Numerical simulation of the effects of a suction line heat exchanger on vapor compression refrigeration cycle performance

Most modern refrigerators incorporate heat transfer between the refrigerant in a capillary tube and the refrigerant in a suction line. This heat transfer is achieved by a non-adiabatic capillary tube called a capillary tube-suction line heat exchanger and is supposed to improve the performance of the small vapor compression refrigeration cycle by removing some enthalpy of the refrigerant at the evaporator entrance. To investigate the effects of this heat transfer on the refrigeration cycle, a computer program was developed based on conservation equations of mass, momentum, and energy. The non-adiabatic capillary tube model is based on a homogeneous two-phase flow model. The simulation results show that both the location and length of the heat exchange section influence the coefficient of performance (COP) as well as the cooling capacity. It is noteworthy that the influence was not monotonic; that is, the performance may be deteriorated under certain conditions.     

Formation of Ge nanocrystals in a silicon dioxide layer using pulsed plasma-immersion ion implantation

Pulsed plasma-immersion ion implantation (PIII) or Pulsed PLAsma Doping (P²LAD) is known as a cost effective solution for ultra shallow junction formation due to its capability to implant doping species at ultra-low energies (0.05–5 keV), the advantages of P²LAD, high concentration and sharp distribution of the implanted species, also make this technique a good candidate to fabricate nanocrystals (NCs) within silicon dioxide (SiO₂) layer. In this work, we report Ge NC fabrication within a SiO₂ layer by using the pulsed PIII technique for the first time. GeH₄ (4 sccm) and He (100 sccm) gases were flown to the plasma chamber, and a voltage of 4.5 kV was applied. After pulsed PIII process, furnace annealing was performed at 900 °C in nitrogen atmosphere for Ge agglomeration. By using such a process, we fabricated non-volatile memory devices and obtained relevant program/erase, retention, and cycling characteristics.     

NAND flash memory technology utilizing fringing electric field

In this review article, basic properties of NAND flash memory cell strings which consist of cells with virtual source/drain (S/D) (or without S/D) were discussed. The virtual S/D concept has advantages of better scalability, less cell fluctuation due to effectively longer channel length at the same technology node, and less program disturbance. The fringing electric field from the control-gate and/or the floating-gate is essential to induce the virtual S/D (charges) in the space region of the body between control-gates and becomes effective as cell size shrinks. A cell string consisting of planar channel silicon-oxide-nitride-oxide-silicon (SONOS) cells formed in bulk Si substrate needs to have a bit-line body doping of ～5 × 10¹⁷ cm^?3 in the channel and a less doping in the space region to keep high bit-line read current. The floating gate (FG) flash memory cell string gives larger bit-line current compared to that of SONOS flash memory cell string at given similar body doping. Non-planar channel cells like arch and fin-type body structures were more effective to focus the fringing electric field on the space region. The virtual S/D concept is also useful in 3-dimensional (3-D) stacked NAND flash memory where thin film (or nanowire, nanotube) body is adopted.     

Removal of antibiotics by coagulation and granular activated carbon filtration

Treatment of seven tetracycline classes of antibiotic (TAs) from raw waters (synthetic and river) was evaluated using coagulation and granular activated carbon (GAC) filtration in this study. Both coagulation and GAC filtration were effective for removal of TAs, and the removal efficiency depended on the type of TAs. GAC filtration was relatively more effective for removal of tetracycline (TC), doxycycline-hyclate (DXC), and chlortetracycline-HCl (CTC), which were difficult to remove by coagulation. It was speculated that TAs would be removed through the charge neutralization and sweep coagulation when poly-aluminum chloride (PACl) was added into the raw waters. The charge neutralization of zwitterionic or negative TAs by cationic Al (III) species drove removal of TAs from the synthetic water. When sufficient alkalinity was available (river water), aluminum hydroxide precipitates were formed. TAs could be removed by being enmeshed into or adsorbed onto the precipitates when PACl was added to the river water.     

Modeling of $V_{rm th}$ Shift in nand Flash-Memory Cell Device Considering Crosstalk and Short-Channel Effects

A threshold-voltage (V_th) shift of sub-100-nm NAND flash-memory cell transistors was modeled systematically, and the modeling was verified by comparing with the data from measurement and 3-D device simulation. The V_th shift of the NAND flash-memory cell was investigated by changing parameters such as gate length, width, drain voltage, dielectric material between cells, space between cells, lightly doped-drain depth, and adjacent-cell bias. The proposed model covers two dominant device physics: capacitance coupling effect between adjacent cells and short-channel effect. Our model showed an accurate prediction of the V_th shift of NAND flash-memory array and a good agreement with the data from simulation and measurement.