对国内外阻燃剂研究现状进行可视化分析。利用Web of Science数据库,以flame retardant为主题词,检索了1990-2015年的文献作为数据基础,利用CiteSpace对阻燃剂相关研究进行知识图谱分析。欧洲国家、中国和美国是阻燃剂研究的活跃地区;...对国内外阻燃剂研究现状进行可视化分析。利用Web of Science数据库,以flame retardant为主题词,检索了1990-2015年的文献作为数据基础,利用CiteSpace对阻燃剂相关研究进行知识图谱分析。欧洲国家、中国和美国是阻燃剂研究的活跃地区;中国科学技术大学在阻燃剂相关研究领域机构中发文量居于首位。从关键词共现分析可知,纳米复合材料、聚丙烯、易燃性、聚合物等关键词的共现频次较高,热解、聚合物、磷、聚烯烃、聚丙烯等具有最高的中心性。从文献共被引分析可知,纳米复合阻燃材料、膨胀阻燃剂等是阻燃剂相关研究领域的研究重点。近些年国内外阻燃剂研究更倾向于多氯联苯、多溴二苯醚、聚烯烃、膨胀阻燃剂等方向。展开更多
AIM： To study the influence of high-frequency electric surgical knives on healing of abdominal incision. METHODS： Two hundred and forty white rats were divided into 10^0, 10^2, 10^5, and 10^8 groups and rat models o...AIM： To study the influence of high-frequency electric surgical knives on healing of abdominal incision. METHODS： Two hundred and forty white rats were divided into 10^0, 10^2, 10^5, and 10^8 groups and rat models of abdominal operation were induced by using electric surgical knives and common lancets respectively. Then they were respectively given hypodermic injections of normal saline and 0.2 mL quantitative mixture of Escherichia coil, Staphylococcus aureus and Pseudornonas aeruginosa at a concentration of 10^2, 10^5 and 10^8. On the basis of the animal experiment, 220 patients undergoing abdominal operations （above type Ⅱ） were randomly allocated into one of following three groups： electric knife （EK, 93 cases）, electro-coagulation （EC, 55 cases） and control （72 cases）. High-frequency electric surgical knives were used to dissect abdominal tissues and electro-coagulation for hemostasis in EK group. Common lancets and electro-coagulation were applied in EC group. Common lancets and tieing silk suture were used in the controls. RESULTS： In all the groups except group 10^0, infection rate of incisional wounds made by electric surgical knives were remarkably higher than that with common lancets. Furthermore, there were significant differences in groups 10^2, 10^5, and 10^8 （P 〈 0.05）, but not in group 10^0 （P 〉 0.05） between EK and EC groups. Clinical studies showed a delayed wound healing in 16 cases （17.20%） in EK, 11 cases （16.36%） in EC and 2 cases （2.86%）in the control groups. A significant difference between EK and the control groups （χ^2= 8.57, P 〈 0.01）, and between EC and the control groups （χ^2 = 5.66, P 〈 0.05） was observed, but not between EK and EC （χ^2= 0.017, P 〉 0.05）. CONCLUSION： High-frequency electric knives may remarkably delay abdominal incision healing. Its application should be minimized so as to reduce the possibility of postoperative complications.展开更多
This paper presents a new improved term frequency/inverse document frequency (TF-IDF) approach which uses confidence, support and characteristic words to enhance the recall and precision of text classification. Synony...This paper presents a new improved term frequency/inverse document frequency (TF-IDF) approach which uses confidence, support and characteristic words to enhance the recall and precision of text classification. Synonyms defined by a lexicon are processed in the improved TF-IDF approach. We detailedly discuss and analyze the relationship among confidence, recall and precision. The experiments based on science and technology gave promising results that the new TF-IDF approach improves the precision and recall of text classification compared with the conventional TF-IDF approach.展开更多
The 21st century Maritime Silk Road(MSR) proposed by China strongly promotes the maritime industry. In this paper, we use wind and ocean wave datasets from 1979 to 2014 to analyze the spatial and temporal distribution...The 21st century Maritime Silk Road(MSR) proposed by China strongly promotes the maritime industry. In this paper, we use wind and ocean wave datasets from 1979 to 2014 to analyze the spatial and temporal distributions of the wind speed, significant wave height(SWH), mean wave direction(MWD), and mean wave period(MWP) in the MSR. The analysis results indicate that the Luzon Strait and Gulf of Aden have the most obvious seasonal variations and that the central Indian Ocean is relatively stable. We analyzed the distributions of the maximum wind speed and SWH in the MSR over this 36-year period. The results show that the distribution of the monthly average frequency for SWH exceeds 4 m(huge waves) and that of the corresponding wind speed exceeds 13.9 ms^(-1)(high wind speed). The occurrence frequencies of huge waves and high winds in regions east of the Gulf of Aden are as high as 56% and 80%, respectively. We also assessed the wave and wind energies in different seasons. Based on our analyses, we propose a risk factor(RF) for determining navigation safety levels, based on the wind speed and SWH. We determine the spatial and temporal RF distributions for different seasons and analyze the corresponding impact on four major sea routes. Finally, we determine the spatial distribution of tropical cyclones from 2000 to 2015 and analyze the corresponding impact on the four sea routes. The analysis of the dynamic characteristics of the MSR provides references for ship navigation as well as ocean engineering.展开更多
The objective of the investigation was to study the application of ultrasound reactor technology (USRT) as a disin-fectant for reduction of fungi from sewage effluent. Fungi are carbon heterotrophs that require prefor...The objective of the investigation was to study the application of ultrasound reactor technology (USRT) as a disin-fectant for reduction of fungi from sewage effluent. Fungi are carbon heterotrophs that require preformed organic compounds as carbon sources. USRT is an attractive means to improve water quality because of the system simplicity and no production of toxic by-products. An ultrasound reactor produces strong cavitation in aqueous solution causing shock waves and reactive free radicals by the violent collapse of the cavitation bubble. These effects should contribute to the physical disruption of microbial structures and inactivation of organisms. There was significant reduction in fungal growth, with decreased fungal growth with increasing USRT. In this study, ultrasound irradiation at a frequency of 42 kHz was used to expose suspensions of fungi to evaluate the disinfection efficacy of the ultrasound reactor. Also, this study showed that in this system more than 99% reduction of sewage fungi was achieved after 60 min.展开更多
This paper identifies metaphors in newspaper English, specifically the articles in China Daily, as the research object. Many linguists have studies metaphors in newspaper English, but research perspective is only limi...This paper identifies metaphors in newspaper English, specifically the articles in China Daily, as the research object. Many linguists have studies metaphors in newspaper English, but research perspective is only limited to the classification of metaphor, and not analyses the trends for each type of metaphor from the diachronic approach, therefore, this paper aims to make up for this deficiency. Thirty-six articles are randomly sampled from China Daily in the year of 2010, to make up a small corpus. Then the occurrence frequency of every kind of metaphor of recent years in this corpus is analyzed. Finally, it is found that the occurrence frequency of orientational metaphors shows a decreasing tendency, while those of the ontological and structural metaphors are relatively stable. We have found two reasons for this trend appears. Firstly, orientational metaphors are used less frequently, because they often appear when it comes to the description of numbers, and digital change itself has a lot of direct expression Secondly, structural metaphor and ontological metaphor are relatively stable, because the former helps the readers to understand the new things; the latter can expressed lively展开更多
Dynamic investigations revealed that lower order harmonic resonance phenomenon exists in the three ring gear transmission. That is, when the input speed is close to 1/3, 1/6, 1/9,…, 1/3 n of the primary natural frequ...Dynamic investigations revealed that lower order harmonic resonance phenomenon exists in the three ring gear transmission. That is, when the input speed is close to 1/3, 1/6, 1/9,…, 1/3 n of the primary natural frequency of the transmission, the loads on the bearings and gears are especially high. This paper explained this phenomenon from the viewpoint of parametric resonance in terms of perturbation technique. A conclusion was drawn that the basic reason for this phenomenon is the primary resonance caused by forcing excitation and parametric resonance caused by parametric change.展开更多
文摘对国内外阻燃剂研究现状进行可视化分析。利用Web of Science数据库,以flame retardant为主题词,检索了1990-2015年的文献作为数据基础,利用CiteSpace对阻燃剂相关研究进行知识图谱分析。欧洲国家、中国和美国是阻燃剂研究的活跃地区;中国科学技术大学在阻燃剂相关研究领域机构中发文量居于首位。从关键词共现分析可知,纳米复合材料、聚丙烯、易燃性、聚合物等关键词的共现频次较高,热解、聚合物、磷、聚烯烃、聚丙烯等具有最高的中心性。从文献共被引分析可知,纳米复合阻燃材料、膨胀阻燃剂等是阻燃剂相关研究领域的研究重点。近些年国内外阻燃剂研究更倾向于多氯联苯、多溴二苯醚、聚烯烃、膨胀阻燃剂等方向。
文摘AIM： To study the influence of high-frequency electric surgical knives on healing of abdominal incision. METHODS： Two hundred and forty white rats were divided into 10^0, 10^2, 10^5, and 10^8 groups and rat models of abdominal operation were induced by using electric surgical knives and common lancets respectively. Then they were respectively given hypodermic injections of normal saline and 0.2 mL quantitative mixture of Escherichia coil, Staphylococcus aureus and Pseudornonas aeruginosa at a concentration of 10^2, 10^5 and 10^8. On the basis of the animal experiment, 220 patients undergoing abdominal operations （above type Ⅱ） were randomly allocated into one of following three groups： electric knife （EK, 93 cases）, electro-coagulation （EC, 55 cases） and control （72 cases）. High-frequency electric surgical knives were used to dissect abdominal tissues and electro-coagulation for hemostasis in EK group. Common lancets and electro-coagulation were applied in EC group. Common lancets and tieing silk suture were used in the controls. RESULTS： In all the groups except group 10^0, infection rate of incisional wounds made by electric surgical knives were remarkably higher than that with common lancets. Furthermore, there were significant differences in groups 10^2, 10^5, and 10^8 （P 〈 0.05）, but not in group 10^0 （P 〉 0.05） between EK and EC groups. Clinical studies showed a delayed wound healing in 16 cases （17.20%） in EK, 11 cases （16.36%） in EC and 2 cases （2.86%）in the control groups. A significant difference between EK and the control groups （χ^2= 8.57, P 〈 0.01）, and between EC and the control groups （χ^2 = 5.66, P 〈 0.05） was observed, but not between EK and EC （χ^2= 0.017, P 〉 0.05）. CONCLUSION： High-frequency electric knives may remarkably delay abdominal incision healing. Its application should be minimized so as to reduce the possibility of postoperative complications.
基金Project (No. 60082003) supported by the National Natural Science Foundation of China
文摘This paper presents a new improved term frequency/inverse document frequency (TF-IDF) approach which uses confidence, support and characteristic words to enhance the recall and precision of text classification. Synonyms defined by a lexicon are processed in the improved TF-IDF approach. We detailedly discuss and analyze the relationship among confidence, recall and precision. The experiments based on science and technology gave promising results that the new TF-IDF approach improves the precision and recall of text classification compared with the conventional TF-IDF approach.
基金supported by the National Key R&D Program of China under contract No. 2016YFC1402703the National Youth Natural Science Foundation under contract No. 61501130supported by the Fundamental Research Funds for the Central Universities under contract No. 16CX02033A
文摘The 21st century Maritime Silk Road(MSR) proposed by China strongly promotes the maritime industry. In this paper, we use wind and ocean wave datasets from 1979 to 2014 to analyze the spatial and temporal distributions of the wind speed, significant wave height(SWH), mean wave direction(MWD), and mean wave period(MWP) in the MSR. The analysis results indicate that the Luzon Strait and Gulf of Aden have the most obvious seasonal variations and that the central Indian Ocean is relatively stable. We analyzed the distributions of the maximum wind speed and SWH in the MSR over this 36-year period. The results show that the distribution of the monthly average frequency for SWH exceeds 4 m(huge waves) and that of the corresponding wind speed exceeds 13.9 ms^(-1)(high wind speed). The occurrence frequencies of huge waves and high winds in regions east of the Gulf of Aden are as high as 56% and 80%, respectively. We also assessed the wave and wind energies in different seasons. Based on our analyses, we propose a risk factor(RF) for determining navigation safety levels, based on the wind speed and SWH. We determine the spatial and temporal RF distributions for different seasons and analyze the corresponding impact on four major sea routes. Finally, we determine the spatial distribution of tropical cyclones from 2000 to 2015 and analyze the corresponding impact on the four sea routes. The analysis of the dynamic characteristics of the MSR provides references for ship navigation as well as ocean engineering.
基金Project supported by the Medical Sciences/University of Tehran, I.R. Iran
文摘The objective of the investigation was to study the application of ultrasound reactor technology (USRT) as a disin-fectant for reduction of fungi from sewage effluent. Fungi are carbon heterotrophs that require preformed organic compounds as carbon sources. USRT is an attractive means to improve water quality because of the system simplicity and no production of toxic by-products. An ultrasound reactor produces strong cavitation in aqueous solution causing shock waves and reactive free radicals by the violent collapse of the cavitation bubble. These effects should contribute to the physical disruption of microbial structures and inactivation of organisms. There was significant reduction in fungal growth, with decreased fungal growth with increasing USRT. In this study, ultrasound irradiation at a frequency of 42 kHz was used to expose suspensions of fungi to evaluate the disinfection efficacy of the ultrasound reactor. Also, this study showed that in this system more than 99% reduction of sewage fungi was achieved after 60 min.
文摘This paper identifies metaphors in newspaper English, specifically the articles in China Daily, as the research object. Many linguists have studies metaphors in newspaper English, but research perspective is only limited to the classification of metaphor, and not analyses the trends for each type of metaphor from the diachronic approach, therefore, this paper aims to make up for this deficiency. Thirty-six articles are randomly sampled from China Daily in the year of 2010, to make up a small corpus. Then the occurrence frequency of every kind of metaphor of recent years in this corpus is analyzed. Finally, it is found that the occurrence frequency of orientational metaphors shows a decreasing tendency, while those of the ontological and structural metaphors are relatively stable. We have found two reasons for this trend appears. Firstly, orientational metaphors are used less frequently, because they often appear when it comes to the description of numbers, and digital change itself has a lot of direct expression Secondly, structural metaphor and ontological metaphor are relatively stable, because the former helps the readers to understand the new things; the latter can expressed lively
基金Partly supported by the Open Fund of theState Key Lab.of Mechanical TransmissionChongqing U niv
文摘Dynamic investigations revealed that lower order harmonic resonance phenomenon exists in the three ring gear transmission. That is, when the input speed is close to 1/3, 1/6, 1/9,…, 1/3 n of the primary natural frequency of the transmission, the loads on the bearings and gears are especially high. This paper explained this phenomenon from the viewpoint of parametric resonance in terms of perturbation technique. A conclusion was drawn that the basic reason for this phenomenon is the primary resonance caused by forcing excitation and parametric resonance caused by parametric change.
