In the period of the first twenty years after World War II the number of fires in Polish hard coal mines reached annually the value of several thousands of cases. About 80% of fires constituted spontaneous fires. Inve...In the period of the first twenty years after World War II the number of fires in Polish hard coal mines reached annually the value of several thousands of cases. About 80% of fires constituted spontaneous fires. Investigations into the development of new methods of fire hazard prediction and implementation of new methods and means of fire prevention as well as the introduction of prohibition concerning the use of products manufactured of combustible organic materials in underground mine workings re-duced considerably the hazard of underground fire rise. The worked out at the Central Mining Institute (GIG) new method of un-derground fire prediction allows the correct selection of fire prevention means. The introduction into common use of fire-resistant conveyor belts, the main factor giving rise to spontaneous fires, and methods of assessment of their fire resistance eliminated prac-tically the fire hazard. These activities contributed in an efficient way to the reduction of the number of underground fires to a sat-isfactory level.展开更多
The readers of the prose The music of this sphere are usually carded away by the singing of various animals in nature, and for this reason, this article is always regarded as an ode to nature. The vivid description of...The readers of the prose The music of this sphere are usually carded away by the singing of various animals in nature, and for this reason, this article is always regarded as an ode to nature. The vivid description of the natural world evokes modem human beings＇ longing for the bosom of nature.展开更多
Double diffusion convection in a cavity with a hot square obstacle inside is simulated using the lattice Boltzmann method. The results are presented for the Rayleigh numbers 104,105 and 106, the Lewis numbers 0.1, 2 a...Double diffusion convection in a cavity with a hot square obstacle inside is simulated using the lattice Boltzmann method. The results are presented for the Rayleigh numbers 104,105 and 106, the Lewis numbers 0.1, 2 and 10 and aspect ratio A(obstacle height/cavity height) of 0.2, 0.4 and 0.6 for a range of buoyancy number N = 0 to- 4 with the effect of opposing flow. The results indicate that for |N| b 1, the Nusselt and Sherwood numbers decrease as buoyancy ratio increases, while for |N| N 1, they increase with |N|. As the Lewis number increases, higher buoyancy ratio is required to overcome the thermal effects and the minimum value of the Nusselt and Sherwood numbers occur at higher buoyancy ratios. The increase in the Rayleigh or Lewis number results in the formation of the multi-cell flow in the enclosure and the vortices will vanish as |N| increases.展开更多
This paper divides the history of global trade since 1000AD into three periods using Rahl Prebisch＇s center-periphery pattern and summarizes the effects of resource trade on periphery economies during each period. Ho...This paper divides the history of global trade since 1000AD into three periods using Rahl Prebisch＇s center-periphery pattern and summarizes the effects of resource trade on periphery economies during each period. However, this paper argues that the resource curse paradox does not justify isolation between developing and developed countries. On the contrary, developing countries should be encouraged to integrate into the existing center-periphery pattern and achieve economic growth through resource trade. This paper supplements the existing literature＇s analysis of resource endowment＇s role in global trade and offers recommendations for resource-rich developing countries to avoid the resource curse, identify a viable path to development, and achieve sustainable development by harnessing natural resources more productively.展开更多
As a daily necessity and an important cash crop in China and many other countries, tea has received increasing attention. Using production concentration index model and in- dustry＇ s barycenter theory, we analyzed th...As a daily necessity and an important cash crop in China and many other countries, tea has received increasing attention. Using production concentration index model and in- dustry＇ s barycenter theory, we analyzed the spatio-temporal distribution of tea production and barycenter movement trajectory of tea plantations and production in China between 1986 and 2015. Driving forces of the movement were also analyzed. From 1986 to 2000, tea production in China＇s Mainland of grew slowly （by 210x103 t）. The continuous increase in tea yield per unit area was the primary contributor （more than 60%） to the growth in tea production during this period. Since China joined the World Trade Organization （WTO） in 2001, tea production has grown rapidly, by 1.59x106 t between 2001 and 2015. The increase in the tea plantations area is the main contributor. Over the last 30 years, the barycenters of tea production in China have moved westward from the Dongting Lake Plain to the eastern fringe of the Yun- nan-Guizhou Plateau. Guizhou, Guangxi, and Sichuan in southwestern China have gradually become regions of new concentrated tea plantations and main tea production provinces. Lower cost of land and labor in southwestern China are the main drivers of the westward movement of China＇s tea industry. In addition, supportive policies and the favorable natural geographical environment contribute to the westward movement of tea industry. Our research highlights the spatio-temporal variation of China＇s tea production in the last three decades. The result indicates importance to make appropriate policies to promote the development of tea industry in China.展开更多
A large number of sesquiterpene quinone/hydroquinone natural products including （＋）-ent-chromazonarol have been isolated and received great attention from the synthetic community. Herein, we report a nature-inspire...A large number of sesquiterpene quinone/hydroquinone natural products including （＋）-ent-chromazonarol have been isolated and received great attention from the synthetic community. Herein, we report a nature-inspired concise synthesis of （＋）-ent-chromazonarol in 4 steps from a readily available starting material. The synthesis relied on a Lewis acid mediated cy- clization which correctly installed two vicinal stereocenters in one step. This highly efficient synthetic route allows us to fur- ther prepare natural product congeners for further biological studies.展开更多
文摘In the period of the first twenty years after World War II the number of fires in Polish hard coal mines reached annually the value of several thousands of cases. About 80% of fires constituted spontaneous fires. Investigations into the development of new methods of fire hazard prediction and implementation of new methods and means of fire prevention as well as the introduction of prohibition concerning the use of products manufactured of combustible organic materials in underground mine workings re-duced considerably the hazard of underground fire rise. The worked out at the Central Mining Institute (GIG) new method of un-derground fire prediction allows the correct selection of fire prevention means. The introduction into common use of fire-resistant conveyor belts, the main factor giving rise to spontaneous fires, and methods of assessment of their fire resistance eliminated prac-tically the fire hazard. These activities contributed in an efficient way to the reduction of the number of underground fires to a sat-isfactory level.
文摘The readers of the prose The music of this sphere are usually carded away by the singing of various animals in nature, and for this reason, this article is always regarded as an ode to nature. The vivid description of the natural world evokes modem human beings＇ longing for the bosom of nature.
文摘Double diffusion convection in a cavity with a hot square obstacle inside is simulated using the lattice Boltzmann method. The results are presented for the Rayleigh numbers 104,105 and 106, the Lewis numbers 0.1, 2 and 10 and aspect ratio A(obstacle height/cavity height) of 0.2, 0.4 and 0.6 for a range of buoyancy number N = 0 to- 4 with the effect of opposing flow. The results indicate that for |N| b 1, the Nusselt and Sherwood numbers decrease as buoyancy ratio increases, while for |N| N 1, they increase with |N|. As the Lewis number increases, higher buoyancy ratio is required to overcome the thermal effects and the minimum value of the Nusselt and Sherwood numbers occur at higher buoyancy ratios. The increase in the Rayleigh or Lewis number results in the formation of the multi-cell flow in the enclosure and the vortices will vanish as |N| increases.
文摘This paper divides the history of global trade since 1000AD into three periods using Rahl Prebisch＇s center-periphery pattern and summarizes the effects of resource trade on periphery economies during each period. However, this paper argues that the resource curse paradox does not justify isolation between developing and developed countries. On the contrary, developing countries should be encouraged to integrate into the existing center-periphery pattern and achieve economic growth through resource trade. This paper supplements the existing literature＇s analysis of resource endowment＇s role in global trade and offers recommendations for resource-rich developing countries to avoid the resource curse, identify a viable path to development, and achieve sustainable development by harnessing natural resources more productively.
基金National Natural Science Foundation of China,No.41571162National Social Science Foundation of China,No.17ZDA061
文摘As a daily necessity and an important cash crop in China and many other countries, tea has received increasing attention. Using production concentration index model and in- dustry＇ s barycenter theory, we analyzed the spatio-temporal distribution of tea production and barycenter movement trajectory of tea plantations and production in China between 1986 and 2015. Driving forces of the movement were also analyzed. From 1986 to 2000, tea production in China＇s Mainland of grew slowly （by 210x103 t）. The continuous increase in tea yield per unit area was the primary contributor （more than 60%） to the growth in tea production during this period. Since China joined the World Trade Organization （WTO） in 2001, tea production has grown rapidly, by 1.59x106 t between 2001 and 2015. The increase in the tea plantations area is the main contributor. Over the last 30 years, the barycenters of tea production in China have moved westward from the Dongting Lake Plain to the eastern fringe of the Yun- nan-Guizhou Plateau. Guizhou, Guangxi, and Sichuan in southwestern China have gradually become regions of new concentrated tea plantations and main tea production provinces. Lower cost of land and labor in southwestern China are the main drivers of the westward movement of China＇s tea industry. In addition, supportive policies and the favorable natural geographical environment contribute to the westward movement of tea industry. Our research highlights the spatio-temporal variation of China＇s tea production in the last three decades. The result indicates importance to make appropriate policies to promote the development of tea industry in China.
文摘A large number of sesquiterpene quinone/hydroquinone natural products including （＋）-ent-chromazonarol have been isolated and received great attention from the synthetic community. Herein, we report a nature-inspired concise synthesis of （＋）-ent-chromazonarol in 4 steps from a readily available starting material. The synthesis relied on a Lewis acid mediated cy- clization which correctly installed two vicinal stereocenters in one step. This highly efficient synthetic route allows us to fur- ther prepare natural product congeners for further biological studies.
