Complex Cavity Research Articles

Comparison of Micro-Leakage around Temporary Restorative Materials Placed in Complex Endodontic Access Cavities: An In-Vitro Study.

To compare mean micro-leakage around 3 types of temporary restorative materials in-vitro, when placed adjacent to permanent restorations (amalgam) in complex endodontic access cavities. Randomized controlled trial. Dental Clinics, Dental Laboratory and Research Laboratory at The Aga Khan University Hospital, Karachi, from January to June 2014. After random allocation of 60 teeth into 3 experimental groups, each group had conventional class II cavities prepared and amalgam placed. After 14 days, endodontic access cavities were made in these teeth, followed by placement of Cavit, IRM and CLIP(depth of 4 mm each). After thermo-cycling and immersion in 0.5% methylene blue dye, the teeth were sectioned mesio-distally and observed under stereoscopic microscope (magnification x4) along 2 interfaces 'a' and 'b' (tooth-temporary restoration and temporary restoration-primary restoration), respectively. Depth of dye penetration was measured in millimeters. IRM was leakiest at interface 'a', cavit had highest dye penetration at interface 'b', while CLIP exhibited least micro-leakage at 'a' and 'b'. The mean dye penetration for Cavit was 0.80 ± 0.23 mm at 'a', and 2.24 ± 0.48 mm at 'b'. For IRM, it was 1.82 ± 0.09 mm at 'a', and 0.44 ± 0.13 mm at 'b'. For CLIP, the mean dye penetration was 0.43 ± 0.05 mm at 'a', and 0.32 ± 0.12 mm at 'b'. The difference in dye penetration observed between the 3 groups at both interfaces was statistically significant. In a complex access cavity made adjacent to a pre-existing amalgam restoration, CLIP exhibits the least micro-leakage, followed by IRM and Cavit.

Untethered Recyclable Tubular Actuators with Versatile Locomotion for Soft Continuum Robots.

Stimuli-responsive materials offer a distinguished platform to build tether-free compact soft robots, which can combine sensing and actuation without a linked power supply. In the past, tubular soft robots have to be made by multiple components with various internal channels or complex cavities assembled together. Moreover, robust processing, complex locomotion, simple structure, and easy recyclability represent major challenges in this area. Here, it is shown that those challenges can be tackled by liquid crystalline elastomers with allyl sulfide functional groups. The light-controlled exchange reaction between allyl sulfide groups allows flexible processing of tubular soft robots/actuators, which does not need any assisting materials. Complex locomotion demonstrated here includes reversible simultaneous bending and elongation; reversible diameter expansion; and omnidirectional bending via remote infrared light control. Different modes of actuation can be programmed into the same tube without the routine assembly of multiple tubes as used in the past. In addition, the exchange reaction also makes it possible to use the same single tube repeatedly to perform different functions by erasing and reprogramming.

An optimized Monte Carlo ray tracing optical simulation model and its applications to line-focus concentrating solar collectors

The Monte Carlo Ray Tracing (MCRT) method has been confirmed flexible and efficient in the optical simulation of Concentrating Solar Collectors (CSCs), but it usually needs higher computing cost and longer runtime or its results fluctuate in multiple runs. The parameters of the way of random number generation, the number of rays, running times, grid numbers, and random number generation times all exerted effects on the simulation results. It was found that running the MCRT model with less number of rays for several more times could mitigate the fluctuation of results and decrease the total runtime simultaneously. Taken the Line-focus CSC with a metal-glass receiver and a parabolic reflector as an example, the maximum (emax) and average (eavg) relative errors of the MCRT method with 1 × 108 rays running for once, 2 × 107 rays running for once and 3 × 106 rays running for five times were all lower than the threshold values (Emax = 5% and Eavg = 0.5%), but the total runtime was about 410 s, 82 s and 63 s respectively. On these bases, an optimized MCRT model was proposed by combining the MCRT method with the iteration method, where the minimum running times (tmin) and the maximum running times (tmax) were introduced, and they could be changed conveniently to meet the requirements of different optical simulations. By applying the proposed model to the Line-focus CSC with a more complex cavity receiver or compound parabolic reflector, the total runtime varied in the range of 268–413 s and 26–102 min respectively, indicating that the runtime reduction was significant when the limit of relative errors were acceptable. The proposed model is beneficial to mitigate the fluctuation, improve the accuracy and reduce the runtime of the MCRT method. It can also be further used to the optical simulation of various kinds of CSCs.

A new method for spatial structure detection of complex inner cavities based on 3D γ-photon imaging

This paper presents a new three-dimensional (3D) imaging method for detecting the spatial structure of a complex inner cavity based on positron annihilation and γ-photon detection. This method first marks carrier solution by a certain radionuclide and injects it into the inner cavity where positrons are generated. Subsequently, γ-photons are released from positron annihilation, and the γ-photon detector ring is used for recording the γ-photons. Finally, the two-dimensional (2D) image slices of the inner cavity are constructed by the ordered-subset expectation maximization scheme and the 2D image slices are merged to the 3D image of the inner cavity. To eliminate the artifact in the reconstructed image due to the scattered γ-photons, a novel angle-traversal model is proposed for γ-photon single-scattering correction, in which the path of the single scattered γ-photon is analyzed from a spatial geometry perspective. Two experiments are conducted to verify the effectiveness of the proposed correction model and the advantage of the proposed testing method in detecting the spatial structure of the inner cavity, including the distribution of gas–liquid multi-phase mixture inside the inner cavity. The above two experiments indicate the potential of the proposed method as a new tool for accurately delineating the inner structures of industrial complex parts.

Investigation of the specific adhesion between polyurethane foams and thermoplastics to suited material selection in lightweight structures

Lightweight construction combines various materials to create resource efficient components. Thermoplastics (TPs) combined with polyurethane (PUR) foams are increasingly used to create hybrid composites. Optimizing the energy efficiency is one of the main issues in the development of production processes of components. Reducing the number of process steps offers great potential in this respect. PUR foam develops a strong adhesive bond with most materials. This is used for the manufacturing of hybrid composite components by filling complex cavities with PUR foam simultaneously bonded with other TP polymer components. This way, one process step for joining is saved. The interfaces in this composite structures are critical points of the failure. A huge variety of TP is used for the production of hybrid composite components and PUR foam develops varying bonding strengths with all of them. Selecting the suitable TPs for a durable bonding with PUR foam in the desired production process necessarily requires information about the respective specific adhesion. In this investigation, different TPs were processed with PUR foams in order to manufacture sandwich composites. The TP facings are produced in the injection moulding process. Subsequently, the facings are combined with the foam core during reaction injection moulding. The wetting behaviour was examined using the contact angle measurement and the mechanical strength of the interface in the sandwich composite was determined using a tensile test. A precise order of the selected TPs concerning their specific adhesion to PUR foams was achieved with these investigative methods.

Mode Coupling and Scattering Parameters in a Parity-Time Symmetric Resonant Integrated Coupler

We investigate theoretically, in the frame of coupled-mode theory, a parity-time symmetric directional coupler inserted into a symmetric resonant cavity, all ports being terminated by four identical lossless reflectors. The scattering parameters are expressed under analytic closed forms in several equivalent bases, underlining the fact that PT Symmetry can be thought of as mode coupling between the old Eigenmodes of the passive structure. We also derive the oscillation threshold of such a complex cavity, and comment upon this apparent paradox: as a matter of fact, a laser effect is not necessarily expected from a device with more losses than gain.

LOCAL CRYOTHERAPY IN TREATMENT OF PURULENT SKIN DISEASES AND SUBCUTANEOUS TISSUE

Purulent diseases in surgery are the oldest and at the same time not-over-the-topical problem, accounting for at least a third of all surgical diseases, 12 % of deaths after planned and 27 % after emergency operations. There is a constant search for new methods of treatment. The most promising are methods with the use of physical influence on the wound. One of such, known for a long time, but has become widespread only recently is the use of ultra-low temperatures in wound processing -local cryotherapy It has both advantages for the all physical methods: lack of microorganisms resistant to intensive exposure, locality of action, absence of significant side effects and allergic reactions, and unique features for local cryotherapy -it does not cause severe tissue damage, anesthetic properties, efficacy in chronic processes, ease of use for complex cavities debridment. At the same time, the local cryotherapy is largely unexplored topic, requiring further study and adaptation of the technique for the purulent surgery requirements.

Surface integrity of AISI H13 under different pulse time and depths by EDM process

Electrical Discharge Machining (EDM) is a commonly used process to manufacture of die and molds, due to the capacity of generating deep and complex cavities. The removal of material occurs from a series of discharges between electrode and workpiece. Discharges melt and vaporize material in form of debris, flushed away by the dielectric flow. This work presents AISI H13 steel surface integrity study, machined by EDM process using constant parameters and a copper electrode with different depths of cavity and pulse times. Textures, crack density, roughness and affected layer were investigated. The collected data was submitted to an ANOVA statistical test. The study showed cavity depth as the only significant factor in roughness. Affected layer thickness is not affected by cavity depth and pulse time. Cracks depth and concentration rise with the increase of pulse time and depth of the cavity.

Anodic behavior of amorphous and nanocrystal alloys during the electrochemical processing

Magnetically soft alloys possessing unique characteristics, which determine corrosive, magnetic and other properties, are used as a construction material in the amorphous structural state. The amorphous alloys have a high hardness and unusual fragility along with unique magnetic properties. Due to this fact, there are some limitations in using these alloys as construction materials, which is related to the problems of their processing. Applying traditional methods of mechanical processing is impossible. Thus, the electro-diamond grinding based on the combined action of anodic dissolving and mechanical cutting by the diamond grains is used for processing the open surfaces, for instance, for grooving in the machine stator made of 5BDSR alloy. However, the use of the electrochemical size processing by the cathode-tool based on localizing the anodic dissolving of the machined material is considered to be perspective for processing geometrically complex cavities or holes with a small diameter. To develop the technology of surface forming in details made of 5BDSR and 82K3HSR alloys, the analysis of their anodic behavior during the electrochemical processing was conducted. The reasons for the anode surface passivation during the electrochemical processing of the investigated alloys were found both in amorphous and in amorpho-nanocrystal structural state in 10% electrolytes NaNO3, Na2SO4 and NaCl.

Three‐dimensional simulations of non‐isothermal flow for gas penetration in complex cavity during gas assisted injection moulding process

AbstractIn this paper an R‐function is employed to construct the shape level set (LS) function for representing the complex mould cavity in a gas‐assisted injection moulding (GAIM) process. With the shape LS function, the continuity, momentum, and energy equations can be extended for solving the gas‐liquid two‐phase flows using the finite volume and immersed boundary methods. Firstly, an improved simple coupled level set and volume of fluid (S‐CLSVOF) method is proposed to track the moving interfaces of gas‐liquid interface and polymer melt front. Then the benchmark problems of the two‐ and three‐dimensional deformation tests are carried out to verify the ability of the improved S‐CLSVOF method. At last, the gas penetration processes are simulated in two different complex mould cavities. The numerical results show that the improved S‐CLSVOF method has higher accuracy than the S‐CLSVOF method, and the coupled numerical framework can successfully depict the asymmetry phenomenon of gas flow, racetracking, and fountain phenomena, which has great significance in determining processing conditions and designing mould cavities.

Observation of Mode Competition in Operation of a 420 GHz, TE17.4Second Harmonic Gyrotron With Complex Cavity

The lack of terahertz sources, especially the high-power ones, is one of the main obstacles in the developments of terahertz science and technology. A gyrotron, based on the electron cyclotron masers, is one of the most promising sources to generate high-power terahertz radiation. Therefore, a 0.42-THz gyrotron with a gradually tapered complex cavity operating at the second harmonic is designed and experimentally tested in this paper. Experimental results show that the designed gyrotron can generate high-power THz radiation of 19.2 kW at 0.42 THz with the beam voltage ${V}_{\textsf {0}}$ of 51 kV, beam current ${I}_{\textsf {0}}$ of 4.4 A and the external magnetic field ${B}_{\textsf {0}}$ of 8.03 T, corresponding to an efficiency of 8.6%. By comparison with theoretical results, it can be shown that the operating mode in the designed gyrotron is confirmed as the TE17.4 mode. At the same time, the excitation of the fundamental TE0.5 mode is also observed in the experiment when the beam current is increased to 7.3 A, where the operating frequency is 216.143 GHz. Through extensive experimental efforts, it is found that the designed gyrotron can operate stably at the desired TE17.4 mode when the beam current is in the range of 3–7 A.

Перспективність надання гігієністом зубним профілактичної стоматологічної допомоги населенню м. Житомира

Preventive medicine is the basis for the development of health care systems in the European Union, and investment in prevention is recognized as the most effective investment in the industry of preserving and improving health. Prophylactic direction – one of the most important in modern dentistry.The aim of the study – analysis of treatment and prevention performance indicators of Municipal Institution Zhytomyr City Dental Hospital No.1 and defi nition of methods for improving the primary prevention.Materials and Methods. We analyzed the annual reports of internal medicine and surgical departments of Zhytomyr City Dental Hospital No. 1 for the period from 2015 till 2016; we held a poll of 115 patients of the establishment regarding the methods for teeth cleaning and using the accessories and means necessary for oral cavity care. The following methods were used: bibliosemantic, system analysis and logical concluding,interview, and mathematical processing of the collected data. Results and Discussion. Numeric materials refl ecting the work of Zhytomyr City Dental Hospital No.1 indicate that doctors employed in the establishment conduct numerous maneuvers related to oral cavity sanitation using modern fi lling materials and diagnostic methods. However (and predominantly), all the work is directed at secondary prevention. As a result, annually a lot of teeth are removed due to complex caries (23.370–23.898), and there are a lot of patients with signs of periodontal diseases (3.521–3.766). Dispensary for diseases includes 94 patients with pre-tumor pathology. Considering that public hygienic teaching and education is one of the main components of primary treatment, we held a poll involving 115 patients of Zhytomyr City Dental Hospital No. 1. Study results indicate that the patients of the dental care entity have insuffi cient knowledge on using the accessories and means necessary for hygienic procedures. All the respondents are more ready to invest into prevention care than internal medicine and surgical dental treatment. It is possible to reach an upward trend in dental health indicators only with primary caries and periodontal diseases prevention. Adding hygienist in the staffi ng list of dental care entities would allow not only for comprehensive primary prevention, but would also unload the high-class dentists enabling them to conduct more complex oral cavity operations.Conclusions. Zhytomyr City Dental Hospital No. 1 employs no hygienists, that is why its work is aimed at secondary treatment of oral cavity diseases. Low sanitary culture level of Zhytomyr residents is tightly connected with dental health indicators. Further development and reforming of dental care demands training of the new generation of highly qualifi ed junior medical staff (hygienists). Involving of hygienists in treatment care allows improving the quality of preventive dental services and decreasing dental diseases incidence rate.

A three-dimensional thermal model for viscoelastic polymer melt packing process in injection molding

In this study, a 3D weakly compressible viscoelastic flow model with the thermal effect is developed for simulations of the non-isothermal XPP melt packing process. The 3D multi-field coupled model is solved by the collocated finite volume CLEAR algorithm with the AVLSMART scheme. The numerical model is validated against the benchmark problem. The XPP melt packing process in a rectangular cavity is simulated, and the predicted flow-induced birefringence is in agreement with the experimental and numerical results reported in the literature. For a case with a rather complex cavity, the XPP melt packing process in a 3D hemispherical shell cavity is further simulated. The distributions of melt temperatures, flow-induced stresses as well as the corresponding rheological characteristics of XPP melt in 3D cavity are vividly presented, which are difficult to be captured by previous simulations and experiments. Especially, the present model allows the effects of melt temperature and holding pressure on the first normal stress difference and density to be studied. It is shown that with an increase in melt temperature, the absolute values of the first normal stress difference increases slightly and the density decreases gradually, while the high holding pressure improves significantly the first normal stress difference and density. Numerical results demonstrate that the present 3D thermal model is an effective tool for simulating real-world viscoelastic polymer melt packing processes.

Reflection influence on the operation of a 0.42 THz second harmonic gyrotron with complex cavity

Since the average power of a 0.42 THz s harmonic gyrotron with complex cavity is small, the laser calorimeter AC2500H is adopted to measure the pulsed output power. However, the optimal spectral response of AC2500H is far from the operating frequency of the designed gyrotron. Thus the reflection on the laser calorimeter would be large, which would affect the mode competition in the designed gyrotron. In this paper, the influence of reflections from the laser calorimeter and output window is investigated by a multi-mode, time-dependent nonlinear code. From numerical simulation results, it is shown that the output power of the designed gyrotron is greatly decreased by the reflection from AC2500H although it doesn't cause excitations of competing modes. And it is found that when the reflection phase on the output window θr,n,1 is 5π/11, reflection magnitude on the laser calorimeter Γr,n,2 is 0.44 and the corresponding phase θr,n,2 is 3π/7, the variation of the calculated output power is very similar with the experimental result. Moreover, if the beam quality and Ohmic loss in the cavity wall are both considered, the calculated power can fit perfectly with the measured one.

Formability and flow front observation of carbon/polyamide 6 randomly oriented strand composites during compression molding

Chopped carbon fiber tape-reinforced thermoplastics are randomly oriented strand materials that are easy to process and have good mechanical properties. Studying the formability and flow evolution during compression molding is essential; in particular, clarifying the relationship between the forming parameters and mold-filling characteristics of highly concentrated fiber suspensions. Here, we investigated the key parameters of strand size and effective pressure and demonstrated filling a complex mold cavity under practical processing conditions. In addition, a simplified method for observing the progression of the flow front using a video camera was proposed, where the dependence of the applied load on the mold-filling time could be observed. Filling complex-shaped mold cavity using chopped carbon fiber tape-reinforced thermoplastics is achievable using shorter strands and higher pressures. Also, the degradation of mechanical performance should be carefully considered when the material undergoes large deformation to form complex-shaped products.

Coherent beam combining and noise analysis of a colliding pulse modelocked VECSEL.

Optically-pumped SESAM-modelocked semiconductor disk lasers have become interesting ultrafast lasers with gigahertz pulse repetition rates, high average power and adjustable lasing wavelength. It is well established that colliding pulse modelocking (CPM) can generate both shorter pulses and improved stability. These improvements however typically come at the expense of a more complex ring cavity and two output beams. So far similar modelocking results have been obtained with CPM vertical external-cavity surface-emitting lasers (VECSELs) and with SESAM-modelocked VECSELs or modelocked integrated external-cavity surface-emitting lasers (MIXSELs) in a linear cavity. However coherent beam combining of the two output beams of a CPM VECSEL could result in a significantly higher peak power. This is interesting for example for applications in biomedical microscopy and frequency metrology. Here we demonstrate with a more detailed noise analysis that for both output beams of a CPM VECSEL the pulse repetition rates and the carrier envelope offset frequencies are locked to each other. In contrast to standard SESAM-modelocked VECSELs in a linear cavity, we only have been able to actively stabilize the pulse repetition rate of the CPM VECSEL by cavity length control and not by pump-power control. Furthermore, a first coherent beam combining experiment of the two output beams is demonstrated.

Design of Complex Cavity Structure in Air Route System of Automated Peritoneal Dialysis Machine

This paper introduced problems about Automated Peritoneal Dialysis machine(APD) that the lack of technical issues such as the structural design of the complex cavities. To study the flow characteristics of this special structure, the application of ANSYS CFX software is used with k-ε turbulence model as the theoretical basis of fluid mechanics. The numerical simulation of flow field simulation result in the internal model can be gotten after the complex structure model is imported into ANSYS CFX module. Then, it will present the distribution of complex cavities inside the flow field and the flow characteristics parameter, which will provide an important reference design for APD design.

Preparation, characterization and featuring of an inclusion complex of nerol with β-cyclodextrin

Nerol is an acyclic type monoterpene with important biological activities. However, the low solubility in aqueous media is a limiting factor for its user. Cyclodextrins have been widely used in order to improve the solubility, stability and bioavailability of nonpolar molecules through the formation of inclusion complexes. Thus, the present study consists in the development of nerol inclusion complex in combination with the β-cyclodextrin (β-CD) followed by characterizing by thermal analysis and spectrophotometric absorption in the infrared (FTIR). The results suggest a complexation of nerol with β-CD having detours and changed the intensity of various bands. The thermo gravimetric curve of CI found to indicate an output of solvating water molecules from the complex cavity formed for replacement of drug molecules probably included. Thus, it is concluded a possibility to obtain inclusion complexes of nerol monoterpene with β-CD, which will increase its solubility and facilitate delivery process.

GEOMETRIC EVALUATION OF COMPLEX CAVITY INTRUDED IN HEAT GENERATED WALLS

In this work it is presented a numerical study about geometrical evaluation of heat transfer in solids with volumetric heat generation and complex intruded cavity for cooling the wall by means of Constructal Design. Several cavities with varied shapes have been evaluated in literature, such as I-, T- and H-shaped cavities. The purpose here is to evaluate a complex cavity that combines different elemental shapes. More precisely, the resultant cavity is a merge between a H-shaped cavity and a I-shaped one, forming a ramified geometry, which is more expected in the flow between a point and volume in systems with high magnitude. The main purpose is to minimize two times the maximal temperature in the solid domain (Tmax). Here two degrees of freedom are defined for the cavity: H1/L1 (ratio between the second branch thickness and its length) and H0/L0 (ratio between the third branch height and its thickness) and the area of cavity is the constraint. For each geometrical configuration the heat diffusion equation is solved with the Finite Element Method (FEM). Results showed that differences of until five times between the optimal shapes and the worst ones are achieved, showing the importance of application of Constructal Design in the problem. Moreover, the best performance is achieved when the vertical branches are fully intruded in the solid domain for intermediate lengths of horizontal branch.

Stability Prediction and Step Optimization of Trochoidal Milling

When machining narrow grooves, corners, and other complex cavities with trochoidal milling, the irrationally large trochoidal step usually leads to chatter, while the conservative trochoidal step constrains the machining efficiency. In this paper, a stability prediction model of trochoidal milling is established to solve these problems. An approach considering trochoidal steps and spindle speeds is presented to predict stability boundary of trochoidal milling. With considering the varying cutter-workpiece engagements, the stability of trochoidal milling process is predicted by obtaining the stability lobes of different cutter location (CL) points along the trochoidal milling tool paths. Based on the proposed stability model, a trochoidal step optimization strategy is developed to improve the machining efficiency of trochoidal milling under other parameters in a given situation. Cutting experiments are performed on the machining center GMC 1600H/2 to show the effectiveness of the proposed trochoidal milling stability model. Finally, simulations are adopted to illustrate the optimization strategy.