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With the advent of new rare-earth-based scintillators, a variety of Compton cameras with novel features in detector material and structure have been developed for the application to either molecular imaging or gamma-ray observation with space telescopes. In this study, we investigated the performance of a Compton camera consisting of a DSSD as a scatterer and an array-type GAGG scintillator as an absorber. We mainly focused on how to optimize the performance of the Compton camera in imaging resolution as well as in efficiency and thereby determined the optimal geometrical configuration with the Monte Carlo simulation using a GEANT4 toolkit. The energy discrimination levels were set in the simulation so that the general experimental environments could be taken into account. We studied different configurations with a figure of merit accounted for efficiency and resolution as a function of the gamma-ray energy, the pixel size of the absorber, the source-to-scatterer distance, the scatterer-to-absorber distance and the scatterer-to-absorber angle in this study. The figure of merit reached its maximum when the source-to-scatterer distance was 3 cm, the scatterer-to-absorber distance was 5 cm and the scatterer-to-absorber angle, that is, the absorber with 256 pixels was located at an angle of 15° with respect to the scatterer for 356-keV gamma rays used in this study. We also investigated how the event rates for Compton scattering obtained by counting the scattering events were contributed to the reconstructed image and caused unwanted imaging artifacts for the optimal configuration. Finally, calculations were performed by using the gamma-ray tracking method with inclusion of two-fold events occurring within the absorber and showed increase in imaging efficiency by 25%.

This paper reports the digital implementation of analog shaping amplifiers by digital pulse processing in gamma-ray spectroscopy. For digital implementation, a numerical algorithm was developed by referring to the semi-Gaussian filter of the analog shaping amplifier. In order to verify the developed algorithm, we evaluated the obtained energy spectrum and compared the energy resolution with the existing analog processing results. The gamma-ray detector used a double-sided strip detector, and the preamplifier signal of the detector was digitized directly by using a commercial digitizer. Using the standard gamma-ray sources Am-241 (59 keV), Ba-133 (81 keV), and Co-57 (122 keV), we were able to detect gamma rays in a relatively low energy region. The energy resolution was improved at energies below 100 keV compared to the result of treatment with an analog shaping amplifier.

For stable LNG production, the feasibility study of the LNG liquefaction process control logic and the operational characteristics is to be performed before its implementation in actual plant construction where natural gas is cooled down below–160°C. Therefore, it is imperative to understand how the controlled variables are influenced by the manipulated variables for the best process control strategy. In this study, 30 kg/h-bench scale natural gas liquefaction process was optimized by using Propane pre-cooled mixed refrigerant (C3MR) process. Variation of the temperature in the propane refrigerant, mixed refrigerant and the natural gas was studied in response to refrigerant flow rate to assess the effect of manipulated flow rate of natural gas on the controlled variables. Furthermore, the effects of the three manipulated variables on the controlled variables were examined, with major emphasis on analyzing the effect of the natural gas flow rate on the temperature of refrigerant. Each controlled variable is not independent, but closely related to one another. However, some controlled variables displayed relatively larger sensitivities to variation of certain manipulated variables.

In this study, a long term monitering of nonpoint source pollution runoff is conducted at the area of transportation related and EMCs(Event Mean Concentrations) in terms of water quality items, such as BOD, CODMn, SS, T-N and T-P are determined for each not only runoff event and but also observation site. On the other hands, SWMM(Storm Water Management Model) model is constructed using the data collected in the transportation areas selected. Model calibration and verification of SWMM is carried out based on the data collected. And simulated EMCs was compared with observed EMCs by monitoring and prior studies. SWMM applicability estimation was Using the compared result. The results of simulation showed that BOD 5.787 ∼ 14.475 mg/L, CODMn 12.946 ∼ 59.611 mg/L, SS 13.742 ∼ 46.208 mg/L, T-N 2.037 ∼ 5.213 mg/L, T-P 0.117 ∼ 0.415 mg/L. And a differential between simulated EMCs and observed EMCs is too low so comparing result show high fit(BOD 4.27 %, CODMn 4.87%, SS 2.31%, T-N 5.78%, T-P 14.45%). A results of compared with the prior studies, BOD and T-P are included range of prior studies, CODMn and SS are lower than range of prior studies, T-N is higher than range of prior studies. Differential between simulated EMCs and prior studies EMCs was showing for survey seasonal and changing land-use, so from now on, EMCs of using the internal representatives value will be calculated by more monitoring toward various precipitation events.

Software for genuinely event-by-event analysis and event reconstruction of data obtained by using an active target has been developed in the graphical user interface under the CERN ROOT framework. The primary motivation for developing the software was to provide physicists who perform experiments using an active target a more user-friendly environment for the purpose of investigating the performance of detection systems and obtaining ideas about physics from a large amount of experimental data. To test the performance of the software, we analyzed experimental data from a 16N radioactive ion beam experiment for α-decay measurements. As a result of the analysis, we observed the Bragg curve and measured the range of the 16N RI beam in the detector. Data were calibrated against the calculation after comparing the Bragg curve to the one obtained from an energy loss calculation in P-10 gas. We present a detailed description of the analysis software and its test results.

The MFFn(Mass first flush), EMCs(Event mean concentrations) and runoff loads were analyzed for various rainy events(monitoring data from 2011 to 2012) in transportation area(rail road in station). The pollutant EMCs by volume of stormwater runoff showed the BOD5 9.6 mg/L, COD 29.9 mg/L, SS 16.7 mg/L, T-N 3.271 mg/L, T-P 0.269 mg/L in the transportation areas(Railroad in station). The average pollutant loading by unit area of stormwater runoff showed the BOD5 , COD , SS , T-N and T-P in the transportation areas. Estimated NCL-curve(Normalized cumulated-curve) was evaluated by comparison with observed MFFn. MFFn was estimated by varying n-value from 10% to 90% on the rainy events. The n-value increases, MFFn is closed to '1'. As time passed, the rainfall runoff was getting similar to ratio of pollutants accumulation. The result of a measure of the strength of the linear relationship between observed data and expected data under model was good.

【Despite abundant nutritions, krill is barely used for human consumption. The objective of this study was to investigate the nutritional component and amino acid composition of krill and further utilizes it for food resource. Proximate compositions of krill meal were consisted of crude protein 58.85%, ash 13.89%, crude fat 12.45%, carbohydrate 11.01% and moisture 3.80%. The amount of total amino acid was 54.74 g%, and the major amino acids were glutamic acid (7.71 g%), aspartic acid (6.20 g%), leucine (4.72 g%), lysine (4.41 g%), arginine (6.49 g%) and alanine (3.25 g%), respectively. Total essential amino acid content was 21.87%, and the major amino acids were leucine (4.72 g%), lysine (4.41 g%) and isoleucine (2.90 g%), respectively. Content of total free amino acid in krill meal was 20224.30 mg/kg, and the major free amino acids were taurine (4501 mg/kg), arginine (3130.60 mg/kg), proline (2302.90 mg/kg), alanine (2088.10 mg/kg), glycine (1606.40 mg/kg) and lysine (1197.40 mg/kg). Especially, taurine was the most abundant of all free amino acids. Thus, these data indicate that krill seems to be abundant protein source food.】

Antarctic krill (Euphausia superba) is typical of a enormous biomass of marine zooplankton that could provide good nutrition in human body. This study was conducted to identify the nutrition of krill, a live in Antarctic Ocean. The analysis result of fatty acids of krill meal was as follow. The compositions of fatty acid were saturated fatty (SFA) acid 41.41%, monounsaturated fatty acid (MUFA) 21.69%, polyunsaturated fatty acid (PUFA) 36.89%, and p/s ratio was 0.89. The major fatty acids in all parts were eicosapentaenoic acid (EPA, 21.54%), palmitic acid (27.51%), oleic acid (13.35%) and docosahexaenoic acid (DHA, 12.42%). Especially, EPA and DHA were occupied 33.96% of polyunsaturated fatty acid. The mineral contents of krill meal were calcium 24477.21 mg , sodium 14728.69 mg , magnesium 6973.49 mg , potassium 3981.67 mg , iron 395.33 mg and manganese 5.74 mg . The contents of major vitamin were retinol 86717.37 RE, -carotene 44.87 RE, tocopherol 2.60 mg, pantothenic acid 1.61 mg, indicating that krill meal contains large amount of retinol and -carotene.

The purpose of this study was to assess the effects of Cordyceps militaris extract supplementation on the improvement of blood glucose, lipid compositions and hepatic functional enzyme activities in the serum of streptozotocin(STZ, 50 mg/kg BW, IP injection)-induced diabetic rats fed the experimental diets for 5 weeks. The concentrations of blood glucose and lipid compositions(total cholesterol, β-lipoprotein, free cholesterol, cholesteryl ester, triglyceride and phospholipid) and atherosclerotic index in serum were significantly lower in the DM+CM group than in the DM group, whereas the ratio of HDL-cholesterol concentration to total cholesterol in the DM+CM group were higher than in the DM group. The activities of hepatic functional enzymes(aminotransferase, LDH and ALP) in serum were lower in the Cordyceps militaris extract administration group(group DM+CM) than in the hyperglycemic DM group. The results shown above suggested that Cordyceps militaris extract supplementation effectively improves blood glucose and atherosclerosis in the serum of diabetic rats.Key words: Cordyceps militaris, Diabetes, Blood glucose, Lipid compositions, Atherosclerosis

In this study, non-point source(NPS) contribution was investigated based on flow rates and water qualities of streams into the lake during rainfall events. Event mean concentration(EMC) and the pollution loads were calculated to establish a database for NPS control measurement in the survey area, and so on. The runoff characteristics of NPS were investigated and estimated on the basis of the ratio of an agricultural to forest area in the stream of sub-catch basin during rainfall events. Non-point source pollution loads were also calculated to establish a database for NPS control measure in the upstream lake Chinyang. At a rainfall event, BOD concentrations rise sharply at the early peak time of runoff, however, peaks of TSS concentration were observed at the similar time of peak flow. This was a phenomenon shown at the watersheds caused by forest and geological types. The discharged EMC range was 2.9-4.8 mg/L in terms of BOD. The discharged EMC range was 6.2-8.2 mg/L in terms of SS. The discharged EMCs of T-N and T-P were 1.4-2.5 mg/L and 0.059-0.233 mg/L, respectively. Total BOD loading rate through the 3 tributaries to the lake Chinyang was 1,136 kg/d during dry weather. The upper watershed area of the Nam-river dam in this study was divided into 14 catchment basins based on the Korean guideline for total maximum daily load(TMDL) of water quality pollutants. The higher the agricultural land-use ratio, the more NPS loading rate discharged, but the more occupied a forest area, the lower more NPS loading rate discharged. In an agricultural land-use area more than 20%, the increase of NPS loadings might be dramatically diffused by increasing the integrated complex-use like vinyl-house facilities and fertilizer use etc. according to the effective land-use utilization. The NPS loading rates were BOD 0.3 kg/ha․day, SS 0.21 kg/ha․day, TN 0.02 kg/ha․day, TP 0.005 kg/ha․day under less than 10% agricultural land-use. In agricultural land-use of 20%-50%, these values were investigated in the range of 0.32 kg/ha․day-0.73 kg/ha․day for BOD, 0.92 kg/ha․day-3.32 kg/ha․day for SS, 0.70 kg/ha․day-0.90 kg/ha․day TN, 0.03 kg/ha․day-0.044 kg/ha․day for TP.

We have developed an FPGA-based digital signal processing system that performs both online digital signal filtering and pulse-shape analysis for both particle and gamma-ray spectroscopy. Such functionalities were made possible by a state-of-the-art programmable logic device and system architectures employed. The system performance as measured, for example, in the system dead time and accuracy for pulse-height and rise-time determination, was evaluated with standard alpha- and gamma-ray sources using a CsI(Tl) scintillation detector. It is resulted that the present system has shown its potential application to various radiation-related fields such as particle identification, radiography, and radiation imaging.

This study analyzed the characteristics of stormwater runoff by rainfall type in orchard areas and transportation areas for 2 years(2010~2011year). Effluents were monitored to calculate the Event Mean Concentrations(EMCs) and runoff loads of each pollutant.The pollutant EMCs by volume of stormwater runoff showed the ranges of BOD 0.9~13.6 ㎎/L, COD 13.7~45.2 ㎎/L, SS 4.1~236.4 ㎎/L, T-N 2.123~21.111 ㎎/L, T-P 0.495~2.214 ㎎/L in the orchard areas, and was calculated as BOD 2.3~22.5㎎ /L, COD 4.4~91.1 ㎎/L, SS 4.3~138.3 ㎎/L, T-N 0.700~13.500 ㎎/L, T-P 0.082~1.345 ㎎/L in the transportation areas.The correlation coefficient of determination in the orchard area was investigated in the order of Total Rainfall(0.81) > Total Runoff(0.76) > Rainfall Intensity(0.56) > Rainfall Duration(0.46) > Antecedent Dry Days(0.27). Also, in the case of the transportation area was investigated in the order of Total Rainfall (0.55) > Total Runoff(0.54) > Rainfall Intensity(0.53) > Rainfall Duration(0.24) > Antecedent Dry Days(0.14).As the result, comparing valuables relating to runoff of non-pollutant source between orchard areas and transportation areas, orchard area(R2 ≥ 0.5 : X3, X4, X5) was investigated to have more influence of diverse independent valuables compared to the transportation area(R2 ≥ 0.5 : X3, X4) and the difference of discharge influence factor by the land characteristics appeared apparently.

This study was performed to observe the effects of the feeding physiological activity substance in Cordyceps militaris hot-water extract intake on the improvement of lipid components and metabolic enzyme activities in the serum of dietary hyperlipidemic rats (SD strain, male) fed the experimental diets for 5 weeks. The concentrations of cholesterol (total cholesterol, β-lipoprotein, LDL-cholesterol, free cholesterol and cholesteryl ester), atherosclerotic index, triglyceride (TG), phospholipid (PL) and blood glucose in sera were remarkably lower in the Cordyceps militaris extract intake group than in the hyperlipidemic rats. In the ratio of HDL-cholesterol concentration was higher percentage in the Cordyceps militaris extract intake group than in the hyperlipidemic rats. The activities aminotransferase (AST, ALT) in sera were rather lower in the Cordyceps militaris extract administration than in the hyperlipidemic rats. From the above research, Cordyceps militaris extract were effective on the improvement of the lipid compositions in sera of dietary hyperlipidemic rats.

We designed an in-flight radioactive isotope (RI) beam separator with large acceptance and two-stage separation, which is a major feature for next-generation separators today. The large acceptance value made possible efficient production of RI beams while the two-stage separator allowed us to cope with the poor purity of RI beams. The first stage was used for the production and the separation of RI beams, and the second stage was used to identify RI beam species. For the designed separator, we estimated the yield and the purity of several nuclei produced in projectile fragmentation by using the code LISE++ for three different configurations — momentum analysis, momentum analysis plus an energy degrader, and addition of a radio frequency (RF) kicker. We adopted a RF kicker to increase the purity of proton-rich nuclei in the RI beams. Purifications were introduced as figures of merit for the comparison of the purity enhancements for different separation methods. When the RF kicker was combined with the energy degrader, the purifications for selected proton-rich RI beams such as 35Ca, 56Ni, 100Sn, and 129Sm turned out to be 10 ∼ 2,000 times those for the case when only the momentum analysis was used. In particular, the purifications for 100Sn and 129Sm were 2,000 and 200, respectively, for a momentum acceptance of 1%. However, in the case of neutron-rich RI beams such as 58Ca, 78Ni, 132Sn, and 162Sm, the purifications were insensitive to the RF kicker, but increased with decreasing the momentum acceptance.

See paper for full list of authors; The Korea Rare Isotope Accelerator, currently referred to as KoRIA, is briefly presented. The KoRIA facility is aimed to enable cutting-edge sciences in a wide range of fields. It consists of a 70 kW isotope separator on-line (ISOL) facility driven by a 70 MeV, 1 mA proton cyclotron and a 400 kW in-flight fragmentation (IFF) facility. The ISOL facility uses a superconducting (SC) linac for post-acceleration of rare isotopes up to about 18 MeV/u, while the SC linac of IFF facility is capable of accelerating uranium beams up to 200 MeV/u, 8 pμA and proton beams up to 600 MeV, 660 μA. Overall features of the KoRIA facility are presented with a focus on the accelerator design.

The MFFn(Mass First Flush) was analyzed for various rainy events(monitoring data from 2008 to 2009) in Transportation area(Highway, National road, Trunk road). Estimated MFFn using SWMM was evaluated by comparison with observed MFFn. MFFn was estimated by varying n-value from 10% to 90% on the rainy events. The n-value increases, MFFn is closed to ``1``. As time passed, the rainfall runoff was getting similar to ratio of pollutants accumulation. The result of a measure of the strength of the linear relationship between observed data and expected data under model was good (R2=0.89). Pollutants runoff loads by volume showed Highway 26.6%, National road 44.8%, Trunk road 35.0% at the MFF20(20% by total runoff). A case of MFF30, pollutants runoff loads by volume showed Highway 40.2%, National road 54.3%, Trunk road 46.8%. According to the results, Initial precipitation basis were Highway MFF30, National road MFF20, Trunk road MFF30 when the Non-Point source control facilities set up.

This study describes the effects of diesel–biodiesel–bioethanol blending fuels on the combustion and emission characteristics of a compression ignition engine. The experiments were investigated for various blending ratios and various fuel injection parameters. In this study, biodiesel fuel was blended not only to prevent phase separation between bioethanol and diesel but also to compensate for the low viscosity of bioethanol. The bioethanol blending ratio is restricted up to 30 vol. % to maintain the ignition characteristics. The results showed that the ignition delay was extended and that the fuel consumption and the maximum rate of pressure rise deteriorated with increasing bioethanol blending ratio. In addition, the diesel–biodiesel–bioethanol fuel reduced the indicated specific soot emissions. As the bioethanol blending ratio is increased, the indicated specific carbon monoxide (CO), the indicated specific unburned hydrocarbon, and the indicated specific nitrogen oxide emissions increased slightly.

Growth in population and urbanization has progressively increased the loading of pollutants from nonpoint sources as well as point sources. Especially in case of road regions such as city trunk road, national road and highway are rainfall and pollutants runoff intensive landuses since they are impervious and emit a lot of pollutants from vehicle activity. This research was conducted to investigate the nonpoint sources concentration and quantifying stormwater pollutants which are contained in rainfall runoff water. Three different monitoring sites in Jinju and Changwon city were equipped with an automatic rainfall gauge and flow meter for measuring rainfall and the volume of rainfall runoff. In the case of average EMC value, city trunk road was shown the highest value in target water quality items like as BOD, COD, SS, TN and TP. Or the amount of runoff loads by water quality items showed the highest value in city trunk road. And runoff load in city trunk road was 43.8 times high value compared to highway by value of city trunk road 356.7 ㎎/㎡, highway 8.150 ㎎/㎡, national road 19.99 ㎎/ ㎡ in the case of BOD.

A novel digital pulse-shape analysis (DPSA) was performed for high-resolution position-sensitive gamma-ray spectroscopy with coaxial-type high-purity germanium (HpGe) detectors. The DPSA consisted of two stages that determined the pulse height, the interaction point and the start time by using the chi-square fitting the digitally recorded pulse shapes with calculated shapes. As the DPSA was applied to gamma-ray spectroscopy using HpGe coaxial detectors, we obtained the energy spectra, the time-difference spectra and the interaction depth profiles for the gamma rays emitted from 133Ba and 22Na standard sources. The efficiency of the spectroscopic analysis using the DPSA was compared with that using a conventional analog signal process (CASP). Furthermore, we determined the half-lifetime of the first excited state in 133Cs by using the DPSA.

Although the ordered subset expectation maximization (OSEM) algorithm does not converge to a true maximum likelihood solution, it is known to provide a good solution if the projections that constitute each subset are reasonably balanced. The Compton scattered data can be allocated to subsets using scattering angles (SA) or detected positions (DP) or a combination of the two (AP (angles and positions)). To construct balanced subsets, the data were first arranged using three ordering schemes: the random ordering scheme (ROS), the multilevel ordering scheme (MLS) and the weighted-distance ordering scheme (WDS). The arranged data were then split into J subsets. To compare the three ordering schemes, we calculated the coefficients of variation (CVs) of angular and positional differences between the arranged data and the percentage errors between mathematical phantoms and reconstructed images. All ordering schemes showed an order-of-magnitude acceleration over the standard EM, and their computation times were similar. The SA-based MLS and the DP-based WDS led to the best-balanced subsets (they provided the largest angular and positional differences for SA- and DP-based arrangements, respectively). The WDS exhibited minimum CVs for both the SA- and DP-based arrangements (the deviation in mean angular and positional differences between the ordered subsets was smallest). The combination of AP and WDS yielded the best results with the lowest percentage errors by providing larger and more uniform angular and positional differences for the SA and DP arrangements, and thus, is probably optimal Compton camera reconstruction using OSEM.

Emissions of leachate, odor, and landfill gas(LFG) from an open-dumping landfill site do harm to public health by contaminating neighboring soil, underground water, and rivers. Particularly, methane(CH 4 ) and carbon dioxide(CO 2 ), the main components of LFG, are especially noted as the causing material of the global warming that become seriously recognized worldwide issue.As one of alternatives in managing LFG, incineration of inflammable wastes that are generated during excavation process at an open-dumping landfill has been evaluated.Standard on stabilization for evaluation, neither CH 4 density nor CO 2 density could not Because meet 'less than 5%' criterion and so it is right to install a gas collection system during landfill renewal to prevent diffusion of odor and collec t it.Because it shows considerable heating value, incineration of inflammable wastes might be the reasonable solution from the result of our study. Key Words :LFG, Stabilization, Landfill, Reasonable, CH

Pollutants from urban pavement consists various kinds of substances which are originated from dry deposition, a grind out tire, corrosive action of rain to pavement and facilities and raw materials of the road etc.. These are major pollutants of urban NPS (Non-point source) during rainfall period. However there is not enough information to control such pollutants for appropriate management of natural water quality. In this study of transportation areas, three monitoring stations were set up at trunk road, urban highway and national road in Gyeongnam province. Runoff flow rate was measured at every 15minutes by automatic flow meters installed at the end of storm sewer pipe within the road catchment area for water quality analysis. Data was collected every 15 minutes for initial two hours of rainfall. Additional samples were collected 1-4 hours interval till the end of rainfall. The monitoring parameters were CODMn, SS, T-N & T-P and heavy metals. The average EMCs of TSS and CODMn were 62.0 mg/L and 24.2 mg/L on the city trunk road, which were higher than those of urban highway and national road, indicating higher pollutant loads due to activities in the city downtown area beside the vehicle. On the other hand, the average EMC of T-N and T-P were in the range of 2.67-3.23 mg/L and 0.19-3.21 mg/L for all the sampling sites. Heavy metals from the roads were mainly Fe, Zn, Cu and Mn, showing variable EMCs by the type of road. From the TSS wash-off analysis in terms of FF(first flush) index, first flush phenomenon was clearly observed in the trunk road(FF : 0.89-1.43). However, such mass delivery behavior was not apparently shown in urban highway(FF : 0.90-1.11) and national road(FF : 0.81-1.41).

The Compton camera can provide 3-D images of radioactive material distribution based on a single measurement at a fixed position. The Compton camera also can image several different kinds of radioactive materials simultaneously, by means of the “multitracing” capability. In the present study, this multitracing capability was tested for a double-scattering-type Compton camera, or Double-Scattering Compton Imager (DOCI), which utilizes two double-sided silicon strip detectors (DSSDs) and one NaI(Tl) scintillation detector. Our experimental result shows that the 137Cs and 60Co gamma sources can be clearly distinguished in 2-D and 3-D Compton images, and that there is no significant interference between the two gamma sources. The imaging resolutions were determined to be 6.2 and 4.7 mm FWHM for the 137Cs (662 keV) and 60Co (1332 keV) point sources at 4 cm, respectively. The angular resolutions, determined from the angular resolution measure (ARM) distributions, were 7.3° and 6.5° for the source energies of 662 and 1332 keV, respectively. The DOCI remains under development; its imaging resolution will be further improved with the incorporation of more sophisticated detectors and the related electronics, including a faster scintillation detector (LYSO) and higher-spatial-resolution position-sensitive detectors.

A digital pulse-shape method (DPSM) is proposed to improve the time resolution of a BaF2 scintillation detector for low-energy gamma rays. By using chi-square fitting of digitally measured pulse shapes with calculated shapes, the proposed DPSM determined the pulse height and the start time corresponding to the deposited energy and the interaction moment, respectively, of gamma rays incident on the BaF2 scintillator. We calculated theoretical pulse shapes by considering light output, light-attenuation length, and light path within the scintillator. In particular, we calculated the light path inside the scintillator by using a Monte Carlo method. We performed coincidence measurements for gamma rays emitted from 22Na and 133Ba standard sources with two cylindrical BaF2 scintillation detectors and then we obtained a time resolution of around 6 ns for 81-keV and 511-keV gamma rays by using the DPSM. Although time resolution obtained using the DPSM was inferior to that obtained using a conventional analog signal process, it had a consistent value irrespective of gamma-ray energy.

In the present study, a double-scattering-type Compton camera, which incorporates two double-sided silicon strip detectors (DSSDs) as the scatterer detectors and an NaI(Tl) detector as the absorber detector, was constructed as a proof-of-principle system for a compact high-imaging-resolution Compton camera. The energy and timing resolutions of the component detectors were determined accurately for effective Compton imaging. Then, the Compton camera was used to image an 22 Na point source at 3.7 cm. The imaging resolutions of the current system were 9.0 and 4.8 mm FWHM for 511 and 1275 keV, respectively, which are fairly good considering the limitations of the detectors and data acquisition (DAQ) electronics employed. Given the characteristics of the component detectors, it is believed that the double-scattering Compton camera can be developed as a very compact system (similar in size to a hand-held radiation survey meter) providing very high imaging resolution.

A series of laboratory-scale corrosion experiments was carried out to observe the effect of dissolved oxygen (DO) in the presence of other water quality parameters, such as hardness, Cl - , and pH using various pipe materials. In addition, a simulated loop system was installed at a water treatment plant for pilot-scale experiment. Laboratory-scale experiment showed that corrosion rates for galvanized steel pipe (GSP), carbon steel pipe (CSP), and ductile cast iron pipe (DCIP) were decreased to 72%, 75%, and 91% by reducing DO concentration from 9±0.5 mg/L to 2±0.5 mg/L. From the pilot scale experiment, it was further identified that the average ionization rate of zinc in GSP decreased from 0.00533 to 0.00078 mg/ cm 2 /d by controlling the concentration of DO. The reduction of average ionization rate for copper pipe (CP) and stainless steel pipe (SSP) were 71.4% for Cu and 63.5% for Fe, respectively. From this study, it was concluded that DO could be used as a major parameter in controlling the corrosion of water pipes.

A novel type of Compton camera, called a double-scattering Compton imager (DOCI), is under development for nuclear medicine and molecular imaging applications. Two plane-type position-sensitive semiconductor detectors are employed as the scatterer detectors, and a 3 '' x 3 '' cylindrical NaI(TI) scintillation detector is employed as the absorber detector. This study determined the optimal geometrical configuration of these component detectors to maximize the performance of the Compton camera in imaging resolution and sensitivity. To that end, the Compton camera was simulated very realistically, with the GEANT4 detector simulation toolkit, including various detector characteristics such as energy resolution, spatial resolution, energy discrimination, and Doppler energy broadening. According to our simulation results, the Compton camera is expected to show its maximum performance when the two scatterer detectors are positioned in parallel, with similar to 8 cm of separation. The Compton camera will show the maximum performance also when the gamma-ray energy is about 500 keV, which suggests that the Compton camera is a suitable device to image the distribution of the positron emission tomography (PET) isotopes in the human body. (c) 2008 Elsevier B.V. All rights reserved.

Iterative image reconstruction for the Compton camera is computationally challenging since the projection and backprojection operations are performed on conical surfaces rather than along straight lines and there are many possible combinations of positions and energy measurements. Here, we note that implementing a computationally efficient projector–backprojector pair with good accuracy is an important factor to be considered in image reconstruction. In this study, two different approaches to conical surface integration were investigated for rapid calculations of projection and backprojection in 3D reconstruction; the ellipse-stacking method (ESM) and the ray-tracing method (RTM). Our experimental results indicated that while both methods produced equivalent reconstruction accuracies, RTM performed better than ESM in both computation time per iteration and total number of iterations for convergence.

Accurate energy calibration of double-sided silicon strip detectors (DSSDs) is very important, but challenging for high-energy photons. In the present study, the calibration was improved by considering the Compton edge additionally to the existing low-energy calibration points. The result, indeed, was very encouraging. The energy-calibration errors were dramatically reduced, from, on average, 15.5% and 16.9% to 0.47% and 0.31% for the 356 ( 133 Ba) and 662 keV ( 137 Cs) peaks, respectively. The imaging resolution of a double-scattering-type Compton camera using DSSDs as the scatterer detectors, for a 22 Na point-like source, also was improved, by ∼9%.

The spatial resolution from Compton cameras suffers from measurement uncertainties in interaction positions and energies. The degree of degradation in spatial resolution is shift-variant (SV) over the field-of-view (FOV) because the imaging principle is based on the conical surface integration. In our study, the shift-variant point spread function (SV-PSF) is derived from point source measurements at various positions in the FOV and is incorporated into the system matrix of a fully three-dimensional, accelerated reconstruction, i.e. the listmode ordered subset expectation maximization (LMOSEM) algorithm, for resolution recovery. Simulation data from point sources were used to estimate SV and asymmetric parameters for Gaussian, Cauchy, and general parametric PSFs. Although little difference in the fitness accuracy between Gaussian and general parametric PSFs was observed, the general parametric model showed greater flexibility over the FOV in shaping the curve between that for Gaussian and Cauchy functions. The estimated asymmetric SV-PSFs were incorporated into the LMOSEM for resolution recovery. For simulation data from a single point source at the origin, all LMOSEM-SV-PSFs improved the spatial resolution by 2.6 times over the standard LMOSEM. For two point-source simulations, reconstructions also gave a two-fold improvement in spatial resolution and resulted in a greater recovered activity ratio at different positions in the FOV.

To investigate positive and negative thermophoretic effects for polystyrene latex (PSL) spheres of diameter between 0.3 and 0.8 μm, the average deposition velocity toward a horizontal wafer surface in vertical airflow is measured keeping the wafer surface temperature different from the surrounding air temperature. The temperature difference ranges from -10° to 4°C. The number of particles deposited on a wafer surface is obtained from the measurements by using a wafer surface scanner (PMS SAS-3600). Experimental data of particle deposition velocity are compared with those given by the prediction model to validate the model. Since thermophoresis changes greatly the particle deposition velocity, temperature difference necessary for the particle deposition velocity to remain under a given value is sought as a means to control the deposition velocity. The minimum temperature differences required to keep the average deposition velocity smaller than 10−4cm/s and 10−5 cm/s in a clean room environment are suggeste...

The average particle deposition velocity toward a horizontal semiconductor wafer in a vertical airflow was measured by a wafer surface scanner (PMS SAS-3600) to shorten the exposure time and hence to improve repeatability. Polystyrene latex (PSL) spheres with diameters between 0.2 and 1.0 μm were used. For the present experiment, convection, diffusion, and sedimentation comprise important agents of the deposition mechanism. The mean and standard deviation of average deposition velocities were obtained from more than 10 data sets for each PSL sphere size, and the deposition velocity distributions from the measurement data were compared to the theoretical distributions.

A numerical simulation is carried out to analyze the flow field of cooling air through the radiator and engine compartment. In order to consider the strong effect of the suction-type flow by the cooling fan at engine idling condition, a potential flow analysis is attempted by the assumption of a line sink located at the position of the cooling fan. The governing equations for steady two-dimensional, incompressible, turbulent flow are solved with the two-equationk-e model for turbulence. The velocity profiles in the underhood engine compartment and around the front-end of a real vehicle are measured to compare with the numerical results. The agreement between the numerical and experimental results is fairly good. It is concluded that a two-dimensional computation is a fast and efficient tool for predicting the effect of front-end design on the cooling air flow through the radiator.

A Compton camera is an imaging system for three-dimensional (3D) distribution of gamma emitting sources based on Compton scattering interaction. The measurement error on energies and positions directly leads to uncertainties on the formation of cones and degrades the spatial resolution of the reconstructed images. Mostly the limited energy resolution, Doppler broadening and position segmentation of detectors cause angular and positional uncertainties on measurements. Since the conical surfaces are delocalized by angular and positional uncertainties into image space, degradation of spatial resolution may be severe depending on the distance (or depth) from the Compton camera. In order to enhance the deteriorated spatial resolution due to angular and positional uncertainties, this study investigates 3D Gaussian point spread function (PSF) incorporable into listmode ordered subset expectation maximization (LMOSEM) as a part of system matrix. Especially the depth-dependent PSF is applied as resolution recovery (RR) technique by image-space convolution operation. We investigated two different RR approaches: one (denoted by LMOSEM-RR-F) is when the convolution is performed in forward projection step only, and the other (denoted by LMOSEM-RR-FB) is when it is performed in both forward and backward projection steps. Using Monte Carlo data for 7 point sources at different depth from the Compton camera, the fitted axial and radial FWHM functions were obtained as FWHM axial (i)=0.2442i+1.054 and FWHM radial (i)=0.2369i–1.005, respectively. The simulation results showed that both RR approaches with depth dependent PSF gave an improvement on spatial resolution comparing to LMOSEM without RR techniques. Although LMOSEM-RR-F provided better resolution than LMOSEM-RR-FB, LMOSEM-RR-FB could still be useful for low counting statistics in measurement.