• Journal of the Society of Naval Architects of Korea
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• v.33 no.4
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• pp.1-14
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• 1996

Especially in the case of a full form ship, the stability on course can be considered to become severest among 4 items of criteria in Interim Standards for Ship Maneuverability adopted by IMO in 1993. The purpose of this study is to find some ideas for the improvement of stability on course through changes in rudder area with reference to span distance. In this paper, we established the formula on the relation between the experimental constants relevant to rudder normal force and hydrodynamic derivatives of hull-propeller-rudder system. We carried out various kinds of captive model test relevant to rudder normal force etc., and evaluated hydrodynamic derivatives of hull-propeller-rudder system, and analyzed the stability on course with the parameter of changes in rudder area. Furthermore, we also discussed effects of changes in rudder area on maneuvering performance including stability on course, based on computer simulation. As a result, it is clarified that there is a possibility that stability on course may become bad through an increase of rudder area. The reason for the bad stability on course is that the void space between the upper edge of rudder and the lower part of stern overhang decreases. This space change exerts a great influence on straightening coefficient of incoming flow to rudder in maneuvering motion, which has close relation to stability on course.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.10 no.1
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• pp.47-57
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• 2016

In this paper, we measured human body signals in order to verify a active harness system that we developed for gait and balance training. The experimental procedure was validated by tests with 20 healthy male subjects. They conducted motions of Activities of Daily Living(ADL)(Normal Walking, Stand-to-Sit, Sit-to-Stand, Stair Walking Up, and Stair Walking Down) according to body weight support rates (0%, 30%, 50% of subjects' body weight). The effectiveness of the active harness system is verified by using the results of foot pressure distribution. In normal walking, the decrease of fore-foot pressure, lateral soleus muscle and biceps femoris muscle were remarkable. The result of stand-to-sit results motion indicated that the rear-foot pressure and tibialis anterior muscle activities exceptionally decreased according to body weight support. The stair walking down show the marked drop of fore-foot pressure and rectus femoris muscle activities. The sit-to-stand and stair walking up activities were inadequate about the effect of body weight support because the velocity of body weight support system was slower than male's activity.

• PNF and Movement
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• v.16 no.1
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• pp.43-50
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• 2018

Purpose: This study examined the effects of a shoulder-strengthening exercise on muscle strength of shoulder flexors and extensors of caregivers. Methods: The study consisted of 19 caregivers (2 males and 17 females) employed by Medical Center B. All the participants took part in an 8-week shoulder muscle strengthening exercise, based on previous studies. In the first week, the subjects took part in a stretching exercise enhance the range of motion. In the second week, they participated in an exercise aimed at improving shoulder blade stability. From the third to seventh weeks, a resistance exercise of different intensities was applied in a phased manner. Finally, in the eight week, the subjects took part in plyometric exercise. Peak torque, average power, and total work of shoulder flexors and extensors in both sides were measured before and after the exercise at an angular speed of 120deg/sec using an isokinetic device. Wilcoxon's singed-ranks test was conducted to analyze differences in muscle strength before and after the intervention. Results: After the exercise, there was a significant improvement in peak torque and average power of flexors of the right arm. After the exercise, peak torque, total work, and average power showed a significant improvement in the flexors of the left arm (p<0.05). However, there was no statistically significant difference in extensor muscle strength in either arm after the exercise. Conclusion: Shoulder flexors of caregivers are utilized frequently in the workplace. Implementation of extensor-strengthening exercises, in addition to flexor-strengthening exercises, can contribute to reducing the incidence rate of shoulder injuries among caregivers.

• Physical Therapy Korea
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• v.18 no.1
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• pp.57-63
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• 2011

The purpose of this study was to identify the effects of manual facilitation and a stick on lumbar and hip joint flexion angles in subject with lumbar flexion syndrome during forward bending from a sitting position. Fifteen subjects with lumbar flexion syndrome were recruited for this study. As a pretest, all subjects performed three repetitions of bending the trunk forward until the tips of their fingers touched the target bar. After this pretest, the subjects practiced the forward bending of the trunk 10 times, using either manual facilitation or a stick. Then, as a posttest, all subjects repeated the pretest procedure. The flexion angles of lumbar spine and hip joint during forward bending in a sitting position were measured using a three-dimensional motion analysis system. A paired t-test was used to determine the statistical differences between pre-test and post-test flexion angles and pre- and post-test flexion angle differences between forward bending with manual facilitation and forward bending with a stick. The level of statistical significance was set at p=.05. The results of the study showed that the angle of the lumbar flexion decreased significantly and the bilateral hip flexion angle increased significantly when performing forward bending with stick and manual facilitation. Furthermore, the angle of lumbar flexion decreased significantly and the angle of bilateral hip flexion increased significantly in forward bending with a stick compared to forward bending with manual facilitation. The findings of this study indicate that both forward bending with manual facilitation and sticks could be used to prevent excessive lumbar flexion and increase hip flexion, and that forward bending with a stick is more effective than forward bending with manual facilitation for inducing lumbar spine and hip joint angle changes.

• Journal of the Korean earth science society
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• v.38 no.2
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• pp.161-171
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• 2017

Observed ground motions are composed of three factors such as, seismic source, attenuation, and site amplification effect. Among them, the site amplification characteristics should be considered significantly when estimating seismic source and attenuation characteristics with more confidence. The site effect is also necessary when estimating not only seismic hazard in seismic design engineering but also rock mechanical properties. This study uses the method of H/V spectral ratio of observed ground motion between target site and reference site called a reference site method. In addition to using the vertical Fourier spectrum of the reference site, we try out the horizontal Fourier spectrum as a new method in this study. We analyze H/V spectral ratio of six ground motions respectively, observed at four sites close to Yedang Reservoir. We then compare site amplification effects at each site using 3 kinds of seismic energies including S waves, Coda waves energy, and background noise. The results suggest that each site showed similar site amplification patterns in S waves and Coda waves energy. However, the site amplification of background noise shows much different characteristics from those of S waves and Coda wave energy, which suggests that the background noises at each site have their own developing mechanism. Each station shows its own characteristics of specific resonance frequency and site amplification properties in low, high and specific resonance frequency ranges. Comparison of the method used in this study to the others that used different methods can provide us with more information about the dynamic amplification of a site characteristics and site classification.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.500-509
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• 2013

This study reports a numerical analysis of the internal flow characteristics of the integrated urea-SCR muffler system with the various geometries of the multi-perforated tube which is set up between the muffler inlet and in front of SCR catalysts. The multi-perforated tube is generally used to disperse uniformly the urea-water solution spray and to make better use of the SCR catalyst, resulting in the increased $NO_x$ reduction and decreased ammonia slip. The effects of the multi-perforated tube orifice area ratios on the velocity distributions in front of the SCR catalyst, which is ultimately quantified as the uniformity index, were investigated for the optimal muffler system design. The steady flow model was applied by using a general-purpose commercial software package. The air at the room temperature was used as a working fluid, instead of the exhaust gas and urea-water solution spray mixture. From the analysis results, it was clarified that the multi-perforated tube geometry sensitively affected to the formation of the bulk swirling motion inside the plenum chamber set in front of the SCR catalyst and to the uniformity index of the velocity distribution produced at the inlet of the catalyst.

• Journal of Positioning, Navigation, and Timing
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• v.6 no.3
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• pp.125-133
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• 2017

Time comparison is necessary for the verification and synchronization of the clock. Two-way satellite time and frequency (TWSTFT) is a method for time comparison over long distances. This method includes errors such as atmospheric effects, satellite motion, and environmental conditions. Ionospheric delay is one of the significant time comparison error in case of the carrier-phase TWSTFT (TWCP). Global Ionosphere Map (GIM) from Center for Orbit Determination in Europe (CODE) is used to compare with Bernese. Thin shell model of the ionosphere is used for the calculation of the Ionosphere Pierce Point (IPP) between stations and a GEO satellite. Korea Research Institute of Standards and Science (KRISS) and Koganei (KGNI) stations are used, and the analysis is conducted at 29 January 2017. Vertical Total Electron Content (VTEC) which is generated by Bernese at the latitude and longitude of the receiver by processing a Receiver Independent Exchange (RINEX) observation file that is generated from the receiver has demonstrated adequacy by showing similar variation trends with the CODE GIM. Bernese also has showed the capability to produce high resolution IONosphere map EXchange (IONEX) data compared to the CODE GIM. At each station IPP, VTEC difference in two stations showed absolute maximum 3.3 and 2.3 Total Electron Content Unit (TECU) in Bernese and GIM, respectively. The ionospheric delay of the TWCP has showed maximum 5.69 and 2.54 ps from Bernese and CODE GIM, respectively. Bernese could correct up to 6.29 ps in ionospheric delay rather than using CODE GIM. The peak-to-peak value of the ionospheric delay for TWCP in Bernese is about 10 ps, and this has to be eliminated to get high precision TWCP results. The $10^{-16}$ level uncertainty of atomic clock corresponds to 10 ps for 1 day averaging time, so time synchronization performance needs less than 10 ps. Current time synchronization of a satellite and ground station is about 2 ns level, but the smaller required performance, like less than 1 ns, the better. In this perspective, since the ionospheric delay could exceed over 100 ps in a long baseline different from this short baseline case, the elimination of the ionospheric delay is thought to be important for more high precision time synchronization of a satellite and ground station. This paper showed detailed method how to eliminate ionospheric delay for TWCP, and a specific case is applied by using this technique. Anyone could apply this method to establish high precision TWCP capability, and it is possible to use other software such as GIPSYOASIS and GPSTk. This TWCP could be applied in the high precision atomic clocks and used in the ground stations of the future domestic satellite navigation system.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.2
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• pp.151-160
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• 2017

Growing demand and rapid development of the synthetic fiber rope in mooring system have taken place since it has been used in deep water platform lately. Unlike a chain mooring, synthetic fiber rope composed of lightweight materials such as Polyester(polyethylene terephthalate), HMPE(high modulus polyethylene) and Aramid(aromatic polyamide). Non-linear stiffness and another failure mode are distinct characteristics of synthetic fiber rope when compared to mooring chain. When these ropes are exposed to environmental load for a long time, the length of rope will be increased permanently. This is called 'the creep phenomenon'. Due to the phenomenon, The initial characteristics of mooring systems would be changed because the length and stiffness of the rope have been changed as time goes on. The changed characteristics of fiber rope cause different mooring tension and vessel offset compared to the initial design condition. Commercial mooring analysis software that widely used in industries is unable to take into account this phenomenon automatically. Even though the American Petroleum Institute (API) or other classification rules present some standard or criteria with respect to length and stiffness of a mooring line, simulation guide considers the mechanical properties that is not mentioned in such rules. In this paper, the effect of creep phenomenon in the fiber rope mooring system under specific environment condition is investigated. Desiged mooring system for a Mobile Offshore Drilling Unit(MODU) with HMPE rope which has the highest creep is analyzed in a time domain in order to investigate the effects creep phenomenon to vessel offset and mooring tension. We have developed a new procedure to an analysis of mooring system reflecting the creep phenomenon and it is validated through a time domain simulation using non-linear mooring analysis software, OrcaFlex. The result shows that the creep phenomenon should be considered in analysis procedure because it affects the length and stiffness of synthetic fiber rope in case of high water temperature and permanent mooring system.

• Journal of the Korean Institute of Landscape Architecture
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• v.44 no.4
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• pp.66-74
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• 2016

In what way is the urban landscape of North Korea used today, and what features do people prefer in the North Korean landscape? This study analyzed the characteristics of Pyongyang landscapes and their effects, based on an analysis of Western tourists motivation for tourism in North Korea and preferred enjoyment-seeking experiences. Using data from the tourist agency specializing in Western tourism in North Korea and a location based photo-sharing service, the study interprets the visual distinctiveness of Pyongyang landscape. The study concluded that widely known risk to travelers in North Korea is in fact an attraction, making people want to visit directly. However, this risk was mitigated in practical experience by the overall intermediation of the tourism agency and locals' conscious behavior to keep their distance from foreigners. Next, the scope of National ritual attributes was expanded to the locals' daily life as well as large-scale events such as mass games and military parades only if for national holidays. Also, the most preferred factors contributing to North Korean tourism were based on departure from routine through mobilization of the residents. This indicates the extension that the nature of North Korea as a theater state. The Pyongyang landscape represents a world politically isolated, people's congregated motion to display to the world, and people's lives hidden beneath a veil. These visualities fulfill the fantasy of Westerners regarding North Korea. Furthermore, these are superficial images that help create a basis to maintain the North Korea regime.

• Journal of radiological science and technology
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• v.21 no.1
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• pp.52-58
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• 1998

We can and must improve the diagnostic images using available knowledge and technology. At the same time we must strive to reduce the patient's integral and entrance radiation dose. Reducing the integral dose to the patient during the radiologic procedure is a primary concern of the patient, especially the pediatric patient, the radiologist and the technologist. A 100cm focal film distance generally is used for most over-table radiography. The early x-ray tubes and screen film combinations required long exposures, which often resulted in motion artifacts. But nowaday, we have the generators and x-ray tubes that can deliver the energy necessary in a very short time and the receptors that can record the information just as rapidly. And, we performed this studies to evaluate the patient exposure dose and the image quality by increasing focal film distance in diagnostic radiography. There are many factors which affected to exposure factor, but we studied to verify of FFD increase, only. Effect of increasing the focal film distance to a 140 cm distance was tested as follows; 1. The focal film distances were set at 100, 120, and 140cm. 2. A 18cm acryl(tissue equivalent) phantom was placed on the table top. 3. An Capintec 192 electrometer with PM 05 ion chamber was placed at the entrance surface of the phantom, and exposure were made at each focal film distances. 4. The procedure was repeated in the same manner as above except the ion chamber was placed beneath the phantom at the film plane. 5. Exit exposure were normalize to 8mR for each portions of the experiment. Based on the success of the empirical measurements, a detailed mathematical analysis of the dose reduction was performed using the percent depth dose data. The results of this study can be summerized as followings ; 1) Increasing FFD from 100 cm to 140 cm, we would create a situation that would have a significant effect on the overall quality of radiograph and achive the 17.42% reduction of entrance dose and the 18.95% reduction of integral dose that the patient receives. 2) Thickness of Al step wedge for equal film density increased with the long distance. 3) Increasing FFD, Magnification of image was lowered. 4) Resolution of image also increased with the FFD. As the results described above, we strongly recommend using the long FFD to provide better information for our patients and profession in abdomen radiographic studies.