• 제목/요약/키워드: Cubic

검색결과 2,448건 처리시간 0.027초

다중 해상도 영상에서 페이싯 모델을 이용한 초소형 표적 검출 (Small Target Detection in Multi-Resolution Image Using Facet Model)

  • 박지환;이민우;이철원;주재흠;남기곤
    • 융합신호처리학회논문지
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    • 제12권2호
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    • pp.76-82
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    • 2011
  • 본 논문은 다중 해상도 영상에서 3차 페이싯 모델을 이용하여 적외선 영상의 원거리에 위치하고 있는 초소형 표적의 위치와 크기를 검출하기 위한 방법을 제안한다. 먼저, 원 영상을 점차 축소하여 여려 단계의 다중 해상도의 영상들로 구성한다. 각 단계에서의 다중 해상도 영상들에 대해 페이싯 모델과 국부 극대 조건을 적용하여 초소형 표적의 위치를 검출한다. 다중 해상도 영상에서 각 페이싯 모델의 국부 극대값을 의미하는 $D_2$값 중 최대 크기를 가지는 위치를 표적의 위치라고 평가한다. 이 경우 각 단계의 다중 해상도 영상들에 대해 크기가 다른 표적의 검출이 가능하게 된다. 본 논문에서 제안한 초소형 표적 검출 방법은 초소형 표적이 있는 다양한 적외선 영상에서 실험하였다. 기존의 페이싯 모델을 이용한 방법에서는 하나의 마스크만 적용시킨 것에 반해 제안된 방법은 하나의 마스크를 다중 해상도 영상에서 적용하였다. 고정된 마스크를 다중 해상도 영상에 적용함으로써 마스크의 크기를 달리하는 효과를 확인하였고 그에 따라 검출하는 표적의 크기도 다름을 확인하였다. 이를 이용해서 표적의 위치뿐만 아니라 크기도 검출할 수 있음을 확인하였다.

Mn조성비(組成比)가 PEMFC용(用) Pt/C 전극촉매(電極觸媒) 특성(特性)에 미치는 영향(影響)에 관(關)한 연구(硏究) (Effects of PtMn composition on carbon supported PtMn catalysts for PEMFC)

  • 유성열;강석민;이진아;이충균;유호진
    • 자원리싸이클링
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    • 제21권2호
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    • pp.34-40
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    • 2012
  • 기존 Pt/C 전극촉매 제조시 사용되는 Pt를 일정량의 Mn으로 대체하여 PtMn/C 전극촉매를 제조하였다. 환원제로 포름알데히드(HCHO)를 사용하여 화학환원법으로 $Pt_{10}$/C, $Pt_9Mn_1$/C, $Pt_7Mn_3$/C 촉매를 제조하였으며 반쪽 전지(half cell)에서 순환전압전류와 대시간 전류를 측정하였다. $Pt_9Mn_1$/C촉매가 $Pt_{10}$/C, $Pt_7Mn_3$/C촉매보다 높은 산소환원반응(oxygen reduction reaction)을 보였으며 0.9, 0.8, 0.7, 0.6V에서 각각 5분동안 측정한 대 시간 전류측정에서 $Pt_9Mn_1$/C가 $Pt_{10}$/C, $Pt_7Mn_3$/C촉매보다 높은 활성을 나타냈다. 물리적 특성은 XRD, TEM분석을 통하여 알아보았으며 입자의 평균 크기는 $Pt_9Mn_1$/C, $Pt_{10}$/C가 각각 2.7 nm, 3 nm를 나타냈다. XRD분석을 통하여 Pt의 FCC(Face Centered Cubic)결정 구조를 확인할 수 있었다.

탈수한 $Ag^{+}$ 이온과 $Ca^{2+}$ 이온으로 치환한 제올라이트 $A,\;Ag_{12-2x}Ca_x-A\;(x=2\;and\;3)$를 Cs 증기로 처리한 결정구조 (Two Crystal Structures of Dehydrated $Ag^{+}$- and $Ca^{2+}$-Exchanged Zeolite $A,\;Ag_{12-2x}Ca_x-A\;(x=2\;and\;3)$ Treated with Cesium Vapor)

  • 송승환;김양
    • 대한화학회지
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    • 제38권9호
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    • pp.621-627
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    • 1994
  • $Ag^{+}$ 이온과 $Ca^{2+}$ 이온으로 치환된 제올라이트 $A(Ag_{12-2x}Ca_{x}-A$, x=2 및 3)$를 탈수하고 $250^{\circ}C$, 0.15torr의 Cs 증기로 처리한 결정구조를 X-선 단결정 회절법으로 입방공간군 Pm{\bar\3m(a=12.344(2){\AA}$/ 과 12.304(2) $\AA$)을 사용하여 해석하였다. 이들 구조에서 최종 오차인자 값 Rw는 I > $3\sigma(I)$인 180 및 179개의 반사를 이용하여 0.091 및 0.093까지 정밀화시켰다. 이들 구조에서 Cs종은 네 개의 서로 다른 결정학적 자리에 위치하였다. 단위세포당 세 개의 $Cs^{+}$ 이온은 8-링 중심에 위치하여, 6.81~7.14개의 $Cs^{+}$이온은 큰 동공내의 3회 회전축상 6-링상에 위치하고, 1.83~2.03개의 $Cs^{+}$ 이온은 소다라이트 동공내의 3회 회전축상에 위치하고, 0.66~0.71개의 $Cs^{+}$이온은 4-링에 위치하였다. 또한 4.12~4.27개의 Ag 원자는 큰 동공 중심 가까이에 위치하였다. 이들 구조에서 단위세포내에 과잉으로 흡착된 Cs원자들은 3회 회전축상 위에 놓여 있는 $Cs^{+}$이온과 결합하여 선형의 $(Cs_4)^{3+}$ 클라스터를 형성하고 있었다. 또 $Cs^+$ 이온이 8-링을 차지하고 있어서 은 원자가 구조 밖으로 나오지 못하게 막고 있었다. 이들 원자는 큰 동공 중심에서 hexasilver 클라스터를 형성하고 있었으며, 14개의 $Cs^{+}$ 이온과 배위하여 안정화되어 있었다.

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Crystal Structure of Xenon Encapsulate within Na-A Zeolite

  • 임우택;박만;허남호
    • Bulletin of the Korean Chemical Society
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    • 제21권1호
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    • pp.75-80
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    • 2000
  • The positions of Xe atoms encapsulated in the molecular-dimensioned cavities of fully dehydrated Na-A have been determined. Na-A was exposed to 1050atm of xenon gas at 400 $^{\circ}C$ for seven days, followed by cooling at pressure to encapsulate Xe atoms. The resulting crystal structure of Na-A(7Xe) (a = 12.249(1) $\AA$, $R_1$ = 0.065, and $R_2$ = 0.066) were determined by single-crystal X-ray diffraction techniques in the cubic space group Pm3m at 21(1) $^{\circ}C$ and 1 atm. In the crystal structure of Na-A(7Xe), seven Xe atoms per unit cell are distributed over four crystallographically distinct positions: one Xe atom at Xe(1) lies at the center of the sodalite unit, two Xe atoms at Xe(4) are found opposite four-rings in the large cavity, and four Xe atoms, two at Xe(2) and others at Xe(3), respectively, occupy positions opposite and between eight- and six-rings in the large cavity. Relatively strong interactions of Xe atoms at Xe(2) and Xe(3) with $Na^+$ ions of four-, eight-, and six-rings are observed:Na(1)-Xe(2) = 3.09(6), Na(2)-Xe(3) = 3.11(2), and Na(3)-Xe(2) = 3.37(8) $\AA$. In each sodalite unit, one Xe atom is located at its center. In each large cavity, six Xe atoms are found, forming a distorted octahedral arrangement with four Xe atoms, at equatorial positions (each two at Xe(2) and Xe(3)) and the other two at axial positions (at Xe(4)). With various reasonable distances and angles, the existence of $(Xe)_6$ cluster is proposed (Xe(2)-Xe(3) = 4.78(6) and 4.94(7), Xe(2)-Xe(4) = 4.71(6) and 5.06(6), Xe(3)-Xe(4) = 4.11(3) and 5.32(4) $\AA$, Xe(2)-Xe(3)-Xe(2) = 93(1), Xe(3)-Xe(2)-Xe(3) = 87(1), Xe(2)-Xe(4)-Xe(2) = 91(4), Xe(2)-Xe(4)-Xe(3) = 55(2), 59(1), 61(1), and 68(1), and Xe(3)-Xe(4)-Xe(3) = 89($^{\circ}1$)). These arrangements of the encapsulated Xe atoms in the large cavity are stabilized by alternating dipoles induced on Xe(2), Xe(3), and Xe(4) by eight- and six-ring $Na^+$ ions as well as four-ring oxygens, respectively.

Two Anhydrous Zeolite X Crystal Structures, $Pd_{18}Ti_{56}Si_{100}Al_{92}O_{384} and Pd_{21}Tl_{50}Si_{100}Al_{92}O_{384}$

  • 윤보영;송미경;이석희;김양
    • Bulletin of the Korean Chemical Society
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    • 제22권1호
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    • pp.30-36
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    • 2001
  • The crystal structures of fully dehydrated $Pd^{2+}$ - and $TI^{+}$ -exchanged zeolite X, $Pd_{18}TI_{56}Si_{100}Al_{92}O_{384}(Pd_{18}TI_{50-}X$, a = $24.935(4)\AA$ and $Pd_{21}TI_{50}Si_{100}Al_{92}O_{384}(Pd_{21}TI_{50-}X$ a = $24.914(4)\AA)$, have been determined by single-crystal X-ray diffraction methods in the cubic space group Fd3 at $21(1)^{\circ}C.$ The crystals were prepared using an exchange solution that had a $Pd(NH_3)_4Cl_2\;:TINO_3$ mole ratio of 50 : 1 and 200 : 1, respectively, with a total concentration of 0.05M for 4 days. After dehydration at $360^{\circ}C$ and 2 ${\times}$$10^{-6}$ Torr in flowing oxygen for 2 days, the crystals were evacuated at $21(1)^{\circ}C$ for 2 hours. They were refined to the final error indices $R_1$ = 0.045 and $R_2$ = 0.038 with 344 reflections for $Pd_{18}Tl_{56-}X$, and $R_1$ = 0.043 and $R_2$ = 0.045 with 280 reflections for $Pd_{21}Tl_{50-}X$; I > $3\sigma(I).$ In the structure of dehydrated $Pd_{18}Tl_{56-}X$, eighteen $Pd^{2+}$ ions and fourteen $TI^{+}$ ions are located at site I'. About twenty-seven $TI^{+}$ ions occupy site II recessed $1.74\AA$ into a supercage from the plane of three oxygens. The remaining fifteen $TI^{+}$ ions are distributed over two non-equivalent III' sites, with occupancies of 11 and 4, respectively. In the structure of $Pd_{21}Tl_{50-}X$, twenty $Pd^{2+}$ and ten $TI^{+}$ ions occupy site I', and one $Pd^{2+}$ ion is at site I. About twenty-three $TI^{+}$ ions occupy site II, and the remaining seventeen $TI^{+}$ ions are distributed over two different III' sites. $Pd^{2+}$ ions show a limit of exchange (ca. 39% and 46%), though their concentration of exchange was much higher than that of $TI^{+}$ ions. $Pd^{2+}$ ions tend to occupy site I', where they fit the double six-ring plane as nearly ideal trigonal planar. $TI^{+}$ ions fill the remaining I' sites, then occupy site II and two different III' sites. The two crystal structures show that approximately two and one-half I' sites per sodalite cage may be occupied by $Pd^{2+}$ ions. The remaining I' sites are occupied by $TI^{+}$ ions with Tl-O bond distance that is shorter than the sum of their ionic radii. The electrostatic repulsion between two large $TI^{+}$ ions and between $TI^{+}$ and $Pd^{2+}$ ions in the same $\beta-cage$ pushes each other to the charged six-ring planes. It causes the Tl-O bond to have some covalent character. However, $TI^{+}$ ions at site II form ionic bonds with three oxygens because the super-cage has the available space to obtain the reliable ionic bonds.

금속-세라믹용 Pd-Ag-Sn-Au계 합금의 모의소성 시 산화처리 후 급랭에 의한 경화 효과 (The hardening effect by ice-quenching after oxidation of a Pd-Ag-Sn-Au metal-ceramic alloy during porcelain firing simulation)

  • 신혜정;김민정;권용훈;김형일;설효정
    • 대한치과재료학회지
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    • 제44권3호
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    • pp.197-206
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    • 2017
  • 본 연구에서는 포세린 소성과정 동안 금속하부구조물의 경도가 하강하는 문제점을 개선하기 위해 모의소성 시 산화처리 단계에서 서냉(bench cooling) 대신 급랭(ice-quenching)으로 합금을 냉각시킴으로써 나머지 소성단계 동안 경화효과를 얻을 수 있을 것으로 예측하고, 이를 확인하기 위해 실험을 진행하였다. 본 연구에서는 Pd-Ag-Sn-Au계 금속-세라믹용 합금을 사용하여 실험을 진행하여 다음과 같은 결과를 얻었다. 산화처리 후 stage 0으로 냉각한 시편과 산화처리 후 급랭한 시편을 glaze까지 모의소성한 결과, 두 시편 모두 소성 첫 단계에서 경도가 상승한 후 지속적으로 경도가 하강하였으나, 산화처리 후 급랭한 시편의 최종 경도가 더 높게 나타났다. 소성 첫 단계에서 일어난 경도의 상승은 면심입방구조의 Pd-Ag-rich 기지에서 면심정방구조의 Pd3(Sn, Ga, In)상의 석출로 인해 기지와 석출물간의 계면에 생성된 격자변형에 기인하였다. 모의소성과정에 따른 경도의 하강은 석출물이 조대화됨에 따라 석출물과 기지사이의 계면의 면적이 감소되어 격자 뒤틀림이 해소된 것에 기인하였다.

연화 열처리 후 모의소성된 금속-세라믹용 Pd-Ag-Au계 합금의 후열처리에 의한 경화기전 (Hardening mechanism associated with post-firing heat treatment of softening heat treated and then firing simulated Pd-Ag-Au alloy for bonding porcelain)

  • 김성민;유영준;조미향;권용훈;김형일;설효정
    • 대한치과재료학회지
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    • 제42권2호
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    • pp.95-106
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    • 2015
  • Hardening mechanism associated with post-firing heat treatment of softening heat treated and then firing simulated Pd-Ag-Au alloy for bonding porcelain was examined by observing the change in hardness, crystal structure and microstructure. By post-firing heat treatment of as-cast, solution treated and pre-firing heat treated specimens at $650^{\circ}C$ after casting, the hardness value increased within 10 minutes. Then, hardness consistently increased until 30 minutes, and gap of hardness value among the specimens was reduced. The increase in hardness after post-firing heat treatment was caused by grain interior precipitation in the matrix. The softening heat treatment did not affect the increase in hardness by post-firing heat treatment. The precipitated phase from the parent Pd-Ag-Au-rich ${\alpha}$ phase with face-centered cubic structure by post-firing heat treatment was $Pd_3$(Sn, In) phase with face-centered tetragonal structure, which has lattice parameters of $a_{200}=4.0907{\AA}$, $c_{002}=3.745{\AA}$. From above results, appropriate post-firing heat treatment in order to support the hardness of Pd-Ag-Au metal substructure was expected to bring positive effects to durability of the prosthesis.

Remarkable Structure Relaxation of Zeolite Windows in Rb₃- and K₃-A Crystal Structures of $M_3nA_{9-x}H_xSi_{12}Al_{12}O_{48}$ where M-Rb or K and x=1 or 0

  • 박종삼;윤명숙;임우택;김명철;서숭혁;허남호
    • Bulletin of the Korean Chemical Society
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    • 제16권10호
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    • pp.923-929
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    • 1995
  • Four crystal structures of M3-A (M3Na9-xHx-A, M=Rb or K and x=1 or 0), Rb3Na8H-A(a=12.228(1) Å and R1=0.046), Rb3Na9-A (a=12.258(3) Å and R1=0.058), K3Na8H-A (a=12.257(3) Å and R1=0.048) and K3Na9-A (a=12.257(3) Å and R1=0.052), have been determined by single crystal x-ray diffraction technique in the cubic space group Pm3^m at 21 ℃. In all structures, each unit cell contained three M+ ions all located at one crystallographically distinct position on 8-rings. Rb+ ions are 3.12 and 3.21 Å away respectively from O(1) and O(2) oxygens, about 0.40 Å away from the centers of the 8-rings, and K+ ions are 2.87 and 2.81 Å apart from the corresponding oxygens. These distances are the shortest ones among those previously found for the corresoponding ones. Eight 6-rings per unit cell are occupied by eight Na+ ions, each with a distance of 2.31 Å to three O(3) oxygens. The twelfth cation per unit cell is found as Na+ opposite 4-ring in the large cavities of M3Na9-A and assumed to be H+ for M3Na8H-A. With these noble non-framework cationic arrangements, larger M+ ions preferably on all larger 8-rings and the compact Na+ ions on all 6-rings, the bond angles in the 8-rings of M3-A, 145.1 and 161.0 respectively for (Si,Al)-O(1)-(Si,Al) and (Si,Al)-O(2)-(Si,Al), turned out to be remarkably stable and smaller, by more than 12 to 17°, than the corresponding angles found in the crystal structures of zeolites A with high concentration of M+ ions. It is to achieve these remarkably relaxed 8-rings, the main windows for the passage of gas molecules, with simultaneously maximized cavity volumes that M3-A have been selected as one of the efficient zeolite A systems for gas encapsulation.

Kr Atoms and Their Chlustering in Zeolite A

  • 임우택;장장환;정기진;허남호
    • Bulletin of the Korean Chemical Society
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    • 제22권9호
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    • pp.1023-1029
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    • 2001
  • The positions of Kr atoms encapsulated in the molecular-dimensioned cavities of fully dehydrated zeolite A of unit-cell composition Cs3Na8HSi12Al12O48 (Cs3-A) have been determined. Cs3-A was exposed to 1025 atm of krypton gas at 400 $^{\circ}C$ for four days, followed by cooling at pressure to encapsulate Kr atoms. The resulting crystal structure of Cs3-A(6Kr) (a = $12.247(2)\AA$, R1 = 0.078, and R2 = 0.085) has been determined by single-crystal X-ray diffraction techniques in the cubic space group Pm3m at $21(1)^{\circ}C$ and 1 atm. In the crystal structure of Cs3-A(6Kr), six Kr atoms per unit cell are distributed over three crystallographically distinct positions: each unit cell contains one Kr atom at Kr(1) on a threefold axis in the sodalite unit, three at Kr(2) opposite four-rings in the large cavity, and two at Kr(3) on threefold axes in the large cavity. Relatively strong interactions of Kr atoms at Kr(1) and Kr(3) with Na+ ions of six-rings are observed: Na-Kr(1) = 3.6(1) $\AA$ and Na-Kr(3) = $3.08(5)\AA.$ In each sodalite unit, one Kr atom at Kr(1) was displaced $0.74\AA$ from the center of the sodalite unit toward a Na+ ion, where it can be polarized by the electrostatic field of the zeolite, avoiding the center of the sodalite unit which by symmetry has no electrostatic field. In each large cavity, five Kr atoms were found, forming a trigonal-bipyramid arrangement with three Kr(2) atoms at equatorial positions and two Kr(3) atoms at axial positions. With various reasonable distances and angles, the existence of Kr5 cluster was proposed (Kr(2)-Kr(3) = $4.78(6)\AA$ and Kr(2)-Kr(2) = $5.94(7)\AA$, Kr(2)-Kr(3)-Kr(2) = 76.9(3), Kr(3)-Kr(2)-Kr(3) = 88(1), and Kr(2)-Kr(2)-Kr(2) = $60^{\circ}).$ These arrangements of the encapsulated Kr atoms in the large cavity are stabilized by alternating dipoles induced on Kr(2) by four-ring oxygens and Kr(3) by six-ring Na+ ions, respectively.

Crystallographic Studies of Dehydrated $Ag^{+}\;and\;K^{+}$ Exchanged Zeolite A Reacted with Alkali Metal Vapor

  • Yang Kim;Mi Suk Jeong;Karl Seff
    • Bulletin of the Korean Chemical Society
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    • 제14권5호
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    • pp.603-610
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    • 1993
  • The crystal structure of dehydrated $Ag_{5.6}K_{6.4}-A$, zeolite A ion-exchanged with $K^+\;and\;Ag^+$ as indicated and dehydrated at 360$^{\circ}$C, has been determined by single-crystal X-ray diffraction techniques. Also determined were the structures of the products of the reactions of this zeolite with 0.1 Torr of Cs vapor at 250$^{\circ}$C for 48 h and 72 h, and with 0.1 Torr of Rb vapor at 250$^{\circ}$C for 24 h. The structures were solved and refined in the cubic space group Pm3m at 21(l)$^{\circ}$C (a= 12.255(l) ${\AA}$ , 12.367(l) ${\AA}$, 12.350(l) ${\AA}$, and 12.263(l) ${\AA}$, respectively). Dehydrated $Ag_{5.6}K_{6.4}$-A was refined to the final error indices $R_1= 0.044\;and\;R_2=0.037$ with 202 reflections for which I>3${\sigma}$(I). The crystal structures of the reaction products were refined to $R_1=0.087\;and\;R_2= 0.089$ with 157 reflections, $R_1=0.080\;and\;R_2= 0.087$ with 161 reflections, and $R_1= 0.071\;and\;R_2=0.061$ with 88 reflections, respectively. In the structure of $Ag_{5.6}K_{6.4}-A,\;K^+$ ions block all 8-oxygen rings, and one reduced Ag atom is found per sodalite cavity. Also, ca. 4.6 $Ag^+ ions\;and\;3.4 K^+ ions$ are found at 6-ring sites in the large cavity. The crystal structures of the reaction products show that all $K^+$ and $Ag^+$ ions have been reduced, and that all K^+$ atoms have left the zeolite. Cs or Rb species are found at three different crystallographic sites: 3.0 $Cs^+\;or\;3.0Rb^+$ ions per unit cell occupy 8-ring centers, ca. 8.0 $Cs^+ ions\;or\;5.7 Rb^+$ ions, are found on threefold axes opposite 6-rings deep in the large cavity, and ca. 2.5 $Cs^+\;or\;2.3 Rb^+ ions are found on threefold axes in the sodalite unit. Also, 1 $Rb^+$ ion lies opposite a 4-ring. Silver atoms, corresponding to 75% or 40% occupancy of hexasilver clusters stabilized by coordination to $Cs^+\;or\;Rb^+$ ions, are found at the centers of the large cavities. In the crystal structures of dehydrated Ag_{5.6}K_{6.4}-A$ reacted with Cs vapor, excess Cs atoms are absorbed and these form (locally) cationic clusters such as $(Cs_4)3^+\;and\;(Cs_6)4^+$.