Process Parameter Optimization for Laser Powder Bed Fusion of Fe-Si Alloy Considering Surface Morphology and Track Width of Single Scan Track.

A laser power bed fusion (L-PBF) manufacturing process was optimized by analyzing the surface morphology and track width w of single scan tracks (SSTs) on Fe-3.4wt.%Si. An SST was evaluated under process conditions of laser power P, scan speed V, and energy density E = P/V. The SST surface shape was mainly affected by E; desirable thin and regular tracks were obtained at E = 0.3 and 0.4 J/mm. An L-PBF process window was proposed considering the optimal w of SST, and the appropriate range of E for the alloy was identified to be 0.24 J/mm to 0.49 J/mm. w showed a strong relationship with E and V, and an analytic model was suggested. To verify the process window derived from the appropriate w of SST, cubic samples were manufactured with the estimated optimal process conditions. Most samples produced had a high density with a porosity of <1%, and the process window derived from SST w data had high reliability. This study presents a comprehensive approach to enhancing additive manufacturing for Fe-3.4Si alloy, offering valuable insights for achieving high-quality samples without the need for time-intensive procedures.

Metabolic Changes after Hypothermic Cardiopulmonary Bypass Surgery / 대한마취과학회지

Temperature changes after cardiopulmonary bypass surgery(CPB) markedly affect postoperative ventilation. Despite core rewarming after CPB, on admission to the intensive care unit the rectal temperature is about 34~35 degrees C over the next 12 hours, the temperature rises to 38~39 degrees C. Unless minute ventilation is increased hypercarbia occurs presumably because dead space and/or CO2 production are increased. This prospective review was designed to confirm these clinical impressions and to provide direction for future studies. Temperature changes, PaCO2, pH, sodium and potassium values of 42 patients who had undergone cardiac valvular replacement surgery with hypothemic cardiopulmonary bypass were observed during surgery and during the first 12 postoperative hours in the intensive care unit. The results are as follows: 1.The mean nasopharyngeal temperature was 26.3 degrees C, 34.4 degrees C, 34.9 degrees C, and 36.4 degrees C during bypass, rewarming, admission to the intensive care unit, and after 4 hours, respectively. The temperature curve was sigmoid rather than linear. 2. During rewarming, the most common abnormality of PaCO2 on anesthetic mechanical ventilation was acute respiratory acidosis(PaCO2 45mmHg, pH 7.35) which occurred in 48% of the patients. After bypass and in the intensive care unit, respiratory alkalosis occurred in 36% and 45% of the patients, respectively. 3. The serum sodium values decreased in 19% of the patients during bypass but not significantly. 4. The serum potassium value increased in 21% of the patients during bypass surgery, but not significantly, and after surgery it returned to normal limits. This suggests that ventilatory management in the early postoperative period after hypothermic cardiopulmonary bypass surgery should be carefully monitered and adjusted as necessary to the increased metabolic rate during rapid rewarming.

Respiratory Care in Postoperative Acute Respiratory Failure / 대한마취과학회지

This study was undertaken to evaluate the result of intensive respiratery care for 36 patients who developed acute respiratory insufficiency and pulmonary comlications after operation in Busan National University Hospital, and to compare the any difference between the survivors and nonsurvivors. The results were as follows : 1) 20 patients survived (55.6%) . 2) In 19 patients(52.8%) , were received prolonged cancer operation and upper abdominal surgery. 3) 30 patients had abnormal physilogic conditions before operation, in which the COPD was the most oommon problems. 4) 55% of aurvirors had mean operation time less than 5 hrs and 75% of non survivers had mean operation time greater than 5 hrs. 5) In 83.3% of patients, acute respiratory Compiication was developed within 10 hours from the opration, 6) Majority of the Patients (25/69.4%) required less than 24 hrs of ventilatory support. 7) 29 patients, receive the PEEP therapy and the level of PEEP was 6~15 cmH2O. 8) The survivors showed fair general conditions during respiratory care, such as normal range of blood preasure, more improved pulmonary function, more improved atterial blood gases and CVP, and adequate hourly urine output. But the nonsurvlvors had poor general conditions, such as unstable blood pressure, poor pulmonary function, abnormal arterial blood gases in spite of ventilatory support, low urine output, high CVP, and elctrolyte i mbalances.

The Clinical Studies of Sequential Changes of Serum Electrolytes , and Serum Osmolality after Transurethral Resection of the Prostate / 대한마취과학회지

Dilutional hyponatremia and aurum hypoosmolality are commonly abserved during transure-thral resection of the prostate in association with the systemic absorption of the irrigating solution. To assess these sequential changes following surgery, 26 Patients were studies who unclerwent transurethral resection of the prostate because of prostatic tumors at Pusan National University Hospital, Where 4% Dextrose in Water is Still used as irrigating solution. 0.9% NaCl and furosemide were administered to all 26 patients in the recovery room after surgery. Blood samples were examined for serum electrolytes and osmolality 7efore induction of anesthesia, immediate-postoperatively, and at postoperative 1 hour, 6 hours and 24 hours respectively, The results are as fellows : 1) Of the 26 Patients, 19 Patients shoved abnormalities in serum electrolytes, especially serum sodium, in the immediate postoperative period, while 7 patients showed a slight decrease in serum sodium but within normal limits. Mean changes in serum sodium was 10.9 mEq/l in the immediate postoperative period, but after administration of 0.9% NaCl and furosemide, the level of serum sodium returned to normal limits within 1~3 hours. Serum calcium decreased approximately 0.8 mg/dl but returned to normal levels 3 hoers after surgery. But no symptoms of hyponatremia or hypocalcemia were not observed. 2) Serum osmolality decreased to about 8.4 mOsm/kg below the preoperative level in accordiance with hyponatremia, but returned to normal bevels 24 hours postoperatively. 3) Blood glucose levels increased about 231.5 mg% but returned to normal levels 24 hours postoperatively.