Study on Truncation and Roundoff Errors in Numerical Methods

History is full of many examples where errors in numerical calculation have played important role or sometimes proved fatal also. (e.g. The Patriot and the Scud [6], The short flight of the Ariane 5 [7], The Vancouver Stock Exchange [8,9,10], Parliamentary elections in Schleswig-Holstein [11]). So in this paper we review two types of errors occurred while performing calculations: first is truncation error and second is round off error . Examples are given in support of the theory part.

A slow V̇O2 on-response allows comfortable adoption of aerobically unaffordable walking and running speeds on short stair ascents

ABSTRACTThe aim of this study was to investigate the mechanical and metabolic reasons for the spontaneous gait/speed choice when ascending a short flight of stairs, where walking on every step or running on every other step are frequently interchangeable options. The kinematics, oxygen uptake (V̇O2), ventilation and heart rate of 24 subjects were sampled during climbing one and two flights of stairs while using the two gaits. Although motor acts were very short in time (5–22 s), metabolic kinetics, extending into the 250 s after the end of climbing, consistently reflected the (metabolic equivalent of the) required mechanical energy and allowed comparison of the two ascent choices: despite a 250% higher mechanical power associated with running, measured , ventilation and heart rate peaked at only +25% with respect to walking, and in both gaits at much lower values than despite predictions based on previous gradient locomotion studies. Mechanical work and metabolic cost of transport, as expected, showed a similar increase (+25%) in running. For stairs up to a height of 4.8 m (30 steps at 53% gradient), running makes us consume slightly more calories than walking, and in both gaits with no discomfort at all. The cardio-respiratory–metabolic responses similarly delay and dampen the replenishment of phosphocreatine stores, which were depleted much faster during the impulsive, highly powered mechanical event, with almost overlapping time courses. This discrepancy between mechanical and metabolic dynamics allows us to afford climbs ranging from almost to very anaerobic, and to interchangeably decide whether to walk or run up a short flight of stairs.

Unpredictable hummingbirds: Flight path entropy is constrained by speed and wing loading

ABSTRACTUnpredictable movement can provide an advantage when animals avoid predators and other threats. Previous studies have examined how varying environments can elicit unpredictable movement, but the intrinsic causes of complex, unpredictable behavior are not yet known. We addressed this question by analyzing >200 hours of flight performed by hummingbirds, a group of aerial specialists noted for their extreme agility and escape performance. We used information theory to calculate unpredictability based on the positional entropy of short flight sequences during 30-min and 2-hour trials. We show that a bird’s entropy is repeatable, with stable differences among individuals that are negatively correlated with wing loading: birds with lower wing loading are less predictable. Unpredictability is also positively correlated with a bird’s overall acceleration and rotational performance, and yet we find that moment-to-moment changes in acceleration and rotational velocities do not directly influence entropy. This indicates that biomechanical performance must share an underlying basis with a bird’s ability to combine maneuvers into unpredictable sequences. Contrary to expectations, hummingbirds achieve their highest entropy at relatively slow speeds, pointing to a fundamental trade-off whereby individuals must choose to be either fast or unpredictable.

An Effective and Affordable Camera Trap for Monitoring Flower-visiting Butterflies in Sandhills: with Implications for the Frosted Elfin (Callophrys irus)

New advancements in camera trap technology have led to wide-spread use in animal monitoring. In this study we tested whether modern self-contained camera traps could be used to identify small lepidopterans such as the frosted elfin (Callophrys irus). A vast majority of photographed lepidopterans, 76/81 (93.83%), were identifiable to family when moving relatively slowly across the camera’s field of view. Although no C. irus were observed, we were able to identify several species of lepidopterans including those of similar size as C. irus. We find that modern camera traps are adequate to sample small lepidopterans and may open new avenues to survey for small rare species such as C. irus over larger areas than typically possible with small field crews and short flight seasons.

Pine Pitch Canker (PPC): Pathways of Pathogen Spread and Preventive Measures

Fusarium circinatum (Nirenberg and O’ Donnell) is the causal agent of pine pitch canker (PPC) disease, one of the most devastating forest diseases worldwide. Long-distance spread occurs mainly through the movement of infected seeds whereas at regional level, the movement of seedlings, substrates, or containers may play an important role in fungal dispersal. Invasion of nurseries takes place via infected seeds and further spread can occur by planting contaminated seedlings, especially due to the possibility of infected plants remaining symptomless. Once established, F. circinatum spreads by rain, wind, and insects. The natural spread of the pathogen is limited due to the short dispersal distances of the spores and the fairly short flight distances of disseminating insects. In this review, we summarize the currently known dispersal pathways of the pathogen, discussing both natural and human-assisted processes. With the purpose of understanding how to best intervene in the disease’s development in nurseries and forests, we outline the epidemiology of the pathogen describing the key factors influencing its spread. Preventive measures to control the spread of F. circinatum locally and globally are described with special emphasis on the challenges in implementing them.

P5351In-Flight Stroke in Korea

Background During flight, atmospheric pressure drop, low humidity and restricted motion occur. The environmental change can evoke the stroke occurrence. However, description of in-flight stroke case series has been limited until now. We investigated the clinical and flight trip characteristics of in-flight stroke cases in Korea. Method Since the opening of Incheon international airport, which is used by about 50 million people a year, in 2001, our hospital branch has been located at the airport and all the emergency stroke patients have been referred to our hospital. We performed retrospective review of the prospectively collected stroke registry and the information about the flight from January 2001 to December 2018. Results During the study period, 31 in-flight stroke cases were identified among total 1,452 ischemic stroke patients (17 men, 62±15 years old). Twenty-six patients had cerebral infarction, and four patients had transient ischemic attack. On etiological classification of cerebral infarction, 19 large artery atherothrombosis (61.3%), 1 septic embolism, 3 cryptogenic stroke, 3 cardioembolism (9.7%) and 1 cerebral venous thrombosis were identified. Six patients had Patent Foramen Ovale. Twenty-two patients reported to experience symptom around landing. Fourteen patients had flight for six hours or longer. Compared to the patients with long flight time (≥6 hrs), those with short flight time had the higher incidence of stroke occurrence around landings (32 vs 68%) and low incidence of unclear stroke onset. Poor outcome, defined as mRS 4 or higher, was associated with old age, unclear stroke onset, and early neurologic deterioration. Conclusion In-flight stroke is uncommon, and can easily be neglected during flight, which result in poor outcome. The stroke risk seems to be relatively high around landing, especially in the travelers with short flight time. The possibility of paradoxical embolism related to motion restriction seems low for stroke occurrence. Old age and unclear stroke onset are associated with poor outcomes.

Theoretical and practical aspects of the Coandă effect applied in aeronautics

The Coandă Effect, or better said, the deviation of fluid jets to stay attached to a convex surface is a complex gas-dynamic effect, named after the Romanian aviation engineer Henri Coandă and it was for the first time highlighted by him in 1910 during the take-off of one of his first planes, Coandă-1910, which was also the first jet plane to fly. During the short flight, Coandă was able to notice the near-fit alignment of the flue gas jets with the airplane fuselage. Later, both Coandă and other scholars have intensively studied the effect that is named The Coandă Effect, in his honor.

Method of large acceleration change for in-flight alignment of projectiles based on double-vector observations

Aiming at the problem that the purposive maneuver of the guided projectile is difficult to be realized during its short flight time, a method based on large acceleration change using double-vector observations for the in-flight alignment was proposed. First, according to the navigation velocity rate equation, double-vector observations were derived, and the Request algorithm was introduced for the initial attitude estimation. Then, error analysis was discussed, which puts forward a large acceleration change for the in-flight alignment. Simulation experiment analyzed and discussed the effectiveness of the proposed large acceleration change for the in-flight alignment. The simulation result indicated that the in-flight alignment can be achieved quickly, and the heading misalignment error is about 0.3°, the pitch and rolling misalignment errors are less than 0.2°.