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Do Engineering Diploma Students Drop out Due to Reasons Other Than Academic Performance
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作者 Trudy Sutherland 《Journal of Sociology Study》 2014年第2期182-191,共10页
关键词 学业成绩 学生 工程 原因 高等教育事业 课程 学习成绩 教育界
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A data-driven model of drop size prediction based on artificial neural networks using small-scale data sets 被引量:1
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作者 Bo Wang Han Zhou +3 位作者 Shan Jing Qiang Zheng Wenjie Lan Shaowei Li 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2024年第2期71-83,共13页
An artificial neural network(ANN)method is introduced to predict drop size in two kinds of pulsed columns with small-scale data sets.After training,the deviation between calculate and experimental results are 3.8%and ... An artificial neural network(ANN)method is introduced to predict drop size in two kinds of pulsed columns with small-scale data sets.After training,the deviation between calculate and experimental results are 3.8%and 9.3%,respectively.Through ANN model,the influence of interfacial tension and pulsation intensity on the droplet diameter has been developed.Droplet size gradually increases with the increase of interfacial tension,and decreases with the increase of pulse intensity.It can be seen that the accuracy of ANN model in predicting droplet size outside the training set range is reach the same level as the accuracy of correlation obtained based on experiments within this range.For two kinds of columns,the drop size prediction deviations of ANN model are 9.6%and 18.5%and the deviations in correlations are 11%and 15%. 展开更多
关键词 Artificial neural network drop size Solvent extraction Pulsed column Two-phase flow HYDRODYNAMICS
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Visual Outcomes and Risk of Rhegmatogenous Retinal Detachment Following Posterior Capsule Rupture during Cataract Surgery: With vs without Dropped Nuclear Lens Fragments
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作者 Rakan S. Al-Essa Mohammed M. Abusayf Majed S. Alkharashi 《International Journal of Clinical Medicine》 CAS 2023年第5期274-281,共8页
Background: Cataract surgery is the most frequently performed surgery worldwide. Posterior capsule rupture (PCR) remains one of the most common complications of cataract surgery and a major risk factor for poor visual... Background: Cataract surgery is the most frequently performed surgery worldwide. Posterior capsule rupture (PCR) remains one of the most common complications of cataract surgery and a major risk factor for poor visual outcomes. Cataract surgeries complicated by PCR and vitreous loss are managed with anterior vitrectomy at the time of surgery. However, the situation can be further complicated by dropping lens particles into the vitreous cavity necessitating a secondary pars plana vitrectomy (PPV). Purpose: To compare the visual outcomes and risk of rhegmatogenous retinal detachment (RRD) between eyes that required anterior vitrectomy (AV) alone for the management of vitreous loss and eyes that required AV and subsequent PPV for the management of dropped nuclear lens fragments (DNLF) following cataract surgery complicated by PCR in a tertiary care teaching hospital in Saudi Arabia. Methods: Medical records of patients in whom PCR occurred during phacoemulsification cataract surgery requiring AV or subsequent PPV for DNLF were retrospectively reviewed over a 6-year period from January 2016 to December 2021. Results: PCR occurred in 183 (2.3%) of 7757 consecutive eyes that underwent phacoemulsification cataract surgery during the study period. Seven eyes were excluded from analysis for missing data or short follow-up. Of the 176 eyes, 147 eyes (83.5%) were managed with AV alone, and the remaining 29 eyes (16.5%) underwent a secondary PPV for DNLF. After excluding eyes with pre-existing ocular pathology, final best-corrected visual acuity (BCVA) was similar in both groups with a mean of 0.32 logMAR (P = 0.99). Two of 147 eyes (1.4%) in the AV group developed RRD with poor final BCVA whereas none of the eyes in DNLF group developed RRD. Conclusion: The risk of RRD is lower in eyes that required PPV for DNLF than in eyes that were managed with AV alone following PCR during cataract surgery. The poor visual outcomes in eyes that suffered RRD underscore the importance of postoperative retinal examination and early detection of retinal breaks. 展开更多
关键词 Cataract Surgery Posterior Capsule Rupture Anterior Vitrectomy Retinal Detachment dropped Nucleus
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Buckling Properties of Water-Drop-Shaped Pressure Hulls with Various Shape Indices Under Hydrostatic External Pressure
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作者 DING Xiao-de ZHANG Jian +2 位作者 WANG Fang JIAO Hui-feng WANG Ming-lu 《China Ocean Engineering》 SCIE EI CSCD 2024年第1期1-17,共17页
The water-drop-shaped pressure hull has a good streamline,which has good application prospect in the underwater observatory.Therefore,this study conducted analytical,experimental and numerical investigation of the buc... The water-drop-shaped pressure hull has a good streamline,which has good application prospect in the underwater observatory.Therefore,this study conducted analytical,experimental and numerical investigation of the buckling properties of water-drop-shaped pressure hulls under hydrostatic pressure.A water-drop experiment was conducted to design water-drop-shaped pressure hulls with various shape indices.The critical loads for the water-drop-shaped pressure hulls were resolved by using Mushtari’s formula.Several numerical simulations including linear buckling analysis and nonlinear buckling analysis including eigenmode imperfections were performed.The results indicated that the critical loads resolved by Mushtari's formula were in good agreement with the linear buckling loads from the numerical simulations.This formula can be extended to estimate the buckling capacity of water-drop-shaped pressure hulls.In addition,three groups of pressure hulls were fabricated by using stereolithography,a rapid prototyping technique.Subsequently,three groups of the pressure hulls were subjected to ultrasonic measurements,optical scanning,hydrostatic testing and numerical analysis.The experimental results were consistent with the numerical results.The results indicate that the sharp end of the water-drop-shaped pressure hulls exhibited instability compared with the blunt end.This paper provides a new solution to the limitations of experimental studies on the water-drop-shaped pressure hulls as well as a new configuration and evaluation method for underwater observatories. 展开更多
关键词 BUCKLING pressure hull water drop underwater observatory
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Evaluation of frictional pressure drop correlations for air-water and air-oil two-phase flow in pipeline-riser system
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作者 Nai-Liang Li Bin Chen 《Petroleum Science》 SCIE EI CAS CSCD 2024年第2期1305-1319,共15页
Accurate prediction of the frictional pressure drop is important for the design and operation of subsea oil and gas transporting system considering the length of the pipeline. The applicability of the correlations to ... Accurate prediction of the frictional pressure drop is important for the design and operation of subsea oil and gas transporting system considering the length of the pipeline. The applicability of the correlations to pipeline-riser flow needs evaluation since the flow condition in pipeline-riser is quite different from the original data where they were derived from. In the present study, a comprehensive evaluation of 24prevailing correlation in predicting frictional pressure drop is carried out based on experimentally measured data of air-water and air-oil two-phase flows in pipeline-riser. Experiments are performed in a system having different configuration of pipeline-riser with the inclination of the downcomer varied from-2°to-5°to investigated the effect of the elbow on the frictional pressure drop in the riser. The inlet gas velocity ranges from 0.03 to 6.2 m/s, and liquid velocity varies from 0.02 to 1.3 m/s. A total of885 experimental data points including 782 on air-water flows and 103 on air-oil flows are obtained and used to access the prediction ability of the correlations. Comparison of the predicted results with the measured data indicate that a majority of the investigated correlations under-predict the pressure drop on severe slugging. The result of this study highlights the requirement of new method considering the effect of pipe layout on the frictional pressure drop. 展开更多
关键词 Frictional pressure drop Pipeline-riser Gas-liquid two-phase flow Severe slugging CORRELATION
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Ladder Time Stepwise Inertia Coordinated Control Method of Multiple Wind Farms to Suppress System Frequency Secondary Drop
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作者 He Li Xianchao Liu +1 位作者 Jidong Li Yuchen Qiu 《Energy Engineering》 EI 2024年第8期2293-2311,共19页
Currently,both regulated and deregulated power trading exist in China’s power system,which has caused imbalanced funds in the electricity market.In this paper,a simulation analysis of the electricity market with wind... Currently,both regulated and deregulated power trading exist in China’s power system,which has caused imbalanced funds in the electricity market.In this paper,a simulation analysis of the electricity market with wind energy resources is conducted,and the calculation methods of unbalanced funds are investigated systematically.In detail,the calculation formulas of unbalanced funds are illustrated based on their definition,and a two-track electricity market clearing model is established.Firstly,the concept of the dual-track system is explained,and the specific calculation formulas of various types of unbalanced funds are provided.Next,considering the renewable energy consumption,the market clearing model based on DC power flow is constructed and solved;by combining fitting methods of mid-and long-term curves,the unbalanced funds are calculated based on clearing results and formulas. 展开更多
关键词 Wind power stepwise inertial frequency control secondary drop
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Efficacy of recombinant human epidermal growth factor plus sodium hyaluronate eye drops in diabetic dry eye post-cataract surgery
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作者 Jun-Ling Li Jin Zhao +2 位作者 Zhen-Feng Guo Chang Xiao Xuan Liu 《World Journal of Diabetes》 SCIE 2024年第6期1234-1241,共8页
BACKGROUND Dry eye syndrome(DES)after diabetic cataract surgery can seriously affect the patient’s quality of life.Therefore,effective alleviation of symptoms in patients with this disease has important clinical sign... BACKGROUND Dry eye syndrome(DES)after diabetic cataract surgery can seriously affect the patient’s quality of life.Therefore,effective alleviation of symptoms in patients with this disease has important clinical significance.AIM To explore the clinical effect of recombinant human epidermal growth factor(rhEGF)plus sodium hyaluronate(SH)eye drops on DES after cataract surgery in patients with diabetes.METHODS We retrospectively evaluated 82 patients with diabetes who experienced DES after cataract surgery at Tianjin Beichen Hospital,Affiliated Hospital of Nankai University between April 2021 and April 2023.They were classified into an observation group(42 cases,rhEGF+SH eye drops)and a control group(40 cases,SH eye drops alone),depending on the different treatment schemes.The therapeutic efficacy,dry eye symptom score,tear film breakup time(TFBUT),basic tear secretion score[assessed using Schirmer I test(SIt)],corneal fluorescein staining(FL)score,tear inflammatory markers,adverse reactions during treat-ment,and treatment satisfaction were compared between the two groups.RESULTS Therapeutic efficacy was higher in the observation group compared with the control group.Both groups showed improved TFBUT and dry eye,as well as improved SIt and FL scores after treatment,with a more pronounced improvement in the observation group.Although no marked differences in adverse reactions were observed between the two groups,treatment satisfaction was higher in the observation group.CONCLUSION rhEGF+SH eye drops rendered clinical benefits to patients by effectively ameliorating dry eye and visual impairment with favorable efficacy,fewer adverse reactions,and high safety levels.Thus,this treatment should be promoted in clinical practice. 展开更多
关键词 Recombinant human epidermal growth factor Sodium hyaluronate eye drops Diabetic patients Dry eye syndrome after cataract surgery Therapeutic efficacy
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Improvement of Temperature Drop Model Parameters for 4200mm/3500mm Rolling of Baosteel Medium and Thick Plate
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作者 Kong Peng 《Frontiers of Metallurgical Industry》 2024年第1期27-30,共4页
Based on the temperature situation during the rolling process of 4200 mm/3500 mm medium and thick plates at Baosteel,this article analyzes the influencing factors of temperature changes during the rolling process from... Based on the temperature situation during the rolling process of 4200 mm/3500 mm medium and thick plates at Baosteel,this article analyzes the influencing factors of temperature changes during the rolling process from the perspective of heat transfer theory and the temperature change law during the rolling process.The temperature loss during the four rolling processes is tracked on site,and the temperature drop model parameters during the rolling process of 4200mm/3500mm medium and thick plates at Baosteel are quantitatively provided.It is applied to actual rolling production and has achieved good results. 展开更多
关键词 medium thickness plate rolling process temperature drop
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Channel Drop Out: A Simple Way to Prevent CNN from Overfitting in Motor Imagery Based BCI
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作者 Jing Luo Yaojie Wang +3 位作者 Rong Xu Guangming Liu Xiaofan Wang Yijing Gong 《国际计算机前沿大会会议论文集》 2021年第1期443-452,共10页
With the development of deep learning, many motor imagerybrain-computer interfaces based on convolutional neural networks(CNNs) show outstanding performances. However, the trial number ofEEG in the training set is usu... With the development of deep learning, many motor imagerybrain-computer interfaces based on convolutional neural networks(CNNs) show outstanding performances. However, the trial number ofEEG in the training set is usually limited, and redundancy extensivelyexists in multiple channel EEG. Thus, overfitting often appears in CNNbased motor imagery recognition model and greatly affects the performancesof model. In this paper, channel drop out is proposed to addressthis problem by data augmentation and ensemble learning. Specifically,one of all EEG channels will be dropped and replaced by the mean signalof all EEG channels. In this way, the trial number in the training setwas enlarged by channel drop out. And at the testing stage, all the EEGtrials processed by channel drop out were fed to the CNN model and theaverage output probabilities of them were applied to determine the prediction.The experiments were conducted on two popular CNN modelsapplied in motor imagery BCI and BCI Competition IV datasets 2a toverify the performances of the proposed channel drop out approach. Theresults show that average improvements provided by channel drop outin two-category or four-category motor imagery classification are 2.83%and 2.65% compared with the original CNN model. So the channel dropout approach significantly improves the performances of motor imagerybased BCI. 展开更多
关键词 Brain-computer interface(BCI) Channel drop out Motor imagery(MI) Convolutional neural network(CNN)
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Clinical outcomes of combined flow-pressure drop measurements using newly developed diagnostic endpoint:Pressure drop coefficient in patients with coronary artery dysfunction 被引量:2
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作者 Mohamed A Effat Srikara Viswanath Peelukhana Rupak K Banerjee 《World Journal of Cardiology》 CAS 2016年第3期283-292,共10页
AIM:To combine pressure and flow parameter, pressure drop coefficient(CDP) will result in better clinical outcomes in comparison to the fractional flow reserve(FFR) group. METHODS:To test this hypothesis, a comparison... AIM:To combine pressure and flow parameter, pressure drop coefficient(CDP) will result in better clinical outcomes in comparison to the fractional flow reserve(FFR) group. METHODS:To test this hypothesis, a comparison was made between the FFR < 0.75 and CDP > 27.9 groups in this study, for the major adverse cardiac events [major adverse cardiac events(MACE): Primary outcome] and patients’ quality of life(secondary outcome). Further, a comparison was also made between the survival curves for the FFR < 0.75 and CDP > 27.9 groups. Two-tailed χ~2 test proportions were performed for the comparison of primary and secondary outcomes. Kaplan-Meier survival analysis was performed to compare the survival curves of FFR < 0.75 and CDP > 27.9 groups(MedcalcV10.2, Mariakerke, Belgium). Results were considered statistically significant for P < 0.05. RESULTS: The primary outcomes(%MACE) in the FFR < 0.75 group(20%, 4 out of 20) was not statistically different(P = 0.24) from the %MACE occurring in CDP > 27.9 group(8.57%, 2 out of 35). Noteworthy is the reduction in the %MACE in the CDP > 27.9 group, in comparison to the FFR < 0.75 group. Further, the secondary outcomes were not statistically significant between the FFR < 0.75 and CDP > 27.9 groups. Survival analysis results suggest that the survival time for the CDP > 27.9 group(n = 35) is significantly higher(P = 0.048) in comparison to the survival time for the FFR < 0.75 group(n = 20). The results remained similar for a FFR = 0.80 cut-off. CONCLUSION: Based on the above, CDP could prove to be a better diagnostic end-point for clinical revascularization decision-making in the cardiac catheterization laboratories. 展开更多
关键词 Pressure drop coefficient INTERVENTIONAL CARDIOLOGY Intermediate coronary STENOSIS
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Delineation of epicardial stenosis in patients with microvascular disease using pressure drop coefficient:A pilot outcome study 被引量:2
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作者 Ullhas Udaya Hebbar Mohamed A Effat +2 位作者 Srikara V Peelukhana Imran Arif Rupak K Banerjee 《World Journal of Cardiology》 CAS 2017年第12期813-821,共9页
AIM To investigate the patient-outcomes of newly developed pressure drop coefficient(CDP) in diagnosing epicardial stenosis(ES) in the presence of concomitant microvascular disease(MVD).METHODS Patients from our clini... AIM To investigate the patient-outcomes of newly developed pressure drop coefficient(CDP) in diagnosing epicardial stenosis(ES) in the presence of concomitant microvascular disease(MVD).METHODS Patients from our clinical trial were divided into two subgroups with:(1) cut-off of coronary flow reserve(CFR) < 2.0;and(2) diabetes.First,correlations were performed for both subgroups between CDP and hyperemic microvascular resistance(HMR),a diagnostic parameter for assessing the severity of MVD.Linear regression analysis was used for these correlations.Further,in each of the subgroups,comparisons were made between fractional flow reserve(FFR) < 0.75 and CDP > 27.9 groups for assessing major adverse cardiac events(MACE:Primary outcome).Comparisons were also made between the survival curves for FFR < 0.75 and CDP > 27.9 groups.Two tailed chi-squared and Fischer's exact tests were performed for comparison of the primary outcomes,and the log-rank test was used to compare the Kaplan-Meier survival curves.P < 0.05 for all tests was considered statistically significant.RESULTS Significant linear correlations were observed between CDP and HMR for both CFR < 2.0(r = 0.58,P < 0.001) and diabetic(r = 0.61,P < 0.001) patients.In the CFR < 2.0 subgroup,the %MACE(primary outcomes) for CDP > 27.9 group(7.7%,2/26) was lower than FFR < 0.75 group(3/14,21.4%);P = 0.21.Similarly,in the diabetic subgroup,the %MACE for CDP > 27.9 group(12.5%,2/16) was lower than FFR < 0.75 group(18.2%,2/11);P = 0.69.Survival analysis for CFR < 2.0 subgroup indicated better event-free survival for CDP > 27.9 group(n = 26) when compared with FFR < 0.75 group(n = 14);P = 0.10.Similarly,for the diabetic subgroup,CDP > 27.9 group(n = 16) showed higher survival times compared to FFR group(n = 11);P = 0.58.CONCLUSION CDP correlated significantly with HMR and resulted in better %MACE as well as survival rates in comparison to FFR.These positive trends demonstrate that CDP could be a potential diagnostic endpoint for delineating MVD with or without ES. 展开更多
关键词 Fractional flow reserve Pressure drop coefficient MICROVASCULAR disease Intermediate coronary STENOSIS INTERVENTIONAL CARDIOLOGY
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Effects of endogenous dopamine induced by low concentration atropine eye drops on choroidal neovascularization in high myopia mice 被引量:2
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作者 Yan-Yan Ji Shi-Xi Zhang +1 位作者 Ye Kang Song Chen 《International Journal of Ophthalmology(English edition)》 SCIE CAS 2023年第7期1034-1040,共7页
AIM:To evaluate effects of endogenous dopamine induced by low concentration atropine eye drops on choroidal neovascularization(CNV)in high myopia mice.METHODS:The C57BL/6J mice were deprived of the right eye for 4wk,a... AIM:To evaluate effects of endogenous dopamine induced by low concentration atropine eye drops on choroidal neovascularization(CNV)in high myopia mice.METHODS:The C57BL/6J mice were deprived of the right eye for 4wk,and the high myopia was diagnosed by optometry,the diopter was less than-6.00 D,and CNV was induced by 532 nm laser.The changes of dopamine D1 receptor(DRD1),dopamine D2 receptor(DRD2),and vascular endothelial growth factor A(VEGFA)were detected by Western blot technology at 0.5,1,2h,and 7d after 0.01%,0.05%,and 0.1%atropine eye drops,respectively,the area of CNV was measured.RESULTS:Significant increases were observed on the expression of DRD2 in mouse high myopia model at 0.5,1,2h,7d with 0.05%and 0.1%atropine eye drops(P<0.05).Significant decreases were observed on the expression of DRD1 and VEGFA in mouse high myopia model at 0.5,1,2h,7d with 0.05%and 0.1%atropine eye drops(P<0.05).The area of CNV induced by laser in the drug-treated group was significantly smaller than that in the control group,and the higher the concentration,the more significant the inhibitory effect(P<0.05).CONCLUSION:The 0.01%,0.05%,0.1%atropine eye drops can decrease the level of VEGFA and inhibit high myopia CNV indirectly by up-regulating the level of DRD2 and down-regulating the level of DRD1,and the effect of 0.05%and 0.1%atropine eye drops is more significant. 展开更多
关键词 high myopia choroidal neovascularization low concentration atropine eye drops dopamine D1 receptor dopamine D2 receptor
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Meta analysis about the efficacy and safety of anti-ocular hypertension eye drops without benzalkonium chloride
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作者 Yan-Qing Wang Xin Wang Ping Liu 《Asian Pacific Journal of Tropical Medicine》 SCIE CAS 2013年第12期1004-1008,共5页
Objective:To explore the safety and efficacy of eye drops without benzalkonium chloride(BAK)in treating glaucoma and ocular hypertension.Methods:The clinical case-control literatures about eye drops without BAK treati... Objective:To explore the safety and efficacy of eye drops without benzalkonium chloride(BAK)in treating glaucoma and ocular hypertension.Methods:The clinical case-control literatures about eye drops without BAK treating glaucoma and ocular hypertension were retrieved in PubMed,EMBASE,Cochrane and Chinese Biological and Medical database.Mela 5.0 software was used to analyze the literatures.Results:Five clinical control studies were included.The results indicated both eye drops could lower the intraocular pressure,and the intraocular pressurelowering difference between two eye drops was 0.07 mmHg(95%CI:0.04,0.19)(P>0.05).Two adverse reactions occurred more were conjunctival injection(10.78%)and allergic conjunctivitis(4.78%).The odd ratio of two eye drops occurring conjunctival injection and allergic conjunctivitis was 0.67(95%CI,0.25,1.10)and 0.82(95%CI,0.09,1.54),respectively(P<0.05)in fixed effect model.Conclusions:There is no difference between the eye drops with or without BAK in lowering intraocular pressure.but the latter is of higher safety.In consideration of the relatively small sample size of this research,more high-quality clinical research contrasts are needed as evidence. 展开更多
关键词 Benzalkonium CHLORIDE META analysis Eye dropS GLAUCOMA
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The role of cochlear implantation in alleviating Tumarkin drop attacks of Meniere's disease;a case report 被引量:1
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作者 Chiara Filippi Edoardo Covelli +2 位作者 Haitham H.Elfarargy Simonetta Monini Maurizio Barbara 《Journal of Otology》 CAS CSCD 2023年第3期168-172,共5页
Ménière’s disease(MD)patients may suffer episodes of sudden falls,named Tu markin drop attacks(DAs).This fall occurs abruptly and without warning or loss of consciousness.DAs usually aggravate the clinical ... Ménière’s disease(MD)patients may suffer episodes of sudden falls,named Tu markin drop attacks(DAs).This fall occurs abruptly and without warning or loss of consciousness.DAs usually aggravate the clinical picture of MD and are challenging to manage.The present report describes a case treated by cochlear implantation(CI)due to concomitant deafness and offers some clinical considerations for this condition.A male patient aged 48 years with a 10-year history of definite bilateral MD had profound SNHL on the right and severe SNHL on the left side.He suffered from intermittent attacks of vertigo,ear fullness,and tinnitus and,in the last year,had developed DAs and experienced 14 episodes in the previous six months.The preoperative category of acoustic performance was 3.The Dizziness Handicap Inventory(DHI)questionnaire showed a total score of 46,which indicated a moderate degree of disability.A CI was planned for the right side.The patient did not report any further DAs episode for two years since then.The postoperative category of acoustic performance became 11,and the postoperative DHI questionnaire showed a decrease in the total score(from 46 to 19),which indicated a mild disability.Unilateral CI effectively alleviated the DAs associated with bilateral MD.Our report proposes a new modality for managing vertiginous symptoms in cases of MD with hearing loss without the need for more aggressive surgical interventions with the need for clinical trials to confirm our results. 展开更多
关键词 Meniere's disease Tumarkin drop attacks Hearing loss Cochlear implant
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Numerical simulation of drop weight impact sensitivity evaluation criteria for pressed PBXs 被引量:1
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作者 Hong-zheng Duan Yan-qing Wu +1 位作者 Kun Yang Feng-lei Huang 《Defence Technology(防务技术)》 SCIE EI CAS CSCD 2023年第1期76-90,共15页
A thorough understanding of drop-weight impacted responses for polymer-bonded explosives(PBXs)is significant to evaluate their impact sensitivity.The characteristics of the drop-weight impacted pressed PBXs including ... A thorough understanding of drop-weight impacted responses for polymer-bonded explosives(PBXs)is significant to evaluate their impact sensitivity.The characteristics of the drop-weight impacted pressed PBXs including deforming,fracturing,forming a local high-temperature region and igniting,were simulated using a coupled mechanical-thermo-chemical model integrating micro-defects evolution.A novel evaluation method for impact sensitivity is established using the relation between the input kinetic energy and the output energy due to deformation,crushing energy,local hot spot energy and ignition.The effects of impact velocity on sensitivity were analyzed and the critical local ignition impact velocity is determined as 4.0-4.5 m/s.The simulated results show that shear-crack friction heating is the dominant ignition mechanism.The region along the boundary of PBXs sample is the most hazardous regions where ignition first occur.The propagation of stress wave in PBXs causes shear-crack hotspot and bulk temperature exhibiting an approximate 45°direction evolution path,which is the main reason that dominated damage-ignition region transits from the boundary to the central of sample. 展开更多
关键词 Polymer-bonded explosives(PBXs) drop weight impact Numerical simulation Sensitivity evaluation criterion Hotspot mechanism
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Effect of dynamic loading conditions on the dynamic performance of MP1 energy-absorbing rockbolts:Insight from laboratory drop test 被引量:1
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作者 Jinfu Lou Fuqiang Gao +2 位作者 Jianzhong Li Guiyang Yuan Mostafa Sharifzadeh 《International Journal of Mining Science and Technology》 SCIE EI CAS CSCD 2023年第2期215-231,共17页
Energy-absorbing rockbolts have been widely adopted in burst-prone excavation support, and their serviceability is closely related to the frequency and magnitude of seismic events. In this research, the splittube drop... Energy-absorbing rockbolts have been widely adopted in burst-prone excavation support, and their serviceability is closely related to the frequency and magnitude of seismic events. In this research, the splittube drop test with varying impact energy was conducted to reproduce the dynamic performance of MP1rockbolts under a wide range of seismic event magnitudes. The test results showed that the impact process could be subdivided into four distinct stages, i.e. mobilization, strain hardening, plastic flow(ductile), and rebound stage, of which strain hardening and plastic flow are the primary energy absorbing stages. As the impact energy per drop increases from 8.1 to 46.7 k J, the strain rate of the shank varies between 1.20 and 2.70 s^(-1), and the average impact load is between 240 and 270kN, which may be considered as constant. The MP1 rockbolt has a cumulative maximum energy absorption(CMEA) of 31.9–40.0 k J/m, with an average of 35.0 k J/m, and the elongation rate is 11.4%–14.7%, with an average of 12.7%, both of which are negatively correlated with the impact energy per drop. Regression analysis shows that energy absorption and shank elongation, as well as momentum input and impact duration,conform to the linear relationship. The complete dynamic capacity envelope of MP1 rockbolts is proposed, which reflects the dynamic bearing capacity, elongation, and distinct stages. This study is helpful to better understand the dynamic characteristics of energy-absorbing rockbolts and assist design engineers in robust reinforcement systems design to mitigate rockburst damage in seismically active underground excavations. 展开更多
关键词 Energy-absorbing rockbolt Dynamic performance drop test Residual elastic energy(REE) Energy absorption rate(EAR) Dynamic capacity envelope
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The Causes of Distress in Paediatric Outpatients Receiving Dilating Drops
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作者 Nashila Hirji Sophie Jones Graham Thompson 《Open Journal of Ophthalmology》 2012年第2期21-25,共5页
Background/aims: Paediatric outpatients are often dilated with cyclopentolate drops. These cause discomfort and distress, which may impede subsequent examination. We aimed to determine the distress caused by cyclopent... Background/aims: Paediatric outpatients are often dilated with cyclopentolate drops. These cause discomfort and distress, which may impede subsequent examination. We aimed to determine the distress caused by cyclopentolate drops, and other factors in the clinic environment. Methods: Over an 8 week period, questionnaires were issued to guardians of all paediatric outpatients aged under 10 years receiving cyclopentolate. The childrens’distress was graded on a scale of 1 - 10 (1 = no distress, 10 = severe distress). Waiting time and ease of examination were recorded. Data was analysed using Stata statistics, and significant differences were reported at the P < 0.05 level. Results: The 72 children were grouped as under 4 years (n = 43, Group A), aged 4 - 7 years (n = 19, Group B), and aged 7-10 years (n = 10, Group C). Median distress levels at home (baseline), on arrival, on dilation, and on examination were as follows: Group A;1, 2, 7, 6 respectively;Group B;1, 1, 6, 2 and Group C;1, 1, 4.5, 1. All age groups were significantly more distressed on examination compared to baseline. Distress scores on examination were significantly greater for Group A, in keeping with the greatest number of suboptimal examinations. Guardians reported that a prolonged waiting time and bright examination lights also contributed to distress. Conclusions: This study confirms that cyclopentolate causes significant distress in young children, and in 45% of very young children, the examination is difficult. Proxymetacaine prior to cyclopentolate is a possible solution, but other distressing factors should also be addressed for optimal outcomes. 展开更多
关键词 PAEDIATRIC CYCLOPENTOLATE Proxymetacaine HYDROCHLORIDE Dilating dropS
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Tendon Transfer for Foot Drop: A Simple Procedure with Effective Outcome Local Experience
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作者 Hesham El Sobky Nabil Ali Amr Farid Khalil 《Open Journal of Modern Neurosurgery》 2019年第3期258-268,共11页
Introduction:?Patients presented with old neglected common peroneal nerve injuries, failed 2ry repair, compression neuropathies not improved after decompression and closed injuries with no improvement on conservative ... Introduction:?Patients presented with old neglected common peroneal nerve injuries, failed 2ry repair, compression neuropathies not improved after decompression and closed injuries with no improvement on conservative measures which are still unsolved problems. Poor recovery of this nerve after repair or decompression gives great importance to tendon transfer in these situations. Material and Methods: This study was conducted in Neurosurgery Department of Mansoura University from 2015 to 2018 on twenty-six patients (16 males and 10 females). Their age ranged from 6 - 58 years. All of them presented with persistent foot drop at least for one year after injury with no signs of improvement clinically or in electrophysiological studies. All patients underwent tibialis posterior tendon transfer through the interosseous membrane to the tendons of the leg anterior compartment. All of them were put in a plaster cast for four weeks postoperative. A physiotherapeutic program was applied for all patients as preoperative preparation and postoperative rehabilitation. Results: Twenty-two patients showed satisfactory results, three patients fair improvement and one patient no improvement. Two patients had wound infection and there was no mortality in this study. Conclusion:?Tendon transfer is an effective valid solution to be considered in the management of foot drop in these patients. 展开更多
关键词 FOOT drop Tibialis POSTERIOR TRANSFER
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Pressure drop of structured packing in pilot column and comparison to common correlations
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作者 Emil Madsen Randi Neerup +3 位作者 Arne Gladis Jens K.Jørsboe Nicolas von Solms Philip L.Fosbøl 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2023年第12期281-291,共11页
Packed columns are widely used in the chemical industry such as absorption,stripping,distillation,and extraction in the production of e.g.organic chemicals,and pharmaceuticals.Pressure loss and pressure drop correlati... Packed columns are widely used in the chemical industry such as absorption,stripping,distillation,and extraction in the production of e.g.organic chemicals,and pharmaceuticals.Pressure loss and pressure drop correlations are of special interest when it comes to the hydrodynamic properties of a column.The pressure loss across the column is of interest in the design phase when the size of the blower to drive the gas stream through the column has to be decided.The loading point and flooding point are also influenced by the pressure loss and the area of operation is determined from these points.This work examines four different correlations on pressure drop.The correlations are(i)Ergun’s equation(1952),(ii)an improved version of Ergun’s equation by Stichlmair,Bravo,and Fair(1989),(iii)an equation developed by Billet and Schultes(1999),and(iv)an equation by Rocha,Bravo,and Fair(1993).The complexity of the correlations is increasing in the mentioned order,Ergun’s equation being the simplest one.This study investigates if the more complicated correlations give better predictions to pressure drop in packed columns.This is determined by comparing the correlations to experimental data for pressure drop in a packed column with 8.2 m of structured packing using water as the liquid and atmospheric air as the gas.Seven experiments were carried out for determining the pressure drop in the column with liquid flows varying from 0 to 500 kg·h^(-1).At constant liquid flow,the gas flow was varied from approximately 10 to 70 kg·h^(-1).The pressure drop across the non-wetted column was best described by the correlation by Rocha et al.while the pressure drop for liquid flows from 100 to 500 kg·h^(-1)was,in general,best described by Stichlmair’s equation.For an irrigated column,the highest deviation was a predicted pressure drop 69.6%lower than measured.The best prediction was 0.1%higher than the measured.This study shows,surprisingly,that for a system of water and atmospheric air,complicated correlations on pressure drop determination do not provide better estimates than simple equations. 展开更多
关键词 Pressure drop correlations Packed columns Structured packing Fluid dynamics
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Study of main factors influencing unsteady-state temperature drop in oil tank storage under dynamic thermal environment coupling
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作者 Wei Sun Ming-Yang Li +4 位作者 Yu-Duo Liu Qing-Lin Cheng Li-Xin Zhao Shuai Shao Zhi-Hua Wang 《Petroleum Science》 SCIE EI CAS CSCD 2023年第6期3783-3797,共15页
With the increasing oil demand, the construction of oil energy reserves in China needs to be further strengthened. However, given that there has been no research on the main influencing factors of crude oil temperatur... With the increasing oil demand, the construction of oil energy reserves in China needs to be further strengthened. However, given that there has been no research on the main influencing factors of crude oil temperature drop in storage tanks under actual dynamically changing environments, this paper considers the influence of dynamic thermal environment and internal crude oil physical properties on the fluctuating changes in crude oil temperature. A theoretical model of the unsteady-state temperature drop heat transfer process is developed from a three-dimensional perspective. According to the temperature drop variation law of crude oil storage tank under the coupling effect of various heat transfer modes such as external forced convection, thermal radiation, and internal natural convection, the external dynamic thermal environment influence zone, the internal crude oil physical property influence zone, and the intermediate transition zone of the tank are proposed. And the multiple non-linear regression method is used to quantitatively characterize the influence of external ambient temperature, solar radiation, wind speed, internal crude oil density, viscosity, and specific heat capacity on the temperature drop of crude oil in each influencing zone. The results of this paper not only quantitatively explain the main influencing factors of the oil temperature drop in the top, wall, and bottom regions of the tank, but also provide a theoretical reference for oil security reserves under a dynamic thermal environment. 展开更多
关键词 Oil temperature drop Forced convection Natural convection Dynamic thermal environment Quantitative analysis
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