Large Flaws Research Articles

Mud brick houses as a suitable alternative to emergency shelters for internally displaced persons (IDPs): evidence from Northern Syria

Purpose The purpose of this paper is to explore the feasibility of mud brick houses as an alternative to the more widely adopted emergency shelters used in war-torn Syria. It focuses on the mud houses’ sustainability, cost effectiveness, cultural preference, income generation and security. Design/methodology/approach This study uses a qualitative research approach to a single case study. Interviews were conducted with field experts from the Qatar Red Crescent Society and members of the internally displaced persons (IDPs) community living in mud brick houses. Findings The findings reveal that the utilisation of mud houses is a good alternative in relief efforts. The houses are sustainable and cost-effective, take into consideration cultural dynamics and provide economic empowerment to IDPs. However, the maintenance of mud brick houses turns out to be the largest flaw, and this problem requires further research. Originality/value The paper highlights the inefficiency of current emergency sheltering practices in Syria and reveals that tents are not a preferred mode of shelter. It further sheds light on a unique case study in which mud houses were used by an aid and development organisation, highlighting its strengths and weaknesses. This paper contributes to practical discussion and ideation on more appropriate housing for IDPs.

Dynamic strength and full-field cracking behaviours of pre-cracked rocks under impact loads

The impact loads have a significant influence on the dynamic strength and cracking behaviours of pre-cracked rocks, which plays a key role in the stability and safety of rock engineering. In this study, impact tests were performed by using a split Hopkinson pressure bar (SHPB) in conjunction with the high-speed photography technique. The dynamic strength of pre-cracked rocks under different strain rates and flaw angles was analysed, and the full-field cracking behaviours were elucidated by the evolution of strain localization zones based on the digital image correlation (DIC) analysis. By means of discrete element method (DEM), the impact tests were numerically reproduced to study the strength enhancement and the cracking processes. The results illustrate that the increase in the strain rate and flaw angle would lead to the increasing dynamic strength, the change of tensile and shear crack number is consistent with the strength variation, implying that the microcracking processes has a significant influence on the rate dependency of dynamic strength. As for the cracking behaviours, the strain localization zones would form around the flaw, and the crack branching phenomenon could be witnessed in dynamic tests. Furthermore, the complexity of cracking patterns becomes larger with the increasing strain rate, while the samples with the large flaw angle are difficult to generate strain localization zones and macroscopic cracks. By using a DIC-based method to analyse the crack initiation mechanisms, three types of stress-induced cracks were identified, i.e., mode I, II, and mixed mode I/II cracks. Among these cracks, the mode II cracks are the dominate type of cracks. Based on the mathematical analysis of Griffith model, the combined action of the tangential stress distribution and sliding deformation might be the reason for the crack initiation, and the rate-dependent strength might be induced by the increase of the maximum tangential stress regarding external stress.

Detection of interface flaws in Concrete-FRP composite structures using linear and nonlinear ultrasonics based techniques

Timely and appropriate retrofitting of existing structures holds paramount importance to ensure the structural integrity and sustainability. Fiber Reinforced Polymer (FRP) composites with high corrosion resistance, strength and durability, have been increasingly used in recent years for retrofitting of concrete infrastructure. The effectiveness of retrofitting is primarily dependent on the appropriate integrity at the interface between FRP and concrete substrate. Presence of any interface flaw can jeopardize the structural performance. In the present study, investigations are carried out to detect the early stage flaws at the FRP-concrete interface using ultrasonic waves. Artificial flaws of different size are introduced in the adhesive (epoxy) layer of carbon based FRP composite concrete beam. Rayleigh waves (at different frequencies) are generated for measuring the response from different FRP composite-concrete specimens. The specimens consist of three different types of materials, namely, concrete, epoxy and FRP. Two different input excitation frequencies, i.e., 75 KHz and 250 KHz, are tried out during the experimental investigations. The output signals are processed using different linear and nonlinear ultrasonic methods. Numerical simulations are also performed to better understand the wave signals’ interactions with the multi-layer composite medium. The results showed that the linear ultrasonic methods are not able to provide a consistent information on presence and extent of flaws. Nonlinear ultrasonic methods showed significantly better performance for characterizing both small and large flaws considered in this investigation. Sensitivity analysis reveals that relatively new and promising nonlinear ultrasonic technique, namely, the Sideband Peak Count-Index (SPC-I) performs remarkably well for detection of flaws in FRP-concrete interface.

Solving Economic Problems of Government Support as a Basis for Kyrgyzstan Agricultural Development

Research relevance: article reveals modern problems related to state support for the agricultural sector of Kyrgyzstan in the conditions of a market economy system, taking into account the application of the practice of foreign countries. Government support for agriculture is not only a solution to the problems of the agricultural sector of the economy, but also an opportunity to solve issues related to employment, the production of agricultural consumer goods, the supply of products to both domestic and foreign markets, the development of local infrastructure, and most importantly food security addressing food security issues. Research objectives: the market system of management revealed quite large flaws in agriculture, which in turn had a negative impact on the economic condition of society, which, in turn, confirms the need for government support for the further development of this industry. Today, solving the problem of state support for agriculture will eliminate negative phenomena not only in this sector, but can also positively affect the further implementation of innovative economic and social tasks of the country, such as the possibility of expanding markets for agricultural products, replenishing the relevant budgets to solve economic problems, tasks, will create an opportunity to search for new marketing channels for agricultural products, provide additional jobs, etc. Research objects are procedures for supporting the agricultural sector of the economy of the Kyrgyz Republic, as well as the processes of relations between participants in this industry. Research materials and methods: government mechanisms are analyzed that are used to support not only persons using agricultural land, but the distinctive features of agricultural producers, taking into account the positive side of the domestic practice of past years, which in turn will provide an opportunity for effective achievement. Research results: reducing the number unprofitable agricultural enterprises associated with factors such as establishing the necessary partnerships; developed mechanisms of enterprises, gradually turning into positive traditions for further actions; enterprises are gradually developing “anti-viruses” regarding external and internal factors. Conclusions: despite the stringent requirements of the market economy system and no matter how free the economic entities that carry out economic activities feel, the mechanisms of state intervention through various types of support should be permanent and targeted.

Fallen Castles in the Air: Marriage, Labor, and Suppression in Louisa May Alcott’s 'Little Women'

Suppression of one’s emotions is defined as a shared experience among the March sisters in Louisa May Alcott’s Little Women, and a large portion of women after the Civil War. Drawing on the failed careers of Jo and Amy and the struggling marriage of Meg, this essay argues that in learning how to suppress oneself and be seen as socially acceptable, the sisters lose their prospects for success and happiness. When the sisters stray from home, their flaws are exposed: Meg’s jealousy, Jo’s anger, and Amy’s greed. A return trip home and time completing labor provide them training for wifehood. Within this labor, each sister confronts their greatest desire, forcing them to contain their desires toward what they want in order to prevent another outburst. The domestic sphere becomes a place for them to come face-to-face with their largest flaw and use the home as a testing ground for how to suppress their true emotions and survive within the expectations of being a wife. In stifling their ambitions and desires outside the domestic sphere through suppression training, the March sisters lose the prospects for unhappy marriages with men that continuously inflame their flaws through belittling behavior and condemnation.

In-situ detection of redeposited spatter and its influence on the formation of internal flaws in laser powder bed fusion

The pervasive adoption of laser powder bed fusion (LPBF) as an industrial manufacturing technique relies on the improvement of its repeatability, currently limited by the stochastic formation of flaws. Considering that large flaws can form randomly and despite the optimization of process parameters, an in-situ monitoring technique suitable for detecting deviations that originate these critical flaws is paramount. The redeposition of spatters on the build area has previously been identified as one of the factors responsible for the rise of internal flaws, but so far limited are the efforts towards their detection. This study aims to detect spatter redeposits via in-situ monitoring and to couple the detections to lack of fusion. For that, long-exposure near-infrared in-situ monitoring associated with image analysis is employed to determine the exact locations and quantify the incidence of spatter redeposits across three full builds performed at varying layer thicknesses. The existence and distribution of internal flaws is verified ex-situ by means of ultrasonic inspection and metallography. The formation of internal flaws is attributed to spatter redeposits after detailed characterization of size, particle and surface morphology of spatter and identification of particles with identical characteristics on the fracture surface in the adjacencies of lack of fusion. It is found that spatters preferentially redeposit on the adjacencies of the gas outlet, but that the affected portion of the build area and the prevalence of detections is heavily dependent on the powder layer thickness employed in the manufacturing process. The monitoring system setup preferentially acquires signal from spatters redeposited on print regions, making it particularly suitable for flaw detection.

Superior robustness of anomalous non-reciprocal topological edge states

Robustness against disorder and defects is a pivotal advantage of topological systems1, manifested by the absence of electronic backscattering in the quantum-Hall2 and spin-Hall effects3, and by unidirectional waveguiding in their classical analogues4,5. Two-dimensional (2D) topological insulators4–13, in particular, provide unprecedented opportunities in a variety of fields owing to their compact planar geometries, which are compatible with the fabrication technologies used in modern electronics and photonics. Among all 2D topological phases, Chern insulators14–25 are currently the most reliable designs owing to the genuine backscattering immunity of their non-reciprocal edge modes, brought via time-reversal symmetry breaking. Yet such resistance to fabrication tolerances is limited to fluctuations of the same order of magnitude as their bandgap, limiting their resilience to small perturbations only. Here we investigate the robustness problem in a system where edge transmission can survive disorder levels with strengths arbitrarily larger than the bandgap—an anomalous non-reciprocal topological network. We explore the general conditions needed to obtain such an unusual effect in systems made of unitary three-port non-reciprocal scatterers connected by phase links, and establish the superior robustness of anomalous edge transmission modes over Chern ones to phase-link disorder of arbitrarily large values. We confirm experimentally the exceptional resilience of the anomalous phase, and demonstrate its operation in various arbitrarily shaped disordered multi-port prototypes. Our results pave the way to efficient, arbitrary planar energy transport on 2D substrates for wave devices with full protection against large fabrication flaws or imperfections.

An enzymatic self-healing cementitious material

Concrete is the most widely used material in the world and is responsible for 8% of global carbon emissions. It is inherently brittle, and it requires frequent repair or replacement, which are expensive and generate large volumes of CO2. Current methods of repair by agents such as mortar and epoxies result in structures with reduced strength and resiliency due to material mismatch, therefore, a self-healing cement paste (concrete’s main matrix) is needed to overcome this problem. The leading self-healing mechanism is based on the use of bacteria and microbes, which are slow and have limited applications, as well as unknown health effects. Inspired by the extremely efficient process of CO2 transfer in biological cells, this study introduces a method to develop a self-healing mechanism in a cementitious matrix using trace amounts of the enzyme Carbonic Anhydrase (CA). CA catalyzes the reaction between Ca2+ ions and atmospheric CO2 to create calcium carbonate crystals with similar thermomechanical properties as the cementitious matrix. The crystal growth rate using this method is orders of magnitude faster and more efficient than bacterial methods, resulting in the healing of large flaws on timescale orders of magnitude shorter. This method is capable of self-healing samples with millimeter-scale flaws within 24-hours and is significantly faster than all current methods that need a minimum of 28-days for strength recovery of microscale cracks. This inexpensive method is biologically safe, actively consumes CO2, and avoids using unhealthy reagents. It can be an efficient mechanism to repair and strengthen the existing concrete structures.

Fitness-for-purpose assessment of cracked offshore wind turbine monopile

In this paper, the procedure for flaw acceptability assessment is examined through a case study of a semi-elliptical surface crack in an offshore monopile as it grows till it forms a through thickness crack. Using the procedure prescribed in an industrial standard (BS 7910), the fracture ratio, Kr is shown to increase monotonically with increasing crack depth. The load ratio, Lr, is initially insensitive to the crack depth. However, there is a rapid increase in Lr when the crack depth to thickness ratio exceeds 80%. Lr values obtained from detailed 3D FE limit analysis using elastic-perfectly-plastic material behaviour do not exhibit the asymptotic behaviour predicted by BS 7910 as the flaw transitions from deep crack to through-thickness crack. Furthermore, Kr predicted by BS 7910 is shown to be an over-estimation for the typical dimensions of offshore monopiles. The findings suggest that a structure with a deep flaw may be identified as unacceptable based on BS 7910 when it may still possess a non-trivial amount of structural residual life. This is a concern for monopiles where crack growth as a large flaw forms a significant part of the total life.

Toward in-situ flaw detection in laser powder bed fusion additive manufacturing through layerwise imagery and machine learning

Process monitoring in additive manufacturing may allow components to be certified cheaply and rapidly and opens the possibility of healing defects, if detected. Here, neural networks (NNs) and convolutional neural networks (CNNs) are trained to detect flaws in layerwise images of a build, using labeled XCT data as a ground truth. Multiple images were recorded after each layer before and after recoating with various lighting conditions. Classifying networks were given a single image or multiple images of various lighting conditions for training and testing. CNNs demonstrated significantly better performance than NNs across all tasks. Furthermore, CNNs demonstrated improved generalizability, i.e., the ability to generalize to more diverse data than either the training or validation data sets. Specifically, CNNs trained on high-resolution layerwise images from one build showed minimal loss in performance when applied to data from an independent build, whereas the performance of the NNs degraded significantly. CNN accuracy was also demonstrated to be a function of flaw size, suggesting that smaller flaws may be produced by mechanisms that do not alter the surface morphology of the build plate. CNNs demonstrated accuracies of 93.5 % on large (>200 μm) flaws when testing and training on components from the same build and accuracies of 87.3 % when testing on a previously unseen build. Finally, evidence linking the formation of large lack-of-fusion defects to the presence of process ejecta is presented.

Tạo hình khuyết hổng bằng vạt SCIP sau phẫu thuật cắt nửa lưỡi do ung thư tại bệnh viện trung ương huế cơ sở 2: nhân 1 trường hợp

Objective: This study to evaluate the effectiveness of superficial circumflex iliac artery perforator (SCIP) flap in reconstruction after hemiglossectomy due to cancer. Method: The author reports a clinical case using SCIP flap to reconstruct tongue of the patient with half-tongue defects after tongue cancer surgery at Oncology-Palliative care Department of Hue Central Hospital branch 2. Result: The patient did not have accumulating of liquid, wound infection and bleeding after surgery, the flap survived well. The patient was taken nasogastric tube out after ten days and discharged after two weeks. Postoperative functional assessments (speech, swallowing) as well as aesthetic of tongue (symmetry) have significant improvement over the 1 month, 3 months and 6 months. Conclusion: SCIP flap is a choice for the patients with large flaws at tongue and floor of the mouth. It ensures both functional and aesthetic for the regenerative tongue and donor-site. The disadvantage of the flap: the length of the flap is moderate, the diameter of the arteries and veins is small.

Strain localization and cracking behavior of sandstone with two gypsum-infilled parallel flaws

The infilled flaws within rocks significantly influence the mechanical behavior of non-through flawed rocks. To investigate the influence of infilling on strain localization in the pre-cracking, cracking and cracking coalesce stages, experimental and numerical investigations were conducted on sandstone containing two gypsum-infilled parallel flaws, but of different flaw geometric configurations. The full-field strain evolution and progressive cracking process are analyzed using the acoustic-optical-mechanical methods, while the stress evolution and stress transfer by infilling were studied by the particle flow code modeling. The results show that the major principal strain of flawed sandstone with infilling changes from the diffused ellipse to highly localized linear strip with the increase of loading level, while the shear strain keeps a diffused ellipse shape invariable. The shear strain localization of infillings with a large flaw inclination initiates at a lower loading level than that of small one. The peak strength and Young’s modulus of flawed sandstone show a first decrease, then increase and finally decrease trend with the ligament angle increasing from 0° to 150°, and both achieve their minimums at 60°. Ten types of cracks were observed, and four patterns of crack coalescence were identified. By comparison with sandstone of open flaws, the flaw infilling simplifies the geometric pattern of produced crack networks, which is quantitatively characterized by fractal dimension analysis. The numerical modeling shows that the infilling enlarges the compressive bond force zone and decreases the tensile bond force zone in the surrounding areas of pre-existing flaw, thus increasing the reinforcement coefficient. Moreover, the flaw geometric configuration has a significant influence on the reinforcement coefficient. It is also found that the increment of reinforcement coefficient defined by crack initiation stress is greater than those defined by either crack coalescence or peak stresses.

Practical strength of damage-resistant CaO–Al2O3–SiO2 glass-ceramic

The strength of glass depends on the size of flaws existing on its surface. Therefore, its strength considerably deteriorates once a large flaw is generated upon contact with harder materials. Such mechanical failure renders the glass unreliable, which can cause severe problems in practice. In this work, the damage resistance of CaO–Al2O3–SiO2 (CAS) glass-ceramic (GC) was evaluated through bending tests. The test was conducted using abraded samples with conventional soda–lime–silica (SLS) glass as a reference. Although the strength of the SLS glass decreased to less than 50 MPa after abrasion, CAS-GC maintained an average strength of 100 MPa with a higher Weibull distribution number. Large sharp flaws, which act as a stress concentrator, were not observed in CAS-GC. This observation was consistent with the microcrack formation instead of the radial crack around Vickers indentation in CAS-GC.

О качестве советской военной продукции в период Великой Отечественной войны (1941–1945 гг.)

<span>Автором предложен методологический подход к оценке качества советской военной продукции в период Великой Отечественной войны, который включает три взаимосвязанные характеристики сравнимых по своему назначению «военных машин»: конструктивно-технические, производственно-технологические и эксплуатационные. Показаны достоинства и недостатки работы отделов технического контроля и военной приемки на предприятиях военно-промышленного комплекса СССР и оценен риск проникновения в действующую армию изделий со скрытым производственно-технологическим браком</span><span class="myHorizontalScaleForEmDashSpaceBefore"> </span><span>–</span><span class="myHorizontalScaleForEmDashSpaceAfter"> </span><span>наиболее высокий для авиационной и бронетанковой промышленности и промышленности боеприпасов. Доказывается, что по совокупности выделенных критериев качества советское стрелковое и артиллерийско-минометное вооружение по сравнению с аналогичными видами вооружений противника не было ни ущербным, ни превосходящем его. Тогда как качество советской авиационной и бронетанковой техники характеризуется большими и малыми конструктивными недостатками, нестабильностью (особенно в начальный период войны) производственно-технологического процесса и низкими, по сравнению с аналогичной военной техникой противника, эксплуатационными возможностями (моторесурс). Отставание в качестве военной техники приходилось уравновешивать большим количеством сравнительно недолговечных в эксплуатации и более дешевых в изготовлении «военных машин», из-за чего некоторые из них, например, самолеты-штурмовики Ил-2, становились изделиями «одноразового использования».</span>

Simulation and Visual Tester Verification of Solid Propellant Slurry Vacuum Plate Casting

AbstractUsing an improved Carreau constitutive model, a numerical simulation of the casting process of a type of solid propellant slurry vacuum plate casting was carried out using the Flow3D software. Through the flow process in the orifice flow channel and the combustion chamber, the flow velocity of the slurry passing through the plate flow channel was quantitatively analyzed, and the viscosity, shear rate, and leveling characteristics of the slurry in the combustion chamber were qualitatively analyzed and predicted. The pouring time, pouring quality, and flow state predicted by the numerical simulation were verified using a visual tester consisting of a vacuum plate casting system in which a pouring experiment was carried out. Studies have shown that HTPB three‐component propellant slurry is a typical yielding pseudoplastic fluid. When the slurry flows through the flower plate and the airfoil, the fluid shear rate reaches its maximum value and the viscosity of the slurry decreases. The visual pouring platform was built and the experiment was controlled according to the numerically‐calculated parameters, ensuring the same casting speed. The comparison between the predicted casting quality and the one obtained in the verification test resulted in an error less than 10 %. Moreover, the error between the simulated casting completion time and the process verification test result was also no more than 10 %. Last, the flow state of the slurry during the simulation was consistent with the one during the experimental test. The overall leveling of the slurry in the combustion chamber was adequate and no relatively large holes and flaws developed during the pouring process.

A Questionnaire Analysis on the Status Quo of Contemporary College Students’ Ideological and Political Quality

This article compiles a questionnaire from the three dimensions of “political literacy”, “ideological ethics” and “mental health”. The survey finds that the university is living in the problems of large individual differences in political literacy, individual ideological and moral flaws, and low levels of mental health. The author proposes that in terms of concepts, the intensity of education in the critical period of ideological and political education for college students should be increased; in terms of ways, the educational function of ideological and political courses and the ideological and political theories teaching in all courses need to be integrated; in terms of content, the life and context of ideological and political education content should be promoted; in terms of methods, a diversified strategy system of ideological and political education that is experiential, verification, and generative should be adopted.

Experimental Study on Cracking Behaviour of Intermittent Double S-shaped Fissures under Uniaxial Compression

Extensive efforts have been made in the understanding of the failure characteristics of straight fissure, but the failure patterns of rock mass with intermittent non-straight fissures have not been examined comprehensively. To address this problem, the present study investigated the cracking behaviors of natural marble specimens containing double S-shaped fissures under compression. Seven types of coalescence patterns for S-shaped fissures are classified, two of which are firstly reported and featured by the occurrence of the self-coalescence phenomenon. It is found that the decrease of strength is accompanied by the internal crack at the stage of crack growth and propagation, following the occurrence of the external crack, at relatively large flaw and ligament angle. The numerical simulations with the corresponding parameters were carried out for comparison. This research provides helpful information for understanding the failure modes induced by crack propagation of intermittent double S-shaped fissures.

Determination of ceramic flaw populations from component strengths.

A procedure is outlined for determining the population of flaws in manufactured ceramics from strength measurements of sampled components. The broad applicability of the procedure is demonstrated in a quantitative manner, using strength measurements from a range of ceramic materials (eg, glass, glass-ceramic, single crystal, and polycrystal) with different flaw types (eg, bulk, surface, and edge). The deconvoluted flaw populations are mostly dominated by small flaws with extended large flaw tails and are all in domains of tens of micrometers. The procedure greatly extends the useful information to be gained by ceramics manufacturers and designers from strength distribution measurements and emphasizes the importance of identifying strength-limiting characteristics within a flaw population.

Experimental Investigation on Failure Modes and Mechanical Properties of Rock‐Like Specimens with a Grout‐Infilled Flaw under Triaxial Compression

Flaws existing in rock mass are one of the main factors resulting in the instability of rock mass. Epoxy resin is often used to reinforce fractured rock mass. However, few researches focused on mechanical properties of the specimens with a resin‐infilled flaw under triaxial compression. Therefore, in this research, epoxy resin was selected as the grouting material, and triaxial compression tests were conducted on the rock‐like specimens with a grout‐infilled flaw having different geometries. This study draws some new conclusions. The high confining pressure suppresses the generation of tensile cracks, and the failure mode changes from tensile‐shear failure to shear failure as the confining pressure increases. Grouting with epoxy resin leads to the improvement of peak strengths of the specimens under triaxial compression. The reinforcement effect of epoxy resin is better for the specimens having a large flaw length and those under a relatively low confining pressure. Grouting with epoxy resin reduces the internal friction angle of the samples but improves their cohesion. This research may provide some useful insights for understanding the mechanical behaviors of grouted rock masses.

Treatment of reliability in fracture assessments using BS 7910 Annex K

This paper presents the background to the development of Annex K (‘Probabilistic assessment’) of BS 7910:2013, in particular the use of Partial Safety Factors (PSFs) in fracture assessment. These were originally derived using Probabilistic Fracture Mechanics (PFM) calculations, and in principle allow the user to estimate the probability of failure (Pf) associated with a deterministic fracture assessment simply by dividing (or multiplying) the inputs by a series of PSFs given in look-up tables.Calculations carried out using modern PFM software have shown that the PSFs given in Annex K are appropriate only for a narrow range of fracture scenarios, reflecting the conditions used to derive the PSFs in the first place – namely, thick-section plates with low fracture toughness and large through-thickness flaws. The use of Annex K tends to over-estimate Pf for other situations, and the use of direct PFM calculations is preferable where possible. The implications for the next revision of BS 7910 are discussed.