Effects of Blowing Ratios on Heat Transfer to the Throat Region of a Porous-Walled Nozzle

The effects of transpiration cooling on heat transfer in the throat region of a porous-walled nozzle were investigated. The experiments were performed in the AFIT low speed shock tube fitted with a Mach 2 nozzle. A blowing region was limited to the area from 1.3 cm prior to the throat to 1.2 cm downstream of the throat. The blowing ratios from -0.0002 (suction) to 0.0117 (blowing) of the main stream flow were studied. Heat flux data were taken from both sides of the nozzle. One side was transpiration cooled by secondary air injection through a porous wall, while the other side was an impermeable surface. The transpiration cooled side results showed up to a 40% reduction in heat transfer coefficient at the blowing ratio of 0.0116. Also, with this small blowing region (from 1.3 cm upstream of the nozzle throat to 1.2 cm downstream of the nozzle throat), the results of the exit Mach number and boundary layer thickness showed good improvement compared to a larger blowing region (from 1.3 cm upstream of the throat to 8.8 cm downstream of the throat). (MM

Fault-free longest paths in star networks with conditional link faults

AbstractThe star network, which belongs to the class of Cayley graphs, is one of the most versatile interconnection networks for parallel and distributed computing. In this paper, adopting the conditional fault model in which each node is assumed to be incident with two or more fault-free links, we show that an n-dimensional star network can tolerate up to 2n−7 link faults, and be strongly (fault-free) Hamiltonian laceable, where n≥4. In other words, we can embed a fault-free linear array of length n!−1 (n!−2) in an n-dimensional star network with up to 2n−7 link faults, if the two end nodes belong to different partite sets (the same partite set). The result is optimal with respect to the number of link faults tolerated. It is already known that under the random fault model, an n-dimensional star network can tolerate up to n−3 faulty links and be strongly Hamiltonian laceable, for n≥3

THE CALCULATION ON THE ROTATIONAL KINEMATICS ABOUT THE LONGITUDINAL AXIS OF JAVELIN BY THREE METHODS

The motion of javelin is complicated after it is released. Itis necessary to use some skills to calculate the rotation kinematics about the longitudinal axis of javelin. In this study, the Euler angle, the Cardan angle and the screw axis methods were used to calculate these kinematic variables. Two synchronized Redlake high-speed cameras (250 Hz) and a javelin with three fixed reflective markers were used in the experiment. Generally the results by three methods were close, and all of the three methods are suitable for the calculation on these variables. In the Euler angle and Cardan angle methods, the order of rotation sequence needs to be taken account, however no similar problem occurred in screw method. The results suggested that the longitudinal axis should be set as second axis in either Euler angle or Cardan angle methods to avoid Gimbal Lock (singularity) problem

DIFFERENCES BETWEEN MALE AND FEMALE PLAYERS IN THE FRONTAL PLANE BIOMECHANICS DURING VOLLEYBALL SPIKE LANDING

The purpose of this study was to investigate differences of kinematic variables between male and female volleyball players after a spiking, to understand the mechanism of volleyball spike landing. Eight males and eight females were recruited to participate in this study from the university volleyball team. The kinematic data were collected by ten Vicon cameras (300Hz) and two force plates (1500Hz). The results presented the right hip joint, and both knee joints are significant differences between male and female volleyball players at initial contact. Similarly, at the moment of peak force during the landing phase, the right hip joint and both knee joints are significant differences between male and female volleyball players. These differences demonstrated that male and female players performed different strategies during volleyball spike landing

SAGITTAL AND FRONTAL LOWER LIMBS KINETICS DURING STEPPING DOWN IN TAICHI ELDERLY

The aim was to compare the kinetic characteristics of the beginning stance phase during stepping down in Taichi and normal elderly. Nine elderly taichi subjects and eleven matched controls participated in the study. Whole body kinematics and ground reaction forces (GRF) were recorded using 10 Vicon cameras (250Hz) and two Kistler force plates (1000Hz). Sagittal and frontal kinetic parameters were calculated by using Visual3D software. Differences in variables between groups were tested using t-test. The results indicated hip extensor / knee flexor / ankle plantarflexor / support moment and peak hip/knee/ankle power were greater in Taichi group. It was concluded that Taichi group has ability to translate forward movement (hip moment / power), to control body (knee moment /power) and to absorption energy (ankle moment / power) in sagittal plane

THE BIOMECHANICAL ANALYSIS OF THE TAEKWONDO FRONT-LEG AXE-KICK

The purpose of the study was to analyze the biomechanics of taekwondo front-leg axekick. One force plates, two synchronized high-speed cameras were used to measure biomechanical parameters in each phase of the front-leg axe-kick. The results included: 1. The average reaction time and movement time were 0.423 sand 0.327 s, which respectively occupied about 56% and 44% of attack time. 2. The maximum velocity of hip, knee and ankle were 1.74 m/s, 5.25 m/s and 7.43 m/s respectively. When the kicking leg touched the target, the velocity of knee and ankle were 0.78m/s, 1.72m1s, and 4.64m1s respectively. 3. The peak vertical GRF and impulse were 0.96 SW and 77.57N-s. For decreasing the movement time, it's suggested that an athlete should increase the power and flexibility of lower extremities during the training section

Beyond the Innovation: An Exploratory Study of Designing Web-based Self-services

AbstractCustomized web-based self-services play an important role in today's product/service innovation. Compared to traditional tangible services, helpful web-based self-services and off-line services may better facilitate creativity, accelerate value co-creation, and reduce the costs and risks of development and commercialization. Therefore, in order to offer a conceptual framework for a web-based self-service system that enhances the fuzzy-front end (FFE) of new product/service development, this study analyzed the needs and challenges found during the transition of the Dechnology (Design Thinking plus Technology Innovation) project at the Industrial Technology Research Institute (ITRI), the largest R&D organization in Taiwan. Through literature review, in-depth interviews, and participatory action research, we formalized five core system modules, including: 1) user behavior and lifestyle, 2) thematic trend analysis, 3) technology screening and translation, 4) idea visualization, and 5) O2O service connection, with corresponding design principles for supporting user creativity in a web-based self-services environment. Finally, this study proposes a conceptual framework integrated with service design to serve as an important reference for enterprises that undergo similar innovation projects in the future

Structural insights into the gating of DNA passage by the topoisomerase II DNA-gate.

Type IIA topoisomerases (Top2s) manipulate the handedness of DNA crossovers by introducing a transient and protein-linked double-strand break in one DNA duplex, termed the DNA-gate, whose opening allows another DNA segment to be transported through to change the DNA topology. Despite the central importance of this gate-opening event to Top2 function, the DNA-gate in all reported structures of Top2-DNA complexes is in the closed state. Here we present the crystal structure of a human Top2 DNA-gate in an open conformation, which not only reveals structural characteristics of its DNA-conducting path, but also uncovers unexpected yet functionally significant conformational changes associated with gate-opening. This structure further implicates Top2's preference for a left-handed DNA braid and allows the construction of a model representing the initial entry of another DNA duplex into the DNA-gate. Steered molecular dynamics calculations suggests the Top2-catalyzed DNA passage may be achieved by a rocker-switch-type movement of the DNA-gate