• 한국응급구조학회지
• /
• 제28권1호
• /
• pp.21-34
• /
• 2024

Purpose: This study aimed to observe change in factors over time in the first cohort of the 2018 Children and Adolescent Panel Middle School. In addition, this study attempted to examine the causal relationship and influence between variables by setting a time gap between independent and dependent variables. Methods: Frequency and descriptive statistical analyses were conducted to determine the general characteristics of the study participants. Hierarchical regression analysis was conducted to analyze the effects of smartphone dependence on health, sleep quality, and depression. After inputting the control variables (Model 2), the influence of the variables was identified based on the input model. Results: Smartphone dependence positively impacted depression in both male and female students and negatively impacted sleep and health. Conclusion: Smartphones are closely associated with teenagers' lives. Additionally, as adolescents experience various psychological anxieties owing to rapid physical changes, there are concerns that psychological dependence may increase, considering that adolescence is the most emotionally unstable period. Therefore, the results of this study consistently prove that smartphone dependence has a causal relationship with emotion-related variables, such as emotional stress, depression, and anxiety.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1991년도 추계학술대회 논문집
• /
• pp.73-78
• /
• 1991

In this study of stacked type film chip capacitor, the important parameters are heat-treated temperature, pressure and time. We measured the temperature dependence of dielectric properties and dissipation factor and the frequency dependence of dielectric properties, dissipation factor, ESR(Equivalent Series Resistance) and impedance in stacked type film capacitor. As a result, the best conditions of heat-treated temperature, pressure and time were proved to be 130$^{\circ}C$, 10kg/$\textrm{cm}^2$ and 3hrs, respectively.

• 전자공학회논문지D
• /
• 제35D권4호
• /
• pp.101-108
• /
• 1998

We examine experimentally the dependence of output width on DC bias, RF power, and RF frequency in a gain-switched semiconductor laser. The optimum short pulses are obtained around threshold DC bias. The DC bias to generatoe shorter pulses decreases the RF power increases, whereas it increases to above threshold as the RF freqnecy increases. The pulse width becomes less sensitive to the variations of the DC bias, as the RF bias, or frquency increases.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1996년도 추계학술대회 논문집
• /
• pp.425-428
• /
• 1996

Treeing deterioration which is one of the main cause of breakdown in insulating materials is affected by temperature, applied voltage and frequency. In this study, GN was introduced to improve impact strength of DGEBA/MDA system and the temperature dependence of AC treeing deterioration in this system was investigated. Dielectric breakdown strength decreased with the increment of temperature. As temperature increased, the growth rate of tree Increased.

• 조명전기설비학회논문지
• /
• 제24권1호
• /
• pp.98-104
• /
• 2010

고주파수성분을 포함하는 뇌격전류나 또는 고장전류에 대한 접지시스템의 성능을 평가하기 위해 접지저항보다는 접지임피던스에 대한 고려가 필요하다. 접지임피던스를 평가하기 위해서는 토양의 저항률과 비유전율의 주파수의존성이 규명되어야 한다. 본 논문은 3가지 다른 토양에 대하여 수분함유량에 따른 저항률과 비유전율의 주파수의존성을 나타낸다. 결론적으로 토양의 저항률은 수분함유량이 증가함에 따라서 작아지게 되고, 1[MHz]보다 낮은 주파수에서 거의 변화하지 않으며 1[MHz]이상의 주파수에서는 감소한다. 반면에 비유전율은 1[MHz]이하의 주파수에서 매우 급격하게 감소하며, 1[MHz]이상의 주파수에서는 거의 변화하지 않는 것으로 나타났다. 본 실험 결과로 부터 낙뢰 또는 개폐서지에 대한 보호를 목적으로하는 접지시스템의 설계시 토양의 저항률과 비유전율을 고려하는 것이 바람직한 것으로 밝혀졌다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제40회 동계학술대회 초록집
• /
• pp.234-234
• /
• 2011

Electron-neutral collision frequency is one of the important parameters in the plasma physics and in industrial plasma engineering. We can understand the momentum, energy, and charge transport properties of the plasma using electron-neutral collision frequency.[1] The wave-cutoff method is a diagnostic method for the electron density measurement, but the cutoff peak value depends on gas pressure. The wave-cutoff signal becomes unclear as increasing gas pressure. The reason of pressure dependence is that the electron-neutral collision disturbs electron motion so that microwave can propagate through plasma at plasma frequency.[2] Using the pressure dependence of wave-cutoff method we can find the electron-neutral collision frequency. At first we tried to confirm this method using well known gas such as Ar. The cutoff signal decrease as increasing gas pressure (the simulation result). The wave-cutoff signal is unclear at a gas pressure of 500 mTorr. (electron density $1.0{\times}10^{10}/cm^3$, electron temperature 1.7 eV, electron -neutral collision frequency~1 GHz). In this condition, the electron-neutral collision frequency is closed to the wave-cutoff frequency.

• Journal of Astronomy and Space Sciences
• /
• 제32권2호
• /
• pp.137-140
• /
• 2015

The results of the study of ionospheric variations in the summer months of 1998-2002 at an ionospheric station of vertical sounding "Petropavlovsk-Kamchatsky" are presented. Anomalous variations of virtual sporadic-E height (h'Es), Es blanketing frequency (fbEs), and the critical frequency of the ionospheric F2 layer (foF2) (which can be attributed to the possible earthquake precursors) are selected. The high efficiency of the selection of ionospheric earthquake precursors based on the several parameters of Es and F2 layers is shown. The empirical dependence, which reflects the connection between the lead-time of the earthquake moment, the distance to the epicenter from the observation point, and the magnitude of the earthquake are obtained. This empirical dependence is consistent with the results of the detection of earthquake precursors by measuring the physical parameters of the Earth's crust in the same region.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 하계학술대회 논문집
• /
• pp.303-306
• /
• 2001

Composite insulating materials used in outdoor high voltage equipment are required to have high electric performance because of the miniaturization. The frequence dependence of the permittivity and the loss tangent have important information. In this paper we describe the frequency dependence of the permittivity and the loss tangent for epoxy resin filled with silica and the influence of filler shape on the dielectric properties. The increment of tan $\delta$ in the low frequency region is caused by the increment of both of the electrical conductivity and the polarization due to the shape of filler and water sbsorbed in and near the interface between the fillers and resins. Result of charge current and discharge measure, electric conduction increased according to voltage.

• 대한안전경영과학회지
• /
• 제3권3호
• /
• pp.231-241
• /
• 2001

The epoxy resin materials used in outdoor high voltage equipments are required to have the high electric performance because of the miniaturization. The frequence dependence of the permittivity and the loss tangent have important information. In this paper we describe the frequency dependence of the permittivity and the loss tangent for epoxy resin filled with silica and the influence of filler shapes on the dielectric properties. The increment of tan $\delta$ in the low frequency region is caused by the increment of both the electrical conductivity and the polarization due to the shape of filler and the water absorbed in and near the interface between fillers and resins. The result of charge current and discharge measure, electric conduction is increased according to voltage.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1989년도 추계학술대회 논문집 학회본부
• /
• pp.65-67
• /
• 1989

To study hopping conducting mechanism in PAN(polyacrylonitrile) carbon fiber, the temperature and frequency dependence of electrical conductivity and magnetoresistance characteristics were investigated. Electrical conductivity in the range of $60^{\circ}K-300^{\circ}K$ show VRH(variable range hopping) properties which introduced by Mott's theory, and also such properties can be explained by the frequency dependence of electrical conductivity below $5{\times}10^6$ Hz. The negative magnetoresistance observed below 35KG magnetic field, and the properties difference between M40 and T300 with increasing magnetic field is supposed due to on effect connected with crystalline state and orientation of structure.