Visualization and Sound Measurements of Vibration Plate in a Boiling Bubble Resonator

We developed a boiling bubble resonator (BBR) as a new heat transfer enhancement method aided by boiling bubbles. The BBR is a passive device that operates under its own bubble pressure and therefore does not require an electrical source. In the present study, high-speed visualization of the flow motion of the microbubbles spouted from a vibration plate and the plate motion in the BBR was carried out using high-speed LED lighting and high-speed cameras; the sounds in the boiling chamber were simultaneously captured using a hydrophone. The peak point in the spectrum of the motion of the vibration plate and the peak point in the spectrum of the boiling sound were found to be matched near a critical heat-flux state. Therefore, we found that it is important to match the BBR vibration frequency to the condensation cycle of the boiling bubble as its own design specification for the BBR.

Freeze-thaw Assessment of Plants Based on Envelope Analysis of Stem Volume Water Content Sequence

Background: Frost stress is an abiotic stressor for plant growth that impacts the health and the regional distribution of plants. The freeze-thaw characteristics of plants during the overwintering period help to understand relevant issues in plant physiology, including plant cold resistance and cold acclimation. Therefore, we aimed to develop a non-invasive instrument and method for accurate in situ detection of changes in stem freeze-thaw characteristics during the overwintering period. Results: A sensor was designed based on standing wave ratio method (SWR) to measure stem volume water content (StVWC). We were able to measure stem volume ice content (StVIC) and stem freeze-thaw rate of ice (StFTRI) during the overwintering period. The resolution of the StVWC sensor is less than 0.05 %, the mean absolute error and root mean square error are less than 1 %, and the dynamic response time is 0.296 s. The peak point of the daily change rate of the lower envelope of the StVWC sequence occurs when the plant enters and exits the overwintering period. The peak point can be used to determine the moment of freeze-thaw occurrence, whereas the time point corresponding to the moment of freeze-thaw coincides with the rapid transition between high and low ambient temperatures. In the field, the StVIC and StFTRI of Juniperus virginiana L., Lagerstroemia indica L. and Populus alba L. gradually increased at the beginning, fluctuated steadily during, and then gradually decreased by the end of the overwintering period. The StVIC and StFTRI also showed significant variability due to differences among the tree species and latitude.Conclusions: The StVWC sensor has good resolution, accuracy, stability, and sensitivity. The envelope changes of the StVWC sequence and the correspondence between the freeze-thaw moment and the ambient temperature indicate that the determination of the freeze-thaw moment based on the peak point of the daily change rate of the lower envelope is reliable. The results show that the sensor is able to monitor changes in the freeze-thaw characteristics of plants and effectively characterize freeze-thaw differences and cold resistance of different tree species. Furthermore, this is a cost-effective tool for monitoring freeze-thaw conditions during the overwintering period.

Study on Damage Constitutive Model of Rock under Freeze-Thaw-Confining Pressure-Acid Erosion

Aiming at the acid-etched freeze-thaw rock for geotechnical engineering in cold regions, chemical damage variables, freeze-thaw damage variables, and force damage variables were introduced to define the degree of degradation of rock materials, the law of damage evolution, the total damage variable of acid-corroded rock under the coupling action of freeze-thaw and confining pressure was deduced. The continuous damage mechanics theory was adopted to derive the damage evolution equation and constitutive model of acid-eroded rock under the coupling action of freeze-thaw and confining pressure. The theoretical derivation method was used to obtain the required model parameter expressions. Finally, the model’s rationality and accuracy were verified by the triaxial compression test data of frozen-thawed rocks. Comparing the test curve’s peak point with the peak point of the model theoretical curve, the results show that the two are in suitable agreement. The damage constitutive model can better reflect the stress-strain peak characteristics of rock during triaxial compression, verifying the rationality and reliability of the model and the method for determining the model parameters. The model extends the damage model of rock under the coupling action of freeze-thaw and confining pressure in the chemical environment and further reveals the damage mechanism and failure law of acid-corroded rock under the coupling action of freeze-thaw and confining pressure.

Study on the Meso-Energy Damage Evolution Mechanism of Single-Joint Sandstone under Uniaxial and Biaxial Compression

Energy conversion and release occur through the entire deformation and failure process in jointed rock masses, and the accumulation and dissipation of rock mass energy in engineering can reveal the entire process of deformation and instability. This study uses PFC2D to carry out numerical simulation tests on single-joint sandstone under uniaxial compression and biaxial compression, respectively, and analyse the influence of joint inclination, length, and confining pressure on the meso-energy conversion process and phase evolution of jointed sandstone. Through analysis, it is found that the input meso total strain energy is transformed into meso dissipated energy and meso-elastic strain energy. Macroscopic and microscopic joint sandstone law is consistent with the overall energy evolution; and the difference is reflected in two aspects: (1) the microlevel energy evolution has no initial compaction energy consumption section and (2) the linear energy storage section before the macroenergy evolution peak can be subdivided into two sections in the meso-level energy evolution. Under uniaxial compression, the energy values at the characteristic points of the meso-level energy evolution phases first asymmetrically decrease and then increase with the increase of the joint inclination. The initiation point of jointed sandstone is significantly affected by the length of the joint, and the degradation effect of the meso-energy at the damage point and peak point weakens with the increase of the joint length. Comparing the data obtained from the PFC numerical simulation with the experimental data, it is found that the error is small, which shows the feasibility of the numerical model in this paper. Under biaxial compression, the accumulation rate of meso-elastic strain at the peak point of the jointed sandstone first decreases and then increases with the joint inclination angle. After the peak of jointed sandstone, the rate of sudden change of meso-energy change decreases with the increase of joint length. The conditions of high confining pressure will promote the meso-accumulated damage degree of the jointed sandstone before the peak, while inhibiting the meso-energy and the mutation degree of the damage after the peak. The higher the confining pressure, the more obvious the joint length and inclination effect characteristics of the elastic strain energy at the peak point of the jointed sandstone.

Fetal Heart Rate Extraction Based on Wavelet Transform to Prevent Fetal Distress In Utero

In order to improve the effective extraction of fetal heart rate and prevent fetal distress in utero, a study of fetal heart rate feature extraction based on wavelet transform to prevent fetal distress in utero was proposed. This paper adopts a fetal heart rate detection method based on the maximum value of the binary wavelet transform modulus. The method is simulated by the Doppler fetal heart signal obtained from the clinic. Compared with the original curve, the transformed curve can roughly see the change rule of the original signal and identify the peak point of the signal, but due to the large disturbance of the peak point, the influence on the computer processing is also great. The periodicity of the transformed signal is greatly enhanced, making it easier to deal with the computation. A total of 300 pregnant women with full-term fetal heart monitoring from January 2018 to January 2020 were selected as the research subjects and divided into the observation group and the control group. The observation group consisted of 100 patients with abnormal fetal heart monitoring, and the control group consisted of 200 patients with normal fetal heart monitoring. The uterine contractions and fetal heart rate were recorded, and the incidence of fetal distress, cesarean section, neonatal asphyxia, and amniotic fluid and fecal contamination were observed. The incidence of fetal distress, cesarean section, neonatal asphyxia, and amniotic fluid fecal stain in the observation group were significantly higher than those in the control group. Fetal heart monitoring can accurately judge the situation of the fetus in pregnant women and timely diagnose the abnormal fetal heart rate, which has a better effect on the prognosis of perinatal infants and can reduce their mortality. It can effectively solve the problems existing in the autocorrelation algorithm and extract the fetal heart rate more accurately. It is an effective improved scheme of fetal heart rate extraction. It is very helpful in preventing fetal distress in utero.

Effects of Post-Injection Characteristics on the Combustion, Emission, and Performance in a Diesel-Syngas Reactivity Controlled Compression Ignition Engine

This paper presents a numerical investigation of the separate effects of post-injection characteristics in a heavy-duty turbocharged direct injection diesel engine under pure diesel combustion (PDC) and diesel-syngas combustion (DSC) operating conditions. Converge CFD code was used coupled with a detailed n-heptane/toluene/PAH chemical kinetic mechanism (consists of 71 species and 360 reactions) for diesel-syngas dual-fuel combustion simulation. A total of 36 strategies based on the post-injection characteristics (post-injection timing, fuel quantity, spraying pressure, and main-post dwell time) on the combustion characteristics, exhaust gas emissions, and engine performance under PDC and DSC conditions were investigated. Numerical achievements revealed that 40% substitution of diesel fuel with syngas significantly decreased particulate matter emission and enhanced the indicated thermal efficiency (ITE), compared to the baseline PDC case. However, carbon monoxide noticeably increased. In addition, retarding the post-injection timing prolonged the combustion duration and also reduced the nitrogen oxides emissions and ITE. By increasing the post-injection quantity up to 15%, the combustion process deteriorated, and carbon-based emissions such as particulate matter, carbon monoxide, and unburnt hydro-carbon in the exhaust gases increased under PDC and DSC conditions. Furthermore, increasing post-injection pressure (PIP) from 1000 to 1450 bar under both PDC and DSC conditions led to higher flame temperature, and as a result, the heat release rate peak point and temperature peak point for the second combustion event increased. However, at a PIP of 1600 bar, the ITE deteriorated under PDC and DSC operating cases.

Extracellular Calcium Ion Concentration Regulates Chondrocyte Elastic Modulus and Adhesion Behavior

Extracellular calcium ion concentration levels increase in human osteoarthritic (OA) joints and contribute to OA pathogenesis. Given the fact that OA is a mechanical problem, the effect of the extracellular calcium level ([Ca2+]) on the mechanical behavior of primary human OA chondrocytes remains to be elucidated. Here, we measured the elastic modulus and cell–ECM adhesion forces of human primary chondrocytes with atomic force microscopy (AFM) at different extracellular calcium ion concentration ([Ca2+]) levels. With the [Ca2+] level increasing from the normal baseline level, the elastic modulus of chondrocytes showed a trend of an increase and a subsequent decrease at the level of [Ca2+], reaching 2.75 mM. The maximum increment of the elastic modulus of chondrocytes is a 37% increase at the peak point. The maximum unbinding force of cell-ECM adhesion increased by up to 72% at the peak point relative to the baseline level. qPCR and immunofluorescence also indicated that dose-dependent changes in the expression of myosin and integrin β1 due to the elevated [Ca2+] may be responsible for the variations in cell stiffness and cell-ECM adhesion. Scratch assay showed that the chondrocyte migration ability was modulated by cell stiffness and cell-ECM adhesion: as chondrocyte’s elastic modulus and cell-ECM adhesion force increased, the migration speed of chondrocytes decreased. Taken together, our results showed that [Ca2+] could regulate chondrocytes stiffness and cell-ECM adhesion, and consequently, influence cell migration, which is critical in cartilage repair.

Ancient Latin grammarians on suppletion

The term “suppletion”, introduced by Osthoff (1899. Vom Suppletivwesen der indogermanischen Sprachen. Heidelberg: Universitätsbuchdruckerei Hörning), was traditionally used to refer to an inflectional paradigm containing forms based on two or more etymologically different stems. In the last decades, however, it has been argued that etymology does not contribute to our understanding of the phenomenon, and it should be strictly defined on synchronic terms: simply as the peak point on the formal irregularity scale, regardless of the actual origin of the irregularity. Under this approach, all forms reported by speakers as two potentially different lexical items are considered to be suppletive. To be able to determine what users of a living language consider to be a case of suppletion, it is possible to analyze data collected from speakers. The situation is considerably more difficult for dead languages, which however have played an important role in the debate and provided many of the canonical examples. As a closest equivalent to eliciting the required information from a native speaker, the informed but from the present-day perspective naïve expressions of linguistic introspection in the works of Late Latin Grammarians, namely their use of specific terms (defectivum, anomalum, inaequale) to refer to different degrees and lexical examples of irregularity, are highly valuable, as it also may reflect the difficulties confronted by non-native learners.

Karakterisasi Sumber Cahaya Menggunakan Spektrofotometer Vis-Nir untuk Optimasi Optical Non-Contact Speedometer

Characterization the light source has been carried out using a Vis-Nir spectrophotometer with the Ocean Optics DTmini-2 model. The purpose of this characteristic is to obtain the optimum wavelength as a light source in making a digital optical non-contact speedometer model. There are 5 light sources tested, namely blue, green, yellow, red and white light. From the characterization results, the wavelengths were blue (450 nm), green (540 nm), yellow (570 nm), red (640 nm) and white (550 nm). In making the digital optical non-contact speedometer model, a photodiode sensor is used which has an absorbance peak point at 479 nm, 680, and 900 nm. The working principle of the prototype is to detect changes in light intensity as a result of the reflectance by the wheel. The sensor reads every color changes on the wheel and the results will be sent to the microcontroller for further processing. The results obtained are that the red LED is excellent to this prototype because it has the highest ADC value compared to other light sources tested. This is consistent with the results of the sensor spectrophotometer characterization.

Wood and quartz substituted composite material characteristics

Many engineering designs focus on the production of durable, ergonomic, and economical new materials. In today’s world where natural resources are rapidly decreasing, recycling waste materials is of great importance. As a result of the bending test, the sample’s return to its original dimensions shows the plastic feature of the material. It was observed that the tensile strength can be increased if the speed of the injection machine is well adjusted in the production of tensile strength testing samples. There was an increase in the screw tensile strength of the samples and the joint hardness strength. Thermogravimetric analysis (TGA) showed that the reference samples were completely crumbled around 480 °C, and it was observed that only quartz remained from the input materials. Differential scanning calorimetry (DSC) showed that the peak point in the reference sample was at the heat flow rate of 29 m/W, while it was 18 to 19 m/W in the doped groups. Melting temperature was observed in the range of 125 to 135 °C in all groups. The mechanical properties of the quartz-substituted samples increased compared to the reference sample. It was observed that the quartz and wood powder contained in the mixture worked in harmony.