RESUMO
The incremental step pulse programming slope (ISPP) with random variation was investigated by measuring numerous three-dimensional (3D) NAND flash memory cells with a vertical nanowire channel. We stored multiple bits in a cell with the ISPP scheme and read each cell pulse by pulse. The excessive tunneling from the channel to the storage layer determines the program efficiency overshoot. Then, a broadening of the threshold voltage distribution was observed due to the abnormal program cells. To analyze the randomly varying abnormal program behavior itself, we distinguished between the read variation and over-programming in measurements. Using a 3D Monte-Carlo simulation, which is a probabilistic approach to solve randomness, we clarified the physical origins of over-programming that strongly influence the abnormal program cells in program step voltage, and randomly distributed the trap site in the nitride of a nanoscale 3D NAND string. These causes have concurrent effects, but we divided and analyzed them quantitatively. Our results reveal the origins of the variation and the overshoot in the ISPP, widening the threshold voltage distribution with traps randomly located at the nanoscale. The findings can enhance understanding of random over-programming and help mitigate the most problematic programming obstacles for multiple-bit techniques.
RESUMO
A machine-learning (ML) technique was used to optimize the energetic-trap distributions of nano-scaled charge trap nitride (CTN) in 3D NAND Flash to widen the threshold voltage (Vth) window, which is crucial for NAND operation. The energetic-trap distribution is a critical material property of the CTN that affects the Vth window between the erase and program Vth. An artificial neural network (ANN) was used to model the relationship between the energetic-trap distributions as an input parameter and the Vth window as an output parameter. A well-trained ANN was used with the gradient-descent method to determine the specific inputs that maximize the outputs. The trap densities (NTD and NTA) and their standard deviations (σTD and σTA) were found to most strongly impact the Vth window. As they increased, the Vth window increased because of the availability of a larger number of trap sites. Finally, when the ML-optimized energetic-trap distributions were simulated, the Vth window increased by 49% compared with the experimental value under the same bias condition. Therefore, the developed ML technique can be applied to optimize cell transistor processes by determining the material properties of the CTN in 3D NAND Flash.
RESUMO
OBJECTIVE: We retrospectively analyzed the surgical outcomes of 42 patients with growth hormone (GH)-secreting pituitary adenoma to evaluate the clinical manifestations and to determine which preoperative factors that significantly influence the remission. METHODS: Forty-two patients with GH-secreting pituitary adenoma underwent transsphenoidal surgery (TSS) between 1995 and 2007. The patient group included 23 women and 19 men, with a mean age of 40.2 (range 13-61) years, and a mean follow-up duration of 49.4 (range 3-178) months after the operation. For comparable radiological criteria, we classified parasellar growth into five grades according to the Knosp classification. We analyzed the surgical results of the patients according to the most recent stringent criteria for cure. RESULTS: The overall rate of endocrinological remission in the group of 42 patients after primary TSS was 64% (26 of 42). The remission rate was 67% (8 of 12) for microadenoma and 60% (18 of 30) for macroadenoma. The remission rate was 30% (3 of 10) for the group with cavernous sinus invasion and 72% (23 of 32) for the group with intact cavernous sinus. Cavernous sinus invasion in Knosp grade III and IV was significantly correlated with the remission rate. There was a significant relationship between preoperative mean GH concentration and early postoperative outcome, with most patients in remission having a lower preoperative GH concentration. CONCLUSION: TSS is thought to be an effective primary treatment for GH-secreting pituitary adenomas according to the most recent criteria of cure. Because the remission rate in cases with cavernous sinus invasion is very low, early detection of the tumor before it extends into the cavernous sinus and a long-term endocrinological and radiological follow-up are necessary in order to improve the remission rate of acromegaly.
RESUMO
OBJECTIVE: The purpose of this study is to identify the factors affecting the failure of trials (<50% pain reduction in pain for trial period) to improve success rate of spinal cord stimulation (SCS) trial. METHODS: A retrospective review of the failed trials (44 patients, 36.1%) among the patients (n=122) who underwent SCS trial between January 1990 and December 1998 was conducted. We reviewed the causes of failed trial stimulation, age, sex, etiology of pain, type of electrode, and third party support. RESULTS: Of the 44 patients, 65.9% showed unacceptable pain relief in spite of sufficient paresthesia on the pain area with trial stimulation. Four of six patients felt insufficient paresthesia with stimulation had the lesions of the spinal cord. Seventy five percent of the patients experienced unpleasant or painful sensation during stimulation had allodynia dominant pain. Third-party involvement, sex, age and electrode type had no influence on the outcome. CONCLUSION: We conclude that SCS trial is less effective for patients with neuropathic pain of cord lesions, postherpetic neuropathy or post-amputation state. Further, patients with allodynia dominant pain can feel unpleasant or painful during trial stimulation.
