Vibration model and frequency characteristics of the piezoelectric transducer in airflow-induced acoustic generator

Piezoelectric transducers, which convert airflow induced vibrational energy into electrical energy, can be applied to self-powered supply and auxiliary power supply for various aircraft electronic systems. Micro-ringtone airflow piezoelectric generator, designed by the principle of airflow induced acoustic, is one kind among them. The vibrating piezoelectric generator, is usually mounted on the aircraft during the flight. The incoming airflow produces hydrodynamic acoustic source, which is the vibration source of the piezoelectric generator, actively vibrates the piezoelectric plate to convert energy. According to the vibration theory, a one-dimensional vibration model of piezoelectric generator with fixed peripheral pressure, under hydrodynamic excitation is established. The vibration and frequency characteristics of the piezoelectric transducers are analyzed by measuring the sound pressure and the piezoelectric generator voltage. Theoretical analysis and experimental results show that the frequency of hydrodynamic acoustic source is slightly lower than that of piezoelectric generator’s natural frequency. Maximum output power is obtained when the inflow speed is in the range of 128 m/s-148 m/s, the corresponding hydrodynamic acoustic source frequency is 6.9 %-8.7 % lower than the natural frequency of the piezoelectric generator. Excitation force Fex and the displacements of piezoelectric plate are in same frequency. But Fex is ahead of phase angle ψ than the displacement of piezoelectric plate

A trust-based formal model for fault detection in wireless sensor networks

Wireless Sensor Networks (WSNs) are prone to failures and malicious attacks. Trust evaluation is becoming a new method for fault detection in WSNs. In our previous work, a comprehensive trust model based on multi-factors was introduced for fault detection. This model was validated by simulating. However, it needs to be redeployed when adjustment to network parameters is made. To address the redeployment issue, we propose a Trust-based Formal Model (TFM) that can describe the fault detection process and check faults without simulating and running a WSN. This model derives from Petri nets with the characteristics of time, weight, and threshold. Basic structures of TFM are presented with which compound structures for general purposes can be built. The transition firing and marking updating rules are both defined for further system analysis. An efficient TFM analysis algorithm is developed for structured detection models. When trust factor values, firing time, weights, and thresholds are loaded, precise assessment of the node can be obtained. Finally, we implement TFM with the Generic Modeling Environment (GME).With an example, we illustrate that TFM can efficiently describe the fault detection process and specify faults in advance for WSNs

A Trust-Based Formal Model for Fault Detection in Wireless Sensor Networks

Wireless Sensor Networks (WSNs) are prone to failures and malicious attacks. Trust evaluation is becoming a new method for fault detection in WSNs. In our previous work, a comprehensive trust model based on multi-factors was introduced for fault detection. This model was validated by simulating. However, it needs to be redeployed when adjustment to network parameters is made. To address the redeployment issue, we propose a Trust-based Formal Model (TFM) that can describe the fault detection process and check faults without simulating and running a WSN. This model derives from Petri nets with the characteristics of time, weight, and threshold. Basic structures of TFM are presented with which compound structures for general purposes can be built. The transition firing and marking updating rules are both defined for further system analysis. An efficient TFM analysis algorithm is developed for structured detection models. When trust factor values, firing time, weights, and thresholds are loaded, precise assessment of the node can be obtained. Finally, we implement TFM with the Generic Modeling Environment (GME). With an example, we illustrate that TFM can efficiently describe the fault detection process and specify faults in advance for WSNs

¹³⁷Cs-Based Variation of Soil Erosion in Vertical Zones of a Small Catchment in Southwestern China

The study of the variability of soil erosion in mountainous areas provides the basis for soil and water conservation work and forest ecological construction in a targeted way. In this study, Liangshan Town catchment, a typical catchment in the Hengduan Mountains region, southwest China, was selected to investigate the variation of soil erosion in different vertical zones using the 137Cs tracing technique. The mean 137Cs reference inventories varied between 573.51 and 705.54 Bq/m2, with the elevation increasing from 1600 to 2600 m. The rates of soil erosion exhibited a significant variation. Under the same land cover condition, the average annual soil erosion modulus of high-elevation forest (elevation > 2200 m) was 400.3 t/(km2·a). However, the average annual soil erosion modulus of a low-elevation sparse forest (elevation < 1600 m) was as high as 1756 t/(km2·a). The average annual soil erosion modulus of the sloping farmland, mainly distributed at elevations of 1600–2200 m, was estimated to be 2771 t/(km2·a). These results indicate that effective soil management measures need to be implemented on the cultivated sloping land in the future

Experimental determination of sediment transport capacity of rill flow over sandified loess slope

Rill erosion is affected by the sand particle content in soil, especially in the wind and water erosion transition region of the Loess Plateau. The sediment transport capacity (STC) is a key parameter in rill erosion research, assessing the impact of aeolian sand intrusion on the STC of rill flow is of importance for a better understanding of rill erosion. This study aimed to assess the effect of aeolian sand intrusion on the STC on sandified loess slopes, with typical slopes and flow discharges, using a flume system which consisting of a sediment-feeding and a sediment-supply/settlement flume. The sediment feeding flume was jointed by 10° higher than that of the sediment measurement flume section. Three flow discharges (2, 4, and 8 L min−1) and four slope gradients (5°, 10°, 15°, and 25°) were used to represent the natural hydrological conditions under three intrusion rates (SIR) of aeolian sands (10%, 20%, and 50%). The results show that STC increased with slope gradient and flow discharge, and the relationship between the STC and the SIR was significantly affected by the slope gradient; the STCs decreased with the SIR on a slope of 5° but increased with the SIR on steep slopes of 15°–25°, implying a significant impact of slope gradient on the relationship between SIR and STC. The SIR of 50% resulted in the highest sediment concentration nearly 1200 kg m−3 on slopes of 25°. On sandified loess slopes of 10%, 20%, and 50% SIR, the STC were about 30%, 46%, and 57% higher than on loess slopes, indicating an increased erosion rate by sand particle intrusion into loess soil. These results highlight the impact of sand intrusion on STC of rill flow and provide deeper insights into the soil loss process on the sandified loess slope

The difference of sediment sources between high flows and low flows in the Hailuogou Glacier stream

2 Pags. © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License.During a 2 weeks field campaign in May 2016 in the frame of IAEA INT5153 project, source sediment samples and channel bed sediment mixtures were collected along the river valley of the Hailuogou Glacier. Three main sources were identified: surface glacier materials, old moraines and recent moraines. Composite surface samples (2 cm) were created of 10 subsamples in each representative site for surface glacier materials. Following the same scheme on old lateral moraines 10 sites were selected from the more mineral blocky deposits to the most vegetated parts at higher altitudes. On recent moraines 12 sites with different stages of vegetation cover were sampled. Starting from the glacier tongue a total of 7 fine sediment mixtures were collected along the river of which 3 composite samples corresponded to the dry season with low flow and 4 samples corresponded to high flow. A new consensus test method and an unmixing model were used to estimate the apportionments of the sediment sources to the sediment loads.Peer reviewe

A study on a 210Pbex accumulation-decay model for dating moraine soils to trace glacier retreat time

31 Pags.- 3 Tabls.- 5 Figs.This paper reports work exploring the potential for using the natural fallout radionuclide 210Pbex to date moraine soils for tracing glacier retreat. Based on the physical processes of 210Pbex deposition, decay and losses due to runoff, a210Pbex accumulation-decay model ( ) was developed, where = 210Pbex inventory (Bq·m−2); = annual inventory of 210Pbex deposition (Bq·m−2); = 210 Pb decay coefficient (0.969); = time span (years); b and c = 210Pbex loss coefficients for the runoff pathway. Furthermore, 137Cs was used to identify the ages of the study sites and to support the 210Pbex model results. The model was validated with data obtained from the Hailuogou Glacier Valley, Mt. Gongga, in 2016, where nine glacier retreat moraine points were recorded from 1910 to 1990 along a retreat length of 1750 m in the valley. 210Pbex inventories increased from 3,669.6 ± 218.5 Bq·m−2 at the site where the glacier retreated in 1990 to 10,718.9 ± 167.4 Bq·m−2 in 1910. The coefficients of b = 0.6006 and c = 0.9764 were derived from the 210Pbex inventories at the nine sites with recorded glacier retreat times that were marked with special stone and terrain features. The goodness-of-fit (GOF) for the model predictions of glacier retreat times is 65.5%. The results obtained confirm that the fallout radionuclide 210Pbex has potential for dating moraine soils in other cryosphere regions throughout the world as well as for other types of records forming sedimentary landform sequences such as soils on debris flows and alluvial fans.The study reported in this paper was supported by the National Natural Science Foundation of China (41873025) and by the International Atomic Energy Agency (IAEA; program INT5153).Peer reviewe

Tracing sediment sources at the foot of Hailuogou Glacier for low and high flows (Mt. Gongga, China)

1 .pdf copy (1 Pag.) of the abstract published by the Organization. © Author(s) 2018. CC Attribution 4.0 license.Concerns for environmental problems associated with the presence of sediment in streams and rivers derived from shrinking glaciers is driving attention because of the impact of new sources of sediments in alpine and cryosphere regions where snow and glaciers are melting faster. In river systems, sediments generated at headwaters have impacts not only on downstream water quality but also on siltation of water bodies what fostered studies on sediment provenance, transport and dynamic balance in recent years. The rapid disappearance of glaciers and snow at Mt. Gongga, where most glaciers are experiencing considerable retreat and mass loss since the early 20th century will affect the patterns of sediment delivery to river systems. The distinction between low flows and high flows is mainly reflected in glacier river load, hydrological peak and sediment load, and the sediment carried by river water body is also significantly different, so it is important to identify if there is diverse contribution of main sources supplying sediments to the drainage system under low and high flow conditions in proglacial areas. For this purpose during a 2 weeks field campaign in May 2016 in the frame of IAEA INT5153 project, source sediment samples and channel bed sediment mixtures were collected along the river valley of the Hailuogou Glacier.Peer reviewe