Verifying the symmetry of differential scanning calorimeters concerning heating and cooling using liquid crystal secondary temperature standards

2006 ◽  
Vol 446 (1-2) ◽  
pp. 55-65 ◽  
Author(s):  
Steffen Neuenfeld ◽  
Christoph Schick
Keyword(s):  
Liquid Crystal ◽  
Temperature Standards ◽  
Heating And Cooling ◽  
Differential Scanning Calorimeters

Step Response Characteristics of Anisotropic Gel Actuator Hybridized with Nanosheet Liquid Crystal

2019 ◽  
Vol 31 (5) ◽  
pp. 647-656 ◽  
Author(s):  
Hitoshi Kino ◽  
◽  
Akihiro Kiyota ◽  
Takumi Inadomi ◽  
Tomonori Kato ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Steady State ◽  
Time Constant ◽  
Step Response ◽  
Response Property ◽  
First Order ◽  
Response Characteristics ◽  
Thermal Change ◽  
Heating And Cooling ◽  
Original Size

In this study, we focus on a soft anisotropic gel actuator hybridized with nanosheet liquid crystal. This gel actuator is highly hydrophilic and can be operated underwater. Gel actuators can contract when heated and expand back to their original size when cooled down. It is anisotropic in the contraction direction, aligned with the orientation of the nanosheet liquid crystal. However, details of this step response property against the actuator undergoing thermal change have not been clarified. In this paper, we introduce a method to measure the step response using a square test sheet with a side length of 2–10 mm and thickness of 0.1–1.0 mm. This measurement was used to measure the heating and cooling step response. The obtained result was approximated using a first-order lag system to determine a steady-state value and time constant. In addition, the characteristics of steady-state value and time constant were clarified from the viewpoint of shapes such as specific surface area and thickness.

Effects of Cyclic Heating and Cooling on the Banana-Phase Growing Behaviors of Banana-Shaped Liquid Crystal 1,3-Phenylene-bis[4-(4-octyl phenylimino)methyl]benzoate

2010 ◽  
Vol 428-429 ◽  
pp. 322-325 ◽  
Author(s):  
Yuan Ming Huang ◽  
Qing Lan Ma ◽  
Bao Gai Zhai
Keyword(s):  
Liquid Crystal ◽  
Nucleation And Growth ◽  
Methyl Benzoate ◽  
Isotropic Phase ◽  
Cyclic Heating ◽  
Phase Growth ◽  
Scanning Calorimetry ◽  
Polarized Optical Microscopy ◽  
Heating And Cooling ◽  
Phase Transition Temperatures

The effects of cyclic heating and cooling on the banana-phase growth behaviors of the prototype banana-shaped liquid crystal 1,3-phenylene-bis[4-(4-octylphenylimino)methyl]benzoate were investigated with differential scanning calorimetry and polarized optical microscopy, respectively. Cyclic heating and cooling can reduce the phase transition temperatures and increase the domain sizes of the banana phases of the banana-shaped liquid crystal. These results can be interpreted in terms of the nucleation and growth of the banana phases out of its isotropic phase of the banana-shaped liquid crystal.

Synthesis and Mesomorphic Properties of Three-Benzene-Ring Containing Bent-Core Liquid Crystal 1,3-Phenylene-bis[4-(nonylcarboyloxyl) benzylideneamine]

2010 ◽  
Vol 428-429 ◽  
pp. 79-82 ◽  
Author(s):  
Yuan Ming Huang ◽  
Qing Lan Ma ◽  
Bao Gai Zhai
Keyword(s):  
Phase Transition ◽  
Differential Scanning Calorimetry ◽  
Liquid Crystal ◽  
Benzene Ring ◽  
Cyclic Heating ◽  
Scanning Calorimetry ◽  
Polarized Optical Microscopy ◽  
Heating And Cooling ◽  
Phase Transition Temperatures ◽  
Mesomorphic Properties

A bent-core compound with three benzene-ring cores 1,3-phenylene-bis [4-(nonylcarboyloxyl)benzyl ideneamine] was synthesized. Its mesomorphic properties were characterized with differential scanning calorimetry and polarized optical microscopy, respectively. This kind of bent-core compound exhibited mesophases in the temperature range of 155-185oC for the first cooling but cyclic heating and cooling could lower the phase transition temperatures for this bent-core liquid crystal. Our results demonstrated that bent-core molecules with three benzene-ring cores can also form mesophases as those five benzene-ring containing bent-core molecules do.

Verifying the symmetry of ultra-fast scanning calorimeters using liquid crystal secondary temperature standards

2011 ◽  
Vol 526 (1-2) ◽  
pp. 58-64 ◽  
Author(s):  
Minzhi Chen ◽  
Muting Du ◽  
Jing Jiang ◽  
Dawei Li ◽  
Wei Jiang ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Temperature Standards

Hysteresis in Liquid Crystal Thermography

2004 ◽  
Vol 126 (3) ◽  
pp. 339-346 ◽  
Author(s):  
M. R. Anderson ◽  
J. W. Baughn
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystals ◽  
Narrow Band ◽  
Broad Band ◽  
Peak Temperature ◽  
Temperature Calibration ◽  
Hysteresis Behavior ◽  
Liquid Crystal Thermography ◽  
Heating And Cooling ◽  
Start Temperature

Hysteresis in five different Thermochromic Liquid Crystals (TLCs), both narrow-band and broad-band, has been investigated. All were found to exhibit a similar hysteresis behavior during cooling relative to heating. This hysteresis is characterized by a decrease in reflectivity and a shift in the temperature associated with the peak reflected intensity for each of the R, G, and B components during cooling. This causes a shift in the hue-temperature calibration of the TLC causing temperature biases, when cooled rather than heated, of 20–60% of the useful calibration range. The hysteresis effect increases as the peak temperature during a heating and cooling cycle is increased. Repeatable heating calibrations were obtained when the TLC was cooled below the red start temperature to an apparent low reset temperature. Somewhat repeatable cooling calibrations, different from the heating calibrations, were obtained when the TLC was heated somewhat above the blue stop temperature. A possible explanation of the hysteresis based on the texture of the liquid crystal helices is provided. In addition to hysteresis, a permanent decrease in reflectivity and a shift in the temperature associated with the peak reflected intensity was observed when the TLCs were exposed to extended higher temperatures (60°C–80°C).

True Presence Detection via Passive Infrared Sensor Network Using Liquid Crystal Infrared Shutters

2020 ◽  
Author(s):  
Libo Wu ◽  
Ya Wang
Keyword(s):  
Liquid Crystal ◽  
Sensor Network ◽  
False Negative ◽  
Threshold Value ◽  
Daily Routine ◽  
Heating And Cooling ◽  
Average Accuracy ◽  
Sensor Module ◽  
Polymer Dispersed ◽  
Passive Infrared

Abstract Recently, smart home applications are increasing fast, including but not limited to occupancy-dependent control of lighting, heating and cooling. Passive infrared (PIR) sensors play an important role in these applications to perceive the presence and/or the motion of human. However, PIR sensors are not able to detect stationary occupants while stationary presence takes up most time of the day. And thus, the resulted false negative detection leads to uncomfortable light/temperature swings, shortened equipment’s lifespan, and/or energy waste, etc. To address this issue, our group has developed Synchronized Low-Energy Electronically-chopped PIR (SLEEPIR) sensors that integrate an electronic liquid crystal (LC) infrared shutter with an off-the-shelf PIR sensor. In this work, the infrared shutter made of polymer dispersed liquid crystal (PDLC) sandwiched by two germanium windows is proposed to periodically chop the long-wave infrared signal received by the PIR sensor so that stationary human presence can still be detected due to the electronical shuttering. A sensor module is fabricated, consisting of a wireless microcontroller, a SLEEPIR sensor and a traditional PIR sensor, with a field of view of 103° × 103°. Then, a sensor network consists of two sensor modules is developed. Three types of experiments are conducted in this paper: individual action-based, continuous activity-based, and daily routine-based. The detection logic is made by using the threshold value classification method, where the threshold values are determined from the action-based dataset and applied to the other two datasets. The results show that for activity-based dataset, the average accuracy reached 98.96%. For daily routine-based dataset, the average accuracy is 99.57%.

Synthesis and Mesomorphic Properties of Three-Ring Containing Bent-Core Liquid Crystal 1,3-Phenylene-bis(4-butoxybenzylideneamine)

2010 ◽  
Vol 428-429 ◽  
pp. 167-170
Author(s):  
Yuan Ming Huang
Keyword(s):  
Differential Scanning Calorimetry ◽  
Liquid Crystal ◽  
Optical Microscopy ◽  
Cyclic Heating ◽  
Scanning Calorimetry ◽  
Polarized Optical Microscopy ◽  
Temperature Range ◽  
Heating And Cooling ◽  
Mesomorphic Properties

A three-ring containing bent-core compound 1,3-phenylene-bis(4-butoxybenzylidene amine) was synthesized and characterized with differential scanning calorimetry and polarized optical microscopy. It exhibited mesophases in the temperature range of 48-54oC for the first cyclic heating and cooling. Our results demonstrated that three-ring containing bent-core molecules can form mesophases.

Synthesis and Phase Behavior of a New Thiophene Monomer as Nematic Liquid Crystal

2014 ◽  
Vol 989-994 ◽  
pp. 185-188
Author(s):  
Lin Wang ◽  
Yu Jiao Xie ◽  
Xing Xing Zhang ◽  
Jian She Hu
Keyword(s):  
Differential Scanning Calorimetry ◽  
Liquid Crystal ◽  
Phase Behavior ◽  
Optical Microscopy ◽  
Nematic Liquid Crystal ◽  
Chemical Structure ◽  
Scanning Calorimetry ◽  
H Nmr ◽  
Heating And Cooling ◽  
Ft Ir

The synthesis of a new liquid crystal thiophene monomer of (E)-4-(6-(3-(thiophen-3-yl)- acryloyloxy) hexyloxy) biphenyl-4’-ethylbenzoate (LC-M) is presented. The chemical structure of this monomer and intermediate compounds was characterized by FT-IR and1H-NMR. The phase behavior was investigated by polarizing optical microscopy and differential scanning calorimetry. LC-M showed nematic threaded and schlieren textures on heating and cooling cycles.

Freeze-fracture TEM of the helical smectic A* phase

1992 ◽  
Vol 50 (1) ◽  
pp. 278-279
Author(s):  
K.J. Ihn ◽  
R. Pindak ◽  
J. A. N. Zasadzinski
Keyword(s):  
Liquid Crystal ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Freeze Fracture ◽  
Smectic Phase ◽  
Layer Spacing ◽  
Screw Dislocations ◽  
Smectic A ◽  
Smectic Phases ◽  
Discrete Amount

A new liquid crystal (called the smectic-A* phase) that combines cholesteric twist and smectic layering was a surprise as smectic phases preclude twist distortions. However, the twist grain boundary (TGB) model of Renn and Lubensky predicted a defect-mediated smectic phase that incorporates cholesteric twist by a lattice of screw dislocations. The TGB model for the liquid crystal analog of the Abrikosov phase of superconductors consists of regularly spaced grain boundaries of screw dislocations, parallel to each other within the grain boundary, but rotated by a fixed angle with respect to adjacent grain boundaries. The dislocations divide the layers into blocks which rotate by a discrete amount, Δθ, given by the ratio of the layer spacing, d, to the distance between grain boundaries, lb; Δθ ≈ d/lb (Fig. 1).

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