Numerical assessment of directional energy performance for 3D printed midsole structures

Energy can be represented in the form of deformation obtained by the applied force. Energy transfer is defined in physics as the energy is moved from one place to another. To make the energy transfer functional, energy should be moved into the right direction. If it is possible to make a better use of the energy in the right direction, the energy efficiency of the structure can be enhanced. This idea leads to the concept of directional energy transfer (DET), which refers to transferring energy from one direction to a specific direction. With the recent development of additive manufacturing and topology optimization, complex structures can be applied to various applications to enhance performances, like a wheel and shoe midsole. While many works are related to structural strength, there is limited research in optimization for energy performance. In this study, a theoretical approach is proposed to measure the directional energy performance of a structure, which can be used to measure the net energy in an intended direction. The purpose is to understand the energy behavior of a structure and to measure if a structure is able to increase energy in the desired direction

Experimental Investigation of Near-limit Gaseous Detonations in Small Diameter Spiral Tubing

The near-limit propagation of gaseous detonations in seven explosive mixtures with different reaction sensitivities is investigated. Experiments were performed in transparent tubing of four different inner diameters with relatively long tubing length (l/d > 2500 except l/d > 1000 for the largest diameter) arranged in a spiral configuration. Up to 83 fiber optics spaced at regular intervals along the tube were used to provide high resolution velocity measurement. Up to 8 cycles of the galloping mode were recorded, and the spiral boundary did not influence the persistence of galloping detonations. Results confirm that for mixtures with increasing argon dilution, making the detonation more stable with regular cellular pattern, the occurrence of galloping detonation diminishes. For stable mixtures with sufficiently large amount of argon dilution (e.g., stoichiometric C2H2/O2 with 70%Ar), the galloping mode was not observed in all tested tubing. For unstable mixtures, smaller diameters were necessary to achieve the galloping mode. The range of initial pressures, within which galloping detonations were observed decreases rapidly with increasing tubing diameter. These results suggest that both the instability and the boundary effect are essential for galloping detonations. From the velocity histogram and the probability distribution function, a bimodal behavior was also observed in all galloping regimes of different unstable mixtures, with dominant modes near half of the Chapman-Jouguet detonation velocity (DCJ) and DCJ. With decreasing pressure, the lower velocity mode became more prevalent until no more galloping detonation occurred. The normalized wavelength of the galloping cycle (L/d) ranges from 250 to 450 within experimental variation. Nevertheless, few results show a clear minor trend that the wavelength increases with decreasing initial pressure. By looking at the velocity amplitude in the galloping cycle, the lower value as well as the average is relatively constant, while the upper peak has larger fluctuations

Computational study of gaseous cellular detonation diffraction and re-initiation by small obstacle induced perturbations

A gaseous detonation wave that emerges from a channel into an unconfined space is known as detonation diffraction. If the dimension of the channel exit is below some critical value, the incident detonation fails to re-initiate (i.e., transmit into a self-sustained detonation propagating) in the unconfined area. In a previous study, Xu et al. [“The role of cellular instability on the critical tube diameter problem for unstable gaseous detonations,” Proc. Combust. Inst. 37(3), 3545–3533 (2019)] experimentally demonstrated that, for an unstable detonable mixture (i.e., stoichiometric acetylene–oxygen), a small obstacle near the channel exit promotes the re-initiation capability for cases with a sub-critical channel size. In the current study, two-dimensional numerical simulations were performed to reveal this obstacle-triggered re-initiation process in greater detail. Parametric studies were carried out to examine the influence of obstacle position on the re-initiation capability. The results show that a collision between a triple-point wave complex at the diffracting shock front and the obstacle is required for a successful re-initiation. If an obstacle is placed too close or too far away from the channel exit, the diffracting detonation cannot be re-initiated. Since shot-to-shot variation in the cellular wave structure of the incident detonation results in different triple-point trajectories, for an obstacle at a fixed position, the occurrence of re-initiation is of a stochastic nature. The findings of this study highlight that flow instability generated by a local perturbation is effective in enhancing the re-initiation capability of a diffracting cellular detonation wave in an unstable mixture

The effects of pre-ignition turbulence by gas jets on the explosion behavior of methane-oxygen mixtures

Most of the previous studies investigating explosion characteristics of combustible mixtures were performed at quiescent state. However, in realistic accidental explosion scenarios, the ignition of the combustible mixture usually occurs under a turbulent environment. In this study, we examine the maximum explosion pressure pmax and explosion time τe of CH4-2O2 mixtures under the pre-ignition turbulence condition in a spherical closed chamber at a room temperature of 298 K. Turbulence is generated using fluidic jet of three different gases (O2, CO2 and N2) and its intensity is controlled by changing the initial pressure of the gas jet pJ0 (i.e., 200 and 500 kPa) and the explosion chamber pressure p0 (i.e., 40 and 60 kPa). The dual effects of turbulence and gas dilution on the explosion behavior of CH4-2O2 mixtures are investigated in detail. The results indicate that by adding O2 into CH4-2O2 mixture at quiescent condition, pmax increases but the rate of overpressure rise is reduced. By introducing turbulence through gas jets into the combustible mixture, the explosion behavior is affected by both the turbulence and gas dilution. With O2 injection, turbulence overall enhances the explosion, but the amount of O2 dilution increases at higher pJ0/p0 and longer jet duration time (tJ0), rendering the mixture to tend toward fuel-lean side and slow down the explosion rate. The present results also demonstrate that the turbulence effect of CO2 is more profound than that of N2 jet. Both pmax and τe are enhanced by CO2 jet turbulence when tJ0 is relative short (tJ0 < 400 ms). However, for longer tJ0, the dominance of CO2 dilution becomes more noticeably than N2 dilution with a longer explosion time τe

Propagation of near-limit gaseous detonations in rough walled tubes

In this study, experiments were carried out to investigate the detonation velocity behavior near limits in rough-walled tubes. The wall roughness was introduced by using different spiral inserts in 76.2-mm-diameter, 50.8-mm-diameter, 38.1-mm-diameter, and 25.4-mm-diameter tubes. Different pre-mixed mixtures, CH4 + 2O2, C2H2 + 2.5O2, C2H2 + 2.5O2 + 70%Ar, and 2H2 + O2 were tested in the experiments. Different spiral wire diameters were used, and the pitch of each spiral was twice of the diameter to keep the same level of roughness in all experiments for each tube. Fiber optics were used to record the detonation time of arrival to deduce the velocity. The normalized velocity V/VCJ and the velocity deficit δ were computed and analyzed to describe the detonation behavior near the limit. The cellular structure near the limit was recorded by the smoked foils

The role of cellular instability on the critical tube diameter problem for unstable gaseous detonations

The transmission of detonation waves, propagating in a homogeneous, gaseous, reactive medium, from a tube into an unconfined space is well known to succeed or fail based on the tube diameter. Below a certain diameter, the detonation fails to transition into the unconfined space, while for a large enough geometry, the transition succeeds. This critical diameter is well correlated to the incoming detonation cell size. For common undiluted hydrocarbon mixtures with a strong degree of transverse instability, the ratio of critical tube diameter to cell size has been measured at Dc = 13λ. In this paper, stoichiometric acetylene-oxygen mixture at different initial pressures is detonated in a circular tube that transitions into an effectively unconfined space. The transition is observed with simultaneous schlieren photography and soot foil records to look at the role of transverse cellular instability. Three regimes of transition are observed: supercritical, where the cellular pattern is continuously connected from the donor tube to the larger space; subcritical, where the wave fails and the cellular pattern disappears; and a critical regime, where the wave initially fails, asymptoting to a weakly decoupled shock-reaction front regime, and exhibits a subsequent re-initiation in a critical zone of pre-shocked gas through the onset of an explosion bubble. A substantial amount of transverse instability remains even after the expansion wave reaches the central axis, sustaining the diffracted wave at a critical thermodynamic state for the re-initiation. The location of this critical zone is identified at about 22λ and a small obstacle is used to promote the generation of transverse waves and a re-initiation kernel. The re-initiation is effected by placing an obstacle in the critical region. The role of the resulting instability is also illustrated through a simple numerical simulation using an obstacle in the sub-critical regime to perturb the flow and promote the re-initiation

Informedia at TRECVID 2003: Analyzing and searching broadcast news video

We submitted a number of semantic classifiers, most of which were merely trained on keyframes. We also experimented with runs of classifiers were trained exclusively on text data and relative time within the video, while a few were trained using all available multiple modalities. 1.2 Interactive search This year, we submitted two runs using different versions of the Informedia systems. In one run, a version identical to last year&apos;s interactive system was used by five researchers, who split up the topics between themselves. The system interface emphasizes text queries, allowing search across ASR, closed captions and OCR text. The result set can then be manipulated through: • storyboards of images spanning across video story segments • emphasizing matching shots to a user’s query to reduce the image count to a manageable size • resolution and layout under user control • additional filtering provided through shot classifiers such as outdoors, and shots with people, etc. • display of filter count and distribution to guide their use in manipulating storyboard views. In the best-performing interactive run, for all topics a single researcher used an improved version of the system, which allowed more effective browsing and visualization of the results of text queries using

Development and potential role of type-2 sodium-glucose transporter inhibitors for management of type 2 diabetes

There is a recognized need for new treatment options for type 2 diabetes mellitus (T2DM). Recovery of glucose from the glomerular filtrate represents an important mechanism in maintaining glucose homeostasis and represents a novel target for the management of T2DM. Recovery of glucose from the glomerular filtrate is executed principally by the type 2 sodium-glucose cotransporter (SGLT2). Inhibition of SGLT2 promotes glucose excretion and normalizes glycemia in animal models. First reports of specifically designed SGLT2 inhibitors began to appear in the second half of the 1990s. Several candidate SGLT2 inhibitors are currently under development, with four in the later stages of clinical testing. The safety profile of SGLT2 inhibitors is expected to be good, as their target is a highly specific membrane transporter expressed almost exclusively within the renal tubules. One safety concern is that of glycosuria, which could predispose patients to increased urinary tract infections. So far the reported safety profile of SGLT2 inhibitors in clinical studies appears to confirm that the class is well tolerated. Where SGLT2 inhibitors will fit in the current cascade of treatments for T2DM has yet to be established. The expected favorable safety profile and insulin-independent mechanism of action appear to support their use in combination with other antidiabetic drugs. Promotion of glucose excretion introduces the opportunity to clear calories (80–90 g [300–400 calories] of glucose per day) in patients that are generally overweight, and is expected to work synergistically with weight reduction programs. Experience will most likely lead to better understanding of which patients are likely to respond best to SGLT2 inhibitors, and under what circumstances