• Journal of the Korean Society of Visualization
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• v.14 no.1
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• pp.57-61
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• 2016

We report a finding of fast(exceeding 2,000 K/s) heating of polydimethylsiloxane(PDMS), one of the most commonly-used microchannel materials, under cyclic loadings at high(~MHz) frequencies. A microheater was created based on the finding. The heating mechanism utilized vibration damping of sound waves, which were generated and precisely manipulated using a conventional surface acoustic wave(SAW) microfluidic system, in PDMS. The penetration depths were measured to range from $210{\mu}m$ to $1290{\mu}m$, enough to cover most microchannel heights in microfluidic systems. The energy conversion efficiency was SAW frequency-dependent and measured to be the highest at around 30 MHz. Independent actuation of each interdigital transducer(IDT) enabled independent manipulation of SAWs, permitting spatiotemporal control of temperature on the microchip. All the advantages of this microheater facilitated a two-step continuous flow polymerase chain reaction(CFPCR) to achieve the billion-fold amplification of a 134 bp DNA amplicon in less than 3 min. In addition, a technique was developed for establishing dynamic free-form temperature gradients(TGs) in PDMS as well as in gases in contact with the PDMS.

• Journal of Korean Society of Forest Science
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• v.98 no.4
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• pp.451-457
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• 2009

This study was conducted to evaluate the felling productivity by chain saw in thinning operation of Korean pine (Pinus koraiensis) stands. Time study data were collected from 4 thinning site in Korean pine stands. This study derived a regression model to estimate the average felling cycle time for evaluating the productivity in felling, which was used to analyze the felling productivity by thinning period. In the study sites, the average felling cycle time per a tree was 463 sec/cycle and the productivity was $2.26m^3/hr$. Thinning period in Korean pine is divided into three groups by producing purposes; small-diameter log, medium-diameter log, and large-diameter log. And analyzed working time and productivity from thinning period fixed by producing purposes. For the small-diameter log producing purpose estimated to be thinning period operated once when the mean DBH was 16 cm and its productivity was $8.94m^3/man{\cdot}day$. For the medium-diameter and large-diameter log producing purposes, thinning period was twice and three times when the mean DBH of the 1st and 2nd thinning period was 16 cm and 21 cm, and its productivity was $9.06m^3/man{\cdot}day$ and $10.86m^3/man{\cdot}day$. The 30 cm in DBH and $15.12m^3/man{\cdot}day$ in productivity was operated 3rd thinning for the large-diameter log producing purposes.

• Research in Plant Disease
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• v.16 no.3
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• pp.299-305
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• 2010

Objective of this study is to examine whether pine wood nematode (PWN: Bursaphelenchus xylophilus) in the sawdust discharged from infected trees cause pine wood disease or not. For this, survival time of PWN in soil was examined in which soil moisture was controlled as 15%, 22.5%, and 30% in volume ratio, respectively. The pathogenicity tests were conducted under greenhouse and field conditions. Survival time of PWN in soil was about three days in the saturated (about soil moisture of 23% in volume ratio) and dark condition between 25 and $28^{\circ}C$ of room temperature. None of potted seedlings with non-wounded roots was infected by PWN in sawdust. In field, pine wood disease was not occur in any pine trees. These results indicated that PWN discharged on soil when the infected trees were cut by chain saw can not cause pine wood disease.

• Journal of Korea Port Economic Association
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• v.39 no.3
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• pp.191-210
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• 2023

The Covid-19 pandemic has had a significant impact on global logistics and supply chains, leading to major discrepancies in logistics performance across countries worldwide. Through an examination of logistics performance index and supply chain tracking data, this study aimed to identify the changes in global supply chains and logistics environments during the pandemic. The analysis of the logistics performance index showed that overall, countries around the world, especially developed nations, showed improvements in metrics such as customs and border management efficiency, the quality of trade and transport infrastructure, capability and quality of logistics services, and cargo tracking abilities. However, the competitive pricing feasibility of international transportation and the on-time delivery frequency of goods saw a decline due to the pandemic's effects. The supply chain tracking data revealed that ports in Asian countries demonstrated high processing efficiency. In contrast, the U.S. and European countries took comparatively more time. Particularly for air cargo, parcels, and express shipments, the U.S. showed relatively longer processing times, leading to logistical delays. In conclusion, during the Covid-19 pandemic, Asian countries maintained relatively high efficiency in their logistics and trade environments. Conversely, the U.S. and some European countries showed delays and decreased efficiency in various metrics. In the future, efforts should be made to address delays and congestion, namely, the deceleration of logistics processes.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.3
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• pp.271-281
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• 2021

Pinus densiflora and Larix kaempferi forests not only extended the plantation management area but also cultivated to the sustainable wood supply chain during the last 5-years. These prescriptions are primarily done by manual operation activities, particularly in young tree tending. Two types of tending activities, brashing by brush cutter(BB) and pruning by pruning shear and saw(PP), were selected for the investigate of musculoskeletal disorders' level and postural risks using Ovako Working Posture Analysis System (OWAS). The postural risk indexes (BB and PP) ranged from 115 to 125 and 102 to 105, respectively. There is no significant difference between the species. The young tree tending operations had low postural risks. The results may be used as basic data to develop technical guideline for safe young trees.

• Journal of muscle and joint health
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• v.28 no.2
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• pp.161-173
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• 2021

Purpose: This study examined: 1) what it meant for patients to have multimorbidity 2) how they manage their illness using health care facilities, and 3) what contextual backgrounds exist regarding the health care system. Methods: This qualitative research obtained individual in-depth interviews from 22 patients. Participants were selected by purposive sampling among those who saw physicians more often than the national average from the 2013 medical-claim data. The transcribed data were analyzed using Ground theory. Results: Multimorbidity patients suffered from "chain-like serial symptoms" and "pain without a breakthrough". They expressed themselves as "indeed patients among patients", "my body is a general hospital", and "an incompletely normal person". There was a demand to resolve the anxiety arising from the situation in which the body keeps getting sicker without showing any signs of recovery. In a state of reduced social support and a lack of trust in the doctor, their desire to be healed led them to receive a temporary relief through dependence on medical institutions. Conclusion: This research recognized the desire of multimorbidity patients to seek temporary relief through dependence on medical institutions. A more patient-centered directed care plan, specific to the needs of the patients with multimorbidity is required.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.178-185
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• 2012

In Korea, researches on the exposure assessment of the hand-transmitted vibration started from the mid-90, however, they were performed in the limited industries such as auto-assembly plants and the evaluation of the vibration was mostly conducted by ISO 5349(1986). Therefore, it was necessary to assess hand-transmitted vibration levels of workplace such as ship building/repairing industry or mining industry where occupational injuries are largely occurred and to evaluate the vibration levels using revised ISO 5349(2001). The SVAN 949 Four Channels Sound & Vibration Analyser was used for the measurement. The workers using a chain saw were exposed to $1.7{\sim}2.8m/s^2$ of daily vibration level. Workers using a rock drill in a coal mining were exposed to the highest vibration acceleration among workers and the levels were $7.1{\sim}10.8m/s^2$. Vibration levels of grinders were different according to the types of grinders. The hand-transmitted vibration of 3 types of grinders were measured and the levels were $3.3{\sim}11.1m/s^2$. Workers using a impact wrench were exposed to $1.5{\sim}1.6m/s^2$ of vibration. Out of 20 kinds of machines, only 4 tools provided the information of vibration acceleration on the instructions. In addition, the current condition of workplaces to control vibration was not much different from the past because there are no vibration exposure limit.

• Journal of Korean Society of Forest Science
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• v.104 no.2
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• pp.230-238
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• 2015

This study was analyzed the operational cost of logging and chipping operations in order to develop the efficient logging operation system for the utilization of forest-biomass. Analysis of the operational cost of logging operation systems, the operation system D which include chain saw, tower-yarder, mini-forwarder and truck was calculated the lowest cost to be $68,498Won/m^3$. In the utilization of forest-biomass, the operation system E which include chipping by mini-chipper at the site, forwarding of chips by mini-forwarder, transportation of chips by truck was estimated to be 90,770 Won/Ton. Thus, These results are determined as an effective operating system for logging operation and the utilization of forest-biomass.

• Journal of Korean Society of Forest Science
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• v.102 no.2
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• pp.300-304
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• 2013

Pine wilt disease caused by pine wood nematode, Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle, has become the most serious threat to pine trees in Korea since 1988. Pine wood nematode is transferred to healthy trees by Monochamus alternatus (Coleoptera: Cerambycidae) during its maturation feeding and female oviposition. A typical control method against insect vectors in Korea is fumigation of the dead trees by using metam-sodium SL (25%). However, this method is not environment friendly because of the forest contamination by chemical application and destroying landscape by plastic cover. Portable Bark Remover (PBR) was invented to reduce these environmental problems. The vectors oviposit under the bark of the newly dead trees only. Debarking infested trees prevents the vectors from laying eggs and eventually, they can not complete their life cycle. The PBR is a modified debarking device that is attached on the top of the electrical chain saw, which allows ease and rapid debarking of the infested trees. The new method by PBR is expected to be more economic and effective than other conventional methods such as "crushing", "burning" and "fumigation".

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.22 no.10
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• pp.940-948
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• 2012

In Korea, researches on the exposure assessment of the hand-transmitted vibration started from the mid-90, however, they were performed in the limited industries such as auto-assembly plants and the evaluation of the vibration was mostly conducted by ISO 5349(1986). Therefore, it was necessary to assess hand-transmitted vibration levels of workplace such as ship building/repairing industry or mining industry where occupational injuries are largely occurred and to evaluate the vibration levels using revised ISO 5349(2001). The SVAN 948 Four Channels Sound & Vibration Analyser was used for the measurement. The workers using a chain saw were exposed to 1.7~2.8 $m/s^2$ of daily vibration level. Workers using a rock drill in a coal mining were exposed to the highest vibration acceleration among workers and the levels were 7.1~10.8 $m/s^2$. Vibration levels of grinders were different according to the types of grinders. The hand-transmitted vibration of 3 types of grinders were measured and the levels were 3.3~11.1 $m/s^2$. Workers using a impact wrench were exposed to 1.5~1.6 $m/s^2$ of vibration. Out of 20 kinds of machines, only 4 tools provided the information of vibration acceleration on the instructions. In addition, the current condition of workplace to control vibration was not much different from the past because there are no vibration exposure limit.