A sphere-type fully substituted oligosaccharide-β-alanine-poly(lysine) dendrimer having a sharp molecular weight distribution was synthesized. Sphere-type poly(lysine) dendrimers were prepared using 1,4-diaminobutane as an initiator core and N,N′-bis(tert-butyloxycarbonyl)-L-lysine as a branching unit. β-Alanine was bound to the poly(lysine) dendrimer generation 3 to form β-alanine-poly(lysine) dendrimer generation 3, which has 16 terminal amino groups on its surface. A series of sphere-type oligosaccharide-β-alanine-poly(lysine) dendrimers were obtained by binding such an oligosaccharide as maltose, lactose, cellobiose, maltotriose, or a mixture of lactose and maltose to the surface of the β-alanine-poly(lysine) dendrimer scaffolding by reductive amination using the borane-pyridine complex. Oligosaccharide-β-alanine-poly(lysine) dendrimers having 32 oligosaccharide residues were obtained in high yields. NMR and MALDI-TOF mass measurements revealed that the oligosaccharide-polypeptide dendrimers have a monodispersed molecular weight distribution, the molecular weight of which was 13 418.36, 13 472.50, and 13 507.28 g/mol for cellobiose, maltose, and lactose, respectively, indicating that a complete substitution of the amino group by the oligosaccharide occurred.
A space vehicle which undergoes the atmospheric re-entry or a planetary entry needs the heat shield system to protect inner equipments against severe aerodynamic heating environments. Charring ablator is usually used for the heat shield system. In order to design the heat shield system, it is necessary to predict the thermal behavior under aerodynamic heating by ablation analysis. A computer code for charring ablation and thermal response analysis is newly developed for simulation of one-dimensional transient thermal behavior of charring ablation materials. The mathematical model for the charring ablation including basic equation and computational method of ablation analysis is briefly described. A new ultra light weight phenolic carbon ablator called LATS (Lightweight Ablator series for Transfer vehicle) was recently developed. Arc-heated tests of the LATS ablator were carried out and measured results of the temperature response and surface mass loss are compared with the simulation results of the ablation analysis program. The agreement between the results of simulation and measurement is found to be good. It is also found that the mathematical model used in the ablation code can be applied to the ablation analysis of the low density LATS ablator.
Dimethyl ether (DME) is an innovative clean fuel that can be used in various ways in many different sectors including household, transportation, power generation, etc. In order to use DME as a fuel, it must be produced in a highly efficient manner. As part of fundamental research, a new efficient catalyst and slurry phase process for DME synthesis were developed. After testing was carried out at a pilot plant (5 tons/day), the demonstration plant (100 tons/day) project was implemented from 2002 to 2006. The conversion of DME in the slurry phase reactor is dominated by W/F (W: Charged catalyst weight, F: Gas flow rate in the reactor), regardless of reactor scale (1 kg/day 100 tons/day). The gas hold up was measured by increasing the velocity of the gas up to 40 cm/s. Within this range, gas hold up increased smoothly without any sudden change of fluid phenomena or any negative effect on the chemical reaction. There is no clear dependence of the gas hold up on the reactor diameter. The mixing diffusion coefficient in the slurry phase and the heat transfer coefficient from slurry to heat exchanger tubes were determined. Based on these data, a process simulator has been developed that predicts that commercial scale production of 3,000 tons/day can be realized by a single reactor 7m in diameter and 50m high.
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