Cavity Wall Research Articles

Effects of Building Materials on Building Thermal Load in Malaysian Institutional Library

Green building, net-zero energy building, low energy building, and sustainable building are the common terms being used in the building industry nowadays, with the primary aim to produce buildings with low energy and low carbon dioxide (CO2) emissions. Different types of building materials can have significant implications for energy efficiency, especially in the warming climate. The energy crisis, future global warming, and climate change can be mitigated by choosing the right building materials, which will also lower the building's energy consumption and carbon dioxide emissions. This paper presents the effects of different building materials on the cooling capacity and cooling energy consumption of a building for four (4) different climate change weather data, namely, the present time scenario, the 2020s, 2050s, and 2080s time scenario using TRNSYS simulation software. The main library of a university in Petaling Jaya, Malaysia, was chosen as the case study. Three (3) types of building materials were studied, namely, Type 1 (brick walls with single-glazed windows), Type 2 (foam insulation cavity walls with double-glazed windows), and Type 3 (air gap cavity walls with double-glazed windows). The simulation results showed that the Type 2 building materials could reduce the yearly cooling energy consumption by 14.5%, compared with the current building materials (brick walls with single-glazed windows). The Type 3 building materials (air gap cavity walls with double-glazed windows) with the lower installation were wound to reduce the yearly cooling energy consumption by 9% compared with the Type 1 building materials. For architects, designers, politicians, and library administrators, the research's conclusions have immediate practical implications that will help them make decisions and implement energy-saving plans. In the end, this research helps libraries in Malaysia remain sustainable and resilient in the face of global warming and the energy crisis.

Effect of plasma confinement on laser ablation propulsion parameters by using external semi-elliptical cavities for Aluminum and Silver propellants

Ablative laser propulsion (ALP) is a type of beam-powered propulsion in which thrust is produced by ablating a target using a high-intensity laser beam. In this research work, we calculated the ALP parameters momentum coupling coefficient (Cm) and specific impulse (Isp) by confining the plasma with the help of external semi-elliptical cavities. The cavity minor axis was fixed at 2.5 mm while the major axis varied to 7 mm, 9 mm, 11 mm, 13 mm and 15 mm. Silver and aluminum samples were used as propellants. A pulsed Q-smart Nd:YAG laser operating at 532 nm wavelength was used to ablate the target. A significant increase in the value of Cm and Isp was observed using confined ablative propulsion. The highest Cm and Isp were recorded for the 9 mm major axis cavity, for which Cm was increased from 5.01 × 10−5 N-s/J to1.75 × 10−4 nearly 249% for silver and from 3.4 × 10−5 N-s/J to 8.9 × 10−5 N-s/J nearly 161% for aluminum. Hence the use of semielliptical cavities is an effective technique for enhancing propulsion parameters. Cavity acts as a trap for plasma and shockwaves. Confinement of plasma and reflection of shockwaves from the cavity walls results in enhanced laser ablation propulsion parameters.

The effect of silver diamine fluoride on the microleakage of glass ionomer restoration in primary teeth at different time intervals

Silver diamine fluoride (SDF) has shown effectiveness in hardening tooth structure and killing bacteria. Therefore, it can be used to prevent and arrest dental caries. Riva Star (SDF) treatment alone will stop cavities but will not reverse the cavitation. The Silver Modified Atraumatic Procedure, often known as Smart, is the optimum technique for regaining the tooth's structure and function. Glass ionomer was introduced in (1972) as a new material that has become one of the most widely used materials in restorative dentistry. By releasing fluoride ions, this material has a therapeutic impact on the surrounding tooth structure. Microleakage is the ingress of bacteria, its byproducts, toxins, chemicals, oral fluids, and ions between the margins of the restoration and the cavity walls. Dental restoration lifetime is significantly influenced by microleakage at the toothrestoration contact. Material and method: In this study, we used 32 primary molars, class V cavities prepared on the buccal surface of all teeth. The teeth were divided into 2 groups: Group 1: 16 teeth treated with 38%SDF 8 of them restored directly with GIC filling and the other 8 restored after 14 days; Group 2: 16 teeth as control group left untreated with 38% SDF,8 teeth restored directly and 8 restored after 14 days. Samples were thermocycled, immersed in 2% methylene blue and then sectioned in a buccolingual direction. Dye penetration was measured with a digital camera connected to a stereo microscope. Result: results of this study showed a significant difference in microleakage between two-time intervals in which microleakage in GIC filling decreased at 14-day intervals than that of first-day interval in the experimental group, while in the control group, microleakage at 14 days intervals was higher than first-day interval, but it was not significant. Conclusion: Pretreatment of the primary teeth with SDF can decrease the microleakage of GIC restoration. If placed after 14 days, the microleakage would be lesser than that if the restoration was placed directly after SDF treatment. Therefore, it is recommended that SDF treatment be done, followed by a permanent restoration after 14 days, so the null hypothesis cannot be accepted. Keywords: Microleakage, Silver diamine fluoride, Glass ionomer filling, noninvasive dentistry

Clinical Justification for Preliminary Thermal Exposure to Composite in the Treatment of Caries: Randomized Clinical Trial

Background. Polymer composites have good aesthetic characteristics and pronounced physicochemical properties, as compared to traditional restorative materials such as amalgam. However, the polymerization reaction of composite material containing bismethacrylate group commonly used in clinical practice is always accompanied by a different degree of volumetric shrinkage (2.7%~7.1%). The resulting stress can lead to adhesion failure and some other unfavorable clinical consequences, such as enamel destruction, microcracking of composite material and formation of microleakage between composite and tooth cavity wall, which can result in recurrent caries and postoperative sensitivity, thereby affecting the long-term effect of restoration. Therefore, studying the effect of preheating on composite restoration is important for its clinical application. Objective. To improve the effectiveness of treatment of patients with dental caries by improving the physicochemical properties of composite restorations.Methods. A randomized clinical trial enrolled 180 patients aged 18 to 45 years, diagnosed with dentin caries class I, according to Black (K02.1 in ICD). The study was conducted in the Dental Clinic of Kuban State Medical University, Russia. 180 composite restorations were performed in the treatment of dentin caries of molars. Patients were randomized into 2 groups): the control group — 90 patients and the main group — 90 patients. The control and main groups, in turn, were divided into three subgroups, depending on the composite used — Estelite Sigma Quick (Tokuyama Dental, Japan), Filtek Bulk Fill Posterior Restorative (3M Espe, USA) and DentLight (VladMiVa, Russia). Each subgroup consisted of 30 patients. In the control group, the classical method of filling with a composite material at “room temperature” was applied. In the main group, a composite heating conditioner “Ena Heat” (Micerium, Italy) was used to heat the composite to 55 °C before adapting the material in the formed cavity with subsequent photopolymerization. The quality of composite restorations within the clinical study was evaluated using the modified Ryge criterion immediately after treatment and after 6, 12, 18, 24 months. Statistical processing of the obtained data was carried out by means of one-factor analysis of variance using the GraphPadPrism 9 program (GraphPad Software, USA).Results. The duration of the clinical study comprised 24 months. The study revealed a statistically significant decrease in the quality of marginal fit of composite restorations (according to the Ryge score) by 20.1% (p = 0.0001) in the control group and by 5.7% (p = 0.0328) in the main group. At the same time, no statistically significant changes in Ryge scores were reported in the subgroups of composite materials of the main group (pF = 0.9480, pE = 0.1837, pD = 0.2529). As a result of the study, an optimal time algorithm (7 seconds) for using a special furnace for preheating the composite before sealing with subsequent photopolymerization was obtained.Conclusion. The study revealed a statistically significant positive effect of the proposed algorithm for working with a heated composite on the quality of marginal fit in the long term after treatment in comparison with the classical method of working with a composite at “room temperature”.

Productivity Decline Mechanisms in Gravel Packed Perforations

In a cased hole gravel pack completion, perforations are packed with proppant to both mechanically support the perforation cavity, and to filter any produced sand before it reaches the surface. Poor perforation packing sometimes occurs in which the perforation is partially or completely unsupported, leading to earlier productivity reduction than in cases of good packing. We investigated productivity reduction and the associated mechanisms in a series of hollow cylinder experiments on outcrop and field cores with varying proppant packing. Packed perforations maintained significantly higher productivity than unsupported perforations by preventing macroscopic shear failure around the cavity and erosion due to sand production. Partial packing may in some instances maintain productivity almost as well as complete packing, but this likely depends on perforation orientation. Compaction tests and numerical simulations suggest that compaction failure is unlikely at the cavity wall in the current experiments, and that proppant-formation interface damage or proppant filtering of produced sand are more probable explanations for the productivity reduction seen in packed perforations.

The impurity effect on the capacitance of ionic liquid-based supercapacitors: A classical density functional theory study of ionic liquids inside the spherical cavity of the porous electrode

The effect of impurities on the capacitance curve has been investigated for ionic liquid-based supercapacitors. The coarse-grained model in the framework of classical density functional theory (CDFT) was used to predict the electric double layer (EDL) formed at the concave wall of the spherical cavity of a porous electrode. Our results demonstrate that the adsorption and desorption of impurities by the cavity have a significant impact on the shape of the capacitance curve. In some cases, a bell-camel shape transition in the capacitance curve occurs due to the adsorption of impurities. By increasing the impurity concentration and its attraction with the cavity, the position of the observed maximums in the camel shape of the capacitance curves shifts toward a higher electrode potential. In addition, we have shown that impurity adsorption affects the value of the zeta potential by reducing the total net ion charges stored inside the cavity. Increasing the electrode potential to a specific value causes the total desorption of impurities; hereinafter, we call that the potential of zero impurity adsorption, ΨZIA. The amount of this potential depends on the concentration of impurities, cavity size, impurity-cavity attraction, and the shape of ions in ionic liquids. As we expected, the impurity has no effect on the amount of capacitance for electrode potentials higher than ΨZIA. Finally, the differential capacitance curves for symmetric impure ionic liquid in spherical cavities have been compared to those for slit pores. Results show the same behavior for both of them, but the effect of impurity can be ignored at lower electrode potential in the case of spherical cavities due to the more confinement effect.

Acoustics in Flameholding Solid-Fuel-Ramjet Fuel Grains

Experiments are conducted to determine how acoustic perturbations affect the performance and flameholding of solid-fuel ramjets with nonstandard combustion chambers. The focus is on the effect of wall cavities carved in the fuel grain using additive manufacturing. An improved understanding of how the wall geometry contributes to the establishment of acoustic modes is sought. A novel combustion mechanism was developed using a counterflow burner to study the combustion and regression of solid model fuel polymethyl methacrylate. The diffusion flame between the fuel and oxidizer was studied numerically using a solid-fuel decomposition and melt layer model to simulate convection and pyrolysis of the material. This model was validated using new experimental data as well as previously published works. The foam layer parameters are critical to the success of the validation, showing that the increased residence time of the gas in the bubbles facilitates the fuel breakdown. Fourth-order computational simulations of ramjet combustion without regressing fuel walls using a novel discontinuous Galerkin approach are performed with a fully conjugate solution for the thermal wave in the solid. Turbulent transport strongly affects the heat feedback to the walls, and low-frequency vortical modes (e.g., with a vortical wavemaker) associated with a recirculation region at the injector upstream wall are linked to an increase in chamber pressure and fuel mass flux.

Natural Convection Cooling of a Heat Source Placed at the Bottom of a Square Cavity Filled with Water-Based Nanofluid

The present work deals with the cooling process of a heat source, placed in the center of the bottom wall of a square cavity. A numerical resolution using finite volume method was carried out. The cavity is filled with a water-based Nanofluid, where four different types have been assumed. The vertical and top walls are under low temperature TC. Two thermal conditions were assumed at the source (q-imposed or T-imposed), while the remaining parts of the same wall are isolated. The effects of Rayleigh number (Ranf), source length (SL), volume concentration of nanoparticles (Φ) and their types were analyzed. The case of pure water (Φ = 0%), studied first, served as a reference case. The results obtained for this case, showed the increase of disturbances in the dynamic and thermal fields, in addition to the average rate of heat transfer (Nu) when Ra increases and SL decreases. SL = 1.0 case showed exception. These effects are more important for the T-imposed case than the other. Subsequently, the Al2O3-Water Nanofluid is considered with 0 <Φ≤ 10%. An increase in circulation intensity with improvement of local (Nu) and average (Nu) heat exchange rates have been recorded when Φ increases, although mentioning that its effect is significantly stronger for the q-imposed case. In the last part of the work, three other types of Nanofluids were assumed, where the obtained results showed the main improving effect of higher thermal conductivity on the heat transfer intensity. An important result which can be summed up in the great rapprochement of the heat exchange intensities for strong Ranf and Φ for SL close to 1.0, for the two heating types. In other words, the condition on the source loses its importance for such considerations.

Design of an Emittance Compensation Superconducting Magnet Package for LCLS-II-HE's SRF Photo-Injector

An SRF photo-injector (low frequency, quarter-wave resonator plus emittance compensation magnet) is planned for LCLS-II-HE as it can provide a higher cathode gradient and better electron beam quality than other types of CW electron guns. The magnet package is located immediately downstream of the SRF cavity, and incorporates a solenoid doublet, bucking coils for reduction of the fringe field, normal/skew quadrupoles and horizontal/vertical dipoles. All the magnets are wound of NbTi wire and operate in liquid helium environment. The solenoid package is located inside the SRF gun cryomodule. Design considerations include space limitations, optimal emittance compensation, the magnetic field limits in the superconducting wire and quench protection. The solenoid coils must provide a peak excitation > 25 kgauss <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ·cm, a fringe field < 20 gauss at the wall of the SRF cavity, an integrated dipole field < 90 gauss·cm and an integrated quadrupole field < 10 gauss. A genetic algorithm was used to optimize the solenoid design. Correction dipoles and quadrupoles were designed using coil dominated Walstrom style coils.

Enhancement of Boiling Histotripsy by Steering the Focus Axially During the Pulse Delivery.

Boiling histotripsy (BH) is a pulsed high-intensity focused ultrasound (HIFU) method relying on the generation of high-amplitude shocks at the focus, localized enhanced shock-wave heating, and bubble activity driven by shocks to induce tissue liquefaction. BH uses sequences of 1-20 ms long pulses with shock fronts of over 60 MPa amplitude, initiates boiling at the focus of the HIFU transducer within each pulse, and the remainder shocks of the pulse then interact with the boiling vapor cavities. One effect of this interaction is the creation of a prefocal bubble cloud due to reflection of shocks from the initially generated mm-sized cavities: the shocks are inverted when reflected from a pressure-release cavity wall resulting in sufficient negative pressure to reach intrinsic cavitation threshold in front of the cavity. Secondary clouds then form due to shock-wave scattering from the first one. Formation of such prefocal bubble clouds has been known as one of the mechanisms of tissue liquefaction in BH. Here, a methodology is proposed to enlarge the axial dimension of this bubble cloud by steering the HIFU focus toward the transducer after the initiation of boiling until the end of each BH pulse and thus to accelerate treatment. A BH system comprising a 1.5 MHz 256-element phased array connected to a Verasonics V1 system was used. High-speed photography of BH sonications in transparent gels was performed to observe the extension of the bubble cloud resulting from shock reflections and scattering. Volumetric BH lesions were then generated in ex vivo tissue using the proposed approach. Results showed up to almost threefold increase of the tissue ablation rate with axial focus steering during the BH pulse delivery compared to standard BH.

CALCULATION METHOD OF LATERAL STIFFNESS OF PVC CAVITY PARTITION WALL WITH DIFFERENT CONNECTION FORMS

To explore the difference in seismic performance of walls with different connections, this paper designs a pseudo-static test of three groups of steel frames infilled with walls and a group of empty steel frame as a control. The test phenomena and the datum are used to evaluate the performance of structures. The results show that: (I) the initial stiffness and the peak load of the cast-in-place wall are large. The main failure modes are cracking at the joint between the wall and the frame, crushing at the corner, and internal splitting as well as curving outwards under large displacement. (II) The wall with L-shaped connectors dissipates energy by bolt slip and the yield deformation of connectors, which has the lowest contribution to the frame in stiffness and strength. The main failure is the cracking of cement mortar at the joint. (III) The connection mode of U-shaped and L-shaped connectors is relatively safe and reliable, which could make the steel frame and wall panel work better together under the action of earthquake. It could be recommended to use according to the bearing capacity requirements; Walls connected by reinforcement are not recommended because of brittleness failure, poor ductility, ordinary bearing capacity and energy dissipation capacity. Based on the principle of equivalent tension and compression bar, a simplified formula for calculating the lateral stiffness of polyvinyl chloride (PVC) cavity wall panel embedded in fabricated steel frame is proposed, and the accuracy of the calculation results is verified.

A Numerical Study of The Heat Transfer Intensification Using High Amplitude Acoustic Waves

The current practice in the efforts aiming to improve cooling conditions is to place emphasis on the application of non-stationary flow effects, such as the unsteady jet heat transfer or the heat transfer intensification by means of a high-amplitude oscillatory motion. The research presented in this paper follows this direction. A new concept is put forward to intensify the heat transfer in the cooling channels with the use of an acoustic wave generator. The acoustic wave is generated by a properly shaped fixed cavity or group of cavities. The sound generated by the cavity is a phenomenon analysed in various publications focused on the methods of its reduction. The phenomenon is related to the feedback mechanism between the vortices flowing from the leading edge and the acoustic waves generated within the cavity. The acoustic waves are generated by the interaction between the vortices and the cavity walls. Strong instabilities can be observed within a certain range of the free flow velocities. The investigations presented in this paper are oriented towards the use of the phenomenon for the purposes of the heat transfer process intensification. The first part of the work presents the numerical model used in the analysis, as well as its validation and comparison with empirical relations. The numerical model is constructed using the commercial CFD Ansys CFX-16.0 commercial program. The next part includes determining of the relationship between the amplitude of the acoustic oscillations and the cooling conditions within the cavity. The calculations are performed for various flow conditions.

Evaluation of Effect of Vitamin C on Streptococcus Mutans Induced Secondary Caries: An In vitro Study

This study aimed to assess and understand the protective effect of vitamin C against secondary caries formation around the margins of class V restorations with the help ofan in-vitro bacterial caries model. In this study, a total of 30 mandibular premolars were chosen and assigned to three groups (n=10). In this study, Class V composite restorations were prepared and along with pretreatment of the cavity walls with various solutions like Vitamin C (ascorbic acid solution), HEPES buffer solution and chlorhexidinedigluconate. After incubating specimens with Streptococcus mutans, dentin and enamel were assessed using Fluorescence Microscopy.The study showed Vitamin C (Ascorbic acid) inhibited the formation of secondary caries near the dentin resin interface. No inhibitory effects were observed in enamel margins. From the study, it could be concluded that the incorporation of ascorbic acid in the restorative procedure of resin composite may inhibit secondary caries formation. Neither the application of chlorhexidine nor HEPES buffer had much effect on the inhibitory effect on secondary caries.

EERZ (Effective Equilibrium Reaction Zone) Model of Gas-Slag-Metal Reactions in the Application of Unconstrained Al-Ni-Cr-Co-Cu Metal Powders in Submerged Arc Welding: Model and 3D Slag SEM Evidence

The scope of this work is to improve the SAW process understanding and present an improved description of the SAW process in terms of gas-slag-metal reactions with alloy powder and Al powder additions. The scope does not include the materials properties of the weld metal. The latter may easily be optimised in the future by changing the weld metal chemistry once the process reactions of different element powders in SAW are understood. Aluminium as de-oxidiser element was applied to SAW to lower the oxygen partial pressure in the process. The results show the Al-Ni-Cr-Co-Cu alloyed weld metal total oxygen content was reduced to 257 ppm O, compared to the base case weld metal at 499 ppm O, made with the same flux and no metal powder additions. Thus, the aluminium that was added as a de-oxidiser element to the SAW process effectively lowered the original flux-induced partial oxygen pressure, both in the arc cavity and at the interface of the molten flux–weld pool phases. This partial oxygen pressure lowering effect of Al also prevents oxidation of Cr, preventing loss of Cr to the slag. Carbon steel was alloyed to 3.9% Al, 4.8% Ni, 4.9% Cr, 4.8% Co, 4.7% Cu at 62% Al yield, 76% Ni yield, 77% Cr yield, 75% Co yield, 74% Cu yield. SEM (scanning electron microscope) work on the three-dimensional (3D) post-weld slag sample show dome cavities with 3D rounded structures embedded in the dome cavity walls, as well as shards and nano-strands on the dome cavity walls. The 3D structures indicate vapour formation and re-condensation of oxy-fluorides. The novel application of the EERZ (effective equilibrium reaction zone) model simulates the mass transfer effects in the SAW process. This model is novel because it is the first model used to calculate the gas-slag-metal phase chemistry changes in SAW as a function of welding time. The novel SAW process modification of adding Al de-oxidiser powder with alloying element powders of the unique combination of Co-Cr-Co-Ni-Al was successfully applied. The results confirm that the gas phase and its reactions must be included in the interpretation and modelling of SAW process metallurgy.

Active control of pressure fluctuations in an incompressible turbulent cavity flow

Large-eddy simulations of incompressible turbulent boundary layer flows over an open cavity are conducted to investigate the effects of wall-normal steady blowing on the suppression of pressure fluctuations on the cavity walls. The length (L) to depth (D) ratio (L/D) of the cavity is 2 and the Reynolds number based on the cavity depth (ReD) is 12,000. Wall-normal steady blowing is imposed through a limited transverse slot in an upstream region of the cavity leading edge while varying the momentum coefficient (Cμ). As the value of Cμ increases, the pressure fluctuations on the cavity walls decrease mostly due to weakened impingement of turbulent vortical structures residing in the shear layer on the aft wall by lifting effects, reaching a maximum reduction of −7.61% compared to a baseline when Cμ=0.015. However, as the value of Cμ increases further, the pressure fluctuations increase gradually, exceeding that of a baseline when Cμ>0.05. Because intensified turbulent vortical structures in the shear layer with an increase of Cμ lead to strong interactions of small-scale vortices with the cavity walls with an accompanying large motion of the primary recirculation zone within the cavity, additional pressure fluctuations generated on the cavity walls deteriorate the control performance due to the blowing.

Numerical and Experimental Investigation on a "Tai Chi"-Shaped Planar Passive Micromixer.

(1) Background: Microfluidic chips have found extensive applications in multiple fields due to their excellent analytical performance. As an important platform for micro-mixing, the performance of micromixers has a significant impact on analysis accuracy and rate. However, existing micromixers with high mixing efficiency are accompanied by high pressure drop, which is not conducive to the integration of micro-reaction systems; (2) Methods: This paper proposed a novel "Tai Chi"-shaped planar passive micromixer with high efficiency and low pressure drop. The effect of different structural parameters was investigated, and an optimal structure was obtained. Simulations on the proposed micromixer and two other micromixers were carried out while mixing experiments on the proposed micromixer were performed. The experimental and simulation results were compared; (3) Results: The optimized values of the parameters were that the straight channel width w, ratio K of the outer and inner walls of the circular cavity, width ratio w1/w2 of the arc channel, and number N of mixing units were 200 μm, 2.9, 1/2, and 6, respectively. Moreover, the excellent performance of the proposed micromixer was verified when compared with the other two micromixers; (4) Conclusions: The mixing efficiency M at all Re studied was more than 50%, and at most Re, the M was nearly 100%. Moreover, the pressure drop was less than 18,000 Pa.

Chemo-hydro-mechanics in a reactive rock under cylindrical fluid pressurization

Cylindrical cavity expansion in a geomaterial due to internal fluid pressurization occurs in many geo-energy and geo-environmental engineering problems involving fluid injection into the subsurface. Often, acidic substances are incorporated in the fluid injection posing a chemically aggressive environment at the cavity wall which diffuses into the matrix affecting the rock’s mechanical as well as hydraulic properties via mineral mass removal. Here we propose a coupled chemo-hydro-mechanical model for such scenarios to study the complex interplay between the process of chemical mass removal, damage evolution, rock strength degradation and an alteration of the hydraulic field due to chemical erosion. A homogeneous fully saturated carbonate rock is chosen for qualitative and quantitative assessments as a representative of chemically reactive geomaterials. Plane strain conditions are assumed and all the fields involved in the reaction-transport-deformation process zone are axisymmetric. The rock behaviour is chemically controlled in both the elastic and plastic domain adopting a chemo-elasticity concept and a yield limit depending on the accumulated mass removal, i.e. the total amount of mineral dissolution under high Damköhler number conditions. The rate of chemical dissolution at a continuum scale is described as a function of a variable specific surface area of the solid–fluid interface per unit volume affected by the irreversible micro-cracking process, as well as the local acidity. The irreversible damage evolution is coupled to the hydraulic field via the porosity generation by chemical mass removal, affecting the acid delivery. The presented framework is the first rock cavity expansion model to our knowledge that underpins a spontaneous transition from the diffusion-dominant to a diffusion–advection regime enabled by damage-enhanced chemical mass removal.

Thermal analysis for gas storage in salt cavern based on an improved heat transfer model

Oversimplification of the heat transfer mechanism and assumption of uniform temperature and pressure in the salt cavern could cause significant errors when modeling temperature fields. This work proposed a coupled transient flow and heat transfer model for gas storage in the underground salt cavern to reflect the thermal behaviors between gas and surrounding rock, particularly the gas Joule-Thomson effect during gas operation. Then, a fully coupled numerical solution method based on a unified matrix is presented. An average error of 3.26% was observed between the model and field data quoted in literature. The case study indicates that during the gas withdrawal period, the maximum temperature difference in the salt cavern can reach 14.94 °C, while the temperature drop of the cavity wall is only about 4.07 °C, which is quite different from the traditional assumption. A special focus was given to the gas withdrawal rate, which seemed to have the most significant influence on the evolution of the temperature field in the salt cavern. Compared with the gas withdrawal rate of 35 m3/s, reducing the gas withdrawal rate to 20 m3/s can increase the minimum temperature by approximately 23.41%. This study could add further insights into the thermal performance during gas operation in the salt cavern and help to reveal the evolution of the temperature field in the cavity and surrounding rock.

Surgical approach analysis of endoscopic resection of juvenile nasopharyngeal angiofibroma

Objective:To investigate the surgical approach for the resection of juvenile nasopharyngeal angiofibroma（JNA） under nasal endoscopy. Methods:The clinical data of 87 patients undergoing endoscopic resection of nasopharyngeal fibroangioma were retrospectively analyzed. We classified JNA according to tumor site, size, invasion scope and anatomic position relationship between tumor and midline of pupil. Three endoscopic surgical approaches were selected according to the classification, and the postoperative symptoms, complications and recurrence were investigated and analyzed. Results:The tumor resection rate of 87 cases by nasal endoscopic surgery was 100%. Thirty-five cases were approached through the middle nasal passage（small tumors located in the nasal sinuses and pterygopalatine fossa）, forty-five cases were approached through the lateral wall of the nasal cavity（tumor invaded the pterygopalatine fossa but did not exceed the midline of the pupil） , and seven cases were approached via the lateral wall of nasal cavity + ipsilateral anterior wall of maxillary sinus（tumor invaded the infratemporal fossa beyond the midline of pupil or invaded the cavernous sinus and the middle cranial fossa epidural）, Postoperative patients with nasal congestion, nasal bleeding, headache, dizziness, vision loss and other symptoms showed varying degrees of improvement. No surgical death or intracranial infection occurred. The postoperative follow-up was 6-78 months, and the recurrence rate was 3.44%. Conclusion:Endoscopic resection of nasopharyngeal fibroangioma is the main treatment method for JNA. Selecting suitable endoscopic approach to resect JNA, To maximize the advantage of nasal endoscopic equipment according to the inherent anatomical space of the human nasal cavity, In order to achieve the purpose of JNA resection, reduce intraoperative and postoperative complications, reduce the recurrence rate and improve the prognosis.

Simulation study for efficiency optimization of multi-beam klystron output cavity

Increasing klystron tubes’ efficiency is essential in developing new-generation colliders and free-electron lasers. Different factors can affect the efficiency of a multi-beam klystron. One of the significant factors is the electric field symmetry inside cavities, especially in the output section. In this research, two different types of couplers are investigated in the extraction cavity of a 40-beam klystron. The first approach is a single slot coupler, which is frequently utilized and easier to fabricate but disturbs the electric field symmetry inside the extraction cavity. The second method has a more complex structure with symmetric electric fields. In this design, the coupler consists of 28 mini slots on the inner wall of the coaxial extraction cavity. Both designs are evaluated via particle in cell simulations, and the results exhibit around 30% more power extracted from the structure with a symmetric field distribution. The symmetric structures can also decrease the number of back-streamed particles by up to 70%.