• 항공우주기술
• /
• 제10권1호
• /
• pp.129-135
• /
• 2011

본 연구는 중앙 물분사 방식을 채택한 액체로켓엔진 후류의 냉각에 대해 전산유체역학을 통한 특성을 고찰하였다. 중앙 물분사 방식의 냉각은 측면 물분사 방식과는 달리, 잘 알려져 있지 않기 때문에 다양한 물분사량과 유량을 통해 효율적으로 후류를 냉각시킬 수 있는 조건을 찾았으며, 해석을 통해 후류의 변화 특성을 살펴보았다. 이로부터 물분사 유량이 총추진제 유량의 2배 이상, 위치는 L/De=1.2일 때가 적당함을 알 수 있었다.

• 대한후두음성언어의학회지
• /
• 제28권2호
• /
• pp.112-117
• /
• 2017

Background and Objectives : The purpose of this study was to classify patients with unilateral vocal fold paralysis according to their fixed location and to analysis the effects of two treatment methods by early voice therapy and injection laryngoplasty. Materials and Methods : Twenty patients who were classified as full abduction and slight abduction according to the position of paralysis were treated injection laryngoplasy, and 23 patients were treated by voice therapy. Twenty patients were treated injection laryngoplasy and 23 patients were treated voice therapy. Results were evaluated by acoustic analysis, electroglottography, cepstrum analysis before and after therapy. The voice therapy was conducted by improving the larynx movement and glottal contact, whilst removing hypertension of the supraglottic and use the breathing. Results : Significant improvement was found in the acoustic parameter, cepstrum parameter, and EGG before and after treatment in both groups. There was no significant difference between the two groups when compared before and after treatment to compare the effects of injection laryngoplasty and voice therapy. Conclusion : The initial treatments for unilateral vocal cord paralysis are injection laryngoplasty and voice therapy. however, there is no precise standard about which method should be applied first. Therefore, in this study, we tried to classify patients according to their paralysis position and then apply two methods. The results of this study suggest that voice therapy and Injection laryngoplasty at the initial stage is a very useful method to improve voice quality of vocal fold paralysis and improve laryngeal function.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2010년도 제35회 추계학술대회논문집
• /
• pp.739-740
• /
• 2010

1단용 액체로켓엔진 후류 때문에 발생하는 유도로의 열적 부하를 감소시키기 위한 방법 중 물분사 방식의 효과적인 냉각 성능을 고찰하기 위해 두 가지 방법과 다양한 물분사 조건에 대해 수치적 계산을 수행하였다. 중앙분사 방식이 측면분사 방식보다 보다 효과적으로 후류를 냉각시켜 유도로의 열적부하를 감소시킴을 알 수 있었다.

• 한국기계가공학회지
• /
• 제8권3호
• /
• pp.90-97
• /
• 2009

In the study, a design methodology for robust minimization of a warpage in injection-molded part is presented. Taguchi's parameter design method is integrated with a computer simulation tool for injection molding to search for best design with robustness against the process variability by noises. The proposed methodology is based on a two-stage process: (1) reducing a warpage in the part by optimizing the part geometry including the layout and size of ribs, and (2) additionally minimizing the warpage by optimizing process conditions. An example is used to illustrate the usefulness of the design methodology.

• Clinical and Experimental Reproductive Medicine
• /
• 제25권2호
• /
• pp.233-237
• /
• 1998

We demonstrated that the normal pregnancy and delivery by round spermatid injection (ROSI) into oocytes was achieved from nonobstructive azoospermia patient. In this case, the normal fertilization rate was 50%. All of the two pronuclear stage embryos cleaved and were transferred to the patient's uterus. A singleton pregnancy was achieved and resulted in the birth of normal female infant. This resuJt show that intracytoplasraic injection of round spermatid seems to be new treatment of nonobstmctive azoospermia male infertility. Further research is needed to evaluate the required culture conditions to induce progression of the round spermatid into a more elongated stage.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2004년도 제22회 춘계학술대회논문집
• /
• pp.449-452
• /
• 2004

“Flameless combustion” of lean to ultra lean mixtures, supported by high-temperature burned gas, can resolve the dilemma between complete combustion versus ultra-low NOx emissions in gas turbine combustors. The characteristics of NOx emissions and combustion in “lean-lean” two-stage combustion were investigated for fuel vapor and droplets / air mixture jets injected from the main injection tube that was placed perpendicular to the combustor wall into the primary hot burned gas prepared by combustion of lean mixtures on a perforated flame holder. The present results clearly show that the ultra-low NOx combustion supported by the reaction of lean mixtures well mixed with the hot burned gas from the primary stage is much more advantageous in achieving ultra-low NOx emissions while maintaining high combustion efficiency.

• 한국추진공학회:학술대회논문집
• /
• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
• /
• pp.196-199
• /
• 2011

고압관, 가압관, 발사관으로 구성된 2단식 경가스 총을 사용하는 축소형 초고압 분사 시스템은 액체 제트를 초음속으로 생성할 수 있다. 이러한 초음속 액체 제트는 전방에 발생하는 충격파로 인한 액적 미립화를 촉진 시킬 수 있다. 본 연구에서는 초음속 액체 제트의 미립화 특성을 파악하기 위해 직선 원추형 노즐을 사용하여 기하학적인 형상 변화에 따른 실험을 진행하였다. 미립화 특성을 나타내는 SMD는 L/d가 증가할수록 $151.2{\mu}m$에서 $52.25{\mu}m$로 감소하는 경향을 나타내었다.

• 한국자동차공학회논문집
• /
• 제12권4호
• /
• pp.24-30
• /
• 2004

As the environmental pollution becomes serious global problem, the regulation of emission exhausted from automobiles is strengthened. Therefore, it is very important to know how to reduce the NOx and PM simultaneously in diesel engines, which has lot of merits such as high thermal efficiency, low fuel consumption and durability. By this reason, the new concept called as Homogeneous Charge Compression Ignition(HCCI) engines are spotlighted because this concept reduced NOx and P.M. simultaneously. However, there is trade off between output and NOx in a HCCI engine. In this study, output and emission characteristics for a gasoline direct injection type HCCI engine were investigated to clarify the effects of intake air temperature, injection time and mixture formation. From these experiments, we found that the smoke was not produced when the fuel was injected earlier than BTDC 90$^{\circ}$. In addition, the output was increased because of delay of ignition time and NOx emission was decreased because of homogeneous charge of first injection in case of split injection.

• 한국지열·수열에너지학회논문집
• /
• 제10권3호
• /
• pp.1-7
• /
• 2014

Heat pumps have received a fair amount of attention all over the world for their high efficiency and low environmental impact. Employing heat pumps for residential heating and cooling produces only about 2038 kg-$CO_2$/year, an amount which is less than half that of conventional boiler systems. However, the use of single-stage heat pumps becomes uneconomical when they are operated at very low evaporating temperature or high condensing temperature. Two-stage heat pumps systems can be used successfully for low or high temperature applications. In this paper, the experimental study on the performance of two-stage heat pump with an economizer was executed in heating mode. When the secondary fluid inlet temperature to the indoor heat exchanger increased, the COP enhancement rate of two-stage heat pump with an economizer was increased. For all outdoor inlet temperature conditions, the performance of the heat pump with an economizer was higher than it without an economizer.

• 한국수정란이식학회지
• /
• 제12권3호
• /
• pp.259-267
• /
• 1997

To improve the efficiency of production of cloned embryos and animals by nuclear transplantation in the rabbit, the effect of cell cycle of donor nuclei and type of recipient cytoplasm on the in vitro developmental potential and production efficiency of offspring was determined. The embryos of 16-cell stage were collected from the mated does at 48h post-hCG injection and they were synchronized to G$_1$ phase of 32-cell stage. The oocytes collected at 14h post-hCG injection were freed from cumulus cells and then enucleated. One group of the enucleated cytoplasms was activated by electrical stimulation prior to injection of donor nucleus, and the other group was not pre-activated. The separated G$_1$phase blastomeres of 32-cell stage embryos were injected into the perivitelline space of recipient cytoplasms. After culture for 20h post-hCG injection, the nuclear transplant oocytes were electrofused and activated by electrical stimulation and the fused nuclear transplant embryos were co-cultured for 120h and the nuclear transplant embryos developed to blastocyst stage were stained with Hoechst 33342 dye and their blastomeres were counted. Some of the nuclear transplant embryos developed in vitro to 2- to 4-cell stage were transferred into the oviducts of synchronized recipient does. The electrofusion rate was similar between the types of donor nuclei and recipient cytoplasms used. However, the nuclear transplant embryos using G$_1$ phase donor nuclei were developed to blastocyst at higher rate(60.3%) than those using S phase ones(24.7%). Also, when non-preactivated oocytes were used as recipient cytplasms, the develop-mental rates of nuclear transplant embryos to blastocysts were significantly(P< 0.05) higher(57.1%) than those using preactivated ones(20.8%). The cell counts of nuclear transplant embryos developed to blastosyst stage were increased signficantly(P<0.05) more in the non-preactivated recipient cytoplasm(163.7 cells), as compared whit the preactivated recipient cytoplasm(85.4 cells), A total of 49 nuclear transplant embryos were tranferrid into 5 recipient does, of which two offsprings were produced from a foster mother 31 days after embryo transfer. these results showed that the blastomeres of G1 phase and non-preactivated oocytes might be utillzed efficiently as donor nuclei and recipient cytoplasms in the nuclear transplant procedure, thought the offspring production remained still low.