Wall Dimensions Research Articles

Rao-3 algorithm for the weight optimization of reinforced concrete cantilever retaining wall

The paper represents an optimization algorithm for reinforced concrete retaining wall design. The proposed method, called Rao-3 optimization algorithm, is a recently developed algorithm. The total weight of the steel and concrete, which are used for constructing the retaining wall, were chosen as the objective function. Building Code Requirements for Structural Concrete (ACI 318-05) and Rankine\'s theory for lateral earth pressure were considered for structural and geotechnical design, respectively. Number of the design variables are 12. Eight of those express the geometrical dimensions of the wall and four of those express the steel reinforcement of the wall. The safety against overturning, sliding and bearing capacity failure were regarded as the geotechnical constraints. The safety against bending and shear failure, minimum and maximum areas of reinforcement, development lengths of steel reinforcement were regarded as structural constraints. The performance of proposed algorithm was evaluated with two design examples.

Comparative Study on Using Ultrasonic Array-Based Techniques for Detection of Flaws in Thick and Attenuating Materials

This paper reports the influence of thickness and material attenuation on volumetric inspection using conventional and advanced ultrasonic array-based techniques through suitable examples. The sensitivity achieved in conventional phased array ultrasonic testing technique with focusing at specific depth using delay laws and advanced array-based techniques for simultaneous focusing at all depths such as Full Matrix Capture-Total Focusing Method and plane wave imaging-TFM are compared in the present study. Finally, experimental results are discussed for advanced ultrasonic array-based techniques for detection and characterization of a 4 mm through wall dimension vertical planar defect (simulating a lack of side wall fusion in a thick narrow gap weld) in a nickel base alloy forging having fine and coarse grains. The sensitivities and signal-to-noise ratio achieved in the different techniques are discussed in detail.

Microencapsulation of lambda-cyhalothrin with polyurethane-urea and application on peppermint plant leaves containing a two-spotted red spider mite (tetranychus urticae)

In this study, lambda-cyhalothrin (LC) used as a pesticide was microencapsulated with polyurethaneurea (PUU) at 55°C temperature for 180 min. Wall thickness and dimensions of the microcapsules, the effect of mixing speed on the capsule size, active substance release times of LC-PUU microencapsules under UV rays and alcohol/water medium, microencapsulation yields and the effect of microencapsulated active substance on the red spider on peppermint plant leaves (mentha piperita) were investigated. The microcapsule yield was found 77.4–85.5%, also capsule shell thickness was 512.3–724.5 nm. The highest release percentage of the microcapsules was found to be 35.00% at 20°C for 4 h under UV light. When the LC-PUU microcapsules applied to the peppermint plant leaves (mentha piperita) which contained a two-spotted red spider mites (tetranychus urticae), it remained active for 8 weeks and during this period no insect formation was observed on the peppermint leaves.

Observational study of cone beam computed tomography based interfractional urinary bladder filling variation during image guided radiation therapy in pelvic malignancies.

Organ motion is an important factor that limits the precision of radiation treatment. Bladder filling variation has significant impact on the position of target volumes in pelvic malignancies. This study was an effort to maintain a consistent urinary bladder volume after following a bladder protocol, which was then analyzed by in-room cone-beam computed tomography (CBCT) imaging. A total number of 26 patients/300 scans, i.e. 26 planning scan and 274 CBCT were analyzed. The bladder volumes and bladder wall dimension were analyzed comprehensively, thus adding considerable understanding to the bladder wall motions. The mean bladder volume for all 26 patients was 183.07 cc with standard deviation of 90.43 cc. The mean +/- standard deviation of transverse, anteroposterior and longitudinal diameter was 8.35+/- 1.03, 6.69+/-1.05 and 5.59+/-1.79 cm. This study showed considerable reduction of margin could be done on the lateral side, as there is less displacement on transverse diameter and more liberal margins should be considered in anteroposterior dimension and longitudinal dimensions. This study has reached the conclusion that bladder-filling protocol is necessary to maintain the consistent bladder volume, but it is too preliminary to state that it will translate into reduction of margin.

Structural behavior of concrete walls reinforced with ferrocement laminates

The present work focuses on experimental and numerical performance of the ferrocement RC walls reinforced with welded steel mesh, expanded steel mesh, fiber glass mesh and tensar mesh individually. The experimental program comprised twelve RC walls having the dimensions of 450 mmx100 mmx1000 mm under concentric compression loadings. The studied variables are the type of reinforcing materials, the number of mesh layers and volume fraction of reinforcement. The main aim is to assess the influence of engaging the new inventive materials in reinforcing the composite RC walls. Non-linear finite element analysis; (NLFEA) was carried out to simulate the behavior of the composite walls employing ANSYS-10.0 Software. Parametric study is also demonstrated to check out the variables that can mainly influence the mechanical behavior of the model such as the change of wall dimensions. The obtained numerical results indicated the acceptable accuracy of FE simulations in the estimation of experimental values. In addition, the strength gained of specimens reinforced with welded steel mesh was higher by amount 40% compared with those reinforced with expanded steel mesh. Ferrocement specimens tested under axial compression loadings exhibit superior ultimate loads and energy absorbing capacity compared to the conventional reinforced concrete one.

Investigation of The Accuracy of Earth Pressure Values Obtained Using Rankne Theorem (Dept.C)

The application of Rankine theorem to calculate the earth pressure forces on earth retaining structures is widely used due to its simplicity. In this work, the theorem results are tested for a cantilever retaining wall in pure dry sandy soil. The tests included the comparison with a more sophisticated numerical model as well as with results of centrifuge simulation works. The study included the investigation of the effect of retaining wall dimensions on wall and soil behavior. Bending moments as calculated using the Rankine's theory are tested against the other methods. Rankine's theory provided generally low straining action values as compared with the finite element and the centrifuge testing results.

Cell wall dimensions reign supreme: cell wall composition is irrelevant for the temperature signal of latewood density/blue intensity in Scots pine

Many microdensitometric techniques are available for deriving maximum latewood density (MXD), which is the state-of-the-art proxy parameter for local to hemispheric-scale temperature reconstructions of the last millennium. Techniques based on X-ray radiation and visible light reflection, such as “blue intensity” (BI), integrate both the density/composition and the dimensions of the cell walls to derive microdensitometric data. In contrast, the dendroanatomical technique relies only on the dimensions of the cell walls. It is therefore possible to isolate cell wall variables by subtracting data derived using the dendroanatomical technique from data derived using X-ray and BI-based techniques.In this study, we explore differences in well-replicated data from parallel X-ray, BI, and dendroanatomical measurements of temperature-sensitive Pinus sylvestris trees from northern Finland. We aim to determine whether cell wall density is critical to the success of X-ray-based MXD, and whether the BI-based parameter counterpart, here termed MXBI, contains useful information about the composition of the cell wall (specifically the lignin).Our results indicate that cell wall density and cell wall BI have no relevant influence on MXD and MXBI measurements. Even in years with severely reduced lignification, identified as so-called “blue rings”, dendroanatomical MXD (aMXD) measurements do not deviate significantly from their MXD or MXBI counterparts. Moreover, derived chronologies of cell wall density and cell wall BI contain no significant climate signals when correlated with local climate. Maximum latewood density of conifers can thus be obtained without bias using the dendroanatomical technique. Because lignin content appears to play a negligible role for cell wall BI, the cell wall BI likely presents the biggest challenge when producing unbiased MXBI data. This is because BI data is notorious for cell wall color distortion across the heartwood and sapwood, and between living wood and dead wood, and may therefore distort the otherwise strong link with wood density on multidecadal scales.

Association between severity of disease and thoracic wall dimensions among chronic obstructive pulmonary disease patients – A cross sectional study

Introduction and Aim: Pulmonary function worsens with the intensification of disease severity. Chronic obstructive pulmonary disease (COPD) may cause changes in the shape of the thoracic cage due to increasing lung volumes and dynamic hyperinflation. To assess the association between the severity of COPD and thoracic wall dimensions among COPD patients.
 Materials and Methods: A cross-sectional study was conducted in a tertiary care teaching hospital on 80 COPD subjects aged above 18 years. Based on the severity of obstruction of COPD, subjects were divided into two groups-moderate obstruction and severe obstruction. Severity of obstruction constituted the primary outcome variable. The primary explanatory variables were the dimensions of the thoracic wall. Their association was assessed by calculating the Spearman correlation and Pearson correlation coefficient and represented in a scatter diagram.
 Results: Majority (60%) had an MMRC dyspnea grading of 3. Moderate Obstruction was seen in 62.5% of subjects while 37.50% had severe obstruction. There was no statistically significant difference between the groups with respect to antero posterior (AP) diameter, transverse diameter, AP to transverse diameter ratio and Height of Diaphragm (HDI). There was a moderate negative correlation FVC (L) and HDI, FEV1/FVC (%) and HDI which was statistically significant. There was also a weak negative statistically significant correlation between FVC (L) and AP diameter, FVC (L) and transverse Diameter, FVC (L) and AP to transverse diameter ratio, FEV1/FVC (%) and AP diameter, FEV1/FVC (%) and transverse diameter.
 Conclusion: There was a significant moderate negative correlation between the height of the diaphragm and severity of COPD (FVC, FEV1/FVC %). In COPD, the mechanical deformation leads to difficulty in breathing because of reduction in the lung capacity of patients. Early and aggressive treatment in patients with COPD can be beneficial.
 Keywords: Chronic obstructive pulmonary disease; global initiative for chronic obstructive lung disease; medical research council dyspnoea scale; barrel-shaped chest; spirometry, diaphragm.

The frequency spectrum and geometry of the Ħal Saflieni Hypogeum appear tuned

The Ħal Saflieni Hypogeum is a unique subterranean Maltese Neolithic sanctuary with a well-documented history of interest in its acoustics (Till, 2017; Debertolis et al., 2015; Reznikoff, 2014; Devereux, 2009; Skeates, 2008; Mifsud and Mifsud 1999; Devereux, 1996; Evans, 1971; Zammit, 1910; Griffiths, 1920). Previous studies have noted its unusual strongly-defined frequency spectrum (Debertolis et al., 2015), but it is unknown if this was coincidental. In this paper, we present evidence that the Hypogeum’s creators shaped the site’s geometry to create or amplify its frequency spectrum, or another property closely correlated with the spectrum. Specifically, we show that the observed spectrum required jointly fine-tuning the dimensions of multiple non-contiguous cave walls across multiple independent chambers, to a degree that seems unlikely to be coincidental. We also note that the peak frequencies are evenly spaced and resemble a whole-tone scale in music, which is also unlikely to be coincidental and suggests the spectrum itself might have held some cultural significance. Taken together, it suggests acoustic or spectral properties may have played a motivational or cultural role for the site's Neolithic creators. This work identifies one of the earliest known examples of a manmade structure with a significant musical element to its interior architecture.

Modeling esophageal protection from radiofrequency ablation via a cooling device: an analysis of the effects of ablation power and heart wall dimensions

BackgroundEsophageal thermal injury can occur after radiofrequency (RF) ablation in the left atrium to treat atrial fibrillation. Existing methods to prevent esophageal injury have various limitations in deployment and uncertainty in efficacy. A new esophageal heat transfer device currently available for whole-body cooling or warming may offer an additional option to prevent esophageal injury. We sought to develop a mathematical model of this process to guide further studies and clinical investigations and compare results to real-world clinical data.ResultsThe model predicts that the esophageal cooling device, even with body-temperature water flow (37 °C) provides a reduction in esophageal thermal injury compared to the case of the non-protected esophagus, with a non-linear direct relationship between lesion depth and the cooling water temperature. Ablation power and cooling water temperature have a significant influence on the peak temperature and the esophageal lesion depth, but even at high RF power up to 50 W, over durations up to 20 s, the cooling device can reduce thermal impact on the esophagus. The model concurs with recent clinical data showing an 83% reduction in transmural thermal injury when using typical operating parameters.ConclusionsAn esophageal cooling device appears effective for esophageal protection during atrial fibrillation, with model output supporting clinical data. Analysis of the impact of ablation power and heart wall dimensions suggests that cooling water temperature can be adjusted for specific ablation parameters to assure the desired myocardial tissue ablation while keeping the esophagus protected.

External Stability Analysis of Narrow Backfilled Gravity Retaining Walls

A three wedge failure mechanism is proposed to determine active earth pressure exerted by narrow backfills on gravity retaining walls and its point of application. Gravity retaining wall proportions are optimized against external failure modes using proposed active earth pressure and its line of action of resultant thrust. Overturning failure, eccentricity failure of the resultant force, sliding failure on its base, and bearing capacity failure are given due consideration for the determination of optimum proportions of gravity wall. Optimum dimensions of the gravity wall are evaluated such that factors of safety against overturning, eccentricity, sliding, and bearing capacity should be greater than 2.0, 1.0, 1.5, and 2.5 respectively. Significant reduction in active earth pressure in narrow backfill width gravity retaining walls is noticed due to the inadequate development of shear bands because of the constraint of rock face boundary. The study recommends employing an appropriate failure mechanism for the development of shear bands behind retaining wall based on depth and width of narrow backfill. The proposed study indicates that significant savings in the cross sectional area may be accomplished as compared to a classical design by Coulomb’s theory.

Prevalence of the prelacrimal recess in maxillary sinus and its medial bony wall dimensions.

To investigate the occurrence rate of the prelacrimal recess (PLR) and its medial bony wall dimensions based on the radiological analysis to help surgeons enhance the understanding of anatomic structures for the endoscopic prelacrimal recess approach. Cone-beam computed tomography images of 255 patients were evaluated retrospectively. The prevalence of the PLR in maxillary sinus was investigated and the thickness of its medial bony wall was measured and statistically assessed. Meanwhile, the width of the PLR was measured. The correlation between the width of the PLR and its medial bony wall thickness was assessed. The data were compared between the left side and right side, male and female. The PLR was present in 82.5% of the maxillary sinus, with no significant differences between the left and right sides, as well as different gender groups. The mean thickness of the medial bony wall of the PLR was 2.84 ± 1.41mm, without statistical difference between the left and right sides but significantly larger in males than in females. The mean width of the PLR was 4.62 ± 1.74mm and it had a significant negative correlation with the thickness of the medial bony wall of the PLR. A large individual variation exists in the anatomy of PLR, including its prevalence and dimensions of its medial bony wall. When considering the intranasal endoscopic prelacrimal recess approach, the surgeons should carefully evaluate the anatomical structure of the PLR preoperatively so as to minimize the risks of surgical complications.

Management of complex hernias with loss of domain using daily and fractioned preoperative progressive pneumoperitoneum: a retrospective single-center cohort study.

The incidence of complex hernias with loss of domain (CHLD) has been increasing and the treatment of these cases may require auxiliary techniques in addition to surgery. This study aims to refine the progressive preoperative pneumoperitonium (PPP) in patients with CHLD, to achieve an increased in wall dimensions. Patients presented with a CHLD undergoing PPP protocol were analyzed between May 2017 and May 2019. Our PPP protocol was to use two daily insufflations of 1000ml of ambient air during a period of 14days. We compared the abdominal cavity volume (ACV), the hernial sac volume (HSV) and the volume ratio (VR), before and after our refined PPP. During our evaluation period, the protocol was performed on 16 patients. The mean age was 55.73 (± 12.87), and the mean BMI was 31.35 (± 7.33). The median of HSV was 2104.53ml; Mean ACV was 6722.36ml, and median of VR was 29.97% (27.46-34.38 IIQ). The averages were: daily volume of gas ± 1526.66ml, total volume ± 17,350ml, and the PPP period of ± 10.7days. The increase in post-PPP ACV was 52.13% (p < 0.0001), and the VR decreased to 26.9% (p < 0.609). All patients' symptoms and complications were mild (according Clavien-Dindo grades I and II), and there were no loop injuries, no catheter complications, or any surgical re-interventions. The study suggests that the use of this method results in a significant increase in ACV, and reduction of the herniated content in a safe and efficient manner, with mild complications.

Orta ve Yüksek Katlı Betonarme Binalarda Optimum Perde Duvar Alanının Belirlenmesi Yönelik Parametrik Çalışma

In this article, a structural analysis was conducted on a total of 40 building models withvarying building height and wall dimensions in order to determine the optimum ratio of shear wall areato floor area in a reinforced concrete building. For this purpose, 20, 30 and 40 story buildings wereselected to investigate the effect of varying building heights on their structural behaviors. A parametricstudy on shear wall areas was conducted base on varying shear wall area to floor area ratios. Buildingmodels, therefore, included no wall and walls with 0.5%, 1%, 1.5% and 2.0% area ratios applied incombined x and y directions. Each of these models was subjected to response spectrum analysis usingthe forces generated according to the 2018 dated Turkish Earthquake Code (TEC 18) and 2016 datedAmerican Building Code (ASCE 7-16). The buildings were assumed to be all office buildings located in asevere seismic zone region, Avcilar, Istanbul. The 30 and 40 story buildings due to their total heights hadto be considered tall in line with the requirements in TEC 18. The additional requirements were alsoincluded in the analysis to understand the impact of tall buildings on the optimum shear walldetermination. Therefore, the following parameters were investigated for the optimum shear wall areato floor area ratio: (a) building periods, (b) base shear and shear forces resisted by all shear walls, and (c)maximum lateral displacements and story drifts. The impact of effective wall layout configuration onstructural behavior was also investigated by studying the 2.0% wall area ratio. The results indicated thatthe most effective ratios of shear wall area to floor area for the 20 and 30 story buildings were equal to1.5% and 2.0%, respectively. However, the need for the wall area of the 40 story building was slightlymore than 2.0%. However, as the wall layout was revised for the building with the 2.0% wall area ratio,the requirement for the wall area was nearly met indicating that the 2.0% wall area ratio could also berecommended for the 40 story building.

System Reliability Framework for Design of MSE Walls for Vertical Expansion of MSW Landfills

In the past few decades, waste generation has increased significantly in India, as well as across the globe. Therefore, to avoid the acquisition of new landfill sites, vertical expansion of existing municipal solid waste (MSW) landfills is a requirement of the present scenario. Owing to the heterogeneous nature of waste and varying degrees of decomposition in MSW, the conventional practices to calculate safety margins may not be suitable to handle the variability of the design parameters. Therefore, a system reliability framework is proposed for the optimum design of mechanically stabilized earth (MSE) retaining walls against external failure modes. The properties associated with MSW landfills, their foundation soil, and MSE walls are considered as random variables. The overturning, sliding, and bearing capacity failure modes are considered using a three-part wedge mechanism. The design charts are provided to obtain the adequate length of the reinforcement and the dimensions of the MSE wall. For satisfactory performance of the MSE wall, the minimum ratio of the length of the reinforcement to the height of the MSE wall should be 0.55 to 0.6 when an additional waste mass is placed on the existing height of the landfill.

No benefit of HDL mimetic CER-001 on carotid atherosclerosis in patients with genetically determined very low HDL levels

Background and aimsInfusion of high-density lipoprotein (HDL) mimetics failed to induce regression of atherosclerosis in recent randomized clinical trials. However, patients in these previous trials had normal levels of HDL-cholesterol, which potentially limited efficacy. Patients with very low levels of HDL-cholesterol and impaired cholesterol efflux capacity can be expected to derive the most potential benefit from infusion of HDL mimetics. This randomized clinical trial evaluated the efficacy of infusions of the HDL mimetic CER-001 in patients with genetically determined very low levels of HDL cholesterol. MethodsIn this multicenter, randomized clinical trial, we recruited patients with familial hypoalphalipoproteinemia (due to ABCA1 and/or APOA1 loss-of-function variants). Participants were randomized to intravenous infusions of 8 mg/kg CER-001 or placebo (2:1 ratio), comprising 9 weekly infusions followed by infusions every two weeks. Patients underwent repeated 3T-MRI to assess mean vessel wall area and 18F-FDG PET/CT to quantify arterial wall inflammation. ResultsA total of 30 patients with a mean age of 52.7 ± 7.4 years and HDL-cholesterol of 0.35 ± 0.25 mmol/L were recruited. After 24 weeks, the absolute change in mean vessel wall area was not significantly different in the CER-001 group compared with placebo (n = 27; treatment difference: 0.77 mm2, p = 0.21). Furthermore, there was no significant difference in carotid arterial wall inflammation (n = 24, treatment difference: 0.10 target-to-background ratio of the most diseased segment, p = 0.33) after 24 weeks. ConclusionIn patients with genetically determined very low HDL-cholesterol, 24 weeks of treatment with HDL mimetic CER-001 did not reduce carotid vessel wall dimensions or arterial wall inflammation, compared with placebo.

Exploring the fabrication limits of thin-wall structures in a laser powder bed fusion process

Although additive manufacturing (AM) is becoming increasingly popular for various applications, few studies have addressed design and potential problems in thin wall fabrication for the laser powder bed fusion (LPBF) process. In the LPBF process, rapid cooling induces thermal shrinkage, which in turn, results in high residual stress and complicates thin wall fabrication. The minimum wall thickness is limited by the parameters and machine settings while the dimensional accuracy is controlled by the powder size, scan strategy, and part geometry. The ability to fabricate thin-wall components is important for applications such as heat exchangers (HX). This study explores the performance of the LPBF process by fabricating thin walls with extreme geometries in different processing conditions and alloys using an EOS M290 LPBF machine. Results show that the material, part design, and scanning strategy contribute to the variation in thin wall dimensions. A maximum inclination angle of 60° and a minimum wall thickness of ~ 100 μm in Ti-6Al-4V, Inconel 718, and AlSi10Mg were achieved using optimized part design and processing conditions. The effects of part design and material on the thermal distortion and surface finish of thin walls were also investigated leading to a discussion on how the scan mode assigned by the EOS software affects design and fabrication. Additionally, synchrotron-based X-ray micro-tomography (μSXCT) was utilized to quantify the porosity in thin-wall structures and to correlate it with the integrity of the structures. Comprehensive design guidelines presented in this work can increase the success rate of fabricating thin-wall geometries.

Retinal and Choroidal Vasculature in Patients with Marfan Syndrome.

PurposeTo assess the retinal and choroidal vasculature in patients with genetically confirmed Marfan syndrome (MfS).MethodsThis prospective, case-control, observational study included 48 eyes of 24 patients with a genetic diagnosis of MfS and compared them with 52 eyes of 26 healthy controls. Best-corrected visual acuity, choroidal and retinal thickness measured by spectral domain-optical coherence tomography, retinal and choroidal vasculature characterized by optical coherence tomography angiography, were collected. A genetic counseling was carried out. A transthoracic echocardiogram was performed to evaluate the dimension of the aortic root, the ascending aorta and the left ventricle function and dimensions.ResultsA significant decrease in the superficial and deep retinal capillary plexi vessel density (VD) was evident, such as a decrease in the choriocapillaris plexus VD. In patients with MfS, a negative correlation between left ventricular diameter and the VD of the superficial and deep plexi was observed. Patients with MfS with greater posterior wall and interventricular septum dimensions had lower VD in both plexi (P < 0.05). Moreover, there was a negative correlation between the dimension of the ascending aorta and foveal choriocapillary VD. In patients with MfS, increasing diameter of the ascending aorta was associated with a lower foveal choriocapillary VD (P < 0.05).ConclusionsThe severity of MfS correlates with the impairment of the retinal and choroidal vasculature.Translational RelevanceOptical coherence tomography angiography may be a reproducible and noninvasive tool to study retinal blood flow in patients with MfS, with potential diagnostic and prognostic value.

Perde-Çerçeve Sistemlerde Rijitlik ve Kayma Merkezi

Binalarda burulma olması durumunda yapıya ilave deprem kuvvetleri etkimekte ve iç kuvvetler ve yer değiştirmeler artmaktadır. Bu nedenle düşey taşıyıcı sistemlerin planda mümkün olduğunca burulma etkisini azaltıcı şekilde yerleştirilmesi önemlidir. Burulma etkilerini en aza indirmek için rijitlik merkezi ile ağırlık merkezinin mümkün olduğunca yakın olması gerekmektedir. Her ne kadar mevcut deprem yönetmeliklerinin birçoğunda analiz aşamasında rijitlik merkezinin belirlenmesine ihtiyaç duyulmasa da özellikle burulma etkilerinin azaltılması açısından rijitlik merkezinin yerinin bilinmesi önemlidir. Uygulamada rijitlik merkezi ve kayma merkezi kavramları zaman zaman karıştırılmakta ve yanlış olarak bulunabilmektedir. Perde-çerçeve sistemlerde perde ve çerçevede hâkim davranışın farklı olması nedeniyle, perde ve çerçevelerin boyutlarının yapı yüksekliği boyunca sabit olması durumunda bile rijitlik merkezi kattan kata değişmektedir. Rijitlik merkezi bu tür yapılarda bazı katlarda plan dışına bile çıkabilmektedir. Bu çalışmada öncelikle rijitlik merkezi ve kayma merkezi kavramları kısaca açıklanmıştır. Daha sonra rijitlik merkezi ve kayma merkezinin bulunması için bir yaklaşım önerilmiştir. Sunulan yaklaşım literatürden alınan iki örnek üzerinde uygulanarak elde edilen sonuçlar literatür ve ETABS yazılımı ile karşılaştırılmış ve sunulan yöntemin uygunluğu gösterilmiştir.

Ячеечная модель теплопроводности в многослойной среде с переменным числом слоев

The heat conduction is an important part of heat transfer processes in power engineering, civil engineering, chemical technologies, etc. Variety of researches is devoted to theoretical and experimental study of the heat transfer by the heat conduction. At present, the considerable attention is concentrated on the heat conduction in media with variable boundaries (the so-called Stephan’s problem). A reason of a boundary motion can be burning-out of material, its wear, its melting with carry-over of a melt, other physic-chemical processes. Analytical solutions to the Stephan’s problem exist only after far-going assumptions, which lead to the loss of their practical value. The development of effective numerical methods of its solution becomes an actual scientific and practical problem. Such methods are to combine universality and physical clearness and convenience for engineering practice. In order to solve the problem, the method of mathematical modeling is used. The model uses the mathematical tools of the theory of Markov chains. It is adapted to the cell model of a medium, in which the number of cells can vary due to this or that mechanism of the edge cells interaction with outside medium. The heat transfer by the heat conduction and the heat interaction with the heat sources are described by the classical heat balance equations. The study of the influence of parameters on the process is performed by numerical methods. A mathematical model that allows describing transient heat processes in a multi-layer medium with variable number of layers is developed. The results of heat process calculation inside a plane wall with the moving boundary form the heat source side due to the boundary thermal distruction at a certain critical temperature are presented. The obtained results are physically consistent and approve the model workability. The principle differences between the heat processes in the walls with immovable and movable boundaries are found. It is shown that the temperature in a wall with moving boundary does not overbalance the critical temperature of the thermal distraction when the wall still exists, and the rate of the wall dimension decrease is growing with its dimension decrease.