Expansion Device Research Articles

The stretchable carbon black-based strain fiber with a remarkable linearity in a wide sensing range

ABSTRACT Ascribed to its wide sensing range, high sensitivity, and low stiffness to match target objects with complex 3D shapes, the stretchable strain sensor has shown its promising applications in various fields, ranging from healthcare, bodynet, and intelligent traffic system, to the robotic system. This paper presents a low-cost and straightforward fabrication technology for the stretchable strain fiber with the combined attributes of a wide sensing range, exceptional linearity, and high durability. The hybrid composite consisting of carbon black and silicone is utilized as the functional material to respond to the external mechanical deformation due to the piezoresistive effect. To address the remarkable hysteresis of the CB-silicone composites, the latex tubes with excellent mechanical robustness and a considerable accessible tensile strain are introduced as the outer supporting components. After injecting the conductive CB-silicone composite into these tubes, the stretchable strain fibers are successfully prepared. Notably, the stretchable strain sensor exhibits linearity (R2 = 0.9854) in a wide sensing range (0–400%) and remarkable durability even after the 2500 cycles under 100% tension. Additionally, the potential of this stretchable strain fiber as the wearable strain sensor and the real-time feedback is demonstrated by detecting the body motion and the expansion devices.

Sheathless inertial microfluidic cell separation via a serpentine–contraction–expansion device coupled with a combinatorial extraction regulator

Sheathless inertial microfluidic cell separation via a serpentine–contraction–expansion device coupled with a combinatorial extraction regulator

Efficacy of Miniscrew-Assisted Rapid Palatal Expansion (MARPE) in late adolescents and adults with the Dutch Maxillary Expansion Device: a prospective clinical cohort study

ObjectivesTo provide a higher degree of evidence on the efficacy of Miniscrew-Assisted Rapid Palatal Expansion (MARPE) in late adolescents and adults, thereby applying the Dutch Maxillary Expansion Device (D-MED).Materials and methodsD-MED was developed as an individualized, 3D-designed, and fabricated MARPE appliance supported by 4 palatal miniscrews. Patients from the age of 16 onwards with transverse maxillary deficiency were enrolled consecutively. Pre-expansion and immediate post-expansion CBCTs and intra-oral scans were acquired and measurements of skeletal, alveolar, and dental expansion as well as dental and periodontal side-effects were performed.ResultsThirty-four patients were enrolled (8 men, 26 women) with mean age 27.0 ± 9.4 years. A success rate of 94.1% was achieved (32/34 patients). The mean expansion duration, or mean observation time, was 31.7 ± 8.0 days. The mean expansion at the maxillary first molars (M1) and first premolars (P1) was 6.56 ± 1.70 mm and 4.19 ± 1.29 mm, respectively. The expansion was 60.4 ± 20.1% skeletal, 8.1 ± 27.6% alveolar, and 31.6 ± 20.1% dental at M1 and 92.2 ± 14.5% skeletal, 0.0 ± 18.6% alveolar, and 7.8 ± 17.7% dental at P1, which was both statistically (p < 0.001) and clinically significant. Buccal dental tipping (3.88 ± 3.92° M1; 2.29 ± 3.89° P1), clinical crown height increase (0.12 ± 0.31 mm M1; 0.04 ± 0.22 mm P1), and buccal bone thinning (− 0.31 ± 0.49 mm M1; − 0.01 ± 0.45 mm P1) were observed, while root resorption could not be evaluated.ConclusionsMARPE by application of D-MED manifested its efficacy in a prospective clinical setting, delivering a high amount of skeletal expansion with limited side-effects in late adolescents and adults.Clinical relevanceHigher quality evidence is supportive of MARPE as a safe and successful non-surgical treatment option for transverse maxillary deficiency.

Evaluation of bone depth, cortical bone, and mucosa thickness of palatal posterior supra-alveolar insertion site for miniscrew placement

BackgroundThe use of palatal miniscrew offers the possibility to improve the effectiveness of orthodontic expansion devices. Palatal expanders supported by miniscrew can be applied with different clinical protocols. Some authors proposed the use of four palatal miniscrews during miniscrew-supported palatal expansion to maximize skeletal effects in young adults’ treatment. However, bone availability decreases in the posterior paramedian palatal regions, making the positioning of the two-posterior paramedian palatal miniscrews challenging, when it is performed avoiding nasal cavities invasion. Some authors proposed miniscrews insertion in a specific region located laterally to the palatal process of the maxillary bone, and apically relatively to the dento-alveolar process. The aim of this study was to evaluate the bone thickness, cortical bone thickness, and mucosae depth of this anatomical site that, in this study, was defined as palatal posterior supra-alveolar insertion site.ResultsThe evaluation of bone availability of palatal posterior supra-alveolar insertion site at different antero-posterior levels showed that the maximum amount of total bone thickness was found between the second premolar and the first molar. At this level total bone, thickness is significantly (p < .05) greater compared to the other sagittal sites and it offers on average around 2 mm of extra bone depth for miniscrew placement. Cortical bone thickness is adequate for primary miniscrew stability. Overall, cortical bone thickness considered at different insertion sites showed significant statistically (p < .05) differences. The findings of this study showed that palatal mucosa is particularly thick with average values ranging from 4 to 7 mm, and its extension ultimately affects miniscrew length selection. Palatal mucosa thickness showed no clinically significant differences comparing different sagittal and vertical insertion sites. Data also showed that palatal mucosal thickness slightly significantly increases (p < .05) with the inclination of the insertion axis relative to the occlusal plane. Finally, study findings showed that vertical growth pattern can significantly affect considered outcomes (p < .05).ConclusionsPalatal posterior supra-alveolar insertion site is an appropriate site for posterior insertion of palatal miniscrews. Considering high anatomical variation preliminary CBCT evaluation is important to achieve optimal miniscrew placement.

Design and Fabrication of Refrigerant Based Air Cooler

Abstract: With the recent government organization and regulation for saving the water, trees, curtains to the use of these sources which contribute to global warming present day mankind uses various equipment in their daily need which includes conventional cooler, AC etc. This consumes large amount of water and electricity so for reducing the use of these main sources research involves the use of VCRS system which include eco-friendly refrigerant R134a in cooler system. This system is mounted in the research model in a proper manner so that it is compact in size. The refrigerant R134a absorbs the heat from air and makes the air cooled, itself getting vaporized in evaporator and then the cooled air is sent outward from the opening. In the research model with help of fan running on motor and gives the cooling effect. This use of VCRS system with eco -friendly refrigerant reduces the consumption of the water, electricity consumption and tree which is used for making wood wool in conventional cooler. This ultimately reduces the global warming. For making these purposes the project is developed. Keywords: Compressor, condenser, evaporator, refrigerant(R134a), expansion device

Literature Review on Design and Fabrication of Refrigerant Based Air Cooler

Abstract: With the recent government organization and regulation for saving the water, trees, curtains to the use of these sources which contribute to global warming present day mankind uses various equipment in their daily need which includes conventional cooler, AC etc. This consumes large amount of water and electricity so for reducing the use of these main sources research involves the use of VCRS system which include eco-friendly refrigerant R134a in cooler system. This system is mounted in the research model in a proper manner so that it is compact in size. The refrigerant R134a absorbs the heat from air and makes the air cooled, itself getting vaporized in evaporator and then the cooled air is sent outward from the opening. In the research model with help of fan running on motor and gives the cooling effect. This use of VCRS system with eco -friendly refrigerant reduces the consumption of the water, electricity consumption and tree which is used for making wood wool in conventional cooler. This ultimately reduces the global warming. For making these purposes the project is developed. Keywords: Compressor, condenser, evaporator, refrigerant(R134a), expansion device

Comparison of the short-term effects of tooth-bone-borne and tooth-borne rapid maxillary expansion in older adolescents.

To compare the short-term effects of tooth-bone-borne and tooth-borne rapid maxillary expansion (RME) devices on dentofacial structures in older adolescents. The retrospective study reviewed pre- and posttreatment lateral and posteroanterior cephalometric images and orthodontic model records of patients who underwent maxillary expansion. Two groups were formed, in which the same upper jaw expansion protocol was applied with two different maxillary expansion devices: the first group consisted of 15individuals treated with tooth-bone-borne (hybrid) RME (HRME; 9girls and 6boys; mean age, 16.9 ± 0.42years) and the second group consisted of 15individuals treated with tooth-borne (conventional) RME (CRME; 8girls and 7boys; mean age, 16.74 ± 0.54years). Cephalometric and orthodontic model measurements were conducted on the records taken before and after treatment. Significant skeletal and dental expansions were observed in both groups (p < 0.05). However, the increase in nasal width measurements in the HRME group (2.24 ± 0.61 mm) was significantly higher than the increase in the CRME group (1.12 ± 0.25 mm; p < 0.01). Buccal tipping of the premolars was significantly less in the HRME group (0.46 ± 0.35°) than in the CRME group (2.46 ± 0.63°; p < 0.01). The amount of tipping of the molars was higher in the HRME group (4.76 ± 0.88°) compared to the CRME group (2.9 ± 1.03°; p < 0.01). Although the HRME device increase the nasal width in older adolescents to agreater extent, more dental side effects were seen at the maxillary first molars.

Thermal Operation Maps for Lamm–Honigmann Thermo-Chemical Energy Storage—A Quasi-Stationary Model for Process Analysis

The Lamm–Honigmann energy storage is a sorption-based storage that can be arbitrarily charged and discharged with both heat and electrical power. The mechanical charging and discharging processes of this storage are characterized by an internal heat transfer between the main components, absorber/desorber and evaporator/condenser, that is driven by the working-fluid mass transferred between those components with the help of an expansion or compression device, respectively. In this paper, thermal operation maps for the mechanical charging and discharging processes are developed from energy balances in order to predict power output and storage efficiency depending on the system state, which, in particular, is defined by the mass flow rate of vapor and the salt mass fraction of the absorbent. The conducted method is applied for the working-fluid pair LiBr/H2O. In a first step, a thermal efficiency is defined to account for second-order losses due to the internal heat transfer; e.g., for discharging from a salt mass fraction of 0.7 to one of 0.5 (kg LiBr)/(kg sol.) at a temperature of 130 °C, it is found that the reversible shaft work output is reduced by 1.1–2.9%/(K driving temperature difference). For lower operating temperatures, the reduction is larger; e.g., at 80 °C, the efficiency loss due to heat transfer rises to 3.5%/K for a salt mass fraction of 0.5 (kg LiBr)/(kg sol.). In a second step, a quasi-stationary assumption leads to the thermal operation map from which the discharging characteristics can be found; e.g., at an operating temperature of 130 °C for a constant power output of 0.4 kW/m2 heat exchanger area at volumetric and inner machine efficiencies of ηi=ηvol=0.8 and for an overall heat-transfer coefficient of 1500 W/(K m2), the mass flow rate has to rise continuously from 1.5 to 4.2 g/(s m2), while the thermal efficiency is reduced from 97% to 83% due to this rise and due to the dilution of the sorbent. For this discharging scenario, the corresponding discharge time is 4.4 (min·m2)/(kg salt). This results in an exergetic storage density of around 29 Wh/(kg salt mass). For a charge-to-discharge ratio of 2 (charging times equals two times discharging time) and with the same heat-transfer characteristic and machine efficiencies for constant power charging with adiabatic compression, the system is charged at around 0.75 kW/m2, resulting in a round-trip efficiency of around 27%. Besides those predictions for arbitrary charging and discharging scenarios, the derived thermal maps are especially useful for the dimensioning of the storage system and for the development of control strategies. It has to be noted that the operation maps do not illustrate the transient behavior of the system but its quasi-stationary state. However, it is shown, mathematically, that the system tends to return to this state when disturbed.

Effect of cut-off and compression ratio on the isentropic efficiency during off-design and part-load operations of a Wankel rotary steam expander used for small scale cogeneration

• A new Wankel rotary expander has been developed for use with saturated steam. • Peak isentropic efficiency is 88% and in the range 60 to 88% for off-design. • Analysis reveals clear impact of cut-off on isentropic efficiency. • Any cut-off and pressure ratio combination can provide peak isentropic efficiency. • Dynamic admission-volume control can maintain high efficiency for all mass flow. Expanding steam from boiler pressure to process pressure using an expansion device instead of a pressure reducing valve is recommended for improving energy efficiency and reducing operational costs. However, there are challenges in realizing this potential with existing technologies (such as turbines) due to wetness of process steam and mass flow rate variations caused by load changes. Positive displacement expanders, such as screw and reciprocating engines, can handle wet steam but, they are designed to handle variable mass flow only by throttling leading to exergy destruction and poor economic performance. In this paper we present an improved Wankel steam expander by analysing the impact of mass flow variations and translating it into key design elements: cut-off and compression ratio of the expander. Theoretical analysis in this study resolves conflicting definitions found in literature on compression ratio and cut-off used for designing a positive displacement expander (such as Wankel) and its impact on isentropic efficiency prediction. Experimental analysis of the Wankel expander reveals that a peak isentropic efficiency of over 85% can be achieved for high cut-off. The range of measured isentropic efficiencies were from 60 to 88% for different pressure ratios and at 40% and 62% cut-off. As the pressure ratio increased, the peak efficiency shifted to a lower cut-off condition. When compared to the Wankel, the peak efficiency of a reciprocating expander was only in the range of 50–55% . Thus, the Wankel expander developed in this study presents an opportunity to improve the exergetic efficiency of process steam.

Smooth Versus Textured Tissue Expander Breast Reconstruction: Complications and Efficacy.

Ongoing recognition of breast implant-associated anaplastic large cell lymphoma (BIA-ALCL) and its link with textured devices has brought a paradigm shift in prosthetic-based breast reconstruction. Many institutions no longer offer textured expansion devices for staged reconstruction. However, there is a paucity of data regarding the efficacy of smooth tissue expanders (TE). We hypothesized that the time to final reconstruction and complication profile between smooth and textured TEs would be similar in breast reconstruction patients. A retrospective chart review was performed of all patients who underwent TE breast reconstruction during a 6-year period at the Penn State Hershey Medical Center. Rates of complications treated nonoperatively and those requiring reoperation were assessed. Mechanical complications, including expander malposition and rupture, were evaluated. Time to final breast reconstruction was quantified. Mixed-effects logistic regression and linear regression models, as appropriate, were used to compare textured to smooth TEs. Patient characteristics and anatomic plane placement were adjusted for in all analyses of outcomes. Data were collected on 389 patients, encompassing 140 smooth and 604 textured TEs. Textured devices had an increased incidence of complications treated nonsurgically (16.7% vs 10.7%; P = 0.14). However, smooth TEs had an increased incidence of reoperation (12.1% vs 7.6%; P = 0.06). Most noteworthy was that although smooth TEs had a 40-fold increase in malposition (13.6% vs 0.3%; P < 0.001), no reoperation for this complication was warranted. Further, the time to final reconstruction was comparable between the 2 devices (textured expanders: 221 days and smooth expanders: 234 days; P = 0.15). Staged, implant-based reconstruction is the most common surgical approach to recreate the breast mound following mastectomy. Textured TEs were the cornerstone to this approach. Unfortunately, the association between textured devices and BIA-ALCL now mandates an alternative. We postulated that smooth expanders would compare favorably for breast reconstruction. Although our study suggests that smooth TEs suffer more malposition, this has a negligible impact on the reconstructive timeline. Thus, smooth TEs may prove beneficial when considering the risk of BIA-ALCL associated with textured devices.

A novel design, implementation and performance evaluation of the first electronic expansion ejector for energy saving of a mini split air conditioner controlled by inverter

Due to the global warming impact, which has resulted in rising energy costs, it has become vital to adopt energy-efficient air conditioners and improve their performance at a low power consumption rate, which is considered a big challenge. Ejectors have received much attention over the last decade because of their simplicity, cheap maintenance, high operating capacity, low-temperature handling, no risk of blockage, and longer lifespan at reduced costs. For the first time in the current study, a novel electronic ejector as an expansion device is designed and implemented in conjunction with a mini-split air conditioner that uses the refrigerant R-410A and is controlled by an inverter.The effects of several design and operation factors, such as primary nozzle diameter, primary nozzle length, mixing throttle diameter, capillary tube diameter, capillary tube length, air average velocity, external air temperature, and conditioned space thermal load, are also considered. The study aims to investigate the system performance by integrating a new electronic ejector technology that may be used as an expansion device in conjunction with an inverter-controlled air conditioner. According to the findings, the electronic ejector has a greater COP and saves more energy than the electronic expansion device. Dimensionless correlations of COP and EER incorporating the experimental results are also obtained.

Thermal analysis and development of PID control for electronic expansion device of vapor compression refrigeration systems

One of the reasons for replacing conventional expansion devices with electronic expansion valves in vapor compression refrigeration systems is associated with the fact that electronic valves promote savings in energy consumption. However, for the electronic expansion valve to be more efficient its PID controller must be properly tuned. Therefore, a refrigeration prototype of simple cycle by vapor compression, who uses R404A and an ethylene glycol solution as a secondary fluid, with nominal capacity of approximately 1 kW has been developed and analyzed. An optimization strategy of a black box model using Matlab® software to tune the PI control was used, while the Ziegler-Nichols method was also used to tune the PID control of the expansion device of the refrigeration prototype system. Developing a strategy to optimize the parameters of PI and PID controls to improve the energy efficiency ratio (EER) of refrigeration systems using superheat and valve opening as input variables is the novel contribution of this paper. The PI and PID control models improved the EER of the refrigeration system by 21% to 32% and the factory-set PI control by 28%, respectively. Applying the Ziegler-Nichols method for the PI and PID controls improved the EER by 10–17% and by 24 to 28%, respectively, compared to the factory-configured PI controller. The control parameters found with the discrete linear model provided better energy efficiency than the factory setting of the electronic expansion device and with the first Ziegler-Nichols, the PID control had a better EER than the one with the discrete linear model.”.

Penentuan ukuran pipa kapiler dengan program aplikasi CapSel Versi 1.0 pada AC trainer unit jenis ekspansi langsung dengan R-410A

The use of air conditioning system currently mostly uses the vapor compression cycle. One such air conditioning machine is a direct expansion type AC. In this type of air conditioner, the air is directly cooled by the refrigerant. Cold air is flowed through the air duct to be entered into the room to be cooled. The refrigerant used is R-410A which does not contain chlorine so it does not cause depletion of the ozone layer because it has an ODP = 0. This direct expansion unit trainer uses an expansion device in the form of a capillary tube and an external equalizer type TXV. To determine the size of the capillary tube on the trainer unit, the direct expansion type uses the CapSel version 1.0 application program. By using the input data for refrigerant type R-134A, refrigeration capacity 2,637.6 Watt (9000 BTU/hour), evaporation temperature 5 °C condensation temperature 47 °C, and return gas temperature 12 °C, the recommended capillary pipe size data is obtained, namely the length of the pipe. capillary 1.47 m with an inner diameter of 2.50 mm. The test was carried out by varying the velocity of the air leaving the airways at high speed (22.3 ft/s) and at low speed (7.9 ft/s). The refrigerant temperature and pressure data are measured at 4 measurement points and the measurement of the electric current entering the system. After processing the data and entering it into the Coolpack application program, the average COP and EER in the low speed position produce a higher price than the high speed position.

Promotion of dermal tissue engineering in a rat model using a composite 3D-printed scaffold with electrospun nanofibers and recipient-site preconditioning with an external volume expansion device.

We hypothesized that use of a composite three-dimensionally (3D) printed scaffold with electrospun nanofibers in conjunction with recipient-site preconditioning with an external volume expansion (EVE) device would enable successful dermal tissue regeneration of a synthetic polymer scaffold. Cell viability, cell infiltration, extracellular matrix deposition, scaffold contraction, and mRNA expression by dermal fibroblasts cultured on three different scaffolds, namely, 3D-printed scaffold with a collagen coating, 3D-printed scaffold with an electrospun polycaprolactone nanofiber and collagen coating, and 3D-printed scaffold with an electrospun polycaprolactone/collagen nanofiber, were measured. Before scaffold implantation, rats were treated for 2h with an EVE device to evaluate the effect of this device on the recipient site. Cell proliferation rates were significantly higher on the 3D-printed scaffold with electrospun polycaprolactone nanofiber and collagen coating than on the other scaffolds. In cell invasion studies, the 3D-printed scaffold with electrospun polycaprolactone nanofiber and collagen coating showed better cell integration than the other scaffolds. Under stereomicroscopy, fibroblasts adhered tightly to the electrospun area, and the fibroblasts effectively produced both collagen and elastin. Rat skin treated with an EVE device exhibited increased HIF-1α protein expression and capillary neoformation compared with control skin. Invasion of CD8+ cytotoxic lymphocytes surrounding the scaffold decreased when the recipient site was preconditioned with the EVE device. The composite 3D printed scaffold with electrospun nanofibers provided a favorable environment for proliferation, migration, and extracellular matrix synthesis by fibroblasts. Recipient-site preconditioning with an EVE device allowed for scaffold incorporation with less inflammation due to improved angiogenesis.

Outcomes of Femtosecond Laser-Assisted Cataract Surgery Compared to Conventional Phacoemulsification in Eyes with Pseudoexfoliation Syndrome

ABSTRACT Objective To compare the outcomes including complications, in a large cohort of eyes with pseudoexfoliation syndrome that underwent Femtosecond Laser-Assisted Cataract Surgery (FLACS) versus conventional phacoemulsification. Design Retrospective cohort study. Participants A total of 513 eyes from 366 patients with pseudoexfoliation syndrome that underwent cataract surgery between April 1, 2014, and December 31, 2018. Methods Charts were reviewed for preoperative examination findings, intraoperative complications, and post-operative outcomes. Best-corrected visual acuity (BCVA) was measured by logMAR and compared between groups at one month and the final follow-up visit. Results Of 513 eyes, 71 (13.8%) underwent FLACS, and 442 (86.2%) eyes underwent conventional cataract surgery. Between the two groups, there was no difference in the incidence of vitreous prolapse, capsular tear, pupillary expansion device usage, capsular tension support device usage, or postoperative cystoid macular edema (p > .05 for all). At the final visit, there was no significant difference in BCVA between FLACS and conventional phacoemulsification groups (mean logMAR 0.26 vs. 0.25, p = .87). Conclusions When comparing FLACS and conventional phacoemulsification in eyes with pseudoexfoliation syndrome, no difference was seen in the incidence of complications. BCVA was comparable between the two groups. Zonular weakness significantly increased the risk of complications in both groups.

A State-of-the-Art Review on Two-Phase Flow-Induced Noise in Expansion Devices

This paper presents a state-of-the-art review of the literature concerning flow-induced noise in expansion devices. The topics covered are theoretical natural frequency models of bubbles with spherical and cylindrical shapes and flow-induced noise in capillary tubes, such as orifice, thermal and electric expansion valve. Several parametric conditions affect the flow-induced noise in capillary tubes, such as outlet capillary geometry, capillary inner diameter and length, flow orientation, outlet vapor quality, mass velocity, pressure drop, in/outlet flow pattern, evaporation temperature, and refrigeration cycle operational conditions. Despite the broad use of orifice, there is a lack of knowledge in the literature of flow-induced noise in these devices. The flow-induced noise seems primarily a function of mass velocity, vapor quality, and flow pattern. It seems that outlet intermittent flow patterns lead to significant noise in capillary tubes and expansion valves. In general, for the noise evaluated outside the expansion device, electric expansion valves exhibited higher sound pressure levels than capillary tubes. Furthermore, the present literature review indicates that efforts should be made to perform tests for a wide range of conditions evaluating the noise within and outside the expansion device, device wall acceleration and flow topology for current and new refrigerants, simultaneously.

Parathyroid hormone promotes maxillary expansion and reduces relapse in the repeated activation maxillary expansion rat model by regulating Wnt/\u03b2-catenin pathway

BackgroundConstricted maxillary bone is a common skeletal deformity, which may lead to crowding and posterior crossbite. Mid-palatal suture expansion is often used to increase the maxillary width, but its skeletal effects are limited and tend to relapse, even with prolonged retention. We hypothesized that parathyroid hormone (PTH) may reduce the relapse of maxillary expansion.MethodsWe established a novel rat maxillary expansion model using palatal tubes with an insertable “W”-shaped spring which can be repeatedly activated. A total of 32 male healthy Wistar rats were randomly divided into six groups: the control group, the PTH group, the expansion group, the expansion + PTH group, the expansion + relapse group and the expansion + PTH + relapse group. All animals in the first 4 groups were killed after 10 days and the 2 relapse groups were killed after 15 days. The maxillary arch widths and histological staining were used to assess the expansion and relapse effects. The immunohistochemical staining, micro-CT, RT-qPCR and Western blot were used to evaluate the bone remodeling during expansion.ResultsThe suture width was increased by the expansion device, and the repeated activation maxillary expansion rat model showed better expansion effects than the conventional model. PTH significantly promoted the expansion width and reduced the relapse ratio. Meanwhile, in the expansion + PTH group, histological and immunohistochemical staining showed that osteoblasts, osteoclasts, new cartilage and osteoid were significantly increased, micro-CT showed increased bone mass, and PCR and Western blot results confirmed up-regulation of RANKL, β-catenin, type II collagen and OCN.ConclusionThe novel repeated activation maxillary expansion rat model has better effects than the conventional model. PTH enhances the maxillary expansion and reduces its relapse by regulating Wnt/β-catenin and RANKL pathways. PTH administration may serve as an adjunctive therapy in addition to mechanical expansion for treatment of maxillary constriction.

Thermodynamic analysis of auto-cascade refrigeration cycles, with and without ejector, for ultra low temperature freezing using a mixture of refrigerants R600a and R1150

• A mixture of R600a and R1150 was thermodynamically evaluated in auto-cascade cooling cycles. • The influence of the mass fraction, the discharge pressure and the phase-separator temperature were evaluated. • The results are especially sensitive to the temperature at the phase-separator and the mass fraction of the refrigerants. • The ejector as an expansion device can improve the COP by up to 12% with regard to the reference case. The temperatures required by ultra-low temperature applications, ranging from −50 °C to −100 °C, cannot be reached economically with single stage systems because of the limitation of the compression ratio. Different types of solutions such as cascade or two-stage systems could be implemented to achieve the desired working conditions. However, these systems are usually complex or too expensive. The solution might be found in the use of auto-cascade systems working with zeotropic mixtures. The present article proposes two modifications of the auto-cascade system by including an ejector device to improve the COP. The first modification includes the ejector as an expansion device at the outlet of the phase-separator, while the second includes the ejector as a pre-compression stage. A mixture of the hydrocarbons iso -butane (R600a) and ethylene (R1150) was used as an alternative to conventional refrigerants, which have a very high GWP. The study performed firstly assessed the sensitivity analysis of the free variables on the operating conditions of each cycle. The evaluated variables were the compressor pressure discharge, the mass fraction of the mixture and the phase separator temperature. In the case of the ejector enhanced cycles, the ejector efficiency and the motive pressure were additionally included. Then, the optimal operating conditions were found by means of an optimization process. The results showed a potential improvement in the COP of 12% for the case of the ejector as an expansion device, with an optimal mass fraction of 0.45 of ethylene. On the other hand, the ejector as a pre-compression stage did not show any improvement with regard to the reference case. The present study concludes that the mixture of ethylene and iso -butane is a suitable combination for auto-cascade cycles and that the ejector can be implemented to improve the COP without adding excessive complexity and cost.

Study on Mechanical Properties of Simply Supported Girder Bridge after Jointless

The jointless bridges includes integral bridges, semi-integral bridges and extended deck bridges. The integral bridges adopts an integral abutment, and its main girder, abutment and pile under abutment are fixed together to bear the force together. The expansion joint and expansion device are cancelled, and the integrity, durability and driving comfort of the bridge are improved. In this paper, a simply supported girder bridge in Fujian Province of China is taken as the research background, and it is transformed into an integral bridge. Midas/Civil software is used to establish the finite element models of the original bridge and the integral bridge, and the mechanical properties of the main girder and the pile under the combined action of dead load and overall temperature rise of 25 °C are analyzed. The results show that due to the consolidation of the main girder and abutment of the integral bridge, the internal force at the girder end under the combined action of temperature and dead load is greater than that of the simply supported beam bridge. The pile deformation of the integral bridge is significant under the combination of temperature and dead load. With the increase of the height-to-thickness ratio of the abutment of integral bridge, the bending moment at the girder end and the mid-span are increasing. Different abutment height-to-thickness ratio has little influence on the horizontal displacement of the girder end of integral bridge. With the increase of height-to-thickness ratio of the abutment of integral bridge, the deformation of pile decreases. The flexible abutment with large height-to-thickness ratio can improve the mechanical properties of pile and achieve the purpose of protecting the pile.

Comparison between homogeneous and separated flow models of isobutane flowing through adiabatic capillary tubes

Capillary tubes have been widely used as expansion devices in small-scale refrigeration and heat-pump systems. However, adiabatic flow through a capillary tube is extremely complicated, despite its simple geometry. This work presents a comparative study on the homogenous flow model and separated flow model, which were used to simulate the flow of isobutene (R600a) through adiabatic capillary tubes. The influence of different combinations of friction factor and two-phase viscosity correlations, and the effect of metastable flow on the flow characteristics were investigated. The predicted mass flow rate was lower when the separated flow model was used. The separated flow model performed better in predicting a mass flow rate over 2 kg·h&lt;sup&gt;−1&lt;/sup&gt;. The Colebrook friction factor correlation combined with the Dukler or McAdams viscosity correlation yielded smaller deviations of 5.43%, 5.49% and 5.44%, 5.43% when ignoring and considering the metastable flow, respectively. Additionally, the homogenous flow model adopting the Bittle and Pate friction factor and Dukler viscosity correlations achieved the highest accuracy with a mass flow rate under 2 kg·h&lt;sup&gt;−1&lt;/sup&gt;. The mean error was 4.12% in the case without metastable flow, and 3.37% in the case with metastable flow.