Vacuum-dried flexible hydrophobic aerogels using bridged methylsiloxane as reinforcement: performance regulation with alkylorthosilicate or alkyltrimethoxysilane co-precursors

2019 ◽  
Vol 43 (5) ◽  
pp. 2204-2212 ◽  
Author(s):  
Dangjia Chen ◽  
Keyi Dong ◽  
Hongyi Gao ◽  
Tao Zhuang ◽  
Xiubing Huang ◽  
...  
Keyword(s):  
Precursor Method ◽  
Hydrophobic Aerogels ◽  
Method Show

Aerogels prepared by the co-precursor method show good flexibility.

scholarly journals Joining of Electrodes to Ultra-Thin Metallic Layers on Ceramic Substrates in Cryogenic Sensors

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4919
Author(s):  
Marcin Lebioda ◽  
Ryszard Pawlak ◽  
Jacek Rymaszewski
Keyword(s):  
Cryogenic Temperatures ◽  
Thermal And Mechanical Properties ◽  
Reflow Soldering ◽  
Ceramic Substrates ◽  
Temperature Range ◽  
Wave Soldering ◽  
Materials Used ◽  
Standard Designs ◽  
Electrical Connections ◽  
Method Show

Microjoining technologies are crucial for producing reliable electrical connections in modern microelectronic and optoelectronic devices, as well as for the assembly of electronic circuits, sensors, and batteries. However, the production of miniature sensors presents particular difficulties, due to their non-standard designs, unique functionality and applications in various environments. One of the main challenges relates to the fact that common methods such as reflow soldering or wave soldering cannot be applied to making joints to the materials used for the sensing layers (oxides, polymers, graphene, metallic layers) or to the thin metallic layers that act as contact pads. This problem applies especially to sensors designed to work at cryogenic temperatures. In this paper, we demonstrate a new method for the dynamic soldering of outer leads in the form of metallic strips made from thin metallic layers on ceramic substrates. These leads can be used as contact pads in sensors working in a wide temperature range. The joints produced using our method show excellent electrical, thermal, and mechanical properties in the temperature range of 15–300 K.

Platinum and cobalt intermetallic nanoparticles confined within MIL-101(Cr) for enhanced selective hydrogenation of the carbonyl bond in α,β-unsaturated aldehydes: synergistic effects of electronically modified Pt sites and Lewis acid sites

2021 ◽  
Author(s):  
Muhammad Zahid ◽  
Jiang Li ◽  
Ahmed Ismail ◽  
Francisco Zaera ◽  
Yujun Zhu
Keyword(s):  
Synergistic Effect ◽  
Reduction Method ◽  
Synergistic Effects ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Unsaturated Aldehydes ◽  
Uniform Dispersion ◽  
Carbonyl Bond ◽  
Method Show ◽  
Intermetallic Nanoparticles

PtCo/MIL-101(Cr) with high uniform dispersion Pt–Co IMNs synthesized by a polyol reduction method show higher activity for selective catalytic hydrogenation of α,β-unsaturated aldehydes due to the synergistic effect of PtCo and MIL-101(Cr) support.

COMPARATIVE STUDY OF DIELECTRIC BEHAVIOR OF Mn0.4Zn0.6Fe2O4 NANOFERRITE BY CITRATE PRECURSOR METHOD

2008 ◽  
Vol 22 (16) ◽  
pp. 2537-2544 ◽  
Author(s):  
PREETI MATHUR ◽  
ATUL THAKUR ◽  
M. SINGH
Keyword(s):  
Particle Size ◽  
Dielectric Constant ◽  
Comparative Study ◽  
Average Particle Size ◽  
Dielectric Behavior ◽  
Average Particle ◽  
Oxidizing Agent ◽  
Precursor Method ◽  
Citrate Precursor ◽  
Citrate Precursor Method

In the present work, comparative study of the dielectric behavior of Mn 0.4 Zn 0.6 Fe 2 O 4 ferrite synthesized with and without H 2 O 2 (hydrogen peroxide) has been presented. The dc resistivity has been improved by the citrate precursor method as compared to the ceramic method, and it is further improved by the addition of H 2 O 2, which acts as a strong oxidizing agent. We have shown by means of X-ray diffraction that the resulting ferrite is made up of nanocrystallites and the average size of these nanocrystallites–calculated by Scherrer's formula–depends on the polarizer. The average particle size was found to be ~70 nm with H 2 O 2 and ~88 nm without H 2 O 2. The particle size is further confirmed by scanning electron microscopy. Both the results are found to be in good agreement. The decrease in dielectric constant and dielectric loss factor by addition of oxidizing agent is justified by inverse proportionality between the resistivity and dielectric constant. Possible mechanisms contributing to these processes have been discussed.

A novel liquid hybrid precursor method via sol-gel for the preparation of ZrB 2 films

2017 ◽  
Vol 128 ◽  
pp. 80-85 ◽  
Author(s):  
Yong Liu ◽  
Ran Geng ◽  
Yongjie Cui ◽  
Shuai Peng ◽  
Xuefeng Chang ◽  
...  
Keyword(s):  
Sol Gel ◽  
Precursor Method ◽  
Hybrid Precursor

Re-dispersible chitin nanofibrils with improved stability in green solvents for fabricating hydrophobic aerogels

2022 ◽  
pp. 119138
Author(s):  
Huangjingyi Chen ◽  
Liang Liu ◽  
Feier Chen ◽  
Yimin Fan ◽  
Qiang Yong
Keyword(s):  
Green Solvents ◽  
Improved Stability ◽  
Hydrophobic Aerogels

Estimating Critical Speeds of Stepped Shafts with Flexible Bearings

1971 ◽  
Vol 8 (03) ◽  
pp. 327-333
Author(s):  
R. H. Salzman
Keyword(s):  
High Speed ◽  
Critical Speed ◽  
Design Stage ◽  
Normal Range ◽  
Critical Speeds ◽  
Stepped Shaft ◽  
Bearing Stiffness ◽  
Variable Support ◽  
Method Show ◽  
Good Agreement

This paper presents a semi-graphical approach for finding the first critical speed of a stepped shaft with finite bearing stiffness. The method is particularly applicable to high-speed turbine rotors with journal bearings. Using Rayleigh's Method and the exact solution for whirling of a uniform shaft with variable support stiffness, estimates of the lowest critical speed are easily obtained which are useful in the design stage. First critical speeds determined by this method show good agreement with values computed by the Prohl Method for the normal range of bearing stiffness. A criterion is also established for determining if the criticals are "bearing critical speeds" or "bending critical speeds," which is of importance in design. Discusser E. G. Baker

scholarly journals The Geography of Taste: Using Yelp to Study Urban Culture

2018 ◽  
Vol 7 (9) ◽  
pp. 376 ◽  
Author(s):  
Sohrab Rahimi ◽  
Sam Mottahedi ◽  
Xi Liu
Keyword(s):  
Urban Communities ◽  
Language Processing ◽  
Social Dynamics ◽  
Food Purchases ◽  
User Comments ◽  
The Social ◽  
Service Oriented ◽  
Restaurant Reviews ◽  
Ambient Population ◽  
Method Show

This study aims to put forth a new method to study the sociospatial boundaries by using georeferenced community-authored reviews for restaurants. In this study, we show that food choice, drink choice, and restaurant ambience can be good indicators of socioeconomic status of the ambient population in different neighborhoods. To this end, we use Yelp user reviews to distinguish different neighborhoods in terms of their food purchases and identify resultant boundaries in 10 North American metropolitan areas. This dataset includes restaurant reviews as well as a limited number of user check-ins and rating in those cities. We use Natural Language Processing (NLP) techniques to select a set of potential features pertaining to food, drink and ambience from Yelp user comments for each geolocated restaurant. We then select those features which determine one’s choice of restaurant and the rating that he/she provides for that restaurant. After identifying these features, we identify neighborhoods where similar taste is practiced. We show that neighborhoods identified through our method show statistically significant differences based on demographic factors such as income, racial composition, and education. We suggest that this method helps urban planners to understand the social dynamics of contemporary cities in absence of information on service-oriented cultural characteristics of urban communities.

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