• Journal of Ecology and Environment
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• 제32권2호
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• pp.67-73
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• 2009

Soil $CO_2$ efflux can vary markedly in magnitude over both time and space, and understanding this variation is crucial for the correct measurement of $CO_2$ efflux in ecological studies. Although considerable research has quantified temporal variability in this flux, comparatively little effort has focused on its spatial variability. To account for spatial heterogeneity, we must be able to determine the number of sampling points required to adequately estimate soil $CO_2$ efflux in a target ecosystem. In this paper, we report the results of a study of the number of sampling points required for estimating soil $CO_2$ efflux using a closed-dynamic chamber in young and old Japanese cedar plantations in central Japan. The spatial heterogeneity in soil $CO_2$ efflux was significantly higher in the mature plantation than in the young stand. In the young plantation, 95% of samples of 9 randomly-chosen flux measurements from a population of 16 measurements made using 72-$cm^2$ chambers produced flux estimates within 20% of the full-population mean. In the mature plantation, 20 sampling points are required to achieve means within $\pm$ 20% of the full-population mean (15 measurements) for 95% of the sample dates. Variation in soil temperature and moisture could not explain the observed spatial variation in soil $CO_2$ efflux, even though both parameters are a good predictor of temporal variation in $CO_2$ efflux. Our results and those of previous studies suggest that, on average, approximately 46 sampling points are required to estimate the mean and variance of soil $CO_2$ flux in temperate and boreal forests to a precision of $\pm$ 10% at the 95% confidence level, and 12 points are required to achieve a precision of $\pm$ 20%.

• 한국컴퓨터정보학회논문지
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• 제27권6호
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• pp.139-147
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• 2022

본 연구는 신체활동수준, 주관적 건강상태, 코로나19 염려의 관계를 분석하는 것에 목적이 있다. 이를 위하여 2020년 지역사회건강조사를 바탕으로 전국 만 19세 이상 성인 229,269명의 설문데이터 자료를 분석하였다. 복합표본설계로 가중치, 층화변수, 집락변수를 지정하여 분석하였다. SPSS 통계분석 프로그램을 이용하여 복합표본 빈도분석, 복합표본 교차분석, 복합표본 회귀분석을 실시하고, 다음과 같은 결과를 얻었다. 첫째, 신체활동수준이 높은 그룹이 신체활동수준이 낮은 그룹에 비하여 주관적 건강상태가 높은 것으로 나타났다. 둘째, 신체활동수준이 높은 그룹이 신체활동수준이 낮은 그룹에 비하여 코로나19 염려가 낮은 것으로 나타났다. 셋째, 주관적 건강수준이 높은 그룹이 낮은 그룹에 비하여 코로나19 염려가 낮은 것으로 나타났다. 다만 본 연구에서는 실제 코로나19 감염여부는 분석에 포함하지 않았다는 제한점이 있다.

• Journal of Ecology and Environment
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• 제47권4호
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• pp.250-260
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• 2023

Background: Crabgrass (Digitaria ciliaris, Poaceae) is a globally distributed weed, including in Afro-Eurasia, America, and Australia. As a highly gregarious plant, crabgrass is an important habitat for a diverse array of insects, and a potential habitat for agricultural pests. To compare the insect communities associated with the crabgrass community, insects were sampled using sweep sampling (100 sweeps per sample) at five sites, including Daejeon (Daejeon and Gap rivers), Anseong, Namhae, and Inje, with a focus on the Daejeon River. Results: A total of 5,888 individual insects belonging to eight orders, 42 families, and 115 species were collected from the five sites. Both the number of species and individuals of Hemiptera were the highest at all of the sites. In the present study, 73% of the insect population fed on D. ciliaris as a host plant. The dominant species in the D. ciliaris community was Laodelphax striatellus (Delphacidae), being ubiquitous at all the sites which showed a high abundance of rice pests in the communities and the suitability of D. ciliaris as an alternative host plant for them. The Shannon-Wiener diversity index was highest in Inje on 17 September (2.88), and the Chao1-bc diversity index was highest in the Gap River on 5 September (80). The sampling efficiency of 100 sweep samples (sample coverage) was calculated to be as high as 90%. The results of the samples taken from September to November in the Daejeon River showed that the number of species and individuals decreased gradually over time, and the number of dominant species decreased sharply between September and October. Similarity analysis indicated that sampling dates that were closer together yielded sampled assemblages with higher faunal similarity. In addition, in each sampling, the difference in the minimum temperature during the two-week period prior to sampling and faunal similarities were negatively correlated. Conclusions: This study provides foundational data that could enhance our understanding of insect diversity in D. ciliaris. The data can facilitate ecological conservation and management of Korean grasslands generally, as well as identification of potential pests that may disperse from D. ciliaris communities to nearby farmland.

• 응용통계연구
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• 제24권3호
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• pp.477-484
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• 2011

반응/미반응 목표변수를 갖는 모집단에서 관심 목표범주의 빈도가 극히 작을 경우, 즉 희귀할(rare) 경우, 모형 구축을 위한 데이터마트를 형성할 때 반응/미반응 범주 구성비는 구축된 모형의 성능에 영향을 준다. 본 연구는 이러한 점에 착안하여 반응/미반응 범주 구성비와 모형성능의 관련성을 모형평가 통계량에 기반하여 판단한다. 이로써 데이터마트 형성에 이상적인 반응/미반응 범주 구성비를 탐지하려는데 본 연구의 목적을 두고 있다. 또한 일반적으로 목표범주의 빈도가 희귀할 경우, 분할 표본추출에 의하여 희귀사건(rare event)을 과대표본추출(oversampling)하는 것이 일반적이며, 이로부터 기인하는 사후확률에 대한 편향을 조정하게 된다. 본 연구에서는 사후확률 조정방법으로 오프셋(offset) 방법과 가중치 방법(sampling weights)을 적용하고 이를 비교하였다.

• 보건교육건강증진학회지
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• 제19권4호
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• pp.61-76
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• 2002

The purpose of this study is to identify differences in processes of change, decision making, and self-efficacy by exercise behavioral stages and determine variables significantly affecting the older people's participation in exercises. The subjects of this study included 299 people aged 65 or over who were residents of G and S districts in Busan Metropolitan City. They were selected through purposive quota sampling at colleges and centers for old people and homes in order that they could be evenly distributed over stages of pre-contemplation, contemplation, preparation, action and maintenance. Data were analyzed using descriptive, ANOVA, Logistic Regression. Variables that discriminate between participants and non-participants in exercise include self-reevaluation, reinforcing management, cons and self-efficacy. Thus if variables that discriminate between participant and non-participation in exercise such as self-reevaluation, reinforcing management, cons and self-efficacy are fully considered in designing nursing interventions for inducing old people to become exercise participants, it would provide guidelines for nursing intervention programs as appropriate for the people's exercise stages. The purpose of this study is to identify differences in processes of change, decision making, and self-efficacy by exercise behavioral stages and determine variables significantly affecting the older people's participation in exercises. The subjects of this study included 299 people aged 65 or over who were residents of G and S districts in Busan Metropolitan City. They were selected through purposive quota sampling at colleges and centers for old people and homes in order that they could be evenly distributed over stages of pre-contemplation, contemplation, preparation, action and maintenance. Data were analyzed using descriptive, ANOVA, Logistic Regression. Variables that discriminate between participants and non-participants in exercise include self-reevaluation, reinforcing management, cons and self-efficacy. Thus if variables that discriminate between participation and non-participation in exercise such as self-reevaluation, reinforcing management, cons and self-efficacy are fully considered in designing nursing interventions for inducing old people to become exercise participants, it would provide guidelines for nursing intervention programs as appropriate for the people's exercise stages.

• 한국산업융합학회 논문집
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• 제23권5호
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• pp.747-756
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• 2020

In recent years, measurement in a smart-phone environment is attracting attention in various fields due to its easy set-up process, various functions, convenience and expandability. Even in the field of safety evaluation and maintenance of large-scale infra-structures, the appropriate application of these effective and convenient measurement techniques can be of great help. In this paper, an experimental study was conducted to investigate the effectiveness, problems and complementary methods of applying smart-phone accelerometers to the measurement in infra-structure such as bridges. In model bridge subjected to impact and moving loads, the measured accelerations using a smart-phone and a professional accelerometer were directly compared in time domain. And the statistical and frequency characteristics of the measured signal and transfer function were also examined in frequency domain. The results show that the accuracy of measurement using smart-phone sensor is primarily affected by its incomplete sampling performance. In conclusion, smart-phone sensors cannot be considered suitable for precise assessment, where measurements must be accurate over a wide frequency range, but we can say that the technique is still useful and fairly accurate for some purpose over a limited frequency range, such as the low pass frequency range, which is a major concern for civil structures.

• ETRI Journal
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• 제40권3호
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• pp.366-375
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• 2018

Recently, techniques involving head-mounted displays (HMDs) have attracted much attention from academia and industry owing to the increased demand for virtual reality and augmented reality applications. Because HMDs are positioned near to users' eyes, it is important to solve the accommodation-vergence conflict problem to prevent dizziness. Therefore, holography is considered ideal for implementing HMDs. However, within the Nyquist region, the accommodation effect is limited by the space-bandwidth-product of the signal, which is determined by the sampling number of spatial light modulators. In addition, information about the angular spectrum is duplicated over the Fourier domain, and it is necessary to filter out the redundancy. The size of the exit-pupil of the HMD is limited by the Nyquist sampling theory. We newly propose a holographic HMD with an expanded exit-pupil over the Nyquist region by using the time-multiplexing method, and the accommodation effect is enhanced. We realize time-multiplexing by synchronizing a high-speed digital micromirror device and a liquid-crystal shutter array. We also demonstrate the accommodation effect experimentally.

• 전기학회논문지
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• 제66권9호
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• pp.1364-1372
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• 2017

In this paper, a problem of event-triggered model predictive control is investigated for continuous-time Takagi-Sugeno (T-S) fuzzy systems with input quantization. To efficiently utilize network resources, event-trigger is employed, which transmits limited signals satisfying the condition that the measurement of errors is over the ratio of a certain level. Considering sampling and quantization, continuous Takagi-Sugeno (T-S) fuzzy systems are regarded as a sector bounded continuous-time T-S fuzzy systems with input delay. Then, a model predictive controller (MPC) based on parallel distributed compensation (PDC) is designed to optimally stabilize the closed loop systems. The proposed MPC optimize the objective function over infinite horizon, which can be easily calculated and implemented solving linear matrix inequalities (LMIs) for every event-triggered time. The validity and effectiveness are shown that the event triggered MPC can stabilize well the systems with even smaller average sampling rate and limited actuator signal guaranteeing optimal performances through the numerical example.

• 대한약침학회지
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• 제15권3호
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• pp.7-12
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• 2012

Objective: This study aimed to summarize and analyze the usage of and the satisfaction levels with combined treatment including Oriental and Western medicine. Methods: We searched studies on the usage of and the satisfaction levels with combined treatment including Oriental and Western medicine over the past 10 yrs (2001-2011) from 3 Korean databases (National Assembly Library, Research Information Service System, and National Discovery for Science Leaders). The reviewers also conducted a summarizing analysis by sampling the literature according to the type of study, study period, region, study subjects, sample size, type of sampling, research method, data analysis, study instruments, main results, etc. Results: When the main results of six studies on combined treatment usage and satisfaction levels were considered together, the most important decisive factor in determining the usage of combined treatment was the illness of the patient, followed by the patient's occupation, sex, age, education, marital status, religion, treatment cost, and treatment results. In addition, the most important factor that determined satisfaction levels with combined treatment was age, followed by education, religion, income, health status, treatment procedures, staff attitude, and cleanliness. Conclusions: Elderly patients with musculoskeletal, cerebro-vascular, and circulatory system illnesses are more likely to prefer combined treatment over independent Oriental or Western treatment and are more likely to request specialized, adjusted medical care.

• 디지털산업정보학회논문지
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• 제10권3호
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• pp.237-247
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• 2014

This paper describes a 2D discrete-time wavelet transform for which the Q-factor is easily specified. Hence, the transform can be tuned according to the oscillatory behavior of the image signal to which it is applied. The tunable Q-factor wavelet transform (TQWT) is a fully-discrete wavelet transform for which the Q-factor, Q, of the underlying wavelet and the asymptotic redundancy (over-sampling rate), r, of the transform are easily and independently specified. In particular, the specified parameters Q and r can be real-valued. Therefore, by tuning Q, the oscillatory behavior of the wavelet can be chosen to match the oscillatory behavior of the signal of interest, so as to enhance the sparsity of a sparse signal representation. The TQWT is well suited to fast algorithms for sparsity-based inverse problems because it is a Parseval frame, easily invertible, and can be efficiently implemented. The TQWT can also be used as an easily-invertible discrete approximation of the continuous wavelet transform. The transform is based on a real valued scaling factor (dilation-factor) and is implemented using a perfect reconstruction over-sampled filter bank with real-valued sampling factors. The transform is parameterized by its Q-factor and its oversampling rate (redundancy), with modest oversampling rates (e. g. 3-4 times overcomplete) being sufficient for the analysis/synthesis functions to be well localized. Therefore, This method services good performance in image processing fields.