Path Inclination Research Articles

側方滑走運動時の作業側犬歯の運動路の前頭面内傾斜角とか路との関連性

The purpose of this study was to determine whether or not there was any correlation between canine guidance and condylar paths during mandibular lateral movement. Lateral movements were measured on 40 normal young adults using the six-degrees of freedom mandibular movement analyzing system, and the movement data were analyzed on 75 sides where no balancing-side contacts were observed. Canine guidance was evaluated as the frontal inclination of the working-side canine path at 2.0mm from the intercuspal position. The variables to analyze condylar movement were the anterior, lateral and inferior components of the working-side and balancing-side condylar paths. The results were as follows:1. There were significant correlations between the canine guidance and the anterior (r=0.59, p<0.0001) and inferior components (r=0.41, p<0.0005) of the working-side condylar path. This indicates that the subject with a steep canine guidance has a large amount of the anterior and inferior components of the working-side condylar path, and that, the subject with a flat canine guidance has a large amount of the posterior and superior components of the working-side condylar path.2. On the other hand, no significant correlation was found between the canine guidance and any components of the balancing-side condylar path.

Robust predictor-corrector guidance for aeroassisted orbital transfer

The safety zone guidance, relative to the exit phase of the atmospheric pass of an aeroassisted orbital transfer (AOT) vehicle is extended, so as to incorporate both the entry and exit phases of the atmospheric pass and to include the automatic determination of the switch time from entry to exit guidance. The guidance goals are 1) to contain the peak heating rate during the atmospheric pass, 2) to ensure that the AOT vehicle exits the atmosphere in the correct orbital plane, ascending afterward to the specified apogee, and 3) to achieve robustness vis-a-vis severe parameter dispersion effects resulting from navigation errors, atmospheric density errors, aerodynamic coefficient errors, and system errors. Numerical tests show that this guidance scheme exhibits high performance and relatively high robustness vis-a-vis dispersion effects resulting from these errors. The guidance robustness is due to two factors: 1) the switch time from entry phase to exit phase is the result of a proper engineering compromise and 2) for the exit phase, the control is not determined by aiming only at the desired apogee; instead, for each altitude-velocity pair, a special value of the path inclination is determined by maximizing the control margin while aiming at the desired apogee during the atmospheric pass.

Near-optimal highly robust guidance for aeroassisted orbital transfer

One of the difficulties in aeroassisted orbital transfer vehicle design is the complexity of the guidance scheme. In present aeroassisted orbital transfer guidance schemes, the reference value of the bank angle or the climb rate is determined via a predictor-corrector algorithm so that the desired apogee can be reached after the vehicle exits the atmosphere. These guidance schemes are quite sensitive to parameter dispersion effects due to atmospheric density errors, system errors, navigation errors, and aerodynamic coefficient errors. An innovative guidance scheme, called safety zone guidance, is developed. In this highly robust guidance, the control is not determined by aiming only at the desired apogee; instead, for each altitude-velocity pair, a special value of the path inclination is determined by maximizing the control margin while aiming at the desired apogee during the atmospheric pass. This results in a robust and accurate guidance scheme as shown by extensive numerical tests.

矢状面内そしゃく閉口路に及ぼすこう合平面傾斜度と歯牙ガイドの影響

The purpose of this study was to compare the contribution of the inclination of the occlusal plane to the masticatory closing path to that of tooth guidance. Masticatory movements were measured on 38 normal adults using 3-dimensional Mandibular Movement Analyzing System. The direction of the masticatory closing path was calculated at each closing level. The tooth guidance was evaluated as the sagittal inclination of the incisal path during laterotrusion. The inclination of the occlusal plane was evaluated as the sagittally-viewed inclination of the line between the incisal edge and the distobuccal cusp on 2nd molar in the lower jaw. The masticatory closing path outside the intercuspal range was influenced by only the inclination of the occlusal plane. The closing path right before entering the intercuspal position was influenced by the tooth guidance. The inclination of the occlusal plane had great and durable effects on masticatory closing path as compared to tooth guidance.

側方滑走運動時の平衡側臼歯部離開に関する運動論的，形態学的解析

The purpose of this study was to analyze the mechanism of the disclusion of balancing-side teeth during mandibular lateral movement. Clinical examination was performed, and 59 normal young adults were divided into two groups, disclusion group and non-disclusion group. Lateral movements were measured with the six-degrees of freedom mandibular movement analyzing system, and the cuspla inclination was evaluated on the balancing-side second molars using a 3-dimensional digitizer.In the frontal plane, the inclination of the working-side canine path was significantly smaller in the non-disclusion group than in the disclusion group, whereas there was no significant difference between the groups in the inclination of the balancing-side condylar path. There was significant difference in the cuspal inclination between the groups ; the cuspal inclination in the non-disclusion group was greater than that in the disclusion group. The results of this study suggest that the inclination of the anterior guidance plays an important role in the occurrence of the balancing-side disclusion during lateral movement, in comparison with the inclination of the posterior guidance, as well as in the occurrence of the posterior disclusion during protrusive movements.

Study of path inclination effects on performance of LOS microwave links in southern India

Investigations of the effect of path inclination on fading, based on the data collected from three line-of-sight (LOS) microwave links over the Indian subcontinent, are reported. It is observed that as the path inclination increases, the number and depth of fades caused by layers are reduced. In regions where temperature inversions prevail for a considerable percentage of the time, the design of LOS links should incorporate the concept of path inclination to overcome fading.

前方滑走運動時の臼歯部離開に関する運動論的，形態学的解析

The purpose of this study was to analyze the mechanism of the disclusion of posterior teeth during mandibular protrusive movement. Clinical examination was performed on 67 normal young adults, and they were divided into two groups: disclusion group and non-disclusion group. The protrusive movement was measured with the 3-dimensional mandibular movement analyzing system which can analyze movements in six-degrees of freedom, and the occlusal curve on the lower 2 nd molar was evaluated using the 3-dimensional digitizer.The sagittal inclinations of both incisal and condylar paths were significantly greater in the disclusion group than in the non-disclusion group. Especially, the difference of the incisal path inclination between them was almost 15 degrees. There was also a significant difference in their occlusal curves ; the occlusal curve in the disclusion group was steeper than that in non-disclusion group. The method of anterior guidance determination proposed by Kohno and Nakano was found to be effective for establising the posterior disclusion during protrusive movement. The findings of this study suggest that the inclination of the anterior guidance greatly contributes to the occurrence of the posterior disclusion, in comparison with the inclination of the posterior guidance and the steepness of the occlusal curve.

下顎運動要素の歯牙路への影響 その６ 平衡側矢状か路角

The object of this study was analyze mathematically the effect of condylar inclination of the nonworking-side condyle path on the tooth path.Conclusions of the calculation are;1. Error of the tooth path was proportinate to and smaller than that of condylar inclination of the nonworking-side condyle path.2. The relation of errors between condylar inclination of the nonworking-side condyle path and tooth path was hardly affected, even when the direction of condyle movement and the inclination of the sagittal incisal path was altered.3. Amount of error of the nonworking-side molar path was generally equivalent to a half amount of the condylar inclination of the nonworking-side condyle path, while that of the workingside molar path was a sixth thereof.

フィッシャー角に関する研究

Based on the results measured by the extraoral tracing device such as mechanical pantograph, it has been widely believed that sagittal lateral condylar path is longer in length and steeper in inclination than sagittal protrusive condylar path. The difference of the angle between sagittal lateral and protrusive condylar path has been known as Fischer's angle and its value is to be 5° in average.In this study, the various data of sagittal condylar path inclinations measured electronically were recalibrated to the same horizontal reference plane, and compared. As the result, it was shown that the average value of Fischer's angle is -0.1°. Therefore, it is concluded that Fischer's angle is zero.Fischer's angle is observed by mechanical pantograph measurement. Tracings are drawn on the recording table which is placed outside of the condyles. Thus, the inclinations of lateral condylar paths are drawn apparently longer than protrusive paths, although the both paths are not different in inclination. Through this study, it is concluded that the difference between lateral and protrusive condylar path inclinations is not necessary to reproduce on the articulator.

General solution for the optimal trajectory of an AFE-type spacecraft

The aeroassisted flight experiment (AFE) refers to an experimental spacecraft to be launched and then recovered by the Space Shuttle. It simulates a transfer from a geosynchronous Earth orbit (GEO) to a low Earth orbit (LEO). In this paper, with reference to an AFE-type spacecraft, an actual GEO-to-LEO transfer is considered under the following assumptions: the GEO and LEO orbital planes are identical; both the initial and final orbits are circular; the initial phase angle is given, while the final phase angle is free. The aeroassisted orbital transfer trajectory involves three branches: a preatmospheric branch, GEO-to-entry; an atmospheric branch, entry-to-exit; a post-atmospheric branch, exit-to-LEO. The optimal trajectory is determined by minimizing the total characteristic velocity. The optimization is performed with respect to the velocity impulses at GEO, LEO, and the time history of the angle of bank during the atmospheric pass. It is assumed that the entry path inclination is free and that the angle of attack is constant, α = 17.0 deg. The sequential gradient-restoration algorithm is used to compute the optimal trajectory and it is shown that the best atmospheric pass is to be performed with constant angle of bank. The resulting optimal trajectory constitutes an ideal nominal trajectory for the generation of guidance trajectories for two reasons: the fact that the low value of the characteristic velocity is accompanied by relatively low values of the peak heating rate and the peak dynamic pressure; and the simplicity of the control distribution, requiring constant angle of bank.

Study of the sagittal condylar path in edentulous patients

The inclination of the condylar path is a fundamental consideration in the prosthodontic treatment of the totally edentulous patient. The authors studied 55 patients at the University of the Basque Country, making three graphic registrations of the protrusive condylar movement on each side. Three examiners, working independently, used the tangential method to measure the angulation relative to Camper's plane. The results show that angulation varies greatly on each side and from one individual to another. In the treatment of edentulous patients, graphic registering techniques that can determine these variations should be used.

下顎運動の加齢による変化に関する研究 第２報 側方滑走運動の解析

Mandibular movements as a whole have not been sufficiently investigated, due to the great difficulty of recording them. In order to clarify those features in three-dimensions, we measured 62 cases whose ages ranged from 20 to 79, and whose dentitions were either complete or nearly so, and whose intercuspal positions were firm. Part 1 of this study revealed the differrent types of sagittal movements seen among various age groups. We then investigated lateral excursions, gaining the following results: 1) no statistical difference could be found in the movement direction at incisor, canine or first molar either on the working or non-working sides, among any of the age groups studied; 2) the inclination of the condylar path tended to lessen with advancing age; 3) the sagittal inclination of the second molar path on the non-working side tended to be gentler in subjects 60 years and older than in younger subjects, which would reflect the previous result, and 4) there was no statistical difference in path-length of the working-side condyle among the various age groups. These results showed that the posterior guidance on the non-working side tended to change with age, even in subjects with nearly-complete dentition, probably due to the morphological changes of the temporomandibular joint.

Optimization of endurance performance

The endurance performance of aircraft is considered and various methods for its optimization are described. These methods concern classical techniques as well as new procedures which are the result of recent research. According to classical theory, endurance cruise is considered as a quasi steady-state flight where mass changes due to fuel consumption are taken into account but other effects (acceleration or flight path inclination) are neglected. An approximate analytical method is presented in order to provide results of a general nature. This method also includes a generalized analytical model for fuel consumption so that a unified approach covering different types of powerplant systems is possible. Furthermore, a graphical method for optimization of endurance cruise is presented. This method may be applied when aerodynamics and powerplant system show characteristics not covered by the analytical approach. Another endurance flight task considered is holding prior to landing. The trajectory of a holding pattern consists of a combination of straight and curved segments. It is shown how this combination may be optimized in order to minimize fuel consumption. According to recent research of aircraft performance, steady-state endurance cruise cannot be considered as generally optimal but there may be a periodic type of trajectory which yields a superior performance. An optimization technique based on the minimum principle and the method of multiple shooting is presented for constructing a solution for periodic optimal endurance cruise. It is shown that a significant improvement of endurance performance can be achieved with this type of a non-steady control. The improvement can be further increased when variable camber control is considered.

A geometry-based investigation of the tool path generation for zigzag pocket machining

We present a detailed description of a zigzag algorithm for pocket machining. The algorithm is capable of computing correct zigzag tool paths for multiply-connected planar areas (“pockets”) bounded by a wide class of curves. It features a number of optimizations with respect to geometrical and technological objectives. In particular, a near-optimum inclination of the tool path is automatically determined. The underlying geometric principles are simple enough to allow the algorithm to be included in a numerical control computer.

Aircraft control for take-off in windshear

Aircraft take-off control under conditions of windshear has recently received considerable attention in the control-theory literature. Severe windshear may cause difficulties during aircraft take-off, it has been a major cause of at least 30 aircraft accidents during the two last decades. We study the controlled take-off of an aircraft flying through an unavoidable windshear. The purpose of the guidance is to guarantee aircraft take-off without crash; no other performance criteria are applied. The proposed aircraft take-off control scheme consists of a memoryless state feedback control strategy for a class of continuous-time aircraft models including unpredictable but bounded windshear. The design of the take-off control scheme is carried out by applying a theory of deterministic control of uncertain systems. The time or the place of encountering a windshear is not known but, according to the basic assumption, the upper bound of the uncertainty—here the maximum rate of the change of the wind velocity—is assumed to be known. Such knowledge allows one to design a deterministic controller to stabilize the relative path inclination of the aircraft.

Optimal control of ascent trajectories and rotary dynamics for wingless orbital stages

For a rocket type orbital stage of a space transportation system with an airbreathing first stage, an investigation on ascent performance is presented. Particular emphasis is given to the lifting capability of the wingless orbital stage because of its decisive influence on ascent performance. A rocket type orbital stage without a lifting capability can perform an ascent to an orbit only when the flight path angle is rather large for a separation condition in hypersonic flight at high altitude. However, rocket type vehicles without a wing have a limited lifting capability which enables the vehicle to achieve an ascent to an orbit even if the separation flight path inclination is small. It is shown how this capability can be utilized in an optimum manner. This concerns the optimal control of lift, thrust setting and thrust vector angle. In addition to point mass dynamics, a model including pitching moment balancing and rotary dynamics is also investigated. It is shown which effects for ascent control and performance result.

Decomposition technique and optimal trajectories for the aeroassisted flight experiment

The aeroassisted flight experiment (AFE) refers to a spacecraft to be launched and then recovered by the space shuttle in 1994. It simulates a transfer from a geosynchronous Earth orbit (GEO) to a low Earth orbit (LEO). Specifically, the AFE spacecraft is released from the space shuttle and is accelerated by means of a solid rocket motor toward Earth, so as to achieve atmospheric entry conditions close to those of a spacecraft returning from GEO. Following the atmospheric pass, the AFE spacecraft ascends to the specified LEO via an intermediate parking Earth orbit (PEO). The final maneuver includes the rendezvous with and the capture by the space shuttle. The entry and exit orbital planes of the AFE spacecraft are identical with the orbital plane of the space shuttle.In this paper, with reference to the AFE spacecraft, an actual GEO-to-LEO transfer is considered and optimal trajectories are determined by minimizing the total characteristic velocity. The optimization is performed with respect to the time history of the controls (angle of attack and angle of bank), the entry path inclination and the flight time being free. Two transfer maneuvers are considered: (DA) direct ascent to LEO; (IA) indirect ascent to LEO via PEO.While the motion of the AFE spacecraft in a 3D-space is described by a system of six ODEs, substantial simplifications are possible if one exploits these facts: (i) the instantaneous orbital plane is nearly identical with the initial orbital plane; (ii) the bank angle is small; and (iii) the Earth's angular velocity is relatively small. Under these assumptions, the complete system can be decoupled into two subsystems, one describing the longitudinal motion and one describing the lateral motion.The angle of attack history, the entry path inclination, and the flight time are determined via the longitudinal motion subsystem; in this subsystem, the total characteristic velocity is minimized subject to the specified LEO requirement. The angle of bank history is determined via the lateral motion subsystem; in this subsystem, the difference between the instantaneous bank angle and a constant bank angle is minimized in the least square sense subject to the specified orbital inclination requirement.It is shown that both the angle of attack and the angle of bank are constant. This result has considerable importance in the design of nominal trajectories to be used in the guidance of AFE and AOT vehicles.

Vectorial analysis of the static equilibrium of forces generated in the mandible in centric occlusion, group function, and balanced occlusion relationships

Mechanical analyses supporting various and prevailing stomatognathic concepts of occlusal function are sparse. This study, using a mechanical model, simulates a system in function and provides a vectorial analysis based on a static equilibrium of forces generated in a mandible at 10 different positions. The positions analyzed were one in centric occlusion and nine in eccentric positions. Four eccentric positions were in a balanced occlusal relationship and five were in group function. Among other conclusions that were drawn, the most relevant seems to be the finding that cusp inclines and condylar path inclination have a profound influence on the forces acting within the joints and dentition.

Fading reduction in LOS microwave links due to path inclination

Investigations of the effect of path inclination on multipath fading caused by super-refractive layers and ducts, based on the data collected from various LOS links over the Indian subcontinent are reported. It is observed that as the path inclination increases, deep fades caused by layers and ducts get reduced. In regions where layers and ducts prevail for a considerable percentage of time, the design of LOS links should incorporate the concept of path inclination to overcome fading.

ＬＬ‐８５｀Ｒ´こう合器の切歯路指導板の調節についての１基準 第１報 こう合器指導板の傾斜が運動路に及ぼす影響について

The purpose of this study is to show the guideline for incisal table adjustment of the semi-adjustable articulator LL-85®. In this report, we discuss the influence of the guide plane of the articulator on the pathway of the upper first molar determined by geometrical method.The following results were obtained:1. The sagittal condylar path inclination affected the pathway of the upper first molar in the frontal and the sagittal planes at the balancing side. The lateral condylar inclination affected the pathway at both the balancing and the working sides but not so much.2. The sagittal incisal guide angle affected the pathway in the sagittal plane more significantly at the working than balancing side. The inclination of lateral wing was the most impotant factor in guidance of the articulator.3. The pathway of the upper first molar was almost independent of its position in the horizontal distance of 15 to 18mm from the incisal pin.