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A natural dependence among diameters measured within-tree is expected in taper data due to the hierarchical structure. The aim of this paper was to introduce the covariance generalized linear model (CGLM) framework in the context of forest biometrics for Pinus taeda stem form modeling. The CGLMs are based on marginal specification, which requires a definition of the mean and covariance components. The tree stem mean profiles were modeled by a nonlinear segmented model. The covariance matrix was built considering four strategies of linear combinations of known matrices, which expressed the variance or correlations among observations. The first strategy modeled only the variance of the diameters over the stem as a function of covariates, the second modeled correlation among observations, the third was defined based on a random walk model, the fourth was based on a structure similar to a mixed-effect model with a marginal specification, and the fourth was a traditional mixed-effect model. Mean squared error and bias showed that the approaches were similar for describing the mean profile for fitting and validation dataset. However, uncertainties expressed by confidence intervals of the relative diameters were significant and related to the matrix covariance structures of the CGLMs.

The form-factor for the stem surface area is directly proportional to the square root of the form-factor for the stem volume, i.e., the square root law of the form-factor. Although the square root law addresses the stems of coniferous trees, the nature of the proportional coefficient of the law has not been discussed. In this study, we demonstrated that the coefficient indicates the stem taper; therefore, it is named “Taper Index based on Form-Factor (TIFF).” We also examined the relationship between the form-factor for the culm surface area and the form-factor for the apparent culm volume of 570 culms across three bamboo species (Phyllostachys pubescensMazel ex Houz.,P.bambusoidesSieb. et Zucc., andP.nigravar.henonis). The square root law held true for all three bamboo species. The species-specific TIFF was determined to be 0.873 forP. pubescens, 0.897 forP. bambusoides, and 0.901 forP. nigra. This result implied thatP. pubescenshad a more tapering culm form compared to the other two species, while culm taper was similar betweenP. bambusoidesandP. nigra. Our findings align with empirical observations of the culm taper of the bamboo species. Intra-species variation in TIFF was considerably small, allowing us to evaluate the species-specific culm taper from a small number of samples. Therefore, we conclude that TIFF provides a simple and useful method for quantifying species-specific culm or stem taper, and facilitates the estimation of merchantable or total volume.

White birch (Betula platyphylla Sukaczev) and costata birch (Betula costata Trautv.) are valuable hardwood tree species growing in northeast China. Several taper studies have analysed birch species in the countries harbouring the boreal forests. However, this study presents an initial attempt to develop stem taper models using the fixed-and mixed-effects modelling for white birch and costata birch in Xiaoxing'an Mountains, northeast China. Ten commonly used taper models were evaluated by using 228 destructively sampled trees of both tree species comprising of 4582 diameter and height measurements. The performance of these models was tested in predicting diameter at any height, total volume and merchantable volume (10 and 20 cm top diameters). We incorporated a second-order continuous-time error structure to adjust the inherent autocorrelation in the data. The segmented model of Clark best predicted the diameter and total or merchantable volume when the upper stem diameter at 5.3 m was available. When diameter measurements at 5.3 m were not available, the models of Kozak and Max and Burkhart were superior to other models for white birch and costata birch, respectively. After model comparison, the best model of Clark was refitted as the NLME model. National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [31570624]; Heilongjiang Touyan Innovation Team Program Published version National Natural Science Foundation of China (31570624); Heilongjiang Touyan Innovation Team Program.

Stem taper equations, which predict the change in stem form from ground to tip, have become the primary means for estimating bole volume. Stem taper equations can provide predictions with similar levels of accuracy as volume equations, but with greater flexibility, a wider range of potential uses, and consistency between taper and volume. This review is a synthesis of the current state of knowledge on stem taper equations and an assessment of challenges for future model refinement. It includes the history and evolution of stem taper model forms, which have received tremendous attention and focus over the last several decades. Additional focal areas covered are (i) the use of additional covariates beyond tree diameter at breast height (DBH) and total height; (ii) alternative statistical methods for developing stem taper equations such as parametric, semiparametric, and nonparametric approaches; (iii) key considerations for proper development, application, and use of stem taper equations such as sample size requirements, local calibration, and evaluation; and (iv) a synthesis of key findings, future opportunities, and ongoing challenges. Current and developing technologies such as terrestrial laser scanning (TLS) offer an unprecedented opportunity to measure stem form in much greater detail at significantly lower costs and time requirements than traditional methods. Overall, continued development, refinement, and application of stem taper equations will remain important given the critical nature of tree volume for science, accurate inventories, and ultimately, sustainable forest management.

Taper models are one of several necessary tools in modern forest inventory, giving information on diameter at any point along the tree stem and this information can also be used to estimate stem volume. In this study, we used nonlinear mixed-effects (NLME) modeling approach to minimize existing statistical problems in constructing taper equations. A segmented taper model of Max and Burkhart (1976) was fitted using this approach to consider for within- and between-tree variation in brutian pine (Pinus brutia Ten.) stem taper. Based on evaluation statistics, the model including random-effects parameters β1, β3 and β4 were found to be the best. Inclusion of random parameters were not completely eliminated heterogenous variance and autocorrelation in residuals. Incorporating variance function and a continuous autoregressive error structure (CAR(1)) to NLME Max and Burkhart model removed the heteroscedasticity and autocorrelation in residuals. Upper stem diameters were used to localized stem taper model to individual tree. For this, two different measurement scenarios were evaluated as one and two upper stem diameter measurements. Inclusion of random parameters were improved the predictive capability of taper model in particularly the middle and lower sections of stem based on upper stem diameter measurements. The calibration using upper stem diameter measurements can improve the tree-level accuracy of stem taper model is therefore recommended.

Dahurian larch (Larix gmelinii Rupr.), Korean spruce (Picea koraiensis Nakai), and Manchurian fir (Abies nephrolepis Maxim) are valuable tree species of northeast China. Management tools are requir...

Black alder (Alnus glutinosa subsp. barbata (C.A. Mey.) Yalt.) is an important tree species in Turkey both economically and ecologically. Accurate taper and volume equations are required by most inventory systems to estimate upper stem diameter, form, and tree volume. Stem analysis data were used to examine the differences in taper and volume of black alder trees grown in naturally regenerated, plantation, and coppice stands. Statistically significant differences were observed in taper and volume of black alder trees grown in stands from these three origins. Error in total stem volume inside bark was the greatest when the taper model was fitted to plantation data and applied to seed data compared with the model fitted to coppice data and applied to seed data. Therefore, to accurately predict upper stem diameter and total or merchantable stem volume, in addition to selecting species-specific taper models, forest managers should consider the origin of the model-fitting data when choosing an appropriate taper model for their stands.

Accurate prediction of stem diameter is an important prerequisite of forest management. In this study, an appropriate stem taper function was developed for upper stem diameter estimation of white birch (Betula platyphylla Sukaczev) in ten sub-regions of the Daxing'an Mountains, northeast China. Three commonly used taper functions were assessed using a diameter and height dataset comprising 1344 trees. A first-order continuous-time error structure accounted for the inherent autocorrelation. The segmented model of Max and Burkhart (For Sci 22:283-289, 1976. 10.1093/forestscience/22.3.283) and the variable exponent taper function of Kozak (For Chron 80:507-515, 2004. 10.5558/tfc80507-4) described the data accurately. Owing to its lower multicollinearity, the Max and Burkhart (1976) model is recommended for diameter estimation at specific heights along the stem for the ten sub-regions. After comparison, the Max and Burkhart (1976) model was refitted using nonlinear mixed-effects techniques. Mixed-effects models would be used only when additional upper stem diameter measurements are available for calibration. Differences in region-specific taper functions were indicated by the method of the non-linear extra sum of squares. Therefore, the particular taper function should be adjusted accordingly for each sub-region in the Daxing'an Mountains. National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [31570624]; Applied Technology Research and Development Plan Project of Heilongjiang Province [GA19C006]; Fundamental Research Funds for Central UniversitiesFundamental Research Funds for the Central Universities [2572019CP15] This study was financially supported by the National Natural Science Foundation of China (31570624), Applied Technology Research and Development Plan Project of Heilongjiang Province (GA19C006), and Fundamental Research Funds for Central Universities (2572019CP15).

Stem taper function is an important concept in forest growth and yield modeling, and forest management. However, the additivity of the function and the inherent correlations between stem components (diameter outside bark—dob, diameter inside bark—dib, and double-bark thickness—dbt) are seldom considered. In this paper, a total disaggregation model (TDM) structure was developed based on the well-known Kozak (2004) model to ensure the additivity of the stem components. The reconstructed model was fitted with the data of 1281 felled Dahurian larch trees from three regions of Daxing’anling Mountains in Northeast China. The results from TDM were compared with other additive model structures including adjustment in proportion (AP), non-additive taper models (NAM), and three logical structures of NSUR (AMO, SMI, SMB). The results showed that the difference was significant among the three regions. The performance of TDM was slightly better than those of other model structures. Therefore, TDM was considered as another optimal additive system to estimate stem, bark thickness, and volume predicting for Dahurian larch in Northeast China besides NSUR, a method widely used in calculating additive volume or biomass throughout the world. We believe this work is cutting-edge, and that this methodology can be applied to other tree species.

Stem taper functions are valuable tools for the study of stem profile and predict volume estimates. Such functions have long been analyzed for different birch species in the world. However, Asian white birch (Betula platyphylla Suk.) has not yet been investigated as an individual species in China or abroad. This study presents stem taper and volume equations for B. platyphylla in Northeast China. Eight commonly used taper functions were fit to the data of 615 destructively sampled trees from two regions of Northeast China. A second-order continuous autoregressive error structure was incorporated to address the autocorrelation in the data and to achieve the valid parameter estimation. The condition number was used to detect the multicollinearity in the models. The taper functions were compared in terms of overall evaluation statistics and by examining the box plots of diameter and volume residuals against relative heights and diameter classes. The equations of A. Kozak (2004, For. Chron. 80(4): 507–515; model 2), Z. Fang et al. (2000, For. Sci. 46(1): 1–12), and H. Bi (2000, For. Sci. 46(3): 397–409) were the leading models for diameter and volume estimates. Overall, the equation of Z. Fang et al. (2000, For. Sci. 46(1): 1–12) exhibited the best results for estimating diameter and total and merchantable volumes in terms of statistical performance and lower multicollinearity.

A high degree of stem taper limits the potential value of giant sequoia (Sequoiadendron giganteum (Lindl.) J. Buchholz) when grown for timber. I measured the effects of pruning to different height targets (0, 2.0, 3.5, and 5.5 m), resulting in the removal of 25%–85% of crown length, on the growth of 360 S. giganteum trees over 17 years. Height growth and growth of diameter at breast height were both negatively related to pruning intensity to a similar degree. Within the 17 years following pruning, repeated measurements of stem growth at different heights above the ground revealed that radial stem growth reductions were localized on the stems from which branches were removed. The higher up that trees were pruned, the more that stem radial growth was reduced compared with control trees, with the greatest reductions occurring at stem bases. The effects of pruning decreased over time, but there were still significant differences after 17 years. Girard form class was only influenced by the most intense pruning at a stem height of 5.5 m. A benefit of pruning was reduced taper, but this came at the cost of reduced stem growth. Pruning in S. giganteum must be done carefully with respect to its timing, intensity, and interactions with other management treatments on young stands.

To study the fretting tribological behavior of a PEEK hip prosthesis, Ti6Al4V was used as the stem taper material, PEEK was used as the head material, and CoCrMo was used as the contrast material for the PEEK. Fretting friction and wear experiments between the stem taper and head were carried out to demonstrate the feasibility of PEEK as a metal substitute. The results show that the wear values of the Ti6Al4V/PEEK and Ti6Al4V/CoCrMo pairs were all of a small order of magnitude. The Ti6Al4V/PEEK pairs had a better corrosion resistance than the Ti6Al4V/CoCrMo pairs. Meanwhile, the fretting characteristics and damage mechanism of the Ti6Al4V/PEEK pairs were obtained.

The paper summarizes the experience of tree stem form investigation; therefore we can draw the conclusion that mathematical modelling of stem profiles overperforms alternative methods for analysing stem taper. Based on the study material collected in oak stands of Dnieper Right-bank Forest-Steppe of Ukraine on 17 temporally sample plots, the relationship of common oak (Quercus robur L.) tree stem form with tree height and diameter at 1.3 m has been studied. We have conducted both graphical and statistical analyses of Schiffel's form quotients in dependence on tree heights and diameters at breast height. Visual inspection of stem profiles and t-test at 5 % significance level have pointed to high variation of stem form for trees having different diameters. Inside height classes differences in taper has not been revealed. Thus, it substantiated the necessity of stem taper modelling of common oak trees regardless of tree height but for three diameter classes such as 20-28 cm, 32-40 cm, and 44-64 cm. As a model of stem taper, we have tested two variable-exponent equations by A. Kozak (1988) and R. Newnham (1992). The models were fitted to the test data representing stem measurements of 171 model trees of oak. We have used a nls (nonlinear least-square regression) algorithm for R to get estimates of parameters. The R. Newnham (1992) function was fitted using relative diameter and height values while A. Kozak (1988) – absolute ones. Totally, we have developed six taper equations (two models for three diameter classes). The systematical error of both types of equations has been revealed to be nearly equal to zero (0.9-1.7 %) that allowed us to adopt them as appropriate models of stem taper for established diameter classes. The developed models predict diameters of oak tree stems at any height with high accuracy and have small standard error of 1.5-3.2 cm. We have analysed the distributions of residuals of models in dependence of relative tree height and revealed the autocorrelation of residuals of R. Newnham (1992) equation which has also been proved by Durbin-Watson test at 5 % significance level. The test has not indicated the presence of autocorrelation of residuals of A. Kozak (1988) model for any diameter classes of oak trees. As a result, we have adopted A. Kozak (1988) equation as a mathematical model of stem taper and would recommend it for estimation of total and merchantable volume of the oak trees.

Made available in DSpace on 2019-10-04T12:13:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-05-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Anglo American Arauco Arborgen Arcelor-Mittal Cenibra CMPC Comigo Copener Duratex Eldorado Fazenda Campo Bom Fibria Florestal Itaquari Forestal Oriental Gerdau GMR International Paper Jari Klabin Lwarcel Montes del Plata Plantar Rigesa Suzano Vallourec Veracel University of Sao Paulo Sao Paulo State University Federal University of Lavras Federal University of Rio Grande do Norte Colorado State University North Carolina State University USDA Forest Service Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Lack of generalized equations has prevailed in Brazil, because it is assumed that localized or climate-specific equations are needed. This study aimed to develop generalized stem taper and volume equations applicable to 11 eucalyptus clones and evaluate if climate variation impacts the accuracy of the estimates. A total of 693 trees evenly distributed across 11 clones at 21 sites were used for model fittings and predictive validation. The penalized mixed spline (PMS) approach was developed for predicting stem taper and volume along the stem profile. The Schumacher and Hall (1933) equation was used to predict total tree volume, while volume ratio equations were applied to predict merchantable volume. For every fitted equation, an annual climatic variable was included to assess the improvement in model performance. The overall results highlighted that climatic variation does not need to be accounted for in stem taper and volume modeling. All of the equations displayed desirable accuracy, but the generalized PMS equation may be preferred when the forestry enterprise looks to furnish a range of multiple forest products. The generalized total tree volume equation, combined with the ratio equations, is highly recommended when the forestry enterprise produces a single product. North Carolina State Univ, Dept Forestry & Environm Resources, Raleigh, NC 27695 USA Virginia Polytech Inst & State Univ, Dept Forest Resources & Environm Conservat, Blacksburg, VA 24061 USA Forestry Sci & Res Inst, BR-13415000 Sao Paulo, Brazil State Univ Sao Paulo, Dept Forest Sci, BR-18610034 Sao Paulo, Brazil State Univ Sao Paulo, Dept Forest Sci, BR-18610034 Sao Paulo, Brazil CNPq: 249979/2013-6

This study was conducted to develop a stem volume table for Quercus mongolica in Korea by using Kozak’s stem taper equation. A total of 958 Quercus mongolica sample trees were collected around the country and a growth performance was investigated through compiling data of diameters by stem height and stem analysis. Fitness Index (FI), Bias, and Mean Absolute Deviation (MAD) were used to test the stem taper equation’s fitness. The fitness of the equation was estimated at 98%, bias as −0.0024, and MAD turned out as 0.6814. Furthermore, there was a statistically significant volume difference between the current volume table and the new volume table (p

Degradation at the modular head-neck interface in total hip arthroplasty (THA) is predominately expressed in the form of corrosion and fretting, potentially causing peri-prosthetic failure by adverse reactions to metal debris. This retrieval study aimed to quantify variations in stem taper surface topographies and to assess the influence on the formation of corrosion and/or fretting in titanium alloy stem tapers combined with metal and ceramic heads. Four hip stem designs (Alloclassic, CLS, Bicontact and SL-Plus) were characterized using high-resolution 3D microscopy, and corrosion and fretting were rated using the Goldberg scoring scheme. Quantification of the taper surface topographies revealed a high variability in surface characteristics between threaded stem tapers: Alloclassic and CLS tapers feature deeply threaded trapezoid-shaped profiles with thread heights over 65 µm. The sawtooth-shaped Bicontact and triangular SL-Plus taper are characterized by low thread heights below 14 µm. Significantly lower corrosion and fretting scores were observed in lightly threaded compared to deeply threaded tapers in ceramic head combinations. No significant differences in corrosion or fretting scores with thread height were found in pairings with metal heads. Understanding the relationship between stem taper surface topography and the formation of corrosion and fretting could help to improve the performance of modern THAs and lead to longer-lasting clinical results.

Crown architecture has long been evaluated for its impact on taper modeling. However, most of the research has focused on a limited number of crown dimensions. This study examined the effect of adding several crown dimensions in improving the diameter and volume estimates of Dahurian larch, Korean spruce, and Manchurian fir in northeast China. The crown dimensions included crown length, crown ratio, crown width, height to live crown base, diameter at the crown base, and crown shape. A well-known taper model of Clark et al. (1991) was fitted to the data of 276 trees from natural stands. To adjust the inherent autocorrelation in the data, we added a third-order continuous-time error structure in the model fit. Model fitting was carried out with the NLMIXED procedure (Non-linear Mixed Procedure), followed by the MODEL procedure of SAS using the generalized nonlinear least-squares method. Fit statistics and graphical assessments were used to evaluate the original and modified models. Above 98% of the total variance of d was explained by the models for all species. The addition of crown variables showed slight improvements for root mean square error (RMSE) values in the analyzed species. The RMSE plots indicated that the models with crown variables slightly improved the diameter and volume predictions for the species but only for the upper stem (&gt, 50%–90%). The study demonstrated that crown dimensions influence the stem taper, but the original model of Clark et al. (1991) reasonably realized that effect.

Terrestrial laser scanning (TLS) plays a significant role in forest resource investigation, forest parameter inversion and tree 3D model reconstruction. TLS can accurately, quickly and nondestructively obtain 3D structural information of standing trees. TLS data, rather than felled wood data, were used to construct a mixed model of the taper function based on the tree effect, and the TLS data extraction and model prediction effects were evaluated to derive the stem diameter and volume. TLS was applied to a total of 580 trees in the nine larch (Larix olgensis) forest plots, and another 30 were applied to a stem analysis in Mengjiagang. First, the diameter accuracies at different heights of the stem analysis were analyzed from the TLS data. Then, the stem analysis data and TLS data were used to establish the stem taper function and select the optimal basic model to determine a mixed model based on the tree effect. Six basic models were fitted, and the taper equation was comprehensively evaluated by various statistical metrics. Finally, the optimal mixed model of the plot was used to derive stem diameters and trunk volumes. The stem diameter accuracy obtained by TLS was &gt, 98%. The taper function fitting results of these data were approximately the same, and the optimal basic model was Kozak (2002)-II. For the tree effect, a6 and a9 were used as the mixed parameters, the mixed model showed the best fit, and the accuracy of the optimal mixed model reached 99.72%.The mixed model accuracy for predicting the tree diameter was between 74.22% and 97.68%, with a volume estimation accuracy of 96.38%. Relative height 70 (RH70) was the optimum height for extraction, and the fitting accuracy of the mixed model was higher than that of the basic model.

Background: Manchurian fir (Abies nephrolepis Maxim) and Korean spruce (Picea koraiensis Nakai) are primary conifer species of economic and ecological importance in northeast China. Several taper studies have analyzed for fir and spruce species in the countries harboring the boreal forests. However, taper models do not exist for Manchurian fir and Korean spruce in China or abroad. This study aimed to develop stem taper models for these species. A dataset of 188 destructively sampled trees (Manchurian fir 123 and Korean spruce 65) was used to evaluate eight well-known taper models. These models were fitted with generalized non-linear least squares by using 3,570 diameter and height measurements. We incorporated a first-order continuous-time error structure to adjust the inherent autocorrelation. Results: The form-class segmented model of Clark et al. (1991) best predicted the diameter, merchantable volume, and stem volume of the species when the upper stem diameter at 5.3 m was available or predicted. Conclusion: When diameter measurements at 5.3 m were not available, the Kozak (2004) and Max and Burkhart (1976) models were superior to other models in estimating the diameter of both species and volume of Korean spruce. For Manchurian fir, the Fang et al. (2000) model was more accurate in volume estimates.

In cut-to-length logging, the harvester operator adjusts the bucking in accordance with visible defects on processed stems. Some of the defects, such as a sweep on the bottom of the stem, decrease the yield and quality of sawn products and are difficult for the operator to notice. Detecting the defects with improved sensors would support the operator in his qualitative decision-making and increase value recovery of logging. Predicting the maximum bow height of the bottom log in Norway spruce (Picea abies (L.) Karst.) with log end face image and stem taper was investigated with two modelling approaches. A total of 101 stems were selected from five clear-cut stands in southern Finland. The stems were crosscut and taper measured, and the butt ends of the bottom logs were photographed. The stem diameter, out-of-roundness, and pith eccentricity were measured from the images while the max. bow height was measured by a 3D log scanner at a sawmill. The bottom logs with an eccentric pith had higher max. bow height. In addition, a highly conical bottom part of the stem was more common on the bottom logs with a large max. bow height. Applying both log end face image and stem taper measurements gave the best model fit and detection accuracy (76%) for bottom logs with a large max. bow height. The results indicate that the log end face image and stem taper measurements can be utilised to aid harvester operator in deciding an optimised length for logs according to the bow height.

En los últimos años, en el sureste de México se han establecido plantaciones forestales de Pinus caribaea, que tienen como propósito la extracción de resina y la producción de madera. Ambas variables se han correlacionado positivamente con características morfológicas como la forma del fuste. Generalmente, para la descripción del perfil fustal se utilizan dos expresiones: factor de forma y ahusamiento. En este sentido, el objetivo del presente estudio fue construir un sistema de cubicación para estimar el ahusamiento y el volumen comercial de tres progenies de pinos tropicales establecidos en una plantación forestal en las Choapas, Veracruz, México, así como evaluar sus diferencias en la geometría del fuste a través de enfoque de variables indicadoras. Por medio del modelo de la variable combinada lineal y la utilización de variables indicadoras, se analizó el efecto de la procedencia en el factor de forma, encontrándose que el híbrido entre Pinus caribaea y Pinus elliotti presenta una geometría cercana al paraboloide. Se probaron diferentes modelos de ahusamiento, de los cuales, el de Demaerschalk presentó el mejor ajuste y, a partir de su integración matemática, se derivó una ecuación de volumen comercial variable, que se ajustó de manera simultánea con la de ahusamiento para generar un sistema compatible de ahusamiento-volumen comercial. Los resultados indican que el híbrido es superior en la geometría del fuste y en el volumen comercial maderable frente a las otras dos procedencias de Pinus caribaea.

Taper degradation in Total Hip Replacements (THR) has been identified as a clinical concern, and the degradation occurring at these interfaces has received increased interest in recent years. Wear and corrosion products produced at the taper junction are associated with adverse local tissue responses, leading to early failure and revision surgery. Retrieval and in-vitro studies have found that variations in taper design affect degradation. However, there is a lack of consistent understanding within the literature of what makes a good taper interface. Previous studies assessed different design variations using their global parameters assuming a perfect cone such as: taper length, cone angle and diameters. This study assessed geometrical variations of as-manufactured head and stem tapers and any local deviations from their geometry. The purpose of this study was to provide a greater insight into possible engagement, a key performance influencing parameter predicted by Morse taper connection theory. This was achieved by taking measurements of twelve different commercially available male tapers and six female tapers using a coordinate measurement machine (CMM). The results suggested that engagement is specific to a particular head-stem couple. This is subject to both their micro-scale deviations, superimposed on their macro-scale differences. Differences in cone angles between female and male tapers from the same manufacturer was found to create a predominately proximal contact. However, distally mismatched couples are present in some metal-on-metal head-stem couples. On a local scale, different deviation patterns were observed from the geometry which appeared to be linked to the manufacturing process. Future work will look at using this measurement methodology to fully characterise an optimal modular taper junction for a THR prosthesis.

Aims The aim of this study was to develop a novel computational model for estimating head/stem taper mechanics during different simulated assembly conditions. Methods Finite element models of generic cobalt-chromium (CoCr) heads on a titanium stem taper were developed and driven using dynamic assembly loads collected from clinicians. To verify contact mechanics at the taper interface, comparisons of deformed microgroove characteristics (height and width of microgrooves) were made between model estimates with those measured from five retrieved implants. Additionally, these models were used to assess the role of assembly technique—one-hit versus three-hits—on the taper interlock mechanical behaviour. Results The model compared well to deformed microgrooves from the retrieved implants, predicting changes in microgroove height (mean 1.1 μm (0.2 to 1.3)) and width (mean 7.5 μm (1.0 to 18.5)) within the range of measured changes in height (mean 1.4 μm (0.4 to 2.3); p = 0.109) and width (mean 12.0 μm (1.5 to 25.4); p = 0.470). Consistent with benchtop studies, our model found that increasing assembly load magnitude led to increased taper engagement, contact pressure, and permanent deformation of the stem taper microgrooves. Interestingly, our model found assemblies using three hits at low loads (4 kN) led to decreased taper engagement, contact pressures and microgroove deformations throughout the stem taper compared with tapers assembled with one hit at the same magnitude. Conclusion These findings suggest additional assembly hits at low loads lead to inferior taper interlock strength compared with one firm hit, which may be influenced by loading rate or material strain hardening. These unique models can estimate microgroove deformations representative of real contact mechanics seen on retrievals, which will enable us to better understand how both surgeon assembly techniques and implant design affect taper interlock strength. Cite this article: Bone Joint J 2020;102-B(7 Supple B):33–40.

This study examines the performance of 11 tree taper models to predict the diameter of bark at any given height and the total stem volume of eight dominant tree species in the boreal forests of Lithuania. Here, we develop eight new models using stochastic differential equations (SDEs). The symmetrical Vasicek model and asymmetrical Gompertz model are used to describe tree taper evolution, as well as geometric-type diffusion processes. These models are compared with those traditionally used for four tree taper models by using performance statistics and residual analysis. The observed dataset consists of longitudinal measurements of 3703 trees, representing the eight dominant tree species in Lithuania (pine, spruce, oak, ash, birch, black alder, white alder, and aspen). Overall, the best goodness of fit statistics of diameter predictions produced the SDE taper models. All results have been implemented in the Maple computer algebra system using the &ldquo, Statistics&rdquo, and &ldquo, VectorCalculus&rdquo, packages.

Visual scoring of damage at taper junctions is the sole method to quantify corrosion in large-scale retrieval studies of failed hip replacement implants. This study introduces an intelligent image analysis-based method that objectively rates corrosion at stem taper of retrieved hip implants according to the well-known Goldberg scoring method. A Support Vector Machine classifier was used that takes in vectors of global and local textural features and assigns scores to the corresponding images. Bayesian optimisation fine-tunes the hyperparameters of the classifier to minimise the cross-validation error.

Volume and taper equations are used for estimating timber volume and biomass of a tree. Despite their usefulness, precise and site specific equations are still lacking for commercially important tree species in Nepal. The study was carried out at Chandak Chatiya Mahila Community Forest in Bardia district and Lumbini Collaborative Forest of Saljhandi in Rupandehi district in western Terai of Nepal. A destructive sampling method was used and selected fifteen Sal trees (Shorea robusta Gaertn. f.) from Saljhandi (site 1) and eighteen trees from Bagnaha (site 2) randomly to calibrate an individual tree volume and a stem taper function. At first, a non-linear stem taper function was calibrated using stem diameters outside bark at different heights above ground as response variable and D (diameter at breast height), H (total height), h (height of interest) as predictors. Then, effect of crown characteristics on stem taper was evaluated. As stem HCB (height to crown base) was found to affect stem taper, its usefulness in existing stem volume equation was tested. Empirical relationships between V (stem volume) as a response variable and D, H, HCB and sites in Bardia and Rupandehi districts as predictors were established using a linear mixed modeling approach. Our result showed that, instead of H, use of HCB in stem volume equation increased model prediction accuracy and reduced prediction bias. Applicability of the suggested models for predicting individual S. robusta tree volume and stem taper is discussed. Banko JanakariA Journal of Forestry Information for Nepal Special Issue No. 4, 2018, Page: 76-83

Leaf area on branches is linked to the stem through hydraulic and physiological functions. We investigated whether this relationship extends to growth responses by examining coordinated growth between leaf area on selected branches in the crown and growth in form and taper of the main stem. The growth impact of leaf area carried on individual branch whorls on the stem profile and internodes was tested using a series of defoliation and shade treatments. The data were analyzed using a linear mixed-effects model relating relative diameter to the relative height of the measured internodes. Defoliation and shade treatments on selected branches significantly affected the stem profile compared with untreated trees. The effect of reduced leaf area due to defoliation and shading of branch whorls was localized to internodes immediately below or above treated whorls. The stem profile showed curvature in the regions affected by reduced leaf area. These findings demonstrate that branch and stem growth is sensitive to minor changes in leaf area. The results emphasize the localized contribution of branches to stem growth.

An 81-year-old woman presented with progressive groin pain after metal-on-polyethylene total hip arthroplasty with a modular neck stem and was found to have adverse local tissue reaction. As we report for the first time with this implant, we observed titanium neck-titanium stem taper corrosion intraoperatively. We also found head-neck taper corrosion. The patient underwent revision surgery to a modular fluted tapered stem with ceramic head and was asymptomatic at 3-year follow-up visit. In conclusion, consideration should be given to avoiding the routine use of this modular neck stem in total hip arthroplasty. Patients with this prosthesis should be closely monitored for adverse local tissue reaction. Keywords: Total hip arthroplasty, Taper corrosion, Dual modular stem, Adverse local tissue reaction, Zimmer Kinectiv

Tree bark, as the outermost protective layer of tree stems, is an important indicator to evaluate the fire resistance properties of trees and to assess the tree mortality induced by fire. Despite its importance, many existing bark thickness models were not primarily developed for predicting bark thickness directly, i.e. with bark thickness as a response variable, and most past studies were focused on modeling bark thickness in conifers. Thus, the objective of this study was to compare the efficacy of various bark thickness models/methods for three common hardwood species in the southeastern US. A total number of 47,281 measurements from 2,070 trees were used in analysis. Results showed that bark thickness at breast height (1.37 m or 4.5 ft above ground) varies by tree size and species, which can be predicted by a species-specific linear regression model with DBH as a single predictor. To predict bark thickness profile, a combination of stem taper function and bark thickness model, a two-stage method, is suggested, which generally performs better than a single bark thickness function (one-stage method) in terms of bias and precision. For a given model form, the two-stage method produced more reliable prediction of bark thickness at upper and lower portions of tree stem than the one-stage method. With the three species examined, the segmented stem taper functions provided more accurate predictions than the variable-exponent function. The results of this study can provide guidance for ecologists and forest managers when selecting appropriate approaches to predict bark thickness.