• Journal of Korean Society of Forest Science
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• v.109 no.1
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• pp.72-80
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• 2020

Two strategies for calculating economic feasibility are the machine rate and cash-flow methods. This study used the cash-flow method to evaluate the economic feasibility of the HAM300 yarding operation for extracting tree length logs in Larix kaempferi forest stands. In financial analysis based on 7-year cash-flow, the net present value and pay-back period method were used. We analyzed two scenarios: operating opportunities (50, 100, 150, and 200 days per year) and productivity change yield (7.5 and 10.5 ㎥/scheduled machine hour: SMH). The analysis indicated that high rates of return on extraction activity investment can be achieved when machines are used for >150 days per year. In addition, improved productivity (10.5 ㎥/SMH) increased financial feasibility compared to current productivity (7.5 ㎥/SMH) when machines were operated for 100 days per year. These results suggest that the appropriateness of HAM300 harvesting depends on the number of annual operating days and productivity.

• Journal of Korean Society of Forest Science
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• v.110 no.2
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• pp.210-216
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• 2021

Musculoskeletal disorders affect workers' safety in most industries, and forest operations are classified as a musculoskeletal burden according to the Occupational Safety and Health Act in South Korea. In particular, felling and delimbing operations are mainly conducted by manpower, and then, it is necessary to evaluate ergonomic risk assessment for safety of felling and delimbing workers. Three ergonomic risk assessment methods, such as Ovako Working posture Analysis System (OWAS), Rapid Upper Limb Assessment (RULA), and Rapid Entire Body Assessment (REBA), are available for assessing exposure to risk factors associated with timber harvesting operations. Here, three ergonomic risk assessment methods were applied to examine ergonomic risk assessments in chainsaw felling and delimbing operations. Additionally, exposure to risk factors in each method was analyzed to propose an optimal working posture in felling and delimbing operations. The risk levels of these operations were evaluated to be highest in the RULA method, followed by the OWAS and REBA methods, and most of the exposed working postures were examined with a low-risk level of two and three without requiring any immediate working posture changes. However, two significant working postures, including the bending posture of the waist and leg in felling operation and standing posture on the fallen trees in delimbing operation, were assessed as the high-risk level and needed immediate working posture changes. Low-risk work levels were examined in the squatting posture for felling operation and the straightened posture of the waist and leg for delimbing operation. Moreover, the slope in felling operation and the tree height in delimbing operation significantly affected risk level assessment of working posture. Therefore, our study supports that felling and delimbing workers must operate with low-risk working postures for safety.

• Journal of Biosystems Engineering
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• v.35 no.1
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• pp.37-45
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• 2010

Since SRC (Short-term Rotation Coppice) such as poplar and willow can be harvested in three years, they are known to be a potential forest biomass as fuel for a power plant. The production system including transplanting and harvesting is, however, necessary to be mechanized because such a biomass should be handled in a massive volumetric size. A pull-type stem-cutting transplanter was developed in the research as the first step to realize the production of SRC. A needle-like transplanting device pushes a stem-cutting into the prepared soil bed by a pneumatic cylinder, and another device firms soil around a stem-cutting transplanted. Since this is an intermittent operation, it was necessary to develop a zero horizontal velocity mechanism which enabled only the transplanting needle part to continue a zero horizontal movement relative to the ground during the transplanting operation even when the tractor kept moving forward. The 2-row transplanter can transplant stem-cuttings at the rate of 6.5 seconds per row without missing a single attempt. The planting depth and distance were well maintained and controlled. Their CVs were between 2.1~3.4% and 0.87~1.7% for the depth and the distance, respectively. Although, the transplanted stem-cuttings tended to lean outward from the back-view and forward from the side view, they were planted within the range of $3^{\circ}$ from the upright position.

• Journal of Biosystems Engineering
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• v.15 no.4
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• pp.310-318
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• 1990

The amount of grain loss incurred during harvesting operation through the chaff-outlet of combine may not be negligible. To minimize this grain loss and optimize condition of combining, it may be necessary that the amout of chaff-outlet loss dependent on varying crop condition is to be estimated as exactly as possible. This study was thus intended to develop the monitor that could indicate the amount of grain lost through the chaff-outlet of combine during haravesting operation, and to find out driving and operating method of combine that could reduce chaff-outlet loss. In the study(1), the frequency distributions of each sound generated by the impact of kernels and chaff, the sound generated by the impact of the mixture of kernels and chaff, and vibration or noise created by the combine engine and other moving parts were investigated experimentally. Based on the results of frequency analyses, the loss monitor was developed which could measure the impact sound of paddy kernels that could be distinguished from those of other threshing products through chaff-outlet, and from vibration or noise created by the combine engine and other moving parts. Also in this study, detecting capability of monitor was tested by comparing the amount of grain lost through chaff-outlet with the amount of grain detected by the loss monitor, and changes in chaff-outlet grain loss on the increase of traveling speed, location of chaff-outlet loss control plate and variety of paddy rice were measured using the loss monitor. The monitor developed in this study efficiently measured the amount of grain lost through the chaff-outlet of combine. It was found that the chaff-outlet grain loss ratio was affected greatly by the variety of paddy rice, the location of chaff-outlet loss control plate and traveling speed of combine.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.539-546
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• 1996

The physical condition of rapeseed delivered to fat industry plants plays a significant role in the formation of the qualitative features of the raw material for oil production and, consequently , of the oil itself. Rapeseed is stored in silos , frequently for months, before it is subjected to processing. During the long storage, the conditions of the seed cover is very important, as the seed cover provides natural protection of the seed against the effect of the environment. Seeds with damaged seed cover are more easily affected by mildew, and the rate of chemical processes. Deteriorating the quality of oil contained in the cotyledons is faster in such seeds. Cracked seed covers facilitates also the growth and development of microorgaism. So as rapeseed damage occurring inthe course of harvest and the post-harvest processing have a negative effect of the quality and quantity of oil the sees contain. The study presented here was aimed at examining the typical process of purcha ing and handling of rapeseed in fat industry plants, in the aspect of the occurrence of mechanical damage to the seeds. Special attention was paid to the condition of rapeseed immediately after combine harvesting : next , the successive stages of technological handling of the seed were examined. observing the operation parameters of the particular machinery and equipment in order to identify those operations which caused deterioration in the quality of the material (sees). Seed samples were taken successively from the following the hopper, prior to cleaning , after cleaning , prior to drying , after drying, from dry rape silo. The total level of damage increased through the handling. The content of unusable contaminants had the tendency to decrease in the successive operations. though the actual values still exceeded levels permitted by standards. The study allow to indicate the operation fo postharvest technological process, which cause the most seed damage as well as gave quantita ive description of the losses occurred.

• Journal of Sensor Science and Technology
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• v.28 no.5
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• pp.311-317
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• 2019

Rotating devices are commonly installed in power plants and factories. This study proposes a self-powered sensor node that is powered by converting the vibration energy of a rotating device into electrical energy. The self-powered sensor consists of a piezoelectric harvester for self-power generation, a rectifier circuit to rectify the AC signal, a sensor unit for measuring the vibration frequency, and a circuit to control the light emitting diode (LED) lighting. The frequency of the vibration source was measured using a piezoelectric-cantilever-type vibration frequency sensor. A green LED was illuminated when the measured frequency was within the normal range. The power generated by the piezoelectric harvester was determined, and the LED operation was assessed in terms of the vibration frequency. The piezoelectric harvester was found to generate a power of 3.061 mW or greater at a vibration acceleration of 1.2 g ($1g=9.8m/s^2$) and vibration frequencies between 117 and 123 Hz. Notably, the power generated was 4.099 mW at 122 Hz. As such, our self-powered sensor node can be used as a module for monitoring rotating devices, because it can convert vibration energy into electrical energy when installed on rotating devices such as air compressors.

• Journal of Electrochemical Science and Technology
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• v.13 no.4
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• pp.472-478
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• 2022

Solar energy harvesting is practiced by various nations for the purpose of energy security and environment preservation in order to reduce overdependence on oil. Converting solar energy into electrical energy through Photovoltaic (PV) module can take place either in on-grid or off-grid applications. In recent time Lithium battery is exhibiting its presence in on-grid applications but its role in off-grid application is rarely discussed in the literature. The preliminary capacity and Peukert's study indicated that the battery quality is good and can be subjected for life cycle test. The capacity of the battery was 10.82 Ah at 1 A discharge current and the slope of 1.0117 in the Peukert's study indicated the reaction is very fast and independent on rate of discharge. In this study Lithium Iron Phosphate battery (LFP) after initial characterization was subjected to life cycle test which is specific to solar off-grid application as defined in IEC standard. The battery has delivered just 6 endurance units at room temperature before its capacity reached 75% of rated value. The low life of LFP battery in off-grid application is discussed based on State of Charge (SOC) operating window. The battery was operated both in high and low SOC's in off-grid application and both are detrimental to life of lithium battery. High SOC operation resulted in cell-to-cell variation and low SOC operation resulted in lithium plating on negative electrode. It is suggested that to make it more suitable for off-grid applications the battery by default has to be overdesigned by nearly 40% of its rated capacity.

• Archives of Reconstructive Microsurgery
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• v.10 no.2
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• pp.124-130
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• 2001

Both of latissimus dorsi and rectus abdominis muscles are workhorse for various reconstructive surgeries. These muscle flaps have been used widely for soft tissue coverage, tissue augmentation, and functional muscle transfer. However, the traditional method for muscle harvest requires a long incision that often results in an unsightly scar and becomes the main concern of the patient. The purpose of this study is to introduce our clinical experience of endoscopic harvest of latissimus dorsi muscle and rectus abdominis muscle, and to make comparison with traditional harvest of these two muscle flaps. Of the 13 rectus abdominis muscles free flaps, 6 muscles were harvested traditionally and 7 muscles were harvested with endoscopic assistance. Of the 21 latissimus dorsi muscle free flaps, 12 muscles were harvested traditionally and 9 muscles were harvested with endoscopic assistence. Follow up period was between 6 months and 24 months. The patients age ranged from 7 to 70 years old. The result revealed no statistically significant differences in the amount of intraoperative bleeding, incidence of postoperative hematoma and seroma, and the incidence of donor-site wound infection. However, patients feel less pain and start earlier and better movement after the operation with endoscopically assisted harvest. This technique is easy to learn, is safe, and can reduce substantially the donor site morbidity comparing traditional harvesting technique.

• Journal of Korea Society of Industrial Information Systems
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• v.17 no.4
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• pp.17-23
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• 2012

Ultra low-power design and energy harvesting applications require digital systems to operate under extremely low voltages approaching the point of balance between dynamic and static power consumption which is attained in the sub-threshold operation mode. Delay variations are extremely large in this mode. Therefore, in this paper, a new low-power logic design methodology using asynchronous NCL circuits is proposed to reduce power consumption and not to be affected by various technology variations in nanoscale MOSFET technology. The proposed NCL is evaluated using various benchmark circuits at 0.4V supply voltage, which are designed using 45nm MOSFET predictive technology model. The simulation results are compared to those of conventional synchrouns logic circuits in terms of power consumption and speed.

• Journal of the Korean Society for Nondestructive Testing
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• v.32 no.6
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• pp.661-668
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• 2012

Wireless sensor network is one of prospective methods for railway monitoring due to the long-term operation and low-maintenance performances. How to supply power to the wireless sensor nodes has drawn much attention recently. In railway monitoring, the idea of converting ambient vibration energy from vibration of railway track induced by passing trains to electric energy has made it a potential way for powering the wireless sensor nodes. In this paper, a bimorph cantilever piezoelectric energy harvester was designed based on a single degree-of-freedom model. Experimental test was also performed to validate the design. The first natural frequency of the bimorph piezoelectric energy harvester was decreased from 117.1 Hz to 65.2 Hz by adding 4 gram tip mass to the free end of the 8.6 gram energy harvester. In addition, the power generation of the piezoelectric energy harvester with 4 gram tip mass at resonant frequency was increased from 0.14 mW to 0.74 mW from $2.06m/s^2$ base excitation compared to stand-alone piezoelectric energy harvester without tip mass.