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Interplay of laser power and pore characteristics in selective laser melting of ZK60 magnesium alloys:A study based on in-situ monitoring and image analysis

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Journal of Magnesium and Alloys 2024年第4期12卷 1346-1366页

作者： Weijie Xie Hau-Chung Man Chi-Wai Chan department of Industrial and Systems Engineering The Hong Kong Polytechnic UniversityHong KongChina School of Mechanical and Aerospace Engineering Queen’s UniversityBelfast BT95AHUK Research Institute for Advanced Manufacturing The Hong Kong Polytechnic UniversityHong KongChina

This study offers significant insights into the multi-physics phenomena of the SLM process and the subsequent porosity characteristics of ZK60 Magnesium(Mg)***-speed in-situ monitoring was employed to visualise process signals in real-time,elucidating the dynamics of melt pools and vapour plumes under varying laser power conditions specifically between 40 W and 60 *** morphological analysis was performed using Scanning-Electron Microscopy(SEM),demonstrating a critical correlation between laser power and pore *** laser power led to increased pore coverage,whereas a denser structure was observed at higher laser *** laser power influence on porosity was further confirmed via Optical Microscopy(OM)conducted on both top and cross-sectional surfaces of the *** increase in laser power resulted in a decrease in pore coverage and pore size,potentially leading to a denser printed part of Mg alloy.X-ray Computed Tomography(XCT)augmented these findings by providing a 3D volumetric representation of the sample internal structure,revealing an inverse relationship between laser power and overall pore *** laser power appeared to favour the formation of interconnected pores,while a reduction in interconnected pores and an increase in isolated pores were observed at higher *** interplay between melt pool size,vapour plume effects,and laser power was found to significantly influence the resulting porosity,indicating a need for effective management of these factors to optimise the SLM process of Mg alloys.

关键词： Selective laser melting(SLM) Magnesium(Mg)alloys Biodegradable implants Porosity In-situ monitoring

WirelessLLM:Empowering Large Language Models Towards Wireless Intelligence

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Journal of Communications and Information Networks 2024年第2期9卷 99-112页

作者： Jiawei Shao Jingwen Tong Qiong Wu Wei Guo Zijian Li Zehong Lin Jun Zhang department of Electronic and Computer Engineering The Hong Kong University of Science and TechnologyHong Kong 999077China

The rapid evolution of wireless technologies and the growing complexity of network infrastructures necessitate a paradigm shift in how communication networks are designed,configured,and managed. Recent advancements in large language models (LLMs) have sparked interest in their potential to revolutionize wireless communication systems. However, existing studies on LLMs for wireless systems are limited to a direct application for telecom language understanding. To empower LLMs with knowledge and expertise in the wireless domain, this paper proposes WirelessLLM, a comprehensive framework for adapting and enhancing LLMs to address the unique challenges and requirements of wireless communication networks. We first identify three foundational principles that underpin WirelessLLM:knowledge alignment, knowledge fusion, and knowledge evolution. Then,we investigate the enabling technologies to build WirelessLLM, including prompt engineering, retrieval augmented generation, tool usage, multi-modal pre-training, and domain-specific fine-tuning. Moreover, we present three case studies to demonstrate the practical applicability and benefits of WirelessLLM for solving typical problems in wireless networks. Finally, we conclude this paper by highlighting key challenges and outlining potential avenues for future research.

关键词： large language models multi-modal models wireless communications power allocation spectrum sensing protocol understanding

A hierarchical multi-UAV cooperative framework for infrastructure inspection and reconstruction

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Control Theory and Technology 2024年第3期22卷 394-405页

作者： Chuanxiang Gao Xinyi Wang Xi Chen Ben M.Chen department of Mechanical and Automation Engineering The Chinese University of Hong KongHong KongShatinNTChina

Unmanned aerial vehicles(UAVs)are emerging as a powerful tool for inspections and repair works in large-scale and unstructured 3D infrastructures,but current approaches take a long time to cover the entire *** using UAVs for inspections and repair works puts forward a requirement of improving time efficiency in large-scale and cluster *** paper presents a hierarchical multi-UAV cooperative framework for infrastructure inspection and reconstruction to balance the workload and reduce the overall task completion *** proposed framework consists of two stages,the exploration stage and the exploitation stage,resolving the task in a sequential *** the exploration stage,the density map is developed to update global and local information for dynamic load-balanced area partition based on reconstructability and relative positions of UAVs,and the Voronoi-based planner is used to enable the UAVs to reach their best *** obtaining the global map,viewpoints are generated and divided while taking into account the battery capacity of each ***,a shortest path planning method is used to minimize the total traveling cost of these viewpoints for obtaining a high-quality *** experiments are conducted in both a simulated and real environment to show the time efficiency,robustness,and effectiveness of the proposed ***,the whole system is implemented in real applications.

关键词： Multi-UAV Coverage path planning Infrastructure inspection and reconstruction

Surgical cystogastrostomy: Is it still worthwhile?

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World Journal of Gastroenterology 2024年第17期30卷 2298-2301页

作者： Kin Pan Au Kenneth Siu Ho Chok department of Surgery Queen Mary HospitalThe University of Hong KongHong Kong 999077China department of Surgery The Chinese University of Hong KongHong Kong 999077China

The article by Ker et al explores the treatment of peripancreatic fluid collection(PFC).The use of percutaneous drainage,endoscopy,and surgery for managing PFC are *** drainage is noted for its low risk profile,while endoscopic cystogastrostomy is more effective due to the wider orifice of the metallic *** cystogastrostomy is a definitive treatment with a reduced need for reintervention,especially for cases with extensive collections and significant *** choice of treatment modality should be tailored to individual patient characteristics and disease factors,considering the expertise available.

关键词： Endoscopic cystgastrostomy Surgical cystgastrostomy Pancreatitis Pancreatic necrosis Peripancreatic collection

Use of subword tokenization for domain generation algorithm classification

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Cybersecurity 2024年第2期7卷 1-12页

作者： Sea Ran Cleon Liew Ngai Fong Law university of Waterloo WaterlooCanada department of Electrical and Electronic Engineering The Hong Kong Polytechnic UniversityKowloonHong Kong

Domain name generation algorithm(DGA)classification is an essential but challenging *** feature-extract-ing machine learning(ML)methods and deep learning(DL)models such as convolutional neural networks and long short-term memory have been ***,the performance of these approaches varies with different types of *** features in the ML methods can characterize random-looking DGAs better than Word-looking *** improve the classification performance on word-looking DGAs,subword tokenization is employed for the DL *** experimental results proved that the subword tokenization can provide excellent classification performance on the word-looking *** then propose an integrated scheme that chooses an appropriate method for DGA classification depending on the nature of the *** show that the integrated scheme outperformed existing ML and DL methods,and also the subword DL methods.

关键词： Botnet detection Domain names Network security Machine learning-based botnet detection

Advancing large-scale thin-film PPLN nonlinear photonics with segmented tunable micro-heaters

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Photonics Research 2024年第8期12卷 1703-1708页

作者： XIAOTING LI HAOCHUAN LI ZHENZHENG WANG ZHAOXI CHEN FEI MA KE ZHANG WENZHAO SUN CHENG WANG department of Electrical Engineering City University of Hong KongHong KongChina School of Physics Sun Yat-sen UniversityGuangzhou 510275China City university of hong kong(Dongguan) Dongguan 523808China Center of Information and Communication Technology City University of Hong Kong Shenzhen Research InstituteShenzhen 518057China State Key Laboratory of Terahertz and Millimeter Waves City University of Hong KongHong KongChina

Thin-film periodically poled lithium niobate(TF-PPLN)devices have recently gained prominence for efficient wavelength conversion processes in both classical and quantum ***,the patterning and poling of TF-PPLN devices today are mostly performed at chip scales,presenting a significant bottleneck for future largescale nonlinear photonic systems that require the integration of multiple nonlinear components with consistent performance and low ***,we take a pivotal step towards this goal by developing a wafer-scale TF-PPLN nonlinear photonic platform,leveraging ultraviolet stepper lithography and an automated poling *** address the inhomogeneous broadening of the quasi-phase matching(QPM)spectrum induced by film thickness variations across the wafer,we propose and demonstrate segmented thermal optic tuning modules that can precisely adjust and align the QPM peak wavelengths in each *** the segmented micro-heaters,we show the successful realignment of inhomogeneously broadened multi-peak QPM spectra with up to 57%enhancement of conversion *** achieve a high normalized conversion efficiency of 3802%W-1cm-2in a 6 mm long PPLN waveguide,recovering 84%of the theoretically predicted efficiency in this *** advanced fabrication techniques and segmented tuning architectures presented herein pave the way for wafer-scale integration of complex functional nonlinear photonic circuits with applications in quantum information processing,precision sensing and metrology,and low-noise-figure optical signal amplification.

关键词： tuning tunable waveguide

Monolithic integrated optoelectronic chip for vector force detection

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Microsystems & Nanoengineering 2024年第3期10卷 245-257页

作者： Jiansong Feng Zhongqi Wang Mengyuan Zhanghu Xu Zhang Yong Shen Jing Yang Zhibin Li Bin Chen Taihong Wang Xiaolong Chen Zhaojun Liu department of Electrical and Electronic Engineering Southern University of Science and TechnologyShenzhen 518055China department of Electrical and Electronic Engineering The University of Hong KongHong KongChina

Sensors with a small footprint and real-time detection capabilities are crucial in robotic surgery and smart wearable *** device footprint while maintaining its high performance is a major challenge and a significant limitation to their ***,we proposed a monolithic integrated micro-scale sensor,which can be used for vector force *** sensor combines an optical source,four photodetectors,and a hemispherical silicone elastomer component on the same sapphire-based AlGaInP *** chip-scale optical coupling is achieved by employing the laser lift-off techniques and the flip-chip bonding to a processed sapphire *** hemispherical structure device can detect normal and shear forces as low as 1mN within a measurement range of 0–220 mN for normal force and 0–15 mN for shear *** packaging,the sensor is capable of detecting forces over a broader range,with measurement capabilities extending up to 10 N for normal forces and 0.2 N for shear *** has an accuracy of detecting a minimum normal force of 25 mN and a minimum shear force of 20 ***,this sensor has been validated to have a compact footprint of approximately 1.5 mm^(2),while maintaining high real-time *** also demonstrate its promising potential by combining this sensor with fine surface texture perception in the fields of compact medical robot interaction and wearable devices.

关键词： robot force smart

Characterization and Analysis of Inconel 718 Alloy Ground at Different Speeds

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Chinese Journal of Mechanical Engineering 2024年第2期37卷 137-149页

作者： Hao Liu Huili Han Qinghong Jiang Minglin He Bi Zhang department of Mechanical and Energy Engineering Southern University of Science and TechnologyShenzhen 518055China department of Mechanical Engineering Hong Kong Polytechnic UniversityHong KongChina

Inconel 718(IN718)alloy is widely applied to fabricate high temperature resistant or corrosion resistant parts due to its excellent mechanical ***,the machining of IN718 alloy is difficult as it may cause serious tool wear and poor surface quality(SQ)of the *** this work,grinding experiments on IN718 alloy at different speeds were conducted by using a CBN grinding *** relationship between grinding speed,SQ and subsurface damage(SSD)was well *** increasing grinding speed,surface roughness decreased,and SQ was greatly ***,the microhardness of the grinding surface declined as the grinding speed *** SSD depth was almost unchanged when the grinding speed was lower than 15 m/s,then it decreased with higher grinding *** was attributed to the mechanical-thermal synergistic effect in the grinding *** results indicated that increasing grinding speed can effectively improve the SQ and reduce the SSD of IN718 *** conclusion in the work may also provide insight into processing other hard-to-machining materials.

关键词： Surface integrity Grinding speed IN718 alloy Precision machining CBN grinding wheel

Options and survival benefits of conversion therapy for unresectable hepatocellular carcinoma

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World Journal of Gastroenterology 2024年第18期30卷 2479-2481页

作者： Wong Hoi She Tan To Cheung department of Surgery The University of Hong KongHong Kong 999077China

In the study by Wu et al,patients with unresectable hepatocellular carcinoma were subjected to transarterial chemoembolization(TACE)as a conversion therapy in order to render their tumors suitable for resection.A nomogram was devised and shown to be effective in predicting the survival of these *** of the results,however,is questionable since the study subjects consisted of patients who had resection after TACE while excluding patients with the same disease but not suitable for *** can be considered to be an option for conversion ***,markers for determining responses to a conversion therapy and for guiding the decision between TACE and sequential immunotherapy have been *** question of whether effective conversion therapy can truly enhance overall survival remains unanswered.

关键词： Conversion therapy Immunotherapy Liver resection Survival Transarterial chemoembolization Unresectable hepatocellular carcinoma