Flow Visualization of Downhill Ski Racers Using Computational Fluid Dynamics

AbstractIn downhill alpine skiing, racers often exceed speeds of 120km/h, with air resistance substantially affecting the overall race times. To date, studies on air resistance in alpine skiing have used wind tunnels and actual skiers to examine the relationship between the gliding posture and magnitude of drag, as well as for the design of skiing equipment. However, these studies have not revealed the flow velocity distribution and vortex structure around the skier. In the present study, we used computational fluid dynamics with the lattice Boltzmann method to derive the relationship between flow velocity in the full tuck position (the downhill racer's speed) and total drag. Furthermore, we visualized the flow around the downhill racer and examined its vortex structure. The results show that the total drag force in the downhill racer model is 27.0N at a flow velocity of 15 m/s, increasing to 185.8N at 40 m/s. Moreover, the visualization of the flow field indicates that the primary drag locations at a flow velocity of 40 m/s are the head, upper arms, lower legs, and thighs (including the buttocks)

A Reading Model from the Perspective of Japanese Orthography: Connectionist Approach to the Hypothesis of Granularity and Transparency

This study presents a computer simulation model of reading in Japanese syllabic Kana and morphographic Kanji. The model was based on the simulation model developed by Harm and Seidenberg (1999) for reading in English. The purpose of building the current model was to verify the validity of the Hypothesis of Granularity and Transparency (HGT) postulated by Wydell and Butterworth (1999), focusing on the granularity dimension. The HGT was developed in order to explain the behavioral dissociation between excellent reading skills in Japanese and poor reading skills in English of an English-Japanese bilingual individual as well as the relatively low incidence of developmental dyslexia in Japan. The current model was successful in simulating the granularity dimension of the HGT. The study also identified several limitations, which need to be addressed in future research.This work was supported by the JSPS-Kakenhi, Grant No. 19530672, where Mutsuo Ijuin was the PI, while Taeko N. Wydell was one of the CIs

A novel echocardiographic-based classification for the prediction of peri-device leakage following left atrial appendage occluder implantation

(1) Background: The assessment of residual peri-device leakages (PDL) after left atrial appendage occlusion (LAAO) remains crucial for post-procedural management. Our study aimed to verify a novel echocardiographic classification for the prediction of PDL. (2) Methods: Echocardiographic data of 72 patients who underwent percutaneous LAAO were evaluated. All echo images were analyzed by two independent investigators using standard analysis software (Image-Arena IA-4.6.4.44 by TomTec ® , Munich, Germany). A total number of 127 studies was evaluated. Forty-four patients had baseline studies, at 45 days and at 6 months post-implantation. We propose a morphological classification of LAA devices based on the amount of echodensity inside the devices into three types: type A showing complete homogenous thrombosis, type B incompletely thrombosed device with inhomogeneous echo-free space 50% of device in various planes, which we called the “ice-cream cone” sign. Each type was matched to the degree of PDL and clinical outcome parameters. (3) Results: Patients with type C had the highest percentage of PDL at 45 days follow-up (type A: 24%, type B: 31%, type C 100% PDL, p < 0.001) and at 6 months follow-up (type A: 7%, type B: 33%, type C 100% PDL, p < 0.001). Notably, device size in patients with PDL was larger than that in patients without PDL at 6 months follow-up (25.6 ± 3.5 mm vs. 28.7 ± 3.4 mm, p = 0.004). Device size in patients with type C appearance was the largest of the three types (type A: 25.9 ± 3.6 mm, type B: 25.8 ± 3.4 mm, type C 29.8 ± 3.0 mm, type A vs. C; p = 0.019; type B vs. C, p = 0.007). (4) Conclusions: In conclusion, PDL are common post-LAAO, and their frequency is underestimated and under-recognized. PDL are much more common in patients with larger LAA ostial sizes and likely lower longitudinal compression. Type C appearance of the LAAO devices (“ice-cream cone sign”) has a high positive predictive value for PDL. Further studies are needed for better delineation of the clinical importance of this proposed classification

エディプス ノ モノガタリ ト シテノ ラ ジュテ ノ デザイン ナニ ガ エイゾウ ヲ デザイン スル ノカ

La Jetée (Chris Marker, 1962) is a film where the hero who has been obsessed from his childhood by an image that reveals an unknown man’s death and a woman who is terrified by it. Marker’s statement about this film is as follows; “It was made like a piece of automatic writing… I photographed a story I hardly understood. It’s in the cutting room that the pieces of the puzzle came together, and it wasn’t me who designed the puzzle.” The question is, who edited the film? From Marker’s declaration, it follows that Marker’s “unconscious” edited it. Interestingly in his statement, Marker compares his editing to “automatic writing” and “designing the puzzle.” As is well known, “automatic writing” is based on Freud’s “free association.” So, we can interpret La Jetée from a psychoanalytic point of view. We will find that this story has a scenario of Oedipus Rex. If this is true, we can interpret that both her blinking eyes which look back at the hero and the story’s circular structure represent the death drive’s repetition compulsion. Then, what about “designing the puzzle”? As architecture follows structural mechanics, La Jetée also follows a psychical structure. However, we can also find something uncanny to shake the psychical structure in La Jetée. Needless to say, it comes from the death drive and its repetition compulsion. So, Marker’s “design” expresses something contradictory that is both structural and dysmorphic.学術論