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알칼리 자극제와 고로슬래그의 비표면적이 고로슬래그 시멘트의 압축강도에 미치는 영향
안지환,조진상,韓基天,柳光錫 한국자원공학회 2004 한국자원공학회지 Vol.41 No.5
The effects of specific surface area of blast furnace slag(BFS) and alkaline activator on the compressive strength of blast furnace slag cement were investigated. Sodium sulfate(Na2SO4) was used as alkaline activator. The addition amounts of alkaline activator, calculated in terms of Na2O, were 2.5 and 5.0wt.% to BFS weight, respectively. The flow and compressive strength of mortar were examined when the BFS power of which the specific surface area are 4,000, 6,000 and 8,000cm2/g were substituted for 30, 50, and 70wt.% of ordinary portland cement(OPC), respectively. As the results, the compressive strength of mortar increased with the increase of specific surface area of BFS and alkaline activator content when the mortar cured for 1 day and 3days. For the mortar cured for 7days, only the specific surface area of BFS affected the increase of compressive strength. 고로슬래그의 비표면적 및 알칼리 자극제가 고로슬래그 시멘트의 압축강도에 미치는 영향을 조사하였다. 알칼리 자극제로는 Na2SO4를 사용하였으며 Na2O로 환산하여 고로슬래그의 2.5, 5.0wt.% 첨가하였다. 비표면적이 각각 4,000, 6,000, 8,000cm2/g인 고로슬래그 미분말을 보통 포틀랜드 시멘트에 대해 30, 50, 70wt.% 치환하였을 경우 모르타르의 유동성 및 압축강도를 측정하여 반응표면분석에 의한 통계적인 방법으로 분석하였다. 재령 1일과 3일의 초기강도는 고로슬래그의 비표면적이 크고, 알칼리 자극제의 첨가량이 높을수록, 재령 7일 이후의 경우 알칼리 자극제의 첨가량이 적을수록, 또한 고로슬래그의 비표면적이 클수록 압축강도가 증가하였다.
폐콘크리트로부터 회수된 시멘트 페이스트 미분말의 시멘트 원료화 연구
안지환,김형석,조진상,한기천,한기석,김환,Ahn, Ji-Whan,Kim, Hyung-Seok,Cho, Jin-,Sang,Han, Gi-Chun,Han, Ki-Suk,Kim, Hwan 한국세라믹학회 2003 한국세라믹학회지 Vol.40 No.8
건설폐기물 중 폐콘크리트를 40$0^{\circ}C$로 가열한 후 ball mill로 분쇄하여 재생골재를 생산할 때 발생된 미분말을 보통 포틀랜드 시멘트의 SiO$_2$, CaO, A1$_2$O$_3$원에 대한 대체원료물질로서 활용하고자 하였다. 클링커를 제조하기 위한 주원료는 석회석, shale, 전로슬래그, fly ash를 이용하였고, modulus는 LSF:91.0, SM:2.60, IM:1.60로 고정한 후 shale에 대해 미분말을 25, 50, 15, 100%까지 치환하여 클링커를 제조하였다. 클링커의 주요생성광물은 1,45$0^{\circ}C$에서 OPC와 같은 광물상인 $C_3$S, $\beta$-C$_2$S, $C_3$A, $C_4$AF 상으로 나타났다. 조합원료의 반응성을 비교하기 위해 시차열분석을 실시하고, 소성성지수를 구한 결과, 클링커의 광물상 생성온도는 plain과 유사했으며, 소성성지수는 48.6-51.4 정도로 나타났다. The fine powder produced by heating and grinding of the waste concrete in the waste construction was investigated whether utilize as substitution raw material of SiO$_2$, CaO, and Al$_2$O$_3$ source for OPC clinker manufacture is possible or not. In order to synthesize OPC clinker, limestone, shale, converter slag and fly ash were used as main raw materials, and modulus was fixed LSF 91.0, SM 2.60, IM 1.60. The synthesized clinkers were characterized. The Main products of synthesized clinker were C$_3$S, ${\beta}$-C$_2$S, C$_3$A, C$_4$AF as OPC clinker at 1,43$^{\circ}C$. As a result of TG-DTA and burnability index(B.U) analysis of each raw mixtures, the formation temperature of clinker phases was similar and B.I was showed easy burning as 48.6∼51.4.
안지환,강병주,홍선인,이정수,이재승,오연목,이상도 대한의학회 2014 Journal of Korean medical science Vol.12 No.12
We aimed to identify a vasoreactive subset of patients with idiopathic pulmonary arterialhypertension (IPAH) in Korea and to show their clinical characteristics and prognosis. Dataon patients who were diagnosed with IPAH at Asan Medical Center between January 1994and March 2013 were retrospectively collected. Acute vasodilator testing was performedwith inhaled nitric oxide during diagnostic right heart catheterization. A positive acuteresponse was defined as a reduction in mean pulmonary arterial pressure (PAP) ≥ 10 mmHgto an absolute level of mean PAP < 40 mmHg without a decrease in cardiac output. Among a total of 60 IPAH patients included for analysis, 9 (15%) showed a positive acuteresponse to acute vasodilator testing. Acute responders showed significantly lower peakvelocity of a tricuspid regurgitation jet on echocardiography (4.1 ± 0.3 m/s vs. 4.6 ± 0.6m/s; P = 0.01) and significantly lower mean PAP hemodynamically (47 ± 10 mmHg vs. 63 ± 17 mmHg; P = 0.003) than non-responders at baseline. The survival rate of acuteresponders was 88% at 1, 3, 5, and 10 yr, respectively, which was significantly higher thanthat of non-responders (85%, 71%, 55%, and 40%, respectively; P = 0.029). In conclusion,Korean IPAH patients with vasoreactivity showed better baseline hemodynamic featuresand survival than those without vasoreactivity.
2.3GHz 휴대인터넷 시스템을 위한 적응형 무선 커버리지 제어기법
안지환,염동화,김영일,강창순 에스케이텔레콤 (주) 2006 Telecommunications Review Vol.16 No.4
휴대인터넷 시스템(와이브로)은 셀 반경 1Km 정도의 무선 커버리지와 최대 시속 60Km 내외의 이동성을 지원하면서 고품질의 데이터 서비스를 제공하기 위하여 2.3GHz 주파수 대역과 직교 주파수 분할 다중접속 기술 및 모든 셀에서 동일한 주파수를 사용한다. 이러한 고주파수 대역은 전형적인 도심지의 비가시선 전파 환경에서 상대적으로 취약하며 고품질 데이터 서비스는 높은 송수신 전력 레벨을 요구하는 특징이 있다. 따라서 휴대인터넷 시스템은 기존의 이동통신시스템에 비하여 무선 커버리지가 축소될 수 있을 뿐만 아니라 트래픽 과부하 상태가 빈번하게 발생하여 무선자원 사용효율과 서비스품질이 급격히 저하할수 있다. 본 논문에서는 이와 같은 문제점을 개선하기 위하여 무선 커버맂를 가상적으로 홈 셀 영역, 인트라 셀 핸드오버 영역과 인터 셀 핸드오버 영역으로 구분하여 트래픽 부하에 따라 핸드오버 파라미터의 변경으로 이들 영역을 조정하는 적응형 무선 커버리지 제어 기법을 제안한다. 제안하느 기법은 국내 휴대인터넷 시스템뿐만 아니라 무선 인터넷의 국제표준인 와이맥스 시스템(802.16)에도 적용할 수 있을 것으로 기대된다.
Advanced Process for Recovery of High Quality Recycled Aggregate from Waste Concrete
안지환,조희찬,엄남일,Gwang-Suk You,Gi-Chun Han 한국자원공학회 2006 Geosystem engineering Vol.9 No.2
Preheating and grinding method was examined as a way for recovery of high quality recycled aggregates from waste concrete. As results, as the preheating temperature increased, the removal rate of cement mortar from waste concrete increased. And when it was treated over 400oC of preheating temperature, the absorption was reduced and cement mortar was effectively separated from waste concrete. It could meet the Korean Standards on aggregates for concrete. It means that recycled aggregates treated by preheating and grinding method can be expected to be used as the utilization which is same to natural aggregates.
수세에 의한 생활폐기물 소각재 중 비산재로부터 염소성분의 제거
안지환,한기천,김형석 한국자원리싸이클링학회 2001 資源 리싸이클링 Vol.10 No.5
The chlorine component in fly ash from municipal solid waste incineration ash was removed by water washing for the purpose of recycling fly ash as a raw material of ordinary portland cement. The samples were a different kind of 리y ashes using $Ca(OH)_2$and NaOH as media of wet scrubber for flue gas cleaning. The content of soluble salts of fly ash using $Ca(OH)_2$and NaOH was 32.8%, 50.1% and the content of chlorine component, 22.9% and 26.0% respectively, which was KCl, NaCl, CaC1OH mainly. When each fly ash was washed using water under conditions of a agitation speed of 300 rpm, a liquid to solid ratio of 10, most soluble salts in fly ash were dissolved within 30 minutes and the content of chlorine component in ash was diminished to the content of 4.4%, 2.O% at $20^{\circ}C$ and 1.7%, 0.8% at $50^{\circ}C$ respectively. And the main compound of residual chlorine component in ash after water washing was friedel`s salt ($3CaO.A1_2$$O_3$.$CaCl_2$.$10H2$O). From analysis results of water quality for wastewater by water washing, the components exceeding discharged wastewater standard were only Pb and Cd. But As pH was controlled to 10 with addition of $CO_2$(g) or $Na_2$$_CO3$in water, the concentration of heavy metals such as Pb and Cd was also under discharged wastewater standard.