• Title/Summary/Keyword: Wide Range Pressure

Search Result 516, Processing Time 0.027 seconds

Landslide Analysis of River Bank Affected by Water Level Fluctuation I (저수위 변동에 영향을 받는 강기슭의 산사태 해석 I)

  • Kim, You-Seong;Wang, Yu-Mei
    • Journal of the Korean Geosynthetics Society
    • /
    • v.9 no.3
    • /
    • pp.77-85
    • /
    • 2010
  • The change of water level in reservoirs is an important factor causing failure of bank slopes, i.e. landslide. The water level of Three Gorges reservoir in China fluctuate between 145 m and 175 m, as a matter of flood control. During its normal operational state, the rate of water level fluctuation is supposed to range from 0.67 m/d to 3.0 m/d. Majiagou slope is located on the left bank of Zhaxi River, 2.1 km up from the outlet. Zhaxi River is a tributary of the Yangtze River within the Three Gorges area, of which the water level changes with the reservoir. At the back of Majiagou slope, a 20 m long and 3~10 cm wide fissure developed just after the reservoir water level rose from 95 m to 135 m in 2003. This big fissure was a full suggestion of potential failure of this slope. In this study, unsaturated-saturated seepage analyses were carried out to simulate the change of pore-water pressures in the bank slope subjected to the reservoir water level change. The obtained pore-water pressures were then used to evaluate the change in factor of safety (FS) with reservoir water level. It was found that the phreatic line showed a delayed response with respect to the change of the reservoir water level, because the seepage through soil layer was generally slower than water flows itself. During the rising and drawdown process, the phreatic lines take the shapes of concave and convex, respectively. And the fluctuation of reservoir water level just affected the front part of the bank slope, but had little influence on the back of the slope.

  • PDF

High Permeability, High Selectivity Carbon-Silica Membranes for Gas Separation (기체분리용 고투과선택성 탄소-실리카막)

  • 이영무;박호범
    • Membrane Journal
    • /
    • v.12 no.2
    • /
    • pp.107-119
    • /
    • 2002
  • Carbon-silica ($C-SiO_2$) membranes can be easily prepared by the pyrolysis of two-phase copolymers containing an aromatic imide block and a siloxane block and remarkably high permselectivities of $He/N_2, O_2/N_2,$ and $CO_2/N_2$. The pyrolysis of the imide-siloxane block copolymers was carried out at different final temperatures, $600^{\circ}C, 800^{\circ}C,$ and $1000^{\circ}C$ under an inert atmosphere, and is the first reported case of the precursors being used for the preparation of carbon membrane. The polymeric precursors were synthesized in a wide range of siloxane content and different final morphology, and the pyrolozed membranes were tested with a high vacuum time-lag method at $25^{\circ}C$ and 76cmHg of feed pressure. In experiments with He, $CO_2, O_2 \;and \;N_2$, the membranes were found to have good $O_2/N_2$ selectivity up to 32.2 and $O_2$ permeability on the order of $10-8/cm^2(STP)cm/cm^2seccmHg.$.

Preliminary study on a spoke-type EPB shield TBM by discrete element method (개별요소법을 활용한 스포크 타입 토압식 쉴드TBM의 예비 해석 연구)

  • Lee, Chulho;Chang, Soo-Ho;Choi, Soon-Wook;Park, Byungkwan;Kang, Tae-Ho;Sim, Jung Kil
    • Journal of Korean Tunnelling and Underground Space Association
    • /
    • v.19 no.6
    • /
    • pp.1029-1044
    • /
    • 2017
  • The Discrete Element Method (DEM) is one of the useful numerical methods to analyze the behavior of the ground formation by computing the motion and interaction using particles. The DEM has not been applied in civil engineering but also a wide range of industrial fields, such as chemical engineering, pharmacy, material science, food engineering, etc. In this study, to review a performance of the spoke-type earth pressure balance (EPB) shield TBM (Tunnel Boring Machine), the commercial software based on the DEM technology was used. An analysis of the TBM during excavation was conducted according to two pre-defined excavation conditions with the different rotation speed of a cutterhead. During the analysis, the resistant torque at the face of the cutterhead, the compressive force at the cutterhead and shield surface, the muck discharge at the screw auger were measured and compared. Upon the two kinds of excavation conditions, the applicability of the DEM analysis was reviewed as a modelling method for the TBM.

Rheological Behavior of Lyotropilc Solutions of Cellulose in the $NH_3/NH_4SCN$ Solvent System

  • Jo, Jae-Jeong;Cuculo, J.A.;Theil, M.H.
    • Proceedings of the Korean Fiber Society Conference
    • /
    • 1990.06b
    • /
    • pp.36-37
    • /
    • 1990
  • In the past, facile dissolution of cellulose has been hampered by the lack of suitable nondegrading solvents. Recently, this problem has been solved in our laboratory by the discovery of an inexpensive, convenient solvent system, that is the mixture of $NH_3\;and\;NH_4SCN$, for cellulose. Also, the $cellulose/NH_3/NH_4SCN$ solution system has been found to form the anisotropic, i.e., liquid crystalline phase. It is believed that both the cholesterio and the nematic phase occur. This finding has prompted extensive on-going researoh on the formation of the liquid crystalline phase from an inexpensive natural source such as cellulose since the nematic phase is envisioned as an excellent precursor sources for products with desirable properties, for example, high modulus and high strength. This interest naturally leads to a desire to understand the theological properties of the nematic phase so that the transformation of the nematic phase to the solid state with desirable properties can be efficiently accomplished, ;From this point of view, the theological behavior of the $cellulose/NH3_/NH_4SCN$ system has been studied as a function of shear rate and shear stress over a wide range of solvent compositions, cellulose concentration, centrifugation and urea contents, Results indicate that the viscosity decreases with increasing shear rate. A marked shear thinning behavior and a quasi-Newtonian behavior were observed in the low shear rate region and in the high shear rate region, respectively for all solvent compositions. The $cellulose/NH_3/NH_4SCN$ solution system only exhibited the viscosity increase with increasing cellulose concentration and failed to show the viscosity drop generally observed at the point of incipience of liquid crystal formation, This may be due to the gel-like nature of the solution by the association of the rodlike molecules into bundles which may serve as crosslinking points giving the cellulose solution a network structure. Also, simply hydrogen bonding may be so restrictive of molecular mobility that a viscosity drop is blocked. In addition to the above results, yield stress and thixotropy were also observed in the $cellulose/NH_3/NB_4SCN$ solution system which are characteristics of liquid crystal and gel, The results of the effect of centrifugation on viscosity show that viscosity decreases by the application of centrifugation. This may be explained by the change of the piled polydomain structure to the dispersed polydomain structure due to the pressure gradient generated during centrifugation.ation.

  • PDF

Cost-Benefit Analysis Method for Ageing Equipment of Chemical Plants Using Risk Assessment (위험성평가를 이용한 노후설비에 대한 비용 편익분석 방법)

  • Jung, Soomin;Jung, Changmo;Kang, Seok-Min;Chae, Seungbeen;Kang, Seung-Gyun;Ko, Jae Wook
    • Journal of the Korean Institute of Gas
    • /
    • v.24 no.4
    • /
    • pp.84-92
    • /
    • 2020
  • Most facilities in chemical plants operate in environments that are outside the range of temperature and pressure that can be encountered on a daily basis, and are vulnerable to aging due to these stresses and environmental conditions. The facilities exposed to these conditions are not only likely to fail due to cumulative damage, but also lead to accidents if maintenance and replacement are not performed.Recommendation guidelines called risk-based inspection are widely used around the world-wide. However, limits exist for facilities that have already elapsed for a certain. As a result of the survey on the aging of Ulsan industrial complex in Korea, which carries out proper inspection, many of the facilities have been used for 20 years. Also, most of the facilities where the accident occurred have been in operation for more than 20 years. Therefore, this study suggested criteria for classifying devices that have exceeded a certain period of use as obsolete facilities. In addition, quantitative risk assessment was conducted. The safety investment method using the cost-benefit analysis method was proposed in order to calculate the loss cost and reduce the risk by expressing the risks of the corresponding aged facility as an Economic index. By utilizing the method of cost-benefit analysis of old facilities using the quantitative risk assessment presented in this study, it can be expected to improve the performance and life of old facilities, improve production efficiency and reliability of the system of facilities, change the recognition of safety management costs, increase employee stability, and reduce loss costs.

Effect of Casting Temperature and Speed on Formation of Surface Defect in Al-8Zn-2Mg-2Cu Billets Fabricated by Direct-Chill Casting Process (수직 연속주조 공정으로 제조된 Al-8Zn-2Mg-2Cu 빌렛의 표면 결함 형성에 미치는 주조 온도와 주조 속도의 영향)

  • Lee, Yoon-Ho;Kim, Yong-You;Lee, Sang-Hwa;Kim, Min-Seok;Euh, Kwangjun;Lee, Dong-Geun
    • Journal of Korea Foundry Society
    • /
    • v.41 no.3
    • /
    • pp.241-251
    • /
    • 2021
  • 7000-series aluminum alloys are noted for their superior strength compared with other Al alloys, and their billets are generally fabricated by direct-chill (DC) casting. Surface defects in a DC-cast aluminum billet are mainly related to exudation and the meniscus freezing phenomenon, which are influenced by alloy compositions, casting speed, and casting temperature. 7000-series aluminum alloys have a wide freezing range during solidification, which makes it easy for casting defects to occur. In this study, we investigated surface defect evolution in casting billets of Al-8Zn-2Mg-2Cu alloy fabricated by a DC casting process. The billets showed "wavy" or "dotted" surfaces. The wavy surface was formed by meniscus freezing at a lower casting speed (200 mm/min) and temperature (655 ℃). In the wavy surface, refined dendritic cells were observed in a concave region due to the constitutional supercooling caused by meniscus freezing. Meanwhile, at a higher casting temperature (675 ℃), the dotted surface was formed by pore formation. In the dotted surfaces in the billet formed at a high casting speed (230 mm/min), an exudation layer was formed by the high metallostatic head pressure. The dotted region and the smooth region had a refined dendritic morphology and a columnar morphology at the exudation layer, respectively. This is attributed to the formation of gas pores in the dotted region.

BEEF MEAT TRACEABILITY. CAN NIRS COULD HELP\ulcorner

  • Cozzolino, D.
    • Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
    • /
    • 2001.06a
    • /
    • pp.1246-1246
    • /
    • 2001
  • The quality of meat is highly variable in many properties. This variability originates from both animal production and meat processing. At the pre-slaughter stage, animal factors such as breed, sex, age contribute to this variability. Environmental factors include feeding, rearing, transport and conditions just before slaughter (Hildrum et al., 1995). Meat can be presented in a variety of forms, each offering different opportunities for adulteration and contamination. This has imposed great pressure on the food manufacturing industry to guarantee the safety of meat. Tissue and muscle speciation of flesh foods, as well as speciation of animal derived by-products fed to all classes of domestic animals, are now perhaps the most important uncertainty which the food industry must resolve to allay consumer concern. Recently, there is a demand for rapid and low cost methods of direct quality measurements in both food and food ingredients (including high performance liquid chromatography (HPLC), thin layer chromatography (TLC), enzymatic and inmunological tests (e.g. ELISA test) and physical tests) to establish their authenticity and hence guarantee the quality of products manufactured for consumers (Holland et al., 1998). The use of Near Infrared Reflectance Spectroscopy (NIRS) for the rapid, precise and non-destructive analysis of a wide range of organic materials has been comprehensively documented (Osborne et at., 1993). Most of the established methods have involved the development of NIRS calibrations for the quantitative prediction of composition in meat (Ben-Gera and Norris, 1968; Lanza, 1983; Clark and Short, 1994). This was a rational strategy to pursue during the initial stages of its application, given the type of equipment available, the state of development of the emerging discipline of chemometrics and the overwhelming commercial interest in solving such problems (Downey, 1994). One of the advantages of NIRS technology is not only to assess chemical structures through the analysis of the molecular bonds in the near infrared spectrum, but also to build an optical model characteristic of the sample which behaves like the “finger print” of the sample. This opens the possibility of using spectra to determine complex attributes of organic structures, which are related to molecular chromophores, organoleptic scores and sensory characteristics (Hildrum et al., 1994, 1995; Park et al., 1998). In addition, the application of statistical packages like principal component or discriminant analysis provides the possibility to understand the optical properties of the sample and make a classification without the chemical information. The objectives of this present work were: (1) to examine two methods of sample presentation to the instrument (intact and minced) and (2) to explore the use of principal component analysis (PCA) and Soft Independent Modelling of class Analogy (SIMCA) to classify muscles by quality attributes. Seventy-eight (n: 78) beef muscles (m. longissimus dorsi) from Hereford breed of cattle were used. The samples were scanned in a NIRS monochromator instrument (NIR Systems 6500, Silver Spring, MD, USA) in reflectance mode (log 1/R). Both intact and minced presentation to the instrument were explored. Qualitative analysis of optical information through PCA and SIMCA analysis showed differences in muscles resulting from two different feeding systems.

  • PDF

Safety and efficacy of target controlled infusion administration of propofol and remifentanil for moderate sedation in non-hospital dental practice

  • Douglas Lobb;Masoud MiriMoghaddam;Don Macalister;David Chrisp;Graham Shaw;Hollis Lai
    • Journal of Dental Anesthesia and Pain Medicine
    • /
    • v.23 no.1
    • /
    • pp.19-28
    • /
    • 2023
  • Background: Fearful and anxious patients who find dental treatment intolerable without sedative and analgesic support may benefit from moderate sedation. Target controlled infusion (TCI) pumps are superior to bolus injection in maintaining low plasma and effect-site concentration variability, resulting in stable, steady-state drug concentrations. We evaluated the safety and efficacy of moderate sedation with remifentanil and propofol using TCI pumps in non-hospital dental settings. Methods: A prospective chart review was conducted on 101 patients sedated with propofol and remifentanil using TCI pumps. The charts were completed at two oral surgeons and one general dentist's office over 6 months. Hypoxia, hypotension, bradycardia, and over-sedation were considered adverse events and were collected using Tracking and Reporting Outcomes of Procedural Sedation (TROOPS). Furthermore, patient recovery time, sedation length, drug dose, and patient satisfaction questionnaires were used to measure sedation effectiveness. Results: Of the 101 reviewed sedation charts, 54 were of men, and 47 were of women. The mean age of the patients was 40.5 ±18.7 years, and their mean BMI was 25.6 ± 4.4. The patients did not experience hypoxia, bradycardia, and hypotension during the 4694 min of sedation. The average minimum Mean Arterial Pressure (MAP) and heartbeats were 75.1 mmHg and 60.4 bpm, respectively. 98% of patients agreed that the sedation technique met their needs in reducing their anxiety, and 99% agreed that they were satisfied with the sedation 24 hours later. The average sedation time was 46.9 ± 55.6 min, and the average recovery time was 12.4 ± 4.4 min. Remifentanil and propofol had mean initial effect-site concentration doses of 0.96 µ/.ml and 1.0 ng/ml respectively. The overall total amount of drug administered was significantly higher in longer sedation procedures compared to shorter ones, while the infusion rate decreased as the procedural stimulus decreased. Conclusion: According to the results of this study, no patients experienced adverse events during sedation, and all patients were kept at a moderate sedation level for a wide range of sedation times and differing procedures. The results showed that TCI pumps are safe and effective for administering propofol and remifentanil for moderate sedation in dentistry.

A Study of the Measurement of Nonwoven Geotextile Deformation with Strain Gauges (스트레인 게이지를 이용한 부직포의 변형거동 계측에 관한 연구)

  • Won, Myoung-Soo;Kim, You-Seong;Kim, Hyeong-Joo;Park, Byung-Soo
    • Journal of the Korean Geotechnical Society
    • /
    • v.23 no.4
    • /
    • pp.25-32
    • /
    • 2007
  • Because of the increasing use of clayey soil as the backfill in reinfurced soil structures and embankments, nonwoven geotextiles of drain capability have been receiving much attention. However, there are few studies on the deformation behavior analysis of nonwoven geotextiles in reinforced soil structures in the site because nonwoven geotextiles which have low tensile stiffness and higher deformability than geogrids and woven geotextiles, are difficult to measure their deformation by using strain gauges. In this study, it was suggested that a new and more convenient method could measure the deformation behaviour of nonwoven geotextile using a strain gauge and examine the availability of the method by conducting laboratory tests and applying to two geosynthetics reinforced soil (GRS) walls in the site. The result of wide-width tensile test conducted under confining pressure of 70 kPa shows that the local deformation of nonwoven geotextile to be measured with strain gauges has a similar pattern to the total deformation measured with LVDT. In the GRS walls, nonwoven geotextile shows a larger deformation range than the woven geotextile and geogrid. However, the deformation patterns of these three reinforcement materials are similar. The function of strain gauges attached to nonwoven geotextile in the walls works normally for 16 months. Therefore, the method proposed in this study for measuring nonwoven geotextile deformation using a strain gauge has proved useful.

Theoretical analysis of erosion degradation and safety assessment of submarine shield tunnel segment based on ion erosion

  • Xiaohan Zhou;Yangyang Yang;Zhongping Yang;Sijin Liu;Hao Wang;Weifeng Zhou
    • Geomechanics and Engineering
    • /
    • v.37 no.6
    • /
    • pp.599-614
    • /
    • 2024
  • To evaluate the safety status of deteriorated segments in a submarine shield tunnel during its service life, a seepage model was established based on a cross-sea shield tunnel project. This model was used to study the migration patterns of erosive ions within the shield segments. Based on these laws, the degree of deterioration of the segments was determined. Using the derived analytical solution, the internal forces within the segments were calculated. Lastly, by applying the formula for calculating safety factors, the variation trends in the safety factors of segments with different degrees of deterioration were obtained. The findings demonstrate that corrosive seawater presents the evolution characteristics of continuous seepage from the outside to the inside of the tunnel. The nearby seepage field shows locally concentrated characteristics when there is leakage at the joint, which causes the seepage field's depth and scope to significantly increase. The chlorine ion content decreases gradually with the increase of the distance from the outer surface of the tunnel. The penetration of erosion ions in the segment is facilitated by the presence of water pressure. The ion content of the entire ring segment lining structure is related in the following order: vault < haunch < springing. The difference in the segment's rate of increase in chlorine ion content decreases as service time increases. Based on the analytical solution calculation, the segment's safety factor drops more when the joint leaks than when its intact, and the change rate between the two states exhibits a general downward trend. The safety factor shows a similar change rule at different water depths and continuously decreases at the same segment position as the water depth increases. The three phases of "sudden drop-rise-stability" are represented by a "spoon-shaped" change rule on the safety factor's change curve. The issue of the poor applicability of indicators in earlier studies is resolved by the analytical solution, which only requires determining the loss degree of the segment lining's effective bearing thickness to calculate the safety factor of any cross-section of the shield tunnel. The analytical solution's computation results, however, have some safety margins and are cautious. The process of establishing the evaluation model indicates that the secondary lining made of molded concrete can also have its safety status assessed using the analytical solution. It is very important for the safe operation of the tunnel and the safety of people's property and has a wide range of applications.