Molecular Dynamics Simulation to Investigate the Rake Angle Effects on Nanometric Cutting of Single Crystal Ni3Al

Rui-cheng Feng,Yong-nian Qi,Zong-xiao Zhu,Wen-yuan Song,Hai-yan Li,Mao-mao Wang,Zhi-yuan Rui,Feng-shou Gu 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.21 No.4

Molecular dynamics, an eff ective method to gain an insight into nanometric behaviour of materials, was employed to studythe nano-cutting behaviour of single crystal Ni 3 Al in nanometric scale. In this paper, comparisons were made for compressive/tensile stress, subsurface damage and surface roughness with three rake angles of a diamond tool. Subsurface damage waspartitioned by region and studied with work hardening in detail. A model for precise characterization of surface roughnesswas established with consideration of local surface fl uctuation. Simulation results showed that the chip thickness increasedas rake angle changed from negative to positive, and the boundary formed between tensile and compressive stress was inconsistent with the glide direction of stacking fault. Subsurface damage decreased as the increase of rake angle, and regularglide planes of stacking faults were found in front of the cutting tool. Further, the pinned dissociated 1/2 < 110 > superpartialdislocation with anti-phase boundary was demonstrated. The model was tested and characterized by implanted pits onperfect surface. Results showed that surface roughness can be well characterized, and an evident discrepancy was observedamong three rake angles, especially for 30° rake angle, which showed an distinct smooth surface compared with the others.

The Influence of Vegetation Variation on Northeast Asian Dust Activity

Rui Mao,허창회,Song Feng,Dao-Yi Gong,Yaping Shao 한국기상학회 2013 Asia-Pacific Journal of Atmospheric Sciences Vol.49 No.1

In this study, we investigate the influence of vegetation variations on dust activity (dust load, dust transport in the troposphere,and dust weather frequency) over Northeast Asia during springtime. By using the Integrated Wind Erosion Modeling System,two model experiments are run over four-month periods, from February 1 to May 31, for each year from 1982 to 2006; one experiment uses the observed atmospheric conditions and vegetation (OBS), and the other uses the specified atmospheric conditions in 2006 and the observed vegetation (CTRL). Comparison of the two model experiments reveals that there are sensitive regions in southeastern Mongolia and central northern China, in which vegetation has a large potential to influence dust activity due to both the high dust emission rate and large variations in vegetation coverage. Over these sensitive regions,vegetation effectively lessens dust loads on interannual and interdecadal timescales; dust load is decreased by 2864 μg m−2 for an increment of 0.1 in the normalized difference vegetation index (NDVI). Vegetation increase in the sensitive areas also reduces two major branches of dust transports in the low troposphere; one stretches from eastern Mongolia to regions northeastward, and the other flows across the south of northeastern China to Korea. In addition to dust loads and transports, vegetation increase in the sensitive areas evidently decreases dust storm frequency and blowing dust frequency, but it exerts a weak influence on the floating dust frequency. In the sensitive regions, as NDVI increases by 0.1, dust storms, blowing dust,and floating dust decrease by 4.0 days/spring, 1.5 days/spring, and 0.2 days/spring, respectively. In summary, vegetation variations in southeastern Mongolia and central northern China have considerable impact on northeast Asian dust during springtime.

Two Typical Synoptic‑Scale Weather Patterns of Dust Events over the Tibetan Plateau

Xingya Feng,Rui Mao,Dao‑Yi Gong,Guangjian Wu,Cuicui Shi,Guohao Liang,Yufei Wang 한국기상학회 2023 Asia-Pacific Journal of Atmospheric Sciences Vol.59 No.4

Synoptic-scale weather systems play dominant roles in inducing high tropospheric dust over the Tibetan Plateau (TP). However, few studies have summarized the typical synoptic-scale weather patterns when high tropospheric dust occursover the TP, as well as the difference between the distribution and transport methods of dust under weather patterns. Basedon dust optical depth (DOD) from remote sensing data and reanalysis data during 2000 to 2019, two typical synoptic-scaleweather patterns (T1 and T2) in the middle troposphere in association with high DOD in spring over the TP were obtainedby using the self-organizing map (SOM) clustering method. The results show that the T1 features a deep trough over theAltai Mountains and the westerly wind increases over the TP. As a result, dust is transported from the Taklimakan Desertand Qaidam Basin to the upper troposphere and extends to the TP and northern China. T2 shows a low-pressure system overthe western TP and decreased westerly winds over the TP, resulting in dust from the Taklimakan Desert, Qaidam Basin, andwestern TP to downstream areas. T1 (T2) contributes more to DOD over the eastern (western) TP. Therefore, we believe thata small increase (decrease) in DOD in the western (eastern) part of the TP from 2000 to 2019 may be related to an increase(decrease) in the occurrence of the T2 (T1). This work may provide a new possibility for projecting dust transport and itsinfluence on tropospheric dust over the TP.

Changes in Dust Activity in Spring over East Asia under a Global Warming Scenario

Qi Zong,Rui Mao,Dao-Yi Gong,Chenglai Wu,Bing Pu,Xingya Feng,Yijie Sun 한국기상학회 2021 Asia-Pacific Journal of Atmospheric Sciences Vol.57 No.4

Dust activity not only influences human health through dust storms but also affects climate at local and regional scales through the direct effects of dust aerosols on both solar and longwave radiative heating. In this study, based on dust simulations from seven Coupled Model Intercomparison Project Phase 5 (CMIP5) models, the spatial and temporal changes in dust activity over East Asia under a Representative Concentration Pathway 8.5 global warming scenario were examined for the periods of 2016– 2035 (P1), 2046–2065 (P2) and 2080–2099 (P3). The results show that the multimodel ensemble mean (MME) of the CMIP5 models largely captures the spatial distribution of dust emissions and dust optical depth (DOD) over East Asia during 1986–2005 (P0). The MME reproduces the increasing trend in dust emissions and DOD over dust sources in East Asia during P0. Accompanying emission reductions during P1 to P3, the DOD simultaneously decreases, and the evident DOD decline can also be found over downwind areas in eastern China and the Korean Peninsula. Simulations project increases in precipitation and the LAI (leaf area index). Simultaneously, the weakened East Asian trough leads to anomalous southerly winds and lower wind speeds at the surface. All these results indicate unfavorable conditions for dust emissions over the sources regions, resulting in a decreased DOD over East Asia during P1 to P3.

Does the recent warming hiatus exist over Northern Asia for winter wind chill temperature?

Ma, Ying,Mao, Rui,Feng, Sheng‐,Hui,Gong, Dao‐,Yi,Kim, Seong‐,Joong John Wiley Sons, Ltd 2017 International journal of climatology Vol.37 No.7

<P><B>ABSTRACT</B></P><P>Wind chill temperature (WCT) describes the joint effect of wind velocity and air temperature on exposed body skin and could support policymakers in designing plans to reduce the risks of notably cold and windy weather. This study examined winter WCT over Northern Asia during 1973–2013 by analysing <I>in situ</I> station data. The winter WCT warming rate over the Tibetan Plateau (TP) slowed during 1999–2013 (−0.04 °C decade<SUP>−1</SUP>) compared with that of during 1973–1998 (0.67 °C decade<SUP>−1</SUP>). The winter WCT warming hiatus has also been observed in the remainder of Northern Asia with trends of 1.11 °C decade<SUP>−1</SUP> during 1973–1998 but −1.02 °C decade<SUP>−1</SUP> during 1999–2013, except for the Far East (FE) of Russia, where the winter WCT has continued to heat up during both the earlier period of 1973–1998 (0.54 °C decade<SUP>−1</SUP>) and the recent period of 1999–2013 (0.75 °C decade<SUP>−1</SUP>). The results indicate that the influence of temperature on winter WCT is greater than that of wind speed over Northern Asia. Atmospheric circulation changes associated with air temperature and wind speed were analysed to identify the causes for the warming hiatus of winter WCT over Northern Asia. The distributions of sea‐level pressure and 500‐hPa height anomalies during 1999–2013 transported cold air from the high latitudes to middle latitudes, resulting in low air temperature over Northern Asia except for the FE of Russia. Over the TP, the increase in wind speed offset the increase in air temperature during 1999–2013. For the FE, the southerly wind from the Western Pacific drove the temperature up during the 1999–2013 period through warm advection.</P>

Risk factors associated with impaired ovarian reserve in young women of reproductive age with Crohn’s disease

( Yue Zhao ),( Baili Chen ),( Yao He ),( Shenghong Zhang ),( Yun Qiu ),( Rui Feng ),( Hongsheng Yang ),( Zhirong Zeng ),( Shomron Ben-horin ),( Minhu Chen ),( Ren Mao ) 대한장연구학회 2020 Intestinal Research Vol.18 No.2

Background/Aims: Crohn’s disease (CD) primarily affects young female adults of reproductive age. Few studies have been conducted on this population’s ovarian reserve status. The aim of study was to investigate potential risk factors associated with low ovarian reserve, as reflected by serum anti-Müllerian hormone (AMH) in women of reproductive age with CD. Methods: This was a case-control study. Cases included 87 patients with established CD, and healthy controls were matched by age, height and weight in a 1:1 ratio. Serum AMH levels were measured by enzyme-linked immunosorbent assay. Results: The average serum AMH level was significantly lower in CD patients than in control group (2.47±2.08 ng/mL vs. 3.87±1.96 ng/mL, respectively, P<0.001). Serum AMH levels were comparable between CD patients and control group under 25 years of age (4.41±1.52 ng/mL vs. 3.49±2.10 ng/mL, P=0.06), however, serum AMH levels were significantly lower in CD patients over 25 years of age compared to control group (P<0.05). Multivariable analysis showed that an age greater than 25 (odds ratio [OR], 10.03; 95% confidence interval [CI], 1.90-52.93, P=0.007), active disease state (OR, 27.99; 95% CI, 6.13-127.95, P<0.001) and thalidomide use (OR, 15.66; 95% CI, 2.22-110.65, P=0.006) were independent risk factors associated with low ovarian reserve (serum AMH levels <2 ng/mL) in CD patients. Conclusions: Ovarian reserve is impaired in young women of reproductive age with CD. Age over 25 and an active disease state were both independently associated with low ovarian reserve. Thalidomide use could result in impaired ovarian reserve. (Intest Res 2020; 18:200-209)

Gut Microbiota Community and Its Assembly Associated with Age and Diet in Chinese Centenarians

( Fang Wang ),( Ting Yu ),( Guo Hong Huang ),( Da Cai ),( Xiaolin Liang ),( Hai Yan Su ),( Zhenjun Zhu ),( Danlei Li ),( Yang Yang ),( Pei Hong Shen ),( Rui Feng Mao ),( Lian Yu ),( Mou Ming Zhao ),( 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.8

Increasing evidence suggests that gut microbiota underpin the development of health and longevity. However, our understanding of what influences the composition of this community of the longevous has not been adequately described. Therefore, illumina sequencing analysis was performed on the gut microbiota of centenarians (aged 100-108 years; RC) and younger elderlies (aged 85-99 years; RE) living in Bama County, Guangxi, China and the elderlies (aged 80-92 years; CE) living in Nanning City, Guangxi, China. In addition, their diet was monitored using a semiquantitative dietary questionary (FFQ 23). The results revealed the abundance of Roseburia and Escherichia was significantly greater, whereas that of Lactobacillus, Faecalibacterium, Parabacteroides, Butyricimonas, Coprococcus, Megamonas, Mitsuokella, Sutterella, and Akkermansia was significantly less in centenarians at the genus level. Both clustering analysis and UniFraq distance analysis showed structural segregation with age and diet among the three populations. Using partial least square discriminate analysis and redundancy analysis, we identified 33 and 34 operational taxonomic units (OTUs) as key OTUs that were significantly associated with age and diet, respectively. Age-related OTUs were characterized as Ruminococcaceae, Clostridiaceae, and Lachnospiraceae, and the former two were increased in the centenarians; diet-related OTUs were classified as Bacteroidales, Lachnospiraceae, and Ruminococcaceae. The former two were deceased, whereas the later one was increased, in the high-fiber diet. The age and high-fiber diet were concomitant with changes in the gut microbiota of centenarians, suggesting that age and high-fiber diet can establish a new structurally balanced architecture of gut microbiota that may benefit the health of centenarians.