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Search Results: 1 - 10 of 493 matches for " Thein Than Tun "
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250 MHz to 30 GHz, Unilateral Circuitmodel for Ingap/GaAs Hbt
Than Tun Thein;Choi Look Law;Kai Fu
PIER C , 2012, DOI: 10.2528/PIERC11101702
Abstract: A unilateral circuit model, which precisely predicts small signal response over a wide range of frequencies and bias points, is quantitatively analyzed and presented. The shortfall of current unilateral assumption and transformation technique is presented. A complete and explicit analysis is provided to develop a compact unilateral circuit model. The model is intended to predict input reflection, forward transmission and output reflection coefficients over wide range of frequencies. The technique is validated by transforming bilateral a small signal model of 3 x 3 μm x 40 μm, InGaP/GaAs HBT into its unilateral equivalent over the frequency range of 250 MHz to 30 GHz. The accuracy of the technique is corroborated at various bias conditions; collector current from 3 mA to 150 mA and collector-emitter voltage from 1 V to 5 V. Simulated results show very good agreement between small signal responses of transformed unilateral and bilateral circuit models.
Frequency Domain Dynamic Thermal Analysis in GaAs Hbt for Power Amplifier Applications
Than Tun Thein;Choi Look Law;Kai Fu
PIER , 2011, DOI: 10.2528/PIER11050301
Abstract: Dynamic temperature distributions in GaAs HBT are numerically analyzed in frequency domain as a function of power dissipation, frequency and space. Complete thermal characteristics, including frequency-dependent thermal impedance and phase lag behavior, are presented. The analysis is also extended for arbitrary periodic or aperiodic pulse heating operation to predict junction temperature of a Power Amplifier (PA) with non-constant envelope input signal. Dynamic junction temperatures of a single finger 2 μm x 20 μm GaAs HBT are predicted for square pulse envelope signal input with power levels varying with up to 10 dB above a nominal average level of 40 mW and with pulse widths ranging from 10 ns to 100 μs. With the input envelope signal amplitude of 10 dB above the average, the analytical results show that junction temperature rises from room temperature of 27C to 39C when heated by 10 ns pulse, increase to 36C by 100ns pulse, 105C by 1μs pulse and to 198C by 100 μs pulse. A novel setup is developed for nano-second pulsed measurements, and the analysis is validated through time domain on wafer pulsed measurements at three different power levels: 0 dB, 3 dB, and 6 dB above the average level. Results show that analytical results track well with measured junction temperature within the accuracy of ±5C over the entire measurement set.
Engineering Adaptive Digital Investigations using Forensics Requirements
Liliana Pasquale. Yijun Yu,Luca Cavallaro,Mazeiar Salehie,Thein Than Tun,Bashar Nuseibeh
Computer Science , 2014,
Abstract: A digital forensic investigation aims to collect and analyse the evidence necessary to demonstrate a potential hypothesis of a digital crime. Despite the availability of several digital forensics tools, investigators still approach each crime case from scratch, postulating potential hypotheses and analysing large volumes of data. This paper proposes to explicitly model forensic requirements in order to engineer software systems that are forensic-ready and guide the activities of a digital investigation. Forensic requirements relate some speculative hypotheses of a crime to the evidence that should be collected and analysed in a crime scene. In contrast to existing approaches, we propose to perform proactive activities to preserve important - potentially ephemeral - evidence, depending on the risk of a crime to take place. Once an investigation starts, the evidence collected proactively is analysed to assess if some of the speculative hypotheses of a crime hold and what further evidence is necessary to support them. For each hypothesis that is satisfied, a structured argument is generated to demonstrate how the evidence collected supports that hypothesis. Our evaluation results suggest that the approach provides correct investigative findings and reduces significantly the amount of evidence to be collected and the hypotheses to be analysed.
Melting and Solidification Heat Transfer Characteristics of a Phase-Change Material in a Latent Heat Storage Vessel: Effects of a Perforated Partition Plate and Metal Fiber  [PDF]
Than Tun Naing, Akihiko Horibe, Naoto Haruki, Yutaka Yamada
Journal of Power and Energy Engineering (JPEE) , 2017, DOI: 10.4236/jpee.2017.58002
Abstract: Today, latent heat storage technology has advanced to allow reuse of waste heat in the middle-temperature range. This paper describes an approach to develop a latent heat storage system using middle-temperature waste heat (~100oC - 200oC) from factories. Direct contact melting and solidification behavior between a heat-transfer fluid (oil) and a latent heat storage material mixture were observed. The mixture consisted of mannitol and erythritol (Cm = 70 mass %, Ce = 30 mass %) as a phase-change material (PCM). The weight of the PCM was 3.0 kg and the flow rate of the oil, foil, was 1.0, 1.5, or 2.0 kg/min. To decrease the solidified height of the PCM mixture during the solidification process, a perforated partition plate was installed in the PCM region in the heat storage vessel. PCM coated oil droplets were broken by the perforated partition plate, preventing the solidified height of the PCM from increasing. The solidification and melting processes were repeated using metal fiber. It was found that installing the metal fiber was more effective than installing the perforated partition plate to prevent the flow out problem of the PCM.
Prevention and Treatment of Venous Thromboembolism with New Oral Anticoagulants: A Practical Update for Clinicians
Nay Min Tun,Thein Hlaing Oo
Thrombosis , 2013, DOI: 10.1155/2013/183616
Abstract:
Prevention and Treatment of Venous Thromboembolism with New Oral Anticoagulants: A Practical Update for Clinicians
Nay Min Tun,Thein Hlaing Oo
Thrombosis , 2013, DOI: 10.1155/2013/183616
Abstract: Traditional anticoagulants, such as warfarin and enoxaparin, have several limitations, including parenteral administration, need for laboratory monitoring, and ongoing dose adjustment, which may limit optimal patient care. Newer oral anticoagulants, such as direct thrombin inhibitors (e.g., dabigatran etexilate) and direct factor Xa inhibitors (e.g., rivaroxaban, apixaban, and edoxaban), have been developed to overcome these drawbacks, and thereby improve patient care. Several of these agents have been approved for use in the prevention and treatment of venous and/or systemic thromboembolism. The objective of this paper is to provide an overview of the available clinical trial data for these new oral anticoagulants in the prevention and treatment of venous thromboembolism and a practical update for clinicians. 1. Introduction Venous thromboembolism (VTE) comprises deep vein thrombosis (DVT) and pulmonary embolism (PE). Although the exact incidence of VTE is not known, it is estimated to affect 900,000 patients each year in the United States [1]. Approximately one-third of these cases are fatal pulmonary emboli, and the remaining two-thirds are nonfatal episodes of symptomatic DVT or PE [1]. VTE is the second most common cause of extended hospital stay and the third most common cause of in-hospital mortality [2]. Because it causes considerable morbidity and mortality, VTE places a substantial burden on healthcare resources [3, 4]. Without thromboprophylaxis, the incidence of hospital-acquired DVT based on objective diagnostic screening is 10–40% among medical or general surgical patients and 40–60% among patients who have undergone major orthopedic surgery such as total knee replacement (TKR), total hip replacement (THR), and hip fracture surgery [5]. Patients with cancer are at a greater risk of new or recurrent VTE than patients without cancer. VTE risk is 3- to 5-fold higher in cancer patients who are undergoing surgery and 6.5-fold higher in cancer patients receiving chemotherapy than in patients who do not have cancer [6, 7]. The efficacy of traditional anticoagulants in preventing VTE in patients undergoing major orthopedic surgery and in hospitalized acutely ill medical patients is well established [5, 8–11]. However, these agents have several limitations that may limit optimal patient care, such as their parenteral administration, need for laboratory monitoring, and ongoing dose adjustment (Table 1) [12–16]. Newer oral anticoagulants, such as direct thrombin inhibitors (e.g., dabigatran etexilate) and direct factor Xa inhibitors (e.g.,
Active surveillance for congenital rubella syndrome in Yangon, Myanmar
Thant Kyaw-Zin,Oo Win-Mar,Myint Thein-Thein,Shwe Than-Nu
Bulletin of the World Health Organization , 2006,
Abstract: OBJECTIVE: Rubella vaccine is not included in the immunization schedule in Myanmar. Although surveillance for outbreaks of measles and rubella is conducted nationwide, there is no routine surveillance for congenital rubella syndrome (CRS). Therefore, we organized a study to assess the burden of CRS. METHODS: From 1 December 2000 to 31 December 2002 active surveillance for CRS was conducted among children aged 0-17 months at 13 hospitals and 2 private clinics in Yangon, the capital city. Children with suspected CRS had a standard examination and a blood sample was obtained. All serum samples were tested for rubella-specific IgM; selected samples were tested for rubella-specific IgG and for rubella RNA by reverse transcriptase-polymerase chain reaction (RT-PCR). FINDINGS: A total of 81 children aged 0-17 months were suspected of having CRS. Of these, 18 children had laboratory-confirmed CRS (7 were IgM positive; 7 were RT-PCR positive; and 10 were IgG positive at > 6 months of age). One additional child who tested positive by RT-PCR and whose mother had had rubella during pregnancy but who had a normal clinical examination was classified as having congenital rubella infection. During 2001-02 no rubella outbreaks were detected in Yangon Division. In the 31 urban townships of Yangon Division, the annual incidence was 0.1 laboratory-confirmed cases of CRS per 1000 live births. CONCLUSION: This is the first population-based study of CRS incidence from a developing country during a rubella-endemic period; the incidence of CRS is similar to endemic rates found in industrialized countries during the pre-vaccine era. Rubella-specific IgG tests proved practical for diagnosing CRS in children aged > 6 months. This is one of the first studies to report on the use of rubella-specific RT-PCR directly on serum samples; further studies are warranted to confirm the utility of this method as an additional means of diagnosing CRS.
Effects of malaria volunteer training on coverage and timeliness of diagnosis: a cluster randomized controlled trial in Myanmar
Ohnmar,Tun-Min,San-Shwe,Than-Win
Malaria Journal , 2012, DOI: 10.1186/1475-2875-11-309
Abstract: Background The use of community volunteers is expected to improve access to accurate diagnosis and timely treatment of malaria, using rapid diagnostic test (RDT) and artemisinin-based combination therapy (ACT). However, empirical data from the field are still limited. The aim of this study was to assess whether training village volunteers on the use of Paracheck-Pf RDT and ACT (artemether-lumefantrine (AL)) for Plasmodium falciparum and presumptive treatment with chloroquine for Plasmodium vivax had an effect on the coverage of timely diagnosis and treatment and on mortality in malaria-endemic villages without health staff in Myanmar. Methods The study was designed as a cluster randomized controlled trial with a cross-sectional survey at baseline, a monthly visit for six months following the intervention (village volunteers trained and equipped with Paracheck-Pf ) and an endline survey at six months follow-up. Survey data were supplemented by the analysis of logbooks and field-based verbal autopsies. Villages with midwives (MW) in post were used as a third comparison group in the endline survey. Intention-to-treat analysis was used. Results Of 38 villages selected, 21 were randomly assigned to the intervention (two villages failed to participate) and 17 to the comparison group. The two groups had comparable baseline statistics. The blood tests provided by volunteers every month declined over time from 279 tests to 41 but not in MW group in 18 villages (from 326 to 180). In the endline survey, among interviewed subjects (268 intervention, 287 in comparison, 313 in MW), the coverage of RDT was low in all groups (14.9%, SE 2.4% in intervention; 5.7%, SE 1.7% in comparison; 21.4%, SE 2.6% in MW) although the intervention (OR 3.2, 95% CI 1.5-6.7) and MW (OR 5.4, 95% CI 2.6-11.0) were more likely to receive a blood test. Mean (SE) of blood tests after onset of fever in days was delayed (intervention 3.6 (0.3); comparison 4.8 (1.3); MW 3.2 (0.4)). Malaria mortality rates per 100,000 populations in a year were not significantly different (intervention 130 SE 37; comparison 119 SE 34; MW 50 SE 18). None of the dead cases had consulted volunteers. Conclusions The results show that implementing volunteer programmes to improve the coverage of accurate and timely diagnosis with RDT and early treatment may be beneficial but the timeliness of detection and sustainability must be improved.
Active surveillance for congenital rubella syndrome in Yangon, Myanmar
Thant,Kyaw-Zin; Oo,Win-Mar; Myint,Thein-Thein; Shwe,Than-Nu; Han,Aye-Maung; Aye,Khin-Mar; Aye,Kay-Thi; Moe,Kyaw; Thein,Soe; Robertson,Susan E;
Bulletin of the World Health Organization , 2006, DOI: 10.1590/S0042-96862006000100009
Abstract: objective: rubella vaccine is not included in the immunization schedule in myanmar. although surveillance for outbreaks of measles and rubella is conducted nationwide, there is no routine surveillance for congenital rubella syndrome (crs). therefore, we organized a study to assess the burden of crs. methods: from 1 december 2000 to 31 december 2002 active surveillance for crs was conducted among children aged 0-17 months at 13 hospitals and 2 private clinics in yangon, the capital city. children with suspected crs had a standard examination and a blood sample was obtained. all serum samples were tested for rubella-specific igm; selected samples were tested for rubella-specific igg and for rubella rna by reverse transcriptase-polymerase chain reaction (rt-pcr). findings: a total of 81 children aged 0-17 months were suspected of having crs. of these, 18 children had laboratory-confirmed crs (7 were igm positive; 7 were rt-pcr positive; and 10 were igg positive at > 6 months of age). one additional child who tested positive by rt-pcr and whose mother had had rubella during pregnancy but who had a normal clinical examination was classified as having congenital rubella infection. during 2001-02 no rubella outbreaks were detected in yangon division. in the 31 urban townships of yangon division, the annual incidence was 0.1 laboratory-confirmed cases of crs per 1000 live births. conclusion: this is the first population-based study of crs incidence from a developing country during a rubella-endemic period; the incidence of crs is similar to endemic rates found in industrialized countries during the pre-vaccine era. rubella-specific igg tests proved practical for diagnosing crs in children aged > 6 months. this is one of the first studies to report on the use of rubella-specific rt-pcr directly on serum samples; further studies are warranted to confirm the utility of this method as an additional means of diagnosing crs.
Implications of Discordance in World Health Organization 1997 and 2009 Dengue Classifications in Adult Dengue
Victor C. Gan, David C. Lye, Tun L. Thein, Frederico Dimatatac, Adriana S. Tan, Yee-Sin Leo
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0060946
Abstract: Background Revised dengue guidelines were published by the World Health Organization (WHO) in 2009 addressing severe dengue cases not classified by dengue hemorrhagic fever (DHF) and shock syndrome (DSS). Methods and Principal Findings We conducted a retrospective cohort study to compare WHO 2009 and 1997 classifications using 1278 adult dengue cases confirmed by polymerase chain reaction assay from Singapore epidemics in 2004 and 2007 (predominantly serotype 1 and 2 respectively).DHF occurred in 14.3%, DSS 2.7% and severe dengue 16.0%. The two WHO dengue classifications were discordant in defining severe disease (p<0.001). Five DSS patients (15%) were classified as non-severe dengue without warning signs. Of severe dengue patients, 107 did not fulfil DHF criteria. Of these, 14.9% had self-resolving isolated elevated aminotransferases, 18.7% gastrointestinal bleeding without hemodynamic compromise and 56.1% plasma leakage with isolated tachycardia. We compared both guidelines against requirement for intensive care including the single death in this series: all six had severe dengue; only four had DHF as two lacked bleeding manifestations but had plasma leakage. Increasing length of hospitalization was noted among severe cases with both classifications but the trend was only statistically significant for WHO 2009. Length of hospitalization was significantly longer for severe plasma leakage compared with severe bleeding or organ impairment. Requirement for hospitalization increased using WHO 2009 from 17.0% to 51.3%. Conclusions While the WHO 2009 dengue classification is clinically useful, we propose retaining criteria for plasma leakage and hemodynamic compromise from WHO 1997, and refining definitions of severe bleeding and organ impairment to improve clinical relevance having found that differences in these accounted for the discordance between classifications. Findings from our retrospective study may be limited by the study site - a tertiary referral center in a hyperendemic country - and should be evaluated in a wider range of geographic settings.
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