• Particle and aerosol research
• /
• v.5 no.3
• /
• pp.123-131
• /
• 2009

This paper presents simulation results of particle transport in low-pressure, low-temperature plasma environment. The size dependent transport of particles in the plasma is investigated with a two-dimensional simulation tool developed in-house for plasma chamber analysis and design. The plasma model consists of the first two and three moments of the Boltzmann equation for ion and electron fluids respectively, coupled to Poisson's equation for the self-consistent electric field. The particle transport model takes into account all important factors, such as gravitational, electrostatic, ion drag, neutral drag and Brownian forces, affecting the motion of particles in the plasma environment. The particle transport model coupled with both neutral fluid and plasma models is simulated through a Lagrangian approach tracking the individual trajectory of each particle by taking a force balance on the particle. The size dependant trap locations of particles ranging from a few nm to a few ${\mu}m$ are identified in both electropositive and electronegative plasmas. The simulation results show that particles are trapped at locations where the forces acting on them balance. While fine particles tend to be trapped in the bulk, large particles accumulate near bottom sheath boundaries and around material interfaces, such as wafer and electrode edges where a sudden change in electric field occurs. Overall, small particles form a "dome" shape around the center of the plasma reactor and are also trapped in a "ring" near the radial sheath boundaries, while larger particles accumulate only in the "ring". These simulation results are qualitatively in good agreement with experimental observation.

• Journal of the Korean Society for Precision Engineering
• /
• v.32 no.4
• /
• pp.387-394
• /
• 2015

We analyze heat generation as well as temperature distribution induced by accelerated electron impact on a target in a closed x-ray tube. For the sake of accuracy, we use Monte carlo analysis. This method gives accurate energy deposit in a medium with additional information such as secondary and backscattered electron as well as their paths. A Tungsten coated layer is divided by small rectangular cell which accumulate energy loss of primary electron beam. The cells and their accumulated energy datum are used for the input of finite element analysis. The Maximum temperature rising and temperature distribution were analyzed by transient heat analysis. Some temperature parameters such as target size and coating thickness were varied to investigate temperature sensitivity. Temperatures were compared each other to find primary variable that affect temperature rising on the x-ray target. The results will be helpful in development highresolution x-ray tube and related industries.

• Korean Journal of Microbiology
• /
• v.16 no.3
• /
• pp.111-121
• /
• 1978

About 40 temperature-sensitive mutants have been isolated as a preliminary step to study the spore germination, the cell cycle, and the control of macromolecular synthesis in Aspergillus nidulans. To obtain temperature-sensitive mutants rapidly and effectively, the selective enrichment method using antifungal antibiotic nystatin was developed. Based on the data which had applied to the concentration of auxotrophic mutants by the earlier investigators, the optimal concentration and the time of treatment at the nonpermissive temeprature were determined as 50 to 100 units per ml and 4.5 hr., respectively. Out of 41 ts mutants assigned to the strain symbol PK, thirteen that seemed to be arrested at the earlystage of spore germination were subjected to the further cytological and genetic analysis. Elght of these mutants are able to form germ tube and five not. Staining with acid fuchsin for the 5PK strains shows that one irreversible mutant, PK6 strain able to form germ tube, accumulate mitotic spindle, being arrested in mitosis. Another PK15 and PK23 strain have more than one intact nucleolus without germ tube formation at the restrictive temperature. the temperature-senstive mutation in PK12 strain, the onlystrain which is able occurred in certain gene specific for the germination of spore. All of the ts markers are recessive and complement each other in heterokaryon between two different ts markers at the restrictive temperature.

• Journal of Microbiology
• /
• v.35 no.4
• /
• pp.334-340
• /
• 1997

A collection of 132 temperature sensitive (ts) mutants was generated by the chemical mutagenesis of Schizosaccharomyces pombe wild type strain and screened for tRNA splicing defects on Northern blots by hybridization with an oligonucleotide that recognizes the exon of the S. pombe tRNA^Val as a probe. We identidied 6 mutants which accumulate precursor $tRNA^{Val}$. Among them, 2 mutants exhibited remarkable morphological differences compared to wild type cells. One tRNA splicing mutant showed elongated cell shape in permissive as well as non-permissive cultures. The other mutant exhibited shortened cell morphology only in nonpermissive culture. The total RNA pattern in the splicing mutants appeared to be normal. Genetic analysis of four $tRNA^{Val}$ splicing mutants demonstrated that the mutation reside in different genes.

• Tribology and Lubricants
• /
• v.10 no.4
• /
• pp.82-88
• /
• 1994

This paper deals with a FEM computation as well as measurement of the contact force and distribution of the temperature in rubber lip seals when the sealing interference between the rotating shaft and the lip edge is present. The study of the contact forces and distributions of the temperature and the sealing contact stress has always been one of the basic steps in the process of designing a lip seal. The calculated FEM results indicate that as the sealing interference increases, the contact force moderately increases compared with decreased sealing interference at the seal lip edge and radically increases the contacting width. And the FEM computation of oontact forces including nonlinear problems has been compared with experimental measurements with good agreement. The frictional heat does not dissipate promptly in the rubber seal lip and tends to accumulate at the contacting lip edge especially.

• Structural Engineering and Mechanics
• /
• v.82 no.2
• /
• pp.259-270
• /
• 2022

The paper investigates the residual stresses arising in a thermoviscoelastic cylinder as a result of layer-by-layer deposition of material on its lateral surface. Internal stresses are caused by incompatible deformations that accumulate in the assembly as a result of joining parts with different temperatures. For the analysis of internal stresses, an analytical solution to the axisymmetric quasi-static problem of thermoelasticity for a growing cylinder is constructed. It is shown that the distribution of residual stresses depends on the scenario of the surfacing process. In this case, the supply of additional heat to the growing body can significantly reduce the unevenness of temperature fields and reduce the intensity of residual stresses. The most effective is uneven heating, which can be realized, by the action of an alternating current with a tunable excitation frequency. The temperature and residual stresses fields on the growing surface is analyzed numerically for Titanium and Copper materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.04c
• /
• pp.69-72
• /
• 2008

Decay processes of accumulated charge in e-beam irradiated polymers during elevating temperature are observed using pulsed electro-acoustic measurement system. Since the polymeric materials have many superior properties such as light-weight, good mechanical strength, high flexibility and low cost, they are inevitable materials for spacecrafts. In space environment, however, the polymers sometimes have serious damage by irradiation of high energy charged particles. When the polymers of the spacecraft are irradiated by high energy charged particles, some of injected charges accumulate and remain for long time in the bulk of the polymers. Since the bulk charges sometimes cause the degradation or breakdown of the materials, the investigation of the charging and the decay processes in polymeric materials under change of temperature is important to decide an adequate material for the spacecrafts. By measuring the charge behavior in e-beam irradiated polymer, such as polyimide or polystyrene, it is found that the various accumulation and decay patterns are observed in each material. The results seem to be useful and be helpful to progress in the reliability of the polymers for the spacecraft.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.329-330
• /
• 2007

Decay processes of accumulated charge in e-beam irradiated polymers during elevating temperature are observed using pulsed electro-acoustic measurement system. Since the polymeric materials have many superior properties such as light-weight, good mechanical strength, high flexibility and low cost, they are inevitable materials for spacecrafts. In space environment, however, the polymers sometimes have serious damage by irradiation of high energy charged particles. When the polymers of the spacecraft are irradiated by high energy charged particles, some of injected charges accumulate and remain for long time in the bulk of the polymers. Since the bulk charges sometimes cause the degradation or breakdown of the materials, the investigation of the charging and the decay processes in polymeric materials under change of temperature is important to decide an adequate material for the spacecrafts. By measuring the charge behavior in e-beam irradiated polymer, such as polyimide or polystyrene, it is found that the various accumulation and decay patterns are observed in each material. The results seem to be useful and be helpful to progress in the reliability of the polymers for the spacecraft.

• 보존과학연구
• /
• s.22
• /
• pp.155-171
• /
• 2001

The facilities of exhibition and collection for cultural properties is affected by environmental pollution. In order to accumulate a store of basic data, we was investigated eight points(three points at exhibition room and five points at collection room) at four institutes, from December 2000 to March 2001.As a result of investigation, the temperature of A-Exhibition room measured low because of don’t moved HVAC(Heating, Ventilation and Air-Conditioning) System, B Exhibition room is dry for the effect of air-conditioner and the air pollutants concentration of C-Exhibition room is high for the kind of an exhibition room. The air-condition was varied within the open period. The air pollutants concentration of A-Collection room is measured high because the air-pollutants is generated in a new buildings and the air pollutants concentration of C-1 & C-2-Collection room is high for the kind of an collection room. It is necessary to ventilate sufficiently.

• Proceedings of the KIEE Conference
• /
• 2008.09a
• /
• pp.229-230
• /
• 2008

The investigations included the measurements of volume currents and also internal space charges on epoxy samples of mm thicknesses. The current versus time relations were shown to correspond well with classical forms of dielectric response such as the Curie-von Schweidler model. After the time transient, near steady currents were extremely small and exhibited a significant temperature dependence, similar in relation to the Poole-Frenkel hoping transport model. Equivalent resistances were on the order of $10^{19}$ ohms and represent very weak charge transport. Electrically stimulated acoustic waves were used to quantify the small internal charges that would accumulate within the epoxy. There was a notable homocharge near both anode and cathode. The dielectric response and the internal charge were related to show a consistent model for charge transport within unfilled epoxy.