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A joint computational-experimental study of intracranial aneurysms:Importance of the aspect ratio

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Journal of Hydrodynamics 2016年第3期28卷 462-472页

作者： Simon Sui-Man LAI Abraham Yik-Sau TANG Anderson Chun-On TSANG Gilberto Ka-Kit LEUNG Alfred Cheuk-Hang YU kwok wing chow Department of Electrical and Electronic Engineering University of Hong Kong Hong Kong China Department of Mechanical Engineering University of Hong Kong Hong Kong China Department of Surgery Li Ka Shing Faculty of Medicine University of Hong Kong Hong Kong China Department of Electrical and Computer Engineering University of Waterloo Ontario Canada

Rupture of a cerebral aneurysm （abnormal swelling of blood vessel in the brain） will cause subarachnoid hemorrhage, and will result in an alarming rate of mortality and morbidity. A joint computational-experimental study is conducted to assess the importance of the aspect ratio in the dynamics of blood flow. The aspect ratio is defined here to be the ratio of the height of the aneurysm to the linear dimension of the neck. Idealized models of such aneurysms located near a bifurcation point were investigated. Numerical simulations for hemodynamic properties like shear stress and flow rate were performed. The computational results were verified experimentally with specially fabricated phantoms, blood mimicking fluid and Doppler ultrasound imaging. Excellent agreements were obtained. Two features are highlighted, providing information in the intensely debated link between rupture risk and geometric factors. On increasing the aspect ratios, firstly, a jet impinging on the distal part of the neck can be observed, and secondly, a region of positive shear stress gradient can be found there. Furthermore, computational analyses for four patient-specific models were conducted to correlate with the results of idealized models and to provide further clinical insight.

关键词： intracranial aneurysms aspect ratio Doppler ultrasound

Endovascular repair of type B aortic dissection: a study by computational fluid dynamics

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Journal of Biomedical Science and Engineering 2010年第9期3卷 900-907页

作者： Yi Fan Stephen wing-Keung Cheng Kai-Xiong Qing kwok-wing chow 不详

Aortic dissection is a dangerous pathological condition where blood intrudes into the layers of the arterial walls, creating an artificial channel (false lumen). In the absence of thrombosis or surgical intervention, blood will enter the false lumen through the proximal tear, and join the true lumen again through a distal tear. Rupture of the weakened outer wall will result in extremely high mortality rates. Type B thoracic aortic dissection (TAD), occurring along the descending aorta, can be repaired surgically by the deployment of an endovascular stent graft, concealing the proximal entry tear. Blood might still flow into the false lumen (FL) through the distal tear. The domain of such flow should be minimized, as complete thrombosis of the FL is generally believed to be more beneficial for the patient. The dependence on the area ratios of the lumens and size of these tears is studied by computational fluid dynamics.

关键词： Aortic Dissection Endovascular Repair Stent Graft Computational Fluid Dynamics

Influence of the aspect ratio on the endovascular treatment of intracranial aneurysms: A computational investigation

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Journal of Biomedical Science and Engineering 2012年第8期5卷 422-431页

作者： Abraham Yik-Sau Tang Siu-Kai Lai Kar-Ming Leung Gilberto Ka-Kit Leung kwok-wing chow Department of Mechanical Engineering University of Hong Kong Pokfulam Hong Kong Department of Neurosurgery Kwong Wah Hospital Hong Kong Division of Neurosurgery Department of Surgery Li Ka Shing Faculty of Medicine University of Hong Kong Queen Mary

Intracranial aneurysm, a localized dilation of arterial blood vessels in the Circle of Willis and its branches, is potentially life threatening, due to massive bleeding in the subarachnoid space upon rupture. In clinical practice, one minimally invasive surgical procedure is the implantation of a metallic stent to cover the aneurysm neck. This flow diverting device can reduce the flow into the aneurysm and enhance the prospect of thrombosis, a condition expected to reduce the risk of growth and rupture. The biomechanical and haemo-dynamic factors in stented and nonstented situations are studied by computational fluid dynamics. Unlike earlier models with straight or curved parent blood vessels, the aneurysm is now located near an arterial bifurcation. The influence of the aspect (depth to neck) ratio of the aneurysm on the flow dynamics will be emphasized, especially in the post-operation stages. More precisely, the maximum flow velocity, the variations of wall shear stress, the risk of stent migration and volumetric flow rate after endovascular treatment will be studied. Aneurysms with larger aspect ratios (i.e. smaller neck sizes for constant depth) generally pose a greater risk in terms of these flow parameters. These results will assist the applications and design of stents in future neurosurgical therapy. The approach is limited to a nonelastic model, without taking into account of questions like stent expansion and interaction with tissue.

关键词： Intracranial Aneurysm Endovascular Treatment Stent Aspect Ratio Computational Fluid Dynamics

An Improved Golden Jackal Optimization Algorithm Based on Multi-strategy Mixing for Solving Engineering Optimization Problems

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Journal of Bionic Engineering 2024年第2期21卷 1092-1115页

作者： Jun Wang Wen-chuan Wang kwok-wing Chau Lin Qiu Xiao-xue Hu Hong-fei Zang Dong-mei Xu College of Water Resources North China University of Water Resources and Electric PowerZhengzhou450046People’s Republic of China Department of Civil and Environmental Engineering The Hong Kong Polytechnic UniversityHong KongPeople’s Republic of China

Nowadays,optimization techniques are required in various engineering domains to find optimal solutions for complex *** a result,there is a growing tendency among scientists to enhance existing nature-inspired algorithms using various evolutionary strategies and to develop new nature-inspired optimization methods that can properly explore the feature *** recently designed nature-inspired meta-heuristic,named the Golden Jackal Optimization(GJO),was inspired by the collaborative hunting actions of the golden jackal in nature to solve various challenging ***,like other approaches,the GJO has the limitations of poor exploitation ability,the ease of getting stuck in a local optimal region,and an improper balancing of exploration and *** overcome these limitations,this paper proposes an improved GJO algorithm based on multi-strategy mixing(LGJO).First,using a chaotic mapping strategy to initialize the population instead of using random parameters,this algorithm can generate initial solutions with good diversity in the search ***,a dynamic inertia weight based on cosine variation is proposed to make the search process more realistic and effectively balance the algorithm's global and local search ***,a position update strategy based on Gaussian mutation was introduced,fully utilizing the guidance role of the optimal individual to improve population diversity,effectively exploring unknown regions,and avoiding the algorithm falling into local *** evaluate the proposed algorithm,23 mathematical benchmark functions,CEC-2019 and CEC2021 tests are *** results are compared to high-quality,well-known optimization *** results of the proposed method are compared from different points of view,including the quality of the results,convergence behavior,and *** superiority and high-quality performance of the proposed method are demonstrated by comparing the ***,to demonstrate

关键词： Golden jackal optimization Chaotic mapping Dynamic inertia weight Dimensional Gaussian variation Muskingum

基于非线性浮力频率分布分层流的三波共振畸形波分析

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Acta Mechanica Sinica 2023年第7期39卷 141-151页

作者：殷会敏潘青赵天乐周国荣 Department of Mechanical Engineering University of Hong KongPokfulamHong Kong

本文对位于海洋上层温跃层中的大幅波动进行了理论分析.该内畸形波可能由具有二次非线性的三波共振而引起.虽然三波共振中的畸形波精确解析解已经在数学物理文献中被推导出,但其在流体动力学中的应用尚未被充分研究.本文计算了在非线性... 详细信息

本文对位于海洋上层温跃层中的大幅波动进行了理论分析.该内畸形波可能由具有二次非线性的三波共振而引起.虽然三波共振中的畸形波精确解析解已经在数学物理文献中被推导出,但其在流体动力学中的应用尚未被充分研究.本文计算了在非线性浮力频率分布下三波共振演化方程中的系数.调制不稳定性是指由色散和非线性效应之间的相互作用引起的干扰增长,虽然不稳定性分析是基于线性化研究的,但来自增长率谱的信息可以与畸形波的非线性、数值鲁棒性测试的结果相关联.最后,通过解析延拓将空间变量扩展为复数进行了解析畸形波解的极点分析.对于具有一个或两个峰值的畸形波,物理空间中最大位移的位置与轨迹转折点处的极点的实部相同或近似相等.这些数值和分析研究构成了理解海洋上层大规模瞬态运动的框架.

关键词：数学物理二次非线性调制不稳定性解析延拓空间变量分层流精确解析解非线性效应

The effects of stent porosity on the endovascular treatment of intracranial aneurysms located near a bifurcation

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Journal of Biomedical Science and Engineering 2013年第8期6卷 812-822页

作者： Abraham Yik-Sau Tang Hiu-Ning Chan Anderson Chun-On Tsang Gilberto Ka-Kit Leung Kar-Ming Leung Alfred Cheuk-Hang Yu kwok-wing chow Department of Mechanical Engineering University of Hong Kong Hong Kong China Department of Neurosurgery Kwong Wah Hospital Hong Kong China Division of Neurosurgery Department of Surgery Li Ka Shing Faculty of Medicine University of Hong Kong Queen Mary Hos-pital Hong Kong China Medical Engineering Program Department of Electrical and Electronic Engineering University of Hong Kong Hong Kong China

Intracranial aneurysm occurs when a cerebral artery develops an abnormal sac-like dilatation, and will cause massive bleeding in the subarachnoid space upon rupture. Endovascular stenting is a minimally invasive procedure in which a flow-diverting stent is deployed to cover the aneurysm neck, thereby restricting blood from entering the aneurysm and reducing the risk of rupture. The stent porosity, a crucial factor determining the intra-aneurysmal hemodynamics following treatment, is investigated by computational fluid dynamics techniques. Based on the computational results, a low porosity stent will dramatically reduce the flow velocity and the flow rate inside the side branch vessel. Conversely, a high porosity stent may not provide adequate flow reduction inside the aneurysm, possibly causing treatment failure. An advisable range of optimal stent porosity would be 60% to 75%, which can drastically reduce the flow rate into the aneurysm while preserving enough blood flow for the side branch vessel. Clinically, deployment of two or more flow-diverting stents may not increase treatment efficacy but can potentially lead to adverse effects due to side-branch hypoperfusion. The present quantitative analysis can also provide practical insight for future stent design.

关键词： Intracranial aneurysm Endovascular Treatment Stent Stent Porosity Computational Fluid Dynamics

Association of accelerometer-measured sleep duration and different intensities of physical activity with incident type 2 diabetes in a population-based cohort study

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Journal of Sport and Health Science 2024年第2期13卷 222-232页

作者： Xinyi Jin Yilin Chen Hongliang Feng Mingqing Zhou Joey W.Y.Chang Yaping Liu Alice Pik Shan Kong Xiao Tan Yun-kwok wing Yannis Yan Liang Jihui Zhang Guangdong Cardiovascular Institute Guangdong Provincial People’s HospitalGuangdong Academy of Medical SciencesGuangzhou 510080China Guangdong Provincial Key Laboratory of Coronary Heart Disease Prevention Guangdong Cardiovascular InstituteGuangdong Provincial People’s Hospital(Guangdong Academy of Medical Sciences)Southern Medical UniversityGuangzhou 510080China School of Medicine South China University of TechnologyGuangzhou 510641China Center for Sleep and Circadian Medicine The Affiliated Brain Hospital of Guangzhou Medical UniversityGuangzhou 510180China The Second School of Clinical Medicine Southern Medical UniversityGuangzhou 510282China Guangdong Mental Health Center Guangdong Provincial People’s Hospital(Guangdong Academy of Medical Sciences)Southern Medical UniversityGuangzhou 510120China Li Chiu Kong Family Sleep Assessment Unit Department of PsychiatryFaculty of MedicineThe Chinese University of Hong KongHong Kong 999077China Department of Psychiatry Faculty of MedicineThe Chinese University of Hong KongHong Kong 999077China Department of Medicine and Therapeutics Faculty of MedicineThe Chinese University of Hong KongHong Kong 999077China Department of Medical Sciences Uppsala UniversityUppsala 75185Sweden Department of Big Data in Health Science Zhejiang University School of Public HealthHangzhou 310058China Key Laboratory of Neurogenetics and Channelopathies of Guangdong Province and the Ministry of Education of China Guangzhou 510260China

Purpose:The aim of the current study was to investigate the association of accelerometer-measured sleep duration and different intensities of physical activity(PA)with the risk of incident type 2 diabetes in a population-based prospective cohort ***:Altogether,88,000 participants(mean age=62.2±7.9 years,mean±SD)were included from the UK *** duration(short:8 h/day)and PA of different intensities were measured using a wrist-won accelerometer over a 7-day period between 2013 and *** was classified according to the median or World Health Organization-recommendation:total volume of PA(high,low),moderate-to-vigorous PA(MVPA)(recommended,not recommended),and light-intensity PA(high,low).Incidence of type 2diabetes was ascertained using hospital records or death ***:During a median follow-up of 7.0 years,1615 incident type 2 diabetes cases were *** with normal sleep duration,short(hazard ratio(HR)=1.21,95%confidence interval(95%CI):1.03-1.41)but not long sleep duration(HR=1.01,95%CI:0.89-1.15)was associated with excessive type 2 diabetes *** increased risk among short sleepers seems to be protected against by *** with normal sleepers with high or recommended PA,short sleepers with low volume of PA(HR=1.81,95%CI:1.46-2.25),not recommended(below the World Health Organization-recommended level of)MVPA(HR=1.92,95%CI:1.55-2.36),or low light-intensity PA(HR=1.49,95%CI:1.13-1.90)had a higher risk of type 2 diabetes,while short sleepers with a high volume of PA(HR=1.14,95%CI:0.88-1.49),recommended MVPA(HR=1.02,95%CI:0.71-1.48),or high light-intensity PA(HR=1.14,95%CI:0.92-1.41)did ***:Accelerometer-measured short but not long sleep duration was associated with a higher risk of incident type 2 diabetes.A higher level of PA,regardless of intensity,potentially ameliorates this excessive risk.

关键词： Light physical activity Sleep duration Triaxial accelerometer Type 2 diabetes UK Biobank

Epitranscriptomic Regulation of NMDA Receptors Rears its Ugly Head in Chemotherapy-Induced Neuropathic Pain

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Neuroscience Bulletin 2024年第8期40卷 1209-1211页

作者： wing Lam Yu Gerald W.Zamponi Department of Clinical Neurosciences Hotchkiss Brain InstituteAlberta Children's Hospital Research InstituteUniversity of CalgaryCalgaryAB T2N 4N1Canada

number of different cancer chemotherapy agents such as cisplatin,oxaliplatin,and paclitaxel can lead to nerve damage,thereby giving rise to neuropathic pain states that present with mechanical and cold allodynia[1].Although these pain conditions often resolve after completion of the chemotherapy,a significant portion of patients exhibit longlasting pain that can persist longer than 12 months with a negative impact on the quality of life of affected individuals[1].

关键词： chemotherapy pain damage

A study of the effect of local scour on the flow field near the spur dike

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Theoretical & Applied Mechanics Letters 2024年第2期14卷 98-105页

作者： Yu-Tian Li Jie-Min Zhan wing-Hong Onyx Wai Department of Industrial Design School of Industrial Design and Ceramic ArtFoshan UniversityFoshan 528000China Department of Applied Mechanics and Engineering Shenzhen Campus of Sun Yat-sen UniversityShenzhen 518107China Department of Civil and Environmental Engineering The Hong Kong Polytechnic UniversityHong Kong 999077China

The flow field near a spur dike such as down flow and horseshoe vortex system(HVS)are susceptible to the topographic changes in the local scouring process,resulting in variation of the sediment transport with *** this study,large eddy simulations with fixed-bed at different scouring stages were conducted to investigate the changes in flow *** results imply that the bed deformation leads to an increase in flow rate per unit area,which represent the capability of sediment transportation by water,in the scour ***,the intensity of turbulent kinetic energy and bimodal motion near the sand bed induced by the HVS were also ***,the peak moments between the two sediment transport mechanisms were ***,understanding the complex feedback mechanism between topography and flow field is essential for the local scour problem.

关键词： Spur dike Local scour Large eddy simulation Down flow Horseshoe vortex system