• Title/Summary/Keyword: Flow noise

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A Study on the Image Quality According to the Change of Flip Angle in Flow-Related Enhancement Magnetic Resonance Angiography (유속증강 자기공명혈관조영술에서 숙임각 변화에 따른 영상의 질 연구)

  • Goo, Eun-Hoe
    • Journal of the Korean Society of Radiology
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    • v.12 no.2
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    • pp.201-208
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    • 2018
  • The purpose of this study was to investigate the optimal flip angle by measuring the SNR and CNR according to the angle of changes of the MRI technique using the Image J program. A total of 30 normal volunteers were assessed by using a 1.5T magnetic resonance imaging system (Philips, Medical System, Achieva). For the MRI angiography, we set the region of interest in four regions and evaluated the SNR and CNR. The statistical significance of SNR and CNR was calculated by one-way ANOVA using quantitative analysis at five different positions. The Bonferroni method was used for post-hoc analyzes. Statistical significance was determined by using ANOVA analysis at p<0.05 and Bonferroni method was used as a post-hoc analysis. The results of this study, the measurement values of ACA(SNR:$876.59{\pm}14.22$, CNR:$1999.7{\pm}12.5$), PCA(SNR:$863.48{\pm}13.29$, CNR:$1870.18{\pm}12.56$), ICA(SNR:$1116.87{\pm}08.34$, CNR:$2979.37{\pm}14.69$) and MCA(SNR:$848.66{\pm}15.25$, CNR:$2199.25{\pm}13.48$) were obtained with the high signal intensity at $25^{\circ}$(p<0.05). The values of a1, a2, a3, p1, p2, p3, m1, m2 and m3 were also the same (p<0.05). Post-hoc analysis results, There was a statistically significant difference (p=0.000) between $10^{\circ}$, $15^{\circ}$, $20^{\circ}$ on the $25^{\circ}$ reference for the flip angle, but no significant results were obtained with $30^{\circ}$(p<0.05). In concision, because the signal intensity decreased at $30^{\circ}$, this study revealed that the optimal flip angles were $25^{\circ}$ in cerebrovascular MR angiography.

Recent Progress in Air-Conditioning and Refrigeration Research: A Review of Papers Published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2014 (설비공학 분야의 최근 연구 동향: 2014년 학회지 논문에 대한 종합적 고찰)

  • Lee, Dae-Young;Kim, Sa Ryang;Kim, Hyun-Jung;Kim, Dong-Seon;Park, Jun-Seok;Ihm, Pyeong Chan
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.27 no.7
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    • pp.380-394
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    • 2015
  • This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2014. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of heat and mass transfer, cooling and heating, and air-conditioning, the flow inside building rooms, and smoke control on fire. Research issues dealing with duct and pipe were reduced, but flows inside building rooms, and smoke controls were newly added in thermal and fluid engineering research area. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results for thermal contact resistance measurement of metal interface, a fan coil with an oval-type heat exchanger, fouling characteristics of plate heat exchangers, effect of rib pitch in a two wall divergent channel, semi-empirical analysis in vertical mesoscale tubes, an integrated drying machine, microscale surface wrinkles, brazed plate heat exchangers, numerical analysis in printed circuit heat exchanger. In the area of pool boiling and condensing, non-uniform air flow, PCM applied thermal storage wall system, a new wavy cylindrical shape capsule, and HFC32/HFC152a mixtures on enhanced tubes, were actively studied. In the area of industrial heat exchangers, researches on solar water storage tank, effective design on the inserting part of refrigerator door gasket, impact of different boundary conditions in generating g-function, various construction of SCW type ground heat exchanger and a heat pump for closed cooling water heat recovery were performed. (3) In the field of refrigeration, various studies were carried out in the categories of refrigeration cycle, alternative refrigeration and modelling and controls including energy recoveries from industrial boilers and vehicles, improvement of dehumidification systems, novel defrost systems, fault diagnosis and optimum controls for heat pump systems. It is particularly notable that a substantial number of studies were dedicated for the development of air-conditioning and power recovery systems for electric vehicles in this year. (4) In building mechanical system research fields, seventeen studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, and renewable energies, piping in the buildings. Proposed designs, performance performance tests using numerical methods and experiments provide useful information and key data which can improve the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the evaluation of work noise in tunnel construction and the simulation and development of a light-shelf system. The subjects of building energy were worked on the energy saving of office building applied with window blind and phase change material(PCM), a method of existing building energy simulation using energy audit data, the estimation of thermal consumption unit of apartment building and its case studies, dynamic window performance, a writing method of energy consumption report and energy estimation of apartment building using district heating system. The remained studies were related to the improvement of architectural engineering education system for plant engineering industry, estimating cooling and heating degree days for variable base temperature, a prediction method of underground temperature, the comfort control algorithm of car air conditioner, the smoke control performance evaluation of high-rise building, evaluation of thermal energy systems of bio safety laboratory and a development of measuring device of solar heat gain coefficient of fenestration system.

Study for Correlation between Objective and Subjective Voice Parameters in Patients with Dysphonia (발성장애 환자에서 주관적 음성검사와 객관적 음성검사의 연관성 연구)

  • Park, Jung Woo;Kim, Boram;Oh, Jae Hwan;Kang, Tae Kyu;Kim, Dong Young;Woo, Joo Hyun
    • Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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    • v.30 no.2
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    • pp.118-123
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    • 2019
  • Background and Objectives Voice evaluation is classified into subjective tests such as auditory perception and self-measurement, and objective tests such as acoustic and aerodynamic analysis. When evaluating dysphonia, subjective and objective test results do not always match. The purpose of this study was to analyze the relationship between subjective and objective evaluation in patients with dysphonia and to identify meaningful parameters by disease. Materials and Method The total of 322 patients who visited voice clinic from May 2017 to May 2018 were included in this study. Laryngeal lesions were identified using stroboscopy. Pearson correlation test was performed to analyse correlation between subjective tests including GRBAS scale and voice handicap index, and objective tests including jitter, shimmer, noise to harmonic ratio (NHR), cepstral peak prominence (CPP), maximal phonation time (MPT), mean flow rate, and subglottic pressure. Results In vocal nodule and sulcus vocalis, among GRBAS system, grade and breathiness showed good correlation with CPP, and roughness showed good correlation with jitter or shimmer. In unilateral vocal cord paralysis (UVCP), grade and breathiness showed a very good correlation with CPP, and also good correlation with jitter, shimmer, NHR, and MPT. Also asthenia showed good correlation with CPP and MPT. Vocal polyp has a limited association with other diseases. Conclusion In patients with dysphonia, grade and breathiness showed good correlation with CPP, jitter, and shimmer, and reflect the state of voice change well especially in UVCP, CPP, and MPT.

Injection Laryngoplasty for The Treatment of Vocal Fold Scar, and Sulcus (성대구증 및 성대 반흔 환자에서 주사후두성형술의 효과)

  • Woo, Joo Hyun;Baek, Min Kwan;Kim, Dong Young;Park, Hyoung-Min;An, Sanghee;Moon, Kwang Ha;Cha, Heung Eog
    • Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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    • v.27 no.1
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    • pp.25-29
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    • 2016
  • Background and Objectives : The clinical reports for the treatment of vocal fold scar and sulcus vocalis are limited, also there is no best one for the treatment of them. This study is to evaluate the effect of Injection laryngoplasty (IL) for the treatment of vocal fold scar and sulcus vocalis. Materials and Methods : from January 2013 to May 2015, the Nineteen patients who were diagnosed as vocal fold scar, sulcus and atrophy, and underwent IL, were engaged in this study. Clinical information and voice parameters were analyzed by retrospective chart review. Pre and post voice parameters were compared. Results : Subgroups of diagnosis were classified into sulcus vocalis for 12 patients, vocal fold scar for 5, and atrophy for 2. IL was performed under local anesthesia through cricothyroid membrane except one patient. Atesense$^{(R)}$, Radiessess$^{(R)}$, and Rofilan$^{(R)}$ were used as injected materials in 9, 9, and 1 patients respectively. Maximal phonation time (p=0.0124), dynamic range (p=0.0028), pitch range (p=0.0141), voice handicap index (p=0.028), glottal closure (p=0.0229), and mucosal wave (p=0.0132) had significant improvement for post-IL voice assessment than Pre-IL. While GRBAS, Mean flow rate, Jitter, Shimmer, Harmony to Noise ratio didn't have improvement. Conclusion : IL is a feasible option for the treatment of glottis incompetence with normally mobile vocal folds such as sulcus vocalis and vocal fold scar.

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DESIGN AND DEVELOPMENT OF MULTI-PURPOSE CCD CAMERA SYSTEM WITH THERMOELECTRIC COOLING I. HARDWARE (열전냉각방식의 범용 CCD 카메라 시스템 개발 I. 하드웨어)

  • Kang, Y.W.;Byun, Y.I.;Rhee, J.H.;Oh, S.H.;Kim, D.K.
    • Journal of Astronomy and Space Sciences
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    • v.24 no.4
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    • pp.349-366
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    • 2007
  • We designed and developed a multi-purpose CCD camera system for three kinds of CCDs; KAF-0401E($768{\times}512$), KAF-1602E($1536{\times}1024$), KAF-3200E($2184{\times}1472$) made by KODAK Co.. The system supports fast USB port as well as parallel port for data I/O and control signal. The packing is based on two stage circuit boards for size reduction and contains built-in filter wheel. Basic hardware components include clock pattern circuit, A/D conversion circuit, CCD data flow control circuit, and CCD temperature control unit. The CCD temperature can be controlled with accuracy of approximately $0.4^{\circ}C$ in the max. range of temperature, ${\Delta}33^{\circ}C$. This CCD camera system has with readout noise $6\;e^-$, and system gain $5\;e^-/ADU$. A total of 10 CCD camera systems were produced and our tests show that all of them show passable performance.

Development of a Real-Time Position Tracking System for a Manufacturing Process Based on a UWB Sensor Using a Kalman Filter (칼만필터를 적용한 UWB 센서기반 제조업 조립공정작업의 실시간 위치추적 시스템 개발)

  • Jeong, Seung-Hyun;Choi, Deuk-Sung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.21 no.2
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    • pp.627-633
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    • 2020
  • Assembly process data can be gathered in real time in a manufacturing execution system (MES) server using proximity sensors, barcodes, RFID, ZigBee, Bluetooth, wireless sensor networks, etc. Although this is suitable for identifying process flow and checking production progress, it is difficult to trace the location of individual workers in real time for missing work or trajectories within the work area. To overcome this, the location and trajectory of the working tool can be analyzed in real time through a position tracking system of an operator's working tool. It can instruct the operator to perform a consistent working process. Productivity and quality improvement can be achieved by an alarming or blocking operator with possible assembly defects during the assembly process in real time. To this end, we developed a real-time tool position-tracking sensor system based on Ultra Wide Band (UWB) trilateration using a Kalman filter to eliminate mechanical vibration and radio communication noise.

A Novel Cooling Method by Acoustic Streaming Induced by Ultrasonic Resonator (초음파 진동자에 의해 유도된 음향유동을 이용한 첨단 냉각법)

  • 노병국;이동렬
    • The Journal of the Acoustical Society of Korea
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    • v.22 no.3
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    • pp.217-223
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    • 2003
  • A novel cooling method induced by acoustic streaming generated by ultrasonic vibration at 30㎑ is presented. Ultrasonic vibration is obtained by piezoelectric devices and the maximum vibration amplitude of 50 m is achieved by including a horn, mechanical vibration amplifier in the system and making the complete system resonate. To investigate the enhancement of heat transfer capability of acoustic streaming, the temperature variations of heat source and air in the vicinity of heat source are measured in real-time. It is observed that acoustic streaming is instantly induced by ultrasonic vibration, resulting in the significant temperature drop due to the bulk air flow caused by acoustic streaming. In addition, it is observed that the cooling effect on the heat source is maximized when the gap between the ultrasonic vibrator and heat source coincides with the multiples of half-wavelength of the ultrasonic wave. This fact results from the resonance of the sound wave. The theoretical analysis of the dependence on the gap is also accomplished and verified by experiment. The advantage of the proposed cooling method by acoustic streaming is noise-free due to the ultrasonic vibration and maintenance-free because of the absence of moving parts. Moreover. This cooling method can be utilized to the nano and micro-electro mechanical systems, where the fan-based conventional cooling method can not be employed.

Bulk Shear-Wave Transduction Experiments Using Magnetostrictive Transducers with a Thin Fe-Co Alloy Patch (철-코발트 합금 패치로 구성된 자기변형 트랜스듀서를 이용한 체적 전단파 발생 및 측정)

  • Park, Jae-Ha;Cho, Seung-Hyun;Ahn, Bong-Young;Kwon, Hyu-Sang
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.8
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    • pp.1075-1081
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    • 2010
  • Recently, the results of many studies have clarified the successful performance of magnetostrictive transducers in which a ferromagnetic patch is used for the transduction of guided shear waves; this is because a thin ferromagnetic patch with strong magnetostriction is very useful for generating and detecting shear wave. This investigation deals with bulk shear wave transduction by means of magnetostriction; on the other hand, the existing studies have been focused on guided shear waves. A modular transducer was developed; this transducer comprised a coil, magnets, and a thin ferromagnetic patch that was made of Fe-Co alloy. Some experiments were conducted to verify the performance of the developed transducer. Radiation directivity pattern of the developed transducer was obtained, and a test to detect the damage on a side drill hole of a steel block specimen was carried out. From the results of these tests, the good performance of the transducer for nondestructive testing was verified on the basis of the signal-to-noise ratio and narrow beam directivity.

Development of Acid Resistance Velocity Sensor for Analyzing Acidic Fluid Flow Characteristics (산성 용액 내 유속 측정을 위한 내산성 센서 개발)

  • Choi, Gyujin;Yoon, Jinwon;Yu, Sangseok
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.40 no.10
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    • pp.629-636
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    • 2016
  • This study presents the development of an acid resistance velocity sensor that is used for measuring velocity inside a copper sulfate plating bath. First, researchers investigated the acid resistance coating to confirm the suitability of the anti-acid sensor in a very corrosive environment. Then, researchers applied signal processing methods to reduce noise and amplify the signal. Next, researchers applied a pressure-resistive sensor with an operation amplifier (Op Amp) and low-pass filter with high impedance to match the output voltage of a commercial flowmeter. Lastly, this study compared three low-pass filters (Bessel, Butterworth and Chebyshev) to select the appropriate signal process circuit. The results show 0.0128, 0.0023, and 5.06% of the mean square error, respectively. The Butterworth filter yielded more precise results when compared to a commercial flowmeter. The acid resistive sensor is capable of measuring velocities ranging from 2 to 6 m/s with a 2.7% margin of error.

Flood Inflow Estimation at Large Multipurpose Dam using Distributed Model with Measured Flow Boundary Condition at Direct Upstream Channels (직상류 계측유량경계조건과 분포형모델을 이용한 대규모 다목적댐 홍수유입량 산정)

  • Hong, Sug-Hyeon;Kang, Boosik
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.35 no.5
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    • pp.1039-1049
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    • 2015
  • The inflow estimation at large multipurpose dam reservoir is carried out by considering the water balance among the discharge, the storage change during unit time interval obtained from the observed water level near dam structure and area-volume curve. This method can be ideal for level pool reservoir but include potential errors when the inflow is influenced by the water level slope due to backwater effects from upstream flood inflows and strong wind induced by typhoon. In addition, the other uncertainties arisen from the storage reduction due to sedimentation after the dam construction and water level noise due to mechanical vibration transmitted from the electric power generator. These uncertainties impedes the accurate hydraulic inflow measurement requiring exquisite hydrometric data arrangement for reservoir waterbody. In this study, the distributed hydrologic model using UBC-3P boundary setting was applied and its feasibility was evaluated. Finally, the modeling performance has been verified since the calculated determination coefficient has been in between 0.96 to 0.99 after comparing with observed peak inflow and total inflow at Namgang dam reservoir.