• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1018-1021
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• 2006

Powdered metal parts and components may be carburized successfully in a vacuum furnace by combining carburizing technology $VacCarb^{TM}$ with a hi-tech control system. This approach is different from traditional carburizing methods, because vacuum carburizing is a non-equilibrium process. It is not possible to set the carbon potential as in a traditional carburizing atmosphere and control its composition in order to obtain a desired carburized case. This paper presents test results that demonstrate that vacuum carburizing system $VacCarb^{TM}$ carburized P.M. materials faster than traditional steel with acceptable results. In the experiments conducted, PM samples with the lowest density and open porosity showed a dramatic increase in the surface carbon content up to 2.5%C and a 3 times deeper case. Currently the boost-diffusion technique is applied to control the surface carbon content and distribution in the case. In the first boost step, the flow of the carburizing gas has to be sufficient to saturate the austenite, while avoiding soot deposition and formation of massive carbides. To accomplish this goal, the proper gas flow rate has to be calculated. In the case of P.M. parts, more carbon can be absorbed by the part's surface because of the additional internal surface area created by pores present in the carburized case. This amount will depend on the density of the part, the densification grade of the surface layer and the stage of the surface. "as machined" or "as sintered". It is believed that enhanced gas diffusion after initial evacuation of the P.M. parts leads to faster carburization from within the pores, especially when pores are open . surface "as sintered" and interconnected . low density. A serious problem with vacuum carburizing is delivery of the carbon in a uniform manner to the work pieces. This led to the development of the different methods of carburizing gas circulation such as the pulse/pump method or the pulse/pause technique applied in SECO/WARWICK's $VacCarb^{TM}$ Technology. In both cases, each pressure change may deliver fresh carburizing atmosphere into the pores and leads to faster carburization from within the pores. Since today's control of vacuum carburizing is based largely on empirical results, presented experiments may lead to better understanding and improved control of the process.

• 대한금속재료학회지
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• 제48권7호
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• pp.667-673
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• 2010

Copper filling into TSV (through-silicon-via) and reduction of the filling time for the three dimensional chip stacking were investigated in this study. A Si wafer with straight vias - $30\;{\mu}m$ in diameter and $60\;{\mu}m$ in depth with $200\;{\mu}m$ pitch - where the vias were drilled by DRIE (Deep Reactive Ion Etching) process, was prepared as a substrate. $SiO_2$, Ti and Au layers were coated as functional layers on the via wall. In order to reduce the time required complete the Cu filling into the TSV, the PPR (periodic pulse reverse) wave current was applied to the cathode of a Si chip during electroplating, and the PR (pulse-reverse) wave current was also applied for a comparison. The experimental results showed 100% filling rate into the TSV in one hour was achieved by the PPR electroplating process. At the interface between the Cu filling and Ti/ Au functional layers, no defect, such as a void, was found. Meanwhile, the electroplating by the PR current showed maximum 43% filling ratio into the TSV in an hour. The applied PPR wave form was confirmed to be effective to fill the TSV in a short time.

• International Journal of Automotive Technology
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• 제8권4호
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• pp.437-444
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• 2007

This paper experimentally investigates the effects of oxygen-enriched air (OEA) on the running behaviors of an LPG SI engine during both start/warm-up (SW) and hot idling (HI) stages. The experiments were performed on an air-cooled, single-cylinder, 4-stroke, LPG SI engine with an electronic fuel injection system and an electrically-heated oxygen sensor. OEA containing 23% and 25% oxygen (by volume) was supplied for the experiments. The throttle position was fixed at that of idle condition. A fueling strategy was used as following: the fuel injection pulse width (FIPW) in the first cycle of injection was set 5.05 ms, and 2.6 ms in the subsequent cycles till the achieving of closed-loop control. In closed-loop mode, the FIPW was adjusted by the ECU in terms of the oxygen sensor feedback. Instantaneous engine speed, cylinder pressure, engine-out time-resolved HC, CO and NOx emissions and excess air coefficient (EAC) were measured and compared to the intake air baseline (ambient air, 21% oxygen). The results show that during SW stage, with the increase in the oxygen concentration in the intake air, the EAC of the mixture is much closer to the stoichiometric one and more oxygen is made available for oxidation, which results in evidently-improved combustion. The ignition in the first firing cycle starts earlier and peak pressure and maximum heat release rate both notably increase. The maximum engine speed is elevated and HC and CO emissions are reduced considerably. The percent reductions in HC emissions are about 48% and 68% in CO emissions about 52% and 78%; with 23% and 25% OEA, respectively, compared to ambient air. During HI stage, with OEA, the fuel amount per cycle increases due to closed-loop control, the engine speed rises, and speed stability is improved. The HC emissions notably decrease: about 60% and 80% with 23% and 25% OEA, respectively, compared to ambient air. The CO emissions remain at the same low level as with ambient air. During both SW and HI stages, intake air oxygen enrichment causes the delay of spark timing and the increased NOx emissions.

• Transactions on Electrical and Electronic Materials
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• 제14권3호
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• pp.139-142
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• 2013

Silicon nanowire (SiNW) silicon-oxide-nitride-oxide-silicon (SONOS) flash memory devices were fabricated and their electrical characteristics were analyzed. Compared to planar SONOS devices, these SiNW SONOS devices have good program/erase (P/E) characteristics and a large threshold voltage ($V_T$) shift of 2.5 V in 1ms using a gate pulse of +14 V. The devices also show excellent immunity to short channel effects (SCEs) due to enhanced gate controllability, which becomes more apparent as the nanowire width decreases. This is attributed to the fully depleted mode operation as the nanowire becomes narrower. 3D TCAD simulations of both devices show that the electric field of the junction area is significantly reduced in the SiNW structure.

• 한국통신학회논문지
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• 제35권7A호
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• pp.682-687
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• 2010

The IEEE 802.15.4a specification targets the low-rate (LR) Impulse-radio (IR) ultra-wideband (UWB) system which is now widely applied in the WPANs considering rather short distance communications with low complexity and power consumption. The physical (PHY) layer uses concatenated coding with mixed binary phase-shift keying and binary pulse-position modulation (BPSK-BPPM), and direct sequence spreading with time hopping in order that both coherent and non-coherent receiver architectures are supported. In this paper, the performances of multiple access schemes compliant with IEEE 802.15.4a specification are investigated with energy detection receiver, which allow avoiding the complex channel estimation needed by a coherent receiver. However, the performance of energy detection receiver is severely degraded by multi-user interference (MUI), which largely diminishes one of the most fascinating advantages of UWB, namely robustness to MUI as well as the possibility to allow parallel transmissions. So as to improve the performance of multiple access schemes, we propose to apply the novel TH sequences as well as to increase the number of TH positions. The simulation results show that our novel multiple access schemes significantly improve the performance against MUI.

• 성인간호학회지
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• 제14권3호
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• pp.418-427
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• 2002

Purpose: The Purpose of this research was to develop the integrative exercise program for the elderly. Method: The first step was to survey the elder's health status and general health problems. The second step was to design the exercise type, intensity, time and frequency. Result: 1. Elders who implement the integrative exercise program had weaker health status, lower physical performance and more depression than any other places. 2. The integrative exercise program developed the preparation stage composed of stretching and Yudongkong-Ki exercise, the central stage was composed of range of motion exercise, muscle strength exercise and aerobic exercise with favorite and popular Korean music. The finishing stage was composed of joint rounding and Yudongkong-Ki exercise. The exercise intensity was RPE(rating perceived exertion) 10-11, maximal pulse rate 40-60%, duration started from 20min to 50min and frequency is 2-3times/wk. Conclusion: The integrative exercise program developed by the researcher is tailored exercise that is more applicable to individual cases in community settings. Eventually, the program is safely applicable to the elders, and is expected to improve the elders' physical function and quality of life.

• 한국자동차공학회논문집
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• 제13권5호
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• pp.64-74
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• 2005

The effect of fuel injection spray on engine performance has been known as one of the major concerns for improving fuel economy and reducing emissions. In general, reducing the spray droplet size could prevent HC emission in gasoline engine. As far as PFI gasoline engine is concerned, the mixture of air and fuel may not be uniform under a certain condition, because breakup and production of spray droplets are made in a short distance between the fuel injector and intake valve. This study, by constituting PFI gasoline spray system, was performed to study the transient spray characteristics and dynamic behavior of droplets from two-holes two-sprays type injector used in DOHC gasoline engine. Mean droplet size and optical concentration in accordance with various conditions were measured by LDPA and CCD camera. Through this study, the variation of drop size and optical concentration could be used for understanding the behavior of unsteady spray was declared and the existing the small droplets between each pulse spray could be estimated caused to the development of wall film was conformed.

• 재활간호학회지
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• 제5권1호
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• pp.18-26
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• 2002

The purpose of this study was to elucidate the effects of inhalation method using essential oils on the preoperative anxiety of hystrectomy patients, and to provide effective and holistic nursing care to them. The research design was a nonequivalent control group non synchronized design. The data were collected from February 1 to March 31, 2002 at D Medical Center in Busan. The subjects were forty one patients that were operated on under general anesthesia for hystrectomy. They were assigned to two groups, twenty one subjects in the experimental group and twenty subjects in the control group. The tool of the Visual Analogue Scale(VAS) was used to anxiety on all patients the day before surgery and the preoperative period. Then systolic and diastolic blood pressure, pulse rate levels were measured the day before surgery and the preoperative period. The experimental group received two treatments of inhalation method using essential oils of with lavender, ylang ylang, and bergamot oil. The data were analyzed by the $X^2$ test and the independent t-test. The results of this study were summarized as follows: 1. Hypothesis 1: It has been supported that the experimental group received inhalation method using essential oils might cause lower level of the preoperative VAS anxiety than that of the control group(t=-2.93, p=.006). 2. Hypothesis 2: It has been rejected that the experimental group received inhalation method using essential oils might cause lower level in the preoperative systolic blood pressure than the control group(t=-.120, p=.905). It has been rejected that the experimental group received inhalation method using essential oils might cause lower level in the preoperative diastolic blood pressure than the control group.(t=1.766, p=.085). 3. Hypothesis 3: It has been supported that the experimental group received inhalation method using essential oils might cause lower level in preoperative pulse rate than the control group(t=5.853, p=.000). According to these results, inhalation method using essential oils can be considered an effective nursing intervention that relieves the preoperative anxiety of hysterectomy patients and stabilizes vital sign partially.

• The Korean Journal of Pain
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• 제9권1호
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• pp.46-56
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• 1996

Many surgeons and anesthesiologists prefer using vasoconstrictor mixed with local anesthetic agent to reduce the incidence of side effects and prolong the duration of analgesia because most local anesthetic agents, except cocaine, were believed to possess vasodilating effect. However, some investigators recently reported vasoconstricting effect of local anesthetic agents. There is still controversy on the vasoactive effect of local anesthetic agents. So this study is aimed to clarify the vasoactive effect of local anesthetics in the animal model resembling clinical settings. Rabbits were anesthesized with ketamine and haloghane, and respirations were controlled with Harvard animal ventilator. Lidocaine (0.5%, 1.0%, 1.5%) and bupivacaine (0.125%, 0.25% and 0.5%) with or without 1:100,000 epinephrine were subdermaly injected on the femoral bupivacaine of the femoral artery were measured with Doppler flow meter in vivo. The mean arterial pressure, pulse rate, arterial blood gases, pH and level of serum electrolytes were measured at every 2 minute interval for 30 minutes. Results were as follows: 1) There was no significant vasoconstriction with 0.5% lidocaine and 0.125% bupivacaine. 2) Statistically significant (p<0.05) vasodilations were observed with lidocaine (1.0~2.0%) and bupivacaine (0.25~0.5%). 3) There were no changes on the duration of vasodilation induced by local anesthetic agents of various concentrations. 4) Onset of vasodilation induced by local anesthetic agents of high concentration were faster than that of lower concentrations. 5) In the mixed injection group of epinephrine and local anesthetic agent, the vasoconstriction induced by epinephrine was completely reversed by local anesthetics, approximately 5 minutes later. In conclusion, local anesthetic agents at dose exceeding 1.0% lidocaine and 0.25% bupivacaine increase local blood flow significantly in animal study in vivo which is applicable in human clinical settings. The increase blood flow may be due to dilatation of blood vessel. Further study on the analysis of association between amount of absorbed local anesthetics in blood vessels and dilatation of blood vessels is needed.

• Fisheries and Aquatic Sciences
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• 제11권2호
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• pp.103-112
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• 2008

Compressional sound velocities of shelf sediments in the South Sea of Korea, were measured in situ and in the laboratory for six cores. In situ sound velocity was measured using the Acoustic Lance (frequency of 7.5-15 kHz), while laboratory velocity was measured by the pulse transmission technique (frequency of 1MHz). Physical properties were relatively uniform with sediment depth, suggesting little effect of sediment compaction and/or consolidation. Average in situ velocity at each core site ranged from 1,457 to 1,488 m/s, which was less than the laboratory velocity of 1,503 and 1,604m/s. In muddy sediments the laboratory velocity was 39-47 m/s higher than in situ velocity. In sandy sediments, the difference was greater by an average of 116 m/s. Although the velocity data were corrected by the velocity ratio method based on bottom water temperature, the laboratory velocity was still higher than the in situ velocity (11-21 m/s in muddy sediments and 91 m/s in sandy sediments). This discrepancy may be caused by sediment disturbance during core collection and/or by the pressure of Acoustic Lance insertion, but it was most likely due to the frequency difference between in situ and laboratory measurement systems. Thus, when correcting laboratory velocity to in situ velocity, it is important to consider both temperature and frequency.