• Title/Summary/Keyword: Primary Si

Search Result 534, Processing Time 0.028 seconds

On-site Investigation of Hazardous Substances in Floor Dust of Several Primary Schools (일부 초등학교 바닥 먼지내 포함하고 있는 유해물질 성분에 대한 현장 평가)

  • Kim, Ki Youn;Kim, Hyeon Tae;Lee, Kwon Seob
    • Journal of Korean Society of Occupational and Environmental Hygiene
    • /
    • v.24 no.4
    • /
    • pp.478-483
    • /
    • 2014
  • Objectives: The main objective of this study is to assess the levels of hazardous substances in floor dust in primary schools located in the city of Busan in Korea. Materials and Methods: An on-site investigation of three primary schools was performed between April and May 2013. The hazardous substances measured in this study were 14 heavy metals (Cu, Fe, Pb, Mn, Ni, Zn, Cr, Cd, As, Al, Sn, Co, Mo and Si) and the biological agents were bacteria, fungi and endotoxin). Results: Among the heavy metals, Cd, Co, Pb and Cr were not detected in the floor dust from the three primary schools. The mean levels of other heavy metals were as follows: $20({\pm}10)ng/cm^2$ for As, $30({\pm}20)ng/cm^2$ for Al, $5({\pm}4)ng/cm^2$ for Sn, $20({\pm}20)ng/cm^2$ for Mo, $1,340({\pm}620)ng/cm^2$ for Si, $110({\pm}100)ng/cm^2$ for Cu, $240({\pm}50)ng/cm^2$ for Fe, $30({\pm}30)ng/cm^2$ for Mn, $10({\pm}10)ng/cm^2$ for Ni, and $50({\pm}30)ng/cm^2$ for Zn. It was found that mean concentrations of bacteria, fungi and endotoxin in the floor dust of primary schools were $4.7{\time}10^7({\pm}2.2{\time}10^7)cfu/cm^2$, $6.3{\time}10^6({\pm}6.4{\time}10^6)cfu/cm^2$, and $8,140({\pm}5,801)EU/cm^2$, respectively. The predominant species identified in the floor dust of the primary schools were Pseudomonas spp. for bacteria and Penicillium spp.,Cladosporidium spp.,and Aspergillus spp. for fungi, which would be somewhat similar to the microbial distribution pattern of other general environments. Conclusions: Based on the results obtained from this study, the levels of heavy metals, microbes and endotoxin distributed in the floor dust of primary school were higher than those reported for other general facilities. Thus, preventive measures should be prepared for the health care of children.

Effect of Auricular Acupuncture on Nonsteroidal Antiinflammatory Drug Dose in Primary Dysmenorrhea : A Randomized Controlled Trials (비스테로이드성 소염진통제를 복용하는 원발성 월경곤란증 환자에 대한 이침치료의 무작위대조군임상시험)

  • Hur, Da-Hee;Kang, So-Hyeon;Kwon, Han-Seul;Ahn, Ha-Young;Baek, Hyung-Chan;Kim, Hyeong-Jun
    • The Journal of Korean Obstetrics and Gynecology
    • /
    • v.35 no.4
    • /
    • pp.161-173
    • /
    • 2022
  • Objectives: This study was conducted to evaluate the effectiveness of acupuncture in patients with primary menstrual difficulties taking NSAIDs. Methods: 30 women with primary menstrual difficulties with NSAIDs were assigned to treatment groups (n=15) and control groups (n=15). On their first visit, both groups were provided with a menstrual diary and were required to record the intensity of pain and the dosage of painkillers during each menstrual cycle. The treatment group received two acupuncture treatments per cycle during two cycles, and the control group did not receive acupuncture. Pain strength during menstruation was evaluated using Visual Analogue Scale (VAS), and the total number of painkillers taken during menstruation and the average number of painkillers taken during a single dose was measured. Results: The treatment group had significant pain relief compared to the pre-test group and significant differences from the control group. In addition, there was a significant difference between the treatment group and the control group in the frequency of taking painkillers during the menstrual period and the dose in the test group was significantly lower than before treatment. Conclusions: This clinical trial showed that this acupuncture can help alleviate primary menstruation and reduce the use of nonsteroidal anti-inflammatory drugs.

A Study on the Fabrication of Semi-solid Al Alloys by EMS Horizontal Continuous Casting Process (전자교반식 수평연속주조법에 의한 반응고 Al 합금의 제조에 관한 연구)

  • Park, Gi-Beom;Song, Yeong-Bae;Kim, Yeong-Hwan;Kim, Gyeong-Heon;Kim, In-Bae
    • Korean Journal of Materials Research
    • /
    • v.10 no.2
    • /
    • pp.117-123
    • /
    • 2000
  • In this study, to fabricate the semi-solid Al alloy, the 3phase-2poles electromagnetic stirring system was adopted. The changes of primary grain size, aspect ratio, standard deviation, hardness and the size morphology of eutectic Si with pouring temperatures and input voltages were investigated. At the same pouring temperature, with increasing input voltage, aspect ratio, standard deviation and primary grain size were decreased. The optimum condition for fabrication of semisolid Al alloys by EMS horizontal continuous casting process was determined that the input voltage was 220V and the pouring temperature was 68$0^{\circ}C$. At this optimum conditions the primary grain size was 54$\mu\textrm{m}$, the aspect ratio was 1.56 and the size of eutectic Si was 0.5$\mu\textrm{m}$. The micro-hardness of the Al alloy was 72.1 Hv. The semi-solid A356 Al alloy which has very low aspect ratio and standard deviation value could be fabricated by adopting the EMS horizontal continuous casting facility that was manufactured for this study.

  • PDF

Determination of the Strength Characteristics of c-Si Solar Cells using Partially Processed Solar Cells (부분공정 태양전지를 이용한 결정질 태양전지의 강도 특성에 관한 연구)

  • Choi, Su Yeol;Lim, Jong Rok
    • Journal of the Korean Solar Energy Society
    • /
    • v.40 no.5
    • /
    • pp.35-45
    • /
    • 2020
  • Photovoltaic (PV) power system prices have been steadily dropping in recent years due to their mass production and advances in relevant technology. Crystalline silicon (c-Si wafers) account for the largest share of the price of solar cells; reducing the thickness of these wafers is an essential part of increasing the price competitiveness of PV power systems. However, reducing the thickness of c-Si wafers is challenging; typically, phenomena such as bowing and cracking are encountered. While several approaches to address the bowing phenomenon of the c-Si solar cells exist, the only method to study the crack phenomenon (related to the strength of the c-Si solar cells) is the bending test method. Moreover, studies on determining the strength properties of the solar cells have focused largely on c-Si wafers, while those on the strength properties of front and rear-side electrodes and SiNx, the other components of c-Si solar cells, are scarce. In this study, we analyzed the strength characteristics of each layer of c-Si solar cells. The strength characteristics of the sawing mark direction produced during the production of c-Si wafers were also tested. Experiments were conducted using a 4bending tester for a specially manufactured c-Si solar cell. The results indicate that the back side electrode is the main component that experienced bowing, while the front electrode was the primary component regulating the strength of the c-Si solar cell.

Growth of High Uniform Polycrystalline Grain on the Highly Ordered Porous Anodic Alumina (다공질 양극산화 피막을 이용한 고균일 다결정 살리콘의 성장)

  • Kim, Jong-Yeon;Han, Jin-Woo;Kim, Young-Hwan;Kim, Byoung-Yong;Seo, Dae-Shik
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
    • /
    • 2007.06a
    • /
    • pp.375-375
    • /
    • 2007
  • In the conventional crystallization method, thepoly-Si TFTs show poor device-to-device uniformity because of the random location of the grain boundaries. However, our new crystallization method introduced in this paper employed substrate-embedded seeds on the highly ordered anodic alumina template to control both the location of seeds and the number of grain boundaries intentionally. In the process of excimer laser crystallization (ELC), a-Si film deposited on the anodic alumina by low pressure chemical vapor deposition (LPCVD) is transformed into fine poly-Si grains by explosive crystallization (XC) prior to primary melting. At the higher energy density, the film is nearly completely melted and laterally grown by super lateral growth (SLG) from remained small part of the fine poly-Si grains as seeds at the Si/anodic alumina interface. Resultant grain boundaries have almost linear functions of the number of seeds in concavities of anodic alumina which have a constant spacing. It reveals the uniformity of. device can be enhanced prominently by controlling location and size of pores which contains fine poly~Si seeds under artificial anodizing condition.

  • PDF

Effects of Secondary Forming Process on Mechanical Properties of $SiC_p$/Al Composites Fabricated by Squeeze Casting (용탕단조법에 의하여 제조한 $SiC_p$/Al 복합재료의 2차 성형공정이 기계적 성질에 미치는 영향)

  • Seo, Y.H;Kang, C.G
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.20 no.11
    • /
    • pp.3474-3490
    • /
    • 1996
  • A metal matrix composites(MMCs) for A16061 reinforced with silicon carbide particles is fabricated by melt-stirring method. The primary products of MMCs billets are prepared by volume fractions 5 vol% to 20 vol% and particle size $13\mu m$ to $22\mu m$.This paper will be made to examine the microstructure and mechanical properties of fabricated $SiC_p$/Al 6061 composite by melt-stirring and squeeze casting method. The MMC billets is extruded at $500^{\circ}C$ under the constant extrusion velocity $V_e$=2mm/min using curved shape die. Extrusion force, particle rearrangement, micro structure and mechanical properties of extruded composites will be investigated. The mechanical properties of primary billets manufactured by melt-stirring and squeeze casting method will be compared with extrusion specimen. The effect of volume fraction and size of the reinforcements will be studied. The increase in uniformity of particle dispersion is the major reason for an improvement in reliability due to hot extrusion with optimal shape die. Experimental Young's modulus and 0.2% offset yield strength for the extruded MMCs will be compared with theretical values calculated by the Eshelby method. A method will be proposed for the prediction of Young's modulus and yield strength in $SiC_p$ reinforced MMCs.

Application of Synthetic Mineral Microparticles with Various Metal Species

  • Lee, Sa-Yong;Hubbe, Martin A.
    • Journal of Korea Technical Association of The Pulp and Paper Industry
    • /
    • v.40 no.5
    • /
    • pp.1-10
    • /
    • 2008
  • Synthetic mineral microparticles (SMM) is a patented system which has been developed to promote drainage of water and retention of fine particles during papermaking. It is shown in patents that the SMM system can have advantages in both of drainage and retention, compared with montmorillonite (bentonite), which is one of the most popular materials presently used in this kind of application. Turbidity and gravity drainage time were measured using a Britt-Jar test with representative SMM formulations, in order to confirm the efficacy of SMM covering a wide range of compositions and discover effects of some key variables that have the potential to lead to unexpected advantages in terms of the effectiveness of the microparticles, when used in combination with a cationic polyacrylamide treatment of papermaking furnish. An iron silicate showed highest retention performance, as well as suitably fast drainage time relative to other metal silicate and bentonite. Zinc silicate improved retention and drainage. SMM synthesized from aluminum sulfate ($Al_2(SO_4){_3}$) did not show a benefit in retention and drainage, relative to bentonite. SMM synthesized from aluminum chloride ($AlCl_3$) performed better in drainage and retention than bentonite when the Al/Si ratios were 0.76 and 1.00. It was found that when the Al/Si ratio and neutralization are considered, pH variation due to the change of Al/Si ratio can be a key factor to control the size of primary metal silicate particles and the degree of coagulation of the primary particles.

Primary Leptomeningeal Glioblastomatosis Detected in Cerebrospinal Fluid Cytology -A Case Report- (뇌척수액 세포검사를 통해 발견된 원발성 아교모세포종증 -증례 보고-)

  • Jang, Ki-Seok;Jang, Si-Hyong;Song, Young-Soo;Park, Moon-Hyang
    • The Korean Journal of Cytopathology
    • /
    • v.16 no.2
    • /
    • pp.110-114
    • /
    • 2005
  • Primary leptomeningeal glioblastomatosis is a rare and fatal tumor of the central nervous system, the condition is characterized by diffuse infiltration of the tumor in the meninges without evidence of primary tumor within the brain or spinal cord. We reported an unusual case of leptomengial glioblastomatosis, which was detected by the consecutive cerebrospinal fluid (CSF) cytology with application of immunohistochemistry, in addition to its cytologic findings. A healthy 21 year old man, who was enlisted in the army, presented with a stuporous mental state and diffuse enhancement of meninges without evidence of primary mass lesion in the brain and spinal cord on magnetic resonance imaging(MRI). CSF cytology showed small loose clusters of tumor cells with single cells and lymphocytes. The tumor showed variable pleomorphism with coarse chromatin, irregular nuclear membranes and multi lobated nuclei. On immunohistochemical staining, the tumor cells were founded to be positive for GFAP. In conjunction with radiologic findings, brain biopsy confirmed the diagnosis of leptomenigeal glioblastomatosis. The use of immunohistochemistry is helpful in confirming CSF cytologic diagnosis in patients with primary leptomeningeal glioblastomatosis.

Heart Rate Variability (HRV) Characteristics of Patients with Primary Dysmenorrhea at the Menstrual Phase: A Literature Review and Meta-Analysis (원발성 월경통 환자의 월경기 HRV 특성에 대한 문헌고찰 및 메타분석)

  • Cho, Si-Yoon;Lee, Ji-Yeon
    • The Journal of Korean Obstetrics and Gynecology
    • /
    • v.35 no.3
    • /
    • pp.122-136
    • /
    • 2022
  • Objectives: The aim of this study is to investigate Heart Rate Variability (HRV) characteristics of patients with primary dysmenorrhea at the menstrual phase. Methods: 7 databases (Pubmed, Cochrane library, CNKI, RISS, KISS, OASIS, ScienceON) were searched for eligible studies published before 2021 December. The studies comparing HRV between patients with primary dysmenorrhea and controls were included. A random-effects model was used to evaluate differences of HRV parameters between patients with primary dysmenorrhea and controls. Results: 4 articles were included in this review based on inclusion and exclusion criteria. SDNN (Standard deviation of NN intervals), RMSSD (Square root of the mean squared difference of successive NN intervals), mean PR (Mean of pulse rate), LF (Low frequency), HF (High frequency), was the most frequently used as HRV parameters. RMSSD was significantly lower in patients with primary dysmenorrhea than controls. There was no statistically significant difference of other HRV parameters between patients with primary dysmenorrhea and controls. Conclusions: This study suggests that parasympathetic activity and overall functions of autonomic nervous system might be decreased in patients with primary dysmenorrhea at the menstrual phase. In the future, well-designed clinical studies using HRV and additional meta-analysis should be conducted to obtain a wealth of information about HRV characteristics of patients with primary dysmenorrhea.

Sympathetic Block for Treating Primary Erythromelalgia

  • Bang, Yoo-Jin;Yeo, Jin-Seok;Kim, Si-Oh;Park, Young-Hoon
    • The Korean Journal of Pain
    • /
    • v.23 no.1
    • /
    • pp.55-59
    • /
    • 2010
  • Primary erythromelalgia is a rare condition that’s characterized by erythema, an increased skin temperature and burning pain in the extremities. The pain is often very severe, and treating erythromelalgia is frustrating and difficult. We report here on the case of a 12-year old girl with primary erythromelalgia in both lower extremities. The pain was refractory to medical treatment, but a bilateral sympathetic block with lidocaine and triamcinolone resulted in relief from the pain. Our experience with this disease demonstrates that sympathetic blocks are effective in improving the symptoms and they may be attempted on erythromelalgia patients who do not respond to other treatments, including medication and epidural blocks.