• International Journal of Air-Conditioning and Refrigeration
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• 제16권3호
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• pp.77-82
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• 2008

For heat pumps used in a cold region, it is very important to obtain appropriate heating capacity. Several studies using a variable speed compressor and an additional heater have been performed to enhance heating capacity at low ambient temperatures. However, for outdoor temperature conditions below $-15^{\circ}C$, it is still difficult to obtain enough heating capacity above the rated value. In recent studies, the application of gas injection technique into a two-stage heat pump yielded noticeable heating performance improvement at low temperature conditions. In this study, the heating performance of a two-stage gas injection heat pump with a rated capacity of 3.5 kW was measured and analyzed by varying refrigerant charge amount and EEV opening at the standard heating condition. The heating performance of the two-stage gas injection heat pump was compared with that of a two-stage non-injection heat pump. The heating capacity and COP of the two-stage gas injection heat pump were improved by 2-10% at the optimal charging condition over those of the two-stage non-injection heat pump.

• 한국산학기술학회논문지
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• 제14권11호
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• pp.5352-5356
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• 2013

최근 플라스틱 성형품은 기능적인 측면뿐만 아니라 디자인 및 광택과 같이 시각적으로 즉각 식별이 가능한 부분에 까지 많은 관심과 주의를 기울이고 있다. 이와 관련하여 성형품 광택의 제어를 위하여 성형조건이 광택에 미치는 영향에 대한 연구가 필요하지만 관련 연구는 아직 충분히 이루어지지 않고 있다. 따라서 본 연구는 플라스틱 성형품의 외관에 주로 사용되는 ABS (Acrylonitrile-Butadiene-Styrene) 플라스틱 성형품에 대하여 사출압력, 사출속도, 보압력, 수지온도, 금형온도 등의 사출조건의 변화가 성형품의 외관 광택에 미치는 영향에 대하여 사출실험을 통하여 연구하였다. 연구 결과에서 보압력이 가장 큰 영향을 미침을 알 수 있었다. 특히, 보압력 55 - 75MPa 범위에서는 광택도가 증가하지만 그 이상 증가하면 광택이 감소하는데, 그 원인은 SEM(Scanning Electron Microscope)을 통하여 수지 내부의 고무 입자의 변형에 기인한다고 유추할 수 있었다.

• 한국자동차공학회논문집
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• 제9권5호
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• pp.23-29
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• 2001

This paper is the second of companion papers, which investigate port-masking effects on emission and fuel economy. Port-masking was applied to commercial SOHC 3-valve engine by inserting masking plates between manifold and port. To induce various conditions of stratification, six types of masking plates were applied. In this paper, main interest is focused on the influence of injection timing on emission and fuel economy. Various injection timing was applied to the six cases, under the stoichiometric and lean-limit air-fuel ratio. Under the stoichiometric condition, an explanation about the reason of the change in emission level due to injection timing change is given. It is observed that NOx emission under the LML condition varies significantly when the injection timing changes.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.180-183
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• 2006

The contraction rate is a very important element that dominate quality of product in plastic injection molding. To get wanted products, the contraction rate of used resin must be considered necessarily when designing plastic injection molds, and suitable deform conditions must be chosen with this. In this paper, important parts used in LED department were produced by injection mold using POM resin, and dimension error that happened by contraction rate of resin was corrected and reflected in die design and suitable deform conditions were decided.

• 대한기계학회논문집A
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• 제30권6호
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• pp.615-621
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• 2006

Increased application of optical disks requires more improved dynamic stability of rotating disks. In this study, a new concept of controlling the processing conditions of injection molded disks was developed to improve vibration characteristics. The critical speed, which shows stiffness and dynamic stability of disk, is affected by the residual stress distribution; this varies as functions of distance from the gate and processing condition. The critical speed of disk was calculated with the initial stress taken into consideration, which was determined from injection molding simulation. Choosing melt temperature, mold temperature, filling speed and packing pressure as design parameters, critical speed is maximized with the method of response surface. It is shown that the stability of injection molded disk has been improved for the new condition obtained as a result of the study proposed.

• 한국안전학회지
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• 제13권1호
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• pp.19-25
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• 1998

In this study, proper injection molding condition has been studied through stress relaxation tests in order to experimentally investigate the effect of the condition on softening of mold product, using specimens produced under the different conditions according to the recommendation of resin manufactures. As a result, softening of the specimens was found to be strongly influenced by material melting temperature. The specimen with higher material melting temperature is found to have lower softening. However, softening of the specimen with lower mold temperature has an decrement, compared with other specimens. In particular, specimen with notch is influenced by mold temperature. The softening increase with higher injection speed and pressure. Finally in order to improve softening, material melting temperature, injection speed and injection pressure were found to be increased with low mold temperature.

• 한국분무공학회지
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• 제13권1호
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• pp.51-57
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• 2008

The objective of this study was to investigate the spray characteristics of commercial biodiesel fuel at various fuel injection conditions. To examine the effect of various factors on the development of a biodiesel sprays, experiments were conducted at the various injection pressures, ambient pressures and blending ratio of bio-diesel fuels. As a result of experimental study, it was shown that the increase of blending ratio of biodiesel had little influence on spray behaviors under applied fuel injection condition in this study. Because macroscopic characteristics of biodiesel-blended diesel fuel were almost same as that of petrodiesel fuels, it was found that the commercial biodisel is applicable to conventional diesel engine.

• Journal of Dental Anesthesia and Pain Medicine
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• 제19권3호
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• pp.159-165
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• 2019

Background: Dental procedures commonly involve the injection of local anesthetic agents, which causes apprehension in patients. The objective of dental practice is to provide painless treatment to the patient. The purpose of this study was to evaluate the effect of Low Level Laser Therapy (LLLT) in reducing the pain due to local anesthetic injection. Materials and Methods: A prospective, split-mouth study was conducted on 25 patients. In Condition A, LLLT was administered followed by the administration of a standard local anesthetic agent. Patients' perception of pain with use of LLLT was assessed based on a Visual Analogue Scale (VAS). In Condition B, LLLT was directed to the mucosa but not activated, followed by the administration of local anesthesia. VAS was used to assess the pain level without the use of LLLT. Results: Comparison between Condition A and Condition B was done. A P value < 0.001 was considered significant, indicating a definite statistical difference between the two conditions. Conclusion: In our study, we observed that LLLT reduced pain during injection of local anesthesia. Further multi-centric studies with a larger sample size and various modifications in the study design are required.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2005년도 추계 학술대회논문집
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• pp.39-44
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• 2005

In HANARO, a multi-purpose research reactor of 30 MWth, the emergency water supply system consists essentially of an emergency water storage tank located in the level of about thirteen meter (13 m) above the reactor core, a three inch ('3\%') diameter water injection pipe line including injection valves from the tank to the reactor cooling inlet pipe and a test loop to do periodic system performance test. When the water level of the reactor pool comes down to the extremely low due to a loss of reactor pool water accident the emergency water stored in the tank should be fed to the core by the gravity force and at that time the design flow rate is eleven point four kilogram per second (11.4 kg/s). But it is impossible periodically to measure the injection flow rate under the emergency condition because the normal water level should be maintained during the reactor operation. This paper describes a flow network analysis to simulate the flow rate under the emergency condition. As results, it was confirmed through the analysis results that the calculated flow rate agrees with the design requirement under the emergency condition.

• 한국유체기계학회 논문집
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• 제17권6호
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• pp.104-108
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• 2014

The recent Fukushima nuclear power plant accidents shows that the core make up at high RCS pressure condition is very important to prevent core melting. The core make up flow at high pressure condition should be driven by gravity force or passive forces because the AC-powered safety features are not available during a Station Black Out (SBO) accident. The reactor Coolant System (RCS) mass inventory is continuously decreased by releasing steam through the pressurizer safety valves after reactor trip during a SBO accident. The core will be melted down within 2~3 hours without core make up action by active or passive mode. In the new design concept of a Hybrid Safety Injection Tank (Hybrid SIT) both for low and high RCS pressure conditions, the low pressure nitrogen gas serves as a charging pressure for a LBLOCA injection mode, while the PZR high pressure steam provides an equalizing pressure for a high pressure injection mode such as a SBO accident. After the pressure equalizing process by battery driven initiation valve at a high pressure SBO condition, the Hybrid SIT injection water will be passively injected into the reactor downcomer by gravity head. The SBO simulation by MARS code show that the core makeup injection flow through the Hybrid SIT continued up to the SIT empty condition, and the core heatup is delayed as much.