• Journal of Korean Academy of Fundamentals of Nursing
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• v.1 no.1
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• pp.77-97
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• 1994

The circadian system represents a temporal order which is mediated by the mutual coupling of oscillators and by the synchronizing effects of zeitgebers. It is known that well-being of man depends partly on the maintenance of this order, and that repeated or long lasting disturbances to it such as shift work will Cause harmful effects. This study was a quasi-experimental study to test the effect of shift directions for the clinical nurses on the circadian rhythm. Fourteen nurses working at the general units of Y hospital were selected according to the established criteria. Fourteen subjects were assigned to a weekly shift but the directions of shift work were phase delay first and then phase advance or vice versa. Oral temperature, total sleeping time, frequency of sleep-wake cycle, fatigue, mental performance, and physical symptom were measured during these days except holidays. The data collection period was from April 26, 1993 to July 3, 1993. MANOVA and Wilcoxon signed rank test were used for statistical analysis. The results are summarized as follows. 1. Having worked on evening and night shifts in either phase delay or phase advance schedules, temperature rhythms of shift workers were gradually adapted to the new sleep-wake cycles. A complete adaptation to work on the night shift was achieved the sixth day of the night shift in the phase delay schedule compared to the partial adaptation to the work on the night shift in the phase advance schedule. Accordingly, by putting evening shift between day and night shifts, it will be possible for circadian rhythm to adapt easily to the night shift. 2. There were differences in the total sleeping time, frequency of steep-wake cycle, fatigue, and physical symptom except for mental performance between night shift and day, evening shift. This indicates further that shift workers working on the night shift have a hard time adapting to the shift work compared to the other shifts. 3. Evaluating all the acrophases of temperature rhythm either in phase delay or phase ad-vance schedules, it was shown that night to evening shift in the phase ad-vance schedule revealed the smallest phase move. Also phase advance schedule showed poorer adaptation to shift work than phase delay schedule in connection with total sleeping time, frequency of sleep-wake cycle, fatigue, mental performance, and physical symptom. It is suggested, taken together, these findings reflect that phase delay schedule facilitated the degree of adjustment to the shift work compared to the phase advance schedule.

• Journal of Bio-Environment Control
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• v.11 no.4
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• pp.163-167
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• 2002

This study was carried out to investigate the effect of minimum night temperature in the PE house on growth of seedlings of Pinus densiflora and Betula platyphylla in winter season. The experiment was performed with three minimum night temperature regimes,5~8$^{\circ}C$, 10~13$^{\circ}C$ and 15~18$^{\circ}C$. The temperature regimes were maintained for 8 weeks (to April 6) after germination peak, and then were broken by increasing natural temperature. The temperature did not affect the germination rate but delayed the germination by 10 days. Height, root collar diameter growth, and dry weight of two species were reduced by relatively low night temperature. The reduction was more obvious in the dry weight of above the ground measured at 8 weeks after germination. The seedlings grown for 8 weeks at 5~8$^{\circ}C$ showed the lowest T/R ratio. It was also observed that the height growth response in Betula platyphylla seedlings to relatively low temperature was more sensitive than Pinus densiflora.

• Animal cells and systems
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• v.6 no.3
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• pp.239-245
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• 2002

Plasma melatonin, thyroid-stimulating hormone (TSH) and body temperature were measured simultaneously and continuously before and after the sleep-wake cycle was shifted in 4 healthy males and changes in the circadian rhythm itself and in the phase relationship among these circadian rhythms were determined. Normal sleep-wake cycle (sleep hours: 2300-0700) was delayed by 10 h (sleep hours: 0900-1700) during the experiment. Even after this shift the typical melatonin rhythm was maintained: low during daytime and high during night. The melatonin rhythm was gradually delayed day by day. The TSH rhythm was also maintained fundamentally during 3 consecutive days of altered sleep-wake cycle. The phase was also delayed gradually but remarkably. The daily rhythm of body temperature was changed by the alteration of sleep-wake cycle. The body temperature began to decrease at the similar clock time as in the control but the decline during night awake period was less steep and the lowered body temperature persisted during sleep. The hormonal profiles during the days of shifted sleep/wake cycle suggest that plasma melatonin and TSH rhythms are basically regulated by an endogenous biological clock. The parallel phase shift of melatonin and TSH upon the change in sleep-wake cycle suggests that a common unitary pacemaker probably regulates these two rhythms. The reversal phase relationship between body temperature and melatonin suggests that melatonin may have a hypothermic effect on body temperature. The altered body temperature rhythm suggests that the awake status during night may inhibit the circadian decrease in body temperature and that sleep sustains the lowered body temperature. It is probable but uncertain that there ave causal relationships among sleep, melatonin, TSH, and body temperature.

• Atmosphere
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• v.21 no.4
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• pp.361-371
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• 2011

In this study, characteristics and trends of tropical night (TN) are investigated by using the KMA 14 observation data for the recent 50 years (1958-2007) over South Korea. The TN is defined as a day with a daily minimum temperature exceeds the absolute threshold temperature ($25^{\circ}C$), and the relative deviation from normal temperature, 95th percentile of all observed daily minimum temperature. Although the spatial distribution of TN occurrence depends on the choice of the definitions, the frequency of TN shows strong spatial and interannual variations with the minimum at high land area (Chupungnyeong and wet years) and maximum at southern coastal area and large city area (Jeju, Busan, Seoul, Daegu). Most of TN occurs in August (56%) and July (41%), and the duration date of TN is proportional to the frequency of TN without regard to the definition method. In general, increasing trends are found in the TN time series without regard to the analysis method, but the trends are clearly depending on the analysis period and geographic locations. Decreasing trends are prominent during the most of analysis period, especially until the mid of 1990, whereas strong increasing trends are found during recent 30 years (1988-2007), especially at Jeju, Ulsan, Daegu and Pohang. Also the severity of TN is significantly increased in recent years.

• Journal of the Korea Safety Management & Science
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• v.10 no.2
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• pp.53-60
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• 2008

A test was conducted using two high density discharge lamps, the H2D and the structurally new H4D. They were tested for luminous illumination and luminous temperature in the day and night time. The test was conducted without crippling the performance of the H2D by adding a magnetic actuator, enabling it to move left to right, and up and down. By making these modifications we constructed a sample of the H4D. We compared the H2D and the H4D sample's luminous illumination and luminous temperature by using a photometer and a digital thermometer in the day and night time. We discovered that the H2D and H4D performed similarly from the data we gathered. Now we know the H4D has potential use and extensive research needs to be made to gather more detailed data.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.1
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• pp.113-118
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• 2011

To analyze and verify the effect of replacing thermal storage heater by a cascade cycle heat pump using midnight electricity was installed and tested at a customer's house in Wonju, Korea. The electric night storage heater is consist of 30kW electric heater and 2,700 liters of thermal storage water tank to supply hot water for warming house floor. The power for electric heater was cut off and hot water was only generated by cascade cycle heat pump. Current thermal storage water tank was not eliminated and electric heater wiring was modified. Some operation logic of the heat pump was also modified for proper operation. The required capacity of the heat pump and hot water temperature for given warming condition were estimated. The estimated capacity of heat pump was about 19kW and estimated hot water temperature for proper heating was at least $75^{\circ}C$.

• Journal of Bio-Environment Control
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• v.20 no.4
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• pp.326-332
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• 2011

The growth and bolting characteristics of spring Chinese cabbage cultivars at two night-time temperature treatments such as $5^{\circ}C$ and $10^{\circ}C$ during seedling stage were investigated to establish a safe environmental management strategy for raising seedlings. The low night-time temperature treatments were applied at 5, 10, and 15 days after sawing and the treatment durations were 5, 10, and 15 days in each of treatment beginning. The growth of seedlings in all the tested cultivars were linearly reduced as the treatment duration was extended and no symptoms of bolting were found. The reduction rate in seedling growth of 'Chunkwang' reached to 59.3% at most by 15 days of $5^{\circ}C$ treatment when it be compared to that of control. However, no symptoms of bolting were shown in the treatments of two night-time temperatures until the harvest at 90 days after sawing, indicating that the vernalization effect by low night-time temperature could be mitigated by subsequent day-time optimal temperature management. This study showed that the major spring Chinese cabbage cultivars require more ultimate level of low night-time temperature treatment for the vernalization than this study. It is also supposed that the optimal day-time temperature management can reduce or delay the rate of bolting, even if the seedlings were exposed to short-term low temperature below $5^{\circ}C$ during night-time.

• Journal of Bio-Environment Control
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• v.4 no.2
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• pp.131-135
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• 1995

In winter, most of the energy for a greenhouse crop is supplied during the night. Since watermelon is grown under high night temperature, the experiments were set up to investigate night temperature influence on watermelon in order to obtain the best economic output. Day temperatures ranged from $25^{\circ}C$ and 3$0^{\circ}C$ ; night temperatures ranged from 2$0^{\circ}C$ to 3$0^{\circ}C$ at 5$^{\circ}C$ interval. Two cultivars of watermelon(Citrullus vulgaris S. ‘Binna’ and ‘Kamro’) treated with 30/3$0^{\circ}C$ yielded maximum leaf areas, flowers and leaf numbers. 30(14h)/25(10h)$^{\circ}C$ or 30(12h)/25(12h)$^{\circ}C$ grown plants had higher germination ratio and more dry weight and chlorophyll than those of 30/3$0^{\circ}C$ which were the highest temperature integral. Although 25/$25^{\circ}C$ and 30/2$0^{\circ}C$ regime are same average temperature, the growth of watermelons at 30/2$0^{\circ}C$ was significantly higher than 25/$25^{\circ}C$. ‘Binna’ was growing more than ‘Kamro’ at the same temperature. Leaf area ratio(LAR) was reduced with increasing DIF temperature from 30/3$0^{\circ}C$ to 30/2$0^{\circ}C$, but leaf weight ratio(LWR) was increased.

• Journal of Environmental Science International
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• v.22 no.6
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• pp.667-677
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• 2013

This study aims to examine the actual status of the urban heat island in Daegu by analyzing the data of 17 automatic weather stations installed in the Daegu area. And the results can be summarized as follows: First, regarding the temperature distribution in Daegu by summer time zones, for the 31 days(August 1st till 31st), 18 days showed daily maximum temperature over $30^{\circ}C$, and 11 days indicated daily minimum temperature over $25^{\circ}C$. The day that showed the highest daily maximum temperature was August 5th, which indicated $36^{\circ}C$. Second, about the spatial distribution of time ratio exceeding $30^{\circ}C$ and $25^{\circ}C$, the area with the highest time ratio exceeding $30^{\circ}C$ is mostly the downtown(central area), eastern area, and northern area. Meanwhile, regarding the time ratio exceeding $25^{\circ}C$, the downtown area centering around the central area were high as over 70%, and the outskirts were low as under 65%. Third, considering the temporal distribution of daily maximum temperature and daily minimum temperature, daily maximum temperature was shown around 14:00 to 15:00 while the daily minimum temperature was indicated around 17:00 to 18:00. Daily maximum and minimum temperature were appeared at northeast and downtown, respectively. Fourth, regarding the spatial distribution of tropical days and tropical night days, tropical days showed 77% and tropical night days indicated 42% before and after the 24th and also the 13th each. Tropical days were occurred up to 24 days at northeastern area. And the southwestern area of Daegu showed under 22 days. The downtown showed the 14 days of the tropical night. However, the outskirts indicated relatively few days as under 10 days. Fifth, about the spatial distribution of the average daily temperature range (the difference between the highest temperature and lowest temperature), the central area, the central part of the city, showed the smallest as $7.2^{\circ}C$, and as it was closer to the northern area, it became larger, so in the eastern and northern area, it was over $8.8^{\circ}C$ or so.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.11
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• pp.421-427
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• 2016

The indoor temperature of a building increases during the day due to solar radiation. This behavior is significant in school buildings that are finished with high thermal capacity materials. Moreover, in school buildings, windows cannot be opened until the class has finished owing to the security policy of schools. Consequently, classrooms maintain a high temperature throughout the morning. It is thus important to remove the indoor heat before the commencement of classes in order to reduce the cooling energy needed. The Energy Recovery Ventilator (ERV) system is currently being installed in school buildings for ventilating the classrooms. Night-purge control using ERV can be a good strategy to cool the classroom in advance of the operation of the cooling system. However, the optimal operation method of the ERV for night-purge control has not yet been reported. In this study, the effect of night-purge control with ERV in school buildings is analyzed by simulation method. The results of this study showed that the energy saving effect of night-purge control with ERV is most effective in the case of 2 hours operation prior to the commencement of the first lass and when enthalpy based outdoor air cooling is used.