Right arm pain after strength training: ultrasound imaging for pectoralis major tendon strain

Ting-Yu Lin,Ke-Vin Chang,Wei-Ting Wu,Levent Özçakar 영남대학교 의과대학 2023 Yeungnam University Journal of Medicine Vol.40 No.1

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Mitigating SYN flooding Attack and ARP Spoofing in SDN Data Plane

Ting-Yu Lin,Jhen-Ping Wu,Pei-Hsuan Hung,Ching-Hsuan Shao,Yu-Ting Wang,Yun-Zhan Cai,Meng-Hsun Tsai 한국통신학회 2020 한국통신학회 APNOMS Vol.2020 No.09

As the number of network devices increases rapidly, it becomes more and more difficult to defend network attacks. Large-scaled attacks, such as SYN flooding, may lead to heavy burden to the switches as well as the controller in a software defined network (SDN). In this paper, we investigate the SYN flooding and Address Resolution Protocol (ARP) spoofing attacks in SDN, and then propose mechanisms to address these two attacks. We also present a new scheme to detect SYN flooding by using only a few forwarding rules. Moreover, we utilize the Programming Protocol-independent Packet Processors (P4) technique to mitigate the burden of the controller.

SOLUTIONS OF A CLASS OF COUPLED SYSTEMS OF FUZZY DELAY DIFFERENTIAL EQUATIONS

Yu-ting Wu,Heng-You Lan,Fan Zhang 경남대학교 기초과학연구소 2021 Nonlinear Functional Analysis and Applications Vol.26 No.3

The purpose of this paper is to introduce and study a class of coupled systems of fuzzy delay differential equations involving fuzzy initial values and fuzzy source functions of triangular type. We assume that these initial values and source functions are triangular fuzzy functions and define solutions of the coupled systems as a triangular fuzzy function matrix consisting of real functional matrices. The method of triangular fuzzy function, fractional steps and fuzzy terms separation are used to solve the problems. Furthermore, we prove existence and uniqueness of solution for the considered systems, and then a solution algorithm is proposed. Finally, we present an example to illustrate our main results and give some work that can be done later.

Numerical investigation of the mechanical component design of a hexacopter drone for real-time fine dust monitoring

Yu-Ting Wu,Zhen Qin,Amre Eizad,Sung-Ki Lyu 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.7

Multi-rotor unmanned aerial vehicles (UAVs) are being widely used in various military and civilian fields because they can replace manned systems in the performance of a variety of difficult and/or hazardous tasks. Various UAV designs have been developed to fulfill the requirements of various applications. The current work investigates the design of a hexacopter drone with foldable arms to support the six propulsion units that is designed for realtime fine dust monitoring. The propeller and foldable arm are the key mechanical power transmission components in this design, so their propulsion performance and safety reliability have been numerically investigated in this research. The finite volume method (FVM) based aerodynamic characteristics simulation is utilized to calculate and observe the operational performance of eight different proposed propeller blade designs. The optimal design was obtained through a series of comparisons of the simulation outcomes. The flow field force acting on the propeller blade was analyzed using the fluid-structure interaction (FSI) based simulation method. In addition, the design philosophy of using carbon fiber composite material to replace the traditional aluminum alloy in the manufacture of the foldable arm is presented. The rationality of this design philosophy is verified through finite element method (FEM) based structural analysis. The design experience gained from this study provides a theoretical basis for the development of components for multi-rotor UAVs.

Numerical Investigation of Flow Characteristics in a Viscous Damping System with Symmetrical Hydraulic Cylinders

Yu-Ting Wu,Zhen Qin,Amre Eizad,Sung-Ki Lyu,Choon-Man Lee 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.4

Hydraulic dampers are widely applied due to their characteristics of absorbing huge impact energy, stable and reliable working performance, and easy on-demand design. The hydraulic cylinder is an important part of the hydraulic damping system and the flow conditions inside the cylinder significantly affect its performance. However, only a few researches related to the flow field inside the hydraulic cylinder have been reported. In this study, a novel viscous damping system with opposing symmetrical hydraulic cylinders that can guarantee the smoothness of vibration absorption in a single degree of freedom is proposed. The advantage of this design is that the damping characteristic can be regulated using the external flow valve provided in the external hydraulic loop. The hydraulic damping system is simulated using the commercial software ANSYS Fluent software environment, different strokes and frequencies are applied to observe the internal flow characteristics. As can be seen from the results of numerical investigation, when the piston on one side moves, the piston on the other side also moves, and the pressure change in the cylinder is caused by the collective effect of the cavity volume change and the flow change of the hydraulic oil. In addition, by comparing the streamline and velocity distribution in the cavity under different strokes and frequencies, the relationship between vortex and velocity and compression distance is summarized. These results provide valuable information to facilitate the design of viscous damping system with symmetrical hydraulic cylinders

노벨 정량 분말 공급 장치의 설계 및 연구

우위팅(Yu-Ting Wu),진진(Zhen Qin),이윤승(Yunseung Lee),류성기(Sungki Lyu),백승호(Seoungho Back),박상후(Sanghu Park) 대한기계학회 2021 大韓機械學會論文集A Vol.45 No.8

분말을 친환경적이고 정량적으로 공급하기 위하여 본 논문에서는 노벨 분말 공급 장치의 설계를 제안하고 그 메커니즘 설계 원리에 대해 분석한다. 장치내 분말의 유동 특성을 관찰하기 위하여 분유를 연구 대상으로 선정하였다. 분말 입자 사이의 공극률과 충돌효과를 고려하여 유동영역 내에서 고밀도의 입자 유동 모델을 구축하였으며 Fluent를 활용하여 순간적인 CFD 시뮬레이션을 수행하였다. 무거운 하중을 받는 장치의 구조적 안전성을 고려하여 일련의 유한요소법 기반 구조 강도의 시뮬레이션을 실시하고 메커니즘의 신뢰성을 검증하였다. 또한 3D 프린터를 활용하여 분말 공급 장치의 시제품을 제작하였으며 섭취량 실험을 수행하였다. 결론적으로 제안된 분말 공급 장치는 내부 유동 특성, 구조적 안전성, 실제 분말 공급의 정량 정밀성 등 측면에서 만족스럽다고 평가할 수 있다. 본 연구에서 사용된 설계 및 검증 방법과 다양한 메커니즘의 설계를 위한 유용한 이론을 제시하였다. To precisely feed powders or particles in an environmentally friendly manner, a novel apparatus for powder feeding is proposed. The kinematics and design principles of the mechanism were analyzed. To observe the flow characteristics of the powder in the apparatus, milk powder was selected as the study object. By considering the voidage and collision effect between particles, the dense discrete phase method–discrete element method collision model was established and investigated based on the commercial computational fluid dynamics software ANSYS Fluent. To observe the structural stability of the proposed apparatus under an extreme load condition, a series of finite-element-method-based structural simulations were implemented and the reliability of the design was verified. A prototype was made based on three-dimensional printing technology, and the feeding precision was compared with that of the traditional measuring spoon. The design was satisfactory in terms of flow characteristics, structural safety, and quantitative feeding. The design and investigation methods used in this study can provide an important theoretical reference for the design of a variety of apparatus.

유압 구동시스템용 체크 밸브의 유동특성 및 구조안정성에 관한 연구

우위팅(Yu-Ting Wu),진진(Zhen Qin),곽기명(Gimyeong Gwak),류성기(Sungki Lyu),조용민(Yongmin Cho),백승호(Seoungho Back),박상후(Sanghu Park) 대한기계학회 2021 大韓機械學會論文集A Vol.45 No.7

유압 구동시스템은 여러 산업기계에서 널리 사용되며 체크 밸브는 유압 동력전달시스템의 중요한 부품이다. 하지만 유로와 하우징의 부적절한 설계로 인하여 고압의 오일이 전달될 때 체크 밸브의 누유 및 손상과 같은 문제가 빈번하게 나타난다. 이러한 문제를 해결하기 위하여 본 연구에서는 유한체적법(FVM)과 유체 동역학 기반의 수치적 연구 수단을 활용하여 유압 기계에 사용하는 “L”자형 고압 체크밸브를 바탕으로 설계를 평가하였다. 또한 유한요소법(FEM)을 바탕으로 내부 고압을 고려하여 체크 밸브 하우징의 구조적 안정성에 대해 시뮬레이션을 진행하였다. 본 논문에서 사용한 연구방법은 다양한 유압시스템용 체크 밸브에 적용이 가능하며 유압 동력전달 과정의 안전성을 보장하기 위하여 중요한 설계 평가 사례를 보였다. Hydraulic drive systems are widely used in the equipment used in various industries, such as agriculture and construction. The internal check valve is an important part of the hydraulic power transmission system in a hydraulic machinery. Because of improper design of the flow circuit and housing, check valves are exposed to various problems, such as leakage and damage, frequently during high pressure transmission. To solve this problem, the L-shaped high-pressure check valve used in hydraulic machinery was designed and evaluated using the finite volume method and numerical research method based on fluid dynamics. Furthermore, considering the impact of high internal pressure on the check valve shell, the structural stability of the valve was simulated using the finite element method. The research method adopted in this study can be applied to check valves in various hydraulic systems. Additionally, an important design and evaluation example is provided to ensure the safety of the hydraulic power transmission process.

새로운 케이블 감쇠 시스템의 이론 모델에 관한 연구

우위팅(Yu-Ting Wu),진진(Zhen Qin),류성기(Sung-Ki Lyu) 대한기계학회 2020 대한기계학회 춘추학술대회 Vol.2020 No.12

항공기용 견인봉의 구조적 안정성에 관한 수치 연구

우위팅(Yu-Ting Wu),진진(Zhen Qin),김남용(Namyong Kim),전남술(Namsool Jeon),박상후(Sanghu Park),류성기(Sungki Lyu) 대한기계학회 2021 大韓機械學會論文集A Vol.45 No.1

항공기 견인봉은 주로 지상에서 항공기의 견인 작업 및 유지보수 목적으로 사용된다. 작동 중에 과부하, 인적 요인으로 작업 과실 및 환경(지면) 요인의 영향으로 인하여 견인봉 굽힘 또는 파손과 같은 고장 문제가 자주 발생하여 항공기의 정상적인 비행 스케줄에도 영향을 미친다. 이러한 종류의 문제는 비행 중에 발생하지 않지만 높은 발생 빈도로 인하여 항공산업에서는 견인봉의 설계단계에서 구조적 안정성을 매우 중요시하고 있다. 본 연구에서는 소형 무장헬기용 견인봉을 기반으로 모델링 및 수치 연구를 수행하여 최적의 견인봉 구조설계 방법에 대하여 고찰하였다. 실제 작업 극한 조건을 고려하여 각각 특성이 있는 tubular 식 및 solid 식 견인봉에 대하여 구조 강도 평가, 좌굴 임계 하중 분석 및 전단핀 설계를 수행하였다. 본 논문에서 사용한 연구 방법은 다양한 작업 조건 및 견인봉 모델 개발에 적용이 가능하며 항공기의 견인 작업의 안전성을 보장하기 위하여 중요한 설계 이론을 적용하였다. Mainly an aircraft tow bar is used for the operation and maintenance of an aircraft on the ground. Failure problems such as tow bar bending and fracture frequently occur owing to the influences of overload conditions, man-made destruction, and environmental factors. These problems may even affect the normal flight mission of the aircraft during the operation. Although this type of problem does not occur during flight, owing to the high occurrence frequency of this problem, the structural stability of the tow bar in the design stage is of importance to the aerospace industry. In this study, a series of modeling and numerical analyses were carried out to investigate the optimal design method with a high structural stability based on a tow bar for small military helicopters. A structural strength evaluation, ultimate buckling load analysis, and design of the breakaway pin were performed for tubular and solid bar-type tow rods with specific characteristics by considering the actual extreme working conditions and different characteristics of the tubular and solid tow bars. The method used in this study is applicable under various working conditions and for tow bar model development. It provides an important design theory reference to ensure the safety of the towing operation of the aircraft.

Adherence to Cancer Prevention Guidelines and Endometrial Cancer Risk: Evidence from a Systematic Review and Dose-Response Meta-analysis of Prospective Studies

Hui Sun,Qing Chang,Ya-Shu Liu,Yu-Ting Jiang,Ting-Ting Gong,Xiao-Xin Ma,Yu-Hong Zhao,Qi-Jun Wu 대한암학회 2021 Cancer Research and Treatment Vol.53 No.1

Purpose The evidence of adherence to cancer prevention guidelines and endometrial cancer (EC) risk has been limited and controversial. This study summarizes and quantifies the relationship between adherence to cancer prevention guidelines and EC risk. Materials and Methods The online databases PubMed, Web of Science, and EMBASE were searched for relevant publications up to June 2, 2020. This study had been registered at PROSPERO. The registration number is CRD42020149966. Study quality evaluation was performed based on the Newcastle-Ottawa Scale. The I2 statistic was used to estimate heterogeneity among studies. Egger’s and Begg’s tests assessed potential publication bias. Summary hazard ratios (HRs) and 95% confi dence intervals (CIs) for the relationship between adherence to cancer prevention guidelines score was assigned to participants by summarizing individual scores for each lifestyle-related factor. The scores ranged from least healthy (0) to most healthy (20) and the EC risk was calculated using a random-effects model. Results Five prospective studies (four cohort studies and one case‑cohort study) consisted of 4,470 EC cases, where 597,047 participants were included. Four studies had a low bias risk and one study had a high bias risk. Summary EC HR for the highest vs. lowest score of adherence to cancer prevention guidelines was 0.54 (95% CI, 0.40 to 0.73) and had a high heterogeneity (I2=86.1%). For the dose-response analysis, an increment of 1 significantly reduced the risk of EC by 6%. No signifi cant publication bias was detected. Conclusion This study suggested that adherence to cancer prevention guidelines was negatively related to EC risk.