• Title/Summary/Keyword: Cold flow

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Investigation of Cooling Performance of Injection Molds Using Pulsed Mold Temperature Control (가변 금형온도 제어기법을 적용한 사출금형의 냉각성능 고찰)

  • Sohn, Dong Hwi;Park, Keun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.37 no.1
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    • pp.35-41
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    • 2013
  • In injection molding, the mold temperature is one of most important process parameters that affect the flow characteristics and part deformation. The mold temperature usually varies periodically owing to the effects of the hot polymer melt and the cold coolant as the molding cycle repeats. In this study, a pulsed mold temperature control was proposed to improve the part quality as well as the productivity by alternatively circulating hot water and cold water before and after the molding stage, respectively. Transient thermal-fluid coupled analyses were performed to investigate the heat transfer characteristics of the proposed pulsed mold heating and cooling system. The simulation results were then compared with those of the conventional mold cooling system in terms of the heating and cooling efficiencies of the proposed pulsed mold temperature control system.

Design and Performance Tests of a Cryogenic Blower for a Thermal Vacuum Chamber (열진공 챔버용 극저온 블로워 설계 및 성능평가)

  • Seo, Heejun;Cho, Hyokjin;Park, Sungwook;Moon, Gueewon;Huh, Hwanil
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.43 no.11
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    • pp.1008-1015
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    • 2015
  • Thermal vacuum test should be performed prior to launch to verify satellites' functionality in extremely cold/hot temperatures and vacuum conditions. A thermal vacuum chamber used to perform the thermal vacuum tests of a satellite system and its components. A cryogenic blower is a core component of the gaseous nitrogen (GN2) closed loop thermal control system for thermal vacuum chambers. A final goal of this research is development of cryogenic blower. Design requirements of a blower are 150 CFM flow rate, 0.5 bara pressure difference, hot and cold temperatures. This paper describes the performance analysis of impeller by 1D, CFD commercial software, the design of the thermal protection interface between the driving part and the fluid part. The performance of the cryogenic blower is confirmed by test at the standard air condition and is verified by on the thermal vacuum chamber at the real operating condition.

A Case Study of Heavy Snowfall with Thunder and Lightning in Youngdong Area (뇌전을 동반한 영동지역 대설 사례연구)

  • Kim, Hae-Min;Jung, Sueng-Pill;In, So-Ra;Choi, Byoung-Choel
    • Atmosphere
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    • v.28 no.2
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    • pp.187-200
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    • 2018
  • The heavy snowfall phenomenon with thunder and lightning occurred in Yeongdong coastal region on 20 January 2017. Amount of snow on that day was a maximum of 47 cm and was concentrated in a short time (2 hours) at the Yeongdong coastal area. The mechanism of thundersnow was investigated to describe in detail using observational data and numerical simulation (Weather Research and Forecast, WRF) applied lightning option. The results show that a convective cloud occurred at the Yeongdong coastal area. The east wind flow was generated and the pressure gradient force was maximized by the rapidly developed cyclone. The cold and dry air in the upper atmosphere has descended (so called tropopause folding) atmospheric lower layer at precipitation peak time (1200 LST). In addition, latent heat in the lower atmosphere layer and warm sea surface temperature caused thermal instability. The convective cloud caused by the strong thermal instability was developed up to 6 km at that time. And the backdoor cold front was determined by the change characteristics of meteorological elements and shear line in the east sea. Instability indexes such as Total totals Index (TT) and Lightning Potential Index (LPI) are also confirmed as one of good predictability indicates for the explosive precipitation of convective rainfall.

The Literature Study on Jung point venesection therapy (정혈(井穴) 자락요법(刺絡療法)에 관(關)한 문헌고찰(文獻考察))

  • Kim, Yoon-hee;Lee, Hyun;Lee, Byung-ryul
    • Journal of Haehwa Medicine
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    • v.10 no.1
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    • pp.237-245
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    • 2001
  • I have come to next conclusions in consequnce of documentary study about medical books of many generations regarding Jung point venesection therapy. 1. Jung point is significant as the beginning of pulse energy flow on meridian, the origin of all meridional pulse energy being located at extrimity terminal, confluence of three yin and three yang, and emergent treatment point. 2. Jung point venesection therapy was much used for the first-aid treatment for acute and thermic disease, and that is the combination of the meaning as of restoration from death and emergent treatment of Jung point and function of openning of orifice, leakage of fever, circulation of blood, remove of edema of venesection therapy. 3. It is very much used for emergency case, five sensory organ disease and CVA, heating shock and so on. Besides that digestive disease, cough, fever with cold, childhood disease, cardiac ache, thoracic disease, numbness of digitus terminal, mental disorder follow that in order. 4. Sosang, Jung point of Arm Greater Yin Lung meridian, is very much used for five sensory organ disease. Sosang is for orbital disease, sangyang for auditory disease, sosang for nasal disease, and sosnag for introitus-throat disease. 5. Ten Jung point is most used for first-aid diseases of CVA, heating shock. 6. Ten Jung point is most used for digestive disease of stomach ache, vomiting, diarrhea, intestinal convulsion. 7. Ten Jung point is most used for cold disease of cough, fever, malaria. 8. Ten Jung point, sosang, kwanchung are much used for childhood disease of acute convulsion and fever. 9. Among Jung point, sosang is most used, 34 times. Next there are Ten Jung point, kwanchung, sangyang, sotaek, jungchung, unbaek, taedon in order. In the order of frequency in use, arm channel is more used than leg channel.

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THE USE OF LASER DOPPLER FLOWMETER FOR PULP VITALITY TEST (치수생활력 검사를 위한 Laser Doppler Flowmeter의 이용)

  • Su, Wan-Jong;Kim, Hyun-Jung;Nam, Soon-Hyeun;Kim, Young-Jin
    • Journal of the korean academy of Pediatric Dentistry
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    • v.25 no.3
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    • pp.562-568
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    • 1998
  • Various diagnostic methods, such as electric pulp test, cold test, test cavity etc., have been used to determine the pulp vitality. At least two or more methods should be used with supplemental information to diagnose each case because using one method doesn't provide sufficient accuracy. These conventional methods have depended on nervous responses, but Laser Doppler Flowmeter determines the pulp vitality by measuring pulpal blood flow. In this case, we tested the vitality of the traumatized teeth with incomplete root apices and autotransplanted teeth with conventional methods and Laser Doppler Flowmeter. Conventional methods, such as electric pulp test and cold test can produce various responses according to the development state of the pulpal nerve and the sensory threshold of the patient. But, Laser Doppler Flowmeter has a lower false response rate than any other pulp vitality test methods and it can determine the vitality somewhat earlier than the other method.

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Treatment of Numbness in Hyungsang Medicine (마목의 형상의학적 치료)

  • Kang Kyung Hwa;Son Jae Ik;Kim Kyung Chul;Lee Yong Tae
    • Journal of Physiology & Pathology in Korean Medicine
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    • v.17 no.4
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    • pp.879-892
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    • 2003
  • This thesis makes a review of symptoms and cause of the numbness in the literature. clinical case are studied and classified according to the Hyungsang of the patients. The followings are the conclusions: In case of Dam type persons, numbness is mainly caused by Fire with blood deficiency and so cured by tonifying the Jung and blood. In case of Bang Kwang type persons. it is generally caused by the deficiency of Ki and damp-phlegm and treated by reinforcing Ki and removing dampness. Persons of Jung and Hyal types are apt to be afflicted with numbness of deficiency symptoms which can be cured by tonifying the Jung and blood. Those of Ki and Shin types are inclined to get numb from the congestion and stagnancy and so treated by promotion the flow of Ki, dispelling stagnancy, resolving phlegm and promoting digestion. Numbness is common to the old people and women. The deficiency of blood and primordial energy is a cause of old people's numbness. Women get numb due to the pent-up feelings and emotional disturbance. The function disharmony of five Jang and six Bu makes the body lose the control of heat and cold or deficiency and excessiveness, which can be a cause of numbness. Especially the deficiency of the spleen results in numbness. When the special parts of the body become numb treatment must be decided after due consideration on which of the Jang and Bu or meridians is related to that affected area. In case of person with six meridian types. unbalance of Ki and blood leads the six atmospheric influences(wind, cold, heat, dampness, dryness and fire) get into the body through the most developed meridian and brings in numbness.

Water masses and circulation around Cheju-Do in summer (하계 제주도 주변의 해역 및 해수순환)

  • Kim, Kuh;Rho, Hong-Kil;Lee, Sang-Ho
    • 한국해양학회지
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    • v.26 no.3
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    • pp.262-277
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    • 1991
  • Hydrographic data taken at stations spaced 8-16 nautical miles in the Cheju Strait and the southeastern part of the Yellow Sea in June 1980 and August 1981 show for the first time that oceanic water of high temperature and high salinity exists within 20 km from the northern and western coast of Cheju-Do. It is confirmed that the low salinity trough in the sea around Cheju-Do originates from the river plume on the Yantze Bank. The salinity trough separates the high temperature and high salinity water around Cheju-Do from the surface water of the Yellow Sea and below the seasonal thermocline this distance water meets the Yellow Sea Cold Water forming a thermal front. The Yellow Sea Cold Water seems to spread southward along the Yantze Bank centered at the isobath of 70 m. Its characteristics also appear in the northern part of the Cheju Strait. these complex structures contradict the yellow Sea Warm current suggested by Uda 1934), which is supposed to flow northward into the Yellow Sea along the western coast of Korea. Our data show that dense hydrographic surveys in space and time are prerequisite to understand the circulation around Cheju-Do.

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Design and Cold Test of Semi-Freejet High Altitude Environment Simulation Test Facility for High-Speed Vehicle (초고속 비행체를 위한 준 자유흐름식 고공환경 모사시험설비의 설계 및 상온실험)

  • Lee, Seongmin;Yu, Isang;Park, Jinsu;Ko, Youngsung;Kim, Sunjin;Lee, Jungmin
    • Journal of the Korean Society of Propulsion Engineers
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    • v.22 no.2
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    • pp.115-124
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    • 2018
  • In this study, a cold flow test was carried out on a high-speed vehicle facility with a high-altitude environment simulator. Variable test was carried out according to the blockage ratio, angle, and length of the test model. It is confirmed that the blockage rate can be operated in the range of 40%, and that the model should be selected at an angle of 45 degrees or less. The variables of length are less dominant compared to the variables of blockage rate and angle. Through this, a database is obtained according to the parameters of the conical model of the high-speed vehicle test facility.

Observation and Understanding of Snowfall Characteristics in the Yeongdong Region (영동 지역에서 강설 특성 관측 및 이해)

  • Kim, Byung-Gon;Kim, Mi-Gyeong;Kwon, Tae-Young;Park, Gyun-Myung;Han, Yun-Deok;Kim, Seung-Bum;Chang, Ki-Ho
    • Atmosphere
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    • v.31 no.4
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    • pp.461-472
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    • 2021
  • Yeongdong has frequently suffered from severe snowstorms, which generally give rise to societal and economic damages to the region in winter. In order to understand its mechanism, there has been a long-term measurement campaign, based on the rawinsonde measurements for every snowfall event at Gangneung since 2014. The previous observations showed that a typical heavy snowfall is generally accompanied with northerly or northeasterly flow below the snow clouds, generated by cold air outbreak over the relatively warmer East Sea. An intensive and multi-institutional measurement campaign has been launched in 2019 mainly in collaboration with Gangwon Regional Office of Meteorology and National Institute of Meteorological Studies of Korean Meteorological Administration, with a special emphasis on winter snowfall and spring windstorm altogether. The experiment spanned largely from February to April with comprehensive measurements of frequent rawinsonde measurements at a super site (Gangneung) with continuous remote sensings of wind profiler, microwave radiometers and weather radar etc. Additional measurements were added to the campaign, such as aircraft dropsonde measurements and shipboard rawinsonde soundings. One of the fruitful outcomes is, so far, to identify a couple of cold air damming occurrences, featuring lowest temperature below 1 km, which hamper the convergence zone and snow clouds from penetrating inland, and eventually make it harder to forecast snowfall in terms of its location and timing. This kind of comprehensive observation campaign with continuous remote sensings and intensive additional measurement platforms should be conducted to understand various orographic precipitation in the complex terrain like Yeongdong.

Formation of Military Dictatorship and Anti-Communism in Paraguay (파라과이 군부독재정권의 성립과 반공주의의 역할)

  • Gu, Gyoung-Mo
    • Cross-Cultural Studies
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    • v.45
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    • pp.145-166
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    • 2016
  • The aim of this investigation was to determine the historical relationship between anti-communism in the United States and military dictatorship in Paraguay. Relations between the two countries have been of great importance since the U.S attempt to obtain hemispheric solidarity in World War II, the Cold War in Latin America, and the balance of power in the La Plata region. The Archives of Terror are official documents of police repression between Alfredo Stroessner's dictatorship and the U.S. U.S provided support and aid to Paraguay dictator. Alfredo Stroessner spanned more than half a century. The course of Paraguay-U.S. relation during his regime is illustrative of the flow of real politics in both nations. Not only did Washington had definite diplomatic goals, so did $Asunci{\acute{o}}n$. The relative disparity in power and wealth between the two nations did not necessarily hinder Paraguay's pursuit of international advantage in its relations with the United States.