• Title/Summary/Keyword: The 10-second test

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Delayed Analysis of Hydrogen-Methane Breath Samples

  • Willemsen, Marjolein;Van De Maele, Kristel;Vandenplas, Yvan
    • Pediatric Gastroenterology, Hepatology & Nutrition
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    • v.25 no.1
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    • pp.13-20
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    • 2022
  • Purpose: Hydrogen-methane breath tests are used to diagnose carbohydrate malabsorption and small intestinal bacterial overgrowth. The COVID-19 pandemic has driven the modification of procedures as breath tests are potentially aerosol-generating procedures. We assessed the effect of delayed analysis of breath samples, facilitating the at-home performance of breath testing. Methods: Children provided two breath samples at every step of the lactose breath test. The samples were brought back to the clinic, and one set of samples was analyzed immediately. The second set was stored at room temperature and analyzed 1-4 days later. Results: Out of the 73 "double" lactose breath tests performed at home, 33 (45.8%) were positive. The second samples were analyzed 20 to 117 hours after the first samples (41.7±24.3 hours). There was no significant difference in the hydrogen concentration between the first and second sets (Z=0.49, p=0.62). This was not the case for methane, which had a significantly higher concentration in the second breath samples (Z=7.6). Conclusion: Expired hydrogen levels remain stable in plastic syringes if preserved at room temperature for several days. On the other hand, the delayed analysis of methane appeared to be less reliable. Further research is needed to examine the impact of delayed analysis on methane and hydrogen concentrations.

A Novel Control Algorithm of a Three-phase PWM Inverter with LC Filter (정현파 출력 필터를 가지는 3상 PWM 인버터 제어 기법)

  • Kim, Kwang-Seob;Hyun, Dong-Seok
    • The Transactions of the Korean Institute of Power Electronics
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    • v.20 no.3
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    • pp.239-246
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    • 2015
  • A novel control method of a three-phase PWM inverter with LC filter is proposed. The transfer function of LC filter is the same as that of second-order low pass filter(LPF), which has a zero damping ratio. A simple method of implementing second-order LPF with damping ratio is to add a resistor in an LC circuit. However, in a real power system, adopting damping resistors is impractical because it results in losses proportional to the square of the current flowing through the resistors. Instead of inserting resistors, the proposed control strategy utilizes the measured capacitor voltages to control the oscillation of LC circuit. The overall transfer function of the proposed method is the same as a second-order LPF, and its damping ratio is controllable via control variables. The current controller can have overshoots caused by LC filter. Improved current controller is implemented by an equivalent second-order of LC filter. A 7.5 kVA PWM converter and a PWM inverter with a 5.5 kW induction motor are set up to verify the proposed control algorithm. Test waveforms are also presented to verify the proposed LC filter control algorithm.

Test of a Multi-Reference Many-Body Perturbation Theory for the Description of Electron Correlations in four Valence Electron States of Transition Metal Atoms

  • Lee, Yoon-Sup;Sun, Ho-Sung;Freed, Karl F.;Hagstrom, S.
    • Bulletin of the Korean Chemical Society
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    • v.7 no.4
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    • pp.262-266
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    • 1986
  • A multi-reference many-body perturbation theory (MRMBPT) method is critically tested in second order by comparing with the corresponding configuration interaction (CI) calculations. Excitation energies of the four-valence-electron states of transition metal atoms and ions are used for the comparison. The agreement between the second order MRMBPT and CI calculations is very reasonable, confirming the reliability of the second order MRMBPT method. The reliability of calculations with the present second order MRMBPT method was only been inferred empirically in the past since most results have been gauged by the agreement with experiment and/or with other MRMBPT calculations based upon different sets of orbitals and configuration spaces. The present MRMBPT method appears to be an efficient ab initio multi-reference method for the calculation of electron correlation effects in atoms and molecules, and it is shown how MRMBPT can be used to estimate core-core and core-valence correlation effects which are often omitted in CI calculations because too many configurations and correlating electrons are involved.

A Preliminary Study for a Academic Probation Target Individual Learning Coaching Program Development (학사경고자 대상 개별 학습코칭 프로그램 개발을 위한 예비연구)

  • KIM, Hee-Jung
    • Journal of Fisheries and Marine Sciences Education
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    • v.28 no.4
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    • pp.971-983
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    • 2016
  • This study is a preliminary research to develop an individual learning coaching program for college students who received academic probation. It aims to test applicability as a program in the future, and t revise it and make up for its problems. To achieve the research aim, this study, based on self-directed learning, constructed the program dividing it into two kinds: the first basic learning special lecture and the second individual learning coaching. This program used those students in universities in Gyeongbok province who received two or more scholastic probations from the second semester of 2012 to the second semester of 2014, and who were judged by professors who had interviewed them as those who needed learning coach. The researcher of this study introduced those students about the program and schedule. And, this study did in-depth analysis for the six students who attended the first and second parts of the program. It was found that those students understood the importance and necessity of self-directed learning, and tried to apply it to actual learning process and overcome learning difficulty. Based on such findings, this study suggested the development of a program for students who receive academic probation and ideas on how to develop it.

Estimation of PTC (Powertrain Cooling) Performance with Heat Rejection Rate (열방출량 (Heat Rejection Rate)을 이용한 PTC (Powertrain Cooling) 성능 추정)

  • Min, Sunki
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.5
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    • pp.3030-3034
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    • 2015
  • It is important to consider powertrain cooling performance, when engine is applied to new vehicle. If the performance is poor, engine will be damaged by overheating. But, the development timing of engine is faster than timing of vehicle, it is difficult to test the cooling performance of new engine and vehicle. In this study the powertain cooling performance was estimated with some test and calculation data. First, the heat rejection test was conducted. From this test, the heat rejection data at required rpm and load was acquired. Second, coolant flow test was conducted. From this test coolant flow rate to radiator was measured. Then engine torque and rpm was calculated from vehicle load and speed. Vehicle load and speed was calculated from test mode. Then by comparing these data, the powertrain cooling performance was estimated.

A Study on The Flame Stability of Pellet Combustor Using Swirling Flow (선회유동을 이용한 펠릿연소기의 화염안정화 연구)

  • Lee, Do-Hyung;Yun, Bong-Seok;Wang, Zhen-Wei
    • Journal of Power System Engineering
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    • v.18 no.5
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    • pp.35-41
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    • 2014
  • The wood pellet, which is one of the woody biomass energy, has very high economic efficiency and combustion efficiency during their combustion. The existing pellet burner have many problems such as low combustion efficiency, flame stabilization, ash problem and ignition time etc. We developed cyclonic wood pellet burner aim to 20,000kcal/hr boiler and measured temperature profiles and exhaust gases in order to investigate the flame stability and optimum combustion condition at any air flow conditions. As results, we confirmed the reappearance and the isotropy of the experimental results in the burner. At the first air flow inlet condition of excess air ratio ${\alpha}=0.02$, second air flow $490{\ell}/min$ had the best combustion condition when pellet supplied 30g. This result means that we need much air supply only for the swirling of second air flow. So we tested various second air flux at first air excess air ratio ${\alpha}=0.7$ condition. At this condition, we could find out that we don't need much second air and total air flux compared to the former condition. We will continuously test this work of air flow distribution, and swirl effect of first air flow, and ash elimination.

Modal Analysis and FEA of a Compressor Motor for 120Hz Resonance Reducing (컴프레서용 모터 120Hz 공진 저감을 위한 연구)

  • Shin, Hyun-Jang
    • Transactions of the KSME C: Technology and Education
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    • v.5 no.2
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    • pp.81-87
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    • 2017
  • 315Fr compressor motor exceeds vibration specifications. To find the reason, first a modal impact test with free-free condition is done. Second a modal test with fixed condition is done. Thereafter the test results are compared with FEM simulation results. Using free-free condition modal impact test, FEM simulation conditions (boundary, mesh..) are modified. The motor has rolling motion around 120Hz. FEM simulation also shows same result. FEM simulation will be used to develop other series compressor motors. Using this, manufacturing test model and doing test will be useless.

A cone-beam computed tomography study of the prevalence and location of the second mesiobuccal root canal in maxillary molars

  • Seong-Ju Lee ;Eun-Hye Lee ;Se-Hee Park ;Kyung-Mo Cho ;Jin-Woo Kim
    • Restorative Dentistry and Endodontics
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    • v.45 no.4
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    • pp.46.1-46.8
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    • 2020
  • Objectives: This study aimed to investigate the incidence and location of the second mesiobuccal root (MB2) canal in maxillary molars with the aid of various measuring points and lines using cone-beam computed tomography (CT). Materials and Methods: A total of 205 images of patients who underwent cone-beam CT examinations between 2011 and 2015 as part of their dental diagnosis and treatment were included. There were 76 images of the maxillary first molar and 135 images of the maxillary second molar. Canal orifices were detected at -1 mm from the top of the pulpal floor on cone-beam CT images. Image assessment was performed by 2 observers in reformatted image planes using software. Assessments included measurement of the distance between the MB1 and MB2 canals, and the angles between the lines connecting the MB1-MB2 and distobuccal (DB)-palatal (P) canals. The data were analyzed using the student's t-test. Results: The prevalence of the MB2 canal was 86.8% in the first molar and 28.9% in the second molar. The angle between the lines connecting the MB1-MB2 and DB-P canals was 2.3° ± 5.7° in the first molar and -3.95° ± 7.73° in the second molar. The distance between the MB1 and MB2 canals was 2.1 ± 0.44 mm in the first molar and 1.98 ± 0.42 mm in the second molar. Conclusions: The angles between the lines connecting the MB1-MB2 and DB-P canals was almost parallel. These findings may aid in the prediction of the location of the MB2 canal orifice.

Factors affecting the intention of Chinese and Vietnamese migrant women to have a second child: Comparison between the "National Survey on the Multi-Cultural Families" of 2009 and 2015 (중국, 베트남 결혼이주여성의 둘째자녀 출산의도 영향요인: 2009년, 2015년 전국다문화가족실태조사의 비교)

  • Ding, Jingya;Chin, Meejung;Ok, Sunwha
    • Journal of Family Relations
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    • v.23 no.2
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    • pp.133-155
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    • 2018
  • Objectives: This study examined the differences in the intention of having a second child and the related factors among Chinese and Vietnamese migrant women from the perspective of adaptation theory. Methods: Data were drawn from the National Survey on Multi-Cultural Families in 2009 and 2015. Among the total 7,615 married migrant women (Korean-Chinese, Chinese-Han, Vietnamese), those within the age group 20-39 within the first 5 years of marriage who had one child were selected. A frequency analysis, chi-squared test, and logit regression analysis were performed. Results: Different ethnic groups had different reasons for having a second child and the related factors also differed between 2009 and 2015. In 2009, after controlling the related variables, the intention of Korean-Chinese and Chinese-Han married immigrant women to have a second child was higher than that of Vietnamese women, but no such difference was found in 2015. Participation in their local community, first marriage, the gender of the first child, and whether they were living with their parents-in-law were associated with the intention of migrant women having a second child in the 2009 analysis model but these factors were not significant in the 2015 analysis model. In the latter model, the household income, a variable related to economic conditions, has a positive effect on the intention of having a second child. Conclusions: The significance of this study supports adaptation theory by addressing the similarity in the childbirth intention between recently married immigrant women and Korean women.

Behavior of Initiation and Propagation of Fatigue Crack under Periodic Overstressing (In the case of Fatigue Limit Stresses) (과대, 과소 응력하에서의 피로크랙 발생거동 (피로한도 응력을 중심으로))

  • 송남홍;원시태
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.6
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    • pp.1839-1851
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    • 1991
  • Fatigue crack behavior is studied through the two-level rotary bending test with the deep non-through radial holed notch specimens of low carbon steels(SM22C). The main factors investigated are the effects of the damage zone size around crack tip and phenomena of closing or opening of the crack tip. Obtained results are summarized as follows. Fatigue crack behavior in second level stressing slightly lower than fatigue limit is closely related to the size of damage zone produced by the first level stress higher than fatigue limit and to the phenomena of crack closing and opening for the second level stress. The non-propagating crack limit condition depends upon the crack length l$_{1}$ propagated under the first level stress and the magnitude of second level stress .sigma.$_{2}$ lower than the fatigue limit. The non-propagating crack limit condition is expressed by following eq. $\sigma_2^{6.1}{\times}l_{1}=7.35{\times}10^{6}[(kg_{f}mm^{6.1}(mm)]$