Visco-Elastic Properties of Semi-Solid Alloys

Oscillation and creep experiments have been performed with Semi-Solid Material (SSM) AlSi7 with 35% solid fraction to investigate the early visco-elastic properties after shearing of the material in a Searle Rheometer. The preparation of the SSM has been done in situ using a standard procedure to guarantee for all experiments the same initial properties of the material. First, oscillation experiments at low amplitude allowed to study the evolution of material structure with time. Subsequently, creep experiments have been performed changing the resting period based on previous results. Creep experiments are characterized by exposing the material to a sudden increase of shear stress. The resolution in time has been 0.01 seconds, which allows observing the dynamics of the development of visco-elastic properties.The material exhibits viscoelastic properties that are becoming more pronounced with longer resting time. This is in accordance with previous experiments where the ratio between elastic and viscous properties increases with increasing resting time. The development of the elastic properties follows the increase of the yield stress due to the creation of an internal structure of the material, which starts immediately after stopping shearing. The investigation of the short-term response of SSM can be particularly relevant for industrial practice, where material deformation during die filling is very fast and the material flow does not take place in steady-state condition.

TRANSIENT OPERATION OF SENSIBLE FIXED-BED REGENERATORS

Fixed-bed regenerator is a type of air-to-air energy exchanger and recently introduced for energy recovery application in HVAC systems because of their high heat transfer effectiveness. Testing of FBRs is essential for performance evaluation and product development. ASHRAE and CSA recently included guidelines for testing of FBRs in their respective test standards. The experiments on FBRs are challenging as they never attain a steady state condition, rather undergoes a quasi-steady state operation. Before reaching the quasi-steady state, FBRs undergo several transient cycles. Hence, the test standards recommend getting measurements after one hour of operation, assuming FBR attains the quasi-steady state regardless of test conditions. However, the exact duration of the initial transient cycles is unknown and not yet studied so far. Hence, in this paper, the duration of FBR's transient operation is investigated for a wide range of design and operating conditions. The test standards' recommendation for the transient duration is also verified. The major contributions of this paper are (i) quantifying the effect of design parameters (NTUo and Cr*) on the duration of transient operation and (ii) investigation of the effect of sensor time constant on the transient temperature measurements. The results will be useful to predict and understand the transient behavior of FBRs accurately.

How Reliable is the Thermal Conductivity of Biobased Building Insulating Materials Measured with Hot Disk Device?

Thermal conductivity is of high importance for insulating materials since it strongly influences the thermal performance of the building. Generally, it is recommended to measure this property with steady-state methods like guarded hot plate (GHP) or heat flow meter (HFM). These methods are reliable, but steady-state condition can take a long time to be reached. Therefore, transient methods were developed to speed-up the measurements. For instance, the hot disk transient plane source method is a widely used standard technique (ISO 22007-2) for measuring thermal conductivity of various materials. In the last 20 years, this technique has been applied also to bio-based insulating materials. However, overestimated thermal conductivity (compared to steady state method) are frequently measured. More generally, such differences are also observed for low thermal conductivity materials. The aim of this work is to evaluate the influence of numerous factors to explain the origin of these differences. The factors include the experimental setting parameters, the measurement analysis parameter or even the discrepancies between the theoretical model and the real experimental set-up. The analysis is performed for a light-earth biobased concrete made of raw earth and hemp shiv. Recommendations are proposed in conclusion.

Synovial and Systemic Pharmacokinetics of Florfenicol and PK/PD Integration against Streptococcus suis in Pigs

Florfenicol is a member of the phenicol group, a broad-spectrum antibacterial agent. It has been used for a long time in veterinary medicine, but there are some factors regarding its pharmacokinetic characteristics that have yet to be elucidated. The aim of our study was to describe the pharmacokinetic profile of florfenicol in synovial fluid and plasma of swine after intramuscular (i.m.) administration. In addition, the dosage regimen of treatment of arthritis caused by S. suis was computed for florfenicol using pharmacokinetic/pharmacodynamic (PK/PD) indices. As the first part of our investigation, the pharmacokinetic (PK) parameters of florfenicol were determined in the plasma and synovial fluid of six pigs. Following drug administration (15 mg/kgbw, intramuscularly), blood was drawn at the following times: 10, 20, 30, 40, 50 and 60 min, 2, 3, 4, 5, 6, 7, 8, 12, 24, 48 and 72 h; synovial fluid samples were taken after 1, 2, 3, 4, 6, 8, 12, 24, 48 and 72 h. The concentration of florfenicol was determined by a validated liquid chromatography-mass spectrometry (LC-MS/MS) method via multiple reaction monitoring (MRM) modes. As the second part of our research, minimum inhibitory concentration (MIC) values of florfenicol were determined in 45 S. suis strains isolated from clinical samples collected in Hungary. Furthermore, a strain of S. suis serotype 2 (SS3) was selected, and killing-time curves of different florfenicol concentrations (0.5 µg/mL, 1 µg/mL and 2 µg/mL) were determined against this strain. Peak concentration of the florfenicol was 3.58 ± 1.51 µg/mL in plasma after 1.64 ± 1.74 h, while it was 2.73 ± 1.2 µg/mL in synovial fluid 3.4 ± 1.67 h after administration. The half-life in plasma was found to be 17.24 ± 9.35 h, while in synovial fluid it was 21.01 ± 13.19 h. The area under the curve (AUC24h) value was 54.66 ± 23.34 μg/mL·h for 24 h in plasma and 31.24 ± 6.82 μg/mL·h for 24 h in synovial fluid. The drug clearance scaled by bioavailability (Cl/F) in plasma and synovial fluid was 0.19 ± 0.08 L/h/kg and 0.29 ± 0.08 L/h/kg, respectively. The mean residence time (MRT) in plasma and synovial fluid was 24.0 ± 13.59 h and 27.39 ± 17.16 h, respectively. The steady-state volume of distribution (Vss) in plasma was calculated from Cl/F of 0.19 ± 0.08 L/h/kg, multiplied by MRT of 24.0 ± 13.59 h. For the PK/PD integration, average plasma and synovial fluid concentration of florfenicol was used in a steady-state condition. The obtained MIC50 value of the strains was 2.0 µg/mL, and MIC90 proved to be 16.0 µg/mL. PK/PD integration was performed considering AUC24h/MIC breakpoints that have already been described. This study is the first presentation of the pharmacokinetic behavior of florfenicol in swine synovia as well as a recommendation of extrapolated critical MICs of S. suis for therapeutic success in the treatment of S. suis arthritis in swine, but it should be noted that this requires a different dosage regimen to that used in authorized florfenicol formulations.

ANALISIS METODE BAYESIAN PADA KINERJA SISTEM ANTREAN INSTALASI RAWAT JALAN RSUP DR. KARIADI (Studi Kasus: Poliklinik Mata, Poliklinik THT, Laboratorium, dan Pendaftaran)

Indonesian people’s awareness of the importance of health has increased significantly so that it has a positive impact on the development of the health sector in Indonesia. The largest service facility in Central Java Province is RSUP Dr. Kariadi. The number of patients who came for an examination at Dr. Kariadi’s arrival rate is unpredictable. This can cause the service system to be busy and result in queues. The purpose of this study was to find out how the service system in Dr. Kariadi especially eye polyclinic, ENT polyclinic, laboratory, and registration. Queue theory has random arrivals and services. Bayesian method is used to analyze the queue system, that has been running for a long time by combining the prior and likelihood distribution of samples. Prior distribution is obtained from previous research, namely the Poisson distribution. Meanwhile, the likelihood of the sample obtained from the current study is the Poisson distribution and the Negative Binomial distribution. The resulting queue models for the eye polyclinic are (GAMM/BETA/4):(GD/∞/∞), ENT polyclinic (GAMM/GAMM/2):(GD/∞/∞), laboratory (GAMM/GAMM/4):(GD/∞/∞), and registration (GAMM/GAMM/3):(GD/∞/∞). Based on the results of the study, it was found that the patient care system at the eye polyclinic, ENT polyclinic, laboratory, and registration met steady state condition, meaning that the service system was running well. The value of the unemployment rate at the eye polyclinic is 96,36%; ENT polyclinic 31,86%; laboratory 34,87% and registration 32.85%. Thus, at the eye polyclinic, the unemployment rate is greater than the busy level. Meanwhile, in ENT polyclinics, laboratories, and registration is the opposite occurs.

Diffusion and surface reaction in porous cubical catalyst: A mathematical approach

Background: Catalysts are the most vital part of any chemical industry. Catalyst is a substance that affects the rate of reaction, but the catalyst itself does not take part in the reaction. Catalysts offer different pathways of reaction by diffusing the reactant inside it to provide a large surface area within a small volume, thus, lowering the activation energy of molecules for reaction. Most of the catalytic reactions take place in liquid-solid or gas-solid interface where catalysts are mostly porous in nature. Spherical and cubic-shaped catalyst particles are commonly used in different industries. Methods: In the first phase of the present study, the physics behind the diffusion inside the catalyst pellet has been discussed. In the second part, governing differential equations have been established at a steady-state condition. For solving the differential equation, the equation is made dimensionless. Physical boundary conditions were used to solve the diffusion equation. The assumption of writing the differential equation of the reaction is elementary. Then the Thiele modulus is derived in terms of the reaction and geometrical parameter (Length) Results and Conclusion: In the third part, the differential equation is solved for first-order reaction with some constant values of the Thiele modulus and three-dimensional plots are obtained using numerical analysis. After that, the obtained Thiele modulus and effectiveness factor plot are compared to draw the conclusion of reaction rate limited and internal diffusion limited.

Mitigation of Circulating Currents for Parallel Connected Sources in a Standalone DC Microgrid

In a standalone DC microgrid, sources are interconnected in a parallel configuration. When sources of different power ratings are parallel connected, there arises a major issue of circulating currents which disturb current sharing by sources as per their capacity. Consequently, the voltage regulation becomes poorer. Additionally, connecting line resistances also play their part to contribute to abnormal current sharing. Droop controllers are normally preferred for the mitigation of circulating currents among parallel-connected sources. However, droop controllers cannot eliminate circulating currents for different rating sources. Hence, current sharing and voltage regulation cannot be ensured simultaneously. To address the issues, a distributed architecture-based Sliding Mode Control (SMC) technique is proposed in this paper. An analysis of the circulating currents for a two-source system is presented. Simulation results are presented to show the effectiveness and fail-safe operation of the proposed technique in a steady-state condition.

Paper-based Triboelectric Nanogenerator and Activities of Salt Ions

This work presents a triboelectric nanogenerator (TENG) fabrication using polytetrafluoroethylene, aluminum foil, and cellulose paper. Mechanical interactions lead to atomic defects that stimuli the delocalized electrostatic charge carriers and kinetic energy. The addition of ionic salt’s microdroplets improved the TENG’s performance. Eventually, surface charge activities have escalated the electrical signals. Further, studied spontaneously increased charge transport performance at the steady-state condition in the presence of NaCl ionic droplets. We considered that these ionic activities actively participated in detecting salt ions.

Transient evolution of basal drag during glacier slip

Glacier slip is usually described using steady-state sliding laws that relate drag, slip velocity and effective pressure, but where subglacial conditions vary rapidly transient effects may influence slip dynamics. Here we use results from a set of laboratory experiments to examine the transient response of glacier slip over a hard bed to velocity perturbations. The drag and cavity evolution from lab experiments are used to parameterize a rate-and-state drag model that is applied to observations of surface velocity and ice-bed separation from the Greenland ice sheet. The drag model successfully predicts observed lags between changes in ice-bed separation and sliding speed. These lags result from the time (or displacement) required for cavities to evolve from one steady-state condition to another. In comparing drag estimates resulting from applying rate-and-state and steady-state slip laws to transient data, we find the peaks in drag are out of phase. This suggests that in locations where subglacial conditions vary on timescales shorter than those needed for cavity adjustment transient slip processes control basal drag.