• Journal of Korean Neurosurgical Society
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• v.61 no.2
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• pp.212-218
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• 2018

Objective : Surgical clipping of the cerebral aenurysm is considered as a standard therapy with endovascular coil embolization. The surgical clipping is known to be superior to the endovascular coil embolization in terms of recurrent rate. However, a recurrent aneurysm which is initially treated by surgical clipping is difficult to handle. The purpose of this study was to research the management of the recurrent cerebral aneurysm after a surgical clipping and how to overcome them. Methods : From January 1996 to December 2015, medical records and radiologic findings of 14 patients with recurrent aneurysm after surgical clipping were reviewed retrospectively. Detailed case-by-case analysis was performed based on preoperative, postoperative and follow-up radiologic examinations and operative findings. All clinical variables including age, sex, aneurysm size and location, type and number of applied clips, prognosis, and time to recurrence are evaluated. All patients are classified by causes of the recurrence. Possible risk factors that could contribute to those causes and overcoming ways are comprehensively discussed. Results : All recurrent aneurysms after surgical clipping were 14 of 2364 (0.5%). Three cases were males and 11 cases were females. Mean age was 52.3. At first treatment, nine cases were ruptured aneurysms, four cases were unruptured aneurysms, and one case was unknown. Locations of recurrent aneurysm were determined; anterior communicating artery (A-com) (n=7), posterior communicating artery (P-com) (n=3), middle cerebral artery (n=2), anterior cerebral artery (n=1) and basilar artery (n=1). As treatment of the recurrence, 11 cases were treated by surgical clipping and three cases were treated by endovascular coil embolization. Three cases of all 14 cases occurred in a month after the initial treatment. Eleven cases occurred after a longer interval, and three of them occurred after 15 years. By analyzing radiographs and operative findings, several main causes of the recurrent cerebral aneurysm were found. One case was incomplete clipping, five cases were clip slippage, and eight cases were fragility of vessel wall near the clip edge. Conclusion : This study revealed main causes of the recurrent aneurysm and contributing risk factors to be controlled. To manage those risk factors and ultimately prevent the recurrent aneurysm, neurosurgeons have to be careful in the technical aspect during surgery for a complete clipping without a slippage. Even in a perfect surgery, an aneurysm may recur at the clip site due to a hemodynamic change over years. Therefore, all patients must be followed up by imaging for a long period of time.

• MALSORI
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• no.59
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• pp.69-87
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• 2006

Among the conventional time-scale modification (TSM) methods, the synchronized overlap and add (SOLA) method is widely used due to its good performance relative to computational complexity But the SOLA method remains complex due to its synchronization procedure using the normalized cross-correlation function. In this paper, we introduce a computationally efficient SOLA method utilizing 3 level center clipping method, as well as zero-crossing and level-crossing information. The result of subjective preference test indicates that the proposed method can reduce the computational complexity by over 80% compared with the conventional SOLA method without serious degradation of synthesized speech quality.

• Journal of Korean Neurosurgical Society
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• v.48 no.2
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• pp.109-114
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• 2010

Objective : To evaluate the clinical outcome of coil embolization for unruptured intracranial aneurysm (UIA) with oculomotor nerve palsy (ONP) compared with surgical clipping. Methods : A total of 19 patients presented with ONP caused by UIAs between Jan 2004 and June 2008. Ten patients underwent coil embolization and nine patients surgical clipping. The following parameters were retrospectively analyzed to evaluate the differences in clinical outcome observed in both coil embolization and surgical clipping : 1) gender, 2) age, 3) location of the aneurysm, 4) duration of the symptom, and 5) degree of ONP. Results : Following treatment, complete symptomatic recovery or partial relief from ONP was observed in 15 patients. Seven of the ten patients were treated by coil embolization, compared to eight of the nine patients treated by surgical clipping (p = 0.582). Patient's gender, age, location of the aneurysm, size of the aneurysm, duration of symptom, and degree of the ONP did not statistically correlate with recovery of symptoms between the two groups. No significant differences were observed in mean improvement time in either group (55 days in coil embolization and 60 days in surgical clipping). Conclusion : This study indicates that no significant differences were observed in the clinical outcome between coil embolization and surgical clipping techniques in the treatment of aneurysms causing ONP. Coil embolization seems to be more feasible and safe treatment modality for the relief and recovery of oculomotor nerve palsy.

• Journal of Cerebrovascular and Endovascular Neurosurgery
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• v.25 no.4
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• pp.390-402
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• 2023

Objective: Chronic subdural hematoma (CSDH) is a neurological complication following clipping surgery. However, the natural course and ideal approach for the treatment of clipping-related-CSDH (CR-CSDH) have not been clearly established. We aimed to investigate the course of CR-CSDH using chronological radiological findings. Methods: We performed a retrospective analysis of 28 (3.8%) patients who developed CSDH among 736 patients who underwent surgical clipping using pterional approach for unruptured aneurysms at our institution between December 2010 and December 2018. Patients underwent follow-up CT scan 6-8 weeks after clipping surgery and decision to pursue surgical intervention rests upon the patient's symptom based on the Markwalder's grading scale (MGS) and numeric rating scale (NRS). Results: Of the 28 patients, 3 patients (10.7%) underwent surgery, while 25 (89.2%) showed spontaneous resolution of CR-CSDH. Eighteen patients (64.2%) had mild headache with MGS of 0-1. The mean maximum hematoma volume was 41.9±30.9 ml (5.8-135 ml), and 26 patients (92.8%) had homogeneous hematoma. The mean time to hematoma resolution was 126.7±52.9 days (46-228 days). Comparing group of CR-CSDH volume ≥43 ml or a midline shift ≥5 mm, the difference in presence of linear low-density area (p=0.002) and age (p=0.026) between the conservative and operative groups were found to be statistically significant. Conclusions: Most CR-CSDH cases spontaneously resolved within 4 months. Therefore, we suggest that close observation should be performed if patient's symptoms are mild and special radiologic findings are present, despite its relatively large volume and midline shifting.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.1
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• pp.104-111
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• 1997

Since seeds of Italian ryegrass should be imported every year, it is necessary to investigate the prossible production of seeds in Italian ryegrass field after rice. Seven Italian ryegrass varieties were planted on October 8, 1986 at National Honam Crop Experiment Station at Iksan and clippings were made on April 10 and April 30 in 1987. Headings of K-11 and T.N.T were earlier than those of Tetrone and Bettina. For all varieties tested, heading date was delayed and 1,000 grain weight was decreased linearly as the clipping was made later. Length, width and thickness of a grain were reduced by clipping and later clipping, while tetraploid varieties produced larger grains than diploid varieties. The germination percentage and germination speed at $25^{\circ}C$ were higher than at 15$^{\circ}C$. The final germination percentage was lower at the later clippings and was higher at 15$^{\circ}C$, and earlier varieties showed higher germination percentage. Uniformity of germination was greater at $25^{\circ}C$ and was decreased as the clipping was made later, and the eariler varieties such as K-11 were germinated more uniformly. Average number of days to germination was longer at 15$^{\circ}C$ than at $25^{\circ}C$ and was longer at later clipping. The germination percentage was decreased linearly as the heading was delayed, while it increased linearly as the 1,000 grain weight was increased.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.7 s.361
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• pp.17-22
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• 2007

OFDM (Orthogonal Frequency Division Multiplexing) is a special case of multicarrier transmission, where a single data stream is transmitted over a number of lower-rate subcarrier. One of the main reasons to use OFDM is to increase robustness against frequency-selective fading or narrowband interference. Unfortunately, an OFDM signal consists of a number of independently modulated subcarriers, which can give a large PAPR (Peak-to-Average Power Ratio) when added up coherently. In this paper, we investigate the performance of a simple PAPR reduction scheme, which requires no change of a receiver structure or no additional information transmission. The approach we employed is clipping in the time and frequency domains. The time-domain clipping is carried out with a predetermined clipping level while the frequency-domain clipping is done within EVM (Error Vector Magnitude). This approach is suboptimal with lower computational complexity compared to the optimal method. This evaluation is carried out on the OFDM system with an nonlinear amplifier. The simulation results demonstrated that the PAPR reduction algorithm is one of ways to reduce the effects of the nonlinear distortion of an HPA (High Power Amplifier).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9A
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• pp.710-716
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• 2003

OFDM is a very attractive technique for achieving high-bit-rate data transmission and high spectrum efficiency. However one of disadvantages of OFDM signal is the high PAPR characteristic when multicarriers are added up coherently. In this paper, we propose an adaptive PTS scheme using two threshold levels for PAPR reduction and reducing the amount of PAPR calculations with clipping scheme. Simulation results show that it is almost same between average bit error rate performance of the proposed scheme and that of a conventional scheme. Also, we obtain a great performance gain in the amount of calculations compared to the conventional scheme. Therefore, proposed system has a good performance in data processing time in OFDM wireless communication systems.

• Korean Journal of Applied Biomechanics
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• v.23 no.1
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• pp.45-51
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• 2013

The current study developed the analysis program by employing the Polygon Clipping Algorithm to calculate the open area on the court when players try to spike a ball. The program consists of two kinds of output screen. First, on the main output screen, it is possible to calculate both blocked area by net and blockers, and opened area to avoid the blocked area when players spike the ball. Additionally, the secondary output screen shows the moving path of setter and the location of set. Main output screen indicates hitting points of spiking, blocking, and open area. Also, it is possible to analyze the movement of setter, location of set, and hitting point of attacker. The program was tested by comparing real coordinate value and location coordinate value which is operated on the program. To apply this program in the field, future study needs to develop the program that can calculate three dimensions coordinate fast by tracking the location of players or ball in real time.

• Journal of Korean Neurosurgical Society
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• v.51 no.6
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• pp.334-337
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• 2012

Objective : The lateral supraorbital (LSO) approach is a modified method of the classic pterional approach and it has advantages of short skin incision and small craniotomy compared with the pterional approach. This study was designed to compare the two approaches in the surgical treatment of unruptured intracranial aneurysms. Methods : We retrospectively reviewed 122 patients with 137 unruptured intracranial aneurysms treated by clipping, from July 2009 to April 2011. Between August 2010 and April 2011, 61 patients were treated by clipping via the lateral supraorbital approach and the same number of patients treated by clipping via the pterional approach were retrospectively enrolled. We analyzed the two groups and compared demographic, radiologic and clinical variables. Results : The mean age of patients in the two groups was 54.6 years (LSO group) and 55.7 years (Pterion group). The mean duration of hospitalization was shorter in the LSO group than in the Pterion group (7.9 days vs. 9.0 days, p=0.125) and the mean operation time was also significantly shorter in the LSO group (117.1 minutes vs. 164.3 minutes, p<0.001). Furthermore, the mean craniotomy area was much smaller in the LSO group (1275.4 $mm^2$ vs. 2858.9 $mm^2$, p<0.001). The two groups showed similar distributions of aneurysm location and postoperative complications. Conclusion : The lateral supraorbital approach for the clipping of unruptured intracranial aneurysm could be a good alternative to the classic pterional approach.

• Journal of Korean Neurosurgical Society
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• v.48 no.4
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• pp.330-334
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• 2010

Objective : Residual aneurysm from incomplete clipping or slowly recurrent aneurysm is associated with high risk of subarachnoid hemorrhage. We describe complete treatment of the lesions by surgical clipping or endovascular treatment. Methods : We analyzed 11 patients of residual or recurrent aneurysms who had undergone surgical clipping from 1998 to 2009. Among them, 5 cases were initially clipped at our hospital. The others were referred from other hospitals after clipping. The radiologic and medical records were retrospectively analyzed. Results : All patients presented with subarachnoid hemorrhage at first time, and the most frequent location of the ruptured residual or recurrent aneurysm was in the anterior communicating artery to posterior-superior direction. Distal anterior cerebral artery, posterior communicating artery, and middle cerebral artery was followed. Repositioning of clipping in eleven cases, and one endovascular treatment were performed. No residual aneurysm was found in postoperative angiography, and no complication was noted in related to the operations. Conclusion : These results indicate the importance of postoperative or follow up angiography and that reoperation of residual or slowly recurrent aneurysm should be tried if such lesions being found. Precise evaluation and appropriate planning including endovascular treatment should be performed for complete obliteration of the residual or recurrent aneurysm.