Passive ranging algorithm in terms of polar coordinates

For the missile with passive seeker,the improvement of passive ranger's precision is one of the key issues in development of the defense penetrate strategy. On the offensive warheads,the infrared imaging device was used to measure the line-of-sight angle information of the blocker,and then using the algorithm of Kalman Filter under polar coordinates,the distance from the blocker to the warheads was obtained. The simulation result under polar coordinates was compared with that of Cartesian coordinate. The validity of the method was analyzed,and the schemes of improvement were brought out.

Visual Passive Ranging Method Based on Re-entrant Coaxial Optical Path and Experimental Verification

To overcome the shortcomings of the traditional passive ranging technology based on image, such as poor ranging accuracy, low reliability and complex system, a new visual passive ranging method based on re-entrant coaxial optical path is presented. The target image is obtained using double cameras with coaxial optical path. Since there is imaging optical path difference between the cameras, the images are different. In comparison of the image differences, the target range could be reversed. The principle of the ranging method and the ranging model are described. The relationship among parameters in the ranging process is analyzed quantitatively. Meanwhile,the system composition and technical realization scheme are also presented. Also, the principle of the method is verified by the equivalent experiment. The experimental results show that the design scheme is correct and feasible with good robustness. Generally, the ranging error is less than 10% with good convergence. The optical path is designed in a re-entrant mode to reduce the volume and weight of the system. Through the coaxial design,the visual passive range of the targets with any posture can be obtained in real time. The system can be widely used in electro-optical countermeasure and concealed photoelectric detection.

Dry needling at myofascial trigger points mitigates chronic post-stroke shoulder spasticity

Post-stroke spasticity is associated with restriction in the range of motion of the shoulder.Reducing muscular dystrophy may help relieve muscular dysfunction in patients with post-stroke shoulder spasticity.Dry needle therapy is a method of needling the trigger points using a syringe needle without the use of a drug.Dry needle therapy is commonly used for pain at the shoulder,neck,waist,and back.In this case study,a 62-year-old male patient affected with cerebral hemorrhage of the right frontal lobe had received rehabilitative treatment for 12 years.However,he still experienced shoulder spasticity.The patient received daily dry needling at the trigger points of infraspinatus,teres minor,posterior deltoid,and pectoralis major on 9 days.After the first and ninth treatment,the Modified Ashworth Scale and the passive range of motion of the shoulder was used to assess the effect of the treatment.The spasticity and range of motion of the shoulder showed obvious improvement.These results indicate that dry needling at the myofascial trigger points can effectively treat chronic poststroke shoulder spasticity.

A new method of passive ranging for underwater target:distance information extraction based on wave guide invariant

The study of wave guide invariant in underwater acoustics is one of attracted topics in recent 30 years. The interferences of direct wave and reflect wave from sea surface and sea bottom of underwater target radiated noise inherent the information of target distance. Extraction of these distance information will provide a possible new way in passive ranging for underwater target. The theoretical analysis and the results of at sea experiments show that the LOFAR （Low Frequency Analysis Record） figure inherently contains the range and moving information of passive acoustic sources, even in the situation that the receiver is only one single hydrophone. The theoretical analysis of extraction of target distance information by using wave guide invariant is presented in this paper. It is shown that, based on the interference striation pattern of target, the hydrophone array system is possible to extract the distance information with quite high array gain. Although the mathematical constrain conditions in forming interference striation pattern are different for individual array element, but it is proved that the differences of time delays between array elements can be used in compensation of beamforming. The theoretical analysis, system simulation and some results of at sea experiment show a new way in passive ranging and target recognition.

The status of the cervical spine in preschool children with a history of congenital muscular torticollis

Background: Infants with congenital muscular torticollis are born with an asymmetric range of motion and a muscular imbalance in the cervical spine, as a result of a shortening or excessive contraction of the sternocleidomastoid muscle. Purpose: The study aimed to investigate passive range of motion (PROM) for rotation and lateral flexion, and muscle function of the cervical spine in children that had a history of CMT as infants. Study design: a prospective cohort study. Patient sample: 58 children at the age of 3.5 to 5 years that had been treated for CMT have infants participated in the study. Method: PROM was measured with protractors and muscle function was estimated with a modified Muscle Function Scale. Data from infancy were taken from earlier records. Result: PROM in rotation of the neck was mean 98.7&#176 and PROM in lateral flexion of the neck was mean 69.1&#176. Symmetric PROM of the neck was found in 74% of the children for rotation and in 88% of the children for lateral flexion. Multiple regression showed that gender and PROM in rotation as infants had a significant impact on asymmetric PROM. Forty-five percent of the children had some degree of muscular imbalance in the lateral flexors of the neck. Conclusion: Possible risk factors for later asymmetric PROM are: gender, birth weight, gestation week and PROM in rotation as infants. These factors ought to be taken into consideration when developing guidelines for long-term follow-up.

Frequency invariability of acoustic field and passive source range estimation in shallow water

The frequency invariability of the warped modal signal and the warped signal autocorrelation function in shallow water is discussed.A method is proposed for passive source-range estimation based on the frequency invariability and warping transform of signal autocorrelation function received by a single hydrophone in a range-independent or weak range-dependent shallow water environment.In the method,a guided source with a known range is employed to provide the crucial and relative invariant scaled features.The experimental data in shallow water with an iso-speed profile and a fluctuated thermocline are used to verify this approach.The relative errors of the source range estimation are basically less than 10%.

Passive source range estimation with a single receiver in shallow water

An approach for long-range passive impulsive source ranging with a single receiver in shallow water is proposed, which utilizes the frequency spectrum of the warped signal autocor- relation function via warping transform. For an ideal waveguide, there are invariable frequency features both in the frequency spectrum of the warped signal corresponding to modal cut-off frequencies and the warped signal autocorrelation function due to modal interference. These intrinsic frequency features can be used to passive source ranging. So, the approximate rela- tionship between the frequency of warped signal at an unknown source range and the intrinsic frequency extracted by the time warping transform is derived. These rules can be generalized to an actual shallow water waveguide. Employing an acoustic model to offer the invariable frequency spectrum features, the impulsive signal data collected by a single hydrophone in the North Yellow Sea in December 2011 are analyzed to verify the proposed source ranging ap- proach. The estimated ranges are in good agreement with the ranges measured by GPS, and the mean relative error of range estimation is less than 10%.

Bispectrum and reconstruction of modulation signal extracted from ship-radiated noise

The ship radiated noise is analyzed by higher-order spectra, which preserve the phase characteristics of signals. Phase information is suppressed in power spectrum and double fre quency power spectrum. Bispectrum analysis on ship noise's modulation signal reveals that the phase relationships among the harmonics of periodical envelope is regular. Because phase val ue's sharp change near the peaks stands for the harmonics in frequency domain, to find the ex act phase value of the peak is difficult. So interpolation in frequency domain is needed. After interpolation, there are more points in the narrow band at the peak, phase value's change be comes more smooth, and the peak's exact phase value can be obtained which meets our re quirement for it's precision. From the amplitude and the phase of these harmonics, thc period ical components of the envelope can be reconstructed, which can be called 'Signature' of the ship noise. The signature can be used to recognize ships. Results of the analysis of real data show that this method is useful. One important discovery of our experiments is that the enve lope signals in all subbands of the ship-radiated noise are alike very much. This phenomenon can be utilized to devcloped a new approach of passive localization. It is a general knowledge that the sOund wave of different frequency propagates in shallow water at different group veloci ty. Ship noise's components in different subbands arrive the receiver at different time. The time delay can be obtained from the correlation function between the envelopes of the two com ponents. The time delay reflects the distance between the source and the receiver. One advan tage of this approach over the traditional is that only one sensor is needed instead of three.