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风洞分布测压试验校准技术发展现状 认领
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作者 李峰 王洪博 《计测技术》 2020年第1期1-7,共7页
调研了目前国内外表面压力分布测试试验校准技术,分别总结了风洞试验中稳态压力分布和脉动压力分布的测试及校准现状。选取分布测压技术中具有代表性的压力扫描阀及压敏漆(PSP)测试校准技术展开论述,介绍了包括校准原理、试验流程及校... 调研了目前国内外表面压力分布测试试验校准技术,分别总结了风洞试验中稳态压力分布和脉动压力分布的测试及校准现状。选取分布测压技术中具有代表性的压力扫描阀及压敏漆(PSP)测试校准技术展开论述,介绍了包括校准原理、试验流程及校准溯源链等校准试验的关键要素。通过对比国内外风洞测压试验校准技术现状,分析了我国测压校准体系存在的问题及相关解决方法,提出了我国风洞压力分布测试校准技术的发展方向。 展开更多
关键词 风洞试验 压力 压力扫描阀 压敏漆
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Osmotic pressure of serum and cerebrospinal fluid in patients with suspected neurological conditions 认领
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作者 Tetsuya Akaishi Toshiyuki Takahashi +3 位作者 Ichiro Nakashima Michiaki Abe Masashi Aoki Tadashi Ishii 《中国神经再生研究:英文版》 SCIE CAS CSCD 2020年第5期944-947,共4页
Interstitial fluid movement in the brain parenchyma has been suggested to contribute to sustaining the metabolism in brain parenchyma and maintaining the function of neurons and glial cells.The pulsatile hydrostatic p... Interstitial fluid movement in the brain parenchyma has been suggested to contribute to sustaining the metabolism in brain parenchyma and maintaining the function of neurons and glial cells.The pulsatile hydrostatic pressure gradient may be one of the driving forces of this bulk flow.However,osmotic pressure- related factors have not been studied until now.In this prospective observational study,to elucidate the relationship between osmolality (mOsm/kg) in the serum and that in the cerebrospinal fluid (CSF),we simultaneously measured the serum and CSF osmolality of 179 subjects with suspected neurological conditions.Serum osmolality was 283.6 ± 6.5 mOsm/kg and CSF osmolality was 289.5 ± 6.6 mOsm/kg.Because the specific gravity of serum and CSF is known to be 1.024–1.028 and 1.004–1.007,respectively,the estimated average of osmolarity (mOsm/L) in the serum and CSF covered exactly the same range (i.e.,290.5–291.5 mOsm/L).There was strong correlation between CSF osmolality and serum osmolality,but the difference in osmolality between serum and CSF was not correlated with serum osmolality,serum electrolyte levels,protein levels,or quotient of albumin.In conclusion,CSF osmolarity was suggested to be equal to serum osmolarity.Osmolarity is not one of the driving forces of this bulk flow.Other factors such as hydrostatic pressure gradient should be used to explain the mechanism of bulk flow in the brain parenchyma.This study was approved by the Institutional Review Board of the Tohoku University Hospital (approval No.IRB No.2015-1-257) on July 29,2015. 展开更多
关键词 brain PARENCHYMA bulk flow CEREBROSPINAL FLUID hydrostatic PRESSURE interstitial FLUID OSMOLARITY OSMOTIC PRESSURE
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水润滑轴承水膜压力损失机理研究 认领
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作者 王伦 王楠 +2 位作者 王鹏 杜宇波 岳晓奎 《轴承》 北大核心 2020年第5期36-42,共7页
针对已有水膜压力无线传感测试方法中由于设置L型管道从而导致传递过程中水膜压力的损失问题,采用数值分析法建立了水润滑轴承系统管道压力损失数学模型,用ANSYS软件建立了物理模型,通过仿真分析了压力损失机理,并对试验结果进行了校正... 针对已有水膜压力无线传感测试方法中由于设置L型管道从而导致传递过程中水膜压力的损失问题,采用数值分析法建立了水润滑轴承系统管道压力损失数学模型,用ANSYS软件建立了物理模型,通过仿真分析了压力损失机理,并对试验结果进行了校正与分析。结果表明:管道入口处润滑水的流量越高,水膜压力损失越大;轴转速越高,局部压力损失越大;管道越长,L型管道直管段压力损失越大,在动态工况下管道的压力损失与能耗比静态工况下的大。 展开更多
关键词 滑动轴承 水润滑轴承 压力 导流孔 管道 压力损失 能耗
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General axisymmetric active earth pressure obtained by the characteristics method based on circumferential geometric condition 认领
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作者 XIONG GuoJun CHEN JinJian +1 位作者 LI MingGuang Li YaoLiang 《中国科学:技术科学英文版》 SCIE EI CAS CSCD 2020年第2期341-356,共16页
Existing solutions for axisymmetric active earth pressure are based on certain hypotheses of the circumferential stress, lacking of strict basis. This article presents a technique for deriving the actual circumferenti... Existing solutions for axisymmetric active earth pressure are based on certain hypotheses of the circumferential stress, lacking of strict basis. This article presents a technique for deriving the actual circumferential stress according to the circumferential geometric condition, the Drucker-Prager criterion and incremental theory. Based on the actual circumferential stress, a new characteristics method for determining the axisymmetric active earth pressure in plastic flow is developed in this article. In this new method, the inclined angle of boundaries, interface friction of contact interface, dilatation effect and flow velocity of soil are considered at the same time. The validity of the new method is confirmed using several sets of experimental data from the literature. The pressure coefficients are investigated individually in detail, and some different conclusions are found. Finally, a practical formula for calculating axisymmetric active earth pressure is presented based on the linear superposition principle, and related tables of coefficients are also provided for engineering application. 展开更多
关键词 AXISYMMETRIC active EARTH PRESSURE characteristics method practical calculation formula EARTH PRESSURE coefficients DILATATION effect the DRUCKER-PRAGER yield criterion
Choice and management of negative pressure drainage in anterior cervical surgery 认领
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作者 Qi-Hang Su Kai Zhu +4 位作者 Yong-Chao Li Tao Chen Yan Zhang Jun Tan Song Guo 《世界临床病例杂志》 SCIE 2020年第11期2201-2209,共9页
BACKGROUND Postoperative unobstructed drainage is an important measure for avoiding hematoma formation and preventing complications from anterior cervical surgery.AIM To discuss the characteristics and key points of c... BACKGROUND Postoperative unobstructed drainage is an important measure for avoiding hematoma formation and preventing complications from anterior cervical surgery.AIM To discuss the characteristics and key points of clinical management of two types of commonly used negative pressure drainage systems in clinical settings.METHODS Two types of commonly used silica gel negative pressure drainage balls and a type of gastrointestinal decompression apparatus were fully emptied and then injected with different amounts of water and air.Following this,the negative pressure values of the three devices were measured.Meanwhile,we undertook a retrospective analysis of the clinical data of 1328 patients who had been treated with different negative pressure drainage apparatuses during their anterior cervical surgery in our department between January 2007 and January 2018.RESULTS As the amount of injected air or water increased,the negative pressure of the silica gel negative pressure drainage ball decreased rapidly,dropping to zero when 150 mL of water or air was injected.In contrast,the negative pressure of gastrointestinal decompression apparatus decreased slowly,maintaining an ideal value even when 300 mL of water or air was injected.And statistical analysis demonstrated that patients who had been treated with the gastrointestinal decompression apparatus were less likely to develop severe complications than those who had been treated with the silica gel negative pressure drainage ball(P<0.05).CONCLUSION This study showed that the gastrointestinal decompression apparatus has the advantages of large suction capacity,long duration of continuous negative pressure,and good drainage effect,all of which are the favorable factors for the use of this apparatus for negative pressure drainage in anterior cervical surgery. 展开更多
关键词 SPINE Anterior cervical surgery Negative pressure Drainage Gastrointestinal decompression apparatus Silica gel negative pressure drainage ball
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Effects of durotomy versus myelotomy in the repair of spinal cord injury 认领
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作者 Dionne Telemacque Feng-Zhao Zhu +7 位作者 Zheng-Wei Ren Kai-Fang Chen Deepak Drepaul Sheng Yao Fan Yang Yan-Zheng Qu Ting-Fang Sun Xiao-Dong Guo 《中国神经再生研究:英文版》 SCIE CAS CSCD 2020年第10期1814-1820,共7页
Current management for spinal cord injury aims to reduce secondary damage and recover sensation and movement.Acute spinal cord injury is often accompanied by spinal cord compartment syndrome.Decompression by durotomy ... Current management for spinal cord injury aims to reduce secondary damage and recover sensation and movement.Acute spinal cord injury is often accompanied by spinal cord compartment syndrome.Decompression by durotomy and/or myelotomy attempts to relieve secondary damage by completelyrelieving the compression of the spinal cord,removing the necrotic tissue,decreasing edema,reducing hemorrhage,and improving blood circulation in the spinal cord.However,it is controversial whether durotomy and/or myelotomy after spinal cord injury are beneficial to neurological recovery.This review compares the clinical effects of durotomy with those of myelotomy in the treatment of spinal cord injury.We found that durotomy has been performed more than myelotomy in the clinic,and that durotomy may be safer and more effective than myelotomy.Durotomy performed in humans had positive effects on neurological function in 92.3% of studies in this review,while durotomy in animals had positive effects on neurological function in 83.3% of studies.Myelotomy procedures were effective in 80% of animal studies,but only one clinical study of myelotomy has reported positive results,of motor and sensory improvement,in humans.However,a number of new animal studies have reported that durotomy and myelotomy are ineffective for spinal cord injury.More clinical data,in the form of a randomized controlled study,are needed to understand the effectiveness of durotomy and myelotomy. 展开更多
关键词 decompression durotomy INTRASPINAL PRESSURE LAMINECTOMY MYELOTOMY neurological recovery SPINAL CORD compartment syndrome SPINAL CORD injury SPINAL CORD interstitial PRESSURE
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基于压差式施肥罐的均匀施肥方法 认领
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作者 胡昕宇 严海军 陈鑫 《农业工程学报》 EI CAS CSCD 北大核心 2020年第1期119-127,共9页
压差式施肥罐是水肥一体化中应用较为广泛的施肥装置,但它容易产生施肥不均匀的问题,会因局部过量施肥造成土壤污染,还会影响作物的产量和品质。为利用计算机控制压差式施肥罐进行田间作物的恒定浓度和流量施肥,该文基于肥料连续方程推... 压差式施肥罐是水肥一体化中应用较为广泛的施肥装置,但它容易产生施肥不均匀的问题,会因局部过量施肥造成土壤污染,还会影响作物的产量和品质。为利用计算机控制压差式施肥罐进行田间作物的恒定浓度和流量施肥,该文基于肥料连续方程推导了解析解,由计算机控制流入施肥罐的流量和直接流过主管道进入灌溉系统的流量。在此基础上,该文通过试验数据验证了施肥罐内水肥流动数学模型,对解析解控制压差式施肥罐的恒定浓度和流量施肥进行了模拟,模拟结果与解析解的相对偏差小于15%,验证了该均匀施肥方法的合理性。结果表明以最优肥液浓度的±50%为界,传统压差式施肥罐使用过程中约有70%~80%的肥料处于过量施肥或不充分施肥范围内,通过均匀施肥方法,可以基本实现灌溉过程中基于压差式施肥罐的施肥均匀。 展开更多
关键词 肥料 模型 压力 水肥一体化 压差式施肥罐 均匀施肥 解析解
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Physicians Attitude towards Pressure Injury Prevention and Management 认领
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作者 Abdullah Bany Hamdan Balaji Duraisamy +2 位作者 Sherwynn Javison Tariq Wani Musa Alharbi 《癌症治疗(英文)》 2020年第4期189-198,共10页
Background: Cancer and its management can cause cachexia, which, along with prolonged immobility could lead to the development of chronic pressure ulcers (PU). These complications result into infection and/or pressure... Background: Cancer and its management can cause cachexia, which, along with prolonged immobility could lead to the development of chronic pressure ulcers (PU). These complications result into infection and/or pressure injury. Though pressure injury related tasks, are deemed to be given to staff nurses alone. Little of literature is available on the physician’s attitude towards PU prevention and management. Medical interns in 2015 concluded that 70% of them need more education in pressure injury. Present study is about physicians involved in pressure injury identification and management in a Cancer Center. Material and methods: A cross-sectional study was conducted in King Fahad Medical City among oncology physicians using self-administered 11 statement survey questionnaire. Physician residents, fellows, assistant consultants’ and consultants’ attitudes were compared. Statistical analyses were performed using SPSS. Results: In total 50 physicians completed the survey. The physicians demonstrated a positive attitude with an average mean score of 42.35 ± 4.65 (32, 51). The difference in the attitude scores among sub-groups was not statistically significant. Conclusions: Our study demonstrated a positive attitude towards pressure ulcer prevention and management among physicians working in Cancer Center. We have also highlighted the challenges in maintaining this positive attitude and possible strategies for improvement in the future. 展开更多
关键词 Cancer ONCOLOGY ATTITUDE PHYSICIAN PRESSURE SKIN Injury
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Abdominal compartment syndrome: Often overlooked conditions in medical intensive care units 认领
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作者 Venkat Rajasurya Salim Surani 《世界胃肠病学杂志:英文版》 SCIE CAS 2020年第3期266-278,共13页
Intra-abdominal hypertension(IAH)and abdominal compartment syndrome are well recognized entities among surgical patients.Nevertheless,a number of prospective and retrospective observational studies have shown that IAH... Intra-abdominal hypertension(IAH)and abdominal compartment syndrome are well recognized entities among surgical patients.Nevertheless,a number of prospective and retrospective observational studies have shown that IAH is prevalent in about half of the critically ill patients in the medical intensive care units(ICU)and has been widely recognized as an independent risk factor for mortality.It is alarming to note that many members of the critical care team in medical ICU are not aware of the consequences of untreated IAH and the delay in making the diagnosis leads to increased morbidity and mortality.Frequently it is underdiagnosed and undertreated in this patient population.Elevated intraabdominal pressure decreases the blood flow to the kidneys and other abdominal viscera and also results in reduced cardiac output and difficulties in ventilating the patient because of increased intrathoracic pressure.When intraabdominal hypertension is not promptly recognized and treated,it leads to abdominal compartment syndrome,multiorgan dysfunction syndrome and death.Large volume fluid resuscitation is very common in medical ICU patients presenting with sepsis,shock and other inflammatory conditions like pancreatitis and it is one of the major risk factors for the development of intra-abdominal hypertension.This article presents an overview of the epidemiology,definitions,risk factors,pathophysiology and management of IAH and abdominal compartment syndrome in critically ill medical ICU patients. 展开更多
关键词 INTRA-ABDOMINAL PRESSURE INTRA-ABDOMINAL hypertension ABDOMINAL COMPARTMENT syndrome Acute kidney injury Large volume RESUSCITATION Open ABDOMEN Bladder PRESSURE Medical intensive care unit
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Soil pressure and pore pressure for seismic design of tunnels revisited: considering water-saturated, poroelastic half-space 认领
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作者 Zhu Jun Liang Jianwen 《地震工程与工程振动:英文版》 SCIE EI CSCD 2020年第1期17-36,共20页
This paper describes a systematic study on the fundamental features of seismic soil pressure on underground tunnels, in terms of its magnitude and distribution, and further identifi es the dominant factors that signif... This paper describes a systematic study on the fundamental features of seismic soil pressure on underground tunnels, in terms of its magnitude and distribution, and further identifi es the dominant factors that signifi cantly infl uence the seismic soil pressure. A tunnel embedded in water-saturated poroelastic half-space is considered, with a large variety of model and excitation parameters. The primary features of both the total soil pressure and the pore pressure are investigated. Taking a circular tunnel as an example, the results are presented using a fi nite element-indirect boundary element(FE-IBE) method, which can account for dynamic soil-tunnel interaction and solid frame-pore water coupling. The effects of tunnel stiffness, tunnel buried depth and input motions on the seismic soil pressure and pore pressure are also examined. It is shown that the most crucial factors that dominate the magnitude and distribution of the soil pressure are the tunnel stiffness and dynamic soil-tunnel interaction. Moreover, the solid frame-pore water coupling has a prominent infl uence on the magnitude of the pore pressure. The fi ndings are benefi cial to obtain insight into the seismic soil pressure on underground tunnels, thus facilitating more accurate estimation of the seismic soil pressure. 展开更多
关键词 SEISMIC SOIL PRESSURE SEISMIC pore PRESSURE dynamic soil-tunnel interaction water-saturated POROELASTIC
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Progress in achieving high-performance piezoresistive and capacitiveflexible pressure sensors: A review 认领
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作者 Wufan Chen Xin Yan 《材料科学技术:英文版》 SCIE EI CAS CSCD 2020年第8期175-188,共14页
Electronic skin(e-skin) and flexible wearable devices are currently being developed with broad application prospects. Transforming electronic skin(e-skin) into true ¨skin¨is the ultimate goal. Tactile sensin... Electronic skin(e-skin) and flexible wearable devices are currently being developed with broad application prospects. Transforming electronic skin(e-skin) into true ¨skin¨is the ultimate goal. Tactile sensing is a fundamental function of skin and the development of high-performance flexible pressure sensors is necessary to realize thus. Many reports on flexible pressure sensors have been published in recent years,including numerous studies on improving sensor performance, and in particular, sensitivity. In addition,a number of studies have investigated self-healing materials, multifunctional sensing, and so on. Here,we review recent developments in flexible pressure sensors. First, working principles of flexible pressure sensors, including piezoresistivity, capacitance, and piezoelectricity, are introduced, as well as working mechanisms such as triboelectricity. Then studies on improving the performance of piezoresistive and capacitive flexible pressure sensors are discussed, in addition to other important aspects of this intriguing research field. Finally, we summarize future challenges in developing novel flexible pressure sensors. 展开更多
关键词 Electronic skin Flexible pressure sensor PIEZORESISTIVITY Capacitive pressure sensor
Radial Permeability Measurements for Shale Using Variable Pressure Gradients 认领
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作者 FAN Kunkun SUN Renyuan +6 位作者 DEREK ELS WORTH DONG Mingzhe LI Yajun YIN Congbin LI Yanchao CHEN Zhongwei WANG Chunguang 《地质学报:英文版》 SCIE CAS CSCD 2020年第2期269-279,共11页
Shale gas is becoming an important component of the global energy supply, with permeability a critical controlling factor for long-term gas production. Obvious deviation may exist between helium permeability determine... Shale gas is becoming an important component of the global energy supply, with permeability a critical controlling factor for long-term gas production. Obvious deviation may exist between helium permeability determined using small pressure gradient(SPG) methods and methane permeability obtained under actual field production with variable pressure gradients(VPG). In order to more accurately evaluate the matrix permeability of shale, a VPG method using real gas(rather than He) is established to render permeability measurements that are more representative of reservoir conditions and hence response. Dynamic methane production experiments were performed to measure permeability using the annular space in the shale cores. For each production stage, boundary pressure is maintained at a constant and the gas production with time is measured on the basis of volume change history in the measuring pump. A mathematical model explicitly accommodating gas desorption uses pseudo-pressure and pseudo-time to accommodate the effects of variations in pressuredependent PVT parameters. Analytical and semi-analytical solutions to the model are obtained and discussed. These provide a convenient approach to estimate radial permeability in the core by nonlinear fitting to match the semi-analytical solution with the recorded gas production data. Results indicate that the radial permeability of the shale determined using methane is in the range of 1×10-6– 1×10-5 mD and decreases with a decrease in average pore pressure. This is contrary to the observed change in permeability estimated using helium. Bedding geometry has a significant influence on shale permeability with permeability in parallel bedding orientation larger than that in perpendicular bedding orientation. The superiority of the VPG method is confirmed by comparing permeability test results obtained from both VPG and SPG methods. Although several assumptions are used, the results obtained from the VPG method with reservoir gas are much closer to reality and may be directly us 展开更多
关键词 SHALE RADIAL PERMEABILITY VARIABLE PRESSURE gradients PSEUDO PRESSURE PSEUDO time
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趋势图在麦尔兹窑生产运行中的实践应用 认领
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作者 李磊 《耐火与石灰》 2020年第1期9-11,共3页
介绍了麦尔兹窑趋势图的运行特点和规律,通过对趋势图曲线分析,对日常生产运行中存在的一系列问题进行有效判断,以便更好的服务于生产实践。
关键词 麦尔兹窑 趋势图 压力 流量
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Systematic review and Meta-analysis of treating open angle glaucoma with gonioscopy-assisted transluminal trabeculotomy 认领
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作者 Chun-Yan Guo Xiao-Hui Qi Jian-Ming Qi 《国际眼科杂志:英文版》 SCIE CAS 2020年第2期317-324,共8页
●AIM:To systematically review and Meta-analyze studies of managing open angle glaucoma(OAG)with gonioscopyassisted transluminal trabeculotomy(GATT)and to evaluate its effectiveness and safety.●METHODS:Eligible studi... ●AIM:To systematically review and Meta-analyze studies of managing open angle glaucoma(OAG)with gonioscopyassisted transluminal trabeculotomy(GATT)and to evaluate its effectiveness and safety.●METHODS:Eligible studies were retrieved and screened from five main electronic databases.Mean difference(MD)was hired to show the pooled effectiveness of intraocular pressure(IOP)and medication decrease achieved by GATT.In addition,combined surgical success and reoperation rates were calculated,and complications were also summarized.●RESULTS:Ten studies were included for systematic review,but one study was not pooled for Meta-analysis due to the repeated data.The combined IOP decrease after GATT was 9.81 mm Hg(95%CI:7.98-11.63 mm Hg)which showed significant reduction from the baselines(Z=10.52,P<0.0001).Similarly,the number of medications after GATT also decreased distinctly compared with that of medication before the surgery(Z=9.09,P<0.0001),and the pooled medication decrease was 1.68(95%CI:1.31-2.04).In addition,the combined surgical success rate was 85%,while the pooled reoperation rate was 20%.Sightthreatening complications occurred scarcely,whereas the pooled occurrence rate of hyphemia was as high as 36.0%.●CONCLUSION:GATT could effectively lower IOP and decrease medications for patients with OAG.Moreover,the procedure appears to be a safe and promising treatment for OAG due to its minimally-invasive and conjunctiva-sparing nature. 展开更多
关键词 gonioscopy-assisted TRANSLUMINAL TRABECULOTOMY open angle glaucoma INTRAOCULAR pressure complication META-ANALYSIS
Association between dietary sodium intake and blood pressure variability in Chinese patients with hypertension 认领
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作者 Chi Wang Tong-Bo Liu +5 位作者 Lei Mu Miao Wang Yao Li Si-Yu Yao Mao-Xiang Zhao Hao Xue 《中华医学杂志:英文版》 SCIE CAS CSCD 2020年第9期1066-1072,共7页
Background:The association between dietary sodium intake and blood pressure variability(BPV)in hypertensive patients remains unclear.The objective of this study was to demonstrate whether dietary sodium intake is a pr... Background:The association between dietary sodium intake and blood pressure variability(BPV)in hypertensive patients remains unclear.The objective of this study was to demonstrate whether dietary sodium intake is a predictor of elevated BPV in Chinese patients with hypertension.Methods:A total of 235 patients with essential hypertension were enrolled in the Department of Cardiology,Chinese People’s Liberation Army(PLA)General Hospital in 2018 to 2019,all of whom underwent 24-h ambulatory blood pressure monitoring.BPV was calculated as the standard deviation(SD),coefficient of variation(CV),variation independent of mean(VIM)of blood pressure measurements,respectively,and divided into diurnal systolic BPV(SBPV),diurnal diastolic BPV(DBPV),nocturnal SBPV,and nocturnal DBPV.24-h urine samples were collected to measure 24-h urine sodium excretion,which represents dietary sodium intake.The relationship between dietary sodium intake and BPV was analyzed by using Spearman correlations and multiple linear regression analysis.Results:Nocturnal SBPV-SD,CV,VIM,and nocturnal DBPV-SD in the high urine sodium excretion group were significantly higher than those in the medium and low urine sodium excretion groups,whereas diurnal SBPV-SD,CV,VIM,diurnal DBPV-SD,CV,VIM,and nocturnal DBPV-CV,VIM were not.Using the Spearman correlation analysis,we found a linear correlation between 24-h urine sodium excretion and nocturnal SBPV-SD,CV,VIM(SD,r=0.22,P=0.001;CV,r=0.17,P=0.009;VIM,r=0.16,P=0.020),nocturnal DBPV-SD(r=0.21,P=0.001),respectively.After further adjusting for confounding factors by multiple linear regression,the positive correlations remained between 24-h urine sodium excretion and nocturnal SBPV-SD,CV,VIM(SD,β=0.224,P<0.001;CV,β=0.211,P=0.001;VIM,β=0.213,P=0.001),nocturnal DBPV(SD,β=0.215,P=0.001),respectively.Conclusions:Dietary sodium intake is associated with nocturnal SBPV in Chinese patients with hypertension. 展开更多
关键词 HYPERTENSION Sodium intake Blood pressure variability
Relationship between metabolic syndrome and hypercapnia among obese patients with sleep apnea 认领
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作者 Yuka Kimura Takatoshi Kasai +5 位作者 Yasuhiro Tomita Satoshi Kasagi Hisashi Takaya Mitsue Kato Fusae Kawana Koji Narui 《世界呼吸病学杂志》 2020年第1期1-10,共10页
BACKGROUND In the obese patient population,some patients have severe obstructive sleep apnea(OSA)with daytime hypoventilation.Such patients are generally identified on the basis of the presence or absence of daytime h... BACKGROUND In the obese patient population,some patients have severe obstructive sleep apnea(OSA)with daytime hypoventilation.Such patients are generally identified on the basis of the presence or absence of daytime hypercapnia,and the condition is called obesity hypoventilation syndrome.However,mechanisms for such daytime hypoventilation remain unclear.AIM To investigate metabolic syndrome and daytime hypercapnia association based on hypercapnia prevalence in obese OSA patients in a nested case-control study.METHODS Consecutive obese patients(body mass index≥30 kg/m2)who underwent polysomnography due to suspected OSA were included.Among them,patients with severe OSA(apnea hypopnea index≥30/h)were divided into two groups according to the presence or absence of hypercapnia during wakefulness(arterial partial pressure of carbon dioxide≥or<45 Torr,respectively).The characteristics and clinical features of these two groups were compared.RESULTS Among 97 eligible patients,25 patients(25.8%)had daytime hypercapnia.There were no significant differences in age,gender,body mass index,apnea-hypopnea index,and Epworth Sleepiness Scale scores between the two groups.However,patients with hypercapnia had a significantly lower arterial partial pressure of oxygen level(75.8±8.2 torr vs 79.9±8.7 torr,P=0.042)and higher arterial partial pressure of carbon dioxide level(46.6±2.5 torr vs 41.0±2.9 torr,P<0.001).Additionally,patients with hypercapnia were more likely to have metabolic syndrome(72.0%vs 48.6%,P=0.043)and a higher metabolic score(the number of satisfied criteria of metabolic syndrome).In multivariate logistic regression analysis,the presence of metabolic syndrome was associated with the presence of hypercapnia(OR=2.85,95%CI:1.04-7.84,P=0.042).CONCLUSION Among obese patients with severe OSA,26%of patients had hypercapnia during wakefulness.The presence of metabolic syndrome was independently correlated with the presence of daytime hypercapnia. 展开更多
关键词 Arterial partial pressure of carbon dioxide HYPERCAPNIA Metabolic SYNDROME Obesity HYPOVENTILATION SYNDROME Obstructive SLEEP APNEA SLEEP DISORDERED breathing
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Controlling effects of differential swelling index on evolution of coal permeability 认领
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作者 Chuanzhong Jiang Zhenfeng Zhao +3 位作者 Xiwei Zhang Jishan Liu Derek Elsworth Guanglei Cui 《岩石力学与岩土工程学报:英文版》 SCIE CSCD 2020年第3期461-472,共12页
Coal permeability measurements are normally conducted under the assumption that gas pressure in the matrix is equalized with that in fracture and that gas sorption-induced swelling/shrinking strain is uniformly distri... Coal permeability measurements are normally conducted under the assumption that gas pressure in the matrix is equalized with that in fracture and that gas sorption-induced swelling/shrinking strain is uniformly distributed within the coal.However,the validity of this assumption has long been questioned and differential strain between the fracture strain and the bulk strain has long been considered as the primary reason for the inconsistency between experimental data and poroelasticity solutions.Although efforts have been made to incorporate the impact into coal permeability models,the fundamental nature of those efforts to split the matrix strain between fracture and coal bulk remains questionable.In this study,a new concept of differential swelling index(DSI)was derived to theoretically define the relation among sorption-induced strains of the coal bulk,fracture,and coal matrix at the equilibrium state.DSI was a function of the equilibrium pressure and its magnitudes were regulated by the Langmuir constants of both the matrix and the coal bulk.Furthermore,a spectrum of DSI-based coal permeability models was developed to explicitly consider the effect of differential strains.These models were verified with the experimental data under the conditions of uniaxial strain,constant confining pressure,and constant effective stress. 展开更多
关键词 Coal permeability Differential swelling behavior Gas adsorption Equilibrium pressure
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Numerical study on flow and heat transfer characteristics of microchannel designed using topological optimizations method 认领
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作者 HU DingHua ZHANG ZhiWei LI Qiang 《中国科学:技术科学英文版》 SCIE EI CAS CSCD 2020年第1期105-115,共11页
Microchannel has demonstrated advantages in the thermal management of integrated chip. In this study, the topology optimization method is applied for designing a topological microchannel to optimize the performances o... Microchannel has demonstrated advantages in the thermal management of integrated chip. In this study, the topology optimization method is applied for designing a topological microchannel to optimize the performances of both heat dissipation and pressure drop. To validate the performance of the topological structure, the flow and heat transfer characteristics of topological microchannel under non-uniform heating flux are numerically studied. The topological structure is designed to cool a heating area of 10 mm×10 mm with 4 hotspots. Heat flux is 40 W/cm^2 in the hotspot area, while it is only 15 W/cm^2 in the rest heating area. The results of heat dissipation performance and pressure drop are compared with those of conventional straight microchannel. Numerical result shows that, compared to the straight microchannel, the hotspot temperature and pressure drop of topological microchannel can be reduced by 4 and 0.6 k Pa, respectively, under the flow rate of 2.2×10^-4 kg/s. The coefficient of performance(COP) of topological microchannel can be 16.1% better than that of straight microchannel, which can be attributed to the effects of optimized bifurcation and confluence structural of topological microchannel. 展开更多
关键词 TOPOLOGY optimization MICROCHANNEL heat DISSIPATION pressure DROP HOTSPOT
煤油贮箱冷氦鼓泡增压过程数值研究 认领
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作者 周芮 程光平 +3 位作者 张浩 任枫 王舜浩 张小斌 《化工学报》 EI CAS CSCD 北大核心 2020年第3期965-973,共9页
火箭飞行过程中,约90 K的低温氦气用以加压室温下的煤油贮箱使煤油流出,保障发动机燃料供应。为尽可能减少氦气用量,设计低温氦气从液相中喷入,使得氦气在贮箱内上升过程先和液态煤油充分换热升温,再进入气相空间增压。但该过程可能引... 火箭飞行过程中,约90 K的低温氦气用以加压室温下的煤油贮箱使煤油流出,保障发动机燃料供应。为尽可能减少氦气用量,设计低温氦气从液相中喷入,使得氦气在贮箱内上升过程先和液态煤油充分换热升温,再进入气相空间增压。但该过程可能引起两个不利的结果,首先浸没在煤油中的低温氦气管路表面可能结冰,结冰沉底或可能堵塞发动机滤网;其次氦气可能被煤油携带,从而排出口位置可能出现气液两相流。这两种情况都对火箭发动机稳定运行造成负面影响,因此是不允许的。对低温氦气在贮箱中心喷入和环向多孔喷入两种结构的气液两相流过程进行了数值研究,构建了基于Euler-Euler模型的两相传热非稳态模型,数值结果与地面实验观察到的现象进行了定性对比,定性验证了模型的准确性。重点考察了煤油排出过程两种喷入结构的气液两相流分布以及煤油结冰可能性。研究结果从机理上解释了实验现象,并为煤油贮箱增压排出方案设计提供了参考。 展开更多
关键词 煤油 氦气 贮箱 两相流 增压 设计 数值分析
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微极流体方程组在Besov空间中弱解的正则性准则 认领
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作者 刘讲军 曲桢 胡钢 《数学季刊:英文版》 2020年第1期46-55,共10页
In this paper,we investigate the regularity criterion via the pressure of weak solutions to the micropolar fluid equations in three dimensions.We obtain that for 0<α<1 if p€L^(2/a)(0,T;B^α∞,∞),then the weak ... In this paper,we investigate the regularity criterion via the pressure of weak solutions to the micropolar fluid equations in three dimensions.We obtain that for 0<α<1 if p€L^(2/a)(0,T;B^α∞,∞),then the weak solution(u,ω)is regular on(0,T). 展开更多
关键词 MICROPOLAR fluid equations pressure REGULARITY CRITERIA BESOV space
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