Defects In Walls Research Articles

A non-destructive test method for assessment of cement-sand mortar quality on blockwalls finishes: A short-cut method for achieving acceptance criteria

Monitoring quality of cement-sand mortars used for plastering/rendering masonry surfaces has not been given utmost attention thereby adversely encouraging damp rising and other defects in walls. An attempt is made in this paper to propose a methodology for monitoring the quality of mortars using non-destructive testing method. It enables categorization of the quality of mortar mixes for making decision on acceptance criteria for short-term and long-term strengths of the composite mixture. Firstly, a factorial experimental design using the Central Composite Design (CCD) was used, to design the mix and compressive strengths at 28-day was obtained within the design domain considered. Secondly, a hardness test using the Mohs’ hardness scale was used on both the laboratory specimens and field tests on plastered walls of some selected housing estates. The method clearly exhibited defect patterns on the blockwall finishes which are closely related to the quality of the mix which also varied based on heights above ground level. The Mohs’ hardness test has proven to be a reliable non-destructive test method which can be used to reveal quality and categorization of cement mortar mix used on blockwall finishes. Consequently, the upper bound mix with ratio 1:4 cement to sand mortar remains a reliable mixture proportion based on the scale of hardness and strength performance both in the short-term and long-term values measured. This method would enable a reward system measurement/assessment on contractors and consultants on various building projects.

Depth super-resolved imaging of infrastructure defects using a terahertz-wave interferometer

We present a depth super-resolved 3D imaging method for inspection of defects in walls using terahertz swept-source optical coherence tomography. A depth profile analysis based on an annihilating filter method with noise reduction was applied for signal processing, and the results were compared with those of conventional inverse fast Fourier transform (IFFT) analysis. To evaluate the depth resolution, we measured a plastic step sample with 1 mm thickness, and its front and back surfaces were discriminated. This is corresponding to about 1/3 of the theoretical depth resolution of the conventional IFFT analysis. Moreover, we demonstrated 3D imaging of the void with a 10 mm width behind a ceramic tile and succeeded in reconstructing a significantly sharper cross-sectional void image than in the conventional analysis.

The Analysis of the Influence of Various Factors on the Development of Stress Corrosion Defects in the Main Gas Pipeline Walls in the Conditions of the European Part of the Russian Federation

This paper considers the factors influencing the formation and development of stress corrosion defects detected during the inspection and overhaul of the main gas pipeline section. The surveyed gas pipeline is made of large diameter steel pipes made by controlled rolling, produced by various companies, with the predominance of pipes produced by the Khartsyzsk Pipe Plant (KhPP). The correlation between the geometric parameters of defects is described, which makes it possible to estimate the depth of cracks by external parameters. Mechanical tests by cyclic loading of samples containing cracks, based on the site operation data for the last 11 years, showed no crack growth in the absence of a corrosive medium. Micro-X-ray spectral analysis of metal and corrosion products showed no trace of the influence of hydrogen sulphide and nonmetallic inclusions (sulphides) on the development process of SCC. According to the results of the research, the process of development of stress corrosion on the main gas pipelines located in the European part of the Russian Federation is described. The organization operating the gas pipeline is recommended to take into consideration the results of this work during drawing up their repair plan.

Immobile defects in ferroelastic walls: Wall nucleation at defect sites

Randomly distributed, static defects are enriched in ferroelastic domain walls. The relative concentration of defects in walls, Nd, follows a power law distribution as a function of the total defect concentration C: Nd∼Cα with α=0.4. The enrichment Nd/C ranges from ∼50 times when C = 10 ppm to ∼3 times when C = 1000 ppm. The resulting enrichment is due to nucleation at defect sites as observed in large scale MD simulations. The dynamics of domain nucleation and switching is dependent on the defect concentration. Their energy distribution follows the power law with exponents during yield between ε∼1.82 and 2.0 when the defect concentration increases. The power law exponent is ε≈2.7 in the plastic regime, independent of the defect concentration.

Electrostatic force microscopy evaluation of the conductivity of individual multiwalled carbon nanotubes

The electric conductivity of individual multiwalled carbon nanotubes (CNTs) doped with nitrogen has been studied in as-synthesized, heat-treated, and argon-ion-irradiated states by the method of electrostatic force microscopy (EFM). Modelling of transverse cross-section profiles of EFM images were used to determine the potential difference across the probe tip–CNT gap (Utip-CNT), which is a parameter related to the conductivity of CNTs. A strong correlation between the specific volume conductivity of a CNT layer and average Utip-CNT value has been found for all types of samples. It is established that a change in the conductivity of N-doped CNTs upon thermal annealing and argon-ion irradiation is caused by modification of the composition and/or concentration of defects in CNT walls.

Application of RBF Neural Network and Finite Element Analysis to Solve the Inverse Problem of Defect Identification

This paper presents an approach which is based on the use of radial basis function (RBF) neural network and finite element analysis to solve the inverse problem of defect identification. The approach is used to identify unknown defects in metallic walls. The methodology used in this study consists in the simulation of a large number of defects in a metallic wall, using the finite element method (FEM). Both variations in with and height of the defects are considered. Then the obtained results are used to generate a set of vectors for the training of a RBF neural network. Finally, the obtained neural networks are used to identify a group of new defects, simulated by the FEM, but not belonging to the original dataset. Performance of the RBF network was also compared with the most commonly used multilayer perceptron (MLP) network model. The reached results demonstrate the efficiency of the proposed approach, and that RBF network performs better than MLP network model

Why Do We Not Need CT in Patients Who Undergo Type I Tympanoplasty?

Introduction Since its advent in the 1980s, high-resolution computed tomography (HRCT) of the temporal bone has played an important role in the evaluation of chronic otitis media (COM) (1). It provides a detailed assessment of complex bony structures of the middle ear and mastoid cavity; thus, surgeons can visualize the extent of disease, status of the ossicular chain, presence of bony erosion, or existing cholesteatoma prior to surgery (2, 3). HRCT has gained wide acceptance in the diagnostic workup of suppurative COM. Most ear surgeons order HRCT to make a rational operative plan, especially in the presence of symptoms, such as refractory otorrhea with bad odor, epithelial debris at retraction pockets, and defects in bony walls of the middle ear. Previous studies showed contradictory results with regard to the sensitivity and specificity of the preoperative HRCT scan. A preoperative HRCT scan was suggested to underestimate the actual pathology in the middle ear and was unreliable in some of the articles (4, 5). The study group in those studies included patients with diverse clinical findings and different surgical plans, including tympanomastoidectomy or open cavity mastoidectomy. This diversity of patient groups may cause certain shortcomings in the assessment of the necessity for preoperative HRCT. It is a common belief that preoperative HRCT is not necessary in patients with dry perforation and mild hearing loss in the absence of destructive middle ear pathology. But, unfortunately, few surgeons insist on ordering HRCT prior to tympanoplasty in their daily practice. This malpractice leads patients to exposure to avoidable radiation. Although there is almost a consensus that HRCT prior to surgery is unnecessary in these patients, it has not been proven yet objectively. Thus, we aimed to show the lack of necessity of preoperative HRCT by assessing its predictive value in patients who undergo type I tympanoplasty. Methods This retrospective study with data collection was conducted at department of Otolaryngology in Uludag University. The study group was selected from patients who underwent tympanoplasty with or without ossicular reconstruction with a diagnosis of chronic otitis media between August 2010 and February 2013. The inclusion criteria were as follows: i) presence of tympanic membrane perforation, ii) no refractory ear drainage, iii) dry ear for at least 3 months, iv) no cholesteatoma on microotoscopic examination, and v) no bony erosion or retraction pocket. At our institution, we certainly do not order preoperative CT in patients who undergo type I tympanoplasty. However, we have other patients who were referred by other colleagues for surgery with a prior HRCT. We had 43 patients who fulfilled the aforementioned criteria with a prior HRCT in the study group. The mean age of the study group was 32.44±13.78 77

Определение причин разрушения материалов кирпичной кладки на участках фасадов строящихся зданий жилого квартала в микрорайоне «Октябрьский» г. Новочеркасска Ростовской области.

IThis article discusses the problem related to the appearance of defects in masonry cladding layer self-supporting walls of buildings with monolithic concrete frame for example inspection of buildings under construction of residential quarters in the October district of Novocherkassk. As a result of the survey by OOO "STC" identified and described the characteristic defects in the veneering layer self-supporting walls of buildings and identify their causes. Based on the experience of experts, instrumental studies of structural materials, conducted by a certified testing laboratory in materials survey gives an overview of the causes of defects are manifestations of research of other spe-cialists and organizations leading of which is CNIISK. VA Kucherenko. According to the results of the system analysis of detected defects and data instrumental studies, the authors proposed solutions to eliminate the defects and bring the building up to standard.

XANES Investigation of Pristine and Fluorinated Single-Walled Carbon Nanotubes Before and After Annealing

X-ray absorption near-edge structure (XANES) spectroscopy has been used for comparative investigation of the electronic structure of pristine and fluorinated single-walled carbon nanotubes (SWCNTs) before and after annealing. The SWCNTs were produced by catalytic chemical vapor deposition method and fluorinated using a gaseous mixture of BrF3 and Br2 at room temperature. The samples were annealed at 250°C for 0.5 hour directly in the vacuum chamber of the X-ray spectrometer. C K-edge XANES spectra showed increase in the π* resonance intensity after the treatment of as-produced and fluorinated SWCNTs that was attributed to the detachment of adsorbed molecules and defunctionalization of nanotubes with the heating. Furthermore, analysis of the spectra revealed the annealing of the SWCNT samples produces topological defects in the nanotube walls.

Bolt‐and‐Nut Pairs Made from Carbon Nanotubes with Artificial Defects

Structures of double‐wall carbon nanotubes (DWNTs) with atomic scale defects that can operate as bolt‐and‐nut pair are analyzed. The relative thread depth for such bolt‐and‐nut pair is calculated for various types of defects in inner and outer walls of (4,6)@(12,8) and (8,2)@(16,4) DWNTs. It is found that a type of defect determines only the absolute thread depth but weakly influences on the relative thread depth. Possibility of producing of the DWNT (which can operate as bolt‐and‐nut pair) by self‐organization is proposed.

Identification of weak spots in the sound insulation of walls using a spherical microphone array

A beamforming microphone array can be useful for the identification of directions of arrival of stronger components of the sound field. When these directions can be traced back to locations in the room containing the array, they can indicate the source of the detected sound. A previously developed spherical array [J. Acoust. Soc. Am. 112, 1980–1991 (2002)] has been used for the identification of localized weak spots in otherwise highly insulating walls. A sound source and the array were placed on opposite sides of a wall sample constructed between two reverberation rooms. The omnidirectional impulse response was measured to each of the 32 array microphones, and subsequent beamforming resulted in 60 directional impulse responses at the array position, distributed over all directions. This set of responses was analyzed to identify directions of peak sound transmission through the wall. The walls tested had STC ratings greater than 50, intentionally modified to contain weak spots or defects, most not severe enough to affect the STC. The results obtained with the array approach were compared to a brute force scan with a microphone located 0.25 m from the wall. The array approach was capable of detecting even minor defects in walls.

Machining of simulated defects in pipeline steels: A neutron diffraction study of local stress effects

The most commonly used in-line pipeline inspection tools utilize the magnetic flux leakage (MFL) technique, which is sensitive to the stress state of the pipe wall. Calibration of these MFL tools is often carried out using unstressed pipeline sections containing simulated defects, usually produced by mechanical drilling. There is also strong interest in creating simulated defects in stressed pipe walls, thus simulating corrosion in the field. In this study, neutron diffraction is used to map the local stresses surrounding mechanically and electrochemically drilled holes in a steel plate sample. Holes were drilled in unstressed samples, as well as samples held at a constant 80 MPa uniaxial stress. Mechanical drilling into a stressed sample was found to induce considerable residual stresses around the hole. Conversely, electrochemical drilling did not create a residual stress field in the vicinity of the hole.

Domain defects in strings and walls.

A type of model is considered where the Witten mechanism allows the breaking of a discrete symmetry within the core of a cosmic string or a domain wall. The formation of a real scalar field condensate results in the creation of different, but energetically degenerate, domains which are separated by massive domain defects. The defects within strings (domain kinks) are particlelike states, whereas the defects within walls (domain ribbons) resemble stringlike states. Relativistic kink-antikink pairs annihilate after their initial formation, with the release of boson radiation, and kink-antikink pairs can be created through string intercommutations. Ribbons and antiribbons can be either infinite in extent or form closed loops. Ribbon loops can be involved in fission or fusion processes producing boson radiation, and oscillating ribbon loops decay mainly through the production of boson radiation, with a negligible fraction of the released energy being emitted in the form of gravitational radiation.

Bladder Mucosal Grafts: Experiments with Allografts in Repairing Bladder Wall Defects

Free patch grafts of bladder mucosa and underlying lamina propria have been used to cover large defects in canine bladder walls. Both autografts and allografts were successfully transferred. Sex chromatin studies showed the final urothelial covering was from the recipient and not the donor bladder.

Stresses in the neighborhoods of defects in bunker walls

During laboratory and full-scale studies of loads on the protecting surfaces of structures for storing and reworking bulk materials, the requirement to set up pressure gauges during their construction has been firmly maintained. This requirement has been demanded on the basis of numerous experimental data, which indicate that during discharge of bulk materials, the gauges, whose measuring surfaces have been submerged even to an insignificant amount in the adjusting recess, will register pressures that are substantially higher than in the cases where the surfaces of these same gauges project into the bunker or silo, or lie in the plane of their protecting surfaces [i, 2]. These facts have served as a basis for the conclusion that submerged gauges register some value which does not reflect the true picture of the stresses at the contact between the bulk material and the construction; the true stress values may only be obtained when the set-up of the measuring areas is flush with the wall (or insignificantly projecting inwards), and therefore, in all cases, the areas must be arranged in just this way. The reasons for the "irregular" readings of buried gauges still remain uncertain. Such a situation cannot be accepted because the position involved during measurements of buried areas has a purely practical aspect.