Aging is characterized by a progressive deterioration of physiological integrity,leading to impaired functional ability and ultimately increased susceptibility to death.It is a major risk factor for chronic human dise...Aging is characterized by a progressive deterioration of physiological integrity,leading to impaired functional ability and ultimately increased susceptibility to death.It is a major risk factor for chronic human diseases,including cardiovascular disease,diabetes,neurological degeneration,and cancer.Therefore,the growing emphasis on “healthy aging” raises a series of important questions in life and social sciences.In recent years,there has been unprecedented progress in aging research,particularly the discovery that the rate of aging is at least partly controlled by evolutionarily conserved genetic pathways and biological processes.In an attempt to bring full-fledged understanding to both the aging process and age-associated diseases,we review the descriptive,conceptual,and interventive aspects of the landscape of aging composed of a number of layers at the cellular,tissue,organ,organ system,and organismal levels.展开更多
SIRT7,a sirtuin family member implicated in aging and disease,is a regulator of metabolism and stress responses.It remains elusive how human somatic stem cell populations might be impacted by SIRT7.Here,we found that ...SIRT7,a sirtuin family member implicated in aging and disease,is a regulator of metabolism and stress responses.It remains elusive how human somatic stem cell populations might be impacted by SIRT7.Here,we found that SIRT7 expression declines during human mesenchymal stem cell(hMSC)aging and that SIRT7 deficiency accelerates senescence.Mechanistically,SIRT7 forms a complex with nuclear lamina proteins and heterochromatin proteins,thus maintaining the repressive state of heterochromatin at nuclear periphery.Accordingly,deficiency of SIRT7 results in loss of heterochromatin,derepression of the LINE1 retrotransposon(LINE1),and activation of innate immune signaling via the cGAS-STING pathway.These agingassociated cellular defects were reversed by overexpression of heterochromatin proteins or treatment with a LINE1 targeted reverse-transcriptase inhibitor.Together,these findings highlight how SIRT7 safeguards chromatin architecture to control innate immune regulation and ensure geroprotection during stem cell aging.展开更多
progeria syndrome （HGPS） and Wemer syndrome （WS） are two of the best characterized human progeroid syndromes. HGPS is caused by a point mutation in lamin A （LMNA） gene, resulting in the production of a truncated...progeria syndrome （HGPS） and Wemer syndrome （WS） are two of the best characterized human progeroid syndromes. HGPS is caused by a point mutation in lamin A （LMNA） gene, resulting in the production of a truncated protein product-progerin. WS is caused by mutations in 14/RN gem）, encoding a loss-of-function RecQ DNA helicase. Here, by gene editing we created isogenic human embryonic stem cells （ESCs） with heterozygous （G608G/＋） or homozygous （G608G/G608G） LMNA mutation and biallelic WRN knockout, for modeling HGPS and WS pathogenesis, respectively. While ESCs and endothelial cells （ECs） did not present any features of premature senescence, HGPS- and WS-mesenchymal stem cells （MSCs） showed aging-associated phenotypes with different kinetics. WS-MSCs had early-onset mild premature aging phenotypes while HGPS-MSCs exhibited iate-onset acute premature aging characterisitcs. Taken together, our study compares and contrasts the distinct pathologies underpinning the two premature aging disorders, and provides reliable stem-cell based models to identify new therapeutic strategies for pathological and physiological aging.展开更多
Aging increases the risk of various diseases. The main goal of aging research is to find therapies that attenuate aging and alleviate aging-related diseases. In this study, we screened a natural product library for ge...Aging increases the risk of various diseases. The main goal of aging research is to find therapies that attenuate aging and alleviate aging-related diseases. In this study, we screened a natural product library for geroprotective compounds using Werner syndrome (WS) human mesenchymal stem cells (hMSCs), a premature aging model that we recently established. Ten candidate compounds were identified and quercetin was investigated in detail due to its leading effects. Mechanistic studies revealed that quercetin alleviated senescence via the enhancement of cell proliferation and restoration of heterochromatin architecture in WS hMSCs. RNA-sequencing analysis revealed the transcriptional commonalities and differences in the geroprotective effects by quercetin and Vitamin C. Besides WS hMSCs, quercetin also attenuated cellular senescence in Hutchinson-Gilford progeria syndrome (HGPS) and physiological-aging hMSCs. Taken together, our study identifies quercetin as a geroprotective agent against accelerated and natural aging in hMSCs, providing a potential therapeutic intervention for treating age-associated disorders.展开更多
Vascular cell functionality is critical to blood vessel homeostasis. Constitutive NF-κB activation in vascular cells results in chronic vascular inflammation, leading to various cardiovascular diseases. However, how ...Vascular cell functionality is critical to blood vessel homeostasis. Constitutive NF-κB activation in vascular cells results in chronic vascular inflammation, leading to various cardiovascular diseases. However, how NF-κB regulates human blood vessel homeostasis remains largely elusive. Here, using CRISPR/Cas9-mediated gene editing, we generated RelA knockout human embryonic stem cells （hESCs） and differentiated them into various vascular cell derivatives to study how NF- KS modulates human vascular cells under basal and inflammatory conditions. Multi-dimensional phenotypic assessments and transcriptomic analyses revealed that RelA deficiency affected vascular cells via modulatinginflammation, survival, vasculogenesis, cell differentia- tion and extracellular matrix organization in a cell type- specific manner under basal condition, and that RelA protected vascular cells against apoptosis and modu- lated vascular inflammatory response upon tumor necrosis factor a （TNFa） stimulation. Lastly, further evaluation of gene expression patterns in IKBo knockout vascular cells demonstrated that IKBa acted largely independent of RelA signaling. Taken together, our data reveal a protective role of NF-κB/ReiA in modulating human blood vessel homeostasis and map the human vascular transcriptomic landscapes for the discovery of novel therapeutic targets.展开更多
RAP1 is a well-known telomere-binding protein, but its functions in human stem cells have remained unclea匚 Here we generated RAP1 -deficient human embryonic stem cells (hESCs) by using CRISPR/Cas9 technique and obtai...RAP1 is a well-known telomere-binding protein, but its functions in human stem cells have remained unclea匚 Here we generated RAP1 -deficient human embryonic stem cells (hESCs) by using CRISPR/Cas9 technique and obtained RAP1-deficient human mesenchymal stem cells (hMSCs) and neural stem cells (hNSCs) via directed differentiation. In both hMSCs and hNSCs, RAP1 not only negatively regulated telomere length but also acted as a transcriptional regulator of RELN by tuning the methylation status of its gene promoter. RAP1 deficiency enhanced self-renewal and delayed senescence in hMSCs, but not in hNSCs, suggesting complicated lineage-specific effects of RAP1 in adult stem cells.Altogether, these results demonstrate for the first time that RAP1 plays both telomeric and nontelomeric roles in regulating human stem cell homeostasis.展开更多
Dear Editor, The retina is a light-sensitive highly-organized tissue,which is vulnerable to aging and age-related retinal diseases.Specifically,progressive retinal degeneration leads to visual function deterioration a...Dear Editor, The retina is a light-sensitive highly-organized tissue,which is vulnerable to aging and age-related retinal diseases.Specifically,progressive retinal degeneration leads to visual function deterioration and vision impairment in the elderly(Lin et al.,2016).In diseases such as age-related macular degeneration(AMD),retinitis pigmentosa(RP)and diabetic retinopathy(DR),pathological process lacking effective treatments profoundly and negatively impact on the quality of life in the elderly(Lin et al.,2016;Chen et al.,2019).Thus,an in-depth molecular assessment of the mechanisms driv-ing retinal aging is of urgent scientific and medical importance.展开更多
Dear Editor,Myocardial infarction(MI)is the irreversible cardiomyocyte death resulting from prolonged oxygen deprivation due to obstructed blood supply(ischemia),leading to contractile dysfunction and cardiac remodeli...Dear Editor,Myocardial infarction(MI)is the irreversible cardiomyocyte death resulting from prolonged oxygen deprivation due to obstructed blood supply(ischemia),leading to contractile dysfunction and cardiac remodeling.In recent decades,stem cell transplantation has been extensively investigated for the repair of injured heart in animal studies and clinical trials(Kanelidis et al.,2017;Gyongyosi et al.,2018).展开更多
As an important non-ferrous metal structural material most used in industry and production,aluminum(Al) alloy shows its great value in the national economy and industrial manufacturing.How to classify Al alloy rapidly...As an important non-ferrous metal structural material most used in industry and production,aluminum(Al) alloy shows its great value in the national economy and industrial manufacturing.How to classify Al alloy rapidly and accurately is a significant, popular and meaningful task.Classification methods based on laser-induced breakdown spectroscopy(LIBS) have been reported in recent years. Although LIBS is an advanced detection technology, it is necessary to combine it with some algorithm to reach the goal of rapid and accurate classification. As an important machine learning method, the random forest(RF) algorithm plays a great role in pattern recognition and material classification. This paper introduces a rapid classification method of Al alloy based on LIBS and the RF algorithm. The results show that the best accuracy that can be reached using this method to classify Al alloy samples is 98.59%, the average of which is 98.45%. It also reveals through the relationship laws that the accuracy varies with the number of trees in the RF and the size of the training sample set in the RF. According to the laws, researchers can find out the optimized parameters in the RF algorithm in order to achieve,as expected, a good result. These results prove that LIBS with the RF algorithm can exactly classify Al alloy effectively, precisely and rapidly with high accuracy, which obviously has significant practical value.展开更多
Room air conditioners (RACs) are crucial household appliances that consume substantial amounts of electricity. Their efficiency tends to deteriorate over time, resulting in unnecessary energy wastage. Smart meters hav...Room air conditioners (RACs) are crucial household appliances that consume substantial amounts of electricity. Their efficiency tends to deteriorate over time, resulting in unnecessary energy wastage. Smart meters have become popular to monitor electricity use of home appliances, offering underexplored opportunities to evaluate RAC operational efficiency. Traditional supervised data-driven analysis methods necessitate a large sample size of RACs and their efficiency, which can be challenging to acquire. Additionally, the prevalence of zero values when RACs are off can skew training. To overcome these challenges, we assembled a dataset comprising a limited number of window-type RACs with measured operational efficiencies from 2021. We devised an intuitive zero filter and resampling protocol to process smart meter data and increase training samples. A deep learning-based encoder–decoder model was developed to evaluate RAC efficiency. Our findings suggest that our protocol and model accurately classify and regress RAC operational efficiency. We verified the usefulness of our approach by evaluating the RACs replaced in 2022 using 2022 smart meter data. Our case study demonstrates that repairing or replacing an inefficient RAC can save electricity by up to 17 %. Overall, our study offers a potential energy conservation solution by leveraging smart meters for regularly assessing RAC operational efficiency and facilitating smart preventive maintenance.展开更多
The melting process of solid-liquid phase change materials(PCM)has a significant impact on their energy storage performance.To more effectively apply solid-liquid PCM for energy storage,it is crucial to study the regu...The melting process of solid-liquid phase change materials(PCM)has a significant impact on their energy storage performance.To more effectively apply solid-liquid PCM for energy storage,it is crucial to study the regulation of melting process of solid-liquid PCM,which is numerically investigated based on double multiple relaxation time lattice Boltzmann method(MRT-LBM)in this work.In this work we pay more attention to the effects of different Stefan numbers(Ste)and Rayleigh numbers(Ra)on the melting process.The results indicate that the PCM melting is greatly influenced by the Ste number and Ra number,which can be divided into the heat conduction dominant stage and the convection dominant stage,according to the onset time of convection Fo_(C).In order to describe the contribution of the heat conduction dominant stage to the whole melting process quantitatively,we firstly propose the ratio of the heat conduction dominant stage R_(pc),which can be defined as the ratio of Fo_(C)to the complete melting time Fo_(M).R_(pc)gradually decreases as the Ra number increases,and when the Ste number rises:R_(pc)=90.0%when Ste=1.0 and Ra=1×10^(5),R_(pc)=39.6%when Ste=0.1 and Ra=1×10^(5),and R_(pc)=14.0%when Ste=1.0 and Ra=1×10~7.A regime map about the effects of different Ste numbers and Ra numbers on R_(pc)has been further summarized.The discovered findings would be helpful in regulating melting process in the energy storage of solid-liquid PCM.展开更多
基金supported by the National Natural Science Foundation of China(31871380,32000500,32070730,32170756,32170804,81330008,81671377,81725010,81725010,81872874,81921006,81922027,81971312,81991512,82030041,82103167,82122024,82125009,82125011,82130044,91749126,91949101,91949207,92049302)the National Key Research and Development Program of China(2017YFA0506400,2018YFA0800200,2018YFA0800700,2018YFA0900200,2018YFC2000100,2018YFC2000400,2018YFE-0203700,20192ACB70002,2019YFA0802202,2020YFA0113400,2020YFA0803401,2020YFA0804000,2020YFC2002800,2020YFC-2002900,2021ZD0202401)+11 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA16010100,XDA16010603,XDA16020400,XDB29020000,XDB39000000,XDB39000000,XDB39030300)the China Association for Science and Technology(2021QNRC001)the Beijing Municipal Science and Technology Commission(Z200022)the Natural Science Foundation of Shanghai(21JC1406400)the Key Programs of the Jiangxi ProvinceChina(20192ACB70002)the“Shu Guang”Project supported by the Shanghai Municipal Education Commission and Shanghai Education Development Foundation(19SG18)the Shanghai Sailing Program(22YF1434300)the Research Project of Joint Laboratory of University of Science and Technology of China and Anhui Mental Health Center(2019LH03)the Fundamental Research Funds for the Central Universities(WK2070210004)the Young Elite Scientists Sponsorship Program by China Association for Science and Technology(YESS20210002)the Youth Innovation Promotion Association of Chinese Academy of Sciences(2022083)。
文摘Aging is characterized by a progressive deterioration of physiological integrity,leading to impaired functional ability and ultimately increased susceptibility to death.It is a major risk factor for chronic human diseases,including cardiovascular disease,diabetes,neurological degeneration,and cancer.Therefore,the growing emphasis on “healthy aging” raises a series of important questions in life and social sciences.In recent years,there has been unprecedented progress in aging research,particularly the discovery that the rate of aging is at least partly controlled by evolutionarily conserved genetic pathways and biological processes.In an attempt to bring full-fledged understanding to both the aging process and age-associated diseases,we review the descriptive,conceptual,and interventive aspects of the landscape of aging composed of a number of layers at the cellular,tissue,organ,organ system,and organismal levels.
文摘SIRT7,a sirtuin family member implicated in aging and disease,is a regulator of metabolism and stress responses.It remains elusive how human somatic stem cell populations might be impacted by SIRT7.Here,we found that SIRT7 expression declines during human mesenchymal stem cell(hMSC)aging and that SIRT7 deficiency accelerates senescence.Mechanistically,SIRT7 forms a complex with nuclear lamina proteins and heterochromatin proteins,thus maintaining the repressive state of heterochromatin at nuclear periphery.Accordingly,deficiency of SIRT7 results in loss of heterochromatin,derepression of the LINE1 retrotransposon(LINE1),and activation of innate immune signaling via the cGAS-STING pathway.These agingassociated cellular defects were reversed by overexpression of heterochromatin proteins or treatment with a LINE1 targeted reverse-transcriptase inhibitor.Together,these findings highlight how SIRT7 safeguards chromatin architecture to control innate immune regulation and ensure geroprotection during stem cell aging.
文摘progeria syndrome （HGPS） and Wemer syndrome （WS） are two of the best characterized human progeroid syndromes. HGPS is caused by a point mutation in lamin A （LMNA） gene, resulting in the production of a truncated protein product-progerin. WS is caused by mutations in 14/RN gem）, encoding a loss-of-function RecQ DNA helicase. Here, by gene editing we created isogenic human embryonic stem cells （ESCs） with heterozygous （G608G/＋） or homozygous （G608G/G608G） LMNA mutation and biallelic WRN knockout, for modeling HGPS and WS pathogenesis, respectively. While ESCs and endothelial cells （ECs） did not present any features of premature senescence, HGPS- and WS-mesenchymal stem cells （MSCs） showed aging-associated phenotypes with different kinetics. WS-MSCs had early-onset mild premature aging phenotypes while HGPS-MSCs exhibited iate-onset acute premature aging characterisitcs. Taken together, our study compares and contrasts the distinct pathologies underpinning the two premature aging disorders, and provides reliable stem-cell based models to identify new therapeutic strategies for pathological and physiological aging.
基金supported by the National Key Research and Development Program of China(2017YFA0103304)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA16010100)+5 种基金the National Key Research and Development Program of China(2015CB964800,2017YFA0102802,2014CB910503 and 2018YFA0107203)the National High Tech no logy Research and Development Program of China(2015AA020307)the National Natural Science Foundation of China(Grant Nos.31671429,91749202,91749123,81625009,81330008,81371342,81471414,81422017,81601233,81671377,31601109,31601158,81771515 and 81701388)Program of Beijing Municipal Science and Technology Commission(Z151100003 915072)Key Research Program of the Chinese Academy of Sciences(KJZDEW-TZ-L05),Beijing Municipal Commission of Health and Family Planning(PXM2018_026283_000002)Advanced Innovation Center for Human Brain Protection(117212).
文摘Aging increases the risk of various diseases. The main goal of aging research is to find therapies that attenuate aging and alleviate aging-related diseases. In this study, we screened a natural product library for geroprotective compounds using Werner syndrome (WS) human mesenchymal stem cells (hMSCs), a premature aging model that we recently established. Ten candidate compounds were identified and quercetin was investigated in detail due to its leading effects. Mechanistic studies revealed that quercetin alleviated senescence via the enhancement of cell proliferation and restoration of heterochromatin architecture in WS hMSCs. RNA-sequencing analysis revealed the transcriptional commonalities and differences in the geroprotective effects by quercetin and Vitamin C. Besides WS hMSCs, quercetin also attenuated cellular senescence in Hutchinson-Gilford progeria syndrome (HGPS) and physiological-aging hMSCs. Taken together, our study identifies quercetin as a geroprotective agent against accelerated and natural aging in hMSCs, providing a potential therapeutic intervention for treating age-associated disorders.
文摘Vascular cell functionality is critical to blood vessel homeostasis. Constitutive NF-κB activation in vascular cells results in chronic vascular inflammation, leading to various cardiovascular diseases. However, how NF-κB regulates human blood vessel homeostasis remains largely elusive. Here, using CRISPR/Cas9-mediated gene editing, we generated RelA knockout human embryonic stem cells （hESCs） and differentiated them into various vascular cell derivatives to study how NF- KS modulates human vascular cells under basal and inflammatory conditions. Multi-dimensional phenotypic assessments and transcriptomic analyses revealed that RelA deficiency affected vascular cells via modulatinginflammation, survival, vasculogenesis, cell differentia- tion and extracellular matrix organization in a cell type- specific manner under basal condition, and that RelA protected vascular cells against apoptosis and modu- lated vascular inflammatory response upon tumor necrosis factor a （TNFa） stimulation. Lastly, further evaluation of gene expression patterns in IKBo knockout vascular cells demonstrated that IKBa acted largely independent of RelA signaling. Taken together, our data reveal a protective role of NF-κB/ReiA in modulating human blood vessel homeostasis and map the human vascular transcriptomic landscapes for the discovery of novel therapeutic targets.
基金This work was supported by the National Key Research and Development Program of China (2018YFA0107001)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDA16010100)+5 种基金the National Key Research and Development Program of China (2018YFC2000100,2018YFA0107203,2017YFA0103304,2017 YFA0102802,2015CB964800,2014CB910503)the National Natural Science Foundation of China (81625009,81330008,91749202, 91749123,31671429,81671377,81771515,31601109,31601158, 81701388,81422017,81601233,81471414,81870228,81822018, 81801399,31801010,81801370 and 81861168034)Program of Beijing Mun icipal Science and Technology Commission (Z151100003915072)Key Research Program of the Chinese Academy of Sciences (KJZDEWTZ-L05)Beijing Municipal Commission of Health and Family Planning (PXM2018_026283_ 000002)Advanced Innovation Center for Human Brain Protection (117212) and the State Key Laboratory of Membrane Biology.
文摘RAP1 is a well-known telomere-binding protein, but its functions in human stem cells have remained unclea匚 Here we generated RAP1 -deficient human embryonic stem cells (hESCs) by using CRISPR/Cas9 technique and obtained RAP1-deficient human mesenchymal stem cells (hMSCs) and neural stem cells (hNSCs) via directed differentiation. In both hMSCs and hNSCs, RAP1 not only negatively regulated telomere length but also acted as a transcriptional regulator of RELN by tuning the methylation status of its gene promoter. RAP1 deficiency enhanced self-renewal and delayed senescence in hMSCs, but not in hNSCs, suggesting complicated lineage-specific effects of RAP1 in adult stem cells.Altogether, these results demonstrate for the first time that RAP1 plays both telomeric and nontelomeric roles in regulating human stem cell homeostasis.
文摘Dear Editor, The retina is a light-sensitive highly-organized tissue,which is vulnerable to aging and age-related retinal diseases.Specifically,progressive retinal degeneration leads to visual function deterioration and vision impairment in the elderly(Lin et al.,2016).In diseases such as age-related macular degeneration(AMD),retinitis pigmentosa(RP)and diabetic retinopathy(DR),pathological process lacking effective treatments profoundly and negatively impact on the quality of life in the elderly(Lin et al.,2016;Chen et al.,2019).Thus,an in-depth molecular assessment of the mechanisms driv-ing retinal aging is of urgent scientific and medical importance.
文摘Dear Editor,Myocardial infarction(MI)is the irreversible cardiomyocyte death resulting from prolonged oxygen deprivation due to obstructed blood supply(ischemia),leading to contractile dysfunction and cardiac remodeling.In recent decades,stem cell transplantation has been extensively investigated for the repair of injured heart in animal studies and clinical trials(Kanelidis et al.,2017;Gyongyosi et al.,2018).
基金supported by National High Technology Research and Development Program of China (863 Program. No. 2013AA102402)
文摘As an important non-ferrous metal structural material most used in industry and production,aluminum(Al) alloy shows its great value in the national economy and industrial manufacturing.How to classify Al alloy rapidly and accurately is a significant, popular and meaningful task.Classification methods based on laser-induced breakdown spectroscopy(LIBS) have been reported in recent years. Although LIBS is an advanced detection technology, it is necessary to combine it with some algorithm to reach the goal of rapid and accurate classification. As an important machine learning method, the random forest(RF) algorithm plays a great role in pattern recognition and material classification. This paper introduces a rapid classification method of Al alloy based on LIBS and the RF algorithm. The results show that the best accuracy that can be reached using this method to classify Al alloy samples is 98.59%, the average of which is 98.45%. It also reveals through the relationship laws that the accuracy varies with the number of trees in the RF and the size of the training sample set in the RF. According to the laws, researchers can find out the optimized parameters in the RF algorithm in order to achieve,as expected, a good result. These results prove that LIBS with the RF algorithm can exactly classify Al alloy effectively, precisely and rapidly with high accuracy, which obviously has significant practical value.
基金supported by Sustainable Smart Campus as a Living Lab of Hong Kong University of Science and Technology and the Strategic Topics Grant from Hong Kong Research Grants Council(STG2/E-605/23-N).
文摘Room air conditioners (RACs) are crucial household appliances that consume substantial amounts of electricity. Their efficiency tends to deteriorate over time, resulting in unnecessary energy wastage. Smart meters have become popular to monitor electricity use of home appliances, offering underexplored opportunities to evaluate RAC operational efficiency. Traditional supervised data-driven analysis methods necessitate a large sample size of RACs and their efficiency, which can be challenging to acquire. Additionally, the prevalence of zero values when RACs are off can skew training. To overcome these challenges, we assembled a dataset comprising a limited number of window-type RACs with measured operational efficiencies from 2021. We devised an intuitive zero filter and resampling protocol to process smart meter data and increase training samples. A deep learning-based encoder–decoder model was developed to evaluate RAC efficiency. Our findings suggest that our protocol and model accurately classify and regress RAC operational efficiency. We verified the usefulness of our approach by evaluating the RACs replaced in 2022 using 2022 smart meter data. Our case study demonstrates that repairing or replacing an inefficient RAC can save electricity by up to 17 %. Overall, our study offers a potential energy conservation solution by leveraging smart meters for regularly assessing RAC operational efficiency and facilitating smart preventive maintenance.
基金financially supported by Natural Science Foundation of Heilongjiang Province(Grant No.ZD2021E002)。
文摘The melting process of solid-liquid phase change materials(PCM)has a significant impact on their energy storage performance.To more effectively apply solid-liquid PCM for energy storage,it is crucial to study the regulation of melting process of solid-liquid PCM,which is numerically investigated based on double multiple relaxation time lattice Boltzmann method(MRT-LBM)in this work.In this work we pay more attention to the effects of different Stefan numbers(Ste)and Rayleigh numbers(Ra)on the melting process.The results indicate that the PCM melting is greatly influenced by the Ste number and Ra number,which can be divided into the heat conduction dominant stage and the convection dominant stage,according to the onset time of convection Fo_(C).In order to describe the contribution of the heat conduction dominant stage to the whole melting process quantitatively,we firstly propose the ratio of the heat conduction dominant stage R_(pc),which can be defined as the ratio of Fo_(C)to the complete melting time Fo_(M).R_(pc)gradually decreases as the Ra number increases,and when the Ste number rises:R_(pc)=90.0%when Ste=1.0 and Ra=1×10^(5),R_(pc)=39.6%when Ste=0.1 and Ra=1×10^(5),and R_(pc)=14.0%when Ste=1.0 and Ra=1×10~7.A regime map about the effects of different Ste numbers and Ra numbers on R_(pc)has been further summarized.The discovered findings would be helpful in regulating melting process in the energy storage of solid-liquid PCM.
