Sangwon Park

Single-Port Laparoscopic Salpingectomy for the Surgical Treatment of Ectopic Pregnancy

STUDY OBJECTIVE To evaluate the feasibility of a single-port laparoscopic salpingectomy in the surgical treatment of tubal pregnancy. DESIGN Prospective cohort study (Canadian Task Force classification II-2). SETTING University teaching hospital PATIENTS Twenty women with tubal pregnancy, as determined by ultrasonography. INTERVENTION All patients have undergone single-port laparoscopic salpingectomy. Entry through a single port was established with a wound retractor as fascial retractor and a surgical glove, which served as the working channels for the laparoscopic equipment. A 30-degree laparoscope and a rigid or flexible grasper were used during the procedure. MEASUREMENTS AND MAIN RESULTS Single-port laparoscopic salpingectomy was successfully performed in all 20 patients with ectopic pregnancy. The median operative time was 55 minutes (range 25-85 minutes), and blood loss in all patients was minimal. The median difference between preoperative and postoperative hemoglobin was 1.8 g/dL (range 0-3.2 g/dL). The median postoperative hospital stay was 2 days (range 2-4 days). No complication was encountered, nor was there any need for conversion to conventional laparoscopy. CONCLUSIONS Single-port laparoscopic salpingectomy is feasible and promising. However, for drawing the definite conclusion of the surgical efficacy, additional investigations to compare this approach with conventional laparoscopy are needed.

Screening test for aqueous solvents used in CO2 capture: K2CO3 used with twelve different rate promoters

K2CO3 solution is widely used in the CO2-capture industry. In particular, it has advantages for treating CO2 in flue gas under high-temperature and high-pressure conditions. However, it has a lower CO2-loading capacity and slower absorption kinetics than those of amines, which are its major disadvantages. Thus, in this study, we investigated ten loading-rate promoters, five primary amines and five secondary amines, to develop higher CO2-loading capacity and faster absorption kinetics. The screening tests of the absorption and desorption processes were conducted at 70 °C and 90 °C, respectively. Based on the results, we concluded that all the amines used improved the CO2-loading and absorption kinetics compared with the use of K2CO3 alone. At a certain value CO2 loading, the respective performance of the primary and secondary amines was twice and thrice better, respectively, than the neat K2CO3 solution. Thus, secondary amines had superior absorption capacity and absorption/desorption rate compared to primary amines. Among the secondary amines, pipecolic acid, sarcosine, and isonipecotic acid were determined as the most effective absorption rate promoters.

The estimation of N2O emissions from municipal solid waste incineration facilities: The Korea case.

The greenhouse gases (GHGs) generated in municipal solid waste (MSW) incineration are carbon dioxide (CO(2)), methane (CH(4)), and nitrous oxide (N(2)O). In South Korea case, the total of GHGs from the waste incineration facilities has been increasing at an annual rate 10%. In these view, waste incineration facilities should consider to reduce GHG emissions. This study is designed to estimate the N(2)O emission factors from MSW incineration plants, and calculate the N(2)O emissions based on these factors. The three MSW incinerators examined in this study were either stoker or both stoker and rotary kiln facilities. The N(2)O concentrations from the MSW incinerators were measured using gas chromatography-electron capture detection (GC-ECD) equipment. The average of the N(2)O emission factors for the M01 plant, M02 plant, and M03 plant are 71, 75, and 153g-N(2)O/ton-waste, respectively. These results showed a significant difference from the default values of the intergovernmental panel on climate change (IPCC), while approaching those values derived in Japan and Germany. Furthermore, comparing the results of this study to the Korea Energy Economics Institute (KEEI) (2007) data on waste incineration, N(2)O emissions from MSW incineration comprised 19% of the total N(2)O emissions.

Effect of the relative permittivity of oxides on the performance of triboelectric nanogenerators

Since the working mechanism of triboelectric nanogenerators (TENGs) is based on triboelectrification and electrostatic induction, it is necessary to understand the effects of the inherent properties of dielectric materials on the performance of TENGs. In this study, the relationship between the relative permittivity and the performance of TENGs was demonstrated by fabricating TENGs using both pure oxide materials (SiO2, Al2O3, HfO2, Ta2O5 and TiO2) and oxide–PMMA composites. As oxide materials and PMMA are triboelectrically positive, PTFE film was selected as the counter tribo-material, which has highly negative triboelectric polarity. The triboelectric series of the above-mentioned oxides was experimentally organized to clarify the major parameter for the performance of TENGs. The electrical data values for both oxides and composites clearly showed a tendency to increase as the relative permittivity of the tribo-material increased. It is also well-matched with the theoretical analysis between the electrical performances (e.g. open-circuit voltage) and relative permittivity. However, such a tendency is not observed with the triboelectric polarity. Due to the tribo-material’s high relative permittivity, an open-circuit voltage of 124.1 V, a short-circuit current of 14.88 μA and a power of 392.08 μW were obtained in a pure TiO2 thin film.

A Differential Trellis-Coded Quantization for FDD Massive MIMO Systems in a Spatially Correlated Channel

To obtain the beamforming gain of a frequency-division duplex massive multiple-input multiple-output system, extensive channel state information (CSI) should be accurately quantized and fed back to the base station. Trellis-coded quantization (TCQ) can reduce codebook size and codebook-searching complexity that are the main drawbacks of vector-quantization-based CSI feedback schemes. However, the beamforming gain of the conventional TCQ cannot be fully obtained in a spatially correlated channel that is inevitably involved in massive transmit arrays. In this letter, we propose a differential TCQ that exploits the channel correlation by using a compressive constellation and phase difference quantization. We present an algorithm for generating a phase difference constellation and a decoding process for the proposed differential TCQ. The proposed scheme can reduce the overhead of the codebook size problem by trellis decoding and improve the quantization performance at the same feedback rate compared to the conventional TCQ scheme.

A Space Shift Keying for Downlink Multi-User Transmission With Partial CSI in Massive MIMO Systems

To reduce the burden of channel state information (CSI) acquisition in downlink massive multiple input and multiple output systems, we propose a non-codebook-based precoding scheme for multi-user space shift keying (SSK). The proposed scheme consists of two precoding processes: one precoder to suppress multi-user interference and another to adjust the modulation order for the SSK. The proposed scheme can support downlink multi-user transmission by exploiting the transmit covariance matrix without instantaneous CSI at the transmitter. Moreover, the proposed scheme can achieve better performance than the conventional precoding-aided SSK, regardless of the number of receive antennas.

Base Station Selection for Per-cell Precoding with Limited Feedback in Cooperative Multi-point Systems

Though per-cell precoding is an efficient coordinated multipoint transmission/reception transmission mode for frequency-division duplex systems, it has the problems of channel feedback and computational complexity. Especially, when base station has large antennas, these problems are worsened. To overcome these drawbacks, we propose a base station selection precoding that searches an optimal combination of cooperative base stations. By selecting transmission mode at each base station, the feedback overhead and complexity can be relieved and user can acquire additional throughput gains. Also, the analytical approximation of proposed scheme is derived. Simulation results show that the base station precoding has a higher throughput gains in the large antennas environment than conventional schemes and the analytical results approximate the numerical results well.

Two-dimensional growth of germanium under a diffusion limited aggregation environment

The discovery of graphene has triggered immense interest in two-dimensional (2D) nanomaterials. However, the 2D growth of several layerstructured crystals such as graphene, MoS2, and black phosphorus is difficult and limited. Here, we report the gas-phase 2D growth of germanium (Ge) with a cubic structure to form Ge nanosheets (GeNSs) using the chemical vapor deposition method. Our investigation revealed that a diffusion limited aggregation (DLA) environment is essential for the 2D growth of Ge that induces a dendritic growth in the <110> direction and suppresses the growth in the [111] direction. The growth behavior was similar to the 2D growth of silicon reported previously. Thus, it can be concluded that a DLA environment is essential for the 2D growth of cubic structured materials. The electron density and mobility of GeNSs were found to be 1.3 × 1015 cm−3 and 792 cm2/Vs, respectively, and their resistivity varied with the intensity of light.

Growth of single crystalline germanium thin film on (100) silicon substrate

Epitaxial growth of germanium thin films (GeTFs) on Si (111) and Si (100) substrates was investigated, and the prepared films were compared with the films grown on SiO2 substrates. Ge films were prepared in three steps. Initially, a Ge interlayer film with thickness of ∼ 10 nm was deposited on the substrate followed by annealing and recrystallization of the film. A Ge film with a thickness of 500 nm was then deposited. A single crystalline Ge film was grown on Si (100) whereas polycrystalline films were grown on the other substrates. The growth rate of the films depends on the type of the substrates used, which in turn determines the crystallinity of the films. Highly crystalline films were obtained with slow growth rates. The single crystalline epitaxial layer of GeTFs formed on Si (100) exhibited a lower threading dislocation density as compared with those grown on Si (111) and SiO2.