Generalized Skolem-type Sequence的相關探討
本研究探討 Skolem sequence之推廣generalized Skolem-type sequence,是否能類比Skolem sequence 探討奇偶性 (parity) 的問題,也就是依照各數字所處位置模重複度 𝑠 所得餘數分類,觀察必不能填滿數列的組合,以找到數列存在的必要條件。接著以奇偶性 (parity) 及密度 (density) ,也就是比較數列位置差最大值與放入數列各數字的位置差總和,找出generalized Skolem sequence 的推廣 generalized Skolem-type sequence 存在的必要條件。 至於充分性,我構造出 hooked (1, 𝑚)-near Skolem sequence 在 𝑛 ≡ 2, 3 (mod 4), 𝑚 ≡ 1 (mod 2) 的情形,並猜想推導出的 hooked (1, 𝑚)-near Skolem sequence 必要條件也具充分性。接著我透過串接 Lanford sequence 的方式,構造出 𝑛 ≥ 3𝑚𝑘 + 1, 𝑚𝑖 ≥ 3𝑚𝑖−1 + 1 ∀ 3 ≤ 𝑖 ≤ 𝑘 的 (𝑚1, 𝑚2, … , 𝑚𝑘)-near Skolem sequence 及 hooked (𝑚1, 𝑚2, … , 𝑚𝑘)-near Skolem se- quence 存在的充分必要條件。
從心開始-三角形的四心到各邊距離和
此研究討論三角形𝐴𝐵𝐶的外心、重心、垂心、內心到三邊之距離,並依銳角、直角及鈍角三角形,去比較各距離總和之大小關係及相互之間的關聯性。其主要結果為: 1.用外接圓半徑𝑅及∠𝐴,∠𝐵,∠𝐶表示各心到三邊之距離。 2.設外心、重心、垂心、內心到三邊之距離總和依序為𝑑1, 𝑑2, 𝑑3, 𝑑4 ,其大小關係為: (1)在銳角∆中,𝑑1 ≥ 𝑑2 ≥ 𝑑4 ≥ 𝑑3,僅當正∆ 時,等號成立。 (2)在直角∆中,𝑑1 > 𝑑2 > 𝑑4 > 𝑑3。 (3)在鈍角∆中,𝑑1 > 𝑑2 > 𝑑4 恆成立。𝑑3與𝑑1、𝑑2、𝑑4比較,並無絕對關係,但在等腰鈍角∆,我們給出其大小順序的臨界值。 (4)在鈍角∆中,若最大內角≥ 120° ,則𝑑3 > 𝑑1 > 𝑑2 > 𝑑4。 3.在銳角∆ 及直角∆ 中,等式𝑑2=2/3 𝑑1+1/3 𝑑3和 𝑑2+1/3 𝑑1-1/3 𝑑3-1/3 𝑑4 = 𝑅 恆成立。
Development of a nano-filtration membrane using different linear aliphatic amines and linear cross-linkers for purification of expensive and precious organic solvents
Theseparation, purification, and recovery of precious organic solvents is a huge challenge for many industriesincludingpetroleumandpharmaceuticalcompanies,sincethesecompaniesusehugequantities of organic solvents [1-2]. Natural dissolvable nanofiltration(ON)has atremendous potential for supplantingafewenergy-concentratedcrudepurgingtechniques,similartorefiningandextraction[3-4- 5]. The importance of OSN is obvious from the fact that one cubic meter of methanol requires 1750 MJ of energy for distillation since the process of distillation is comprised of heating, evaporation, and condensation while OSN can purify the same volume of methanol by consuming 3 MJ of energy [6-7]. Additionally, OSN is a useful technology since it is simpler to use than conventional purification and separationmethods.Themembrane'sporestructure,whichinfluencesbothitsselectivityandpermeance, hasasignificantimpactonhowwellthemembranesperform[8-9].Ingeneral,thetrade-offbetweenflux andselectivityaffectsthemembrane'sperformance.Asaresult,themembranes'fluxandpermeabilityare affectedbythetailoringandtuningoftheirporestructure.Therefore,designinganefficientnanofiltration membranes with ideal porosity is highly desirable. Interfacial polymerization (IP) is highly versatile as it provides a freedom of selection of various monomersfortargetingaspecificapplicationsuchasnanofiltrationandreverseosmosisThepotentialfor organicsolventnanofiltration(ON)toreplacevariousenergy-intensivetraditionalpurificationtechniques, suchasdistillationandextraction,isenormous.[8-9].Despitethefactthatmanydifferentmonomershave been successfully used by utilizing IP to create thin film composite nanofiltration TFC-NF membranes, one of the main limitations of such membranes continues to be the poor selection of closely related comparable nanometer sized solutes. Many efforts are still being made to develop potential monomers with the perfect properties for creating membranes that operate excellently [10-11]. Another strategy is also getting more popular in which different porous additives are added to the TFC membrane either at thesupportleveloractivelayerlevel.Theseadditivesincludecarbonorganicframeworks(COFs),metal organic frameworks (MOFs), hyper-cross-linked porous polymers (HCPs), and natural polymers such as chitosan[12-13-14-15]. However,maintainingthecrystallinity ofsuch additives,particularlyMOFsthat lead to crystalline membranes, is extremely difficult while other additions suffer from aggregation and agglomeration that results in membrane flaws that impair the performance of the membranes [16]. Therefore,changingthechemistryofthereacting monomerduringIPcansignificantlyalterthestructure of the resultant active layers of the membranes. The current study was carried out by using linear aliphatic amines 4A-3P and 4A on a crosslinked PAN support. The study was carried out through interfacial polymerization between either 4A-3P and TPC or 4A and TPC on crosslinked PAN. In comparison to the previous studies where cyclic amines such as piperazine or aromatic amines such as meta-phenylenediamine (MPD) are used, we have used linear aliphatic amines 4A and 4A-3P crosslinked with organic phase containing terephthaloyl chloride (TPC) asacross-linker.TheIPreactionwascarriedoutbetweenamineandTPConacrosslinkedPANsupport. The fabricated membrane was extensively characterized by using scanning electron microscope (SEM), ATR-FTIR, water contact angle (WCA), energy dispersive X-ray (EDX) and elemental mapping . The fabricated membrane was used for OSN applications by using dead-end filtration setup.