• The Korean Journal of Physiology and Pharmacology
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• 제1권4호
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• pp.355-366
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• 1997

Although cerebellar Purkinje cells display spontaneous electrical activity in vivo and in slice experiments, the mechanism of the spontaneous activity generation has not been clearly understood. The aim of this study was to investigate whether cerebellar Purkinje cells of postnatal rats generate spontaneous electrical activity without synaptic inputs. Dissociated cerebellar Purkinje cells were used for reducing synaptic inputs in the present study. Cerebellar Purkinje cells with dendrites were dissociated from postnatal rats using enzymatic treatment followed by mechanical trituration. Spontaneous electrical activities were recorded from dissociated cells without any stimulus using whole-cell patch clamp configuration. Two types, spontaneously firing or quiescent, of dissociated Purkinje cells were observed in postnatal rats. Both types of cells were identified as Purkinje cells using immunocytochemical staining technique with anti-calbindin after recording. Spontaneously active cells displayed two patterns of firing, repetitive and burst firings. Two thirds of dissociated Purkinje cells displayed repetitive firing and the rest of them did burst firing under same recording condition. Repetitive firing activities were maintained even after further isolation using either physical or pharmacological techniques. Neither high magnessium solution nor excitatory synaptic blockers, AP-5 and DNQX, block the spontaneous activity. These results demonstrate that spontaneous electrical activity of isolated cerebellar Purkinje cells in postnatal rats is generated by intrinsic membrane properties rather than synaptic inputs.

• Journal of Construction Engineering and Project Management
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• 제3권2호
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• pp.21-34
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• 2013

Various risk factors affect construction projects. Due to the uncertainties created by risk factors, actual activity durations frequently deviate from the estimated durations in either favorable or adverse direction. For this reason, evaluation of schedule uncertainty is required to make decisions accurately when managing construction projects. In this regard, this paper presents a new computer simulation model - the Repetitive Schedule Risk Analysis Model (RSRAM) - to evaluate unit-based repetitive building project schedules under uncertainty when activity durations and risk factors are correlated. The proposed model utilizes Monte Carlo Simulation and a Critical Path Method based repetitive scheduling procedure. This new procedure concurrently provides the utilization of resources without interruption and the maintenance of network logic through successive units. Furthermore, it enables assigning variable production rates to the activities from one unit to another and any kind of relationship type with or without lag time. Details of the model are described and an example application is presented. The findings show that the model produces realistic results regarding the extent of uncertainty inherent in the schedule.

• 한국산업보건학회지
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• 제16권2호
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• pp.81-90
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• 2006

The Strain Index(SI) has been commonly used to evaluate the musculoskeletal disorders(MSDs) of upper extremities. Recently, the American Conference of Governmental Industrial Hygienists(ACGIH) adopted the Threshold Limit Value for hand activity level (HAL TLV) focused on the hand, wrist, and forearm. The MSDs risks of 37 repetitive works conducted at an automobile climate control system manufacturing factory were evaluated using both the HAL TLV and the SI, and the results by two methods were compared. Also, measured repetitive frequencies of upper limbs joint were mesured using electromyogram and electrogoniometer. The evaluation results of the HAL were related with the repetitive frequency data of upper limbs joint by electrogoniometer, and the NPF was related with %MVC of ECU. The evaluation result of HAL TLV was highly related with the SI score(r=0.66, p<0.01). Of total 37 tasks, 25 tasks(67.6%) were exceeded the TLV and 34 tasks(91.9%) exceeded the SI limit. Although there was a high relationship between the HAL TLV and SI score, the HAL TLV underestimated the risk in comparison with the SI. The correlation coefficients(r) between the HAL TLV data and the repetitive frequency of upper limbs joint were 0.45~0.55(p<0.01). The MSD symptoms was significantly different between high risk groups and low risk groups evaluated by HAL TLV(p<0.01), but was not different between two groups by SI. In conclusion, the HAL TLV is a proper tool for repetitive works.

• Toxicological Research
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• 제18권3호
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• pp.293-300
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• 2002

Chemical carcinogen-induced alteration of aldehyde metabolic enzymes were examined in clone 9 cell. Diethylnitrosamine (DENA), N-nitrosoethylurea (NEU) and N-nitrosomorpholine (NNM) were wed as model carcinogens. Changes in enzyme activities by repetitive treatment of DENA, NEU or NNM were analyzed in terms of specific activities and activity stainings of the enzymes on the gel. Upon treatment of DENA, lipid peroxide level increased upto 10 fold, indicating strong oxidative stress state of the cell. Notable enhancement of ADH and ALDH activity occurred after DENA treatment, while glutathione-S-transferase activity was slightly increased. Furthermore, about 2.5 fold higher superoxide dismutase (SOD) activity was detected during deactivation of catalase (CAT) activity by repetitive treatment of DENA. However in NEU-treated cell, about 2.3 fold higher ALDH activity was found while ADH activity was slightly increased. Notable increase CAT and SOD could also be found. In contrast, maximum 3.5 fold higher CAT activity occurred during SOD deactivation in NNM-treated cell. These results suggest that there might be different enzymatic responses in relation to cell protection against DENA, NEU or NNM.

• 응용통계연구
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• 제21권6호
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• pp.1027-1035
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• 2008

스쿠버 무감압한계 잠수환경에서의 반복 잠수 활동이 인체의 생리적 반응과 스트레스 호르몬에 미치는 영향을 알아보기 위하여 동일 장소와 수온 그리고 수심에서 잠수경력이 비슷한 다이버 8명을 대상으로 반복 잠수를 실시하였다. 잠수 전, 첫 잠수 후, 반복 잠수 후 개별 측정 및 채혈한 결과 생리적 반응은 심박수, 체온, 수축기 혈압이 잠수 전과 첫 잠수 후, 반복 잠수 후 간의 유의한 차이가 있었고 이완기 혈압은 잠수 전과 첫 잠수 후에는 증가하였으나 반복 잠수 후에는 다시 감소하여 유의한 차이가 없었다. 스트레스 호르몬 변화에서는 잠수 전, 첫 잠수 후, 반복 잠수 후의 유의한 차이가 없었다. 스포츠 스쿠버 잠수표 계획에 따른 무감압 한계 반복 잠수 활동은 심박수, 체온, 수축기혈압을 감소시키는 반면 스트레스 호르몬에는 영향을 미치지 않는 것으로 나타났다. 안전한 다이빙을 위해서는 보다 많은 생리학적 연구가 필요하다고 생각된다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 춘계 학술논문 발표대회
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• pp.41-42
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• 2018

Various methods that crash the project completion time have been studied. Line-of-Balance (LOB) is well accepted as a useful method that enables steady resource utilization without frequent hire-and-fire of resources for a project having repetitive units. Existing studies involved in LOB-CPM focuses on thesis such as resource leveling and optimization in construction scheduling community. However, crashing methods are not arrived at a full maturity in LOB scheduling, because no one handles steady resource utilization while keeping activity-relationships. This paper proposes a method that crashes project completion time by hybridizing concurrent engineering and LOB scheduling without using additional resources.

• 한국경영과학회지
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• 제30권3호
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• pp.137-149
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• 2005

This study proposes a framework enhancing the accuracy of estimation for project duration by combining linear Bayesian updating scheme with the learning curve effect. Activities in a particular project might share resources in various forms and might be affected by risk factors such as weather Statistical dependence stemming from such resource or risk sharing might help us learn about the duration of upcoming activities in the Bayesian model. We illustrate, using a Monte Carlo simulation, that for partially repetitive projects a higher degree of statistical dependence among activity duration results in more variation in estimating the project duration in total, although more accurate forecasting Is achievable for the duration of an individual activity.

• 한국전문물리치료학회지
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• 제16권3호
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• pp.16-23
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• 2009

The purpose of this study was to investigate the effects of a repetitive lifting task on the level of activation and median frequency of the paraspinal muscles, and to provide basic data of the maximal acceptable duration of the lifting task to avoid muscle fatigue. Ten healthy male subjects were recruited as participants and they repetitively (12 lifts/min) lifted a box ($46cm{\times}30cm{\times}30cm$, 15 kg) for 10 minutes. Electromyographic data (muscle activation and median frequency), heart rate, and Borg CR10 score were recorded at 1, 3, 5, 7, and 9 minutes after the lifting task. Electromyographic data was recorded from the elector spinalis, mutifidus, external oblique abdominis, and rectus abdominis for 1 minute. The results showed that as the repetitive lifting task progressed, the heart rate and Borg CR10 score significantly increased. In addition, activation of the muscles increased. The median frequency significantly decreased over time in the elector spinalis, mutifidus, and external oblique abdominis (right side), except for the external oblique abdominis (left side) and rectus abdominis. It is suggested that the median frequency recorded from a dynamic task is used to monitor muscle fatigue. Furthermore, the repetitive lifting task (15 kg, 12 lifts/min) should not continue for more than 3 minutes in order to avoid muscle fatigue.

• 대한인간공학회지
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• 제33권6호
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• pp.565-575
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• 2014

Objective: The aim of this study is to evaluate the effect of weight of load and time on the physical workload of repetitive upper-limb tasks with handling light weight loads using EMG and perceived discomfort, and to investigate the relationship between EMG and perceived discomfort for those repetitive tasks of moving light weight loads. Background: Repetitive upper-limb motion is known as one of the main risk factors of musculoskeletal disorders, and a lot of repetitive tasks are carried out while handling light weight loads in the industry. In evaluating the workload of repetitive tasks handling light weight loads, EMG and perceived discomfort can be used, though their relationship in those work conditions are not much investigated. Method: A laboratory experiment with 18 healthy males were conducted to record EMG signals from 5 muscle sites of the right arm and shoulder and rate perceived discomforts for the body parts and the whole body while carrying out repetitive materials-handling tasks for 52min. The subjects were divided into 3 groups which handled the loads of 1kg, 2kg and 3kg, respectively. ANOVAs were conducted to analyze the effects of the weight and time on RMS of EMG amplitude (normalized RMS: NRMS), median frequency of power spectrum of EMG (normalized MDF: NMDF) and perceived discomfort. The correlations between NRMS and NMDF and perceived discomfort were also analyzed. Results: Statistically significant muscular fatigue effects were not found from NRMS and NMDF in most muscles, while there were significant increases of discomfort as the task time elapsed. It was shown that there were an increasing trend of the muscular activity as the weight of load increased and a decreasing trend of median frequency of EMG of upper and lower arms as time elapsed. It was found that there were significant negative correlations between NMDFs from the lower arm and discomfort ratings, though the relationships were weak. Conclusion: It can be concluded that the working conditions adopted in this study were not enough to induce muscular fatigue, while there was significant increase in perceived discomfort. A further study is necessary to integrate the objective and subjective measures for more reliable and sensitive evaluation of workload of repetitive tasks of handling light weight loads. Application: This study can be used as a basic study for the evaluation of workload of repetitive tasks handling light weight loads.

• 대한통합의학회지
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• 제11권4호
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• pp.167-175
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• 2023

Purpose : The study aim was to apply high-frequency repetitive transcranial magnetic stimulation to and investigate the effects on upper extremity function and activities of daily living. Methods : This study was conducted at Hospital D in U City from April to June 2018. Thirty-two patients diagnosed with stroke according to prior research criteria were selected and divided into two groups. Sixteen people in the experimental group received high-frequency repetitive transcranial magnetic stimulation and traditional occupational therapy, and sixteen people in the received sham stimulation and traditional occupational therapy. Both groups received 20 minutes of transcranial magnetic stimulation and 30 minutes of traditional occupational therapy per session, five times per week, for a total of 10 sessions over two weeks. Upper extremity functional evaluation, MFT and activities of daily living (Korean Version of the Modified Barthel Index, K-MBI) were conducted before and after the intervention, and an independent t test was used to confirm the effects of the intervention. Results : No statistically significant difference between the aforementioned groups' MFT and K-MBI scores was noted before the intervention. After the intervention, however, a statistically significant difference was found in K-MBI scores (p<.001). Additionally, after the intervention, a significant difference between the groups' MFT scores was found (p<.05). Conclusion : The results of this study showed that the combination of high-frequency repetitive transcranial magnetic stimulation and occupational therapy was effective in recovering upper extremity function and activities of daily living in patients diagnosed with acute stroke.