检索结果-南通市图书馆

Video quality based link adaptation for low latency video transmission over WLANs

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第5期7卷 847-856页

作者： FERR Pierre DOUFEXI Angela chung-HOW James NIX Andrew BULL david University of Bristol Department of Electrical and Electronic Engineering Centre for Communications Research Bristol BS8 1UB UK ProVision Communication Technologies Bristol BS4 4EU UK

Wireless Local Area Networks (WLANs) such as IEEE 802.11a/g and Hiperlan/2 utilise numerous transmission modes, each providing different throughputs and reliability levels. Many link adaptation algorithms proposed in the literature either maximise the error-free data throughput based on channel conditions or are based on the number of failed transmissions. However, these algo- rithms do not take into account the content of the data stream and strongly rely on the use of Automatic Repeat Requests (ARQs). Low latency video applications such as real-time video transmission may require no retransmission, or only a limited number of retrans- missions. Moreover, completely error-free communication is not essential, especially if robust video compression techniques are applied. In such scenarios, improved decoded video quality can be obtained with a video stream transmitted at a higher bit rate using a higher link speed but with some degree of transmission error, rather than an error-free video stream at a lower bit rate using a lower link speed. In this work, we investigate a link adaptation scheme that improves the Quality of Service (QoS) for video transmission, based on the overall received video quality (Peak Signal to Noise Ratio, PSNR), rather than by maximising the error-free throughput. We also study a practical link adaptation approach that uses PER thresholds at the PHY layer. An empirical study showed that thresholds for switching from one mode to another are much lower (almost error free) than those currently used by throughput based schemes. We show that traditional link adaptation strategies are not appropriate for real-time video transmission with no retransmis- sion. Simulation results using the H.264 video compression standard over IEEE 802.11a are presented.

关键词： Link adaptation Wireless LAN Video quality Peak Signal to Noise Ratio (PSNR) Packet Error Rate (PER)

Effect of thickness of planar nozzles on erosion depth of levee soils subjected to plunging water

在线全文

学校读者我要写书评

暂无评论

International Journal of Sediment Research 2018年第3期33卷 243-249页

作者： chung Rak Song Jinwon Kim James Tyler Kidd Alexander Cheng david Admiraal Department of Civil Engineering University of Nebraska-Lincoln

In this study, the effect of the thickness of a planar jet on the erosion depth when the jet impinges on a surface composed of cohesive soil was analytically and numerically evaluated. The results showed that the erosion depth was practically independent of the nozzle thickness for erosion depths shallower than the potential core length(i.e. the region of the jet in which the central flow velocity is the same as the nozzle velocity). The relation between nozzle thickness and erosion depth was non-linear with continuously variable slope for erosion depths deeper than the potential core length. Finally, the relation was approximately linear when the erosion depth converged to the equilibrium erosion depth. The findings of this study indicate that direct and fast prediction of the erosion depth in the field is possible using the data from a small scale soil erosion test with similar flow velocities.

关键词： Nozzle thickness Levee erosion Erosion depth Plunging water Planar nozzle

Fluorescence lifetime imaging of molecular rotors to map microviscosity in cells

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Optics Letters 2010年第10期8卷 926-930页

作者： James A. Levitt Marina K. Kuimova Gokhan Yahioglu Pei-Hua chung Klaus Suhling david Phillips Department of Physics King's College London Department of Chemistry Imperial College London PhotoBiotics Ltd.

Fluorescence liftime imaging （FLIM） of modified hydrophobic bodipy dyes that act as fluorescent molecular rotors shows that the fluorescence lifetime of these probes is a function of the microviscosity of their environment. Incubating cells with these dyes, we find a punctate and continuous distribution of the dye in cells. The viscosity value obtained in what appears to be endocytotic vesicles in living cells is around 100 times higher than that of water and of cellular ***-resolved fluorescence anisotropy measurements also yield rotational correlation times consistent with large microviscosity values. In this way, we successfully develop a practical and versatile approach to map the microviscosity in cells based on imaging fluorescent molecular rotors.

关键词： Fluorescence lifetime imaging of molecular rotors to map microviscosity in cells

The role of complement C5a receptor in DPSC odontoblastic differentiation and in vivo reparative dentin formation

在线全文

学校读者我要写书评

暂无评论

International Journal of Oral Science 2022年第1期14卷 71-79页

作者： Muhammad Irfan Ji-Hyun Kim Hassan Marzban david AReed Anne George Lyndon FCooper Seung chung Department of Oral Biology University of Illinois at ChicagoChicagoUSA Department of Human Anatomy and Cell Science University of ManitobaWinnipegCanada

Therapeutic dentin regeneration remains difficult to achieve,and a majority of the attention has been given to anabolic strategies to promote dentinogenesis directly,whereas,the available literature is insufficient to understand the role of inflammation and inflammatory complement system on *** aim of this study is to determine the role of complement C5a receptor(C5aR)in regulating dental pulp stem cells(DPSCs)differentiation and in vivo dentin *** DPSCs were subjected to odontogenic differentiation in osteogenic media treated with the C5aR agonist and C5aR *** vivo dentin formation was evaluated using the dentin injury/pulp-capping model of the C5a-deficient and wildtype *** vitro results demonstrate that C5aR inhibition caused a substantial reduction in odontogenic DPSCs differentiation markers such as DMP-1 and DSPP,while the C5aR activation increased these key odontogenic genes compared to control.A reparative dentin formation using the C5a-deficient mice shows that dentin regeneration is significantly reduced in the C5a-deficient *** data suggest a positive role of C5aR in the odontogenic DPSCs differentiation and tertiary/reparative dentin *** study addresses a novel regulatory pathway and a therapeutic approach for improving the efficiency of dentin regeneration in affected teeth.

关键词： C5a vivo inflammation

Steroid for chronic subdural hematoma? A prospective phase IIB pilot randomized controlled trial on the use of dexamethasone with surgical drainage for the reduction of recurrence with reoperation

在线全文

学校读者我要写书评

暂无评论

Chinese Neurosurgical Journal 2015年第1期1卷 -页

作者： david Yuen chung Chan Tin Fung david Sun Wai Sang Poon Division of Neurosurgery Department of Surgery Prince of Wales HospitalThe Chinese University of Hong Kong 30-32 Ngan Shing Street Shatin NTHong Kong

Background: Chronic subdural hematoma is a common neurosurgical condition especially in the aging *** hole for drainage is an effective treatment, yet recurrence is reported at 8 to 22 ％ worldwide, and 1-year mortality rates could be as high as 32 ％.Our previous study on the use of dexamethasone as a primary nonsurgical treatment showed good response in selected group of *** study aims to assess the efficacy of dexamethasone with surgical drainage in the reduction of recurrence requiring ***: From October 2000 to September 2006, patients with chronic subdural hematoma admitted to the Prince of Wales Hospital, The Chinese University of Hong Kong, were randomized to surgical drainage with steroid versus surgical drainage *** primary endpoint was symptomatic recurrence requiring ***: Two hundred forty-eight patients were recruited and consented for the randomization during the study *** hundred twenty-two received both surgery and steroid (the intervention arm) while 126 received surgery only (the control arm).The recurrence rate requiring reoperation was 6.6 ％ (8/122) and 13.5 ％ (17/126),respectively (p =0.109).There was no significant difference in complications such as chest infection (p =0.201) or wound infection (p =0.987).Favorable outcome (Glasgow Outcome Score 4-5) was 104/122 (85.2 ％) in the intervention group versus 105/126 (83.3 ％) in the control group, respectively (p =0.811).Based on the recurrence rate in our study, we generate a potential sample size of at least 594 patients (type Ⅰ error =5 ％, power =80 ％,two-sided test) to detect a significant ***, brief summary, and potential implications: In this prospective pilot phase IIB randomized controlled study, steroid with surgical drainage had a lower recurrence with reoperation though statistically *** was safe with no significant difference in complication *** pilot study generates a potential sample s

关键词： Chronic subdural hematoma Steroid Burr hole for drainage

Is quantum capacitance in graphene a potential hurdle for device scaling？

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2014年第4期7卷 453-461页

作者： Jaeho Lee Hyun-Jong chung david H. Seo Jaehong Lee Hyungcheol Shin Sunae Seo Seongjun Park Sungwoo Hwang Kinam Kim Samsung Advanced Institute of Technology Samsung Electronics Yongin-Si Gyeonggi-Do 446-712 Korea Inter-University Semiconductor Research Center (ISRC) School of Electrical Engineering and Computer Science Seoul National University Seoul 151-742 Korea Division of Quantum Phases and Devices Department of Physics Konkuk University Seou1143-701 Korea Semiconductor R&D Center Somsung Electronics Hwasung-City Gyeonggi-Do 446-711 Korea Department of Physics Sejong University Seou1143-74 7 Korea Memory Division Samsung Electronics Hwasung-City Gyeonggi-Do 446-711 Korea

Transistor size is constantly being reduced to improve performance as well as power consumption. For the channel length to be reduced, the corresponding gate dielectric thickness should also be reduced. Unfortunately, graphene devices are more complicated due to an extra capacitance called quantum capacitance （CQ） which limits the effective gate dielectric reduction. In this work, we analyzed the effect of CQ on device-scaling issues by extracting it from scaling of the channel length of devices. In contrast to previous reports for metal-insulator- metal structures, a practical device structure was used in conjunction with direct radio-frequency field-effect transistor measurements to describe the graphene channels. In order to precisely extract device parameters, we reassessed the equivalent circuit, and concluded that the on-state model should in fact be used. By careful consideration of the underlap region, our device modeling was shown to be in good agreement with the experimental data. CQ contributions to equivalent oxide thickness were analyzed in detail for varying impurity concentrations in graphene. Finally, we were able to demonstrate that despite contributions from CQ, graphene＇s high mobility and low-voltage operation allows for ~raphene channels suitable for next generation transistors.

关键词： graphene equivalent circuit quantum capacitance intrinsic delay

Determinants of the impact of blood pressure variability on neurological outcome after acute ischaemic stroke

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Stroke & Vascular Neurology 2017年第1期2卷 1-6页

作者： Adam de Havenon Alicia Bennett Gregory J Stoddard Gordon Smith Lee chung Steve O’Donnell J Scott McNally david Tirschwell Jennifer J Majersik Department of Neurology University of UtahSaltLake CityUtahUSA University of Utah SaltLake CityUtahUSA University of Washington SeattleWashingtonUSA

Introduction: Increased blood pressure variability (BPV) is detrimental after acute ischaemic stroke, but the interaction between BPV and neuroimaging factors that directly influence stroke outcome has not been explored. Methods: We retrospectively reviewed inpatients from 2007 to 2014 with acute anterior circulation ischaemic stroke, CT perfusion and angiography at hospital admission, and a modified Rankin Scale (MRS) 30- 365 days after stroke onset. BPV indices included SD, coefficient of variation and successive variation of the systolic blood pressure between 0 and 120 hours after admission. Ordinal logistic regression models were fitted to MRS with predictor variables of BPV indices. Models were further stratified by CT perfusion volumetric measurements, proximal vessel occlusion and collateral score. Results: 110 patients met the inclusion criteria. The likelihood of a 1-point rise in the MRS increased with every 10 mm Hg increase in BPV (OR for the 3 BPV indices ranged from 2.27 to 5.54), which was more pronounced in patients with larger ischaemic core volumes (OR 8.37 to 18.0) and larger hypoperfused volumes (OR 6.02 to 15.4). This association also held true for patients with larger mismatch volume, proximal vessel occlusion and good collateral vessels. Conclusions: These results indicate that increased BPV is associated with worse neurological outcome after stroke, particularly in patients with a large lesion core volume, concurrent viable ischaemic penumbra, proximal vessel occlusion and good collaterals. This subset of patients, who are often not candidates for or fail acute stroke therapies such as intravenous tissue plasminogen activator or endovascular thrombectomy, may benefit from interventions aimed at reducing BPV.

关键词： impaired perfusion cerebral

Recent advances in the managements of type 2 diabetes mellitus and natural hypoglycemic substances

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Food Science and Human Wellness 2022年第5期11卷 1121-1133页

作者： Chong Ning Yuhan Jiao Jiaqi Wang Weiwei Li Jingqiu Zhou Yi-Chieh Lee Dik-Lung Ma chung-Hang Leung Rugang Zhu Hui-Min david Wang College of Light Industry Liaoning UniversityShenyang 110036China Department of Life Sciences National Chung Hsing UniversityTaichung 402TaiwanChina Department of Chemistry Hong Kong Baptist UniversityKowloon Tong 999077Hong KongChina State Key Laboratoryof Quality Research in Chinese Medicine Institute of Chinese Medical SciencesUniversity of MacaoMacao 999078China Graduate Institute of Biomedical Engineering National Chung Hsing UniversityTaichung 402TaiwanChina Graduate Institute of Medicine College of MedicineKaohsiung Medical UniversityKaohsiung City 807TaiwanChina Department of Medical Laboratory Science and Biotechnology China Medical UniversityTaichung City 404TaiwanChina

Diabetes has become a global concern at present,among which type 2 diabetes mellitus(T2DM)accounts for approximately 90%-95%of patients.T2DM is a type of metabolic disorder syndrome that results from a genetic defect,and it is based on insulin resistance and an insulin secretion *** occurrence of T2DM is usually the outcome of both genetic and environmental factors and their *** etiology and pathogenesis of diabetes have not been fully elucidated,and no radical therapeutic cure has been *** with T2DM suffer from complications such as the development of a chronic hyperglycemic condition and even serious metabolic disorders and organ damage in the body and depression and dementia,in addition to other chronic *** studies have suggested that diet is crucial in the development of diabetes and the control of blood *** substances have the characteristics of low toxicity and few side effects and may be key to the development of diabetic health products and preventive *** paper reviews the etiology,pathogenesis,risks,treatments and diets related to T2DM to summarize the types of recently available natural products,from both local and foreign sources,for lowering blood glucose at home and their application in supplementary hypoglycemic *** key findings and conclusions suggest that there are various known T2DM-inducing factors,including genetic and environmental factors and three types of hybrid factors.

关键词： Obesity Type 2 diabetes mellitus Etiological agent Diet Insulin resistance Natural substances

同方期刊数据库

Acute liver injury induced by weight-loss herbal supplements

在线全文

学校读者我要写书评

暂无评论

World Journal of Hepatology 2010年第11期2卷 410-415页

作者： Gary C Chen Vivek S Ramanathan david Law Pauline Funchain George C Chen Samuel French Boris Shlopov Viktor Eysselein david chung Sonya Reicher Binh V Pham Department of Gastroenterology and Pathology Harbor UCLA Medical Center

We report three cases of patients with acute liver injury induced by weight-loss herbal supplements. One patient took Hydroxycut while the other two took Herbalife supplements. Liver biopsies for all patients dem onstrated f indings consistent with drug-induced acute liver injury. To our knowledge, we are the fi rst instit ute to report acute liver injury from both of these two typ es of weight-loss herbal supplements together as a case series. The series emphasizes the importance of taking a cautious approach when consuming herbal supp lements for the purpose of weight loss.

关键词： Hydroxycut Herbalife Hepatotoxicity Herbal Weight-loss