Chulalongkorn University
  • Bangkok, Thailand
Recent publications
Multirobot systems are used in operations where a single robot is not capable. In this paper, a team of multirobot system is used to transport an object which the carried object is much larger than a single robot can carry. To transport the oversized object smoothly, control and communication between robots is crucial for smooth object manipulation. In this application, the robots move linearly along rails. The different position between robots was measured by using an incremental encoder attached at a support point on the robot to measure the angle between robots. A control feedback method was implement using P control to eliminate the relative position between the master and slave robot. Through experiments, it has been shown that the slave robot can follow the master robot with relative positioning error less than 4 cm, or less than 5° of misalignment.
As one of the most effective strategies for the storage and utilization of solar energy, the development of photocatalytic technology has received extensive attention. The core work, the design and modification of photocatalysts, is very significance. Herein, we prepared C, N co-doped Co3O4 (CN-CoO) by a simple method and composited it with CdS to form CN-CoO/CdS p-n type heterojunctions. The prepared materials are characterized by numerous tests, such as XRD, SEM, TEM, XPS, and photoelectrochemical measurement. Due to the excellent electrochemical performance of CN-CoO and the built-in electric field in CN-CoO/CdS, the efficient separation of photogenerated charges is realized. Compared with CdS (1.11 ns), the average carrier lifetimes of the 15%CN-CoO/CdS (1.63 ns) is prolonged, which enhances photocatalytic hydrogen evolution activity of the composite materials. The hydrogen evolution rate of the optimal 15%CN-CoO/CdS is 6.78-fold greater than that of pristine CdS, and is as high as 64.36 mmol·g⁻¹·h⁻¹. Meanwhile, the 15%CN-CoO/CdS exhibits outstanding chemical stability after cyclic hydrogen production experiment for 30 h, and its apparent quantum efficiency (AQE) reaches 27.47% under monochromatic light at 405 nm. In addition, the formation process and photocatalytic hydrogen evolution mechanism of the CN-CoO/CdS p-n type heterojunctions are analyzed and discussed. This work provides a new idea for the construction of efficient photocatalytic heterojunctions through the modification and combination of semiconductors.
Selective hydrogenation of soybean oil-derived fatty acid methyl esters (FAMEs) with low oxidative stability over supported Pd catalysts is crucial to the production of monounsaturated counterparts (mono-FAME), whose oxidative stability and cold flow properties are suitable for producing fuels with high blend ratios. However, supported Pd catalysts are easily deactivated by sulfur-containing FAMEs. Herein, the performance and sulfur poisoning of Pd-Pt/SiO2, Pd-Pt/γ-Al2O3, and Pd-Pt/SiO2-Al2O3 bimetallic catalysts containing 3–10 nm Pt-Pd alloy particles and possessing surface acidity of 0.1–2.4 mmol NH3 g⁻¹ were examined. Pd-Pt/SiO2 with large Pd-Pt alloy particles (10 nm) and weak acidity (0.1 mmol NH3 g⁻¹) favored the selective hydrogenation of polyunsaturated-FAME (poly-FAME) to mono-FAME, while Pd-Pt/γ-Al2O3 and Pd-Pt/SiO2-Al2O3 with smaller Pd-Pt alloy particles and stronger acidity favored the formation of saturated-FAME. These Pd-Pt catalysts were poisoned when using FAME containing 3.4–5.3 ppm of sulfur. However, the performance of the Pd-Pt/SiO2 catalyst physically mixed with γ-Al2O3 did not deteriorate when using a feedstock containing 5.3 ppm of sulfur because the acidic γ-Al2O3 support could adsorb sulfur. Thus, the combination of acidic γ-Al2O3 and Pd-Pt/SiO2 catalysts can be efficiently used to produce mono-FAME through the selective hydrogenation of commercial biodiesel fuels containing high poly-FAME concentrations.
This paper studies discrete-time risk models with insurance premiums adjusted according to claims experience. The premium correction mechanism follows the well-known principle in the non-life insurance industry, the so-called bonus-malus system. The bonus-malus framework that we study here extends the current literature by allowing the premium correction rules to vary according to the current surplus level of the insurance company. The main goal of this paper is to evaluate the risk of ruin for the insurer who implements the proposed bonus-malus system. Two premiums correction principles are examined: by aggregate claims or by claim frequency. Further, the Parisian type of ruin is also considered, where the premium adjustment rules are different in positive- and negative-surplus environment.
Advertising plays an essential role for creating brand awareness that leads to consumer behavior toward services and products. The objective of this research is to investigate the role of mid-roll video advertising regarding its perceived intrusiveness and value on viewers’ response to those ads. Data from 200 users who have experienced mid-roll video advertising were analyzed in a two-step method via structural equation modeling (SEM) and confirmatory factor analysis (CFA). The indirect impacts were investigated and compared via the bootstrap approach. The analysis confirms that the value of mid-roll video advertising is significantly and positively associated with attitude toward mid-roll video advertising and word-of-mouth (WOM) intention. In addition, the positive connection between WOM intention and attitude as well as viewers’ response are observed. However, the negative association between perceived intrusiveness and attitude is found as well in this research. For the contributions, the result not only strengthens the importance of the advertising value theory as a framework to explain the impact of advertising, but also provides recommendations for advertisers and content creators regarding some managerial actions that may need to be taken in order to satisfy consumers.
Pulmonary hypertension (PH) is a common complication in dogs with degenerative mitral valve disease (DMVD). The aim of this study was to determine the survival time and to determine factors related to the survival time of dogs with PH secondary to DMVD stage C. A retrospective study was conducted in 37 dogs with PH secondary to DMVD stage C to analyse the median survival time and associated factors such as age, sex, breed, body weight, the presence of syncope, heart rate, systolic blood pressure, manifestation of congestive heart failure (CHF), vertebral heart score (VHS), the presence of left or right heart enlargement, probability of PH and medication. Data were analysed using the Log-Rank test and plotted with the Kaplan-Meier curve. The results showed that the median survival time of dogs with PH secondary to DMVD stage C was 368 days, and factors that shortened the median survival time of dogs with PH secondary to DMVD stage C were mixed breeds, VHS > 11.5, the presence of right heart enlargement, ascites and high probability of PH. Factors associated with an increased hazard of death were mixed breed dogs, dogs with right heart enlargement and ascites. These findings may be useful for the prognosis and management of dogs with PH secondary to DMVD stage C.
Insulin is the peptide hormone used to treat the diabetes patient. The hormone is normally taken by injection. The transdermal drug delivery system (TDDS) is an alternative route. The silk fibroin (SF) hydrogels were fabricated via solution casting as the insulin matrix. The release and release-permeation experiments of the insulin loaded SF hydrogels were carried out using a modified Franz-diffusion cell at 37 °C for 36 h, under the effects of SF concentrations, pH, and electric field. The release-permeation mechanism through the pig skin was from the Case-II transport with the constant release rate. The diffusion coefficient (D) increased with decreasing SF concentration due to a larger mesh size, and with increasing electric field due to the electroreplusive forces between the insulin and the SF hydrogels against the negatively-charged electrode, and the induced SF hydrogel expansion. The rate and amount of insulin release-permeation became relatively lower as it required a longer time to generate aqueous pathways through the pig skin. The present SF hydrogels are demonstrated here deliver insulin with the required constant release rate, and the suitable amount within a prescribed duration. © 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
Background After the initiation of the COVID-19 vaccination program in Thailand, thousands of patients have experienced unusual focal neurological symptoms. We report 8 patients with focal neurological symptoms after receiving inactivated virus vaccine, CoronaVac. Case series Patients were aged 24–48 years and 75% were female. Acute onset of focal neurological symptoms occurred within the first 24 h after vaccination in 75% and between 1-7d in 25%. All presented with lateralized sensory deficits, motor deficits, or both, of 2–14 day duration. Migraine headache occurred in half of the patients. Magnetic resonance imaging of the brain during and after the attacks did not demonstrate any abnormalities suggesting ischemic stroke. All patients showed moderately large regions of hypoperfusion and concurrent smaller regions of hyperperfusion on SPECT imaging while symptomatic. None developed permanent deficits or structural brain injury. Discussions Here, we present a case series of transient focal neurological syndrome following Coronavac vaccination. The characteristic sensory symptoms, history of migraine, female predominant, and abnormal functional brain imaging without structural changes suggest migraine aura as pathophysiology. We propose that pain related to vaccine injection, component of vaccine, such as aluminum, or inflammation related to vaccination might trigger migraine aura in susceptible patients.
Background During revision total knee arthroplasty (TKA), knee joint line restoration may be difficult due to bone loss or structural changes. Although bony landmarks are consistent and can be used as references, there are limited data in Asian patients. We studied the knee joint line related to bony landmarks of the knee in a Thai population. Materials and methods Magnetic resonance imaging (MRI) of 140 healthy knees of Thai patients (70 males, 70 females) were investigated. In all knees, a perpendicular line from knee joint line to the medial epicondyle (distance A ) and the lateral epicondyle (distance B ) in the coronal plane were measured. In the sagittal plane, a perpendicular line from the knee joint line to the fibular head (distance C ), the tibial tubercle (distance D ), and the inferior patellar pole (distance E ) were measured. The femoral transepicondylar width (FW) was measured along the transepicondylar axis. The ratios of distances A , B , C , D , and E related to FW were evaluated (epicondylar ratio). Results The mean and standard deviation (SD) of distances A , B , C , D , E , and FW were 27.1 ± 2.7 mm, 21.7 ± 2.5 mm, 12.6 ± 3 mm, 21.3 ± 3.6 mm, 7.6 ± 4.8 mm, and 76.7 ± 3.99, respectively. There was wide variation of measured values, with statistically significant differences between genders in distances A , B , C , and FW. The mean and SD of epicondylar ratios A /FW, B /FW, C /FW, D /FW, and E /FW were 0.35 ± 0.02, 0.29 ± 0.02, 0.16 ± 0.05, 0.28 ± 0.04, and 0.09 ± 0.04, respectively. All epicondylar ratios demonstrated less variation than all measured distances, with statistical differences between genders in the A /FW and D /FW ratios. However, the B /FW ratio had the highest consistent mean value. In addition, it had narrower SD than the rest (0.29 ± 0.02; range, 0.22–0.33). Conclusions In Thai knees, the measured distances from bony landmarks to the knee joint line had higher variation than the epicondylar ratio. Among all studied epicondylar ratios, the ratio between lateral epicondyle to joint line distance (distance B )/FW demonstrated the narrowest range of mean and SD values; therefore, this could be the most reliable landmark for intraoperative knee joint line verification by multiplying the FW of the patient by 0.29 to get distance B in that patient.
Background Adverse drug event (ADE) reporting is a significant process to increase consumer care and consumer safety associated with the use of medicines. An in-depth investigation into low ADE reporting by consumers and community pharmacists was undertaken to uncover interventions to improve reporting. Method In-depth interviewing of the three parties; consumers, pharmacists and employees of the Pharmacovigilance Center in Thailand, was used to collect the data. They were interviewed about ADE reporting experiences and contributing factors and problems of ADE reporting. Thematic analysis was used to interpret the results. Result The HPVC received few ADE reports from consumers. Most community pharmacists received ADE reports from consumers; however, the Pharmacovigilance Center received few ADE reports from community pharmacists. ADE reporting of community pharmacists and consumers were influenced by many factors which were categorized into four themes which were (1) “Cognition” (awareness, attitude and responsibility); (2) “Reporting process” (complication, competency, information deficiency, feedback, and resource); (3) “Inducer” (service orientation, acquaintanceship, motivation, severity level, regulatory and reward); and (4) “Obstacle” (doubt, belief and prosecution). Conclusion Health professionals should motivate consumers to report ADEs. Building social responsibility and benefits and increasing knowledge of reporting process, channels, and system to both community pharmacists and consumers were recommended. Providing rewards and making community pharmacists feel comfortable to report ADEs by simplifying the ADE form and providing training, guidelines, and an ADR assessment tool can drive them to report ADEs. Feedback to consumers by confirming whether it was ADE and feedback to pharmacists that the Pharmacovigilance Center received their reports and their reports were utilized were also important.
Background Regional citrate anticoagulation (RCA) is recommended for continuous renal replacement therapy (CRRT). However, filter life varies and premature filter clotting can occur. The aims of this explorative prospective study were to investigate the effects of RCA on thrombin generation, fibrinolysis and platelet function in critically ill patients receiving CRRT, to compare clotting parameters between systemic and intra-circuit blood samples, and to screen participants for coagulation disorders. We recruited critically ill adult patients admitted to a 30-bedded Intensive care unit in a tertiary care hospital who required CRRT with RCA for acute kidney injury (AKI). Patients with pre-existing thrombotic, bleeding tendencies or a CRRT duration less than 48 h were excluded. We measured coagulation and thrombophilia parameters at baseline. Thrombin generation, D-dimer and platelet function were measured pre-CRRT and at 12, 24, 36, 48 and 72 h after commencing CRRT using blood samples taken from the arterial line and the circuit. Results At baseline, all eleven patients (mean age 62.4 years, 82% male) had Factor VIII and von Willebrand Factor concentrations above reference range and significantly increased peak thrombin generation. During CRRT, there were no significant changes in systemic maximum peak thrombin generation, time to peak thrombin generation, fibrinogen, D-dimer and platelet function analysis. We observed no significant difference between paired samples taken from the patient's arterial line and the circuit. Conclusions Critically ill patients with AKI requiring CRRT are hypercoagulable. Citrate used for anticoagulation during CRRT does not affect thrombin generation, D-dimer or platelet function. Systemic clotting parameters reflect intra-circuit results. Trial registration : Identifier: NCT02486614. Registered 01 July 2015—Registered after recruitment of first patient.
Correlation between rainfall and short period GPS-TEC (total electron content) variations are investigated by using the precipitation data obtained on the ground and estimated from satellite observations (JAXA/GSMaP) as a proxy of lower atmospheric wave activity. The GPS-TEC data obtained at a tropical station, PHIM, in Phimai, Thailand, for 2014–2020, and the data obtained at a mid-latitude station, NAKG, in Tokara Nakanoshima Island, Japan, for 2017–2019, are examined. A statistical analysis of MEM (maximum entropy method) power spectral density (PSD) in the period range from 50 to 1200 s over PHIM clearly shows an enhancement in the cases of rainfall from that in no-rainfall cases, in particular, on the dusk side. The enhancement is observed both acoustic wave periods less than 5–6 min and internal gravity wave periods more than 10 min. The enhancement after sunset could be an effect of strong rainfall more frequent on the dusk side than that in other local time, or it could suggest the importance of ionospheric electron density profile change for the TEC variation. On the other hand, the PSD does not show such clear enhancement over NAKG on the dusk side, although it shows a small enhancement on both dayside and night-side. A clear PSD bulge near the main vertical acoustic resonance periods, i.e., around 275 s, appears in the average PSD profile of the TEC at PHIM, which suggests that the resonance effect contribute to some extent the PSD enhancement under rainy condition. An event analysis also suggests the contribution of acoustic resonance to the enhancement of the short period TEC variation. A complicated spatial distribution of TEC oscillation over a rainfall area around PHIM, where the TEC oscillations with various periods co-exist, is presented. Graphical Abstract
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16,666 members
Jettanong Klaewsongkram
  • Department of Medicine
Padet Tummaruk
  • Department of Obstetrics Gynaecology and Reproduction
Vachara Peansupap
  • Department of Civil Engineering
Surasith Chaithongwongwatthana
  • Department of Obstetrics and Gynecology
Jintana Yunibhand
  • Faculty of Nursing
Payathai, 10330, Bangkok, Thailand