We demonstrate an ultrahigh-sensitivity gas pressure sensor based on the Fabry-Perot interferometer employing a fiber-tip diaphragm-sealed cavity. The cavity is comprised of a silica capillary and ...ultrathin silica diaphragm with a thickness of 170 nm, with represents the thinnest silica diaphragm fabricated thus far by an electrical arc discharge technique. The resulting Fabry-Perot interferometer-based gas pressure sensor demonstrates a gas pressure sensitivity of about 12.22 nm/kPa, which is more than two orders of magnitude greater than that of a similarly configured fiber-tip air bubble sensor. Moreover, our gas pressure sensor has a low temperature cross-sensitivity of about 106 Pa/°C, and the sensor functions well up to a temperature of about 1000 °C. As such, the sensor can potentially be employed in high-temperature environments.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
We demonstrated femtosecond laser inscription of fiber Bragg gratings (FBGs) in a twin-core few-mode fiber (TC-FMF) for directional bend sensing. An FBG was selectively inscribed in one core of the ...TC-FMF by using an 800 nm femtosecond laser through a phase mask. Three resonance peaks at the wavelengths of 1549.05, 1547.65, and 1546.08 nm were observed in the reflection spectrum of the TC-FM FBG, and were generated by the LP 01 mode resonance, LP 01 -LP 11 mode cross-coupling resonance, and LP 11 mode resonance, respectively. Moreover, the TC-FM FBG exhibited the capability of directional bend sensing and achieved a maximum bend sensitivity of -37.41 pm/m -1 . Hence, the proposed TC-FM FBG directional bend sensors could further be developed as promising solutions for detecting vectorial seismic or acoustic waves and 3-D shape sensing.
We demonstrated a unique rectangular air bubble by means of splicing two sections of standard single mode fibers together and tapering the splicing joint. Such an air bubble can be used to develop a ...promising high-sensitivity strain sensor based on Fabry-Perot interference. The sensitivity of the strain sensor with a cavity length of about 61 μm and a wall thickness of about 1 μm was measured to be up to 43.0 pm/με and is the highest strain sensitivity among the in-fiber FPI-based strain sensors with air cavities reported so far. Moreover, our strain sensor has a very low temperature sensitivity of about 2.0 pm/°C. Thus, the temperature-induced strain measurement error is less than 0.046 με/°C.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Haptic guidance in a shared steering assistance system has drawn significant attention in intelligent vehicle fields, owing to its mutual communication ability for vehicle control. By exerting ...continuous torque on the steering wheel, both the driver and support system can share lateral control of the vehicle. However, current haptic guidance steering systems demonstrate some deficiencies in assisting lane changing. This study explored a new steering interaction method, including the design and evaluation of an intention-based haptic shared steering system. Such an intention-based method can support both lane keeping and lane changing assistance, by detecting a driver's lane change intention. By using a deep learning-based method to model a driver's decision timing regarding lane crossing, an adaptive gain control method was proposed for realizing a steering control system. An intention consistency method was proposed to detect whether the driver and the system were acting towards the same target trajectories and to accurately capture the driver's intention. A driving simulator experiment was conducted to test the system performance. Participants were required to perform six trials with assistive methods and one trial without assistance. The results demonstrated that the supporting system decreased the lane departure risk in the lane keeping tasks and could support a fast and stable lane changing maneuver.
Departing from previous complicated attempts, this paper studies the self-calibration of 2-D precision metrology stages seriously from an accuracy- and simplicity-oriented perspective. Based on three ...measurement views with different permutations of an artifact plate on the metrology stage, symmetry, transitivity, and redundance are obtained and utilized to exactly extract the stage error from the measurement data. Particularly, as the determination of the misalignment-error components of the translation measurement view is rather complicated but important in previous research studies, the proposed scheme does not need this costly computation, which significantly simplifies the calculation process. The algorithm is tested by computer simulation, and the results validate that the proposed method can exactly realize the stage error even under the existence of various random measurement noises. The procedure for performing a standard 2-D self-calibration following the proposed scheme is finally introduced for engineers in practical implementations.
As a significant active safety technology towards fully autonomous driving, driver-automation co-piloting provides a new thinking for enhancing vehicle active safety and relieving driver's workload. ...However, the preview pattern divergence between driver and steering assistance system (SAS) may give rise to serious steering conflicts, which reduces driver's faith in SAS, cause him/her to turn off it, and even result in fatal traffic accidents. Focusing on mimicking the driver's steering behaviour, this paper proposes a human-like steering assistance scheme by adaptively varying the preview time and assistance gain of the SAS controller. Driver's preview behaviour of the road curvature is numerically identified using simulator tests along a multi-curves road, based on which a nominal preview-scheduled driver model is established. Based on the nominal driver model, a co-piloting system featuring human-like preview behaviour and a time-varying assistance penalty is proposed to formulate the steering torque-overlay dynamics of both agents in path-tracking. Next, a linear parameter varying (LPV)/H∞ controller satisfying pole placement is integrated to ensure the robustness and stability within the entire parameter space. This enables the steering assistance scheme to have a scheduled preview pattern like a human driver. Results of driving simulator experiment indicate that the proposed steering assistance scheme is able to mitigate driver-SAS conflicts and improve driver's path-tracking performance.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Inducing self-motion illusions referred as vection are critical for improving the sensation of walking in virtual environments (VE). Adding viewpoint oscillations to a constant forward velocity in VE ...is effective for improving vection strength under static conditions. However, the effects of oscillation frequency and amplitude on vection strength under treadmill walking conditions are still unclear. Besides, due to the visuomotor entrainment mechanism, these visual oscillations would affect gait patterns and be detrimental for achieving natural walking if not properly designed. This study was aimed at determining the optimal frequency and amplitude of vertical viewpoint oscillations for improving vection strength and reducing gait constraints. Seven subjects walked on a treadmill while watching a visual scene. The visual scene presented a constant forward velocity equal to the treadmill velocity with different vertical viewpoint oscillations added. Five oscillation patterns with different combinations of frequency and amplitude were tested. Subjects gave verbal ratings of vection strength. The mediolateral (M-L) center of pressure (CoP) complexity was calculated to indicate gait constraints. After the experiment, subjects were asked to give the best and the worst oscillation pattern based on their walking experience. The oscillation frequency and amplitude had strong positive correlations with vection strength. The M-L CoP complexity was reduced under oscillations with low frequency. The medium oscillation amplitude had greater M-L CoP complexity than the small and large amplitude. Besides, subjects preferred those oscillation patterns with large gait complexity. We suggested that the oscillation amplitude with largest M-L CoP complexity should first be chosen to reduce gait constraints. Then, increasing the oscillation frequency to improve vection strength until individual preference or the boundary of motion sickness. These findings provide important guidelines to promote the sensation of natural walking in VE.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A lot of research has been done to model and predict a driver's behaviors to improve driving safety. Inferring lane change maneuver can be a critical one among them. However, the lane change ...prediction problem is generally treated as a classification task in which the labels represent the probability of whether the driver will make a lane change in the upcoming few seconds. In our work, we formulate this problem as a regression task. The process of lane change behavior is analyzed to build a Gated Recurrent Units (GRU) network for predicting two time points during lane change behavior: a) When the driver will shift lane. b) When the lane change will be completed. We make a comparison of Long Short Term Memory (LSTM) network and Support Vector Machine (SVM) regression performance to show that our method can give a more precise prediction time. This work can be used to improve the safety performance of driver assistance systems and help other traffic participants having a safer environment.
We proposed and demonstrated a novel scheme for simultaneous measurement of temperature and refractive index (RI) by cascading a liquid-filled photonics crystal fiber (PCF) to a long period fiber ...grating (LPFG) written in a single-mode fiber. The liquid-filled PCF showed a high-temperature sensitivity of 1.695 nm/°C, which is two orders of magnitude higher than that of the LPFG (0.0642 nm/°C). The LPFG exhibited a blue shift with the increased RI. In contrast, liquid-filled PCF showed a total immunity to the surrounding RI. So, the temperature was solely measured by the liquid-filled PCF, and the RI information was extracted from the total response of the LPFG with the temperature effect having been compensated by the liquid-filled PCF.
Schizophrenia is a group of common psychosis of unknown etiology and GRIN2A gene has been a risk gene for schizophrenia. In order to understand the relationship between the GRIN2A and schizophrenia, ...we generated a GRIN2A-KO human embryonic stem cell line by CRISPR/Cas9 system, which could provide a valuable resource for investing pathogenic mechanisms underlying schizophrenia and facilitating the development of targeted medicine.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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