Partial Cuts Research Articles

Assessment of Fuel Wood Values and the Influence of Wood Cutting on the Easily Flooded Plain Woodland of the Sahelian Area, Cameroon

The study focused on fuel wood economic value and the influences of woody cutting on woody species in the flooded plains woodland area. Sahelian woodland suffers from cutting down trees for fuel wood, to insure household energy demands. Investigations were carried out near a sample of users of resources and an inventory of stems of exploited species in woodland. Households in 15 villages and four markets were explored and 496 actors included in the exploitation and the use of firewood and charcoal, as regard 204 men and 292 women, were interviewed individually. Fuel wood quantity and economic value was made through a register. Through 48 transects of 2 000 m length and 20 m each, the availability, the intensity of cutting down trees, measurements and observations were made and noted on stems. Stems which the circumference > 10 cm were counted and their diameter was measured. The sources of domestic energy mostly used were firewood and charcoal which remained easily accessible and available. Completely stem cut down and partial stems cut were noted as the exploitation mode. The charcoal was produced traditionally, using furnace. Significant quantity of firewood (2186.59 t) and charcoal (28340 t) were estimated. It varied periodically a year with a substantial drop. The quantity sale represent 95 % and brought annual income of 122035.8 $ (Firewood) and 31 630 $ (charcoal). The incomes contributed significantly in the rural households’ economy and brought an additive to their much reduced agricultural yields. A number of 33 woody species were noted as the mostly exploited for fuel wood. Among them Anogeissus leiocarpus, Balanites aegyptiaca, Prosopis Africana, Detarium microcarpum and Pseudocedrela kotschyi were firstly mention. The total number of stumps and the partial cut of stems were significant representing respectively 20.91 % and 9.64 % of stems counted. The exploitation was intensive and selective on stems. Cutting down of stems was constituted a major factor for requested species degradation. Results indicated evidence of the impacts of fuel wood exploitation on the woody species. The study concludes that fuel wood yield in the sahelian woodland has not yet reached alarming proportions and can be contained. It could be an imperative to set up an alternative system to ensure sustainable management of resources. Solutions through introduction and popularization of natural gas, biogas, solar energy and the improved hearths could effectively contribute to reduce the intensity of this activity and to guarantee the maintenance of the ecological balance on the already fragile sahelian ecosystems.

Windthrow modelling in old-growth and multi-layered boreal forests

Windthrow is a recurring disturbance process in regions that are influenced by maritime climates, including boreal forests. Within the circumboreal region, forest management approaches have been adapted to emulate natural disturbance in order to promote biodiversity and ecosystem resilience. Few studies have evaluated windthrow outcomes in natural or managed old-growth boreal mixed-species stands, and these studies are primarily empirical. The objective of this study was to adapt the hybrid empirical-mechanistic ForestGALES_BC model, to investigate windthrow dynamics in natural and managed boreal old-growth stands, under various wind regimes. ForestGALES_BC was updated by adding biomechanical data for balsam fir (Abies balsamea (L.) Mill.) and black spruce (Picea mariana (Mill.) B.S.P.). The model has the ability to simulate damage propagation during wind events by recalculating wind loading on a subject tree after failure of upwind trees. The number of iterations of this recalculation provides insights into the potential for propagation during longer duration storms. A simulation space made up of 500, 20m×20m cells, was created using tree-lists from silviculture systems experiments in north eastern Quebec. The tree-lists for cells within the simulation space were edited to represent the plot conditions at the Quebec experimental sites, allowing simulation of a range of cell- (plot) and matrix-level (landscape) partial harvesting regimes. Above-canopy winds of various speeds were applied in order to test the initiation and propagation of damage within the simulated forest. Simulated outcomes were compared to observations of windthrow 6–7 years after partial harvesting at the field experimental site. Observed damage at the experimental site ranged from 1 to 40% of plot total basal area (mean=14%, se=1.96). For above-canopy wind speeds within the range expected for the experimental site, simulated windthrow levels in partial cuts ranged from 7 to 32% (mean=12%, se=1.94). When the combined effects of wind speed and number of iterations (∼event duration) were investigated, event duration was more important for wind speeds over 20m/s. By enabling simulation of outcomes at the tree, plot (cell) and stand (simulation space) levels, the model allows investigation of a wide range of harvesting strategies, and sets the stage for inclusion of wind disturbance in ecosystem succession models and other stand or landscape-level decision-support tools for forests in windy climates.

Effects of Timber Harvest on Water Quantity and Quality in Small Watersheds in the Piedmont of North Carolina

This paired watershed study tested the effects of timber harvest on water quantity and quality in the North Carolina Piedmont physiographic region. Four headwater watersheds at Hill Demonstration Forest (HF1, HF2, HFW1, and HFW2) and two at Umstead Research Farm (UF1 and UF2) were continuously monitored for discharge and water quality from 2007 to 2013. The HF1 and UF1 watersheds were clearcut (treatment), leaving a 15.2-m vegetated riparian buffer around the streams to protect water quality as described in the North Carolina Neuse River Basin Riparian Buffer Rule. HF2 and UF2 were uncut and used as reference watersheds. Merchantable timber was selectively removed from the riparian buffer, reducing tree basal area by 27% in HF1 and 48% in UF1. HF1 and HF2 were nested within HFW1; thus, HFW1 was considered a partial cut where 33% of the watershed area was harvested, and HFW2 was the reference. We found that discharge in treatment watersheds increased dramatically, averaging 240% in HF1 and 200% in UF1 and 40% in HFW1 during the postharvest period, 2011–2013. Total suspended sediment export in the treatment watersheds also increased significantly in HF1 after harvest, probably due to the increase of discharge and movement of in-channel legacy sediment. Stormflow peak nitrate reached its maximum concentration during the first 2 years after harvest in the treatment watersheds and then declined, corresponding to the rapid regrowth of woody and herbaceous plants in the riparian buffer and uplands. We found that 36% of the UF1 streambank trees were blown down but did not cause a measurable increase in mean daily stormflow total suspended sediment concentration. Most buffer tree blowdown occurred during the first few years after a harvest. Bioclassification of benthic macroinvertebrates indicated that stream water quality remained good/fair to excellent in the treatment watersheds after the harvest. We conclude that the temporary increases in discharge were relatively large for the Piedmont region compared with those for other regions in the southeastern United States. However, the increases in channel sediment transport and nutrient exports associated with the hydrologic change did not have a measurable impact on the indicators of aquatic invertebrate community health or bioclassification rankings. Management and Policy Implications: There are three distinct land provinces across North Carolina: the mountains, Piedmont, and coastal plain. Understanding how region-specific watershed hydrology responds to land management and natural disturbances can provide useful information to land managers as they set flow targets needed to maintain ecological integrity in surface waters or to design riparian buffers for water quality protection. We found that after a clearcut timber harvest with a riparian buffer zone around the streams, the percent increases in annual discharge and mean nitrate concentrations tended to be higher in the Piedmont region than in the other two regions. Our study also found that tree blowdown in the riparian buffer was more likely to occur in the Piedmont Triassic region than in the Piedmont Carolina Slate Belt region. In the Triassic region, additional management activities should be part of the preharvest planning process as they may help mitigate windthrow and uprooting of streambanks and improve the overall riparian buffer functions and flow dynamics. For example, land planners or loggers should assess whether soils have Triassic or Slate Belt characteristics to determine if they need to refrain from creating gaps and retain more windfirm species within the riparian buffer. Although there was variation in blowdown occurrences among regions, Triassic soils comprise about 3.5% of North Carolina's total land area, so any statewide implications would be low and recommendations would be localized.

Effects of timber harvest on small mammal captures in experimental forestry plots

To investigate effects of timber harvest on small mammals, we compared capture rates in experimental forestry arrays of uncut forest, partial cut forest, and clearcuts with high and low coarse downed wood in Missouri, USA. Past studies show that effects of timber harvest on small mammals depend on species and forest type. We used an information theoretic approach to compare the effects of timber harvest treatment and habitat characteristics on capture rates. Sorex longirostris captures were best predicted by timber harvest treatment. S. longirostris had higher captures in the clearcut with low downed wood, intermediate numbers of captures in the partial cut and clearcut with high downed wood, and low captures in uncut forest. However, despite differences in captures between the clearcuts with high and low downed wood, we found no difference in habitat variables between the two clearcut types. Blarina spp., Microtus pinetorum, and Peromyscus spp. captures were best predicted by habitat variables rather than timber harvest treatment. Blarina spp. captures were associated with lower leaf litter depth. Peromyscus spp. and M. pinetorum captures were associated with increased coarse downed wood, possibly due to their preference for nest building under logs. Some of these relationships differ from results in other areas of the United States, which may reflect differences in species-habitat relationships in different forest types or regions. Relationships between species and habitat variables will be useful in adjusting forestry practices to meet species management objectives.

Identification of a Crack in Clamped-Clamped Beam using Frequency-based Method and Genetic Algorithm

The natural frequencies of cracked and uncracked clamped-clamped beam are measured using single-input multi-output (SIMO) based experimental modal analysis (EMA). The crack present at various locations on the beam is generated using wire cut electro discharge machining process (WEDM). The crack is assumed to be transverse and one dimensional partial cut of a beam and is modeled as equivalent elastic rotational spring. Using Euler-Bernoulli beam theory, a closed form solution of the structural/mechanical member is presented. The measured frequencies of the beam with crack are utilized to identify crack location and its severity by the frequency-based approach as well as genetic algorithm (GA) based intelligent search for the same test points. GA is executed to find global minima of a fitness function that is a function of measured and theoretical frequencies of the cracked beam. The results of predicted crack location and its severity by both the approaches are compared and found to be good agreement with the actual crack parameters.

Can partial‐cut harvesting be used to manage terrestrial lichen habitat? A review of recent evidence

Recent research suggests that partial-cut harvesting techniques can be used to alter successional trajectories in pine- and spruce-lichen woodlands, allowing forest managers to extend the period of reindeer lichen growth in mid- to late seral boreal forest stands. In Quebec, a fully replicated partial-cutting trial found that terrestrial lichen abundance remained at least as high in the partial cut as in the clearcuts or unlogged stands, and that the partial cut appeared to be on a trajectory to have even more terrestrial lichen due to sustained higher growth rates. In Alberta, a retrospective study found higher terrestrial lichen abundance in an early horse-logged partial cut than in undisturbed adjacent old forests or in clearcuts. Follow-up studies of partial-cut harvesting trials in British Columbia found that group selection plots 10 years after harvesting had lichen cover equivalent to that of undisturbed forest. In contrast, studies on lichen woodlands that have been defoliated by mountain pine beetle showed a major decline in reindeer lichen cover and a corresponding increase in vascular plant cover, similar to the results of previous studies on clear-cut logging impacts. Taken together these studies provide qualified support for the hypothesis that partial-cut harvesting can be used to enhance, or at least maintain, terrestrial lichen mats used as forage by caribou.

Impact of forestry practices at a landscape scale on the dynamics of amphibian populations.

Forest loss is a primary cause of worldwide amphibian decline. Timber harvesting in the United States has caused dramatic changes in quality and extent of forest ecosystems, and intensive forest management still occurs. Although numerous studies have documented substantial reductions in amphibian densities related to timber harvest, subsequent extinctions are rare. To better understand the population dynamics that have allowed so many amphibian species to persist in the face of widespread forest disturbance, we developed spatially explicit metapopulation models for four forest-dependent amphibian species (Lithobates sylvaticus, Ambystoma opacum, A. talpoideum, and A. maculatum) that incorporated demographic and habitat selection data derived from experiments conducted as part of the Land Use Effects on Amphibian Populations Project (LEAP). We projected local and landscape-scale population persistence under 108 different forestry practice scenarios, varying treatment (partial cut, clear-cut with coarse woody debris [CWD] removed, and clearcut with CWD retained), cut patch size (1, 10, or 50 ha), total area cut (10, 20, or 30%), and initial amphibian population size (5, 50, or 500 adult females per local breeding population). Under these scenarios, landscape-scale extinction was highly unlikely, occurring in < 1% of model runs and for only 2 of the 4 species, because landscape-scale populations were able to persist via dispersal even despite frequent local extinctions. Yet for all species, population sizes were reduced to -50% in all clear-cut scenarios, regardless of the size of harvested patches. These findings suggest that debate over timber harvesting on pool-breeding amphibian populations in the United States should focus not on questions of landscape-scale extinction but on the ecological consequences of dramatic reductions in amphibian biomass, including changes in trophic interactions, nutrient cycling, and energy transfer. Additionally, we conclude that amphibian declines and extinctions are far more likely to occur as a result of permanent habitat loss resulting from development than from the temporary degradation of habitat caused by current forestry practices.

Influencia del rolado selectivo de baja intensidad (RBI) sobre las comunidades de aves de bosques del Chaco Occidental

Low intensity roller-chopping (RBI) is a technology applied to develop low impact silvopastoral systems in the Chaco Region. The RBI reduces the lower woody stratum (<3 m high) and increases the herbaceous cover, and it can be applied in combination with partial cuts of the forest. The aim of this study was to evaluate the influence at the local scale of two RBI treatments of different age (after one and seven years) on alpha and beta diversity and the trophic guild structure of forest birds in the Western Chaco, in the breeding and non-breeding seasons. Results suggest that, compared to undisturbed forest: i) the RBI created habitats of low contrast, ii) the older treatment was the less contrasted, iii) alpha diversity did not decrease in response to treatments and both seasons had low beta diversity, and iv) recent treatment had the greatest dissimilarity in bird assemblage composition, since both seasons had the highest beta diversity and bigger changes in abundance of the guilds associated with RBI. This study suggest that: i) forests treated whit RBI maintain habitat conditions and compositions of bird assemblages similar to the undisturbed forest, particularly in older treatments, and ii) RBI has potential to meet simultaneously the goals of bird conservation and sustainable production.

Vibration-based non-destructive technique to detect crack in multi-span beam

This article presents the study on identification of a single open crack in a straight multi-span beam using natural frequency-based non-destructive technique. The crack is assumed to be transverse and one-dimensional partial cut of a beam, and is modelled as equivalent elastic rotational spring. The effects of crack location and depth on the natural frequency for multi-span uniform beam are demonstrated. The reduction in natural frequency due to presence of crack is utilised to detect crack location and its severity. The formulation is validated experimentally.

Analysis of minimal cut and path sets based on direct partial Boolean derivatives

Principal steps in reliability engineering include estimation of system reliability and identification and quantification of situations which cause a system failure. There are several techniques that can be used to solve these tasks. Some of them are based on minimal cut (path) sets, which represent minimal sets of basic events, whose simultaneous occurrence leads to a failure (repair) of the system. In this article, applications of minimal cut (path) sets in reliability analysis are summarized, and their connection with direct partial Boolean derivatives is studied. In reliability analysis, direct partial Boolean derivatives identify situations in which a failure (repair) of one system component results in a system failure (repair). Therefore, they reveal the influence of one system component on the whole system. However, minimal cut (path) sets define the influence of a simultaneous failure (repair) of a group of system components on the system activity. Therefore, there should be some correlation between direct partial Boolean derivatives and minimal cut (path) sets. This correlation is studied in this article, and as a result, new algorithms for identification of minimal cut (path) sets are proposed based on this correlation.

Light availability and soil compaction influence the growth of underplanted Nothofagus following partial shelterwood harvest and soil scarification

We evaluated effects of topsoil scarification by heavy machinery on growth of two valuable, shade-intolerant tree species — Nothofagus dombeyi (Mirb.) Oerst. (evergreen and considered to be very plastic to different soil fertility levels) and Nothofagus alpina (Poepp. &amp; Endl.) Oerst. (deciduous and considered to be sensitive to soil fertility) — seedlings that were underplanted in Nothofagus old-growth forests, which were subjected to shelterwood cuttings without the final cut in the Chilean Andes. We compared tree basal diameter growth as it responds to light availability and soil compaction (as measured by resistance to penetration) by fitting a growth model based on the Michaelis–Menten equation. Predicted growth of N. dombeyi was greater than N. alpina in high and low light levels; however, there were no significant differences between the species. Both species showed significant differences at high levels of penetration resistance (&gt;2000 kPa). Differences for N. dombeyi occurred above ∼40% in total light, and differences occurred for N. alpina above ∼20% in total light. However, they were not different when compared at low and intermediate levels of penetration resistance. The results suggest that partial shelterwood cuts may provide adequate light levels to achieve appropriate growth of underplanted Nothofagus seedlings. However, if regeneration of N. alpina is desired, scarification of topsoil needs to be implemented with more caution in canopy openings, as traffic and soil removal by heavy machinery can have detrimental effects on growth of this species and other species that are more sensitive to soil compaction.

Effect of three partial cutting practices on stand structure and growth of residual black spruce trees in north-eastern Quebec

Partial cutting practices are increasingly used in boreal forests for two major reasons: (1) maintaining age structure and tree diameter distribution according to the principles of ecosystem-based management and (2) increasing tree growth by decreasing competition. This study evaluated the effects of three different partial cutting treatments applied to even- and uneven-aged black spruce (Picea mariana (Mill.) B.S.P.) stands in north-eastern Quebec, Canada. The effect of partial cutting was assessed by comparing treated and control plots in terms of age structure, diameter and spatial distribution, amount of deadwood and tree radial growth. Age structure and diameter distribution were not different from control plots after partial cuttings applied in both uneven-aged and even-aged stands, but lower deadwood basal area was observed. Tree radial growth generally increased in uneven-aged stands but can be limited by tree age and inter-tree competition. In even-aged stands, tree removal was more uniformly distributed and the overall reduction in inter-tree competition resulted in an increased tree radial growth. Overall, these results suggest that the studied partial cuttings were adequate for maintaining structural attributes and increasing tree growth, but adjustments should be made to treatments to increase the amount of deadwood to a level observed in natural forests and to lower inter-tree competition.

American beech and sugar maple sapling relative abundance and growth are not modified by light availability following partial and total canopy disturbances

Studies have reported divergent results on the effect of soil fertility and canopy opening on understory density and growth of sugar maple (AS; Acer saccharum Marsh.) and American beech (FG; Fagus grandifolia Ehrh.). The main objective of this study was to evaluate the effect of a gradient of canopy opening and soil fertility on the density and growth of AS and FG saplings in southwestern Quebec, Canada. We investigated 56 stands containing both AS and FG that were subjected to different disturbance history types (DHTs) (UF, unmanaged forest; PC, partial cut; and CC, clearcut) on various soil types. AS and FG absolute and relative sapling density varied greatly among the 56 stands; however, no significant effects of DHT, soil nutrient availability, or their interaction were found. Both species responded positively in terms of radial growth to canopy openings, with FG growth being slightly better than AS growth in PC stands compared with other canopy treatments. Contrary to our hypothesis, AS did not show significantly higher growth than FG following clear-cutting. These results do not support the idea that AS abundance and growth could be promoted by increasing the intensity of the canopy opening during harvest, at least on the generally acidic and base-poor soils that were investigated.

Nine-year changes in carbon dynamics following different intensities of harvesting in boreal aspen stands

Mixedwood forests occupy a large extent of boreal regions and have the potential for sequestering large amounts of carbon. In the context of forest ecosystem management, partial cutting prescriptions are increasingly being applied to boreal mixedwood stands. Partial harvesting is expected to maintain carbon pools and dynamics within the limits of those of natural stands. Changes in live tree, deadwood (standing snags, downed logs), forest floor and mineral soil carbon pools were assessed over a 9-year period in a replicated large-scale experiment, which included unharvested controls, two variants of partial harvesting and clear-cuts. We also measured leaf litter and deadwood inputs and decay rates. Carbon flux through leaf litterfall recovered rapidly following partial harvesting. Carbon flux from live trees to deadwood pools was a dominant process in partially harvested stands where snags and downed log carbon pools remained similar to those of natural stands. Hence, the nature of litter inputs diverged strongly among clear-cut and partially harvested treatments. Leaf and wood decay rates were higher in the partial cuts and controls than in clear-cuts. No significant differences in forest floor and mineral soil carbon were observed 9 years after harvesting. Carbon sequestration in live tree biomass was the carbon pool that most strongly differentiated the treatments allowing partial harvesting to maintain forest stands as net carbon sinks.

Computational strategies for improved MINLP algorithms

In order to improve the efficiency for solving MINLP problems, we present in this paper three computational strategies. These include multiple-generation cuts, hybrid methods and partial surrogate cuts for the Outer Approximation and Generalized Benders Decomposition. The properties and convergence of the strategies are analyzed. Based on the proposed strategies, five new MINLP algorithms are developed, and their implementation is discussed. Results of numerical experiments for benchmark MINLP problems are reported to demonstrate the efficiency of the proposed methods.

Effect of unintentional partial Achilles tenotomy on Ponseti clubfoot management outcomes.

The congenital talipes equinovarus (clubfoot) is one of the most common congenital conditions requiring orthopedic intervention. This study was carried out to evaluate the effect of unintentional partial Achilles tendon cut during percutaneous tenotomy on the success rate of Ponseti management. Percentage of Achilles tendon cut following percutaneous tenotomy was measured by ultrasound in 16 clubfeet (11 patients). After a mean of 21 months of follow-up, the final results (Dimeglio score) were compared between two groups of patients: those with complete tendon cut and those with partial cut. Complications and parameters such as feeling of pop during tenotomy and ankle dorsiflexion during tenotomy were also compared. There was no significant correlation between the percentage of Achilles tendon cut and increase in ankle joint dorsiflexion, age at diagnosis, or pop sensation. There was no statistically significant difference between the two groups in their ankle joint dorsiflexion, feeling of pop, and final follow-up Dimeglio score. No complications were encountered following tenotomy. One patient needed tibialis anterior transfer at his last follow-up visit. Partial cut of Achilles tendon following tenotomy does not necessarily compromise the final results of Ponseti management. Achieving more than 10°-20° ankle dorsiflexion even with a partial tendon cut can ensure good final results.

Growth of planted jack pine (Pinus banksiana) and natural regeneration ten years after pre- and post-harvest spraying and partial cutting in an Ontario boreal mixedwood forest

The conventional plantation approach to regenerating jack pine (Pinus banksiana) after harvesting maximizes pine growth but may reduce wood quality. In this study we examined growth of planted jack pine and natural regeneration after herbicide spraying and partial cutting treatments on a boreal mixedwood site in northeastern Ontario. Treatments were pre-harvest aerial spray, post-harvest ground spray in strips (partial spray), partial cut, and post-harvest aerial broadcast spray; an untreated reference stand was used for comparison. Pre-harvest spray was as effective as partial cutting and post-harvest broadcast spray in suppressing trembling aspen regeneration and providing adequate light for survival and growth of planted jack pine. Ten years after planting, mortality and growth of pines in the pre-harvest treatment were comparable to those in the partial and broadcast spray treatments. Due to vigorous growth of broadleaf species [mostly red maple; (Acer rubrum)], and shade from the residual overstory, jack pine was smallest in the partial cut treatment; however, based on branch size, branch-free stem length and stem taper, wood quality was highest in this treatment. Considering factors important to forest managers such as growth and quality of planted jack pine, treatment costs, and proportion of the harvested blocks allocated to conifer production, the preferred treatment was pre-harvest spray.

Short-term hydrological responses to silvicultural treatments withina stream buffer zone: a case study

The thinning of stream buffer zones (SBZs) is gaining popularity as a silvicultural management practice in order to reduce the risk of wildfire and insect hazard, provide economic return, and improve the effectiveness of SBZs. In this study, streamflow over a 1-year period was monitored at 2 small paired watersheds (treated vs. reference). The short-term impacts of a partial cutting within a SBZ as well as the relative effects of pastoral, forested, and clearcut areas on changes in downstream hydrology were examined. Upstream pastoral areas had a higher water yield than downstream forested sections during the no-harvest (calibration) period of 6 months. The partial cut (about 50% of the basal area) within the SBZ changed the hydrologic pattern by remarkably increasing the water yield on the treated downstream sections during the 6-month-long postharvest period. The harvest operation also caused an increase in direct runoff at 2 downstream sections, WT2 and WT3 (~200% and ~100%, respectively). No significant changes were observed in the water yield pattern of the control watershed. Because harvested areas within the SBZs constitute a fraction of the monitored sub-watersheds and only partial harvesting (~50% of the basal area) was implemented, the observed increase in flow at the treated downstream sections (100% and 250%, respectively) is unprecedented. The partial harvesting within the SBZs also resulted in a significantly flashier hydrological system. Because silvicultural treatments are part of regular, repeated management operations, these short term (in this study, 6-month-long) but substantial changes in water yield, direct runoff, and flashiness could have important implications for water quality, water resources, and downstream biota.

Predictive Modelling of Internal Pitting Corrosion of Aged Non-Piggable Pipelines

A multivariate regression analysis and time-dependent maximum pit depth growth model was developed using maximum pit depths and pipeline operational parameters, which includes temperature, CO2 partial pressure, flow rate, pH, sulfate ion, chloride ion and water cut. This statistical analysis, which used ten years Ultrasonic Thickness Measurement (UTM) data from non-piggable onshore pipelines, accounted for different categories of maximum pitting rates - low, moderate, high and severe. The model was validated using field data from twelve operating pipelines and the results agreed well with the field data.

Two case reports of lower limb posttraumatic angular deformities correction by dynamic hinged external fixation

The aim of this study was to present two patients with lower limb posttraumatic angular deformity treated by dynamic hinged external fixation. CD-V mode Mitkovic type external fixator had been used in both cases for correction of these deformities. The method is based on hemicallotasis - bone callus distraction after a partial transversal bone cut (hemocorticotomy). The first patient had varus-recurvatum posttraumatic deformity of the ankle joint. Operation time was 65 min and hospital stay was 9 days. Superficial pin-track infection was resolved by the pin removal and by daily wound toilette. The second patient had varus-antecurvatum malunion deformity of the femoral diaphysis. Operation time was 50 min and hospital stay was 6 days. Mild knee contracture had been successfully treated by physical therapy. Angular deformity correction had been performed by distraction (for the first patient) and compression (for the second patient) in the fixator frame. Hemicallotasis of femur or tibia using CD-V mode Mitkovic type external fixator is a good alternative in the treatment of posttraumatic lower limb angular deformities, providing minimal surgical trauma and maximal use of the bone osteogenetic capacity. Gradual compression or distraction in the fixator frame allows to perform accurate angular correction in both coronal and sagital plane in one act.