Conventional Expansion Research Articles

Comparison of dentoskeletal and soft tissue changes between tooth-borne and tooth-bone-borne hybrid nonsurgical rapid maxillary expansions in adults: a retrospective observational study

BackgroundDespite the gradual increase in the use of rapid maxillary expansion (RME), specifically RME with the aid of skeletal anchorage in adults, there have been no reports comparing dentoskeletal and soft tissue changes between nonsurgical tooth-borne and tooth-bone-borne RMEs in adults. This study aimed to analyse differences in dentoskeletal and soft tissue changes between tooth-borne and tooth-bone-borne RMEs using a similar appliance design and the same expansion protocol in adult patients.MethodsTwenty-one patients with tooth-borne expansion (a conventional expansion screw with two premolars and two molar bands for dental anchorage [T-RME]) and the same number of patients with tooth-bone-borne hybrid expansion (a conventional expansion screw with two premolar and two molar bands for dental anchorage and four mini-implants in the palate for skeletal anchorage [H-RME]) were included. Dentoskeletal and soft tissue variables at pretreatment (T1) and after expansion (T2) were measured using posteroanterior and lateral cephalograms and frontal photographs. The sex distribution of the two groups was analysed using the chi-square test, and the change after RME in each group was evaluated using the Wilcoxon signed-rank test. Differences in pretreatment age, expansion duration, post-expansion duration, and dentoskeletal and soft tissue changes after RME between the two groups were determined using the Mann–Whitney U test.ResultsThere were no significant differences in the expansion protocol, pretreatment conditions, and sex distribution between the two groups. Despite similar degrees of dental expansion at the crown level between the two groups, H-RME induced increased skeletal and parallel expansion of the maxilla compared to T-RME. After expansion, H-RME demonstrated increased forward displacement of the maxilla without significant changes in the vertical dimension, while T-RME exhibited increased backward displacement of the mandible, increased vertical dimension, and decreased overbite. Both groups showed significant retroclination and extrusion of the maxillary incisors without significant intergroup differences. There were no significant soft tissue changes between the two groups.ConclusionThis study suggests that using skeletal anchorage in RME may induce increased skeletal and parallel expansion of the maxilla without significant effects on the vertical dimension.

Life cycle assessment of an experimental solar HVAC system and a conventional HVAC system

Solar heating ventilating air conditioning systems are useful tools to meet the objectives of the European Commission in terms of sustainability in buildings, since their use can reduce the environmental impact, including CO2 emissions, due to their low energy consumption. In order to quantify the improvement that in environmental terms the use of this type of system could entail, in this work it was carried out (a) a comparative life cycle assessment of a solar heating ventilating air conditioningsystem based on evaporative cooling and desiccant wheel with a conventional direct expansion system; and (b) an analysis of feasible modifications of the desiccant wheel based system and their influence on the life cycle analysis results. The experimental desiccant wheel based system showed a slightly higher environmental performance than the conventional direct expansion based system, between 2% and 10%, for the 3 impact categories evaluated: human health, ecosystem quality and resource consumption. When weight optimisation and the reuse of materials were considered, the environmental performance of the experimental based system became even up to between 22% and 50% higher than that of the conventional direct expansion based system. That involved a 60 % reduction in climate change potential indicator, which mainly was influenced by CO2 emissions.

Rational Energy Recovery from the Condensed Steam as a Component of HEN Retrofit

The paper is concerned with retrofitting a heat exchanger network (HEN) using a Pinch-based method (PT) and simultaneously minimizing energy losses caused by the expansion of steam condensate. The disadvantages of conventional multi-stage condensate expansion are identified, and the application of condensate subcooling is proposed. The case study considers a Methyl-Tert-Butyl Ether (MTBE) process plant where the consumption of hot utility (steam) in the existing HEN is 4,386 kW. Using the PT method to determine the maximum possible heat recovery, it is found that heat recovery from hot process streams can be increased, leading to an increase by 510 kW in the combined heat recovery from hot process streams and condensate. Additionally, electricity production in the CHP plant (coupled with the MTBE plant by steam and condensate streams) can increase by 120 kW. HEN reconfiguration is proposed considering local constraints like the existing heat transfer areas and locations of heat-transfer equipment units. The proposal leads to a new HEN structure and a new arrangement of the equipment units in the steam and condensate system.

A study on strengthening and machining integrated ultrasonic peening drilling of Ti-6Al-4V

In aircraft assembly filed, introducing compressive residual stress by cold expansion around the fastening hole is considered as a common method to enhance hole fatigue resistance. However, the conventional cold expansion technology inevitably extends the processing cycle of fastening hole. Therefore, this study proposes a strengthening and machining integrated ultrasonic peening drilling (UPD) to solve this problem by introducing ultrasonic vibration perpendicular to the hole surface during drilling. Both the strengthening principle and dimension accuracy improvement mechanism in UPD were analyzed to better understand the cutting mechanism. The feasibility experiments of UPD of Ti-6Al-4V were conducted to evaluate surface integrity and machining accuracy. The results show that compared to conventional drilling (CD), smoother machined surface and narrower dimensional tolerance were obtained with UPD. Moreover, the subsurface plastic deformation was increased by as high as 4 times with severer deformation degree. Accordingly, the surface residual stress and the depth of circumferential residual stress in the subsurface was increased by 115.7% and 125% respectively. In addition, surface micro-hardness and subsurface hardening layer depth were also significantly increased. The results demonstrated that UPD achieved the integration of strengthening and precision-machining and could be a promising method for finish drilling of aircraft fastening holes.

An innovative design of a high strength and low weight sudden micro expansion by considering a nanofluid: Electronic cooling application

The present study has been numerically surveyed the effect of different expansion angles on the heat transfer and pressure drop characteristics of a sudden expansion in a microtube. For this purpose, Cu/water nanofluids flowing with Reynolds numbers (Re) of 10, 25, 50, and 100 through expansion angles of 30°, 45°, 60°, and 90° were modeled. Governing equations were solved by the finite volume method (FVM). The findings indicated that the heat transfer coefficient (HTC) could enhance by nanoparticles concentration and Re augmentation. Also, It was revealed that HTC of a sudden expansion with an angle of 45° has optimum hydrodynamic performance; then, sudden expansions of 30°, 90°, and 60° are followed. The highest HTC was achieved for a microtube containing 4 vol% nanofluids at Re = 100 with a 45° expansion angle, 43.63% higher than conventional expansion angle (90°) working with distilled water at Re = 10. By comparing HTC at various angles, it can be found that there is a 14.57% further HTC by changing the expansion angle from α = 90° with α = 45°. Furthermore, the pressure drop investigation showed that the expansion angle with α = 30° has the lowest pressure drop. In contrast, α = 45° produced the highest pressure drop because of giant vortices created along the tube wall. The velocity streamlines and contours explained the reason for a lower pressure drop of α = 30°, 45°, and 60° which was regular streamlines along the tube wall due to the Coanda effect.

A general method for calculation of Faraday rotation and transmittance in two-dimensional magneto-optic photonic crystals by solving vector-Helmholtz equation in anisotropic media

We propose a general method based on the plane wave expansion method for the calculation of the Faraday rotation and transmittance spectrum of the two-dimensional magneto-optic photonic crystal. The method is an extension of the conventional plane wave expansion method by and taking into account all the three components of the electromagnetic fields and considering the permittivity tensor with off-diagonal imaginary components representing the Faraday effect and then solving the vector Helmholtz equation. The formulation is explained in detail from the implementation points of view and the computation cost of the method. In the end, numerical results are presented to verify the accuracy and convergence of the method.

Comparison of Conventional Rapid Palatal Expansion with Bone Anchored and Tooth-Bone Anchored Rapid Palatal Expansion Appliances

In modern orthodontics, several types of designs for bone anchored expansion appliances have been developed with the objective to increase the amount of skeletal expansion with rapid palatal expansion. In the present review, the skeletal and dental effects of rapid palatal expansion have been evaluated immediately following expansion and in the long-standing interval following expansion. The effects of conventional rapid palatal expansion appliances are compared with bone anchored maxillary expansion appliances and tooth-bone anchored maxillary expansion appliances. Temporary Anchorage Devices (TADs), or mini-screws, or mini-implants are used for the insertion of bone anchored and tooth-bone anchored maxillary expansion appliances. These lead to higher forces on the bone while expansion is undertaken and consequently more orthopedic effects. This article will discuss how the modern bone anchored expansion appliance used in modern orthodontics compare to conventional rapid palatal expansion appliances.

Conventional posterior cranial vault expansion: indications and results-review of the literature.

In the late 1980s, craniofacial surgery units reported suboptimal cosmetic results, cranial volume restriction, and intracranial hypertension after anterior cranial vault remodeling in bilateral coronal synostosis associated with severe brachyturricephaly. A possible explanation was a severe associated growth restriction of the posterior calvaria with radiological synostosis at the lambda sutures. "Conventional" or "fixed" posterior cranial vault expansion techniques were developed to address these limitations, sometimes as the first surgical step in a two-staged protocol of total calvarial reconstruction, combined with suboccipital decompression in cases of symptomatic cerebellar tonsillar herniation or, more easily, to resolve the characteristic occipital flattening of lambdoid synostosis. Various surgical approaches have been described; however, the indications for and timing of surgical treatment and postoperative evaluation of results still remain controversial. Although more invasive, conventional posterior cranial vault expansion has proven to be safe and offers a remodeled and protective bony vault immediately after surgery, but the underlying cranial base malformation remained untreated, with implications in the postoperative growth of the facial skeleton. Overcorrection, rigid stabilization, and grafting are also concerns to be addressed.

CD28 Superagonist D665-mediated activation of mouse regulatory T cells maintains their phenotype without loss of suppressive quality

Regulatory T cells (Tregs) maintain immune homeostasis by regulating the activation of other immune cells. Preclinical studies show that the infusion of Tregs can promote immunological tolerance to allografts and prevent or cure multiple autoimmune diseases. However, Treg therapy is limited by high numbers of cells required to induce tolerance. In this study, we aimed at improving the in vitro expansion of sort purified mouse Tregs using the CD28 Superagonist (CD28-SA) D665 and comparing it to the conventional expansion using anti-CD3/anti-CD28 Dynabeads®. CD28-SA—stimulated Tregs expanded more than Dynabead®-stimulated Tregs while maintaining their phenotype by expressing the same level of CD4, CD25 and Foxp3. CD28-SA—expanded Tregs produced comparable amounts of IL-10 and TGFβ while showing a slightly superior suppressive capacity compared to Dynabead®-stimulated Tregs. Thus, stimulating murine Tregs with the CD28-SA is a promising alternative since it maintains their suppressive capacity without altering their phenotype and yields a higher fold expansion within 14 days.

Use of scratch tracking method to study the dissolution of alpine aggregates subject to alkali silica reaction

Alkali silica reaction (ASR) can significantly affect the service life of concrete. The dissolution of aggregates has a direct impact on gel formation and thus on the macroscopic expansion. The conventional expansion tests and other investigations confirmed ASR reactivity of three aggregates from different locations in Switzerland. The reactive minerals within alpine and composite aggregates were identified using an innovative scratch-tracking method. This method helps to study aggregate dissolution if measuring the amount of released Si is not enough, because: several minerals release Si or Al and/or new phases are probable to form during dissolution experiment. The scratch-tracking method on theses alpine aggregates showed faster dissolution of feldspars and quartz while muscovite was hardly affected. The dissolution of the aggregates in solution confirmed these differences between minerals.

Tube Expansion by Single Point Incremental Forming: An Experimental and Numerical Investigation

In this paper, we revisit the formability of tube expansion by single point incremental forming to account for the material strain hardening and the non-proportional loading paths that were not taken into consideration in a previously published analytical model of the process built upon a rigid perfectly plastic material. The objective is to provide a new insight on the reason why the critical strains at failure of tube expansion by single point incremental forming are far superior to those of conventional tube expansion by rigid tapered conical punches. For this purpose, we replaced the stress triaxiality ratio that is responsible for the accumulation of damage and cracking by tension in monotonic, proportional loading paths, by integral forms of the stress triaxiality ratio that are more adequate for the non-proportional paths resulting from the loading and unloading cycles of incremental tube expansion. Experimental and numerical simulation results plotted in the effective strain vs. stress triaxiality space confirm the validity of the new damage accumulation approach for handling the non-proportional loading paths that oscillate cyclically from shearing to biaxial stretching, as the single point hemispherical tool approaches, contacts and moves away from a specific location of the incrementally expanded tube surface.

Performance enhancement and multi-objective optimization of a double-flash binary geothermal power plant

Initiating cost-effective and technological frameworks to exploit geothermal energy is a fundamental incentive for scientists and engineers; in this regard, flash-binary geothermal power plants are plausible for high-temperature geothermal resources. Stemming from an in-depth literature review, it is conspicuous that the thermal and exergy losses of the expansion process are significant. To shed light on this matter, an ejector-expander is integrated into the conventional expansion valve of a double-flash binary geothermal power plant to enhance the plant performance. The feasibility of the contrived notion is scrutinized from energy, exergy, thermal, and cost balance standpoints and results converged in the increase in turbine output power, energy efficiency, and exergy efficiency of approximately 7.66%, 7.64%, and 7.69%, respectively. Among all components, the condenser constituted a 45.06% share of the overall exergy destruction, whilst the turbine had an exergy destruction ratio of 22.07%. An intensive parametric study is implemented that outlined that the turbine output power, energy efficiency, and exergy efficiency of the ejector-expander power system have a maximum in a specified pressure value of the first and second separator. Another merit was a marked decrease in the unit cost of power when ejector-expander is employed.

Skeletal effects of mini-implant assisted rapid palatal expansion (MARPE) on the sagittal dimensions of the maxilla an in-vivo cone-beam computed tomography (CBCT) study

Introduction -Transverse discrepancies of the maxilla are one of the most prevalent skeletal problems. Due to drawbacks of conventional RPE and invasive surgical expansion methods alternative methods were developed such as Mini Implant-supported rapid maxillary expansion (MARPE).Haas17 , Davis and Kronman18, Akkaya et al19 and many other studies have reported the maxillary response after MARPE on the sagittal dimensions, but their results were inconclusive.
 Aim - This study analyzed the effects on the maxilla in the sagittal dimension after Mini Implant assisted rapid palatal expansion (MARPE) in adolescents using CBCT.
 Material and method -A pretreatment CBCT image (T1) was taken as a standard initial record for all patients and post treatment CBCT (T2) was taken after three months in retention. The parameters SNA angle, Frankfort horizontal plane to NA angle, A-N perpendicular, ANS –PNS were measured and calculated for evaluation of the sagittal maxillary changes. Comparisons were then made between the two treatment groups (T1, T2).
 Result -There was a positive increase in both angular and linear measurements from pretreatment to post treatment measurements showing significant skeletal changes in sagittal dimension.
 Conclusion -The study concludes that there was statistically significant forward displacement of maxilla after transverse skeletal expansion in patients with transverse problems achieved through MARPE in adolescent patients.

Short-term skeletal and dentoalveolar effects of overexpansion.

To evaluate whether the amount of rapid maxillary expansion differentially affects the skeletal and dentoalveolar changes that occur. This randomized controlled trial included 23 patients who had rapid maxillary expansion (RME). Subjects were randomly assigned to a conventional expansion control group (n = 12) or an overexpansion group (n = 11), who started treatment at 13.2 ± 1.5 and 13.8 ± 1 years of age, respectively. Cone beam computed tomography scans (11 cm) were obtained prior to rapid maxillary expander (RME) delivery and approximately 3.7 months later. Initial hand-wrist radiographs were used to determine the participants' skeletal maturity. The RME screws were activated 5.6 ± 1.2 mm and 10.1 ± 0.6 mm in the conventional and overexpansion groups, respectively. Overexpansion produced significantly greater expansion of the nasal cavity (2.1X-2.5X), maxillary base (2.3X), buccal alveolar crest (1.4X), and greater palatine foramina (1.9X). Significantly greater intermolar width increases (1.8X) and molar inclination (2.8X) changes were also produced. The nasal cavity and maxillary base expanded 23%-32% as much as the screws were activated. Skeletal expansion was positively correlated with RME screw activation (R = 0.61 to 0.70) and negatively correlated (R = -0.56 to -0.64) with the patients' skeletal maturation indicators (SMIs). Together, screw activation and the patients' SMI scores explained 48%-66% of the variation in skeletal expansion. This pilot study shows that overexpansion produces greater changes than conventional expansion, with greater skeletal effects among less mature patients.

New Manufacturing Method of Glass Foam by Cold Expansion of Glass Waste


 
 
 
 Abstract 
 An innovation cold manufacturing method of glass foams is presented in the paper. Traditional foaming agents used in conventional expansion processes of glass waste at high temperature were substituted with aluminium powder in aqueous solution of calcium hydroxide, which releases hydrogen forming gas bubbles in the viscous sludge and then, by solidification, a porous structure typical for the glass foam. The manufactured foam is adequate for using as a thermal insulation material for inner wall of buildings, having the apparent density of 0.31 g·cm-3, the thermal conductivity of 0.070 W/m·K and the compressive strength of 1.32 MPa. The process originality is the use of recycled aluminum waste, melted by an own microwave heating technique and sprayed with nitrogen jets. The process effectiveness is remarkable in economical and energy terms.
 
 
 

Monitoring of steel corrosion and cracking in cement paste exposed to combined sulfate–chloride attack with X-ray microtomography

The degradation process of reinforced cement paste exposed to cyclic wetting and drying with a designated salt solution was monitored through X-ray microtomography (μCT). Three exposure conditions (a 3 wt% NaCl solution, a 5 wt% Na2SO4 solution, or a mixed solution of 3 wt% NaCl and 5 wt% Na2SO4) were studied to investigate the potential synergistic effects between chloride and sulfate ions on the deterioration of reinforced cement-based materials. The time-dependent evolution of steel corrosion and cracking of cement paste cover were tracked and visualized, while the volumes of steel loss, corrosion products and cracks were quantified by image analysis. The results indicated that the presence of sulfate ions significantly delayed the initiation of chloride-induced corrosion, but did not seem to greatly affect the corrosion rate once the corrosion occurred. The existence of chloride ions, in turn, also mitigated the damage of cement paste cause by sulfate attack as evidenced by the reduced volumes of cracks. The conventional volume expansion coefficient of corrosion products can be measured by μCT, but this coefficient may not be applicable for modelling the corrosion-induced cracking process when sulfate ions were present. The use of μCT provides a new angle to directly measure the interfacial displacement in reinforced cement paste, which can be used as a valuable input for modelling non-uniform chloride-induced corrosion in the presence of sulfate ions.

Numerical investigation on the effects of circuit parameters on the plastic deformation of fastener holes in thin aluminum alloy via electromagnetic expansion process

The size of the plastic deformation zone caused by fastener hole strengthening is a critical indicator of the strengthening performance. In this study, 2A12-T4 aluminum alloy specimens with a hole diameter of 6 mm and thickness of 1.5 mm were strengthened by Lorentz force through the electromagnetic strengthening method. The numerical results show that the Lorentz force can introduce tensile stress in both hoop and radial directions in the specimen during the strengthening process and produce a high compressive hoop residual stress around holes without serious axial deformation compared with the conventional cold hole expansion process. The simulation results are experimentally validated by the grid method in verifying the residual strain, and the fatigue life can be improved by several times after strengthening. Furthermore, under the same discharge energy, there is an optimal capacitance of around 40 μF in this work to achieve the maximum size of the plastic deformation zone. In addition, a larger crowbar resistance can cause a stronger radial inward Lorentz force during the unloading process and result in lower residual stress; therefore, the crowbar resistance should be as small as possible.

A calibrated organic Rankine cycle dynamic model applying to subcritical system and transcritical system

The organic Rankine cycle (ORC) technology is an attractive candidate for waste heat recovery and clean energy utilization. The operating condition of ORC system would change constantly under fluctuant heat source and a dynamic model is able to predict the transient behavior. The ORC dynamic model generally contains some unknown parameters while their identification is often ignored. This paper proposes a detailed calibration mechanism for ORC dynamic model including subcritical and transcritical system. Component models including pump, expansion valve and evaporator are well calibrated and the integrated calibrated system model is validated based on experimental data. Results indicate that calibrated model can capture the system dynamic behavior well. For key system state parameters such as working fluid evaporator pressure and outlet temperature, model prediction can achieve mean absolute relative deviation of less than 2% for both subcritical and transcritical system. Meanwhile, the conventional expansion valve model for transcritical system is found not efficient enough and a modification form is provided. This work can contribute to the calibration mechanism of similar thermodynamic system and enhance the confidence in model application.

Predictive Ability of Ultraearly Hematoma Growth and Spot Sign for Redefined Hematoma Expansion in Patients with Spontaneous Intracerebral Hemorrhage

BackgroundRedefined hematoma expansion (rHE) including intraventricular hematoma expansion (IVHE) is a new concept in intracerebral hemorrhage (ICH), with better prognostic ability compared to the conventional hematoma expansion. Ultraearly hematoma growth (uHG) and computed tomography angiography (CTA) spot sign are both useful indictors to predict HE and poor clinical outcome. This study aims to explore the clinical characteristics of rHE in retrospective cohort and evaluate the predictive ability of uHG and spot sign in rHE. Materials and MethodsThis study included nontraumatic spontaneous ICH patients from June 1st 2013 and January 1st 2018 in West China Hospital. Multivariate logistic regression was used to determine risk factors for HE/IVHE/rHE and primary outcomes of ICH patients. Receiver operating characteristic (ROC) analysis was performed to assess the accuracy of uHG and spot sign for predicting HE/IVHE/rHE. ResultsThis retrospective cohort included 469 consecutive patients with ICH. rHE was significantly associated with clinical variables including Glasgow coma scale (GCS), time to initial CT, presence of IVH, hematoma volume, presence of spot sign, and uHG. uHG and spot sign were independent risk factors for rHE. ROC analysis indicated that both uHG (AUC 0.726, 95%CI 0.680-0.773) and spot sign (AUC 0.735, 95%CI 0.686-0.785) possessed high predictive accuracy for rHE. HE and rHE were independent risk factors for 1-month mortality and 3-month functional outcome. ConclusionsBoth uHG and the spot sign were considered to be good predictors for rHE, and the spot sign appeared to have a better predictive accuracy.

Application and Evaluation of Load Management Systems in Urban Low-Voltage Grid Planning

Not all urban low-voltage grids will be able to integrate new loads such as charging infrastructure for electric mobility or electrical heat pumps into existing structures without further measures. Therefore, this article analyzes to what extent load management is more cost-effective than conventional grid expansion. Methodically, the different load types are first apportioned from country to grid-level on the basis of different parameters. Subsequently, both conventional grid planning as a reference variant and innovative grid planning with different variants of load management are carried out. As a result, it can be summarized that the future success of load management is strongly dependent on its costs and whether the necessary information and communication technology is already deployed in the grids. Regardless of the costs, there is also considerable potential for savings in conventional grid expansions.