1,954 research outputs found
Discussions of Effects of Surface Tension on Water Vapor Absorbed by Triethylene Glycol Solution Films
The surface tension gradient can result from releasing a surfactant from the liquid film or feeding a vapor into the liquid film, and the interfacial disturbance will be induced by them. The flowing phenomena were termed “Marangoni effect,” and the mass transfer performance was enhanced by the effect. The objective of this study was to apply the Marangoni effect, such as water vapors absorbed by the liquid film of triethylene glycol (TEG) solution, and to analysze mass transfer behaviors with and without surfactants’ addition in the liquid film. The interfacial disturbance resulted from the surface tension gradient was considered in this study, and the mass transfer behaviors for packed-bed absorbers were discussed to elucidate the influence of the Marangoni effect on the absorbers. It was observed that the trends of mass transfer rates could be increased significantly as the surfactant is added into the absorption system. Experimental results showed that feeding a vapor or adding a surfactant with lower surface tension and/or higher volatility in the liquid will result in the surface tension gradient on the gas-liquid interface. The induced flowing disturbance will lead to an increment of mass transfer rate for a gas-liquid contact system
Maternal Baicalin Treatment Increases Fetal Lung Surfactant Phospholipids in Rats
Baicalin is a flavonoid compound purified from the medicinal plant Scutellaria baicalensis Georgi and has been reported to stimulate surfactant protein (SP)-A gene expression in human lung epithelial cell lines (H441). The aims of this study were to determine whether maternal baicalin treatment could increase lung surfactant production and induce lung maturation in fetal rats. This study was performed with timed pregnant Sprague-Dawley rats. One-day baicalin group mothers were injected intraperitoneally with baicalin (5 mg/kg/day) on Day 18 of gestation. Two-day baicalin group mothers were injected intraperitoneally with baicalin (5 mg/kg/day) on Days 17 and 18 of gestation. Control group mothers were injected with vehicle alone on Day 18 of gestation. On Day 19 of gestation, fetuses were delivered by cesarean section. Maternal treatment with 2-day baicalin significantly increased saturated phospholipid when compared with control group and total phospholipid in fetal lung tissue when compared with control and 1-day baicalin groups. Antenatal treatment with 2-day baicalin significantly increased maternal growth hormone when compared with control group. Fetal lung SP-A mRNA expression and maternal serum corticosterone levels were comparable among the three experimental groups. Maternal baicalin treatment increases pulmonary surfactant phospholipids of fetal rat lungs and the improvement was associated with increased maternal serum growth hormone. These results suggest that antenatal baicalin treatment might accelerate fetal rat lung maturation
PESCO: Prompt-enhanced Self Contrastive Learning for Zero-shot Text Classification
We present PESCO, a novel contrastive learning framework that substantially
improves the performance of zero-shot text classification. We formulate text
classification as a neural text matching problem where each document is treated
as a query, and the system learns the mapping from each query to the relevant
class labels by (1) adding prompts to enhance label matching, and (2) using
retrieved labels to enrich the training set in a self-training loop of
contrastive learning. PESCO achieves state-of-the-art performance on four
benchmark text classification datasets. On DBpedia, we achieve 98.5\% accuracy
without any labeled data, which is close to the fully-supervised result.
Extensive experiments and analyses show all the components of PESCO are
necessary for improving the performance of zero-shot text classification.Comment: accepted by ACL 202
Disordered Fe vacancies and superconductivity in potassium-intercalated iron selenide (K2-xFe4+ySe5)
The parent compound of an unconventional superconductor must contain unusual
correlated electronic and magnetic properties of its own. In the high-Tc
potassium intercalated FeSe, there has been significant debate regarding what
the exact parent compound is. Our studies unambiguously show that the
Fe-vacancy ordered K2Fe4Se5 is the magnetic, Mott insulating parent compound of
the superconducting state. Non-superconducting K2Fe4Se5 becomes a
superconductor after high temperature annealing, and the overall picture
indicates that superconductivity in K2-xFe4+ySe5 originates from the Fe-vacancy
order to disorder transition. Thus, the long pending question whether magnetic
and superconducting state are competing or cooperating for cuprate
superconductors may also apply to the Fe-chalcogenide superconductors. It is
believed that the iron selenides and related compounds will provide essential
information to understand the origin of superconductivity in the iron-based
superconductors, and possibly to the superconducting cuprates
Optimal Work Shift Scheduling with Fatigue Minimization and Day Off Preferences
Shift work disrupts the sleep-wake cycle, leading to sleepiness, fatigue, and performance
impairment, with implications for occupational health and safety. For example, aircraft
maintenance crew work a 24-hour shift rotation under the job stress of sustaining the
flight punctuality rate. If an error occurs during the aircraft maintenance process, this
error may become a potential risk factor for flight safety. This paper focuses on optimal
work shift scheduling to reduce the fatigue of shiftworkers. We proposed a conditional
exponential mathematical model to represent the fatigue variation of workers. The fatigue model is integrated with the work shift scheduling problem with considerations of
workers’ preferences of days off, company or government regulations, and manpower
requirements. The combined problem is formulated as a mixed-integer program, in
which the shift assignments are described by binary variables. Using the proposed
method, we can find a feasible work shift schedule and also have a schedule that minimizes the peak fatigue of shiftworkers while satisfying their days off demands. Several
examples are provided to demonstrate the effectiveness of the proposed approach
Time-Based Separation for Aircraft Landing Using Danger Value Distribution Flow Model
This study proposes a flow model using a modified Lighthill-Whitham-Richards highway model. The proposed model treats each aircraft on an airway as a continuous distribution of air collision probability, which is called the danger value distribution. With the proposed flow model, collision can be easily predicted by the peak value of the overlap of the danger value distribution of each aircraft. The study further proposes a velocity adjustment method that can be used to resolve the conflict. The proposed method can be applied for aircraft separation during the landing process, in which the separation time is different for different combinations of aircraft types
An Improvement Stereo Vision Images Processing for Object Distance Measurement
Human has the ability to roughly estimate the distance of objects because of the stereo vision of human’s eyes. In this paper we proposed an improved stereo vision system to accurately measure the distance of objects in real world. Object distance is very useful for obstacle avoidance and navigation of autonomous vehicles. Recent researches have used stereo cameras for different applications such as 3D image construction, distance measurement, and occlusion detection. The proposed measurement procedure is a three-phase process: object detection, segmentation, and distance calculation. In distance calculation, we proposed a new algorithm to reduce the error. The result shows our measurement system is capable of providing objects distance with less than 5% of measurement error
Nonparetic Knee Extensor Strength Is the Determinant of Exercise Capacity of Community-Dwelling Stroke Survivors
Objective. To investigate the relationship among walking speed, exercise capacity, and leg strength in community dwelling stroke subjects and to evaluate which one was the leading determinant factor of them. Design. This is a descriptive, cross-sectional study. Thirty-five chronic stroke patients who were able to walk independently in their community were enrolled. Walking speed was evaluated by using the 12-meter walking test. A maximal exercise test was used to determine the stroke subjects’ exercise capacity. Knee extensor strength, measured as isokinetic torque, was assessed by isokinetic dynamometer. Results. The main walking speed of our subjects was 0.52 m/s. Peak oxygen uptake (VO2 peak) was 1.21±0.43 L/min. Knee extensor strength, no matter whether paretic or nonparetic side, was significantly correlated to 12-meter walking speed and exercise capacity. Linear regression also showed the strength of the affected knee extensor was the determinant of walking speed and that of the nonparetic knee extensor was the determinant of exercise capacity in community dwelling stroke subjects. Conclusions. Walking speed and peak oxygen uptake were markedly decreased after stroke. Knee extensor strength of nonparetic leg was the most important determinant of exercise capacity of the community-dwelling stroke subjects. Knee extensor strengthening should be emphasized to help stroke patient to achieve optimal community living
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