Drag Tests Research Articles

Investigation of a bio-inspired lift-enhancing effector on a 2D airfoil

A flap mounted on the upper surface of an airfoil, called a ‘lift-enhancing effector’, has been shown in wind tunnel tests to have a similar function to a bird's covert feathers, which rise off the wing's surface in response to separated flows. The effector, fabricated from a thin Mylar sheet, is allowed to rotate freely about its leading edge. The tests were performed in the NCSU subsonic wind tunnel at a chord Reynolds number of 4 × 105. The maximum lift coefficient with the effector was the same as that for the clean airfoil, but was maintained over an angle-of-attack range from 12° to almost 20°, resulting in a very gentle stall behavior. To better understand the aerodynamics and to estimate the deployment angle of the free-moving effector, fixed-angle effectors fabricated out of stiff wood were also tested. A progressive increase in the stall angle of attack with increasing effector angle was observed, with diminishing returns beyond the effector angle of 60°. Drag tests on both the free-moving and fixed effectors showed a marked improvement in drag at high angles of attack. Oil flow visualization on the airfoil with and without the fixed-angle effectors proved that the effector causes the separation point to move aft on the airfoil, as compared to the clean airfoil. This is thought to be the main mechanism by which an effector improves both lift and drag. A comparison of the fixed-effector results with those from the free-effector tests shows that the free effector's deployment angle is between 30° and 45°. When operating at and beyond the clean airfoil's stall angle, the free effector automatically deploys to progressively higher angles with increasing angles of attack. This slows down the rapid upstream movement of the separation point and avoids the severe reduction in the lift coefficient and an increase in the drag coefficient that are seen on the clean airfoil at the onset of stall. Thus, the effector postpones the stall by 4–8° and makes the stall behavior more gentle. The benefits of using the effector could include care-free operations at high angles of attack during perching and maneuvering flight, especially in gusty conditions.

Nanoparticulate lipid dispersions for bromocriptine delivery: Characterization and in vivo study

The physico-chemical properties and in vivo efficacies of two nanoparticulate systems delivering the antiparkinsonian drug bromocriptine (BC) were compared in the present study. Monoolein Aqueous Dispersions (MADs) and Nanostructured Lipid Carriers (NLCs) were produced and characterized. Cryogenic transmission electron microscopy (cryo-TEM) and X-ray diffraction revealed the morphology of MAD and NLC. Dimensional distribution was determined by Photon Correlation Spectroscopy (PCS) and Sedimentation Field Flow Fractionation (SdFFF). In particular, BC was shown to be encapsulated with high entrapment efficiency both in MAD and in NLC, according to SdFFF combined with HPLC. Two behavioral tests specific for akinesia (bar test) or akinesia/bradykinesia (drag test) were used to compare the effects of the different BC formulations on motor disabilities in 6-hydroxydopamine hemilesioned rats in vivo, a model of Parkinson’s disease. Both free BC and BC–NLC reduced the immobility time in the bar test and enhanced the number of steps in the drag test, although the effects of encapsulated BC were longer lasting (5h). Conversely, BC–MAD was ineffective in the bar test and improved stepping activity in the drag test to a much lower degree than those achieved with the other preparations. We conclude that MAD and NLC can encapsulate BC, although only NLC provide long-lasting therapeutic effects possibly extending BC half-life in vivo.

Research of Measurement Method of Two Dimensional Configuration Drag Test in Wind Tunnel in Case of High Lift

Computational fluid dynamics and wind tunnel test are two main technical means to examine the aerodynamic performance of airfoil and two-dimensional(2-D) configuration. Two dimensional wind tunnel tests use commonly wake flow field measurement to integrate for drag of airfoil or two-dimensional configuration, but the integral formulas are based on certain assumptions and of certain bounds of application. In this paper, based on Navier-Stokes equations numerical simulation and two dimensional wind tunnel testing, the drag measuring technique for high lift configuration in low speed wind tunnel is researched. Navier-Stokes equations is solved for the flow around a multi-element airfoil, the wake flow characteristics behind the multi-element airfoil and the assumptions for conventional drag measuring method are analyzed, then a new more precise drag formula for two dimensional wind tunnel test is put forward; Based on the simulation results of multi-element airfoil flow, it’s aerodynamic performance is obtained respectively by integrating the surface pressure and friction drag, and computing with the information of wake flow according to conventional and newly proposed drag calculation formulas, and the three results are compared to verify the accuracy of the new drag formula; The wind tunnel test is carried out to ascertain the accuracy of the new drag formula. It is shown from the results that in the high-lift case the conventional drag formula with the wake information is of many limitations and must be improved, and the new drag formula presented in this paper is more accurate because of consideration of the wake flow characteristics of airfoil or two-dimensional configuration.

Nociceptin/orphanin FQ receptor knockout rats: In vitro and in vivo studies

Nociceptin/orphanin FQ (N/OFQ) regulates several biological functions via selective activation of the N/OFQ peptide (NOP) receptor. Recently knockout rats for the NOP receptor gene (NOP(−/−)) have been generated; these animals were used in the present study to investigate their emotional (open field, elevated plus maze, and forced swimming test), locomotor (drag and rotarod test), and nociceptive (plantar and formalin test) phenotypes in comparison with their NOP(+/+) littermates. In addition, N/OFQ sensitivity has been assessed in electrically stimulated vas deferens tissues taken from NOP(+/+) and NOP(−/−) rats. In the elevated plus maze and forced swimming tests NOP(−/−) rats showed anxiety- and anti-depressant-like phenotype, respectively. No differences were found in the open field test. NOP(−/−) rats outperformed their NOP(+/+) littermates in two motor behaviour assays. Genetic ablation of the NOP receptor gene produced a statistically significant increase in nociceptive behaviour of the mutant rats in the formalin test. Finally, in the electrically stimulated rat vas deferens taken from NOP(+/+) tissues, N/OFQ inhibited in a concentration-dependent manner the electrically induced twitches while the peptide was inactive in tissues taken from NOP(−/−) animals. These results, in line with previous findings obtained with selective NOP receptor antagonists in mice and rats and with mouse knockout studies, clearly indicate that endogenous N/OFQ–NOP receptor signalling plays an important role in controlling anxiety- and mood-related behaviours, exercise-driven locomotor activity and nociception. These observations are relevant for defining the therapeutic indications (and contraindications) of NOP receptor antagonists.

Full-Configuration Drag Estimation

Accurate drag estimation is critical in making computational design studies. Drag may be estimated thousands of times during a multidisciplinary design optimization, and computational fluid dynamics is not yet possible in these studies. The current model has been developed as part of an air-vehicle conceptual-design multidisciplinary design optimization framework. Its use for subsonic and transonic aircraft configurations is presented and validated. We present our parametric geometry definition, followed by the drag model description. The drag model includes induced, friction, wave, and interference drag. The model is compared with subsonic and transonic isolated wings, and a wing/body configuration used previously in drag prediction workshops. The agreement between the predictions of the drag model and test data is good, but lessens at high lift coefficients and high transonic Mach numbers. In some cases the accuracy of this drag estimation method exceeds much more elaborate analyses.

Dual motor response to l-dopa and nociceptin/orphanin FQ receptor antagonists in 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) treated mice: Paradoxical inhibition is relieved by D 2/D 3 receptor blockade

Motor activity of mice acutely treated with the parkinsonian toxin 1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine (MPTP) was monitored for 6 days using behavioral tests which provide complementary information on motor function: the bar, reaction time, drag, stair climbing, grip, rotarod and footprinting tests. These tests consistently disclosed a prolonged motor impairment characterized by akinesia, bradykinesia, speed reduction, loss of coordination and gait patterns. This impairment was associated with ∼ 60% loss of striatal dopamine terminals, as revealed by tyrosine hydroxylase immunohistochemistry, and was attenuated by dopaminergic drugs. Indeed, the dopamine precursor, l-dopa (1–10 mg/kg), and the D 3/D 2 receptor agonist pramipexole (0.0001–0.001 mg/kg) promoted stepping activity in the drag test (a test for akinesia/bradykinesia). The novel nociceptin/orphanin FQ receptor (NOP) antagonist 1-[1-(cyclooctylmethyl)-1,2,3,6-tetrahydro-5-(hydroxymethyl)-4-pyridinyl]-3-ethyl-1,3-dihydro-2 H-benzimidazol-2-one (Trap-101, 0.001–0.1 mg/kg), an analogue of 1-[(3 R,4 R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2 H-benzimidazol-2-one (J-113397), also promoted stepping and synergistically or additively (depending on test) attenuated parkinsonism when combined to dopamine agonists. High doses of l-dopa (100 mg/kg), pramipexole (0.1 mg/kg), Trap-101 and J-113397 (1 mg/kg), however, failed to modulate stepping, worsening immobility time and/or rotarod performance. Low doses of amisulpride (0.1 mg/kg) reversed motor inhibition induced by l-dopa and J-113397, suggesting involvement of D 2/D 3 receptors. This study brings further evidence for a dopamine-dependent motor phenotype in MPTP-treated mice reinforcing the view that this model can be predictive of symptomatic antiparkinsonian activity provided the appropriate test is used. Moreover, it offers mechanistic interpretation to clinical reports of paradoxical worsening of parkinsonism following l-dopa. Finally, it confirms that NOP receptor antagonists may be proven effective in reversing parkinsonism when administered alone or in combination with dopamine agonists.

Endogenous nociceptin/orphanin FQ (N/OFQ) contributes to haloperidol-induced changes of nigral amino acid transmission and parkinsonism: a combined microdialysis and behavioral study in naïve and nociceptin/orphanin FQ receptor knockout mice

The contribution of endogenous nociceptin/orphanin FQ (N/OFQ) to neuroleptic-induced parkinsonism has been evaluated in haloperidol-treated mice. Pharmacological blockade of N/OFQ receptors (NOP) via systemic administration of 1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H benzimidazol-2-one (J-113397, 0.01–10 mg/kg i.p.) or central injection of [Nphe 1,Arg 14,Lys 15]N/OFQ-NH 2 (UFP-101, 10 nmol i.c.v.) attenuated (0.8 mg/kg) haloperidol-induced motor deficits as evaluated by a battery of behavioral tests providing complementary information on motor parameters: the bar, drag and rotarod tests. A combined neurochemical and behavioral approach was then used to investigate whether the substantia nigra reticulata could be involved in antiakinetic actions of J-113397. Microdialysis combined to the bar test revealed that haloperidol (0.3 and 0.8 mg/kg i.p.) caused a dose-dependent and prolonged elevation of immobility time (i.e. akinesia) which was associated with an increase in nigral glutamate and a reduction in GABA release. Conversely, J-113397 (1 mg/kg) alone reduced glutamate and elevated nigral GABA release, and when challenged against haloperidol, counteracted its behavioral and neurochemical effects. Microdialysis coupled to behavioral testing also demonstrated that NOP receptor knockout mice were resistant to haloperidol (0.3 mg/kg) compared to wild-type mice, lack of response being associated with a reversal of glutamate release facilitation into inhibition and no change in nigral GABA release. This study provides pharmacological and genetic evidence that endogenous N/OFQ contributes to haloperidol-induced akinesia and changes of amino acid transmission in mice. Moreover, it confirms the view that NOP receptor antagonists are capable of reversing akinesia across species and genotypes and may prove effective in relieving neuroleptic-induced parkinsonism.

The selective D3 receptor antagonist, S33084, improves parkinsonian-like motor dysfunction but does not affect l-DOPA-induced dyskinesia in 6-hydroxydopamine hemi-lesioned rats

Despite evidence linking dopamine D(3) receptors to the etiology of Parkinson's disease and L-DOPA-induced dyskinesia, the potential therapeutic utility of D(3) receptor ligands remains unclear. In the present study, we investigated whether the selective D(3) receptor antagonist, S33084, affects development and expression of abnormal involuntary movements (AIMs), a behavioural correlate of dyskinesia, in rats hemi-lesioned with 6-hydroxydopamine and chronically treated with L-DOPA. The ability of S33084, alone or in combination with L-DOPA, to attenuate 6-hydroxydopamine induced motor deficits was also investigated employing a battery of behavioural tests. Acute administration of S33084 (0.64 mg/kg, s.c.) did not attenuate the induction of AIMs in dyskinetic rats upon challenge with L-DOPA (6 mg/kg, s.c.). Moreover, S33084 (0.64 mg/kg) did not prevent the development of AIMs affecting axial, limb and orolingual muscles when chronically administered together with L-DOPA (6 mg/kg for 21 days). However, both acute and chronic administration of S33084 enhanced L-DOPA-induced contralateral turning, suggesting potential antiparkinsonian properties. Furthermore, S33084 (0.01-0.64 mg/kg) dose-dependently attenuated parkinsonian disabilities, including bradykinesia, in drag and rotarod tests, although, in these procedures, the combination of S33084 with L-DOPA did not produce synergistic effect. It is concluded that sustained D(3) receptor blockade does not blunt L-DOPA-induced dyskinesia in hemiparkinsonian rats. However, D(3) receptor antagonism may be associated with antiparkinsonian properties. The clinical relevance of these observations will be of interest to explore further.

The novel delta opioid receptor agonist UFP-512 dually modulates motor activity in hemiparkinsonian rats via control of the nigro-thalamic pathway

The present study aimed to characterize the ability of the novel delta opioid peptide (DOP) receptor agonist H-Dmt-Tic-NH-CH(CH 2–COOH)-Bid (UFP-512) to attenuate motor deficits in 6-hydroxydopamine (6-OHDA) hemilesioned rats. Lower doses (0.1–10 μg/kg) of UFP-512 administered systemically (i.p.) stimulated stepping activity in the drag test and overall gait abilities in the rotarod test whereas higher doses (100–1000 μg/kg) were ineffective or even worsened Parkinsonism. Microdialysis coupled to an akinesia test (bar test) was then used to determine the circuitry involved in the motor actions of UFP-512. An antiakinetic dose of UFP-512 (10 μg/kg) decreased GABA in globus pallidus (GP) as well as GABA and glutamate (GLU) release in substantia nigra reticulata (SNr). On the other hand, a pro-akinetic dose (1000 μg/kg) of UFP-512 increased pallidal GABA, simultaneously producing a decrease in GABA and an increase in nigral GLU release. Moreover, to test the hypothesis that changes in motor behavior were associated with changes in nigro–thalamic transmission, amino acid release in ventromedial thalamus (VMTh, a target of nigro–thalamic GABAergic projections) was also measured. The anti-akinetic dose of UFP-512 reduced GABA and increased thalamic GLU release while the pro-akinetic dose increased GABA without affecting thalamic GLU release. Finally, regional microinjections were performed to investigate the brain areas involved in motor actions of UFP-512. UFP-512 microinjections into GP increased akinesia whereas UFP-512 microinjections into SNr reduced akinesia. Furthermore, the selective DOP receptor antagonist naltrindole (NTD) increased akinesia when injected into either area, GP being more sensitive. We conclude that UFP-512, depending on dose, improves or worsens motor activity in hemiparkinsonian rats by acting differentially as a DOP receptor agonist in SNr and a DOP receptor antagonist in GP, ultimately decreasing or increasing the activity of nigro–thalamic GABAergc output neurons, respectively.

Drag force mechanical power during an actual propulsion cycle on a manual wheelchair

The object of this study was to compute the mechanical power of the resultant braking force during an actual propulsion cycle with a manual wheelchair on the field. The resultant braking force was calculated from a mechanical model taking into account the rolling resistances of the front and rear wheels. Both the resultant braking force and the wheelchair velocity were not constant during the propulsion cycle and varied according to the subject's fore-and-aft and vertical movements in the wheelchair. These variations had logical repercussions on the braking force mechanical power, which ranged from 20.6 to 34.5 W (mean = 29.6 W) during the propulsion cycle. The mechanical power was also calculated from the conditions of a classical drag test, by the product of the cycle mean velocity and a constant braking force corresponding to a 60% rear wheels distribution of the subject-and-wheelchair's weight. This second mechanical power (32.4 W) was 10% higher than the average of the instantaneous power. Beyond the need of a clear definition of the two phases of the propulsion cycle, this study showed that the assumption on wheelchair locomotion usually admitted on laboratory ergometers cannot be applied in field studies, and that the kinetic energy variations during the cycle propulsive phase should be considered for evaluating the subject's mechanical work and power.

Differential effect of NR2A and NR2B subunit selective NMDA receptor antagonists on striato‐pallidal neurons: relationship to motor response in the 6‐hydroxydopamine model of parkinsonism

We previously demonstrated that NMDA receptors containing the NR2A or NR2B subunits differentially regulate striatal output pathways. We now investigate whether such a differential control is altered under parkinsonian conditions and whether subunit selective antagonists have different abilities to attenuate parkinsonian-like motor deficits. Three microdialysis probes were simultaneously implanted in the dopamine-depleted striatum, globus pallidus and substantia nigra reticulata of 6-hydroxydopamine hemilesioned rats. The NR2A antagonist NVP-AAM077 perfused in the striatum reduced pallidal GABA, but not glutamate, levels whereas the NR2B antagonist Ro 25-6981 was ineffective. Neither antagonist affected striatal or nigral amino acid levels. To investigate whether these neurochemical responses were predictive of different antiparkinsonian activities, antagonists were administered systemically and motor activity evaluated in different motor tasks. Neither antagonist attenuated akinesia/bradykinesia in the bar and drag test. However, NVP-AAM077 dually modulated rotarod performance (low doses being facilitatory and higher ones inhibitory) while Ro 25-6981 monotonically improved it. Microdialysis revealed that motor facilitating doses reduced pallidal GABA levels while motor inhibiting doses increased them. We conclude that, under parkinsonian conditions, the striato-pallidal pathway is driven by striatal NR2A subunits. Motor improvement induced by NVP-AAM077 and Ro 25-6981 is accomplished by blockade of striatal NR2A and extrastriatal NR2B subunits, respectively.

Grafting Lubricant Molecular Chains to the Carbon Overcoat

It was conceived and demonstrated that irradiation of magnetic disks coated with PFPE (perfluoropolyether) lubricants terminated with a carboxylic group at one terminus with long-UV (254 nm) would lead to grafting, via a bona fide C–C chemical bond, of genuine PFPE molecular chains to the carbon overcoat all at one terminus with all the remaining chain segments being free to sway. The water contact angle of disks coated with PFPE lubricants terminated with end-groups having hydroxyl unit(s) (e.g., Z-dol and Z-tetraol) decreases gradually, after the initial contact of the droplet, reaching an asymptote in 20–30 s. The gradual temporal change is accounted for by shifting of the equilibrium disposition of hydroxyl units of the lubricant molecules from that determined by the interaction with the surface of the carbon overcoat to that determined by the interaction with surfaces of both the carbon overcoat and the liquid droplet. The water contact angle of disks prepared by the presently conceived photo-grafting method is high (>110 degrees) and shows no temporal change. In a preliminary spin-stand drag test, disks with PFPE chains photo-grafted by this method and also the heads (for the read/write process) with similar photo-grafted PFPE chains exhibited extraordinary durability.

Vehicle wheel aerodynamic testing, using the double-symmetry technique

Within the scope of wheel drag investigation, a mirror image method for simulating relative motions of wheels and moving ground for road vehicle aerodynamics was developed using a double-symmetry technique. An initial study using no-wheeled bluff body demonstrated feasibility. The current paper further extends this technique to a wheeled model vehicle. The concept, measuring approach and EFD and CFD evaluations are described. The double-symmetry approach enabled simulated on-road vehicle drag tests. With the ability to replicate deformations at tyre contact patch, the approach presents evaluation of rotating wheel effects on accessories and their actual contribution to the vehicle road load.

Power output and metabolic cost of synchronous and asynchronous submaximal and peak level hand cycling on a motor driven treadmill in able-bodied male subjects

Purpose To evaluate external power output and physiological responses of synchronous (SYNC) and asynchronous hand cycling (ASYNC) at submaximal and peak levels of exercise. Methods n = 9 able-bodied male subjects (age: 20.1 ± 2.1 years) performed two (sub)maximal continuous hand cycle exercise tests, using the SYNC and ASYNC mode in a standardized commercial add-on hand cycle unit (counter-balanced order). Treadmill speed (1.89 and 2.17 m s −1) and slope (steps of +1%) were changed in a fixed sequence of 3-min exercise steps. Gears were adjusted to 65 rpm. External power output (PO) was continuously monitored with a strain-gauge instrumented chain ring ((SRM) Schoberer Rad Messtechnik). A conventional wheelchair drag test was performed to validate mean external power for each speed-slope combination. Heart rate (HR; bpm) and oxygen uptake (VO 2; ml kg −1 min −1, SMTP) were continuously monitored. Paired T-tests and ANOVA for repeated measures evaluated effects of mode and exercise level ( p < 0.05). Results Subjects reached peak levels of performance (RER: 1.05 ± 0.07 versus 1.10 ± 0.1 for SYNC and ASYNC). Peak PO and V O 2 were significantly higher for SYNC (81.6 ± 11.8 W versus 68.5 ± 10.6 W; 26.4 ± 4.5 ml kg −1 min −1 versus 21.2 ± 3.0 ml kg −1 min −1). At submaximal exercise levels, gross mechanical efficiency (ME) was significantly higher for SYNC (12.1 ± 0.9% versus 9.7 ± 1.4% at 41 W). No significant differences were found for PO (at equal velocity and slope), as derived from the SRM (SYNC and ASYNC), and from the drag test. Discussion The absence of any differences in PO between SYNC and ASYNC, and with respect to the drag test, rules out ‘additional external work due to maintain the desired heading’ in the ASYNC as an explanation for the lower performance in this mode. Lower peak performance and ME in ASYNC may be explained by the increased stabilizing muscle effort in the upper extremities and trunk in order to combine power production with stable steering. ASYNC is less efficient compared to SYNC. Similarly, peak performance capacity was higher for SYNC. Conclusion External work does not differ between SYNC and ASYNC hand cycling. SRM readings appear valid for PO monitoring in hand cycling within the studied range of PO. SYNC is more efficient than ASYNC and leads to higher peak performance.

Fabrication, Microstructure, Magnetic, and Recording Properties of Percolated Perpendicular Media

In this paper, a new type of perpendicular magnetic media which we have termed percolated perpendicular media is discussed. We present the method we used to fabricate the media as well as an energetic rationale for the driving force to produce the desired microstructure. The microstructures of samples with various amounts of oxide material are presented and the optimum one for our investigation is presented. We also present some preliminary drag test data that can be used to evaluate the recording properties of this media

Air-bearing surface chemical modification for low-friction head–disk interface

As a chemical modification of slider air bearing surface (ABS), fluorine ion implantation (FII) was conducted. FII treated ABS was fabricated to reduce slider surface energy, which is expected to reduce adhesion and friction force between the slider and disk. Tribological performance, such as slider flyability, was experimentally investigated. Touchdown speed, corresponds to a flying height of about 0.4 nm, was reduced by FII treatment. Slider touch-down and take-off hysteresis was also improved by reducing the adhesive force of the lubricant by fluorine-ion implantation. AE output and friction force were also reduced in the drag test. FII treated slider showed a 45% reduction of AE amplitude and 14% reduction of friction force. FII treatment was confirmed to be effective in improving slider flyability.

PIV를 이용한 범포 주위의 유동장 특성

This research aims at establishing the fundamental characteristics of the kite through the analysis of the flow field around various types of kites. The approach of this study were adopted for the analysis; visualization by PIV(particle image velocimetry). Also, the lift and drag tests of kites had been performed in our previous finding(Bae et al., 2004a; Bae et al., 2004b). For this situation, models of canvas kite were deployed in the circulating water channel for the PIV test using the same conditions as in the lift and drag tests. The results obtained from the above approach are summarized as follows: Given the rectangular and triangular kites when attack angle is <TEX>$20^{\circ}$</TEX>, vortex by the boundary layer separation was seen in the leading edge and the flow towards the trailing edge was more turbulent. But, the inverted triangular type kite was seen to be stable without any boundary layer separation or turbulence. The increase of the attack angle resulted in the eddy in order of the rectangular, triangular and inverted triangular type. The magnitude of the eddy followed the same order. The effect of edge-eddy was biggest in the triangular type followed by the rectangular and then the inverted triangular type. The kite as the buoyancy device or the opening device will be very useful when the appropriate applications and the stability are met.

Standardization of measuring power output during wheelchair propulsion on a treadmill: Pitfalls in a multi-center study

Objective In a multi-center study the power output of wheelchair propulsion, attained by a wheelchair drag test, differed among rehabilitation centers. The purpose of this study was to investigate what causes the differences in drag force among centers. Methods A set of standardized drag tests was performed while systematically varying the calibration set of the force transducer, the tester and the wheelchair. In addition, the actual calibrated velocity and slope of the treadmill were measured. Results Difference in drag force among centers was due to variation in wheelchair set-up and differences in the slopes between treadmills. The drag force was not significantly different when different testers performed the test. The belt velocity in almost all centers was lower than the manufacturer specified (assumed) velocity. Conclusion The drag test appeared a robust test as far as the tester is considered. Variation in wheelchairs and differences in the actual slopes of the treadmills affected the imposed drag force. The assumed velocity of the treadmill led to an overestimation of the power output. The power output in the multi-center study should be recalculated using the measured velocities and the wheelchair set-up should be more standardized.

Validation of Solutions of Construction Problems in Dynamic Geometry Environments

This paper discusses issues concerning the validation of solutions of construction problems in Dynamic Geometry Environments (DGEs) as compared to classic paper-and-pencil Euclidean geometry settings. We begin by comparing the validation criteria usually associated with solutions of construction problems in the two geometry worlds – the ‘drag test’ in DGEs and the use of only straightedge and compass in classic Euclidean geometry. We then demonstrate that the drag test criterion may permit constructions created using measurement tools to be considered valid; however, these constructions prove inconsistent with classical geometry. This inconsistency raises the question of whether dragging is an adequate test of validity, and the issue of measurement versus straightedge-and-compass. Without claiming that the inconsistency between what counts as valid solution of a construction problem in the two geometry worlds is necessarily problematic, we examine what would constitute the analogue of the straightedge-and-compass criterion in the domain of DGEs. Discovery of this analogue would enrich our understanding of DGEs with a mathematical idea that has been the distinguishing feature of Euclidean geometry since its genesis. To advance our goal, we introduce the compatibility criterion, a new but not necessarily superior criterion to the drag test criterion of validation of solutions of construction problems in DGEs. The discussion of the two criteria anatomizes the complexity characteristic of the relationship between DGEs and the paper-and-pencil Euclidean geometry environment, advances our understanding of the notion of geometrical constructions in DGEs, and raises the issue of validation practice maintaining the pace of ever-changing software.

캔버스 카이트의 유체역학적 특성에 관한 연구 - 1. 사각형 캔버스 카이트의 특성 -

종횡비, 다각형 모양에 따른 평판과 범포의 유체역학적 특성을 규명하고자 직사각형, 사다리꼴 모양으로 모형 평판과 범포를 제작하고 회류수조에서 양 <TEX>${\cdot}$</TEX> 항력 실험을 수행하였다. 그 결과를 요약하면 다음과 같다. 1. 직사각형 평판의 경우, 종횡비가 1 이하인 모형에서는 영각 40<TEX>${\sim}$</TEX>42<TEX>$^{\circ}$</TEX>에서 최대 <TEX>$C_L$</TEX>이 1.46<TEX>${\sim}$</TEX>1.54, 1.5 이상인 모형에서는 20<TEX>${\sim}$</TEX>22<TEX>$^{\circ}$</TEX>에서 10.7<TEX>${\sim}$</TEX>1.11 정도였다. 직사각형 범포의 경우, 종횡비가 1 이하인 모형에서는 영각 32<TEX>${\sim}$</TEX>40<TEX>$^{\circ}$</TEX>에서 최대 <TEX>$C_L$</TEX>이 1.75<TEX>${\sim}$</TEX>1.91, 1.5 이상인 모형에서는 18<TEX>${\sim}$</TEX>22<TEX>$^{\circ}$</TEX>에서 1.248<TEX>${\sim}$</TEX>1.40 정도였다. 같은 직사각형 모형에서는 범포가 평판보다 <TEX>$C_L$</TEX>은 크게, 양항비는 작게 나타났다. 2. 사다리꼴 범포의 경우, 종횡비가 1.5 이하인 모형에서는 영각 34<TEX>${\sim}$</TEX>44<TEX>$^{\circ}$</TEX>에서 최대 <TEX>$C_L$</TEX>이 1.65<TEX>${\sim}$</TEX>1.89, 2인 모형에서는 14<TEX>${\sim}$</TEX>48<TEX>$^{\circ}$</TEX>에서 <TEX>$C_L$</TEX>이 약 1.00 전후였다. 역사다리꼴 범포의 경우, 종횡비가 1.5 이하인 모형에서는 영각 24<TEX>${\sim}$</TEX>36<TEX>$^{\circ}$</TEX>에서 최대 <TEX>$C_L$</TEX>이 1.57<TEX>${\sim}$</TEX>1.74, 2인 모형에서는 18<TEX>$^{\circ}$</TEX>에서 1.21이었다. 같은 사다리꼴 범포 모형에서는 전자의 모형이 후자보다 <TEX>$C_L$</TEX>은 조금 크게, 양항비는 작게 나타났다. 3. 모형에서 물의 유체력을 많이 받을 수 있는 곳에서 만곡꼭지점이 만들어지며, 직사각형, 사다리꼴 모형에서는 종횡비가 클수록, 역사다리꼴 모형에서는 종횡비가 클수록, 역사다리꼴 모형에서는 작을수록 만곡꼭지점의 위치도 컸다. 4. 만곡도는 전 모형에서 종횡비가 클수록 컸으며, 직사각형, 사다리꼴 모형에서 영각의 클수록 컸고 직사각형 모형이 사다리꼴 모형보다 컸다. As far as an opening device of fishing gears is concerned, applications of a kite are under development around the world. The typical examples are found in the opening device of the stow net on anchor and the buoyancy material of the trawl. While the stow net on anchor has proved its capability for the past 20 years, the trawl has not been wildly used since it has been first introduced for the commercial use only without sufficient studies and thus has revealed many drawbacks. Therefore, the fundamental hydrodynamics of the kite itself need to ne studied further. Models of plate and canvas kite were deployed in the circulating water tank for the mechanical test. For this situation lift and drag tests were performed considering a change in the shape of objects, which resulted in a different aspect ratio of rectangle and trapezoid. The results obtained from the above approaches are summarized as follows, where aspect ratio, attack angle, lift coefficient and maximum lift coefficient are denoted as A, B, <TEX>$C_L$</TEX> and <TEX>$C_{Lmax}$</TEX> respectively : 1. Given the rectangular plate, <TEX>$C_{Lmax}$</TEX> was produced as 1.46<TEX>${\sim}$</TEX>1.54 with A<TEX>${\leq}$</TEX>1 and 40<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>42<TEX>$^{\circ}$</TEX>. And when A<TEX>${\geq}$</TEX>1.5 and 20<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>22<TEX>$^{\circ}$</TEX>, <TEX>$C_{Lmax}$</TEX> was 10.7<TEX>${\sim}$</TEX>1.11. Given the rectangular canvas, <TEX>$C_{Lmax}$</TEX> was 1.75<TEX>${\sim}$</TEX>1.91 with A<TEX>${\leq}$</TEX>1 and 32<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>40<TEX>$^{\circ}$</TEX>. And when A<TEX>${\geq}$</TEX>1.5 and 18<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>22<TEX>$^{\circ}$</TEX>, <TEX>$C_{Lmax}$</TEX> was 1.24<TEX>${\sim}$</TEX>1.40. Given the trapezoid kite, <TEX>$C_{Lmax}$</TEX> was produced as 1.65<TEX>${\sim}$</TEX>1.89 with A<TEX>${\leq}$</TEX>1.5 and 34<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>44<TEX>$^{\circ}$</TEX>. And when A=2 and B=14<TEX>${\sim}$</TEX>48, <TEX>$C_L$</TEX> was around 1. Given the inverted trapezoid kite, <TEX>$C_{Lmax}$</TEX> was 1.57<TEX>${\sim}$</TEX>1.74 with A<TEX>${\leq}$</TEX>1.5 and 24<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>36<TEX>$^{\circ}$</TEX>. And when A=2, <TEX>$C_{Lmax}$</TEX> was 1.21 with B=18<TEX>$^{\circ}$</TEX>. 2. For a model with A=1/2, an increase in B caused an increase in <TEX>$C_L$</TEX> until <TEX>$C_L$</TEX> has reached the maximum. Then there was a tendency of a gradual decrease in the value of <TEX>$C_L$</TEX> and in particular, the rectangular kite showed a more rapid decrease. For a model with A=2/3, the tendency of <TEX>$C_L$</TEX> was similar to the case of a model with A=1/2 but the tendency was a more rapid decrease than those of the previous models. For a model with A=1, and increase in B caused an increase in <TEX>$C_L$</TEX> until <TEX>$C_L$</TEX> has reached the maximum. Soon after the tendency of <TEX>$C_L$</TEX> decreased dramatically. For a model with A=1.5, the tendency of <TEX>$C_L$</TEX> as a function of B was various. For a model with A=2, the tendency of <TEX>$C_L$</TEX> as a function of B was almost the same in the rectangular and trapezoid model. There was no considerable change in the models with 20<TEX>$^{\circ}$</TEX><TEX>${\leq}$</TEX>B<TEX>${\leq}$</TEX>50<TEX>$^{\circ}$</TEX>. 3. The tendency of kite model's <TEX>$C_L$</TEX> in accordance with increase of B was increased rapidly than plate models until <TEX>$C_L$</TEX> has reached the maximum. Then <TEX>$C_L$</TEX> in the kite model was decreased dramatically but in the plate model was decreased gradually. The value of <TEX>$C_{Lmax}$</TEX> in the kite model was higher than that of the plate model, and the kite model's attack angel at <TEX>$C_{Lmax}$</TEX> was smaller than the plate model's. 4. In the relationship between aspect ratio and lift force, the attack angle which had the maximum lift coefficient was large at the small aspect ratio models, At the large aspect ratio models, the attack angle was small. 5. There was camber vertex in the position in which the fluid pressure was generated, and the rectangular & trapezoid canvas had larger value of camber vertex when the aspect ratio was high, while the inverted trapezoid canvas was versa. 6. All canvas kite had larger camber ratio when the aspect ratio was high, and the rectangular & trapezoid canvas had larger one when the attack angle was high.