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At least 541 records · Page 30Linked to original sources
PubMed2005

A point-selection algorithm based on spatial-stiffness analysis of rigid registration.

OBJECTIVE: We propose a model of shape-based registration that leads to a task-specific algorithm for preoperatively selecting a set of model registration points. MATERIALS AND METHODS: We performed five sets of computer simulations using registration points generated by our algorithm and two noise amplification index (NAI) algorithms on the basis of the research of Simon 20. We used several different bone surface models (distal radius, proximal femur and tibia) computed from CT images of patient volunteers. The number of registration points used varied between 6 and 30. RESULTS: Our algorithm was faster than the NAI-based algorithms by factors of approximately 4 and 200. It had equal or better performance in terms of target registration error (TRE) when compared with the other algorithms. Our simulations also showed that point selection can have a large effect on TRE behavior; in particular, poor point selection does not necessarily decrease TRE as more registration points are added. CONCLUSIONS: Our point-selection algorithm produces model registration points with similar or better TRE behavior than the NAI-based algorithms we tested, and it does so with significantly less computation time.

Algorithms↗
PubMed1995

[Interrelationship between the facial expression and familiarity: analysis using spatial filtering and inverted presentation].

We investigated interrelationship between the facial expression and familiarity using spatial filtering and inverted presentation. The stimuli were facial images (smiling and neutral faces) band-pass filtered in the spatial domain. If the filtering is carried out at low spatial frequencies, the images convey more global features than the local ones, whereas the local features are emphasized in the images filtered at high frequencies. The task of subjects was to judge the expression (Experiment 1) or familiarity (Experiment 2) of such images, which were presented in the upright or inverted orientation. The following results were obtained. 1) Spatial frequency components in the middle range (12.4 and 24.8 cycles/face-width) were important in recognizing both expression and familiarity, 2) there was close relationship between the facial expression and familiarity, and 3) smiling faces were harder to recognize when they are shown in the inverted orientation. These results suggest that there are the common and different recognition processes between facial expression and familiarity.

Adult↗
PubMed1999

EEG topographical analysis of spatial disorientation.

BACKGROUND: We examined EEG topography while subjects experienced spatial disorientation (SD) such as vection and somatogravic illusion (SGI). METHODS: Five healthy male subjects were exposed to a rotating image evoking vection (Experiment 1) and to a 0.58 G linear forward acceleration evoking SGI (Experiment 2). The data were analog-to-digital converted with an epoch length of 1 s and a sampling frequency of 256 Hz. Polynomial coefficient vectors were calculated for the following analyses of EEG under the illusion: a) objective evaluation of topographical difference by two-way MANOVA; b) visual inspection of the power spectra maps; and c) logarithmic deviation ratio topography (log DRT). RESULTS: MANOVA demonstrated significant differences in EEG topography in the high alpha band while the vection was evoked. No significant difference was revealed in any bands for SGI. Characteristic patterns common to all subjects were hardly identified on the power spectra maps. By log DRT under vection, a decrease of power was observed in the centro-parietal area on the left side in one subject, on the right in another subject, and in the mid-right frontal area in a third subject compared with the control with eyes open. As for SGI, log DRT revealed a decrease of power in the occipital area in most of the trials as the magnitude was reduced by a visible horizon. CONCLUSIONS: MANOVA revealed a significant change in EEG topography while the subjects felt vection. Log DRT reflected characteristic patterns under vection and SGI. Thus EEG topography may be useful for the study of SD.

Acceleration↗
PubMed2000

[Geostatistical analysis on spatial patterns of Aphis gossypii and Propylaca japonica].

The spatial construction and distribution of Aphis gossypii and Propylaca japonica at different period were investigated with geostatistics. The results showed that the semivariogram of Aphis gossypii was described by spherical model, indicating an aggregated spatial arrangement, the range was 8.21-10.81 m. The semivariograms of Propylaca japonica was fitted by spherical model too, also indicating an aggregated spatial arrangement, its range was 8.01-14.25 m. The amount and spatial distribution of Propylaca japonica was closely related to that of Aphis gossypii. It reveals that Propylaca japonica is dominant natural enemies of influencing population of Ahphis gossypii.

Animals↗
PubMed2002

[Geostatistical analysis on spatial patterns of Erythroneura sudra and Erigonidium graminicola].

The spatial construction and distribution of Erythroneura sudra and Erigonidum gramimicola at different periods were investigated with geostatisics. The results showed that the semivariogram of Erythroneura sudra was described by spherical model, indicating an aggregated spatial arrangement. The range was 25.71-37.14 m. The semivariograms of Erigonidum graminicola was fitted by spherical model too, also indicating an aggregated spatial arrangement, and its range was 25.12-44.06 m. The amount and spatial distribution of Erigonidium graminicola was closely related to that of Erythroneura sudra. It reveals that Erigonidium graminicola is the dominant natural enemies influencing the population of Erythroneura sudra.

Animals↗
PubMed2003

[Geostatistical analysis on spatial patterns of Didesmococcus koreanus Borchs and Chilocorus rubidus Hope].

The spatial pattern and correlation of Didesmococcus koreanus Borchs and Chilocorus rubidus Hope in different periods were investigated with geostatistics. The results showed that the semivariogram of Didesmococcus koreanus Borchs and Chilocorus rubidus Hope could be described by spherical model, indicating that their spatial pattern were in agreement. The spatial variation was arosed by its spatial autocorrelation in small scales, and the spatial pattern had no apparent changes in different periods. The range varied from 9.56-15.70 m and from 18.83-19.74 m, respectively. The amount and spatial distribution of Chilocorus rubidus Hope was closely related to that of Didesmococcus koreanus Borchs, which revealed that Chilocorus rubidus Hope was the dominant natural enemy of Didesmococcus koreanus Borchs.

Animals↗
PubMed2004

An analysis on spatial variation of urban human thermal comfort in Hangzhou, China.

Urban human thermal comfort (UHTC) is affected for interacting of weather condition and underlying surface framework of urban area. Urban underlying surface temperature value and Normalized Difference Vegetation Index (NDVI) were calculated using image interpreting and supervised classification technique by ERDAS IMAGE software using 1991 and 1999 Landsat TM images data. Reference to the relational standard of assessing human thermal comfort and other meteorology data of Hangzhou City in summer, air temperature and relative humidity variation of different land types of underlying surface were inversed. By choosing discomfort index as an indictor, the spatial distribution characteristic and the spatial variation degree of UHTC were estimated and mapped on a middle scale, that is, in six districts of Hangzhou. The main characteristics of UHTC spatial variation from 1991 to 1999 were revealed using a GIS-based calculation model. The variation mechanism were analyzed and discussed from the viewpoint of city planning, construction and environmental protection.

China↗
PubMed2004

[Geostatistic analysis on spatial patterns of Aphis gossypii and Erigonidium graminicola].

The spatial structure and spatial correlativity of Aphis gossypii and Erigonidium graminicola populations during different periods were investigated by geostatistic methods. The results showed that the semivariogram of A. gossypii appeared as spherical type, indicating its spatial pattern was an aggregated type with a range of 7.33-12.40 cm, while that of E. graminicola was also fitted into spherical model, indicating an aggregated spatial arrangement with a range of 6.47-20.88 cm. The amount and spatial distribution of E. graminicola were closely related to those of A. gossypii, suggesting that E. graminicola was the dominant natural enemy influencing A. gossypii population.

Animals↗
PubMed2005

[Geostatistics analysis on spatial patterns of Myzus persicae and Erigonidium graminicola in plum orchard].

Investigations on the spatial construction and distribution of Myzus persicae and Erigonidium graminicola in a plum orchard were conducted from March 2003 to November 2003. The results indicated that the semivariogram of Myzus persicae could be described by spherical model, except on June 27 and November 22, which should be described by lined model, and that of Erigonidium graminicola could be described by spherical model, except on May 21, May 31, October 19 and November 22, which should be described by lined model. It could be concluded that the amount and spatial distribution of Erigonidium graminicola was closely related to those of Myzus persicae.

Animals↗
PubMedDate not supplied

[A comparative analysis of spatial orientation in a changing environment in rats with differing preliminary experience].

Comparison of rats behaviour with different preliminary experience in elaboration of the strategy of return to place of reinforcement was conducted. Significant differences in the number of selective replacements to the place of reinforcement in previous tests in experienced, inexperienced and naive rats were found. It was proved that decisive role in the appearance of the found differences played gained experience and the process of engram extraction from memory. Inhibition of search in naive rats and ability to selective use of strategies corresponding to situation in the experienced ones in condition of stress of permanent changes were shown.

Adaptation, Physiological↗