A proper operating strategy is helpful to improve the off-design performance of combined cooling,heating and power(CCHP)systems,providing high efficiency and low emission.The energy level difference graphic analysis m...A proper operating strategy is helpful to improve the off-design performance of combined cooling,heating and power(CCHP)systems,providing high efficiency and low emission.The energy level difference graphic analysis method is used to identify energy level as well as exergy destruction of the part-load process.This method illustrates the energy efficiency upgrading mechanism of the flue gas reinjecting(FGR)operating strategy.It is referenced to a reducing turbine inlet temperature(TIT)operating strategy.By comparison,the FGR operating strategy leads to a 2.62%exergy distribution reduction in a gas turbine at an 85%load level due to the decrease of the energy level difference.When the output power is reduced further,the FGR operating strategy is supplanted by the TIT operating strategy with the limit of compressor inlet temperature.However,the opposite results of exergy distribution are presented in the exhaust-heat recovery devices.A heat-driven refrigeration and power cycle is introduced in a typical CCHP system as a solution.Moreover,the results suggest that the operational flexibility of the CCHP system is improved by enlarging the ratio of cooling to electricity.展开更多
Objectives:This study aimed to survey the geriatric nursing competencies of clinical nursing staff in Chongqing City,China,and provide suggestions to enhance these competencies.Methods:This study was conducted in 204 ...Objectives:This study aimed to survey the geriatric nursing competencies of clinical nursing staff in Chongqing City,China,and provide suggestions to enhance these competencies.Methods:This study was conducted in 204 hospitals in Southwest China from December 24,2022 to January 7,2023.The“Geriatric Nursing Competence of Clinical Nurse Investigation Tool”was used to explore factors that influence geriatric nurses’competencies via stratified sampling.The survey was conducted by distributing and collecting questionnaires through the online platform Wenjuanxing.Results:A total of 10,692 nurses answered the questionnaires.Of these questionnaires,9,442 were valid.The total geriatric nursing competence score of the clinical nursing staff was 2.29±0.81,the secondary hospital score was 2.23±0.78,and the tertiary hospital’s overall mean score was 2.33±0.83.The factors that influenced secondary hospitals included the department of medicine,age of nurses and total length of career(P<0.05).The factors that influenced tertiary hospitals included the department of medicine,age of nurses,nurses’professional title,and geriatric practical advanced nurses’certification(P<0.05).Conclusions:Geriatric nursing competence among clinical nursing staff is imbalanced at a lower-middle level and is influenced by various factors.Thefindings highlight the need for further clinical training in geriatric nursing.The training of geriatric nurses should focus on necessary clinical skills and on preparing them to adequately manage comprehensive geriatric syndromes.展开更多
Thresholding is a popular image segmentation method that often requires as a preliminary and indis- pensable stage in the computer aided image process, particularly in the analysis of X-ray welding images. In this pap...Thresholding is a popular image segmentation method that often requires as a preliminary and indis- pensable stage in the computer aided image process, particularly in the analysis of X-ray welding images. In this paper, a modified gray level difference-based transition region extraction and thresholding algorithm is presented for segmentation of the images that have been corrupted by intensity inhomogeneities or noise. Classical gray level difference algorithm is improved by selective output of the result of the maximum or the minimum of the gray level with the pixels in the surrounding, and multi-structuring of neighborhood window is used to represent the essence of transition region. The proposed algorithm could robustly measure the gray level changes, and accurately extract transition region of an image. Comparisons with other approaches demonstrate the superior performance of the proposed algorithm. K展开更多
The research concluded peasants' willingness on homestead exiting and influential factors by questionnaire survey and interviewing in two villages with varied levels of economic development in Anhui Province.Comparis...The research concluded peasants' willingness on homestead exiting and influential factors by questionnaire survey and interviewing in two villages with varied levels of economic development in Anhui Province.Comparisons were performed on subjective factors and objective factors were explored by Logistic regression.The results showed that both of education background and homestead use have positive correlation with peasants' willingness on homestead exit;the number of family members has negative effects on peasants in advanced village but the number of migrant workers or members living in cities has positive effects;the area of homestead has positive effects on peasants in underdeveloped village.Therefore,the emphasis should be varied on homestead exit upon village economy and it is necessary to reinforce homestead exit promotion at improving immigrants' reception work,social security,employment,and education.展开更多
Ammonium nitrogen inhibited NR activity in sugar beet,NR activity was lower in endogenous substrate after ammonium nitrogen was used,and the correlation between NR activity and ammonium nitrogen levels was negative.Bu...Ammonium nitrogen inhibited NR activity in sugar beet,NR activity was lower in endogenous substrate after ammonium nitrogen was used,and the correlation between NR activity and ammonium nitrogen levels was negative.But NR activity raised with the ammonium nitrogen levels raising in exogenous.Ammonium nitrogen prompted GS activity:the correlation between GS activity and ammonium nitrogen was positive,GS activity raised with ammonium nitrogen levels raising,GS activity of roots and leaves had same change trend in sugar beet in the whole growth duration after ammonium nitrogen was used,but GS activity in roots was higher than that in leaves.展开更多
In a study on erythrocyte polyamine levels in 20 leukemia patients and 18 healthy individuals, following results were obtained. Putrescine(Pu) in ery-throcytes was nearly undetectable but in 2 AMoL patients; Spermidin...In a study on erythrocyte polyamine levels in 20 leukemia patients and 18 healthy individuals, following results were obtained. Putrescine(Pu) in ery-throcytes was nearly undetectable but in 2 AMoL patients; Spermidine(Spd) level in ALL was higher than the control volue (P<0.05), in AML (M1, M2) and APL the Spd level was in the range of control group (P>0.1), while that in AMoL and AMMoL was considerably lower as compared to control (P< 0.001); Spermine (Spm) level in all types of leukemia was increased (P<0.001); Spd/Spm ratio was significantly decreased, showing 1.525 in control group, 0.938 in ALL (P<0.025), 0.779 in AML (M1, M2) P< 0.01), 0.319 in APL (P<0.001) and 0.296 in AMoL & AMMoL (P<0.001), and the differences between the Spd/Spm ratio in AMoL and AMMoL and in ALL were noted (P<0.05). These results suggested that determination of erythrocyte polyamines in leukemia patients may be helpful in diagnosis, differential diagnosis and prognosis.展开更多
Most existing algorithms for the underdetermined blind source separation(UBSS) problem are two-stage algorithm, i.e., mixing parameters estimation and sources estimation. In the mixing parameters estimation, the previ...Most existing algorithms for the underdetermined blind source separation(UBSS) problem are two-stage algorithm, i.e., mixing parameters estimation and sources estimation. In the mixing parameters estimation, the previously proposed traditional clustering algorithms are sensitive to the initializations of the mixing parameters. To reduce the sensitiveness to the initialization, we propose a new algorithm for the UBSS problem based on anechoic speech mixtures by employing the visual information, i.e., the interaural time difference(ITD) and the interaural level difference(ILD), as the initializations of the mixing parameters. In our algorithm, the video signals are utilized to estimate the distances between microphones and sources, and then the estimations of the ITD and ILD can be obtained. With the sparsity assumption in the time-frequency domain, the Gaussian potential function algorithm is utilized to estimate the mixing parameters by using the ITDs and ILDs as the initializations of the mixing parameters. And the time-frequency masking is used to recover the sources by evaluating the various ITDs and ILDs. Experimental results demonstrate the competitive performance of the proposed algorithm compared with the baseline algorithms.展开更多
As the stiffness discontinuous of large diameter steel tube and concrete combined pile, the complicated stress state is caused by the combination of the pile foundation and the base rock, the steel casing and the bedr...As the stiffness discontinuous of large diameter steel tube and concrete combined pile, the complicated stress state is caused by the combination of the pile foundation and the base rock, the steel casing and the bedrock structure. It is needed to put forward a scientific basis to determine the pile foundation effective depth of embedded. For this purpose, the physical model and the numerical model of single pile with large diameter steel tube and reinforced concrete combined force are established. Through numerical simulation and contrast test of a large number of variable parameters, the various factors that affect the lateral bearing capacity of the embedded piles are discussed in detail, the mechanical properties of the foundation under the action of the steel tube and the pile foundation are obtained.展开更多
According to low earth orbit(LEO) satellite systems with users of different levels, a dynamic channel reservation scheme based on priorities is proposed. Dynamic calculation of the thresholds for reserved channels i...According to low earth orbit(LEO) satellite systems with users of different levels, a dynamic channel reservation scheme based on priorities is proposed. Dynamic calculation of the thresholds for reserved channels is the key of this strategy. In order to obtain the optimal thresholds, the traffic is predicted based on the high-speed deterministic movement property of LEO satellites firstly. Then, a channel allocation model based on Markov is established. Finally, the solution of the model is obtained based on the genetic algorithm. Without user location, this strategy effectively reduces handover failures and improves channel utilization by adjusting dynamically the thresholds according to traffic conditions. The simulation results show that the system's overall quality of service can be improved by this strategy.展开更多
This article tries to find out the few discrepancies between the teachers and their scholars as to oral activity, which shows that scholars' expectations and needs are not quite responded to. The versions chosen as a...This article tries to find out the few discrepancies between the teachers and their scholars as to oral activity, which shows that scholars' expectations and needs are not quite responded to. The versions chosen as a sample for this study come from different schools in the academy of Rabat Sal~ Zemmour Zaer area and belong to three different educational levels including common core, first year, and second year in addition to a total number of 40 teachers who have contributed to this research throughout the whole process. This research has relied on different instruments to collect the data including questionnaires, interviews, and class observation grids. Results showed that scholars' perceptions highly favour thematic variety. Findings also reported match findings of previous research in highlighting the importance of using tech facilities and multimedia to improve oral activity.展开更多
EAP class offers opportunities to international students doing various courses at both undergraduate and postgraduate levels. The EAP course could not only enhance the communication skills of the international student...EAP class offers opportunities to international students doing various courses at both undergraduate and postgraduate levels. The EAP course could not only enhance the communication skills of the international students, but also improve their knowledge of English grammar, vocabulary, spelling, sentence structure and composition skills. The purpose of this paper is to analyze the useful teaching method teacher used in class, and help different students improving their English skills.展开更多
The heavy metals in atmospheric fine particles are of great concern to human health. To understand the pollution characteristics and health risks of heavy metals in particulate matter with an aerodynamic equivalent di...The heavy metals in atmospheric fine particles are of great concern to human health. To understand the pollution characteristics and health risks of heavy metals in particulate matter with an aerodynamic equivalent diameter ≤2.5 μm (PM<sub>2.5</sub>) during winter in the suburb of Cangzhou, PM<sub>2.5</sub> samples were collected with an intelligent medium-flow atmospheric particulate matter sampler from January to February 2019. The Fe, Cu, Mn, Pb and Zn contents in PM<sub>2.5</sub> were determined via inductively coupled plasma optical emission spectrometry (ICP-OES). The sources and health risks of heavy metals in PM<sub>2.5</sub> were analysed via the enrichment factor (EF) method and the United States Environmental Protection Agency (US EPA) health risk assessment model. The results showed that the average PM<sub>2.5</sub> concentration in the suburb of Cangzhou reached 71.6 μg/m<sup>3</sup>, ranging from 23.7 to 169.5 μg/m<sup>3</sup>. The exceeding standard rate was 29.4% during the sampling period. The PM<sub>2.5</sub> concentration during the nighttime was higher than that during the daytime. The heavy metal concentrations in PM<sub>2.5</sub> decreased in the order of Fe > Mn > Zn > Cu > Pb, and the Fe, Mn, Pb and Zn concentrations decreased in the order of clean days < pollution days < heavy pollution days. The Fe and Mn concentrations were higher during the daytime than those during the nighttime, while the Cu, Pb and Zn concentrations were higher during the nighttime than those during the daytime. EF analysis revealed that Zn, Pb and Cu were significantly enriched, and Pb was highly enriched on heavy pollution days with increasing pollution degree. The enrichment level of heavy metals during the nighttime was higher than that during the daytime. Health risk assessment demonstrated that Mn posed non-carcinogenic risks to both adults and children, following the sequence of clean days < pollution days < heavy pollution days. Pb posed a carcinogenic risk to adults on heavy pollution days. The study revealed that the pollution levels of heavy metals in PM<sub>2.5</sub> in the suburb of Cangzhou were low, and Pb and Mn in PM<sub>2.5</sub> posed certain health risks to the population.展开更多
The thermal buoyancy generated by the difference in air density in a building can drive hot-pressed natural ventilation,which is an energy-efficient means of ventilation used to obtain higher air quality.Therefore,the...The thermal buoyancy generated by the difference in air density in a building can drive hot-pressed natural ventilation,which is an energy-efficient means of ventilation used to obtain higher air quality.Therefore,the effect of a single-point heat source with limited sides at different heights on stratified flow was studied in a naturally ventilated room in this paper.Based on the classical plume diffusion law of an independent point heat source and the mirroring principle,a calculation model of the thermal stratification height with a restricted source elevated to different levels was derived and validated.The quantitative effects of the heat source height from the floor,the effective opening area and other factors on the natural ventilation of hot pressure were analyzed.A threshold X_(T)for the separation between a point source and a sidewall was defined to estimate whether the thermal plume was independent or restricted by a sidewall.And a method for calculating the threshold xt was obtained.This research can provide a reference basis for designing natural ventilation for buildings with a restricted heat source at different levels to achieve a desired indoor environment.展开更多
Two detection techniques of broadband terahertz(THz)time-domain spectroscopy-THz air-biased coherent detection(THz-ABCD;from 0.3 to 14 THz)and electro-optical(EO)detection(from 0.3 to 7 THz)-are both performed...Two detection techniques of broadband terahertz(THz)time-domain spectroscopy-THz air-biased coherent detection(THz-ABCD;from 0.3 to 14 THz)and electro-optical(EO)detection(from 0.3 to 7 THz)-are both performed at several different relative humidity levels.The THz power exponentially decays with the increase in relative humidity.The dynamic range of the main pulse in the time domain linearly decreases as the relative humidity increases from 0%to 40%,and linear fittings show that the slopes are-0.017 and-0.019 for THz-ABCD and EO detection,respectively.Because of the multiple reflections caused by the crystal in the common EO detection,THz-ABCD has better spectral resolution(17 GHz)than that of EO detection(170 GHz).The spectrum of water vapor absorption measured by THz-ABCD is also compared with that measured by the Fourier transform infrared spectroscopy(FTIR).展开更多
Objective The present study investigated the sodium/iodide symporter mRNA expression in mouse lactating mammary gland cells under different iodine levels and the effects of thyroid-stimulating hormone(TSH),estradiol(E...Objective The present study investigated the sodium/iodide symporter mRNA expression in mouse lactating mammary gland cells under different iodine levels and the effects of thyroid-stimulating hormone(TSH),estradiol(E2)and prolactin(PRL)on NIS mRNA expression in mouse lactating mammary gland cells.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.52006213)。
文摘A proper operating strategy is helpful to improve the off-design performance of combined cooling,heating and power(CCHP)systems,providing high efficiency and low emission.The energy level difference graphic analysis method is used to identify energy level as well as exergy destruction of the part-load process.This method illustrates the energy efficiency upgrading mechanism of the flue gas reinjecting(FGR)operating strategy.It is referenced to a reducing turbine inlet temperature(TIT)operating strategy.By comparison,the FGR operating strategy leads to a 2.62%exergy distribution reduction in a gas turbine at an 85%load level due to the decrease of the energy level difference.When the output power is reduced further,the FGR operating strategy is supplanted by the TIT operating strategy with the limit of compressor inlet temperature.However,the opposite results of exergy distribution are presented in the exhaust-heat recovery devices.A heat-driven refrigeration and power cycle is introduced in a typical CCHP system as a solution.Moreover,the results suggest that the operational flexibility of the CCHP system is improved by enlarging the ratio of cooling to electricity.
基金supported by a key Program of the Chongqing Scientific and Technological Commission(Grant Number.CSTB2022TIAD-KPX0165).
文摘Objectives:This study aimed to survey the geriatric nursing competencies of clinical nursing staff in Chongqing City,China,and provide suggestions to enhance these competencies.Methods:This study was conducted in 204 hospitals in Southwest China from December 24,2022 to January 7,2023.The“Geriatric Nursing Competence of Clinical Nurse Investigation Tool”was used to explore factors that influence geriatric nurses’competencies via stratified sampling.The survey was conducted by distributing and collecting questionnaires through the online platform Wenjuanxing.Results:A total of 10,692 nurses answered the questionnaires.Of these questionnaires,9,442 were valid.The total geriatric nursing competence score of the clinical nursing staff was 2.29±0.81,the secondary hospital score was 2.23±0.78,and the tertiary hospital’s overall mean score was 2.33±0.83.The factors that influenced secondary hospitals included the department of medicine,age of nurses and total length of career(P<0.05).The factors that influenced tertiary hospitals included the department of medicine,age of nurses,nurses’professional title,and geriatric practical advanced nurses’certification(P<0.05).Conclusions:Geriatric nursing competence among clinical nursing staff is imbalanced at a lower-middle level and is influenced by various factors.Thefindings highlight the need for further clinical training in geriatric nursing.The training of geriatric nurses should focus on necessary clinical skills and on preparing them to adequately manage comprehensive geriatric syndromes.
文摘Thresholding is a popular image segmentation method that often requires as a preliminary and indis- pensable stage in the computer aided image process, particularly in the analysis of X-ray welding images. In this paper, a modified gray level difference-based transition region extraction and thresholding algorithm is presented for segmentation of the images that have been corrupted by intensity inhomogeneities or noise. Classical gray level difference algorithm is improved by selective output of the result of the maximum or the minimum of the gray level with the pixels in the surrounding, and multi-structuring of neighborhood window is used to represent the essence of transition region. The proposed algorithm could robustly measure the gray level changes, and accurately extract transition region of an image. Comparisons with other approaches demonstrate the superior performance of the proposed algorithm. K
文摘The research concluded peasants' willingness on homestead exiting and influential factors by questionnaire survey and interviewing in two villages with varied levels of economic development in Anhui Province.Comparisons were performed on subjective factors and objective factors were explored by Logistic regression.The results showed that both of education background and homestead use have positive correlation with peasants' willingness on homestead exit;the number of family members has negative effects on peasants in advanced village but the number of migrant workers or members living in cities has positive effects;the area of homestead has positive effects on peasants in underdeveloped village.Therefore,the emphasis should be varied on homestead exit upon village economy and it is necessary to reinforce homestead exit promotion at improving immigrants' reception work,social security,employment,and education.
文摘Ammonium nitrogen inhibited NR activity in sugar beet,NR activity was lower in endogenous substrate after ammonium nitrogen was used,and the correlation between NR activity and ammonium nitrogen levels was negative.But NR activity raised with the ammonium nitrogen levels raising in exogenous.Ammonium nitrogen prompted GS activity:the correlation between GS activity and ammonium nitrogen was positive,GS activity raised with ammonium nitrogen levels raising,GS activity of roots and leaves had same change trend in sugar beet in the whole growth duration after ammonium nitrogen was used,but GS activity in roots was higher than that in leaves.
文摘In a study on erythrocyte polyamine levels in 20 leukemia patients and 18 healthy individuals, following results were obtained. Putrescine(Pu) in ery-throcytes was nearly undetectable but in 2 AMoL patients; Spermidine(Spd) level in ALL was higher than the control volue (P<0.05), in AML (M1, M2) and APL the Spd level was in the range of control group (P>0.1), while that in AMoL and AMMoL was considerably lower as compared to control (P< 0.001); Spermine (Spm) level in all types of leukemia was increased (P<0.001); Spd/Spm ratio was significantly decreased, showing 1.525 in control group, 0.938 in ALL (P<0.025), 0.779 in AML (M1, M2) P< 0.01), 0.319 in APL (P<0.001) and 0.296 in AMoL & AMMoL (P<0.001), and the differences between the Spd/Spm ratio in AMoL and AMMoL and in ALL were noted (P<0.05). These results suggested that determination of erythrocyte polyamines in leukemia patients may be helpful in diagnosis, differential diagnosis and prognosis.
基金supported by the National Natural Science Foundation of China(Grant Nos.61162014,61210306074)the Natural Science Foundation of Jiangxi Province of China(Grant No.20122BAB201025)the Foundation for Young Scientists of Jiangxi Province(Jinggang Star)(Grant No.20122BCB23002)
文摘Most existing algorithms for the underdetermined blind source separation(UBSS) problem are two-stage algorithm, i.e., mixing parameters estimation and sources estimation. In the mixing parameters estimation, the previously proposed traditional clustering algorithms are sensitive to the initializations of the mixing parameters. To reduce the sensitiveness to the initialization, we propose a new algorithm for the UBSS problem based on anechoic speech mixtures by employing the visual information, i.e., the interaural time difference(ITD) and the interaural level difference(ILD), as the initializations of the mixing parameters. In our algorithm, the video signals are utilized to estimate the distances between microphones and sources, and then the estimations of the ITD and ILD can be obtained. With the sparsity assumption in the time-frequency domain, the Gaussian potential function algorithm is utilized to estimate the mixing parameters by using the ITDs and ILDs as the initializations of the mixing parameters. And the time-frequency masking is used to recover the sources by evaluating the various ITDs and ILDs. Experimental results demonstrate the competitive performance of the proposed algorithm compared with the baseline algorithms.
文摘As the stiffness discontinuous of large diameter steel tube and concrete combined pile, the complicated stress state is caused by the combination of the pile foundation and the base rock, the steel casing and the bedrock structure. It is needed to put forward a scientific basis to determine the pile foundation effective depth of embedded. For this purpose, the physical model and the numerical model of single pile with large diameter steel tube and reinforced concrete combined force are established. Through numerical simulation and contrast test of a large number of variable parameters, the various factors that affect the lateral bearing capacity of the embedded piles are discussed in detail, the mechanical properties of the foundation under the action of the steel tube and the pile foundation are obtained.
基金supported by the National Natural Science Foundation of China(7130108161373137)+1 种基金the Natural Science Foundation of Jiangsu Province(BK20130877BK2012833)
文摘According to low earth orbit(LEO) satellite systems with users of different levels, a dynamic channel reservation scheme based on priorities is proposed. Dynamic calculation of the thresholds for reserved channels is the key of this strategy. In order to obtain the optimal thresholds, the traffic is predicted based on the high-speed deterministic movement property of LEO satellites firstly. Then, a channel allocation model based on Markov is established. Finally, the solution of the model is obtained based on the genetic algorithm. Without user location, this strategy effectively reduces handover failures and improves channel utilization by adjusting dynamically the thresholds according to traffic conditions. The simulation results show that the system's overall quality of service can be improved by this strategy.
文摘This article tries to find out the few discrepancies between the teachers and their scholars as to oral activity, which shows that scholars' expectations and needs are not quite responded to. The versions chosen as a sample for this study come from different schools in the academy of Rabat Sal~ Zemmour Zaer area and belong to three different educational levels including common core, first year, and second year in addition to a total number of 40 teachers who have contributed to this research throughout the whole process. This research has relied on different instruments to collect the data including questionnaires, interviews, and class observation grids. Results showed that scholars' perceptions highly favour thematic variety. Findings also reported match findings of previous research in highlighting the importance of using tech facilities and multimedia to improve oral activity.
文摘EAP class offers opportunities to international students doing various courses at both undergraduate and postgraduate levels. The EAP course could not only enhance the communication skills of the international students, but also improve their knowledge of English grammar, vocabulary, spelling, sentence structure and composition skills. The purpose of this paper is to analyze the useful teaching method teacher used in class, and help different students improving their English skills.
文摘The heavy metals in atmospheric fine particles are of great concern to human health. To understand the pollution characteristics and health risks of heavy metals in particulate matter with an aerodynamic equivalent diameter ≤2.5 μm (PM<sub>2.5</sub>) during winter in the suburb of Cangzhou, PM<sub>2.5</sub> samples were collected with an intelligent medium-flow atmospheric particulate matter sampler from January to February 2019. The Fe, Cu, Mn, Pb and Zn contents in PM<sub>2.5</sub> were determined via inductively coupled plasma optical emission spectrometry (ICP-OES). The sources and health risks of heavy metals in PM<sub>2.5</sub> were analysed via the enrichment factor (EF) method and the United States Environmental Protection Agency (US EPA) health risk assessment model. The results showed that the average PM<sub>2.5</sub> concentration in the suburb of Cangzhou reached 71.6 μg/m<sup>3</sup>, ranging from 23.7 to 169.5 μg/m<sup>3</sup>. The exceeding standard rate was 29.4% during the sampling period. The PM<sub>2.5</sub> concentration during the nighttime was higher than that during the daytime. The heavy metal concentrations in PM<sub>2.5</sub> decreased in the order of Fe > Mn > Zn > Cu > Pb, and the Fe, Mn, Pb and Zn concentrations decreased in the order of clean days < pollution days < heavy pollution days. The Fe and Mn concentrations were higher during the daytime than those during the nighttime, while the Cu, Pb and Zn concentrations were higher during the nighttime than those during the daytime. EF analysis revealed that Zn, Pb and Cu were significantly enriched, and Pb was highly enriched on heavy pollution days with increasing pollution degree. The enrichment level of heavy metals during the nighttime was higher than that during the daytime. Health risk assessment demonstrated that Mn posed non-carcinogenic risks to both adults and children, following the sequence of clean days < pollution days < heavy pollution days. Pb posed a carcinogenic risk to adults on heavy pollution days. The study revealed that the pollution levels of heavy metals in PM<sub>2.5</sub> in the suburb of Cangzhou were low, and Pb and Mn in PM<sub>2.5</sub> posed certain health risks to the population.
基金supported by the Natural Science Foundation of Shaanxi Province(No.2020JQ-670)China Postdoctoral Science Foundation(No.2020M673353).
文摘The thermal buoyancy generated by the difference in air density in a building can drive hot-pressed natural ventilation,which is an energy-efficient means of ventilation used to obtain higher air quality.Therefore,the effect of a single-point heat source with limited sides at different heights on stratified flow was studied in a naturally ventilated room in this paper.Based on the classical plume diffusion law of an independent point heat source and the mirroring principle,a calculation model of the thermal stratification height with a restricted source elevated to different levels was derived and validated.The quantitative effects of the heat source height from the floor,the effective opening area and other factors on the natural ventilation of hot pressure were analyzed.A threshold X_(T)for the separation between a point source and a sidewall was defined to estimate whether the thermal plume was independent or restricted by a sidewall.And a method for calculating the threshold xt was obtained.This research can provide a reference basis for designing natural ventilation for buildings with a restricted heat source at different levels to achieve a desired indoor environment.
基金supported by the NSC(No.100-2917-I-564-045)the National Science FoundationDefense Threat Reduction Agency,and the Department of Homeland Security through the DHS-ALERT Center under Award(No.2008-ST-061-ED0001)
文摘Two detection techniques of broadband terahertz(THz)time-domain spectroscopy-THz air-biased coherent detection(THz-ABCD;from 0.3 to 14 THz)and electro-optical(EO)detection(from 0.3 to 7 THz)-are both performed at several different relative humidity levels.The THz power exponentially decays with the increase in relative humidity.The dynamic range of the main pulse in the time domain linearly decreases as the relative humidity increases from 0%to 40%,and linear fittings show that the slopes are-0.017 and-0.019 for THz-ABCD and EO detection,respectively.Because of the multiple reflections caused by the crystal in the common EO detection,THz-ABCD has better spectral resolution(17 GHz)than that of EO detection(170 GHz).The spectrum of water vapor absorption measured by THz-ABCD is also compared with that measured by the Fourier transform infrared spectroscopy(FTIR).
文摘Objective The present study investigated the sodium/iodide symporter mRNA expression in mouse lactating mammary gland cells under different iodine levels and the effects of thyroid-stimulating hormone(TSH),estradiol(E2)and prolactin(PRL)on NIS mRNA expression in mouse lactating mammary gland cells.