It is known that the electromagnetic coupling effect is a disturbance factor in induced‐polarization measurements. Based on the different appearances of EM coupling effect and IP effect in measured dual‐frequency waveform, a direct decoupling scheme by chop‐wave is presented in this paper. The method is able to eliminate EM coupling effect directly during the field data acquisition, and it does not suffer loss of IP information by and large. This paper has mainly discussed several aspects, which include the fundamentals of chop‐wave, the distortion of normal dual‐frequency wave resulting from chopping wave, chopper of existing pure EM coupling effect and IP effect's loss due to chop‐wave. The numerical results show that the scheme reduces and eliminates EM coupling effect markedly and can provide some parameter bases for the development and design on the correlative instrument. Thereby, it is worth generalizing the chop‐wave for decoupling scheme in the induced polarization method.
Based on the analysis of existing observation schemes for natural source induced polarization (NSIP) and on the numerical modeling results of two‐dimensional geoelectrical sections with horizontal and vertical electrical non‐uniformity, it is pointed out that the MT anomaly produced by the conductive and electromagnetic effects is overwhelming superiority to the IP anomaly produced by the induced polarization effects. It is very difficulty to pick up the weak IP anomaly which is inundated in the strong EM anomaly. The existing observation schemes for NSIP are not of universal feasibility. The practical application prospects of NSIP are not optimistic. The control source IP with long offset is intrinsically same as NSIP. They are both taking IP observation in the “far zone of electromagnetic field”. So its practical application prospects are not optimistic either.
Objective: Due to the different force exerted during the posterior malleolus fracture (PMF), the difference in sagittal angle (SA) between the fracture fragments may affect ankle stability. But this aspect is less well studied and the aim of this study was to investigate the relationship between SA and the stability of PMF. Methods:The imaging data of 120 patients with PMFs from January 2014 to November 2022 were collected retrospectively and reconstructed. We first measured SA, posterior fragment area (PFA) and fragment area ratio (FAR), reanalyzing the correlation of SA with PFA and FAR, respectively. To better describe the morphological characteristics of the fracture fragments, we further measured the fragment width diameter ratio (FWR), the fragment length ratio (FLR), fragment height (FH), contact area (CA), and finally carried these data into the regression model of SA versus FAR to conduct the intermediary role.Results: SA was negatively correlated with PFA(s) (r = À0.583, P < 0.001), with regression equation s = À0.063SA + 3.066; SA was negatively correlated with FAR (r = À0.204, P < 0.05), with regression equation FAR = À0.002SA + 0.198; A significant correlation was found between FWR, FLR, FH, CA and SA (P < 0.05), as well as between FWR, FLR, FH and FAR (P < 0.05); Further intermediary role analysis showed that FWR, FLR, FH had a partial intermediary role between SA and FAR. Conclusions:As SA increased, PFA and FAR decreased, so the larger the SA was due to the effect of vertical shear force, reflecting higher ankle stability, meanwhile, FWR, FLR and FH should also be considered on the fixation method of fracture fragments.
BackgroundPrevious studies have studied more factors on the ankle stability of the posterior ankle fracture, which is related to a stereostructure of the fracture fragment. Previous studies have shown that the ankle stability may be affected by the sagittal surface of the fracture block, with less research in this field. The aim of this study was to explore the influence of the sagittal angle(SA) on ankle joint stability by scanning and reconstructing three types of posterior malleolus fractures(PMFs) with different sagittal angle (SA).MethodsThe CT data of 87 patients with PMFs were collected retrospectively and reconstructed. PMFs were divided into three types: posterolateral-oblique type (type I), medial-extension type (type II) and small-shell type (type III).The collected sagittal angle data were statistically analyzed with the posterior fragment area, fragment area ratio (FAR), fragment transverse diameter ratio (FWR), fragment length ratio (FLR), fragment height (FH), and contact area (CA).Results(1)SA was positively correlated with posterior fragment area(r = 0.804,P < 0.01),with regression equation s = 0.085*SA + 0.34;(2)SA was positively correlated with FAR(r = 0.392,P < 0.01),with regression equation FAR = 0.004*SA + 0.092;(3)SA was positively correlated with FWR(r = 0.261,P < 0.05), with regression equation FWR = 0.03*SA + 0.4624;(4)SA was positively correlated with FLR(r = 0.481,P < 0.01), with regression equation FLR = 0.05*SA + 0.209;(5) SA was positively correlated with CA (r = 0.474, P < 0.01),with regression equation CA = 7.942*SA + 160.866;(6)SA was positively correlated with FH(r = 0.474,P < 0.01), with regression equation FH = 0.046*SA + 1.406.ConclusionThe sagittal angle was positively correlated with posterolateral-oblique type (type I) of Posterior malleolus fractures, and SA could be considered to reflect the ankle joint stability of PMFs.Level of evidence: Level III, retrospective comparative study.
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