• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.249-254
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• 2022

With the rapid advance of the semiconductor and Information and communication technologies, remote environment monitoring technology, which can detect and analyze surrounding environmental conditions with various types of sensors and wireless communication technologies, is also drawing attention. However, since the conventional remote environmental monitoring systems require external power supplies, it causes time and space limitations on comfortable usage. In this study, we proposed the concept of the self-powered remote environmental monitoring system by supplying the power with the levitation-electromagnetic generator (L-EMG), which is rationally designed to effectively harvest biomechanical energy in consideration of the mechanical characteristics of biomechanical energy. In this regard, the proposed L-EMG is designed to effectively respond to the external vibration with the movable center magnet considering the mechanical characteristics of the biomechanical energy, such as relatively low-frequency and high amplitude of vibration. Hence the L-EMG based on the fragile force equilibrium can generate high-quality electrical energy to supply power. Additionally, the environmental detective sensor and wireless transmission module are composed of the micro control unit (MCU) to minimize the required power for electronic device operation by applying the sleep mode, resulting in the extension of operation time. Finally, in order to maximize user convenience, a mobile phone application was built to enable easy monitoring of the surrounding environment. Thus, the proposed concept not only verifies the possibility of establishing the self-powered remote environmental monitoring system using biomechanical energy but further suggests a design guideline.

• The Korean Journal of Nuclear Medicine Technology
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• v.17 no.2
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• pp.59-66
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• 2013

Purpose: Recently, there is an increase of the number of hospitals using auto dispenser to reduce occupational radiation exposure when drawing up of the $^{18}F-FDG$ dose (5.18 MBq/kg) in a syringe from the dramatic high activity of $^{18}F-FDG$ multidose vial. The aim of this study is to confirm that using auto dispenser actually reduces the radiation exposure for technologists. Also we analyzed the reproducibility of auto dispenser to find optimized dispensing method for the device. Materials and Methods: We conducted three experiments. Comparison of radiation exposure on chest and hands: The chest and hands exposure dose received by technologists during the injection were measured by electronic personal dosimeter (EPD) and ring TLD respectively. Reproducibility of dispensed volume: We draw up the normal saline into 5 and 2 mL syringe using auto dispenser by changing the volume from 1 to 15 mm for 5 times in the same setting of the volume. The weight of 5 normal saline dispensed from the device at same volume was measured using micro balance and calculated standard deviation and coefficient of variation. Reproducibility of dispensed radioactivity: We dispensed 362.6 $MBq{\pm}10%$ of $^{18}F-FDG$ in 5 and 2 mL syringes from the multidose vial of different specific activity. In the same setting of volume, we repeated dispensing for 4 times and compared standard deviation and coefficient of variation of radioactivity between 5 syringes. Results: There was significant difference in the average of chest exposure dose according to the dispensing methods (P<0.05). Also, when dispensing $^{18}F-FDG$ in manual method, exposure dose was 11.5 times higher in right hand and 4.8 times higher in left hand than in auto method. In the result of reproducibility of dispensed volume, standard deviation and coefficient of variation shows decline as the dispensing volume increases. As a result of reproducibility of dispensed radioactivity, standard deviation and coefficient of variation increases as the specific activity increases. Conclusion: We approved that the occupational radiation exposure dose of technologists were reduced when dispensing $^{18}F-FDG$ using auto dose dispenser. Secondly, using small syringes helps to increase reproducibility of auto dose dispense. And also, if you lower the specific activity of $^{18}F-FDG$ in multidose vial below 915-1,020 MBq/mL, you can use auto dispenser more effectively keeping the coefficient of variation lower than 10%.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.12
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• pp.937-942
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• 2013

Fluid generated within the sonic or ultrasonic waves are reflected by the wall, while the opposite direction forming a predetermined sound wave to the acoustic standing wave is referred to. In this study, the frequency of 1.0 MHz and 2.0 MHz acoustic standing wave generation module is installed in a continuous particle separation device, the laminar flow of influent, taking into account the hydraulic retention time (HRT) in accordance with changes in particle separation characteristics investigated. Operation of a standing wave in the particle separation device about $1.3{\sim}2.8^{\circ}C$ temperature is increased, but did not significantly affect the formation of standing waves. During operation, the HRT 1 hr frequency 1.0 MHz 2 hr, 4 hr longer as the particle separation efficiency (turbidity) were 64.1%, 70.0%, 74.3% and, 2.0 MHz has 58.0%, respectively, depending on HRT, 61.8%, 70.7% in the respectively. That is, the same frequency, the HRT treatment efficiency is 10% or more, depending on differences in generation and, 1.0 MHz frequency, 2 hr, 2.0 MHz 4 hr at about 70% or more of the processing efficiency can be maintained. Frequency of 1.0 MHz and 2.0 MHz operation at the same time, as a result, HRT 1 hr, 2 hr, 4 hr particle separation efficiency of 63.8%, respectively, 70.6%, 77.6%, rather than the generation of standing waves appear continuous HRT is affecting a lot of particles to separate could know.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.6
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• pp.427-446
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• 2008

A review on the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering in 2006 has been accomplished. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environments. The conclusions are as follows. (1) The research trends of fluid engineering have been surveyed as groups of general fluid flow, fluid machinery and piping, etc. New research topics include micro heat exchanger and siphon cooling device using nano-fluid. Traditional CFD and flow visualization methods were still popular and widely used in research and development. Studies about diffusers and compressors were performed in fluid machinery. Characteristics of flow and heat transfer and piping optimization were studied in piping systems. (2) The papers on heat transfer have been categorized into heat transfer characteristics, heat exchangers, heat pipes, and two-phase heat transfer. The topics on heat transfer characteristics in general include thermal transport in a cryo-chamber, a LCD panel, a dryer, and heat generating electronics. Heat exchangers investigated include pin-tube type, plate type, ventilation air-to-air type, and heat transfer enhancing tubes. The research on a reversible loop heat pipe, the influence of NCG charging mass on heat transport capacity, and the chilling start-up characteristics in a heat pipe were reported. In two-phase heat transfer area, the studies on frost growth, ice slurry formation and liquid spray cooling were presented. The studies on the boiling of R-290 and the application of carbon nanotubes to enhance boiling were noticeable in this research area. (3) Many studies on refrigeration and air conditioning systems were presented on the practical issues of the performance and reliability enhancement. The air conditioning system with multi indoor units caught attention in several research works. The issues on the refrigerant charge and the control algorithm were treated. The systems with alternative refrigerants were also studied. Carbon dioxide, hydrocarbons and their mixtures were considered and the heat transfer correlations were proposed. (4) Due to high oil prices, energy consumption have been attentioned in mechanical building systems. Research works have been reviewed in this field by grouping into the research on heat and cold sources, air conditioning and cleaning research, ventilation and fire research including tunnel ventilation, and piping system research. The papers involve the promotion of efficient or effective use of energy, which helps to save energy and results in reduced environmental pollution and operating cost. (5) Studies on indoor air quality took a great portion in the field of building environments. Various other subjects such as indoor thermal comfort were also investigated through computer simulation, case study, and field experiment. Studies on energy include not only optimization study and economic analysis of building equipments but also usability of renewable energy in geothermal and solar systems.

• Korean Journal of Environment and Ecology
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• v.35 no.6
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• pp.594-600
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• 2021

The purpose of this study is to observe the period of mating calls of cicadas in South Korea to identify the emergence period and geographic distribution for each cicada species. The study sites were 19 protection areas nationwide. The mating calls of cicadas were collected over the 12 months of 2019. A bioacoustics measuring device was installed to record the mating calls of cicadas in WAV, 44,100Hz format for 1 minute every hour. The temperature was recorded once or twice every hour using a micro-meteorological measuring device. Nine species of Korean cicadinae were studied. The start and end periods of mating calls were recorded for each cicada species for the subsequent analysis. The analysis results showed that nine cicada species appeared in the 19 protection areas. The chronological order of mating call periods for each species was as follows: Cryptotympana atrata (7/12 - 9/30), Meimuna opalifera (7/27 - 10/20), Hyalessa fuscata (7/25 - 10/9), Graptopsaltria nigrofuscata (7/28 - 9/5), Platypleura kaempferi (7/3 - 9/29), Suisha coreana (9/14 - 10/30), Leptosemia takanonis (6/26 - 8/2), Auritibicen intermedius (7/27 - 9/28), and Meimuna mongolica (8/8 - 9/11). The mating call period was between 35 (Meimuna mongolica) and 89 (Platypleura kaempferi) days, with the average being 62 days. The elevation above sea level for the habitats of each species was as follows: 5 - 386 m for Cryptotympana atrata, 7 - 759 m for Meimuna opalifera, 7 - 967 m for Hyalessa fuscata, 42 - 700m for Graptopsaltria nigrofuscata, 7 - 700 m for Platypleura kaempferi, 5 - 759 m for Suisha coreana, 7 - 759 m for Leptosemia takanonis, 397 - 967 m for Auritibicen intermedius, and 7 - 42 m for Meimuna mongolica. The average temperature of the habitats of each species was as follows: 23.9℃ for Cryptotympana atrata, 21.8℃ for Meimuna opalifera, 22℃ for Hyalessa fuscata, 23℃ for Graptopsaltria nigrofuscata, 22.9℃ for Platypleura kaempferi, 14.6℃ for Suisha coreana, 20.6℃ for Leptosemia takanonis, 19.3℃ for Auritibicen intermedius, and 24.4℃ for Meimuna mongolica. In terms of the habitat distribution of species, Meimuna opalifera, Hyalessa fuscata, and Platypleura kaempferi were distributed in more than 15 protection sites. Cryptotympana atrata was distributed in the lowlands in the southwest. Graptopsaltria nigrofuscata was distributed in the western area of the Korean Peninsula. Suisha coreana was distributed in areas excluding high mountain areas and parts of the southeast area. Leptosemia takanonis was distributed in areas near the mountains. Auritibicen intermedius was distributed locally in the high mountain areas. Meimuna mongolica was distributed locally in flat wetlands.

• Tuberculosis and Respiratory Diseases
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• v.44 no.1
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• pp.69-84
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• 1997

Background : Although the overall prognosis of patients with lung cancer is poor, highly effective treatment exists for the small subset of patients with early lung cancer(carcinoma in situ/micro- invasive cancer). But very few patients have benefit from them because these lesions are difficult to detect and localize with conventional white-light bronchoscopy. To overcome this problem, a Lung Imaging Fluorescence Endoscopic device(LIFE) was developed to detect and clearly delineate the exact location and extent of premalignant and early lung cancer lesions using differences in tissue autofluorescence. Purpose : The purpose of this study was to determine the difference of sensitivity and specificity in detecting dysplasia and carcinoma between fluorescence imaging and conventional white light bronchoscopy. Material and Methods : 35 patients (16 with abnormal chest X-ray, 2 with positive sputum study, 2 with undiagnosed pleural effusion, 15 with respiratory symptom) have been examined by LIFE imaging system. After a white light bronchoscopy, the patients were submitted to fluorescence bronchoscopy and the findings of both examinations have been classified in 3 categories(class I, II, III). From of all class n and III sites, 79 biopsy specimens have been collected for histologic examination: a comparison between histologic results and white light or fluorescence bronchoscopy has been performed for assessing sensitivity and specificity of the two methods. Results : 1) Total 79 sires in 35 patients were examined. Histology demonstrated 8 normal mucosa, 21 hyperplasia, 23 dysplasia, and 27 microinvasive and invasive carcinoma. 2) The sensitivity of white light or fluorescence bronchoscopy in detecting dysplasia was 60.9% and 82.6%, respectively. 3) The results of this study showed 70.3 % sensitivity for microinvasive or invasive carcinoma with LIFE system, versus 100% sensitivity for white light in 27 cases of carcinoma. The false negative study of LIFE system was 8 cases(3 adenocarcinoma and 5 small cell carcinoma), which were infiltrated in submucosal area and had normal epithelium. Conclusion : To improve the ability 10 diagnose and stage more accurately, fluorescence imaging may become an important adjunct to conventional bronchoscopic examination because of its high detection rate of premalignant and malignant epithelial lesion. But. it has limitation to detect in submucosal infiltrating carcinoma.

• Korean Journal of Soil Science and Fertilizer
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• v.42 no.6
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• pp.513-521
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• 2009

The primary goal of this research was to develop an optimized analytical procedure for soil analysis based on ion-selective microelectrodes for agricultural purposes, which can perform on-site measurement of various ions in soil easily and rapidly. For the simple and rapid on-site diagnosis, an analysis of soil chemicals was performed employing a multicomponent-in-situ-extractant and an evaluation of ionselective microelectrodes were conducted through the regressive correlation method with a standard analytical approach widely employed in this area. Examination of sensor responses between various soil nutrient extractants revealed that 0.01M HCl and 1M LiCl provided the most ideal Nernstian response. However, 1M LiCl deteriorated the selective response for analytes due to high concentration (1M) of lithium cation. Thus, employing either 0.1M HCl as an extractant followed by 10 times dilution, or 0.01M HCl as an extractant without further dilution was chosen as the optimal extractant composition. A study of regressive correlation between results from ion-selective microelectrodes and those from the standard analytical procedure showed that analyses of $K^+$, $Na^+$, $Ca^{2+}$, and $NO_3{^-}$ showed the excellent consistency between two methods. However, the response for $NH_4{^+}$ suffered the severe interference from $K^+$. In addition, the selectivity for $Mg^{2+}$ over $Ca^{2+}$ was not sufficient enough since available ionophores developed so far do not provide such a high selectivity for $Mg^{2+}$. Therefore, as an agricultural on-site diagnostic instrument, the device in development requires further research on $NH_4{^+}$ analysis in the soil sample, development of $Mg^{2+}$-selective ionophore, and more detailed study focused on potassium, one of the most important plant nutrients.

• Journal of the Korean Vacuum Society
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• v.18 no.2
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• pp.85-91
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• 2009

There has been a rapid progress for flexible polymer-based MEMS(Microelectromechanical Systems) technology. Polycarbonate (PC) and Poly Methyl Methacrylate (PMMA), so-called acrylic, have many advantages for optical, non-toxic and micro-device application. We studied dry etching of PC and PMMA as a function of % gas ratio in the $O_2/SF_6/CH_4$ temary plasma. A photoresist pattern was defined on the polymer samples with a mask using a conventional lithography. Plasma etching was done at 100 W RIE chuck power and 10 sccm total gas flow rate. The etch rates of PMMA were typically 2 times higher than those of PC in the whole experimental range. The result would be related to higher melting point of PC compared to that of PMMA. The highest etch rates of PMMA and PC were found in the $O_2/SF_6$ discharges among $O_2/SF_6$, $O_2/CH_4$ and $SF_6/CH_4$ and $O_2/SF_6/CH_4$ plasma composition (PC: ${\sim}350\;nm/min$ at 5 sccm $O_2/5$ sccm $SF_6$, PMMA: ${\sim}570\;nm/min$ at 2.5 sccm $O_2/7.5$ sccm $SF_6$). PC has smoother surface morphology than PMMA after etching in the $O_2/SF_6/CH_4$ discharges. The surface roughness of PC was in the range of 1.9$\sim$3.88 nm. However, that of PMMA was 17.3$\sim$26.1 nm.

• Journal of Korea Water Resources Association
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• v.53 no.1
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• pp.15-27
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• 2020

Streamflow discharge as a fundamental riverine quantity plays a crucial role in water resources management, thereby requiring accurate in-situ measurement. Recent advances in instrumentations for the streamflow discharge measurement has complemented or substituted classical devices and methods. Among various potential methods, surface current meter using microwave has increasingly begun to be applied not only for flood but also normal flow discharge measurement, remotely and safely enabling practitioners to measure flow velocity postulating indirect contact. With minimized field preparedness, this method facilitated and eased flood discharge measurement in the difficult in-situ conditions such as extreme flood in active ways emitting 24.125 GHz microwave without relying on natural lights. In South Korea, a rectangular shaped instrument named with Microwave Water Surface Current Meter (MWSCM) has been developed and commercially released around 2010, in which domestic agencies charging on streamflow observation shed lights on this approach regarding it as a potential substitute. Considering this brand-new device highlighted for efficient flow measurement, however, there has been few noticeable efforts in systematic and comprehensive evaluation of its performance in various measurement and riverine conditions that lead to lack in imminent and widely spreading usages in practices. This study attempted to evaluate the MWSCM in terms of instrumen's monitoring configuration particularly regarding tilt and yaw angle. In the middle of pointing the measurement spot in a given cross-section, the observation campaign inevitably poses accuracy issues related with different tilt and yaw angles of the instrument, which can be a conventionally major source of errors for this type of instrument. Focusing on the perspective of instrument configuration, the instrument was tested in a controlled outdoor river channel located in KICT River Experiment Center with a fixed flow condition of around 1 m/s flow speed with steady flow supply, 6 m of channel width, and less than 1 m of shallow flow depth, where the detailed velocity measurements with SonTek micro-ADV was used for validation. As results, less than 15 degree in tilting angle generated much higher deviation, and higher yawing angle proportionally increased coefficient of variance. Yaw angles affected accuracy in terms of measurement area.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.12
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• pp.1102-1139
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• 2002

A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 2000 and 2001 has been done. Focus has been put on current status of research in the aspect of heating, cooling, ventilation, sanitation and building environment. The conclusions are as follows. (1) Most of fundamental studies on fluid flow were related with heat transportation of facilities. Drop formation and rivulet flow on solid surfaces were interesting topics related with condensation augmentation. Research on micro environment considering flow, heat, humidity was also interesting for comfortable living environment. It can be extended considering biological aspects. Development of fans and blowers of high performance and low noise were continuing topics. Well developed CFD technologies were widely applied for developing facilities and their systems. (2) Most of papers related with heat transfer analysis and heat exchanger shows dealt with convection, evaporation, and channel flow for the design application of heat exchanger. The numerical heat transfer simulation studies have been peformed and reported to show heat transfer characteristics. Experimental as well as numerical studies on heat exchanger were reported, while not many papers are available for the system analysis including heat exchanger. (3) A review of the recent studies on heat pump system shows that performance analysis and control of heat pump have been peformed by various simulations and experiments. The research papers on multi-type heat pump system increased significantly. The studies on heat pipe have been examined experimently for change of working characteristics and strut lure. Research on the phase change has been carried out steadily and operation strategies of encapsulated ice storage tank are reported experimentally in several papers. (4) A review of recent studies on refrigeration/air conditioning system have focused on the system performance and efficiency for new alternative refrigerants. Evaporation and condensation heat transfer characteristics are investigated for tube shapes and new alternative refrigerants. Studies on components of refrigeration/air conditioning system are carried to examine efficiency for various compressors and performance of new expansion devices. In addition to thermophysical properties of refrigerant mixtures, studies on new refrigerants are also carried out, however research works on two-phase flow seemed to be insufficient. (5) A review of the recent studies on absorption cooling system indicates that heat and mass transfer phenomena have been investigated to improve absorber performance. Various experimental data have been presented and several simulation models have been proposed. A review of the recent studies on duct and ventilation shows that ventilation indices have been proposed to quantify the ventilation performance in buildings and tunnels. Main efforts have been focused on the applications of ventilation effectiveness in practice, either numerically using computational fluid dynamics or experimentally using tracer gas techniques. (6) Based on a review of recent studies on indoor thermal environment and building service systems, research issues have mainly focused on many innovative ideas such as underfloor air-conditioning system, personal environmental modules, radiant floor cooling and etc. Also, the new approaches for minimizing energy consumption as well as improving indoor environmental conditions through predictive control of HVAC systems, various activities of building energy management and cost-benefit analysis for economic evaluation were highlighted.