Search

The variations in the lake area, water level, and water volume change of the Aral Sea from 1987 to 2018 were analyzed in this study, which is based on the multi-temporal Landsat images and remote sensing water body index (Normalized Difference Water Index, NDWI). Lake shorelines were automatically digitized and visualized using Net Shoreline Movement (NSM) and Linear Regression Rate (LRR) by Digital Shoreline Analysis System (DSAS). The surface area, water level, and water volume change of the North Aral Sea were not changed significantly in 1987-2018. The maximum lake area appeared in March 2015 with 3550.15 km2, the minimum lake area appeared in October 2001with 2830.56 km2. However, since 2010 the South Aral Sea split into the East Aral Sea and the West Aral Sea, the area change has shrunk dramatically. The area of the East Aral Sea decreased by 17852.65 km2 (89.99 %) from March 2011 to September 2018. The area of the West Aral Sea decreased by 2203.62 km2 (35.96 %) from August 2014 to March 2017. The distance of lake shoreline changes and rates of net movement along transects were determined by DSAS. The two largest positive values of NSM were 18715.93 and 12268.67 m, which showed lake shoreline retreat, occurred in the periods of 2010-2018 in the East Aral Sea and 1987-1999 in the South Aral Sea, respectively. The two periods in which the largest negative value of NSM appeared was (1987-1993) and (2001-2010) in the North Aral Sea, and the lake shoreline expanding distance was 145.43 and 545.84 m, respectively.

BACKGROUND: Aortic root evaluation is conventionally based on two-dimensional measurements at a single phase of the cardiac cycle. This work presents an image analysis method for assessing dynamic three-dimensional changes in the aortic root of minimally calcified bicuspid aortic valves (BAVs) with and without moderate to severe aortic regurgitation. METHODS: The aortic root was segmented over the full cardiac cycle in three-dimensional transesophageal echocardiographic images acquired from 19 patients with minimally calcified BAVs and from 16 patients with physiologically normal tricuspid aortic valves (TAVs). The size and dynamics of the aortic root were assessed using the following image-derived measurements: absolute mean root volume and mean area at the level of the ventriculoaortic junction, sinuses of Valsalva, and sinotubular junction, as well as normalized root volume change and normalized area change of the ventriculoaortic junction, sinuses of Valsalva, and sinotubular junction over the cardiac cycle. RESULTS: Normalized volume change over the cardiac cycle was significantly greater in BAV roots with moderate to severe regurgitation than in normal TAV roots and in BAV roots with no or mild regurgitation. Aortic root dynamics were most significantly different at the mid-level of the sinuses of Valsalva in BAVs with moderate to severe regurgitation than in competent TAVs and BAVs. CONCLUSIONS: Echocardiographic reconstruction of the aortic root demonstrates significant differences in dynamics of BAV roots with moderate to severe regurgitation relative to physiologically normal TAVs and competent BAVs. This finding may have implications for risk of future dilatation, dissection, or rupture, which warrant further investigation.

Climate change is strongly affecting the Himalayas. Geologically young and fragile, the Himalayas are sensitive to even minor changes in the climate. Regional warming in Himalayas has been observed between 0.15 and 0.60°C per decade, which is higher than the mean global warming rate of 0.74°C per 100years. Consequent to this warming trend, the glaciological changes in Himalayas are obvious, which has resulted in the formation, expansion and disappearance of various types of glacial lakes. The dangerous lakes among these pose threat to downstream community and infrastructure. In this study, an attempt has been made to critically analyze the progress in Glacier Lake Outburst Floods (GLOF) research and understand its dynamism from multiple approaches through a meta-analysis of peer-reviewed scholarly literature for a period of 2001–2020. The study has found that the glacial lakes in the study region are increasing in number and expanding rapidly owing to the climate change and anthropogenic causes as the Glacier Lake Outburst Floods (GLOFs) are becoming common. The expansion rates of pro-glacial lakes connected to glaciers and moraine-dammed lakes are faster than other type of lakes. Findings from the studies on area change analysis in the region reveal that a number of expanding glacial lakes can emerge as potential sites for future GLOFs, hence need immediate monitoring and observation. Geospatial tools and techniques coupled with field investigations have been found as a potent tool for mapping the evolution and propagation of GLOF hazards resulting from accelerated shrinking and thinning of glaciers and continued lake expansion. Further, the satellite-based remote sensing and modeling has been found as an excellent tool for GLOF management as well as reconstruction of previous GLOF events and prediction of future outburst potential. The idea of this study is linked to the increased incidence of GLOF events in the Himalayan region. This study will help in better understanding of glacial lake expansion and provide scope for future research in devising risk management action plans of potential GLOFs by selecting expanding glacial lakes as case studies.

OBJECTIVES Fat quality and quantity may affect health similarly or differently. Fat quality can be assessed by measuring fat density on CT scan (greater density = smaller, higher quality adipocytes). We assessed the effects of tesamorelin, a growth hormone-releasing hormone analogue that reduces visceral fat (VAT) quantity in some people living with HIV (PWH), on fat density. DESIGN Participants from two completed, placebo-controlled, randomized trials of tesamorelin for central adiposity treatment in PWH were included if they had either a clinical response to tesamorelin (VAT decrease ≥8%, ≈70% of participants) or were placebo-treated. METHODS CT VAT and subcutaneous fat (SAT) density (Hounsfield Units, HU) were measured by a central blinded reader. RESULTS Participants (193 responders, 148 placebo) were 87% male and 83% white. Baseline characteristics were similar across arms, including VAT (-91 HU both arms, P = 0.80) and SAT density (-94 HU tesamorelin, -95 HU placebo, P = 0.29). Over 26 weeks, mean (SD) VAT and SAT density increased in tesamorelin-treated participants only [VAT: +6.2 (8.7) HU tesamorelin, +0.3 (4.2) HU placebo, P

Objective: This research aimed at evaluating the changing conditions and experiences of urological practice during the COVID-19 pandemic. Methods: The data of all patients who were admitted to outpatient clinics at Hisar Intercontinental Hospital or the hospital’s online patient portal system between March 11th and May 30th, 2020 were analyzed retrospectively. Of all patients, 545 in outpatient clinics and 25 in online portal system, (17%) were hospitalized for medical treatment, and 53 underwent surgery. There were 1032 patients admitted to Urology Clinics and 104 patients who underwent surgery in the same period of 2019. The pre-operative assessment of patients who were candidates of urological surgery included certain criteria for COVID-19. Results: Of patients included in this study, the median age was 41 years (18–90). The mean hospital stay was 1 day (1–12), and the mean duration of operation was 25 min (3–250). Thirty-seven patients (69.8%) underwent general anesthesia, while only 11(20.8%) underwent combined spinal epidural anesthesia. Four patients (7.5%) required local and only one patient (1.9%) underwent sedo-analgesia. Complications were encountered in six patients (11.4%), urosepsis in two, pneumonia in one, and urinary tract infection in three patients. Compared to last year’s numbers, the number of patients admitted to the hospital’s outpatient clinic and that of hospitalized patients decreased by 47.2% and 49.1%, respectively. Conclusion: Emergent surgeries in urological practices can be performed safely under routine preoperative testing for COVID-19 and with the use of adequate protective equipment for both the surgical team and the patient.

In this paper, a previous model for char surface area change during atmospheric coal pyrolysis was modified to include the effect of particle swelling and gasification to predict the N2 adsorption specific surface area of high-volatile bituminous char generated at high pressures with or without gasification. A correlation between the change of char surface area and P0ΔVP/mcm (the ratio of the expansion work for particle swelling to the mass of metaplast cross-linked with coal matrix) was developed and analyzed. The number of the defect regions generated by gasification was considered in calculating adsorption sites quantitatively. Particle swelling opens (at P0ΔVP/mcm

While the number of highway tunnels is increasing, the current Chinese criteria and Uniform Traffic Control Equipment Manual (MUTCD) 2009 guidelines provide no clear method for setting exit advance guide signs in highway tunnels. To solve this problem, this paper proposes separate guide signs, consisting of location and distance signs. Location signs on the tops of tunnels use Chinese characters with a height of 40 cm and a width 20 cm. The distance signs are 62.6 m from the location signs with a character height and width of 1.5 m and a total sign length of 22.5 m. Four schemes were tested, in which the distance sign was on the left or right wall of the tunnel and the vehicle was in the left or right lane. At the “Perception” and “Recognition” stages, the pupil area change rate of the four schemes had a slight difference to no sign but were always less than the 20% threshold line. A Markov chain was employed to analyze the driver’s eye movement characteristics to evaluate the effect of separate guide signs. The results are the following. In the left lane, when a distance sign on the left wall of the tunnel appeared, the driver’s fixation points were relatively balanced, except in the left area. After the sign disappeared, the driver’s fixation points were no different than before, except in the front area. However, when a distance sign appeared on the right wall, 77.84% of the driver’s fixation points were concentrated in the front and right areas, which decreased the driving safety. Similar results were obtained in the right lane. Therefore, distance signs should be placed on the left wall of the highway tunnel. This study can forewarn a driver in a tunnel of the exit location and distance and help the driver to exit the highway safely.

This study aims to determine the relationship between Hounsfield Unit shift ( $\Delta {\mathrm{ HU}}$ ), tissue temperature change ( $\Delta T$ ), and tissue’s relative cross-sectional area change ( $\Delta A$ ) of ex vivo bovine liver tissues. The fresh bovine livers ( $n = 3$ ) were heated from 21 °C to 100 °C within 24 min using a custom-made ceramic hot plate and left for cooling to room temperature (~70 min). HU and tissue temperature measurement were obtained at 3-min intervals during the experiment. After that, the cross-sectional tissue area changes, and $\Delta A$ was calculated. Finally, a multivariate linear regression analysis was performed to determine the relationship between $\Delta {\mathrm{ HU}}$ , $\Delta T$ , and $\Delta A$ . The results were compared with that of the conventional $\Delta {\mathrm{ HU}}$ - $\Delta T$ linear model. Tissues that underwent a larger thermal dose experienced a higher degree of tissue contraction, an irreversible process that contributed to the non-linear behavior in the $\Delta {\mathrm{ HU}}$ - $\Delta T$ characteristic curve. This finding was in agreement with the histological test, in which the tissues nearer to the heat source had higher cell counts than those farther away. A phenomenological equation for $\Delta {\mathrm{ HU}}$ in the function of $\Delta T$ and $\Delta A$ shows better regression with the experimental data ( $R^{2} \in $ [0.838, 0.977]) than the conventional $\Delta {\mathrm{ HU}}$ - $\Delta T$ linear model. This finding indicates that tissue contraction is an important parameter to be considered in the development of CT thermometry. The $\Delta {\mathrm{ HU}}$ - $\Delta T$ - $\Delta A$ characteristic equation presented in this work offers accurate estimation of tissue temperature based on the HU change and magnitude of tissue contraction during a CT-guided thermal ablation procedure.

PURPOSE To determine if parasagittal gastric cine magnetic resonance imaging (MRI) is able to measure gastric oscillatory contractions around 0.05 Hz and to determine its relationship with electrical activity as measured by electrogastrography (EGG). METHODS Assessment of the gastric motility is important for the research of the enteric nervous system and for the diagnosis of functional gastric disorders. Electrogastrography is a non-invasive method that can measure gastric oscillatory electrical activity around 0.05 Hz (slow wave) using electrodes on the abdominal skin, but its sensitivity and specificity of the slow wave detection is limited. We used parasagittal gastric cine MRI around the angular incisure to measure gastric oscillatory contraction around 0.05 Hz in 24 healthy volunteers. Cine MRI was acquired with time resolution of 1 s for 10 min while freely breathing participants were lying on the bed. The gastric area of the cross section was measured for each MR image and assessed its change over time. The results were compared with those for simultaneously recorded EGG. RESULTS The main frequency of the gastric area change for each participant ranged from 0.041 to 0.059 Hz (mean ± S.D. = 0.049 ± 0.004), which corresponds to the gastric slow wave frequency (mean ± S.D. = 0.049 ± 0.004) as measured by EGG (p = 7.9585 × 10 -8, Kendall 's tau test). Cross correlation analysis showed that 22 of 24 participants' gastric area changes were significantly (p

For a pulse tube cryocooler, the expansion efficiency of the pulse tube is important and is strongly related to the flow inside. Conventionally, flow straighteners are used at both ends of the empty pulse tube to ensure a uniform flow. This approach complicates the system and also becomes a source of flow losses. In this paper, a partly tapered pulse tube that has a tapered section at the ambient end is used to replace the flow straightener. Its performance was compared with that of a conventional straight pulse tube without or with flow straightener at the ambient end numerically and experimentally. Simulation results show that the flow straightener is necessary in the straight pulse tube due to the influence of jet-driven streaming in the location where abrupt cross-sectional area change occurs. The partly tapered pulse tube can effectively eliminate the need for flow straightener. The expansion efficiency is the highest (about 94%) for the partly tapered pulse tube, while an efficiency of 88% is obtained with the straight pulse tube with a flow straightener. Experiments have been conducted; the cooling power of the straight pulse tube without flow straightener, the straight pulse tube with flow straightener, and the partly tapered pulse tube is 3.9, 28, and 29 W, respectively. The cooling power of the straight pulse tube with flow straightener and that of the partly tapered pulse tube are almost the same, which indicates that the partly tapered pulse tube can effectively eliminate the need for an ambient flow straightener.

We present a long-term assessment (1965–2018) of recessional and area change patterns as well as the recent decade surface velocity ( υ ‾ , 2000–2001 and 2017–2018) and elevation change ( d h / d t...

In spite of importance of the ice shelves as a probable sign of global climate change, temporal changes of Antarctic ice shelf margins are largely unknown. In the present article, an attempt has been made for chronological mapping of major four Antarctic ice shelf fronts for the period 2001–2016, using MODerate resolution Imaging Satellite images. Vector layers of individual ice shelves from 2001 to 2015 have been overlaid on the image of 2016. It is found that all the four ice shelves have advanced; the Filchner ice shelf advanced maximum (24 km) and the Ross ice shelf advanced minimum (16 km). Maximum range in yearly rate of advance is observed at Ronne Ice Shelf and the highest variability in rate of advance is observed over Filchner ice shelf. In terms of area change, maximum expansion occurred at Ronne ice shelf (8813 km2) and least expansion is observed over Amery ice shelf (2520 km2). Poor correlation between rates of change at different ice shelves suggests that different atmospheric and oceanic drivers are responsible for changes at individual ice shelves. Interestingly, the highest rate of advance as well as higher variability in rate of advance is observed over the latter half of the study period.

The use of three satellite imagery data at the same location and different time are 2003, 2013 and 2018, resulting in three potential maps of landslide with different time series of 2003, 2013, and 2018.. Map of potential landslides generated classified in three classes of potential landslide levels. The result of a potential landslide map indicates there is a difference in potential level classes. In the span of years 2003 to 2013 there was a total change in the class of potential levels of 10082.25 hectares of the total area of Trenggalek Regency. From 2013 to 2018 there were a change of 14882.77 hectares. Calculation of correlation between land cover area change with potential landslide change is equal + 1. This value indicates a very strong positive correlation between changes in the area of landslide potential with the change in land cover. The use of three satellite imagery data at the same location and different time are 2003, 2013 and 2018, resulting in three potential maps of landslide with different time series of 2003, 2013, and 2018.. Map of potential landslides generated classified in three classes of potential landslide levels. The result of a potential landslide map indicates there is a difference in potential level classes. In the span of years 2003 to 2013 there was a total change in the class of potential levels of 10082.25 hectares of the total area of Trenggalek Regency. From 2013 to 2018 there were a change of 14882.77 hectares. Calculation of correlation between land cover area change with potential landslide change is equal + 1. This value indicates a very strong positive correlation between changes in the area of landslide potential with the change in land cover.

Climate-induced cryospheric changes can have a significant impact on the downstream water availability. In this study, the Open Global Glacier Model (OGGM) and the Glacio-hydrological Degree-day Model (GDM) are integrated to project the response of cryospheric and hydrological systems to climate change until 2100. The study area comprises six sub-basins of glacierized Koshi River basin covering Nepalese and Chinese territories. The output from OGGM is provided as input to GDM along with the spatial and hydro-meteorological data. The average glacier area change in all the sub-basins from 2021 to 2100 is estimated as 65 and 85% decrease and the average glacier volume change is estimated as 76 and 86% decrease for RCP 4.5 and 8.5 scenarios, respectively. The future simulated discharge shows an increasing trend in pre-monsoon and monsoon seasons and a decreasing trend in post-monsoon and winter seasons after 2060 in all the sub-basins, which can lead to wetter wet seasons and drier dry seasons in the far future. A shift in peak flow is observed from August to July in most of the sub-basins. The coupled modelling technique used in this study can largely improve our understanding of glacio-hydrological dynamics in the Himalayan region.

With the development of China’s industrialization, the reduction problem of grassland area caused by unglazed land occupation has become increasingly prominent. The driving factors of the decrease of forage land area gradually changed from the beginning of livestock overloading to the non-animal husbandry factors such as industrial occupation. On the basis of classification and summary of the related research results of the change of pasture grassland resources, this paper analyses the distribution characteristics and utilization status of grassland resources in China. Өвөр монголын өөртөө засах орны бэлчээрийн талбайн өөрчлөлтийг түргэсгэгч хүчин зүйлсийн судалгаа Өвөр монголын бэлчээрийн талбай жил бүр буурах хандлагатай байна. Гэвч цаг хугацааны ялгаатай үеүдэд нөлөөлөгч хүчин зүйлс нь өөр өөр байсаар иржээ. Энэхүү өгүүлэл нь БНХАУ- ын хойд нутгийн төлөөлөл бүс болохуйц Өвөр Монголыг судалгааны объёктоор сонгон, 1997-2015 оны тоо материалд тулгаарлан, бэлчээрийн нөөц, хэрэглээний өөрчлөлтийн талаар судалсан судалгааны ажлуудын үр дүнг ангилан нэгтгэж математик, статистикийн тооцооллын аргыг ашиглан, эдийн засаг, нийгмийн хөгжлийн долоон үзүүлэлтийг сонгон бэлчээрийн өөрчлөлтийн түргэсгэгч механизмыг судалсан болно. Түлхүүр үг: бэлчээрийн талбайн өөрчөлт, түргэсгэгч хүчин зүйл, хүчин зүйлийн шинжилгээ

Glacial retreat in response to warming climates in the arid Xinjiang region of northwestern China directly impacts downstream water resources available for local communities. We used high-resolution satellite imagery from 1969 to 2014 to delineate spatial changes in 54 active glaciers in the upper Kaidu River Basin in the Tian Shan as well as their past expanses during the Little Ice Age (LIA). We manually delineated their boundaries based on the interpretation of glacial, geomorphic and topographic features. From the total glacier surface area, we estimated glacier volume and mass. From 1969 to 2014, glacier area decreased by 10.1 ± 1.0 km2 (relative loss of 34.2 ± 3.5%) and mass by 1.025 ± 0.108 Gt (relative loss of 43 ± 4.6%). From the LIA maximum (est. 1586 CE) to 1969, relative losses were less (25.7 ± 4.3% area loss and 33.1 ± 5.7% mass loss). Our results indicate that glacier recession is accelerating over time and that the glaciers are currently losing over 1.5 times more relative area than elsewhere in the Tian Shan. Using linear and non-linear projections, we estimate that these glaciers may disappear between 2050 and 2150 CE if climatic warming continues at the same pace.

This study employs a panel dataset on forest area of 22 countries and for the time period 1995–2016 in order to provide an up-todate assessment on determinants of forest area change. Our set of explanatory variables is drawn from the Environmental Kuznets curve hypothesis and well-established factors affecting forest area change. In this respect, macroeconomic stability, socioeconomic development, institutional efficiency and quality of governance are taken into account to assess the cumulative nature of changes in forest cover. Using static and dynamic specifications our analysis produce different results with an inverted U-shape curve only in the static case and an inverted N-shape relationship in the dynamic specifications. Specifically, using an appropriate fixed effects model validates the EKC hypothesis finding an inverted U-shaped curve with high within-the-sample turning points. The random coefficients method applied does not support the EKC hypothesis in all possible specifications while the orthogonal deviations GMM estimates indicate the presence of an inverted U-shape relationship in all cases with lower cases within-the-sample turning points. A slow adjustment rate is found in all dynamic specifications indicating the need of around four time periods for a country to adjust to the LR equilibrium level of forest recovery.

Using remote sensing technology to study the distribution and change of surface water is an important application of remote sensing technology. It is also an important means of water resources protection. This paper takes the Lijiang River Basin in Guilin, Guangxi as the research object. Landsat satellite images were used as the data source. After classifying the images, the surface water distribution area of Lijiang River Basin in Guilin City was extracted, and the area change and its spatial distribution are compared. On this basis, combined with the actual situation in Guilin, the paper analyzes the causes of surface water distribution change in Lijiang river basin from two aspects of natural factors and human factors.

BACKGROUND AND OBJECTIVES: To quantitatively evaluate diabetic retinopathy (DR) lesions using the authors' validated machine learning algorithms and provide physicians with an automated and precise method to follow the progression of DR and outcome of interventions. PATIENTS AND METHODS: Retrospective analyses were conducted of 3,496 color fundus photography images from 19 patients with clinically significant diabetic macular edema receiving conbercept treatment. The modified seven-field fundus images were obtained at baseline and at the third, sixth, and twelfth month visit, whereas the modified two-field fundus images were obtained at the other monthly visits. The area of intraretinal hemorrhage and hard exudate lesions was traced by the authors' validated algorithms. RESULTS: The mean central foveal thickness at baseline was 459.9 μm ± 127.5 μm. Mean central foveal thickness was 316.5 μm ± 53.0 μm at the twelfth month visit, which decreased by 143.4 μm when compared with the baseline optical coherence tomography. The mean total area of intraretinal hemorrhage in the study eye in seven fields was 5.656 ± 1.176 mm 2 at baseline, 2.438 ± 0.976 mm 2 at the third month, 2.901 ± 0.521 mm 2 at the sixth month, and 2.122 ± 0.582 mm 2 at the end of the study. The area of intraretinal hemorrhage was reduced by 62.49% from baseline to the end of study ( P < .0001). The mean total area of hard exudates in the study eye was 2.549 ± 0.776 mm 2 at baseline, 2.233 ± 0.576 mm 2 at the third month, 2.710 ± 0.621 mm 2 at the sixth month, and 1.473 ± 0.564 mm 2 at the end of the study. The mean total area of hard exudates decreased by 41.1% at the twelfth month ( P < .0001) compared with the first visit. Significant decrease was observed in the area of intraretinal hemorrhage during conbercept treatment. The hard exudates area fluctuated during loading then subsequently decreased at the twelfth month. CONCLUSIONS: The present study quantitatively analyzed the change in the area change of intraretinal hemorrhage and hard exudate lesions during the course of conbercept treatment. The automated system is promising to be a precise and objective method for monitoring the progression of DR and outcomes of interventions in clinical settings. [ Ophthalmic Surg Lasers Imaging Retina. 2020;51:95–100.]

During pregnancy the maternal heart undergoes significant physiological change. Technological advancements in echocardiography (echo) have improved our ability to assess the right heart in detail and yet there is little research into adaptation during pregnancy. In this pilot study, we considered how three measures of right heart function changed in normal women from the 1st trimester through to the post-partum period. We observed a significant increase in tricuspid annulus planar systolic excursion (TAPSE) and right ventricular systolic velocity (RV S’) from the 1st to the 2nd trimester; both measures of longitudinal right ventricular function. There was no significant difference in right ventricular systolic area change, which is more difficult to accurately measure, and reflects radial function. TAPSE and RV S’ are easy to accurately measure with modern echo technology. This pilot study suggests that any reduction in these values from the 1st to the 2nd trimester should prompt more detailed assessment, and correlation with clinical symptoms. It would be valuable to undertake a comprehensive study to define normal ranges for common measures of right ventricular function, using echo, during pregnancy. The ability to assess the right heart, with an understanding of expected normal values, has the potential to significantly improve our understanding and management of maternal cardiovascular disease.

Based on the revised First Chinese Glacier Inventory (FCGI), the Second Chinese Glacier Inventory (SCGI) and Landsat OLI images for 2015–2016, we analyzed the spatial-temporal variation characteristics of glaciers in the Gangdise Mountains from 1970 to 2016. The results showed that there were 3953 glaciers with a total area of 1306.45 km2 and ice volume of ~58.16 km3 in the Gangdise Mountains in 2015–2016. Glaciers with sizes of 0.1–5 km2 and

The Yellow River delta (YRD) is regarded as one of the most rapid sedimentation deltas in the worldwide and the youngest land in China. Existing studies more focused on evolutions of river mouth region, thus provided limited knowledge on the evolution of the entire YRD and its corresponding trajectories of shrinkage and expansion. Here, we used 1984–2018 Landsat images and the change detection analysis algorithm to track annual area change trajectories of present YRD with the help of Google Earth Engine cloud platform. Results showed that entire YRD area documented a significantly shrinking trend with slope of –18.5 km2/decade ( p p p

This study measures the acoustic power loss that occurs when an acoustic wave passes through a tube with an abrupt change in area. It is determined that the power loss is proportional to the third power of the velocity amplitude, and that the proportionality coefficient depends upon the area change ratio of the tube. On the other hand, the proportionality coefficient is almost independent of the acoustic impedance and frequency in the 80-250 Hz range. Furthermore, the effect of a tapered tube in reducing the coefficient is experimentally investigated. Based on these experimental results, an empirical estimation method for the acoustic power loss is proposed and validated using a high-pressure-helium-filled tube.