Opening Width Research Articles

Study of cervico-oral synergies in patients undergoing orthodontic treatment

Introduction. The use of orthodontic treatment is becoming more and more common in the modern world. At the same time, it becomes acute to develop methods for identifying patients with an increased risk of undesirable side effects of treatment (pain, dysfunction of the temporomandibular joint, root resorption, etc.). The aim of the study is to investigate cervical-oral synergies in patients undergoing orthodontic treatment and compare it with their osteopathic status.Materials and methods. 154 patients examined by an orthodontist were selected for the study and divided into 2 groups: Norm and Dyskinesia — according to the difference in the mouth opening width (the opening width in the extensional position minus the width in the neutral position of the head, E–N). The mouth opening width was measured by a caliper with thin lips. The Norm group included 86 people with a positive E–N difference, and the Dyskinesia group included 68 with a negative E–N difference. The patients age was the same in both groups (p>0,05). There were 31 % of men in the Norm group, and 16 % in the Dyskinesia group. In both groups, the angle of neck extension with open and closed mouth was measured, and the osteopathic status was assessed. At the same time, the osteopathic physician did not know which group the patients belonged to.Results. The groups differed signifi cantly by the difference of the width mouth opening (p<0,000001), and it indicates the correctness of the choice of this sign for the groups separation. The absolute value of the mouth opening width in the neutral position did not differ statistically signifi cantly between the groups, and it was slightly below the norm of 49–50 mm (42 mm in the Norm group and 39 mm in the Dyskinesia group). The difference in the extension of the cervical spine with an open and closed mouth was also calculated (the angle of extension with an open mouth minus the angle of extension with a closed mouth). A statistically signifi cant difference between the groups was obtained (p<0,0001). Absolute values of neck extension did not differ statistically signifi cantly in the two groups. During the osteopathic examination, there was found a statistically signifi cant (p<0,05) difference of the detection frequency of the following somatic dysfunctions (SD): SD of the neck region, the somatic component, in the Norm group in 34,1 % and in the Dyskinesia group in 57,4 %; as well as global SD: in the Norm group there were diagnosed only in 3,5 %, and in the Dyskinesia group — in 14,7 %.Conclusion. Thus, patients with a negative E–H difference (the Dyskinesia group) differ statistically signifi cantly from patients with a positive E–H difference in the difference of the movements′ volume in the neck, and by the set of somatic dysfunctions. The osteopathic status of these patients may cause a disorder of cervical-oral synergies. The measuring the width of the mouth opening in different positions of the head and calculating the difference in E–H could be used as an indicator that the patient needs correction of somatic dysfunctions during orthodontic treatment. It is planned to further study these synergies in relation to the practice of a dentist.

IDENTIFIKASI SIFAT FISIOLOGIS DAN PRODUKSI TANAMAN JAMBU METE PADA KETINGGIAN TEMPAT BERBEDA DI KOTA BAUBAU, SULAWESI TENGGARA

[IDENTIFICATION OF PHYSIOLOGICAL AND PRODUCTION PROPERTIES OF CASHEW AT DIFFERENT ALTITUDE IN BAUBAU CITY, SOUTHEAST SULAWESI]. Identification of physiological properties and production of cashew plants are very important to know as a reference for the community in managing cashew plants in Baubau City. The aim of this study was to identify the physiological properties and production of cashew at different altitudes in Baubau City Southeast Sulawesi Province. This research was conducted by survey method. The Samples observed were 10 plants that had productive age, which were about 20 years old per different altitude and came from farmers’ garden in Baubau City. The research was carried out through several stages namely the preparation stage, sampling, laboratory analysis and field observations. The plant variables observed were chlorophyll content, nitrate reductase activity, stomata density, stomata opening width, average production per tree, average production per hectare and weight of cashew nuts. The observational data were analyzed using analysis of variance with confidence level 5 % and if a significant difference was obtained between treatments, it was continued with Duncan’s Multiple Range Test. The result showed that the difference in altitude significantly affected the physiological properties and production of cashew in Baubau City. Physiologically, the research location with an altitude of 0-500 masl has higher chlorophyll content, nitrat reductase activity and stomata density than cashew platnts at locations >1000 masl. While in terms of crop production, the research location with an altitude of 500-1000 masl has a higher average production per hectare than cashew plants at locations 0-500 masl and >1000 masl.

USING COMPOSITE PLASTICS FOR RESTORATION OF DAMAGED REINFORCED CONCRETE STRUCTURES

A method is proposed to restore the operational suitability of bent reinforced concrete structures with increased deflections and excessive crack opening. Modern methods of reinforcement by surface gluing composite fibro-reinforced plastics (FRP) on the stretched zone of exploited reinforced concrete structures increase the strength and rigidity of reinforcing elements, but do not reduce deflections and the width of crack opening. To restore the operational suitability of damaged reinforced concrete structures, a preliminary stress is proposed, which is used to strengthen FRP, which is provided by the creation of a temporary construction lift in the damaged elements.

Influence of fixed titanium plate position on the effectiveness of open-door laminoplasty for cervical spondylotic myelopathy

BackgroundDuring open-door laminoplasty, the position of the bone gutter is not fixed, and when the gutter migrates inward, the outer end of the titanium plate must be fixed on the lamina edge. It is unclear whether this will affect the clinical efficacy. This study aimed to observe the influence of the titanium plate fixation position on the effectiveness of open-door laminoplasty for cervical spondylotic myelopathy (CSM).MethodsA total of 98 patients with CSM who underwent open-door laminoplasty from August 2016 to October 2019 were included in this retrospective study. Fifty-five patients had the titanium plate fixed on the lateral mass (lateral mass group), and 43 patients had the titanium plate fixed on the lamina edge (lamina group). The opening angle, opening width, occurrence of hinge fracture, spinal cord drift distance, cervical curvature index (CCI), neurological function recovery (JOA score), neck function (NDI), C5 palsy and severity of axial symptoms were observed and compared between the two groups.ResultsThe opening angle in the lamina group was significantly larger than that in the lateral mass group, while the opening width and the spinal cord drift distance were significantly smaller than those in the lateral mass group (P < 0.05). The occurrence of hinge fracture in the lamina group was significantly higher than that in the lateral group (25.6% and 9.1%, respectively) (P < 0.05). The CCI was maintained well in both groups (P > 0.05), and there was no significant difference between the groups (P > 0.05). After surgery, the JOA score significantly increased in both groups (P < 0.05), and the neurological recovery rates were similar between the two groups (62.6% vs. 64.5%). The NDI score significantly decreased in both groups (P < 0.05), but the lateral mass group recovered to a greater degree than the lamina group (P < 0.05). The occurrence of C5 palsy was 2.3% in the lamina group and 14.5% in the lateral mass group, and there was a significant difference between the groups (P < 0.05). Postoperative axial symptom severity was significantly worse in the lamina group than in the lateral mass group (P < 0.05).ConclusionsIn open-door laminoplasty, it is feasible to fix the titanium plate on the lateral mass or to the lamina due to the same neurological function recovery. However, fixing it to the lamina will increase the opening angle and decrease the opening width, making the hinge prone to fracture and increasing the severity of postoperative axial symptoms.

Wind-Induced Response and Equivalent Static Wind Loads on Waiting Hall Building of Regular Railway Stations

This paper investigates the influence of the canopy span, canopy opening width and waiting hall building height on the loads and equivalent static wind loads (ESWL) of the waiting hall building. The results show both the mean and standard deviation wind pressure coefficients at the roof of waiting hall buildings are affected by the interference effects caused by the upstream canopies. The wind-induced response of the waiting hall building roof is usually dominated by the first vibration mode, 0∘, 90∘ and 180∘ are the three adverse wind directions. Based on the wind tunnel tests, parameters of the fitted spectrum of the first modal generalized wind pressure for waiting hall buildings are obtained at the adverse wind directions. The semi-analytical expressions of equivalent static wind loads (ESWL) on waiting hall building roofs are derived using the first modal inertial force as a function of the structural reduced frequency. The good accuracy of the proposed ESWL is verified by comparing the nodal displacements and member stresses calculated by the proposed method to the actual dynamic peak results.

Radiographic evaluation of the bicipital groove morphology does not predict intraarticular changes in the long head of biceps tendon

Introduction and objectivesThis study aimed to examine the clinical utility of the radiographic evaluation of the bicipital groove in predicting long head of biceps tendon (LHBT) pathology. Material and methodsA prospective study was conducted, and sixty consecutive patients proposed to shoulder arthroscopic surgery were selected. Before surgery, a radiographic evaluation was performed with a supine and a Fisk radiograph. Most supine radiographs (>75%) were non-interpretable and were excluded from the study. As some Fisk radiographs (26.7%) were also non-interpretable, that left 44 interpretable radiographs in the study. These were measured for medial opening angle, total opening angle, width and depth of the bicipital groove. The radiographic measurements and the presence of LHBT pathology, as assessed at arthroscopy, were correlated. ResultsRadiographic evaluation of the bicipital groove showed a mean medial opening angle of 53 ± 15° (23–90), a mean total opening angle of 80 ± 26° (30–135), a mean width of 10.3 ± 2.5 mm (6–19) and a mean depth of 4.1 ± 1.5 mm (1–8). Men had higher medial opening angle (60 vs 50°, p = 0.044) and wider grooves (11.9 vs 9.7 mm, p = 0.019). Twenty-five patients (56.8%) were found to have an abnormal LHBT. No correlation was found between the radiographic measurements and LHBT pathology. Only age was correlated with a LHBT lesion (61.8 vs 46.3 years, p < 0.001). ConclusionsOur results show that there is no correlation between radiographic morphologic evaluation of the bicipital groove and LHBT pathology.

Performance Analysis of Magnetically Geared Permanent Magnet Brushless Motor for Hybrid Electric Vehicles

The magnetic field modulated variable speed permanent magnet (PM) brushless motor (MFMVS-PMBM) is a new type of power shunting device for hybrid electric vehicles (HEVs), which is composed of a magnetic gear (MG) and a PM brushless motor (PMBM). Compared with the conventional double rotor motor, the MFMVS-PMBM shows a more complex electromechanical energy conversion relationship due to its special magnetic field modulation principle. In order to obtain better electromagnetic characteristics of the motor, the key parameters of MG and PMBM are optimized in this study. The effects of gear ratio, the number of blocks per pole of the Halbach array, and the angle of connecting bridge and magnetic isolation bridge on the torque of MG are analyzed. The electromagnetic characteristics of the motor, such as pole slot matching, PM thickness, and slot opening width of PMBM, are also analyzed. Finally, the prototype is made, and the experimental platform is built. The results show that MFMVS-PMBM has a good sinusoidal back electromotive force (EMF), high transmission efficiency, and power factor.

Stability analysis of rib pillars in highwall mining under dynamic and static loads in open-pit coal mine

The retained coal in the end slope of an open-pit mine can be mined by the highwall mining techniques. However, the instability mechanism of the reserved rib pillar under dynamic loads of mining haul trucks and static loads of the overlying strata is not clear, which restricts the safe and efficient application of highwall mining. In this study, the load-bearing model of the rib pillar in highwall mining was established, the cusp catastrophe theory and the safety coefficient of the rib pillar were considered, and the criterion equations of the rib pillar stability were proposed. Based on the limit equilibrium theory, the limit stress of the rib pillar was analyzed, and the calculation equations of plastic zone width of the rib pillar in highwall mining were obtained. Based on the Winkler foundation beam theory, the elastic foundation beam model composed of the rib pillar and roof under the highwall mining was established, and the calculation equations for the compression of the rib pillar under dynamic and static loads were developed. The results showed that with the increase of the rib pillar width, the total compression of the rib pillar under dynamic and static loads decreases nonlinearly, and the compression of the rib pillar caused by static loads of the overlying strata and trucks has a decisive role. Numerical simulation and theoretical calculation were also performed in this study. In the numerical simulation, the coal seam with a buried depth of 122 m and a thickness of 3 m is mined by highwall mining techniques. According to the established rib pillar instability model of the highwall mining system, it is found that when the mining opening width is 3 m, the reasonable width of the rib pillar is at least 1.3 m, and the safety factor of the rib pillar is 1.3. The numerical simulation results are in good agreement with the results of theoretical calculation, which verifies the feasibility of the theoretical analysis of the rib pillar stability. This research provides a reference for the stability analysis of rib pillars under highwall mining.

Preliminary study of photomask pattern inspection by beam-shaped knife-edge interferometry

This paper presents a photomask inspection and defect analysis technique to accurately measure the pattern dimensions and to detect the defects of the photomask in a convenient, fast, reliable manner. The beam-shaped knife-edge interferometry (BSKEI) was developed to collect the interferogram created by the superposition of the reference incident wave and the edge-diffracted wave while scanning the photomask. BSKEI consists of a pulsed laser diode, an aperture, an objective lens, and a fiber-coupled photodiode. The objective lens enabled the beam shaping to create a spherical wave as a new source of light, and the beam shaping was effective to enhance the spatial frequency of the interferogram. The interferograms were characterized based on a Fresnel number model, and the corresponding interferogram analysis methods were developed. BSKEI produced different interferograms according to the photomask patterns and defects while scanning the photomask. As a result, BSKEI is capable of the measurement of pattern width, opening width, line-edge quality, and opening area surface quality of the photomask, and is expected to be an alternative tool for critical dimension metrology in many semiconductor applications.

A Vision-Based Robot Grasping System

Grasping is critical for intelligent robots to accomplish sophisticated tasks. Even with multimodal sensor fusion, accurately and reliably estimating grasp poses for complex-shaped objects remains a challenge. In this paper, we design a vision-based grasping platform for a more general case, that is, grasping a variety of objects by a simple parallel gripper with the grasp detection model consuming RGB sensing or depth sensing. Focusing on the grasp pose estimation part, we propose a deep grasp detector that uses a densely connected Feature Pyramid Network (FPN) feature extractor and multiple two-stage detection units to achieve dense grasp pose predictions. Specifically, for the feature extractor, the fusion of different layer feature maps can increase both the model’s capacity to detect the various size grasp areas and the accuracy of the regressed grasp positions. For each of the two-stage detection unit, the first stage generates horizontal candidate grasp areas, while the second stage refines them to predict the rotated grasp poses. We train and validate our grasp pose estimation algorithm on the Cornell Grasp Dataset and the Jacquard Dataset. The model achieves the detection accuracy of 93.3% and 89.6%, respectively. We further design real-world grasp experiments to verify the effectiveness of our vision-based robotic grasping system. The real scenario trials validate that the system is capable of grasping unseen objects, in particular, achieving robust and accurate grasp pose detection and gripper opening width measurement based on depth sensing only.

Numerical study of the combustion regimes in naturally-vented compartment fires

Numerical simulations are performed to investigate the classical compartment fire problem involving a single door opening. Three different configurations were considered, namely a full-scale (ISO 9705), an intermediate and a small-scale enclosure with various opening heights and widths. A large number of numerical simulations was carried out using the CFD code Fire Dynamics Simulator (FDS)(version 6.7.0). Based on the variation of the average temperature inside the compartment, three combustion regimes were identified namely well-ventilated, transitional and under-ventilated regime. This variation also allowed us to identify the boundaries between regimes. Furthermore, by adopting a non-dimensional representation of the fire heat release rate inside the compartment as a function of the Global Equivalence Ratio (GER), a clear demarcation between these combustion regimes was obtained. A linear correlation has been established between the maximum heat release rate inside the compartment and the ventilation factor. The latter is expressed as Q̇inmax=850AH. A linear relation between the maximum air flow rate ṁin and the ventilation factor AH was found, i.e. ṁinmax=0.46AH where A is the door surface area and H its height.

An analytical model for stator yokeless radial flux dual rotor permanent magnet synchronous machine

PurposeThe purpose of this study is to propose an analytical model with consideration of the permeability of soft-magnetic materials, which can predict the magnetic field distribution more accurately and facilitate the initial design and parameter optimization of the machine.Design/methodology/approachThis paper proposes an analytical model of stator yokeless radial flux dual rotor permanent magnet synchronous machine (SYRFDR-PMSM) with the consideration of magnetic saturation of soft-magnetic material. The analytical model of SYRFDR-PMSM is divided into seven regions along the radial direction according to the different excitation source and magnetic medium, and the iron permeability in each region is considered based on the Maxwell–Fourier method and Cauchy’s product theorem. The magnetic vector potential of each region is obtained by the Laplace’s or Poisson’s equation, and the magnetic field solution is determined using the boundary conditions of adjacent regions.FindingsThe inner and outer air-gap flux density, flux linkage, output torque, etc., of SYRFDR-PMSM are predicted by analytical model, resulting in good agreement with that of finite element model. Additionally, the SYRFDR-PMSM prototype is manufactured and the correctness of analytical model is further verified by experiments on no-load back electromotive force and current–torque curve. Reasonable design of the slot opening width and pole arc coefficient can improve the average output torque and reduce output torque ripple.Research limitations/implicationsThe analytical model proposed in this paper assumes that the permeability of soft-magnetic material is a fixed value. However, the actual iron’s permeability varies nonlinearly; thus, the prediction results of the analytical model will have some deviations from the actual machine.Originality/valueThe main contribution of this paper is to propose an accurate magnetic field analytical model of SYRFDR-PMSM. It takes into account the permeability of soft-magnetic material and slot opening, which can quickly and accurately predict the electromagnetic performance of SYRFDR-PMSM. It can provide assistance for the initial design and optimization of SYRFDR-PMSM.

The Influence of Joint Inclination and Opening Width on Fracture Characteristics of Granite under Triaxial Compression

The Influence of Joint Inclination and Opening Width on Fracture Characteristics of Granite under Triaxial Compression

Effect of Web Post Width on Strength Capacity of Steel Beams with Web Openings: Experimental and Analytical Investigation

Day by day, technology has been changing progressively because of the remarkable hastening of research and development activities. Perforated beams are one such example of advancement in construction technology. Steel beams with web openings are those that have regularly spaced web openings along the length of the beam. The web openings are created in various ways such as wire cutting and welding. Castellated and cellular beams differ in the creation of web openings. Studies addressing the effect of web post width of steel beams with web openings on the strength capacity of beams are rare. Therefore, the objective of the present work was to examine the influence of web post width on the strength capacity of beams with web openings. First, experimental tests were carried out on three full-scale specimens of a steel beam with oval-shaped web openings, cellular beam, and solid web beam. The same beam was modeled using finite-element software ANSYS and the behavior was compared in terms of load–displacement curve and failure modes. Later, a detailed parametric study was carried out to study the behavior of beams with web openings having variation in web post width using nonlinear finite-element analysis. The simply supported steel beams with web openings subjected to midspan concentrated load with varying web post width and shape of openings were modeled and analyzed. From the analysis results, it was found that the shape of web openings and the web post width play an important role in the strength capacity of the perforated beams. The maximum strength reduction capacity was found to be 51.78% for hexagonal openings of depth 150 mm and having a web post width of 50 mm. The minimum strength reduction capacity was found to be 8.93% for hexagonal openings of depth 100 mm having a web post width of 500 mm. Web post width plays a significant role in the ultimate strength capacity of beams. Web post buckling is a predominant failure mode in steel beams with web openings and it can be prevented by maintaining sufficient web post width.

Surrogate-based optimization and experiment validation of a fan-shaped film cooling hole with a large lateral space

The exit shape of a fan-shaped hole plays an important role to improve the film cooling effectiveness. In this study, a fan-shaped cooling hole on a flat plate was optimized through Reynolds Averaged Navier-Stokes (RANS) analysis for a specific cooling application of unusually large lateral span. A novel hole was configured with four linear dimensions including the leading and trailing edge lateral widths, the exit longitude, and the round metering length. Two rounds of Latin Hypercube Samples were used to narrow the design space for an accurate surrogate model. The first samples were used to evaluate individual variable sensitivity. The second samplings of predominant variables were then combined with the first sampling to build a Kriging surrogate model to predict the film cooling effectiveness of new candidates. A multi-island algorithm was adopted to obtain the optimization solution. The enhanced cooling effectiveness of the final optimal design got verified in an experiment. Results show the improved prediction accuracy of Kriging model and the fast convergence rate of the optimization solution. For a cooling case with a relatively large lateral span, an optimal fan-shaped hole intends to increase the lateral expansion width and to reduce longitude opening width. The spatial averaged cooling effectiveness of the optimized hole achieved a 70% increment over the baseline one.

Theoretical and experimental investigation of a lateral broad-crested contraction as a flow measurement device

The article looked at the possibility of making use of a lateral contraction as a flow measurement device in a rectangular open channel. The contraction under consideration consisted of two removable prismatic elements placed on either side of the walls of the channel. This configuration resulted in the creation of a throat of length L and opening width b less than the channel width B so that the contraction rate has been defined as β = b/B. This ratio actually reflects the degree of the lateral contraction while there is no vertical contraction because the device is devoid of crest height. Its longitudinal axis thus merges with that of the channel, which gives the device a self-cleaning property. Due to the changeover of the subcritical flow upstream of the device to a supercritical flow inside the throat, firmly confirmed by laboratory observations, a control section has been created in a given section at the entrance of the throat. This is the prerequisite for the correct functioning of a flow measuring device in open channels.The essential steps undertaken during the study were firstly the research for the theoretical relationship governing the flow rate Q for forthwith deriving the resulting discharge coefficient Cd equation. This aim has been successfully achieved through the simultaneous application of the momentum and the energy equations taking care to include the effect of the approach flow velocity. The obtained theoretical flow rate QTh was identified in the form of explicit functions depending both on the geometric characteristics of the device and the upstream depthh1 which is fully consistent with semi-modular devices. Likewise, the resulting discharge coefficient Cd,Th was formally identified as being exclusively dependent on the contraction rate β and this finding was predicted by the dimensional analysis.The statistical analysis of the 157 collected experimental values allowed observing an excellent agreement between the theoretical and experimental discharge coefficients. The maximum deviation calculated over the tested range of β was only 1.22%. The use of linear least-squares fitting method involving experimental and theoretical data gave the following trend line relationship Cd,Exp=0.9911Cd,Th obtained with a coefficient of determination R2=0.9906. Thereby, using the previous equation, the accuracy on the discharge coefficient Cd,Th computation has been highly improved since the maximum deviation reduced to only 0.66%.

Reinforcement of concrete principal and secondary trusses after service damages

The paper studies reinforced concrete principal and secondary trusses of a one-floor industrial building made as a precast reinforced concrete frame. The aim of the work is to restore the serviceability of reinforced principal and secondary trusses after instrumental examination with regard to the detected significant corrosion damage of reinforcement and longitudinal cracks in the protective concrete layer with opening width of several millimeters. After the analysis of the building structural scheme, its stress-strain state is simulated in the MicroFe software, and a calculation model is developed allowing for the identified damages of reinforced concrete structures and the proposed design solution for the truss reinforcement. The serviceability restoration of principal and secondary trusses implies the creation of solid truss elements, the joint operation of the reinforcement with the repaired protective concrete layer, and secondary truss reinforcement with polymer fibers.

Correlation between Microstructure and Mechanical Properties of Welded Joint of X70 Submarine Pipeline Steel with Heavy Wall Thickness

This paper aims to study the relationship between the microstructure and the mechanical properties of X70 submarine pipeline steel with 40.5 mm thickness. The microstructure was examined by using optical microscopy, scanning electron microscopy and an electron backscattered diffractometer, while the mechanical properties were examined by using a hardness test, a tensile test, a Charpy impact test and a drop weight tear test (DWTT), respectively. The results show that the base metal (BM) of the pipe has a low yield ratio of 0.83 and an excellent elongation of more than 45%. The DWTT shear area of the steel plate reaches 87%, showing excellent low-temperature toughness. The Charpy impact energy increases when the distance from the fusion line increases, and it reaches a maximum at the BM near the heat-affected zone (HAZ) due to the small martensite-austenite (MA) constituents and fine grains. The concentrated distribution of blocky/slender MA constituents along the prior austenite grain boundaries of the intercritically reheated coarse-grained HAZ and the large MA constituents are the main reasons for the deteriorating impact toughness. Delamination cracks in the DWTT fracture surface only occurred in the midthickness of a sample with a small opening width that spread about 2.1 mm perpendicular to the DWTT fracture surface and were finally arrested at the acicular ferrite clusters containing a high density of high-angle boundaries.

Mapping of cracking sequence of polyvinyl alcohol-steel hybrid fiber reinforced high-strength engineered cementitious composite under uniaxial tension

In the present paper, cracking sequence of high-strength engineered cementitious composite with the characteristic of low drying shrinkage (LSECC) under tension was experimentally studied by continually photographing during loading. The specific objective is to investigate the development of crack opening of each individual crack occurred during loading. Four Engineered cementations composite mixtures with water to binder ratio of 0.20, 0.25, 0.30, and 0.35 (LSECC-0.20, LSECC-0.25, LSECC-0.30, and LSECC-0.35) were used in the tests. Using the photographers taken during the test, crack width of each crack occurred during loading are determined according to the difference between solid material and crack on gray level. The test results show that cracks in ECC under tensile load are formed according to a temporal sequence. The opening width of each crack grows in a controllable and gradual manner with the increase of tensile strain. At a given strain level, crack width of different crack is not equal and the distribution of crack width is affected by matrix strength of the composite. Maximum crack width and the tensile strain capacity at the moment may be utilized to characterize the tensile performance of the composite that can guarantee both of tensile ductility and long-term durability. As maximum crack width equals 60 μm, at which the permeability of ECC may not be influenced by the cracks, higher strength ECC with water to binder ratio of 0.20 and 0.25 (LSECC-0.20 and LSECC-0.25) shows obvious higher tensile strain capacity and more cracks of narrow opening. By contrast, lower strength ECC with water to binder ratio of 0.30 and 0.35 (LSECC-0.30 and LSECC-0.35) shows relatively lower tensile strain and fewer cracks of narrow crack opening as crack width is limited below 60 μm. With the increase of tensile strain and the maximum crack width, much wider cracks (larger than 60 μm) are formed in lower strength ECC comparing to that of higher strength ECC.

Establishment of correlations for the thermo-hydraulic parameters due to perforation in a multi-V rib roughened single pass solar air heater

ABSTRACT The effect of variation in open area ratio (β) in a multi-V rib roughened Single-Pass Solar Air Heater (SPSAH) is analyzed in this work. Fixing values of other parameters, such as open area ratio (β) and relative roughness width (W/w), were studied with a certain range of Reynolds number (Re) ranging from 2000 to 18000. The improvement in Nusselt number ratio (Nu/Nus) and thermo-hydraulic performance (THPP) and the decline in duct friction ratio (f/fs) support the application of perforation. The empirical correlations of Nu and f are also generated with ±12% and ±7.5% accuracy.