• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.56-62
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• 2000

The purpose of this study was to assess the effects of restorative materials on the marginal leakage of wedge-shaped class V cavity. The study was performed in vitro in 25 defect-free permanent, extracted teeth. Wedge-shaped class V cavities were prepared and then the teeth were randomly selected and restored according to the following. Group A : restoration with Tetric Ceram(composite resin) Group B : restoration with Tetric flow(flowable resin) Group C : restoration with Compoglass after acid etching(compomer) Group D : restoration with Compoglass(compomer) Group E : restoration with Fuji II LC improved(resin-modified GIC) After thermocycling, the specimens were immersed in 5% basic fuchsin solution for 6 hours and sectioned longitudinally through the center of the restoration. The degree of marginal leakage was measured as the extent of dye penetration under the stereomicroscope. The data were analysed using one-way ANOVA. When significant differences found, multiple comparisons were made using Duncan's Multiple Range Test. The results were as follows: 1. The occlusal margins of all groups except for Fuji II LC improved showed lesser leakage than gingival margins and there was statistically significant difference(p<0.05). 2. At the occlusal margins, group A, B showed same marginal leakage scores, and others were decreased as group C, D, E in that order. There were statistically significant difference between group A, Band group D, E, group C and group E(p<0.05). 3. At the gingival margins, group B, C showed same marginal leakage scores, and others were decreased as group A, D, E in that order. But there was statistically significant difference between group B, C and group E(p<0.05). 4. In the Compoglass restoration, acid-etching technique was beneficial for marginal sealing ability at all of margins. But there was no statistically significant difference (p>0.05). In the restorations for wedge-shaped class V cavities, resin restoration with acid etching technique is recommended.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.11 no.3
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• pp.190-197
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• 2001

Noise-induced hearing loss(NIHL) was the highest rate (43.5%~58.5% from 1996 to 1998) of positive findings through specific medical program in Korea. There were much more NIHL at workers of automobile manufacturing factories than other manufacturing factories. The specific aim of the present study was to determine the noise exposure of automobile press lines, according to their job titles, press line types(auto, semiauto), dosimeter parameters setting. There were a total 11 press lines sampled at a automobile manufacturing company. Among those press lines, 10 press lines were autolines with acoustic enclosure, one semiauto press line was no aucostic enclosure Noise exposure data were sampled for an work shift using noise dosimeter, which recorded both time-weighted average(TWA) and 1-min average. The mean OSHA TWA(Korea TWA with threshold 90) was $80.7dB(A){\pm}4.7dB(A)$ for leader, $82.8dB(A{\pm}4.5dB(A)$ for pallette man, $76.7dB(A){\pm}4.3dB(A)$ for press operators, $76.6dB(A){\pm}5.6dB(A)$ for crane operators, $77.1dB(A){\pm}2.8dB(A)$ for forklift drivers, whereas the mean NIOSH TWA was $88.9dB(A){\pm}1.7dB(A)$ for leader, $89.6dB(A){\pm}2.1dB(A)$ for pallette man, $86.7dB(A){\pm}1.8dB(A)$ for press operators, $88.5dB(A){\pm}2.0dB(A)$ for crane operators, $87.7dB(A){\pm}1.0dB(A)$ for forklift drivers. While L10 for NIOSH TWA samples was 84.8 dB(A) ~ 87.3 dB(A), L10 for OSHA TWA samples was 69.5 dB(A) ~ 77.4 dB(A). L10 means that the TWA for 90% of the samples exceeded L10. Among OSHA TWA(Korea TWA with threshold 90) samples for pallette man, 7.7 % exceeded 90 dB(A), the OSHA permissible exposure level, but OSHA TWA samples for the other job titles didn't. Among NIOSH TWA samples, the samples over 85 dB(A), the NIOSH recommended exposure limit, was 100% (leaders), 83.3 %(operators), 97.4%(palletteman), 100%(forklift drivers), 91.7 %(crane operator). The results of One-way random effects analysis of variance models shows that the difference between job titles was significant by OSHA TWA(p<0.05), but not significant by NIOSH TWA(p>0.05). NIOSH TWA samples were significantly higher than OSHA TWA samples(P<0.05). Regression analysis was used to obtain relationships between OSHA TWA samples and NIOSH TWA samples. In this case the coefficient of determination = 0.90, which shows the high degree association between two methods. Regression equation, NIOSH TWA = 0.552 * OSHA TWA + 42.13 dB(A), shows that if OSHA TWA is known, NIOSH TWA can be predicted by the equation. The mean TWA difference between threshold 80 dBA and 90 dBA was significant(p<0.01). While the TWA noise exposures were 7.7% above the Korea(OSHA) PEL, they were more than 83.3% over NIOSH REL. Automobile workers were exposed to noise level that could be potentially damaging to their hearing. It found that there is approximately 25% excess risk of hearing loss even if a worker is protected to the PEL in according to NIOSH study.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.4
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• pp.356-362
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• 2003

In this paper, we propose a predistortion technique which uses a novel combination of the second harmonic technique and the difference frequency technique to achieve independent control of the 3rd and 5th order intermodulation products generated by the PA. The second harmonic and difference frequency terms are generated using an envelope detector and two frequency multipliers. The RF predistorter has capability to independently control of the 3rd and 5th order intermodulation products so that high power amplifier is optimized for linear characteristics. From the measurement results, over the frequency band 2137.5 MHz to 2142.5 MHz, ACPR reduction of 11 dB is obtained for a single 30 dBm W-CDMA carrier.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.12 s.115
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• pp.1156-1163
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• 2006

This paper presents an ultra wideband(UWB) direct conversion mixer for IEEE 802.15.3a applications with simulation and measurement results. Since the direct conversion mixing causes dc-offset and even-order distortion, the proposed mixer adopts an anti-parallel diode pairs(APDPs) to solve these problems. The proposed mixer consists of an in-phase wilkinson power divider over $3.1{\sim}4.8GHz$, a wideband $45^{\circ}$ power divider over $1.5{\sim}2.4GHz$, and miniatured band pass filters(BPFs) for RF-LO isolations. The conversion loss is optimized with impedance matchings between APDPs and wideband components. The measured mixer shows the conversion loss of 13.5 dB, input third-order intercept-point($IIP_3$) of 7 dBm, and 1-dB gam compression point($P_{1dB}$) of -4 dBm. Quadrature(I/Q) outputs have the magnitude difference of about 1 dB and phase difference of ${\pm}3^{\circ}$.

• Journal of Acupuncture Research
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• v.20 no.2
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• pp.68-76
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• 2003

Objective : In the pain control, Bee Venom Acupuncture therapy is highly effective but cause allergic side-effects frequently. This study was performed to compare Bee Venom(BV) with BV Partner(BVP) in decreasing side-effects of BV. Methods : BV partner(BVP) which dilutes the Morus bombycis Koiduzumi Herbal Acupuncture was developed to decrease the side effects of the Bee Venom. We used D.I.T.I. to verify the effectiveness of BVP in decreasing side-effect of BV. We injected BV to Group I (n=18) at 4 points of body [Fengmen(風門 : B12), Feishu(肺兪 : B13), Fufen(附分 : B41), Pohu(魄戶 : B42)], and BVP to group II (N=18) at the same points. We observed the chages of temperature at beginning, 5 minutes, 1 hour, 1 day, 2days and 7days after injection. Results : The following results were obtained; 1. The difference of temperature had been continued until 2days in BV group, but 1day in BVP group. 2. The difference of temperature was significantly greater than time at 1hour in BV and at 5 minutes in BVP. 3. Other side-effects(the local pain, redness, angioedema and pruritus) were less appeared in BVP than BV group, too.

• Journal of Broadcast Engineering
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• v.16 no.3
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• pp.483-489
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• 2011

In this paper, we propose a new antenna, which has wide bandwidth, good radiation patterns, and high-gain characteristics. We analysis the antenna using FDTD(Finite Difference Time Domain) method. And the antenna parameters are optimized to get maximum bandwidth. From the measured results, the bandwidth of the antenna is 0.839 octave, for the S11${\leq}$-10 dB. And the measured cross polarization level of the proposed antenna is less than -25 dB at the center frequency. Experimental data of the return loss and the radiation pattern of the proposed antenna are also presented, and the experimental bandwidth characteristics are relatively in good agreement with the FDTD results. The proposed antenna can be applied to MIMO, LAN, biomedical instruments, broadcasting-network system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.5
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• pp.839-848
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• 2000

This paper presents the results of an electromagnetic field analysis for a reverberation chamber that is an alternative method of a shielded anechoic chamber, which is widely used for the analysis and measurement of electromagnetic interference and immunity test. Inside the defined test volume of the rectangular and triangular type, the Schroeder Quadratic Residue Diffuser was employed. FDTD(Finite-Difference Time-Domain) simulation method was applied to produce the field characteristics inside those reverberation chambers. According to the results, field uniformities on the aforementioned two types of reverberation chambers were correlated within $\pm$3dB, and $\pm$4.4dB tolerances, and rectangular type reverberation chamber shows an independent polarization result.

• Journal of Preventive Medicine and Public Health
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• v.28 no.4 s.51
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• pp.765-771
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• 1995

This study was performed to investigate the possibility of temporary threshold shift (TTS) of vibration sense could induced by exposure to high-frequency vibration or by work position taking by dentists in drilling or polishing. The vibratory perception thresholds (VPT) of 28 healthy men were measured on the index fingertip pulp of dominant hand at 250 Hz. The vibrating tool used in test was a low-speed handpiece of 34,000 rpm. For the TTS test, the dominant hand was exposed to high-frequency vibration and to work position for five minutes, respectively. The VPTs before and after vibratory exposure were $23.5{\pm}3.5dB,\;30.8{\pm}4.2dB$, respectively and VPT after work position was $23.7{\pm}4.6dB$. The difference between before and after vibartory exposure was statistically significant (p<0.001). The correlation of height, weight and BMI with baseline VPTs was not statistically significant. Also, there was no difference of VPTs by smoking. These results suggest that high-frequency vibration from dental handpieces might cause the impairment of vibration sensation.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.4
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• pp.62-72
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• 1997

The optical power splitter/couplers based on MMI(multimode interference) in GaAs/AlGaAs are studied. We presetn a design of optical power splitter/couplers, which have deeply etched multimode waveguide. The properties and fabrication tolerance on the etching depth, multimode waveguide width are simulatedusing a FD-BPM (finite difference beam propgation method). Proposed 1*N optical of designed device is 0.7dB smaller than the optical power splitter with a shallowly etched MMI section. For 0.5dB excess loss, the predicted fabrication tolerance is 0.6.mu.m on the multimode waveguide width of the 14 optical power splitter with a deeply etched MMI section. Also excess loss and uniformity of poposed 32*32 optical power coupler are below 0.3dB. The excess loss of proposed 32*32 optical power coupler is 2dB smaller than the optical power coupler with a shallowly etched MMI section. It is shown that the optical power splitters/couplers with a deeply etched mMI section have low loss, good uniformity, and improved fabriction tolerance.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.2
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• pp.237-244
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• 2022

We measured the clutter loss (CL) and building entry loss (BEL) of signals in a low-rise high-density suburban environment. Three propagation models for BEL, CL, and a combination of BEL and CL were measured in the selected environment. We then derived the figures when the BEL was combined with the CL. At the two frequencies, the measured value of combination of BEL and CL is 27.55 dB and 26.12dB, respectively, and the differences between the measured value and the sum were -4.19 dB and 5.82 dB. Considering that the measurement was performed inside a building, such a difference seems to be small. Therefore, when BEL and CL were measured separately and summed, and then combined and summed, differences of -4.19 dB and 5.82 dB were apparent. This this result can be referenced when similar case of a propagation model was analyzed.