• Journal of the Optical Society of Korea
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• v.16 no.2
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• pp.107-114
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• 2012

In this paper, we propose a new modulation scheme called multi-coded variable pulse position modulation (MC-VPPM) for visible light communication systems. Two groups of signals (Pulse Width Modulation (PWM) and Pulse Position Modulation (PPM) groups) are multi-coded by orthogonal codes for transmitting data simultaneously. Then, each multi-level value of the multi-coded signal is converted to pulse width and position which results in not only an improved data rate, but also a processing gain in reception. In addition, we introduce average duty ratio and cyclic shift concepts in PWM through which dimming control for light illumination can be supported without any degradation in communication performance. Through simulation, we confirm that the proposed MC-VPPM shows a comparable BER curve and much greater achievable data rate than the conventional VPPM scheme using a visible light optical channel environment.

• Korean Journal of Veterinary Research
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• v.33 no.3
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• pp.455-460
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• 1993

In the present study, the effects of 4 agricultural chemicals commonly used in this conuntry were experimentally assessed on Lymnaea viridis the intermediate host of Fasciola hepatica, which in non-target organism of these chemicals. The major habitat of the snail is rice paddies in Korea and many agricultural chemicals are used for weed, fungi or insect control in rice paddies and there is a general concern that certain levels of these chemicals could reach the aquatic ecosystem and possible alter the snail life. Agricultural chemicals used in this study included two herbicides, an insecticide and a fungicide. The tenth generation of laboratory reared snails were selected and exposed to the varying concentrations(0-100 ppm) of these chemicals. As concentrations and time of exposure increase, the per cent mortality increases(p<0.01). $LC_{50}$(lethal concentration for 50% mortality) values of these chemicals on snail after 96-hour exposure were variable; iprobenfos showed the highest acute toxicity(12.6 ppm), while carbofuran showed the lowest acute toxicity(74.5ppm). Sublethal concentrations of chemicals after 96-hour exposure were also variable ; bentazone showed the highest chronic toxicity(0.81ppm), while carbofuran showed the lowest chronic toxicity(5.04 ppm).

• The Journal of Asian Finance, Economics and Business
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• v.8 no.1
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• pp.37-43
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• 2021

The main objective of this study is to discuss the effect of free cash flow as a moderating variable on managers' decisions as regard earnings management. Companies with free cash flow are expected to refrain from taking opportunistic actions such as earnings management. The research used quantitative methods with sub-group moderating analysis. It is found that there is a significant relationship between past performance and earnings management, where the free cash flow is the moderating variable. The effect of past performance on earnings management is shown to slightly increase as free cash flow is considered. The findings of this study prove that earnings management is a practice that is often done by utilizing the flexibility of accounting recording and recognition mechanisms. Past performance becomes the main variable in encouraging managers to manage earnings by reducing revenue in the current period. This research can also be a reference in explaining managerial behavior and can be a reference to improving ethical human resource capabilities. This research focuses on companies in Indonesia that conduct earnings management by lowering profits as a result of declining past performance and examines aspects of free cash flow that reinforces the conduct of earnings management.

• Journal of the Korea Safety Management & Science
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• v.9 no.4
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• pp.137-142
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• 2007

This paper is to introduce attribute acceptance sampling plan based on statistical inference of binomial proportions such as PPM or PPB. In addition, this paper presents three variable sampling acceptance sampling plans based on $C_{pm},\;C_{pmk}$, and Taguchi's loss function. Producers are able to consider as not only external vendors but also internal customers.

• Clean Technology
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• v.8 no.4
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• pp.217-222
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• 2002

The effects of initial cadmium ion concentrations (50, 100, 200, 300ppm), and feeding velocities (30, 45, 60mL/hr) on the removal ratio of cadmium ion by Pseudomonas aeruginosa ATCC 27853 immobilized in Ca-alginate gel beads in a packed-bed column reactor were investigated at operating temperature $37^{\circ}C$. The removal ratio of cadmium ion with variable initial concentration was decreased in the following order : 50ppm > 100ppm > 200ppm > 300ppm. The optimum removal conditions of cadmium ion by Pseudomonas aeruginosa ATCC 27853 were initial concentration 50ppm, feeding velocity 30mL/hr.

• Korean Journal of Food Science and Technology
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• v.13 no.4
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• pp.299-306
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• 1981

Contents of heavy metals in fruits and vegetables collected from Jinju district of Korea during June 1980 to March 1981 were determined. Statistical analysis of the data showed the maximum, minimum, mean and standard deviation for each variable. The ranges of their amounts in fruits and vegetables were lead, $trace{\sim}0.829\;ppm\;;mercury,\:ND{\sim}0.368\;ppm;cadmium,\;ND{\sim}0.264\;ppm;\;arsenic,\;trace{\sim}1.289\;ppm;\;copper,0.200{\sim}3.759\;ppm;\;zinc,\;0.327{\sim}21.663\;ppm;\; manganese,\;0.828{\sim}22.413\;ppm;\;iron,\;0.201{\sim}32.425 ppm,$ respectively and the content of chromium was in trace for 4 samples.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.91-92
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• 2007

LR-UWB utilizes BPSK and PPM for the transmission, which embeds the information in the transmitted pulse position. Meanwhile, by using coherent method, there is approximately 3dB enhancement on the BER performance over that using non-coherent method. However, due to the variable channel conditions, conventional system which uses fixed modulation is not efficient. To maximize the efficient and performance, in this paper, we propose an adaptive method including 4PPM+BPSK mode and 2PPM mode, in which the modulation method is dynamically changed depending on the channel condition which is determined according to the preamble correlation output.

• Asian-Australasian Journal of Animal Sciences
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• v.14 no.11
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• pp.1616-1620
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• 2001

Two feeding trials were conducted to study the effects of different chelated copper and zinc compounds on the performance and fecal excretions of weanling pigs. In Exp. 1, 150 weanling pigs ($L{\times}Y{\times}D$, $12.30{\pm}2.07kg$) were randomly assigned to five dietary treatments: 170 ppm Cu from $CuSO_4$, 85 ppm Cu from Cu amino-chelate (CAC), 170 ppm Cu from CAC, 85 ppm Cu from Cu-Lysine (CL), and 170 ppm Cu from CL. In Exp. 2, 150 weanling pigs ($L{\times}Y{\times}D$, $12.52{\pm}1.80kg$) were randomly assigned to five dietary treatments: 120 ppm Zn from $ZnSO_4$, 60 ppm Zn from Zn-amino-chelate (ZAC), 120 ppm Zn from ZAC, 60 ppm Zn from Zn-Methionine (ZM), and 120 ppm Zn from ZM. In both experiments, pigs were randomly distributed to the treatments following a randomized complete block design on the basis of body weight as the blocking variable. Each experiment was conducted for 28 days. Blood and fecal samples were collected to determine mineral contents as affected by the dietary treatments. There was no difference (p>0.05) in ADG and ADFI among treatments, but F/G was improved (p<0.05) in pigs fed diet with 170 ppm CAC than 85 ppm CL but not different (p>0.05) to the control (170 ppm $CuSO_4$). Regardless of copper source, concentration of Cu in serum and feces were higher in pigs fed diet with 170 ppm Cu than pigs fed diet with 85 ppm Cu (Exp 1). In Exp 2 the ADG was higher (p<0.05) in pigs fed diet with 120 ppm ZM than in pigs fed diets with 120 ppm $ZnSO_4$ and 60 ppm ZAC and ZM. The serum zinc concentration was generally higher (p<0.05) in pigs fed diet with organic source than the control group ($ZnSO_4$). Also, there was a trend towards a decrease in fecal excretions of zinc when dietary zinc level was low. The efficacy of the two chelated copper and zinc sources is similar in terms of growth performance. The fecal excretions for Cu and Zn could be reduced in pigs fed low level of these minerals using organic sources.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12B
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• pp.1695-1702
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• 2001

This paper describes a design of CMOS infrared (IR) wireless data link IC which can be used in IrDA(Infrared Data Association) application from 4 Mb/s to 100 Mb/s The implemented chip consists of variable gain transimpedance amplifier which has a gain range from 60 dB to 100 dB, AGC (automatic gain control) circuits, AOC(automatic offset control) loop, 4 PPM (pulse position modulation) modulator/demodulator and DLL(delay locked loops). This infrared optical link If was implemented using commercial 0.25 um 1-poly 5-metal CMOS process. The chip consumes 25 mW at 100 Mb/s with 2.5 V supply voltage excluding buffer amplifier. The die area of prototype IC is 1.5 mm $\times$ 1 mm.

• Korean Journal of Veterinary Research
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• v.17 no.2
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• pp.63-71
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• 1977

During the period of March, 1976 to December, 1976, 48 raw milk samples were taken from dairy cows at 48 different dairy farms in Korea analyzed by gas liquid chromatography to determine the seasonal variation of the amount of organochlorine pesticide residues. At the same time 80 market milk, 10 beef and 10 pork samples were analyed by the same procedure for checking residual levels. The results were summarized as follows; 1. Milk samples from 17 dairy farms (36 per cent of tatal) were shown to be contaminated with various organochlorine pesticides. The residua lrate of ${\gamma}-BHC$ in tested samples were 44per cent (14 sam ples) that of aldrine was 28 per cent (9 samples) and those of pp'-DDT, dieldrin and heptachlor were 9.3 percent (3 samples) respectively. 2. In raw milk pp'-DDT, ${\gamma}-BHC$, aldrin, dieldrin and heptachlor were detected, and aldrin, dieldrin and heptachlor were detected in the market milk. Any kinds of organochlorine pesticides were not detected in beef samples but dieldrin and heptachlor were detected in pork samples. Average residual values of aldrin, dieldrin and heptachlor in the market milk were 0.0077 ppm (0.0000~1.1100 ppm), 0.0001ppm (0.0000~0.0500 ppm) and 0.0008 ppm (0.0000~2.0520 ppm), respectively, and those of dieldrin and heptachlor in pork samples were 0.0010 ppm (0.0000~0.0100 ppm) and 0.0033 ppm (0.0000~0.0330 ppm). respectively. 3. Residues of organochlorine pesticides in raw milk were extremely variable; in fact pp'-DDT was detected in milk samples from A, B, C and D districts and endrin was not detected from all districts. The ${\gamma}-BHC$ and dieldrin were detected at the district of A, C and D, aldrin at the districts of A and C and heptachlor at the districts of both A and D. 4. Seasonal trends of residual values of organochlorine pesticides were, in general, noticeable. The residual level was much higher in Spring than in other seasons and showed the tendeney of decrease from spring through summer and autumn generally; in the case of pp'-DDT average residual values were 0.0121 ppm in spring, 0.0022 ppm in summer and not detected in autumn. But in winter ${\gamma}-BHC$ and aldrin residues were increased a little. Residual values in raw milk (when cow are fed on hay and silage) were appeared higher in winter than the other seasons. 5. Residues of organochlorine pesticides in raw milk were not related in respect to hygienic conditions of dairy farms pp'-DDT and heptachlor were, in general, detected in all farms and aldrin was more detected in milk from well sanitated farms than poor sanitated ones.