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1.
C. G. Youngs A. Epp B. M. Craig H. R. Sallans 《Journal of the American Oil Chemists' Society》1957,34(3):107-108
Summary A rapid method has been found for preparing the long-chain fatty acid chlorides, which eliminates purification by distillation.
It gave a quantitative yield of product containing less than 1.5% free acid. The method involves treating the free acid with
phosphorus pentachloride or trichloride in an inert organic solvent and removing the excess chlorinating agent by washing
the solvent phase with water. Phosphorus pentachloride and Skellysolve “F” were preferred for laboratory preparations. For
commercial purposes however either chlorinating agent could be used in a variety of inert organic solvents.
Infrared analysis was found to give a rapid measure of the free acid content of the prepared acid chlorides.
Presented at the fall meeting, American Oil Chemists' Society, Philadelphia, Pa., Oct. 10–12, 1955.
Issued as N. R. C. No. 4240. 相似文献
2.
This paper is motivated by the performance evaluation of circulating vertical conveyor systems (CVCSs). CVCSs are bulk queues of transportation type. These material handling systems feature generally distributed inter-arrival times, which can be longer than the bulk service time. This leads to interdependencies between the number of arrivals in consecutive service intervals and the number of loads in the queue. We propose a new discrete-time approach for the steady-state analysis of such bulk service queues of transportation type with general arrival and service processes and finite server and limited queue capacities. The approach is based on a finite Markov chain that generates complete probability distributions for the key performance measures, including the queue length, waiting time and departing batch size. The proposed approach is exact in the cases of discrete-time slots, e.g. as in communication systems. We investigate the discretisation error that arises if the approach is used as an approximation for the continuous time using a numerical comparison to a discrete-event simulation. Moreover, we examine the impact of arrival stream variability on the system performance and compare the positive effects of a higher frequency of server visits with the effects arising from larger pickup capacities. 相似文献
3.
A compact dual-polarized 8.51-GHz rectenna for high-voltage (50 V)actuator applications 总被引:2,自引:0,他引:2
This paper describes a dual-polarized rectenna capable of producing a 50-V output voltage that can be used for driving mechanical actuators. This study demonstrates a circuit topology that allows the output of multiple rectenna elements to be combined in order to step up the output voltage. In this paper, an independent rectifying circuit is used for each of two orthogonal polarizations. By proper combination, the output voltage is doubled over that of the single polarization case. Such panels are being explored for use on the next-generation space telescope to eliminate wiring between actuators and provide for true mechanical isolation 相似文献
4.
The loading of a periodic surface with time-varying negative resistance diodes is discussed. The method predicts the transmitted and reflected power at the source frequency and the harmonic frequencies generated by the time-varying devices. The analysis uses an equivalent circuit representation at the load location in the unit cell, which is derived from the moment method solution of the periodic problem. It is therefore applicable to all angles of incidence, arbitrarily shaped surfaces, arbitrarily placed loading, lossy conductors, and surfaces supported by dielectric layers 相似文献
5.
6.
WC Groutas LS Chong R Venkataraman JB Epp R Kuang N Houser-Archield JR Hoidal 《Canadian Metallurgical Quarterly》1995,3(2):187-193
Metal ion-promoted binding of Saccharomyces cerevisiae alcohol dehydrogenase to Cibacron Blue 3GA was used for its isolation by affinity precipitation with Eudragit-bound dye. The yeast cells were broken and the cell debris was separated by flocculation with poly(ethylene imine). The supernatant containing the enzyme activity was mixed with Eudragit--Cibacron Blue in the presence of zinc ions. The precipitation of the affinity complex was induced by the addition of 50 mM CaCl2 and a subsequent increase in temperature to 40 degrees C. The enzyme was desorbed by treating the precipitate with iminodiacetic acid solution. The procedure resulted in about 66% recovery of enzyme activity with more than 20-fold purification. Recycling of Eudragit--dye for enzyme purification was also shown to be possible. 相似文献
7.
Crystallographic structural studies of a human Fc fragment. II. A complete model based on a Fourier map at 3.5 A resolution 总被引:1,自引:0,他引:1
The crystal structure analysis of a human Fc fragment was pursued to 3.5 A resolution and a complete model was built and refined into the isomorphous Fourier map. The CH2 and CH3 domains show the immunoglobulin fold, with CH3 being closely similar to CH1, but CH2 intermediate in structure between V and CH3. The carbohydrate is rigidly attached to CH2, covering the C face. CH3 dimerizes as CH1-CL, but CH2 has no contact to the second chain. Residues involved in the lateral CH3-CH3 and the longitudinal CH3-CH2 contact are conserved in Ig classes and sub-classes. In IgM and IgE the two C-terminal domains also show this characteristic distribution of contact residues. 相似文献
8.
Epp L.W. Stanton P.H. Jorgenson R.E. Mittra R. 《Antennas and Propagation, IEEE Transactions on》1994,42(6):878-882
In order to add the capability of an X-band up-link onto the NASA/JPL Deep Space Network (DSN) 70-m antenna, a new dichroic plate is needed to replace the Pyle-guide shaped dichroic plate currently in use. The replacement dichroic plate must exhibit an additional pass band at the new up-link frequency of 7.165 GHz, while maintaining a pass band at the existing down-link frequency of 8.425 GHz. Because of the wide frequency separation of these two pass bands, conventionally designed air-filled dichroic plates exhibit grating lobe problems. A new method of solving this problem using a dichroic plate with cross-shaped holes is presented and verified experimentally. Two checks of the integral equation solution are described here. One is the comparison to a modal analysis for the limiting cross shape of a square hole. As a final check a prototype dichroic plate with cross-shaped holes was built and measured 相似文献
9.
Al-Shanfari Lamiya Demmans Epp Carrie Baber Chris Nazir Mahvish 《User Modeling and User-Adapted Interaction》2020,30(1):159-194
User Modeling and User-Adapted Interaction - Knowledge monitoring is a component of metacognition which can help students regulate their own learning. In adaptive learning software, the... 相似文献
10.
We describe the fabrication and characterization of a nanoelectromechanical (NEM) switch based on carbon nanotubes. Our NEM structure consists of single-walled nanotubes (SWNTs) suspended over shallow trenches in a SiO(2) layer, with a Nb pull electrode beneath. The nanotube growth is done on-chip using a patterned Fe catalyst and a methane chemical vapor deposition (CVD) process at 850 degrees C. Electrical measurements of these devices show well-defined ON and OFF states as a dc bias up to a few volts is applied between the CNT and the Nb pull electrode. The CNT switches were measured to have speeds that are 3 orders of magnitude higher than MEMS-based electrostatically driven switches, with switching times down to a few nanoseconds, while at the same time requiring pull voltages less than 5 V. 相似文献