• Title, Summary, Keyword: range of confinement

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A study on the field tests and development of quantitative two-dimensional numerical analysis method for evaluation of effects of umbrella arch method (UAM 효과 평가를 위한 현장실험 및 정량적 2차원 수치해석기법 개발에 관한 연구)

  • Kim, Dae-Young;Lee, Hong-Sung;Chun, Byung-Sik;Jung, Jong-Ju
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.1
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    • pp.57-70
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    • 2009
  • Considerable advance has been made on research on effect of steel pipe Umbrella Arch Method (UAM) and mechanical reinforcement mechanism through numerical analyses and experiments. Due to long analysis time of three-dimensional analysis and its complexity, un-quantitative two-dimensional analysis is dominantly used in the design and application, where equivalent material properties of UAM reinforced area and ground are used, For this reason, development of reasonable, theoretical, quantitative and easy to use design and analysis method is required. In this study, both field UAM tests and laboratory tests were performed in the residual soil to highly weathered rock; field tests to observe the range of reinforcement, and laboratory tests to investigate the change of material properties between prior to and after UAM reinforcement. It has been observed that the increase in material property of neighboring ground is negligible, and that only stiffness of steel pipe and cement column formed inside the steel pipe and the gap between steel pipe and borehole contributes to ground reinforcement. Based on these results and concept of Convergence Confinement Method (CCM), two dimensional axisymmetric analyses have been performed to obtain the longitudinal displacement profile (LDP) corresponding to arching effect of tunnel face, UAM effect and effect of supports. In addition, modified load distribution method in two dimensional plane-strain analysis has been suggested, in which effect of UAM is transformed to internal pressure and modified load distribution ratios are suggested. Comparison between the modified method and conventional method shows that larger displacement occur in the conventional method than that in the modified method although it may be different depending on ground condition, depth and size of tunnel, types of steel pipe and initial stress state. Consequently, it can be concluded that the effect of UAM as a beam in a longitudinal direction is not considered properly in the conventional method.

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Growth Performance, Carcass Traits and Meat Quality of Slower-growing and Fast-growing Chickens Raised with and without Outdoor Access

  • Mikulski, Dariusz;Celej, Joanna;Jankowski, Jan;Majewska, Teresa;Mikulska, Marzena
    • Asian-Australasian Journal of Animal Sciences
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    • v.24 no.10
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    • pp.1407-1416
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    • 2011
  • The objective of this study was to determine the effect of genotype (slower-growing vs. fast-growing) and production system (access to outdoors vs. indoor) on the growth performance, carcass yield and meat quality (chemical composition, physicochemical and sensory properties) of chickens. The experiment was performed on 1,040 day-old hybrid male chickens of two genotypes. Slower-growing chickens (Hubbard JA957, certified) and fast-growing chickens (Hubbard F15) were fed identical diets until 65 days of age. Both genotypes (each represented by 520 birds) were divided into two subgroups and were raised in pens on litter with outdoor access or in indoor confinement without outdoor access (four replications per subgroup, each of 65 birds). Until day 21, the birds stayed in the indoor facility, in deep-litter pens. The birds could forage on pasture 12 h daily, commencing at three weeks of age. Stocking density was 0.13 $m^2$ floor space per bird in pens on litter, and 0.8 $m^2$ per bird in grassy yards. Compared with fast-growing, slower-growing chickens were significantly lighter (by 17%), had a lower breast and thigh muscle yield and a higher abdominal fat content, but they were characterized by higher survival rates at 65 days, a higher protein content and a lower fat content of breast meat. Outdoor access had no negative effects on the growth performance, muscle yield, the fatty acid profile and oxidative status of meat lipids. The meat of free-range chickens was darker in color, it had a higher protein content and a better water-holding capacity, but it was less juicy than the meat of birds raised indoors.

Thermoelectric properties of individual PbTe nanowires grown by a vapor transport method

  • Lee, Seung-Hyun;Jang, So-Young;Lee, Jun-Min;Roh, Jong-Wook;Park, Jeung-Hee;Lee, Woo-Young
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.7-7
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    • 2009
  • Lead telluride (PbTe) is a very promising thermoelectric material due to its narrow band gap (0.31 eV at 300 K), face-centered cubic structure and large average excitonic Bohr radius (46 nm) allowing for strong quantum confinement within a large range of size. In this work, we present the thermoelectric properties of individual single-crystalline PbTe nanowires grown by a vapor transport method. A combination of electron beam lithography and a lift-off process was utilized to fabricate inner micron-scaled Cr (5 nm)/Au (130 nm) electrodes of Rn (resistance of a near electrode), Rf (resistance of a far electrode) and a microheater connecting a PbTe nanowire on the grid of points. A plasma etching system was used to remove an oxide layer from the outer surface of the nanowires before the deposition of inner electrodes. The carrier concentration of the nanowire was estimated to be as high as $3.5{\times}10^{19}\;cm^{-3}$. The Seebeck coefficient of an individual PbTe nanowire with a radius of 68 nm was measured to be $S=-72{\mu}V/K$ at room temperature, which is about three times that of bulk PbTe at the same carrier concentration. Our results suggest that PbTe nanowires can be used for high-efficiency thermoelectric devices.

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Energy separation and carrier-phonon scattering in CdZnTe/ZnTe quantum dots on Si substrate

  • Man, Min-Tan;Lee, Hong-Seok
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.191.2-191.2
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    • 2015
  • Details of carrier dynamics in self-assembled quantum dots (QDs) with a particular attention to nonradiative processes are not only interesting for fundamental physics, but it is also relevant to performance of optoelectronic devices and the exploitation of nanocrystals in practical applications. In general, the possible processes in such systems can be considered as radiative relaxation, carrier transfer between dots of different dimensions, Auger nonradiactive scattering, thermal escape from the dot, and trapping in surface and/or defects states. Authors of recent studies have proposed a mechanism for the carrier dynamics of time-resolved photoluminescence CdTe (a type II-VI QDs) systems. This mechanism involves the activation of phonons mediated by electron-phonon interactions. Confinement of both electrons and holes is strongly dependent on the thermal escape process, which can include multi-longitudinal optical phonon absorption resulting from carriers trapped in QD surface defects. Furthermore, the discrete quantized energies in the QD density of states (1S, 2S, 1P, etc.) arise mainly from ${\delta}$-functions in the QDs, which are related to different orbitals. Multiple discrete transitions between well separated energy states may play a critical role in carrier dynamics at low temperature when the thermal escape processes is not available. The decay time in QD structures slightly increases with temperature due to the redistribution of the QDs into discrete levels. Among II-VI QDs, wide-gap CdZnTe QD structures characterized by large excitonic binding energies are of great interest because of their potential use in optoelectronic devices that operate in the green spectral range. Furthermore, CdZnTe layers have emerged as excellent candidates for possible fabrication of ferroelectric non-volatile flash memory. In this study, we investigated the optical properties of CdZnTe/ZnTe QDs on Si substrate grown using molecular beam epitaxy. Time-resolved and temperature-dependent PL measurements were carried out in order to investigate the temperature-dependent carrier dynamics and the activation energy of CdZnTe/ZnTe QDs on Si substrate.

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The Operating Characteristics of DBR-LD with Wavegudies Coupling Structure (도파로 결합 구조에 따른 DBR-LD의 동작특성)

  • 오수환;박문호
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.40 no.9
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    • pp.666-672
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    • 2003
  • In this paper, we described the fabrication and the performance of wavelength tunable distributed bragg reflector (DBR) laser diode (LD), having different waveguide coupling mechanisms; integrated-twin-guide (ITG) DBR-LD and butt coupled (BT) DBR-LD. This deviceis fabricated by metal organic vapor phase epitaxy (MOVPE) growth and planar buried heterostructure (PBH)-type transverse current confinement structure. The result of measurement, the optical performance of BT-DBR-LD is better over 2 times than that of ITG-DBR-LD at the variation of threshold current and output power, and slop efficiency due to the higher coupling efficiency of the butt coupled structure than the integrated twin guide structure. The maximum wavelength tuning range is about 7.2nm for ITG DBR-LD and 7.4nm for BT DBR-LD. Both types of lasers have a very high yield of single mode operation with a side-mode suppression ratio of more than 35dB.

A Study on the Dispersion Characteristics of PP/MMT Composites (PP/MMT 복합체의 분산특성에 관한 연구)

  • 김규남;김형수
    • Polymer Korea
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    • v.24 no.3
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    • pp.374-381
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    • 2000
  • Composites of polypropylene (PP) and organically modified montmorillonite (org-MMT) were prepared by melt mixing in an intensive mixer. Three grades of PP's having different melt viscosities were employed to investigate the dispersion characteristics of the composites with various org-MMT's. Depending on the matrix viscosity and nature of the interlayer in org-MMT significant variations of the phase structure were found. Under the constant mixing condition and matrix viscosity, intercalation of PP chains into the interlayer of org-MMT was possible when initial interlayer distance and packing density were maintained in the optimum range; by which the loss in entropy associated with the confinement of polymer chains was compensated. The state of org-MMT particle dispersion was improved by increasing the matrix viscosity only in the case that dispersed phase is suitable for intercalation process thermodynamically, otherwise little variation was occurred regardless of the matrix viscosity. Due to the lack of specific interaction between PP and erg-MMT considered here, although the intercalation was possible for an appropriate org-MMT, the composites revealed unstable phase structure upon increasing the mixing time, which was characterized by agglomeration of the org-MMT domains.

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A Dielectric Slab Rotman Lens (유전판 로트맨 렌즈)

  • 김재흥;조춘식
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.11
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    • pp.1108-1115
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    • 2004
  • A new type of a Rotman lens is presented in this paper fur millimeter-wave applications, such as collision avoidance radar. A dielectric slab Rotman lens is proposed to reduce the conductor loss and to create an appropriate farm for favorable implementation at millimeter-wave frequency. The proposed lens consists of a dielectric slab and slot lines whereas the conventional lenses are constructed with parallel conducting plates. The dielectric slab Rotman lens excited in TE$\_$0/ mode shows a high degree of confinement for the fields, low dispersion, and has an appropriate feed structure. A prototype lens has been designed and fabricated with 9 beam ports and 9 array ports together with 9 tapered slot antennas. This lens has been tested in the range from 10 GHz to 15 GHz and the measured beam widths are about 15$^{\circ}$ at 13 GHz. The measurements also show low mutual coupling between beam ports and an efficiency of about 34.6 %. The overall performance is comparable to that of conventional Rotman lenses even though the prototype was tested at lower than desired frequencies in the microwave frequency range due to our limited resources for fabrications and measurements. It is expected that at millimeter-wave frequency the dielectric slab Rotman lens will have lower conductor loss and lower mutual coupling than conventional Rotman lenses.an lenses.

Plasma Sources for Production of High Flux Particle Beams in Hyperthermal Energy Range (하이퍼써멀 에너지 영역에서 높은 플럭스 입자빔 생성을 위한 플라즈마 발생원)

  • Yoo, S.J.;Kim, S.B.
    • Journal of the Korean Vacuum Society
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    • v.18 no.3
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    • pp.186-196
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    • 2009
  • Since it is difficult to extract a high flux ion beam directly at an energy of hyperthermal range ($1{\sim}100\;eV$), especially, lower than 50 eV, the ions should be neutralized into neutral particles and extracted as a neutral beam. A plasma source required to generate and efficiently transport high flux hyperthermal neutral beams should be easily scaled up and produce a high ion density (${\ge}10^{11}\;cm^{-3}$) even at a low working pressure (${\le}$ 0.3 mTorr). It is suggested that the required plasma source can be realized by Electron Cyclotron Resonance (ECR) plasmas with diverse magnetic field configurations of permanent magnets such as a planar ECR plasma source with magnetron field configuration and cylindrical one with axial magnetic fields produced by permanent magnet arrays around chamber wall. In both case of the ECR sources, the electron confinement is based on the simple mirror field structure and efficiently enhanced by electron drifts for producing the high density plasma even at the low pressure.

A Comparative Study of Reported Nursing Needs and Nursing Care During Labor and Delivery (산부의 간호요구와 간호원의 간호활동과의 비교 연구)

  • 안혜숙
    • Journal of Korean Academy of Nursing
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    • v.6 no.1
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    • pp.51-59
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    • 1976
  • Contemporary nursing is concerned with meeting patients physical psychological and secio-economical needs and with helping persons to sore their own problems. At the time of confinement and delivery, women often have physical and psychological disco- mort related to fear, tension or anxiety. Pain related to these causes varies with the individual woman. Effective nursing care to meet individual needs during labor and delivery is important if nurses are to understand and relieve woman's physical and psychological pain. A questionnaire prepared for the purpose by the investigator was administered to 162 women in two general hospitals, one in Seoul and one in TaeGu, during August 1 and September 20, 1975 and to the 13 delivery-room nurses who cared for them. It was hoped that the study would contribute to comprehensive nursing care during labor and delivery and to improve maternal and child health. 1. The sample of mothers ranged in age from 18 to 39; the majority were from 25 to 29 years old (54.3%). Most of them were housewives (87.6%). Sixty-three percent had high school or higher education. They had a range of one to seven deliveries. Sixty-one percent were primiparas Most had some prenatal care (87.6%). 2. The age of the group of nurses ranged from 22 to 39. Ten were 22 or 23. Five of the 13 had from six to ten months experience in the de]ivory room. Twelve were single and ten had a religious affiliation. 3. Both primiparas and multiparas thought equally that physical and psychological care, nursing skills and attitudes were important during labor and delivery, but did not relate basic nursing care directly to normal delivery. Need for nursing care was rated more highly by primiparas (2.83-3.48) than by multiparas (2.51-3.17) (p〈0.05). 4. There was no difference in need for nursing care according to the educational level of the women nor according to whether they had a religious affiliation or not (p〉0.05). 5. There was no difference in the reported nursing care given regarding of the educational preparation of the nurses (p〉 0.05). 6. There the reported nursing needs of the women and the reported nursing care given were compared, physical and psychological nursing care directed toward protecting the mother and fetus and a safe do]ivory were considered important by both groups. Neither group related simple nursing care directly to protection of the mother and fetus or to a safe delivery. The women rated highly their needs for nourishment (3.05) and having a relative with them (2.90) for emotional support but there was little evidence (2.39) that the nurses provided care to meet these needs (p〈0.05). In conclusion, the nursing needs of the women during the three stages of labor and the nursing care given were generally similar. The women had more psychological needs than physical needs but in comparison, nurses gave a little more physical than psychological care. The results point up the need to make adjustments in labor and delivery room nursing care the nurse should Prepared to pay more attention and bigger consideration in psychological comfort care than physical care.

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