• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.20 no.7
• /
• pp.639-647
• /
• 2009

In this work, wrapping conductors with thin magnetic materials is proposed as a magnetic shielding method. The 0.1 mm thick metal sheets of mu-metal, grain-oriented electrical steel, and non-oriented electrical steel were produced from commercial alloy sheets through cold rolling and followed high temperature annealing. In case of 3-phase electric currents, mu-metal was the best in shielding performance at a B-field magnitude of about 100 ${\mu}T$, whereas silicon steels were better than mu-metal at a B-magnitude over 500 ${\mu}T$. In addition, wrapping with silicon steel(inner) together with mu-metal(outer) resulted in a shielding factor less than 0.1 even at 500 ${\mu}T$. These results are due to changes in hierarchy of magnetic permeabilities of the materials with increasing magnetic field strength. In case of single-phase electric current, B-magnitude outside the magnetic shell was rather increased compared to the unshielded case. This result is explained by vector composition of B-fields near magnetic shielding materials.

• Journal of Communications and Networks
• /
• v.6 no.4
• /
• pp.352-361
• /
• 2004

In this paper, we study how to achieve the maximum capacity under delay constraints for large mobile wireless networks. We develop a systematic methodology for studying this problem in the asymptotic region when the number of nodes n in the network is large. We first identify a number of key parameters for a large class of scheduling schemes, and investigate the inherent tradeoffs among the capacity, the delay, and these scheduling parameters. Based on these inherent tradeoffs, we are able to compute the upper bound on the maximum per-node capacity of a large mobile wireless network under given delay constraints. Further, in the process of proving the upper bound, we are able to identify the optimal values of the key scheduling parameters. Knowing these optimal values, we can then develop scheduling schemes that achieve the upper bound up to some logarithmic factor, which suggests that our upper bound is fairly tight. We have applied this methodology to both the i.i.d. mobility model and the random way-point mobility model. In both cases, our methodology allows us to develop new scheduling schemes that can achieve larger capacity than previous proposals under the same delay constraints. In particular, for the i.i.d. mobility model, our scheme can achieve (n-1/3/log3/2 n) per-node capacity with constant delay. This demonstrates that, under the i.i.d. mobility model, mobility increases the capacity even with constant delays. Our methodology can also be extended to incorporate additional scheduling constraints.

• Journal of the Korean Society of Costume
• /
• v.52 no.2
• /
• pp.59-70
• /
• 2002

For the purpose of providing basic data for the development of size specifications for middle-aged women in Busan, one dimensional measurements were made with the subjects. ranging 45 to 59 in age. The following are the conclusions : 1) According to ages, the middle and elder groups of the middle-aged women shared similar body types, having shorter height, more lowered bust. and increased upper-body depth and girth factors, compared with the earlier middle-aged women group. But the thigh girth of the elder middle-aged group (age: 55∼59) was the lowest, maybe owing to the aged lower-body muscles. 2) In the comparison with national averages. armhole girth, elbow girth, wrist girth. back waist length, side neck point-B.P.-waist line, and sleeve length showed great differences. This is problematic in that the national size standards fail to reflect each legion\`s peculiar body type characteristics. 3) Even though body types were classified according to drop value criteria suggested by KS specifications, 23.05% did not belong to the criteria. They were thus classified as A, N, and H body types, following the distribution of the present experiment. 4) In consideration of the economy factor of the production and sales of the clothes industry, the combinations of height and chest garth for the middle-aged Busan women were as follows: 155cm-85cm (Body Type A) 150cm-88cm (Body Type N), and 155cm-94cm (Body Type H).

• The Korean Journal of Nuclear Medicine Technology
• /
• v.13 no.1
• /
• pp.67-72
• /
• 2009

Purpose: ISCD (International Society for Clinical Densitometry) requests that users perform mandatory Precision test to raise their quality even though there is no recommendation about patient selection for the test. Thus, we investigated the effect on precision test by measuring reproducibility of 3 bone density groups (normal, osteopenia, osteoporosis). Materials and Methods: 4 users performed precision test with 420 patients (age: $57.8{\pm}9.02$) for BMD in Asan Medical Center (JAN-2008 ~ JUN-2008). In first group (A), 4 users selected 30 patient respectively regardless of bone density condition and measured 2 part (L-spine, femur) in twice. In second group (B), 4 users measured bone density of 10 patients respectively in the same manner of first group (A) users but dividing patient into 3 stages (normal, osteopenia, osteoporosis). In third group (C), 2 users measured 30 patients respectively in the same manner of first group (A) users considering bone density condition. We used GE Lunar Prodigy Advance (Encore. V11.4) and analyzed the result by comparing %CV to LSC using precision tool from ISCD. Check back was done using SPSS. Results: In group A, the %CV calculated by 4 users (a, b, c, d) were 1.16, 1.01, 1.19, 0.65 g/$cm^2$ in L-spine and 0.69, 0.58, 0.97, 0.47 g/$cm^2$ in femur. In group B, the %CV calculated by 4 users (a, b, c, d) were 1.01, 1.19, 0.83, 1.37 g/$cm^2$ in L-spine and 1.03, 0.54, 0.69, 0.58 g/$cm^2$ in femur. When comparing results (group A, B), we found no considerable differences. In group C, the user_1's %CV of normal, osteopenia and osteoporosis were 1.26, 0.94, 0.94 g/$cm^2$ in L-spine and 0.94, 0.79, 1.01 g/$cm^2$ in femur. And the user_2's %CV were 0.97, 0.83, 0.72 g/$cm^2$ L-spine and 0.65, 0.65, 1.05 g/$cm^2$ in femur. When analyzing the result, we figured out that the difference of reproducibility was almost not found but the differences of two users' several result values have effect on total reproducibility. Conclusions: Precision test is a important factor of bone density follow up. When Machine and user's reproducibility is getting better, it’s useful in clinics because of low range of deviation. Users have to check machine's reproducibility before the test and keep the same mind doing BMD test for patient. In precision test, the difference of measured value is usually found for ROI change caused by patient position. In case of osteoporosis patient, there is difficult to make initial ROI accurately more than normal and osteopenia patient due to lack of bone recognition even though ROI is made automatically by computer software. However, initial ROI is very important and users have to make coherent ROI because we use ROI Copy function in a follow up. In this study, we performed precision test considering bone density condition and found LSC value was stayed within 3%. There was no considerable difference. Thus, patient selection could be done regardless of bone density condition.

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.123-125
• /
• 2004

This paper describes an optimal configuration of Community Energy System (CES) for the multi-energy consumers and analyzes economical feasibility for such system. The most of previous feasibility studies for Co-Generation plants of CES in Korea have shown negative results due to the abnormally low price of power rate in Korea. However, in order to overcome this situation a new approach was examined in this Paper. The efforts of this approach the selection of the low price but reliable facility and maximizing the capacity factor of the facility. MGT was selected in view of low price and good reliability. In order to maximize the capacity factor the system capacity should be quite lower than the actual required Electrical and Heat load of the subject entity. In this report 100 kW Co-Generation facility was selected in view of conservative analysis. The results of the analysis showed that pay back period may vary from 4 to 5 yens according to the application of LNG rates whether it is to-generation rate or the normal business rate. With the analysis in this paper we confirmed that CES is feasible even in Korea if we do not insist to select the capacity of CES to cover all the energy required but select a smaller size of CES compared to the actual requirement, which can allow full load operation of the system continuously.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.11
• /
• pp.1379-1389
• /
• 1999

A new technique for control of size and shape of flame-made particles is Introduced. The characteristic sintering time can be controlled Independently of collision time by heating the particles with irradiation of laser because the sintering time strongly depends on temperature. A coflow oxy-hydrogen diffusion flame burner was used for $SiCl_4$ conversion to silica particle. Nanometer sized aggregates irradiated by a high power CW $CO_2$ laser beam were rapidly heated up to high temperatures and then were sintered to approach volume-equivalent spheres. The sphere collides much slower than the aggregate, which results in reduction of sizes of particles maintaining spherical shape. Light scattering of Ar ion laser and TEM observation using a local sampling device were used to confirm the above effects. When the $CO_2$ laser was irradiated at low position from the burner surface, particle generation due to gas absorption of laser beam occurred and thus scattering intensity increased with $CO_2$ laser power. At high irradiation position, scattering intensity decreased with $CO_2$ laser power and TEM image showed a clear mark of evaporation and recondensation of particles for high $CO_2$ laser power. When the laser was irradiated between the above two positions where small aggregates exist, average size of spherical particles obviously decreased to 58% of those without $CO_2$ laser irradiation with the spherical shape. Even for increased carrier gas flow rate by a factor of three, TEM photograph also revealed considerable reduction of particle size.

• Korean Journal of Environmental Agriculture
• /
• v.27 no.1
• /
• pp.1-9
• /
• 2008

The main purpose of this study is to accumulate the fundamental data representing groundwater of plastic film houses by means of water quality and its multivariate statistical analysis. Groundwater samples were collected in every two years since 2000 to 2004 from total 211 sites. According to the result of water quality analysis, ground water quality was suitable for irrigation purpose averagely. Correlation analysis showed that EC was highest positively correlated with $Mg^{2+}$ to 0.810(p<0.01), 0.776(p<0.01) in April and July, respectively. $NO_3-N$ was highest positively correlated with T-N to 0.794(p<0.01) in October. This result shows that it can lead to a different result even in similar case sometimes. Four factors were extracted through factor analysis in April and July, but five factors were extracted in October. The proportions of cumulative variance by the factor were 64.9, 60.2, and 70.7 in April, July, and October, respectively. The first factor was highly related to anions and cations such as $Ca^{2+},\;Mg^{2+},\;Cl^-,\;{SO_4}^{2-}$, and EC in contrast to that of stream water. According to the cluster analysis, 211 sites are classified into four groups. Common type of ground water quality was shown in group A. The pH and $PO_4-P$ were highest in Group B. The anions and cations were highest in Group C. $COD_{Cr}$ was highest in Group D.

• Journal of agricultural medicine and community health
• /
• v.44 no.4
• /
• pp.209-219
• /
• 2019

Objectives: This study investigated musculoskeletal symptoms in upper limbs according to the working environment (job stress) of dental hygienists and examine their relationship with upper limb functions. Methods: The subjects include 198 dental hygienists in dental hospitals and dental clinics in Pusan and Gyeongnam. The questionnaire was consisted of general characteristics of the subjects, job stress, musculoskeletal symptoms in upper limbs and function (Disability Measurement Tool for Upper Extremity Disorders-11, DASH-11). Results: The study was analyzed their musculoskeletal symptoms in upper limbs according to their general characteristics and found that the symptoms occurred in the neck (39.4%), the shoulders (54.6%), elbows (14.7%), and the hands (50.0%). Job stress was associated with upper limb functions (DASH-11) (model 3, B=5.210, p=0.012) and repeated elbow bending and spreading posture was associated with DASH-11 (model 3, B=6.561, p=0.029). Elbow symptoms were associated with DASH-11 in the upper limbs (B=10.679, p=0.003). Conclusion: Dental hygienists are experiencing limitations of upper limb function due to job stress. In particular, even if the correction of their uncomfortable posture is significantly related to the job stress and upper limb function, in order to improve the upper limb function of the dental hygienist, efforts to reduce the job stress as well as the uncomfortable posture are necessary.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.4
• /
• pp.487-493
• /
• 2017

The main purpose of this study is to evaluate the main parameters involved in the asphalt pavement distresses, including IRI (International Rough Index), fatigue, and permanent deformation. The main parameters are the region (Seoul and Busan), traffic level, asphalt binder, maximum aggregate of surface course, thickness of the surface course and base. A total of 64 case studies were carried out under the auspices of the KPRP (Korea Pavement Research Program). From the analysis of the KPRP test results, the key factors for the asphalt pavement distress were determined. Considering the effect of one variable in the basic condition, asphalt binder was the major factor having an effect on the distresses for an AADT (Annual Average Daily Traffic) of 5000 in the Seoul area. Among the remaining factors, the results were found to be in the order of the base layer thickness (A), surface layer thickness (B), and aggregate particle size thickness (D). The same results were obtained for an AADT of 10000. In the case of Busan with an AADT of 5000, the same result was obtained as for Seoul. Among the remaining factors, the results were in the order of the base layer thickness (A), aggregate particle thickness (D), and surface layer thickness (B). Even though there was a slight difference in the effect of the traffic level and region, asphalt binder was the parameter having the greatest effect on the asphalt pavement distress. In the case where the effect of multiple parameters was analyzed, the combination of the asphalt binder and base thickness showed a relatively strong effect.

• THE INTERNATIONAL COMMERCE & LAW REVIEW
• /
• v.45
• /
• pp.85-109
• /
• 2010

L/C provides the exporter and the importer with safe assurance in the exchange of goods for payment in international trade. It involves a number of parties. Although the parties may have confidence in their client, bad faith or ignorance of international banking practice by any of these parties could cause the failure of transaction, which makes international trade a risky business. Most of the risks are found in transport document, which can cause disputes. There are many factors in the risk of transport documents under L/C transaction. One most common risk factor for the beneficiary in all transport documents is even if there is no discrepancy in document, the issuing bank or the applicant refuses to pay or delay payment insisting there is a discrepancy. In some very rare cases, the beneficiary may not get paid due to unfair injunction of the local court of the applicant. For the applicant, most common risk factors are fake bill and fraud. Risks classified according to the sorts of transport documents are as follows. 1. In B/L, payment can be refused because it is regarded as charter party B/L, although there is no real charter party contract. And the applicant can bear the potential risk of the loss or deterioration of cargo through transhipment of the cargo loaded on board in container if transhipment is prohibited without excluding of UCP 600 article 20 (c). 2. In charter party B/L, the applicant may take delivery without paying when charter party B/L is signed by charterer, which can result in a big loss for the beneficiary and the negotiating bank. And risks may arise when cargo is seized because the charterer does not pay the hire. The applicant and the issuing bank are also vulnerable to a risk - Against whom should they file a suit when cargo gets damaged during transportation? 3. In multimodal transport document, which is subject to a conflict because there is a big difference in viewpoints between transport industry and banks, conflicts may also arise when L/C requires ocean B/L and accepts multimodal transport document at the same time, but does not specify the details. 4. In air waybill, where the consignee is not the issuing bank but the applicant, risks may take place to the beneficiary when the applicant takes delivery but refuses to pay asserting minor discrepancies in document. The applicant may also bear the risk when cargo may not be loaded because air waybill is a received bill. Another risk may arise when although the applicant prohibits transhipment without excluding UCP 600 article 23 (c), the cargo may be transhipped, provided that the entire carriage is covered by one and the same air waybill.