extractable lipids accounted for 0.6% of the dry weight. In addition to the conventional lipid classes of tubers, the presence of tri- and tetragalactosyl diglycerides was confirmed. The predominant fatty acid in each lipid class was linoleic acid with palmitic, oleic and linolenic acids being the other ones. In general, a high degree of unsaturation (66%), similar for most tuber lipids, was established for the component fatty acids of Alocasia.     

Bonding of densified beech wood using adhesives based on thermally modified soy proteins

The bondability/glueability of aged and sanded thermo-hydro-mechanically (THM) densified beech wood (Fagus sylvatica L.) was tested and compared with undensified sanded beech wood as a control. THM and control specimens were bonded with five different soy protein isolate (SPI) based adhesives. Commercial SPI powder was thermally modified in the vacuum chamber at 50 or 100?°C and pH adjusted (to pH 10.0) dispersions in water prepared at 24, 50 or 90?°C. Wettability was determined with measuring the sessile drop contact angles of water. Effective penetrations (EPs) and tensile shear strengths of THM and control specimens were determined. THM and control wood had similar wettability. Although THM wood had lower moisture content than control wood, it absorbed the water more slowly than control wood. THM specimens showed lower EPs than control specimens when comparing individual adhesives due to increased density of THM wood. Adhesives prepared with SPI thermally modified at 50?°C showed statistically significantly lower tensile shear strength of bonded THM specimens than that of bonded control specimens. THM densification had no significant effect on the bonding strengths of adhesives prepared with non-modified SPI and SPI thermally modified at 100?°C.     

Design and implementation of flexible and stretchable systems

This paper presents a summary of the modeling and technology developments for flexible and stretchable electronics. These technologies can achieve mechanically bendable and stretchable subsystems by incorporating the electronic circuit into a matrix made of a soft polymer. The base substrate used for the fabrication of flexible circuits is a uniform polyimide layer, while silicones or polyurethanes materials are preferred for the stretchable circuits. The method developed for chip embedding and interconnections is named Ultra Thin Chip Package (UTCP). Extensions of this technology can be achieved by stacking and embedding thin dies in polyimide, providing large benefits in electrical performance and still allowing some mechanical flexibility. These flexible circuits can be converted into stretchable circuits by replacing the polyimide by a soft and elastic silicone material.The integration of ultra thin dies at package level, with thickness in the range of 10-30 μm, into flexible and/or stretchable materials are demonstrated. Furthermore, the design and reliability test of stretchable metal interconnections at board level are analyzed by both experiments and finite element modeling. We have shown through finite element modeling and experimental validation that an appropriate thermo-mechanical design is necessary to achieve mechanically reliable circuits and thermally optimized packages.     

Transverse compression behavior of Douglas-fir (Pseudotsuga menziesii) in saturated steam environment

The transverse compression behavior of Douglas-fir wood (Pseudotsuga menziesii) at high temperature (170 °C) and saturated steam conditions was studied and compared with previously reported compression behavior of hybrid poplar (Populus deltoides × Populus trichocarpa). The effect of the compression on the stress–strain response, non-linear strain function, and relative density change was examined by a modified Hooke’s law based on the load-compression behavior of flexible foams. Transverse compressive loading followed a typical stress–strain curve of wood. The compressive modulus of Douglas-fir was higher than hybrid poplar. The yield stress of Douglas-fir specimens was higher than yield stress of hybrid poplar specimens, while densification stress of both wood species was the same. The comparison of the non-linear strain function of Douglas-fir and hybrid poplar specimens revealed significant differences. The observed differences are assumed to be due to different cellular structure and chemical composition of softwoods versus hardwoods.     

俞孔坚的景观设计探索 回归“田园”理想的实践主义者

桑德斯——雄心勃勃的改革者俞孔坚提出了中国国土生态安全格局提案,并不断推广。这一国家尺度的宏伟提案的目的在于实现国土的最优化管理:保护水系统安全及生物多样性、防止水土流失及土地荒漠化、快速且有效地应对洪水危害等。这种多目标的理念和思考方式也体现在公园尺度的设计上,这种理念使他的景观设计作品与众不同。在他的设计方案中能够同时看到对健康生态系统的创造、对生机勃勃的公共生活的促进、对审美体验的关注、对丰产的景观的推广、对文化遗产保护的加强以及对公众教育